Velocity deviation measuring device and method

Patent metadata

Field	Value
Publication number	US-9952245-B2
Application number	US-201514790742-A
Country	US
Kind code	B2
Filing date	Jul 2, 2015
Priority date	Jul 3, 2014
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A velocity deviation measuring device includes: a laser driver that causes a semiconductor laser to oscillate; a counting portion that counts run lengths of binary signals wherein interference waveforms included in the output of a photodiode that converts the output of the semiconductor laser into an electric signal have been binarized; and a calculating portion that calculates the deviation in the surface velocity of a web from the counting result by the counting portion. The counting portion binarizes the interference waveform synchronized to a sampling clock, measures the respective run lengths of the binary signal during a reference interval and a comparison interval, creates respective frequency distributions of the run lengths for the reference interval and the comparison interval, and calculates, respectively, for the reference interval and the comparison interval, the total numbers of run lengths that are at or above a threshold value Th, from the frequency distribution.

First claim

The invention claimed is:

1. A velocity deviation measuring device, comprising:
a semiconductor laser that emits a laser beam toward an object to be measured;
an oscillating wavelength modulator that causes the semiconductor laser to operate so as to alternatingly be in a first oscillating interval in which an oscillating wavelength continuously increases monotonically and a second oscillating interval in which the oscillating wavelength continuously decreases monotonically;
a detector that detects an electric signal that includes an interference waveform that is produced through a self-coupling effect between the laser beam that is emitted from the semiconductor laser and return light from the object;
a binarizing portion that binarizes, synchronized with a sampling clock, the interference waveform that is included in an output signal from the detector;
a run length measuring portion that measures a run length of a binary signal when there is a change in the binary signal that is outputted from the binarizing portion in a reference interval and in a comparison interval;
a frequency distribution generating portion that generates respective frequency distributions of run lengths in the reference interval and in the comparison interval from measurement results of the run length measuring portion;
a counting portion that calculates respective total numbers of run lengths at or above a threshold value Th for the reference interval and the comparison interval from the frequency distribution generated by the frequency distribution generating portion; and
a calculating portion that calculates a deviation in a surface velocity of the object in the comparison interval, relative to a surface velocity of the object in the reference interval, from respective counting results by the counting portion in the reference interval and the comparison interval.

2. The velocity deviation measuring device as set forth in claim 1 , wherein:
the threshold value Th is a value that is set in advance.

3. The velocity deviation measuring device as set forth in claim 1 , further comprising:
a probability calculating portion that calculates a probability p that an output of the binarizing portion will change, from the measurement results of the run length measuring portion in the reference interval;
a noise frequency distribution calculating portion that calculates a frequency distribution of noise from the measurement results of the run length measuring portion during the reference interval and the probability p; and
a threshold value setting portion that sets, as the threshold value Th, a bin value in wherein a total frequency for noise of bins of value in and above will be a prescribed value, from a calculation result of the noise frequency distribution calculating portion in the reference interval.

4. The velocity deviation measuring device as set forth in claim 1 , further comprising:
a representative value calculating portion that calculates a representative value T 0 for the distribution of the run lengths, from the frequency distribution generated by the frequency distribution generating portion in the reference interval; and
a threshold value setting portion that calculates a reference deviation σ for a case wherein the distribution of run lengths in a vicinity of the representative value T 0 is considered to be a normal distribution, from a measurement result of the run length measuring portion in the reference interval, and sets the threshold value Th based on the reference deviation σ and the representative value T 0 .

5. A velocity deviation measuring method, comprising:
an oscillating step of causing a semiconductor laser that emits a laser beam toward an object that is subject to measurement to operate so as to alternatingly be in a first emitting interval in which an oscillating wavelength continuously increases monotonically and a second emitting interval in which the oscillating wavelength continuously decreases monotonically;
a detecting step of detecting an electric signal that includes an interference waveform that is produced through a self-coupling effect between the laser beam that is emitted from the semiconductor laser and return light from the object;
a binarizing step of binarizing, synchronized with a sampling clock, the interference waveform that is included in an output signal obtained in the detecting step;
a run length measuring step of measuring the binarized run length of a sign when there is a change in a binary signal that is outputted in the binarizing step for a reference interval and a comparison interval respectively;
a frequency distribution generating step of generating respective frequency distributions of run lengths in the reference interval and in the comparison interval from measurement results of the run length measuring step;
a counting step of calculating respective total numbers of run lengths at or above a threshold value Th for the reference interval and the comparison interval from the frequency distribution generated in the frequency distribution generating step; and
a calculating step of calculating a deviation in a surface velocity of the object in the comparison interval, relative to a surface velocity of the object in the reference interval, from respective counting results in the counting step in the reference interval and the comparison interval.

6. The velocity deviation measuring method as set forth in claim 5 , wherein:
the threshold value Th is a value that is set in advance.

7. The velocity deviation measuring method as set forth in claim 5 , further comprising:
a probability calculating step of calculating a probability p that an output of the binarizing step will change, from the measurement results of the run length measuring step in the reference interval;
a noise frequency distribution calculating step of calculating a frequency distribution of noise from the measurement results of the run length measuring step during the reference interval and the probability p; and
a threshold value setting step of setting, as the threshold value Th, a bin value m wherein a total frequency for noise of bins of value m and above will be a prescribed value, from a calculation result of the noise frequency distribution calculating step in the reference interval.

8. The velocity deviation measuring method as set forth in claim 5 , further comprising:
a representative value calculating step of calculating a representative value T 0 for the distribution of the run lengths, from the frequency distribution generated by the frequency distribution generating step in the reference interval; and
a threshold value setting step of calculating a reference deviation σ for a case wherein the distribution of run lengths in a vicinity of the representative value T 0 is considered to be a normal distribution, from a measurement result of the nm length measuring step in the reference interval, and setting the threshold value Th based on the reference deviation σ and the representative value T 0 .

Assignees

• Azbil Corp

Inventors

• Ueno Tatsuya

Classifications

• G01P3/50

  for measuring linear speed (G01P3/56 takes precedence) · CPC title

• G01S7/4916

  using self-mixing in the laser cavity · CPC title

• G01S17/58

  Velocity or trajectory determination systems; Sense-of-movement determination systems · CPC title

• G01P3/36 Primary

  Devices characterised by the use of optical means, e.g. using infrared, visible, or ultraviolet light (G01P3/68 takes precedence; gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams G01C19/64) · CPC title

• G01S17/34 Primary

  using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal · CPC title