| 摘要 |
PROBLEM TO BE SOLVED: To enable generation of various frequencies with high accuracy with a simple means by deriving a pair of frequencies with tightly adjacent frequencies from a frequency oscillator. SOLUTION: As a reference signal 16', an optical switch 22 transmits a transmission signal 16 reflected at an object 18. A frequency divider 28 performs frequency division on a frequency f0 , generated by a quartz oscillator 52 into frequencies f10 to f30 to become amplifying signals of frequencies f1 -f3 via a filter 30 and an amplifier 32. In addition, a switched frequency divider 34 performs frequency division on the frequency f0 into frequencies f'10 to f'30 to become the amplifying signals of frequencies f'1 -f'3 via a filter 36 and an amplifier 38, and an optical transmitter 12 receives the input of the signals f'1 -f'3 for modulating the transmission signal 16. Then sequentially continuous electrical signals are impressed on an optical receiver 14 and converts them into an evaluation signal 42, including each of the phase angles of an object signal 20 and the reference signal 16' by mixing. By forming two phase angle differences for each measured frequency, reference amount falls out, a phase angle is obtained for each measured frequency pair f'1 -f1 to f'3 -f3 , and a pair from among them having the minimum frequency in the univocal region of distance measurement is determined.
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