Method and device for display color adjustment

1. A color adjustment method for a display apparatus including a display device, a color correction circuit, and drive circuitry configured to drive the display device, the method comprising:

measuring first luminance coordinate data for a color displayed on the display device when image data corresponding to a white point is supplied to the drive circuitry;

measuring second luminance coordinate data for a color displayed on the display device when image data corresponding to a white color of at least one intermediate grayscale value is supplied to the drive circuitry;

measuring third luminance coordinate data for respective colors displayed on the display device when image data corresponding to each of a plurality of elementary color points is supplied to the drive circuitry;

calculating, based on the first luminance coordinate data and on the second luminance coordinate data, first gamma values for the white color;

calculating, based on the first gamma values and on a conversion matrix indicating a property of the first luminance coordinate data and the third luminance coordinate data, second gamma values for at least one of a plurality of elementary colors;

calculating, using the second gamma values, desired values for displaying the white point and for displaying an adjustment target color; and

calculating, based on the first luminance coordinate data, on the second luminance coordinate data, and on the third luminance coordinate data, correction parameters to be set to the color correction circuit,

wherein the correction parameters configure the color correction circuit to output the desired values for displaying the white point responsive to the image data corresponding to the white point, and to output the desired values for displaying the adjustment target color responsive to image data corresponding to the adjustment target color.

2. The method according to claim 1 ,

wherein the plurality of elementary color points comprises R, G, and B elementary color points, and

wherein calculating the desired values comprises calculating desired RGB values of the white point and of the adjustment target color.

3. The method according to claim 2 ,

wherein the conversion matrix comprises an XYZ-RGB conversion matrix,

wherein calculating the second gamma values comprises calculating gamma values for an elementary color R, gamma values for an elementary color G, and gamma values for an elementary color B, and

wherein calculating the desired RGB values of the white point and of the adjustment target color is based on the gamma values for the elementary color R, the gamma values for the elementary color G, and the gamma values for the elementary color B.

4. The method according to claim 3 ,

wherein the adjustment target color includes the R, G, and B elementary color points,

wherein calculating the desired RGB values of the white point is further based on desired chromaticity coordinates specified with respect to the white point, and

wherein the desired RGB values of the R, G, and B elementary color points are calculated based on desired chromaticity coordinates specified for the R, G, and B elementary color points, respectively.

5. The method according to claim 4 , wherein chromaticity coordinates (W Y ′, Wx′, Wy′) are the desired chromaticity coordinates specified with respect to the white point in the Yxy color system, W R , W G , W B are R, G, and B grayscale values of the desired RGB values of the white point, respectively, M −1 is the XYZ-RGB conversion matrix, Rγ n is a gamma value of a grayscale value n with respect to the elementary color R, Gγ n is a gamma value of a grayscale value n with respect to the elementary color G, and Bγ n is a gamma value of a grayscale value n with respect to the elementary color B, and

wherein calculating the desired RGB values of the white point comprises:

calculating RGB values {W R ′, W G ′, W B ′} in accordance with the following expressions (1a) to (1c):

W

X

′

=

W

Y

′

×

W

x

′

÷

W

y

′

,

(

1

⁢

a

)

W

Z

′

=

W

Y

′

×

(

1

-

W

x

′

-

W

y

′

)

÷

W

y

′

,

and

(

1

⁢

b

)

(

W

R

′

W

G

′

W

B

′

)

=

M

-

1

⁡

(

W

X

′

W

Y

′

W

Z

′

)

;

(

1

⁢

c

)

calculating RGB values {W R NRM , W G NRM , W B NRM } by normalizing the RGB values {W R ′, W G ′, W B ′} with an allowed maximum grayscale value;

determining an R grayscale value W R of the desired RGB values of the white point as a grayscale value n determined such that a value W R tmp defined by the following expression (2a) is the closest to the R grayscale value W R NRM ;

determining an G grayscale value W G of the desired RGB values of the white point as a grayscale value n determined such that a value W G tmp defined by the following expression (2b) is the closest to the G grayscale value W G NRM ; and

determining an B grayscale value W B of the desired RGB values of the white point as a grayscale value n determined such that a value W B tmp defined by the following expression (2b) is the closest to the G grayscale value W B NRM :

W

R

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

R

⁢

⁢

γ

⁢

⁢

n

,

(

2

⁢

a

)

W

G

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

G

⁢

⁢

γ

⁢

⁢

n

,

and

(

2

⁢

b

)

W

B

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

B

⁢

⁢

γ

⁢

⁢

n

.

(

2

⁢

c

)

6. The method according to claim 4 , wherein chromaticity coordinates (R Y ′, Rx′, Ry′) are the desired chromaticity coordinates specified with respect to the R elementary color point in the Yxy color system, R R , R G , R B are R, G and B grayscale values of the desired RGB values of the R elementary color point, respectively, M −1 is the XYZ-RGB conversion matrix, Rγ n is a gamma value of a grayscale value n with respect to the elementary color R, Gγ n is a gamma value of a grayscale value n with respect to the elementary color G, and Bγ n is a gamma value of a grayscale value n with respect to the elementary color B, and

wherein calculating the desired RGB values of the R elementary color point comprises:

calculating RGB values {R R ′, R G ′, R B ′} in accordance with the following expressions (3a) to (3c):

R

X

′

=

R

Y

′

×

R

x

′

÷

R

y

′

(

3

⁢

a

)

R

Z

′

=

R

Y

′

×

(

1

-

R

x

′

-

R

y

′

)

÷

R

y

′

,

and

(

3

⁢

b

)

(

R

R

′

R

G

′

R

B

′

)

=

M

-

1

⁡

(

R

X

′

R

Y

′

R

Z

′

)

;

(

3

⁢

c

)

calculating RGB values {R R NRM , R G NRM , R B NRM } by normalizing the RGB values {R R ′, R G ′, R B ′} with an allowed maximum grayscale value;

calculating RGB values {R R ″, R G ″, R B ″} by multiplying each of the RGB values {R R NRM , R G NRM , R B NRM } by a correction coefficient calculated from a desired relative luminance;

determining an R grayscale value R R of the desired RGB values of the R elementary color point as a grayscale value n determined such that a value R R tmp defined by the following expression (4a) is the closest to the R grayscale value R R ″;

determining a G grayscale value R G of the desired RGB values of the R elementary color point as a grayscale value n determined such that a value R G tmp defined by the following expression (4b) is the closest to the R grayscale value R G ″; and

determining a B grayscale value R B of the desired RGB values of the R elementary color point as a grayscale value n determined such that a value R B tmp defined by the following expression (4c) is the closest to the R grayscale value R B ″:

R

R

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

R

⁢

⁢

γ

⁢

⁢

n

,

(

4

⁢

a

)

R

G

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

G

⁢

⁢

γ

⁢

⁢

n

,

and

(

4

⁢

b

)

R

B

tmp

=

RGB

MAX

×

(

n

RGB

MAX

)

B

⁢

⁢

γ

⁢

⁢

n

.

(

4

⁢

c

)

7. The method of claim 1 , wherein each of the first luminance coordinate data, the second luminance coordinate data, and the third luminance coordinate data comprises a respective luminance and respective chromaticity coordinates.

8. A color adjustment apparatus for performing color adjustment of a display apparatus including a display device, a color correction circuit, and drive circuitry configured to drive the display device, the apparatus comprising:

a luminance meter configured to measure:

first luminance coordinate data for a color displayed on the display device when image data corresponding to a white point is supplied to the drive circuitry;

second luminance coordinate data for a color displayed on the display device when image data corresponding to a white color of at least one intermediate grayscale value is supplied to the drive circuitry; and

third luminance coordinate data for respective colors displayed on the display device when image data corresponding to each of a plurality of elementary color points is supplied to the drive circuitry; and

a processing unit configured to:

calculate, based on the first luminance coordinate data and on the second luminance coordinate data, first gamma values for the white color;

calculate, based on the first gamma values and on a conversion matrix indicating a property of the first luminance coordinate data and the third luminance coordinate data, second gamma values for at least one of a plurality of elementary colors;

calculate, using the second gamma values, desired values for displaying the white point and for displaying an adjustment target color; and

calculate, based on the first luminance coordinate data, on the second luminance coordinate data, and on the third luminance coordinate data, correction parameters to be set to the color correction circuit,

wherein the correction parameters configure the color correction circuit to output the desired values for displaying the white point responsive to the image data corresponding to the white point, and to output the desired values for displaying the adjustment target color responsive to image data corresponding to the adjustment target color.

9. The color adjustment apparatus according to claim 8 ,

wherein the plurality of elementary color points comprises R, G, and B elementary color points, and

wherein calculating the desired values comprises calculating desired RGB values of the white point and of the adjustment target color.

10. The color adjustment apparatus according to claim 9 ,

wherein the conversion matrix comprises an XYZ-RGB conversion matrix,

wherein calculating the second gamma value comprises calculating gamma values for an elementary color R, gamma values for an elementary color G, and gamma values for an elementary color B, and

wherein calculating the desired RGB values of the white point and of the adjustment target color is based on the gamma values for the elementary color R, the gamma values for the elementary color G, and the gamma values for the elementary color B.

11. The color adjustment apparatus according to claim 10 ,

wherein the adjustment target color includes the R, G, and B elementary color points,

wherein calculating the desired RGB values of the white point is further based on desired chromaticity coordinates specified with respect to the white point, and

wherein the desired RGB values of the R, G, and B elementary color points are calculated based on desired chromaticity coordinates specified for the R, G, and B elementary color points, respectively.

12. The color adjustment apparatus of claim 8 , wherein each of the first luminance coordinate data, the second luminance coordinate data, and the third luminance coordinate data comprises a respective luminance and respective chromaticity coordinates.

13. A display driver, comprising:

a drive circuitry configured to drive a display device;

a nonvolatile memory storing:

first luminance coordinate data for a color displayed on the display device when image data corresponding to a white point is supplied to the drive circuitry;

second luminance coordinate data for a color displayed on the display device when image data corresponding to a white color of at least one intermediate grayscale value is supplied to the drive circuitry;

third luminance coordinate data for respective colors displayed on the display device when image data corresponding to each of a plurality of elementary color points is supplied to the drive circuitry; and

correction parameters that are based on the first luminance coordinate data, on the second luminance coordinate data, and on the third luminance coordinate data; and

a color correction circuit configured to output, based on the correction parameters, desired values to the drive circuitry for displaying the white point responsive to the image data corresponding to the white point, and for displaying an adjustment target color responsive to image data corresponding to the adjustment target color,

wherein the desired values are based on first gamma values for at least one of a plurality of elementary colors,

wherein the first gamma values are based on second gamma values for the white color and on a conversion matrix indicating a property of the first luminance coordinate data and the third luminance coordinate data,

wherein the second gamma values are based on the first luminance data and on the second luminance data.

14. The display driver of claim 13 ,

wherein the plurality of elementary color points comprises R, G, and B elementary color points, and

wherein calculating the desired values comprises calculating desired RGB values of the white point and of the adjustment target color.

15. The display driver of claim 14 ,

wherein the conversion matrix comprises an XYZ-RGB conversion matrix,

wherein calculating the second gamma values comprises calculating gamma values for an elementary color R, gamma values for an elementary color G, and gamma values for an elementary color B, and

wherein calculating the desired RGB values of the white point and of the adjustment target color is based on the gamma values for the elementary color R, the gamma values for the elementary color G, and the gamma values for the elementary color B.

16. The display driver of claim 15 ,

wherein the adjustment target color includes the R, G, and B elementary color points,

wherein calculating the desired RGB values of the white point is further based on desired chromaticity coordinates specified with respect to the white point, and

wherein the desired RGB values of the R, G, and B elementary color points are calculated based on desired chromaticity coordinates specified for the R, G, and B elementary color points, respectively.

17. A display system, comprising:

a display apparatus including a display device and a display driver comprising:

a color correction circuit;

a drive circuitry configured to drive the display device; and

a nonvolatile memory storing:

first luminance coordinate data for a color displayed on the display device when image data corresponding to a white point is supplied to the drive circuitry;

second luminance coordinate data for a color displayed on the display device when image data corresponding to a white color of at least one intermediate grayscale value is supplied to the drive circuitry; and

third luminance coordinate data for respective colors displayed on the display device when image data corresponding to each of a plurality of elementary color points is supplied to the drive circuitry;

a host configured to:

receive the first luminance coordinate data, the second luminance coordinate data, and the third luminance coordinate data from the display driver;

calculate, based on the first luminance coordinate data and on the second luminance coordinate data, first gamma values for the white color;

calculate, based on the first gamma values and on a conversion matrix indicating a property of the first luminance coordinate data and the third luminance coordinate data, second gamma values for at least one of a plurality of elementary colors;

calculate, using the second gamma values, desired values for displaying the white point and for displaying an adjustment target color;

calculate, based on the first luminance coordinate data, on the second luminance coordinate data, and on the third luminance coordinate data, correction parameters that configure the color correction circuit to output the desired values for displaying the white point responsive to the image data corresponding to the white point, and to output the desired values for displaying the adjustment target color responsive to image data corresponding to the adjustment target color; and

transfer the correction parameters to the display driver.

18. The display system according to claim 17 ,

wherein the plurality of elementary color points comprises R, G, and B elementary color points, and

wherein calculating the desired values comprises calculating desired RGB values of the white point and of the adjustment target color.

19. The display system according to claim 18 ,

wherein the conversion matrix comprises an XYZ-RGB conversion matrix;

wherein calculating the second gamma values for an elementary color R, gamma values for an elementary color G, and gamma values for an elementary color B, and

wherein calculating the desired RGB values of the white point and of the adjustment target color is based on the gamma values for the elementary color R, the gamma values for the elementary color G, and the gamma values for the elementary color B.

20. The display system according to claim 19 ,

wherein the adjustment target color includes the R, G, and B elementary color points,

wherein calculating the desired RGB values of the white point is further based on desired chromaticity coordinates specified with respect to the white point, and

wherein the desired RGB values of the R, G, and B elementary color points are calculated based on desired chromaticity coordinates specified for the R, G, and B elementary color points, respectively.