JP6311923B2 - Temperature measuring apparatus and temperature measuring method - Google Patents

Description

  The present invention relates to a technique for measuring the temperature of an object to be measured, and more particularly to temperature measurement using an optical fiber cable.

  Conventionally, a method of measuring the temperature of an object to be measured using an optical fiber cable has been considered. For example, Patent Document 1 describes a technique for measuring the temperature of an object to be measured by applying Rayleigh scattered light that is return light in an optical fiber cable. Patent Document 2 describes a technique for measuring the temperature of an object to be measured using an optical fiber cable having a diffraction grating in which a high refractive index portion and a low refractive index portion are periodically formed in a core portion. ing.

  Furthermore, in recent years, a technique has been considered in which an optical comb, which is light composed of frequency components with equal frequency in the frequency domain, is used for measurement. For example, Patent Document 3 describes a technique for measuring a distance using an optical comb.

JP 2009-042005 A JP2012-088155A JP 2013-178169 A

  However, in the technique described in Patent Document 1 described above, it is necessary to provide a means for accumulating Rayleigh scattered light data in the temperature measurement device. In the technique described in Patent Document 2, an optical fiber cable having a diffraction grating in which a high refractive index portion and a low refractive index portion are periodically formed in a core portion must be used. Further, the techniques described in Patent Documents 1 and 2 are not considered to apply the technique related to the optical comb described in Patent Document 3.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a temperature measurement device and a temperature measurement method that can accurately measure the temperature of an object to be measured using an optical comb.

  A temperature measuring device according to one aspect of the present invention is a temperature measuring device that measures the temperature of an object to be measured, and emits an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals. A comb light source, a light splitting unit that splits light emitted from the optical frequency comb light source into reference light and measurement light, and an optical fiber cable for sensors that passes the measurement light split by the light splitting unit, The sensor unit has a sensor optical fiber cable that is expanded and contracted by change and is arranged so as to come into contact with the measurement object, the reference light divided by the light dividing unit, and the sensor optical fiber cable of the sensor unit. The light detection unit that detects an optical interference signal with the measurement light, the sensor length acquisition unit that acquires the length of the optical fiber cable for the sensor that has been expanded and contracted based on the detection result of the light detection unit, and the sensor length acquisition unit Extension It was based on the length of the optical fiber cable sensor, and a temperature calculation section for calculating a temperature of the measurement object.

  According to this aspect, the temperature of the object to be measured is measured by measuring the length of the optical fiber cable for sensor, which is emitted from the optical frequency comb light source (optical comb). Thereby, this aspect can measure the length of the optical fiber cable for sensors correctly with the light wave of the several frequency contained in an optical comb, and can perform accurate temperature measurement.

  Preferably, the sensor unit has a plurality of sensor optical fiber cables having different lengths, and each of the plurality of sensor optical fiber cables is connected to the optical switch, and is connected to the sensor optical fiber cable selected by the optical switch. Measurement light passes.

  According to this aspect, the sensor unit has a plurality of sensor optical fiber cables having different lengths, and the optical fiber cable for sensors is selected according to the length of the measurement object by the optical switch. Thereby, this aspect can select the optical fiber cable for sensors according to the length of a measuring object, and can perform temperature measurement.

  Preferably, an etalon that multiplies the frequency interval of the optical comb by m (m is an arbitrary integer) is provided between the optical frequency comb light source and the optical splitter.

  According to this aspect, the frequency interval of the optical comb used for temperature measurement can be appropriately adjusted by the etalon. As a result, it is possible to measure at intervals of various frequencies, to subdivide the measurement pitch, and to achieve an effect that the temperature can be measured more accurately.

  Desirably, the measurement object is a solid or a liquid.

  Preferably, the temperature measuring device includes an optical path length adjustment unit that adjusts the length of the optical path of the reference light, and the optical path of the reference light is the optical fiber cable for the sensor acquired by the sensor length acquisition unit by the optical path length adjustment unit. It is adjusted based on the length.

  According to this aspect, the length of the optical path of the reference light can be adjusted using the optical comb in accordance with the length of the optical fiber cable for sensor. Thereby, this aspect can adjust the length of the optical path of reference light, and can perform more accurate temperature measurement.

  Desirably, a temperature calculation part calculates the average temperature of a measuring object.

  According to this aspect, the temperature calculation unit calculates the average temperature of the measurement object. Thereby, this aspect can obtain | require correctly the average temperature of the part by which the optical fiber cable for sensors was distribute | arranged.

  Desirably, the sensor optical fiber cable of the sensor unit is provided inside the measurement object.

  According to this aspect, since the sensor optical fiber cable contacts the measurement object with a larger surface area, the temperature of the measurement object can be measured with higher accuracy.

  Desirably, the optical fiber cable for sensor of the sensor unit is covered except for the part in contact with the measurement object.

  According to this aspect, since the sensor optical fiber cable other than the portion in contact with the measurement target is covered, the influence of the temperature other than the measurement target on the sensor optical fiber cable is reduced, and the measurement target The temperature can be measured with higher accuracy.

  A temperature measurement method according to another aspect of the present invention is a temperature measurement method for measuring the temperature of an object to be measured, and an optical comb that emits an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals. An output step; a light splitting step for splitting the light emitted in the optical comb exiting step into reference light and measurement light; and an optical fiber cable for a sensor through which the measurement light split in the light splitting step passes. A sensing step for sensing the temperature of the measurement object by a sensor optical fiber cable arranged to expand and contract by change and to be in contact with the measurement object, the reference light divided in the light dividing step, and the sensor optical fiber The optical detection step for detecting the optical interference signal with the measurement light via the cable, and the length of the optical fiber cable for the sensor that is expanded and contracted based on the detection result of the optical detection step. To include a sensor length acquisition step, based on the length of the telescopic the optical fiber cable sensor for acquiring the sensor length acquisition step, and the temperature calculating a temperature of the measurement object, the.

  According to the present invention, the optical fiber cable for sensor is brought into contact with the object to be measured, the length of the optical fiber cable for sensor expanded and contracted according to the temperature of the object to be measured is measured by the optical comb, and based on the measurement result. Since the temperature of the measurement object is measured, the accurate temperature of the measurement object can be measured.

It is the schematic which shows the structure of a temperature measuring apparatus. It is sectional drawing of an optical fiber cable. It is a conceptual diagram explaining the temperature distribution of a measurement object. It is a figure which shows the example of arrangement | positioning of the optical fiber cable for sensors. It is the flowchart which showed the flow of the temperature measurement of a temperature measuring device. It is the schematic which shows the structure of the modification of a temperature measuring device. It is an enlarged view of the optical switch and optical fiber cable for sensors. It is the schematic which shows the structure of the modification of a temperature measuring device. It is a figure explaining installation of an optical fiber cable. It is a conceptual diagram which shows the example of installation of the optical fiber cable for sensors. It is a conceptual diagram which shows the example of installation of the optical fiber cable for sensors. It is a conceptual diagram which shows the example of installation of the optical fiber cable for sensors.

  Embodiments of a temperature measuring device and a temperature measuring method according to the present invention will be described below with reference to the accompanying drawings.

<Configuration of temperature measuring device>
FIG. 1 is a schematic diagram showing the configuration of the temperature measuring apparatus 10. The temperature measurement apparatus 10 mainly includes an optical frequency comb light source 20, a splitter (light splitting unit) 22, a first optical path 23, a second optical path 24, a sensor unit 11, a mixer 25, a light detection unit 26, a sensor length acquisition unit 27, A temperature calculation unit 32, an optical fiber cable for optical path 28 (represented by a double line in the drawing) for connecting these parts, and a connector 29 for connecting the optical fiber cables for optical path 28 are provided. In FIG. 1, the temperature measuring apparatus 10 measures a solid measurement object 100. Note that the measurement object 100 is a solid and a liquid. When the measurement object 100 is solid, for example, the measurement object 100 is an upper plate. In addition, various sizes of the measurement object 100 can be adopted.

  The optical frequency comb light source 20 emits an optical comb (also referred to as an optical frequency comb) 31 used for temperature measurement. The optical comb 31 is light having frequency components in which frequencies are arranged at equal intervals in the frequency domain. As the optical frequency comb light source 20, for example, in a femtosecond mode-locked fiber laser, a laser oscillator having a configuration in which a ring resonator formed of an erbium-doped optical fiber (EDF) is driven by a laser diode can be used. The optical frequency comb light source 20 always emits the optical comb 31 at least during temperature measurement. The optical comb 31 emitted from the optical frequency comb light source 20 is input to the splitter 22 via the optical fiber cable 28 for optical path.

  The splitter 22 is connected to the first optical path 23 and the second optical path 24. The splitter 22 divides the input optical comb 31 into reference light 35 and measurement light 36, outputs the reference light 35 to the first optical path 23, and outputs the measurement light 36 to the second optical path 24. The splitter 22 divides the optical comb 31 so that the ratio of the reference light 35 and the measurement light 36 is, for example, 5:95.

  In the first optical path 23, a first collimator 38, an acousto-optic modulator (AOM) 34, a first prism reflector 39, a second prism reflector 40, a scanning stage 41, and a second collimator 42 are provided.

  The first collimator 38 emits the reference light 35 input from the splitter 22 as parallel light toward the acoustooptic modulator 34.

  The acoustooptic modulator 34 is disposed between the first collimator 38 and the first prism reflector 39. The acousto-optic modulator 34 can change the frequency of the input light (frequency shifter). In the case shown in FIG. 1, the acousto-optic modulator 34 appropriately changes the frequency of the reference light 35 input from the first collimator 38 and emits it to the first prism reflector 39. By appropriately changing the frequency of the reference light 35 by the acousto-optic modulator 34, a frequency difference is generated between the reference light 35a whose frequency is modulated and the measurement light 36a that has passed through the sensor optical fiber cable 30. By causing the interference, a beat signal 50a corresponding to the frequency difference is obtained.

  The first prism reflector 39 reflects the reference light 35a input from the acousto-optic modulator 34 toward the second prism reflector 40, and the reference light 35a incident from the second prism reflector 40 to the second collimator 42. Reflect toward you.

  The second prism reflector 40 is disposed on the optical path of the reference light 35 a reflected by the first prism reflector 39. The second prism reflector 40 reflects the reference light 35 a incident from the first prism reflector 39 toward the first prism reflector 39 again.

  The scanning stage 41 is attached to the second prism reflector 40. The scanning stage 41 reciprocates the second prism reflector 40 along a direction parallel to the optical path of the reference light 35 a reflected by the first prism reflector 39. For example, the scanning stage 41 reciprocates the second prism reflector 40 with a stroke of several mm to several cm. Thereby, the amplitude of the optical interference signal 50 between the reference light 35a and the measurement light 36a described later can be temporally varied. By integrating the measurement data of the optical interference signal 50 that varies with time, the accuracy of the measurement data can be increased. Instead of the scanning stage 41, for example, a PZT stage (voltage actuator) may be used.

  The second collimator 42 collects the reference light 35 a incident from the first prism reflector 39 and outputs it to the optical path optical fiber cable 28.

  The optical path length adjustment unit 37 is disposed between the second collimator 42 and the mixer 25 via the connector 29. The optical path length adjustment unit 37 adjusts the length of the first optical path 23. The optical path length adjustment unit 37 is composed of an optical fiber cable and adjusts the length of the first optical path 23.

  The sensor unit 11 is provided in the second optical path 24 via the connector 29. The measurement light 36 that has passed through the sensor unit 11 is emitted toward the mixer 25.

  The sensor unit 11 includes a sensor optical fiber cable 30 and senses the temperature of the measurement object 100 based on the length of the sensor optical fiber cable 30 that is expanded and contracted by the temperature. The sensor optical fiber cable 30 is connected to the optical path optical fiber cable 28 via a connector 29. The incident part 46 of the sensor optical fiber cable 30 is a part where the measurement light 36 enters the sensor optical fiber cable 30, and the emission part 48 of the sensor optical fiber cable 30 passes through the sensor optical fiber cable 30. This is where the measuring light 36 returns to the optical fiber cable 28 for optical path.

  FIG. 2 is a cross-sectional view of the optical fiber cable 28 for optical path and the optical fiber cable 30 for sensor. FIG. 2A shows a state in which the reference light 35 or the measurement light 36 travels inside the optical fiber cable 28 for optical path. The optical fiber cable 28 for an optical path has a core part 60, a clad part 62, and a covering part 64. FIG. 2B shows a state in which the measurement light 36 travels inside the sensor optical fiber cable 30. The sensor optical fiber cable 30 shown in FIG. 2B has a core part 60 and a clad part 62, and does not have a covering part 64. This is because the sensor optical fiber cable 30 senses the temperature of the measurement object 100 in contact with the sensor with high sensitivity.

  That is, since the sensor optical fiber cable 30 is in contact with the temperature measurement object 100 without using the covering portion 64, the temperature of the measurement object 100 can be sensed with high sensitivity. The sensor optical fiber cable 30 may have a covering portion 64 at a portion that does not come into contact with the measurement object 100. Moreover, generally manufactured optical fiber cables can be used for the optical fiber cable 28 for optical paths and the optical fiber cable 30 for sensors. For example, an optical fiber cable using a completely fluorinated polymer, polymethyl methacrylate, polycarbonate, or the like can be used as the material of the core portion 60. Further, for example, an optical fiber cable using a fluorine-based polymer having a low refractive index can be used as the material of the clad portion 62.

  FIG. 3 is a conceptual diagram illustrating the measurement object 100 having a temperature distribution. FIG. 3A shows that the measurement object 100 has patches (reference numerals 102 and 104) having different temperatures. The temperature of the patch 102 is higher than the area 106 and the temperature of the patch 104 is lower than the area 106. As shown in FIG. 3A, the temperature of the measurement object 100 (solid or liquid) is generally distributed as a coherent patch. FIG. 3B shows that the temperature of the measuring object 100 having the temperature distribution shown in FIG. 3A is measured by the temperature measuring device 10 of the present invention. By providing the sensor optical fiber cable 30 in contact with the measurement object 100 having a temperature distribution, the temperature of the measurement object 100 in consideration of the temperature distribution can be obtained. The temperature of the measuring object 100 required in this case is the representative temperature or the average temperature of the measuring object 100.

  Returning to FIG. 1, the measurement light 36 a via the sensor optical fiber cable 30 and the reference light 35 a whose frequency is modulated by the acousto-optic modulation unit 34 are input to the mixer 25.

  As the mixer 25, for example, an optical mixer is used. The mixer 25 optically multiplies, for example, optically the reference light 35a whose frequency is input from the first optical path 23 and the measurement light 36a which is input from the second optical path 24 and passes through the sensor optical fiber cable 30. Thus, an optical interference signal 50 between the reference light 35a whose frequency is modulated and the measurement light 36a that has passed through the sensor optical fiber cable 30 is generated. The intensity of the optical interference signal 50 varies (beats) according to the frequency difference between the reference light 35a and the measurement light 36a. A signal obtained from the optical interference signal 50 is referred to as a beat signal 50a.

  The light detection unit 26 receives the optical interference signal 50 output from the mixer 25, converts it into a beat signal 50a that is an electrical signal, and outputs the beat signal 50a to the sensor length acquisition unit 27 as a detection result.

  The sensor length acquisition unit 27 acquires the length of the sensor optical fiber cable 30 using a known pulse interference measurement technique based on the beat signal 50 a input from the light detection unit 26. The acquisition of the length of the sensor optical fiber cable 30 utilizes the fact that the length of expansion / contraction of the sensor optical fiber cable 30 is related to the difference between the first optical path 23 and the second optical path 24.

  For example, first, the sensor length acquisition unit 27 sets the reference point (zero point) without installing the sensor optical fiber cable 30. In the case shown in FIG. 1, the reference point is set by connecting the connectors 29 without installing the sensor optical fiber cable 30, and setting the lengths of the first optical path 23 and the second optical path 24 to the optical path length adjusting unit 37. By adjusting more equally. Thereafter, the sensor optical fiber cable 30 is installed in the temperature measurement device 10 via the connector 29, and the interference fringe pattern detection unit 52 detects the interference fringe pattern between the measurement light 36 a and the reference light 35 a. The sensor optical fiber cable 30 used in this case has a known length (reference length) at a specific temperature (reference temperature). That is, the sensor optical fiber cable 30 is previously measured for a length at a certain temperature, and has the temperature as a reference temperature and the length as a reference length.

  Further, the sensor length acquisition unit 27 can adjust the reference point even when the sensor optical fiber cable 30 is installed in the temperature measurement device 10. Specifically, the temperature measuring device 10 is placed in a specific temperature environment with the sensor optical fiber cable 30 installed, and is adjusted so that the lengths of the first optical path and the second optical path are equal. . Then, the point where the lengths of the first optical path and the second optical path at a specific temperature are equal is used as a reference. Thereafter, the sensor optical fiber cable 30 is installed on the measurement object 100 and expands and contracts under the influence of the temperature of the measurement object 100. The calibration of the reference point is not limited to the above method, and a known method can be adopted.

  In the interference fringe pattern detected by the interference fringe pattern detection unit 52, the phase of the measurement light 36a is shifted by the length of the sensor optical fiber cable 30 that is expanded and contracted by the temperature of the measurement object 100. And the sensor length acquisition part 27 acquires the length of the optical fiber cable 30 for sensors expanded and contracted with the temperature of the measuring object 100 by the shift | offset | difference of the phase of this measurement light 36a. Thereafter, the sensor length acquisition unit 27 compares the reference length of the sensor optical fiber cable 30 that is provided in advance with the length of the sensor optical fiber cable 30 acquired by the phase shift of the measurement light 36, The stretched length of the sensor optical fiber cable 30 is obtained.

  For example, a lock-in amplifier is used for the interference fringe pattern detection unit 52 in the sensor length acquisition unit 27. The lock-in amplifier detects an interference fringe pattern between the beat signal 50a input from the above-described light detection unit 26 and a reference signal separately input from the optical frequency comb light source 20 (not illustrated). The sensor length acquisition unit 27 can acquire the phase information of the measurement light 36a from the interference fringe pattern and obtain the length of the sensor optical fiber cable 30 that has been expanded or contracted.

  Here, the frequency of the reference signal input to the lock-in amplifier is set to a frequency corresponding to a frequency difference between adjacent frequency components in the frequency region of the reference light 35a and the measurement light 36a. Since the beat signal 50a is an electric signal having a signal level corresponding to the light intensity of the optical interference signal 50 obtained by superimposing the reference light 35a and the measurement light 36a, the beat signal 50a has the reference light 35a and the measurement light as a result. This is because the frequency component of 36a has a frequency component corresponding to the frequency difference between adjacent frequency components in the frequency domain. Therefore, the frequency of the reference signal is set to a frequency corresponding to the frequency difference between the frequency components close to each other in the frequency domain between the reference light 35a and the measurement light 36a, and the interference fringe pattern between the beat signal 50a and the reference signal interferes. If detected by the fringe pattern detection unit 52, the length of the sensor optical fiber cable 30 depending on the temperature of the measurement object 100 can be calculated from the interference fringe pattern. Refer to Japanese Patent Laid-Open No. 2013-178169 for details of setting the frequency of the reference signal.

The temperature calculation unit 32 calculates the temperature of the measurement object 100 from the length of the sensor optical fiber cable 30 obtained by the sensor length acquisition unit 27. Specifically, the temperature calculation unit 32 uses the stretched length of the sensor optical fiber cable 30, the thermal expansion coefficient of the sensor optical fiber cable 30, and the above-described reference temperature to determine the temperature of the measurement object 100. Is calculated. Further, when the sensor optical fiber cable 30 is arranged so as to be in contact in a certain region of the measurement object 100, the temperature calculation unit 32 calculates the average temperature of that region of the measurement object 100. be able to. That is, when the sensor optical fiber cable 30 is arranged so as to contact over a certain area of the measurement object 100, the sensor optical fiber cable 30 is connected to the measurement object 100 in the certain area. It expands and contracts under the influence of temperature. Therefore, in this case, the temperature obtained from the stretched length of the sensor optical fiber cable 30 can be the average temperature (representative temperature) of the arranged region. Here, the thermal expansion coefficient of the sensor optical fiber cable 30 varies depending on the material of the sensor optical fiber cable 30, but is, for example, 6 × 10 ⁻⁶ / ° C. Further, a linear expansion coefficient may be used instead of the thermal expansion coefficient.

  FIG. 4 is a diagram showing different arrangements of the sensor optical fiber cable 30 in the sensor unit 11. As shown in FIG. 4, the sensor optical fiber cable 30 may have a form in which several branch points 12 are connected and the measurement points 13 having respective lengths are connected to the branch points 12. In this case, the measurement light 36 enters the sensor optical fiber cable 30 from the connector 29. Thereafter, the measurement light 36 enters the measurement point 13 at the preset branch point 12, is reflected by the measurement point 13, and enters the optical path optical fiber cable 28 via the connector 29. The measurement light 36 is reflected at the measurement point 13 and becomes measurement light 36 a having length information of the sensor optical fiber cable 30 that is expanded and contracted by the temperature of the measurement object 100, and enters the optical path optical fiber cable 28. Incident. When the distance to be measured is determined in advance, the measurement light 36 is reflected from the desired measurement point 13 by setting the branch point 12. On the other hand, when the temperature measurement is performed using all the measurement points 13, the measurement light 36 a reflected at each measurement point 13 is caused by a time lag when the measurement light 36 a reflected at each measurement point 13 reaches a certain point. Can be specified.

  FIG. 5 is a flowchart for explaining the temperature measurement operation of the temperature measurement apparatus 10. First, the optical frequency comb light source 20 emits the optical comb 31 to the splitter 22 (step S10, optical comb emission step). Thereafter, the splitter 22 splits the optical comb 31 into the reference light 35 and the measurement light 36 (step S12, light splitting step). Then, the measurement light 36 passes through the sensor optical fiber cable 30 (step S14, sensing step). At this time, the sensor optical fiber cable 30 is disposed so as to be in contact with the measurement object 100, and expands and contracts depending on the temperature of the measurement object 100.

  Thereafter, the light detection unit 26 detects the beat signal 50a from the optical interference signal 50 between the reference light 35a and the measurement light 36a that has passed through the sensor optical fiber cable 30 (step S16, light detection step). And the sensor length acquisition part 27 takes out the phase information of the measurement light 36a using the interference fringe pattern detection part 52 from the beat signal 50a which the light detection part 26 detected. Thereafter, the sensor length acquisition unit 27 calculates the length of the sensor optical fiber cable 30 that has been expanded and contracted from the phase information of the measurement light 36a (step S18, sensor length acquisition step). Thereafter, the temperature calculation unit 32 calculates the temperature of the measurement object 100 based on the calculation result of the sensor length acquisition unit 27 (step S20, temperature calculation step).

  As described above, the temperature measuring apparatus 10 of the present invention measures the length of the sensor optical fiber cable 30 by the heterodyne interferometry using the optical comb 31 and obtains the temperature of the measuring object 100. . In general, it is difficult to detect an optical path difference greater than or equal to the wavelength by heterodyne interferometry, but the optical comb 31 includes light of various wavelengths as described above, so that the detection range of the optical path difference is widened.

  Moreover, since the temperature measuring device 10 of the present invention uses the optical comb 31 to measure the stretched length of the sensor optical fiber cable 30, it can measure the exact length. That is, when measurement of the stretched length of the sensor optical fiber cable 30 is performed using low-coherence light instead of the optical comb 31, the optical interference signal 50 cannot be obtained. The stretched length may not be measured. In addition, when the length of the optical fiber cable 30 for sensor is expanded and contracted by using light having a long coherence distance instead of the optical comb 31, there is noise of reflected light from the splitter 22 or the like. There are cases where it is not possible. Since the temperature measuring apparatus 10 of the present invention uses the optical comb 31 having the frequency components with the frequencies arranged at regular intervals in the frequency domain, the length of the optical fiber cable 30 for sensor is expanded and contracted. It is possible to measure the temperature accurately. The effect of the measurement performed using the optical comb 31 is the same in the above-described reference point setting. That is, since the temperature measuring apparatus 10 of the present invention performs measurement using the optical comb 31, the reference point (zero point) can be set with high accuracy.

  In addition, since the optical comb 31 is a light having a frequency component such that the frequencies are equally spaced, the present invention can acquire a plurality of beat signals 50a of the reference light 35a and the measurement light 36a, and more accurately. Temperature measurement can be performed.

[Modification 1]
Next, a modified example of the temperature measuring device 10 will be described. This example is characterized in that a plurality of sensor optical fiber cables 30 having different lengths are connected via an optical switch 45 in the sensor unit 11. In addition, in this example, the part which overlaps with the description mentioned above attaches | subjects the same code | symbol, and abbreviate | omits description.

  FIG. 6 shows the configuration of the temperature measuring apparatus 10 of this example. In the first optical path 23 of this example, an acousto-optic modulator 34 is disposed between the first prism reflector 39 and the second prism reflector 40.

  In the second optical path 24 of this example, a circulator 44 and a sensor unit 11 are provided. The circulator 44 outputs the measurement light 36 input from the splitter 22 toward the optical switch 45 of the sensor unit 11, and the measurement light 36 a that has passed through the sensor optical fiber cable 30 from the optical switch 45 to the mixer 25. Output toward.

  The sensor unit 11 mainly includes an optical switch 45 and a sensor optical fiber cable 30. Further, the optical switch 45 may be selected under the control of the switch control unit 49, and a beam for measuring the length (length measuring beam) may be emitted.

  FIG. 7 is an enlarged view of the optical switch 45 and the sensor optical fiber cable 30 of the sensor unit 11. The optical switch 45 is connected to a plurality of sensor optical fiber cables 30 (30a to 30e).

  The optical switch 45 switches the sensor optical fiber cables 30 (30a to 30e) connected to the optical path optical fiber cable 28 under the control of the switch control unit 49. Specifically, the optical switch 45 changes the optical path of the measurement light 36, thereby allowing the sensor optical fiber cables (30a to 30e) through which the measurement light 36 passes from among the plurality of sensor optical fiber cables (30a to 30e). Any).

  The optical switch 45 in FIGS. 6 and 7 has a length measurement beam emitting unit 72 that emits the measurement light 36 to a distance measurement target. This is because the temperature measuring device 10 described in FIGS. 6 and 7 includes the length measuring beam emitting section 72, and thus can measure the distance by the measuring light 36 (or 36a). Further, in the circuits having the configurations shown in FIGS. 6 and 7, the reference point can be adjusted by reflected light from the connection between the optical switch 45 and the sensor optical fiber cable 30. That is, at the connection portion between the optical switch 45 and the optical fiber cable for sensor 30, about 4% of the measurement light 36 becomes reflected light and is detected by the light detection unit 26, and the reference point (zero point) is detected by the reflected light. Can be set.

  As described above, in the temperature measurement device 10 of this example, a plurality of sensor optical fiber cables 30 are connected via the optical switch 45. Thereby, the temperature measuring apparatus 10 of this example can perform temperature measurement according to the length of the measuring object 100.

[Modification 2]
Next, Modification 2 of the temperature measuring device 10 will be described.

  FIG. 8 shows the configuration of the temperature measuring apparatus 10 of this example. The main features of the temperature measuring apparatus 10 of this example are that the optical frequency comb light source 20 emits the optical comb 31 to the etalon 66, the circulator 44 is disposed between the etalon 66 and the splitter 22, That is, the delay device unit 70 is disposed in the optical path 23. FIG. 8 illustrates an example in which the temperature of the block gauge 68 is measured as the measurement object 100.

  In the temperature measurement device 10 of this example, the optical comb 31 emitted from the optical frequency comb light source 20 enters the etalon 66. As the etalon 66, for example, a Fabry-Perot etalon is used. The etalon 66 multiplies the frequency interval of the optical comb 31 by m (m is an arbitrary integer). Thereby, the frequency interval of the optical comb 31 can be expanded as appropriate. For example, the frequency interval of the optical comb 31 emitted from the optical frequency comb light source 20 is generally 100 MHz and 250 MHz, but this frequency interval can be expanded to 15 GHz. Thereby, the temperature measuring device 10 has an effect that the frequency interval is appropriately adjusted according to the size of the measurement object 100 and the accuracy thereof, and the temperature can be accurately measured even for the large measurement object 100. .

  In this example, the circulator 44 is disposed between the etalon 66 and the splitter 22. The optical comb 31 emitted from the etalon 66 enters the splitter 22 via the circulator 44. On the other hand, the optical interference signal 50 emitted from the splitter 22 enters the light detection unit 26 via the circulator 44.

  The splitter 22 acquires the optical comb 31 that has passed through the circulator 44, and divides the optical comb 31 into reference light 35 and measurement light 36. The reference light 35 travels to the first optical path 23, and the measurement light 36 travels to the second optical path 24.

  The reference light 35 that has traveled to the first optical path 23 passes through the optical path length adjustment unit 37, and the frequency is modulated by the delay device unit 70. The delay device unit 70 is arranged in the first optical path 23 instead of the acousto-optic modulation unit 34, the first prism reflector 39, and the second prism reflector 40 described in FIG. For example, the delay device unit 70 is configured by a PZT stage (voltage actuator). The reference light 35 a whose frequency is modulated by the delay device unit 70 is returned to the splitter 22.

  The measurement light 36 that has traveled to the second optical path 24 enters the sensor optical fiber cable 30. The sensor optical fiber cable 30 is disposed in contact with the block gauge 68 and measures the temperature of the block gauge 68. The measurement light 36 a that has passed through the sensor optical fiber cable 30 returns to the splitter 22.

  The splitter 22 has the same function as the mixer 25 described above, and generates an optical interference signal 50 between the incident reference light 35a and the measurement light 36a.

  In the circuit having the configuration shown in FIG. 8, the reference point (zero point) can be adjusted by reflected light from the connection portion between the optical fiber cable for optical path 28 and the optical fiber cable for sensor 30. That is, at the connection portion between the optical fiber cable 28 for optical path and the optical fiber cable 30 for sensor, about 4% of the measurement light 36 becomes reflected light and is detected by the light detection unit 26, and the reference point (zero) is detected by the reflected light. Point) can be set.

  As described above, the temperature measuring apparatus 10 of the present example uses the optical comb 31 and can perform a very robust and accurate measurement against disturbance, and changes the frequency of the optical comb 31. Thus, it is possible to cope with various sizes of the measurement object 100. Further, the temperature measuring device 10 of the present example brings the sensor optical fiber cable 30 and the measurement object 100 into contact with each other and integrates them (by covering the portions other than the contacted portions with the covering portion 64). The temperature of only the measuring object 100 can be accurately measured without being affected by the temperature of the atmosphere. Furthermore, the temperature measuring apparatus 10 of this example has an effect that the temperature of the measuring object 100 can be accurately measured even when the measuring object 100 is large or long.

[Modification of sensor unit arrangement]
The sensor optical fiber cable 30 of the sensor unit 11 is arranged to come into contact with the measurement object 100 in various forms. Below, the example of installation to the measuring object 100 of the optical fiber cable 30 for sensors is demonstrated.

  The sensor optical fiber cable 30 expands and contracts when the temperature (heat) of the measurement object 100 is transmitted. In the sensor optical fiber cable 30, the heat of the measurement object 100 is transmitted according to the following formula 1.

(Formula 1) ΔQ / Δt = λ · S · ΔT / Δx
ΔQ / Δt in Equation 1 above is the amount of heat moving per unit time, λ is the heat transfer coefficient, and S is the contact area (heat transfer area) between the sensor optical fiber cable 30 and the measurement object 100. ΔT / Δx indicates a temperature gradient between the temperature of the measurement object 100 and the optical fiber cable 30 for the sensor. As Equation 1 shows, the larger the contact area between the sensor optical fiber cable 30 and the measurement object 100, the more sensitive the sensor optical fiber cable 30 can sense the temperature of the measurement object 100.

  Moreover, the temperature transfer by such heat transfer moves very quickly compared to the temperature change by convection or radiation. Therefore, in order to accurately measure the temperature of the measuring object 100 with high accuracy, it is desirable to increase the contact area and to avoid disturbance due to atmospheric temperature as much as possible. By doing so, the temperature difference between the sensor optical fiber cable 30 and the measurement object 100 can be eliminated, so that the temperature of the measurement object 100 can be accurately measured.

  FIG. 9 is a conceptual diagram showing an example of installation of the sensor optical fiber cable 30 when the temperature measuring device 10 measures the temperature of the block gauge 68 that is the measurement object 100.

  FIG. 9A shows an example in which the sensor optical fiber cable 30 is installed in a block gauge 68 in a wave shape. The temperature measuring apparatus 10 can measure the temperature above and below the block gauge 68 (up and down direction in FIG. 9) by installing the sensor optical fiber cable 30 in a wave shape in this way. FIG. 9B shows an example in which the sensor optical fiber cable 30 is installed in a wave shape so as to reciprocate with respect to the block gauge 68. The temperature measuring device 10 is installed in such a manner that the wave-shaped sensor optical fiber cable 30 is reciprocated with respect to the block gauge 68, so that the sensor optical fiber cable 30 and the block gauge 68 are in contact with each other over a large area. More accurate temperature can be measured. FIG. 9C shows an example in which the sensor optical fiber cable 30 is installed on the block gauge 68 in a U-shape. The temperature measuring device 10 can efficiently measure the entire temperature of the block gauge 68 by installing the sensor optical fiber cable 30 in a U-shape in this way. FIG. 9D shows an example in which the sensor optical fiber cable 30 is installed so as to circulate on the block gauge 68. The temperature measuring device 10 can perform temperature measurement in consideration of the temperature distribution of the peripheral part and the central part of the block gauge 68 by installing the sensor optical fiber cable 30 so as to circulate in this way.

  FIGS. 10 to 12 are conceptual diagrams illustrating an example in which the sensor optical fiber cable 30 is brought into contact with the block gauge 68 when the temperature measuring device 10 measures the temperature of the block gauge 68 that is the measurement object 100.

  In FIG. 10, the sensor optical fiber cable 30 is installed so as to contact the surface of the block gauge 68, and is fixed by a tape 71. The sensor optical fiber cable 30 is the one described with reference to FIG. 2B, and includes a core part 60 and a clad part 62. The sensor optical fiber cable 30 is fixed by the tape 71 and is installed in stable contact with the block gauge 68. In addition, since the sensor optical fiber cable 30 is fixed so as to be covered with the tape 71, the sensor optical fiber cable 30 is hardly affected by the temperature of outside air or the like. As a result, the temperature measuring device 10 can accurately measure the temperature of the block gauge 68.

  In FIG. 11, the sensor optical fiber cable 30 does not have the covering portion 64 at a portion in contact with the block gauge 68, and is provided with a covering portion 64 at a portion other than the portion in contact with the block gauge 68. As described above, the sensor optical fiber cable 30 can measure the temperature of the block gauge 68 with high accuracy because the covering portion 64 is not provided at the portion in contact with the block gauge 68. Further, since the sensor optical fiber cable 30 is provided with the covering portion 64 at a portion that does not contact the block gauge 68, the sensor optical fiber cable 30 is not affected by temperature other than the block gauge 68 (measurement object 100). Temperature can be measured.

  In FIG. 12, the sensor optical fiber cable 30 is provided inside the block gauge 68. Since the sensor optical fiber cable 30 is provided inside the block gauge 68, it can come into contact with the block gauge 68 with a larger surface area, and the temperature of the block gauge 68 can be measured with higher accuracy. Further, the sensor optical fiber cable 30 is provided inside the block gauge 68, so that the temperature of the block gauge 68 can be measured more accurately without being affected by the temperature other than the block gauge 68 (measurement object 100). Can do. As described above, the sensor optical fiber cable 30 can be installed on the measurement object 100 in various forms.

  It goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  DESCRIPTION OF SYMBOLS 10 ... Temperature measuring device, 11 ... Sensor part, 20 ... Optical frequency comb light source, 22 ... Splitter, 23 ... 1st optical path, 24 ... 2nd optical path, 25 ... Mixer, 26 ... Light detection part, 27 ... Sensor length acquisition part 28 ... Optical fiber cable for optical path, 29 ... Connector, 30 ... Optical fiber cable for sensor, 31 ... Optical comb, 32 ... Temperature calculator, 34 ... Acousto-optic modulator, 35 ... Reference light, 36 ... Measuring light, 37 DESCRIPTION OF SYMBOLS ... Optical path length adjustment part, 38 ... 1st collimator, 39 ... 1st prism reflector, 40 ... 2nd prism reflector, 41 ... Scanning stage, 42 ... 2nd collimator, 44 ... Circulator, 45 ... Optical switch, 46 ... Incident part , 48 ... emitting section, 49 ... switch control section, 50 ... optical interference signal, 50a ... beat signal, 52 ... interference fringe pattern detection section, 66 ... etalon, 68 ... block gauge, 7 ... delay device portion, 72 ... measurement beam emitting portion

Claims (10)

A temperature measuring device for measuring the temperature of a measurement object,
An optical frequency comb light source that emits an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals;
A light splitting unit that splits the light emitted from the optical frequency comb light source into reference light and measurement light;
A sensor optical fiber cable for passing the measurement light split by the light splitting unit, the sensor optical fiber cable extending and contracting due to a temperature change, and arranged so as to contact the measurement object And
A light detection unit that detects an optical interference signal between the reference light divided by the light division unit and the measurement light via the sensor optical fiber cable of the sensor unit;
Based on the detection result of the light detection unit, a sensor length acquisition unit that acquires the length of the optical fiber cable for the sensor that has been expanded and contracted;
Based on the length of the stretched optical fiber cable for sensor acquired by the sensor length acquisition unit, a temperature calculation unit that calculates the temperature of the measurement object;
Equipped with a,
The sensor unit includes a plurality of sensor optical fiber cables having different lengths, and each of the plurality of sensor optical fiber cables is connected to an optical switch, and the sensor optical fiber cable selected by the optical switch A temperature measuring device through which the measuring light passes. An optical path length adjustment unit for adjusting the length of the optical path of the reference light;
Optical path of the reference beam by the optical path length adjusting unit, based on the length of the optical fiber cable sensor the sensor length acquisition unit has acquired, a temperature measuring device according to claim 1 is adjusted. A temperature measuring device for measuring the temperature of a measurement object,
An optical frequency comb light source that emits an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals;
A light splitting unit that splits the light emitted from the optical frequency comb light source into reference light and measurement light;
A sensor optical fiber cable for passing the measurement light split by the light splitting unit, the sensor optical fiber cable extending and contracting due to a temperature change, and arranged so as to contact the measurement object And
A light detection unit that detects an optical interference signal between the reference light divided by the light division unit and the measurement light via the sensor optical fiber cable of the sensor unit;
Based on the detection result of the light detection unit, a sensor length acquisition unit that acquires the length of the optical fiber cable for the sensor that has been expanded and contracted;
Based on the length of the stretched optical fiber cable for sensor acquired by the sensor length acquisition unit, a temperature calculation unit that calculates the temperature of the measurement object;
Equipped with a,
An optical path length adjustment unit for adjusting the length of the optical path of the reference light;
The temperature measurement device in which the optical path of the reference light is adjusted by the optical path length adjustment unit based on the length of the sensor optical fiber cable acquired by the sensor length acquisition unit. The etalon which multiplies the frequency interval of the said optical comb by m (m is arbitrary integers) between the said optical frequency comb light source and the said optical division part is provided in any one of Claim 1 to 3 The temperature measuring device described. The object to be measured, the temperature measuring device according to claim 1, any one of 4, which is solid or liquid.   The temperature measuring device according to claim 1, wherein the temperature calculating unit calculates an average temperature of the measurement object.   The temperature measuring device according to any one of claims 1 to 6, wherein the sensor optical fiber cable of the sensor unit is provided inside the measurement object.   The temperature measuring device according to any one of claims 1 to 6, wherein the sensor optical fiber cable of the sensor unit is covered except for a portion in contact with the measurement object. A temperature measurement method for measuring the temperature of a measurement object,
An optical comb emitting step for emitting an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals;
A light splitting step for splitting the light emitted in the optical comb emitting step into reference light and measurement light;
An optical fiber cable for a sensor through which the measurement light divided in the optical division step passes, wherein the measurement is performed by the optical fiber cable for the sensor arranged to expand and contract due to a temperature change and to come into contact with the measurement object. A sensing step for sensing the temperature of the object;
A light detection step of detecting an optical interference signal between the reference light divided in the light division step and the measurement light via the sensor optical fiber cable;
Based on the detection result of the light detection step, a sensor length acquisition step for acquiring the length of the optical fiber cable for sensor that has been expanded and contracted;
Based on the length of the sensor optical fiber cable that has been stretched and acquired in the sensor length acquisition step, a temperature calculation step that calculates the temperature of the measurement object;
Only including,
The sensor optical fiber cables are a plurality of sensor optical fiber cables having different lengths, and each of the plurality of sensor optical fiber cables is connected to an optical switch and is selected by the optical switch. A temperature measurement method in which the measurement light passes through an optical fiber cable. A temperature measurement method for measuring the temperature of a measurement object,
An optical comb emitting step for emitting an optical comb that is light having a plurality of frequency components arranged at equal frequency intervals;
A light splitting step for splitting the light emitted in the optical comb emitting step into reference light and measurement light;
An optical fiber cable for a sensor through which the measurement light divided in the optical division step passes, wherein the measurement is performed by the optical fiber cable for the sensor arranged to expand and contract due to a temperature change and to come into contact with the measurement object. A sensing step for sensing the temperature of the object;
A light detection step of detecting an optical interference signal between the reference light divided in the light division step and the measurement light via the sensor optical fiber cable;
Based on the detection result of the light detection step, a sensor length acquisition step for acquiring the length of the optical fiber cable for sensor that has been expanded and contracted;
Based on the length of the sensor optical fiber cable that has been stretched and acquired in the sensor length acquisition step, a temperature calculation step that calculates the temperature of the measurement object;
Only including,
An optical path length adjusting step for adjusting the length of the optical path of the reference light,
The temperature measurement method in which the optical path of the reference light is adjusted based on the length of the sensor optical fiber cable acquired in the sensor length acquisition step in the optical path length adjustment step.

Images