Re-interpolation with edge detection for extracting an aging pattern for AMOLED displays

• US 9,536,465 B2
• Filed: 02/23/2016
• Issued: 01/03/2017
• Est. Priority Date: 03/14/2013
• Status: Active Grant

• Current Assignee: IGNIS Innovation Incorporated
• Original Assignee: IGNIS Innovation Incorporated
• Inventors: Chaji, Gholamreza, Torbatian, Mehdi
• Primary Examiner(s): Hoang, Phi
• Application Number:
  US15/050,700
• Publication Number:
  US 20160171923A1
• Time in Patent Office: 315 Days
• US Class Current: 1/1
• CPC Class Codes: G06T 3/403 Edge-driven scaling; Edge-based scaling
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• 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 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2340/10 Mixing of images, i.e. displayed pixel being the result of an operation, e.g. adding, on the corresponding input pixels
• 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 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2007 Display of intermediate tones
• CPC Class Codes: G09G 3/2085 Special arrangements for addressing the individual elements of the matrix, other than by driving respective rows and columns in combination
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 5/026 Control of mixing and/or overlay of colours in general G09G5/022 and G09G5/024 take precedence

Abstract

A method that includes an initial uniform pixel measurement and interpolation followed by an edge detection algorithm to recognize the areas that contribute mostly to the estimation error due to the interpolation. The pixels on the detected edges and around their vicinity are also measured, and an aging pattern of the entire display is obtained by re-interpolating the entire measured set of data for the initially measured pixels as well as the pixels around the detected edges. The estimation error is reduced particularly in the presence of aging patterns having highly spatially correlated areas with distinctive edges.

Claims

1. An image compensation method for a display having pixels that are aging due to shifts in one or more aging characteristics of the pixels, each of the pixels comprising a light emitting device, the method comprising:

measuring, using a measurement circuit, an aging characteristic of each pixel of a spaced apart subset of the pixels of the display to produce a set of initial pixel measurements;

determining localized maximums of a gradient magnitude defined by the set of initial pixel measurements;

defining a second subset of pixels of the display with use of the determined localized maximums of the gradient magnitude;

measuring, using the measurement circuit, the aging characteristic of each pixel of the second subset of pixels of the display to produce a second set of pixel measurements;

producing an aging pattern based on the set of initial pixel measurements and the second set of pixel measurements;

storing the aging pattern in a memory device;

generating, with use of the aging pattern, an estimation matrix corresponding to a pixel resolution of the display for improving an image uniformity of the light emitting devices across the display.

2. The method of claim 1, wherein the spaced subset of the pixels of the display comprises a spaced uniform distribution of pixels.

3. The method of claim 2, wherein the spaced uniform distribution of pixels comprises a spaced rectilinear distribution of pixels.

4. The method claim 3, wherein the spaced rectilinear distribution of pixels comprises at least some but not all pixels of the display using a down-sampling rate of KV×

KH, such that the aging characteristic of at least every KVth pixel is measured along a column and the aging characteristic of at least every KHth pixel is measured along a row.

5. The method of claim 1, wherein producing the aging pattern based on the set of initial pixel measurements and the second set of pixel measurements comprises interpolating a combination of the set of initial pixel measurements and the second set of pixel measurements.

6. The method of claim 5 wherein determining localized maximums of the gradient magnitude comprises interpolating the set of initial pixel measurements to produce an initial aging pattern and using an edge detection algorithm on the initial aging pattern.

7. The method of claim 1, wherein defining the second subset of pixels comprises selecting one or more pixels within a local vicinity of each of the determined localized maximums of the gradient magnitude.

8. The method of claim 1, wherein each entry in the estimation matrix corresponds to a respective pixel of the display, and wherein each value of each entry in the estimation matrix corresponds to an amount by which the respective pixel is aging such that a corresponding compensation value is applied to increase the programmed brightness for the pixel to compensate for the amount of aging.

9. The method of claim 1, wherein the aging characteristic is related to at least one of:

a shift in a threshold voltage of a drive transistor that drives the light emitting device in each of the pixels;

a change in a voltage across the light-emitting device in each of the pixels;

a change in a drive current of the drive transistor needed to cause the light-emitting device in each of the pixels to emit a programmed brightness; and

a change in a current of the light emitting devices needed to emit a programmed brightness.

10. The method of claim 1, wherein interpolating the combination of the set of initial pixel measurements and the second set of pixel measurements generates estimated aging characteristics for pixels of the display other than those for which set of initial pixel measurements and the second set of pixel measurements were made.

11. The method of claim 1, wherein determining localized maximums of the gradient magnitude comprises performing a Canny edge detection algorithm on the magnitudes defined by the set of initial pixel measurements.