High speed color display system and method of using same

• US 5,225,875 A
• Filed: 09/21/1990
• Issued: 07/06/1993
• Est. Priority Date: 07/21/1988
• Status: Expired due to Fees

• Current Assignee: Proxima Corporation (Ask ASA)
• Original Assignee: Proxima Corporation (Ask ASA)
• Inventors: Shaw, Robert, Shapiro, Leonid, Farwell, Randall S.
• Primary Examiner(s): HJERPE, RICHARD A
• Application Number:
  US07/586,506
• Time in Patent Office: 1,019 Days
• Field of Search: 340/701, 340/703, 340/717, 340/720, 340/784, 340/793, 340/805, 340/811, 340/813, 340/814, 358/11, 358/21 R, 358/60, 358/61, 358/141, 358/160, 358/230, 358/231, 358/236, 358/240, 358/455, 359/54, 359/58, 359/59, 395/100, 395/118
• US Class Current: 345/690
• CPC Class Codes: G02F 1/13473 for wavelength filtering or for colour display without the use of colour mosaic filters
• CPC Class Codes: G02F 1/1397 the twist being substantially higher than 90°, e.g. STN-, SBE-, OMI-LC cells
• CPC Class Codes: G09G 2300/023 Display panel composed of stacked panels
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/36 using liquid crystals
• 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: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 5/028 Circuits for converting colour display signals into monochrome display signals
• CPC Class Codes: H04N 2005/745 Control circuits therefor
• CPC Class Codes: H04N 5/57 Control of contrast or brightness
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84
• CPC Class Codes: H04N 9/646 for image enhancement, e.g. vertical detail restoration, cross-colour elimination, contour correction, chrominance trapping filters

Abstract

A high speed color display system including a modulation circuit electrically coupled between a high speed display device, such as an active matrix liquid crystal display panel, and a video output signal source, such as a video output card of a personal computer. The modulation circuit including both a scaling circuit for eliminating or substantially reducing contouring caused by quantizing errors associated with approximations of digital pictures and a duty cycle scaling circuit for eliminating or substantially reducing repetitive beats in a displayed image.

Claims

1. A high speed color display unit for interfacing a personal computer to a high speed display device having a plurality of pixel elements for forming a full color image displayed repeatedly over a large number of successive frames, said unit, comprising:

coupling means for electrically connecting the personal computer to the high speed display device;

said coupling means including analog to digital conversion means for transforming an analog color video signal into a digital signal having N bits;

quantizing means coupled to said analog to digital conversion means for compressing said digital signal to M bit without introducing any substantial quantizing errors in a displayed video image over the large number of successive frames;

said N bit digital signal having a substantially greater number of bits than said M bit digital signal;

acceleration means for modulating the M bit digital signals to drive a high speed display device and for causing individual ones of the plurality of pixel elements to be activated selectively so that over the large number of successive frames pixel images are produced that closely approximate desired pixel shading levels corresponding to levels defined by said digital signals having n bits and without introducing any substantial extraneous heat patterns or flicker in said displayed video image.

2. A high speed color display unit as recited in claim 1, wherein said coupling means further includes:

low speed video means for coupling the unit to the personal computer; and

high speed video cable means for coupling the unit to the high speed display device.

3. A high speed color display unit as recited in claim 2 wherein said low speed video means is partially disposed in said personal computer and partially disposed in the unit.

4. A display control system for use with a high speed display device having a plurality of pixel elements for forming a full color visual image displayed repetitively over a large number of successive frames, in response to input signals being indicative of a desired pixel image shading level for individual ones of said plurality of pixel elements, said system comprising:

interface means including analog to digital conversion means for digitizing the input signals into digital signals each having N bits of digital information;

means for generating quantizing averaging signals arranged in recurring groups of quantizing averaging signals;

quantizing means responsive to said digital signals and to said quantizing signals for comparing them to generate averaged pixel shading level signals to substantially eliminate contouring in the full color visual image over the large number of successive frames;

bit map memory means for storing said averaged pixel color shading level signals;

high speed duty cycle means for retrieving the averaged pixel color shading level signal at a sufficient rate to drive the high speed display device and for causing individual ones of the plurality of pixel elements to be activated selectively so that over the large number of successive frames each pixel image produced in the full color visual image closely approximates the desired pixel image shading level without introducing any substantial extraneous beat patterns and flicker in the full color visual image;

wherein said quantizing means includes;

buffer means for temporarily storing said digital signal; and

low speed duty cycle means coupled to said buffer means for quantizing said digital signals without introducing any substantial quantization errors over the large number of successive frames, said digital signals being quantized into averaged pixel color shading level signals each having M bits of digital information, where M is substantially smaller than N.

5. A display system as recited in claim 4, wherein said low speed duty cycle means includes:

comparing means for generating said averaged signal whenever the value of the temporarily stored digital signal exceeds or equals the value of a corresponding one of said quantizing signals.

6. A method for displaying a full color visual image comprising:

generating pixel clock signals for controlling the displaying of the visual image in successive frames, each one of said frames being defined by a frame time interval, said frame time interval being defined by a frame time predetermined number of said pixel clock signals;

producing groups of digital signals, each digital signal in said groups of digital signals being indicative of a desired colored pixel image having a substantially large finite number of color shading levels, said finite number being defined by a predetermined number of N digital bits in each one of said digital signals;

producing in response to said pixel clock signals a series of quantizing averaging signals arranged in recurring groups of said quantizing averaging signals;

comparing certain ones of said predetermined number of N digital bits in each one of said digital signals and individual corresponding ones of said quantizing averaging signals to develop a quantized pixel color signal whenever the value of the certain ones of said predetermined number of digital bits is at least equal to the value of said corresponding quantizing averaging signal so that said quantized pixel color signals over a large number of successive frames closely approximates the color shading level of said desired pixel image to eliminate substantially contouring in the full color visual image;

each said quantized pixel color signal having M digital bits where M is substantially smaller than N;

temporarily storing said quantized pixel color signals in a frame array adapted for a high speed display device;

retrieving the stored quantized pixel color signals (;

producing a series of color shading level averaging signals arranged in recurring groups of said color shading level averaging signals; and

comparing individual ones of the retrieved quantized pixel color signals and individual corresponding ones of said color shading level averaging signals to develop an output signal to cause the high speed display device to produce individual pixel images whenever the value of the quantized pixel color signal is at least equal to the value of said corresponding color shading level averaging signal;

said output signal having P digital bits, where P is substantially less than M, whereby the average intensity level for each pixel image over a large number of successive frames closely approximates a desired colored pixel image shading level without introducing extraneous beat patterns or any substantial flicker in the full color visual image.