Color correction methods for electronic displays

• US 6,243,059 B1
• Filed: 05/14/1996
• Issued: 06/05/2001
• Est. Priority Date: 05/14/1996
• Status: Expired due to Fees

• Current Assignee: TransPacific Exchange, LLC
• Original Assignee: Rainbow Displays, Inc.
• Inventors: Greene, Raymond G., Katyl, Robert H., Yost, Boris, Krusius, J. Peter
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Tran, Henry N.
• Application Number:
  US08/649,240
• Time in Patent Office: 1,848 Days
• Field of Search: 345/72, 345/77, 345/88, 345/150, 345/151, 345/152, 345/903, 345/103, 345/207, 345/153, 345/1, 345/4, 345/81, 345/154, 348/805, 348/807, 348/808, 348/383
• US Class Current: 345/88
• CPC Class Codes: G09G 2300/026 Video wall, i.e. juxtaposition of a plurality of screens to create a display screen of bigger dimensions
• CPC Class Codes: G09G 2310/0221 with use of split matrices G09G3/3644 and G09G3/3666 take precedence
• CPC Class Codes: G09G 2310/0275 Details of drivers for data electrodes, other than drivers for liquid crystal, plasma or OLED displays, not related to handling digital grey scale data or to communication of data to the pixels by means of a current
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 5/006 Details of the interface to the display terminal specific for a display terminal using a CRT G09G1/167; using a flat panel G09G3/2096; circuits for interfacing with colour displays G09G5/04
• CPC Class Codes: H04N 17/045 Self-contained testing apparatus
• CPC Class Codes: H04N 9/12 Picture reproducers H04N9/11 takes precedence
• CPC Class Codes: H04N 9/30 using solid-state colour display devices
• CPC Class Codes: H04N 9/3147 Multi-projection systems displays in general H04N9/12; video walls G06F3/1446, G09G2300/026
• 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: Y10S 345/903 Modular display

Abstract

The present invention features methods and apparatus for the correction of spatial non-uniformities in color only, and color and brightness combined, that arise from materials, manufacturing, and operational variations in tiled, color flat-panel displays. Such uniformities can introduce gradual or abrupt color and brightness variations in monolithic and tiled displays. Correction methods are based on control of the manufacturing and assembly process, and/or remapping of the colors of the display to match uniformity requirements of the average human observer. Correction methods can be implemented using serial and parallel versions using electronic circuits commonly used in video signal processing. Apparatus for a self-calibration method are also described.

Claims

1. A method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display, the steps comprising:

a) measuring tri-stimulus values of a predetermined set of pixels in a tiled, flat-panel color video display for a predetermined number of pixel excitation conditions, thereby defining a three-dimensional color space for each of said pixels, said color spaces comprising sets of tri-stimulus values representative of each of said pixels'"'"' responses to said predetermined excitation conditions;

b) mathematically computing the intersection of at least two of said three-dimensional color spaces, thereby defining a common, resultant three-dimensional color space being the common, intersecting volumes of said at least two three-dimensional color spaces; and

c) establishing a color system, operable within said common, resultant three-dimensional color space, for selectively adjusting drive signals to said pixels, whereby identical excitations supplied to each of said pixels results in substantially identical, matched tri-stimulus values.

2. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 1, wherein said color system comprises one from the group of linear color systems and compressed color systems.

3. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 1, wherein said tri-stimulus values comprise absolute CIE tri-stimulus values.

4. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 3, wherein said predetermined number of pixel excitation conditions comprises a predetermined number of unique excitation conditions wherein at least one of the X, Y and Z parameters of said absolute CIE tri-stimulus values is varied for each of said predetermined number of pixel excitation conditions.

5. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 3, wherein said tiled, flat-panel color video display comprises a plurality of individual AMLCD display tiles comprising pixels and having seams therebetween.

6. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 5, wherein said predetermined set of pixels in said tiled, flat-panel color video display comprises pixels selected from at least two of said plurality of individual AMLCD display tiles.

7. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 6, wherein at least one of said predetermined set of pixels in said tiled, flat-panel color video display comprises pixels disposed proximate said seam.

8. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 7, wherein said color video display comprises a tiled, flat-panel display comprising a plurality of individual AMLCD display tiles comprising pixels and having seams therebetween.

9. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 8, wherein said predetermined set of pixels in said tiled, flat-panel color video display comprises pixels selected from at least two of said plurality of individual AMLCD display tiles.

10. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 9, wherein said predetermined set of pixels is substantially representative of all pixels in said display.

11. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 10, the steps further comprising:

e) modifying pixel excitations that create tri-stimulus values outside said resultant, three-dimensional color space so as to produce tri-stimulus values within said resultant, three-dimensional color space.

12. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 11, wherein said produced tri-stimulus values within said resultant, three-dimensional color space are optimized to be substantially on the surface of said resultant, three-dimensional color space.

13. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 6, wherein said predetermined set of pixels is substantially representative of all pixels in said display.

14. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 6, wherein said establishing a color system step (c) comprises determining a set of corrections to be applied to pixel drive signals such that substantially all pixels in said display produce substantially identical tri-stimulus values in response to substantially identical excitations.

15. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 14, the steps further comprising:

d) modifying pixel excitations that create tri-stimulus values outside said resultant, three-dimensional color space so as to produce tri-stimulus values within said resultant, three-dimensional color space.

16. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 14, the steps further comprising:

d) operating both said first and said second liquid crystal display tiles substantially simultaneously within said resultant, three-dimensional color space;

whereby chromaticity and luminance are made substantially uniform across said seam resulting in said seam being substantially visually imperceptible.

17. A method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display, the steps comprising:

a) characterizing a tiled, flat-panel color video display by measuring tri-stimulus values of a predetermined set of pixels therein for a predetermined number of pixel excitation conditions, thereby defining a three-dimensional color space for each of said pixels, said color spaces comprising discrete sets of tri-stimulus values representative of each of said pixels'"'"' responses to said predetermined excitation conditions;

b) mathematically computing the intersection of at least two of said discrete sets of tri-stimulus values associated with at least two of said three-dimensional color spaces, thereby defining a common, resultant three-dimensional color space being the common, intersecting volumes of said at least two three-dimensional color spaces, said resultant three-dimensional color space being a resultant set of tri-stimulus values;

c) computing correction coefficients from said at least two sets of tri-stimulus values and said resultant set of tri-stimulus values; and

d) operating said tiled, flat-panel color video display by applying said correction coefficients to pixel drive signals such that identical drive signals applied to each of said pixels results in substantially identical, matched tri-stimulus values, whereby non-uniformities in chromaticity and luminance are reduced below a perceptual threshold.

18. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 17, wherein said tri-stimulus values comprise absolute CIE tri-stimulus values.

19. The method for matching tri-stimulus values of pixels in a tiled, flat-panel color video display as recited in claim 18, wherein said predetermined number of excitation conditions comprises a predetermined number of unique excitation conditions, wherein at least one of the X, Y and Z parameters of said absolute CIE tri-stimulus values is varied for each of said predetermined number of excitations.

20. A method for substantially eliminating non-uniformities of chromaticity or luminance in a tiled, flat-panel color video display by matching tri-stimulus values of pixels, the steps comprising:

a) providing a tiled, flat-panel color video display comprising a plurality of pixels each having a sub-pixel associated with a primary color;

b) selecting at least one reference pixel from said plurality of pixels for matching tri-stimulus values;

c) characterizing said tiled, flat-panel color video display by measuring tri-stimulus values of said reference pixel and an additional predetermined set of said plurality of pixels for a predetermined number of primary color excitation conditions, thereby defining a three-dimensional color space for said reference pixel and each pixel of said predetermined set of pixels, said color spaces comprising sets of tri-stimulus values representative of each of said predetermined set of pixels'"'"' responses to said predetermined excitation conditions, said set of tri-stimulus values for said reference pixel being a reference set of tri-stimulus values;

d) mathematically computing the intersection of at least two of said discrete sets of tri-stimulus values associated with at least two of said three-dimensional color spaces, thereby defining a common, resultant three-dimensional color space being the common, intersecting volumes of said at least two three-dimensional color spaces, said resultant three-dimensional color space being a resultant set of tri-stimulus values;

e) storing values representative of selected ones of said tri-stimulus values of primary color excitations, said selected tri-stimulus values falling within said resultant color space;

f) if said reference pixel has not already been measured, measuring tri-stimulus values of said reference pixel for a predetermined number of primary color excitation conditions, thereby defining a three-dimensional color space for said reference pixel, said color spaces comprising a set of tri-stimulus values representative of each of said reference pixel'"'"'s response to said predetermined excitation conditions;

g) computing corrected color coordinates from said sets of tri-stimulus values and said tri-stimulus values associated with said at least one reference pixel; and

h) operating said tiled, flat-panel color video display by applying drive signals modified in accordance with said corrected color coordinates to said pixels such that identical drive signals applied to each of said pixels results in substantially identical, matched, tri-stimulus values and whereby non-uniformities in chromaticity and luminance are substantially eliminated.