A Synchronous Observation Method and Device for Visual Signals and Particle Signals of Yuhui

Abstract

The present invention provides a method and device for synchronously observing the visual signal and particle signal of a plume, belonging to the technical field of laser material processing. It includes a material to be processed, with a processing area arranged on the upper surface of the material to be processed. Above the processing area, a processing laser is arranged. On both sides of the processing area, a photodetector and a detection laser are respectively arranged. One side of the detection laser is connected with a signal amplifier, and both the signal amplifier and the photodetector are connected to an oscilloscope. A high-speed camera is also arranged on one side of the detection laser, and both the high-speed camera and the oscilloscope are connected to a computer. By adopting the above-mentioned method and device for synchronously observing the visual signal and particle signal of a plume, the present invention has the advantages of simple structure, small volume, easy adjustment, no need for external interference, low cost, etc., and can realize the synchronous observation of the visual signal and particle signal of the plume.

Description

Technical Field

[0001] The present invention relates to the technical field of laser material processing, and particularly to a method and device for synchronously observing the visual signal and particulate signal of plume. Background Art

[0002] Compared with traditional laser processing technologies, high-power fiber laser processing technology exhibits significant advantages such as excellent beam quality, high energy density, and high electro-optical conversion efficiency. Combining fiber laser technology with intelligent manufacturing can promote the realization of more efficient, precise, and flexible production methods, injecting more innovative vitality and development opportunities into the manufacturing industry.

[0003] During the laser processing process, plume, as one of the most intuitive physical phenomena in laser processing with a wavelength of about 1 micron, appears as a glowing body above the keyhole, composed of liquid particles and high-temperature gas. The dynamic behavior of plume is closely related to the laser processing process and is the most intuitive external manifestation in fiber laser processing. By observing the dynamic behavior of plume, we can conduct real-time quality monitoring of the processing process, which lays a solid foundation for the intelligence of fiber laser processing.

[0004] Currently, the monitoring means for plume mainly include visual signals, acoustic signals, optical signals, and electrical signals, etc. In the research on plume, significant progress has been made in aspects such as morphological observation, temperature diagnosis, and the influence of plume on the processing process. However, in a complex industrial environment, the dynamic behavior of plume is easily interfered by external factors such as strong light, protective gas flow, and noise, which affects the quality of signal collection and even leads to signal distortion.

[0005] Although the particles in the plume, as its main component, are relatively less affected by the above factors, the luminescence of the plume mainly comes from its gaseous part. In addition, the diameter range of the particles in the plume is between several nanometers and several micrometers, which makes it extremely difficult to achieve in-situ measurement of particle size or movement speed through high-speed photography. Therefore, there is currently no method for characterizing the dynamic behavior of plume based on the particulate signal in the plume, that is, the connection between the particulate signal and the visual signal of the plume has not been clarified.

[0006] To overcome these limitations, the present invention proposes an innovative multi-signal synchronous observation method that combines the particulate signal in the plume with the visual signal of the plume. This method can not only accurately correspond the particulate signal with the plume image, thereby more accurately characterizing the dynamic behavior of the plume; but also combine the advantages of both to obtain a more comprehensive and real plume signal, and further provide strong support for the monitoring of the laser intelligent processing process. Summary of the Invention

[0007] The object of the present invention is to provide a method and device for synchronously observing the visual signal and particle signal of plume, which have the advantages of simple structure, small volume, easy adjustment, no need for external interference, low cost, etc., and can realize the synchronous observation of the visual signal and particle signal of plume.

[0008] To achieve the above object, the present invention provides a device for synchronously observing the visual signal and particle signal of plume, including a material to be processed. A processing area is provided on the upper surface of the material to be processed. A processing laser is provided above the processing area. A photodetector and a detection laser are respectively provided on both sides of the processing area. A signal amplifier is connected to one side of the detection laser. Both the signal amplifier and the photodetector are connected to an oscilloscope. A high-speed camera is also provided on one side of the detection laser. Both the high-speed camera and the oscilloscope are connected to a computer.

[0009] Preferably, the processing laser vertically emits a processing laser beam to the processing area. The included angle between the processing laser beam and the detection laser beam emitted by the detection laser is 10 - 90°; the included angle between the detection laser beam and the processing direction is 0 - 180°; the distance between the detection laser beam and the keyhole is 0.1 - 100 mm.

[0010] Preferably, the shooting frame rate of the high-speed camera is 1000 - 50000 frames / s. The height of the high-speed camera is flush with the surface of the material to be processed, and its shooting direction is perpendicular to the processing direction of the processing laser.

[0011] Preferably, the photodetector is a silicon photodetector, and the response wavelength range is 200 - 1100 nm.

[0012] Preferably, the wavelength of the detection laser beam is 0.1 - 20 μm, and the spot diameter is 0.1 - 8 mm.

[0013] Based on the above device for synchronously observing the visual signal and particle signal of plume, the present invention also provides a method for synchronously observing the visual signal and particle signal of plume, including the following steps:

[0014] Step S1: Connect the detection laser and the photodetector to the oscilloscope. The photodetector is used as a medium for synchronous observation. The detection laser is used to measure the particle characteristics inside the plume, and the high-speed camera is used to record the visual signal of the plume.

[0015] Step S2: When the processing starts, the detection laser, the photodetector, and the high-speed camera are started simultaneously.

[0016] Step S3: When there are particles passing through the detection laser beam of the detection laser, part of the detection laser beam is reflected by the particles in the plume back into the detection laser cavity to generate the self-mixing effect. After performing photoelectric signal conversion and generating an interference signal, according to the time difference between the two electrical signals of the detection laser and the photodetector, determine the moment when the first particle signal is generated;

[0017] Then, according to the set shooting frame rate of the high-speed camera, find the frame number corresponding to that moment in the plume pictures taken by the high-speed camera, realize its correspondence with the first particle signal, and determine the time interval between the first frame picture of the plume and the first particle signal;

[0018] Step S4: According to the shooting frame rate of the high-speed camera and the sampling rate of the oscilloscope, realize the synchronous observation of the plume visual signal and the particle signal.

[0019] Therefore, the present invention adopts the above-mentioned synchronous observation method and device for the visual signal and particle signal of a plume, and the beneficial technical effects are as follows:

[0020] (1) The present invention can realize the in-situ real-time synchronous observation of the plume visual signal and the plume particle signal. Compared with the existing plume observation methods, the present invention can establish the connection between the plume particle signal and the dynamic behavior of the plume on the premise of avoiding the influence of the processing environment on information collection, and determine the correspondence between the plume particle signal and the laser processing process.

[0021] (2) The present invention can combine the advantages of both to obtain a more comprehensive plume signal, and further obtain real processing process information, promoting the development of laser intelligent processing process monitoring.

[0022] (3) The present invention has the advantages of simple structure, small volume, easy adjustment, no need for external interference, not affected by the fluctuation of the detection laser power, low cost, etc. Description of the Drawings

[0023] Figure 1 It is a schematic structural diagram of a synchronous observation device for the visual signal and particle signal of a plume according to the present invention;

[0024] Figure 2 It is the plume particle signal and the photoelectric detection signal obtained from experiments in the same processing process;

[0025] Figure 3 It is the continuous high-speed camera observation of the plume morphology obtained from experiments;

[0026] Figure 4 It is the correspondence between the plume image and the particle signal obtained from experiments.

[0027] Reference Signs

[0028] 1. Laser processing plume; 2. Processing area; 3. High-speed camera; 4. Power supply for detection laser; 5. Detection laser; 6. Signal amplifier; 7. Photoelectric detector; 8. Oscilloscope; 9. Computer; 10. Photoelectric detection signal; 11. Plume particle signal; 12. Bottom swinging plume; 13. Processing laser; 14. Processing laser beam. Detailed implementation mode

[0029] The technical solution of the present invention will be further described below with reference to the drawings and embodiments.

[0030] Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs.

[0031] Embodiment 1

[0032] As Figure 1 shown, it is a schematic structural diagram of a synchronous observation device for the visual signal and particle signal of a plume of the present invention, including a material to be processed. A processing area 2 is provided on the upper surface of the material to be processed. A processing laser 13 is provided above the processing area 2. A photoelectric detector 7 and a detection laser 5 are respectively provided on both sides of the processing area 2. A signal amplifier 6 is connected to one side of the detection laser 5. The signal amplifier 6 and the photoelectric detector 7 are both connected to an oscilloscope 8. A high-speed camera 3 is also provided on one side of the detection laser 5. The high-speed camera 3 and the oscilloscope 8 are both connected to a computer 9.

[0033] The processing laser 13 vertically emits a processing laser beam 14 towards the processing area 2 and generates a laser processing plume 1.

[0034] In this embodiment, the processing laser 13 is an IPG YLS-6000 fiber laser with a wavelength of 1.07 μm. The processing laser beam 14 is transmitted through an optical fiber with a core diameter of 200 μm. The focal length of the output coupling collimating mirror is 200 mm, and it is focused through a lens with a focal length of 300 mm to obtain a focused spot with a diameter of 0.32 mm. The material to be processed used in the experiment is low-carbon steel, with dimensions of 100 mm × 50 mm × 10 mm. The processing parameters are: laser power is 5 kW, and the processing speed is 2 m / min.

[0035] The high-speed camera 3 uses a PHOTRON Fastcam Mini UX100 color high-speed camera from the United States, and the fixed frame rate during shooting is 10000 frames / s.

[0036] The detection laser 5 is a semiconductor laser with a wavelength of 1.31 μm and a power of 500 μW. The sampling rate is set to 5 MSa / s, the acquisition height is 5 mm, and the detection direction is perpendicular to the scanning processing direction of the processing laser beam 14.

[0037] The photodetector 7 is a Dsi300 photodetector, and its response wavelength range is 300 - 1100 nm. The response time of the photodetector 7 to the optical signal is on the order of hundreds of nanoseconds, which is much less than the plume swing period (about 0.5 ms), and can meet the requirements of synchronous observation.

[0038] The oscilloscope 8 is an RTB2004 oscilloscope produced by R&S Company in Germany, and its maximum real-time sampling rate is 2.5 GSa / s. In the synchronous observation experiment, after the detection laser beam of the detection laser 5 passes through the plume, part of the light is reflected by the particles in the plume back into the detection laser cavity to generate self-mixing effect and new resonance. After the optoelectronic signal conversion, the signal is amplified by the signal amplifier 6, and then connected to the same oscilloscope 8 with the photodetector 7 for synchronous triggering, and at the same time, the high-speed camera 3 is used to record the laser processing process.

[0039] At the moment when the laser processing starts, high-power processing laser-induced splashing particles and laser-induced vaporization occur almost simultaneously. At this time, the photodetector 7 and the high-speed camera 3 will collect strong optical signals, and the photodetector 7 converts the optical signal into a suddenly rising electrical signal. According to Figure 2 It can be known that the photodetection signal 10 and the plume particle signal 11 are generated almost simultaneously, and the time difference between them is less than 5 μs, which is much less than a period of the bottom swinging plume (about 0.5 ms). In the synchronous observation experiment, it can be approximately considered that they occur simultaneously. At this time, the generated rising electrical signal also corresponds to the first light-exposed processing image captured by the high-speed camera 3. Therefore, the time difference between the photodetection signal and the plume particle signal in the experiment can be ignored. To obtain the corresponding image of the plume particle signal and the plume dynamics at any moment, only need to calculate the time interval T between the generation of the nth particle signal and the first particle signal, and then find the plume image after T time from the first light-exposed image captured by the high-speed camera 3. This image corresponds to the nth particle signal.

[0040] It can be seen from the images captured by the high-speed camera 3 that the bottom plume will swing irregularly periodically (the bottom swinging plume 12), as Figure 3 shown. By corresponding the images captured by the high-speed camera 3 with the detection direction perpendicular to the scanning direction to the plume particle signal, it is found that when the bottom swinging plume is in the vertical state, the intensity of the plume particle signal and the number of interference fringes are relatively large, as Figure 4 shown. This phenomenon indicates that when the bottom swinging plume erupts against the direction of the high-power fiber laser beam, there are relatively more particles in the detection laser detection area, so the signal induced by the particles carried in the erupting plume is stronger.

[0041] It should be noted that the content not elaborated in detail in the present invention is the prior art and is well-known to those skilled in the art.

[0042] Therefore, the present invention adopts the above-mentioned method and device for synchronously observing the visual signal and particle signal of the plume, which has the advantages of simple structure, small volume, easy adjustment, no need for external interference, low cost, etc., and can realize the synchronous observation of the visual signal and particle signal of the plume.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A synchronous observation device for the visual signal and particle signal of Yuhui, characterized in that, It includes the material to be processed. There is a processing area on the upper surface of the material to be processed. Above the processing area, there is a processing laser. On both sides of the processing area, there are respectively a photodetector and a detection laser. One side of the detection laser is connected to a signal amplifier. Both the signal amplifier and the photodetector are connected to an oscilloscope. There is also a high-speed camera on one side of the detection laser. Both the high-speed camera and the oscilloscope are connected to a computer.

2. The synchronous observation device for the visual signal and particulate signal of Yuhui according to claim 1, characterized in that, The processing laser vertically emits a processing laser beam towards the processing area. The included angle between the processing laser beam and the detection laser beam emitted by the detection laser is 10 - 90°; the included angle between the detection laser beam and the scanning direction of the processing laser beam is 0 - 180°; the distance between the detection laser beam and the keyhole is 0.1 - 100 mm.

3. The synchronous observation device for the visual signal and particle signal of Yuhui according to claim 2, wherein The shooting frame rate of the high-speed camera is 1000 - 50000 frames / s. The height of the high-speed camera is flush with the surface of the material to be processed, and its shooting direction is perpendicular to the processing direction of the processing laser.

4. The synchronous observation device for the visual signal and particulate signal of Yuhui according to claim 3, wherein The photodetector is a silicon photodetector, and the response wavelength range is 200 - 1100 nm.

5. The synchronous observation device for the visual signal and particle signal of Yuhui according to claim 4, characterized in that, The wavelength of the detection laser beam is 0.1 - 20 μm, and the spot diameter is 0.1 - 8 mm.

6. A synchronous observation method for the visual signal and particulate signal of Yu Hui, characterized in that, It includes the following steps: Step S1: Connect the detection laser and the photodetector to the oscilloscope. The photodetector serves as the medium for synchronous observation. Use the detection laser to measure the particle characteristics inside the plume, and use the high-speed camera to record the visual signal of the plume. Step S2: When processing starts, the detection laser, the photodetector, and the high-speed camera are started simultaneously. Step S3: When there are particles passing through the detection laser beam of the detection laser, the detection laser beam is reflected by the particles in the plume back into the detection laser cavity to generate a self-mixing effect. After performing photoelectric signal conversion and generating an interference signal, determine the moment when the first particle signal is generated according to the time difference between the two electrical signals of the detection laser and the photodetector. Then, according to the set shooting frame rate of the high-speed camera, find the frame number corresponding to the moment in the plume pictures taken by the high-speed camera, realize its correspondence with the first particle signal, and determine the time interval between the first frame picture of the plume and the first particle signal. Step S4: According to the shooting frame rate of the high-speed camera and the sampling rate of the oscilloscope, realize the synchronous observation of the plume visual signal and the particle signal.

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