DE102012015209B3 - Ring laser gyro - Google Patents

Abstract

The invention relates to a ring laser gyro (1) having a laser light source (2) for emitting laser light (4) and at least three mirror elements (10) which are arranged such that they define a closed laser light beam (8), wherein at least one of the mirror elements ( 10) is a double mirror having a first mirror surface (12) and a second mirror surface (14) and arranged so that laser light (4) propagating in a first direction along the closed laser light path (8), first at the first mirror surface (12) and then on the second mirror surface (14) is reflected.

Description

The invention relates to a ring laser gyroscope having a laser light source for emitting laser light and at least three mirror elements, which are arranged such that they define a closed laser light path.

Ring laser gyros have been known in the art for a long time and are used in particular as a replacement for conventional mechanical gyros and gyroscopes. Ring laser gyros require a light source that emits coherent light as much as possible. Therefore, laser light sources are predestined for this type of application. By way of example, a beam splitter, the laser light emitted by the laser light source is divided and directed in two opposing paths. At a suitable location in the beam path both beam directions are read together and brought to the interference. Such a beam path or closed laser light path is defined, for example, by three mirror elements which respectively provide for a deflection of the laser light by 60 °, so that a closed laser light path results. Of course, embodiments with more than three mirror elements are conceivable and known.

In the event that the ring laser gyroscope does not rotate, the optical distances that must cover the two partial beams of the emitted laser light, the same length, so that no phase shift occurs between the two partial light beams. However, if the ring laser gyro rotates, for example, about an axis of rotation which is perpendicular to the area enclosed by the closed laser light path, the optical path lengths of the two partial light beams change, resulting in a phase shift measurable in the interference image.

Ring laser gyro is available in different embodiments. One of the most common is, for example, the construction as a helium-neon ring laser. However, several difficult to miniaturize modules must be used. By using a luminous gas, for example, the actual light path, in which the closed laser light path is defined, must be closed in a gas-tight manner and sufficiently secured against diffusion. In addition, isolated high voltage anodes and cathodes must point into the propagation space.

In other embodiments, instead of the glowing gas, a solid state laser such as the YAG crystal is used. This eliminates the high voltages directly at the Lichtgang and the need for gas-tightness and the movement of the contained gas filling. Nevertheless, this type of ring laser gyro is also difficult to miniaturize, since such a solid laser emits its laser light undirected and also with fluctuating intensity. This implies that further assemblies must be used within the closed laser light path, which may include, for example, movable mirrors and lenses. Each of these elements provides additional reflections and internal attenuations, so that the emitted laser light can travel only a few revolutions on the closed laser light path. This reduces the quality and measurement accuracy of such a ring laser gyroscope. In addition, this structure is difficult to miniaturize due to the additional modules used. An alternative embodiment of a ring laser gyro uses, instead of a laser light path defined by a plurality of mirror elements, an optical waveguide which is applied, for example, wound or helically. This is a multiple traversing the same path, as is the case with generic mirror-based rotors, not provided. A corresponding arrangement is for example from the US 6,885,456 82 known. For mirror-based ring laser gyros are exemplary the US 7,511,821 B2 and the US 5,412,475 82 called.

From the JP 2009-294165 A For example, a three-axis ring laser gyro is known in which several of the required mirror surfaces are etched out of a single workpiece for the three different light paths. The JP 2003-139539 A discloses a ring laser gyro having four mirror elements arranged so that the closed light path is in the form of an "8". From the US 2009/0021744 A1 is also known a ring laser gyro, in which different light paths ensure that rotations of the ring laser gyroscope can be detected around different axes.

The EP 0 332 412 A1 describes a triaxial ring laser gyro, in which both the rotation and the rotational speed of the gyro as well as the energy level of the laser beam can be selected.

The DE 196 35 942 A1 discloses a diode-pumped solid-state laser gyro, wherein the laser beam is guided within a material and is reflected at the interface with the surrounding air by total reflection. The laser material is split into two components.

In order to be able to miniaturise mirror-based ring laser gyros, the individual mirror elements naturally have to be downsized. However, this makes the alignment and arrangement of the mirror elements problematic. The smallest deviations can lead to reflection errors, the if necessary, guide the irradiated laser light out of the closed laser light path and thus cause the inoperative function of the ring laser gyroscope. However, even if this worst case does not occur, misalignment, assembly and manufacturing errors of the individual mirrors will lead to quality losses.

The present invention is therefore based on the object, a ring laser gyro further so that it is easy to miniaturize and yet the individual mirror elements can be easily, reproducibly and accurately arranged. In addition, a method for producing corresponding mirror elements is to be proposed.

The invention achieves the stated object by a generic ring laser gyro, which is characterized in that at least one of the mirror elements is a double mirror having a first mirror surface and a second mirror surface and arranged such that laser light propagating along the closed laser light path, is reflected at the first mirror surface and at the second mirror surface.

In conventional mirror-based ring laser gyros, a closed laser light path lying in one plane is defined by the at least three mirror elements. To ensure this, it is of course important that the mirror surface is exactly perpendicular to this plane. This can be achieved relatively easily and safely by appropriate processing methods. However, the orientation of the individual mirror elements relative to each other is of crucial importance. When three mirror elements are used, it is essential for the closedness of the laser light path that the irradiated laser light strike the respective mirror element at as precisely as 60 °. If, for example, four mirror elements are used to define the closed laser light path, the irradiated laser light must be radiated at an angle of 45 °. A built-in or control error that has a pivoting of the mirror element about an axis perpendicular to the plane defined by the laser light path axis results in an angle error that adds up with each revolution of the incident laser light to the laser light path and in the worst case leads to that irradiated laser light leaves the closed laser light path after a finite number of cycles. This error can be counteracted by the inventive provision of double mirrors as a mirror element. A high-axis error described here, in which the error lies in a pivoting of the mirror element about an axis which is perpendicular to the surface defined by the closed laser light path, does not lead to a reflection error in a double mirror, so that such double mirrors are not aligned so accurately as mirror elements must, as is the case with conventional individual mirror elements. As a result, even small and very small mirror elements can be positioned such that the closed laser light paths of irradiated laser light are not left even after a large number of circulations.

It has proven to be particularly advantageous if all the mirror elements are double mirrors. As a result, angle errors are prevented in all mirror elements, so that a very accurate, as with many cycles of the irradiated laser light working ring laser gyro can be produced, which is very well miniaturized.

For decoupling the two partial light beams which are irradiated into the closed laser light path, a separate decoupling element, for example a partially transparent mirror or beam splitter, may be provided. Thus, it is no longer necessary to design one of the mirrors semipermeable, but all mirror elements can be formed in the advantageous embodiment as a double mirror. In a particularly advantageous embodiment of the ring laser gyro, the laser light source is arranged outside the closed laser light path and the ring laser gyroscope has a coupling device which is arranged such that laser light emitted by the laser light source is coupled into the closed laser light path. This too is a measure that allows further miniaturization of the ring laser gyroscope. Unlike in the known from the prior art embodiments in which a gas or solid laser is arranged directly in the closed laser light path, and thus defines a minimum extent of the closed laser light path, this is not necessary in the embodiment described here. It is only necessary to arrange the coupling device at least partially in the beam path or the closed laser light path in order to be able to couple the laser light emitted by the laser light source into the closed laser light path. As a result, the actual laser light source does not even have to be arranged in the vicinity of the closed laser light path. The laser light emitted by it can be transported, for example, by an optical conductor, for example a fiber optic cable, over a very large distance and led to the coupling device, by means of which it is coupled into the closed laser light path.

This makes it possible to compensate for fluctuations in the laser light intensity or beam widening or other disturbances and inaccuracies of the laser light and to correct before the laser light in the closed laser light path is coupled. As a result of this external preparation of the laser light to be irradiated, the actual gyroscope, which mainly comprises the closed laser light path, can be further miniaturized. Such ring laser gyroscopes have, for example, lens systems which collect light in addition to the external light source, filters which restrict wavelength ranges, beam splitters or further coupling elements. As a result, the ring laser gyroscope for a variety of different applications can be used without the space required for the actual ring laser gyro increases significantly.

A particularly advantageous ring laser gyro has exactly three mirror elements. This is the minimum number of mirror elements to be used, so that in this way also the number of possible sources of error by Fehlausrichtungen-, orientations or manufacturing qualities are reduced. In addition, the space required for the ring laser gyroscope is reduced in this way.

• a) Bearbeiten eines Einkristalls so, dass eine Bearbeitungsoberfläche des Einkristalls in einem vorbestimmten Winkel zu einer vorbestimmten Kristallebene des Einkristalls verläuft,
• b) Einätzen wenigstens einer Vertiefung in die Bearbeitungsoberfläche, wobei die wenigstens eine Vertiefung wenigstens eine Flanke aufweist, die entlang der vorbestimmten Kristallebene verläuft, und sich eine Kantenlinie zwischen der Bearbeitungsoberfläche und der wenigstens einen Flanke ergibt,
• c) Verbinden zweier derart bearbeitete Einkristalle mit jeweils wenigstens einer eingeätzten Vertiefung an den Bearbeitungsoberflächen derart, dass die Kantenlinien aneinander anliegen,
• d) Herstellen des Doppelspiegels durch Zertrennen der verbundenen Einkristalle derart, dass die Flanke des einen Einkristalls die erste Spiegelfläche und die Flanke des zweiten Einkristalls die zweite Spiegelfläche bildet.

An inventive method for producing a double mirror for a ring laser gyroscope is characterized by the following steps:

• a) processing a single crystal so that a processing surface of the single crystal is at a predetermined angle to a predetermined crystal plane of the single crystal,
• b) inserting at least one depression into the processing surface, the at least one depression having at least one flank extending along the predetermined crystal plane and resulting in an edge line between the processing surface and the at least one flank,
• c) connecting two such processed single crystals each having at least one etched recess on the processing surfaces such that the edge lines abut each other,
• d) producing the double mirror by dividing the connected single crystals such that the flank of the one single crystal forms the first mirror surface and the flank of the second single crystal forms the second mirror surface.

The present invention makes use of the finding that recesses etched in single crystals have at least one flank which advantageously extends along a predetermined crystal plane of the respective single crystal. The angle of the respective flank arises because different crystal lattice planes have different etching speeds. For example, in monocrystalline silicon it has been found that the (111) plane can be etched approximately 400 times slower than the (100) plane. In this way, these angles are very accurate and reproducible.

However, the angle at which certain crystal planes extend to each other is determined by the crystal structure of the respective single crystal. Therefore, in order to achieve the desired angle of a double mirror to be manufactured, a processing surface of the single crystal must be at a predetermined angle to the predetermined crystal plane. This can be achieved, for example, by sawing or otherwise working the monocrystal at a certain angle. This results in a planar area that runs at the predetermined angle to the respective predetermined crystal plane. This area forms the processing surface.

At least one depression is etched into this processing surface in a second process step. Due to the different etching speeds along different crystal planes of the single crystal, this at least one depression has at least one flank extending along this predetermined crystal plane. This flank usually runs on the crystal plane, along which the lowest etching speed occurs. At the edge line between the processing surface and the at least one recess now forms the previously predetermined angle.

These two process steps are carried out with a plurality of single crystals or a single crystal is divided into at least two parts after etching the at least one recess. Two appropriately processed single crystals prepared in this way, each having at least one etched recess, are now connected to the processing surfaces. This can be done for example by a bonding. It is important that the two single crystals are arranged in such a way that the respective edge lines between the two processing surfaces and the respective edges of the respective recess abut each other. Consequently, voids which may be open to the outside are formed in the monocrystals connected in this way, but in which the flanks of the depressions originally etched into two monocrystals rest against each other in such a way that the desired angle for the double mirror is created between them.

In a final process step, the double mirrors only have to be produced by dicing the single crystals so connected. In this way, the desired double mirrors are formed in which the flank in the recess of the one single crystal forms the first mirror surface and the flank in the recess of the second single crystal forms the second mirror surface.

Advantageously, the machining surfaces are polished and / or ground before the etching of the at least one recess. This ensures that optimal positioning is possible when connecting the two single crystals and that no additional angle errors occur here. In principle, this polishing and / or grinding of the processing surfaces would also be possible after the etching of the depression, but such a procedure has the disadvantages that the particularly evenly and smoothly etched flanks of the depressions are soiled with processing residues and thus impaired in their reflectivity can. Because the etching speeds in the direction of different crystal planes of the single crystals have distinct differences, the flanks thus formed have a particularly high surface quality and thus an extremely good reflectivity and suitability as a mirror surface.

Advantageously, the single crystals used are silicon monocrystals. This material has a high reflectivity and is easy and easy to work with, making it particularly suitable for use as a dual mirror element.

With the aid of drawings, an embodiment of the present invention will be explained in more detail below. Show it:

1 1 is a schematic representation of a ring laser gyro according to a first embodiment of the present invention;

2a to 2d different steps during the implementation of a method according to an embodiment of the present invention.

1 shows the schematic representation of a ring laser gyro 1 according to a first embodiment of the present invention. He has a laser light source 2 , through the laser light 4 can be sent out. This laser light 4 meets a coupling device 6 , which is shown only schematically as a semitransparent mirror in the embodiment shown.

Through this coupling device 6 This is done by the laser light source 2 emitted laser light in a closed laser light path 8th coupled. This is through three mirror elements 10 formed, which are formed in the embodiment shown as a double mirror.

Each of the mirror elements 10 has a first mirror surface 12 and a second mirror surface disposed adjacent thereto 14 , The laser light 4 that via the coupling device 6 in the closed laser light path 8th is now coupled with each mirror element 10 from the first mirror surface 12 and from the second mirror surface 14 reflected.

The embodiment shown has the advantage that the closed laser light path 8th Also in the case inventory has that one or more of the mirror elements 10 has a placement error caused by the corresponding mirror element 10 has been arranged pivoted about an axis which is perpendicular to the image plane shown. Due to the nature of the dual mirrors, such an alignment and alignment error does not result in a resulting angular displacement such that the closed laser light path 8th is also valid in this case and has stock.

In 1 becomes the laser light 4 through the coupling device 6 also split into two partial light beams, the closed laser light path 8th go through in opposite directions. The second laser light beam therefore also becomes from the first mirror surface 12 and from the second mirror surface 14 reflected.

The 2a to 2d show different stages during the performance of a method for producing a double mirror according to an embodiment of the present invention.

2a shows a single crystal 16 , which may be, for example, monocrystalline silicon. Schematically represented are crystal planes 18 that run at a known angle. One recognizes that a processing surface 20 at a predetermined angle γ to the crystal planes 18 runs. The angle γ is 120 ° in the present example.

The editing interface 20 arises, for example, by sawing or milling of the single crystal 16 in a corresponding angle. After making the machining surface 20 at the predetermined angle γ to the crystal planes 18 runs, the editing surface can 20 be reworked for example by polishing or grinding and so be particularly flat.

2 B shows the single crystal 16 with the schematically illustrated crystal planes 18 , which already has a recess 22 into the editing interface 20 was etched. Due to the different etching speeds along the different crystal planes, the indentation has 22 over a flank 24 , the one of a crystal plane 18 follows. The predetermined angle γ is therefore now at an edge line 26 that exist between the editing interface 20 and the flank 24 runs.

2c shows two connected single crystals 16 , with schematically illustrated crystal planes 18 , The two single crystals are at their processing surfaces 20 connected together, so that now has a cavity 28 forms, passing through the two wells 22 in the respective editing surfaces 20 is formed. Important to the alignment is that the edge lines 26 abut each other, so that there is a mirror angle α between the two flanks 24 which is 360 degrees minus twice the predetermined angle γ. The mirror angle α is determined by the desired deflection, which is a laser light beam incident on the mirror element 10 meets, should experience.

2d shows the finished mirror element 10 that consists of two single crystals 16 with the schematically illustrated crystal planes 20 consists. The connected single crystals 16 as they are in 2c are shown, are divided accordingly, so that in 2d illustrated mirror element 10 remains. The two flanks 24 now form the first mirror surface 12 and the second mirror surface 14 , Since they are formed by etching, they have a particularly high surface quality and reflectivity, so that they are particularly suitable for use in a ring laser gyro described here 1 as a mirror element 10 to be used.

LIST OF REFERENCE NUMBERS

γ

Predetermined angle

α

mirror angle

1

Ring laser gyro

2

Laser light source

4

laser light

6

launching device

8th

Closed laser light path

10

mirror element

12

First mirror surface

14

Second mirror surface

16

single crystal

18

crystal plane

20

editing interface

22

deepening

24

flank

26

edge line

28

cavity

Claims (7)

Ring laser gyros ( 1 ) with a laser light source ( 2 ) for emitting laser light ( 4 ) and at least three mirror elements ( 10 ) arranged to form a closed laser light path ( 8th ), characterized in that at least one of the mirror elements ( 10 ) is a double mirror having a first mirror surface ( 12 ) and a second mirror surface ( 14 ) and is arranged such that laser light ( 4 ) extending in a first direction along the closed laser light path (FIG. 8th ), first at the first mirror surface ( 12 ) and then at the second mirror surface ( 14 ) is reflected. Ring laser gyros ( 1 ) according to claim 1, characterized in that all mirror elements ( 10 ) Double mirrors are. Ring laser gyros ( 1 ) according to claim 1 or 2, characterized in that the laser light source ( 2 ) outside the closed laser light path ( 8th ) and the ring laser gyro ( 1 ) a coupling device ( 6 ), which is arranged so that from the laser light source ( 2 ) emitted laser light ( 4 ) in the closed laser light path ( 8th ) is coupled. Ring laser gyros ( 1 ) according to one of the preceding claims, characterized by exactly three mirror elements ( 10 ). Method for producing a double mirror for a ring laser gyro ( 1 ) according to one of the preceding claims, characterized by the following steps: a) processing of a single crystal ( 16 ) such that a processing surface ( 20 ) of the single crystal ( 16 ) at a predetermined angle γ to a predetermined crystal plane ( 18 ) of the single crystal ( 16 ), b) inserting at least one depression ( 22 ) into the editing interface ( 20 ), wherein the at least one depression ( 22 ) at least one flank ( 24 ) along the predetermined crystal plane ( 18 ), and an edge line ( 26 ) between the processing surface ( 20 ) and the at least one flank ( 24 ), c) connecting two single crystals processed in this way ( 16 ) each having at least one etched recess ( 22 ) on the processing surfaces ( 20 ) such that the edge lines ( 26 ) abut each other, d) producing the double mirror by dividing the connected single crystals ( 16 ) such that the flank ( 24 ) of the single crystal ( 16 ) the first mirror surface ( 12 ) and the flank ( 24 ) of the second single crystal ( 16 ) the second mirror surface ( 14 ). Method according to claim 5, characterized in that the processing surface ( 20 ) before the at least one well ( 22 ) is polished and / or ground. Method according to claim 5 or 6, characterized in that the single crystal ( 16 ) is a silicon single crystal.

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