| 摘要 |
PURPOSE:To adjust a light spot quickly and easily with a high precision, by arranging a detector, to which the light spot is made incident interruptedly at a certain period, on a scanning stage where a dry plate is put and grasping the state of the light spot on a basis of the differential waveform of the output of this detector and comparing it with a reference value to adjust a light spot generating part. CONSTITUTION:The output of a detector 10 is inputted to an amplifier 60 and is amplified. This output is inutted to a differentiation circuit 51 and becomes primary and secondary differential signals there, and they are inputted to a detecting part 52, and information concerning the light spot is read out from the differential waveform and is outputted to a comparing part 53. A preliminarily inputted reference value 54 and the output of the detecting part 52 are compared with each other in the comparing part 53, and a signal corresponding to the comparison result is inputted to a controlling part 55. The controlling part 55 adjusts a light spot generating part 90 in accordance with this input signal. |
