Micro-engraving machine

Abstract

This application discloses a miniature engraving machine, comprising a pumping system and an optical resonant cavity arranged in sequence. Pump light generated by the pumping system enters the optical resonant cavity to excite a pulsed laser, which oscillates within the cavity. The miniature engraving machine also includes a frequency conversion unit and a collimation scanning system. The frequency conversion unit includes a frequency-doubling crystal converter and a short-pass filter, with the short-pass filter positioned outside the optical resonant cavity. The collimation scanning system includes a collimation system, a scanning galvanometer, and a field mirror arranged in sequence. The frequency-doubling crystal converter is positioned either inside or outside the optical resonant cavity. The pulsed laser, after oscillating within the cavity, is converted into green pulsed light after passing through the frequency-doubling crystal converter and the short-pass filter. Through this method, this application solves the problems of large size, high cost, and complex internal structure inherent in existing dual-wavelength miniature engraving machines.

Description

Technical Field

[0001] This application relates to the field of laser marking technology, and in particular to a miniature engraving machine. Background Technology

[0002] A miniature engraving machine is a small engraving machine that utilizes laser marking technology. Laser marking technology is a new type of marking process that is non-contact, pollution-free, and damage-free. It integrates laser technology, computer technology, and mechatronics technology, and is currently one of the most widely used advanced manufacturing technologies for laser processing.

[0003] Laser marking works by using a high-energy-density laser to locally irradiate a workpiece, causing the surface material to vaporize or undergo a chemical reaction that changes color, thus leaving a permanent mark. However, the light source of most micro-engraving machines on the market is usually a single-wavelength laser. Different materials absorb different laser wavelengths differently, which means that most micro-engraving machines can only mark a single type of product and cannot meet the needs of marking multiple materials.

[0004] Existing technology (CN208696546U) proposes a dual-wavelength miniature marking machine using both fiber lasers and blue lasers as marking light sources for marking various materials. However, this miniature marking machine requires two lasers of different wavelengths, increasing its size and cost. Furthermore, the beams of the two lasers need to be collimated and focused collinearly onto the same point on the surface to be marked, making the structure complex and difficult to assemble and adjust. Therefore, with the research and development of civilian laser marking and engraving technology, there is an urgent need for a miniature engraving machine applicable to both infrared and blue light bands, suitable for civilian use, portable, and capable of marking various materials. Summary of the Invention

[0005] This application provides a miniature engraving machine to solve the problems of large size, high cost, and complex internal structure of existing dual-wavelength miniature engraving machines.

[0006] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a micro-engraving machine, including a pumping system and an optical resonant cavity arranged in sequence, wherein the pump light generated by the pumping system enters the optical resonant cavity to excite a pulsed laser, and the pulsed laser oscillates within the optical resonant cavity; the micro-engraving machine also includes a frequency conversion unit and a collimation scanning system; the frequency conversion unit includes a frequency doubling crystal converter and a short-pass filter, the short-pass filter being disposed outside the optical resonant cavity; the collimation scanning system includes a collimation system, a scanning galvanometer, and a field lens arranged in sequence; wherein the frequency doubling crystal converter is disposed inside or outside the optical resonant cavity, and the pulsed laser oscillating within the optical resonant cavity is converted into green pulsed light after sequentially passing through the frequency doubling crystal converter and the short-pass filter.

[0007] Optionally, the frequency doubling crystal inverter is an LBO nonlinear crystal inverter, a KTP nonlinear crystal inverter, a BiBO nonlinear crystal inverter, a PPLN nonlinear crystal inverter, or an MgO:PPLN nonlinear crystal inverter.

[0008] Optionally, the optical resonant cavity includes a laser output mirror; the frequency doubling crystal converter is an LBO nonlinear crystal converter, and the frequency doubling crystal converter is disposed inside the optical resonant cavity, and the laser output mirror is located between the frequency doubling crystal converter and the short-pass filter; the pulsed laser is output from the optical resonant cavity after passing through the frequency doubling crystal converter, and is filtered by the short-pass filter.

[0009] Optionally, the frequency doubling crystal inverter has dual-wavelength anti-reflection coatings for infrared pulse light and green pulse light on both the opposite sides facing and away from the laser output mirror.

[0010] Optionally, the optical resonant cavity includes a laser output mirror; the frequency doubling crystal frequency converter is a KTP nonlinear crystal frequency converter, and the frequency doubling crystal frequency converter is disposed outside the optical resonant cavity, and the frequency doubling crystal frequency converter is located between the laser output mirror and the short-wavelength pass filter; the pulsed laser is output from the optical resonant cavity and passes through the frequency doubling crystal frequency converter and the short-wavelength pass filter in sequence.

[0011] Optionally, the frequency doubling crystal inverter has an infrared pulse light anti-reflection film on the side facing the laser output mirror, and the frequency doubling crystal inverter has a green pulse light anti-reflection film on the side facing the short-wave pass filter.

[0012] Optionally, the short-pass filter is a plane mirror, with a multilayer dielectric film on the side of the short-pass filter facing the frequency doubling crystal inverter, and a green pulse light anti-reflection film on the side of the short-pass filter away from the frequency doubling crystal inverter.

[0013] Optionally, the optical resonant cavity includes a gain medium and a saturable absorber; the pump light enters the gain medium of the optical resonant cavity after passing through the laser input mirror to generate laser light; the gain medium is an Nd:YAG crystal, Nd:YVO4 crystal, Nd:GdVO4 crystal, Nd:YLF crystal, Yb:YAG crystal, or Nd:YAG ceramic, wherein the Nd:YAG crystal, Nd:YVO4 crystal, and Nd:YAG ceramic generate 1064nm laser light, the Nd:GdVO4 crystal generates 1063nm laser light, the Nd:YLF crystal generates 1047nm or 1053nm laser light, and the Yb:YAG crystal generates 1030nm or 1050nm laser light; the laser light generated by the gain medium is converted into pulsed laser light through the saturable absorption of the saturable absorber, which is a Cr4+:YAG crystal or a semiconductor saturable absorber.

[0014] Optionally, when the gain medium is an Nd:YAG crystal or a Yb:YAG crystal, and the saturable absorber is a Cr4+:YAG crystal, the gain medium and the saturable absorber can be bonded together.

[0015] Optionally, it also includes a collimation system, a scanning galvanometer, and a field lens arranged sequentially. The collimation system includes a concave mirror with a negative focal length and a convex mirror with a positive focal length arranged opposite each other. The scanning galvanometer includes an X-axis lens arranged in the X direction, a Y-axis lens arranged in the Y direction, and an electronic control system. The X-axis lens and the Y-axis lens are both connected to the electronic control system and can rotate in the X and Y directions respectively under the control of the electronic control system. The green pulse light passes through the collimation system and the scanning galvanometer sequentially to form a scanning image, and the scanning image is focused by the field lens and emitted.

[0016] This application discloses a miniature engraving machine equipped with a frequency conversion unit consisting of a frequency doubling crystal inverter and a short-pass filter. The frequency doubling crystal inverter converts infrared pulsed laser light generated by a laser into green pulsed light, while the short-pass filter filters the pulsed laser light, improving the purity of the green pulsed light. This green pulsed light then enters a collimation and scanning system for collimation, focusing, and scanning imaging, thus using green pulsed light with a wavelength between blue and infrared light as the marking light source. Because the wavelength of green pulsed light is between blue and infrared light and it also has high peak power, green pulsed light as a marking light source can handle both blue and infrared laser marking, making it suitable for more materials. This avoids the need for existing miniature engraving machines to simultaneously use both fiber optic infrared and blue lasers. Therefore, this application only requires one laser, and through the frequency conversion unit, green pulse light with a wavelength between infrared and blue light can be obtained as a marking light source, thereby meeting the needs of simultaneous application to products of various materials, greatly reducing the size of the micro engraving machine, reducing the cost of the micro engraving machine, and simplifying the structure of the micro engraving machine. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0018] Figure 1 This is a schematic diagram of the structure of one embodiment of the micro engraving machine of this application;

[0019] Figure 2 and Figure 1 Similarly, this application relates to a miniature engraving machine. Figure 1The embodiment uses a schematic diagram of the structure after crystal bonding;

[0020] Figure 3 This is a schematic diagram of another embodiment of the micro engraving machine of this application;

[0021] Figure 4 This is a schematic diagram showing the placement angle of the KTP nonlinear crystal frequency converter in the micro engraving machine of this application;

[0022] Figure 5 This is a schematic diagram of the collimation and scanning system of the miniature engraving machine of this application;

[0023] Figure 6 This is a schematic diagram of the structure of the scanning galvanometer in this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0025] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of one embodiment of the micro engraving machine 100 of this application.

[0028] This application provides a micro engraving machine 100, which includes a pumping system 10, an optical resonant cavity 20, a frequency conversion unit 30, and a collimation scanning system 40, wherein the pumping system 10 and the optical resonant cavity 20 are arranged sequentially.

[0029] The frequency conversion unit 30 includes a frequency doubling crystal inverter 31 and a short-pass filter 32. The short-pass filter 32 is disposed outside the optical resonant cavity 20, while the frequency doubling crystal inverter 31 is disposed inside or outside the optical resonant cavity 20. The pump light generated by the pump system 10 enters the gain medium 22 within the optical resonant cavity 20, exciting an infrared laser within the gain medium 22, which then propagates and oscillates within the optical resonant cavity 20. When the infrared light passes through the saturable absorber 23, it generates high-peak-power infrared pulse light. When the infrared pulse light passes through the frequency doubling crystal inverter 31, it undergoes frequency conversion and generates green pulse light. The frequency-converted green pulse light passes through the laser output mirror 24 and is output via the short-pass filter 32. This green pulse light then enters the collimation scanning system 40 for collimation, focusing, and scanning imaging operations, thereby enabling the micro-engraving machine 100 of this application to use this green pulse light as a marking light source for laser marking.

[0030] The frequency doubling crystal inverter 31 converts the oscillating infrared pulse light into green pulse light, while the short-pass filter 32 filters the output pulse laser to improve the purity of the frequency doubling pulse laser, thus making green pulse light, with a wavelength between blue and infrared light, the marking light source. Since the wavelength of green pulse light is between blue and infrared light, it can be used for laser marking of both blue and infrared wavelengths, making it suitable for more materials. This avoids the need for both infrared and blue wavelength lasers in existing micro-engraving machines 100. Therefore, this application only requires one laser, and a green pulse light with a wavelength between infrared and blue light can be obtained as the marking light source through a frequency conversion unit. This meets the needs of simultaneous application to products made of various materials, greatly reducing the size and cost of the micro-engraving machine 100 and simplifying its structure.

[0031] For example, the wavelength of infrared light can be 1064nm, the wavelength of blue light can be 450nm, and the wavelength of green pulse light can be 532nm, with wavelengths between infrared and blue light.

[0032] Specifically, the pumping system 10 includes a pump source 11 and a pump optical coupling device 12. The pump source 11 can be used to generate pump light, and the pump optical coupling device 12 can couple and focus the pump light into the gain medium 22. The pump source 11 and the pump optical coupling device 12 form a pumping system 10 for pulsed laser.

[0033] In one specific embodiment, for example, the pump source 11 can be an 808nm fiber-coupled semiconductor laser. This semiconductor laser has an output power of 30W, a fiber core diameter of 0.4mm, and a numerical aperture (NA) of 0.22. Alternatively, the pump source 11 can also be a fast-axis compressed c-mount or COS-packaged 808nm semiconductor laser with an output power of 10W and a stripe width of 0.2mm. Users can choose pump sources 11 with different output powers according to their actual needs; this application does not impose any limitations on this. The pump optical coupling device 12 can consist of two plano-convex mirrors with convex surfaces facing each other, each with a focal length of 10mm, or an aspherical lens with a focal length of 2mm. Users can also choose pump optical coupling devices 12 with different focal lengths according to their actual needs; this application does not impose any specific limitations on this.

[0034] Specifically, the optical resonant cavity 20 includes a laser input mirror 21, a gain medium 22, a saturable absorber 23, and a laser output mirror 24 arranged sequentially. When the pump source 11 is electrically excited, it converts electrical power into pump light, such as 808nm pump light. After the pump light is output through the coupling fiber, it is coupled and focused onto the laser input mirror 21 by the pump light coupling device 12, and then enters the gain medium 22 of the optical resonant cavity 20 to generate laser light. Subsequently, it propagates and oscillates between the laser input mirror 21 and the laser output mirror 24 of the optical resonant cavity 20. When the infrared laser passes through the saturable absorber 23, it can generate high peak power infrared pulse light through the saturable absorption effect of the saturable absorber 23.

[0035] In some specific embodiments, both the laser input mirror 21 and the laser output mirror 24 are plane mirrors, located at opposite ends of the optical resonant cavity 20. More specifically, to improve the transmittance of pulsed laser light entering the optical resonant cavity 20 and the reflectivity of pulsed laser light oscillating within the optical resonant cavity 20, a pump light antireflection coating, such as an 808nm wavelength antireflection coating, can be provided on the surface of the laser input mirror 21 near the pump light coupling device 12. This antireflection coating, also known as an anti-reflection film, primarily functions to reduce or eliminate reflected light from optical surfaces such as lenses, prisms, and plane mirrors, thereby increasing the transmittance of these components and reducing or eliminating stray light in the system. A multilayer dielectric film is provided on the surface of the laser input mirror 21 facing away from the pump light coupling device 12. For example, a multilayer dielectric film with 808nm antireflection and 1064nm high reflectivity can be provided. The dielectric film is a non-metallic compound coating material, and this multilayer dielectric film simultaneously functions as an antireflection pump light coating and a high-reflectivity pulsed laser coating.

[0036] For example, in some specific embodiments, the gain medium 22 can be an Nd:YAG crystal, an Nd:YVO4 crystal, an Nd:GdVO4 crystal, an Nd:YLF crystal, a Yb:YAG crystal, or an Nd:YAG ceramic, etc., wherein the Nd:YAG crystal, Nd:YVO4 crystal, and Nd:YAG ceramic generate 1064nm laser light, the Nd:GdVO4 crystal generates 1063nm laser light, the Nd:YLF crystal generates 1047nm or 1053nm laser light, and the Yb:YAG crystal generates 1030nm or 1050nm laser light.

[0037] For example, in some specific embodiments, the saturable absorber 23 can be a Cr4+:YAG crystal or a semiconductor saturable absorber.

[0038] It should be noted that the above-mentioned gain medium 22 and saturable absorber 23 can be made of any material that can achieve the corresponding function, and this application does not limit them.

[0039] Please refer to this application. Figure 2 , Figure 2 and Figure 1 Similarly, this application relates to the miniature engraving machine 100. Figure 1 The embodiments are illustrated in the structural diagram after crystal bonding. In a specific embodiment, when the gain medium 22 is an Nd:YAG crystal or a Yb:YAG crystal, and the saturable absorber 23 is a Cr4+:YAG crystal, the gain medium 22 and the saturable absorber 23 can be bonded together, and the input mirror 21 is fabricated on the pump light input surface of the gain medium 22.

[0040] Please refer to the following: Figures 1 to 3 Specifically, along the emission path of the pulsed laser, the aforementioned frequency-doubling crystal inverter 31 is located before the short-pass filter 32. The short-pass filter 32 is a plane mirror, and a multilayer dielectric film is disposed on the side of the short-pass filter 32 facing the frequency-doubling crystal inverter 31. This multilayer dielectric film simultaneously functions to enhance the transmission of green pulse light and reflect infrared pulse light. A green pulse light anti-reflection film, such as a 532nm wavelength anti-reflection film, is disposed on the side of the short-pass filter 32 away from the frequency-doubling crystal inverter 31. Therefore, when infrared pulse light and green pulse light pass through the short-pass filter 32, the infrared pulse light is filtered out, retaining only the green pulse light.

[0041] For example, the side of the short-pass filter 32 facing the frequency-doubling crystal inverter 31 is provided with a multilayer dielectric film of 532nm anti-reflection and 1064nm high reflectance, while the side of the short-pass filter 32 away from the frequency-doubling crystal inverter 31 is provided with a 532nm wavelength anti-reflection film. Therefore, when 1064nm infrared pulse light and 532nm green pulse light pass through the short-pass filter 32, the 1064nm infrared pulse light will be filtered out, leaving only the 532nm green pulse light.

[0042] Specifically, the frequency doubling crystal inverter 31 of the micro-engraving machine 100 of this application can be an LBO nonlinear crystal inverter (lithium triborate crystal, i.e., LiB3O5), a KTP nonlinear crystal inverter (potassium titanium phosphate crystal, i.e., KTiOPO4), a BiBO nonlinear crystal inverter (bismuth triborate crystal, i.e., BiB3O6), a PPLN nonlinear crystal inverter (periodically polarized lithium niobate crystal, i.e., Periodically Poled Lithium Niobate), or a MgO:PPLN nonlinear crystal inverter (magnesium oxide-doped periodically polarized lithium niobate crystal). That is, regardless of whether the frequency doubling crystal inverter 31 is located inside or outside the optical resonant cavity 20, the frequency doubling crystal inverter 31 can be selected as an LBO nonlinear crystal inverter or a KTP nonlinear crystal inverter as needed.

[0043] Please see Figure 1 and / or Figure 2 In one specific embodiment, the frequency doubling crystal inverter 31 is disposed within the optical resonant cavity 20, and the frequency doubling crystal inverter 31 is configured as an LBO nonlinear crystal inverter. The short-pass filter 32 is disposed outside the optical resonant cavity 20, and the laser output mirror 24 is located between the frequency doubling crystal inverter 31 and the short-pass filter 32; the pulsed laser is output from the optical resonant cavity 20 after passing through the frequency doubling crystal inverter 31, and is filtered by the short-pass filter 32.

[0044] Specifically, the length of the LBO nonlinear crystal frequency converter can be set to 10mm, and the light transmission aperture is 3x3mm. 2 According to θ = 90, The LBO nonlinear crystal inverter is cut at an angle, and its z-axis forms a 0-degree angle with the polarization direction of the infrared pulsed laser. Of course, users can also configure other types of crystal inverters according to specific circumstances; this application does not limit this.

[0045] In operation, the pump source 11 is electrically excited, converting electrical power into pump light. The pump light coupling device 12 couples and focuses this pump light into the gain medium 22. If the gain medium 22 is a neodymium-doped YAG laser crystal (yttrium aluminum garnet, i.e., Y3Al5O12), infrared light will be generated. This infrared light will propagate and oscillate between the laser input mirror 21 and the laser output mirror 24 within the optical resonant cavity 20 to form an infrared laser. When the infrared laser passes through the saturable absorber 23, the saturable absorber 23 will generate saturable absorption, accumulating pulse energy for the infrared laser, thereby obtaining a high peak power infrared pulse light. When this infrared pulse light passes through the frequency doubling crystal frequency converter 31, it will undergo frequency doubling, thus forming a green pulse light. Subsequently, the green pulse light will be output outside the optical resonant cavity 20 through the laser output mirror 24. The laser output mirror 24 has a multilayer dielectric film on the side facing the frequency doubling crystal inverter 31. For example, a multilayer dielectric film with high reflection at 1064nm and anti-reflection at 532nm can be provided. This multilayer dielectric film has the function of reflecting infrared pulse light and anti-reflection of green pulse light. The side of the laser output mirror 24 facing the short-pass filter 32 has a green pulse light anti-reflection film, such as a 532nm wavelength anti-reflection film. This enables repeated oscillation of infrared pulse light in the optical oscillation cavity and enhances the output rate of green pulse light. When the pulsed laser is output from the optical oscillation cavity, in addition to the green pulse light, there may also be a small amount of infrared pulse light. Therefore, the surface of the short-pass filter 32 facing the laser output mirror 24 is provided with a multilayer dielectric film, such as a multilayer dielectric film with high reflection at 1064nm and antireflection at 532nm. This multilayer dielectric film has the function of both antireflection of green pulse light and reflection of infrared pulse light. The surface of the short-pass filter 32 away from the laser output mirror 24 is provided with a green pulse light antireflection film, such as a 532nm wavelength antireflection film. Thus, when infrared pulse light and green pulse light pass through the short-pass filter 32, the infrared pulse light will be filtered out, and only the green pulse light will be retained, thereby obtaining a purer green pulse light.

[0046] It is noteworthy that, in this specific embodiment, the frequency doubling crystal inverter 31 is provided with dual-wavelength anti-reflection coatings for infrared pulse light and green pulse light on both the opposite sides facing and away from the laser output mirror 24. For example, dual-wavelength anti-reflection coatings of 1064nm and 532nm are provided. These dual-wavelength anti-reflection coatings allow both infrared pulse light and green pulse light to pass through the high-transmittance substrate, thereby enabling the frequency doubling of infrared pulse light as much as possible while ensuring the passage of green pulse light.

[0047] Please see Figure 3 , Figure 3This is a schematic diagram of another embodiment of the micro-engraving machine 100 of this application. In another specific embodiment, the frequency doubling crystal inverter 31 is disposed outside the optical resonant cavity 20, and the frequency doubling crystal inverter 31 is configured as a type II phase-matched KTP nonlinear crystal inverter. It is located between the laser output mirror 24 and the short-pass filter 32; after the pulsed laser is output from the optical resonant cavity 20, it passes sequentially through the frequency doubling crystal inverter 31 and the short-pass filter 32.

[0048] Specifically, the length of the KTP nonlinear crystal frequency converter can be set to 10mm, and the light transmission aperture is 3x3mm. 2 According to θ = 90, Cut at an angle. Please refer to [the document / reference]. Figure 4 , Figure 4 This is a schematic diagram showing the placement angle of the KTP nonlinear crystal frequency converter in the micro-engraving machine 100 of this application. Figure 4 In this embodiment, the angle α between the main axis z-axis of the KTP nonlinear crystal frequency converter and the polarization direction L of the infrared pulse light is 45 degrees. Of course, users can also set other types of crystal frequency converters according to specific circumstances, and this application does not limit them.

[0049] In operation, the pump source 11 is electrically excited, converting electrical power into pump light. The pump light coupling device 12 couples and focuses this pump light into the gain medium 22. If the gain medium 22 is a neodymium-doped YAG laser crystal, infrared light will be generated. This infrared light propagates and oscillates between the laser input mirror 21 and the laser output mirror 24 within the optical resonant cavity 20 to form an infrared laser. When the infrared laser passes through the saturable absorber 23, the saturable absorber 23 will generate saturable absorption, accumulating pulse energy for the infrared laser, thereby obtaining high peak power infrared pulsed light. The laser output mirror 24, on the side facing away from the frequency doubling crystal inverter 31, has an infrared pulse light partial reflection film. This film reflects a portion of the infrared pulse light incident on the laser output mirror back into the optical resonant cavity 20, allowing the infrared pulse light to propagate, oscillate, and be amplified between the laser input mirror 21 and the laser output mirror 24 within the optical resonant cavity 20. A portion of the infrared pulse light is output outside the optical resonant cavity 20. The surface of the laser output mirror 24 facing the frequency doubling crystal inverter 31 has an infrared pulse light anti-reflection film, such as a 1064nm wavelength anti-reflection film. After the portion of the pulsed infrared light propagates out of the optical resonant cavity 20, it enters the frequency doubling crystal inverter 31 for frequency doubling, thereby generating green pulse light. Although most of the infrared pulse light is converted into green pulse light after passing through the frequency doubling crystal inverter 31, infrared pulse light may still exist in the pulse laser passing through the frequency doubling crystal inverter 31. Therefore, after the pulse laser passes through the frequency doubling crystal inverter 31, it will also pass through the short-pass filter 32. The surface of the short-pass filter 32 facing the frequency doubling crystal inverter 31 is provided with a multilayer dielectric film. For example, a multilayer dielectric film with high reflection at 1064nm and antireflection at 532nm can be provided. This multilayer dielectric film has the function of antireflection of green pulse light and reflection of infrared pulse light. The surface facing away from the frequency doubling crystal inverter 31 is provided with a green pulse light antireflection film, such as a 532nm wavelength antireflection film. The film on the short-pass filter 32 can achieve high transmittance of green pulse light and filtering of infrared pulse light to obtain purer green pulse light.

[0050] It is worth noting that, in this specific embodiment, the frequency doubling crystal inverter 31 may have an infrared pulse light anti-reflection film, such as a 1064nm wavelength anti-reflection film, on the surface facing the laser output mirror 24, and a green pulse light anti-reflection film, such as a 532nm wavelength anti-reflection film, on the surface facing the short-pass filter 32, so as to greatly improve the frequency doubling efficiency of the frequency doubling crystal inverter 31.

[0051] For details, please refer to Figure 5 , Figure 5This is a schematic diagram of the collimation scanning system 40 of the micro-engraving machine 100 of this application. Based on the pump system 10, optical resonant cavity 20, and frequency conversion unit 30 described above, the micro-engraving machine 100 of this application further includes a collimation system 41, a scanning galvanometer 42, and a field mirror 44 arranged sequentially. The collimation system 41 includes a concave mirror with a negative focal length and a convex mirror with a positive focal length arranged opposite each other. For example, the focal length of the double concave mirror can be set to -2mm, and the focal length of the convex mirror can be set to 30mm, to better achieve calibration of the pulsed laser beam and magnification of the beam spot.

[0052] Please see Figure 6 , Figure 6 This is a schematic diagram of the scanning galvanometer 42 of this application. The scanning galvanometer 42 includes an X-axis lens 46 disposed in the X direction, a Y-axis lens 47 disposed in the Y direction, and an electronic control system 43. The X-axis lens 46 and the Y-axis lens 47 are both connected to the electronic control system 43 and can rotate in the X and Y directions respectively under the control of the electronic control system 43. The green pulse light passes through the collimation system 41 and the scanning galvanometer 42 in sequence to form a scanning image. The scanning image is finally focused by the field lens 44 and emitted, thereby enabling laser marking of the target item 45.

[0053] The above are merely embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A miniature engraving machine, comprising a pumping system and an optical resonant cavity arranged in sequence, wherein, The optical resonant cavity includes a laser input mirror and a laser output mirror. The pump light generated by the pumping system enters the optical resonant cavity to excite a pulsed laser, and the pulsed laser oscillates within the optical resonant cavity. The micro-engraving machine is characterized by further including a frequency conversion unit and a collimation scanning system; The frequency conversion unit includes a frequency doubling crystal frequency converter and a short-pass filter, the short-pass filter being disposed outside the optical resonant cavity; the collimation scanning system includes a collimation system, a scanning galvanometer, and a field mirror arranged sequentially. The frequency doubling crystal inverter is disposed inside or outside the optical resonant cavity. The pulsed laser generated after oscillation in the optical resonant cavity is converted into green pulse light after passing through the frequency doubling crystal inverter and the short-wave pass filter in sequence. The green pulse light is then scanned and focused by the collimating scanning system and emitted. When the frequency doubling crystal inverter is disposed in the optical resonant cavity, and the laser output mirror is located between the frequency doubling crystal inverter and the short-wavelength pass filter, the frequency doubling crystal inverter is provided with infrared pulse light and green pulse light dual-wavelength anti-reflection coatings on both the opposite sides facing and away from the laser output mirror. When the frequency doubling crystal frequency converter is disposed outside the optical resonant cavity and located between the laser output mirror and the short-pass filter, the frequency doubling crystal frequency converter has an infrared pulse light anti-reflection film on the side facing the laser output mirror and a green pulse light anti-reflection film on the side facing the short-pass filter.

2. The miniature engraving machine as described in claim 1, characterized in that, The frequency doubling crystal inverter is an LBO nonlinear crystal inverter, a KTP nonlinear crystal inverter, a BiBO nonlinear crystal inverter, a PPLN nonlinear crystal inverter, or an MgO:PPLN nonlinear crystal inverter.

3. The miniature engraving machine as described in claim 1, characterized in that, When the frequency doubling crystal inverter is disposed in the optical resonant cavity, the pulsed laser is output from the optical resonant cavity after passing through the frequency doubling crystal inverter and is filtered by the short-wave pass filter.

4. The miniature engraving machine as described in claim 1, characterized in that, When the frequency doubling crystal inverter is disposed outside the optical resonant cavity, the pulsed laser output from the optical resonant cavity passes sequentially through the frequency doubling crystal inverter and the short-wave pass filter.

5. The miniature engraving machine as described in any one of claims 1-4, characterized in that, The short-pass filter is a plane mirror. The side of the short-pass filter facing the frequency doubling crystal inverter is provided with a multilayer dielectric film, and the side of the short-pass filter facing away from the frequency doubling crystal inverter is provided with a green pulse light anti-reflection film.

6. The miniature engraving machine as described in any one of claims 1-4, characterized in that, The optical resonant cavity includes a gain medium and a saturable absorber; The pump light passes through the laser input mirror and enters the gain medium of the optical resonant cavity to generate the laser. The gain medium is Nd:YAG crystal, Nd:YVO4 crystal, Nd:GdVO4 crystal, Nd:YLF crystal, Yb:YAG crystal or Nd:YAG ceramic, wherein Nd:YAG crystal, Nd:YVO4 crystal and Nd:YAG ceramic generate 1064nm laser, Nd:GdVO4 crystal generates 1063nm laser, Nd:YLF crystal generates 1047nm or 1053nm laser, and Yb:YAG crystal generates 1030nm or 1050nm laser; The laser generated by the gain medium is converted into pulsed laser through the saturable absorption of the saturable absorber, which is Cr. 4+ YAG crystal or semiconductor saturable absorber.

7. The miniature engraving machine as described in claim 6, characterized in that, When the gain medium is an Nd:YAG crystal or a Yb:YAG crystal, and the saturable absorber is a Cr4+:YAG crystal, the gain medium and the saturable absorber can be bonded together.

8. The miniature engraving machine as described in any one of claims 1-4, characterized in that, The collimation system includes a concave mirror with a negative focal length and a convex mirror with a positive focal length, which are arranged opposite each other. The scanning galvanometer includes an X-axis lens disposed in the X direction, a Y-axis lens disposed in the Y direction, and an electronic control system. The X-axis lens and the Y-axis lens are both connected to the electronic control system and can rotate in the X direction and the Y direction respectively under the control of the electronic control system. The green pulse light passes sequentially through the collimation system and the scanning galvanometer to form a scanning image, and the scanning image is focused by the field lens and then emitted.

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