Display apparatus and method

• US 7,782,280 B2
• Filed: 05/02/2006
• Issued: 08/24/2010
• 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:
  US11/415,422
• Publication Number:
  US 20060250336A1
• Time in Patent Office: 1,575 Days
• Field of Search: 345/32, 345 84- 87, 345/102, 345/690, 348742-744
• 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 display apparatus for displaying a sequence of frames having a frame repetition rate, comprising:

a spatial light modulator;

a light source for shining light on said spatial light modulator; and

a rotatable mounted color wheel positioned in an optical path from said light source to said spatial light modulator, said color wheel comprising at least one red region, at least one green region, at least one blue region, and at least one light-attenuating region, wherein said at least one light-attenuating region reduces the intensity of the light reaching said spatial light modulator,

wherein said color wheel is rotated faster than the frame repetition, rate,

wherein the spatial light modulator is a digital micromirror device (DMD) having a plurality of micromirrors that are movable between ON and OFF positions, all of the micromirrors of the DMD being simultaneously moved to their OFF positions at least once during each frame as the sequence of frames is displayed.

2. The display apparatus of claim 1, wherein said color wheel is rotated substantially faster than four times the frame repetition rate.

3. The display apparatus of claim 1, wherein said light-attenuating region reduces the intensity of the light reaching said spatial light modulator by a greater level than said at least one red region, or said at least one green region, or said at least one blue region.

4. The display apparatus of claim 1, wherein said light attenuating region additionally colors the light red, green, or blue.

5. The display apparatus of claim 1, wherein the light that impinges on the spatial light modulator as the color wheel rotates has a sequence of light intervals, the light intervals including red light intervals, green light intervals, and blue light intervals, each light interval of a given one of the colors being preceded and followed by a light interval of at least one of the other colors, and wherein the spatial light modulator is exposed to the red light intervals at a rate substantially faster than four times the frame repetition rate.

6. The display apparatus of claim 1, wherein the spatial light modulator is exposed to the red light intervals at a rate not less than about seven times the frame repetition rate.

7. The display apparatus of claim 1, wherein all of the micromirrors of the DMD are simultaneously moved to their OFF positions more than once during the display of each frame.

8. The display apparatus of claim 7, wherein all of the micromirrors of the DMD are simultaneously move to their OFF positions at least once during each revolution of the color wheel.

9. A display apparatus for displaying a sequence of frames having a frame repetition rate, comprising:

a digital micromirror device (DMD); and

lighting means for substantially steadily exposing the DMD to light that varies substantially in intensity while each frame is displayed, the lighting means including light source means for emitting light that impinges on the DMD and a plurality of filters to color the light after emission from the light source means,

wherein the light to which the DMD is substantially steadily exposed is incident light that is then reflected by micromirrors of the DMD, the incident light including light having a first color for producing a first color component of each frame, light having a second color for producing a second color component of each frame, and light having a third color for producing a third color component of each frame, and wherein the incident light having a first color varies substantially in intensity while the first color component of each frame is displayed.

10. The display apparatus of claim 9, wherein the filters are provided on a color wheel, and wherein the lighting means further comprises a motor to rotate the color wheel.

11. The display apparatus of claim 10, wherein the filters of the color wheel include a first filter region that transmits light of a particular color to the DMD at a first light intensity level when the color wheel is at a first rotary position and a second filter region that transmits light of the particular color to the DMD at an attenuated second light intensity level when the color wheel is at a second rotary position.

12. The display apparatus of claim 11, wherein the second light intensity level is not more than half the first light intensity level.

13. The display apparatus of claim 11, wherein the motor rotates the color wheel substantially faster than four times the frame repetition rate.

14. The display apparatus of claim 11, wherein the motor rotates the color wheel not less than about seven times the frame repetition rate.

15. The display apparatus of claim 10, wherein the light to which the DMD is exposed as the color wheel rotates has a sequence of light intervals, the light intervals including first color component intervals, second color component intervals, and third color component intervals, each light interval of a given one of the color components being preceded and followed by a light interval of at least one of the other color components, and wherein the DMD is exposed to the first color component intervals at a rate substantially faster than four times the frame repetition rate.

16. The display apparatus of claim 15, wherein the DMD is exposed to the first color component intervals at a rate not less than about seven times the frame repetition rate.