Abstract: High-precision turning of a metal mirror is accomplished by causing a measuring beam to be reflected on a freshly turned area of the reflecting surface to be formed in a metal blank being turned to produce a metal mirror and, at the same time, causing reference beams to be reflected on areas turned prior to the aforementioned freshly turned area, measuring the positions of incidence of the resultant reflected beams on a position detection device thereby performing the Hartmann test on the aforementioned turned areas of the reflecting surface and, based on the results of the measurement, controlling the nose position of the cutting tool now being used in turning the reflecting surface.

Abstract: A device for the detection of the center of rotation of a rotating object under test comprises means for illuminating a laser beam on at least one position on the surface of the object thereby generating an interference fringe, means for subjecting the resultant reflected scattered laser beams to spectral analysis by the laser Doppler effect thereby finding the velocity of rotation of the position at which the interference fringe is formed on the surface, and means for determining the center of rotation on the basis of the velocity so found. Protection of the spectral analysis from the adverse effect of the pedestal component is accomplished by causing interference fringes to be formed at a plurality of positions on the surface of the object under test or by placing in the optical path for one of the pair of laser beams a prism capable of continuously modulating the laser frequency.