Laser-processing apparatus, light-intensity correction method, and light-intensity correction program

Abstract

This laser-processing apparatus comprises: a light source that emits laser light; an optical fiber for propagating the laser light and heat radiation light emitted at an irradiation point, in a processing object, irradiated with the laser light; a monitor unit that has connected thereto the optical fiber, causes the laser light from the light source to enter the optical fiber, and detects the light intensity of the heat radiation light in response to entering of the heat radiation light propagated through the optical fiber; an optical scanning unit that has a reflection surface for reflecting the laser light outgoing from the optical fiber and the heat radiation light emitted at the irradiation point, scans the processing object with the laser light by varying the angle of the reflection surface, and causes the heat radiation light to enter the optical fiber; and a correction unit that corrects the light intensity detected by the monitor unit.

Description

Laser processing device, light intensity correction method, and light intensity correction program

[0001] The present disclosure relates to a laser processing apparatus, a light intensity correction method, and a light intensity correction program.

[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 for detecting the thermal radiation and measuring the temperature is provided outside the optical scanning unit for scanning the laser beam and 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, the present disclosure aims to provide a laser processing device, a light intensity correction method, and a light intensity correction program that can obtain accurate light intensity of thermal radiation light while coaxially aligning the processing laser light and thermal radiation light.

[0008] 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 at an irradiation point that is a portion of the object to be processed irradiated with the laser light; a monitor unit to which the optical fiber is connected and that causes the laser light from the light source to enter the optical fiber and that receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the object to be processed and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light; and a correction unit that corrects the light intensity detected by the monitor unit, wherein the correction unit corrects the light intensity using a correction value that is based on the reflectivity of the thermal radiation light on the reflective surface for at least each angle of the reflective surface.

[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, this laser processing device includes a correction unit that corrects the light intensity detected by the monitor unit. The correction unit corrects the light intensity using a correction value based on at least the reflectance of the thermal radiation light at each angle of the reflecting surface of the optical scanning unit. This reduces the dependency of the light intensity of the thermal radiation light on the angle of the reflecting surface of the optical scanning unit. Therefore, this laser processing device makes it possible to obtain accurate light intensity of the thermal radiation light.

[0011] The laser processing apparatus according to the present disclosure may be [2] "the laser processing apparatus described in [1] above, including a storage unit that stores a table associating each of the plurality of angles with the correction value based on the reflectivity on the reflecting surface at each of the plurality of angles, and the correction unit acquires a target angle, which is the angle of the reflecting surface when the light intensity to be corrected is detected, and refers to the table, thereby correcting the light intensity to be corrected using the correction value associated with the target angle." In this way, by the correction unit referring to the table stored in the storage unit, it is possible to improve the processing speed related to the correction of light intensity.

[0012] The laser processing apparatus according to the present disclosure may be [3] "the laser processing apparatus described in [1] above, wherein the correction unit corrects the light intensity using the correction value for each coordinate of the irradiation point corresponding to the angle of the reflecting surface." In this case, light intensity can be corrected without converting the coordinate of the irradiation point of the laser light on the workpiece to the angle of the reflecting surface of the optical scanning unit. Therefore, it is possible to improve the processing speed for correcting light intensity in response to a request to specify the coordinate of the irradiation point and acquire the light intensity (i.e., temperature).

[0013] The laser processing apparatus according to the present disclosure may be [4] "the laser processing apparatus described in the above [3], which includes a storage unit that stores a table that associates each of the plurality of coordinates with the correction value at each of the plurality of coordinates, and the correction unit acquires target coordinates that are the coordinates of the irradiation point when the light intensity of the correction target is detected and refers to the table, thereby correcting the light intensity of the correction target using the correction value associated with the target coordinates." In this way, by the correction unit referring to the table stored in the storage unit, it is possible to further improve the processing speed related to the correction of light intensity.

[0014] The laser processing apparatus according to the present disclosure may be [5] "the laser processing apparatus according to any one of [1] to [4] above, including an fθ lens that focuses the laser light reflected by the reflecting surface toward the workpiece, and the correction unit corrects the light intensity using the correction value further based on the characteristics of the fθ lens." 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. Furthermore, when an fθ lens is used in this manner, correction based on the characteristics of the fθ lens makes it possible to obtain more accurate light intensity.

[0015] The laser processing apparatus according to the present disclosure may be [6] "the laser processing apparatus according to any one of the above [1] to [5], including a calculation unit that calculates the temperature of the irradiation point from the light intensity corrected by the correction 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.

[0016] The laser processing apparatus according to the present disclosure may be [7] "the laser processing apparatus according to the above [6], in which the correction unit and the calculation unit are built into the monitor unit." In this case, a laser processing apparatus in which the light intensity correction unit and the temperature calculation unit are integrated is obtained.

[0017] The light intensity correction method according to the present disclosure is "8" "a light intensity correction method for correcting the light intensity detected by the monitor unit of a laser processing apparatus including: 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 at an irradiation point that is a portion of the object to be processed 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 be incident on the optical fiber and that receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the object to be processed and causes the thermal radiation light to be incident on the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light, the light intensity correction method comprising: a correction step of correcting the light intensity using a correction value based on the reflectivity of the thermal radiation light on the reflective surface for at least each angle of the reflective surface."

[0018] The light intensity correction program according to the present disclosure is [9] "a light intensity correction program for correcting the light intensity detected by the monitor unit of a laser processing apparatus including: a light source that emits laser light for processing an object; an optical fiber that propagates the laser light and thermal radiation light emitted at an irradiation point that is a portion of the object 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 receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the object and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light, wherein the light intensity correction program causes a computer to operate as a correction unit that corrects the light intensity using a correction value that is based on the reflectivity of the thermal radiation light on the reflective surface for at least each angle of the reflective surface."

[0019] According to these light intensity correction methods and programs, the light intensity is corrected using a correction value based on the reflectance of the thermal radiation light at the reflecting surface for each angle of the reflecting surface of at least the optical scanning unit of the laser processing device, thereby reducing the dependency of the light intensity of the thermal radiation light on the angle of the reflecting surface of the optical scanning unit. Therefore, according to these light intensity correction methods and programs, it is possible to obtain the accurate light intensity of the thermal radiation light in a laser processing device in which the processing laser light and the thermal radiation light are coaxially aligned by sharing an optical fiber and an optical scanning unit.

[0020] According to the present disclosure, it is possible to provide a laser processing device, a light intensity correction method, and a light intensity correction program that can accurately measure the light intensity of thermal radiation light while coaxially aligning the processing laser light and thermal radiation light.

[0021] 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 flowchart showing one step of a light intensity correction method according to this embodiment. FIG. 6 is a graph showing the relationship between the angle of the reflecting surface of the optical scanning unit and the light intensity of thermal radiation light. FIG. 7 is a flowchart showing one step of a light intensity correction method according to a modified example. FIG. 8 is a schematic cross-sectional view showing the relationship between the fθ lens shown in FIGS. 1, 4, etc. and the incident and exiting light. FIG. 9 is a configuration diagram of a three-dimensional galvano system according to a modified example. FIG. 10 is a configuration diagram of a three-dimensional galvano system according to a modified example. FIG. 11 is a configuration diagram of a galvano system according to another modified example. FIG. 12 is a configuration diagram of a galvano system according to another modified example. FIG. 13 is a diagram showing the configuration of a light intensity correction program according to this embodiment, together with a recording medium.

[0022] Hereinafter, an embodiment of a laser processing apparatus, a light intensity correction method, and a light intensity correction program will be described in detail with reference to the drawings. In each drawing, identical or corresponding elements are assigned the same reference numerals, and redundant explanations may be omitted.

[0023] 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, a laser processing monitor (monitor unit) 10, and a light intensity correction device 100. 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) emitted from a portion of the workpiece S irradiated with the laser beam L1a (hereinafter sometimes referred to as the "irradiation point").

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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).

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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 light intensity of the thermal radiation light L2 that has been focused by the lens 33 and passed through the filter 34. A detection signal including the light intensity 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 a 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 light intensity of the thermal radiation light L2.

[0045] 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.

[0046] 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).

[0047] 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.

[0048] 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, at 45° with respect to the optical axis of the laser beam L1a as a reference state, and is oscillated within a range of approximately ±8° from the reference state. The first scanning unit 6A has an angle detection unit 61a, such as an encoder, for detecting the rotation angle of the rotation shaft 65 (i.e., the angle of the reflecting surface 63s).

[0049] 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.

[0050] 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 has an angle detection unit 62a, such as an encoder, for detecting the rotation angle of the rotation shaft 66 (i.e., the angle of the reflecting surface 64s).

[0051] The reflecting surfaces 63s, 64s are each formed of a dielectric multilayer film (e.g., designed to maximize reflectivity at the wavelength of the laser light L1a). As an example, the mirrors 63, 64 may each be configured by forming the reflecting surfaces 63s, 64s made of a dielectric multilayer film on a base body made of a glass-based material, a SiC substrate, or the like. However, the reflecting surfaces 63s, 64s may each be formed of a metal material containing, for example, Ag, Al, or Au.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] Here, the reflectance of the thermal radiation light L2 on the reflecting surfaces 63s, 64s (formed, for example, of a dielectric multilayer film) is angularly dependent. As a result, if the laser light L1a and the thermal radiation light L2 are coaxial, the light intensity of the thermal radiation light L2 detected via the light scanning unit 6 also becomes angularly dependent, which may make it difficult to accurately measure the light intensity of the thermal radiation light L2. Therefore, the laser processing apparatus 1 is provided with a configuration for accurately acquiring the light intensity of the thermal radiation light L2.

[0058] That is, the light intensity correction device 100 corrects the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10 (the light detection unit 25 of the optical unit 20). The light intensity correction device 100 has a correction unit 110 and a storage unit 120. The light intensity correction device 100 is a computer including hardware such as a CPU (Central Processing Unit), a memory, a communication module, etc. The above-mentioned functions of the light intensity correction device 100 are achieved by these components operating through programs, etc. The light intensity correction device 100 is connected to the laser processing monitor 10 so as to be able to send and receive information to and from the laser processing monitor 10.

[0059] The correction unit 110 corrects the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10. More specifically, the correction unit 110 corrects the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10 using a correction value based on the reflectance of the thermal radiation light L2 on the reflecting surfaces 63s, 64s for at least each angle of the reflecting surfaces 63s, 64s.

[0060] For example, if the reflectance of the thermal radiation light L2 at the reflecting surfaces 63s, 64s fluctuates when the reflecting surfaces 63s, 64s oscillate around the reference state, even if the temperature of the processing surface Sa is constant, the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10 will fluctuate. Therefore, the correction unit 110 corrects the light intensity of the thermal radiation light L2 using a correction value based on the reflectance of the thermal radiation light L2 at the reflecting surfaces 63s, 64s for each angle of the reflecting surfaces 63s, 64s so as to cancel out such fluctuations in the light intensity of the thermal radiation light L2, and generates a corrected light intensity.

[0061] As described above, the angles of the reflecting surfaces 63s and 64s can be obtained by the angle detection units 61a and 62a, such as encoders. The phrase "for each angle of the reflecting surfaces 63s and 64s" includes the case where the angle is the angle of the reflecting surfaces 63s and 64s itself, and the case where the coordinates (of the first axis and the second axis) of the irradiation point Pi are determined by the angle of the reflecting surfaces 63s and 64s and the focusing characteristics of the fθ lens 7.

[0062] When the correction unit 110 uses the angle of the reflecting surfaces 63s, 64s itself, the holding unit 120 holds a table that associates each of the multiple angles of the reflecting surfaces 63s, 64s with a correction value based on the reflectance of the thermal radiation light L2 at the reflecting surfaces 63s, 64s at each of the multiple angles, and the correction unit 110 can correct the light intensity of the thermal radiation light L2 to be corrected using the correction value associated with the target angle by obtaining the target angle, which is the angle of the reflecting surfaces 63s, 64s when the light intensity of the thermal radiation light L2 to be corrected is detected, via the angle detection units 61a, 62a, and referring to the table.

[0063] Furthermore, when the correction unit 110 uses the coordinates of the irradiation point Pi, the storage unit 120 stores a table that associates each of a plurality of coordinates with a correction value at each of the plurality of coordinates, and the correction unit 110 can correct the light intensity of the thermal radiation light L2 to be corrected by the correction value associated with the target coordinate by acquiring the target coordinate, which is the coordinate of the irradiation point Pi when the light intensity of the thermal radiation light L2 to be corrected is detected, and referring to the table.

[0064] Next, a light intensity correction method according to this embodiment will be described, and specific operations of the laser processing apparatus 1 will be described. Fig. 5 is a flowchart showing one step of the light intensity correction method according to this embodiment. Note that the example of Fig. 5 is an example of a case where, after laser processing using the laser light L1a and measurement of the light intensity of the thermal radiation light L2 are completed, the light intensity of the thermal radiation light L2 is corrected using the coordinates of the irradiation point Pi.

[0065] 5, in the light intensity correction method according to this embodiment, a table is first created in which the coordinates of the irradiation point Pi are associated with correction values ​​(step S101). One example of a method for creating the table is to first obtain the light intensity (sample intensity) of the thermal radiation light L2 from each coordinate of an object at a constant temperature, regardless of the coordinates, and then obtain a correction value required to cancel fluctuations in the sample intensity relative to the light intensity of the thermal radiation light L2 corresponding to the actual temperature of the object. The obtained correction value is then associated with the coordinates to create a table. The created table is stored in the storage unit 120.

[0066] Note that, since the sample intensity is acquired via the optical scanning unit 6, it reflects fluctuations in the reflectance of the thermal radiation light L2 in response to the oscillation of the reflecting surfaces 63s, 64s. Therefore, the correction value also reflects fluctuations in the reflectance of the thermal radiation light L2 in response to the oscillation of the reflecting surfaces 63s, 64s. In other words, the correction value is based on the reflectance of the thermal radiation light L2 on the reflecting surfaces 63s, 64s. Furthermore, the object to be used in creating the table may be a hot plate or a flat-type blackbody furnace (or a flat-type blackbody furnace if accuracy is taken into consideration).

[0067] In the next step, the workpiece S is set in the laser processing device 1, and measurement (detection) of the light intensity of the thermal radiation light L2 of the workpiece S is started by the laser processing monitor 10 (step S102). Laser processing of the workpiece S is then started by irradiating the workpiece S with the laser light L1a while scanning it (step S103). In step S103, scanning of the laser light L1a is performed according to a pre-specified scan pattern. As a result, irradiation points Pi of the laser light L1a are generated along the scan pattern, and the light intensity of the thermal radiation light L2 from each irradiation point Pi of the laser light L1a is measured. The series of measurement results of the light intensity of the thermal radiation light L2 can be stored, for example, in the storage unit 120.

[0068] Next, upon completion of scanning of the laser light L1a along the scan pattern, laser processing of the workpiece S is terminated (step S104), and measurement (detection) of the light intensity of the thermal radiation light L2 by the laser processing monitor 10 is terminated (step S105).

[0069] Next, based on the scan pattern, the time and coordinates are acquired for each measurement result of the light intensity of the thermal radiation light L2 (step S106). More specifically, in step S106, based on the scan pattern, it is calculated which time and from which coordinate of the irradiation point Pi each measurement result of the light intensity of the thermal radiation light L2 corresponds, and this is associated with each measurement result.

[0070] Next, the correction unit 110 refers to the table stored in the storage unit 120 and obtains from the table a correction value associated with each time (i.e., each coordinate) (step S107). Then, the correction unit 110 corrects each measurement result of the light intensity of the thermal radiation light L2 using each correction value obtained in step S107, thereby generating a corrected light intensity of the thermal radiation light L2 (step S108: correction step). That is, in step S108, the correction unit 110 obtains target coordinates, which are the coordinates of the irradiation point Pi when the light intensity to be corrected is detected, and refers to the table to correct the light intensity to be corrected using the correction value associated with the target coordinates. Information indicating the corrected light intensity generated in step S108 can be stored in the storage unit 120.

[0071] In this way, in the light intensity correction method according to the present embodiment, the light intensity is corrected using a correction value based on the reflectance of the thermal radiation light L2 at the reflecting surfaces 63s, 64s for each angle of the reflecting surfaces 63s, 64s (here, for each coordinate of the irradiation point Pi). Thereafter, in the laser processing apparatus 1, the circuit unit 13 can calculate the temperature of each irradiation point Pi based on the corrected light intensity generated in step S108.

[0072] As described above, in the laser processing device 1 according to this embodiment, the processing laser light L1a 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 portion of the workpiece S irradiated with the laser light L1a (irradiation point Pi) is made incident on the second optical fiber 4 that propagates the processing laser light L1a via the optical scanning unit 6, 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 according to this embodiment, the processing laser light L1a and the thermal radiation light L2 are coaxially connected by sharing the second optical fiber 4 and the optical scanning unit 6, making it possible to detect the thermal radiation light L2 from each irradiation point Pi.

[0073] The laser processing apparatus 1 according to this embodiment also includes a correction unit 110 that corrects the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10. In the laser processing apparatus 1 and the light intensity correction method according to this embodiment, the correction unit 110 corrects the light intensity using a correction value based on the reflectance of the thermal radiation light L2 at the reflecting surfaces 63s, 64s of the optical scanning unit 6 for each angle of the reflecting surfaces 63s, 64s (for each coordinate of the irradiation point Pi). This reduces the dependency of the light intensity of the thermal radiation light L2 on the angle of the reflecting surfaces 63s, 64s of the optical scanning unit 6. Therefore, the laser processing apparatus 1 and the light intensity correction method according to this embodiment make it possible to obtain the accurate light intensity of the thermal radiation light L2.

[0074] FIG. 6 is a graph showing the relationship between the angle of the reflecting surface of the optical scanning unit and the light intensity of the thermal radiation light. In the example of FIG. 6, the angle of the reflecting surface is varied at a constant time period, and therefore, in FIG. 6, the angle of the reflecting surface (i.e., coordinate) is represented as time (TIME). Also, in FIG. 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 FIG. 6 shows a case where the detection position of the thermal radiation light from an object (hot plate) with a diameter φ of 30 mm and a constant temperature is scanned in a circular pattern. FIG. 6(a) shows the light intensity before correction, and FIG. 6(b) shows the light intensity after correction.

[0075] 6A, it can be seen that the light intensity of the thermal radiation light L2 before correction varies greatly due to fluctuations in the angle of the reflecting surfaces 63s and 64s, even though the temperature of the object is constant. In particular, because the angles of the reflecting surfaces 63s and 64s are changed at a constant time period, periodic fluctuations are also observed in the light intensity of the thermal radiation light L2.

[0076] In contrast, as shown in Fig. 6(b), in the corrected light intensity of the thermal radiation light L2, fluctuations accompanying fluctuations in the angle of the reflecting surfaces 63s, 64s are suppressed. Furthermore, in the example of Fig. 6(b), periodic fluctuations caused by changing the angle of the reflecting surfaces 63s, 64s at a constant time period are also suppressed. Thus, it can be seen that the laser processing apparatus 1 and the light intensity correction method according to this embodiment make it possible to obtain a more accurate light intensity of the thermal radiation light L2.

[0077] In the above embodiment, the light intensity of the thermal radiation light L2 is corrected after the laser processing using the laser light L1a and the measurement of the light intensity of the thermal radiation light L2 are completed, so that the processing speed of the laser processing (scanning speed of the laser light L1a) can be increased regardless of the processing speed of the correction of the light intensity of the thermal radiation light L2.

[0078] Furthermore, in the laser processing apparatus 1 according to this embodiment, the correction unit 110 corrects the light intensity using a correction value for each coordinate of the irradiation point Pi corresponding to the angle of the reflecting surfaces 63s, 64s. This makes it possible to correct the light intensity without converting the coordinate of the irradiation point Pi of the laser light L1a on the workpiece S into the angle of the reflecting surfaces 63s, 64s of the optical scanning unit 6. This makes it possible to improve the processing speed for correcting the light intensity in response to a request to acquire the light intensity (i.e., temperature) by specifying the coordinate of the irradiation point Pi.

[0079] The laser processing apparatus 1 according to this embodiment also includes a storage unit 120 that stores a table associating each of a plurality of coordinates with a correction value for each of the plurality of coordinates. The correction unit 110 acquires target coordinates, which are the coordinates of the irradiation point Pi when the light intensity of the correction target is detected, and refers to the table to correct the light intensity of the correction target using the correction value associated with the target coordinates. In this way, the correction unit 110 refers to the table stored in the storage unit 120, thereby further improving the processing speed for correcting the light intensity.

[0080] Furthermore, the laser processing device 1 according to this embodiment includes a circuit unit 13 that calculates the temperature of the irradiation point Pi from the light intensity corrected by the correction unit 110. Therefore, it is possible to obtain the temperature of each irradiation point Pi based on the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10.

[0081] The above embodiment has described one aspect of the present disclosure. Therefore, the present disclosure is not limited to the above embodiment and may be modified as desired. Next, modified examples will be described.

[0082] Fig. 7 is a flowchart showing one step of a light intensity correction method according to a modified example. The light intensity correction method shown in Fig. 7 shows a modified example of the operation of the laser processing apparatus 1. The example shown in Fig. 7 is an example of a case where laser processing is performed using the laser light L1a and the light intensity of the thermal radiation light L2 is measured, and the light intensity of the thermal radiation light L2 is corrected in real time using the angles of the reflecting surfaces 63s and 64s.

[0083] As shown in FIG. 7 , a table associating the angles of the reflecting surfaces 63s and 64s with correction values ​​is first created (step S201). One example of a method for creating the table involves first acquiring the light intensity (sample intensity) of the thermal radiation light L2 from each coordinate of an object having a constant temperature, regardless of the coordinates. At this time, the angles of the reflecting surfaces 63s and 64s detected by the angle detection units 61a and 62a are associated with the sample intensity. Next, a correction value required to cancel fluctuations in the sample intensity relative to the light intensity of the thermal radiation light L2 corresponding to the actual temperature of the object is acquired. The acquired correction value is then associated with the angles of the reflecting surfaces 63s and 64s to create a table. The created table is stored in the storage unit 120. The object used to create the table may be a hot plate or a flat-type blackbody furnace (or a flat-type blackbody furnace, if accuracy is taken into consideration).

[0084] In the next step, the workpiece S is set in the laser processing device 1, and measurement (detection) of the light intensity of the thermal radiation light L2 of the workpiece S is started by the laser processing monitor 10 (step S202). Then, the workpiece S is irradiated with the laser light L1a while being scanned, thereby starting laser processing of the workpiece S (step S203). In step S203, scanning with the laser light L1a is performed according to a pre-specified scan pattern.

[0085] As a result, an irradiation point Pi of the laser light L1a is generated on the workpiece S along the scan pattern, and the light intensity of the thermal radiation light L2 from the irradiation point Pi of the laser light L1a is measured (detected) (step S204). The measurement result of the light intensity of the thermal radiation light L2 can be stored in the storage unit 120, for example.

[0086] Next, the correction unit 110 acquires the angles of the reflecting surfaces 63s and 64s when the light intensity was detected in step S204 from the angle detection units 61a and 62a (step S205). Next, the correction unit 110 acquires correction values ​​associated with the angles of the reflecting surfaces 63s and 64s acquired in step S205 by referring to the table stored in the storage unit 120 (step S206).

[0087] Next, the correction unit 110 corrects the light intensity of the thermal radiation light L2 measured in step S204 using the correction value acquired in step S206, thereby generating a corrected light intensity (step S207: correction step).The correction unit 110 then stores information indicating the corrected light intensity generated in step S207 in, for example, the storage unit 120 (step S208).

[0088] Thereafter, it is determined whether scanning of the laser light L1a along the scan pattern and measurement (detection) of the light intensity of the thermal radiation light L2 have been completed (step S209). If the result of the determination in step S209 is that scanning of the laser light L1a and measurement of the light intensity of the thermal radiation light L2 have not been completed (step S209: NO), step S204 and subsequent steps are executed again. If the result of the determination in step 209 is that scanning of the laser light L1a and measurement of the light intensity of the thermal radiation light L2 have been completed (step S209: YES), laser processing of the workpiece S is terminated (step S210), and measurement of the light intensity of the thermal radiation light L2 by the laser processing monitor 10 is terminated (step S211), thereby completing the series of steps.

[0089] As described above, in the light intensity correction method and laser processing apparatus 1 according to this modification, the correction unit 110 corrects the light intensity using a correction value based on the reflectance of the thermal radiation light L2 on the reflecting surfaces 63s, 64s for each angle of the reflecting surfaces 63s, 64s. In particular, here, the holding unit 120 holds a table that associates each of a plurality of angles of the reflecting surfaces 63s, 64s with a correction value based on the reflectance of the reflecting surfaces 63s, 64s at each of the plurality of angles, and the correction unit 110 acquires a target angle, which is the angle of the reflecting surfaces 63s, 64s when the light intensity to be corrected is detected, and refers to the table, thereby correcting the light intensity to be corrected using the correction value associated with the target angle.

[0090] As described above, even when the light intensity of the thermal radiation light L2 is corrected using the angle of the reflecting surfaces 63s, 64s as in the light intensity correction method and laser processing apparatus 1 according to this modified example, it is possible to obtain the accurate light intensity of the thermal radiation light L2, as in the above embodiment. In particular, in this case, the light intensity can be corrected by directly obtaining a correction value from the angle of the reflecting surfaces 63s, 64s, thereby improving the processing speed. Therefore, it is possible to more preferably correct the light intensity in real time. As a result, it is possible to obtain the accurate temperature of each irradiation point Pi on the workpiece S in real time.

[0091] 1, 4, etc., and the incident and exiting light beams. As shown in Fig. 8, when the angles of the reflecting surfaces 63s, 64s of the optical scanning unit 6 vary, the incident position and incident angle of the laser beam L1a and the thermal radiation light L2 with respect to the fθ lens 7 change. Fig. 8 illustrates an optical path T1 in which the laser beam L1a and the thermal radiation light L2 are incident perpendicularly to the center of the fθ lens 7, an optical path T2 in which the laser beam L1a and the thermal radiation light L2 are incident slightly inclined from perpendicular outside the center of the fθ lens 7, and an optical path T3 in which the laser beam L1a and the thermal radiation light L2 are incident further outward from the center of the fθ lens 7 at a further inclined angle from perpendicular.

[0092] 8, when the optical path of the thermal radiation light L2 is inclined from optical path T1 to T3, the optical path length of the thermal radiation light L2 within the fθ lens 7 changes, and the optical transmittance of the thermal radiation light L2 through the fθ lens 7 changes. Such a change in optical transmittance caused by a change in the optical path length of the thermal radiation light L2 may affect the detection result of the light intensity of the thermal radiation light L2 in the laser processing monitor 10.

[0093] Furthermore, when the optical path of the thermal radiation light L2 tilts from optical path T1 to T3, the angle of incidence of the thermal radiation light L2 on the fθ lens 7 changes from angle θ1 to angle θ3. When the angle of incidence of the thermal radiation light L2 on the fθ lens 7 changes, the reflectance of the thermal radiation light L2 on the surface of the fθ lens 7 changes (for example, depending on the transmittance of the lens coating of the fθ lens 7), and the optical transmittance of the thermal radiation light L2 through the fθ lens 7 changes. Therefore, in this case as well, there is a risk that the detection result of the light intensity of the thermal radiation light L2 in the laser processing monitor 10 will fluctuate.

[0094] Therefore, in the laser processing apparatus 1 and the light intensity correction method, the light intensity can be corrected based on the characteristics of the fθ lens 7. Therefore, in the laser processing apparatus 1 and the light intensity correction method, the correction unit 110 can correct the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10 using a correction value based on the characteristics of the fθ lens 7.

[0095] As an example, the correction unit 110 can correct the light intensity of the thermal radiation light L2 detected by the laser processing monitor 10 using a correction value based on the light transmittance of the thermal radiation light L2 through the fθ lens 7 for each incident position (incident angle) of the thermal radiation light L2 on the fθ lens 7.

[0096] In this case, as a more specific example, the holding unit 120 holds a table that associates each of a plurality of incident positions of the thermal radiation light L2 on the fθ lens 7 with a correction value based on the light transmittance of the thermal radiation light L2 of the fθ lens 7 at each of the plurality of incident positions, and the correction unit 110 acquires the target incident position, which is the incident position of the fθ lens 7 when the light intensity to be corrected is detected, and refers to the table, thereby being able to correct the light intensity to be corrected using the correction value associated with the target incident position.

[0097] At this time, the correction unit 110 may correct the light intensity using a correction value based only on the characteristics of the fθ lens 7 as described above, or may correct the light intensity using a correction value obtained by adding a correction amount based on the characteristics of the fθ lens 7 as described above to the correction value used when correcting the light intensity using a correction value based on the reflectance of the thermal radiation light L2 on the reflecting surfaces 63s, 64s of the optical scanning unit 6 for each angle of the reflecting surfaces 63s, 64s as in the above embodiment. In other words, the correction unit 110 may correct the light intensity using a correction value that is further based on the characteristics of the fθ lens 7. Note that the "incident position (incident angle)" of the thermal radiation light L2 on the fθ lens 7 may be interpreted as the angle of the reflecting surfaces 63s, 64s or the coordinates of the irradiation point Pi, for example.

[0098] As described above, by including the fθ lens 7, the laser processing device 1 can form a focal point of the laser light L1a on the same plane of the workpiece S due to the optical characteristics of the fθ lens 7 when the laser light L1a is reflected by the optical scanning unit 6 and scanned onto the workpiece S. Furthermore, when the fθ lens 7 is used in this manner, correction based on the characteristics of the fθ lens 7 can be performed to obtain more accurate light intensity.

[0099] When the optical path of the laser beam L1a is tilted from optical path T1 to T3, the beam shape B of the laser beam L1a at the irradiation point Pi changes, for example, from a perfect circle to an ellipse. Therefore, in the laser processing apparatus 1, the light source 2 may be controlled to adjust, for example, the light intensity of the laser beam L1a in accordance with the change in the beam shape B of the laser beam L1a based on the characteristics of the fθ lens 7.

[0100] Next, a modified example will be described. 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 9 and 10 are configuration diagrams of three-dimensional galvano systems according to modified examples.

[0101] 9 and 10, 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. 9 and 10, the fθ lens 7 is not provided downstream of the optical scanning unit 6.

[0102] 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. 9, 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.

[0103] 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. 10, 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.

[0104] 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.

[0105] 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 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.

[0106] 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.

[0107] 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 11 and 12, 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.

[0108] The motor 55 moves the condenser lens 56 along the optical axis direction of the laser beam L1a. In Fig. 11, 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.

[0109] 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. 12, 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.

[0110] 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.

[0111] In this way, in the example shown in Figures 11 and 12, 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 1, the light intensity correction device 100 is configured separately from the laser processing monitor 10 and exchanges information with the laser processing monitor 10. However, the light intensity correction device 100 may be built into the laser processing monitor 10.

[0116] Furthermore, in the above embodiment and modified examples, an example has been described in which the table is created in step S101 or step S201 of the series of steps in the light intensity correction method. However, steps S101 and S201 do not need to be performed every time the light intensity correction method is performed, and the timing of execution may also be any timing before the actual correction is performed.

[0117] 13, a light intensity correction program 200 according to this embodiment is inserted into a computer and accessed, or is stored in a program storage area 211 formed in a computer-readable recording medium 210 provided in the computer. The recording medium 210 may be a non-transitory recording medium.

[0118] The light intensity correction program 200 is configured to include a correction module 201 and a storage module 202. The functions realized by executing the correction module 201 and the storage module 202 are the same as the functions of the correction unit 110 and the storage unit 120 of the laser processing apparatus 1 described above, respectively. Note that the light intensity correction program 200 may be configured so that a part or all of it is transmitted via a transmission medium such as a communication line, and is received and recorded (including installed) by another device. Furthermore, each module of the light intensity correction program 200 may be installed not in one computer but in one of multiple computers. In this case, the above-described series of processes is performed by a computer system consisting of the multiple computers.

[0119] 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), 63s...reflecting surface (first reflecting surface), 64s...reflecting surface (second reflecting surface), 110...correction unit, 120...holding unit, 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 irradiated with the laser light; a monitor unit to which the optical fiber is connected and that causes the laser light from the light source to enter the optical fiber and that receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the workpiece and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light; and a correction unit that corrects the light intensity detected by the monitor unit, wherein the correction unit corrects the light intensity using a correction value based on the reflectivity of the thermal radiation light on the reflective surface for at least each angle of the reflective surface.

2. A laser processing device as described in claim 1, comprising a storage unit that stores a table that associates each of the plurality of angles with a correction value based on the reflectivity on the reflecting surface at each of the plurality of angles, and the correction unit acquires a target angle, which is the angle of the reflecting surface when the light intensity to be corrected is detected, and refers to the table to correct the light intensity to be corrected using the correction value associated with the target angle.

3. The laser processing device according to claim 1, wherein the correction unit corrects the light intensity using the correction value for each coordinate of the irradiation point corresponding to the angle of the reflecting surface.

4. A laser processing device as described in claim 3, further comprising a storage unit that stores a table that associates each of the plurality of coordinates with the correction value at each of the plurality of coordinates, and the correction unit acquires target coordinates, which are the coordinates of the irradiation point when the light intensity of the correction target is detected, and refers to the table to correct the light intensity of the correction target using the correction value associated with the target coordinates.

5. A laser processing device according to any one of claims 1 to 4, further comprising an fθ lens that focuses the laser light reflected by the reflecting surface toward the object to be processed, and wherein the correction unit corrects the light intensity using the correction value that is further based on the characteristics of the fθ lens.

6. The laser processing device according to any one of claims 1 to 5, further comprising a calculation unit that calculates the temperature of the irradiation point from the light intensity corrected by the correction unit.

7. The laser processing device according to claim 6, wherein the correction unit and the calculation unit are built into the monitor unit.

8. A light intensity correction method for correcting the light intensity detected by the monitor unit of a laser processing device comprising: a light source that emits laser light for processing an object; an optical fiber that propagates the laser light and thermal radiation light emitted at an irradiation point that is a portion of the object 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 receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the object and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light, the light intensity correction method comprising a correction step of correcting the light intensity using a correction value based on the reflectance of the thermal radiation light on the reflective surface for at least each angle of the reflective surface.

9. A light intensity correction program for correcting the light intensity detected by the monitor unit of a laser processing device comprising: a light source that emits laser light for processing an object; an optical fiber that propagates the laser light and thermal radiation light emitted at an irradiation point that is a portion of the object 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 receives the thermal radiation light that has propagated through the optical fiber and detects the light intensity of the thermal radiation light; 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 scans the laser light over the object and causes the thermal radiation light to enter the optical fiber by varying the angle of the reflective surface with respect to the optical axis of the laser light, the light intensity correction program causing a computer to operate as a correction unit that corrects the light intensity using a correction value based on the reflectance of the thermal radiation light on the reflective surface for at least each angle of the reflective surface.

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