Patent ID: 7864332
Filing Date: 2011-01-04
Classification: G01B

Abstract:
1. A differential-phase interferometric system for measuring a specimen, comprising: a polarized heterodyne interferometer for generating a reference beam that travels along a reference channel and that includes two mutually orthogonal first and second linear polarized waves, and a signal beam that travels along a signal channel and that includes two mutually orthogonal first and second linear polarized waves, the reference and signal beams having a beat frequency therebetween, the signal beam being directed to the specimen and containing measured information of the specimen, said polarized heterodyne interferometer further generating a first optical heterodyne electrical signal output corresponding to the first linear polarized waves of the reference and signal beams, and a second optical heterodyne electrical signal output corresponding to the second linear polarized waves of the reference and signal beams; a differential amplifier receiving the first and second optical heterodyne electrical signal outputs from said polarized heterodyne interferometer, and generating a differential signal output therefrom; a data acquisition unit receiving the first and second optical heterodyne electrical signal outputs from said polarized heterodyne interferometer and the differential signal output from said differential amplifier, and measuring amplitudes of the first and second optical heterodyne electrical signal outputs and the differential signal output; and a computing unit for computing the amplitudes measured by said data acquisition unit to determine at least one parameter corresponding to the measured information of the specimen.