| 摘要 |
PURPOSE:To provide the automatic focusing device which is small in size and makes a quick response and can detect focusing even on a plain work. CONSTITUTION:The laser light emitted by a semiconductor laser 21 is collimated by a lens 22, made incident on a lambda/4 plate 24 from a polarization beam splitter 23, and made into circular polarized light, which irradiates the work 5 from a mirror 25 through an objective 2. The light reflected by the work 5 is made incident on the mirror 25 and lambda/4 plate 24 from the objective 2 to become linear polarized light parallel to this paper surface and this light is passed through the polarization beam splitter 23 and supplied to a four-split photodetector 28 from a condenser lens 26 and a semicylindrical lens 27, thereby detecting defocusing. An automatic focusing controller 30 finely moves an actuator 10 by a piezoelectric element 13 in the direction of the optical axis of the objective 2 corresponding to out-of-focus. |
