Angle metrology of dispersion prisms

We present a new technique for calibrating the apex angles of dispersion prisms, which are used in the measurement of the index of refraction of optical glasses. The new method requires only a phase measuring interferometer, together with an electronic autocollimator, and eliminates the need for a rotary or indexing table. The apex angles of a nominally equilateral prism of fused silica were measured and the results compare favorably with a traditional calibration using an indexing table comparator.