WO2024080198A1 - Polarized light adjustment device and laser processing machine - Google Patents

Polarized light adjustment device and laser processing machine Download PDF

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Publication number
WO2024080198A1
WO2024080198A1 PCT/JP2023/036169 JP2023036169W WO2024080198A1 WO 2024080198 A1 WO2024080198 A1 WO 2024080198A1 JP 2023036169 W JP2023036169 W JP 2023036169W WO 2024080198 A1 WO2024080198 A1 WO 2024080198A1
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Prior art keywords
polarized light
linearly polarized
optical element
laser beam
polarization
Prior art date
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PCT/JP2023/036169
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French (fr)
Japanese (ja)
Inventor
亮平 伊藤
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株式会社アマダ
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Publication of WO2024080198A1 publication Critical patent/WO2024080198A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/062—Shaping the laser beam, e.g. by masks or multi-focusing by direct control of the laser beam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/067—Dividing the beam into multiple beams, e.g. multifocusing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating

Definitions

  • This disclosure relates to a polarization adjustment device and a laser processing machine.
  • Laser processing machines cut metal workpieces with a laser beam emitted from a laser oscillator.
  • the laser beam emitted by the laser oscillator is randomly polarized light that contains two mutually orthogonal linearly polarized components (hereafter referred to as p-polarized light and s-polarized light). It is known that the absorption rate of the laser beam by the workpiece when cutting with a randomly polarized laser beam varies depending on the angle of incidence of the laser beam onto the workpiece.
  • the absorption rate of a randomly polarized laser beam is the average value of the absorption rates of p-polarized light and s-polarized light.
  • the laser beam is incident on the workpiece at an angle of 82 degrees to 88 degrees, cutting the workpiece.
  • the workpiece is made of iron metal and the laser beam has a wavelength in the 1 ⁇ m range
  • the absorption rate of p-polarized light is a maximum of about 90%, while the absorption rate of s-polarized light is less than 10%.
  • the absorption rate of a randomly polarized laser beam is the average value of the absorption rates of p-polarized light and s-polarized light, so the absorption rate of a randomly polarized laser beam is 40% or less, which is one of the factors that reduce the processing efficiency when cutting a workpiece.
  • Patent Document 1 discloses a laser processing machine that aligns the polarization directions of two linearly polarized lights contained in a randomly polarized laser beam in parallel and controls the polarization direction of the two parallel linearly polarized lights to match the direction in which cutting is performed (hereinafter referred to as the cutting direction).
  • the cutting direction By matching the polarization direction of the linearly polarized light with the cutting direction, the polarization direction of the laser beam with respect to the cutting front becomes p-polarized light, and the absorption rate of the laser beam in the workpiece becomes the absorption rate of p-polarized light. This improves the absorption rate of the laser beam in the workpiece, thereby improving processing efficiency.
  • the cutting front here refers to the cut surface at the boundary between the non-melted area and the molten area in the cutting direction when the workpiece is melted and cut.
  • the laser processing machine described in Patent Document 1 focuses two linearly polarized laser beams with the same polarization direction and wavelength by one focusing lens and irradiates the workpiece.
  • two laser beams with the same polarization direction and wavelength cannot be focused at the same position. Therefore, in practice, it is necessary to focus the two laser beams at different positions and arrange the two laser beams, for example, side by side.
  • the two laser beams since two laser beams with parallel polarization directions travel along two different axes, the two laser beams have anisotropy with respect to the cutting direction. If the two laser beams have anisotropy with respect to the cutting direction, the cutting quality will not be constant in laser cutting processing in which the cutting direction of the workpiece changes arbitrarily, which may lead to a deterioration of the cutting quality.
  • a polarization adjustment device that can align the polarization directions of two linearly polarized beams contained in a randomly polarized laser beam to be parallel, and can eliminate the anisotropy of the two laser beams with parallel polarization directions in the cutting direction, as well as a laser processing machine equipped with such a polarization adjustment device.
  • a first aspect of one or more embodiments is a polarization adjustment device comprising: a first optical element that separates a randomly polarized laser beam, which includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction, into the first linearly polarized light and the second linearly polarized light; a second optical element that converts the polarization direction of the second linearly polarized light separated by the first optical element to the first polarization direction; an axicon lens that expands the second linearly polarized light emitted from the second optical element or the second linearly polarized light incident on the second optical element into a ring shape; and a third optical element that is used in combination with the first optical element or is separate from the first optical element and that coaxially emits the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens.
  • a second aspect of one or more of the embodiments is a laser processing machine that includes the polarization adjustment device of the first aspect, and a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light and the second linearly polarized light emitted coaxially from the polarization adjustment device so that the polarization direction is parallel to the cutting direction when a laser beam is irradiated onto a workpiece to cut the workpiece.
  • the polarization adjustment device can align the polarization directions of two linearly polarized lights contained in a randomly polarized laser beam in parallel, and can eliminate the anisotropy of the two laser beams with parallel polarization directions in the cutting direction.
  • the laser processing machine can process the workpiece with two laser beams with no anisotropy and with parallel polarization directions.
  • FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine according to a first embodiment.
  • FIG. 2 is a diagram showing an example of the configuration of the machining head according to the first embodiment.
  • FIG. 3 is a diagram showing an example of the configuration of a special polarizing beam splitter provided in the processing head shown in FIG.
  • FIG. 4 is a diagram showing the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship between the first and second linearly polarized light beams when they are emitted coaxially.
  • FIG. 5 is a diagram showing a configuration example of a lens array provided in the processing head shown in FIG. FIG.
  • FIG. 6A is a diagram showing the relationship between the cutting direction of the workpiece and the polarization direction of the laser beam irradiated onto the workpiece W.
  • FIG. 6B is a diagram showing the relationship between the cutting direction of the workpiece W when the cutting direction of the workpiece W forms a curve and the polarization direction of the laser beam irradiated to the workpiece W.
  • FIG. 7A is a diagram showing the relationship between the cutting front and the polarization direction and the cutting proceeding direction when the cutting front has a semicircular shape.
  • FIG. 7B is a diagram showing the relationship between the cutting front and the polarization direction and the cutting proceeding direction when the cutting front has a rectangular shape.
  • FIG. 8 is a diagram showing an example of the configuration of a machining head according to the second embodiment.
  • FIG. 9 is a diagram showing the polarization direction and shape of the laser beam in FIG. 8 and the positional relationship between the first and second linearly polarized light beams when they are emitted coaxially.
  • FIG. 10 is a diagram showing a special mirror provided in the processing head shown in FIG.
  • the polarization adjustment device includes a first optical element, a second optical element, an axicon lens, and a third optical element.
  • the first optical element separates a randomly polarized laser beam, which includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction perpendicular to the first polarization direction, into the first linearly polarized light and the second linearly polarized light.
  • the second optical element converts the polarization direction of the second linearly polarized light separated by the first optical element to the first polarization direction.
  • the axicon lens expands the second linearly polarized light output by the second optical element or the second linearly polarized light incident on the second optical element into a ring shape.
  • the third optical element coaxially outputs the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens.
  • the third optical element is used in combination with the first optical element, or is separate from the first optical element.
  • FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine 100 equipped with a polarization adjustment device according to the first embodiment.
  • the laser processing machine 100 is a processing machine that cuts and processes a workpiece W using a laser beam.
  • the workpiece W to be processed is, for example, a mild steel plate.
  • the workpiece W may be an iron-based sheet metal other than a mild steel plate, such as stainless steel, or may be a non-iron-based sheet metal such as aluminum, an aluminum alloy, or copper.
  • the laser processing machine 100 includes a laser oscillator 10 that generates and emits a laser beam, a laser processing unit 20, and a process fiber 12 that transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20.
  • the laser processing machine 100 also includes an NC (Numerical Control) device 50 and an assist gas supply device 60.
  • the NC device 50 is an example of a control device that controls each part of the laser processing machine 100.
  • a laser oscillator that amplifies the excitation light emitted from a laser diode to emit a laser beam of a specified wavelength, or a laser oscillator that directly uses the laser beam emitted from a laser diode is suitable.
  • the laser oscillator 10 is, for example, a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, or a direct diode laser oscillator (DDL oscillator).
  • the laser oscillator 10 emits a laser beam in the 1 ⁇ m band with a wavelength of 900 nm to 1100 nm.
  • a fiber laser oscillator and a DDL oscillator as examples, a fiber laser oscillator emits a laser beam with a wavelength of 1060 nm to 1080 nm, and a DDL oscillator emits a laser beam with a wavelength of 910 nm to 950 nm.
  • the process fiber 12 transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20.
  • the laser beam transmitted by the process fiber 12 is a randomly polarized laser beam that includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction perpendicular to the first polarization direction.
  • the laser processing unit 20 cuts the workpiece W using a laser beam transmitted by the process fiber 12.
  • the laser processing unit 20 has a processing table 21 on which the workpiece W is placed, a gate-shaped X-axis carriage 22, a Y-axis carriage 23, and a processing head 30A.
  • the X-axis carriage 22 is configured to be freely movable along the X-axis direction on the processing table 21.
  • the Y-axis carriage 23 is configured to be freely movable along the Y-axis direction perpendicular to the X-axis on the X-axis carriage 22.
  • the X-axis carriage 22 and the Y-axis carriage 23 function as a moving mechanism that moves the processing head 30A along the surface of the workpiece W in the X-axis direction, Y-axis direction, or any combined direction of the X-axis and Y-axis.
  • the processing head 30A irradiates the workpiece W with the laser beam transmitted by the process fiber 12.
  • the detailed configuration of the processing head 30A will be described later with reference to Figures 2 to 4.
  • a nozzle 24 that emits a laser beam is detachably attached to the tip of the processing head 30A.
  • a circular opening 25 is provided at the tip of the nozzle 24, and the laser beam is irradiated from the opening 25 to the workpiece W.
  • the machining head 30A is fixed to a Y-axis carriage 23 that is movable in the Y-axis direction, and the Y-axis carriage 23 is mounted on an X-axis carriage 22 that is movable in the X-axis direction. Therefore, the machining head 30A, i.e., the position where the laser beam is irradiated onto the workpiece W, can be moved along the surface of the workpiece W (in the X-axis and Y-axis directions). Note that instead of a configuration in which the machining head 30A moves along the surface of the workpiece W, a configuration in which the workpiece W moves while the position of the machining head 30A is fixed may also be used.
  • the laser processing machine 100 only needs to be equipped with a movement mechanism that moves the machining head 30A relative to the surface of the workpiece W.
  • the NC device 50 reads out a processing program for cutting the workpiece W from a processing program database (not shown) and information for controlling the first motor 41 and the second motor 42 (described below) in accordance with the processing program.
  • the processing program contains codes that define a series of operations of the laser processing machine 100 required to cut the workpiece W, such as setting processing conditions, starting and stopping laser beam emission, and the movement path (cutting processing path) of the processing head 30A.
  • the NC device 50 controls the first motor 41 and the second motor 42 based on the read information, while controlling the X-axis carriage 22 and the Y-axis carriage 23 to cut the workpiece W based on the processing program.
  • the assist gas supply device 60 supplies assist gas to the processing head 30A when processing the workpiece W.
  • the assist gas is nitrogen, oxygen, a mixture of nitrogen and oxygen, or air.
  • nitrogen is used as the assist gas
  • oxygen is used as the assist gas.
  • the assist gas is sprayed from the opening 25 of the nozzle 24 in a direction perpendicular to the workpiece W. The assist gas expels molten metal from the cutting groove where the workpiece W has melted.
  • FIG. 2 shows a configuration example of the processing head 30A.
  • the processing head 30A has a collimator lens 31, a special polarizing beam splitter 32, a quarter-wave plate 33, a first reflecting mirror 34, an axicon lens 35, and a second reflecting mirror 36.
  • the special polarizing beam splitter 32, the quarter-wave plate 33, the first reflecting mirror 34, the axicon lens 35, and the second reflecting mirror 36 in Figure 2 function as a polarization adjustment unit (polarization adjustment device) that outputs the first linearly polarized light L1 in the randomly polarized laser beam L including a first linearly polarized light L1 having a first polarization direction and a second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction as the first linearly polarized light L1, and converts the second linearly polarized light L2 into a second linearly polarized light L22 having a first polarization direction and outputs it.
  • polarization adjustment unit polarization adjustment device
  • the special polarizing beam splitter 32 functions as a dual-purpose optical element that serves both as the first optical element and the third optical element.
  • the quarter-wave plate 33 and the first reflecting mirror 34 function as the second optical element.
  • the processing head 30A also has a half-wave plate 37, a first motor 41 that rotates the half-wave plate 37, a lens array 38, a second motor 42 that rotates the lens array 38, and a focusing lens 39.
  • a double circle with a black center indicates the first linearly polarized light
  • a double-headed arrow indicates the second linearly polarized light.
  • the collimating lens 31 is incident with the diverging laser beam emitted from the exit end of the process fiber 12.
  • the diverging laser beam incident on the collimating lens 31 is a randomly polarized laser beam L including a first linearly polarized light L1 having a first polarization direction and a second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction.
  • the collimating lens 31 converts the incident randomly polarized laser beam L into parallel light (collimated light).
  • the randomly polarized laser beam L converted into collimated light by the collimating lens 31 is incident on the special polarizing beam splitter 32.
  • the special polarizing beam splitter 32 is arranged so that its surface is at a 45 degree angle with respect to the optical axis.
  • FIG. 3 shows an example of the configuration of the special polarizing beam splitter 32.
  • the special polarizing beam splitter 32 has an elliptical polarizing separation region 321 in the center, and a transmission region 322 around the polarizing separation region 321.
  • FIG. 4 shows the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship of the first and second linearly polarized light L1, L2 when the first and second linearly polarized light L1, L2 are emitted coaxially.
  • FIG. 4 shows the outline of the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized light L2, L21, and L22.
  • the arrows in the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized light L2, L21, and L22 in FIG. 4 simply show the polarization direction of each laser beam, and the difference in the length of the arrows is not particularly significant.
  • the polarization separation region 321 is a polarizing beam splitter that separates the first linearly polarized light L1 and the second linearly polarized light L2 in the randomly polarized laser beam L incident thereon, as shown in FIG. 4, by reflecting the first linearly polarized light L1 and transmitting the second linearly polarized light L2 in the randomly polarized laser beam L.
  • the transmission region 322 is provided with an anti-reflection coating, and transmits the incident laser beam.
  • the randomly polarized laser beam L emitted from the collimator lens 31 enters the polarization separation region 321 of the special polarizing beam splitter 32.
  • the polarization separation region 321 reflects the first linearly polarized light L1 contained in the randomly polarized laser beam L downward in the Z-axis direction perpendicular to the X-axis and Y-axis.
  • the polarization separation region 321 also transmits the second linearly polarized light L2 contained in the randomly polarized laser beam L, causing it to enter the quarter-wave plate 33.
  • the quarter-wave plate 33 is disposed between the special polarizing beam splitter 32 and the first reflecting mirror 34, and converts the second linearly polarized light L2 transmitted through the polarization separation region 321 of the special polarizing beam splitter 32 into the first circularly polarized light.
  • the quarter-wave plate 33 is preferably formed of, for example, quartz, and is preferably configured so that the phase delay of the laser beam that is incident on and transmitted through the quarter-wave plate 33 is 90°+n ⁇ 360° (n is an integer).
  • the quarter-wave plate 33 may be fabricated, for example, by bonding two quartz plates together so that their optical axes are perpendicular to each other.
  • the first circularly polarized light converted by the quarter-wave plate 33 is incident on the first reflecting mirror 34.
  • the first reflecting mirror 34 reflects the first circularly polarized light incident thereon and emits it as a second circularly polarized light whose phase is inverted from that of the first circularly polarized light.
  • the second circularly polarized light emitted from the first reflecting mirror 34 is incident on the quarter-wave plate 33.
  • the quarter-wave plate 33 converts the second circularly polarized light reflected by the first reflecting mirror 34 into the first polarization direction.
  • the quarter-wave plate 33 and the first reflecting mirror 34 convert the second linearly polarized light L2 separated by the special polarizing beam splitter 32 into second linearly polarized light L21 having a first polarization direction, as shown in FIG. 4.
  • the second linearly polarized light L21 emitted from the quarter-wave plate 33 enters the polarization separation region 321 of the special polarizing beam splitter 32.
  • the polarization separation region 321 reflects the second linearly polarized light L21 emitted from the quarter-wave plate 33 upward in the Z-axis direction.
  • the axicon lens 35 is disposed between the special polarizing beam splitter 32 and the second reflecting mirror 36.
  • the entrance surface of the axicon lens 35 for the laser beam is a conical inclined surface
  • the exit surface is a flat surface.
  • the inclined surface of the axicon lens 35 expands the second linearly polarized light L21 reflected upward by the polarization separation region 321 of the special polarizing beam splitter 32 into a ring shape, as shown in FIG. 4.
  • the second linearly polarized light L22 expanded into a ring shape by the axicon lens 35 in FIG. 4 is incident on the second reflecting mirror 36.
  • the second reflecting mirror 36 reflects the second linearly polarized light L22 emitted from the axicon lens 35.
  • the second linearly polarized light L22 reflected by the second reflecting mirror 36 is incident on the flat surface of the axicon lens 35 and emerges from the inclined surface.
  • the axicon lens 35 converts the incident ring-shaped second linearly polarized light L22 into collimated light and directs it into the transmission area 322 of the special polarizing beam splitter 32.
  • the transmission region 322 transmits the ring-shaped second linearly polarized light L22 emitted from the axicon lens 35.
  • the ring-shaped second linearly polarized light L22 transmitted through the transmission region 322 is positioned outside the first linearly polarized light L1 reflected by the polarization separation region 321, as shown in FIG. 4.
  • the polarization adjustment unit places a ring-shaped second linearly polarized light L22 having a first polarization direction outside the first linearly polarized light L1 reflected downward by the polarization separation region 321 of the special polarizing beam splitter 32, and emits the first linearly polarized light L1 and the second linearly polarized light L22 coaxially.
  • This makes it possible to align the polarization directions of the two linearly polarized light beams L1 and L2 contained in the randomly polarized laser beam L in parallel, and to eliminate the anisotropy in the cutting progression direction of the two laser beams whose polarization directions are aligned in parallel.
  • the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarizing beam splitter 32 are incident on the half-wave plate 37.
  • the half-wave plate 37 is disposed on the optical path of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarizing beam splitter 32, and is configured to be rotatable on the XY plane by the first motor 41 (first rotation mechanism).
  • the first motor 41 is controlled by an NC device 50 (first control unit) and rotates the half-wave plate 37 on the XY plane.
  • the NC device 50 controls the first motor 41 so that the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L22 transmitted through the half-wave plate 37 are parallel to the cutting direction of the laser processing machine 100.
  • the half-wave plate 37, the first motor 41, and the NC device 50 function as a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light L1 and the second linearly polarized light L22 emitted from the special polarized beam splitter 32 so that they are parallel to the cutting direction when the workpiece W is cut by irradiating the workpiece W with the laser beam.
  • the laser processing machine 100 aligns the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L2 contained in the randomly polarized laser beam to a first polarization direction, and controls the polarization direction of the laser beam whose polarization direction is aligned to the first polarization direction to be parallel to the cutting direction.
  • the polarization direction of the laser beam with respect to the cutting front which is the cut surface at the boundary between the non-melted area and the molten area in the cutting direction as the workpiece W is melted and cut, becomes p-polarized, thereby improving the absorption rate of the laser beam in the workpiece W.
  • the laser beam emitted from the half-wave plate 37 and controlled so that its polarization direction is parallel to the cutting direction is incident on the lens array 38.
  • the lens array 38 is disposed on the optical path of the laser beam controlled by the half-wave plate 37 so that its polarization direction is parallel to the cutting direction, and is configured to be rotatable by a second motor 42 (second rotation mechanism).
  • FIG. 5 shows an example of the configuration of the lens array 38.
  • the lens array 38 includes a plurality of rectangular lenses 38a arranged two-dimensionally.
  • a laser beam whose polarization direction is controlled by a half-wave plate 37 to be parallel to the cutting progression direction is incident on each of the plurality of lenses 38a.
  • Each of the plurality of lenses 38a may be a convex lens or a concave lens, and the lens array 38 is configured such that the entire plurality of lenses 38a are either convex lenses or concave lenses.
  • the focusing lens 39 focuses the laser beams that have passed through each lens 38a in the lens array 38 so that they overlap with each other, thereby irradiating a rectangular laser beam with a uniform intensity distribution onto the processing point WP of the workpiece W.
  • the second motor 42 is controlled by an NC device 50 (second control unit).
  • the NC device 50 controls the second motor 42 so that one side of the rectangular laser beam that passes through the lens array 38 and the focusing lens 39 and is irradiated to the processing point WP of the workpiece W is parallel to the cutting progression direction.
  • the NC device 50 functions as the first and second control units, but a control unit that controls the first motor 41 and a control unit that controls the second motor 42 may be provided separately.
  • the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 function as a rectangular beam angle control mechanism that shapes the laser beam, whose polarization direction is controlled by the polarization direction control mechanism so that it is parallel to the cutting direction, into a rectangular shape and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
  • FIG. 6A shows the relationship between the cutting direction of the workpiece W and the polarization direction of the laser beam irradiated to the workpiece W.
  • FIG. 6A shows the general shape of the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated to the workpiece. As shown in FIG.
  • the polarization direction control mechanism controls the polarization direction P of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 and shaped into a rectangular shape by the lens array 38 so that it is parallel to the cutting direction D when the workpiece W is cut by irradiating the workpiece W with the laser beam.
  • the rectangular beam angle control mechanism shapes the laser beam, which is controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape, and controls one side of the rectangularly shaped laser beam to be parallel to the cutting direction.
  • Figure 6B shows the relationship between the cutting direction of the workpiece W when the cutting direction of the workpiece W is curved and the polarization direction of the laser beam irradiated to the workpiece W.
  • Figure 6B shows the general shape of the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated to the workpiece.
  • Figure 6B shows the case of cutting the corner R of a product as an example of a case where the cutting direction of the workpiece W is curved.
  • the NC device 50 controls the first and second motors 41, 42 to rotate the half-wave plate 37 and the lens array 38 so that the polarization direction P and one side of the laser beam shaped into a rectangular shape are always parallel to the cutting direction D.
  • the polarization direction P of the laser beam at the cutting front and one side of the rectangular laser beam at the cutting front are always parallel to the cutting direction.
  • Figure 7A is a comparative example assuming that the processing head 30A does not have a lens array 38, and shows the relationship between the cutting front and the polarization direction and cutting direction when the cutting front has a semicircular shape.
  • Figure 7B shows the relationship between the cutting front and the polarization direction and cutting direction when the processing head 30A has a lens array 38 and the cutting front has a rectangular shape.
  • the shape of the cutting front here refers to the shape of the boundary between the non-melted area and the molten area in the cutting direction as the workpiece W melts and is cut, as viewed from the surface of the workpiece W.
  • the wavelength of the laser beam was 1.08 ⁇ m
  • the material of the workpiece W was iron
  • the thickness was 8 mm.
  • the absorption rate was approximately 55% when cutting was performed using the conventional laser beam.
  • the absorption rate of the laser beam in the workpiece W when cutting was performed using the laser processing machine 100 according to this embodiment was approximately 74%, confirming an improvement in absorption rate of approximately 19%.
  • the polarization adjustment device aligns the polarization directions of the first linearly polarized light L1 having a first polarization direction and the second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction contained in the randomly polarized laser beam L to the first polarization direction, and emits them coaxially.
  • the polarization adjustment device places a ring-shaped second linearly polarized light L22 having a first polarization direction outside the first linearly polarized light L1 reflected by the polarization separation region 321 of the first optical element (special polarized beam splitter 32), and emits the first linearly polarized light L1 and the second linearly polarized light L22 coaxially.
  • This makes it possible to align the polarization directions of the two linearly polarized lights L1 and L2 contained in the randomly polarized laser beam L in parallel, and to eliminate the anisotropy of the cutting progression direction of the two laser beams whose polarization directions are aligned in parallel.
  • the laser processing machine 100 equipped with the polarization adjustment device according to the first embodiment controls the polarization direction of the two laser beams, the polarization directions of which are aligned in parallel, so that they are parallel to the cutting direction.
  • the polarization direction of the laser beam with respect to the cutting front becomes p-polarized, thereby improving the absorption rate of the laser beam in the workpiece W.
  • the laser processing machine 100 which is equipped with the polarization adjustment device and polarization direction control mechanism according to the first embodiment, controls the polarization direction P of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the polarization adjustment device so that the polarization direction P is parallel to the cutting direction D when the workpiece W is cut by irradiating the workpiece W with a laser beam.
  • the rectangular beam angle control mechanism of the laser processing machine 100 shapes the laser beam, which has been controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape, and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
  • the workpiece W can be processed using two non-anisotropic laser beams with parallel polarization directions. Furthermore, during cutting, the polarization direction P of the laser beam at the cutting front and one side of the laser beam shaped into a rectangle at the cutting front are always parallel to the cutting direction. At any position in the width direction of the cutting groove, the polarization direction P is incident in a direction N perpendicular to the cutting front. Therefore, p-polarized light acts efficiently on the cutting front, improving the absorption rate of the laser beam in the workpiece W. This improves processing efficiency during cutting.
  • Fig. 8 shows an example of the configuration of the processing head 30B according to the second embodiment.
  • the laser processing machine 100 according to the second embodiment has a different internal configuration of the processing head compared to the laser processing machine 100 according to the first embodiment.
  • the other configurations are the same as those of the laser processing machine 100 according to the first embodiment. Therefore, in the laser processing machine 100 according to the second embodiment, the parts that differ from the laser processing machine 100 according to the first embodiment will be mainly described, and the same parts will not be described again.
  • the processing head 30B has a collimator lens 31, a polarizing beam splitter 71, a third reflecting mirror 72, axicon lenses 73 and 74, a fourth reflecting mirror 75, a half-wave plate 76, and a special mirror 77.
  • polarization adjustment unit polarization adjustment device
  • L1' polarization adjustment unit
  • L2' linearly polarized light L2' having a second polarization direction perpendicular to the first polarization direction, as the first linearly polarized light L1'
  • the polarizing beam splitter 71 functions as the first optical element.
  • the half-wave plate 76 functions as the second optical element.
  • the special mirror 77 functions as a third optical element separate from the first optical element.
  • the processing head 30B of the laser processing machine 100 has a half-wave plate 37, a first motor 41, a lens array 38, a second motor 42, a fifth reflecting mirror 78, and a focusing lens 39.
  • a double circle with a black center indicates the first linearly polarized light
  • a double-headed arrow indicates the second linearly polarized light.
  • the diverging laser beam emitted from the exit end of the process fiber 12 is incident on the collimating lens 31.
  • the diverging laser beam incident on the collimating lens 31 is a randomly polarized laser beam L' that includes a first linearly polarized light L1' having a first polarization direction and a second linearly polarized light L2' having a second polarization direction perpendicular to the first polarization direction.
  • the collimating lens 31 converts the incident randomly polarized laser beam L' into collimated light.
  • the randomly polarized laser beam L' converted into collimated light by the collimating lens 31 is incident on the polarizing beam splitter 71.
  • FIG. 9 shows the polarization direction and shape of the laser beam in FIG. 8, and the positional relationship of the first and second linearly polarized light L1', L2' when the first and second linearly polarized light L1', L2' are emitted coaxially.
  • FIG. 9 shows the outline of the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized light L2', L21', L22'.
  • the arrows in the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized light L2', L21', L22' in FIG. 9 simply show the polarization direction of each laser beam, and the difference in the length of the arrows is not particularly significant.
  • the polarizing beam splitter 71 is a polarizing beam splitter that separates the first linearly polarized light L1' from the second linearly polarized light L2' as shown in FIG. 9 by transmitting the first linearly polarized light L1' in the randomly polarized laser beam L' and reflecting the second linearly polarized light L2'.
  • the polarizing beam splitter 71 transmits the first linearly polarized light L1' contained in the randomly polarized laser beam L' and makes it incident on the special mirror 77.
  • the first linearly polarized light L1' that has transmitted through the polarizing beam splitter 71 is incident on the transmission area 771 (see FIG. 10) of the special mirror 77, which will be described later.
  • the polarizing beam splitter 71 also reflects the second linearly polarized light L2' contained in the randomly polarized laser beam L' upward in the Z-axis direction perpendicular to the X-axis and Y-axis.
  • the second linearly polarized light L2' reflected upward by the polarizing beam splitter 71 is incident on the third reflecting mirror 72.
  • the third reflecting mirror 72 reflects the second linearly polarized light L2' reflected by the polarizing beam splitter 71 in the X-axis direction.
  • the second linearly polarized light L2' reflected by the third reflecting mirror 72 is incident on the axicon lens 73.
  • the axicon lens 73 is arranged with its conical inclined surface facing the third reflecting mirror 72 and its flat surface facing the axicon lens 74.
  • the inclined surface of the axicon lens 73 expands the second linearly polarized light L2' reflected by the third reflecting mirror 72 into a ring shape, as shown in FIG. 9.
  • the second linearly polarized light L21' expanded into a ring shape by the axicon lens 73 enters the axicon lens 74.
  • the axicon lens 74 is positioned with its flat surface facing the axicon lens 73 and its conical inclined surface facing the fourth reflecting mirror 75.
  • the axicon lens 74 converts the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 into collimated light and makes it incident on the fourth reflecting mirror 75.
  • the fourth reflecting mirror 75 reflects the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 and converted into collimated light by the axicon lens 74 downward in the Z-axis direction and makes it incident on the half-wave plate 76.
  • the half-wave plate 76 converts the polarization direction of the ring-shaped second linearly polarized light L21' reflected by the fourth reflecting mirror 75 into the first polarization direction.
  • the half-wave plate 76 converts the second linearly polarized light L21', which has been separated by the polarizing beam splitter 71 and expanded into a ring shape by the axicon lens 73, into a ring-shaped second linearly polarized light L22' having the first polarization direction, as shown in FIG. 9.
  • the ring-shaped second linearly polarized light L22' emitted from the half-wave plate 76 is incident on the special mirror 77.
  • FIG. 10 shows an example of the configuration of special mirror 77.
  • special mirror 77 has an elliptical transmissive area 771 in the center, and a reflective area 772 around the transmissive area 771.
  • Transmissive area 771 is coated with an anti-reflective coating, and transmits the incident laser beam.
  • Reflective area 772 is coated with a highly reflective coating, and reflects the incident laser beam.
  • the first linearly polarized light L1' that has passed through the polarizing beam splitter 71 is incident on the transmission region 771 of the special mirror 77.
  • the transmission region 771 transmits the first linearly polarized light L1' that has passed through the polarizing beam splitter 71.
  • the ring-shaped second linearly polarized light L22' that has been emitted from the half-wave plate 76 is incident on the reflection region 772 of the special mirror 77.
  • the reflection region 772 reflects the incident ring-shaped second linearly polarized light L22' in the X-axis direction.
  • the ring-shaped second linearly polarized light L22' that has been reflected by the reflection region 772 is positioned outside the first linearly polarized light L1' that has passed through the transmission region 771, as shown in FIG. 9.
  • the polarization adjustment unit places a ring-shaped second linearly polarized light L22' having a first polarization direction outside the first linearly polarized light L1' that has passed through the polarizing beam splitter 71 and the transmission area 771 of the special mirror 77, and emits the first linearly polarized light L1' and the second linearly polarized light L22' coaxially.
  • This makes it possible to align the polarization directions of the two linearly polarized lights L1' and L2' contained in the randomly polarized laser beam L' in parallel, and to eliminate anisotropy with respect to the cutting direction of the laser beam.
  • the first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77 are incident on the half-wave plate 37.
  • the half-wave plate 37 is disposed on the optical path of the first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77, and is configured to be rotatable on the XZ plane by the first motor 41.
  • the laser beam emitted from the half-wave plate 37 and controlled so that its polarization direction is parallel to the cutting direction is incident on the lens array 38.
  • the lens array 38 is disposed on the optical path of the laser beam controlled by the half-wave plate 37 so that its polarization direction is parallel to the cutting direction, and is configured to be rotatable on the XZ plane by the second motor 42.
  • the fifth reflecting mirror 78 reflects the laser beam that has passed through the lens array 38 downward in the Z-axis direction, and makes it enter the focusing lens 39.
  • the focusing lens 39 focuses the laser beam reflected by the fifth reflecting mirror 78, and irradiates a rectangular laser beam with a uniform intensity distribution onto the processing point WP of the workpiece W.
  • the first motor 41 is controlled by the NC device 50 to rotate the half-wave plate 37.
  • the NC device 50 controls the first motor 41 so that the polarization directions of the first linearly polarized light L1' and the second linearly polarized light L22' that pass through the half-wave plate 37 and the lens array 38, are reflected by the fifth reflecting mirror 78, and are transmitted through the focusing lens 39, are parallel to the cutting progression direction.
  • the half-wave plate 37, the first motor 41, and the NC device 50 function as a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77 so that they are parallel to the cutting direction when the workpiece W is cut by irradiating the workpiece W with the laser beam.
  • the second motor 42 is controlled by the NC device 50 to rotate the lens array 38.
  • the NC device 50 controls the second motor 42 so that one side of the rectangular laser beam that passes through the lens array 38, is reflected by the fifth reflecting mirror 78, passes through the focusing lens 39, and is irradiated onto the processing point WP of the workpiece W is parallel to the cutting progression direction.
  • the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 function as a rectangular beam angle control mechanism that shapes the laser beam, whose polarization direction is controlled by the polarization direction control mechanism so that it is parallel to the cutting direction, into a rectangular shape and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
  • the polarization adjustment device aligns the polarization direction of the randomly polarized laser beam L', which includes the first linearly polarized light L1' and the second linearly polarized light L2', to the first polarization direction by using a polarizing beam splitter 71, a third reflecting mirror 72, axicon lenses 73 and 74, a fourth reflecting mirror 75, a half-wave plate 76, and a special mirror 77.
  • Each optical element of the polarization adjustment device according to the second embodiment can be arranged so as not to reflect the laser beam toward the exit end of the process fiber 12.
  • the present invention is not limited to the first or second embodiment described above, and various modifications are possible without departing from the gist of the present invention.

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Abstract

In the present invention, a first optical element (32, 71) divides a randomly polarized laser beam (L) into first linear polarized light (L1, L1') having a first polarization direction and second linear polarized light (L2, L2') having a second polarization direction orthogonal to the first polarization direction. A second optical element (33, 34, 76) converts the polarization direction of the second linear polarized light (L2, L21') divided by the first optical element (32, 71) to the first polarization direction. An axicon lens (35, 73, 74) spreads either the second linear polarized light (L21) emitted by the second optical element (33) or the second linear polarized light (L2') incident on the second optical element (76) into a ring form. A third optical element (32, 77) emits the first linear polarized light (L1, L1') divided by the first optical element (32, 71) and the second linear polarized light (L22, L22') that was spread into a ring form by the axicon lens (35, 73, 74) on the same axis.

Description

偏光調整装置及びレーザ加工機Polarization adjustment device and laser processing machine
　本開示は、偏光調整装置及びレーザ加工機に関する。 This disclosure relates to a polarization adjustment device and a laser processing machine.
　レーザ加工機は、レーザ発振器より射出されたレーザビームによって金属の被加工材を切断加工する。レーザ発振器が射出するレーザビームは、互いに直交する２つの直線偏光成分（以下、ｐ偏光、ｓ偏光と言う）を含むランダム偏光である。ランダム偏光のレーザビームにより切断加工を行う際の被加工材のレーザビームの吸収率は、レーザビームが被加工材へ入射する入射角度に応じて変化することが知られている。ランダム偏光のレーザビームの吸収率は、ｐ偏光の吸収率とｓ偏光の吸収率の平均値となる。 Laser processing machines cut metal workpieces with a laser beam emitted from a laser oscillator. The laser beam emitted by the laser oscillator is randomly polarized light that contains two mutually orthogonal linearly polarized components (hereafter referred to as p-polarized light and s-polarized light). It is known that the absorption rate of the laser beam by the workpiece when cutting with a randomly polarized laser beam varies depending on the angle of incidence of the laser beam onto the workpiece. The absorption rate of a randomly polarized laser beam is the average value of the absorption rates of p-polarized light and s-polarized light.
　レーザ加工機による一般的な切断加工においては、レーザビームは被加工材に対して８２度～８８度の入射角度で入射されて、被加工材が切断される。被加工材の金属が鉄、レーザビームの波長が１μｍ帯である場合を例として、レーザビームの入射角が８２度～８８度であると、p偏光の吸収率が最大で９０％程度となるのに対し、s偏光の吸収率は１０％未満となる。ランダム偏光のレーザビームの吸収率はｐ偏光の吸収率とｓ偏光の吸収率との平均値となるため、ランダム偏光のレーザビームの吸収率は４０％またはそれ以下となってしまい、被加工材を切断加工するときの加工効率を低下させる要因の一つとなっている。 In typical cutting processes using laser processing machines, the laser beam is incident on the workpiece at an angle of 82 degrees to 88 degrees, cutting the workpiece. For example, if the workpiece is made of iron metal and the laser beam has a wavelength in the 1 μm range, when the incident angle of the laser beam is 82 degrees to 88 degrees, the absorption rate of p-polarized light is a maximum of about 90%, while the absorption rate of s-polarized light is less than 10%. The absorption rate of a randomly polarized laser beam is the average value of the absorption rates of p-polarized light and s-polarized light, so the absorption rate of a randomly polarized laser beam is 40% or less, which is one of the factors that reduce the processing efficiency when cutting a workpiece.
　この問題を解決する方法として、特許文献１には、ランダム偏光のレーザビームに含まれる２つの直線偏光の偏光方向を平行に揃え、偏光方向が平行に揃った２つの直線偏光の偏光方向を、切断加工を行う方向（以下、切断進行方向と言う）と一致させるように制御するレーザ加工機が開示されている。直線偏光の偏光方向を切断進行方向と一致させることにより、カッティングフロントに対するレーザビームの偏光方向がｐ偏光となり、被加工材のレーザビームの吸収率がｐ偏光の吸収率となる。これにより、被加工材のレーザビームの吸収率が向上して加工効率を向上させることができる。なお、ここでのカッティングフロントとは、被加工材が溶融して切断されていくときの切断進行方向の非溶融領域と溶融領域との境界の切断面である。 As a method for solving this problem, Patent Document 1 discloses a laser processing machine that aligns the polarization directions of two linearly polarized lights contained in a randomly polarized laser beam in parallel and controls the polarization direction of the two parallel linearly polarized lights to match the direction in which cutting is performed (hereinafter referred to as the cutting direction). By matching the polarization direction of the linearly polarized light with the cutting direction, the polarization direction of the laser beam with respect to the cutting front becomes p-polarized light, and the absorption rate of the laser beam in the workpiece becomes the absorption rate of p-polarized light. This improves the absorption rate of the laser beam in the workpiece, thereby improving processing efficiency. The cutting front here refers to the cut surface at the boundary between the non-melted area and the molten area in the cutting direction when the workpiece is melted and cut.
特開平７－２６６０７１号公報Japanese Patent Application Laid-Open No. 7-266071
　特許文献１に記載されているレーザ加工機は、偏光方向が同一且つ波長が同一である２つの直線偏光のレーザビームを一つの集束レンズによって集束させて、被加工材に照射する。しかしながら、原理的に、偏光方向が同一且つ波長が同一の２つのレーザビームを同じ位置に集束させることはできない。したがって、実際には、２つのレーザビームを集束させる位置を異ならせて、２つのレーザビームを例えば横並びに隣接するように配置する必要がある。すなわち、偏光方向を平行に揃えた２つのレーザビームは互いに異なる２つの軸に沿って進行するため、２つのレーザビームは切断進行方向に対して異方性を有する。２つのレーザビームが切断進行方向に対する異方性を有すると、被加工材の切断進行方向が任意に変化するレーザ切断加工において切断品質が一定とならず、切断品質の低下を招くことがある。 The laser processing machine described in Patent Document 1 focuses two linearly polarized laser beams with the same polarization direction and wavelength by one focusing lens and irradiates the workpiece. However, in principle, two laser beams with the same polarization direction and wavelength cannot be focused at the same position. Therefore, in practice, it is necessary to focus the two laser beams at different positions and arrange the two laser beams, for example, side by side. In other words, since two laser beams with parallel polarization directions travel along two different axes, the two laser beams have anisotropy with respect to the cutting direction. If the two laser beams have anisotropy with respect to the cutting direction, the cutting quality will not be constant in laser cutting processing in which the cutting direction of the workpiece changes arbitrarily, which may lead to a deterioration of the cutting quality.
　ランダム偏光のレーザビームに含まれる２つの直線偏光の偏光方向を平行に揃えることができ、且つ、偏光方向を平行に揃えた２つのレーザビームの切断進行方向に対する異方性をなくすことができる偏光調整装置、及びそのような偏光調整装置を備えるレーザ加工機の登場が望まれている。 There is a demand for a polarization adjustment device that can align the polarization directions of two linearly polarized beams contained in a randomly polarized laser beam to be parallel, and can eliminate the anisotropy of the two laser beams with parallel polarization directions in the cutting direction, as well as a laser processing machine equipped with such a polarization adjustment device.
　１またはそれ以上の実施形態の第１の態様は、第１の偏光方向を有する第１の直線偏光と、前記第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光とを含むランダム偏光のレーザビームを、前記第１の直線偏光と前記第２の直線偏光とに分離する第１の光学素子と、前記第１の光学素子によって分離された前記第２の直線偏光の偏光方向を前記第１の偏光方向に変換する第２の光学素子と、前記第２の光学素子より射出された前記第２の直線偏光、または前記第２の光学素子に入射される前記第２の直線偏光をリング状に広げるアキシコンレンズと、前記第１の光学素子によって分離された前記第１の直線偏光と、前記アキシコンレンズによってリング状に広げられた前記第２の直線偏光とを同軸で射出する、前記第１の光学素子と兼用されている、または前記第１の光学素子とは別体であるの第３の光学素子と、を備える偏光調整装置である。 A first aspect of one or more embodiments is a polarization adjustment device comprising: a first optical element that separates a randomly polarized laser beam, which includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction, into the first linearly polarized light and the second linearly polarized light; a second optical element that converts the polarization direction of the second linearly polarized light separated by the first optical element to the first polarization direction; an axicon lens that expands the second linearly polarized light emitted from the second optical element or the second linearly polarized light incident on the second optical element into a ring shape; and a third optical element that is used in combination with the first optical element or is separate from the first optical element and that coaxially emits the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens.
　１またはそれ以上の実施形態の第２の態様は、第１の態様の偏光調整装置と、前記偏光調整装置より同軸で射出された前記第１の直線偏光及び前記第２の直線偏光の偏光方向を、被加工材にレーザビームを照射して前記被加工材を切断するときの切断進行方向と平行となるように制御する偏光方向制御機構と、を備えるレーザ加工機である。 A second aspect of one or more of the embodiments is a laser processing machine that includes the polarization adjustment device of the first aspect, and a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light and the second linearly polarized light emitted coaxially from the polarization adjustment device so that the polarization direction is parallel to the cutting direction when a laser beam is irradiated onto a workpiece to cut the workpiece.
　１またはそれ以上の実施形態に係る偏光調整装置によれば、ランダム偏光のレーザビームに含まれる２つの直線偏光の偏光方向を平行に揃えることができ、且つ、偏光方向を平行に揃えた２つのレーザビームの切断進行方向に対する異方性をなくすことができる。１またはそれ以上の実施形態に係るレーザ加工機によれば、偏光方向を平行に揃えた異方性のない２つのレーザビームによって被加工材を加工することができる。 The polarization adjustment device according to one or more embodiments can align the polarization directions of two linearly polarized lights contained in a randomly polarized laser beam in parallel, and can eliminate the anisotropy of the two laser beams with parallel polarization directions in the cutting direction. The laser processing machine according to one or more embodiments can process the workpiece with two laser beams with no anisotropy and with parallel polarization directions.
図１は、第１実施形態に係るレーザ加工機の全体的な構成例を示す図である。FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine according to a first embodiment. 図２は、第１実施形態に係る加工ヘッドの構成例を示す図である。FIG. 2 is a diagram showing an example of the configuration of the machining head according to the first embodiment. 図３は、図２に示す加工ヘッドが備える特殊偏光ビームスプリッタの構成例を示す図である。FIG. 3 is a diagram showing an example of the configuration of a special polarizing beam splitter provided in the processing head shown in FIG. 図４は、図２におけるレーザビームの偏光方向及び形状と、第１及び第２の直線偏光が同軸で射出されるときの第１及び第２の直線偏光の位置関係を示す図である。FIG. 4 is a diagram showing the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship between the first and second linearly polarized light beams when they are emitted coaxially. 図５は、図２に示す加工ヘッドが備えるレンズアレイの構成例を示す図である。FIG. 5 is a diagram showing a configuration example of a lens array provided in the processing head shown in FIG. 図６Ａは、被加工材の切断進行方向と、被加工材Ｗに照射されるレーザビームの偏光方向との関係を示す図である。FIG. 6A is a diagram showing the relationship between the cutting direction of the workpiece and the polarization direction of the laser beam irradiated onto the workpiece W. 図６Ｂは、被加工材の切断進行方向が曲線を描くときの切断進行方向と、被加工材Ｗに照射されるレーザビームの偏光方向との関係を示す図である。FIG. 6B is a diagram showing the relationship between the cutting direction of the workpiece W when the cutting direction of the workpiece W forms a curve and the polarization direction of the laser beam irradiated to the workpiece W. 図７Ａは、カッティングフロントの形状が半円状であるときの、カッティングフロントと偏光方向及び切断進行方向との関係を示す図である。FIG. 7A is a diagram showing the relationship between the cutting front and the polarization direction and the cutting proceeding direction when the cutting front has a semicircular shape. 図７Ｂは、カッティングフロントの形状が矩形状であるときの、カッティングフロントと偏光方向及び切断進行方向との関係を示す図である。FIG. 7B is a diagram showing the relationship between the cutting front and the polarization direction and the cutting proceeding direction when the cutting front has a rectangular shape. 図８は、第２実施形態に係る加工ヘッドの構成例を示す図である。FIG. 8 is a diagram showing an example of the configuration of a machining head according to the second embodiment. 図９は、図８におけるレーザビームの偏光方向及び形状と、第１及び第２の直線偏光が同軸で射出されるときの第１及び第２の直線偏光の位置関係を示す図である。FIG. 9 is a diagram showing the polarization direction and shape of the laser beam in FIG. 8 and the positional relationship between the first and second linearly polarized light beams when they are emitted coaxially. 図１０は、図８に示す加工ヘッドが備える特殊ミラーを示す図である。FIG. 10 is a diagram showing a special mirror provided in the processing head shown in FIG.
　１またはそれ以上の実施形態に係る偏光調整装置は、第１の光学素子、第２の光学素子、アキシコンレンズ、第３の光学素子を備える。 The polarization adjustment device according to one or more embodiments includes a first optical element, a second optical element, an axicon lens, and a third optical element.
　第１の光学素子は、第１の偏光方向を有する第１の直線偏光と、第1の偏光方向と直交する第２の偏光方向を有する第２の直線偏光とを含むランダム偏光のレーザビームを、第１の直線偏光と第２の直線偏光とに分離する。第２の光学素子は、第１の光学素子によって分離された第２の直線偏光の偏光方向を第１の偏光方向に変換する。アキシコンレンズは、第２の光学素子により射出された第２の直線偏光、または第２の光学素子に入射される第２の直線偏光を、リング状に広げる。第３の光学素子は、第１の光学素子によって分離された第１の直線偏光と、アキシコンレンズによってリング状に広げられた第２の直線偏光とを同軸で射出する。第３の光学素子は、第１の光学素子と兼用されている、または第１の光学素子とは別体である。 The first optical element separates a randomly polarized laser beam, which includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction perpendicular to the first polarization direction, into the first linearly polarized light and the second linearly polarized light. The second optical element converts the polarization direction of the second linearly polarized light separated by the first optical element to the first polarization direction. The axicon lens expands the second linearly polarized light output by the second optical element or the second linearly polarized light incident on the second optical element into a ring shape. The third optical element coaxially outputs the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens. The third optical element is used in combination with the first optical element, or is separate from the first optical element.
　［第１実施形態］
　以下、第１実施形態に係る偏光調整装置及びレーザ加工機について、図面を参照して具体的に説明する。 [First embodiment]
Hereinafter, the polarization adjustment device and the laser processing machine according to the first embodiment will be specifically described with reference to the drawings.
　図１は、第１実施形態に係る偏光調整装置を備えるレーザ加工機１００の全体的な構成例を示す図である。図１において、レーザ加工機１００は、レーザビームによって被加工材Ｗを切断加工する加工機である。加工対象の被加工材Ｗは例えば軟鋼板である。被加工材Ｗは、ステンレス鋼等の軟鋼板以外の鉄系の板金であってもよいし、アルミニウム、アルミニウム合金、銅等の鉄系以外の板金であってもよい。 FIG. 1 is a diagram showing an example of the overall configuration of a laser processing machine 100 equipped with a polarization adjustment device according to the first embodiment. In FIG. 1, the laser processing machine 100 is a processing machine that cuts and processes a workpiece W using a laser beam. The workpiece W to be processed is, for example, a mild steel plate. The workpiece W may be an iron-based sheet metal other than a mild steel plate, such as stainless steel, or may be a non-iron-based sheet metal such as aluminum, an aluminum alloy, or copper.
　図１に示すように、レーザ加工機１００は、レーザビームを生成して射出するレーザ発振器１０と、レーザ加工ユニット２０と、レーザ発振器１０より射出されたレーザビームをレーザ加工ユニット２０へと伝送するプロセスファイバ１２とを備える。また、レーザ加工機１００は、ＮＣ（数値制御：Numerical Control）装置５０と、アシストガス供給装置６０とを備える。ＮＣ装置５０は、レーザ加工機１００の各部を制御する制御装置の一例である。 As shown in FIG. 1, the laser processing machine 100 includes a laser oscillator 10 that generates and emits a laser beam, a laser processing unit 20, and a process fiber 12 that transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20. The laser processing machine 100 also includes an NC (Numerical Control) device 50 and an assist gas supply device 60. The NC device 50 is an example of a control device that controls each part of the laser processing machine 100.
　レーザ発振器１０としては、レーザダイオードより発せられる励起光を増幅して所定の波長のレーザビームを射出するレーザ発振器、またはレーザダイオードより発せられるレーザビームを直接利用するレーザ発振器が好適である。レーザ発振器１０は、例えば、固体レーザ発振器、ファイバレーザ発振器、ディスクレーザ発振器、ダイレクトダイオードレーザ発振器（ＤＤＬ発振器）である。 As the laser oscillator 10, a laser oscillator that amplifies the excitation light emitted from a laser diode to emit a laser beam of a specified wavelength, or a laser oscillator that directly uses the laser beam emitted from a laser diode, is suitable. The laser oscillator 10 is, for example, a solid-state laser oscillator, a fiber laser oscillator, a disk laser oscillator, or a direct diode laser oscillator (DDL oscillator).
　レーザ発振器１０は、波長９００ｎｍ～１１００ｎｍの１μｍ帯のレーザビームを射出する。ファイバレーザ発振器及びＤＤＬ発振器を例とすると、ファイバレーザ発振器は、波長１０６０ｎｍ～１０８０ｎｍのレーザビームを射出し、ＤＤＬ発振器は、波長９１０ｎｍ～９５０ｎｍのレーザビームを射出する。 The laser oscillator 10 emits a laser beam in the 1 μm band with a wavelength of 900 nm to 1100 nm. Taking a fiber laser oscillator and a DDL oscillator as examples, a fiber laser oscillator emits a laser beam with a wavelength of 1060 nm to 1080 nm, and a DDL oscillator emits a laser beam with a wavelength of 910 nm to 950 nm.
　プロセスファイバ１２は、レーザ発振器１０より射出されたレーザビームをレーザ加工ユニット２０へと伝送する。なお、第１実施形態においてプロセスファイバ１２で伝送されるレーザビームは、第１の偏光方向を有する第１の直線偏光と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光とを含むランダム偏光のレーザビームである。 The process fiber 12 transmits the laser beam emitted from the laser oscillator 10 to the laser processing unit 20. In the first embodiment, the laser beam transmitted by the process fiber 12 is a randomly polarized laser beam that includes a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction perpendicular to the first polarization direction.
　レーザ加工ユニット２０は、プロセスファイバ１２によって伝送されたレーザビームを用いて、被加工材Ｗを切断する。レーザ加工ユニット２０は、被加工材Ｗを載せる加工テーブル２１と、門型のＸ軸キャリッジ２２と、Ｙ軸キャリッジ２３と、加工ヘッド３０Ａとを有している。Ｘ軸キャリッジ２２は、加工テーブル２１上でＸ軸方向に沿って移動自在に構成されている。Ｙ軸キャリッジ２３は、Ｘ軸キャリッジ２２上でＸ軸に垂直なＹ軸方向に沿って移動自在に構成されている。Ｘ軸キャリッジ２２及びＹ軸キャリッジ２３は、加工ヘッド３０Ａを被加工材Ｗの表面に沿って、Ｘ軸方向、Ｙ軸方向、または、Ｘ軸とＹ軸との任意の合成方向に移動させる移動機構として機能する。 The laser processing unit 20 cuts the workpiece W using a laser beam transmitted by the process fiber 12. The laser processing unit 20 has a processing table 21 on which the workpiece W is placed, a gate-shaped X-axis carriage 22, a Y-axis carriage 23, and a processing head 30A. The X-axis carriage 22 is configured to be freely movable along the X-axis direction on the processing table 21. The Y-axis carriage 23 is configured to be freely movable along the Y-axis direction perpendicular to the X-axis on the X-axis carriage 22. The X-axis carriage 22 and the Y-axis carriage 23 function as a moving mechanism that moves the processing head 30A along the surface of the workpiece W in the X-axis direction, Y-axis direction, or any combined direction of the X-axis and Y-axis.
　加工ヘッド３０Ａは、プロセスファイバ１２によって伝送されたレーザビームを被加工材Ｗに照射する。加工ヘッド３０Ａの詳細な構成については、図２～図４を参照して後述する。加工ヘッド３０Ａの先端には、レーザビームを射出するノズル２４が着脱自在に取り付けられている。ノズル２４の先端部には円形の開口２５が設けられており、レーザビームは開口２５から被加工材Ｗに照射される。 The processing head 30A irradiates the workpiece W with the laser beam transmitted by the process fiber 12. The detailed configuration of the processing head 30A will be described later with reference to Figures 2 to 4. A nozzle 24 that emits a laser beam is detachably attached to the tip of the processing head 30A. A circular opening 25 is provided at the tip of the nozzle 24, and the laser beam is irradiated from the opening 25 to the workpiece W.
　加工ヘッド３０Ａは、Ｙ軸方向に移動自在のＹ軸キャリッジ２３に固定され、Ｙ軸キャリッジ２３は、Ｘ軸方向に移動自在のＸ軸キャリッジ２２に設けられている。よって、加工ヘッド３０Ａ、即ち、レーザビームを被加工材Ｗに照射する位置を、被加工材Ｗの面（Ｘ軸方向及びＹ軸方向）に沿って移動させることができる。なお、加工ヘッド３０Ａを被加工材Ｗの面に沿って移動させる構成に代えて、加工ヘッド３０Ａの位置を固定したまま、被加工材Ｗを移動する構成であってもよい。レーザ加工機１００は、被加工材Ｗの面に対して加工ヘッド３０Ａを相対的に移動させる移動機構を備えていればよい。 The machining head 30A is fixed to a Y-axis carriage 23 that is movable in the Y-axis direction, and the Y-axis carriage 23 is mounted on an X-axis carriage 22 that is movable in the X-axis direction. Therefore, the machining head 30A, i.e., the position where the laser beam is irradiated onto the workpiece W, can be moved along the surface of the workpiece W (in the X-axis and Y-axis directions). Note that instead of a configuration in which the machining head 30A moves along the surface of the workpiece W, a configuration in which the workpiece W moves while the position of the machining head 30A is fixed may also be used. The laser processing machine 100 only needs to be equipped with a movement mechanism that moves the machining head 30A relative to the surface of the workpiece W.
　ＮＣ装置５０は、加工プログラムデータベース（図示せず）より、被加工材Ｗを切断加工するための加工プログラムと、加工プログラムに対応して、後述する第１のモータ４１及び第２のモータ４２を制御するための情報とを読み出す。 The NC device 50 reads out a processing program for cutting the workpiece W from a processing program database (not shown) and information for controlling the first motor 41 and the second motor 42 (described below) in accordance with the processing program.
　加工プログラムには、加工条件の設定、レーザビームの射出開始及びレーザビームの射出停止、加工ヘッド３０Ａの移動経路（切断加工経路）等の、被加工材Ｗを切断加工するために必要なレーザ加工機１００の一連の動作を規定するコードが記述されている。ＮＣ装置５０は、読み出した情報に基づいて、第１のモータ４１及び第２のモータ４２を制御しつつ、加工プログラムに基づいて被加工材Ｗを切断加工するようＸ軸キャリッジ２２及びＹ軸キャリッジ２３を制御する。 The processing program contains codes that define a series of operations of the laser processing machine 100 required to cut the workpiece W, such as setting processing conditions, starting and stopping laser beam emission, and the movement path (cutting processing path) of the processing head 30A. The NC device 50 controls the first motor 41 and the second motor 42 based on the read information, while controlling the X-axis carriage 22 and the Y-axis carriage 23 to cut the workpiece W based on the processing program.
　アシストガス供給装置６０は、被加工材Ｗの加工時に、アシストガスを加工ヘッド３０Ａに供給する。アシストガスは、窒素、酸素、窒素と酸素との混合気体、または空気である。例えば、被加工材Ｗがステンレス鋼であれば窒素がアシストガスとして用いられ、被加工材Ｗが軟鋼板であれば酸素がアシストガスとして用いられる。アシストガスは、ノズル２４の開口２５から被加工材Ｗに対して垂直な方向に吹き付けられる。アシストガスは、被加工材Ｗが溶融した切断溝内の溶融金属を排出する。 The assist gas supply device 60 supplies assist gas to the processing head 30A when processing the workpiece W. The assist gas is nitrogen, oxygen, a mixture of nitrogen and oxygen, or air. For example, if the workpiece W is stainless steel, nitrogen is used as the assist gas, and if the workpiece W is a mild steel plate, oxygen is used as the assist gas. The assist gas is sprayed from the opening 25 of the nozzle 24 in a direction perpendicular to the workpiece W. The assist gas expels molten metal from the cutting groove where the workpiece W has melted.
　［加工ヘッド３０Ａの構成例］
　図２～図５を参照して、加工ヘッド３０Ａの詳細な構成例について説明する。図２は、加工ヘッド３０Ａの構成例を示す。図２に示すように、加工ヘッド３０Ａは、コリメートレンズ３１、特殊偏光ビームスプリッタ３２、１／４波長板３３、第１の反射ミラー３４、アキシコンレンズ３５、第２の反射ミラー３６を有する。図２における特殊偏光ビームスプリッタ３２、１／４波長板３３、第１の反射ミラー３４、アキシコンレンズ３５、第２の反射ミラー３６は、第１の偏光方向を有する第１の直線偏光Ｌ１と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光Ｌ２とを含むランダム偏光のレーザビームＬにおける第１の直線偏光Ｌ１を第１の直線偏光Ｌ１として射出し、第２の直線偏光Ｌ２を第１の偏光方向を有する第２の直線偏光Ｌ２２に変換して射出する偏光調整部（偏光調整装置）として機能する。 [Configuration example of machining head 30A]
A detailed configuration example of the processing head 30A will be described with reference to Figures 2 to 5. Figure 2 shows a configuration example of the processing head 30A. As shown in Figure 2, the processing head 30A has a collimator lens 31, a special polarizing beam splitter 32, a quarter-wave plate 33, a first reflecting mirror 34, an axicon lens 35, and a second reflecting mirror 36. The special polarizing beam splitter 32, the quarter-wave plate 33, the first reflecting mirror 34, the axicon lens 35, and the second reflecting mirror 36 in Figure 2 function as a polarization adjustment unit (polarization adjustment device) that outputs the first linearly polarized light L1 in the randomly polarized laser beam L including a first linearly polarized light L1 having a first polarization direction and a second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction as the first linearly polarized light L1, and converts the second linearly polarized light L2 into a second linearly polarized light L22 having a first polarization direction and outputs it.
　第１実施形態においては、特殊偏光ビームスプリッタ３２は、第１の光学素子と第３の光学素子とを兼用する兼用光学素子として機能する。また、１／４波長板３３及び第１の反射ミラー３４は、第２の光学素子として機能する。また、加工ヘッド３０Ａは、１／２波長板３７、１／２波長板３７を回転させる第１のモータ４１、レンズアレイ３８、レンズアレイ３８を回転させる第２のモータ４２、集束レンズ３９を有する。なお、図２において、中心が黒の二重丸は第１の直線偏光を示し、両矢印は第２の直線偏光を示す。 In the first embodiment, the special polarizing beam splitter 32 functions as a dual-purpose optical element that serves both as the first optical element and the third optical element. The quarter-wave plate 33 and the first reflecting mirror 34 function as the second optical element. The processing head 30A also has a half-wave plate 37, a first motor 41 that rotates the half-wave plate 37, a lens array 38, a second motor 42 that rotates the lens array 38, and a focusing lens 39. In FIG. 2, a double circle with a black center indicates the first linearly polarized light, and a double-headed arrow indicates the second linearly polarized light.
　コリメートレンズ３１は、プロセスファイバ１２の射出端より射出された発散光のレーザビームが入射される。コリメートレンズ３１に入射される発散光のレーザビームは、第１の偏光方向を有する第１の直線偏光Ｌ１と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光Ｌ２とを含むランダム偏光のレーザビームＬである。コリメートレンズ３１は、入射されたランダム偏光のレーザビームＬを平行光（コリメート光）に変換する。コリメートレンズ３１によりコリメート光に変換されたランダム偏光のレーザビームＬは、特殊偏光ビームスプリッタ３２へ入射する。特殊偏光ビームスプリッタ３２は光軸に対して面が４５度の角度となるように配置されている。 The collimating lens 31 is incident with the diverging laser beam emitted from the exit end of the process fiber 12. The diverging laser beam incident on the collimating lens 31 is a randomly polarized laser beam L including a first linearly polarized light L1 having a first polarization direction and a second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction. The collimating lens 31 converts the incident randomly polarized laser beam L into parallel light (collimated light). The randomly polarized laser beam L converted into collimated light by the collimating lens 31 is incident on the special polarizing beam splitter 32. The special polarizing beam splitter 32 is arranged so that its surface is at a 45 degree angle with respect to the optical axis.
　図３は、特殊偏光ビームスプリッタ３２の構成例を示す。図３に示すように、特殊偏光ビームスプリッタ３２は、中心部に楕円状の偏光分離領域３２１を有し、偏光分離領域３２１の周囲に透過領域３２２を有する。図４は、図２におけるレーザビームの偏光方向及び形状と、第１及び第２の直線偏光Ｌ１、Ｌ２が同軸で射出されるときの第１及び第２の直線偏光Ｌ１、Ｌ２の位置関係を示す。図４は、ランダム偏光のレーザビームＬ、第１の直線偏光Ｌ１、及び第２の直線偏光Ｌ２、Ｌ２１、Ｌ２２の外形を模式的に示している。また、図４のランダム偏光のレーザビームＬ、第１の直線偏光Ｌ１、及び第２の直線偏光Ｌ２、Ｌ２１、Ｌ２２の中の矢印は、単に各々のレーザビームの偏光方向を模式的に示すものであり、矢印の長さの違いに特に意味はない。 FIG. 3 shows an example of the configuration of the special polarizing beam splitter 32. As shown in FIG. 3, the special polarizing beam splitter 32 has an elliptical polarizing separation region 321 in the center, and a transmission region 322 around the polarizing separation region 321. FIG. 4 shows the polarization direction and shape of the laser beam in FIG. 2, and the positional relationship of the first and second linearly polarized light L1, L2 when the first and second linearly polarized light L1, L2 are emitted coaxially. FIG. 4 shows the outline of the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized light L2, L21, and L22. The arrows in the randomly polarized laser beam L, the first linearly polarized light L1, and the second linearly polarized light L2, L21, and L22 in FIG. 4 simply show the polarization direction of each laser beam, and the difference in the length of the arrows is not particularly significant.
　偏光分離領域３２１は、入射されたランダム偏光のレーザビームＬにおける第１の直線偏光Ｌ１を反射させ、第２の直線偏光Ｌ２を透過させることによって、図４に示すように、ランダム偏光のレーザビームＬにおける第１の直線偏光Ｌ１と第２の直線偏光Ｌ２とを分離する偏光ビームスプリッタである。透過領域３２２には反射防止コーティングが施されており、透過領域３２２は入射されたレーザビームを透過させる。 The polarization separation region 321 is a polarizing beam splitter that separates the first linearly polarized light L1 and the second linearly polarized light L2 in the randomly polarized laser beam L incident thereon, as shown in FIG. 4, by reflecting the first linearly polarized light L1 and transmitting the second linearly polarized light L2 in the randomly polarized laser beam L. The transmission region 322 is provided with an anti-reflection coating, and transmits the incident laser beam.
　コリメートレンズ３１より射出されたランダム偏光のレーザビームＬは、特殊偏光ビームスプリッタ３２の偏光分離領域３２１へ入射する。偏光分離領域３２１は、ランダム偏光のレーザビームＬに含まれる第１の直線偏光Ｌ１をＸ軸及びＹ軸に垂直なＺ軸方向下方に向けて反射させる。また、偏光分離領域３２１は、ランダム偏光のレーザビームＬに含まれる第２の直線偏光Ｌ２を透過させて、１／４波長板３３へ入射させる。 The randomly polarized laser beam L emitted from the collimator lens 31 enters the polarization separation region 321 of the special polarizing beam splitter 32. The polarization separation region 321 reflects the first linearly polarized light L1 contained in the randomly polarized laser beam L downward in the Z-axis direction perpendicular to the X-axis and Y-axis. The polarization separation region 321 also transmits the second linearly polarized light L2 contained in the randomly polarized laser beam L, causing it to enter the quarter-wave plate 33.
　１／４波長板３３は、特殊偏光ビームスプリッタ３２と、第１の反射ミラー３４との間に配置され、特殊偏光ビームスプリッタ３２の偏光分離領域３２１を透過した第２の直線偏光Ｌ２を、第１の円偏光に変換する。１／４波長板３３は例えば水晶により形成され、１／４波長板３３に入射して透過するレーザビームの位相遅れが９０°＋ｎ×３６０°（ｎは整数）となるように構成されることが好ましい。１／４波長板３３は、例えば互いに直交する方向に光学軸を持つように２枚の水晶板が貼り合わされることにより作製されてもよい。１／４波長板３３により変換された第１の円偏光は、第１の反射ミラー３４へ入射する。 The quarter-wave plate 33 is disposed between the special polarizing beam splitter 32 and the first reflecting mirror 34, and converts the second linearly polarized light L2 transmitted through the polarization separation region 321 of the special polarizing beam splitter 32 into the first circularly polarized light. The quarter-wave plate 33 is preferably formed of, for example, quartz, and is preferably configured so that the phase delay of the laser beam that is incident on and transmitted through the quarter-wave plate 33 is 90°+n×360° (n is an integer). The quarter-wave plate 33 may be fabricated, for example, by bonding two quartz plates together so that their optical axes are perpendicular to each other. The first circularly polarized light converted by the quarter-wave plate 33 is incident on the first reflecting mirror 34.
　第１の反射ミラー３４は、入射された第１の円偏光を反射して、第１の円偏光と位相が反転した第２の円偏光として射出する。第１の反射ミラー３４より射出された第２の円偏光は、１／４波長板３３へ入射する。１／４波長板３３は、第１の反射ミラー３４で反射した第２の円偏光を、第１の偏光方向に変換する。 The first reflecting mirror 34 reflects the first circularly polarized light incident thereon and emits it as a second circularly polarized light whose phase is inverted from that of the first circularly polarized light. The second circularly polarized light emitted from the first reflecting mirror 34 is incident on the quarter-wave plate 33. The quarter-wave plate 33 converts the second circularly polarized light reflected by the first reflecting mirror 34 into the first polarization direction.
　以上のような構成により、１／４波長板３３及び第１の反射ミラー３４は、特殊偏光ビームスプリッタ３２によって分離された第２の直線偏光Ｌ２を、図４に示すように、第１の偏光方向を有する第２の直線偏光Ｌ２１に変換する。１／４波長板３３より射出された第２の直線偏光Ｌ２１は、特殊偏光ビームスプリッタ３２の偏光分離領域３２１へ入射する。偏光分離領域３２１は、１／４波長板３３より射出された第２の直線偏光Ｌ２１を、Ｚ軸方向上方に向けて反射させる。 With the above configuration, the quarter-wave plate 33 and the first reflecting mirror 34 convert the second linearly polarized light L2 separated by the special polarizing beam splitter 32 into second linearly polarized light L21 having a first polarization direction, as shown in FIG. 4. The second linearly polarized light L21 emitted from the quarter-wave plate 33 enters the polarization separation region 321 of the special polarizing beam splitter 32. The polarization separation region 321 reflects the second linearly polarized light L21 emitted from the quarter-wave plate 33 upward in the Z-axis direction.
　アキシコンレンズ３５は、特殊偏光ビームスプリッタ３２と、第２の反射ミラー３６との間に配置されている。特殊偏光ビームスプリッタ３２から見て、アキシコンレンズ３５におけるレーザビームの入射面は円錐状の傾斜面、射出面は平坦面となっている。アキシコンレンズ３５の傾斜面は、特殊偏光ビームスプリッタ３２の偏光分離領域３２１で上方に向けて反射した第２の直線偏光Ｌ２１を、図４に示すように、リング状に広げる。なお、図４アキシコンレンズ３５によりリング状に広げられた第２の直線偏光Ｌ２２は、第２の反射ミラー３６へ入射する。 The axicon lens 35 is disposed between the special polarizing beam splitter 32 and the second reflecting mirror 36. When viewed from the special polarizing beam splitter 32, the entrance surface of the axicon lens 35 for the laser beam is a conical inclined surface, and the exit surface is a flat surface. The inclined surface of the axicon lens 35 expands the second linearly polarized light L21 reflected upward by the polarization separation region 321 of the special polarizing beam splitter 32 into a ring shape, as shown in FIG. 4. The second linearly polarized light L22 expanded into a ring shape by the axicon lens 35 in FIG. 4 is incident on the second reflecting mirror 36.
　第２の反射ミラー３６は、アキシコンレンズ３５より射出されたた第２の直線偏光Ｌ２２を反射する。第２の反射ミラー３６で反射した第２の直線偏光Ｌ２２は、アキシコンレンズ３５の平坦面に入射して傾斜面より射出する。アキシコンレンズ３５は、入射したリング状の第２の直線偏光Ｌ２２をコリメート光に変換し、特殊偏光ビームスプリッタ３２の透過領域３２２へ入射させる。 The second reflecting mirror 36 reflects the second linearly polarized light L22 emitted from the axicon lens 35. The second linearly polarized light L22 reflected by the second reflecting mirror 36 is incident on the flat surface of the axicon lens 35 and emerges from the inclined surface. The axicon lens 35 converts the incident ring-shaped second linearly polarized light L22 into collimated light and directs it into the transmission area 322 of the special polarizing beam splitter 32.
　透過領域３２２は、アキシコンレンズ３５より射出されたリング状の第２の直線偏光Ｌ２２を透過させる。透過領域３２２を透過した、リング状の第２の直線偏光Ｌ２２は、図４に示すように、偏光分離領域３２１により反射した第１の直線偏光Ｌ１の外側に配置される。 The transmission region 322 transmits the ring-shaped second linearly polarized light L22 emitted from the axicon lens 35. The ring-shaped second linearly polarized light L22 transmitted through the transmission region 322 is positioned outside the first linearly polarized light L1 reflected by the polarization separation region 321, as shown in FIG. 4.
　以上の構成により、偏光調整部は、特殊偏光ビームスプリッタ３２の偏光分離領域３２１により下方に反射した第１の直線偏光Ｌ１の外側に、第１の偏光方向を有するリング状の第２の直線偏光Ｌ２２を配置して、第１の直線偏光Ｌ１と第２の直線偏光Ｌ２２とを同軸で射出する。これにより、ランダム偏光のレーザビームＬに含まれる２つの直線偏光Ｌ１、Ｌ２の偏光方向を平行に揃えることができ、且つ、偏光方向を平行に揃えた２つのレーザビームの切断進行方向に対する異方性をなくすことができる。 With the above configuration, the polarization adjustment unit places a ring-shaped second linearly polarized light L22 having a first polarization direction outside the first linearly polarized light L1 reflected downward by the polarization separation region 321 of the special polarizing beam splitter 32, and emits the first linearly polarized light L1 and the second linearly polarized light L22 coaxially. This makes it possible to align the polarization directions of the two linearly polarized light beams L1 and L2 contained in the randomly polarized laser beam L in parallel, and to eliminate the anisotropy in the cutting progression direction of the two laser beams whose polarization directions are aligned in parallel.
　特殊偏光ビームスプリッタ３２より同軸で射出された、第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２は、１／２波長板３７へ入射する。１／２波長板３７は、特殊偏光ビームスプリッタ３２より同軸で射出された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２の光路上に配置され、第１のモータ４１（第１の回転機構）によりＸＹ平面上で回転可能に構成される。 The first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarizing beam splitter 32 are incident on the half-wave plate 37. The half-wave plate 37 is disposed on the optical path of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarizing beam splitter 32, and is configured to be rotatable on the XY plane by the first motor 41 (first rotation mechanism).
　第１のモータ４１はＮＣ装置５０（第１の制御部）により制御され、１／２波長板３７をＸＹ平面上で回転させる。ＮＣ装置５０は、１／２波長板３７を透過した第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２の偏光方向が、レーザ加工機１００の切断進行方向と平行となるように、第１のモータ４１を制御する。 The first motor 41 is controlled by an NC device 50 (first control unit) and rotates the half-wave plate 37 on the XY plane. The NC device 50 controls the first motor 41 so that the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L22 transmitted through the half-wave plate 37 are parallel to the cutting direction of the laser processing machine 100.
　以上のように、１／２波長板３７と、第１のモータ４１と、ＮＣ装置５０は、特殊偏光ビームスプリッタ３２より射出された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２の偏光方向を、被加工材Ｗにレーザビームを照射して被加工材Ｗを切断するときの切断進行方向と平行となるように制御する偏光方向制御機構として機能する。 As described above, the half-wave plate 37, the first motor 41, and the NC device 50 function as a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light L1 and the second linearly polarized light L22 emitted from the special polarized beam splitter 32 so that they are parallel to the cutting direction when the workpiece W is cut by irradiating the workpiece W with the laser beam.
　レーザ加工機１００は、ランダム偏光のレーザビームに含まれる第１の直線偏光Ｌ１と第２の直線偏光Ｌ２の偏光方向を第１の偏光方向に揃え、偏光方向が第１の偏光方向に揃えられたレーザビームにおける偏光方向を、切断進行方向と平行となるように制御する。レーザビームの偏光方向を切断進行方向と一致させることにより、被加工材Ｗが溶融して切断されていくときの切断進行方向の非溶融領域と溶融領域との境界の切断面であるカッティングフロントに対するレーザビームの偏光方向がｐ偏光となるため、被加工材Ｗのレーザビームの吸収率を向上させることができる。 The laser processing machine 100 aligns the polarization directions of the first linearly polarized light L1 and the second linearly polarized light L2 contained in the randomly polarized laser beam to a first polarization direction, and controls the polarization direction of the laser beam whose polarization direction is aligned to the first polarization direction to be parallel to the cutting direction. By aligning the polarization direction of the laser beam with the cutting direction, the polarization direction of the laser beam with respect to the cutting front, which is the cut surface at the boundary between the non-melted area and the molten area in the cutting direction as the workpiece W is melted and cut, becomes p-polarized, thereby improving the absorption rate of the laser beam in the workpiece W.
　１／２波長板３７より射出され、偏光方向が切断進行方向と平行となるように制御されたレーザビームは、レンズアレイ３８へ入射する。レンズアレイ３８は、１／２波長板３７により偏光方向が切断進行方向と平行となるように制御されたレーザビームの光路上に配置され、第２のモータ４２（第２の回転機構）により回転可能に構成される。 The laser beam emitted from the half-wave plate 37 and controlled so that its polarization direction is parallel to the cutting direction is incident on the lens array 38. The lens array 38 is disposed on the optical path of the laser beam controlled by the half-wave plate 37 so that its polarization direction is parallel to the cutting direction, and is configured to be rotatable by a second motor 42 (second rotation mechanism).
　図５は、レンズアレイ３８の構成例を示す。図５に示すように、レンズアレイ３８は、２次元配列された複数の矩形状のレンズ３８ａを含む。複数のレンズ３８ａの各々には、１／２波長板３７により偏光方向が切断進行方向と平行となるように制御されたレーザビームが入射される。なお、複数のレンズ３８ａにおける各レンズ３８ａは、凸レンズであっても凹レンズであってもよく、レンズアレイ３８は、複数のレンズ３８ａの全体が凸レンズと凹レンズとのうちのいずれか一方で構成される。 FIG. 5 shows an example of the configuration of the lens array 38. As shown in FIG. 5, the lens array 38 includes a plurality of rectangular lenses 38a arranged two-dimensionally. A laser beam whose polarization direction is controlled by a half-wave plate 37 to be parallel to the cutting progression direction is incident on each of the plurality of lenses 38a. Each of the plurality of lenses 38a may be a convex lens or a concave lens, and the lens array 38 is configured such that the entire plurality of lenses 38a are either convex lenses or concave lenses.
　集束レンズ３９は、レンズアレイ３８における各レンズ３８ａを透過したレーザビームを互いに重畳させるように集束させることにより、強度分布が均一な矩形状のレーザビームを被加工材Ｗの加工点ＷＰに照射する。 The focusing lens 39 focuses the laser beams that have passed through each lens 38a in the lens array 38 so that they overlap with each other, thereby irradiating a rectangular laser beam with a uniform intensity distribution onto the processing point WP of the workpiece W.
　第２のモータ４２はＮＣ装置５０（第２の制御部）により制御される。ＮＣ装置５０は、レンズアレイ３８及び集束レンズ３９を透過して、被加工材Ｗの加工点ＷＰに照射される矩形状のレーザビームにおける一辺が切断進行方向と平行となるように、第２のモータ４２を制御する。なお、ＮＣ装置５０が第１及び第２の制御部として機能しているが、第１のモータ４１を制御する制御部と第２のモータ４２を制御する制御部とが別々に設けられていてもよい。 The second motor 42 is controlled by an NC device 50 (second control unit). The NC device 50 controls the second motor 42 so that one side of the rectangular laser beam that passes through the lens array 38 and the focusing lens 39 and is irradiated to the processing point WP of the workpiece W is parallel to the cutting progression direction. Note that the NC device 50 functions as the first and second control units, but a control unit that controls the first motor 41 and a control unit that controls the second motor 42 may be provided separately.
　以上のように、レンズアレイ３８と、第２のモータ４２と、集束レンズ３９と、ＮＣ装置５０は、偏光方向制御機構により偏光方向が切断進行方向と平行となるように制御されたレーザビームを矩形状に整形し、矩形状に整形されたレーザビームにおける一辺が切断進行方向と平行となるように制御する矩形ビーム角度制御機構として機能する。 As described above, the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 function as a rectangular beam angle control mechanism that shapes the laser beam, whose polarization direction is controlled by the polarization direction control mechanism so that it is parallel to the cutting direction, into a rectangular shape and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
　図６Ａは、被加工材Ｗの切断進行方向と、被加工材Ｗに照射されるレーザビームの偏光方向との関係を示している。図６Ａは、特殊偏光ビームスプリッタ３２より同軸で射出された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２が、レンズアレイ３８により矩形状に整形され、被加工材に照射されるときのレーザビームの概形を示している。図６Ａに示すように、偏光方向制御機構は、特殊偏光ビームスプリッタ３２より同軸で射出され、レンズアレイ３８により矩形状に整形された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２の偏光方向Ｐを、被加工材Ｗにレーザビームを照射して被加工材Ｗを切断するときの切断進行方向Ｄと平行となるように制御する。矩形ビーム角度制御機構は、偏光方向Ｐが切断進行方向Ｄと平行となるように制御されたレーザビームを矩形状に整形し、矩形状に整形されたレーザビームにおける一辺が切断進行方向と平行となるように制御する。 FIG. 6A shows the relationship between the cutting direction of the workpiece W and the polarization direction of the laser beam irradiated to the workpiece W. FIG. 6A shows the general shape of the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated to the workpiece. As shown in FIG. 6A, the polarization direction control mechanism controls the polarization direction P of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 and shaped into a rectangular shape by the lens array 38 so that it is parallel to the cutting direction D when the workpiece W is cut by irradiating the workpiece W with the laser beam. The rectangular beam angle control mechanism shapes the laser beam, which is controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape, and controls one side of the rectangularly shaped laser beam to be parallel to the cutting direction.
　図６Ｂは、被加工材Ｗの切断進行方向が曲線を描くときの切断進行方向と、被加工材Ｗに照射されるレーザビームの偏光方向との関係を示している。図６Ｂは、特殊偏光ビームスプリッタ３２より同軸で射出された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２が、レンズアレイ３８により矩形状に整形され、被加工材に照射されるときのレーザビームの概形を示している。図６Ｂは、被加工材Ｗの切断進行方向が曲線を描く場合の一例として、製品のコーナＲを切断する場合を示している。図６Ｂに示すように、レーザ加工機１００が被加工材Ｗの切断加工経路に沿ってコーナＲの切断加工をする際、ＮＣ装置５０は、第１及び第２のモータ４１、４２を制御して、偏光方向Ｐと矩形状に整形されたレーザビームの一辺が常に切断進行方向Ｄと平行となるように、１／２波長板３７及びレンズアレイ３８を回転させる。これにより、切断加工時に、カッティングフロントにおけるレーザビームの偏光方向Ｐ及びカッティングフロントにおいて矩形状に整形されたレーザビームの一辺が、常に切断進行方向と平行となる。 Figure 6B shows the relationship between the cutting direction of the workpiece W when the cutting direction of the workpiece W is curved and the polarization direction of the laser beam irradiated to the workpiece W. Figure 6B shows the general shape of the laser beam when the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the special polarized beam splitter 32 are shaped into a rectangular shape by the lens array 38 and irradiated to the workpiece. Figure 6B shows the case of cutting the corner R of a product as an example of a case where the cutting direction of the workpiece W is curved. As shown in Figure 6B, when the laser processing machine 100 cuts the corner R along the cutting processing path of the workpiece W, the NC device 50 controls the first and second motors 41, 42 to rotate the half-wave plate 37 and the lens array 38 so that the polarization direction P and one side of the laser beam shaped into a rectangular shape are always parallel to the cutting direction D. As a result, during cutting, the polarization direction P of the laser beam at the cutting front and one side of the rectangular laser beam at the cutting front are always parallel to the cutting direction.
　図７Ａは、加工ヘッド３０Ａがレンズアレイ３８を備えないと仮定した場合の比較例であり、カッティングフロントの形状が半円状であるときの、カッティングフロントと偏光方向及び切断進行方向との関係を示している。図７Ｂは、加工ヘッド３０Ａがレンズアレイ３８を備えることによりカッティングフロントの形状が矩形状であるときの、カッティングフロントと偏光方向及び切断進行方向との関係を示している。ここでのカッティングフロントの形状とは、被加工材Ｗの表面から見た、被加工材Ｗが溶融して切断されていくときの切断進行方向の非溶融領域と溶融領域との境界の形状である。 Figure 7A is a comparative example assuming that the processing head 30A does not have a lens array 38, and shows the relationship between the cutting front and the polarization direction and cutting direction when the cutting front has a semicircular shape. Figure 7B shows the relationship between the cutting front and the polarization direction and cutting direction when the processing head 30A has a lens array 38 and the cutting front has a rectangular shape. The shape of the cutting front here refers to the shape of the boundary between the non-melted area and the molten area in the cutting direction as the workpiece W melts and is cut, as viewed from the surface of the workpiece W.
　図７Ａに示すように、カッティングフロントの形状が半円状である場合には、レーザビームの偏光方向Ｐが切断進行方向Ｄと平行であったとしても、切断溝の幅方向の外側に近付くにしたがって、偏光方向Ｐがカッティングフロントに対して垂直に入射しなくなる。ｐ偏光は、偏光方向Ｐがカッティングフロントに対して垂直な方向Ｎで入射するときに作用するため、切断溝の幅方向の外側に近付くにしたがって、ｐ偏光の作用が弱くなり、被加工材Ｗのレーザビームの吸収率が低下する。 As shown in Figure 7A, when the cutting front is semicircular in shape, even if the polarization direction P of the laser beam is parallel to the cutting progression direction D, the polarization direction P no longer enters perpendicularly to the cutting front as it approaches the outside of the width of the cutting groove. Since p-polarized light works when the polarization direction P enters in a direction N perpendicular to the cutting front, the effect of p-polarized light becomes weaker as it approaches the outside of the width of the cutting groove, and the absorption rate of the laser beam by the workpiece W decreases.
　これに対し、図７Ｂに示すように、カッティングフロントの形状が矩形状である場合には、レーザビームの偏光方向Ｐが切断進行方向Ｄと平行であれば、切断溝の幅方向のどの位置においても、偏光方向Ｐがカッティングフロントに対して垂直な方向Ｎで入射する。したがって、カッティングフロントに対して効率よくｐ偏光が作用し、被加工材Ｗのレーザビームの吸収率が向上する。 In contrast, as shown in Figure 7B, when the cutting front is rectangular in shape, if the polarization direction P of the laser beam is parallel to the cutting progression direction D, the polarization direction P is incident in a direction N perpendicular to the cutting front at any position in the width direction of the cut groove. Therefore, p-polarized light acts efficiently on the cutting front, improving the absorption rate of the laser beam in the workpiece W.
　従来のランダム偏光のレーザビームであって、カッティングフロントが半円状、すなわち断面形状が円形のレーザビームにより切断加工を行った場合の被加工材Ｗのレーザビームの吸収率と、本実施形態に係るレーザ加工機１００において切断加工を行った場合の被加工材Ｗのレーザビームの吸収率とを、コンピュータ上のシミュレーションにより比較した。シミュレーションでは、レーザビームの波長を１．０８μｍ、被加工材Ｗの材質を鉄、厚さを８ｍｍとした。その結果、従来のレーザビームにより切断加工を行った場合の吸収率は約５５％であった。これに対し、本実施形態に係るレーザ加工機１００において切断加工を行った場合の被加工材Ｗのレーザビームの吸収率は約７４％となり、約１９％吸収率が向上することが確認された。 A comparison was made by computer simulation between the absorption rate of the laser beam in the workpiece W when cutting was performed using a conventional randomly polarized laser beam with a semicircular cutting front, i.e., a circular cross-sectional shape, and the absorption rate of the laser beam in the workpiece W when cutting was performed using the laser processing machine 100 according to this embodiment. In the simulation, the wavelength of the laser beam was 1.08 μm, the material of the workpiece W was iron, and the thickness was 8 mm. As a result, the absorption rate was approximately 55% when cutting was performed using the conventional laser beam. In contrast, the absorption rate of the laser beam in the workpiece W when cutting was performed using the laser processing machine 100 according to this embodiment was approximately 74%, confirming an improvement in absorption rate of approximately 19%.
　［第１実施形態の作用効果］
　以上説明したように、第１実施形態によれば、以下の作用効果が得られる。 [Effects of the First Embodiment]
As described above, according to the first embodiment, the following advantageous effects can be obtained.
　第１実施形態に係る偏光調整装置は、ランダム偏光のレーザビームＬに含まれる、第１の偏光方向を有する第１の直線偏光Ｌ１と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光Ｌ２の偏光方向を、第１の偏光方向に揃え、同軸で射出する。第１実施形態に係る偏光調整装置は、第１の光学素子（特殊偏光ビームスプリッタ３２）の偏光分離領域３２１により反射した第１の直線偏光Ｌ１の外側に、第１の偏光方向を有するリング状の第２の直線偏光Ｌ２２を配置して、第１の直線偏光Ｌ１と第２の直線偏光Ｌ２２とを同軸で射出する。これにより、ランダム偏光のレーザビームＬに含まれる２つの直線偏光Ｌ１、Ｌ２の偏光方向を平行に揃えることができ、且つ、偏光方向を平行に揃えた２つのレーザビームの切断進行方向に対する異方性をなくすことができる。 The polarization adjustment device according to the first embodiment aligns the polarization directions of the first linearly polarized light L1 having a first polarization direction and the second linearly polarized light L2 having a second polarization direction perpendicular to the first polarization direction contained in the randomly polarized laser beam L to the first polarization direction, and emits them coaxially. The polarization adjustment device according to the first embodiment places a ring-shaped second linearly polarized light L22 having a first polarization direction outside the first linearly polarized light L1 reflected by the polarization separation region 321 of the first optical element (special polarized beam splitter 32), and emits the first linearly polarized light L1 and the second linearly polarized light L22 coaxially. This makes it possible to align the polarization directions of the two linearly polarized lights L1 and L2 contained in the randomly polarized laser beam L in parallel, and to eliminate the anisotropy of the cutting progression direction of the two laser beams whose polarization directions are aligned in parallel.
　また、第１実施形態に係る偏光調整装置を備えるレーザ加工機１００は、偏光方向を平行に揃えた２つレーザビームにおける偏光方向を、切断進行方向と平行となるように制御する。偏光方向を切断進行方向と一致させることにより、カッティングフロントに対するレーザビームの偏光方向がｐ偏光となるため、被加工材Ｗのレーザビームの吸収率を向上させることができる。 In addition, the laser processing machine 100 equipped with the polarization adjustment device according to the first embodiment controls the polarization direction of the two laser beams, the polarization directions of which are aligned in parallel, so that they are parallel to the cutting direction. By matching the polarization direction with the cutting direction, the polarization direction of the laser beam with respect to the cutting front becomes p-polarized, thereby improving the absorption rate of the laser beam in the workpiece W.
　また、第１実施形態に係る偏光調整装置と、偏光方向制御機構を備えるレーザ加工機１００は、偏光調整装置より同軸で射出された第１の直線偏光Ｌ１及び第２の直線偏光Ｌ２２の偏光方向Ｐを、被加工材Ｗにレーザビームを照射して被加工材Ｗを切断するときの切断進行方向Ｄと平行となるように制御する。第１実施形態に係るレーザ加工機１００の矩形ビーム角度制御機構は、偏光方向Ｐが切断進行方向Ｄと平行となるように制御されたレーザビームを矩形状に整形し、矩形状に整形されたレーザビームにおける一辺が切断進行方向と平行となるように制御する。 The laser processing machine 100, which is equipped with the polarization adjustment device and polarization direction control mechanism according to the first embodiment, controls the polarization direction P of the first linearly polarized light L1 and the second linearly polarized light L22 emitted coaxially from the polarization adjustment device so that the polarization direction P is parallel to the cutting direction D when the workpiece W is cut by irradiating the workpiece W with a laser beam. The rectangular beam angle control mechanism of the laser processing machine 100 according to the first embodiment shapes the laser beam, which has been controlled so that the polarization direction P is parallel to the cutting direction D, into a rectangular shape, and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
　これにより、偏光方向を平行に揃えた異方性のない２つのレーザビームによって被加工材Ｗを加工することができる。また、切断加工時に、カッティングフロントにおけるレーザビームの偏光方向Ｐ及びカッティングフロントにおいて矩形状に整形されたレーザビームの一辺が、常に切断進行方向と平行となる。切断溝の幅方向のどの位置においても、偏光方向Ｐがカッティングフロントに対して垂直な方向Ｎで入射する。したがって、カッティングフロントに対して効率よくｐ偏光が作用し、被加工材Ｗのレーザビームの吸収率が向上する。よって、切断加工時の加工効率が向上する。 As a result, the workpiece W can be processed using two non-anisotropic laser beams with parallel polarization directions. Furthermore, during cutting, the polarization direction P of the laser beam at the cutting front and one side of the laser beam shaped into a rectangle at the cutting front are always parallel to the cutting direction. At any position in the width direction of the cutting groove, the polarization direction P is incident in a direction N perpendicular to the cutting front. Therefore, p-polarized light acts efficiently on the cutting front, improving the absorption rate of the laser beam in the workpiece W. This improves processing efficiency during cutting.
　［第２実施形態］
　以下、図８～図１０を参照して、第２実施形態に係る偏光調整装置及びレーザ加工機１００を説明する。図８は、第２実施形態に係る加工ヘッド３０Ｂの構成例を示す。図８において、図２と同一部分には同一符号を付して詳細な説明を省略することがある。第２実施形態に係るレーザ加工機１００は、第１実施形態に係るレーザ加工機１００と比べて、加工ヘッドの内部の構成に違いを有する。その他の構成は、第１実施形態に係るレーザ加工機１００と同一である。よって、第２実施形態に係るレーザ加工機１００においては、第１実施形態に係るレーザ加工機１００と相違する部分を中心に説明し、同一部分については再度の説明を省略する。 [Second embodiment]
Hereinafter, the polarization adjustment device and the laser processing machine 100 according to the second embodiment will be described with reference to Figs. 8 to 10. Fig. 8 shows an example of the configuration of the processing head 30B according to the second embodiment. In Fig. 8, the same parts as those in Fig. 2 are given the same reference numerals and detailed description may be omitted. The laser processing machine 100 according to the second embodiment has a different internal configuration of the processing head compared to the laser processing machine 100 according to the first embodiment. The other configurations are the same as those of the laser processing machine 100 according to the first embodiment. Therefore, in the laser processing machine 100 according to the second embodiment, the parts that differ from the laser processing machine 100 according to the first embodiment will be mainly described, and the same parts will not be described again.
　図８に示すように、加工ヘッド３０Ｂは、コリメートレンズ３１、偏光ビームスプリッタ７１、第３の反射ミラー７２、アキシコンレンズ７３及び７４、第４の反射ミラー７５、１／２波長板７６、特殊ミラー７７を有する。図８における偏光ビームスプリッタ７１、第３の反射ミラー７２、アキシコンレンズ７３及び７４、第４の反射ミラー７５、１／２波長板７６、特殊ミラー７７は、第１の偏光方向を有する第１の直線偏光Ｌ１’と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光Ｌ２’とを含むランダム偏光のレーザビームＬ’における第１の直線偏光Ｌ１’を第１の直線偏光Ｌ１’として射出し、第２の直線偏光Ｌ２’を第１の偏光方向を有する第２の直線偏光Ｌ２２’に変換して射出する偏光調整部（偏光調整装置）として機能する。 As shown in FIG. 8, the processing head 30B has a collimator lens 31, a polarizing beam splitter 71, a third reflecting mirror 72, axicon lenses 73 and 74, a fourth reflecting mirror 75, a half-wave plate 76, and a special mirror 77. The polarizing beam splitter 71, the third reflecting mirror 72, the axicon lenses 73 and 74, the fourth reflecting mirror 75, the half-wave plate 76, and the special mirror 77 in FIG. 8 function as a polarization adjustment unit (polarization adjustment device) that outputs the first linearly polarized light L1' in the randomly polarized laser beam L', which includes a first linearly polarized light L1' having a first polarization direction and a second linearly polarized light L2' having a second polarization direction perpendicular to the first polarization direction, as the first linearly polarized light L1', and converts the second linearly polarized light L2' into a second linearly polarized light L22' having the first polarization direction and outputs it.
　第２実施形態においては、偏光ビームスプリッタ７１は、第１の光学素子として機能する。また、１／２波長板７６は、第２の光学素子として機能する。さらに、特殊ミラー７７は、第１の光学素子とは別体の第３の光学素子として機能する。また、第２実施形態に係るレーザ加工機１００の加工ヘッド３０Ｂは、１／２波長板３７、第１のモータ４１、レンズアレイ３８、第２のモータ４２、第５の反射ミラー７８、集束レンズ３９を有する。なお、図８において、中心が黒の二重丸は第１の直線偏光を示し、両矢印は第２の直線偏光を示す。 In the second embodiment, the polarizing beam splitter 71 functions as the first optical element. The half-wave plate 76 functions as the second optical element. The special mirror 77 functions as a third optical element separate from the first optical element. The processing head 30B of the laser processing machine 100 according to the second embodiment has a half-wave plate 37, a first motor 41, a lens array 38, a second motor 42, a fifth reflecting mirror 78, and a focusing lens 39. In FIG. 8, a double circle with a black center indicates the first linearly polarized light, and a double-headed arrow indicates the second linearly polarized light.
　図８において、コリメートレンズ３１は、プロセスファイバ１２の射出端より射出された発散光のレーザビームが入射される。コリメートレンズ３１に入射される発散光のレーザビームは、第１の偏光方向を有する第１の直線偏光Ｌ１’と、第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光Ｌ２’とを含むランダム偏光のレーザビームＬ’である。コリメートレンズ３１は、入射されたランダム偏光のレーザビームＬ’をコリメート光に変換する。コリメートレンズ３１によりコリメート光に変換されたランダム偏光のレーザビームＬ’は、偏光ビームスプリッタ７１へ入射する。 In FIG. 8, the diverging laser beam emitted from the exit end of the process fiber 12 is incident on the collimating lens 31. The diverging laser beam incident on the collimating lens 31 is a randomly polarized laser beam L' that includes a first linearly polarized light L1' having a first polarization direction and a second linearly polarized light L2' having a second polarization direction perpendicular to the first polarization direction. The collimating lens 31 converts the incident randomly polarized laser beam L' into collimated light. The randomly polarized laser beam L' converted into collimated light by the collimating lens 31 is incident on the polarizing beam splitter 71.
　図９は、図８におけるレーザビームの偏光方向及び形状と、第１及び第２の直線偏光Ｌ１’、Ｌ２’が同軸で射出されるときの第１及び第２の直線偏光Ｌ１’、Ｌ２’の位置関係を示す。図９は、ランダム偏光のレーザビームＬ’、第１の直線偏光Ｌ１’、及び第２の直線偏光Ｌ２’、Ｌ２１’、Ｌ２２’の外形を模式的に示している。また、図９のランダム偏光のレーザビームＬ’、第１の直線偏光Ｌ１’、及び第２の直線偏光Ｌ２’、Ｌ２１’、Ｌ２２’の中の矢印は、単に各々のレーザビームの偏光方向を模式的に示すものであり、矢印の長さの違いに特に意味はない。 FIG. 9 shows the polarization direction and shape of the laser beam in FIG. 8, and the positional relationship of the first and second linearly polarized light L1', L2' when the first and second linearly polarized light L1', L2' are emitted coaxially. FIG. 9 shows the outline of the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized light L2', L21', L22'. The arrows in the randomly polarized laser beam L', the first linearly polarized light L1', and the second linearly polarized light L2', L21', L22' in FIG. 9 simply show the polarization direction of each laser beam, and the difference in the length of the arrows is not particularly significant.
　偏光ビームスプリッタ７１は、ランダム偏光のレーザビームＬ’における第１の直線偏光Ｌ１’を透過させ、第２の直線偏光Ｌ２’を反射させることによって、図９に示すように、第１の直線偏光Ｌ１’と第２の直線偏光Ｌ２’とを分離する偏光ビームスプリッタである。 The polarizing beam splitter 71 is a polarizing beam splitter that separates the first linearly polarized light L1' from the second linearly polarized light L2' as shown in FIG. 9 by transmitting the first linearly polarized light L1' in the randomly polarized laser beam L' and reflecting the second linearly polarized light L2'.
　偏光ビームスプリッタ７１は、ランダム偏光のレーザビームＬ’に含まれる第１の直線偏光Ｌ１’を透過させ、特殊ミラー７７へ入射させる。偏光ビームスプリッタ７１を透過した第１の直線偏光Ｌ１’は、後述する特殊ミラー７７の透過領域７７１（図１０参照）へ入射する。また、偏光ビームスプリッタ７１は、ランダム偏光のレーザビームＬ’に含まれる第２の直線偏光Ｌ２’をＸ軸及びＹ軸に垂直なＺ軸方向上方に向けて反射させる。偏光ビームスプリッタ７１により上方に反射された第２の直線偏光Ｌ２’は、第３の反射ミラー７２へ入射する。 The polarizing beam splitter 71 transmits the first linearly polarized light L1' contained in the randomly polarized laser beam L' and makes it incident on the special mirror 77. The first linearly polarized light L1' that has transmitted through the polarizing beam splitter 71 is incident on the transmission area 771 (see FIG. 10) of the special mirror 77, which will be described later. The polarizing beam splitter 71 also reflects the second linearly polarized light L2' contained in the randomly polarized laser beam L' upward in the Z-axis direction perpendicular to the X-axis and Y-axis. The second linearly polarized light L2' reflected upward by the polarizing beam splitter 71 is incident on the third reflecting mirror 72.
　第３の反射ミラー７２は、偏光ビームスプリッタ７１より反射された第２の直線偏光Ｌ２’をＸ軸方向に反射する。第３の反射ミラー７２より反射された第２の直線偏光Ｌ２’は、アキシコンレンズ７３へ入射する。アキシコンレンズ７３は、円錐状の傾斜面を第３の反射ミラー７２に向け、平坦面をアキシコンレンズ７４に向けて配置されている。 The third reflecting mirror 72 reflects the second linearly polarized light L2' reflected by the polarizing beam splitter 71 in the X-axis direction. The second linearly polarized light L2' reflected by the third reflecting mirror 72 is incident on the axicon lens 73. The axicon lens 73 is arranged with its conical inclined surface facing the third reflecting mirror 72 and its flat surface facing the axicon lens 74.
　アキシコンレンズ７３の傾斜面は、第３の反射ミラー７２より反射された第２の直線偏光Ｌ２’を、図９に示すように、リング状に広げる。アキシコンレンズ７３によりリング状に広げられた第２の直線偏光Ｌ２１’は、アキシコンレンズ７４へ入射する。アキシコンレンズ７４は、平坦面をアキシコンレンズ７３に向け、円錐状の傾斜面を第４の反射ミラー７５に向けて配置されている。 The inclined surface of the axicon lens 73 expands the second linearly polarized light L2' reflected by the third reflecting mirror 72 into a ring shape, as shown in FIG. 9. The second linearly polarized light L21' expanded into a ring shape by the axicon lens 73 enters the axicon lens 74. The axicon lens 74 is positioned with its flat surface facing the axicon lens 73 and its conical inclined surface facing the fourth reflecting mirror 75.
　アキシコンレンズ７４は、アキシコンレンズ７３より射出されたリング状の第２の直線偏光Ｌ２１’をコリメート光に変換し、第４の反射ミラー７５へ入射させる。第４の反射ミラー７５は、アキシコンレンズ７３より射出され、アキシコンレンズ７４によりコリメート光に変換されたリング状の第２の直線偏光Ｌ２１’をＺ軸方向下方に向けて反射させ、１／２波長板７６へ入射させる。 The axicon lens 74 converts the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 into collimated light and makes it incident on the fourth reflecting mirror 75. The fourth reflecting mirror 75 reflects the ring-shaped second linearly polarized light L21' emitted from the axicon lens 73 and converted into collimated light by the axicon lens 74 downward in the Z-axis direction and makes it incident on the half-wave plate 76.
　１／２波長板７６は、第４の反射ミラー７５より反射されたリング状の第２の直線偏光Ｌ２１’の偏向方向を、第１の偏光方向に変換する。以上のような構成により、１／２波長板７６は、偏光ビームスプリッタ７１によって分離され、アキシコンレンズ７３によりリング状に広げられた第２の直線偏光Ｌ２１’を、図９に示すように、第１の偏光方向を有するリング状の第２の直線偏光Ｌ２２’に変換する。１／２波長板７６より射出されたリング状の第２の直線偏光Ｌ２２’は、特殊ミラー７７へ入射する。 The half-wave plate 76 converts the polarization direction of the ring-shaped second linearly polarized light L21' reflected by the fourth reflecting mirror 75 into the first polarization direction. With the above configuration, the half-wave plate 76 converts the second linearly polarized light L21', which has been separated by the polarizing beam splitter 71 and expanded into a ring shape by the axicon lens 73, into a ring-shaped second linearly polarized light L22' having the first polarization direction, as shown in FIG. 9. The ring-shaped second linearly polarized light L22' emitted from the half-wave plate 76 is incident on the special mirror 77.
　図１０は、特殊ミラー７７の構成例を示す。図１０に示すように、特殊ミラー７７は、中心部に楕円状の透過領域７７１を有し、透過領域７７１の周囲に反射領域７７２を有する。透過領域７７１には反射防止コーティングが施されており、入射されたレーザビームを透過させる。反射領域７７２には高反射コーティングが施されており、反射領域７７２は入射されたレーザビームを反射する。 FIG. 10 shows an example of the configuration of special mirror 77. As shown in FIG. 10, special mirror 77 has an elliptical transmissive area 771 in the center, and a reflective area 772 around the transmissive area 771. Transmissive area 771 is coated with an anti-reflective coating, and transmits the incident laser beam. Reflective area 772 is coated with a highly reflective coating, and reflects the incident laser beam.
　偏光ビームスプリッタ７１を透過した第１の直線偏光Ｌ１’は、特殊ミラー７７の透過領域７７１へ入射する。透過領域７７１は、偏光ビームスプリッタ７１を透過した第１の直線偏光Ｌ１’を透過させる。１／２波長板７６より射出されたリング状の第２の直線偏光Ｌ２２’は、特殊ミラー７７の反射領域７７２へ入射する。反射領域７７２は、入射されたリング状の第２の直線偏光Ｌ２２’をＸ軸方向に反射させる。反射領域７７２により反射された、リング状の第２の直線偏光Ｌ２２’は、図９に示すように、透過領域７７１を透過した第１の直線偏光Ｌ１’の外側に配置される。 The first linearly polarized light L1' that has passed through the polarizing beam splitter 71 is incident on the transmission region 771 of the special mirror 77. The transmission region 771 transmits the first linearly polarized light L1' that has passed through the polarizing beam splitter 71. The ring-shaped second linearly polarized light L22' that has been emitted from the half-wave plate 76 is incident on the reflection region 772 of the special mirror 77. The reflection region 772 reflects the incident ring-shaped second linearly polarized light L22' in the X-axis direction. The ring-shaped second linearly polarized light L22' that has been reflected by the reflection region 772 is positioned outside the first linearly polarized light L1' that has passed through the transmission region 771, as shown in FIG. 9.
　以上の構成により、偏光調整部は、偏光ビームスプリッタ７１及び特殊ミラー７７の透過領域７７１を透過した第１の直線偏光Ｌ１’の外側に、第１の偏光方向を有するリング状の第２の直線偏光Ｌ２２’を配置して、第１の直線偏光Ｌ１’と第２の直線偏光Ｌ２２’とを同軸で射出する。これにより、ランダム偏光のレーザビームＬ’に含まれる２つの直線偏光Ｌ１’、Ｌ２’の偏光方向を平行に揃えることができ、且つ、レーザビームの切断進行方向に対する異方性をなくすことができる。 With the above configuration, the polarization adjustment unit places a ring-shaped second linearly polarized light L22' having a first polarization direction outside the first linearly polarized light L1' that has passed through the polarizing beam splitter 71 and the transmission area 771 of the special mirror 77, and emits the first linearly polarized light L1' and the second linearly polarized light L22' coaxially. This makes it possible to align the polarization directions of the two linearly polarized lights L1' and L2' contained in the randomly polarized laser beam L' in parallel, and to eliminate anisotropy with respect to the cutting direction of the laser beam.
　特殊ミラー７７より同軸で射出された、第１の直線偏光Ｌ１’及び第２の直線偏光Ｌ２２’は、１／２波長板３７へ入射する。１／２波長板３７は、特殊ミラー７７より同軸射出された第１の直線偏光Ｌ１’及び第２の直線偏光Ｌ２２’の光路上に配置され、第１のモータ４１によりＸＺ平面上で回転可能に構成される。 The first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77 are incident on the half-wave plate 37. The half-wave plate 37 is disposed on the optical path of the first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77, and is configured to be rotatable on the XZ plane by the first motor 41.
　１／２波長板３７より射出され、偏光方向が切断進行方向と平行となるように制御されたレーザビームは、レンズアレイ３８へ入射する。レンズアレイ３８は、１／２波長板３７により偏光方向が切断進行方向と平行となるように制御されたレーザビームの光路上に配置され、第２のモータ４２によりＸＺ平面上で回転可能に構成される。 The laser beam emitted from the half-wave plate 37 and controlled so that its polarization direction is parallel to the cutting direction is incident on the lens array 38. The lens array 38 is disposed on the optical path of the laser beam controlled by the half-wave plate 37 so that its polarization direction is parallel to the cutting direction, and is configured to be rotatable on the XZ plane by the second motor 42.
　第５の反射ミラー７８は、レンズアレイ３８を透過したレーザビームをＺ軸方向下方に向けて反射し、集束レンズ３９へ入射する。 The fifth reflecting mirror 78 reflects the laser beam that has passed through the lens array 38 downward in the Z-axis direction, and makes it enter the focusing lens 39.
　集束レンズ３９は、第５の反射ミラー７８により反射されたレーザビームを集束させ、強度分布が均一な矩形状のレーザビームを被加工材Ｗの加工点ＷＰに照射する。 The focusing lens 39 focuses the laser beam reflected by the fifth reflecting mirror 78, and irradiates a rectangular laser beam with a uniform intensity distribution onto the processing point WP of the workpiece W.
　第１のモータ４１はＮＣ装置５０により制御され、１／２波長板３７を回転させる。ＮＣ装置５０は、１／２波長板３７及びレンズアレイ３８を透過し、第５の反射ミラー７８により反射されて集束レンズ３９を透過した第１の直線偏光Ｌ１’及び第２の直線偏光Ｌ２２’の偏光方向が切断進行方向と平行となるように、第１のモータ４１を制御する。 The first motor 41 is controlled by the NC device 50 to rotate the half-wave plate 37. The NC device 50 controls the first motor 41 so that the polarization directions of the first linearly polarized light L1' and the second linearly polarized light L22' that pass through the half-wave plate 37 and the lens array 38, are reflected by the fifth reflecting mirror 78, and are transmitted through the focusing lens 39, are parallel to the cutting progression direction.
　以上のように、１／２波長板３７と、第１のモータ４１と、ＮＣ装置５０は、特殊ミラー７７より同軸で射出された、第１の直線偏光Ｌ１’及び第２の直線偏光Ｌ２２’の偏光方向を、被加工材Ｗにレーザビームを照射して被加工材Ｗを切断するときの切断進行方向と平行となるように制御する偏光方向制御機構として機能する。 As described above, the half-wave plate 37, the first motor 41, and the NC device 50 function as a polarization direction control mechanism that controls the polarization direction of the first linearly polarized light L1' and the second linearly polarized light L22' emitted coaxially from the special mirror 77 so that they are parallel to the cutting direction when the workpiece W is cut by irradiating the workpiece W with the laser beam.
　第２のモータ４２はＮＣ装置５０により制御され、レンズアレイ３８を回転させる。ＮＣ装置５０は、レンズアレイ３８を透過し、第５の反射ミラー７８により反射されて集束レンズ３９を透過して、被加工材Ｗの加工点ＷＰに照射される矩形状のレーザビームにおける一辺が切断進行方向と平行となるように、第２のモータ４２を制御する。 The second motor 42 is controlled by the NC device 50 to rotate the lens array 38. The NC device 50 controls the second motor 42 so that one side of the rectangular laser beam that passes through the lens array 38, is reflected by the fifth reflecting mirror 78, passes through the focusing lens 39, and is irradiated onto the processing point WP of the workpiece W is parallel to the cutting progression direction.
　以上のように、レンズアレイ３８と、第２のモータ４２と、集束レンズ３９と、ＮＣ装置５０は、偏光方向制御機構により偏光方向が切断進行方向と平行となるように制御されたレーザビームを矩形状に整形し、矩形状に整形されたレーザビームにおける一辺が切断進行方向と平行となるように制御する矩形ビーム角度制御機構として機能する。 As described above, the lens array 38, the second motor 42, the focusing lens 39, and the NC device 50 function as a rectangular beam angle control mechanism that shapes the laser beam, whose polarization direction is controlled by the polarization direction control mechanism so that it is parallel to the cutting direction, into a rectangular shape and controls one side of the rectangularly shaped laser beam so that it is parallel to the cutting direction.
　［第２実施形態の作用効果］
　以上説明したように、第２実施形態によれば、以下の作用効果が得られる。 [Effects of the Second Embodiment]
As described above, according to the second embodiment, the following advantageous effects can be obtained.
　第２実施形態に係る偏光調整装置は、偏光ビームスプリッタ７１、第３の反射ミラー７２、アキシコンレンズ７３及び７４、第４の反射ミラー７５、１／２波長板７６、特殊ミラー７７により、第１の直線偏光Ｌ１’と第２の直線偏光Ｌ２’を含むランダム偏光のレーザビームＬ’の偏光方向を、第１の偏光方向に揃える。第２実施形態に係る偏光調整装置の各光学素子は、プロセスファイバ１２の射出端の方向に向かってレーザビームを反射しないように配置できる。これにより、第１実施形態に係る偏光調整装置において、第１の反射ミラー３４により反射され、１／４波長板３３より射出された第２の直線偏光Ｌ２１の一部が特殊偏光ビームスプリッタ３２を透過してしまい、プロセスファイバ１２の射出端に入射するリスクを低減できる。 The polarization adjustment device according to the second embodiment aligns the polarization direction of the randomly polarized laser beam L', which includes the first linearly polarized light L1' and the second linearly polarized light L2', to the first polarization direction by using a polarizing beam splitter 71, a third reflecting mirror 72, axicon lenses 73 and 74, a fourth reflecting mirror 75, a half-wave plate 76, and a special mirror 77. Each optical element of the polarization adjustment device according to the second embodiment can be arranged so as not to reflect the laser beam toward the exit end of the process fiber 12. This reduces the risk that part of the second linearly polarized light L21 reflected by the first reflecting mirror 34 and exiting from the quarter-wave plate 33 in the polarization adjustment device according to the first embodiment will pass through the special polarizing beam splitter 32 and enter the exit end of the process fiber 12.
　本発明は以上説明した第１または第２実施形態に限定されるものではなく、本発明の要旨を逸脱しない範囲において種々変更可能である。 The present invention is not limited to the first or second embodiment described above, and various modifications are possible without departing from the gist of the present invention.
　本願は、２０２２年１０月１３日に日本国特許庁に出願された特願２０２２－１６４５３１号、及び２０２３年９月２０日に日本国特許庁に出願された特願２０２３－１５２５２８号に基づく優先権を主張するものであり、その全ての開示内容は引用によりここに援用される。 This application claims priority to Patent Application No. 2022-164531, filed with the Japan Patent Office on October 13, 2022, and Patent Application No. 2023-152528, filed with the Japan Patent Office on September 20, 2023, the entire disclosures of which are incorporated herein by reference.

Claims (4)

  1. 　第１の偏光方向を有する第１の直線偏光と、前記第１の偏光方向と直交する第２の偏光方向を有する第２の直線偏光とを含むランダム偏光のレーザビームを、前記第１の直線偏光と前記第２の直線偏光とに分離する第１の光学素子と、
    　前記第１の光学素子によって分離された前記第２の直線偏光の偏光方向を前記第１の偏光方向に変換する第２の光学素子と、
    　前記第２の光学素子より射出された前記第２の直線偏光、または前記第２の光学素子に入射される前記第２の直線偏光をリング状に広げるアキシコンレンズと、
    　前記第１の光学素子によって分離された前記第１の直線偏光と、前記アキシコンレンズによってリング状に広げられた前記第２の直線偏光とを同軸で射出する、前記第１の光学素子と兼用されている、または前記第１の光学素子とは別体の第３の光学素子と、
    を備える偏光調整装置。     a first optical element that separates a randomly polarized laser beam, the randomly polarized laser beam including a first linearly polarized light having a first polarization direction and a second linearly polarized light having a second polarization direction orthogonal to the first polarization direction, into the first linearly polarized light and the second linearly polarized light;
    a second optical element that converts the polarization direction of the second linearly polarized light separated by the first optical element into the first polarization direction;
    an axicon lens that expands the second linearly polarized light emitted from the second optical element or the second linearly polarized light incident on the second optical element into a ring shape;
    a third optical element which is used as the first optical element or is separate from the first optical element and which coaxially emits the first linearly polarized light separated by the first optical element and the second linearly polarized light expanded into a ring shape by the axicon lens;
    A polarization adjustment device comprising:
  2. 　前記第１の光学素子と前記第３の光学素子とを兼用する兼用光学素子を備え、
    　前記兼用光学素子は、入射された前記ランダム偏光のレーザビームにおける前記第１の直線偏光を反射させ、前記第２の直線偏光を透過させることによって、前記第１の直線偏光と前記第２の直線偏光とを分離する偏光分離領域を中心部に有し、前記偏光分離領域の周囲に前記第１の偏光方向の直線偏光を透過させる透過領域を有し、
    　前記第２の光学素子は、前記偏光分離領域を透過した前記第２の直線偏光を第１の円偏光に変換する１／４波長板と、前記第１の円偏光を反射させて第２の円偏光として射出する第１の反射ミラーとを有し、
    　前記１／４波長板は、前記第１の反射ミラーより反射された前記第２の円偏光を前記第１の偏光方向の前記第２の直線偏光に変換し、
    　前記偏光分離領域は、前記１／４波長板より射出された前記第２の直線偏光を反射させ、
    　前記アキシコンレンズは、前記偏光分離領域で反射した前記第２の直線偏光をリング状に広げ、
    　前記アキシコンレンズより射出された前記第２の直線偏光を反射する第２の反射ミラーをさらに備え、
    　前記アキシコンレンズは、前記第２の反射ミラーより反射された前記第２の直線偏光を前記透過領域に入射させ、
    　前記兼用光学素子は、前記偏光分離領域により反射した前記第１の直線偏光と、前記透過領域を透過した前記第２の直線偏光とを同軸で射出する
    請求項１に記載の偏光調整装置。     a dual-purpose optical element serving as both the first optical element and the third optical element;
    the dual-purpose optical element has a polarization separation region in its center that separates the first linearly polarized light from the second linearly polarized light by reflecting the first linearly polarized light in the incident randomly polarized laser beam and transmitting the second linearly polarized light, and has a transmission region around the polarization separation region that transmits linearly polarized light in the first polarization direction;
    the second optical element includes a quarter-wave plate that converts the second linearly polarized light transmitted through the polarization separation region into a first circularly polarized light, and a first reflecting mirror that reflects the first circularly polarized light and outputs it as a second circularly polarized light,
    the quarter-wave plate converts the second circularly polarized light reflected by the first reflecting mirror into the second linearly polarized light in the first polarization direction,
    the polarization separation region reflects the second linearly polarized light emitted from the quarter-wave plate,
    the axicon lens expands the second linearly polarized light reflected by the polarization separation region into a ring shape;
    a second reflecting mirror that reflects the second linearly polarized light emitted from the axicon lens,
    the axicon lens causes the second linearly polarized light reflected by the second reflecting mirror to enter the transmission region;
    2 . The polarization adjusting device according to claim 1 , wherein the dual-purpose optical element emits the first linearly polarized light reflected by the polarization separation region and the second linearly polarized light transmitted through the transmission region coaxially.
  3. 　前記第３の光学素子は、
    　前記第１の光学素子とは別体であり、
    　入射されたレーザビームを透過させる透過領域を中心部に有し、前記透過領域の周囲に、入射されたレーザビームを反射させる反射領域を有し、
    　前記第１の光学素子は、前記ランダム偏光のレーザビームにおける前記第１の直線偏光を透過させて前記透過領域に入射させ、前記第２の直線偏光を反射させることにより前記第１の直線偏光と前記第２の直線偏光とを分離し、
    　前記第１の光学素子より反射された前記第２の直線偏光を反射させる第１の反射ミラーをさらに備え、
    　前記アキシコンレンズは、前記第１の反射ミラーより反射された前記第２の直線偏光をリング状に広げ、
    　前記アキシコンレンズより射出された前記第２の直線偏光を反射する第２の反射ミラーをさらに備え、
    　前記第２の光学素子は、
    　１／２波長板であり、
    　前記第２の反射ミラーより反射された前記第２の直線偏光の偏光方向を前記第１の偏光方向に変換して前記反射領域に入射させ、
    　前記第３の光学素子は、前記透過領域を透過した前記第１の直線偏光と、前記反射領域により反射した前記第２の直線偏光とを同軸で射出する
    請求項１に記載の偏光調整装置。     The third optical element is
    is separate from the first optical element,
    A transmission region for transmitting an incident laser beam is provided at a central portion, and a reflection region for reflecting the incident laser beam is provided around the transmission region.
    the first optical element transmits the first linearly polarized light in the randomly polarized laser beam to cause it to enter the transmission region, and reflects the second linearly polarized light to separate the first linearly polarized light and the second linearly polarized light;
    a first reflecting mirror that reflects the second linearly polarized light reflected by the first optical element,
    the axicon lens expands the second linearly polarized light reflected by the first reflecting mirror into a ring shape;
    a second reflecting mirror that reflects the second linearly polarized light emitted from the axicon lens,
    The second optical element is
    It is a half wave plate,
    converting a polarization direction of the second linearly polarized light reflected by the second reflecting mirror into the first polarization direction and causing the second linearly polarized light to enter the reflecting area;
    2 . The polarization adjusting device according to claim 1 , wherein the third optical element emits the first linearly polarized light transmitted through the transmission region and the second linearly polarized light reflected by the reflection region coaxially.
  4. 　請求項１～３のいずれか１項に記載の偏光調整装置と、
    　前記偏光調整装置より同軸で射出された前記第１の直線偏光及び前記第２の直線偏光の偏光方向を、被加工材にレーザビームを照射して前記被加工材を切断するときの切断進行方向と平行となるように制御する偏光方向制御機構と、
    を備えるレーザ加工機。     A polarization adjustment device according to any one of claims 1 to 3,
    a polarization direction control mechanism that controls the polarization directions of the first linearly polarized light and the second linearly polarized light output from the polarization adjustment device so as to be parallel to a cutting direction when a laser beam is irradiated onto a workpiece to cut the workpiece;
    A laser processing machine comprising:
PCT/JP2023/036169 2022-10-13 2023-10-04 Polarized light adjustment device and laser processing machine WO2024080198A1 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59127990A (en) * 1983-01-13 1984-07-23 Matsushita Electric Ind Co Ltd Laser cutting device
JPH03193281A (en) * 1989-12-20 1991-08-23 Hitachi Ltd Liquid crystal mask type laser beam marker
US20160004074A1 (en) * 2013-03-22 2016-01-07 Shanghai Institute Of Optics And Fine Mechanics Chinese Academy Of Sciences Pupil shaping optical system for lithography machine and method for generating off-axis illumination modes
US20210098973A1 (en) * 2018-11-06 2021-04-01 Zhejiang University Structured beam generation device and method based on beam shaping

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS59127990A (en) * 1983-01-13 1984-07-23 Matsushita Electric Ind Co Ltd Laser cutting device
JPH03193281A (en) * 1989-12-20 1991-08-23 Hitachi Ltd Liquid crystal mask type laser beam marker
US20160004074A1 (en) * 2013-03-22 2016-01-07 Shanghai Institute Of Optics And Fine Mechanics Chinese Academy Of Sciences Pupil shaping optical system for lithography machine and method for generating off-axis illumination modes
US20210098973A1 (en) * 2018-11-06 2021-04-01 Zhejiang University Structured beam generation device and method based on beam shaping

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