DE102005024085A1 - Laser processing step e.g. laser welding/cutting process, monitoring device for workpiece, has radiation-sensitive receiver e.g. photodiode, and camera e.g. CCD image sensor, that simultaneously supply output signals to evaluation circuit - Google Patents

Abstract

The device has a radiation-sensitive receiving arrangement to detect radiation from an area of an interaction zone (20) between a laser beam and a workpiece (21). The arrangement has a radiation-sensitive receiver (16) e.g. photodiode, and a camera e.g. CCD image sensor, that simultaneously supply respective output signals to an evaluation circuit (22). The circuit processes the received signals to deliver the output signals which characterize characteristics of laser processing steps. An independent claim is also included for a laser processing head for processing a workpiece by laser beams.

Description

The The invention relates to a device for monitoring a laser processing operation, in particular a laser welding or laser cutting process, as well as a laser processing head for Machining a workpiece by means of a laser beam equipped with such a device, for the goodness a laser processing operation by an appropriate control or regulation guarantee or at least the goodness of the laser processing process parallel to the processing.

to process monitoring in laser processing, in particular laser beam welding or cutting, so in the monitoring of laser processing operations become monitoring devices used as radiation-sensitive receiver photodiodes or CCD image sensors use the optical emissions during the machining process capture and record.

For this Among other things, external systems are used, the outside of a Laser processing head mounted sensors, such as area cameras, So CCD image sensors with surface arranged Receiver elements, Line scan cameras, ie CCD image sensors with line-shaped receiver elements, or use photodiode systems.

From the DE 100 13 892 A1 is such an external device for determining the quality of welding at a weld between workpieces known. The apparatus comprises first and second sensor means, both connected to a measuring device, which sense the emission intensity of light emitted laterally from the weld at different angles.

From the DE 39 08 187 A1 Another method for quality assurance in laser beam welding and cutting is known in which radiation from the region of the interaction zone between the laser beam and the workpiece is detected by one or more receiver arrangements in order to obtain, after suitable signal processing, a signal indicating whether in laser processing an error has occurred.

Next external monitoring systems of laser processing operations Systems are also used in which for the radiation transport of the interaction zone between laser beam and workpiece to the radiation-sensitive receivers at least individual elements of the laser beam guidance system within the Laser processing head are used.

For example, is from the DE 101 20 251 A1 a method and a device for monitoring a workpiece to be performed on a laser processing operation, in which the process radiation from the interaction region between the laser beam and the workpiece on the focusing lens for the working laser beam, passes to a splitter mirror, with the aid of which coming from the interaction zone radiation from the working beam path is decoupled. An imaging optics subordinate to the splitter mirror then focuses the radiation onto a spatially resolving receiver arrangement which has a diaphragm for determining an observation field on the workpiece.

Next the spatially resolving receiver arrangement is in this known device an observation camera, for example a video camera by means of a connection housing on the housing of the laser processing head appropriate. The video camera serves to observe the workpiece surface during the Adjustment of the receiver arrangement.

The DE 101 60 623 A1 relates to another device for monitoring a laser processing operation. This known monitoring device is used with a laser processing head, in which a collimated working laser beam is deflected via a deflecting mirror to a concave mirror serving as focusing optics. The concave mirror has an effective opening which is larger than that of the deflecting mirror. Thus, part of the radiation emanating from the interaction zone between the laser beam and the workpiece, which strikes the concave mirror, is guided annularly past the deflecting mirror and can be focused onto an entrance aperture of a receiver arrangement by a converging lens arranged behind the deflecting mirror. If the distance between diaphragm and converging lens is varied, the observation area in the area of the interaction zone is shifted accordingly. The receiver assembly is equipped with a posi tion sensitive detector which provides a signal corresponding to the center of gravity of the spectral distribution of the received optical radiation.

In addition to these monitoring devices that use the beam guiding imaging elements of the working beam path, is from the DE 198 52 302 A1 a process monitoring device is known in which a focusing mirror for the working laser beam is provided with a hole through which radiation originating from the interaction zone between the laser beam and the workpiece passes can be to be directed by a arranged behind the hole optics on a detector. Line or area sensors can be used as detector here.

at Such monitoring devices have the used receiver in each case after the to be carried out Machining process and / or the property to be monitored are selected.

Of the Invention is based on the object, a further device for monitoring a laser processing operation and a laser processing head which allows the quality of a Processing process and / or the processing history process independent capture and / or monitor.

These The object is achieved by the device according to claim 1 and the Laser processing head solved according to claim 17. Advantageous developments and embodiments of the invention are described in the respective subclaims.

A inventive device for monitoring a laser processing head thus has a radiation sensitive Receiver arrangement, at least one imaging device and an evaluation circuit for signals from the receiver assembly which, in turn, provides output signals representing the course of the Characterize laser processing operation. To create a high-quality, process-independent monitoring of the machining process to be able to includes the receiver assembly for detecting radiation from the area of the interaction zone between the laser beam and the workpiece at least one radiation-sensitive receiver, for. B. a photodiode, and at least one camera, z. B. with a CCD image sensor whose respective output signals are simultaneously supplied to the evaluation circuit.

On this way it is possible the specific strengths the individual recipient and the camera, which is process-dependent are, according to the respective processing process and / or processing history in a monitoring device to use.

Around the adaptation of the surveillance the laser machining process to specific machining processes To further improve is in an advantageous embodiment the invention provides that the receiver arrangement has a first and second radiation-sensitive receiver comprising different Have spectral sensitivities, wherein the one or more radiation sensitive receiver each comprise a photodiode. Depending on the type of to be performed Laser processing operation, it may also be appropriate that the or radiation-sensitive receiver a photodiode array, a PSD or a CMOS receiver.

When In particular, one or two-dimensional camera CCD image sensors used.

Around the area to be observed on the characteristics of the radiation-sensitive receiver and / or the camera, it is useful if this one to is assigned to the observing area. The aperture can be designed as a positive or negative diaphragm, so that only radiation from a certain area in the vicinity of the interaction zone to the recipient passes or radiation from a specific region of the interaction zone is prevented from striking the recipient.

Around a particularly compact design of the monitoring device according to the invention To achieve, it is provided that the at least one imaging device a focusing optics defining the working beam path for the laser beam, an element for decoupling radiation from the region of the interaction zone between the laser beam and the workpiece from the working beam path and at least one focusing optics for Focusing the decoupled radiation on the at least one radiation-sensitive receiver and comprising at least one camera of the receiver arrangement, wherein expediently the at least one radiation-sensitive receiver and the at least one Camera of the receiver assembly respectively a separate focusing optics is assigned, and in particular each the radiation-sensitive receiver its own focusing optics is assigned.

To decouple the radiation coming from the area of the interaction zone from the working beam path, different beam splitter elements can be provided, each of which allows a portion of the radiation to pass, while deflecting the other in the direction of the radiation receivers. In addition to conventional divider mirrors, which cause an intensity-dependent or wavelength-dependent division of the radiation, it is also possible to use so-called scraper mirrors, which effect a spatial distribution of the radiation, which thus for example allows an outer or inner region of the radiation bundle to pass, while redirecting the outer area of the beam. In an advantageous embodiment of the invention, however provided that the element for coupling radiation from the working beam path is a partially transmissive mirror, in particular a dichroic mirror which transmits the laser beam and deflects radiation from a spectral range other than that of the laser beam in the direction of the receiver arrangement, wherein the deflection of the radiation from the zu observing range by means of the mirror is 90 °.

Further it is useful if the decoupled from the working beam radiation by means of at least a beam splitter mirror is divided into different beams, each directed to the individual receiver and the camera become.

at Another embodiment of the invention provides that the Camera with its associated focusing optics the area of the interaction zone directly observed.

at a particularly preferred embodiment The invention provides that the output signals of the receiver array processing evaluation circuit output signals for a control or control circuit that controls the laser beam and / or the laser processing operation or regulates. It is particularly useful, the output signals of Evaluation circuit also for a documentation of quality to use the laser processing operation. Such documentation can then be added to any machined workpiece, so that at later appearance of damage of the workpiece Cause for this can be determined more easily.

For the practical Use in manufacturing, it is useful if a laser processing head, the a housing, through which a working beam path for the laser beam is guided, and a focusing optics for focusing the laser beam into one outside of the housing provided working focus, with a device according to the invention for monitoring the laser processing operation is equipped. It is useful if at least the at least one radiation-sensitive receiver of receiver arrangement in the case is integrated.

at an alternative embodiment of the invention, it is provided that the radiation-sensitive receivers the receiver arrangement each in a housing are added to the housing the laser processing head are mounted, wherein the at least one Camera for receiving the decoupled from the working laser beam Radiation from the area of the interaction zone on the housing of the Laser processing head is mounted. This also allows retrofitting already existing laser processing heads with a monitoring device according to the invention.

The Invention, we explained in more detail below, for example, with reference to the drawing. It demonstrate:

1 a highly simplified schematic representation of an apparatus for monitoring a laser processing operation according to a first embodiment of the invention and

2 a schematic sectional view of a laser processing head with a monitoring device according to another embodiment of the invention.

In The various figures of the drawing are corresponding to each other Components provided with the same reference numerals.

In 1 schematically a device according to the invention for monitoring a laser processing operation, hereinafter referred to as monitoring device, shown in a laser processing head 10 integrated, the only by a focusing optics 11 and a working beam path defined thereby 12 is indicated. An imaging device provided in the monitoring device according to the invention comprises in addition to the focusing optics 11 for the laser beam 13 a first semitransparent mirror 14 for decoupling the radiation to be observed from the working beam path 12 , a second semitransparent mirror 15 for splitting the decoupled radiation onto a radiation-sensitive receiver 16 and a camera 17 , a focusing optics 18 for focusing the radiation coupled out of the working beam path onto the radiation-sensitive receiver 16 and an unspecified focusing optics in the camera 17 ,

In front of the radiation-sensitive receiver 16 is an aperture in many ways 19 arranged, with which an area in an interaction zone 20 between laser beam 13 and workpiece 21 can be selected. A corresponding aperture can also be before or preferably in the camera 17 to be ordered.

The radiation-sensitive receiver 16 and the camera 17 provide the received radiation corresponding output signals to an evaluation circuit 22 containing the signals of the receiver 16 and the camera 17 in turn, to provide suitable outputs for quality assurance and for the control of a laser processing machine. The output signals of the evaluation circuit 22 for example, the quality or quality of the laser processing operation may be characterizing status signals, for example, a control or regulating circuit 23 are fed, which provides at an output A corresponding control signals for operation of the laser processing machine, in the laser processing head 10 the monitoring device according to the invention is integrated.

Especially when as a camera 17 provided with a two-dimensional receiver, such as a CCD image sensor equipped camera, the output signal of the camera 17 Also be supplied at an output B for the connection of a screen, so that even during the laser processing operation, the laser processing can be optically evaluated by an operator.

During operation of the laser processing machine, while, for example, a laser welding or cutting process is running, the laser beam 13 from the focusing optics 11 on the surface of the workpiece 21 focused, where the laser interacts with the workpiece, so that the material of the workpiece in the area of the interaction zone 20 is melted. The radiation coming from the area of the interaction zone 20 then goes out of the focusing optics 11 back into the working beam path 12 where it passes through the first semitransparent mirror 14 from the working beam path 12 is decoupled.

The partially transparent mirror 14 is expediently a dichroic mirror, which allows the working laser radiation to pass practically unhindered, while it almost completely reflects radiation from other spectral regions. The partially transparent mirror 14 but could also as the working laser beam 13 be formed surrounding Scraperspiegel.

The from the working beam path 12 decoupled radiation is then using a second partially transparent mirror 15 to the camera 17 and the radiation-sensitive receiver 16 divided up. The partially transparent mirror 15 can also have dichroic properties that are related to the spectral sensitivity of the camera 17 and the radiation-sensitive receiver 16 are adjusted.

With the help of the aperture 19 , a certain observation area can be located in the area of the interaction zone 20 which also corresponds to the spectral sensitivity of the receiver 16 can be chosen. In other words, the radiation-sensitive receiver 16 be selected in view of its spectral sensitivity according to the range to be observed. If it is intended that the radiation from a plasma cloud above the interaction zone is to be detected, preferably before a UV-sensitive receiver 16 In contrast, if radiation from the area of the molten bath or the edge thereof is to be detected, then the sensitivity of the receiver is set to visible and / or near infrared light.

As a radiation-sensitive receiver 16 appropriate photodiodes can be provided. However, it is also possible to use position-sensitive detectors or CMOS receivers.

The output signal of the photo- or radiation-sensitive receiver 16 will coincide with the output of the camera 17 to the evaluation circuit 22 which processes them suitably to form quality, status and / or error signals. Such quality, status or error signals can then be in the control or regulating circuit 23 be used for the control or regulation of a laser processing machine to form corresponding signals for adjusting the laser power and / or for setting operating parameters for the machining process, which are transferred to an output A of a corresponding machine control.

Conveniently, the evaluation circuit 22 provided with a further output C, at which the corresponding signals for recording and / or display are provided, so that the monitoring process is documented.

As in 2 are shown are on a laser processing head 10 passing only through a section of his housing 30 , the focusing optics 11 and the working beam path 12 with laser beam 13 is indicated, a first radiation-sensitive receiver 16 ' , a second radiation-sensitive receiver 16 '' and a camera 17 by means of appropriate connection housing 31 . 32 assembled. The housing 30 of the laser processing head 10 has a connection section 33 on, in which the splitter mirror 14 is arranged to radiation from the observed area or areas in the region of the interaction zone 20 between laser beam 13 and workpiece 21 from the working beam path 12 decouple and direct in the direction of the receiver assembly.

In the connection housing 31 of the first radiation-sensitive receiver 16 ' is a beam splitter 15 ' arranged, which is a part of the coupled-out radiation in the direction of the radiation-sensitive receiver 16 ' directs. Between the semitransparent mirror 15 ' and the radiation-sensitive receiver 16 ' are a corresponding focusing optics 18 ' and optionally a filter 34 provided so that the spectral characteristic through the spectra len transmission properties of the filter 34 and the spectral sensitivity of the radiation-sensitive receiver 16 ' be determined.

The connection housing 31 serves on the one hand for receiving and holding the first radiation-sensitive receiver 16 ' on the housing 30 of the laser processing head 10 and on the other hand also for holding the second connection housing 32 in which again a partially transparent mirror 15 '' is arranged, which is part of the partially transmissive mirror 15 ' transmitted radiation to the camera 17 passes and another on the second radiation-sensitive receiver 16 '' directs.

In the direction of the decoupled radiation behind the semitransparent mirror 15 '' again lies a focusing optics 18 '' to the radiation coming from the area to be observed on the radiation-sensitive receiver 16 '' to focus.

Even though it basically possible is, the decoupled from the working beam radiation the area to be observed with a single focusing optics to focus all connected radiation-sensitive receivers and cameras, it is advantageous according to the invention every radiation-sensitive receiver and every camera one Assign your own focusing optics, as so radiation sensitive receiver also a separate observation area can be assigned.

The spectral characteristics of the individual receivers can be further extended by corresponding dichroic splitter mirrors 15 ' . 15 '' each of which decouples only the radiation of interest to the downstream radiation-sensitive receiver and the remainder to the one or more cameras (not shown) 17 pass through.

Thus, according to the invention from one or more areas in the area of the interaction zone incoming radiation for process monitoring while a laser processing operation with one, two or more (not shown) radiation-sensitive receivers and with at least a camera recorded simultaneously in different spectral ranges, to take advantage of the different monitors depending on what is to be done To make full use of the editing process. The ones from the different ones recipients and the camera supplied signals are then used to control and / or Regulation of the respective laser processing operation used. In particular, it is possible depending on the type of processing or the type of processing material preferably the output signals of one of the receiver or solely for the evaluation of the quality or effectiveness of the To use machining process.

With the monitoring device according to the invention is it thus possible for one special editing process to select each of the receiver assembly or camera, the for this process the most significant correlation between editing quality and signal having.

Claims (20)

Device for monitoring a laser processing operation, in particular a laser welding or laser cutting operation, comprising - a radiation-sensitive receiver arrangement ( 16 . 17 ) for detecting radiation from a region of an interaction zone ( 20 ) between a laser beam ( 13 ) and a workpiece ( 21 ) containing at least one radiation-sensitive receiver ( 16 ) and at least one camera ( 17 ), - at least one imaging device ( 11 . 14 . 15 . 18 ) containing at least one region to be observed from the region of the interaction zone ( 20 ) to the receiver arrangement ( 16 . 17 ), and - an evaluation circuit ( 22 ), the output signals of the at least one radiation-sensitive receiver ( 16 ) and the at least one camera ( 17 ) are supplied at the same time and which processes the received output signals of the receiver arrangement to in turn provide output signals characterizing the course of the laser processing operation. Apparatus according to claim 1, characterized in that the receiver arrangement comprises a first and second radiation-sensitive receiver ( 16 ' . 16 '' ) having different spectral sensitivities. Device according to Claim 1 or 2, characterized in that the radiation-sensitive receiver or receivers ( 16 . 16 ' . 16 '' ) each comprise a photodiode. Device according to one of the preceding claims, characterized in that the radiation-sensitive receiver or receivers ( 16 . 16 ' . 16 '' ) comprise a photodiode array, a PSD or a CMOS receiver. Device according to one of the preceding claims, characterized in that the at least one camera ( 17 ) has a single or preferably a two-dimensional CCD image sensor. Device according to one of the preceding claims, characterized in that at least one of the radiation-sensitive receivers ( 16 ) and / or the camera ( 17 ) to watch the one the area defining aperture ( 19 ) assigned. Apparatus according to claim 6, characterized in that as a diaphragm ( 19 ) a positive or negative aperture is provided. Device according to one of the preceding claims, characterized in that the at least one imaging device - one the working beam path ( 12 ) defining focusing optics ( 11 ) for the laser beam ( 13 ), - an element ( 14 ) for decoupling radiation from the region of the interaction zone ( 20 ) between laser beam ( 13 ) and workpiece ( 21 ) from the working beam path ( 12 ) and - at least one focusing optics ( 18 ) for focusing the coupled-out radiation onto the at least one radiation-sensitive receiver ( 16 ) and the at least one camera ( 17 ) of the receiver assembly. Apparatus according to claim 8, characterized in that the at least one radiation-sensitive receiver ( 16 ) and the at least one camera ( 17 ) of the receiver arrangement each have their own focusing optics ( 18 ) assigned. Device according to Claim 9, characterized in that each of the radiation-sensitive receivers ( 16 ' . 16 '' ) has its own focusing optics ( 18 ' . 18 '' ) assigned. Device according to claim 8, 9 or 10, characterized in that the element for decoupling radiation from the working beam path ( 12 ) a partially transmissive mirror, in particular a dichroic mirror ( 14 ), which is the laser beam ( 13 ) and radiation from a spectral range other than that of the laser beam ( 13 ) deflects in the direction of the receiver arrangement. Apparatus according to claim 11, characterized in that the deflection of the radiation from the area to be observed by means of the mirror ( 14 ) Is 90 °. Device according to one of claims 8 to 12, characterized in that the from the working beam path ( 12 ) decoupled radiation by means of at least one beam splitter mirror ( 15 ) is divided into different beams, each one 16 ) and the camera ( 17 ) are steered. Device according to one of claims 1 to 7, characterized in that the camera ( 17 ) with its associated imaging device the area of the interaction zone ( 20 ) directly observed. Device according to one of the preceding claims, characterized in that the output signals of the receiver arrangement ( 16 . 17 ) processing evaluation circuit ( 22 ) Output signals for a control or regulating circuit ( 23 ) supplying the laser beam ( 13 ) and / or controls the laser processing operation. Device according to one of the preceding claims, characterized in that the output signals of the receiver arrangement ( 16 . 17 ) processing evaluation circuit ( 22 ) Provides output signals for monitoring and / or documenting the quality of the laser processing operation. Laser processing head for machining a workpiece ( 21 ) by means of a laser beam ( 13 ) with: - a housing ( 30 ), through which a working beam path ( 12 ) for the laser beam ( 13 ) is guided; - a focusing optics ( 11 ) for focusing the laser beam ( 13 ) into an outside of the housing ( 30 ) work focus (interaction zone 20 ); and with - a device for monitoring the laser processing operation according to one of claims 1 to 16. Laser processing head according to claim 17, characterized in that at least the at least one radiation-sensitive receiver ( 16 ) of the receiver arrangement in the housing ( 30 ) is integrated. Laser processing head according to claim 17, characterized in that the radiation-sensitive receivers ( 16 ' . 16 '' ) of the receiver arrangement in each case in a housing ( 31 . 32 ) are housed on the housing ( 30 ) of the laser processing head ( 10 ) are mounted. Laser processing head according to claim 17, 18 or 19, characterized in that the at least one camera ( 17 ) to receive the from the working beam ( 12 ) coupled out radiation from the region of the interaction zone ( 20 ) on the housing ( 30 ) of the laser processing head ( 10 ) is mounted.