| 摘要 |
Consists of a linearly polarised laser frequency(fo) source(3) having a mirror(2) which is highly reflecting at a frequency near to the frequency(fo). It has a acousto-optic modulator(1) with an operational frequency(f) used a double passage, a Faraday polarising rotator(4), a polarising separator(5) and a photo-detector(6). The system also has means for equalising the luminous power of each of the interferometer channels by means of a half wave strip(3) or by rotating the laser along the axis of the beam. The polarisation rotation is realised by means of a quarter wave strip or an electro-optic rotator. The laser beam is split into two, one is directed onto the detector and the other reaches the detector after being retro-diffused on the sample(7) and reflected on the mirror(2). The two beams are heterodyned at a beat frequency equal to double the excitation frequency of the modulator(1). Analysis of the beam spectrum shows a consecutive phase modulation of the vibration of the sample.
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