Some errors in calibrating polyhedral prisms

Conclusions

• 1. The results of the calibrations can be influenced by the systematic error in the “scale factor,” which is due not only to the calibration error of the readout device of the autocollimators, but also by the extent to which identical conditions are observed in the measurements. In addition, one of the parameters of a polyhedral prism, viz. the deviations of the angles between working faces from the nominal value, also exert an indirect effect on the correctness of the calibration results.

• 2. In view of the possibility of a progressive change in the “constant” angle between the line-up axes of the autocollimators, it is appropriate to select a modified method of measurements, by rotating the polyhedral prism in one direction only, in the structuring of the physical standard arrangement. When the method outlined here is employed, the possibility of that happening is established on the basis of the d_i values obtained, and the systematic error can be duly determined and eliminated.

• 3. The systematic errors cited in the article are not the only ones encountered in the calibration of polyhedral prisms. In a joint resolution adopted by PKS SÉV in the field of angular measurements, the necessity of studying still other factors responsibility for errors in the measurements (effect of nonplanarity of the working surfaces accuracy in determining the plane of measurements, and so forth) is emphasized.