JP2003048095A - Laser beam machining head and method for machining using the head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser beam machining head with which a slim and parallel laser beam having an energy density sufficient for machining is formed and the uniformity of the intensity distribution on the cross section of the parallel laser beam is also attained. SOLUTION: A laser beam 4 condensed with a condensing optical system 3 is formed into a parallel laser beam 7 which is a parallel light beam of a long focal length by employing a parallel light optical system 6 composed of a plane-convex lens or the like. The resultant parallel laser beam 7 is made incident on a prism 8 to obtain a parallel laser beam 10 of which the intensity distribution on the cross section is uniformized as emitted light of the laser beam machining head.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing head and a processing method using the same, and is particularly useful when applied to surface modification and build-up welding of a workpiece. Is. 2. Description of the Related Art Conventionally, processing such as surface modification and build-up welding of a steel material using a large energy of a laser beam has been performed. As shown in FIG. 5, for example, laser light oscillated by a YAG laser oscillator is guided to the vicinity of the processing position by the optical fiber 1, and the laser light 2 emitted from the end face of the optical fiber 1 is condensed by the condensing optical system 3. Thus, the condensed laser beam 4 having a small diameter is obtained, and the focused laser beam 4 is irradiated onto the surface of a steel material or the like as the workpiece 5. At this time, in the case of performing processing such as butt welding and fusing, a laser processing head including the condensing optical system 3 so that the processing portion of the workpiece 5 is located at the position of the focal point F of the condensing optical system 3. The height position of is adjusted. This is because predetermined processing is performed at a position where the energy density of the focused laser beam 4 is maximum. However, in the case of surface modification and overlay welding,
Since the energy density may be smaller than this, the position is adjusted so that the processing portion of the workpiece 5 is occupied slightly above the position of the focal point F. In the case of surface modification of the workpiece 5 and overlay welding, the laser processing head is moved in a processing area having a predetermined spread. The strength is not uniform over the entire cross-sectional shape, and generally has a tendency that the central portion is the largest and decreases toward the peripheral portion. Therefore, when machining the part of the next pass adjacent to a certain path at the time of machining, the moving path of the laser machining head is controlled so that the machining parts in both passes slightly overlap at the end. In the prior art as described above, the focused laser beam 4 emitted from the focusing optical system 3 built in the laser processing head is focused on the surface of the workpiece 5. Therefore, when the focal length of the condensing optical system 3 is short, the laser processing head having this condensing optical system interferes with surrounding members, making it difficult to perform predetermined processing in a narrow place. It was. Further, there is a problem that it is difficult to control the lapping margin when the machining of the end portion of the machining site caused by the non-uniformity of the intensity in the cross section of the laser beam is overlapped. On the other hand, a kaleidoscope is used for the purpose of making the intensity uniform within the cross-sectional shape of the focused laser beam 4. This is intended to average the beam intensity by introducing the focused laser beam 4 into a cylindrical member and performing multiple reflection inside thereof. In this case, the more the number of reflections in the kaleidoscope, the more the beam intensity can be averaged.
The energy of the focused laser beam 4 gradually decreases. That is, the homogenization of the intensity distribution of the focused laser beam 4 causes a problem that the intensity is reduced at the same time. In view of the above prior art, the present invention forms a small-diameter parallel laser beam having an energy density sufficient for processing, and can achieve uniform intensity distribution in the cross-section of the parallel laser beam. It is an object of the present invention to provide a machining head and a cutting / welding method using the same. The structure of the present invention which achieves the above object is characterized by the following points. 1) A condensing optical system that condenses and emits incident laser light, and a condensing laser beam condensed and narrowed by the condensing optical system is incident, and this is converted into long-focus parallel light. A first parallel light optical system which is shaped into a parallel laser beam and emitted, and a prism which takes in the parallel laser beam emitted by the parallel light optical system and emits the light with a uniform intensity distribution in its cross-sectional shape; And a second parallel light optical system for forming the laser beam emitted from the prism into a parallel laser beam and emitting the parallel laser beam. Here, the first parallel optical system can be preferably configured with a concave lens. That is, both a plano-concave lens and a biconcave lens can be used. The second parallel optical system can be preferably configured as a concave lens that collimates the diffusing emitted light from the prism again. 2) In the laser processing head described in 1) above, the condensing optical system is composed of a combined lens in which a plurality of lenses are combined so as to remove the aberration of the condensing laser beam emitted from the condensing optical system. 3) In the laser processing head described in 1) above, the prism is formed of a triangular prism. 4) In the laser processing head described in 1) above, the prism is formed of a polygonal pyramid. 5) In the laser processing head described in 1) above, the prism is configured to rotate about a rotation axis perpendicular to the optical axis of the parallel laser beam. 6) The laser processing head described in any one of 1) to 5) above, a state detection sensor disposed at least above the workpiece and detecting the state of the processing portion of the workpiece. A data analysis unit that analyzes an output signal of the state detection sensor and outputs information indicating a state of the machining site; and an output, a waveform, and the like of a laser oscillator that emits a laser beam toward the machining head. Laser control means for controlling based on the above information, and machining head travel control means for controlling the travel speed of a drive source for causing the machining head to travel along the machining site. Here, as the state detection sensor, an imaging unit such as a CCD camera that obtains image information including a lot of information related to the state of the processing site is optimal, but not limited to this, a sound for specifying the state,
It may be light or the like. 7) The laser processing head described in any one of 1) to 5) above, and a state of detecting the state of the build-up welded portion of the processed member disposed above the processed member. A detection sensor, data analysis means for analyzing the output signal of the state detection sensor and outputting information indicating the state of the build-up welding site, and the output, waveform, etc. of the laser oscillator that emits laser light toward the machining head Laser control means for controlling based on the information of the data analysis means, welding material supply means for supplying a welding material such as filler wire to the build-up welding site, and information on the build-up welding site output by the data analysis means Welding material supply control means for controlling the supply speed of the welding material supplied via the welding material supply means, and machining head running for controlling the running speed of the drive source for running the machining head along the welding site Having a row controller. Here, as the state detection sensor, an imaging unit such as a CCD camera that obtains image information including a lot of information related to the state of the processing site is optimal, but not limited to this, a sound, light, or the like that specifies the state is used. There may be. Moreover, as a welding material, you may use any of filler wire, a sheet | seat, and powder conventionally used as a welding material of overlay welding. 8) The focused laser beam focused by condensing the laser beam is shaped into a parallel laser beam, which is a long-focus parallel beam, and the parallel laser beam is incident on a prism to obtain an intensity in its cross-sectional shape. Uniform distribution and irradiating the surface of the workpiece with a parallel laser beam obtained by collimating the emitted light again to perform surface treatment of the workpiece. 9) The focused laser beam condensed by condensing the laser beam is shaped into a parallel laser beam, which is a long-focus parallel beam, and the parallel laser beam is incident on a prism to obtain an intensity in the cross-sectional shape. A parallel laser beam obtained by equalizing the distribution and re-collimating the emitted light is supplied to a welding portion of the workpiece together with a welding material such as a filler wire, and overlay welding of the workpiece is performed. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory view showing a laser processing head according to an embodiment of the present invention. FIG. 1 (a) is an overall view, FIG. 1 (b) is an enlarged view showing an extracted portion A, and FIG. The enlarged view showing the extracted portion B, (d) is a diagram for explaining the intensity distribution of the emitted light of the portion shown in (c). As shown in the figure, the optical fiber 1 guides the laser beam emitted from the laser oscillator to the position of the laser processing head I, and irradiates the laser beam 2 from its tip. The condensing optical system 3 emits a condensed laser beam 4 that condenses and narrows the incident laser light 2. The condensing optical system 3 in this embodiment is composed of a combined lens in which a plurality of lenses are combined so as to remove the aberration of the condensing laser beam 4 emitted from the condensing optical system 3.
Thereby, the parallelism of the parallel laser beam 7 obtained as the emitted light of the first parallel light optical system 6 described later can be favorably maintained. The first parallel light optical system 6 receives the condensed laser beam 4 condensed by the condensing optical system 3 and narrowed down, and forms it into a parallel laser beam 7 which is a long-focus parallel light. Then exit. The first parallel light optical system 6 is shown in FIG.
As shown in FIG. 4, it can be suitably formed with, for example, a plano-concave lens 6a. Of course, a biconcave lens may be used. In the figure, 6b
Is protective glass. The parallel laser beam 7 emitted from the first parallel light optical system 6 is a prism 8, as shown in more detail in FIG. 1B, so that the intensity distribution in the cross-sectional shape is uniform. After removing the direction dependency of the beam 7, the workpiece 5 is irradiated as a homogenized parallel laser beam 10 through the second parallel optical system 9.
That is, as shown in FIG. 1D, the circular parallel laser beam 10 has a homogenized intensity across the entire cross-sectional shape. Here, the prism 8 is a parallel optical system 6.
The parallel laser beam 7 emitted from the laser beam is taken in and the intensity distribution in the cross-sectional shape is made uniform and emitted, and the second parallel light optical system 9 emits the laser beam 11 which is the diffused light emitted from the prism 8 to the parallel laser. The beam 10 is collimated and emitted. The prism 8 in this embodiment is a triangular prism (triangular prism). Therefore, as shown in FIG. 2 (a), the intensity distribution of the parallel laser beam 7 having a diameter φ ₁ having a certain cross-sectional shape is the largest at the center and gradually decreases toward the periphery (the left-right direction in the figure). If it has the characteristic, when it is incident on the prism 8, it is refracted by the refractive index inherent to the prism 8, and as shown by the two-dot chain line in FIG. An inverted intensity distribution can be obtained. Therefore, the intensity distribution of the laser beam 11 which is the emitted light of the prism 8 obtained by adding the intensity distributions is substantially uniform at each point from the central portion to the peripheral portion as shown by a solid line in FIG. It becomes. As a result, the collimated laser beam 10 obtained by collimating the laser beam 11 also has a uniform intensity distribution. Although the prism 8 in this embodiment is a triangular prism, it is of course not limited to this.
In general, it may be a polygonal pyramid such as a triangular pyramid or a quadrangular pyramid. In the case of a triangular pyramid, the incident parallel laser beam 7 is divided into three parts, and in the case of a quadrangular pyramid, it is divided into four parts. Therefore, the number of corners may be appropriately selected in consideration of the desired degree of homogenization. The prism 8 may be configured to rotate around a rotation axis perpendicular to the optical axis of the parallel laser beam 7. In this case, the same effect as when a polygonal pyramid having an arbitrary number of angles is used according to the number of rotations is obtained. By using the laser processing head I according to the embodiment as described above, it is possible to obtain substantially the same parallel laser beams 7 and 10 in the range where the energy density in the cross section of each part in the axial direction is long. The diameters of the parallel laser beams 7 and 10 themselves can be arbitrarily thin, for example, about 5 mmφ. As a result, the workpiece 5
The laser processing head I through the narrow part leading to
However, even at a position far away from the workpiece 5, the workpiece 5 can be irradiated with the parallel laser beam 10 having a large energy sufficient to process the workpiece 5. That is, even if it is a place where other members are scattered around the member 5 to be processed, the desired processing can be performed satisfactorily. Furthermore, the laser processing head I according to this embodiment.
Since the parallel laser beam 10 finally irradiated from the laser beam has a uniform laser intensity density in the entire cross-sectional shape area,
Sufficiently uniform processing can be performed without controlling complicated lapping margins between adjacent passes of the processing site. In addition, since the prism 8 is used for the homogenization, there is no problem of attenuation of the laser beam when a kaleidoscope is used. That is, desired homogenization can be achieved without attenuating the parallel laser beam 7. FIG. 3 is a block diagram showing a laser processing apparatus according to an embodiment of the present invention. Here, the machining head I is as shown in FIG. That is, it is possible to irradiate the workpiece 5 with the long-focused parallel laser beam 10 in which the intensity distribution in the cross-sectional shape is made uniform.
The state detection sensor 21 is disposed above the workpiece 5 and detects the state of the processed part of the workpiece 5. Since the processing in this case is a modification processing that melts the surface of the member 5 to be processed, a CCD camera or the like that can capture an image of the processing portion is suitable. The data analysis device 22 analyzes the output signal of the state detection sensor 21 (a video signal when the state detection sensor 21 is a CCD camera) and outputs information indicating the state of the processing site. The laser control device 23 controls the output, waveform, and the like of the laser oscillator 24 that emits laser light toward the processing head I based on information of the data analysis device 22. That is, based on the information of the data analysis device 22, control is performed so that the laser beam having the optimum intensity is output using the plate thickness of the workpiece 5 and the moving speed of the machining head I as parameters. The optical fiber 25 is for introducing the laser beam irradiated by the laser oscillator 24 into the machining head I. The machining head travel control device 25 controls the drive speed of the drive source 26 that causes the machining head I to travel along the machining line of the workpiece 5 based on the machining site information output by the data analysis device 22.
Here, the machining head travel control device 25 does not need to perform predetermined travel control based on the information on the cutting portion output from the data analysis device 22, and can be a speed control system independent of the data analysis device 22. It is. In this case, the machining head travel control device 25 controls the machining head I to travel at a preset speed. In such a laser processing apparatus, the parallel laser beam 10 is irradiated along the processing line of the member 5 while the processing head I is driven by the drive source 26. At this time, the parallel laser beam 10 is a beam having the same cross-sectional area, that is, equal energy density, over the long range of the workpiece 5 in the longitudinal direction. The beam 10 can be irradiated. Therefore, the processed shape of the workpiece 5,
Good desired processing can be performed regardless of the location. At the same time, the parallel laser beam 10 applied to the processing portion of the member 5 to be processed has a uniform beam intensity in the entire region within the cross-sectional shape.
It is only necessary to control the travel route of the machining head I so that there is no gap between the two passes, and it is not necessary to accurately control the overlap allowance between adjacent passes. For this reason, traveling control is greatly simplified as compared with the conventional case. FIG. 4 is a block diagram showing a laser welding apparatus according to an embodiment of the present invention. The laser welding apparatus according to the present embodiment is a welding apparatus for performing overlay welding, and the machining head I thereof is as shown in FIG. In other words, a long focal parallel laser beam 10 that is intended to make the intensity distribution uniform within the cross-sectional shape is irradiated onto the processing portion of the member 5 to be processed. Moreover, it becomes the structure similar to the laser processing apparatus shown in FIG. 3 except having provided the supply system which supplies the filler wire which is the welding material of overlay welding to the process site | part. Therefore, FIG.
In FIG. 3, the same parts as those in FIG. The filler wire supply device 31 supplies filler wire to the welded part of the workpiece 5. The filler wire supply control device 32 controls the supply speed or the like of the filler wire supplied via the filler wire supply device 31 based on the information on the welded part output from the data analysis device 22. Here, the filler is not limited to filler wire. Needless to say, powdery welding material or sheet-like welding material may be supplied. In such a laser welding apparatus, a parallel laser beam 10 is irradiated along with the filler wire along the weld line of the workpiece 5 while the machining head I is driven by the drive source 26. At this time, since the parallel laser beam 10 similar to the processing apparatus shown in FIG.
The parallel laser beam 10 can be irradiated from a distance through the narrow portion. Therefore, good desired processing can be performed regardless of the processing shape, location, and the like of the workpiece 5. At the same time, the parallel laser beam 10 irradiated to the processing portion of the member 5 to be processed has a uniform beam intensity in the entire region within the cross-sectional shape.
Similar to the machining apparatus shown in FIG. 3, it is only necessary to control the travel route of the machining head I so that there is no gap between both paths. As specifically described in conjunction with the above embodiments, the invention described in claim 1 is a condensing optical system that condenses and emits incident laser light, and this condensing system. A collimated laser beam that is condensed and narrowed by an optical optical system is incident, shaped into a parallel laser beam, which is a long-focus parallel light, and emitted, and this parallel light optics A parallel laser beam which is emitted from the system, which is emitted with a uniform intensity distribution in its cross-sectional shape and emitted, and a second parallel light optical which emits the laser light emitted from this prism into a parallel laser beam. Therefore, it is possible to obtain a parallel laser beam having almost the same small diameter within a long range of energy density in the cross section of each part in the axial direction, and the laser processing head can be removed from the workpiece through the narrow part. Even in a distant position, the member to be processed can be irradiated with a parallel laser beam having a large energy sufficient to process the member to be processed. That is, the desired processing can be performed satisfactorily even in a place where other members are scattered around the workpiece. Furthermore, since the intensity of the parallel laser beam finally irradiated from the laser processing head can be made uniform, it is sufficiently homogeneous without controlling complicated lap margins between adjacent passes of the processing site. Processing can be performed. In addition, since the prism is used for this homogenization, the desired homogenization can be achieved without attenuating the parallel laser beam. The invention described in claim 2 is the laser processing head according to claim 1, wherein the condensing optical system has a plurality of lenses so as to remove the aberration of the condensing laser beam emitted from the condensing optical system. Therefore, a high-quality parallel laser beam having a high degree of parallelism can be obtained, and the operation and effect of the invention described in [Claim 1] can be made sure and remarkable. The invention described in [Claim 3] is the laser processing head according to [Claim 1]. Since the prism is formed of a triangular prism, the intensity of the parallel laser beam in the cross-sectional shape is homogenized. This parallel laser beam can be realized without being attenuated, and the operations and effects described in [Claim 1] can be reliably realized with the simplest member. In the invention described in [Claim 4], in the laser processing head described in [Claim 1], since the prism is formed in a polygonal pyramid, the intensity of the parallel laser beam in the cross-sectional shape is homogenized. The parallel laser beam can be realized without attenuation, the degree of homogenization can be arbitrarily selected, and the operations and effects described in [Claim 1] can be realized satisfactorily and reliably. According to a fifth aspect of the present invention, in the laser processing head according to the first aspect, the prism is configured to rotate about a rotation axis perpendicular to the optical axis of the parallel laser beam. Therefore, it is possible to achieve the same homogenization as when the polygonal cone prism is used. The invention described in [Claim 6] is arranged at least above the laser processing head according to any one of [Claim 1] to [Claim 5] and the workpiece.
A state detection sensor for detecting the state of the processing part of the workpiece, a data analysis unit for analyzing the output signal of the state detection sensor and outputting information indicating the state of the processing part, and a laser beam toward the processing head The output of the laser oscillator to emit,
Since it has a laser control means for controlling the waveform and the like based on information of the data analysis means, and a machining head travel control means for controlling the traveling speed of a drive source that causes the machining head to travel along the machining site, the drive The parallel laser beam can be irradiated along the processing line of the workpiece while the processing head is driven by the source. Since the parallel laser beam at this time is a beam having the same cross-sectional area, that is, the same energy density, in the longitudinal direction of the workpiece, the parallel laser beam is transmitted from a distance through a narrow portion. Can be irradiated. Therefore, good desired processing can be performed regardless of the processing shape, location, etc. of the workpiece. At the same time, the parallel laser beam applied to the processing part of the workpiece has a uniform beam intensity in the entire region within the cross-sectional shape, so that there is no gap between both paths. It is only necessary to control the travel route, and it is not necessary to accurately control the overlap between adjacent paths. For this reason, traveling control is greatly simplified as compared with the conventional case. According to a seventh aspect of the present invention, there is provided a laser processing head according to any one of the first to fifth aspects of the present invention, and a member to be processed above the workpiece. A state detection sensor for detecting the state of the build-up welding part of the workpiece, data analysis means for analyzing the output signal of the state detection sensor and outputting information indicating the state of the build-up welding part, and toward the machining head Laser control means for controlling the output, waveform, etc. of the laser oscillator that emits laser light based on the information of the data analysis means, welding material supply means for supplying a welding material such as filler wire to the overlay welding site, and Welding material supply control means for controlling the supply speed of the welding material supplied via the welding material supply means based on the information of the buildup welding part output by the data analysis means, and the processing head is caused to travel along the welding part. Driving Because it has a machining head travel control device for controlling the traveling speed of the source, can be irradiated in the same manner as devices described, the parallel laser beams from a distance through the narrow portion to [claim 6]. Therefore, favorable desired overlay welding can be performed regardless of the processing shape, location, etc. of the workpiece. At the same time, the parallel laser beam applied to the welded part of the workpiece has a uniform beam intensity in the entire region within the cross-sectional shape thereof, and therefore, similar to the apparatus described in [Claim 6]. Thus, it is not necessary to accurately control the overlap margin between adjacent paths, and there is an effect that traveling control is greatly simplified as compared with the prior art. In the invention described in claim 8, the focused laser beam condensed by condensing the laser beam is formed into a parallel laser beam which is a long-focus parallel beam, and the parallel laser beam is further converted into a prism. The incident surface is made uniform in intensity distribution in its cross-sectional shape, and the surface of the member to be processed is irradiated with a parallel laser beam obtained by re-collimating the emitted light. The effect similar to that of the invention described in claim 6 is obtained. According to the ninth aspect of the present invention, the focused laser beam condensed by condensing the laser beam is shaped into a parallel laser beam which is a long-focus parallel beam, and this parallel laser beam is further converted into a prism. Incident and uniformizing the intensity distribution in the cross-sectional shape, and supplying a parallel laser beam obtained by re-collimating the emitted light to the welded part of the workpiece together with a welding material such as a filler wire. Since overlay welding is performed, the same effect as that of the invention described in [Claim 7] is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view showing a laser processing head according to an embodiment of the present invention, in which (a) is an overall view, (b) is an enlarged view showing an extracted portion A; (C) is an enlarged view showing the B portion extracted, and (d) is a diagram for explaining the intensity distribution of the emitted light in the portion shown in (c). 2 is a characteristic diagram showing an intensity distribution (a) of a parallel laser beam before entering the prism of the laser processing head shown in FIG. 1 and an intensity distribution (b) of the parallel laser beam after emission. FIG. 3 is a block diagram showing a laser processing apparatus according to an embodiment of the present invention. FIG. 4 is a block diagram showing a laser welding apparatus according to an embodiment of the present invention. FIG. 5 is an explanatory view showing a laser processing head according to a conventional technique. DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Laser light 3 Condensing optical system 4 Condensing laser beam 5 Work piece 6 First parallel light optical system 7 Parallel laser beam 8 Prism 9 Second parallel light optical system 10 Parallel laser Beam 21 state detection sensor

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Claims (1)

[Claims] [Claim 1] A condensing optical system that condenses and emits incident laser light, and a condensing laser beam condensed and narrowed by the condensing optical system is incident, A first parallel light optical system that is shaped into a parallel laser beam, which is a long-focused parallel light, and the parallel laser beam emitted from the parallel light optical system, and the intensity distribution in the cross-sectional shape is uniform. A laser processing head comprising: a prism that emits light after being converted; and a second parallel light optical system that forms and emits laser light emitted from the prism into a parallel laser beam. 2. The laser processing head according to claim 1, wherein the condensing optical system is constituted by a combined lens in which a plurality of lenses are combined so as to remove the aberration of the condensing laser beam emitted from the condensing optical system. Laser processing head characterized by 3. The laser processing head according to claim 1, wherein the prism is formed of a triangular prism. 4. The laser processing head according to claim 1, wherein the prism is formed of a polygonal pyramid. 5. The laser processing head according to claim 1, wherein the prism is configured to rotate about a rotation axis perpendicular to the optical axis of the parallel laser beam. . 6. The laser processing head according to any one of [Claim 1] to [Claim 5] and at least an upper part of a workpiece to detect a state of a machining portion of the workpiece. A state detection sensor that analyzes the output signal of the state detection sensor and outputs information indicating the state of the processing site, and the output, waveform, and the like of the laser oscillator that emits laser light toward the processing head A laser control unit that controls the data based on the information of the data analysis unit; and a processing head travel control unit that controls a travel speed of a drive source that travels the processing head along the processing site. Processing equipment. 7. The laser processing head according to claim 1, wherein the laser processing head is disposed above the workpiece, and the welded portion of the workpiece is welded. A state detection sensor for detecting a state, data analysis means for analyzing the output signal of the state detection sensor and outputting information representing the state of the build-up welding site, and a laser oscillator for emitting laser light toward the machining head Laser control means for controlling output, waveform, etc. based on information of the data analysis means, welding material supply means for supplying welding material such as filler wire to the overlay welding site, and overlay welding output from the data analysis means Welding material supply control means for controlling the supply speed and the like of the welding material supplied via the welding material supply means based on the part information; and control of the traveling speed and the like of the drive source for causing the machining head to travel along the welding part. A laser welding apparatus comprising: a processing head travel control means. 8. A focused laser beam condensed by condensing a laser beam is shaped into a parallel laser beam which is a parallel light having a long focal point, and the parallel laser beam is incident on a prism so as to have an intensity in its cross-sectional shape. A laser processing method characterized in that the surface of a member to be processed is subjected to surface treatment by irradiating the surface of the member to be processed with a parallel laser beam obtained by making the distribution uniform and parallelizing the emitted light again. 9. A focused laser beam condensed by condensing a laser beam is shaped into a parallel laser beam, which is a long-focus parallel beam, and the parallel laser beam is incident on a prism to obtain an intensity in its cross-sectional shape. The distribution beam is made uniform, and a parallel laser beam obtained by re-parallelizing the emitted light is supplied to a welded portion of the workpiece together with a welding material such as a filler wire, and overlay welding of the workpiece is performed. Laser welding method.