Patent ID: 7432965

Claim:
A black level correcting device comprising an A/D converting section converting a result of subtracting a feedback signal from an analog pixel signal output from an image sensor into a digital signal, and outputting the digital signal as a pixel value, and a feedback controlling section generating said feedback signal, wherein said feedback controlling section includes: a comparator outputting a difference between a standard value and the pixel value output from said A/D converting section as a digital feedback signal; a holding section having a maintaining section and carrying out clamp operation, which brings a maintaining level of said maintaining section near to a level of said feedback signal in response to said feedback signal output from said comparator, while a pixel signal from an optical black pixel of said image sensor is output, and said holding section maintaining and outputting the maintaining level of said maintaining section while a pixel signal from a valid pixel of said image sensor is output; a subtracting section subtracting the maintaining level of said holding section from said analog pixel signal before said analog pixel signal is input into said A/D converting section; and a feedback gain adjusting section inserted into a feedback loop of said feedback signal in series and starting to multiply said feedback signal by clamp accelerating gain which is larger than 1 in synchronization with starting readout of the pixel signal from said optical black pixel, and multiplying said feedback signal by gain which is smaller than said clamp accelerating gain before completion of said clamp operation.