System and method for compensation of non-uniformities in light emitting device displays

• US 10,235,933 B2
• Filed: 09/18/2014
• Issued: 03/19/2019
• Est. Priority Date: 04/12/2005
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Nathan, Arokia, Chaji, Gholamreza, Alexander, Stefan, Servati, Peyman, Huang, Richard I-Heng, Church, Corbin
• Primary Examiner(s): Regn, Mark
• Application Number:
  US14/490,513
• Publication Number:
  US 20150002378A1
• Time in Patent Office: 1,643 Days
• Field of Search: 345 77
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• 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 2320/0295 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 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• 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

Abstract

A display degradation compensation system and method for adjusting the operating conditions for pixels in an OLED display to compensate for non-uniformity or aging of the display. The system or method sets an initial value for at least one of peak luminance and an operating condition, calculates compensation values for the pixels in the display, determines the number of pixels having compensation values larger than a predetermined threshold compensation value, and if the determined number of pixels having compensation values larger than said predetermined threshold value is greater than a predetermined threshold number, adjusts the set value until said determined number of pixels is less than said predetermined threshold number.

Claims

1. A display system comprising:

a plurality of pixel circuits arranged in an array, each pixel circuit including a light emitting device and at least one thin film transistor (TFT);

a measurement circuit for measuring, independently for each individual pixel circuit of the plurality of pixel circuits, at least one of a voltage and a current of the at least one TFT of the individual pixel circuit independent of a degradation of the light emitting device of the individual pixel circuit and without directly measuring a light output from the light emitting device of the individual pixel circuit, generating measured TFT electrical data for each individual pixel circuit representing the at least one of a voltage and a current of the at least one TFT of the individual pixel circuit;

a TFT-to-Pixel conversion algorithm module for estimating a luminance degradation of each individual pixel circuit with use of a value of the at least one of a voltage and a current of the at least one TFT of the individual pixel represented by the measured TFT electrical data and at least one additional input; and

a compensation module for compensating for non-uniformity in the display system based on the estimated luminance degradation of each individual pixel circuit.

2. The display system of claim 1, wherein the compensation module further compensates for changes in the display system due to at least one condition of each individual pixel circuit or the display system represented by the at least one additional input.

3. The display system of claim 1, wherein the at least one additional input includes at least one of a temperature reading, a mechanical stress reading, an environmental stress reading, and feedback from a test structure in the display system.

4. The display of claim 1, wherein the TFT-to-Pixel conversion algorithm module further estimates the luminance degradation of each individual pixel circuit with use of one or more empirical parameters.

5. The display of claim 4, wherein the one or more empirical parameters include at least one of brightness loss in an organic light emitting device (OLED) of the pixel circuit due to decreasing efficiency (Δ

L), shift in the OLED'"'"'s voltage over time (Δ

Voled), dynamic effects of Vt shift, parameters related to TFT performance including Vt, Δ

Vt, 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, and pixel-circuit operating voltage variation due to IR-drop and ground bounce.

6. The display of claim 1, wherein the non-uniformity in the display system includes at least one of a brightness non-uniformity and a color non-uniformity.

7. The display of claim 1, wherein the measured TFT electrical data includes TFT degradation data.

8. The display of claim 1, wherein the measurement circuit is further for measuring at least one of a voltage and a current of the individual pixel circuit dependent upon the degradation of the light emitting device of the individual pixel circuit and without directly measuring a light output from the light emitting device of the individual pixel circuit, generating measured electrical data representing the at least one of a voltage and a current of the individual pixel circuit, the measured electrical data including light emitting device degradation data, and wherein the TFT-to-Pixel conversion algorithm module estimates said luminance degradation of each individual pixel circuit with use of a value of the at least one of a voltage and a current of the individual pixel circuit represented by the measured electrical data.