JPH09251036A - Optical electric-field sensor and transformer for optical instrument using sensor thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the optical electric-field sensor, which has the simple structure without the limit on a dynamic range, and the transformer for an optical instrument having the high measuring accuracy using this sensor. SOLUTION: Transparent electrodes 9 are provided on both side surfaces of a Pockels element 3 such as LiNbO3 facing a polarizer 2 and an analyzer 5. Light is transmitted in the axial direction of a crystal (z). A voltage is applied on the same direction as the tranmitting direction of the light. When the voltage is applied, the pulse-shaped output waveform is generated, and the pulses are counted by a counter circuit 8. Furthermore, in this transformer for the optical instrument, the above described optical electric-field sensor is provided in the inside of a bushing, and the charged voltage is directly applied between both edges of the optical electric-field sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel optical electric field sensor and a transformer for optical instruments using the same.

[0002]

2. Description of the Related Art As shown in FIG. 6, a conventional general optical electric field sensor has a light source 31, a polarizer 32, a Pockels element 33, and a 1/4.
The wave plate 34, the analyzer 35, the light receiving element 36,
Electrodes 37, 37 are provided on both side surfaces of the Pockels element 33 perpendicular to the light transmission direction. When a voltage to be measured is applied between the electrodes 37, 37 of such an optical electric field sensor,
The phase difference Γ is generated in the x and y polarization components, and the phase difference is analyzed by the analyzer.
It is converted to intensity modulation at 35, and this is taken out as an electrical signal to measure the voltage.

The 1/4 wave plate 34 used here is for converting the output waveform in the case without the wave plate as shown in the upper stage of FIG. It functions as a bias device. Also, the light receiving element
The output of 36 is separated into an AC component and a DC component by a high pass filter 38 and a low pass filter 39, and AC / DC is calculated by a division circuit 40. By using this division circuit 40, the output can be made constant irrespective of the light emission power of the light source 31 and the optical path loss. Thus, the conventional optical electric field sensor requires not only a complicated optical system including the quarter-wave plate 34, but also the signal processing circuit and the division circuit.
There were complex issues, including 40.

FIG. 8 is a graph showing the relationship between the voltage and the output of the optical electric field sensor. As shown in this figure, the output changes in a curve shown in FIG. 8 according to the voltage, and decreases when the voltage exceeds the half-wave voltage Vπ. The dynamic range suitable for voltage measurement is a portion where this curve is close to a straight line, but the half-wave voltage Vπ is determined by the element length of the Pockels element 33 (distance between the electrodes 37, 37). Therefore, the measurable dynamic range is the Pockels element.
There was a limit depending on the size of 33, and there was a problem that the error would increase if it exceeded that range.

Therefore, in the conventional transformer for an optical instrument using such an optical electric field sensor, when the voltage to be measured is large, the measured voltage is divided by the capacitor 41 as shown in FIG. As shown, the measurement voltage must be divided by the resistor 42 and then the voltage must be applied to the optical electric field sensor, which causes a problem that the structure becomes complicated. Further, such a divided voltage is easily affected by a dirty state or a wet state of the surface of the porcelain insulator 43 that supports the voltage applying unit,
There is also a problem that measurement errors are likely to occur.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides an optical electric field sensor in which the optical system and the signal processing circuit can be simplified and the dynamic range is not substantially limited. Is the first purpose. Further, it is a second object of the present invention to provide a transformer for an optical instrument, which can directly apply the voltage to be measured to the optical electric field sensor without dividing the voltage, and can simplify the structure and improve the measurement accuracy. It is intended.

[0007]

The optical electric field sensor of the present invention made to solve the above problems has a transparent electrode on both end faces of a Pockels element having no natural optical rotatory power, which faces a polarizer and an analyzer. It is provided so that light can be transmitted in the crystal Z-axis direction and a voltage can be applied in the same direction as the light transmission direction, and a counter circuit for counting pulses generated by the applied voltage is provided in the output signal processing circuit. It is characterized by that. The optical instrument transformer of the present invention is characterized in that the above-mentioned optical electric field sensor is installed inside the porcelain tube, and the applied voltage is directly applied between both end faces of the optical electric field sensor.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. As shown in FIG. 1, the optical electric field sensor of the present invention comprises a light source 1, a polarizer 2, a Pockels element 3, an analyzer 5, a light receiving element 6, an amplifier 7, and a counter circuit 8. As shown in FIG. 2, the voltage is applied to the Pockels element of the conventional optical electric field sensor perpendicularly to the light transmission direction, whereas the polarization is applied to the Pockels element 3 of the optical electric field sensor of the present invention. Transparent electrodes 9, 9 are provided on both end surfaces facing the probe 2 and the analyzer 5, light is transmitted in the crystal Z-axis direction, and a voltage is applied in the same direction as the light transmission direction. As the Pockels element 3, an element having no natural optical rotatory power is used, and for example, LiNbO ₃ or the like may be used. Thus, when light is transmitted in the crystal Z-axis direction and a voltage is applied in the same direction as the light transmission direction, the half-wave voltage Vπ is not determined by the element thickness or element length of the Pockels element, but by the crystal material. It is determined.

As shown in FIG. 3, the transparent electrodes 9 and 9 described above are used.
When an AC voltage V ₁ is applied between them, the optical output from the analyzer 5 has a pulsed waveform. The frequency of the pulse is determined by the sensor applied voltage. When the applied voltage is low, the number of pulses in one cycle of the applied voltage decreases, and when the applied voltage is high, the number of pulses in one cycle of the applied voltage increases. For example, if the half-wave voltage Vπ of this waveform is 1 kV, the voltage V of 50 kV _{OP
When 1} is applied, per sensor applied voltage per cycle
A pulse of 100 peaks will occur. Therefore, if the counter circuit 8 counts this pulse, the voltage can be measured. In this case, the measurement range is not limited by the half-wave voltage Vπ as in the conventional case, and the voltage can be measured substantially unlimitedly within the allowable range of the withstand voltage characteristic of the Pockels element 3.

As described above, since the optical electric field sensor of the present invention adopts the method of counting the number of pulses, the conventional 1/4 wavelength plate and the dividing circuit are not required, and the optical system and the signal processing circuit are simplified. it can. Moreover, since the dynamic range is practically unlimited, there is an advantage that a high voltage can be directly measured.

FIG. 4 shows an embodiment of a transformer for an optical instrument according to the present invention, in which the above-mentioned optical electric field sensor is housed inside the porcelain insulator 10 and the voltage of the power supply section 11 is directly applied to the optical electric field sensor. ing. FIG. 5 is an enlarged view of an essential part of the Pockels element 3. A polarizer 2 and an analyzer 5, which also function as prisms, are provided at both upper and lower ends of the Pockels element 3, and rod lenses 12, 13 are provided.
Light is input and output through the optical fibers 14 and 15.

As shown in these figures, the transformer for an optical instrument according to the present invention can directly apply a voltage to the Pockels element 3, so that a voltage dividing capacitor and a voltage dividing resistor as in the prior art are unnecessary. Therefore, the structure can be simplified. Moreover, since the voltage can be measured by directly applying the applied voltage to the Pockels element 3, there is an advantage that the high voltage can be accurately detected without being affected by the stain or the wetting of the surface of the porcelain insulator 10.

[0013]

As described above, the optical electric field sensor of the present invention does not require a quarter-wave plate or a dividing circuit, which simplifies the optical system and the signal processing circuit and substantially limits the dynamic range. High voltage can be measured directly because there is no. Further, the optical instrument transformer of the present invention does not require a voltage dividing capacitor or a voltage dividing resistor as in the prior art, can simplify the structure, and is not affected by contamination or wetting of the surface of the insulator. There is an advantage that a high voltage can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an optical electric field sensor of the present invention.

FIG. 2 is an enlarged view of a portion of a Pockels element.

FIG. 3 is an output waveform diagram when a voltage is applied to the Pockels element.

FIG. 4 is a sectional view of a transformer for an optical instrument according to the present invention.

FIG. 5 is an enlarged view of a main part.

FIG. 6 is a diagram showing a configuration of a conventional general optical electric field sensor.

FIG. 7 is a graph showing a difference in output waveform with and without a quarter-wave plate.

FIG. 8 is a graph showing the relationship between the voltage and the output of the optical electric field sensor.

FIG. 9 is a cross-sectional view of a conventional condenser voltage dividing type transformer for an optical meter.

FIG. 10 is a cross-sectional view of a conventional resistance-voltage-dividing transformer for an optical meter.

[Explanation of symbols]

1 light source, 2 polarizer, 3 Pockels element, 5 analyzer, 6 light receiving element, 7 amplifier, 8 counter circuit, 9
Transparent electrode, 10 porcelain bushing, 11 power supply section, 12 rod lens, 13 rod lens, 14 optical fiber, 15
Optical fiber

Claims (2)

[Claims] 1. A Pockels element having no natural optical rotatory power is provided with transparent electrodes on both end surfaces facing a polarizer and an analyzer to transmit light in the crystal Z-axis direction, and a voltage is applied in the same direction as the light transmission direction. An optical electric field sensor, which is capable of being applied, and whose output signal processing circuit is provided with a counter circuit for counting the pulses generated by the applied voltage. 2. A transformer for an optical measuring instrument, wherein the optical electric field sensor according to claim 1 is installed inside a porcelain insulator, and a voltage of a voltage applying unit is directly applied between both end faces of the optical electric field sensor. .