| 摘要 |
PURPOSE:To eliminate the need for an expensive ftheta lens and to use a conventional a rotary multi-surface mirror consisting of planar reflecting surface, by driving a movable part with an error signal obtained by comparing a timing signal from a motor which rotates the rotary multi-surface mirror with a position signal in the movable part. CONSTITUTION:When the light emitting source of a semiconductor laser (LD) 101 is placed on an O point ahead of a focal point F on a front side on the optical axis of a collimator lens (CL) 102, the divergent light from the LD is condensed on the O' point backward on the optical axis. Assuming that the main point of the CL is set S and OS=y, O'S=x, equation y=f+f<2>/(x-y) is satisfied [(f) means the focal distance of the CL]. In case of x>>f, the optical system is an enlarging optical system and the fine displacement of (y) can be converted into the large displacement of (x). By changing the value of y-f synchronously with the change of the angle on a reflecting surface, an arc- shaped focal surface can be corrected to a linear focal surface. Thus, the conventional rotary multi-surface mirror consisting of planar reflecting surfaces can be used and the expensive ftheta lens cannot be needed. |
