Laser device and laser processing device

Abstract

The laser device (100) includes a seed light source that outputs pulsed laser light and is capable of controlling the repetition frequency of the pulsed laser light, an amplifier that amplifies and emits the pulsed laser light, a mask (50) that shapes at least one of the beam diameter and beam shape of the pulsed laser light emitted from the amplifier, an optical switching element (30) that is arranged on the optical path between the amplifier and the mask (50) and has a transmittance modulated so that fluctuations over time of at least one of the output and energy of the pulsed laser light emitted from the amplifier, which occur as the repetition frequency of the pulsed laser light is changed, fall within a predetermined range, and a beam propagation adjustment unit (40) that is arranged on the optical path between the amplifier and the mask (50) and adjusts the beam propagation of the pulsed laser light emitted from the amplifier.

Description

[Technical field]

[0001] The present disclosure relates to a laser device that emits laser light used in laser processing, and a laser processing device. [Background technology]

[0002] In recent years, laser processing equipment using a short-pulse laser as a light source has been widely used in micromachining for a wide variety of applications, such as drilling holes in printed circuit boards, cutting glass, and precision machining of metals. Laser equipment installed in such laser processing equipment often adopts the MOPA (Master Oscillator Power Amplifier) ​​method, which amplifies and outputs the short-pulse laser light output from a seed light source using a solid-state amplifier. The advantages of the MOPA method include the ease of controlling pulse characteristics such as repetition frequency, and the ability to increase the output of pulse laser light by increasing the number of stages of solid-state amplifiers according to the application of the processing. In addition, laser equipment installed in laser processing equipment may output short-wavelength short-pulse laser light that shortens the wavelength of the short-pulse laser light by harmonic generation using a nonlinear optical crystal, using the short-pulse laser light output from a MOPA light source as the fundamental wave.

[0003] When performing micromachining using a laser processing device using a short-pulse laser as a light source, productivity can be improved by changing the repetition frequency of the laser in response to the machining shape. However, in a typical short-pulse laser, the output characteristics or beam propagation characteristics of the output pulse laser light change in response to the repetition frequency. These changes are accompanied by thermal changes inside the short-pulse laser, and therefore do not complete instantaneously, but progress over time. For this reason, there is a problem in that the output characteristics or beam propagation characteristics at the machining point fluctuate over time after the repetition frequency is changed. If the output characteristics or beam propagation characteristics of the short-pulse laser light fluctuate, the intensity distribution at the machining point changes, making it difficult to maintain constant machining quality after the repetition frequency is changed.

[0004] Patent document 1 describes a laser processing device that uses a laser in which parameters need to be changed in accordance with changes in the laser output, in which the laser light emitted from the laser is made incident on an acousto-optical element that modulates the transmittance of the laser light, and the output of the laser light emitted from the acousto-optical element is kept constant by changing the transmittance of the laser light by the acousto-optical element. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-161329 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the laser processing device described in the above Patent Document 1 does not take into consideration the fluctuation over time of the beam propagation characteristics of the pulsed laser light when the repetition frequency of the laser is changed. In other words, in the laser processing device described in the above Patent Document 1, when the repetition frequency of the pulsed laser light is changed, the beam propagation characteristics of the pulsed laser light change over time, and as a result, the beam diameter and beam shape at the processing point change over time, so that there is a problem that it is difficult to perform stable processing immediately after changing the repetition frequency.

[0007] The present disclosure has been made in consideration of the above, and aims to obtain a laser device that can suppress time-dependent variations in the output characteristics and beam propagation characteristics of amplified pulsed laser light due to changes in the repetition frequency of a seed light source. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems and achieve the object, the laser apparatus of the present disclosure includes a seed light source that outputs pulsed laser light and is capable of controlling the repetition frequency of the pulsed laser light, an amplifier that amplifies and emits the pulsed laser light, a mask that shapes at least one of the beam diameter and beam shape of the pulsed laser light emitted from the amplifier, an optical switching element that is arranged on an optical path between the amplifier and the mask and has a transmittance modulated so that fluctuations over time of at least one of the output and energy of the pulsed laser light emitted from the amplifier, which fluctuations occur as the repetition frequency of the pulsed laser light is changed, fall within a predetermined range, and a beam propagation adjustment unit that is arranged on the optical path between the amplifier and the mask and adjusts the beam propagation of the pulsed laser light emitted from the amplifier. Effect of the Invention

[0009] According to the present disclosure, it is possible to obtain a laser device that can suppress fluctuations over time in the output characteristics and beam propagation characteristics of amplified pulsed laser light caused by changing the repetition frequency of a seed light source. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a block diagram showing a schematic example of a configuration of a laser processing device including a laser device according to a first embodiment; [Diagram 2] FIG. 1 is a schematic diagram showing an example of the configuration of a laser oscillator included in a laser device according to a first embodiment; [Diagram 3] FIG. 11 is a characteristic diagram showing an experimental result of measuring the output characteristics of amplified pulse light emitted from the laser oscillator when the repetition frequency of the pulse light is switched in the laser oscillator according to the first embodiment. [Figure 4] FIG. 1 is a characteristic diagram showing experimental results of measuring the pulse energy and beam diameter of amplified pulse light emitted from a laser oscillator when the repetition frequency of the pulse light is switched in the laser oscillator according to the first embodiment. [Diagram 5]FIG. 1 is a schematic diagram showing an example of a configuration in which an optical sensor is provided in a laser processing device including a laser device according to a first embodiment; [Figure 6] FIG. 1 is a schematic diagram showing an example of a configuration in which a beam diameter monitor is provided in a laser processing apparatus including a laser apparatus according to a first embodiment; [Figure 7] A characteristic diagram showing the results of calculating the transmittance modulation pattern set when compensating for the change over time in average output that occurred after changing the repetition frequency of the pulsed light in the experiment shown in Figure 3 by modulating the transmittance of the optical switching element. [Figure 8] FIG. 11 is a block diagram showing a schematic example of a configuration of a laser processing apparatus including a laser apparatus according to a second embodiment; [Figure 9] FIG. 11 is a plan view showing an example of a mask provided in the laser processing apparatus according to the second embodiment; [Figure 10] 11 is a flowchart showing a procedure for performing drilling of holes with different diameters in the laser processing device according to the second embodiment. [Figure 11] FIG. 1 is a diagram showing a configuration in which the functions of the control unit according to the first and second embodiments are realized by hardware. [Figure 12] FIG. 1 is a diagram showing a configuration in which the functions of the control unit according to the first and second embodiments are realized by software. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a laser device and a laser processing device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. Note that the embodiments described below are merely examples, and the scope of the present disclosure is not limited to the embodiments described below.

[0012] Embodiment 1 FIG. 1 is a block diagram showing a schematic example of a configuration of a laser processing apparatus including a laser apparatus according to a first embodiment. The laser processing apparatus 1 is an apparatus for processing an object W by irradiating the object W with a pulsed laser beam output from a laser apparatus 100. The object W is, for example, a printed circuit board, a glass board, or a metal plate. The processing includes, for example, cutting, welding, and drilling. The laser processing apparatus 1 can perform processing such as drilling holes in a printed circuit board, cutting glass, and precision processing of metal.

[0013] The laser processing apparatus 1 includes a laser device 100 that outputs a pulsed laser beam, a scanning unit 60, a mask transfer optical system 70, and a processing table 80.

[0014] The laser device 100 includes a laser oscillator 10, a control unit 20, an optical switching element 30, a beam propagation adjustment unit 40, a driving device 41, and a mask 50.

[0015] The laser oscillator 10 outputs a pulsed laser beam. The pulse width of the pulsed laser beam output from the laser oscillator 10 varies from femtoseconds to microseconds depending on the type of the workpiece W and the content of the laser processing. When fine and precise laser processing is required, a short-pulse laser beam having a pulse width of several tens of picoseconds or less is used as the pulsed laser beam output from the laser oscillator 10. In particular, ablation processing using a short-pulse laser beam is suitable for fine processing because it can reduce the thermal effects generated during processing. In the first embodiment, the pulsed laser beam output from the laser oscillator 10 is a short-pulse laser beam having a pulse width of several tens of picoseconds or less suitable for fine processing. Hereinafter, the "short-pulse laser beam" output from the laser oscillator 10 may be simply referred to as "pulse beam".

[0016] 2 is a diagram illustrating an example of the configuration of a laser oscillator included in the laser device according to the first embodiment. The laser oscillator 10 includes a seed light source 11, an optical fiber amplifier 12, a solid-state amplifier 13, and a nonlinear optical crystal 14. The laser oscillator 10 is a wavelength conversion MOPA type laser that employs a MOPA method in which pulsed light L output from the seed light source 11 is amplified by the optical fiber amplifier 12 and the solid-state amplifier 13 and output. The laser oscillator 10 emits a short pulse laser light.

[0017] The seed light source 11 outputs pulsed light L, which is laser light with a pulse width of several tens of picoseconds or less. The pulsed light L output from the seed light source 11 is laser light that is amplified in an optical fiber amplifier 12 and a solid-state amplifier 13. As the seed light source 11, for example, a gain-switch-driven semiconductor laser, a mode-locked fiber laser oscillator, or a solid-state laser oscillator is used.

[0018] The optical fiber amplifier 12 amplifies the pulsed light L output from the seed light source 11. Since the pulsed light L output from the seed light source 11 has a low output, in order to use the seed light source 11 as a processing light source, an amplifier for amplifying the pulsed light L output from the seed light source 11 is required in a stage following the seed light source 11. The optical fiber amplifier 12 is capable of amplifying low-output pulsed light with high efficiency. For one example, an ytterbium (Yb)-doped fiber is used for the optical fiber amplifier 12. For one example, the output characteristics of the pulsed light output from the optical fiber amplifier 12 are an average output of several mW or more and several hundred mW or less, and a peak output of several kW.

[0019] In addition, the "output characteristics of the pulsed laser beam" in the first embodiment refers to characteristics such as the average output of the pulsed laser beam, the pulse energy of the pulsed laser beam, and the peak output of the pulsed laser beam.

[0020] The solid-state amplifier 13 amplifies the pulsed amplified light output from the optical fiber amplifier 12 to a high output region usable for processing the workpiece W and outputs the amplified light. The solid-state amplifier 13 includes a solid-state active medium and an excitation light source. The solid-state active medium is excited by the excitation light source. The pulsed light incident on the solid-state active medium is amplified and emitted as pulsed amplified light. The output characteristics of the pulsed amplified light output from the solid-state amplifier 13 are, for example, an average output of several W to several tens of W and a peak output of several MW to several tens of MW.

[0021] As an example of the solid-state active medium of the solid-state amplifier 13, Nd:YVO4, Nd:YAG, Yb:YAG, and Yb:KGW are used. The excitation light source is a light source that outputs laser light for exciting the solid-state active medium. A semiconductor laser is preferably used as the excitation light source. The wavelength of the laser light output from the excitation light source is selected in accordance with the absorption spectrum of the solid-state active medium. Examples of the wavelength of the laser light output from the excitation light source are 808 nm, 878.6 nm, 880 nm, 885 nm, 940 nm, and 980 nm.

[0022] Although one solid-state amplifier 13 is used in the first embodiment, the solid-state amplifier 13 may be configured in multiple stages.

[0023] The nonlinear optical crystal 14 functions as a wavelength conversion crystal that converts the wavelength of the pulsed amplified light amplified in the solid-state amplifier 13. The nonlinear optical crystal 14 converts the wavelength of the pulsed amplified light amplified in the solid-state amplifier 13 to 1 / 2, 1 / 3, or 1 / 4 times by harmonic generation, which is a second-order nonlinear optical effect. In other words, the nonlinear optical crystal 14 converts the wavelength of the pulsed amplified light amplified in the solid-state amplifier 13 to the second harmonic, third harmonic, or fourth harmonic by harmonic generation. The nonlinear optical crystal 14 can be, for example, LiB3O5 (Lithium Triborate: LBO), CsLiB6O 10(Cesium Lithium Borate: CLBO), β-BaB2O4 (Barium Metaborate: BBO) crystals are used. When the wavelength of the pulsed amplified light amplified in the solid-state amplifier 13 is to be multiplied by 1 / 3 or 1 / 4, two or more nonlinear optical crystals 14 are used. In this case, the nonlinear optical crystals 14 are, for example, a combination of LBO and LBO, or LBO and CLBO.

[0024] In order to control the characteristics of the pulsed light output from the laser oscillator 10, an optical switching element may be incorporated inside the laser oscillator 10. The optical switching element incorporated inside the laser oscillator 10 is disposed between the optical fiber amplifier 12 and the solid-state amplifier 13, between the solid-state amplifier 13 and the nonlinear optical crystal 14, or after the nonlinear optical crystal 14.

[0025] With the above configuration, the laser oscillator 10 emits amplified pulsed light having a wavelength determined by the nonlinear optical crystal 14 .

[0026] Hereinafter, the pulsed light obtained by amplifying the pulsed light L output from the seed light source 11 will be referred to as pulsed amplified light L1. In other words, the pulsed amplified light L1 is a pulsed laser amplified light obtained by amplifying the pulsed laser light output from the seed light source 11.

[0027] Returning to Fig. 1, the control unit 20 controls various parameters such as the wavelength, repetition frequency, pulse width, average output, and pulse energy of the amplified pulsed light L1, which is pulsed light output from the laser oscillator 10. The repetition frequency is the number of pulses generated per second at a constant period. The control unit 20 also controls the optical switching element 30, the driving device 41, the scanning unit 60, the mask transfer optical system 70, and the processing table 80.

[0028] The optical switching element 30 modulates the transmittance of the amplified pulsed light L1 output from the laser oscillator 10. The amplified pulsed light L1 output from the laser oscillator 10 is incident on the optical switching element 30, passes through the optical switching element 30 at a set transmittance, and then is incident on the beam propagation adjustment unit 40 along the optical axis La of the amplified pulsed light L1. The transmittance of the optical switching element 30 is modulated in accordance with a signal transmitted from the control unit 20.

[0029] The transmittance of the optical switching element 30 is defined as 100% when the optical switching condition is such that the output of the pulsed amplified light L1 that passes through the optical switching element 30 and travels toward the mask 50 is at its maximum. In the laser processing device 1, for example, an acousto-optical element (AOM: Acousto-Optic Modulator) is used as the optical switching element 30, and the first-order diffracted light of the pulsed amplified light L1 output from the AOM can be used for laser processing. In this case, the diffraction efficiency of the first-order diffracted light of the pulsed amplified light L1 output from the AOM is at most about 85%. In other words, in terms of the usual transmittance, the transmittance of the AOM is 85%.

[0030] In the laser processing apparatus 1, the output of the first-order diffracted light at the maximum diffraction efficiency when the output of the pulsed amplified light L1 passing through the optical switching element 30 and traveling toward the mask 50 is maximum is redefined as a transmittance of 100%. That is, for example, when the maximum diffraction efficiency of the first-order diffracted light of the pulsed amplified light L1 emitted from the AOM is 85%, the optical switching condition at this time is defined as a transmittance of 100%. Also, similar to the normal concept of transmittance, when the amount of light of the pulsed amplified light L1 passing through the AOM and traveling toward the mask 50 is 0, the transmittance is 0%.

[0031] Note that "modulating the transmittance" refers to changing the transmittance over time. By setting the transmittance of the pulsed light in the optical switching element 30 to 0% or 100%, it is also possible to switch the output of the amplified pulsed light L1 from the optical switching element 30 on and off.

[0032] As an example, an acousto-optic (AO) element or an electro-optic (EO) element is used for the optical switching element 30. When an acousto-optic element is used for the optical switching element 30, the zeroth order light or the first order diffracted light of the acousto-optic element is used for processing.

[0033] The optical switching element 30 is disposed on the optical axis La of the pulsed amplified light L1 between the laser oscillator 10 and the beam propagation adjustment unit 40. When the optical switching element 30 controls the modulation of the transmittance of the pulsed amplified light L1 for each pulse, the modulation frequency of the transmittance in the optical switching element 30 is set to the repetition frequency of the pulsed amplified light L1, i.e., the repetition frequency of the pulsed light L output from the seed light source 11. A material of the optical switching element 30 is selected according to the wavelength of the pulsed amplified light L1 used to process the workpiece W. In addition, in the optical switching element 30, a pulsed light incident surface on which the pulsed amplified light L1 is incident and a pulsed light exit surface from which the pulsed light exits are provided with an anti-reflective film for the wavelength of the pulsed amplified light L1.

[0034] The beam propagation adjustment unit 40 adjusts the beam propagation of the pulsed amplified light L1 output from the optical switching element 30. "Beam propagation" refers to the propagation of the pulsed amplified light L1 relative to the travel of the pulsed amplified light L1. of This refers to the change in beam diameter. When discussing beam propagation at a cross section perpendicular to the propagation direction of the pulsed amplified light L1, the beam propagation is determined by the beam diameter, the radius of curvature of the wavefront, the beam quality M2, and the wavelength of the pulsed amplified light L1 at that position.

[0035] The beam propagation adjustment unit 40 has at least one optical element selected from a spherical lens and a curved mirror as a component. The beam propagation adjustment unit 40 is composed of, for example, one plano-convex lens, one plano-concave lens, and one convex mirror. The pulsed amplified light L1 transmitted through the beam propagation adjustment unit 40 is irradiated onto the mask 50.

[0036] The driving device 41 is provided in the beam propagation adjustment unit 40. The driving device 41 has a function of moving an optical element, which is a component of the beam propagation adjustment unit 40, in the optical axis direction of the pulsed amplified light L1 output from the optical switching element 30. The driving device 41 can adjust at least one of the beam diameter and the radius of curvature of the wavefront of the pulsed amplified light L1 irradiated to the mask 50 by moving the optical element of the beam propagation adjustment unit 40 in the optical axis direction of the pulsed amplified light L1 output from the optical switching element 30. That is, the driving device 41 can adjust at least one of the beam diameter and the radius of curvature of the wavefront of the pulsed amplified light L1 on the mask 50. Note that the positional relationship between the optical switching element 30 and the beam propagation adjustment unit 40 on the optical axis La of the pulsed amplified light L1 between the laser oscillator 10 and the mask 50 may be reversed.

[0037] The laser processing apparatus 1 is capable of stabilizing processing quality by manipulating at least one of the beam diameter and the radius of curvature of the wavefront of the pulsed amplified light L1 on the mask 50 by moving the optical elements that constitute the beam propagation adjustment unit 40.

[0038] Mask 50 has an opening 50a that passes a portion of pulsed amplified light L1 that has passed through beam propagation adjustment unit 40, and limits the transmission area of ​​pulsed amplified light L1 that has passed through beam propagation adjustment unit 40 to shape the beam profile of pulsed amplified light L1. By mask 50 limiting the transmission area of ​​pulsed amplified light L1 that has passed through beam propagation adjustment unit 40, at least one of the beam diameter and beam shape of pulsed amplified light L1 that has passed through beam propagation adjustment unit 40 is shaped, and the beam profile of pulsed amplified light L1 is shaped. Controller 20 controls the position of beam propagation adjustment unit 40 so that the beam diameter of pulsed amplified light L1 on mask 50 is larger than the opening diameter of opening 50a.

[0039] For example, a metal plate having openings 50a formed therein is used for the mask 50. The shape of the transmission region of the mask 50, i.e., the shape of the openings 50a in the in-plane direction of the mask 50, is circular or rectangular, for example. The shape of the transmission region of the mask 50 may be a shape surrounded by a pattern formed of a plurality of lines or circles. When the shape of the transmission region of the mask 50 is a shape surrounded by a pattern formed of a plurality of lines or circles, a transparent material through which the pulsed amplified light L1 transmits is used for the substrate of the mask 50, and a metal film that prevents the transmission of the pulsed amplified light L1 is provided on the pattern portion of the substrate.

[0040] The processing table 80 holds the workpiece W and moves in two orthogonal axial directions to move the workpiece W. In the first embodiment, the two orthogonal axial directions in which the processing table 80 moves are defined as the X direction and the Y direction.

[0041] The scanning unit 60 forms an optical path to guide the pulsed amplified light L1 transmitted through the opening 50a of the mask 50 to the workpiece W, and transmits and focuses the pulsed amplified light L1 transmitted through the opening 50a of the mask 50 at a desired position on the workpiece W. The scanning unit 60 scans the pulsed amplified light L1 transmitted through the opening 50a of the mask 50, and irradiates the pulsed amplified light L1 at a desired position on the processed surface of the workpiece W. The scanning unit 60 is composed of one or more mirrors. In one example, the scanning unit 60 is composed of a galvanometer mirror. The galvanometer mirror may be composed of two mirrors that scan in the X and Y directions on the processing point, respectively.

[0042] The mask transfer optical system 70 transfers the pattern of the amplified pulsed light L1 that has passed through the mask 50 onto the workpiece W. That is, the amplified pulsed light L1 that has passed through the openings 50a of the mask 50 and been scanned by the scanner 60 is incident on the mask transfer optical system 70, and the mask transfer optical system 70 transfers an image of the openings 50a onto the processed surface of the workpiece W. That is, when the mask transfer optical system 70 is used, the processed shape of the workpiece W is determined by the transmission shape of the mask 50, i.e., by the shape of the openings 50a of the mask 50.

[0043] The mask transfer optical system 70 is composed of a group of condenser lenses. Alternatively, the mask transfer optical system 70 may be composed of a collimating lens that collimates the amplified pulse light L1 diffracted when passing through the mask 50, and a group of condenser lenses. For example, an fθ lens is used as the condenser lens. The position of the fθ lens is adjusted so that the image of the opening 50a of the mask 50 is appropriately transferred to a desired position on the workpiece W. When the position adjustment of the fθ lens is performed by an automatic stage, the position of the automatic stage is controlled by the control unit 20 to adjust the position of the fθ lens.

[0044] In the laser processing apparatus 1, the scanning unit 60 and the mask transfer optical system 70 constitute a processing optical system 65. The processing optical system 65 forms an optical path to guide the pulsed amplified light L1 emitted from the laser device 100 to the workpiece W, focuses the pulsed amplified light L1 at a desired position on the workpiece W, and irradiates the workpiece W with the pulsed amplified light L1.

[0045] Next, a response of the laser oscillator 10 shown in Fig. 2 when the repetition frequency of the pulsed light L output from the seed light source 11 is changed will be described. Note that a semiconductor laser is used as the seed light source 11 of the laser oscillator 10. The assumed repetition frequency of the pulsed light is 100 kHz to several MHz, which is typically used in laser drilling.

[0046] First, the repetition frequency of pulsed light is determined by the repetition frequency of a current pulse injected into a semiconductor laser to cause the semiconductor laser to oscillate. Therefore, the repetition frequency of pulsed light output from a semiconductor laser is changed by changing the repetition frequency of a current pulse injected into the semiconductor laser. Hereinafter, the "repetition frequency of pulsed light output from a semiconductor laser" may be simply referred to as the "repetition frequency of pulsed light."

[0047] The pulsed light output from the semiconductor laser is input to optical fiber amplifier 12 and amplified in optical fiber amplifier 12. When the pumping output of optical fiber amplifier 12 is constant regardless of the repetition frequency of the pulsed light, the output characteristics of pulsed amplified light L1, which is the pulsed light after being amplified in optical fiber amplifier 12, i.e., characteristics such as the average output and pulse energy of pulsed amplified light L1, change as the repetition frequency of the pulsed light input to optical fiber amplifier 12 changes.

[0048] On the other hand, the beam propagation of the pulsed amplified light L1 that is amplified in and output from the optical fiber amplifier 12 is determined by the propagation mode of the optical fiber that constitutes the optical fiber amplifier 12. A single-mode fiber is used in the optical fiber amplifier 12 to amplify the pulsed light used in microfabrication. Therefore, there is only one propagation mode of the optical fiber that constitutes the optical fiber amplifier 12. Therefore, the beam propagation of the pulsed amplified light L1 that is output from the optical fiber amplifier 12 is constant regardless of the repetition frequency of the pulsed light incident on the optical fiber amplifier 12.

[0049] Next, a response will be described when amplified pulsed light L1 having different characteristics such as average output and pulse energy output from optical fiber amplifier 12 is incident on solid-state amplifier 13 whose pump output is fixed at a constant output.

[0050] First, consider a case where a change in the repetition frequency of the pulsed light output from the semiconductor laser changes the average output of the pulsed amplified light L1 output from the optical fiber amplifier 12. When high repetition pulsed light having a repetition frequency of 100 kHz or more is amplified by the solid-state amplifier 13, the average output of the pulsed amplified light L1 after being amplified in the solid-state amplifier 13 depends on the average output of the pulsed light incident on the solid-state amplifier 13.

[0051] Therefore, when the average output of the incident pulse amplified light entering the solid-state amplifier 13 from the optical fiber amplifier 12 changes due to a change in the repetition frequency of the pulse light output from the semiconductor laser, the average output of the amplified pulse amplified light L1 in the solid-state amplifier 13 changes in accordance with the change in the repetition frequency of the pulse light output from the semiconductor laser.

[0052] That is, when the repetition frequency of the pulsed light input from the semiconductor laser to the optical fiber amplifier 12 is changed, the average output of the pulsed amplified light L1, which is the pulsed light after being amplified in the optical fiber amplifier 12, changes. And when the average output of the pulsed amplified light L1 output from the optical fiber amplifier 12 and input to the solid-state amplifier 13 changes, the average output of the pulsed amplified light L1 after being amplified in the solid-state amplifier 13 changes.

[0053] Furthermore, the extracted output in the amplification of the incident pulse amplified light in the solid-state amplifier 13 changes depending on the repetition frequency of the incident pulse amplified light. The extracted output is the difference between the output of the pulse amplified light L1 after the incident pulse amplified light has been amplified in the solid-state amplifier 13 and the output of the incident pulse amplified light before it is amplified in the solid-state amplifier 13. When the extracted output changes, the thermal lens effect generated in the solid-state amplifier 13 changes.

[0054] A change in the thermal lens effect in the solid-state amplifier 13 causes a change in the beam propagation of the emitted pulsed amplified light, which is the pulsed amplified light L1 that is amplified and emitted in the solid-state amplifier 13. For this reason, the beam propagation of the emitted pulsed amplified light after being amplified in the solid-state amplifier 13 changes with a change in the repetition frequency of the pulsed light output from the semiconductor laser.

[0055] The change in the thermal lens effect occurring in the solid-state amplifier 13 due to the change in the repetition frequency of the pulsed light output from the semiconductor laser does not end instantly, but takes several seconds to several minutes until the change is complete. Therefore, when the repetition frequency of the pulsed light is changed, it takes several seconds to several minutes until the change in the beam propagation of the output pulsed amplified light output from the solid-state amplifier 13 is complete.

[0056] Next, consider a case where the pulse energy of the amplified pulse light L1 emitted from the optical fiber amplifier 12 changes due to a change in the repetition frequency of the pulse light output from the semiconductor laser.

[0057] In the solid-state amplifier 13, when amplifying pulsed light having a pulse width of several tens of picoseconds or less to a level of several tens of watts that can be used for processing, it becomes impossible to ignore nonlinear effects occurring in the solid-state amplifier 13. Nonlinear effects of particular concern are stimulated Raman scattering and the optical Kerr effect.

[0058] Stimulated Raman scattering is a phenomenon in which the wavelength of the amplified light is shifted to a different wavelength by Raman scattering. When stimulated Raman scattering occurs in the solid-state amplifier 13, a reduction in the output of the amplified pulsed amplified light L1 is caused, and a reduction in the output of the output pulsed amplified light output from the solid-state amplifier 13 occurs.

[0059] The optical Kerr effect is a phenomenon in which the refractive index of a medium is modulated by the intensity distribution of pulsed light. When the intensity distribution of the pulsed light incident on the solid-state amplifier 13 is Gaussian, a Gaussian-shaped refractive index distribution is formed in the solid-state active medium in the solid-state amplifier 13, and the beam propagation of the amplified pulsed amplified light L1 changes. These nonlinear effects occurring in the solid-state amplifier 13 depend on the peak intensity of the pulsed light. In other words, stimulated Raman scattering and the optical Kerr effect occurring when the solid-state amplifier 13 amplifies pulsed light with a pulse width of tens of picoseconds or less to a level of tens of watts that can be used for processing depend on the peak intensity of the pulsed light.

[0060] In pulsed light of a certain pulse width, the peak intensity depends on the pulse energy. Therefore, if the pulse energy of the pulsed amplified light L1 emitted from the optical fiber amplifier 12 changes due to a change in the repetition frequency of the pulsed light, this means that the output and beam propagation characteristics of the pulsed amplified light L1 emitted from the solid-state amplifier 13 change due to a change in the repetition frequency of the pulsed light.

[0061] It is believed that the change in the characteristics of the pulsed light due to the nonlinear effect occurring in the solid-state amplifier 13 caused by the change in the repetition frequency of the pulsed light is completed instantaneously. However, since the change in the characteristics of the pulsed light due to the nonlinear effect induces a change in the thermal lens effect of the solid-state amplifier 13, it takes several seconds to several minutes for the beam propagation characteristics of the amplified pulsed light L1 emitted from the solid-state amplifier 13 to stabilize.

[0062] In the above explanation, it is assumed that the pumping output of the solid-state amplifier 13 is constant regardless of the repetition frequency of the pulsed light. If the pumping output of the solid-state amplifier 13 is changed in response to a change in the repetition frequency of the pulsed light, a thermal state change occurs in the solid-state amplifier 13, so it goes without saying that it takes several seconds to several minutes, as described above, for the output characteristics and beam propagation characteristics of the pulsed amplified light L1 emitted from the solid-state amplifier 13 to stabilize.

[0063] Therefore, in both cases where the excitation output of the solid-state amplifier 13 is constant regardless of the repetition frequency of the pulsed light, and where the excitation output of the solid-state amplifier 13 is changed in response to a change in the repetition frequency of the pulsed light, it takes several seconds to several minutes for the output characteristics and beam propagation characteristics of the pulsed amplified light L1 emitted from the solid-state amplifier 13 to stabilize.

[0064] 3 is a characteristic diagram showing the experimental results of measuring the output characteristics of the pulsed amplified light emitted from the laser oscillator according to the first embodiment when the repetition frequency of the pulsed light is switched. FIG. 3 shows the time fluctuation of the average output and beam diameter of the pulsed amplified light L1 emitted from the laser oscillator 10 when the repetition frequency of the pulsed light is switched in the laser oscillator 10. The output characteristics of the pulsed amplified light L1 emitted from the laser oscillator 10 can be said to be the output characteristics of the pulsed amplified light L1 emitted from the solid-state amplifier 13.

[0065] The horizontal axis of Fig. 3 indicates time. On the horizontal axis of Fig. 3, the time when the repetition frequency was changed is set to 0 minutes. The left axis of Fig. 3 indicates the fluctuation (%) of the average output of the pulsed amplified light L1, which is the output characteristic of the pulsed amplified light L1 emitted from the solid-state amplifier 13. The right axis of Fig. 3 indicates the fluctuation (%) of the beam diameter of the pulsed amplified light L1, which is the output characteristic of the pulsed amplified light L1. For the fluctuation (%) of the average output and the fluctuation (%) of the beam diameter, the value at the time when the repetition frequency was changed is set to 100%.

[0066] According to the results of this experiment, it took 2 seconds for the average output of the amplified pulsed light L1 emitted from the solid-state amplifier 13 to stabilize. Also, it took 180 seconds for the beam diameter of the amplified pulsed light L1 emitted from the solid-state amplifier 13 to stabilize.

[0067] In this experiment, the output characteristics of the pulsed amplified light L1 emitted from the solid-state amplifier 13 were evaluated by the average output. The average output of the pulsed amplified light L1 is the pulse energy of the pulsed amplified light L1 multiplied by the repetition frequency. Therefore, if the moving average of multiple pulses is evaluated in the same manner as above, the pulse energy will also show the same tendency.

[0068] FIG. 4 is a characteristic diagram showing the average output, pulse energy, and beam diameter of the pulsed amplified light emitted from the laser oscillator when the repetition frequency of the pulsed light is switched in the laser oscillator according to the first embodiment. FIG. 4 shows the time fluctuations of the average output, pulse energy, and beam diameter of the pulsed amplified light L1 emitted from the laser oscillator 10 when the repetition frequency of the pulsed light is switched in the laser oscillator 10. The pulse energy of the pulsed amplified light L1 here is calculated by dividing the measurement result of the average output of the pulsed amplified light L1 by the repetition frequency. The horizontal axis of FIG. 4 shows time. On the horizontal axis of FIG. 4, the time when the repetition frequency is changed is set to 0 minutes. The left axis of FIG. 4 shows the fluctuation (%) of the average output of the pulsed amplified light L1, which is the output characteristic of the pulsed amplified light L1 emitted from the solid-state amplifier 13, and the fluctuation (%) of the pulse energy of the pulsed amplified light L1. The right axis of FIG. 4 shows the fluctuation (%) of the beam diameter of the pulsed amplified light L1, which is the output characteristic of the pulsed amplified light L1. For the average output fluctuation (%), pulse energy fluctuation (%), and beam diameter fluctuation (%) of the pulsed amplified light L1, the value at the time the repetition rate was changed is set to 100%.

[0069] As described above, when the repetition frequency of the pulsed light L output from the seed light source 11 is changed, the output characteristics and beam propagation characteristics of the pulsed amplified light L1 output from the solid-state amplifier 13 vary over time. Therefore, when the repetition frequency of the pulsed amplified light L1 output from the laser oscillator 10 is changed, the output characteristics and beam propagation characteristics of the pulsed amplified light L1 output from the laser oscillator 10 vary over time.

[0070] Next, the influence of the change in the characteristics of the pulsed amplified light L1 output from the laser oscillator 10 over time due to the change in the repetition frequency of the pulsed light on the processing will be described. If the change in the characteristics of the pulsed amplified light L1 output from the laser oscillator 10 over time occurs due to the change in the repetition frequency of the pulsed light, the intensity distribution of the pulsed amplified light L1 at the processing point after the change in the repetition frequency of the pulsed light fluctuates over time, the processing quality becomes unstable, and it becomes difficult to keep the processing quality constant after the change in the repetition frequency of the pulsed light. In this case, in order to stabilize the processing quality, it is necessary to interrupt processing until the characteristics of the pulsed amplified light L1 stabilize after the change in the repetition frequency of the pulsed light, which reduces productivity.

[0071] In the configuration of the laser processing apparatus 1 according to the first embodiment, the intensity distribution of the amplified pulsed light L1 at the processing point is determined by the mask 50. For this reason, in order to stabilize the processing quality in the laser processing apparatus 1, it is effective to stabilize the intensity distribution of the amplified pulsed light L1 on the mask 50.

[0072] The intensity distribution of the pulsed amplified light L1 on the mask 50 is determined by the elements of the pulse width, pulse energy, beam diameter, and beam shape of the pulsed amplified light L1 on the mask 50. Among these elements, the elements that vary over time with a change in the repetition frequency of the pulsed light are the pulse energy, beam diameter, and beam shape of the pulsed amplified light L1 on the mask 50. Among these elements, the element that has a particularly large effect on processing in the mask transfer processing in the laser processing apparatus 1 is the pulse energy of the pulsed amplified light L1. In other words, the element that varies over time with a change in the repetition frequency of the pulsed light and has a particularly large effect on the intensity distribution of the pulsed amplified light L1 on the mask 50 is the pulse energy of the pulsed amplified light L1 on the mask 50.

[0073] In response to the above problem, in the laser processing apparatus 1, the transmittance of the optical switching element 30 arranged on the optical path of the pulsed amplified light L1 between the laser oscillator 10 and the mask 50 is modulated so that the pulse energy of the pulsed amplified light L1 on the mask 50 after the repetition frequency of the pulsed light is kept constant before and after the repetition frequency of the pulsed light is changed. Here, "constant" refers to the fluctuation in the pulse energy of the pulsed amplified light L1 before and after the repetition frequency of the pulsed light being within a predetermined range.

[0074] This makes it possible for the laser processing apparatus 1 to suppress fluctuations over time in the pulse energy of the pulsed amplified light L1 irradiated to the mask 50 when the repetition frequency of the pulsed light is changed. That is, the laser processing apparatus 1 can suppress fluctuations over time in the pulse energy of the pulsed amplified light L1 irradiated to the mask 50 before and after a change in the repetition frequency of the pulsed light. As a result, the laser processing apparatus 1 can stabilize the intensity distribution of the pulsed amplified light L1 at the processing point even when the repetition frequency of the pulsed light is changed, making it possible to maintain constant processing quality, and stabilizing the processing quality.

[0075] Next, a method for modulating the transmittance of pulsed amplified light L1 in the optical switching element 30 of the laser processing device 1 will be described. The following description focuses on suppressing fluctuations in the pulse energy of pulsed amplified light L1 on the mask 50 when the repetition frequency of the pulsed light is changed. As described above, the fact that the pulse energy of pulsed amplified light L1 emitted from the optical fiber amplifier 12 changes due to a change in the repetition frequency of the pulsed light means that the output characteristics and beam propagation characteristics of pulsed amplified light L1 emitted from the solid-state amplifier 13 change due to a change in the repetition frequency of the pulsed light.

[0076] Fluctuations in the pulse energy of the amplified pulsed light L1 emitted from the laser oscillator 10 accompanying a change in the repetition frequency of the pulsed light, as shown in FIG. 4, can be divided into a component with a short time constant, which changes instantaneously as the repetition frequency of the pulsed light changes, and a component with a long time constant, which changes over time as the repetition frequency of the pulsed light changes.

[0077] In this case, a component with a short time constant, which changes instantaneously in response to a change in the repetition frequency of the pulsed light, can be said to be a component whose pulse energy fluctuation range within a predetermined time range is equal to or greater than a predetermined threshold value, whereas a component with a long time constant, which changes over time in response to a change in the repetition frequency of the pulsed light, can be said to be a component whose pulse energy fluctuation range within a predetermined time range is less than a predetermined threshold value.

[0078] In the plot of average power vs. pulse energy in Figure 4, the component that rises almost vertically just after time 0 minutes is a component with a short time constant whose fluctuation changes instantaneously. Also, in the plot of average power vs. pulse energy in Figure 4, the component that rises just after time 0 minutes and then fluctuates up to time 10 minutes is a component with a long time constant whose fluctuation changes over time.

[0079] For components with short time constants, the transmittance of the optical switching element 30 is modulated so that the transmittance through the mask 50 of the amplified pulsed light L1 irradiated onto the mask 50 is constant before and after the change in the repetition frequency of the pulsed light. Here, "constant" means that the fluctuation in the transmittance through the mask 50 of the amplified pulsed light L1 before and after the change in the repetition frequency of the pulsed light falls within a predetermined range.

[0080] The amplified pulsed light L1 transmitted through the optical switching element 30 enters the beam propagation adjustment unit 40 along the optical axis La of the amplified pulsed light L1, and is then irradiated onto the mask 50. The transmittance of the optical switching element 30 is modulated in accordance with a signal transmitted from the control unit 20.

[0081] The transmittance of the mask 50 is repetition The frequency can be calculated using the following formula (1) before and after the frequency change.

[0082] (Pulse energy of the amplified pulsed light L1 after passing through the mask) / (Pulse energy of the amplified pulsed light L1 before passing through the mask) (1)

[0083] When the intensity distribution of the pulsed amplified light L1 before passing through the mask 50 is Gaussian, the transmittance of the mask 50 affects not only the pulse energy of the pulsed amplified light L1 after passing through the mask 50, but also the beam shape of the pulsed amplified light L1 after passing through the mask 50. The higher the transmittance of the mask 50, the closer the beam shape of the pulsed amplified light L1 after passing through the mask 50 is to the original Gaussian distribution, i.e., the Gaussian distribution of the pulsed amplified light L1 before passing through the mask 50. Also, the lower the transmittance of the mask 50, the closer the beam shape of the pulsed amplified light L1 after passing through the mask 50 is to a top hat distribution.

[0084] Therefore, in order to stabilize the processing quality of the laser processing apparatus 1, it is necessary to make the transmittance of the mask 50 approximately equal before and after the change in the repetition frequency of the pulsed light.

[0085] The modulation of the transmittance of the optical switching element 30 for the component with a short time constant is performed based on a transmittance modulation pattern that is individually determined in advance in correspondence with a pair of repetition frequencies before and after the change in the repetition frequency of the pulsed light. The transmittance modulation pattern is a pattern by which the control unit 20 modulates the transmittance of the optical switching element 30.

[0086] The transmittance modulation pattern for the component with a short time constant is determined so that the transmittance of the amplified pulsed light L1 irradiated onto the mask 50 is constant for each pair of different repetition frequencies before and after changing the repetition frequency of the pulsed light. The transmittance modulation pattern is stored in the control unit 20. Hereinafter, the pair of repetition frequencies before and after changing the repetition frequency of the pulsed light may be simply referred to as a "pair of repetition frequencies."

[0087] The control unit 20 controls the transmittance of the optical switching element 30 based on a transmittance modulation pattern corresponding to a pair of repetition frequencies, thereby keeping the transmittance of the pulsed amplified light L1 through the mask 50 constant before and after changing the repetition frequency of the pulsed light.

[0088] When determining the transmittance modulation pattern, data on the transmittance of the pulsed amplified light L1 through the mask 50 is acquired for various pairs of repetition frequencies before and after changing the repetition frequency of the pulsed light. Then, for each of the various pairs of repetition frequencies, a transmittance modulation pattern that keeps the transmittance of the pulsed amplified light L1 irradiated onto the mask 50 constant through the mask 50 is determined based on the acquired data.

[0089] However, in cases where the beam diameter of the pulsed amplified light L1 on the mask 50 changes significantly due to a change in the repetition frequency of the pulsed light, modulating the transmittance of the optical switching element 30 alone may not be enough to keep the transmittance of the pulsed amplified light L1 through the mask 50 constant before and after the repetition frequency of the pulsed light is changed.

[0090] In this case, in addition to modulating the transmittance of the optical switching element 30, the beam diameter of the pulsed amplified light L1 after passing through the optical switching element 30 is adjusted. The beam diameter of the pulsed amplified light L1 after passing through the optical switching element 30 is adjusted by moving an optical element, which is a component of the beam propagation adjustment unit 40, in the direction of the optical axis La of the pulsed amplified light L1 output from the optical switching element 30 by a driving device 41 provided in the beam propagation adjustment unit 40.

[0091] That is, the laser processing apparatus 1 modulates the transmittance of the optical switching element 30, and further adjusts the beam diameter of the amplified pulsed light L1 emitted from the optical switching element 30 and irradiated onto the mask 50, so that the transmittance of the amplified pulsed light L1 through the mask 50 can be kept constant before and after the change in the repetition frequency of the pulsed light. The method of moving the optical elements of the beam propagation adjustment unit 40 by the driving device 41 will be described later.

[0092] For components with long time constants, the transmittance of the optical switching element 30 is modulated over time so that the pulse energy of the pulsed amplified light L1 after the repetition frequency of the pulsed light is changed remains constant. Here, "constant" means that the fluctuation in the pulse energy of the pulsed amplified light L1 after the repetition frequency of the pulsed light is changed falls within a predetermined range. In this case, there are two methods for modulating the transmittance of the optical switching element 30, as shown below.

[0093] The first transmittance modulation method is a method of applying a modulation pattern of the transmittance of the optical switching element 30, which is individually determined in advance in correspondence with a pair of repetition frequencies before and after changing the repetition frequency of the pulsed light. In this case, the modulation pattern is determined based on time series data of the pulse energy fluctuation of the amplified pulsed light L1 emitted from the laser oscillator 10 for various pairs of repetition frequencies, which data is acquired.

[0094] Machine learning may also be applied when determining the modulation pattern. By applying machine learning to the determination of the modulation pattern, it is possible to improve the accuracy of the modulation of the transmittance of the optical switching element 30 for keeping constant the component with a long time constant of the pulse energy of the pulsed amplified light L1 after changing the repetition frequency of the pulsed light. By applying machine learning to the determination of the modulation pattern, it is possible to predict the modulation pattern of the transmittance of the optical switching element 30 for keeping constant the component with a long time constant of the pulse energy of the pulsed amplified light L1 after changing the repetition frequency of the pulsed light, even for a pair of repetition frequencies for which experimental data has not been acquired.

[0095] The second transmittance modulation method is a method in which an optical sensor 90 that measures the pulse energy of pulsed amplified light L1 is disposed after the mask 50, and the transmittance of the optical switching element 30 is dynamically modulated based on data on the pulse energy of pulsed amplified light L1 measured by the optical sensor 90. Fig. 5 is a diagram showing a schematic example of a configuration in which an optical sensor is provided in a laser processing device equipped with the laser apparatus according to the first embodiment.

[0096] Optical sensor 90 receives pulsed amplified light L1 that has passed through mask 50, and measures the pulse energy of the pulsed amplified light L1. Optical sensor 90 transmits data on the pulse energy of pulsed amplified light L1, which is the measurement result, to control unit 20. Optical sensor 90 includes an element such as a photodiode that functions as a light receiving unit.

[0097] In this case, the control unit 20 dynamically controls the transmittance of the optical switching element 30 through feedback based on the measurement result of the optical sensor 90 .

[0098] 5, folding mirrors 91a and 91b and an optical sensor 90 are disposed between the mask 50 and the scanning unit 60. The optical sensor 90 is disposed on the rear side of the folding mirror 91a, that is, on the light transmitting side of the folding mirror 91a.

[0099] A portion of the amplified pulsed light L1 that has passed through mask 50 passes through folding mirror 91a and is incident on optical sensor 90. Optical sensor 90 receives the amplified pulsed light L1 that has passed through folding mirror 91a, and measures the pulse energy of the amplified pulsed light L1.

[0100] The remainder of the amplified pulse light L 1 that has passed through the mask 50 is reflected by the return mirror 91 a and enters the return mirror 91 b , and is reflected by the return mirror 91 b and enters the scanning unit 60 .

[0101] The position of the optical sensor 90 may be any position subsequent to the mask 50, and is not limited to a position between the mask 50 and the scanning unit 60. The optical sensor 90 can be disposed, for example, at a position behind a transmission mirror that transmits the pulsed amplified light L1 subsequent to the mask 50, where the transmitted light of the pulsed amplified light L1 that has passed through the transmission mirror can be measured. The optical sensor 90 can be disposed, for example, at a position where the scattered reflected light of the pulsed amplified light L1 reflected on the surface of a transmission mirror that transmits the pulsed amplified light L1 subsequent to the mask 50 can be measured, or at a position where the scattered reflected light reflected on the surface of a lens that transmits the pulsed amplified light L1 subsequent to the mask 50 can be measured.

[0102] In both of the above-mentioned first and second transmittance modulation methods, when the time-dependent fluctuation of the pulsed amplified light L1 after the change in the repetition frequency of the pulsed light becomes small enough to be ignored with respect to processing quality, the modulation of the transmittance of the optical switching element 30 may be terminated. That is, the control unit 20 terminates the modulation of the transmittance of the optical switching element 30 when the time-dependent fluctuation of the pulsed amplified light L1 after the change in the repetition frequency of the pulsed light falls within a predetermined range that is considered to be negligible with respect to processing quality.

[0103] By modulating the transmittance of the optical switching element 30 as described above, the laser processing apparatus 1 controls the transmittance of the pulsed amplified light L1 through the mask 50 to be constant before and after the change in repetition frequency, and can stabilize the intensity distribution of the pulsed amplified light L1 on the mask 50 before and after the change in repetition frequency.

[0104] In the above, the description has been focused on suppression of fluctuations in the pulse energy of the pulsed amplified light L1 on the mask 50 when the repetition frequency of the pulsed light is changed. Fluctuations in the average output of the pulsed amplified light L1 emitted from the laser oscillator 10 accompanying changes in the repetition frequency of the pulsed light can also be divided into a component with a short time constant, which changes instantaneously when the repetition frequency of the pulsed light is changed, and a component with a long time constant, which changes over time when the repetition frequency of the pulsed light is changed, as shown in Fig. 3.

[0105] Therefore, the fluctuation in the average output of the pulsed amplified light L1 on the mask 50 when the repetition frequency of the pulsed light is changed can also be suppressed by modulating the transmittance of the optical switching element 30 in the same manner as the suppression of the fluctuation in the pulse energy of the pulsed amplified light L1 on the mask 50 when the repetition frequency of the pulsed light is changed as described above. As a result, the laser processing apparatus 1 can stabilize the intensity distribution of the pulsed amplified light L1 at the processing point even when the repetition frequency of the pulsed light is changed, making it possible to maintain constant processing quality, and stabilizing the processing quality.

[0106] Next, a method for moving the optical elements of beam propagation adjustment unit 40 by driving device 41 will be described. As shown in Fig. 4, similar to the fluctuation in pulse energy, the fluctuation in the beam diameter of amplified pulsed light L1 emitted from laser oscillator 10 accompanying a change in the repetition frequency of pulsed light includes a component with a short time constant that changes instantaneously when the repetition frequency of pulsed light is changed, and a component with a long time constant that changes over time when the fluctuation in the repetition frequency of pulsed light is changed.

[0107] In this case, a component with a short time constant, which changes instantaneously when the repetition frequency of the pulsed light is changed, can be said to be a component whose fluctuation width of the beam diameter within a predetermined time range is equal to or greater than a predetermined threshold value, whereas a component with a long time constant, which changes over time when the repetition frequency of the pulsed light is changed, can be said to be a component whose fluctuation width of the beam diameter within a predetermined time range is less than a predetermined threshold value.

[0108] In the beam diameter plot in Figure 4, the component that rises almost vertically just after time 0 minutes is a component with a short time constant whose fluctuation changes instantaneously. Also, in the beam diameter plot in Figure 4, the component that rises just after time 0 minutes and then fluctuates up to time 10 minutes is a component with a long time constant whose fluctuation changes over time.

[0109] For components with short time constants, fluctuations in the beam diameter of pulsed amplified light L1 emitted from optical switching element 30 are compensated for so that the beam diameter of pulsed amplified light L1 before and after changing the repetition frequency of the pulsed light is constant. Here, "constant" means that the fluctuations in the beam diameter of pulsed amplified light L1 before and after changing the repetition frequency of the pulsed light are within a predetermined range.

[0110] The compensation of the beam diameter fluctuation for the component with a short time constant is performed based on a predetermined drive pattern of the driver 41. The drive pattern of the driver 41 for the component with a short time constant is determined so that the beam diameter of the amplified pulsed light L1 after the repetition frequency of the pulsed light is changed is constant for each pair of different repetition frequencies before and after the change in the repetition frequency of the pulsed light. The drive pattern of the driver 41 is stored in the control unit 20.

[0111] Control unit 20 compensates for components with a short time constant in the beam diameter of pulsed amplified light L1 irradiated to mask 50 by moving the optical elements of beam propagation adjustment unit 40 using drive unit 41 based on a drive pattern of drive unit 41 that corresponds to a pair of repetition frequencies. In this way, control unit 20 performs control so that the beam diameter of pulsed amplified light L1 on mask 50 is constant before and after the change in repetition frequency, and keeps the transmittance of pulsed amplified light L1 through mask 50 constant before and after the change in repetition frequency.

[0112] When determining the drive pattern of the driver 41, data on beam diameter fluctuation of the pulsed amplified light L1 emitted from the optical switching element 30 is acquired for various pairs of repetition frequencies before and after changing the repetition frequency of the pulsed light. Then, for each of the various pairs of repetition frequencies, a drive pattern of the driver 41 that compensates for the beam diameter fluctuation of the pulsed amplified light L1 emitted from the optical switching element 30 is determined based on the acquired data.

[0113] Furthermore, machine learning may be applied when determining the drive pattern of the drive device 41. That is, machine learning may be performed using data of the beam diameter fluctuation of the pulsed amplified light L1 for the acquired pairs of various repetition frequencies as learning data, thereby generating a trained model for inferring the drive pattern of the drive device 41, and the drive pattern of the drive device 41 may be inferred using the trained model. The inferred drive pattern of the drive device 41 is stored in the control unit 20. The above machine learning and inference of the drive pattern of the drive device 41 may be performed in the control unit 20 or in another device.

[0114] By applying machine learning to determine the drive pattern of the driver 41, it is possible to improve the accuracy of the drive pattern of the driver 41 for keeping constant the fluctuation range of the beam diameter of the pulsed amplified light L1 after the repetition frequency of the pulsed light is changed.In addition, by applying machine learning to determine the drive pattern of the driver 41, it is possible to predict the drive pattern of the driver 41 even for pairs of repetition frequencies for which experimental data has not been obtained.

[0115] For components with long time constants, fluctuations in the beam diameter of pulsed amplified light L1 emitted from optical switching element 30 are compensated for so that the beam diameter of pulsed amplified light L1 after the repetition frequency of pulsed light is changed remains constant. Here, "constant" means that the fluctuations in the beam diameter of pulsed amplified light L1 after the repetition frequency of pulsed light is changed falls within a predetermined range.

[0116] The compensation of the beam diameter fluctuation for the component with a long time constant is performed based on a predetermined drive pattern of the drive device 41. The drive pattern of the drive device 41 for the component with a long time constant is also determined in the same manner as the component with a short time constant. The drive pattern of the drive device 41 is stored in the control unit 20.

[0117] The control unit 20 compensates for the component with a long time constant of the beam diameter of the pulsed amplified light L1 irradiated to the mask 50 by moving the optical elements of the beam propagation adjustment unit 40 using the driving pattern of the driving unit 41 corresponding to a pair of repetition frequencies, thereby keeping the transmittance of the pulsed amplified light L1 through the mask 50 constant.

[0118] The control unit 20 determines the pair of repetition frequencies ToBased on the corresponding drive pattern of drive device 41, drive device 41 moves the optical elements of beam propagation adjustment unit 40, thereby compensating for components with a short time constant in the beam diameter of pulsed amplified light L1 irradiated to mask 50. In this way, control unit 20 performs control so that the beam diameter of pulsed amplified light L1 on mask 50 is constant before and after the change in repetition frequency, and keeps the transmittance of pulsed amplified light L1 through mask 50 constant before and after the change in repetition frequency.

[0119] In addition, a beam diameter monitor 92 that measures the beam diameter of the pulsed amplified light L1 may be disposed downstream of the beam propagation adjustment unit 40, and the driving device 41 may control the movement of the optical elements of the beam propagation adjustment unit 40 so that the beam diameter of the pulsed amplified light L1 measured by the beam diameter monitor 92 is constant.

[0120] The beam diameter monitor 92 receives the pulsed amplified light L1 that has passed through the beam propagation adjustment unit 40, and measures the beam diameter of the pulsed amplified light L1. The beam diameter monitor 92 transmits data on the beam diameter of the pulsed amplified light L1, which is the measurement result, to the control unit 20. The beam diameter monitor 92 includes a camera using an image sensor such as a Charge Coupled Device (CCD) sensor and a Complementary Metal Oxide Semiconductor (CMOS) sensor.

[0121] In this case, the control unit 20 dynamically feedback-controls the movement of the optical elements of the beam propagation adjustment unit 40 based on the measurement results of the beam diameter monitor 92 .

[0122] Fig. 6 is a schematic diagram showing an example of a configuration in which a beam diameter monitor is provided in a laser processing apparatus including the laser apparatus according to the first embodiment. In Fig. 6, folding mirrors 93a and 93b and a beam diameter monitor 92 are disposed between the beam propagation adjustment unit 40 and the mask 50. The beam diameter monitor 92 is disposed on the rear side of the folding mirror 93a, i.e., on the light transmitting side of the folding mirror 93a.

[0123] A portion of the pulsed amplified light L1 that has passed through beam propagation adjustment unit 40 passes through folding mirror 93a and is incident on beam diameter monitor 92. Beam diameter monitor 92 receives the pulsed amplified light L1 that has passed through folding mirror 93a, and measures the beam diameter of the pulsed amplified light L1.

[0124] The remainder of the amplified pulse light L 1 that has been transmitted through the beam propagation adjustment unit 40 is reflected by the return mirror 93 a and enters the return mirror 93 b , and is reflected by the return mirror 93 b and enters the mask 50 .

[0125] As described above, the control unit 20 compensates for components with short time constants of the pulsed amplified light L1 emitted from the optical switching element 30 so that the beam diameter of the pulsed amplified light L1 is constant before and after changing the repetition frequency of the pulsed light, based on the drive pattern of the drive device 41 corresponding to the pair of repetition frequencies. The control unit 20 also compensates for components with long time constants of the pulsed amplified light L1 emitted from the optical switching element 30 so that the beam diameter of the pulsed amplified light L1 is constant after changing the repetition frequency of the pulsed light, based on the drive pattern of the drive device 41 corresponding to the pair of repetition frequencies.

[0126] As a result, the laser processing apparatus 1 can perform control so that the beam diameter of the pulsed amplified light L1 on the mask 50 is constant before and after the change in repetition frequency, thereby stabilizing the intensity distribution of the pulsed amplified light L1 on the mask 50.

[0127] By controlling the movement of the optical elements of the beam propagation adjustment unit 40 as described above, the laser processing apparatus 1 can control the beam diameter of the pulsed amplified light L1 on the mask 50 to be constant before and after the change in repetition frequency, and can stabilize the intensity distribution of the pulsed amplified light L1 on the mask 50 before and after the change in repetition frequency.

[0128] In addition, the processing quality ofFor stabilization, it is effective for the driver 41 to move the beam propagation adjustment unit 40 so that the state of the wavefront of the pulsed amplified light L1 on the mask 50 does not change before and after the change in the repetition frequency, that is, so that the divergent or convergent state of the wavefront of the pulsed amplified light L1 does not change. When the thickness of the workpiece W is thicker than a specific thickness, the taper angle of the groove or hole formed by processing changes depending on whether the wavefront state of the pulsed amplified light L1 at the processing point is in a divergent state or a convergent state. Since the taper angle is an important evaluation item that determines the processing quality, it is preferable that it is constant regardless of the repetition frequency of the pulsed light.

[0129] Therefore, the laser processing apparatus 1 is able to stabilize processing quality by controlling the position of the beam propagation adjustment unit 40 so that the wavefront state of the pulsed amplified light L1 at the processing point does not change before and after a change in the repetition frequency, and so that the wavefront state of the pulsed amplified light L1 on the mask 50 does not change before and after a change in the repetition frequency.

[0130] FIG. 7 is a characteristic diagram showing the results of calculating the transmittance modulation pattern to be set when compensating for the change over time in the average output that occurs after the repetition frequency of the pulsed light is changed in the experiment whose experimental results are shown in FIG. 3 by modulating the transmittance of the optical switching element 30. The horizontal axis of FIG. 7 indicates time. On the horizontal axis of FIG. 7, the time when the repetition frequency is changed is set to 0 minutes. The left axis of FIG. 7 indicates the optical switching element transmittance (%) of the transmittance modulation pattern. The right axis of FIG. 7 indicates the average output (%) of the pulsed amplified light L1 after passing through the optical switching element. For the optical switching element transmittance (%) of the transmittance modulation pattern and the average output (%) of the pulsed amplified light L1 after passing through the optical switching element, the value at the time when the repetition frequency is changed is set to 100%.

[0131] It can be seen from Fig. 7 that by modulating the transmittance of the optical switching element 30 based on the transmittance modulation pattern, the fluctuation in the average output (%) of the pulsed amplified light L1 after passing through the optical switching element is reduced compared to the case of Fig. 3. In other words, when the average output or pulse energy of the pulsed amplified light L1 output from the laser oscillator 10 changes over time due to a change in the repetition frequency, it is possible to keep the average output approximately constant by modulating the transmittance of the optical switching element 30. Note that it is assumed here that the change over time in the beam diameter of the pulsed amplified light L1 that occurs after the repetition frequency is changed is compensated for by the beam propagation adjustment unit 40.

[0132] According to the laser device 100 of the above-described first embodiment, a laser device is realized that includes: a seed light source that outputs pulsed laser light and is capable of controlling the repetition frequency of the pulsed laser light; an amplifier that amplifies and emits the pulsed laser light; a mask that shapes at least one of the beam diameter and the beam shape of the pulsed laser light emitted from the amplifier; an optical switching element that is arranged on an optical path between the amplifier and the mask and has a transmittance modulated so that a fluctuation over time of at least one of the output and the energy of the pulsed laser light emitted from the amplifier, which occurs in association with a change in the repetition frequency of the pulsed laser light, falls within a predetermined range; and a beam propagation adjustment unit that is arranged on the optical path between the amplifier and the mask and adjusts the beam propagation of the pulsed laser light emitted from the amplifier.

[0133] As described above, in the laser processing apparatus 1 according to the first embodiment, the optical switching element 30 modulates the transmittance so that the fluctuation over time of at least one of the output and energy of the pulsed amplified light L1 amplified by the optical fiber amplifier 12 and the solid-state amplifier 13, which occurs when the repetition frequency of the pulsed laser light is changed, falls within a predetermined range. As a result, the laser processing apparatus 1 can stabilize the intensity distribution of the pulsed amplified light L1 at the processing point even when the repetition frequency of the pulsed light is changed, and the processing quality can be kept constant, resulting in stable processing quality.

[0134] The laser processing apparatus 1 also includes a beam propagation adjustment unit 40 that is disposed on the optical path between the solid-state amplifier 13 and the mask 50 and adjusts the beam propagation of the pulsed amplified light L1 emitted from the solid-state amplifier 13. The laser processing apparatus 1 can further stabilize the processing quality by manipulating at least one of the beam diameter and the wavefront of the pulsed amplified light L1 on the mask 50 by moving the optical elements that constitute the beam propagation adjustment unit 40.

[0135] Therefore, the laser device 100 and the laser processing device 1 according to the first embodiment have the effect of suppressing the fluctuation over time of the output characteristics and the beam propagation characteristics of the pulsed amplified light L1, which is the amplified pulsed laser light, caused by changing the repetition frequency of the seed light source 11. The laser processing device 1 has the effect of suppressing the fluctuation over time of the average output, the pulse energy, the beam diameter, and the beam shape at the processing point, which occurs after changing the repetition frequency of the pulsed light. The laser processing device 1 can stabilize the processing quality immediately after changing the repetition frequency of the pulsed light output from the seed light source 11, and can improve the processing productivity.

[0136] Embodiment 2 In wiring boards for electronic components or semiconductor integrated circuits (ICs), it is sometimes necessary to process holes of different diameters within one wiring board. When processing holes of different diameters using the same laser processing device, it is necessary to make the beam diameter of the pulsed laser light at the processing point relatively small when processing holes with a relatively small diameter, and to make the beam diameter of the pulsed laser light at the processing point relatively large when processing holes with a relatively large diameter.

[0137] Each material to be processed has its own processing threshold for the irradiated laser light, and to perform stable laser processing, it is necessary to irradiate the laser light with characteristics such as energy that exceed the processing threshold. The processing threshold is the minimum characteristic value of the laser light at which the decomposition of the workpiece begins when the laser light is irradiated onto the workpiece. If the processing threshold is Fth and the hole diameter is r, the minimum energy Eth of the laser light required for processing is expressed by the following formula (2).

[0138] Eth = πr 2 Fth (2)

[0139] The processing threshold Fth is a constant value depending on the material. Therefore, the minimum energy Eth of the laser beam required to process the object increases as the hole diameter r increases. In other words, the larger the hole diameter, the greater the energy of the laser beam required for processing.

[0140] Generally, the pulsed laser beam emitted from a pulsed laser oscillator has a property that the lower the repetition frequency, the greater the pulse energy. According to this property, when performing hole drilling using a pulsed laser beam, the small diameter portion having a relatively small hole diameter is machined at a relatively high repetition frequency, and the large diameter portion having a relatively large hole diameter is machined at a relatively low repetition frequency, thereby enabling efficient machining.

[0141] In a mask transfer processing optical system in which the beam diameter of the laser light at the processing point is determined by the opening diameter of the mask, efficient processing can be achieved by using a mask with a relatively small opening diameter when processing holes with a relatively small diameter, and by using a mask with a relatively large opening diameter when processing holes with a relatively large diameter.

[0142] 8 is a block diagram showing a schematic example of a configuration of a laser processing apparatus including a laser device according to embodiment 2. The laser processing apparatus 2 according to embodiment 2 differs from the laser processing apparatus 1 according to embodiment 1 in that the laser processing apparatus 2 includes a laser device 110 instead of the laser device 100. The laser processing apparatus 110 differs from the laser processing apparatus 1 according to embodiment 1 in that the laser processing apparatus 2 includes a mask 51 instead of the mask 50, a control unit 21 instead of the control unit 20, and further includes a mask changer 52.

[0143] Fig. 9 is a plan view showing an example of a mask provided in the laser processing apparatus according to the second embodiment. In the mask 51, a plurality of openings having different diameters, which are opening regions, are formed for one substrate. The mask 51 shown in Fig. 9 is a circular metal plate in which a plurality of circular openings 51a are formed. The mask 50 according to the first embodiment described above has one opening 50a formed therein. In contrast, the mask 51 according to the second embodiment has a plurality of circular openings 51a formed therein.

[0144] In the mask 51, a plurality of circular openings 51a are formed on concentric circles centered on a center C of the circle of the mask 51 in the in-plane direction of the mask 51. That is, in the mask 51, a plurality of circular openings 51a are formed having centers on a virtual circle V that is concentric with the circle of the mask 51.

[0145] Furthermore, the mask 51 may be configured such that an opening part 51b made of a transparent material through which the amplified pulsed light L1 passes is fitted and fixed in the opening 51a.

[0146] The mask changer 52 rotates the mask 51 around an axis that passes through the center C of the mask 51 and is perpendicular to the in-plane direction of the mask 51. 51 By rotating the mask changer 52, the opening 51a through which the pulsed amplified light L1 passes is changed. The mask changer 52 changes the position of the opening 51a so that the optical axis La of the pulsed amplified light L1 passes through the opening 51a, thereby changing the opening 51a through which the pulsed amplified light L1 passes. The driving of the mask changer 52 is controlled by the control unit 21.

[0147] In the mask transfer optical system 70, the mask 51 The aperture diameter of the aperture 51a and the transfer magnification determine the beam diameter of the laser light at the processing point. The laser device 110 can change the beam diameter at the processing point in accordance with the hole diameter to be processed by changing the aperture 51a through which the pulsed amplified light L1 passes by the mask changer 52. In addition, the laser device 110 uses the correlation between the pulse energy of the pulsed amplified light L1 output from the laser oscillator 10 and the repetition frequency of the pulsed light L output from the seed light source 11 to determine the repetition frequency of the pulsed light L output from the seed light source 11 in accordance with the hole diameter, and performs processing.

[0148] As a result, when performing hole drilling using the pulsed amplified light L1, the laser device 110 can process a small diameter portion having a relatively small hole diameter, which can be processed with relatively low energy, at high speed using a relatively high repetition frequency. Also, when performing hole drilling using the pulsed amplified light L1, the laser device 110 can process a large diameter portion having a relatively large hole diameter, which requires relatively high energy, at low speed using a relatively low repetition frequency. As a result, the laser device 110 can efficiently process a plurality of types of holes with different hole diameters.

[0149] The control unit 21 has a function of controlling the mask changer 52 in addition to the functions of the control unit 20 according to the first embodiment.

[0150] 10 is a flowchart showing a procedure for drilling holes of different diameters in the laser processing apparatus according to the embodiment 2. Here, a case will be described in which the repetition frequency of the pulsed light is set to repetition frequency A to drill a hole of diameter a in the laser processing apparatus 2, and then the repetition frequency of the pulsed light is changed to repetition frequency B to drill a hole of diameter b, which is different from the hole diameter a.

[0151] First, in step S110, the laser processing device 2 performs drilling of a hole diameter a with the repetition frequency of the pulsed light set to repetition frequency A. After the drilling of the hole diameter a is completed, the irradiation of the amplified pulsed light L1 from the laser device 110 to the workpiece W is temporarily stopped. When the laser oscillator 10 is stopped and then driven again, it takes time to obtain a stable amplified pulsed light L1. Therefore, even when the irradiation of the amplified pulsed light L1 from the laser device 110 to the workpiece W is temporarily stopped, the generation of the amplified pulsed light L1 inside the laser device 110 continues.

[0152] Examples of a method for stopping the irradiation of the amplified pulsed light L1 on the workpiece W include a method using a beam on / off function provided in the laser device 110 itself, or a method for stopping the output of the amplified pulsed light L1 from the laser device 110 by setting the transmittance of the optical switching element 30 to 0%. The beam on / off function is a function for switching between the presence and absence of the output of the amplified pulsed light L1 from the laser device 110. Then, proceed to step S120.

[0153] In step S120, in order to perform drilling with a hole diameter b, the repetition frequency of the pulsed light is changed from repetition frequency A to repetition frequency B. Then, the process proceeds to step S130.

[0154] In step S130, the control unit 21 determines whether or not it is necessary to change the opening 51a of the mask 51 in response to the change in the repetition frequency of the pulsed light. The control unit 21 pre-stores information on whether or not it is necessary to change the opening 51a of the mask 51 when drilling a hole with a hole diameter b using amplified pulsed light L1 with a repetition frequency B. The control unit 21 determines whether or not it is necessary to change the opening 51a of the mask 51 in response to the change in the repetition frequency of the pulsed light based on the information.

[0155] If it is determined that the openings 51a of the mask 51 need to be changed in accordance with the change in the repetition frequency of the pulsed light, the result in step S130 is Yes, and the process proceeds to step S140. If it is determined that the openings 51a of the mask 51 need not be changed in accordance with the change in the repetition frequency of the pulsed light, the result in step S130 is No, and the process proceeds to step S150.

[0156] In step S140, the opening 51a of the mask 51 is changed. Specifically, the mask changer 52 changes the opening 51a that transmits the pulsed amplified light L1 under the control of the control unit 21. The control unit 21 stores in advance information on the opening 51a of the mask 51 to be used when drilling a hole with a hole diameter b using the pulsed amplified light L1 with a repetition frequency B. The control unit 21 instructs the mask changer 52 which opening 51a to use based on the information. Then, the process proceeds to step S150.

[0157] In step S150, the control unit 21 determines whether or not it is necessary to change at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 in association with a change in the repetition frequency of the pulsed light. The control unit 21 pre-stores information on whether or not it is necessary to change at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 when drilling a hole with a hole diameter b using the pulsed amplified light L1 with a repetition frequency B. The control unit 21 determines whether or not it is necessary to change at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 based on the information.

[0158] If it is determined that at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 needs to be changed in accordance with the change in the repetition frequency of the pulsed light, the answer is Yes in step S150 and the process proceeds to step S160. If it is determined that at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 does not need to be changed in accordance with the change in the repetition frequency of the pulsed light, the answer is No in step S150 and the process proceeds to step S170.

[0159] In step S160, at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 is changed. Specifically, the driving device 41 changes at least one of the wavefront and beam diameter of the pulsed amplified light L1 on the mask 51 by moving the optical element of the beam propagation adjustment unit 40 in accordance with the control of the control unit 21. The control unit 21 stores in advance information on the position of the optical element of the beam propagation adjustment unit 40 to be used when drilling a hole with a hole diameter b using the pulsed amplified light L1 with a repetition frequency B. The control unit 21 instructs the driving device 41 on the position of the optical element of the beam propagation adjustment unit 40 to be used based on the information. Then, the process proceeds to step S170.

[0160] In step S170, the control unit 21 starts modulating the transmittance of the optical switching element 30. After that, the process proceeds to step S180.

[0161] In step S180, output of amplified pulsed light L1 from laser device 110 is started, and a hole having diameter b is drilled by amplified pulsed light L1 having a repetition frequency B.

[0162] As described above, the laser device 110 performs drilling of hole diameter a using pulsed amplified light L1 having a repetition frequency A, and then performs drilling of hole diameter b using pulsed amplified light L1 having a repetition frequency B, thereby efficiently performing drilling of hole diameter a and drilling of hole diameter b.

[0163] In the above, the case where the hole diameter a and the hole diameter b are continuously drilled in the laser processing device 2 have been described, but when drilling holes of three or more different hole diameters, the processing conditions can be changed in the same manner as above to continuously drill holes of different diameters. For example, after drilling hole diameter b as described above, the repetition frequency of the pulsed light is changed to repetition frequency C to drill hole diameter a and hole diameter b. bIn this case, the process returns to step S120 after drilling the hole diameter b in step S180. In the second round of steps S120 to S170, the process changes the machining conditions to accommodate the drilling of the hole diameter c in the same manner as described above, and the second round of step S180 drills the hole diameter c.

[0164] The laser processing device 2 according to the second embodiment described above includes a mask 51 having a plurality of openings 51a that are different in shape or size and through which the pulsed amplified light L1 can pass. The laser processing device 2 can change the processing point beam diameter in accordance with the hole diameter to be processed by changing the openings 51a through which the pulsed amplified light L1 passes by the mask changer 52. This allows the laser device 110 to process a small diameter portion having a relatively small hole diameter at a high repetition frequency that is a relatively high repetition frequency and to process a large diameter portion having a relatively large hole diameter at a low repetition frequency that is a relatively low repetition frequency when performing hole processing using the pulsed amplified light L1, and can perform processing efficiently. Therefore, the laser processing device 2 can efficiently process a plurality of holes having different hole diameters when performing hole processing using the pulsed amplified light L1.

[0165] Next, the hardware configuration of each of the control units 200 according to the first and second embodiments will be described. The control units 200 according to the first and second embodiments correspond to the control unit 20 of the laser device 100 and the control unit 21 of the laser device 110, respectively. The functions of each of the control units 200 according to the first and second embodiments are realized by a processing circuit. The processing circuit may be dedicated hardware, or may be a processing device that executes a program stored in a storage device.

[0166] When the processing circuit is a dedicated hardware, the processing circuit may be a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit, a field programmable gate array, or a combination of these. Fig. 11 is a diagram showing a configuration in which the functions of the control unit according to the first and second embodiments are realized by hardware. A logic circuit 201a that realizes the functions of the control unit 200 is incorporated in the processing circuit 201.

[0167] When the processing circuit 201 is a processing device, the functions of the control unit 200 are realized by software, firmware, or a combination of software and firmware.

[0168] FIG. 12 is a diagram showing a configuration in which the functions of the control unit according to the first and second embodiments are realized by software. The processing circuit 201 has a processor 202 that executes a program 201b, a random access memory 203 that the processor 202 uses as a work area, and a storage device 204 that stores the program 201b. The processor 202 expands the program 201b stored in the storage device 204 on the random access memory 203 and executes it, thereby realizing the function of the control unit 200. The software or firmware is written in a program language and stored in the storage device 204. The processor 202 can be exemplified by a central processing unit, but is not limited to this. The storage device 204 can be a semiconductor memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable read only memory (EPROM), or an electrically erasable programmable read only memory (EEPROM (registered trademark)). The semiconductor memory may be a non-volatile memory or a volatile memory. Further, in addition to a semiconductor memory, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc) can be applied to the storage device 204. The processor 202 may output data such as a calculation result to the storage device 204 for storage, or may store the data in an auxiliary storage device (not shown) via the random access memory 203. By integrating the processor 202, the random access memory 203, and the storage device 204 on one chip, the function of the control unit 200 can be realized by a microcomputer.

[0169] The processing circuit 201 realizes the functions of the control unit 200 by reading and executing the program 201b stored in the storage device 204. It can also be said that the program 201b causes a computer to execute procedures and methods for realizing the functions of the control unit 200.

[0170] In addition, the processing circuit 201 may be configured so that some of the functions of the control unit 200 are realized by dedicated hardware, and some of the functions of the control unit 200 are realized by software or firmware.

[0171] Thus, the processing circuitry 201 can realize each of the above-described functions by hardware, software, firmware, or a combination of these.

[0172] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[0173] 1,2 laser processing device, 10 laser oscillator, 11 seed light source, 12 optical fiber amplifier, 13 solid-state amplifier, 14 nonlinear optical crystal, 20,21 control unit, 30 optical switching element, 40 beam propagation adjustment unit, 41 drive unit, 50,51 mask, 50a,51a aperture, 51b aperture part, 52 mask changer, 60 scanning unit, 65 processing optical system, 70 mask transfer optical system, 80 processing table, 90 optical sensor, 91a,91b,93a,93b folding mirror, 92 beam diameter monitor, 100,110 laser device, 200 control unit, 201 processing circuit, 201a logic circuit, 201b program, 202 processor, 203 random access memory, 204 storage device, C center, Eth minimum energy, Fth processing threshold, L pulse light output from seed light source, L1 Pulsed amplified light, La the optical axis, V the virtual circle, W the workpiece.

Claims

1. a seed light source that outputs a pulsed laser beam and is capable of controlling a repetition frequency of the pulsed laser beam; an amplifier that amplifies and emits the pulsed laser light; a mask for shaping at least one of a beam diameter and a beam shape of the pulsed laser light output from the amplifier; an optical switching element arranged on an optical path between the amplifier and the mask, the optical switching element having a transmittance modulated so that a fluctuation over time of at least one of the output and energy of the pulsed laser beam emitted from the amplifier, which occurs in association with a change in the repetition frequency of the pulsed laser beam, falls within a predetermined range; a beam propagation adjusting unit that is disposed on an optical path between the amplifier and the mask and adjusts beam propagation of the pulsed laser light output from the amplifier; A laser device comprising:

2. a driving device that moves an optical element constituting the beam propagation adjustment unit in a direction of an optical axis of the pulsed laser light output from the optical switching element; 2. The laser device according to claim 1 .

3. the driving device moves the optical element so as to adjust a beam diameter of the pulsed laser light emitted from the amplifier and irradiated onto the mask after the repetition frequency of the pulsed laser light is changed; 3. The laser device according to claim 2 .

4. the driving device moves the optical element such that a diverging state or a converging state of a wavefront of the pulsed laser beam outputted from the amplifier and irradiated onto the mask after the repetition frequency of the pulsed laser beam is changed does not change before and after the change in the repetition frequency of the pulsed laser beam; 3. The laser device according to claim 2 .

5. a sensor that measures pulse energy of the pulsed laser light emitted from the amplifier and transmitted through the mask; the optical switching element modulates transmittance based on the measurement result of the sensor; 2. The laser device according to claim 1 .

6. the mask has a plurality of transmission regions that are different in shape or size and that can transmit the pulsed laser beam, and the transmission region that transmits the pulsed laser beam emitted from the amplifier can be changed; 2. The laser device according to claim 1 .

7. A laser device according to any one of claims 1 to 6; a processing optical system that irradiates a workpiece with the pulsed laser light emitted from the laser device; A laser processing apparatus comprising:

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