| 摘要 |
PURPOSE:To provide an automatic focus scanning type optical device capable of compensating a focus so as not to be deviated from focal depth due to a curve, an inclination, etc., on a plotting face even when the F number of an optical system is reduced. CONSTITUTION:This optical device is provided with a gas laser 10 for radiating plotting optical beams, a polygon mirror 20 for defecting the beams radiated from the laser 10 to execute scanning, a platting face side telecentric scanning lens 40 for forming an image of the beams deflected by the mirror 20 on a plotting face 30, a focus detecting means 50 for detecting the focused state of the lens 40 to the plotting face 30, a focusing means 60 for focusing the lens 40 to the plotting face 30 based upon an output from the means 50. |
