Lifetime uniformity parameter extraction methods

• US 8,994,617 B2
• Filed: 03/17/2011
• Issued: 03/31/2015
• Est. Priority Date: 03/17/2010
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza, Jaffari, Javid, Nathan, Arokia
• Primary Examiner(s): Eisen, Alexander
• Assistant Examiner(s): Patel, Sanjiv D
• Application Number:
  US13/050,006
• Publication Number:
  US 20110227964A1
• Time in Patent Office: 1,475 Days
• Field of Search: 702106-126, 348175-191, 345/76
• US Class Current: 345/76
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 2330/12 Test circuits or failure detection circuits included in a display system, as permanent part thereof
• CPC Class Codes: G09G 2360/14 Detecting light within display terminals, e.g. using a single or a plurality of photosensors
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3225 using an active matrix

Abstract

A system and method for deriving a sequence of OLED non-uniformity test patterns. A pattern generator generates a full sequence of display patterns according to a transform function, such as a discrete cosine transformation or wavelet transformation. A driver drives a display with each of the sequence of patterns. A sensor senses a property of the display, such as a total current for the display, for each of the sequence of patterns. An extraction unit derives a pixel non-uniformity model using the sensed properties and an inverse of the transform function. Patterns that contribute less than a threshold amount to the non-uniformity model can be identified and deleted to derive a sparse sequence of patterns, which can be stored in a memory. The sparse sequence of patterns can be used to test the display and extract a set of pixel non-uniformity values. The pixel non-uniformity values can be used to generate a correction signal for the display.

Claims

1. A method of evaluating OLED display pixel status and compensating for degradation of individual pixels within the display, said method comprising:

generating a sequence of patterns representing pixel values for a display panel, wherein the sequence of patterns is a subset of a full sequence of patterns;

driving the OLED panel with the sequence of patterns;

sensing a sequence of values representing the responses of the panel to the respective ones of the sequence of patterns, said sequence of values including at least one of power supply current and brightness of the display panel;

using a non-uniformity model based on said sensed sequence of values representing said responses of the panel to the respective ones of the sequence of patterns, mathematically deriving from the sensed sequence of values a matrix of status values representing at least one of the ageing and non-uniformity of each of the individual pixels in the panel;

storing the matrix of status values in a memory; and

using said status values to compensate individual pixels in the display panel for at least one of ageing and non-uniformity.

2. The method of claim 1, further comprising applying to the panel a correction signal corresponding to the matrix of status values.

3. The method of claim 1, wherein the generating uses at least one of a discrete cosine transformation and a wavelet transformation to generate at least one of the patterns, and wherein the deriving uses an inverse of the at least one transformation.

4. The method of claim 3, further comprising:

discarding from the sequence of patterns a pattern that contributes less than a threshold amount to the matrix of status values; and

repeating the generating, driving, sensing, deriving, and storing steps.

5. The method of claim 4, further comprising:

reintroducing the discarded pattern to the sequence of patterns; and

repeating the generating, driving, sensing, deriving, and storing steps.

6. The method of claim 1, wherein the generating comprises generating at least one pattern based on a principal component analysis.

7. The method of claim 6, wherein the principal component analysis comprises generating a principal component through at least one of a predefined non-uniformity pattern and a moving averaging of an input to the OLED display.

8. The method of claim 1, wherein

driving the OLED panel comprises operating the pixel driving transistors in a first operating position and a second operating position;

the sequence of patterns includes patterns corresponding to each of the first operating position and the second operating position; and

the matrix of status values includes values corresponding to two discrete display characteristics.

9. The method of claim 8, wherein the first operating position is a linear region and the second operating position is a saturation region.

10. The method of claim 8, wherein the first operating position and the second operating position are offset by an offset voltage.

11. An apparatus for evaluating OLED display status, comprising:

a pattern generator configured to generate a sequence of pixel patterns, wherein the sequence of patterns is a subset of a full sequence of patterns;

a pixel driver coupled to the pattern generator configured to drive a display panel with the sequence of pixel patterns generated by the pattern generator;

a sensor configured to sense panel response values corresponding to a pattern generated by the pattern generator, said response values including at least one of power supply current and brightness of the display panel;

an extraction module coupled to the sensor configured to mathematically extract, using a non-uniformity model based on said sensed panel response value corresponding to a pattern generated by the pattern generator, a set of status values corresponding to at least one of the ageing and non-uniformity of each of the individual pixels of the panel from the panel response values;

a memory configured to store the set of status values; and

using said status values to compensate individual pixels in the display panel for at least one of ageing and non-uniformity.

12. The apparatus of claim 11, further comprising a correction module coupled to the pixel driver configured to generate a set of correction signals corresponding to the status values.

13. The apparatus of claim 11, wherein the sensor is one of a current sensor configured to sense an OLED panel V_DD current, an optical sensor configured to sense a light intensity of the OLED display, or a thermal sensor configured to sense a thermal value of the OLED display.

14. The apparatus of claim 11, wherein a pattern is generated using at least one of a discrete cosine transformation and a wavelet transformation.

15. The apparatus of claim 11, wherein the pattern generator is configured to discard a pattern that contributes less than a threshold amount to the matrix of status values.

16. The apparatus of claim 11, wherein the pattern generator is configured to generate at least one pattern based on a principal component analysis.

17. The apparatus of claim 16, wherein the pattern generator is configured to generate at the least one pattern through at least one of a predefined status pattern and a moving averaging of an input to the OLED display.

18. The apparatus of claim 11, wherein

the pixel driver is further configured to alternately drive the pixel driving transistors in a first operating position and a second operating position;

the sequence of patterns includes patterns corresponding to each of the first operating position and the second operating position; and

the extraction module is further configured to extract status values representative of two discrete display characteristics.

19. The apparatus of claim 18, wherein the first operating position and the second operating position are offset by an offset voltage.

20. The apparatus of claim 18, wherein the two discrete display characteristics are driving transistor ageing and OLED pixel ageing.