Laser processing apparatus, optical system of laser processing apparatus

Abstract

The present invention aims to provide an optical system of a laser processing apparatus in which the energy utilization efficiency of laser light is high, and the intensity distribution shape of the laser light at an irradiation point does not change even if the focal point position deviates due to thermal lens effect, and a laser processing apparatus using the optical system of the laser processing apparatus. To achieve this aim, the laser processing apparatus for processing a work by irradiating laser light according to the present invention has an optical system having optical surfaces in which a plurality of different focal points are provided on the same optical axis, and an irradiation point of the laser light on the work is at a different position from the focal points, and the intensity distribution of the laser light on a plane perpendicular to the optical axis at the irradiation point is annular at least with the optical axis as the center.

Description

Technical Field

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

[0002] Laser processing equipment focuses a laser beam onto a workpiece at a single point, causing a rapid rise in surface temperature that melts or evaporates the irradiated surface, enabling processes such as cutting, drilling, and welding. Because the laser is focused at a single point, precise and intricate machining can be performed with accurate pinpoint positioning. Furthermore, using higher-energy lasers 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, during laser focusing, the laser intensity distribution at the irradiation point is preferably annular on the plane of the irradiation point. However, if the annular diameter at the irradiation point is large, the light energy cannot be sufficiently concentrated, thus requiring more time for the melting of the workpiece or resulting in a deterioration in the quality of the processed profile. Furthermore, if the focal depth used to maintain a certain annular diameter is shallow, it will cause the processing dimensions to differ in the thickness direction of the workpiece.

[0004] Therefore, Patent Document 1 discloses a laser processing method: before focusing the laser beam, a shield is placed at the center of the laser beam's cross-section to block the laser beam in the center. As a result, the laser beam not blocked by the shield forms a ring, and a laser irradiation head is used to focus this ring-shaped laser beam.

[0005] In addition, Patent Document 2 discloses a laser welding device: a laser is focused by using a focusing lens obtained by cutting the central part of the convex surface of a focusing lens into a concave shape, so that the intensity distribution of the laser is higher at the periphery than at the center.

[0006] Furthermore, Patent Document 3 discloses a laser processing head that uses at least one of a spherical lens for focusing the laser and an aspherical lens capable of generating spherical aberration, wherein the intensity distribution of the irradiated laser is such that the peripheral region is higher than the central region, the intensity distribution is annular, and the focal point is offset from the irradiation point of the workpiece.

[0007] Prior art literature

[0008] Patent documents

[0009] [Patent Document 1] Japanese Patent Application Publication No. 07-214360

[0010] [Patent Document 2] Japanese Patent Application Publication No. 2003-305581

[0011] [Patent Document 3] WO2012 / 164663 Publication No. Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, the optical system of the laser processing apparatus described in Patent Document 1 blocks the laser beam at its center by placing a shield in the center of the laser beam's cross-section, thereby obtaining a laser beam with a ring-shaped intensity distribution. Therefore, in the processing of the workpiece by the laser, the energy utilization efficiency of the laser output from the laser oscillator is low. Furthermore, a laser oscillator with a larger output is required to obtain the desired laser energy at the irradiation point on the workpiece.

[0014] Furthermore, the optical system of the laser processing apparatus described in Patent Document 2 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 light, thereby obtaining a laser intensity distribution where the intensity is higher at the periphery than at the center. Here, the laser light passing through the concave part of the condenser lens is refracted from the center in the direction to be diffused. Therefore, the laser light to be refracted in the concave part of the condenser lens is not focused on the irradiation point of the workpiece. That is, during the processing of the workpiece by laser, the energy utilization efficiency of the laser light output from the laser oscillator is low.

[0015] Furthermore, in the optical system of the laser processing apparatus described in Patent Document 3, if the optical system for focusing the laser is heated by the laser, the refractive index of the heated portion of the lens constituting the optical system changes (thermal lensing effect). If the focal point deviates due to this change in refractive index, the annular laser intensity distribution changes. Specifically, the annular diameter increases, the laser intensity at the processing point weakens, or the laser intensity distribution changes from annular to other shapes, thus potentially preventing the desired processing from being performed.

[0016] The object of the present invention is to provide: an optical system for a laser processing apparatus in which the energy utilization efficiency of the laser is high, and the intensity distribution shape of the laser at the irradiation point does not change even if the focal position deviates due to the thermal lensing effect; and a laser processing apparatus using such an optical system.

[0017] Methods for solving problems

[0018] In order to solve the above problems, in-depth research was conducted, and the following invention was achieved.

[0019] The laser processing apparatus of the present invention, which processes a workpiece by irradiating it with a laser, includes an optical system having multiple optical surfaces with different focal points arranged on the same optical axis. The irradiation point of the laser on the workpiece is located at a different position from the focal point. At the irradiation point, the intensity distribution of the laser on the surface perpendicular to the optical axis is at least annular about the optical axis.

[0020] In addition, the optical system of the laser processing apparatus that processes a workpiece by irradiating it with a laser, as described in this application, has multiple optical surfaces with different focal points set on the same optical axis. These optical surfaces with multiple different focal points are multiple different spherical and / or aspherical surfaces.

[0021] Invention Effects

[0022] The laser processing apparatus of this invention, by having an optical system with multiple focal points arranged on the same optical axis, enables the focal points of the optical system to be located at different positions from the irradiation point of the workpiece, and the intensity distribution of the laser on a plane perpendicular to the optical axis at the irradiation point of the workpiece to be at least annular with the optical axis as the center. Therefore, even if the focal point position deviates due to the thermal lensing effect, the shape and intensity of the laser intensity distribution at the irradiation point remain unchanged, enabling stable laser processing. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of an optical element having different aspherical surfaces on the same optical surface, as described in this embodiment.

[0024] Figure 2 This is a schematic cross-sectional view of an optical element with different aspherical surfaces on two different optical surfaces, as described in this embodiment.

[0025] Figure 3 It means in Figure 1 The diagram (a) shows the approximate optical path of the laser between the entrance pupil and the illumination point when the focal point of the aspherical surface 21 in the optical element is behind the illumination point and the focal point of the aspherical surface 22 is in front of the illumination point, and the diagram (b) shows the lateral aberration at the coordinates of the entrance pupil and the illumination point.

[0026] Figure 4 It means in Figure 1 The diagram (a) shows the approximate optical path of the laser between the entrance pupil and the illumination point when the focal point of the aspherical surface 21 in the optical element is in front of the illumination point and the focal point of the aspherical surface 22 is behind the illumination point, and the diagram (b) shows the lateral aberration at the coordinates of the entrance pupil and the coordinates of the illumination point.

[0027] Figure 5 It means in Figure 1 The diagram (a) shows the approximate optical path of the laser between the entrance pupil and the illumination point when the focal point of the aspherical surface 21 in the optical element is behind the illumination point and the focal point of the aspherical surface 22 is in front of the illumination point, and the diagram (b) shows the lateral aberration at the coordinates of the entrance pupil and the illumination point.

[0028] Figure 6 It means in Figure 1 The diagram (a) shows the approximate optical path of the laser between the incident pupil and the irradiation point when the focal point of the aspherical surface 21 in the optical element is in front of the irradiation point and the focal point of the aspherical surface 22 is behind the irradiation point, and the diagram (b) shows the lateral aberration at the coordinates of the incident pupil and the coordinates of the irradiation point.

[0029] Figure 7 This refers to the laser processing apparatus described in this embodiment.

[0030] Figure 8 This is a graph of position and curvature C obtained by dividing the optical axis position into 10 equal parts with the position of the optically effective region end as 1, as described in Example 1.

[0031] Figure 9 The graph in Example 2 shows the relationship between position and curvature C, obtained by dividing the optical axis position into 10 equal parts with the position of the optically effective area end as 1.

[0032] Figure 10 This is a diagram of the relationship between position and curvature C obtained by dividing the optical axis position into 10 equal parts with the position of the optically effective region end as 1, as described in Example 3.

[0033] Figure 11 This is the relationship between position and curvature C obtained by dividing the optical axis position into 10 equal parts with the position of the optically effective area end as 1, as in Example 4.

[0034] Figure 12 This is a comparative example, showing the relationship between position and curvature C obtained by dividing the optical axis position into 10 equal parts with the position of the optically effective region end as 1.

[0035] Figure 13 This is a graph showing the intensity distribution of the laser, which serves as a benchmark for optical simulation.

[0036] Figure 14 This is a diagram of the intensity distribution of laser light at the irradiation point of the workpiece, on a plane perpendicular to the optical axis and along a straight line containing the optical axis, according to Example 1.

[0037] Figure 15This is a diagram of the intensity distribution of laser light on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point of the workpiece, according to Example 2.

[0038] Figure 16 This is a diagram of the intensity distribution of laser light at the irradiation point of the workpiece, on a plane perpendicular to the optical axis and along a straight line containing the optical axis, according to Example 3.

[0039] Figure 17 This is a diagram of the intensity distribution of laser light on a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point of the workpiece, as described in Example 4.

[0040] Figure 18 This is a comparative example, a diagram showing the intensity distribution of the laser at the irradiation point on the workpiece, along a straight line containing the optical axis on a plane perpendicular to the optical axis.

[0041] Explanation of reference numerals in the attached figures:

[0042] 10. Optical components (lenses)

[0043] 11 Substrate

[0044] 12 optical surfaces

[0045] 13 Optical surfaces

[0046] 21. Aspherical

[0047] 22 Aspherical

[0048] 10' Optical element (lens)

[0049] 11' Substrate

[0050] 12' Optical surface

[0051] 13' Optical surface

[0052] 21' Aspherical

[0053] 22' Aspherical

[0054] 50 Laser processing equipment

[0055] 51 Laser Oscillator

[0056] 52 optical paths

[0057] 53 Optical System

[0058] 54. Machining worktable

[0059] 60 Workpieces Detailed Implementation

[0060] Hereinafter, embodiments of the laser processing apparatus and the optical system for the laser processing apparatus according to the present invention will be described.

[0061] 1. Implementation methods of laser processing apparatus and optical systems for laser processing apparatus

[0062] The laser processing apparatus and optical system of the present invention relate to a laser processing apparatus that processes a workpiece by irradiating it with a laser, and the optical system of the laser processing apparatus having multiple optical surfaces with different focal points arranged on the same optical axis. The laser processing apparatus of the present invention irradiates the workpiece with the laser irradiation point and each focal point located at different positions, such that at the irradiation point, the intensity distribution of the laser on a plane perpendicular to the optical axis is at least ring-shaped around the optical axis. Furthermore, the optical system of the laser processing apparatus of the present invention is configured such that at the laser irradiation point, the intensity distribution of the laser on a plane perpendicular to the optical axis is at least ring-shaped around the optical axis.

[0063] According to the present invention, as described below, the laser processing apparatus for processing a workpiece by irradiation with a laser has an optical system comprising multiple optical surfaces with different focal points arranged on the same optical axis, and the irradiation point of the laser on the workpiece is located at a different position from the focal point. Therefore, at the irradiation point of the workpiece, the intensity distribution of the laser on a plane perpendicular to the optical axis (hereinafter referred to as "the intensity distribution of the laser on the plane at the irradiation point") is at least annular around the optical axis. Furthermore, at the irradiation point of the workpiece, the intensity distribution of the laser on a straight line containing the optical axis on a plane perpendicular to the optical axis (hereinafter referred to as "the intensity distribution of the laser on the straight line at the irradiation point") is at least bimodal around the optical axis. Even if the focal point deviates due to the thermal lensing effect, the intensity distribution of the laser on the plane at the irradiation point (the position and peak value of the laser intensity) remains almost unchanged. Therefore, the processing quality of the workpiece is maintained.

[0064] 1-1. Implementation method with multiple optical surfaces having different focal points

[0065] Preferably, the optical surface with multiple different focal points involved in this invention is composed of multiple different spherical and / or aspherical surfaces. This is because the incident light refracted at the interfaces of the multiple different spherical and / or aspherical surfaces converges towards different focal points, so the intensity distribution of the laser on the plane at the irradiation point is at least annular about the optical axis.

[0066] Preferably, at least one optical surface of the plurality of different spherical and / or aspherical surfaces involved in the present invention is an aspherical surface. This is because aspherical surfaces readily produce lateral aberrations that are difficult to achieve with spherical surfaces, thus enabling the setting of different focal points on the plurality of optical surfaces involved in the present invention.

[0067] Furthermore, preferably, the multiple different spherical and / or aspherical surfaces involved in this invention are each two different optical surfaces. This is because it is easy to construct the optical system involved in this invention, which consists of multiple optical surfaces with different focal points.

[0068] Furthermore, preferably, the multiple different spherical and / or aspherical surfaces involved in this invention are each two different aspherical surfaces. This is because aspherical surfaces readily produce lateral aberrations that are difficult to achieve with spherical surfaces, thus allowing for the simple construction of the optical system involved in this invention, which consists of multiple optical surfaces with different focal points, and also facilitating the adjustment of the focal distance.

[0069] The following describes the specific implementation method using an aspherical surface as an example.

[0070] 1-2. Implementation methods for multiple different aspherical surfaces 1

[0071] Preferably, the present invention involves multiple different spherical and / or aspherical surfaces arranged in multiple concentric circular regions centered on the optical axis on the same optical surface. This is to focus the laser beam along the same optical axis. Figure 1 This is a schematic cross-sectional view of an optical element 10 having different aspherical surfaces on the same optical surface. The optical element 10 is constructed from a substrate 11, the material of which is not particularly limited as long as it is made of an optical material. The substrate 11 has optical surfaces 12 and 13 for laser light to pass through, and the dashed line O represents the central axis of the optical element 10. Furthermore, on optical surface 12, aspherical surfaces 21 and 22 are arranged concentrically around the central axis O of the optical element. At this time, incident light refracted at the interface of the two concentric aspherical surfaces 21 and 22 converges towards two different focal points.

[0072] 1-3. Implementation methods for multiple different aspherical surfaces 2

[0073] Furthermore, preferably, the multiple different spherical and / or aspherical surfaces involved in this invention are arranged on multiple different optical surfaces to allow each of its own different beams to pass through, and are multiple concentric circular regions centered on the optical axis. This is to focus the laser beam along the same optical axis. Here, the multiple different optical surfaces can be different optical surfaces on the same optical element, or they can be optical surfaces on different optical elements.

[0074] Figure 2This is a schematic cross-sectional view of an optical element 10' having different aspherical surfaces on two different optical surfaces on the same optical element. The optical element 10' is composed of a substrate 11', which has optical surfaces 12' and 13' for laser light to pass through. The aspherical surface 21' on optical surface 12' and the aspherical surface 22' on optical surface 13' are arranged concentrically around O', which is the central axis of the optical element. At this time, the aspherical surfaces 21' and 22' are positioned to allow their respective different light beams to pass through. Furthermore, the incident light refracted at the interface between the two concentric aspherical surfaces 21' and 22' converges towards two different focal points.

[0075] 2. Implementation methods based on the characteristics of laser processing apparatus and optical systems used in laser processing apparatus.

[0076] 2-1. Implementation method of focal distance

[0077] Preferably, at least two of the multiple different spherical and / or aspherical surfaces involved in this invention have different focal distances, which are respectively 150 mm or more and 1000 mm or less. Furthermore, from the viewpoint of not complicating the shape of the aspherical surface, it is preferable that there are two aspherical surfaces with different focal distances. Here, it is preferable that if the focal distances of the multiple different aspherical surfaces are defined as f1 and f2, then when f1 < f2, f1 / f2 is greater than 0.2 and less than 0.8. Furthermore, it is preferable that when f1 > f2, f2 / f1 is preferably greater than 0.2 and less than 0.8. Here, the units of f1 and f2 are mm.

[0078] When f1 < f2, if f1 / f2 is less than 0.2, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis. When f1 < f2, if f1 / f2 is greater than 0.8, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis.

[0079] Furthermore, when f1 > f2, if f2 / f1 is less than 0.2, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis. When f1 > f2, if f2 / f1 is greater than 0.8, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis.

[0080] 2-2. Implementation of radius of curvature

[0081] Preferably, if the radii of curvature of two aspherical surfaces among the plurality of different spherical and / or aspherical surfaces involved in this invention are respectively set as r1 and r2, then the absolute value of r1 / r2 is greater than 0.5 and less than 2. Here, the units of r1 and r2 are mm. If the absolute value of r1 / r2 is less than 0.5, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring shape centered on the optical axis. If the absolute value of r1 / r2 is greater than 2, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring shape centered on the optical axis.

[0082] Here, the optical surface shape of the aspheric surface can be represented by the even-order aspheric form shown in equation (1).

[0083] z(r)=cr 2 / [1+{1-(1+k)·c 2 r 2} 1 / 2 ]+a1r 2 +a2r 4 +a3r 6 +a4r 8 +a5r 10 +a6r 12 +a7r 14 +a8r 16 ···(1)

[0084] in,

[0085] z(r): The surface position (droop) along the optical axis at a distance r from the optical axis.

[0086] c: the reciprocal of the central radius of curvature

[0087] k: Conic constant

[0088] a n : The aspheric coefficient of degree n.

[0089] 2-3. Implementation of curvature

[0090] Regarding the curvature C at any position of the optically effective region of the optical surface, in a coordinate system with the optical axis as the z-axis and axes orthogonal to the z-axis as the r-axis, after dividing the r-axis into 10 equal parts from the position of the optical axis as the origin to the position of the end of the optically effective region, let the curvature of the origin be C. 0.0 (m －1 The curvature at the end of the optically effective region is C. 1.0 (m －1 ).

[0091] At this point, it is preferable that, on at least two of the multiple different spherical and / or aspherical surfaces, when C 0.0 >C 1.0 At that time, C 1.0 / C 0.0 The absolute value of C is less than 0.9. 1.0 / C 0.0 If the absolute value of the laser intensity is greater than 0.9, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis.

[0092] Furthermore, preferably, when C 0.0 <C 1.0 At that time, C 0.0 / C 1.0 The absolute value of C is less than 0.9. 0.0 / C 1.0 If the absolute value of the laser intensity is greater than 0.9, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis.

[0093] Next, preferably, on at least two of the multiple different spherical and / or aspherical surfaces, the curvature at a position at 1 / 10 of the coordinate system defined by dividing the surface into 10 equal parts in the aforementioned r-axis coordinate system is C. 0.1 (m －1 When C) 0.1 / C 0.0 The absolute value of C is greater than 0 and less than 4. 0.1 / C 0.0 If the absolute value of the laser is 4 or higher, the intensity distribution of the laser on the plane at the irradiation point of the workpiece will not form a ring centered on the optical axis.

[0094] Furthermore, preferably, on at least two of the multiple different spherical and / or aspherical surfaces, the curvature at the position of 2 / 10 (divided into 10 equal parts) in the coordinate system of the aforementioned r-axis is C. 0.2 (m －1 The curvature at the 8 / 10th position of the 10th division is C. 0.8 (m －1 When C) 0.8 / C 0.2 The absolute value of C is greater than 0.5 and less than 1.5. 0.8 / C 0.2 If the absolute value of C is less than 0.5, the laser will not focus. 0.8 / C 0.2 If the absolute value is 1.5 or higher, a suitable back focal length cannot be obtained.

[0095] 3. Implementation method based on the intensity distribution characteristics of the laser at the irradiation point of the workpiece.

[0096] 3-1. Intensity distribution characteristics of laser at the irradiation point of the workpiece in this invention

[0097] First, let's explain lateral aberration. Lateral aberration is the deviation from the origin of the evaluation plane used to assess the focusing state of incident light. Therefore, a lateral aberration diagram is obtained by establishing a correspondence between the through coordinates on the incident pupil plane and the arrival coordinates on the evaluation plane used to assess the focusing state of the incident light.

[0098] Laser beams refracted at multiple aspherical interfaces converge toward different focal points on the optical axis. At the laser irradiation point on the workpiece, located at a different position from the focal point, the laser intensity distribution on the plane at the irradiation point is at least annular about the optical axis. Furthermore, the laser intensity distribution on the straight line at the irradiation point is at least bimodal about the optical axis.

[0099] Figure 3 (a) indicates Figure 1 The diagram shows the approximate optical path of the laser between the entrance pupil and the irradiation point when the focal point of aspherical surface 21 on the optical element is behind the irradiation point and the focal point of aspherical surface 22 is in front of the irradiation point. The shaded areas represent the laser's optical path. The laser refracted on aspherical surface 21 travels towards the focal point located behind the irradiation point on the workpiece, converging with certain lateral aberrations at the irradiation point on the workpiece during its journey. The laser refracted on aspherical surface 22 travels towards the focal point located in front of the irradiation point on the workpiece, and then crosses and travels parallel to each other along the optical axis, converging with the same lateral aberrations at the irradiation point on the workpiece as the laser refracted on aspherical surface 21.

[0100] Figure 3 (b) indicates Figure 1 The diagram shows the lateral aberration of the incident pupil coordinates versus the illumination point coordinates when the focal point of aspherical surface 21 on the optical element is behind the illumination point and the focal point of aspherical surface 22 is in front of the illumination point. Thus, the individual laser beams refracted on aspherical surfaces 21 and 22 converge towards the illumination point of the workpiece with the same lateral aberration. At this time, the intensity distribution of the combined laser beam refracted on aspherical surfaces 21 and 22 on the plane at the illumination point of the workpiece is at least annular around the optical axis.

[0101] In addition, from Figure 3 As shown in the lateral aberration diagram (b), the lateral aberration changes smoothly near the origin of the incident pupil coordinates, while outside the origin, it becomes a fixed lateral aberration. Furthermore, because... Figure 3The laser path diagram in (a) is a schematic diagram, so the origin of the incident pupil coordinates and the path of the incident light near the origin are not yet shown in Figure 3(a) for the changes in the lateral aberrations mentioned above.

[0102] Figure 4 (a) indicates Figure 1 The diagram shows the approximate optical path of the laser between the entrance pupil and the irradiation point when the focal point of aspherical surface 21 on the optical element is in front of the irradiation point and the focal point of aspherical surface 22 is behind the irradiation point. The shaded areas represent the laser's optical path. The laser refracted on aspherical surface 21 travels towards the focal point located in front of the irradiation point on the workpiece, and then crosses and travels in parallel along the optical axis. At the irradiation point on the workpiece, located along the path of the laser light, it converges with certain lateral aberrations. The laser refracted on aspherical surface 22 travels towards the focal point located behind the irradiation point on the workpiece, and at the irradiation point on the workpiece, it converges with the same lateral aberrations as the laser refracted on aspherical surface 21.

[0103] Figure 4 (b) indicates Figure 1 The diagram shows the lateral aberration of the incident pupil coordinates versus the illumination point coordinates when the focal point of aspherical surface 21 on the optical element is in front of the illumination point and the focal point of aspherical surface 22 is behind the illumination point. Thus, the laser light refracted on aspherical surfaces 21 and 22 converges towards the illumination point of the workpiece with the same lateral aberration. At this time, the intensity distribution of the combined laser light from the individual lasers refracted on aspherical surfaces 21 and 22 on the plane at the illumination point of the workpiece is at least annular around the optical axis.

[0104] In addition, from Figure 4 As shown in diagram (b), the lateral aberrations near the origin of the incident pupil coordinate system change smoothly, while outside the origin, the lateral aberrations become fixed. Furthermore, because... Figure 4 The laser path diagram in (a) is a schematic diagram, so for the aforementioned changes in lateral aberration, the origin of the incident pupil coordinates and the optical path of the incident light near the origin are... Figure 4 This is not yet reflected in (a).

[0105] If there are three or more aspherical surfaces, then, similarly as described above, each of the three or more aspherical surfaces is a different aspherical surface. The laser light refracted on each of these different aspherical surfaces travels towards a focal point located at a position different from the laser irradiation point on the workpiece, converging with the same lateral aberration at the laser irradiation point on the workpiece. Furthermore, the intensity distribution of the laser light synthesized from the individual lasers refracted on the different aspherical surfaces on the plane at the irradiation point on the workpiece is at least annular about the optical axis.

[0106] 3-2. Intensity distribution characteristics of laser light during thermal lensing effect

[0107] First, let's explain the thermal lensing effect. Because laser processing equipment is used to process metals and other materials, the energy of the laser light used is very high. In the case of transmissive optical elements, an anti-reflective film with a wavelength matching the laser wavelength is formed on the surface of the optical element, making it a high-transmittance optical element used in the optical system of the laser processing equipment. However, since 100% transmittance is difficult to achieve, the energy of the laser light that does not pass through is absorbed by the substrate of the optical element, converting light energy into heat energy. The density and refractive index of the substrate and the anti-reflective film of the optical element change at the locations where the temperature rises. This is commonly referred to as the thermal lensing effect.

[0108] If an optical element undergoes a change in refractive index and partial convexity due to the thermal lensing effect, the focal point position shifts. Although this varies depending on the optical properties of the substrate, such as the refractive index and curvature of the aspherical surface, for example, sometimes the focal distance is shortened by 5 to 10 mm due to the thermal lensing effect when the focal distance is 200 mm. As a result, if the intensity distribution of the laser on the plane at the irradiation point on the workpiece changes, problems such as deterioration in the processing quality of the workpiece may occur.

[0109] Here, Figure 5 (a) indicates Figure 3 In (a), the approximate optical path of the laser between the incident pupil and the irradiation point under the condition of thermal lensing effect is shown. The shaded areas represent the laser's optical path. Additionally, Figure 5 (b) represents the lateral aberration diagram of the incident pupil coordinates and the illumination point coordinates at this point. Due to the thermal lensing effect, the refractive index of aspherical surface 22 changes, and the focal point of aspherical surface 22 moves further forward. Therefore, as... Figure 5 (a) and Figure 5 As shown in (b), the laser refracted on the aspherical surface 22 converges toward the moved focal point and travels in parallel at the optical axis. Furthermore, at the laser irradiation point on the workpiece, the laser converges with the following lateral aberration characteristics: as the laser moves away from the origin in the coordinate system of the incident pupil, the lateral aberration changes from the initial lateral aberration in a gradually increasing direction.

[0110] On the other hand, because the aspherical surface 21 is located in the central part of the substrate, it is not easily affected by the linear expansion caused by heat, and the change in refractive index caused by the thermal lensing effect is almost non-existent. Therefore, the laser refracted on the aspherical surface 21 maintains the same lateral aberration as before the heat effect. Therefore, even if the focal point of the aspherical surface 22 shifts due to the thermal lensing effect, the intensity distribution of the laser synthesized from the individual lasers refracted on the aspherical surface 21 and the aspherical surface 22 on the plane at the laser irradiation point on the workpiece remains almost unchanged and maintains at least a ring shape centered on the optical axis. Furthermore, regarding the... Figure 5 of (a), Figure 5 The origin of the incident pupil coordinates and the area near the origin in (b) are the same as described above.

[0111] Similarly, Figure 6 (a) indicates in Figure 4 In (a), the approximate optical path of the laser between the incident pupil and the irradiation point under the condition of thermal lensing effect is shown. The shaded areas represent the laser's optical path. Additionally, Figure 6 (b) represents the lateral aberration diagram under the coordinates of the incident pupil and the illumination point. Due to the thermal lensing effect, the refractive index of aspherical surface 22 changes, and the focal point of aspherical surface 22 moves further rearward. Therefore, as... Figure 6 (a) and Figure 6 As shown in (b), the laser refracted on the aspherical surface 22 travels toward the moved focal point. Furthermore, at the point of laser irradiation on the workpiece, the lateral aberration converges with the following characteristics: as the laser moves away from the origin in the coordinate system of the incident pupil, the lateral aberration changes from the initial lateral aberration in a gradually increasing direction.

[0112] On the other hand, because the aspherical surface 21 is located in the central part of the substrate, it is not easily affected by the linear expansion caused by heat, and the change in refractive index caused by the thermal lensing effect is almost non-existent. Therefore, the laser refracted on the aspherical surface 21 maintains the same lateral aberration as before the heat effect. Therefore, even if the focal point of the aspherical surface 22 shifts due to the thermal lensing effect, the intensity distribution of the laser synthesized from the individual lasers refracted on the aspherical surface 21 and the aspherical surface 22 on the plane at the laser irradiation point on the workpiece remains almost unchanged and maintains at least a ring shape centered on the optical axis. Furthermore, regarding the... Figure 6 of (a), Figure 6 The origin of the incident pupil coordinates and the area near the origin in (b) are the same as described above.

[0113] As described above, even if focal deviation occurs due to the thermal lensing effect, the intensity distribution of the laser on the plane at the irradiation point of the workpiece remains almost unchanged. In other words, in the optical system of this invention, the focal depth is relatively deep to maintain the annular intensity distribution of the laser at the irradiation point of the workpiece. Therefore, in the laser processing apparatus, even if the thermal lensing effect occurs during processing, the processing quality of the workpiece is maintained.

[0114] 4. Implementation methods of laser processing equipment

[0115] The laser processing apparatus of the present invention, which processes a workpiece by irradiating it with a laser as described above, is characterized in that it has an optical system having an optical surface with multiple different focal points set on the same optical axis, the irradiation point of the laser on the workpiece being located at a different position from the focal point, and at the irradiation point, the intensity distribution of the laser on the surface perpendicular to the optical axis is at least in a ring shape with the optical axis as the center.

[0116] Figure 7 This describes the laser processing apparatus 50 according to this embodiment. The laser processing apparatus 50 generally comprises a laser oscillator 51, an optical path 52, an optical system 53, and a processing table 54. A workpiece 60 is mounted on the processing table 54. The laser oscillator 51 is a device that outputs laser light for processing. The type or output of the laser to be used is selected based on the material of the workpiece 60, the thickness to be processed, the processing precision, etc. The optical path 52 is a path for transmitting the laser light output from the laser oscillator to the optical system; it may be a type using a mirror or a type using optical fibers. The optical system 53 then focuses the transmitted laser light into a predetermined shape and irradiates the irradiation point of the workpiece 60. The processing table 54 is equipped with a device for fixing the workpiece 60 in place and for moving the workpiece 60 or the optical system 53, or both, in coordination with the movement of the irradiation point of the workpiece 60.

[0117] The laser processing apparatus of the present invention, by using the aforementioned optical system 53, ensures that the intensity distribution of the laser at the irradiation point of the workpiece 60 is at least annular about the optical axis. Furthermore, even if focal deviation occurs due to the thermal lensing effect, the optical system of the present invention maintains a relatively deep focal depth for preserving the annular intensity distribution of the laser at the irradiation point of the workpiece, thus ensuring that the intensity distribution of the laser at the irradiation point of the workpiece 60 remains almost unchanged. Therefore, the processing quality of the workpiece 60 is maintained.

[0118] The following describes embodiments of the present invention. Furthermore, in each embodiment, [the following is used as a reference to]... Figure 1 The optical element shown is used as an example for explanation.

[0119] [Example 1]

[0120] An optical element with an effective diameter of 18.5 mm is used for the optical surface 12. Furthermore, the aspherical surfaces 21 and 22 on the optical surface 12 are arranged as concentric circles. And, as... Figure 3 As shown, the focal point of aspherical surface 21 is behind the irradiation point, and the focal point of aspherical surface 22 is in front of the irradiation point. Furthermore, if equation (1) is used, aspherical surface 21 has a shape that satisfies the following values.

[0121] c = -0.005

[0122] k = -5.0 × 10 5

[0123] a² = 4.702 × 10 －3

[0124] a4 = 4.450 × 10 －8

[0125] Similarly, if equation (1) is used, the aspherical surface 22 is a shape that satisfies the following values.

[0126] c = 0.005

[0127] k = -5.0 × 10 5

[0128] a² = 4.702 × 10 －3

[0129] a4 = 4.450 × 10 －8

[0130] Here, on optical surface 12, the region extending from the optical axis to a radius of 8 mm is defined as aspherical surface 21, and the region extending from a radius of 8 mm to a radius of 18.5 mm is defined as aspherical surface 22. The curvature C (in meters) of the aspherical surfaces at positions perpendicular to and away from the optical axis is then... －1 As shown in Table 1. Here, distance A (in mm) in Table 1 represents the distance from the z-axis in an r-axis coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis. Position B represents the position obtained by dividing the r-axis into 10 equal parts with the optical axis position as the origin (0) and the position of the optically effective region end (1). Furthermore, the graph showing the relationship between the position obtained by dividing the r-axis into 10 equal parts with the optical axis position as the origin (0) and the position of the optically effective region end (1) and the curvature C is shown below. Figure 8 As shown.

[0131] [Table 1]

[0132] Distance A Position B Curvature C 18.50 1.00 9.156 16.65 0.90 9.202 14.80 0.80 9.243 12.95 0.70 9.280 11.10 0.60 9.312 9.25 0.50 9.340 7.40 0.40 9.367 5.55 0.30 9.383 3.70 0.20 9.393 1.85 0.10 9.385 0.00 0.00 4.404

[0133] According to the above even-order aspherical form, the paraxial focal distances of aspherical surface 21 and aspherical surface 22 are f1 = 505.7 mm and f2 = 154.6 mm, respectively. At this point, since f1 > f2, it is the value of f2 / f1; the absolute value of the ratio of the radii of curvature of aspherical surface 21 and aspherical surface 22, r1 / r2; and since C... 0.0 <C 1.0 Therefore, it is C. 0.0 / C 1.0 absolute value, C 0.1 / C 0.0 absolute value, C 0.8 / C 0.2 The absolute values ​​are shown in Table 2.

[0134] [Table 2]

[0135] project value f2 / f1 0.31 The absolute value of r1 / r2 1.0 <![CDATA[C 0.0 / C 1.0 absolute value 0.481 <![CDATA[C 0.1 / C 0.0 absolute value 2.131 <![CDATA[C 0.8 / C 0.2 absolute value 0.984

[0136] [Example 2]

[0137] An optical element with an effective diameter of 18.5 mm is used for the optical surface 12. Furthermore, the aspherical surfaces 21 and 22 on the optical surface 12 are arranged as concentric circles. And, as... Figure 4 As shown, the focal point of aspherical surface 21 is in front of the irradiation point, and the focal point of aspherical surface 22 is behind the irradiation point. Furthermore, if equation (1) is used, aspherical surface 21 has a shape that satisfies the following values.

[0138] c = 0.005

[0139] k = -5.0 × 10 5

[0140] a² = 4.702 × 10 -3

[0141] a4 = 4.450 × 10 -8

[0142] Similarly, if equation (1) is used, the aspherical surface 22 is a shape that satisfies the following values.

[0143] c = -0.005

[0144] k = -5.0 × 10 5

[0145] a² = 4.702 × 10 -3

[0146] a4 = 4.450 × 10 -8

[0147] Here, on optical surface 12, the region extending from the optical axis to a radius of 8 mm is defined as aspherical surface 21, and the region extending from a radius of 8 mm to a radius of 18.5 mm is defined as aspherical surface 22. The curvature C (in meters) of the aspherical surfaces at positions perpendicular to and away from the optical axis is then... -1 As shown in Table 3. Here, distance A (in mm) in Table 3 represents the distance from the z-axis in an r-axis coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis. Position B represents the position on the r-axis obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1. Furthermore, the graph showing the relationship between the position obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1 and the curvature C is shown below. Figure 9 As shown.

[0148] [Table 3]

[0149] Distance A Position B Curvature C 18.50 1.00 9.169 16.65 0.90 9.214 14.80 0.80 9.254 12.95 0.70 9.290 11.10 0.60 9.320 9.25 0.50 9.346 7.40 0.40 9.362 5.55 0.30 9.381 3.70 0.20 9.395 1.85 0.10 9.418 0.00 0.00 14.404

[0150] According to the above even-order aspherical form, the paraxial focal distances of aspherical surface 21 and aspherical surface 22 are f1 = 154.6 mm and f2 = 505.7 mm, respectively. At this point, since f1 < f2, it is the value of f1 / f2, the absolute value of the ratio of the radii of curvature of aspherical surface 21 to aspherical surface 22, r1 / r2, and since C... 0.0 >C 1.0 Therefore, it is C. 1.0 / C 0.0 absolute value, C 0.1 / C 0.0 absolute value, C 0.8 / C 0.2 The absolute values ​​are shown in Table 4.

[0151] [Table 4]

[0152] project value f1 / f2 0.31 The absolute value of r1 / r2 1.0 <![CDATA[C 1.0 / C 0.0 absolute value 0.637 <![CDATA[C 0.1 / C 0.0 absolute value 0.654 <![CDATA[C 0.8 / C 0.2 absolute value 0.985

[0153] [Example 3]

[0154] An optical element with an effective diameter of 18.5 mm is used for the optical surface 12. Furthermore, the aspherical surfaces 21 and 22 on the optical surface 12 are arranged in a concentric circle shape. Figure 5 As shown, the focal point of aspherical surface 21 is behind the irradiation point, and the focal point of aspherical surface 22 is in front of the irradiation point. Furthermore, if equation (1) is used, aspherical surface 21 has a shape that satisfies the following values.

[0155] c = -0.005

[0156] k = -5.0 × 10 5

[0157] a² = 4.702 × 10-3

[0158] a4 = 4.450 × 10 -8

[0159] Set the focal point of the aspherical surface 22 to a deviation of -1.5 mm. In this case, if equation (1) is used, the aspherical surface 22 will have a shape that satisfies the following values.

[0160] c = 0.005

[0161] k = -5.0 × 10 5

[0162] a² = 4.733 × 10 -3

[0163] a4 = 4.450 × 10 -8

[0164] Here, on optical surface 12, the region extending from the optical axis to a radius of 8 mm is defined as aspherical surface 21, and the region extending from a radius of 8 mm to a radius of 18.5 mm is defined as aspherical surface 22. The curvature C (in meters) of the aspherical surfaces at positions perpendicular to and away from the optical axis is then... -1 As shown in Table 5. Here, distance A (in mm) in Table 5 represents the distance from the z-axis in an r-axis coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis. Position B represents the position obtained by dividing the r-axis into 10 equal parts with the optical axis position as the origin (0) and the position of the optically effective region end (1). Furthermore, the graph showing the relationship between the position obtained by dividing the r-axis into 10 equal parts with the optical axis position as the origin (0) and the position of the optically effective region end (1) and the curvature C is shown below. Figure 10 As shown.

[0165] [Table 5]

[0166] Distance A Position B Curvature C 18.50 1.00 9.209 16.65 0.90 9.257 14.80 0.80 9.300 12.95 0.70 9.338 11.10 0.60 9.371 9.25 0.50 9.400 7.40 0.40 9.367 5.55 0.30 9.383 3.70 0.20 9.393 1.85 0.10 9.385 0.00 0.00 4.404

[0167] According to the even-order aspherical form described above, the paraxial focal distances of aspherical surface 21 and aspherical surface 22 are f1 = 505.7 mm and f2 = 154.0 mm, respectively. At this point, since f1 > f2, it is the value of f2 / f1; the absolute value of the ratio of the radii of curvature of aspherical surface 21 to aspherical surface 22, r1 / r2; and since C... 0.0 <C 1.0 Therefore, it is C. 0.0 / C 1.0 absolute value, C 0.1 / C 0.0 absolute value, C 0.8 / C 0.2 The absolute values ​​are shown in Table 6.

[0168] [Table 6]

[0169] project value f2 / f1 0.30 The absolute value of r1 / r2 1.0 <![CDATA[C 0.0 / C 1.0 absolute value 0.478 <![CDATA[C 0.1 / C 0.0 absolute value 2.131 <![CDATA[C 0.8 / C 0.2 absolute value 0.990

[0170] [Example 4]

[0171] An optical element with an effective diameter of 18.5 mm is used for the optical surface 12. Furthermore, the aspherical surfaces 21 and 22 on the optical surface 12 are arranged in a concentric circle shape. Figure 6 As shown, the focal point of aspherical surface 21 is in front of the irradiation point, and the focal point of aspherical surface 22 is behind the irradiation point. Furthermore, if equation (1) is used, aspherical surface 21 has a shape that satisfies the following values.

[0172] c = 0.005

[0173] k = -5.0 × 10 5

[0174] a² = 4.702 × 10 －3

[0175] a4 = 4.450 × 10 －8

[0176] Set the focal point of aspherical surface 22 to a deviation of +1.5mm. In this case, if equation (1) is used, aspherical surface 22 will have a shape that satisfies the following values.

[0177] c = -0.005

[0178] k = -5.0 × 10 5

[0179] a² = 4.670 × 10 －3

[0180] a4 = 4.450 × 10 －8

[0181] Here, on optical surface 12, the region extending from the optical axis to a radius of 8 mm is defined as aspherical surface 21, and the region extending from a radius of 8 mm to a radius of 18.5 mm is defined as aspherical surface 22. The curvature C (in meters) of the aspherical surfaces at positions perpendicular to and away from the optical axis is then... －1 As shown in Table 7. Here, distance A (in mm) in Table 7 represents the distance from the z-axis in an r-axis coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis. Position B represents the position on the r-axis obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1. Furthermore, the graph showing the relationship between the position obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1 and the curvature C is shown below. Figure 11 As shown.

[0182] [Table 7]

[0183] Distance A Position B Curvature C 18.50 1.00 9.113 16.65 0.90 9.156 14.80 0.80 9.195 12.95 0.70 9.230 11.10 0.60 9.259 9.25 0.50 9.284 7.40 0.40 9.362 5.55 0.30 9.381 3.70 0.20 9.395 1.85 0.10 9.418 0.00 0.00 14.404

[0184] According to the above even-order aspherical form, the paraxial focal distances of aspherical surface 21 and aspherical surface 22 are f1 = 154.6 mm and f2 = 513.2 mm, respectively. At this point, since f1 < f2, it is the value of f1 / f2, the absolute value of the ratio of the radii of curvature of aspherical surface 21 and aspherical surface 22, r1 / r2, and since C... 0.0 >C 1.0 Therefore, it is C. 1.0 / C 0.0 absolute value, C 0.1 / C 0.0 absolute value, C 0.8 / C 0.2 The absolute values ​​are shown in Table 8.

[0185] [Table 8]

[0186] project value f1 / f2 0.30 The absolute value of r1 / r2 1.0 <![CDATA[C 1.0 / C 0.0 absolute value 0.633 <![CDATA[C 0.1 / C 0.0 absolute value 0.654 <![CDATA[C 0.8 / C 0.2 absolute value 0.979

[0187] [Comparative Example]

[0188] An optical element with an effective diameter of 18.5 mm is used. Furthermore, an aspherical surface is provided on the optical surface. The focal point of the aspherical surface of this optical element is one, located behind the illumination point. In this case, if equation (1) is used, the aspherical surface has a shape that satisfies the following values.

[0189] c = 0.0055

[0190] k = -1.327 × 10 6

[0191] a² = 2.276 × 10 -3

[0192] At this point, the curvature C (in meters) of the aspherical surface at each position perpendicular to and away from the optical axis -1 As shown in Table 9. Here, distance A (in mm) in Table 9 represents the distance from the z-axis in an r-axis coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis. Position B represents the position on the r-axis obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1. Furthermore, the relationship between the position obtained by dividing the optical axis position into 10 equal parts with the optical effective area end position as 1 and the curvature C is shown in the graph below. Figure 12 As shown.

[0193] [Table 9]

[0194] Distance A Position B Curvature C 18.50 1.00 4.503 16.65 0.90 4.512 14.80 0.80 4.520 12.95 0.70 4.528 11.10 0.60 4.534 9.25 0.50 4.539 7.40 0.40 4.544 5.55 0.30 4.547 3.70 0.20 4.550 1.85 0.10 4.555 0.00 0.00 10.077

[0195] According to the even-order aspheric form described above, the paraxial focus distance of this aspheric surface is f1 = 132.3 mm. At this point, since C... 0.0 >C 1.0 Therefore, it is C. 1.0 / C 0.0 absolute value, C 0.1 / C 0.0 absolute value, C 0.8 / C 0.2 The absolute values ​​are shown in Table 10.

[0196] [Table 10]

[0197] project value <![CDATA[C 1.0 / C 0.0 absolute value 0.447 <![CDATA[C 0.1 / C 0.0 absolute value 0.452 <![CDATA[C 0.8 / C 0.2 absolute value 0.993

[0198] [Evaluation Results]

[0199] Optical simulations were performed using Zemax's Optical Design Program to confirm the intensity distribution of the laser along a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point on the workpiece when using the optical elements of Examples 1 to 4. The light source for the simulation was assumed to be a fiber laser source, with the following conditions: core diameter... 80 mrad. Figures 14-17 These represent the respective simulation results. The horizontal axis represents the coordinate position of the workpiece at the irradiation point on a straight line containing the optical axis, perpendicular to the optical axis, with units of mm. Additionally, Figures 14-17 The values ​​such as -1mm, 0mm, and +1mm in the figures represent... Figure 3 (b) Figure 6 The lateral aberration diagram in (b) shows the laser intensity distribution at the illumination point with the illumination point position set to 0 mm. -1 mm and +1 mm represent the laser intensity distribution at positions -1 mm and +1 mm along the optical axis from the illumination point position, respectively. The negative sign here indicates the front side (optical system side) of the illumination point position.

[0200] Furthermore, optical simulations were performed using Zemax's Optical Design Program to confirm the intensity distribution of the laser along a straight line containing the optical axis on a plane perpendicular to the optical axis at the irradiation point of the workpiece when using the optical elements of the comparative example. The laser source conditions during the simulation were: core diameter... 80 mrad. Figure 18 The simulation results are shown. The descriptions of the figures are the same as above.

[0201] in addition, Figure 13This is a simulation result of the laser intensity distribution at a position -3 mm from the irradiation point in the comparative example. In the comparative example, an aspherical surface is provided on the optical surface with a single focal point, thus there exists a position where the laser intensity distribution follows a Gaussian distribution. Figures 14-18 The vertical axis of the graph of the simulation results is used as a representation of the distance from the vertical axis. Figure 13 The axis is drawn based on the relative intensity of the laser.

[0202] from Figure 14 , Figure 15 It is self-evident that, by using the optical system described in this application, the intensity distribution of the laser along a straight line at the irradiation point is at least bimodal, centered on the optical axis. This means that, at the irradiation point on the workpiece, in a plane perpendicular to the optical axis, the intensity distribution of the laser is at least annular, centered on the optical axis. Furthermore, it is self-evident that even at positions deviating from the irradiation point by -1 mm or 1 mm, the position and peak value of the laser intensity peak remain almost unchanged.

[0203] from Figure 16 , Figure 17 It is self-evident that, by using the optical system described in this application, even if the focal position of the aspherical surface deviates, the intensity distribution of the laser along the straight line at the irradiation point will exhibit at least a bimodal shape centered on the optical axis. This means that, at the irradiation point on the workpiece, on a plane perpendicular to the optical axis, the intensity distribution of the laser will exhibit at least a ring-shaped shape centered on the optical axis. Furthermore, it is self-evident that even at positions deviating from the irradiation point by -1 mm or 1 mm, the position and peak value of the laser intensity peak will remain almost unchanged.

[0204] On the other hand, from Figure 18 It is self-evident that when using the optical system of the comparative example, the intensity distribution of the laser is bimodal with respect to the optical axis. However, at positions deviating from the irradiation point by -1 mm and 1 mm, the position and peak value of the laser intensity peak change significantly.

[0205] In other words, the laser processing apparatus, by having an optical system with multiple focal points arranged on the same optical axis, enables the focal points of the optical system to be located at different positions from the irradiation point of the workpiece, and ensures that the intensity distribution of the laser on the plane at the irradiation point is at least ring-shaped with respect to the optical axis. Furthermore, most of the laser incident on the optical system of this application can be utilized as a ring-shaped laser at the irradiation point, resulting in high laser energy utilization efficiency. Additionally, it is self-evident that even if the focal point position is deviated, the intensity distribution shape, the position of the intensity peak, and the peak value of the laser at the irradiation point remain unchanged.

[0206] Industrial applicability

[0207] The laser processing apparatus of this invention enables the intensity distribution of the laser on the plane at the irradiation point to be at least annular about the optical axis. Even if the focal position deviates due to the thermal lensing effect, the intensity distribution and intensity of the laser on the plane at the irradiation point will not change. Therefore, it is suitable for optical systems used in laser processing apparatuses for cutting or drilling workpieces. Furthermore, by using the laser processing apparatus of this invention, stable laser processing can be performed, maintaining the processing quality of the workpiece.

Claims

1. A laser processing apparatus for processing a workpiece by irradiating it with a laser, characterized in that, It is equipped with an optical system having two optical surfaces with different focal points set on the same optical axis. At the two different focal points, the laser beams emitted from the optical surfaces with the two different focal points each have lateral aberrations and intersect the optical axis. The laser irradiation point on the workpiece is located between the two different focal points, and at a position where the lasers emitted from the optical surfaces with the two different focal points have the same lateral aberration and converge in a ring shape. At the location of the irradiation point, the intensity distribution of the laser obtained by combining the lasers emitted from the two optical surfaces with different focal points on the plane perpendicular to the optical axis is in a ring shape with the optical axis as the center.

2. The laser processing apparatus as described in claim 1, The optical surfaces with two different focal points are two different spherical and / or aspherical surfaces.

3. The laser processing apparatus as described in claim 2, The two different spherical and / or aspherical surfaces are arranged in two concentric circular regions on the same optical surface.

4. The laser processing apparatus as described in claim 2, The two different spherical and / or aspherical surfaces are arranged on two different optical surfaces to allow different light beams to pass through, and are two different regions in concentric circles.

5. The laser processing apparatus as described in claim 2, Of the two different spherical and / or aspherical surfaces, at least one optical surface is an aspherical surface.

6. The laser processing apparatus as described in claim 2, The two different spherical surfaces and / or aspherical surfaces are each two different aspherical surfaces.

7. The laser processing apparatus as described in claim 6, The two different aspherical surfaces have different focal distances. If their focal distances are set as f1 and f2, then when f1 < f2, f1 / f2 is greater than 0.2 and less than 0.8; when f1 > f2, f2 / f1 is greater than 0.2 and less than 0.

8. in, The units for f1 and f2 are mm.

8. The laser processing apparatus as described in claim 6, If the radii of curvature of the two different aspherical surfaces are set as r1 and r2 respectively, then the absolute value of r1 / r2 is greater than 0.5 and less than 2. in, The units for r1 and r2 are mm.

9. The laser processing apparatus as described in claim 6, On the two distinct aspherical surfaces, when C 0.0 >C 1.0 At that time, C 1.0 / C 0.0 The absolute value of C is less than 0.

9. 0.0 <C 1.0 At that time, C 0.0 / C 1.0 The absolute value is less than 0.

9. in, In a coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis, if the r-axis is divided into 10 equal parts from the position of the optical axis as the origin to the position of the end of the optically effective region, let the curvature of the origin be C. 0.0 Its unit is m －1 The curvature at the end of the optically effective region is C. 1.0 Its unit is m －1 .

10. The laser processing apparatus as described in claim 6, On the two distinct aspherical surfaces, C 0.1 / C 0.0 The absolute value is greater than 0 and less than 4. in, In a coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis, if the position of the optical axis is divided into 10 equal parts from the origin to the end of the optically effective region, let the curvature at 1 / 10 of these 10 parts be C. 0.1 Its unit is m －1 .

11. The laser processing apparatus as described in claim 6, On the two distinct aspherical surfaces, C 0.8 / C 0.2 The absolute value is greater than 0.5 and less than 1.

5. in, In a coordinate system with the optical axis as the z-axis and the axis orthogonal to the z-axis as the r-axis, if the position of the optical axis is divided into 10 equal parts from the origin to the end of the optically effective region, let the curvature at 2 / 10 of these 10 parts be C. 0.2 Its unit is m －1 The curvature at the 8 / 10th position of the 10 equal divisions is C. 0.8 Its unit is m －1 .

12. An optical system, comprising a laser processing apparatus that processes a workpiece by irradiating it with a laser, characterized in that, It has an optical surface with two different focal points set on the same optical axis, wherein the optical surface with two different focal points is two different spherical and / or aspherical surfaces. Such that: at the positions of the two different focal points, the lasers emitted from the optical surfaces with the two different focal points respectively have lateral aberrations and intersect the optical axis; the position of the irradiation point of the laser on the workpiece is located between the positions of the two different focal points, and is located at a position where the lasers emitted from the optical surfaces with the two different focal points respectively have the same value of lateral aberration and converge in a ring shape; at the position of the irradiation point, the intensity distribution of the laser obtained by combining the lasers emitted from the optical surfaces with the two different focal points respectively on the plane perpendicular to the optical axis is in a ring shape with the optical axis as the center.

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