Patent ID: 6744523
Filing Date: 2004-06-01
Classification: G01B

Abstract:
An imaging optical system for an oblique incidence interferometer in which a part of light source light is turned into parallel light so as to become measurement light obliquely incident on a surface to be inspected in a sample, a part of the remainder of said light source light is used as reference light constituted by parallel light, and said measurement light and said reference light are combined together and caused to interfere with each other so as to superpose interference fringes onto an image of said surface to be inspected formed on an imaging surface;said imaging optical system comprising: a first imaging optical system comprising two groups of telecentric lenses G1, G2 having respective focal lengths different from each other, said telecentric lens G1 having a longer focal length and said telecentric lens G2 having a shorter focal length being arranged afocal to each other successively from said surface to be inspected side; an intermediate imaging surface; and a second imaging optical system comprising two groups of telecentric lenses G3, G4 having respective focal lengths different from each other, said telecentric lens G3 having a longer focal length and said telecentric lens G4 having a shorter focal length being arranged afocal to each other successively from said surface to be inspected side; wherein a first image of said surface to be inspected, reduced from said surface to be inspected, having a deformed aspect ratio with respect to said surface to be inspected is formed on said intermediate imaging surface by said combined light of said measurement light and reference light by way of said first imaging optical system; and wherein said second imaging optical system is arranged with respect to said intermediate imaging surface such that said first image of said surface to be inspected is focused by said second imaging optical system onto said imaging surface as a second image of said surface to be inspected which is reduced from said first image of said surface to be inspected and corrected so as to have substantially the same aspect ratio as that of said surface to be inspected.