| 摘要 |
PURPOSE:To reduce the variance of luminance due to the noise or the like superposed to an input signal by subtracting a clamp code signal, which prescribes a restoration level, from an input digital signal and subtracting the average value of this subtraction value from the input signal to project an image. CONSTITUTION:An input digital signal D from an A/D converter 5 is inputted to the first and the second subtracting circuits 6 and 11. The circuit 11 subtracts the clamp code signal, which is outputted from a clamp code generating circuit 7 and has a preliminarily prescribed clamp level, from the signal D and outputs the difference to a storage part 12. The storage part 12 outputs one-picture components of difference signal to an averaging circuit 13 after storing one-picture components of input difference signal. The circuit 13 detects the average level of one-picture components of difference signal and inputs this average level to the circuit 6. The circuit 6 subtracts the average level from the circuit 13 from the signal D and clamps the signal D at the average level to restore the DC, and it is stored in a memory part 8 and is displayed as an image on a display part 10 through a picture processing part 9. Thus, the variance of the clamp point is reduced to reduce the variance of luminance on the display part 10.
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