| 摘要 |
PURPOSE: To increase a scanning velocity inexpensively by forming positioning holes at a position corresponding to the mount position of a polygon mirror on a chassis so that one hole may be partly overlapped on the other and fixing a motor with the corresponding polygon mirror mounted in one hole. CONSTITUTION: The 1st and 2nd positioning holes 71 and 72 are formed at such the position that desired optical characteristics can be obtained when the motor 4 with the five-plane polygon mirror 3 fixed and a motor 4 with the six-plane polygon mirror fixed are fixed. In the case the scanning positions on an irradiated body are made almost the same, the six-plane polygon mirror is kept away from an fθlens, and the six-plane polygon mirror whose diameter is larger than that of the five-plane polygon mirror 3 is used. In this case, only by fixing the motor 4 with the six-plane polygon mirror fixed instead of the five-plane polygon mirror 3 in the 2nd positioning hole 72, the scanning veleocity can be increased, then, the scanning velocity can be onverted in a short time. |
