Display apparatus and method

• US 20020093477A1
• Filed: 02/11/2002
• Published: 07/18/2002
• Est. Priority Date: 01/31/1995
• Status: Active Grant

• Current Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Original Assignee: Acacia Patent Acquisition Corporation (Acacia Research Corporation)
• Inventors: Wood, Lawson A.
• Granted Patent: US 7,253,794 B2
• Time in Patent Office: Days
• US Class Current: 345/89
• 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 spatial light modulator on or off in accordance with values of the video words for the respective bit rank;

(b) continuously exposing the spatial light modulator to light from a light source during substantially the entire time that step (a) is conducted; and

(c) driving the light source at energy levels that depend on the bit rank.

2. The method of claim 1, wherein the spatial light modulator is any LCD panel.

3. The method of claim 1, wherein the spatial light modulator is a digital micromirror device.

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

(a) for each bit rank, 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 continuously exposing the spatial light modulator to light that varies substantially in intensity while step (a) is conducted.

5. The method of claim 4, wherein the light has an intensity at one moment that is at least about twice its intensity at another moment.

6. The method of claim 4, wherein the spatial light modulator is an LCD panel.

7. The method of claim 4, wherein the spatial light modulator is a digital micromirror device.

8. 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;

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

9. The method of claim 8, wherein the spatial light modulator is an LCD panel.

10. The method of claim 8, wherein the spatial light modulator is a digital micromirror device.