Abstract:
The laser beam optics for a robot link, wherein a first beam path of a first working laser beam is arranged on the longitudinal axis of the robot link, the first beam path is deflected at an end facing a workpiece into an axis-parallel second beam path, and a third beam path of a second working laser beam is axis-parallel to the first beam path in the robot link, have two optical elements arranged successively in one of the first and second beam paths of the first working laser beam. The two optical elements are transmissive for the first working laser beam in a transmission direction toward a workpiece and are adjusted relative to one another so as to compensate laser beam displacement of the first working laser beam. The second optical element arranged downstream receives the second working laser beam and reflects it toward the workpiece.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The invention relates to laser beam optics in a robot link, wherein a first beam path of a first working laser beam is to be arranged in the longitudinal axis of the robot link, which first laser working beam is deflectable at an end facing the workpiece into an axis-parallel second beam path, and wherein a third beam path of a second working laser beam is to be arranged axis-parallel to the first beam path of the first working laser beam in the robot link.  
           [0003]    2. Description of the Related Art  
           [0004]    Optics with the aforementioned features are known from EP-A-0 901 875. The first working laser beam of the known robot is guided to an attachment unit which has the task of deflecting the first laser beam from the first beam path into the second beam path which is axis-parallel to the first beam path. In the known laser robot a third beam path of a second working laser beam can be provided, in particular, such that it is to be arranged parallel to the first beam path of the first working laser beam. However, this is possible only when the attachment unit for deflection of the first working laser beam is removed. This is so because the attachment unit projects into the second and also into the third beam path since these two aforementioned beam paths are aligned with one another. Accordingly, when different types of working laser radiation are to be employed, for example, a CO 2  laser radiation or a diode laser radiation, a retrofitting of the robot link must be carried out during which the attachment unit is to be either mounted or demounted. This is complex and requires a subsequent adjustment. Moreover, it is not possible to operate the robot simultaneously with two laser beams.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to improve laser beam optics with the aforementioned features such that they are suitable for an alternating use of different working laser radiation without requiring retrofitting, and primarily are suitable for the simultaneous use of two different working laser radiations.  
           [0006]    In accordance with the present invention, this is achieved in that in one of the beam paths of the first working laser beam two optical elements are successively arranged which are transmissive for the working laser beam in the direction toward the workpiece and which are adjusted to one another in the sense of a compensation of a beam displacement, and in that the second working laser beam is guided to the second one of the two optical elements and can be reflected by it toward the workpiece.  
           [0007]    It is important in regard to the invention that by means of the laser beam optics two working laser beams can be combined such that both can perform alternatingly or together the desired machining of a workpiece in one working step. In this connection, the working laser beams should be able to have different radiation, respectively, i.e., radiation having different radiation parameters. The first working laser radiation should be, for example, CO 2  radiation and the second working laser radiation should be Nd:YAG radiation. It is to be taken care of that the laser beam optics can combine the beams error-free. This is achieved particularly in that the first working laser beam passes through optical elements successively which are adjusted relative to one another in the sense of avoiding beam displacement. As a result of this, the combination location of the laser beam optics is constructively fixed. It is not required to provide other optical measures in order to compensate the beam displacement. Otherwise, it would be required to mount components at a location downstream where no space is available within the robot link for the purpose of performing compensating measures.  
           [0008]    An advantageous embodiment of the laser beam optics is characterized in that the first optical element is a beam-transmissive compensation plate, that the second optical element is a reflector plate, which is also beam-transmissive but reflects the second working laser beam, and that the entry symmetry axis of the compensation plate and the exit symmetry axis of the reflector plate are aligned. In this way, the beam displacement can be compensated by two plates whose refractive properties are identical and which act relative to one another in a compensating way with regard to the beam displacement.  
           [0009]    In this connection it is to be preferred that the two optical elements are arranged at an angle to one another which compensates a beam displacement.  
           [0010]    Instead of plates, all optically active components can be employed with which a beam compensation can be eliminated. In this respect, it can be expedient to configure the laser beam optics such that at least one optical element is comprised of two prisms which act optically as a plate.  
           [0011]    When the two optical elements are transmissive for CO 2  laser radiation, conventional plate materials can be used which, with respect to 10.6 μm radiation of a CO 2  laser, are well researched and established, for example, zinc selenide.  
           [0012]    It is then advantageous and necessary to configure the laser optics such that the second optical element is highly reflective for the Nd:YAG radiation.  
           [0013]    In order to achieve a substantially loss-free radiation passage, the laser optics can be configured such that the two optical elements are coated with an anti-reflective coating at the entry side and exit side for the beams. An anti-reflective coating prevents radiation losses at the entry and exit surfaces of the optical elements.  
           [0014]    Moreover, the laser optics can be configured such that the second optical element is coated on a reflector surface facing the second working laser beam so as to be highly reflective for the second laser beam. Such a highly reflective coating is particularly required when radiation losses of the second laser beam are to be prevented. Such radiation losses would have to be expected particularly when the second optical element were radiation-transmissive even if only for a radiation of a different wavelength.  
           [0015]    An expedient configuration of the laser optics is achieved in that for feeding the second working laser beam to the second optical element a deflection mirror is present which is parallel to the reflector surface of the second optical element. This achieves a right angle deflection of the second laser beam relative to the second beam path.  
           [0016]    A constructively particularly advantageous configuration of the laser optics can be achieved in that the two optical elements and, if needed, a deflection mirror are arranged in a single housing. This provides a modular unit which ensures a fixed correlation of the optical elements relative to one another independent of the assembly of this modular unit on the robot link. The housing can be robust so that the configuration and function of the two optical elements are not endangered, in particular, during mounting of the housing on the robot link.  
           [0017]    In another embodiment of the invention, the laser optics can be embodied such that a housing having a beam exit is mounted on an end face of the robot link facing the workpiece and is provided at the end facing away from the workpiece with a first beam entrance for the first working laser beam and a second beam entrance for the second working laser beam. This provides a simple and reliable attachment of the housing as well as a matching correlation of the beam entrances relative to the beam paths.  
           [0018]    The laser beam optics can have a configuration such that a beam displacement module is attached to the housing in the area of its first beam entrance and has a first displacement mirror in the area of the first beam path and a second displacement mirror at the beginning of the second beam path. The deflection of the first working laser beam is realized accordingly by means of a special component which is configured especially with regard to its deflection or displacement task and can be attached additionally to the housing that contain the two optical elements.  
           [0019]    A special configuration of the laser beam optics can be provided in that the housing in the area of the second beam path has a mounting cutout in which an element support comprising the optical elements is mounted. The element support enables particularly a matched arrangement of the elements relative to one another. As for the rest, the housing can be configured independent of the element support, and it is only necessary that the housing in the area of the attachment of the element support has a precise enough configuration in order to fulfill the optical requirements with regard to avoiding beam displacement.  
           [0020]    The laser beam optics can moreover be improved in that the deflection mirror optically arranged upstream of the second optical element is secured on an exterior housing wall which is parallel to a wall of the mounting cutout facing the workpiece. The exterior wall of the housing and the wall of the mounting cutout can be manufactured parallel with high precision. This is advantageous in regard to the optical precision of the beam combination.  
           [0021]    In order to make the laser beam optics suitable for use with such a robot link, which has arranged downstream further links of a robot hand, the laser beam optics can be configured such that the second beam path and a fourth beam path, beginning at the reflecting optical element and common to both laser beams, are arranged in a plane, defined by the longitudinal axis of the robot link and a pivot axis perpendicular thereto of an additional robot link, and spaced at a predetermined spacing from the longitudinal axis of the robot link. As a result of this, the beam path common to both working beams can be located in the vicinity of an outer periphery of the robot link, components required for the downstream links can be arranged in its longitudinal axis, and only one single mirror is required for beam deflection into the pivot axis of the additional robot link. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0022]    In the drawing:  
         [0023]    [0023]FIG. 1 is a schematic illustration of a buckling arm robot;  
         [0024]    [0024]FIG. 2 is a bottom view, partially in a sectioned illustration, of a robot link on which at a side facing the workpiece two additional hand links are arranged;  
         [0025]    [0025]FIG. 3 is a simplified side view of the robot link of FIG. 2 with sectioned details;  
         [0026]    [0026]FIG. 3 a  shows an enlarged detail illustration A of FIG. 3;  
         [0027]    [0027]FIG. 4 shows a schematic beam path in a robot link;  
         [0028]    [0028]FIG. 4 a  shows the detail B of FIG. 4; and  
         [0029]    [0029]FIG. 5 shows a schematic beam path in a robot link. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]    The buckling arm robot illustrated schematically in FIG. 1 is configured such that it can perform the required movements in all directions of Cartesian coordinates x, y, and z within the limit of the range of its links  37 ,  38 ,  39 ,  10 ,  35 , and  36 . All of the aforementioned links are rotational links whose rotational adjustment is realized by motors. FIG. 2 show schematically the arrangement of a drive motor  37  for the robot link  10 . The servomotor  37 , like the servomotors of the other rotational links, are loaded by a continuous-path control, not explained in detail in this context, such that the desired rotational movement of the links is actuated. The robot is to be used for a three-dimensional machining of workpieces by means of laser radiation, for which purpose a special robot hand is provided which is illustrated in FIGS. 2, 3. This robot arm is comprised substantially of the robot link  10  at the side of the robot and two hand links  35 ,  36  which are combined with one another constructively. The link  36  is rotatable by means of pivot bearings  40  about its longitudinal axis which is indicated in FIG. 1 by double arrow  36 ′. In this link  36  the focusing optics  40  are provided with which two working laser beams  13 ,  16  can be focused onto a workpiece. The hand link  35  can be pivoted about a pivot axis  34  which is formed by a pivot bearing  42 . The double arrows  35 ′ in FIGS. 1 and 3 indicate the resulting rotational adjustability of the link  35  of the hand so that the link  36  of the hand can be moved into the positions illustrated in FIG. 3. The link  35  of the hand is otherwise held fixedly by the robot link  10  which has an end face  24  for this attachment at a facing the workpiece.  
         [0031]    The robot link  10  is comprised in accordance with FIGS. 2, 3 substantially of a tubular housing  43  which is mounted with its end opposite the end face  24  on the gear box  44  of the motor. The gear box  44  has mounting flanges  45  for a first laser  46  illustrated schematically in FIG. 1. The laser radiation generated by this laser  46  is introduced via a laser radiation feedline  47  and a radiation inlet  48 , indicated in FIG. 2, into a first beam path  12  which has a coinciding axis with the longitudinal axis  11  of the robot link  10 . Moreover, a non-illustrated second laser is present whose laser radiation is introduced into a third beam path  15  by means of an additional laser radiation feedline  49  which is located within the tubular housing  43  parallel to the first beam path  12 . While the first laser  46 , for example, is a CO 2  laser, the second laser, for example, is an Nd:YAG laser so that the working laser beams  13 ,  16  generated by the two lasers have correspondingly different wavelengths. The laser  46 , for example, has a power of 300 Watt with a beam quality of k=0.7 while the non-illustrated Nd:YAG laser has a power of 200 Watt. The feedline of the laser radiation of the second working laser beam  16  is realized, for example, by means of a flexible line in the form of a glass fiber line connected to a connector element  50  or also to the gear box  44 .  
         [0032]    In order to be able to guide the working laser beams  13 ,  16  to the workpiece  18  in the desired and space-saving way, they must be combinable in a predetermined way. This combination is realized primarily with the laser beam optics near the end face  24  which is arranged in a housing  22 . The housing  22  is fastened on the end face  34  with fastening means  22 ′ and has here a beam exit  23  which opens into a beam passage  24 ′ of the end wall  24 . Opposite the beam exit  23 , i.e., facing away from the workpiece, the housing  22  supports a beam displacement module  27 . This module  27  has a first displacement mirror  28  which is arranged in the first beam path  12  of the first working laser beam  13  so that this working laser beam  13  impinges on the displacement mirror  28  and is deflected vertically to the first beam path  12 . As a result of this deflection, the first working laser beam  13  impinges on a second displacement mirror  29  by which the first working laser beam  13  is deflected into a second beam path  14 . The first working laser beam  13  reaches the housing  22  along the second beam path  14  up to the point of its beam exit  23 .  
         [0033]    The third beam path  14  for the second working laser beam  16  is aligned with a second beam entrance  26  of the housing  22 . The second working laser beam  16  impinges on a deflection mirror  22  from where it is deflected perpendicularly to the longitudinal axis  11  and impinges on a reflector surface  20 ′ of a reflector plate  20  which reflects the second working laser beam  17  again at a right angle, i.e., into a fourth beam path  33 .  
         [0034]    In addition to deflecting the second working laser beam  16 , the reflector plate  20  serves also for providing a beam passage of the first working laser beam  13 . It passes on its way via the second beam path  40  to the beam path  33  common to both laser beams  13 ,  16  through two optical elements successively arranged in the beam direction, i.e., first a compensation plate  19  and then a reflector plate  20 . The compensation plate  19  has refractive properties causing a beam deflection  17 . The reflector plate  20  has also refractive properties which cause an opposite beam deflection which is not explained in detail. Both plates  19 ,  20  are configured and arranged such that the entry symmetry axis  19 ′ of the compensation plate  19  and the exit symmetry axis  20 ″ of the reflector plate  20  are aligned with one another. Accordingly, the beam deflection  17  relative to the beam exit location  20 ′″ of the reflector plate  20  is compensated. Mounting of the compensation plate  19  has the effect that the working laser beam  13  leaving the reflector plate  20  exits precisely at a predetermined beam exit location  20 ′″. This beam exit location  20 ′″ can coincide precisely with the reflection location which is predetermined for the reflection of the working laser beam  16  on the reflector plate  20 ′. This results in the possibility illustrated in FIG. 4 of employing the working beams  13 ,  16  coaxially without having to provide special constructive or other adjusting features with respect to the beam deflection  17  in the area of the laser beam optics. Instead, the laser optics can be formed as a modular unit which operates with great precision.  
         [0035]    The housing  22  is provided with a mounting cutout  30  illustrated in the plane of illustration of FIG. 3 a.  This mounting cutout  30  is V-shaped and has an angle a at the tip. This angle is preferably a right angle. An element support  31  which supports both plates  19 ,  20  can be mounted in this mounting cutout  30 . These two plates  19 ,  20  are also arranged at a right angle so that a mechanically advantageous, i.e., precise, assembly of the element support  31  and the mounting cutout  30  of the housing  22  results. With this assembly it is ensured that the refractive properties of the plates  19 ,  20  can be compensated as precisely as possible. Further requirements for this are that the plates  19 ,  20  have the same refractive properties and, for the same material, are especially of the same thickness.  
         [0036]    In order for the exit symmetry axis  20 ″ and the center of the second working laser beam  16  impinging on the reflector surface  22  to be identical or to coincide, the deflection mirror  21  must also be precisely arranged. This is achieved in that the deflection mirror  21  is secured on an external housing wall  32  which is parallel to the wall  30 ′ of the mounting cutout  30  facing the workpiece. Both the walls  30 ′,  32  can be produced to be exactly parallel in order to fulfill the precision requirements.  
         [0037]    The laser beam optics should be configured to be as loss-free as possible. For example, zinc selenide is provided for the two plates  19 ,  20 . Moreover, by means of coatings it can be achieved that the laser beam optics have as little optical losses as possible. For example, each plate side of the plates  19 ,  20  can be coated anti-reflectively. This is realized, for example, by means of a dielectric layer which is comprised of two layers with different refractive index, respectively, selected from the group of fluorides BaF 2 , MgF 2 , or YbF 3 . The reflector surface  20  of the reflector plate  20 ′, on the other hand, must be reflective as much as possible for the radiation of the second working laser beam  16 , and this can be achieved by a high-reflective coating. Such a coating was achieved with more than five layers of the aforementioned materials so that it was anti-reflective for CO 2  laser radiation but highly reflective for the Nd:YAG laser radiation.  
         [0038]    The fourth beam path  33  which is common to both working laser beams  13 ,  16  leads through the end wall  24  to the link  35 . A deviation prism  35 ″ is arranged here in the area of the pivot axis  34  at a spacing  66  to a symmetry axis of a focusing mirror  41  rotatable together with the hand link  36  so that the working laser beams  13 ,  16  are deflected to the focusing mirror  41 .  
         [0039]    A comparison of FIGS. 4, 5 shows that the working laser beams  13 ,  16  in the common fourth beam path  33  must not be arranged necessarily with coinciding axes. It is instead also possible to provide parallel axes. While in the case of an arrangement of the working laser beams  13 ,  16  with coinciding axes a simultaneous and/or cycled successive machining of the workpiece  18  can be performed, in that, for example, a cutting location  52  and a welding location  53  are formed, in the case of an arrangement with parallel axes it can be achieved that machining locations  54  or  55  at a predetermined spacing from one another are machined simultaneously and/or successively in a cycled fashion. In all cases a configuration of the laser beam optics is advantageous which, as a result of the afore described configurations, is indifferent to adjusting.  
         [0040]    While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.