JP2017194437A - Telemetry device and telemetering method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a telemetry device in which a measuring device head thereof has a compact and simple structure and which, even if an object is put in a place where large spatial restrictions exist, enables irregularities on a surface of the object to be measured.SOLUTION: A telemetry device of the present disclosure comprises: a sensor section (3-3) in which measurement light is emitted from an emission port and on which reflection light reflected by a surface of an object is incident through an incident port; an optical fiber (3-2) for propagating the measurement light and the reflection light; and an analysis unit (3-1) that measures irregularities on the surface of the object using a change in phase of interference fringes between the measurement light and the reflection light.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to a measurement apparatus that remotely measures unevenness of an object surface and a measurement method thereof.

  Measurement of unevenness of relatively small cm to μm on the surface of the object includes numerical control such as precision wear inspection and airtightness inspection of machine parts, and differences in product appearance and touch when touched directly. It is used for. As a specific measurement technique, measurement with a stylus, a microscope, a white interferometer, or the like is used (for example, see Non-Patent Document 1).

  However, these techniques measure by fixing the surface of the object to be measured to a certain part of the measuring instrument, and it is difficult to measure a surface that is so large that it cannot be moved or a surface that is not simple in shape. For this reason, it is conceivable to measure by cutting out and processing the position portion, but it is difficult to measure an object that cannot be directly processed, for example, a large structure such as an infrastructure.

  On the other hand, when such a large structure deteriorates, it is considered that distortion occurs and the surface shape changes. By continuously monitoring and detecting the small changes, it is possible to analyze the deterioration time of the structure and issue a warning before failure occurs. Various so-called sensor technologies for detecting the strain of such a structure have been researched and developed. For example, various optical fiber sensors such as Non-Patent Document 2 have been considered as optical fiber sensors that can flexibly cope with the shape of a structure and can perform sensing without energization. However, it is difficult to measure the unevenness of the surface of the structure with an accuracy of μm with the sensor technology for a large structure such as an infrastructure that has been devised at present.

  In the related art, in order to measure the surface of an object with an accuracy of μm, it is difficult to measure unless the object is cut and processed and fixed to a measuring instrument. In addition, it is difficult to accurately measure the surface of an object such as an infrastructure or the like that cannot be cut or processed, and there is a limit to the accuracy of deterioration analysis and failure prediction of the structure.

http: // www. keyence. co. jp / microscope / special / 3dprofiler / arasa / P. R. Hoffman, et al, “Position determination of an acoustic burst a sagnac interferometer,” Journal of Lightwave Technology, vol. 22, no. 2, February, 2004

  An object of the present disclosure is to measure surface irregularities with high accuracy without breaking even in a large structure.

The telemetry device of the present disclosure is
A sensor unit that emits measurement light from the exit port, and the reflected light reflected from the object surface enters from the entrance port;
An optical fiber that propagates the measurement light and the reflected light;
An analysis unit that measures unevenness of the object surface using a change in phase of interference fringes of the measurement light and the reflected light;
Is provided.

The telemetry method of the present disclosure is:
The measurement light propagated from the analysis unit through the optical fiber is emitted from the sensor unit toward the object surface, and the reflected light reflected by the object surface and incident on the sensor unit is transmitted to the analysis unit through the optical fiber. The procedure to propagate;
The analysis unit measures irregularities on the surface of the object using a change in phase of interference fringes of the measurement light and the reflected light, and
In order.

  According to the present disclosure, surface irregularities can be measured with high accuracy in a nondestructive manner even in a large structure.

An example of the structure of the telemetry apparatus which concerns on embodiment is shown. The example of application to the structure under test of another form of the telemetry device concerning an embodiment is shown. An example of the measurement principle is shown.

  Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In addition, this indication is not limited to embodiment shown below. These embodiments are merely examples, and the present disclosure can be implemented in various modifications and improvements based on the knowledge of those skilled in the art. In the present specification and drawings, the same reference numerals denote the same components.

  A configuration example of a telemetry device according to the present embodiment is shown in FIG. Here, 1-1 is an analysis unit that performs data analysis, 1-2 is an optical fiber that performs data transmission with the analysis unit 1-1, and 1-3 is a sensor unit that measures the surface of the object to be measured. The telemetry device according to the embodiment includes an analysis unit 1-1, an optical fiber 1-2, and a sensor unit 1-3.

  1-4 is an object to be measured. Although the shape of the measured object 1-4 is arbitrary, in FIG. 1, as an example of the measured object 1-4, a cylinder simulating a tunnel is shown. The sensor unit 1-3 that performs sensor measurement is installed at a plurality of locations of the measured object 1-4, and the analysis unit 1-1 and the sensor unit 1-3 are connected by the optical fiber 1-2. The analysis unit 1-1 analyzes the surface data such as the shape of each place or the change thereof measured in (1).

  FIG. 2 shows a case where the object to be measured 1-4 is shape-measured in a spatially restricted place such as a pipe-shaped product. Also in this case, by using the optical fiber 1-2, the sensor unit 1-3 can be inserted deep inside the object to be measured 1-4, and surface irregularities and the like can be measured flexibly. .

  Next, a specific unevenness measuring method is shown. FIG. 3 is a diagram showing the proposed unevenness measurement method. Reference numeral 3-1 denotes an analysis unit in this method. In order to measure unevenness with high resolution, it is preferable to use a coherent light reflectometer capable of spatially high resolution measurement for the analysis unit 3-1. As a specific type of the light reflectometer, any kind of device that detects the electric field amplitude (amplitude and phase) with respect to the distance of the reflected light may be used, but in this embodiment, measurement is performed using the frequency-swept measurement light. OFDR (Optical Frequency Domain Reflexometry), which is a measuring device that specifies the scattering position of the measurement light by associating the distance of the light with the frequency of the measurement light, is used. Since it is a coherent light reflectometer, a light source with high coherence is used. For this reason, the measurement light in the following description can be handled as thin light such as light rays. Reference numeral 3-3 connected through the optical fiber 3-2 denotes a sensor unit, 3-4 denotes an entrance lens, 3-5 denotes an exit lens, 3-6 denotes a diffraction grating, and 3-7 denotes an object to be measured 1-4. It is a sample to be measured corresponding to the surface.

  The measurement light incident through the optical fiber 3-2 enters the diffraction grating 3-6 through the incident part lens 3-4. In the diffraction grating 3-6, the incident light is separated for each optical frequency, and a near-field image is formed on the surface of the sample 3-7 to be measured through the exit lens 3-5. At this time, if the position on the surface of the sample 3-7 to be measured is expressed one-dimensionally on the x axis, the imaged near-field image is given a linear delay with respect to x. Let θ be the angle between the near-field image and the diffraction grating.

  If the spatial resolution of the coherent reflectometer is Δz = cΔτ (Δτ: temporal resolution, c: speed of light), the reflected light from the position of a specific delay τ is observed as a pulse having a spread of about Δτ, and its phase is 2π. × Optical frequency × τ delayed.

ただし、Ａ（ｔ）は、コヒーレント反射計で単一点からの反射を観測したときのパルス波形（電界振幅）であり、その広がりは約Δτである。ν_０は光源の光周波数である。 When the sample 3-7 to be measured is completely flat, the time delay of the beam reflected from the point x on the sample 3-7 to be measured is τ = ax (where a = tan θ / c). The reflected light is observed as a pulse as follows in a coherent reflectometer.

However, A (t) is a pulse waveform (electric field amplitude) when reflection from a single point is observed with a coherent reflectometer, and its spread is about Δτ. ν ₀ is the optical frequency of the light source.

As is clear from Equation (1), the phase of the electric field complex amplitude observed by C-OFDR changes in proportion to 2πν ₀ ax. If the shape of the sample changes and the local tilt changes by Δ (tan θ) = Δd / Δx, the phase there is given by the following equation, and the tilt of the sample surface is the phase of the interference fringes of the measurement signal: It appears as a change. If this is used, the unevenness | corrugation of the sample surface can be detected from the measured signal.

The measurement limit of the tilt angle will be described. The time resolution Δτ of C-OFDR is expressed by the following equation where the optical frequency width swept by OFDR is ΔF, which is simultaneously equal to the sampling time interval.

Therefore, when a phase change of 2π or more occurs during Δτ, an error of 2π × integer occurs in detection. For this reason, there are the following restrictions on the change in measurable inclination angle.

Since the resolution of C-OFDR is possible up to about ΔF to ₁₀ THz, if ν ₀ = 200 THz is expected, the following equation is obtained, which represents the limit of the tilt angle of the sample.

Further, the spatial resolution capability Δx _{res in} the x direction of this measurement is expressed by the following equation.

  The unevenness of the sample can be measured one-dimensionally by the above procedure. Further, at each time of changing the θ, by rotating the diffraction grating also about an axis perpendicular to the rotation axis of θ, measurement in the direction perpendicular to the x axis can be performed. It is also possible to measure two-dimensionally by measuring the rotation of.

  The coherence light reflectometer is not limited to OFDR, and any measurement method can be used as long as the location can be specified. The optical fiber 3-2 connecting the sensor unit 3-3 and the analysis unit 3-1 is not one-to-one, and a plurality of optical fibers 3-2 and the sensor unit 3-3 are connected to one analysis unit 3-1. Then, if the optical fiber 3-2 on which the measurement light is incident is selected by the switch, a large number of optical fibers can be connected in one measurement, and the entire surface of the object to be measured 1-4 can be efficiently covered. It can be measured by one analysis unit 3-1.

  Note that the present disclosure is not limited to the above-described embodiment as it is, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various disclosures can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiment examples may be appropriately combined.

(Effects of the present disclosure)
The telemetry method according to the present disclosure is considered to have the following advantages over the related art. Since the sensor unit and the analysis unit can be remotely installed using an optical fiber, it is possible to flexibly measure the surface roughness of a large object to be measured. It is also possible to measure the measurement accuracy of unevenness with a high resolution by using a reflectometer that uses coherent light, which is highly compatible with the transmission by this optical fiber. In addition, the sensor unit only needs to be directed to the object to be measured, and processing / cutting is not required, so that the surface irregularities can be made nondestructively and with high accuracy. As a result, detailed structural state measurement becomes possible, more accurate abnormality detection / preventive maintenance becomes possible, and it contributes to improving the efficiency and reliability of maintenance management for structures such as infrastructure.

  The present disclosure can be applied to the information communication industry.

1-1, 3-1: Analysis unit 1-2, 3-2: Optical fiber 1-3, 3-3: Sensor unit 1-4: Object to be measured 3-4: Incident unit lens 3-5: Emission unit Lens 3-6: Diffraction grating 3-7: Sample to be measured

Claims (3)

A sensor unit that emits measurement light from the exit port, and the reflected light reflected from the object surface enters from the entrance port;
An optical fiber that propagates the measurement light and the reflected light;
An analysis unit that measures unevenness of the object surface using a change in phase of interference fringes of the measurement light and the reflected light;
A telemetry device comprising: The sensor unit is
A diffraction grating for separating the measurement light into a plurality of incident lights having different optical frequencies;
An exit lens that forms an image of the incident light on the object surface so that the phase is shifted according to the unevenness of the object surface;
Comprising
The telemetry device according to claim 1. The measurement light propagated from the analysis unit through the optical fiber is emitted from the sensor unit toward the object surface, and the reflected light reflected by the object surface and incident on the sensor unit is transmitted to the analysis unit through the optical fiber. The procedure to propagate;
The analysis unit measures irregularities on the surface of the object using a change in phase of interference fringes of the measurement light and the reflected light, and
A telemetry method comprising:

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