| 摘要 |
PROBLEM TO BE SOLVED: To maintain the whole video image including an OSD high definition by improving contrast ratio of the video image and displaying the OSD without a sense of incongruity while reducing power consumption. SOLUTION: In the liquid crystal display device, an OSD signal S3 is superimposed on an input video signal S1. At this time, luminance of the OSD signal S3 is set to a value sufficiently smaller than the maximum value of the video signal. Then, the input video signal S1 and the OSD signal S3 are extended, considered as video signals S1', S3', respectively, light source luminance L1 is simultaneously lowered to be considered as L1'. The maximum luminance of the video signal S1' after extension is located near the maximum luminance which can be taken by the video signal and gradation expression is improved by effectively using a dynamic range by such control. Then, power consumption of a light source is reduced while improving the gradation expression of the video image by reducing the light source luminance according to the maximum luminance of the video signal. The OSD signal is processed similar to the input video signal and luminance of OSD display is maintained as constant. COPYRIGHT: (C)2008,JPO&INPIT
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