Method of and apparatus for detecting foreign substance

摘要

A method of and an apparatus for detecting a fine foreign substance in which the surface of a specimen is illuminated with linearly-polarized laser beam to detect light scattered from the surface and having passed through a polarization filter, the back side of the specimen is illuminated with light from a light source such as a mercury lamp to obtain the light and darkness information or phase information on the specimen surface by transmitted light from the specimen, and fine massive and filmy foreign substances on the specimen surface are detected on the basis of information given by the scattered light and transmitted light.