JP3210517B2 - Optical vibration detection method and optical vibration detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical vibration detection method and a device for stably detecting vibration in the presence of low-frequency oscillation as disturbance.

[0002]

2. Description of the Related Art Hitherto, an optical vibration detection method and an optical vibration detection device as described below have been proposed.
For example, in the example illustrated in FIG. 6A, the object to be measured is irradiated with laser light (not shown), and the reflected light R <b> 12 reaches the beam splitter 102 via the objective lens 100 and the convex lens 101. And the same beam splitter 102
, The reflected light R12 and the reference light R13 undergo optical interference with substantially parallel light rays, and this output light R14 (hereinafter, referred to as interference light) is detected on the detection surface 103 of the photoelectric converter.
The signal is converted to an electric signal, and FM
The signal is demodulated to measure the vibration of the device under test (hereinafter referred to as prior art 1).

In the prior art 1, the reflected light R12
The reference light R13 is incident on the beam splitter 102 as parallel rays, and is output in the same space. The interference light R14 is incident on the detection surface 103 of the photoelectric converter as a parallel light beam including a beat signal having a frequency difference between the two lights, converts the beat signal into an electric signal, and performs FM demodulation.
Vibration detection was being performed.

In the example shown in FIG. 6B, the reflected light R12 and the reference light R13 are made to interfere with each other as parallel rays as in the prior art 1, and then the interference light R14 is condensed by the convex lens 114 to be detected. 115 (hereinafter, referred to as
Conventional technology 2).

In the above prior arts 1 and 2, the reflected light R12 and the reference light R13 are caused to interfere with each other as parallel rays because the reflected light R12 and the reference light R13 are treated as one-dimensional traveling waves (plane waves) at arbitrary positions. This is because theoretical analysis is easy and the degree of freedom in arranging parts is high.

[0006]

The present inventor conducted experiments using the above-mentioned prior arts 1 and 2. The insulator as the object to be measured is mechanically rocked with an amplitude of 3.5 mm (FIG. 7).
(A)), the irradiation beam diameter was 2 to 2.5 mm, the irradiation light intensity was 10 to 15 mW, and the distance to the insulator was 15 m, and the level variation of the interference beat was measured. The test conditions in the prior art 1 were such that the objective lens 100 (aperture: 50
mm, focal length: 280 mm), convex lens 101 (focal length: 20 mm), and reference light R13 (parallel ray having a beam diameter of 3 mm).

The test conditions in the prior art 2 are as follows: the objective lens 110 (aperture: 50 mm, focal length: 400 m)
m), a concave lens 111 (focal length: -30 mm), a convex lens 114 (focal length: 80 mm), and a reference light R13 (parallel ray having a beam diameter of 3 mm).

As a result of the above experiment, FIGS. 7 (c) and 7 (d)
As shown in FIG. 7, the prior art 1 (FIG. 7C) and the prior art 2
In both cases (FIG. 7D), it can be seen that the level fluctuation of the interference beat is irregular (the level does not always increase when the insulator is at the center) and large. For this reason, in the related art, when the insulator is in the swinging state, it has not been possible to stably detect the vibration.

Here, the cause of the level fluctuation will be considered. When the measured object has a curved surface, the reflection point changes with the swing of the measured object, and the optical axis of the reflected light R12 shifts,
The angle between the reflected light R12 and the reference light R13 deviates from the normal state. As a result, a planar phase difference occurs in the interference light R14.

When the two lights are superimposed, the interval δ between the interference fringes is given by
λ / sin θ. Assuming that the wavelength λ = 532 nm, δ =
6 mm (interference light R14: twice the beam diameter, interference light R14
Under the condition that a phase difference of 180 ° is generated at both ends of the above), the allowable angle shift is 0.09 mrad. Also,
Since the deviation angle is enlarged 14 times by the convex lens (objective lens) 100 and the convex lens 101, the angular deviation of the reflected light R12 incident on the convex lens is 6 μrad. This is 0.1 mm when converted to a displacement of 15 m ahead.

Therefore, it can be seen that a phase difference of 180 ° occurs due to a swing sufficiently small with respect to the swing amount performed in the experiment. When the surface of the device under test is viewed in the order of the wavelength of light, there are irregularities, and the reflected light R12 has a bright and dark pattern (phase difference).
This pattern also moves as the insulator swings, so that the level fluctuation of the interference beat becomes more complicated.

From these two points, even if the insulator is slightly swung by about 0.1 mm, a phase difference is generated in the interference light R14, local beat components are canceled by the optical-electrical converter, and the output is reduced. Is extremely reduced.

The present invention has been made in view of the problems existing in the prior art described above.
An object of the present invention is to provide an optical vibration detection method and apparatus capable of performing stable vibration detection even when an insulator as an object to be measured is in a swinging state.

[0014]

Means for Solving the Problems In order to achieve the above object, according to the present invention, an object to be measured is irradiated with laser light, and reflected light from the object to be measured and reference light serving as a frequency reference are placed in the same space. Superimposed on each other to cause optical interference, and this optical interference signal is
In the optical vibration detection method of measuring the vibration of the object to be measured by demodulating M, the reflected light and the reference light are overlapped while being converged on the same focal position, and the optical interference signal detection surface is positioned near the focal position. Is what you do.

Further, according to the present invention, there is provided an irradiation optical system for irradiating the object to be measured with a laser beam, and an optical receiving system for receiving reflected light from the object to be measured, which serves as a reference for the reflected light and frequency. In an optical vibration detection device for measuring the vibration of the object by superimposing the reference light and the reference light in the same space to cause optical interference and FM demodulating the optical interference signal, the reflected light and the reference light have the same focus. It is configured such that the light interference signal detection surface is close to the focal point position while being overlapped while converging to the position.

Further, in the present invention, the F number (focal length / aperture) of the optical system of the reflected light and the reference light is the same or near the same.

[0017]

The reflected light and the reference light can be regarded as plane waves in the vicinity of the focal position, so that optical interference occurs at the focal position as in the prior art. Here, the advantages of the method and configuration of the present invention are as follows.

Since the beam expander is not used, the angle deviation of the reflected light is not enlarged unlike the prior art. Further, the beam diameter at the interference position is small. This 2
From the point of view, unlike the related art, the phase difference does not occur in the interference light due to the change of the reflection point.

Since the reflected light pattern disappears at the focal position, it is not affected by the reflected light pattern. From the above, the phase difference hardly occurs in the interference light, and the level of the transient interference beat does not decrease.

The measurable range is determined by the beam diameter due to light diffraction. When λ = 532 nm and the diameter of the convex lens 16 in the optical system of FIG. 1 is 50 mm, the beam diameter at the focal position is about 20 μm. When this is converted into the amount of displacement at a distance of 50 m, it is about 0.4 mm. Therefore, the measurable deviation amount does not become narrow as compared with the conventional technology.

[0021]

First Embodiment Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings. First, the transmission line insulator device measured by the optical vibration detection device 7 will be described. As shown in FIG. 5, a suspension insulator 4 formed by connecting a plurality of suspension insulators 3 as objects to be measured in series is suspended from a support arm 2 of the tower 1. Same suspension insulator series 4
A transmission line 5 is supported at the lower end of the power transmission line 5. A speaker 6 for applying vibration to the suspension insulator 3 by sound waves is arranged on the ground near the tower 1. On the ground, an optical vibration detecting device 7 for detecting the vibration of the suspension insulator 3 by utilizing the interference of laser light is disposed.

Next, the optical vibration detecting device 7 will be described. As shown in FIG. 1, a laser light generator 9 is disposed in a main body case 8 of the optical vibration detection device 7. The laser light generator 9 outputs irradiation laser light R1 and reference laser light R3.

On the optical axis in front of the laser light generator 9, a first polarization beam splitter 10 for splitting a reference laser light R3 to be described later from the irradiation laser light R1 is arranged. A first concave lens 11 is arranged on a straight optical axis of the first polarization beam splitter 10, and the beam diameter of the irradiation laser beam R1 is expanded. On the optical axis in front of the first concave lens 11, a second polarization beam splitter 12 for directing the irradiation laser beam R1 is disposed. A quarter-wave plate 13 for changing the plane of polarization of light from linearly polarized light to circularly polarized light is disposed in front of the second polarization beam splitter 12.

In the main body case 8, the １ ／ wavelength plate 13
A through-hole 14 is formed in front of the lens, and a lens holding tube 15 is attached so as to surround the through-hole 14. In the lens holding cylinder 15, the second polarization beam splitter 12
The objective lens 16 is arranged on the straight optical axis of the optical system. The objective lens 16 is held by a support frame 17, and the support frame 17 is movable along the optical axis. That is, the motor 19 has the linear motion mechanism 18 on its output shaft,
By the forward / reverse rotation of 9, the objective lens 16 is moved on the optical axis. The objective lens 16 is moved by the linear motion mechanism 18, whereby the focus of the irradiation laser light R1 is adjusted.

An acousto-optic modulator 20 is arranged on the optical axis of the first polarization beam splitter 10 at a right angle reflection.
The acousto-optic modulator 20 is connected to a drive circuit (not shown) for applying a high frequency thereto. The acousto-optic modulator 20 is driven to apply a high frequency by the drive circuit, and the frequency of the reference laser beam R3 is shifted. On the optical axis of the acousto-optic modulator 20, a reflection mirror 21 for reflecting the reference laser beam R3 at right angles is arranged. A second concave lens 22 for expanding the beam diameter of the reference laser beam R3 is disposed on the reflection optical axis of the reflection mirror 21. On the optical axis of the second concave lens 22, a pair of first laser beams for focusing and condensing a reference laser beam R3 on a detection surface 26 of a photo-electric converter 25 as an optical interference signal detection surface, which will be described later. Convex lens group 2
3 are arranged facing each other. On the straight optical axis of the first convex lens group 23, a reference laser beam R3
A first beam splitter 24 that reflects light in the same direction as 2 is arranged.

An optical / electrical converter 25 is disposed on the straight optical axis of the reflected laser beam R2 incident on the first beam splitter 24 via the objective lens 16 and the second polarizing beam splitter 12, and the first beam The reference laser light R3 and the reflected laser light R2 reflected by the splitter 24 are superimposed in the same space, and are incident on the detection surface 26 of the photoelectric converter 25 as interference laser light R4.
The interference laser light R4 incident on 6 is converted from an optical signal into an electric signal. The optical-electrical converter 25 is connected to a demodulator 27 for converting an electric signal into an output signal proportional to the vibration speed of the suspension 3. A frequency (vibration) analyzer (FFT analyzer) 28 for analyzing the frequency and level of the suspension 3 is connected to the demodulator 27.

Next, the operation of the optical vibration detecting device 7 configured as described above will be described. The irradiation laser light R1 output from the laser light generator 9 is applied to the irradiation optical system 1 described above.
The porcelain insulator 3 is irradiated with light through 0, 11, 12, 13, and 16. The irradiation laser beam R1 applied to the suspension insulator 3 is reflected by the suspension insulator 3 and is incident on the objective lens 16 as a reflected laser beam R2. The reflected laser light R2 is focused on the detection surface 26 of the objective lens 16 and is incident thereon.
The first polarized beam reflected by the second polarizing beam splitter 12
The beam reaches the beam splitter 24. In the first beam splitter 24, the reflected laser light R2 is
In the same manner as described above, the reference laser beam R3 focused and focused on the detection surface
It becomes 4. The interference laser light R4 is guided to the detection surface 26 of the optical / electrical converter 25, where it is converted from an optical signal to an electric signal, and the vibration is converted into a velocity by the demodulator 27. The vibration of the insulator 3 main body is measured by this measurement, and the natural frequency of the insulator 3 is analyzed by the frequency analyzer 28.

The F-numbers (focal length / diameter) of the optical components of the reflection optical system and the reference optical system are the same so that the reflected laser light R2 has the same diameter as the reference laser light R3 in the first beam splitter 24. It is made to become.

In the vibration detecting device 7 configured as described above, the reflected laser light R2 and the reference laser light R
3 have the same diameter at the interference position (first beam splitter 24), and are focused on the detection surface 26 to converge. Therefore, the angular deviation of the reflected laser beam R2 when the suspension insulator 3 swings is not enlarged, and the beam diameter at the interference position is small. Further, the pattern of the reflected laser light R2 disappears on the detection surface 26. Due to these effects, even when the suspension insulator 3 is in a swinging state, it is possible to perform stable vibration detection as compared with the related art. Since this operation is also achieved in the second to fourth embodiments described later, the description of this operation in the second to fourth embodiments will not be repeated.

Experiments similar to those of the above-mentioned prior arts 1 and 2 were performed under the same conditions in this embodiment. At the time of this experiment, the numerical values set for each optical element were set to the objective lens 16 (aperture: 5
(0 mm, focal length: 800 mm), and the reference laser beam R3 was converged by the second concave lens 22 and the first convex lens group 23 so that the detection surface 26 of the photoelectric converter 25 becomes a focal point at F number = 16.

As a result of this experiment, as shown in FIG. 7 (b), the fluctuation of the peak level of the interference beat is smaller than in the prior arts 1 and 2 (when the suspension insulator 3 is at the center position, The level is almost at peak value). Here, to perform the FFT analysis, the S / N
It is necessary to capture vibration data with a high ratio, and during this time, it is essential that the level of the interference beat be kept at a high value. Comparing the frequency with which the interference beat is at a high level is an improvement over the prior art. Therefore, when the suspension insulator 3 as the object to be measured is in a swinging state, the frequency at which measurement can be performed is increased, and efficient vibration measurement can be performed.

[0032]

Second Embodiment Hereinafter, a second embodiment of the optical vibration detecting apparatus according to the present invention will be described in detail with reference to the drawings. The second embodiment and third and fourth embodiments described later in detail
The arrangement position at the time of measurement, the object to be measured, and the like (shown in FIG. 5) of the optical vibration detection device of the embodiment are the same as those of the first embodiment.

As shown in FIG. 2, an acousto-optic modulator 32 is arranged on the optical axis in front of the laser light generator 9. The acousto-optic modulator 32 is driven by a high-frequency driving device (not shown) to separate the components of the laser light output from the laser light generator 9 into zero-order light and first-order diffracted light whose frequency is shifted. . The zero-order light goes straight and becomes the irradiation laser light R1, and the first-order diffraction light is used as the reference laser light R3 with the optical axis shifted.

The first-order diffracted light is the first laser light R3
The light is reflected by the reflection mirror 42 and the second reflection mirror 43. On the reflection optical axis of the second reflection mirror 43, the reference laser light R3
A lens group 44 is disposed for expanding the beam diameter once and then focusing and converging on the detection surface 26. A first beam splitter 2 is provided on the front optical axis of the lens group 44.
4 are arranged, and an optical / electrical converter 25 is arranged on the reflected optical axis.

The interference laser beam R4 between the reference laser beam R3 and the reflected laser beam R2, which has been subjected to the optical interference in the first beam splitter 24, is incident on the detection surface 26 of the photoelectric converter 25. In the second embodiment, the laser light generator 9
Irradiation laser light R1 output from is irradiated on the suspension insulator 3 through the above-described irradiation optical systems 32, 11, 12, 16, and 13, and is incident on the objective lens 16 as reflected laser light R2. The reflected laser light R2 is focused on the detection surface 26 by the objective lens 16 and is condensed. Then, the reflected laser light R2 reaches the first beam splitter 24 via the second polarization beam splitter 12, and the first laser splitter 24 outputs the reference laser light. Interfered with R3. At this time, the reference laser beam R3 is also focused by the lens group 44 on the detection surface 26 and collected.

As described above, in the second embodiment, the normally discarded zero-order light is used as the irradiation laser light R1 (the reference laser light R3 in the first, third, and fourth embodiments). The first-order diffracted light whose frequency is shifted by the acousto-optic modulator 20 is used, and the remaining zero-order light is discarded.) For this reason, it is not necessary to split the laser beam into the irradiation laser beam R1 and the reference laser beam R3 using a polarizing beam splitter, and the optical vibration detecting device can be downsized.

[0037]

Third Embodiment An optical vibration detecting device according to a third embodiment of the present invention will now be described with reference to the drawings.
As shown in FIG. 3, in the irradiation optical system, a linear motion mechanism 60 is attached to the first concave lens 11, and the first concave lens 11 can move on the optical axis by the linear motion mechanism 60. First
When the concave lens 11 moves on the optical axis, the beam diameter of the irradiation laser beam R1 is expanded, and the irradiation laser beam R1 is irradiated as a reflection confirmation laser beam (not shown). Although not described in detail, the reflection confirming laser light is a beam having a larger diameter than the irradiation laser light R1. This is for the operator to find out.

A second convex lens 61 is disposed in front of the first concave lens 11, and the irradiation laser beam R1 whose beam diameter has been expanded by the first concave lens 11 is converted into a parallel beam. The objective lens 16 is not provided with a linear motion mechanism.
A third concave lens 62 is arranged between the 波長 wavelength plate 13 and the second polarization beam splitter 12. A linear motion mechanism 63 is attached to the third concave lens 62, thereby moving the third concave lens 62 to perform focus adjustment.

The reflected laser beam R2 incident on the objective lens 16 is converted into a parallel beam by the third concave lens 62 shared with the irradiation optical system. The reflected laser light R2 is reflected at right angles by the second polarization beam splitter 12. A third convex lens 64 is arranged on a right-angle optical axis of the second polarization beam splitter 12, and the reflected laser beam R 2 converted into a parallel light beam by the third concave lens 62 is focused on the detection surface 26 of the photoelectric converter 25. Are collected together.

In the optical vibration detecting device having the above-described structure, the reflected laser beam R2 is once converted into a parallel beam by the third concave lens 62 and then condensed by the third convex lens 64. It causes light interference.

According to the optical vibration detecting device of this embodiment,
Since the focus adjustment is performed by moving the third concave lens 62, the objective lens 16 can be fixed in the lens holding tube 15. Therefore, the size of the objective lens 16 can be increased, so that the vibration detection operation can be performed even when the distance to the object to be measured (the suspension 3) is large.

[0042]

Fourth Embodiment Hereinafter, an optical vibration detecting apparatus according to a fourth embodiment of the present invention will be described in detail with reference to the drawings. This embodiment differs from the first to third embodiments in that the irradiation optical system and the light receiving optical system have independent focus adjustment functions.

As shown in FIG. 4, a first concave lens 11 is arranged on the straight optical axis of the polarizing beam splitter 10, and the beam diameter of the irradiation laser beam R1 is expanded. The first concave lens 11 is moved on the optical axis by a translation mechanism 70 connected to the first concave lens 11, and is switched to an irradiation confirming laser light (not shown) and the focus of the irradiation laser light R1 is adjusted. A second convex lens 71 is disposed on the front optical axis of the first concave lens 11. A third concave lens 72 is arranged on the front optical axis of the second convex lens 71, and the beam diameter of the irradiation laser light R1 is expanded.

The fourth polarization beam splitter 12 has a fourth reflection laser beam R2 on the right-angle reflection optical axis.
A concave lens 73 is arranged. The fourth concave lens 73 is moved by the translation mechanism 74 to adjust the focus of the reflected laser beam R2. A third convex lens 75 is arranged on the optical axis of the fourth concave lens 73, and focuses and focuses the reflected laser light R2 on the detection surface 26 of the photoelectric converter 25.

In this embodiment, the optical elements 11 and 73 for adjusting the focus and the linear movement mechanisms 70 and 74 are provided respectively. In the present embodiment configured as described above, the irradiation optical system and the light receiving optical system can be independently adjusted in focus by the linear motion mechanism 70 of the first concave lens 11 and the linear motion mechanism 74 of the third concave lens 73. is there. Therefore, the vibration can be detected regardless of the beam diameter of the irradiation laser light R1.

It should be noted that the present invention is not limited to the above embodiment, and can be implemented in the following modes without departing from the spirit of the present invention. (1) The irradiation optical system and the receiving optical system are provided independently, and the optical elements of the receiving optical system and the reference optical system are overlapped while converging the reflected light and the reference light to the same focal position, and an optical interference signal Position the detection surface near the focal point. (2) Measurement is performed on the DUT other than the suspension insulator.

In addition to the technical ideas described in the claims, the technical ideas grasped by each of the above embodiments are as follows. (1) The vibration detection method according to claim 1, wherein zero-order light is used as the irradiation laser light. (2) The vibration detecting device according to claim 2, wherein a focus adjusting mechanism is provided in each of the irradiation optical system and the light receiving optical system.

[0048]

According to the present invention as described in detail above,
For example, even when the insulator as the object to be measured is in a swinging state, there is an excellent effect that stable vibration detection can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a first embodiment of an optical vibration detection device according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the optical vibration detecting device according to the present invention.

FIG. 3 is a sectional view showing a third embodiment of the optical vibration detecting device according to the present invention;

FIG. 4 is a sectional view showing a fourth embodiment of the optical vibration detecting device according to the present invention.

FIG. 5 is a front view showing a use state of the optical vibration detection device.

FIG. 6 is a schematic diagram of an apparatus used in a comparative experiment performed by the present inventor with a conventional technique.
(B) shows prior art 2.

FIG. 7 is a graph showing experimental results, in which (a) is a graph showing a vibration waveform of an insulator. (B) is a graph showing the level fluctuation of the interference beat detected by the optical vibration detection device of the present invention. (C) and (d) are graphs showing the level fluctuation of the interference beat detected by the conventional optical vibration detection device.

[Explanation of symbols]

Reference numeral 3 denotes a suspension insulator as an object to be measured; 24 a beam splitter disposed at an interference position; 25 an optical-electrical converter constituting a vibration measuring unit; 26 a detection surface as an optical interference signal detection surface; Laser light, R2 ... reflected laser light, R3 ...
Reference laser light.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yukihiro Akizuki 2-56, Suda-machi, Mizuho-ku, Nagoya Japan Insulator Co., Ltd. (72) Inventor Yasuto Suzuki 2-56, Suda-cho, Mizuho-ku, Nagoya Japan Insulator Co., Ltd. (56) References JP-A-5-281019 (JP, A) JP-A-5-264516 (JP, A) JP-A-57-192833 (JP, A) JP-A-5-172787 ( JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01H 9/00 G01N 29/00 501

Claims (3)

(57) [Claims] 1. An object to be measured is irradiated with laser light, and reflected light from the object to be measured and reference light, which is a frequency reference, are superposed in the same space to cause optical interference.
In the optical vibration detection method of measuring the vibration of the device under test by demodulating, the reflected light and the reference light are overlapped while being converged on the same focal position, and the optical interference signal detection surface is set near the focal position. An optical vibration detection method, comprising: 2. An illumination optical system for irradiating a laser beam to an object to be measured, and an optical receiving system for receiving reflected light from the object to be measured, wherein the reflected light and a reference light serving as a frequency reference are used. The optical interference is caused by superposing in the same space and causing the optical interference,
An optical vibration detection device for measuring the vibration of the device under test by performing M demodulation, wherein the reflected light and the reference light are overlapped while being converged on the same focal position, and the optical interference signal detection surface is positioned near the focal position. An optical vibration detection device characterized by being configured as follows. 3. The optical vibration detecting device according to claim 2, wherein the F number (focal length / aperture) of the optical system of the reflected light and the reference light is the same or near the same. apparatus.