| 摘要 |
PURPOSE: To reduce linear errors of measurement by generating two measuring signals presenting mutually right-angled optical components of outputs of a heterodyne interferometer and detecting a phase difference between these measur ing signals. CONSTITUTION: A receiver RU is connected to an output terminal of an interferometer unit, this receiver RU divides a presenting light into two right-angled optical components, and these components are fed to photoelectric measurement converters Dm1, Dm2 so as to generate two measuring signals Im1, Im2. Output signals of these converters Dm1, Dm2 are inputted into phase comparators PH1, PH2, two phase difference signalsΔϕ1m,Δϕ2 are found by separately comparing them with applied reference signal Ir, and these are inputted into a mean value generating circuit MV so that respective mean values are calculated. The phase difference signals, or outputs of the heterodyne interferometer, is compensated by using averaged respective phase difference signalsΔϕ1,Δϕ2 so as to reduce linear errors.
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