JPH02146517A - Azimuth rotator - Google Patents

Abstract

PURPOSE:To prevent a detected value from being affected by temperature variation by combining a 1st phase plate which makes incident linear polarized light into elliptic polarized light with a desired azimuth and ellipticity with a 2nd phase plate which makes light transmitted through the 1st phase plate into linear polarized light. CONSTITUTION:The linear polarized light which is incident on the 1st phase plate 11 generates a phase plate theta and then comes to linear polarized light again by striking on the 2nd phase plate as a 2nd stage. Namely, the two phase plates 11 and 12 are combined together to constitute the azimuth rotator, which is provided with temperature characteristics for correction. Consequently, the quantity of variation in angle of rotation around an S2 axis with temperature is set to a desired value and rotation is performed around an S1 axis to constitute the azimuth rotator which has desired temperature characteristics. Consequently, a small-sized current transformer which is not affected by temperature variation is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical rotator, and more particularly to an optical rotator that can correct Faraday rotation angle fluctuations due to temperature fluctuations of a Faraday rotation element.

(Prior Art) A Faraday rotary element has the characteristic that its optical rotation power changes depending on the strength of the magnetic field applied to it.Using this characteristic, in recent years, instrument chambers 11i for wattmeters have been used! i! It is used in so-called optical CT.

The sixth factor is the schematic structure 1 of 90T using Faraday rotation element.
1i! In this figure, light emitted from a light source 1 enters a polarizer 2 to obtain linearly polarized light. For example, if linearly polarized light having an azimuth parallel to the X-axis is irradiated onto the next stage 7-Araday rotation element, the vibration direction of the linearly polarized light emitted from the Faraday rotation element will vary depending on the magnetic field applied to it. ,
The emitted light is input to a polarizing beam splitter and separated into an X-axis direction component and a Y-axis direction component, each of which is received by a light receiver 5.6, and the linearly polarized light is rotated by about 1 based on the amount of received light.
That is, it is possible to determine how much of the magnetic field is applied to the Faraday rotation element.

However, the optical rotation power of the 7-Alade single-rotation element is temperature dependent, so even if it is in a magnetic field of the same strength, the optical rotation angle changes with changes in ambient temperature, causing measurement errors. In order to reduce the amount of rotation, it is necessary to select a material for the Faraday rotation element that has a small amount of change in the angle of optical rotation due to temperature changes.

However, a Faraday rotator using such a material generally has a small Perdet constant and has the disadvantage that the Faraday rotator must be made large in order to obtain the desired optical rotation power.

(Object of the Invention) The present invention has been made in view of the above-mentioned drawbacks, and uses a small Faraday rotary element with a high Bellb constant, and its detected value is affected by JK temperature changes that constitute, for example, a small transformer. An object of the present invention is to provide an optical rotator in which the amount of change in the angle of optical rotation due to temperature can be arbitrarily set in order to prevent the optical rotation from occurring.

(Summary of the Invention) In order to achieve this object, the optical rotator of the present invention includes a first phase plate that converts incident linearly polarized light into elliptically polarized light with a desired orientation and ellipticity, and a light beam transmitted through the first phase plate. and a second phase plate that linearly polarizes the polarized light, and the amount of rotation angle change with respect to temperature change of the first phase plate is set to 2 of the desired optical rotation angle correction amount.
The thickness of the first phase plate is set so as to double the thickness of the first phase plate, and the amount of change in the angle of optical rotation with respect to temperature is set arbitrarily.

(Examples) Hereinafter, the present invention will be described in detail based on nine embodiments shown in the drawings.

First, in order to facilitate understanding of the present invention, each fi! of the Faraday rotation element will be explained before explaining the present invention. Let me explain a little bit about gender.

For example, the optical rotation angle θ of the Faraday rotation element in the state shown in FIG. 7 can be expressed as θ=V@N,I.

That is, the larger the Verdet constant, the equivalent linkage number, and the current flowing through the conductor, the larger the optical rotation angle 0, and the ability to detect the height can be obtained. Therefore, when a Faraday rotary element is used as a current transformer for small current detection and is miniaturized, a large Verdet constant (2) is preferred. The Verdet constant is particularly large for ferromagnetic materials containing rare earth elements, but this has the disadvantage that the angle of rotation varies with temperature, making accurate detection difficult. It is shi.

Figure 8 is a diagram showing an example of the change in temperature-optical rotation of a Faraday rotation element. As shown in the figure, the angle of optical rotation when no magnetic field is applied at 25°C is 45deg, which is 1 for a temperature of 70°C. If there is a change in the optical rotation angle of .5 deg, the temperature-optical rotation characteristic Δ0/ΔT of the Faraday rotation element is Δ5 F/ΔT = (45 deg−46,5 de)
g/(25℃-90℃)=-1,5deg/-70
℃ = 0.0214deg/'C-...■.Therefore, to correct the temperature characteristics of the Faraday rotary element, ΔaC/ΔT=-0,0214deg/'C.=...
= ■Characteristics! The optical component may be placed before or after the Faraday rotation element.

FIG. 1 is a diagram showing the principle of the present invention. In the same figure, 11
12 is a first phase plate whose optical axis is rotated by 45 degrees relative to the incident linearly polarized light, and 12 is a second phase plate whose optical axis is parallel to the linearly polarized light incident on the first phase plate.

The linearly polarized light incident on the first phase plate 11 generates a phase difference θ, and when it enters the second phase plate 12 at the next stage, it becomes linearly polarized light again. When this state is expressed on a Poincaré sphere, as shown in Figure 2, the linearly polarized light at the first eight points enters the first phase plate and becomes S.

It rotates by 90 degrees around the axis to become circularly polarized light, and then returns to linearly polarized light by rotating by 90 degrees around the 80 axis at the second phase plate in the next stage.

In other words, it is sufficient to construct a optical rotator by combining two phase plates and provide it with temperature characteristics for correction.For this purpose, the amount of change in the rotation angle of S and shaft rotation due to temperature change can be adjusted to a desired value. Set the value to 90 degrees around the KS1 axis.
What is necessary is to rotate it to construct an optical rotator having desired temperature characteristics.

Based on this method, to configure the optical component for correcting the temperature characteristics of the Faraday rotation element described above, the material of the phase plate, the optical axis direction, The cutting angle, length, wavelength to be used, etc. may be selected, and a method for setting various parameters will be explained below using mathematical formulas.

To simplify the explanation, a Y-cut crystal plate is used as the phase plate, the wavelength used is 780 nm, and the incident angle of light is Ode.
g. The operating temperature range will be explained as 25°C to 90°C. However, the disk refractive properties peculiar to quartz are ignored.

The birefringence of quartz is n (λ)=1.53152+4369/λ”+137
8-10'/λ4=1.53152+4369/780
+1378・10/780'=1.538738
・−・・・・・・・■n (λ)=1.54022+
45057λ+1521-10 /λ=1.54766
6 ・・・・・・・・・ ■Ashi, Maki The birefringence due to temperature change is nol (λ, 'f)=n0+
(Δn,,/ΔT)ΔT=n,,+(-0,547
-10)ΔT=1.538738-0.547-101
1ΔT...■n + (λ, T) = n + (-0,65
1-10) ΔTe e =1.54766-0.651-10-'・ΔT...
...■ (However, ΔT=T-25°C) It can be expressed as follows.

10,000, coefficient of linear expansion in crystal 1/j (Δl/ΔT) 1
/l(Δl/ΔT)=(13CO3r+7sial)
-to /'C=(130)SO+7sinO)・1
0 /'C=13-10 /'C・・・・・・・・・
・■ and υ, and the angle r at which the polarization direction rotates when light enters the phase plate is r = 360/λ・llIΔne(1+1/l(Δl/
ΔT)ΔT)/ω57(Δn=ne-"<7.')
It can be expressed as ・・・・・・・・・■. Here, for example, assuming that the rotation angle F is 90 degrees, the temperature is 25 degrees Celsius.
The board thickness is 1! =90・780・10/36
0 fist 8.928・1O-8=0.0218366sm
・・・・・・・・・ ■＝21.8366/7m is calculated. If a crystal plate with this thickness is used, how much the rotation angle r changes with respect to a temperature change of 70°C. When testing the length using the formula, the results shown in Table 1 are obtained.

As is clear from Equation 0, it is sufficient to select a phase plate that is 4.61 times as thick as the above plate thickness. Therefore, the selected thickness of the phase plate is 21.8366x4.6154=100.784am.

Table 1, rotation angle '4! :90deg filter plate thickness 21.83
In the 6677m phase plate, the rotation angle changes by 0.65deg for a temperature change of 70°C, and in order to correct the fluctuation in the rotational angle due to the temperature change of the 7-Alade single-rotation element as described above, 1.5degX2=0. 65Xa a=3deg10.65 =4゜61 ・・・・・・・・・t-[Co., Ltd.] Table 2 Table 2 shows the rotation angle P with respect to temperature change when using a phase plate with a plate thickness of 100.784 am. It was calculated using Equation 8, and as is clear from the table, the rotation angle r changes by 3.01 degrees for a temperature change of 70°C.

If this phase plate with a thickness of 100.784 mm is used as a first phase plate, and the phase plate with a thickness of 21.83667 mm is used as a second phase plate, and the configuration shown in FIG. It will look like the one shown in the figure.

Figure (a) is a diagrammatic representation of the characteristics at 25°C on the Poincaré sphere, where the linearly polarized light at 8 points enters the first phase plate S, rotates around the axis K by 415 degrees and 38 degrees, and then P , aK moves. Next, when it enters the second phase plate, S
□ Rotates 90 degrees around the axis, so 27.69 degrees
It becomes linearly polarized light with a slope of . Furthermore, when the temperature changes by 70°C, the linearly polarized light at eight points enters the first phase plate S as shown in FIG.

It rotates 412.37 degrees around the axis and moves to Po.

Next, when it enters the second phase plate, S! 89°35 around the axis
Since the light is rotated by 26.19 degrees, it becomes almost linearly polarized light with an inclination of 26.19 degrees.

That is, the overall characteristics of the 1.2 phase plate are as shown in Figure 4, where the light at 8 points becomes linearly polarized light with an inclination of 27.69 deg at 25°C, and 26°19 deg at 95°C.
It converts the light into almost linearly polarized light with a slope of g, and functions as a so-called optical rotator.

When the first and second phase plates constructed in this way are constructed as shown in FIG. 5 in order to correct the temperature characteristics of the 7-Araday rotary element having the above-mentioned characteristics, the temperature change that occurs in the Faraday rotary element is The temperature-optical rotation characteristics of the optical system as a whole remain constant because the changes in the rotation angle caused by the temperature changes in the first and second phase plates have opposite characteristics and cancel each other out. I understand.

That is, the plate thickness 1 of the first phase plate may be set so that the amount of change in rotation angle ΔF of the first phase plate due to the temperature change ΔT is twice the degree of change in optical rotation ΔθF generated by the Faraday rotation element.

In the embodiment of the present invention, the optical rotation angle at 25°C of the optical rotator constructed by combining two phase plates is 1 to 2.
7.69 deg The number is not limited to this, and the desired optical rotation power can be obtained by appropriately selecting the incident angle of the light, the cutting angle of the phase plate, etc. For example, when the magnetic field is Adjust the entire optical system so that the output of the Faraday rotator when not adding 45 degrees x n (n = integer) polarization direction.When dividing the output at t'fPB8, the light amount of each spectral output is 1: 1 or 1:o, it is possible to construct a current transformer that has high detection accuracy and can be easily measured.

As mentioned above, in order to make the output of the Faraday rotation element at 25° C. and in the absence of a magnetic field into linearly polarized light with a polarization direction of 45×n, the rotation angle r in the first phase plate is set to 7′=11×180+90, In addition, the plate thickness may be selected to be 11 so that the variation Δrw of the rotation angle due to temperature change becomes the desired value. For example, in this embodiment, the rotation angle r of the first phase plate is set to 450 deg.
If a plate thickness of 109.183umY is selected so that the temperature is 450deg at 25°C as shown in Table 3.

The temperature-optical rotation characteristic of the Faraday rotating element is almost constant. It can be done.

Table 3 Also, in the embodiments of the present invention, two independent phase plates were used, but it is clear that the invention is not limited to this, and an integrated type with two layers joined together may also be used. .

(Effects of the Invention) Since the present invention is configured and functions as described above, it is possible to arbitrarily set the amount of change in the optical rotation due to temperature change, and the present invention can be used as a correcting optical component for, for example, a Faraday rotation element. By using the optical rotator according to the invention, a small current transformer can be constructed without being affected by temperature changes.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the present invention in detail, Fig. 2 is a diagram showing the principle of the invention on the Poincare sphere, and Figs. 3 and 4 are diagrams showing the function of the optical rotator of the present invention on the Poincare sphere. The diagrams shown above, FIG. 5, are diagrams showing an embodiment in which the optical rotator of the present invention is used for correcting the temperature characteristics of a Faraday rotation element, and FIG.
The figure shows an example of a current transformer using a conventionally used Faraday rotary element, Figure 7 is a diagram explaining the characteristics of the Faraday rotator, and Figure 8 shows the temperature-optical rotation of the Faraday rotator. FIG. 3 is a diagram showing an example of characteristics. １・・・・・・・・・Light source, ２・・・・・・・・・
・Polarizer, 3.7...Faraday rotation element, 4...Polarizing beam splitter, 5.
6......Receiver, 11...
...First phase plate, 12... Second phase plate. Patent applicant: Toyo Tsushinki Co., Ltd.

Claims (1)

[Claims] By combining a first phase plate that converts incident linearly polarized light into elliptically polarized light with a desired orientation and ellipticity and a second phase plate that converts the light transmitted through the first phase plate into linearly polarized light, An optical rotator characterized in that the amount of change can be arbitrarily set.