Display apparatus and method

• US 7,253,794 B2
• Filed: 02/11/2002
• Issued: 08/07/2007
• Est. Priority Date: 01/31/1995
• Status: Expired due to Fees

• Current Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Original Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Inventors: Wood, Lawson A.
• Primary Examiner(s): Liang, Regina
• Application Number:
  US10/068,871
• Publication Number:
  US 20020093477A1
• Time in Patent Office: 2,003 Days
• Field of Search: 345 84- 87, 345/102, 345/690, 345/692, 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 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• 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 2340/0428 Gradation resolution change
• 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 3/2018 by time modulation using two or more time intervals
• 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 3/34 by control of light from an independent source
• 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 spatial light modulator, such as a digital micromirror device or an LCD panel, and a lighting unit that illuminates the spatial light modulator. The lighting unit may include red, green, and blue lamps which emit light that impinges on a 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. The illumination unit may include a lamp unit and a color wheel. The light from the lamp unit can be integrated, and the data displayed on the spatial light modulator can be changed when the integrated light reaches a predetermined value. The color wheel may be rotated faster than the frame repetition rate of video information that is being displayed. The intensity of the light may be controlled in accordance with the bit rank or significance of the bits that are being displayed by the spatial light modulator. Several techniques for achieving different intensity levels are disclosed.

Claims

1. A method for displaying an image described by video words of a frame, the video words having bits with different bit ranks, said method comprising the steps of:

(a) for each bit rank, turning pixels of a digital micromirror device on or off in accordance with values of the video words for the respective bit rank; and

(b) discontinuously exposing the digital micromirror device to brief-duration flashes of light, the flashes having intensities that depend on the respective bit rank,

wherein step (b) comprises exposing the digital micromirror device to flashes impinging on the digital micromirror device from a first direction, and also to flashes impinging on the digital micromirror device from a second direction, and also to flashes impinging on the digital micromirror device from a third direction.

2. The method of claim 1, wherein some of the flashes are emitted from a red light source, others of the flashes are emitted from a green light source, and still others of the flashes are emitted from a blue light source.

3. A method for displaying a first color component of an image described by video words for the first color component of a frame, the video words having bits with different bit ranks, said method comprising the steps of:

(a) for each bit rank of the first color component of the frame, turning pixels of a spatial light modulator on or off in accordance with values of the video words of the first color component for the respective bit rank;

(b) steadily exposing the spatial light modulator to light of the first color component during substantially the entire time that step (a) is conducted, the light being generated by a light source; and

(c) driving the light source at a first energy level for one of the bit ranks and at a substantially greater second energy level for another of the bit ranks,

wherein the light source comprises a plurality of light emitters, and

wherein step (c) comprises turning on less than all of the light emitters to drive the light source at the first energy level and turning on all of the light emitters to drive the light source at the second energy level.

4. The method of claim 3, wherein the spatial light modulator comprises a liquid crystal display.

5. The method of claim 3, wherein the spatial light modulator comprises a digital micromirror device.

6. The method of claim 3, wherein step (c) further comprises detecting light emitted by the light source, integrating the detected light, and changing from the first energy level to the second energy level when the integrated light reaches a predetermined value.

7. A method for displaying a first color component of an image described by video words for the first color component of a frame, the video words having bits with different bit ranks, said method comprising the steps of:

(a) for each bit rank of the first color component for a plurality of rows of the frame, turning pixels of a spatial light modulator on or off in accordance with values of the video words for the respective bit rank; and

(b) substantially steadily exposing the spatial light modulator to light that varies substantially in intensity while step (a) is conducted,

wherein step (b) comprises shining light generated by a light source onto the spatial light modulator, the light source having a plurality of light emitters, and actuating at least one of the light emitters substantially continuously as step (a) is being conducted and turning at least one other of the light emitters on or off as step (a) is being conducted.

8. The method of claim 7, wherein the light has an intensity at one moment that is at least about twice its intensity at another moment.

9. The method of claim 7, wherein the spatial light modulator comprises a liquid crystal display.

10. The method of claim 7, wherein the spatial light modulator comprises a digital micromirror device.

11. The method of claim 7, wherein the first color component is a red component.

12. A method for displaying a first color component of an image described by video words for the first color component of a frame, the video words having bits with different bit ranks, said method comprising the steps of:

(a) for each bit rank of the first color component for a plurality of rows of the frame, turning pixels of a spatial light modulator on or off in accordance with values of the video words for the respective bit rank; and

(b) substantially steadily exposing the spatial light modulator to light that varies substantially in intensity while step (a) is conducted,

wherein step (b) comprises shining light generated by a light source onto the spatial light modulator, detecting the light, integrating the detected light, and changing the intensity of the light generated by the light source when the integrated light reaches a predetermined value.

13. A method for displaying a first color component of an image that is generated by a spatial light modulator having pixels in rows, the first color component of the image being described by video words for the first color component, said method comprising the steps of:

(a) for a first one of the bit ranks of the video words for the first color component, turning pixels in a plurality of the rows of the spatial light modulator on or off in accordance with values of the video words for the first one of the bit ranks;

(b) for a second one of the bit ranks of the video words for the first color component, turning pixels in said plurality of rows of the spatial light modulator on or off in accordance with values of the video words for the second one of the bit ranks; and

(c) steadily exposing the spatial light modulator to light of the first color component while steps (a) and (b) are conducted, the light having an intensity that changes substantially while steps (a) and (b) are being conducted,

wherein step (c) comprises shining light generated by a light source onto the spatial light modulator, the light source having a plurality of light emitters, and actuating at least one of the light emitters substantially continuously as steps (a) and (b) are being conducted and turning at least one other of the light emitters on or off as steps (a) and (b) are being conducted.

14. The method of claim 13, wherein the spatial light modulator comprises a liquid crystal display.

15. The method of claim 13, wherein the spatial light modulator comprises a digital micromirror device.

16. The method of claim 13, wherein the first color component is a red component.

17. The method of claim 13, wherein step (b) comprises shining light generated by a light source onto the spatial light modulator, detecting the light, integrating the detected light, and changing the intensity of the light generated by the light source when the integrated light reaches a predetermined value.

18. A method for displaying a first color component of an image that is generated by a spatial light modulator having pixels in rows, the first color component of the image being described by video words for the first color component, said method comprising the steps of:

(a) shining light of the first color component on the spatial light modulator, the light being generated by a light source;

(b) for a first one of the bit ranks of the video words for the first color component, turning pixels in a plurality of the rows of the spatial light modulator on or off in accordance with values of the video words for the first one of the bit ranks;

(c) detecting light from the light source;

(d) integrating the light detected after step (b) is conducted; and

(e) for a second one of the bit ranks of the video words for the first color component, turning pixels in said plurality of rows of the spatial light modulator on or off in accordance with values of the video words for the second one of the bit ranks when the integrated light reaches a predetermined value.

19. The method of claim 18, further comprising the step of changing the intensity of the light generated by the light source.

20. The method of claim 19, wherein the light source comprises a plurality of light emitters, and the step of changing the intensity comprises actuating at least one of the light emitters steadily and turning at least one other of the light emitters on or off.

21. A method for displaying a sequence of image frames described by video words, the video words having bits with different bit ranks, said method comprising the steps of:

(a) exposing a spatial light modulator to light generated by a light source;

(b) displaying the bit ranks of the video words describing a given frame of the sequence on the spatial light modulator in a predetermined order;

(c) displaying the bit ranks of the video words describing the next frame of the sequence on the spatial light modulator in a different order; and

(d) coloring the light to which the spatial light modulator is exposed with a rotating color wheel,

wherein the predetermined order of step (a) is an ascending order for each color, from least significant bits to most significant bits, and

wherein the different order of step (c) is a descending order for each color, from most significant bits to least significant bits.

22. The method of claim 21, further comprising varying the intensity of the light to which the spatial light modulator is exposed substantially.

23. A method for displaying a first color component of an image described by video words for the first color component of a frame, the video words having bits with different bit ranks, from least significant bits to most significant bits, said method comprising the steps of:

(a) exposing a spatial light modulator to light generated by a light source;

(b) coloring the light to which the spatial light modulator is exposed with a rotating color wheel, the color wheel having at least one segment for the first color component;

(c) displaying the least significant bits and the next-least significant bits of the video words for the first color component on the spatial light modulator during one revolution of the color wheel; and

(d) displaying the most significant bits of the video words for the first color component on the spatial light modulator during at least two additional revolutions of the color wheel.

24. A method for displaying a colored image, comprising the steps of:

(a) supplying a first set of data to a digital micromirror device 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;

(b) exposing the digital micromirror device to light of a first color that impinges on the digital micromirror device from a first direction;

(c) supplying a second set of data to the digital micromirror device;

(d) exposing the digital micromirror device to light of a second color that impinges on the digital micromirror device from a second direction;

(e) supplying a third set of data to the digital micromirror device; and

(f) exposing the digital micromirror device to light of a third color that impinges on the digital micromirror device from a third direction.