Single panel color projection video display having control circuitry for synchronizing the color illumination system with reading/writing of the light valve

• US 5,416,514 A
• Filed: 12/10/1992
• Issued: 05/16/1995
• Est. Priority Date: 12/27/1990
• Status: Expired due to Term

• Current Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Original Assignee: North American Philips Corp. (Koninklijke Philips N.V.)
• Inventors: Janssen, Peter, Guerinot, William
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): Cohen, Cheryl
• Application Number:
  US07/988,617
• Time in Patent Office: 887 Days
• Field of Search: 348/760, 348/761, 348/551, 348/742, 348/196
• US Class Current: 348/196
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/0297 Special arrangements with multiplexing or demultiplexing of display data in the drivers for data electrodes, in a pre-processing circuitry delivering display data to said drivers or in the matrix panel, e.g. multiplexing plural data signals to one D/A converter or demultiplexing the D/A converter output to multiple columns
• CPC Class Codes: G09G 3/34 by control of light from an independent source
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: H04N 9/3117 by using a sequential colour filter producing two or more colours simultaneously, e.g. by creating scrolling colour bands

Abstract

A color projection video system utilizing only a single light valve. A white light source is separated into into red, green and blue bands. Scanning optics cause the RGB bands to be sequentially scanned across a light valve, such as a transmission LCD panel. Prior to each color passing over a given row of panels on the light valve, that row will be addressed, by the display electronics with the appropriate color content of that portion of the image which is being displayed. The image is projected by a projection lens onto a viewing surface, such as a screen. The device includes circuitry to synchronize the illumination of the light valve with the video signal and to minimize video breakup when changing video sources.

Claims

1. A system for synchronization of a color projection television system with a video signal comprising:

a video source having a video output and a synchronization signal;

video memory means coupled to said video output of said video source;

light valve means connected to said video memory means;

an illumination system for moving first, second and third color bands of light across said light valve means;

a first control circuit having a control output to said video memory means to control the writing of the video to said video memory means in response to the synchronization signal of said video source;

a second control circuit controlling the writing to said light valve means, said second control circuitry further including means for controlling the position of the color bands in relation to the light valve means and means for receiving an input based on the position of said color bands on said light valve; and

means for connecting and disconnecting said first and second control circuits from each other so that said first and second control circuits can be operated synchronously when connected and asynchronously when disconnected.

2. The synchronization system as claimed in claim 1 wherein at least one of said first and second control circuits comprise phase lock loop circuits..

3. The synchronization system as claimed in claim 1 wherein said illumination system comprises a rotating prism for moving said color bands across said light valve.

4. The synchronization system as claimed in claim 3 wherein said rotating prism includes a phase lock loop control motor coupled to the output of said second control circuit.

5. The synchronization system as claimed in claim 4 wherein said rotating prism includes an encoder for providing an output representative of the position of the rotating prism.

6. A system for synchronization of a color projection television system having an input video signal having a synchronization signal comprising:

a video memory for storing a frame of said video signal and connected to a video output of a video source;

a light valve connected to the video output of said video memory;

an illumination system for moving color bands of unmodulated light across said light valve to illuminate said light valve and to modulate said bands with said video signal;

a first control circuit having a control output to said video memory to control the writing of the video signal to the video memory in response to the synchronization signal;

a second control circuit controlling the writing to said light valve, said second control circuitry further including means for controlling the position of the color bands on the light valve and means for receiving an input from said illumination system based on the position of said color bands on said light valve; and

interconnection means for connecting and disconnecting said first and second control circuits from each other so that said first and second control circuits can be operated synchronously when connected and asynchronously when disconnected.

7. A video synchronization system as claimed in claim 6 wherein said first and second control circuits comprise phase locked loops.

8. The video control circuitry as claimed in claim 6 wherein said illumination system comprises rotating means for moving said color bands across said light valve.

9. The video synchronization system as claimed in claim 8 wherein said illumination system includes a phase locked loop control motor having a control input connected to said second control circuit.