Display apparatus with digital micromirror device

• US 6,348,907 B1
• Filed: 01/31/1995
• Issued: 02/19/2002
• Est. Priority Date: 08/22/1989
• Status: Expired due to Term

• Current Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Original Assignee: Lawson A. Wood
• Inventors: Wood, Lawson A.
• Primary Examiner(s): WU, XIAO MIN
• Application Number:
  US08/381,156
• Time in Patent Office: 2,576 Days
• Field of Search: 345/84, 345/85, 345/86, 345/108, 345/109, 345/111, 345/214, 345/207, 345/764, 345/755, 345/770, 345/771, 359/223, 359/224, 359/225, 359/261, 359/263, 359/264, 359/846, 359/847, 359/848, 359/849, 348/764, 348/771
• US Class Current: 345/84
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0633 by amplitude modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/346 based on modulation of the reflection angle, e.g. micromirrors micromirrors devices per se G02B26/0833
• CPC Class Codes: G09G 3/3629 using liquid crystals having memory effects, e.g. ferroelectric liquid crystals

Abstract

A display apparatus includes a digital micromirror device and red, green and blue lamps which illuminate it. The light from the lamps impinges on the DMD from at least two different directions. The lamps may be flash tubes which are fired at different binary levels in accordance with the rank of the bits that are being displayed on the DMD. The lamps may be fluorescent lamps which are driven steadily at predetermined levels while the rows of micromirrors are turned on in sequence and subsequently turned off in sequence. Resetting to dislodge micromirrors that have become stuck can be accomplished by emitting current pulses through the micromirrors while exposing them to a magnetic field, or by coating the actuation electrodes of the DMD with piezoelectric material which moves mechanically when pulses are applied to the micromirrors.

Claims

1. A display apparatus, comprising:

a digital micromirror device having an array of movable micromirrors, and

exposing means for exposing the array of micromirrors to light of a first primary color, to light of a second primary color, and to light a third primary color, the light of the first primary color and the light of the third primary color impinging on the array from a first direction and the light of the second primary color impinging on the array from a second direction, the exposing means comprising a partially-transmissive, partially reflective optical element which transmits the light of the first primary color before it impinges on the array and which reflects the light of the third primary color before it impinges on the array.

2. The display apparatus of claim 1, wherein the exposing means further comprises generating means for generating light in brief flashes having different levels.

3. The display apparatus of claim 2, wherein the generating means comprises timer means for setting the duration of a flash.

4. The display apparatus of claim 2, wherein the generating means comprises means for sensing the amount of light generated during a flash.

5. The display apparatus of claim 2, wherein the generating means comprises a first capacitor, and means for selectively charging the first capacitor to at least two voltage levels.

6. The display apparatus of claim 5, wherein the generating means further comprises a second capacitor, and means for selectively connecting the second capacitor in parallel with the first capacitor so as charge both capacitors to the same voltage level.

7. The display apparatus of claim 1, wherein the exposing means further comprises generating means for steadily generating light having a first level during a first period and a second level during a second period.

8. The display apparatus of claim 1, further comprising resetting means for dislodging any micromirrors that become stuck, the resetting means including means for exposing the array of micromirrors to a magnetic field.

9. The display apparatus of claim 1, further comprising resetting means for dislodging any micromirrors that become stuck, the resetting means including piezoelectric material beneath the micromirrors.

10. The display apparatus of claim 1, wherein the micromirrors are disposed so that a common plane passes through all of the micromirrors, wherein each micromirror is pivotable with respect to the common plane between a first position and a second position, wherein the first direction is such that, when a given one of the micromirrors is in its first position, light impinging on said given one of the micromirrors from the first direction is reflected in a direction perpendicular to the common plane, and wherein the second direction is such that, when said given one of the micromirrors is in its second position, light impinging on said given one of the micromirrors from the second direction of reflected in the direction perpendicular to the common plane.

11. A display apparatus, comprising:

a digital micromirror device having an array of movable micromirrors; and

resetting means for dislodging any micromirrors that become stuck, the resetting means including means for exposing the array of micromirrors to a magnetic field and means for causing current to flow through the micromirrors.

12. A display apparatus, comprising:

a digital micromirror device having an array of movable micromirrors, and

resetting means for dislodging any micromirrors that become stuck, the resetting means including piezoelectric material beneath the micromirrors.

13. A method of displaying a sequence of frames of video information on a digital micromirror device having an array of micromirrors that are disposed in rows and that are movable between a first position and a second position, the video information for a frame including a plurality of first multi-bit video words, each micromirror corresponding to one of the first multi-bit video words, each of the first multi-bit video words including at least a most significant bit and a least significant bit, comprising:

(a) moving micromirrors which correspond to first video words whose least significant bit has a predetermined value from their first positions to their second positions, the micromirrors of a first one of the rows being moved before the micromirrors of a last one of the rows;

(b) returning the micromirrors that were moved during step (a) to their first positions, the micromirrors of the first row being returned before the micromirrors of the last row; and

(c) steadily exposing the micromirrors to light at a first level while step (a) is conducted and while step (b) is conducted.

14. The method of claim 13, further comprising the steps of:

(d) moving micromirrors which correspond to first video words whose most significant bit has the predetermined value from their first positions to their second positions, the micromirrors of the first row being moved before the micromirrors of the last row;

(e) returning the micromirrors that were moved during step (d) to their first positions, the micromirrors of the first row being returned before the micromirrors of the last row; and

(f) steadily exposing the micromirrors to light at a second level while step (d) is conducted and while step (e) is conducted.

15. The method of claim 13, wherein the first video words correspond to a first primary color, wherein the video information for a frame additionally includes a plurality of second multi-bit video words which correspond to a second primary color, each second video word including at least a most significant bit and a least significant bit, wherein step (c) is conducted by shining light of the first primary color on the micromirrors so that the light impinges on them from a first direction, and wherein the method further comprises the steps of:

(d) moving micromirrors which correspond to second video words whose least significant bit has the predetermined value from their second positions to their first positions, the micromirrors of the first row being moved before the micromirrors of the last row;

(e) returning the micromirrors that were moved during step (d) to their second positions, the micromirrors of the first row being returned before the micromirrors of the last row; and

(f) steadily exposing the micromirrors to light of the second primary color at the first level while step (d) is conducted and while step (e) is conducted, the light of the second primary color impinging on the micromirrors from a second direction.

16. The method of claim 13, further comprising the step of dislodging any micromirrors that become stuck by exposing the micromirrors to a magnetic field and running current through them.

17. The method of claim 13, further comprising the step of dislodging any micromirrors that become stuck by jolting them with piezoelectric material that is disposed beneath the micromirrors.

18. A display apparatus, comprising:

a digital micromirror having an array of pivotable micromirrors which have pivot axes, the pivot axes of some of the micromirrors being transverse to the pivot axes of others of the micromirrors; and

exposing means for exposing the array of micromirrors to light of a first primary color which impinges on the array from a first direction, to light of a second primary color which impinges on the array from a second direction, and to light of a third primary color which impinges on the array from a third direction.

19. The display apparatus of claim 18, wherein the first and second directions define a plane, and wherein the third direction is transverse to the plane.

20. The display apparatus of claim 18, wherein the exposing means further comprises generating means for generating light in brief flashes having different levels.

21. The display apparatus of claim 20, wherein the generating means comprises timer means for setting the duration of a flash.

22. The display apparatus of claim 20, wherein the generating means comprises means for sensing the amount of light generated during a flash.

23. The display apparatus of claim 20, wherein the generating means comprises a first capacitor, and means for selectively charging the first capacitor to at least two voltage levels.

24. The display apparatus of claim 23, wherein the generating means further comprises a second capacitor, and means for selectively connecting the second capacitor in parallel with the first capacitor so as charge both capacitors to the same voltage level.

25. The display apparatus of claim 18, wherein the exposing means further comprises generating means for steadily generating light having a first level during a first period and a second level during a second period.

26. The display apparatus of claim 18, further comprising resetting means for dislodging any micromirrors that become stuck, the resetting means including means for exposing the array of micromirrors to a magnetic field.

27. The display apparatus of claim 18, further comprising resetting means for dislodging any micromirrors that become stuck, the resetting means including piezoelectric material beneath the micromirrors.

28. A display apparatus for displaying a sequence of frames of video information, the video information for a frame including a plurality of first video words for a first primary color component of the frame and a plurality of second video words for a second primary color component of the frame, each of the first video words having a predetermined number of bits and each of the second video words having a predetermined number of bits, said display apparatus comprising:

a digital micromirror device having an array of micromirrors that are movable between two positions, each of the first video words corresponding to one of the micromirrors and each of the second video words corresponding to one of the micromirrors;

moving means, responsive to the first and second video words, for selectively moving the micromirrors during a predetermined number of first time periods to display the bits of the first video words and for selectively moving the micromirrors during a predetermined number of second time periods to display bits of the second video words, the number of first time periods being the same as the number of bits in the first video words and the number of second time periods being the same as the number of bits in the second video words, the first time periods having durations that are substantially equal to one another and the second time periods having durations that are substantially equal to one another; and

exposing means for exposing the array of micromirrors to light of the first primary color which impinges on the array from a first direction and to light of the second primary color which impinges on the array from a second primary color which impinges on the array from a second direction, the exposing means comprising generating means for generating first brief flashes of light of the first primary color during the first time periods and second brief flashes of light of the second primary color during the second time periods, the first brief flashes having different levels during different ones of the first time periods and the second brief flashes having different levels during different ones of the second time periods.

29. The display apparatus of claim 28, wherein the first brief flashes have durations that are shorter than the first time periods and the second brief flashes have durations that are shorter than the second time periods.

30. The display apparatus of claim 28, wherein the video information for a frame also includes a plurality of third video words for a third primary color component of the frame, each of the third video words corresponding to one of the micromirrors and having a predetermined number of the bits, wherein the moving means is also responsive to the third video words and comprises means for selectively moving the micromirrors during a predetermined number of third time periods to display the bits of the third video words, the number of third time periods being the same as the number of bits in the third video words, the third time periods having durations that are substantially equal to one another, and wherein the exposing means further comprises means for exposing the array of micromirrors to light of the third primary color.

31. The display apparatus of claim 30, wherein the number of bits in the first video words is the same as the number of bits in the second video words and is also the same as the number of bits in the third video words.

32. The display apparatus of claims 30, wherein the light of the third primary color impinges on the array from the first direction, and wherein the durations of the first time periods, the second time periods, and the third time periods are substantially equal.

33. The display apparatus of claim 30, wherein the first and second directions define a plane, wherein the light of the third primary color impinges on the array of micromirrors from a third direction which is transverse to the plane, wherein the directions of the first time periods are substantially equal the durations of the second time periods, and wherein the durations of the third time periods are longer than the durations of the first time periods.

34. The display apparatus of claim 28, wherein the generating means comprises timer means for setting the duration of a flash.

35. The display apparatus of claim 28, therein the generating means comprises means for sensing the amount of light generated during a flash.

36. The display apparatus of claim 28, wherein the generating means comprises a first capacitor, and means for selectively charging the first capacitor to at least two voltage levels.

37. The display apparatus of claim 36, wherein the generating means further comprises a second capacitor, and means for selectively connecting the second capacitor in parallel with the first capacitor so as charge both capacitors to the same voltage level.

38. A display apparatus for displaying a sequence of frames of video information, the video information for a frame including a plurality of first video words for a first primary color component of the frame and a plurality of second video words for a second primary color component of the frame, each of the first video words having a predetermined number of bits and each of the second video words having a predetermined number of bits, said display apparatus comprising:

a digital micromirror device having an array of micromirrors that are movable between two positions, each of the first video words corresponding to one of the micromirrors and each of the second video words corresponding to one of the micromirrors;

moving means, responsive to the first and second video words, for selectively moving the micromirrors during a predetermined number of first time periods to display the bits of the first video words and for selectively moving the micromirrors during a predetermined number of second time periods to display bits of the second video words, the number of first time periods being the same as the number of bits in the first video words and the number of second time periods being the same as the number of bits in the second video words, at least two of the first time periods having substantially the same duration and at least two of the second time periods having substantially the same duration; and

exposing means for exposing the array of micromirrors to light of the first primary color which impinges on the array from a first direction and to light of the second primary color which impinges on the array from a second direction, the exposing means comprising means for steadily generating light having different levels during different ones of the at least two first time periods having substantially the same duration and for steadily generating light having different levels during different ones of the at least two second time periods having substantially the same duration.

39. The display apparatus of claim 38, wherein the video information for a frame also includes a plurality of third video words for a third primary color component of the frame, each of the third video words corresponding to one of the micromirrors and having a predetermined number of bits, wherein the moving means is also responsive to the third video words and comprises means for selectively moving the micromirrors during a predetermined number of third time periods to display the bits of the third video words, the number of third time periods being the same as the number of bits in the third video words, at least two of the third time periods having substantially the same duration, and wherein the exposing means further comprises means for exposing the array of micromirrors to light of the third primary color.

40. The display apparatus of claim 39, wherein the light of the third primary color impinges on the array of micromirrors from the first direction.

41. The display apparatus of claim 40, wherein the exposing means comprises a partially-transmissive, partially-reflective optical element which transmits the light of the first primary color before the light of the first primary color impinges on the array and which reflects the light of the third primary color before the light of the third primary color impinges on the array.

42. The display apparatus of claim 39, wherein the first and second directions define a plane, and wherein the light of the third primary color impinges on the array from a third direction which is transverse to the plane.

43. The display apparatus of claim 42, wherein the micromirrors of the array have pivot axes, the pivot axes of some of the micromirrors being transverse to the pivot axes of others of the micromirrors.

44. The display apparatus of claim 38, wherein the duration of the at least two of the first time periods which have substantially the same duration is a first duration, wherein the exposing means generates light with a first light level during one of the at least two first time periods having the first duration and light with a second light level during another of the at least two first time periods having the first duration, the second light level being higher than the first light level, wherein at least two others of the first time periods have a common second duration that is longer than the first duration, and wherein the exposing means generates light with the first light level during one of the at least two of the first time periods having the second duration and light with the second light level during another of the at least two of the first time periods having the second duration.

45. The display apparatus of claim 38, wherein the moving means comprises means for selectively moving micromirrors from an off position to an on position during a first portion of the each of the first time periods and then for returning the micromirrors that were moved during the first portion to their off position during second portion of each of the first time periods.

46. The display apparatus of claim 45, wherein some of the first time periods additionally have an intermediate portion, which is at least as long as the first portion, during which none of the micromirrors is moved by the moving means.

47. The display apparatus of claim 45, wherein the micromirrors are disposed in rows, and wherein the moving means comprises means for moving micromirrors in a first one of the rows before moving micromirrors in a last one of the rows during the first portion of the first time periods and for moving micromirrors in the first one of the rows before moving micromirrors in a last one of the rows during the second portion of the first time periods.