| 摘要 |
A phase difference measuring apparatus of the present invention obtains a first receive signal by transmitting and receiving a to-be-measured material in a reference state and a second receive signal by transmitting and receiving a signal wave to and from that material in a measured state. The apparatus finds a reference phase difference .THETA.1 from the transmit wave and first receive signal and an apparent phase difference .THETA.2' from the transmit wave and second receive signal. The apparatus adds the apparent phase difference .THETA.2' to a product of the number of rotations, n, the apparent phase difference .THETA.2' passes through a given reference point and an angle of 360.degree. to find a true phase difference .THETA.2. The apparatus varies the number of rotations, n, to n+1 when the apparent phase difference .THETA.2', while being increased, passes through the reference point and that number of rotations, n, to n=n-1 when the apparent phase difference .THETA.2', while being decreased, passes through the reference point.
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