DE19834805C2 - Method and device for the symmetrization of laser beams from laser diode arrays - Google Patents

Description

The invention relates to a method for material processing device with laser radiation, in particular a laser diode Array, with means for beam guidance and beam shaping are provided. The invention further relates to a Interface optics module for performing the method.

DE 29 17 221 C2 describes an optical image system to fo the radiation from a laser diode kiss that the intensity (performance per area) maxi is lubricated. This is achieved through a system which different reproduction scales in the two spatial directions gene (a so-called anamorphic). There is also a system from the front, collecting lens group and from the rear, collecting lens group provided, the front Group should represent an anamorphic system. So shows a figure two crossed cylindrical lenses. The before their lens group can consist of a spherical lens and a beam expander consist of cylindrical lenses. The disadvantage is that this system is not necessarily contains an exact collimation. Also, no suggestion given for a symmetrization. Most problematic is, however, that this system is not for high performance suitable diode laser; it only affects light temp sensitive recording systems.  

DE 42 34 342 A1 describes a method for material album processing with high-power diode laser, as well as a Beam guidance and beam shaping; a cylin derlinse be designed as a collimator lens. About that it is also provided that one or more laser diodes of the array with coupling optics or directly to one Glass fiber are coupled, with multiple fibers into one Bundles are summarized; ultimately that becomes fiber bundle with or without optics aimed at the workpiece.

DE 196 45 150 A1 describes an optical arrangement for Symmetry of the radiation from in a fixed assignment ne arranged next to each other known laser diodes. Here will the output radiation of the individual laser diodes collimated in the x direction and closed offset each other. Then is followed by a most directing element the radiation in the y-direction redirected with different deflection angles and through a subsequent redirection element to opti axis compensated again. The disadvantage here is that collimation only takes place in the x direction and the order of the collimation only in the x direction and then has to take place in the y direction.

The material processing with laser beams has in the experienced an enormous upswing in the past 10 years. in particular especially the development of the diode laser or high Power diode lasers (HLDL) open up new application possibilities opportunities. High-power diode lasers have one extremely compact design excellent electrical wir degrees of efficiency and can be easily integrated into conventional onelle machine tools and production plants. by virtue of  their power (up to 2000 watts) they are in the Material processing is indispensable. marked are diode lasers made up of many individual lasers in one Line are arranged. The simple focus of this Laser beam on a processing surface therefore results a line.

High-performance diode lasers for material processing are currently only used with direct beam transmission in laser material processing, ie an optical system is located directly in front of the laser head. However, direct beam guidance has disadvantages:

• - On the leading machine, e.g. B. a robot or egg ner portal machine, is a component of very high hem value, namely the laser head attached. In the event of a programming error or a crash of the La serkopfes with the component or another part the laser system can cause damage in not unbe pregnant height arise.
• - The dimensions and the weight of the laser head for Direct processing restrict access to to be machined workpiece and beyond the dynamics of the leading machine also be limits.
• - The beam profile of the laser beam on the workpiece is neither homogeneous nor rotationally symmetrical, weswe it is too bad for many machining processes results or low efficiency.

To overcome these problems, it has been proposed been laser beams from diode lasers through a lens to symmetrize. However, only the La focused into a two-dimensional beam, just one line (cf. Heinemann / Leininger, "Fiber coupled diode lasers and beam-shaped high-power stacks " Photonics West 1998, SPIE-Paper, 3267-13).

A lens system is also known from US Pat. No. 4,762,395 Coupling of laser light from a diode laser known which, however, is also only a two-dimensional one Focusing the laser light leads.

The basic problem that has not yet been solved with Development of systems for beam transmission of laser light consists of diode lasers, the asymmetrical Beam parameters of the diode laser, which are in x and y Direction strongly deviate from each other, so too symmetrical that the laser beam passes through with minimal losses a rotationally symmetrical optical element (e.g. a Processing lens) can be performed.

The normal radiation field of high-power laser diodes arrays forms an elongated rectangle with a typi aspect ratio of 5: 1 (dx: dy), when used the beam ratio is the aspect ratio approx. 10: 1. The associated divergence angles have a ver Ratio of about 1:10 (wx: wy).

So far, the radiation field is either directly with "ge ordinary "i.e. spherical optics on the workpiece focused. The result is an elongated, dash shaped focus, which can only be used for special applications  is. Alternatively, a single cylinder lens between radiation source (laser diode array) and Machining optics arranged. To get a symmetri To achieve that focus, however, cylindrical lens and Machining optics always individually adapted to each other so that no universal interface is available is.

Based on this state of the art, it is the task of present invention, a method and a device device for effective material processing with diode diode to create this originating laser light.

This object is achieved by creating a method by means of which the asymmetrical beam of the diode laser is collimated symmetrically, namely by the fact that the laser beams of a diode laser within a lens system consisting of three lens groups ( 20 , 21 , 22 ) in the three Spatial directions x, y and z are influenced such that the laser beams in the x direction are collimated by the first and third lens groups ( 20 , 22 ) and the lasers are collimated in the y direction by the second and third lens group ( 21 , 22 ) , the ef fective focal lengths fx, fy and fz of the individual lens groups ( 21 , 22 , 23 ) and the distances Sx and Sy of the respectively effective group or the distance Sz of the radiation source, in particular a laser diode array, from the last group be designed so that the laser beams are also symmetrized.

This creates an interface that makes it possible light, further modules for various applications connected to the diode laser. As an example here a coupling module in a fiber optic cable and a Objective for direct machining of workpieces.

With the solution according to the invention, the known. Disadvantages of direct processing with a diode laser avoided. The advantage of the invention is that Laser beam of a diode laser flexible using a Light guide cable to the respective processing point on Workpiece can be guided. So far this has not been the case possible because even small diode laser heads in industrial Weigh the approx. 10 kg version and therefore unwieldy are and hinder access to the workpiece.  

By light transmission using a light guide cable can the sensitive diode laser from machining station itself and be kept in an environment be set up, the safe operation and the usual system maintenance allowed.

The invention The proposed interface optics module (SOM) is an opti system, which is an asymmetrical and divergent Radiation field in a symmetrical and collimated Radiation field transferred. The device is known characterized by a lens system consisting of three lens groups with variable focal lengths and mutually variable Ab stand, the first two lens groups from Zylin derlinsen and the last lens group from spherical Lenses exist, and being the first two lens groups together with the last group of lenses mator with connected telescope for two to each other form perpendicular directions of the radiation cross section (x and y if z is the direction of propagation). Through the nested construction becomes Lin saved, on the other hand, aberrations of the optical system can be corrected. With the focal lengths f of the three lens groups and their distance from each other there are sufficient degrees of freedom to make an asymmetry trical radiation field with the half-diameters dx and dy and the divergence angles wx and wy (each different for the directions x and y) in a symmetrical and colli emitted radiation field with the radius dz (same for x and y direction).

The advantages of the present invention can be illustrated as follows:

• - The exact collimation of the laser beam can to the interface optics module a wide range of editing lenses, oh ne that the "working distance", d. H. the distance of the Optics to the workpiece for an optimal focus position each because must be reset. this makes possible the use of lens change systems.
• - By symmetrizing the radiation field the free diameter of the connected optics optimally used, which leads to a higher working distance, smaller focus diameter or higher lei leads transmission.
• - With the symmetrization of both the divergence and also the focus diameter becomes the loss of lei performance and / or beam quality when coupling in a fiber optic cable to an absolute minimum ed.

Correcting the opening error ensures minimal possible focus diameter behind the processing object tiv, which maximizes the processing speed can be.

Further advantageous measures are in the remaining Un claims included.

The invention is in the anlie illustrated drawings and will be described in more detail below described. It shows:

Figure 1 is a schematic representation of the entire system with optical fiber cable and processing optics.

Figure 2 is schematic representation of the beam guidance of the laser light of a diode laser within the interface optics module in the x direction.

Fig. 3 is schematic representation of the beam guidance of the laser light of a diode laser within the interface optics module in y-direction;

Fig. 4 is a schematic representation in cross section through an interface optics module according to the invention.

The arrangement 10 shown in FIG. 1 for coupling laser light from a diode laser for material processing shows in a schematic representation a supply unit 13 for a diode stack 12 of a diode laser, the laser light of which by means of a so-called interface optical module 11 and a - essentially known - downstream fiber coupling module 14 is coupled into a fiber optic cable 15 . Through the glass fiber 15 , the laser light leads to a machining optics head 16 connected to a guide machine 18 , where it can be used for machining a workpiece 17 .

Fig. 2 shows a schematic representation of the beam guidance of the laser light 19 of a diode laser 12 within the interface optics module 11 in a view in the X direction; FIGS. 3, however, in the Y direction.

The interface optics module 11 (SOM) shown in FIGS . 2, 3 and 4 consists of 3 lens groups x, y and z. If laser light 19 is emitted from a diode stack 12 of a diode laser, this leads to a two-dimensional radiation field with the dimensions dx in the x direction and dy in the y direction. The first and third lens groups 20 and 22 collimate the laser light 19 in the x direction, while the second and third lens groups 21 and 22 collimate it in the y direction. The definition of x-direction and y-direction is of course interchangeable.

The focal lengths fx, fy and fz and distances Sx, Sy and Sz of the lenses of the individual lens groups 20 , 21 and 22 are connected according to the invention by the following equations, as is also illustrated in FIG. 4 in a two-dimensional representation:

in which means:
Sx the distance of the group active in the x direction to the last group;
Sy the distance of the group effective in the y direction to the last group;
Sz the distance of the radiation source (laser diode array) to the last group;
fx the effective focal length of the (cylindrical) lens group effective in the x direction;
fy the effective focal length of the (cylindrical) lens group effective in the y direction;
fz the effective focal length of the last (spherical) lens group;
dx the radius of the radiation source in the x direction;
dy the radius of the radiation source in the y direction;
dz the radius of the collimated radiation field after the interface optics module;
wx the divergence angle of the radiation source in the x direction;
wy the divergence angle of the radiation source in the y direction.

Through the relationships according to the invention, the laser beam of the diode laser symmetrized.

embodiment

The radiation field of a compact diode laser array has the following dimensions:

dx = 2 mm
dy = 20 mm
wx = 0.1 rad
wy = 0.01 rad

The following parameters can be selected:

dz = 12 mm
sz = 140 mm
fz = -94 mm

Using the relationships according to the invention, the distances and focal lengths of the lens groups can be found:

sx = 18 mm
sy = 68 mm
fx = 62 mm
fy = 151 mm

This results in the following optical system, characterized by the radii (of the lenses) and distances (of the individual surfaces from each other) of the lens apex:

reference numeral

10

experimental arrangement

11

Interface optical module

12

Diode stack with compacting

13

Supply for diode lasers

14

Fasereinkopplungsmodul

15

glass fiber

16

Processing optical head

17

Workpiece with machining

18

guiding machine

19

laser light

20

1st lens group, cylindrical

21

2. Lens group, cylindrical

22

3rd lens group, spherical

Claims (6)

1. A method for processing materials with laser radiation, in particular by a laser diode array, it produces, means for beam guidance and beam formation being provided, characterized in that the laser beams of a diode laser within a line consisting of three lens groups ( 20 , 21 , 22 ) sensor systems in the three spatial directions x, y and z are influenced such that the laser beams in the x direction by the first and third lens groups ( 20 , 22 ) and the laser beams in y- by the second and third lens groups ( 21 , 22 ) Direction are colli mated, the effective focal lengths fx, fy and fz of the individual lens groups ( 21 , 22 , 23 ) and the distances Sx and Sy of the respective effective group or the distance Sz of the radiation source, in particular a laser diode array, to the last Group are designed so that the laser beams are also symmetrized. 2. The method according to claim 1, characterized in that the distance Sz of the radiation source to the last lens group, the effective focal length fz of the last lens group and the radiation characteristic of the radiation source (dx, dy, dz, wx, wy, wz) the effective focal lengths fx, Determine fy of the effective groups and the distances Sx, Sy from the last lens group as follows:
in which means:
Sx the distance of the group active in the x direction to the last group;
Sy the distance of the group effective in the y direction to the last group;
Sz the distance of the radiation source (laser diode array) to the last group;
fx the effective focal length of the (cylindrical) lens group effective in the x direction;
fy the effective focal length of the (cylindrical) lens group effective in the y direction;
fz the effective focal length of the last (spherical) lens group;
dx the radius of the radiation source in the x direction;
dy the radius of the radiation source in the y direction;
dz the radius of the collimated radiation field after the interface optics module;
wx the divergence angle of the radiation source in the x direction;
wy the divergence angle of the radiation source in the y direction. 3. The method according to claim 1 or 2, characterized records that the laser beams on a Glasfaserka be focused and focused into the same and for editing away from the laserdio the array are available. 4. Device for symmetrizing laser beams of a laser diode array ("interface optics module"), consisting of a multi-part lens system for focusing laser beams, characterized in that
that the lens system ( 11 ) consists of three lens groups ( 20 , 21 , 22 ) with variable focal lengths and to each other at the variable distances,
the first two lens groups ( 20 , 21 ) consisting of cylindrical lenses and the last lens group ( 22 ) consisting of spherical lenses,
and the first two lens groups ( 20 , 21 ) together with the last lens group ( 22 ) form a collimator with a connected telescope. 5. Interface optics module according to claim 4, characterized in that with the module ( 11 ) an end piece ( 15 ) is connected for workpiece processing. 6. Interface optics module according to claim 5, characterized characterized in that the end piece is a light guide cable is.