METHODS OF GRAYSCALE CALIBRATION OF SUBPIXELS OF LIQUID CRYSTAL PANELS DURING IMAGING

• US 20160343289A1
• Filed: 05/21/2015
• Published: 11/24/2016
• Est. Priority Date: 05/21/2015
• Status: Active Grant

• Current Assignee: Shenzhen China Star Optoelectronics Technology Co., Ltd. (TCL Technology Group Corp.)
• Original Assignee: Shenzhen China Star Optoelectronics Technology Co., Ltd. (TCL Technology Group Corp.)
• Inventors: CHEN, Lixuan
• Granted Patent: US 9,589,497 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0447 for multi-domain technique to improve the viewing angle in a liquid crystal display, such as multi-vertical alignment [MVA]
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/028 by changing the viewing angle properties, e.g. widening the viewing angle, adapting the viewing angle to the view direction
• CPC Class Codes: G09G 2320/0673 for control of gamma adjustment, e.g. selecting another gamma curve
• CPC Class Codes: G09G 2320/0693 Calibration of display systems
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607
• CPC Class Codes: G09G 3/2011 by amplitude modulation
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A method of grayscale calibration of subpixels of liquid crystal panels during imaging includes: obtaining a first brightness value when the subpixel of the i-th color has a maximum grayscale; calculating a second brightness value of each grayscale(j); obtaining a third brightness value of each grayscale(r) of the main subpixel area and a fourth brightness value of each grayscale (s) of the secondary subpixel area of under the direct view condition; determining value combinations for the main and the secondary subpixel area of the subpixel having the grayscale (j) and satisfying a predetermined criteria; calculating total color differences of the grayscale images respectively for the direct and a squint view condition when the value combination being applied; determining the value combination of the minimum total color difference as the value combination applied for the subpixel. With such configuration, the color shift of the liquid crystal panel may be reduced.

Claims

1. A method of grayscale calibration of subpixels of liquid crystal panels during imaging, each of the pixels of the liquid crystal panel comprises a plurality of subpixels of n number of colors, wherein n is an integer larger than 0, each of the subpixels comprises a main subpixel area and a secondary subpixel area, the method comprising:

(a) measuring a Gamma curve of i-th color among n numbers of colors under a direct view condition to obtain a first brightness value when the subpixel of the i-th color has a maximum grayscale (m), wherein iε

[1, n];

(b) calculating a second brightness value L(j) corresponding to each of grayscale of the subpixel of the i-th color in accordance with the first brightness value and a predetermined Gamma value, wherein jε

[t, m], t representing a minimum grayscale;

(c) obtaining a third brightness value Lm(r) corresponding to each of the grayscale (r) of the main subpixel area of the subpixel of the i-th color is calculated under the direct view condition, wherein rε

[t, m];

(d) obtaining a fourth brightness value Ls(s) corresponding to each of the grayscale of the secondary pixel area of the subpixel of the i-th color under the direct view condition, wherein sε

[t, m];

(e) determining value combinations for the grayscale of the main subpixel area and the grayscale of the secondary subpixel area of the subpixel of the i-th color basing on the second brightness value L(j), and the third brightness value Lm(r) and the fourth brightness value Ls(s) corresponding to the j-th grayscale satisfying a predetermined criteria;

(f) calculating total color differences of the grayscale images respectively for the direct view condition and a squint view condition for the subpixel of the i-th color having the grayscale (j) when the value combination being applied; and

(g) determining the value combination corresponding to the minimum total color difference as the value combination applied for the subpixel of the i-th color having the grayscale (j).

2. The method as claimed in claim 1, wherein the step (f) further comprises:

(f1) obtaining tristimulus values of grayscale images displayed by the liquid crystal panel respectively when applying one of the value combination under a direct view condition and a squint view condition, wherein the subpixel of the i-th color having the grayscale (j);

(f2) calculating psychrometric lightness and psychrometric chromaticity in accordance with the tristimulus values under the direct view condition, and calculating psychrometric lightness and psychrometric chromaticity in accordance with the tristimulus values under the squint view condition; and

(f3) calculating the total color difference of the grayscale images respectively for the direct view condition and the squint view condition in accordance with the psychrometric lightness and psychrometric chromaticity under the direct view condition and the squint view condition.

3. The method as claimed in claim 1, wherein the step (b) further comprises:

calculating the second brightness value L(j) corresponding to each of the grayscale (j) of the subpixel of the i-th color in accordance with the first brightness value and the predetermined Gamma value by the equation;

L(j)=L(m)×

(j/m)^γ

;

wherein γ

represents a predetermined Gamma value, and L(m) represents the first brightness value when the subpixel of the i-th color has a maximum grayscale (m).

4. The method as claimed in claim 1, wherein the step (c) further comprises:

turning off the secondary subpixel area of the subpixel of the i-th color;

measuring the Gamma curve of the i-th color of the liquid crystal panel under the direct view condition so as to obtain the third brightness value Lm (R) corresponding to the r-th grayscale of the main subpixel area of the subpixels of the i-th color;

and the step (d) further comprises;

turning off the main subpixel area of the subpixel of the i-th color; and

measuring the Gamma curve of the i-th color of the liquid crystal panel under the direct view condition so as to obtain the fourth brightness value Ls(s) corresponding to the s-th grayscale of the secondary subpixel area of the subpixels of the i-th color.

5. The method as claimed in claim 1, wherein the predetermined criteria of the step (e) is:

[Lm(r)+Ls(s)−

L(j)]/L(j)<

S;

wherein S is the predetermined value.

6. A method of grayscale calibration of subpixels of liquid crystal panels during imaging, each of the pixels of the liquid crystal panel comprises a plurality of subpixels of n number of colors, wherein n is an integer larger than 0, each of the subpixels comprises a main subpixel area and a secondary subpixel area, the method comprising:

(a) measuring a Gamma curve of i-th color among n numbers of colors under a direct view condition to obtain a first brightness value when the subpixel of the i-th color has a maximum grayscale (m), wherein iε

[1, n];

(b) calculating a second brightness value L(j) corresponding to each of grayscale of the subpixel of the i-th color in accordance with the first brightness value and a predetermined Gamma value, wherein jε

[t, m], t representing a minimum grayscale;

(c) selecting at least one value combination of the grayscale (r) of the main subpixel area of the i-th color and the grayscale (s) of the secondary subpixel area of the i-th color, such that the total color difference of grayscale images of the liquid crystal panel between a direct view conditions and a squint view condition is smaller than a predetermined value, and rε

[t, m], sε

[t, m];

(d) calculating a third brightness value corresponding to the grayscale of the main subpixel area of the subpixel of the i-th color of the selected value combination under the direct view condition;

(e) calculating a fourth brightness value corresponding to the grayscale of the secondary pixel area of the subpixel of the i-th color of the selected value combination under the direct view condition;

(f) determining whether the value combinations of the third brightness value and the fourth brightness value corresponding to the grayscale (j) satisfying the predetermined criteria in accordance with the second brightness value L(j); and

(g) selecting the value combination of the subpixel of the i-th color having grayscale (j).

7. The method as claimed in claim 6, wherein the step (c) further comprises:

(c1) obtaining tristimulus values of grayscale images displayed by the liquid crystal panel respectively for a direct view condition and a squint view condition;

(c2) calculating psychrometric lightness and psychrometric chromaticity in accordance with the tristimulus values under the direct view condition, and calculating psychrometric lightness and psychrometric chromaticity in accordance with the tristimulus values under the squint view condition; and

(c3) calculating a total color difference of the grayscale images of the liquid crystal panel respectively for the direct view condition and the squint view condition in accordance with the psychrometric lightness and psychrometric chromaticity under the direct view condition and the squint view condition.

8. The method as claimed in claim 6, wherein the step (b) further comprises:

calculating the second brightness value L(j) corresponding to each of the grayscale (j) of the subpixel of the i-th color in accordance with the first brightness value and the predetermined Gamma value by the equation;

L(j)=L(m)×

(j/m)^γ

;

wherein γ

represents a predetermined Gamma value, and L(m) represents the first brightness value when the subpixel of the i-th color has a maximum grayscale (m).

9. The method as claimed in claim 6, wherein the step (d) further comprises:

turning off the secondary subpixel area of the subpixel of the i-th color;

measuring the Gamma curve of the i-th color of the liquid crystal panel under the direct view condition so as to obtain the third brightness value corresponding to the grayscale of the main subpixel area of the subpixels of the i-th color of the selected value combination;

wherein the step (e) further comprises;

turning off the main subpixel area of the subpixel of the i-th color; and

measuring the Gamma curve of the i-th color of the liquid crystal panel under the direct view condition so as to obtain the fourth brightness value corresponding to the grayscale of the secondary subpixel area of the subpixels of the i-th color of the selected value combination.

10. The method as claimed in claim 6, wherein the predetermined criteria is selected such that the equation below owns the minimum value:

[Lm(x)+Ls(y)−

L(j)]/L(j);

wherein Lm(x) represents a third brightness value corresponding to the grayscale (x) of the main subpixel area of the value combination, and Ls(y) represents a fourth brightness value corresponding to the grayscale (y) of the secondary subpixel area of the value combination.