WO2009124609A1

WO2009124609A1 - Deviation device for a beam of an electromagnetic wave

Info

Publication number: WO2009124609A1
Application number: PCT/EP2008/066713
Authority: WO
Inventors: Tjalf Pirk; Stefan Pinter; Hubert Benzel; Heribert Weber; Michael Krueger; Robert Sattler; Frederic Njikam Njimonzie; Joerg Muchow; Joachim Fritz; Christoph Schelling; Christoph Friese
Original assignee: Robert Bosch Gmbh
Priority date: 2008-04-08
Filing date: 2008-12-03
Publication date: 2009-10-15
Also published as: DE102008001056A1

Abstract

The invention relates to a deviation device for the beam of an electromagnetic wave, comprising two cascading reflection elements (1, 2) that can be pivoted individually in various directions in a controlled manner. The reflection surfaces (3,4) are arranged opposite each other at a distance and are oriented towards each other. Additional reflection elements are unnecessary and said device can be compact.

Description

DESCRIPTION

title

Deflection device for a beam of an electromagnetic wave

The invention is in the field of optics or micromechanics and deals with deflection devices for electromagnetic radiation such as laser beams, light rays and UV rays, which can be controlled by means of movable reflection elements.

More specifically, the invention deals with the possibilities of a little expensive and easy to produce deflection device for a light beam.

Various applications of light rays, in particular laser beams, are known in the art, which must be controlled very quickly and reliably, such as in scanners and projectors working with individual beams as well as in head-up displays, in the automotive sector and in air traffic be used. In these applications, multi-dimensional images are often written by a moving beam that is modulated during its motion. The actual movement of the beam takes place through a controlled deflection by one or more mirrors whose pivot axes are independent of each other so that it can be controlled in several directions.

The required high speed in the image structure or the fast image sequences that are to be displayed, extremely fast mirror controls are required, which must also be very reliable and accurate.

STATE OF THE ART

Such an arrangement is described, for example, in EP 0778657 A1, where a corresponding mirror is to be realized in a wafer by micromechanical production techniques. The entire assembly is positioned between two magnets to move the mirror by means of a Lorentz force. For this purpose, different current-carrying windings are arranged perpendicular to each other in the corresponding wafer, which are subject to a Lorenzkraft in the field of magnets and thus generate deflection forces for the mirror in different pivot directions. In the example mentioned, one operates with a single magnetic field which, in order to be able to interact with mutually perpendicular windings, runs at an angle of 45 ° to the corresponding winding parts.

Another solution is known from international patent application WO 2005078509 A2. There is also worked with a gimbal-mounted mirror, which is driven by a single coil in a rotated by 45 ° with respect to the axes of rotation magnetic field. Rotations around the different axes are realized by stimulating coupled oscillations around several axes (rocking mode).

ADVANTAGES OF THE INVENTION

The present invention is based on the background of the prior art, the task with a minimum of effort to create a fast-working and reliable deflection, which allows a beam deflection with the required accuracy and is low in design effort and low cost.

The object is achieved according to the invention with the features of claim 1.

According to the invention, the biaxial deflection of the beam with two independent

Reached reflection elements, which are also driven independently of each other, so that no coupling between the drive directions take place. In the invention, in contrast to an arrangement of a plurality of mirrors in a plane which requires the additional provision of a fixed reflection mirror to obtain a W-shaped beam path, an arrangement with only two mirrors is proposed, which face each other such that the beam of a first reflection element to the second reflected directly and can be further reflected from there into the target area. This results in various advantages. For example, the deflection device can be planned as a passage element, in which the beam entry direction does not differ or only slightly from the beam exit direction, so that a corresponding light source can be arranged behind the deflection device, while the image area or scan area is positioned in front of the deflection device.

Due to the small number of necessary reflection elements the adjustment requirements are kept low. In addition, when a micromechanical mass production is desired, small

Wafer units are used with appropriately integrated reflection elements, so that you can work with a high component concentration and a high yield per wafer. After the separation of the reflection elements or the corresponding carrier, these can be spaced apart from one another by an intermediate element arranged between them and be positioned relative to one another, which, for example, can advantageously be embodied as a transparent plate. The actual light beam can then pass the second reflection element to the first reflection element through the transparent plate, are reflected by the first reflection element through the plate on the second reflection element and emerge from this again by an outlet opening next to the first reflection element from the deflection.

As a material for such a transparent plate is, for example, glass or a transparent

Plastic conceivable. The corresponding plate can be produced with sufficient accuracy plane-parallel or as a wedge plate, so that it aligns the reflection elements to each other. The corresponding reflection elements can then be placed with their carriers directly on the plate or glued or bonded. Instead of a transparent plate, the reflection elements can also be spaced apart from each other by a housing and positioned. Such a housing can then be filled with air or gas or evacuated and have a frame with two bearing surfaces, which are arranged opposite each other and allow the support of the corresponding carrier of the reflection elements. Also in this case, the carriers or the reflection elements can be aligned parallel to one another or at a suitable angle, and inlet windows must be provided next to each of the reflection elements for entry or exit of the beam, if this is not to enter through the side walls of the housing.

Such a housing may for example consist of plastic or a coated glass. It can advantageously be provided that the reflection surfaces in the housing parallel to

Entrance window and the housing bottom and / or housing top are aligned. However, it can also be provided that the reflection surfaces are angled in the housing between 20 ° and 70 °, in particular by 45 ° relative to the Gehäusunter- and top. In this case, a particularly space-saving arrangement of the reflection elements in the housing may result. A further advantageous embodiment of the invention provides that each reflection element is an integral part of a separate wafer part.

Thus, a production of the reflection elements as a mirror, in particular as a plane mirror is particularly economically possible by the means of micromechanics in a wafer by trench etching a mirror is released. This may be before or after the final pruning be coated in addition to increasing the reflectance. There is a certain minimum distance to adjacent components necessary to allow a swinging of the mirror, for example, when the wafer is glued directly onto a plate, which forms the spacer between the two reflection elements as a transparent plate.

To protect the individual reflection elements or wafer parts, it may be provided that each of the wafer parts is covered with a protective layer on its side facing away from the respective other wafer. This ensures that the overall arrangement of the deflection after assembly on all sides is well protected against the ingress of dirt and other environmental influences. Since the reflection elements are arranged relative to one another such that the beam passes through the deflection device and continues on the other side, possibly reflected radiation components of the incident beam are harmless.

It can be provided that the protective layer is formed as a substrate and carries the respective wafer. The wafer can be processed in this case on the substrate according to the formation of a reflection element.

In addition, the orientation of the reflection elements based on the substrates and the fixation of the individual components is thereby simplified. In a micromechanical mass production only the wafer parts and the substrate parts need to be sawn according to the separation.

In order to enable a reliable drive of the reflection elements, it is advantageously provided that the reflection elements have electrical drive components in the form of a conductor or electrode which can be acted upon by current. It can then be provided either a suitable magnetic field in which the individual reflection elements are driven due to a Lorenzwirkung by a current-carrying, magnetic field-exposed, conductor winding or it can be provided an electrostatic drive with electrodes targeted for generating a deflection force with variable electrical potentials can be applied.

The reflection elements can have different sizes, since in particular the first reflection element is struck by a static, undeflected beam and a relative movement occurs only by the slight tilting of the reflection element. In contrast, the second reflection element must be made slightly larger, since this is struck by a deflected beam to varying degrees and must reflect this in full width.

It proves advantageous when the reflection elements must be moved at different speeds that the fastest movement is transmitted to the first reflection element, since this has the lower moment of inertia because of its small size required. Also, at least one of the reflection elements are operated in the so-called eigenfrequenten mode, which is determined by the restoring forces of the resilient suspension and in which particularly low driving forces required and particularly high frequencies are possible.

The individual reflection elements, if micromachined from a wafer, can be formed by leaving torsion bars as a connection to the rest of the wafer, whereby restoring forces of the desired order of magnitude can be easily achieved.

The invention relates in addition to a deflection of the type described on a scanning device with a light source and a corresponding deflection.

In addition, the invention also provides a method for producing a deflection device according to claim 12.

This production method is particularly efficient possible if the wafers are assembled before separation, since this requires only a single adjustment process and, after assembly, the deflection devices can be further processed as ready-to-use units. By appropriate design of the wafer, the accuracy of fit is guaranteed and the joining can be done under clean room conditions, so that impurities are not to be feared, especially if the wafers are already protected on their outer sides by a protective layer, such as the corresponding carrier substrate.

Otherwise, a protective layer can also be applied to the wafer immediately before the wafers are joined together.

In addition, it can be provided that the reflection elements are released and / or mirrored only after the covering of the respective wafer by means of a protective layer. This ensures that the reflection elements are already protected by a corresponding protective layer at the time they receive their final processing, which makes them shock-sensitive and prone to damage.

DRAWINGS In the following the invention will be shown with reference to an embodiment in a drawing and described below.

1 shows a schematic sectional view of a deflection device according to the invention;

Figure 2 is an exploded view of a deflection device;

FIG. 3 shows a first reflection element;

FIG. 4 shows a second reflection element;

Figure 5 shows a deflection device with a housing as a positioning element;

Figure 6 shows a further section through a deflection device according to the invention and

Figure 7 is a perspective view of a deflection device with marked beam path.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 schematically shows, in a sectional view, a deflection device with a first reflection element 1 and a second reflection element 2, each in the form of a planar mirror. The mirrors 1, 2 are each formed as part of a wafer part and positioned laterally offset from one another parallel to one another. Thus, the reflection surfaces 3, 4 of the reflection elements are inclined to each other.

FIG. 1 also shows a typical beam path with a light beam 5 which enters through an entrance window 6 within an optically transparent substrate 7 and initially strikes the first reflection element 1.

This is due to its pivoting about the dashed pivot axis 8 in a position to deflect the light beam 5 perpendicular to the plane and thus to control.

The reflected beam then strikes the second reflection element 2, which is pivotable about an axis 24 which is perpendicular to the plane of the drawing. As a result, the steering beam, as shown, deflected within the plane of the drawing. The emerging light beam in the region of the exit window 9 in the second substrate 10 is approximately in the extension of the incoming beam, so that the deflection device can be planned in a beam path as a more or less linearly traversed element.

The adjustment of the reflection elements 1, 2 is particularly simple if they are each made as a section of a wafer part 11, 12 (Figure 2), so that the wafer parts 11, 12 can be easily connected by bonding. Such a connection can occur in micromechanical mass production prior to the division of a wafer into wafer parts, so that only a single adjustment process is necessary for a large number of deflection devices.

In the wafer parts 11, 12 corresponding recesses for the beam path and for the mobility of the reflection elements 1, 2 must be provided.

In the figure 1 also so-called cover wafer, also referred to as a substrate 7, 10 are provided, which provide a capping of the deflection and thus the protection against contamination and other

Effect environmental influences. Within the caps / substrates 7, 10 also recesses 13, 14 must be provided in order to ensure the pivoting of the reflection elements / mirror about the axes 8, 24. These depressions can be provided, for example, by embossing or etching in the corresponding substrates 7, 10.

The bonding of the substrates to the respective wafers can also be done by bonding, for example, before joining the wafers, but also after joining the wafers and a sawing process.

If the joining of the substrates and the wafers takes place before the division, then the corresponding substrates are likewise to be sawed or etched or etched.

FIG. 2 shows in an exploded view the layering of the caps / substrates and the wafer parts with the reflection elements. At the top, a first substrate 7 with a corresponding recess 14 is shown, followed by a wafer part 12, a further wafer part 11 and a further substrate / wafer 10, likewise with a depression 13.

The corresponding recesses 13, 14 are each formed double wedge-shaped to allow the smallest possible depth as high as possible deflection angle of the respective reflection elements 1, 2. Electrostatically controllable electrodes for an electrostatic drive of the reflection elements can be provided within the depressions. In this case, corresponding counter electrodes are likewise to be provided on the reflection elements.

Alternatively, a magnetic drive is conceivable. In this case, electrical conductors, for example in the form of turns of a winding, advantageously each be provided parallel to the pivot axis of a reflection element on this, which are subject to a Lorenzkraft in a static magnetic field, which is controllable by the current in the conductor.

In the figure 2, the shape of the mirror is shown in more detail, each of the

Mirror / reflection elements 1, 2 consists of a separate wafer part surface, which is separated by micromechanical separation methods by means of a slot 15 from the rest of the wafer part, wherein torsion bars 16, 17 remain for holding and generating a restoring force. The shape of such a reflection element 1, 2 may be basically round or square and the size is given essentially by the swept over by the possible incident rays surface. In the case of mirrors which are to be controlled quickly, the respective mirror is designed to be as small as possible in order to enable high acceleration through the lowest possible mass.

Since the images possibly to be displayed by a deflection device usually require a line and a column deflection, wherein the line deflection entails much faster movements, the first mirror / the first reflection element is usually used for this faster control, since this usually receives a deflection-free incident beam, and therefore relatively small can be planned. In addition, this faster mirror can be operated in natural frequency mode, that is, at Auslenkfrequenzen that are in the range of the natural frequency of the mirror, for example, at 20 kHz.

The second reflection element 2 is then usually made larger in order to be able to catch and deflect the deflected beam in full width.

The second mirror deflects the beam in a direction perpendicular to the deflection direction of the first mirror. The pivot axes 8, 24 of the reflection elements 1, 2 are for this purpose advantageously perpendicular to each other, but in principle it is sufficient that the axes are not parallel and the corresponding reflection elements are driven independently of each other.

The caps / wafers 7, 10 may be transparent and, for example, after being bonded to the remaining wafers, are polished at least in the region of the entrance windows or finished by a suitable other method for improving the optical quality. After applying the substrate wafers / caps to the wafers containing the reflective elements, the Reflective elements separated / released and advantageously additionally mirrored by metallizing. A metallization can also be introduced into the recesses of the cover wafers to serve as a stator electrode for the electrostatic drive.

In addition, an intermediate wafer or a transparent intermediate layer can be inserted between the wafers 11, 12 containing the reflection elements, which can further optimize the light path by the refraction of the incident beam. Such an intermediate layer will be explained in more detail with reference to FIG.

In FIGS. 3 and 4, by way of example, wafer parts are illustrated with reflecting elements which are correspondingly provided with slots in them.

FIG. 5 shows an embodiment of the deflection device according to the invention, in which a housing 18 serves for relative alignment and positioning of the wafer parts 11, 12 or of the corresponding reflection elements / mirrors 1, 2. The housing 18 is formed by a frame, on the top of a first cover plate 19 and from the bottom of a second cover plate 20 are inserted. The cover plates 19, 20 are at least partially transparent and consist for example of glass or a transparent plastic. On the bottom 21 of the housing 18, the first wafer part 11 is placed and secured there by gluing.

In the housing 18, a holding block 22 is also integrated, which forms a bearing surface for the second wafer part 12.

The housing 18 may be made, for example, by an injection molding process that provides sufficiently accurate results in the surface definition to ensure the relative orientation of the reflective elements.

The individual parts of the deflection are advantageously assembled in a clean room atmosphere to prevent the ingress of dirt before the seal.

FIG. 6 shows an exemplary embodiment in which the reflection elements 1a, 2a are arranged substantially parallel to one another, but at an angle of 45 ° to the incident beam 5, within a housing which is shown only schematically in cross section. This can be ensured, for example, by integration of corresponding retaining blocks in the housing 18a.

The housing 18a also provides an entrance window 6a and an exit window 9a for the light beams. With this construction, an incident direction of the incident beam perpendicular to the entrance window 6a and an alignment of the outgoing beam with not too great deviation from the perpendicular from the exit window 9a are realized, thereby minimizing partial reflections. In addition, such a deflection can be realized with a very small size.

FIG. 7 shows a deflection device in which the first wafer part 11 and the second wafer part 12 are positioned and spaced relative to one another by a transparent intermediate layer lying between them. The intermediate layer is designated in the figure with 23 and consists of glass or a transparent plastic. In addition to the components mentioned in the figure, the incident beam 5 and the outgoing beam cone 25 is shown.

The manufacturing process for such an arrangement is particularly simple in that the wafer parts 11, 12 can be applied to the intermediate layer 23, for example by bonding. Before or after this bonding process, the respective wafer part 11, 12 can be provided with a cap wafer on the outside for protection. Advantageously, the capping is still done in connection with the micromechanical mass production process, so that the finished masked wafer parts can be further processed with the corresponding intermediate layer. The intermediate layer is advantageously mirrored in the areas that are not needed for the entry and exit of the light, to avoid interference.

In order to enable a movement of the mirror / reflection elements 1, 2, the corresponding wafer parts must be thinned out and / or a respective depression in the intermediate layer as well as in the cap wafer must be provided.

With the inventive arrangement of reflection elements as a cascaded mirror arrangement with independent pivot axes and drives can be structurally particularly simple and space-saving realize a deflection device for electromagnetic radiation.

Claims

1. deflection device for a beam of an electromagnetic wave with two in the beam path arranged one behind the other, each having a reflection surface (3,4) having reflection elements (1,2) which are individually pivotable about an axis (8,24) controlled by a drive, characterized in that the reflection surfaces (3, 4) face each other at a distance and face each other.

2. deflection device according to claim 1, characterized in that the reflection elements (1,2) spaced by an intermediate element between them (23) and are positioned to each other.

3. deflection device according to claim 2, characterized in that the intermediate element (23) is designed as a transparent plate.

4. deflection device according to claim 1, characterized in that the reflection elements (1,2) by a housing (18) spaced from each other and are positioned.

5. deflection device according to claim 4, characterized in that the reflection surfaces (3,4) in the housing (18) parallel to the entrance window (6) and the

Housing bottom and / or housing top are aligned.

6. deflection device according to claim 4, characterized in that the reflection surfaces (3,4) in the housing between 0 ° and 90 °, in particular between

20 ° and 70 °, in particular by 45 ° with respect to the Gehäusunter- and top are angled.

7. deflection device according to claim 1 or one of the following, characterized in that each reflection element (1, 2) is an integral part of a separate wafer part (11, 12).

8. deflection device according to claim 7, characterized in that each of the wafer parts (11,12) on its side facing away from the respective other wafer side, with a protective layer (7, 10) is covered.

9. deflection device according to claim 8, characterized in that the protective layer (7,10) is formed as a substrate and carries the respective wafer part.

10. deflection device according to claim 9, characterized in that the respective protective layer (7,10) at least partially made of a transparent material, in particular glass.

11. deflection device according to claim 1 or one of the following, characterized in that the reflection elements (1,2) comprise electrical drive components in the form of a conductor can be acted upon with electricity or an electrode.

12. Scanning device with a light source and a deflection device according to claim 1 or one of the following.

13. A method for producing a deflection device according to one of claims 1 to 11, characterized by the following method steps:

Micromechanically forming a plurality of reflection elements (1, 2) on a first and second wafer;

Connecting the first and a second wafer optionally with the interposition of an intermediate element (23); Separating the deflecting devices.

14. The method according to claim 13, characterized in that before the joining of the first and second wafer, these are covered by means of a protective layer (7, 10).

15. The method according to claim 14, characterized in that the reflection elements (1,2) are released after covering the respective wafer by means of a protective layer (7,10) and / or mirrored.