| 摘要 |
PURPOSE:To achieve high-precision, high-reliability correction by a focus compensating mechanism for the focusing of a photoscanner, by driving a dynamic linear motor. CONSTITUTION:Light 21 obtained when a rotary mirror 2 has a scan 21 on a point A to be measured is imaged on a photodetector 16 through a focusing mirror 17 and a focus compensating mirror 11. Since optical path length varies in accordance with the rotation of the rotary mirror, a detector 3 detects a mark (a) for rotation detection, and a PLL circuit generates a sine wave having a prescribed relation with the rotary mirror by a correction signal. The correction signal is inputted to a servo amplifier 19 to drive a dynamic linear motor which has an armature 13 wound with a coil, thus putting the focus compensating mirror 11 in necessary reciprocal motion. |
