JP3250922B2 - How to fix optical components - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing an optical component in a voltage sensor having an electro-optical effect used for an optical PT for detecting a voltage between a power distribution line and a power supply voltage of a motor or the like.

[0002]

2. Description of the Related Art Conventionally, an optical voltage sensor comprises, for example, a sensor section 26, an input optical system 21, an output optical system 22, and an optical signal processing section (not shown) as shown in FIG. The unit 26 is arranged such that the deflector 1 and λ /
4 wavelength plate 2, Pokke Luz element 3 is constituted by the analyzer 4,
Each optical component has an optical axis surface (a surface including the optical axis, a light incident surface or a light emitting surface) that is in contact with each other, all of which are 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 applying a voltage, 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 optical system 21 and an output optical system 22. That is, the input-side optical axis surface of the sensor unit 26 is bonded to the sensor-side optical axis surface of the input-side optical system 21, and the output-side optical axis surface is bonded to the sensor-side optical axis surface of the output-side optical system 22. It is adhesively fixed with an agent. The input-side optical system 21 is composed of an input optical fiber, a ferrule 8, and a lens 9 on the optical axis. The optical axis surfaces of the respective optical components are bonded with an adhesive, and the output-side optical system 22 is also provided. The configuration is the same as that of the input side optical system 21.

An epoxy resin is used as the adhesive for the optical component, and a Bockels element is a Bockels 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 plane is a plane 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 optical system 21, and the output optical system 22, which are bonded and fixed, are mechanically fixed to the lower case 25.

Next, a known optical voltage sensor will be described. As a light source of the input optical fiber 6, for example, an LED having a center wavelength of 0.88 μm is used, and a non-polarized LED is used.
Is converted into linearly polarized light after passing through the polarizer 1 of the sensor section 24. When this linearly polarized light passes through the λ / 4 wavelength plate 2, it becomes circularly polarized light, 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 the elliptically polarized light passes through the analyzer 4, the output of the elliptically polarized light changes via the output optical fiber 7 in the photodetector in accordance with the polarization state of the light passing through the Pockels element 3. Is monitored and the degree of modulation of the light quantity (intensity) is calculated to apply the applied voltage 27.
Can be measured.

Here, the degree of modulation of the light amount is the A of the light amount.
This is the ratio between the C component and the CD component of the light amount. by the way,
The photovoltaic sensor is often used under severe outdoor temperature conditions, demanding strict performance in temperature characteristics, and a modulation degree change of ± 1% or less at −20 to 80 ° C. Is desired.

[0007] Regarding this temperature characteristic, the λ / 4 wavelength plate 2
The Pockels element 3 has a natural birefringence or Pockels effect that changes due to the stress of the bonding portion thereof, and the temperature characteristic of the natural birefringence due to the shift of the incident light axis even when the Z axis of LiNbO ₃ or the like is used as the optical axis. It has been reported that various phenomena occur such as appearance. The change in the birefringence of the λ / 4 wavelength plate 2 due to the stress can be reduced by using the 0th order as the λ / 4 wavelength plate 2. In addition, the occurrence of natural birefringence due to the axis deviation is achieved by setting the precision of the optical axis surface of the optical component to 30 minutes or less, thereby reducing the axis deviation angle to 0.2 ° or less, and overcoming the temperature characteristics due to the axis deviation. be able to.

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

[0009]

As described above, in the conventional method, since the optical axis surfaces that are in contact with each other are all adhered by the adhesive, it is impossible to control the stress applied to the Pockels element. The temperature characteristics are also poor, and the temperature characteristics are not uniform among the optical voltage sensors, so accurate voltage measurement cannot be performed. Had become.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems and to provide a method of fixing a Pockels element constituting a voltage sensor with a simple structure without using an adhesive.

[0011]

According to the present invention, in order to achieve this object, only the Pockels element whose Pockels effect fluctuates due to external stress among the optical components constituting the sensor section 24 of the conventional example is bonded with an adhesive. A method of fixing on the optical axis without using a λ / 4 wavelength plate which is on the same optical axis as the Pockels element and is disposed on each of the light incident side and the light exit side of the Pockels element. By applying an elastic external force to each of the photons in a direction parallel to the optical axis of the Pockels element in the direction of the Pockels element, the photons are brought into surface contact with the Pockels element, and the frictional force generated at that time causes It is characterized in that the Pockels element is fixed.

Further, the Pockels device is characterized in that an external force having an appropriate elasticity is applied in a direction perpendicular to the optical axis direction, which is weaker than an external force having an appropriate elasticity in a direction parallel to the optical axis. 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 coefficient of thermal expansion from the adhesive. The measured voltage can be accurately measured without being affected by the above.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples will be described below in detail. FIG.
FIG. 2 is a schematic view of an optical voltage sensor as an embodiment of the method for fixing an optical component according to the present invention, and FIG. 2 is an assembly view of the 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 a polarizer 1-0 order λ
The optical axis surface is bonded with an adhesive only between the 波長 wavelength plates 2. A voltage terminal 14, a lead wire 13 , and an electrode 5 are electrically connected to the Pockels element 3 for applying a voltage, and a measured voltage 25 is applied to the repression terminal 14.

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

As described above, the optical part of the optical voltage sensor is formed by the bonding of the adhesive with the Pockels element 3 as the first part, the polarizer 1 as the second part, the zero-order λ / 4 wavelength plate 2, the input side optical element, and the like. The system 21 is structurally divided into three parts, namely, 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 whose optical axis is bent at a right angle, but the light input / output surface of each optical component coincides with the respective optical axis surface. ing.

The lower case 15 is provided with a groove in which the three parts can be arranged so that their optical axes are aligned with each other, and the polarizer 1 and the analyzer 4 are respectively aligned with the optical axis of the first part. Accommodating portions 23 are provided on both side surfaces so that two horizontal springs 11 that urge in the direction of the Pockels element in a parallel direction can be arranged. Next, a method of assembling the optical voltage sensor according to the present invention will be described with reference to the assembly diagram of FIG. When the three parts are arranged in a groove provided in the lower case so that the optical axes thereof substantially coincide with each other, and two lateral springs 11 are arranged in a housing portion 23 provided on a side surface of the lower case, a second part is obtained. Forces are applied to the part and the third part in directions opposite to each other in parallel with the optical axis of the first part, and the polarizer 1 of the second part is moved in the direction of the Pockels element, and the analyzer 4 of the third part is also moved. The three parts are urged in the direction of the Pockels element, and the three parts are a λ / 4 wave plate 2-a Pockels element 3
The non-adhesive surface is closely adhered to the space 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 two upper springs 12 can be inserted, and the upper spring 12 is compressed so that the force of the upper spring 12 is applied perpendicularly to the optical axis. 24. In a state where the lateral spring 11 and the upper spring 12 are compressed, a 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
2 is fixed in a compressed state, and the three parts constituting the optical part of the sensor are also set with the optical axis permanently fixed.

[0019] As described above, the spring retainer type optical voltage sensor of the present invention, since Pokke Luz element has no adhesive surface by the adhesive, without being affected by temperature, the temperature characteristic 3
As shown in Table 2, the results were good within ± 1%. However, the spring constant and the case size are considered so that the elastic force of the upper spring 12 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 side spring 11 is about 360 g.
On the other hand, the elastic force of the upper spring 12 is about 100 g. The role of the upper spring 12, only the side spring 11 can freedom in the vertical direction in each part, the method comprising: preventing the vibration is generated, the optical component elastic force of the upper spring 12 is large down When the case is pressed down on the lower side of the case and the case is deformed due to a temperature change, a force from the case is applied to the optical component, and there is a possibility that the optical axis is shifted. Therefore, the interaction between the optical component and the case can be minimized by making the force of the lateral spring 11 stronger than the force of the upper spring 12 .

The same epoxy resin as before is used for bonding other than between the Pockels element 3 and the 0th order λ / 4 wavelength plate 2 and between the Pockels 3 and the analyzer 4. Pockels element 3
For example, Bi ₁₂ SiO ₂₀ (BSO), KDP, LiNbO ₃ having natural birefringence, LiTaO ₃ or the like is used. Although the 0th order is used as a λ / 4 wavelength plate for stress relaxation due to adhesion, when a higher order λ wavelength plate is used, it is necessary to make this λ wavelength plate non-adhesive as in the present invention. it can.

An optical component such as the polarizer 1 and the analyzer 4 has an optical axis surface having a flatness accuracy of 30 minutes or less, and an axis misalignment angle of 0.2 ° or less is used. Temperature characteristics are suppressed. As the case material, an inorganic material having a small case deformation due to a temperature change, for example, a ceramic material is preferable. However, even if an organic material such as an ABS resin is used, there is no particular problem in characteristics.

Regarding the number of the lateral springs 11, the surface of either 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 other side is connected to 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 ceramic material whose case deformation due to temperature change is small as the case material. Also, the upper spring 1
Regarding the number of three, the number does not matter particularly if it is weaker than the force of the lateral spring. In the embodiment, a spring (spring) is used as a means for generating an elastic external force. However, other means having an elastic force such as rubber or a leaf spring may be used.

The optical voltage sensor of FIG. 1 is a pigtail type in which almost all of the sensor section 20, the input side optical system 21, and the output side optical system 22 are housed in a case, and only the optical fiber protrudes 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 shown in FIG. 2 has an advantage that an optical fiber can be prepared after assembling the optical voltage sensor. However, 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 light of the three parts is emitted. There is also a demerit that the axis shift characteristic deteriorates, and it is preferable to use the lens holder 10 in applications where external force is unlikely to be applied.

[0024]

As described above, according to the present invention, the surface of the Pockels element using the adhesive is eliminated, and the Pockels element is released from the stress generated due to the difference in thermal expansion with the adhesive. The measured voltage can be measured accurately without being affected by temperature, and the temperature characteristics can be easily managed. It has the effect that it can be performed.

[Brief description of the drawings]

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

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

FIG. 3 is a temperature characteristic diagram of the spring pressing optical voltage sensor according to the 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 bonding-type optical voltage sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarizer 2 0th order 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 Lateral spring 12 Upper spring 13 Lead wire 14 Voltage terminal 15 Lower case Reference Signs List 16 Upper spring guide plate 17 Spring holding case frame 18 Second part 19 Third part 20 Sensor unit 21 Input optical system 22 Output optical system 23 Housing 24 Hole 25 Conventional lower case 26 Conventional sensor 27 Applied voltage (Measured voltage) 28 Optical axis

Claims (2)

(57) [Claims] 1. A method of fixing, on an optical axis, a first optical component having an optical coefficient that fluctuates due to an external stress in an assembly of optical components, wherein the first optical component is mounted 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 output side of the first optical component in a direction parallel to the optical axis of the first optical component. suitable <br/> bullet resistance force surface contact is through the first optical component and a non-adhesive surface by adding, to fix the first optical component by a frictional force generated in the contact surface by an external force Characteristic optical component fixing method. Wherein the first optical component, claims, characterized in that the addition of weak suitable elastic force than suitable elastic force of the optical axis direction parallel to the optical axis direction and a direction perpendicular 2. The method for fixing an optical component according to item 1.