Method for enhanced bit depth in an imaging apparatus using a spatial light modulator

• US 6,574,043 B2
• Filed: 11/07/2001
• Issued: 06/03/2003
• Est. Priority Date: 11/07/2001
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Ramanujan, Sujatha
• Primary Examiner(s): Lester, Evelyn
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US10/045,216
• Publication Number:
  US 20030086166A1
• Time in Patent Office: 573 Days
• Field of Search: 359/237, 359/238, 359/276, 359/290, 359/291, 359/298, 359/462, 359/464, 359/466, 359/618, 359/245, 359/634, 359/637, 359/487, 359/29, 349/25, 349/174, 345/97, 345/58, 345/94, 345/99, 345/89, 345/95, 345/208, 345/210, 353/20, 353/31, 353/33, 353/34, 353/37, 353/7, 353/10, 355/22, 355/32, 382/274, 347/239
• US Class Current: 359/464
• CPC Class Codes: B41J 2/465 using masks, e.g. light-switching masks
• CPC Class Codes: G06K 15/02 using printers
• CPC Class Codes: G06K 15/1849 using an intermediate representation, e.g. a list of graphical primitives
• CPC Class Codes: G06K 15/1851 parted in a plurality of segments per page

Abstract

A method for increasing the number of intensity levels available on one or more color channels in an imaging apparatus (10) using a spatial light modulator (22). Multiple LUTs (52) are loaded into the imaging data path as data is directed to multiple spatial light modulators (22), wherein each spatial light modulator (22) has a separate bias voltage setting. In an alternate embodiment a single spatial light modulator (22) can be used with multiple LUTs (52) and with a changed bias voltage setting appropriate for use with each LUT (52).

Claims

1. A method for enhancing bit depth in an imaging apparatus using a spatial light modulator comprising:

applying a first bias voltage to said spatial light modulator;

mapping a set of first input image data values to a first look-up table to provide a first set of input codes values to said spatial light modulator;

modulating an incident light beam at said spatial light modulator according to said first set of input code values;

applying a second bias voltage to said spatial light modulator;

mapping a second set of input image data values to a second look-up table to provide a second set of input code values; and

modulating said incident light beam at said spatial light modulator according to said second set of input code values.

2. In an imaging apparatus using a spatial light modulator for forming a first image from input image data values wherein said spatial light modulator, at a predetermined bias voltage setting, is capable of providing, at each output pixel in said first image, for any one of n input code values, any one of n corresponding output intensity levels, a method of forming a second image having an increased number of output intensity levels m for a group of input data values, where m>

n, the method comprising the following sequence;

(a) applying a first bias voltage to said spatial light modulator,

(b) mapping each input image data value in said group of said input image data values to a corresponding first input code value obtained from a first look-up table, wherein said first input code value is selected from a first set containing up to n input code values, and providing each said first input code value to the spatial light modulator;

(c) modulating an incident light beam at the spatial light modulator according to each said first input code value in order to form a first array of output image pixels, wherein said intensity of each output image pixel in said first array of output image pixels is conditioned by each said first input code value;

(d) applying a second bias voltage to the spatial light modulator;

(e) mapping each input image data value in said group of said input image data values to a corresponding second input code value obtained from a second look-up table, wherein said second input code value is selected from a second set containing up to n input code values, wherein said second set contains at least one input code value that is not in said first set, and providing each said second input code value to the spatial light modulator; and

(f) modulating said incident light beam at said spatial light modulator according to each said second input code value in order to form a second array of output image pixels, wherein said intensity of each output image pixel in said second array of output image pixels is conditioned by each said second input code value.

3. The method of claim 2 further comprising the step of directing said first array of said output image pixels towards a photosensitive medium.

4. The method of claim 3 wherein said imaging apparatus detects the type of said photosensitive medium.

5. The method of claim 4 wherein said step of applying said first bias voltage is conditioned by the type of said photosensitive medium.

6. The method of claim 4 wherein said step of applying said second bias voltage is conditioned by the type of said photosensitive medium.

7. The method of claim 4 wherein said step of mapping each input image data value to a corresponding first input code value is conditioned by the type of said photosensitive medium.

8. The method of claim 4 wherein said step of mapping each inputs image data value to a corresponding second input code value is conditioned by the type of said photosensitive medium.

9. The method of claim 2 further comprising the step of projecting said first array of said output image pixels towards a display surface.

10. The method of claim 2 wherein said group of input image data values comprises a frame.

11. The method of claim 2 wherein said input image data value comprises data that conditions said first look-up table.

12. The method of claim 2 wherein said spatial light modulator forms an array of said output image pixels by selectively reflecting portions of said incident light beam.

13. The method of claim 2 wherein said spatial light modulator forms an array of said output image pixels by selectively transmitting portions of said incident light beam.

14. The method of claim 2 wherein the step of applying said first bias voltage to the spatial light modulator comprises the step of applying a first bias voltage to an LCD.

15. The method of claim 2 wherein the step of applying said first bias voltage to the spatial light modulator comprises the step of applying a first bias voltage to a digital micromirror device.

16. In an imaging apparatus using a spatial light modulator to provide one or more image frames, wherein said spatial light modulator has a bit depth range limited to a number n bits, a method of increasing said bit depth range to a number m bits, where m>

n, the method comprising;

(a) generating, for each input image data value, a first look-up table for mapping said each input image data value to a first code value using the steps of;

(a1) applying a first bias voltage to said spatial light modulator;

(a2) iteratively providing each of n first code values as input to said spatial light modulator, measuring a first light intensity at each of n first code values, and, based on said light intensity, correlating said each of n first code values to each of said image data values;

(b) generating, for each input image data value, a second look-up table for mapping said each input image data value to a second code value using the steps of;

(b1) applying a second bias voltage to said spatial light modulator;

(b2) iteratively providing each of n second code values as input to said spatial light modulator, measuring a second light intensity at each of n second code values, and, based on said light intensity, correlating said each of n second code values to each of said image data values; and

(c) successively repeating the following sequence of steps for each successive image frame;

(c1) correlating each input image data value in said each successive image frame to a corresponding said first code value from said first look-up table to create a first set of said code values;

(c2) with said first bias voltage applied to the spatial light modulator, providing said first set of said code values to the spatial light modulator;

(c3) correlating each input image data value in said each successive image frame to a corresponding said second code value from said second look-up table to create a second set of said code values;

(c4) with said second bias voltage applied to the spatial light modulator, providing said second set of said code values to the spatial light modulator.

17. The method of claim 16 wherein the step of applying said first bias voltage to said spatial light modulator comprises the step of applying a first bias voltage to an LCD.

18. The method of claim 16 wherein the step of applying said first bias voltage to said spatial light modulator comprises the step of applying a first bias voltage to a digital micromirror device.

19. In an imaging apparatus using, in a color channel, a first and a second spatial light modulator to modulate an incident light beam in order to form an image-bearing modulated beam according to a frame of input image data values, a method for increasing the number of intensity levels within said image-bearing modulated beam, the method comprising:

(a) for said first spatial light modulator, generating a first look-up table that correlates each input image data value in said frame to a corresponding first code value;

(b) for said second spatial light modulator, generating a second look-up table that correlates each input image data value in said frame to a corresponding second code value, wherein the set of said second code values in said second look-up table is not identical with the set of said first code values in said first look-up table;

(c) using said first look-up table, forming a first set of code values for modulating said first spatial light modulator by assigning, to each input image data value in said frame, one of said corresponding first code values from said first look-up table;

(d) using said second look-up table, forming a second set of code values for modulating said second spatial light modulator by assigning, to each input image data value in said frame, one of said corresponding second code values from said second look-up table;

(e) modulating said incident light beam at said first spatial light modulator according to said first set of code values; and

(f) modulating said incident light beam at said second spatial light modulator according to said second set of code values.

20. The method of claim 19 wherein the step of modulating said incident light beam at said first spatial light modulator comprises the step of applying a first bias voltage to said spatial light modulator.

21. The method of claim 20 wherein the step of applying a second bias voltage is conditioned by information about a photosensitive medium loaded in the imaging apparatus.

22. The method of claim 19 wherein the step of applying a first bias voltage is conditioned by information about a photosensitive medium loaded in the imaging apparatus.

23. The method of claim 19 wherein the step of modulating said incident light beam at said second spatial light modulator comprises the step of applying a second bias voltage to said spatial light modulator.

24. The method of claim 19 wherein the step of modulating said incident light beam at said first spatial light modulator comprises the step of modulating said incident light beam at an LCD.

25. The method of claim 19 wherein the step of modulating said incident light beam at said second spatial light modulator comprises the step of modulating said incident light beam at an LCD.

26. A method for providing increased light intensity levels in a stereoscopic display wherein a left spatial light modulator generates a left eye image and a right spatial light modulator generates a right eye image, the method comprising:

(a) providing the left-eye image by;

(a1) applying a first bias voltage to said left spatial light modulator and maintaining a first look-up table for mapping input image data values to input code values for said left spatial light modulator;

(a2) providing, from said first look-up table, for each input image data value in a left frame, a corresponding first input code value;

(a3) providing a left incident light beam to said left spatial light modulator for forming a first array of said left output image pixels, the intensity of each said left output image pixel conditioned by each said first input code value;

(a4) applying a second bias voltage to said left spatial light modulator and maintaining a second look-up table for mapping input image data values to input code values for said left spatial light modulator;

(a5) providing, from said second look-up table, for each input image data value in said left frame, a corresponding second input code value;

(a6) providing said left incident light beam to said left spatial light modulator for forming a second array of said left output image pixels, the intensity of each said left output image pixel conditioned by each said second input code value;

(b) providing the right-eye image by;

(b1) applying a third bias voltage to said right spatial light modulator and maintaining a third look-up table for mapping input image data values to input code values for said right spatial light modulator,

(b2) providing, from said third look-up table, for each input image data value in a right frame, a corresponding third input code value;

(b3) providing a right incident light beam to said right spatial light modulator for forming a third array of said right output image pixels, the intensity of each said right output image pixel conditioned by each said third input code value;

(b4) applying a fourth bias voltage to said right spatial light modulator and maintaining a fourth look-up table for mapping input image data values to input code values for said right spatial light modulator;

(b5) providing, from said fourth look-up table, for each input image data value in said right frame, a corresponding fourth input code value;

(b6) providing said right incident light beam to said right spatial light modulator for forming a fourth array of said right output image pixels, the intensity of each said right output image pixel conditioned by each said fourth input code value.

27. An image forming apparatus for forming, from an incident beam in at least one color channel, according to input image data, an image-bearing modulated beam comprising a frame of image pixels, wherein each image pixel has a predetermined intensity, the apparatus comprising:

(a) a light source for providing said incident beam on said at least one color channel;

(b) a first look-up table for assigning a first input code value to each input image data value in said frame;

(c) a first spatial light modulator for modulating said incident light beam to form a first modulated beam according to each said first input code value;

(d) a second look-up table for assigning a second input code value to each input image data value in said frame;

(e) a second spatial light modulator for modulating said incident light beam to form a second modulated beam according to each said second input code value; and

(f) a beam combining element for combining said first modulated beam and said second modulated beam to form said image-bearing modulated beam.

28. The apparatus of claim 27 wherein said light source comprises a filter.

29. The apparatus of claim 27 wherein said light source comprises at least one LED.

30. The apparatus of claim 27 wherein said light source comprises at least one laser.

31. The apparatus of claim 27 wherein said beam-combining element comprises a polarizing beamsplitter.

32. The apparatus of claim 27 wherein said first spatial light modulator is a digital micromirror.

33. The apparatus of claim 27 wherein said second spatial light modulator is a digital micromirror.

34. The apparatus of claim 27 wherein said first spatial light modulator is a liquid crystal device.

35. The apparatus of claim 34 wherein said liquid crystal device is reflective.

36. The apparatus of claim 34 wherein said liquid crystal device is transmissive.

37. The apparatus of claim 27 wherein said second spatial light modulator is a liquid crystal device.

38. The apparatus of claim 37 wherein said liquid crystal device is reflective.

39. The apparatus of claim 37 wherein said liquid crystal device is transmissive.

40. A stereoscopic imaging apparatus for forming a left-eye and a right-eye image according to input image data in a left frame and input image data in a right frame, the apparatus comprising:

(a) a left optical system for providing a left-eye image-bearing modulated beam, comprising;

(a1) a first light source for providing an incident beam on at least one color channel;

(a2) a first look-up table for assigning a first input code value to each input image data value in said left frame;

(a3) a first spatial light modulator for modulating said incident light beam to form a first modulated beam according to each said first input code value;

(a4) a second look-up table for assigning a second input code value to each input image data value in said left frame;

(a5) a second spatial light modulator for modulating said incident light beam to form a second modulated beam according to each said second input code value;

(a6) a left beam combining element for combining said first modulated beam and said second modulated beam to form said left-eye image-bearing modulated beam;

(b) a right optical system for providing a right-eye image-bearing modulated beam, comprising;

(b1) a second light source for providing an incident beam on at least one color channel;

(b2) a third look-up table for assigning a third input code value to each input image data value in said right frame;

(b3) a third spatial light modulator for modulating said incident light beam to form a third modulated beam according to said third input code value;

(b4) a fourth look-up table for assigning a fourth input code value to each input image data value in said right frame;

(b5) a fourth spatial light modulator for modulating said incident light beam to form a fourth modulated beam according to said fourth input code value; and

(c) a second beam combining element for combining said third modulated beam and said fourth modulated beam to form said right-eye image-bearing modulated beam.

41. The apparatus of claim 40 wherein said first light source comprises a filter.

42. The apparatus of claim 40 wherein said second light source comprises a filter.

43. The apparatus of claim 40 wherein said first light source comprises at least one LED.

44. The apparatus of claim 40 wherein said second light source comprises at least one LED.

45. The apparatus of claim 40 wherein said first light source comprises at least one laser.

46. The apparatus of claim 40 wherein said second light source comprises at least one laser.

47. The apparatus of claim 40 wherein said first beam-combining element comprises a polarizing beamsplitter.

48. The apparatus of claim 40 wherein said second beam-combining element comprises a polarizing beamsplitter.

49. The apparatus of claim 40 wherein said first spatial light modulator is a digital micromirror device.

50. The apparatus of claim 40 wherein said second spatial light modulator is a digital micromirror device.

51. The apparatus of claim 40 wherein said third spatial light modulator is a digital micromirror device.

52. The apparatus of claim 40 wherein said fourth spatial light modulator is a digital micromirror device.

53. The apparatus of claim 40 wherein said first spatial light modulator is a liquid crystal device.

54. The apparatus of claim 53 wherein said first spatial light modulator is reflective.

55. The apparatus of claim 53 wherein said first spatial light modulator is transmissive.

56. The apparatus of claim 40 wherein said second spatial light modulator is a liquid crystal device.

57. The apparatus of claim 56 wherein said second spatial light modulator is reflective.

58. The apparatus of claim 56 wherein said second spatial light modulator is transmissive.

59. The apparatus of claim 40 wherein said third spatial light modulator is a liquid crystal device.

60. The apparatus of claim 59 herein said third spatial light modulator is reflective.

61. The apparatus of claim 59 herein said third spatial light modulator is transmissive.

62. The apparatus of claim 40 wherein said fourth spatial light modulator is a liquid crystal device.

63. The apparatus of claim 62 wherein said fourth spatial light modulator is reflective.

64. The apparatus of claim 62 wherein said fourth spatial light modulator is transmissive.

65. An image forming apparatus for forming, from an incident beam in at least one color channel, according to input image data values an image-bearing modulated beam comprising a frame of image pixels, wherein each image pixel has a predetermined intensity, the apparatus comprising:

(a) a light source for providing said incident beam for said at least one color channel;

(b) a first look-up table for assigning a first input code value to each input image data value in said frame;

(c) a spatial light modulator for modulating said incident light beam to form a first modulated beam according to each said first input code value;

(d) a second look-up table for assigning a second input code value to each input image data value in said frame; and

(e) wherein said spatial light modulator modulates said incident light beam to form a second modulated beam according to each said second input code value.

66. An image forming apparatus as in claim 65 wherein each of said first input code values correlates a first output intensity with a first bias voltage.

67. An image forming apparatus as in claim 65 wherein each of said second input code values correlates a second intensity level to a second bias voltage.

68. An image forming apparatus for forming an image-bearing modulated beam from an incident beam for at least one color channel according to input image data values, wherein each image pixel of said modulated beam has a predetermined intensity, said apparatus comprising:

(a) a light source for providing said incident beam for said at least one color channel;

(b) a first look-up table for assigning a first input code value to each input image data value in a first frame;

(c) a spatial light modulator for modulating said incident light beam to form a first modulated beam according to each said first input code value;

(d) a second look-up table for assigning a second input code value to each input image data value in a second frame; and

(e) wherein said spatial light modulator modulates said incident light beam to form a second modulated beam according to each said second input code value.

69. An image forming apparatus as in claim 68 wherein each of said first input code values correlates a first output intensity with a first bias voltage.

70. An image forming apparatus as in claim 68 wherein each of said second input code values correlates a second intensity level to a second bias voltage.

71. An image forming apparatus as in claim 68 wherein a time interval between said first frame and said second frame is less than {fraction (1/16)} mscc.