DISPLAY APPARATUS AND BRIGHTNESS ADJUSTING METHOD THEREOF

• US 20090002400A1
• Filed: 03/25/2008
• Published: 01/01/2009
• Est. Priority Date: 06/29/2007
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Ha, Tae-hyeun, Park, Yung-jun, Sung, Jun-ho, Chen, Han Feng
• Granted Patent: US 9,064,459 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2320/0653 Controlling or limiting the speed of brightness adjustment of the illumination source
• CPC Class Codes: G09G 2320/066 for control of contrast
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3607 for displaying colours or for displaying grey scales with a specific pixel layout, e.g. using sub-pixels display of colours in flat matrix panels other than liquid crystal displays G09G3/2003; grey scales specific for television H04N3/127
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 5/10 Intensity circuits

Abstract

A display apparatus and a brightness adjusting method thereof are provided. The display apparatus includes a panel unit which displays an image signal, a backlight unit which provides a light to the panel unit to visualize the image signal, a luminance value regulator which calculates representative values to be applied for adjusting a brightness of a plurality of partial areas of the backlight unit corresponding to the input image signal, a contrast enhancer which compensates for a brightness of the image signal compromised by the representative value through a contrast enhancement, and a pixel value compensator which compensates for pixel values of the image signal compensated using the contrast enhancement. Accordingly, the contrast ratio of the entire image can be enhanced by compensating for the brightness loss of the image signal caused from the brightness adjustment of the luminous element, and the image quality can be more finely improved.

Claims

1. A display apparatus comprising:

a panel unit which displays an image signal;

a backlight unit which provides a light to the panel unit to visualize the image signal;

a luminance value regulator which calculates a plurality of representative values to be applied for adjusting a brightness of a plurality of partial areas of the backlight unit corresponding to the image signal;

a contrast enhancer which compensates for a brightness of the image signal compromised by the application of the representative values, through a contrast enhancement; and

a pixel value compensator which compensates for pixel values of the image signal compensated through the contrast enhancement.

2. The display apparatus of claim 1, wherein the contrast enhancer compensates for loss of the brightness of the image signal with respect to an entire image and at least one of the plurality of partial areas, through the contrast enhancement.

3. The display apparatus of claim 2, wherein the contrast enhancer compensates for a contrast of the entire image using an average representative value acquired by averaging the representative values of the partial areas, and compensates for the brightness loss of the image in the partial areas using an interpolation representative value acquired by interpolating the representative values of the partial areas through the contrast enhancement.

4. The display apparatus of claim 1, further comprising:

a pre-processor which removes noise in the image signal and calculates a luminance value of a pixel at a certain position in the image signal in which the noise was removed,

wherein the luminance value regulator calculates the representative values using an initial representative value acquired by multiplying luminance values of pixels in the partial areas by a pre-stored weight and summing products of the multiplication.

5. The display apparatus of claim 4, wherein the luminance value regulator calculates the initial representative value by applying luminance values of a specific partial area k to the following equation:

BLK_init(k)=min(BLK1(k),BLK2(k))

where BLK_init(k) is an initial representative value in the partial area k BLK1(k) is a first luminance value in the partial area k, and BLK2(k) is a second luminance value in the partial area k.

6. The display apparatus of claim 4, wherein the luminance value regulator calculates the initial representative value by applying luminance values of a specific partial area k to the following equation:

BLK_init(k)=w1*BLK1(k)+(1−

w1)*(BLK2(k))

where BLK_init(k) is an initial representative value in the partial area k, w1 is a preset weight, BLK1(k) is a first luminance value in the partial area k, and BLK2(k) is a second luminance value in the partial area k.

7. The display apparatus of claim 4, wherein the luminance value regulator comprises:

a first calculator which calculates a first brightness value for compensate the image signal, by summing products of the initial representative values of the partial areas multiplied by pre-stored optical profile data;

a first regulator which calculates a first adjustment value for adjusting brightness of the image signal using the first brightness value calculated at the first calculator, the initial representative values, and a preset maximum luminance value;

a second calculator which calculates a second brightness value for compensating the image signal of which the brightness is adjusted by the first regulator, wherein the second brightness value is a brightness value after scaling the first brightness value; and

a second regulator which calculates a second adjustment value for adjusting the brightness of the image signal, of which the brightness is adjusted using the first adjustment value, using the second brightness value calculated at the second calculator, the first adjustment value, and the maximum luminance value.

8. The display apparatus of claim 4, wherein the luminance value regulator comprises:

a first calculator which calculates a first brightness value which is a brightness value in a specific partial area of the image signal after scaling the image signal;

a first regulator which calculates a first adjustment value for adjusting the brightness of the image signal in the specific partial area;

a second calculator which calculates a second brightness value which is a brightness value in partial areas adjacent to the specific partial area of the image signal; and

a second regulator which calculates a second adjustment value for adjusting the brightness of the image signal in the partial areas adjacent to the specific partial area of the image signal.

9. The display apparatus of claim 8, wherein the luminance value regulator further comprises:

a space filter which space-filters the partial area of which the brightness is adjusted using the second adjustment value; and

a time filter which time-filters the space-filtered partial area.

10. The display apparatus of claim 1, wherein the pixel value compensator comprises:

an interpolator which calculates a brightness value of each partial area from the respective representative value, and calculates an interpolation representative value which is an interpolated brightness value of a pixel at a certain position by applying one of a bi-cubit interpolation and a bi-linear interpolation to the calculated brightness value;

a compensation coefficient calculator which calculates a compensation coefficient for compensating the pixel values of the image signal using the interpolation representative value and a luminance value of the pixels of the partial area; and

a compensator which compensates for the pixel values of the image signal of which contrast is enhanced, by multiplying the compensation coefficient by the pixel values used to enhance the contrast at the contrast enhancer.

11. The display apparatus of claim 10, wherein the compensation coefficient calculator calculates a first compensation coefficient by applying the interpolation representative value to the following equation:

BLK_LC(i,j)=(Y(i,j))<sup>γ

p</sup>/BLK_pro(i,j)

where BLK_LC(i,j) is the first compensation coefficient of an (i, j)-th pixel, Y(i,j) is a luminance value of the pixel at (i, j), BLK_pro(i,j) is an interpolation representative value of the pixel at (i, j), and γ

_p is a preset gamma parameter, the compensation coefficient calculator calculates a saturation coefficient by applying the first compensation coefficient to the following equation;

${\mathrm{BLK}}_{\mathrm{sat}}<br><br>\left(i,j\right)=\{\begin{array}{c}<br><br>\begin{array}{c}{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)-g<br><br><br><br>4·<br><br>\\ {\left(Y<br><br>\left(i,j\right)\right)}^{{\mathrm{\gamma <br><br>}}_p}-{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\end{array}<br><br><br><br>\mathrm{if}<br><br><br><br>{\left(Y<br><br>\left(i,j\right)\right)}^{{\mathrm{\gamma <br><br>}}_p}><br><br>{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\\ <br><br>\mathrm{else}\\ <br><br>{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\end{array}$

where BLK_sat(i,j) is a saturation coefficient of the (i, j)-th pixel, Y(i,j) is the luminance value of the (i, j)-th pixel, BLK_pro(i,j) is the interpolation representative value of the (i, j)-th pixel, g4 is a preset control parameter, and γ

_p is the preset gamma parameter, and

the compensation coefficient calculator calculates the compensation coefficient used to compensate for the pixel values of the image signal by calculating a second compensation coefficient by applying the saturation coefficient to the following equation;

PC_gain(i,j)=(1/BLK_sat(i,j))<sup>1/γ

p</sup>BLK_LC(i,j)

where PC_gain(i,j) is a second compensation coefficient of the (i, j)-th pixel, BLK_sat(i,j) is the saturation coefficient of the (i, j)-th pixel, BLK_LC(i,j) is the first compensation coefficient of the (i, j)-th pixel, and γ

_p is the preset gamma parameter.

12. The display apparatus of claim 1, wherein the pixel value compensator compensates for the pixel values of the image signal by adjusting the pixel values to make a dark pixel less dark and make a bright pixel brighter among pixels of the image signal compensated using the contrast enhancement.

13. A brightness adjusting method of a display apparatus, the method comprising:

calculating a plurality of representative values to be applied for adjusting a brightness of a plurality of partial areas of a luminous element which produces light to a panel, corresponding to an input image signal;

compensating for a brightness of the image signal compromised by the application of the representative values through a contrast enhancement; and

compensating for pixel values of the image signal compensated through the contrast enhancement.

14. The brightness adjusting method of claim 13, wherein the compensating for the brightness of the image signal comprises compensating for loss of the brightness of the image signal with respect to the entire image and at least one of the plurality of partial areas of the image, through the contrast enhancement.

15. The brightness adjusting method of claim 14, wherein the compensating for the brightness of the image signal comprises compensating for a contrast of the entire image using an average representative value acquired by averaging the representative values of the partial areas, and compensating for the brightness loss of the image using an interpolation representative value acquired by interpolating the representative values of the partial areas through the contrast enhancement.

16. The brightness adjusting method of claim 13, further comprising:

before the calculating the representative values, removing noise from the image signal and calculating a luminance value of a pixel at a certain position in the noise-free image signal,

wherein the calculating the representative values comprises calculating the representative values using an initial representative value acquired by multiplying luminance values of pixels in the partial areas by a pre-stored weight and summing the products of the multiplication.

17. The brightness adjusting method of claim 16, wherein the calculating the representative values comprises calculating the initial representative value by applying luminance values of a specific partial area k to the following equation:

BLK_init(k)=min(BLK1(k),BLK2(k))

where BLK_init(k) is an initial representative value in the partial area k BLK1(k) is a first luminance value in the partial area k, and BLK2(k) is a second luminance value in the partial area k.

18. The brightness adjusting method of claim 16, wherein the calculating the representative values comprises calculating the initial representative value by applying luminance values of a specific partial area k to the following equation:

BLK_init(k)=w1*BLK1(k)+(1−

w1)*(BLK2(k))

where BLK_init(k) is an initial representative value in the partial area k, w1 is a preset weight, BLK1(k) is a first luminance value in the partial area k, and BLK2(k) is a second luminance value in the partial area k.

19. The brightness adjusting method of claim 16, wherein the calculating the representative values comprises:

calculating a first brightness value for compensating the image signal, by summing products of the initial representative values of the partial areas multiplied by pre-stored optical profile data;

calculating a first adjustment value for adjusting brightness of the image signal using the calculated first brightness value, the initial representative values, and a preset maximum luminance value;

calculating a second brightness value, which is a brightness value after scaling the first brightness value, for compensating the image signal of which the brightness is adjusted using the first adjustment value; and

calculating a second adjustment value for adjusting the brightness of the image signal, of which the brightness is adjusted using the first adjustment value, using the calculated second brightness value, the first adjustment value, and the maximum luminance value.

20. The brightness adjusting method of claim 16, wherein the first operation comprises:

calculating a first brightness value which is a brightness value in a specific partial area of the image signal after scaling the image signal;

calculating a first adjustment value for adjusting the brightness of the image signal in the specific partial area;

calculating a second brightness value which is a brightness value in partial areas adjacent to the specific partial area of the image signal; and

calculating a second adjustment value for adjusting the brightness of the image signal in the partial areas adjacent to the specific partial area of the image signal.

21. The brightness adjusting method of claim 20, wherein the first operation further comprises:

space-filtering the partial area of which the brightness is adjusted using the second adjustment value; and

time-filtering the space-filtered partial area.

22. The brightness adjusting method of claim 13, wherein the third operation comprises:

calculating a brightness value of each partial area from the respective representative value, and calculating an interpolation representative value which is an interpolated brightness value of a pixel at a certain position by applying one of a bi-cubit interpolation and a bi-linear interpolation to the calculated brightness value;

calculating a compensation coefficient used to compensate for the pixel values of the image signal using the interpolation representative value and a luminance value of the pixels of the partial area; and

compensating for the pixel values of the image signal of which contrast is enhanced, by multiplying the compensation coefficient by the pixel values used to enhance the contrast.

23. The brightness adjusting method of claim 22, wherein the calculating the compensation coefficient calculates a first compensation coefficient by applying the interpolation representative value to the following equation:

BLK_LC(i,j)=(Y(i,j))<sup>γ

p</sup>/BLK_pro(i,j)

where BLK_LC(i,j) is the first compensation coefficient of an (i, j)-th pixel, Y(i,j) is a luminance value of the pixel at (i,j), BLK_pro(i,j) is an interpolation representative value of the pixel at (i,j), and γ

_p is a preset gamma parameter,

the calculating the compensation coefficient calculates a saturation coefficient by applying the first compensation coefficient to the following equation;

${\mathrm{BLK}}_{\mathrm{sat}}<br><br>\left(i,j\right)=\{\begin{array}{c}<br><br>\begin{array}{c}{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)-g<br><br><br><br>4·<br><br>\\ {\left(Y<br><br>\left(i,j\right)\right)}^{{\mathrm{\gamma <br><br>}}_p}-{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\end{array}<br><br><br><br>\mathrm{if}<br><br><br><br>{\left(Y<br><br>\left(i,j\right)\right)}^{{\mathrm{\gamma <br><br>}}_p}><br><br>{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\\ <br><br>\mathrm{else}\\ <br><br>{\mathrm{BLK}}_{\mathrm{pro}}<br><br>\left(i,j\right)\end{array}$

where BLK_sat(i,j) is a saturation coefficient of the (i, j)-th pixel, Y(i,j) is the luminance value of the (i, j)-th pixel, BLK_pro(i,j) is the interpolation representative value of the (i, j)-th pixel, g4 is a preset control parameter, and γ

_p is the preset gamma parameter, and

the calculating the compensation coefficient calculates the compensation coefficient used to compensate for the pixel values of the image signal by calculating a second compensation coefficient by applying the saturation coefficient to the following equation;

PC_gain(i,j)=(1/BLK_sat(i,j))<sup>1/γ

p</sup>BLK_LC(i,j)

where PC_gain(i,j) is a second compensation coefficient of the (i, j)-th pixel, BLK_sat(i,j) is the saturation coefficient of the (i, j)-th pixel, BLK_LC(i,j) is the first compensation coefficient of the (i, j)-th pixel, and γ

_p is the preset gamma parameter.

24. The brightness adjusting method of claim 13, wherein the third operation compensates for the pixel values of the image signal by adjusting the pixel values to make a dark pixel less dark and make a bright pixel brighter among pixels of the image signal compensated using the contrast enhancement.

25. The brightness adjusting method of claim 13, further comprising:

after the third operation, dithering a flickering of the image signal of which the pixel values are compensated in the third operation, and adjusting a white balance.