| 摘要 |
PROBLEM TO BE SOLVED: To precisely measure a displacement varied over a range wider than a wavelength, with sufficiently fine resolution, compared with the wavelength. SOLUTION: This instrument/method comprises a transmission element 31 for inputting signals output from oscillation means 11, 12 to transmit ultrasonic waves, a receiving element 41 for receiving the ultrasonic wave to output signals, a phase shifting means 61 for generating signals shifted by levels different each other based on the signals output from the oscillation means, a phase difference computing means 81 for computing phase differences between the signals output from the oscillation means and the signals output from the receiving element, based on the phase differences between the plurality of phase-shifted signals and the output signals from the receiving element, and a displacement computing means 101 for computing the displacement of an object, based on the phase differences between the signals output from the oscillation means and the signals output from the receiving element as to the respective first and second signals, based on respective frequencies of the first and second signals, and based on a sonic velocity between the transmission element and the receiving element. COPYRIGHT: (C)2004,JPO&NCIPI
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