| 摘要 |
PROBLEM TO BE SOLVED: To enable the stable correction in real time of the measurement errors of an object to be measured associated with refractive index fluctuations regardless of the amount of displacement of the object to be measured by providing the first and second detectors, the first to third processing systems, and an operational system which obtains the real amount of displacement on the basis of a specific equation. SOLUTION: This device is provided with the first and second detecting systems and an operational system which obtains the real amount of displacementΔD(tr) on the basis of the outputΔX(td)+β} from the first processing system, the outputΔD(f3, tr) from the second processing system, the outputΔM(td)+α} from the third processing system, and an equation. Assuming that the compositional proportion of mediums through which light propagates is constant and letting a function only dependent on the frequency f of light be K(f) an equation is expressed asΔD(tr)=ΔD(f3, tr)×[1-AΔX(td)+β}/ΔM (td)+α}] [here, A=K(f3)/ K(f2)-K(f1)}, N: concentration of mediums,αandβ: constants, K(f): letting this be a given function only dependent on the frequency of light,β=α.N.K(f3) [A 1+N.K(f3)}]).
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