PURPOSE: To make a shaded form uniform by determinizing the position of a light source so that the digital signal of the output of a photoelectric transfer element converting an object image to an image signal, satisfies the prescribed condition.
CONSTITUTION: Object irradiating light from the light source passing-through an optical system is received by the photoelectric transfer element C; the output from the element C is converted to the digital signal F by a digital converting means D. An average, a maximum and a minimum of the signal F are calculated by an average calculating means, a maximum detecting means and a minimum detecting means, respectively. Each calculated result is multiplied by constants (a), (b) and (c), and Z, which satisfies a formula I, is calculated by a Z calculating means H; a maximum Z detecting means I detects a maximum Z, where the light source A is positioned by a position controlling means J and a position adjusting means B. Thus, even when the light source A is replaced, etc., the shaded form is made most uniform without the influence of filament form, therefore, an image is read even through the use of a aehler illumination system.
SATO YUICHI
WATANABE HIROYUKI
