| 摘要 |
PROBLEM TO BE SOLVED: To provide a focus detector capable of easily focusing on a desired surface of a translucent testee body. SOLUTION: The focus detector has an objective lens 21, an index projection optical system 40 projecting two index images comprising a translucent patterns to the testee body S from different directions in order to determine focusing, and a light detection optical system 50 detecting reflected light from the testee body S. The index projection optical system 40 includes a light source 41, an aperture part 42, a lens 43, an optical path division prism 45, an index 46 and a half mirror 47, wherein the aperture part 42 is arranged at a position conjugate to the exit pupil of the objective lens 21, and the optical path division prism 45 is arranged at a position conjugate to the testee body S in a focused state. The light detection optical system 50 includes the half mirror 51 and a pair of photodetectors 52a and 52b, and the photodetectors 52a and 52b are arranged at the position conjugate to the testee body S in the focused state. Furthermore, the focus detector has a decision part 61 to decide output from the photodetectors 52a and 52b, and output equipment 62 to output results of the decision. COPYRIGHT: (C)2009,JPO&INPIT |
