Laser processing device

Abstract

This laser processing device includes: a light source that emits laser light; an optical fiber that propagates the laser light and heat radiation light emitted at an irradiation point which is on an object to be processed and which is irradiated with the laser light; a monitor unit, to which the optical fiber is connected, causes the laser light from the light source to enter the optical fiber, receives the entry of the heat radiation light propagated through the optical fiber, and detects the heat radiation light; and an optical scanning unit that includes a reflection surface for reflecting the laser light emitted from the optical fiber and the heat radiation light emitted at the irradiation point, scans the object to be processed with the laser light by varying an angle of the reflection surface, and causes the heat radiation light to enter the optical fiber. The reflection surface is formed of a metal material.

Description

Laser Processing Equipment

[0001] The present disclosure relates to a laser processing apparatus.

[0002] Patent Document 1 describes a wobble welding head that includes 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 by 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.

[0003] JP 2023-91290 A

[0004] The wobble welding head described in Patent Document 1 determines whether or not a welding defect has occurred based on the measurement results of 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. The beam scanner in this wobble welding head uses a galvanometer mirror made of quartz material coated with a dielectric multilayer film.

[0005] 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 irradiated with the laser beam (the irradiation point). However, if an optical system is provided outside the optical scanning unit for scanning the laser beam to detect the thermal radiation from the irradiation point 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 for scanning the processing laser beam, it becomes possible to obtain the temperature of each irradiation point.

[0006] The inventors have discovered the following while conducting research into a laser processing apparatus in which the processing laser beam and the thermal radiation beam are coaxially aligned as described above. Specifically, an optical scanning unit for scanning the processing laser beam typically uses a dielectric multilayer film designed to maximize the reflectivity at the wavelength of the laser beam as a 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 having wavelengths different from that of the processing laser beam. As a result, when the processing laser beam and the 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, when a mirror using a dielectric multilayer film is designed to accommodate two wavelengths, that is, the wavelength region of the processing laser beam and the wavelength region of the thermal radiation beam, the reflectivity of the processing laser beam decreases due to the design, and it is difficult to accommodate thermal radiation beams having a broad wavelength.

[0007] Therefore, an object of the present disclosure is 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.

[0008] The laser processing device according to the present disclosure is [1] "a laser processing device comprising: 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 light source to enter the optical fiber and that 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."

[0009] In this laser processing device, processing laser light from a light source is made incident on an optical fiber by a monitor unit, and after propagating through the optical fiber, is used to scan the workpiece by an optical scanning unit. Furthermore, thermal radiation light emitted from a portion 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. In this way, in this laser processing device, the processing laser light and thermal radiation light are coaxially connected using a common optical fiber and optical scanning unit, making it possible to detect thermal radiation light from each irradiation point.

[0010] Furthermore, in this laser processing device, the reflective surfaces of the optical scanning unit that reflect the laser light and thermal radiation light are made of a metal material. Reflective surfaces made of a metal material are less likely to exhibit angle dependency in the reflectance of thermal radiation light compared to reflective surfaces made of a dielectric multilayer film. Therefore, with this laser processing device, the monitor unit can accurately measure the light intensity of the thermal radiation light.

[0011] The laser processing apparatus according to the present disclosure may be [2] "the laser processing apparatus according to the above [1], including 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.

[0012] The laser processing apparatus according to the present disclosure may be [3] "the laser processing apparatus described in [1] above, including 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 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 moving unit moves the focusing unit along the optical axis direction of the laser light, 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.

[0013] The laser processing apparatus according to the present disclosure may be [4] "the laser processing apparatus according to 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.

[0014] The laser processing apparatus according to the present disclosure may be [5] "the laser processing apparatus according to any one of the above [1] to [4], including 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.

[0015] The laser processing apparatus according to the present disclosure may be the laser processing apparatus according to any one of [1] to [5] above, [6] "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 intersecting 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 intersecting 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, 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 reflecting surfaces are present in the optical path of the thermal radiation light from the irradiation point to the monitor via the optical scanning unit, if each reflecting surface is made of a dielectric multilayer film, the angle dependency of the reflectance of the thermal radiation light becomes more pronounced, and therefore it is more effective to form the reflecting surfaces from a metal material.

[0016] According to the present disclosure, it is 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.

[0017] FIG. 1 is a configuration diagram of a laser processing apparatus according to this embodiment. FIG. 2 is a configuration diagram of a laser processing monitor of the laser processing apparatus of FIG. 1. FIG. 3 is a configuration diagram of an optical unit of the laser processing monitor of FIG. 2. FIG. 4 is a configuration diagram of the laser processing head, optical scanning unit, and fθ lens of FIG. 1. FIG. 5 is a graph according to a comparative example showing the relationship between the angle of a reflecting surface and the light intensity of thermal radiation light when thermal radiation light is detected via reflection on a reflecting surface formed of a dielectric multilayer film. FIG. 6 is a graph showing the relationship between the angle of a reflecting surface and the light intensity of thermal radiation light when thermal radiation light is detected via reflection on a reflecting surface formed of a metal material according to this embodiment. FIG. 7 is a configuration diagram of a three-dimensional galvano system according to a modified example. FIG. 8 is a configuration diagram of a three-dimensional galvano system according to a modified example. FIG. 9 is a configuration diagram of a galvano system according to another modified example. FIG. 9 is a configuration diagram of a galvano system according to another modified example.

[0018] Hereinafter, an embodiment of a laser processing apparatus will be described in detail with reference to the drawings. In each drawing, identical or corresponding elements are designated by the same reference numerals, and redundant explanations may be omitted.

[0019] 1, the laser processing apparatus 1 includes a light source 2, a first optical fiber 3, a second optical fiber (optical fiber) 4, a laser processing head 5, an optical scanning unit 6, an fθ lens 7, and a laser processing monitor (monitor unit) 10. The laser processing apparatus 1 processes (e.g., cutting, welding, surface treatment, etc.) the workpiece S using a processing laser beam L1a of the laser beam L1 having 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, etc.) emitted from a portion of the workpiece S irradiated with the laser beam L1a (hereinafter, sometimes referred to as the "irradiation point").

[0020] The light source 2 includes, for example, a laser diode, and emits laser light L1. The first optical fiber 3 propagates the laser light L1 from the light source 2 to the laser processing monitor 10. The second optical fiber 4 propagates laser light L1a from the laser processing monitor 10 to the laser processing head 5. Furthermore, the laser processing head 5 irradiates the workpiece S with the laser light L1a propagated through the second optical fiber 4 via the optical scanning unit 6 and the fθ lens 7. Thermal radiation light L2 emitted from the irradiation point by irradiation with the laser light L1a is incident on the fθ lens 7, the optical scanning unit 6, and the laser processing head 5. The second optical fiber 4 propagates the thermal radiation light L2 from the laser processing head 5 to the laser processing monitor 10.

[0021] 2 , the laser processing monitor 10 has a box 11, a power supply unit 12, a circuit unit (calculation unit) 13, and an optical unit 20. The box 11 houses the power supply unit 12, the circuit unit 13, and the optical unit 20. The power supply unit 12 supplies driving power from an external power source to the circuit unit 13. 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.

[0022] As shown in Figure 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.

[0023] 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 so as 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 by inserting the end of the first optical fiber 3, 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).

[0024] 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 on 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 by inserting the end of the second optical fiber 4, 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 provided with an AR coating to prevent the laser light L1a from becoming a return light.

[0025] The first dichroic mirror 23 reflects the laser beam L1a of the laser beam 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 beam L1b of the laser beam L1, which has a second wavelength band corresponding to the wavelength band of the thermal radiation beam L2. The first dichroic mirror 23 is configured by providing a reflective layer 23a made of a dielectric multilayer film that reflects the laser beam L1a and transmits the measurement wavelength beam L1b on the incident surface of the laser beam L1, the reflective layer 23a being made of a material that hardly absorbs the laser beam L1 (e.g., synthetic quartz). The first dichroic mirror 23 has a reflectance of 90% or more for the laser beam L1a and a transmittance of 90% or more for the measurement wavelength beam L1b.

[0026] 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 collected by a 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, the reflective layer 24a being made of a material that hardly absorbs the laser light L1 (e.g., synthetic quartz). The second dichroic mirror 24 has a reflectance of 90% or more for the laser light L1a and a transmittance of 90% or more for the thermal radiation light L2.

[0027] 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 a lens 33 and a filter 34, and the photodiode support portion 25b supports a 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, the filter 34, and the photodiode 35 and to cover the optical path formed between the lens 33 and the photodiode 35.

[0028] The lens 33 is given chromatic aberration 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 will have almost no effect on the detection of the thermal radiation light L2 by the photodiode 35.

[0029] 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 a second side wall 29b of the cover 29, which will be described later.

[0030] 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 absorbing 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 absorbing unit 26.

[0031] The base 28 includes a pair of first side walls 28b. The pair of first side walls 28b are opposed to 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 are opposed to each other in the Y-axis direction and are arranged parallel to each other. The base 28 and cover 29 are combined to form 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, an inner surface 29c of the cover 29, including the inner surfaces of the pair of second side walls 29b, is subjected to a light-absorbing treatment, such as the application of black paint.

[0032] 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.

[0033] The inner surface of the bottom wall 28a has recesses formed therein 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 being disposed in the respective recesses. Note that recesses may be formed in the first dichroic mirror 23, the second dichroic mirror 24, and the light absorbing portion 26, and protrusions to be disposed in the respective recesses for positioning them may be formed on the inner surface of the bottom wall 28a.

[0034] As described above, the first optical fiber holding part 21 and the second optical fiber holding part 22 are provided on the same first side wall 28 b of the pair of first side walls 28 b. In other words, the first optical fiber holding part 21 and the second optical fiber holding part 22 are provided on the same side surface (i.e., one of the first side walls 28 b) of the multiple side surfaces that make up the base 28.

[0035] 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.

[0036] In the optical unit 20 configured as described above, the laser light L1 propagating from the light source 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.

[0037] 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 that has been subjected to a light absorbing treatment.

[0038] The laser light L1a that is reflected by the first dichroic mirror 23 and travels 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. The laser light L1a that is reflected by the second dichroic mirror 24 and travels toward the second optical fiber holding unit 22 is collected by the lens 32 in the second optical fiber holding unit 22, enters the end face 4a of the second optical fiber 4, and propagates through the second optical fiber 4 to the laser processing head 5. Even if a portion of the measurement wavelength light L1b travels toward the second dichroic mirror 24 without passing through the first dichroic mirror 23, a portion 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, and is absorbed by the inner surface 29c of the second side wall 29b that has been subjected to a light-absorbing treatment.

[0039] The thermal radiation light L2 propagating through the second optical fiber 4 from the irradiation point on the workpiece S is emitted from the end face 4a of the second optical fiber 4 in the second optical fiber holding part 22, 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 detecting part 25. The thermal radiation light L2 traveling toward the light detecting part 25 is collected by the lens 33 in the light detecting part 25, passes through the filter 34, and is detected by the photodiode 35.

[0040] In this way, the second optical fiber 4 propagates the laser light L1a for processing the work-piece S and the thermal radiation light L2 emitted from the portion (irradiation point) of the work-piece S that is irradiated with the laser light L1a. The laser processing monitor 10 is connected to the second optical fiber 4, and causes a portion of the laser light L1a from the light source 2 to be incident on the second optical fiber 4, and receives the thermal radiation light L2 that has propagated through the second optical fiber 4 and detects the thermal radiation light L2.

[0041] 4, the laser processing head 5 has a head unit 51 including a lens 52. The head unit 51 collimates the laser light L1a emitted from the end face 4b of the second optical fiber 4 opposite to the end (end including the end face 4a) connected to the laser processing monitor 10, using the lens 52, and emits the collimated laser light L1a toward the optical scanning unit 6. The head unit 51 also collects the thermal radiation light L2 from the optical scanning unit 6 using the lens 52, and causes the collected light to be incident on the end face 4b of the second optical fiber 4.

[0042] 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 relative 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 made incident on the second optical fiber 4 (via the laser processing head 5).

[0043] 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 drive of the motor 61, thereby oscillating.

[0044] The laser beam L1a emitted from the laser processing head 5 is incident on the reflecting surface 63s. The reflecting surface 63s is tilted, for example, 45° relative to the optical axis of the laser beam L1a as a reference state, and is oscillated within a range of approximately ±8° relative to the reference state. The first scanning unit 6A may include 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).

[0045] The second scanning unit 6B includes a motor 62, a mirror 64, and a rotation shaft 66. The motor 62 and the 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, thereby causing it to oscillate.

[0046] The laser beam L1a incident on the reflecting surface 63s and reflected by the reflecting surface 63s is incident on the reflecting surface 64s. The reflecting surface 64s is in a reference state, for example, tilted 45° with respect to the optical axis of the laser beam L1a, and is oscillated within a range of approximately ±8° from the reference state. The second scanning unit 6B may have an angle detection unit, such as an encoder, for detecting the rotation angle of the rotation shaft 66 (i.e., the angle of the reflecting surface 64s).

[0047] The reflecting surfaces 63s, 64s are each formed of a metal material containing Al, Ag, Au, etc. As an example, the mirrors 63, 64 can be configured by forming the reflecting surfaces 63s, 64s containing Ag (for example, made of Ag) on ​​a base body formed of a glass-based material, a SiC substrate, or the like.

[0048] The second scanning unit 6B uses the reflecting surface 64s to reflect the laser light L1a toward the work-piece S. That is, in the optical scanning unit 6, the laser light L1a emitted from the laser processing head 5 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 work-piece S. At this time, the reflecting surfaces 63s, 64s are swung around mutually intersecting rotation axes 65, 66, so that the laser light L1a is scanned two-dimensionally within the processing surface Sa (e.g., the front surface) of the work-piece S.

[0049] That is, the first scanning unit 6A has a reflective surface (first reflective surface) 63s that reflects the laser beam L1a and the thermal radiation beam L2, and scans the laser beam L1a along a first axis that intersects with the optical axis of the laser beam L1a by varying the angle of the reflective surface 63s with respect to the optical axis of the laser beam L1a. The second scanning unit 6B has a reflective surface (second reflective surface) 64s that reflects the laser beam L1a and the thermal radiation beam L2, and scans the laser beam L1a along a second axis that intersects with the optical axis of the laser beam L1a and the first axis by varying the angle of the reflective surface 64s with respect to the optical axis of the laser beam L1a. The first axis and the second axis are axes that define a plane along the processing surface Sa.

[0050] On the other hand, the optical scanning unit 6 causes the thermal radiation light L2 from the irradiation point on the workpiece S to be incident on the laser processing head 5 by sequentially reflecting it off the reflecting surface 64s of the second scanning unit 6B and the reflecting surface 63s of the first scanning unit 6A. The thermal radiation light L2 incident on the laser processing head 5 is focused by the lens 52 and incident on the end face 4b of the second optical fiber 4. As described above, the thermal radiation light L2 incident on the end face 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 apparatus 1, the laser light L1a and the thermal radiation light L2 are completely coaxial.

[0051] The fθ lens 7 is disposed on the optical path of the laser light L1a emitted from the optical scanning unit 6. The fθ lens 7 forms a focal point Pc of the laser light L1a by focusing the (parallel light) laser light L1a emitted from the optical scanning unit 6 toward the processing surface Sa of the workpiece S. The fθ lens 7 forms the focal 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 focal point Pc on the processing surface Sa. In this case, the irradiation point Pi on the workpiece S coincides with the focal point Pc.

[0052] The fθ lens 7 receives the thermal radiation light L2 emitted at the irradiation point Pi, collimates the thermal radiation light L2, and makes it incident on the optical scanning unit 6. The thermal radiation light L2 incident on the optical scanning unit 6 is made incident on the second optical fiber 4 as described above.

[0053] As described above, in the laser processing device 1 according to this embodiment, the laser light L1a, which is a part of the processing laser light L from the light source 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, the thermal radiation light L2 emitted from the part 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.

[0054] In this way, in the laser processing apparatus 1, the processing laser beam L1a and the thermal radiation beam L2 are coaxially aligned through the second optical fiber 4 and the optical scanning unit 6 (and further through the fθ lens 7), making it possible to detect the thermal radiation beam L2 from each irradiation point Pi sequentially generated by the scanning of the laser beam L1a. Furthermore, in the laser processing apparatus 1, the reflective surfaces 63s and 64s of the optical scanning unit 6 that reflect the laser beam L1a and the thermal radiation beam L2 are formed of a metal material. The reflective surfaces 63s and 64s formed of a metal material are less likely to cause angle dependency in the reflectance of the thermal radiation beam L2 compared to reflective surfaces formed of a dielectric multilayer film. Therefore, the laser processing apparatus 1 allows the laser monitor unit to accurately measure the light intensity of the thermal radiation beam L2. This point will be explained in more detail.

[0055] FIG. 5 is a graph showing a comparative example illustrating 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 formed from a dielectric multilayer film, and 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 formed from a metal material in accordance with this embodiment.

[0056] Here, since the angle of the reflecting surface is varied at a constant time period, the angle of the reflecting surface is represented as time (TIME) in Figures 5 and 6. 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 circularly scanned while the diameter φ is changed from 10 mm to 30 mm.

[0057] 5, when the thermal radiation light is detected through reflection on a reflecting surface formed by a dielectric multilayer film (in the case of the comparative example), it can be seen that the light intensity of the thermal radiation light varies greatly depending on the angle of the reflecting surface, even though the temperature of the object is constant. In particular, because the angle of the reflecting surface is changed at a constant time period, periodic fluctuations are also observed in the light intensity of the thermal radiation light.

[0058] In contrast, as shown in Fig. 6, when the thermal radiation light is detected via reflection on a reflective surface made of 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 Fig. 5. In particular, in the example of Fig. 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 period are suppressed. Therefore, it can be seen that the light intensity of the thermal radiation light can be detected more accurately.

[0059] Furthermore, the laser processing device 1 according to this embodiment 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 onto 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.

[0060] Furthermore, in the laser processing apparatus 1 according to this embodiment, the metal material forming the reflective surfaces 63s, 64s contains Ag (for example, consists of Ag), which suppresses 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 the metal material formed on the base) can be set to, for example, 1 μm or more in order to sufficiently reflect the laser light L1a and the thermal radiation light L2.

[0061] 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.

[0062] Furthermore, in the laser processing apparatus 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 beam L1a and the thermal radiation beam L2 and scanning the laser beam L1a along a first axis intersecting the optical axis of the laser beam L1a by varying the angle of the reflective surface 63s with respect to the optical axis of the laser beam L1a, and a second scanning unit 6B having a reflective surface 64s that reflects the laser beam L1a and the thermal radiation beam L2 and scanning the laser beam L1a along a second axis intersecting the optical axis of the laser beam L1a and the first axis by varying the angle of the reflective surface 64s with respect to the optical axis of the laser beam L1a. The reflective surfaces 63s and 64s are each formed of a metal material.

[0063] This allows 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 formed of a dielectric multilayer film, the angular dependency of the reflectance of the thermal radiation light L2 becomes more pronounced. Therefore, it is more effective to form the reflecting surfaces 63s, 64s from a metal material.

[0064] The above embodiment describes one aspect of the laser processing apparatus according to the present disclosure. Therefore, the present disclosure is not limited to the laser processing apparatus 1 according to the above embodiment, and may be modified as desired.

[0065] For example, in the above embodiment, the laser processing apparatus 1 is provided with an fθ lens 7, and a two-dimensional galvano system is configured by the optical scanning unit 6 and the fθ lens 7. However, a three-dimensional galvano system may be configured in the laser processing apparatus 1. Figures 7 and 8 are configuration diagrams of three-dimensional galvano systems according to modified examples.

[0066] 7 and 8, the laser processing apparatus 1 is provided with a laser processing head 5A instead of the laser processing head 5. The laser processing head 5A differs from the laser processing head 5 in that it is provided with a focusing head 53 (focusing unit) instead of the head unit 51, and in that it further includes a motor (moving unit) 55. Also, in the example shown in FIGS. 7 and 8, the fθ lens 7 is not provided downstream of the optical scanning unit 6.

[0067] The focusing head 53 focuses the laser beam L1a emitted from the end face 4b of the second optical fiber 4 by a lens 54 toward the work-piece S via the optical scanning unit 6. A motor 55 moves the focusing head 53 along the optical axis direction of the laser beam L1a. In Fig. 7, the position of the focusing head 53 in the optical axis direction of the laser beam L1a is set to a first position A1 where a focusing point Pc1 of the laser beam L1a is formed on the processing surface Sa when the reflecting surfaces 63s, 64s of the optical scanning unit 6 are both set to a reference state and the laser beam L1a is reflected at the centers of the reflecting surfaces 63s, 64s.

[0068] When the focusing head 53 is at the first position A1, if the angle of the reflecting surfaces 63s, 64s relative to the optical axis of the laser beam L1a is changed from the reference state, the focal point Pc2 of the laser beam L1a reflected by the reflecting surfaces 63s, 64s at the angle changed from the reference state will deviate from the processing surface Sa. In contrast, as shown in Fig. 8, by moving the focusing head 53 to the second position A2 along the optical axis direction of the laser beam L1a by the motor 55, the focal point Pc2 of the laser beam L1a reflected by the reflecting surfaces 63s, 64s at the angle changed from the reference state can be positioned on the processing surface Sa.

[0069] At this time, the focal point Pc1 of the laser beam L1a reflected by the centers of the reflecting surfaces 63s, 64s in the reference state deviates from the processing surface Sa. Therefore, by synchronizing the oscillation (fluctuation in angle) 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.

[0070] In this way, in the example shown in Figures 7 and 8, the first scanning unit 6A and the second scanning unit 6B of the optical scanning unit 6 scan the focal point Pc of the laser light L1a two-dimensionally along the first axis and the 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.

[0071] In the above example, the light source 2 includes a laser diode, and the laser light L1a emitted from the light source 2 is propagated through the second optical fiber 4. However, the light source 2 may be a fiber laser. In this case, the light source 2 includes a semiconductor laser for excitation and an optical fiber for amplification, and the light incident end face of the first optical fiber 3 is connected to the light emitting end face of the optical fiber for amplification. In this case, the laser light L1a emitted from the end face 4b of the second optical fiber 4 becomes a substantially parallel beam.

[0072] In this way, even when the light source 2 is a fiber laser, a three-dimensional galvano system can be configured in the laser processing apparatus 1. That is, as shown in Figures 9 and 10, in this case, the laser processing apparatus 1 can be equipped with a laser processing head 5B instead of the laser processing head 5A. The laser processing head 5B differs from the laser processing head 5A in that it is equipped with a focusing lens 56 (focusing unit) instead of the focusing head 53.

[0073] The motor 55 moves the condenser lens 56 along the optical axis direction of the laser beam L1a. In Fig. 9, the position of the condenser lens 56 in the optical axis direction of the laser beam L1a is set to a first position B1 where a focal point Pc1 of the laser beam L1a is formed on the processing surface Sa when the reflecting surfaces 63s, 64s of the optical scanning unit 6 are both set to the reference state and the laser beam L1a is reflected at the centers of the reflecting surfaces 63s, 64s.

[0074] When the condenser lens 56 is at the first position B1, if the angle of the reflecting surfaces 63s, 64s relative to the optical axis of the laser beam L1a is changed from the reference state, the focal point Pc2 of the laser beam L1a reflected by the reflecting surfaces 63s, 64s at the angle changed from the reference state will deviate from the processing surface Sa. In contrast, as shown in Fig. 10, by moving the condenser lens 56 to the second position B2 along the optical axis direction of the laser beam L1a by the motor 55, the focal point Pc2 of the laser beam L1a reflected by the reflecting surfaces 63s, 64s at the angle changed from the reference state can be positioned on the processing surface Sa.

[0075] At this time, the focal point Pc1 of the laser beam L1a reflected by the centers of the reflecting surfaces 63s, 64s in the reference state deviates from the processing surface Sa. Therefore, by synchronizing the oscillation (fluctuation in angle) of the reflecting surfaces 63s, 64s with the movement of the focusing lens 56 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.

[0076] In this way, in the example shown in Figures 9 and 10, the first scanning unit 6A and the second scanning unit 6B of the optical scanning unit 6 scan the focal point Pc of the laser light L1a two-dimensionally along the first axis and the second axis that intersect with the optical axis direction of the laser light L1a, and the motor 55 moves the focusing lens 56, 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.

[0077] Even when a two-dimensional galvanometer mirror is configured in the laser processing device 1 as in the above embodiment, the light source 2 may be a fiber laser.

[0078] Furthermore, in the laser processing apparatus 1, the optical scanning unit 6 is not limited to a two-dimensional or three-dimensional galvano system having 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.

[0079] Furthermore, the laser processing device 1 may be configured to output the detection signal of the photodiode 35 to the outside, for example, and may not be provided with 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.

[0080] 1...laser processing device, 2...light source, 4...second optical fiber (optical fiber), 6...light scanning unit, 7...fθ lens, 10...laser processing monitor (monitor unit), 13...circuit unit (calculation unit), 53...light focusing head (light focusing unit), 55...motor (moving unit), 56...light focusing lens (light focusing 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

1. A laser processing device comprising: 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 that is irradiated with the laser light; a monitor unit to which the optical fiber is connected, that causes the laser light from the light source to enter the optical fiber and that receives and detects the thermal radiation light that has propagated through the optical fiber; and a light 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.

2. The laser processing device according to claim 1, further comprising an fθ lens that focuses the laser light reflected by the reflecting surface toward the object to be processed.

3. A laser processing device as described in claim 1, comprising: 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 workpiece via the optical scanning unit; and a moving unit that moves the focusing unit along the optical axis direction of the laser light.

4. The laser processing device according to any one of claims 1 to 3, wherein the metal material contains Ag.

5. The laser processing device according to any one of claims 1 to 4, further comprising a calculation unit that calculates the temperature of the irradiation point based on the light intensity of the thermal radiation light detected by the monitor unit.

6. The laser processing device according to any one of claims 1 to 5, wherein the optical scanning unit comprises: a first scanning unit having as its reflecting surface a first 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 the angle of the first reflecting surface with respect to the optical axis of the laser beam; and a second scanning unit having as its reflecting surface a second 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 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.

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