| 摘要 |
PURPOSE:To automatically correct variation in the angle of irradiation of the light beam of each irradiation system by guiding part of the light beam of each of plural irradiation systems as a monitor beam and detecting the relative position shift between the irradiation point of the light beam and an inspection point. CONSTITUTION:The inspection point on the surface of a body to be inspected is irradiated with S-polarized laser beam generated by S-polarized light laser oscillators 18 of two irradiation systems 16A and 16B through cylindrical lenses 20, movable mirrors 22, and half-mirrors 24 respectively. Part of each laser beam is extracted as a monitor beam by each half-mirror 24 and made incident on a pin photodiode 36, and a movable mirror 22 is driven with a single corresponding to the relative position shift between the irradiation point and inspection point, thereby correcting the direction of irradiation of an S-polarized laser beam. Reflected laser light from the inspection point, on the other hand, enters an S-polarized light f rom the inspection point, on the other hand, enters an S-polarized light cut filter 56 through an objective 52 and a slit 54 to extract only the P-polarized component, which is made incident on a photomultiplier 58 to decide whether there is foreign matter or not.
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