| 摘要 |
PURPOSE: To measure a wide ranging wave field in a short time by determining and recording the amplitude of a measuring signal in a phase sensing manner in relation to a reference signal by using a pulse-like laser beam with a pulse repetition frequency smaller than the frequency of an elastic wave. CONSTITUTION: An interdigital converter of a surface wave device PR is driven by a signal generator SG through an intermediate circuit of an amplifier V1. An AC voltage with a frequency fOFW applied to an electrode of the converter causes a cyclic deformation of a crystal surface by an piezo-electric effect. A detection of the surface deformation is performed utilizing a pulse-like laser beam LA which is generated within a light pulse generator PLA and deflected by a mirror S to be focused on the device PR through a lens system OL. The pulse repetition frequency fLA of a laser source PLA is made smaller than the frequency fOFW to generate a reference signal REF with a frequency FR =|fOFW-nfLA|(n: natural number), which is introduced to a phase sensitive detector PDT. The detector PDT outputs a signal AS proportional to deflection on the crystal surface.
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