  We present an application of a quadrature phase interferometer to the
measurement of the angular position of a parallel laser beam with
interferometric precision. In our experimental realization we reach a
resolution of 6.8e-10 rad (1.4e-4 arcsec) for 1 kHz bandwidth in a 2e-2 rad (1
deg) 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.
