| 摘要 |
PURPOSE:To make accurate focusing using a simple configuration even with no pattern formed, even in case interface having different reflection factor exists. CONSTITUTION:Light from a light source 30 is cast on an object 33 by an irradiation optical system 31, and the reflected beam having passed a beam splitter 36 is taken out from an objective lens 43. The taken-out beam is diverged in two directions by a branching optical system 46, and one of the divergent beams is passed through the first optical system 47 and the first pinhole plate 48, installed for example ahead of the focal point of this system 47, to be received by the first photo-receiving element 49, while time other divergent beam is forwarded via the second optical system 50 and the second pinhole plate 51, arranged for example behind the focal point of the system 50, to be received by the second photo-receiving element 52. An adjusting means 60 adjusts the position of the objective lens 43 relative to the object 33 so that the photo- reception amounts of these first and second receiving elements 51, 52 are identical. |
