LASER PROCESSING MONITORING DEVICE, LASER PROCESSING MONITORING METHOD, AND LASER PROCESSING DEVICE

The present laser processing device has a laser oscillator, a laser power supply, a control unit, an optical fiber cable, an electric cable, a processing head, an operation panels and a laser processing monitor unit. The laser processing monitor unit includes the control unit, the operation panel a sensor signal processing unites and a sensor unites as a basic configuration for a main function, that is, a monitoring function, and additionally includes a reference beam source, a reference beam source power supply, an optical measuring instrument and an optical path switching unit as a calibration unites for calibrating an optical sensor incorporated in the sensor unit.

TECHNICAL FIELD

The present invention relates to a laser processing monitoring device, a laser processing monitoring method, and a laser processing device.

BACKGROUND ART

Conventionally, in a laser processing device, a technology for determining the quality of laser processing has been used. Specifically, a laser processing device has a photodetector or an optical sensor incorporated into a processing head that irradiates workpiece with a laser beam. A beam to be measured which is generated or reflected near a processing point of the workpiece is received by the optical sensor through an optical system in the processing head. The laser processing device performs a predetermined signal process for an electric signal (sensor output signal) obtained by photoelectric conversion of the optical sensor, so that the quality of the laser processing is determined.

In this kind of laser processing monitoring technology, not only hardware and software are simpler compared to a technique of image analysis of a processing situation near the processing point using an imaging device, but also qualitative improvement of monitoring is achieved depending on ingenuity of a signal process technology. For example, in laser welding, it is also possible to precisely monitor or analyze subtle behavior and change of a weld part.

CITATION LIST

Patent Literature

SUMMARY

However, while the present inventors promote the research and development of the laser processing monitoring technology as described above, an error in a photoelectric conversion characteristic of the optical sensor becomes a major hindrance in improvement of monitoring performance. That is, the photoelectric conversion characteristic of a photodiode used in the optical sensor inevitably changes over time and, furthermore, is also influenced by an environmental condition such as an ambient temperature. When the photoelectric conversion characteristic of the photodiode changes, even when a beam to be measured having the same light intensity is received from the workpiece side, a value of a sensor output signal obtained after photoelectric conversion of the beam. Therefore, even when the performance of a digital signal process technology is made higher, it is not possible to monitor and analyze laser processing precisely, and it is not possible to determine the quality accurately.

In order to cope with this problem, the present inventors use the following calibration method. First, at the time of shipment or setting of the laser processing device, as part of initialization, a reference workpiece sample is irradiated with a laser beam with reference power. Then, a waveform of a sensor output signal obtained from the optical sensor in the processing head is acquired as a reference waveform SW such as a waveform illustrated inFIG.18A.

As illustrated inFIG.18B, upper and lower limit value envelopes JW+δ and JW−δ that are offset up and down by a certain allowable range (±δ) from the value of the reference waveform SW in the whole interval (or partial interval) of the reference waveform SW are set. The allowable range ±δ illustrated in the figure is enlarged for ease of illustration, but in practice, the envelope setting is performed in an infinitely small range to enhance calibration accuracy.

When the optical sensor is calibrated, a waveform RW of a sensor output signal obtained by irradiating the same workpiece sample with a laser beam with the same reference power is displayed on a monitor screen (maintenance screen) together with the upper and lower limit value envelopes JW+δ and JW−δ. Then, the waveform RW of the sensor output signal protrudes outside the upper and lower limit value envelopes JW+δ and JW−δ, for example, as illustrated inFIG.18C, the on-site person operates screen input or the like to adjust the gain of sensor output such that the waveform RW falls within the inside of the upper and lower limit value envelopes JW+δ and JW−δ (allowable range).

However, it is found that the above optical sensor calibration method is not a valid solution. That is, a laser oscillation unit and the workpiece sample involve a radiation source of a test beam received by the optical sensor during calibration, and a laser optical system is interposed in an optical path of the test beam. Therefore, an error between the reference waveform SW in initial acquisition and the waveform RW of the sensor output signal in current acquisition includes not only the variation of the photoelectric conversion characteristic of the optical sensor, but also the variation of the optical characteristic or the physical characteristic of an involving element or an interposing element thereof. Therefore, it is not possible to perform calibration focused on the photoelectric conversion characteristic of the optical sensor. Furthermore, there is no guarantee that the light intensity of the test beam for calibration is always constant. Therefore, it is not possible to correct the error of the photoelectric conversion characteristic of the optical sensor correctly. In addition, in order to involve the laser oscillation unit and the workpiece sample in the calibration of the optical sensor, calibration work is troublesome and large-scale.

Furthermore, the optical sensor calibration method described above is a method for performing calibration based on relative comparison between the reference waveform SW unique to a device and the waveform RW of the sensor output signal in current acquisition, and a calibration reference value of the optical sensor varies per device. Therefore, a difference in monitoring performance and accuracy between an actually indicated value and a value to be originally indicated causes variation as the individual difference of the laser processing device of the same model using the optical sensor of the same product. That is, the instrument error between laser processing devices of the same model varies among the same model, and therefore it is not possible to perform the same quality evaluation under the setting of the same processing condition.

A laser processing monitoring device of an aspect of the present invention is a laser processing monitoring device for photoelectrically converting a predetermined beam to be measured by an optical sensor disposed in a processing head or in proximity to the processing head to acquire a sensor output signal representing light intensity of the beam to be measured, and monitoring the laser processing based on the sensor output signal, during irradiation to a workpiece with a laser beam for laser processing by the processing head, the predetermined beam to be measured being generated or reflected in a vicinity of a processing point of the workpiece, the laser processing monitoring device including: a reference beam source provided in the processing head, and configured to generate a reference beam for calibrating the optical sensor; a reference beam source power supply unit configured to supply, to the reference beam source, adjustable power for generating the reference beam; and an optical measuring instrument having a beam receiver for receiving the reference beam from the reference beam source in order to calibrate the reference beam source, and configured to measure light intensity of the received reference beam or a predetermined physical quantity equivalent to the light intensity.

In the laser processing monitoring device of the aspect of the present invention, the optical sensor for monitoring laser processing is calibrated using the reference beam source built in the processing head, and this reference beam source is calibrated through the optical measuring instrument built in the device, and therefore even when the electrical-to-optical conversion characteristic of the reference beam source changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. Additionally, even when the photoelectric conversion characteristic of the optical sensor changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately.

A laser processing monitoring method of an aspect of the present invention is a laser processing monitoring method for photoelectrically converting a beam to be measured by an optical sensor disposed in a processing head or in proximity to the processing head to acquire a sensor output signal representing light intensity of the beam to be measured, and monitoring the laser processing based on the sensor output signal, during irradiation to a workpiece with a laser beam for laser processing by the processing head, the beam to be measured being generated or reflected in a vicinity of a processing point of the workpiece, the laser processing monitoring method including: providing the optical sensor in a sensor unit built into the processing head, or disposed in proximity to the processing head; mounting, on the sensor unit, a reference beam source that generates a reference beam for calibrating the optical sensor; setting a first optical path optically connecting the processing point of the workpiece and the optical sensor inside the sensor unit when the laser processing is performed; setting a second optical path optically connecting the reference beam source and the optical sensor inside the sensor unit when the optical sensor is calibrated; and causing the reference beam emitted from the reference beam source to be incident on a beam receiver of an optical measuring instrument in order to calibrate the reference beam source, and adjusting output of the reference beam source such that a measured value of the optical measuring instrument coincides with a reference value.

In the laser processing monitoring method of the aspect of the present invention, when laser processing is monitored, the first optical path is set in the sensor unit and the beam to be measured is made incident on the optical sensor from the workpiece side. Additionally, when the optical sensor is calibrated, the second optical path is set in the sensor unit, and the reference beam from the reference beam source is made incident on the optical sensor. Then, when the reference beam source is calibrated, the reference beam from the reference beam source is made incident on the beam receiver of the optical measuring instrument. Consequently, even when the electrical-to-optical conversion characteristic of the reference beam source changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. Additionally, even when the photoelectric conversion characteristic of the optical sensor changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately.

A laser processing device of an aspect of the present invention includes: a laser oscillation unit configured to oscillate and output a laser beam for laser processing; a processing head optically connected to the laser oscillation unit via an optical fiber cable, and configured to focally irradiate a processing point of a workpiece with the laser beam from the laser oscillation unit; and a laser processing monitor unit configured to monitor laser processing, wherein the laser processing monitor unit has: an optical sensor disposed in the processing head or in proximity to the processing head, and configured to output a sensor output signal representing light intensity of a predetermined beam to be measured, the predetermined beam to be measured being generated or reflected in a vicinity of the processing point of the workpiece; a sensor signal processing unit configured to generate digital waveform data for the sensor output signal from the optical sensor, and display and output a waveform of the sensor output signal based on the waveform data; a reference beam source configured to generate a reference beam for calibrating the optical sensor; a reference beam source power supply unit configured to supply, to the reference beam source, adjustable power for generating the reference beam; and an optical measuring instrument having a beam receiver for receiving the reference beam from the reference beam source in order to calibrate the reference beam source, and configured to measure light intensity of the received reference beam or a predetermined physical quantity equivalent to the light intensity.

In the laser processing device of the aspect of the present invention, the optical sensor of the laser processing monitor unit is calibrated using the reference beam source built in the device, and this reference beam source is calibrated through the optical measuring instrument built in the device, and therefore even when the electrical-to-optical conversion characteristic of the reference beam source changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. Additionally, even when the photoelectric conversion characteristic of the optical sensor changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. The monitoring performance of the laser processing monitor unit is thus improved, so that it is possible to perform qualified quality determination for laser processing.

According to the laser processing monitoring device or the laser processing monitoring method of the aspect of the present invention, with the above configuration and operation, it is possible to improve the accuracy, reproducibility and workability of calibration for the optical sensor used for monitoring laser processing, and improve monitoring performance.

According to the laser processing device of the aspect of the present invention, with the above configuration and operation, it is possible to perform qualified quality determination for laser processing.

DESCRIPTION OF EMBODIMENT

[Configuration of Entire Laser Processing Device]

FIG.1illustrates an entire configuration of a laser processing device including a laser processing monitoring device according to an embodiment of the present invention. This laser processing device is, for example, a laser processing machine that irradiates a workpiece W with a high output CW laser beam or a pulse laser beam and melts a processing point Q of the workpiece W with laser energy to perform desired laser melting processing. This laser processing device has a laser oscillator10, a laser power supply12, a control unit14, an optical fiber cable16, an electric cable18, a processing head20, an operation panel22, and a laser processing monitor unit (laser processing monitoring device of the embodiment)24.

In this laser processing device, the laser oscillator10, the laser power supply12, the control unit14, and the operation panel22are usually disposed in one place or close together to form a main body of the device. On the other hand, the processing head20is configured as a separate and independent unit from the main body of the device, and is disposed at any processing place within an area according to the length of the optical fiber cable16.

The laser processing monitor unit24includes the control unit14, the operation panel22, a sensor signal processing unit26and a sensor unit30as a basic configuration for a main function, that is, a monitoring function, and includes a reference beam source100, a reference beam source power supply102, an optical measuring instrument104and an optical path switching unit105as a calibration unit32for calibrating an optical sensor50incorporated in the sensor unit30.

The laser oscillator10is composed of, for example, a YAG laser, a fiber laser, or a semiconductor laser. For example, when laser spot welding is applied to the workpiece W, the laser oscillator10receives supply of excitation power from the laser power supply12under the control of the control unit14to excite an internal medium, and oscillates and outputs laser beams LB of pulses with wavelengths unique to the medium. The laser beams LB oscillated and output by the laser oscillator10are transmitted to the processing head20through the optical fiber cable16.

The processing head20has an emission unit28which is a head body, and a sensor unit30integrally or detachably connected to the emission unit28through a unit connection opening45. The emission unit28has a cylindrical housing. An upper end of the housing of the emission unit28is connected to the optical fiber cable16from the laser oscillator10, and a laser emission port of a lower end of the housing of the emission unit28is directed to the workpiece W directly under the laser emission port. In the housing of the emission unit28, a collimating lens38, a dichroic mirror40, a focusing lens42and a protective glass44are arranged in a vertical line from a top to a bottom, as the laser optical system. Herein, the protective glass44is mounted on the laser emission port. The dichroic mirror40is disposed so as to be inclined obliquely at 45° towards the unit connection opening45. The dichroic mirror40is coated with a dielectric multilayer film that transmits the laser beams LB from the optical fiber cable16and reflects a beam to be measured and a visible ray from the vicinity of the processing point Q of the workpiece W.

During laser processing, the laser beams LB propagating through the optical fiber cable16are emitted vertically downward at a constant flare angle from an end surface of the optical fiber cable16within the emission unit28. The laser beams LB pass through the collimating lens38to become parallel beams, pass through the dichroic mirror40to be focused through the focusing lens42and the protective glass44, and are incident on the processing point Q of the workpiece W. Then, laser energy of the laser beams LB melts and solidifies the vicinity of the processing point Q to form a weld nugget and further a weld joint. The weld joint is arbitrary, for example, a butt joint, a T-shaped joint, an L-shaped joint, a lap joint, or the like, and is selected by a user.

The sensor unit30also has an integral or assembled cylindrical housing. In the housing of the sensor unit30, the optical sensor50is provided in an upper end of the housing, a folding mirror46, a dichroic mirror58and a condenser lens48are arranged in a vertical line from a bottom to a top, as a monitor optical system directly below the optical sensor50. Herein, the folding mirror46is disposed so as to be inclined obliquely at 45° at the same height as the unit connection opening45. The optical path switching unit105of the calibration unit32is provided between the dichroic mirror58and the condenser lens48.

The dichroic mirror58is provided in order to monitor and photograph the vicinity of the processing point Q of the workpiece W. The dichroic mirror58is disposed so as to be inclined obliquely at 45° at the same height as a folding mirror60provided on the lateral side of the dichroic mirror58. This dichroic mirror58is coated with a dielectric multilayer film that transmits a beam to be measured and reflects a visible ray. The folding mirror60is also disposed so as to be inclined obliquely at 45°, and is mounted with a CCD camera62directly above the folding mirror60. An image signal output by the CCD camera62is transmitted to a display device66through an electric cable64. The display device66is generally disposed on the device main body side. Although not illustrated, an optical system that irradiates the vicinity of the processing point Q of the workpiece W with a guide beam of the visible ray can be incorporated in the sensor unit30.

The optical sensor50of this embodiment includes, for example, a photodiode56as a photoelectric transducer. The optical sensor50includes, in front of (below) the photodiode56, a wavelength filter or a band pass filter54which transmits only beams LM each having a wavelength in a specific band and blocks other beams. Behind the optical sensor50, a substrate of an amplification and output circuit70is provided.

At the time of the laser processing, electromagnetic waves (beams) having a broadband wavelength is emitted from the vicinity of the processing point Q of the workpiece W which is irradiated with the laser beams LB by the emission unit28. In vertically upward electromagnetic waves among the electromagnetic waves emitted from the workpiece W, beams that pass through the focusing lens42in the emission unit28and are reflected horizontally by the dichroic mirror40passing through the unit connection opening45to be guided into the sensor unit30. Among the beams guided into the sensor unit30, a beam reflected vertically upward by the folding mirror46and then transmitted through the dichroic mirror58is incident on the band pass filter54through the optical path switching unit105and the condenser lens48. Then, the beams LM having a wavelength component in a predetermined band selected by the band pass filter54are focused and incident on a light receiving surface of the photodiode56. In this case, the optical path switching unit105is switched such that the processing point Q of the workpiece W and the optical sensor50are optically connected by a first optical path K1indicated by a dashed line inFIG.1.

Among beams that pass from the emission unit28through the unit connection opening45to enter the sensor unit30, a visible ray is folded vertically upwards by the folding mirror46. The folded visible ray is horizontally reflected by the dichroic mirror58as illustrated by a broken line inFIG.1, folded vertically upward by the folding mirror60, and is incident on an imaging surface of the CCD camera62. A condenser lens (not illustrated) may be provided in front of the CCD camera62. An output signal (video signal) of the CCD camera62is sent to the display device66, and an image of the vicinity of the processing point Q of the workpiece W is displayed on a screen of the display device66.

In the optical sensor50, a wavelength band in which a beam is transmitted through the band pass filter54is preferably set to the most suitable band for grasping the influence of a predetermined factor on a welding characteristic of the vicinity of the processing point for a plurality of types of materials and a variety of processing forms to be selected for the workpiece W as the intensity or change of the radiant energy, in comprehensive consideration of sensitivity, versatility, cost, and the like, in monitoring method using a single photodiode56.

In this regard, well-known black body radiation spectrum distribution illustrated inFIG.2can be favorably used. As illustrated in a graph ofFIG.2, there is a certain relation between the spectrum of an electromagnetic wave emitted by a black body and the surface temperature. When the temperature of an object is high, the peak of radiant energy shifts to a short wavelength, and when the temperature of an object is low, the peak of radiant energy shifts to a long wavelength, and the peak radiant energy changes exponentially with temperature change. According to this graph, the wavelength of a peak point of energy density emitted from a black body with a temperature of 1500° C. is about 1800 nm.

On the other hand,FIG.3illustrates a result obtained by measuring, from various angular positions with respect to the processing point, the intensity (relative count value) of a beam of 1000 nm or more detected when iron-based stainless steel (melting point is about 1500° C.) is irradiated with a laser beam, and analyzing the spectrum distribution with a spectrum analyzer by the present inventors. A display waveform of a spectrum analyzer illustrates each peak value as a relative intensity without distinguishing over time the intensity of the detected beam of 1000 nm or more. Although the intensity of the whole of the indicated waveform varies depending on each angular position at the time of measurement, a constant characteristic is obtained. According to this, the intensity (radiant energy density) of infrared rays emitted from a molten part of the stainless steel has a steep mountain-shaped characteristic over a band of about 1000 nm to 1100 nm and a broad mountain-shaped characteristic over a band of about 1200 nm to 2500 nm. When focusing on the latter broad mountain-shaped characteristic, the wavelength of the peak point is about 1800 nm, and generally approximates the wavelength (about 1800 nm) of the peak point of the energy density emitted from the black body with a temperature of 1500° C.

From this fact, it is possible to determine a practical optimal wavelength band in laser processing monitoring method using the single photodiode56, by using, as an index, a melting point of each of a plurality of types of metals that can be assumed as the material of the workpiece W, with reference to the graph inFIG.2. As an example, the respective melting points of an iron-based metal, copper-based metal, and an aluminum-based metal which are the main materials for laser melting processing are around 1500° C., around 1000° C., and around 600° C., and therefore inFIG.2, the band of 1.3 μm (1300 nm) to 2.5 μm (2500 nm) may be used as the wavelength band that is photoelectrically converted by the optical sensor50.

Referring again toFIG.1, a sensor output signal CS output from the amplification and output circuit70in the sensor unit30is transmitted to the sensor signal processing unit26on the device main body side via the electric cable18. The sensor output signal CS is converted into a digital signal by an A/D converter82and a digital signal processing is performed in the arithmetic processing unit84.

The arithmetic processing unit84is composed of a hardware or middleware arithmetic processing device, preferably an FPGA (Feed Programmable Gate Array), capable of performing specific arithmetic processing at high speed. The arithmetic processing unit84converts an instantaneous voltage value of the sensor output signal CS into a count value (relative value) representing the intensity of a radiated beam by using a data memory88, and generates the converted value as digital waveform data DCS. The generated waveform data DCS is stored in the data memory88. The arithmetic processing unit84displays a waveform of the sensor output signal CS on a display of a display unit22aof the operation panel22via the control unit14based on the waveform data DCS. Alternatively, the arithmetic processing unit84also executes quality determination processing described later, and displays a determination result together with the waveform of the sensor output signal CS. The control unit14converts the waveform data DCS and the determination result data given from the arithmetic processing unit84into a video signal, and displays an image of the waveform of the sensor output signal CS and the determination result information and the like on the display of the display unit22aof the operation panel22.

Thus, according to the laser processing monitor unit24of this embodiment, the radiated beam (infrared rays) when the processing point of the workpiece reaches a molten state is an object to be monitored. Then, instead of conversion of the radiated beam into temperature, change in the amount of the radiated beam during processing is converted into an instantaneous integrated value or a count value in a specific band and is displayed, so that the processing status of the workpiece is visualized as a waveform.

The operation panel22has, for example, the display unit22acomposed of a liquid crystal display, and a keyboard or touch panel type input unit22b, and displays a setting screen, a monitor screen, a maintenance screen, or the like under display control of the control unit14. For example, as one of the setting screens, a laser output waveform corresponding to a setting condition of the laser beam LB is displayed on the display of the display unit22a. In addition, as one of the monitor screens, for example, as illustrated inFIG.4toFIG.6described below, a waveform of a very fine sensor output signal acquired without loss of intensity variation in the laser processing monitor unit24is visualized and displayed on the display of the display unit22a. Furthermore, as one of the maintenance screens, gain adjustment (digital gain adjustment) for the output of an optical sensor50can be performed on the screen.

[Monitoring Function of Laser Processing Monitor Unit]

In order to verify the monitoring function of the laser processing monitor unit24in this embodiment, the present inventors conducted Experiments 1, 2, and 3 as illustrated inFIG.4toFIG.6, respectively. A waveform illustrated in each figure is a waveform of the sensor output signal CS displayed on the monitor screen of the display unit22aof the operation panel22. A finely zigzagging portion in the waveform indicates that metal melting occurs in the vicinity of the processing point, and radiated beam disturbances from a wave surface of a molten pool are detected. A point at which the waveform, which increases upwards on the time axis, reaches a peak is a point at which the irradiation with the laser beams LB is stopped, and the waveform falls from this point.

In Experiment 1 (FIG.4), two stainless steel plates (SUS304) W1and W2with a thickness of 1.0 mm were arranged side by side to form a workpiece W, and butt welding was performed using a pulse laser beam. In this butt welding, the laser beam spot diameter was 0.3 mm, the laser output was 500 W, and the pulse width was 20 ms. Then, in a case (a) where there is no gap (clearance) between W1and W2of the workpiece and in a case (b) where there is a gap of 0.09 mm, which is 30% of a spot diameter of 0.3 mm, it was verified how the influence of the gap (specific factor) on the processing characteristic of the butt welding of the workpiece (W1, W2) can be monitored and analyzed in the laser processing monitor unit24.

The waveform of the case (a) where there is no gap in a butted part and the waveform of the case (b) where there is a gap in a butted part are compared. The former (a) has a characteristic that a detection starting point is high immediately after the start of the rise of the waveform and the fall of the waveform is relatively gentle. On the other hand, the latter (b) has a characteristic that the detection starting point immediately after the beginning of the rise of the waveform is low and the fall of the waveform is relatively sharp. This phenomenon indicates the followings. That is, in the case (b) where there is a gap in the butted part, a laser beam is also incident on a part (gap) where there is no metal. Therefore, due to the presence of the gap with respect to the spot diameter at the irradiation point, a phenomenon that an amount of molten metal, which forms a molten pool, decreases occurs. A difference in the molten metal amount also appears as a difference in the radiated beam amount in the radiated beam detected in the vicinity of the molten pool, and the detection starting point immediately after the rise of the waveform becomes low. In addition, the molten metal amount decreases due to the phenomenon that vaporized metal flies together with a transmitted beam that passes through the gap. Therefore, in a case where there is a gap, the fall of the waveform is detected quickly.

In Experiment 2 (FIG.5), two stainless steel plates (SUS304) W1and W2with a thickness of 0.3 mm were stacked to form a workpiece W, and lap welding was performed using a pulse laser beam. In this lap welding, the laser beam spot diameter was 0.3 mm, the laser output was 500 W, and the pulse width was 45 ms. Then, in a case (a) where there is no gap in the workpiece (between W1and W2) and in a case (b) where there is a gap of 0.06 mm, which is 20% of a spot diameter of 0.3 mm between the workpiece materials (W1and W2), it was verified how the influence of the gap (specific factor) on the processing characteristic of the lap welding of the workpiece (W1, W2) can be monitored and analyzed.

The case (b) where there is a gap of 0.06 mm in this lap welding and the case (a) where there is no gap in this lap welding are compared. It was difficult to distinguish the intensity change of a radiated beam in the rising part of the waveform. However, in the falling portion of the waveform, that is, after the pulse laser irradiation was stopped, the fall of the waveform in the case (b) of the waveform with a gap was more gentle than that in the case (a) of the waveform with no gap. This phenomenon indicates the followings. That is, in the lap welding, in the case (a) where there is no gap in the workpiece material, it is considered that the irradiation laser beam melts and penetrates the first metal W1, and thereafter melts the second metal W2as it is. On the other hand, in the case (b) where there is a small gap in the workpiece materials, the heat transfer in the workpiece material is delayed due to the influence of an air layer existing in the gap, compared to the case (a) where there is no gap between the metal layers, so that it is detected that the fall of the waveform is gentle.

In Experiment 3 (FIG.6), two plate materials W1and W2of the stainless steel SUS304 with a thickness of 0.3 mm were stacked with no gap to form a workpiece W, and lap welding was performed using a pulse laser beam. In this lap welding, the laser beam spot diameter was 0.3 mm, the laser output and the pulse width were parameters. That is, for the laser output, six stage values from 300 W to 550 W were selected in 50 W increments, and for the pulse width, three stage values of 25 ms, 35 ms, and 45 ms were selected. Then, it was verified how the influence of the laser output (first specific factor) and the pulse width (second specific factor) on the processing characteristic of the lap welding of workpiece (W1and W2) can be monitored and analyzed.

FromFIG.6, it is found that as the laser output setting value of the laser beam LB increases, the radiated beam intensity indicated by the waveform of the sensor output signal CS also increases proportionally, and as the laser output setting value of the laser beam LB increases, the fall of the waveform of the sensor output signal CS is delayed. Furthermore, it can be seen that the larger the pulse width, the higher the radiated beam intensity (especially the maximum peak value immediately before the fall) displayed by the waveform of the sensor output signal. Consequently, the radiated beam from the workpiece in the laser processing is accurately detected in units of tens of watts and in units of 10 ms.

As described above, according to the laser processing monitor unit24of this embodiment, monitoring and analysis of the action of the laser beam LB in the laser processing, monitoring and analysis of the degree of influence of a predetermined factor related to the processing state or the processing quality of the laser processing, quality determination of the laser welding processing can be simply and precisely performed from the waveform characteristic of the sensor output signal CS displayed on the monitor screen of the operation panel22during the laser processing.

[Configuration and Operation of Calibration Unit]

In the laser processing monitor unit24of this embodiment, a photodetector or an optical sensor50is incorporated into the sensor unit30built into the processing head20. However, the photoelectric conversion characteristic of the photodiode56that constitutes this optical sensor50not only inevitably changes over time, but also depends on an environmental condition such as an ambient temperature. When the photoelectric conversion characteristic of the photodiode56changes, even when a beam LM to be measured having the same light intensity is received from the workpiece W side, a value of an analog sensor output signal CS obtained by photoelectric conversion changes. Therefore, even when the sensor signal processing unit26has higher performance, the accuracy and the reliability of the waveform information of the sensor output signal CS provided on the monitor screen are low, and the detailed monitoring and analysis of the laser processing and the appropriate quality determination is not possible.

In order to cope with this problem, the laser processing monitor unit24of this embodiment includes the calibration unit32that enables highly accurate and reliable calibration for change over time in the photoelectric conversion characteristic of the sensor50and variation according to an environmental condition. Hereinafter, the configuration and the operation of the calibration unit32will be described in detail.

As illustrated inFIG.1, the calibration unit32includes the reference beam source100, the reference beam source power supply102, the optical measuring instrument104and the optical path switching unit105provided inside and outside the sensor unit30.

The reference beam source100is a beam source that generates infrared rays containing the wavelength of beam LM to be measured, and preferably has radiation characteristics close to the radiation spectrum distribution of the ideal black body inFIG.2.

FIG.7Aillustrates a preferred configuration example of the reference beam source100. This reference beam source100has an infrared ray emitting element110enabling black body radiation. This infrared ray emitting element110is composed of a light-emitting diode having surface layer composed of a crystalline body, and a black body layer (black body film) is deposited and formed on a surface of the crystalline body. A surface of the black body layer is preferably formed in a dendritic shape, and radiated beams are emitted in multiple directions from the dendritic surface. As a result, there is no uneven distribution in the radial direction, a highly reliable reference beam can be obtained, and heat generation (light emission) in an extremely short time is possible. In addition, the surface area of the dendritic surface is large and the heat dissipation is high, and therefore the diffusion speed of heat is fast when the light emission is stopped, and it can be used as a stable black body light source without output reduction even after repeated use. In this reference beam source100, reference numeral107denotes a collimating lens, reference numeral112denotes a housing, reference numeral114denotes internal electrical wiring, reference numeral115denotes a connector, reference numeral116denotes a circuit board, reference numeral118denotes a cylindrical holding part, reference numeral120denotes an opening, reference numeral122denotes a thermistor, reference numeral124denotes protective glass, and reference numeral126denotes a permanent magnet (for detachably fixing the housing112to the unit30).

In a reference beam source100inFIG.7B, the cylindrical holding part118is extended axially and a diffuser plate128is disposed inside the cylindrical holding part118. Configuration other than the above is the same as those inFIG.7A. A beam (reference beam) emitted from a light emitting surface of an infrared ray emitting element110at a constant flare angle passes through the diffuser plate128and goes out to become a radiated beam with high directivity. Therefore, a collimating lens (107) becomes unnecessary.

Referring again toFIG.1, the reference beam source power supply102can arbitrarily control power and an oscillation mode (continuous wave or repetitive pulse) of the reference beam generated by the reference beam source100through variable excitation power supplied to the reference beam source100. The optical measuring instrument104may be a well-known power meter or actinometer, measures the power or luminous flux of beams received by a beam receiver104a, and numerically displays a measured value on a display104cof a main body104b.

The optical path switching unit105switches in order to select the first optical path K1that optically connects the processing point Q of the workpiece W and the optical sensor50, a second optical path K2that optically connects the reference beam source100and the optical sensor50, or a third optical path K3that optically connects the reference beam source100and the beam receiver104aof the optical measuring instrument104.

In order to realize this switching function, the optical path switching unit105has one (or more) folding mirror(s)106capable of moving among a first position P1(FIG.1) for retreating from the first optical path K1in order to select the first optical path K1, and a second position P2(FIG.8) for blocking the first optical path K1and reflecting the reference beam from the reference beam source100toward the optical sensor50in order to select the second optical path K2, and a third position P3(FIG.9) for retreating from the third optical path K3in order to select the third optical path K3.

In this embodiment, the optical path switching unit105is provided between the dichroic mirror58and the condenser lens48in the housing of the sensor unit30. The reference beam source100and the beam receiver104aof the optical measuring instrument104are mounted on a side wall of the housing of the sensor unit30adjacent to the optical path switching unit105. An optical filter103having the same or similar wavelength selection characteristic as the band pass filter54of the optical sensor50may be disposed in front of the beam receiver104aof the optical measuring instrument104. The reference beam source power supply102and the main body104bof the optical measuring instrument104are provided outside the sensor unit30.

Now, operation of the calibration unit32will be described. The calibration unit32has three modes that are selected according to an operation status of the laser processing device and the determination of an on-site person. That is, there are a first mode in which interference with the light reception and photoelectric conversion of the optical sensor50during monitoring of laser processing does not occur, a second mode in which the optical sensor50is calibrated by use of the reference beam source100, and a third mode in which the reference beam source100is calibrated by use of the optical measuring instrument104.

In the first mode, as described above, the folding mirror106of the optical path switching unit105is switched to the first position P1illustrated inFIG.1. The reference beam source100, the reference beam source power supply102and the optical measuring instrument104are turned off. Each unit operates on the device main body side, especially in the sensor signal processing unit26, the control unit14and the operation panel22, waveform display processing to the sensor output signal CS is performed as described above.

The second mode is selected (performed) from time to time or periodically during laser processing monitoring. In this mode, when the folding mirror106of the optical path switching unit105is switched to the second position P2illustrated inFIG.8, and the reference beam source power supply102is turned on, and a reference beam is generated by the reference beam source100. At this time, the reference beam source power supply102supplies, to the reference beam source100, excitation power at a volume position adjusted or updated in the third mode prior to this second mode.

In the second mode, each unit except for the laser oscillator10and the laser power supply12is operated even on the device main body side. However, the sensor signal processing unit26, the control unit14and the operation panel22are switched to have not the function of waveform display processing in the first mode for the sensor output signal CS sent from the sensor unit30, but the calibration function for displaying the measured value (measurement count value) of the power or the luminous flux numerically and performing gain adjustment.

In the second mode, the reference beam emitted from the reference beam source100passes through the second optical path K2to be guided to the optical sensor50. More specifically, the reference beam emitted horizontally from the reference beam source100is folded vertically upward by the folding mirror106of the optical path switching unit105. Then, the reference beam folded vertically upward is incident on the band pass filter54of the optical sensor50via the condenser lens48, and the beam in a specific wavelength band that passes through this filter54is incident on the photodiode56. The photodiode56photoelectrically converts the wavelength selected from the received reference beam and outputs an analog sensor output signal CS. This sensor output signal CS is amplified in the latter amplification and output circuit70in the same manner as above, and then sent to the sensor signal processing unit26on the device main body side via the electric cable18.

In the sensor signal processing unit26, the sensor signal processing unit26calculates the light intensity of the reference beam photoelectrically converted by the optical sensor50or a measured value, namely, a measurement count value of a luminous flux of the reference beam based on the sensor output signal CS converted into a digital signal by the A/D converter82, and stores the calculated value in the data memory88. The control unit14reads the measurement count value from the data memory88and displays the measurement count value on the display of display unit22aof operation panel22.

An on-site person who performs the second mode reads the measurement count value displayed on the monitor screen (maintenance screen) of display unit22a. The on-site person performs gain adjustment or offset adjustment to the output of the optical sensor50by input operation on the operation panel22such that the measurement count value coincides with a predetermined reference count value.

The third mode is selected (performed) from time to time or periodically during laser processing monitoring, and selected (performed) immediately before the second mode. In this mode, the folding mirror106of the optical path switching unit105is switched to the third position P3illustrated inFIG.9, and the reference beam source100, the reference beam source power supply102and the optical measuring instrument104are turned on. All units on the device main body are each kept in an off state. The reference beam emitted from the reference beam source100passes through the third optical path K3and is incident on the beam receiver104aof the optical measuring instrument104. At this time, the reference beam source power supply102supplies, to the reference beam source100, excitation power at a volume position adjusted or updated in the previous third mode prior.

An on-site person who performs the third mode reads the measured value of the reference beam displayed on the display104cof the optical measuring instrument104, and checks whether or not the measured value coincides with an absolute reference value preset as the output of the optical sensor50. If not, the on-site person adjusts (updates) the volume position of the reference beam source power supply102such that the measured value and the absolute reference value coincide with each other. Thus, the light intensity of the reference beam emitted from the reference beam source100is calibrated to the absolute reference value via the optical measuring instrument104. In addition, the measurement accuracy of the normal optical measuring instrument104is guaranteed by separate calibration management.

The reference beam source100is composed of a semiconductor element such as a light-emitting diode as described above, and the electrical-to-optical conversion characteristics inevitably change over time or fluctuate according to an environmental condition. Therefore, when the constant excitation power is regularly supplied to the reference beam source100from the reference beam source power supply102, the light intensity of the reference beam emitted from the reference beam source100changes undesirably and irregularly. According to the calibration unit32of this embodiment, it is possible to correct change and fluctuation in the electrical-to-optical conversion characteristic of the reference beam source100at any time or frequently by the third mode. Therefore, in the second mode (calibration of the optical sensor50), a reference beam having higher accuracy than the reference beam source100can always be given to the optical sensor50.

As described above, the laser processing monitor unit24of this embodiment uses the reference beam source100equipped in the device for calibration of the optical sensor50incorporated into the sensor unit30, and further calibrates the reference beam source100with the optical measuring instrument104equipped in the device. In this laser processing monitor unit24, even when the electrical-to-optical conversion characteristic of the reference beam source100changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. Additionally, even when the photoelectric conversion characteristic of the optical sensor50changes over time or fluctuates due to an environmental condition, it is possible to correct this timely and appropriately. Consequently, accuracy, reproducibility and workability of calibration for the optical sensor50can be largely improved, and the monitoring performance can be dramatically improved. In addition, the calibration reference value of the optical sensor50is the absolute reference value of the optical measuring instrument104, and therefore it is possible to obtain monitoring performance without any machine difference.

Furthermore, in this embodiment, the optical path switching unit105is provided near the optical sensor50inside the sensor unit30, and the reference beam source100and the beam receiver104aof the optical measuring instrument104are mounted on the side wall of the housing of the sensor unit30adjacent to the optical path switching unit105. Consequently, without disassembling of the sensor unit30or removal of the optical sensor50, calibration focusing on the photoelectric conversion characteristic of the optical sensor50can be performed easily and safely. In addition, at the laser processing site, without exposing the optical sensor50and the monitor optical system in the sensor unit30to the surrounding dusty environment, the calibration of the optical sensor50and the calibration of the reference beam source100can be performed frequently in a daily inspection and or a periodic inspection.

[Preferred Configuration Example of Optical Path Switching Unit]

As described above, in the laser processing monitor unit24of this embodiment, the optical path switching unit105is provided together with (preferably near) the optical sensor50inside the sensor unit30. Hereinafter, a preferred configuration example of the optical path switching unit105will be described with reference toFIG.10toFIG.16C.

FIG.10andFIG.11illustrate an appearance configuration of a principal part of the sensor unit30. The illustrated housing of the sensor unit30is composed of a lower cylindrical part130, an intermediate square cylindrical part132, an upper cylindrical part134and a sensor box136which are connected in a vertically line from a bottom to a top.

The folding mirror46and the dichroic mirror58(FIG.1) of the monitor optical system are housed in the lower cylindrical part130. The reference beam source100and the beam receiver104aof the optical measuring instrument104are mounted on the side wall of the intermediate square cylindrical part132, and a rotary knob138is rotatably installed. Herein, the reference beam source100and the rotary knob138are located on opposite side surfaces of the intermediate square cylindrical part132facing each other. The beam receiver104aof the optical measuring instrument104is located on a side surface between the reference beam source100and the rotary knob138in the circumferential direction of the intermediate square cylindrical part132. The optical path switching unit105according to this configuration example is provided in the intermediate square cylindrical part132. The condenser lens48(FIG.1) of the monitor optical system is housed in the upper cylindrical part134. The optical sensor50is housed in the sensor box136.

Thus, the reference beam source100and the beam receiver104aof the optical measuring instrument104are not housed inside the sensor unit30but mounted on the side wall from the outside, and the rotary knob138of the optical path switching unit105is also provided outside the side wall of the sensor unit30. The providing of the calibration unit32does not substantially increase the size (particularly the transvers width) of the internal cavity (optical path) of the sensor unit30.

FIG.12toFIG.15illustrate a configuration of the optical path switching unit105of this embodiment,FIG.12andFIG.13are perspective views,FIG.14is a side view, andFIG.15is a sectional view taken along the line A-A ofFIG.14.

As illustrated inFIG.12andFIG.13, the optical path switching unit105has a cylindrical mirror support140and a plurality of mirrors, and has holes facing the mirrors. Specifically, the mirror support140extends in the direction perpendicular to the first optical path K1(X-direction) and is rotatable around the axis HX. An end surface opening142is formed in one end surface140aof the mirror support140. The end surface opening142is mounted so as to face the emission of the reference beam source100. The end surface140bon the opposite side is closed, and a rotating shaft144protrudes from the center of this end surface140bon the axis HX (X-direction). The rotary knob138is mounted on the tip end of the rotating shaft144outside the sensor unit30.

Three side openings146,148and150are formed in a side surface of the mirror support140at intervals in the circumferential direction. The first and second side openings146and148face each other, and the third side opening150is located in the middle between both the openings.

Inside the mirror support140, a first folding mirror106A is provided inside the end surface140bfacing the end surface opening142, and a second folding mirror106B is provided inside a side surface facing the third side opening150. Herein, the first folding mirror106A is disposed at a predetermined inclination angle so as to receive a reference beam introduced from the reference beam source100through the end surface opening142at an oblique incident angle and reflect the received reference beam in the predetermined direction, that is, toward the second folding mirror106B. On the other hand, the second folding mirror106B is disposed at a predetermined inclination angle so as to receive the reference beam from the first folding mirror106A at an oblique incident angle and reflect the reference beam outward through the third side opening150.

As illustrated inFIG.16AtoFIG.16C, the reference beam source100is fixed to a side wall of the intermediate square cylindrical part132through the cylindrical mounting member160. A bearing162is provided between the mounting member160and a tip end of the mirror support140. On the other hand, a bearing164is provided between the rotating shaft144of the mirror support140and the side wall of the intermediate square cylindrical part132. When the rotary knob138is rotated outside the sensor unit30, the mirror support140rotates around the axis HX while supported by both the bearings162and164inside the sensor unit30.

The rotational position of the mirror support140is selected in three ways (or two ways) according to the three modes of the calibration unit32. In the first mode, in order to select the first optical path K1, the rotational position of the mirror support140is selected or adjusted such that the first and second side openings146and148vertically face each other and are located on the first optical path K1.

FIG.16Aillustrates positional relation of each unit of the optical path switching unit105in the first mode. In this case, the first and second folding mirrors106A and106B are set to the first position P1. Herein, the second folding mirror106B takes the same upright posture as the first folding mirror10A and retreats beside the first optical path K1.

The beam to be measured propagating inside the lower cylindrical part130through the dichroic mirror58(FIG.1) enters the mirror support140through the side opening148on the lower side in the optical path switching unit105. The beam to be measured that enters the mirror support140passes near the first and second folding mirrors106A and106B, and passes out of the mirror support140through the side opening146on the upper side. The beam to be measured that passes through the optical path switching unit105as described above propagates inside the upper cylindrical part134, and is incident on the optical sensor50through the condenser lens48.

In the second mode, in order to select the second optical path K2, the rotational position of the mirror support140is selected or adjusted such that the third side opening150faces the optical sensor50.

FIG.16Billustrates positional relation of each unit of the optical path switching unit105in the second mode. In this case, the first and second folding mirrors106A and106B are set to the second position P2. Herein, the second folding mirror106B takes the lowest position in the Z-direction and faces the optical sensor50directly above the second folding mirror through the third side opening150. The first folding mirror106A is interlocked with the rotation of the optical path switching unit105and turns obliquely downward to face the reference beam source100.

When the reference beam emitted from the reference beam source100enters the mirror support140from the end surface opening142, the reference beam advances straight and is incident on the first folding mirror106A in the innermost part at an oblique incident angle, reflects obliquely downward on the first folding mirror106A to be incident on the second folding mirror106B at an oblique incident angle. Then, the reference beam incident on the second folding mirror106B reflects vertically upward on the second folding mirror106B, and exits from the third side opening150. The reference beam that exits from the third side opening150described above propagates inside the upper cylindrical part134, and is incident on the optical sensor50through the condenser lens48.

In the third mode, in order to select the third optical path K3, the rotational position of the mirror support140is selected or adjusted such that the third side opening150faces horizontally (Y-direction) the beam receiver104aof the optical measuring instrument104located just beside the optical path switching unit105.

FIG.16Cillustrates positional relation of each unit of the optical path switching unit105in the second mode. In this case, the first and second folding mirrors106A and106B are set to the third position P3. Herein, the second folding mirror106B has a reflection surface set in the Y-direction and faces the beam receiver104aof the optical measuring instrument104located just beside the optical path switching unit105through the third side opening150. The first folding mirror106A is interlocked with the rotation of the optical path switching unit105and faces the reference beam source100.

When the reference beam from the reference beam source100enters the mirror support140through the end surface opening142, the reference beam advances straight and is incident on the first folding mirror106A in the front innermost part at an oblique incident angle, reflects obliquely sideways on the first folding mirror106A to be incident on the second folding mirror106B at an oblique incident angle. Then, the reference beam incident on the second folding mirror106B further reflects obliquely sideways (Y-direction) on the second folding mirror106B, and exits from the third side opening150. The reference beam thus exits in the horizontal direction (Y-direction) perpendicular to the rotation axis HX and is incident on the beam receiver104aof the optical measuring instrument104.

The rotational positions in the first mode and the third mode of the mirror support140are different by 180° in the above description, but can be made to be the same (common). That is, when the mirror support140is rotated by 180° from the rotational position illustrated inFIG.16A, the rotational position of the mirror support140becomes the same as that inFIG.16C. The rotational position (first position P1) in the first mode of the mirror support140and the rotational position (third position P3) in the third mode of the mirror support140are thus set to the same (common), so that the first mode (monitoring of the laser processing) and the third mode (calibration of the reference beam source100) can be performed at the same time.

In this case, as illustrated inFIG.16C, the third optical path K3in the lateral direction from the second folding mirror106B to the beam receiver104aof the optical measuring instrument104, and the longitudinal first optical path K1passing through the dichroic mirror58on the lower side and directed to the optical sensor50on the upper side intersect perpendicularly near the center inside the optical path switching unit105, but do not mutually interfere with each other.

The optical path switching unit105of this configuration example is mounted with the folding mirrors106(106A and106B) inside the rotatable cylindrical mirror support140having a plurality of the openings on the end surface and the side surface as described above. The rotational position of the mirror support140is selected or adjusted, so that the folding mirrors106(106A and106B) are selectively moved to the first, second and third positions P1, P2and P3. Consequently, it is possible to select either the first, second and third optical paths K1, K2and K3alternatively, or either the first and third optical paths (K1, K3) or the second optical path K2. According to such a configuration, it is possible to efficiently and smoothly perform required optical path selection or switching within a limited cavity of the sensor unit30.

Other Embodiment or Modification

The preferred embodiment of the present invention is described above, but the embodiment described above does not limit the present invention. It is possible for those skilled in the art to make various modifications and changes to the specific embodiments without departing from the technical idea and the technical scope of the present invention.

For example, it is possible to modify or change the arrangement configuration of the optical path switching unit105, the reference beam source100and the beam receiver104aof the optical measuring instrument104. That is, either or all of the reference beam source100, the beam receiver104aof the optical measuring instrument104, and the optical path switching unit105can be provided in the sensor unit30or in the processing head20away from the optical sensor50, or at least one of the reference beam source100and the beam receiver104aof the optical measuring instrument104can be detachably mounted on the sensor unit30.

Furthermore, as illustrated inFIG.17, the reference beam source100can be detachably mounted on the sensor unit30, and the beam receiver104aof the optical measuring instrument104can be disposed separately from the sensor unit30, and the reference beam source100can be calibrated outside the sensor unit30.

Alternatively, in a case where the optical path switching unit105of the above preferred configuration example (FIG.10toFIG.16C) is provided, the third positions P3of the first and second folding mirrors106A and106B in the third mode can also be set to such a position as to be vertically inverted with the second position P2(that is, the position where the reflection surface of the second folding mirror106B is directed on the dichroic mirror58side directly below the third side opening150through the third side opening150). In this case, the beam receiver104aof the optical measuring instrument104is disposed near the laser emission port of the emission unit28. Consequently, the third optical path K3is as follows: the reference beam source100→the optical path switching unit105→the dichroic mirror58→the folding mirror46→the unit connection opening45→the dichroic mirror40→the focusing lens42→the protective glass44→3the beam receiver104aof the optical measuring instrument104.

In the sensor unit30, the reference beam source100and the beam receiver104aof the optical measuring instrument104can face with the optical path switching unit105therebetween, and a single folding mirror106of the optical path switching unit105can also be enough. In this case, the single folding mirror106can be moved between the first position P1for retreating from the first optical path K1in order to select the first optical path K1, and the second position P2for blocking the first optical path K1at an inclination angle 45° and reflecting the reference beam from the reference beam source100toward the optical sensor50in order to select the second optical path K2. Furthermore, in this case, the first position P1of the folding mirror106can be set to such a position as to retreat from the third optical path K3, so that the first position P1and the third position P3can be common.

In the laser processing device of the above embodiment, the sensor unit30is integrated with the emission unit28and built into the processing head20. However, the sensor unit30can be separated from the emission unit28to be used as an independent unit, and can be disposed near the processing head20or the emission unit28so as to be directed toward the workpiece W.

When the sensor unit30is thus used as the independent unit, an entrance window is provided in the front stage (unit end surface) of the monitor optical system of the sensor unit30so as to directly take a beam to be measured generated or reflected near the processing point Q of the workpiece W. Then, in this case, not only the beam receiver104aof the optical measuring instrument104but also the reference beam source100can be used outside the sensor unit30. That is, in the second mode, the emission surface of the reference beam source100is applied (directed) to the entrance window of the sensor unit30from the outside, the reference beam emitted from the reference beam source100is taken from the entrance window into the sensor unit30, and the taken reference beam can be received in the optical sensor50at the innermost part through the monitor optical system on the inner side. Consequently, it is possible to omit the optical path switching unit (105) from the sensor unit30.

In the laser beam monitor unit24in the above embodiment, the beam to be measured is an infrared ray emitted from the vicinity of the processing point Q of the workpiece W. However, the beam to be measured can be a plasma beam emitted from the vicinity of the processing point Q of the workpiece W, a reflected beam from the vicinity of the processing point Q (reflected laser beam for processing) or a visible ray. Therefore, the reference beam source100is not limited to a black body radiated beam source, and various light-emitting diodes or semiconductor lasers with radiation characteristics according to the wavelength band of a beam to be measured can be used. In this case, a band pass filter with a wavelength selection characteristic according to the radiation characteristic of the reference beam source to be used or the wavelength of a beam to be measured, or an optical filter can be provided on the second optical path K2that optically connects the reference beam source100and the optical sensor50.

The laser processing monitoring method or device of the present invention is not limited to application to a laser processing device that performs laser welding, and a laser processing device that performs other laser processing, for example, laser cutting, laser brazing, laser hardening, laser surface modification, or the like can be applied.

The disclosure of this application relates to the subject matter described in Japanese Patent Application No. 2020-068853 filed on Apr. 7, 2020, the entire disclosure of which is incorporated herein by reference.