<title>Common-path multichannel heterodyne laser interferometer for subnanometer surface metrology</title>

Abstract

A multi-channel heterodyne laser interferometer is proposed for measurement of optical surface deformations at the sub- nanometer level. This interferometer employs a common-path configuration and heterodyne detection, by which fringe errors due to laser frequency fluctuations and optical path variations due to vibration can be reduced. By measuring the heterodyne signal phase among sub-apertures (pixels) with a 2- D detector array, the surface height can be reconstructed and surface deformation can be measured by comparing consecutive measurements. Detection of sub-nanometer level surface deformation is achieved using high precision digital phase meters and athermalized opto-mechanical systems. This paper describes the interferometer design criteria and experiment methodologies.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.