Laser beam centering adjustment method and device

Abstract

The invention relates to the technical field of laser cutting, in particular to a laser beam centering adjusting method and device. According to the laser beam centering adjustment method provided by the invention, the light spot formed by the red light beam in the visual field of the camera can be automatically exposed, and the focus of the red light beam can be automatically focused to obtain the optimal focus position, so that the coordinate of the light spot center in the machine tool coordinate system can be obtained; according to the obtained coordinates, the cutting head is controlled to move so that the distance between the nozzle center and the coordinates of the light spot center and the nozzle center is smaller than a preset distance, and the purpose of laser beam centering adjustment is achieved. As the image of the light spot at the optimal focus is minimum and closest to the circle, the precision of fitting the circle is highest, the precision of the center position of the red light at the detection position is also highest, and the precision of centering adjustment of the laser beam is also improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser cutting, and in particular to a laser beam centering adjustment method and device. Background Art

[0002] In the production scenario of plane laser cutting, the nozzle is the structure through which the laser beam passes directly. If there is a problem of non-concentricity between the laser beam and the inner hole of the nozzle, the laser will deviate to one side of the nozzle during light cutting, which will not only cause local overheating of the nozzle, shorten the service life of the nozzle or even damage it, but also significantly affect the cross-sectional effect of the cutting, resulting in inconsistencies on the four sides, etc.

[0003] In the manual operation scenario, after replacing the nozzle, the worker will manually check and adjust the coaxiality of the laser and the nozzle by "applying tape". The process of manual adjustment by "applying tape" is as follows: the worker manually sticks tape on the lower surface of the nozzle, then uses low-power laser spot shooting, removes the tape, and the inner circle of the nozzle and the circle formed by the spot shooting will be left on the tape. Next, the worker judges the offset direction and offset of the centers of the two circles by eye, and then manually turns the adjustment screw on the cutting head to control the movement of the laser center toward the center of the nozzle; repeat the above operation until after a certain application of tape, the worker believes that the center of the nozzle coincides with the center of the spot shooting hole. Therefore, to realize the automated replacement of nozzles, automatic inspection and adjustment of coaxiality is also necessary.

[0004] Therefore, a laser beam centering adjustment method is urgently needed to solve the above technical problems. Summary of the invention

[0005] The purpose of the present invention is to provide a laser beam centering adjustment method and device, which can automatically obtain the red light spot that is easiest to detect the center for lasers of various powers and red light intensities, thereby improving the accuracy of subsequent centering.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] A laser beam centering adjustment method comprises the following steps:

[0008] S101, obtaining the nozzle center coordinates of the nozzle lower end surface image center in the image coordinate system;

[0009] S102, controlling the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle;

[0010] S103, automatically exposing and automatically focusing the light spot to obtain an optimal focal position and adjusting the focus of the red light beam to the optimal focal position;

[0011] S104, obtaining the coordinates of the light spot center and the nozzle center in the machine tool coordinate system, obtaining the direction and distance that the red light beam needs to move, and controlling the cutting head to move in the direction that the red light beam needs to move to align the light spot center and the nozzle center;

[0012] Repeat steps S101-S104 until the distance between the center of the light spot and the center of the nozzle is lower than the preset distance, and the centering adjustment is completed.

[0013] As a preferred technical solution of the above laser beam centering adjustment method, automatically exposing the light spot includes:

[0014] The exposure time of the camera in the visual module is adjusted within a preset range. Each time the exposure time is adjusted, the changed image is evaluated to obtain an evaluation value. If the evaluation value reaches the preset evaluation value, the automatic exposure process ends and the automatic exposure is successful.

[0015] As a preferred technical solution of the above laser beam centering adjustment method, evaluating the changed image to obtain an evaluation value includes:

[0016] The changed image obtained by the camera after each adjustment of the exposure time is converted into a single-channel image and the grayscale mean of the single-channel image is calculated. If the difference with the target grayscale mean obtained in the pre-test is within the threshold range, it is considered that the optimal exposure has been achieved.

[0017] As a preferred technical solution for the above-mentioned laser beam centering adjustment method, the currently exposed image is saved before the exposure time is modified; after the exposure time is modified, the image is taken repeatedly for multiple times, and then the obtained image is differentiated from the image before the exposure time is modified, and the difference between the two is quantified from the perspective of pixel grayscale; if the difference reaches a preset threshold, it is considered that the image after the exposure time is modified has been obtained.

[0018] As a preferred technical solution of the above laser beam centering adjustment method, automatically focusing the light spot includes:

[0019] Adjusting the position of the lens in the cutting head to control the focus position of the red light beam to move within the adjustable range of the focus lens position of the cutting head;

[0020] Each time the focus of the red light beam moves to a specified position, the focus degree of the red light beam needs to be evaluated;

[0021] Acquire the spot image at the current position with the exposure time calculated in the automatic exposure process;

[0022] The spot image is processed to obtain an evaluation score for the current spot image, and the laser focus position with the best evaluation score is selected as the best focus position.

[0023] As a preferred technical solution for the above-mentioned laser beam centering adjustment method, processing the spot image includes: sequentially performing single-channel, filtering and thresholding processing on the spot image, then performing contour extraction and circle fitting on the processed image, and finally giving a final evaluation score based on the comprehensive roundness and the size of the fitted circle.

[0024] As a preferred technical solution of the above laser beam centering adjustment method, controlling the cutting head to move in the direction in which the red light beam needs to move includes:

[0025] Adjust the focus of the red light beam to the best focus position obtained;

[0026] The exposure time is adjusted to the best exposure time obtained to obtain the best spot image;

[0027] Performing image processing on the best spot image to obtain the coordinates of the spot center in the machine tool coordinate system, and obtaining the coordinates of the nozzle center in the machine tool coordinate system;

[0028] According to the coordinates of the center of the light spot in the machine tool coordinate system and the coordinates of the center of the nozzle in the machine tool coordinate system, the direction and distance that the red light beam needs to move are obtained, and the cutting head is controlled to move in this direction.

[0029] As a preferred technical solution for the above-mentioned laser beam centering adjustment method, after the cutting head moves, the light spot is obtained again and the light spot is automatically exposed and automatically focused to obtain the optimal focal position until the distance between the center of the light spot and the center of the nozzle is lower than the preset distance.

[0030] As a preferred technical solution of the above-mentioned laser beam centering adjustment method, image processing is performed on the optimal spot image to obtain the coordinates of the spot center in the machine tool coordinate system, and the coordinates of the nozzle center in the machine tool coordinate system are obtained, including:

[0031] Performing image processing on the best spot image to obtain the coordinates of the spot center in the image coordinate system;

[0032] The coordinates of the center of the light spot in the image coordinate system are converted into the coordinates of the center of the light spot in the machine tool coordinate system, and the coordinates of the center of the nozzle in the image coordinate system are converted into the coordinates of the center of the nozzle in the machine tool coordinate system.

[0033] In a second aspect, a laser beam centering adjustment device is provided, which is used to perform the method described in any of the above schemes, including:

[0034] A first acquisition module is used to obtain the nozzle center coordinates of the nozzle lower end surface image center in the image coordinate system;

[0035] A second acquisition module is used to control the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle;

[0036] A processing and acquisition module, used for automatically exposing and automatically focusing the light spot to obtain an optimal focal position and adjusting the focus of the red light beam to the optimal focal position;

[0037] A processing execution module is used to obtain the coordinates of the center of the light spot and the center of the nozzle in the machine tool coordinate system, obtain the direction and distance that the red light beam needs to move, and control the cutting head to move in the direction that the red light beam needs to move so as to align the center of the light spot and the center of the nozzle;

[0038] The comparison execution module is used to compare the distance between the center of the light spot and the center of the nozzle with a preset distance. When the distance between the center of the light spot and the center of the nozzle is lower than the preset distance, the centering adjustment is completed.

[0039] The present invention has at least the following beneficial effects:

[0040] The laser beam centering adjustment method provided by the present invention can automatically expose the light spot formed by the red light beam in the camera field of view, and automatically focus the focus of the red light beam to obtain the best focus position, so as to obtain the coordinates of the center of the light spot in the machine tool coordinate system, and control the movement of the cutting head according to the obtained coordinates so that the distance between the nozzle center and the light spot center and the nozzle center coordinates is lower than the preset distance, so as to achieve the purpose of laser beam centering adjustment. Since the image of the light spot at the best focus is the smallest and closest to the circle (because the energy density of the red light on the imaging surface is the highest at this time), the accuracy of the fitted circle is the highest, and the accuracy of the red light center position detected is also the highest, so the accuracy of the laser beam centering adjustment will also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0042] Figure 1 A schematic diagram of the structure of a visual inspection system provided by an embodiment of the present invention;

[0043] Figure 2 A main flow chart of a laser beam centering adjustment method provided by an embodiment of the present invention;

[0044] Figure 3 A detailed flow chart of a laser beam centering adjustment method provided by an embodiment of the present invention;

[0045] Figure 4 A block diagram of a laser beam centering adjustment device provided in an embodiment of the present invention.

[0046] In the figure:

[0047] 1. Red light beam; 2. Cutting head; 3. Nozzle; 4. Camera;

[0048] 301, first acquisition module; 302, second acquisition module; 303, processing acquisition module; 304, processing execution module; 305, comparison execution module. DETAILED DESCRIPTION

[0049] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0050] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" 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 an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between 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.

[0051] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0052] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0053] In order to solve the problem in the prior art that the coaxiality of the laser and the nozzle can only be checked and adjusted manually, the present invention provides a laser beam centering adjustment method and device, which can automatically obtain the red light spot that is easiest to detect the center for lasers of various powers and red light intensities, thereby improving the accuracy of subsequent centering.

[0054] Figure 1 A schematic diagram of the structure of a visual inspection system provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the method provided by the present invention is applied to a visual inspection system, which includes a visual module, a cutting head 2, a master control software / industrial control software, a visual software, a motor and a nozzle 3 installed on the cutting head 2, wherein the cutting head 2 provides a function of intelligently adjusting the laser focus position; the visual module has a camera 4, and the visual software is used to control the visual module. The laser is connected to the cutting head 2, and the laser emits a red light beam 1 with controllable position and intensity under the control of the master control software; the motor is responsible for the movement of the cutting head 2 on the machine tool; the visual module is arranged opposite to the nozzle 3 to obtain an image of the nozzle 3; the master control software / industrial control software controls the movement of the cutting head 2 and the laser position and focus adjustment, and the visual software performs centering detection.

[0055] The master control software / industrial control software is used to control the movement of the machine tool and the cutting head 2. The master control software controls the visual software to perform automatic exposure, focus evaluation, distance calculation and other actions through communication.

[0056] The master control software issues a command to control the cutting head 2 to move to the top of the vision module. The vision module is used to capture the image of the lower end surface of the nozzle 3. The image detection algorithm is applied to fit the inner circle of the nozzle and obtain the coordinates of its center in the image coordinate system. At this time, the laser is in a non-emitting state.

[0057] Figure 2 The main flow chart of the laser beam centering adjustment method provided by the present invention is as follows: Figure 2 As shown, the laser beam centering adjustment method includes the following steps:

[0058] S101, obtaining the nozzle center coordinates of the image center of the lower end surface of the nozzle 3 in the image coordinate system;

[0059] Specifically, the image of the lower end of the nozzle 3 can be obtained through the visual module. Before obtaining the image of the lower end face of the nozzle 3, an instruction is issued through the master control software to control the cutting head 2 to move to the top of the visual module, and the auxiliary light source of the camera 4 is turned on to ensure that the lower end face of the nozzle 3 is obtained. After obtaining the image of the lower end face of the nozzle 3, the image detection algorithm is applied to fit the inner circle of the nozzle 3 in the image to obtain the coordinates of the center of the inner circle in the image coordinate system, that is, the position of the inner hole of the nozzle is found through the circle fitting algorithm, and then the coordinates of the center of the nozzle are obtained. At this time, the laser is in a state of not emitting light. It should be noted that the image detection algorithm is a prior art and will not be repeated here.

[0060] S102, controlling the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle 3;

[0061] Specifically, the light spot is obtained through a visual module. The red light beam is a red laser beam.

[0062] S103, automatically exposing and automatically focusing the light spot to obtain an optimal focal position and adjusting the focus of the red light beam to the optimal focal position;

[0063] S104, obtaining the coordinates of the center of the light spot and the center of the nozzle 3 in the machine tool coordinate system, obtaining the direction and distance that the red light beam needs to move, and controlling the cutting head 2 to move in the direction that the red light beam needs to move to align the center of the light spot and the center of the nozzle 3;

[0064] Obtain the coordinates of the center of the light spot in the image coordinate system. The coordinates of nozzle 3 in the image coordinate system have been obtained in advance. Then, the coordinates of the center of the light spot and the center of the nozzle are converted from the image coordinate system to the machine tool coordinate system. The conversion relationship between the two coordinate systems is determined by the camera installation posture.

[0065] Repeat steps S101-S104 until the distance between the center of the light spot and the center of the nozzle 3 is lower than the preset distance, and the centering adjustment is completed.

[0066] The laser beam centering adjustment method provided by the present invention can automatically expose the light spot formed by the red light beam in the field of view of the camera 4, and automatically focus the focus of the red light beam to obtain the best focus position, so as to obtain the coordinates of the center of the light spot in the machine tool coordinate system, and control the movement of the cutting head 2 according to the obtained coordinates so that the distance between the center of the nozzle 3 and the center of the light spot and the center of the nozzle 3 is lower than the preset distance, so as to achieve the purpose of laser beam centering adjustment. Since the image of the light spot at the best focus is the smallest and closest to the circle (because the energy density of the red light on the imaging surface is the highest at this time), the accuracy of the fitted circle is the highest, and the accuracy of the detected red light center position is also the highest, so the accuracy of the laser beam centering adjustment will also be improved.

[0067] It should be noted that the position of the best focus is affected by many factors, including but not limited to the cutting head model, laser model, laser intensity, etc. After determining the best focus, it is possible to avoid changes in the focus due to the above-mentioned factors, which may cause changes in the spot image. This can avoid a decrease in the detection accuracy of the spot center.

[0068] To obtain the coordinates of the light spot center and the nozzle center in the machine tool coordinate system, first calculate the coordinates of the light spot center in the image coordinate system, and then convert the two coordinates of the light spot center and the nozzle center from the image coordinate system to the machine tool coordinate system. The conversion relationship between the two coordinate systems is determined by the camera installation posture.

[0069] In some embodiments, automatically exposing the light spot includes: adjusting the exposure time of the camera 4 in the visual module within a preset range, evaluating the changed image each time the exposure time is adjusted to obtain an evaluation value, and if the evaluation value reaches the preset evaluation value, the automatic exposure process ends and the automatic exposure is successful.

[0070] Specifically, the vision software automatically adjusts the exposure time of the camera 4 in the vision module within a preset range. Each time the exposure time is adjusted, the changed image is evaluated by an algorithm. If the evaluation value reaches a preset evaluation value, the automatic exposure process ends and the automatic exposure is successful.

[0071] The preset range is obtained through multiple test experiments. During the test, a value is taken for each available exposure time, and an image corresponding to the exposure time is collected; an algorithm is applied to evaluate each exposed image to obtain an evaluation score; when the evaluation score reaches the preset threshold range, the exposure time corresponding to the image is taken as the optimal exposure time.

[0072] Furthermore, the changed image is evaluated, including converting the changed image obtained by the camera after each exposure time adjustment into a single-channel image, then calculating its grayscale mean, and obtaining the target grayscale mean under ideal conditions through testing; if the difference is within the threshold range, it is considered that the optimal exposure has been achieved. Among them, the single-channel image is a digital image containing only a single color dimension, and each pixel only stores a brightness value, which is used to represent the grayscale level. By obtaining the grayscale mean of the single-channel image to determine whether the image has achieved the optimal exposure, the coordinates of the center of the image obtained later can be guaranteed to be more accurate.

[0073] Since there may be a delay in the response of camera 4 to the modification of the exposure time parameters, in order to ensure that the corresponding image after the exposure parameters are modified is obtained, the present embodiment is performed in the following manner: the currently exposed image is saved before the exposure time is modified; after the exposure time is modified, the image is taken repeatedly for multiple times, and then the obtained image is differentiated from the image before the exposure time is modified, and the difference between the two is quantified from the perspective of pixel grayscale (that is, the grayscale mean of the difference image is calculated, and the larger the grayscale mean value, the larger the difference between the two images); if the difference reaches the preset threshold, it is considered that the image after the exposure time is modified has been obtained.

[0074] In some embodiments, after exposing the image, it is necessary to automatically focus the light spot, and automatically focusing the light spot includes:

[0075] Adjust the position of the lens in the cutting head 2 to control the focus position of the red light beam to move within the adjustable range of the focus lens position of the cutting head 2;

[0076] Each time the focus of the red light beam moves to a specified position, the focus degree of the red light beam needs to be evaluated;

[0077] Acquire the spot image at the current position with the exposure time calculated in the automatic exposure process;

[0078] Specifically, the camera 4 in the visual module is controlled to obtain the spot image of the current position of the red light beam according to the exposure time calculated in the automatic exposure process.

[0079] The spot image is processed to obtain an evaluation score for the current spot image, and the laser focus position with the best evaluation score is selected as the best focus position.

[0080] The automatic exposure process obtains a clear edge of the light spot in the image, and the purpose of focusing the light spot is to adjust the laser focus so that the white area of ​​the light spot in the image is the smallest and closest to a perfect circle. At this time, the obtained light spot has the highest accuracy in fitting a circle from the image.

[0081] Therefore, an evaluation score is given to the light spot image based on the two dimensions of the roundness and size of the light spot, and the position with the best evaluation score is the best focusing position required by the method.

[0082] Furthermore, the spot image is processed including: performing single-channel, filtering and threshold processing on the spot image in sequence, then performing contour extraction and circle fitting on the processed image, and finally providing a final evaluation score based on the comprehensive roundness and the size of the fitted circle.

[0083] It should be noted that the roundness and the size of the fitted circle are two specific values, and the evaluation score is obtained by weighted summing the two values, where the strengthening coefficient is obtained based on multiple tests.

[0084] After the image is automatically exposed and automatically focused, the most ideal spot image can be obtained, and then the algorithm is processed to obtain the center coordinates with the highest accuracy. In this way, the cutting head 2 can be controlled to move in the direction in which the red light beam 1 needs to move, so as to adjust the red light beam 1. The specific adjustment includes the following steps:

[0085] Adjust the focus of the red light beam 1 to the best focus position obtained;

[0086] The exposure time is adjusted to the best exposure time obtained to obtain the best spot image;

[0087] Performing image processing on the best spot image to obtain the coordinates of the center of the spot in the machine tool coordinate system, and obtaining the coordinates of the center of the nozzle 3 in the machine tool coordinate system;

[0088] According to the coordinates of the center of the light spot in the machine tool coordinate system and the coordinates of the center of the nozzle 3 in the machine tool coordinate system, the direction and distance that the red light beam 1 needs to move are obtained, and the cutting head 2 is controlled to move in this direction.

[0089] The above-mentioned execution steps can determine the direction and distance that the red light beam 1 needs to move, thereby achieving the purpose of adjusting the position of the cutting head 2.

[0090] After the movement, the light spot is obtained again and the light spot is automatically exposed and automatically focused to obtain the best focal position until the distance between the center of the light spot and the center of the nozzle 3 is lower than the preset distance.

[0091] Performing image processing on the best spot image to obtain the coordinates of the spot center in the machine tool coordinate system, and obtaining the coordinates of the nozzle 3 center in the machine tool coordinate system includes:

[0092] Performing image processing on the best spot image to obtain the coordinates of the spot center in the image coordinate system;

[0093] The coordinates of the center of the light spot in the image coordinate system are converted into the coordinates of the center of the light spot in the machine tool coordinate system, and the coordinates of the center of the nozzle 3 in the image coordinate system are converted into the coordinates of the center of the nozzle 3 in the machine tool coordinate system.

[0094] Since the image coordinate system is different from the machine tool coordinate system, in order to enable the center of the light spot and the center of the nozzle 3 to move in direction and distance in the same coordinate system, the center of the light spot and the center of the nozzle 3 need to be converted to the same coordinate system, so that the alignment purpose of the center of the light spot and the center of the nozzle 3 can be achieved.

[0095] Figure 3 The detailed flow chart of the laser beam centering adjustment method is as follows: Figure 3 As shown, the laser beam centering adjustment method specifically includes the following steps:

[0096] S201, obtaining the center coordinates of the nozzle 3 at the center of the image of the lower end surface of the nozzle 3 in the image coordinate system;

[0097] S202, controlling the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle 3;

[0098] S203, adjusting the exposure time of the camera in the visual module within a preset range, and evaluating the changed image to obtain an evaluation value each time the exposure time is adjusted. If the evaluation value reaches a preset evaluation value, the automatic exposure process ends and the automatic exposure is successful;

[0099] S204, adjusting the position of the lens in the cutting head 2 to control the focus position of the red light beam 1 to move within the adjustable range of the focus lens position of the cutting head 2;

[0100] S205, each time the focus of the red light beam 1 moves to a specified position, the focus degree of the red light beam 1 needs to be evaluated;

[0101] S206, acquiring a spot image at the current position using the exposure time calculated in the automatic exposure process;

[0102] S207, processing the spot image to obtain an evaluation score for the current spot image, and selecting a laser focus position with the best evaluation score as the best focus position;

[0103] S208, adjusting the focus of the red light beam 1 to the best focus position obtained;

[0104] S209, adjusting the exposure time to the obtained optimal exposure time to obtain the best spot image;

[0105] S210, performing image processing on the best light spot image to obtain the coordinates of the light spot center in the image coordinate system;

[0106] S211, based on the coordinates of the light spot center in the image coordinate system and the coordinates of the nozzle center in the image coordinate system, obtain the coordinates of the light spot center in the machine tool coordinate system and the coordinates of the nozzle center in the machine tool coordinate system, and according to the coordinates of the light spot center in the machine tool coordinate system and the coordinates of the nozzle center in the machine tool coordinate system, obtain the direction and distance that the red light beam 1 needs to move, and control the cutting head 2 to move in this direction;

[0107] S212, after the cutting head 2 moves, the light spot is obtained again and the light spot is automatically exposed and automatically focused to obtain the best focal position until the distance between the center of the light spot and the center of the nozzle is lower than the preset distance.

[0108] The present invention also provides a laser beam centering adjustment device, which is used to perform the method provided by the present invention. Figure 4The block diagram of the laser beam centering adjustment device provided by the present invention comprises a first acquisition module 301, a second acquisition module 302, a processing acquisition module 303, a processing execution module 304 and a comparison execution module 305, wherein the first acquisition module 301 is used to obtain the image of the lower end surface of the nozzle and the coordinates of the nozzle center in the image coordinate system; the second acquisition module 302 is used to control the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle; the processing acquisition module 303 is used to automatically expose and automatically focus the light spot to obtain the best focal position; the processing execution module 304 is used to calculate the coordinates of the light spot center and the nozzle center, calculate the direction and distance that the red light beam needs to move, and control the cutting head to move in the direction that the red light beam needs to move to center the light spot center and the nozzle center; the comparison execution module 305 is used to compare the distance between the light spot center and the nozzle center with a preset distance, and the centering adjustment is completed when the distance between the light spot center and the nozzle center is lower than the preset distance.

[0109] Due to the laser beam centering adjustment device provided by the present invention, the light spot formed by the red light beam in the camera field of view can be automatically exposed, and the focus of the red light beam can be automatically focused to obtain the best focus position, so as to obtain the coordinates of the center of the light spot in the machine tool coordinate system, and the cutting head is controlled to move according to the obtained coordinates so that the distance between the nozzle center and the light spot center and the nozzle center coordinates is lower than the preset distance, so as to achieve the purpose of laser beam centering adjustment. Since the image of the light spot at the best focus is the smallest and closest to the circle (because the energy density of the red light on the imaging surface is the highest at this time), the accuracy of the fitted circle is the highest, and the accuracy of the detected red light center position is also the highest.

[0110] In order to ensure that the appropriate red light spot can be automatically obtained in any situation, the automatic adjustment process is carried out, including the automatic exposure and automatic focusing control process and the image detection algorithm used therein, so as to ensure that for lasers of various powers and red light intensities, the red light spot with the easiest center detection can be automatically obtained, thereby improving the accuracy of subsequent centering.

[0111] In addition, the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A laser beam centering adjustment method, characterized in that: The steps include: S101, obtaining the nozzle center coordinates of the nozzle lower end surface image center in the image coordinate system; S102, controlling the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle; S103, automatically exposing and automatically focusing the light spot to obtain an optimal focal position and adjusting the focus of the red light beam to the optimal focal position; S104, obtaining the coordinates of the center of the light spot and the center of the nozzle in the machine tool coordinate system, obtaining the direction and distance that the red light beam needs to move, and controlling the cutting head to move in the direction that the red light beam needs to move to align the center of the light spot and the center of the nozzle; Repeat steps S101-S104 until the distance between the center of the light spot and the center of the nozzle is lower than the preset distance, and the centering adjustment is completed.

2. The laser beam centering adjustment method according to claim 1, characterized in that: Automatic exposure of the spot includes: The exposure time of the camera in the visual module is adjusted within a preset range. Each time the exposure time is adjusted, the changed image is evaluated to obtain an evaluation value. If the evaluation value reaches the preset evaluation value, the automatic exposure process ends and the automatic exposure is successful.

3. The laser beam centering adjustment method according to claim 2, characterized in that: Evaluating the changed image to obtain an evaluation value includes: The changed image obtained by the camera after each adjustment of the exposure time is converted into a single-channel image and the grayscale mean of the single-channel image is calculated. If the difference with the target grayscale mean obtained in the pre-test is within the threshold range, it is considered that the optimal exposure has been achieved.

4. The laser beam centering adjustment method according to claim 2, characterized in that: Before modifying the exposure time, save the currently exposed image; after modifying the exposure time, take images repeatedly for several times, then make a difference between the obtained image and the image before modifying the exposure time, and quantify the difference between the two from the perspective of pixel grayscale; If the difference reaches a preset threshold, it is considered that the image after the modified exposure time has been acquired.

5. The laser beam centering adjustment method according to claim 1, characterized in that: Automatic focusing of the light spot includes: Adjusting the position of the lens in the cutting head to control the focus position of the red light beam to move within the adjustable range of the focus lens position of the cutting head; Each time the focus of the red light beam moves to a specified position, the focus degree of the red light beam needs to be evaluated; Acquire the spot image at the current position with the exposure time calculated in the automatic exposure process; The spot image is processed to obtain an evaluation score for the current spot image, and the laser focus position with the best evaluation score is selected as the best focus position.

6. The laser beam centering adjustment method according to claim 5, characterized in that: The processing of the spot image includes: performing single-channel, filtering and threshold processing on the spot image in sequence, then performing contour extraction and circle fitting on the processed image, and finally giving the final evaluation score by combining the roundness and the size of the fitted circle.

7. The laser beam centering adjustment method according to claim 1, characterized in that: Controlling the cutting head to move in the direction where the red light beam needs to move includes: Adjust the focus of the red light beam to the best focus position obtained; The exposure time is adjusted to the best exposure time obtained to obtain the best spot image; Performing image processing on the best spot image to obtain the coordinates of the spot center in the machine tool coordinate system, and obtaining the coordinates of the nozzle center in the machine tool coordinate system; According to the coordinates of the center of the light spot in the machine tool coordinate system and the coordinates of the center of the nozzle in the machine tool coordinate system, the direction and distance that the red light beam needs to move are obtained, and the cutting head is controlled to move in this direction.

8. The laser beam centering adjustment method according to claim 7, characterized in that: After the cutting head moves, the light spot is obtained again and the light spot is automatically exposed and automatically focused to obtain the best focal position until the distance between the center of the light spot and the center of the nozzle is lower than the preset distance.

9. The laser beam centering adjustment method according to claim 7, characterized in that: Image processing is performed on the optimal spot image to obtain the coordinates of the spot center in the machine tool coordinate system, and the coordinates of the nozzle center in the machine tool coordinate system are obtained including: Performing image processing on the best spot image to obtain the coordinates of the spot center in the image coordinate system; The coordinates of the center of the light spot in the image coordinate system are converted into the coordinates of the center of the light spot in the machine tool coordinate system, and the coordinates of the center of the nozzle in the image coordinate system are converted into the coordinates of the center of the nozzle in the machine tool coordinate system.

10. A laser beam centering adjustment device, characterized in that: The method for executing any one of claims 1 to 9 comprises: A first acquisition module is used to obtain the nozzle center coordinates of the nozzle lower end surface image center in the image coordinate system; A second acquisition module is used to control the laser to emit a red light beam to obtain a light spot formed by the red light beam on the lower end surface of the nozzle; A processing and acquisition module, used for automatically exposing and automatically focusing the light spot to obtain an optimal focal position and adjusting the focus of the red light beam to the optimal focal position; A processing execution module is used to obtain the coordinates of the center of the light spot and the center of the nozzle in the machine tool coordinate system, obtain the direction and distance that the red light beam needs to move, and control the cutting head to move in the direction that the red light beam needs to move so as to align the center of the light spot and the center of the nozzle; The comparison execution module is used to compare the distance between the center of the light spot and the center of the nozzle with a preset distance. When the distance between the center of the light spot and the center of the nozzle is lower than the preset distance, the centering adjustment is completed.

Images