| 摘要 |
PROBLEM TO BE SOLVED: To detect an adhered foreign matter by irradiating the entire surface of a substrate with parallel laser light and detecting a change in illuminance of a passing light with an illuminance meter. SOLUTION: A glass substrate 6 is fixed through suction by supporting pins 4. A laser beam 100 from which an extra light has been eliminated by a slit 3 passes a position separated such a slight distance that the beam nearly touches a lower face of the substrate 6. An illuminance meter 8 is set to the side opposite to a laser light-projecting part 1, and measures an intensity of the laser beam 100 every time the swept laser beam enters the meter. The illuminance meter 8 moves in a lateral direction by the rotation of a ball screw 9 and the therefore can obtain an illuminance signal to a move distance as a function. If a foreign matter 7 is present, the illuminance decreases because of the shadow. The foreign matter 7 can be discovered accordingly. Moreover, a position coordinate of the foreign matter 7 can be obtained from a coordinate of the ball bearing 9 at the time when the signal is obtained.
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