Laser device and laser processing device

Abstract

A laser device (100) comprises: 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 disposed on an optical path between the amplifier and the mask (50), and modulates transmittance such that fluctuations over time of at least one of the output and energy of the pulsed laser light emitted from the amplifier, which occur due to a change in the repetition frequency of the pulsed laser light, are within a predetermined range; and a beam propagation adjustment unit (40) that is disposed on the optical path between the amplifier and the mask (50), and adjusts the propagation of a beam of the pulsed laser light emitted from the amplifier.

Description

Laser device and laser processing device

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

[0002] In recent years, laser processing devices using short-pulse lasers as light sources have been widely used in a variety of micromachining applications, such as drilling holes in printed circuit boards, cutting glass, and precision metal machining. Laser devices implemented in such laser processing devices often employ a master oscillator power amplifier (MOPA) system, in which short-pulse laser light output from a seed light source is amplified and output using a solid-state amplifier. Advantages of the MOPA system include easy control of pulse characteristics such as repetition rate and the ability to increase the output power of pulsed laser light by increasing the number of solid-state amplifier stages depending on the processing application. Laser devices implemented in laser processing devices may also output short-wavelength short-pulse laser light by using a MOPA light source as the fundamental wave and shortening the wavelength of the short-pulse laser light through harmonic generation using a nonlinear optical crystal.

[0003] When performing micromachining using a laser processing device that uses a short-pulse laser as a light source, productivity can sometimes be improved by changing the laser repetition frequency according to the machining shape. However, with a typical short-pulse laser, the output characteristics or beam propagation characteristics of the output pulsed laser light change according to the repetition frequency. Because these changes involve thermal changes inside the short-pulse laser, they do not complete instantaneously but progress over time. This has led to the problem of the output characteristics or beam propagation characteristics at the machining point fluctuating over time after the repetition frequency is changed. Fluctuations in the output characteristics or beam propagation characteristics of the short-pulse laser light change the intensity distribution at the machining point, making it difficult to maintain consistent machining quality after changing the repetition frequency.

[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 laser output, in which the laser light emitted from the laser is made incident on an acousto-optic element that modulates the transmittance of the laser light, and the transmittance of the laser light by the acousto-optic element is changed to keep the output of the laser light emitted from the acousto-optic element constant.

[0005] Japanese Patent Application Laid-Open No. 2005-161329

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

[0007] The present disclosure has been made in consideration of the above, and aims to provide a laser device that can suppress fluctuations over time 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.

[0008] In order to solve the above-mentioned problems and achieve the object, the laser apparatus according to 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 in 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.

[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 changes in the repetition frequency of a seed light source.

[0010] FIG. 1 is a block diagram schematically illustrating an example of the configuration of a laser processing apparatus equipped with a laser device according to a first embodiment; FIG. 2 is a diagram schematically illustrating an example of the configuration of a laser oscillator equipped in the laser apparatus according to the first embodiment; FIG. 3 is a characteristic diagram illustrating experimental results of measuring the output characteristics of amplified pulsed light emitted from the laser oscillator when the repetition frequency of pulsed light is switched in the laser oscillator according to the first embodiment; FIG. 1 is a diagram schematically illustrating an example of a configuration in which a monitor is provided; FIG. 2 is a characteristic diagram showing the results of calculating a transmittance modulation pattern set when compensating for the change in average output over time that occurred after changing the repetition frequency of pulsed light in the experiment whose experimental results are shown in FIG. 3 by modulating the transmittance of an optical switching element; FIG. 3 is a block diagram schematically illustrating an example of a configuration of a laser processing apparatus including a laser apparatus according to a second embodiment; FIG. 4 is a plan view showing an example of a mask provided in the laser processing apparatus according to the second embodiment;

[0011] Hereinafter, a laser apparatus and a laser processing apparatus according to embodiments 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] First Embodiment. Fig. 1 is a block diagram showing a schematic example of the configuration of a laser processing apparatus including a laser apparatus according to a first embodiment. The laser processing apparatus 1 is an apparatus that processes a workpiece W by irradiating the workpiece W with pulsed laser light output from a laser apparatus 100. The workpiece W is, for example, a printed circuit board, a glass substrate, or a metal plate. Processing includes, for example, cutting, welding, and drilling. The laser processing apparatus 1 can perform processing such as drilling holes in printed circuit boards, cutting glass, and precision processing of metals.

[0013] The laser processing apparatus 1 includes a laser device 100 that outputs pulsed laser light, 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 workpiece W and the type of 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. Ablation processing using a short-pulse laser beam is particularly suitable for fine processing because it can reduce the thermal effects that occur 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, which is 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 schematically illustrating an example of the configuration of a laser oscillator included in the laser apparatus 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-converted MOPA laser that employs a MOPA system 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 then output. The laser oscillator 10 emits 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 the optical fiber amplifier 12 and the 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. Because 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 that amplifies the pulsed light L output from the seed light source 11 is required downstream of the seed light source 11. The optical fiber amplifier 12 is capable of amplifying low-output pulsed light with high efficiency. For example, an ytterbium (Yb)-doped fiber is used for the optical fiber amplifier 12. For example, the output characteristics of the pulsed light output from the optical fiber amplifier 12 are an average output of several mW to several hundred mW, and a peak output of several kW.

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

[0020] The solid-state amplifier 13 amplifies the pulsed amplified light output from the optical fiber amplifier 12 to a high output range that can be used 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 watts to several tens of watts and a peak output of several megawatts to several tens of megawatts.

[0021] The solid-state active medium of the solid-state amplifier 13 is, for example, Nd:YVO ４ , Nd:YAG, Yb:YAG, Yb:KGW are used. The excitation light source is a light source that outputs laser light to excite the solid 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 according to the absorption spectrum of the solid active medium. Examples of wavelengths 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 may be, for example, LiB3O5 (Lithium Triborate: LBO), CsLiB6O 10(Cesium Lithium Borate: CLBO) or 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 one-third or one-quarter, 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 some cases, an optical switching element is incorporated into the laser oscillator 10 to control the characteristics of the pulsed light output from the laser oscillator 10. The optical switching element incorporated into 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 at a stage subsequent to 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 pulsed laser amplified light obtained by amplifying the pulsed laser light output from the seed light source 11.

[0027] 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 drive device 41, the scanning unit 60, the mask transfer optical system 70, and the processing table 80.

[0028] Optical switching element 30 modulates the transmittance of amplified pulsed light L1 output from laser oscillator 10. Amplified pulsed light L1 output from laser oscillator 10 is incident on optical switching element 30, passes through optical switching element 30 at a set transmittance, and then enters beam propagation adjustment unit 40 along optical axis La of amplified pulsed light L1. The transmittance of optical switching element 30 is modulated in accordance with a signal transmitted from 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 apparatus 1, for example, an acousto-optic modulator (AOM) 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 normal transmittance, the transmittance of the AOM is 85%.

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

[0031] It should be noted 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 as the optical switching element 30. When an acousto-optic element is used as the optical switching element 30, zero-order light or 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 for the optical switching element 30 is selected according to the wavelength of the pulsed amplified light L1 used to process the work-piece W. Furthermore, in the optical switching element 30, a pulsed light incident surface onto which the pulsed amplified light L1 enters and a pulsed light exit surface from which the pulsed light exits are provided with anti-reflective coatings for the wavelength of the pulsed amplified light L1.

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

[0035] The beam propagation adjustment unit 40 has at least one optical element selected from the group consisting of a spherical lens and a curved mirror. The beam propagation adjustment unit 40 is configured, for example, with 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 adjusting unit 40. The driving device 41 has a function of moving optical elements, which are components of the beam propagation adjusting unit 40, in the optical axis direction of the pulsed amplified light L1 output from the optical switching element 30. The driving device 41 is able to adjust at least one of the beam diameter and the radius of curvature of the wavefront of the pulsed amplified light L1 irradiated onto the mask 50 by moving the optical elements of the beam propagation adjusting unit 40 in the optical axis direction of the pulsed amplified light L1 output from the optical switching element 30. In other words, the driving device 41 is able to 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 adjusting 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 device 1 can stabilize 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 make up 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, thereby shaping 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] The mask 50 is made of, for example, a metal plate with openings 50a formed therein. 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, for example, circular or rectangular. The shape of the transmission region of the mask 50 may also 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 that transmits the pulsed amplified light L1 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 in 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 that has passed through the opening 50a of the mask 50 to the workpiece W, and transmits and focuses the pulsed amplified light L1 that has passed 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 that has passed through the opening 50a of the mask 50, and irradiates the pulsed amplified light L1 at a desired position on the surface to be processed 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 opening 50 a of the mask 50 and been scanned by the scanning unit 60 is incident on the mask transfer optical system 70, and the mask transfer optical system 70 transfers an image of the opening 50 a 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., the shape of the opening 50 a 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 pulsed 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, thereby adjusting the position of the fθ lens.

[0044] In the laser processing device 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 description will be given of the 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. Here, it is assumed 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 current pulses 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 current pulses 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 incident on the optical fiber amplifier 12 and amplified in the optical fiber amplifier 12. When the pumping output of the optical fiber amplifier 12 is constant regardless of the repetition frequency of the pulsed light, the output characteristics of the pulsed amplified light L1, which is the pulsed light after being amplified in the optical fiber amplifier 12, i.e., the characteristics such as the average output and pulse energy of the pulsed amplified light L1, change as the repetition frequency of the pulsed light incident on the optical fiber amplifier 12 changes.

[0048] On the other hand, the beam propagation of the amplified pulsed 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 amplified pulsed light L1 that is output from the optical fiber amplifier 12 is constant regardless of the repetition frequency of the pulsed light that is 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 pumping output is fixed at a constant output.

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

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

[0054] A change in the thermal lens effect in the solid-state amplifier 13 causes a change in the beam propagation of the output pulsed amplified light, which is the pulsed amplified light L1 that is amplified and output in the solid-state amplifier 13. Therefore, the beam propagation of the output 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 that occurs in the solid-state amplifier 13 due to a change in the repetition frequency of the pulsed light output from the semiconductor laser does not end instantaneously, 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 pulsed light having a pulse width of several tens of picoseconds or less is amplified to a power of several tens of watts that can be used for processing, nonlinear effects occurring in the solid-state amplifier 13 cannot be ignored. Nonlinear effects that are 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 due to Raman scattering. When stimulated Raman scattering occurs in the solid-state amplifier 13, a decrease in the output of the amplified pulsed amplified light L1 is caused, and a decrease in the output of the amplified pulsed light emitted 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 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 usable for processing depend on the peak intensity of the pulsed light.

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

[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 resulting from the change in the repetition frequency of the pulsed light is completed instantaneously. However, because 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 solid-state amplifier 13 is constant regardless of the repetition frequency of the pulsed light. If the pumping output of solid-state amplifier 13 is changed in response to a change in the repetition frequency of the pulsed light, a thermal change in state occurs within solid-state amplifier 13, and it goes without saying that, as described above, it takes several seconds to several minutes for the output characteristics and beam propagation characteristics of pulsed amplified light L1 emitted from 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 characteristics diagram showing the results of an experiment measuring the output characteristics of pulsed amplified light L1 emitted from the laser oscillator according to embodiment 1 when the repetition frequency of pulsed light is switched. Fig. 3 shows the time fluctuations of the average output and beam diameter of pulsed amplified light L1 emitted from laser oscillator 10 when the repetition frequency of pulsed light is switched in laser oscillator 10. The output characteristics of pulsed amplified light L1 emitted from laser oscillator 10 can be said to be the output characteristics of pulsed amplified light L1 emitted from solid-state amplifier 13.

[0065] The horizontal axis of Fig. 3 represents 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 represents the fluctuation (%) of the average output of pulsed amplified light L1, which is an output characteristic of pulsed amplified light L1 emitted from solid-state amplifier 13. The right axis of Fig. 3 represents the fluctuation (%) of the beam diameter of pulsed amplified light L1, which is an output characteristic of 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 in terms of average output. The average output of the pulsed amplified light L1 is calculated by multiplying the pulse energy of the pulsed amplified light L1 by the repetition frequency. Therefore, when the moving average of multiple pulses is evaluated in the same manner as above, the pulse energy also shows a similar tendency.

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

[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 fluctuate 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 fluctuate over time.

[0070] Next, we will explain the effect on machining of changes in the characteristics of the pulsed amplified light L1 output from the laser oscillator 10 over time that occur as the repetition frequency of the pulsed light is changed. If changes in the characteristics of the pulsed amplified light L1 output from the laser oscillator 10 over time occur due to a change in the repetition frequency of the pulsed light, the intensity distribution of the pulsed amplified light L1 at the machining point after the repetition frequency of the pulsed light changes over time, making the machining quality unstable and making it difficult to maintain constant machining quality after the repetition frequency of the pulsed light is changed. In this case, in order to stabilize the machining quality, it is necessary to suspend machining until the characteristics of the pulsed amplified light L1 stabilize after the repetition frequency of the pulsed light is changed, 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. Therefore, 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. Of these elements, the elements that vary over time as the repetition frequency of the pulsed light is changed are the pulse energy, beam diameter, and beam shape of the pulsed amplified light L1 on the mask 50. Of these, the element that has a particularly large effect on processing in 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 as the repetition frequency of the pulsed light is changed and that 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] To address the above-mentioned problem, the laser processing device 1 modulates 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 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" means that the fluctuation in the pulse energy of the pulsed amplified light L1 before and after the repetition frequency of the pulsed light is kept within a predetermined range.

[0074] As a result, the laser processing apparatus 1 can suppress fluctuations over time in the pulse energy of the amplified pulsed light L1 irradiated onto 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 amplified pulsed light L1 irradiated onto 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 amplified pulsed 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 processing quality.

[0075] Next, a description will be given of a method for modulating the transmittance of pulsed amplified light L1 in the optical switching element 30 of the laser processing device 1. 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 when the repetition frequency of the pulsed light is changed means that the output characteristics and beam propagation characteristics of pulsed amplified light L1 emitted from the solid-state amplifier 13 change when the repetition frequency of the pulsed light is changed.

[0076] As shown in FIG. 4, the fluctuation in the pulse energy of the amplified pulsed light L1 emitted from the laser oscillator 10 due to a change in the repetition frequency of the pulsed light 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 as the repetition frequency of the pulsed light changes, 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, whereas a component with a long time constant, which changes over time as the repetition frequency of the pulsed light changes, can be said to be a component whose pulse energy fluctuation range within a predetermined time range is less than a predetermined threshold.

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

[0079] For components with short time constants, the transmittance of optical switching element 30 is modulated so that the transmittance through mask 50 of pulsed amplified light L1 irradiated onto mask 50 is constant before and after changing the repetition frequency of the pulsed light. Here, "constant" means that the fluctuation in the transmittance through mask 50 of pulsed amplified light L1 before and after changing 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 is incident on 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 before and after changing the frequency of the pulsed light can be calculated by the following formula (1).

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

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

[0084] Therefore, in order to stabilize the processing quality of the laser processing device 1, it is necessary to make the transmittance of the mask 50 approximately equal before and after changing 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 predetermined corresponding to a pair of repetition frequencies before and after changing the repetition frequency of the pulsed light. The transmittance modulation pattern is a pattern that the control unit 20 uses to modulate 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 amplified pulsed 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 amplified pulsed light L1 irradiated onto the mask 50 constant through the mask 50 is determined based on the acquired data.

[0089] However, in some cases, such as when 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 on 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 optical switching element 30, compensation is performed on the beam diameter of pulsed amplified light L1 after passing through optical switching element 30. The compensation of the beam diameter of pulsed amplified light L1 after passing through optical switching element 30 is performed by moving an optical element, which is a component of beam propagation adjustment unit 40, in the direction of optical axis La of pulsed amplified light L1 output from optical switching element 30 by means of drive device 41 included in 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 at the mask 50 can be kept constant before and after changing 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 temporally modulated so that the pulse energy of the pulsed amplified light L1 remains constant after the repetition frequency of the pulsed light is changed. "Constant" here means that the fluctuation in the pulse energy of the pulsed amplified light L1 remains within a predetermined range after the repetition frequency of the pulsed light is changed. 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 transmittance modulation pattern of the optical switching element 30 that is individually predetermined corresponding to a pair of repetition frequencies before and after changing the repetition frequency of the pulsed light. In this case, time-series data of pulse energy fluctuations of the amplified pulsed light L1 emitted from the laser oscillator 10 is acquired for various pairs of repetition frequencies, and the modulation pattern is determined based on the time-series data.

[0094] Furthermore, machine learning may be applied when determining the modulation pattern. By applying machine learning to determine the modulation pattern, it becomes possible to improve the accuracy of modulating the transmittance of the optical switching element 30 so as to keep 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. Furthermore, by applying machine learning to determine the modulation pattern, it becomes possible to predict the modulation pattern of the transmittance of the optical switching element 30 so as to keep 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 pairs 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 schematically showing an example of a configuration in which an optical sensor is provided in a laser processing apparatus that includes 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 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 feedback controls the transmittance of the optical switching element 30 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, i.e., 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 enters 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 then reflected by the return mirror 91 b and enters the scanning unit 60 .

[0101] The position of the optical sensor 90 need only be downstream of 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, behind a transmission mirror that transmits the pulsed amplified light L1 downstream of the mask 50, at a position where it can measure the transmitted light of the pulsed amplified light L1 that has passed through the transmission mirror. The optical sensor 90 can also be disposed, for example, at a position where it can measure the scattered reflected light of the pulsed amplified light L1 that has reflected off the surface of a transmission mirror that transmits the pulsed amplified light L1 downstream of the mask 50, or at a position where it can measure the scattered reflected light that has reflected off the surface of a lens that transmits the pulsed amplified light L1 downstream of the mask 50.

[0102] In either of the above-described first transmittance modulation method and second transmittance modulation method, if the fluctuation over time of the pulsed amplified light L1 after changing 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. In other words, the control unit 20 terminates the modulation of the transmittance of the optical switching element 30 when the fluctuation over time of the pulsed amplified light L1 after changing 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 changing the repetition frequency, thereby stabilizing the intensity distribution of the pulsed amplified light L1 on the mask 50 before and after changing the repetition frequency.

[0104] The above description has focused on suppressing fluctuations in the pulse energy of pulsed amplified light L1 on mask 50 when the repetition frequency of pulsed light is changed. Fluctuations in the average output of pulsed amplified light L1 emitted from laser oscillator 10 that accompany changes in the repetition frequency of pulsed light can also be divided into 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 repetition frequency of pulsed light is changed, as shown in Figure 3.

[0105] Therefore, fluctuations in the average output of 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 way as the suppression of 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. As a result, the laser processing apparatus 1 can stabilize the intensity distribution of 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 processing quality.

[0106] Next, a description will be given of a method for moving the optical elements of beam propagation adjustment unit 40 by drive device 41. 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 also includes a component with a short time constant that changes instantaneously as the fluctuation accompanying a change in the repetition frequency of pulsed light, and a component with a long time constant that changes over time as the fluctuation accompanying a change in the repetition frequency of pulsed light.

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

[0108] In the beam diameter plot in Fig. 4, the component that rises almost vertically immediately after time 0 minute is a component with a short time constant that changes instantaneously. Also, in the beam diameter plot in Fig. 4, the component that rises immediately after time 0 minute and then fluctuates up to time 10 minute is a component with a long time constant that 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 remains constant before and after changing the repetition frequency of pulsed light. Here, "constant" means that the fluctuations in the beam diameter of pulsed amplified light L1 before and after changing the repetition frequency of pulsed light fall within a predetermined range.

[0110] The compensation for 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 change in the repetition frequency of the pulsed light 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 short time constants in the beam diameter of pulsed amplified light L1 irradiated onto 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 remains constant before and after changing the repetition frequency, and keeps the transmittance of pulsed amplified light L1 through mask 50 constant before and after changing the repetition frequency.

[0112] When determining the drive pattern of driver 41, data on beam diameter fluctuations of amplified pulsed light L1 emitted from 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 driver 41 that compensates for beam diameter fluctuations of amplified pulsed light L1 emitted from 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 acquired data on the beam diameter fluctuations of the pulsed amplified light L1 for various pairs of repetition frequencies as learning data, thereby generating a trained model for inferring the drive pattern of the drive device 41, and the trained model may be used to infer the drive pattern of the drive device 41. The inferred drive pattern of the drive device 41 is stored in the control unit 20. The above-described 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 drive device 41, it is possible to improve the accuracy of the drive pattern of the drive device 41 to keep the fluctuation range of the beam diameter of the pulsed amplified light L1 constant after changing the repetition frequency of the pulsed light, and by applying machine learning to determine the drive pattern of the drive device 41, it is possible to predict the drive pattern of the drive device 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 remains constant after the repetition frequency of pulsed light is changed. 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 determined in the same manner as for 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 components of the beam diameter of the pulsed amplified light L1 irradiated onto the mask 50 that have a long time constant by moving the optical elements of the beam propagation adjustment unit 40 using the drive device 41 based on the drive pattern of the drive device 41 that corresponds to the pair of repetition frequencies, thereby maintaining a constant transmittance of the pulsed amplified light L1 through the mask 50.

[0118] Control unit 20 compensates for components with short time constants in the beam diameter of pulsed amplified light L1 irradiated onto mask 50 by moving the optical elements of beam propagation adjustment unit 40 using drive unit 41 based on the drive pattern of drive unit 41 corresponding to the 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 remains constant before and after changing the repetition frequency, and keeps the transmittance of pulsed amplified light L1 through mask 50 constant before and after changing the repetition frequency.

[0119] In addition, a beam diameter monitor 92 that measures the beam diameter of the pulsed amplified light L1 may be placed 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 that uses an image sensor such as a charge coupled device (CCD) sensor or 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] 6 is a diagram schematically illustrating 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 adjusting 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 pulsed amplified light L1 that has passed through beam propagation adjustment unit 40 passes through folding mirror 93a and enters beam diameter monitor 92. Beam diameter monitor 92 receives pulsed amplified light L1 that has passed through folding mirror 93a and measures the beam diameter of pulsed amplified light L1.

[0124] The remainder of the amplified pulsed light L 1 that has passed 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, based on the drive pattern of drive device 41 corresponding to the pair of repetition frequencies, control unit 20 compensates for components with short time constants of pulsed amplified light L1 emitted from optical switching element 30 so that the beam diameter of pulsed amplified light L1 remains constant before and after changing the repetition frequency of the pulsed light. Furthermore, based on the drive pattern of drive device 41 corresponding to the pair of repetition frequencies, control unit 20 compensates for components with long time constants of pulsed amplified light L1 emitted from optical switching element 30 so that the beam diameter of pulsed amplified light L1 remains constant after changing the repetition frequency of the pulsed light.

[0126] As a result, the laser processing apparatus 1 controls the beam diameter of the pulsed amplified light L1 on the mask 50 to be 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 changing the repetition frequency, and can stabilize the intensity distribution of the pulsed amplified light L1 on the mask 50 before and after changing the repetition frequency.

[0128] Furthermore, to stabilize the processing quality, it is effective for the driver 41 to move the beam propagation adjuster 40 so that the state of the wavefront of the pulsed amplified light L1 on the mask 50 does not change before and after changing the repetition frequency, i.e., so that the divergence or convergence 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 divergence or convergence state. Because the taper angle is an important evaluation item that determines the processing quality, it is preferable that it be constant regardless of the repetition frequency of the pulsed light.

[0129] Therefore, the laser processing apparatus 1 can stabilize processing quality by controlling the position of the beam propagation adjustment unit 40 so that the state of the wavefront 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 state of the wavefront 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 a transmittance modulation pattern to be set when modulating the transmittance of the optical switching element 30 to compensate for the change over time in the average output power that occurred after changing the repetition frequency of the pulsed light in the experiment whose experimental results are shown in FIG. 3 . The horizontal axis of FIG. 7 represents time. On the horizontal axis of FIG. 7 , the time when the repetition frequency was changed is set to 0 minutes. The left axis of FIG. 7 represents the optical switching element transmittance (%) of the transmittance modulation pattern. The right axis of FIG. 7 represents the average output power (%) 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 power (%) of the pulsed amplified light L1 after passing through the optical switching element, the value at the time when the repetition frequency was changed is set to 100%.

[0131] 7 shows that modulating the transmittance of optical switching element 30 based on the transmittance modulation pattern reduces fluctuations in the average output (%) of pulsed amplified light L1 after passing through the optical switching element compared to the case of FIG. 3. That is, when the average output or pulse energy of pulsed amplified light L1 output from laser oscillator 10 changes over time due to a change in repetition frequency, it is possible to maintain the average output approximately constant by modulating the transmittance of optical switching element 30. Here, it is assumed that the change over time in the beam diameter of pulsed amplified light L1 that occurs after a change in repetition frequency is compensated for by beam propagation adjustment unit 40.

[0132] According to the laser device 100 of the first embodiment described above, 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 fluctuations over time in 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 adjusting 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 fluctuations over time in 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 occur as the repetition frequency of the pulsed laser light is changed, remain within a predetermined range. This allows the laser processing apparatus 1 to 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 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 processing quality by manipulating at least one of the beam diameter and wavefront of the pulsed amplified light L1 on the mask 50 by moving the optical elements that make up the beam propagation adjustment unit 40.

[0135] Therefore, the laser apparatus 100 and laser processing apparatus 1 according to the first embodiment have the advantage of being able to suppress fluctuations over time in the output characteristics and 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 apparatus 1 also has the advantage of being able to suppress fluctuations over time in the average output, pulse energy, beam diameter, and beam shape at the processing point that occur after changing the repetition frequency of the pulsed light. The laser processing apparatus 1 can stabilize processing quality immediately after changing the repetition frequency of the pulsed light output from the seed light source 11, thereby improving processing productivity.

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

[0137] Each workpiece material has its own processing threshold for the irradiated laser light, and stable laser processing requires irradiation with laser light having properties such as energy that exceed the processing threshold. The processing threshold is the minimum characteristic value of the laser light at which decomposition of the workpiece begins when irradiated with the laser light. 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 workpiece 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 drilling holes with a pulsed laser beam, efficient drilling can be achieved by drilling the small-diameter portion with a relatively small hole diameter at a high repetition frequency, and drilling the large-diameter portion with a relatively large hole diameter at a low repetition frequency.

[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 relatively small diameters, and by using a mask with a relatively large opening diameter when processing holes with relatively large diameters.

[0142] 8 is a block diagram schematically illustrating an example of the configuration of a laser processing apparatus including a laser apparatus 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 it includes a laser apparatus 110 instead of the laser apparatus 100. The laser apparatus 110 differs from the laser processing apparatus 1 according to embodiment 1 in that it includes a mask 51 instead of the mask 50, a control unit 21 instead of the control unit 20, and 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. The mask 51 has a plurality of openings with different diameters, which are opening regions, 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] The mask 51 has a plurality of circular openings 51a formed on concentric circles centered on a circular center C of the mask 51 in the in-plane direction of the mask 51. That is, the mask 51 has a plurality of circular openings 51a formed on a virtual circle V that is concentric with the circle of the mask 51.

[0145] The mask 51 may also be configured such that an opening part 51b made of a transparent material that transmits the amplified pulsed light L1 is fitted into and fixed to the opening 51a.

[0146] Mask changer 52 changes opening 51a through which pulsed amplified light L1 passes by rotating mask 50 about an axis that passes through center C of the circle of mask 51 and is perpendicular to the in-plane direction of mask 51. Mask changer 52 changes the position of opening 51a through which pulsed amplified light L1 passes by changing the position of opening 51a so that optical axis La of pulsed amplified light L1 passes through opening 51a. Driving of mask changer 52 is controlled by control unit 21.

[0147] In the mask transfer optical system 70, the processing-point beam diameter, which is the beam diameter of the laser light at the processing point, is determined by the opening diameter of the opening 51 a in the mask 50 and the transfer magnification. The laser device 110 can change the processing-point beam diameter corresponding to the hole diameter to be processed by changing the opening 51 a through which the pulsed amplified light L1 passes using the mask changer 52. In addition, the laser device 110 utilizes 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 corresponding to 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 small-diameter portions, which require relatively low energy, at high speed using a relatively high repetition frequency. Furthermore, when performing hole drilling using the pulsed amplified light L1, the laser device 110 can process large-diameter portions, which require relatively high energy, at low speed using a relatively low repetition frequency. As a result, the laser device 110 can efficiently process multiple types of holes with different diameters.

[0149] The control unit 21 has the 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 embodiment 2. Here, a case will be described in which the laser processing apparatus 2 drills a hole of diameter a with the repetition frequency of pulsed light set to repetition frequency A, and then changes the repetition frequency of pulsed light to repetition frequency B to drill a hole of diameter b, which is different from 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 pulsed light set to repetition frequency A. After drilling of the hole diameter a is completed, irradiation of the workpiece W with the amplified pulsed light L1 from the laser device 110 is temporarily stopped. Note that if the laser oscillator 10 is stopped and then driven again, it takes time for stable amplified pulsed light L1 to be obtained. For this reason, even when irradiation of the amplified pulsed light L1 from the laser device 110 to the workpiece W is temporarily stopped, generation of the amplified pulsed light L1 within the laser device 110 continues.

[0152] Examples of methods for stopping the irradiation of the workpiece W with the amplified pulsed light L1 include using a beam on / off function provided in the laser device 110 itself, or 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 on and off of the output of the amplified pulsed light L1 from the laser device 110. Then, the process proceeds to step S120.

[0153] In step S120, in order to perform drilling of 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 51 a of the mask 51 in accordance with 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 51 a of the mask 51 when drilling a hole with a hole diameter b using amplified pulsed light L1 with a repetition frequency B. Based on this information, the control unit 21 determines whether or not it is necessary to change the opening 51 a of the mask 51 in accordance with the change in the repetition frequency of the pulsed light.

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

[0156] In step S140, the opening 51 a of the mask 51 is changed. Specifically, the mask changer 52 changes the opening 51 a that transmits the pulsed amplified light L1 under the control of the control unit 21. The control unit 21 stores in advance information about the opening 51 a 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 51 a to use based on this information. Then, the process proceeds to step S150.

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

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

[0159] In step S160, at least one of the wavefront and beam diameter of pulsed amplified light L1 on mask 51 is changed. Specifically, drive device 41 changes at least one of the wavefront and beam diameter of pulsed amplified light L1 on mask 51 by moving the optical elements of beam propagation adjustment unit 40 in accordance with the control of control unit 21. Control unit 21 stores in advance information about the positions of the optical elements of beam propagation adjustment unit 40 to be used when drilling a hole with hole diameter b using pulsed amplified light L1 with repetition frequency B. Control unit 21 instructs drive device 41 on the positions of the optical elements of beam propagation adjustment unit 40 to be used based on this 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, the output of the amplified pulsed light L1 from the laser device 110 is started, and the amplified pulsed light L1 with the repetition frequency B is used to drill a hole having a diameter b.

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

[0163] Although the above description has been given of the case where the laser processing apparatus 2 continuously performs drilling of hole diameter a and drilling of hole diameter b, it is also possible to continuously perform drilling of different hole diameters by changing the processing conditions in a similar manner to that described above when drilling three or more different hole diameters. For example, after drilling hole diameter b as described above, the repetition frequency of the pulsed light can be changed to repetition frequency C to drill hole diameter c, which is a hole diameter different from hole diameters a and c. In this case, after drilling hole diameter b in step S180, the process returns to step S120. In the second round of steps S120 to S170, the processing conditions are changed to accommodate drilling of hole diameter c in a similar manner to that described above, and drilling of hole diameter c is performed in the second round of step S180.

[0164] The laser processing apparatus 2 according to the second embodiment described above includes a mask 51 having a plurality of openings 51a that are transmissive to the pulsed amplified light L1 and have different shapes or dimensions. The laser processing apparatus 2 can change the processing point beam diameter corresponding to the desired hole diameter by changing the openings 51a that transmit the pulsed amplified light L1 using a mask changer 52. This allows the laser device 110 to efficiently process holes with a small diameter using a high repetition frequency and a large diameter using a low repetition frequency when drilling holes with the pulsed amplified light L1. Therefore, the laser processing apparatus 2 can efficiently process holes with a plurality of different diameters when drilling holes with 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 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 thereof. Figure 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. The processing circuit 201 incorporates a logic circuit 201a that realizes the functions of the control unit 200.

[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 illustrating a configuration in which the functions of the control unit according to the first and second embodiments are implemented by software. The processing circuit 201 includes 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 loads the program 201b stored in the storage device 204 onto the random access memory 203 and executes it, thereby realizing the functions of the control unit 200. The software or firmware is written in a programming language and stored in the storage device 204. The processor 202 may be, but is not limited to, a central processing unit. The storage device 204 may 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). The semiconductor memory may be either a non-volatile memory or a volatile memory. In addition to semiconductor memory, storage device 204 may be a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc). Processor 202 may output data such as calculation results to storage device 204 for storage, or may store the data in an auxiliary storage device (not shown) via random access memory 203. By integrating processor 202, random access memory 203, and storage device 204 on a single chip, the functions of control unit 200 can be realized by a microcomputer.

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

[0170] The processing circuit 201 may be configured to implement some of the functions of the control unit 200 using dedicated hardware and some of the functions of the control unit 200 using software or firmware.

[0171] In this way, 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 different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0173] 1, 2 laser processing apparatus, 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 pulsed light output from seed light source, L1 Pulsed amplified light, La: optical axis, V: virtual circle, W: workpiece.

Claims

1. A laser device comprising: 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 modulates transmittance so that fluctuations over time in 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 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.

2. The laser device according to claim 1, further comprising a drive device that moves the optical elements constituting the beam propagation adjustment unit in the optical axis direction of the pulsed laser light emitted from the optical switching element.

3. The laser device according to claim 2, wherein the driving device moves the optical element so as to adjust the 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 has been changed.

4. The laser device according to claim 2 or 3, characterized in that the driving device moves the optical element so that the divergence state or the convergence state of the wavefront 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 does not change before and after the repetition frequency of the pulsed laser light.

5. A laser device according to any one of claims 1 to 4, further comprising a sensor that measures the pulse energy of the pulsed laser light emitted from the amplifier after passing through the mask, and the transmittance of the optical switching element is modulated based on the measurement result of the sensor.

6. A laser device according to any one of claims 1 to 5, characterized in that the mask has a plurality of transmission areas that are different in shape or size and that can transmit the pulsed laser light, and the transmission areas that transmit the pulsed laser light emitted from the amplifier can be changed.

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

Images