Optical system, method for arranging point light sources in the optical system, and image scanning exposure apparatus

摘要

A plurality of LED chips is turned on at theoretical arrangement pitches. The distance between a theoretical imaging point of one LED chip located farthest from an optical axis and the optical axis, and the distance between an actual imaging point and the optical axis are obtained. With the increasing ratio of the distances being set as a reference, the positions where the LED chips are arranged are shifted in a direction opposite to that of the displacement caused by distortion aberration. The further the LED chip is located from the optical axis, the larger the amount of displacement thereof becomes. Further, the nearer the LED chips is located to the optical axis, the smaller the amount of displacement thereof becomes. As a result, the LED chips are arranged on a substrate in such a configuration that compensation for the distortion aberration produced on the photosensitive material can be achieved.