IMAGE READER

摘要

PROBLEM TO BE SOLVED: To make an entire reader small by utilizing an image forming system for image pickup as it is so as to detect the distribution of contrast and controlling an auxiliary light so as to focus the image forming lens. SOLUTION: CPU 300 is operated as follows: at first, the storage signal of an image sensor 16 is read for a default prescribed storage time, and data equivalent to a prescribed bit around a center picture element in the main scanning direction are received as a discrimination object. Succeedingly, a maximum luminance Bmax and a minimum luminance Bmin are detected from the luminance of a discrimination object to obtain the difference of the both and the result is written in a 1st luminance difference variable Bsub1 . Then the contents of the Bsub1 are transferred in a 2nd luminance difference variable Bsub2 to reverse a lens drive motor 60 thereby decrementing a lens pulse counter Paf . The operation is repeated in the case of Paf <0 and Bsub21 Bsub1 is discriminated, the focusing is discriminated at the position of the image forming lens. When the focusing cannot be detected in a moving range of the lens, an auxiliary light is lighted to drive a motor 60 forward and the similar discrimination to above is conducted.