Laser projection display system

• US 6,577,429 B1
• Filed: 01/15/2002
• Issued: 06/10/2003
• Est. Priority Date: 01/15/2002
• Status: Expired due to Term

• Current Assignee: IMAX Theatres International Limited (IMAX Corporation)
• Original Assignee: Eastman Kodak Company
• Inventors: Kurtz, Andrew F., Ramanujan, Sujatha, Kruschwitz, Brian E.
• Primary Examiner(s): Ben, Loha
• Application Number:
  US10/050,003
• Time in Patent Office: 511 Days
• Field of Search: 359/231, 359/245, 359/237, 359/238, 359/279, 359/310, 359/316, 359/291, 359/558, 359/559, 359/618, 359/621, 359/622, 359/712, 353/31, 353/33, 353/84, 353/122, 347/239, 347/255, 348/750, 348/756, 355/53, 355/67, 362/268
• US Class Current: 359/279
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: H04N 9/3132 using one-dimensional electronic spatial light modulators

Abstract

A display apparatus includes a laser light source for emitting a light beam having a coherence length; a beam expander for expanding the light beam; a spatial light modulator; beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator, the beam shaping optics including a fly'"'"'s eye integrator having an array of lenslets; a diffuser located in the light beam between the laser light source and the beam shaping optics; an electrically controllable de-speckling modulator for modifying the temporal and spatial phase of the light beam; and a projection lens for producing an image of the spatial light modulator on a distant screen.

Claims

1. A display apparatus, comprising:

a) a laser light source for emitting a light beam having a coherence length;

b) a beam expander for expanding the light beam;

c) a spatial light modulator;

d) beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator, the beam shaping optics including a fly'"'"'s eye integrator having an array of lenslets;

e) a diffuser located in the light beam between the laser light source and the beam shaping optics;

f) an electrically controllable de-speckling modulator for modifying the temporal and spatial phase of the light beam; and

g) a projection lens for producing an image of the spatial light modulator on a distant screen.

2. The display apparatus claimed in claim 1, wherein the electrically controllable de-speckling modulator comprises a bulk electro-optic substrate and a series of modulator sites, wherein each modulator imparts controlled phase delays to the beam of light passing through each of said modulator sites.

3. The display apparatus claimed in claim 2, wherein the controlled phase delays are randomly time variant.

4. The display apparatus claimed in claim 2, wherein the modulator sites are defined by patterned electrodes on a surface of the substrate.

5. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are small relative to the coherence length of the laser light source;

the number of modulator sites is much larger than the number of lenslets; and

the de-speckling modulator is located in a far field of an imaged plane within the illumination system, or in one of its conjugates.

6. The display apparatus claimed in claim 5, wherein the beam shaping optics includes a pair of fly'"'"'s eye lenslet arrays and the de-speckling modulator is located between the fly'"'"'s eye lenslet arrays, such that the de-speckling modulator is located in a far field of the illumination plane conjugate to the image plane where the spatial light modulator resides.

7. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are small relative to the coherence length of the laser light source;

the number of modulator sites is much larger than the number of lenslets; and

the de-speckling modulator is located within the near field of an imaged plane within the illumination system, or in one of its conjugates.

8. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are on the same order as the coherence length of the laser light source, and the de-speckling modulator is located between the diffuser and the beam shaping optics.

9. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are on the same order as the coherence length of the laser light source, the beam shaping comprises a pair of fly'"'"'s eye lenslet arrays and the de-speckling modulator is located between the fly'"'"'s eye lenslet arrays.

10. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are on the same order as the coherence length of the laser light source, the beam shaping optics includes a fly'"'"'s eye integrator with a pair of lenslet arrays each consisting of a number of lenslets, and the de-speckling modulator has a number of modulator sites which are greater than the number of lenslets of the first lenslet array, such that the phase delays alter the temporal and spatial coherence of the beam of light passing through each lenslet of a lenslet array without diffusing or scattering light.

11. The display apparatus claimed in claim 2, wherein phase delays introduced by the de-speckling modulator are on the same order as the coherence length of the laser light source, the beam shaping optics includes a fly'"'"'s eye integrator with a first lenslet array and second lenslet array, and the de-speckling modulator has a number of modulator sites which is much greater than the number of lenslets of the first lenslet array, such that light is diffused or scattered, and the de-speckling modulator is located within the near field of the first lenslet array, which is image conjugate to the spatial light modulator.

12. The display apparatus claimed in claim 1, wherein the de-speckling modulator is adapted to operate on a plurality of wavelengths of light simultaneously.

13. The display apparatus claimed in claim 1, wherein the de-speckling modulator introduces phase delays from a spatial arrangement of modulator sites, relative to the extent of the beam of light passing through the modulator sites, such that the imaging wavefronts within the beam of light are altered in a spatially variant manner.

14. The display apparatus claimed in claim 1, wherein the de-speckling modulator has modulator sites which define different regions of the beam of light passing through the modulator sites, the de-speckling modulator introduces phase delays from the spatial arrangement of modulator sites, such that the temporal coherence is temporally and spatially variable amongst the regions.

15. The display apparatus claimed in claim 14, wherein the beam shaping optics includes a fly'"'"'s eye integrator with a pair of lenslet arrays, and the number of modulator sites is larger than the number of lenslets in a lenslet array.

16. The display apparatus claimed in claim 1, where the beam expander comprises an array of partially reflecting mirrors to split the light beam into N beamlets, wherein adjacent beamlets propagate paths through the array of partially reflecting mirrors that differ by an amount on the order of the coherence length;

and where the beam shaping optics modify the N beamlets to provide uniform illumination of the spatial light modulator.

17. The display apparatus claimed in claim 16, wherein the de-speckling modulator introduces phase delays from a spatial arrangement of modulator sites, relative to the extent of the beam of light passing through the modulator sites, such that the imaging wavefronts within the beam of light are altered in a spatially variant manner.

18. The display apparatus claimed in claim 16, wherein the de-speckling modulator has modulator sites which define different regions of the beam of light passing through the modulator sites, the de-speckling modulator introduces phase delays from the spatial arrangement of modulator sites, such that the temporal coherence is temporally and spatially variable amongst the regions.

19. The display apparatus claimed in claim 1, where the spatial light modulator is a liquid crystal display.

20. The display apparatus claimed in claim 1, where the spatial light modulator is an electro-mechanical mirror array.

21. Display apparatus, comprising:

a) a laser light source for emitting a light beam;

b) a beam expander for expanding the light beam;

c) a linear spatial light modulator;

d) beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator, the beam shaping optics including a fly'"'"'s eye integrator having an array of lenslets;

e) an electrically controllable de-speckling modulator for modifying the temporal and spatial phase of the light beam; and

f) a projection lens and a scanning means for producing a two dimensional image on a distant screen.

22. Display apparatus according to claim 21, including a diffuser located in the light beam between the laser light source and the beam shaping optics.

23. Display apparatus according to claim 22, wherein the diffuser is a one-dimensional diffuser, providing light diffusion along the long axis of the linear spatial light modulator.

24. Display apparatus according to claim 22, wherein the spatial light modulator is an electro-optical diffraction grating.

25. Display apparatus claimed in claim 21, wherein the de-speckling modulator comprises a bulk electro-optic substrate and a series of modulator sites, wherein each modulator imparts controlled phase delays to the beam of light passing through each of said modulator sites.

26. Display apparatus claimed in claim 25, wherein the controlled phase delays are randomly time variant.

27. Display apparatus claimed in claim 21, wherein the de-speckling modulator introduces phase delays from a spatial arrangement of modulator sites, relative to the extent of the beam of light passing through the modulator sites, such that the imaging wavefronts within the beam of light are altered in a spatially variant manner.

28. Display apparatus claimed in claim 21, wherein the de-speckling modulator has modulator sites which define different regions of the beam of light passing through the modulator sites, the de-speckling modulator introduces phase delays from the spatial arrangement of modulator sites, such that the temporal coherence is temporally and spatially variable amongst the regions.

29. Display apparatus claimed in claim 28, wherein the beam shaping optics includes a fly'"'"'s eye integrator with a pair of lenslet arrays, and the number of modulator sites is larger than the number of lenslets in a lenslet array.

30. Display apparatus claimed in claim 21, where the beam expander comprises an array of partially reflecting mirrors to split the light beam into N beamlets, wherein adjacent beamlets propagate paths through the array of partially reflecting mirrors that differ by an amount on the order of the coherence length;

and where the beam shaping optics modify the N beamlets to provide uniform illumination of the spatial light modulator.

31. Display apparatus according to claim 21, wherein the spatial light modulator is an electro-mechanical diffraction grating.

32. Display apparatus, comprising:

a) a laser light source for emitting a light beam;

b) a beam expander for expanding the light beam;

c) a spatial light modulator;

d) beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator, the beam shaping optics including a beam homogenizer to provide uniform illumination of the spatial light modulator;

e) a diffuser located in the light beam between the laser light source and the beam shaping optics;

f) an electrically controllable de-speckling modulator to modify the temporal and spatial phase of the light beam; and

g) a projection lens for producing an image of the spatial light modulator on a distant screen.

33. The display apparatus claimed in claim 32, wherein the controlled phase delays are randomly time variant.

34. The display apparatus claimed in claim 32, wherein the de-speckling modulator introduces phase delays from a spatial arrangement of modulator sites, relative to the extent of the beam of light passing through the modulator sites, such that the imaging wavefronts within the beam of light are altered in a spatially variant manner.

35. The display apparatus claimed in claim 32, wherein the de-speckling modulator has modulator sites which define different regions of the beam of light passing through the modulator sites, the de-speckling modulator introduces phase delays from the spatial arrangement of modulator sites, such that the temporal coherence is temporally and spatially variable amongst the regions.

36. The display apparatus claimed in claim 32, where the beam expander comprises an array of partially reflecting mirrors to split the light beam into N beamlets, wherein adjacent beamlets propagate paths through the array of partially reflecting mirrors that differ by an amount on the order of the coherence length, and where the beam shaping optics modify the N beamlets to provide uniform illumination of the spatial light modulator.

37. A method of displaying an image, comprising the steps of:

a) providing a laser projector having;

i) a laser light source for emitting a light beam;

ii) a beam expander for expanding the light beam;

iii) a spatial light modulator;

iv) beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator; and

v) a diffuser located in the light beam between the laser light source and the beam shaping optics;

b) locating an electrically controllable de-speckling modulator in the light beam; and

c) projecting an image on a screen with the laser projector, while operating the de-speckling modulator to modify the temporal and spatial phase of the light beam, thereby reducing the visibility of speckle in the projected image.

38. The display method in claim 37, wherein the temporal and spatial phase changes are imparted to the light beam in a randomly controlled time variant manner.

39. The display method claimed in claim 37, wherein the de-speckling modulator is operated as an analog voltage driven modulator.

40. The display method claimed in claim 37, wherein the de-speckling modulator is operated as a pulse width modulated device.

41. The display method claimed in claim 37, wherein the de-speckling modulator includes an electro-optic substrate having top and bottom electrodes that define modulator sites to which voltages are applied in accordance to control signals.

42. The display method claimed in claim 37, wherein the spatial light modulator comprises a linear array of modulator pixels, and the display method further comprises a scanning means for providing a two dimensional image.

43. The display method claimed in claim 37, wherein the beam shaping optics includes a fly'"'"'s eye integrator comprising at least one array of lenslets.

44. A method of displaying an image, comprising the steps of:

a) providing a laser projector having;

i) a laser light source for emitting a light beam;

ii) a beam expander for expanding the light beam;

iii) a spatial light modulator; and

iv) beam shaping optics for shaping the expanded laser beam to provide uniform illumination of the spatial light modulator;

b) locating an electrically controllable de-speckling modulator in the light beam; and

c) projecting an image on a screen with the laser projector, while operating the de-speckling modulator to modify the temporal and spatial phase of the light beam, thereby reducing the visibility of speckle in the projected image.