| 摘要 |
PURPOSE:To simplify the positioning of photoreceiving element at a focalized position by using no mechanical shifting element by a method wherein an array type element is used as a photoreceiving element and luminous flux reflected from a specimen surface is detected and then the focalization is performed by making a comparison between a reference position and a position being detected. CONSTITUTION:A projecting optical path 5 makes arrangement so that light emitted from a light source 6 may be magnified by a collimator lens 7 to be entered into a slit 8 which is provided with at least two or more openings 8a while a lens 9 and a reflector 10 may form images 8b on a wafer 2. On the other hand, reflecting light 11 from the wafer 2 likewise makes arrangement so that another reflector 12 and another lens 13 may form images 8c on a photoreceiving element 14. The output from photoreceiving element 14 temporarily memorizes waveforms by a memory circuit 16 through the intermediary of an A/D converter 15 and then calculates the central position address of each wave form image of the memory circuit 16 by a point of intersection detecting circuit 17. When the focalization is carried out, said detected results calculated by an adder 18 are compared with the results detected by the other memory circuits 2, 19 to drive a driving source 4 by a drive control circuit 21 in terms of the results. |
