JP2012234978A - Laser irradiation device and laser machining device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high quality beam while suppressing reduction in output in a laser irradiation device having an optical fiber.SOLUTION: Optical fibers (11B, 12) transmit laser light from a laser light source. The optical fibers (11B, 12) have a free portion (11B) in a free state of movement. Furthermore, in the vicinity of an emission end of the optical fiber 12, the optical fiber 12 is bent in a ring shape (a ring part 12A). In the vicinity of the emission end of the optical fiber, the optical fiber is bent at a prescribed curvature, so that a beam shape of the laser light can be made excellent without removing light in a higher-order mode.

Description

  The present invention relates to a laser irradiation apparatus and a laser processing apparatus, and more particularly to a laser irradiation apparatus using an optical fiber and a processing apparatus including the irradiation apparatus.

  There are various types of laser processing apparatuses. For example, laser processing apparatuses using optical fibers have been proposed. With the diversification of applications and needs of laser processing apparatuses, high output, high stability, high beam quality, and miniaturization are desired for laser processing apparatuses.

  In order to increase the output of a laser processing apparatus using an optical fiber, there are problems such as damage to the fiber itself due to the glass breaking limit and damage to the fiber due to stimulated scattered light generated by the nonlinear optical effect. In order to avoid these problems, a method of reducing the energy density in the core by enlarging the core diameter of the fiber can be considered. However, when the core diameter is increased, higher-order mode light is included in the propagated laser light. As a result, the spatial intensity distribution of the laser beam fluctuates due to slight vibration of the fiber, and it becomes difficult to ensure the stability of the laser beam.

  Non-Patent Document 1 (Jeffrey P. Koplow, Dahv A. V Kliner, Lew Goldberg, "Single-mode operation of a coiled multimode fiber amplifier", OPTICS LETTERS, Vol. 25, No. 7, April 1, 2000) A means for removing higher order mode laser light is disclosed. Specifically, an extremely small winding portion is provided in the amplification fiber by utilizing the fact that the loss due to the bending of the fiber is large in the high-order mode laser light.

  Non-Patent Document 2 (JA Alvarez-Chavez, AB Grudinin, J. Nilsson, PW Turner and WA Clarkson "Mode selection in high power cladding pumped fiber lasers with tapered section", CLEO / QLES '99 Baltimore (23-28 May, 1999 CWE7) also discloses a means for removing higher order mode laser light. Specifically, a portion having a small core diameter is provided by a tapered fiber.

  Japanese Patent Application Laid-Open No. 2007-103751 discloses an optical amplifying fiber provided with ring portions having different curvatures. The high-order mode laser light is previously removed from the ring portion having a small curvature, and the laser light is amplified in the ring portion having a large curvature.

JP 2007-103751 A

Jeffrey P. Koplow, Dahv A. V Kliner, Lew Goldberg, "Single-mode operation of a coiled multimode fiber amplifier", OPTICS LETTERS, Vol. 25, No. 7, April 1, 2000 J. A. Alvarez-Chavez, A. B. Grudinin, J. Nilsson, P.W.Turner and W. A. Clarkson "Mode selection in high power cladding pumped fiber lasers with tapered section", CLEO / QLES '99 Baltimore (23-28 May, 1999) CWE7

  According to the technique disclosed in Non-Patent Document 1, it is possible to stabilize the mode of the laser device. However, since a part of the amplified light is removed, not only the output from the amplified fiber is lowered, but there is a concern that the optical fiber generates heat. Furthermore, in order to provide a very small winding portion on the optical fiber, it is necessary to stably fix the optical fiber. For this reason, the manufacturing cost of an apparatus rises. Furthermore, since the burden on the optical fiber is increased by providing a very small winding portion, there is a concern that the reliability may deteriorate during long-term use.

  According to the technique disclosed in Non-Patent Document 2, there is a concern that the output of the fiber is reduced due to an increase in the dissipation of light. Furthermore, there is a problem that a processing cost for forming the taper is required.

  In the configuration disclosed in Patent Document 1, the spatial intensity distribution of the laser light emitted from the optical amplifying fiber fluctuates due to a change in shape or vibration of the ring portion in an actual usage environment, and the beam diameter is inconsistent. It becomes stable. When the beam diameter is unstable, there is a problem that the processing marks formed by the laser light are not uniform.

  An object of the present invention is to make it possible to obtain a high-quality beam while suppressing a decrease in output in a laser irradiation apparatus including an optical fiber.

  A laser irradiation apparatus according to an aspect of the present invention includes an optical fiber having an emission end for emitting laser light, and a laser light source for generating laser light propagating through the optical fiber. The optical fiber has a free part in a freely movable state and is bent in a ring or arc shape in the vicinity of the exit end.

  Preferably, the laser irradiation apparatus includes a main body including a laser light source and a head including an optical component for irradiating a target with laser light emitted from an emission end of the optical fiber. The emission end is located inside the head portion. The free part is a part for propagating laser light from the main body part to the head part.

Preferably, the diameter of the ring or arc is not less than 60 mm and not more than 150 mm.
Preferably, the diameter is 60 mm or more and 120 mm or less.

Preferably, the diameter is 60 mm or more and 90 mm or less.
Preferably, the laser irradiation apparatus further includes a base member and a fiber guide. The fiber guide is made of a light shielding member, has an arcuate outer surface, and is formed so that a fixing member for fixing the optical fiber can be attached. The optical fiber is bent along the outer surface of the fiber guide and fixed to the fiber guide by a fixing member. An attachment portion for attaching the fiber guide to the base member with a screw is provided on the inner surface side of the fiber guide located on the side opposite to the outer surface.

  Preferably, the optical fiber is bent in a ring shape or an arc shape at a location different from the vicinity of the exit end in addition to the vicinity of the exit end.

Preferably, the optical fiber is a multimode fiber.
Preferably, the optical fiber includes an optical amplification fiber. The optical amplification fiber amplifies the signal laser light with the excitation laser light in order to generate the laser light emitted from the emission end. The laser light source includes a first light source that generates signal laser light and a second light source that generates excitation laser light.

  Preferably, the laser light source includes a resonator including an amplification medium and an excitation light source that supplies excitation light for exciting the amplification medium.

Preferably, the amplification medium includes an optical amplification fiber.
Preferably, the amplification medium is any one of a solid medium, a liquid medium, and a gas medium.

  A laser processing apparatus according to another aspect of the present invention includes any one of the laser irradiation apparatuses described above.

  ADVANTAGE OF THE INVENTION According to this invention, in a laser processing apparatus provided with the optical fiber, a high quality beam can be obtained while suppressing a decrease in output.

It is the schematic which shows the whole structure of the laser processing apparatus which concerns on embodiment of this invention. It is a block diagram which shows in more detail the structure of the laser control part of the laser processing apparatus shown in FIG. It is a figure explaining the structure of optical fiber 11A, 11B shown in FIG. 2, and the light which propagates optical fiber 11A, 11B. It is the figure which showed the structural example of the laser head part of the laser processing apparatus shown in FIG. It is a figure for demonstrating the beam shape (spatial intensity distribution) of a laser beam. It is a flowchart for comparing the conventional control method of a laser beam and the control method by embodiment of this invention. It is the figure which compared the power of the laser beam output from an optical fiber with the presence or absence of a fiber ring. It is the figure which showed the experimental result about stability of spot shape. It is the figure which showed the experimental result about the relationship between the power of the laser beam radiate | emitted from an optical fiber, and stability of a beam diameter with respect to the diameter of the ring part of an optical fiber. It is a block diagram which shows in more detail the structure of the laser head part with which the laser processing apparatus which concerns on Embodiment 2 is provided. 6 is a perspective view showing an example of a specific configuration of a portion related to a bent portion of a laser head portion according to Embodiment 2. FIG. FIG. 12 is a perspective view of a part of the laser head portion viewed from the direction A in FIG. 11. FIG. 12 is a top view of a part of the laser head portion viewed from the direction B in FIG. 11. It is a perspective view of a fiber guide. It is a schematic diagram for demonstrating the part of the optical fiber in the boundary vicinity of the inside of an optical fiber storage box, and the exterior of an optical fiber box. It is a block diagram which shows in more detail the structure of the laser light source with which the laser processing apparatus which concerns on Embodiment 3 is provided. It is a block diagram which shows an example of another structure of the laser light source with which the laser processing apparatus which concerns on Embodiment 3 is provided. It is a block diagram which shows an example of another structure of the laser light source with which the laser processing apparatus which concerns on Embodiment 3 is provided. It is a block diagram which shows in more detail the structure of the laser transmission part with which the laser processing apparatus which concerns on Embodiment 4 is provided. It is a block diagram which shows another structure of the laser transmission part with which the laser processing apparatus which concerns on Embodiment 4 is provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram showing the overall configuration of a laser processing apparatus according to an embodiment of the present invention. Referring to FIG. 1, a laser processing apparatus 100 includes a laser control unit 110 corresponding to a main body unit, a laser head unit 120, and a laser transmission unit for transmitting laser light from the laser control unit 110 to the laser head unit 120. 130.

  The laser control unit 110 generates laser light and emits the laser light. The laser control unit 110 includes a laser light source 150, a control board 20, a driver 32, and a driver power supply 30. The laser light source 150 is driven by the driver 32 to perform laser oscillation. As a result, laser light is output from the laser light source 150. The control board 20 controls laser oscillation conditions, laser light output, and output stop.

  The driver power supply 30 operates the driver 32 by supplying power to the driver 32. As a result, the driver 32 drives the laser light source 150.

  The control board 20 controls the laser light output and stop of output by the laser light source 150. Note that the control board 20 may control the operation and stop of the driver 32 with respect to the driver 32.

  The laser head unit 120 irradiates the workpiece 50 with the laser light L. The laser transmission unit 130 transmits the laser light from the laser control unit 110 to the laser head unit 120.

  In the embodiment of the present invention, the light from the laser irradiation apparatus is used for processing an object. That is, in this embodiment, the laser irradiation apparatus is used as a laser processing apparatus. Therefore, the laser processing apparatus 100 according to the present embodiment includes a laser irradiation apparatus.

  The application of the laser processing apparatus 100 is not particularly limited, and can be used for laser marking, drilling, welding, cutting, heat treatment, shape processing, trimming, and the like.

  When introducing a laser processing apparatus into a factory production line or the like, it is particularly important that the laser processing apparatus is miniaturized. As shown in FIG. 1, a laser processing apparatus according to an embodiment of the present invention has a configuration in which a laser control unit including a laser oscillation device and a laser head unit including a laser beam scanning mechanism are separated. ing. With such a configuration, a relatively small laser head unit 120 can be installed on the production line.

Next, a specific configuration of the laser processing apparatus according to the embodiment of the present invention will be described.
[Embodiment 1]
FIG. 2 is a configuration diagram showing the configuration of the laser control unit in the laser processing apparatus shown in FIG. 1 in more detail. Referring to FIG. 2, laser control unit 110 includes a laser light source 150, control board 20, driver 32, and driver power supply 30. The laser light source 150 includes an optical fiber 1, semiconductor lasers 2, 3, 9 </ b> A to 9 </ b> D, isolators 4, 6, optical couplers 5, 10, and a bandpass filter 7.

  The optical fiber 1 is an optical amplification fiber. Specifically, the optical fiber 1 is a rare earth-doped fiber and has a core to which a rare earth element that is an optical amplification component is added. The kind of rare earth element is not particularly limited, and examples thereof include Er (erbium), Yb (ytterbium), and Nd (neodymium). In the embodiment of the present invention, the rare earth element added to the core is Yb (ytterbium).

  The semiconductor laser 2 is a seed light source that emits seed light. The wavelength of the seed light is, for example, 1064 ± 2 nm. The semiconductor laser 2 is driven by a driver 32 to emit pulsed seed light.

  The isolator 4 transmits only light in one direction and blocks light incident in the opposite direction to the light. Specifically, the isolator 4 allows the seed light emitted from the semiconductor laser 2 to pass and blocks the return light from the optical fiber 1. Thereby, damage to the semiconductor laser 2 can be prevented.

  The semiconductor laser 3 is an excitation light source that emits excitation light for exciting the rare earth element added to the core of the optical fiber 1. The wavelength of the excitation light is determined based on the kind of rare earth element added to the core of the optical fiber. When the rare earth element is Yb, the wavelength of the excitation light is, for example, 915 ± 10 nm.

  The optical coupler 5 combines the seed light from the semiconductor laser 2 and the pumping light from the semiconductor laser 3 so as to enter the optical fiber 1. As the optical coupler 5, for example, a WDM (Wavelength Division Multiplexing) coupler can be applied.

  The excitation light incident on the optical fiber 1 from the semiconductor laser 3 through the optical coupler 5 is absorbed by the rare earth element contained in the core of the optical fiber 1. Thereby, the rare earth element is excited (transition from the ground level to the upper level), and an inversion distribution state is obtained. In this state, when the seed light from the semiconductor laser 2 enters the core of the optical fiber 1, stimulated emission occurs. The seed light (pulse light) is amplified by this stimulated emission. That is, the optical fiber 1 amplifies the seed light with the excitation light.

  The isolator 6 allows the pulsed light output from the optical fiber 1 to pass and blocks light returning to the optical fiber 1.

  The band pass filter 7 is configured to pass light of a predetermined wavelength band. Specifically, the “predetermined wavelength band” is a wavelength band including the peak wavelength of the pulsed light output from the optical fiber 1. When spontaneous emission light is emitted from the optical fiber 1, the spontaneous emission light is removed by the band pass filter 7.

  The laser light that has passed through the bandpass filter 7 enters the laser transmission unit 130 via the optical coupler 10. The semiconductor lasers 9 </ b> A to 9 </ b> D emit excitation light to amplify the laser light that has passed through the bandpass filter 7 in the laser transmission unit 130. In the first embodiment, four excitation light sources are provided, but the number of semiconductor lasers as excitation light sources is not limited to four. The power of the excitation light and the number of excitation light sources can be determined based on the power of the laser light output from the laser processing apparatus 100, the amplification factor of the pulse light in the laser transmission unit 130, and the like.

  The optical coupler 10 combines the pulsed light that has passed through the bandpass filter 7 and the light from the semiconductor lasers 9 </ b> A to 9 </ b> D so as to enter the laser transmission unit 130.

  The control board 20 includes a control unit 21 and a pulse generation unit 22. The control unit 21 controls the entire operation of the laser control unit 110 by controlling the pulse generation unit 22 and the driver 32. The pulse generator 22 generates an electrical signal having a predetermined repetition frequency and a predetermined pulse width. The pulse generator 22 outputs an electric signal or stops outputting the electric signal under the control of the control unit 21. An electrical signal from the pulse generator 22 is supplied to the semiconductor laser 2.

  The driver power supply 30 supplies power to the driver 32. As a result, the driver 32 supplies a drive current to the semiconductor lasers 2, 3, 9A to 9D. Each of the semiconductor lasers 2, 3, 9A to 9D oscillates when supplied with a drive current. The drive current supplied to the semiconductor laser 2 is modulated by an electric signal from the pulse generator 22. Thus, the semiconductor laser 2 oscillates and outputs pulsed light having a predetermined repetition frequency and a predetermined pulse width as seed light. On the other hand, a continuous drive current is supplied to each of the semiconductor lasers 3, 9 </ b> A to 9 </ b> D by the driver 32. As a result, each of the semiconductor lasers 3, 9A to 9D continuously oscillates and outputs continuous light as excitation light.

  Although not shown in FIG. 2, a temperature controller for controlling the temperature of the semiconductor laser may be provided for each semiconductor laser. By stabilizing the temperature of the semiconductor laser using the temperature controller, the output of the semiconductor laser can be stabilized. Furthermore, a temperature controller may be provided corresponding to the bandpass filter 7 and / or the isolator 6.

  In this embodiment, a double clad fiber in which a clad is provided twice around the core is applied to each of the optical fibers 11A and 11B.

  FIG. 3 is a diagram for explaining the structure of the optical fibers 11A and 11B shown in FIG. 2 and light propagating through the optical fibers 11A and 11B. Referring to FIG. 3, an optical fiber 11A is provided around a core 41A, a first clad 42A provided around the core 41A and having a refractive index lower than that of the core 41A, and around the first clad 42A. A second clad 43A having a refractive index lower than that of the first clad 42A and a coating 44A are included.

  The optical fiber 11B has the same configuration as the optical fiber 11A. Specifically, the optical fiber 11B is provided around the core 41B, the first clad 42B provided around the core 41B and having a lower refractive index than the core 41B, the first clad 42B, and the first clad 42B. A second clad 43B having a refractive index lower than that of the first clad 42B and a coating 44B are included.

  The end face of the optical fiber 11A and the end face of the optical fiber 11B are fused. The pulsed light A that has passed through the bandpass filter 7 enters the core 41A of the optical fiber 11A via the optical coupler 10. The pulsed light A incident on the core 41A of the optical fiber 11A propagates through the core 41A and the core 41B of the optical fiber 11B and is emitted to the laser head unit 120.

  Excitation light B from the semiconductor lasers 9A to 9D enters the first cladding 42A of the optical fiber 11A via the optical coupler 10. The excitation light B propagates through the optical fiber 11A while being reflected at the boundary between the first cladding 42A and the second cladding 43A. The pumping light B propagated through the optical fiber 11A enters the first cladding 42B of the optical fiber 11B, and propagates through the optical fiber 11B while being reflected at the boundary between the first cladding 42B and the second cladding 43B.

  Since the rare earth element (specifically Yb) is not substantially added to the core 41A of the optical fiber 11A, even if the excitation light B passes through the core 41A, the absorption of the excitation light B by the core 41A is substantially reduced. Does not occur. For this reason, the pulsed light A is not substantially amplified in the optical fiber 11A.

  On the other hand, since the rare earth element (specifically Yb) is added to the core 41B of the optical fiber 11B, when the excitation light B passes through the core 41B, a part of the excitation light B is included in the core 41B. Absorbed by rare earth elements. As a result, the rare earth element is excited, and when the pulsed light A is incident on the core 41B, the pulsed light A is amplified by stimulated emission of the rare earth element.

  Note that the bandpass filter 7 may not be provided, but in that case, spontaneous emission light emitted from the optical fiber 1 enters the optical fibers 11A and 11B. When the spontaneous emission light is amplified by the optical fiber 11B, the amplification factor of the pulsed light A is lowered. By removing spontaneously emitted light emitted from the optical fiber 1 by the band-pass filter 7, high-efficiency optical amplification can be performed in the optical fiber 11B.

  FIG. 4 is a diagram showing a configuration example of a laser head unit in the laser processing apparatus shown in FIG. Referring to FIG. 4, the laser head unit 120 includes an optical fiber 12, an end cap 13, a collimating lens 14, dichroic mirrors 15A and 15B, an isolator 16, a magnifier 17, a galvano scanner 18, a collector. And an optical lens 19.

  The incident end of the optical fiber 12 is optically coupled to the exit end of the optical fiber 11B. An end cap 13 is provided at the output end of the optical fiber 12. The optical fiber 12 has a ring portion 12A wound in a ring shape. In the embodiment of the present invention, the “ring shape” is a state in which the optical fiber is wound in a circle or more, and the “arc shape” means that the optical fiber is a part of the circumference. It is in a bent state.

  The end cap 13 is provided to prevent damage that occurs at the boundary surface between the end face of the optical fiber 12 and the atmosphere when a light pulse having a high peak power is emitted from the optical fiber 12 to the atmosphere.

  The collimating lens 14 is for adjusting the beam diameter of the pulsed light emitted from the optical fiber 12. The pulsed light that has passed through the collimating lens 14 is reflected by the dichroic mirror 15A and enters the isolator 16.

  The isolator 16 allows the pulsed light incident on the isolator 16 from the dichroic mirror 15 </ b> A to pass, while blocking the light returning to the isolator 16. The pulsed light that has passed through the isolator 16 is output from the expander 17 attached to the isolator 16 to the atmosphere and enters the galvano scanner 18.

  The galvano scanner 18 scans the laser beam in at least one of the X axis and the Y axis direction orthogonal to the X axis. The condensing lens 19 is, for example, an fθ lens, and condenses the laser light L scanned by the galvano scanner 18. The workpiece 50 is irradiated with the laser light L condensed by the condenser lens 19.

  For example, ablation occurs on the surface of the workpiece 50 by condensing the laser light amplified by the optical fiber 1 and the optical fiber 11B by the condenser lens 19. When laser light is irradiated on the surface of an object such as a polymer, ceramics, glass, or metal material at a high energy density, the material undergoes decomposition, vaporization, and transpiration due to the instantaneous breakage of the bonds between the molecules and atoms constituting the material. The surface is removed explosively, resulting in a very sharp removal that does not damage the surroundings. This is a phenomenon called ablation. Various processes are possible by using ablation.

  The optical fibers 1, 11A, 11B, and 12 used in this embodiment are all multimode fibers. Multimode fibers have a larger core diameter than single mode fibers. Since the core diameter is large, the energy in the core can be increased, so that high-power laser light can be generated by the laser processing apparatus. However, by increasing the core diameter, higher-order mode laser light can also propagate through the core. Increasing the number of modes makes it difficult to improve the beam shape (spatial intensity distribution) of the laser light.

  Conversely, the mode of laser light propagating through the core is limited as the core diameter is smaller. By limiting the mode, the beam shape of the laser beam can be improved. However, since the core diameter is small, the power of the laser beam cannot be increased.

  As described above, according to the conventional concept, there is a trade-off relationship between increasing the power of the laser beam emitted from the optical fiber and stabilizing the beam shape of the laser beam, and thus cannot achieve both.

  Furthermore, the laser processing apparatus 100 has a configuration in which the main body and the head are connected by a laser transmission unit 130 (optical fibers 11A and 11B). The laser transmission unit 130 is a part that is free to move. Since the laser transmission unit 130 is not fixed, the laser transmission unit 130 may move when the laser beam is emitted from the laser processing apparatus 100. When the laser transmission unit 130 vibrates, the optical path in the laser transmission unit 130 (optical fiber) changes. As a result, high-order mode laser light is generated, and the spatial intensity distribution of the laser light finally emitted from the laser processing apparatus 100 may vary.

  FIG. 5 is a diagram for explaining the beam shape (spatial intensity distribution) of laser light. FIG. 5A is a diagram showing an ideal spatial intensity distribution of laser light and a spot shape corresponding to the intensity distribution. FIG. 5B is a diagram showing a spot shape when fluctuation occurs in the spatial intensity distribution of the laser light.

  Referring to FIG. 5, the spatial intensity distribution of laser light is ideally represented according to a Gaussian curve. Therefore, when the spatial intensity distribution is close to the ideal distribution, the intensity of the laser light is distributed concentrically on the plane irradiated with the laser light (FIG. 5A). However, when fluctuations occur in the spatial intensity distribution of the laser light, the intensity of the laser light on the plane is a biased distribution (FIG. 5B). If the intensity distribution of the laser beam fluctuates in this way, the processing quality may vary.

  In the first embodiment, the optical fiber is bent with a predetermined curvature in the vicinity of the emission end of the optical fiber (11A, 11B, 12) that transmits the laser light from the laser light source 150. Specifically, the optical fiber 12 has a ring portion 12A bent into a ring shape with a predetermined curvature. Since the optical fiber is bent with a predetermined curvature in the vicinity of the emission end of the optical fiber, the beam shape of the laser light can be improved without removing the higher-order mode light. Therefore, it is possible to obtain a high-quality beam while suppressing a decrease in output. The “predetermined curvature” is a curvature that does not cause bending loss of the optical fiber, and can be appropriately determined depending on the optical fiber used.

  Furthermore, according to the first embodiment, the beam shape of the laser light emitted from the optical fiber can be improved even when a part of the optical fiber is free to move like the laser transmission unit 130. .

  FIG. 6 is a flowchart for comparing the conventional control method of laser light with the control method according to the embodiment of the present invention. Referring to FIG. 6, in step S1, there is a problem that the shape of the outgoing beam from the optical fiber varies due to the movement of the laser transmission unit. Whether or not the core diameter is reduced to make the V number 2.405 or less is examined (step S2).

The V number is expressed according to the following equation (1).
V = 2π / λ × NA × a (1)
λ is the wavelength of light propagating through the core, NA is the numerical aperture of the core, and a is the core diameter. If the V number is 2.405 or less, the mode of light propagating through the core is a single mode.

  However, if it is selected to reduce the core diameter (V number is 2.405 or less) (Yes in step S2), it is difficult for light with high energy density to propagate through the core, so it is difficult to increase output. (Step S3).

  On the other hand, if it is selected not to reduce the core diameter (No in step S2), it is examined whether or not the V number is reduced to 2.405 or less by reducing the core NA (step S4). According to equation (1), the V number can be reduced to 2.405 or less by reducing the NA of the core. In this case, since it is possible to propagate a single mode without reducing the core diameter, it is considered that the beam shape can be stabilized while achieving high output.

  However, when it is selected to reduce the NA of the core (Yes in step S4), not only the refractive index of the core but also the refractive index of the two-layer clad is controlled as the refractive index control of the double clad fiber or the like. Is also required. For this reason, the price of the optical fiber increases and the control can be complicated (step S5).

  If it is selected not to reduce the NA of the core (No in step S4), whether or not to remove the higher-order mode by microbending is examined (step S6). Microbending refers to bending of the optical fiber axis with a smaller radius of curvature than the core diameter by applying pressure to the side surface of the optical fiber. High-order mode light can be removed by microbending (see, for example, Non-Patent Document 1). However, if the removal of the higher order mode is selected by microbending (Yes in step S6), a loss of the optical fiber occurs, so that the output of the optical fiber decreases.

  On the other hand, the control method according to the present invention can stabilize the beam shape without reducing the core diameter, reducing the core NA, or removing higher-order modes by microbending. Therefore, the beam shape can be stabilized while increasing the output.

  FIG. 7 is a diagram comparing the power of laser light output from an optical fiber according to the presence or absence of a fiber ring. Referring to FIG. 7, the horizontal axis of the graph indicates the drive current supplied to the excitation LD, and the vertical axis of the graph indicates the average output of the laser light emitted from the optical fiber. As shown in FIG. 7, even if the ring portion is provided in the optical fiber, the output is hardly reduced.

  FIG. 8 is a diagram showing experimental results regarding the stability of the spot shape. In this experiment, a double clad fiber having a core diameter of 15 μm and a core NA of 0.13 was used as the optical fiber. The wavelength of the signal light was 1064 nm, and about 30 W of excitation light was incident on the optical fiber of the laser transmission unit.

  Referring to FIG. 8, the beam spot diameter is defined as a range in which the beam intensity is 1 / e or more (e is the base of natural logarithm) of the peak intensity. Further, the stability of the beam spot diameter is defined as a variation rate of the beam spot diameter. That is, the lower the numerical value indicating the stability of the beam spot diameter, the smaller the fluctuation of the beam spot diameter.

  As shown in Examples 1 to 3, the beam spot diameter is stabilized as compared with the straight fiber by providing the ring portion in the vicinity of the emission end of the optical fiber regardless of the core NA. Further, even when the vicinity of the exit end of the optical fiber is bent with a predetermined curvature, the beam spot diameter is stabilized as compared with the straight fiber.

  In addition, when Examples 1 to 3 are compared with each other, it can be seen that as the V number is increased, the effect of the stability of the spot diameter by providing the ring portion or the bent portion in the optical fiber becomes higher. Since the number of modes propagating through the optical fiber can be increased by increasing the V number, the power of the laser beam propagating through the optical fiber can be increased.

  FIG. 9 is a diagram showing experimental results regarding the relationship between the power of the laser beam emitted from the optical fiber and the stability of the beam diameter with respect to the diameter of the ring portion of the optical fiber. This experiment was performed using the conditions when the results shown in FIG. 8 were obtained. Referring to FIG. 9, the power of the laser light emitted from the optical fiber hardly changes when the diameter of the ring portion is 150 mm, 120 mm, 90 mm, and 60 mm when there is no ring. On the other hand, the numerical value indicating the stability of the beam diameter is about 1.2% when there is no ring or when the diameter of the ring portion is 150 mm, whereas the diameter of the ring portion is 120 mm or less. Then, it becomes 1.0% or less. In particular, when the ring portion has a diameter of 90 mm or less, the numerical value indicating the stability of the beam diameter is about 0.8%.

  From FIG. 9, it is preferable that the diameter of a ring part is 60 mm or more and 150 mm or less. When the diameter of the ring portion is larger than 150 mm, the stability of the beam diameter is almost the same as when there is no ring portion. On the other hand, when the diameter of the ring portion is 60 mm or less, it becomes difficult to bend the optical fiber. More preferably, the diameter of the ring part is 60 mm or more and 120 mm or less. By setting the diameter of the ring portion within this range, the stability of the beam diameter can be further improved. More preferably, the ring portion has a diameter of 60 mm or more and 90 mm or less. By setting the diameter of the ring portion within this range, the stability of the beam diameter can be further enhanced.

  Thus, in Embodiment 1, the optical fiber is bent in the vicinity of the emission end of the optical fiber. More specifically, the optical fiber is bent into a ring shape in the vicinity of its emission end. Thereby, it is possible to increase the output of the laser processing apparatus and improve the beam quality.

[Embodiment 2]
The laser processing apparatus according to the second embodiment is different from the laser processing apparatus according to the first embodiment in the configuration of the laser head unit.

  FIG. 10 is a configuration diagram showing in more detail the configuration of the laser head unit included in the laser processing apparatus according to the second embodiment. Referring to FIGS. 10 and 4, the laser head unit 120 </ b> A according to the second embodiment is the laser head unit 120 according to the first embodiment in that a bent portion 12 </ b> B bent in an arc shape is provided in the optical fiber 12. And different. Two times the radius of curvature of the bent portion 12B is defined as the diameter of the bent portion 12B. The range of the diameter of the bent portion 12B is the same as the range of the diameter of the ring portion 12A according to the first embodiment. That is, the diameter of the bent part 12B is 60 mm or more and 150 mm or less, more preferably 60 mm or more and 120 mm or less, and still more preferably 60 mm or more and 90 mm or less.

  FIG. 11 is a perspective view showing an example of a specific configuration of a portion related to a bent portion of the laser head portion according to the second embodiment. 12 is a perspective view of a part of the laser head portion viewed from the direction A in FIG. FIG. 13 is a top view of a part of the laser head portion viewed from the direction B of FIG.

  With reference to FIGS. 11 to 13, the laser head portion 120 </ b> A includes a bottom surface base 60, a fiber storage box 61, a fiber guide 62, and a side surface base 68. The fiber guide 62 is attached to the bottom base 60. The fiber storage box 61 is attached to the side base 68.

  The optical fiber 12 is stored in the fiber storage box 61. The optical fiber 12 drawn out from the fiber storage box 61 is inserted into a resin tube 63. A resin bushing 67 is provided at a portion of the fiber storage box 61 from which the optical fiber 12 is drawn. A through hole is formed in the bushing 67, and the optical fiber 12 passed through the tube 63 is drawn out from the through hole.

  The optical fiber 12 drawn out from the fiber storage box 61 is bent along the outer surface of the fiber guide 62 and fixed to the outer surface of the fiber guide 62 by a binding band 64. The outer surface of the fiber guide 62 is bent in an arc shape. Accordingly, the bent portion 12 having a diameter within the above range is formed. The binding band 64 functions as a fixing member for fixing the optical fiber 12 to the fiber guide 62. The binding band 64 is shown in FIGS. 11 to 13 as one embodiment of a fixing member, but can be applied as a fixing member as long as it is a member capable of fixing the optical fiber 12 to the fiber guide 62. It is.

  The fiber guide 62 is formed of a light shielding member. Even when leakage light is generated in the bent portion 12, the fiber guide 62 can prevent the leakage light from entering the laser head. In addition, the material of the fiber guide 62 is not specifically limited, For example, it can produce with a metal (aluminum as an example) or a flame-retardant resin.

  The tube 63 covers the portion of the optical fiber 12 between the fiber storage box 61 and the isolator 13 without a gap. The tube 63 is for preventing the optical fiber 12 from being damaged. For example, if the binding band 64 is in direct contact with the optical fiber 12 or if an adjustment tool is in direct contact with the optical fiber 12 during optical adjustment, the optical fiber 12 may be damaged. By covering the optical fiber 12 with the tube 63, such damage to the optical fiber 12 can be prevented.

  FIG. 14 is a perspective view of the fiber guide. Referring to FIGS. 13 and 14, a pair of holes 65 for passing the binding band 64 are provided at three positions of the fiber guide 62. Note that the position and number of the pair of holes 65 are not limited as shown in FIGS.

  On the inner side of the fiber guide 62, there is formed an attachment portion 66 in which a through hole for passing a screw (not shown in FIGS. 11 to 14) is formed. The fiber guide 62 is fixed to the bottom surface base 60 by passing a screw through a through hole formed in the attachment portion 66 and screwing the screw into a screw hole formed in the bottom surface base 60.

  As described above, the optical fiber 12 is attached to the outer surface of the fiber guide 62. By providing the attachment portion 66 inside the fiber 62, the fiber guide 62 can be attached to and detached from the bottom base 60 while avoiding contact of the tool with the optical fiber 12, so that workability is improved during optical adjustment. Can do.

  FIG. 15 is a schematic diagram for explaining an optical fiber portion in the vicinity of the boundary between the inside of the optical fiber storage box and the outside of the optical fiber storage box. Referring to FIG. 15, the tube 63 containing the optical fiber 12 is passed through a through hole formed in the bushing 67. The tube 63 is not fixed to the bushing 67 and is freely rotatable in a through hole formed in the bushing 67. If the tube 63 is completely fixed by the bushing 67 (not rotatable), the tube 63 may be twisted during assembly. Such a problem can be prevented because it can freely rotate within the through-hole formed in the bushing 67. Further, since the bushing 67 functions as a damper, it is possible to prevent damage to the optical fiber 12 due to excessive impact applied to the optical fiber 12.

  The fiber guide 62 may be formed in a cylindrical shape, and the optical fiber 12 may be wound along the outer surface. Thereby, a ring-shaped bending part can also be formed.

  Since the configuration of the other part of laser head unit 120A according to Embodiment 2 is the same as the configuration of the corresponding part of laser head unit 120 shown in FIG. 4, the following description will not be repeated.

  As shown in FIG. 8, even when a bent portion is provided in the optical fiber, the effect of stabilizing the beam spot diameter is higher than that of the straight optical fiber. The greater the V number, the higher the stability of the beam spot diameter by providing a bend in the fiber.

  That is, according to the second embodiment, as in the first embodiment, by providing a bent portion in the vicinity of the emission end of the optical fiber, the power of the laser beam emitted from the optical fiber is increased and the quality of the laser beam is improved. It can be stabilized.

[Embodiment 3]
The laser processing apparatus according to the third embodiment is different from the laser processing apparatus according to the first embodiment in the configuration of the laser light source.

  FIG. 16 is a configuration diagram showing in more detail the configuration of the laser light source provided in the laser processing apparatus according to the third embodiment. Referring to FIGS. 16 and 2, laser light source 150 </ b> A omits optical fiber 1, semiconductor lasers 2 and 3, isolators 4 and 6, optical coupler 5, and bandpass filter 7. In FIG. That is, the laser light source 150C includes the semiconductor lasers 9A to 9D and the optical coupler 10. The configuration of the laser head unit 120 is the same as that shown in FIG.

  The laser transmission unit 130A differs from the laser transmission unit 130 in that the fiber Bragg gratings 8A and 8B are provided at both ends of the optical fiber 11B. The fiber Bragg gratings 8A and 8B and the optical fiber 11B constitute a fiber resonator. In this configuration, the “laser light source” of the laser irradiation apparatus according to the present invention is realized by the semiconductor lasers 9A to 9D and the fiber resonator, and the optical fiber 12 (see FIG. 4) optically coupled to the optical fiber 11B. The laser light from the laser light source is transmitted.

  The fiber Bragg grating 8A transmits the excitation light from the semiconductor lasers 9A to 9D. The optical fiber 11B is excited by this excitation light, and stimulated emission light is generated inside the optical fiber 11B. The fiber Bragg grating 8A reflects the stimulated emission light generated in the optical fiber 11B. The fiber Bragg grating 8B transmits a part of the stimulated emission light generated in the optical fiber 11B.

  As described above, in the embodiment of the present invention, a laser light source including a fiber resonator can be used in a laser processing apparatus. The configuration of the laser light source is not limited to the above configuration. Hereinafter, an example of a laser light source applicable to the embodiment of the present invention will be described.

  FIG. 17 is a configuration diagram illustrating an example of another configuration of the laser light source included in the laser processing apparatus according to the third embodiment. Referring to FIG. 17, laser light source 150B is a laser oscillator using a Q switch. 17 and 2, the laser light source 150B is different from the laser light source 150 in that the semiconductor laser 2, the isolator 4, and the band pass filter 7 are omitted. Further, the laser light source 150B is different from the laser light source 150 in that it includes a Q switch 8C and fiber Bragg gratings 8D and 8E.

  The semiconductor laser 3 outputs pumping light for pumping the rare earth element added to the core of the optical fiber 1 (rare earth doped fiber). Excitation light enters the optical fiber 1 through the optical coupler 5, the fiber Bragg grating 8D, and the Q switch 8C. The fiber Bragg grating 8D transmits the excitation light and reflects the stimulated emission light output from the optical fiber 1. On the other hand, the fiber Bragg grating 8E transmits part of the stimulated emission light output from the optical fiber 1.

  The Q switch 8C is ON / OFF controlled by the control unit 21. For the Q switch 8C, for example, an electro-optic element (E / O element) or an acousto-optic element (A / O element) that can be turned on and off at high speed is used. In a state where energy is stored in the optical fiber 1 by the excitation of the optical fiber 1, the Q switch 8C is turned on. As a result, stimulated emission of the optical fiber 1 occurs, and pulsed light is emitted. As described above, the configuration shown in FIG. 17 is different from the configuration shown in FIG. 16 in that the fiber resonator is provided in the laser control unit.

  Further, the configuration of the resonator is not limited to the configurations shown in FIGS. FIG. 18 is a configuration diagram illustrating an example of still another configuration of the laser light source included in the laser processing apparatus according to the third embodiment. With reference to FIG. 18, the laser light source 150 </ b> C includes a solid-state laser resonator 200. The solid-state laser resonator 200 includes a laser medium 201, excitation light sources 202 and 203, a reflection mirror 204, an output mirror 205, a Q switch 206, and a condenser lens 207.

  The laser medium 201 is a solid medium, for example, an Nd: YAG crystal. The excitation light sources 202 and 203 irradiate the laser medium 201 with excitation light for exciting the laser medium 201. The Q switch 206 is periodically turned on and off by the control unit 21. Thereby, pulsed light is repeatedly emitted as seed light from the solid-state laser resonator 200.

  The seed light (pulse light) emitted from the emission mirror 205 is collected by the condenser lens 207 and enters the optical fiber 1. The seed light is combined with the excitation light emitted from the semiconductor lasers 9 </ b> A to 9 </ b> D by the optical coupler 10 and enters the laser transmission unit 130 (optical fiber 11 </ b> A).

Note that a dye laser or a gas laser may be used instead of the solid-state laser. In the case of a dye laser, a liquid medium in which a dye is dissolved in an organic solvent is used as a laser medium. In the case of a gas laser, a gas medium such as CO ₂ gas or Ar gas is used as the laser medium.

  The configuration of the laser head unit 120 shown in each of FIGS. 10 to 18 is the same as the configuration shown in FIG. However, the laser processing apparatus according to Embodiment 3 may include the laser head unit 120 </ b> A shown in FIG. 10 instead of the laser head unit 120. Furthermore, as a specific configuration of the laser head portion 120A, the configurations shown in FIGS. 11 to 15 can be applied. That is, also in the third embodiment, the optical fiber is bent into a ring shape or an arc shape with a predetermined curvature in the vicinity of the emission end of the optical fiber. According to the third embodiment, it is possible to increase the output and improve the beam quality of a laser processing apparatus including a fiber without limiting the type of laser light source.

[Embodiment 4]
The laser processing apparatus according to the fourth embodiment is different from the laser processing apparatus according to the first embodiment in the configuration of the laser transmission unit.

  FIG. 19 is a configuration diagram illustrating in more detail the configuration of the laser transmission unit included in the laser processing apparatus according to the fourth embodiment. Referring to FIGS. 19 and 2, the laser processing apparatus according to the fourth embodiment has a laser transmission unit 130B. The ring part 11C is provided in the optical fiber 11B of the laser transmission part 130B. In this respect, the laser transmission unit 130B is different from the laser transmission unit 130.

  The structure of the other part of the laser processing apparatus according to Embodiment 4 is the same as the structure of the corresponding part of the laser processing apparatus shown in FIG. That is, also in the laser processing apparatus according to Embodiment 4, the optical fiber is bent into a ring shape in the vicinity of the emission end of the optical fiber. In the fourth embodiment, the optical fiber is bent not only in the vicinity of the emission end thereof but also in other parts (part in the middle of the optical fiber, that is, the optical fiber 11B). Thus, the location where the optical fiber is bent is not limited to one, and may be a plurality of locations including the vicinity of the exit end of the optical fiber. In each location, the optical fiber may be bent in a ring shape or may be bent in an arc shape.

  According to the fourth embodiment, as in the first embodiment, since the optical fiber is bent in the vicinity of the output end of the optical fiber, it is possible to increase the output of the laser processing apparatus and improve the beam quality. .

  For example, depending on the location of the laser processing apparatus, there may be a case where the distance between the laser control unit and the laser main unit must be reduced. In this case, for example, an optical fiber that is a laser transmission unit is bent. Even in such a case, since the optical fiber is bent in the vicinity of the emission end of the optical fiber, it is possible to increase the output of the laser processing apparatus and improve the beam quality. That is, the quality of the laser beam can be stabilized regardless of the location of the laser processing apparatus.

  FIG. 20 is a configuration diagram illustrating another configuration of the laser transmission unit included in the laser processing apparatus according to the fourth embodiment. Referring to FIG. 20, the emission end of optical fiber 11B (ie, optical amplification fiber) is introduced into laser head portion 120B, and end cap 13 is connected to the emission end of optical fiber 11B. Furthermore, the output end of the optical fiber 11B is bent in a ring shape (ring portion 11C). That is, the configuration of the laser head unit 120B is different from the configuration of the laser head unit 120 shown in FIG. 3 in that the optical fiber 12 is not provided in the laser head unit. Even in such a configuration, since the optical fiber is bent in the vicinity of the emission end of the optical fiber, it is possible to increase the output of the laser processing apparatus and improve the beam quality.

  Various laser light sources according to the third embodiment can be applied as the laser light source provided in the laser processing apparatus according to the fourth embodiment.

  Furthermore, the present invention also relates to an apparatus in which an optical system for irradiating a laser beam emitted from an optical fiber to a workpiece and an optical fiber that transmits the laser beam from the laser light source and the laser beam is integrated. Applicable. Even in such an apparatus, a part of the optical fiber may not be fixed. For example, when cooling air is introduced into the apparatus to cool the inside of the apparatus, the unfixed portion may vibrate. When the optical fiber vibrates, the problem that the spot diameter of the beam fluctuates as described above may occur. Therefore, the present invention can be applied to an apparatus having the above configuration.

  In the embodiment of the present invention, a multimode fiber is used. However, the optical fiber applicable to the present invention is not limited to the multimode fiber, and may be a single mode fiber.

  In the embodiment of the present invention, a double clad fiber is used as the optical fiber. However, the optical fiber applicable to the present invention is not limited to the double clad fiber, and may be a single clad fiber. Moreover, you may use both a double clad fiber and a single clad fiber.

  Further, in the embodiment of the present invention, the laser light emitted from the laser head unit is used for processing the workpiece. However, the laser irradiation apparatus according to the present invention can be used for purposes other than processing. For example, the laser irradiation apparatus according to the present invention can be used in sensors, optical tweezers, laser accelerators, laser microscopes, laser medical apparatuses, fusion apparatuses, and the like. Therefore, the laser irradiation apparatus according to the present invention is not limited to the laser processing apparatus, and can be applied to various fields.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  1, 11A, 11B, 12 optical fiber, 2, 3, 9A-9D semiconductor laser, 4, 6, 16 isolator, 5, 10 optical coupler, 7 bandpass filter, 8A, 8B, 8D, 8E fiber Bragg grating, 8C, 206 Q switch, 11C, 12A Ring part, 12B Bend part, 13 End cap, 14 Collimate lens, 15A, 15B Dichroic mirror, 17 Magnifier, 18 Galvano scanner, 19,207 Condensing lens, 20 Control board, 21 Control unit, 22 pulse generation unit, 30 driver power supply, 32 driver, 41A, 41B core, 42A, 42B first clad, 43A, 43B second clad, 44A, 44B coating, 50 workpiece, 60 bottom base, 61 fiber Storage box, 62 fiber ga , 63 tube, 64 binding band, 65 holes, 66 mounting part, 67 bushing, 68 side base, 100 laser processing device, 110 laser control part, 120, 120A, 120B laser head part, 130, 130A, 130B laser transmission part , 150, 150A, 150B, 150C laser light source, 200 solid-state laser resonator, 201 laser medium, 202, 203 excitation light source, 204 reflection mirror, 205 exit mirror.

Claims (13)

An optical fiber having an exit end for emitting laser light;
A laser light source for generating the laser light propagating through the optical fiber,
The laser irradiation apparatus, wherein the optical fiber has a free part in a freely movable state and is bent in a ring or arc shape in the vicinity of the emission end. The laser irradiation apparatus is
A main body including the laser light source;
A head portion including an optical component for irradiating an object with laser light emitted from the emission end of the optical fiber;
The emission end is located inside the head part,
The laser irradiation apparatus according to claim 1, wherein the free part is a part for propagating laser light from the main body part to the head part.   The laser irradiation apparatus according to claim 1 or 2, wherein a diameter of the ring or the arc is 60 mm or more and 150 mm or less.   The laser irradiation apparatus according to claim 3, wherein the diameter is 60 mm or more and 120 mm or less.   The laser irradiation apparatus according to claim 4, wherein the diameter is 60 mm or more and 90 mm or less. The laser irradiation apparatus is
A base member;
A fiber guide made of a light-shielding member, having an arc-shaped outer surface, and a fixing member for fixing the optical fiber formed to be attachable;
The optical fiber is bent along the outer surface of the fiber guide and fixed to the fiber guide by the fixing member,
The laser irradiation apparatus according to claim 1, wherein an attachment portion for attaching the fiber guide to the base member with a screw is provided on the inner surface side of the fiber guide located on the opposite side to the outer surface.   The laser irradiation apparatus according to claim 1, wherein the optical fiber is bent in a ring shape or an arc shape at a location different from the vicinity of the emission end in addition to the vicinity of the emission end.   The laser irradiation apparatus according to claim 1, wherein the optical fiber is a multimode fiber. The optical fiber is
Including an optical amplification fiber that amplifies the signal laser light with the excitation laser light to generate the laser light emitted from the emission end;
The laser light source is
A first light source for generating the signal laser light;
The laser irradiation apparatus according to claim 1, further comprising a second light source that generates the excitation laser light. The laser light source is
A resonator including an amplification medium;
The laser irradiation apparatus according to claim 1, further comprising: an excitation light source that supplies excitation light for exciting the amplification medium.   The laser irradiation apparatus according to claim 10, wherein the amplification medium includes an optical amplification fiber.   The laser irradiation apparatus according to claim 10, wherein the amplification medium is any one of a solid medium, a liquid medium, and a gas medium.   A laser processing apparatus provided with the laser irradiation apparatus of any one of Claims 1-12.

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