| 摘要 |
PROBLEM TO BE SOLVED: To provide a device capable of measuring the whole shape of an aspheric surface by one operation by transforming spherical waves to be reference into spherical waves corresponding to an aspheric test surface with respect to spherical waves diffracted by a pinhole. SOLUTION: A reflecting surface to create a point light source is arranged between a light source 1 and a test surface. A beam of light for reference is a beam of light emitted from the point light source, and a beam of light for measurement is a beam of light emitted from the point light source and reflected by a reflecting surface. Then an optical element to transform spherical waves into desired aspheric waves is arranged in an optical path between the point light source and a test surface 5. With respect to spherical waves diffracted by a pinhole 3, spherical waves to be reference are transformed into aspherical waves corresponding to the aspheric test surface 5. Or aspheric waves generated by the reflection of the spherical waves to be reference at the aspheric test surface 5 are transformed into spherical waves and plane waves. By making intervals of interference fringes in the whole surface of an aspheric test surface coarse through the use of what is called a null element 4, it becomes possible to measure the whole shape of the aspheric surface by one operation.
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