| 摘要 |
PURPOSE: To increase the beam receiving efficiency of a beam detector by providing a polygon mirror for scanning main polarization rotatable around its axis, a beam scanning fθlens system for injecting laser beam against the surfaces of an object to be inspected, a beam detecting means installed at a position apart from the fθlens system, and others. CONSTITUTION: A laser beam radiated from a semi-conductor laser element 1 becomes a beam light 13 through a collimator lens 12, and collided against the mirror surface of a polygon mirror 14 to become a reflected beam 15. Because the polygon mirror 14 is rotated around its axis, the reflected beam 15 is polarized to one direction, and made incident on a beam scanning fθlens system 17 arranged between the polygon mirror 14 and a mounted substrate 16. Because the lens system 17 gives a convergent lens action from coaxially arranged multiple lenses to the reflected beam 15, the reflected beam 15 scans the surfaces of the substrate 16. Thus, a scattered reflected beam 19 produced on the surfaces of the substrate 16 by the scanning of light is used to inspect the surface conditions by comparing the photoelectric conversion output taken out from one of first and second beam detectors 20 and 21 with a standard electric signal.
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