Sharp Kabushiki Kaisha Corporation

Eishi Oda

Michiaki Takeda

Hiroyoshi Kure

Toshiyuki Fujine

Takashi Kanda

Michiyuki Sugino

Masahiro Okui

The present invention causes noise in a low-luminance portion to become less prominent when a backlight is divided into a plurality of regions and the luminance of the backlight is controlled in accordance with a video signal corresponding to each of the regions. An area active control portion () divides a video signal into a plurality of regions and outputs a first feature amount for every region. An LED control portion () determines a first luminance for each of the divided regions of an LED backlight () in accordance with the first feature amount of every region. Within a range where the total value of an LED drive current is no greater than a predetermined allowable current value, a magnification constant is uniformly multiplied by the first luminance to determine a second luminance. The second luminance and a threshold value are compared, and, only with respect to those regions where the second luminance is lower than the threshold value, the second luminance is again lowered to make a third luminance. The third luminance and also the second luminance of the regions where the second luminance has not been lowered are used to control the LED light emission in each of the divided regions.

Video display device

The present invention effectively suppresses not only occurrences of halos but also degradation of the black level. This image display device has a liquid crystal panel () that displays images according to an image signal and a backlight () in which LEDs are used and controls the light emission brightness of the LEDs for each division region, which is obtained by dividing the backlight () into a plurality of regions, on the basis of a prescribed relation between a gradation value for an image region corresponding to each division region and the LED light emission brightness. When the gradation value for an image satisfies prescribed conditions, a first luminance adjusting portion () adjusts the LED light emission brightness such that the range of variation in LED light emission brightness in a first range for the gradation value of the image region, which is determined on the basis of the prescribed conditions above, is smaller than the range of variations for the LED light emission brightness that is determined on the basis of the prescribed relation above, and a second luminance adjusting portion () adjusts the LED light emission brightness in a second range for which the value is smaller than the first range such that the light emission brightness is smaller than a lower limit value for the LED light emission brightness adjusted above.

Light leakage and black float are reduced in dark ambient while a perception of high contrast is achieved when a backlight is divided into a plurality of areas and backlight brightness is controlled depending on a video signal corresponding to each area. An area active control portion () divides a video signal into a plurality of areas and outputs a first feature value for each area. An LED control portion () acquires a first brightness for each divided area of an LED backlight () depending on the first feature value of each area, and acquires a second brightness for each area that is acquired by uniformly multiplying a specific multiplying factor acquired depending on the lighting ratio of the LED backlight () with respect to the first brightness within a range where a total value of the LED driving current does not exceed a predetermined permissible current value. When the lighting ratio of the LED backlight () is at or below a predetermined value, the second brightness is reduced in accordance with ambient lighting detected by a photosensor () to acquire a third brightness.

Video display apparatus including brightness control based on ambient illuminance

In general, when a user views an image displayed on a display apparatus, visual environments, such as ambient brightness, a distance from the user to the display apparatus and so on, may disadvantageously cause the image displayed on the display apparatus to become difficult to view. Moreover, it is complicated and troublesome for the user to enter information of ambient light amount and others when setting a picture quality. An image display apparatus holds both question constituent information related to visual environments and choice information serving as answers to questions constituted by the question constituent information, and further holds a plurality of picture quality control rules suitable for visual environments assumed in accordance with the choice information serving as the answers. When sensing a power-up, the image display apparatus outputs the questions; acquires result information that is choices serving as answers from the user to those questions and that is used to acquire the picture quality control rules; and controls the picture quality in accordance with the picture quality control rules acquired in accordance with the result information.

Growing community of inventors

Osaka, Japan

Eishi Oda