Three-dimensional removal processing system, generation device for processing program, method for manufacturing three-dimensional molded object, and program

Abstract

To avoid deterioration of processing quality that may occur as the size of a workpiece increases.SOLUTION: A three-dimensional removal processing system utilizing pulse laser irradiation includes a laser scanning head, a stage that supports a workpiece, and a control unit. The laser scanning head and the stage are movable relative to each other. The control unit controls irradiation of the laser beam from the laser scanning head on the workpiece and the relative movement between the laser scanning head and the stage on the basis of a processing program. The processing program includes instructions regarding the irradiation order of the laser beam on a plurality of irradiation regions, each having a predetermined size. The plurality of irradiation regions is obtained by dividing each of a plurality of layers which is obtained by dividing a three-dimensional model in the target shape in the thickness direction such that the division lines are offset from each other.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] The present invention relates to a three-dimensional removal processing system, a processing program generation device, and a method for manufacturing a three-dimensional object. The present invention also relates to a program for a processing program generation device for a three-dimensional removal processing system.

Background Art

[0002] Three-dimensional removal processing using laser beam irradiation instead of using machine tools such as end mills is known. For example, Patent Document 1 below discloses a laser processing device having a laser beam irradiation mechanism and a stage for holding a workpiece. In the laser processing device of Patent Document 1, a processing target region of the workpiece is divided into a plurality of regions, and laser beam scanning is performed for each of the divided regions.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a method of dividing a processing target region into a plurality of regions and performing laser beam scanning for each of these plurality of regions, a non-negligible difference in processing quality may occur between the vicinity of the center and the peripheral portion of each region. That is, due to the discontinuity of the scanning, a relative decrease in processing quality may be observed at the boundary portion between adjacent regions.

Means for Solving the Problems

[0005] According to the present invention, the following inventions are provided. [1] A three-dimensional removal processing system using pulsed laser irradiation, comprising a laser scanning head, a stage for supporting a workpiece, and a control unit, wherein the laser scanning head and the stage are relatively movable with respect to each other, and the control unit controls the irradiation of a laser beam from the laser scanning head to the workpiece and the relative movement between the laser scanning head and the stage based on a processing program. Here, the processing program includes instructions regarding the irradiation order of the laser beam for a plurality of irradiation regions each having a predetermined size, and the plurality of irradiation regions are regions defined by dividing each of a plurality of layers obtained by dividing a three-dimensional model of a target shape in the thickness direction such that the dividing lines are offset from each other. The laser scanning head removes a part of the workpiece by scanning the surface of the workpiece with a laser beam in units of the irradiation regions. [2] The system according to [1], wherein the control unit controls the laser scanning head and the stage so as not to change the distance from the laser scanning head to the stage and the position of the beam waist of the laser beam in the removal processing for a part of the layers that are continuous in the thickness direction among the plurality of layers. [3] The system according to [1] or [2], wherein the control unit causes the laser scanning head to perform removal processing in units of the irradiation regions in an irradiation order that minimizes the distance of the relative movement locus of the laser scanning head with respect to the stage or the processing time from the irradiation of the laser beam from the laser scanning head until the target shape is obtained from the workpiece. [4] The system according to any one of [1] to [3], wherein the control unit causes the laser scanning head to selectively perform laser scanning on the irradiation regions among the plurality of irradiation regions that include at least a part of the target shape. The system according to any one of [1] to [4], wherein the control unit determines the irradiation order by rearranging the labels of the irradiation regions based on predetermined conditions, and causes the laser scanning head to perform removal processing in units of the irradiation regions in the irradiation order. The system according to any one of [1] to [5], further comprising a laser light source optically coupled to the laser scanning head, wherein the laser scanning head has a scanning optical system and an fθ lens. The system according to any one of [1] to [6], wherein the laser scanning head irradiates the workpiece with a femtosecond laser. A generation device for a machining program for a three-dimensional removal machining system having a laser scanning head that scans a surface of a workpiece with a laser beam in units of irradiation regions of a predetermined size to remove a part of the workpiece, and a stage that holds the workpiece, wherein the laser scanning head and the stage are relatively movable with respect to each other, the generation device comprising one or more processors, the one or more processors obtaining a plurality of layers by dividing the three-dimensional model of the target shape in the thickness direction with the three-dimensional model as an input, and further generating a plurality of irradiation regions by dividing each layer into a predetermined size such that the division lines are offset from each other; a step (a); extracting a set of irradiation regions including at least a part of the target shape from the plurality of irradiation regions; and step (b); and rearranging the irradiation order of the irradiation regions included in the set based on predetermined conditions and outputting the rearrangement as a machining instruction for the three-dimensional removal machining system. Step (c). The generation device according to [8], wherein the step (c) includes a step (d) of rearranging the irradiation order of the irradiation regions included in the set so that the distance of the trajectory of the relative movement of the laser scanning head with respect to the stage or the machining time from the irradiation of the laser beam from the laser scanning head until the target shape is obtained from the workpiece is minimized. The production device according to

[10] , [8] or [9], further comprising a step (e) of dividing the plurality of layers into layer groups each having one or more layers included in an effective part where each layer has a beam diameter equal to each other in a range centered on the beam waist in the thickness direction before the step (c), and in the step (b), a set of irradiation regions included in the same layer group is extracted.

[11] A method for manufacturing a three-dimensional shaped object, comprising: a step (A) of dividing a three-dimensional model of a target shape into a plurality of layers in the thickness direction, and further dividing each layer such that the dividing lines are offset from each other to set a plurality of irradiation regions each having a predetermined size; a step (B) of extracting a set of irradiation regions including at least a part of the target shape from the plurality of irradiation regions; and a step (C) of obtaining the target shape by rearranging the irradiation order of the irradiation regions included in the set based on a predetermined condition and scanning the surface of a workpiece with a laser beam in units of the irradiation regions to remove a part of the workpiece in the irradiation order.

[12] The manufacturing method according to

[11] , further comprising a step (D) of dividing the plurality of layers into layer groups each having one or more layers included in an effective part where each layer has a beam diameter equal to each other in a range centered on the beam waist in the thickness direction before the step (C), and in the step (B), a set of irradiation regions included in the same layer group is extracted.

[13] A program directed to a generating device for a machining program for a three-dimensional removal machining system that removes a part of a workpiece by scanning the surface of the workpiece with a laser beam using an irradiation area of a predetermined size as a unit. The program causes a computer to obtain a plurality of layers by dividing the three-dimensional model of the target shape in the thickness direction with the three-dimensional model of the target shape as an input, and further divides each layer into a predetermined size so that the dividing lines are offset from each other to generate a plurality of irradiation areas. Step (a); step (b) of extracting a set of irradiation areas including at least a part of the target shape from the plurality of irradiation areas; and step (c) of rearranging the irradiation order of the irradiation areas included in the set based on a predetermined condition and outputting the result as a machining instruction for the three-dimensional removal machining system. A program for execution.

[14] The program according to

[13] , wherein the computer further executes, before step (c), step (d) of dividing the plurality of layers into layer groups each having one or a plurality of layers included in an effective part that is a range where the beam diameter is equal around the beam waist in the thickness direction, and in step (b), a set of irradiation areas included in the same layer group is extracted.

[15] A computer-readable non-transitory recording medium recording the program according to

[13] or

[14] .

Effect of the Invention

[0006] According to at least any one of the embodiments of the present invention, it is possible to avoid a decrease in machining quality that may occur as the size of the workpiece increases.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

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Figure 8

Figure 9

Figure 10

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Figure 13

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each feature shown in the embodiments described below can be combined with each other. Further, an invention can be established independently for each feature.

[0009] FIG. 1 shows an exemplary appearance of a three-dimensional removal processing system according to an embodiment of the present invention. The processing system 1 shown in FIG. 1 is a three-dimensional removal processing system using pulsed laser irradiation, and generally includes a processing unit 10 and a control unit 20. As will be described later, the processing unit 10 has a laser scanning head and a stage, and the control unit 20 controls the operations of these laser scanning head and stage based on a processing program.

[0010] <1. Configuration example of processing unit 10> FIG. 2 shows the processing system 1 with the exterior of the processing unit 10 removed. In FIG. 2, for convenience of explanation, three arrows indicating the X-axis, Y-axis, and Z-axis that are orthogonal to each other are drawn. Here, the Z-axis in the figure is parallel to the vertical direction. In other drawings following FIG. 2, arrows indicating these X-axis, Y-axis, and Z-axis may also be illustrated.

[0011] The processing unit 10 includes a frame 11, a laser scanning head 12, a stage 14, and an optical surface plate 15. The frame 11 is a structure that supports the laser scanning head 12, the stage 14, and the optical surface plate 15. At least one of the laser scanning head 12 and the stage 14 is movable up and down in the Z direction with respect to the frame 11 based on an instruction from the control unit 20, for example, by a combination of a stepping motor and a ball screw. Here, the laser scanning head 12 is supported by the frame 11 so as to be movable in the Z direction with respect to the frame 11.

[0012] On the other hand, the stage 14 of the processing unit 10 is supported by the frame 11 in a manner movable within the XY plane of the figure with respect to the laser scanning head 12 by a drive mechanism including a linear motor or the like. The drive mechanism for moving the stage 14 may be configured by a combination of a stepping motor and a ball screw, etc., instead of the linear motor.

[0013] The stage 14 has an upper surface 14a on which the workpiece (e.g., a metal bulk) is placed during the machining process. The upper surface 14a of the stage 14 is parallel to the XY plane in the figure. During the actual machining process, the workpiece is fixed to the stage 14 by a jig or the like on the upper surface 14a and is translated in a plane perpendicular to the Z direction as the stage 14 moves.

[0014] Figure 3 schematically shows an overview of the optical system of the machining unit 10. The optical system of the machining unit 10 includes the above-described laser scanning head 12 and a laser light source 16 optically coupled to the laser scanning head 12. In the configuration illustrated in Figure 3, the laser scanning head 12 includes a scanning optical system 122 and an fθ lens 124.

[0015] The laser light source 16 is disposed in the machining unit 10 by being fixed to an optical surface plate 15 (see Figure 2) supported on the upper part of the frame 11, for example. The laser light emitted from the laser light source 16 is guided to the scanning optical system 122 of the laser scanning head 12 by being reflected by mirrors 18a, 18b, etc. Other optical elements such as a collimator and a beam expander may be interposed between the laser light source 16 and the scanning optical system 122.

[0016] As the laser light source 16, a YAG laser, a fiber laser, a gas laser, etc. can be applied without particular limitation as long as it is a light source of a pulsed laser capable of realizing a fluence exceeding the ablation threshold of the material constituting the workpiece. The typical pulse width (full width at half maximum) of the laser irradiated from the laser scanning head 12 toward the workpiece is on the order of 500 nanoseconds or less. The pulse width of the laser irradiated toward the workpiece may be in the range of 1 to 500 nanoseconds, or may be in the range of 1 to 100 nanoseconds. Alternatively, it may be on the order of several nanoseconds.

[0017] The laser light source 16 may be a femtosecond laser oscillator. That is, the processing system 1 can be a three-dimensional removal processing system including a laser scanning head that irradiates the workpiece with a femtosecond laser. By applying the femtosecond laser, deterioration of the workpiece due to heat during processing can be avoided.

[0018] In the configuration illustrated in FIG. 3, the laser scanning head 12 includes a galvanometer as the scanning optical system 122. As is well known, a galvanometer includes two galvanometer mirrors each connected to an actuator. In the example shown in FIG. 3, the scanning optical system 122 includes a first galvanometer mirror 22a rotatable about a first axis and a second galvanometer mirror 22b rotatable about a second axis not parallel to the first axis. The light introduced from the laser light source 16 into the laser scanning head 12 travels toward the fθ lens 124 after being reflected in sequence by the first galvanometer mirror 22a and the second galvanometer mirror 22b.

[0019] FIG. 4 shows another example of the scanning optical system 122. As illustrated in FIG. 4, instead of a galvanometer, the scanning optical system 122 may be configured by a digital micromirror device (DMD) 22c. Alternatively, the scanning optical system 122 may be realized by a combination of a polygon mirror and a motor or the like. Any configuration can be adopted for the scanning optical system 122 as long as two-dimensional scanning of the laser beam is possible.

[0020] The laser scanning head 12 includes a flat field lens in addition to the scanning optical system 122. In the examples shown in FIGS. 3 and 4, the laser scanning head 12 includes an fθ lens 124. The fθ lens 124 may be a telecentric fθ lens or a non-telecentric fθ lens. Here, a telecentric fθ lens is used as the fθ lens 124, and the light that has passed through the fθ lens 124 in the scanning of the laser beam travels parallel to the optical axis of the lens. In the examples shown in FIGS. 3 and 4, the optical axis of the telecentric fθ lens is parallel to the Z axis. That is, here, the light that has passed through the scanning optical system 122 and the fθ lens 124 in sequence is incident perpendicularly to the upper surface 14a of the stage 14. By adopting a telecentric fθ lens, the advantage can be obtained that the shape of the laser spot can be prevented from approaching an ellipse.

[0021] In this way, the laser scanning head 12 is configured to be able to two-dimensionally scan the laser beam in a plane parallel to the XY plane of the figure. While switching the on / off of the laser pulse based on a command from the control unit 20, by scanning the surface of the workpiece supported on the stage 14 with the laser beam from the laser scanning head 12, a part of the workpiece can be removed to obtain a desired shape (hereinafter, sometimes referred to as the "target shape").

[0022] However, the range in which the laser beam can be two-dimensionally scanned with the relative positions of the laser scanning head 12 and the stage 14 fixed with respect to the frame 11 is limited by the configuration of the optical system of the laser scanning head 12. For example, when a telecentric fθ lens is used as the fθ lens 124, the range in which two-dimensional scanning can be performed is limited to the range in which the beam that has passed through the fθ lens 124 can be scanned at a constant speed on the flat field, for example, a circular region with a diameter of 120 mm. Therefore, when the size of the target shape is larger, it is necessary to repeat the two-dimensional scanning of the laser beam with the relative positions of the laser scanning head 12 and the stage 14 fixed and the movement of the laser scanning head 12 or the stage 14.

[0023] Here, the laser scanning head 12 is fixed in the XY plane with respect to the frame 11, and the stage 14 is movable in the XY plane with respect to the laser scanning head 12. However, the present invention is not limited to this example, and the laser scanning head 12 and the stage 14 may be movable relative to each other in a plane perpendicular to the Z axis. For example, the stage 14 may be fixed in the XY plane with respect to the frame 11, and the laser scanning head 12 may be movable in the XY plane with respect to the stage 14. Alternatively, both the laser scanning head 12 and the stage 14 may be configured to be independently movable in the XY plane with respect to the frame 11.

[0024] <2. Example of control system> As described above, the control unit 20 controls the operations of the laser scanning head 12 and the stage 14 of the processing unit 10. In a typical embodiment of the present invention, the processing system 1 performs automatic processing to which computer-aided manufacturing (CAM) is applied. In the application of CAM, first, data representing a three-dimensional model related to the final target shape (hereinafter, conveniently referred to as a "CAD model") is prepared by using CAD or the like. The control unit 20 controls the operations of each part of the processing unit 10 according to a processing program generated based on the CAD model. Details of the generation of the processing program will be described later.

[0025] FIG. 5 shows an example of a control system in the processing system 1. In a typical embodiment of the present invention, the control unit 20 of the processing system 1 includes one or more processors such as a CPU and one or more memories including a RAM. In the configuration illustrated in FIG. 5, the control unit 20 includes, for example, a controller 23 constituted by a CPU. In the example shown in FIG. 5, the control unit 20 further includes a first interface 21, a second interface 22, a Z-axis driver 24, an X-axis driver 26, and a Y-axis driver 28.

[0026] The controller 23 receives a machining program via the first interface 21, and generates control signals for operating each part of the machining unit 10 based on the machining program. Here, the first interface 21 is an external interface that realizes connection with an external device such as a computer installed with CAM software. The first interface 21 can take forms such as a connector, jack, or socket for a wired connection with an external device or the Internet. The first interface 21 may also be a device for a wireless connection with an external device or the Internet.

[0027] As shown in FIG. 5, in this example, the control unit 20 includes a Z-axis driver 24 that controls the movement of the laser scanning head 12, and an X-axis driver 26 and a Y-axis driver 28 that control the movement of the stage 14. The Z-axis driver 24 controls the vertical movement of the laser scanning head 12 in the Z direction based on a control signal from the controller 23. The X-axis driver 26 and the Y-axis driver 28 control the horizontal movement of the stage 14 based on a control signal from the controller 23.

[0028] Focusing on the machining unit 10. Here, the machining unit 10 has a galvano controller 18. As shown in FIG. 5, when the scanning optical system 122 includes, for example, a galvanometer, the galvano controller 18 drives an actuator connected to the first galvanometer mirror 22a and an actuator connected to the second galvanometer mirror 22b (see FIG. 3). Here, the galvano controller 18 also has the function of a laser driver for controlling the operation of the laser light source 16.

[0029] The above machining program includes not only instructions regarding the vertical movement of the laser scanning head 12 and the horizontal movement of the stage 14, but also instructions regarding two-dimensional scanning by the scanning optical system 122. The galvano controller 18 downloads part or all of the machining program from the controller 23 and controls the operations of the first galvano mirror 22a, the second galvano mirror 22b, and the laser light source 16 according to the machining program. In this sense, the entire galvano controller 18 and the controller 23 may be said to constitute the control unit 40 of the machining system 1.

[0030] The machining program for obtaining the final target shape can be prepared by an external device 30 (for example, a personal computer) separate from the machining system 1, as described below. In the configuration illustrated in FIG. 5, the external device 30 includes an arithmetic unit 32 having an arithmetic circuit 321 and a memory 322. A typical example of the memory 322 is a non-volatile storage device such as a magnetic disk drive or a solid state drive. Here, CAM software is installed in the memory 322, and the arithmetic unit 32 can function as a CAM device.

[0031] The arithmetic circuit 321 of the arithmetic unit 32 is composed of a processor such as a CPU, for example, receives the import of a CAD model file, and generates and outputs a machine-readable machining program in which instructions for driving each part of the machining unit 10 are described. As described above, this machining program may include instructions regarding the operations of the galvano mirrors 22a and 22b, and instructions regarding the operations of the laser scanning head 12 and the stage 14. The external device 30 (or its arithmetic unit 32) of the present embodiment can be said to be a machining program generation device.

[0032] The machining program generated in the external device 30 is passed to the control unit 20 via the first interface 21. The machining program may be transmitted by either a wired or wireless method. When the controller 23 of the control unit 20 receives the machining program that is the output from the arithmetic unit 32, it causes the machining unit 10 to execute machining to obtain the target shape according to the machining program. More specifically, after the controller 23 controls the relative movement between the laser scanning head 12 and the stage 14 to set them in a predetermined relative arrangement, it sends an instruction regarding two-dimensional scanning of the area to be irradiated to the galvano controller 18. Based on the machining instruction, the galvano controller 18 operates the galvano mirrors 22a, 22b and the laser light source 16 to remove unnecessary portions of the area of the workpiece that is the target of two-dimensional scanning by laser irradiation. By repeating such irradiation of the laser beam from the laser scanning head 12 to the workpiece under the control of the controller 23 and the relative movement between the laser scanning head 12 and the stage 14, unnecessary portions can be removed from the workpiece to obtain the shape of the finished product. The transmission of the drive signal and / or control signal from the control unit 20 to the machining unit 10 may be executed by either a wired or wireless method, similar to the exchange of the machining program.

[0033] As illustrated in FIG. 5, the control unit 20 may further have a second interface 22. The second interface 22 receives commands from the operator of the machining system 1. Examples of the second interface 22 are a touch panel, a keyboard or buttons, or a combination of two or more of these. By including a touch panel as the second interface 22, the control unit 20 may cause the second interface 22 to display a simulation of the operation of the machining unit 10 when the machining program is run. Further, the control unit 20 may be configured such that the operator can modify the machining program by inputting an instruction via the touch panel.

[0034] Additionally, the processing unit 10 may have a camera or the like for photographing the workpiece on the stage 14. The controller 23 of the control unit 20 may control the camera and the second interface 22 so as to display the video obtained by a camera (not shown in FIG. 5). By providing such a camera in the processing system 1, it is beneficial because the workpiece on the stage 14 can be observed during processing.

[0035] <3. Generation of Processing Program> Next, an example of generating a processing program will be described. As is well known, in general machining applying CAM, the generation of a processing program is roughly divided into two stages. The first stage is the determination of the tool path, and the second stage is the generation of a numerical control program (referred to as post - processing) corresponding to the determined tool path.

[0036] In the embodiment of the present invention, as the target shape, a shape having a size exceeding the range that the laser scanning head 12 can scan with the arrangements of the laser scanning head 12 and the stage 14 fixed is assumed. That is, the cross - sectional area of the target shape at a certain height with respect to the upper surface 14a of the stage 14 is larger than the area of the region that the laser scanning head 12 can scan at one time. Therefore, in a typical embodiment of the present invention, as will be described in detail below, first, a plurality of layers obtained by dividing the three - dimensional model of the target shape in the thickness direction (which may also be referred to as the height direction) are defined, and further, each layer is divided into a plurality of irradiation regions each having a predetermined size. Then, after setting a plurality of irradiation regions for each processing layer, processing is performed using the irradiation region as a unit.

[0037] As will be described in detail below, in the embodiments of the present invention, the dividing lines that define the irradiation regions for each processing layer are offset from each other little by little among a plurality of processing layers, and each processing layer is divided into a plurality of irradiation regions. For example, in the example described below, between two processing layers adjacent to each other in the thickness direction of the three-dimensional model, a part of the irradiation region of one processing layer overlaps with a corresponding one of the irradiation regions of the other processing layer in plan view. In other words, the boundaries of the plurality of irradiation regions (which may also be referred to as dividing lines) in a certain processing layer do not coincide with the boundaries of the plurality of irradiation regions in the processing layer one above or one below that processing layer. By intentionally avoiding the overlapping of the boundaries of the plurality of irradiation regions among the plurality of processing layers in this way, it is possible to prevent a structure such as a streak from remaining at a position corresponding to the boundary of the irradiation region on the surface of the workpiece. That is, even if the target shape is larger than the range of a single irradiation region, it is possible to achieve processing that avoids deterioration in quality.

[0038] The processing program according to a typical embodiment of the present invention includes an instruction on the order in which a plurality of irradiation regions are scanned with a laser beam (hereinafter, may sometimes be simply referred to as an "instruction regarding the irradiation order"). It can be said that the determination of this "irradiation order" corresponds to the determination of the tool path in a CNC machine tool. As will be apparent from the following description, by appropriately setting the irradiation order, it is possible to shorten the processing time while avoiding deterioration in processing quality.

[0039] FIG. 6 is a flowchart showing an example of generating a processing program according to another embodiment of the present invention. As shown in FIG. 6, the arithmetic unit 32 of the external device 30 executes, for example, a step S1 of generating a plurality of irradiation regions by dividing a plurality of processing layers, a step S2 of extracting a set of irradiation regions including at least a part of the target shape, and a step S3 of rearranging the extracted irradiation regions and outputting them as a processing instruction.

[0040] (3-1. Step S1 of generating a plurality of irradiation regions) When the arithmetic circuit 321 of the arithmetic unit 32 receives a CAD model file, it checks from the geometric shape surface whether the target shape contains an unprocessable shape. If no error regarding the geometric shape is found, the arithmetic circuit 321 generates slice data of the target shape from the CAD model by dividing the CAD model in the thickness direction. The arithmetic circuit 321 further generates a plurality of processing layers each containing a slice of the target shape, and meshes each of the processing layers into a plurality of irradiation regions.

[0041] FIG. 7 schematically shows the relationship between a slice at a certain height of the three-dimensional model of the target shape and the area that the laser scanning head 12 can scan at one time. The three-dimensional model of the target shape can be represented as a set of slice data obtained by cutting the target shape with a plurality of planes having different heights in the Z direction. In the example shown in FIG. 7, a slice Sk (hatched for convenience of explanation) at a certain height of the target shape is within a square area of 400 mm on each side. A rectangular area that includes the cross-section when the target shape is cut, like the square area shown in FIG. 7, is conveniently referred to as a "processing layer" in this specification.

[0042] In an embodiment of the present invention, the area that the laser scanning head 12 can scan at one time is smaller than the entire processing layer. The range that can be scanned by the laser scanning head 12 with the arrangement of the laser scanning head 12 and the stage 14 fixed with respect to the frame 11 is limited to, for example, a circular area with a diameter of 120 mm (schematically shown by a dotted circle C in FIG. 7). Therefore, when the size of the target shape is larger, it is necessary to move the laser scanning head 12 and / or the stage 14 to repeat the two-dimensional scanning of the laser beam.

[0043] As schematically shown by the dashed rectangle in FIG. 7, here, a rectangular area R (for example, a square area of 80 mm on each side), which is smaller than the maximum range that can be scanned by the laser scanning head 12, is assumed with the arrangements of the laser scanning head 12 and the stage 14 fixed. Then, the two-dimensional scanning range of the laser beam with the arrangements of the laser scanning head 12 and the stage 14 fixed is limited to this rectangular area R. In this specification, such a rectangular area is referred to as an "irradiation area". By mesh-dividing each processing layer into a plurality of irradiation areas of a predetermined size, the entire processing layer can be covered with a plurality of irradiation areas. In other words, by repeating two-dimensional scanning in units of irradiation areas within the processing layer, scanning of the entire processing layer can be achieved.

[0044] FIG. 8 shows an example of the division of a processing layer into a plurality of irradiation areas. When a square area of 80 mm on each side is adopted as the rectangular area R, as schematically shown by the dashed lines in FIG. 8, a processing layer with a size of 400 mm on each side can be divided into a total of 25 irradiation areas R1 to R25, each having a size of 80 mm on each side. And by designating a representative point in the irradiation area, these irradiation areas can be respectively specified. If, for example, one of the vertices of the rectangular area, the lower left one, is taken as the representative point, the positions of the irradiation areas R1 and R2 shown in FIG. 8 can be specified as (0,0) and (80000,0) respectively by the coordinate values of the representative point. In other words, the coordinate values of the representative point can be used as the label of each irradiation area.

[0045] In this way, for example, each irradiation area can be labeled according to the coordinate values of the representative points. Therefore, all of the plurality of irradiation areas obtained for each processing layer can be represented by a set of a plurality of numerical values such as coordinates. The set of a plurality of numerical values can be in the form of, for example, (serial number of the irradiation area in the processing layer of interest, serial number of the processing layer, X coordinate of the representative point, Y coordinate of the representative point). Here, the serial number of the processing layer is a label indicating which layer among the slice data it is. When the slice Sk shown in FIG. 8 belongs to, for example, the k-th layer (k is a natural number) of the processing layer, the irradiation areas R1 and R2 can be represented as (1, k, 0, 0) and (2, k, 80000, 0), respectively.

[0046] In an embodiment of the present invention, the plurality of processing layers obtained by dividing in the thickness direction include a first layer and a second layer adjacent to each other. Here, the second layer is a layer located one above or one below the first layer in the thickness direction.

[0047] FIG. 9 shows the division in the first layer superimposed on the division in the second layer. In the example shown in FIG. 9, the second layer L2 is, for example, the k-th layer in the thickness direction (which coincides with the Z direction here) of the target shape. Similar to the example described with reference to FIG. 8, the second layer L2 includes 25 irradiation areas R1 to R25 each having a predetermined size. On the other hand, for example, the first layer L1 which is the (k + 1)-th layer also includes irradiation areas Q1 to Q25 each having the same size as each of the irradiation areas R1 to R25. However, as schematically shown in FIG. 9, when paying attention to, for example, the irradiation area Q2 among the irradiation areas Q1 to Q25 of the first layer L1, this irradiation area Q2 has an overlap with a part of the irradiation area R2 corresponding to the irradiation area Q2 in the second layer L2 in a plan view. In other words, a part of the outer shape of the rectangular shape defining the irradiation area Q2 overlaps with the irradiation area R2 in a plan view.

[0048] Assume that the label representing the irradiation region R2 of the second layer L2 is, for example, (2, k, 80000, 0). Then, the label representing the irradiation region Q2 of the first layer L1 can be, for example, (2, k + 1, 81000, 1000). That is, in this example, the irradiation region Q2 of the first layer L1 is offset by 1 mm in the X direction and 1 mm in the Y direction with respect to the irradiation region R2 of the second layer L2. Not limited to this example, the offset amount between layers may be set as appropriate, and it is not necessary for the offset amounts in the X direction and the Y direction to be the same.

[0049] As the offset between layers adjacent in the thickness direction, for example, a magnitude can be adopted such that the total offset amount in the 1000 layers of the processing layer is ((the length L of one side of the irradiation region) / (the total number N of the processing layers)). The diameter of a general telecentric fθ lens is, for example, approximately 1000 times the spot diameter of a femtosecond laser, which is 10 to 30 μm. When the irradiation region is rectangular, the length of one side of the rectangle is also approximately 1000 times the spot diameter of the laser. Therefore, it is reasonable to calculate the offset amount in units of approximately 1000 layers of the processing layer. Let Z be the value obtained by rounding the total number N of the processing layers divided by 1000 to an integer. As the offset amount T between the processing layers, a magnitude calculated from T = L / (N / (Z + 1)) can be adopted. Adopting an offset of such a magnitude is beneficial because it can make the distribution of the boundaries of the irradiation region uniform.

[0050] As can be understood from FIG. 9, in this example, the entire first layer L1 is offset in the XY plane with respect to the entire second layer L2. In FIG. 9, for convenience of explanation, the offset between the first layer L1 and the second layer L2 is exaggeratedly illustrated. Note that it is not essential in the present invention that the outer shapes of the processing layers match among a plurality of processing layers. Also, it is not essential that the number of irradiation regions included in the processing layers matches among a plurality of processing layers.

[0051] (Step S2 of extracting a set of irradiation regions including at least a part of the target shape) As can be understood from FIG. 8, when focusing on a certain processing layer, the plurality of irradiation regions include those having at least a part of the slice of the target shape (here slice Sk) and those not having the slice of the target shape. In the processing of the workpiece, it can be said that there is no meaning in performing scanning with a laser beam on the irradiation region that does not have the slice of the target shape. Therefore, it is beneficial to include information regarding whether or not the irradiation region has a slice of the target shape in the set of numerical values for designating the irradiation region. For example, a flag may be set for the irradiation region having the slice of the target shape. In this case, for example, the irradiation regions R1, R2, and R3 shown in FIG. 8 can be expressed as (1, k, 0, 0, 0), (2, k, 80000, 0, 0), and (3, k, 160000, 0, 1), respectively. The last one of the set of five numerical values for designating the irradiation region corresponds to the above-mentioned flag. That the flag is set to "1", like the label given to the irradiation region R3, indicates that the irradiation region includes a slice of the target shape in a part thereof.

[0052] In the present embodiment, after the arithmetic circuit 321 performs labeling on the plurality of irradiation regions of each processing layer by a set of numerical values or the like, it extracts a set of irradiation regions including at least a part of the target shape from among the plurality of irradiation regions. In the example of the k-th layer shown in FIG. 8, the arithmetic unit 32 extracts R3 to R4, R7 to R9, R12 to R13, R17 to R18, and R22 to R24 from among the irradiation regions R1 to R25. The extraction of the set of irradiation regions can be easily performed by selecting those for which the above-mentioned flag is set (that is, those for which the value of the flag is "1") from among the labels (for example, sets of numerical values) representing each of the irradiation regions.

[0053] Similarly, the arithmetic circuit 321 extracts Q2 to Q4, Q6 to Q8, Q11 to Q13, Q16 to Q18, and Q22 to Q24 from the irradiation regions Q1 to Q25 (see FIG. 9) of the first layer L1, which is the processing layer of the (k + 1)-th layer. As described above, here, the first layer L1 includes the irradiation region Q2 (the first irradiation region) that overlaps a part of the irradiation region R2 (the second irradiation region) of the second layer L2 in a plan view.

[0054] Here, for simplicity, it is assumed that the shape of the slice of the target shape included in the first layer L1 of the (k + 1)-th layer is the same as the shape of the slice of the target shape included in the second layer L2 of the k-th layer. Generally, the shape of the slice of the target shape may be different between different processing layers.

[0055] (3-3. Step S3 of rearranging the extracted irradiation regions and outputting them as a processing instruction) When the extraction of the irradiation regions with the flags set is completed, the arithmetic circuit 321 rearranges the labels (for example, a set of numerical values) designating each of these extracted irradiation regions based on a predetermined condition. The irradiation regions with the flags set are the irradiation regions to be scanned by the laser beam among all the irradiation regions. That is, the list of the irradiation regions rearranged based on a predetermined condition constitutes an instruction regarding the "irradiation order" for the processing unit 10.

[0056] FIG. 10 shows an example of a list after rearranging the labels (for example, a set of numerical values) representing each of the irradiation regions under a predetermined condition. In FIG. 10, an example of a list in which data in the form of (sequence number, serial number of the irradiation region, serial number of the processing layer, X coordinate of the representative point, Y coordinate of the representative point, flag) is described in each row is shown. Although not shown in FIG. 10, such a list as a processing program is also accompanied by an instruction for each irradiation region regarding the operation of the scan optical system 122 (for example, a galvanometer). After obtaining a list as shown in FIG. 10, the simulation result of the processing may be displayed on the second interface 22 (for example, a touch panel) of the control unit 20.

[0057] When a list as shown in FIG. 10 is obtained, the arithmetic circuit 321 converts the content of the list into a numerically controlled program that can be machine-read (corresponding to the post-process described above), and outputs the numerically controlled program as a machining instruction. FIG. 11 shows an example of a numerically controlled program corresponding to the list shown in FIG. 10. The numerically controlled program as the output from the arithmetic unit 32 can be said to correspond to G-code in a CNC machine tool. This post-process may be executed by the arithmetic unit 32 of the external device 30, or may be executed by a processor (for example, the controller 23) on the control unit 20 side. The numerically controlled program may further include data related to laser irradiation conditions such as spot size, fluence, and irradiation frequency.

[0058] The numerically controlled program generated by, for example, the arithmetic circuit 321 of the arithmetic unit 32 is sent to the controller 23 of the control unit 20 via the first interface 21. The controller 23 and the galvano controller 18 that have received the numerically controlled program generate control signals for operating each part of the machining unit 10 based on the numerically controlled program. In the present embodiment, for example, the laser scanning head 12 scans the surface of the workpiece with a laser beam in units of irradiation areas based on the drive signal generated by the galvano controller 18, and removes a part of the workpiece. By sequentially scanning the surface of the workpiece with a laser beam according to the numerically controlled program as shown in FIG. 11 or the content of the list as shown in FIG. 10, a finished product having a desired shape can be obtained.

[0059] As can be understood from the above description, in the method for manufacturing a three-dimensional object according to still another embodiment of the present invention, as shown in FIG. 12, schematically, it includes a step T1 of setting a plurality of irradiation regions, and a step T2 of obtaining a target shape by scanning the surface of a workpiece with a laser beam in units of the irradiation regions. In the example described here, the arithmetic unit 32 of the external device 30 generates a processing program that causes the laser scanning head 12 to selectively perform laser scanning on the irradiation regions including at least a part of the target shape among all of the plurality of irradiation regions defined for each processing layer, and gives a command to the galvanometer controller 18 of the processing unit 10. In this way, by selectively performing laser scanning on the irradiation regions including at least a part of the target shape, it is possible to avoid a decrease in processing quality at the boundary portions of adjacent irradiation regions, and to obtain the effect of shortening the lead time related to processing. In particular, when a galvanometer is adopted as the scan optical system 122, the effect of shortening the downtime of the galvanometer can be expected under control to stop the operation of laser beam scanning during the movement of the stage 14. The shortening of the lead time required for the entire processing process leads to the saving of energy required for processing.

[0060] <4. Determination of Irradiation Order> As described above, here, after rearranging the labels of the irradiation regions with flags set based on a predetermined condition, the laser beam scanning is performed in the order after rearrangement. In this way, the step S3 of outputting a processing instruction may additionally include a step of rearranging the irradiation order regarding the irradiation regions included in the set of irradiation regions extracted according to whether or not the target shape is included in a part thereof. Here, the "predetermined condition" is, for example, a condition such that the total processing time is minimized. The "predetermined condition" may be appropriately determined according to manufacturing needs.

[0061] In an embodiment of the present invention, the laser scanning head 12 executes removal processing in units of irradiation areas in a specified irradiation order according to a machining program. The laser scanning head 12 may execute the processing sequentially for each machining layer. However, as can be understood from FIG. 10 and the like, the irradiation areas to be scanned by the laser beam can be discontinuous within one machining layer. Furthermore, the scanning order of the laser beam may be specified across a plurality of machining layers.

[0062] In an embodiment of the present invention, in generating a machining program, the calculation unit 32 rearranges the irradiation areas to be scanned by the laser beam in an order that minimizes the set "cost". Determining the irradiation order corresponds to solving a so-called combinatorial optimization problem under the condition that the "cost" is minimized.

[0063] When executing laser beam scanning in units of irradiation areas, after the scanning of one irradiation area is completed, the machining unit 10 moves the laser scanning head 12 and / or the stage 14 so that the laser spot moves onto the next irradiation area. Therefore, the distance of the relative movement locus of the laser scanning head 12 with respect to the stage 14 can be the "cost" in the total machining time. For example, the calculation unit 32 rearranges the irradiation areas included in the set of extracted irradiation areas in an order that minimizes the movement distance in the plane of the stage 14 (or the laser scanning head 12). Alternatively, the machining time itself until the target shape is obtained from the workpiece by irradiation with the laser beam from the laser scanning head 12 may be set as the "cost".

[0064] The solution to the combinatorial optimization problem for determining the irradiation order may be obtained by a known method. Techniques such as simulated annealing and quantum annealing may be applied to determine the irradiation order. The control unit 40 of the control unit 20 can cause the laser scanning head 12 to execute removal processing in units of irradiation areas in an irradiation order that minimizes the appropriately determined "cost" according to the machining program generated by the calculation unit 32.

[0065] In addition, an irradiation sequence may be allowed in which, following the scanning of a certain irradiation area of a certain processing layer, while fixing the positions of the laser scanning head 12 and / or the stage 14 in the Z direction, the irradiation area located substantially directly above or substantially directly below that irradiation area is scanned.

[0066] As is well known, a Gaussian beam has a beam waist where the beam diameter takes the minimum value. In ablation processing, the use of this beam waist is advantageous in terms of processing efficiency. In addition to this, near the beam waist, there is no significant change in the beam diameter. Therefore, for an irradiation area located within a predetermined range centered on the beam waist in the Z direction, scanning can be performed while fixing the positions of the laser scanning head 12 and / or the stage 14 in the Z direction.

[0067] FIG. 13 schematically shows an example in which irradiation areas of a plurality of processing layers are located within a predetermined range centered on the beam waist. A range with no significant change in the beam diameter centered on the beam waist is defined as the “effective part Ef”. For the irradiation areas included in this effective part Ef, for example, scanning of these irradiation areas may be sequentially performed without lowering the laser scanning head 12 in the Z direction. In that case, before the rearrangement of the labels of the irradiation areas (for example, after the extraction of the irradiation areas with the flag set), a step of dividing the entire plurality of processing layers into two or more layer groups may be performed. The number of processing layers included in each layer group is the number of processing layers included in the effective part Ef. The number of processing layers included in the effective part Ef can be obtained by dividing the length of the effective part Ef in the Z direction by the interval between adjacent processing layers (which can also be referred to as the processing depth per layer). If the length of the effective part Ef in the Z direction is, for example, 50 μm and the processing depth in one scan is, for example, 1 μm, processing with the movement of the laser scanning head 12 and the like omitted can be realized for up to 50 layers of irradiation areas. Note that the length of the effective part Ef can be set to about the Rayleigh length in the case of a Gaussian beam, for example.

[0068] Thus, in the removal process for some of the processing layers that are continuous in the Z direction among the plurality of processing layers, control may also be adopted such that the distance from the laser scanning head 12 to the stage 14 and the position of the beam waist of the laser beam are not changed. In setting the combinatorial optimization problem for determining the irradiation order, a condition may be imposed that the rearrangement of the irradiation regions that transition between the processing layers is limited to between the irradiation regions belonging to the same effective part Ef. For example, before rearranging the labels of the irradiation regions, a step of grouping the processing layers in units of the length of the effective part Ef in the Z direction and dividing one or more processing layers into layer groups is performed. Then, a step of extracting a set of irradiation regions including at least a part of the target shape from the processing layers included in the same layer group and rearranging the irradiation order for the irradiation regions included in the extracted set of irradiation regions may be performed.

[0069] By considering such constraint conditions, it is beneficial because the number of vertical movements of the laser scanning head 12 can be reduced. The maximum number of processing layers that can be included in the effective part Ef may be appropriately determined according to the processing depth in one scan.

[0070] <5. Other Modification Examples> As described above, in the embodiment of the present invention, intentionally avoiding the overlapping of the boundaries of the plurality of irradiation regions between the plurality of processing layers. By offsetting one of the processing layers adjacent in the thickness direction with respect to the other in a direction perpendicular to the thickness direction, even if the target shape is larger than the range of a single irradiation region, processing that avoids quality degradation can be realized. Note that it is not essential to cause an offset in all of the processing layers, and the entire set of processing layers may include a set of two or more processing layers in which the boundaries of the irradiation regions overlap in the thickness direction.

[0071] In the above example, the external device 30 as the machining program generation device determines the irradiation order of the irradiation regions based on predetermined conditions. However, the present invention is not limited to this example. For example, the controller 23 of the control unit 20 may be caused to execute the rearrangement of the labels designating each of the irradiation regions. Alternatively, the controller 23 may be caused to execute two or more of the steps of extracting a set of irradiation regions including at least a part of the target shape, rearranging the labels designating each of these irradiation regions, and converting them into a numerical control program.

[0072] As described with reference to FIG. 5, the generation of the machining program can be executed by an information processing apparatus separate from the machining system 1. As the external device 30, a personal computer installed with CAD tools in addition to CAM software may be used to generate a machining program. In such a configuration, the transfer of the CAD model from the CAD tool to the CAM software is completed inside the computer.

[0073] The software or application for generating the machining program according to the present invention can be downloaded through a telecommunication line, or read from a machine-readable recording medium such as an optical disk, and installed in a storage device provided in a personal computer or the like. In this case, by installing the above-described software or application, for example, a general-purpose personal computer can be used as a machining program generation device.

[0074] The machining program output from the external device 30 can be provided to the machining system 1 via a recording medium such as a USB flash memory or an optical disk. Transmission and reception of the machining program may be executed through a network such as a LAN or the Internet. The machining method according to the present invention may be realized in the form of providing a machining program in which instructions for causing a processor or the like to execute are described. It is not always necessary for the personal computer as the machining program generation device to be constantly connected to the machining system 1 by wire or wirelessly.

[0075] As described above, various embodiments of the present invention have been explained, but these are presented as examples and are not intended to limit the scope of the invention. The novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. Such embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Explanation of Reference Numerals

[0076] 1: Processing system 10: Processing unit 11: Frame 12: Laser scanning head 14: Stage 14a: Upper surface of the stage 15: Optical surface plate 16: Laser light source 18: Galvano controller 18a, 18b: Mirrors 20: Control unit 21: First interface 22: Second interface 22a: First galvano mirror 22b: Second galvano mirror 22c: Digital micromirror device (DMD) 23: Controller 24: Z-axis driver 26: X-axis driver 28: Y-axis driver 30: External device 32: Arithmetic unit 40: Control section 122: Scanning optical system 124: fθ lens 321: Arithmetic circuit 322: Memory Ef: Effective part L1: First layer L2: Second layer R1~R25, Q1~Q25: Irradiation regions R: Rectangular area Sk: Slice of the target shape

Claims

1. A three-dimensional removal processing system using pulsed laser irradiation, comprising: a laser scanning head; a stage for supporting a workpiece; a control unit; wherein the laser scanning head and the stage are relatively movable with respect to each other; the control unit controls irradiation of a laser beam from the laser scanning head onto the workpiece and relative movement between the laser scanning head and the stage based on a machining program, wherein the machining program includes an instruction regarding an irradiation order of the laser beam with respect to a plurality of irradiation regions each having a predetermined size, and the plurality of irradiation regions are regions defined by dividing each of a plurality of layers obtained by dividing a three-dimensional model of a target shape in a thickness direction such that dividing lines are offset from each other; the laser scanning head removes a part of the workpiece by scanning the surface of the workpiece with a laser beam in units of the irradiation regions.

2. The system according to claim 1, wherein in the removal processing for a part of the plurality of layers that are continuous in the thickness direction, the control unit controls the laser scanning head and the stage so as not to change the distance from the laser scanning head to the stage and the position of the beam waist of the laser beam.

3. The system according to claim 1 or claim 2, wherein the control unit causes the laser scanning head to perform removal processing in units of the irradiation regions in an irradiation order that minimizes the distance of the trajectory of the relative movement of the laser scanning head with respect to the stage or the machining time from the start of irradiation of the laser beam from the laser scanning head until the target shape is obtained from the workpiece.

4. The system according to claim 1 or claim 2, wherein the control unit causes the laser scanning head to selectively perform laser scanning on the irradiation regions that at least partially include the target shape among the plurality of irradiation regions.

5. The system according to claim 1 or claim 2, wherein the control unit determines the irradiation order by rearranging the labels of the irradiation regions based on a predetermined condition, and causes the laser scanning head to perform removal processing in units of the irradiation regions in the irradiation order.

6. The system according to claim 1 or claim 2, wherein the system further comprises a laser light source optically coupled to the laser scanning head, the laser scanning head has a scanning optical system and an fθ lens.

7. The system according to claim 1 or claim 2, wherein the laser scanning head irradiates the workpiece with a femtosecond laser.

8. A device for generating a machining program for a three-dimensional removal machining system having a laser scanning head that removes a part of a workpiece by scanning the surface of the workpiece with a laser beam in units of irradiation regions of a predetermined size, and a stage that holds the workpiece, wherein the laser scanning head and the stage are relatively movable with respect to each other, the device comprising: one or more processors, the one or more processors: obtaining a plurality of layers by dividing the three-dimensional model in the thickness direction with a three-dimensional model of a target shape as an input, and further generating a plurality of irradiation regions by dividing each layer into a predetermined size such that the division lines are offset from each other (step (a)); extracting a set of irradiation regions including at least a part of the target shape from the plurality of irradiation regions (step (b)); rearranging the irradiation order of the irradiation regions included in the set based on a predetermined condition and outputting the result as a machining instruction for the three-dimensional removal machining system (step (c)); and executing the above steps.

9. The generating device according to claim 8, wherein step (c) includes a step (d) of rearranging the irradiation order of the irradiation regions included in the set such that the distance of the trajectory of the relative movement of the laser scanning head with respect to the stage, or the machining time from the irradiation of the laser beam from the laser scanning head until the target shape is obtained from the workpiece is minimized.

10. The generating device according to claim 8 or claim 9, wherein before step (c), the method further includes a step (e) of dividing the plurality of layers into layer groups each having one or more layers included in an effective portion where the beam diameter is equal in a range centered on the beam waist in the thickness direction, and in step (b), a set of irradiation regions included in the same layer group is extracted.

11. A method for manufacturing a three-dimensional shaped object, comprising: A step (A) of dividing a three-dimensional model of a target shape into a plurality of layers in the thickness direction, and further dividing each layer so that the dividing lines are offset from each other to set a plurality of irradiation regions each having a predetermined size; A step (B) of extracting a set of irradiation regions including at least a part of the target shape among the plurality of irradiation regions; A step (C) of rearranging the irradiation order of the irradiation regions included in the set based on a predetermined condition, and scanning the surface of the workpiece with a laser beam in units of the irradiation regions to remove a part of the workpiece in the irradiation order, thereby obtaining the target shape; A method including the above steps.

12. The manufacturing method according to claim 11, Before the step (C), the method further includes a step (D) of dividing the plurality of layers into a plurality of layer groups each having one or more layers included in an effective portion which is a range having an equal beam diameter centered on the beam waist in the thickness direction, In the step (B), a set of irradiation regions included in the same layer group is extracted.

13. A program directed to a device for generating a machining program for a three-dimensional removal machining system that removes a part of a workpiece by scanning the surface of the workpiece with a laser beam in units of irradiation regions of a predetermined size, The program causes a computer to Obtain a plurality of layers by dividing a three-dimensional model of a target shape in the thickness direction with the three-dimensional model as an input, and further generate a plurality of irradiation regions by dividing each layer into a predetermined size so that the dividing lines are offset from each other (step (a)); Extract a set of irradiation regions including at least a part of the target shape among the plurality of irradiation regions (step (b)); Rearrange the irradiation order of the irradiation regions included in the set based on a predetermined condition and output it as a machining instruction for the three-dimensional removal machining system (step (c)); A program for causing the above steps to be executed.

14. The program according to claim 13, Before the step (c), the computer is further caused to execute a step (d) of dividing the plurality of layers into a plurality of layer groups each having one or more layers included in an effective portion which is a range having an equal beam diameter centered on the beam waist in the thickness direction, and in the step (b), a set of irradiation regions included in the same layer group is extracted. ​

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