Image display apparatus and driving method thereof, and image display apparatus assembly and driving method thereof

1. An image display apparatus comprising:

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels each including a first sub-pixel for displaying a first elementary color, a second sub-pixel for displaying a second elementary color, a third sub-pixel for displaying a third elementary color and a fourth sub-pixel for displaying a fourth color; and

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to a (p, q)th pixel where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following processes of

(B-1) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of sub-pixel input signals in said pixels,

(B-2) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels,

(B-3) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) , and

(B-4) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

2. The image display apparatus according to claim 1 wherein said signal processing section is capable of finding output signal values X 1-(p, q) , X 2-(p, q) and X 3-(p, q) on the basis of the following equations:

X 1-(p, q) =α 0 ·x 1-(p, q) −χ·X 4-(p, q) ;

X 2-(p, q) =α 0 ·x 2-(p, q) −χ·X 4-(p, q) ; and

X 3-(p, q) =α 0 ·x 3-(p, q) −χ·X 4-(p, q) ,

where, in said above equations, reference notation χ denotes a constant dependent on said image display apparatus whereas reference notations X 1-(p, q) , X 2-(p, q) and X 3-(p, q) each denote an output signal value in said (p, q)th pixel.

3. The image display apparatus according to claim 2 wherein said constant χ is expressed by the following equation:

χ= BN 4 /BN 1-3

where, in said above equation, reference notation BN 1-3 denotes the luminance of a set of first, second and third sub-pixels for a case in which

a signal having a value corresponding to the maximum signal value of said first sub-pixel output signal is supplied to said first sub-pixel,

a signal having a value corresponding to the maximum signal value of said second sub-pixel output signal is supplied to said second sub-pixel, and

a signal having a value corresponding to the maximum signal value of said third sub-pixel output signal is supplied to said third sub-pixel

whereas reference notation BN 4 denotes the luminance of said fourth sub-pixel for a case in which a signal having a value corresponding to the maximum signal value of said fourth sub-pixel output signal is supplied to said fourth sub-pixel.

4. The image display apparatus according to claim 1 wherein a saturation S (p, q) and a lightness value V (p, q) in said HSV color space in a (p, q)th pixel are found on the basis of the following equations:

S (p, q) =(Max (p, q) −Min (p, q) )/Max (p, q) ; and

V (p, q) =Max (p, q) ,

where, in said above equations,

notation Max (p, q) denotes the maximum value of the signal values of said three sub-pixel input signals x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ,

notation Min (p, q) denotes the minimum value of the signal values of said three sub-pixel input signals x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ,

said saturation S can have a value in the range 0 to 1 and said lightness value V can have a value in said range 0 to (2 n −1) whereas notation n in the expression (2 n −1) is an integer representing the number of display gradation bits.

5. The image display apparatus according to claim 4 wherein said output signal value X 4-(p, q) is determined on the basis of said minimum value Min (p, q) and said extension coefficient α 0 .

6. The image display apparatus according to claim 1 wherein the smallest value among the values of said ratios V max (S)/V(S) found in said pixels is taken as said extension coefficient α 0 .

7. The image display apparatus according to claim 1 wherein said fourth color is the white color.

8. The image display apparatus according to claim 1

wherein said image display apparatus is a color liquid-crystal display apparatus which includes

a first color filter placed between said first sub-pixel and the image observer to serve as a filter for passing light of said first elementary color,

a second color filter placed between said second sub-pixel and said image observer to serve as a filter for passing light of said second elementary color, and

a third color filter placed between said third sub-pixel and said image observer to serve as a filter for passing light of said third elementary color.

9. The image display apparatus according to claim 1 wherein all (P×Q) pixels are taken as a plurality of pixels for each of which said saturation S and said lightness value V(S) are to be found.

10. The image display apparatus according to claim 1 wherein (P/P 0 ×Q/Q 0 ) pixels are taken as a plurality of pixels for each of which said saturation S and said lightness value V(S) are to be found where notations P 0 and Q 0 represent values satisfying equations P≧P 0 and Q≧Q 0 whereas at least one of ratios P/P 0 and Q/Q 0 are integers each equal to or greater than 2.

11. The image display apparatus according to claim 1 wherein said extension coefficient α 0 is determined for every image display frame.

12. An image display apparatus comprising:

(A-1) a first image display panel having a two-dimensional matrix with (P×Q) first sub-pixels each used for displaying a first elementary color;

(A-2) a second image display panel having a two-dimensional matrix with (P×Q) second sub-pixels each used for displaying a second elementary color;

(A-3) a third image display panel having a two-dimensional matrix with (P×Q) third sub-pixels each used for displaying a third elementary color;

(A-4) a fourth image display panel having a two-dimensional matrix with (P×Q) fourth sub-pixels each used for displaying a fourth color;

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to (p, q)th first, second and third sub-pixels where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q; and

(C) synthesis means for synthesizing images output by said first, second, third and fourth image display panels,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following processes of

(B-1) finding said saturation S and said lightness value V(S) for each of a plurality of sets each having said first, second and third sub-pixels on the basis of the signal values of sub-pixel input signals in said sets each having said first, second and third sub-pixels,

(B-2) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said sets each having said first, second and third sub-pixels,

(B-3) finding said output signal value X 4-(p, q) in said (p, q)th fourth sub-pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) , and

(B-4) finding said output signal value X 1-(p, q) in said (p, q)th first sub-pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th second sub-pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th third sub-pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

13. An image display apparatus adopting a field sequential system, comprising:

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels; and

(B) a signal processing section configured to receive

a first input signal provided with a signal value of x 1-(p, q) ,

a second input signal provided with a signal value of x 2-(p, q) and

a third input signal provided with a signal value of x 3-(p, q) , and to output

a first output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of a first elementary color,

a second output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of a second elementary color,

a third output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of a third elementary color as well as

a fourth output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of a fourth color

with regard to a (p, q)th pixel where notations p and q are integers satisfying said equations 1≦p≦P and 1≦q≦Q,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following processes of

(B-1) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of first, second and third input signals in said pixels,

(B-2) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels,

(B-3) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) , and

(B-4) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

14. An image display apparatus assembly comprising:

an image display apparatus including

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels each including a first sub-pixel for displaying a first elementary color, a second sub-pixel for displaying a second elementary color, a third sub-pixel for displaying a third elementary color and a fourth sub-pixel for displaying a fourth color, and

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to a (p, q)th pixel where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q; and

a planar light-source apparatus for radiating light to the rear face of said image display apparatus,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following processes of

(B-1) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of sub-pixel input signals in said pixels,

(B-2) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels,

(B-3) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) , and

(B-4) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

15. The image display apparatus assembly in accordance with claim 14 wherein the luminance of said planar light-source apparatus is reduced on the basis of said extension coefficient α 0 .

16. A method for driving an image display apparatus including

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels each including a first sub-pixel for displaying a first elementary color, a second sub-pixel for displaying a second elementary color, a third sub-pixel for displaying a third elementary color and a fourth sub-pixel for displaying a fourth color, and

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to a (p, q)th pixel where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following steps of:

(a) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of said signal values of sub-pixel input signals in said pixels;

(b) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels;

(c) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ; and

(d) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

17. A method for driving an image display apparatus including

(A-1) a first image display panel having a two-dimensional matrix with (P×Q) first sub-pixels each used for displaying a first elementary color,

(A-2) a second image display panel having a two-dimensional matrix with (P×Q) second sub-pixels each used for displaying a second elementary color,

(A-3) a third image display panel having a two-dimensional matrix with (P×Q) third sub-pixels each used for displaying a third elementary color,

(A-4) a fourth image display panel having a two-dimensional matrix with (P×Q) fourth sub-pixels each used for displaying a fourth color,

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to (p, q)th first, second and third sub-pixels where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q, and

(C) synthesis means for synthesizing images output by said first, second, third and fourth image display panels,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following steps of:

(a) finding said saturation S and said lightness value V(S) for each of a plurality of sets each having said first, second and third sub-pixels on the basis of said signal values of sub-pixel input signals in said sets each having said first, second and third sub-pixels;

(b) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said sets each having said first, second and third sub-pixels;

(c) finding said output signal value X 4-(p, q) in said (p, q)th fourth sub-pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ; and

(d) finding said output signal value X 1-(p, q) in said (p, q)th first sub-pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th second sub-pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th third sub-pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

18. A method for driving an image display apparatus adopting a field sequential system,

said image display apparatus including

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels, and

(B) a signal processing section configured to receive

a first input signal provided with a signal value of x 1-(p, q) ,

a second input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) , and to output

a first output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of a first elementary color,

a second output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of a second elementary color,

a third output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of a third elementary color as well as a fourth output signal provided with

a signal value of X 4-(p, q) and used for determining the display gradation of said fourth color

with regard to a (p, q)th pixel where notations p and q are integers satisfying said equations 1≦p≦P and 1≦q≦Q,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following steps of:

(a) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of first, second and third input signals in said pixels;

(b) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels;

(c) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ; and

(d) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) .

19. A method for driving an image display apparatus assembly comprising

an image display apparatus including

(A) an image display panel having a two-dimensional matrix with (P×Q) pixels each including a first sub-pixel for displaying a first elementary color, a second sub-pixel for displaying a second elementary color, a third sub-pixel for displaying a third elementary color and a fourth sub-pixel for displaying a fourth color, and

(B) a signal processing section configured to receive

a first sub-pixel input signal provided with a signal value of x 1-(p, q) ,

a second sub-pixel input signal provided with a signal value of x 2-(p, q) and

a third sub-pixel input signal provided with a signal value of x 3-(p, q) and to output

a first sub-pixel output signal provided with a signal value of X 1-(p, q) and used for determining the display gradation of said first sub-pixel,

a second sub-pixel output signal provided with a signal value of X 2-(p, q) and used for determining the display gradation of said second sub-pixel,

a third sub-pixel output signal provided with a signal value of X 3-(p, q) and used for determining the display gradation of said third sub-pixel as well as

a fourth sub-pixel output signal provided with a signal value of X 4-(p, q) and used for determining the display gradation of said fourth sub-pixel

with regard to a (p, q)th pixel where notations p and q are integers satisfying equations 1≦p≦P and 1≦q≦Q, and

a planar light-source apparatus for radiating light to the rear face of said image display apparatus,

wherein a maximum lightness value V max (S) expressed as a function of variable saturation S in an HSV color space enlarged by adding said fourth color is stored in said signal processing section, and

said signal processing section carries out the following steps of:

(a) finding said saturation S and said lightness value V(S) for each of a plurality of pixels on the basis of the signal values of sub-pixel input signals in said pixels;

(b) finding an extension coefficient α 0 on the basis of at least one of ratios V max (S)/V(S) found in said pixels;

(c) finding said output signal value X 4-(p, q) in said (p, q)th pixel on the basis of at least said input signal values x 1-(p, q) , x 2-(p, q) and x 3-(p, q) ;

(d) finding said output signal value X 1-(p, q) in said (p, q)th pixel on the basis of said input signal value x 1-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) , finding said output signal value X 2-(p, q) in said (p, q)th pixel on the basis of said input signal value x 2-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) and finding said output signal value X 3-(p, q) in said (p, q)th pixel on the basis of said input signal value x 3-(p, q) , said extension coefficient α 0 and said output signal value X 4-(p, q) ; and

(e) reducing the luminance of said planar light-source apparatus on the basis of said extension coefficient α 0 .