Patent ID: 6633387
Filing Date: 2003-10-14
Classification: G01B

Abstract:
An apparatus for measuring the parallelism of two opposite surfaces, comprising:an interference optical system for leading parallel beam to a pair of opposed test surfaces and then leading, from said test surfaces via different optical paths, interference fringe images formed by radiation of said parallel beam to said test surfaces, respectively; and means for imaging said interference fringe images led via said different optical paths, respectively; said interference optical system includes: a measurement head being interposed between said test surfaces and having a pair of opposite reference surfaces formed thereon so as to oppose to said test surfaces, said reference surfaces being defined with a highly accuracy parallelism and distance; a lens system for collimating a light emitted from a light source into said parallel beam; and a splitting optical system for splitting said parallel beam from said lens system into two optical paths, leading said two split parallel beam to said test surfaces via said reference surfaces and then leading said interference fringe images to said means for imaging, each of said interference fringe images being created through interference between a light reflected at each of said test surfaces and a light reflected at the corresponding reference surface opposing thereto.