Coaxial visual inspection image processing method and device for laser cutting head

Abstract

The invention discloses a laser cutting head coaxial visual inspection image processing method and device, and the method comprises the steps: a static processing method, fixing a laser cutting head and a workpiece, dotting to form a static grayscale image, selecting a bright spot and a nozzle bright ring, extracting a first bright spot center point and a nozzle first contour center point, and adjusting the cutting head until the bright spot is coaxial with a nozzle. Generating a reference circular frame area and an annular frame area; the dynamic processing method comprises the following steps: collecting a dynamic gray level image, detecting a second bright spot center point and a second contour center point in real time, and ensuring the coaxiality of a dynamic cutting process; the device is composed of an imaging module, a light filtering module, a beam combining module, a focusing module and an upper computer, all the modules are connected in sequence, the upper computer is electrically connected with a camera, and the functions of image collecting and processing and cutting head adjusting are achieved.

Description

Technical Field

[0001] The present invention relates to the field of laser cutting, and in particular to a method and device for processing coaxial visual detection images of a laser cutting head. Background Art

[0002] Laser cutting technology, especially continuous laser cutting with fiber output, has developed to a power level of tens of kilowatts. In order to achieve effective interaction between laser and material, the design of the laser cutting head is crucial, among which the coaxiality between the nozzle and the bright spot directly affects the uniformity and stability of the cutting. If the bright spot deviates from the center of the nozzle, it will not only lead to a decrease in cutting quality, but also may cause damage to the equipment, especially when using a small nozzle for processing.

[0003] During the laser cutting process, the beam guide module of the laser cutting head may be offset due to high-speed processing and component matching problems. For example, a slight shake of the fiber interface or the rebound gap of the XY centering module may cause the bright spot to shift. Therefore, it is particularly important to detect the coaxiality of the bright spot and the nozzle in real time. In addition, in high-power laser processing, the thermal lens effect will cause the focus of the optical lens to shift, affecting the cutting stability, so real-time monitoring of the bright spot size is also necessary.

[0004] At present, the traditional mechanical vision inspection technology is widely used in the market for bright spot and coaxiality inspection. This method usually completes image processing based on post-processing, and the steps include image acquisition, pre-processing, segmentation and feature extraction. This method has significant shortcomings in processing speed and cannot meet the needs of high-speed laser cutting. Summary of the invention

[0005] The purpose of the present invention is to provide a real-time detection method for the coaxiality of the bright spot of a laser cutting head with the nozzle and the size of the bright spot, which greatly improves the detection efficiency through single-pixel processing function and area segmentation processing technology.

[0006] In a first aspect, the present invention provides a method for processing images of a coaxial visual inspection of a laser cutting head, comprising the steps of: A method for processing images of coaxial visual inspection of a laser cutting head comprises S1: forming a static grayscale image of the laser cutting head on a workpiece surface, the static grayscale image comprising a laser bright spot and a nozzle bright ring, and respectively identifying and extracting a bright spot center point of the laser bright spot as a first bright spot center point and a contour center point of the nozzle bright ring as a first contour center point; S2: If the center point of the first bright spot coincides with the center point of the first contour, a reference circular frame area is formed according to the center point of the first bright spot, and a reference ring frame area is formed according to the center point of the first contour; if the center point of the first bright spot does not coincide with the center point of the first contour, the laser cutting head is adjusted until the center point of the first bright spot coincides with the center point of the first contour; S3: The laser cutting head forms a dynamic grayscale image by collecting pictures in real time while cutting on the workpiece surface, and respectively identifies and extracts the bright spot center point of the reference circular frame area in the dynamic grayscale image as the second bright spot center point, and the contour center point of the reference ring frame area as the second contour center point. If the second bright spot center point coincides with the second contour center point, it is determined that the bright spot of the laser cutting head is coaxial with the nozzle.

[0007] Furthermore, the step S1 of identifying and extracting the bright spot center point of the laser bright spot and the contour center point of the nozzle bright ring includes the following steps: S11: Select the laser bright spot and the nozzle bright ring respectively; S12: extracting the center point of the first bright spot based on the framed area of ​​the laser bright spot; S13: Extracting the first contour center point based on the framed area of ​​the nozzle bright ring.

[0008] Further, step S12 includes: Step S121: The framed area of ​​the laser bright spot, where the edge pixels in the framed area occupy an area greater than 1 / 2, are counted into the framed area for grayscale value comparison; Step S122: extracting the pixel with the largest gray value as the center point of the first bright spot.

[0009] Further, step S13 includes: Step S131: The framed area of ​​the nozzle bright ring, the edge pixels in the framed area that occupy an area greater than 1 / 2 are counted into the framed area for grayscale value comparison; Step S132: compare the grayscale values ​​of the pixels in the selected area of ​​the nozzle bright ring row by row or column by column, take the average coordinates of the inner circle pixels when the grayscale value jump of two adjacent pixels meets the first threshold as the nozzle contour distribution point, and calculate the first contour center point based on the contour distribution point.

[0010] Further, in step S132: the first threshold is t times the high grayscale value of two adjacent pixels as much as the low grayscale value, where t≥1.5.

[0011] Further: In step S132: if there are multiple groups of adjacent two pixel points in the same row or the same column whose grayscale value jumps meet the first threshold, the mean value of the coordinates of the multiple groups of adjacent pixel points is compared with the nozzle contour distribution points of the front and rear f rows or columns, and the mean value of the adjacent two pixel coordinate points closest to the nozzle contour distribution points of the front and rear f rows or columns is selected as the nozzle contour distribution point.

[0012] Furthermore, step S2 specifically includes: generating a reference circular frame area with a diameter D based on the center point of the first bright spot, generating a reference ring frame area with a radius R based on the center point of the first contour, acquiring and storing pixel point data of the reference circular frame area and the reference ring frame area, and resetting the grayscale values ​​of pixels in non-areas to zero and uploading them.

[0013] Further, step S3 includes: S31: Detect the grayscale values ​​of all pixels in the reference circle frame, and when the ratio of the grayscale value of a pixel and its P neighboring pixels to the grayscale value of the maximum pixel in the reference circle frame is (K+Δt)%, calculate the relative radius of the relative bright spot area or the equivalent number of pixels; if no pixel with a grayscale value below (K+Δt)% of the maximum grayscale value can be obtained, repeat step S2; S32: Obtain the contour distribution points within the reference ring frame area. If the complete contour distribution points cannot be obtained, repeat step S2.

[0014] Furthermore, in step S132, the first contour center point is calculated based on the contour distribution points, with the best arc segment of the contour distribution points being used as a selection basis.

[0015] Further, in step S2: a reference circular frame area with a diameter D is generated according to the first bright spot center point, and the grayscale value of at least C pixels on the boundary of the reference circular frame area is (n+Δt)% of the grayscale value of the first bright spot center point. A reference ring frame area with a radius R is generated according to the first contour center point, and the number of pixel points in the row or column direction within the reference ring frame area is greater than m.

[0016] On the other hand, a coaxial visual inspection image processing device for a laser cutting head is provided, comprising: an imaging module, a filtering module, a beam combining module, a focusing module and a host computer; the imaging module, the filtering module, the beam combining module and the focusing module are assembled together in sequence through a switching or connecting structure, and the host computer is electrically connected to the imaging module camera.

[0017] Furthermore, the imaging module includes a camera and an imaging lens, the filtering module includes a bandpass filter and an attenuation plate, the beam combining module mainly includes a beam combining mirror, and the focusing module includes a focusing mirror, a protective mirror and a fluid structure component including a nozzle, wherein the camera of the imaging module is coaxially arranged with the central axis of the imaging lens, the bandpass filter and the attenuation plate of the filtering module are coaxially arranged with the central axis, and the focusing mirror and the protective mirror of the focusing module are coaxially arranged with the central axis of the beam combining mirror of the beam combining module.

[0018] Furthermore, a flat mirror is added between the imaging module, the filtering module and the beam combining module to perform structural transition.

[0019] Furthermore, the wavelength band filtering range of the bandpass filter at least includes all wavelength bands between 300nm-1100nm except the passing wavelength band.

[0020] Furthermore, a gas flow channel structure is arranged inside the nozzle of the focusing module to provide auxiliary airflow to prevent smoke and dust generated during the cutting process from affecting the light beam transmission.

[0021] The beneficial effects of the embodiments of the present invention are: a static grayscale image is formed by a laser cutting head in a static state, a first bright spot center point and a first contour center point of the static grayscale image are identified through image processing, and a reference circular frame area and a reference ring frame area are formed, and a cutting screen is captured in real time during dynamic cutting by the laser cutting head to form a dynamic grayscale image, and a second bright spot center point and a second contour center point of the dynamic grayscale image are identified through image processing. When the second bright spot center point coincides with the second contour center point during dynamic cutting, it indicates that the bright spot of the laser cutting head is coaxial with the nozzle during dynamic cutting. When the coaxial judgment condition is met, the reference circular frame area and the reference ring frame area remain unchanged during dynamic cutting. Only when the coaxial judgment condition is not met, the reference circular frame area and the reference ring frame area are dynamically adjusted, thereby reducing the processing time of the system and improving the detection efficiency and detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of a coaxial visual inspection image processing device for a laser cutting head provided in an embodiment of the present invention; Figure 2 A schematic diagram of a static grayscale processed image provided by an embodiment of the present invention.

[0024] Icons: 1-imaging module; 2-filter module; 3-beam combining module; 4-focusing module; 5-host computer; 11-camera; 12-imaging lens; 21-bandpass filter; 22-attenuation plate; 31-beam combining mirror; 41-focusing mirror; 42-protective mirror; 43-nozzle; 61-bright spot; 62-nozzle bright ring; 63-stray light area; 64-dark area. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0028] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0029] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0030] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] like Figure 1 As shown, the present invention provides a laser cutting head coaxial visual detection image processing method comprising the steps of: S1: forming a static grayscale image of the laser cutting head on the workpiece surface, the static grayscale image including a laser bright spot and a nozzle bright ring, and respectively identifying and extracting a bright spot center point of the laser bright spot as a first bright spot center point and a contour center point of the nozzle bright ring as a first contour center point; In step S1, the laser cutting head and the workpiece are fixed. In a static state, the laser cutting head marks dots on the surface of the workpiece. The marking power is consistent with the power of the laser cutting head when working. The imaging module receives the light signal and converts it into a static grayscale image. The static grayscale image is as follows: Figure 2 The image includes: a bright spot 61 , a nozzle bright ring 62 , a stray light area 63 and a dark area 64 .

[0032] In step S1, the steps of identifying and extracting the bright spot center point of the laser bright spot and the contour center point of the nozzle bright ring include: S11: Select the laser bright spot and the nozzle bright ring respectively; S12: Based on the framed area of ​​the laser bright spot, extract the center point of the first bright spot; S13: Extract the center point of the first contour based on the framed area of ​​the nozzle bright ring.

[0033] In the above steps, the bright spot and the nozzle bright ring are selected to reduce the amount of calculation for identifying and extracting the center point of the first bright spot and the center point of the first contour, thereby improving processing efficiency. The center point of the first bright spot and the center point of the first contour are the basis for judging whether the bright spot formed by the laser cutting head is coaxial with the nozzle in a static state.

[0034] Step S12 includes: Step S121: The framed area of ​​the laser bright spot, the edge pixels in the framed area that occupy an area greater than 1 / 2 are counted into the framed area for grayscale value comparison; Step S122: extract the pixel with the largest gray value as the center point of the first bright spot.

[0035] If there are multiple pixels with the largest grayscale value, the coordinate average of the multiple pixels is calculated as the center point of the first bright spot.

[0036] By comparing the grayscale values ​​and selecting the pixel with the largest grayscale value as the bright spot center point, noise interference can be effectively eliminated and the accuracy of bright spot center point extraction can be improved.

[0037] Step S13 includes: Step S131: a frame selection area of ​​the nozzle bright ring, edge pixels in the frame selection area whose area is greater than 1 / 2 are counted into the frame selection area for grayscale value comparison; Step S132: Compare the grayscale values ​​of the pixels in the selected area of ​​the nozzle bright ring row by row or column by column, use the average coordinates of the inner circle pixels when the grayscale value jump of two adjacent pixels meets the first threshold as the nozzle contour distribution point, and calculate the first contour center point based on the contour distribution point.

[0038] By comparing the gray values ​​row by row or column by column, the pixel points that meet the first threshold of the gray value jump are selected as the nozzle contour distribution points, and the contour center point is calculated, thereby improving the extraction accuracy of the nozzle contour center point.

[0039] In step S132: the first threshold is t times the grayscale value of the high grayscale value of two adjacent pixels as much as the grayscale value of the low grayscale value, where t≥1.5.

[0040] In step S132: if there are multiple groups of adjacent two pixel points in the same row or the same column whose grayscale value jumps meet the first threshold, the coordinate mean of the multiple groups of adjacent two pixel points are compared with the nozzle contour distribution points of the front and back f rows or columns, and the mean of the adjacent two pixel coordinate points closest to the nozzle contour distribution points of the front and back f rows or columns is selected as the nozzle contour distribution point.

[0041] If there are multiple groups of jump points in the same row or column, the point with the best continuity is selected by combining the data of the previous and next rows, and the continuity of the nozzle contour is used to avoid noise, thereby improving the recognition accuracy of the contour distribution points.

[0042] In step S132, the first contour center point is calculated based on the contour distribution points, and the first contour center point is calculated based on the best arc segment of the contour distribution points as the selection basis.

[0043] The contour center point is calculated by fitting the best arc segment of the contour distribution points, which can improve the fitting accuracy and thus improve the coaxial detection accuracy.

[0044] S2: If the center point of the first bright spot coincides with the center point of the first contour, a reference circular frame area is formed according to the center point of the first bright spot, and a reference ring frame area is formed according to the center point of the first contour; if the center point of the first bright spot does not coincide with the center point of the first contour, adjust the laser cutting head until the center point of the first bright spot coincides with the center point of the first contour.

[0045] If the center point of the first bright spot does not coincide with the center point of the first contour, the centering structure of the laser cutting head needs to be adjusted to re-dot until the center point of the first bright spot coincides with the center point of the first contour. The coincidence deviation accuracy of the center point of the first bright spot and the center point of the first contour is controlled within 50um, and the optimal range is within 10um. The above-mentioned static dotting, i.e., static processing, adjusts the bright spot of the laser cutting head to be coaxial with the nozzle, ensures the coaxiality of the bright spot and the nozzle of the laser cutting head before dynamic cutting, and improves the accuracy and stability of laser cutting.

[0046] Step S2 specifically includes: A reference circular frame area with a diameter of D is generated based on the center point of the first bright spot, and a reference ring frame area with a radius of R is generated based on the center point of the first contour. The pixel point data of the reference circular frame area and the reference ring frame area are acquired and stored, and the grayscale values ​​of pixels outside the area are reset to zero and uploaded.

[0047] Step S2 generates a reference area and stores data, providing a reference area for real-time acquisition and processing during the subsequent dynamic cutting process of the laser cutting head. Zeroing the non-reference area can reduce interference and improve the accuracy of data processing.

[0048] In step S2: a reference circular frame area with a diameter of D is generated according to the center point of the first bright spot, and the grayscale value of at least C pixels on the boundary of the reference circular frame area is (n+Δt)% of the grayscale value of the center point of the first bright spot. A reference ring frame area with a radius R is generated according to the center point of the first contour, and the number of pixel points in the row or column direction within the reference ring frame area is greater than m.

[0049] Generate a reference circular frame area with a diameter of D based on the center point of the bright spot, and satisfy the requirement that the grayscale value of at least C pixels on the boundary of the reference circular frame area is (n+∆t)% of the grayscale value of the center point of the bright spot, where C≥3, n ranges from 1 to 30, and the optimal value of n is 10; ∆t is the grayscale value deviation, ranging from ±1 to ±5. The above conditions are used to ensure that the boundary of the reference circular frame area matches the boundary of the actual bright spot.

[0050] A reference ring frame area with a radius R is generated based on the center point of the contour, satisfying that the number of pixels in the radial row or column direction within the reference ring frame area is greater than m, where m ranges from 5 to 50 and the optimal value of m is 20. The above limitation ensures that the reference ring frame area contains sufficient nozzle contour information.

[0051] The reference circular frame area and the reference ring frame area are used by the laser cutting head to detect the bright spot and nozzle coaxiality in real time during actual dynamic cutting, which reduces the amount of calculation and improves the detection efficiency. It can also more accurately extract the characteristics of the bright spot and nozzle during real-time dynamic cutting and improve the detection accuracy.

[0052] S3: The laser cutting head collects images in real time while cutting on the workpiece surface to form a dynamic grayscale image. The center point of the bright spot in the reference circular frame area in the dynamic grayscale image is identified and extracted as the second center point of the bright spot, and the center point of the contour in the reference ring frame area is identified and extracted as the second center point of the contour. If the center point of the second bright spot coincides with the center point of the second contour, it is determined that the bright spot of the laser cutting head is coaxial with the nozzle.

[0053] During the dynamic cutting process, based on the position deviation of the center point of the second bright spot and the center point of the second nozzle contour, the coaxiality of the bright spot and the nozzle can be evaluated in real time.

[0054] Step S3 includes: S31: detecting the grayscale values ​​of all pixels in the reference circle frame, and when the ratio of the grayscale value of a pixel and its P neighboring pixels to the grayscale value of the maximum pixel in the reference circle frame is (K+Δt)%, calculating the relative radius of the relative bright spot area or the equivalent number of pixels; if no pixel with a grayscale value below (K+Δt)% of the maximum grayscale value can be obtained, repeating step S2; Extract the center point of the bright spot in the reference circular frame area, detect the grayscale values ​​of all pixels in the reference circular frame, and when the ratio of the grayscale value of the pixel and its adjacent P pixels to the grayscale value of the maximum pixel in the reference circular frame is (K+Δt)%, calculate the relative radius or equivalent number of pixels in the relative bright spot area according to the coordinate average of the adjacent Q pixels including the pixel; where P≥2, Q≥3; K is in the range of 31-70, and the optimal value is 50; Δt is the grayscale value deviation, and the value range is ±1-±5; compared with step S2, K>n; where the equivalent number of pixels refers to the number of all pixels in the relative bright spot area. If the pixel whose grayscale value is less than (K+Δt)% of the maximum grayscale value cannot be obtained, repeat step S2. Calculating the relative radius or equivalent number of pixels of the relative bright spot area can detect whether the bright spot becomes larger or shifts when the laser cutting head is working dynamically. If the bright spot becomes larger or shifts, defocus compensation can be performed during operation, that is, repeating step S2 to keep the coaxiality of the bright spot and the nozzle of the laser cutting head during operation.

[0055] S32: Obtain the contour distribution points within the reference ring frame area. If the complete contour distribution points cannot be obtained, repeat step S2.

[0056] If the complete contour distribution points cannot be obtained, it means that there is deformation in the nozzle contour distribution points. Based on this, the damage condition of the nozzle can be judged, and the problem can be discovered in time to reduce the risk of nozzle damage and burning.

[0057] In this case, a static grayscale image is formed by a laser cutting head in a static state, and the first bright spot center point and the first contour center point of the static grayscale image are identified through image processing, and a reference circular frame area and a reference ring frame area are formed. When the laser cutting head is dynamically cutting, the cutting screen is collected in real time to form a dynamic grayscale image, and the second bright spot center point and the second contour center point of the dynamic grayscale image are identified through image processing. When the second bright spot center point coincides with the second contour center point during dynamic cutting, it means that the bright spot of the laser cutting head is coaxial with the nozzle during dynamic cutting. When the coaxial judgment condition is met, the reference circular frame area and the reference ring frame area remain unchanged during dynamic cutting. Only when the coaxial judgment condition is not met, the reference circular frame area and the reference ring frame area are dynamically adjusted, which reduces the processing time of the system and improves the detection efficiency and detection accuracy.

[0058] In another embodiment, the present invention also provides a coaxial visual detection image processing device for a laser cutting head, which can apply a coaxial visual detection image processing method for a laser cutting head of the above embodiment, including: an imaging module 1, a filter module 2, a beam combining module 3, a focusing module 4 and a host computer 5; the imaging module 1, the filter module 2, the beam combining module 3 and the focusing module 4 are assembled together in sequence through a switching or connecting structure, and the host computer 5 is electrically connected to the imaging module 1.

[0059] The imaging module 1 includes a camera 11 and an imaging lens 12, the filtering module 2 includes a bandpass filter 21 and an attenuation plate 22, the beam combining module 3 mainly includes a beam combining mirror 31, and the focusing module 4 includes a focusing mirror 41, a protective mirror 42 and a fluid structure component including a nozzle 43, wherein the camera 11 of the imaging module 1 is coaxially arranged with the central axis of the imaging lens 12, the central axis of the bandpass filter 21 and the attenuation plate 22 of the filtering module 2 is coaxially arranged, and the central axis of the focusing mirror 41 and the protective mirror 42 of the focusing module 4 is coaxially arranged with the central axis of the beam combining mirror 31 of the beam combining module 3.

[0060] The camera 11 is an in-pixel processing camera, and each pixel thereof includes three micro units: a sensor, a memory, and a processor. The memory stores the data obtained by the sensor, and the processor processes the data obtained by the sensor. Each pixel is coplanar and electrically connected. Each pixel of the camera has data storage and processing capabilities, and can quickly process image data to improve detection efficiency. The imaging lens includes but is not limited to a fixed-focus lens and a zoom lens, and at least has the function of adjusting the amount of light entering and the imaging position. Its effective focal length covers 10mm-150mm, and typically has 25mm, 35mm, 50mm, 75mm or a continuously adjustable focal length within the range. The imaging lens can support fixed focus and zoom, with a wide focal length range, and can be adjusted according to different cutting scenes.

[0061] A flat mirror can be added between the imaging module 1, the filter module 2, and the beam combining module 3 to achieve structural transition.

[0062] The band filter range of the bandpass filter 21 includes at least all bands between 300nm-1100nm except the passing band, typically 480nm, 532nm, 580nm, 650nm, 780nm, 940nm, etc., and the half-wave width is within 20nm, typically 10nm, 5nm, 3nm, etc. The attenuation plate 22 is used in conjunction with the bandpass filter 21 to attenuate the transmittance of the passing band, including fixed OD and gradient OD, OD represents the cut-off depth. The bandpass filter and the attenuation plate can accurately control the band and intensity of light to ensure imaging quality.

[0063] The focusing mirror 41 and the protective mirror 42 in the focusing module 4 can efficiently transmit the laser and the wavelength band passed by the filter module. The focusing mirror 41 converges the laser to the end of the nozzle 43 and is also used to cooperate with the imaging lens 12 of the imaging module 1 for imaging.

[0064] The beam combiner 31 can transmit or reflect the laser, and correspondingly, can also reflect or transmit the wavelength band passed by the filter module 2 .

[0065] A gas flow channel structure is arranged inside the nozzle 43 of the focusing module 4 to provide an auxiliary gas flow to prevent smoke and dust generated during the cutting process from affecting the light beam transmission.

[0066] The host computer 5 is electrically connected to the camera 11 of the imaging module 1, and has the functions of acquiring pixel data of the camera 11, image processing and display, and issuing processing commands. The host computer integrates control to achieve rapid acquisition, processing and display of image data, and has the function of issuing commands to facilitate automated operation.

[0067] In terms of the light beam transmission method, during the laser light cutting process, light beams of different wavelengths are generated and enter the laser cutting head through the nozzle 43, and then pass through the protective mirror 42 and the focusing mirror 41 of the focusing module 4, and then are reflected or transmitted by the beam combining mirror 31 of the beam combining module 3. The reflected or transmitted light is filtered and attenuated by the bandpass filter 21 and the attenuation plate 22 of the filter module 2, and the transmitted band is finally converged by the imaging lens 12 of the imaging module 1 to form an image on the camera 11.

[0068] The above-mentioned coaxial visual detection image processing device of the laser cutting head is suitable for visual detection during the laser cutting process. It can monitor the cutting effect in real time, detect whether the bright spot 61 is coaxial with the nozzle 43 in real time, detect whether the nozzle 43 is deformed or damaged in real time, etc., to improve the cutting accuracy and quality.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser cutting head coaxial visual inspection image processing method, characterized in that: S1: forming a static grayscale image of the laser cutting head on the surface of the workpiece, the static grayscale image including a laser bright spot and a nozzle bright ring, and respectively identifying and extracting a bright spot center point of the laser bright spot as a first bright spot center point and a contour center point of the nozzle bright ring as a first contour center point; S2: If the center point of the first bright spot coincides with the center point of the first contour, a reference circular frame area is formed according to the center point of the first bright spot, and a reference ring frame area is formed according to the center point of the first contour; if the center point of the first bright spot does not coincide with the center point of the first contour, the laser cutting head is adjusted until the center point of the first bright spot coincides with the center point of the first contour; S3: The laser cutting head forms a dynamic grayscale image by collecting pictures in real time while cutting on the workpiece surface, and respectively identifies and extracts the bright spot center point of the reference circular frame area in the dynamic grayscale image as the second bright spot center point, and the contour center point of the reference ring frame area as the second contour center point. If the second bright spot center point coincides with the second contour center point, it is determined that the bright spot of the laser cutting head is coaxial with the nozzle.

2. A laser cutting head coaxial visual inspection image processing method according to claim 1, characterized in that: In step S1, identifying and extracting the bright spot center point of the laser bright spot and the contour center point of the nozzle bright ring includes the following steps: S11: Select the laser bright spot and the nozzle bright ring respectively; S12: extracting the center point of the first bright spot based on the framed area of ​​the laser bright spot; S13: Extracting the first contour center point based on the framed area of ​​the nozzle bright ring.

3. A laser cutting head coaxial visual inspection image processing method according to claim 2, characterized in that: Step S12 includes: Step S121: The framed area of ​​the laser bright spot, the edge pixels in the framed area that occupy an area greater than 1 / 2 are counted into the framed area for grayscale value comparison, Step S122: extracting the pixel with the largest gray value as the center point of the first bright spot.

4. The method for coaxial visual inspection image processing of a laser cutting head according to claim 2, characterized in that: Step S13 includes: Step S131: The framed area of ​​the nozzle bright ring, the edge pixels in the framed area that occupy an area greater than 1 / 2 are counted into the framed area for grayscale value comparison; Step S132: compare the grayscale values ​​of the pixels in the selected area of ​​the nozzle bright ring row by row or column by column, take the average coordinates of the inner circle pixels when the grayscale value jump of two adjacent pixels meets the first threshold as the nozzle contour distribution point, and calculate the first contour center point based on the contour distribution point.

5. The method for coaxial visual inspection image processing of a laser cutting head according to claim 4 is characterized in that: In step S132: the first threshold is t times the high grayscale value of two adjacent pixels as the low grayscale value, where t≥1.

5.

6. A method for coaxial visual inspection image processing of a laser cutting head according to claim 4 or 5, characterized in that: In step S132: if there are multiple groups of adjacent two pixel points in the same row or the same column whose grayscale value jumps meet the first threshold, the coordinate mean of the multiple groups of adjacent two pixel points are compared with the nozzle contour distribution points of the front and back f rows or columns, and the average of the adjacent two pixel coordinate points closest to the contour distribution points of the front and back f rows or columns is selected as the nozzle contour distribution point.

7. The method for coaxial visual inspection image processing of a laser cutting head according to claim 1, characterized in that: Step S2 specifically includes: Generate a reference circular frame area with a diameter of D based on the center point of the first bright spot, and generate a reference ring frame area with a radius of R based on the center point of the first contour, obtain and store pixel point data of the reference circular frame area and the reference ring frame area, and reset the grayscale values ​​of pixels outside the area to zero and upload.

8. The method for coaxial visual inspection image processing of a laser cutting head according to claim 1, characterized in that: Step S3 includes: S31: Detect the grayscale values ​​of all pixels in the reference circle frame, and when the ratio of the grayscale value of a pixel and its P neighboring pixels to the grayscale value of the maximum pixel in the reference circle frame is (K+Δt)%, calculate the relative radius of the relative bright spot area or the equivalent number of pixels; if no pixel with a grayscale value below (K+Δt)% of the maximum grayscale value can be obtained, repeat step S2; S32: Obtain the contour distribution points within the reference ring frame area. If the complete contour distribution points cannot be obtained, repeat step S2.

9. The method for coaxial visual inspection image processing of a laser cutting head according to claim 6, characterized in that: The first contour center point is calculated based on the contour distribution points in step S132, with the best arc segment of the contour distribution points being used as a selection basis.

10. A laser cutting head coaxial visual inspection image processing method according to claim 1 or 2, characterized in that: In step S2: A reference circular frame area with a diameter of D is generated based on the first bright spot center point, and the grayscale value of at least C pixels on the boundary of the reference circular frame area is (n+Δt)% of the grayscale value of the first bright spot center point. A reference ring frame area with a radius R is generated according to the first contour center point, and the number of pixel points in the row or column direction within the reference ring frame area is greater than m.

11. A laser cutting head coaxial visual inspection image processing device, applied to a laser cutting head coaxial visual inspection image processing method according to any one of claims 1 to 10, characterized in that: include: The system is composed of an imaging module, a filter module, a beam combining module, a focusing module and a host computer; the imaging module, the filter module, the beam combining module and the focusing module are assembled together in sequence through a switching or connecting structure, and the host computer is electrically connected to the imaging module camera.

12. The laser cutting head coaxial visual inspection image processing device according to claim 11, characterized in that: The imaging module includes a camera and an imaging lens, the filtering module includes a bandpass filter and an attenuation plate, the beam combining module includes a beam combining mirror, and the focusing module includes a focusing mirror, a protective mirror, and a fluid structure component including a nozzle, wherein the camera of the imaging module is coaxially arranged with the central axis of the imaging lens, the bandpass filter and the attenuation plate of the filtering module are coaxially arranged with the central axis, and the focusing mirror and the protective mirror of the focusing module are coaxially arranged with the central axis of the beam combining mirror of the beam combining module.

13. The laser cutting head coaxial visual inspection image processing device according to claim 11, characterized in that: A flat mirror is added between the imaging module, the filtering module and the beam combining module to perform structural transition.

14. The laser cutting head coaxial visual inspection image processing device according to claim 12, characterized in that: The band-pass filter has a wavelength-removal range of at least including all wavelengths between 300 nm and 1100 nm except the passing wavelength.

15. The laser cutting head coaxial visual inspection image processing device according to claim 11, characterized in that: A gas flow channel structure is arranged inside the nozzle of the focusing module to provide auxiliary airflow to prevent smoke and dust generated during the cutting process from affecting the light beam transmission.

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