| 摘要 |
PURPOSE:To keep the deviation in focusing position of a laser beam spot caused by a malfunction to a minimum by moving a focusing correcting means to a set position which is regarded as a focusing position on a design and stopping the focusing correcting means by a focusing means in the case that defocusing cannot be fully detected. CONSTITUTION:The scanning device is provided with a defocusing detecting means 8 for condensing a luminous flux from a light source 2 on a body to be irradiated 9 so as to perform scanning with the luminous flux and also for detecting the condensed state of the luminous flux on the body to be irradiated 9 based on the luminous flux with which the body to be irradiated 9 is scanned and the focusing means 4 for adjusting the condensed state based on a signal from the detecting means 8. And in the case of recognizing that the expected function of an automatic focusing (AF) mechanism cannot function for some reason, the focusing correcting means 2 and 3 are moved to the set position and stopped at this position irrespective of a defocusing detecting signal. Thus, the meaningless adjustment of the defocusing is not performed by the AF mechanism and the deviation in focusing position of the beam spot is kept to a minimum. |
