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 holographic straightness meter comprising an optical element and a hologram disposed on a moving member and one pair of reflection elements disposed on a fixed member. The object beam and reference beam from the optical element are reflected by the reflection elements so as to impinge upon the hologram and form interference fringes on the screen placed behind the hologram. The number, interval, and inclination of these interference fringes vary with the amount of lateral displacement of the moving member. Thus by analyzing the interference fringes for such factors, the amount of the lateral displacement of the moving member can be determined.

Abstract: A reflecting mirror is disposed behind a single Fabry-Perot interferometer non-perpendicularly relative to the optical axis of the interferometer. The light transmitted through the interferometer parallelly to the optical axis is reflected by the reflecting mirror and, therefore, caused to pass reversely through the interferometer at an angle relative to the optical axis. In this way, a single interferometer offers two different mirror gaps, one for the light path in the forward transmission and the other for the light path in the reverse transmission through the interferometer. The forward and reverse transmission of the light through the interferometer at different mirror gaps serves to enlarge the free spectral range to a notable extent.