A new method, using a novel double-ended interferometer, is described for the highly efficient calibration of gauge blocks. Unlike the conventional Kösters interferometric method, the new method does not require wringing of the gauge block onto an auxiliary platen. Although the gauge block length defined by International Standard 3650 (Gauge blocks) can be obtained using the Kösters method, the wringing operation is a laborious process, which requires skill, sometimes causes contact errors and decreases measuring efficiency, and prevents a fully automated measuring operation. The new interferometer can also be used as a conventional Kösters interferometer by changing some of the optical systems. Thus, after preliminary investigations measuring some samples using the Kösters method, we can determine an accurate correction value, dependent on the phase shift of light at the reflecting surface, to obtain the gauge block length defined by ISO 3650. The results, obtained from experimental work and theoretical analysis, show that the combined standard uncertainty of a gauge block length up to 100 mm is less than 16 nm, and this value is nearly the same as that obtained by the conventional Kösters method.
A description is given of an automaic recording laser interferometer for calibrating line standards up to 2 m based on Eppenstein's principle, and various factors which limit the measuring accuracies are also investigated in detail. This fringe-counting interferometer uses two corner cube reflectors. One reflector is mounted with the objective of a photoelectric miscroscope on a carriage which moves at a uniform speed of 10 to 300 mm/min on an air track. An electric pulse, which corresponds to the center of a graduation line and is a gate signal for counting interference fringes, is produced by the zero crossing method from the derivative of a signal obtained when the graduation line image goes across a slit. The reflectors generate two different interference fringes in phase quadrature by using their polarization properties in reflection, so that fringe resolving power is raised to h/16.The experimental results on line standards show that the standard deviation of a graduation line positioning is 0.04 ym and the accuracy of measurement on a 1 m line-interval is 0.08 ym in standard deviation.
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