JP2017161492A - Vibration displacement measuring apparatus and vibration displacement measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost vibration displacement measuring apparatus having a wide dynamic range and capable of performing more accurate measurement than before.SOLUTION: A vibration displacement measuring apparatus 1 includes: a light source unit 11 for outputting continuous light L1 that is subjected to frequency modulation so that a measuring site of a measuring object DUT is disposed within a correlation peak; a joint and branch unit 12 for branching the continuous light L1 into probe light LP and reference light LR; a light receiving unit 15 for receiving interference light of the probe light LP reflected by the measuring object DUT with the reference light LR; and an operation unit 17 for obtaining vibration or displacement of the measuring object DUT using a light receiving signal S1 output from the light receiving unit 15.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vibration displacement measuring apparatus and a vibration displacement measuring method for measuring vibration or displacement of an object to be measured.

  The vibration displacement measuring device is used in various fields in order to measure vibration or displacement of a measurement object. For example, various devices provided in the plant (for example, valve devices such as flow control valves and on-off valves, rotating devices such as fans and motors, piping, and other devices) and various engines (for automobiles, aircraft, ships) It is used to measure vibrations and displacements generated in an engine used for other purposes.

  Such a vibration displacement measuring device is roughly classified into a contact type vibration displacement measuring device and a non-contact type vibration displacement measuring device. Typical examples of contact-type vibration displacement measuring devices include piezoelectric and capacitive semiconductor acceleration sensors, and typical examples of non-contact type vibration displacement measuring devices include laser interferometers. The laser Doppler velocimeter (Laser Doppler Velocimeter, Velocimetry, or Vibrometer: hereinafter referred to as “LDV”) is used.

  A piezoelectric semiconductor acceleration sensor, which is a type of contact-type vibration displacement measuring device, is small in size, does not require an external power supply, does not require a displacement reference point, and has no static sensitivity. Features such as no zero shift due to component). On the other hand, LDV, which is a kind of non-contact type vibration displacement measuring device, has the features that it can measure from a distant position, does not affect the weight of the object to be measured, and has a wide measurement dynamic range. The following Patent Document 1 discloses an example of the above-described piezoelectric semiconductor acceleration sensor, and the following Non-Patent Document 1 discloses an example of the above-described LDV.

Japanese Patent No. 5494803

G. Siegmund, “Sources of Measurement Error in Laser Doppler Vibrometers and Proposal for Unified Specifications”, Proc. SPIE, 7098, 70980Y

  By the way, in order to measure the vibration or displacement of the measurement target using the piezoelectric semiconductor acceleration sensor described above, it is necessary to contact (attach) the piezoelectric semiconductor acceleration sensor to the measurement target. Since the weight of the measurement target increases by the weight of the attached piezoelectric semiconductor acceleration sensor, there is a problem that the resonance frequency of the vibration of the measurement target may change. In addition, the acceleration sensor disclosed in Patent Document 1 described above has a structure in which the weight portion is supported by the beam portion, so that the maximum displacement amount of the weight portion is limited, so that the measurement dynamic range is limited. There was a problem of being.

  On the other hand, the above-mentioned LDV has no problems (a resonance frequency changes, a dynamic range is limited) like the piezoelectric semiconductor acceleration sensor, and has an advantage of higher measurement accuracy than the piezoelectric semiconductor acceleration sensor. Have However, since LDV needs to secure a spatial light path (generally, a straight light path) of laser light, it cannot measure, for example, the inside of a measurement target that cannot be directly observed. There's a problem.

  Another problem common to both the piezoelectric semiconductor acceleration sensor and the LDV described above is that an error due to integration occurs. That is, in the case of a piezoelectric semiconductor acceleration sensor, it is necessary to integrate the detection result (detection result indicating acceleration) twice in order to obtain the displacement amount. In the case of LDV, the detection result is obtained in order to obtain the displacement amount. Although it is necessary to integrate the (detection result indicating the speed) once, in any case, an error occurs when the detection result is integrated. If the displacement of the object to be measured can be directly measured without using an integral calculation that may cause such a deterioration of the measurement result, it is considered that measurement with high accuracy can be realized.

  As a non-contact type vibration displacement measuring apparatus other than the LDV, there is a laser interferometer that variably sweeps an optical path difference using an optical modulator. Although such a laser interferometer has an extremely excellent feature that it is possible to perform displacement measurement with high accuracy at high speed, the optical modulator provided in the laser interferometer is a passive optical component or semiconductor electronic device. Since it is more expensive than parts, there is a problem in terms of cost.

  The present invention has been made in view of the above circumstances, and has an object to provide a vibration displacement measuring device and a vibration displacement measuring method that have a wide dynamic range and can perform measurement with higher accuracy than conventional methods. To do.

In order to solve the above-described problems, a vibration displacement measuring apparatus according to the present invention is a vibration displacement measuring apparatus (1 to 3) that measures the vibration or displacement of a measurement target (DUT) in a non-contact manner. A light source unit (11) that outputs continuous light (L1) that is frequency-modulated so that the measurement site is located within the correlation peak (CP), and the continuous light is used as probe light (LP) and reference light (LR). A branching portion (12, 21) that branches into a light receiving portion, a light receiving portion (15) that receives interference light between the probe light and the reference light reflected by the object to be measured, and a light receiving output from the light receiving portion. A calculation unit (17) for obtaining vibration or displacement of the measurement object using a signal (S1).
In the vibration displacement measuring apparatus of the present invention, at least the modulation period and the modulation amplitude are set so that the light source unit has the measurement site to be measured within the correlation peak.
In the vibration displacement measuring apparatus of the present invention, the modulation period and the modulation amplitude of the light source unit are arranged such that the measurement site of the measurement target is in the first half (H1) or the second half (H2) of the correlation peak. Is set to
Further, in the vibration displacement measuring apparatus according to the present invention, the modulation period of the light source unit is a length of the first optical path from when the probe light branched by the branch unit is reflected by the measurement target to the light receiving unit. And an integer multiple of a value obtained by dividing the difference between the length of the second optical path until the reference light branched at the branching portion reaches the light receiving portion by the speed of light, or a value close to the integral multiple Is done.
In the vibration displacement measuring apparatus of the present invention, the modulation amplitude of the light source unit is set according to the magnitude of vibration or displacement of the measurement site of the measurement target.
In addition, the vibration displacement measuring apparatus of the present invention includes an optical fiber (F10) that guides the probe light branched at the branching portion to an irradiation position that is a position at which the probe light is irradiated toward the measurement target.
Further, the vibration displacement measuring apparatus of the present invention is arranged between the irradiation position and the measurement target, and condenses the probe light emitted from the optical fiber on the measurement site of the measurement target, or Lenses (14a, 14b) for converting the probe light emitted from the optical fiber into parallel light and irradiating the measurement site of the measurement target.
In addition, the vibration displacement measuring apparatus of the present invention includes a control unit (18) that controls the light source unit while referring to the calculation result of the calculation unit.
The vibration displacement measuring method of the present invention is a vibration displacement measuring method for measuring vibration or displacement of a measurement target (DUT) in a non-contact manner, wherein the measurement site of the measurement target is arranged in a correlation peak (CP). A first step (S21) for outputting continuous light (L1) frequency-modulated in such a manner, and a second step (S22) for branching the continuous light into probe light (LP) and reference light (LR), A third step (S23) for receiving interference light between the probe light and the reference light reflected by the measurement target, and vibration or displacement of the measurement target using a light reception signal obtained in the third step. And a fourth step (S24) for obtaining.
Further, the vibration displacement measuring method of the present invention is performed prior to measurement of vibration or displacement of the measurement target, and irradiates the probe light to a reflection mirror installed at a reference position on the optical path of the probe light, A first initial step (S11) for obtaining a modulation frequency of the continuous light that maximizes the light reception signal, and irradiating the probe light to the object to be measured in a state where the reflection mirror is removed from the reference position; A second initial step (S12) of measuring the intensity of the received light signal while changing the modulation frequency of the continuous light, and using the measurement result of the second initial step, the measurement site of the measurement target is within the correlation peak. And a third initial step (S16) for determining the modulation frequency of the continuous light to be arranged in

  According to the present invention, the continuous light output from the light source unit is frequency-modulated so that the measurement site to be measured is located within the correlation peak, the continuous light is branched into the probe light and the reference light, and the measurement is performed. Interference light between the probe light reflected by the object and the reference light is received, and the vibration or displacement of the object to be measured is obtained using the received light signal. For this reason, the dynamic range is not limited as in the conventional acceleration sensor, and it is not necessary to perform integral calculation as in the conventional acceleration sensor. There is an effect that it can be performed.

It is a block diagram which shows the principal part structure of the vibration displacement measuring apparatus by 1st Embodiment of this invention. It is a figure which shows an example of the correlation peak in 1st Embodiment of this invention. It is an enlarged view of the correlation peak in 1st Embodiment of this invention. It is a flowchart which shows the initial setting process performed in 1st Embodiment of this invention. It is a figure which shows an example of the intensity | strength of the received light signal measured when the to-be-measured object is vibrating in 1st Embodiment of this invention. It is a flowchart which shows the measurement process performed in 1st Embodiment of this invention. It is a block diagram which shows the principal part structure of the vibration displacement measuring apparatus by 2nd Embodiment of this invention. It is a block diagram which shows the principal part structure of the vibration displacement measuring apparatus by 3rd Embodiment of this invention. It is a figure which shows the structural example of the injection part in the 1st-3rd embodiment of this invention. It is a figure which shows the other structural example of the injection part in the 1st-3rd embodiment of this invention.

  Hereinafter, a vibration displacement measuring apparatus according to an embodiment of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
<Configuration of vibration displacement measuring device>
FIG. 1 is a block diagram showing a main configuration of the vibration displacement measuring apparatus according to the first embodiment of the present invention. As shown in FIG. 1, the vibration displacement measuring apparatus 1 of the present embodiment includes a light source unit 11, a coupling / branching unit 12 (branching unit), a reflecting unit 13, an emitting unit 14, a light receiving unit 15, an acquiring unit 16, a computing unit 17, A control unit 18 and polarization maintaining optical fibers F1 to F4 are provided, and the measurement target DUT is irradiated with the probe light LP to measure the vibration or displacement of the measurement target DUT without contact. The DUT to be measured includes, for example, various devices provided in the plant, various engines, and the like, but is not particularly limited and may be an arbitrary object.

  The light source unit 11 includes, for example, a semiconductor laser element such as a distributed feedback laser diode (DFB-LD), and is controlled by the control unit 18 to continuously frequency-modulate linearly polarized waves. Outputs light L1. Although details will be described later, the continuous light L1 output from the light source unit 11 has a frequency such that the measurement site of the DUT to be measured (the site irradiated with the probe light LP) is arranged within the correlation peak. It is modulated. A polarization maintaining optical fiber F1 is connected to the output end of the light source unit 11, and the continuous light L1 output from the light source unit 11 is guided to the combining / branching unit 12 via the polarization maintaining optical fiber F1.

  Although not shown, the light source unit 11 is provided with an isolator for stabilizing the operation of the semiconductor laser element on the emission end side of the semiconductor laser element. The continuous light L1 emitted from the semiconductor laser element is output to the outside of the light source unit 11 through the isolator, but the return light (for example, reflected light of the continuous light L1) to the semiconductor laser element is blocked by the isolator. The Since the return light to the semiconductor laser element is blocked by the isolator, the operation of the semiconductor laser element is stabilized.

  The combining / branching unit 12 has four input / output ends to which the polarization maintaining optical fibers F1 to F4 are respectively connected, and combines or branches light input from these input / output ends. For example, an optical coupler or an optical circulator can be used as the coupling / branching unit 12. Specifically, the combining / branching unit 12 receives the light (continuous light L1) input from the input / output end to which the polarization maintaining optical fiber F1 is connected, while maintaining the polarization state, and the reference light LR and the probe light LP. The branched reference light LR is output from the input / output end connected to the polarization maintaining optical fiber F2, and the branched probe light LP is output from the input / output end connected to the polarization maintaining optical fiber F3. . The branching ratio of the combining / branching unit 12 can be arbitrarily set. For example, the intensity ratio of the reference light LR and the probe light LP is set to 1: 1.

  Further, the combining / branching unit 12 receives light (reflected light of the reference light LR) input from the input / output end to which the polarization maintaining optical fiber F2 is connected and the input / output end to which the polarization maintaining optical fiber F3 is connected. The input light (the reflected light of the probe light LP) is multiplexed while maintaining its polarization state, and the combined light is output from the input / output end to which the polarization maintaining optical fiber F4 is connected. It should be noted that the light combined at the combining / branching unit 12 is output only from the input / output end to which the polarization maintaining optical fiber F4 is connected, and is not output from the input / output end to which the polarization maintaining optical fiber F1 is connected. It is desirable to do.

  The reflection unit 13 is arranged at the end (or the vicinity thereof) of the polarization maintaining optical fiber F2, and reflects the reference light LR guided by the polarization maintaining optical fiber F2 while maintaining the polarization state. To do. The reflected light of the reference light LR enters the polarization maintaining optical fiber F2, and is guided to the coupling / branching unit 12 via the polarization maintaining optical fiber F2. The emitting unit 14 emits the probe light LP guided through the polarization maintaining optical fiber F3 to the outside of the vibration displacement measuring apparatus 1 while maintaining the polarization state. The probe light LP emitted from the emission unit 14 may be light condensed on the measurement site of the measurement target DUT or may be collimated light. In addition, the reflected light of the probe light LP reflected by the measurement target DUT is incident on the emission unit 14.

  The light receiving unit 15 includes a light receiving element such as a photodiode or an avalanche photodiode, and the light guided by the polarization maintaining optical fiber F4 (the reflected light of the reference light LR and the reflected light of the probe light LP). Receives (combined light). Here, since the light guided to the light receiving unit 15 by the polarization maintaining optical fiber F4 is the interference of the reference light LR and the probe light LP, the light receiving unit 15 transmits the reference light LR and the probe light LP. A light reception signal S1 indicating the interference intensity is output.

  The acquisition unit 16 converts the light reception signal S1 output from the light reception unit 15 into a signal that can be processed by the calculation unit 17. For example, the acquisition unit 16 converts the light reception signal S1 into an analog voltage signal or a digital signal. As the acquisition unit 16, for example, a sampling device such as an oscilloscope, a digitizer device, an A / D (analog / digital) converter, or the like can be used.

  The calculation unit 17 calculates the position (displacement amount) of the measurement target DUT by using the signal output from the acquisition unit 16. This calculation unit 17 does not perform integration calculation as in a conventional piezoelectric semiconductor acceleration sensor, LDV, or the like, and based on the shape of the correlation peak and the magnitude of the signal output from the acquisition unit 16, the measurement target DUT Find the position. Details of the calculation performed by the calculation unit 17 will be described later.

  The control unit 18 controls light emission and non-light emission of the light source unit 11 by controlling an injection current to the semiconductor laser element provided in the light source unit 11. Specifically, when the light source unit 11 emits light, the control unit 18 outputs the light source unit 11 while controlling so that a direct current exceeding the emission threshold value of the semiconductor laser element is injected into the semiconductor laser element. Control is performed so that an alternating current having an arbitrary waveform for frequency-modulating the continuous light L1 is injected into the semiconductor laser element. Although details will be described, the control unit 18 may control the light source unit 11 while referring to the calculation result of the calculation unit 17.

<Correlation peak and measurement principle>
Next, the measurement principle of the vibration or displacement of the measurement target DUT using the correlation peak and the correlation peak will be described. The vibration displacement measuring device 1 causes the reference light LR and the probe light LP to interfere with each other by combining the reflected light of the reference light LR and the reflected light of the probe light LP at the combining / branching unit 12, and receives light indicating the interference intensity. A signal S1 is obtained. If the frequency of the continuous light L1 output from the light source unit 11 is unmodulated, the period of intensity change of the light reception signal S1 is one period of the wavelength of the continuous light L1.

In the present embodiment, since the continuous light L1 output from the light source unit 11 is frequency-modulated, the intensity of the light reception signal S1 is a correlation peak period different from the above period (one period of the wavelength of the continuous light L1). Will change. Here, the correlation peak indicates that the correlation between the reference light LR and the probe light LP is high, and the optical path difference between the reference light LR and the probe light LP is the difference between the reference light LR and the probe light LP. Appears when is in an intensifying state. In particular, as the reference light LR and the probe light LP and correlation peak zero-order correlation peak optical path difference appears in the case of zero (0 ^th Order Correlation Peak).

  Now, it is assumed that the continuous light L1 output from the light source unit 11 is modulated by a sine wave having a frequency fm. First, to simplify the description, it is assumed that the polarization maintaining optical fiber F2 has a length of 1 [m] and the polarization maintaining optical fiber F3 has a length of 11 [m]. As a result, the round-trip optical path length between the coupling / branching unit 12 and the reflection unit 13 is 2 [m], and the round-trip optical path length between the coupling / branching unit 12 and the emission unit 14 is 22 [m]. . In addition, it is assumed that the measurement target DUT is disposed on the end face of the injection unit 14 and the distance from the injection unit 14 to the measurement target DUT is 0 [m].

  In such a situation, the zero-order correlation peak appears at a position of 1 [m] from one end of the polarization maintaining optical fiber F3 (the end connected to the coupling / branching unit 12). That is, a zero-order correlation peak appears at a position where the round-trip optical path length of the probe light LP is equal to the round-trip optical path length of the reference light LR. If reflected light or Rayleigh scattered light is generated at the position where the zeroth-order correlation peak appears, it may cause a measurement error because it interferes with the reference light LR. However, since the 0th-order correlation peak appears in the middle of the polarization maintaining optical fiber F3, no reflected light is generated, and the intensity of Rayleigh scattered light is extremely small compared to the intensity of the reflected light from the DUT to be measured. Measurement error hardly occurs.

Further, a correlation peak that appears when the optical path difference between the reference light LR and the probe light LP is N times (N is an integer) the modulation period (1 / fm) of the continuous light L1 is an N ^th Order Correlation. Peak). Specifically, as shown in the following equation (1), a value obtained by dividing the optical path difference (2L) between the reference light LR and the probe light LP by the speed of light V is a modulation period (1 / An Nth order correlation peak appears when it matches N times fm). In addition, the light speed V in the following (1) Formula is the light speed in an optical fiber.
L = N · V / (2 · fm) (1)

For example, assuming that the modulation frequency fm of the continuous light L1 is 10 [MHz] and the speed of light V in the optical fiber is 2 × 10 ⁸ [m / sec], for example, N = 1 in the above equation (1). The correlation peak in this case (primary correlation peak) appears at the position of L = 10 [m]. That is, the primary correlation peak appears at a position 10 [m] away from the position where the zero-order correlation peak appears (that is, the position of the emission unit 14). As described above, since the DUT to be measured is arranged on the end face of the emitting portion 14, reflected light (reflected light of the probe light LP) is generated at the position where the primary correlation peak appears. The reflected light of the probe light LP interferes with the reference light LR (the reference light LR reflected by the reflecting unit 13), and the intensity of the received light signal S1 output from the light receiving unit 15 is maximized. As described above, when the DUT to be measured is arranged at the position where the correlation peak appears, the reflected light of the probe light LP is generated at the position where the correlation peak appears. Strength is maximized.

  FIG. 2 is a diagram illustrating an example of a correlation peak in the first embodiment of the present invention. In FIG. 2, the horizontal axis represents the position of the measurement target DUT with the position of the emitting portion 14 as the origin, and the vertical axis represents the correlation between the reference light LR and the probe light LP. The vertical axis may be read as “intensity of light reception signal S1”. In FIG. 2, the correlation peak CP is a portion where the correlation degree increases in a δ function. In the example shown in FIG. 2, a primary correlation peak appears at a position (origin) of 0 [m], a secondary correlation peak appears at a position of 10 [m], and thereafter every 3 [m]. The correlation peaks after the next appear periodically.

  FIG. 3 is an enlarged view of a correlation peak in the first embodiment of the present invention. FIG. 3 is an enlarged view of the secondary correlation peak shown in FIG. As shown in FIG. 3, the correlation peak CP has a symmetrical mountain shape (convex shape upward), and a plurality of mountain shapes called “side lobes” (height is the height of the correlation peak CP) on both sides of the correlation peak CP. It can be seen that (lower than the height) exists repeatedly. Further, when only the first half H1 of the correlation peak CP is viewed, the correlation peak CP has a portion showing a change close to a monotonically increasing line. When only the second half H2 of the correlation peak CP is viewed, the correlation peak CP is monotonous. It can be seen that there is a portion showing a change close to a decreasing straight line.

  In the present embodiment, a portion showing a change close to a straight line in the first half H1 or the second half H2 of the correlation peak CP is used, and the measurement site of the measurement target DUT is the first half H1 or the second half H2 of the correlation peak CP. The vibration or displacement of the DUT to be measured is accurately measured. For example, the light source unit using the above-described equation (1) so that the measurement site of the measurement target DUT in a stationary state is a position DP (a position where the correlation degree is about 0.5) shown in FIG. 11 modulation frequencies fm and integer N are determined. If the modulation frequency fm is increased, the value of the integer N is increased, and if the modulation frequency fm is decreased, the value of the integer N is decreased.

  When the modulation frequency fm is kept constant, the position of the correlation peak CP does not fluctuate. Therefore, the measurement site of the DUT to be measured is away from the emitting portion 14 of the vibration displacement measuring device 1 (right side of the drawing in FIG. 3). Displacement in the direction), the degree of correlation between the reference light LR and the probe light LP increases, and the intensity of the light reception signal S1 increases. On the other hand, when the modulation frequency fm is kept constant, if the measurement site of the DUT to be measured is displaced in the direction approaching the injection unit 14 of the vibration displacement measuring device 1 (the left side in FIG. 3), the reference is made. The degree of correlation between the light LR and the probe light LP decreases, and the intensity of the light reception signal S1 decreases. In this embodiment, using the phenomenon that the intensity of the light reception signal S1 changes in accordance with the amount of displacement of the measurement site of the DUT to be measured, the measurement result of the intensity of the light reception signal S1 is used in this embodiment. The amount of displacement of the target DUT is obtained.

  Here, as shown in FIG. 3, in the first half H1 or the second half H2 of the correlation peak CP, the correlation peak CP changes in a curve at a portion where the correlation degree is high (a part where the correlation degree is about 0.8 or more). If this part is used, there is a possibility that the measurement accuracy may deteriorate. Further, in the first half H1 or the second half H2 of the correlation peak CP, the intensity of the received light signal S1 is low in a portion where the correlation is low (a portion where the correlation is about 0.2 or less). There is a possibility that the measurement accuracy may deteriorate due to the influence of noise or the like.

  For this reason, with reference to the position DP shown in FIG. 3 (the position where the correlation degree is about 0.5), the displacement amount (including the amplitude of vibration) of the DUT to be measured is the position DL (shown in FIG. 3). It is considered that the deterioration of measurement accuracy can be prevented by keeping it between the position DH (position where the correlation degree is about 0.2) and the position DH shown in FIG. 3 (position where the correlation degree is about 0.8). It is done. In the following, the position DP shown in FIG. 3 is referred to as “operation point OP”, the position DL shown in FIG. 2 is called “minimum displacement point OL”, and the position DH shown in FIG. OH ".

  The shape of the correlation peak CP shown in FIG. 3 is the wavelength of the continuous light L1 output from the light source unit 11, the refractive index of the polarization maintaining optical fibers F1 to F4, and the refractive index of the optical path from the emitting unit 14 to the measurement target DUT. The modulation frequency fm, the modulation amplitude Δf, and the modulation waveform of the continuous light L1 can be obtained. The calculation unit 17 shown in FIG. 1 obtains the shape of the correlation peak CP using these, and uses the obtained shape of the correlation peak CP and the signal output from the acquisition unit 16 to calculate the displacement amount of the measurement target DUT. Looking for. Note that the vibration of the measurement target DUT can be obtained by continuously obtaining the displacement amount of the measurement target DUT.

<Vibration displacement measurement method>
Next, a vibration displacement measuring method will be described. In order to measure the vibration or displacement of the DUT to be measured by the vibration displacement measuring apparatus 1, as described with reference to FIG. 3, the measurement site of the DUT to be measured in the stationary state is the operating point shown in FIG. It is necessary to determine the modulation frequency fm and the like of the light source unit 11 so as to be OP. In the following, first, processing for determining the modulation frequency fm and the like of the light source unit 11 (hereinafter referred to as initial setting processing) will be described, and then processing for measuring vibration or displacement of the DUT to be measured (hereinafter referred to as measurement processing). Will be described.

Initial Setting Process FIG. 4 is a flowchart showing the initial setting process performed in the first embodiment of the present invention. First, as shown in FIG. 4, a reflection mirror (not shown) is installed on the end surface (reference position on the optical path of the probe light LP) of the emission unit 14 provided in the vibration displacement measuring apparatus 1, and the probe light LP is applied to the reflection mirror. Irradiation is performed to determine the modulation frequency fm that maximizes the intensity of the light reception signal S1 (step S11: first initial step). In this process, it is practically difficult to accurately grasp the lengths of the polarization maintaining optical fibers F2 and F3. Therefore, the optical path length difference between the probe light LP and the reference light LR is accurately determined by adjusting the modulation frequency fm. Done to figure out.

  The installation of the reflection mirror (not shown) on the end face of the emission unit 14 is performed by an operator who performs installation, maintenance, and the like of the vibration displacement measuring device 1, for example. As the reflection mirror, for example, a flat mirror having a flat reflection surface can be used. However, the reflection mirror can be made to reflect the probe light LP emitted from the end face of the emission unit 14 and enter the emission unit 14. Any mirror can be used.

  When the installation of the reflection mirror is completed and the process of step S11 is started, the light source unit 11 is controlled by the control unit 18, and the continuous light L1 modulated at a predetermined modulation frequency fm is output from the light source unit 11. Is done. The continuous light L1 output from the light source unit 11 enters the combining / branching unit 12 via the polarization maintaining optical fiber F1, and is branched into the reference light LR and the probe light LP while maintaining the polarization state.

  The branched reference light LR is propagated through the polarization maintaining optical fiber F2 and then reflected by the reflecting unit 13 while maintaining the polarization state, and after propagating through the polarization maintaining optical fiber F2 in the reverse direction, the combining / branching unit 12 Is incident on. On the other hand, the branched probe light LP is reflected while the polarization state is maintained by a reflection mirror (not shown) installed on the end face of the emitting unit 14 after propagating through the polarization maintaining optical fiber F3. After propagating through the holding optical fiber F3 in the reverse direction, the light enters the junction 12.

  The reflected light of the reference light LR and the reflected light of the probe light LP incident on the combining / branching unit 12 are combined while maintaining the polarization state. The light combined by the combining / branching unit 12 is received by the light receiving unit 15 after propagating through the polarization maintaining optical fiber F4. As a result, the light receiving unit 15 outputs a light reception signal S1 indicating the interference intensity between the reference light LR and the probe light LP. The light reception signal S1 output from the light receiving unit 15 is converted into a signal that can be processed by the calculation unit 17 in the acquisition unit 16, and then input to the calculation unit 17 to measure the intensity of the light reception signal S1.

  When the above processing ends, the modulation frequency fm of the continuous light L1 is changed by a predetermined frequency under the control of the control unit 18, and the light reception signal S1 at the changed modulation frequency fm is converted by the acquisition unit 16 to be calculated. 17 is performed to measure the intensity of the received light signal S1. Thereafter, the process of changing the modulation frequency fm of the continuous light L1 by a predetermined frequency and measuring the intensity of the received light signal S1 at the changed modulation frequency fm is repeatedly performed under the control of the control unit 18. When such repetitive processing is completed, processing for determining the modulation frequency fm that maximizes the intensity of the received light signal S1 measured by the arithmetic unit 17 is performed by the control unit 18. The modulation frequency fm determined here is such that one of the correlation peaks (for example, the primary correlation peak) appears at the position of the end face of the emitting portion 14.

  Next, a reflection mirror (not shown) installed on the end face of the emitting unit 14 is removed, the probe light LP is irradiated to the measurement target DUT, and the intensity of the light reception signal S1 while changing the modulation frequency fm of the continuous light L1. Is calculated by the calculation unit 17 (step S12: second initial step). Here, it is assumed that the probe light LP irradiated to the measurement target DUT is set so as to be reflected by the measurement target DUT and to enter the end face of the emitting unit 14. The removal of the reflection mirror (not shown) is performed by, for example, an operator who performs installation or maintenance of the vibration displacement measuring apparatus 1.

  When the process of step S12 is started, the control frequency of the control unit 18 first sets the modulation frequency fm of the continuous light L1 to a frequency different from the modulation frequency fm determined in the above-described step S11 by a predetermined frequency. Is done. For example, the modulation frequency fm of the continuous light L1 is set to a frequency slightly lower than the modulation frequency fm determined in step S11. When such a frequency is set, the value of L in the above-described equation (1) is slightly increased. Thereby, the correlation peak (for example, primary correlation peak) appearing on the end face of the emitting unit 14 is moved from the end face of the emitting unit 14 in the direction toward the measurement target DUT. Then, processing for measuring the maximum value (peak intensity) of the light reception signal S1 in this state is performed by the arithmetic unit 17.

  Thereafter, similarly, the process of measuring the peak intensity of the received light signal S1 is repeatedly performed while changing the modulation frequency fm of the continuous light L1. That is, the process of measuring the peak intensity of the received light signal S1 is performed while scanning the modulation frequency fm and gradually moving the position of the correlation peak. By performing such processing, a received light intensity distribution indicating the relationship between the distance from the vibration displacement measuring apparatus 1 (the distance from the end face of the emitting unit 14) and the change in the peak intensity of the received light signal S1 is obtained.

  Here, when the DUT to be measured is stationary, the received light intensity distribution obtained by the above processing shows the waveform of the correlation peak. Further, the position where the maximum value of the received light intensity distribution is obtained is the position where the measurement site of the DUT to be measured is arranged. For this reason, the position of the measurement target DUT in a stationary state can be obtained by performing the above-described processing to obtain the received light intensity distribution.

  On the other hand, when the DUT to be measured is not stationary (for example, when it is vibrating), even if the modulation frequency fm is constant, the intensity of the light reception signal S1 measured by the calculation unit 17 is It varies with time. FIG. 5 is a diagram illustrating an example of the intensity of the received light signal measured when the measurement target is vibrating in the first embodiment of the present invention. In FIG. 5, as in FIGS. 2 and 3, the vertical axis may be read as “intensity of the received light signal S <b> 1”.

  For example, when the position of the DUT to be measured moves to the left side of the paper relative to the position of the correlation peak, the received light intensity when the correlation peak moves to the right side of the paper relative to the DUT to be measured is obtained. . On the other hand, when the position of the DUT to be measured moves to the right side of the drawing relative to the position of the correlation peak, the received light intensity when the correlation peak moves to the left side of the drawing relative to the DUT to be measured. can get. As described above, when the measurement target DUT is not stationary, the intensity of the light reception signal S1 measured by the calculation unit 17 varies with time.

  In the present embodiment, by measuring the maximum intensity (peak intensity) of the light reception signal S1, the stationary position of the measurement target DUT (position when the measurement target DUT is stationary) is obtained. I have to. Specifically, the curve with the symbol PK in FIG. 5 is a curve indicating the peak intensity measured by the calculation unit 17. The peak intensity holds, for example, the maximum value of the intensity measured by the computing unit 17 during at least one period of vibration of the DUT to be measured (peak) when the modulation frequency fm is set to a certain frequency. It is calculated by holding.

  Referring to FIG. 5, it can be seen that the range in which the maximum value of the correlation peak can be obtained is expanded by the amount of fluctuation of the DUT to be measured. That is, in the example shown in FIG. 5, the maximum value of the correlation peak is obtained in the range indicated by the symbol W in the figure. Therefore, when the DUT to be measured is not stationary, the calculation unit 17 obtains the center position Q of the range to which the symbol W is attached as the stationary position of the DUT to be measured, and the range to which the symbol W is attached. Is obtained as the displacement amplitude.

  Next, from the position where the intensity of the light reception signal S1 is maximized (or the center position Q of the range where the intensity of the light reception signal S1 is maximum), one of the correlation peaks is taken as the stationary position (or when stationary) of the DUT to be measured. Processing for determining the modulation frequency fm0 to be arranged at (position) is performed by the computing unit 17 (step S13). Further, the processing unit 17 performs a process of determining the modulation amplitude Δf from the range of the code W (step S14).

  Subsequently, based on the obtained modulation frequency fm0 and modulation amplitude Δf, processing for calculating the waveform of the correlation peak is performed by the computing unit 17 (step S15). By this processing, for example, the waveform of the correlation peak CP shown in FIG. 3 is obtained. When the above processing is completed, the modulation frequency fm is set so that the measurement part of the measurement target DUT that is stationary or the measurement part of the measurement target DUT that is at a stationary position becomes the operating point OP shown in FIG. Adjustment is made (step S16: third initial step).

Measurement Process FIG. 6 is a flowchart showing the measurement process performed in the first embodiment of the present invention. When the processing is started, the light source unit 11 is controlled by the control unit 18, and the continuous light L1 modulated with the modulation frequency fm and the modulation amplitude Δf finally determined by the above-described initial setting processing is output from the light source unit 11. (Step S21: first step). The continuous light L1 output from the light source unit 11 enters the combining / branching unit 12 via the polarization maintaining optical fiber F1, and is branched into the reference light LR and the probe light LP while maintaining the polarization state (step). S22: Second step).

  The branched reference light LR is propagated through the polarization maintaining optical fiber F2 and then reflected by the reflecting unit 13 while maintaining the polarization state, and after propagating through the polarization maintaining optical fiber F2 in the reverse direction, the combining / branching unit 12 Is incident on. On the other hand, the branched probe light LP propagates through the polarization-maintaining optical fiber F3 and then exits from the vibration displacement measuring apparatus 1 while maintaining the polarization state from the emitting unit 14, and the optical path shown in FIG. After being propagated, the measurement site of the DUT to be measured is irradiated. The reflected light of the probe light LP applied to the DUT to be measured is propagated in the reverse direction in the optical path shown in FIG. 1 and then incident on the emission unit 14 and then propagated in the reverse direction through the polarization maintaining optical fiber F3. Incident on the portion 12.

  The reflected light of the reference light LR and the reflected light of the probe light LP incident on the combining / branching unit 12 are combined while maintaining the polarization state. The light combined by the combining / branching unit 12 is received by the light receiving unit 15 after propagating through the polarization maintaining optical fiber F4 (step S23: third step). As a result, the light receiving unit 15 outputs a light reception signal S1 indicating the interference intensity between the reference light LR and the probe light LP. The light reception signal S <b> 1 output from the light receiving unit 15 is converted into a signal that can be processed by the calculation unit 17 in the acquisition unit 16 and then input to the calculation unit 17.

  When the signal from the acquisition unit 16 is input, the calculation unit 17 obtains the shape of the correlation peak CP as described above, and uses the obtained shape of the correlation peak CP and the signal output from the acquisition unit 16, Processing for obtaining the displacement amount of the DUT to be measured is performed (step S24: fourth step). In addition, the vibration of the measurement target DUT is obtained by continuously performing the process for obtaining the displacement amount of the measurement target DUT.

  Here, when the shape of the correlation peak CP is obtained, the calculation unit 17 performs function fitting on the obtained shape of the correlation peak CP using a generally known optimization method. Also good. In general, there are many linear functions or quadratic functions as functions used for fitting. However, a higher-order function or a non-linear function may be used, and an arbitrary function can be used. If a linear function can be used for the fitting, the displacement amount of the DUT to be measured can be obtained by an extremely easy calculation.

  When the above fitting is performed by the calculation unit 17, the control unit 18 controls the light source unit 11 so that the error of the function fitted by the calculation unit 17 falls within an allowable range. The point OL and the maximum displacement point OH may be automatically set. For example, when the measurable distance range (the interval between the minimum displacement point OL and the maximum displacement point OH) is narrower than the maximum displacement amount of the DUT to be measured, the control unit 18 controls the light source unit 11, By changing the shape of the correlation peak CP, the measurable distance range can be expanded. Specifically, when the modulation of the continuous light L1 is performed using a sine wave, the width of the correlation peak CP is widened by reducing the modulation amplitude Δf, so that the measurable distance range can be widened. .

  Conversely, if the measurable distance range (interval between the minimum displacement point OL and the maximum displacement point OH) is too wide than the maximum displacement amount of the DUT to be measured, only a small part of the slope of the correlation peak CP is present. It will not be used. In such a case, the control unit 18 controls the light source unit 11 to change the shape of the correlation peak CP and narrow the measurable distance range, thereby improving the sensitivity of the displacement amount of the measurement target DUT. be able to. Specifically, when the modulation of the continuous light L1 is performed using a sine wave, if the modulation amplitude Δf is increased, the width of the correlation peak CP becomes narrower and the inclination becomes steeper. The sensitivity of the displacement amount of the DUT can be improved.

  As described above, in the present embodiment, the continuous light L1 output from the light source unit 11 is frequency-modulated so that the measurement site of the measurement target DUT is arranged in the first half H1 or the second half H2 of the correlation peak CP, The light L1 is branched into the reference light LR and the probe light LP by the combining / branching unit 12. Then, the reference light LR reflected by the reflection unit 13 and the probe light LP reflected by the measurement target DUT are combined and received by the combining / branching unit 12, and the measurement target is obtained using the obtained light reception signal S1. The vibration or displacement of the DUT is obtained.

  For this reason, in this embodiment, the dynamic range is not limited as in the conventional acceleration sensor, and it is not necessary to perform the integral calculation as in the conventional case. It is possible to perform highly accurate measurement. Further, in the present embodiment, since there is no need to variably sweep the optical path difference using an optical modulator as in a conventional laser interferometer, the vibration displacement measuring device can be produced at a low cost without causing a significant increase in cost. 1 can be realized.

  In the present embodiment, prior to measurement of the measurement target DUT, the position where the correlation peak appears is changed by scanning the modulation frequency fm of the continuous light L1, and one of the correlation peaks is measured. The modulation frequency fm0 to be arranged at the stationary position (or stationary position) of the target DUT is determined. Then, the waveform of the correlation peak is calculated based on the determined modulation frequency fm0 and modulation amplitude Δf, and the measurement part of the measurement target DUT that is stationary or the measurement part of the measurement target DUT that is at a stationary position is obtained. The modulation frequency fm is adjusted so that the operating point OP shown in FIG. As described above, in this embodiment, the modulation frequency fm necessary for measuring the vibration or displacement of the DUT to be measured without contact can be automatically adjusted in a short time.

[Second Embodiment]
FIG. 7 is a block diagram showing a main configuration of the vibration displacement measuring apparatus according to the second embodiment of the present invention. In FIG. 7, the same components as those shown in FIG. As shown in FIG. 7, the vibration displacement measuring device 2 of the present embodiment has a configuration in which the injection unit 14 of the vibration displacement measuring device 1 shown in FIG. 1 is replaced with a connector portion CN. Such a vibration displacement measuring apparatus 2 is capable of measuring even a part such as the inside of the measurement target DUT that cannot be directly observed.

  The other end of the polarization-maintaining optical fiber F10 (optical fiber) provided with the emitting portion 14 at one end is attached to the connector portion CN. The polarization maintaining optical fiber F10 is for guiding the probe light LP via the polarization maintaining optical fiber F3 to an irradiation position that is a position where the probe light LP is irradiated toward the measurement target DUT. By making it possible to attach such a polarization maintaining optical fiber F10, it is possible to irradiate the probe light LP from an arbitrary position and an arbitrary direction with respect to the measurement target DUT, and also, inside the measurement target DUT. Also, the probe light LP can be guided. For this reason, it becomes possible to measure the vibration or displacement of a part such as the inside of the measurement target DUT.

  In the present embodiment as well, as in the first embodiment, continuous light output from the light source unit 11 so that the measurement site of the DUT to be measured is arranged in the first half H1 or the second half H2 of the correlation peak CP. L1 is frequency-modulated, and the continuous light L1 is branched into the reference light LR and the probe light LP by the combining / branching unit 12. Then, the reference light LR reflected by the reflection unit 13 and the probe light LP reflected by the measurement target DUT are combined and received by the combining / branching unit 12, and the measurement target is obtained using the obtained light reception signal S1. The vibration or displacement of the DUT is obtained. For this reason, similarly to the first embodiment, it has a wide dynamic range and can perform measurement with higher accuracy than in the past.

[Third Embodiment]
FIG. 8 is a block diagram showing a main configuration of the vibration displacement measuring apparatus according to the third embodiment of the present invention. In FIG. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals. As shown in FIG. 8, the vibration displacement measuring device 3 of the present embodiment is branched instead of the branching unit 12, the reflecting unit 13, and the polarization maintaining optical fibers F <b> 2 to F <b> 4 of the vibration displacement measuring device 1 shown in FIG. 1. This is a configuration in which a section 21, an optical circulator 22, a multiplexing section 23, and polarization maintaining optical fibers F21 to F25 are provided. Such a vibration displacement measuring device 3 is intended to improve the S / N (signal-to-noise ratio) by reducing the loss of the probe light LP.

  The branching unit 21 has one input end to which the polarization maintaining optical fiber F1 is connected and two output ends to which the polarization maintaining optical fibers F21 and F22 are respectively connected, and is input from the input end. The light to be split into two and output from the output end. Specifically, the branching unit 21 converts the light (continuous light L1) input from the input end to which the polarization maintaining optical fiber F1 is connected into the reference light LR and the probe light LP while maintaining the polarization state. The branched probe light LP is output from the output end connected to the polarization maintaining optical fiber F21, and the branched reference light LR is output from the output end connected to the polarization maintaining optical fiber F22. In addition, the branching ratio of the branching part 21 is arbitrary like the combining branching part 12 shown in FIG.

  The optical circulator 22 includes an input / output end P1 to which the polarization maintaining optical fiber F21 is connected, an input / output end P2 to which the polarization maintaining optical fiber F23 is connected, and an input / output end to which the polarization maintaining optical fiber F24 is connected. P3. The optical circulator 22 outputs light input from the input / output terminal P1 from the input / output terminal P2, outputs light input from the input / output terminal P2 from the input / output terminal P3, and inputs from the input / output terminal P3. Light is output from the input / output terminal P1. The optical circulator 22 performs the above-described light input / output while maintaining the polarization state. The polarization maintaining optical fiber F23 is also connected to the emitting unit 14.

  The multiplexing unit 23 has two input ends to which the polarization maintaining optical fibers F22 and F24 are respectively connected, and one output end to which the polarization maintaining optical fiber F25 is connected. The multiplexing unit 23 includes light (reference light LR) input from the input end to which the polarization maintaining optical fiber F22 is connected and light (probe) input from the input end to which the polarization maintaining optical fiber F24 is connected. The reflected light of the light LP is multiplexed while maintaining its polarization state, and the combined light is output from the output end to which the polarization maintaining optical fiber F25 is connected.

  Next, the operation of the vibration displacement measuring device 3 will be briefly described. When the operation is started, as in the first and second embodiments, the light source unit 11 is controlled by the control unit 18, and the continuous light L1 modulated at the modulation frequency fm determined in the initial setting process described above is the light source. Output from the unit 11. The continuous light L1 output from the light source unit 11 enters the branching unit 21 via the polarization maintaining optical fiber F1, and is branched into the reference light LR and the probe light LP while maintaining the polarization state.

  The branched probe light LP is input to the input / output terminal P1 of the optical circulator 22 after propagating through the polarization maintaining optical fiber F21, and is output from the input / output terminal P2 of the optical circulator 22 while maintaining the polarization state. . Then, after propagating through the polarization-maintaining optical fiber F21, it is emitted from the emission unit 14 to the outside of the vibration displacement measuring apparatus 1 while maintaining the polarization state, and after propagating through the optical path shown in FIG. The measurement site is irradiated. On the other hand, the branched reference light LR is input to the multiplexing unit 23 after propagating through the polarization maintaining optical fiber F22.

  The reflected light of the probe light LP applied to the DUT to be measured is incident on the emission unit 14 after propagating in the reverse direction along the optical path shown in FIG. This reflected light propagates in the polarization maintaining optical fiber F23 in the reverse direction and then enters the input / output terminal P2 of the optical circulator 22, and is output from the input / output terminal P3 of the optical circulator 22 while maintaining the polarization state. . Then, after propagating through the polarization maintaining optical fiber F24, the light enters the multiplexing unit 23 and is combined with the reference light LR. The light combined by the combining unit 23 (interference light between the reference light LR and the reflected light of the probe light LP) is propagated by the polarization maintaining optical fiber F25 and then received by the light receiving unit 15.

  As a result, the light receiving unit 15 outputs a light reception signal S1 indicating the interference intensity between the reference light LR and the reflected light of the probe light LP. The light reception signal S <b> 1 output from the light receiving unit 15 is converted into a signal that can be processed by the calculation unit 17 in the acquisition unit 16 and then input to the calculation unit 17. Then, as described above, the calculation unit 17 obtains the shape of the correlation peak CP, and uses the obtained shape of the correlation peak CP and the signal output from the acquisition unit 16 to obtain the displacement amount of the measurement target DUT. Is done.

  As described above, in the present embodiment, the optical circulator 22 is provided between the branching portion 21 and the emitting portion 14, and all the reflected light of the probe light LP input to the input / output end P2 of the optical circulator 22 is input / output end P3. Output. As a result, unlike the first and second embodiments, the reflected light of the probe light LP is not branched by the combining / branching unit 12, so that the loss of the probe light LP can be reduced. As a result, the S / N (signal to noise ratio) can be improved.

  Next, a specific configuration example of the injection unit 14 used in the first to third embodiments described above will be described. FIG. 9 is a diagram illustrating a configuration example of the injection unit in the first to third embodiments of the present invention. As shown in FIG. 9A, the emitting unit 14 is a polarization maintaining optical fiber F3, a polarization maintaining optical fiber F10, or a polarization maintaining optical fiber F23 (hereinafter abbreviated as a polarization maintaining optical fiber F3 or the like). A biconvex lens 14a (lens) is provided that is spaced from the end portion by a predetermined distance. In this biconvex lens 14a, the probe light LP emitted from the end of the polarization maintaining optical fiber F3 or the like is condensed on the measurement site of the measurement target DUT, and the probe light LP reflected by the measurement target DUT is polarized. It arrange | positions between edge parts, such as polarization-maintaining optical fiber F3, and to-be-measured object DUT so that it may concentrate on edge parts, such as wave-maintaining optical fiber F3.

  The numerical aperture (NA) of the biconvex lens 14a preferably matches the numerical aperture of the polarization maintaining optical fiber F3 or the like. Further, it is desirable that the polarization maintaining optical fiber F3 and the biconvex lens 14a are modularized so that the positional relationship between the end of the polarization maintaining optical fiber F3 and the biconvex lens 14a is not shifted. As a method for modularizing the polarization maintaining optical fiber F3 and the like and the biconvex lens 14a, for example, an arbitrary method such as fixing the polarization maintaining optical fiber F3 and the biconvex lens 14a with resin so as not to block the optical path of the probe light LP is used. Can be used.

  Here, as shown in FIG. 9B, the probe light LP condensed by the biconvex lens 14a is not condensed at a complete point, but is condensed in a spot shape having a certain width. The position where the spot diameter is minimum is the beam waist BW, and the distance in the optical axis direction where the probe light LP spreads to a predetermined size with respect to the radius of the beam waist BW is the depth of focus DOF.

  When the measurement target DUT is oscillating within the above-described depth of focus DOF, the probe light LP reflected from the measurement target DUT is polarization-maintaining light by the biconvex lens 14a as shown in FIG. The light is condensed at the end of the fiber F3 or the like and enters the polarization maintaining optical fiber F3 or the like. For this reason, when the vibration or displacement of the DUT to be measured is a minute vibration or a minute displacement that can be accommodated within the focal depth DOF, the measurement is preferably performed by the emission unit 14 having the configuration shown in FIG. Can do.

  On the other hand, when the DUT to be measured greatly deviates from the depth of focus DOF, the probe light LP reflected by the DUT to be measured exceeds the aperture of the biconvex lens 14a as shown in FIG. 9B. May spread. Thus, since the probe light LP that has spread beyond the aperture of the biconvex lens 14a is not condensed on the end of the polarization maintaining optical fiber F3 or the like, the intensity of the probe light LP (the intensity of the light reception signal S1). ), And a large vibration or displacement cannot be measured with high accuracy.

  FIG. 10 is a diagram showing another configuration example of the injection unit in the first to third embodiments of the present invention. As shown in FIG. 10, the emission unit 14 includes a cylindrical lens 14 b (lens) that is disposed at a predetermined distance from an end of the polarization maintaining optical fiber F <b> 3 or the like. The cylindrical lens 14b is disposed between the end of the polarization maintaining optical fiber F3 and the measurement target DUT so that the focal position is disposed at the end of the polarization maintaining optical fiber F3 and the like.

  The cylindrical lens 14b converts the probe light LP emitted from the end of the polarization maintaining optical fiber F3 or the like into parallel light, and converts the probe light LP reflected by the measurement target DUT to the end of the polarization maintaining optical fiber F3 or the like. Focus on the part. When such a cylindrical lens 14b is used, even if the vibration or displacement of the measurement target DUT is increased, the probe light LP reflected by the measurement target DUT is separated from the cylindrical lens 14b, and the polarization maintaining optical fiber There is no situation where the light is not collected at the end of F3 or the like. For this reason, even if the vibration or displacement of the measurement target DUT is large, the vibration or displacement of the measurement target DUT can be measured with high accuracy.

  The vibration displacement measuring apparatus according to the embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and can be freely changed within the scope of the present invention. For example, in the first and second embodiments described above, an example in which the light source unit 11, the coupling / branching unit 12, the reflection unit 13, the emission unit 14, and the light receiving unit 15 are connected by the polarization maintaining optical fibers F1 to F4 will be described. did. In the third embodiment, the light source unit 11, the branch unit 21, the optical circulator 22, the emission unit 14, the multiplexing unit 23, and the light receiving unit 15 are connected by the polarization maintaining optical fibers F1, F21 to F25. An example was described. However, an optical waveguide may be used instead of the polarization maintaining optical fibers F1 to F4 and F21 to F25, or a spatial transmission line may be used. The emitting unit 14 may use a flat lens having a refractive index distribution.

  In the above embodiment, the example in which the continuous light L1 is frequency-modulated so that the measurement site of the DUT to be measured is arranged in the first half H1 or the second half H2 of the correlation peak CP has been described. However, if the measurement site of the measurement target DUT is arranged within the correlation peak CP, the vibration or displacement of the measurement target DUT can be measured. For example, even if the measurement site of the DUT to be measured vibrates so as to straddle the first half H1 and the second half H2 of the correlation peak CP, the vibration can be measured. However, from the viewpoint of measurement accuracy, it is desirable to use a portion showing a change close to a straight line in the first half H1 or the second half H2 of the correlation peak CP.

  In the above-described embodiment, an example in which the polarization maintaining optical fibers F1 to F4, F10, and F21 to F25 are used has been described. However, instead of these, it is also possible to use a normal optical fiber having no polarization maintaining function. However, when a normal optical fiber having no polarization maintaining function is used, it is necessary to scramble the polarization states of the reference light LR and the probe light LP using a polarization scrambler or the like.

  Finally, the laser light (frequency-modulated laser light) emitted from the light source is branched into two, and the scattered light obtained by making one laser light incident on the optical fiber interferes with the other laser light, A reflectometer that observes scattered light generated according to the state in an optical fiber in a distributed manner is called an optical correlation domain reflectometer (OCDR). Since the vibration displacement measuring apparatus of the present invention is not a reflectometer but an interferometer, it can be called an optical correlation domain interferometer (OCDI).

1 to 3 Vibration displacement measuring device 11 Light source unit 12 Joint branching unit 14a Biconvex lens 14b Cylindrical lens 15 Light receiving unit 17 Calculation unit 18 Control unit 21 Branching unit CP Correlation peak DUT Measurement target F10 Polarization-maintaining optical fiber H1 First half of correlation peak Part H2 Second half of correlation peak L1 Continuous light LP Probe light LR Reference light S1 Light reception signal

For this reason, with reference to the position DP shown in FIG. 3 (the position where the correlation degree is about 0.5), the displacement amount (including the amplitude of vibration) of the DUT to be measured is the position DL (shown in FIG. 3). It is considered that the deterioration of measurement accuracy can be prevented by keeping it between the position DH (position where the correlation degree is about 0.2) and the position DH shown in FIG. 3 (position where the correlation degree is about 0.8). It is done. In the following, the position DP shown in FIG. 3 is referred to as “operation point OP”, the position DL shown in FIG. 3 is called “minimum displacement point OL”, and the position DH shown in FIG. OH ".

The branched probe light LP is input to the input / output terminal P1 of the optical circulator 22 after propagating through the polarization maintaining optical fiber F21, and is output from the input / output terminal P2 of the optical circulator 22 while maintaining the polarization state. . Then, after propagating through the polarization-maintaining optical fiber F23 , it is emitted from the emission unit 14 to the outside of the vibration displacement measuring device 3 while maintaining the polarization state, and after propagating through the optical path shown in FIG. The measurement site is irradiated. On the other hand, the branched reference light LR is input to the multiplexing unit 23 after propagating through the polarization maintaining optical fiber F22.

The reflected light of the probe light LP irradiated on the measurement target DUT is incident on the emission unit 14 after propagating in the reverse direction in the optical path shown in FIG . This reflected light propagates in the polarization maintaining optical fiber F23 in the reverse direction and then enters the input / output terminal P2 of the optical circulator 22, and is output from the input / output terminal P3 of the optical circulator 22 while maintaining the polarization state. . Then, after propagating through the polarization maintaining optical fiber F24, the light enters the multiplexing unit 23 and is combined with the reference light LR. The light combined by the combining unit 23 (interference light between the reference light LR and the reflected light of the probe light LP) is propagated through the polarization maintaining optical fiber F25 and then received by the light receiving unit 15.

Claims (10)

A vibration displacement measuring device for measuring vibration or displacement of a measurement object in a non-contact manner,
A light source unit that outputs continuous light that is frequency-modulated so that the measurement site of the measurement target is disposed within a correlation peak;
A branching section for branching the continuous light into probe light and reference light;
A light receiving unit that receives interference light between the probe light and the reference light reflected by the measurement target;
A calculation unit for obtaining vibration or displacement of the measurement object using a light reception signal output from the light reception unit;
A vibration displacement measuring device comprising:   The vibration displacement measuring apparatus according to claim 1, wherein at least a modulation period and a modulation amplitude are set in the light source unit so that the measurement site of the measurement target is disposed within a correlation peak.   The vibration displacement measuring apparatus according to claim 2, wherein the modulation period and the modulation amplitude of the light source unit are set so that the measurement site of the measurement target is arranged in the first half or the second half of the correlation peak.   The modulation period of the light source unit includes the length of the first optical path from when the probe light branched by the branching unit is reflected by the measurement target to the light receiving unit, and the reference branched by the branching unit. 4. The vibration displacement measurement according to claim 3, wherein the vibration displacement measurement is set to an integral multiple of a value obtained by dividing a difference from the length of the second optical path until the light reaches the light receiving portion by the speed of light, or a value close to the integral multiple. apparatus.   The vibration displacement measuring apparatus according to claim 3 or 4, wherein the modulation amplitude of the light source unit is set according to the magnitude of vibration or displacement of the measurement site of the measurement target.   6. The vibration displacement according to claim 1, further comprising an optical fiber that guides the probe light branched at the branching portion to an irradiation position that is a position at which the probe light is irradiated toward the object to be measured. measuring device.   The probe light that is arranged between the irradiation position and the object to be measured and that is emitted from the optical fiber is condensed on the measurement site of the object to be measured, or the probe light that is emitted from the optical fiber The vibration displacement measuring apparatus according to claim 6, further comprising a lens that converts the light into parallel light and irradiates the measurement site of the measurement target.   The vibration displacement measuring apparatus according to any one of claims 1 to 7, further comprising a control unit that controls the light source unit while referring to a calculation result of the calculation unit. A vibration displacement measuring method for measuring vibration or displacement of an object to be measured without contact,
A first step of outputting continuous light that is frequency-modulated so that the measurement site of the measurement object is located within a correlation peak;
A second step of branching the continuous light into probe light and reference light;
A third step of receiving interference light between the probe light and the reference light reflected by the measurement target;
A fourth step of obtaining vibration or displacement of the measurement object using the light reception signal obtained in the third step;
A vibration displacement measuring method comprising: Performed prior to measurement of vibration or displacement of the object to be measured,
A first initial step of irradiating a reflection mirror installed at a reference position on the optical path of the probe light with the probe light to obtain a modulation frequency of the continuous light at which the light reception signal is maximized;
A second initial step of irradiating the object to be measured with the probe light in a state where the reflection mirror is removed from the reference position, and measuring the intensity of the received light signal while changing the modulation frequency of the continuous light;
Using the measurement result of the second initial step, a third initial step of determining the modulation frequency of the continuous light so that the measurement site of the measurement target is disposed within a correlation peak;
The vibration displacement measuring method according to claim 9.