Patent ID: 7385169

Claim:
A method for aligning a light-receiving element array substrate in a contact image sensor which comprises a housing; one or two light sources for irradiating light onto a original, the one or two light sources being fixed into the housing; a slit plate including a slit opening for passing light reflected from the original, the slit plate being fixed into the housing and the slit opening having an elongated-shape extended in a main-scanning direction; a lens for forming an erecting unit magnification image by focusing the reflected light from the original through the slit opening of the slit plate on at least one light-receiving element array, the lens being composed of a plurality of micro-lens array plates; and the light-receiving element array substrate including the at least one light-receiving element array, the light-receiving element array substrate being supported in the housing, the method comprising the steps of: (a) setting a reference original of uniform lightness distribution over the slit opening; (b) irradiating light onto the reference original by means of the one or two light sources; (c) receiving light reflected from the reference original and passed through the slit opening to detect a sensor-output from a photo-electric converted signal by means of the at least one light-receiving element array; and (d) aligning the width of the light-receiving element array substrate in a sub-scanning direction perpendicular to the main-scanning direction so as to obtain a maximum of the sensor-output detected in the step (c).