| 摘要 |
PURPOSE:To make it possible to detect only foreign matters on the surface of a substrate by providing one light receiving means which receives the scattered light from the surface of the substrate comprising a transmitting material and the scattered light which is transmitted through the substrate and scattered with a scattering plate. CONSTITUTION:The laser beam which is emitted from a laser light source 1 is reflected with a polygonal rotary mirror 4 through a beam expander 2 and a total reflection mirror 3. The reflected light is vertically projected on the surface of a specimen 7 with a total reflection mirror 6 through an ftheta lens 5. The surface is scanned as shown with an arrow 11. The specimen comprises a transparent material. Patterns 8 and 8' comprising opaque material are formed. The light 18 among scanning laser lights 16 - 20 which is projected on a part other than the pattern 8 is transmitted through the specimen 7. A locus 12 is drawn on the surface of a scattering plate 9 which is provided in parallel with the specimen 7. The scattered reflected light from the surface of the specimen 7 is synthesized with the lights 18b, 18e and 18c among the scattered reflected light 18a - 18d from the surface of the scattering plate 9 which have passed through the specimen 7 again. The synthesized light is received with a light receiving part 10. Only the foreign matters 21 and 22 appear as the change in electric level in the output of an optoelectronic transducer. |
