NULL LENS OPTICAL SYSTEM FOR MEASURING THE SHAPE OF CONCAVE HYPERBOLOID MIRROR SHAPE

摘要

PURPOSE: A null lens optical system is provided to be easy to fabricate and to arrange an optical system when measuring a hyperboloid by making a surface receiving a ray of light flat. CONSTITUTION: Parallel rays of light from an interferometer are incident on an imaging lens(30). A field lens(31) makes an image of the imaging lens(30) formed on the hyperboloid of the object. A surface of the imaging lens on which the parallel rays of light are incident has a planed surface, and an opposite surface has a convex surface. A surface of the field lens on which the image of the imaging lens is incident has a concave surface, and an opposite surface has a convex surface. The imaging lens(30) and the field lens(31) are arranged so that a light axis(32) of the imaging lens(30) is identical to that of the field lens(31).