Optical system of a laser processing device, laser processing device

Abstract

Provided is an optical system of a laser processing device and a laser processing device in which the energy utilization efficiency of laser light is high and the energy intensity distribution of an irradiation point (spot) of laser light that is suitable for a processing target of various materials can be selected. To achieve this, the optical system of the laser processing device has an optical surface in which a plurality of different focal points are provided on an optical axis, the energy intensity distribution of laser light on a surface perpendicular to the optical axis differs depending on the position on the optical axis, and by using different positions on the optical axis as the irradiation point of laser light of a processed object, the energy intensity distribution of laser light at the irradiation point of laser light of the processed object can be selected.

Description

Technical Field

[0001] This invention relates to the optical system of a laser processing apparatus, and to the laser processing apparatus itself. Background Technology

[0002] Laser processing equipment focuses a laser beam onto a workpiece at a single point, causing a rapid rise in the workpiece's surface temperature. This melts or evaporates the irradiated surface, enabling processes such as cutting, drilling, and welding. Because the laser beam is focused at a single point, precise and intricate machining can be performed with pinpoint accuracy. Furthermore, using high-energy laser beams can shorten processing time and allows for the machining of high-hardness workpieces that are difficult to machine with cutting tools.

[0003] As is well known, when a laser beam is focused, the intensity distribution of the laser beam at the irradiation point is preferably a ring shape on the plane of the irradiation point. However, if the ring diameter at the irradiation point is large, the light energy is difficult to concentrate sufficiently, thus increasing the melting time of the workpiece and deteriorating the quality of the processed profile. In addition, if the focal depth for maintaining a certain ring diameter is shallow, focal deviation will occur due to thermal lensing effects, resulting in a non-ring-shaped intensity distribution of the laser beam at the irradiation point, which can lead to problems such as deterioration of the welding quality of the workpiece.

[0004] In addition, Patent Document 1 discloses a laser welding device: by using a condenser lens obtained by cutting the central part of the convex surface of a condenser lens into a concave shape to focus the laser beam, the intensity distribution of the laser beam in the peripheral part is higher than that in the central part.

[0005] Patent document 2 discloses an optical system that, by introducing a function to shift the phase of a laser beam into the optical system, sets a phase difference on a portion of the laser beam, thereby converting the energy intensity distribution of an input laser beam with a Gaussian energy intensity distribution at the spot of its synthesized light into an intensity distribution with a ring shape (bimodal) or a top-hat shape.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2003-305581

[0009] Patent Document 2: US Patent No. 9285593 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, the optical system of the laser processing apparatus described in Patent Document 1 uses a condenser lens, obtained by cutting the central part of the convex surface of the condenser lens into a concave shape, to focus the laser beam, resulting in a higher intensity distribution of the laser beam at the periphery than at the center. Here, the laser beam passing through the concave part of the condenser lens is refracted from the center in the direction to be diffused. Therefore, the laser beam refracted at the concave part of the condenser lens does not focus on the irradiation point of the workpiece. That is, in the processing of the workpiece by the laser beam, the energy utilization efficiency of the laser beam output from the laser oscillator is low.

[0012] Furthermore, the optical system of the laser processing apparatus described in Patent Document 2 is not suitable for processing objects with high light reflectivity.

[0013] The purpose of this invention is to provide an optical system for a laser processing apparatus, and a laser processing apparatus, which has high energy utilization efficiency of laser light and can select an irradiation point (spot) with energy intensity distribution suitable for processing objects of various materials.

[0014] Methods for solving problems

[0015] In order to solve the above problems, in-depth research was conducted, resulting in the following invention.

[0016] The optical system of the laser processing apparatus of the present invention processes the workpiece by irradiating it with laser light. It has multiple optical surfaces with different focal points set on the optical axis. The energy intensity distribution of the laser light on the surface perpendicular to the optical axis varies depending on the position on the optical axis. By using different positions on the optical axis as the irradiation points (spots) of the laser light on the workpiece, the energy intensity distribution of the laser light at the irradiation points (spots) of the laser light on the workpiece can be selected.

[0017] The laser processing apparatus of the present invention includes the optical system of the laser processing apparatus described above.

[0018] Invention Effects

[0019] The optical system of the laser processing apparatus of this invention has multiple optical surfaces with different focal points along the optical axis. This allows the energy intensity distribution of laser light on the surfaces perpendicular to the optical axis to vary depending on their position on the optical axis. By using different positions on the optical axis as the irradiation points (spots) of the laser light on the workpiece, the energy intensity distribution of the laser light at the irradiation points (spots) can be selected. Therefore, laser processing can be performed by selecting an appropriate energy intensity distribution at the spot corresponding to the workpiece. Attached Figure Description

[0020] Figure 1 a and b are schematic cross-sectional views of the optical system of the laser processing apparatus according to this embodiment.

[0021] Figure 2 It is a schematic cross-sectional view of an optical element having different spherical and / or aspherical surfaces on the same optical plane.

[0022] Figure 3 It is a schematic cross-sectional view of an optical element having different spherical and / or aspherical surfaces on two different optical surfaces.

[0023] Figure 4 This is a schematic cross-sectional view of the laser processing apparatus involved in this embodiment.

[0024] Figure 5 The energy intensity distribution of Example 1 is a lateral aberration map of the irradiation point with a central ring shape, relative to the coordinates of the incident pupil.

[0025] Figure 6 The energy intensity distribution of Example 1 is the ratio of the intensity of laser rays on a straight line containing the optical axis on a plane perpendicular to the optical axis at an annular irradiation point with a central part.

[0026] Figure 7 The energy intensity distribution of Example 1 is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at a central annular irradiation point.

[0027] Figure 8 This is a lateral aberration map of the irradiation point in Example 1, where the energy intensity distribution is annular, relative to the coordinates of the incident pupil.

[0028] Figure 9 It is the ratio of the intensity of laser light on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of Example 1 is annular.

[0029] Figure 10 It is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is annular in Example 1.

[0030] Figure 11 This is a lateral aberration map of the irradiation point with respect to the coordinates of the incident pupil, where the energy intensity distribution is Gaussian in Example 1.

[0031] Figure 12 It is the ratio of the intensity of laser light rays on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is Gaussian in Example 1.

[0032] Figure 13It is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is Gaussian in Example 1.

[0033] Figure 14 The energy intensity distribution of Example 2 is a lateral aberration map of the irradiation point with a central ring shape, relative to the coordinates of the incident pupil.

[0034] Figure 15 The energy intensity distribution of Example 2 is the ratio of the intensity of laser rays on a straight line containing the optical axis on a plane perpendicular to the optical axis at an annular irradiation point with a central part.

[0035] Figure 16 The energy intensity distribution of Example 2 is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at an annular irradiation point with a central part.

[0036] Figure 17 This is a transverse aberration map of the irradiation point in Example 2, where the energy intensity distribution is annular, relative to the coordinates of the incident pupil.

[0037] Figure 18 It is the ratio of the intensity of laser light on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of Example 2 is annular.

[0038] Figure 19 It is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is annular in Example 2.

[0039] Figure 20 This is a lateral aberration map of the irradiation point with respect to the coordinates of the incident pupil, where the energy intensity distribution is Gaussian in Example 2.

[0040] Figure 21 It is the ratio of the intensity of laser light on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is Gaussian in Example 2.

[0041] Figure 22 It is the ratio of the intensity of laser light on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is Gaussian in Example 2.

[0042] Figure 23 This is a lateral aberration map of the illumination point relative to the coordinates of the incident pupil, where the energy intensity distribution is Gaussian in the comparative example.

[0043] Figure 24 The ratio of the intensity of laser rays on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point of the comparative example, where the energy intensity distribution is Gaussian.

[0044] Figure 25The ratio of the intensity of laser light on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is Gaussian is a comparative example.

[0045] Figure 26 This is a lateral aberration map of the illumination point with respect to the coordinates of the incident pupil at the point where the energy intensity distribution is in a ring shape, as in the comparative example.

[0046] Figure 27 The energy intensity distribution of the comparative example is the ratio of the intensity of the laser beam on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point perpendicular to the optical axis on a plane with an annular energy intensity distribution.

[0047] Figure 28 The energy intensity distribution of the comparative example is the ratio of the laser light intensity on a plane perpendicular to the optical axis at the irradiation point.

[0048] Figure 29 This is a lateral aberration map of the illumination point with respect to the coordinates of the incident pupil at the point where the energy intensity distribution is in a ring shape, as in the comparative example.

[0049] Figure 30 The energy intensity distribution of the comparative example is the ratio of the intensity of the laser beam on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point perpendicular to the optical axis on a plane with an annular energy intensity distribution.

[0050] Figure 31 The energy intensity distribution of the comparative example is the ratio of the laser light intensity on a plane perpendicular to the optical axis at the irradiation point.

[0051] Explanation of reference numerals in the attached figures:

[0052] 1. First configuration of optical system

[0053] 2. Second configuration of the optical system

[0054] 5 Optical elements for energy distribution control

[0055] 6 Optical elements for energy distribution control

[0056] 10 optical axes

[0057] 11 Optical Surface Area

[0058] 12 Optical Surface Areas

[0059] 21 Optical Surface Area

[0060] 22 Optical surface area

[0061] 31 Optical surface area

[0062] 32 Optical Surface Area

[0063] 41 Optical surface area

[0064] 42 Optical surface area

[0065] 50 Irradiation point R (ring-shaped)

[0066] 51 Irradiation point C (a ring-shaped area with a central part)

[0067] 52 Irradiation point G (Gaussian shape)

[0068] 70 Optical Components

[0069] 71 Substrate

[0070] 72 Optical surfaces

[0071] 73 Optical surfaces

[0072] 74 First Optical Region

[0073] 75 Second Optical Region

[0074] 70' Optical Components

[0075] 71' Substrate

[0076] 72' optical surface

[0077] 73' Optical surface

[0078] 74' First optical region

[0079] 75' Second optical region

[0080] 80 Laser processing equipment

[0081] 81 Laser Oscillator

[0082] 82 optical paths

[0083] 83 Optical System

[0084] 84. Machining worktable

[0085] 85 Workpiece

[0086] 101 beams

[0087] 102 beams

[0088] 201 beams

[0089] 202 beams

[0090] 301 beam

[0091] 302 beams

[0092] 401 beam

[0093] 402 beams Detailed Implementation

[0094] The optical system used in the laser processing apparatus according to the present invention, and the embodiments of the laser processing apparatus will be described below.

[0095] 1. Implementation method of the optical system used in laser processing equipment

[0096] The present invention relates to an optical system used in a laser processing apparatus, an optical system used in a laser processing apparatus that processes a workpiece by irradiating it with laser light, and a laser processing apparatus equipped with the optical system. This optical system has multiple optical surfaces with different focal points arranged along the optical axis. Therefore, the energy intensity distribution of the laser light on the surface perpendicular to the optical axis varies depending on its position on the optical axis.

[0097] At this time, the optical system can select the energy intensity distribution of the laser beam at the irradiation point on the workpiece by using different positions on the optical axis as the irradiation point (spot) of the laser beam. Specifically, the optical system can convert the incident laser beam into at least three modes: Gaussian, annular (ring-shaped, bimodal), and annular with a central portion (a shape formed by the ring shape and the central portion of the ring shape), thereby selecting the energy intensity distribution of the laser beam at the irradiation point on the workpiece.

[0098] According to the present invention, as described below, when the energy intensity distribution at the spot is, for example, Gaussian, it is suitable for welding and cutting of iron, etc.; when it is ring-shaped, it is suitable for lap welding and butt welding of workpieces such as copper and hot-dip galvanized steel sheets; and when it is a shape formed by the ring shape and the center part of the ring shape, it is suitable for welding and cutting of workpieces with high light reflectivity such as aluminum. It is possible to select an appropriate energy intensity distribution at the spot for laser processing according to the workpiece.

[0099] A schematic cross-sectional view of the optical system of the laser processing apparatus involved in this embodiment is shown below. Figure 1 As shown in a and b. Figure 1 The letter 'a' indicates that the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the laser beam on the optical axis 10, starting from the side of the energy distribution control optical element 5, is sequentially a Gaussian, a ring, and a first configuration of a ring-shaped energy intensity distribution with a central portion. Furthermore, Figure 1 The 'b' indicates that the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the laser beam on the optical axis 10 is a second configuration with a central ring-shaped, ring-shaped, and Gaussian-shaped energy intensity distribution, starting from the side of the energy distribution control optical element 6.

[0100] [Optical system with first configuration of energy intensity distribution]

[0101] First, refer to Figure 1 A will describe the optical system 1 of the first configuration. Figure 1 The letter 'a' represents the approximate trajectory of the laser beam emitted from the energy distribution control optical element 5 when a laser beam is incident on the energy distribution control optical element 5, starting from the side where the energy distribution control optical element 5 is located. The optical axis 10 passes through the optical center of the energy distribution control optical element 5. The energy distribution control optical element 5 has optical surface region 11, optical surface region 12, optical surface region 21, and optical surface region 22. Furthermore, optical surface region 11 and optical surface region 21 are concentric circles centered on the optical center of the energy distribution control optical element 5. Similarly, optical surface region 12 and optical surface region 22 are concentric circles centered on the optical center of the energy distribution control optical element 5.

[0102] The focal point of the concentric circular region of the energy distribution control optical element 5, which includes optical surface region 11 and optical surface region 21, is located at the illumination point C51 on the optical axis 10. On the other hand, the focal point of the concentric circular region of the energy distribution control optical element 5, which includes optical surface region 12 and optical surface region 22, is located at the illumination point G52 on the optical axis 10. Thus, the first configured optical system 1 has optical surfaces with multiple different focal points set on the optical axis. Furthermore, in Figure 1 In a, the laser beam 101 emitted from optical surface region 11, the laser beam 201 emitted from optical surface region 21, the laser beam 102 emitted from optical surface region 12, and the laser beam 202 emitted from optical surface region 22 are represented in a way that simplifies the laser beams emitted from their respective optical surface regions into a single line.

[0103] Here, the laser beam 101, which includes the laser light emitted from optical surface region 11, and the laser beam 201, which includes the laser light emitted from optical surface region 21, both emitted from the energy distribution control optical element 5, converge at the irradiation point C51. Furthermore, after passing through the irradiation point C51, this beam gradually expands in a diffused manner and passes through the irradiation points R50 and G52. Additionally, the laser beam 102, which includes the laser light emitted from optical surface region 12, and the laser beam 202, which includes the laser light emitted from optical surface region 22, both emitted from the energy distribution control optical element 5, gradually converges towards the focal point and passes through the irradiation points C51 and R50. This beam then converges at the irradiation point G52.

[0104] At this time, at the irradiation point C51, the beams containing laser beams 102 and 202 emitted from the energy distribution control optical element 5 pass near the beams containing laser beams 101 and 201 emitted from the energy distribution control optical element 5. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point C51 is a ring shape with the optical axis 10 as the center.

[0105] Furthermore, the beams containing laser rays 101 and 201 emitted from the energy distribution control optical element 5 converge at the focal point at the irradiation point C51, then diffuse and reach the irradiation point R50. Conversely, the beams containing laser rays 102 and 202 emitted from the energy distribution control optical element 5 converge at the focal point at the irradiation point C52 and reach the irradiation point R50. Thus, the beams containing laser rays 101 and 201 emitted from the energy distribution control optical element 5, and the beams containing laser rays 102 and 202 emitted from the energy distribution control optical element 5, pass through the same position on the plane perpendicular to the optical axis 10. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point R50 is a ring shape centered on the optical axis 10.

[0106] Furthermore, at the irradiation point G52, the beams containing laser beams 101 and 201 emitted from the energy distribution control optical element 5 gradually expand in a diffused manner after passing through the irradiation point C51. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point G52 is Gaussian centered on the optical axis 10.

[0107] In other words, the optical system 1 with the first configuration of energy intensity distribution has the following configuration: the energy intensity distributions on the plane perpendicular to the optical axis 10 at the positions of the laser beam irradiation point C51, irradiation point R50, and irradiation point G52 on the optical axis 10 are sequentially annular, annular, and Gaussian energy intensity distributions with a central portion. At this time, by placing the workpiece at the irradiation point C51, laser processing can be performed with the energy intensity distribution at the annular spot with a central portion. Similarly, by placing the workpiece at the irradiation point R50, laser processing can be performed with the energy intensity distribution at the annular spot. Furthermore, by placing the workpiece at the irradiation point G52, laser processing can be performed with the energy intensity distribution at the Gaussian spot.

[0108] The optical system 1 with the first configuration of the energy intensity distribution described above preferably satisfies the following condition (1). This is because, by the optical system 1 with the first configuration of the energy intensity distribution satisfying condition (1), the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the laser beam on the optical axis 10 is sequentially annular, annular, and Gaussian in shape with a central part, starting from the side of the optical element 5 for energy distribution control.

[0109] fB1<fB0<fB2····(1)

[0110] Wherein, fB0: the position of the laser beam on the optical axis where the energy intensity distribution is annular on the plane perpendicular to the optical axis, and the distance from the optical surface closest to the workpiece (excluding devices without optical significance such as cover glass).

[0111] fB1: The energy intensity distribution of the laser beam on the plane perpendicular to the optical axis is the position on the optical axis with a central ring, and the distance from the optical surface closest to the workpiece (excluding devices without optical significance such as cover glass).

[0112] fB2: The position of the laser beam on the optical axis with a Gaussian energy intensity distribution on the plane perpendicular to the optical axis, and the distance from the optical surface closest to the workpiece (excluding devices without optical significance such as cover glass).

[0113] [Optical system with second configuration of energy intensity distribution]

[0114] Next, refer to Figure 1 b will describe the second configuration of the optical system 2. Figure 1 The letter 'b' represents the approximate trajectory of the laser beam emitted from the energy distribution control optical element 6 when a laser beam is incident on the energy distribution control optical element 6, starting from the side where the energy distribution control optical element 6 is located. The optical axis 10 passes through the optical center of the energy distribution control optical element 6. The energy distribution control optical element 6 has optical surface region 31, optical surface region 32, optical surface region 41, and optical surface region 42. Furthermore, optical surface region 31 and optical surface region 41 are concentric circles centered on the optical center of the energy distribution control optical element 6. Similarly, optical surface region 32 and optical surface region 42 are concentric circles centered on the optical center of the energy distribution control optical element 6.

[0115] The focal point of the concentric circular region of the energy distribution control optical element 6, which includes optical surface region 31 and optical surface region 41, is located at the illumination point C51 on the optical axis 10. On the other hand, the focal point of the concentric circular region of the energy distribution control optical element 6, which includes optical surface region 32 and optical surface region 42, is located at the illumination point G52 on the optical axis 10. Thus, the second-configured optical system 2 has optical surfaces with multiple different focal points set along the optical axis. Furthermore, in Figure 1 In b, the laser beam 301 emitted from optical surface region 31, the laser beam 401 emitted from optical surface region 41, the laser beam 302 emitted from optical surface region 32, and the laser beam 402 emitted from optical surface region 42 are represented in a way that simplifies the laser beams emitted from their respective optical surface regions into a single line.

[0116] Here, the laser beam 301, which includes the laser light emitted from optical surface region 31, and the laser beam 401, which includes the laser light emitted from optical surface region 41, and the laser beam emitted from the energy distribution control optical element 6, gradually converge towards the focal point and pass through the positions of irradiation point G52 and irradiation point R50. Furthermore, this beam converges at a single point at irradiation point C51. Additionally, the laser beam 302, which includes the laser light emitted from optical surface region 32, and the laser beam 402, which includes the laser light emitted from optical surface region 42, and the laser beam emitted from the energy distribution control optical element 6, converge at a single point at irradiation point G52. Furthermore, after passing through irradiation point G52, this beam gradually expands in a diffused manner and passes through the positions of irradiation point R50 and irradiation point C51.

[0117] At this point, at the irradiation point G52, the beams containing laser light beams 301 and 401 emitted from the energy distribution control optical element 6 are not fully converged relative to the optical axis 10. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point G52 is Gaussian centered on the optical axis 10.

[0118] Furthermore, the beams containing laser rays 301 and 401 emitted from the energy distribution control optical element 6 converge toward the focal point at the irradiation point C51 and reach the irradiation point R50. On the other hand, the beams containing laser rays 302 and 402 emitted from the energy distribution control optical element 6 converge at the focal point at the irradiation point G52, then diffuse and reach the irradiation point R50. Thus, the beams containing laser rays 301 and 401 emitted from the energy distribution control optical element 6, and the beams containing laser rays 302 and 402 emitted from the energy distribution control optical element 6, pass through the same position on the plane perpendicular to the optical axis 10. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point R50 is a ring shape centered on the optical axis 10.

[0119] Furthermore, at the irradiation point C51, the beams containing laser beams 302 and 402 emitted from the energy distribution control optical element 6 pass near the beams containing laser beams 301 and 401 emitted from the energy distribution control optical element 6. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the irradiation point C51 is a ring shape with a central portion centered on the optical axis 10.

[0120] In other words, the optical system 2 with the second configuration of energy intensity distribution has the following configuration: the energy intensity distributions on the plane perpendicular to the optical axis 10 at the positions of the laser beam irradiation point G52, irradiation point R50, and irradiation point C51 are successively Gaussian, annular, and annular energy intensity distributions with a central portion. At this time, by placing the workpiece at the irradiation point G52, laser processing can be performed with the energy intensity distribution at the Gaussian spot. Furthermore, by placing the workpiece at the irradiation point R50, laser processing can be performed with the energy intensity distribution at the annular spot. Finally, by placing the workpiece at the irradiation point C51, laser processing can be performed with the energy intensity distribution at the annular spot with a central portion.

[0121] The optical system 2 with the second configuration of the energy intensity distribution described above preferably satisfies the following condition (2). This is because, by the optical system 2 with the second configuration of the energy intensity distribution satisfying condition (2), the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the laser beam on the optical axis 10 is, from the side of the energy distribution control optical element 6, successively Gaussian, annular, and annular with a central part.

[0122] fB2<fB0<fB1····(2)

[0123] [Common conditions for the first and second configurations of the optical system regarding energy intensity distribution]

[0124] The optical system of the laser processing apparatus according to this embodiment preferably satisfies the following condition (3). By satisfying condition (3), the optical system of the laser processing apparatus according to this embodiment can reliably ensure the distance between the irradiation point R50 and the irradiation point C51. This is because, even if an optical element having multiple optical surfaces with different focal points is heated by the laser beam and the focal point deviates, the energy intensity distribution at the irradiation point remains unchanged, preventing the inability to perform processes such as welding and cutting.

[0125] 1mm≤|fB0-fB1|····(3)

[0126] Furthermore, based on achieving the aforementioned effects, a lower limit of 2 mm is more preferable for conditional expression (3). Additionally, the upper limit of conditional expression (3) need not be specifically limited; for example, if it is 50 mm, then when the energy intensity distribution at the irradiation point is changed, Figure 4 The distance between the optical system 83 and the workpiece 85 is easily adjustable, and is therefore preferred, more preferably 40 mm, and even more preferably 20 mm.

[0127] Furthermore, the optical system of the laser processing apparatus according to this embodiment preferably satisfies the following condition (4). By satisfying condition (4), the optical system of the laser processing apparatus according to this embodiment can reliably ensure the distance between the irradiation point R50 and the irradiation point G52. This is because even if the optical element having multiple optical surfaces with different focal points is heated by the laser beam and the focal point deviates, the energy intensity distribution at the irradiation point remains unchanged, preventing the inability to perform processes such as welding and cutting.

[0128] 1mm≤|fB0-fB2|····(4)

[0129] Furthermore, based on achieving the aforementioned effects, a lower limit of 2 mm is more preferable for conditional expression (4). Additionally, the upper limit of conditional expression (4) need not be specifically limited; for example, if it is 50 mm, then when the energy intensity distribution at the irradiation point is changed, Figure 4 The distance between the optical system 83 and the workpiece 85 is easily adjustable, and is therefore preferred, more preferably 40 mm, and even more preferably 20 mm.

[0130] [Optical surfaces with different focal points]

[0131] The optical system of the laser processing apparatus according to this embodiment has multiple optical surfaces with different focal points arranged on the optical axis. Figure 1 a and Figure 1 In the optical system shown in b, the optical elements 5 and 6 for energy distribution control have optical surfaces with multiple different focal points set on the optical axis. Preferably, the optical surfaces with multiple different focal points are multiple different spherical and / or aspherical surfaces. By using multiple different spherical and / or aspherical surfaces, multiple different focal points can be set on these optical surfaces.

[0132] Furthermore, it is preferable that the aforementioned multiple different spherical and / or aspherical surfaces are arranged in multiple different concentric circular regions on the same optical surface. Figure 2 This is a schematic cross-sectional view of an optical element 70 having different spherical and / or aspherical surfaces on the same optical surface. The optical element 70 is constructed from a substrate 71, the material of which is not particularly limited as long as an optical material is used to form the substrate 11. The substrate 11 has optical surfaces 72 and 73 for laser light to pass through, and the dashed line O represents the central axis of the optical element 70. Furthermore, on the optical surface 72, the first optical region 74 and the second optical region 75, two spherical and / or aspherical surfaces, are arranged as concentric circles centered on the central axis O of the optical element. In this case, the incident light refracted at the interface between the two concentric circular first optical regions 74 and second optical regions 75 converges towards two different focal points.

[0133] Here, if the optical element is 5 for energy distribution control, then optical surface region 12 and optical surface region 22 correspond to the first optical region 74, and optical surface region 11 and optical surface region 21 correspond to the second optical region 75. Furthermore, if the optical element is 6 for energy distribution control, then optical surface region 32 and optical surface region 42 correspond to the first optical region 74, and optical surface region 31 and optical surface region 41 correspond to the second optical region 75.

[0134] In addition, multiple different spherical and / or aspherical surfaces are preferably regions for different optical surfaces to allow different light beams to pass through, and are arranged in multiple different regions in a concentric circle. Figure 3This is a schematic cross-sectional view of an optical element 70' having different spherical and / or aspherical surfaces on two different optical surfaces within the same optical element. The optical element 70' is constructed from a substrate 71', which has optical surfaces 72' and 73' for laser light to pass through. The two spherical and / or aspherical surfaces, a first optical region 74' on optical surface 72' and a second optical region 75' on optical surface 73', are arranged as concentric circles centered on the central axis O' of the optical element. At this time, the first optical region 74' and the second optical region 75' are positioned to allow their respective beams to pass through. Furthermore, the incident light, refracted at the interface between the two concentric circular first optical regions 74' and second optical regions 75', converges towards two different focal points.

[0135] If the optical element is 5 for energy distribution control, then optical surface region 12 and optical surface region 22 correspond to the first optical region 74', and optical surface region 11 and optical surface region 21 correspond to the second optical region 75'. Furthermore, if the optical element is 6 for energy distribution control, then optical surface region 32 and optical surface region 42 correspond to the first optical region 74', and optical surface region 31 and optical surface region 41 correspond to the second optical region 75'.

[0136] Preferably, among the various spherical and / or aspherical surfaces involved in this invention, at least one optical surface is aspherical. This is because aspherical surfaces readily achieve lateral aberrations that are difficult to achieve with spherical surfaces, thus enabling the setting of different focal points on the various optical surfaces involved in this invention.

[0137] Furthermore, it is preferable that the multiple different spherical and / or aspherical surfaces involved in the present invention are each two different optical surfaces. This is because it is possible to easily construct the optical system involved in the present invention, which consists of multiple optical surfaces with different focal points.

[0138] Furthermore, it is preferable that the multiple different spherical and / or aspherical surfaces involved in this invention are each two different aspherical surfaces. This is because aspherical surfaces can easily achieve lateral aberrations that are difficult to achieve with spherical surfaces, thus making it easy to construct the optical system involved in this invention, which consists of multiple optical surfaces with different focal points, and also making it easy to adjust the focal distance.

[0139] 2. Implementation methods of laser processing equipment

[0140] The laser processing apparatus of the present invention includes the optical system described above. In this optical system, by using different positions on the optical axis as the irradiation points of the laser beam onto the workpiece, the energy intensity distribution of the laser beam at the irradiation points can be selected. Specifically, the incident laser beam can be converted into at least three modes: Gaussian, ring-shaped (bimodal), and a shape formed by the ring shape and its center portion, thereby selecting the energy intensity distribution of the laser beam at the irradiation points on the workpiece.

[0141] Figure 4 This describes a laser processing apparatus 80 according to this embodiment. The laser processing apparatus 80 generally comprises a laser oscillator 81, an optical path 82, an optical system 83, and a processing table 84. The optical system 83 is the optical system of the aforementioned laser processing apparatus. A workpiece 85 is disposed on the processing table 84. The laser oscillator 81 is a device that outputs laser light used for processing. The type and output of the laser light to be used are selected according to the material of the workpiece 85, the thickness to be processed, the processing precision, etc. The optical path 82 is used to transmit the laser light output from the laser oscillator 81 to the optical system 83, and can be of the type using a mirror or the type using an optical cable. The optical system 83 then focuses the transmitted laser light into a predetermined shape to irradiate the irradiation point of the workpiece 85. The processing table 84 is fixedly disposed on the workpiece 85 and, in order to select the energy intensity distribution of the laser light at the irradiation point of the workpiece 85, includes a device for moving the workpiece 85 or the optical system 83, or both.

[0142] The laser processing apparatus 80 uses the aforementioned optical system 83 to designate different positions on the optical axis as the irradiation points of the laser beam onto the workpiece 85, thereby converting the incident laser beam into at least three modes: Gaussian, ring-shaped (bimodal), and a shape formed by the ring shape and its center. This allows for selection of the energy intensity distribution of the laser beam at the irradiation point on the workpiece 85. Thus, a Gaussian energy intensity distribution at the spot is suitable for welding and cutting iron; a ring shape is suitable for lap welding and butt welding of workpieces such as copper and hot-dip galvanized steel; and a shape formed by the ring shape and its center is suitable for welding and cutting workpieces with high light reflectivity, such as aluminum. The apparatus can select an appropriate energy intensity distribution at the spot for laser processing, tailored to the workpiece.

[0143] The optical system 83 of the laser processing apparatus 80 may also include a collimating lens to make the laser beam approximately parallel, a focusing lens to focus the laser beam, etc. Alternatively, the energy distribution control optical element 5 (or energy distribution control optical element 6) may also function as a collimating lens, and a focusing lens may be placed on the workpiece side of the energy distribution control optical element 5 (or energy distribution control optical element 6). In these cases, fB0, fB1, and fB2 are the distances from the optical surface of the optical system 83 closest to the workpiece (excluding devices without optical significance such as cover glass).

[0144] The embodiments described above are one approach of the present invention, and appropriate modifications can be made without departing from the spirit of the invention. Furthermore, the following examples provide a more detailed description of the invention, but the invention is not limited to these examples.

[0145]

Example 1

[0146] right Figure 1 The first configuration of the energy intensity distribution described in Example 1 will be used for illustration. The optical element used for energy distribution control in Example 1 is as follows: Figure 2 As shown, this is an element obtained by setting multiple optical surfaces with different focal points in multiple concentric circular regions on the same optical surface. Here, the shape of the aspherical optical surface can be represented by the even-order aspherical form shown in equation (5) below.

[0147] z(r)=(r 2 / R) / [1+{1-ε·r 2 / R 2} 1 / 2 ]+Ar 2 +Br 4 +Cr 6 +Dr 8 +Er 10 ····(5)

[0148] in,

[0149] z(r): The surface position (depression) in the direction of the optical axis perpendicular to the optical axis at a distance r from it.

[0150] R: Radius of curvature.

[0151] ε: is (1+k), where k is the conic constant.

[0152] A, B, C, D, E: Aspheric coefficients.

[0153] As the optical element for energy intensity distribution control in Example 1, an optical element with an effective diameter of 37.3 mm is used. This optical element is equivalent to... Figure 2 The first optical region 74 is a region with a surface diameter of less than 16.0 mm. If equation (5) is used, the aspherical surface of this region is a shape that satisfies the following values.

[0154] R = -200.0

[0155] ε=-1.5237×10 6

[0156] A = 2.6803 × 10 －3

[0157] B = 9.1279 × 10 －10

[0158] C = 0.0

[0159] D = 0.0

[0160] E = 0.0

[0161] Similarly, the optical element is equivalent to Figure 2 The second optical region 75 is a region with a surface diameter of 16.0 mm or more. If equation (5) is used, the aspherical surface of this region is a shape that satisfies the following values.

[0162] R = 200.0

[0163] ε=-1.5237×10 6

[0164] A = 2.6974 × 10 －3

[0165] B = 4.5648 × 10 －9

[0166] C = 0.0

[0167] D = 0.0

[0168] E = 0.0

[0169] At this point, the lateral aberration diagram relative to the entrance pupil coordinates at a position 219.4 mm away from the optical surface of the optical element on the optical axis is as follows: Figure 5 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0170] exist Figure 5In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 1 have different focal points as described above, the lateral aberration characteristics at the entrance pupil coordinates corresponding to the first optical region 74 and the second optical region 75 are different. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 exhibits a lateral aberration amount of approximately constant magnitude. On the other hand, the lateral aberration of the corresponding portion of the second optical region 75 exhibits a lateral aberration value close to zero.

[0171] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 6 as well as Figure 7 As shown. Figure 6 It is shown Figure 5 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 7 It is shown Figure 5 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 6 as well as Figure 7 It can be clearly seen that at a position 219.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 5 The energy intensity distribution at the irradiation point of the lateral aberration characteristic is a ring shape with a central part.

[0172] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 221.9 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 8 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0173] exist Figure 8 In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 1 have different focal points as described above, the lateral aberration characteristics at the entrance pupil coordinates corresponding to the first optical region 74 and the second optical region 75 are different. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 exhibits a lateral aberration amount of approximately constant magnitude. Similarly, the lateral aberration of the corresponding portion of the second optical region 75 also exhibits a lateral aberration amount of constant magnitude.

[0174] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 9 as well as Figure 10 As shown. Figure 9 It is shown Figure 8 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 10 It is shown Figure 8 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 9 as well as Figure 10 It can be clearly seen that at a position 221.9 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 8 The energy intensity distribution at the irradiation point of the lateral aberration characteristic is ring-shaped.

[0175] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 228.4 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 11 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0176] exist Figure 11 In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 1 have different focal points as described above, the lateral aberration characteristics of the portion corresponding to the first optical region 74 and the portion corresponding to the second optical region 75 at the entrance pupil coordinates are different. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 as a whole exhibits a smaller lateral aberration characteristic. On the other hand, the lateral aberration of the corresponding portion corresponding to the second optical region 75 exhibits a larger lateral aberration characteristic, and the lateral aberration increases with distance from the origin of the entrance pupil coordinates.

[0177] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 12 as well as Figure 13 As shown. Figure 12 It is shown Figure 11 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 13 It is shown Figure 11The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 12 as well as Figure 13 It can be clearly seen that at a position 228.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 11 The energy intensity distribution at the illumination point of the lateral aberration characteristic is Gaussian.

[0178] It can be clearly seen from the above that the optical system of Embodiment 1 has the following characteristics: the energy intensity distribution characteristics, starting from the optical element side, are successively ring-shaped, ring-shaped, and Gaussian-shaped illumination points with a central part. Furthermore, the distances from each illumination point to the optical surface of the optical element on the optical axis are fB1 = 219.4 mm, fB0 = 221.9 mm, and fB2 = 228.4 mm. In other words, it can be clearly seen that the optical system of Embodiment 1 satisfies condition (1).

[0179] and then,

[0180] |fB0-fB1|=2.5

[0181] |fB0-fB2|=6.5

[0182] Therefore, it can be clearly seen that the optical system of Example 1 satisfies condition (3) and condition (4).

[0183]

Example 2

[0184] Next, regarding Figure 1 The second configuration of the energy intensity distribution described in Example 2 will be illustrated. The optical element used for energy distribution control in Example 2 is as follows: Figure 2 As shown, this is a component obtained by setting multiple optical surfaces with different focal points in multiple concentric circular regions on the same optical surface.

[0185] As the optical element for energy intensity distribution control in Example 2, an optical element with an effective diameter of 37.3 mm is used. This optical element is equivalent to... Figure 2 The first optical region 74 is a region with a surface diameter of less than 16.0 mm. If equation (5) is used, the aspherical surface of this region is a shape that satisfies the following values.

[0186] R = 200.0

[0187] ε=-1.5237×10 6

[0188] A = 2.6791 × 10 －3

[0189] B = 4.9802 × 10 －9

[0190] C = 0.0

[0191] D = 0.0

[0192] E = 0.0

[0193] Similarly, the optical element is equivalent to Figure 2 The second optical region 75 is a region with a surface diameter of 16.0 mm or more. If equation (5) is used, the aspherical surface of this region is a shape that satisfies the following values.

[0194] R = -200.0

[0195] ε=-1.5237×10 6

[0196] A = 2.6626 × 10 －3

[0197] B = 3.5921 × 10 －9

[0198] C = 0.0

[0199] D = 0.0

[0200] E = 0.0

[0201] At this point, the lateral aberration diagram relative to the entrance pupil coordinates at a position 218.4 mm away from the optical surface of the optical element on the optical axis is as follows: Figure 14 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0202] exist Figure 14 In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 2 have different focal points as described above, the lateral aberration characteristics of the portion corresponding to the first optical region 74 at the entrance pupil coordinates differ from those of the portion corresponding to the second optical region 75. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 as a whole exhibits a smaller lateral aberration characteristic. On the other hand, the lateral aberration of the corresponding portion of the portion corresponding to the second optical region 75 exhibits a larger lateral aberration characteristic, and the lateral aberration increases with distance from the origin of the entrance pupil coordinates.

[0203] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 15 as well as Figure 16 As shown. Figure 15 It is shown Figure 14 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 16 It is shown Figure 14 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 15 as well as Figure 16 It can be clearly seen that at a position 218.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 14 The energy intensity distribution at the illumination point of the lateral aberration characteristic is Gaussian.

[0204] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 224.9 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 17 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0205] exist Figure 17 In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 2 have different focal points as described above, the lateral aberration characteristics of the portion corresponding to the first optical region 74 at the entrance pupil coordinates differ from those of the portion corresponding to the second optical region 75. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 exhibits a lateral aberration amount of approximately the same magnitude. Similarly, the lateral aberration of the corresponding portion of the portion corresponding to the second optical region 75 also exhibits a lateral aberration amount of approximately the same magnitude.

[0206] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 18 as well as Figure 19 As shown. Figure 18 It is shown Figure 17 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 19 It is shown Figure 17 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 18 as well as Figure 19 It can be clearly seen that at a position 224.9 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 17The energy intensity distribution at the irradiation point of the lateral aberration characteristic is ring-shaped.

[0207] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 227.4 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 20 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0208] exist Figure 20 In the example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical elements of Embodiment 2 have different focal points as described above, the lateral aberration characteristics of the portion corresponding to the first optical region 74 at the entrance pupil coordinates differ from those of the portion corresponding to the second optical region 75. Specifically, the lateral aberration of the portion corresponding to the first optical region 74 exhibits a lateral aberration amount of approximately a certain magnitude. On the other hand, the lateral aberration of the corresponding portion of the second optical region 75 exhibits a lateral aberration value close to zero.

[0209] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 21 as well as Figure 22 As shown. Figure 21 It is shown Figure 20 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 22 It is shown Figure 20 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 21 as well as Figure 22 It can be clearly seen that at a position 227.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 20 The energy intensity distribution at the irradiation point of the lateral aberration characteristic is a ring shape with a central part.

[0210] It can be clearly seen from the above that the optical system of Embodiment 2 has the following characteristics: the energy intensity distribution characteristics, starting from the optical element side, are successively Gaussian, annular, and an annular illumination point with a central part. Furthermore, the distances on the optical axis from each illumination point to the optical surface of the optical element are fB2 = 218.4 mm, fB0 = 224.9 mm, and fB1 = 227.4 mm. In other words, it can be clearly seen that the optical system of Embodiment 2 satisfies condition (2).

[0211] and then,

[0212] |fB0-fB1|=2.5

[0213] |fB0-fB2|=6.5

[0214] Therefore, it can be clearly seen that the optical system of Example 2 satisfies condition (3) and condition (4).

[0215] [Comparative Example]

[0216] The comparative example uses an optical element for energy distribution control with a single focal point. The comparative example uses an optical element with an effective diameter of 37.3 mm for the optical surface. If equation (5) is used, the aspherical surface of this optical element has a shape that satisfies the following values.

[0217] R = 200.0

[0218] ε=-1.4666×10 6

[0219] A = 2.6747 × 10 －3

[0220] B = 1.3586 × 10 －8

[0221] C = 0.0

[0222] D = 0.0

[0223] E = 0.0

[0224] At this point, the lateral aberration diagram relative to the entrance pupil coordinates at a position 218.4 mm away from the optical surface of the optical element on the optical axis is as follows: Figure 23 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0225] exist Figure 23 In the comparative example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical element of the comparative example is configured with a single focal point as described above, no abruptly changing lateral aberration characteristics are observed outside the origin of the entrance pupil coordinate system. Moreover, the lateral aberration value changes more slowly with increasing distance from the origin of the entrance pupil coordinate system, and at the midpoint of the entrance pupil coordinate system, the lateral aberration value becomes zero.

[0226] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 24 as well as Figure 25 As shown. Figure 24 It is shown Figure 23 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 25 It is shown Figure 23 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 24 as well as Figure 25 It can be clearly seen that at a position 218.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 23 The energy intensity distribution at the illumination point of the lateral aberration characteristic is Gaussian.

[0227] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 223.4 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 26 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0228] exist Figure 26 In the comparative example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical element of the comparative example is configured with a single focal point as described above, no abruptly changing lateral aberration characteristics are observed outside the origin of the entrance pupil coordinates. Moreover, the lateral aberration exhibits a lateral aberration amount of a fixed magnitude.

[0229] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 27 as well as Figure 28 As shown. Figure 27 It is shown Figure 26 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 28 It is shown Figure 26 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 27 as well as Figure 28 It can be clearly seen that at a position 223.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 26 The energy intensity distribution at the irradiation point of the lateral aberration characteristic is ring-shaped.

[0230] Next, the lateral aberration diagram relative to the entrance pupil coordinates at a position 227.4 mm away from the optical surface of the optical element on the optical axis is shown below. Figure 29 As shown. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. Furthermore, ex and ey represent lateral aberrations.

[0231] exist Figure 29 In the comparative example, the entrance pupil coordinates Px and Py both exhibit the same lateral aberration characteristics. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Furthermore, since the optical element of the comparative example is configured with a single focal point as described above, no abruptly changing lateral aberration characteristics are observed outside the origin of the entrance pupil coordinates. Moreover, the lateral aberration value changes more slowly with increasing distance from the origin of the entrance pupil coordinates.

[0232] The results of optical simulations using Zemax's Optical Design Program on the energy intensity distribution characteristics at the illumination point exhibiting such lateral aberrations are as follows: Figure 30 as well as Figure 31 As shown. Figure 30 It is shown Figure 29 The ratio of the intensity of laser rays on any straight line containing the optical axis on a plane perpendicular to the optical axis at the point of illumination of the lateral aberration characteristic. Figure 31 It is shown Figure 29 The ratio of the intensity of laser light rays on a plane perpendicular to the optical axis at the point of illumination, representing the lateral aberration characteristics. Figure 30 as well as Figure 31 It can be clearly seen that at a position 227.4 mm away from the optical surface of the optical element on the optical axis, the following is shown: Figure 29 The energy intensity distribution at the irradiation point of the lateral aberration characteristic is ring-shaped.

[0233] It is clear from the above that the energy intensity distribution characteristics of the comparative example's optical system, from the optical element side, are Gaussian, annular, and annular in sequence. In other words, it is clear that because the comparative example has a single focal point and not multiple different focal points, it does not satisfy the "first configuration of energy intensity distribution" and "second configuration of energy intensity distribution" required by the optical system of the laser processing apparatus of the present invention. Similarly, it is clear that the comparative example does not satisfy conditional expressions (1), (2), (3), and (4).

[0234] Industrial applicability

[0235] The optical system of the laser processing apparatus of this invention has multiple optical surfaces with different focal points set on the optical axis. This allows the energy intensity distribution of the laser beam on the surface perpendicular to the optical axis to vary depending on its position on the optical axis. By using different positions on the optical axis as the irradiation points of the laser beam onto the workpiece, the incident laser beam can be converted into at least three modes: Gaussian, toroidal (bimodal), and a shape formed by the toroidal shape and its center portion. This allows for selection of the energy intensity distribution of the laser beam at the irradiation point on the workpiece. Therefore, a Gaussian energy intensity distribution at the spot is suitable for welding and cutting iron; a toroidal (bimodal) distribution is suitable for lap welding and butt welding of copper and hot-dip galvanized steel sheets; and a shape formed by the toroidal shape and its center portion is suitable for welding and cutting aluminum materials with high light reflectivity. This allows for laser processing by selecting an appropriate energy intensity distribution at the spot corresponding to the workpiece. In other words, it is a laser processing device that can perform processes such as cutting, drilling, and welding on a workpiece by focusing a laser beam and irradiating it.

Claims

1. An optical system for a laser processing apparatus, which processes a workpiece by irradiating it with laser light, characterized in that, have: The optical surface is composed of multiple different spherical and / or aspherical surfaces, with multiple different focal points set along the optical axis. The energy intensity distribution of the laser beam on the plane perpendicular to the optical axis varies depending on its position on the optical axis. By using different positions on the optical axis as the irradiation points of the laser beam on the workpiece, the energy intensity distribution of the laser beam at the irradiation point on the workpiece can be selected.

2. The optical system of the laser processing apparatus as described in claim 1, The energy intensity distribution, which varies depending on the position on the optical axis, is configured as follows: From the laser oscillator side toward the workpiece side, there are sequentially arranged ring-shaped, annular, and Gaussian-shaped configurations with a central portion, and... From the laser oscillator side toward the workpiece side, the configuration is any one of the following: Gaussian, annular, or an annular configuration with a central portion.

3. The optical system of the laser processing apparatus as described in claim 2, In the first configuration of the energy intensity distribution, the following condition is satisfied: fB1<fB0<fB2····(1), in, fB0: The position on the optical axis where the energy intensity distribution of the laser beam on the plane perpendicular to the optical axis is annular, and the distance from the optical surface closest to the workpiece. fB1: The energy intensity distribution of the laser beam on the plane perpendicular to the optical axis is a ring-shaped distribution with a central portion, located at the distance from the optical surface closest to the workpiece. fB2: The position of the laser beam on the optical axis with a Gaussian energy intensity distribution on the plane perpendicular to the optical axis, and the distance from the optical surface closest to the workpiece.

4. The optical system of the laser processing apparatus as described in claim 2, In the second configuration of the energy intensity distribution, the following condition is satisfied: fB2<fB0<fB1····(2), in, fB0: The position on the optical axis where the energy intensity distribution of the laser beam on the plane perpendicular to the optical axis is annular, and the distance from the optical surface closest to the workpiece. fB1: The energy intensity distribution of the laser beam on the plane perpendicular to the optical axis is a ring-shaped distribution with a central portion, located at the distance from the optical surface closest to the workpiece. fB2: The position of the laser beam on the optical axis with a Gaussian energy intensity distribution on the plane perpendicular to the optical axis, and the distance from the optical surface closest to the workpiece.

5. The optical system of the laser processing apparatus as described in claim 3 or 4, The following conditions must be met: 1mm≤|fB0-fB1|····(3).

6. The optical system of the laser processing apparatus as described in claim 3 or 4, The following conditions must be met: 1mm≤|fB0-fB2|····(4).

7. The optical system of the laser processing apparatus as described in claim 1, The plurality of different spherical and / or aspherical surfaces are arranged in multiple different concentric circular regions on the same optical surface.

8. The optical system of the laser processing apparatus as described in claim 1, The multiple different spherical and / or aspherical surfaces are regions of different optical surfaces through which different light beams pass, and are arranged in multiple different regions in a concentric circle.

9. The optical system of the laser processing apparatus as described in any one of claims 1, 7-8, At least one optical surface of the plurality of different spherical and / or aspherical surfaces is an aspherical surface.

10. The optical system of the laser processing apparatus as described in any one of claims 1, 7-8, The multiple different spherical and / or aspherical surfaces are each two different optical surfaces.

11. The optical system of the laser processing apparatus as described in any one of claims 1, 7-8, The multiple different spherical and / or aspherical surfaces are each two different aspherical surfaces.

12. A laser processing apparatus, characterized in that, have: The optical system of the laser processing apparatus as claimed in any one of claims 1 to 11.

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