Laser welding real-time monitoring system and method

Abstract

The embodiment of the invention relates to a laser welding real-time monitoring system and method. The system comprises a laser emission system, an adapter and a processing beam monitoring system connected with the laser emission system through the adapter, the laser emission system comprises a first 45-degree dichroic mirror; the processing light beam monitoring system comprises a window mirror connected with the adapter, a second 45-degree dichroic mirror, an optical sensor, a first interface and a second interface; the optical sensor is used for detecting reflected light of different wavebands reflected by the machined part and monitoring electric signal peak values, identifying fluctuation conditions of the reflected light of different wavebands and judging laser welding defects. By combining the optical sensor, the spectroscope, the light reducing piece, the optical filter and other assemblies, multiple wave band optical signals (infrared light, visible light and backlight reflected light) in the laser welding process are monitored in real time, welding defects are found in time through electric signal peak monitoring, frequency domain analysis and other methods, and the welding quality and the production efficiency are ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of laser welding, and in particular relates to a laser welding real-time monitoring system and method. Background Art

[0002] As an efficient and precise metal connection technology, laser welding is widely used in automobile manufacturing, aerospace, electronic equipment and precision instruments. Due to its excellent welding quality, high welding speed and good adaptability, laser welding has gradually become the preferred method in many high-precision manufacturing fields. In the existing technology of CO2, Nd: YAG, fiber laser welding, semiconductor laser welding or ultra-short pulse laser welding (femtosecond laser, picosecond laser lamp) or hot melt welding (due to the different power spectrum density of the emitted laser) Figure 1 ) or deep penetration welding ( Figure 2 ). However, during the laser welding process, due to factors such as high temperature, rapid heating and cooling, various welding defects are prone to occur, such as pores, cracks, incomplete penetration, overheating, uneven molten pool, etc. These defects seriously affect the welding quality and reliability.

[0003] In order to improve the quality of laser welding, real-time monitoring and detection of defects in the welding process become the key. Traditional laser welding quality inspection methods mostly rely on post-inspection, usually by cutting samples or using X-rays and other means for inspection. These methods are not only time-consuming and labor-intensive, but also unable to achieve instant feedback and adjustment during the welding process. Therefore, how to achieve real-time, accurate, and non-destructive laser welding monitoring has become a technical problem that needs to be solved in the industry.

[0004] Figure 3 It is shown that in the prior art, the monitoring system of laser welding mainly relies on cameras or CCD imaging technology to capture images during the welding process, and combines image analysis algorithms to judge the welding quality. However, image monitoring is limited by light source, ambient light changes and image resolution, and it is difficult to capture tiny optical changes during the welding process in real time. At the same time, single-band optical signal monitoring often cannot fully reflect various dynamic changes during the welding process, resulting in the monitoring system being inaccurate when dealing with complex welding defects.

[0005] In recent years, with the development of optical sensors and spectroscopic technology, real-time monitoring systems based on multi-band reflected light have gradually been applied. By combining signals from different bands (such as visible light, infrared light, backlight reflected light, etc.), the status and changes of different areas in the welding process can be more comprehensively captured, thereby improving the accuracy of defect detection.

[0006] However, current multi-band optical monitoring systems usually have some problems, such as difficulty in accurately separating reflected light signals of different bands, or inability to perform real-time analysis and feedback of signal fluctuations during welding, which results in failure to detect welding defects in a timely manner and inability to effectively improve welding quality and efficiency. Therefore, how to design a high-precision, real-time feedback, non-destructive testing laser welding monitoring system, one or at least part of the technologies have become technical problems that current technology needs to solve. Summary of the invention

[0007] In response to the above problems, the present disclosure provides a real-time monitoring system for laser welding. The goal of the present disclosure is to monitor multiple bands of light signals (infrared light, visible light, backlight reflected light) in the laser welding process in real time by combining components such as optical sensors, spectroscopes, dimming films and filters, and to promptly detect welding defects through methods such as electrical signal peak monitoring and frequency domain analysis, thereby ensuring welding quality and production efficiency.

[0008] According to one aspect of the present disclosure, a laser welding real-time monitoring system is provided. The laser welding real-time monitoring system includes: a laser emission system, an adapter, and a processing beam monitoring system connected to the laser emission system through the adapter; the laser emission system includes a first 45-degree dichroic mirror, which is arranged at the corner of the galvanometer unit and the laser light source; the adapter is arranged on the light transmission direction side of the first 45-degree dichroic mirror, and the galvanometer unit is arranged on the reflected light direction side of the first 45-degree dichroic mirror; the processing beam monitoring system includes a window mirror connected to the adapter, a second 45-degree dichroic mirror arranged on the side of the window mirror away from the adapter, an optical sensor arranged on the reflected light direction side of the second 45-degree dichroic mirror, and a first interface and a second interface arranged on the light transmission side of the second 45-degree dichroic mirror; the optical sensor is used to detect infrared light reflection light, visible light reflection light and backlight reflection light reflected from the workpiece, monitor the peak value of the reflected light in different bands, identify the fluctuation of reflected light in different bands, and judge laser welding defects.

[0009] According to another aspect of the present disclosure, a monitoring method for a real-time monitoring system for laser welding is provided, the method comprising: laser light emitted by a laser is reflected by a first 45-degree dichroic mirror, enters a galvanometer unit, and is then emitted by the galvanometer unit to a back-processed workpiece surface; different processing areas are formed on the surface of the processed workpiece, and reflected light in different processing areas is transmitted to the first 45-degree dichroic mirror through the galvanometer unit, and further reaches the second 45-degree dichroic mirror through the adapter; after being reflected by the second 45-degree dichroic mirror, it enters an optical sensor; the optical sensor detects infrared reflected light, visible reflected light, and backlight reflected light reflected from the workpiece, performs electrical signal peak monitoring on reflected light in different bands, identifies fluctuations in reflected light in different bands, and determines laser welding defects.

[0010] In some implementations, the optical sensor includes: a spectroscopic unit, including a 45-degree total reflection mirror, a first 45-degree spectroscope, and a second 45-degree spectroscope, which are sequentially arranged above the sensor interface from top to bottom; a focusing lens unit, including a first focusing lens, a second focusing lens, and a third focusing lens, which are sequentially arranged from top to bottom; a filtering and dimming unit, including a first optical sheet assembly, a second optical sheet assembly, and a third optical sheet assembly, which are sequentially arranged from top to bottom; the first optical sheet assembly, the second optical sheet assembly, and the third optical sheet assembly each include a number of filters and / or dimming sheets with overlapping center lines; a photoelectric signal conversion unit, including a first photodiode, a second photodiode, and a third photodiode, which are sequentially arranged from top to bottom; an electrical signal peak detection unit, including three electrical signal peak monitoring circuits electrically connected to the first photodiode, the second photodiode, and the third photodiode in sequence: a first electrical signal peak monitoring circuit, a second peak current detection circuit, and a third electrical signal peak monitoring circuit.

[0011] In some implementations, the optical signal incident sides of the first photodiode, the second photodiode, and the third photodiode are further provided with a first filter, a second filter, and a third filter, respectively.

[0012] In some implementations, the first optical plate assembly includes a first filter and a first dimming film arranged in sequence along the light propagation direction; the second optical plate assembly includes a second dimming film, a third dimming film, and a fourth dimming film arranged in sequence along the light propagation direction; the third optical plate assembly includes a second filter and a third filter arranged in sequence along the light propagation direction, or the third optical plate assembly includes a fifth dimming film and a sixth dimming film arranged in sequence along the light propagation direction.

[0013] In some implementations, the first optical sheet assembly includes a first dimming film, a second dimming film, and a third dimming film along the light propagation direction; the second optical sheet assembly includes a first filter and a fourth dimming film sequentially arranged along the light propagation direction; the third optical sheet assembly includes a second filter and a third filter sequentially arranged along the light propagation direction; or the third optical sheet assembly includes a fifth dimming film and a sixth dimming film sequentially arranged along the light propagation direction.

[0014] In some implementations, the first photodiode, the second photodiode, and the third photodiode are an infrared monitoring diode, a back reflection light monitoring diode, and a visible laser monitoring diode, respectively.

[0015] In some implementations, the first photodiode, the second photodiode, and the third photodiode are a back reflection light monitoring diode, an infrared monitoring diode, and a visible laser monitoring diode, respectively.

[0016] In some implementations, the infrared monitoring diode is an InGaAs diode, the back reflection light diode is an InGaAs diode, and the visible laser monitoring diode is a silicon diode.

[0017] In some implementations, each of the electrical signal peak monitoring circuits includes a resistive voltage divider component, a first Schottky diode D1 connected to the resistive voltage divider component, an electrical signal first operational amplifier and feedback adjustment component, a second Schottky diode D2, a high-frequency noise filtering component, and an electrical signal second operational amplifier and feedback adjustment component;

[0018] The resistive voltage divider component includes a first resistor R1 connected to the cathode of the photodiode, and a second resistor R2 connected to the other end of the first resistor R1; the first operational amplifier and feedback adjustment component for the electrical signal includes a third resistor R3 connected to the other end of the second resistor R2, a first operational amplifier U1, a third Schottky diode D3, and a fourth resistor R4; the high-frequency noise filtering component includes a fifth resistor R5 and a first capacitor C1; the second operational amplifier and feedback adjustment component for the electrical signal includes a sixth resistor R6, a second operational amplifier U2, a seventh resistor R7, and an eighth resistor R8; the second operational amplifier U2 outputs the detected peak value of the electrical signal.

[0019] The disclosed laser welding real-time monitoring system realizes multi-band monitoring of infrared light reflection, visible light reflection and backlight reflection during welding through multiple optical elements (such as dichroic mirrors, window mirrors, optical sensors, etc.). The multi-band monitoring method can comprehensively capture the status of the molten pool and welded joint during welding from different angles, thus improving the monitoring capability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present disclosure will be better understood and other objects, details, features and advantages of the present disclosure will become more apparent through the description of specific embodiments of the present disclosure given with reference to the following drawings.

[0021] Figure 1 A schematic diagram showing the working principle of laser heat fusion welding is shown;

[0022] Figure 2 A schematic diagram showing the working principle of laser deep fusion welding is shown;

[0023] Figure 3 A partial structural schematic diagram of a laser welding system is shown;

[0024] Figure 4 A schematic diagram of a laser welding real-time monitoring system according to an embodiment of the present disclosure is shown;

[0025] Figure 5 A schematic diagram of a laser welding monitoring system with a laser calibration function according to an embodiment of the present disclosure is shown;

[0026] Figure 6 A first technical solution of the optical sensor of the laser welding monitoring system disclosed in the present invention is shown;

[0027] Figure 7 A technical solution of a light filtering and dimming unit of the first technical solution of the optical sensor disclosed in the present invention is shown;

[0028] Figure 8 Another technical solution of the light filtering unit of the first technical solution of the optical sensor disclosed in the present invention is shown;

[0029] Fig. 9 A second technical solution of the optical sensor of the laser welding monitoring system disclosed in the present invention is shown;

[0030] Fig.10 A technical solution of the light filtering unit of the second technical solution of the optical sensor disclosed in the present invention is shown;

[0031] Fig.11 Another technical solution of the light filtering unit of the second technical solution of the optical sensor disclosed in the present invention is shown;

[0032] Fig.12 A schematic diagram showing an electrical signal peak monitoring circuit in an electrical signal peak detection unit of the present disclosure is shown;

[0033] Fig.13 The waveform diagram of reflected light signals of different wavebands when the galvanized steel plate is uniformly welded in the embodiment of the present disclosure is shown;

[0034] Fig.14The statistical analysis diagram of reflected light signals of different wavebands during uniform welding is shown;

[0035] Fig.15 The waveform diagram of reflected light signals in different bands when defects are generated in the wire-filling welding of galvanized steel plates in the embodiment of the present disclosure is shown;

[0036] Fig.16 A statistical analysis diagram of reflected light signals in different bands when defects are generated in the filler wire welding of the present disclosure is shown;

[0037] Fig.17 A spectrum diagram showing the frequency band analysis of reflected light signals of different wavelength bands when defects are generated in the filler wire welding of the present disclosure;

[0038] Fig.18 The molten pool conditions on the surface and side of the workpiece when the method and system of the present disclosure are welded to the workpiece are shown;

[0039] Fig.19 The schematic diagrams of the Gaussian beam plane and stereoscopic reconstruction after the method and system disclosed in the present invention monitor the reflected light of different wavelength bands during welding are shown;

[0040] Fig. 20 A schematic diagram of a welding quality defect monitored by the method and system of the present disclosure is shown in plan and side views. DETAILED DESCRIPTION

[0041] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0042] As used herein, the term "including" and its variations mean open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "based at least in part on". The terms "one embodiment" and "some embodiments" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc. may refer to different or the same objects.

[0043] Figure 1 The working principle of laser heat fusion welding is shown. In this case, the laser power spectrum density is about 10 4 W / cm 2 ~10 6 W / cm 2, the power of the laser beam is relatively low, and it is mainly used to heat the surface of the workpiece. At this time, the heat energy of the laser beam is absorbed by the surface of the workpiece, and the temperature near the focus of the laser beam rises rapidly, forming a welding area. Due to the low power density, the laser beam can only affect a small area of ​​the surface, so the welding depth is shallow. At this power, the molten pool is shallow during the welding process. The solid-liquid interface of the workpiece is relatively smooth, and the depth and width of the molten pool are small. Due to the limited depth of the laser beam, this welding method is usually suitable for welding thin materials or occasions where a deep molten pool is not required.

[0044] Figure 2 The working principle of laser deep penetration welding is shown. In this case, the laser power spectrum density increases to 10 6 W / cm 2 Up to 10 8 W / cm 2 , that is, the power density of the laser beam is higher. At this time, the laser beam not only heats the surface of the material, but also penetrates into the interior of the material to form a deeper molten pool. The high-power laser beam causes the surface of the workpiece to heat up rapidly, and at the same time, the heat is transferred to a deeper level, causing the laser beam to penetrate the surface and produce a deeper molten pool, achieving the effect of deep fusion welding.

[0045] In this welding method, the increase in laser power during welding will produce a deeper keyhole in the longitudinal direction of the laser spot. Due to the high power density, the depth and width of the molten pool are larger. Under high power density, the laser can form obvious holes and deep penetration welding holes, which are usually used for deep welding or where high penetration is required.

[0046] Figure 4 A laser welding real-time monitoring system 10 is shown, which includes:

[0047] A laser emitting system 11, an adapter 12, and a processing beam monitoring system 13 connected to the laser emitting system via the adapter;

[0048] The laser emitting system 11 comprises a first 45-degree dichroic mirror 111, a galvanometer unit 112 and a laser light source (i.e. Figure 3 The laser 101 emitted by the laser in the welding monitoring system is set at the corner (the trajectory of the laser 101 in the welding monitoring system is indicated by a yellow arrow). The laser 101 emitted by the laser indicated by the yellow arrow is refracted 90 degrees at the corner 102 and enters the galvanometer unit 112. After being refracted 90 degrees again in the galvanometer unit 112, it is ideally irradiated vertically on the surface of the workpiece 103 to be welded. Figure 1 , Figure 2As shown, a molten pool is formed on the surface of the workpiece 103 by the laser. When the laser power used is greater than the penetration welding technology, a small penetration hole (also called a penetration hole or a keyhole) is further formed in the vertical Z-axis direction of the workpiece. In addition, when the laser acts on the surface of the workpiece (metals of different materials), the high temperature formed by the laser on the surface of the workpiece will cause partial splashing of the workpiece, and a plasma exchange region (this region mainly includes high-temperature gas and metal vapor) is formed above the molten pool on the surface of the workpiece. It is a columnar or conical region. By monitoring the peaks of light signals of different wavelengths (visible light and backlight reflected light), the The plane area and longitudinal depth of this area are monitored in real time. The fluctuation of the visible light signal reflects the radiation of the laser and plasma, that is, the plane area of ​​the plasma area. Infrared light is the photothermal effect of the laser on the surface of the workpiece during the welding process, which heats the workpiece to form a molten solid-liquid reaction, forming a high-temperature area in the molten pool area, and the high temperature forms infrared radiation. The fluctuation of the backlight reflected light reflects the depth of the bottom of the molten pool, the shape of the molten pool, the flow and the uneven cooling process. Since the reflected light can reflect the uneven state of the surface of the workpiece, it can further reflect whether there are defects such as holes and cracks in the laser welding process.

[0049] Figure 4 In the embodiment, the adapter 12 is arranged on the light transmission direction side of the first 45-degree dichroic mirror 111, and the galvanometer unit 112 is arranged on the light reflection direction side of the first 45-degree dichroic mirror 111;

[0050] The processing beam monitoring system 13 includes a window mirror 131 connected to the adapter 12, a second 45-degree dichroic mirror 132 on the side of the window mirror 131 away from the adapter 12, an optical sensor 14 arranged on the light reflecting side of the second 45-degree dichroic mirror 132, and a first interface 105 and a second interface 106 arranged on the light transmitting side of the second 45-degree dichroic mirror 132; an external light source (the green arrow represents the incident direction of the light source) enters the processing beam monitoring system 13 through the second interface 106, and enters the optical sensor 14 after being transmitted through the second 45-degree dichroic mirror 132. The optical sensor 14 monitors the peak value changes of the electrical signals obtained by converting light signals of different wavelengths in real time, and compares them with the peak value changes of the known analog control of the external light source, so as to judge whether the optical sensor is working normally and the accuracy of the peak detection.

[0051] The optical sensor 14 is used to detect infrared light, visible light and backlight reflection light (the reflected light trajectory is indicated by a blue arrow) reflected from the workpiece, monitor the peak value of the electrical signal of the reflected light in different bands, identify the fluctuation of the reflected light in different bands, and judge the laser welding defects.

[0052] The second 45-degree dichroic mirror 132 is used to reflect the detection light signal fed back from the galvanometer unit.

[0053] As an example of the present invention, in a laser welding monitoring system equipped with a CCD camera, the first interface 105 is used to connect the CCD camera connected to the galvanometer unit 112. The above connection is both a physical connection and a communication connection. The second interface is used to connect the collimated measuring light to determine whether the laser welding real-time monitoring system is working normally. It can also be used to detect whether the product meets the factory standards.

[0054] As an example of the present invention, when the processing beam monitoring system 13 needs to check whether the light signal of the emitted laser is collimated, Figure 5 It shows that the laser pen 108 and the collimation module 109 are replaced and connected at the optical sensor 14 in the processing beam monitoring system 13. After emitting calibration light to the second 45-degree dichroic mirror 132, the calibration light passes through the window mirror 131, and then reaches the galvanometer unit 112 after passing through the adapter 12. After being transmitted through the first 45-degree dichroic mirror 111 in the galvanometer unit 112, it is finally emitted vertically by the galvanometer unit 112 to the surface of the processing piece 103. The laser pen 108 can be selectively connected to the collimation module 109 through an optical fiber. A collimation lens is arranged in the collimation module 109 to ensure that the emitted laser is vertical light, which is used to verify and compare whether the optical path is collimated when the laser emits laser in the galvanometer unit 112.

[0055] The second 45-degree dichroic mirror 132 in the processing beam monitoring system 13 is placed on an adjustment frame 107 having a 45-degree inclined surface. The adjustment frame 107 can be adjusted along Figure 4 The optical center point of the second 45-degree dichroic mirror is adjusted to coincide with the center line of the components in the optical sensor 133 by moving left and right or up and down in the plane direction. After the adjustment 107 is adjusted, it is ensured that the optical axis of the external light source connected through the second interface 106 also passes through the optical center point of the second 45-degree dichroic mirror, and the optical center point of the second 45-degree dichroic mirror is also on the center line of the window mirror 131. The reflected light monitored by the laser emission system 11 of the present disclosure can also be collimated to achieve that the optical center point of the first 45-degree dichroic mirror 111, the axis of the adapter 12, the window mirror 131 and the optical center point of the second 45-degree dichroic mirror 132 are on the same straight line.

[0056] As an example of the present invention, Figure 6 The optical sensor 14 shown comprises:

[0057] The spectroscopic unit 141 includes a 45-degree total reflection mirror 1411, a first 45-degree spectroscope 1412, and a second 45-degree spectroscope 1413, which are sequentially arranged above the sensor interface 133 from top to bottom; it should be noted that if the propagation of the feedback light signal is reversely vertical (i.e., no offset occurs, and it is vertical relative to the horizontal plane), it is sequentially transmitted through the second 45-degree spectroscope 1413, the first 45-degree spectroscope 1412, and the 45-degree total reflection mirror 1411, and is sequentially reflected and transmitted in the horizontal direction when the incident light or the transmitted light reaches the second 45-degree spectroscope 1413, the first 45-degree spectroscope 1412, and the 45-degree total reflection mirror 1411; the 45-degree total reflection mirror 1411, the first 45-degree spectroscope 1412, and the second 45-degree spectroscope 1413 are all arranged at 90 degrees (vertical) to the first 45-degree dichroic mirror 132.

[0058] The focusing lens unit 142 includes a first focusing lens 1421, a second focusing lens 1422 and a third focusing lens 1423 arranged in sequence from top to bottom; in the above-mentioned ideal state, that is, when the propagation of the feedback light signal is reversed and vertical, the reflected light that is reflected in sequence at the second 45-degree beam splitter 1413, the first 45-degree beam splitter 1412 and the 45-degree total reflection mirror 1411 and then propagates in parallel passes horizontally along the center line of the third focusing lens 1423, the center line of the second focusing lens 1422 and the center line 1421 of the first focusing lens and enters the following light filtering and dimming unit 143, and the first focusing lens 1421 to the third focusing lens 1423 can be selected as aspherical focusing lenses, and the convex side of the lenses is close to the monitoring spectroscopic unit 141;

[0059] The filtering and dimming unit 143 includes a first optical sheet assembly 15, a second optical sheet assembly 16 and a third optical sheet assembly 17 which are sequentially arranged from top to bottom; the first optical sheet assembly 15, the second optical sheet assembly 16 and the third optical sheet assembly 17 each include a plurality of filters and / or dimming films whose center lines coincide, that is, each optical sheet assembly includes a plurality of filters and / or dimming films, and the plurality of filters and / or dimming films in each optical sheet assembly are arranged perpendicular to the horizontal plane, and in an ideal case, if the reflected light does not deviate, the propagation reverse direction parallel to the horizontal plane is maintained. In this ideal state, the center lines of all filters and / or dimming films in each optical sheet assembly are in the propagation direction of the reflected light, so as to filter and / or dim the three parallel light beams after the focused transmission respectively;

[0060] As an example of the present invention, Figure 6 , Figure 7The diagram shows the filters and / or dimming films included in each optical plate assembly in a filtering and dimming unit 143. The first optical plate assembly 15 includes a first optical filter 191 and a first dimming film 181 sequentially arranged along the light propagation direction; the second optical plate assembly 16 includes a second dimming film 182, a third dimming film 183 and a fourth dimming film 184 sequentially arranged along the light propagation direction; the third optical plate assembly 17 includes a second optical filter 192 and a third optical filter 193 sequentially arranged along the light propagation direction.

[0061] In this setting, the first 45-degree beam splitter 1412 is set to allow the backlight reflected light to be reflected and pass through the second optical chip assembly 16 in a parallel direction, and allow the infrared light to be transmitted and continue to propagate along the direction of the monitored reflected light incident from the sensor interface 133, and then reach the top 45-degree total reflection mirror for total reflection, and propagate through the first optical chip assembly 16 in a parallel direction. At this point, the first 45-degree beam splitter 1412 reflects the reflected light incident into the filter visible light unit 143 through the second 45-degree beam splitter 1413 to obtain visible light, and the visible light enters the third optical chip assembly 17 in a horizontal direction, and after being dimmed and filtered by the third optical chip assembly 17, it enters the third photodiode 1443 to convert the visible light in the 400nm-800nm ​​band into photoelectric signals; after the second 45-degree beam splitter The reflected light of other bands after being transmitted by the mirror 1413 arrives at the first 45-degree beam splitter 1412 along the light propagation direction from bottom to top. The first 45-degree beam splitter 1412 reflects the reflected light of other bands to obtain the separated light propagating along the horizontal direction of its reflection surface (the separated light propagates to the second photodiode 1442 along its propagation direction), and the separated transmitted light remaining after the reflection transmitted by its transmission surface and propagating from bottom to top. The separated transmitted light continues to propagate to the 45-degree total reflection mirror 1411, and after being reflected by the 45-degree total reflection mirror 1411, it propagates to the third photodiode 1443 in the horizontal direction, thereby completing the separation of all the reflected light generated by the welding of the workpiece during the laser welding process. It should be noted that the visible light reflected light is mainly generated and reflected by plasma metal vapor.

[0062] The first 45-degree beam splitter 1412 of this example is configured as a first coating whose reflective surface (i.e., the mirror surface close to the side where the second 45-degree beam splitter 1413 is located) allows the backlight reflected light in the 1000nm-1100nm band to reflect, and a second coating whose transmissive surface (i.e., the mirror surface close to the side where the 45-degree total reflector is located) allows the infrared light in the 1200nm-1700nm band to transmit; in this example, the first coating is made of a high refractive index material (e.g., TiO 2 、 2 O 5 or Nb 2 O 5One of them) and a low refractive index material (such as SiO 2 MgF 2 One of them) is alternately stacked to form a multilayer dielectric film, which achieves high reflection through interference effect; the thickness of each layer is λ 1 / 4(λ 1 The second coating uses a low refractive index material (such as SiO 2 MgF 2 ) as the outer layer to reduce surface reflection and enhance transmission; as the second option for the second coating, an anti-reflection film (AR film) such as SiO 2 / TiO 2 (i.e. one or more layers of SiO 2 layer with one or more layers of TiO 2 A combination of layers) or a multilayer combination of MgF 2 / Ta 2 O 5 A multilayer combination (i.e. one or more layers of MgF 2 Layer with one or more layers of Ta 2 O 5 The thickness of each layer is λ 2 / 4(λ 2 is the center wavelength of the target band of transmitted light, such as 1350nm).

[0063] The base material of the first 45-degree dichroic mirror between the reflective film (first coating) and the transmissive film (second coating) is selected to be an optical glass suitable for the infrared band (such as fused silica or calcium fluoride).

[0064] As another example of the present invention, Figure 8 It is shown that the third optical sheet assembly 17 includes a fifth dimming film 185 and a sixth dimming film 186 in sequence along the light propagation direction.

[0065] Figure 6 The photoelectric signal conversion unit 144 is shown, including a first photodiode 1441, a second photodiode 1442 and a third photodiode 1443 arranged in sequence from top to bottom; the photodiode is used to convert the optical signals of visible light, infrared light and backlight reflection light separated by each optical component in the filter and dimming unit into electrical signals, which is convenient for subsequent current peak detection.

[0066] The electrical signal peak detection unit 145 includes three electrical signal peak monitoring circuits electrically connected to the first photodiode 1441, the second photodiode 1442 and the third photodiode 1443 in sequence: a first electrical signal peak monitoring circuit 1451, a second peak current detection circuit 1452 and a third electrical signal peak monitoring circuit 1453.

[0067] The parallel reflected light obtained by the monitoring light transmission and reflection unit passes through the focusing lens unit and the light filtering and dimming unit in parallel and then enters the photoelectric signal conversion unit to complete the optical signal collection in different photothermal treatment areas formed on the surface of the workpiece during laser welding and the conversion of the optical signal to the electrical signal required for the subsequent monitoring result analysis. The peak detection circuit of the electrical signal performs peak detection of the electrical signal obtained by converting the optical signal of different bands. Using the peak monitoring technology of the electrical signal, the system can detect the peak changes of the optical signals of different bands, and judge the potential defects in the laser welding process, such as pores, cracks, incomplete penetration or overheating, in combination with the signal fluctuations. This real-time defect detection capability can provide instant feedback during the welding process, which helps to adjust the welding parameters and reduce the occurrence of unqualified welding.

[0068] In this example, the first photodiode 1441 , the second photodiode 1442 , and the third photodiode 1443 are respectively an infrared monitoring diode, a back reflection light monitoring diode, and a visible laser monitoring diode.

[0069] As another preferred example, the first filter, the second filter and the third filter are respectively provided on the optical signal incident sides of the first photodiode 1441, the second photodiode 1442 and the third photodiode 1443. In the above ideal case, the center line of the first filter coincides with the center lines of several filters and / or several dimming films in the first light filtering and dimming unit, and the second filter and the third filter also coincide with the center lines of several filters and / or several dimming films of the light filtering and dimming unit corresponding to the corresponding reflected light.

[0070] As another embodiment of the light filtering and dimming unit of the present invention, Fig. 9 , Fig.10 The first optical plate assembly 25 in the light filtering and dimming unit 243 is shown, including a first dimming plate 281, a second dimming plate 282 and a third dimming plate 283 along the light propagation direction; the second optical plate assembly 26 includes a first filter 291 and a fourth dimming plate 284 sequentially arranged along the light propagation direction; the third optical plate assembly 27 includes a second filter 292 and a third filter 293 sequentially arranged along the light propagation direction; as another example of the present invention, Fig.11 It is shown that the third optical sheet assembly 27 in the light filtering and dimming unit 243 includes a fifth dimming sheet 285 and a sixth dimming sheet 286 which are sequentially arranged along the light propagation direction.

[0071] In this example, the first 45-degree beam splitter 1412 is configured to have a reflective surface (i.e., the mirror surface close to the side where the second 45-degree beam splitter 1413 is located) coated with a third coating that allows infrared light reflected in the 1200nm-1700nm range, and a transmissive surface (i.e., the mirror surface close to the side where the 45-degree total reflector is located) coated with a fourth coating that allows backlight reflected light in the 1000nm-1100nm band to be transmitted; in this example, the third coating is made of a low refractive index material (e.g., SiO 2 MgF 2 A single layer film of one of the above) may also be used, an anti-reflection film (AR film), such as SiO 2 / TiO 2 (i.e. one or more layers of SiO 2 layer with one or more layers of TiO 2 layer) or MgF 2 / Ta 2 O 5 A multilayer combination (i.e. one or more layers of MgF 2 Layer with one or more layers of Ta 2 O 5 The thickness of each layer is λ 3 / 4(λ 3 The fourth coating is to use a high refractive index material (such as TiO 2 、 2 O 5 or Nb 2 O 5 ) and low refractive index materials (such as SiO 2 MgF 2 ) are stacked alternately to form a multilayer dielectric film, which achieves high reflection through interference effect. The thickness of each layer is λ 4 / 4(λ 4 To reflect the center wavelength of the target band of light, such as 1080nm), 10-30 layers are usually required.

[0072] In this example, the first photodiode 1451, the second photodiode 1452 and the third photodiode 1453 are a back reflection light monitoring diode, an infrared monitoring diode and a visible laser monitoring diode, respectively.

[0073] The infrared monitoring diode used in the present invention is an InGaAs diode (indium gallium arsenic diode), the back reflection light diode is an InGaAs diode (indium gallium arsenic diode), and the visible laser monitoring diode is a silicon diode.

[0074] By using dichroic mirrors and other optical elements, and equipping the reflective surface and the transmission surface with different coating material combinations, the backlight reflected light and the infrared reflected light can be further physically separated after the visible light is reflected. The system can effectively separate the optical signals of different bands by choosing to separate the infrared reflected light or the backlight reflected light first, providing a clear signal source for subsequent signal processing. This separation technology ensures that the signals of each band will not interfere with each other, effectively improving the accuracy of the signal.

[0075] Fig.12 It is shown that each electrical signal peak monitoring circuit includes a resistive voltage divider component, a first Schottky diode D1 connected to the resistive voltage divider component, an electrical signal first operational amplifier and feedback adjustment component, a second Schottky diode D2, a high-frequency noise filtering component, and an electrical signal second operational amplifier and feedback adjustment component;

[0076] The resistive voltage divider component includes a first resistor R1 connected to the cathode of the photodiode (i.e., the output end of the electrical signal obtained by converting the optical signal), and a second resistor R2 connected to the other end of the first resistor R1. The anode of the first Schottky diode D1 is connected to the other end of the first resistor R1 and then connected to the second resistor R2. The first operational amplifier and feedback adjustment component of the electrical signal includes a third resistor R3 connected to the other end of the second resistor R2, a first operational amplifier U1, a third Schottky diode D3, and a fourth resistor R4; the high-frequency noise filtering component includes a fifth resistor R5 and a first capacitor C1. The second operational amplifier and feedback adjustment component of the electrical signal includes a sixth resistor R6, a second operational amplifier U2, a seventh resistor R7 and an eighth resistor R8. The second operational amplifier U2 outputs the detected peak value of the electrical signal.

[0077] The first resistor R1 and the second resistor R2 together form a resistive voltage divider component, which reduces the voltage of the input electrical signal to an appropriate level. The two resistors are connected in series to distribute the voltage of the input terminal IN to the two resistors, thereby completing the voltage drop, so that the electrical signal level of the non-inverting input terminal of the input value U1 is suitable for the input range of U1, avoiding excessive input voltage from causing amplifier saturation or distortion. The first Schottky diode D1 clamps the input voltage below the minimum threshold of D1's own conduction voltage (approximately 0.2V) to prevent the voltage from being too high. If the input voltage of U1 exceeds 0V plus the diode voltage drop of D1 (0.2V), D1 will be turned on to prevent the input voltage from being too high. The third resistor R3 is connected before the non-inverting input terminal of U1, and is used to adjust the voltage bias of the signal input terminal of U1 to ensure that the signal can enter and be processed in U1 with the required amplification factor and overall gain.

[0078] The other end of the second resistor R2 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to the non-inverting input end of the first operational amplifier U1 (i.e., the signal input end of U1), the cathode of the third Schottky diode D3 is connected to the inverting input end of the first operational amplifier U1, and the feedback signal rectified by D3 is fed back to U1 for feedback regulation, the positive electrode of the first operational amplifier U1 is connected to the external +8.5V power supply, the negative electrode of the first operational amplifier U1 is grounded, and the peak value of the electrical signal detected by the operational amplification of the first operational amplifier U1 is connected to the U1 signal output end. The signal output end of U1 is connected to the positive electrode of the third Schottky diode D3 through a branch lead, and the negative electrode of the third Schottky diode D3 is also connected to the fourth resistor R4 through a branch node; the other end of the fourth resistor R4 is connected to the external -8.5V power supply; the fourth resistor R4 is connected between the third Schottky diode D3 and the second external power supply -8.5V power supply, and the fourth resistor R4 is set to provide a suitable bias for the feedback signal of the inverting input end of U1, and provide a reference voltage for the feedback signal, thereby ensuring the processing accuracy of the peak detection in the first operational amplifier U1.

[0079] The U1 signal output terminal of the first operational amplifier U1 is also connected to the positive electrode of the second Schottky diode D2, the negative electrode of the second Schottky diode D2 is connected to one end of the fifth resistor R5, the other end of the fifth resistor R5 is connected to one end of the first capacitor C1 and then converged and connected to one end of the sixth resistor R6 again, and connected to the non-inverting input terminal of the second operational amplifier U2 (i.e., the signal input terminal of U2), and the other end of the first capacitor C1 and the other end of the sixth resistor R6 are both grounded;

[0080] The gain of the operational amplifier is set by the feedback network and the input impedance. Usually, for the inverting operational amplifier configuration, its gain is determined by the ratio between the input resistance and the feedback resistance. Therefore, the gain adjustment of the feedback signal of the second operational amplifier U2 is determined by the ratio of the fifth resistor R5 to the fourth resistor R4. Through the fifth resistor R5, the gain of the U2 feedback signal is precisely controlled to ensure that the electrical signal input by the photodiode reaches a certain amplification factor through the two cascaded operational amplifiers to achieve the desired peak detection effect. At the same time, the ratio of the fifth resistor R5 to the fourth resistor R4 also adjusts and affects the sensitivity and response speed of the peak detection.

[0081] In addition, through the configuration of the fifth resistor R5 and the first capacitor C1, the high-frequency noise of the electrical signal entering the second operational amplifier U2 is filtered out to ensure that the electrical signal output by U2 is smoother and convenient for subsequent processing. The sixth resistor R6 is used to adjust the level of the electrical signal input to the second operational amplifier U2 to ensure that the amplitude of the electrical signal input to U2 for processing is within a reasonable range.

[0082] After the signal output end of the second operational amplifier U2 is connected to the seventh resistor R7 through a branch lead, the other end of the seventh resistor R7 is connected to the inverting input end of the second operational amplifier U2 through a lead, and the other end of the seventh resistor R7 is connected to the eighth resistor R8 through a branch lead, the other end of the eighth resistor R8 is grounded, and the eighth resistor R8 is connected between the signal output end of the second operational amplifier U2 and the inverting input end of U2 to form a feedback circuit, and then the output signal of the second operational amplifier U2 is fed back to the second operational amplifier U2 again. The eighth resistor R8 is used as a feedback resistor to gain the signal output by U2. The ratio of the resistance of the eighth resistor R8 to the seventh resistor R7 determines the gain ratio of the feedback circuit of U2, and then adjusts the amplitude of the output signal of U2 after operational amplification. If the resistance of the eighth resistor R8 is larger, the output signal will be relatively larger, and vice versa, thereby ensuring that the peak amplitude of the electrical signal detected and output after the U2 operation is within a reasonable range; the resistance value of the seventh resistor R7 will also affect the input impedance related to the non-inverting input end of U2, thereby determining the strength of the electrical signal entering U2. The positive pole of the second operational amplifier U2 is connected to an external +8.5V power supply, and the signal output end of the second operational amplifier U2 outputs the detected peak electrical signal to a central control computer or processor for further electrical signal spectrum analysis, optical signal power spectrum density analysis, etc.

[0083] By connecting the positive poles of the first operational amplifier U1 and the second operational amplifier U2 to a +8.5V power supply, the signal output end of the first operational amplifier U1 is connected to the fourth resistor R4 through a branch lead to another power supply: -8.5V power supply, and then powered by dual power supplies, the analog signal processing in the first operational amplifier U1 and the second operational amplifier U2 (i.e., the processing of the electrical signal obtained by converting the optical signal) helps to provide a larger dynamic range for the AC signal obtained by converting the optical signal, so that the AC signal oscillates up and down within the positive and negative voltage range, avoiding the limitation of a single power supply and preventing the signal from being clipped.

[0084] The monitoring method for the laser welding real-time monitoring system comprises the following steps:

[0085] The laser emitted by the laser enters the galvanometer unit after being reflected by the first 45-degree dichroic mirror, and then is emitted by the galvanometer unit to the back of the laser welding real-time monitoring system, which is characterized by comprising the following steps:

[0086] The laser emitted by the laser is reflected by the first 45-degree dichroic mirror, enters the galvanometer unit, and then emitted by the galvanometer unit to the back processing workpiece surface;

[0087] Different processing areas are formed on the surface of the processed workpiece, and the reflected light in the different processing areas is transmitted to the first 45-degree dichroic mirror through the galvanometer unit, and further reaches the second 45-degree dichroic mirror through the adapter;

[0088] After being reflected by the second 45-degree dichroic mirror, it enters the optical sensor;

[0089] The optical sensor detects infrared light, visible light and backlight reflected from the workpiece, monitors the peak value of electrical signals of reflected light in different bands, identifies fluctuations of reflected light in different bands, and determines laser welding defects.

[0090] During the implementation of the method, as an example of the present invention, laser welding is performed on galvanized steel plates, the laser output power is selected to be 1500W, the focal length of the focusing lens is 120mm, and the welding speed is controlled at 2.8m / min to 3.5m / min.

[0091] As an example of the present invention, after the optical sensor receives infrared light reflection light, visible light reflection light and backlight reflection light reflected from the workpiece, in the process of monitoring the peak value of the electrical signal, the three electrical signal peak value monitoring circuits simultaneously perform the following steps:

[0092] S1: Visible light reflected light signal I in the time domain monitored by the photodiode v (t), infrared light reflected light signal I r (t), backlight reflected light signal I b (t):

[0093] Fig.13 (a) shows the time domain waveform of the visible light reflected light signal under normal welding conditions. Fig.13 (b) shows the time domain waveform of the infrared light reflected light signal under normal welding conditions. Fig.13 (c) shows the time domain waveform of the backlight reflected light signal under normal welding conditions. Fig.14 (a) Fig.14 (b) and Fig.14 (c) further shows that Fig.13 The statistical analysis of the corresponding reflected light waveform changes in Fig.14 The solid lines in represent the mean of the optical signal in the time domain, and the dotted lines represent the variance of the optical signal in the time domain.

[0094] Fig.15 (a) shows the time domain waveform of the visible light reflected light signal of defects generated during welding. Fig.15 (b) shows the time domain waveform of the infrared light reflected light signal of the defect generated during the welding process. Fig.15(c) shows the time domain waveform of the backlight reflected light signal of the defect generated during welding; Fig.16 (a) Fig.16 (b) and Fig.16 (c) further shows that Fig.15 Statistical analysis of the corresponding reflected light waveform in the , the solid line and dotted line still represent the mean and variance of the corresponding optical signal in the time domain, respectively.

[0095] S3: Perform Fourier transform on the optical signal to obtain the optical distribution signal in the frequency domain

[0096]

[0097] Among them, A=v,r or b, that is, when A=v, I A (t) is I v (t), which is the visible light reflected light signal, obtained by Fourier transform That is, the frequency domain light distribution signal of the visible light reflected light signal When A = r or b, the frequency domain light distribution signal of the infrared light reflection signal can be obtained. Backlight reflected light signal Frequency domain light distribution signal j is the imaginary unit, j = -1;

[0098] S2: Each electrical signal peak monitoring circuit monitors the optical signal I corresponding to the photodiode A (t) frequency domain light distribution signal Perform frequency band separation and distribute the optical signal in the frequency domain To perform frequency band separation:

[0099] S21: Calculate the Gaussian beam power spectral density S(f A ):

[0100]

[0101] in, is the average power of the laser 101 emitted by the laser, f A ∈[f Amin ,f Amax ], Δf A is the effective frequency width of reflected light in different frequency domains, σ A is the frequency variance of the reflected light;

[0102]

[0103] That is, S(f A ) in [f Amin ,fAmax ] region, and then extract the reflected light in [f Amin ,f Amax ] high frequency bands in the region,

[0104] S22: Determine multiple peak areas of the power spectrum density of the reflected light:

[0105] S p1 (f A ),S p2 (f A ),…,S pn (f A );

[0106] S23: Reduce the power spectrum density of each peak area to its half power point (ie -3dB point) S hn (f A ), determine the minimum and maximum thresholds of the frequency band in the nth peak area:

[0107] That is to determine S hn (f A )=0.5S pn (f A ), according to S hn (f A ) value, i.e., the lowest frequency threshold value f A,n,min , the highest threshold value of the frequency band f A,n,max , and obtain the frequency band corresponding to the nth peak area [f A,n,min ,f A,n,max ], and the light distribution signal in the nth peak area Thus, frequency band separation is completed;

[0108] S3: Calculate the light distribution signal within each peak area Amplitude

[0109]

[0110] in, To calculate the light distribution signal in the nth peak area The real part calculation function of To calculate the light distribution signal in the nth peak area The imaginary part calculation function of ;

[0111] S4: Determine the welding quality of the monitored workpiece surface during welding according to the amplitude change;

[0112] S5: If it is detected that the frequency band amplitude of the light distribution signal of each band fluctuates relative to the reference signal of each band during normal welding, it is determined that a cold weld or a gap occurs during the welding process;

[0113] If it is monitored that the frequency band amplitudes of the light distribution signals of the visible light reflection light and the infrared light reflection light fluctuate relative to the reference signals of their respective bands during normal welding, and the frequency band amplitude of the light distribution signal of the backlight reflection light does not fluctuate relative to its reference signal during normal welding, it is determined that holes, pores, oil stains or contamination are generated during the welding process;

[0114] If it is monitored that the frequency band amplitude of the light distribution signal of the backlight reflected light fluctuates relative to the reference signal during normal welding, and the frequency band amplitudes of the light distribution signals of the visible light reflected light and the infrared light reflected light do not fluctuate relative to the reference signals of their respective bands during normal welding, it is judged that cracks are generated in the keyhole during the welding process.

[0115] Depend on Fig.13 and Fig.14 It is shown that when there are no defects in the welding process and the welding is in a stable deep penetration welding state, the output signals of the two optical sensors (visible laser monitoring diode and infrared monitoring diode) are relatively stable, showing fluctuations around a certain amplitude, and the fluctuation frequency of the visible light signal is higher than that of the infrared light signal. Since the visible light reflects the plasma fluctuations, and the infrared light signal reflects the temperature change of the molten pool, it is obvious that the fluctuation of the plasma is faster than the temperature change of the molten pool. Therefore, the visible light signal changes more violently than the infrared light signal, which is in good agreement with the theory. The backlight reflected light signal in stable welding is also maintained in a relatively stable state.

[0116] Depend on Fig.15 and Fig.16 It is shown that when the welding reaches the part where the filler wire is placed, the signal changes significantly, which is manifested by a significant decrease in the amplitude of the optical signal, and then returns to normal amplitude. This is mainly because when the laser is irradiated on the filler wire, the defocus amount changes, resulting in incomplete welding; at this time, no plasma is generated, so the visible light intensity drops to near zero; and the molten pool temperature also drops significantly, resulting in a decrease in the infrared signal amplitude; the backlight reflected light signal is related to the plasma eruption from the small hole and the molten pool, so its signal is significantly reduced but still maintains a certain intensity. Moreover, the changes in the three signals collected when the same welding defect occurs have a great correlation, so compared with single-channel collection, more information can be obtained, reducing the uncertainty in defect judgment.

[0117] Fig.17 The visible light reflected light separated after band analysis ( Fig.17 (a)), infrared reflected light ( Fig.17 (b)) and backlight reflection ( Fig.17(c)) spectrum distribution. The value of the horizontal axis is proportional to the signal frequency, and the value of the vertical axis is proportional to the signal intensity of a specific frequency. It can be seen from the figure that the plasma light signal, the infrared signal radiated by the molten pool, and the sound signal during laser welding are all concentrated in the low frequency band.

[0118] Fig.18 The figure shows the situation of the molten pool solidified on the side of the workpiece surface after welding of the workpiece made of AISI 316L (sus316L, 316L stainless steel, S31603) with different laser power spectrum densities (i.e., laser power peak value / laser spot area) when the power of the laser light source emitted by the laser is 500W and the moving speed along the welding direction is 300mm / s. It can be seen that different laser power spectrum densities will also produce molten pools of different sizes for the workpiece made of the same material, as well as different plasma (solid-liquid reaction metal vapor generation area) reaction areas in the molten pool. Therefore, the spectrum analysis after the sub-band collection of visible light reflection light, infrared light reflection light and backlight reflection light of different wavelengths on the surface of the workpiece is helpful to reflect the processing situation of the laser on the surface of the workpiece, analyze the amplitude changes of different frequency bands, and according to the fluctuations of special frequency bands, it can be judged what kind of quality problems (false welding, gaps, protrusions, pores, holes or cracks, etc.) occurred in the welding process. Fig.19 The Gaussian beam intensity distribution reconstruction model of reconstructing the reflected light of different bands of the molten pool generated by the laser spot focused on the surface of the workpiece (xy plane) is shown. It can be seen that different bands will have laser intensity distribution on the surface of the workpiece and in the longitudinal direction (perpendicular to the surface of the workpiece, that is, the longitudinal direction of the xy plane). The greater the laser intensity, the greater the photothermal effect, and thus a higher temperature will be generated on the surface of the workpiece. The intensity distribution reconstructed according to the frequency band analysis reflects the thermal distribution of the molten pool generated by the laser spot on the workpiece. Fig. 20 The schematic diagram of the welding pores generated by the method and system of the present invention on the surface of the workpiece is shown in FIG. Fig. 20 Left side) and schematic diagram of longitudinal defects in the welding area of ​​the AA section on the surface of the workpiece ( Fig. 20 right schematic).

[0119] Those skilled in the art will understand that Figure 4 , Figure 5 and Figure 4 , Figure 5 The laser welding real-time monitoring system 10 shown is only illustrative.

[0120] In some embodiments, the laser welding real-time monitoring system 10 may include more or fewer components.

[0121] The above describes the real-time monitoring of laser welding and the real-time monitoring method of laser welding according to the present disclosure in conjunction with the accompanying drawings. However, those skilled in the art will appreciate that the execution of the real-time monitoring system 10 and the real-time monitoring method of laser welding is not limited to the sequence shown in the drawings and described above, but can be executed in any other reasonable sequence. In addition, the real-time monitoring system 10 does not necessarily include Figure 4 , Figure 5 and Figure 4 , Figure 5 All components shown in the figure may include only some of the components or more components necessary to perform the functions described in the present disclosure, and the connection method of these components is not limited to the form shown in the figure.

[0122] The present invention may be implemented as a method, a computing device, a system and / or a computer program product.

[0123] A computer-readable storage medium may be included, on which computer-readable program instructions for executing various aspects of the present disclosure are loaded. A computing device may include at least one processor and at least one memory coupled to the at least one processor, the memory may store instructions for execution by the at least one processor. When the instructions are executed by the at least one processor, the computing device may perform the above-mentioned asymmetric synchronization method.

[0124] In one or more exemplary designs, the functions described in the present disclosure may be implemented using hardware, software, firmware, or any combination thereof. For example, if implemented using software, the functions may be stored as one or more instructions or codes on a computer-readable medium, or transmitted as one or more instructions or codes on a computer-readable medium.

[0125] The various units of the apparatus disclosed herein may be implemented using discrete hardware components or may be integrated on a hardware component, such as a processor. For example, the various exemplary logic blocks, modules, and circuits described in conjunction with the present disclosure may be implemented or executed using a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof for performing the functions described herein.

[0126] Those skilled in the art should also understand that the various illustrative logical blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments of the present disclosure may be implemented as electronic hardware, computer software, or a combination of the two.

[0127] The above description of the present disclosure is intended to enable any person of ordinary skill in the art to implement or use the present disclosure. Various modifications of the present disclosure are obvious to those of ordinary skill in the art, and the general principles defined herein may also be applied to other variations without departing from the spirit and scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but is consistent with the broadest scope of the principles and novel features disclosed herein.

Claims

1. A laser welding real-time monitoring system, comprising: A laser emission system, an adapter, and a processing beam monitoring system connected to the laser emission system via the adapter; The laser emission system comprises a first 45-degree dichroic mirror, which is arranged at the corner of the galvanometer unit and the laser light source; It is characterized in that the adapter is arranged on the light transmission direction side of the first 45-degree dichroic mirror, and the galvanometer unit is arranged on the reflected light direction side of the first 45-degree dichroic mirror; The processing beam monitoring system includes a window mirror connected to the adapter, a second 45-degree dichroic mirror arranged on a side of the window mirror away from the adapter, an optical sensor arranged on the light-reflecting side of the second 45-degree dichroic mirror, and a first interface and a second interface arranged on the light-transmitting side of the second 45-degree dichroic mirror; The optical sensor is used to detect infrared light, visible light and backlight reflected from the workpiece, monitor the peak value of electrical signals of reflected light in different bands, identify fluctuations of reflected light in different bands, and judge laser welding defects.

2. The laser welding real-time monitoring system according to claim 1, characterized in that: The optical sensor comprises: The light splitting unit comprises a 45-degree total reflection mirror, a first 45-degree light splitting mirror, and a second 45-degree light splitting mirror which are sequentially arranged above the sensor interface from top to bottom; A focusing lens unit, comprising a first focusing lens, a second focusing lens and a third focusing lens arranged in sequence from top to bottom; The light filtering and dimming unit comprises a first optical sheet assembly, a second optical sheet assembly and a third optical sheet assembly which are arranged in sequence from top to bottom; the first optical sheet assembly, the second optical sheet assembly and the third optical sheet assembly all comprise a plurality of filters and / or dimming sheets whose center lines coincide with each other; The photoelectric signal conversion unit includes a first photodiode, a second photodiode and a third photodiode arranged in sequence from top to bottom; The electrical signal peak detection unit includes three electrical signal peak monitoring circuits electrically connected to the first photodiode, the second photodiode and the third photodiode in sequence: a first electrical signal peak monitoring circuit, a second peak current detection circuit and a third electrical signal peak monitoring circuit. The parallel reflected light reflected by the monitoring light transmission and reflection unit passes through the focusing lens unit and the filtering and dimming unit in parallel and then enters the photoelectric signal conversion unit, completing the optical signal collection in different photothermal treatment areas formed on the surface of the workpiece by laser welding and the conversion of the optical signal into the electrical signal required for the subsequent monitoring result analysis, and the electrical signal peak detection circuit performs electrical signal peak detection obtained by converting optical signals of different bands.

3. The laser welding real-time monitoring system according to claim 2, characterized in that: The light signal incident sides of the first photodiode, the second photodiode and the third photodiode are also provided with a first filter, a second filter and a third filter respectively.

4. The laser welding real-time monitoring system according to claim 3 is characterized in that: The first optical plate assembly includes a first filter and a first dimming film arranged in sequence along the light propagation direction; the second optical plate assembly includes a second dimming film, a third dimming film and a fourth dimming film arranged in sequence along the light propagation direction; the third optical plate assembly includes a second filter and a third filter arranged in sequence along the light propagation direction, or the third optical plate assembly includes a fifth dimming film and a sixth dimming film arranged in sequence along the light propagation direction.

5. The laser welding real-time monitoring system according to claim 3, characterized in that: The first optical plate assembly includes a first dimming film, a second dimming film and a third dimming film along the light propagation direction; the second optical plate assembly includes a first filter and a fourth dimming film arranged in sequence along the light propagation direction; the third optical plate assembly includes a second filter and a third filter arranged in sequence along the light propagation direction; or the third optical plate assembly includes a fifth dimming film and a sixth dimming film arranged in sequence along the light propagation direction.

6. The laser welding real-time monitoring system according to claim 4, characterized in that: The first photodiode, the second photodiode and the third photodiode are respectively an infrared monitoring diode, a back reflection light monitoring diode and a visible laser monitoring diode.

7. The laser welding real-time monitoring system according to claim 5, characterized in that: The first photodiode, the second photodiode and the third photodiode are respectively a back reflection light monitoring diode, an infrared monitoring diode and a visible laser monitoring diode.

8. The laser welding real-time monitoring system according to claim 6 or 7, characterized in that: The infrared monitoring diode is an InGaAs diode, the back reflection light diode is an InGaAs diode, and the visible laser monitoring diode is a silicon diode.

9. According to the laser welding real-time monitoring system of claim 8, each of the electrical signal peak monitoring circuits comprises a resistive voltage divider component, a first Schottky diode D1 connected to the resistive voltage divider component, an electrical signal first operational amplifier and feedback adjustment component, a second Schottky diode D2, a high-frequency noise filtering component, and an electrical signal second operational amplifier and feedback adjustment component; The resistive voltage divider component includes a first resistor R1 connected to the cathode of the photodiode, and a second resistor R2 connected to the other end of the first resistor R1; the first operational amplifier and feedback adjustment component for the electrical signal includes a third resistor R3 connected to the other end of the second resistor R2, a first operational amplifier U1, a third Schottky diode D3, and a fourth resistor R4; the high-frequency noise filtering component includes a fifth resistor R5 and a first capacitor C1; the second operational amplifier and feedback adjustment component for the electrical signal includes a sixth resistor R6, a second operational amplifier U2, a seventh resistor R7, and an eighth resistor R8; the second operational amplifier U2 outputs the detected peak value of the electrical signal.

10. A monitoring method for a real-time monitoring system for laser welding, characterized in that: The following steps are involved: The laser emitted by the laser is reflected by the first 45-degree dichroic mirror, enters the galvanometer unit, and then emitted by the galvanometer unit to the back processing workpiece surface; Different processing areas are formed on the surface of the processed workpiece, and the reflected light in the different processing areas is transmitted to the first 45-degree dichroic mirror through the galvanometer unit, and further reaches the second 45-degree dichroic mirror through the adapter; After being reflected by the second 45-degree dichroic mirror, it enters the optical sensor; The optical sensor detects infrared light, visible light and backlight reflected from the workpiece, monitors the peak value of electrical signals of reflected light in different bands, identifies fluctuations of reflected light in different bands, and determines laser welding defects.

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