Patent ID: 8054285

Claim:
A liquid crystal television, comprising: a backlight provided with a plurality of cold-cathode tubes; a backlight control unit for controlling a lighting time of the backlight with a duty factor; a liquid crystal panel to which light is irradiated from back by the backlight; a tuner for extracting a video signal from a television broadcast signal and outputting the video signal; a video processing unit for producing image data, which is matched with a pixel number of the liquid crystal panel, from the video signal input from the tuner, causing the image data to be subjected to image quality adjusting processing, and outputting the produced image data; an output processing circuit for performing gamma correction with respect to the image data output from the video processing unit, producing a drive signal from the image data after being subjected to the gamma correction, and driving a plurality of liquid crystal cells forming the liquid crystal panel; and a control unit for directing the duty factor to the backlight control unit and inputting gamma correction data into the output processing circuit; said control unit receives brightness data of video signals from the video processing unit, which correspond to regions that are set at least at three points at an upper portion, three points at a middle portion, and three points at a lower portion of the liquid crystal panel, and calculates brightness average values of the received brightness data for every frame image; when the brightness average values of the frame images are not more than 10%: said control unit causes the duty factor directed to the backlight control unit to be made 50% of a PWM signal (pulse width modulation), lowers brightness of an entire screen, lowers a lower limit of a black level to widen an adjusting range at low gradation, causes the output processing circuit to perform gamma correction with gamma correction data for increasing the black level to enhance contrast at the low gradation, and improves power of representation at the low gradation; when the brightness average values of the frame images are 10-30%, said control unit causes the duty factor directed to the backlight control unit to be 70% of the PWM signal, lowers the brightness of the entire screen, lowers a black level to widen the adjusting range at the low gradation, but suppresses lowering of brightness at high gradation as compared with a case where the brightness average value is 10%, causes the output processing circuit to perform gamma correction with gamma correction data for increasing the black level to enhance the contrast at the low gradation, and improves the power of representation at the low gradation.