| 摘要 |
PURPOSE:To eliminate the occurrence of the vignetting of lens of a laser beam on an objective lens by a reflecting mirror by locating the turning center of the reflecting mirror on the extension line of the reflection optical axis, and setting the turning radius thereof at the length approximately twice the optical path distance between the reflecting mirror and the objective lens. CONSTITUTION:The turning radius of a reflecting mirror 6 is set at the distance 2m about twice the optical path distance m between the reflecting mirror 6 and an objective lens 8. Now, when the mirror 6 turns by an angle phi and comes to the position 6', the incident angle of the laser beam to the lens 8 is 2phi. The laser beam irradiation position of the reflecting mirror 6 moves approximately to 2mphi. This results in that the laser beam reflected from the mirror 6 passes near the point O which is half the turning radius. Now, the lens 8 is located at the point O and this turns out that the laser beam passes always near the center of the lens 8, thereby eliminating the vignetting of lens of the laser beam owing to tracking. |
