On the Calibration of Angle Comparators (Autocollimators)

Angle measurements are one of the main branches of production metrology. It includes measurements of angles in absolute values or deviations from specified reference angles. The angle comparators play important roles in the determination of small angles with high accuracy. Autocollimators are angle comparator type that can measure small angles with accuracy up to 0.05 arcs or better. Calibration of autocollimator becomes necessary demand not only for measurement of errors but also to ensure the traceability for other standards calibrated by them i.e. rotary tables, index tables, and angle blocks. In this paper, a proposed method based on laser interferometers is used for the calibration of a 0.05/±1000 arcs autocollimator system. The calibration is carried out for the axes X and Y of the autocollimator successively since the laser interferometer can calibrate one axis each time. The obtained results are analyzed and compared with tolerances according to predetermined tolerances and relevant standards