# US 2019/0378474 A1 · Method of determining fitting functions for sub-pixels of a display panel

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- Number: US 2019/0378474 A1
- Document ID: US20190378474A1
- Status: Published application
- Kind: A1
- Application number: 16/540,651
- Filed: 2019-08-14
- Published: 2019-12-12
- Earliest claimed: 2018-06-11
- Inventors: Hung-Cheng KUO
- Web page: https://patentgrep.com/patent/US20190378474A1

## CPC

- 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)}
- G09G 5/10: Intensity circuits
- G09G 3/20: for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix {no fixed position being assigned to or needed to be assigned to the individual characters or partial characters}
- G09G 3/3208: organic, e.g. using organic light-emitting diodes [OLED]
- G09G 2320/0233: Improving the luminance or brightness uniformity across the screen
- G09G 2320/0276: for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
- G09G 2320/029: by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
- G09G 2320/0295: by monitoring each display pixel
- G09G 2320/0673: for control of gamma adjustment, e.g. selecting another gamma curve
- G09G 2320/0693: Calibration of display systems
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

A method of determining fitting functions for sub-pixels of a same color element of a display panel is proposed. After a plurality of fitting functions are obtained for the sub-pixels, a predetermined filtering criterion is used to re-determine a fitting function from among the obtained fitting function for each sub-pixel, thereby reducing a total number of the fitting functions used for demura operation. The predetermined filtering criterion for a sub-pixel includes a single-pixel criterion that relates to a fitting deviation, which relates to a mismatch between a fitting function and data points measured for the sub-pixel.

## Claims

### Claim 1

A method of determining fitting functions for sub-pixels of a same color element of a display panel, the method to be performed by a computer device and comprising:
acquiring, for each of the sub-pixels, a data point set that includes a plurality of data points respectively corresponding to multiple predetermined luminance codes, wherein each of the data points is composed of the corresponding one of the predetermined luminance codes and a luminance value of the sub-pixel measured at the corresponding one of the predetermined luminance codes;
obtaining a plurality of fitting functions by performing curve fitting based on the data point sets acquired for the sub-pixels; and
for each of the sub-pixels, determining a filtered fitting function, which is one of the fitting functions that conforms to a predetermined filtering criterion, to fit the data point set acquired for the sub-pixel, the filtered fitting functions determined for the sub-pixels being to be used in demura operation for the display panel;
wherein, for each of the sub-pixels, the predetermined filtering criterion includes a single-pixel criterion that relates to a fitting deviation, which corresponds to the sub-pixel and which relates to a mismatch between the filtered fitting function and the data points corresponding to the sub-pixel.

### Claim 2 (depends on 1)

The method of claim 1, wherein each of the fitting functions is a polynomial function of which a degree is greater than or equal to two.

### Claim 3 (depends on 1)

The method of claim 1, wherein the obtaining a plurality of fitting functions includes:
acquiring, for each of the sub-pixels, a measurement-based curve function that serves as one of the fitting functions, by performing curve fitting on the data point set acquired for the sub-pixel;
said method further comprising:
arranging the fitting functions in order, wherein the measurement-based curve functions of the fitting functions are arranged from a highest frequency of occurrence among the measurement-based curve functions to a lowest frequency of occurrence among the measurement-based curve functions;
wherein, for each of the sub-pixels, the filtered fitting function is one of the fitting functions that has a highest order among those of fitting functions conforming to the predetermined filtering criterion with respect to the sub-pixel.

### Claim 4 (depends on 1)

The method of claim 1, wherein the obtaining a plurality of fitting functions includes:
classifying the sub-pixels into multiple sub-pixel groups based on the data point sets acquired for the sub-pixels; and
for each of the sub-pixel groups, acquiring a reference curve function based on the data point sets acquired for the sub-pixels of the sub-pixel group;
wherein, for each of the sub-pixels, the filtered fitting function is the reference curve function acquired for the corresponding one of the sub-pixel groups when the reference curve function acquired for the corresponding one of the sub-pixel groups conforms to the predetermined filtering criterion with respect to the sub-pixel.

### Claim 5 (depends on 4)

The method of claim 4, wherein the acquiring the reference curve function for each of the sub-pixel groups includes:
obtaining, for the sub-pixel group, a reference data point set that includes a plurality of reference data points, each of the reference data points is composed of a respective one of the predetermined luminance codes and a reference luminance value that is calculated by averaging the luminance values of the data points that are measured at the corresponding one of the predetermined luminance codes for the sub-pixels of the sub-pixel group; and
performing curve fitting on the reference data points to obtain the reference curve function for the sub-pixel group.

### Claim 6 (depends on 4)

The method of claim 4, wherein the acquiring the reference curve function for each of the sub-pixel groups includes:
obtaining a plurality of measurement-based curve functions for the sub-pixel group by performing curve fitting on each of the data point sets acquired for the sub-pixels of the sub-pixel group; and
averaging the measurement-based curve functions obtained for the sub-pixel group to obtain the reference curve function for the sub-pixel group.

### Claim 7 (depends on 4)

The method of claim 4, wherein the obtaining a plurality of fitting functions includes, for each of the sub-pixel groups:
acquiring, for each of the sub-pixels of the sub-pixel group, a measurement-based curve function that serves as one of the fitting functions, by performing curve fitting on the data point set acquired for the sub-pixel;
said method further comprising, for each of the sub-pixel groups:
arranging the measurement-based curve functions acquired for the sub-pixels of the sub-pixel group in order from a highest frequency of occurrence among the measurement-based curve functions corresponding to the sub-pixel group to a lowest frequency of occurrence among the measurement-based curve functions corresponding to the sub-pixel group;
wherein, for each of the sub-pixels, when the reference curve function acquired for the corresponding one of the sub-pixel groups does not conform to the predetermined filtering criterion with respect to the sub-pixel, the filtered fitting function is one of the measurement-based curve functions that has a highest order among those of the measurement-based curve functions corresponding to one of the sub-pixel groups including the sub-pixel and conforming to the predetermined filtering criterion with respect to the sub-pixel.

### Claim 8 (depends on 1)

The method of claim 1, wherein, for each of the sub-pixels, the predetermined filtering criterion further includes a pixel-difference criterion that relates to differences between the fitting deviation corresponding to the sub-pixel and the fitting deviations corresponding to some of the sub-pixels that are adjacent to the sub-pixel.

### Claim 9 (depends on 8)

The method of claim 8, wherein, for each of the sub-pixels, the fitting deviation includes a set of fitting deviation values each of which is a difference between the filtered fitting function and a respective one of the data points of the data point set acquired for the sub-pixel, and the single-pixel criterion for the sub-pixel is defined by setting, for each of the predetermined luminance codes, a deviation range for the corresponding one of the fitting deviation values of the fitting deviation, and requires that each of the fitting deviation values falls within the corresponding deviation range; and
wherein the pixel-difference criterion for each of the sub-pixels is defined by setting, for each of the predetermined luminance codes, a deviation difference range for a deviation difference between the fitting deviation values respectively corresponding to the sub-pixel and one of adjacent sub-pixels for the sub-pixel, and requires that the deviation difference falls within the corresponding deviation difference range.

### Claim 10 (depends on 1)

The method of claim 1, wherein, for each of the sub-pixels, the fitting deviation includes a set of fitting deviation values each of which is a difference between the filtered fitting function and a respective one of the data points of the data point set acquired for the sub-pixel, and the single-pixel criterion for the sub-pixel is defined by setting, for each of the predetermined luminance codes, a deviation range for the corresponding one of the fitting deviation values of the fitting deviation, and requires that each of the fitting deviation values falls within the corresponding deviation range.