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WO2000057217A1 - Systeme d'eclairage utilisant la retroaction optique - Google Patents

Systeme d'eclairage utilisant la retroaction optique Download PDF

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Publication number
WO2000057217A1
WO2000057217A1 PCT/US2000/007657 US0007657W WO0057217A1 WO 2000057217 A1 WO2000057217 A1 WO 2000057217A1 US 0007657 W US0007657 W US 0007657W WO 0057217 A1 WO0057217 A1 WO 0057217A1
Authority
WO
WIPO (PCT)
Prior art keywords
light
bandwidth
holographic optical
control signals
optical element
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/US2000/007657
Other languages
English (en)
Inventor
Milan M. Popovich
John J. Storey
Michael R. Adams
C. David Nabors
Jonathan D. Waldern
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
DigiLens Inc
Original Assignee
DigiLens Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by DigiLens Inc filed Critical DigiLens Inc
Priority to EP00916615A priority Critical patent/EP1082626A1/fr
Priority to AU37693/00A priority patent/AU3769300A/en
Priority to KR1020007013177A priority patent/KR20010090432A/ko
Priority to JP2000607033A priority patent/JP2002540448A/ja
Publication of WO2000057217A1 publication Critical patent/WO2000057217A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/32—Holograms used as optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/203—Filters having holographic or diffractive elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/13306—Circuit arrangements or driving methods for the control of single liquid crystal cells
    • G02F1/13318—Circuits comprising a photodetector
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1334—Constructional arrangements; Manufacturing methods based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
    • G02F1/13342—Holographic polymer dispersed liquid crystals

Definitions

  • the present invention relates generally to illumination systems, and more particularly to an illumination system using optical feedback.
  • Illumination systems generate light for illuminating objects including image displays.
  • the output light of conventional illumination systems often varies in intensity.
  • the variance in intensity may be uniform across the spectral frequency of the output light or localized in a non-uniform fashion to one or more visible bandwidths (e.g. red, green, or blue light) thereof.
  • the inconsistencies may result from a variety of factors including temperature variations of the light source of the illumination system, age related physical changes in the light source, or changes in the ambient conditions in which the light source operates.
  • the present invention relates to an illumination system using optical feedback to maintain a predetermined light intensity output.
  • the illumination system employs an electrically controllable optical filter for filtering light received thereby.
  • the illumination system also includes a light detector for detecting at least a portion of the light filtered by the electrically controllable optical filter.
  • the light detector is in data communication with the electrically controllable optical filter. Some or all light filtered by the electrically controllable optical filter is detected by the light detector, which, in turn generates a corresponding signal that is compared to at least one predetermined value.
  • one or more filtering characteristics of the electrically controllable optical filter are varied which, in turn, varies the amount of light filtered by the electrically controllable optical filter.
  • the filtering characteristics of the electrically controllable optical filter continue to be varied until the signal generated by the light detector substantially matches the at least one predetermined value.
  • the electrically controllable optical filter includes one or more electrically switchable holographic optical elements.
  • Each of the electrically switchable holographic optical elements operates between an active state and an inactive state depending upon the magnitude of a voltage received thereby.
  • the inactive state light incident upon the electrically switchable holographic optical element is transmitted therethrough without substantial alteration.
  • the electrically switchable holographic optical element diffracts a select bandwidth of the received incident light into at least a zero order- diffracted component and a first order diffracted component. The remaining, imdiflfracted portions of incident light are transmitted by the activated electrically switchable holographic optical element without substantial alteration.
  • the intensity of light in the zero order-diffracted component and the first order diffracted component depends on the magnitude of the voltage received by the electrically switchable holographic optical element.
  • Fig. 1 is a block diagram of an illumination system according to one embodiment of the present invention.
  • Fig. 2 is a block diagram of an illumination system according to another embodiment of the present invention.
  • Fig. 3 is a block diagram of a feedback system that may be used to control the electrically controllable optical filter shown in Figs. 1 and 2;
  • Fig. 4 is a cross sectional view of an electrically switchable holographic optical element employable in the electrically controllable optical filter shown in Figs. 1 and 2;
  • Fig. 5 is a block diagram of an electrically switchable holographic optical element filter employable in the electrically controllable optical filter shown in Figs. 1 and 2;
  • Fig. 5 A illustrates the electrically switchable holographic optical element filter of Fig. 5 configured as a transmissive type filter operating in an additive mode
  • Fig. 5B illustrates the electrically switchable holographic optical element filter of Fig. 5 configured as a transmissive type filter operating in an subtractive mode
  • Fig. 5C illustrates the electrically switchable holographic optical element filter of Fig. 5 configured as a reflective type filter operating in an additive mode
  • Fig. 5D illustrates the electrically switchable holographic optical element filter of Fig. 5 configured as a reflective type filter operating in an subtractive mode
  • Fig. 6 illustrates one embodiment of the illumination system shown in Fig. 1;
  • Fig. 7 illustrates another embodiment of the illumination system shown in Fig. 1 ;
  • Fig. 8 illustrates yet another embodiment of the illumination system shown in Fig. 1;
  • FIG. 9 illustrates still another embodiment of the illumination system shown in Fig. 1;
  • Fig. 10 is a block diagram of an illumination system according to still another embodiment of the present invention.
  • Figure 1 shows one embodiment of an illumination system using optical feedback to produce an illumination light at one or more predetermined intensities in accordance with the present invention.
  • the illumination system in Figure 1 includes a light source 102, a lens 104, an electrically controllable optical filter 106, a light deflector 108, and a feedback system 1 10.
  • the light source 102 shown in Figure 1 generates light in the visible bandwidth.
  • This light includes the primary color components (e.g., red, green, and blue bandwidth light).
  • light source 102 is a single light source that continuously emits, the red, green, and blue bandwidth components.
  • light source 102 may include three individual light sources each continuously emitting one of the red, green, and blue bandwidth light.
  • light source 102 whether a single light source or three individual light sources, may sequentially emit red, green, and blue bandwidth light.
  • the light sources could be lasers.
  • lens 104 In the embodiment shown in Figure 1, light emitted by light source 102 is collimated by lens 104 into collimated or parallel light 112.
  • Collimating lens 104 may be defined by a traditional optical element or system of lens and/or mirror elements formed from glass, plastic, etc. This embodiment of lens 104 is static in nature.
  • lens 104 may take embodiment in one or more electrically switchable holographic optical elements described in copending US Patent application number 09/366,449 entitled Pancake Window Display System Employing One Or More Switchable Holographic Optical Elements filed August 3, 1999, which is incorporated herein by reference.
  • Collimated light 1 12 transmitted by lens 104 falls incident upon electrically controllable optical filter 106.
  • Filter 106 operates to filter collimated light 112 in accordance with one or more feed back control signals generated by feedback system 1 10.
  • Filtered light 1 14 emitted by filter 106 falls incident on deflector 108 which, in turn, deflects all or a portion of filtered light 1 14 to feedback system 1 10.
  • Filtered light 114 which is not deflected, emits from deflector 108 as illumination light 1 16 for illuminating some object.
  • Deflector 108 may be a static device that continuously deflects a portion of filtered light 1 14 incident thereon to feedback system 1 10.
  • deflector 108 may be embodied in one or more electrically switchable holographic optical elements which continuously deflect a portion of the filtered light 1 14 incident thereon or which deflects a portion or all of filtered light 1 14 incident thereon to feedback system 1 10 at predetermined intervals in time.
  • Feedback system 1 10 receives deflected light 1 18 from deflector 108 and in response thereto, generates one or more feedback control signals which control one or more of the filtering characteristics of filter 106.
  • feedback system 1 10 functions to measure the intensity of deflected light 118, continuously or at discrete intervals, to determine if the intensity of deflected light 1 18 is at one or more predetermined intensities. More particularly, the intensity of deflected light 118 at a point in time is compared by feedback system 1 10 to a predetermined intensity. If deflected light 118 intensity is equal or substantially equal to the predetermined intensity, then filtered light 1 14 and illumination light 1 16 are presumed to have intensities equal or substantially equal to predetermined values, respectively.
  • feedback system detects the deviation and adjusts the one or more control signals provided to control filter 106 which, in turn, adjusts the filter 106 until deflected light 1 18 returns to its predetermined intensity.
  • Feedback system 110 is described above as controlling the filtering characteristics of filter 106 as a function of the intensity of a portion of filtered light 1 12.
  • the present invention should not be limited thereto. Rather, the present invention contemplates alternative embodiments in which, for example, a feedback system controls a filter in response to measuring and comparing the intensity of all or substantially all of the filtered light 1 14 at predetermined intervals of time.
  • Figure 2 shows an alternative embodiment of an illumination system using optical feedback to maintain an illumination light output at one or more predetermined intensities in accordance with the present invention.
  • the embodiments shown in Figures 1 and 2 operate in similar manner. Whereas Figure 1 shows a transmissive type illumination system, Figure 2, in contrast, shows as a reflective type illumination system.
  • the illumination system includes a light source 102, a lens 104, an electrically controllable optical filter 206, deflector 108, and feedback system 1 10.
  • the system shown in Figure 2 employs many of the same elements of Figure 1. Common reference numbers are used to identify common elements in the systems shown in Figures 1 and 2.
  • filter 206 receives and filters collimated light 112 in accordance with control signals received from feedback system 1 10. Whereas filter 106 emits filtered light 1 14 from a surface opposite to that which receives the collimated light 1 12, filter 206 of Figure 2 emits filtered light 1 14 from the same surface that receives the collimated light 112. Deflector 108 deflects a portion or all of the filtered light 1 14. This deflected light is provided to feedback system 1 10. The remaining portion of filtered light 1 14 not deflected, emits from deflector 108 as illumination light 1 16.
  • Feedback system 110 shown in Figure 2 operates in a manner substantially similar to that described with reference to Figure 1.
  • the feedback system in Figure 2 receives deflected light 1 18 and generates one or more feedback control signals that control filter 206.
  • Feedback system 110 measures deflected light 1 18 to determine if it equals or substantially equals one or more predetermined intensities.
  • the one or more predetermined intensities in this embodiment may differ from the one or more predetermined intensities employed in the system shown in Figure 1.
  • Filters 106 and 206 filter collimated light 112 by removing or reducing light energy or intensity in one or more select bandwidth components thereof.
  • filters 106 and 206 at any given point in time, remove all or substantially all of the intensity of two of the red, green, and blue bandwidth components of collimated light 112 while variably reducing the intensity in the remaining bandwidth component. The amount by which the remaining bandwidth component is reduced depends on the target intensity of the illumination light 116.
  • filters 106 and 206 in accordance with a first set of control signals generated by feedback system 110, remove all or substantially all of the green and blue bandwidth components from collimated light 112 while variably reducing the red bandwidth component thereof.
  • filters 106 and 206 emit a variable portion of the red bandwidth component of collimated light 1 12 as filtered light 1 14.
  • Filtered light 1 14 may contain trace elements of blue or green bandwidth components of collimated light 1 12.
  • the emitted red bandwidth filtered light 1 14 is measured by feedback system 1 10 via deflected light 118.
  • the emitted red bandwidth filtered light 1 14 should have an intensity equal to or substantially equal to a first predetermined value. If the intensity of the red bandwidth filtered light 1 14 deviates from the first predetermined value, feedback system 1 10 generates a new set of first control signals. Feedback system 1 10 corrects intensity deviations by adjusting the filtering characteristics of filters 106 and 206 using the new first set of feedback control signals.
  • filters 106 and 206 In a second stage of the cycle subsequent to the first stage, filters 106 and 206, in accordance with a second set of control signals generated by feedback system 110, remove all or substantially all of the red and blue bandwidth components from collimated light 1 12 while variably reducing the green bandwidth component thereof. Thus, filters 106 and 206 emit a variable portion of the green bandwidth component of collimated light 1 12 as filtered light 1 14. Filtered light 1 14 may contain trace elements of blue or red bandwidth components of collimated light 112. - 6 -
  • the emitted green bandwidth filtered light 1 14 is measured by feedback system 1 10 via deflected light 1 18.
  • the emitted green bandwidth filtered light 1 14 should have an intensity equal to or substantially equal to a second predetermined value. If the intensity of the green bandwidth filtered light 1 14 deviates from the second predetermined value, feedback system 110 generates a new set of second control signals. Feedback system 110 corrects intensity deviations by adjusting the filtering characteristics of filters 106 and 206 using the new second set of feedback control signals.
  • filters 106 and 206 In a third stage of the cycle subsequent to the second stage, filters 106 and 206, in accordance with a third set of control signals generated by feedback system 110, remove all or substantially all of the green and red bandwidth components from collimated light 112 while variably reducing the blue bandwidth component thereof.
  • filters 106 and 206 emit a variable portion of the blue bandwidth component of collimated light 1 12 as filtered light 1 14.
  • Filtered light 1 14 may contain trace elements of red or green bandwidth components of collimated light 112.
  • the emitted blue bandwidth filtered light 1 14 is measured by feedback system 110 via deflected light 1 18.
  • the emitted blue bandwidth filtered light 114 should have an intensity equal to or substantially equal to a third predetermined value. If the intensity of the blue bandwidth filtered light 114 deviates from the third predetermined value, feedback system 110 generates a new set of third control signals. Feedback system 110 corrects intensity deviations by adjusting the filtering characteristics of filters 106 and 206 using the new third set of feedback control signals.
  • filters 106 and 206 remove all or substantially all of the energy in one of the red, green, and blue bandwidth components of collimated light 1 12 while variably reducing the intensity contained in the remaining two bandwidth components. Again, the filtering is performed in a repeated cycle.
  • filters 106 and 206 in accordance with a first set of control signals generated by feedback system 1 10 remove all or substantially all of the blue bandwidth component from collimated light 1 12 while variably reducing the red and green bandwidth components of collimated light 1 12.
  • the first set of control signals in this mode is distinct from the first set of control signals employed in the preferred mode.
  • filters 106 and 206 emit a variable portion of the red and green bandwidth components of collimated light 1 12 as filtered light 1 14.
  • Filtered light 114 may contain trace elements of blue bandwidth light.
  • the emitted red and green bandwidth filtered light 114, in combination, should have an intensity equal to or substantially equal to a first predetermined value.
  • the first predetermined value used in this mode may be different from the first predetermined value used in the preferred mode. If the intensity of the red and green bandwidth filtered light 1 14 deviates from the first predetermined value, the deviation is detected by feedback system 1 10 via deflected light 1 18, and feedback system 1 10 generates a new set of first control signals. Feedback system 1 10 corrects the deviation by adjusting filters 106 and 206 using the new first set of feedback control signals.
  • filters 106 and 206 in accordance with a second set of control signals generated by feedback system 1 10 remove all or substantially all of the green WO 00/57217 PCT/US00 ,- .
  • the second set of control signals in this mode is distinct from the second set of control signals employed in the preferred mode.
  • filters 106 and 206 emit a variable portion of the red and blue bandwidth components of collimated light 1 12 as filtered light 1 14.
  • Filtered light 1 14 may contain trace elements of green bandwidth light.
  • the emitted red and blue bandwidth filtered light 114, in combination, should have an intensity equal to or substantially equal to a second predetermined value.
  • the second predetermined value used in this mode may be different from the second predetermined value used in the preferred mode.
  • the deviation is detected by feedback system 110 via deflected light 118, and feedback system 110 generates a new set of second control signals.
  • Feedback system 110 corrects the deviation by adjusting filters 106 and 206 using the new second set of feedback control signals.
  • filters 106 and 206 in accordance with a third set of control signals generated by feedback system 1 10 remove all or substantially all of the red bandwidth component from collimated light 112 while variably reducing the blue and green bandwidth components of collimated light 112.
  • the third set of control signals in this mode is distinct from the third set of control signals employed in the preferred mode.
  • filters 106 and 206 emit a variable portion of the blue and green bandwidth components of collimated light 112 as filtered light 1 14.
  • Filtered light 1 14 may contain trace elements of red bandwidth light.
  • the emitted blue and green bandwidth filtered light 1 14, in combination, should have an intensity equal to or substantially equal to a third predetermined value.
  • the third predetermined value used in this mode may be different from the third predetermined value used in the preferred mode. If the intensity of the blue and green bandwidth filtered light 1 14 deviates from the third predetermined value, the deviation is detected by feedback system 1 10 via deflected light 1 18, and feedback system 1 10 generates a new set of third control signals. Feedback system 1 10 corrects the deviation by adjusting filters 106 and 206 using the new third set of feedback control signals.
  • filters 106 and 206 operate to variably reduce the light intensity contained in all three of the red, green, and blue bandwidth components of collimated light 1 12 in accordance with one feedback control signal generated by feedback system 110.
  • filters 106 and 206 emit a variable portion of each of the red, green and blue bandwidth components of collimated light 1 12 as filtered light 1 14.
  • the red, green, and blue bandwidth filtered light 1 14 emitted by filters 106 and 206, respectively, should have an intensity equal to or substantially equal to a predetermined value. If the intensity of combined red, green, and blue bandwidth filtered light 1 14 deviates from the predetermined value, the deviation is detected by feedback system 110 via deflected light 1 18.
  • Feedback system 1 10 corrects the deviation by adjusting filters 106 and 206 using a new control signal generated by feedback system 1 10.
  • Figure 3 shows one embodiment of feedback system 1 10. More particularly, Figure 3 shows feedback system having a lens 302, a light detector 304, and a control circuit 306. In one embodiment, lens - 8 -
  • the conventional lens 302 is a conventional collection lens that focuses deflected light 1 18.
  • the conventional lens 302 may take form in glass, plastic or other static material.
  • lens 302 may take form in one or more electrically switchable holographic optical elements that record a collection lens therein.
  • a collection lens embodied in one more electrically switchable holographic optical elements is described in U.S. Patent Application 09/313,431 entitled Switchable Holographic Optical System, filed May 17, 1999 which is incorporated herein by reference.
  • control circuit 306 could be extended to provide signals for controlling a collection lens 302 embodied in one or more electrically switchable holographic optical elements.
  • Lens 302 collects or focuses deflected light 1 18 onto detector 304.
  • Light detector 304 takes form in any one of several types of light detectors including photo capacitors, photo diodes, etc. Essentially, light detector 304 generates an output signal as a function of the intensity of deflected light 118 incident thereon. The magnitude of the detector's output signal corresponds to the intensity of light detected. This correspondence can be linear. The detector 304 may continuously generate an output signal as a function of the light intensity incident thereon. Alternatively, the detector 304 may detect deflected light and generate a corresponding output signal at predetermined intervals in accordance with a control or sample signal received from control circuit 306.
  • Deflected light 1 18 may contain one or more of the red, green, or blue bandwidths depending on the mode in which filter 106 or 206 operates.
  • filters 106 and 206 remove all or substantially all of the energy of two of the red, green, and blue bandwidth components of collimated light 112 while variably reducing the energy in the remaining bandwidth component
  • deflected light 1 18 includes only one of the red, green, or blue bandwidths. Trace components of the remaining bandwidths may be present in the deflected light 1 18. In this embodiment, deflected light 1 18 cycles through the red, green, and blue bandwidth components.
  • deflected light 118 includes only two of the red, green, or blue bandwidths. Trace components of the remaining bandwidth may be present in the deflected light 1 18. In this embodiment, deflected light 118 cycles through combinations of two of the red, green, and blue bandwidth components. In the embodiment where filters 106 and 206 operate to variably reduce the energy contained in all three of the red, green, and blue bandwidth components of collimated light 1 12, deflected light 1 18 contains all three of the bandwidth components.
  • Control circuit 306 functions in a variety of modes corresponding to the variety of modes in which filter 106 or 206 operates.
  • Control circuit 304 will be described with reference to the mode described above in which filter 106 or 206 removes all or substantially all of the energy of two of the red, green, and blue bandwidth components of collimated light 112 while variably reducing the energy in the remaining bandwidth component, it being understood that control - 9 - circuit 106 or 206 can operate in other modes.
  • the red bandwidth associated output register stores a red bandwidth control signal for controlling the amount of red bandwidth light removed by filter 106 or 206.
  • the red bandwidth output register stores either a first red bandwidth control signal that causes filter 106 or 206 to remove all or substantially all of the red bandwidth component from collimated light 112, or a second red bandwidth control signal that causes filter 106 or 206 to remove a variable portion of the red bandwidth component of collimated light 112.
  • the first red bandwidth control signal is stored in a first red bandwidth control register while the second red bandwidth control signal is stored in a second red bandwidth control register.
  • the green bandwidth associated output register stores a green bandwidth control signal for controlling the amount of green bandwidth light removed by filter 106 or 206.
  • the green bandwidth output register stores either a first green bandwidth control signal that causes filter 106 or 206 to remove all or substantially all of the green bandwidth component from collimated light 112, or a second green bandwidth control signal that causes filter 106 or 206 to remove a variable portion of the green bandwidth component of collimated light 112.
  • the first green bandwidth control signal is stored in a first green bandwidth control register while the second green bandwidth control signal is stored in a second green bandwidth control register.
  • the blue bandwidth associated output register stores a blue bandwidth control signal for controlling the amount of blue bandwidth light removed by filter 106 or 206.
  • the blue bandwidth output register stores either a first blue bandwidth control signal that causes filter 106 or 206 to remove all or substantially all of the blue bandwidth component from collimated light 112, or a second blue bandwidth control signal that causes filter 106 or 206 to remove a variable portion of the blue bandwidth component of collimated light 112.
  • the first blue bandwidth control signal is stored in a first blue bandwidth control register while the second blue bandwidth control signal is stored in a second blue bandwidth control register.
  • the contents of the three output registers are maintained by the control circuit 306 and depend on the cycle stage in which filter 106 or 206 is operating at the time.
  • the red bandwidth output register stores the second red bandwidth control signal
  • the green and blue bandwidth output registers store the first green and first blue bandwidth control signals, respectively.
  • the green bandwidth output register stores the second red bandwidth control signal
  • the red and blue bandwidth output registers store the first red and first blue bandwidth control signals, respectively.
  • the blue bandwidth output register stores the second blue bandwidth control signal
  • the green and red bandwidth output registers store the first green and first red bandwidth control signals, respectively.
  • the second red, green, and blue bandwidth control signals stored in the second red, green, and blue bandwidth control registers, respectively, may change during operation of the illumination system to offset intensity deviations in deflected light 1 18.
  • the intensity of deflected light 1 18 is checked during each stage of the three-stage cycle.
  • the deflected light 1 18 includes essentially, only - 10 - red bandwidth light.
  • a detector output signal is generated that is proportional to the red bandwidth deflected light 1 18.
  • control circuit 306 compares the detector output signal to a first predetermined value previously stored in memory of control circuit 306.
  • the second red bandwidth control signal is left unchanged, and filter 106 or 206, in the first stage of the next cycle, is provided with the same second red bandwidth control signal in addition to the first green and first blue bandwidth control signals.
  • the second red bandwidth control signal, the first green bandwidth control signal and the first blue bandwidth control signal collectively constitute the first set of control signals mentioned above. If the detector output signal does not equal or substantially equal the first predetermined value, then the second red bandwidth control signal is updated accordingly. In next first stage, the updated second red bandwidth control signal is provided to filter 106 or 206 along with the first green and blue bandwidth control signals, all three signals being provided as the new first set control signals.
  • the intensity of red bandwidth filtered light emitted by filter 106 or 206 in response to receiving the new set of first control signals is different when compared to the intensity of filtered red bandwidth light emitted by filter 106 or 206 in response to receiving the first set of control signals.
  • the first red bandwidth control signal may be updated in a number of ways. More particularly, the first red bandwidth control signal may be increased or decreased by a set amount depending on whether the detector output signal is smaller or greater than the first predetermined value. Alternatively, a difference can be calculated between the detector output signal and the first predetermined value, and the first red bandwidth control signal may be increased or decreased by an amount proportional to the difference. In this embodiment, the intensity of the deflected light 118 is checked during each first stage of each cycle.
  • the intensity of deflected light 118 is also checked during the second stage of the three-stage cycle in essentially the same way deflected light 1 18 is checked in the first stage.
  • the deflected light 118 includes essentially, only green bandwidth light.
  • a detector output signal is generated that is proportional to the green bandwidth deflected light 118.
  • control circuit 306 compares the detector output signal to a second predetermined value previously stored in memory of control circuit 306. If the detector output signal equals or substantially equals the second predetermined value, then the second green bandwidth control signal is left unchanged, and filter 106 or 206, in the second stage of the next cycle, is provided with the same second green bandwidth control signal in addition to the first red and first blue bandwidth control signals.
  • the second green bandwidth control signal, the first red bandwidth control signal and the first blue bandwidth control signal collectively constitute the second set of control signals mentioned above. If the detector output signal does not equal or substantially equal the second predetermined value, then the second green bandwidth control signal is updated accordingly. In next second stage, the updated second green bandwidth control signal is provided to filter 106 or 206 along with the first red and blue bandwidth control signals, all three signals being provided as the new second set control signals. The intensity of green bandwidth filtered light emitted by filter 106 or 206 in response to receiving the new set of second control signals is different when compared to the intensity of filtered green bandwidth light emitted by filter 106 or 206 in response to receiving the second set of control signals.
  • the second green bandwidth control signal may be updated in a manner similar to the manner in which the second red bandwidth control signal as updated. More particularly, the second green bandwidth control signal may be increased or decreased by a set amount depending on whether the detector output signal is smaller or greater than the second predetermined value. Alternatively, a difference can be calculated between the detector output signal and the second predetermined value, and the second green bandwidth control signal may be increased or decreased by an amount proportional to the difference. In this embodiment, the intensity of the deflected light 118 is checked during each second stage of each cycle.
  • the intensity of deflected light 118 is checked during the third stage of the three-stage cycle in essentially the same way deflected light 1 18 is checked in the first and second stages.
  • the deflected light 1 18 includes essentially, only blue bandwidth light.
  • a detector output signal is generated that is proportional to the blue bandwidth deflected light 1 18.
  • control circuit 306 compares the detector output signal to a third predetermined value previously stored in memory of control circuit 306. If the detector output signal equals or substantially equals the third predetermined value, then the second blue bandwidth control signal is left unchanged, and filter 106 or 206, in the third stage of the next cycle, is provided with the same second blue bandwidth control signal in addition to the first green and first red bandwidth control signals.
  • the second blue bandwidth control signal, the first green bandwidth control signal and the first red bandwidth control signal collectively constitute the third set of control signals mentioned above. If the detector output signal does not equal or substantially equal the third predetermined value, then the second blue bandwidth control signal is updated accordingly. In next third stage, the updated second blue bandwidth control signal is provided to filter 106 or 206 along with the first green and red bandwidth control signals, all three signals being provided as the new third set control signals. The intensity of blue bandwidth filtered light emitted by filter 106 or 206 in response to receiving the new set of third control signals is different when compared to the intensity of filtered blue bandwidth light emitted by filter 106 or 206 in response to receiving the third set of control signals.
  • the second blue bandwidth control signal may be updated in the same way that the second red bandwidth and second green bandwidth control signals are updated. More particularly, the second blue bandwidth control signal may be increased or decreased by a set amount depending on whether the detector output signal is smaller or greater than the third predetermined value. Alternatively, a difference can be calculated between the detector output signal and the third predetermined value, and the second blue bandwidth control signal may be increased or decreased by an amount proportional to the difference. In this embodiment, the intensity of the deflected light 1 18 is checked during each third stage of each cycle.
  • Filters 106 and 206 are solid state systems. Filters 106 and 206 may take form in one of several embodiments. More particularly, Filters 106 and 206 may be embodied in one or more layers of conventional liquid crystal material. Alternatively, Filters 106 and 206 may be embodied in conventional interference filters combined with electronically controllable neutral density filters based on liquid crystal.
  • Filters 106 or 206 may be formed of one or more electrically switchable holographic optical elements each of which can independently operate in an active state or an inactive state in accordance with a control signal.
  • each electrically switchable holographic optical element In the inactive state, each electrically switchable holographic optical element passes collimated light 1 12 without substantial alteration.
  • each electrically switchable holographic optical element diffracts a select bandwidth (e.g., red bandwidth) of collimated light 1 12 while passing the remaining portions (e.g., green and blue bandwidths) of collimated light 112 without substantial alteration.
  • the diffracted light emerges from the electrically switchable holographic optical element as zero order and first order diffracted light having an angle therebetween.
  • the zero order-diffracted component emerges from the electrically switchable holographic optical element normal to the emitting surface thereof.
  • the electrically switchable holographic optical element may diffract the select bandwidth into higher order components.
  • this disclosure will presume that all of the select bandwidth is diffracted into zero order or first order diffracted light. Further, the amount of light energy contained in the zero order and first order diffracted components depends on a magnitude of a voltage of the control signal applied to the electrically switchable holographic optical element as will be more fully described below.
  • Figure 4 shows a cross sectional view of one embodiment of an electrically switchable holographic optical element that can be used in filters 106 or 206.
  • the switchable holographic optical element of Figure 4 includes a pair of substantially transparent and electrically non-conductive layers 402, a pair of substantially transparent and electrically conductive layers 404, and a switchable holographic layer 406 formed, in one embodiment, from the polymer dispersed liquid crystal material described in U.S. Patent Application 09/478,150 which, as noted above, is incorporated herein by reference.
  • the substantially transparent, electrically non-conductive layers 402 comprise glass
  • the substantially transparent, electrically conductive layers 404 comprise indium tin oxide (ITO).
  • An anti-reflection coating (not shown) may be applied to selected surfaces of the switchable holographic optical element, including surfaces of the ITO and the electrically nonconductive layers, to improve the overall transmissive efficiency of the optical element and to reduce stray light. As shown in the embodiment of Figure 4, all layers 402-406 are arranged like a stack of pancakes on a common axis 408.
  • Layers 402-406 may have substantially thin cross-sectional widths, thereby providing a substantially thin aggregate in cross section. More particularly, switchable holographic layer 406 may have a cross- sectional width of 5 - 12 microns (the precise width depending on a spectral bandwidth and required diffraction efficiency), while glass layers 402 may have a cross-sectional width of .4 - .8 millimeters. Obviously, ITO layers 404 must be substantially thin to be transparent. It should be noted that holographic layers may be deposited on thin plastic substrates. The plastic substrates may also be flexible.
  • the switchable holographic optical element when the ITO layers 404 are coupled to a voltage below the first voltage, the switchable holographic optical element operates in the active state as described above.
  • the electrically switchable holographic optical element diffracts, for example, the red bandwidth component of collimated incident light 1 12 while passing the remaining components of collimated incident light 112, including green and blue bandwidth components, without substantial alteration.
  • the diffracted light emerges as zero order and first order components.
  • the intensity of light in the first and zero order components depends on the magnitude of the voltage applied to the ITO layers 404.
  • a reduction of the voltage applied to the ITO layers 404 reduces the energy in the zero-order diffracted component while simultaneously and proportionately increasing the energy in the first diffracted component.
  • linearly lowering the voltage applied to the ITO layers 404 causes a linear transfer of light energy (i.e., intensity) from the zero order to the first order components.
  • Either the zero order or the first order diffracted light could be used as filtered light 1 14 shown in Figure 1.
  • the first order diffracted light could be used as filtered light 1 14 shown in Figure 2.
  • the switchable holographic optical element shown in Figure 4 may be reflective or transmissive type.
  • Figure 4 shows switchable holographic optical element with oppositely facing front and back surfaces 410 and 412. Whether reflective or transmissive type, collimated light 112 falls incident on the front surface 410 at normal incidence angle. Note that it is not essential for the incident light to be at normal incidence, althought this is likely to be the preferred option in most applications
  • the switchable holographic optical element is configured as transmissive type, the zero order and first order diffracted light components emerge from back surface 412.
  • the electrically switchable holographic optical element is configured as reflective type hologram, the first order diffracted light component emerges from front surface 410 while the zero order diffracted component emerges from the back surface.
  • Either one or more reflective or transmissive type electrically switchable holographic optical elements could be used in the filter 106 of Figure 1.
  • Filter 206 shown in Figure 2 may employ one or more reflective type electrically switchable holographic optical elements.
  • Switchable holographic layer 406 records a hologram using conventional techniques.
  • the resulting hologram is characterized by a high diffraction efficiency and a fast rate at which the optical element can be switched between active and inactive states.
  • the recorded hologram can be switched from a diffracting state to a transmitting state with the creation and elimination of the electric field mentioned above.
  • the holograms recorded in the holographic layer 406 would be Bragg (also know as thick or volume phase) type in order to achieve high diffraction efficiency.
  • Raman-Nath or thin phase type holograms may also be employed.
  • the hologram recorded in switchable holographic layer 406 can be based on PDLC materials described in the 09/478,150 application which is incorporated herein by reference.
  • the hologram results in an interference pattern creating by recording beams, i.e., a reference beam and an object beam, within layer 406. Interaction of the laser light with the PDLC material causes photopolymerization. Liquid crystal droplets become embedded in the dark regions of the fringe patterns that are formed by the intersection of the recording beams during the recording process.
  • the recording material may be a polymer dispersed liquid crystal mixture which undergoes phase separation during the recording process, creating regions densely populated by liquid crystal microdroplets, interspersed by regions of clear photopolymer.
  • the liquid crystal droplets When a voltage of sufficient magnitude is supplied to ITO layers 404, the liquid crystal droplets reorient and change the refractive index of the hologram layer 406 thereby essentially erasing the hologram recorded therein so that all collimated light 1 12 incident thereon passes without noticeable alteration.
  • the material used within layer 406 is configured to operate at a high switching rate (e.g., the material can be switched in tens of microseconds, which is very fast when compared with conventional liquid crystal display materials) and a high diffraction efficiency.
  • FIG. 5 shows one embodiment of filter 106 or 206 employing three separate electrically switchable holographic optical elements 502R, 502G, and 502B.
  • Each of the electrically switchable holographic optical elements 502R through 502B is configured to diffract a select bandwidth of collimated light 1 12 incident thereon when the element operates in the active state. More particularly, electrically switchable holographic optical elements 502R is configured to diffract red bandwidth light when active while passing the remaining components of collimated light 112 without substantial alteration. Similarly the electrically switchable holographic optical elements 502G and 502B are configured to diffract green bandwidth and blue bandwidth components, respectively, of collimated light 112 when active while passing the remaining components of collimated light 112 without substantial alteration. Each of the electrically switchable holographic optical elements 502R through 502B pass substantially all bandwidths of collimated light 1 12 without substantial alteration when operating in the inactive state.
  • Each of the three electrically switchable holographic optical elements 502R through 502G is activated or deactivated in accordance with a respective feedback control signal provided by feedback system 110 shown in Figure 3.
  • each of the optical elements diffracts a select bandwidth of collimated light 1 12 into zero and first order diffracted components.
  • the intensity of the light contained in the zero and first order diffracted components depends on the magnitude of the feedback control signal provided to the electrically switchable holographic optical element.
  • each of the electrically switchable holographic optical elements 502R, 502G, and 502B receives the first or second red bandwidth control signals, the first or second green bandwidth control signals, and the first or second blue bandwidth control signals, respectively, described above. More particularly, the first or second red bandwidth control signals are selectively applied to the ITO layers of electrically switchable holographic optical element 502R, the first or second green bandwidth control signals are selectively applied to the ITO layers of electrically switchable holographic optical element 502G, and the first or second blue bandwidth control signals are selectively applied to the ITO layers of electrically switchable holographic optical element 502B.
  • Filter 500 of Figure 5 may be configured as transmissive or reflective.
  • filter 500 operates in one of several distinct modes in accordance with feedback control signals provided thereto.
  • Figure 5A illustrates a reflective filter 500 configured operating in an additive mode.
  • electrically switchable holographic optical element 502R is activated while electrically switchable holographic optical elements 502G and 502B are deactivated.
  • collimated light 112 passes through the deactivated electrically switchable holographic optical elements 502B and 502G without substantial alteration.
  • activated electrically switchable holographic optical element 502R diffracts the red bandwidth component of collimated light 1 12 into zero order and first order diffracted red bandwidth components.
  • light 504 emerging from filter 500 includes first order diffracted red bandwidth light and possibly trace elements of other bandwidth components of collimated light 112.
  • Light 506 emerging from filter 500 in contrast includes the zero order diffracted red bandwidth light in addition to the blue and green bandwidth components of collimated light 112, both of which pass through filter 500 without substantial alteration.
  • Filter 500 in Figure 5A is shown diffracting red bandwidth light while substantially transmitting all green and blue bandwidth light.
  • This operational mode of filter 500 may result in response to filter 500 receiving the first set of control signals or the new first set of control signals during the first stage of the three stage cycle described above.
  • the second or the updated second red bandwidth control signal is applied to the ITO layers of electrically switchable holographic optical element 502R while the first green and blue bandwidth control signals are applied to the ITO layers of electrically switchable holographic optical elements 502G and 502B, respectively.
  • the first green and blue bandwidth control signals completely deactivate electrically switchable holographic optical elements 502G and 502B, respectively.
  • light 504 constitutes filtered light 1 14 shown in Figure 1
  • the second or updated second red bandwidth control signals are generated by feedback system 1 10 in order to maintain light 504 (or filtered light 1 14) at the first predetermined intensity.
  • Filter 500 in Figure 5 A may also operate in the additive mode to diffract green bandwidth light while substantially transmitting all red and blue bandwidth light in response to receiving the second set of control signals or the new second set of control signals during the second stage of the three stage cycle described above. Additionally, filter 500 of Figure 5 A may operate in the additive mode to diffract blue bandwidth light while substantially transmitting all red and green bandwidth light in response to receiving the third set of control signals or the new third set of control signals during the third stage of the three stage cycle described above.
  • FIG. 5B illustrates filter 500 configured as a transmissive type operating in a subtractive mode.
  • each electrically switchable holographic optical element 502R through 502B is activated.
  • each of electrically switchable holographic optical elements 502R through 502B diffract components of collimated light 1 12.
  • Electrically switchable holographic optical elements 502G and 502B are fully activated in that all or substantially all of the energy contained in the green and blue bandwidth components, respectively, of collimated light 1 12 are diffracted into first order components 510G and 51 OB, respectively.
  • Electrically switchable holographic optical element 502R is also activated. Electrically switchable holographic optical element 502R diffracts the red bandwidth component of collimated light 1 12 into zero order and first order diffracted components. The first order diffracted red bandwidth light emits from filter 500 as first order diffracted red bandwidth light 510R while the zero order red bandwidth component emits as light 512. If electrically switchable holographic optical elements 502G and 502B operate at maximum theoretical diffraction efficiency, light 512 essentially contains only zero order diffracted red bandwidth light. In the preferred mode, light 512 is used as filtered light 1 14 as shown in Figure 1.
  • Filter 500 in Figure 5B is shown diffracting all visible components of collimated light 112.
  • This operational mode of filter 500 may result in response to filter 500 receiving the first set of control signals or the new first set of control signals during the first stage of the three stage cycle described above.
  • the magnitudes of the first set of control signals and the new first set of control signals in this mode of operation are distinct from the first set of control signals and the new first set of control signals provided to filter 500 operating in the additive mode described above.
  • the second or the updated second red bandwidth control signal is applied to the ITO layers of electrically switchable holographic optical element 502R while the first green and blue bandwidth control signals are applied to the ITO layers of electrically switchable holographic optical elements 502G and 502B, respectively.
  • the first green and blue bandwidth control signals completely activate electrically switchable holographic optical elements 502G and 502B, respectively.
  • light 512 constitutes filtered light 114 shown in Figure 1
  • the second or updated second red bandwidth control signals are generated by feedback system 1 10 in order to maintain light 512 (or filtered light 1 14) at the first predetermined intensity.
  • Filter 500 in Figure 5B may also operate in the subtractive mode to diffract all or substantially all of the red and blue bandwidth components of collimated light 112 into first order diffracted components while diffracting the green bandwidth component of collimated light 112 into zero order and first order diffracted components in response to filter 500 receiving the second set of control signals or the new second set of control signals during the second stage of the three stage cycle described above.
  • filter 500 of Figure 5B operate in the subtractive mode to diffract all or substantially all of the red and green bandwidth components of collimated light 1 12 into first order diffracted components while diffracting the blue bandwidth component of collimated light 1 12 into zero order and first order diffracted components in response to filter 500 receiving the third set of control signals or the new third set of control signals during the third stage of the three stage cycle described above.
  • filter 500 of Figure 5 may be configured as a reflective type filter.
  • Figure 5C illustrates a reflective type filter 500 operating in the additive mode.
  • electrically switchable holographic optical element 502R is activated while electrically switchable holographic optical elements 502G and 502B are deactivated.
  • collimated light 1 12 passes through the deactivated electrically switchable holographic optical elements 502B and 502G without substantial alteration.
  • activated electrically switchable holographic optical element 502R diffracts the red bandwidth component of collimated light 112 into zero order and first order diffracted red bandwidth components.
  • light 504 emerging from filter 500 includes first order diffracted red bandwidth light and possibly trace elements of other bandwidth components of collimated light 112.
  • Light 706 emerging from filter 500 in contrast includes the zero order diffracted red bandwidth light in addition to the blue and green bandwidth components of collimated light 112, both of which pass through filter 500 without substantial alteration.
  • Filter 500 in Figure 5C is shown diffracting red bandwidth light while substantially transmitting all green and blue bandwidth light.
  • This operational mode of filter 500 may result in response to filter 500 receiving the first set of control signals or the new first set of control signals during the first stage of the three stage cycle described above.
  • the second or the updated second red bandwidth control signal is applied to the ITO layers of electrically switchable holographic optical element 502R while the first green and blue bandwidth control signals are applied to the ITO layers of electrically switchable holographic optical elements 502G and 502B, respectively.
  • the first green and blue bandwidth control signals completely deactivate electrically switchable holographic optical elements 502G and 502B, respectively.
  • light 504 constitutes filtered light 114 shown in Figure 2, and the second or updated second red bandwidth control signals are generated by feedback system 110 in order to maintain light 504 (or filtered light 1 14) at the first predetermined intensity.
  • Filter 500 in Figure 5C may also operate in the additive mode to diffract green bandwidth light while substantially transmitting all red and blue bandwidth light in response to receiving the second set of control signals or the new second set of control signals during the second stage of the three stage cycle described above. Additionally, filter 500 of Figure 5C may operate in the additive mode to diffract blue bandwidth light while substantially transmitting all red and green bandwidth light in response to receiving the third set of control signals or the new third set of control signals during the third stage of the three stage cycle described above.
  • FIG. 5D illustrates reflective type filter 500 operating in a subtractive mode.
  • each electrically switchable holographic optical element 502R through 502B is activated.
  • each of electrically switchable holographic optical elements 502R through 502B diffract components of collimated light 1 12.
  • Electrically switchable holographic optical elements 502G and 502B are fully activated in that all or substantially all of the energy contained in the green and blue bandwidth components, respectively, of collimated light 1 12 are diffracted into first order components 510G and 510B, respectively.
  • Electrically switchable holographic optical element 502R is also activated. Electrically switchable holographic optical element 502R diffracts the red bandwidth component of collimated light 1 12 into zero order and first order diffracted components. The first order diffracted red bandwidth light emits from filter 500 as first order diffracted red bandwidth light 510R while the zero order red bandwidth component emits as light 512. If electrically switchable holographic optical elements 502G and 502B operate at maximum theoretical diffraction efficiency, light 512 essentially contains only zero order diffracted red bandwidth light. In the preferred mode, light 512 is used as filtered light 1 14 shown in Figure 1.
  • Filter 500 in Figure 5D is shown diffracting all visible components of collimated light 1 12.
  • This operational mode of filter 500 may result in response to filter 500 receiving the first set of control signals or the new first set of control signals during the first stage of the three stage cycle described above.
  • the magnitudes of the first set of control signals and the new first set of control signals in this mode of operation are distinct from the first set of control signals and the new first set of control signals provided to reflective type filter 500 operating in the additive mode described above.
  • the second or the updated second red bandwidth control signal is applied to the ITO layers of electrically switchable holographic optical element 502R while the first green and blue bandwidth control signals are applied to the ITO layers of electrically switchable holographic optical elements 502G and 502B, respectively.
  • the first green and blue bandwidth control signals completely activate electrically switchable holographic optical elements 502G and 502B, respectively.
  • light 512 constitutes filtered light 114 shown in Figure 1
  • the second or updated second red bandwidth control signals are generated by feedback system 110 in order to maintain light 512 (or filtered light 1 14) at the first predetermined intensity.
  • Filter 500 in Figure 5D may also operate in the subtractive mode to diffract all or substantially all of the red and blue bandwidth components of collimated light 112 into first order diffracted components while diffracting the green bandwidth component of collimated light 112 into zero order and first order diffracted components in response to filter 500 receiving the second set of control signals or the new second set of control signals during the second stage of the three stage cycle described above.
  • filter 500 of Figure 5D may also operate in the subtractive mode to diffract all or substantially all of the red and green bandwidth components of collimated light 112 into first order diffracted components while diffracting the blue bandwidth component of collimated light 112 into zero order and first order diffracted components in response to filter 500 receiving the third set of control signals or the new third set of control signals during the third stage of the three stage cycle described above.
  • Figures 6 and 7 show alternative embodiments of the system shown in Figure 1.
  • deflector 108 of Figure 1 takes form in beam splitter 608.
  • deflector 108 of Figure 1 takes form in prism 708.
  • a beam splitter or prism could also be employed as deflector 108 in the system shown in Figure 2.
  • the deflector would use multilayer coatings to reflect some specified small portion of the incident light.
  • Figures 8 and 9 show alternative embodiments of the illumination system shown in Figure 1 in which deflector 108 takes form in one or more electrically switchable holographic optical elements.
  • the deflector 108 of Figure 1 is embodied in one or more transmissive electrically switchable holographic optical elements 808.
  • the deflector 108 in Figure 1 takes form in one or more reflective electrically switchable holographic optical elements 908.
  • Each of the one or more transmissive or reflective electrically switchable holographic optical elements shown in Figures 8 or 9 may be controlled by feedback system 1 10 properly extended.
  • deflectors 808 and or 908 include three distinct electrically switchable holographic optical elements each one of which is individually operable to diffract one of the red, green, and blue bandwidths of filtered light 1 14 incident thereon.
  • filtered light 114 which is subsequently diffracted by deflector 808 or 908, falls incident on feedback control system 1 10. The remaining components of filtered light 114 that pass through deflector 808 or 908 without substantial alteration emerge therefrom as illumination light 1 16.
  • deflectors 808 and 908 are controlled by feedback system 1 10.
  • the deflectors 808 and 908 shown in Figures 8 and 9 could be employed in similar fashion in the reflective type system shown in Figure 2.
  • Figure 10 shows an alternative embodiment of the system shown in Figure 1 using the filter 500 shown in Figure 5.
  • control circuit 1002 operates filter 500 between a sample mode and an illumination mode. In the illumination mode, control circuit 1002 generates control signals which operate filter 500 in the subtractive mode shown in Figure 5B. In the illumination mode, zero order diffracted light 506 is used as illumination light 116. However, in the sample mode, control circuit 1002 operates filter 500 in the additive mode shown in Figure 5 A. In the sample mode, circuit 1002 samples and compares the intensity of first order diffracted component 504 to one or more predetermined value. A variation in intensity between diffracted component 504 and the one or more predetermined values causes circuit 1002 adjust the control signals provided to filter 500 when filter 500 operates in the illumination mode.
  • the illumination systems described above may have a number of applications. For example, it could be used to control color balance by compensating for color changes arising from light source temperature variation and color shift due to aging.

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  • Crystallography & Structural Chemistry (AREA)
  • Dispersion Chemistry (AREA)
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Abstract

L'invention concerne un système d'éclairage utilisant la rétroaction optique à des fins de maintien d'une sortie d'éclairage prédéterminée. Le système d'éclairage utilise un filtre optique à commande électrique (106) pour filtrer la lumière qui lui est incidente (304). Le détecteur de lumière est en communication de données avec le filtre optique à commande électrique. Une partie ou la totalité de la lumière filtrée par ce filtre optique à commande électrique est détectée par le détecteur de lumière et comparée à une moins des valeurs prédéterminées. Si le signal généré par le détecteur de lumière diffère lors de sa comparaison avec au moins une valeur prédéterminée, on modifie en conséquence une ou plusieurs caractéristiques de filtrage du filtre optique à commande électrique, ce qui modifie à son tour la quantité de lumière filtrée par le filtre optique à commande électrique. On continue à modifier les caractéristiques de filtrage du filtre optique à commande électrique jusqu'à ce que le signal généré par le détecteur de lumière s'apparie sensiblement à une au moins des valeurs prédéterminées.
PCT/US2000/007657 1999-03-23 2000-03-23 Systeme d'eclairage utilisant la retroaction optique Ceased WO2000057217A1 (fr)

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Application Number Priority Date Filing Date Title
EP00916615A EP1082626A1 (fr) 1999-03-23 2000-03-23 Systeme d'eclairage utilisant la retroaction optique
AU37693/00A AU3769300A (en) 1999-03-23 2000-03-23 Illumination system using optical feedback
KR1020007013177A KR20010090432A (ko) 1999-03-23 2000-03-23 광학 피드백을 사용하는 조명 시스템
JP2000607033A JP2002540448A (ja) 1999-03-23 2000-03-23 光学的フィードバックを用いる照明システム

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US12592699P 1999-03-23 1999-03-23
US60/125,926 1999-10-05
CA002326635A CA2326635A1 (fr) 1999-03-23 2000-11-22 Systeme d'eclairage a retroaction optique

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WO2015019035A1 (fr) 2013-08-06 2015-02-12 The Secretary Of State For Defense Filtre à cristaux liquides à rejet adaptable
US11942751B2 (en) 2020-10-23 2024-03-26 Hamamatsu Photonics K.K. Laser device

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US366449A (en) 1887-07-12 Ornamenting window-shades
GB2183331A (en) * 1985-11-21 1987-06-03 Plessey Co Plc Optical sensing arrangements
EP0491429A1 (fr) * 1990-12-19 1992-06-24 Koninklijke Philips Electronics N.V. Dispositif d'affichage par projection
US5684612A (en) * 1993-06-11 1997-11-04 Board Of Trustees Of The Leland Stanford Junior University Method and system for maintaining and controlling the signal-to-noise ratio of hologams recorded in ferroelectric photorefractive materials
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WO2015019035A1 (fr) 2013-08-06 2015-02-12 The Secretary Of State For Defense Filtre à cristaux liquides à rejet adaptable
US11942751B2 (en) 2020-10-23 2024-03-26 Hamamatsu Photonics K.K. Laser device

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JP2002540448A (ja) 2002-11-26
EP1082626A1 (fr) 2001-03-14
CA2326635A1 (fr) 2002-05-22

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