By adjusting a Kösters prism interferometer so that the zero-order fringe is parallel to the beam splitter and to the apex, and is as far from the apex as possible, a parallel-beam Michelson-type interferometer was produced which is capable of pointing with a precision of 0.02 sec of arc. The sensitivity is proportional directly to the beam spacing and inversely to the wavelength. With beam separation of approximately 56 mm and green Hg light, each fringe passage represents 1 sec of arc mirror rotation. Angles of over 2000 sec can easily be measured. Described are schemes for using the instrument for measurement of film thickness, plane mirror rotation, divided circle accuracy by use of a stepping mirror, refractive index and difference, ball-bearing sphericity, absolute pressure, tilt, etc. Observation of fringes, which are located at the mirror surface, is conveniently accomplished by means of a standard alignment telescope, which may be attached to the interferometer or separated many meters from it. Use of mixed monochromatic and white light permits identification of the zero-order fringe in the presence of higher order fringes.
© 1964 Optical Society of AmericaFull Article | PDF Article
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