| 摘要 |
PURPOSE:To increase accuracy by providing two parallel reflecting mirrors on the way of an optical path from a rotary reflecting mirror to an image forming plane, thereby increasing the optical distance. CONSTITUTION:A light beam P which is emitted from a light source 4 is converged by a light source lens 5 and imputted to the rotary reflecting mirror 7 at a constant angle. Two pieces of reflecting mirrors are provided on the way of the optical path from the rotary reflecting mirror 7 to the image forming plane with a specified distance l being provided. The reflected light P' from the rotary reflecting mirror 7 is repeatedly reflected by the two reflecting mirrors 9 and 10 n times and reaches the image forming plane 8. In this constitution, since the optical distance is increased by L=2nlsectheta, the accuracy is increased, and the device can be miniaturized. |
