HETERODYNE INTERFERENCE MEASUREMENT METHOD, HETERODYNE INTERFERENCE DEVICE, THICKNESS MEASURING DEVICE, AND THICKNESS MEASUREMENT METHOD

摘要

PROBLEM TO BE SOLVED: To measure a phase difference precisely by removing an error caused by state variations in the propagation path of measurement light and an error caused by the crosstalk of measurement light, when measuring the phase difference between object light and reference light by a heterodyne interference method.;SOLUTION: Measurement light P1, P2 is allowed to interfere each other by an interferometer Q1 for detecting a beat signal Sg1 in the interference light, is guided closer to a measurement part 1a from the interferometer Q1 by an optical fiber 20, is allowed to interfere each other by an interferometer Q2 for detecting a beat signal Sg2 in the interference light, and is allowed to interfere each other as object light and reference light in the later stage for detecting a beat signal Sg3 in the interference light. Based on a phase difference Δθ₁ of the beat signals Sg1, Sg2 and a phase difference Δθ₂ in the beat signals Sg1, Sg2, the phase difference between the object light and the reference light where crosstalk noise components have been removed is calculated.;COPYRIGHT: (C)2009,JPO&INPIT