WO2004110769A1

WO2004110769A1 - Device for projecting the light of a semiconductor laser unit comprising a plurality of emitters onto a working plane, and illuminating device comprising such a projection device

Info

Publication number: WO2004110769A1
Application number: PCT/EP2004/005863
Authority: WO
Inventors: Vitalij Lissotschenko; Fedor Karpushko; Mikhail Petrov
Original assignee: Hentze-Lissotschenko Patentverwaltungs Gmbh & Co Kg
Priority date: 2003-06-18
Filing date: 2004-05-29
Publication date: 2004-12-23
Also published as: EP1638779A1; JP2006527857A; DE10327735A1; KR20060016816A

Abstract

The invention relates to a device for projecting the light of a semiconductor laser unit (1) comprising a plurality of emitters onto a working plane. Said projection device comprises a collimating means (6) for at least partly collimating the light emitted by the semiconductor laser unit (1) in at least one direction which extends essentially perpendicular to the spreading direction (Z) of the light, and focusing means for at least partly focusing or projecting the at least partly collimated light onto the working plane. The inventive projection device (2, 12) further comprises light-guiding means (8, 13) which are provided with an incident area for light emitted by the collimating means (6) and an emission area from which light can be emitted to the focusing means. Said imaging device (2, 12) is embodied such that light from at least two of the emitters can enter the incident area. The invention also relates to an illuminating device encompassing such a projection device.

Description

Imaging device for imaging the light of a semiconductor laser unit with a plurality of emitters in a working plane and lighting device with such an imaging device

The present invention relates to an imaging device for imaging the light of a semiconductor laser unit with a plurality of emitters in a working plane, comprising a collimation means for the at least partial collimation of the light coming from the semiconductor laser unit in at least one

Direction of propagation of the light essentially perpendicular direction, and focusing means for the at least partial focusing or imaging of the at least partially collimated light in the working plane. Furthermore, the present invention relates to an illumination device for illuminating a predeterminable region of a working plane, comprising a semiconductor laser unit and an imaging device of the aforementioned type.

An imaging device and a lighting device of the aforementioned type are known from US Pat. No. 6,433,934 B1. In the lighting device described therein, a laser diode bar is used as the semiconductor laser unit, which has a multiplicity of emitters which are arranged next to one another at a distance from one another in a first direction. With this first

Direction is the so-called slow axis, within which the divergence of the light emerging from the laser diode bar is smaller than in a direction perpendicular thereto, referred to as the fast axis. Following the laser diode bar, the imaging device sees a fast

Axis collimation lens for collimating the divergence in the fast axis direction. Next to it are two arrays of cylindrical lenses provided, the cylinder axes extend in the fast axis. Each of these cylindrical lenses is assigned to one of the emitters of the laser diode bar and is used for collimation or for focusing the slow-axis component of the light. With these two cylindrical lens arrays, the slow

Axis creates a near-field image of the emitters, in which the light of the individual emitters is not overlapping. This near-field image is imaged in a working plane by further collimation or focusing lenses or field lenses. This working level can be, for example, the modulation level of a modulator for a

Pressure application.

A disadvantage of a lighting device and an imaging device according to the aforementioned prior art has been found to be that the individual emitters of one

Laser diode bars are correlated with one another, so that very often each of the emitters has an intensity distribution of the emitted light that is not even, particularly in the direction of the slow axis. An example of such correlated emitters can be seen in FIG. 5a, in which the intensity distribution 14 of two is exemplary

Emitter with regard to the propagation of the emitter in the slow axis direction, which is denoted by X in FIG. 5a, is shown. If the light of the individual emitters is superimposed on the working plane via corresponding focusing lenses designed as field lenses, an overall intensity distribution 15 is produced, which can be seen from FIG. 5b. With this total intensity distribution 15, the intensity distributions 14 of the individual emitters add up, so that, for example in FIG. 5b, there is a total intensity distribution 15 which has a significantly greater intensity on its left side than on its right side. For the printing industry, for example, such an intensity distribution is hardly acceptable because a rectangular intensity distribution is usually required. From the international patent application WO 03/00051 03 A1 an arrangement for imaging the light emanating from a laser diode bar onto a focal plane is known which at least partially solves the aforementioned problem. In this arrangement, a comb-shaped waveguide means, which has a plurality of waveguides, is inserted between the fast-axis collimation lens and the lens array used for slow-axis collimation or instead of the fast-axis collimation lens. Each of these waveguides is assigned to one of the emitters. I in each one

The light of an individual emitter is reflected back and forth so often by waveguides that it is at least partially homogenized. As a result of this homogenization, the intensity distribution 14 of each of the emitters can be partially straightened, so that when the intensity distribution of the individual emitters is superimposed, an intensity distribution ultimately results which has a more rectangular shape than the prior art. A particular disadvantage of the embodiment according to the aforementioned international patent application is that a large number of optical components are used which the

On the one hand, the lighting device is expensive to manufacture and, on the other hand, it is less effective because the large number of optical components results in greater losses.

The problem underlying the present invention is

Creation of an imaging device and an illumination device of the type mentioned at the outset, which are of simpler construction and provide a more uniform intensity distribution of the light in the working plane.

With regard to the imaging device, this is achieved with an imaging device of the type mentioned at the beginning Characteristic features of claim 1 and with respect to the lighting device achieved by a lighting device of the type mentioned with the characterizing features of claim 13. The subclaims relate to preferred developments of the invention.

According to claim 1, it is provided that the imaging device comprises light guide means which have an entry surface for light emerging from the collimating means and an exit surface from which light can exit to the focusing means, the imaging device being designed such that light from at least two enters the entry surface the emitter can enter. The light guide means are preferably designed in such a way that the light from the at least two emitters can be at least partially mixed within the light guide means. In particular, the light of the at least two emitters is mixed within the light guide means only in a direction perpendicular to the direction of propagation. This can be, for example, the slow axis direction. The imaging device is preferably designed such that light from essentially all of the emitters of the

Semiconductor laser unit can enter the entry surface of the light guide. According to the invention it can be achieved that not only is the light from an individual emitter superimposed on itself and possibly homogenized in the light guide means, but that the light from two or more, in particular all, emitters is superimposed or mixed. On the one hand, this results in a significantly more effective overlay than in the prior art known from the aforementioned international patent application. On the other hand, significantly fewer parts can be used because, in particular when all emitters are superimposed, the lens arrays which associate each of the emitters with a single cylindrical lens can be omitted. I n particular the lens arrays contribute significantly to the manufacturing costs of an imaging device of the type mentioned.

According to a preferred embodiment of the present

According to the invention, the light guide means are designed as an at least partially transparent plane-parallel plate which extends essentially in the direction of propagation of the light. The extent of the entry surface can be smaller in a first direction than in a second direction perpendicular to it. In particular, the extent of the entry surface in the slow axis direction can be significantly smaller than in the fast axis direction. Due to a very small expansion of the light guide in the slow axis direction, the number of reflections with regard to the slow axis portion of the light is significantly increased, so that a significantly greater mixing of the slow

Axis share takes place. Under certain circumstances, if the light of all emitters is to enter the entry surface, a focusing lens with regard to the slow axis component must be provided in front of the entry surface in order to couple the light of all emitters into the entry surface, which is comparatively narrow in the slow axis direction.

According to an alternative embodiment of the present invention, the light guide means are designed as an at least partially transparent body which extends essentially in the direction of propagation of the light and which has a smaller extent in the direction of propagation in the middle in a direction perpendicular to the direction of propagation than on its side facing the semiconductor laser unit. In particular, the body can be comparatively wide in the slow axis direction

Have entry surface into which the light of all emitters can be coupled without additional focusing lenses. Following the entry surface, however, the body tapers in the slow axis direction until it has a very small thickness in the slow axis direction. As a result of this tapering, the number of reflections of the slow-axis portion is in turn significantly increased, so that the slow-axis portion is thoroughly mixed.

The body of the light-guiding means preferably has a larger extension in its direction perpendicular to the direction of propagation on its outlet side facing away from the semiconductor laser unit than in its center. This widening of the body adjoining the narrow center ensures that the light emerging from the exit surface is already partially collimated and does not have to be passed through additional collimation lenses before it can be imaged by the focusing means in the working plane. In this way, additional components are saved, so that the imaging device manages with a minimal number of optical elements. The losses within the imaging device can thereby be minimized. Furthermore, the manufacturing costs can be reduced.

In both embodiments of the light-guiding means, it can be provided that the fast-axis portion of the light can pass through the light-guiding means largely unhindered, so that the collimation of the fast-axis portion is essentially not influenced.

According to the invention, there is the possibility that the entry surface and / or the side surfaces and / or the exit surface of the light guide means are structured. This structuring of the entry surface and / or the side surfaces and / or the exit surface can preferably be realized by roughening, in particular by targeted roughening. Such a structuring can diθ mixing can be improved because, in particular, a comparatively arbitrary or chaotic reflection or transmission takes place on the corresponding surfaces.

As in the prior art, the collimation means can be used as

Fast-axis collimation lens. Similarly, similar to the prior art, the focusing means can comprise a first focusing lens and a second focusing lens, which can serve in particular as a field lens.

The lighting device according to the invention is characterized by an imaging device according to the invention.

In particular, there is the possibility that in the lighting device according to the invention the semiconductor laser unit and the imaging device are arranged on a common carrier. In this way, the semiconductor laser unit and imaging device can be permanently preassembled at the factory.

Like the prior art, the lighting device according to the invention can comprise a semiconductor laser unit with a laser diode bar.

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

1 shows a perspective view of an illumination device according to the invention with an imaging device according to the invention;

Fig. 2 is a view according to the arrow I l in Fig. 1;

Fig. 3 is a view according to the arrow I I I in Fig. 1;

Fig. 4 is a perspective view of another embodiment of an inventive

Illumination device with a further embodiment of an imaging device according to the invention;

5a schematically shows the intensity distribution of individual emitters of a laser diode bar;

5b schematically shows the superposition of the intensity distributions according to FIG. 5a;

5c schematically shows the overall intensity distribution that can be achieved with an illumination device according to the invention.

1 to 4 are Cartesian for better clarity

Coordinate systems shown. 1 that an illumination device according to the invention comprises a semiconductor laser unit 1 and an imaging device 2, which are arranged on a common carrier 3. In the exemplary embodiment shown, the semiconductor laser unit 1 comprises a laser diode bar 4 and corresponding heat sinks 5. A laser diode bar generally has emitters arranged next to one another in one direction, in the illustrated direction in the X direction. Furthermore, a laser diode bar has a smaller divergence in the X direction in which the emitters are arranged next to one another than in the Y direction perpendicular to it. For this reason, the Y direction is called the fast axis and the X direction is called the slow axis.

The light in FIG. 1 essentially emanates from the laser diode bar 4 in the positive Z direction. The imaging device

2 has on its side facing the laser diode bar 4 a collimation means 6, which is designed as a fast-axis collimation lens. The fast-axis collimation lens is essentially a cylindrical lens with a cylindrical axis in the X direction. The collimation means 6 collimates the laser radiation emerging from the laser diode bar 4 in the Y direction.

The fast-axis collimation lens is followed in the positive Z direction by a further cylindrical lens 7, the cylinder axis of which extends in the Y direction. The cylindrical lens 7 is used to focus the light emerging from the collimation means 6 onto the entry surface of a light guide 8 arranged behind the cylinder lens 7 in the positive Z direction. The light guide 8 is comparatively thin in the embodiment shown in FIGS. 1 to 3 , plane-parallel plate made of an at least partially transparent material, which extends essentially in the Z direction. The dimension of the light guide is 8 in X direction significantly smaller than in the Y direction and in the Z direction. The cylindrical lens 7 and the light-guiding means 8 are in particular arranged in such a way that light from several emitters of the laser diode bar 4, in particular the light from all emitters of the laser diode bar 4, enters the entrance surface, that is to say the side of the light-guiding means 8 facing the cylindrical lens 7 in FIG. 1 , The light from the emitters of the laser diode bar 4 is forwarded in the Z direction within the light guide means, in particular the exit from the side surfaces due to total rejection is largely prevented, so that this in the

Light-guiding means 8 light that has left it leaves in the positive Z direction at the right-hand end in FIG. 1.

A further cylindrical lens 9 is arranged behind the light guide 8 in the positive Z direction and at least partially collimates the light emerging from the light guide 8 in the X direction. The cylinder axis of the cylindrical lens 9 extends in the Y direction.

In the positive Z direction behind the cylindrical lens 9, the imaging device 2 comprises two focusing lenses 10, 11, which can focus or image the light into a working plane (not shown). The first focusing lens 10 is designed as a cylindrical lens with a cylindrical axis in the Y direction. The second focusing lens 1 1 is designed as a spherical lens. It is entirely possible to design the focusing lenses 10, 11 differently, for example to combine them in a single lens. Furthermore, a cylindrical lens with a cylindrical axis in the X direction can be used instead of the spherical focusing lens 11. Ultimately, the focusing lenses 10, 1 1, together with the cylindrical lens 9 used for collimation, have the task of imaging the light emerging from the light guide 8 into a certain predetermined area of the working plane. It is achieved by the light guide 8 that the light emanating from several emitters of the laser diode bar 4 is randomly superimposed within the light guide in such a way that the light of the different ones is superimposed in the working plane

Emitter of the laser diode bar 4 is formed, which has a very uniform intensity distribution over the illuminated area. In particular, the light-guiding means 8 is designed such that the fast-axis portion of the light emanating from the laser diode bar 4 is not influenced by the light-guiding means, so that a mixture, in particular an arbitrary or chaotic mixture of the light, only in the slow-axis direction takes place.

In contrast to the prior art, in which the light emanating from individual emitters was superimposed in such a way that, for example, all the emitters on the left side (see intensity distribution 14 of the individual emitters in FIG a very disadvantageous increase in total intensity (see total intensity distribution 15 in FIG. 5b) on the left-hand side, in the imaging device 2 according to the invention the light emanating from different emitters of the laser diode bar 4 is so randomly and chaotically superimposed that even if, for example, all emitters on it have an intensity increase on the left side, the superimposition of the light taking place in the working plane has no intensity increase on the left side (see total intensity distribution 16 after passing through the imaging device 2 according to the invention in FIG ig.5c).

This arbitrary and chaotic overlay effect can be reinforced in particular by the fact that the entrance area and / or the side surfaces of the light guide 8 are roughened in a targeted manner. For example, a sine structure can be applied that has axes of symmetry in the Y direction, so that only the slow-axis component of the light passing through the light guide 8 is influenced, but not the fast-axis component.

Instead of a sine-like or cylinder-like structure, a random, arbitrary structure can also be applied.

Furthermore, there is also the possibility of roughening the exit surface in a targeted manner in order to support the mixing or blending of the slow-axis portion.

In the embodiment of a lighting device according to the invention shown in FIG. 4, the same parts are denoted by the same reference numerals. The semiconductor laser unit 1 does not differ from the semiconductor laser unit of the embodiment according to FIGS. 1 to 3. The imaging device

12 fulfills the same function as the imaging device 2, but has fewer components. Behind the collimation means 6 that the

Corresponds to collimation means 6 from FIGS. 1 to 3, there is no further cylindrical lens, but a light guide means 13 is arranged directly, which has a different shape than the light guide means 8. The light guide means

13 has a larger width in the X direction at its front and rear ends in the Z direction than in the middle thereof, the entry surface facing the laser diode bar 4 in particular having a greater extent in the X direction than the exit surface facing the working plane. In particular, the entry area in the X direction can be approximately twice as wide as the exit area. In the embodiment according to FIG. 4, the imaging device 12 likewise does not have a second cylindrical lens arranged behind the light guide 13 and used to collimate the slow axis. Rather, in the positive Z direction, the focusing lenses 10 adjoin the exit surface of the light guide 13,

1 1, which fulfill the same function as the focusing lenses 10, 1 1 of the imaging device 2 according to FIGS. 1 to 3.

Due to the special geometry of the light guide 13, the cylindrical lenses 7, 9 in front of and behind the light guide 13 can be omitted. In particular, the entry surface of the light guide 13 in the X direction is so wide that the light of several, in particular all, emitters of the laser diode bar 4 enters the entry surface. The constriction of the width in the X direction of the light guide 13 approximately in the central region makes it effective

Mixture achieved with regard to the slow axis portion of the light. Due to the widening of the light guide towards the exit side, the light emerging from the exit surface is at least partially collimated in such a way that it can be focused or imaged into the working plane by the appropriately designed focusing lenses 1 0, 1 1. The embodiment according to FIG. 4 therefore presupposes a higher manufacturing outlay for the light guide 13, but overall requires fewer parts, so that the imaging device 12 has lower losses than the imaging device 2.

The light-guiding means 13 can be structured similarly to the light-guiding means 8 on the entry surface and / or on the side surfaces and / or the exit surface in order to support the mixing of the light with regard to the slow-axis component. There is also the possibility of designing the focusing lenses 10, 11 differently, for example combining them in one lens.

Claims

claims:

1 . Imaging device for imaging the light of a semiconductor laser unit (1) with a plurality of emitters in a working plane, comprising

- Collimation means (6) for the at least partially

Collimation of the light emanating from the semiconductor laser unit (1) in at least one direction (Y) substantially perpendicular to the direction of propagation (Z) of the light;

- Focusing means for at least partially focusing or imaging the at least partially collimated light in the working plane;

characterized in that

the imaging device (2, 12) comprises light guide means (8, 13) which have an entry surface for the

Collimating means (6) have emerging light and an exit surface from which light can exit to the focusing means, the imaging device (2, 12) being designed such that light from at least two of the emitters can enter the entry surface.

2. Imaging device according to claim 1, characterized in that the light guide means (8, 13) are designed such that the light from the at least two emitters within the light guide means (8, 13) can be at least partially mixed.

3. Imaging device according to claim 2, characterized in that the mixing of the light of the at least two emitters within the light guide means (8, 13) can take place at least with respect to a direction (X) perpendicular to the direction of propagation (Z).

4. Imaging device according to one of claims 1 to 3, characterized in that the imaging device (2, 12) is designed such that light from substantially all of the emitters of the semiconductor laser unit (1) enter the entry surface of the light guide means (8, 13) can.

5. Imaging device according to one of claims 1 to 4, characterized in that the light guide means (8) are designed as an at least partially transparent plane-parallel plate which extends essentially in the direction of propagation (Z) of the light.

6. Imaging device according to claim 5, characterized in that the extent of the entry surface is smaller in a first direction than in a second direction perpendicular thereto.

7. Imaging device according to one of claims 1 to 4, characterized in that the light-guiding means are designed as an at least partially transparent body which extends essentially in the direction of propagation (Z) of the light and which has a smaller extent in one direction in the direction of propagation (Z) to the direction of propagation

(Z) has vertical direction (X) as on its side facing the semiconductor laser unit (1).

8. Imaging device according to claim 7, characterized in that the body of the light guide means (13) on its exit side facing away from the semiconductor laser unit (1) has a greater extent in a direction (X) perpendicular to the direction of propagation (Z) than in its center.

9. Imaging device according to one of claims 1 to 8, characterized in that the entry surface and / or the side surfaces and / or the exit surface of the light guide means (8, 13) are structured.

10. Imaging device according to claim 9, characterized in that the structuring of the entry surface and / or the side surfaces and / or the exit surface is realized by roughening, in particular targeted roughening.

1 1. Imaging device according to one of claims 1 to 1 0, characterized in that the collimation means (6) are designed as a fast-axis collimation lens.

12. Imaging device according to one of claims 1 to 1 1, characterized in that the focusing means comprise a first focusing lens (10) and a second focusing lens (1 1).

1 3. Illumination device for illuminating a predeterminable area of a working plane, comprising a semiconductor laser unit (1) and an imaging device (2, 12) for imaging the light of the semiconductor laser unit (1) in one

Working plane, characterized by an imaging device (2, 12) according to one of claims 1 to 12.

14. Lighting device according to claim 13, characterized in that the semiconductor laser unit (1) and the imaging device (2, 12) are arranged on a common carrier (3).

15. Lighting device according to one of claims 13 or 14, characterized in that the semiconductor laser unit (1) comprises a laser diode bar (4).