| 摘要 |
PURPOSE:To obtain a titled device which has a high accuracy and also is inexpensive by providing a focusing controlling circuit for detecting an image forming position of a reflected image of a photodetecting part, and moving a movable lens placed between a light source and a focusing lens in accordance with a difference to a reference position in which a spot diameter of the reflected image becomes minimum. CONSTITUTION:A projecting system 2 converts a light 22 generated from a light source 21 consisting of a semiconductor laser device, to parallel lights by a collimating lens 23, and thereafter, irradiates them to an object to be measured 1 through a movable lens 24 and a focusing lens 26. Also, a photodetecting system 3 photodetects a reflected light 31 by a photodetector 33 through an image forming lens 32, and also detects a light quantity distribution of a photodetecting spot. Moreover, a focusing controlling circuit 4 consists of a spot position detecting circuit 41, a CPU42 and a movement controlling circuit 43, derives a difference between center position information of the photodetecting spot and reference position information stored in advance in an internal memory, and moves the lens 24 so that the spot diameter becomes minimum, by driving a moving mechanism 25. |
