JP2025022340A - Laser oscillator and laser processing device equipped with same - Google Patents

Abstract

To provide a laser oscillator which enables fast and highly accurate monitoring of the output of first laser beam for use in laser beam machining.SOLUTION: A laser oscillator 80 emitting laser beam LB0 comprise a plurality of laser modules 10, a focusing optical unit 40, and an output monitoring mechanism 30A. The output monitoring mechanism 30A includes a partial reflection mirror 24, a mixing rod 35, and a photodetector 36. The partial reflection mirror 24 splits the laser beam LB0 into a first laser beam LB1 and a second laser beam LB2. The mixing rod 35 has an incident end face 35a and an exit end face 35b, and guides the second laser beam LB2 incident from the incident end face 35a to the exit end face 35b while totally reflecting the second laser beam LB2 inside. The photodetector 36 outputs an output signal on the basis of the amount of the second laser beam LB2 emitted from the exit end face 35b.SELECTED DRAWING: Figure 2

Description

This disclosure relates to a laser oscillator and a laser processing device equipped with the same.

Laser light output is one of the important processing parameters in laser processing using a laser oscillator, and the laser oscillator is required to appropriately control the laser light output. On the other hand, since it is difficult to directly monitor the laser light output during laser processing, various methods for indirectly monitoring the laser light output have been proposed.

For example, as shown in Patent Document 1, a configuration is described in which a portion of the processing laser light is branched off and the branched laser light is made incident on a power meter. The power meter generates a voltage according to the power of the incident laser light, and the power of the processing laser light is calculated and evaluated based on this voltage. This power meter is used in a state where it is cooled by a water-cooled cooler via a heat conductive member.

Special Publication No. 2020-046390

However, when a portion of the original laser light is branched off and monitored by a photodetector as disclosed in Patent Document 1, if the optical axis of the incident laser light deviates from a set value, the magnitude of the output signal from the photodetector may change due to the optical axis deviation. Similarly, if the beam profile of the laser light fluctuates with time or the power level of the laser light, the magnitude of the output signal from the photodetector may fluctuate due to the fluctuation.

In order to accurately calculate the output of the original laser light based on the amount of incident laser light, regardless of optical axis misalignment or fluctuations in the beam profile, it is necessary to reliably receive the entire amount of incident laser light with the photodetector.

In addition, when a photoelectric conversion element such as a photodiode is used as a photodetector, if the sensitivity within the light receiving surface is not constant, the magnitude of the output signal from the photodetector may fluctuate even if the entire amount of incident laser light is received.

The present disclosure has been made in consideration of these points, and its purpose is to provide a laser oscillator equipped with an output monitor mechanism capable of evaluating the power of incident laser light at high speed and with high accuracy, and a laser processing device equipped with the same.

To achieve the above object, the laser oscillator according to the present disclosure includes at least a laser light source that emits laser light, a focusing optical unit that focuses a first laser light, which is a part of the laser light, and outputs it to the outside, and an output monitor mechanism that monitors the output of the first laser light, and the output monitor mechanism includes at least a light branching element that branches the laser light into the first laser light and a second laser light traveling in a direction different from that of the first laser light, a light homogenizing element having an entrance end face and an exit end face, a focusing optical element that focuses the second laser light toward the entrance end face, and a photodetector that has a light receiving surface that receives the second laser light and outputs an output signal based on the amount of light of the received second laser light, and the photodetector is arranged so that the light receiving surface is in contact with the exit end face or faces the exit end face at a predetermined interval, and further includes a control unit that calculates the output of the first laser light based on the output signal of the photodetector.

The laser processing device according to the present disclosure is characterized by having at least the laser oscillator and a laser head that receives the first laser light and irradiates it toward a workpiece.

According to the present disclosure, the output of the first laser light can be monitored at high speed and with high accuracy. Furthermore, even if the optical axis of the laser light is misaligned or the beam profile fluctuates, the output of the first laser light can be accurately monitored without being affected by these.

1 is a schematic configuration diagram of a laser processing device according to a first embodiment. FIG. 2 is a schematic diagram showing the configuration of a main part of a laser oscillator. FIG. FIG. 3B is a cross-sectional view taken along line IIIB-IIIB in FIG. 3A. FIG. 2 is a schematic diagram of an output monitor mechanism. FIG. 4 is a schematic configuration diagram of an output monitor mechanism according to a first comparative example. FIG. 11 is a schematic configuration diagram of an output monitor mechanism according to a second comparative example. FIG. 11 is a schematic configuration diagram of an output monitor mechanism according to a third comparative example. FIG. 13 is a schematic configuration diagram of an output monitor mechanism according to a fourth comparative example. FIG. 11 is a schematic configuration diagram of a main part of a laser oscillator according to a first modified example. FIG. 11 is a schematic configuration diagram of a main part of a laser oscillator according to a second modified example. FIG. 11 is a schematic configuration diagram of a main part of a laser oscillator according to a second embodiment. FIG. 11 is a schematic diagram illustrating the internal configuration of a beam combiner according to a second embodiment. FIG. 11 is a diagram showing the wavelength dependence of sensitivity of a photodetector according to the second embodiment. 11 is a schematic cross-sectional view of a photodetector with a sensitivity correction function according to a second embodiment. FIG.

Embodiments of the present disclosure will be described below with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses.

(Embodiment 1)
[Configuration of laser processing device]
1 is a schematic diagram showing the configuration of a laser processing apparatus according to this embodiment. In the following description, the traveling direction of a first laser beam _LB1 (described later) emitted from a beam combiner 20 toward a focusing optical unit 40 may be referred to as an X-direction. The X-direction is also the optical axis direction of the first laser beam _LB1 inside a fourth housing 41 of the focusing optical unit 40. The arrangement direction of the multiple laser modules 10 may be referred to as a Y-direction. A direction perpendicular to the X-direction and the Y-direction may be referred to as a Z-direction.

In this specification, "orthogonal," "parallel," or "same" means that the two are orthogonal, parallel, or the same, including the assembly tolerances and processing tolerances of the laser processing device 200 and its components, and does not mean that the objects being compared are orthogonal, parallel, or the same in the strict sense.

The laser processing device 200 includes a fifth housing 50, a laser oscillator 80, an optical fiber 90, and a laser head 100. Except for the control unit 60 and the power supply 70, the laser oscillator 80 is housed inside the fifth housing 50. In addition, a portion of the optical fiber 90 is also housed inside the fifth housing 50.

The laser oscillator 80 has a plurality of laser modules 10, a beam combiner 20, an output monitor unit 30, a focusing optical unit 40, a control unit 60, and a power supply 70. The laser modules 10 are laser light sources having a plurality of laser diodes or laser diode bars. Module laser beams LB _M1 to LB _M4 (see FIGS. 10 and 11) combined within the laser modules 10 are emitted from each of the laser modules 10.

The beam combiner 20 combines the module laser beams LB _M1 to LB _M4 (see FIGS. 10 and 11) emitted from the multiple laser modules 10 into one laser beam LB _0. Also, a part of the laser beam LB ₀ is made incident on the focusing optical unit 40 as a first laser beam LB ₁ (see FIG. 2). The configuration of the beam combiner 20 will be described later.

The output monitor unit 30 is connected to the beam combiner 20, receives the second laser light _LB2 which is the remaining part of the laser light _LB0 , and calculates and evaluates the output of the first laser light _LB1 based on the amount of light of the received second laser light _LB2 (see FIG. 2). The configuration of the output monitor unit 30 will be described later.

The focusing optical unit 40 receives the first laser light _LB1 emitted from the beam combiner 20, and focuses the light toward the incident end of the optical fiber 90. The configuration of the focusing optical unit 40 will be described later.

The optical fiber 90 has at least a core and a cladding (not shown). The core is provided at the axial center of the optical fiber 90 and functions as an optical waveguide that guides the first laser light _LB1 incident from the focusing optical unit 40 to the laser head 100. The cladding is provided so as to surround the outer periphery of the core and functions as an optical confinement layer that confines the first laser light _LB1 inside the core.

The control unit 60 controls the laser oscillation of the laser oscillator 80. Specifically, the control unit 60 controls the laser oscillation of each laser module 10 by supplying control signals such as output voltage and on-time to the power supply 70. It is also possible to control the laser oscillation of each laser module 10 individually. For example, the laser oscillation output and on-time may be different for each laser module 10.

The control unit 60 also has a calculation unit 62. The calculation unit 62 receives an output signal from a photodetector 36 (see FIGS. 2 and 4) described later, and calculates an output value of the first laser light _LB1 emitted from the optical fiber 90 based on this output signal.

The calculation unit 62 is configured, for example, by a CPU (Central Processing Unit). The control unit 60 may also include one or more CPUs in addition to the calculation unit 62.

The control unit 60 controls the power supply 70 so that the output of the first laser light _LB1 becomes a predetermined target value used in laser processing based on the output value calculated by the calculation unit 62. Specifically, the control unit 60 controls the power supplied from the power supply 70 to the laser light source included in each laser module 10 so that the output of the first laser light _LB1 becomes a predetermined target value.

The control target of the control unit 60 may be the output of the laser beam LB _0. In other words, the control unit 60 may control the power supplied from the power source 70 to the laser light source included in each laser module 10 so that the output of the laser beam LB ₀ becomes a predetermined target value.

The control unit 60 also has a memory unit 61, which stores laser processing conditions and processing operation programs. The memory unit 61 is composed of semiconductor memory such as a random access memory (RAM) or a read only memory (ROM). The memory unit 61 may also be composed of a hard disk drive (HDD) or a solid state drive (SSD). The control unit 60 may also control the operation of a robot (not shown) to which the laser head 100 is attached.

The display unit 63 is configured to visualize and display the output value of the first laser beam _LB1 calculated by the calculation unit 62 in a time series. The display unit 63 may display data other than the above. For example, processing parameters during laser processing may be displayed at the same time. The display unit 63 usually includes a display device such as a liquid crystal display or an organic EL display.

As described above, the power supply 70 supplies power for laser oscillation to each of the multiple laser modules 10. The power supplied to each laser module 10 may be different based on a command from the control unit 60. The power supply 70 may also supply power to a moving part of the laser processing device 200, such as the robot mentioned above. Note that power may be supplied to the moving part of the laser processing device 200 from a separate power supply (not shown).

By configuring the laser oscillator 80 in this manner, it is possible to obtain a high-output laser processing apparatus 200 in which the output of the first laser light _LB1 exceeds several kW.

The laser head 100 irradiates the first laser light _LB1 transmitted through the optical fiber 90 toward the outside. For example, in the laser processing device 200 shown in Fig. 1, the first laser light _LB1 is emitted toward a workpiece W, which is an object to be processed and is arranged at a predetermined position. In this manner, the workpiece W is laser processed.

In this embodiment, four laser modules 10 are mounted on the laser oscillator 80, but this is not particularly limited. The number of laser modules 10 mounted can be changed as appropriate depending on the output specifications required for the laser processing device 200 and the output specifications of each laser module 10.

For example, in the case where there is one laser module 10, the above-mentioned laser light _LB0 becomes a module laser light emitted from the laser module 10. Also, the beam combiner 20 is omitted. In this case, for example, the first housing 11A (see FIG. 10) of the laser module 10 and the third housing 31 of the output monitor unit 30 are connected, and the second condenser lens 33 is disposed on the partition wall separating the two. Also, the partial reflection mirror 24 is disposed inside the first housing 11A. The module laser light incident on the partial reflection mirror 24 is branched into the first laser light _LB1 incident on the condensing optical unit 40 and the second laser light _LB2 incident on the output monitor unit 30.

[Configuration of laser oscillator and output monitor mechanism]
Fig. 2 is a schematic diagram of the main part of the laser oscillator, Fig. 3A is a perspective view of a mixing rod, and Fig. 3B is a cross-sectional view taken along line IIIB-IIIB in Fig. 3A.

Note that, inside the beam combiner 20, there are several optical components other than those shown in FIG. 2 (see FIGS. 10 and 11), but for the sake of convenience, these are not shown or described in FIG. 2.

The beam combiner 20 has at least a quarter-wave plate 23 and a partial reflection mirror (light branching element) 24 inside the second housing 21. The laser light _LB0 traveling in the Z direction inside the beam combiner 20 is converted from linearly polarized light to circularly polarized light by transmitting through the quarter-wave plate 23, and then enters the partial reflection mirror 24.

The partial reflection mirror 24 is a plate-shaped member, and the incident surface of the laser light LB ₀ is inclined at 45 degrees with respect to the optical axis of the laser light LB _0. The partial reflection mirror 24 is configured to reflect most of the laser light LB ₀ and transmit the remaining part. Therefore, the laser light LB ₀ incident on the partial reflection mirror 24 is branched into a first laser light LB ₁ traveling in the X direction and a second laser light LB ₂ traveling in the Z direction. The first laser light LB ₁ is incident on the focusing optical unit 40, and the second laser light LB ₂ is incident on the output monitor unit 30. The output of the first laser light LB ₁ is 99.99% of the output of the laser light LB ₀ , and the output of the second laser light LB ₂ is 0.01% of the output of the laser light LB _0. However, the output ratio of the first laser light LB ₁ and the second laser light LB ₂ is not particularly limited to this value and can be changed as appropriate.

The output monitor unit 30 has a third housing 31 and a second focusing lens (focusing optical element) 33. Inside the third housing 31, a holder 32, a neutral density filter 34, a mixing rod (light homogenizing element) 35, and a photodetector 36 are arranged.

The third housing 31 is connected to the second housing 21, and the two share a partition 31a. The partition 31a has an opening, and the second focusing lens 33 is fitted into this opening.

The first to fifth housings 11A, 21, 31, 41, 50, and the partition wall 31a, including the first housing 11A described later, are all made of a material that does not transmit the laser light LB _0. By separating the third housing 31 and the second housing 21 with the partition wall 31a, except for the second condenser lens 33, stray light generated when the laser light LB ₀ or the first laser light LB ₁ is reflected inside the beam combiner 20 is prevented from leaking into the output monitor unit 30.

The second condenser lens 33 is disposed on the optical path of the second laser light _LB2 incident from the beam combiner 20, and condenses the second laser light _LB2 and makes it incident on the neutral density filter .

The holder 32 is a cylindrical member having openings on both ends, and is attached and fixed to the third housing 31. A neutral density filter 34 is attached to the holder 32 so as to cover one of the openings of the holder 32. A photodetector 36 is attached to the holder 32 so as to cover the other opening. A mixing rod 35 is disposed inside the holder 32. In other words, the mixing rod 35 is held by the holder 32.

The neutral density filter 34 reduces the amount of light of the incident second laser light _LB2 . The amount of light of the second laser light _LB2 that has passed through the partial reflection mirror 24 is sufficiently reduced compared to the original laser light _LB0 . However, when the output of the laser light _LB0 is several kW, the output of the second laser light _LB2 becomes several tens of mW, and there is a risk that the output signal of the photodetector 36 will become saturated. For this reason, by passing the second laser light LB2 through the neutral density filter 34, the output of the second laser light _LB2 can be reduced to, for example, several mW or less, thereby preventing saturation of the output signal.

The mixing rod 35 is made of a material that is transparent to light having the same wavelength as the second laser light _LB2 , such as fused quartz.

3A and 3B, the mixing rod 35 is shaped like a hexagonal prism having opposing end faces. One end face is an incident end face 35a through which the second laser beam _LB2 is incident, and the other end face is an incident end face 35a through which the second laser beam _LB2 is emitted.

The second laser light _LB2 transmitted through the neutral density filter 34 passes through one opening of the holder 32 and is incident on the incident end face 35a of the mixing rod 35. The incident end face 35a and the exit end face 35b are each a regular hexagon, and have the same shape as the cross section of the mixing rod 35 shown in FIG.

The second laser light _LB2 incident on the inside of the mixing rod 35 from the incident end face 35a is refracted and reaches the side face of the mixing rod 35. At this time, the second laser light _LB2 is incident on the side face at an angle equal to or greater than the critical angle, and is therefore totally reflected by the side face and returned to the inside of the mixing rod 35. By repeating such reflections, the second laser light _LB2 is guided to the exit end face 35b of the mixing rod 35 and is emitted to the outside of the mixing rod 35 from the exit end face 35b.

In addition, the second laser light _LB2 is guided while being reflected once or multiple times inside the mixing rod 35, and the second laser light _LB2 emitted to the outside of the mixing rod 35 is diffused and the light intensity is spatially uniformed.

The photodetector 36 is a photodiode. However, it is not limited to this and may be any photoelectric conversion element that converts received light into an electrical signal by photoelectric conversion.

The second laser beam _LB2 emitted from the emission end face 35b of the mixing rod 35 is incident on the light receiving surface 36a of the photodetector 36. The area of the light receiving surface 36a is set to be larger than the area of the emission end face 35b of the mixing rod 35.

It is preferable that the light receiving surface 36a and the output end surface 35b of the mixing rod 35 are in contact with each other. This is because the second laser light _LB2 emitted from the output end surface 35b of the mixing rod 35 is received by the photodetector 36 without any loss. However, if the light receiving surface 36a and the mixing rod 35 are in direct contact with each other, stress may be applied to the photodetector 36, causing the output characteristics to fluctuate. Therefore, a gap may be provided between the light receiving surface 36a and the output end surface 35b of the mixing rod 35. This gap is appropriately set according to the dimensions of the output end surface 35b of the mixing rod 35. For example, when the length of the diagonal line at the output end surface 35b of the mixing rod 35, that is, the diameter R shown in FIG. 3B, is about 3 mm, the above-mentioned gap is allowed to be up to about 1 mm. The gap may be filled with a translucent adhesive having a refractive index intermediate between the refractive index of the air (=1) and the refractive index of the mixing rod 35.

The second laser light _LB2 incident on the light receiving surface 36a is converted into an electric signal by photoelectric conversion and input to the control unit 60 as an output signal of the photodetector 36. The magnitude of this output signal corresponds to the light amount of the second laser light _LB2 . The control unit 60 calculates the output of the first laser light _LB1 based on the output signal of the photodetector 36. Specifically, a conversion coefficient is first derived in the following procedure.

The output of the laser beam _LB0 is changed, and the output signal of the photodetector 36 is obtained each time. Also, the output of the first laser beam _LB1 actually emitted from the light emission port 44 of the focusing optical unit 40 is obtained separately. The correlation between this output signal and the output of the first laser beam _LB1 is obtained in advance, and a conversion coefficient is calculated.

When monitoring the actual output of the first laser beam _LB1 , the output signal of the photodetector 36 is multiplied by the conversion coefficient described above to calculate the output of the first laser beam _LB1 .

The focusing optical unit 40 has at least a first focusing lens 43 inside a fourth housing 41. The first laser light _LB1 incident from the light exit port 22 provided in the second housing 21 of the beam combiner ₂₀ is incident into the inside of the fourth housing 41 through a light entrance port 42 provided in the fourth housing 41. The first laser light LB1 is further focused by the first focusing lens 43 and is incident on the entrance end of the optical fiber 90. The first laser light _LB1 guided by the optical fiber 90 reaches the laser head 100 and is irradiated from the laser head 100 toward the workpiece W.

In the following description, the partial reflection mirror 24, the second focusing lens 33, the neutral density filter 34, the mixing rod 35, and the photodetector 36 may be collectively referred to as the output monitor mechanism 30A. Each of the optical components that make up the output monitor mechanism 30A is a known optical component. Note that even when some of the optical components are omitted or replaced with other components, they may still be referred to as the output monitor mechanism 30A. The function of the output monitor mechanism 30A will be further described below.

[Configuration of output monitor mechanism]
Fig. 4 is a schematic diagram of the output monitor mechanism. In Fig. 4 and Figs. 5A to 7 shown below, the beam diameters of the laser beam _LB0 and the second laser beam _LB2 are shown by dashed lines. However, these are not accurate sizes due to the size of other components.

4, of the laser beam _LB0 , the second laser beam _{LB2 transmitted through the partial reflection mirror 24 is collected by the second collecting lens 33. At this time, the second laser beam LB2} is collected by the second collecting lens 33 so that the cross-sectional area of the second laser beam _LB2 cut by a virtual plane perpendicular to its optical axis (hereinafter referred to as the beam cross-sectional area) is sufficiently smaller than the _area of the emission end surface 35b of the mixing rod 35.

The second laser beam _LB2 transmitted through the second condenser lens 33 is further transmitted through the neutral density filter 34, and in a state where the amount of light is reduced, enters the mixing rod 35. The second laser beam _LB2 is homogenized by the mixing rod 35, and in this state, enters the light receiving surface 36a of the photodetector 36. As described above, the area of the light receiving surface 36a is set to be larger than the area of the exit end surface 35b of the mixing rod 35.

[Effects, etc.]
As described above, the laser oscillator 80 according to this embodiment includes at least one laser module 10, a focusing optical unit 40, an output monitor mechanism 30A, and a control unit 60.

One or more laser modules 10 each have a laser diode or a laser diode bar, and emit a module laser beam. The laser oscillator 80 emits a laser beam _LB0 . When there is one laser module 10, the module laser beam emitted from the single laser module 10 is the laser beam _LB0 . When there are multiple laser modules 10, the module laser beams emitted from the multiple laser modules 10 are combined to produce a single laser beam _LB0 , which is the laser beam _LB0 .

The focusing optical unit 40 emits a first laser beam LB _{1 ,} which is a part of the laser beam LB _{0 ,} to the outside of the laser oscillator 80 .

The output monitor mechanism 30A monitors the output of the first laser beam LB _1. The output monitor mechanism 30A has at least a partial reflection mirror (light branching element) 24, a mixing rod (light homogenizing element) 35, and a photodetector .

The partial reflection mirror 24 splits the laser light _LB0 into a first laser light _LB1 and a second laser light _LB2 traveling in a direction different from that of the first laser light _LB1 .

The mixing rod 35 has an incident end surface 35a and an exit end surface 35b. The mixing rod 35 guides the second laser light _LB2 incident from the incident end surface 35a to the exit end surface 35b while totally reflecting the second laser light LB2 therein.

The photodetector 36 has a light receiving surface 36a that receives the second laser light LB ₂ , and outputs an output signal based on the amount of light of the received second laser light LB _2. The photodetector 36 is disposed such that the light receiving surface 36a is in contact with the incident end surface 35a of the mixing rod 35 or faces the incident end surface 35a of the mixing rod 35 with a predetermined gap therebetween.

The control unit 60 calculates the output of the first laser light _LB1 based on the output signal of the photodetector 60.

By configuring the laser oscillator 80, particularly the output monitor mechanism 30A in this manner, the entire amount of the second laser light _LB2 branched by the partial reflection mirror 24 can be made to enter the mixing rod 35. In other words, the photodetector 36 receives the entire amount of the second laser light _LB2 and generates an output signal. For this reason, even if the beam profile of the second laser light _LB2 fluctuates due to fluctuations in the beam profile of the laser light _LB0 , for example, the photodetector 36 outputs an output signal corresponding to the amount of light of the second laser light _LB2 without being affected by these fluctuations. In other words, the output of the first laser light _LB1 can be accurately monitored without being affected by fluctuations in the beam profile of the second laser light _LB2 .

Here, the beam profile refers to the light intensity distribution of the laser light on a virtual plane perpendicular to the optical axis of the laser light. The beam profile not only varies spatially but also varies over time. For example, when the power supplied from the power source 70 to the laser module 10 varies over time, the beam profile also varies over time. The beam profile can also vary when the output difference of the laser light _LB0 is changed.

As a result, the output of the first laser beam _LB1 can be monitored at high speed and with high accuracy. Furthermore, since the output monitor mechanism 30A can be configured using known optical components, the output monitor mechanism 30A and, in turn, the laser oscillator 80 can be realized at low cost. Furthermore, since the output monitor mechanism 30A can be configured using several components, the output monitor mechanism 30A and, in turn, the laser oscillator 80 can be made compact.

In designing the shape of the mixing rod 35, it is necessary to take care that the angle between the traveling direction of the second laser light _LB2 incident from the incident end face 35a and the side face of the mixing rod 35 does not exceed the critical angle. In this embodiment, the mixing rod 35 is made of fused quartz, and the refractive index thereof is about 1.4. Since the refractive index of air is about 1.0, the critical angle is about 45 degrees.

Furthermore, this embodiment has several advantages over known laser light monitoring mechanisms. To explain this, let us compare the output monitoring mechanism 30A of this embodiment shown in FIG. 4 with the output monitoring mechanism 30A of known configurations shown in FIGS. 5A to 7.

Figure 5A is a schematic diagram of an output monitor mechanism according to a first comparative example. Figure 5B is a schematic diagram of an output monitor mechanism according to a second comparative example. Figure 6 is a schematic diagram of an output monitor mechanism according to a third comparative example. Figure 7 is a schematic diagram of a laser light output monitor mechanism according to a fourth comparative example.

The output monitor mechanism 30A shown in Figures 5A and 5B differs from the output monitor mechanism 30A shown in Figure 4 in that the second condenser lens ₃₃ , the neutral density filter 34, and the mixing rod 35 are omitted. In the output monitor mechanism 30A shown in Figure 5A, the area of the light receiving surface 36a is set to be approximately the same as the beam cross-sectional area of the second laser light LB2. In the output monitor mechanism 30A shown in Figure 5A, the area of the light receiving surface 36a is set to be sufficiently larger than the beam cross-sectional area of the second laser light _LB2 .

5A, if the optical axis of the second laser light _LB2 directed toward the photodetector 36 is misaligned, a part of the second laser light _LB2 may extend beyond the light receiving surface 36a. The optical axis misalignment of the second laser light _LB2 occurs, for example, when the angle between the optical axis of the laser light _LB0 and the light incident surface of the partial reflection mirror ₂₄ is not within a set value (45 degrees in this case). The optical axis misalignment of the second laser light _LB2 also occurs when the incident position of the laser light LB0 with respect to the partial reflection mirror 24 is misaligned in a direction perpendicular to the optical axis of the laser light _LB0 .

Also, when the beam diameter of the second laser light _LB2 becomes larger than the set value, a part of the second laser light _LB2 may extend beyond the light receiving surface 36a. When the beam diameter or divergence angle of the laser light _LB0 itself becomes larger than the set value, the beam diameter of the second laser light _LB2 becomes larger than the set value.

When such an optical axis deviation or beam diameter fluctuation occurs, a part of the second laser beam _LB2 cannot be received by the photodetector 36, and as a result, the output of the first laser beam _LB1 cannot be accurately monitored.

On the other hand, according to the present embodiment, even if the optical axis of the second laser light _LB2 is misaligned or the beam diameter of the second laser light _LB2 varies, the entire amount of the second laser light _LB2 can be made to enter the mixing rod 35. This makes it possible to accurately monitor the output of the first laser light _LB1 using the output signal of the photodetector 36 that is output based on the amount of light of the second laser light _LB2 .

In the case shown in FIG. 5B , the area of the light receiving surface 36 _a is made sufficiently larger than the beam cross-sectional area of the second laser light _LB2 . Therefore, even if the optical axis of the second laser light LB2 is misaligned or the beam diameter of the second laser light _LB2 varies, the entire amount of the second laser light _LB2 can be made to enter the mixing rod 35.

However, if the area of the light receiving surface 36a is large, the light receiving sensitivity is more likely to vary across the surface, and the variation itself becomes larger. Furthermore, if this variation is large, there is a risk that the magnitude of the output signal from the photodetector 36 will fluctuate.

In this embodiment, the laser light LB ₀ is generated by combining the module laser light LB _M1 to LB _M4 emitted from the multiple laser modules 10. In such a case, if the laser light LB 0 is generated using, for example, a spatial combining technique, the beam cross-sectional area of the laser light LB ₀ and therefore the second laser light _{LB 2 becomes} large, and the effect of variations in light receiving sensitivity within the light receiving surface 36a becomes greater.

Furthermore, if stray light is generated inside the third housing 31, if the area of the light receiving surface 36a is large, the noise component caused by the stray light becomes large in the output signal. In this case, the output of the first laser light _LB1 cannot be monitored accurately.

As described above, the photodetector 36 is a photodiode, and a pn junction formed on a silicon chip functions as a photodiode. If the area of the light receiving surface 36a is large, the junction capacitance of the pn junction also becomes large. This causes the response time constant of the photodetector 36 to increase with respect to the time change in the output of the second laser light _LB2 . In other words, the time response of the photodetector 36 decreases.

On the other hand, according to the present embodiment, the entire amount of the second laser light _LB2 can be received by the light receiving surface 36a without significantly increasing the area of the light receiving surface 36a. This allows the output of the first laser light _LB1 to be accurately monitored. In addition, since an increase in the junction capacitance of the pn junction can be suppressed, the time response of the photodetector 36 is not significantly degraded.

In order to make the entire amount of the second laser light _LB2 incident on the mixing rod 35, it is preferable to provide a second condenser lens (condensing optical element) 33 between the partial reflection mirror 24 and the incident end surface 35a of the mixing rod 35. The second condenser lens 33 condenses the second laser light _LB2 toward the incident end surface 35a of the mixing rod 35. It is preferable that the beam diameter of the second laser light _{LB2 transmitted through the second condenser lens 33 in the vicinity of the incident end surface 35a is smaller than the diameter R of the incident end surface 35a. In other words, it is preferable that the beam cross-sectional area of the second laser light LB2 transmitted through the second condenser lens 33} is smaller than the area of the incident end surface 35a.

In this manner, the entire amount of the second laser light _LB2 can be reliably incident on the mixing rod 35. The focal length of the second condenser lens 33 and the distance from the second condenser lens 33 to the incident end face 35a are set so that the beam diameter of the second laser light _LB2 is smaller than the diameter R of the incident end face 35a.

The output monitor mechanism 30A shown in FIG. 6 also differs from the output monitor mechanism 30A shown in FIG. 4 in that the neutral density filter 34 and the mixing rod 35 are both omitted.

6, the second laser beam _LB2 is focused by the second focusing lens 33 and then incident on the light receiving surface 36a. Therefore, the entire amount of the second laser beam _LB2 can be received by the light receiving surface 36a without significantly increasing the area of the light receiving surface 36a.

In this case, however, if a deviation occurs in the optical axis of the second laser light _LB2 heading toward the photodetector 36, the incident position of the second laser light _LB2 on the light-receiving surface 36a will fluctuate. If there is variation in the light-receiving sensitivity within the light-receiving surface 36a, the fluctuation in the incident position of the second laser light _LB2 may cause the magnitude of the output signal from the photodetector 36 to fluctuate.

Furthermore, by transmitting the second laser light _LB2 through the second condenser lens 33, the power density of the second laser light _LB2 on the light receiving surface 36a becomes higher than that before transmitting through the second condenser lens 33. This may cause damage to the photodetector 36, and may also cause the photodetector 36 to deteriorate due to the damage.

On the other hand, according to the present embodiment, the mixing rod 35 guides the second laser light _LB2 incident from the incident end face 35a to the exit end face 35b while totally reflecting it inside. In this manner, the second laser light _LB2 emitted from the exit end face 35b becomes divergent light and enters the light receiving surface 36a of the photodetector 36. In addition, since the second laser light _LB2 is diffused and sufficiently uniformed inside the mixing rod 35, even if there is variation in light receiving sensitivity within the light receiving surface 36a of the photodetector 36, the influence of this variation can be sufficiently suppressed.

Furthermore, by transmitting the second laser beam _LB2 through the mixing rod 35, the power density of the second laser beam _LB2 on the light receiving surface 36a is made uniform, and the power density is lower than that before transmitting through the mixing rod 35. This prevents damage to the photodetector 36 due to non-uniformity in the power density, and prevents deterioration of the photodetector 36 due to the damage.

The output monitor mechanism 30A also includes a neutral density filter 34. In this embodiment, the neutral density filter 34 is disposed between the partial reflection mirror 24 and the incident end face 35a in the vicinity of the incident end face 35a. The neutral density filter 34 is also disposed between the second condenser lens 33 and the incident end face 35a in the vicinity of the incident end face 35a. The neutral density filter 34 reduces the amount of light of the second laser light _LB2 incident on the incident end face 35a.

In this way, the output of the second laser light _LB2 transmitted through the neutral density filter 34 can be reduced to, for example, a few mW or less, thereby preventing the output signal of the photodetector 36 from being saturated.

The output monitor mechanism 30A shown in FIG. 7 differs from the output monitor mechanism 30A shown in FIG. 4 in that the neutral density filter 34 and the mixing rod 35 are omitted, and an integrating sphere 37 is provided instead.

7, the area of the light entrance of the integrating sphere 37 is set to be larger than the beam cross-sectional area of the second laser light _LB2 focused by the second focusing lens 33. Therefore, the entire amount of the second laser light _LB2 can be made incident on the integrating sphere 37. Furthermore, the second laser light _LB2 is made sufficiently uniform inside the integrating sphere 37 before it is incident on the light receiving surface 36a of the photodetector 36. As a result, even if there is variation in light receiving sensitivity within the light receiving surface 36a of the photodetector 36, the effect of this can be sufficiently suppressed.

However, in order to reliably receive the entire amount of the second laser beam _LB2 and sufficiently homogenize it inside, the size of the integrating sphere 37 needs to be increased, which increases the size of the laser oscillator 80. Furthermore, the cost of the integrating sphere 37 is high, and the installation cost is also high.

On the other hand, according to this embodiment, the mixing rod 35 that homogenizes the second laser light _LB2 is a very small member. As shown in Fig. 3B, the diameter R of the mixing rod 35 in this embodiment is about 3 mm, and the length, i.e., the distance from the incident end face 35a to the exit end face 35b, is about 25 mm. This prevents the output monitor mechanism 30A, and in turn the laser oscillator 80, from becoming large. In addition, because the size of the mixing rod 35 is small, costs including installation costs can be kept low.

It is also preferable to use a partial reflection mirror 24 as a light branching element that branches the laser light _LB0 into the first laser light _LB1 and the second laser light _LB2 . The partial reflection mirror 24 reflects the first laser light _LB1 and transmits the second laser light _LB2 . The first laser light _LB1 accounts for most of the output of the laser light _LB0 , and the second laser light _LB2 corresponds to the remainder of the output of the laser light _LB0 . The first laser light _LB1 and the second laser light _LB2 reflected by or transmitted through the partial reflection mirror 24 have optical characteristics similar to those of the laser light _LB0 , except for the output.

The partial reflection mirror 24 may transmit the first laser beam _LB1 and reflect the second laser beam _LB2 .

In addition, it is preferable that an anti-reflection coating (not shown) is applied to the incident end surface 35a and the exit end surface 35b of the mixing rod 35. This anti-reflection coating is configured so that the reflectance of at least light having the same wavelength as the second laser beam _LB2 is equal to or lower than a predetermined value.

In this manner, the second laser light _LB2 branched by the partial reflection mirror 24 can be made incident on the light receiving surface 36a of the photodetector 36 without being eclipsed by the incident end surface 35a or the exit end surface 35b of the mixing rod 35. This makes it possible to accurately monitor the output of the first laser light _LB1 using the output signal of the photodetector 36 that is output based on the light amount of the second laser light _LB2 .

It is also preferable that the sides of the mixing rod 35 are coated with a light-blocking coating from the outside. This light-blocking coating is, for example, a metal film or a black insulating film.

By doing this, if stray light is generated inside the third housing 31, the stray light can be prevented from entering the inside of the mixing rod 35 from the side of the mixing rod 35. However, stray light can enter the inside of the mixing rod 35 from the incident end surface 35a.

Moreover, the amount of stray light incident on the photodetector 36 via the mixing rod 35 can be reduced, thereby reducing the noise components superimposed on the output signal. This makes it possible to accurately monitor the output of the first laser beam _LB1 .

The photodetector 36 is a photodiode, which is a photoelectric conversion element. By generating an output signal using the photoelectric conversion effect, even if the output of the second laser light _LB2 fluctuates over time, an output signal corresponding to the fluctuation can be output. In other words, the high-speed response of the photodetector 36 can be ensured.

In order to reliably receive the entire amount of the second laser beam _LB2 at the light receiving surface 36a, the area of the light receiving surface 36a is preferably larger than the area of the emission end surface 35b, although the difference in area is preferably within a predetermined range.

This is because if the area of the light receiving surface 36a becomes too large compared to the area of the emission end surface 35b, the junction capacitance becomes too large, lowering the response time constant of the photodetector 36. As described above, since the second laser beam _LB2 emitted from the emission end surface 35b is converted into divergent light, in order to reliably receive the light at the light receiving surface 36a, it is necessary to appropriately set the distance from the second condenser lens 33 to the incident end surface 35a. For example, in this embodiment, when the diameter or diagonal length of the light receiving surface 36a is 3.6 mm, it is preferable that the distance from the second condenser lens 33 to the incident end surface 35a be 3 mm or less.

The control unit 60 controls the power supplied from the power source 70 to the laser module 10 so that the output of the first laser light _LB1 calculated based on the output signal of the photodetector 36 becomes a predetermined target value.

According to this embodiment, even when the optical axis of the laser beam _LB0 and therefore the first laser beam _LB1 fluctuates or the beam profile fluctuates, the output of the first laser beam _LB1 can be accurately monitored. This makes it possible to accurately evaluate the difference between the actual output of the first laser beam _LB1 and the target value, and to reliably bring the output of the first laser beam _LB1 closer to the target value in a short time.

The laser processing apparatus 200 according to this embodiment includes at least a laser oscillator 80 and a laser head 100 that receives a first laser beam LB1 and irradiates the workpiece W with the first laser beam _LB1 .

According to the present embodiment, the output of the first laser light LB ₁ used in the laser processing of the workpiece W can be reliably brought close to the target value, thereby suppressing deterioration in processing quality due to fluctuations in the output of the first laser light LB _1. Even if the output of the first laser light LB ₁ fluctuates in a short period of time, the output of the first laser light LB ₁ can be brought close to the target value in a short period of time, thereby suppressing deterioration in processing quality.

In addition, by connecting the laser oscillator 80 and the laser head 100 with an optical fiber 90 and guiding the first laser light _LB1 emitted from the laser oscillator 80 to the laser head 100, it is possible to perform laser processing on a workpiece W placed at a position away from the laser oscillator 80. This ensures the safety of the processing operator.

<Modification 1>
Fig. 8 is a schematic diagram of a main part of a laser oscillator according to Modification 1. For ease of explanation, in Fig. 8 and the following drawings, the same parts as those in the first embodiment are denoted by the same reference numerals, and detailed explanations thereof will be omitted.
The output monitor mechanism 30A of the present modified example 1 shown in FIG. 8 differs from the output monitor mechanism 30A of the first embodiment shown in FIG.

The reflection mirror 38 is disposed inside the third housing 31 and reflects the second laser light _LB2, which is branched by the partial reflection mirror 24 and travels in the Z direction, in the X direction, i.e., in the same direction as the travel direction of the first laser light _LB1 . In this modification, the partial reflection mirror 24 is disposed at the connection between the second housing 21 and the third housing 31.

The second laser beam _LB2 reflected by the reflecting mirror 38 is focused by the second focusing lens 33, then enters the mixing rod 35, and is received by the light receiving surface 36a of the photodetector 36. The second focusing lens 33, the mixing rod 35, and the photodetector 36 are disposed at intervals from one another in the X direction.

According to this modification, it is possible to achieve the same effects as those achieved by the configuration shown in the first embodiment. That is, even if the optical axis misalignment or beam profile of the second laser light _LB2 varies, the output of the first laser light _LB1 can be accurately monitored without being affected by these. In addition, the output of the first laser light _LB1 can be monitored at high speed and with high accuracy.

Furthermore, according to this modification, the traveling direction of the second laser light _LB2 incident on the photodetector 36 via the mixing rod 35 is changed to the X direction by the reflecting mirror 38. In this way, the direction in which the second condenser lens 33, the mixing rod 35, and the photodetector 36 are arranged can be changed from the Z direction shown in the first embodiment to the X direction. This allows the height of the output monitor unit 30 in the Z direction to be reduced, and the laser oscillator 80 to be made smaller in size in the Z direction.

<Modification 2>
Fig. 9 is a schematic diagram of a main part of a laser oscillator according to Modification 2. The output monitor mechanism 30A of Modification 1 shown in Fig. 9 differs from the output monitor mechanism 30A of Modification 1 shown in Fig. 8 in that the second condenser lens 33 is omitted and a concave mirror 39 is provided instead of the reflecting mirror 38.

The concave mirror 39 has the functions of both the reflecting mirror 38 and the second condenser lens 33. That is, the concave mirror 39 reflects, in the X direction, the second laser light _LB2 that is branched by the partial reflecting mirror 24 and travels in the Z direction. The concave mirror 39 also condenses the second laser light _LB2 toward the incident end surface 35a of the mixing rod 35.

According to this modification, it is possible to achieve the same effects as those achieved by the configuration shown in modification 1. That is, even if there is a misalignment of the optical axis or a fluctuation in the beam profile of the second laser light _LB2 , it is possible to accurately monitor the output of the first laser light _LB1 without being affected by these. Also, it is possible to monitor the output of the first laser light _LB1 at high speed and with high accuracy.

In addition, compared to the laser oscillator 80 of embodiment 1 shown in FIG. 4, the height of the output monitor unit 30 in the Z direction can be reduced, and the laser oscillator 80 can be made smaller in size in the Z direction.

In addition, according to this modified example, the second focusing lens 33 can be omitted, which reduces the number of parts required for the laser oscillator 80, thereby enabling the laser oscillator 80 to be further miniaturized and reducing costs.

(Embodiment 2)
Fig. 10 is a schematic diagram of a main part of a laser oscillator according to embodiment 2. Fig. 11 is a schematic diagram of the inside of a beam combiner according to embodiment 2. For convenience of explanation, Fig. 10 shows only a laser module 11 that emits a module laser beam LB _M1 .

In the laser oscillator 80 shown in embodiment 2, a laser module 11 is arranged instead of the laser module 10 shown in FIG. 1.

The laser module 11 has a plurality of laser diode bars 11B and a diffraction grating 11C inside a first housing 11A. An external resonator mirror 11D is provided to cover a first light inlet 21a of a second housing 21 of a beam combiner 20 that communicates with the first housing 11A. As shown in FIG. 11, the second housing 21 is provided with first to fourth light inlets 21a to 21d. The first housing 11A is connected to each of the first to fourth light inlets 21a to 21d, and an external resonator mirror 11D is provided to cover each of the light inlets 21a to 21d.

The laser diode bar 11B has a plurality of emitters (not shown), each of which emits an emitter laser beam _LBE (not shown). The emitter laser beams _LBE have different wavelengths.

A plurality of emitter laser beams _LBE emitted from a plurality of emitters provided in each of the plurality of laser diode bars 11B travel toward the diffraction grating 11C.

The diffraction grating 11C receives the multiple emitter laser beams _LBE , diffracts each emitter laser beam _LBE , and directs it toward the external cavity mirror 11D. Although the diffraction grating 11C is of a type that transmits each emitter laser beam _LBE in this embodiment, the diffraction grating 11C may be of a type that reflects each emitter laser beam _LBE .

At this time, the diffraction grating 11C diffracts each of the emitter laser beams _LBE so that the optical axes of the emitter laser beams _LBE coincide with each other.

The external cavity mirror 11D transmits a part of each of the incident emitter laser beams _LBE and reflects the remaining part toward the diffraction grating 11C. In this manner, an external cavity is formed between the external cavity mirror 11D and each of the laser diode bars 11B. This will be described in further detail.

As described above, each emitter laser beam _LBE emitted from a plurality of laser diode bars 11B is diffracted by the diffraction grating 11C and then enters the external cavity mirror 11D. A part of the incident emitter laser beam _LBE is transmitted, while the remaining part is reflected toward the diffraction grating 11C and then returns to the laser diode bar 11B. Most of this reflected return beam reaches an end face (hereinafter referred to as a rear end face) of the laser diode bar 11B that faces the emission end face of the emitter laser beam _LBE . Furthermore, the emitter laser beam _LBE is reflected by an end face coating layer (not shown) formed on the rear end face and is again emitted from the emission end face to the outside of the laser diode bar 11B.

Of the emitter laser light _LBE emitted from each emitter in the laser diode bar 11B, only light having a wavelength (hereinafter referred to as the lock wavelength) that satisfies the diffraction condition of the diffraction grating 11C and is reflected by the external resonator mirror 11D is fed back to the original emitter, thereby forming an external resonator between the rear end face of the laser diode bar 11B and the external resonator mirror 11D, and emitter laser light _LBE is emitted from the laser diode bar 11B, specifically, from each of the multiple emitters.

The locking wavelength λ _L of each emitter is expressed by equation (1), where λ L is the period of the diffraction grating 11C, _d is the angle of incidence of the emitter laser light LB _EE with respect to the incident surface of the diffraction grating 11C, α is the angle of emergence, β is the order, and m is the order.

d(sinα+sinβ)=mλ _L ...(1)
Generally, the order m of the diffraction grating 11C is set to 1.

For example, in the laser diode bar 11B, the emitters are formed so that the incident angle α changes for each emitter placement position. In this case, the lock wavelength of the emitters formed in the laser diode bar 11B changes stepwise from one end of the laser diode bar 11B to the other end.

Each emitter can oscillate by external resonance only at wavelengths where the inherent gain wavelength intensity of the laser diode bar 11B is equal to or greater than a predetermined value. In other words, each emitter oscillates at a lock wavelength within a predetermined range from the gain peak wavelength λ _g , and does not oscillate at a lock wavelength outside the predetermined range. Therefore, in the laser module 11 of this embodiment, the laser diode bar 11B and each emitter are optically designed so that the upper and lower limits of the gain peak wavelength λ _g of each emitter fall within the range of the difference Δλ _{L_bar} between the lock wavelengths λ _L of the emitters at both ends of the laser diode bar 11B. The difference Δλ _{L_bar} between the lock wavelengths λ _L of the emitters at both ends changes depending on the distance between the laser diode bar 11B and the diffraction grating 11C.

The positional relationship between the laser diode bar 11B and the diffraction grating 11C is defined so that the optical axes of the emitter laser beams _LBE emitted from the emitters of the laser diode bar 11B overlap each other when they pass through the diffraction grating 11C.

In other words, the emitter laser beams _LBE emitted from the respective emitters provided in the respective laser diode bars 11B are made to overlap with each other when they are incident on the external resonator mirror 11D. In this way, the overlapping and combining of the multiple emitter laser beams _LBE is called wavelength synthesis. The multiple emitter laser beams _LBE emitted from the respective emitters provided in the respective laser diode bars 11B are wavelength-synthesized into one module laser beam, which is then emitted to the outside of the laser module 11.

In this embodiment, four laser modules 11 are mounted on the laser oscillator 80, and the module laser beams emitted from the respective laser modules 11 are called LB _M1 to LB _M4 . As described above, LB _M1 to LB _M4 are obtained by wavelength synthesis of laser beams LB _E having different wavelengths, and have different wavelength ranges.

In this embodiment, the wavelength ranges of the module laser beams LB _M1 and LB _M2 are 950 nm to 1000 nm, respectively. The wavelength ranges of the module laser beams LB _M3 and LB _M4 are 850 nm to 900 nm, respectively. However, the wavelength ranges of the module laser beams LB _M1 to LB _M4 are not particularly limited to these and can be changed as appropriate depending on the semiconductor material constituting the laser diode bar 11B, etc.

10, the module laser beams LB _M1 to LB _M4 are combined inside the beam combiner 20 to generate laser beam LB 0. The beam diameter of laser beam LB ₀ is expanded by the expansion optical system 26 inside the beam combiner 20. The expansion optical system 26 is composed of an expansion lens 26A that expands the beam diameter of laser beam LB ₀ and a collimator lens 26B that collimates the expanded laser beam LB _0. As shown in FIG. 10, the expansion lens _26A is a concave lens, and the collimator lens 26B is a convex lens.

The beam diameter of the laser light LB ₀ can be reduced as necessary. That is, the laser light LB ₀ is adjusted to a desired beam diameter using the magnifying optical system 26 or a reducing optical system (not shown) as necessary, and then enters the focusing optical unit 40. The magnifying optical system 26 and the reducing optical system are both configured with a combination of a concave lens and a convex lens. When it is desired to increase the beam diameter of the laser light LB ₀ , the beam diameter is first increased by the magnifying lens 26A, which is a concave lens, and then the laser light LB ₀ is collimated by the collimating lens, which is a convex lens. When it is desired to decrease the beam diameter of the laser light LB ₀ , the beam diameter is first decreased by the convex lens, and then the laser light LB ₀ is collimated by the concave lens.

11, first to fourth light inlets 21a to 21d for the module laser beams LB _M1 to LB _M4 are provided in the second housing 21 of the beam combiner 20 at intervals in the Y direction. Also, first to fourth rise-up mirrors 25A to 25D are provided near the first to fourth light inlets 21a to 21d, respectively. The first to fourth rise-up mirrors 25A to 25D respectively reflect the module laser beams LB _M1 to LB _M4 that have entered the inside of the second housing 21, and change the traveling direction of each beam from the Y direction to the Z direction.

As shown in FIG. 11, inside the second housing 21, a first reflecting mirror 27A, a second reflecting mirror 27B, a first polarizing beam splitter 28A, a second polarizing beam splitter 28B, two half-wave plates HWP1 and HWP2, and a dichroic mirror 29 are arranged in a predetermined arrangement.

The first reflecting mirror 27A is disposed on the optical path of the module laser light LB _M1 that is reflected by the first raising mirror 25A and travels in the Z direction. The first reflecting mirror 27A reflects the module laser light LB _M1 in the Y direction and makes it incident on the half-wave plate HWP1.

The polarization direction of the module laser light LB _M1 rotates by 90 degrees before and after passing through the half-wave plate HWP1.

The first polarizing beam splitter 28A is disposed on the optical path of the module laser light LB _M2 traveling in the Z direction and on the optical path of the module laser light LB _M1 traveling in the Y direction. The first polarizing beam splitter 28A transmits the module laser light LB _M2 , while reflecting the module laser light LB _M1 to make it travel in the Z direction. The module laser light LB _M1 and the module laser light LB _M2 emitted from the first polarizing beam splitter 28A are combined with each other in a state where their optical axes coincide with each other, and travel in the Z direction. In other words, the module laser light LB _M1 and the module laser light LB _M2 are polarization-combined by the first polarizing beam splitter 28A. The polarization-combined module laser light LB _M1 and the module laser light LB _M2 are incident on the dichroic mirror 29.

The second reflecting mirror 27B is disposed on the optical path of the module laser beam LB- _M4 that is reflected by the fourth raising mirror 25D and travels in the Z direction. The second reflecting mirror 27B reflects the module laser beam LB- _M4 in the Y direction and makes it incident on the half-wave plate HWP2.

The polarization direction of the module laser light LB _M4 rotates by 90 degrees before and after passing through the half-wave plate HWP2.

The second polarizing beam splitter 28B is disposed on the optical path of the module laser light LB _M3 traveling in the Z direction and on the optical path of the module laser light LB _M4 traveling in the Y direction. The second polarizing beam splitter 28B transmits the module laser light LB _M4 , while reflecting the module laser light LB _M3 to make it travel in the Y direction. The module laser light LB _M3 and the module laser light LB _M4 emitted from the second polarizing beam splitter 28B are combined with each other in a state where their optical axes coincide with each other, and travel in the Y direction. In other words, the module laser light LB _M3 and the module laser light LB _M4 are polarization-combined by the second polarizing beam splitter 28B. The polarization-combined module laser light LB _M3 and the module laser light LB _M4 are incident on the dichroic mirror 29.

The dichroic mirror 29 is disposed on the optical paths of the module laser light LB _M1 and the module laser light LB _M2 after being polarization-combined by the first polarizing beam splitter 28A. The dichroic mirror 29 is also disposed on the optical paths of the module laser light LB _M3 and the module laser light LB _M4 after being polarization-combined by the second polarizing beam splitter 28B.

The dichroic mirror 29 transmits light in a specific wavelength range that has been set, while reflecting light in the other wavelength ranges. In this embodiment, the dichroic mirror 29 is configured to transmit light in the same wavelength range as the module laser light LB _-M1 and the module laser light LB _-M2 , and to reflect light in the remaining wavelength ranges.

Therefore, the module laser light LB _M1 and the module laser light LB _M2 are each transmitted through the dichroic mirror 29 and continue traveling in the Z direction. On the other hand, the module laser light LB _M3 and the module laser light LB _M4 are each reflected by the dichroic mirror 29 and change their traveling direction from the Y direction to the Z direction.

In this embodiment, the various components are arranged inside the beam combiner 20 so that the optical axis of the module laser light LB _M1 after passing through the dichroic mirror 29 coincides with the optical axis of the module laser light LB _M3 after being reflected by the dichroic mirror 29. As described above, the module laser light LB _M1 and the module laser light LB _M2 are combined with their optical axes coinciding with each other immediately before entering the dichroic mirror 29. Also, the module laser light LB _M3 and the module laser light LB _M4 are combined with their optical axes coinciding with each other.

Therefore, the dichroic mirror 29 functions as a wavelength combining mirror that combines the module laser lights LB _M1 to LB _M4 so that their optical axes coincide with each other.

The module laser beams LB _M1 to LB _M4 emitted from the dichroic mirror 29 are combined so that their optical axes coincide with each other, and become laser beam LB ₀ .

According to this embodiment, the module laser beams LB _M1 to LB _M4 are combined so that their optical axes coincide with each other, so that the beam quality of the laser beam LB ₀ can be improved.

The second housing 21 is provided with a light exit port 22 communicating with a fourth housing 41 of the focusing optical unit 40, and most of the laser light _LB0 combined inside the beam combiner 20 is reflected in the X direction by a partial reflection mirror 24 (not shown in FIG. 11 ) and enters the focusing optical unit 40 from the light exit port 22 as a first laser light _LB1 . On the other hand, the remaining part of the laser light _LB0 that has passed through the partial reflection mirror 24, that is, a second laser light _LB2 , enters the output monitor unit 30.

The internal configuration of the output monitor unit 30 is the same as that shown in the first embodiment. However, the neutral density filter 34 is provided with a sensitivity correction function, which will be described later. As in the first embodiment, the second laser light _LB2 incident on the output monitor unit 30 is homogenized by the mixing rod 35 and incident on the light receiving surface 36a of the photodetector 36. The photodetector 36 outputs an output signal based on the amount of light of the incident second laser light _LB2 to the control unit 60, and the control unit 60 calculates the output of the first laser light _LB1 based on the magnitude of this output signal.

The first laser light LB ₁ branched by the partial reflection mirror 24 passes through a light entrance port 42 provided in a fourth housing 41 of the focusing optical unit 40 and enters a first focusing lens 43 .

A first receptacle 45 is attached to the light exit port 44 provided in the fourth housing 41. The first receptacle 45 holds a first quartz block holder 46. The first quartz block holder 46 holds a first quartz block 47. The first quartz block 47 is fused to the input end of the optical fiber 90 and is disposed at the light exit port 44.

The first laser light LB ₁ condensed by the first condenser lens 43 enters the optical fiber 90 via the first quartz block 47 .

A second quartz block holder 48 and a second quartz block 49 are attached to the output end of the optical fiber 90. The second quartz block holder 48 holds the second quartz block 49. The second quartz block 49 is fused to the output end of the optical fiber 90 and is disposed at a light output port (not shown) provided in the laser head 100. The second quartz block holder 48 and the second quartz block 49 are held in a second receptacle (not shown) attached to the light input port of the laser head 100.

The first quartz block 47 and the second quartz block 49 adjust the refractive index difference between the internal atmosphere of the fourth housing 41 or the laser head 100 and the core of the optical fiber 90, thereby suppressing unnecessary reflection of the first laser light _LB1 at the input end or output end of the optical fiber 90.

The first laser light _LB1 guided by the optical fiber 90 enters the inside of the laser head 100 via the second quartz block 49, undergoes a predetermined transformation inside the laser head 100, and is then irradiated toward the workpiece W.

In this embodiment, the beam cross section of each of the module laser beams LB _M1 to LB _M4 is elliptical having two axes (fast axis and slow axis) with different polarization characteristics and beam quality. The module laser beams LB _M1 to LB _M4 are collimated in the fast axis direction and the slow axis direction inside the laser module 11, and the beam cross sections of the laser beam LB ₀ obtained by combining these beams and the first laser beam LB ₁ are also elliptical. The beam diameter of the laser beam LB ₀ in the slow axis direction is about 3 mm to 6 mm, and the beam diameter in the fast axis direction is about 1 mm to 3 mm. The beam diameters of the first laser beam LB ₁ in the slow axis direction and the fast axis direction are also about the same as those of the laser beam LB ₀ .

In order to input the first laser light _LB1 into the optical fiber 90 having a core with a diameter of about several tens of μm to 100 μm with an NA (numerical aperture) of 0.1 or less, it is desirable to use the first focusing lens 43 having a focal length of about 20 mm to 50 mm.

As the focal length becomes longer, the scale of the optical system for focusing the first laser beam _LB1 becomes larger, and the beam diameter of the first laser beam _LB1 incident on the first focusing lens 43 must be increased. In order to increase the beam diameter of the first laser beam _LB1 , it is necessary to increase the beam diameter of the laser beam _LB0 .

However, this requires an increase in size of the expansion optical system 26 provided in the beam combiner 20. In addition, the increase in size of the expansion optical system 26 increases the influence of the optical axis fluctuation of the laser beam _LB0 on the second laser beam _LB2 .

On the other hand, if the focal length is too short, the tolerance in the optical axis direction of the first focusing lens 43 may become extremely narrow, making it impossible to tolerate the effects of thermal lens effects, etc.

Furthermore, when the focal length of the first condenser lens 43 and the NA of the first laser light _LB1 are within the aforementioned ranges, it is necessary to set the beam diameter of the first laser light _LB1 incident on the first condenser lens 43 to 4 mm to 10 mm or less. On the other hand, if this beam diameter is made too small, the focused spot size of the first laser light _LB1 when incident on the optical fiber 90 becomes large, and the first laser light _LB1 will no longer fit into a core having a diameter of about several tens of μm.

Also, the second laser beam _LB2 incident on the output monitor mechanism 30A has a significantly lower light amount than the laser beam _LB0 , but its optical characteristics are equivalent to those of the laser beam _LB0 . That is, the beam diameters of the second laser beam _LB2 in the slow axis direction and the fast axis direction are also approximately the same as those of the laser beam _LB0 .

In consideration of the optical axis fluctuation of the second laser light _LB2 , in order to reliably receive the entire amount of the second laser light _LB2 having a maximum diameter of 6 mm, the size of the light receiving surface 36a needs to be about 10 mm x 10 mm. On the other hand, as shown in this embodiment, by using the second condenser lens 33, the area of the light receiving surface 36a can be significantly reduced. When the light receiving surface 36a is circular, its diameter can be about 3.6 mm, and the area of the light receiving surface 36a becomes 1/10 or less compared to the above-mentioned case. The response time constant of the photodetector 36 is proportional to the composite impedance of the resistance and capacitance of the pn junction that constitutes the photodiode. Since the light receiving surface 36a corresponds to the pn junction, the area of the light receiving surface 36a can be reduced to 1/10 or less, and the response time constant also becomes 10 or less. In other words, the response speed of the photodetector 36 becomes 10 times or more.

As mentioned above, the diameter of the light receiving surface 36a is approximately 3.6 mm, which is larger than the diameter R (= 3 mm) of the light emitting end surface 35b of the mixing rod 35.

The beam diameter of the second laser light _LB2 focused by the second focusing lens 33 is smaller than 100 μm. This value is sufficiently small relative to the diameter R of the incident end face 35 a and the exit end face 35 b of the mixing rod 35 functioning as an aperture, and the effect of aberration can be ignored, so that a low-cost spherical lens can be used as the second focusing lens 33.

In addition, when the optical axis angle of the laser beam _LB0 varies with respect to the Z direction, for example, when the angle varies by 1 mrad, the positional variation on the light receiving surface 36a of the second laser beam LB2 focused by the second focusing lens ₃₃ is limited to about 25 μm. Since this value is sufficiently small compared to the diameter R of the incident end surface 35a of the mixing rod 35, the entire amount of the second laser beam _LB2 can be reliably incident on the mixing rod 35.

Here, the sensitivity correction function added to the neutral density filter 34 will be described with reference to FIG. 12. FIG. 12 is a diagram showing the wavelength dependence of the sensitivity of the photodetector according to the second embodiment.

Since the laser light _LB0 is a combination of the module laser lights LB _M1 to LB _M4 , not only does it have a larger spatial spread than the individual module laser lights, but it also has a wider wavelength range as described above. Specifically, the wavelength range of the laser light _LB0 in this embodiment is 850 nm to 1000 nm. On the other hand, the light receiving sensitivity of a general silicon photodiode changes depending on the wavelength in this wavelength range.

As shown in the comparative example of FIG. 12, when the neutral density filter 34 does not have a sensitivity correction function, the light receiving sensitivity of the photodetector 36 changes depending on the wavelength of the incident light. In the wavelength range of the laser light LB ₀ , that is, the wavelength range of the second laser light LB ₂ , the light receiving sensitivity increases as the wavelength increases from 850 nm, while the light receiving sensitivity decreases when the wavelength exceeds 970 nm. If the light amounts of the module laser lights LB _M1 to LB _M4 included in the laser light LB ₀ are the same, the control unit 60 can correct the output signal of the photodetector 36 using the wavelength dependency of the light receiving sensitivity shown in FIG. 12. However, if the light amounts of the module laser lights LB _M1 to LB _M4 differ due to variations in the power supplied to the laser module 11, etc., it becomes difficult for the control unit 60 to correct the sensitivity. This may result in a risk of not being able to accurately monitor the output of the first laser light LB ₁ based on the magnitude of the output signal from the photodetector 36.

Therefore, in this embodiment, the neutral density filter 34 is provided with a sensitivity correction function so that the light receiving sensitivity of the photodetector 36 is constant regardless of the wavelength. More specifically, the sensitivity correction function here refers to appropriately adjusting the transmittance for each wavelength of incident light so that the light receiving sensitivity of the photodetector 36 is uniform for each wavelength of incident light.

By providing the neutral density filter 34 with a sensitivity correction function in this way, even if the light intensities of the module laser beams LB _M1 to LB _M4 differ, the control unit 60 does not need to correct the light receiving sensitivity of the photodetector 36 according to the wavelength. This makes it possible to accurately monitor the output of the first laser beam LB ₁ based on the magnitude of the output signal from the photodetector 36.

In addition, instead of providing the neutral density filter 34 with a sensitivity correction function, a filter having the same function may be provided in the photodetector 36.

Figure 13 is a schematic cross-sectional view of a photodetector with sensitivity correction function according to embodiment 2.

The photodetector 360 with sensitivity correction function shown in FIG. 13 has a photodetector 361 and a filter 362. The photodetector 361 is a photodiode similar to the photodetector 36 shown in FIG. 2 and FIGS. 8 to 10. The filter 362 has the sensitivity correction function shown in FIG. 12.

The filter 362 may have a dimming function to reduce the amount of the incident second laser light LB2. In this embodiment, the dimming filter 34 and the filter 362 are made of a dielectric material.

In this specification, filters that have a sensitivity correction function, such as the neutral density filter 34 and filter 362 of this embodiment, may be referred to as sensitivity correction filters.

As described above, the laser module (laser light source) 11 of the laser oscillator 80 according to this embodiment has at least the following components:

The laser module 11 includes at least a first housing 11A, a plurality of laser diode bars 11B, a diffraction grating 11C, and an external resonator mirror 11D.

Each of the laser diode bars 11B has a plurality of emitters. The diffraction grating 11C combines the emitter laser beams _LBE emitted from the respective emitters. The external resonator mirror 11D reflects the emitter laser beams _LBE combined by the diffraction grating 11C toward the diffraction grating 11C. The first housing 11A accommodates the laser diode bars 11B, the diffraction grating 11C, and the external resonator mirror 11D.

An external resonator is formed between the external resonator mirror 11D and the rear end face of the laser diode bar 11B, and a module laser light generated by combining multiple emitter laser beams _LBE through a diffraction grating 11C is emitted to the outside of the first housing 11A.

By configuring the laser module 11 in this way, multiple emitter laser beams _LBE emitted from multiple emitters can be combined into one module laser beam, and a high-output module laser beam can be obtained. In addition, by using a so-called wavelength synthesis technique, the beam quality of the module laser beam is not significantly degraded.

The laser oscillator 80 also includes a plurality of laser modules 11 and a beam combiner 20 that combines a plurality of module laser beams emitted from the plurality of laser modules 11 to generate a laser beam LB ₀ .

By providing the beam combiner 20, it is possible to combine a plurality of module laser beams to obtain a higher output laser beam LB _0. In addition, it is possible to increase the output of the first laser beam LB ₁ obtained by branching the laser beam LB ₀ , and it is possible to perform laser cutting or laser drilling in a short time, for example, on a thick workpiece W. In addition, it is possible to shorten the laser processing time, including laser welding.

Moreover, according to this embodiment, it is possible to achieve the same effects as those achieved by the configuration shown in the first embodiment. That is, even if the optical axis misalignment or beam profile of the second laser light _LB2 varies, the output of the first laser light _LB1 can be accurately monitored without being affected by these. Moreover, it is possible to monitor the output of the first laser light _LB1 at high speed and with high accuracy.

According to the present embodiment, the output monitor mechanism 30A includes a sensitivity correction filter configured such that, when the wavelength region of the laser beam _LB0 , in other words the second laser beam _LB2, is within a predetermined range, the light receiving sensitivity of the photodetector 36 is constant at least within the above-mentioned predetermined range.

By configuring the output monitor mechanism 30A in this manner, even when the wavelength range of the laser light _LB0 , in other words the second laser light _LB2, is wide, the control unit 60 does not need to correct the light receiving sensitivity of the photodetector 36 according to the wavelength. This makes it possible to accurately monitor the output of the first laser light _LB1 based on the magnitude of the output signal of the photodetector 36.

The neutral density filter 34 can be provided with a sensitivity correction function to function as a sensitivity correction filter. In this case, the sensitivity correction filter is disposed between the partial reflection mirror 24 and the incident end face 35a of the mixing rod 35, in the vicinity of the incident end face 35a, and reduces the amount of the second laser light _LB2 incident on the incident end face 35a.

Also, as shown in FIG. 13, the sensitivity correction filter (filter 362) may be disposed in contact with the light receiving surface 36a.

Other Embodiments
New embodiments can also be created by appropriately combining the components shown in the first and second embodiments and the first and second modifications. For example, a photodetector 360 with sensitivity correction capability shown in FIG. 13 may be disposed in place of the photodetector 36 shown in the first embodiment and the first and second modifications. In addition, the output monitor mechanism 30A shown in the first and second modifications may be applied to the laser oscillator 80 shown in the first and second embodiments.

The wavelength region of the emitter laser light _LBE or the module laser light may be in the blue wavelength region, for example, 380 nm to 460 nm.

The number of laser modules 10, 11 provided in the laser oscillator 80 may be one. The number of laser diode bars provided in each of the laser modules 10, 11 may be one.

The mixing rod 35 is not limited to a hexagonal prism, but may be, for example, a cylinder. The material and side surface of the mixing rod 35 need only be set so that the critical angle described above is an appropriate value.

In the first and second embodiments and the first and second modifications, the partial reflection mirror 24 is provided inside the second housing 21 of the beam combiner 20, and the third housing 31 of the output monitor unit 30 is connected to the second housing 21. However, the positions of the partial reflection mirror 24 and the output monitor unit 30 are not particularly limited to this. For example, the partial reflection mirror 24 may be provided inside the fourth housing 41 of the focusing optical unit 40, and the third housing 31 of the output monitor unit 30 may be connected to the second housing 21. In this case, in order to ensure that the first laser light LB1 is incident on the input end of the optical fiber 90, it is preferable that the partial reflection mirror 24 is disposed between the light input port 42 of the fourth housing 41 and the first focusing lens 43.

For example, if the laser oscillator 80 has one laser module 10, 11, the beam combiner 20 is omitted, and the partial reflection mirror 24 and the output monitor unit 30 are placed in the above-mentioned position.

Even if the partial reflection mirror 24 and the output monitor unit 30 are arranged in this manner, it is possible to achieve the same effects as those achieved by the configurations shown in the first and second embodiments. That is, even if the optical axis misalignment or beam profile of the second laser light _LB2 varies, the output of the first laser light _LB1 can be accurately monitored without being affected by these. In addition, the output of the first laser light _LB1 can be monitored at high speed and with high accuracy.

Also, in the second embodiment, a prism may be used instead of the diffraction grating 11C. Any optical coupling element may be used as long as it couples a plurality of emitter laser beams _LBE emitted from a plurality of emitters into one module laser beam.

The laser oscillator disclosed herein is useful because it can monitor the output of the first laser light used in laser processing at high speed and with high accuracy.

10 Laser module 11 Laser module 11A First housing 11B Laser diode bar 11C Diffraction grating (optical coupling element)
11D external cavity mirror 20 beam combiner 21 second housings 21a to 21d first to fourth light inlets 22 light outlet 23 quarter-wave plate 24 partial reflection mirror (light branching element)
25A to 25D First to fourth raising mirrors 26 Magnifying optical system 27A First reflecting mirror 27B Second reflecting mirror 28A First polarizing beam splitter 28B Second polarizing beam splitter 29 Dichroic mirror 30 Output monitor unit 30A Output monitor mechanism 31 Third housing 31a Partition wall 32 Holder 33 Second condenser lens (condensing optical element)
34 Neutral density filter (sensitivity correction filter)
35 Mixing rod (light homogenizing element)
35a: incident end surface 35b: exit end surface 36: photodetector 36a: light receiving surface 37: integrating sphere 38: reflecting mirror 39: concave mirror (light collecting optical element)
40 Condensing optical unit 41 Fourth housing 42 Light inlet 43 First condensing lens 44 Light outlet 45 First receptacle 46 First quartz block holder 47 First quartz block 48 Second quartz block holder 49 Second quartz block 50 Fifth housing 60 Control unit 61 Memory unit 62 Calculation unit 63 Display unit 70 Power supply 80 Laser oscillator 90 Optical fiber 100 Laser head 200 Laser processing device 360 Photodetector with sensitivity correction function 361 Photodetector 362 Filter (sensitivity correction filter)
HWP1, 2 1/2 Wavelength Plate W Work

Claims (16)

A laser light source that emits laser light;
a focusing optical unit that focuses a first laser beam, which is a part of the laser beam, and outputs the first laser beam to the outside;
an output monitor mechanism for monitoring an output of the first laser light,
The output monitor mechanism includes:
a light branching element that branches the laser light into the first laser light and a second laser light traveling in a direction different from that of the first laser light;
a light homogenizing element having an input end surface and an output end surface;
a focusing optical element that focuses the second laser light toward the incident end surface;
a photodetector having a light receiving surface that receives the second laser light and that outputs an output signal based on the amount of light of the received second laser light,
the photodetector is disposed such that a light receiving surface is in contact with the light emitting end surface or faces the light emitting end surface at a predetermined interval;
4. The laser oscillator according to claim 3, further comprising a control unit that calculates an output of the first laser light based on the output signal of the photodetector. 2. The laser oscillator according to claim 1,
a mixing rod that totally reflects the second laser light incident on the incident end face and guides the second laser light to the output end face; 2. The laser oscillator according to claim 1,
11. A laser oscillator, comprising: said photodetector being a photoelectric conversion element; and an area of said light receiving surface being larger than an area of said light emitting end surface. 2. The laser oscillator according to claim 1,
11. A laser oscillator according to claim 10, wherein the optical branching element is a partial reflection mirror that reflects most of the laser light and transmits the remainder. 2. The laser oscillator according to claim 1,
the output monitor mechanism further includes a focusing optical element disposed between the optical branching element and the incident end surface,
The laser oscillator according to claim 1, wherein the focusing optical element focuses the second laser light toward the incident end surface. 6. The laser oscillator according to claim 5,
a beam diameter of the second laser light in the vicinity of the incident end face being smaller than a diameter of the light receiving face; 2. The laser oscillator according to claim 1,
the output monitor mechanism further includes a light reflecting component disposed between the light branching element and the light input end surface,
the light reflecting component reflects the second laser light branched by the light branching element so that the second laser light travels in the same direction as the first laser light,
a light uniformizing element and a light detector disposed along a traveling direction of the second laser light; 8. The laser oscillator according to claim 7,
The laser oscillator according to claim 1, wherein the light reflecting component focuses the second laser light toward the incident end surface. 2. The laser oscillator according to claim 1,
the output monitor mechanism further includes a neutral density filter disposed between the optical branching element and the incident end face and in the vicinity of the incident end face;
The laser oscillator according to claim 1, wherein the attenuation filter reduces the amount of the second laser light incident on the incident end face. 2. The laser oscillator according to claim 1,
the output monitor mechanism further includes a sensitivity correction filter;
A laser oscillator characterized in that, when the wavelength region of the second laser light is within a predetermined range, the sensitivity correction filter is configured so that the light receiving sensitivity of the photodetector is constant at least within the predetermined range. 11. The laser oscillator according to claim 10,
The sensitivity correction filter is disposed between the optical branching element and the incident end face, in the vicinity of the incident end face, and reduces the amount of light of the second laser light incident on the incident end face. 11. The laser oscillator according to claim 10,
2. A laser oscillator according to claim 1, wherein the sensitivity correction filter is disposed in contact with the light receiving surface. 2. The laser oscillator according to claim 1,
The laser light source includes a laser diode bar having a plurality of emitters;
an optical coupling element for coupling a plurality of emitter laser beams emitted from the plurality of emitters;
an external cavity mirror that reflects the emitter laser light coupled by the optical coupling element toward the optical coupling element;
a first housing that houses one or more of the laser diode bars, the optical coupling element, and the external cavity mirror;
an external cavity is formed between the external cavity mirror and a rear end face of the laser diode bar;
a laser oscillator, characterized in that a module laser light generated by combining a plurality of the emitter laser lights by the optical coupling element is emitted to the outside of the first housing. 14. The laser oscillator according to claim 13,
A plurality of the laser light sources;
A laser oscillator further comprising a beam combiner that combines a plurality of module laser beams emitted from a plurality of said laser light sources to generate said laser beam. 2. The laser oscillator according to claim 1,
The control unit controls power supplied to the laser light source so that the calculated output of the first laser light becomes a predetermined target value. A laser oscillator according to any one of claims 1 to 15,
a laser head that receives the first laser light and irradiates it toward a workpiece.