AUTOMATIC GAIN CONTROLLER FOR IMAGE SIGNAL AND LOG LINEAR MULTIPLIER CIRCUIT, AND IMAGE PICKUP DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an automatic gain controller for an image signal that is digitally configured with a sufficiently warranted dynamic range without incurring the increase in the circuit scale. SOLUTION: The automatic gain controller for an image signal is provided with an AGC amplifier 2a configured with a digital multiplier circuit and with its control means 10 and also provided with a block level detection means 6 that detects a black level component of the image signal, a sbutractor 7 that subtracts the black level component detected by the detection means 6 from a level of the image signal, and an adder 9 that receives an output signal from the sbutractor 7 via the AGC amplifier 2a and adds the block level component having already been subtracted from the level of the image signal at the sbutractor 7 to the received signal level so that the black level component is not amplified by the AGC amplifier 2a. Then a log linear multiplier circuit 8 configured as a digital multiplier conducts its arithmetic processing only through shift and adding arithmetic operations.