Measuring apparatus for measuring vibration or displacement and method for measuring vibration or displacement

Patent metadata

Field	Value
Publication number	US-10018501-B2
Application number	US-201715447681-A
Country	US
Kind code	B2
Filing date	Mar 2, 2017
Priority date	Mar 4, 2016
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

A measuring apparatus for contactlessly measuring vibration or displacement of a measurement target includes a light source configured to emit a continuous wave of light frequency-modulated to arrange a measurement site of the measurement target within a correlation peak, a divider configured to divide the continuous wave of light into first and second divided-waves of light, a light receiver configured to receive interfering light of the first divided-wave of light reflected by the measurement target and the second divided-wave of light, and a calculator configured to calculate the vibration or displacement of the measurement target using an electric signal output from the light receiver.

First claim

What is claimed is:

1. A measuring apparatus for contactlessly measuring vibration or displacement of a measurement target comprising:
a light source configured to emit a continuous wave of light frequency-modulated to arrange a measurement site of the measurement target within a correlation peak;
a divider configured to divide the continuous wave of light into first and second divided-waves of light;
a light receiver configured to receive interfering light of the first divided-wave of light reflected by the measurement target and the second divided-wave of light; and
a calculator configured to calculate the vibration or displacement of the measurement target using an electric signal output from the light receiver,
wherein
the light source has a modulation period set to arrange the measurement site of the measurement target within the correlation peak, and
the modulation period of the light source is set to an integral multiple of a value obtained by dividing a difference between a first length of a first optical path and a second length of a second optical path by a light speed or is set to a value close to the integral multiple, the first optical path leads the first divided-wave of light divided by the divider to the measurement target and leads the first divided-wave of light reflected by the measurement target to the light receiver, and the second optical path leads the second divided-wave of light divided by the divider to the light receiver.

2. The measuring apparatus according to claim 1 , wherein
the light source has a modulation amplitude set to arrange the measurement site of the measurement target within the correlation peak.

3. The measuring apparatus according to claim 2 , wherein
the modulation period and the modulation amplitude of the light source are set to arrange the measurement site of the measurement target at a former or a latter of the correlation peak.

4. The measuring apparatus according to claim 3 , wherein
the modulation amplitude of the light source is set in accordance with a size of the vibration or displacement of the measurement site of the measurement target.

5. The measuring apparatus according to claim 1 , further comprising:
an optical fiber configured to lead the first divided-wave of light divided by the divider to an irradiation position for emitting the first divided-wave of light to the measurement target.

6. The measuring apparatus according to claim 5 , further comprising:
a lens arranged between the irradiation position and the measurement target, the lens being configured to focus the first divided-wave of light emitted from the optical fiber on the measurement site of the measurement target.

7. The measuring apparatus according to claim 5 , further comprising:
a lens arranged between the irradiation position and the measurement target, the lens being configured to collimate the first divided-wave of light emitted from the optical fiber and to irradiate the measurement site of the measurement target with the collimated light.

8. The measuring apparatus according to claim 1 , further comprising:
a controller configured to control the light source while referring calculation results of the calculator.

9. The measuring apparatus according to claim 1 , wherein
the correlation peak appears when an optical path difference between the first divided-wave of light and the second divided-wave of light is equal to zero or a value obtained by dividing the optical path difference by a light speed is an integral multiple of the modulation period of the continuous wave of light.

10. A method for contactlessly measuring vibration or displacement of a measurement target comprising:
emitting a continuous wave of light frequency-modulated to arrange a measurement site of the measurement target within a correlation peak;
dividing the continuous wave of light into first and second divided-waves of light;
receiving interfering light of the first divided-wave of light reflected by the measurement target and the second divided-wave of light to generate an electric signal; and
calculating the vibration or displacement of the measurement target using the electric signal,
wherein
a modulation period is set to arrange the measurement site of the measurement target within the correlation peak, and
the modulation period is set to an integral multiple of a value obtained by dividing a difference between a first length of a first optical path and a second length of a second optical path by a light speed or is set to a value close to the integral multiple, the first optical path leads the first divided-wave of light to the measurement target and leads the first divided-wave of light reflected by the measurement target to a light receiving position, and the second optical path leads the second divided-wave of light to the light receiving position.

11. The method according to claim 10 , further comprising, before emitting the continuous wave of light:
irradiating a reflection mirror arranged at a reference position in an optical path of the first divided-wave of light and calculating a modulation frequency of the continuous wave of light to maximize the electric signal;
irradiating the measurement target with the first divided-wave of light under a condition in which the reflection mirror is removed from the reference position and measuring intensity of the electric signal while changing the modulation frequency of the continuous wave of light; and
determining the modulation frequency of the continuous wave of light to arrange the measurement site of the measurement target within the correlation peak.

12. The method according to claim 10 , wherein
a modulation amplitude is set to arrange the measurement site of the measurement target within the correlation peak.

13. The method according to claim 12 , wherein
the modulation period and the modulation amplitude are set to arrange the measurement site of the measurement target at a former or a latter of the correlation peak.

14. The method according to claim 13 , wherein
the modulation amplitude is set in accordance with a size of the vibration or displacement of the measurement site of the measurement target.

15. The method according to claim 10 , wherein
the first divided-wave of light is led to an irradiation position for emitting the first divided-wave of light to the measurement target by an optical fiber.

16. The method according to claim 15 , wherein
the first divided-wave of light emitted from the optical fiber is focused on the measurement site of the measurement target by a lens arranged between the irradiation position and the measurement target.

17. The method according to claim 15 , wherein
the first divided-wave of light emitted from the optical fiber is collimated by a lens arranged between the irradiation position and the measurement target and the measurement site of the measurement target is irradiated with the collimated light.

18. The method according to claim 10 , wherein
the correlation peak appears when an optical path difference between the first divided-wave of light and the second divided-wave of light is equal to zero or a value obtained by dividing the optical path difference by a light speed is an integral multiple of the modulation period of the continuous wave of light.

Assignees

• Yokogawa Electric Corp

Inventors

• Furukawa Osamu

Classifications

• G01B11/02 Primary

  for measuring length, width or thickness (G01B11/08 takes precedence) · CPC title

• G01D5/35306

  using an interferometer arrangement · CPC title

• G01H9/00 Primary

  Measuring mechanical vibrations or ultrasonic, sonic or infrasonic waves by using radiation-sensitive means, e.g. optical means · CPC title

• G01B9/02002 Primary

  using two or more frequencies · CPC title