IMAGE READING DEVICE, IMAGE FORMING DEVICE, GAIN ADJUSTMENT METHOD AND PROGRAM

摘要

PROBLEM TO BE SOLVED: To provide devices and a method which can set an optimum gain in a short time even when white flaws and the like occur in a reference white board.SOLUTION: An image reading device comprises: reading means for optically reading a manuscript to output an analog image signal; first amplification means for amplifying the analog image signal based on a first gain; conversion means for converting the analog image signal to digital image data; second amplification means for amplifying the digital image data based on a second gain; detection processing means for reading a reference image and detecting a peak value from signal levels of a plurality of lines of the amplified digital image data and calculating an average value by averaging the signal levels of the plurality of lines; and control means for calculating the first gain such that the peak value becomes a predetermined target value and setting the calculated value to the first amplification means, and calculating the second gain by using the peak value, the average value, a peak value detected and an average value calculated by re-reading the reference image after setting of the first gain, and the target value and setting the calculated second gain to the second amplification means.