Optical method and apparatus for detecting low frequency defects
First Claim
1. A method for the inspection of an optical object for the existence therein of inhomogeneities, said method comprisingproviding a beam of inspection radiation and directing said beam on said optical object so that each point thereof is illuminated at a single respective angle;
- projecting said beam through said optical object on a projection screen and obtaining thereby a shadow pattern thereof, said optical inhomogeneities being distinguishable in said shadow pattern owing to a difference in the brightness of the areas corresponding thereto over the background brightness of the pattern;
imaging said shadow pattern through said optical object in such a manner that the rays forming said image pass through each point of the optical object at an angle corresponding to said angle at which said point is illuminated; and
detecting and analyzing said image of the shadow pattern.
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Accused Products
Abstract
Inspection of an optical object for the existence therein of inhomogeneities, comprises providing a diverging beam of inspection radiation and directing the beam on the optical object so that each point thereof is illuminated at a single angle; projecting the beam through the optical object on a projection screen and obtaining thereby a shadow pattern thereof, the optical inhomogeneities being distinguishable in the shadow pattern owing to the difference in the brightness of the areas corresponding thereto over the background brightness of the pattern; imaging the shadow pattern via the optical object in such a manner that the rays forming the image pass through each point of the optical object at an angle corresponding to the angle at which the point is illuminated; and detecting and analyzing the image of the shadow pattern.
35 Citations
20 Claims
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1. A method for the inspection of an optical object for the existence therein of inhomogeneities, said method comprising
providing a beam of inspection radiation and directing said beam on said optical object so that each point thereof is illuminated at a single respective angle; -
projecting said beam through said optical object on a projection screen and obtaining thereby a shadow pattern thereof, said optical inhomogeneities being distinguishable in said shadow pattern owing to a difference in the brightness of the areas corresponding thereto over the background brightness of the pattern; imaging said shadow pattern through said optical object in such a manner that the rays forming said image pass through each point of the optical object at an angle corresponding to said angle at which said point is illuminated; and detecting and analyzing said image of the shadow pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus for the inspection of an optical object for the existence therein of inhomogeneities comprising:
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illumination means for providing a diverging beam of inspection radiation and for the illumination of said optical object thereby so that each point thereof is illuminated at a single angle of the incident radiation, and providing, by means of said optical object, a shadow pattern thereof on a projection screen; imaging means for imaging said shadow pattern through said optical object in such a manner that rays forming said image pass through each point of the optical object at said angle at which said point is illuminated; and image detecting means and image processing means for analyzing said image of the shadow pattern for said inhomogeneities. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification