Single beam interferometric angle measurement

We present a new application of the Nomarski interferometer, to measure the angular position of a parallel laser beam with interfero-metric precision. In our experimental realization we reach a resolution of 3 × 10 −9 rad (6 × 10 −4 ′′) for 1 kHz bandwidth in a 2 × 10 −2 rad (1 •) range. This alternative to the optical lever technique features absolute calibration, independence of the sensitivity on the thermal drifts, and wide range of measurement at full accuracy.