| 摘要 |
PURPOSE:To eliminate danger to destroy an A/D converting part by an excess current by inputting output, the content of which is the subtracted value of the output corresponding to a black reference picture element, to the A/D converting part in a case when the subtracted value ot the output corresponding to the black reference picture element is outputted and inputting the output of a determined range voltage output means in the other cases. CONSTITUTION:Switches 28 and 29 are switched so that the subtracted value of the output corresponding to the black reference picture element can be inputted to an A/D converting part 15 when a subtracting means 26 outputs the subtracted value of the output corresponding to the black reference picture element from the output corresponding to a use picture element. On the other hand, the switches 28 and 29 are switched so that the output of a determined range voltage means 27 can be inputted to the A/D converting part 15 when the subtracting means 26 does not output the subtracted value of the output corresponding to the black reference picture element from the output corresponding to the use picture element, namely, the subtracting means 26 outputs the subtracted value of the black reference picture element from the output of nonuse picture element. Thus, a signal to exceed its dynamic range is never inputted to the A/D converting part 15, and the dager to destroy the A/D converting part 15 is eliminated. |
