JPH06317613A - Optical measuring device - Google Patents

Abstract

PURPOSE:To miniaturize an optical measuring device by making rays emitted from the first optical fiber ray entrance end incident upon a reflecting mirror through a polarizer, an optical element or the like, and then converging the rays at the second optical fiber ray entrance end through the optical element, the polarizer or the like. CONSTITUTION:When an emission section 2 outputs a ray 1, which enters the ray entrance part 3a of the first optical fiber 3 and is led to its emitting end 3b. The ray 1 led to the end 3b enters a polarizer 8 and is converted into a linear polarized light 7, and enters a 1/4 wave length plate 10 and is converted into a circularly polarized light 9 and enters a Pockels element 11. The circularly polarized light 9 entering the element 11 is light-modulated and thereby converted into an elliptically polarized light 12. After reflecting from a concave mirror 13, the elliptically polarized light 12 enters the element 11 again, and is light-modulated similarly to the previous case, and when entering the polarizer 8, the light is rectangularly reflected, and liner polarized light 14 is converged to the ray entrance part 17a of the second optical fiber 17, and led to an emitting end 17 through the fiber 17 and received by a ray receiving section 18 and converted into an electric signal SL showing the quantity of received rays.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measuring device using, for example, a Pockels (electro-optical effect) element.

[0002]

2. Description of the Related Art FIG. 11 shows an optical measuring device using a conventional Pockels element. This optical measuring device is composed of a light emitting diode B or the like, which emits light A
A first optical fiber C for entering and guiding the light A from the light emitting section B; and a first optical fiber C for entering and converting the light A guided by the first optical fiber C into parallel rays E. Lens system D, and a polarizer G that receives parallel rays E from the first lens system D and converts them into linearly polarized light F, and linearly polarized light F from this polarizer G that is circularly polarized M. Converted to 1/4 wave plate N
And a Pockels element H for entering the circularly polarized light M emitted from the quarter-wave plate N and birefringently converting the entered circularly polarized light M into an elliptically polarized light J, and light emitted from the Pockels element H. An analyzer L for converting the elliptically polarized light J into a linearly polarized light T, a second lens system Q for receiving and converging the linearly polarized light T emitted from the analyzer L, and converged by the second lens system Q. From a second optical fiber S for receiving and guiding the reflected light R, and for receiving the light R guided by the second optical fiber S and converting it into an electric signal indicating the amount of received light, for example, from a photodiode, a photoelectric tube, or the like. And a light receiving part W. Then, by utilizing the Pockels effect of the Pockels element H, the voltage V applied to the Pockels element H is measured based on the output of the light receiving section W.

By the way, the above conventional optical measuring device is
Since the optical path is in one direction, there is a drawback that the device body becomes long in the optical axis direction. Further, in order to enhance the electro-optic effect and the measurement sensitivity, it is advantageous to make the Pockels element H thick in the optical axis direction, but when the crystal becomes large, the inertial force due to the vibration becomes large, so that there are restrictions in design. It was happening.
Further, conventionally, the optical axis is adjusted by two sets of optical fibers and a lens system, which has a drawback that the number of adjusting parts is increased. In addition, the demand for the optical axis adjustment accuracy is strict, and unless the optical axis is adjusted with an accuracy of several μm with respect to the ideal position, light loss occurs and correct voltage measurement becomes impossible. For this reason, there is a problem in that the adjustment of the optical axis requires skill and a long working time. In addition, the conventional device has a drawback in that it is easily affected by environment and external conditions such as temperature change and vibration.

Furthermore, the optical components such as the polarizer G, the quarter-wave plate N, the Pockels element H, and the analyzer L are fixed to the pedestal through an adhesive, but the line between the pedestal and the optical component is fixed. In order to mitigate / reduce the effect of stress fluctuations of optical parts due to the difference in expansion coefficient (this is caused by temperature changes in the external environment and causes noise), a relatively soft silicone adhesive is used. It is preferable to use the agent and make the film thickness of the adhesive at this time as thick as possible. On the other hand, in order to mitigate / reduce the effect of mechanical vibration from the external environment, which also causes noise, a relatively hard adhesive is used, and the film thickness of the adhesive at this time is
It is preferable to make the pedestal and the adhesive as thin as possible so that they are in close contact with each other, and to make the thermal expansion coefficients of the pedestal and the optical component as close as possible. On the other hand, the optical measuring device, the temperature is likely to change, and, when placed in an environment susceptible to the influence of mechanical vibration, the thermal expansion coefficient of the pedestal and the optical component as close as possible, and, The relatively soft adhesive is applied as thinly as possible to reduce noise due to heat and vibration. However, it is extremely rare that the thermal expansion coefficients of the pedestal and the optical component are completely the same, and the stress relaxation effect when a soft adhesive is thinly applied cannot be expected so much.

[0005]

As described above, the conventional optical measuring device has the drawback that the device main body becomes long in the optical axis direction, and the optical axis adjustment is complicated and requires skill and long working time. In addition, mechanical vibration from the external environment
It had a problem that it was easily affected by temperature changes. The present invention has been made in consideration of the above circumstances, and an object thereof is to provide an optical measuring device capable of solving the above-mentioned drawbacks.

[0006]

The optical measuring device of the present invention allows light emitted from the light incident end of the first optical fiber to enter a reflecting mirror via a polarizer, an optical element and the like. After
The light is reflected by this reflecting mirror, and is again focused on the light incident end of the second optical fiber via the optical element, the polarizer and the like.

[0007]

In the optical measuring device having the above-mentioned structure, the length in the optical axis direction can be remarkably shortened, so that the device can be downsized and the assembling / adjusting becomes easy.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an optical measuring device of this embodiment. This optical measuring device is composed of a light emitting section 2 which is composed of a light emitting diode or the like and outputs light 1, and a light 1 from this light emitting section 2.
For guiding light from the light entering end 3a to the light exiting end 3b
Of the optical fiber 3, a polarizer 8 which receives the light 1 emitted from the light emitting end 3b of the first optical fiber 3 and converts it into a linearly polarized light 7, and a linearly polarized light 7 from the polarizer 8. A quarter-wave plate 10 that emits light to convert it into circularly polarized light 9 and a circularly polarized light 9 that has emitted from this quarter-wave plate 10 is incident and birefringent to convert the incident circularly polarized light 9 into elliptical polarized light 12. And a pair of electrodes 11a, 11b installed opposite to the sandwiching position.
A Pockels element 11 to which a voltage to be measured is applied, a concave mirror 13 (which may be spherical or aspherical) that receives and reflects the elliptically polarized light 12 emitted from the Pockels element 11, and this concave mirror. The linearly polarized light 14 reflected by 13 and then transmitted through the Pockels element 11 and the quarter-wave plate 10 and reflected by the polarizer 8 in the direction perpendicular to the optical axis direction is incident on the light incident end 17a. Idemitsu end 1
The second optical fiber 17 is guided to 7b, and the light 16 emitted from the light emitting end 17b of the second optical fiber 17 is received and converted into an electric signal SL indicating the amount of received light, for example, a photodiode, a photoelectric tube or the like. The light receiving unit 18, a voltage calculation unit 35 that calculates an applied voltage V applied between the pair of electrodes 11a and 11b based on the electric signal SL output from the light receiving unit 18, and a voltage calculation unit 35 that calculates the applied voltage V. And a display section 36 for displaying the applied voltage V.
Here, as the Pockels element 11, LiNbO _{3 is used.}
(Lithium niobate), TiNbO ₃ (titanium niobate), quartz or the like is used. And Pockels element 1
Electrodes 11a, 1 provided on the upper and lower surfaces facing each other
The distance between 1b is set to, for example, 15 mm, the electrode 11a is connected to the power source 30 to be measured, and the electrode 11b is grounded. Power source 3 to be measured
A voltage is applied to the electrodes 11a and 11b from 0, and the purpose of the optical measuring device of this embodiment is to measure the applied voltage at this time in real time. Thus, in this optical measuring device, the concave mirror 13 is set so as to have the focal point FP in the vicinity of the light exit end 3b of the first optical fiber 3 and the light entrance end 17a of the second optical fiber 17. . That is, as shown in FIGS. 2 and 3, the concave mirror 1
The position of the focal point FP of the third optical fiber 3 is set to the inside (defocus) position of the light exit end 3b of the first optical fiber 3 and the light entrance end 17a of the second optical fiber 17. The diameter of the first optical fiber 3 is relatively larger than that of the second optical fiber 17. Furthermore, the polarizers 8 and 1
/ 4 wave plate 10, Pockels element 11 and concave mirror 13
As shown in FIGS. 4 and 5, the adhesive 21 is attached to the pedestal 20.
It is fixed through. Thus, the optical element fixing surface 20a of the pedestal 20 is provided with a grid-like groove 22 having a depth of about 0.5 mm and a width of about 1 mm, for example, and the trade name "TSE385RTV" (Toshiba Silicone). It is filled with an adhesive 21 which is relatively soft (made by the company) and which can alleviate the effect of internal stress due to the difference in linear expansion coefficient. The adhesive 21 is also applied to the optical element fixing surface 20a so as to have a thickness of about 0.01 mm or less.

Next, the operation of the optical measuring device having the above structure will be described. First, when the light 1 is output from the light emitting unit 2, the light 1 enters the light entering end 3a of the first optical fiber 3 and is guided to the light exiting end 3b. Then, the light 1 guided to the light exit end 3 b enters the polarizer 8 and is converted into linearly polarized light 7. Then, the linearly polarized light 7 emitted from the polarizer 8 is converted into circularly polarized light 9 when entering the ¼ wavelength plate 10. Next, the circularly polarized light 9 emitted from the quarter-wave plate 10 enters the Pockels element 11. At this time, the Pockels element 11 has electrodes 11a,
A high voltage is applied via 11b, for example 160 V / m
It is placed in an electric field of m. Therefore, the circularly polarized light 9 incident on the Pockels element 11 is converted into an elliptically polarized light 12 by being subjected to light modulation by the Pockels effect. Further, the elliptically polarized light 12 emitted from the Pockels element 11 is reflected by the concave mirror 13 and then enters the Pockels element 11 again and undergoes optical modulation in the same manner as before. The elliptically polarized light 40 emitted from the Pockels element 11 is converted into the linearly polarized light 41 by the quarter-wave plate 10 and then enters the polarizer 8 to be reflected in the right-angled direction so that the linearly polarized light 14 becomes the second polarized light. The light is focused on the light incident end 17 a of the optical fiber 17. That is, the light 1 emitted from the light incident end 3 a of the first optical fiber 3 enters the concave mirror 13 after passing through the polarizer 8, the quarter-wave plate 10 and the Pockels element 11, and then the concave mirror 13 At the light entrance end 1 of the second optical fiber 17 via the Pockels element 11, the quarter-wave plate 10 and the polarizer 8 again.
The light is focused on the focal point FP located at 7a. The linearly polarized light 14 is guided by the second optical fiber 17 to the light emitting end 17b, and the light 16 emitted from the light emitting end 17b is received by the light receiving unit 18 and is an electrical signal indicating the amount of light received. The signal SL is converted. Then, the voltage calculation unit 35 calculates the applied voltage V based on the linear relationship between the electric signal SL and the applied voltage V <Pockels effect> (see FIG. 6). , Display unit 36
Is displayed at.

As described above, in the optical measuring apparatus of this embodiment, the light 1 emitted from the light incident end 3a of the first optical fiber 3 is converted into the polarizer 8, the quarter-wave plate 10 and the Pockels element 11. After being made incident on the concave mirror 13 via, and reflected by this concave mirror 13, the Pockels element 11, 1/4 is again made.
The second optical fiber 1 via the wave plate 10 and the polarizer 8.
Since the light is focused on the light entrance end 17a of 7,
1st optical fiber 3 and 2nd optical fiber 1 as before
Compared with the case where 7 and 7 are arranged on the same optical axis, the length in the optical axis direction can be remarkably shortened, and the device can be downsized. Further, in the optical measuring device of this embodiment, since the light 1 emitted from the first optical fiber 3 is reciprocated in the Pockels element 11, the length of the Pockels element 11 in the optical axis direction is set. The fact that it can be halved compared to the conventional one also contributes to downsizing of the device. Furthermore, in the optical measuring device of this embodiment, since the light is condensed by the concave mirror 13, the light exit end 3b of the first optical fiber 3 and the second optical fiber 17 are incident as in the conventional case. It is not necessary to install a lens system in the vicinity of the light end portion 17a, and this also has an effect of further promoting downsizing of the device in combination with the above two effects.

Furthermore, in the optical measuring apparatus of this embodiment, the position of the focal point FP of the concave mirror 13 is at the light exit end 3b of the first optical fiber 3 and the light entrance end 17a of the second optical fiber 17. Since the first optical fiber 3 has a relatively large diameter as compared with the second optical fiber 17 while being set to the inner (defocus) position, FIG.
As shown in, the positioning error is allowed within the range of ΔD where a smooth light intensity distribution can be obtained. That is, it is possible to expand the dead zone (range of the optical error that can obtain the maximum light amount) with respect to the positioning error. This not only facilitates the assembly / positioning adjustment work, but also significantly increases the work efficiency. In addition, it is possible to minimize the influence of deterioration of measurement accuracy due to environmental changes and disturbances.

Furthermore, a polarizer 8 and a quarter wave plate 1
0, the Pockels element 11 and the concave mirror 13 are relatively soft to the pedestal 20 in which the grid-like grooves 22 are formed.
Since the optical element fixing surface 20a acts as a rigid body by being fixed through 1, the optical elements together with the pedestal 20 can vibrate integrally, and the amount of light changes due to displacement. Can be prevented. The occurrence of internal stress due to the difference in linear expansion coefficient due to temperature change is mitigated by the relatively soft adhesive 21 in the groove 22 (the adhesive 21 on the optical element fixing surface 20a is Since it is much thinner than the adhesive 21, the occurrence of internal stress is so small that it can be ignored.) It is possible to prevent deterioration of measurement accuracy due to photoelasticity. Together, these two effects can dramatically improve the stability of measurement accuracy.

Instead of the concave mirror 13 in the optical measuring device of the above embodiment, a plane reflecting mirror 60 may be used as shown in FIG. In this case, the light exit end 3b of the first optical fiber 3 and the light entrance end 1 of the second optical fiber 17
The first lens system 61 and the second lens system 6 are provided in the vicinity of 7a.
It is necessary to install 2. The first lens system 61 is
The light 1 from the first optical fiber 3 is for collimating the light 1, while the second lens system 62 includes the linearly polarized light 14
Is focused on the light incident end 17a of the second optical fiber 17. This embodiment can also achieve substantially the same operational effects as the above embodiment. For the same reason as in the above embodiment, the light exit end 3b of the first optical fiber 3 and the light entrance end 17a of the second optical fiber 17 have the first lens system 61 and the second lens system 62. It is necessary to position it at a defocusing position with respect to.

Further, instead of the concave mirror 13 of the optical measuring apparatus of the above embodiment, a corner cube-shaped reflecting mirror 70 may be used as shown in FIG. Also in this case, the first lens system 61 and the second lens system 61 are provided near the light exit end 3b of the first optical fiber 3 and the light entrance end 17a of the second optical fiber 17 as in the optical measurement device of FIG. Although it is necessary to install the lens system 62, the effect to be obtained is similar to that of the optical measuring device of the above-mentioned embodiment. Also in this case, the light exit end 3b of the first optical fiber 3 and the light entrance end 1 of the second optical fiber 17 are also provided.
7a needs to be positioned at a defocusing position with respect to the first lens system 61 and the second lens system 62.

Furthermore, in the above embodiment, the groove 2
Although the adhesive 21 is applied to both the inside and the optical element fixing surface 20a, the adhesive 21 may be applied only to the groove 22 as shown in FIG. In this case, optical components (polarizer 8, quarter wave plate 10, Pockels element 11
Since the concave mirror 13) and the pedestal 20 are in direct contact with each other,
It is possible to avoid the influence of mechanical vibration in the same manner as in the above embodiment. Further, as shown in FIG. 10, the hemispherical projections 80 are closely arranged, and the groove 8 filled with the adhesive 21 is formed.
1 may be formed in a lattice shape. In this case, since the optical component and the pedestal 20 are in point contact with each other, there is an effect of promoting the effect of mitigating the influence of internal stress due to the difference in linear expansion coefficient due to temperature change. Further, the hemispherical projections 80 may be provided separately without being in close contact with each other.

Furthermore, the first optical fiber 3 is connected to the second optical fiber.
The diameter of the spot is smaller than that of the optical fiber 17, the spot size of the first optical fiber 3 with respect to the second optical fiber 17 is sufficiently small, and even if there is some error in the plane orthogonal to the optical axis, the entire spot The dead zone may be enlarged by preventing the light from coming out of the diameter of the second optical fiber 17.

Further, in the above embodiment, the electrode 11
The a and 11b adopt the vertical modulation method provided on the upper and lower surfaces facing each other of the Pockels element 11, but the horizontal modulation method is formed by forming transparent conductive thin films on the front and rear surfaces orthogonal to the optical axis. It may be an electrode.

Furthermore, in the above embodiment, the optical element utilizing the Pockels effect is illustrated as an example.
The present invention is not limited to this, and an optical element utilizing the Kerr effect (specifically, LiNbO
₃ , TiNbO ₃ , crystal, etc.) to measure the voltage and current, and to measure the magnetic field using an optical element that utilizes the Faraday effect (specific material is the same as that for the Kerr effect). It can also be applied to things.

[0019]

According to the optical measuring device of the present invention, the light emitted from the light input end of the first optical fiber is made incident on the reflecting mirror via the polarizer, the optical element, etc. Since the light is reflected by the reflecting mirror and is again focused on the light incident end of the second optical fiber via the optical element, the polarizer, etc.,
The size of the device can be reduced.

Furthermore, since the light exit end of the first optical fiber and the light entrance end of the second optical fiber are set at the defocus position, the dead zone for positioning error can be expanded, resulting in assembly / assembly. In addition to facilitating the positioning adjustment work, the work efficiency can be significantly improved.

Furthermore, since the polarizer, the optical element, the reflecting mirror and the like are fixed to the pedestal in which the grid-like grooves are engraved with a relatively soft adhesive, the optical element fixing surface is fixed. Since it acts as a rigid body even when subjected to vibration, it is possible to vibrate each optical element together with the pedestal, and it is possible to prevent changes in the amount of light due to displacement. Further, even if an internal stress is generated due to a difference in linear expansion coefficient due to a temperature change, it is alleviated by the relatively soft adhesive in the groove, and it is possible to prevent a decrease in measurement accuracy due to photoelasticity. Thus, the combination of these two effects can dramatically improve the stability of measurement accuracy.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an optical measuring device according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of a first optical fiber of the optical measuring device according to the embodiment of the present invention.

FIG. 3 is an enlarged view of a main part of a second optical fiber of the optical measuring device according to the embodiment of the present invention.

FIG. 4 is an enlarged plan view of a pedestal of the optical measuring device according to the embodiment of the present invention.

5 is a plan view taken along the line XX in FIG.

FIG. 6 is a graph for explaining the Pockels effect.

FIG. 7 is an overall configuration diagram of an optical measuring device according to another embodiment of the present invention.

FIG. 8 is an overall configuration diagram of an optical measuring device according to another embodiment of the present invention.

FIG. 9 is a cross-sectional view showing a pedestal of an optical measuring device according to another embodiment of the present invention.

FIG. 10 is a sectional view showing a pedestal of an optical measuring device according to another embodiment of the present invention.

FIG. 11 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

2: light emitting part, 3: first optical fiber, 8: polarizer, 1
1: Pockels element, 11a, 11b: electrode, 13: concave mirror, 20: pedestal, 21: adhesive, 22: groove

Claims (9)

[Claims] 1. An optical measuring device for measuring the magnitude of an electric field or a magnetic field, comprising: a first optical fiber for guiding light of constant output from a light incident end to a light outgoing end; and a first optical fiber of the first optical fiber. A polarizer for entering and polarizing the light emitted from the light emitting end and reflecting light from the side opposite to the light from the first optical fiber in a direction intersecting the optical axis, and a polarizer from this polarizer An optical element that receives light to be birefringent and to which the electric field or magnetic field is applied, a reflecting mirror that reflects the light emitted from the optical element, and the optical element that is reflected by the reflecting mirror and then passes through the optical element. And a second optical fiber that guides the light reflected by the polarizer in a direction intersecting the optical axis direction from the light input end to the light output end, and from the light output end of the second optical fiber. Receives the emitted light and converts it into an electrical signal indicating the amount of light received That a light receiving portion, an optical measuring apparatus characterized by comprising an arithmetic unit for calculating the magnitude of the electric or magnetic field based on the output electrical signal from the light receiving portion. 2. The optical element is a Pockels element, and the electric field is applied through a pair of electrodes that are arranged opposite to each other at positions sandwiching the Pockels element. Optical measuring device. 3. The reflecting mirror is a concave mirror, and the focal point of the concave mirror is located at the light exit end of the first optical fiber and the light entrance end of the second optical fiber. The optical measuring device according to claim 1. 4. The light exit end of the first optical fiber and the light entrance end of the second optical fiber are provided at positions defocusing with respect to the concave mirror. Optical measuring device. 5. The reflecting mirror is a plane mirror, and is provided with a first lens system which is close to the light emitting end of the first optical fiber and collimates the light from the first optical fiber. At the same time, a second lens system for condensing light from the polarizer is provided in the vicinity of the light entrance end of the second optical fiber, and the optical measuring device according to claim 1. 6. The light exit end of the first optical fiber and the light entrance end of the second optical fiber are provided at positions that are defocused with respect to the first lens system and the second lens system. The optical measuring device according to claim 4, wherein 7. The optical measuring device according to claim 1, wherein the first optical fiber has a relatively large diameter with respect to the second optical fiber. 8. The optical measuring device according to claim 1, wherein at least the polarizer and the optical element are fixed to the pedestal via an adhesive. 9. The optical measurement according to claim 7, wherein the pedestal is provided with a large number of grooves, and at least the polarizer and the optical element are fixed by an adhesive agent filled in the grooves. apparatus.