| 摘要 |
PURPOSE:To attain speedy and secure switching of an image with proper resolution by providing plural polygon mirrors which differ in the number of reflecting surfaces on a spindle, and selecting a polygon mirror to be irradiated with laser light among the polygon mirrors. CONSTITUTION:When two high and low stages of resolutions are requested, the two polygon mirrors 8a and 8b which have different numbers, e.g. 6 and 12 reflecting surfaces are provided on the spindle 3 and the polygon mirror to be irradiated with laser light from a laser light emission device 9 or 10 is selected between them at a request for resolution. Namely, the LD9 and polygon mirror 8a are normally used in combination and when the high resolution is requested, a switch mechanism, etc., combines the LD 10 and polygon mirror 8b together immediately, and consequently although the number of rotations is equal, the number of reflecting surfaces increases to increase the number of reflecting surfaces increases to increase the number of scanning lines on a photosensitive drum 5, thereby forming an electrostatic latent image with the high resolution. Consequently, images can easily, speedily, and accurately be switched. |
