ELECTROLUMINESCENT DEVICE AGING COMPENSATION WITH REFERENCE SUBPIXELS

• US 20110074750A1
• Filed: 09/29/2009
• Published: 03/31/2011
• Est. Priority Date: 09/29/2009
• Status: Active Grant

• Current Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Original Assignee: Global OLED Technology LLC (LG Display Co., Ltd.)
• Inventors: LEON, FELIPE A., White, Christopher J.
• Granted Patent: US 8,339,386 B2
• Time in Patent Office: Days
• US Class Current: 345/207
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2360/141 the light conveying information used for selecting or modulating the light emitting or modulating element
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 3/30 using electroluminescent panels
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

An electroluminescent (EL) device including an illumination area having one or more primary EL emitters; a reference area having a reference EL emitter; a reference driver circuit for causing the reference EL emitter to emit light while the EL device is active; a sensor for detecting light emitted by the reference EL emitter; and a measurement unit for detecting an aging-related electrical parameter of the reference EL emitter while it is emitting light. The device further includes a controller for receiving an input signal for each primary EL emitter in the illumination area, forming a corrected input signal from each input signal using the detected light and the aging-related electrical parameter, and applying the corrected input signals to the respective primary EL emitters in the illumination area.

Claims

1. An electroluminescent (EL) device, comprising:

a) an illumination area having one or more primary EL emitters;

b) a reference area having a reference EL emitter;

c) a reference driver circuit for causing the reference EL emitter to emit light while the EL device is active;

d) a sensor for detecting light emitted by the reference EL emitter;

e) a measurement unit for detecting an aging-related electrical parameter of the reference EL emitter while it is emitting light; and

f) a controller for receiving an input signal for each primary EL emitter in the illumination area, forming a corrected input signal from each input signal using the detected light and the aging-related electrical parameter, and applying the corrected input signals to the respective primary EL emitters in the illumination area.

2. The EL device of claim 1, wherein the controller is adapted to form corrected input signals which compensate for loss of efficiency of the respective primary EL emitters.

3. The EL device of claim 1, wherein the sensor includes a colorimeter, a spectrophotometer or a spectroradiometer for providing color data to the controller, and wherein the controller is adapted to form corrected input signals which compensate for chromaticity shift of the respective primary EL emitters due to aging.

4. The EL device of claim 1, wherein the reference area has a plurality of reference EL emitters, a plurality of corresponding reference driver circuits for causing the respective reference EL emitters to emit light, a plurality of corresponding sensors for detecting light emitted by the respective reference EL emitters, and a plurality of corresponding measurement units for detecting respective aging-related electrical parameters of the respective reference EL emitters while they are emitting light, wherein the controller uses one or more of the plurality of detected light and aging-related electrical parameters to form a corrected input signal from each input signal.

5. The EL device of claim 1, further comprising a temperature measurement unit for measuring a temperature parameter related to the temperature of the reference EL emitter while the reference EL emitter is emitting light, and wherein the controller uses the measured temperature parameter to form the corrected input signals.

6. The EL device of claim 1, wherein the reference driver circuit causes the reference EL emitter to emit light at two levels, a measurement and fade level, at different times, and wherein measurements of the reference EL emitter are taken while it emits light at the measurement level.

7. The EL device of claim 6, wherein the fade level is greater than the measurement level.

8. The EL device of claim 6, wherein each input signal controls a respective emission level of the corresponding primary EL emitter, and wherein the fade level is greater than the maximum of the respective emission levels.

9. The EL device of claim 1, further comprising a memory for storing detected light measurements and corresponding aging-related electrical parameter measurements, and wherein the controller uses the values stored in the memory to form the corrected input signals.

10. The EL device of claim 1, wherein the reference driver circuit causes the reference EL emitter to emit light successively at a plurality of measurement levels, and wherein respective measurements of the reference EL emitter are taken while it emits light at each measurement level.

11. The EL device of claim 1, wherein the reference EL emitter and all primary EL emitters are identical.

12. The EL device of claim 1, wherein the reference driver circuit provides a test current to the reference EL emitter to cause it to emit light.

13. The EL device of claim 1, further comprising a timer which runs while the EL device is active, and wherein measurements of the reference EL emitter are taken at intervals determined by the timer.

14. The EL device of claim 1, wherein a measurement of the reference EL emitter is taken while the EL device is in thermal equilibrium.

15. The EL device of claim 1, wherein a measurement of the reference EL emitter is taken while the EL device is active.

16. The EL device of claim 1, further including a second reference area having a second reference EL emitter.

17. The EL device of claim 1, wherein the EL device is an EL display.

18. The EL device of claim 1, wherein the aging-related electrical parameter is a voltage or a current.

19. The EL device of claim 1, wherein each primary EL emitter and reference EL emitter is an organic light-emitting diode emitter.