CN114682906A

CN114682906A - Optical system of laser processing device, and laser processing device

Info

Publication number: CN114682906A
Application number: CN202111095753.1A
Authority: CN
Inventors: 小森一范; 坂本敬志; 竹本昌纪
Original assignee: Tamron Co Ltd
Current assignee: Tamron Co Ltd
Priority date: 2020-12-25
Filing date: 2021-09-18
Publication date: 2022-07-01
Also published as: JP2022101887A

Abstract

An object of the present invention is to provide an optical system of a laser processing apparatus and a laser processing apparatus, which have high energy utilization efficiency of a laser beam and can select an irradiation point (spot) of energy intensity distribution of a processing object suitable for a plurality of materials. In order to achieve the object, an optical system of a laser processing apparatus is used, which has an optical surface having a plurality of different focal points on an optical axis, and in which the energy intensity distribution of a laser beam on a surface perpendicular to the optical axis differs depending on the position on the optical axis, and the energy intensity distribution of the laser beam at the irradiation point of the laser beam on a workpiece can be selected by setting the different position on the optical axis as the irradiation point of the laser beam on the workpiece.

Description

Optical system of laser processing device, and laser processing device

Technical Field

The present invention relates to an optical system of a laser processing apparatus and a laser processing apparatus.

Background

The laser processing apparatus irradiates a workpiece with a laser beam focused at one point, thereby rapidly increasing the surface temperature of the workpiece, melting or evaporating the irradiated surface of the workpiece, and performing processing such as cutting, drilling, and welding on the workpiece. Since the laser beam is focused at one point, precise and fine processing can be performed with precise positioning. Further, by using a laser beam of high energy, the machining time can be shortened, and a high-hardness workpiece which is difficult to machine with a tool can be machined.

Here, it is known that when the laser beam is condensed, the intensity distribution of the laser beam at the irradiation point of the laser beam is preferably in a ring shape on the plane of the irradiation point. However, if the ring diameter at the irradiation point is large, it is difficult to sufficiently concentrate the light energy, which results in a long time required for melting the workpiece and deterioration in the quality of the processed cross section. Further, if the depth of focus is shallow while maintaining a constant ring diameter, when the focal point is displaced due to thermal lens effect or the like, the intensity distribution of the laser beam at the irradiation point is not in a ring shape or the like, which causes a problem of deterioration in welding quality of the workpiece.

In addition, patent document 1 discloses a laser welding apparatus: the laser beam is condensed by using a condenser lens obtained by cutting a convex central portion of the condenser lens into a concave shape, and the laser beam having a higher intensity distribution in the peripheral portion than in the central portion is irradiated and used.

Patent document 2 discloses an optical system in which a function of shifting the phase of a laser beam is introduced into the optical system, a phase difference is provided to a part of the beam of the laser beam, and the energy intensity distribution of an input laser beam having a gaussian energy intensity distribution is converted into a ring-shaped (double-humped) or top-hat-shaped intensity distribution at the spot of the combined beam.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2003-305581

Patent document 2: U.S. Pat. No. 9285593

Disclosure of Invention

Problems to be solved by the invention

However, the optical system of the laser processing apparatus described in patent document 1 collects the laser beam by using the condenser lens in which the convex central portion of the condenser lens is cut into a concave shape, and thereby obtains the laser beam in which the intensity distribution of the laser beam in the peripheral portion is higher than that in the central portion. Here, the laser beam passing through the concave portion of the condenser lens is refracted from the center in a direction to be diffused. Therefore, the laser beam refracted at the concave portion of the condenser lens is not condensed to the irradiation point of the workpiece. That is, in the processing of a workpiece by a laser beam, the utilization efficiency of the energy of the laser beam output from the laser oscillator is low.

In addition, the optical system of the laser processing apparatus described in patent document 2 cannot be applied to a processing object having a high light reflectance.

An object of the present invention is to provide an optical system of a laser processing apparatus and a laser processing apparatus, which have high energy utilization efficiency of a laser beam and can select an irradiation point (spot) of energy intensity distribution suitable for a processing object of a plurality of materials.

Means for solving the problems

In order to solve the above problems, intensive studies have been made, and the following inventions have been obtained.

An optical system of a laser processing apparatus according to the present invention processes a workpiece by irradiating a laser beam, and includes an optical surface having a plurality of different focal points on an optical axis, wherein an energy intensity distribution of the laser beam on a surface perpendicular to the optical axis differs depending on a position on the optical axis, and the energy intensity distribution of the laser beam at an irradiation point (spot) of the laser beam on the workpiece can be selected by setting the different position on the optical axis as the irradiation point (spot) of the laser beam on the workpiece.

The laser processing apparatus according to the present invention includes the optical system of the laser processing apparatus.

Effects of the invention

The optical system of the laser processing apparatus according to the present invention has the optical surface on which the plurality of different focal points are provided on the optical axis, and thereby the energy intensity distribution of the laser beam on the surface perpendicular to the optical axis is made different depending on the position on the optical axis, and the different position on the optical axis is set as the irradiation point (spot) of the laser beam of the object to be processed, whereby the energy intensity distribution of the laser beam at the irradiation point (spot) of the laser beam of the object to be processed can be selected. Therefore, the laser processing can be performed by selecting an appropriate energy intensity distribution at the spot according to the object to be processed.

Drawings

Fig. 1 a and b are schematic cross-sectional views of an optical system of the laser processing apparatus according to the present embodiment.

Fig. 2 is a schematic cross-sectional view of an optical element having different spherical and/or aspherical surfaces on the same optical surface.

Fig. 3 is a schematic cross-sectional view of an optical element having different spherical and/or aspherical surfaces on two different optical surfaces.

Fig. 4 is a schematic cross-sectional view of the laser processing apparatus according to the present embodiment.

Fig. 5 is a lateral aberration diagram with respect to the entrance pupil coordinate at an irradiation point where the energy intensity distribution is annular with a central portion in example 1.

Fig. 6 shows the energy intensity distribution of example 1 as the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point in the shape of a ring having a central portion.

Fig. 7 shows the energy intensity distribution of example 1 as the intensity ratio of the laser beam on a plane perpendicular to the optical axis at the ring-shaped irradiation point having the center portion.

Fig. 8 is a lateral aberration diagram with respect to the entrance pupil coordinates at the irradiation point where the energy intensity distribution is annular in example 1.

Fig. 9 shows the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point having the annular energy intensity distribution in example 1.

Fig. 10 is an intensity ratio of a laser beam on a plane perpendicular to the optical axis at an irradiation point where the energy intensity distribution of example 1 is annular.

Fig. 11 is a lateral aberration diagram with respect to the entrance pupil coordinates at the irradiation point where the energy intensity distribution is gaussian in example 1.

Fig. 12 is a graph showing the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of example 1 is gaussian.

Fig. 13 is an intensity ratio of a laser beam on a plane perpendicular to the optical axis at an irradiation point where the energy intensity distribution of example 1 is gaussian.

Fig. 14 is a lateral aberration diagram with respect to the entrance pupil coordinates at an irradiation point where the energy intensity distribution is annular with a central portion in example 2.

Fig. 15 shows the energy intensity distribution of example 2 as the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point in the shape of a ring having a central portion.

Fig. 16 shows the energy intensity distribution of example 2 as the intensity ratio of the laser beam on a plane perpendicular to the optical axis at the irradiation point in the shape of a ring having a central portion.

Fig. 17 is a lateral aberration diagram with respect to the entrance pupil coordinates at the irradiation point where the energy intensity distribution is annular in example 2.

Fig. 18 is a graph showing the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point in which the energy intensity distribution is annular in example 2.

Fig. 19 shows the intensity ratio of the laser beam on the plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is annular in example 2.

Fig. 20 is a lateral aberration diagram with respect to the entrance pupil coordinates at the irradiation point where the energy intensity distribution is gaussian in example 2.

Fig. 21 shows the intensity ratio of the laser beam on a straight line including 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.

Fig. 22 shows the intensity ratio of the laser beam on the plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution is gaussian in example 2.

Fig. 23 is a lateral aberration diagram with respect to the entrance pupil coordinates at the irradiation point where the energy intensity distribution of the comparative example is gaussian.

Fig. 24 shows the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the point of irradiation with the energy intensity distribution in the gaussian shape in the comparative example.

Fig. 25 shows the intensity ratio of the laser beam on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of the comparative example is gaussian.

Fig. 26 is a lateral aberration diagram with respect to the entrance pupil coordinate at the irradiation point where the energy intensity distribution is annular in the comparative example.

Fig. 27 shows the intensity ratio of the laser beam on a straight line including the optical axis on a plane perpendicular to the optical axis at the irradiation point of the ring-shaped energy intensity distribution in the comparative example.

Fig. 28 is a graph showing the intensity ratio of the laser beam on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of the comparative example is annular.

Fig. 29 is a lateral aberration diagram with respect to the entrance pupil coordinate at the irradiation point where the energy intensity distribution is annular in the comparative example.

Fig. 30 shows the intensity ratio of the laser beam on a straight line including 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 annular.

Fig. 31 shows the intensity ratio of the laser beam on a plane perpendicular to the optical axis at the irradiation point where the energy intensity distribution of the comparative example is annular.

Description of reference numerals:

1 optical system of a first configuration

2 optical system of the second configuration

5 optical element for controlling energy distribution

6 optical element for controlling energy distribution

10 optical axis

11 optical surface area

12 optical surface area

21 optical surface area

22 optical surface area

31 optical surface area

32 optical surface area

41 optical surface area

42 optical surface area

50 irradiation point R (Ring, Ring shape)

51 irradiation point C (Ring shape with center)

52 illumination point G (Gauss shape)

70 optical element

71 base material

72 optical surface

73 optical surface

74 first optical zone

75 second optical zone

70' optical element

71' base material

72' optical surface

73' optical surface

74' first optical zone

75' second optical zone

80 laser processing device

81 laser oscillator

82 light path

83 optical system

84 processing operation table

85 workpiece to be processed

101 light beam

102 light beam

201 light beam

202 light beam

301 light beam

302 light beam

401 beam of light

402 light beam

Detailed Description

Embodiments of an optical system used in a laser processing apparatus according to the present invention and a laser processing apparatus will be described below.

1. Embodiment of optical system used for laser processing apparatus

An optical system used in a laser processing apparatus according to the present invention and a laser processing apparatus are an optical system used in a laser processing apparatus that processes a workpiece by irradiating a laser beam, and a laser processing apparatus including the optical system. The optical system has an optical surface on which a plurality of different focal points are disposed on an optical axis. Therefore, the energy intensity distribution of the laser light on the plane perpendicular to the optical axis differs depending on the position on the optical axis.

In this case, the optical system can select the energy intensity distribution of the laser beam at the irradiation point of the workpiece by setting different positions on the optical axis as the irradiation point (spot) of the laser beam of the workpiece. Specifically, the optical system can convert the incident laser beam into at least three modes, i.e., a gaussian shape, a ring shape (a double-peak shape), and a ring shape having a central portion (a shape formed by the ring shape and the central portion of the ring shape), and can select the energy intensity distribution of the laser beam at the irradiation point of the laser beam on the workpiece.

According to the present invention, as described below, the laser processing can be performed by selecting an appropriate energy intensity distribution at the flare in accordance with the processing object, and by performing laser processing by applying the energy intensity distribution to the flare, for example, to welding or cutting of iron or the like in the case where the energy intensity distribution is gaussian-shaped, by applying the energy intensity distribution to the flare in the case where the energy intensity distribution is circular-shaped, by applying the energy intensity distribution to the welding or butt welding of a processing object such as copper or hot-dip galvanized steel sheet, and by applying the energy intensity distribution to the welding or cutting of a processing object such as an aluminum material having a high light reflectance in the case where the energy intensity distribution is circular-shaped and the center portion of the circular shape.

Fig. 1 a and b show schematic cross-sectional views of an optical system of the laser processing apparatus according to the present embodiment. Fig. 1 a shows a first arrangement in which the energy intensity distribution on the surface perpendicular to the optical axis 10 at the position on the optical axis 10 of the laser beam is a gaussian, annular, or annular energy intensity distribution having a central portion in order from the energy distribution controlling optical element 5 side. In addition, b in fig. 1 shows a second arrangement in which the energy intensity distribution on the surface perpendicular to the optical axis 10 at the position on the optical axis 10 of the laser beam has an annular, ring-shaped, or gaussian energy intensity distribution having a central portion in order from the energy distribution controlling optical element 6 side.

[ optical System of first configuration of energy intensity distribution ]

First, the optical system 1 of the first configuration is explained with reference to a of fig. 1. Fig. 1 a shows an approximate trajectory of the laser beam emitted from the energy distribution controlling optical element 5 when the laser beam is emitted to the energy distribution controlling optical element 5 from the side where the energy distribution controlling optical element 5 is arranged. The optical axis 10 passes through the optical center of the energy distribution controlling optical element 5. The energy distribution control optical element 5 includes an optical surface region 11, an optical surface region 12, an optical surface region 21, and an optical surface region 22. The optical surface area 11 and the optical surface area 21 are concentric areas having the same optical center of the energy distribution controlling optical element 5 as the center. The optical surface region 12 and the optical surface region 22 are concentric regions having the optical center of the energy distribution controlling optical element 5 as the center.

The energy distribution controlling optical element 5 including the optical surface area 11 and the optical surface area 21 has a concentric area with a focal point at the irradiation point C51 on the optical axis 10. On the other hand, the energy distribution controlling optical element 5 including the optical surface area 12 and the optical surface area 22 has a concentric area, the focal point of which is at the irradiation point G52 on the optical axis 10. As such, the optical system 1 of the first configuration has an optical surface on which a plurality of different focal points are set on the optical axis. In fig. 1 a, a beam 101 of laser light emitted from the optical surface area 11, a beam 201 of laser light emitted from the optical surface area 21, a beam 102 of laser light emitted from the optical surface area 12, and a beam 202 of laser light emitted from the optical surface area 22 are illustrated so as to simplify the beams of laser light emitted from the respective optical surface areas into one line.

Here, the beam emitted from the energy distribution controlling optical element 5, which includes the beam 101 of the laser beam emitted from the optical surface area 11 and the beam 201 of the laser beam emitted from the optical surface area 21, converges at a point at the position of the irradiation point C51. The light flux gradually spreads after passing through the position of the irradiation point C51, and then passes through the positions of the irradiation point R50 and the irradiation point G52. Further, the light flux emitted from the energy distribution controlling optical element 5, which includes the light flux 102 of the laser beam emitted from the optical surface area 12 and the light flux 202 of the laser beam emitted from the optical surface area 22, gradually converges toward the focal point and passes through the position of the irradiation point C51 and the position of R50. The light flux is converged to one point at the position of the irradiation point G52.

At this time, at the position of the irradiation point C51, the light beam emitted from the energy distribution controlling optical element 5, which includes the light beam 102 of the laser beam and the light beam 202 of the laser beam, passes through the vicinity of the light beam emitted from the energy distribution controlling optical element 5, which includes the light beam 101 of the laser beam and the light beam 201 of the laser beam. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point G51 is in a ring shape having a central portion centered on the optical axis 10.

The beam emitted from the energy distribution controlling optical element 5, which includes the beam 101 of the laser beam and the beam 201 of the laser beam, is focused at the position of the irradiation point C51, and then is expanded in a diffused state to reach the position of the irradiation point R50. On the other hand, the beam emitted from the energy distribution controlling optical element 5, which includes the beam 102 of the laser beam and the beam 202 of the laser beam, converges toward the focal point at the position of the irradiation point C52, and reaches the position of the irradiation point R50. As described above, the beam emitted from the energy distribution controlling optical element 5 of the beam 101 including the laser beam and the beam 201 including the laser beam, and the beam emitted from the energy distribution controlling optical element 5 of the beam 102 including the laser beam and the beam 202 including the laser beam pass through the same position on the surface perpendicular to the optical axis 10. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point R50 is ring-shaped with the optical axis 10 as the center.

Further, at the position of the irradiation point G52, the luminous flux emitted from the energy distribution controlling optical element 5, including the luminous flux 101 of the laser beam and the luminous flux 201 of the laser beam, gradually expands in a diffused shape after passing through the position of the irradiation point C51. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point G52 is gaussian-like with the optical axis 10 as the center.

That is, the optical system 1 of the first configuration of the energy intensity distribution has: the energy intensity distribution of the laser beam on the plane perpendicular to the optical axis 10 at the position of the irradiation point C51, the position of the irradiation point R50, and the position of the irradiation point G52 on the optical axis 10 is in the first arrangement of the ring-shaped, and gaussian-shaped energy intensity distribution having the center portion in this order. At this time, by setting the object to be processed at the position of the irradiation point C51, laser processing can be performed with an energy intensity distribution at an annular spot having a central portion. In addition, by providing the object at the position of the irradiation point R50, laser processing can be performed with an energy intensity distribution at the annular spot. Further, by setting the object to be processed at the position of the irradiation point G52, laser processing can be performed with an energy intensity distribution at the gaussian spot.

The optical system 1 of the first arrangement of the energy intensity distribution described above preferably satisfies the following conditional expression (1). This is because the optical system 1 having the first arrangement of the energy intensity distribution satisfies the conditional expression (1), and the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position on the optical axis 10 of the laser beam sequentially has a ring shape, and a gaussian shape having a central portion from the energy distribution controlling optical element 5 side.

fB1＜fB0＜fB2····(1)

Wherein, fB 0: the energy intensity distribution of the laser beam on a plane perpendicular to the optical axis is a distance from an optical surface (excluding devices having no optical significance such as cover glass) closest to the workpiece, which is a position on the optical axis in a ring shape.

fB 1: the energy intensity distribution on the surface perpendicular to the optical axis of the laser beam is a distance from an optical surface (excluding optically insignificant devices such as cover glass) closest to the workpiece, the position on the optical axis being in the shape of a ring having a central portion.

fB 2: the energy intensity distribution of the laser beam on a plane perpendicular to the optical axis is a distance from an optical surface (excluding devices having no optical significance such as cover glass) closest to the workpiece, the position on the optical axis being gaussian.

[ optical System of second configuration of energy intensity distribution ]

Next, the optical system 2 of the second arrangement will be described with reference to b of fig. 1. B in fig. 1 shows an approximate trajectory of the laser beam emitted from the energy distribution controlling optical element 6 when the laser beam is incident on the energy distribution controlling optical element 6 from the side where the energy distribution controlling optical element 6 is arranged. The optical axis 10 passes through the optical center of the energy distribution controlling optical element 6. The energy distribution control optical element 6 includes an optical surface region 31, an optical surface region 32, an optical surface region 41, and an optical surface region 42. The optical surface area 31 and the optical surface area 41 are concentric areas having the same optical center of the energy distribution controlling optical element 6 as the center. The optical surface area 32 and the optical surface area 42 are concentric areas having the same optical center of the energy distribution controlling optical element 6 as the center.

The energy distribution controlling optical element 6 including the optical surface area 31 and the optical surface area 41 has a concentric area, the focal point of which is at the irradiation point C51 on the optical axis 10. On the other hand, the energy distribution controlling optical element 6 including the optical surface area 32 and the optical surface area 42 has a concentric area with a focal point at the irradiation point G52 on the optical axis 10. As such, the optical system 2 of the second configuration has an optical surface in which a plurality of different focal points are set on the optical axis. In fig. 1 b, a beam 301 of the laser beam emitted from the optical surface area 31, a beam 401 of the laser beam emitted from the optical surface area 41, a beam 302 of the laser beam emitted from the optical surface area 32, and a beam 402 of the laser beam emitted from the optical surface area 42 are illustrated so as to simplify the beams of the laser beams emitted from the respective optical surface areas into one line.

Here, the light flux emitted from the energy distribution controlling optical element 6, which includes the light flux 301 of the laser beam emitted from the optical surface area 31 and the light flux 401 of the laser beam emitted from the optical surface area 41, gradually converges toward the focal point and passes through the position of the irradiation point G52 and the position of the irradiation point R50. The light flux is converged to one point at the position of the irradiation point C51. Further, the beam emitted from the energy distribution controlling optical element 6, which includes the beam 302 of the laser beam emitted from the optical surface area 32 and the beam 402 of the laser beam emitted from the optical surface area 42, converges at a point at the position of the irradiation point G52. The light flux gradually spreads after passing through the position of the irradiation point G52, and passes through the position of the irradiation point R50 at the position of the irradiation point C51.

At this time, at the position of the irradiation point G52, the luminous flux emitted from the energy distribution controlling optical element 6, including the luminous flux 301 of the laser beam and the luminous flux 401 of the laser beam, is not completely converged with respect to the optical axis 10 at the position of the irradiation point G52. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point G52 is gaussian with the optical axis 10 as the center.

Further, the beam emitted from the energy distribution controlling optical element 6, which includes the beam 301 of the laser beam and the beam 401 of the laser beam, converges toward the focal point at the position of the irradiation point C51, and reaches the position of the irradiation point R50. On the other hand, the beam emitted from the energy distribution controlling optical element 6, which includes the beam 302 of the laser beam and the beam 402 of the laser beam, is focused at the position of the irradiation point G52, and then is expanded in a diffused state to reach the position of the irradiation point R50. As described above, the beam emitted from the energy distribution controlling optical element 6 of the beam 301 including the laser beam and the beam 401 including the laser beam and the beam 302 including the laser beam and the beam 402 including the laser beam pass through the same position on the surface perpendicular to the optical axis 10. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point R50 is ring-shaped with the optical axis 10 as the center.

Further, at the position of the irradiation point C51, the beam emitted from the energy distribution controlling optical element 6 including the beam 302 of the laser beam and the beam 402 of the laser beam passes through the vicinity of the beam emitted from the energy distribution controlling optical element 6 including the beam 301 of the laser beam and the beam 401 of the laser beam. Therefore, the energy intensity distribution on the plane perpendicular to the optical axis 10 at the position of the irradiation point C51 is in a ring shape having a central portion centered on the optical axis 10.

That is, the optical system 2 of the second configuration of the energy intensity distribution has: the energy intensity distribution of the laser beam on the plane perpendicular to the optical axis 10 at the position of the irradiation point G52, the position of the irradiation point R50, and the position of the irradiation point C51 on the optical axis 10 is a second arrangement of a gaussian shape, a ring shape, and a ring shape having a central portion. At this time, by setting the object to be processed at the position of the irradiation point G52, laser processing can be performed with an energy intensity distribution at a gaussian spot. In addition, by providing the object at the position of the irradiation point R50, laser processing can be performed with an energy intensity distribution at the annular spot. Further, by setting the object to be processed at the position of the irradiation point C51, laser processing can be performed with an energy intensity distribution at an annular spot having a central portion.

The optical system 2 in the second arrangement of the energy intensity distribution described above preferably satisfies the following conditional expression (2). This is because the optical system 2 in the second arrangement of the energy intensity distribution satisfies the conditional expression (2), and the energy intensity distribution on the surface perpendicular to the optical axis 10 at the position on the optical axis 10 of the laser beam is gaussian, annular, and annular with a central portion in order from the energy distribution controlling optical element 6 side.

fB2＜fB0＜fB1····(2)

[ Condition common to optical systems of first and second arrangements of energy intensity distribution ]

The optical system of the laser processing apparatus according to the present embodiment preferably satisfies the following conditional expression (3). The optical system of the laser processing apparatus according to the present embodiment satisfies the conditional expression (3), and thereby can reliably secure the distance between the irradiation point R50 and the irradiation point C51. This is because, even if an optical element having an optical surface provided with a plurality of different focal points is heated by a laser beam and becomes out of focus, the energy intensity distribution at the irradiation point remains unchanged, and it is possible to prevent the processing such as welding or cutting from becoming impossible.

1mm≤|fB0－fB1|····(3)

In addition, in order to obtain the above-described effects, the lower limit value of conditional expression (3) is more preferably 2 mm. The upper limit of the conditional expression (3) is not particularly limited, but is preferably 50mm, for example, because the distance between the optical system 83 and the workpiece 85 in fig. 4 is easily adjusted when the energy intensity distribution at the irradiation point is changed, more preferably 40mm, and still more preferably 20 mm.

Further, the optical system of the laser processing apparatus according to the present embodiment preferably satisfies the following conditional expression (4). The optical system of the laser processing apparatus according to the present embodiment satisfies the conditional expression (4), and thus can reliably secure the distance between the irradiation point R50 and the irradiation point G52. This is because, even if an optical element having an optical surface provided with a plurality of different focal points is heated by a laser beam and becomes out of focus, the energy intensity distribution at the irradiation point remains unchanged, and it is possible to prevent the processing such as welding or cutting from becoming impossible.

1mm≤|fB0－fB2|····(4)

In addition, in order to obtain the above-described effects, the lower limit value of conditional expression (4) is more preferably 2 mm. The upper limit of the conditional expression (4) is not particularly limited, but is preferably 50mm, for example, because the distance between the optical system 83 and the workpiece 85 in fig. 4 is easily adjusted when the energy intensity distribution at the irradiation point is changed, more preferably 40mm, and still more preferably 20 mm.

[ optical surfaces provided with different focal points ]

The optical system of the laser processing apparatus according to the present embodiment has an optical surface on which a plurality of different focal points are provided on an optical axis. In the optical system shown in fig. 1 a and 1 b, the energy distribution controlling optical element 5 and the energy distribution controlling optical element 6 have optical surfaces on which a plurality of different focal points are provided on the optical axis. In this case, the optical surface provided with the plurality of different focal points is preferably a plurality of different spherical and/or aspherical surfaces. By the optical surface being a plurality of different spherical and/or aspherical surfaces, a plurality of different focal points can be provided on the optical surface.

Preferably, the plurality of different spherical and/or aspherical surfaces are provided in a plurality of concentric different regions on the same optical surface. Fig. 2 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 composed of a base 71, and the material thereof is not particularly limited as long as the base 11 is formed using an optical material. The substrate 11 includes an optical surface 72 and an optical surface 73 through which laser light passes, and a broken line O indicates a central axis of the optical element 70. In the optical surface 72, two spherical and/or aspherical surfaces, i.e., the first optical region 74 and the second optical region 75, are provided in concentric circles with the center axis O of the optical element as the center. At this time, incident light refracted through the interface between the two concentric first optical regions 74 and the second optical regions 75 is focused to two different focal points.

Here, in the optical element 5 for energy distribution control, the optical surface area 12 and the optical surface area 22 correspond to the first optical area 74, and the optical surface area 11 and the optical surface area 21 correspond to the second optical area 75. In the energy distribution control optical element 6, the optical surface area 32 and the optical surface area 42 correspond to the first optical area 74, and the optical surface area 31 and the optical surface area 41 correspond to the second optical area 75.

Preferably, the plurality of different spherical and/or aspherical surfaces are regions of the plurality of different optical surfaces through which different light beams pass, and are provided in a plurality of different concentric regions. Fig. 3 is a schematic cross-sectional view of an optical element 70' having different spherical and/or aspherical surfaces on two different optical surfaces of the same optical element. The optical element 70 ' is composed of a base 71 ', and the base 71 ' includes an optical surface 72 ' through which the laser beam passes and an optical surface 73 '. The two spherical and/or aspherical surfaces of the first optical region 74 ' on the optical surface 72 ' and the second optical region 75 ' on the optical surface 73 ' are provided in concentric circles around the center axis O ' of the optical element. At this time, the first optical area 74 'and the second optical area 75' are in positions through which the respective different light beams pass. Incident light refracted through the interface between the first optical region 74 'and the second optical region 75' having two concentric circles converges at two different focal points.

In the energy distribution controlling optical element 5, the optical surface area 12 and the optical surface area 22 correspond to the first optical area 74 ', and the optical surface area 11 and the optical surface area 21 correspond to the second optical area 75'. In the energy distribution controlling optical element 6, the optical surface area 32 and the optical surface area 42 correspond to the first optical area 74 ', and the optical surface area 31 and the optical surface area 41 correspond to the second optical area 75'.

Here, it is preferable that at least one of the plurality of different spherical and/or aspherical surfaces according to the present invention is an aspherical surface. This is because the aspherical surface easily obtains lateral aberration which is difficult to realize in a spherical surface, and therefore different focal points can be set on the plurality of optical surfaces according to the present invention.

In addition, the plurality of different spherical and/or aspherical surfaces according to the present invention are preferably two different optical surfaces. This is because the optical system according to the present invention, which is configured by the optical surfaces having a plurality of different focal points, can be easily configured.

Further, the plurality of different spherical surfaces and/or aspherical surfaces according to the present invention are preferably two different aspherical surfaces. This is because the aspherical surface easily obtains lateral aberration which is difficult to realize in spherical surface, and therefore, the optical system of the present invention, which is configured by the optical surface provided with a plurality of different focal points, can be easily configured, and the focal length can be easily adjusted.

2. Embodiments of the laser processing apparatus

The laser processing apparatus according to the present invention includes the optical system of the laser processing apparatus. In this case, in the optical system, by setting different positions on the optical axis as the irradiation points of the laser beam of the workpiece, the energy intensity distribution of the laser beam at the irradiation points of the laser beam of the workpiece can be selected. Specifically, the incident laser beam can be converted into at least three modes of a gaussian shape, a ring shape (double-peak shape), and a shape formed by the ring shape and the center portion of the ring shape, and the energy intensity distribution of the laser beam at the irradiation point of the laser beam on the workpiece can be selected.

Fig. 4 shows a laser processing apparatus 80 according to the present embodiment. The laser processing apparatus 80 is roughly composed of a laser oscillator 81, an optical path 82, an optical system 83, and a processing table 84. The optical system 83 is an optical system of the laser processing apparatus described above. Further, a workpiece 85 is provided on the machining table 84. The laser oscillator 81 is a device that outputs laser light used for processing. The type and output of the laser beam to be used are selected according to the material, thickness, and accuracy of the workpiece 85. The optical path 82 is used to transmit the laser beam output from the laser oscillator 81 to the optical system 83, and may be of a type using a mirror or a type using an optical cable. The optical system 83 condenses the transmitted laser beam into a predetermined shape, and irradiates the irradiation point of the workpiece 85 with the condensed laser beam. The machining table 84 is fixedly provided for the workpiece 85, and includes a device for moving the workpiece 85, the optical system 83, or both, in order to select the energy intensity distribution of the laser beam at the irradiation point of the workpiece 85.

The laser processing apparatus 80 converts the incident laser beam into at least three modes of a gaussian shape, a ring shape (double-humped shape), and a shape composed of the ring shape and the center of the ring shape by using the optical system 83 at different positions on the optical axis as the irradiation point of the laser beam of the workpiece 85, and selects the energy intensity distribution of the laser beam at the irradiation point of the laser beam of the workpiece 85. Thus, the energy intensity distribution at the flare is suitable for welding or cutting of iron when it is gaussian, for example, for stitch welding or butt welding of a workpiece such as copper or hot-dip galvanized steel sheet when it is in a ring shape, and for welding or cutting of a workpiece having a high light reflectance such as an aluminum material having a high light reflectance when it is in a ring shape and a central portion of the ring shape, and the energy intensity distribution at the flare can be selected appropriately according to the workpiece to be processed, and laser processing can be performed.

The optical system 83 of the laser processing apparatus 80 may include a collimator lens for making the laser beam substantially parallel to the optical axis, a condenser lens for condensing the laser beam, and the like. Further, the energy distribution controlling optical element 5 (or the energy distribution controlling optical element 6) may be provided with a function as a collimator lens, and a condenser lens may be disposed on the object side of the energy distribution controlling optical element 5 (or the energy distribution controlling optical element 6). In these cases, fB0, fB1, and fB2 are distances from the optical surface (excluding optically insignificant devices such as cover glass) of the optical system 83 closest to the workpiece.

The embodiment according to the present invention described above is an embodiment of the present invention, and can be modified as appropriate within a range not departing from the gist of the present invention. The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples.

[ example 1 ]

An example of a first configuration of the energy intensity distribution illustrated in fig. 1 a is illustrated. The optical element for controlling energy distribution used in example 1 is an element in which optical surfaces having a plurality of different focal points are provided in a plurality of concentric different regions on the same optical surface, as shown in fig. 2. Here, the optical surface shape of the aspherical surface can be expressed by an even-order aspherical surface expression shown by the following expression (5).

z(r)＝(r²/R)/[1+{1－ε·r²/R²}^1/2]+Ar²+Br⁴+Cr⁶+Dr⁸+Er¹⁰····(5)

Wherein the content of the first and second substances,

z (r): a surface position (depression amount) in the optical axis direction at a position perpendicular to the optical axis by a distance r therefrom.

R: a radius of curvature.

Epsilon: is (1+ k), k is the conic constant.

A, B, C, D, E: an aspheric surface coefficient.

As the optical element for controlling energy intensity distribution of example 1, an optical element having an effective diameter of an optical surface of 37.3mm was used. A portion of the optical element corresponding to the first optical region 74 in fig. 2 is a region having a surface diameter of 16.0mm or less, and if expression (5) is used, the aspherical surface of the region has a shape satisfying the following numerical value.

R＝－200.0

ε＝－1.5237×10⁶

A＝2.6803×10^－3

B＝9.1279×10^－10

C＝0.0

D＝0.0

E＝0.0

Similarly, the portion of the optical element corresponding to the second optical region 75 in fig. 2 is a region having a surface diameter of 16.0mm or more, and if expression (5) is used, the aspherical surface of the region has a shape satisfying the following numerical value.

R＝200.0

ε＝－1.5237×10⁶

A＝2.6974×10^－3

B＝4.5648×10^－9

C＝0.0

D＝0.0

E＝0.0

At this time, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 219.4mm from the optical surface of the optical element is shown in fig. 5. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 5, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 1 is provided with different focal points as described above, the lateral aberration characteristics are different between the portion corresponding to the first optical zone 74 and the portion corresponding to the second optical zone 75 at the entrance pupil coordinate. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 shows a lateral aberration amount having a substantially constant magnitude. On the other hand, the lateral aberration of the corresponding portion of the portion corresponding to the second optical zone 75 shows a value in which the lateral aberration value approaches zero.

Fig. 6 and 7 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 6 is an intensity ratio of laser light rays on an arbitrary straight line including the optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 5. Fig. 7 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 5. As is clear from fig. 6 and 7, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 5 is a ring shape having a central portion at a position where the distance from the optical surface of the optical element on the optical axis is 219.4 mm.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 221.9mm from the optical surface of the optical element is shown in fig. 8. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 8, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 1 is provided with different focal points as described above, the lateral aberration characteristics are different between the portion corresponding to the first optical zone 74 and the portion corresponding to the second optical zone 75 at the entrance pupil coordinate. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 shows a lateral aberration amount having a substantially constant magnitude. Similarly, the lateral aberration of the portion corresponding to the portion of the second optical zone 75 also shows a lateral aberration amount of a certain magnitude.

Fig. 9 and 10 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 9 is an intensity ratio of a laser beam on an arbitrary straight line including an optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 8. Fig. 10 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 8. As is clear from fig. 9 and 10, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 8 is annular at a position 221.9mm away from the optical surface of the optical element on the optical axis.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 228.4mm from the optical surface of the optical element is shown in fig. 11. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 11, entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 1 is provided with different focal points as described above, the lateral aberration characteristics are different between the portion corresponding to the first optical zone 74 and the portion corresponding to the second optical zone 75 at the entrance pupil coordinate. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 as a whole shows a characteristic that the lateral aberration is small. On the other hand, the lateral aberration of the portion corresponding to the second optical region 75 shows a characteristic that the lateral aberration is large and the lateral aberration is large as the distance from the origin of the entrance pupil coordinate is farther.

Fig. 12 and 13 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 12 is an intensity ratio of laser light rays on an arbitrary straight line including the optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 11. Fig. 13 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 11. As is clear from fig. 12 and 13, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 11 is gaussian at a position on the optical axis at a distance of 228.4mm from the optical surface of the optical element.

As is clear from the above, the optical system of embodiment 1 has: the energy intensity distribution characteristic is a ring-shaped, or gaussian irradiation spot having a central portion in order from the optical element side. The distances from the optical surface of the optical element to the irradiation points on the optical axis are, fB 1-219.4 mm, fB 0-221.9 mm, and fB 2-228.4 mm. That is, it is clear that the optical system of example 1 satisfies the conditional expression (1).

Further, it is possible to prevent the occurrence of,

|fB0－fB1|＝2.5

|fB0－fB2|＝6.5

accordingly, it is clear that the optical system of example 1 satisfies the conditional expressions (3) and (4).

[ example 2 ]

Next, an example of the second arrangement of the energy intensity distribution explained in b of fig. 1 will be explained. The optical element for controlling energy distribution used in example 2 is an element in which optical surfaces provided with a plurality of different focal points are provided in a plurality of different concentric areas on the same optical surface, as shown in fig. 2.

As the optical element for controlling energy intensity distribution of example 2, an optical element having an effective diameter of an optical surface of 37.3mm was used. A portion of the optical element corresponding to the first optical region 74 in fig. 2 is a region having a surface diameter of 16.0mm or less, and if expression (5) is used, the aspherical surface of the region has a shape satisfying the following numerical value.

R＝200.0

ε＝－1.5237×10⁶

A＝2.6791×10^－3

B＝4.9802×10^－9

C＝0.0

D＝0.0

E＝0.0

R＝－200.0

ε＝－1.5237×10⁶

A＝2.6626×10^－3

B＝3.5921×10^－9

C＝0.0

D＝0.0

E＝0.0

At this time, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 218.4mm from the optical surface of the optical element is shown in fig. 14. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 14, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 2 is provided with different focal points as described above, the portion corresponding to the first optical region 74 and the portion corresponding to the second optical region 75 at the entrance pupil coordinate have different lateral aberration characteristics. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 as a whole shows a characteristic that the lateral aberration is small. On the other hand, the lateral aberration of the portion corresponding to the second optical region 75 shows a characteristic that the lateral aberration is large and the lateral aberration is large as the distance from the origin of the entrance pupil coordinate is farther.

Fig. 15 and 16 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 15 is an intensity ratio of a laser beam on an arbitrary straight line including an optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 14. Fig. 16 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 14. As is clear from fig. 15 and 16, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 14 is gaussian at a position on the optical axis at a distance of 218.4mm from the optical surface of the optical element.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 224.9mm from the optical surface of the optical element is shown in fig. 17. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 17, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 2 is provided with different focal points as described above, the portion corresponding to the first optical region 74 and the portion corresponding to the second optical region 75 at the entrance pupil coordinate have different lateral aberration characteristics. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 shows a lateral aberration amount having a substantially constant magnitude. Similarly, the lateral aberration of the portion corresponding to the second optical zone 75 also shows a lateral aberration amount having a certain magnitude.

Fig. 18 and 19 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 18 is an intensity ratio of a laser beam on an arbitrary straight line including an optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 17. Fig. 19 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 17. As is clear from fig. 18 and 19, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 17 is annular at a position on the optical axis at a distance of 224.9mm from the optical surface of the optical element.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position where the distance from the optical surface of the optical element on the optical axis is 227.4mm is shown in fig. 20. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 20, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of example 2 is provided with different focal points as described above, the portion corresponding to the first optical region 74 and the portion corresponding to the second optical region 75 at the entrance pupil coordinate have different lateral aberration characteristics. Specifically, the lateral aberration of the portion corresponding to the first optical zone 74 shows a lateral aberration amount having a substantially constant magnitude. On the other hand, the lateral aberration of the corresponding portion of the portion corresponding to the second optical zone 75 shows a value in which the lateral aberration value approaches zero.

Fig. 21 and 22 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 21 is an intensity ratio of a laser beam on an arbitrary straight line including an optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 20. Fig. 22 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 20. As is clear from fig. 21 and 22, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 20 is a ring shape having a central portion at a position where the distance from the optical surface of the optical element on the optical axis is 227.4 mm.

As is clear from the above, the optical system of embodiment 2 has: the energy intensity distribution characteristic is a Gaussian, annular, or annular irradiation spot having a central portion in order from the optical element side. The distances from the respective irradiation points on the optical surface of the optical element on the optical axis are fB 2-218.4 mm, fB 0-224.9 mm, and fB 1-227.4. That is, it is clear that the optical system of example 2 satisfies the conditional expression (2).

Further, it is possible to prevent the occurrence of,

|fB0－fB1|＝2.5

|fB0－fB2|＝6.5

accordingly, it is clear that the optical system of example 2 satisfies the conditional expressions (3) and (4).

[ COMPARATIVE EXAMPLE ]

The optical element for controlling energy distribution used in the comparative example set a single focal point. As the optical element for controlling energy intensity distribution of the comparative example, an optical element having an effective diameter of an optical surface of 37.3mm was used. When expression (5) is used, the aspherical surface of the optical element has a shape satisfying the following numerical values.

R＝200.0

ε＝－1.4666×10⁶

A＝2.6747×10^－3

B＝1.3586×10^－8

C＝0.0

D＝0.0

E＝0.0

In this case, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 218.4mm from the optical surface of the optical element is shown in fig. 23. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 23, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of the comparative example is provided with a single focus as described above, lateral aberration characteristics that change rapidly are not shown except for the origin of the entrance pupil coordinates. Further, the farther the distance from the origin of the entrance pupil coordinates is, the slower the change in the lateral aberration value becomes, and the lateral aberration value becomes zero at the halfway position of the entrance pupil coordinates.

Fig. 24 and 25 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 24 is an intensity ratio of a laser beam on an arbitrary straight line including an optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 23. Fig. 25 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 23. As is clear from fig. 24 and 25, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 23 is gaussian at a position on the optical axis at a distance of 218.4mm from the optical surface of the optical element.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position on the optical axis at a distance of 223.4mm from the optical surface of the optical element is shown in fig. 26. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 26, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of the comparative example is provided with a single focus as described above, lateral aberration characteristics that change rapidly are not shown except for the origin of the entrance pupil coordinates. The lateral aberration shows a certain amount of lateral aberration.

Fig. 27 and 28 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 27 is an intensity ratio of laser light rays on an arbitrary straight line including the optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 26. Fig. 28 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 26. As is clear from fig. 27 and 28, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 26 is annular at a position of 223.4mm from the optical surface of the optical element on the optical axis.

Next, a lateral aberration diagram with respect to the entrance pupil coordinate at a position where the distance from the optical surface of the optical element on the optical axis is 227.4mm is shown in fig. 29. Here, Px is an arbitrary entrance pupil coordinate, and Py is an entrance pupil coordinate orthogonal to Px. And ex, ey represents the lateral aberration amount.

In fig. 29, the entrance pupil coordinates Px, Py both show the same lateral aberration characteristic. That is, the lateral aberration is rotationally symmetric with respect to the optical axis. Further, since the optical element of the comparative example is provided with a single focus as described above, lateral aberration characteristics that change rapidly are not shown except for the origin of the entrance pupil coordinates. Further, the farther the distance from the origin of the entrance pupil coordinates is, the slower the change in the lateral aberration value is.

Fig. 30 and 31 show the results of Optical simulation of the energy intensity distribution characteristics at the irradiation points showing such lateral aberration characteristics, using an Optical Design Program of Zemax corporation. Fig. 30 is an intensity ratio of laser light rays on an arbitrary straight line including the optical axis on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 29. Fig. 31 is an intensity ratio of laser rays on a plane perpendicular to the optical axis at an irradiation point showing the lateral aberration characteristic of fig. 29. As is clear from fig. 30 and 31, the energy intensity distribution of the irradiation point showing the lateral aberration characteristic of fig. 29 is annular at a position where the distance from the optical surface of the optical element on the optical axis is 227.4 mm.

As is clear from the above, the energy intensity distribution characteristics of the optical system of the comparative example are gaussian, annular, and annular in order from the optical element side. That is, it is clear that the "first arrangement of the energy intensity distribution" and "second arrangement of the energy intensity distribution" which the optical system of the laser processing apparatus according to the present invention satisfies are not satisfied because the comparative example has a single focus and does not have a plurality of different focuses. Similarly, it is clear that the comparative examples do not satisfy the conditional expressions (1), (2), (3) and (4).

Industrial applicability

The optical system of the laser processing apparatus according to the present invention has an optical surface on which a plurality of different focal points are provided on an optical axis, and thus the energy intensity distribution of the laser beam on a surface perpendicular to the optical axis differs depending on the position on the optical axis, and by setting the different position on the optical axis as the irradiation point of the laser beam on the object, the incident laser beam can be converted into at least three modes of a gaussian shape, a ring shape (double-peak shape), and a shape composed of the ring shape and the center portion of the ring shape, and the energy intensity distribution of the laser beam at the irradiation point of the laser beam on the object can be selected. Therefore, the energy intensity distribution at the flare is suitable for welding or cutting of iron when it is gaussian, for example, for stitch welding or butt welding of copper or hot-dip galvanized steel sheet when it is in a ring shape (bimodal), or for welding or cutting of aluminum material having high light reflectance when it is in a ring shape or a ring shape having a central portion, and the energy intensity distribution at the flare can be appropriately selected according to the object to be processed, and laser processing can be performed. That is, the present invention is suitable for a laser processing apparatus that performs processing such as cutting, drilling, and welding on a workpiece by condensing a laser beam and irradiating the workpiece with the laser beam.

Claims

1. An optical system of a laser processing apparatus for processing a workpiece by irradiating a laser beam thereto, comprising:

an optical surface on which a plurality of different focal points are disposed,

the energy intensity distribution of the laser light on a plane perpendicular to the optical axis differs depending on the position on the optical axis,

by setting different positions on the optical axis as irradiation points of the laser beam of the workpiece, the energy intensity distribution of the laser beam at the irradiation points of the workpiece can be selected.

2. The optical system of the laser processing apparatus according to claim 1,

the energy intensity distribution that differs according to the position on the optical axis is configured such that:

a first arrangement of a ring shape, and a Gaussian shape having a central portion in order from the laser oscillator side toward the workpiece side, an

And a second arrangement in which the second arrangement is one of a gaussian shape, an annular shape, and an annular shape having a central portion in order from the laser oscillator side toward the workpiece side.

3. The optical system of the laser processing apparatus according to claim 2,

in the first configuration of the energy intensity distribution, the following condition is satisfied:

fB1＜fB0＜fB2····(1)，

wherein, fB 0: the energy intensity distribution on the surface of the laser beam perpendicular to the optical axis is the distance between the position on the optical axis and the optical surface closest to the processed object,

fB 1: the energy intensity distribution on the surface perpendicular to the optical axis of the laser beam is a distance from the position on the optical axis of the ring shape having the center part to the optical surface closest to the workpiece,

fB 2: and the energy intensity distribution of the laser beam on the surface vertical to the optical axis is Gaussian-shaped, and the distance from the position on the optical axis to the optical surface closest to the processed object is short.

4. The optical system of the laser processing apparatus according to claim 2,

in the second configuration of the energy intensity distribution, the following condition is satisfied:

fB2＜fB0＜fB1····(2)，

5. The optical system of the laser processing apparatus according to claim 3 or 4,

the following conditions are satisfied:

1mm≤|fB0－fB1|····(3)。

6. the optical system of the laser processing apparatus according to claim 3 or 4,

the following conditions are satisfied:

1mm≤|fB0－fB2|····(4)。

7. the optical system of the laser processing apparatus according to any one of claims 1 to 6,

the optical surface provided with a plurality of different focal points is composed of a plurality of different spherical and/or aspherical surfaces.

8. The optical system of a laser processing apparatus according to claim 7,

the plurality of different spherical and/or aspherical surfaces are arranged in a plurality of different areas of concentric circles on the same optical surface.

9. The optical system of a laser processing apparatus according to claim 7,

the plurality of different spherical and/or aspherical surfaces are regions of different optical surfaces through which respective different light beams pass, and are disposed in a plurality of different concentric-circle-shaped regions.

10. The optical system of the laser processing apparatus according to any one of claims 7 to 9,

at least one optical surface of the plurality of different spherical and/or aspherical surfaces is aspherical.

11. The optical system of a laser processing apparatus according to any one of claims 7 to 9,

the plurality of different spherical and/or aspherical surfaces are two optical surfaces that are different from each other.

12. The optical system of a laser processing apparatus according to any one of claims 7 to 9,

the plurality of different spherical and/or aspherical surfaces are two aspherical surfaces each different from each other.

13. A laser processing device is characterized by comprising:

an optical system of a laser processing apparatus according to any one of claim 1 to claim 12.