Image display apparatus having back light with multiple light sources and configured to control luminance for each of a plurality of areas that exceed the number of light sources
View Patent ↗In a local dimming technology for reducing power consumption of a display device using a backlight as in a liquid crystal display, the backlight is configured by a plurality of independently controllable light sources, an image is divided into areas of the same number as that of the controllable light sources and light emission intensity of the light source is calculated based on a feature value of each area. However, this technology has a problem that when a backlight luminance distribution within each area is not uniform, image quality is deteriorated or a power consumption reduction effect is lowered. In the present invention, the image is divided into areas of the number greater than that of the controllable light sources, and the light emission intensity of each light source is determined based on the feature values of a plurality of areas to reduce the above-described problem.
1. An image display apparatus, comprising:
a liquid crystal panel including a plurality of pixels disposed in a matrix, wherein transmittivity of the pixels is controlled based on an input image data, and wherein the liquid crystal panel includes at least:
a first image area on a first end side,
a second image area on a second end side opposite to the first end side, and
a third image area disposed between the first image area and the second image area;
a back light, having a plurality of light sources disposed on the back side of the liquid crystal panel, and configured to irradiate light from the plurality of light sources to the liquid crystal panel, wherein the liquid crystal panel is configured to display an image by changing a luminance through each pixel of the liquid crystal panel, according to a pixel value of the input image data, the luminance originating from the back light, and wherein the plurality of light sources include at least:
a first light source disposed on the first end side of the liquid crystal panel, and
a second light source disposed on the second end side of the liquid crystal panel opposite to the first end side; and
a controller configured to control the luminance of the first and second light sources, including to:
(a) obtain a first luminance value from pixel values of the input image data provided to the first image area, obtain a second luminance value from pixel values of the input image data provided to the second image area, and obtain a third luminance value from pixel values of the input image data provided to the third image area, and
(b) independently control the luminance of the first and second light sources, based on the first luminance value provided to the first image area, the second luminance value provided to the second image area, and the third luminance value provided to the third image area,
thereby independently controlling the luminance provided by each of the first and second light sources to the first image area, the second image area, and the third image area, wherein the first and second image areas are capable of displaying different luminances.
2. The image display apparatus according to claim 1 ,
wherein the luminance value of an image area is obtained from pixels remaining after excluding, from the image area, pixels with a luminance value within a top predetermined percentage.
3. The image display apparatus of claim 1 ,
the plurality of light sources of the back light further comprising: a third light source adjacent to the first light source in a perpendicular direction;
the liquid crystal panel further comprising: a fourth image area lined up in a perpendicular direction according to the first image area and corresponding to the third light source, and a fifth image area disposed between the first image area and fourth image area; and
the controller further configured to:
control a light luminance value provided to the first image area, the fourth image area, and the fifth image area, by obtaining each luminance value of the image area from pixel values of the respective input image data of the first image area, the fourth image area, and the fifth image area, and
individually control intensities of light of the first light source and the third light source, based on the obtained luminance value of each of the first image area, the second image area, and the third image area.
4. The image display apparatus of claim 1 , the controller further configured to:
calculate a first luminance ratio based on the obtained luminance value of the first image area, and a second luminance ratio based on the obtained luminance value of the second image area;
calculate a luminance at the point of the luminance value in the third image area, when the first light source light is at the first luminous ratio and the second light source light is at the second luminous ratio;
compare the luminance value of the third image area and the calculated luminance in the third image area;
use the first luminous ratio and the second luminous ratio as luminous ratios of the first light source and the second light source, when the calculated luminance in the third image area is greater than the luminance value of the third image area; and
use values obtained by multiplying the first luminous ratio and the second luminous ratio by a ratio of the luminance value of the third image area, and the calculated luminance in the third image area, as luminous ratios of the first light source and the second light source when the calculated luminance is less than the luminance value of the third image area.