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Patent Agency Ranking
公开(公告)号：DE2636211B1
公开(公告)日：1977-06-02
申请号：DE2636211
申请日：1976-08-12
Applicant: IBM DEUTSCHLAND
Abstract: In an interferometric measuring system, a collimated monochromatic and coherent beam of light (1, I1-In)impinges on a grating 1 disposed parallel to the test surface 2. It has been found that in the above arrangement, a diffraction order (preferably the first diffraction order S1-S4) of the light reflected from the face of the grating opposite to the test surface is always parallel to three diffraction orders of the radiation which after being first diffracted upon its first passage through the grating and reflected from the test surface is again diffracted upon its second passage through the grating. These four radiations (S1 to S4) generate two interference fields, the combination of which generates a beat pattern. According to the invention, the angle of incidence of the radiation impinging onto the face of the grating opposite to the test surface is chosen in such a way (preferably from 0.5 DEG to 5 DEG ) that the areas in which the beat patterns generate an additional field of interference fringes, related to lambda /4 distances, from the test surface are a maximum. When properly selecting pairs of angles of incidence and of distances between test surface and grating the resolution of the resulting fringe pattern (interference fringes symmetrically interleaved by beat fringes) is improved by the factor of 2, i.e. the distance between two fringes is related to a lambda /4 distance from the test surface, as opposed to the interferometric methods known heretofore where the maximum resolution is defined by fringe distances related to lambda /2 distances from the test surface.
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公开(公告)号：DE2758149B1
公开(公告)日：1979-02-15
申请号：DE2758149
申请日：1977-12-27
Applicant: IBM DEUTSCHLAND
Abstract: Described is a method for interferometric measurement in which a monochromatic, coherent and parallel, convergent or divergent radiation is directed onto the test object so as to generate in a manner of an interference fringe pattern, the distances between two adjacent fringes being correlated to lambda /2 distances in the object space. The radiation reflected from the object and containing an interference field, giving rise to said fringe pattern, is redirected onto the test object, e.g. by a suitable mirror arrangement under an angle of incidence different from the angle of incidence of the radiation first impinging on the test object. This radiation, after reflexion from the test object, forms an interference field comprising four interfering components and producing, e.g. on an observation screen, an interference fringe field. By properly adjusting the angles of incidence of both radiations, the distances between adjacent fringes can be made to correspond to lambda /4 distances in the object space.
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