Method for confirming laser focal length

Abstract

This invention belongs to the field of laser processing technology, and specifically relates to a method for confirming laser focal length. This method divides a first preset focal length range into a first number of first focal length points; selects a fine-tuning focal length point from all the first focal length points, and controls the laser to process a first set of light spots corresponding to the fine-tuning focal length point on the workpiece; wherein each set of first light spots includes multiple first light spots distributed along the X-axis and multiple second light spots distributed along the Y-axis; determines a first overlap rate between the first light spots in each first set of light spots, and a second overlap rate between the second light spots; determines the deviation value between the first overlap rate and the second overlap rate corresponding to each first set of light spots; and determines the fine-tuning focal length corresponding to the first set of light spots with the smallest deviation value as the target focal length. This invention can accurately locate the target focal length position with high precision.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, and in particular relates to a method for determining laser focal length. Background Technology

[0002] With the continuous advancement of laser technology, laser cutting machines are being used more and more widely. Laser cutting machines utilize an F-THETA field lens (hereinafter referred to as "field lens") to focus the laser beam onto a table for cutting. The focal length of the laser cutting machine is adjusted by changing the z-axis height of the platform or laser cutting head. The farther the focal length of the laser cutting machine, the larger the spot size and the lower the cutting efficiency. Therefore, finding the appropriate focal length is a crucial step in laser cutting. However, the laser spot size of a laser cutting machine is focused to a diameter of only tens of micrometers, invisible to the naked eye, making it extremely difficult to accurately find the appropriate focal length.

[0003] In existing technologies, the linewidth method is commonly used to determine the focal length. This method measures the actual linewidth of the pattern cut from the platform and identifies the position with the thinnest linewidth and the most uniform linewidth along the X and Y axes as the location of the laser focal length. However, in certain scenarios (such as 532nm lasers and large focal length field lenses), due to factors such as stray green light and long depth of focus, the linewidth of the platform remains essentially the same over a large z-axis range (e.g., -1mm to +1mm). (In reality, the spot size and shape differ from -1mm to +1mm, resulting in different energy superposition rates and processing efficiencies). Therefore, using linewidth as the determining factor can lead to inaccurate focal length determination in certain scenarios. Summary of the Invention

[0004] This invention solves the technical problem of inaccurate focal length when using the linewidth method to find the focal length in the prior art, and provides a method for confirming the focal length of a laser.

[0005] In view of the above problems, the present invention provides a method for confirming laser focal length, comprising:

[0006] Divide the first preset focal length range into a first number of first focal length points;

[0007] A fine-tuning focal point is selected from all the first focal points, and the focal length of the field lens is adjusted to the fine-tuning focal point. The laser is then controlled to process a first light spot group on the workpiece corresponding to the fine-tuning focal point. Each first light spot group includes a plurality of first light spots distributed along the X-axis and a plurality of second light spots distributed along the Y-axis.

[0008] In each of the first light spot groups, a first overlap rate between each of the first light spots and a second overlap rate between each of the second light spots are determined;

[0009] Determine the deviation between the first overlap rate and the second overlap rate for each of the first light spot groups;

[0010] The fine-tuned focal length corresponding to the first spot group with the smallest deviation value is determined as the target focal length.

[0011] Optionally, before dividing the first preset focal length range into a first number of first focal length points, the method further includes:

[0012] Divide the second preset focal length range, which includes the first preset focal length range, into several second focal length points;

[0013] Select a coarse adjustment focal point from all the second focal points, adjust the focal length of the field lens to the coarse adjustment focal point, and control the field lens to process the second light spot group on the workpiece.

[0014] Determine the diameter of the third spot corresponding to all the second spot groups;

[0015] Determine the coarse focus points corresponding to the second number of second light spot groups with the smallest light spot diameter among the third light spots, and determine a first preset focus range based on the second number of coarse focus points, wherein the first number is greater than the second number and the second number is greater than 2.

[0016] Optionally, determining the first preset focal length range based on the second number of coarse focal length adjustment points includes:

[0017] The maximum value among the second number of coarse focus adjustment points is taken as the upper limit of the first preset focus range;

[0018] The minimum value among the second number of coarse focus adjustment points is taken as the lower limit of the first preset focus range.

[0019] Optionally, each group of second light spots includes multiple third light spots distributed at linear intervals, and the groups of second light spots are arranged in parallel.

[0020] Optionally, determining the diameter of the third spot corresponding to all the second spot groups includes:

[0021] Determine the diameter of the third spot corresponding to all the second spot groups under a microscope.

[0022] Optionally, dividing the first preset focal length range into a first number of first focal length points includes:

[0023] Obtain a preset fine-tuning focal length interval, and divide the first preset focal length range evenly into a first number of first focal length points according to the preset fine-tuning focal length interval.

[0024] Optionally,

[0025] The step of adjusting the focal length of the field lens to the fine-tuning focal length point includes:

[0026] Keeping the laser position unchanged, move the workpiece along the Z-axis to adjust the focal length of the field lens to the fine-tuning focal length point.

[0027] Optionally, the field mirror is mounted at the output end of the laser, which is a picosecond laser or a nanosecond laser.

[0028] Optionally, minimizing the deviation value includes:

[0029] Both the first overlap rate and the second overlap rate are zero.

[0030] Optionally, determining the first overlap rate between each of the first light spots in each first light spot group and the second overlap rate between each of the second light spots includes:

[0031] Under a microscope, the first overlap rate between each first light spot in each first light spot group and the second overlap rate between each second light spot were determined.

[0032] In this invention, the focal length between the field lens and the workpiece is adjusted to a fine-tuning focal length point. At each fine-tuning focal length point, the field lens processes a first light spot distributed along the X-axis and a second light spot distributed along the Y-axis on the workpiece. By observing the overlap rate of the first and second light spots, the fine-tuning focal length point corresponding to the smallest deviation between their overlap rates is determined as the target focal length position. Compared to existing methods that use linewidth as a criterion, the laser focal length confirmation method of this invention can more accurately locate the focal length position, improving its applicability in practical scenarios. Furthermore, based on the accurate determination of the laser focal length, it also improves the processing accuracy and quality of the laser. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0035] Figure 1 A flowchart illustrating a method for confirming laser focal length according to an embodiment of the present invention;

[0036] Figure 2 for Figure 1 Flowchart prior to step S100;

[0037] Figure 3 This is a schematic diagram of a first light spot group provided in an embodiment of the present invention, where the first light spot has a high overlap rate and the second light spot has a low overlap rate.

[0038] Figure 4 This is a schematic diagram showing the overlap rate of the first and second light spots in a first light spot group provided in an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram of a first light spot group provided in an embodiment of the present invention, where the first light spot has a low overlap rate and the second light spot has a high overlap rate.

[0040] Figure 6 This is a schematic diagram of each second spot group of laser focal length provided in an embodiment of the present invention.

[0041] The reference numerals in the accompanying drawings are as follows:

[0042] 1. First light spot group; 11. First light spot; 12. Second light spot;

[0043] 2. Second spot group; 21. Third spot. Detailed Implementation

[0044] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0045] It should be understood that the terms "upper", "lower", "left", "right", "front", "rear", "middle", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. 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 orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations of the present invention.

[0046] like Figure 1 As shown, one embodiment of the present invention provides a method for confirming the focal length of a laser, comprising:

[0047] S100, Divide the first preset focal length range into a first number of first focal length points.

[0048] Understandably, the first preset focal length range is relatively small. When the focal length between the field lens and the workpiece moves within the first preset focal length range, the size and shape of the light spot on the workpiece cannot be directly distinguished by the naked eye. The number of the first focal length points can be set according to actual needs. That is, the first preset focal length range can be divided into multiple small intervals, and the endpoints between each interval are the first focal length points.

[0049] In one specific embodiment, dividing the first preset focal length range into a first number of first focal length points (i.e., S100) includes:

[0050] A preset fine-tuning focal length interval is obtained, and the first preset focal length range is evenly divided into a first number of first focal length points according to the preset fine-tuning focal length interval. It can be understood that, firstly, the fine-tuning focal length interval is determined according to the first preset focal length range, and then the first preset focal length range is divided into a first preset number of first focal length points; that is, the length between two adjacent first focal length points is the fine-tuning focal length interval.

[0051] It should be noted that a laser processing device generally includes a laser and a processing platform. The laser includes a laser body and a field lens installed at the output end of the laser body. The workpiece to be processed is placed on the processing platform, and the laser emitted by the field lens can perform laser processing on the workpiece on the processing platform.

[0052] S200. Select a fine-tuning focal point from all the first focal points, adjust the focal length of the field lens to the fine-tuning focal point, and control the field lens to process a first light spot group 1 corresponding to the fine-tuning focal point on the workpiece; wherein, each first light spot group 1 includes a plurality of first light spots 11 distributed along the X-axis direction and a plurality of second light spots 12 distributed along the Y-axis direction.

[0053] Preferably, the field lens is installed at the output end of the laser, which can be a picosecond laser, nanosecond laser, etc. Understandably, the fine-tuning focal point can be the first focal point or a focal point selected between two adjacent first focal points. Specifically, the focal length of the field lens is progressively controlled to each of the fine-tuning focal points. At each fine-tuning focal point, the laser processes a first light spot group 1 on the workpiece, thus processing the first light spot group 1 on a first number of workpieces. The first light spot group 1 includes two vertically distributed light spots, namely, multiple first light spots 11 distributed along the X-axis and multiple second light spots 12 distributed along the Y-axis.

[0054] In one specific embodiment, adjusting the focal length of the field lens to the fine-tuning focal length point includes:

[0055] Keeping the laser's position constant, the workpiece is moved along the Z-axis to adjust the focal length of the field lens to the fine-tuning focal length point. Understandably, the workpiece can be placed on a processing platform, and the position of the processing platform can be adjusted along the Z-axis to achieve the purpose of moving the workpiece along the Z-axis. It should be noted that during the movement of the workpiece along the Z-axis, the laser parameters (speed, frequency, power, etc.) remain unchanged; only the laser's focal length is changed.

[0056] S300. Determine the first overlap rate between each first light spot 11 and the second overlap rate between each second light spot 12 in each first light spot group 1. It is understood that during the adjustment of the focal length of the field lens, the roundness of both the first light spot 11 and the second light spot 12 will change. Furthermore, during the focusing process from positive to negative focus, the shape of the first light spot 11 and / or the second light spot 12 will become elliptical, and the major axis of the ellipse will gradually change from one direction to another, resulting in a continuous change in the overlap rate of the light spots in the X-axis and Y-axis directions. In a specific embodiment, during the focusing process from positive to negative focus, the overlap rate of the first light spot 11 along the X-axis is low, and the overlap rate of the second light spot 12 along the Y-axis is high (e.g., ...). Figure 3 As shown), it gradually transforms into a situation where the overlap rate of the first light spot 11 and the second light spot 12 is consistent (as shown). Figure 4 As shown), it is finally transformed into the first light spot 11 having a high overlap rate and the second light spot 12 having a low overlap rate (as shown). Figure 5 (As shown).

[0057] In one specific embodiment, determining the first overlap rate between each first light spot in each first light spot group and the second overlap rate between each second light spot (i.e., step S300) includes:

[0058] Under a microscope, the first overlap rate between each first light spot in each first light spot group and the second overlap rate between each second light spot are determined. Understandably, when adjusting the focal length between the laser and the workpiece within a first preset focal length range, the changes in the first light spot 11 and the second light spot 12 are very small. Therefore, it is necessary to observe the overlap rate of the first light spot 11 and the overlap rate of the second light spot 12 under a microscope, thereby improving the accuracy of the laser focal length confirmation method.

[0059] S400. Determine the deviation value between the first overlap rate and the second overlap rate corresponding to each of the first light spot groups 1; it can be understood that the deviation value can be determined according to the accuracy of the focal length that the laser needs to be adjusted, and the higher the accuracy of the focal length required, the smaller the deviation value.

[0060] S500: The fine-tuning focal length corresponding to the first spot group 1 with the smallest deviation value is determined as the target focal length. In a specific embodiment, the fine-tuning focal length corresponding to the first spot group 1 with a deviation value of zero is determined as the target focal length, that is, the laser has the best processing effect at this target focal length.

[0061] Preferably, minimizing the deviation value includes:

[0062] Both the first overlap rate and the second overlap rate are zero. That is, at the target focal length, the first light spots 11 distributed along the X-axis direction do not overlap with each other, and the second light spots 12 distributed along the Y-axis direction also do not overlap with each other. At this time, the deviation between the first overlap rate and the second overlap rate is 0, that is, the deviation value is the minimum.

[0063] In this invention, such as Figure 2 As shown, the focal length of the field lens is adjusted to the fine-tuning focal length point. At each of the fine-tuning focal length points, the field lens processes a first light spot 11 distributed along the X-axis and a second light spot 12 distributed along the Y-axis on the workpiece. By observing the overlap rate of the first light spot 11 and the second light spot 12, and finding the point where the deviation between the overlap rates of the first light spot 11 and the second light spot 12 is minimized, the fine-tuning focal length point corresponding to the smallest deviation is determined as the target focal length position. Compared with the existing method that uses linewidth as the determination criterion, the laser focal length confirmation method of this embodiment can more accurately find the focal length position, which not only improves the applicability to actual scenarios, but also improves the processing accuracy and quality of the laser based on the accurate determination of the laser focal length.

[0064] In one embodiment, such as Figure 2 As shown, before dividing the first preset focal length range into a first number of first focal length points (i.e., step S100), the method further includes:

[0065] S101. Divide the second preset focal length range, which includes the first preset focal length range, into several second focal length points; it can be understood that the first preset focal length range is a subset of the second preset focal length range; it can be understood that the range of the second preset focal length range is relatively large; the number of second focal length points can be set according to actual needs, that is, multiple second focal length points are selected from the second preset focal length range.

[0066] S102. Select a coarse adjustment focal point from all the second focal points, adjust the focal length of the field lens to the coarse adjustment focal point, and control the laser to process the second light spot group 2 on the workpiece. Understandably, the coarse adjustment focal point can be one of the second focal points or a focal point selected between two adjacent second focal points. Specifically, the focal length between the laser and the workpiece is gradually controlled to each of the coarse adjustment focal points. At each coarse adjustment focal point, the laser will process the second light spot group 2 on the workpiece.

[0067] In one specific embodiment, the position of the laser is kept constant, and the workpiece is moved along the Z-axis to adjust the focal length of the field lens to the coarse focal length point. Understandably, the workpiece can be placed on a processing platform, and the position of the processing platform can be adjusted along the Z-axis to achieve the purpose of moving the workpiece along the Z-axis. It should be noted that during the movement of the workpiece along the Z-axis, the parameters of the laser (speed, frequency, power, etc.) remain unchanged; only the focal length of the laser is changed.

[0068] S103. Determine the diameter of the third spot 21 corresponding to all the second spot groups 2. Preferably, the diameter of the third spot corresponding to all the second spot groups 2 is determined under a microscope. The size of the diameter of the third spot 21 in the second spot group 2 can be directly measured under a microscope, or the size of the diameter of the third spot 21 in the second spot group 2 can be directly observed with the naked eye.

[0069] S104. Determine the coarse focus points corresponding to the second number of second spot groups 2 with the smallest spot diameter among the third spot 21, and determine a first preset focal length range based on the second number of coarse focus points, wherein the first number is greater than the second number, and the second number is greater than 2. Understandably, during the process of gradually reducing the focal length between the field lens and the workpiece, the diameter of the third spot 21 first gradually decreases and then gradually increases. In a specific embodiment, three third spot 21s with the smallest spot diameter are found in each second spot group 2 (i.e., the second preset number equals 3), and the focal length range corresponding to these three second spot groups 2 is the first preset spot range; it should be noted that the first preset number is greater than 3. In this embodiment, the first preset focal length range is first searched within the larger second preset focal length range, and then the target focal length position is searched within the smaller first preset focal length range, thereby improving the efficiency of the laser focal length confirmation method.

[0070] In one embodiment, determining the first preset focal length range based on a second number of coarse focus adjustment points includes:

[0071] The maximum value among the second number of coarse adjustment focus points is taken as the upper limit of the first preset focal length range, and the minimum value among the second number of coarse adjustment focus points is taken as the lower limit of the first preset focal length range. It can be understood that when the second number equals 3, the largest of the three coarse adjustment light spots corresponding to the second light spot group 2 is the upper limit of the first preset focal length range, and the smallest of the three coarse adjustment light spots corresponding to the second light spot group 2 is the lower limit of the first preset focal length range.

[0072] In one embodiment, such as Figure 6 As shown, each group of second light spot groups 2 includes a plurality of third light spots 21 arranged in a straight line at intervals, and the groups of second light spot groups 2 are arranged in parallel. It can be understood that each coarse focus adjustment point is used to process the second light spot group 2 on the same workpiece. The second light spot group 2 consists of a plurality of third light spots 21 arranged in a straight line at intervals, and the groups of second light spot groups 2 are parallel to each other. In this embodiment, multiple second light spot groups 2 are processed on the same workpiece, thereby facilitating the comparison of the sizes of the third light spots 21 in each second light spot group 2.

[0073] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of confirming a focal point of a laser, characterized by, include: Divide the first preset focal length range into a first number of first focal length points; A fine-tuning focal point is selected from all the first focal points, and the focal length of the field lens is adjusted to the fine-tuning focal point. The field lens is then controlled to process a first spot group corresponding to the fine-tuning focal point on the workpiece. Each first spot group includes multiple first light spots distributed along the X-axis and multiple second light spots distributed along the Y-axis. The fine-tuning focal point refers to one of the first focal points selected from all the first focal points, or a focal point selected between two adjacent first focal points. Adjusting the focal length of the field lens to the fine-tuning focal point includes: keeping the position of the laser unchanged and moving the workpiece along the Z-axis to adjust the focal length of the field lens to the fine-tuning focal point. In each of the first light spot groups, a first overlap rate between each of the first light spots and a second overlap rate between each of the second light spots are determined; Determine the deviation between the first overlap rate and the second overlap rate for each of the first light spot groups; The fine-tuned focal length corresponding to the first spot group with the smallest deviation value is determined as the target focal length.

2. The method of claim 1, wherein Before dividing the first preset focal length range into a first number of first focal length points, the method further includes: Divide the second preset focal length range, which includes the first preset focal length range, into several second focal length points; Select a coarse adjustment focal point from all the second focal points, adjust the focal length of the field lens to the coarse adjustment focal point, and control the field lens to process the second light spot group on the workpiece. Determine the diameter of the third spot corresponding to all the second spot groups; Determine the coarse focus points corresponding to the second number of second light spot groups with the smallest light spot diameter among the third light spots, and determine a first preset focus range based on the second number of coarse focus points, wherein the first number is greater than the second number and the second number is greater than 2.

3. The method of claim 2, wherein The step of determining the first preset focal length range based on the second number of coarse focal length adjustment points includes: The maximum value among the second number of coarse focus adjustment points is taken as the upper limit of the first preset focus range; The minimum value among the second number of coarse focus adjustment points is taken as the lower limit of the first preset focus range.

4. The method of claim 2, wherein Each group of the second light spot includes multiple third light spots distributed at linear intervals, and the second light spot groups in each group are arranged in parallel.

5. The method of claim 2, wherein Determining the diameter of the third spot corresponding to all the second spot groups includes: Determine the diameter of the third spot corresponding to all the second spot groups under a microscope.

6. The method of claim 1, wherein The step of dividing the first preset focal length range into a first number of first focal length points includes: Obtain a preset fine-tuning focal length interval, and divide the first preset focal length range evenly into a first number of first focal length points according to the preset fine-tuning focal length interval.

7. The method of claim 1, wherein The field mirror is installed at the output end of the laser, which is a picosecond laser or a nanosecond laser.

8. The method of claim 1, wherein The minimum deviation value includes: Both the first overlap rate and the second overlap rate are zero.

9. The method of claim 1, wherein Determining the first overlap rate between each first light spot in each first light spot group and the second overlap rate between each second light spot includes: Under a microscope, the first overlap rate between each first light spot in each first light spot group and the second overlap rate between each second light spot were determined.

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