| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem wherein an inter-image-height deviation of a spot diameter of a main scanning light beam gets large on a scanned face, when using an f*arcsin lens in stead of an fθlens for a conventional polygon mirror, upon using a micromirror for sinewave vibration of resonance structure as an optical deflector, and a problem wherein a scanning velocity constancy gets low, when trying to restrain the problem, to make a scanning velocity not constant on the scanned face, in an optical scanner used in a latent image writing means of an image forming apparatus or the like. SOLUTION: In the optical scanner, a stationary beam spot diameter is set to correct a change of the scanning velocity corresponding to an image height while corresponding to the image height. An elliptic scan beam spot is generated by moving the stationary beam spot diameter during one dot of drawing, when driving the deflector (polygon mirror) to scan the scanned face with a scanning beam. The stationary beam spot diameter is set relatively large, when the scanning velocity gets low by the image height, to make the stationary beam spot diameter substantially constant irrespective of the image height as a result thereof. COPYRIGHT: (C)2009,JPO&INPIT |
