Method and system for compensation of non-uniformities in light emitting device displays

• US 20060273997A1
• Filed: 04/12/2006
• Published: 12/07/2006
• Est. Priority Date: 04/12/2005
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, G. Reza, Servati, Peyman, Nathan, Arokia, Alexander, Stefan, Huang, Rick I-Heng, Church, Corbin
• Granted Patent: US 7,868,857 B2
• Time in Patent Office: Days
• US Class Current: 345/78
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• 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 2320/0295 by monitoring each display 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 3/3241 the current through the light-emitting element being set using a data current provided by the data driver, e.g. by using a two-transistor current mirror
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

A method and system for compensation of non-uniformities in light emitting device displays is provided. The system includes a module for estimating degradation of an entire pixel circuit based on measurement of a part of the pixel circuit. Based on the estimation, a correction factor is produced to correct non-uniformity of the display.

Claims

1. A system for compensating non-uniformities in a light emitting device display which includes a plurality of pixels and a source for providing pixel data to each pixel circuit, comprising:

a module for modifying the pixel data applied to one or more than one pixel circuit, including;

an estimating module for estimating a degradation of a first pixel circuit based on measurement data read from a part of the first pixel circuit; and

a compensating module for correcting the pixel data applied to the first or a second pixel circuit based on the estimation of the degradation of the first pixel circuit.

2. A system according to claim 1, wherein the modifying module implements a constant brightness algorithm for increasing luminance data applied to a degraded pixel circuit such that the brightness of the degraded pixel circuit matches that of a non-degraded pixel circuit.

3. A system according to claim 1, wherein the modifying module implements a decreasing brightness algorithm for decreasing luminance data applied to a non-degraded pixel circuit such that the brightness of the non-degraded pixel circuit matches that of a non-degraded pixel circuit.

4. A system according to claim 1, wherein at least one of the estimating module and the compensating module produces a correction factor in accordance with the constant brightness algorithm.

5. A system according to claim 1, wherein at least one of the estimating module and the compensating module produces a correction factor in accordance with the decreasing brightness algorithm.

6. A system according to claim 1, wherein the pixel circuit includes one or more than one transistor and a light emitting device, the estimating module estimating the degradation of the first pixel circuit based on electrical data measured from the one or more than one transistor.

7. A system according to claim 1, wherein the pixel circuit includes one or more than one transistor and a light emitting device, the estimating module estimating the degradation of the first pixel circuit based on first electrical data measured from the one or more than one transistor, second electrical data measured from the light emitting device, or a combination thereof, the second electrical data being measured separately from the measurement from the transistor.

8. A system according to claim 1, wherein the pixel circuit includes one or more than one transistor and a light emitting device, the estimating module estimating the degradation of the first pixel circuit based on electrical data which is read from the first pixel circuit and is associated with the one or more than one transistor, the light emitting device, or combinations thereof.

9. A system according to claim 1, wherein the modifying module dynamically allocates a timing of the measurement, a timing of the correction, or a combination thereof.

10. A system according to claim 9, wherein the modifying module includes a memory for storing compensation data or the measurement.

11. A system according to claim 1, wherein the estimating module estimates the degradation of the first pixel circuit based on the measurement data from the part of the first circuit together with one or more additional measurement inputs, one or more empirical parameters or combinations thereof.

12. A system according to claim 11, wherein the one or more additional measurement inputs include at least one of voltage reading from one or more current-programming pixels, current reading from one or more voltage-programming pixel, measurement of an ambient light, humidity measurement, temperature measurement, mechanical stress measurement, environmental stress measurement, and feedback from test structures on the display.

13. A system according to claim 11, wherein the one or more empirical parameters include at least one of brightness loss in a light emitting device of the pixel circuit due to decreasing efficiency (Δ

L), a shift in the light emitting device diode voltage over time (Δ

Voled), dynamic effects of threshold shift, parameters related to performance of a pixel transistor including threshold, threshold shift, mobility (μ

), inter-pixel non-uniformity, DC bias voltages in the pixel circuit, changing gain of current-mirror based pixel circuits, short-term and long-term based shifts in pixel circuit performance, pixel-circuit operating voltage variation due to IR-drop and ground bounce.

14. A system according to claim 1, wherein the system compensates for the non-uniformity due to process or construction inequality in the display, aging of one or more pixel circuits, or combinations thereof.

15. A system according to claim 1, wherein the compensating module includes grayscale compression module for implementing a gray scale compression algorithm on luminance data applied to the first or second pixel circuit to reserve grayscale values.

16. A system according to claim 15, wherein the gray scale compression algorithm module transforms the luminance data so as to use luminance values less than those of the original luminance data.

17. A system according to claim 6, wherein the transistor is a thin-film-transistor.

18. A system according to claim 6, wherein the light emitting device is an organic light emitting device.

19. A method of compensating non-uniformities in a light emitting device display having a plurality of pixels, comprising the steps of:

estimating a degradation of a first pixel circuit based on measurement data read from a part of the first pixel circuit; and

correcting pixel data applied to the first or a second pixel circuit based on the estimation of the degradation of the first pixel circuit.

20. A method according to claim 19, wherein the correcting step includes:

increasing luminance data to a degraded pixel circuit such that the brightness of the degraded pixel circuit matches that of a non-degraded pixel circuit.

21. A method according to claim 19, wherein the correcting step includes:

decreasing luminance data to a non-degraded pixel circuit such that the brightness of the non-degraded pixel circuit matches that of a non-degraded pixel circuit.

22. A method according toclaim 19, wherein the pixel circuit includes one or more than one transistor and a light emitting device,

the method including the step of measuring electrical data from the one or more than one transistor,

the estimating module estimating the degradation of the first pixel circuit based on the measurement from the one or more than one transistor only.

23. A method according toclaim 19, wherein the pixel circuit includes one or more than one transistor and a light emitting device,

the method including the steps of:

measuring first electrical data from the one or more than one transistor,

measuring second electrical data from the light emitting device, the second electrical data being measured separately from the measurement of the first electrical data,

the estimating module estimating the degradation of the first pixel circuit based on the first electrical data, the second electrical data, or a combination thereof.

24. A method according toclaim 19, wherein the pixel circuit includes one or more than one transistor and a light emitting device, the estimating step estimating the degradation of the first pixel circuit based on electrical data which is read from the first pixel circuit and is associated with the one or more than one transistors, the light emitting device, or combinations thereof.

25. A method according to claim 19, further including the step of dynamically allocating a timing of the measurement, a timing of the correction, or a combined thereof.

26. A method according to claim 19, further including the step of compressing grayscales of luminance data applied to the first or second pixel circuit to reserve one or more grayscale values.

27. A method according to claim 26, wherein the compressing step includes the step of transforming the luminance data so as to use luminance values less than those of the original luminance data.