JPH0515988B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an electric field measuring device that utilizes an electro-optical effect, and particularly to an optical electric field measuring device that measures a direct current electric field.

[Prior art]

Conventional voltage measuring devices and electric field measuring devices that utilize a medium having an electro-optic effect (hereinafter referred to as an electro-optic crystal) are mostly limited to alternating current voltages and alternating electric fields. The reason is that when an electro-optic crystal is placed in a DC electric field, generally
This is because the measured value changes over time due to its large capacitance and DC resistance, and charge concentration occurs on the crystal surface, forming a so-called surface layer, making measurement impossible.

In the above-mentioned conventional electric field measuring device using an electro-optic crystal (hereinafter referred to as an optical field strength measuring device), the electro-optic crystal is placed in an alternating current electric field, and the electro-optic crystal is placed in an alternating current electric field. The change in birefringence caused by this is detected as a light intensity signal (alternating current signal) using a polarizer, analyzer, etc., and the change in the electric field is measured. For details, see, for example, "Public Patent Publication No. 56-100364, IEICE Technical Research Report, Vol. 80, No. 6 (1980), pp. 19 to 24.
OQE80-4, Optical Applied Electric Field Sensor, etc.

The present inventors previously proposed two methods for extending the measurement target of an electric field measurement device using the electro-optic effect to include DC electric fields: 1. A method of rotating the electro-optic crystal itself; 2. Charging using the photoconductive effect They devised a method to neutralize the electric charge intermittently and filed applications for each method. However, in the above two methods, respectively,
1. The crystal processing and rotation mechanism are refined so that the amount of light transmitted does not change even when the electro-optic crystal is rotated. 2. The effective resistance value of the photoconductor is made high enough to be large enough when not irradiated with light. There are practical problems such as quality issues, and improvement measures are desired.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a new optical DC electric field measuring device that overcomes the above-mentioned difficulties in conventional optical electric field strength measuring devices and makes it possible to measure the strength of a DC electric field.

[Summary of the invention]

In order to achieve the above object, the optical DC electric field measurement device of the present invention includes a light source section, an electric field detection section that changes the intensity of light from the light source section in accordance with the electric field intensity, and an electric field detection section that changes the intensity of light from the detection section. a measurement unit that measures
It also has a transmission path that optically couples the light source section, the detection section, and the measurement section, and the detection section includes both an electro-optic crystal and a rotary switch.

The rotary switch is for intermittently neutralizing the charge caused by the charge concentration on the surface of the electro-optic crystal. As this rotary switch, a rotary switch that uses air and fluid, which does not emit electricity, is preferable to an electric switch that requires an external power source such as an electric motor. Furthermore, it is useful to use a temperature-controlled gas fluid as the gas fluid because the temperature of the electro-optic crystal can be controlled.

In the electric field detection section of this optical DC electric field measurement device, two surfaces of the electro-optic crystal are provided with electrodes.
During measurement, it is placed perpendicular to the applied DC electric field.
The rotary switch is installed near the electro-optic crystal, and both are connected by a conductor. When the rotary switch is turned on, the two surfaces perpendicular to the electric field are short-circuited, and the charges on the two surfaces are neutralized. On the other hand, when it is open, an electric field is applied to the electro-optic crystal, an electro-optic effect is induced, and a measurement state is established.

The time between the closing state and the opening state (opening time, closing time) is controlled by the shape and rotation speed of the rotary switch.

The upper limit of the closed state is not particularly limited, but since the output due to the electro-optic effect disappears when the capacitor is closed, it is determined in consideration of the convenience of measurement. Furthermore, if the charging time is too short, the charged charge cannot be sufficiently discharged, causing a problem, so a lower limit exists, but this can be determined by a simple experiment to confirm the charging time without causing any problems. Further, the upper limit of the open time is the time during which it becomes impossible to measure the electric field intensity due to the charged charges, and can be determined by a simple experiment if necessary. There is no particular lower limit for the open time, but if it is too short, it will cause trouble in measuring the electric field strength, so the open time is set within a range that does not cause any trouble.

As is well known, it is convenient to use an optical fiber as the optical transmission line.

The light source section usually includes a light emitting diode and an excitation power source for the light emitting diode.

The electric field detection section usually includes a lens, a polarizer, an electro-optic crystal, an analyzer, and a lens, in this order, between the optical fiber on the light source side and the optical fiber on the measuring section side, and as described above, the electro-optic crystal and the optical fiber. Rotary switches are arranged in parallel. Further, a λ/4 plate is inserted between the electro-optic crystal and the analyzer, if necessary. In addition to a normal analyzer, a polarizing prism such as a Wollaston prism may be used as the analyzer. The number of lenses on the output light side is one in the case of a normal analyzer, and two in the case of a polarizing prism because the light is separated into two linearly polarized lights. The light emitted from the detection section is guided to the light receiver of the measurement section through an optical fiber, and becomes an output electrical signal. This output electrical signal may be measured as is, or the light branched between the light source section and the electro-optic crystal (light that does not pass through the electro-optic crystal) and the light from the detection section may be measured using an optical receiver. The electric field strength may be calculated by converting it into a signal and inputting both electric signals to a calculation device. Furthermore, when a polarizing prism is used as an analyzer, the output light is
Since it is separated into polarized light beams, both are converted into electrical signals by a photoreceiver, and both electrical signals are input into a calculation device to calculate the electric field strength. Note that the lenses on the incident light side and the exit light side may be omitted.

In any case, in the optical DC electric field measurement device of the present invention, in the electric field detection section, the electro-optic crystal is opened and closed (opened and closed) between two planes perpendicular to the electric field application method using a gas flow or the like. It is important that the rotary switches are inserted in parallel, and other configurations may follow the conventional technology.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in more detail with reference to Examples.

FIG. 1 is a configuration diagram of the optical field strength measuring device in this embodiment. light source section 1, electric field detection section 2,
Measurement unit 3 and optical transmission line 4- that connects them
It is composed of 1, 4-2, and 4-3. The light source section 1 includes a light emitting diode 1-1 that emits light with a wavelength of 0.83 μm and its excitation power source 1-2, and the electric field detection section 2 includes rod lenses 2-1, 2-2, 23,
It consists of a polarizer 5, a Wollaston prism 6, an electro-optic crystal 7, a rotary switch 8, conductors 9-1, 9-2, a gas flow introduction pipe 10, a gas flow outlet 11, and the like. The measuring section 3 includes PIN photodiodes 3-1, 3-2 and an electrical calculation display circuit 3.
For the optical transmission lines 4-1, 4-2, and 4-3, optical fibers with a core diameter of 500 μm, a quartz core, and a plastic cladding are used.

FIG. 2 is an explanatory diagram showing the structural relationship between the rotary switch 8 and the electro-optic crystal 7 in the electric field detection section of FIG. 1, and the structural relationship between the rotary switch 8 and the conductors 9-1 and 9-2.

In the power supply unit 1, the light from the light emitting diode 1-1 excited by the excitation power supply 1-2 is transmitted through the optical fiber 4.
-1, it is guided to the electric field detection section 2. In the electric field detection unit 2, the angle between the vibration direction of the light of the polarizer 5 (direction of linearly polarized light) and the principal axis of the Wollaston prism 6 is set to 45 degrees. The light beam guided from the optical fiber cable 4-1 becomes a linearly polarized parallel light beam by the rod lens 2-1 and the polarizer 5.
The light is incident on the electro-optic crystal 7. In the electro-optic crystal 7, the ellipticity of the birefringence ellipsoid changes depending on the intensity of the electric field E, so that light is emitted from the electro-optic crystal 7 as parallel elliptically polarized light. The emitted light is guided to the Wollaston prism 6, where it becomes linearly polarized light with two orthogonal components, and rod lenses 2-2, 2-
3. Via optical fiber cables 4-2 and 4-3,
The signals are led to PIN photodiodes 3-1 and 3-2 and converted into electric signals _P1 and _P2 . The electrical calculation display circuit 30 performs the calculation S=P ₁ -P ₂ /P ₁ +P ₂ and displays a voltage value according to the external electric field strength.

In the electric field detection section, the electric field E of the electro-optic crystal 7
Electrodes 7-1 and 7-2 are attached on two surfaces perpendicular to , by vacuum evaporation. electro-optic crystal 7,
It is connected to the rotary switch 8 through conductors 9-1 and 9-2, and the rotary switch 8 is held by a rotary holder 12. The potential difference between the conductors 9-1 and 9-2 is determined by the short-circuit electrode 1 provided on the rotary switch 8.
3, as the rotary switch 8 rotates, the electric field is switched between a finite value corresponding to the measured electric field and zero.

A temperature-controlled N ₂ gas flow was used as the rotational gas flow.

In this embodiment, the opening/closing cycle of the rotary switch is approximately 100 ms when the switch is turned on (closed), and approximately 100 ms when it is opened (opened);
It was set to about 200ms.

Electric field strength measurement is possible only when the rotary switch is open, and when the rotary switch is turned on, field strength measurement is in a paused state. Note that FIG. 2a shows the traveling direction of the light, and FIG. 2b shows the rotating direction of the rotary switch.

As the electro-optic crystal 7, a Bi ₁₂ SiO ₂₀ single crystal was used. The crystal has (110), (110), and (001) planes, and the external size is 5 x 5 x 5 mm. An electric field was applied in the (110) direction, and light was propagated in the (110) direction.

FIG. 3 shows actual electric field strength measurement results. FIG. 3 shows that there is a good linear relationship between the DC electric field strength and the electrical output of the arithmetic display circuit, and it is clear that the present invention makes it possible to measure the DC electric field.

〔Effect of the invention〕

According to the present invention, there is an effect that it becomes possible to measure a direct current electric field, which was previously impossible.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the entire configuration of an optical DC electric field measuring device according to an embodiment of the present invention, Fig. 2a
is an explanatory diagram showing the structural relationship between the rotary switch and the electro-optic crystal, FIG. 2b is an explanatory diagram showing the structural relationship between the rotary switch and the conductor, and FIG. It is a graph showing measurement results of DC electric field strength. 1... Light source section, 1-1... Light emitting diode, 1
-2... Power supply, 2... Electric field detection section, 2-1, 2-
2, 2-3, ... Rod lens, 3 ... Measuring section,
3-1, 3-2...PIN photodiode, 4-
1, 4-2, 4-3...optical fiber transmission line, 5...
...Polarizer, 6...Wollaston prism, 7...
Electro-optic crystal, 8...Rotary switch, 9-1, 9
-2...Conductor, 10...Gas flow introduction pipe, 11
... Gas flow outlet, 12 ... Rotary switch holder, 13 ... Short circuit electrode, 30 ... Arithmetic display circuit.

Claims (1)

[Scope of Claims] 1. A light source section, an electric field detection section that changes the intensity of light from the light source section in accordance with electric field intensity, a measurement section that measures the intensity of light from the electric field detection section, and the light source section. and an optical transmission path that optically couples the detection section and the measurement section, and the detection section includes a medium having an electro-optic effect and a medium for discharging at least a portion of the charge near the surface of the medium. 1. An optical direct current electric field measuring device characterized by comprising a rotary switch using a rotating body rotated by a gas flow. 2. An optical direct current electric field measuring device according to claim 1, further comprising means for controlling the temperature of the gas flow.