Patent ID: 7869086
Filing Date: 2011-01-11
Classification: H04N

Abstract:
1. An offset adjusting device, comprising: a sample-hold unit configured to sample-hold an analog image signal obtained by converting reflected light from an original into an electric signal with a photoelectric conversion device to thereby obtain a sample-hold signal; an amplifying unit configured to amplify the sample-hold signal to obtain an amplified signal; an analog-digital converter configured to digitize the amplified signal to obtain a digital signal; a difference detecting unit configured to detect a difference between a black-level detection value of the digital signal and a black-level target value; an adjustment coefficient setting unit configured to set a first adjustment coefficient for a high-speed response and a second adjustment coefficient for a normal response; a reference-value setting unit configured to set one reference value; a selecting unit configured to select at least one of the first and second adjustment coefficients, the first adjustment coefficient selected when the difference is one of equal to and larger than the reference value and the second adjustment coefficient selected when the difference is smaller than the reference value; and a feedback unit configured to subject an offset adjustment value based on the at least one of the first and second adjustment coefficients selected by the selecting unit to feedback processing.