JPH1054849A - Optical voltage/electric field measuring sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the sensitivity of an optical voltage/electric field measuring sensor against polarized light by successively providing a polarizing prism, a λ/8-plate, an electrooptic element, and a mirror on the optical axis from a light source side and by again transmitting reflected light from the mirror through the electrooptic element. SOLUTION: Only linearly polarized light 1 is obtained by making measuring light 1 incident to a polarizing prism 2 and the linearly polarized light is made incident to an electrooptic element 4 as elliptically polarized light through a λ/8-plate 3. The measuring light 1 transmitted through the element 4 is again made incident to the element 4 by reflecting the light 1 with a mirror 5. When a voltage is applied across the element 4, the plane of polarization of the light 1 changes proportionally to the applied voltage. Since the light 1 goes to and returns from the element 4, the length of the optical path of the light 1 becomes double and the plane of polarization changes twice. The light 1 having the changed plane of polarization is again made incident to the λ/8-plate 3 and made incident to the prism 2 after the plane of polarization changes in the direction in which the ellipse expands. Only the changed polarized component generated the voltage is extracted through the prism 2 and the voltage and electric field impressed upon the element 4 can be measured from the light intensity of the component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical voltage / electric field measuring sensor, and more particularly to an optical voltage / electric field measuring sensor with a reduced number of components in an optical system and increased sensitivity to the Pockels effect.

[0002]

2. Description of the Related Art In recent years, as power systems have become larger and more sophisticated, the importance of measurement and control systems in the system has increased. It has been switched to voltage and current sensors for optical applications that have excellent non-inductive properties. As a method for optically measuring a voltage and an electric field, an optical crystal (hereinafter, referred to as an electro-optical element) such as ZnTe, GaP, or LiNbO 3 is used, and the refraction of the electro-optical element is proportional to the intensity of the voltage (electric field intensity). A device utilizing a so-called primary electro-optic effect (also called Pockels effect) in which the rate changes is known.

As a photo-electric sensor using the above principle, a sensor using a one-pass method in which measurement light passes through an electro-optical element only once as shown in FIG. The emitted measurement light is incident on the polarizer 23 via the incident side multimode fiber 22, and only linearly polarized light is emitted by the action of the polarizer 23. The measurement light emitted from the polarizer 23 enters the λ / 4 plate 24, is converted into circularly polarized light by the action of the λ / 4 plate 24, and enters the electro-optical element 25. The electro-optical element 25 is provided with electrodes 26, 26 (transparent conductive film) at both ends as shown in the figure, and when a voltage is applied to the electrodes 26, 26 from a voltage source 27, the electro-optical element 25 moves in the propagation direction of the measurement light. An electric field is applied in parallel, and the polarization component of the measurement light changes in proportion to the applied voltage due to the so-called Pockels effect, resulting in elliptically polarized light. The measurement light emitted from the electro-optical element 25 enters the analyzer 28,
In the electro-optical element 25, a polarization component whose intensity is modulated in proportion to the voltage is extracted. The extracted measuring light passes through the multimode fiber 29 on the emission side, and the light is
The voltage or electric field applied to the electro-optical element 25 (Pockels element) can be measured by measuring the electrical-converted signal.

[0004]

However, in the conventional optical-electric sensor, when a crystal having a small Pockels effect of the electro-optical element is used, there are disadvantages that the measurement sensitivity is low and the number of parts is large. The present invention has been made in order to solve the above-mentioned drawbacks. The sensitivity of the optical voltage / electric field sensor is doubled for the same Pockels effect of the electro-optical element, and the cost is reduced by reducing the number of parts. An object of the present invention is to provide an optical voltage / electric field measurement sensor.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus, comprising: a polarizing prism, a λ / 8 plate, an electro-optical element, and a mirror. The polarization sensitivity is increased by sequentially arranging on the axis, reflecting the measurement light from the light source emitted from the electro-optical element by a mirror, and transmitting the measurement light again through the electro-optical element. The invention according to claim 2 of the present invention is
A polarizing prism, a λ / 8 plate, and an electro-optical element are sequentially arranged on the optical axis as viewed from a light source, and a mirror film is provided on a side surface of the electro-optical element that is perpendicular to a propagation direction of measurement light emitted from the light source. The measurement light from the light source incident on the electro-optical element is reflected by a mirror film by being attached, and the polarization sensitivity is increased by reciprocating in the electro-optical element.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on an embodiment shown in the drawings. FIG. 1 is a schematic diagram showing one embodiment of an optical unit in an optical voltage / electric field measurement sensor according to the present invention. The measuring light 1 enters the polarizing prism 2 and transmits only linearly polarized light by the action of the polarizing prism. The linearly polarized light emitted from the polarizing prism 2 is a λ / 8 plate 3
And the linearly polarized light incident on the λ / 8 plate 3 is converted into elliptically polarized light by the action of the λ / 8 plate 3 and is incident on the electro-optical element 4. The measurement light 1 transmitted through the electro-optical element 4 enters a mirror 5, is reflected by the mirror 5, and enters the electro-optical element 4 again. When a voltage or an electric field is applied to the electro-optical element 4, the polarization plane of the measurement light 1 changes in proportion to the voltage. However, in the sensor optical unit according to the present invention, the measurement light is , The optical path length is doubled, and the change in the polarization plane can be doubled, that is, the measurement sensitivity can be doubled. The measuring light whose polarization plane has changed again enters the λ / 8 plate 3, changes its polarization plane in the direction in which the coast expands, and thereafter enters the polarizing prism 2. Therefore, only the polarization component changed by the voltage or the electric field by the action of the polarizing prism 2 is extracted, and the voltage or the electric field applied to the electro-optical element 4 can be measured by the light intensity. Note that the double circles and arrows shown in the figure indicate the directions of the polarization components of the measurement light.

As another embodiment of the optical portion of the optical-electric sensor, as shown in FIG. 2, one side (the right side in the figure) of the electro-optical element 4 is mirror-polished and mirrored by means such as evaporation. By adding the film 6, the same function as the mirror 5 of FIG. 1 can be performed, and the number of components can be further reduced. In addition,
Double circles and arrows in the figure are the same as above.

FIG. 3 shows an embodiment in which a photo-electric sensor is constructed using the sensor optical section shown in FIG. 1. Electrodes 6 and 6 are added to the electro-optical element 4 of the sensor optical section shown in FIG. A voltage is applied from the voltage source 7 and the measurement light 1
A laser light source 8 as a light source, and an incident side optical fiber 9 for guiding light from the laser light source 8 to a sensor optical unit.
And a light receiving unit 11 for measuring light intensity and the measuring light
And an outgoing side optical fiber 10 for guiding the light. In the photo-electric sensor configured as described above, the measurement light emitted from the laser light source 8 is incident on the incident side optical fiber 9, propagates through the incident side fiber 9 and is incident on the polarizing prism 2. The measuring light converted to linearly polarized light by passing through the polarizing prism 2 enters the λ / 8 plate 3 and
The measurement light is converted into elliptically polarized light by the eight plates 3. Then, λ /
The measuring light emitted from the eight plates 3 enters the electro-optical element 4, and the measuring light having propagated through the electro-optical element 4 is reflected by the mirror 5, re-enters the electro-optical element 4 and passes through the optical path of the electro-optical element 4. Propagate. At this time, if the voltage of the voltage source 7 is applied to the electrodes 6, 6 to the electro-optical element 4, the polarization plane of the measurement light changes in proportion to the voltage applied to the electrodes 6, 6.

The measurement light whose polarization plane has changed is again transmitted to the λ / 8 plate 3.
, The polarization plane is changed in the direction in which the coast expands by the action of the λ / 8 plate 3, and the measurement light is incident on the polarizing prism 2. By the action of the polarizing prism 2, only the polarization component changed by the voltage applied to the electrodes 6, 6 is extracted, enters the emission-side optical fiber 10, and the measurement light transmitted through the fiber 10 is read as a voltage by the light receiving unit 11. The voltage or the electric field can be measured based on the amount of change in light intensity.

FIG. 4 shows another embodiment of the configuration of the optical-electrical sensor, which uses the sensor optical unit shown in FIG. , The input side optical fiber 9 and the output side optical fiber 1
This is an optical voltage / electric field measurement sensor configured by adding 0 and a light receiving unit 11. The operation is the same as that described with reference to FIG.

[0011]

According to the present invention, as described above, it is possible to measure even a crystal having a small Pockels effect of an electro-optical element with good sensitivity, to reduce the number of parts, and to provide an optical voltage / electric field sensor. Has a remarkable effect in realizing size reduction and cost reduction in the configuration.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical unit of an optical voltage / electric field measurement sensor according to the present invention.

FIG. 2 is a diagram showing a configuration of an optical unit of another optical voltage / electric field measurement sensor according to the present invention.

FIG. 3 is a diagram showing a configuration of an embodiment of an optical voltage / electric field measurement sensor according to the present invention.

FIG. 4 is a diagram showing a configuration of another embodiment of the optical voltage / electric field measurement sensor according to the present invention.

FIG. 5 is a diagram showing a configuration of a conventional optical voltage / electric field measurement sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 measurement light 2 polarizing prism 3 λ / 8 plate 4 electro-optic element 5 mirror 6 mirror film 7 voltage source 8 laser light source 9 incident fiber 10 emission fiber 11 light receiving unit

Claims (2)

[Claims] 1. A polarizing prism, a λ / 8 plate, an electro-optical element, and a mirror are sequentially arranged on an optical axis as viewed from a light source,
An optical voltage / electric field measurement sensor optical section, wherein a measurement light from a light source emitted from the electro-optical element is reflected by a mirror and transmitted through the electro-optical element again to increase polarization sensitivity. 2. A polarizing prism, a λ / 8 plate, and an electro-optical element are sequentially arranged on an optical axis as viewed from a light source, and the electro-optical element is perpendicular to a propagation direction of measurement light emitted from the light source from the light source. By attaching a mirror film to the side surface, measurement light from the light source incident on the electro-optical element is reflected by the mirror film, and the polarization sensitivity is increased by reciprocating in the electro-optical element. Optical voltage and electric field measurement sensor optical unit.