| 摘要 |
PROBLEM TO BE SOLVED: To provide a liquid crystal television which can regulate the brightness of a liquid crystal panel to the optimum brightness when viewing and listening to a cinema video image and to provide a back light controller and a back light control method. SOLUTION: A black band detection circuit 26 detects a black band applied vertically to a video to be viewed and listened, such as a letter box type video signal. When the black band is detected, a microcomputer 50 generates a pulse signal P having a predetermined duty cycle as a control signal for lowering the emitting luminance of the back light 61 to an inverter 62. The inverter 62 changes the duty cycle of a drive pulse signal outputted from a switching circuit 62c based on the pulse signal P, and the back light 61 lowers the emitting luminance. A liquid crystal panel 40 emits in an optimum luminance to view and listen a cinema video image. Moreover, the video based on the input video signal can be displayed on the liquid crystal panel 40 as it is, and the gradability originally incorporated in the input video signal can be expressed faithfully on a screen. COPYRIGHT: (C)2006,JPO&NCIPI
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