Method for measuring the thickness of transparent articles

摘要

A method for measuring the thickness of transparent articles utilizing a plural component light beam. In the most general sense, the present invention involves the generation of a plural component light beam which is generally symmetric about the optic axis of the system. The light distribution which results from this arrangement is used to illuminate a transparent article. The result is separate reflections from the front and rear surfaces of the article for all of the components of the light beam. If these reflections are imaged in a detector plane which is conjugate to a plane in the vicinity of the article, a pair of co-planar images are formed, one image representing reflections of all of the plural components from the rear surface and the other image representing reflection of all of the plural components from the front surface. Measurement of the average separation of the images will give a value that is proportional to the thickness of the article at a point lying along the optic axis of the system.