US 4,626,101 AGranted

Surface defect inspecting apparatus

AssigneeKabushiki Kaisha Toshiba

InventorsShigeru Ogawa, Hiroshi Yamaji, Masaaki Kano

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Abstract

The holding mechanism holds an object under inspection in a manner that the substantially entire surface of the object may relatively be scanned by a laser beam. A spherical integrating light collector has an opening disposed close to the inspected surface of the object held by the holding mechanism. A laser beam illuminating mechanism is coupled with the other end of the spherical integrating light collector, and illuminates the inspected surface of the object with the laser beam through the opening. A photo-electric converter receives the scattered light as is reflected by the inspected surface and collected by the spherical integrating light collector, and converts the scattered light into an electrical signal representing an amount of light. An analog to digital converter converts the electrical signal derived from the photo-electric converter into a digital signal. A peak detector receives the digital signal derived from the analog to digital converter to detect peak values at predetermined periods. A mean value calculator calculates a mean value using a digital signal output from the analog to digital converter. A reference value storing memory stores a reference value to determine defects present on the inspected surface of the object. A threshold level calculator calculates the threshold level using the reference value and the mean value. A defect detector compares peak values derived from the peak detector with the threshold level, and detects the surface defects on the basis of the result of the comparison.

Claims19

Dependent claims

An apparatus for inspecting an object under inspection for defects on the surface thereof, comprising:

means for holding the object under inspection in a manner that the substantially entire surface of the object may relatively be scanned by laser beam;
spherical integrating light collecting means provided at one end with an opening disposed close to the inspected surface of the object held by said holding means;
laser beam illustrating means coupled with another end of said spherical integrating light collecting means and for illuminating said inspected surface of the object with the laser beam through said opening;
photo-electric converting means for receiving the scattered light as is reflected by said inspected surface and collected by said spherical integrating light collecting means, and for converting the scattered light into an electrical signal representing an amount of light;
analog to digital converting means for analog to digital converting the electrical signal derived from said photo-electric converting means into a digital signal;
peak detecting means for receiving the digital signal derived from said analog to digital converting means to detect peak values at predetermined periods;
means for calculating a mean value based on a digital signal output from said analog to digital converting means;
means for storing at least one reference value which is for determining at least one threshold level to detect surface defect or defects present on said inspected surface;
means for calculating said threshold level based on said reference value and said mean value;
and
surface defect detecting means for comparing peak values derived from said peak detecting means with said threshold level, and for detecting the surface defect or defects depending on the result of the comparison.

8 more elements

Dependencies are inferred from the claim text.