JPH08146047A - Method for fixing optical part - Google Patents

Abstract

PURPOSE: To provide a method for fixing a Pockels element of a voltage sensor in a simple constitution without using an adhesive. CONSTITUTION: A polarizer 1, a 0-order λ/4 wavelength constant 2, a Pockels element 3 and an analyzer 4 are sequentially arranged on the same optical axis. An external force with suitable elasticity is applied in parallel to the optical axis to each of the λ/4 wavelength constant 2 and analyzer 4 which are on the entering side and emitting side of light to the Pockels element 3, thereby forming a face contact with the Pockels element 3 via a non-bonded face. The Pockels element 3 is fixed by the friction force generated by this face contact. An external force of suitable elasticity smaller than the external force parallel to the optical axis is applied to the Pockels element 3 at least in one direction perpendicular to the direction of the optical axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of fixing an optical component in a voltage sensor having an electro-optical effect, which is used for a light PT or the like for detecting a ground voltage of a distribution line or a drive power source voltage of a motor or the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, for example, an optical voltage sensor has a sensor section 26, an input side optical system 21, an output side optical system 22, and an optical signal processing section (not shown). The section 26 includes the polarizer 1, λ /
Comprised of a four-wave plate 2, a pocket element 3, and an analyzer 4,
Each optical component has an optical axis surface (a surface including the optical axis, which is a light incident surface or a light emitting surface) that is in contact with each other, and is bonded with an adhesive. A voltage terminal 14, a lead wire 13, and an electrode 5 are electrically connected to the Pockels element 3 for voltage application, and a measured voltage 27 is applied to the voltage terminal 14.

The optical signal processing section and the sensor section 26 are connected by an input side optical system 21 and an output side optical system 22. That is, the input side optical axis surface of the sensor section 26 is bonded to the sensor section side optical axis surface of the input side optical system 21, and the output side optical axis surface is bonded to the sensor section side optical axis surface of the output side optical system 22. It is fixed by adhesive. Further, the input side optical system 21 is composed of an input optical fiber, a ferrule 8 and a lens 9 on the optical axis, and mutual optical axis surfaces of the respective optical parts are adhered by an adhesive agent, and the output side optical system 22 also. It has the same configuration as the input side optical system 21.

An epoxy resin is used as the adhesive for the optical parts, and B is used as the Pockels element.
i ₁₂ SiO ₂₀ (BSO), KDP, LiNbO ₃ having natural birefringence, LiTaO ₃ or the like is used. In the above description, the optical axis surface is a surface perpendicular to the optical axis and has two surfaces, a light incident surface and a light emitting surface. Then, the sensor unit 26, the input side optical system 21, and the output side optical system 22 that are adhesively fixed are mechanically fixed to the lower case 25.

Next, a known optical voltage sensor will be described. As the light source of the input optical fiber 6, for example, an LED with a center wavelength of 0.88 μm is used, and a non-polarized LED is used.
Light becomes linearly polarized light after passing through the polarizer 1 of the sensor unit 24. This linearly polarized light becomes circularly polarized light when passing through the λ / 4 wave plate 2, and when this circularly polarized light passes through the Pockels element 3, the refractive index changes due to the voltage 27 applied to the Pockels element 3 and becomes elliptical. When this elliptically polarized light passes through the analyzer 4, its output changes its output intensity via the output optical fiber 7 in the light receiver in accordance with the polarization state of the light passing through the Pockels element 3. The applied voltage 27 is calculated by monitoring the light intensity (intensity).
Can be measured.

Here, the modulation degree of the light quantity is A of the light quantity.
It is the ratio of the C component to the CD component of the amount of light. by the way,
The photovoltage sensor is often used in an environment where the temperature conditions are severe outdoors, and strict performance is required for temperature characteristics, and the modulation degree change is −1% or less at −20 to 80 ° C. Is desired.

Regarding this temperature characteristic, the λ / 4 wave plate 2
In the Pockels element 3, the natural birefringence and the Pockels effect change due to the stress of the adhesive portion, and even if the Z axis of LiNbO ₃ or the like is used as the optical axis, the axial deviation of the incident light occurs, so that the temperature characteristic of the natural birefringence is improved. It has been reported that various phenomena such as appearing occur. The change in the birefringence of the λ / 4 wave plate 2 due to the stress can be relaxed by using the 0th order as the λ / 4 wave plate 2. In addition, the occurrence of natural birefringence due to axis misalignment reduces the axis misalignment angle to 0.2 ° or less by overcoming the optical axis surface precision of the optical component for 30 minutes or less, and overcomes the temperature characteristics due to axis misalignment. be able to.

However, as shown in FIG. 5, the conventional optical voltage sensor has a temperature characteristic of about 10% at maximum, and
Since the stress changes depending on the environmental conditions at the time of manufacturing the optical sensor, its temperature characteristic is not reproducible, and it is very difficult to control the temperature characteristic. A method for relaxing the stress applied to the Pockels element 3 is Not found.

[0009]

As described above, in the conventional method, since the optical axis surfaces which are in contact with each other are all bonded by the adhesive, it is impossible to control the stress applied to the Pockels element. Since the temperature characteristics are also poor and the temperature characteristics are not uniform among the optical voltage sensors, accurate voltage measurement cannot be performed, and it is necessary to evaluate all of them in order to manage the temperature characteristics, which causes a cost increase. It was.

An object of the present invention is to solve the above problems and to provide a method of fixing a Pockels element which constitutes a voltage sensor with a simple structure without using an adhesive.

[0011]

In order to achieve this object, the present invention adheres only the Pockels element, of which the Pockels effect is fluctuated by external stress, among the optical components constituting the sensor section 24 of the conventional example, with an adhesive. And a method of fixing the light on the optical axis of the Pockels element, which is on the same optical axis as the Pockels element and is arranged on the light incident side and the light emitting side of the Pockels element. By applying an elastic external force that biases each of the photons in the direction of the Pockels element in a direction parallel to the optical axis of the Pockels element portion, the photons are brought into surface contact with the Pockels element, and the frictional force generated at that time causes the contact. It is characterized by fixing the Pockels element.

Further, the Pockels element is applied with an external force having an appropriate elasticity weaker than an external force having an appropriate elasticity in a direction parallel to the optical axis in a direction perpendicular to the optical axis direction. is there.

[0013]

When the optical component is fixed by the above method, the Pockels element has no adhesive surface using an adhesive and is released from the stress generated due to the difference in the thermal expansion coefficient from the adhesive, so that the optical voltage sensor has a temperature The voltage to be measured can be accurately measured without being affected by.

[0014]

EXAMPLES Specific examples will be described in detail below. FIG.
FIG. 2 is a schematic view of an optical voltage sensor which is an embodiment of the method for fixing an optical component of the present invention, and FIG. 2 is an assembly drawing of this embodiment. As shown in FIG. 1, the optical voltage sensor includes a sensor unit 2
0, an input side optical system 21, an output side optical system 22, and an optical signal processing unit (not shown). The sensor unit 20 has a polarizer 1, a 0th-order λ / 4 wavelength on the optical axis from the light incident side. It is composed of a plate 2, a Pockels element 3, and an analyzer 4, and has a polarizer of 1-0 order λ.
Only between the / 4 wavelength plates 2, the optical axis surfaces are bonded with an adhesive. A voltage terminal 14, a lead wire 11, and an electrode 5 are electrically connected to the Pockels element 3 for voltage application, and a measured voltage 25 is applied to the voltage terminal 14.

An optical signal processing unit (not shown) and the sensor unit 20 are connected by an input side optical system 21 and an output side optical system 22, and the input side optical axis surface of the sensor unit 20 is the input side. The sensor section side optical axis surface of the optical system 21 and the output side optical axis surface are adhered and fixed to the sensor section side optical axis surface of the output side optical system 22 by an adhesive. The input side optical system 21 is composed of an input optical fiber 6, a ferrule 8 and a lens 9 on the optical axis, and the mutual optical axis surfaces of the respective optical components are adhered by an adhesive agent, and the output side optical system 22. Also has the same configuration as the input side optical system 21.

As described above, the optical parts of the optical voltage sensor are adhered by the adhesive so that the Pockels element 3 which is the first part, the polarizer 1 which is the second part, the 0th-order λ / 4 wave plate 2 and the input side optics. The system 21 is structurally divided into three parts, that is, the analyzer 4 which is the third part and the output side optical system 22.
In this embodiment, the polarizer 1 and the analyzer 4 have a U-shaped optical axis 28 in which the optical axes are bent at right angles, but the light input / output surfaces of the respective optical components coincide with the respective optical axis surfaces. ing.

The lower case 15 is provided with a groove so that the optical axes of the three parts can be aligned with each other, and the polarizer 1 and the analyzer 4 are respectively aligned with the optical axes of the first part. A housing portion 23 is provided on both side surfaces of the lateral springs 11 so that the two lateral springs 11 that urge the Pockels elements in the parallel direction can be arranged. Next, a method of assembling the optical voltage sensor of the present invention will be described based on the assembly diagram of FIG. When the three parts are arranged in the groove provided in the lower case so that their optical axes are substantially aligned with each other, and the two lateral springs 11 are arranged in the housing portion 23 provided on the side surface of the lower case, A force is applied to the part and the third part in parallel to the optical axis of the first part and in opposite directions, so that the polarizer 1 of the second part is directed toward the Pockels element, and the analyzer 4 of the third part is also applied. Each of the three parts is biased in the direction of the Pockels element, and the three parts are λ / 4 wave plates 2-Pockels element 3
The non-adhesive surface is in close contact between the Pockels element 3 and the analyzer 4, and the three parts are fixed so that the optical axes are aligned by the frictional force generated on the contact surface by the lateral spring 11.

In this way, the upper spring guide plate 16 is placed on the upper surface of the three parts while the three parts are fixed on the lower case 15. The upper spring guide plate 16 is provided with a hole 24 into which the two upper springs 13 can be inserted. The upper spring 13 is compressed so that the force of the upper spring 13 is perpendicular to the optical axis. Install in 24. In a state where the lateral spring 11 and the upper spring 13 are compressed, the spring holding case frame 17 is attached so as to cover the lower case 15 and the upper spring guide plate 16 shown in FIG. And the upper spring 1
3 is fixed in the compressed state, and the three parts forming the optical part of the sensor are also set with their optical axes permanently fixed.

As described above, in the spring-pressing optical voltage sensor of the present invention, since the pocket element does not have an adhesive surface by an adhesive, it is not affected by temperature and the temperature characteristic is as shown in FIG.
As shown in (4), it was a favorable value within ± 1%. However, the spring constant and the case size are taken into consideration so that the elastic force of the upper spring 13 in the compressed state is smaller than the elastic force of the lateral spring 11 in the compressed state. For example,
In this embodiment, the elastic force of the lateral spring 11 is about 360 g.
On the other hand, the elastic force of the upper spring 13 is about 100 g. The role of the upper spring 13 is to allow each part to have a degree of freedom in the vertical direction only with the lateral spring 11, and to prevent vibration from occurring. When the case is deformed due to temperature change due to being pressed against the lower side of the case, a force from the case may be applied to the optical component to cause a shift of the optical axis. Therefore, by making the force of the lateral spring 11 stronger than that of the upper spring 13, the interaction between the optical component and the case can be minimized.

The same epoxy resin as in the prior art is used for bonding other than between the Pockels element 3 and the 0th-order λ / 4 wave plate 2 and between the Pockels 3 and the analyzer 4. Pockels element 3
As the material, Bi ₁₂ SiO ₂₀ (BSO), KDP, LiNbO ₃ having natural birefringence, LiTaO ₃ or the like is used. Further, as the λ / 4 wave plate, the 0th order is used for stress relaxation due to adhesion. However, when a higher order λ waveplate is used, the λ waveplate can be made non-adhesive as in the present invention. it can.

The optical axis planes of the optical components such as the polarizer 1 and the analyzer 4 have a surface alignment accuracy of 30 minutes or less, and the axis deviation angle is set to 0 or 2 ° or less. The temperature characteristics are suppressed. As the case material, an inorganic material, which is small in case deformation due to temperature change, such as a ceramic material is preferable, but an organic material such as an ABS resin does not cause any problem in terms of characteristics.

Regarding the number of the lateral springs 11, the surface of the polarizer 1 or the analyzer 4 opposite to the optical axis surface is brought into contact with the inner surface of the case, and the opposite side is one spring. However, in this case, since the interaction between the case and the polarizer or the analyzer is strong, it is preferable to use a case material made of ceramic, which is small in case deformation due to temperature change. Also, the upper spring 1
Regarding the number of 3, the number of 3 does not matter as long as it is weaker than the force of the lateral spring. Further, in the embodiment, the spring is used as the elastic external force generating means, but other means having elastic force such as rubber or leaf spring may be used.

The optical voltage sensor of FIG. 1 is a pigtail type in which almost all of the sensor unit 20, the input side optical system 21 and the output side optical system 22 are housed in the case, and only the optical fiber projects from the case. On the other hand, the optical voltage sensor of FIG. 2 is a fiber insertion type in which a part of the lens holder 10 projects outside the case. The fiber insertion type of FIG. 2 has an advantage that an optical fiber can be prepared after assembling the optical voltage sensor, but on the other hand, since the lens holder 10 is exposed to the outside of the case, when an external force is applied to the lens holder 10, the optical parts of the three parts are exposed. There is also a demerit that the axis shift characteristic deteriorates, and it is suitable for use in applications where the external force is unlikely to be applied to the lens holder 10.

[0024]

As described above, according to the present invention, since the Pockels element has no surface using the adhesive and is released from the stress generated by the difference in thermal expansion from the adhesive, the optical voltage sensor is provided. The voltage to be measured can be accurately measured without being affected by temperature, and the temperature characteristics can be easily managed, so the number of management steps can be greatly reduced compared to the conventional one, and cost can be reduced. It has the effect that it can be performed.

[Brief description of drawings]

FIG. 1 is a schematic view of a spring holding type optical voltage sensor according to an embodiment of the present invention.

FIG. 2 is an assembly view of a spring holding type optical voltage sensor according to an embodiment of the present invention.

FIG. 3 is a temperature characteristic diagram of a spring holding type optical voltage sensor according to an embodiment of the present invention.

FIG. 4 is a schematic view of a conventional adhesive type optical voltage sensor.

FIG. 5 is a temperature characteristic diagram of a conventional adhesive type optical voltage sensor.

[Explanation of symbols]

 1 Polarizer 2 0th λ / 4 Wave Plate 3 Pockels Element 4 Analyzer 5 Electrode 6 Input Optical Fiber 7 Output Optical Fiber 8 Ferrule 9 Lens 10 Lens Holder 11 Side Spring 12 Upper Spring 13 Lead Wire 14 Voltage Terminal 15 Lower Case 16 Upper Spring Guide Plate 17 Spring Holding Case Frame 18 Second Part 19 Third Part 20 Sensor Part 21 Input Side Optical System 22 Output Side Optical System 23 Housing Part 24 Hole 25 Conventional Case Lower Case 26 Conventional Example Sensor Part 27 Applied Voltage (Measured voltage) 28 Optical axis

Claims (2)

[Claims] 1. A method for fixing, on an optical axis, a first optical component of an aggregate of optical components, the optical coefficient of which fluctuates due to an external stress, which is on the same optical axis as the first optical component. There is a second optical component and a third optical component respectively disposed on the light incident side and the light emitting side of the first optical component in a direction parallel to the optical axis of the first optical component. An external force having an appropriate elasticity is applied to bring it into surface contact with the first optical component via a non-adhesive surface, and the first optical component is fixed by a frictional force generated on the contact surface by the external force. How to fix optical parts. 2. An external force having an appropriate elasticity weaker than an external force having an appropriate elasticity in a direction parallel to the optical axis is applied to the first optical component in a direction perpendicular to the optical axis direction. The method for fixing an optical component according to claim 1.