| 摘要 |
A scanner is here disclosed in which the structure of an f theta lens can be simplified to decrease the cost of the scanner and facilitate the installation operation. In order to maintain the f theta properties, it is necessary to carry out control by prolonging a time interval of the radiation of light beams in the vicinity of the center of main scanning, and by shortening the time interval in the vicinity of the end portion of the main scanning so that the image formation spots of the light beams may be arranged at equal intervals. Thus, in the vicinity of the center of the main scanning, in order to prolong the time interval of the radiation, there are arranged, for example, standard radiation patterns in which the radiation is carried out once every 8 clocks, and a radiation pattern in which the radiation is done once every 9 clocks. |
