Laser processing device
By selectively reflecting the laser pulse beam with a galvanometer module in the laser processing device, an energy-stable beam is formed, and the problem of insufficient energy during startup of the pulsed laser is solved, which improves the stability and diversity of the process and reduces the cost.
Patent Information
- Application Number
- CN202311107005.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-30
- Publication Date
- 2025-02-28
AI Technical Summary
When the commercially available pulse laser is started, some pulse energy is insufficient, resulting in unstable process and cannot meet some processing needs that require single-shot and sufficient pulse energy.
By selectively reflecting the laser pulse beam in the first mode or the second mode, a first and second beams of different directions are formed by selectively reflecting the first and second beams of different directions, ensuring that the energy stable second beam is focused on the processing stage.
It effectively improves the stability and diversity of the process, avoids unstable effects caused by insufficient energy, and reduces the cost of the device.
Smart Images
Figure CN119525699A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a processing device, in particular to a laser processing device. Background Art
[0002] Some pulse lasers on the market have the problem of insufficient energy in the first few pulses when they are first started in terms of controlling the light output. Therefore, when some processes require a single pulse with sufficient energy for processing, such pulse lasers cannot be used. If such pulse lasers are still used for the process, the insufficient energy laser pulses may produce unexpected effects on the processed components, causing process instability.
[0003] That is to say, at the moment when the pulse laser is just started, the power of some pulses will be different from the target power (generally lower than the target power). The insufficient power pulses will have unstable and unpredictable adverse effects on the process results.
[0004] One existing technology is to add an optoelectronic modulator to the outlet of the laser device to selectively allow pulses to pass through based on the time of the gate switch. When the pulse laser has not yet reached the rated power of the stable state, the gate will be blocked, and the gate will not be opened until the pulse laser reaches the rated power. However, the optoelectronic modulator is expensive and difficult to be installed in mass production machines on a large scale. Summary of the invention
[0005] The present invention is directed to a laser processing device, which can improve the stability or diversity of the process.
[0006] One embodiment of the present invention provides a laser processing device, including a laser unit, a galvanometer module, a focusing module, a shield and a processing platform. The laser unit is used to emit a laser pulse beam. The galvanometer module is arranged on the path of the laser pulse beam to reflect the laser pulse beam, and has a first mode and a second mode, and is used to selectively reflect the laser pulse beam into a first beam in the first mode, or reflect the laser pulse beam into a second beam in the second mode, and the first beam and the second beam have different directions. The focusing module receives the second beam reflected by the galvanometer module in the second mode and focuses it at a focus. The shield is arranged between the galvanometer module and the focusing module, and has an aperture for at least part of the second beam to pass through. The processing platform is arranged at the focal position to carry a processing element, wherein the processing element receives the irradiation of the second beam.
[0007] One embodiment of the present invention provides a laser processing device, including a laser unit, a galvanometer module, a focusing module and a processing stage. The laser unit is used to emit a laser pulse beam, wherein the laser pulse beam includes a first laser pulse beam and a second laser pulse beam, and the energy of the first laser pulse beam is less than the energy of the second laser pulse beam. The galvanometer module is arranged on the path of the laser pulse beam to reflect the laser pulse beam, and has a first mode and a second mode, and is used to selectively reflect the first laser pulse beam into a first beam in the first mode, or reflect the second laser pulse beam into a second beam in the second mode. The first beam and the second beam have different emission directions. The focusing module receives the second beam reflected by the galvanometer module in the second mode, and focuses it at a focal point. The processing stage is arranged at a focal position to carry a processing element, wherein the processing element receives irradiation of the second beam.
[0008] In the laser processing device of the embodiment of the present invention, since the galvanometer module is used to selectively reflect the laser pulse beam into the first beam in the first mode, or reflect the laser pulse beam into the second beam in the second mode, the second beam with stable energy can be reflected to the focusing module for focusing, thereby effectively improving the stability of the process. Alternatively, the laser processing device of the embodiment of the present invention can make the first beam and the second beam form different process conditions to improve the diversity of the process. BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Figure 1 A schematic diagram of an optical path of a laser processing device according to an embodiment of the present invention;
[0010] Figure 2 for Figure 1 The energy variation diagram of the laser pulse beam emitted by the laser unit over time;
[0011] Figure 3 In another application Figure 1 The energy variation diagram of the laser pulse beam emitted by the laser unit over time;
[0012] Figure 4 A schematic diagram of an optical path of a laser processing device according to another embodiment of the present invention;
[0013] Figure 5 A schematic diagram of an optical path of a laser processing device according to another embodiment of the present invention;
[0014] Fig. 6A A schematic diagram of the optical path of a second light beam of a laser processing device according to another embodiment of the present invention;
[0015] Figure 6B for Fig. 6A A schematic diagram of a local optical path of a first light beam of a laser processing device;
[0016] Figure 7 A schematic diagram showing a variation of an embodiment of aperture reduction;
[0017] Fig. 8A A schematic diagram of the optical path of a second light beam of a laser processing device according to another embodiment of the present invention;
[0018] Figure 8B for Fig. 8A A distribution curve diagram of normalized light intensity of a laser pulse beam relative to a position on a cross section in a laser processing device;
[0019] Fig.9A for Fig. 8A A local optical path diagram of a second light beam reflected by the galvanometer module in a second mode;
[0020] Fig. 9B for Fig. 8A A local optical path diagram of a first light beam reflected by a galvanometer module in a first mode;
[0021] Fig.10 A schematic diagram of an optical path of a laser processing device according to another embodiment of the present invention;
[0022] Fig.11A , Fig. 11B and Fig. 11C for Fig.10 Schematic diagram of the local optical path cross-section of the first light beam in other three variant embodiments of the laser processing device. DETAILED DESCRIPTION
[0023] Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals are used in the drawings and the description to refer to the same or like parts.
[0024] Figure 1 is a schematic diagram of an optical path of a laser processing device according to an embodiment of the present invention, and Figure 2 for Figure 1 The energy variation of the laser pulse beam emitted by the laser unit over time. Figure 1 and Figure 2The laser processing device 100 of the present embodiment includes a laser unit 110, a galvanometer module 120, a focusing module 130, a shield 140 and a processing stage 150. The laser unit 110 is used to emit a laser pulse beam 111. In the present embodiment, the laser unit 110 is, for example, a laser source, which can emit visible light laser, infrared laser, ultraviolet laser or laser of other wavelengths. The galvanometer module 120 is disposed on the path of the laser pulse beam 111 to reflect the laser pulse beam 111, and has a first mode and a second mode, and is used to selectively reflect the laser pulse beam 111 in the first mode to become a first beam 112, or reflect the laser pulse beam 111 in the second mode to become a second beam 114, and the first beam 112 and the second beam 114 have different emission directions. For example, the galvanometer module 120 is at different rotation angles in the first mode and the second mode. For example, the galvanometer module 120 rotates the galvanometer 122 to the first position P1 in the first mode, and rotates the galvanometer 122 to the second position P2 in the second mode.
[0025] The focusing module 130 receives the second light beam 114 reflected by the galvanometer module 120 in the second mode, and focuses it on the focus F1. In the present embodiment, the focusing module 130 is, for example, at least one lens, such as a convex lens. The shield 140 is disposed between the galvanometer module 120 and the focusing module 130, and has an aperture 142 for at least part of the second light beam 114 to pass through. In the present embodiment, the first light beam 112 is irradiated on the shield 140, and the shield 140 can block the first light beam 112, so that the first light beam 112 cannot be transmitted to the focusing module 130 and the processing element 50. In one embodiment, the shield 140 can be a light absorber for absorbing the first light beam 112 or part of the second light beam 114.
[0026] The processing stage 150 is disposed at the focal point F1 to carry the processing element 50, wherein the processing element 50 receives the irradiation of the second light beam 114. The processing element 50 may include a light emitting diode, a micro light emitting diode, other electronic components or other components to be processed.
[0027] In this embodiment, the laser pulse beam 111 emitted by the laser unit 110 includes a first laser pulse beam 111a and a second laser pulse beam 111b (eg, Figure 2). Specifically, the laser unit 110 requires a period of time T1 for warming up. The first few laser pulse beams 111 emitted in the time T1 when just started are the first laser pulse beams 111a, and the energy of the first laser pulse beam 111a is relatively unstable. In the time T2 after the time T1, the laser pulse beam 111 emitted by the laser unit 110 is the second laser pulse beam 111b, and the energy of the second laser pulse beam 111b has stabilized and reached the rated output power. In this embodiment, the energy of the first laser pulse beam 111a emitted in the time T1 is less than the energy of the second laser pulse beam 111b, and the first laser pulse beam 111a is reflected by the galvanometer module 120 in the first mode to form the first beam 112, and the second laser pulse beam 111b is reflected by the galvanometer module 120 in the second mode to form the second beam 114. Therefore, in this embodiment, the first light beam 112 with less stable energy or insufficient output power will not irradiate the processing element 50, but the second light beam 114 with stable energy will irradiate the processing element 50. Therefore, the laser processing device of this embodiment can effectively improve the stability of the process.
[0028] In addition, in the laser processing device of the present embodiment, a galvanometer module 120 is used to replace the expensive photoelectric modulator to screen out the first light beam 112 with unstable energy and the second light beam 114 with stable energy. The cost of the galvanometer module 120 is lower than that of the photoelectric modulator, which can effectively reduce the cost of the electro-jet processing device, and therefore can also be set up in a mass production machine on a large scale. In one embodiment, the galvanometer module 120 is a mirror galvanometer. The principle of the mirror galvanometer is to use the different reflection angles or positions of light to judge the magnitude of the current passing through the mirror galvanometer. In the present embodiment, the reverse operation is adopted, that is, by applying currents of different magnitudes to the mirror galvanometer, the rotation angle of the galvanometer 122 is changed, thereby changing the reflection angle of the light. The cost of the mirror galvanometer is lower than that of the photoelectric modulator.
[0029] Figure 3 In another application Figure 1The energy variation diagram of the laser pulse beam 111 emitted by the laser unit over time. In one embodiment, the laser pulse beam 111 emitted by the laser unit 110 includes a plurality of laser pulse beams having a first frequency, and the galvanometer module 120 switches between the first mode and the second mode at a second frequency. In one embodiment, the second frequency is less than the first frequency, and the second mode overlaps with the timing of at least one of the laser pulse beams 111 having the first frequency. For example, the period of the laser pulse beam 111 emitted by the laser unit 110 is R1, and the first frequency is the reciprocal of R1. The galvanometer module 120 switches from the first mode to the second mode every time a period R2 passes, and the second frequency is the reciprocal of R2. Since the processing element 50 receives the second beam 114 every time a period R2 passes, it is equivalent to that the pulse repetition frequency of the laser pulse beam 111 drops from the first frequency to the second frequency, so that the effect of frequency reduction or frequency division can be achieved.
[0030] Figure 4 This is a schematic diagram of the optical path of a laser processing device according to another embodiment of the present invention. Figure 4 The laser processing device 100a of this embodiment is similar to Figure 1 The laser processing device 100a of this embodiment does not have the following features: Figure 1 , and in this embodiment, the first light beam 112 reflected by the galvanometer module 120 in the first mode deviates from the focusing module 130 and will not be transmitted to the processing element 50. In this embodiment, the laser processing device 100a further includes a light absorber 160, which is disposed on the light path of the first light beam 112. In some embodiments, the focusing module 130 further has a front focus F0 located on a side close to the galvanometer module 120, wherein the front focus F0 and the focus F1 are two conjugate focuses, and the front focus F0 coincides with the intersection point of the laser pulse beam 111 and the galvanometer module 120, wherein when the galvanometer module 120 switches between the first mode and the second mode, the galvanometer 122 will rotate around the aforementioned intersection point as the axis, so that even if the angular positioning of the galvanometer module 120 in the second mode has an error, the second light beam 114 starting from the front focus F0 will still return to the focus F1 after the converging effect of the focusing module 130, thereby reducing the influence of the process tolerance.
[0031] Figure 5 This is a schematic diagram of the optical path of a laser processing device according to another embodiment of the present invention. Figure 5 The laser processing device 100b of this embodiment is similar to Figure 4The laser processing device 100a of the present embodiment is described below. In the laser processing device 100b of the present embodiment, the galvanometer module 120 makes the first light beam 112 incident on the focusing module 130 at an angle different from the angle at which the second light beam 114 is incident on the focusing module 130 in the second mode, and the galvanometer module 120 is used to switch between the first mode and the second mode to change the position of the focus on the focusing plane. For example, the focusing module 130 receives the second light beam 114 incident in the forward direction, and generates a focus F1 on the processing element 50. On the other hand, the focusing module 130 receives the first light beam 112 incident in the oblique direction, and generates a focus F2 on the processing element 50, and the position of the focus F2 is different from the position of the focus F1. In this way, by switching the galvanometer module 120, different positions of the processing element 50 can be processed. In other words, the laser processing device 100b of the present embodiment can make the first light beam 112 and the second light beam 114 form different process conditions to enhance the diversity of the process.
[0032] Fig. 6A FIG. 1 is a schematic diagram of an optical path of a second light beam of a laser processing device according to another embodiment of the present invention. Figure 6B for Fig. 6A Schematic diagram of the local optical path of the first beam of the laser processing device. Please refer to Fig. 6A and Figure 6B The laser processing device 100c of this embodiment is Figure 1 The laser processing device 100c of the present embodiment is similar to the laser processing device 100, and the main differences between the two are as follows. In the laser processing device 100c of the present embodiment, the galvanometer module 120 in the second mode reflects the second light beam 114 to the center of the aperture 142, so most or all of the second light beam 114 can pass through the aperture 142 without being blocked by the shield 140, so the laser energy irradiated on the processing element 50 at this time is relatively high. On the other hand, the galvanometer module 120 in the first mode reflects the first light beam 112 to the edge of the aperture 142, so a part of the first light beam 112 will be blocked by the shield 140 and cannot be transmitted to the processing element 50, while another part of the first light beam 112 will pass through the aperture 142 and be transmitted to the processing element 50, so the laser energy irradiated on the processing element 50 at this time is relatively low. By switching the galvanometer module 120 between the first mode and the second mode, the laser processing device 100c of the present embodiment can adjust the laser energy irradiated on the processing element 50. In another embodiment, as Figure 7As shown, the aperture 142 of the shield 140 can also be reduced to an aperture 142'. The size of the aperture 142' is smaller than the aperture 142, and the aperture 142' only allows a portion of the second light beam 114 (or the first light beam 112) to pass through, while the remaining portion of the second light beam 114 (or the first light beam 112) will be blocked by the shield 140 around the aperture 142'. In this way, the laser energy irradiated on the processing element 50 can also be adjusted.
[0033] Fig. 8A FIG. 1 is a schematic diagram of an optical path of a second light beam 114 of a laser processing device 110 according to another embodiment of the present invention. Figure 8B for Fig. 8A A distribution curve diagram of the normalized light intensity of the laser pulse beam 111 in the laser processing device 110 relative to the position on the cross section, Fig.9A for Fig. 8A The local optical path diagram of the second light beam 114 reflected by the galvanometer module 120 in the second mode, and Fig. 9B for Fig. 8A The local optical path diagram of the first light beam 112 reflected by the galvanometer module 120 in the first mode. Fig. 8A , Figure 8B , Fig.9A and Fig. 9B The laser processing device 100d of this embodiment is Figure 1 The laser processing device 100d of the present embodiment is similar to the laser processing device 100, and the main differences between the two are as follows. In the laser processing device 100d of the present embodiment, the cross-sectional energy of the laser pulse beam 111 is non-uniformly distributed, for example, a Gaussian distribution (such as Figure 8B As shown), the cross-sectional area of the laser pulse beam 111 is larger than the cross-sectional area of the aperture 142. Figure 8B In the figure, position 0 is the central axis of the light beam 111, and positions to the left or right of position 0 are different radial positions of the cross section of the laser pulse light beam 111, that is, positions at different distances from the central axis.
[0034] Modulated by the galvanometer module 120, the cross section of the first light beam 112 or the second light beam 114 partially or completely overlaps with the aperture 142. In this embodiment, the energy density of the portion of the first light beam 112 passing through the aperture 142 in the first mode of the galvanometer module 120 is different from the energy density of the portion of the second light beam 114 passing through the aperture in the second mode, and the galvanometer module 120 is used to switch between the first mode and the second mode to change the energy of the laser pulse beam 111 passing through the focusing module 130. In this embodiment, the focusing module 130 also has a front focus F0 located on a side close to the galvanometer module 120, wherein the front focus F0 and the focus F1 are two conjugate focuses, and the aperture 142 is set at the front focus F0. That is, the distance between the aperture 142 and the focusing module 130 is d1, and the distance between the processing element 50 and the focusing module 130 is d2. In this way, even if the first light beam 112 is directed toward the aperture 142 at an inclined angle, the first light beam 112 starting from the front focus F0 will still return to the focus F1 after the converging effect of the focusing module 130. In other words, both the first light beam 112 and the second light beam 114 will be converged to the focus F1. However, since the cross-sectional energy of the laser pulse beam 111 is non-uniformly distributed, such as a Gaussian distribution, the first light beam 112 generated by the modulation of the galvanometer module 120 passes through the aperture 142 at a portion with a weaker energy density near the edge, while the second light beam 114 passes through the aperture 142 at a portion with a stronger energy density located in the center. Therefore, the first light beam 112 provides lower energy to the focus F1, while the second light beam 114 provides higher energy to the focus F1. Therefore, by switching the galvanometer module 120 between the first mode and the second mode, the laser processing device 100d of this embodiment can adjust the light energy received by the processing element 50 while ensuring that the position of the focus F1 remains unchanged. During laser processing, when processing multiple processing elements 50 on the processing platform 150 in sequence, there is no need to repeatedly align or aim due to adjusting the energy.
[0035] Fig.10 This is a schematic diagram of the optical path of a laser processing device according to another embodiment of the present invention. Fig.10 The laser processing device 100e of this embodiment is similar to Figure 1 The laser processing device 100 is similar to Figure 4 The main difference is that the laser processing device 100e of this embodiment also has Figure 1 Shielding 140 and Figure 4 In the first mode, the galvanometer module 120 reflects the first light beam 112 to the light absorber 160 .
[0036] Fig.11A , Fig. 11B and Fig. 11C for Fig.10Schematic diagram of the partial optical path cross section of the first light beam of the other three variant embodiments of the laser processing device. Fig.11A In this embodiment, the shield 140f is a curved reflector, which changes the reflection angle of the first light beam 112 or a portion of the second light beam 114, and the light absorber 160 is disposed on the path of the light (such as the first light beam 112 or a portion of the second light beam 114) reflected by the curved reflector. Fig.11A In the example, the curved reflector is a convex mirror, while in Fig. 11C In the example, shield 140h is a concave mirror. Fig. 11B , the shield 140g is a plane mirror. The shield 140g and the shield 140h can both reflect the first light beam 112 or a portion of the second light beam 114 to the light absorber 160. The shields 140f, 140g and 140h use reflectors in order to avoid temperature changes caused by absorbing light energy and changes in the shape or size of the aperture 142 caused by temperature changes, thereby effectively improving the accuracy and stability of the process.
[0037] In summary, in the laser processing device of the embodiment of the present invention, since the galvanometer module is used to selectively reflect the laser pulse beam into the first beam in the first mode, or reflect the laser pulse beam into the second beam in the second mode, the second beam with stable energy can be reflected to the focusing module for focusing, thereby effectively improving the stability of the process. Alternatively, the laser processing device of the embodiment of the present invention can make the first beam and the second beam form different process conditions to improve the diversity of the process.
[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A laser processing device, characterized in that: include: A laser unit, for emitting a laser pulse beam; a galvanometer module, disposed on the path of the laser pulse beam, for reflecting the laser pulse beam, and having a first mode and a second mode, for selectively reflecting the laser pulse beam into a first beam in the first mode, or reflecting the laser pulse beam into a second beam in the second mode, wherein the first beam and the second beam have different projection directions; A focusing module receives the second light beam reflected by the galvanometer module in the second mode and focuses the second light beam at a focal point; a shield, disposed between the galvanometer module and the focusing module, and having an aperture for at least a portion of the second light beam to pass through; and The processing stage is arranged at the focal position and is used to carry a processing element, wherein the processing element receives the irradiation of the second light beam.
2. The laser processing device according to claim 1, characterized in that: The laser pulse beam emitted by the laser unit includes a first laser pulse beam and a second laser pulse beam, wherein the energy of the first laser pulse beam is less than the energy of the second laser pulse beam, and the first laser pulse beam is reflected by the galvanometer module in the first mode, and the second laser pulse beam is reflected by the galvanometer module in the second mode.
3. The laser processing device according to claim 1, characterized in that: The laser pulse beam emitted by the laser unit includes a plurality of laser pulse beams with a first frequency, and the galvanometer module switches between the first mode and the second mode at a second frequency.
4. The laser processing device according to claim 3, characterized in that: The second frequency is less than the first frequency, and the second mode overlaps with the timing of at least one of the plurality of laser pulse beams having the first frequency.
5. The laser processing device according to claim 1, characterized in that: The galvanometer module causes the first light beam to enter the focusing module at an angle different from the angle at which the second light beam enters the focusing module in the second mode in the first mode, and the galvanometer module is used to switch between the first mode and the second mode to change the position of the focus on the focusing plane.
6. The laser processing device according to claim 1, characterized in that: The cross-sectional energy of the laser pulse beam is non-uniformly distributed, and the cross-sectional area of the laser pulse beam is larger than the cross-sectional area of the aperture. The energy density of the portion of the first beam passing through the aperture in the first mode by the galvanometer module is different from the energy density of the portion of the second beam passing through the aperture in the second mode. The galvanometer module is used to switch between the first mode and the second mode to change the energy of the laser pulse beam passing through the focusing module.
7. The laser processing device according to claim 6, characterized in that: The focusing module further has a front focus located at a side close to the galvanometer module, wherein the front focus and the focus are two conjugate focuses, and the aperture is arranged at the front focus.
8. The laser processing device according to claim 1, characterized in that: It also includes a light absorber, which is arranged on the light path of the first light beam.
9. The laser processing device according to claim 1, characterized in that: The shield is a light absorber for absorbing the first light beam or a portion of the second light beam.
10. The laser processing device according to claim 1, characterized in that: The shield is a curved reflector, which changes the reflection angle of the first light beam or part of the second light beam, and the laser processing device also includes a light absorber, which is arranged on the path of the light reflected by the curved reflector.
11. A laser processing device, characterized in that: include: A laser unit, configured to emit a laser pulse beam, wherein the laser pulse beam comprises a first laser pulse beam and a second laser pulse beam, and the energy of the first laser pulse beam is less than the energy of the second laser pulse beam; a galvanometer module, disposed on the path of the laser pulse beam, for reflecting the laser pulse beam, and having a first mode and a second mode, for selectively reflecting the first laser pulse beam into a first beam in the first mode, or reflecting the second laser pulse beam into a second beam in the second mode, wherein the first beam and the second beam have different projection directions; a focusing module, receiving the second light beam reflected by the galvanometer module in the second mode, and focusing the second light beam at a focal point; and The processing stage is arranged at the focal position and is used to carry a processing element, wherein the processing element receives the irradiation of the second light beam.
12. The laser processing device according to claim 11, characterized in that: The laser pulse beam emitted by the laser unit includes a plurality of laser pulse beams with a first frequency, and the galvanometer module switches between the first mode and the second mode at a second frequency.
13. The laser processing device according to claim 12, characterized in that: The second frequency is less than the first frequency, and the second mode overlaps with the timing of at least one of the plurality of laser pulse beams having the first frequency.
14. The laser processing device according to claim 11, characterized in that: It also includes a light absorber, which is arranged on the light path of the first light beam.
15. The laser processing device according to claim 11, characterized in that: The galvanometer module causes the first light beam to enter the focusing module at an angle different from the angle at which the second light beam enters the focusing module in the second mode in the first mode, and the galvanometer module is used to switch between the first mode and the second mode to change the position of the focus on the focusing plane.
16. The laser processing device according to claim 11, characterized in that: The focusing module also has a front focus located on a side close to the galvanometer module, wherein the front focus and the focus are two conjugate focuses, and the front focus coincides with the intersection point of the laser pulse beam and the galvanometer module.