Patent ID: 7239588
Filing Date: 2007-07-03
Classification: G01N,G11B

Abstract:
1. An apparatus for detecting a foreign body on an object surface, said apparatus comprising: an irradiation unit for irradiating a light spot onto a surface of an object to be inspected while scanning the surface by irradiating the light spot in a predetermined direction; an optical signal detection unit for receiving a reflected beam from the surface of the inspected object to generate a photodetection signal corresponding to the light intensity of the reflected beam; a foreign body detection unit for generating a foreign body detection signal appearing with respect to a leader and a trailer in the scanning direction of a foreign body adhering to the inspected object, based on the photodetection signal; and a foreign body discrimination unit for generating a foreign body discriminating signal indicating a region in which the foreign body is present based on the foreign body detection signal, wherein said foreign body discrimination unit includes a first comparison unit for comparing the output from said foreign body detection unit with a first reference voltage, and a second comparison unit for comparing the output from said foreign body detection unit with a second reference voltage, and wherein said foreign body discrimination unit further includes an RS flipflop circuit for inputting the respective output signals from said first and second comparison units.