DE2017863A1 - Device for measuring the magnetic field or the current strength by the Faraday effect - Google Patents

Description

C 2169.

PATENT LAWYERS

DR. M0LLER-BOR £ ■ DR. MANITZ · DR. DEUFEL (ΈΪ DIPL-ING. FINSTERWALD ■ DIPL.-ING. GRÄMKOW

45OJ 8 MUNICH 22, ROBERT-KOCH-STR. 1

TELEPHONE 225110

Munich, April 14, 1970

COMPAGNIE GENERALE D'ELECTRICITE 54 rue, la Boe * tie, Paris ^8e, France

DEVICE FOR MEASURING THE MAGNETIC FIELD OR CURRENT

BY FARADAY EFFECT

The invention relates to improvements in an optical device for measuring the magnetic field or the current intensity. This is done by measuring the Faraday angle of rotation.

It is known that such a rotation rotates the plane of polarization of a light beam that is gyrotropic Body runs through which one lying parallel to it Exposed to a magnetic field. Under the term "gyrotropic" is .to understand a material with a considerable Verdetian constant

Magneto-optical measuring devices using the Faraday effect

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- unknown. The French patent specification 1963 »768.4 of December 19, 1969, deposited by the applicant, describes such a device in which a light beam polarized by a polarizer enters a gyrotropic body, exposed to a magnetic field generated by an electric current that is to be measured. The current flows through it the turns surrounding the gyrotropic body · The Faraday rotation angle is proportional to the product of the compression Constants of the gyrotropic body from the magnetic field and the distance traveled

A semi-transparent mirror divides the bundle of light that has traversed the gyrotropic body in two bundles of light which are analyzed by analyzers whose planes of polarization make an angle with the plane of the polarizer between Form 55 ° and 125 °, except for the angle of 90 °, at which there is no light sensitivity.

The strengths of these detected by the photoelectric cells Bundles of light are compared with each other, and the difference is in each case from the sine of the double. Faraday angle of rotation addicted. The existing devices are not very reliable, because they are not built compactly and are therefore subject to mechanical vibrations. They also respond to them atmospheric conditions and dust particles in the air,

Above all, the invention brings about a greater sensitivity to light by doubling the distance traversed in the gyrotropic body, without increasing the dimensions, as well as greater reliability thanks to the compact

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is called a "one-block device that supports the Prevents dust as well as restricts mechanical vibrations, and by a remarkable decrease in light. Loss of electricity through reflection, refraction and scattering,

To achieve these results, the invention employs an apparatus for creating a magnetic field by the Faraday effect. This device is equipped with a light source that emits a bundle of light, one of which is a linear bundle of light polarizing polarizer, a magnetic field to be measured exposed gyrotropic body that picks up the polarized light bundle at one end and rotates its plane of polarization causes an optical system consisting of two mirrors, which divides the light bundle into a first and a second partial bundle that divides each other in a constant light intensity ratio stand, two analyzers, each of which is one of the sub-bundles and the one in relation to the easy axis of the polarizer have preferred axis offset at an angle around the light beams, two electro-optical transducers, each one of the light bundles emerging from the analyzers collect devices that pick up the output signals of these two transducers and supply the value of the angle of rotation, which is proportional to the magnetic field to be measured. The device is characterized in that the optical system consists of two in the line of the second end of the gyrotropic body There is attached mirrors on which the light emerging from this end falls one after the other, the first mirror

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half and the second is completely transparent, and the mirror axes are arranged in such a way that they reflect the two partial bundles towards the second end, in opposite directions Direction to the undivided light beam, and they are at an angle to each other and in relation to the undivided light beam slightly offset, the first end being in the shape of a pyramid with three faces, of which the entry face is the undivided one The light bundle and the two exit surfaces allow the two partial bundles to pass through, and the two mirrors are spherical Concave mirrors whose apparent centers of curvature, taking into account the refraction of light rays in the vicinity of the second end lie on the edges separating the entry surface from the two exit surfaces, so that each mirror - and optically without delimitation of the pupils - the entrance surface assigned to one of the exit surfaces.

The following is a description of an embodiment according to the invention on the basis of drawings 1, 2 and 3. ■

Fig. 1 shows a cross section of the, the gyrotropic Body-containing housing, the polarizer, the two analyzers, the two mirrors, the entrance and the two exits of the light guides on one and the same side.

Fig. 2 shows in profile the gyrotropic body and the arrangement of the polarizer and the two analyzers.

Fig. 3 shows a portion of the mirror glued to a connector, the connector itself. the gyrotropic grains are glued,

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According to the exemplary embodiment shown in FIGS hits an incident light bundle 1 through a light guide on a polarizer 3? on one of the three inclined surfaces one end of a gyrotropic body 5 designed in the form of a pyramid is glued, the incident light bundle initially forming the gyrotropic body 5, such as dense flint glass, before it is reflected by a first semitransparent spherical mirror 6 »This mirror, its reflectivity is precisely determined, directs part of the light beam to a second spherical mirror 7 with total reflection, whose surface is covered with aluminum, for example? this throws the bundle back through the semi-transparent mirror, so that the light intensities of the two reflected LichtbUndel 8 and 9 are the same or in an exactly constant Relate to each other. The centers of curvature O ^ and 0 "of the two mirrors 6 and 7 are eccentric and on the Edges of the pyramid 4 arranged. These two mirrors form an eccentric meniscus lens, one edge of which is thin and the other is thick. The reflected light bundles 8 and 9 run on separate tracks on surfaces 10 and 11 of the Pyramid 4 together after they have passed a second shark the gyrotropic body 5, the one of the not illustrated electrical conductor generated magnetic field is penetrated. When exiting the surfaces 10 and 11 are the Light bundles 8 and 9 deflected so that they run in the axial direction of light guides 15 and 16, onto surfaces 10 and 11 are two analyzers, e.g.

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j whose polarization axes are angles of preferably + 60 ° and -60 ° in relation to the polarization axis of the polarizer 3. The emerging light bundles 13 and 14 of the analyzers 10 and 11 pass through the fiber optics JL5 separately and 16, which are in the immediate vicinity of the surfaces 10 and 11 and which the light bundles to compare their strengths forward two photoelectric cells not shown «

The housing 12 protects the entire device from all external influences. It is made of electrically non-conductive, made of non-magnetic material. In addition, it must be suitable for light and infrared rays of the same spectrum as that in the beams used in the measuring device must be opaque.

All parts, such as the flint glass 5, the mirrors 6 and 7, the polarizer 3, the analyzers 10 and 11 and the three light guides arranged on the same side, are housed in a dielectric material with an index close to the refractive index of the flint glass in a single mechanical, form solid block, the device thus protecting against dust, St'dsse and mechanical vibrations.. the depolarization of the light and the emergence of St'drstrahlungen is restricted.

Eg follows the explanation of some details of the operation the device.

The gyrotropic T body can be made from SF 59 flint glass from 'Schott with a refractive index η »1.915 to 0.9 microns or

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but consist of yttrium iron or yttrium aluminum garnet »

The light source can be monochrome. For example Arc lamps are used whose visible or infrared spectrum is improved by filters. The use of a laser, for example a gas laser, is recommended.

Light guides 2, 15, 16 made of glass fibers, quartz fibers or organic substances can be used. The passage of the incident light bundle 1 and the two reflected light bundles 13 and 14 is, however, possible with a single periscope consisting of several lenses and comprising a sufficient radiation field.

The picture and the object are shown next to each other. In this case, a single beam path replaces the three light guides,

The polarizers 3 and the analyzers 10 and 11 are known type: either they are based on Brewster's law, stacked glass plates, Kicol's prisms or polarizing foils made of surrounding dichroic crystals Plastic. The polarizing foils are easy on the Glue pyramid surfaces. The easy axis of the polarizer » is aligned with the eventual main axis of the gyrotropic body, creating a polarized or parallel to the The main axis of the gyrotropic body is a bundle of light is not double broken.

The device is not based on the use of any material

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limited without birefringence or mechanical stresses. The easy axes of the two analyzers form different angles with the easy axis of the polarizer, after that of the Applicant on December 19, 1969 deposited French Patent 1963.7684 these angles are advantageous symmetrical and are, for example, between + 60 ° and -60 °. The difference between the compared current intensities results a value almost proportional to twice the Faraday angle of rotation.

- The gyrotropic body can be approximately 10 cm long, and the Faraday rotation angle is approximately 1 °.

- The intersection angles of the pyramid surfaces are not greater than 7 °. The entrance surface 3 deflects the incident light bundle 1 so that it falls on the optical center of the meniscus lens. The deflection of the light bundles avoids losses of luminous flux due to the overlap between the light bundle 1 and the meniscus lens 6 ₉ 7 * The exit surfaces 10 and 11 guarantee a deflection of the light bundles 8 and 9 in such a way that the pupils between the light guides 15 and 16 and the meniscus lens 6, 7 are not limited.

The semi-transparent mirror 6 can be given a reflectivity of up to 38 in . The mirror 7 has a maximum reflection factor achieved by a suitable surface treatment? the light intensities of the reflected light bundles 8 and are then the same. The curvature of the surface 6 of the meniscus lens is selected and aligned in such a way that the entry surface 3

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the pyramid 4. optically its exit surface. 10 is assigned, and the curvature of the surface 7 of the meniscus lens is selected and aligned so that the entrance surface 3 of the pyramid is optical the second exit surface 11 is assigned.

- In the AusfUhrungsbeispiel shown in Fig. 3 is an intermediate piece 17, which can be a non-gyrotropic body can and has a surface adapted to the shape of the mirror 6, glued to the meniscus lens 6, 7 with optical adhesive. It is then glued to a surface of the gyrotropic body 5, which can be flat. The processing of this intermediate piece is lighter than that of flint glass. The same procedure can be used for the cutting of the pyramid 4 with three faces can be used, which are then glued to the other end of the gyrotropic body 5 will. The same procedure can also be used to attach one or more parts to the light guides. These parts are made according to the angles of the three Surfaces of the pyramid'4 cut.

- These improvements are common to all magneto-optical measuring devices applicable, which have one or more analyzers or polarizers. The invention enables Measurement of magnetic fields and electrical direct * or alternating currents. Sir finds generally for each, device Use their magnetic field or current despite the occurrence dangerous radiation, voltages or temperatures should be measured. It is used in particular in high-voltage networks. «

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Claims (1)

9 Π1 7 ß R 3 PATENT CLAIMS ^ A * ^w ' ^{/ οο} ° M.) Device for measuring a magnetic field by Faraday effect, equipped with a light beam emitting Light source, one that linearly polarizes this bundle of light Polarizer, exposed to the magnetic field to be measured gyrotropic body that polarized at one end Light bundle picks up and a rotation of its EoIarization level causes an optical system that divides the light beam into a first and second partial beam, the -to each other in a constant strength ratio stand, two analyzers, each of which is one of the Catches the bundle of tears and the one in the ratio ssur Preferred axis of the polarizer at an angle to the light rays have around offset preferred axis, two electro-optical transducers, each one of the from the Analyzers capture the emerging light beams, devices that pick up the output signals of these two transducers and indicate the value of the magnetic field to be measured, thereby g ek θ η η ζ e i without t that the optical system out two near the second end of the gyrotropic body (5) attached mirrors (6,7), on which one after the other; the light emerging from this end falls, the first i mirror (6) being semi-transparent and the second (7) completely transparent and the mirror axes are arranged so, that they the two part-l reflect bundles (8,9) towards the second end, namely in; opposite sighting to the undivided bundle of light, and that they are slightly offset from one another and in relation to the undivided light bundle at an angle O O 9 8 A 7/10 6 3 bad original 2, device according to claim 1, d ad urchge • indicates that the first end is cut in the form of a pyramid with three surfaces, with an entrance surface (3) capturing the undivided light bundle and the two divided light bundles pass through the two exit surfaces, and the Both mirrors (6 _f 7) are spherical concave mirrors, the apparent centers of curvature, taking into account the refraction of the light rays, in the height of the second end on the edges separating the entrance surface from the two exit areas, so that each joint - optically without delimiting the pupils - the Assigns the entry area to one of the exit areas, 3. Apparatus according to claim 2, as recognized by ζ e i c h η e t that the ontic system consists of a permeable meniscus lens, the semi-permeable front surface (6) of which the first mirror and the fully permeable one rear face (7) represents the second mirror, 4 · Device according to claim 3, characterized e η η ζ ei c hn e t that the meniscus lens on that second end of the gyrotroTPic body (5) is glued, the end being cut so that it follows the shape of the front surface (6) fits the meniscus lens. 5 device according to Ansnrueh 3, d u r c h g e identifies, that the meniscus lens is glued to the second end of the gyrotronic body (5), namely. with the help of a permeable 'intermediate piece (17) with a' -009847/1063 flat surface that can be glued to the flat surface of the second end, and with a spherical, convex surface, which is adapted to the shape of the front surface (6) of the meniscus lens. 6. Apparatus according to claim 2, characterized in that that the polarizer is glued to the entry surface (3) and the two analyzers are glued to the two exit surfaces (10, 11), 7. The device according to claim 1, characterized in that the gyrotropic body (5) is a flint glass with an index η = 1.915 to 0.9 microns. 8. Device according to claim 2, characterized in that that the first end of the gyrotropic body (5) made of a non-gyrotropic material cut pyramid (4), one surface of which on a gyrotropic body (5) delimiting plane Surface is glued. 9.Vorrichtung according to claim 1, characterized in that that the whole optical system, consisting of the gyrotropic body (5), the two mirrors (6, 7)> the polarizer (3), the two analyzers (10, 11), from a rigid, electrically insulated and non-magnetic housing is surrounded, the interior in a dielectric material m: +; a refractive index that corresponds to that of the gyrotropic grain (5) comes close, and that the whole forms a closed block. 009847/1063