Counting device, physical quantity sensor, counting method, and physical quantity measuring method

摘要

A tension/speed measuring device comprises a laser driver for driving the oscillation of a semiconductor laser, and a counter for counting interference waveforms included in the output of a photodiode for converting the output of the semiconductor laser into an electrical signal. The counter measures the periods of interference waveforms during a measuring interval, where a frequency distribution for the periods of the interference waveforms during the measuring interval is generated from the measuring results, where a class value wherein the product of the class value and the frequency is a maximum is used as a representative value D0 at the periods of the interference waveform, to calculate a total Ns of the frequencies of the classes that are less than 0.5 times the representative value T0 and to calculate a total Nwn of the frequencies of the classes that are equal to or greater than (n+0.5) times the representative value T0 and less than (n+1.5) times the representative value T0, to correct the counting results based on these frequencies Ns and Nwn.

主权项

1. A counter system counting signals having a substantially single frequency when a physical quantity is constant, wherein the physical quantity has a linear relationship with the signals, the counter system comprising:
a counter counting the number of input signals during given counting intervals; a period measuring unit measuring signal periods of the input signals during the counting interval each time each input signal is inputted; a frequency distribution generator generating a frequency distribution of the signal periods during the counting interval, based on measurement results from the period measuring unit, wherein the frequency distribution represents a distribution of frequencies for each of class values, wherein a magnitude relation between the class values has a physical relation; a representative value calculator setting one of the class values as a representative value for the signal periods, based on the frequency distribution, wherein the representative value has a maximum value obtained by multiplying the class value by the frequency corresponding to the class value; and a corrected value calculator calculating, from the frequency distribution, a total number Ns and a total number Nwn so as to correct the number of the input signals counted by the counter, wherein Ns represents total of the frequencies of the class values that are less than 0.5 times the representative value, and Nwn represents total of the frequencies of class values that are equal to or greater than (n+0.5) and less than (n+1.5) times the representative value, wherein the corrected value calculator calculates the corrected number of the input signals N′ based on the following expression:N′=N-Ns+∑n=1nmax⁢(n×Nwn)nmax≦TmaxT⁢⁢0 wherein the number of the input signals counted by the counter is N, the representative value is T0, and a maximum value of the signal periods is TMax.