| 摘要 |
892,233. Interferometers. GENERAL PRECISION Inc. May 23, 1958 [May 24, 1957], No. 16754/58. Class 97(1). An interferometer comprises a source of electromagnetic radiation, such as light, a beam splitter for dividing a beam from said source into two parallel beams which are incident upon a reflecting body having at least two mutually perpendicular reflective surfaces, so that each beam is reflected from the reflecting body by said surfaces substantially along the path of incidence of the other beam, and means for recombining the two reflected beams to produce an interference pattern. This interferometer may be employed to measure the angle error in such a reflecting body, for example, a cube corner prism, or if the reflecting body has no angle error, or an angle error which is compensated, to determine the angle error as of a wedge prism. As shown, in Fig. 3, a collimated light beam 32 is incident on a transmitting surface 33A of a beam splitter 33, is partially reflected at surface 33B, and then wholly reflected at surface 33C and transmitted at surface 33D, so as to form a beam 35 which is parallel to the beam 36 transmitted by the surface 33B. These beams 35, 36 are successively reflected by the three surfaces of a cube corner prism 34, and are then recombined in a single beam 39, so that the eye 38 in the focal plane of a collimating lens 37 will view an interference pattern representative of the angle error in the cube corner prism 34. Observation of the fringe pattern is carried out for three different orientations of the prism 34 by performing two 60 degrees angular shifts of the prism in the plane of its transmitting face. Alternatively, a camera may be disposed so as to record the various fringe patterns. To provide a numerical indication of the angle error in the prism, a variable wedge angle device, such as a Risley prism, may be disposed in the path of one of the beams 35 or 36. The wedges of this device may be rotated relatively or together, to eliminate the interference pattern caused by the angle errors in prism 34, scales associated with each wedge giving the required measure of the angle error. Instead of measuring the angle error of the cube corner prism 34, the apparatus may be used to calibrate a wedge prism disposed in the light path of one beam as shown at 81 in Fig. 7B. In this embodiment, the angle error of the cube corner prism 74 is nullified by a Risley prism 77, the beam splitter 73 provides two parallel beams, spaced from one another, and an optical element 77 is provided to shift beam 75 parallel to itself before arrival of both beams at the cube corner prism 74. By arranging for one of the beams incident on the reflecting body to pass through a gas, which varies in density across the path, a fringe pattern commensurate with the density variation may be obtained.
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