Full color display with gradient index lens array disposed between phosphor emitters and liquid crystal display

• US 5,504,597 A
• Filed: 06/05/1995
• Issued: 04/02/1996
• Est. Priority Date: 06/17/1992
• Status: Expired due to Term

• Current Assignee: Thomson Licensing (Vantiva SA)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Sprague, Robert A., Bruce, Richard H., Silverstein, Louis D.
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): Duong, Tai V.
• Application Number:
  US08/461,221
• Time in Patent Office: 302 Days
• Field of Search: 359/40, 359/69, 359/41, 359/48, 359/50, 359/619, 359/620, 359/626, 385/116, 345/88, 362/32, 313/111, 313/112, 313/117, 313/505, 313/506, 313/510
• US Class Current: 349/57
• CPC Class Codes: G02B 3/0031 Replication or moulding, e.g. hot embossing, UV-casting, injection moulding
• CPC Class Codes: G02B 3/0056 arranged along two different directions in a plane, e.g. honeycomb arrangement of lenses G02B3/0043 takes precedence; miniaturised objectives for electronic devices employing wafer level optics G02B13/0085
• CPC Class Codes: G02B 3/0062 Stacked lens arrays, i.e. refractive surfaces arranged in at least two planes, without structurally separate optical elements in-between
• CPC Class Codes: G02B 3/0087 with index gradient
• CPC Class Codes: G02F 1/133526 Lenses, e.g. microlenses or Fresnel lenses
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell

Abstract

A full color display is disclosed having a high efficiency light source optically coupled by a light coupling lens array to the active matrix of pixel elements of an image forming means such as a transmissive liquid crystal light valve. The light source is comprised of a patterned matrix of individual, primary colored visible radiation emitters, such as individual phosphor elements, arranged in a manner suitable for the human eye to integrate the individual primary colored lights into a single mixture color. The light coupling lens array collects substantially all of the light rays emitted from each primary colored light emitter and focuses them on a respective one of the transparent electrodes in the active matrix, as a real image smaller than the size of the electrode. A suitable light coupling lens array is a gradient index lens array, a multiple layer, two dimensional array of microlenses functionally analogous to an array of strip lenses, or a microlens array. A twisted nematic liquid crystal cell may be used in the image forming means to achieve a high contrast display. Use of the light coupling lens array to collect and focus the light rays from the light source permits the focused light to pass through an entrance polarizer with minimal scattering or divergence, and then through the respective transparent electrode in the active matrix unobscured by the opaque pixel interconnect elements. More efficient use of a larger percentage of the light from the light source in this manner results in the formation of a bright, high contrast, full color image.

Claims

1. A full color display comprising:

light source means having a light emitting surface and having a plurality of individual visible light emitters for providing to the full color display visible light with wavelength emission spectra in at least three primary colors, the plurality of primary color visible light emitters being arranged spatially on the light emitting surface so that light from at least three different primary color visible light emitters forms a mixture color by additive spatial juxtaposition, primary color visible light emitted from the light emitting surface being spatially separated at the light emitting surface;

image forming means for receiving the primary color visible light from the light source means and for forming a full color image, the image forming means having a matrix of individually addressable light modulating pixels, the matrix having modulation means associated with it for modulating the amount of primary color visible light received from the light source means;

light coupling lens array means disposed between the light emitting surface and the image forming means and not abutted against the modulation means, for optically coupling the spatially separated primary color visible light from one of the plurality of primary color visible light emitters to a respective one of the light modulating pixels;

each lens of the light coupling lens array means having optical properties to collect substantially all of the primary color visible light from more than one of the plurality of primary color visible light emitters and to focus a real image thereof in respective light modulating pixels; and

image display means, disposed to receive the full color image from the image forming means, for displaying the full color image in such a manner as to be visible to a human observer.

2. The full color display according to claim 1 wherein the image display means includes light diffusing means for displaying the visible full color image so that a human observer may view the image from on-axis and off-axis viewing angles.

3. The full color display according to claim 1 wherein the light coupling lens array means includes a two dimensional array of light conducting rod lenses, each rod lens having a graded refractive index distribution and having optical properties to collect the primary color visible light from each primary color visible light emitter and to focus each collection of primary color visible light as a real image into the respective pixel of the image forming means.

4. The full color display according to claim 1 wherein the light coupling lens array means includes a two dimensional array of two phase light conducting rod lenses, each rod lens having a graded refractive index distribution and having optical properties to collect the primary color visible light from each primary color visible light emitter and to focus each collection of primary color visible light as a real, noninverted image into the respective pixel of the image forming means.

5. The full color display according to claim 4 wherein the light coupling lens array means further includes a light absorbing shield disposed between the light source means and the two dimensional array of light conducting rod lenses for masking areas between each rod lens to eliminate stray light.

6. The full color display of claim 1,

wherein the image forming means further comprises

a transmissive liquid crystal cell having a pair of transparent substrates for containing a light conducting liquid crystal material;

the matrix of individually addressable light modulating pixels with associated modulation means being disposed on one of the transparent substrates of the liquid crystal cell; and

a voltage source connected to the transparent substrates for providing an electric field across the liquid crystal material;

and wherein the modulation means modulates optical transmission of the primary color visible light through each individually addressable light modulating pixel according to the image to be formed by the liquid crystal cell in response to signals received from the voltage source.

7. The full color display according to claim 1,

wherein the liquid crystal material is a nematic liquid crystal material of a twisted configuration capable of causing a rotation of a polarization plane of the primary color visible light in response to the electric field applied across the nematic liquid crystal material;

and

the image forming means further includes

a first linear polarizer disposed between the light source means and the liquid crystal cell, for polarizing in a first polarization plane the primary color visible light emitted from the light emitting surface before it enters the liquid crystal cell; and

a second linear polarizer disposed on a light emitting side of the liquid crystal cell for controlling optical transmission of the primary color visible light emanating from the liquid crystal cell according to the rotation of the first polarization plane of the light from the cell.

8. A full color transmissive liquid crystal display comprising:

light source means having a light emitting surface and having a plurality of phosphor emitters for providing to the full color display visible light with wavelength emission spectra in at least three primary colors, the plurality of phosphor emitters being arranged spatially on the light emitting surface so that light from at least three different primary color phosphor emitters forms a mixture color by additive spatial juxtaposition, the light source means including excitation means for exciting the phosphor emitters to emit visible light, primary color visible light emitted from the light emitting surface being spatially separated at the light emitting surface;

a transmissive liquid crystal cell, disposed to receive the primary color visible light from the light emitting surface, having a pair of transparent substrates for containing a light conducting liquid crystal material, and including a planar matrix of individually addressable light modulating pixels with associated modulation means disposed on one of the transparent substrates;

a voltage source connected to the transparent substrates for providing an electric field across the liquid crystal material;

wherein the modulation means modulates optical transmission of primary color visible light through each individually addressable light modulating pixel according to the image to be formed by the liquid crystal cell, in response to signals received from the voltage source;

light coupling lens array means for optically coupling the primary color visible light from each of the plurality of phosphor emitters to a respective one of the light modulating pixels, the light coupling lens array means being disposed between the light emitting surface and the transmissive liquid crystal cell and not abutted against the modulation means and each lens of the light coupling lens array means having optical properties to collect substantially all of the primary color visible light from more than one of the phosphor emitters and to couple the spatially separated primary color visible light to the modulation means and to focus a real image thereof in respective light modulating pixels; and

image display means, disposed to receive the full color image from the transmissive liquid crystal cell, for displaying the full color image, the image display means including light diffusing means for displaying the image so that a human observer may view the image from on-axis and off-axis viewing angles.

9. The full color transmissive liquid crystal display according to claim 8,

wherein the liquid crystal material is a nematic liquid crystal material of a twisted configuration capable of causing a rotation of a polarization plane of the primary color visible light in response to the electric field applied across the nematic liquid crystal material;

and further including

a first linear polarizer disposed between the light emitting surface and the liquid crystal cell, for polarizing in a first polarization plane the primary color visible light emitted from the light emitting surface before it enters the liquid crystal cell; and

a second-linear polarizer disposed on a light emitting side of the liquid crystal cell for controlling the optical transmission of the primary color visible light emanating from the liquid crystal cell according to the rotation of the first polarization plane of the light from the cell.

10. The full color liquid crystal display according to claim 9,

wherein the matrix of individually addressable light modulating pixels and the light coupling lens array means are substantially the same size as, and in substantially aligned registration with, the light emitting surface of the light source means so that each pixel of the matrix is in substantially aligned registration with a respective one of the plurality of primary color visible light emitters;

and

wherein the light coupling lens array means has optical properties to collect substantially all of the primary color visible light from each emitter and to focus a real image thereof in the respectively aligned pixel.

11. A full color display comprising

a light source having a light emitting surface and having a plurality of individual visible light emitters, the light source providing to the full color display visible light with wavelength emission spectra in at least three primary colors, the plurality of primary color visible light emitters being arranged spatially on the light emitting surface so that light from at least three different primary color visible light emitters forms a mixture color by additive spatial juxtaposition;

the primary color visible light emitted from the light emitting surface being spatially separated at the light emitting surface;

an image forming device receiving the primary color visible light from the light source and forming a full color image;

the image forming device having a matrix of individually addressable light modulating pixels, the matrix having a modulator associated with it for modulating the amount of primary color visible light received from the light source;

a lens array, disposed between the light emitting surface and the image forming device and not abutted against the modulator, each lens of the lens array optically coupling the spatially separated primary color visible light from more than one of the plurality of primary color visible light emitters to respective light modulating pixels, each lens of the lens array having optical properties to collect substantially all of the primary color visible light from more than one of the plurality of primary color visible light emitters and to focus a real image thereof in respective light modulating pixels; and

a display device, disposed to receive the full color image from the image forming device, the display device displaying the full color image in such a manner as to be visible to a human observer.

12. The full color display according to claim 11 wherein the image display device includes a light diffuser to display the visible full color image so that a human observer may view the image from on-axis and off-axis viewing angles.

13. The full color display according to claim 11 wherein the lens array includes a two dimensional array of light conducting rod lenses, each rod lens having a graded refractive index distribution and having optical properties to collect the primary color visible light from each primary color visible light emitter and to focus each collection of primary color visible light as a real image into the respective pixel of the image forming device.

14. The full color display according to claim 11 wherein the lens array includes a two dimensional array of two phase light conducting rod lenses, each rod lens having a graded refractive index distribution and having optical properties to collect the primary color visible light from each primary color visible light emitter and to focus each collection of primary color visible light as a real, noninverted image into the respective pixel of the image forming device.

15. The full color display according to claim 14 wherein the lens array further includes a light absorbing shield disposed between the light source and the two dimensional array of light conducting rod lenses for masking areas between each rod lens to eliminate stray light.

16. The full color display of claim 11,

wherein the image forming device further comprises

a transmissive liquid crystal cell having a pair of transparent substrates containing a light conducting liquid crystal material;

the matrix of individually addressable light modulating pixels with associated modulator being disposed on one of the transparent substrates of the liquid crystal cell; and

a voltage source connected to the transparent substrates for providing an electric field across the liquid crystal material;

and wherein the modulator modulates optical transmission of the primary color visible light through each individually addressable light modulating pixel according to the image to be formed by the liquid crystal cell in response to signals received from the voltage source.

17. The full color display according to claim 16,

wherein the liquid crystal material is a nematic liquid crystal material of a twisted configuration capable of causing a rotation of a polarization plane of the primary color visible light in response to the electric field applied across the nematic liquid crystal material;

and

the image forming device further includes

a first linear polarizer disposed between the light source and the liquid crystal cell, for polarizing in a first polarization plane the primary color visible light emitted from the light emitting surface before it enters the liquid crystal cell; and

a second linear polarizer disposed on a light emitting side of the liquid crystal cell for controlling optical transmission of the primary color visible light emanating from the liquid crystal cell according to the rotation of the first polarization plane of the light from the cell.

18. A full color transmissive liquid crystal display comprising:

a light source having a light emitting surface and a plurality of phosphor emitters for providing to the full color display visible light with wavelength emission spectra in at least three primary colors, the plurality of phosphor emitters being arranged spatially on the light emitting surface so that light from at least three different primary color phosphor emitters forms a mixture color by additive spatial juxtaposition;

the light source including excitation means for exciting the phosphor emitters to emit visible light;

the primary color visible light emitted from the light emitting surface being spatially separated at the light emitting surface;

a transmissive liquid crystal cell, disposed to receive the primary color visible light from the light emitting surface, having a pair of transparent substrates for containing a light conducting liquid crystal material, and including a planar matrix of individually addressable light modulating pixels with associated modulator disposed on one of the transparent substrates;

a voltage source connected to the transparent substrates for providing an electric field across the liquid crystal material;

wherein the modulator modulates optical transmission of primary color visible light through each individually addressable light modulating pixel according to the image to be formed by the liquid crystal cell, in response to signals received from the voltage source;

a lens array optically coupling the spatially separated primary color visible light from each of the plurality of phosphor emitters to a respective one of the light modulating pixels;

the lens array being disposed between the light emitting surface and the transmissive liquid crystal cell, and not abutted against the modulator, each lens of the lens array having optical properties to collect substantially all of the primary color visible light from more than one of the phosphor emitters and to focus a real image thereof in respective light modulating pixels; and

a image display device, disposed to receive the full color image from the transmissive liquid crystal cell, the image display device displaying the full color image, the image display device, including a light diffuser displaying the image so that a human observer may view the image from on-axis and off-axis viewing angles.

19. The full color transmissive liquid crystal display according to claim 18,

wherein the liquid crystal material is a nematic liquid crystal material of a twisted configuration capable of causing a rotation of a polarization plane of the primary color visible light in response to the electric field applied across the nematic liquid crystal material;

and further including

a first linear polarizer disposed between the light emitting surface and the liquid crystal cell, for polarizing in a first polarization plane the primary color visible light emitted from the light emitting surface before it enters the liquid crystal cell; and

a second linear polarizer disposed on a light emitting side of the liquid crystal cell for controlling the optical transmission of the primary color visible light emanating from the liquid crystal cell according to the rotation of the first polarization plane of the light from the cell.

20. The full color liquid crystal display according to claim 19,

wherein the matrix of individually addressable light modulating pixels and the lens array are substantially the same size as, and in substantially aligned registration with, the light emitting surface of the light source so that each pixel of the matrix is in substantially aligned registration with a respective one of the plurality of primary color visible light emitters;

and

wherein the lens array has optical properties to collect substantially all of the primary color visible light from each emitter and to focus a real image thereof in the respectively aligned pixel.