DETECTOR APPARATUS FOR DETECING COHERENT MONOHROMATIC POINT-SOURCE RADIATION

摘要

Detector apparatus includes a dispersive prism (10) and a diffraction grating (11) of the type which produces only zero and first order diffraction patterns. Located behind the diffraction grating (11) so as to interact with the first harmonic content of the diffraction patterns is a Moire grating (12) having half the pitch of the diffraction grating (11). Detector means including at least two pairs of detectors (13-16) is located behind the Moire grating (12) to detect the presence of Moire fringes.