System and methods for aging compensation in AMOLED displays

• US 9,786,209 B2
• Filed: 09/05/2014
• Issued: 10/10/2017
• Est. Priority Date: 11/30/2009
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza, Dionne, Joseph Marcel, Azizi, Yaser, Jaffari, Javid, Hormati, Abbas, Liu, Tong, Alexander, Stefan
• Primary Examiner(s): Ngon, Ricky
• Application Number:
  US14/477,971
• Publication Number:
  US 20140375701A1
• Time in Patent Office: 1,131 Days
• Field of Search: 702 58
• CPC Class Codes: G01R 31/44 Testing lamps
• 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 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 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

Methods and systems to provide baseline measurements for aging compensation for a display device are disclosed. An example display system has a plurality of active pixels and a reference pixel. Common input signals are provided to the reference pixel and the plurality of active pixels. The outputs of the reference pixel is measured and compared to the output of the active pixels to determine aging effects. The display system may also be tested applying a first known reference current to a current comparator with a second variable reference current and the output of a device under test such as one of the pixels. The variable reference current is adjusted until the second current and the output of the device under test is equivalent of the first current. The resulting current of the device under test is stored in a look up table for a baseline for aging measurements during the display system operation. The display system may also be tested to determine production flaws by determining anomalies such as short circuits in pixel components such as OLEDs and drive transistors.

Claims

1. A display comprising:

an array of pixels arranged in rows and columns, the array of pixels comprising a pixel including;

a programming voltage input;

a light emitting device for emitting light;

a drive circuit for driving the light emitting device; and

a current output coupled to a monitor line for outputting an output current of a device under test within the pixel while a set programming voltage input is applied to the programming voltage input;

a first reference current source for generating a first reference current;

a second variable reference current source for generating a second variable reference current;

a comparator having a first current input, a second current input, and a signal output, the first current input coupled to the second variable reference current source and coupled to the current output of the pixel via the monitor line and for receiving a combination of the second variable reference current and the output current as a first input current, the second current input coupled to the first reference current source for receiving the first reference current as a second input current, the signal output for providing an output signal based on the first input current and the second input current;

a controller coupled to the second variable reference current source and the output of the comparator and for adjusting the second variable reference current source until a final second variable reference current is reached such that the output signal of the comparator indicates that the first input current and the second input current are the same, and for determining an output current value based on the magnitude of the final second variable reference current.

2. The display of claim 1, wherein the controller is further for storing the determined output current value in a table associated with the device under test.

3. The display of claim 1, wherein the device under test is the light emitting device.

4. The display of claim 1, wherein the device under test is a drive transistor of the drive circuit.