Black-level feedback device, an image reading apparatus and the black-level feedback control method

摘要

PPROBLEM TO BE SOLVED: To reduce offset variations of sub scanning carried out by black level feedback. PSOLUTION: A black level feedback device comprises: a first setting value arithmetic means 161 for calculating a setting value of black level feedback based on a reflection amount to quicken following a black level target value in black level feedback control; a second setting value arithmetic means 162 for calculating a setting value of black level feedback based on a reflection amount to delay following the black level target value in comparison with the first setting value arithmetic means 161; a selection means 164 for selecting either an output of the first setting value arithmetic means 161 or an output of the second setting value arithmetic means 162; and a following speed deciding means 163 for selecting either the output from the first setting value arithmetic means 161 or the output from the second setting value arithmetic means 162 by controlling the output of the selection means 164 in accordance with a black difference value and an amplification factor to image data. PCOPYRIGHT: (C)2007,JPO&INPIT