Patent ID: 7999975

Claim:
An analog front-end circuit comprising: an analog processing circuit that receives an analog input image signal from an image sensor, performs a given process on the analog input image signal, and outputs an analog image signal; an A/D converter that A/D-converts the analog image signal input from the analog processing circuit; a target register, a black level target value being set in the target register; and a correction amount register; and a calculation circuit that monitors an A/D-converted value output from the A/D converter and performs calculations, the analog processing circuit including: a clamp circuit that performs a line clamp operation on the analog input image signal from the image sensor; an offset adjustment circuit that includes an offset adjustment register and performs an offset adjustment on an image signal based on an offset adjustment value set in the offset adjustment register; and a gain adjustment circuit that includes a gain adjustment register and performs a gain adjustment on an image signal based on a gain adjustment value set in the gain adjustment register, a correction amount being set in the correction amount register, the correction amount corresponding to a change amount of the A/D-converted value when changing the offset adjustment value set in the offset adjustment register by 1 LSB and changing corresponding to the gain adjustment value set in the gain adjustment register, the calculation circuit monitoring the A/D-converted value of a black reference pixel after the line clamp operation in a black level monitor period, the black level monitor period being a period after a line clamp period of the clamp circuit but before an effective pixel output period, and performing a black level error correction process relating to the line clamp operation based on the correction amount set in the correction amount register, the A/D-converted value monitored in the black level monitor period, and the black level target value set in the target register.