Optical filter employing holographic optical elements and image generating system incorporating the optical filter
First Claim
1. An apparatus comprising:
- a first holographic optical element having front and back oppositely facing surfaces, wherein the first holographic optical element is switchable between active and inactive states, wherein the first optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the first holographic optical element emerges from the back surface thereof, and wherein the first holographic optical element transmits first bandwidth light incident on the front surface thereof without substantial alteration when operating in the inactive state;
a second holographic optical element having front and back oppositely facing surfaces, wherein the second holographic optical element is switchable between active and inactive states, wherein the second holographic optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the second holographic optical element emerges from the back surface thereof, and wherein the second holographic optical element transmits first bandwidth light without substantial alteration when operating in the inactive state;
a display device coupled to an image signal processor, wherein the display device is configured to display a monochrome image frame in response to receiving a frame of image signals generated by the image signal processor;
wherein the display device is configured to be illuminated directly or indirectly with diffracted first bandwidth emitted from the first and second holographic optical elements;
wherein the first and second holographic optical elements are positioned adjacent each other;
wherein the front surfaces of the first and second holographic optical elements are aligned orthogonal to a common axis so that the back surface of the first holographic optical element faces the front surface of the second holographic optical element.
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Abstract
The present invention relates to a solid state filter used in sequentially illuminating an image display, directly or indirectly, with first, second, and third bandwidth light. The solid state filter includes at least one hologram that is switchable between active and inactive states. While in the active state, the at least one switchable hologram diffracts a first bandwidth light. In contrast, the switchable hologram transmits the first bandwidth light without substantial alteration when operating in the inactive state. In one embodiment, the diffracted first bandwidth light is used to illuminate a monochrome image presented on a display device. In another embodiment, the transmitted first bandwidth light is used to illuminate the monochrome image presented on the image display.
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Citations
32 Claims
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1. An apparatus comprising:
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a first holographic optical element having front and back oppositely facing surfaces, wherein the first holographic optical element is switchable between active and inactive states, wherein the first optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the first holographic optical element emerges from the back surface thereof, and wherein the first holographic optical element transmits first bandwidth light incident on the front surface thereof without substantial alteration when operating in the inactive state;
a second holographic optical element having front and back oppositely facing surfaces, wherein the second holographic optical element is switchable between active and inactive states, wherein the second holographic optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the second holographic optical element emerges from the back surface thereof, and wherein the second holographic optical element transmits first bandwidth light without substantial alteration when operating in the inactive state;
a display device coupled to an image signal processor, wherein the display device is configured to display a monochrome image frame in response to receiving a frame of image signals generated by the image signal processor;
wherein the display device is configured to be illuminated directly or indirectly with diffracted first bandwidth emitted from the first and second holographic optical elements;
wherein the first and second holographic optical elements are positioned adjacent each other;
wherein the front surfaces of the first and second holographic optical elements are aligned orthogonal to a common axis so that the back surface of the first holographic optical element faces the front surface of the second holographic optical element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
a light source for generating incoherent light;
a light condenser positioned adjacent the light source and configured to condense incoherent light generated by the light source into a parallel beam of incoherent light;
wherein the front surface of the first holographic optical element is configured to receive the parallel beam of incoherent light.
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11. The apparatus of claim 1 further comprising:
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a light source for generating incoherent light;
a light condenser positioned adjacent the light source and configured to condense the incoherent light generated by the light source into a parallel beam of incoherent light;
a beam splitting cube positioned adjacent the condenser and the second holographic optical element, wherein the beam splitting cube is configured to receive and split the parallel beam of incoherent light into first and second parallel beams of light, wherein the first and second parallel beams of light are contained in orthogonal planes of polarization, wherein the beam splitting cube is configured to deflect the second parallel beam of light onto the front surface of the second holographic optical element, and wherein the beam splitting cube is configured to pass the first parallel beam of light without substantial deflection;
a total internal reflection prism positioned adjacent the beam splitting cube and the polarization rotation device, wherein the total internal reflection prism is configured to receive the first parallel beam of light, wherein the total internal reflection prism is configured to deflect received first parallel light onto the polarization rotation device.
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12. The apparatus of claim 1 wherein the first holographic optical element is formed from polymer dispersed liquid crystal material.
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13. The apparatus of claim 1 wherein the second holographic optical element is formed from polymer dispersed liquid crystal material.
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14. The apparatus of claim 1 wherein the first and second holographic optical elements are formed from polymer dispersed liquid crystal material which undergoes phase separation during a hologram recording process to create regions populated by liquid crystal droplets and to create regions of clear photopolymer interspersed by regions populated by liquid crystal droplets.
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15. The apparatus of claim 1 wherein each of the first and second holographic optical elements comprises a volume phase hologram recorded in a holographic recording medium.
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16. The apparatus of claim 1 further comprising a control circuit and a voltage source, wherein the control circuit is configured to selectively couple the voltage source to the first and second holographic optical elements, wherein the first and second holographic optical elements operate in the inactive state when coupled to the voltage source, and wherein the first and second holographic optical elements operate in the active state when coupled to the voltage source.
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17. The apparatus of claim 1 wherein the first holographic optical element comprises a layer of material that records a hologram and at least one layer of electrically conductive material positioned adjacent the layer of material that records the hologram.
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18. The apparatus of claim 1 wherein the first holographic optical element comprises a layer of material that records a hologram and a pair of layers of electrically conductive material, wherein the layer of material that records the hologram is contained between the pair of layers of electrically conductive material.
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19. The apparatus of claim 1 wherein the second holographic optical element comprises a layer of material that records a hologram and at least one layer of electrically conductive material positioned adjacent the layer of material that records the hologram.
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20. The apparatus of claim 3 wherein each of the first and second holographic optical elements comprises a layer of material that records a hologram, and wherein the layers of material that record holograms are contained between a pair of layers of electrically conductive material.
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21. The apparatus of claim 17 further comprising a control circuit and a voltage source, wherein the control circuit is configured to selectively couple the at least one layer of electrically conductive material to the voltage source.
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22. The apparatus of claim 13 further comprising a control circuit and a voltage source, wherein the control circuit is configured to selectively couple the at least one layer of electrically conductive material to the voltage source.
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23. The apparatus of claim 17 wherein the at least one layer of electrically conductive material comprises indium tin oxide (ITO).
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24. The apparatus of claim 13 wherein the at least one layer of electrically conductive material comprises indium tin oxide (ITO).
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25. The apparatus of claim 17 wherein the at least one layer of electrically conductive material is configured to be selectively coupled to a voltage source, wherein the first holographic optical element operates in the inactive state when the at least one layer of electrically conductive material of the first holographic optical element is coupled to the voltage source, and wherein the first holographic optical element operates in the active state when the at least one layer of electrically conductive material of the first holographic optical element is not coupled to the voltage source.
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26. The apparatus of claim 13 wherein the at least one layer of electrically conductive material is configured to be selectively coupled to a voltage source, wherein the second holographic optical element operates in the inactive state when the at least one layer of electrically conductive material of the second holographic optical element is coupled to the voltage source, and wherein the second holographic optical element operates in the active state when the at least one layer of electrically conductive material of the second holographic optical element is not coupled to the voltage source.
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27. The apparatus of claim 1 further comprising:
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a light source for generating incoherent light;
a light condenser positioned adjacent the light source and configured to condense incoherent light generated by the light source into a parallel beam of incoherent light;
a prism positioned adjacent the light condenser and the front surface of the first holographic optical element, wherein the prism is configured to deflect the parallel beam of incoherent light onto the front surface of the first holographic optical element.
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28. The apparatus of claim 1 wherein the first holographic optical element comprises a holographic recording medium that records the hologram, wherein the holographic recording medium comprises:
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a monomer dipentaerythritol hydroxypentaacrylate;
a liquid crystal;
a cross-linking monomer;
a coinitiator; and
a photoinitiator dye.
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29. The apparatus of claim 1 wherein the first holographic optical element comprises a hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material, the polymer-dispersed liquid crystal material comprising, before exposure:
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(a) a polymerizable monomer;
(b) a liquid crystal;
(c) a cross-linking monomer;
(d) a coinitiator; and
(e) a photoinitiator dye.
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30. An apparatus comprising:
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a first holographic optical element having front and back oppositely facing surfaces, wherein the first holographic optical element is switchable between active and inactive states, wherein the first optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the first holographic optical element emerges from the front surface thereof, and wherein the first holographic optical element transmits first bandwidth light incident on the front surface thereof without substantial alteration when operating in the inactive state;
a second holographic optical element having front and back oppositely facing surfaces, wherein the second holographic optical element is switchable between active and inactive states, wherein the second holographic optical element diffracts first bandwidth light incident on the front surface thereof when operating in the active state, wherein first bandwidth light diffracted by the second holographic optical element emerges from the front surface thereof, and wherein the second holographic optical element transmits first bandwidth light without substantial alteration when operating in the inactive state;
a display device coupled to an image signal processor, wherein the display device is configured to display a monochrome image frame in response to receiving a frame of image signals generated by the image signal processor;
wherein the display device is configured to be illuminated directly or indirectly with diffracted first bandwidth emitted from the first and second holographic optical elements;
wherein the first and second holographic optical elements are positioned adjacent each other. - View Dependent Claims (31, 32)
a monomer dipentaerythritol hydroxypentaacrylate;
a liquid crystal;
a cross-linking monomer;
a coinitiator; and
a photoinitiator dye.
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32. The apparatus of claim 30 wherein the first holographic optical element comprises a hologram made by exposing an interference pattern inside a polymer-dispersed liquid crystal material, the polymer-dispersed liquid crystal material comprising, before exposure:
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(a) a polymerizable monomer;
(b) a liquid crystal;
(c) a cross-linking monomer;
(d) a coinitiator; and
(e) a photoinitiator dye.
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Specification