| 摘要 |
PURPOSE:To compare the test pattern of standard particles with the interference pattern and to measure invariably correct particle size by sectioning angularly the pattern of interference fringes formed between light scattered by particulates sticking on a wafer surface plate and scattered light by a mirror image of the particulates formed symmetrically about the surface of the plate surface and then photodetecting them by unit photodetectors. CONSTITUTION:A laser beam L is projected on the wafer surface plate 1 which is rotated by a rotary scan type spindle 2, etc., to form a spot Sp and (n) unit photodetectors 7-1, 7-2... 7-n are arranged around the spot Sp to constitute a photodetector 7. Scattered light beams photodetected by those photodetectors 7-1, 7-2... 7-n are converted by photoelectric converters 8-1, 8-2... 8-n into voltage signals, which are inputted to a data processing circuit 9. The interference pattern obtained by the processing circuit is compared with the pattern obtained by testing standard particles to specify the particle size of the fine particles according to the comparison result. |
