MXPA99006704A - Method and apparatus for producing stereoscopic images - Google Patents

Abstract

An apparatus for displaying a stereoscopic image, the apparatus having a predefined field frequency for displaying the image, and including a first filter means for passing a first perspective of an image with a first spectral component of a colour spectrum, a second filter means for passing a second perspective of the image with a second spectral component of the colour spectrum, and an alternating means for alternating the first and second spectral components, wherein the alternating means operates at a rate equal to an odd multiple of the field frequency of the display apparatus.

Description

METHOD AND APPARATUS FOR PRODUCING STEREOSCOPIC IM GENES FIELD OF THE INVENTION The present invention relates to a method and apparatus for producing stereoscopic images, in particular a method for visually displaying stereoscopic images on a TV or computer monitor, a standard without apparent flicker. In order to observe the stereoscopic images, the viewer uses a pair of lenses that make it substantially possible for the entire color spectrum to be seen by each eye.

BACKGROUND OF THE INVENTION In order for a viewer to see stereoscopic images, it is necessary for the eyes of the viewer * to observe the object from a slightly different perspective such that each eye observes a different view of the image. Currently, various methods are used to visually represent stereoscopic images on a TV or computer monitor. The anaglyph system, as practiced in the. Current technique, depends on the use of complementary color filters placed in front of each eye. For example, you can use a red transmission filter for the eye REF: 030813 left, and a blue and green transmission filter (cyan color) can be used for the right eye. After each eye has become accustomed to the bias "of particular color, and by visually representing the left perspective of the object in red and the right perspective in cyan color, a reasonable stereoscopic image can be observed. each eye is observing a very restricted portion of the full color spectrum, only limited color information can be added to what generally looks like a lightly colored paint.A current technique is to produce full-color images on a TV or computer monitor. the left and right perspectives, alternatively.The screen is observed through the eyeglasses which allow each eye to receive only the image of the appropriate perspective.The eyeglasses typically consist of liquid crystal elements that alternately "shut" each eye, in consequence of the generic term of obturating eyeglasses.The problem with this system is that when or it is used at the normal field frequency of 50 Hz for the PAL and 60 Hz for television images of the NTSC, a substantial flicker occurs because the image received by each of the eyes alternates with periods of darkness. In order for this system to be acceptable to a viewer, the images need to be processed electronically to double the frequency of the frame to a minimum of 100 Hz. At this speed the flicker is not observable. However, the video image is now not produced anymore at a normal speed and can not be displayed visually on a standard TV or computer monitor. An alternative approach was proposed by Street in U.S. Patent No. 4,692,792 with which at least two perspectives of an objective field are visually represented so that in use, the components of the color spectrum used to visually represent a perspective are, at a given time, in general. complementary to the components of the spectrum of colors used to visually represent another perspective while, averaged over a period of time, each perspective is represented visually using in general a representative set of components of full spectrum of colors relative to the objective field to be visually represented stereoscopically. In effect, this system transmits the components of the spectrum of colors corresponding to a perspective of an image at a given moment for an eye of a spectator and the components of the spectrum of colors corresponding to a second perspective of the image for the other eye of the viewer . In practice, the invention of Street is not usable when the red / cyan transmission filters are switched at normal field speeds of 50 Hz for the PAL and 60 Hz for the NTSC since the substantial flicker of the image is observed at these switching speeds. In addition to switching at a different speed, for example 100 Hz, would result in a speed which is not normal in relation to TV standards and would require special processing of TV images, for example doubling the line, as well as a special TV monitor or Computer. Additionally, the electromechanical nature of Street's glasses means that they are not comfortable for long periods of use due to their weight and the noise and vibrations felt by the viewer. In addition, it has been found that ~ the system described by Street also produces substantial, peripheral blinking in which the environment around the image seems to flicker. That is, due to the switching of the glasses, the background and other objects around the image seem to flicker. Such a flickering background has been found to be very disconcerting for a viewer.

OBJECTIVE OF THE INVENTION An object of the invention is to provide a method and apparatus for producing a stereoscopic image in which the viewer is provided with an image which can include a substantially complete range of color information for each eye substantially without flicker, and preferably when it is visually represented on a PAL or NTSC computer or TV monitor, unmodified, standard. Another object of the invention is to provide such an apparatus, which can be produced in a completely electronic form preferably than the electromechanical configurations of the prior art. Another object of the invention is to provide such an apparatus at a relatively low cost.

BRIEF DESCRIPTION OF THE INVENTION With the above objects in mind, the present invention provides in one aspect: an apparatus for the visual representation of a stereoscopic image, the apparatus having a predefined field frequency to visually represent the image and includes: a first filter means for passing a first perspective of an image with "a first spectral component of a color spectrum; a second filter means for passing a second perspective of the image with a second spectral component of the color spectrum; an alternative means for alternating the first and second spectral components, wherein the alternative means operates at a frequency equal to an odd multiple of the field frequency of the visual display apparatus In a further aspect, the present invention provides: a method for visually representing a stereoscopic image in a visual representation device that has a fr predefined field sequence wherein: a first perspective of an image to be observed by the left eye of the viewer is passed through a first filter having a first spectral component of a spectrum of colors; a second perspective of an image to be observed by the right eye of the viewer is passed through a second filter having a second spectral component of a spectrum of colors; and the first and second spectral components are caused to alternate at a frequency equal to an odd multiple of the field frequency of the apparatus visual representation. Preferably, the present invention utilizes the first and second spectral components that are complementary to each other. That is, a combination of the first and the second spectral components produce white light. Conveniently, the first spectral component may be red and the second cyan spectral component, or a combination of blue and green color. The present invention will be discussed further with reference to this combination of red and cyan color, however, any color and its complement could also be used. For example, you can also use blue and yellow color, or alternatively green and magenta color. Preferably, the present invention also includes a synchronization means to ensure that the left eye of the viewer observes only the first perspective of the image, and that the right eye of the viewer observes the second perspective of the image. In yet a further aspect, the present invention provides: a system for observing stereoscopic images including: a filter means adapted to produce spectrally filtered images for the left and right eyes for observation by the left and right eyes of the viewer, respectively; a projection means for projecting or visually representing the spectrally filtered images for the left and right eyes in a visual representation means having a predefined field frequency; and a means of observation to enable a viewer to observe the spectrally filtered images for the left and right eyes in the medium of visual representation; wherein the filter means includes: a first spectral filter means for filtering a perspective for the left eye of an image with a first spectral component of a color spectrum; a second spectral filter means for filtering a perspective for the right eye of the image with a second spectral component of the color spectrum; and an alternating means for alternating the first and second spectral components at a frequency equal to an odd multiple of the field frequency of the visual representation means. Ideally, the invention is configured whereby at least two perspectives of an objective field are visually represented so that in use, the components of the color spectrum used to visually represent a perspective are, at a given time, generally complementary to the components of the spectrum of colors used to visually represent another perspective while, averaged over a period of time, each perspective is visually represented using a set that is generally representative of the components of the full spectrum of colors relative to the objective field to be visually represented in a manner stereoscopic In effect, this system transmits the components of the spectrum of colors corresponding to a perspective at a given moment to an eye of a spectator and the components of the spectrum of colors corresponding to a second perspective at that moment to the other eye of the spectator. For example, a view of the left perspective of an object in a target field and a view of the right perspective can be represented visually on a screen, with the right perspective represented visually in red color and the left perspective represented visually in complementary cyan color . The fast switching between the two produces a substantially complete spectrum of colors for each perspective. It has been found in practice that the switching between the red perspective images and the cyan color perspective at PAL and NTSC field frequencies causes a pronounced blinking to be observed. In order to overcome this flicker, it has been found necessary to increase the switching frequency to a minimum of 100 Hz. At this speed, and above, the viewer does not notice any flicker. However, since "there are no TV video standards at this frequency or above, it would be necessary to use some form of standard converter or line duplicator to enable a practical, blink-free implementation of this technique.

In order to switch at speeds of more than 100 Hz, and still maintain compatibility with existing PAL and NTSC standards, it has been found necessary to switch in odd multiples of the field frequency ie 150, 250 Hz etc. for PAL and 180, 300 Hz etc. for the NTSC. The present invention will be further described with reference to the accompanying drawings. It will be appreciated by the person skilled in the art that other embodiments of the present invention are possible, and therefore the particularity of the accompanying drawings should not be understood as a substitution of the generality of the foregoing description of the invention. Figure 1 demonstrates the complementary commutation of the color spectrum components for a field. Figure 2 shows the progressive switching over two fields. Figure 3 shows the relationship between the excitation voltage and the color transmission of an LCD Cell Esmectic, Chiral (CS, for its acronym in English). Figure 4 shows a practical implementation of a stereoscopic visualization system using CS LCD cells constructed as eyeglasses.

Figure 5 shows the stereoscopic video formed, required to operate a decoder of the present invention. Figure 6 shows a possible configuration to enable a CS LCD cell to be operated at odd multiples of the field frequency. Figure 7 shows a possible decoder for use with the present invention. Figure 8a shows a possible switching means, in this case a multiplexer configured to transmit the red color complement of the image to the left eye, and the cyan color complement of the image to the right eye. Figure 8b shows the following example after Figure 8a, where the multiplexer is configured to transmit the cyan color complement of the image to the left eye and the red color complement of the image to the right eye. Figure 9a shows typical frequency spectra of two spectral-, comp-lementary components. Figure 9b shows a graph of a notch filter to direct the crosstalk of two complementary spectral components.

Figure 9c shows frequency spectra resulting from two complementary spectral components after the application of a notch filter. With reference now to the drawings, while the present invention could be combined with 2D-to-3D conversion systems, it is directed primarily towards a system for receiving a 2D signal in conjunction with 3D data, whereby 3D data makes It is possible for a decoder to convert the 2D signal into the images for the left and right eyes, respectively, for stereoscopic observation by a spectator. An exemplary block diagram of a decoder according to the present invention, suitable for converting the conventional, analog field-sequential 3D into a format suitable for use with sequential color lenses is shown in Figure 7. The operation of this decoder it is as follows: Entering the video, which can be "" in a composite or S-Video format, becomes a 24-bit RGB format using an analog to digital video converter. Alternate fields are stored in two 256k x 24 bit field repositories such that field repository 1 contains odd fields and field repository 2 contains even fields. The 24-bit RGB outputs of each field deposit are selected by an 8-bit multiplexer, which, assuming that a Red / Cyan color coding has been used, selects the outputs as shown in Figure 8. This is In a moment, the red component of an image is directed towards the left eye, while the cyan component of the image is directed towards the right eye, as can be seen in Figure 8a. Then in the next moment, the multiplexer switches so that the cyan color component is fed to the left eye and the red component to the right eye, as can be seen in Figure 8b. The output of the multiplexer is fed into a Digital to Analog video encoder, the resulting composite or S-Video output is displayed visually on a Television monitor or standard computer. Other methods for constructing a decoder are possible, for example a 16-bit YUV with a conversion of chromatic space inside and outside the 8-bit, triple multiplexer could also be used. The synchronism generator can operate to switch the multiplexer to an odd multiple of the field frequency, thereby making it possible for both eyes of the viewer to receive a substantially complete color spectrum and the 3D image. That is, each eye observes two spectral components of each field. The selection and type of decoder is not important. What is required is that the decoder be able to receive and process the 2D image and the 3D data, spectrally filter both the left and right eye images with two different spectral components, while effectively switching the spectral components in an odd multiple of the field frequency, such that the alternative filtering of both spectral components results in a stereoscopic image of substantially complete color. For example, consider a system of the present invention that switches at 150 Hz, three times the field frequency for the 50 Hz PAL, as illustrated in Figure 1. The three phases of the first video field are indicated as A, B and C in Figure 1. During phase A, the red color component of the left perspective view is presented to the left eye and the cyan color component of the view from the right perspective to the right eye. During phase B, the cyan color component of the left perspective view is presented to the left eye and the red component of the view from the right perspective to the right eye. During phase C, the red color component of the left perspective view is presented to the left eye and the cyan component of the right perspective view to the right eye. The three phases of the second video field are indicated in figure 2. During phase A, the cyan color component of the left perspective view is presented to the left eye and the red color component of the view from the right perspective to the right eye. During phase B, the red color component of the left perspective view is presented to the left eye and the cyan color component of the view from the right perspective to the right eye. During phase C, the cyan color component of the left perspective view is presented to the left eye and the red color component of the right perspective view to the right eye. In this way, during any phase each eye receives a spectral component of the color spectrum of the perspective image. On two adjacent phases, for example AB, BC, each eye receives substantially the full color spectrum of its view from the respective perspective and since the switching frequency is greater than 100 Hz, flicker is not evident. The previous methods for providing glasses that provide the necessary switching between the red color and the cyan color have depended on mechanical or electromechanical assemblies. A switchable, fully electronic or electro-optical color filter will overcome all the problems associated with a viewer who uses eyeglasses that have mechanical or electromechanical components. Switchable, electro-optical color filters come in two basic varieties: birefringent color filters and dichroic color filters. Both types operate by linearly polarizing the light in a particular way that then allows the electro-optic medium to manipulate those polarizations and transmit one color at a time. The manipulation of the required polarization results in either turning the direction of polarization by 90 ° or leaving the direction unchanged. Both birefringent and dichroic filters were originally constructed with Kerr cells or Daraday rotators to control polarization, but today the liquid crystal retarding elements provide the electro-optic function more conveniently.

The new developments in the Liquid Crystal Visual Representation (LCD) technologies have resulted in the development of a liquid crystal cell, Esméctica, Quiral (CS). This consists of a thin layer of liquid crystal interposed between two glass substrates. The CS devices are half wave, switchable plates with a rotation angle of 45 °. These are binary devices capable of switching between two polarization states, orthogonal. For an application of the present invention, these may be constructed to switch between a color transmission either red or cyan. The transmission times, between the red color and the cyan color, are small compared to the field return time of the PAL and NTSC television standards. The cells are typically excited with balanced, bipolar DC waveforms of +/- 5V as illustrated in Figure 3. A practical, basic implementation of a stereoscopic display system using CS LCD glasses is illustrated in Figure 4 It will be understood that other display devices can also be used, for example an alternative for the CS LCD glasses would be a Twisted Pneumatic LCD (TN) eyeglasses.

Referring now to Figure 4, the composite video, in the PAL or NTSC format, is applied to a synchronization detector which outputs pulses at a horizontal synchronization level and a logical one indicating the odd video fields or pairs. The horizontal synchronizer pulse is used to time a Type D jogger with the input D derived from the odd / even signal. The outputs Q and -Q of the Type D jogger provide the complementary signal, required to directly drive the CS LCD cells. The stereoscopic video format required to excite this decoder form is shown in Figure 5. This is the most basic implementation and since the color transmissions take place at field frequencies, 50 or 60 Hz, the flicker is visible to the viewer. In order to excite the CS LCD cell in odd multiples of the field frequency, an increased configuration is required, a possible implementation is shown in Figure 6. In this configuration a Closed Phase Cycle is used, closed to- a multiple. odd horizontal sync signal is used to provide the highest frequency excitation to the CS LCD cells.

Currently, the time taken for an LCD CS cell to be switched between the red color and the cyan color is approximately 30 microseconds. This is a significant percentage of the scan time of an individual line of the PAL (64 μS). In this way, transmission from red to cyan or from cyan to red will take approximately 1/2 line of exploration. In this way, it is likely that the viewer will perceive this transmission since it will occur twice per field (with 3 times the field scan), and would effectively result in two horizontal lines that are observed by the viewer that extend to through the screen. Until a faster transition of the CS LCD cells becomes available, it is possible to reduce the visibility of the transitions to the viewer by changing the number of video lines the cell switches from red to cyan or cyan. red color in each field. By varying the line number, and therefore the physical position on the TV or computer monitor screen, it detests how the color transition will not be noticeable to the viewer. That is, assuming that the commutation of the cell from one spectral component to the other spectral component for each frame would normally take place on line x. Then to reduce the transition effect, the line on which the switching occurs for each frame can be varied to take place on one or more adjacent lines, for example you can use the lines x, x + 1, x + 2, ... x + n. Ideally, 5 to 10 different video lines can be used to switch the cell and thereby reduce the effect of transitions. The numbers of video lines that transitions take place in each field can be varied in a fixed sequence or in a pseudo-random basis. There are a number of techniques that can be used to synchronize the number of lines the transition takes, which would be obvious to one skilled in the art. One technique would be to insert a synchronization signal at the beginning of the first line of the video signal each time it is required to restart the fixed or pseudo-random sequence. It is expected that future developments of the CS LCD cell will result in faster switching times, or other material with faster switching times may become available. If the transition time could be reduced to a few microseconds, then the transition would occur in the horizontal suppression period and thus would not be observed by the viewer, in which case it would not be necessary to adjust the switching of the video lines as described above. In the preceding discussion, it has been assumed that the lenses allow only one of the two frequency spectra to be observed at a time, ie when the frequency spectrum 1 passes, the spectrum 2 is totally eliminated, and when the frequency spectrum 2, the frequency spectrum 1 is eliminated, however, in practice there is some crosstalk between the two frequency spectra particularly at the point where the two spectra intersect, this is illustrated in Figure 9a. This crosstalk is detrimental to visually represented 3D images and should ideally be removed, as long as future color cells that have a steeper or faster transition from the passband to the blocking band can be available, a present solution for crosstalk is to provide an optical notch filter in front of the cell to reduce or eliminate the spectra at the crossing point. want several filters dependent on the selection of the frequency spectrum. For example, while an individual notch filter for a red and cyan color system may suffice, it is likely that two separate filters would be required in a green and magenta color system. It will be understood that such filters can also be used to equalize the light amplitude of the two frequency spectra. That is, if the natural light amplitude of a spectral component differs from that of the other spectral component, then filters can be used to substantially equalize the two amplitudes, thereby providing the viewer with one or more balanced images.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following claims is claimed as property.

Claims (39)

1. An apparatus for the visual representation of a stereoscopic image, characterized in that the apparatus has a predefined field frequency to visually represent the image, and includes: a first filter means for passing a first perspective of an image with a first spectral component of a spectrum of colors; a second filter means for passing a second perspective of the image with a second spectral component of the color spectrum; an alternation means for altering the first and second spectral components; wherein the alternation means operates at a frequency equal to an odd multiple of the field frequency of the visual representation apparatus.

2. An apparatus according to claim 1, characterized in that the first and second spectral components are complementary to each other.

3. An apparatus according to claim 1 or claim 2, characterized in that it further includes: a synchronization means to ensure that the left eye of the viewer observes the first perspective of the image, and that the right eye of the viewer observes only the second perspective from image.

4. An apparatus according to any of the preceding claims, characterized in that the first spectral component is red and the second spectral component is cyan.

5. An apparatus according to any of claims 1 to 3, characterized in that the first spectral component is blue and the second spectral component is yellow.

6. An apparatus according to any of claims 1 to 3, characterized in that the first spectral component is green and the second spectral component is magenta.

7. An apparatus according to any of the preceding claims, characterized in that the field frequency is 50 Hz.

8. An apparatus according to any of claims 1 to 6, characterized in that the field frequency is 60 Hz.

9. An apparatus according to any of the preceding claims, characterized in that it also includes: a means of control of lines for regulation, in which the switching of the video lines from one spectral component to another spectral component occurs, wherein each frame of the successive image is switched on a different video line to the frame of the previous image.

10. An apparatus according to claim 9, characterized in that the switching occurs in any of a plurality of adjacent video lines.

11. An apparatus according to claim 9 or claim 10, characterized in that the switching occurs in any of 5 to 10 adjacent video lines.

12. An apparatus according to any of claims 9 to 11, characterized in that the switching in the adjacent video lines is regulated in a sequential order over the successive frames of the image.

13. An apparatus according to any of claims 9 to 11, characterized in that the switching in the adjacent video lines is regulated in a pseudo-random sequence over the successive frames of the image.

14. A method for visually representing a stereoscopic image in an apparatus for visual representation having a predefined field frequency, characterized in that: a first perspective of an image to be observed by the left eye of the viewer is passed through a first filter that it has a first spectral component of a spectrum of colors; a second perspective of an image to be observed by the right eye of the viewer is passed through a second filter having a second spectral component of a spectrum of colors; and the first and second spectral components are caused to alternate at a frequency equal to an odd multiple of the field frequency of the apparatus for visual representation.

15. A method according to claim 14, characterized in that the first and second spectral components are complementary to each other.

16. A method according to claim 14 or claim 15, characterized in that the first spectral component is red and the second spectral component is cyan.

17. A method according to claim 14 or claim 15, characterized in that the first spectral component is blue and the second spectral component is -color-yellow.

18. A method according to claim 14 or claim 15, characterized in that the first spectral component is green and the second spectral component is magenta.

19. A method according to any of claims 14 to 18, characterized in that the field frequency is 50 Hz.

20. A method according to any of claims 14 to 18, characterized in that the field frequency is 60 Hz.

21. A method according to any of claims 14 to 20, characterized in that the switching of a spectral component to another spectral component in each frame of the image occurs in a video line different from the frame of the previous image.

22. A method according to claim 21, characterized in that the switching occurs in any of a plurality of adjacent video lines.

23. A method according to claim 21 or claim 22, characterized in that the switching occurs in any of 5 to 10 adjacent video lines.

24. A method according to any of claims 21 to 23, characterized in that the switching in the adjacent video lines is regulated in a sequential order over the successive frames of the image.

25. A method according to any of claims 21 to 23, characterized in that the switching in the adjacent video lines is regulated in a pseudo-random sequence over the successive frames of the image.

26. A system for observing stereoscopic images, characterized in that it includes: a filter medium adapted to produce spectrally filtered images for the left and right eyes for observation by the left and right eyes of the viewer, respectively; a projection means for projecting or visually representing the spectrally filtered images for the left and right eyes in a visual representation means having a predefined field frequency; and a means of observation to enable a viewer to observe the spectrally filtered images for the left and right eyes in the medium of visual representation; wherein the filter means includes: a first spectral filter means for filtering a perspective for the left eye of an image with a first spectral component of a spectrum of colors; a second spectral filter means for filtering a perspective for the right eye of the image with a second spectral component of the color spectrum; and an alternation means for alternating the first and second spectral components at a frequency equal to an odd multiple of the field frequency of the visual representation means.

27. A system according to claim 26, characterized in that the second spectral component is complementary to the prime: spectral component.

28. A system according to claim 26 or claim 27, characterized in that it further includes: a synchronization means to ensure that the left eye of the viewer only observes the perspective for the left eye of the spectrally filtered image, and that the right eye of the viewer only observe the perspective for the right eye of the spectrally filtered image.

29. A system according to any of claims 26 to 28, characterized in that the first component is red and the second component is cyan.

30. A system according to any of claims 26 to 28, characterized in that the first component is blue and ~ the second component is yellow.

31. A system according to any of claims 26 to 28, characterized in that the first component is green and the second component is magenta.

32. A system according to any of claims 26 to 31, characterized in that the field frequency is 50 Hz.

33. A system according to any of claims 26 to 31, characterized in that the field frequency is 60 Hz.

34. A system according to any of claims 26 to 33, characterized in that the observation means includes: a first spectral filter means corresponding to the first spectral component; a second spectral filter means corresponding to the second spectral component; an exchange medium for exchanging the first and second spectral filter means at a frequency equal to the alternation means.

35. A system according to any of claims 26 to 34, characterized in that it also includes: a means of control of lines for regulation in which a video line of the medium for the visual representation that is switched from one spectral component to another occurs Spectral component, where each frame of the next image is switched on a different video line to the frame of the previous image.

36. A system according to claim 35, characterized in that the switching occurs in any of a plurality of adjacent video lines.

37. A system according to claim 35 or claim 36, characterized in that the switching occurs in any of 5 to 10 adjacent video lines.

38. A system according to any of claims 35 to 37, characterized in that the switching in the adjacent video lines is regulated in. a sequential order on the successive frames of the image.

39. A system according to any of claims 35 to 37, characterized in that the switching in the adjacent video lines is regulated in a pseudo-random sequence over the successive frames of the image.