Laser processing monitoring device, laser processing monitoring method, and laser processing device

Abstract

The laser processing device comprises: a laser oscillator (10), a laser power supply (12), a control unit (14), an optical cable (16), an electric cable (18), a processing head (20), an operation panel (22), and a laser processing monitoring unit (24). The laser processing monitoring unit (24) includes a control unit (14), an operation panel (22), a sensor signal processing unit (26), and a sensor unit (30) as a basic structure for a main function, i.e., a monitoring function, and has a reference light source (100), a reference light source power supply (102), a light measuring device (104), and an optical path switching unit (105) as a calibration unit (32) for calibrating a light sensor (50) built into the sensor unit (30).

Description

Technical Field

[0001] The present invention relates to a laser processing monitoring device, a laser processing monitoring method and a laser processing device. Background Art

[0002] In the past, a technique for judging the quality of laser processing has been used in laser processing devices. Specifically, the laser processing device has a light receiving element or a light sensor built into a processing head that irradiates a laser beam to a workpiece. The measured light generated or reflected near the processing point of the workpiece is received by the light sensor via the optical system in the processing head. The laser processing device performs predetermined signal processing on the electrical signal (sensor output signal) obtained by the photoelectric conversion of the light sensor, thereby judging the quality of the laser processing.

[0003] Compared with the technique of using a camera to analyze the processing status near the processing point, this laser processing monitoring technology not only has simpler hardware and software, but also improves the quality of monitoring through the study of signal processing technology. For example, in laser welding, it is also possible to finely monitor or analyze the tiny movements and changes of the molten part.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-30032 Summary of the invention

[0007] However, during the research and development of the laser processing monitoring technology described above by the inventors, the error in the photoelectric conversion characteristics of the optical sensor became a major obstacle to improving the monitoring performance. That is, the photoelectric conversion characteristics of the photodiode used in the optical sensor inevitably change over time and are also affected by environmental conditions such as the ambient temperature. When the photoelectric conversion characteristics of the photodiode change, even if the measured light of the same light intensity is received from the workpiece side, the value of the sensor output signal obtained by photoelectric conversion changes. Therefore, no matter how high the performance of the digital signal processing technology is, it is impossible to perform precise monitoring and analysis of laser processing, and it is impossible to make accurate judgments on quality.

[0008] To address this problem, the present inventors used the following calibration method. First, when the laser processing device is shipped or set up, as part of the initialization, a laser beam of a reference power is irradiated on a reference sample to be processed. Then, the waveform of the sensor output signal obtained by the optical sensor in the processing head is obtained as, for example, Fig.18A Such a reference waveform SW.

[0009] Then, if Fig.18BAs shown, upper and lower limit envelopes JW+δ, JW-δ are set in the entire interval (or a part of the interval) of the reference waveform SW, which are deviated from the value of the reference waveform SW by a certain allowable range (±δ). The allowable range ±δ shown in the figure is expanded to make the diagram easier to explain, but in fact, the envelope is set in an infinitely small range to improve the correction accuracy.

[0010] Later, when the optical sensor is calibrated, the same sample to be processed is irradiated with a laser beam of the same reference power, and the waveform RW of the sensor output signal obtained thereby is displayed on the monitoring screen (maintenance screen) together with the upper and lower limit envelopes JW+δ and JW-δ. Fig.18C When the output value overflows outside the upper and lower limit envelopes JW+δ and JW-δ, the gain of the sensor output is adjusted by the on-site personnel through operations such as screen input so that the output value converges to the inner side (allowable range) of the upper and lower limit envelopes JW+δ and JW-δ.

[0011] However, it has been found that the optical sensor calibration method described above is not an effective solution. That is, the laser oscillator and the processed sample are related to the radiation source of the test light received by the optical sensor during calibration, and the laser optical system is interposed in the optical path of the test light. Therefore, the error generated between the initially obtained reference waveform SW and the waveform RW of the sensor output signal currently obtained includes not only the variation of the photoelectric conversion characteristics of the optical sensor, but also the variation of the optical characteristics or physical characteristics of these related factors or intervening factors. Therefore, it is impossible to perform a calibration focusing on the photoelectric conversion characteristics of the optical sensor. Moreover, it is impossible to ensure that the light intensity of the test light used for calibration is always constant. Therefore, it is impossible to correctly correct the error in the photoelectric conversion characteristics of the optical sensor. In addition, since the laser oscillator and the processed sample are involved in the calibration of the optical sensor, the calibration operation is cumbersome and large-scale.

[0012] Furthermore, the optical sensor calibration method described above performs calibration based on a relative comparison between a reference waveform SW inherent to the device and the waveform RW of the currently acquired sensor output signal, and the calibration reference value of the optical sensor is different for each device. Therefore, the difference between the actually indicated value and the value that should be indicated in the monitored performance and accuracy is different due to individual differences in the same model of laser processing devices using the same product optical sensor. That is, the instrument error of the same model of laser processing devices varies between the same models, and therefore, the same quality evaluation under the same processing condition setting cannot be performed.

[0013] A laser processing monitoring device according to one embodiment of the present invention performs photoelectric conversion on predetermined measured light generated or reflected near a processing point of the workpiece by means of a light sensor arranged in or close to the processing head when a workpiece is irradiated with a laser beam for laser processing from a processing head. A sensor output signal representing the light intensity of the measured light is obtained, and the laser processing is monitored based on the sensor output signal. The laser processing monitoring device comprises: a reference light source, which is arranged in the processing head and generates reference light for calibrating the light sensor; a reference light source power supply unit, which supplies adjustable electric power to the reference light source for generating the reference light; and a light measuring device, which has a light receiving unit for receiving the reference light from the reference light source in order to calibrate the reference light source, and measures the light intensity of the received reference light or a predetermined physical quantity equivalent to the light intensity.

[0014] In a laser processing monitoring device of one embodiment of the present invention, a reference light source equipped with a processing head is used to calibrate the optical sensor used for monitoring the laser processing, and the reference light source is calibrated by a light measuring device equipped with the device. Therefore, even if the electro-optical conversion characteristics of the reference light source change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner. Even if the photoelectric conversion characteristics of the optical sensor change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner.

[0015] A laser processing monitoring method according to one aspect of the present invention, when a laser beam for laser processing is irradiated from a processing head to a processing object, a light to be measured generated or reflected near a processing point of the processing object is photoelectrically converted by a light sensor arranged in or close to the processing head, a sensor output signal indicating the light intensity of the light to be measured is obtained, and the laser processing is monitored based on the sensor output signal. The laser processing monitoring method includes: providing the light sensor in a sensor unit installed in or close to the processing head; installing a reference light source that generates reference light for calibrating the light sensor in the sensor unit; when performing the laser processing, setting a first light path that optically connects the processing point of the processing object and the light sensor in the sensor unit; when calibrating the light sensor, setting a second light path that optically connects the reference light source and the light sensor in the sensor unit; and in order to calibrate the reference light source, causing the reference light radiated from the reference light source to be incident on a light receiving portion of a light measuring device, and adjusting the output of the reference light source so that a measurement value of the light measuring device coincides with a reference value.

[0016] In a laser processing monitoring method according to one aspect of the present invention, when monitoring laser processing, a first optical path is set in the sensor unit so that the measured light from the workpiece side is incident on the optical sensor, and when calibrating the optical sensor, a second optical path is set in the sensor unit so that the reference light from the reference light source is incident on the optical sensor. Furthermore, when calibrating the reference light source, the reference light from the reference light source is incident on the light receiving part of the optical measuring device. Thus, even if the electro-optical conversion characteristics of the reference light source change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner, and even if the photoelectric conversion characteristics of the optical sensor change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner.

[0017] A laser processing device according to one embodiment of the present invention comprises: a laser oscillator that oscillates and outputs a laser beam for laser processing; a processing head that is optically connected to the laser oscillator via an optical cable and focuses the laser beam from the laser oscillator on a processing point of a workpiece; and a laser processing monitoring unit that monitors laser processing, the laser processing monitoring unit comprising: a light sensor that is arranged in the processing head or arranged close to the processing head and outputs a sensor output signal indicating the light intensity of a predetermined light to be measured generated or reflected near the processing point of the workpiece; a sensor signal processing unit that generates digital waveform data for the sensor output signal from the light sensor and displays and outputs a waveform of the sensor output signal based on the waveform data; a reference light source that generates reference light for calibrating the light sensor; a reference light source power supply unit that supplies adjustable power to the reference light source for generating the reference light; and a light measuring device that has a light receiving unit that receives the reference light from the reference light source in order to calibrate the reference light source and measures the light intensity of the received reference light or a predetermined physical quantity equivalent to the light intensity.

[0018] In a laser processing device of one embodiment of the present invention, the reference light source provided in the device is used to calibrate the optical sensor of the laser processing monitoring unit, and the reference light source is calibrated by the optical measuring device provided in the device. Therefore, even if the electro-optical conversion characteristics of the reference light source change due to time change or environmental conditions, it can be timely and accurately corrected, and even if the photoelectric conversion characteristics of the optical sensor change due to time change or environmental conditions, it can be timely and accurately corrected. In this way, by improving the monitoring performance of the laser processing monitoring unit, it is possible to make a qualified judgment on the quality of laser processing.

[0019] According to a laser processing monitoring device or a laser processing monitoring method of one embodiment of the present invention, the above-mentioned structure and function can improve the accuracy, reproducibility and operability of the calibration of the optical sensor used in the monitoring of laser processing, thereby enhancing the monitoring performance.

[0020] According to the laser processing apparatus of one aspect of the present invention, the above-mentioned structure and operation can determine whether the laser processing is acceptable or not. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a block diagram showing the overall configuration of a laser processing apparatus including a laser processing monitoring apparatus according to one embodiment of the present invention.

[0022] Figure 2 It is a graph showing the distribution of the radiation spectrum of a black body.

[0023] Figure 3 This is a diagram showing the spectral distribution of the intensity of infrared rays emitted from the molten portion of stainless steel when the stainless steel is irradiated with a pulsed laser beam.

[0024] Figure 4 The diagram shows the situation of Experiment 1 for verifying the monitoring function of the laser processing monitoring unit in the embodiment and the monitoring display waveform of the sensor output signal obtained in the experiment.

[0025] Figure 5 The following is a diagram showing the situation of Experiment 2 for verifying the above-mentioned monitoring function and the monitoring display waveform of the sensor output signal obtained by the experiment.

[0026] Figure 6 The following is a diagram showing the situation of Experiment 3 for verifying the above-mentioned monitoring function and the monitoring display waveform of the sensor output signal obtained by the experiment.

[0027] Fig. 7A It is a cross-sectional view showing a configuration example of a reference light source in the embodiment.

[0028] Figure 7B It is a cross-sectional view showing another configuration example of the reference light source in the embodiment.

[0029] Figure 8 This is a diagram schematically showing a state in which the folding mirror of the optical path switching section is switched to the second position in order to select the second optical path in the correction section of the embodiment.

[0030] Fig. 9 It is a diagram schematically showing a state in which the folding mirror of the optical path switching section is switched to the third position in order to select the third optical path in the correction section.

[0031] Fig.10It is a perspective view showing the appearance of a sensor unit in which an optical path switching section according to a preferred configuration example is built-in.

[0032] Fig.11 yes Fig.10 Side view of the sensor unit.

[0033] Fig.12 It is a view from a certain angle on the built-in Fig.10 A perspective view of the optical path switching portion of the sensor unit.

[0034] Fig.13 This is a stereoscopic view of the optical path switching unit viewed from another angle.

[0035] Fig.14 This is a side view of the optical path switching unit as viewed from the reference light source side.

[0036] Fig.15 is along Fig.14 Cross-sectional view along line AA.

[0037] Fig.16A It is a longitudinal sectional view of the main parts showing the positional relationship between the components of the optical path switching section in the first mode of the correction section.

[0038] Fig. 16B It is a longitudinal sectional view of the main parts showing the positional relationship of each part of the optical path switching unit in the second mode.

[0039] Fig. 16C It is a cross-sectional view of the main parts showing the positional relationship of each part of the optical path switching unit in the third mode.

[0040] Fig.17 It is a diagram showing a modified example of the laser processing monitoring unit in the embodiment.

[0041] Fig.18A This is a diagram schematically showing a monitoring screen in the first stage of a conventional optical sensor calibration method.

[0042] Fig.18B This is a diagram schematically showing a monitoring screen in the second stage of the conventional optical sensor calibration method.

[0043] Fig.18C This is a diagram schematically showing a monitoring screen in the third stage of the conventional optical sensor calibration method. DETAILED DESCRIPTION

[0044] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0045] [Overall structure of laser processing device]

[0046] Figure 1The overall structure of a laser processing device including a laser processing monitoring device according to an embodiment of the present invention is shown. The laser processing device is configured as, for example, a laser processing machine that irradiates a workpiece W with a high-output CW laser beam or a pulsed laser beam, melts a processing point Q of the workpiece W using the energy of the laser, and performs a desired laser melting process. The laser processing device includes a laser oscillator 10, a laser power source 12, a control unit 14, an optical cable 16, an electric cable 18, a processing head 20, an operation panel 22, and a laser processing monitoring unit (laser processing monitoring device according to the embodiment) 24.

[0047] In the laser processing device, the laser oscillator 10, the laser power source 12, the control unit 14 and the operation panel 22 are usually arranged in one place or close to each other to form the device body. On the other hand, the processing head 20 is configured as a separate unit from the device body and is arranged at any processing location within a region corresponding to the length of the optical cable 16.

[0048] The laser processing monitoring unit 24 includes a control unit 14, an operation panel 22, a sensor signal processing unit 26, and a sensor unit 30 as a basic structure for its main function, i.e., the monitoring function. In addition, the laser processing monitoring unit 24 includes a reference light source 100, a reference light source power supply 102, a light measuring device 104, and an optical path switching unit 105 as a correction unit 32 for calibrating the optical sensor 50 built into the sensor unit 30.

[0049] The laser oscillator 10 is composed of, for example, a YAG laser, a fiber laser, or a semiconductor laser. When, for example, laser spot welding is performed on a workpiece W, the laser oscillator 10 receives excitation power from a laser power source 12 under the control of a control unit 14 to excite a built-in medium, and oscillates and outputs a pulsed laser beam LB having a wavelength inherent to the medium. The laser beam LB oscillated and output by the laser oscillator 10 is transmitted to a processing head 20 via an optical cable 16.

[0050] The processing head 20 has an emission unit 28 as a head body and a sensor unit 30 integrally or detachably connected to the emission unit 28 via a unit connection opening 45. The emission unit 28 has a cylindrical frame. The upper end of the frame of the emission unit 28 is connected to the optical cable 16 from the laser oscillator 10, and the laser emission port at the lower end of the frame of the emission unit 28 faces the workpiece W directly below. In the frame of the emission unit 28, as a laser optical system, a collimating lens 38, a dichroic mirror 40, a focusing lens 42 and a protective glass 44 are arranged in a vertical row from top to bottom. Here, the protective glass 44 is installed at the laser emission port. The dichroic mirror 40 is arranged at an angle of 45° toward the unit connection opening 45. A dielectric multilayer film is coated on the dichroic mirror 40, which allows the laser beam LB from the optical cable 16 to pass through and reflects the measured light and visible light near the processing point Q of the workpiece W.

[0051] During laser processing, the laser beam LB transmitted in the optical cable 16 is emitted vertically downward from the terminal surface of the optical cable 16 in the emission unit 28 at a certain divergence angle. The laser beam LB passes through the collimating lens 38 to become parallel light, passes through the dichroic mirror 40, is focused by the focusing lens 42 and the protective glass 44, and is incident on the processing point Q of the workpiece W. Then, the laser energy of the laser beam LB is used to melt and solidify the vicinity of the processing point Q, and a welding nugget is formed there to form a welded joint. The welded joint is any joint such as a butt joint, a T-joint, an L-joint, an overlapping joint, etc., which is selected by the user.

[0052] The sensor unit 30 also has an integrated or assembled cylindrical frame. In the frame of the sensor unit 30, a light sensor 50 is provided at the upper end of the frame, and directly below the light sensor 50, a folding mirror 46, a dichroic mirror 58, and a focusing lens 48 are arranged vertically in a row from bottom to top as a monitoring optical system. Here, the folding mirror 46 is arranged at the same height position as the unit connection opening 45 and tilted at 45 degrees. The optical path switching unit 105 of the correction unit 32 is provided between the dichroic mirror 58 and the focusing lens 48.

[0053] The dichroic mirror 58 is provided for monitoring and photographing the vicinity of the processing point Q of the workpiece W. The dichroic mirror 58 is arranged at a 45° tilt at the same height position as the return mirror 60 arranged on the side of the dichroic mirror 58. A dielectric multilayer film that allows the measured light to pass through and reflects the visible light is coated on the dichroic mirror 58. The return mirror 60 is also arranged at a 45° tilt, and a CCD camera 62 is installed directly above the return mirror 60. The image signal output from the CCD camera 62 is transmitted to the display device 66 via a cable 64. The display device 66 is usually arranged on the side of the device body. Although omitted in the figure, it is also possible to incorporate an optical system of guide light that irradiates visible light to the vicinity of the processing point Q of the workpiece W into the sensor unit 30.

[0054] The optical sensor 50 in this embodiment has, for example, a photodiode 56 as a photoelectric conversion element. The optical sensor 50 has a wavelength filter or a bandpass filter 54 that transmits only light LM having a wavelength in a specific band and blocks other light at the front stage (below) of the photodiode 56. A substrate of an amplifier output circuit 70 is provided behind the optical sensor 50.

[0055] During laser processing, electromagnetic waves (light) having a wide-band wavelength are emitted from the vicinity of a processing point Q of a workpiece W, and the workpiece W is irradiated with a laser beam LB from the emission unit 28. Among the electromagnetic waves emitted from the workpiece W and directed vertically upward, light reflected in the horizontal direction by the dichroic mirror 40 in the emission unit 28 by the focusing lens 42 is guided into the sensor unit 30 through the unit connection opening 45. Among the light guided into the sensor unit 30, light reflected vertically upward by the return mirror 46 and then passing through the dichroic mirror 58 is incident on the bandpass filter 54 through the optical path switching unit 105 and the focusing lens 48. Then, light LM having a wavelength component of a predetermined band selected by the bandpass filter 54 is converged and incident on the light receiving surface of the photodiode 56. In this case, the optical path switching unit 105 selects the processing point Q of the workpiece W and the optical sensor 50 at a certain distance from the processing point Q of the workpiece W. Figure 1 The optical connection mode of the first optical path K1 indicated by the single-dot chain line is switched.

[0056] In addition, the visible light among the light entering the sensor unit 30 from the emission unit 28 through the unit connection opening 45 is reflected vertically upward by the reflection mirror 46. The reflected visible light is as follows: Figure 1 As shown by the dotted line in the middle, the light is reflected in the horizontal direction by the dichroic mirror 58 and is returned vertically upward by the return mirror 60, thereby entering the imaging surface of the CCD camera 62. A condenser lens (not shown) may also be provided in front of the CCD camera 62. The output signal (image signal) of the CCD camera 62 is transmitted to the display device 66, and an image of the vicinity of the processing point Q of the workpiece W is displayed on the screen of the display device 66.

[0057] In the optical sensor 50, in the monitoring method using a single photodiode 56, the wavelength band passing through the bandpass filter 54 is preferably set to a frequency band that is most suitable for the various materials that can be selected for the workpiece W and the various processing methods, and captures the influence of predetermined factors on the welding characteristics near the processing point as the intensity or change of the radiation energy.

[0058] In this regard, it is possible to use Figure 2 The well-known blackbody radiation spectrum distribution is shown in FIG. Figure 2 As shown in the graph, there is a certain relationship between the spectrum of electromagnetic waves emitted by a black body and the surface temperature. If the temperature of the object is high, the peak of the radiation energy shifts to a shorter wavelength, and if the temperature of the object is low, it shifts to a longer wavelength, and the peak radiation energy changes exponentially with respect to the change in temperature. According to the graph, the wavelength of the peak point of the energy density emitted from a black body at a temperature of 1500°C is about 1800nm.

[0059] On the other hand, the inventors measured the intensity (relative count value) of light of 1000 nm or more detected when a laser beam was irradiated on iron-based stainless steel (melting point about 1500° C.) at various angles at the processing point, and analyzed the spectrum distribution with a spectrum analyzer. The results are shown in FIG. Figure 3 . The displayed waveform of the spectrum analyzer does not distinguish the intensity of the detected light above 1000nm over time, and each peak is expressed as a relative intensity. Regarding the waveform shown, the intensity represented by the entire waveform varies depending on the angular position during the measurement, but a constant characteristic is obtained. As a result, the intensity (radiation energy density) of the infrared light emitted from the molten portion of the stainless steel has a steep mountain-shaped characteristic covering a frequency band of about 1000nm to 1100nm and a wide mountain-shaped characteristic covering a frequency band of about 1200nm to 2500nm. If we focus on the latter wide mountain-shaped characteristic, the wavelength of the peak point is about 1800nm, which is roughly similar to the wavelength (about 1800nm) of the peak point of the energy density radiated from a black body at a temperature of 1500°C.

[0060] Thus, for various metals that can be considered as the material of the workpiece W, by using their respective melting points as indices, it is possible to refer to Figure 2 The curve graph of determines the practically optimal wavelength band in the laser processing monitoring method using a single photodiode 56. For example, the melting points of iron-based metals, copper-based metals, and aluminum-based metals, which are the main materials for laser melting processing, are approximately 1500°C, 1000°C, and 600°C, respectively. Figure 2 In the embodiment of the present invention, the frequency band of 1.3 μm (1300 nm) to 2.5 μm (2500 nm) can be set as the wavelength band in which the photoelectric conversion is performed by the optical sensor 50 .

[0061] Again in Figure 1 In the embodiment, the sensor output signal CS output from the amplifier output circuit 70 in the sensor unit 30 is transmitted to the sensor signal processing unit 26 on the device body side via the cable 18. The sensor output signal CS is converted into a digital signal by the A / D converter 82 and subjected to digital signal processing by the arithmetic processing unit 84.

[0062] The operation processing unit 84 is composed of an operation processing device of hardware or middleware capable of performing specific operation processing at high speed, preferably an FPGA (field programmable gate array). The operation processing unit 84 uses the data memory 88 to convert the instantaneous voltage value of the sensor output signal CS into a count value (relative value) representing the intensity of the radiated light, and generates the converted value as a digital waveform data DCS. The generated waveform data DCS is stored in the data memory 88. The operation processing unit 84 displays the waveform of the sensor output signal CS on the display of the display unit 22a of the operation panel 22 via the control unit 14 based on the waveform data DCS. Alternatively, the operation processing unit 84 also performs the processing of the good or bad judgment described later, and displays the judgment result together with the waveform of the sensor output signal CS. The control unit 14 converts the waveform data DCS and the judgment result data provided by the operation processing unit 84 into an image signal, and displays the waveform of the sensor output signal CS, the judgment result information and other images on the display of the display unit 22a of the operation panel 22.

[0063] Thus, according to the laser processing monitoring unit 24 of this embodiment, the radiated light (infrared rays) when the processing point of the workpiece reaches the molten state is monitored. In addition, the radiated light is not converted into temperature, and the change in the amount of radiated light during processing is converted into an instantaneous integral value or count value in a specific frequency band for display, thereby visualizing the processing status of the workpiece as a waveform.

[0064] The operation panel 22 includes, for example, a display unit 22a formed of a liquid crystal display and a keyboard-type or touch panel-type input unit 22b, and displays a setting screen, a monitoring screen, a maintenance screen, etc. under the display control of the control unit 14. For example, as one of the setting screens, a laser output waveform corresponding to the setting conditions of the laser beam LB is displayed on the display of the display unit 22a. In addition, as one of the monitoring screens, for example, as described later, a laser output waveform corresponding to the setting conditions of the laser beam LB is displayed on the display of the display unit 22a. Figures 4 to 6 As shown, the waveform of the very fine sensor output signal obtained without losing intensity variation in the laser processing monitoring unit 24 is visualized and displayed. In addition, as one of the maintenance screens, gain adjustment (digital gain adjustment) for the output of the optical sensor 50 can be performed on the screen.

[0065] [Monitoring function of the laser processing monitoring unit]

[0066] In order to verify the monitoring function of the laser processing monitoring unit 24 in this embodiment, the present inventors conducted Figures 4 to 6Experiments 1, 2, and 3 are shown in the figures. The waveforms shown in the figures are waveforms of the sensor output signal CS displayed on the monitoring screen of the display unit 22a of the operation panel 22. The part where fine sawtooth is drawn in the waveform indicates that the metal is melted near the processing point, and the radiation light disturbance from the wave surface of the molten pool is detected. The time point when the waveform that increases gradually on the time axis reaches the peak is the time point when the irradiation of the laser beam LB is stopped, and the waveform decreases from this time point.

[0067] About Experiment 1( Figure 4 ), two 1.0 mm thick stainless steel plates (SUS304) W1 and W2 were arranged horizontally as workpieces W, and butt-welded using a pulsed laser beam. In this butt welding, the spot diameter of the laser beam was set to 0.3 mm, the laser output was set to 500 W, and the pulse width was set to 20 milliseconds. In addition, it was verified how the gap (specific factor) can be monitored and analyzed in the laser processing monitoring unit 24 on the processing characteristics of the butt welding of the workpieces (W1, W2) in the case where there is no gap (gap) between the workpieces W1 and W2 (a) and in the case where there is a gap of 0.09 mm, which is 30% of the spot diameter of 0.3 mm (b).

[0068] The waveform in the case where there is no gap in the docking part (a) is compared with the waveform in the case where there is a gap (b). The former (a) has the characteristics that the detection starting point after the rise of the waveform starts is high and the decline of the waveform is relatively gentle. On the other hand, the latter (b) has the characteristics that the detection starting point after the rise of the waveform starts is low and the decline of the waveform is relatively steep. This phenomenon is shown as follows. That is, in the case where there is a gap in the docking part (b), the laser beam also enters the part without metal (gap), so there is a phenomenon that the amount of molten metal in the molten pool formed by the gap relative to the spot diameter at the irradiation point is reduced. In the radiated light detected near the molten pool, the difference in the amount of molten metal is also manifested as the difference in the amount of radiated light, and the detection starting point after the waveform rises becomes lower. In addition, due to the phenomenon that the evaporated metal is scattered together with the transmitted light passing through the gap, the amount of molten metal becomes less, so when there is a gap, the waveform decline is quickly detected.

[0069] About Experiment 2( Figure 5), two 0.3mm thick stainless steel plates (SUS304) W1 and W2 were overlapped as the workpiece W, and overlapped and welded using a pulsed laser beam. In this overlap welding, the spot diameter of the laser beam was set to 0.3mm, the laser output was set to 500W, and the pulse width was set to 45 milliseconds. In addition, it was verified how the presence or degree of the influence of the gap (specific factor) on the processing characteristics of the overlap welding of the workpieces (W1, W2) could be monitored and analyzed in the case where there was no gap between the workpieces (W1, W2) (a) and in the case where there was a gap of 0.06mm, which was 20% of the spot diameter of 0.3mm, between the workpieces (W1, W2) (b).

[0070] In this lap welding, the case where there is a 0.06 mm gap (b) is compared with the case where there is no gap (a). It is difficult to identify the change in the intensity of the radiated light in the ascending part of the waveform, but in the descending part of the waveform, that is, after the irradiation of the pulsed laser is stopped, the case where there is a gap (b) has a gentler decline in the waveform than the case where there is no gap (a). This phenomenon is shown as follows. That is, in lap welding, in the case where there is no gap in the processed material (a), it is believed that the irradiated laser beam acts in a manner that directly converts the second piece of metal W2 into a melt after melting and penetrating the first piece of metal W1. On the other hand, in the case where there is a tiny gap in the processed material (b), due to the influence of the air layer existing in the gap, the heat transfer in the processed material is delayed compared to the case where there is no gap between the metal layers (a), thereby slowly detecting the decline of the waveform.

[0071] About Experiment 3( Figure 6 ), two plates W1 and W2 of stainless steel SUS304 with a thickness of 0.3 mm were overlapped without a gap as the workpiece W, and overlapped and welded using a pulsed laser beam. In this overlap welding, the spot diameter of the laser beam was set to 0.3 mm, and the laser output and pulse width were set as parameters. That is, for the laser output, 6 levels of values ​​were selected from 300W to 550W in increments of 50W, and for the pulse width, 3 levels of values ​​of 25 milliseconds, 35 milliseconds, and 45 milliseconds were selected. In addition, it was verified how the laser output (first specific factor) and pulse width (second specific factor) can be monitored and analyzed for the processing characteristics of overlap welding of the workpieces (W1, W2).

[0072] from Figure 6It can be seen that the more the laser output setting value of the laser beam LB is increased, the more the radiated light intensity represented by the waveform of the sensor output signal CS increases proportionally, and the more the laser output setting value of the laser beam LB is increased, the more the decline of the waveform of the sensor output signal CS is delayed. In addition, it can be observed that the more the pulse width is increased, the higher the radiated light intensity (especially the maximum peak before the decline) shown by the waveform of the sensor output signal becomes. Thus, the radiated light from the workpiece during laser processing can be accurately detected in units of tens of W and 10 milliseconds.

[0073] As described above, according to the laser processing monitoring unit 24 of this embodiment, it is possible to simply and accurately monitor and analyze the effect of the laser beam LB in the laser processing, monitor and analyze the influence of predetermined factors related to the processing state or processing quality of the laser processing, and judge the quality of the laser welding processing based on the waveform characteristics of the sensor output signal CS displayed on the monitoring screen of the operation panel 22 during laser processing.

[0074] [Structure and function of the calibration unit]

[0075] However, the laser processing monitoring unit 24 of this embodiment has a light receiving element or a light sensor 50 built into the sensor unit 30 installed in the processing head 20. However, the photoelectric conversion characteristics of the photodiode 56 constituting the light sensor 50 not only inevitably change over time, but are also affected by environmental conditions such as the ambient temperature. When the photoelectric conversion characteristics of the photodiode 56 change, even if the measured light LM of the same light intensity is received from the workpiece W side, the value of the analog sensor output signal CS obtained by photoelectric conversion changes. Therefore, no matter how high-performance the sensor signal processing unit 26 is, the accuracy and reliability of the waveform information of the sensor output signal CS provided on the monitoring screen are low, and it is impossible to perform precise monitoring, analysis, and accurate quality judgment for laser processing.

[0076] To address this problem, the laser processing monitoring unit 24 of this embodiment includes a calibration unit 32 that can calibrate with high accuracy and reliability the temporal change of the photoelectric conversion characteristics of the sensor 50 and the change corresponding to the environmental conditions. The configuration and function of the calibration unit 32 will be described in detail below.

[0077] like Figure 1 As shown, the calibration section 32 is composed of a reference light source 100 , a reference light source power supply 102 , a light measuring device 104 , and an optical path switching section 105 , which are provided inside and outside the sensor unit 30 .

[0078] The reference light source 100 is a light source that generates infrared light including the wavelength of the light to be measured LM, and preferably has Figure 2 The radiation spectrum distribution of an ideal black body is close to the radiation characteristics.

[0079] Fig. 7A The preferred structural example of the reference light source 100 is shown. The reference light source 100 has an infrared light emitting element 110 capable of blackbody radiation. The infrared light emitting element 110 is composed of a light emitting diode whose surface portion is composed of crystals, and a blackbody layer (blackbody film) is precipitated on the surface of the crystals. The surface of the blackbody layer is preferably formed in a dendrite shape, and radiated light is emitted in multiple directions from the dendrite surface. As a result, there is no unevenness in the radiation direction, and a highly reliable reference light can be obtained, and heat generation (luminescence) can be achieved in a very short time. In addition, the surface area of ​​the dendrite surface is large and the heat dissipation is high. Therefore, the diffusion rate of heat when the light emission stops is also fast, and it can be used as a stable blackbody light source without output reduction when used repeatedly. In the reference light source 100, 107 is a collimating lens, 112 is a frame, 114 is an internal electrical wiring, 115 is a connector, 116 is a circuit substrate, 118 is a cylindrical retaining portion, 120 is an opening portion, 122 is a thermistor, 124 is a protective glass, and 126 is a permanent magnet (a permanent magnet used to detachably fix the frame 112 to the unit 30).

[0080] Figure 7B The reference light source 100 is formed by extending the cylindrical holding portion 118 in the axial direction and arranging a diffusion plate 128 therein. Fig. 7A The structure is the same as that of . The light (reference light) emitted from the light emitting surface of the infrared light emitting element 110 at a certain divergence angle is emitted outward through the diffusion plate 128, thereby becoming a highly directional radiation light. Therefore, the collimating lens (107) is not required.

[0081] Again in Figure 1 In the embodiment, the reference light source power source 102 can arbitrarily control the power and oscillation mode (continuous wave or repetitive pulse) of the reference light generated by the reference light source 100 by supplying variable excitation power to the reference light source 100. The light measuring device 104 can be a known power meter or light quantity meter, which measures the power or light beam received by the light receiving portion 104a and displays the measured value in a numerical form on a display 104c of a main body 104b.

[0082] The optical path switching unit 105 switches to select the first optical path K1 optically connecting the processing point Q of the workpiece W and the optical sensor 50 , the second optical path K2 optically connecting the reference light source 100 and the optical sensor 50 , or the third optical path K3 optically connecting the reference light source 100 and the light receiving unit 104 a of the light measuring device 104 .

[0083] In order to realize the switching function, the optical path switching unit 105 has: one (or more) return mirrors 106, which can be retreated from the first optical path K1 to select the first optical path K1 at the first position P1 ( Figure 1 ), a second position P2 ( Figure 8 ), a third position P3 ( Fig. 9 )

[0084] In the present embodiment, the optical path switching section 105 is provided between the dichroic mirror 58 and the condenser lens 48 in the housing of the sensor unit 30. The reference light source 100 and the light receiving section 104a of the light measuring device 104 are mounted on the side wall of the housing of the sensor unit 30 adjacent to the optical path switching section 105. An optical filter 103 having the same wavelength selection characteristics as the band pass filter 54 of the optical sensor 50 or having the same wavelength selection characteristics may be arranged in front of the light receiving section 104a of the light measuring device 104. The reference light source power supply 102 and the main body 104b of the light measuring device 104 are provided outside the sensor unit 30.

[0085] Next, the function of the calibration unit 32 will be described. The calibration unit 32 has three modes selected according to the operating conditions of the laser processing device, the judgment of the on-site personnel, etc. That is, there are a first mode that does not interfere with the light reception and photoelectric conversion of the optical sensor 50 during the monitoring of laser processing, a second mode that calibrates the optical sensor 50 using the reference light source 100, and a third mode that calibrates the reference light source 100 using the light measuring device 104.

[0086] In the first mode, as described above, the return mirror 106 of the optical path switching unit 105 is switched to Figure 1 The reference light source 100, the reference light source power source 102 and the light measuring device 104 are in the off state. On the device body side, each unit operates, and in particular, the sensor signal processing unit 26, the control unit 14 and the operation panel 22 perform the waveform display processing set as the sensor output signal CS as described above.

[0087] The second mode is selected (implemented) at any time or regularly during the intervals of laser processing monitoring. In this mode, the return mirror 106 of the optical path switching unit 105 is switched to Figure 8 The reference light source power source 102 is turned on to generate reference light from the reference light source 100. At this time, the reference light source power source 102 supplies the reference light source 100 with excitation power for the volume position adjusted or updated in the third mode prior to the second mode.

[0088] In the second mode, on the device main body side, each unit is operated except for the laser oscillator 10 and the laser power source 12. However, the sensor signal processing unit 26, the control unit 14, and the operation panel 22 do not switch to the waveform display processing function as in the first mode with respect to the sensor output signal CS sent from the sensor unit 30, but switch to the calibration function for numerically displaying the measured value (measurement count value) of the power or light beam to perform gain adjustment.

[0089] In the second mode, the reference light emitted from the reference light source 100 is guided to the optical sensor 50 through the second optical path K2. In more detail, the reference light emitted from the reference light source 100 in the horizontal direction is reflected vertically upward by the reflection mirror 106 of the optical path switching unit 105. And the reference light reflected vertically upward is incident on the bandpass filter 54 of the optical sensor 50 via the condenser lens 48, and the light of the specific wavelength band passing through the filter 54 is incident on the photodiode 56. The photodiode 56 performs photoelectric conversion on the wavelength selected from the received reference light and outputs an analog sensor output signal CS. The sensor output signal CS is amplified by the subsequent amplifier output circuit 70 as described above and then transmitted to the sensor signal processing unit 26 on the device body side via the cable 18.

[0090] In the sensor signal processing unit 26, based on the sensor output signal CS converted into a digital signal by the A / D converter 82, the sensor signal processing unit 26 calculates the light intensity of the reference light after the photoelectric conversion by the optical sensor 50 or the measured value of the light beam, that is, the measured count value, and stores it in the data memory 88. The control unit 14 reads the measured count value from the data memory 88 and displays the measured count value on the display of the display unit 22a of the operation panel 22.

[0091] The on-site personnel implementing the second mode reads the measured count value displayed on the monitoring screen (maintenance screen) of the display unit 22a. The on-site personnel perform gain adjustment or offset adjustment on the output of the optical sensor 50 by input operation on the operation panel 22 so that the measured count value matches the predetermined reference count value.

[0092] The third mode is selected (implemented) at any time or regularly during the interval or process of laser processing monitoring, and is selected (implemented) before the second mode. In this mode, the return mirror 106 of the optical path switching unit 105 is switched to Fig. 9The reference light source 100, the reference light source power source 102 and the light measuring device 104 are turned on respectively. All parts on the device body side remain in the off state. The reference light emitted from the reference light source 100 is incident on the light receiving part 104a of the light measuring device 104 through the third optical path K3. At this time, the reference light source power source 102 supplies the excitation power of the volume position adjusted (updated) in the last third mode to the reference light source 100.

[0093] The on-site personnel who implement the third mode read the measured value of the reference light displayed on the display 104c of the light measuring device 104, and check whether the measured value is consistent with the absolute reference value pre-set as the output of the light sensor 50. If it is inconsistent, the on-site personnel adjust (update) the volume position of the reference light source power supply 102 so that the measured value is consistent with the absolute reference value. In this way, the light intensity of the reference light emitted from the reference light source 100 is calibrated to the absolute reference value via the light measuring device 104. In addition, the conventional light measuring device 104 guarantees its measurement accuracy by separately performing calibration management.

[0094] As described above, the reference light source 100 is composed of semiconductor elements such as light emitting diodes, and its electro-optical conversion characteristics inevitably change over time or change in accordance with environmental conditions. Therefore, when a certain excitation power is stably supplied from the reference light source power supply 102 to the reference light source 100, the light intensity of the reference light emitted from the reference light source 100 changes unexpectedly and uncertainly. According to the correction unit 32 of this embodiment, the change and variation of the electro-optical conversion characteristics of the reference light source 100 can be corrected at any time or frequently through the third mode. Therefore, in the second mode (correction of the optical sensor 50), a high-precision reference light can always be provided from the reference light source 100 to the optical sensor 50.

[0095] As described above, the laser processing monitoring unit 24 of the present embodiment uses the reference light source 100 provided in the device for calibration of the optical sensor 50 built into the sensor unit 30, and calibrates the reference light source 100 by the light measuring device 104 provided in the device. In the laser processing monitoring unit 24, even if the electro-optical conversion characteristics of the reference light source 100 change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner. In addition, even if the photoelectric conversion characteristics of the optical sensor 50 change due to time changes or environmental conditions, it can be corrected in a timely and accurate manner. As a result, the accuracy, reproducibility and operability of the calibration of the optical sensor 50 can be greatly improved, and the monitoring performance can be dramatically improved. In addition, the calibration reference value of the optical sensor 50 is set as the absolute reference value of the light measuring device 104, so that monitoring performance without mechanical error can be obtained.

[0096] Furthermore, in this embodiment, the optical path switching section 105 is provided near the optical sensor 50 in the sensor unit 30, and the reference light source 100 and the light receiving section 104a of the light measuring device 104 are mounted on the side wall of the housing of the sensor unit 30 adjacent to the optical path switching section 105. Thus, calibration focusing on the photoelectric conversion characteristics of the optical sensor 50 can be performed simply and safely without disassembling the sensor unit 30 or removing the optical sensor 50. In addition, at the laser processing site, the optical sensor 50 and the reference light source 100 can be frequently calibrated by daily inspection or periodic inspection without exposing the optical sensor 50 and the monitoring optical system in the sensor unit 30 to the surrounding dust environment.

[0097] [Preferred Configuration Example of the Optical Path Switching Unit]

[0098] As described above, in the laser processing monitoring unit 24 of the present embodiment, the optical path switching unit 105 is provided in the sensor unit 30 together with the optical sensor 50 (preferably in the vicinity thereof). Figure 10 to Figure 16C , a preferred structural example of the optical path switching unit 105 is described.

[0099] exist Fig.10 and Fig.11 2 shows the external appearance structure of the main parts of the sensor unit 30. The frame of the sensor unit 30 shown in the figure is composed of a lower cylindrical part 130, an intermediate square cylindrical part 132, an upper cylindrical part 134 and a sensor box 136 connected in a vertical row from bottom to top.

[0100] The lower cylindrical portion 130 accommodates the folding mirror 46 and the dichroic mirror 58 ( Figure 1 ). The reference light source 100 and the light receiving portion 104a of the light measuring device 104 are installed on the side wall of the middle square tube 132, and a rotating knob 138 is provided in a rotatable manner. Here, the reference light source 100 and the rotating knob 138 are located on opposite sides of the middle square tube 132 facing each other. The light receiving portion 104a of the light measuring device 104 is located on the side between the reference light source 100 and the rotating knob 138 in the circumferential direction of the middle square tube 132. The optical path switching portion 105 based on this structural example is provided in the middle square tube 132. The focusing lens 48 ( Figure 1 ). The optical sensor 50 is housed in the sensor box 136 .

[0101] Thus, the reference light source 100 and the light receiving portion 104a of the light measuring device 104 are not housed inside the sensor unit 30 but are mounted on the side wall from the outside, and the rotation knob 138 of the optical path switching portion 105 is also provided outside the side wall of the sensor unit 30. By providing the correction portion 32, the size (particularly the horizontal width) of the internal cavity (optical path) of the sensor unit 30 is not substantially increased.

[0102] Figure 12 to Figure 15 105 shows the structure of the optical path switching unit 105 of this embodiment. Fig.12 and Fig.13 It is a stereogram. Fig.14 is a side view, Fig.15 is along Fig.14 Cross-sectional view along line AA.

[0103] like Fig.12 and Fig.13 As shown, the optical path switching unit 105 has a cylindrical mirror support body 140 and a plurality of mirrors, and there are holes opposite to the mirrors. Specifically, the mirror support body 140 extends in a direction (X direction) intersecting the first optical path K1 at a right angle, and can rotate around the axis HX. An end face opening 142 is formed on an end face 140a of the mirror support body 140. The end face opening 142 is installed in a manner facing the radiation of the reference light source 100. The end face 140b on the opposite side is closed, and the rotation shaft 144 protrudes from the center of the end face 140b toward the axis HX (X direction). The rotation knob 138 is installed at the end of the rotation shaft 144 on the outside of the sensor unit 30.

[0104] Three side openings 146, 148, and 150 are formed at intervals in the circumferential direction on the side surface of the mirror support body 140. The first and second side openings 146 and 148 face each other, and the third side opening 150 is located between the two.

[0105] On the inner side of the mirror support body 140, a first folding mirror 106A is provided on the inner side of the end face 140b opposite to the end face opening 142, and a second folding mirror 106B is provided on the inner side of the side face opposite to the third side face opening 150. Here, the first folding mirror 106A is arranged at a predetermined tilt angle so as to receive the reference light introduced from the reference light source 100 through the end face opening 142 at an inclined incident angle and reflect it toward a predetermined direction, i.e., the second folding mirror 106B. On the other hand, the second folding mirror 106B is arranged at a predetermined tilt angle so as to receive the reference light from the first folding mirror 106A at an inclined incident angle and reflect it outward from the third side face opening 150.

[0106] like Figures 16A to 16CAs shown, the reference light source 100 is fixed to the side wall of the intermediate square tube portion 132 via a cylindrical mounting member 160. A bearing 162 is provided between the mounting member 160 and the end portion of the mirror support body 140. On the other hand, a bearing 164 is provided between the rotating shaft 144 of the mirror support body 140 and the side wall of the intermediate square tube portion 132. If the rotation knob 138 is turned outside the sensor unit 30, the mirror support body 140 is supported by the two bearings 162 and 164 in the sensor unit 30 and rotates around the axis HX.

[0107] The rotational position of the mirror support body 140 is selected into three (or two) types corresponding to the three modes of the correction unit 32. In the first mode, in order to select the first optical path K1, the rotational position of the mirror support body 140 is selected or adjusted in such a way that the first and second side openings 146 and 148 are located opposite to each other in the vertical direction on the first optical path K1.

[0108] Fig.16A The positional relationship of each part of the optical path switching unit 105 in the first mode is shown. In this case, the first and second folding mirrors 106A and 106B are set at the first position P1. Here, the second folding mirror 106B takes an upright posture like the first folding mirror 10A and retreats to the vicinity of the first optical path K1.

[0109] Through the dichroic mirror 58( Figure 1 ) The measured light propagating in the lower cylindrical portion 130 enters the mirror support body 140 from the lower side opening 148 in the optical path switching portion 105. The measured light entering the mirror support body 140 passes through the vicinity of the first and second return mirrors 106A and 106B, and is emitted to the outside of the mirror support body 140 from the upper side opening 146. The measured light passing through the optical path switching portion 105 directly propagates in the upper cylindrical portion 134, and is incident on the optical sensor 50 through the condenser lens 48.

[0110] In the second mode, in order to select the second optical path K2 , the rotational position of the mirror support 140 is selected or adjusted in such a way that the third side opening 150 is opposite the optical sensor 50 .

[0111] Fig. 16B The positional relationship of each part of the optical path switching unit 105 in the second mode is shown. In this case, the first and second folding mirrors 106A and 106B are set at the second position P2. Here, the second folding mirror 106B is located at the lowest position in the Z direction, and is opposite to the optical sensor 50 directly above through the third side opening 150. The first folding mirror 106A is linked to the rotation of the optical path switching unit 105, and is tilted downward to face the reference light source 100.

[0112] If the reference light emitted from the reference light source 100 enters the mirror support body 140 from the end opening 142, it directly moves straight and is incident on the first folding mirror 106A deep inside at an inclined incident angle, and is reflected obliquely downward therefrom, and is incident on the second folding mirror 106B at an inclined incident angle. Furthermore, the reference light incident on the second folding mirror 106B is reflected vertically upward therefrom, and is emitted outward from the third side opening 150. In this way, the reference light emitted outward from the third side opening 150 directly propagates in the upper cylindrical portion 134, and is incident on the optical sensor 50 through the focusing lens 48.

[0113] In the third mode, in order to select the third optical path K3, the rotation position of the mirror support body 140 is selected or adjusted so that the third side opening 150 and the light receiving part 104a of the light measuring device 104 located just next to the optical path switching part 105 are opposite in the horizontal direction (Y direction).

[0114] Fig. 16C 106B is a diagram showing the positional relationship of the components of the optical path switching unit 105 in the second mode. In this case, the first and second folding mirrors 106A and 106B are set at the third position P3. Here, the second folding mirror 106B sets a reflection surface in the Y direction, and faces the light receiving unit 104a of the light measuring device 104 located just next to it through the third side opening 150. The first folding mirror 106A is linked to the rotation of the optical path switching unit 105 and faces the reference light source 100.

[0115] If the reference light from the reference light source 100 enters the mirror support body 140 through the end opening 142, it directly moves straight and is incident on the first folding mirror 106A deep inside the front side at an inclined incident angle, where it is reflected to the oblique side surface and is incident on the second folding mirror 106B at an inclined incident angle. Furthermore, the reference light incident on the second folding mirror 106B is further reflected to the oblique side surface (Y direction) and is emitted outward from the third side opening 150. In this way, the reference light is emitted from the optical path switching unit 105 in the horizontal direction (Y direction) orthogonal to the rotation axis HX and is incident on the light receiving unit 104a of the light measuring device 104.

[0116] In the above description, the rotational position of the mirror support body 140 differs by 180° between the first mode and the third mode, but the rotational position of the mirror support body 140 may be the same (common). Fig.16A If the rotational position shown is rotated 180°, the rotational position of the mirror support 140 will be the same as Fig. 16C In this way, by setting the rotational position of the mirror support body 140 in the first mode (first position P1) and the rotational position in the third mode (third position P3) to be the same (common), the first mode (monitoring of laser processing) and the third mode (calibration of the reference light source 100) can be implemented simultaneously.

[0117] In this case, if Fig. 16C As shown, near the center inside the optical path switching section 105, the lateral third optical path K3 from the second folding mirror 106B toward the light receiving section 104a of the optical measuring device 104 and the longitudinal first optical path K1 passing through the lower dichroic mirror 58 and toward the upper optical sensor 50 perpendicularly intersect, but do not interfere with each other.

[0118] As described above, the optical path switching section 105 of this structural example is equipped with a folding mirror 106 (106A, 106B) inside a rotatable cylindrical mirror support body 140 having multiple openings on the end face and the side face. By selecting or adjusting the rotation position of the mirror support body 140, the folding mirror 106 (106A, 106B) is selectively moved to the first, second and third positions P1, P2, P3. Thus, the first, second and third optical paths K1, K2, K3 can be selected one by one, or any one of the first and third optical paths (K1, K3) or the second optical path K2 can be selected. According to such a structure, the required optical path selection or switching can be performed efficiently and smoothly within the limited cavity of the sensor unit 30.

[0119] [Other embodiments or modifications]

[0120] The preferred embodiments of the present invention have been described above, but the above embodiments do not limit the present invention. For those skilled in the art, various modifications and changes can be made in specific embodiments without departing from the technical concept and technical scope of the present invention.

[0121] For example, various modifications or changes can be made to the arrangement structures of the optical path switching unit 105, the reference light source 100, and the light receiving unit 104a of the light measuring device 104. That is, it is also possible to have a structure in which any one or all of the reference light source 100, the light receiving unit 104a of the light measuring device 104, and the optical path switching unit 105 are provided in the sensor unit 30 or in the processing head 20 separately from the optical sensor 50, or to have a structure in which at least one of the reference light source 100 and the light receiving unit 104a of the light measuring device 104 is detachably mounted to the sensor unit 30.

[0122] And, if Fig.17 As shown, the reference light source 100 may be detachably mounted on the sensor unit 30 , and the light receiving unit 104 a of the light measuring device 104 may be disposed separately from the sensor unit 30 , so that calibration of the reference light source 100 may be performed outside the sensor unit 30 .

[0123] Alternatively, in the case of the preferred structure ( Figure 10 to Figure 16C), the third position P3 of the first and second folding mirrors 106A and 106B in the third mode can also be set to a position upside down from the second position P2 (i.e., a position where the reflection surface of the second folding mirror 106B faces the dichroic mirror 58 side directly below across the third side opening 150). In this case, the light receiving portion 104a of the light measuring device 104 is arranged near the laser emission outlet of the emission unit 28. Thus, the third optical path K3 becomes the reference light source 100→optical path switching portion 105→dichroic mirror 58→folding mirror 46→unit connection opening 45→dichroic mirror 40→focusing lens 42→protective glass 44→light receiving portion 104a of the light measuring device 104.

[0124] In the sensor unit 30, the reference light source 100 and the light receiving unit 104a of the light measuring device 104 may be placed opposite to each other with the light path switching unit 105 interposed therebetween, and the light path switching unit 105 may be provided with a single folding mirror 106. In this case, a configuration may be adopted in which the single folding mirror 106 can be moved between a first position P1 where the folding mirror 106 is withdrawn from the first light path K1 in order to select the first light path K1, and a second position P2 where the folding mirror 106 is blocked at an inclination angle of 45° in order to select the second light path K2 and the reference light from the reference light source 100 is reflected toward the light sensor 50. In this case, by setting the first position P1 of the folding mirror 106 at a position where the folding mirror 106 is withdrawn from the third light path K3, the first position P1 and the third position P3 can be made common.

[0125] The laser processing apparatus of the above embodiment integrates the sensor unit 30 and the injection unit 28 and installs them in the processing head 20. However, the sensor unit 30 may be separated from the injection unit 28 and arranged as an independent unit near the processing head 20 or the injection unit 28 facing the workpiece W.

[0126] In this way, when the sensor unit 30 is set as an independent unit, an incident window is provided at the front stage (unit end surface) of the monitoring optical system of the sensor unit 30 so as to directly take in the measured light generated or reflected near the processing point Q of the workpiece W. In this case, in addition to the light receiving part 104a of the light measuring device 104, the reference light source 100 can also be used outside the sensor unit 30. That is, in the second mode, the radiation surface of the reference light source 100 can be applied to (directed toward) the incident window of the sensor unit 30 from the outside, and the reference light emitted from the reference light source 100 can be taken into the sensor unit 30 from the incident window, so that the optical sensor 50 deep inside receives the taken-in reference light through the internal monitoring optical system. As a result, the optical path switching part (105) can be omitted from the sensor unit 30.

[0127] The laser beam monitoring unit 24 in the above-mentioned embodiment uses infrared light emitted from the vicinity of the processing point Q of the workpiece W as the measured light. However, plasma light emitted from the vicinity of the processing point Q of the workpiece W, reflected light from the vicinity of the processing point Q (light reflected by the laser beam used for processing) or visible light can also be used as the measured light. Therefore, the reference light source 100 is not limited to a black body radiation light source, and various light emitting diodes or semiconductor lasers having radiation characteristics corresponding to the wavelength band of the measured light can be used. In this case, a bandpass filter or an optical filter having a wavelength selection characteristic corresponding to the radiation characteristics of the reference light source used or the wavelength of the measured light can be set on the second optical path K2 that optically connects the reference light source 100 and the optical sensor 50.

[0128] The laser processing monitoring method or device of the present invention is not limited to application to laser processing devices for laser welding, but can also be applied to laser processing devices for other laser processing such as laser cutting, laser brazing, laser quenching, laser surface modification, etc.

[0129] The disclosure of the present application is related to the subject matter described in Japanese Patent Application No. 2020-068853 filed on April 7, 2020, and all disclosed contents thereof are incorporated herein by reference.

Claims

1. A laser processing monitoring device, wherein when a laser beam for laser processing is irradiated from a processing head to a workpiece, a predetermined light to be measured generated or reflected near a processing point of the workpiece is photoelectrically converted by a light sensor arranged in or close to the processing head, and a sensor output signal indicating the light intensity of the light to be measured is obtained, and the laser processing is monitored based on the sensor output signal. It is characterized in that The laser processing monitoring device comprises: A reference light source, which is disposed on the processing head and generates reference light for correcting the photoelectric conversion characteristics of the light sensor; a reference light source power supply unit for supplying adjustable electric power for generating the reference light to the reference light source; as well as The light measuring device includes a light receiving unit for receiving the reference light from the reference light source in order to calibrate the electro-optical conversion characteristics of the reference light source, and measures the light intensity of the received reference light or a predetermined physical quantity corresponding to the light intensity.

2. The laser processing monitoring device according to claim 1, It is characterized in that The laser processing monitoring device comprises: a sensor unit, which has the optical sensor built therein and is installed in the processing head or arranged close to the processing head; At least one of the reference light source and the light receiving unit of the light measuring device is mounted on the sensor unit.

3. The laser processing monitoring device according to claim 2, It is characterized in that An optical path switching unit is provided in the sensor unit, which is used to select a first optical path that optically connects the processing point of the workpiece with the optical sensor, a second optical path that optically connects the reference light source with the optical sensor, or a third optical path that optically connects the reference light source with the light receiving part of the optical measuring device.

4. The laser processing monitoring device according to claim 3, It is characterized in that An optical filter that selects and passes a predetermined wavelength band including the wavelength of the light to be measured is provided on the second optical path.

5. The laser processing monitoring device according to claim 3 or 4, It is characterized in that The processing head comprises: an injection unit which is integrally or detachably connected to the sensor unit via a unit connection opening; The emitting unit is provided with a first optical system, which irradiates the laser beam toward a processing point of the workpiece, separates the measured light from the vicinity of the processing point from the laser beam and allows the measured light to pass through the unit connection opening, The sensor unit is provided with a second optical system for guiding the light to be measured, which enters from the emission unit through the unit connection opening, to the optical sensor.

6. The laser processing monitoring device according to claim 5, It is characterized in that In the sensor unit, the optical path switching section is provided in the second optical system or at a position closer to the optical sensor than the second optical system. The reference light source and the light receiving unit of the light measuring device are provided in the vicinity of the optical path switching unit.

7. The laser processing monitoring device according to claim 3 or 4, It is characterized in that The optical path switching unit has: a cylindrical mirror support body rotatable about a first axis intersecting the first optical path; an end surface opening formed on a first end surface of the mirror support body for introducing the reference light from the reference light source; a first side opening and a second side opening, which are formed opposite to the side surface of the mirror support; a third side opening, which is formed on a side surface of the mirror support body between the first side opening and the second side opening in a circumferential direction; a first folding mirror disposed on the inner side of the second end face of the mirror support body opposite to the end face opening, receiving the reference light introduced from the reference light source through the end face opening at an inclined incident angle and reflecting it in a predetermined direction; and a second folding mirror disposed on the inner side of the side surface of the mirror support body opposite to the third side surface opening, receiving the reference light from the first folding mirror at an inclined incident angle and reflecting the reference light out of the third side surface opening; When the first optical path is selected, the rotational position of the mirror support is selected or adjusted in such a way that the first side opening and the second side opening are opposite to the optical sensor, When the second optical path is selected, the rotational position of the mirror support is selected or adjusted in such a way that the third side opening is opposite to the optical sensor, When the third optical path is selected, the rotational position of the mirror support body is selected or adjusted so that the third side opening faces the light receiving portion of the light measuring device.

8. The laser processing monitoring device according to claim 7, It is characterized in that The reference light source is mounted on a side wall of the sensor unit so as to face the end surface opening of the mirror support body. A light receiving portion of the light measuring device is attached to a side wall of the sensor unit so as to face a side surface of the mirror support body.

9. The laser processing monitoring device according to claim 7, It is characterized in that A rotation knob is coupled to a rotation shaft protruding from the second end surface of the mirror support body.

10. The laser processing monitoring device according to claim 3 or 4, It is characterized in that The optical path switching unit has: one or more folding mirrors, which can move between a first position to retreat from the first optical path in order to select the first optical path and a second position to block the first optical path and reflect the reference light from the reference light source toward the light sensor in order to select the second optical path.

11. The laser processing monitoring device according to claim 10, It is characterized in that The optical path switching unit moves the folding mirror to the first position in order to select the third optical path.

12. The laser processing monitoring device according to claim 3 or 4, It is characterized in that The optical path switching unit has: one or more reflecting mirrors, which are capable of moving between a first position of retreating from the first optical path in order to select the first optical path, a second position of blocking the first optical path and reflecting the reference light from the reference light source toward the light sensor in order to select the second optical path, and a third position of retreating from the third optical path in order to select the third optical path.

13. The laser processing monitoring device according to any one of claims 1 to 4, It is characterized in that The reference light source includes a light emitting diode or a semiconductor laser having radiation characteristics including a wavelength band of the light to be measured.

14. The laser processing monitoring device according to any one of claims 1 to 4, It is characterized in that The reference light source includes a light emitting diode or a semiconductor laser having radiation characteristics close to those of a black body.

15. A method for monitoring laser processing, comprising: when a laser beam for laser processing is irradiated from a processing head to a workpiece, a light to be measured generated or reflected near a processing point of the workpiece is photoelectrically converted by a light sensor arranged in or close to the processing head, and a sensor output signal indicating the light intensity of the light to be measured is obtained, and the laser processing is monitored based on the sensor output signal. It is characterized in that include: The optical sensor is provided in a sensor unit which is incorporated into the processing head or arranged close to the processing head. A reference light source for generating reference light for correcting the photoelectric conversion characteristics of the optical sensor is installed in the sensor unit. When the laser processing is performed, a first optical path is set in the sensor unit to optically connect a processing point of the workpiece with the optical sensor. When calibrating the optical sensor, a second optical path is set in the sensor unit to optically connect the reference light source and the optical sensor. To calibrate the electro-optical conversion characteristics of the reference light source, the reference light emitted from the reference light source is made incident on a light receiving section of a photometer, and the output of the reference light source is adjusted so that a measurement value of the photometer matches a reference value.

16. The laser processing monitoring method according to claim 15, It is characterized in that include: The light receiving unit of the light measuring device is mounted on the sensor unit, and when the reference light source is calibrated, a third optical path optically connecting the reference light source and the light receiving unit is set in the machining head.

17. The laser processing monitoring method according to claim 15, It is characterized in that include: The reference light source is detachably mounted on the sensor unit. When calibrating the reference light source, the reference light source is removed from the sensor unit so that the reference light generated from the reference light source outside the sensor unit is incident on the light receiving portion of the light measuring device.

18. A laser processing device, It is characterized in that have: A laser oscillator that oscillates and outputs a laser beam for laser processing; a processing head optically connected to the laser oscillator via an optical cable, and focusing the laser beam from the laser oscillator onto a processing point of a workpiece; and A laser processing monitoring unit monitors the laser processing. The laser processing monitoring unit comprises: an optical sensor disposed in the processing head or in close proximity to the processing head, and outputting a sensor output signal representing the light intensity of predetermined light to be measured generated or reflected near a processing point of the workpiece; A sensor signal processing unit that generates digital waveform data for the sensor output signal from the optical sensor and displays and outputs a waveform of the sensor output signal based on the waveform data; a reference light source that generates reference light for correcting the photoelectric conversion characteristics of the light sensor; a reference light source power supply unit for supplying adjustable electric power for generating the reference light to the reference light source; as well as The light measuring device includes a light receiving unit for receiving the reference light from the reference light source in order to calibrate the electro-optical conversion characteristics of the reference light source, and measures the light intensity of the received reference light or a predetermined physical quantity corresponding to the light intensity.

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