WO2010084021A1 - Method and device for illuminating a working plane with laser light in a geometrically dense manner - Google Patents

Abstract

The invention relates to a method for illuminating a working plane with laser light in a geometrically dense manner, wherein laser light which is emitted by a first laser diode bar is rotated about 90° by a beam transformation device (3) before the laser light is incident on the working plane that is arranged behind the beam transformation device (3) in the direction of beam propagation, a respective dark zone having little laser light intensity being produced in the working plane between adjacent partial beams (10, 11, 12), and laser light is emitted by at least one second laser light source and is reflected by reflective surfaces (40, 40', 40", 41, 41', 41") of a reflective means (4, 4') in such a manner that the laser light is incident in the working plane on the dark zones between the adjacent partial beams (10, 11, 12) of the first laser light source. The invention further relates to a device for illuminating a working plane with laser light in a geometrically dense manner.

Description

 "Method and device for producing a geometrically dense illumination of a working plane with laser light"

The present invention relates to a method and a device for generating a geometrically dense illumination of a working plane with laser light.

Definitions: Under "propagation direction" is under this

Patent application understood the mean propagation direction of the light, especially if this is not a plane wave or at least partially convergent or divergent. By light beam, sub-beam or beam is meant, unless expressly stated otherwise, an idealized beam of geometric optics, but a real light beam, such as a laser beam with a Gaussian profile, which has no infinitesimal small, but an extended beam cross-section.

Laser diode bars are known in the art as laser light sources and have a plurality of emitters spaced apart in a so-called slow axis from each other. The slow-axis direction is a first direction in which the active layer of the semiconductor diode extends, whereas the so-called fast-axis is the direction perpendicular thereto. By the individual emitters of the

Laser diode beams emitted laser light beams have in a direction corresponding to the fast axis direction substantially greater divergence than in a second, the slow axis direction.

Numerous methods and devices for the symmetrization of laser light, that of a

Laser diode bar is emitted, known. It will be in Propagation behind the light-emitting sections (emitters) a fast-axis collimation (in particular in the form of a fast-axis collimating lens) arranged. This fast-axis collimation means can be designed, for example, as a plano-convex cylindrical lens. In particular, this cylindrical lens may have a very small focal length and be disposed very close to the light emitting portions.

In the beam propagation direction, an optical beam transformation device is arranged behind the fast axis collimation means, as disclosed, for example, in EP 1 006 382 A1. The optical beam transformation device has a light entry surface and a light exit surface with a number of cylinder lens segments arranged parallel to one another. The axes of the cylindrical lens segments close with a base side of the

Beam transformer, which extends in the x direction, an angle of 45 °. During the passage of a light beam incident linearly on the beam transformation device, as can be generated by a first laser diode bar, the partial beams pass through the light beam

Beam transformation device undergo a beam rotation by 90 °.

For example, each of the emitters of the laser diode bar has a length of approximately 1 50 μm in the slow-axis direction, the center distance (the so-called "pitch") of two neighboring emitters in this direction being approximately 500 μm

Sequence that in a spaced from the laser diode bar and in the beam propagation direction behind the

Beam transformation device provided working plane between the emanating from each emitter sub-beams

Dark areas are present that adversely affect the so called "brightness" (specific intensity, brilliance) of the laser radiation.

After the beam rotation thus results along the horizontal axis, a laser light beam with relatively large areas in which there are no significant laser light components. In order to minimize these areas, some solutions are already known from the prior art, in which, for example, a telescope arrangement is arranged in the beam propagation direction behind the optical beam transformation device. Furthermore, a reduction of those areas where no significant

Laser beam components occur, can be reduced by a prism cascade. However, such approaches are associated with relatively large difficulties in the technical implementation.

This is where the present invention starts and makes it to

Task to provide a method and an apparatus of the type mentioned in which a geometrically dense illumination of the working plane with laser light can be obtained in a simple and efficient manner and with little technical effort.

With regard to the method, this object is achieved by a method having the features of claim 1. With regard to the device, this object is achieved by a device having the features of claim 7. The subclaims relate to advantageous developments of the invention.

In a method according to the invention for producing a geometrically dense coupling of laser light in a working plane, it is provided that

Laser light emitted from a first laser diode bar, -A-

is rotated by 90 ° by means of a beam transformation device before it hits the working plane, which is arranged in the beam propagation direction behind the beam transformation device, wherein in the working plane between adjacent sub-beams in each case a dark zone with low laser light intensity is generated, and

- Laser light is emitted from at least one second laser light source and is reflected by reflecting surfaces of a reflection means such that it meets in the working plane to the dark zones between the adjacent partial beams of the first laser light source. By this method, in the working plane, which lies in the ray propagation direction behind the

Beam transformation device is easily obtained a more uniform illumination with laser light, since the laser light emitted from the second laser light source can effectively fill the dark zones. The required initial fill factor behind the beam transformer should preferably be about 50%. By selecting the focal length of a (near-axis) Kollimationsmittels, which is arranged in the beam propagation direction in front of the beam transformer, the

Output fill factor behind the beam transformation device can be adjusted within wide ranges.

In a particularly advantageous embodiment, there is the possibility that the light emitted by the second laser light source

Laser light is rotated by 90 ° before reflection on one of the reflection surfaces by means of a beam transformation device. This beam transformation device can be either that beam transformation device by means of which the laser light of the first laser diode bar is rotated by 90 °. Alternatively, a second beam transformation device may be used. In a preferred embodiment, there is the possibility that a second laser diode bar is used as the second laser light source. This embodiment has the advantage that the second laser diode bar can be operated independently of the first laser diode bar.

In an alternative, particularly preferred embodiment, it is proposed that the second laser light source is formed as a virtual light source which is obtained by beam splitting the laser light emitted by the first laser light source. These

Embodiment has the advantage that only a single laser diode bar must be operated.

It may be provided in a preferred embodiment that the reflection means as a periscope arrangement with a number of first

Reflecting surfaces and a number of second reflection surfaces is formed. The design of the reflection means as a periscope arrangement has the advantage of a relatively simple structural design.

In a particularly advantageous embodiment, it is proposed that the reflection means is formed by a comb-like structure with a base portion from which a plurality of reflection sections extend away, at the end of which a reflection surface is formed, at which the reflection from the second

Laser light emitted laser light source is reflected, wherein between adjacent reflecting portions each one of the gaps is formed through which the laser light emitted from the first laser diode bar passes.

A device according to the invention is characterized in particular by a second laser light source and a reflection means which are embodied and arranged in such a way in that it can reflect the partial beams emitted by the second laser light source in such a way that these partial beams in the working plane strike the dark zones between the partial beams of the first laser light source. As a result, more uniform illumination with laser light can be obtained in the working plane, since the partial beams emitted by the second laser light source and reflected by the reflection means effectively fill the dark zones.

The reflection means may in a preferred embodiment a

Mirror array with a plurality of spaced apart reflection surfaces. Between adjacent reflection surfaces, a gap is advantageously formed, through which the partial beams generated by the first laser light source (after passing through the beam transformation device) can pass. In a particularly advantageous embodiment, the mirror array can have a comb-like structure with a base section, from which a plurality of reflection sections extend, at the end of which a reflection surface is formed, with one of the intermediate spaces being formed between adjacent reflection sections. The reflection surfaces are each bevelled. During operation, the laser light emitted by the second laser light source is reflected at the reflection surfaces. Through the gaps, the laser light emitted from the first laser diode bar passes.

The second laser light source may be a real laser light source, such as a second laser diode bar having a plurality of emitters. There is also the possibility, in an alternative embodiment, that the second laser light source is a virtual laser light source which is generated by beam splitting from the first

Laser light source emitted laser light can be obtained. In a preferred embodiment it can be provided that the Device comprises a beam splitting means, by means of which the laser light emitted from the first laser diode bar laser light can be divided into a first group of partial beams and a second group of partial beams, wherein the second group of partial beams forms the second laser light source.

Further features and advantages of the present invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings. Show in it

Fig. 1 is a perspective view of a

A prior art beam transformation apparatus with three beam bundles exemplified;

FIG. 2 is a schematic representation of the intensity distribution of the

Laser light in a working plane behind the beam transformation device of FIG. 1;

Fig. 3 is a schematic representation of the intensity distribution of the laser light behind the beam transformation device, as can be obtained according to a preferred embodiment of the present invention;

Fig. 4 is a side view of a portion of the beam path of a device according to the invention with a first

Embodiment of a mirror array;

Fig. 5 is a plan view of the device of FIG. 4;

6 is a perspective view of a mirror array, which is designed according to a first embodiment and which is used in the beam path shown schematically in Figures 4 and 5 ..;

7 shows a side view of part of the beam path of a device according to the invention with a second exemplary embodiment of a mirror array; Fig. 8 is a side view of a portion of the beam path of a device according to the invention with a third embodiment of a mirror array.

First, with reference to Fig. 1, which shows a beam transformation device 3 according to EP 1 006 382 A1, the starting situation will be described in more detail, as it results from the prior art. For generating laser light, a first laser light source designed as a laser diode bar is provided, which has emitters arranged side by side in the X direction and spaced apart in the X direction. The light beams 10, 11, 12 emanating from the individual emitters of the first laser diode bar have a significantly greater divergence in a first direction corresponding to the Y direction than in a second direction

X direction corresponding direction. It is common practice to refer to the direction of greater divergence as the "fast-axis direction" and the direction of smaller divergence as the "slow-axis direction".

In the beam propagation direction Z, the arrangement comprises a collimating means (not explicitly shown here) designed as a fast axis collimation lens. This collimation means may in particular be a plano-convex cylindrical lens whose cylinder axis extends in the X direction. In particular, this cylindrical lens can have a very short focal length and can be arranged very close to the emitters of the first laser diode bar.

In the beam propagation direction, an optical beam transformation device 3 is arranged behind the fast axis collimation means, as shown in perspective in FIG. The optical beam transformation device 3 has a light entrance surface and a light exit surface of a number Parallel to each other arranged cylindrical lens segments 8. The axes of the cylindrical lens segments 8 subtend an angle of 45 ° with a base side of the beam transformation device 3 extending in the x direction.

From Fig. 1, the passage of a line incident on the beam transformer 3 light beam, as can be generated by the first laser diode bar, by the beam transformer 3 using the example of partial beams 1 0, 1 1, 12 with the simplification of the illustration drawn individual light beams 10a, b, c, 11a, b, c, 12a, b, c can be seen. The partial beams 1 0, 1 1, 1 2 are shown for simplicity as if the light beam has only an extension in the x direction. The beam transformation device 3 according to the arrangement in Fig. 1, the sub-beams 10, 1 1, 1 2 aligned opposite, i. the optically functional surfaces provided with the cylindrical lens segments 8 are x-y surfaces. As can be seen in Fig. 1, the sub-beams 1 0, 1 1, 1 2 undergo a rotation through 90 ° in the passage through the beam transformation device 3, so that the individual sub-beams 1 0, 1 1, 12 after passing through the

Beam transformation device 3 are each extended only in the y direction. In this case, for example, the light beam 10b passes unhindered through the beam transformation device 3, whereas the light beam 10a striking the entrance surface to the left of it deflects towards the center and downwards and the light beam 10c to the center and to the right of the entrance surface occurs is deflected above. The same applies to the partial beams 1 1 and 12. In this way it is prevented that the resulting example of individual sections of the first laser diode bar partial beams 10, 1 1, 12 overlap due to the before the beam transformer 1 may be relatively strong divergence in the x direction each other , after that the passage through the beam transformation device 3 only a diffraction-limited residual divergence in the x-direction is present, whereas the divergence in the y-direction of the original divergence in the x-direction corresponds.

In Fig. 2, the intensity distribution of the laser light in a working plane which is located in the beam propagation direction behind the beam transformation device 3, shown schematically greatly simplified. It becomes clear that between the outgoing emitters and by means of

Beam transforming device are rotated by 90 ° partial beams 10, 1 1, 12 dark areas are present, which prove to be detrimental to the so-called "Bπghtness" (specific intensity, brilliance) of the laser radiation in a working plane After the beam symmetry thus results in other words along the horizontal axis (x-axis) is a laser light beam with relatively large areas, in which there are no significant laser light portions.These areas are also referred to below as dark zones.

In FIG. 3, a intensity distribution of the laser light in a working plane, which is located in the beam propagation direction behind the beam transformation device 3 and which is produced by means of a preferred embodiment of a method according to the invention or a device according to the invention, is shown schematically in greatly simplified form. It becomes clear that in the working plane behind the beam transformation device 3 a geometrically dense intensity distribution can be obtained. It can be seen additional partial beams 1 0 ', 1 1', 1 2 'in the dark zones, in the from the

Prior art known solution was still present. In the overlapping areas between adjacent sub-beams 1 0, 10 ', 1 1, 1 1 ', 12, 12' form in the working plane loss zones 13, which are very small. The intensity losses in the loss zones 13 can advantageously be determined by the focal length of the fast axis collimation means arranged in the beam propagation direction in front of the beam transformation device 3 between the maximum

Efficiency and maximum brightness.

In order to obtain the intensity distribution shown schematically in FIG. 3 in the working plane behind the beam transformation device 3, there are various possible implementations. Under

Referring to Fig. 4 to 8 three particularly advantageous embodiments will be explained in more detail below.

According to a first embodiment, which is shown in Fig. 4 to 6, a mirror array 4 is introduced into the beam path, by means of which the laser light 1 0 ', 1 1', 1 2 'of a second laser light source can be reflected, either a second A laser diode bar with a plurality of emitters or a virtual laser light source, which is generated by beam splitting of the light emitted from the first laser diode bar, may be.

The mirror array 4 has a number of spaced-apart reflection surfaces 40, by means of which the laser light 10 ', 11', 12 'emitted by the second (real or virtual) laser light source is reflected parallel to the laser light 10, 11, 12 of the first laser diode bar that can be in the

Working plane behind the beam transformation device 3 results in the i ntensitätsverteilung shown in Fig. 3, in which the laser light 1 0 ', 1 1', 12 'of the second laser light source enters the dark zones and this additionally illuminates.

As can be seen in Fig. 6, the mirror array 4 in this embodiment forms a comb-like structure with a number highly reflective reflecting surfaces 40, wherein between adjacent reflecting surfaces 40 each have a gap 43 (cutout) is formed. The width of the intermediate spaces 43 is selected such that the laser light 1 0, 1 1, 1 2 emitted by the first laser diode bar propagates through these intermediate spaces 43 to the working plane in which the intensity distribution shown in FIG. 3 results. The mirror array here has a base section

44, from which a plurality of reflection portions 45 extend parallel to each other and orthogonal to the base portion 44 away, at the end of each a tapered reflection surface 40 is formed, wherein between adjacent reflection sections

45 each one of the intermediate spaces 43 is formed.

An alternative possibility of realization in order to obtain the intensity distribution shown in FIG. 3 in the working plane is shown in FIG. The mirror array 4 'forms a periscope arrangement, with a number of first reflection surfaces 40' and a number of second reflection surfaces 41 ', which are arranged spaced from the first reflection surfaces 40'. It becomes clear that the first and second reflection surfaces 40 ', 41' are each oriented parallel to one another. As a result, for example, a partial beam 1 2 'of the second laser light source which impinges on the mirror array 4' is first reflected on the first reflection surface 40 'in the manner shown in FIG. 7 in the direction of the second reflection surface 41'. From the second reflection surface 41 ', the partial beam 12' is then parallel to

Beam propagation direction of the corresponding partial beam 12 of the laser light emitted from the first laser diode bar laser light, which passes unhindered and thus straight through the mirror array 4 ', reflected. The reflection of the remaining partial beams 1 0 ', 1 1' of the second laser light source is analog, so that finally in the working plane, the intensity distribution shown in Fig. 3 can be obtained. Another alternative realization possibility for obtaining the intensity distribution shown in FIG. 3 is shown in FIG. 8. In this case, the mirror array 4 "forms a periscope arrangement rotated in comparison with FIG. 7, with a number of first reflection surfaces 40" and a number of second reflection surfaces 41 ".It is clear that the first and second reflection surfaces 40", 41 "are oriented offset relative to one another are that, for example, a partial beam 12 'of the second laser light source, the anti-parallel to the corresponding partial beam 1 2 of the first laser diode bar incident on the mirror array 4', first on the first reflection surface 40 "in the manner shown in Fig. 8 in the direction of the second reflection surface From the second reflection surface 41 ", the partial beam 1 2 'is then parallel to the beam propagation direction of the partial beam 12 of the first

Laser diode bars emitted laser light reflected. The partial beam 1 2 again passes unhindered through the mirror array 4. The reflection of the remaining partial beams 10 ', 11' of the second laser light source takes place analogously, so that finally the intensity distribution shown in FIG.

There is the possibility, in particular with regard to the variants shown in FIGS. 7 and 8, that the laser light emitted by the second laser light source by means of an additional beam transformation device, analogous to the above-described

In addition, there is also the possibility that the laser light emitted by the second laser light source is rotated by 90 ° by means of the beam transformation device 3 before it is reflected by the reflection means 4, 4 ', 4 ".

Claims

claims: 1 . Method for generating a geometrically dense illumination of a working plane with laser light, wherein Laser light which is emitted by a first laser diode bar is rotated by 90 ° by means of a beam transformation device (3), before it hits the working plane which lies behind in the beam propagation direction Beam transformation device (3) is arranged, wherein in the working plane between adjacent partial beams (10, 1 1, 12) each have a dark zone (13) is generated with low laser light intensity, and - Laser light (10 \ 1 1 ', 1 2') of at least one second laser light source is emitted and reflected by reflecting surfaces (40, 40 ', 40 ", 41, 41', 41") of a reflection means (4, 4 ') is that, in the working plane, the dark zones (1 3) between the neighboring partial beams (1 0, 1 1, 12) of the first laser light source. 2. The method according to claim 1, characterized in that the laser light emitted by the second laser light source (1 0 ', 1 1', 1 2 ') by means of a beam transformation device is rotated by 90 °, before it at one of the reflection surfaces (40, 40 ', 40 ", 41, 41 ', 41") of the reflection means (4, 4') is reflected. 3. The method according to claim 1 or 2, characterized in that a second laser diode bar is used as the second laser light source. 4. The method according to claim 1 or 2, characterized in that the second laser light source is formed as a virtual light source, which is obtained by beam splitting of the laser light emitted from the first laser light source (10, 1 1, 12). 5. The method according to any one of claims 1 to 4, characterized in that the reflection means (4, 4 ') as a periscope arrangement with a number of first reflection surfaces (40 ¹ ) and a number of second reflection surfaces (41') is formed. 6. The method according to any one of claims 1 to 4, characterized in that the reflection means (4, 4 ') by a comb-like structure with a base portion (44) is formed, from which a plurality of reflection portions (45) extend away, to de ren End is formed in each case a reflection surface (40) at which the laser light emitted by the second laser light source (1 0 ', 1 1', 12 ') is reflected, and wherein between adjacent reflection sections (45) each formed one of the intermediate spaces (43) through which the laser light (10, 11, 12) emitted from the first laser diode bar passes. 7. Apparatus for generating a geometrically dense illumination of a working plane with laser light, comprising at least one first laser diode bar having a plurality of emitters, a beam transformation device (3) by means of which the partial beams (10, 11, 12) emitted by the first laser diode bar can be rotated by 90 ° during the passage, - A second laser light source and a reflection means (4, 4 '), which is designed and so in the beam path of Device is arranged so that it can reflect the emitted from the second laser light source partial beams (1 0 ', 1 1', 12 ') such that these partial beams (1 0', 1 1 ', 12') in the working plane to the dark zones (1 3) between the partial beams (10, 1 1, 1 2) of the first laser diode bar meet. 8. The device according to claim 7, characterized in that the reflection means (4, 4 ') is a mirror array with a plurality of spaced-apart reflecting surfaces (40, 40', 40 "). 9. Apparatus according to claim 8, characterized in that between adjacent reflecting surfaces (40, 40 ', 40 ") in each case an intermediate space (43) is formed, through which the partial beams (10, 11, 12) emitted by the first laser diode bar can pass , 1 0. Device according to one of claims 8 or 9, characterized in that the mirror array as a periscope arrangement with a number of first reflection surfaces (40 ') and a number of second reflection surfaces (41') is formed. 1 1. Apparatus according to claim 10, characterized in that the first and second reflection surfaces (40 ', 41') of the mirror array (4 ') are each oriented in pairs parallel to each other. 12. Device according to one of claims 8 or 9, characterized in that the mirror array has a comb-like structure with a base portion (44) from which a plurality of reflection portions (45) extend away, at the End is formed in each case a tapered reflection surface (40), wherein between adjacent Reflection sections (45) each one of the intermediate spaces (43) is formed. 13. The apparatus according to claim 12, characterized in that the reflection sections (45) orthogonal to the base portion (44) are oriented. 14. Device according to one of claims 7 to 13, characterized in that the second laser light source is a second Lasediodenbarren. 15. Device according to one of claims 7 to 13, characterized in that the device comprises a beam splitting means, by means of which the laser light emitted from the first laser diode bar in a first group of partial beams (10, 1 1, 12) and in a second group of Partial beams (10 \ 1 1 ', 12') can be divided, wherein the second group of partial beams (10 ', 1 1', 12 ') forms the second laser light source.