COUNTER, PHYSICAL QUANTITY SENSOR, COUNTING METHOD, AND PHYSICAL QUANTITY MEASURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a counter capable of correcting counting errors even when noise of a high frequency continuously generates on signals input to the counter. SOLUTION: A vibration frequency measuring device has: a laser driver 4 for oscillating a semiconductor laser 1; the counter 7 for counting interference waveform included in output of a photodiode 2 for converting the output of the semiconductor laser 1 into electric signals; and an arithmetic device 8 for obtaining a physical quantity of an object 10 from the counted result of the counter 7. The counter 7 includes: counting the number of a half cycle of the interference waveform in a fixed counting period; measuring the half cycle of the interference waveform; preparing frequency distribution of the half cycle of the interference waveform during a counting period from the measured result; calculating representative values of distribution of the half cycle of the interference waveform from the frequency distribution; obtaining a total Ns of the number of the half cycle being less than 0.5 times of the representative values and a total Nwnof the number of the half cycle being 2n times or more and less than (2n+2) times of the representative values; and correcting the counted result on the basis of their frequencies Ns and Nwn. COPYRIGHT: (C)2011,JPO&INPIT