Correction methods for brightness in electronic display

• US 6,271,825 B1
• Filed: 10/14/1998
• Issued: 08/07/2001
• Est. Priority Date: 04/23/1996
• 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): NGUYEN, FRANCIS N
• Application Number:
  US09/173,468
• Time in Patent Office: 1,028 Days
• Field of Search: 345/87, 345/103, 345/98, 345/100, 345/147, 345/1-2, 345/3, 345/92, 345/903, 345/207, 345/89, 345/88, 345/63, 345/431, 345/199, 348/383, 348/757, 348/687, 348/631, 348/607, 348/609, 382/167, 382/162
• US Class Current: 345/694
• 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 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• 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 2360/147 the originated light output being determined for each pixel
• 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: H04N 9/12 Picture reproducers H04N9/11 takes precedence

Abstract

The present invention features methods and apparatus for the correction of spatial non-uniformities in brightness that arise from materials, manufacturing, operational and lighting parameter variations in electronic color, flat-panel displays. The methods apply both to gradual non-uniformities usually found in monolithic displays as well as to abrupt variations present in displays composed of a multitude of tiles. Corrections are performed on the electronic drive signals used to control the brightness of selected display pixels. Parameters required for these corrections are acquired via brightness measurements over selected pixels and stored after suitable transformations. The stored parameters are then used to scale and/or interpolate drive signals in real time. Corrections are performed such that any remaining gradual and abrupt brightness non-uniformities fall below the detectable threshold under the intended viewing conditions. The correction methods can also be used for correcting brightness non-uniformities arising from uneven aging of the display. Apparatus for an automatic self-calibrating function is also described.

Claims

1. A method for correcting spatial non-uniformities in luminance outside of a predetermined luminance variation detection range in order to provide a tiled, color flat-panel display with the appearance of having a uniform brightness, said method comprising the steps of:

a) providing a tiled, color, flat-panel display capable of displaying moving images at a predetermined refresh rate, comprising a plurality of individual display tiles having seams therebetween, each of said individual display tiles comprising an array of color pixel elements, each pixel element comprising an individual color space having color coordinate and being adapted to receive a data stream and altering its color characteristics in response thereto, said color, flat-panel display exhibiting gradual non-uniformities or abrupt non-uniformities in luminance;

b) measuring the primary luminance variations between at least two of said individual color spaces associated with at least two of said color pixels of said tiled, color, flat-panel display;

c) determining tristimulus values associated with said measured luminance variations of step (b);

d) electronically storing values representative of said tristimulus values;

e) using luminance scaler/adder means operatively connected to said tiled, color, flat-panel display to receive a continuous video input signal and to recompute color coordinates, in accordance with said electronically stored values, at substantially said predetermined refresh rate to produce a normalized data stream; and

f) selectively applying said normalized data stream to display controller means operatively connected to at least one of;

row driver means and column driver means, operatively connected to at least one of said pixels, thereby adjusting primary luminances of color spaces associated with said pixels in said tiled, color, flat-panel display which will result in matching of the luminances of said two pixels thereby correcting spatial non-uniformities in the luminance between said pixels of said tiled, color flat panel display in accordance with a gradient rule, whereby spatial non-uniformities in luminance are reduced below said predetermined detection range.

2. The method for correcting spatial non-uniformities in luminance for color, flat-panel displays as recited in claim 1, wherein said sub-step of adjusting drive signals comprises at least one from the group of:

adjusting drive voltages, adjusting drive current, adjusting drive pulse width, adjusting drive signal modulation, or adjusting drive pulse repetition rate.

3. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, further comprising the step of:

e) controlling manufacturing parameters of said electronic color, flat-panel display during manufacture so that each color pixel of said electronic color, flat-panel display falls within a predetermined luminance detection range for adjacent pixels and a gradient rule for remote pixels.

4. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, wherein said measurements obtained in step (b) are electronically stored in accordance with step (c) in a non-volatile memory.

5. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, wherein data representative of said measurements obtained in step (b) are electronically stored in accordance with step (c), utilizing interpolation techniques.

6. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 5, wherein said stored data is used in the processing of drive signals for correcting spatial non-uniformities in real time.

7. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, wherein the measurement of said primary luminance variations across color pixels of said tiled, color, flat-panel display in accordance with step (b) is repeated and further wherein said electronically stored values in accordance with step (c) are changed.

8. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 7, wherein said measuring step (b) comprises sampling luminance of selected pixels using photo-sensing means.

9. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, wherein each of said tiles. comprises an array of pixels.

10. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 1, wherein each of said tiles comprises a single pixel.

11. A method for correcting spatial non-uniformities in luminance outside of a predetermined luminance variation detection range, said spatial non-uniformities being gradual non-uniformities, or abrupt non-uniformities arising in an electronic color, flat-panel display having a plurality of tiles comprising color pixels, each pixel comprising an individual color space and being adapted to vary a color characteristic in response to a varying drive signal, in order to provide the tiled, color, flat-panel display with the appearance of having a uniform brightness, said method comprising the steps of:

a) measuring primary luminance variations across predetermined color spaces, each having color coordinates, associated with said color pixels of a tiled, color, flat-panel display;

b) determining tristimulus values associated with said measured primary luminance variations of step (a);

c) electronically storing values representative of said tristimulus values;

d) modifying said electronically stored values by applying a gradient rule thereto, resulting in modified, electronically stored values;

e) using luminance scaler/adder means operatively connected to said flat-panel display to receive a continuous video input signal and to recompute color coordinates, in accordance with said modified, electronically stored values, at a predetermined refresh rate associated with said flat-panel display to produce a normalized data stream; and

f) selectively applying said normalized data stream to at least one of said pixels for adjusting primary luminances for pixels for adjusting primary luminances of color spaces associated with said pixels in said tiled, flat-panel display by adjusting said normalized data stream applied to color pixels in said tiled, color, flat-panel display, which will result in reducing spatial non-uniformities in the luminance of said tiled, color, flat-panel display to below said predetermined luminance variation detection range, thereby facilitating visually imperceptible seams between the tiles of said display.

12. A method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, further comprising the step of:

g) controlling manufacturing parameters of said electronic color, flat-panel display during manufacture thereof, so that each color pixel of said electronic color, flat-panel display falls within a resultant luminance discrimination threshold for adjacent pixels and a gradient rule for remote pixels.

13. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein said measurements obtained in step (a) are electronically stored in accordance with step (b) in a non-volatile memory.

14. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein data representative of said measurements obtained in step (a) are electronically stored in accordance with step (b), utilizing interpolation techniques.

15. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 14, wherein said stored data is used in the processing of drive signals for correcting spatial non-uniformities in real time.

16. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein the measurement of said primary luminance variations across color pixels of said tiled, color, flat-panel display in accordance with step (a) is repeated after a period of usage of said tiled, color, flat-panel display, and further wherein said electronically stored values in accordance with step (b) are changed in order to compensate for aging of said tiled, color, flat-panel display.

17. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 16, wherein said measuring step (b) comprises sampling luminance of selected pixels using photo-sensing means.

18. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein said tiled, color, flat-panel display comprises tiles having an array of pixels.

19. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein said tiled, color, flat-panel display comprises tiles having a single pixel.

20. The method for correcting spatial non-uniformities in luminance for an electronic color, flat-panel display in accordance with claim 11, wherein the primary luminance of any of said predetermined color pixels that is only partially active is adjusted to the luminance level of adjacent pixels so that said partially active pixel has an appearance that is least disturbing to an observer.

21. A method for self-calibrating spatial non uniformities in luminance outside of a predetermined luminance variation detection range in order to provide a tiled, color flat-panel display with the appearance of having a uniform luminance, said method comprising the steps of:

a) providing a tiled, color flat-panel display comprising individual display tiles having seams therebetween, said individual display tiles comprising arrays of color pixels that vary a color characteristic in response to a data stream applied thereto to vary a display color, said color, flat-panel display exhibiting gradual non-uniformities or abrupt non-uniformities in luminance, said color, flat-panel display having built-in luminance calibration capability;

b) measuring primary luminance variations across predetermined color pixels each having an individual color space associated therewith, of said tiled, flat panel color display;

c) determining tristimulus values associated with said measured primary luminance variations of step (b);

d) electronically storing values representative of said tristimulus values;

e) using luminance scaler/adder means operatively connected to said tiled, color, flat-panel display to modify a continuous video input signal in accordance with said electronically stored values, at a predetermined refresh rate to produce a normalized data stream;

f) calibrating primary luminances for selected pixels in said tiled, color flat panel display by applying said normalized data stream to at least one of said color pixels, to calibrate spatial non-uniformities in the luminance of said tiled, color flat panel display.

22. The method for self-calibrating spatial non-uniformities in luminance in a color flat panel display as recited in claim 21, the steps further comprising:

f) periodically repeating steps (b) through (e), thereby electronically storing updated values corresponding to primary luminance variations so that time-varying primary luminance variations across said tiled, color flat panel display may be corrected.

23. The method for self-calibrating spatial non-uniformities in luminance in a color, flat-panel display, as recited in claim 22, wherein said sub-step of adjusting drive signals comprises at least one from the group of:

adjusting drive voltages, adjusting drive current, adjusting drive pulse width, adjusting drive signal modulation, or adjusting drive pulse repetition rate.

24. The method for self-calibrating spatial non-uniformities in luminance in a color, flat-panel display, as recited in claim 22, wherein said measurements obtained in step (b) are electronically stored in accordance with step (d) in a non-volatile memory.

25. The method for self-calibrating spatial non-uniformities in luminance in a color, flat-panel display, as recited in claim 22, wherein data representative of said measurements obtained in step (b) are electronically stored in accordance with step (d), utilizing interpolation techniques.

26. The method for self-calibrating spatial non-uniformities in luminance in a color, flat-panel display, as recited in claim 25, wherein said stored data is used in the processing of drive signals for correcting spatial non-uniformities in real time.