Simple laser interferometers for laser optics testing

A simple laser interferometer for laser and astronomical optics testing is proposed. It consists of a small concave or convex mirror, a gas laser, a semitransparent flat mirror and concave mirror or a system under test, and a register equipment. The interferometer works the, following way: laser beam is reflected by concave or convex micromirror and then it is directed to the semitransparent flat mirror, and to the mirror or the system under test. The light reflected by the flat mirror of the interferometer is the reference wave, the light, reflected by the mirror of the system under test is imperfect wave to be tested. The reference wave and the imperfect wave are recombined to produce a system of Twyman-Green fringes in a receiving screen or in a register equipment to obtain interferograms. It is possible also to test any concave ellipsoidal mirror by properly shifting of the semitransparent flat mirror along the optical axis of the mirror under test. By the way, a spherical surface is a spherical case of an ellipsoid. Hyperboloidal mirror may be tested by means of the incorporation of a null corrector, for example Offner type one. The interferometer was successfully manufactured and tested at the Crimean Astrophysical Observatory.