Image input device with dust detector

摘要

An image input device identifies what part of the optical input system needs cleaning when there is dust or other foreign matter in the optical input system. This image input device has an image noise position detector for capturing image data from a scanner, and detecting the main scanning address of noise information corresponding to image noise present in the image data; a focus calculator for calculating focus information around the main scanning address detected by the image noise position detector; focus information storage for storing focus information for each subscanning line; and a foreign matter position determining circuit for determining the location of foreign matter on the scanner based on the focus information stored in the focus information storage.