| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection type video display device capable of expressing the signal of a black side on a screen even when a room is not sufficiently dark and projecting a video on the screen with original and satisfactory contrast when the room is sufficiently dark. SOLUTION: A gamma correction circuit 4 can change its gain by setting one bent position at a white side and also can change gains at respective bent positions by setting two bent positions at a black side. Moreover, the circuit 4 can change the bent position and a gain (gamma correction characteristic) by instructions from a CPU 10. The CPU 10 knows the illuminace of a screen 7 by it's own brightness of a room by inputting illuminance information from an illuminance measuring device 11 and calculates a bent position in the black side and a gain based on this illuminance to change the gamma correction characteristic in the circuit 4.
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