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| Projection display apparatus |
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| Spatial light modulator with full complex light modulation capability |
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| Holograms in photorefractive materials |
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| Liquid crystal light shutter |
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| Audio-visual display device |
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Color phase control for projection display using spatial light modulator
| Details |
Inventors: Doherty, Donald B.; Meyer, Richard C.; Marshall, Stephen W.; Sampsell, Jefferey B.; Gove, Robert J.;
Assignee: Texas Instruments Incorporated (Dallas, TX)
Primary Examiner: Peng; John K.
Assistant Examiner: Kovacs; Peter
Attorney, Agent or Firm: Reed; Julie L., Kesterson; James C., Donaldson; Richard L.
A SLM-based projection display system (10) samples and processes video data for delivery to a spatial light modulator (SLM) (13c), and uses a color wheel (14a) to color the SLM-generated images. A frame memory (13b) provides data to the SLM (13c) and is managed so that, if the phase of the incoming video signal changes, a desired phase relationship between the color wheel position and the data available to the SLM (13c) can be maintained. Also, a motor control unit (15a) uses a horizontal sync signal to generate a drive signal for the color wheel motor (16a), which limits the transient time during phase-changing events, and which provides a means for adjusting the phase of the drive signal. |
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DETAILED DESCRIPTION A first aspect of the invention is a memory for a display system that uses a SLM and a motor-driven color wheel, which has differently colored filters, to display images from processed video data.
A memory stores the processed data in a form ready for delivery to the SLM.
The memory has a separately addressable section for storing data representing each color to be displayed by the DMD, such that data from a selected section may by read from the memory at a given instant.
A pointer control unit generates a read pointer that represents an address in the memory from where data is to be read out.
The pointer control unit determines the section of the memory to be currently read and the timing of the reading in response to a feedback signal, from the color wheel motor that indicates the phase of said color wheel with respect to the video data in the SLM.
A technical advantage of the memory is that it synchronizes the color wheel and the display.
Phase differences between the color wheel and the data available to the SLM can be resolved by controlling the read pointer.
The color wheel motor is required only to drive the color wheel at a constant rate of revolutions per unit of time.
There is no requirement for speeding up or slowing down the motor to resolve phase differences.
Thus, a much less expensive motor can be used.
Also, the transient time for achieving synchronization is minimized.
For television applications, after a channel change, the data available to the SLM is quickly re-synchronized with the position of the color wheel.
In television, as well as other applications, quick re-synchronization reduces undesired artifacts in the image.
Another aspect of the invention is a color wheel motor control unit for a display system that uses a motor-driven color wheel to display frames of color images from processed data sampled from a video signal.
A phase-locked oscillator receives a horizontal sync signal of the video signal, and generates a pulsed signal having a frequency of said horizontal sync signal times a predetermined multiplier
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LCD 
