| 摘要 |
PURPOSE:To initialize accurately and speedily a scanning position by detecting the spot position of laser light and setting the initial position of an aperture on the basis of the detected value. CONSTITUTION:A half-mirror 5 arranged in the optical path of laser light 1 in front of an aperture mask 2 splits the laser light 1 into light which travels to the aperture mask and light which does not travel thereto. A light spot detector 6 arranged on the optical path of the split laser light 1c detects the center coordinates of the spot of the laser light 1c and sends its detection signal to a control circuit 7. The control circuit 7 shifts and sets the spot of the laser light 1 in initial position to the aperture 2a on the basis of the detection signal and also moves and scans the aperture 2a on the basis of the initial position. |
