Video display system and method of using same

• US 5,300,944 A
• Filed: 09/24/1992
• Issued: 04/05/1994
• Est. Priority Date: 07/21/1988
• Status: Expired due to Term

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Proxima Corporation (Ask ASA)
• Inventors: Shapiro, Leonid, Shaw, Robert W., Farwell, Randall S.
• Primary Examiner(s): HJERPE, RICHARD A
• Application Number:
  US07/950,451
• Time in Patent Office: 558 Days
• Field of Search: 340/701, 340/703, 340/784, 340/793, 340/716, 359/36, 359/54, 359/58, 359/59, 358/11, 358/12, 358/21 R, 358/140, 358/141, 358/241, 358/455, 358/456, 358/457, 358/458, 358/459, 358/230, 395/100, 345/88, 345/152
• US Class Current: 345/88
• CPC Class Codes: G02F 1/133531 characterised by the arrangement of polariser or analyser axes
• CPC Class Codes: G02F 1/133533 Colour selective polarisers G02F1/1347 takes precedence
• 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 9/3182 Colour adjustment, e.g. white balance, shading or gamut white balance per se H04N9/73; control of amplitude of colour signals H04N9/68; colour control circuits for displays in general G09G5/02, G09G3/2003, G09G3/3607
• CPC Class Codes: H04N 9/64 Circuits for processing colour signals H04N9/77 takes precedence; camera processing pipelines for processing colour signals H04N23/84

Abstract

A multiple color display system employing a low speed active matrix panel and a color enhancing unit for defining composite pixel groupings in the active matrix panel and for causing each grouping to produce in excess of 24 thousand different color shading levels.

Claims

1. A method for enhancing the number of image color shading levels produced by a display device in response to a video signal, said video signal for driving an X by Y matrix of pixel image producing devices, and said display device having an m by n matrix array of pixel elements, where m and n are substantially smaller than X and Y respectively, comprising:

receiving and reformatting the video signal into a display input signal for driving the m by n matrix of pixel elements, said input signal being indicative of N number of desired shading levels for the pixel elements in them by n matrix of pixel elements;

assigning pairs of gray scale codes to corresponding adjacent pairs of pixel elements in said m by n matrix, where one of the gray scale codes is indicative of one of an M number of shading levels and the other one of the gray scale codes is indicative of one of a P number of shading levels, and where N is substantially equal to M times P;

energizing selectively certain ones of the pixel elements an average number of times over a large number of successive frame time period intervals to produce pixel images having M number of different shading levels of individual ones of a plurality of individual colors;

energizing selectively certain other ones of the pixel elements adjacent to the last mentioned pixel elements an another average number of times over said large number of successive frame time period intervals to produce pixel images having P number of different shading levels of individual ones of said plurality of individual colors; and

controlling the energizing of said pixel elements to cause a composite pixel image to be displayed by the display device every frame period, said composite pixel image having a composite shading level substantially equal to the desired one of the N shading levels.

2. A method according to claim 1, further comprising:

preventing said display input signal from driving a boundary portion of said X by Y matrix of pixel image producing devices; and

inhibiting said display input signal from driving another boundary portion of said X by Y matrix of pixel image producing devices, so that the resulting displayed image is conformed to an image area defined by the m by n matrix array of pixel elements.

3. A mthod according to claim 2, further comprising:

responding to said display input signal for forming every frame period an individual pixel image having a large number N of possible intensity levels, where said large number N is greater than 2 to substantially prevent contouring between intensity levels of the same primary color.

4. A method for enhancing the number of color shading intensity levels produced by a display device having a pixel element matrix array of a plurality of liquid crystal pixel elements, comprising:

determining any one of N number of desired incoming color intensity levels for a pixel image to be displayed;

generating a coded signal indicative of any one of an M number of duty cycle intensity levels substantially less than said one of N number of desired incoming color intensity levels;

generating another coded signal indicative of any one of a P number of duty cycle intensity levels substantially less than said any one of N number of desired color intensity levels independently of the determined M number;

storing said coded signals to facilitate energizing pairs of adjacent pixel elements in the pixel element matrix array; and

generating a single-bit signal to cause a selected one of the adjacent pixel elements to be energized an average M number of times over a large number of successive frame time periods to produce a sub-pixel image having a given one of the M number of different duty cycle intensity levels where M is greater than one;

generating another single-bit signal to cause another selected one of the adjacent pixel elements to be energizing an average P number of times over a large number of successive frame time periods to produce a sub-pixel image having a given one of the P number of different color intensity levels where P is greater than one;

whereby adjacent sub-pixel images having M and P numbers of different duty cycle intensity levels are combined and perceived by a viewer as a single pixel image having a selected one of N number of desired incoming color intensity levels.

5. A color shade enhancing arrangement for a pixel element matrix array of a plurality of liquid crystal pixel elements, comprising:

means for determining any one of N number of desired incoming color intensity levels for a pixel image to be displayed;

means for generating a coded signal indicative of any one of an M number of duty cycle intensity levels substantially less than said one of N number of desired incoming color intensity levels;

means for generating another coded signal indicative of any one of a P number of duty cycle intensity levels substantially less than said any one of N number of desired color intensity levels independently of the determined M number;

composite pixel arranger means for storing said coded signals to facilitate energizing pairs of adjacent pixel elements in the pixel element matrix array; and

duty cycle means coupled to said composite pixel arranger means for generating a single-bit signal to cause a selected one to the adjacent pixel elements to be energized an average M number of times over a large number of successive frame time periods to produce a sub-pixel image having a given one of the M number of different duty cycle intensity levels where M is greater than one;

said duty cycle means generating another single-bit signal to cause another selected one of the adjacent pixel elements to be energizing an average P number of times over a large number of successive frame time periods to produce a sub-pixel image having a given one of the P number of different duty cycle intensity levels where P is greater than one;

whereby adjacent sub-pixel images having M and P numbers of different duty cycle intensity levels are combined and perceived by a viewer as a single pixel image having a selected one of N number of desired incoming color intensity levels.

6. A color shade enhancing arrangement according to claim 5, wherein said plurality of liquid crystal pixel elements form part of a display device, and wherein said pixel element matrix array is arranged in an m by n matrix array.

7. A color shade enhancing arrangement as recited in claim 6, wherein said display device is a liquid crystal display device.

8. A color shade enhancing arrangement as recited in claim 7, wherein said liquid crystal display device is an active matrix thin film transistor liquid crystal display panel.

9. A color shade enhancing arrangement as recited in claim 8, wherein each pixel element of said plurality of pixel elements has a set of three subpixel components.

10. A shade enhancing arrangement as recited in claim 9, wherein each subpixel component is indicative of a different color for producing a large number of color shades by a combining process as each subpixel component is driven to one of eight levels by said pixel element energizing signals.

11. A shade enhancing arrangement as recited in claim 10, wherein said combining process is a color additive process.

12. A shade enhancing arrangement as recited in claim 10, wherein said combining process is a color subtractive process.

13. A color shade enhancing arrangement according to claim 6, further comprising:

means for receiving a composite television video signal indicative of an image to be displayed, said means for receiving including signal conversion means for converting said composite television signal into at least two sets of analog video signals and analog to digital conversion means for converting said analog video signals into at least two groups of digital signals, each digital signal being indicative of a desired pixel image color shading intensity level; and

wherein said means for determining includes scaling means coupled to said analog to digital conversion means for quantizing each group of digital signals into pairs of quantized digital signals to help form a plurality of low resolution composite pixel images, each composite pixel image being formed by a composite pixel element array and having N possible color shading levels.

14. A color shade enhancing arrangement according to claim 13, further comprising:

means for reformatting the video signal into a display input signal for driving the m by n matrix array of pixel elements, said input signal coupled to said means for determining and being indicative of individual ones of the N number of desired shading levels for individual ones of the pixel elements in the m by n matrix array of pixel elements.

15. An arrangement according to claim 14, wherein said means for reformatting includes:

signal conversion means responsive to the video signal for producing a liquid crystal driving signal to help facilitate forming a television image on the display device, said display device having an X by Y matrix of pixel image producing devices and said display device having an m by n matrix array of pixel elements, where m and n are substantially smaller than X and Y respectively;

image inhibiting means responsive to the video signal for preventing said liquid crystal driving signal from driving a boundary portion of said X by Y matrix of pixel image producing devices; and

image format means responsive to the video signal for preventing said driving liquid crystal signal from driving another boundary portion of said X by Y matrix of pixel image producing devices, so that the resulting displayed image is conformed to an image area defined by the m by n matrix array of pixel elements.

16. An arrangement according to claim 15, further comprising:

means responsive to said liquid crystal driving signal for forming an individual pixel image every frame period having a large number N of possible intensity levels, where said large number N is greater than 2 to substantially prevent contouring between intensity levels of the same primary color.

17. A color shade enhancing arrangement according to claim 14

wherein said composite pixel arranger means includes:

means for generating pixel element location signals indicative of the location of the individual pixel element images in each composite pixel image;

bit map memory means for storing temporarily said pairs of quantized digital signals; and

pattern logic means for retrieving selected pairs of the quantized digital signals and for generating pixel element energizing signals when the individual pairs of the quantized digital signals have a given relationship with a corresponding pair of said pixel element location signals so that certain ones of the plurality of pixel elements are energized to form every frame period an individual one of the composite pixel images to help produce a full color image.

18. A color shade enhancing arrangement according to claim 17, further comprising:

means for substantially eliminating extraneous beat patterns and flicker in said full color image.

19. A color shade enhancing arrangement as recited in claim 17, wherein said scaling mean includes:

buffer means for temporarily storing each digital signal in each group of said digital signals for quantizing purposes; and

encoder means coupled to said buffer means for quantizing every other digital signal in each group of digital signals into the pairs of quantized digital signals without introducing any substantial quantization errors.

20. A color shade enhancing arrangement as recited in claim 17, wherein said pattern logic means includes:

means coupled to the bit map memory means for retrieving the stored quantized digital signals; and

means for formatting the retrieved quantized digital signals with a video clock signal to drive said display device.

21. A color shade enhancing arrangement as recited in claim 20, wherein said means for formatting includes:

temporary storage means for storing said quantized digital signals; and

video signal generating means coupled to said temporary storage means for producing a group of formatted binary video signals for driving the display device;

said binary video signals defining color shading levels for individual ones of the pixel images produced by the display device.

22. A shade enhancing arrangement as recited in claim 21, wherein said group of formatted binary signals includes three binary signals indicative of a large number of different color shading levels.

23. A shade enhancing arrangement as recited in claim 22, wherein said large number is at least 29 different shading levels for a single primary color.