The present disclosure relates to a laser processing apparatus and a coupler.
A tapered fiber bundle (TFB) is conventionally known as a coupler that optically couples a plurality of input optical fibers to one output optical fiber (for example, U.S. Pat. No. 5,864,644).
It would be beneficial if a laser processing apparatus has a TFB that combines laser light from a plurality of light sources to output laser light with a more suitable beam shape.
There is a need for a laser processing apparatus and a coupler that may output laser light with a more suitable beam shape.
According to one aspect of the present disclosure, there is provided a laser processing apparatus including: at least two first input optical fibers that are multi-mode optical fibers; an output optical fiber that is a multi-mode optical fiber; a coupler configured to optically couple a first end of a bundle portion in which the at least two first input optical fibers are bundled so as to be aligned in a circumferential direction, to a second end of the output optical fiber, the second end facing the first end; at least one first light source optically connected to one of the first input optical fibers to output laser light, the at least one first light source being a multi-mode light source; and an optical head optically connected to the output optical fiber to output laser light output by the first light source and passing through the first input optical fiber and the output optical fiber, wherein in a cross section intersecting an axial direction of the first end, a cladding of the first input optical fiber has an extending portion extending linearly in a direction intersecting the axial direction between cores of two first input optical fibers adjacent in a circumferential direction.
According to another aspect of the present disclosure, there is provided a laser processing apparatus including: at least two first input optical fibers that are multi-mode optical fibers; an output optical fiber that is a multi-mode optical fiber; a coupler configured to optically couple a first end of a bundle portion in which the at least two first input optical fibers are bundled so as to be aligned in a circumferential direction, to a second end of the output optical fiber, the second end facing the first end; at least one first light source optically connected to one of the first input optical fibers to output laser light, the at least one first light source being a multi-mode light source; and an optical head optically connected to the output optical fiber to output laser light output by the first light source and passing through the first input optical fiber and the output optical fiber, wherein in a cross section intersecting an axial direction of the first end, a boundary between a core and a cladding of the first input optical fiber in a circumferential direction has a first section and a second section with a radius of curvature smaller than a radius of curvature of the first section.
According to still another aspect of the present disclosure, there is provided a coupler including: at least two first input optical fibers that are multi-mode optical fibers; and an output optical fiber that is a multi-mode optical fiber, the coupler being configured to optically couple a first end of a bundle portion in which the at least two first input optical fibers are bundled so as to be aligned in a circumferential direction, to a second end of the output optical fiber, the second end facing the first end, wherein in a cross section intersecting an axial direction of the first end, a cladding of the first input optical fiber has an extending portion extending linearly in a direction intersecting the axial direction between cores of two first input optical fibers adjacent in a circumferential direction.
In the following, exemplary embodiments and modifications of the present disclosure will be disclosed. The configurations of the embodiments and modifications described below, and the actions and results (effects) brought about by such configurations are examples. The present disclosure may also be implemented by configurations other than those disclosed in the following embodiments and modifications. The present disclosure may provide at least one of various effects (including derivative effects) obtained by the configurations.
A plurality of embodiments described below have similar configurations. The configurations of the embodiments therefore achieve similar actions and effects based on the similar configurations. In the following, those similar configurations are denoted by similar signs and an overlapping description may be omitted.
In the present description, ordinal numbers are allocated for convenience in order to distinguish parts, sections, and the like and not intended to indicate priority or order.
In the drawings, the arrows X, Y, and Z represent the X, Y, and Z directions, respectively. The X, Y, and Z directions intersect each other and are orthogonal to each other.
In the laser processing apparatus 100, laser beams emitted from the light source devices 111 and 112 are combined, and the combined laser light L is emitted from the optical head 120. The optical head 120 performs laser processing of an object W, such as welding or cutting, by irradiating a surface Wa of the object W with the laser light L.
The laser processing apparatus 100 may include a relative movement mechanism (not illustrated) that moves the optical head 120 and the object W relative to each other in a direction intersecting the optical axis of the laser light L (irradiation direction) so that the laser light L is swept over the surface Wa. The laser processing apparatus 100 may include a galvanometer scanner (not illustrated) that changes the radiation direction of the laser light L from the optical head 120 so that the laser light L is swept over the surface Wa. In this case, the galvanometer scanner is provided in the optical head 120. The laser processing apparatus 100 may include both of the relative movement mechanism and the galvanometer scanner.
The light source devices 111 and 112 are each a laser device that outputs laser light.
The light source devices 111 are multi-mode light sources. The light source devices 111 each include, for example, a direct diode laser as a light source and output laser light with a wavelength of 400 [nm] or more and 500 [nm] or less. The light source devices 111 are an example of a first light source. In the present embodiment, the light source devices 111 output laser light with the same wavelength. However, the present embodiment is not limited to this, and the light source devices 111 may output laser light with different wavelengths.
The input optical fibers 11 are optically connected to the light source devices 111. Each of the input optical fibers 11 transmits laser light output by the corresponding light source device 111. The input optical fibers 11 are multi-mode optical fibers.
The coupler 10 optically couples the input optical fibers 11 and one output optical fiber 12. The output optical fiber 12 may also be referred to as delivery optical fiber. The output optical fiber 12 is a multi-mode optical fiber.
The multi-mode optical fiber is an optical fiber that satisfies the following equations for the normalized frequency V.
V>V1=2.405
V=k*a*√(n12−n22)=2π/λ*a*√(n12−n22)
k=ω/c
where ω is the angular frequency, a (>0) is the core radius, n1 is the refractive index of the core (n1>n2), n2 (>0) is the refractive index of the cladding, and λ (>0) is the wavelength.
The output optical fiber 12 is optically connected to the optical head 120. The output optical fiber 12 transmits laser light output by the light source device 111 and passing through the input optical fibers 11 and the coupler 10 to the optical head 120.
The light source device 112 is, for example, a single-mode light source. The light source device 112 includes, for example, a fiber laser as a light source and outputs laser light with a wavelength of 800 [nm] or more and 1200 [nm] or less. The light source device 112 is an example of a third light source.
The delivery optical fiber 130 transmits laser light output by the light source device 112 to the optical head 120. The delivery optical fiber 130 is a single-mode optical fiber.
The controller 200 is a circuit operating as a computer and outputs actuation control signals to switch actuation and deactivation of the light source devices 111 and 112. In other words, the actuation of the light source devices 111 and 112 is controlled by the controller 200.
The optical head 120 is an optical device for emitting laser light input from the light source devices 111 and 112 toward the object W. The optical head 120 includes collimating lenses 121 (121-1, 121-2), a condenser lens 122, a mirror 123, and a filter 124. The collimating lenses 121, the condenser lens 122, the mirror 123, and the filter 124 may also be referred to as optical components. The optical components of the optical head 120 may be changed according to the layout of the output optical fiber 12 and the delivery optical fiber 130, the wavelength of laser light, and the like.
The collimating lenses 121 (121-1, 121-2) each collimate laser light input from the output optical fiber 12 or the delivery optical fiber 130. The collimated laser light becomes collimated light.
The mirror 123 reflects laser light from the collimating lens 121-1 and directs the reflected laser light to the filter 124.
The filter 124 allows laser light from the mirror 123 to pass through and reflects laser light from the collimating lens 121-2 toward the condenser lens 122. The filter 124 is, for example, a dichroic mirror that passes light with a wavelength longer than a threshold wavelength.
The condenser lens 122 gathers laser light from the filter 124 as collimated light and directs the gathered laser light as laser light L (output light) to the surface Wa of the object W. When the optical head 120 has a galvanometer scanner, the galvanometer scanner is provided, for example, between the filter 124 and the condenser lens 122.
The absorption rate of light for metal materials will now be described.
Although the characteristics vary with materials, it may be understood that the absorption rate of energy is higher when blue or green laser light is used than when common infrared (IR) laser light is used, for the metals listed in
When an object W with a relatively low absorption rate for the wavelength used is irradiated with laser light, most of optical energy is reflected and does not affect the object W as heat. It is therefore necessary to apply a relatively high power to obtain a melted section with a sufficient depth. In this case, energy is rapidly applied at the beam center to cause sublimation, resulting in a keyhole.
On the other hand, when an object W with a relatively high absorption rate for the wavelength used is irradiated with laser light, much of the applied energy is absorbed by the object W and converted into thermal energy. In this process, when laser light with a low power density is applied, thermal conduction-type melting results.
In the present embodiment, as described above, the light source device 111 outputs laser light in a wavelength band (for example, 400 [nm] or more and 500 [nm] or less) that has a relatively high absorption rate for copper, gold, and the like and produces thermal conduction-type melting. On the other hand, the light source device 112 outputs laser light in a wavelength band (for example, 800 [nm] or more and 1200 [nm] or less) that has a relatively low absorption rate for copper, gold, and the like and produces keyhole-type melting. The optical head 120 then directs laser light L including laser light in both of these wavelength bands toward the object W. This configuration provides the advantages of radiation of laser light in both wavelength bands.
In the present embodiment, as an example, the input optical fibers 11 include one input optical fiber 11-2 and six input optical fibers 11-1. In other words, the coupler 10 has a total of seven input optical fibers 11. Only two of the six input optical fibers 11-1 are illustrated in
The input optical fibers 11 (11-1, 11-2) each have a core 11a, a cladding 11b formed around the outer periphery of the core 11a, and a coating 11c formed around the outer periphery of the cladding 11b. The core 11a and the cladding 11b may each be made of, for example, glass such as quartz glass. The coating 11c may be made of, for example, a synthetic resin material. The coating 11c is removed at the end in the Z direction. The input optical fiber 11 is, for example, a multi-mode optical fiber with NA of 0.15 to 0.22.
The output optical fiber 12 is a multi-mode optical fiber having a core 12a and a cladding 12b surrounding the periphery of the core 12a. The core 12a and the cladding 12b may be made of, for example, glass such as quartz glass. The output optical fiber 12 has a coating formed around the outer periphery of the cladding 12b. The coating may be made of, for example, a synthetic resin material. The output optical fiber 12 is, for example, a multi-mode optical fiber with NA equal to or greater than that of the input optical fibers 11.
At the end in the Z direction of the input optical fibers 11, the portions having the coating 11c removed are bundled to form an integrated portion 13. The integrated portion 13 has a tapered portion 13a and the end 13b adjacent to the tapered portion 13a in the Z direction. In the integrated portion 13, at least two input optical fibers 11 are bundled. The integrated portion 13 and the coupler 10 having the integrated portion 13 may also be referred to as TFB. The integrated portion 13 is an example of a bundle portion.
In the tapered portion 13a, each core 11a gradually becomes thinner toward the Z direction, and the distance between the cores 11a gradually decreases.
The end 13b extends in the Z direction while keeping the shape of the end in the Z direction of the tapered portion 13a. The end 13b extending in the Z direction while keeping the shape may be eliminated. In this case, the end in the Z direction of the tapered portion 13a is the integrated portion 13, that is, the end of the input optical fibers 11.
Such an integrated portion 13 is formed by drawing the bundled input optical fibers 11 in the axial direction of the optical axis Ax1 under heating. In this case, an oxyhydrogen burner is used for heating. With the use of an oxyhydrogen burner, the core 11a contains OH groups in the integrated portion 13. Since the OH groups restore defects in the Si—O network that constitutes quartz glass, Rayleigh scattering loss due to the defects in quartz glass may be reduced. From this viewpoint, it is preferable that the amount of OH groups in the core 11a is 10 [ppm] or more and 2000 [ppm] or less.
As illustrated in
In a configuration in which the input optical fibers 11-1 are aligned around the periphery of the input optical fiber 11-2 as in the present embodiment, when the circularity of the cross-sectional shape of each of the cores 11a of the input optical fibers 11 is C (=4·π·S/L2, S: area, L: perimeter, C=1 in a perfect circle), and the degree of deviation from perfect circle is Dc (=|1-C|, the absolute value of 1-C), the degree of deviation from perfect circle Dc of the core 11a of the input optical fiber 11-1 is larger than the degree of deviation from pure circle Dc of the core 11a of the input optical fiber 11-2.
The cross-sectional shape as illustrated in
The cladding 11b of each input optical fiber 11 forms a wall surrounding the core 11a. In two input optical fibers 11 adjacent to each other, the claddings 11b of the two input optical fibers 11 are at least partially welded and integrated. In the example in
The cladding 11b has an inner wall 11b1, an outer wall 11b2, and a plurality of partition walls 11b3. At the end 13b, these inner wall 11b1, outer wall 11b2, and partition walls 11b3 extend in the axial direction of the optical axis Ax1.
The inner wall 11b1 is located radially inside the cores 11a of the input optical fibers 11-1 aligned in the circumferential direction around the optical axis Ax1 and has a tubular shape. The inner wall 11b1 surrounds the periphery of the core 11a of the input optical fiber 11-2 and is interposed between the core 11a of the input optical fiber 11-2 and the cores 11a of the input optical fibers 11-1. The inner wall 11b1 includes the cladding 11b of the input optical fiber 11-2 and portions of the claddings 11b of the input optical fibers 11-1.
The outer wall 11b2 is located radially outside the cores 11a of the input optical fibers 11-1 and surrounds the periphery of the cores 11a of the input optical fibers 11-1. The outer wall 11b2 has a tubular shape. The outer wall 11b2 includes portions of the claddings 11b of the input optical fibers 11-1.
The partition walls 11b3 are each interposed between the cores 11a of two input optical fibers 11-1 adjacent to each other in the circumferential direction around the optical axis Ax1 and have a substantially plate-like shape. In a cross section in
In a cross section in
The inventors of the present disclosure have conducted elaborate studies and found that optical coupling of the input optical fibers 11 and one output optical fiber 12 having a cross-sectional shape as illustrated in
In this description, the flatness F (%) of the intensity distribution of laser light is defined by the following equation (1).
F=Pmax/Pmin×100 (1)
Here, Pmax is the maximum value of intensity of laser light in a circular target range with a diameter kD about the optical axis Ax2 in a cross section of the core 12a, Pmin is the minimum value of intensity of laser light in the target range, D is the beam diameter at the focus position, and k is a coefficient that defines the target range for calculation of the flatness F and is a number greater than 0 and smaller than 1. The flatness F is a value of 100 or more, and the closer to 100 the value of the flatness F is, the flatter the intensity distribution is.
As described above, the optical head 120 directs laser light output from the light source device 111 and laser light output from the light source device 112 toward the surface Wa of the object W.
The inventors of the present disclosure have conducted elaborate studies and found that, in laser processing in which the first laser light from the light source device 111 and the second laser light from the light source device 112 are combined and output toward the surface Wa of the object W in the optical head 120 as in the present embodiment, the flatness F of the first laser light is preferably 120 or less and more preferably 110 or less with the coefficient k=0.7, in terms of the quality of laser processing.
The inventors have conducted elaborate studies and also found the following (1) to (6).
The reason for the phenomena observed in (1) to (6) above is presumably that the light source device 111 is a multi-mode light source and the input optical fibers 11 and the output optical fiber 12 are multi-mode optical fibers, and in addition, (a) the core 11a of the input optical fiber 11-1 has a non-circular cross section as illustrated in
For (b), it is preferable that the input optical fiber 11-1 has a relatively thin cladding 11b, as described above. From this viewpoint, the ratio Db/Da of the diameter Db of the cladding to the diameter Da of the core 11a (see
Based on the finding in (2) above, in the laser processing apparatus 100, the intensity of the first laser light may be changed while maintaining a state in which the flatness F is 120 or less with the coefficient k=0.7 for the first laser light, by changing (switching) the number of light source devices 111 that output laser light among the light source devices 111, with an actuation control signal output by the controller 200. With this control, laser processing with higher quality may be performed under more appropriate conditions according to the material of the object W, the surface roughness of the surface Wa, the thickness of the object W, and the like.
The light source device 111 optically connected to the input optical fiber 11-2 located at the center in the integrated portion 13 may output laser light with a wavelength different from that of the light source device 111 optically connected to the input optical fiber 11-1 located on the periphery in the integrated portion 13. The light source device 111 optically connected to the input optical fiber 11-2 is an example of a second light source, and the end 13b of the input optical fiber 11-2 is an example of a third end. The light source device 111 optically connected to the input optical fiber 11-1 may output laser light (first laser light) with a wavelength of 400 [nm] or more and 500 [nm] or less, and the light source device 111 optically connected to the input optical fiber 11-2 may output laser light (second laser light) with a wavelength of 800 [nm] or more and 1200 [nm] or less.
As explained above, in the present embodiment, the cross-sectional shape of each of the cores 11a of the input optical fibers 11-1 has a non-circular shape at the end 13b (first end) of the input optical fibers 11-1 in the coupler 10 in which at least two input optical fibers 11-1 (first input optical fiber) and the output optical fiber 12 are optically coupled.
In the present embodiment, in a cross section intersecting the axial direction of the optical axis Ax1 of the end 13b, the cladding 11b of the input optical fiber 11-1 has the partition wall 11b3 (extending portion) between the cores 11a of two input optical fibers 11-1 adjacent in the circumferential direction around the optical axis Ax1. The partition wall 11b3 extends linearly in a direction intersecting the axial direction.
In the present embodiment, in a cross section intersecting the axial direction of the optical axis Ax1 of the end 13b, the boundary 11d between the core 11a and the cladding 11b of the input optical fiber 11-1 in the circumferential direction around the optical axis Ax1 has the first section 11d1 and the second sections 11d21 and 11d22 with a radius of curvature smaller than that of the first section 11d1.
In the present embodiment, the ratio of the outer diameter of the cladding to the outer diameter of the core in the unstretched segment 11e of the input optical fiber 11-1 that is outside the integrated portion 13 (bundle portion) in a free state with no external force applied is 1.04 or more and 1.25 or less.
In such a configuration, the intensity distribution of laser light on a center line passing through the optical axis Ax2 in a cross section orthogonal to the optical axis Ax2 of the output optical fiber 12 is not unimodal but flat-top or multi-modal. In the intensity distribution, the flatness F with the coefficient k=0.7 is 120 or less. According to the present embodiment, the laser processing apparatus 100 that may provide a suitable beam shape of laser light L may be implemented by a simpler or more compact configuration.
As in the present embodiment, the claddings 11b of the input optical fibers 11 adjacent to each other may be partially welded to each other, and the input optical fibers 11 may be integrated at the end 13b. In this case, for example, it is advantageous that the coupler 10 may be made in a more compact configuration as a member for bundling the input optical fibers 11 is unnecessary, and the manufacturing effort and costs may be reduced as the number of components may be reduced.
The coupler 10 in the present embodiment may be applied to a coupler 10 that couples laser light from the light source devices 111 that output first laser light, in the laser processing apparatus 100 that irradiates a surface Wa of an object W with laser light L in which first laser light with a wavelength of 400 [nm] or more and 500 [nm] or less and second laser light with a wavelength of 800 [nm] or more and 1200 [nm] or less are combined. In this case, the intensity distribution of the first laser light in a cross section intersecting the optical axis of the laser light L may be flat-top or multi-modal rather than being unimodal, and consequently, it is advantageous that laser processing with higher quality may be performed.
The end 13b in the second embodiment has four input optical fibers 11-1 aligned in the circumferential direction around the optical axis Ax1, and the end 13b in the third embodiment has three input optical fibers 11-1 aligned in the circumferential direction around the optical axis Ax1. In the second and third embodiments, the end 13b does not have the input optical fiber 11-2.
Even in the second and third embodiments, the cross-sectional shapes of the cores 11a of the input optical fibers 11-1 each have a non-circular and substantially sector-like shape, in the same manner as in the foregoing first embodiment. However, the end 13b has a gap g between the input optical fibers 11-1 at the center of the cross section.
Even in the second and third embodiments, in a cross section intersecting the axial direction of the optical axis Ax1 of the end 13b, the cladding 11b of the input optical fiber 11-1 has the partition wall 11b3 (extending portion) between the cores 11a of two input optical fibers 11-1 adjacent in the circumferential direction around the optical axis Ax1, in the same manner as in the foregoing first embodiment. The partition wall 11b3 extends linearly in a direction intersecting the axial direction.
Even in the second and third embodiments, in a cross section intersecting the axial direction of the optical axis Ax1 of the end 13b, the boundary 11d between the core 11a and the cladding 11b of the input optical fiber 11-1 in the circumferential direction around the optical axis Ax1 has the first section 11d1 and the second sections 11d21 and 11d22 with a radius of curvature smaller than that of the first section 11d1, in the same manner as in the first embodiment.
Even in the second and third embodiments, the ratio of the outer diameter of the cladding to the outer diameter of the core in the unstretched segment 11e (not illustrated in
Even in these second and third embodiments, the intensity distribution of laser light on a center line passing through the optical axis Ax2 in a cross section orthogonal to the optical axis Ax2 of the output optical fiber 12 is not unimodal but flat-top or multi-modal. In the intensity distribution, the flatness F with the coefficient k=0.7 is 120 or less. The laser processing apparatus 100 to which one of the coupler 10A in the second embodiment and the coupler 10B in the third embodiment is applied instead of the coupler 10 in the first embodiment may have an effect similar to that of the foregoing first embodiment.
The present disclosure may be used for laser processing apparatuses and couplers.
According to the present disclosure, for example, a laser processing apparatus and a coupler that may output laser light with a more suitable beam shape may be obtained.
Although the embodiments and modifications of the present disclosure have been described above, the above embodiments and modifications are described only by way of example and not intended to limit the scope of the disclosure. The above embodiments and modifications may be carried out in various other forms, and various omissions, substitutions, combinations, and changes may be made without departing from the spirit of the disclosure. In addition, the configuration, shape, and other specifications (structure, type, direction, model, size, length, width, thickness, height, number, arrangement, position, material, and the like) may be changed as appropriate.
Number | Date | Country | Kind |
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2021-020924 | Feb 2021 | JP | national |
This application is a continuation of International Application No. PCT/JP2022/005340, filed on Feb. 10, 2022 which claims the benefit of priority of the prior Japanese Patent Application No. 2021-020924, filed on Feb. 12, 2021, the entire contents of which are incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/JP2022/005340 | Feb 2022 | US |
Child | 18363030 | US |