| 摘要 |
PURPOSE:To ensure the switching of the scanning light spot with a high light transmission efficiency and without any marginal vignette caused, by inserting the optical system comprising the round slit and the focusing lens into part of the optical path. CONSTITUTION:The optical system comprising detachable round slit 9 and the light focusing lens is inserted to the optical path between lens 5 and rectangular slit 6 of rotary optical system 1. The laser beam illuminated slit 9 forms image 12 of slit 9 on the surface of the slit 6 through lens 10. The size of image 12 is decided by the density of the scanning line. In this case, the diameter of slit 9 is set large to obtain a reduced image through lens 10. The beam passed through slit 6 forms an image on the film through image forming lens 8. Thus the width of the secondary scanning direction is reduced for the scanning light spot on the film. In this way, system 1 performs the main scanning with turning round the center axis of the optical system after selection of the light spot. While hollow cylinder 2 shifts toward the axis to carry out the secondary scanning. Thus the sharp recording is ensured. |
