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WO2002080579A2 - Affichage 3d a auto-alignement - Google Patents

Affichage 3d a auto-alignement Download PDF

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Publication number
WO2002080579A2
WO2002080579A2 PCT/DK2002/000194 DK0200194W WO02080579A2 WO 2002080579 A2 WO2002080579 A2 WO 2002080579A2 DK 0200194 W DK0200194 W DK 0200194W WO 02080579 A2 WO02080579 A2 WO 02080579A2
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WO
WIPO (PCT)
Prior art keywords
oaslm
observers
light
optical
image
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/DK2002/000194
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English (en)
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WO2002080579A3 (fr
Inventor
Steen Svendstorp Iversen
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DIMENSIONAL DEVELOPMENTS APS
Original Assignee
DIMENSIONAL DEVELOPMENTS APS
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Priority claimed from EP01610037A external-priority patent/EP1245990A1/fr
Application filed by DIMENSIONAL DEVELOPMENTS APS filed Critical DIMENSIONAL DEVELOPMENTS APS
Priority to AU2002246027A priority Critical patent/AU2002246027A1/en
Publication of WO2002080579A2 publication Critical patent/WO2002080579A2/fr
Anticipated expiration legal-status Critical
Publication of WO2002080579A3 publication Critical patent/WO2002080579A3/fr
Ceased legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/332—Displays for viewing with the aid of special glasses or head-mounted displays [HMD]
    • H04N13/337—Displays for viewing with the aid of special glasses or head-mounted displays [HMD] using polarisation multiplexing
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
    • G02B30/20—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes
    • G02B30/22—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the stereoscopic type
    • G02B30/25—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the stereoscopic type using polarisation techniques
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B30/00—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images
    • G02B30/20—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes
    • G02B30/26—Optical systems or apparatus for producing three-dimensional [3D] effects, e.g. stereoscopic images by providing first and second parallax images to an observer's left and right eyes of the autostereoscopic type
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/302—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays
    • H04N13/305—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays using lenticular lenses, e.g. arrangements of cylindrical lenses
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/302—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays
    • H04N13/307—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays using fly-eye lenses, e.g. arrangements of circular lenses
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/302—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays
    • H04N13/32—Image reproducers for viewing without the aid of special glasses, i.e. using autostereoscopic displays using arrays of controllable light sources; using moving apertures or moving light sources
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/363—Image reproducers using image projection screens
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/366—Image reproducers using viewer tracking
    • H04N13/368—Image reproducers using viewer tracking for two or more viewers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/398—Synchronisation thereof; Control thereof
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/30—Image reproducers
    • H04N13/346—Image reproducers using prisms or semi-transparent mirrors

Definitions

  • Stereoscopic displays are based on presenting one image to the right eye and another image to the left eye, the images being two slightly shifted viewpoints of the same object or scene, a left eye view and a right eye view.
  • an observer wears glasses for separating right and left images displayed.
  • Auto-stereoscopic displays let an observer observe stereoscopic images without the need to wear glasses.
  • Auto-stereoscopic displays provides separate images for each eye by employing directional displays, transmitting or reflecting different viewpoint images in different directions, so that the right eye of an observer will observe one viewpoint image, the left eye another viewpoint image. From each pixel of such a display, the right eye will receive light of a specific intensity and a specific colour composition and the left eye will receive light of a different intensity and a different colour composition.
  • Directional displays have been made using mechanical parallax barriers and optical parallax barriers such as lenticular sheets, lens arrays and spatial light modulators.
  • Auto-stereoscopic displays generally fall in two categories: multi parallax and dual parallax.
  • Multi parallax displays employ a plurality of images taken from different viewpoints, and the display emits these images successively in successive directions, so that at any position within the viewing area, an observer will receive two images of shifted viewpoints with right and left eye respectively.
  • Multi parallax displays have the advantage of look-around ability, an observer may move around an object, which will appear steady in space.
  • Multi parallax images are complex to record or synthesise, and require high bandwidth for transmission and require very high resolution of the display to produce reasonable observed resolution. Examples of multi parallax displays are holograms and multi-parallax lenticular displays. Dual parallax displays use only two viewpoints. These do not provide for look- around capability, which is, however, in many applications not of a big concern.
  • Dual parallax auto-stereoscopic displays may further be divided into two categories: fixed barrier displays and observer tracking displays.
  • Another approach is to display alternating patterns based on a synthesised image calculated from an image captured of the observers with an infrared video camera on a monochrome display, acting as back illumination of a transparent type LCD display panel with a large lens element disposed therein between, so that emitted light from the alternating patterns will emit in the directions of the observers left and right eyes altematingly, synchronised with the left and right images being displayed on the led panel altematingly, in a time-division manner.
  • Fig. 5 illustrates such an arrangement.
  • 1 denotes an observer
  • 2 denotes an infrared illumination source
  • 3 denotes an infrared tv camera
  • 4 denotes an image processing system
  • 5 denotes a monochrome display used as back illumination
  • 6 denotes a very large convex lens
  • 7 denotes a transparent colour led display.
  • Fig. 6 illustrates captured and synthesised images.
  • 1 denotes an image of the observer captured in essentially frontal illumination
  • 2 denotes an image of the observer captured with illumination from the observer's right
  • 3 denotes a synthesised binary left half image
  • 4 denotes a synthesised binary left half image.
  • Such a system may provide a high degree of freedom for a number of simultaneous observers, but is limited in size, and hard to make slim, and further it is applicable only to a limited range of display types, therefore not being able to take advantage of recent developments in display technology, such as for example flat-screen plasma displays.
  • An object of the invention is to overcome the above mentioned problems in prior art relating to either the need to wear glasses, to the complexity of producing and transmitting images, to the limitations in viewing angles and number of observers, to the ability to scale to big size displays and take advantage of a wide range of existing and evolving display technologies, including flat panel systems and electronic projection systems.
  • Another object of the invention is to produce an auto-stereoscopic rear projection screen for operation with a projector, or a pair of projectors, capable of projecting polarised, spatially or temporally multiplexed moving or still stereoscopic image pairs, the projectors being of a wide range of types
  • a third object of the invention is to produce an auto-stereoscopic display overlay screen, which can be overlaid on a display capable of displaying polarised, spatially or temporally multiplexed moving or still stereoscopic image pairs, the display being of a wide range of types.
  • an auto- stereoscopic display system comprising: i) image generating means for the generation of a pair of orthogonally polarised images, the one image being vertically orientated with respect to its polarisation and the other image being horizontally orientated with respect to its polarisation, said images being transmitted from said image generating means along respective optical paths towards one or more observers for the illumination of at least a left hand part and a right hand part including the left eye and the right eye, respectively, of the head or heads of said one or more observers, ii) an optically addressed spatial light modulator (OASLM) including a plurality of light transmission elements, each being individually optically addressable, and each having an optical input and an optical output and being shiftable between a V-state and an H-state in which V-state the transmission of vertically polar
  • OFLM optically addressed spatial light modulator
  • the auto-stereoscopic display system according to the first aspect of the present invention is, as is understood, based on a conventional polarised light discrimination well known in the art per se.
  • an auto-stereoscopic display system comprising: i) image generating means for the generation of a pair of images, said images being generated alternatively in a time multiplexed mode, a first image being generated in a first period of time and a second image being generated in a second period of time, said images being transmitted from said image generating means along respective optical paths towards one or more observers for the illumination of at least a left hand part and a right hand part including the left eye and the right eye, respectively, of the head or heads of said one or more observers, ii) an optically addressed spatial light modulator (OASLM) including a plurality of light transmission elements, each being individually electrically and optically addressable, and each having an optical input and an optical output and being shiftable between two states, a first state in which the transmission of light from said optical
  • OFLM optically addressed spatial light modulator
  • an auto- stereoscopic display system comprising: i) image generating means for the generation of a pair of images, said images being generated alternatively in a time multiplexed mode, a first image being generated in a first period of time and a second image being generated in a second period of time, said images being transmitted from said image generating means along respective optical paths towards one or more observers for the illumination of at least a left hand part and a right hand part including the left eye and the right eye, respectively, of the head or heads of said one or more observers, ii) an optically addressed spatial light modulator (OASLM) including a plurality of light transmission elements, each being individually optically addressable, and each having an optical input and an optical output and being shiftable between two states, a first state in which the transmission of light from said optical input to
  • OASLM optically addressed spatial light modulator
  • the auto-stereoscopic display system according to the second and third aspect of the present invention are based on a time multiplexed operation of directing left and right images to the left and right eyes of the observers.
  • the optical controlling and shifting of the light transmitting elements of the OASLM allows for the utilisation of the OASLM technique for providing an optically self-aligning and self-adjusting auto-stereoscopic 3-D display system, as the optically addressable and shiftable light transmitting elements of the OASLM may be addressed individually through the reflection of infrared radiation from a half part of the heads of the observers or a single head of a single observer since, based on the teachings of the present invention, the retransmission, so to say, of the reflected infrared radiation from the one half part of the head or the heads of the one observer or alternatively the observers, establishes a specific addressing of those light transmitting elements positioned in the intentional light transmission path from the one image generating means to be used for illuminating the one eye of the observer or the observers of the half part of the observer or of the heads of the observers, which half part is exposed to the IR illumination.
  • the at least one refractive optical element positioned or located in front of the OASLM between the OASLM and the observer or the observers or alternatively or preferably located juxtaposed in front of the OASLM provide directivity to light transmitted through the OASLM and provide focusing of the reflected light of the infrared radiation from the observer or the observers on to the OASLM.
  • the at least one refractive optical element including a lens system, including at least one circular or cylindrical lens and/or including a multitude of refractive optical elements.
  • the OASLM is continuously updated by patterns of reflections of the infrared illumination of the observers' faces, which are projected onto the OASLM, directly ors acting as "write-light", forming regions or "domains" of the OASLM, and the OASLM is capable of performing an at least essentially binary modulation in these domains, of the transmitted, visible "read-light” from the image generating means controlled by a thresholding function determining whether the received lights characteristics are mostly alike the right observer illumination's or the left observer illumination's characteristics, so that the transmitted, modulated visible light travel back the same path through the optical element, as the incident infrared light, that controlled its modulation, towards the face of the observer or the faces of the observers.
  • the OASLM being a structure including a plurality of discrete OASLM elements or alternatively being a continuous structure.
  • the image generating means is controlled by a clock generator generating a blanking period in which the image generating means are turned off, the optical sensors of the OASLM are controlled by the clock and preferably enabled during the blanking period and disabled outside the blanking period, so that no shifting of the state of the light transmission elements may occur outside the blanking period, and the infrared illumination system is preferably controlled by the clock and turned on during the blanking period.
  • the OASLM may, according to alternative embodiments of the auto-stereoscopic display system according to the present invention, the image generating means being constituted by a CRT (cathode ray tube)- an LCD (liquid crystal display)- a DLP (digital light processing) projector, a film or slide projector or alternatively a CRT-, an LCD- or plasma display.
  • the image generating means being constituted by a CRT (cathode ray tube)- an LCD (liquid crystal display)- a DLP (digital light processing) projector, a film or slide projector or alternatively a CRT-, an LCD- or plasma display.
  • the optical paths from the image generating means to the eyes of the observers may constitute rectilinear optical paths intersecting the OASLM position between the image generating means and the observers.
  • the optical path may be established by the using of a mirror positioned at the OASLM or behind the OASLM, as the image generating means and the observers may be positioned at one and the same side of the mirror.
  • the image generating means may include several discrete elements forming a line or chain of elements and in an image generating means structure of this kind, the OASLM may, in certain applications, be positioned in the chain or line, rather than at the output of the chain or line.
  • the image generating means may include an LCD which is illuminated from behind by means of a light source and in this structure, the OASLM may be positioned between the light source and the LCD.
  • the first period of time being identical to the second period of time and the illumination system being shifted into the first mode prior to the initiation of the first period of time and the illumination system being shifted to the second mode prior to the initiation of the second period of time, or alternatively or additionally the first and second periods of time being spaced by a short blanking period, or alternatively or additionally the first and second periods of time being of the order of 0.1 -20ms, preferably of the order of 10ms corresponding to a multiplexing frequency of 100 Hz and the blanking period being of the order of 1 -10ms.
  • the OASLM is located in front of a display capable of displaying a spatially modulated stereoscopic image pair, and the system further comprises a patterned polariser with a pattern of areas of essentially orthogonal polarisation direction, located between the display and the OASLM, so that display pixels relating to a first image of the stereoscopic image pair are covered by areas of a first polarisation direction, and display pixels relating to a second image of the stereoscopic image pair are covered by areas of a second polarisation direction.
  • a spacer may be provided, establishing a distance or spacing between the polariser and the OASLM.
  • the spacer may be made from glass.
  • the pattern of the polariser may be a striped pattern.
  • the pattern of the polariser may be a checker-board pattern.
  • the pattern of the polariser is of a different shape, adapted to the display.
  • the OASLM is located in front of a display capable of displaying a time-division based stereoscopic image pair, and comprises a polariser, located in front of the display, and a liquid crystal cell, capable of rotating the polarisation direction of transmitted light, located between the polariser and the OASLM.
  • the above described at least one refractive optical system may, as pointed out above, comprise circular lenses, such as a micro lens array sheet.
  • the layer of optical elements comprises cylindrical lens, for example being a lenticular sheet.
  • a spacing element is included in a liquid crystal layer of the OASLM in the form of a film or plate with punched, etched or otherwise produced holes, the holes located so they are aligned with the centres of the optical elements of the optical layer, the holes being cylindrical or of any other shape.
  • the left and right illuminations are differentiated simply by the presence or the absence of illumination, in other words one half part of the face or faces is infrared illuminated, the other or others are not.
  • the thresholding function of the OASLM layer is thus an intensity thresholding, which most types of available OASLM's are capable of performing .
  • the left and right illuminations are differentiated by having different peak wavelength.
  • the thresholding function of the OASLM may in this case be based upon the intensity of light of a first wavelength subtracted the intensity of light of a second wavelength, such that for example reflections from the left illumination tends to pull a domain below the threshold, and reflections from the right illumination tends to pull a domain above the threshold.
  • a wavelength sensitive asynchronous image subtracting OASLM has been demonstrated by Moddel et al., "Materials Research Society Symposium Proceedings", Volume 297, 1993.
  • the two illuminations are differentiated by having different temporal modulation, for example square wave modulations having the same frequency but reversed phases, i.e. the left half part and the right half part are illuminated alternately, for example at a rate of 1000 Hz.
  • a synchronous image subtracting OASLM may be used.
  • One or more of these differentiation and thresholding techniques may be combined, to optimise differentiation and thresholding.
  • the following alternative or complementary interference reducing means may be provided:
  • the interference reducing means include the photodiode substrates being selected so as to reduce the sensitivity to visible light relative to the sensitivity to infrared light.
  • the interference reducing means include that ambient lighting is kept relatively low.
  • the interference reducing means include a display having blanking intervals, and an operating cycle of the OASLM is incorporated, so that the OASLM is essentially only sensitive to write-light during the displays' blanking period. This requires that the OASLM has a memory effect, so that the modulation pattern is maintained between the blanking intervals.
  • This memory effect is achieved using a twisted nematic liquid crystal OASLM and including a rectifying diode in the circuit, so that when the polarity of the operating voltage is negative, the diode is reverse biased, exhibiting a high impedance towards the liquid crystal layer, the discharge time due to the layers' internal RC time constant and the relaxation time of the liquid crystal molecules of domains in the "on" state, essentially causing the OASLM to maintain its modulation pattern fixed in a short interval after the voltage was removed.
  • the memory effect is achieved by using bistable ferroelectric liquid crystals in the OASLM.
  • the interference reducing means include a layer acting as a light valve, alternating between transparent and opaque, and synchronised with the operation cycle of the OASLM.
  • the transparent and opaque intervals may be of different duration.
  • the light valve may be a liquid crystal light valve.
  • the interference reducing means include the use of an OASLM comprising a patterned shading layer, making it essentially only sensitive to write- light incident from the front, thus insensitive to transmitted read-light from the back.
  • OASLM comprising a patterned shading layer
  • the interference reducing means may further or alternatively include infrared blocking filter or filters, located in front of the image generating means.
  • the interference reducing means include a layer of infrared blocking filter included in the screen, located behind the electro-optical layer, or in front thereof.
  • the interference reducing means may include the OASLM being an asynchronous image subtracting OASLM, selectively updateable by write-light of different peak wavelengths.
  • the interference reducing means may include the OASLM being a synchronous or integrating, image subtracting OASLM, and operated so that any constant incident light is cancelled by alternating positive and negative update cycles.
  • a pair of essentially point-like light sources is provided, one located to the left and the other located to the right of a group of one or more observers located in-between the light sources, illuminating the observer or observers from both sides, thereby illuminating the left half part with a left illumination and the right half part with a right illumination.
  • a pair of elongated, directional light sources is provided and located on both sides of the observers, for example located along the walls, illuminating the observers from the sides, thereby illuminating the left half part with a left illumination and the right half side part with a right illumination.
  • pairs of light sources are used, each located with one light source to the left of each observer or subgroup of observers and the other to the right of the observer or subgroup of observers.
  • Either the left or the right illumination sources of the above mentioned illumination systems may be eliminated, for illuminating only one half part of the face of the observer or the faces of the observers.
  • the illumination system may comprise one essentially point-like illumination source placed to the right of one or more observers, illuminating the observers from the right, thereby illuminating only the right half part of the face of the observers.
  • the light sources may, irrespective of its form comprise infrared LED arrays or infrared filtered halogen lamps, and they may be unfocused, focused or directional. They may be located close to or far from the observers, for example but not limited to: on the screen itself, in a sitting chair, on the walls, on the ceilings or on the back of one or more auditorium chairs in front of the observers.
  • one or more adaptive illumination systems may be provided, each comprising one or two infrared imaging projectors, located in front of the observers, for example on the screen itself, and an observer tracking system, which may also be located on the screen.
  • the observer tracking system tracks the observers' head positions and produce one or more images, which are projected by the infrared imaging projectors onto the observers, so that the light incident on the observers' left half part face has a first set of characteristics and the light incident on the observers' right half part face has a second set of characteristics, different from the first set of characteristics.
  • the observer tracking information may be fed to an image processing system, which synthesises a binary image, in turn modulating the infrared imaging projectors, the binary image having a form, so that the projected images illuminate the left half side of the observers' faces with infrared light having a first set of characteristics and the right half side of the observers' faces with infrared light having a second set of characteristics, different from the first set of characteristics.
  • the illumination systems each comprise one infrared imaging projector, which projects the binary image, so that one half side of the observers' faces are illuminated with a high intensity and the other half side of the observers' faces are illuminated with a low intensity.
  • the illumination systems comprise two infrared imaging projectors which are alternately blanked, the first imaging projector projecting the binary image, so that the left half side of the observers' faces are illuminated with a high intensity and the right half side of the observers' faces are illuminated with a low intensity, the other projecting an intensity inverted version of the binary image, so that the left half side of the observers' faces are illuminated with a low intensity and the right half side of the observers' faces are illuminated with a high intensity, hence, the left half side and the right half side of the observers' faces are illuminated with high and low intensities alternately.
  • the illumination systems each comprise one infrared imaging projector, which alternately projects a normal and an inverted version of the binary image, so the left half side and the right half side of the observers' faces are illuminated with high and low intensities of infrared light alternately.
  • the above mentioned imaging projector may comprise an optical system, a binary operated spatial light modulator, electrically, optically or otherwise addressed, and two infrared light sources, emitting infrared polarised light with essentially orthogonal polarisation directions, the two infrared light sources being illuminated alternately, thereby projecting normal and reversed images of the image on the spatial light modulator.
  • the observer tracking systems may further comprise an infrared camera for producing an infrared picture of the observers, for an image processing system to perform the observer tracking.
  • Observer tracking comprising the use of image processing is well known in this and other arts.
  • the infrared camera of an observer tracking system may be sensitive to light of a second wavelength, different from the wavelength of the illumination systems, and of which the OASLM is insensitive.
  • the camera may incorporate its own infrared illumination source, selectively illuminating at this second wavelength.
  • a filter layer may be included in the OASLM to exclude infrared light of second wavelength.
  • the infrared camera uses light at the same wavelength as the illumination systems, and may incorporate its own pulsed or temporally modulated infrared illumination source, synchronised with an operating cycle of the OASLM, so as not to interfere with the desired function of the OASLM by acting as write-light.
  • the camera's illumination source may be in its light emitting state only during a dedicated time slot during the projector's blanking interval, or it may be in its light emitting state only outside of the projector's blanking interval.
  • the observer tracking camera uses the light of the normal and inverted versions of the binary image, alternately projected by the illumination systems' infrared imaging projectors.
  • the infrared camera's shutter may be open during two or more successive alternations, performing a light integration resulting in an image of the observers illuminated by both binary infrared projected images thus essentially evenly illuminated, suitable for image processing.
  • the infrared cameras' shutter function may be synchronised with the phase of the alternation, so that the camera is capable of both capturing infrared images of the observers when illuminated by the normal binary image and when illuminated by the reversed binary image.
  • a first captured infrared image of the observers when illuminated by the normal binary image and a second succeedingly captured infrared image of the observers when illuminated by the inverted binary image may be combined by an image processing system to a differential image, each resulting pixel value given by the absolute value of the difference between the corresponding pixel values of the first captured image and the second captured image.
  • the observers Given a fast enough alternation rate between the normal and inverted binary projected images, the observers can be assumed not to move in-between images, thus the differential image will be an evenly illuminated image of the observers, suitable for image processing.
  • first and second captured infrared image may be compared with the synthesised binary image by an image processing system for detection and correction or compensation of any alignment errors between the infrared camera and the infrared imaging projectors.
  • Corrections may be done either automatically or semi-automatically with the assistance of an operator, either physically, adjusting the camera's or projectors' position and directions or electronically.
  • Compensation may be performed automatically, having the image processing system maintaining parameters for the geometric transformation between captured and projected images.
  • An alternative application of the invention when incorporating observer tracking is to display the same image to both eyes of the observers, but letting two different groups of observers observe two different images, based on some observer selection schedule.
  • Another alternative application of the invention when incorporating observer tracking is to display one same image to both eyes of all observers and another image, which may be a blank image, to any recording device present, such as a camera.
  • FIG. 1 is a plane view of the presently preferred exemplary embodiment of an auto- stereoscopic display element according to the present invention.
  • FIG. 2A is a plan view of the optically addressed spatial light modulator of the presently preferred exemplary embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 2B is a front view of the optically addressed spatial light modulator of the presently preferred exemplary embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 3 is a schematic diagram of the electrical connections of the presently preferred exemplary embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 4 is a plan view of an example of a prior art auto-stereoscopic system.
  • FIG. 5 shows captured and synthesised images by an image processing based observer tracking system.
  • FIG. 6A is a perspective view of a first alternative embodiment of the auto- stereoscopic display element according to the present invention.
  • FIG. 6B is a top view of the arrangement shown in FIG. 7.
  • FIG. 7 is a perspective view of a second alternative embodiment of the auto- stereoscopic display element according to the present invention.
  • FIG. 8 is a plan view of a stripe patterned polariser.
  • FIG. 11 is a perspective view of a spacing element comprised by the liquid crystal layer of a first embodiment for maintaining an accurate spacing in large size screens.
  • FIG. 12 is a a top view of the illumination system of a second alternative embodiment.
  • FIG. 13 is a top view of an alternative illumination system as compared to the system shown in Fig. 12.
  • FIG. 14 is an example of an operating cycle.
  • FIG. 15 is an example of an operating cycle of the presently preferred exemplary embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 16 is a cross sectional view of a backlight distribution panel of a sixth embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 17 is an exploded view of a transparent display of the sixth embodiment of the stereoscopic display element according to the present invention.
  • FIG. 18 is a perspective and schematic view of the sixth embodiment of the auto- stereoscopic display element according to the present invention including the backlight distribution panel shown in Fig. 16 and the transparent display shown in Fig. 17.
  • FIG. 20 is a cross sectional view similar to the view of Fig. 16 of a further or reflection mode embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 20A is an elevational view of a detail of the reflection mode embodiment of the auto-stereoscopic display element according to the present invention shown in Fig.
  • FIG. 22 is a diagrammatic view similar to the view of Fig. 21 of the control signals to be applied to the liquid crystal cells of the transparent display of the sixth embodiment of the auto-stereoscopic display element according to the present invention which display element is shown in Fig. 17.
  • FIG. 23 is a cross sectional view of a further embodiment of a front projection screen embodiment of the auto-stereoscopic display element according to the present invention.
  • FIG. 24 is a cross sectional view similar to the view of Fig. 23 of a still further embodiment of the auto-stereoscopic display element according to the present invention including an optically sensitive electric piper.
  • FIG. 25 is a perspective and schematic view of the front projection screen embodiments shown in Figs. 23 and 24,
  • FIG. 26 is a schematic view of the optical parts of the front projection embodiment of the auto-stereoscopic display element according to the present invention also shown in Fig. 25,
  • FIG. 27 is a perspective and schematic view of a ninth embodiment of the auto- stereoscopic display element according to the present invention including the transparent display shown in FIG. 17,
  • FIGS. 28, 29, 30 and 31 are views illustrating modifications of variants of the ninth embodiment of the auto-stereoscopic display element according to the present invention shown in FIG. 27.
  • FIGS. 35, 36, 37 and 38 are plain views illustrating a so-called "video wall" configuration comprising a total of four auto-stereoscopic display elements according to the present invention.
  • Figure 1 is an overall, plane view of an arrangement according to a presently preferred exemplary prototype embodiment of an auto-stereoscopic display element.
  • This embodiment includes a display overlay screen comprising one single screen element, i.e. a low resolution version of the invention yet qualitatively similar to higher resolution versions, and a display including two pixels, i.e. a low resolution display yet qualitatively similar to higher resolution displays.
  • the "images" constituting the stereoscopic image pair include one pixel each.
  • the arrangement allows a single observer or several observers to observe the pixel as having one colour when watched with the left eye and another color when watched with the right eye, even when moving to a different position, without ever seeing a "pseudoscopic" image of reversed pixel colours, from any position.
  • a display 2 comprises two pixels, a left pixel 16L, showing a left "image", and a right pixel 16R, showing a right "image”.
  • the pixels consist of light emitting diodes, selected so that the left pixel 16L emits blue light and the right pixel 16R emits red light.
  • the pixel values are thus "hard-wired” in this arrangement.
  • the display has an operating cycle alternating between bright and blanking intervals, both pixels being switched off to a dark state in the blanking interval.
  • a polariser 18L of horizontal direction is located and in front of the pixel 16R a polariser 18R of vertical polarisation direction is located.
  • a display overlay screen 1 including a liquid crystal optically addressed spatial light modulator (OASLM) 20.
  • the OASLM 20 includes seven discrete modulation segments, each being settable in a V-state or an H-state for the transmission of vertically polarised light or horizontally polarised light, respectively.
  • the OASLM 20 has an operating cycle synchronised with the display 20. During the display 2's bright interval, the OASLM 20 is synchronised to transmit either vertically or horizontally polarised light from the pixels 16L and 16R depending on the setting of the individual segments of the OASLM 20, as the individual segment of the OASLM 20 transmits, during the display 2's bright interval, vertically polarised light provided the segment in question be set in the V-state or alternatively transmits horizontally polarised light provided the segment in question be set in the H-state.
  • the setting of the individual segments of the OASLM 20 is performed during the blanking interval of the display 20 by means of incident light.
  • the light being vertically polarised or alternatively horizontally polarised light transmitted through the individual segments of the OASLM is referred to as 'read'-light, whereas the light incident to the individual segments of the OASLM during the blanking interval for performing the setting in the V-state or alternatively the H-state of each of the segments of the OASLM is called 'write'-light.
  • the setting of the individual segments of the OASLM performed during the blanking period of the display 20 is so to say stored by the OASLM 20 for the next bright interval for performing the transmission through the individual segments in accordance with the polarisation of the individual segments in the V-state or alternatively in the H-state.
  • the observer With each eye, the observer will observe a region of the surface of the OASLM, thus in the absence of write-light, the lens 14 will appear red to both eyes of the observer.
  • the observer 10 is now constantly illuminated by a left side face illumination from the left by a light bulb 12 in front of which is located an infrared transmitting filter 13, so that the left half side of the observer's face is illuminated by infrared light or radiation.
  • Infrared reflections off the left side illuminated face of the observer is radiated towards the screen and through the lens 14 project an infrared image of the observer's illuminated left half face, on the OASLM 20.
  • the lens 14 appears blue to the observer's left eye and red to the observer's right eye.
  • the right eye will see the pixel as being blue and the left eye will see the pixel as being red.
  • a plurality of auto-stereoscopic display elements are constructed and positioned side by side forming a pattern of pixels and screen elements, a higher resolution display fulfilling the object of the invention is realised.
  • Fig. 2A and 2B are top and front views, respectively, of the OASLM 20 employed in the embodiment shown in Fig. 1 and constitutes a twisted nematic liquid crystal cell comprising liquid crystal elements contained within two glass plates.
  • the one glass plate is coated on the inside with transparent conduction oxide electrodes 28, forming discrete segments each connected to a respective external terminal.
  • the other glass plate is coated with transparent conductive oxide forming a common electrode, connected to ground.
  • On the front of the liquid crystal cell a polarising analyser 24 of horizontal polarisational direction is located.
  • infrared sensitive photodiodes 26 are located on the back of the liquid crystal cell 22 . Each photodiode has its anode connected to the respective external terminal of the transparent conductive electrode positioned in front of it.
  • the cathodes of all the photodiodes are connected to a common terminal 29 of the OASLM.
  • the polarising analyser 24 may be of the type, which absorbs visible light of one polarisation, but does essentially not perform any changes on infrared light.
  • Fig. 3 is a schematic diagram of the connections in the arrangement.
  • a square wave oscillator 32 is connected to the light emitting diodes of the two pixels 16L and 16R through a resistor 36, so that the diodes will only emit light during the oscillator's negative half wave periods.
  • the oscillator is further connected to the common terminal of the OASLM 20 through a rectifying diode 34.
  • each photodiode and liquid crystal segment together constitutes a voltage divider, the voltage across the electrodes depending on the impedance match between the photodiode and the liquid crystals.
  • the polarisational direction of the segment becomes approximately 0 degrees, thereby allowing only transmission of horizontal polarisation direction.
  • the rectifying diode 34 will become biased in the reverse direction and the common terminal of the OASLM will be in a high impedance state.
  • the segment's liquid crystal molecules will start a transition back to their relaxed state.
  • the relaxation time is substantially longer than the transition time from V- state to H-state. Consequently, it is possible to adjust the frequency of the square wave oscillator, so that a full transition from V-state to H-state can occur during a negative half wave, but very little change happens during the positive half wave, effectively maintaining the modulation pattern of the OASLM until the next negative half wave, during which the segments are again updated. If the write-light of a segment is removed, the segment will after several square wave periods eventually relax into its V-state again.
  • the frequency of the square wave oscillator in the above described prototype embodiment was adjusted to approximately 5000 Hz, which produced the desired memory effect.
  • a liquid crystal cell may rotate the polarisational direction of transmitted light differently dependent on the wavelength, which may cause pixel hue change and cross talk between "images".
  • Possible counteractions, including the insertion of an extra liquid crystal cell in the optical path, are well known, vide e.g. "Liquid Crystals",
  • the OASLM 20 is characterised by being segmented and of low spatial resolution.
  • OASLM with higher resolution and preferably a smaller spacing between segments a higher degree of freedom of movement for the observer may be attained.
  • An example of a segmented OASLM having high resolution has been demonstrated by R. Butcher, Australia, in an application as an active masking filter.
  • the photosensitive elements of the segments are not themselves transparent, but they are significantly smaller than the segments, and because a relatively large region around the observer's pupil, in fact half of the face, is illuminated, this presents no problem, unless the observer is positioned exactly so that the photosensitive elements blocks the path of transmitted light towards one or both of her eyes.
  • the lens 14 may simply be adjusted a little out of focus, a diffusing layer incorporated in front of the OASLM or the lens may be made to blur the image slightly vertically only, in which direction less resolution is required. It is noted, that the adjustment of the focus of the lens has nothing to do with the observation of the (one-pixel) "image" as appearing in focus.
  • the lens only relates to the precision and intensity thresholding in the mapping of read-light and write-light between the OASLM surface and the observer's face.
  • Fig. 6A and 6B illustrates a first alternative embodiment of the auto-stereoscopic display element according to the present invention.
  • the single screen element of the above described arrangement is scaled to a rear projection screen V with a plurality of screen elements, allowing observers in front of the screen to observe a rear projected stereo image pair.
  • a large transparent OASLM 20' comprising a light distributing layer designed for rear projection, having the characteristic that it does not alter the polarisation of transmitted light, is located behind a microlens array 14', here shown with exaggerated lens size and spacing for clarity.
  • a pair 70 of gen-locked video projectors project an image pair comprising a first horizontally polarised image and a second vertically polarised image onto the OASLM 20'.
  • An observer 10 is infrared illuminated by an illumination system comprising a left illumination 12L and a right illumination 12R, alternately illuminating the left and right hal side face of the observer, with an alternation frequency of for example 1000 Hz.
  • Each lens element of the microlens array 14' and a region of the OASLM 20' layer operates as a screen element, similar to that of the above described prototype embodiment.
  • the OASLM 20 is constructed with ferroelectric liquid crystals and a thin film photosensor layer, and is operated in an integrating, image subtracting mode, where positive and negative update patterns are integrated over time.
  • the ferroelectric liquid crystals possess a true bistable nature, providing a desired memory effect with a "hold"-state, in which the OASLM 20 is insensitive to light and the modulation pattern is maintained.
  • the operation cycle of the OASLM and the illumination system are synchronised to one another, and they are also synchronised with the video projector pair's blanking intervals.
  • the operation cycle is illustrated in fig. 14.
  • the OASLM update cycle begins, using reflections from the observer's altematingly left-right infrared illuminated face.
  • the OASLM performs a positive update
  • the OASLM performs a negative update, and vice-versa.
  • This operation mode improves control of the thresholding function and reduces interference from light from other sources than the illumination system, such as ambient room light, because these will normally be relatively constant, and therefore cancelled out by the alternating positive and negative updates. Further, dark-current noise in the diode structure will be reduced due to averaging with this operating cycle.
  • Fig. 9 shows an example of a standard OASLM.
  • 96 is a ferroelectric liquid crystal layer, in which the molecules respond to the polarity of an imposed electric field, such that a positive polarity causes a transition to a state where the molecules rotates the polarisational direction of transmitted light approximately 90 degrees, and a negative polarity causes a transition to a state where the molecules rotates the polarisational direction of transmitted light approximately 0 degrees.
  • the polariser 98 transmits only light of horizontal direction. Therefore, when a positive voltage is supplied across a region of the liquid crystal layer, a transition of the molecules in the region to a V-state occurs, in which state only vertically polarised light is transmitted.
  • a voltage of negative polarisation will similarly initiate a transition towards an H-state, in which state the region in question is only transparent to horizontally polarised light.
  • 90A and 90B are bearing glass plates, each coated on the inside with a transparent electrode layer of conduction oxide, 92A and 92B, respectively.
  • 94 is an amorphous silicon photosensitive layer, comprising a number of heterojunctions forming a back- to-back photodiode structure. This arrangement has been shown to provide high sensitivity and fast response (Robinson, Sharp Labs) and requires only a thin layer of a few micrometers, which is desirable to achieve good spatial resolution. Further, it can be produced with low temperature grown amorphous silicon, enabling manufacturing in large areas, as is known from e.g.
  • the OASLM 20' used in the present arrangement is illustrated in Fig. 10, and is a slightly altered version of the standard image subtracting OASLM, in which the dielectric reflector stack, as shown in Fig. 9 is omitted and a diffusing layer 100 is added.
  • An integrating image subtracting behaviour may also be achieved using nematic liquid crystals, when operated with a high frequency square wave voltage.
  • the crystals respond not to the polarity but to the rms value of a supplied voltage, but integrating and subtracting operation may be possible because of the build up time and discharge times of charges across the layer, defined by the OASLM's RC time constant due to its internal capacitance and resistance.
  • a memory effect utilizing this time constant was utilised in the above described prototype embodiment.
  • the thresholding function of the OASLM and the illumination intensity may be adjusted, in order to achieve the desired binary pattern in the OASLM. Thresholding in the OASLM may be controlled by the magnitude, frequency and DC offset of the square wave operating voltage.
  • Another approach, which allows for very precise control, is to include a third terminal in the OASLM, thereby allowing the construction of a voltage divider when further including an external resistor, which may be controlled very accurately.
  • the third terminal may be a structured metal conductor, for example a grid or hole mask, vide e.g. "Dynamic Thresholding with the Three-terminal Optically Addressed Spatial Light Modulator", Material Research Society Symposium Proceedings Vol. 258, 1992. Such an arrangement may be advantageously combined with the above mentioned shading pattern.
  • Still another approach may be to include discrete thin film structures exhibiting electrical characteristics, for example a non-linear diode structure or even an active structure, like a thin film transistor.
  • Constant and exact thickness of the liquid crystal layer is important to achieve the desired rotation of the polarisational direction of transmitted light. Normally, this thickness is controlled by edge spacers.
  • the area of the OASLM used by each lens element is a function of the desired maximum viewing angle and the refractive characteristics of the microlens array layer 14', which can be designed, so as to allow some unused area in-between the used areas, giving room for a spacing structure within the layer of liquid crystals itself, thereby enabling good control of layer thickness even in extremely large constructions.
  • the spacing structure may be a non-conducting grid or a thin polymer film with punched or otherwise produced holes, such as illustrated in fig. 11.
  • 90A is the bearing glass plate coated with a transparent electrode layer 92A
  • 110 is the polymer film with holes
  • 96 are the liquid crystals in the holes, forming the active regions of the OASLM, which must be aligned with the lens elements of the microlens array layer. The capillary forces are sufficient for keeping the construction together.
  • a similar but preferably thicker spacing structure may be inserted between the OASLM and the refractive optical system.
  • This structure may also provide the desired effect of blocking light between screen elements, eliminating the problem of an observer, when moving outside the designed viewing angle, seeing light through a lens element of one screen element from the region of the OASLM layer of the neighbouring screen element. This will not in itself lead to an incorrect perceived image, like the effect does in traditional displays, but it does incur a little risk of multiple different paths for infrared reflections from different observers to incite on the same spot, thereby resulting in an undesired modulation.
  • a transparent, uniform photosensitive layer will introduce some absorption of the read-light, which may not be of uniform spectral distribution, and hence require a hue correction in the form of optical or electronic filters or adjustment of display or projection equipment.
  • the thickness of the photosensitive layer may be reduced, thereby however also reducing the sensitivity.
  • a trade-off between infrared sensitivity and light gain therefore exists, which emphasises the need to employ other techniques for improving signal-to-noise ratio, like e.g. the above mentioned image subtraction technique, the above described blanking interval synchronisation technique and the use of a shading layer.
  • a second alternative embodiment of the auto-stereoscopic display element according to the present invention is shown. This embodiment is similar in its operation of the OASLM 20' to the above described arrangement, but a flat-panel display 2', displaying a spatially multiplexed stereoscopic image pair is used instead of a projector pair, and further an adaptive illumination system is included.
  • a polarising layer 72 comprising a striped pattern of alternate polarisation direction is located in front of the display 2" so that alternate rows of pixels are covered by strips of alternate polarisational direction. Consequently, even number row pixels emit horizontally polarised light towards the screen and odd number row pixels emit vertically polarised light towards the screen.
  • Fig. 8 shows such a layer having strips 80H and 80V of horizontal and vertical polarising direction.
  • a different pattern than a stripe pattern may be used, for example a checkerboard pattern, which will provide equal vertical and horizontal resolution of the images of the stereoscopic image pair, whereas the horizontal stripe pattern will provide full horizontal but half vertical resolution of each of the images, as compared to the display displaying a monoscopic, non-multiplexed image.
  • the stripe pattern is more compatible easily with existing methods of coding stereoscopic images and may be easier to manufacture.
  • An alternative to the patterned polariser is a structured OASLM having its structure matching and aligned with the spatial multiplexing pixel pattern of the display.
  • the OASLM may comprise striped electrodes on one or both glass plates, so that alternating rows of electrodes aligned with rows of lenses in the micro lens layer may be supplied with the operating voltage square wave having altematingly reversed and non-reversed voltage polarisation.
  • Using a structured OASLM aligned with a pattern of pixels of the display enables the use of other types of OASLM's based on other modulation layers than liquid crystals, because in this case the domains in the modulating layer do not have to be selectively transparent to light of different polarisational directions, but may simply vary the transmission rate of transmitted light, polarised or unpolarised.
  • Such a structured OASLM's modulation layer may include the use of the Franz-Keldysh effect or the Quantum confined Stark effect and may be dispersed within the photosensitive layer, so that one layer is both sensing and modulating light.
  • US Patent 6,025,950 which is hereby incorporated in the present specification by reference.
  • the illumination system is shown in greater details in fig. 12 and comprises an infrared camera 40', an image processing system 127 and an infrared projection system.
  • the infrared projection system comprises an optical element 74, a monochrome liquid crystal spatial light modulator 122 and an illumination source alternately emitting light with horizontal and vertical polarisational direction at an alternation frequency of about 1000 Hz and synchronised with the operating cycle of the OASLM.
  • the illumination source comprises an array of infrared light emitting diodes 126, located outside of the focal plane of the lens.
  • the LED array is constructed so, that even or odd rows are illuminated selectively. This may be achieved by wiring the LED's to the same voltage supply leads, but in alternate directions, so that when a positive voltage is applied to the LED array, even rows are illuminated, and when a negative voltage is applied, odd rows are illuminated.
  • a polariser 124 is located in front of the LED array, with strips of alternating horizontal and vertical polarisational directions similar to that of fig 8, and aligned with the rows of LEDs, so that when even rows are illuminated, horizontally polarised light is emitted, and when odd rows are illuminated, vertically polarised light is emitted.
  • the camera continuously captures infrared images of the observers, for example at a frame rate of 60 frames per second, and feed these to the image processing system.
  • the image processing system tracks the individual observer, and continuously synthesises binary images of left half face image of the individual observer and output these to the spatial light modulator.
  • Image processing based observer tracking is for example demonstrated in US Patent 6,069,649 to which reference is made and which is hereby incorporated in the present specification by reference.
  • the LED array emits light of alternating polarisational direction
  • patterns on the spatial light modulator forming normal and reversed images of these synthesised binary left half side face images will alternate and be projected through the lens 74 towards the individual observer.
  • the individual observer will be illuminated by these alternating normal and reversed binary half face images, and when the camera and projector are properly aligned and their optical characteristics are appropriately adjusted by one another, the projection system will alternately illuminate the left half face of the individual observer and illuminate everything except the left half face, including the right half face. Consequently, the desired alternating left half face, right half face infrared illumination is achieved, and synchronised with the OASLM, the operating cycle illustrated in fig. 14, being identical to that of the above described first alternative embodiment.
  • the image processing system needs appropriate illuminated images of the individual observer, for example uniformly frontally illuminated.
  • One way of obtaining this is to use a shutter speed in the camera long enough to cover at least two succeeding alternate normal and reversed images, for example 1/500 second, thereby performing a temporal integration of the reversed images, resulting in a uniformly frontal illuminated image, assuming that the individual observer is essentially not moving during the shutter time.
  • the shutter speed is selected to be equal to or less than one half period of the alternation cycle, so that only a normal or reversed image is captured at a time.
  • the shutter operation is then synchronised with the illuminations systems alternation phase, so that separate succeeding images of normal and reversed illumination is obtained.
  • a difference image is the calculated, each pixel value being given by the numerical difference between corresponding pixel values of the two captured reversely illuminated images.
  • This technique will likewise produce a uniformly frontally illuminated image, again assuming that the individual observer is not moving between alternation cycles.
  • This technique has the advantage of cancelling out any light not originating from the illumination system, ensuring that the images are always captured in a well-defined constant infrared illumination, which is an advantage for the image processing.
  • the separate captured images of reversed illumination may provide data for an automatic correlation of captured and projected images, enabling automatic compensation of geometric errors and inaccuracies due to parallax difference, alignment of camera and projector, difference in optical elements etc.
  • a table of correlation parameters may be stored by the image processing system.
  • a half mirror 132 projects the images of theretematingly illuminated individual observer onto a projection plate 130, and the infrared camera 40' is capturing an image of the projection plate.
  • the background image assists the image processing system in detecting and tracking the individual observer.
  • the background image may be subtracted from the captured images, thereby cancelling reflections from fixed objects in the room such as walls, floor, furniture, etc., effectively isolating moving objects (and their shadows). This principle is well known for example in intruder detection systems.
  • the background image may be obtained by manual assistance, for example a pushbutton function activated when installing the screen and display, activated by the operator when the viewing area in front of the display is empty.
  • the patterned polariser is replaced by a uniform polariser of uniform polarising direction, and a large liquid crystal cell is located in front of it.
  • the liquid crystal cell is capable of rotating the polarisational direction either approximately 0 degrees or approximately 90 degrees, and is synchronised with the alternation frequency of the displayed time division based stereoscopic images.
  • This arrangement may also be used together with other image generating means than a flat plane display, for example a rear projector.
  • An alternative to including a large liquid crystal cell synchronised with the time division stereoscopic images would be to alternate the modulation pattern of the OASLM itself between inverted patterns, for example by alternating the phase of its operating voltage or alternating the phase of the illumination system.
  • a front projection screen is constructed, capable of displaying temporarily multiplexed, or time division based, stereoscopic images from a pair of front projectors.
  • the arrangement resembles that of the above- described third alternative embodiment, but the display is replaced by a reflector.
  • a uniform polariser and a liquid crystal cell are still located in front of it.
  • the liquid crystal cell is synchronised with the projector pairs' alternation frequency.
  • the reflector must be spaced apart from the lens array layer, so that the projected spot of light emitted from the front projection system onto the reflector is not in focus, but is enlarged to approximately the same size as the lens elements of the lens array layer, to allow reflection of projection system light in any angle within the desired viewing angle.
  • An infrared source synchronised with the operating cycle of the illumination system and the OASLM are located close to the projectors, to make the OASLM transparent to light in the direction of the projectors, so that projection light entering the lens is transmitted unobstructed to the reflector.
  • An alternative to including a large liquid crystal cell synchronised with the time division stereoscopic images would be to alternate the modulation pattern of the OASLM itself between inverted patterns, for example by alternating the phase of its operating voltage or alternating the phase of the illumination system.
  • the display is a colour or monochrome electrically addressed LCD display
  • the OASLM is integrated into the LCD display, by the inclusion of an extra photosensitive layer into the LCD.
  • the impedance of the photosensitive layer masks out areas of each electrically addressed pixel, so that the OASLM works with the same liquid crystal layer as the display, hence only one liquid crystal layer is needed.
  • the photosensitive layer may be transparent and located in front of the liquid crystal layer, or it may be opaque, i.e. having a high absorption rate, thereby allowing for high sensitivity, if located behind the liquid crystal layer. In the latter arrangement, a layer reflecting visible light but transmitting infrared light may be included in-between the photosensitive and the liquid crystal layer. If a colour LCD with dyes is used in the latter arrangement, dyes must be transparent to infrared light.
  • a reflector is used, and optical paths are established so that light from the image generating means enters the OASLM from the same side as the viewer or viewers are positioned.
  • the reflector may further be of a different type than the illustrated dielectric reflector stack, for example it may be constituted by the surface of the photosensitive layer, which may be polished to adjust the ratio between reflected light and transmitted or absorbed light.
  • Fig.18 shows an overview of a sixth embodiment of the auto-stereoscopic display system according to the present invention.
  • a time division multiplexed infrared sensitive directional backlight distribution plate 160 is located behind a transparent display 170 having a fast response time and displaying a time division multiplexed still or moving stereoscopic image.
  • the left side(s) and the right side(s) of the face of one or more observer(s) 10 are alternately illuminated with light in the near infrared spectrum by an illumination system (not shown), which may be similar to the illuminations systems described in the specifications of the preferred and first alternative embodiments.
  • Fig.16 shows a cross section of the backlight distribution plate. It comprises a lens array 14' focusing a plurality of images of the infrared illuminated observers onto an infrared optically addressed visible light emitting structure, comprising a transparent substrate 161 , for example a glass plate, a uniform transparent electrode layer 162, for example a thin layer of Indium Tin Oxide, an electro-luminiscent layer 163, which may be of the type used in alternating current thin film electro-luminscence (ACTFEL) displays, capable of emitting light when the electric field across it rises above a certain threshold T, a photoconductive or otherwise photosensitive layer 164, sensitive to at least infrared light, for example comprising amorphous silicon, a second uniform electrode layer 165 which may be opaque, for example comprising aluminium.
  • a generator 166 is feeding an operating voltage to the electrodes. It is noted, that the lenses need not be of the same size and location as the pixels of the transparent display 170, specifically, they may be bigger than the pixels
  • This embodiment may be operated in an operating cycle comprising four states, as shown in Fig. 21.
  • the infrared illumination system illuminates the left side of the observer's face(s), the display 170 is in a "clears, uniformly transparent state, and the backlight plate operating voltage is zero or low. Reflections from the infrared illumination system off the left side of the observer's face(s) are focused by the lenses of the lens element 14' onto the photosensitive layer 164, where they will form illuminated areas in the shape of small left half face images. The impedance across the photosensitive layer will fall in said areas, remaining higher outside said areas.
  • the backlight distribution plate will emit light through the display 170 which is displaying a left eye image, towards only the left half side of the observer's face(s), in a similar way to the principle described in greater detail in the specification of the preferred embodiment.
  • the observer(s) 10 will therefore see the back illuminated left eye image with their left eye(s) and an essentially black image with their right eye(s).
  • the operating cycle returns to the "left sense” state and starts the cycle over.
  • the observer(s) perceive a steady, flickerfree, back illuminated left eye image with their left eye(s) and steady, flickerfree, back illuminated right eye image with their right eye(s).
  • An advantage of turning off the infrared illumination system during "display" states is, that the average intensity of the illumination is hereby reduced, i.e. the rms value can be lowered. This has several advantages both regarding power consumption and heat dissipation in the illumination system, and in meeting safety regulations for infrared illumination of human observers.
  • the timing of the transitions of the infrared observer illumination system, the back plate voltage supplied by the generator 166 and the status of the display 170 may be adjusted by small amounts with respect to each other, to accommodate for phenomena such as for example the re time constant of the photosensitive and electro-luminescent layers and the response time and other characteristics of the display 170.
  • the timing of the transition of the operating voltage supplied by generator 166 from a high level to a low level may be adjusted to occur slightly before the illumination system is turned off in the transition from "sense" to "display" states and, alternatively or additionally, the timing of the transition of the display from the clear state to the left state or the right state may be adjusted by a small amount, so this transition occurs slightly after the illumination is turned off. For clarity, these small adjustments are not shown in Fig. 21.
  • an extra state may be inserted in the last part of the sense states, where the back plate operating voltage supplied by the generator 166 is forced to a medium level, shown in Fig. 21 depicted to the right of the label "back plate voltage, alternative version", said medium level high enough to make the above described memory effect occur, but low enough to limit the amount of visible light emitted during the display 170's clear state to an acceptable level, so the perceived image quality is maintained.
  • a reflector transmitting a low fraction of visual light and transmitting a high fraction of infrared light may be comprised, inserted between the electro-luminescent layer 163 and the photosensitive layer 164, to reduce the fraction of the light emitted from the electro-luminescent layer, that reaches the photosensitive layer, effectively resulting in a higher relative sensitivity towards infrared light, and thereby also reducing sensitivity to ambient visual light.
  • a photosensitive layer with a relatively higher sensitivity towards infrared light than towards visual light may be used.
  • the resulting sensitivity of the photosensitive layer towards light emitted from the electroluminescent layer, counting both the energy in the infrared and visual spectra, need still be high enough to cause the field to rise to above the threshold T, to achieve the memory effect.
  • Integration and image subtraction of the images of the observer's face(s) projected onto the photosensitive layer may be achieved also in this embodiment, by utilising the re time constant between the electrodes 162 and 165, hence noise reduction, i.e. reduction of the undesired interfering effect from ambient light based on image subtraction may be used also in this embodiment.
  • the illumination system may illuminate the observer and update the photosensitive layer in a way equivalent to one of the ways of interference reduction means described in the first alternative embodiment and Fig. 6A, 6B and 14.
  • a transparent type display may be comprised which is sufficiently transparent at all times and over all areas to infrared light, to enable the backlight plate to be addressed by the infrared reflections off the observer's face(s) at any time.
  • the back plate 160 may comprise a segmented or unsegmented transmission mode OASLM, as for example described in the first alternative embodiment, and a uniform back illumination system, for example comprising electro-luminescent lamps and light guides or an electro-luminescent layer.
  • a multitude of small holes 203 are fabricated, for example by drilling, punching or etching.
  • the number of holes 203 may be many times higher the number of lenses in the lens array 14', and the spatial distribution thus denser, for example of equal or higher density than the density of the pixels of the display 170.
  • An aperture shading layer 204 with a multitude of holes located in front of the holes 203, and slightly smaller than these, may be located in front of the electro-luminescent structure.
  • a large liquid crystal cell 206 capable of rotating the polarisation direction essentially 0 or essentially 90 degrees, depending on the voltage applied by generator 207, and in front hereof is a polariser 201 is located.
  • liquid crystal cell 206 is in the state where it rotates the polarisation angle of transmitted light essentially 90 degrees, a negative image of the OASLM pattern is obtained.
  • the liquid crystal cell 206 may be of a faster response time than the OASLM, and synchronised to the operating cycle of the display 170, thereby eliminating the need for synchronising the OASLM to said operation cycle, thus a slower update cycle of the OASLM may be allowed, for example an illumination system operation cycle and a photosensitive layer update cycle may be used, which comprises means for suppression of unwanted interference from light from the electro-luminescent layer and ambient light, in a way equivalent to the interference reducing means described in the first alternative embodiment and Fig. 6A, 6B and 14.
  • Fig. 20A shows a top view of the holes 203, seen as white holes on a shading layer, through the lens array 14'.
  • the lenses are shown in outline and the lens distortions of the holes are not shown.
  • the electro-luminescent structure comprising the layers 161 ,162,163 and 165 may be substituted by an apertured reflection and shading mask and one or more edge lamps, located at the edges of the display 170 illuminating said mask from behind.
  • a beam splitting mirror tilted at an angle which may be 45 degrees, is located in front of the reflecting OASLM 205, directing illumination from an illumination source, which may be light emitting diodes or an electro-luminescent structure, towards the OASLM from the front, allowing light reflected from the OASLM to be transmitted through the beam splitter mirror towards the lens array 14'.
  • the transparent display 170 should be able to switch fast between three states: a "left state”, displaying a left image, a "right state”, displaying a right image and a "clear states”, displaying a uniformly transparent white or grey image.
  • Ferroelectric liquid crystal displays for example, have excellent response times, whereas the slower twisted nematic liquid crystal displays have other advantages such as purity, viewing angle and stability, and are normally the preferred choice for commercial displays, for example in thin film transistor active matrix colour liquid crystal displays, often referred to just as TFT displays.
  • the display 170 is constructed in an especially advantageous way, as shown in Fig. 17, which combines the above described requirements with the virtues of modern type liquid crystal displays, and which can be constructed by modifying commercially available TFT type displays.
  • the display 170 is constructed as four overlaid or "sandwiched" liquid crystal units with a polariser located behind them.
  • a liquid crystal display unit 171R for example a TFT display, removed its rear polariser and reflector or backlight system, is located in front a single, large, electrically addressed liquid crystal cell 172R with a short response time, as for example described in US patent 4,772,943, which is hereby included in the specification by reference.
  • Behind the liquid crystal cell 172R is located another liquid crystal display unit 171L, which may be identical to 171R, and behind that, again another liquid crystal cell 172L, which may be identical to 172R.
  • Behind the liquid crystal cell 172L is located a polariser 173, having horizons polarisation direction.
  • the display units 171 L and 171 R include front analysing polarisers, having vertical polarisation directions.
  • the resolution and pitch size of the displays 170L and 170R may be chosen to be of different value to optimise for reducing Moirees artefacts. Further, the distance between the displays 170L and 170R may be adjusted and the displays 170L and 170R rotated with respect to each other to reduce Moirees artefacts.
  • the liquid crystal cells 172R and 172L are capable of rotating polarised transmitted light and of performing a transition between two states, a first state and a second state, depending on the applied voltage to its electrodes, so that the difference in the rotation angle of said first and second state is essentially 90 degrees. During the transition, the rotation angle is in between the rotation angle of said first state and the rotation angle of said second state.
  • the liquid crystal cells 172R and 172L have shorter response times than those of the liquid crystal displays 171a and 171b, for example half the response time or less. [Large liquid crystal cells with short response times are commercially available from for example StereoGraphics, California.] Light from the back illumination plate enters from the back of the construction, where it is horizontally polarised by polariser 173.
  • Fig. 22 shows a timing diagram, not necessarily to scale, of the voltage applied to the electrodes of the liquid crystal cell 172R, designated “Right cell voltage”, the voltage applied to the electrodes of the liquid crystal cell 172L, designated “Left cell voltage”, and the resulting display state.
  • the display system 170 When the display system 170 is desired to be in its "Left state", displaying a left image supplied to the display unit 171 L, the voltage applied to the electrodes of the liquid crystal cell 172L is forced to a level, for example a "high” level, which forces the cell to a first state where essentially no rotation of the polarisation angle of transmitted light is performed, so the horizontally polarised light enters display unit 171L unchanged from the back, display unit 171L including its front vertical polarising analyser modulates the transmitted light, producing the desired image and outputs vertical polarised light towards the liquid crystal cell 172R in front of it.
  • a level for example a "high” level
  • the liquid crystal cell 172R is operated in a duty cycle, essentially forcing the angle of polarisational rotation performed on transmitted light to traverse all values from essentially O to essentially 90 degrees at essentially constant speed.
  • the time averaged transmitted light over a full duty cycle of every part of the display system will, regardless of the state of the liquid crystals in the liquid crystal display unit 171 R, contain equal amounts of light polarised in every direction between essentially O and essentially 90 degrees. It is noted, that symmetry around the axis are here assumed, so for example 91 degrees is interpreted as 89 degrees, since both values result in the same transmittance.
  • the time averaged transmittance at every part of the display unit 171 R will now be a fixed value of essentially 50% of the display units maximum transmittance.
  • the display unit 171 R will appear to be "clear"; i.e., exhibiting a spatial uniform neutral density, and the observer will see only the image displayed by display unit 171 L.
  • the liquid crystal cell 172L is operated in a duty cycle, essentially forcing the angle of polarisational rotation performed on transmitted light to traverse all values from essentially O to essentially 90 degrees at essentially constant speed, so the time averaged transmittance of display unit 171 L will be uniform, and it will appear clear.
  • the voltage applied to the electrodes of the liquid crystal cell 172R is now forced to a level, for example a flow level", that forces the cell to rotate the polarisation angle of transmitted light essentially 90 degrees, so the light that exits the cell and enters the liquid crystal display unit 171R now has a horizontal polarisation angle.
  • the light is then transmitted and modulated by display unit 171 R, and the observer sees the image displayed by display unit 171 R.
  • both liquid crystal cells 172L and 1 72R are operated in duty cycles, essentially forcing the angle of polarisational rotation performed on transmitted light to traverse all values from essentially O to essentially 90 degrees at essentially constant speed.
  • the frequency of the duty cycles of cell 172L and 172R may have different values, in order to avoid interference phenomena.
  • the duty cycle of one of the cells may have the double frequency of that of the other.
  • Fig. 19 shows an application as a flat panel stereoscopic display intended to be viewed with polarised glasses.
  • a uniform backlight system 191 illuminates from behind the display system 170, operated with an operating cycle alternating between "left" and “right” states and showing time multiplexed stereoscopic still or moving images, and a large liquid crystal cell 192 is located in front of the display, alternately rotating the polarisation angle essentially O and essentially 90 degrees, synchronised with the operating cycle of the display system.
  • a stereoscopic image can then be viewed wearing passive polarised glasses 193, with left and right eyes having orthogonal polarisation angle.
  • the liquid crystal cell 192 may be omitted, and the observer may wear active shutter glasses, synchronised with the alternation frequency of the displaying of left and right eye images.
  • Fig. 25 shows an overview of a seventh embodiment of the auto-stereoscopic display system according to the present invention, comprising a front projection screen 230, onto which a time division multiplexed stereoscopic still or moving image is projected with a projector 70', which may be a single projector or a projector pair, and the screen is observed by one or more observer(s), whose left and/or right side face(s) are illuminated with infrared light by an observer illumination system, which may be similar to one of the systems described in greater details in the specifications of the preferred embodiment and first and second alternative embodiments and their respective alternative configurations.
  • a cross section of the front projection screen 230 is shown in Fig. 23. It includes a reflective OASLM 20" and a lens array 14" comprising a multitude of aspherical lenses. The spatial distribution density of said lenses defines the maximum possible resolution of the front projection screen.
  • the OASLM 20" is similar in construction and operation to the OASLM 20' described in the specification of the first alternative embodiment and shown in Fig. 9, except in this embodiment, the reflector 95 is substituted by a reflector 95', which is transparent to infrared light and reflecting visible light, the electrode 92A is substituted by electrode 92A, which may be opaque, for example of aluminium, and the glass plate 90A may be omitted.
  • the operation mode of the OASLM 20" may be similar to one of the operation modes of OASLM 20 and OASLM 20' described in greater details in the specifications of the preferred embodiment and first and second alternative embodiments and their respective alternative configurations, and is chosen in accordance with the chosen observer illumination system.
  • the reflective OASLM in this embodiment is illuminated from the front by the projector or the projectors through the lens array 14".
  • the lenses are constructed as aspherical lenses, so that a first portion of each lens, which may be the centre portion, has a first focal length and focuses reflections from the left and right half side face(s) of the observer(s) 10 onto the OASLM to form a small image of the left or right half side faces(s) of the observer(s), and projects visible light back towards respectively the left and right half side face(s) of the observers, as described in greater detail in the specifications of the preferred embodiment and first and second alternative embodiments, and a second portion of each lens, which may be the peripheral portion, has different characteristics, so it spreads projected light from the projector, incident at the lens, essentially uniformly over an area of the OASLM 20".
  • Said second portion of each lens may have a different focal length, so that the aspherical lenses have dual focal lengths, a first focal length established by the said first portion of each lens and a second focal length, established by said second portion of each lens.
  • Said second focal length may be four times the focal length of said first focal length.
  • the photosensor layer 94 which may be for example amorphous silicon, can be polished to obtain an acceptable reflection/transmission ratio for both visible and infrared light in the desired spectrum.
  • a front projection system is constructed similar to that of the seventh embodiment, but in the seventh embodiment, the liquid crystal OASLM 20" is substituted by a sheet of optically sensitive electric paper 20'".
  • the optically sensitive electric paper 20" may be a sheet medium 20'", comprising a solid substrate 241 , a large uniform transparent electrode 243a, another large uniform electrode 243b, which may be transparent or opaque and internal bichromal balls 242, which may be capable of changing their electric characteristics depending on incident light.
  • Light falling on the medium 20' under an applied voltage supplied by a voltage source 244, forces the internal bichromic balls 242 to rotate to show either a white or a black side.
  • the operation cycle of the electric paper 20'" and the illumination system may be similar to one of the operation modes of OASLM 20 and OASLM 20' and the corresponding illumination system configurations described in greater details in the specifications of the preferred embodiment and first and second alternative embodiments and their respective alternative configurations, and is chosen in accordance with the chosen observer illumination system.
  • Optically sensitive electric paper including image subtracting behaviour of same, has been suggested by N. Sheridon of Xerox Corp. Reference is made to US patent 6,137,467, which is hereby included in the specification by reference.
  • an advantage of comprising electric paper in this invention is that it has the potential of being fabricated economically in large, flexible sheets.
  • the eighth embodiment may constructed as a large, flexible projection screen.
  • the optical paths of the seventh and eighth embodiments supports particularly well the use of large screen sizes relative to the observer distance, which shall be seen in the following. Large screen size compared to observer distance is desirable for cinematic stereoscopic presentations, because this reduces the parallax restrictions, known as the "stereo window" to persons skilled in the art, potentially enhancing the observer experience, a fact fully exploited in for example I max giant screen 3-D cinemas.
  • Fig. 26 is a schematic diagram of the optical paths in the eighth embodiment, which are also very similar to the optical paths in the seventh embodiment, except that in the seventh embodiment, light falls onto the OASLM 20" instead of onto the electric paper sheet 20'". It is noted, that the diagram is not to scale, particularly lens size, relative lens spacing and lens spacing relative to the electric paper 20'", and also the thickness of the electric paper 20"', are greatly exaggerated for clarity.
  • any observer 10 and the projector or the projectors 70' can be regarded as located far enough away from the screen compared to the distance between the lens array 14" and the sheet 20'" to have essentially identical focal planes, and that the lens aperture of the projector or projectors can be regarded as a point having no extension, which are good approximations.
  • Fig. 26 shows the situation, when the observer(s) have the left half side of their face(s) illuminated, but it should be evident, that a similar description can be made of the situation, when the observer(s) have the right half side of their face(s) illuminated.
  • any part of the projected image has a brightness level higher than black. Black or dark areas often exist in images, but it is the areas having a brightness level higher than black, that carries the stereoscopic information, and therefore is of interest.
  • each aspherical lens of lens array 14" is longer than said first focal length, the light emitted from the projector, will form illuminated areas 262, which may have the form of slightly distorted, unfocused discs, on the sheet 20'" behind the lens array 14".
  • the size of the illuminated areas 262 are defined by said second focal length relative to said first focal length, and covers all of the small focused infrared images 263 of the left half side of the face(s) of observers located within the allowed viewing area.
  • the possible viewing positions are the positions, where the projected face images falls within said illuminated area, hence the possible viewing angles for each lens relative to the angle of incident light from the projector is defined by said second focal length relative to said first focal length.
  • how far off-axis relative to the projector axis an observer can move and still see a stereoscopic image depends on the relationship between the dual focal lengths of the aspherical lenses, as well as of the distance of the observer to the screen.
  • the electric paper sheet 20"' may be of a type having a limited reflection scattering angle or even of a retro reflective type, depending on the lens sizes and focal lengths and distance of the lens array 14" from the sheet 20"', to obtain a better observed light yield of the projection screen.
  • the size of said second portion of each lens may be made bigger than the size of said first portion of the lens, in order to "capture” and spread a larger fraction of the projected light, thereby increasing the illumination of the sheet 20'".
  • the lens array 14" may be anti-reflection treated, to reduce reflections of light originating from the projection lens of the projector(s) 70' from the surfaces of the lenses towards the observers), which may result in cross talk.
  • said first portion of the lens will also focus a very bright spot image of the projector aperture onto a small area of the sheet 20".
  • the sheet 20'" may be operated in an operating cycle, so it is only light sensitive during a blanking interval of the projector(s) 70', ensuring, that the sheet 20'" is not undesirably addressed by the light from the projector(s) 70', and hence is non- reflecting, or low-reflecting, in said small area where the spot image is projected, thereby reducing internal reflections and scatterings and thus, the cross talk.
  • Fig. 27 illustrates a ninth embodiment.
  • An observer 10 with a part of his or her face, including the left eye but not the right eye, or the right eye but not the left eye, illuminated with infrared light, is located in front of a ninth embodiment of the auto- stereoscopic display element according to the present invention.
  • the led display 170 with its rear polariser removed, is located in front of the polarisation layer 72, comprising a striped pattern of alternate polarisation directions, similar to the one used in the second alternative embodiment and illustrated in Fig. 8.
  • the pixel rows of the led display 170 are aligned with the stripes in the polarisation layer 72.
  • the led display 170 displays a still or moving spatially multiplexed stereoscopic image, in which every second row displays pixels of a first image and the other rows displays pixels of a second image. Said first and said second images may constitute a stereoscopic image pair.
  • the electric signals to the pixels are calibrated to accommodate for the different polarisation of transmitted light through the polarisation layer 72, so that all the pixels in the display show correct colour values.
  • the front polariser of the led display 170 may have such characteristics, that it essentially transmits visible light of only one polarisation direction, but essentially transmits infrared light with equal and little absorption, regardless of polarisation.
  • a lens array 14' comprising at least one concave lens, or optical equivalent, is located behind the led display 170.
  • the lens or the lenses are constructed, so that they do not perform any change of the polarisation of transmitted light.
  • a backlight modulation assembly is positioned comprising a transparent OASLM 20"" and a backlight plate 270.
  • the transparent OASLM 20" which may be similar to the OASLM shown in Fig. 10, however differing from the OASLM shown in Fig. 10 in that the diffuser 100 is not present, is positioned between the backlight plate 270 and the lens array 14', oriented so its polariser is facing backwards, towards the backlight plate.
  • the backlight plate may comprise one or more visible light generating cold cathode tube sources and one or more light guides.
  • the OASLM 20'" is operated in an essentially binary mode, so in regions illuminated with infrared light of an intensity below a first threshold, the OASLM 20"' rotates its polarisation of transmitted light from the backlight plate 270 with a first rotation angle, and in regions where the infrared illumination is below a second threshold, the OASLM 20"' rotates its polarisation of transmitted light from the backlight plate 270 with a second rotation angle, the first rotation angle being essentially orthogonal to the second rotation angle.
  • the first threshold and the second threshold may be identical, or the second threshold may be lower than the first threshold.
  • Infrared reflections off regions of the observer's face are transmitted through the display 170 and the lens array 14', and form one or more regions of infrared illumination on the OASLM 20"".
  • the illumination of the observer is performed, so that the infrared reflection of the illuminated face part is of an intensity high enough to create illuminated regions on the OASLM 20"" above the first threshold, and so the infrared reflection of the essentially not illuminated part is of an intensity low enough to create regions on the OASLM 20'" of an intensity below the second threshold.
  • the polarisation angle of the polariser is chosen so that the transmitted light which is rotated the first angle by the OASLM 20"" is absorbed by the stripes of polarisation layer 72 aligned with the pixels of the first image, and the transmitted light rotated the second angle by the OASLM 20'", is absorbed by the stripes of polarisation layer 72, aligned with the second image.
  • the observer will observe the first image with the eye located in the unilluminated region of his or her face, and observe the second image with the eye located in the illuminated region of his or her face.
  • the OASLM 20"" and the backlight plate 270 may be operated in an operating cycle including blanking intervals, similar to the operating cycle of the above described preferred embodiment.
  • Fig. 28 and 29 illustrates a modification of the ninth embodiment, thus constituting a further alternative embodiment, where the OASLM 20"" and the backlight plate 270 is substituted by an alternative backlight modulation assembly, comprising a rear projection plate 281 and one or more OASLM arrangements 282 comprising smaller OASLM units. Further, one or more light shielding plates 283 may be included.
  • the rear projection plate 281 has the characteristic, that it transmits visible incident light from the back to the front, and in doing so, distributes the light over a range of directions, without essentially altering the polarisation of the transmitted light. Further the rear projection plate 281 may be optimised for producing a uniform intensity of distributed light over a specified exit angle. Even further, the rear projection plate may be optimised for maximising intensity of light transmitted in directions within the exit angle or within another angle, to optimise light yield. Infrared light incident on the plate from the front will be transmitted to the back and distributed.
  • One or more OASLM arrangements 282 are located behind the rear projection plate 281. Such an OASLM arrangement 282 is shown in greater detail in Fig. 29.
  • a convex lens 291 having the characteristic, that it essentially does not change the polarisation of transmitted light, is located in front of a transparent OASLM 20', similar to the one illustrated in Fig. 10, however differing from the OASLM illustrated in Fig. 10 in that the diffuser 100 is not present.
  • Behind the OASLM 20' a polariser
  • a visible light source 292 which may be a lamp or fibre optic wire, is located.
  • a light condensing unit 294 may also be included.
  • the transmitted visible light travels back through the lens 291 towards the the plate 281 along the same optical path as the incident infrared light, and form regions where visible illumination of different polarisation is transmitted and distributed, essentially coinciding with the regions of different intensity of the incident infrared illumination.
  • the OASLM 20' is operated in a binary mode with a thresholding function, which may be achieved by using bistable ferroelectric liquid crystals, so that the polarisation of transmitted light changes between a first and a second polarisation angle, the second polarisation angle being orthogonal to the first polarisation angle.
  • the plate 281 In regions where the plate 281 is illuminated from the front with infrared light above a first threshold transmits back visible light of a first polarisation angle, and in regions where it is illuminated with infrared light below the second threshold, which may identical to the first threshold, the plate 281 transmits back visible light of a second polarisation angle, orthogonal to the first polarisation angle. Hence, the plate 281 behaves and could be regarded as the equivalent of an OASLM illuminated with polarised visible light.
  • the OASLM 20' and the light source may be operated in an operating cycle including blanking intervals, similar to the operating cycle of the above described preferred embodiment.
  • the OASLM arrangements 282 may be located side by side, as illustrated in Fig. 28, as they each illuminate a region of the plate 281. They may be located, so that there is an overlap between the illuminated regions on the plate 281 , and shielding plates 283 may be comprised, to enable adjustment of the intensity of the illumination in the overlapping regions by adjusting the position of the shielding plates including their distance from the rear projection plate 281 , thereby establishing means for optimising the construction for uniform illumination by calibration.
  • soft masks or hard masks may be located between the OASLM 20' and the lens 291 , or between the lens 291 and the rear projection plate 281.
  • a time division multiplexed system may be made from this embodiment by including an extra polariser between the OASLM 20' and the plate 281 and by time multiplexing the electrical control signal to the OASLM or the infrared observer illumination, or by including a liquid crystal cell having electrically controlled and alternating rotation angle of the polarisation.
  • a reflective OASLM 20 which may be of the same type as described in the fifth embodiment and illustrated in Fig. 9, comprising a reflector, reflecting only visible light but transmitting infrared light, may be used.
  • Fig. 30 illustrates a possible configuration comprising a beam splitter 301 , directing light from the light source 292 onto the front of the OASLM 20", still allowing for transmission of light from the OASLM 20" towards the lens 291.
  • the reflective OASLM 20" may be replaced by a sandwich structure comprising a transparent led microdisplay 312 with its front and rear polarisers removed, and, located behind this, a reflector 313, having the characteristics, that it reflects visible light but transmits infrared light, and located behind this, a ccd infrared imaging chip 311 , continuously capturing the infrared pattern incident upon it.
  • the pattern captured by the ccd chip 311 is continuously transferred to the transparent led microdisplay 312 through an electronic circuit 314.
  • the electronic circuit 314 may further perform an amplifying and thresholding function on the pixel values, and a geometric correction of the pattern, so that the infrared pattern on the ccd chip 311 is aligned with the liquid crystal pixel pattern of the microdisplay 312.
  • the sandwich structure comprising led microdisplay 312, reflector 313 and ccd chip 311 may be optimised in terms of flatness, so that the distance between the image planes of the microdisplay 312 and the ccd chip 311 is reduced. This may for example include polishing the glass substrate of the microdisplay to a reduced thickness.
  • Fig. 32 illustrates a lens array 14', which may be included in this or any of the other embodiments. It is an optical equivalent of an array of convex lenses.
  • the lens array 14' comprises a multitude of fresnel lens segments arranged in a honeycomb structure. Other structures may be used.
  • the fresnel lens segments may comprise fresnel zone plates, which may include clear and opaque zones on a lithographic film, arranged according to design rules for fresnel lenses, which are well known in the art.
  • the fresnel lens segments may comprise depth structures, following the well known fresnel lens design rules.
  • the depth structures may be printed or embossed into a transparent polymer plate.
  • the manufacturing process may be optimised for preserving the polarisation characteristics of transmitted light.
  • the lens array may be optimised for reducing artefacts from interference with the pixel pattern of the display 170.
  • FIG. 33 illustrates a lens array 14' comprising honeycomb lens segments with zigzag line border sub-structures.
  • the border sub-structures have been inked in for clarity.
  • Fig. 34 illustrates the same lens array, where the border sub-structures have not been inked in.
  • a plurality of displays of the ninth embodiment displaying a first set of image segments, form a stereoscopic video wall, each display displaying an image segment of the first set of image segments, being a section of the same stereoscopic image.
  • a plurality of any of the other embodiments in this description may be comprised.
  • An example of a video wall configuration comprising 4 displays displaying the first set of image segments is illustrated in Fig. 35.
  • a single infrared observer illumination system may be used for all displays in the video wall.
  • a large array of large rectangular fresnel lenses may be comprised in the video wall, in front of the displays, comprising at least one fresnel lens in front of each display.
  • the line pitch of the rectangular fresnel lenses may be selected with respect to the pixel pitch of the displays 170' and line pitch of the fresnel lens array 14', to reduce interference artefacts or Moiree patterns.
  • the first set of image segments may be selected, so that there is no overlap between them, the distance between the displays and the fresnel array may be adjusted to a first distance, yielding a first magnification of the image segments, resulting in the image segments being magnified to appear of essentially same size as the fresnel lenses, and the position of the optical centres of each of the fresnel lenses may be adjusted to a first position, so that the seams between the image segments appear thinner or essentially invisible, when viewed from a specified point of observation.
  • the plurality of displays display a second set of image segments with a specified overlap between the segments in the horizontal, vertical, or both directions, each image segment of the second set of image segments containing a superset of the pixels of a corresponding image segment of the first set of image segments.
  • An example of a video wall configuration comprising 4 displays displaying the second set of image segments is illustrated in Fig. 37
  • the distance between the displays and the fresnel array may be adjusted to a second distance yielding a second magnification, larger than the first magnification of the image segments.
  • the second distance may be adjusted to yield a magnification resulting in smaller subsections of the image segments, corresponding to the image segments of the first set of image segments without overlap, being magnified to appear of essentially same size as the fresnel lenses, and the position of the optical centres of each of the fresnel lenses may be adjusted to a second position, which may be equal to or different from the first position, so the seams between the image segments appear thinner or essentially invisible, when viewed from a specified point of observation.
  • Fig. 38 illustrates an example of a video wall of this alternative configuration, when viewed from an observation point within the area of acceptable viewing comfort.
  • the present invention has been described above with reference to a number of presently preferred embodiments and also certain alternatives of the presently preferred embodiment of auto-stereoscopic display element or arrangement/system according to the present invention, the present invention is by no means limited to the above described embodiments or alternatives.
  • the various elements and components referred to in the above described embodiments may be readily combined with one another, as some elements described in one of the above embodiments may be substituted by elements described in a different embodiment described above and vice versa.
  • certain elements or components of the system have been described as integrated components or elements, however a modification of one of the above described embodiments involving the substitution of an integrated element with an assembly of individual components or vice versa is to be construed part of the present invention.

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Abstract

L'invention concerne un système d'affichage auto-stéréoscopique comprenant un dispositif générateur d'images qui produit deux images à polarisation orthogonale devant être transmises sur des chemins optiques respectifs en direction d'un ou de plusieurs observateurs pour illuminer au moins la partie gauche et la partie droite ainsi que l'oeil gauche et l'oeil droit, respectivement, ainsi qu'un modulateur spatial de lumière à adressage optique (OASLM) comprenant une pluralité d'éléments phototransmetteurs pouvant chacun subir un adressage optique individuel, en plus de comporter une entrée et une sortie optiques et de pouvoir commuter entre un état V et un état H . Dans l'état V, la transmission de la lumière à polarisation verticale est possible, et dans l'état H la transmission de la lumière à polarisation horizontale est possible. Chacun des éléments phototransmetteurs comporte un capteur optique qui permet de commuter entre les états V et H suite à l'exposition au rayonnement infrarouge (IR). Par ailleurs, le modulateur OASLM est placé sur les trajets optiques, entre le dispositif générateur d'images et un ou plusieurs observateurs. Ce système comprend également un système d'illumination qui permet d'illuminer un ou plusieurs observateurs, au moins la partie gauche ou la partie droite de la tête, et exposer ainsi un premier groupe des capteurs optiques de l'OASLM au rayonnement infrarouge réfléchi par la partie gauche ou droite de la tête de chacun des observateurs. Les capteurs optiques du premier groupe décalent leurs éléments photoémetteurs respectifs pour permettre la transmission d'une première image entre les deux images à polarisation orthogonale. Les capteurs optiques qui ne font pas partie du premier groupe décalent leurs éléments phototransmetteurs pour permettre la transmission de l'autre ou de la seconde des deux images à polarisation orthogonale. Enfin, un système optique de réfraction, comportant au moins un élément optique de réfraction, est placé devant l'OASLM, entre l'OASLM et un ou plusieurs observateurs pour établir les trajets optiques.
PCT/DK2002/000194 2001-03-28 2002-03-22 Affichage 3d a auto-alignement Ceased WO2002080579A2 (fr)

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EP01610037.2 2001-03-28
EP01610037A EP1245990A1 (fr) 2001-03-28 2001-03-28 Projecteur 3-D autostéréoscopique auto-aligné
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Cited By (16)

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DE102004048968A1 (de) * 2004-10-07 2006-04-27 Fujitsu Siemens Computers Gmbh Kombination aus Display und Polarisationsbrille
WO2007039846A3 (fr) * 2005-10-05 2007-07-05 Koninkl Philips Electronics Nv Dispositif d'affichage multi-vue configurable
EP2127367A4 (fr) * 2007-02-20 2010-07-21 Daegu Gyeongbuk Inst Science Lecteur multimédia affichant deux images de projection
DE102010009737A1 (de) * 2010-03-01 2011-09-01 Institut für Rundfunktechnik GmbH Verfahren und Anordnung zur Wiedergabe von 3D-Bildinhalten
WO2012047221A1 (fr) * 2010-10-07 2012-04-12 Sony Computer Entertainment Inc. Verres 3d avec système de poursuite de tête utilisant une caméra
EP2744208A1 (fr) * 2012-12-17 2014-06-18 Disney Enterprises, Inc. Système d'affichage 3D à grand public sans lunettes
US8830329B2 (en) 2010-10-07 2014-09-09 Sony Computer Entertainment Inc. 3-D glasses with camera based head tracking
US20150226993A1 (en) * 2013-08-15 2015-08-13 Boe Technology Group Co., Ltd. Apparatus for aligning a to-be-aligned display panel by self-alignment exposure and method for fabricating retardation plate
EP2424250A3 (fr) * 2010-08-24 2016-11-02 LG Electronics Inc. Dispositif de traitement d'image stéréoscopique, procédé de traitement d'image stéréoscopique et système d'affichage multidivision
GB2539941A (en) * 2015-07-01 2017-01-04 Euro Electronics (Uk) Ltd Method and apparatus for autostereoscopic video wall display
CN110312123A (zh) * 2019-06-28 2019-10-08 长春理工大学 利用彩色图像和深度图像的集成成像显示内容生成方法
CN113966481A (zh) * 2019-03-15 2022-01-21 里尔菲克逊有限责任公司 自动多视点有机发光二极管像素
CN114321658A (zh) * 2021-12-29 2022-04-12 北京建筑大学 工业相机轨道及其制备方法
CN115524861A (zh) * 2021-06-25 2022-12-27 京东方科技集团股份有限公司 裸眼3d显示模组、其驱动方法及裸眼3d显示装置
CN116500804A (zh) * 2023-06-29 2023-07-28 成都工业学院 一种时分复用的逆反射立体显示装置
WO2025186666A1 (fr) * 2024-03-05 2025-09-12 Visia Imaging S.R.L. Topographe cornéen intégrant un disque opacifiant pour détecter la couche lipidique de film lacrymal de l'oeil

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Publication number Priority date Publication date Assignee Title
DE102004048968A1 (de) * 2004-10-07 2006-04-27 Fujitsu Siemens Computers Gmbh Kombination aus Display und Polarisationsbrille
WO2007039846A3 (fr) * 2005-10-05 2007-07-05 Koninkl Philips Electronics Nv Dispositif d'affichage multi-vue configurable
EP2127367A4 (fr) * 2007-02-20 2010-07-21 Daegu Gyeongbuk Inst Science Lecteur multimédia affichant deux images de projection
US8297758B2 (en) 2007-02-20 2012-10-30 Daegu Gyeongbuk Institute Of Science And Technology Multimedia player displaying 2 projection images
US8702244B2 (en) 2007-02-20 2014-04-22 Daegu Gyeongbuk Institute Of Science & Technology Multimedia player displaying projection image
DE102010009737A1 (de) * 2010-03-01 2011-09-01 Institut für Rundfunktechnik GmbH Verfahren und Anordnung zur Wiedergabe von 3D-Bildinhalten
EP2424250A3 (fr) * 2010-08-24 2016-11-02 LG Electronics Inc. Dispositif de traitement d'image stéréoscopique, procédé de traitement d'image stéréoscopique et système d'affichage multidivision
WO2012047221A1 (fr) * 2010-10-07 2012-04-12 Sony Computer Entertainment Inc. Verres 3d avec système de poursuite de tête utilisant une caméra
US8830329B2 (en) 2010-10-07 2014-09-09 Sony Computer Entertainment Inc. 3-D glasses with camera based head tracking
EP2744208A1 (fr) * 2012-12-17 2014-06-18 Disney Enterprises, Inc. Système d'affichage 3D à grand public sans lunettes
US9041642B2 (en) 2012-12-17 2015-05-26 Disney Enterprises, Inc. Large audience 3D display system without glasses
US9819932B2 (en) 2012-12-17 2017-11-14 Disney Enterprises, Inc. Large audience 3D display system without glasses
US20150226993A1 (en) * 2013-08-15 2015-08-13 Boe Technology Group Co., Ltd. Apparatus for aligning a to-be-aligned display panel by self-alignment exposure and method for fabricating retardation plate
US9223175B2 (en) * 2013-08-15 2015-12-29 Boe Technology Group Co., Ltd. Apparatus for aligning a to-be-aligned display panel by self-alignment exposure and method for fabricating retardation plate
GB2539941A (en) * 2015-07-01 2017-01-04 Euro Electronics (Uk) Ltd Method and apparatus for autostereoscopic video wall display
CN113966481A (zh) * 2019-03-15 2022-01-21 里尔菲克逊有限责任公司 自动多视点有机发光二极管像素
CN113966481B (zh) * 2019-03-15 2024-06-04 里尔菲克逊实验室有限责任公司 一种针对观察者对图像进行方向性控制的显示器
CN110312123A (zh) * 2019-06-28 2019-10-08 长春理工大学 利用彩色图像和深度图像的集成成像显示内容生成方法
CN115524861A (zh) * 2021-06-25 2022-12-27 京东方科技集团股份有限公司 裸眼3d显示模组、其驱动方法及裸眼3d显示装置
CN114321658A (zh) * 2021-12-29 2022-04-12 北京建筑大学 工业相机轨道及其制备方法
CN116500804A (zh) * 2023-06-29 2023-07-28 成都工业学院 一种时分复用的逆反射立体显示装置
CN116500804B (zh) * 2023-06-29 2023-09-15 成都工业学院 一种时分复用的逆反射立体显示装置
WO2025186666A1 (fr) * 2024-03-05 2025-09-12 Visia Imaging S.R.L. Topographe cornéen intégrant un disque opacifiant pour détecter la couche lipidique de film lacrymal de l'oeil

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