WO2025263379A1 - Laser processing apparatus - Google Patents

Abstract

A laser processing apparatus comprising: a fiber laser as a light source that emits laser light; an optical fiber for propagating the laser light and thermal radiation light emitted at an irradiation point on a workpiece irradiated with the laser light; a monitor unit that is connected with the optical fiber, causes the laser light from the fiber laser to be incident on the optical fiber, receives the thermal radiation light propagated through the optical fiber, and detects the thermal radiation light; and an optical scanning unit that has a reflection surface for reflecting the laser light emitted from the optical fiber and the thermal radiation light emitted at the irradiation point, scans the workpiece with the laser light by varying the angle of the reflection surface, and causes the thermal radiation light to be incident on the optical fiber, wherein the reflection surface is made of metal material.

Description

Laser Processing Equipment

This disclosure relates to a laser processing device.

Patent Document 1 describes a wobble welding head equipped with a beam scanner that scans a laser beam based on a commanded pattern, a processing lens that focuses the laser beam scanned by the beam scanner on the surface of the workpiece, and an optical sensor that measures the intensity of at least one of the following: the intensity of the reflected light that is transmitted through the processing lens out of the light reflected from the laser beam on the surface of the workpiece, and the intensity of the plasma light that is generated by the incidence of the laser beam and transmitted through the processing lens out of the plasma light.

JP 2023-91290 A

The wobble welding head described in Patent Document 1 determines whether or not a welding defect has occurred based on the results of measuring the light intensity of the laser beam reflected from the surface of the workpiece, or the plasma light generated by the incidence of the laser beam. Furthermore, the beam scanner in this wobble welding head uses a galvanometer mirror made of quartz material with a dielectric multilayer film coated on its surface.

In a laser processing device that performs laser processing of a workpiece by irradiating the workpiece with a laser beam while scanning it, there is a need to obtain the temperature of the irradiation point by detecting the thermal radiation emitted from the portion of the workpiece that is irradiated with the laser beam (irradiation point). However, if an optical system is provided outside the optical scanning unit that scans the laser beam to detect and measure the temperature by guiding the thermal radiation from the irradiation point non-coaxially with the laser beam, only the temperature of one irradiation point can be obtained. In contrast, by making the laser beam and the thermal radiation coaxial so that the thermal radiation from the irradiation point is detected via the optical scanning unit that scans the processing laser beam, it becomes possible to obtain the temperature of each irradiation point.

In the course of researching laser processing equipment in which the processing laser beam and thermal radiation beam are coaxially aligned, the inventors discovered the following: In general, the optical scanning unit for scanning the processing laser beam uses a dielectric multilayer film designed to maximize reflectivity at the wavelength of the laser beam as the reflective surface for reflecting the laser beam. However, the reflective surface formed by the dielectric multilayer film exhibits angular dependency in the reflectivity of thermal radiation beams that contain wavelengths different from the wavelength of the processing laser beam. As a result, when the processing laser beam and thermal radiation beam are coaxially aligned, the intensity of the thermal radiation beam detected via the optical scanning unit also exhibits angular dependency, making it difficult to accurately measure the intensity of the thermal radiation beam. Furthermore, if a mirror using a dielectric multilayer film is designed to accommodate two wavelengths, one in the wavelength range of the processing laser beam and the other in the wavelength range of the thermal radiation beam, not only will the reflectivity of the processing laser beam decrease, but it will also be difficult to accommodate thermal radiation beams with broad wavelengths.

The present disclosure therefore aims to provide a laser processing device that can accurately measure the light intensity of thermal radiation light while coaxially aligning the processing laser light and thermal radiation light.

The laser processing device according to the present disclosure is [1] "a laser processing device comprising: a fiber laser as a light source that emits laser light for processing a workpiece; an optical fiber that propagates the laser light and thermal radiation light emitted at an irradiation point that is a portion of the workpiece irradiated with the laser light; a monitor unit to which the optical fiber is connected that causes the laser light from the fiber laser to enter the optical fiber and receives and detects the thermal radiation light that has propagated through the optical fiber; and an optical scanning unit that has a reflective surface that reflects the laser light emitted from the optical fiber and the thermal radiation light emitted at the irradiation point, and that varies the angle of the reflective surface with respect to the optical axis of the laser light to scan the workpiece with the laser light and cause the thermal radiation light to enter the optical fiber, wherein the reflective surface is made of a metal material."

In this laser processing device, the processing laser light from the fiber laser light source is made incident on an optical fiber by the monitor unit, and after propagating through the optical fiber, is used to scan the workpiece by the optical scanning unit. Furthermore, the thermal radiation light emitted at the part of the workpiece irradiated with the laser light (irradiation point) is made incident on the optical fiber that propagates the processing laser light via the optical scanning unit, and after propagating through the optical fiber, is detected by the monitor unit. In this way, in this laser processing device, the processing laser light and thermal radiation light are coaxially connected using a shared optical fiber and optical scanning unit, making it possible to detect the thermal radiation light from each irradiation point.

Furthermore, in this laser processing device, the reflective surfaces in the optical scanning unit that reflect the laser light and thermal radiation light are formed from a metal material. Reflective surfaces made from a metal material are less likely to exhibit angular dependency in the reflectance of thermal radiation light compared to reflective surfaces made from a dielectric multilayer film. Therefore, with this laser processing device, the monitor unit can accurately measure the light intensity of thermal radiation light.

The laser processing device according to the present disclosure may be [2] "the laser processing device described in [1] above, which is equipped with an fθ lens that focuses the laser light reflected by the reflecting surface toward the workpiece." In this case, when the laser light is reflected by the optical scanning unit and scanned onto the workpiece, the optical characteristics of the fθ lens make it possible to form a focal point of the laser light on the same plane of the workpiece.

The laser processing device according to the present disclosure may be [3] "the laser processing device described in [1] above, including a focusing unit that focuses the laser light emitted from the other end of the optical fiber opposite the one end connected to the monitor unit toward the workpiece via the optical scanning unit, and a moving unit that moves the focusing unit along the optical axis direction of the laser light." In this case, the focusing unit is moved along the optical axis direction of the laser light by the moving unit, thereby adjusting the position of the focusing point in the optical axis direction of the laser light. This makes it possible to form a focusing point of the laser light on the same plane of the workpiece when the laser light is reflected by the optical scanning unit and scanned across the workpiece.

The laser processing device according to the present disclosure may be [4] "the laser processing device described in any one of [1] to [3] above, in which the metal material contains Ag." In this case, oxidation of the reflective surface of the optical scanning unit is suppressed.

The laser processing device according to the present disclosure may be [5] "the laser processing device described in any one of [1] to [4] above, which includes a calculation unit that calculates the temperature of the irradiation point on the workpiece based on the light intensity of the thermal radiation light detected by the monitor unit." In this case, it is possible to obtain the temperature of each irradiation point based on the light intensity of the thermal radiation light detected by the monitor unit.

The laser processing device according to the present disclosure may be [6] "the laser processing device according to any one of [1] to [5] above, wherein the level of bending of the optical fiber is such that when laser light having a Gaussian beam profile is incident on one end of the optical fiber, the beam profile of the laser light emitted from the other end of the optical fiber does not change to a top hat shape." In this way, when the level of bending of the optical fiber is relatively small (i.e., when no sharp bending occurs), the laser light can be transmitted while maintaining the beam quality of the laser light incident on the optical fiber. Therefore, it is possible to emit laser light from the optical fiber with an N.A. smaller than the N.A. of the optical fiber itself.

The laser processing apparatus according to the present disclosure may be [7] "the laser processing apparatus described in [6] above, which includes an fθ lens that focuses the laser light reflected by the reflecting surface toward the work-piece, and the laser light emitted from the optical fiber is focused toward the work-piece only by the fθ lens." In this case, the laser light can be focused toward the work-piece without using any lenses other than the fθ lens.

The laser processing device according to the present disclosure may be [8] "the laser processing device described in any one of [1] to [5] above, wherein the level of bending of the optical fiber is such that when laser light having a Gaussian beam profile is incident on one end of the optical fiber, the beam profile of the laser light emitted from the other end of the optical fiber changes to a top hat shape." In this case, the beam profile of the laser light emitted from the optical fiber can be a top hat shape.

The laser processing device according to the present invention may be [9] "the laser processing device described in [8] above, comprising: a collimating lens disposed between the optical fiber and the reflecting surface, which collimates the laser light emitted from the optical fiber and focuses the thermal radiation light directed toward the optical fiber; and an fθ lens which focuses the laser light collimated by the collimating lens and reflected by the reflecting surface toward the work-piece." In this case, by bending the optical fiber as described above, even if the divergence angle of the laser light emitted from the optical fiber becomes relatively large, the laser light can be suitably focused toward the work-piece. In addition, the efficiency of focusing the thermal radiation light onto the optical fiber is improved.

The laser processing device according to the present invention may be [10] "the laser processing device according to any one of [1] to [9] above, wherein the fiber laser is configured from a multimode laser fiber." In this case, it becomes easier to make the beam profile of the laser light emitted from the optical fiber a top-hat type. Furthermore, when the optical fiber is configured as a multimode fiber to suitably couple the fiber laser with the optical fiber, there is little advantage to configuring the fiber laser as a single-mode fiber, so costs can be reduced by using a less expensive multimode fiber in the fiber laser.

The laser processing device according to the present invention may be [11] "a laser processing device according to any one of [1] to [10] above, which irradiates the laser light onto the irradiation point so that the temperature of the irradiation point becomes 400°C or higher." In this case, even if the efficiency of focusing the thermal radiation light onto the optical fiber is relatively low, it is possible to preferably detect the thermal radiation light from each irradiation point.

The laser processing apparatus according to the present disclosure may be [12] "a laser processing apparatus according to any one of [1] to [11] above, wherein the optical scanning unit has a first scanning unit that has, as the reflecting surface, a first reflecting surface that reflects the laser beam and the thermal radiation light, and scans the laser beam along a first axis that intersects with the optical axis of the laser beam by varying the angle of the first reflecting surface with respect to the optical axis of the laser beam; and a second scanning unit that has, as the reflecting surface, a second reflecting surface that reflects the laser beam and the thermal radiation light, and scans the laser beam along a second axis that intersects with the optical axis of the laser beam and the first axis by varying the angle of the second reflecting surface with respect to the optical axis of the laser beam, and wherein the first reflecting surface and the second reflecting surface are each formed of a metal material." In this case, the first scanning unit and the second scanning unit enable two-dimensional scanning of the laser beam. Furthermore, when multiple reflective surfaces are present in the optical path of the thermal radiation light from the irradiation point through the optical scanning unit to the monitor unit, if each reflective surface is made of a dielectric multilayer film, the angular dependency of the reflectance of the thermal radiation light becomes more pronounced. Therefore, it is more effective to form the reflective surfaces from a metal material.

This disclosure makes it possible to provide a laser processing device that can accurately measure the light intensity of thermal radiation light while coaxially aligning the processing laser light and thermal radiation light.

FIG. 1 is a diagram showing the configuration of a laser processing device according to this embodiment. FIG. 2 is a diagram showing the configuration of the laser processing monitor of the laser processing apparatus of FIG. FIG. 3 is a diagram showing the configuration of an optical unit of the laser processing monitor shown in FIG. FIG. 4 is a diagram showing the configuration of the laser processing head, the optical scanning unit, and the fθ lens shown in FIG. FIG. 5 is a graph showing a comparative example showing the relationship between the angle of the reflecting surface and the light intensity of the thermal radiation light when the thermal radiation light is detected via reflection on the reflecting surface formed by the dielectric multilayer film. FIG. 6 is a graph showing the relationship between the angle of the reflecting surface and the light intensity of the thermal radiation light when the thermal radiation light is detected via reflection on a reflecting surface made of a metal material according to this embodiment. FIG. 7 is a graph showing an example of a beam profile. FIG. 8 is a graph showing an example of a beam profile. FIG. 9 is a graph showing an example of a beam profile. FIG. 10 is a graph showing an example of a beam profile. FIG. 11 is a diagram showing a part of a laser processing apparatus according to a modified example. FIG. 12 is a diagram showing a part of a laser processing apparatus according to a modified example. FIG. 13 is a diagram showing a part of a laser processing apparatus according to a modified example. FIG. 14 is a diagram showing a part of a laser processing apparatus according to a modified example. FIG. 15 is a cross-sectional view showing a second optical fiber according to a modified example.

Below, one embodiment of a laser processing device will be described in detail with reference to the drawings. Note that in each drawing, identical or corresponding elements will be assigned the same reference numerals, and duplicate explanations may be omitted.

As shown in FIG. 1, the laser processing device 1 includes a fiber laser 2 serving as a light source, a first optical fiber 3, a second optical fiber (optical fiber) 4, an optical scanning unit 6, an fθ lens 7, and a laser processing monitor (monitor unit) 10. The laser processing device 1 processes (e.g., cutting, welding, surface treatment, etc.) the workpiece S using processing laser light L1a, which is a part of the laser light L1 and has a first wavelength band for processing the workpiece S. The laser processing monitor measures the temperature of the irradiation point by detecting thermal radiation light L2 (e.g., infrared light) emitted from the portion of the workpiece S irradiated with the laser light L1a (hereinafter sometimes referred to as the "irradiation point"). The laser processing device 1 can irradiate the irradiation point with laser light L1a so that the temperature of the irradiation point is 400°C or higher, for example.

The fiber laser 2 may be composed of, for example, a multimode laser fiber and emits laser light L1. The first optical fiber 3, for example, constitutes a part of the fiber laser 2 and provides the output end of the laser light L of the fiber laser 2. More specifically, the fiber laser 2 includes a semiconductor laser for excitation and an optical fiber for amplification, and the light input end face of the first optical fiber 3 can be connected to the light output end face of the optical fiber for amplification. The first optical fiber 3 may be a single-mode fiber, but is, for example, a multimode fiber. The first optical fiber 3 propagates the laser light L1 to the laser processing monitor 10. The second optical fiber 4 is, for example, a multimode fiber. Therefore, in this example, optical coupling is performed between the first optical fiber 3 and the second optical fiber 4, which are multimode fibers. In this embodiment, the N.A. of the second optical fiber 4 may be larger than the N.A. of the first optical fiber 3, and the core diameter of the second optical fiber 4 may be larger than the core diameter of the first optical fiber 3. As an example, the core diameter of the second optical fiber 4 may be 1.5 times or more and 2 times or less than the core diameter of the first optical fiber 3. As a specific example of a numerical value, the core diameter of the second optical fiber 4 may be smaller than 400 μm, or even smaller than 100 μm. Furthermore, the diameter of the beam spot at the focal point of the laser light L1a (focused size) may be smaller than 100 μm.

The second optical fiber 4 (optical fiber) propagates laser light L1a from the laser processing monitor 10 to the optical scanning unit 6. The laser light L1a propagated through the second optical fiber 4 is irradiated onto the workpiece S via the optical scanning unit 6 and fθ lens 7. Thermal radiation light L2 emitted at the irradiation point by irradiation with laser light L1a is incident on the fθ lens 7 and optical scanning unit 6. The second optical fiber 4 propagates thermal radiation light L2 from the optical scanning unit 6 to the laser processing monitor 10.

As shown in FIG. 2, the laser processing monitor 10 has a housing 11, a power supply unit 12, a circuit unit (calculation unit) 13, and an optical unit 20. The housing 11 houses the power supply unit 12, the circuit unit 13, and the optical unit 20. The power supply unit 12 supplies driving power to the circuit unit 13 from an external power source. The circuit unit 13 includes, for example, a two-color radiation thermometer or a monochromatic radiation thermometer, and calculates the temperature of the irradiation point on the workpiece S based on a detection signal including the light intensity of the thermal radiation light L2 detected by the optical unit 20.

As shown in FIG. 3, the optical unit 20 of the laser processing monitor 10 includes a first optical fiber holding unit 21, a second optical fiber holding unit 22, a first dichroic mirror 23, a second dichroic mirror 24, a light detection unit 25, a light absorption unit 26, and a housing 27.

The first optical fiber holding part 21 has a cylindrical lens holding part 21a and a flange-shaped optical fiber holding part 21b. The lens holding part 21a holds a lens 31, and the optical fiber holding part 21b holds the end of the first optical fiber 3. The lens 31 collimates the laser light L1 emitted from the end face 3a of the first optical fiber 3. The first optical fiber holding part 21 is unitized to maintain the positional relationship between the end face 3a of the first optical fiber 3 and the lens 31 and to cover the optical path formed between the end face 3a of the first optical fiber 3 and the lens 31. In the first optical fiber holding part 21, the lens 31 functions as a window material, and when the end of the first optical fiber 3 is inserted, a closed space is formed within the first optical fiber holding part 21 (between the end face 3a of the first optical fiber 3 and the lens 31).

The second optical fiber holding part 22 has a cylindrical lens holding part 22a and a flange-shaped optical fiber holding part 22b. The lens holding part 22a holds a lens 32, and the optical fiber holding part 22b holds the end of the second optical fiber 4. The lens 32 focuses the laser light L1a onto the end face 4a of the second optical fiber 4. Furthermore, the lens 32 collimates the thermal radiation light L2 emitted from the end face 4a of the second optical fiber 4. The second optical fiber holding part 22 is unitized to maintain the positional relationship between the end face 4a of the second optical fiber 4 and the lens 32 and to cover the optical path formed between the end face 4a of the second optical fiber 4 and the lens 32. In the second optical fiber holding part 22, the lens 32 functions as a window material, and when the end of the second optical fiber 4 is inserted, a closed space is formed within the second optical fiber holding part 22 (between the end face 4a of the second optical fiber 4 and the lens 32). The end face 4a of the second optical fiber 4 is coated with an AR coating to prevent the laser light L1a from becoming return light.

The first dichroic mirror 23 reflects the laser light L1a of the laser light L1 emitted from the end face 3a of the first optical fiber 3 and collimated by the lens 31. On the other hand, the first dichroic mirror 23 transmits the measurement wavelength light L1b of the laser light L1, which has a second wavelength band corresponding to the wavelength band of the thermal radiation light L2. The first dichroic mirror 23 is configured by providing a reflective layer 23a made of a dielectric multilayer film that reflects the laser light L1a and transmits the measurement wavelength light L1b on the incident surface of the laser light L1, which is made of a material that hardly absorbs the laser light L1 (e.g., synthetic quartz, etc.). The first dichroic mirror 23 has a reflectance of 90% or more for the laser light L1a and a transmittance of 90% or more for the measurement wavelength light L1b.

The second dichroic mirror 24 reflects the laser light L1a reflected by the first dichroic mirror 23. The laser light L1a reflected by the second dichroic mirror 24 is focused by the lens 32 and incident on the end face 4a of the second optical fiber 4. On the other hand, the second dichroic mirror 24 transmits the thermal radiation light L2 that is emitted from the end face 4a of the second optical fiber 4 and collimated by the lens 32. The second dichroic mirror 24 is configured by providing a reflective layer 24a made of a dielectric multilayer film that reflects the laser light L1a and transmits the thermal radiation light L2 on the incident surface of the laser light L1a made of a material that hardly absorbs the laser light L1 (e.g., synthetic quartz, etc.). The second dichroic mirror 24 has a reflectivity of 90% or more for the laser light L1a and a transmittance of 90% or more for the thermal radiation light L2.

The light detection unit 25 has a cylindrical lens holding portion 25a and a flange-shaped photodiode support portion 25b. The lens holding portion 25a holds the lens 33 and filter 34, and the photodiode support portion 25b supports the photodiode 35. The lens 33 focuses the thermal radiation light L2 that has passed through the second dichroic mirror 24 onto the photodiode 35. The filter 34 has the function of transmitting only light having a wavelength band corresponding to the wavelength band of the thermal radiation light L2. The photodiode 35 detects the thermal radiation light L2 that has been focused by the lens 33 and passed through the filter 34. A detection signal of the thermal radiation light L2 detected by the photodiode 35 is sent to the circuit unit 13. The light detection unit 25 is unitized so as to maintain the positional relationship between the lens 33, filter 34, and photodiode 35 and to cover the optical path formed between the lens 33 and photodiode 35.

Furthermore, chromatic aberration is imparted to the lens 33 so that the focusing position of the thermal radiation light L2 is located on the photodiode 35, while the focusing position of the laser light L1a is shifted from the photodiode 35 (i.e., the laser light L1a is blurred on the photodiode 35). As a result, even if the laser light L1a enters the light detection unit 25 and is focused by the lens 33, it has almost no effect on the detection of the thermal radiation light L2 by the photodiode 35.

The light absorbing section 26 absorbs the measurement wavelength light L1b that has passed through the first dichroic mirror 23. The light absorbing section 26 is a damper that absorbs light and converts it into heat. The light absorbing section 26 is positioned so that even if the measurement wavelength light L1b is reflected by the light absorbing section 26, the reflected measurement wavelength light L1b travels toward the second side wall 29b of the cover 29, which will be described later.

The housing 27 has a base 28 and a cover 29. The base 28 supports the first optical fiber holding unit 21, the second optical fiber holding unit 22, the first dichroic mirror 23, the second dichroic mirror 24, the light detection unit 25, and the light absorption unit 26. The cover 29 covers the optical path formed between the first optical fiber holding unit 21, the second optical fiber holding unit 22, the first dichroic mirror 23, the second dichroic mirror 24, the light detection unit 25, and the light absorption unit 26.

The base 28 includes a pair of first side walls 28b. The pair of first side walls 28b face each other in the X-axis direction and are arranged parallel to each other. The cover 29 includes a pair of second side walls 29b. The pair of second side walls 29b face each other in the Y-axis direction and are arranged parallel to each other. The combination of the base 28 and cover 29 forms a rectangular box-shaped housing 27. In the base 28, the thickness of each first side wall 28b is greater than the thickness of the bottom wall 28a. In addition, in the cover 29, the inner surface 29c of the cover 29, including the inner surfaces of the pair of second side walls 29b, has been subjected to a light-absorbing treatment, such as the application of black paint.

A pair of through holes 28c, 28d are formed in one first side wall 28b of the base 28. The first optical fiber holding unit 21 is provided on one first side wall 28b by fixing the optical fiber holding unit 21b to the outer surface of the one first side wall 28b with the lens holding unit 21a inserted into the through hole 28c. The second optical fiber holding unit 22 is provided on one first side wall 28b by fixing the optical fiber holding unit 22b to the outer surface of the one first side wall 28b with the lens holding unit 22a inserted into the through hole 28d. A through hole 28e is formed in the other first side wall 28b of the base 28 so as to face the through hole 28d in the X-axis direction. The light detection unit 25 is provided on the other first side wall 28b by fixing the photodiode support unit 25b to the outer surface of the other first side wall 28b with the lens holding unit 25a inserted into the through hole 28e.

Concave portions are formed on the inner surface of the bottom wall 28a for positioning the first dichroic mirror 23, the second dichroic mirror 24, and the light absorbing portion 26. The first dichroic mirror 23, the second dichroic mirror 24, and the light absorbing portion 26 are attached to the bottom wall 28a while positioned in their respective concave portions. In addition, a concave portion may be formed in each of the first dichroic mirror 23, the second dichroic mirror 24, and the light absorbing portion 26, and a convex portion may be formed on the inner surface of the bottom wall 28a to be positioned in each of the concave portions for positioning them.

As described above, the first optical fiber holding unit 21 and the second optical fiber holding unit 22 are provided on the same first side wall 28b of the pair of first side walls 28b. In other words, the first optical fiber holding unit 21 and the second optical fiber holding unit 22 are provided on the same side surface (i.e., one of the first side walls 28b) of the multiple side surfaces that make up the base 28.

The first optical fiber holding unit 21, the second optical fiber holding unit 22, the first dichroic mirror 23, the second dichroic mirror 24, the light detection unit 25, and the light absorption unit 26 are arranged along the same plane parallel to the XY plane. The first optical fiber holding unit 21 is arranged on one side of the first dichroic mirror 23, and the light absorption unit 26 is arranged on the other side of the first dichroic mirror 23. The second optical fiber holding unit 22 is arranged on one side of the second dichroic mirror 24, and the light detection unit 25 is arranged on the other side of the second dichroic mirror 24. In other words, the first optical fiber holding unit 21 and the second optical fiber holding unit 22 are arranged on the same side of the first dichroic mirror 23 and the second dichroic mirror 24, respectively.

In the optical unit 20 configured as described above, the laser light L1 propagating from the fiber laser 2 through the first optical fiber 3 is emitted from the end face 3a of the first optical fiber 3 in the first optical fiber holding unit 21, collimated by the lens 31, and travels along the X-axis direction toward the first dichroic mirror 23. Of the laser light L1 traveling toward the first dichroic mirror 23, laser light L1a having a first wavelength band for processing the workpiece S is reflected by the first dichroic mirror 23 and travels along the Y-axis direction toward the second dichroic mirror 24.

Of the laser light L1 that travels toward the first dichroic mirror 23, measurement wavelength light L1b having a second wavelength band corresponding to the wavelength band of the thermal radiation light L2 passes through the first dichroic mirror 23 and travels along the X-axis direction toward the light absorbing section 26. The measurement wavelength light L1b that travels toward the light absorbing section 26 is absorbed by the light absorbing section 26. Even if part of the measurement wavelength light L1b is reflected by the light absorbing section 26 without being absorbed by the light absorbing section 26, part of the measurement wavelength light L1b travels toward the second side wall 29b of the housing 27 and is absorbed by the inner surface 29c of the second side wall 29b, which has been treated with a light absorption coating.

Laser light L1a reflected by the first dichroic mirror 23 and traveling toward the second dichroic mirror 24 is reflected by the second dichroic mirror 24 and travels along the X-axis direction toward the second optical fiber holding unit 22. Laser light L1a reflected by the second dichroic mirror 24 and traveling toward the second optical fiber holding unit 22 is focused by the lens 32 in the second optical fiber holding unit 22 and enters the end face 4a of the second optical fiber 4, propagating through the second optical fiber 4 to the laser processing head 5. Even if part of the measurement wavelength light L1b travels toward the second dichroic mirror 24 without passing through the first dichroic mirror 23, part of the measurement wavelength light L1b passes through the second dichroic mirror 24 and travels toward the second side wall 29b of the housing 27, where it is absorbed by the inner surface 29c of the second side wall 29b, which has been treated with a light absorption agent.

Thermal radiation light L2 propagates through the second optical fiber 4 from the irradiation point on the workpiece S, exits from the end face 4a of the second optical fiber 4 in the second optical fiber holding part 22, is collimated by the lens 32, and travels along the X-axis direction toward the second dichroic mirror 24. The thermal radiation light L2 traveling toward the second dichroic mirror 24 passes through the second dichroic mirror 24 and travels along the X-axis direction toward the light detection part 25. The thermal radiation light L2 traveling toward the light detection part 25 is collected by the lens 33 in the light detection part 25, passes through the filter 34, and is detected by the photodiode 35.

In this way, the second optical fiber 4 propagates the laser light L1a for processing the workpiece S, and the thermal radiation light L2 emitted from the portion of the workpiece S irradiated with the laser light L1a (irradiation point). The laser processing monitor 10 is connected to the second optical fiber 4, and causes a portion of the laser light L1a from the fiber laser 2 to be incident on the second optical fiber 4, and receives and detects the thermal radiation light L2 that has propagated through the second optical fiber 4.

As shown in FIG. 4, the optical scanning unit 6 receives laser light L1a emitted from the end face 4b of the second optical fiber 4, opposite one end (the end face including the end face 4a) connected to the laser processing monitor 10. The optical scanning unit 6 has reflective surfaces 63s, 64s that reflect the laser light L1a emitted from the second optical fiber 4 and the thermal radiation light L2 emitted at the irradiation point, and by varying the angle of the reflective surfaces 63s, 64s with respect to the optical axis of the laser light L1, the laser light L1a is scanned over the workpiece S and the thermal radiation light L2 is incident on the second optical fiber 4.

More specifically, the optical scanning unit 6 has a first scanning unit 6A and a second scanning unit 6B. In this embodiment, the first scanning unit 6A and the second scanning unit 6B are each a galvanometer mirror. The first scanning unit 6A includes a motor 61, a mirror 63, and a rotation shaft 65. The motor 61 and the mirror 63 are connected to each other by the rotation shaft 65. The mirror 63 includes a reflective surface (first reflective surface) 63s. The mirror 63 (i.e., the reflective surface 63s) is rotated around the rotation shaft 65 via the rotation shaft 65 by the rotational drive of the motor 61, thereby causing it to oscillate.

The laser light L1a emitted from the second optical fiber 4 is incident on the reflecting surface 63s. The reflecting surface 63s is in a reference state, tilted, for example, by 45° relative to the optical axis of the laser light L1a, and is oscillated within a range of approximately ±8° relative to this reference state. The first scanning unit 6A may also have an angle detection unit, such as an encoder, for detecting the rotation angle of the rotation shaft 65 (i.e., the angle of the reflecting surface 63s).

The second scanning unit 6B includes a motor 62, a mirror 64, and a rotation shaft 66. The motor 62 and mirror 64 are connected to each other by the rotation shaft 66. The rotation shaft 66 intersects with the rotation shaft 65 of the first scanning unit 6A. As an example, the rotation shaft 65 of the first scanning unit 6A and the rotation shaft 66 of the second scanning unit 6B are perpendicular to each other. The mirror 64 includes a reflective surface (second reflective surface) 64s. The mirror 64 (i.e., the reflective surface 64s) is rotated around the rotation shaft 66 via the rotation shaft 66 by the rotation drive of the motor 62, causing it to oscillate.

Laser light L1a incident on and reflected by reflecting surface 63s is incident on reflecting surface 64s. Reflecting surface 64s is in a reference state where it is tilted, for example, 45° relative to the optical axis of laser light L1a, and is oscillated within a range of approximately ±8° relative to this reference state. The second scanning unit 6B may also have an angle detection unit, such as an encoder, for detecting the rotation angle of the rotation shaft 66 (i.e., the angle of reflecting surface 64s).

Reflective surfaces 63s, 64s are each formed from a metal material containing Al, Ag, Au, or the like. As an example, mirrors 63, 64 can be constructed by forming reflective surfaces 63s, 64s containing Ag (e.g., made of Ag) on a base formed from a glass-based material or a SiC substrate, etc.

The second scanning unit 6B reflects the laser light L1a toward the workpiece S using the reflecting surface 64s. That is, in the optical scanning unit 6, the laser light L1a emitted from the second optical fiber 4 is sequentially reflected by the reflecting surface 63s of the first scanning unit 6A and the reflecting surface 64s of the second scanning unit 6B, thereby irradiating the laser light L1a toward the workpiece S. At this time, the reflecting surfaces 63s, 64s are oscillated around mutually intersecting rotation axes 65, 66, causing the laser light L1a to scan two-dimensionally within the processing surface Sa (e.g., the front surface) of the workpiece S.

In other words, the first scanning unit 6A has a reflective surface (first reflective surface) 63s that reflects the laser light L1a and the thermal radiation light L2, and scans the laser light L1a along a first axis that intersects the optical axis of the laser light L1a by varying the angle of the reflective surface 63s with respect to the optical axis of the laser light L1a. The second scanning unit 6B has a reflective surface (second reflective surface) 64s that reflects the laser light L1a and the thermal radiation light L2, and scans the laser light L1a along a second axis that intersects the optical axis of the laser light L1a and the first axis by varying the angle of the reflective surface 64s with respect to the optical axis of the laser light L1a. The first and second axes are axes that define a plane along the processing surface Sa.

Meanwhile, the optical scanning unit 6 causes the thermal radiation light L2 from the irradiation point on the workpiece S to be incident on the second optical fiber 4 by sequentially reflecting it from the reflecting surface 64s of the second scanning unit 6B and the reflecting surface 63s of the first scanning unit 6A. As described above, the thermal radiation light L2 incident on the end surface 4b of the second optical fiber 4 propagates through the second optical fiber 4 and is detected by the laser processing monitor 10. As described above, in the laser processing device 1, the laser light L1a and the thermal radiation light L2 are completely coaxial.

The fθ lens 7 is arranged on the optical path of the laser light L1a emitted from the optical scanning unit 6. The fθ lens 7 focuses the laser light L1a emitted from the optical scanning unit 6 toward the processing surface Sa of the workpiece S, forming a focusing point Pc of the laser light L1a. The fθ lens 7 forms the focusing point Pc on the same plane regardless of the incident angle of the laser light L1a. As an example, the fθ lens 7 forms the focusing point Pc on the processing surface Sa. In this case, the irradiation point Pi on the workpiece S coincides with the focusing point Pc. Thus, in the example shown in FIG. 4, no other optical elements such as lenses are interposed between the second optical fiber 4 and the fθ lens 7, and the laser light L1a emitted from the second optical fiber 4 is focused toward the workpiece S only by the fθ lens 7. In this embodiment, the working distance of the laser processing apparatus 1 (e.g., the distance from the fθ lens 7 to the processing surface Sa) may be 2000 mm or less.

The fθ lens 7 receives the thermal radiation light L2 emitted at the irradiation point Pi, collimates the thermal radiation light L2, and directs it into the optical scanning unit 6. The thermal radiation light L2 that has entered the optical scanning unit 6 is then directed into the second optical fiber 4 as described above.

When a fiber laser 2 is used as the light source, the spot size (e.g., spot diameter) of the laser light L1a on the processing surface Sa may be as small as about 10 μm. In response to this, if the spot size of the laser light L1a on the processing surface Sa is sufficiently small compared to the desired spot size, the optical scanning unit 6 can artificially increase the spot size of the laser light L1a on the processing surface Sa by oscillating the reflecting surfaces 63s, 64s at high speed. This makes it possible to form a top-hat-like spot of the laser light L1a on the processing surface Sa. The spot shape can be any shape, such as a circular spot or a rectangular spot.

As explained above, in the laser processing device 1 according to this embodiment, laser light L1a, which is part of the processing laser light L from the fiber laser 2, is made incident on the second optical fiber 4 by the laser processing monitor 10, and after propagating through the second optical fiber 4, is used to scan the workpiece S by the optical scanning unit 6. Furthermore, thermal radiation light L2 emitted from the portion of the workpiece S irradiated with the laser light L1a (irradiation point Pi) is made incident via the optical scanning unit 6 on the second optical fiber 4 that propagates the processing laser light L1a, and after propagating through the second optical fiber 4, is detected by the laser processing monitor 10.

In this way, in the laser processing device 1, the processing laser light L1a and the thermal radiation light L2 are coaxially aligned by sharing the second optical fiber 4 and the optical scanning unit 6 (and further the fθ lens 7), making it possible to detect the thermal radiation light L2 from each irradiation point Pi that is sequentially generated by the scanning of the laser light L1a. Furthermore, in the laser processing device 1, the reflective surfaces 63s, 64s in the optical scanning unit 6 that reflect the laser light L1a and the thermal radiation light L2 are formed from a metal material. The reflective surfaces 63s, 64s made from a metal material are less likely to cause angle dependency in the reflectance of the thermal radiation light L2 compared to reflective surfaces made from a dielectric multilayer film. Therefore, the laser processing device 1 makes it possible to accurately measure the light intensity of the thermal radiation light L2 in the laser monitor unit. This point will be explained in more detail.

Figure 5 is a graph showing the relationship between the angle of the reflecting surface and the light intensity of thermal radiation light when thermal radiation light is detected via reflection on a reflecting surface formed from a dielectric multilayer film in a comparative example, and Figure 6 is a graph showing the relationship between the angle of the reflecting surface and the light intensity of thermal radiation light when thermal radiation light is detected via reflection on a reflecting surface formed from a metal material in accordance with this embodiment.

In this example, the angle of the reflecting surface is varied over a fixed time period, and so in Figures 5 and 6, the angle of the reflecting surface is represented as time (TIME). Also, in Figures 5 and 6, the light intensity of the thermal radiation light is represented as the voltage value of the detector's output signal (OUTPUT VOLTAGE). Each graph in Figures 5 and 6 shows the case where the detection position of the thermal radiation light from an object (hot plate) with a constant temperature is scanned in a circular pattern while the diameter φ is varied from 10 mm to 30 mm.

As shown in Figure 5, when thermal radiation light is detected via reflection from a reflective surface formed by a dielectric multilayer film (comparative example), it can be seen that the intensity of the thermal radiation light varies significantly depending on the angle of the reflective surface, even though the temperature of the object is constant. In particular, because the angle of the reflective surface is changed at a constant time cycle, periodic fluctuations are also observed in the intensity of the thermal radiation light.

In contrast, as shown in Figure 6, when thermal radiation light is detected via reflection on a reflective surface formed from a metal material (in the case of this embodiment), fluctuations in the light intensity of the thermal radiation light are suppressed compared to the example of Figure 5. In particular, in the example of Figure 6, periodic fluctuations in the light intensity of the thermal radiation light caused by changing the angle of the reflective surface at a fixed time cycle are suppressed. Therefore, it can be seen that the light intensity of the thermal radiation light can be detected more accurately.

Note that for convenience of illustration, Figure 1 shows the second optical fiber 4 bent twice at right angles. However, in reality, the second optical fiber 4 is not bent as extremely as shown. If the second optical fiber 4 is bent extremely, the laser light L1a incident on the second optical fiber 4 will be reflected repeatedly within the second optical fiber 4, which may increase the divergence angle of the laser light L1a emitted from the second optical fiber 4 or change the beam profile of the laser light L1a emitted from the second optical fiber 4 to a top hat shape.

In the example shown in Figures 1 and 4, the level of bending of the second optical fiber 4 is set to a level such that when laser light having a Gaussian beam profile Pr0 (see Figure 7(a)) is incident on one end of the second optical fiber 4, the beam profile of the laser light emitted from the other end of the second optical fiber 4 does not change to a top-hat beam profile Pr1 (see Figure 7(b)), as shown in Figure 7.

In this embodiment, a top-hat beam profile can be defined as follows. Figure 8 shows an example beam profile Prr. As shown in Figure 8, in this embodiment, when the region (horizontal axis) where the intensity (vertical axis) is 80% or more of the peak is defined as the top-hat determination region Wd and the region where the intensity is 50% or more of the peak is defined as the half-width Wh, if the ratio of the top-hat determination region Wd/the half-width Wh is greater than 0.8, a definition (hereinafter referred to as the "first definition") can be adopted as an example. For the beam profile Prr shown in Figure 8, the top-hat determination region Wd is 1.4 and the half-width Wh is 1.5, so 1.4/1.5 = 0.93, and the beam profile can be determined to be top-hat.

As another example of a definition, when the region (horizontal axis) where the intensity (vertical axis) is 90% or more of the peak is defined as the top hat determination region Wd, and the region where the intensity is 50% or more of the peak is defined as the half-width Wh, if the ratio of the top hat determination region Wd/half-width Wh is greater than 0.8, the beam profile may be defined as top hat (hereinafter referred to as the "second definition").

Below, we will explain whether or not each beam profile can be determined to be top-hat type in accordance with these first and second definitions. First, for beam profile Pr0 shown in Figure 7(a), the top-hat determination region Wd/half-width Wh is 0.56 under the first definition and 0.37 under the second definition. Therefore, (although this is natural given that it is a Gaussian type) beam profile Pr0 can be determined not to be top-hat type under either definition.

Next, for the beam profile Pr2 shown in Figure 9(a) (LD fiber out as an example), the top hat determination region Wd/half width Wh is 0.56 under the first definition and 0.33 under the second definition. Therefore, beam profile Pr2 can also be determined not to be top hat under either definition.

Next, for the beam profile Pr3 (top hat type in a defocused state) shown in Figure 9(b), the top hat determination region Wd/half width Wh is 0.64 under the first definition and 0.50 under the second definition. Therefore, beam profile Pr3 can also be determined not to be a top hat type under either definition.

Next, for the beam profile Pr1 shown in Figure 7(b), the top hat determination region Wd/half width Wh is 0.92 in the first definition and 0.8 in the second definition. Therefore, the beam profile Pr1 can be determined to be top hat type in either definition.

Furthermore, for the beam profile Pr4 shown in Figure 10, the top hat determination region Wd/half width Wh is 0.94 in the first definition and 0.88 in the second definition. Therefore, the beam profile Pr4 can be determined to be top hat type in either definition.

In the example beam profiles shown above, the judgment value expressed by the top hat judgment region Wd/half width Wh increases in the order of beam profile Pr0, beam profile Pr2, beam profile Pr3, beam profile Pr1, and beam profile Pr4, and exceeds 0.8 in beam profiles Pr1 and Pr4, becoming top hat shaped. In other words, as the bending level (e.g., bending radius) of the second optical fiber 4 increases, the beam profile of the laser light emitted from the second optical fiber 4 changes in the order of beam profile Pr0, beam profile Pr2, beam profile Pr3, beam profile Pr1, and beam profile Pr4, and once a certain bending level is exceeded, top hat beam profiles Pr1, Pr4, etc. may occur.

In other words, in this embodiment, when laser light having a Gaussian beam profile is incident on one end of the second optical fiber 4, the bending is limited to a level that prevents the beam profile of the laser light emitted from the other end from becoming a top hat beam profile such as beam profiles Pr1 or Pr4. In other words, in this embodiment, when laser light having a Gaussian beam profile is incident on one end of the second optical fiber 4, the bending is limited to a level that prevents the judgment value of the beam profile of the laser light emitted from the other end (top hat judgment region Wd/half width Wh) from becoming greater than 0.8.

In this way, by making the level of bending of the second optical fiber 4 relatively small (i.e., by preventing sharp bending), it is possible to transmit the laser light L1a incident on the second optical fiber while maintaining the beam quality of the laser light L1a. As a result, it is possible to emit laser light L1a from the second optical fiber 4 with an N.A. smaller than the N.A. of the second optical fiber 4 itself.

The laser processing device 1 according to this embodiment also includes an fθ lens 7 that focuses the laser light L1a reflected by the reflecting surfaces 63s, 64s toward the workpiece S. Therefore, when the laser light L1 is reflected by the optical scanning unit 6 and scanned across the workpiece S, the optical characteristics of the fθ lens 7 make it possible to form a focusing point Pc of the laser light L1a on the same plane (processing surface Sa) of the workpiece S. In particular, with the laser processing device 1 according to this embodiment, the laser light L1a emitted from the second optical fiber 4 is focused toward the workpiece S only by the fθ lens 7.

Furthermore, in the laser processing device 1 according to this embodiment, the metal material that makes up the reflective surfaces 63s, 64s contains Ag (for example, consists of Ag). This prevents oxidation of the reflective surfaces 63s, 64s of the optical scanning unit 6. Note that the thickness of the reflective surfaces 63s, 64s (i.e., the thickness of the layer made of metal material formed on the base) can be set to, for example, 1 μm or more, from the standpoint of sufficiently reflecting the laser light L1a and thermal radiation light L2.

Furthermore, in the laser processing device 1 according to this embodiment, the laser processing monitor 10 includes a circuit unit 13 that calculates the temperature of the irradiation point Pi on the workpiece S based on the light intensity of the thermal radiation light L2 detected by the photodiode 35. This makes it possible to obtain the temperature of each irradiation point Pi based on the light intensity of the thermal radiation light L2.

Furthermore, in the laser processing device 1 according to this embodiment, the optical scanning unit 6 includes a first scanning unit 6A having a reflective surface 63s that reflects the laser light L1a and the thermal radiation light L2, and scanning the laser light L1a along a first axis that intersects with the optical axis of the laser light L1a by varying the angle of the reflective surface 63s with respect to the optical axis of the laser light L1a; and a second scanning unit 6B having a reflective surface 64s that reflects the laser light L1a and the thermal radiation light L2, and scanning the laser light L1a along a second axis that intersects with the optical axis of the laser light L1a and the first axis by varying the angle of the reflective surface 64s with respect to the optical axis of the laser light L1a. The reflective surfaces 63s and 64s are each made of a metal material.

This makes it possible for the first and second scanning units to perform two-dimensional laser light scanning. That is, in this embodiment, the optical scanning unit 6 is configured as a two-dimensional galvanometer mirror. Furthermore, when multiple reflecting surfaces 63s, 64s are present in the optical path of the thermal radiation light L2 from the irradiation point Pi to the laser processing monitor 10 via the optical scanning unit 6, if each reflecting surface is made of a dielectric multilayer film, the angular dependency of the reflectance of the thermal radiation light L2 will have a greater effect. Therefore, it is more effective to form the reflecting surfaces 63s, 64s from a metal material.

The above embodiment describes one aspect of the laser processing device according to the present disclosure. Therefore, the present disclosure is not limited to the laser processing device 1 according to the above embodiment, and can be modified as desired.

For example, as shown in FIG. 11, the laser processing apparatus 1 may further include a collimating lens 51 disposed between the second optical fiber 4 and the reflecting surfaces 63s, 64s. The collimating lens 51 collimates the laser light L1a emitted from the second optical fiber 4 and focuses the thermal radiation light L2 directed toward the second optical fiber 4 (via the reflecting surfaces 63s, 64s).

Furthermore, in the example of FIG. 11, the core diameter of the second optical fiber 4 is made relatively small. Specifically, the core diameter of the second optical fiber 4 is larger than the core diameter of the first optical fiber 3 that provides the output end of the laser light L of the fiber laser 2, and can be smaller than the core diameter of the optical fiber connected to a laser diode (fiber-out LD) if the light source is to be replaced by the fiber laser 2.

With this configuration, even when it is difficult to maintain the beam quality of the laser light L1a, such as when the second optical fiber 4 is unintentionally bent, a decrease in beam quality can be suppressed by making the core diameter of the second optical fiber 4 relatively small. Furthermore, even if the divergence angle of the laser light L1a emitted from the second optical fiber 4 increases due to a decrease in beam quality, by providing a collimating lens 51 downstream of the second optical fiber 4, the collimating lens 51 and the fθ lens 7 can effectively focus the laser light L1a toward the workpiece S. Furthermore, because the collimating lens 51 focuses the thermal radiation light L2 toward the second optical fiber 4, the focusing efficiency of the thermal radiation light L2 toward the second optical fiber 4 is improved.

In the example of Figure 11, the core diameter of the second optical fiber 4 may be, for example, smaller than 400 μm, or, for another example, smaller than 100 μm. Furthermore, the diameter of the beam spot at the focal point of the laser light L1a (focused size) may be smaller than 100 μm. Furthermore, the working distance of the laser processing device 1 may be 500 mm or less.

Here, when the laser processing apparatus 1 has a collimating lens 51, the second optical fiber 4 may include a bent portion 4p, as shown in FIG. 12. In the example of FIG. 12, the level of bending of the second optical fiber 4 is set to a level at least at the bent portion 4p such that when laser light having a Gaussian beam profile is incident on one end of the second optical fiber 4, the beam profile of the laser light emitted from the other end of the second optical fiber 4 changes to a top hat shape. In this case, the beam profile of the laser light L1a emitted from the second optical fiber 4 can be made to be a top hat shape.

Also, in the example of Figure 12, even if the divergence angle of the laser light L1a emitted from the second optical fiber 4 increases, by providing a collimating lens 51 downstream of the second optical fiber 4, the collimating lens 51 and the fθ lens 7 can effectively focus the laser light L1a toward the workpiece S. Furthermore, because the thermal radiation light L2 is focused toward the second optical fiber 4 by the collimating lens 51, the focusing efficiency of the thermal radiation light L2 toward the second optical fiber 4 is improved.

In the example of Figure 12, the core diameter of the second optical fiber 4 may be, for example, greater than 100 μm. Furthermore, the diameter of the beam spot at the focal point of the laser light L1a (focused size) may be greater than 100 μm. Furthermore, the working distance of the laser processing device 1 may be 500 mm or less.

In the above embodiment, the laser processing device 1 is equipped with an fθ lens 7, and the optical scanning unit 6 and the fθ lens 7 form a two-dimensional galvano system. However, the laser processing device 1 may also be configured as a three-dimensional galvano system. Figures 13 and 14 are configuration diagrams of three-dimensional galvano systems according to modified examples.

In the example shown in Figures 13 and 14, the laser processing device 1 differs from the above embodiment in that it includes a focusing head 53 (focusing unit), further includes a motor (moving unit) 55, and does not include an fθ lens 7.

The focusing head 53 focuses the laser light L1a emitted from the end face 4b of the second optical fiber 4 via the optical scanning unit 6 toward the workpiece S using the lens 54. A motor 55 moves the focusing head 53 along the optical axis direction of the laser light L1a. In Figure 13, the position of the focusing head 53 in the optical axis direction of the laser light L1a is set to a first position A1 where a focal point Pc1 of the laser light L1a is formed on the processing surface Sa when the reflecting surfaces 63s, 64s of the optical scanning unit 6 are both in the reference state and the laser light L1a is reflected at the center of the reflecting surfaces 63s, 64s.

When the focusing head 53 is at the first position A1 and the angle of the reflecting surfaces 63s, 64s relative to the optical axis of the laser light L1a is varied from the reference state, the focal point Pc2 of the laser light L1a reflected by the reflecting surfaces 63s, 64s at the angle varied from the reference state deviates from the processing surface Sa. In contrast, as shown in FIG. 14, by moving the focusing head 53 to the second position A2 by the motor 55 along the optical axis direction of the laser light L1a, the focal point Pc2 of the laser light L1a reflected by the reflecting surfaces 63s, 64s at the angle varied from the reference state can be positioned on the processing surface Sa.

At this time, when the laser beam L1a is reflected at the center of the reflecting surfaces 63s, 64s in the reference state, the focal point Pc1 of the laser beam L1a deviates from the processing surface Sa. Therefore, by synchronizing the oscillation (angle change) of the reflecting surfaces 63s, 64s with the movement of the focusing head 53 by the motor 55, it is possible to form the focal point Pc of the laser beam L1a on the same plane, regardless of the angle of the reflecting surfaces 63s, 64s, without using the fθ lens 7.

In this way, in the example shown in Figures 13 and 14, the first scanning unit 6A and second scanning unit 6B of the optical scanning unit 6 scan the focal point Pc of the laser light L1a two-dimensionally along a first axis and a second axis that intersect with the optical axis direction of the laser light L1a, and the motor 55 moves the focusing head 53, making it possible to scan the focal point Pc of the laser light L1a along the optical axis direction of the laser light L1a, thereby forming a three-dimensional galvano system. In other words, the optical scanning unit 6, the focusing head 53 (focusing unit), and the motor 55 (moving unit) can form a 3D galvano scanner.

In the examples of Figures 13 and 14, the core diameter of the second optical fiber 4 may be, for example, smaller than 400 μm, or, for another example, smaller than 100 μm. Furthermore, the diameter of the beam spot at the focal point of the laser light L1a (focused size) may be smaller than 100 μm. Furthermore, the working distance of the laser processing device 1 may be 200 mm or less.

Furthermore, in the laser processing device 1, the optical scanning unit 6 is not limited to a two-dimensional or three-dimensional galvano system including at least a first scanning unit 6A and a second scanning unit 6B, but may also be configured to scan the laser light L1a in one dimension.

Furthermore, the laser processing device 1 may be configured to output the detection signal of the photodiode 35 to the outside, for example, so that it does not need to include a calculation unit (circuit unit 13 in the above embodiment) that calculates the temperature of the irradiation point Pi based on the light intensity of the thermal radiation light L2.

In the above laser processing apparatus 1, the second optical fiber 4 may be configured as shown in FIG. 15. That is, in the example of FIG. 15, the second optical fiber 4 includes a core 41, a cladding 42 covering the core 41, and a coating layer 43 covering the cladding 42. The laser light L1a propagates through the core 41, and the thermal radiation light L2 propagates not only through the core 41 but also through the cladding 42, and is totally reflected at the interface between the cladding 42 and the coating layer 43. In this case, the refractive index of the material of the cladding 42 is greater than the refractive index of the material of the coating layer 43. As an example, the material of the core 41 is pure quartz, the material of the cladding 42 is low-refractive-index quartz, and the material of the coating layer 43 is silicone resin. As an example, the outer diameter of the core 41 is 100 μm, the outer diameter of the cladding 42 is 500 μm, and the thickness of the coating layer 43 is 100 μm.

If the outer diameter of the core 41 is D1 and the outer diameter of the cladding 42 is D2, the second optical fiber 4 satisfies (D2 - D1) > D1 at least at the end face 4a or end face 4b on the laser processing monitor 10 side. As an example, the second optical fiber 4 may satisfy (D2 - D1) > D1 from end face 4a to end face 4b. Furthermore, the second optical fiber 4 may satisfy (D2 - D1) ≧ (D1 × 1.5) from end face 5a to end face 5b.

In this case, because the second optical fiber 4 satisfies (D2 - D1) > D1 (D1: outer diameter of the core 41, D2: outer diameter of the cladding 42) at its end face 4a facing the laser processing monitor 10, the heat capacity of the portion of the laser processing monitor 10 consisting of the core 41 and cladding 42 is increased, making it less likely for heat to concentrate even if it is generated. As a result, the temperature rise at the end face 4a due to the incidence of the laser light L1a is suppressed, and the generation of thermal radiation light at the end face 4a is suppressed. Therefore, in the laser processing monitor 10, the thermal radiation light L2 emitted from the end face 4a is less likely to be obscured by the thermal radiation light (noise light) emitted at the end face 4a due to the incidence of the laser light L1a. Therefore, in this case, the thermal radiation light L2 can be detected with high accuracy.

Furthermore, because the second optical fiber 4 satisfies (D2 - D1) > D1 (D1: outer diameter of the core 41, D2: outer diameter of the cladding 42) at the end face 4a, the temperature rise at the end face 4a caused by the incidence of the laser light L1a is suppressed, thereby preventing damage to the end face 4a due to the incidence of the laser light L1a.

Furthermore, the second optical fiber 4 may satisfy the relationship (D2 - D1) > D1 (D1: outer diameter of the core 41, D2: outer diameter of the cladding 42) from the end face 4a to the end face 4b. In this case, even if the center of the incident area of the laser light L1a at the end face 4a is offset from the center of the core 41, the intensity of the laser light L1a propagating through the cladding 42 of the second optical fiber 4 can be prevented from exceeding the processing threshold. In other words, even if the center of the incident area of the laser light L1a at the end face 4a is offset from the center of the core 41, the workpiece S can be processed with high precision by the laser light L1a propagating through the core 41 of the second optical fiber 4. Furthermore, the thermal radiation light L2 emitted at the irradiation point of the laser light L1a on the workpiece S can be propagated not only through the core 41 of the second optical fiber 4, but also through the cladding 42 of the second optical fiber 4, which is secured to be sufficiently wide from end face 4b to end face 4a, so the thermal radiation light L2 emitted at the irradiation point can be reliably detected.

Furthermore, in this case, because the outer diameter of the cladding 42 of the second optical fiber 4 is large, even if laser light L1a leaks from the core 41 into the cladding 42, the emission area of the component of laser light L1a propagating through the cladding 42 becomes large, and the component becomes diluted to a negligible level. Therefore, even if laser light L1a leaks from the core 41 into the cladding 42, the beam profile of the laser light L1a is unlikely to be deformed.

Furthermore, in this case, if the second optical fiber 4 satisfies (D2 - D1) > D1 (D1: outer diameter of the core 41, D2: outer diameter of the cladding 42) at the end face 4b on the side of the reflecting surfaces 63s and 64s, then, as described above, the thermal radiation light L2 incident not only on the core 41 but also on the cladding 42 can be detected by the laser processing monitor 10. Therefore, even if the core diameter of the second optical fiber 4 is reduced, the thermal radiation light L2 can be suitably measured.

Furthermore, the second optical fiber 4 may further include a coating layer 43 covering the clad 42, and the thermal radiation light L2 propagating from the end face 4b to the laser processing monitor 10 may be totally reflected at the interface between the clad 42 and the coating layer 43. In this case, the thermal radiation light L2 emitted at the irradiation point of the laser light L1a on the workpiece S can be reliably propagated in the clad 42 of the second optical fiber 4, which is secured to be sufficiently wide from the end face 4b to the end face 4a.

Furthermore, the refractive index of the material of the cladding 42 may be greater than the refractive index of the material of the coating layer 43. In this case, the thermal radiation light L2 emitted at the irradiation point of the laser light L1a on the workpiece S can be reliably propagated through the cladding 42 of the second optical fiber 4, which is secured to be sufficiently wide from end face 4b to end face 4a.

Furthermore, the second optical fiber 4 may satisfy (D2 - D1) ≧ (D1 × 1.5) at least at the end face 4a. In this case, the laser processing monitor 10 can more reliably suppress the temperature rise at the end face 4a caused by the incidence of the laser light L1a, and more reliably suppress the generation of thermal radiation light at the end face 4a. As a result, the thermal radiation light L2 emitted at the irradiation point of the laser light L1a on the workpiece S can be detected with greater accuracy.

Furthermore, the outer diameter of the core 41 included in the second optical fiber 4 may be 200 μm or less. In this case, the laser light L1a propagating through the core 41 of the second optical fiber 4 can be focused into a sufficiently small spot, thereby improving the processing accuracy using the laser light L1a.

Furthermore, the outer diameter of the core included in the first optical fiber 3 may be substantially equal to the outer diameter of the core 41 included in the second optical fiber 4. In this case, the beam diameter of the laser light L1a propagating through the first optical fiber 3 can be maintained in the second optical fiber 4, thereby improving the processing accuracy using the laser light L1a.

In addition, in the above-described laser processing device 1, the reflecting surfaces 63s, 64s may be made of a material other than a metal material, such as a dielectric multilayer film.

1...laser processing device, 2...fiber laser, 4...second optical fiber (optical fiber), 6...optical scanning unit, 7...fθ lens, 10...laser processing monitor (monitor unit), 13...circuit unit (calculation unit), 51...collimating lens, 53...focusing head (focusing unit), 55...motor (movement unit), 63s...reflecting surface (first reflecting surface), 64s...reflecting surface (second reflecting surface), L1a...laser light, L2...thermal radiation light, S...object to be processed.

Claims (12)

a fiber laser as a light source that emits laser light for processing an object to be processed;
an optical fiber that propagates the laser light and thermal radiation light emitted from an irradiation point that is a portion of the object that is irradiated with the laser light;
a monitor unit to which the optical fiber is connected, the monitor unit causing the laser light from the fiber laser to enter the optical fiber, and receiving the thermal radiation light that has propagated through the optical fiber and detecting the thermal radiation light;
an optical scanning unit having a reflecting surface that reflects the laser light emitted from the optical fiber and the thermal radiation light emitted at the irradiation point, and that scans the laser light over the workpiece and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflecting surface with respect to the optical axis of the laser light;
Equipped with
The reflecting surface is formed of a metal material.
Laser processing equipment. an fθ lens that focuses the laser light reflected by the reflecting surface toward the object to be processed;
The laser processing device according to claim 1 . a focusing unit that focuses the laser light emitted from the other end of the optical fiber opposite to the one end connected to the monitor unit toward the object via the optical scanning unit;
a moving unit for moving the focusing unit along the optical axis of the laser light;
Equipped with
The laser processing device according to claim 1 . The metal material includes Ag.
The laser processing device according to any one of claims 1 to 3. a calculation unit that calculates a temperature of the irradiation point based on the light intensity of the thermal radiation light detected by the monitor unit,
The laser processing device according to any one of claims 1 to 4. the level of bending of the optical fiber is smaller than the level at which, when laser light having a Gaussian beam profile is incident on one end of the optical fiber, the beam profile of the laser light emitted from the other end of the optical fiber changes to a top hat profile;
The laser processing device according to any one of claims 1 to 5. an fθ lens that focuses the laser light reflected by the reflecting surface toward the object to be processed,
The laser light emitted from the optical fiber is focused toward the object to be processed only by the fθ lens.
The laser processing device according to claim 6. the level of bending of the optical fiber is such that when laser light having a Gaussian beam profile is incident on one end of the optical fiber, the beam profile of the laser light emitted from the other end of the optical fiber changes to a top hat shape;
The laser processing device according to any one of claims 1 to 5. a collimating lens disposed between the optical fiber and the reflecting surface, for collimating the laser light emitted from the optical fiber and for collecting the thermal radiation light directed toward the optical fiber;
an fθ lens that focuses the laser light collimated by the collimator lens and reflected by the reflecting surface toward the object;
Equipped with
The laser processing device according to claim 8. The fiber laser is composed of a multimode laser fiber.
The laser processing device according to any one of claims 1 to 9. irradiating the irradiation point with the laser light so that the temperature of the irradiation point becomes 400°C or higher;
The laser processing device according to any one of claims 1 to 10. The optical scanning unit
a first scanning unit having a first reflecting surface as the reflecting surface that reflects the laser beam and the thermal radiation light, and scanning the laser beam along a first axis that intersects with the optical axis of the laser beam by varying an angle of the first reflecting surface with respect to the optical axis of the laser beam;
a second scanning unit having a second reflecting surface as the reflecting surface that reflects the laser beam and the thermal radiation light, and scanning the laser beam along a second axis that intersects with the optical axis of the laser beam and the first axis by varying an angle of the second reflecting surface with respect to the optical axis of the laser beam;
and
the first reflecting surface and the second reflecting surface are each formed of a metal material.
The laser processing device according to any one of claims 1 to 11.