Image display device and image display method

Patent metadata

Field	Value
Publication number	US-9361835-B2
Application number	US-201013579876-A
Country	US
Kind code	B2
Filing date	Nov 17, 2010
Priority date	Mar 12, 2010
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

In the present liquid crystal display device, an LED output value correction section ( 513 ) included in an area-active drive processing section ( 5 ) corrects LED data Dbl obtained by an LED output value calculation section ( 512 ) with reference to a luminance correction LUT ( 13 ), such that the luminance in the area from an intermediate value to near a maximum value shifts to a higher degree. Thus, even if the backlight luminance is low (typically, the mean luminance of an input image is low), contrast ratio is enhanced, thereby preventing a tone jump (insufficient luminance) at high tone levels due to an insufficient backlight luminance.

First claim

The invention claimed is:

1. An image display device with a function of controlling a backlight luminance, comprising:
a backlight including a plurality of light sources;
a display panel including a plurality of display elements for transmitting light from the light sources therethrough in order to display a plurality of pixels;
an emission luminance calculation section for obtaining emission luminance data indicating a luminance upon emission of the light sources, on the basis of an input image including a plurality of pixels to be displayed with predetermined tones;
a display data calculation section for obtaining display data in accordance with light transmittances of the display elements, on the basis of the input image and the emission luminance data obtained by the emission luminance calculation section;
a panel driver circuit for outputting signals for controlling the light transmittances of the display elements to the display panel, on the basis of the display data; and
a backlight driver circuit for outputting signals for controlling the luminance of the light sources to the backlight, on the basis of the emission luminance data, wherein,
the emission luminance calculation section includes:
an output value calculation section for performing predetermined computation on the tones of the pixels included in the input image, thereby calculating the emission luminance data corresponding to the pixels,
a luminance correction section for correcting the input image to be provided to the output value calculation section or the emission luminance data calculated by the output value calculation section, such that values within a predetermined range of the emission luminance data to be provided to the display data calculation section are increased, and

the emission luminance calculation section divides the input image into a plurality of areas and obtains emission luminance data that indicates luminances upon emission of the light sources corresponding to the areas, on the basis of the input image.

2. The image display device according to claim 1 , wherein the luminance correction section adds a predetermined increment to values within a range from an intermediate value to near a maximum value of the emission luminance data to be provided to the display data calculation section.

3. The image display device according to claim 2 , wherein the increment added to the values within said range by the luminance correction section is determined so as to be minimized at the intermediate value and near the maximum value, the intermediate value being a value greater than or equal to a median of the emission luminance data to be provided to the display data calculation section.

4. The image display device according to claim 1 , wherein the luminance correction section adds a predetermined increment to values within a range from near a minimum value to an intermediate value of the emission luminance data to be provided to the display data calculation section.

5. The image display device according to claim 4 , wherein the increment added to the values within said range by the luminance correction section is determined so as to be maximized near the minimum value of the emission luminance data to be provided to the display data calculation section, and minimized at the intermediate value.

6. The image display device according to claim 1 , wherein the luminance correction section adds a predetermined increment to values within a range from near a minimum value to a first intermediate value of the emission luminance data to be provided to the display data calculation section, and also adds a predetermined increment to values within a range from a second intermediate value to near a maximum value, the second intermediate value being a value greater than or equal to the first intermediate value.

7. The image display device according to claim 6 , wherein the increment added to the values within said range by the luminance correction section is determined so as to be maximized near the minimum value of the emission luminance data to be provided to the display data calculation section, and minimized at the first intermediate value, the second intermediate value, and near the maximum value.

8. The image display device according to claim 1 , wherein,
the emission luminance calculation section performs a reverse gamma correction on an input image provided from outside the device, and
the display data calculation section includes:
image memory for holding the input image provided from outside the device for a predetermined time period;
a display reverse gamma correction section for performing a reverse gamma correction on an input image provided from the image memory after a lapse of the time period; and
a display data output section for obtaining the display data on the basis of the input image subjected to the reverse gamma correction by the display reverse gamma correction section and the emission luminance data obtained by the emission luminance calculation section.

9. The image display device according to claim 8 , wherein,
the emission luminance calculation section further includes an emission luminance reverse gamma correction section for performing the reverse gamma correction on the input image provided from outside the device, and
the output value calculation section calculates the emission luminance data by performing predetermined computation on tones of a plurality of pixels included in the input image subjected to the reverse gamma correction by the emission luminance reverse gamma correction section.

10. The image display device according to claim 9 , wherein,
the emission luminance reverse gamma correction section performs a correction with reference to a first table indicating a correspondence between the tones of the pixels included in the input image and tones of pixels to be obtained by the reverse gamma correction, and
the luminance correction section performs a correction with reference to a second table indicating a correspondence between the tones of the pixels included in the input image and tones of pixels to be obtained by performing a correction for increasing the values within said range of the emission luminance data.

11. The image display device according to claim 8 , wherein,
the luminance correction section simultaneously subjects the input image provided from outside the device to the reverse gamma correction and the correction for increasing the values within said range of the emission luminance data, and
the output value calculation section outputs the emission luminance data calculated by performing predetermined computation on tones of a plurality of pixels included in the input image corrected by the luminance correction section.

12. The image display device according to claim 11 , wherein the luminance correction section performs a correction with reference to a single table indicating a correspondence between the tones of the pixels included in the input image and tones of pixels to be obtained by performing the reverse gamma correction and the correction for increasing the values within said range of the emission luminance data.

13. A method for controlling an image display device having a function of controlling a backlight luminance and provided with a backlight including a plurality of light sources, and a display panel including a plurality of display elements for transmitting light from the light sources therethrough in order to display a plurality of pixels, the method comprising:
an emission luminance calculation step of obtaining emission luminance data indicating a luminance upon emission of the light sources, on the

Assignees

• Ueno Tetsuya
• Fujiwara Kohji
• Sharp Kk

Inventors

• Ueno Tetsuya
• Fujiwara Kohji

Classifications

• G09G3/3611

  Control of matrices with row and column drivers · CPC title

• G09G2360/18

  Use of a frame buffer in a display terminal, inclusive of the display panel · CPC title

• G09G2320/066

  for control of contrast · CPC title

• G09G3/3426 Primary

  the different display panel areas being distributed in two dimensions, e.g. matrix · CPC title

• G09G2320/0646

  Modulation of illumination source brightness and image signal correlated to each other · CPC title