| 摘要 |
PURPOSE:To improve the resolution of a measured amount of displacement by a method wherein two lights having different frequencies are divided to form two signal lights and two reference lights, the two signal lights subjected to Doppler shift are made to interfere with the two reference lights, two reference lights thus obtained are transduced into electric pulses, and a difference in the number of the pulses is integrated. CONSTITUTION:A first light L1 enters a half mirror 40 and divided thereby into a first signal light S1 and a first reference light R1, and a second light L2 having a different frequency is divided likewise into a second signal light S2 and a second reference light R2. Then, the signal light S1 is reflected to be subjected to Doppler shift by a movable mirror 18 which is in the course of movement together with a sample to be measured and turns to be a reflected light S1'. It is transmitted through a half mirror 42 and interferes with the reference light R2 reflected by the mirror 42, and thus a first interference light l1 is obtained. The signal light S2 is reflected likewise by the mirror 18 to be a reflected light S2'. This light interferes with the reference light R1 and thus a second interference light l2 is obtained. Frequencies of the interference lights l1 and l2 are transduced into electric pulses, a difference between them is integrated, and thereby an amount of displacement can be calculated with a resolution of about 1/2 of a usual one.
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