Water guide laser processing depth detection device and detection method

Abstract

This invention belongs to the field of water-guided laser technology and relates to a water-guided laser processing depth detection device and method. The device includes: a probe light source, a beam splitter, a reference plane, a coupling cavity, a processing water flow, a workpiece, and a CCD camera. The probe light source, workpiece, reference plane, and CCD camera are arranged in a cross shape above, below, to the left, and to the right of the beam splitter. An optical interference signal analysis and processing device receives and analyzes the refracted light rays from the reference plane and the upper surface of the workpiece collected by the CCD camera. Based on the two refractions of the light rays, the current real-time processing depth of the water-guided laser can be measured and calculated. This invention can provide real-time depth information with micron-level accuracy, enabling water-guided laser equipment to perform specified blind hole processing, etc. Simultaneously, this non-contact measurement does not damage the workpiece and can effectively improve the processing efficiency of water-guided lasers.

Description

Technical Field

[0001] This invention belongs to the field of water-guided laser technology and relates to a water-guided laser processing depth detection device and detection method. Background Technology

[0002] Water-guided laser processing is an advanced machining technology that uses water as a conductive medium to couple laser energy into a stable water flow to process the surface of a workpiece. It combines the advantages of laser processing and water cooling, offering high efficiency, precision, low heat impact, and environmental friendliness. Currently, it is mainly used for cutting and trimming. Depth detection is crucial during water-guided laser processing. By observing the real-time depth, it's possible to promptly modify the process and selectively process uncut sections. Furthermore, it allows for the processing of blind holes at specified depths, improving the processing capabilities and large-scale application of water-guided laser processing.

[0003] However, current depth measurement technology for water-guided laser processing relies on ultrasonic non-destructive testing. Specifically, ultrasonic waves propagate forward at a specific direction and speed; upon encountering an interface, some waves are reflected. The testing equipment receives and analyzes information such as the amplitude and position of the sound waves to estimate the surface depth of the object. This method is susceptible to noise and workpiece material variations, and its accuracy is generally only at the millimeter level, failing to meet the requirements of precision machining.

[0004] Therefore, a novel real-time detection method for water-guided laser processing depth is needed to solve the technical problems of low accuracy and poor noise resistance of commonly used ultrasonic detection. Summary of the Invention

[0005] The technical solution adopted by this invention to solve the technical problem is: a water-guided laser processing depth detection device, comprising: a detection light source, a beam splitter, a reference plane, a coupling cavity, a processing water flow, a workpiece, and a CCD camera; the detection light source is located directly above the beam splitter, the coupling cavity is located directly below the beam splitter, and the workpiece is located directly below the coupling cavity; the reference plane and the CCD camera are respectively located on the left and right sides of the beam splitter; the beam splitter is tilted, and the vertical distance between the beam splitter and the workpiece remains unchanged; the detection light source, the workpiece, the reference plane, and the CCD camera are respectively arranged in a cross shape on the top, bottom, left, and right sides of the beam splitter, which facilitates the detection light from the detection light source to be refracted and transmitted separately after being irradiated onto the tilted beam splitter surface;

[0006] The probe light from the probe light source illuminates the beam splitter. The first reflected light channel of the beam splitter after being illuminated by the probe light source faces the front of the reference plane, and the first transmitted light channel of the beam splitter after being illuminated by the probe light source faces the interior of the coupling cavity and coincides with the processing water flow. The reference plane is perpendicular to the first reflected light channel of the beam splitter after being illuminated by the probe light source. The processing surface of the workpiece is perpendicular to the first transmitted light channel of the beam splitter after being illuminated by the probe light source. The second transmitted light channel of the beam splitter after being illuminated by the reflected light from the reference plane faces the lens of the CCD camera, and the third reflected light channel of the beam splitter after being illuminated by the reflected light from the processing surface of the workpiece faces the lens of the CCD camera. The probe light from the probe light source is refracted to the reference plane and transmitted to the workpiece after being illuminated by the tilted mirror surface. The light refracted again by the reference plane is transmitted twice by the mirror surface of the beam splitter to the CCD camera. The light refracted again by the upper surface of the workpiece is also refracted twice by the mirror surface of the beam splitter to the CCD camera. This allows the CCD camera to collect the refracted light from the reference plane and the upper surface of the workpiece for subsequent analysis and processing.

[0007] The CCD camera is electrically connected to an optical interference signal analysis and processing device. The optical interference signal analysis and processing device receives and analyzes the refracted light rays from the reference plane and the upper surface of the workpiece collected by the CCD camera. Since the vertical distance between the beam splitter and the workpiece remains constant, the current real-time processing depth of the water-guided laser can be calculated based on the two refractions of the light rays.

[0008] Preferably, the beam splitter is tilted at a 45° angle to the upper surface of the workpiece. The first reflected light channel, the second transmitted light channel, and the third reflected light channel are located on the same horizontal straight line, and the first transmitted light channel and the detection light irradiation direction of the detection light source are located on the same vertical straight line. The 45° tilt angle of the beam splitter ensures that the refracted light and reflected light on the surface of the beam splitter are evenly distributed. At the same time, it makes the incident light on the reference plane and the upper surface of the workpiece coincide with the refracted light channel. The light returns along the original path and irradiates the beam splitter again. The optical path length is the same, and the optical path that finally irradiates the CCD camera also coincides and has the same length, avoiding the generation of measurement errors due to different optical paths.

[0009] Preferably, a processing laser is connected to the side of the coupling cavity. After the processing laser couples with the water jet in the coupling cavity, it forms a vertically downward water-guided laser, which coincides with the processing water flow. The processing laser simultaneously generates a water-guided laser, which coincides with the incident light and refracted light channels on the upper surface of the workpiece. This facilitates real-time measurement of the current processing depth of the water-guided laser and allows for depth monitoring or adjustment at any time.

[0010] Preferably, the detection device is equipped with an electronic machining drawing, which is communicatively connected to an optical interference signal analysis and processing device. The electronic machining drawing and the optical interference signal analysis and processing device work together to prevent further processing of the upper surface portion of the workpiece that has reached the required cutting depth, and to process the portion of the upper surface portion of the workpiece that has not reached the required cutting depth and does not conform to the machining drawing, thereby improving efficiency.

[0011] This invention also discloses a method for detecting the depth of water-guided laser processing. This method uses the aforementioned water-guided laser processing depth detection device and includes the following steps:

[0012] Step S1: Data acquisition. The CCD camera acquires the light reflected from the reference plane, which is transmitted to the CCD camera after illuminating the beam splitter. The CCD camera also acquires the light reflected from the workpiece processing surface, which is reflected to the CCD camera after illuminating the beam splitter.

[0013] Step S2: Interference signal analysis. The light rays collected by the CCD camera in step S1, passing through different optical paths, are analyzed and processed using an optical interferometric signal analysis and processing device. The final signal includes a background component I. R The cross-correlation component I of the reflected light that passes only through the reference plane. auto Interference light caused by the optical path difference between the processed sample and the reference plane, and the autocorrelation component I. cro This is caused by self-interference between the layers of the sample. By performing a Fourier transform on this signal, the frequency domain information can be converted into spatial and temporal depth information. In particular, since the depth information is mainly contained in the cross-correlation component I... auto In this context, the influence of other components should be reduced: background component I R Before processing, the autocorrelation component I can be obtained by capturing only the reflected light from the reference plane using a CCD camera. cro The signal is usually weak and can be ignored.

[0014] I = I R +I auto +I cro

[0015] In addition, to improve the accuracy of measurement results and speed up data processing, the collected data should be denoised: mean denoising ( The invention involves averaging a certain number of frames of data, padding with zeros (controlling the number of data points to a power of 2), windowing (to reduce frequency domain leakage), and then performing a Fourier transform. However, the invention is not limited to the above steps.

[0016] Step S3: Depth reconstruction, the machining depth on the electronic machining drawing is updated in real time through the communication connection of the optical interference signal analysis and processing equipment;

[0017] Step S4: Display implementation: The display device electrically connected to the optical interference signal analysis and processing equipment displays the current processing depth information in real time;

[0018] Step S5: Feedback control. Based on the updated information reflected in real time on the electronic processing drawing in step S3, the operator resets the process parameters according to the completion status of the drawing and as required. The part that has reached the required cutting depth will not be processed, and the part that is not completed in the processing drawing will be processed.

[0019] Preferably, the detailed steps of step S1 are as follows:

[0020] Step S1-1: Turn on the processing laser. By adjusting the coupling cavity, first adjust the focusing mirror inside the coupling cavity to make the focused spot the smallest. Then move the laser beam to the center of the lower nozzle inside the coupling cavity so that the processing laser is coupled into the water jet, forming a stable processing water flow with high energy to reach the workpiece surface.

[0021] Step S1-2: The probe light emitted by the probe light source passes through the beam splitter. Part of the probe light is reflected to the reference plane, then reflected again and redirected to pass through the beam splitter a second time, and is then collected by the CCD camera. The other part of the probe light is transmitted through the beam splitter, passes through the coupling cavity and reaches the workpiece surface. It is then reflected by the workpiece and redirected to the beam splitter a second time, and is then reflected by the beam splitter to be collected by the CCD camera.

[0022] Preferably, in steps S2 to S3, during the laser cutting process, the probe light follows the processing water flow to perform real-time detection of the cut portion; the CCD camera transmits the collected beam signal to the optical interference signal analysis and processing device via communication, and then the optical interference signal analysis and processing device performs interference analysis on the signal, feeding back the obtained depth result and displaying it on the electronic processing drawing in the laser cutting system. The beneficial effects of this invention are:

[0023] This invention provides a depth detection device and method for water-guided laser processing, which can provide real-time depth information with an accuracy of micrometers, enabling water-guided laser equipment to perform specified blind hole processing, etc. At the same time, this non-contact measurement will not damage the workpiece and can effectively improve the processing efficiency of water-guided laser. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a water-guided laser processing depth detection device and detection method;

[0025] Figure 2 This is a flowchart of the detection method.

[0026] In the diagram, 1 is the detection light source; 2 is the beam splitter; 3 is the reference plane; 4 is the coupling cavity; 5 is the processing water flow; 6 is the workpiece; 7 is the processing laser; and 8 is the CCD camera. Detailed Implementation

[0027] The related technologies of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] refer to Figures 1-2 This invention provides a water-guided laser processing depth detection device, comprising: a detection light source 1, a beam splitter 2, a reference plane 3, a coupling cavity 4, a processing water flow 5, a workpiece 6, and a CCD camera 8; the detection light source 1 is located directly above the beam splitter 2, the coupling cavity 4 is located directly below the beam splitter 2, and the workpiece 6 is located directly below the coupling cavity 4; the reference plane 3 and the CCD camera 8 are located on the left and right sides of the beam splitter 2, respectively; the beam splitter 2 is tilted, and the vertical distance between the beam splitter 2 and the workpiece 6 remains constant; the detection light source 1, the workpiece 6, the reference plane 3, and the CCD camera 8 are arranged in a cross shape on the top, bottom, left, and right sides of the beam splitter 2, respectively, to facilitate the detection light from the detection light source 1 to be refracted and transmitted separately after being irradiated onto the tilted surface of the beam splitter 2;

[0029] The probe light from the probe light source 1 illuminates the beam splitter 2. The first reflected light channel of the beam splitter 2, illuminated by the probe light source 1, faces the front of the reference plane 3. The first transmitted light channel of the beam splitter 2, illuminated by the probe light source 1, faces the interior of the coupling cavity 4 and coincides with the processing water flow 5. The reference plane 3 is perpendicular to the first reflected light channel of the beam splitter 2 illuminated by the probe light source 1. The processing surface of the workpiece 6 is perpendicular to the first transmitted light channel of the beam splitter 2 illuminated by the probe light source 1. The second transmitted light channel of the beam splitter 2, illuminated by the reflected light from the reference plane 3, faces the lens of the CCD camera 8. The third reflected light channel, after being irradiated by the reflected light from the machined surface of workpiece 6, faces the lens of CCD camera 8; the probe light from the probe light source 1 is irradiated by the mirror surface of the tilted beam splitter 2 and then refracted to the reference plane 3 and transmitted to workpiece 6 respectively. The light refracted again by the reference plane 3 is transmitted twice by the mirror surface of the beam splitter 2 to CCD camera 8. The light refracted again by the upper surface of workpiece 6 is also refracted twice by the mirror surface of the beam splitter 2 to CCD camera 8. This makes it convenient for CCD camera 8 to collect the refracted light from the reference plane 3 and the upper surface of workpiece 6 respectively for subsequent analysis and processing.

[0030] The CCD camera 8 is electrically connected to an optical interference signal analysis and processing device. The optical interference signal analysis and processing device receives and analyzes the refracted light rays from the reference plane 3 and the upper surface of the workpiece 6 collected by the CCD camera 8. Since the vertical distance between the beam splitter 2 and the workpiece 6 remains constant, the current real-time processing depth of the water-guided laser can be measured and calculated based on the two light refractions.

[0031] Furthermore, the beam splitter 2 is tilted at a 45° angle to the upper surface of the workpiece 6. The first reflected light channel, the second transmitted light channel, and the third reflected light channel are located on the same horizontal straight line, and the first transmitted light channel and the detection light irradiation direction of the detection light source 1 are located on the same vertical straight line. The 45° tilt angle of the beam splitter 2 ensures that the refracted light and reflected light on the mirror surface of the beam splitter 2 are evenly distributed. At the same time, it makes the incident light and refracted light channels of the reference plane 3 and the upper surface of the workpiece 6 coincide. The light returns along the original path and irradiates the beam splitter 2 again. The light path length is the same, and the light path that finally irradiates the CCD camera 8 also coincides and has the same length, avoiding the generation of measurement errors due to different light paths.

[0032] Furthermore, a processing laser 7 is connected to the side of the coupling cavity 4. After the processing laser 7 is coupled with the water jet in the coupling cavity 4, it forms a vertically downward water-guided laser. The water-guided laser coincides with the processing water flow 5. The processing laser 7 generates a water-guided laser at the same time, which coincides with the incident light and refracted light channel on the upper surface of the workpiece 6. This facilitates real-time measurement of the current processing depth of the water-guided laser and allows for depth monitoring or adjustment at any time.

[0033] Furthermore, the detection device is equipped with an electronic machining drawing, which is communicatively connected to an optical interference signal analysis and processing device. The electronic machining drawing and the optical interference signal analysis and processing device work together to stop processing the upper surface portion of the workpiece 6 that has reached the required cutting depth, and to process the portion of the upper surface portion of the workpiece 6 that has not reached the required cutting depth and does not conform to the machining drawing, thereby improving efficiency.

[0034] This invention also discloses a method for detecting the depth of water-guided laser processing. This method uses the aforementioned water-guided laser processing depth detection device and includes the following steps:

[0035] Step S1: Data acquisition. The CCD camera 8 acquires the light reflected from the reference plane 3, which is then transmitted to the CCD camera 8 after illuminating the beam splitter 2. The CCD camera 8 also acquires the light reflected from the workpiece 6's processing surface, which is then reflected to the CCD camera 8 after illuminating the beam splitter 2.

[0036] Step S2: Interference signal analysis, using optical interference signal analysis and processing equipment to analyze and process the two types of light collected by CCD camera 8 in step S1;

[0037] Step S3: Depth reconstruction, the machining depth on the electronic machining drawing is updated in real time through the communication connection of the optical interference signal analysis and processing equipment;

[0038] Step S4: Display implementation: The display device electrically connected to the optical interference signal analysis and processing equipment displays the current processing depth information in real time;

[0039] Step S5: Feedback control. Based on the updated information reflected in real time on the electronic processing drawing in step S3, the operator resets the process parameters according to the completion status of the drawing and as required. The part that has reached the required cutting depth will not be processed, and the part that is not completed in the processing drawing will be processed.

[0040] Furthermore, the detailed steps of step S1 are as follows:

[0041] Step S1-1: Turn on the processing laser 7. By adjusting the coupling cavity 4, first adjust the focusing lens inside the coupling cavity 4 to make the focused spot the smallest. Then move the laser beam to the center of the lower nozzle inside the coupling cavity 4 so that the processing laser 7 is coupled into the water jet, forming a high-energy stable processing water flow 5 that reaches the surface of the workpiece 6.

[0042] Step S1-2: The probe light emitted by the probe light source 1 passes through the beam splitter 2. Part of the probe light is reflected to the reference plane 3, then reflected again and redirected to pass through the beam splitter 2 a second time, and is then collected by the CCD camera 8. The other part of the probe light is transmitted through the beam splitter 2, passes through the coupling cavity 4 and reaches the surface of the workpiece 6. It is then reflected by the workpiece 6 and redirected to the beam splitter 2 a second time, and is further reflected by the beam splitter 2 to be collected by the CCD camera 8.

[0043] Furthermore, in steps S2 to S3, during the laser cutting process, the detection light follows the processing water flow 5 to detect the cut portion in real time; the CCD camera 8 transmits the collected beam signal to the optical interference signal analysis and processing device through communication, and then the optical interference signal analysis and processing device performs interference analysis on the signal, and feeds back the obtained depth result and displays it on the electronic processing drawing in the laser cutting system.

[0044] Example

[0045] 1. Turn on the processing laser 7. By adjusting the coupling cavity 4, first adjust the focusing lens inside it to make the focused spot the smallest. Then move the laser to the center of the lower nozzle in the coupling cavity 4 so that the processing laser 7 is coupled into the water to form a high-energy stable processing water flow 5 that reaches the surface of the workpiece 6.

[0046] 2. The probe light emitted by the probe light source 1 passes through the beam splitter 2. Part of the probe light is reflected to the reference plane 3 and then reflected back through the beam splitter 2, and then collected by the CCD camera 8. The other part of the probe light is projected through the beam splitter 2, passes through the coupling cavity 4 and reaches the upper surface of the workpiece 6, and is then reflected back to the beam splitter 2, and then reflected back to the CCD camera 8 for collection.

[0047] 3. During the laser cutting process, the probe light follows the processing water flow to detect the cut portion in real time. The CCD camera 8 transmits the collected beam signal to the optical interference signal analysis and processing equipment via communication. The equipment then performs interference analysis on the signal and displays the resulting depth on the electronic processing drawing in the laser cutting system.

[0048] Based on the real-time processing depth and processing requirements, the operator adjusts the process parameters in real time using the laser cutting system.

[0049] In summary, this invention provides a depth detection device and method for water-guided laser processing, which can provide real-time depth information with micron-level accuracy, enabling water-guided laser equipment to perform specified blind hole processing, etc. At the same time, this non-contact measurement will not damage the workpiece and can effectively improve the processing efficiency of water-guided laser. Therefore, this invention has broad application prospects.

[0050] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for detecting the depth of water-guided laser processing, characterized in that, Includes the following steps: Step S1: Data acquisition. The light reflected from the reference plane (3) is transmitted to the CCD camera (8) after being irradiated by the beam splitter (2). The light reflected from the workpiece (6) processing surface is also acquired by the CCD camera (8) after being irradiated by the beam splitter (2). Step S2: Interference signal analysis, the two types of light collected by the CCD camera (8) in step S1 are analyzed and processed by the optical interference signal analysis and processing equipment; Step S3: Depth reconstruction, the machining depth on the electronic machining drawing is updated in real time through the communication connection of the optical interference signal analysis and processing equipment; Step S4: Real-time display: The current processing depth information is displayed in real time through the display device electrically connected to the optical interference signal analysis and processing equipment. Step S5: Feedback control. Based on the updated information reflected in real time on the electronic processing drawing in step S3, the operator resets the process parameters according to the completion status of the drawing and the required process parameters. The part that has reached the required cutting depth will no longer be processed, and the part that is not completed in the processing drawing will be processed. In step S2, the final signal obtained includes a background component. : Cross-correlation components of reflected light passing only through the reference plane Interference light caused by the optical path difference between the processed sample and the reference plane, and autocorrelation components. The signal is caused by self-interference between layers of the sample; by performing a Fourier transform on the signal, the frequency domain information can be converted into spatial and temporal depth information. The detection device used in the detection method includes: a detection light source (1), a beam splitter (2), a reference plane (3), a coupling cavity (4), a processing water flow (5), a workpiece (6), and a CCD camera (8). The detection light source (1) is located directly above the beam splitter (2), the coupling cavity (4) is located directly below the beam splitter (2), and the workpiece (6) is located directly below the coupling cavity (4). The reference plane (3) and the CCD camera (8) are located on the left and right sides of the beam splitter (2), respectively; The beam splitter (2) is tilted, and the vertical distance between the beam splitter (2) and the workpiece (6) remains unchanged; The detection light from the detection light source (1) illuminates the beam splitter (2). The first reflected light channel of the beam splitter (2) after being illuminated by the detection light source (1) faces the front of the reference plane (3). The first transmitted light channel of the beam splitter (2) after being illuminated by the detection light source (1) faces the interior of the coupling cavity (4) and coincides with the processing water flow (5). The reference plane (3) is perpendicular to the first reflected light channel of the beam splitter (2) after being illuminated by the detection light source (1); The processing surface of the workpiece (6) is perpendicular to the first transmitted light channel after the beam splitter (2) is irradiated by the detection light source (1); The second transmission light channel of the beam splitter (2) after being irradiated by the reflected light from the reference plane (3) faces the lens of the CCD camera (8), and the third reflection light channel of the beam splitter (2) after being irradiated by the reflected light from the processing surface of the workpiece (6) faces the lens of the CCD camera (8). The CCD camera (8) is electrically connected to an optical interference signal analysis and processing device. The specific detection light source is a frequency sweep light source, whose working frequency and wavelength can be continuously tuned within a certain range and periodically. The two different reflected lights will introduce optical path difference due to the different optical paths. When the optical path difference matches the coherent wavelength of the light wave emitted by the detection light source (1), interference will occur. Since light waves of different frequencies have different coherence lengths, interference signals at different depths of the workpiece (6) can be obtained. A processing laser (7) is connected to the side of the coupling cavity (4). The processing laser (7) is coupled with the water jet in the coupling cavity (4) to form a vertically downward water-guided laser. The water-guided laser coincides with the processing water flow (5). The detection device is equipped with electronic processing drawings, which are communicatively connected to an optical interference signal analysis and processing device. In steps S2 to S3, during the laser cutting process, the probe light follows the processing water flow (5) to detect the cut part in real time; the CCD camera (8) transmits the collected beam signal to the optical interference signal analysis and processing device through communication, and then performs interference analysis on the signal through the optical interference signal analysis and processing device, and feeds back the obtained depth result and displays it on the electronic processing drawing in the laser cutting system.

2. The method for detecting the depth of water-guided laser processing according to claim 1, characterized in that, The beam splitter (2) is inclined at a 45° angle to the upper surface of the workpiece (6). The first reflected light channel, the second transmitted light channel, and the third reflected light channel are located on the same horizontal straight line. The irradiation direction of the first transmitted light channel and the detection light source (1) is located on the same vertical straight line.

3. The method for detecting the depth of water-guided laser processing according to claim 1, characterized in that, The detailed steps of step S1 are as follows: Step S1-1: Turn on the processing laser (7), and adjust the focusing mirror inside the coupling cavity (4) to make the focused spot the smallest. Then move the laser beam to the center of the lower nozzle inside the coupling cavity (4) so ​​that the processing laser (7) is coupled into the water jet to form a stable processing water flow (5) with high energy to reach the surface of the workpiece (6). Step S1-2: The probe light emitted by the probe light source (1) passes through the beam splitter (2). Part of the probe light is reflected to the reference plane (3) and then reflected again to pass through the beam splitter (2) a second time, and is then collected by the CCD camera (8). Another part of the probe light is transmitted through the beam splitter (2), passes through the coupling cavity (4) and reaches the surface of the workpiece (6). It is then reflected by the workpiece (6) and turned to the beam splitter (2) a second time, and is then reflected by the beam splitter (2) to the CCD camera (8) for collection.

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