HETERODYNE SPECTRALLY CONTROLLED INTERFEROMETRY

摘要

Heterodyne interferometry is combined with spectrally-controlled interferometry (SCI) to achieve the advantages of both. Phase shifts produced by SCI produce phase-shifted correlograms suitable for heterodyne interferometric analysis, thereby enabling interferometric measurements with conventional common-path apparatus free of coherence noise and scanning-related errors, and with the precision of conventional heterodyne interferometry. A spectrum-modulating light source suitable for the invention is obtained by combining a rotating spiral grating with a multi-slit grating placed in the front focal plane of a collimating lens that propagates the light toward a blazed diffraction grating. Another exemplary spectrum-modulating light source is obtained by combining a slit spectrometer with an acousto-optic modulator.

主权项

1. A method of producing heterodyne interferometric measurement signals for spectrally controlled interferometry with an interferometric apparatus having a predetermined optical path difference, comprising the following steps:
providing a light source having a temporal coherence such that interference-fringe signals are detected within a measurement space of the interferometric apparatus, said light source being capable of spectral modulation to produce a light beam with a varying spectral distribution; and modulating said light source to introduce a time-varying phase shift in said spectral distribution.