METHOD AND DEVICE FOR MEASURING AND EVALUATING SCANNING BEAM OF SCANNING OPTICAL SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a scanning beam measuring and evaluating method for a scanning optical system which can easily measure a positional shift in a sub-scanning direction due to the surface fall, shaft movement, vibration, etc., of a polygonal mirror of the scanning optical system without actually forming a latent image on a photosensitive body surface and analyze banding generated by the scanning optical system. SOLUTION: The exposure time of a CCD camera 11 which is so arranged as to pick up an image at a position corresponding to the photosensitive body surface is set so long as to correspond to a plurality of horizontal scanning lines. As for those horizontal scanning lines, a light emitting device is made to emit light with evaluation light emission patterns 1, 2, and 3 which are different in timing by the lines, and images are picked up in the same visual field of the CCD camera 11 so that the evaluation pattern images of the different horizontal scanning liens can be picked up at the same time while shifted in the horizontal scanning direction in the same visual field of a two-dimensional camera. The linearity of those evaluation pattern images is analyzed to evaluate whether and how much the images shift in position in a vertical scanning direction.