A gauge for measuring flatness by utilizing the interference of light is composed of a block having a reference or standard surface of a high flatness and surfaces intersecting the reference surface. Three supporting members are fixedly secured to said surfaces in an appropriate arrangement. Each of three pins which is anchored to respective supporting member has a pointed top portion jut beyond the reference surface. The object or specimen to be tested is rested on said top portions of the three pins to support the specimen with the tested surface extending substantially in parallel with said reference surfaces in opposing position.
Disclosed is an interferometer having an optical flat having a coated reference surface of aluminum whose thickness is in the range of 100-500 A (preferably about 300 A) covered with a coating of silicon dioxide of a thickness in the range of 1,000-10,000 A (preferably about 3,000 A). Such a coating on an optical flat when in engagement with a surface of an object to be tested greatly enhances the contrast of the interference fringes.
Surface flatness of a machined work piece, such as a mechanical seal, is determined by placing the surface to be tested against the top surface of a horizontally-disposed "optical flat", projecting monochromatic light rays, such as from a helium lamp, downwardly onto the work piece and the optical flat, and viewing the light rays reflected from the interface of the optical flat and the surface to be tested, by use of a reflective surface placed below the optical flat.
A flatness examining device which comprises a radiation beam generating means, an objective lens, an optical means having a reference plane wherein a test plane to be measured is placed opposite to the reference plane and the optical means introduces the radiation beam onto both the reference plane and the test plane to produce an interference fringe, a parallel plate member in the radiation beam path between the objective lens and the optical member, and the parallel plate member is capable of changing its inclination by a predetermined angle against the radiation beam path. The incidence of the light beam on the reference plane is changed by shifting the radiation beam slightly so that the test plane can be measured whether or not it is convex or concave.
A unit for use with an interferometer for measuring the planeness of thin, stiff disks and has asuction means for maintaining the disks in flat abutment with an equalizer plate which is adjustable by means of micrometer spindles to move an opposite side of the disk into flat abutment with a reference plate. The equalizer plate, spindles and suction grid are supported on a base plate which is axially rotatable about a column for movement from underneath the reference plate to place the disks on the suction grid. A clamping means is provided around the column to hold the assembly in a fixed, rigid position.
An interferometer (10) includes a prism extender (50) appended to a prism (32) for directing a beam of light (42) into a recess (44) of a test piece (34). A first portion (42a) of the beam (42) refracts from a reference surface (54) of the prism extender (50) to an angle (.alpha.) of grazing incidence on a bottom surface (46) of the recess (44), and a second portion (42b) of the beam (42) reflects from the reference surface (54). The two portions (42 aand 42b) of the beam (42) recombine at the reference surface (54) forming an interference pattern indicative of differences between the reference surface (54) and the bottom surface (46) of the recess (44).
