JPH02165077A - Optical measurement of magnetic field and detector - Google Patents
Optical measurement of magnetic field and detectorInfo
- Publication number
- JPH02165077A JPH02165077A JP31947388A JP31947388A JPH02165077A JP H02165077 A JPH02165077 A JP H02165077A JP 31947388 A JP31947388 A JP 31947388A JP 31947388 A JP31947388 A JP 31947388A JP H02165077 A JPH02165077 A JP H02165077A
- Authority
- JP
- Japan
- Prior art keywords
- polarized light
- magnetic
- magnetic core
- magnetic field
- magnetization
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000003287 optical effect Effects 0.000 title claims description 11
- 238000005259 measurement Methods 0.000 title description 7
- 230000010287 polarization Effects 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims description 18
- 238000001514 detection method Methods 0.000 claims description 11
- 239000000696 magnetic material Substances 0.000 claims description 2
- 230000005374 Kerr effect Effects 0.000 abstract description 29
- 230000005415 magnetization Effects 0.000 abstract description 26
- 239000000758 substrate Substances 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 5
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 4
- 230000003321 amplification Effects 0.000 abstract description 2
- 229910052681 coesite Inorganic materials 0.000 abstract description 2
- 229910052906 cristobalite Inorganic materials 0.000 abstract description 2
- 238000003199 nucleic acid amplification method Methods 0.000 abstract description 2
- 239000000377 silicon dioxide Substances 0.000 abstract description 2
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 2
- 229910052682 stishovite Inorganic materials 0.000 abstract description 2
- 229910052905 tridymite Inorganic materials 0.000 abstract description 2
- 230000004907 flux Effects 0.000 description 12
- 230000008859 change Effects 0.000 description 7
- 239000010408 film Substances 0.000 description 3
- 238000000691 measurement method Methods 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000001678 irradiating effect Effects 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005389 magnetism Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P3/00—Measuring linear or angular speed; Measuring differences of linear or angular speeds
- G01P3/42—Devices characterised by the use of electric or magnetic means
- G01P3/44—Devices characterised by the use of electric or magnetic means for measuring angular speed
- G01P3/48—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage
- G01P3/481—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals
- G01P3/486—Devices characterised by the use of electric or magnetic means for measuring angular speed by measuring frequency of generated current or voltage of pulse signals delivered by photo-electric detectors
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Magnetic Variables (AREA)
Abstract
Description
【発明の詳細な説明】
［産業上の利用分野］
本発明は、空間の磁界を光学的方法により検出する方法
、及びその用途に供される検出素子に関する。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for detecting a spatial magnetic field by an optical method, and a detection element used for the method.
［従来技術］
空間磁界を検出する方法としては２例えばまずホール素
子が挙げられる。これはＮ形半導体に流れる電流とこの
電流に印加される磁界とにより。[Prior Art] Two methods for detecting a spatial magnetic field include, for example, a Hall element. This is due to the current flowing through the N-type semiconductor and the magnetic field applied to this current.
これらに比例する電圧が前記電流と印加磁界のいずれに
も直交する方向に表われることを利用するものである。This utilizes the fact that a voltage proportional to these appears in a direction perpendicular to both the current and the applied magnetic field.
さらには媒体上の磁化を検出するヘッドもこの一例とも
いえる。これには媒体上の記録磁化により形成された磁
界を、接近したヘッドに導入しこれを抵抗の変化ととら
える磁気抵抗効果型ヘッドと、磁束の変化としてとらえ
る磁束変化検出型磁気ヘッドとがある。Furthermore, a head that detects magnetization on a medium is also an example of this. These include a magnetoresistive head, which introduces a magnetic field formed by recording magnetization on a medium into a nearby head and interprets this as a change in resistance, and a magnetic flux change detection type magnetic head, which captures this as a change in magnetic flux.
一方磁化の光学的検出方法として、磁気カー効果を利用
し、媒体上の磁化自体を１反射された偏光の偏光面の回
転角度を測定することにより検出する方法がある。この
方法自体は空間磁界を測定するものとはいえないが、磁
化記録の再生に用いられている方式である。On the other hand, as an optical detection method of magnetization, there is a method of detecting magnetization itself on a medium by measuring the rotation angle of the plane of polarization of reflected polarized light using the magnetic Kerr effect. Although this method itself cannot be said to measure a spatial magnetic field, it is a method used for reproducing magnetization records.
［発明が解決しようとする課題］
これらの磁界或は磁化の検出方法は、夫々に長所があり
、或は夫々に欠点があるため特色に応じて応用分野を異
にし、用いられているものである。例えばホール素子は
モータの磁束検知に用いられているが、媒体上の磁化検
知素子としてはその構造上、現在のところは必ずしも適
しているとは言いがたい。[Problems to be Solved by the Invention] Each of these magnetic field or magnetization detection methods has advantages and disadvantages, so they are used in different fields of application depending on their characteristics. be. For example, Hall elements are used to detect magnetic flux in motors, but due to their structure, they are currently not necessarily suitable as magnetization sensing elements on media.
磁気抵抗効果型の磁気ヘッドは、磁束応答型であるので
低速回転する媒体ディスクの磁化検出には適するが１例
えば直線性に欠ける点或は温度特性上の欠点がある。Since magnetoresistive magnetic heads are magnetic flux responsive, they are suitable for detecting the magnetization of medium disks rotating at low speeds, but they have drawbacks such as lack of linearity and temperature characteristics.
磁束変化検出型の磁気ヘッドは最も多く用いられている
磁化の検出方法であるが、信号を磁束の変化としてとら
えるため媒体ディスクとの相対速度が一定以上必要であ
る。A magnetic flux change detection type magnetic head is the most commonly used method for detecting magnetization, but in order to capture a signal as a change in magnetic flux, a relative speed with the medium disk is required to be above a certain level.
更に磁気カー効果を応用し、媒体上の磁化を読みとる従
来の光学的再生方法は、媒体上の磁化に直接偏光を照射
する必要があり、媒体が高速回転している場合にはこれ
に正確かつ迅速にアクセスするための自動トラッキング
装置が不可欠であり、記録磁化へのアクセスが、この精
度、応答性に依存するという欠点がある。Furthermore, the conventional optical reproduction method that applies the magnetic Kerr effect to read the magnetization on the medium requires irradiating polarized light directly onto the magnetization on the medium, and when the medium is rotating at high speed, it is difficult to accurately and An automatic tracking device for quick access is essential, and the disadvantage is that access to recorded magnetization depends on its accuracy and responsiveness.
本発明の目的は、かかる従来の磁界或は媒体上の磁化を
測定する方法に加えて、他の一つの方法、及びその用途
に供される素子を提供することにある。An object of the present invention is to provide, in addition to the conventional method of measuring a magnetic field or magnetization on a medium, another method and an element used for the method.
［課題を解決するための手段］ 本発明の前記目的は 被測定磁界を磁気コア部に導くこと。[Means to solve the problem] The above object of the present invention is To guide the magnetic field to be measured to the magnetic core.
磁気コア表面上に形成された反射面に一定の偏光面を有
する偏光を投射すること。Projecting polarized light having a fixed plane of polarization onto a reflective surface formed on the surface of a magnetic core.
該反射面と、これにあい対して配設される反射鏡との間
において前記偏光の反射を多数回行わせた後偏光面の回
転角度を検出すること
を特徴とする磁界の光学的測定方法によって達成される
。An optical measurement method for a magnetic field, characterized in that the polarized light is reflected many times between the reflective surface and a reflective mirror disposed opposite thereto, and then the rotation angle of the polarized light surface is detected. achieved by
さらにこの方法を使用するにあたっては少なくとも一方
の表面が反射面として形成される軟磁性材料からなる磁
気コア部と。Furthermore, when using this method, a magnetic core portion made of a soft magnetic material having at least one surface formed as a reflective surface.
光の入路及び出路を備え、前記反射面とあい対して配さ
れる鏡面を備えた多重反射鏡部と。A multi-reflection mirror section including an input path and an exit path for light, and a mirror surface disposed opposite to the reflection surface.
から基本的に構成される。磁界の光学的検出素子が供さ
れる。It basically consists of An optical detection element for the magnetic field is provided.
本発明は下記の考え方にもとづくものである。The present invention is based on the following idea.
即ち、最近垂直磁化記録が可能となったことから、極力
−効果を利用する光磁気再生方式は非常に脚光を浴びて
いる。しかし、前記の如く磁化記録へのアクセスが自動
トラッキング方法によって行われるため、ディスクに溝
を形成する必要があり、且つ、自動トラッキングの駆動
機構がサーボ方式を利用するため応答性に問題があった
。従って本発明ではこれを解決するため他の磁気ヘッド
と同様、磁気コアに一旦記録磁化による磁束を導入し、
これを磁気カー効果で検出することによりアクセス性を
改善するものである。That is, since perpendicular magnetization recording has recently become possible, magneto-optical reproducing methods that utilize the -effect as much as possible are attracting much attention. However, as mentioned above, since access to magnetization recording is performed by the automatic tracking method, it is necessary to form grooves on the disk, and the automatic tracking drive mechanism uses a servo system, which causes problems in response. . Therefore, in the present invention, in order to solve this problem, like other magnetic heads, magnetic flux due to recording magnetization is once introduced into the magnetic core.
Accessibility is improved by detecting this using the magnetic Kerr effect.
この変更により、ヘッドの一部として構成した磁気コア
部の磁化を測定するにあたって、３種類の磁気カー効果
、即ち極カー効果、縦カー効果。With this change, three types of magnetic Kerr effects, namely polar Kerr effect and longitudinal Kerr effect, can be measured when measuring the magnetization of the magnetic core portion configured as a part of the head.
横カー効果の内縦カー効果又は横カー効果を用いること
が効率的に有利となる。しかしこれらのカー効果は極力
−効果に比べると数分の一程度の出力しか得られないの
で、信号対ノイズの比、即ちＳＮ比の観点からは測定上
きわめて不利となる。It is efficiently advantageous to use the vertical Kerr effect or the horizontal Kerr effect among the horizontal Kerr effects. However, these Kerr effects provide only a fraction of the output as compared to the Minimum effect, and are extremely disadvantageous in terms of measurement from the standpoint of signal-to-noise ratio, ie, S/N ratio.
そこでこのカー効果を多数回反射して生ぜしめることと
し、ＳＮ比の改善を図ったものである。Therefore, this Kerr effect is generated by multiple reflections to improve the signal-to-noise ratio.
尚この縦カー効果、横カー効果は従来においても、特定
の測定装置においては、楕円偏光利用により十分に検出
されていたものである。ここで従来の縦カー効果、横カ
ー効果を実際に測定した例を第３図に示す。Note that the vertical Kerr effect and the horizontal Kerr effect have been sufficiently detected in the past by using elliptically polarized light in a specific measuring device. FIG. 3 shows an example in which the conventional vertical Kerr effect and horizontal Kerr effect were actually measured.
この方法では直線偏光板２４の後に１／４λ波長板をお
いてレーザ光を円偏光としていること、カー効果により
偏光面角度を変えられたため楕円偏光となった反射光を
ビームスプリッタ１４で正確に５０％づつに分割するこ
と、差動増幅器２８により系統のノイズを消去すること
、がその特徴である。In this method, a 1/4 λ wavelength plate is placed after the linear polarizer 24 to make the laser beam circularly polarized, and the beam splitter 14 accurately converts the reflected light, which has become elliptically polarized because the angle of the polarization plane is changed by the Kerr effect. Its characteristics are that it is divided into 50% units and that noise in the system is eliminated by the differential amplifier 28.
この方法は、ノイズ除去にきわめて有効であるが、 ７
１１１Ｊ定系の構成がきわめて複雑となり、量産に適さ
ないことが大きな欠点である。This method is extremely effective in removing noise, but 7
A major drawback is that the structure of the 111J fixed system is extremely complicated and is not suitable for mass production.
しかし本発明の構成である。複数回の反射を行わせるこ
とにより、磁気カー効果を結果的に増幅することとすれ
ば、このような測定系よりも経済的に有利な構成となり
得る。However, this is the configuration of the present invention. If the magnetic Kerr effect is amplified by performing multiple reflections, the configuration can be more economically advantageous than such a measurement system.
即ち９通常の直線偏光のみでの測定も可能となるのでカ
ー効果利用による磁化測定が容易となることが期待でき
るものである。That is, it is possible to perform measurements using only ordinary linearly polarized light, so it is expected that magnetization measurements using the Kerr effect will become easier.
［作用］
本発明の構成において、磁界が導入される磁気コア部を
設けることにより１例えば媒体上の磁化に容易に、且つ
精度よくアクセスすることができる。又、偏光を照射し
、この偏光面の回転角度を測定するとしたことにより、
媒体ディスク上の記録磁化に対して磁束応答型の検出が
可能となる。[Function] In the configuration of the present invention, by providing a magnetic core portion into which a magnetic field is introduced, for example, magnetization on a medium can be easily and accurately accessed. Also, by irradiating polarized light and measuring the rotation angle of this plane of polarization,
Magnetic flux response type detection becomes possible for recorded magnetization on a medium disk.
更に磁気コア表面と、これにあい対する鏡面との間で多
数回の往復反射を行わせるとしたことにより、磁気カー
効果を多数回行わせることができ、−回のみの反射の場
合に比べ、増幅効果が生じ、ＳＮ比の向上が可能となる
。Furthermore, by causing multiple round trip reflections between the magnetic core surface and the opposing mirror surface, the magnetic Kerr effect can be generated multiple times, compared to the case where the magnetic core is reflected only - times. An amplification effect occurs, and it becomes possible to improve the S/N ratio.
［実施例］
本発明に係る好適な実施例の１つと七で１本発明の方法
を磁気光学的再生ヘッドに応用することができる。[Embodiments] In one of the preferred embodiments of the present invention, the method of the present invention can be applied to a magneto-optical reproducing head.
この実施例について図をもとに説明する。This embodiment will be explained based on the drawings.
第１図は、ヘッドの磁気コア１．１′が媒体ディスク３
上の記録面に空隙２を介してアクセスする様を示してい
る。尚この図ではコア部に付随して光磁気再生を実際に
行う機構は説明のため省略している。媒体３上の磁化は
空隙と直角方向。FIG. 1 shows that the magnetic core 1.1' of the head is connected to the media disk 3.
It shows how the upper recording surface is accessed through the gap 2. In this figure, a mechanism accompanying the core portion that actually performs magneto-optical reproduction is omitted for the sake of explanation. The magnetization on medium 3 is perpendicular to the air gap.
即ち媒体の進行方向と一致して記録されている。In other words, it is recorded in accordance with the traveling direction of the medium.
この磁化はアクセスされた再生ヘッドに１通常の磁束−
電流変換式（磁束変化検出方式）のヘッドと同様、磁気
コア内を貫流する磁束を形成する。This magnetization is applied to the accessed playback head by 1 normal magnetic flux -
Similar to a current conversion type (magnetic flux change detection type) head, a magnetic flux is created that flows through the magnetic core.
第２図は本実施例に係る光再生ヘッドにおける偏光の反
射についての原理図を示している。ガラス基板４上に形
成され、ピンホール８，８′を有し、基板と反対側の面
に鏡面６が形成された反射薄膜５の上には、厚みｄを有
する透明なＳｉ０３層９が形成され、その上には２枚の
磁気薄膜コア１．１′が磁気絶縁膜１０を間にはさんで
形成される。FIG. 2 shows a principle diagram of reflection of polarized light in the optical reproducing head according to this embodiment. A transparent Si03 layer 9 having a thickness d is formed on a reflective thin film 5 formed on a glass substrate 4, having pinholes 8, 8', and a mirror surface 6 formed on the surface opposite to the substrate. Two magnetic thin film cores 1.1' are formed thereon with a magnetic insulating film 10 sandwiched therebetween.
光導波路７，７′の夫々は１図示しない他端において一
定偏光の偏光発生装置及び偏光検出装置に接続されてい
る。Each of the optical waveguides 7, 7' is connected at its other end (not shown) to a polarization generator and a polarization detector for constant polarization.
次に同図に基づいてこの光再生ヘッドの動作原理を説明
する。Next, the principle of operation of this optical reproducing head will be explained based on the same figure.
偏光発生装置で発生した一定の偏光面を有する偏光は、
光導波路７内を通り、基板４及び反射膜５に形成された
ピンホール８を透過し、更に透明Ｓ ｉＯ２層９を通過
し、磁気コア１に形成された反射面に入射する。偏光面
が縦カー効果により回転を受けて反射された偏光は更に
反射膜６で再び反射され、磁気コア１に入射する。多数
回反射往復を繰り返した後再び出路であるピンホール８
′を抜け、基板４を通過して、先導波路７′に入射する
。Polarized light with a constant polarization plane generated by a polarization generator is
The light passes through the optical waveguide 7, passes through the pinhole 8 formed in the substrate 4 and the reflective film 5, further passes through the transparent SiO2 layer 9, and enters the reflective surface formed on the magnetic core 1. The polarized light whose plane of polarization is rotated by the vertical Kerr effect and reflected is further reflected again by the reflective film 6 and enters the magnetic core 1. Pinhole 8, which is the exit route again after repeating many reflections and going back and forth.
', passes through the substrate 4, and enters the leading waveguide 7'.
この反射された偏光は偏光検出装置により、偏光面の回
転角度が測定され、この偏光面の回転角度から磁気媒体
上の磁化が読みとられることとなる。The rotation angle of the polarization plane of this reflected polarized light is measured by a polarization detection device, and the magnetization on the magnetic medium is read from this rotation angle of the polarization plane.
本発明においては、磁気カー効果を多数回、少くとも３
回以上行なわせることとしているので。In the present invention, the magnetic Kerr effect is applied multiple times, at least 3 times.
We are planning to have them do it more than once.
極力−効果に比べ、偏光面回転角度の小さい縦カー効果
をも利用できることとなり、上記実施例のような磁気コ
ア表面上でのいわゆる面内磁化の読みとりが容易となる
ものである。The vertical Kerr effect, which has a smaller rotation angle of the plane of polarization, can also be used compared to the ``Mini-effect'', making it easier to read the so-called in-plane magnetization on the surface of the magnetic core as in the above embodiment.
［発明の効果］
本発明の構成により、磁気光学的効果（カー効果）利用
の磁界測定方法を採用し、更に磁界を導入する磁気コア
部を設けたことにより、迅速且つ精密に波瀾定磁界にア
クセスすることが可能となるので、再生ヘッドに応用し
た場合には自動トラッキング装置不要の光磁気再生ヘッ
ドとすることができる。[Effects of the Invention] With the configuration of the present invention, a magnetic field measurement method using the magneto-optical effect (Kerr effect) is adopted, and a magnetic core part for introducing the magnetic field is provided, so that it is possible to quickly and accurately generate a ripple-constant magnetic field. Since access is possible, when applied to a reproducing head, the magneto-optical reproducing head does not require an automatic tracking device.
又磁束応答型の検出方法を使用するため、媒体との相対
速度に影響されないヘッドの提供が可能となる。Furthermore, since a magnetic flux responsive detection method is used, it is possible to provide a head that is not affected by the relative speed with respect to the medium.
磁気カー効果を多数回行わせるのでＳＮ比の向上が可能
となり、縦カー効果応用の磁化測定方法では従来困難で
あった。ＳＮ比の大きい正確な測定が可能となった。Since the magnetic Kerr effect is performed many times, it is possible to improve the signal-to-noise ratio, which was previously difficult to do with magnetization measurement methods that apply the vertical Kerr effect. Accurate measurement with a high signal-to-noise ratio is now possible.
第１ｖ！Ｊは本発明の原理を応用した一実施例に係る。
磁気コアが媒体上の磁化ヘアドレスする様子を。
第２図は磁気コア上での磁気カー効果利用による磁気−
光変換部を。
第３図は従来例のカー効果の測定系の一例を。
夫々示す図である。
１２、１２’ ・・・集光レンズ
１４・・・ビームスプリッタ
２４、２４’・・・直線偏光板
２５・・・１／４λ波長板
２７・・・反射ミラー
２６・・・１／２λ波長板
２８・・・差動アンプ1st v! J relates to an embodiment to which the principle of the present invention is applied. How the magnetic core addresses the magnetized hair on the medium. Figure 2 shows magnetism using the magnetic Kerr effect on the magnetic core.
light conversion section. Figure 3 shows an example of a conventional Kerr effect measurement system. FIG. 12, 12'... Converging lens 14... Beam splitter 24, 24'... Linear polarizing plate 25... 1/4 λ wavelength plate 27... Reflecting mirror 26... 1/2 λ wavelength plate 28...Differential amplifier
Claims (2)
面上に形成された反射面に一定の偏光面を有する偏光を
投射すること、 該反射面と、これにあい対して配設される反射鏡との間
において前記偏光の反射を多数回行わせた後偏光面の回
転角度を検出すること を特徴とする磁界の光学的測定方法。(1) Guide the magnetic field to be measured to the magnetic core, project polarized light having a constant plane of polarization onto a reflective surface formed on the surface of the magnetic core; 1. A method for optically measuring a magnetic field, comprising: reflecting the polarized light a number of times with a reflecting mirror, and then detecting a rotation angle of a plane of polarization.
軟磁性材料からなる磁気コア部と、 光の入路及び出路を備え、前記反射面とあい対して配さ
れる鏡面を備えた多重反射鏡部と、から基本的に構成さ
れる、磁界の光学的検出素子。(2) A multi-reflector comprising a magnetic core made of a soft magnetic material with at least one surface formed as a reflective surface, and a mirror surface arranged opposite to the reflective surface, with an entrance and exit path for light. An optical detection element for a magnetic field, which basically consists of a part and a part.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31947388A JPH02165077A (en) | 1988-12-20 | 1988-12-20 | Optical measurement of magnetic field and detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31947388A JPH02165077A (en) | 1988-12-20 | 1988-12-20 | Optical measurement of magnetic field and detector |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02165077A true JPH02165077A (en) | 1990-06-26 |
Family
ID=18110593
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP31947388A Pending JPH02165077A (en) | 1988-12-20 | 1988-12-20 | Optical measurement of magnetic field and detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02165077A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0664455A1 (en) * | 1994-01-25 | 1995-07-26 | SEXTANT Avionique | Magneto-optical speedometer |
-
1988
- 1988-12-20 JP JP31947388A patent/JPH02165077A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0664455A1 (en) * | 1994-01-25 | 1995-07-26 | SEXTANT Avionique | Magneto-optical speedometer |
| FR2715473A1 (en) * | 1994-01-25 | 1995-07-28 | Sextant Avionique | Tachometer with magneto-optical effect. |
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