In image concentration detection manner and the image concentration detection manner which detects the device, image concentration

摘要

PROBLEM TO BE SOLVED: To obtain image reproducibility at a human color difference recognition threshold value or below by preventing reduction in detecting accuracy caused by the difference in soiling between two photodetectors. ;SOLUTION: A first infrared LED 21 is lighted so that a first photodiode 22 receives regular reflected light and a second photodiode 23 receives diffuse reflected light. A second infrared LED 24 is lighted so that the second photodiode 23 receives the regular reflected light and the first photodiode 22 receives the diffuse reflected light. The outputs of the respective photodiodes 22 and 23 are calculated to obtain an image density.;COPYRIGHT: (C)1998,JPO