DE10113518B4 - Method for measuring the degree of soiling of a protective glass of a laser processing head and laser processing system for carrying out the method - Google Patents

Abstract

Method for measuring the degree of soiling of a protective glass (9), which is supported by a laser processing head (1) and lies on the beam output side to a lens arrangement (7) present in the laser processing head (1), through which a laser beam (5) passes, in which - an outside The first radiation detector arrangement (13) arranged in the laser beam (5) observes a surface of the protective glass (9) penetrated by the laser beam (5) in order to measure the intensity of scattered radiation (12) which occurs there by scattering of the laser beam (5) by particles ( 11), which adhere to the protective glass (9), - a second radiation detector arrangement (16) measures the intensity of a partial beam deflected from the laser beam (5) and further comprising - a scattered radiation measured value from that of the first radiation detector arrangement (13) is correlated to the second radiation detector array (16) measured radiation reading to a corrected To obtain a scattered radiation reading that is compared to a reference scattered radiation reading to produce a first error signal when the latter is exceeded, wherein the second radiation detector assembly (16) is radially opposed to the first radiation detector assembly (13).

Description

The invention relates to a method for measuring the degree of contamination of a protective glass of a laser processing head according to the preamble of patent claim 1 and to a laser processing system for carrying out the method according to the preamble of patent claim 7.

From the DE 94 03 822 U1 already a method and a laser processing system of the generic type are known. There, a laser generates a laser beam, which is coupled via a focusing optics in an optical waveguide and transmitted via this. On the output side, the laser beam is collimated by another lens optics and focused by means of a focusing lens on a workpiece. Between the focusing lens and the workpiece, a protective glass is arranged. This protective glass protects the focusing lens against contamination during machining of the workpiece, which can be caused by material vapor and material splashes. To measure the degree of contamination, the scattered radiation of the protective glass is measured. For this purpose, a detector is provided which emits a corresponding signal to a measuring device. The detector is located directly on the outer surface of the protective glass, for example on a ground surface of the protective glass whose thickness is a few millimeters.

From the JP H11-86 296 A a laser processing head with a housing is known, on the beam output side, a lens optics is arranged with protective glass plate. A radiation detector for measuring scattered radiation is located at a distance from the beam entry surface of the protective glass plate. It is located to the side of the lens arrangement. The radiation detector measures scattered radiation emerging from the protective glass plate, which initially spread in the plane of the plate by total reflection.

From the DE 299 03 385 U1 an arrangement for monitoring the degree of contamination of a protective glass of a welding optics is known. From time to time the protective glasses are replaced. To determine the degree of contamination, a sensor is arranged laterally on the protective glass, which is insensitive to the laser radiation itself and has a sensitivity to the infrared heat radiation emitted by the dirt particles. The infrared sensor may be a sensitive in the spectral range temperature sensing arrangement. Also, the influence of radiation, which arises during the machining of a workpiece by means of the laser beam and re-enters the laser processing head, can be eliminated to the scattered radiation value.

Further, the DE 200 14 423 U1 a hand-held processing head for a high-power diode laser whose lens optics is protected by a protective glass. The protective glass is placed in a drawer-like support and monitored for temperature and degree of soiling. The monitoring is based on a temperature measurement of the protective glass by means of a thermocouple. The thermocouple is located on the edge of the drawer-shaped support.

Another protective element for a laser optics is from the DE 198 39 930 C1 known. A protective element for a laser optics is described. The protective element is a protective glass pane. Additional light is coupled into a side surface of the protective glass pane. This passes through the material of the protective glass pane and then exits via the side surface where it is detected by a light detector. Cracks and breaks of the protective glass element are thus detected by a change in the light received in the light detector. Above a lens there are several radiation temperature sensors, which each see certain areas of the protective glass, so detect the emanating from these areas heat radiation.

Finally, from W. Brunner et al., Laser Technology: An Introduction, 4th Edition, Heidelberg: Hüthig, 1989, page 291 known to use a partially transmissive mirror in a laser processing system.

The invention has the object of providing a method and a laser processing system of the type mentioned in such a way that a more accurate assessment of the degree of contamination of the protective glass is possible.

The method-side solution of the problem is specified in the characterizing part of patent claim 1. In contrast, the device-side solution of the problem is found in the characterizing part of claim 7. Advantageous embodiments of the invention are described in the respective dependent subclaims.

The method according to the invention is characterized in that the first radiation detector arrangement observes the surface of the protective glass facing the lens arrangement through the lens arrangement.

Thus, a surface of the protective glass penetrated by the laser beam is observed by the first radiation detector arrangement arranged outside the laser beam or laser beam path, in order to obtain the intensity from there Stray radiation caused by scattering of the laser beam on particles adhered to the protective glass to measure a stray radiation reading is compared to a scattered stray reference value to produce a first error signal when the latter is exceeded.

According to an advantageous embodiment of the invention, the radiation intensity of the laser beam is measured to compensate for their influence on the Streustrahlungsmeßwert. The intensity of the laser radiation, which is scattered by adhering to the protective glass particles, depends on the beam power of the laser used. In order to eliminate this influence, the radiation intensity of the laser beam is measured before it enters the protective glass. The detected scattered radiation intensity can then be set, for example, in relation to the measured input radiation intensity of the laser beam so as to keep the scattered radiation value independent of the input radiation intensity of the laser beam. As a result, the degree of contamination of the protective glass can be determined even more accurately.

According to another advantageous embodiment of the invention, a calibration is performed with each new protective glass used in the laser processing head to compensate for the influence of radiation, which occurs during processing of a workpiece by means of the laser beam and re-enters the laser processing head to the Streustrahlungsmeßwert. The measurement of the degree of contamination of the protective glass can thus also be carried out properly when different parts of scattered radiation are fed back from the outside into the laser processing head in different machining processes, such as laser welding, laser cutting, etc.

The scattered radiation value should be determined in that wavelength range in which the wavelength of the laser beam also lies. Frequently, infrared lasers are used, so that according to one embodiment of the invention, at least the scattered radiation value can also be determined by measuring scattered radiation in the infrared part of the optical spectrum.

It is known that larger splashes adhering to the protective glass hardly generate stray radiation and therefore are often not recognized. However, these spatters absorb laser radiation to a greater extent, so that there may be thermal damage to the protective glass, which under certain circumstances affects the entire laser processing head. It is therefore possible according to a very advantageous development of the invention, in addition to measure the temperature of the protective glass and to compare with a reference temperature value to generate a second error signal when the latter is exceeded. Thus, the degree of contamination of the protective glass can be determined even more accurately.

In a further development of this idea, the temperature difference between the protective glass and the laser processing head can be measured and compared to generate a second error signal with a reference temperature difference value. In this way, the influence of the static temperature of the laser processing head on the measuring method can then be eliminated.

A laser processing system consists at least of a laser processing head with a housing in which a lens arrangement for focusing a laser beam and the beam output side to the lens assembly, a protective glass, and in which also a lying outside the laser beam first radiation detector arrangement is present, the scattered radiation intensity measurement of a surface of the Protective glass observed. In this case, the first stray radiation detector arrangement is equipped with at least one stray radiation detector, which is used according to the invention in a wall passageway of the housing, wherein the wall passageway is arranged and inclined so that the radiation detector observes the protective glass through the lens assembly.

In the housing of the laser processing head is located according to an advantageous embodiment of the invention, a further radiation detector for measuring the intensity of the laser beam. In this case, the further radiation detector is preferably located in such a region in which no stray radiation passes. For measuring the intensity of the incident laser beam is a Strahlumlenkeinrichtung in the laser beam, such as a partially transparent mirror to direct a portion of the laser beam to the other radiation detector. As a result, the reference scattered radiation value can be obtained in a simple manner.

In yet a further embodiment of the invention, a thermally insulated temperature detector for measuring the temperature of the protective glass is present in the housing. For example, it can be directly in spring contact with the protective glass, for example with a peripheral end edge of the protective glass. Another temperature detector, which is used approximately in a housing-side recess, can be used to measure the housing temperature. The temperature detector and the further temperature detector should be as close to each other as possible to exactly the influence of the static temperature of the laser processing head on to detect the temperature of the protective glass.

The laser processing system includes an evaluation circuit for processing the output signals supplied by the detectors. This evaluation circuit can be attached directly to the laser processing head or be present in it, but can also be coupled via line connections to the laser processing head and thus arranged separately from it.

The evaluation circuit preferably contains a divider for forming the ratio between the scattered radiation measured by the radiation detector and the intensity of the laser beam measured by the further radiation detector. Thus, it is possible to obtain a scattered radiation value at the output of the divider which is practically independent of variations in the intensity of the laser beam.

In this case, in a further embodiment of the invention, the output of the divider is connected to an input of a comparator whose other input is connected to a threshold value transmitter. If the scattered radiation value thus exceeds the threshold value, a first error signal can be generated which can be used for stopping the laser processing system or for switching off the laser. The first error signal then indicates that the degree of contamination of the protective glass has exceeded a predetermined value and the glass must be replaced.

In yet a further embodiment of the invention, the output of the divider can be connected to an input of a comparator and to an input of a calibration memory whose memory output is connected via a scaling factor encoder to the other input of the comparator. Using this circuit, a calibration process can be performed with laser processing performed to now also detect the influence of the generated during the machining process and fed back into the laser processing head scattered radiation and to eliminate this influence on the scattered radiation. Only when the scattered radiation measured value during machining of the workpiece exceeds a reference value determined by a scaling factor is the output of the first error signal taken, in order then to carry out further steps, for example to cause the plant to be shut down, etc.

The evaluation circuit may also have a further comparator whose one input to the output of the temperature detector and the other input are connected to a reference temperature value transmitter. Therefore, if the temperature of the protective glass exceeds the reference temperature, then a second error signal can be generated, which can also be used to shut down the laser processing system or to eliminate the laser beam.

It is also possible to provide a Substrahierglied in the evaluation, one input to the output of the temperature detector and its subtraction input to the output of the other temperature detector are connected, wherein a comparator is present, whose one input to the output of the subtractor and the other input are connected to a reference temperature difference value transmitter. As a result, when the second error signal is generated, the influence of the static temperature of the laser processing head, preferably in the vicinity of the protective glass, on the temperature measurement value of the protective glass can be eliminated.

It is possible to OR the first and second error signal in order to take further steps or safety measures in the presence of one of these error signals.

Embodiments of the invention are explained below with reference to the drawings in detail. Show it:

1 a longitudinal section through a laser processing head according to the invention with connected evaluation circuit;

2 a first circuit construction of the evaluation circuit;

3 a second structure of the evaluation circuit;

4 a third structure of the evaluation circuit;

5 a fourth structure of the evaluation circuit; and

6 a further circuit detail of the evaluation circuit in 1 ,

A laser processing system according to the invention 1 has a laser processing head 1 on, with an evaluation circuit 2 which in turn is in connection with a machine control 3 stands, which, among other things, the movement of the laser processing head 1 relative to a workpiece 4 controls, a laser, not shown, for generating a laser processing head 1 passing laser beam 5 turns on and off, and the like.

The laser processing head 1 consists of a housing 6 , which is formed hollow cylindrical and at its to the workpiece 4 lying end has a nozzle-shaped course. Inside the case 6 there is a lens arrangement 7 for focusing the laser beam 5 that's the case 6 centrally penetrated in its longitudinal direction. The lens arrangement 7 may for example consist of one or more lenses with a total focusing property. A focal point 8th of the laser beam 5 comes in the area of the surface of the workpiece 4 to lie to work on the latter.

To prevent when machining the workpiece 4 with the help of the laser beam 5 resulting particles or splashes of material inside the housing 6 of the laser processing head 1 arrive, is the laser processing head 1 beam exit side with a protective glass 9 Mistake. This protective glass 9 closes the beam exit side of the laser processing head 1 and is located in the nozzle-shaped area. The protective glass 9 is preferably formed as a plane-parallel plate, which is perpendicular to the central axis 10 of the laser beam 5 to come to rest. The material of the protective glass 9 is chosen so that the laser beam 5 essentially without losses due to the protective glass 9 can pass through. When machining the workpiece 4 with the help of the laser beam 5 Resulting dirt particles or splashes of material can then only on the beam exit side surface of the protective glass 9 deposit and are there by the reference numbers 11 Mistake. The laser beam penetrates 5 the glass plate 9 , so part of the laser radiation on the particles 11 scattered and back inside the laser processing head 5 directed.

This scattered radiation is in 1 with the reference number 12 Mistake.

For measuring scattered radiation 12 is a scattered radiation detector 13 intended. This scattered radiation detector 13 is sensitive in the wavelength range of the laser beam 5 and is in an opening 14 used, located in a wall of the housing 6 located. The opening 14 is formed by a passageway which in 1 above the lens array 7 is located, so on the side of the lens assembly 7 that from the glass plate 9 points away. The inclination of the passageway 14 is chosen so that the radiation detector 13 the entire glass plate 9 or observe part of it, through the lens array 7 therethrough. Via a line connection 15 is the stray radiation detector 13 in electrical connection with the evaluation circuit 2 ,

The stray radiation detector 13 radially opposite there is another radiation detector 16 , which measures the intensity of the laser beam 5 serves. This further radiation detector 16 is located in a radial passage opening 17 the wall of the housing 6 , To pass through this further radiation detector 16 the intensity of the laser beam 5 to be able to measure, is located in the beam path of the laser beam 5 a partially transparent mirror 18 at about 45 ° to the central axis 10 of the laser beam 5 is inclined. Through this partially transparent mirror 18 becomes a small part of the intensity of the laser beam 5 on the further radiation detector 16 diverted. The redirected radiation is in 1 with the reference number 19 Mistake. The partially transparent mirror 18 itself is again designed as a plane-parallel plate. Most of the laser radiation passes through it. The further detector 16 and the partially transmissive mirror 18 So also lie on that side of the lens assembly 7 that from the protective glass 9 points away. In addition, the other detector 16 via a line connection 20 with the evaluation circuit 2 connected.

To the degree of contamination of the protective glass 9 to be able to detect larger splashes, which cause less scattered radiation, the protective glass stands 9 in a temperature detector 21 in connection. This temperature detector 21 is in a radial channel 22 inserted in the wall of the housing 6 located. This radial channel 22 lies the peripheral edge of the protective glass 9 opposite, so that the temperature detector 21 in resilient contact with the edge of the protective glass 9 can be held. Here is the temperature detector 21 over other areas of the laser processing head 1 thermally insulated. The temperature detector 21 is via a line connection 23 in electrical connection with the evaluation circuit 2 , Through him, the temperature of the protective glass 9 measured. Larger particles or spatters, which generate no scattered radiation or hardly scattered radiation, absorb relatively much laser power, which leads to thermal damage to the protective glass 9 can come. To assess the degree of soiling of the protective glass 9 is therefore the temperature of the protective glass 9 of interest and can therefore be additionally measured.

To the influence of the static temperature of the laser processing head 1 on the temperature of the protective glass 9 The temperature of the laser processing head is also eliminated 1 measured, by another temperature detector 24 which is preferred in the vicinity of the protective glass 9 is arranged. This further temperature detector 24 is in a blind hole 25 of the housing 6 just above the temperature detector 21 in 1 , It is in thermally conductive contact with the housing 6 and is via an electrical line connection 26 with the evaluation circuit 2 connected.

The evaluation circuit 2 is via an electrical line connection 27 with the machine control 3 in communication connection. Based on the output signals of a group of said detectors 13 . 16 . 21 and 24 or from the output signals of all these detectors 13 . 16 . 21 and 24 decides the evaluation circuit 2 , whether the degree of contamination of the protective glass 9 due to the deposition of the particles 11 already exceeded a given threshold or not. If he has exceeded this predetermined threshold, then generates the evaluation 2 an alarm signal over the line connection 27 for machine control 3 to induce the latter, the laser processing head 1 either immediately or at the next opportunity to stop and the laser beam 5 off. In this case, the protective glass must 9 change.

The structure of the evaluation circuit 2 is described below with reference to the 2 to 6 explained in more detail.

A first possible structure of the evaluation circuit 2 show the 2 , Here's a divider 28 present at its one entrance with the pipe 15 from the scattered radiation detector 13 and at his other entrance with the pipe 20 from the radiation detector 16 connected is. The over the line 15 The scattered radiation measured value thus obtained is determined by the divider 28 relative to the radiation intensity set by the radiation detector 16 has been measured. This is the scattered radiation value at the output 29 of the divider 28 regardless of the radiation intensity of the laser beam 5 , This corrected stray radiation value at the output 29 is over a line 30 an input of a comparator 31 fed. The other input of the comparator 31 receives over a line 32 the reference scattered radiation value. This is done by a reference value transmitter 33 provided, which is formed for example in the form of a potentiometer. The tap of the potentiometer is with the line 32 connected. At an exit 34 of the comparator 31 Thus, a first error signal appears when the stray radiation measured value normalized to the laser power exceeds the reference stray radiation measurement value.

Another possibility of training the evaluation circuit 2 is in 3 shown. Same elements as in 2 are provided with the same reference numerals and will not be described again.

The circuit arrangement 3 serves to reduce the influence of stray radiation when assessing the degree of soiling of the protective glass 9 to be eliminated, which is irradiated back into the laser processing head from the outside when performing the laser machining.

For this purpose, the output is 29 of the divider 28 with a data input of a memory 35 connected. A control input of the memory 35 is over a normally open switch 36 connected to reference potential, such as ground potential. A data output of the memory 35 is to a multiplier level 37 led, whose output over the line 32 with the other input of the comparator 31 communicates. Over a controllable resistance 38 parallel to the multiplier stage 37 A scaling factor can be set with which in the multiplier stage 37 the one from the store 35 obtained measured value, which is then used as a reference value to the comparator 31 arrives. Exceeds the stray radiation reading on the line 30 the reference value on the line 32 , appears at the exit 34 of the comparator 31 the first error signal.

The calibration is carried out in detail so that with newly inserted protective glass 9 the laser processing plant is put into operation and a machining of the workpiece 4 with the help of the laser beam 5 he follows. The radiation detector measures 16 the intensity of the laser beam 5 , and the radiation detector 13 the scattered radiation, which is now essentially from the workpiece 4 comes, because of the newly inserted protective glass 9 still no dirt particles adhere. The with regard to the intensity of the laser beam 5 corrected stray radiation reading from divider 28 will be in memory 35 stored, including the switch 36 short is closed. Through the resistance 38 is or has already been given a scaling factor with which the stored measured value is to be multiplied.

During later operation of the laser processing system, the measured value stored in this way and multiplied by the scaling factor serves on the line 32 which remains constant, for reference. Only when, over time, the stray radiation reading on the line 30 has increased so far that the reference is exceeded, the first error signal is at the output 34 generated. It is clear that the machining process in the recording of the reference value and in the subsequent processing of the workpiece 4 it must be the same. It must therefore each be a welding process, a cutting process, etc., act. Different measured values can be stored in memory for these different machining processes 35 are stored, which are then called depending on the later editing process accordingly, to be available as a reference.

In addition to one of the above circuits according to the 2 and 3 can be a circuit arrangement 4 in the evaluation circuit 2 to be available. The measured value from the temperature detector 21 is over the line 23 to an input of a comparator 39 delivered at his other entrance via a pipe 40 receives a reference temperature value from a reference value transmitter 41 is made available. With this reference value transmitter 41 it can be, for example, a potentiometer, its tap with the line 40 connected is. At an exit 42 of the comparator 39 then a second error signal will appear if the temperature reading on the line 23 exceeds the reference temperature value.

Instead of the circuit after 4 can the circuit after 5 be provided to the influence of the static temperature of the laser processing head 1 on the measured value of the temperature detector 21 to eliminate. Same elements as in 4 are provided with the same reference numerals and will not be described again.

The measured value of the temperature detector 21 gets here over the line 23 to an input of a subtractor 43 Being at its subtraction input via the wire 26 the temperature reading from the temperature detector 24 receives. The one by the subtractor 43 In this way formed temperature difference value is from this via a line 44 to said one input of the comparator 39 transmitted to the other input via the line 40 receives a reference temperature difference value. At the exit 42 Then, the second error signal will appear when the output of the subtractor 43 the reference temperature difference value on the line 40 exceeds. The reference temperature difference value on the line 40 is determined by a reference temperature difference encoder 41a generated, which may be in the form of a potentiometer. The tap of the potentiometer is with the line 40 connected.

By means of an in 6 shown OR gates 45 the evaluation circuit 2 can be the first and the second error signal at the outputs 34 and 42 be linked together. The signals at the outputs 34 . 42 then get over the line 27 for machine control 3 which then stops the system either immediately or at another appropriate time if one or both signals are present.

Claims (18)

Method for measuring the degree of soiling of a protective glass ( 9 ) generated by a laser processing head ( 1 ) is carried and beam output side to a in the laser processing head ( 1 ) existing lens arrangement ( 7 ), through which a laser beam ( 5 ), in which - one outside the laser beam ( 5 ) arranged first radiation detector arrangement ( 13 ) one of the laser beam ( 5 ) penetrated surface of the protective glass ( 9 ) to determine the intensity of scattered radiation ( 12 ), which by scattering of the laser beam ( 5 ) on particles ( 11 ), which on the protective glass ( 9 ), - a second radiation detector arrangement ( 16 ) the intensity of a laser beam ( 5 ) deflected sub-beam and in the further - one of the first radiation detector arrangement ( 13 ) measured scattered radiation value to that of the second radiation detector arrangement ( 16 ) in order to obtain a corrected scattered radiation value which is compared with a reference scattered radiation value in order to generate a first error signal when the latter is exceeded, wherein the second radiation detector arrangement ( 16 ) of the first radiation detector arrangement ( 13 ) is radially opposite. Method according to claim 1, characterized in that the first radiation detector arrangement ( 16 ) the lens arrangement ( 7 ) facing surface of the protective glass ( 9 ). Method according to one of claims 1 to 2, characterized in that with each new in the laser processing head ( 1 ) used protective glass ( 9 ) a calibration is performed to determine the influence of radiation that is generated during the machining of a workpiece ( 4 ) by means of the laser beam ( 5 ) arises and back into the laser processing head ( 1 ) to compensate for the scattered radiation reading. Method according to one of claims 1 to 3, characterized in that at least the scattered radiation measurement value is determined by measuring scattered radiation in the infrared part of the optical spectrum. Method according to one of claims 1 to 4, characterized in that in addition the temperature of the protective glass ( 9 ) and compared with a reference temperature value to produce a second error signal when the latter is exceeded. A method according to claim 5, characterized in that the temperature difference between protective glass ( 9 ) and laser processing head ( 1 ) and compared with a reference temperature difference value to produce the second error signal. Laser processing system, at least consisting of a laser processing head ( 1 ) with a housing ( 6 ), in which a lens arrangement ( 7 ) for focusing a laser beam ( 5 ) and beam output side to the lens assembly ( 7 ) a protective glass ( 9 ), and in which further one outside the laser beam ( 5 ) first radiation detector arrangement ( 13 ), which for the scattered radiation intensity measurement is one of the laser beam ( 5 ) penetrated surface of the protective glass ( 9 ), wherein the first radiation detector arrangement at least one into a wall passageway ( 14 ) of the housing ( 6 ) radiation detector ( 13 ) and the wall passageway ( 14 ) is arranged and inclined so that the radiation detector ( 13 ) the protective glass ( 9 ) through the lens assembly ( 7 ), and wherein a second radiation detector arrangement (FIG. 16 ) in a radial passage opening ( 17 ) of the wall of the housing ( 6 ) of the first radiation detector arrangement ( 13 ) is arranged radially opposite to intensity of the second radiation detector arrangement ( 16 ) steered part of the laser beam ( 5 ) to eat. Laser processing system according to claim 7, characterized in that in the beam path of the laser beam ( 5 ) a partially transparent mirror ( 18 ) is arranged to a part of the laser beam ( 5 ) on the further radiation detector ( 16 ) to steer. Laser processing system according to one of claims 7 or 8, characterized in that in the housing ( 6 ) one opposite this thermally insulated temperature detector ( 21 ) for measuring the temperature of the protective glass ( 9 ) is available. Laser processing system according to claim 9, characterized in that the housing ( 6 ) with another temperature detector ( 24 ) is connected to measure the case temperature. Laser processing system according to one of claims 7 to 10, characterized in that it comprises an evaluation circuit ( 2 ) for processing of the detectors ( 13 . 16 . 21 . 24 ) has delivered output signals. Laser processing system according to claim 11, characterized in that the housing ( 6 ) of the laser processing head ( 1 ) the evaluation circuit ( 2 ) wearing. Laser processing system according to claim 11 or 12, characterized in that the evaluation circuit ( 2 ) a divider ( 28 ) for forming the ratio between the radiation detector ( 13 ) and the scattered radiation measured by the further radiation detector ( 16 ) measured intensity of the laser beam ( 5 ) having. Laser processing system according to claim 13, characterized in that the output of the divider ( 28 ) with an input of a comparator ( 31 ) whose other input is connected to a threshold value transmitter ( 33 ) connected is. Laser processing system according to claim 13, characterized in that the output of the divider ( 28 ) with an input of a comparator ( 31 ) and with an input of a calibration memory ( 35 ) whose memory output is connected via a scaling factor encoder ( 37 ) with the other input of the comparator ( 31 ) connected is. Laser processing system according to one of claims 13 to 15, characterized in that the evaluation circuit ( 2 ) another comparator ( 39 ), whose one input to the output of the temperature detector ( 21 ) and its other input with a reference temperature transmitter ( 41 ) are connected. Laser processing system according to one of claims 13 to 15, characterized in that the evaluation circuit ( 2 ) a subtractor ( 43 ), whose one input to the output of the temperature detector ( 21 ) and its subtraction input to the output of the further temperature detector ( 24 ) and that a comparator ( 39 ) is present, whose one input to the output of the subtractor ( 43 ) and its other input with a reference temperature differential value transmitter ( 41a ) are connected. Laser processing system according to one of claims 14 to 17, characterized in that the evaluation circuit ( 2 ) an OR gate ( 45 ), whose inputs each having an output of the comparators ( 31 . 39 ) are connected.

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