| 摘要 |
PURPOSE:To execute easily a precise positioning of a scanning position by providing a parabolic reflector having a convex surface, next to a combined lens so that its focus coincides with an image by a combined lens of a reflecting surface of a rotary polyhedral mirror. CONSTITUTION:An infinity point in front of a 3a1 surface of the first lens of a combined lens 3 is made an object point, the 3a1 surface of the first lens is made a plane, 3b2, 3c1 surfaces of the second and the third lenses are made a spherical surface centering around an image of the object point, and 3a2, 3b1 and 3c2 surfaces of the second and the third lenses are made a spherical surface centering around an image of a mirror surface 2a. Also, a parabolic reflector 4 is placed so that its focus coincides with an image of the mirror surface 2a. In this way, a precise light spot is positioned precisely and a plane scanning can be executed. |
