| 摘要 |
PURPOSE:To make detection more exactly by mounting a means for preventing deposition of foreign matter which is formed with a pellicle on a frame to a substrate, scanning the polarized light which is condensed and projected relatively on the substrate, condensing the light reflected from the foreign matter by a condensing optical system and converting the light to a signal. CONSTITUTION:The laser light 30 from a laser oscillator 27 is linearly polarized by a polarizing element 29 and the polarized light is reflected by a galvanomirror 28 connected to a motor 34 so as to arrive at a mirror 32 via an f.theta lens 31. The light 30 is entered at an angle alpha of inclination to the substrate 21 via mirrors 35a, 36a or mirrors 35b, 36b. Detecting devices 37a and 37b consisting of a detector 41a which detects the linearly polarized light, a condenser lens 40a, a slit-shaped light shielding device 39a, and a photoelectric converting element 38a are then disposed perpendicularly to the laser light 30a, 30b and at an angle beta of inclination with the substrate 21 to detect the foreign matter on the substrate 21. The polarized light 30 is, therefore, used and detector 41a, the device 39a, etc., are provided, by which the exact detection is executed with high sensitivity. |
