Color image reading apparatus with a plurality of line sensors in which a white balance operation is performed by determining amplifier gains while reading a white reference plate

摘要

A color image reading apparatus with a plurality of line sensors and an associated plurality of rotary color filter disks produces a plurality of sequential color component signals from each line sensor. An amplifier with an adjustable gain is provided for each of the line sensors. A white balance operation is performed prior to reading a color document by determining gains for each of the amplifiers to use in amplifying corresponding ones of the sequential color component signals on the basis of a plurality of reference color component signals generated by reading a white reference plate with the line sensors. The determined gains are stored in a memory as digital data. The data is read out and used to control the gains of the amplifiers while a color document is being read. Color balance correction switch units enable an operator to selectively modify the determined gains in order to adjust the color balance of the color component signals.