M-type short-focus infrared laser lens

Abstract

The present invention is applicable to the field of laser welding, and provides an M-type short-focus infrared laser lens that can be used for precision welding of thermoplastic plastics, including: an initial beam expansion component, a shaping component for shaping a collimated Gaussian laser beam into a first collimated M-type beam, a secondary beam expansion component, and a focusing objective lens component. In the M-type short-focus infrared laser lens provided by the present invention, after the Gaussian laser beam is expanded and shaped, the lens can output an M-type beam with a large numerical aperture, and the beam can be focused inside the plastic, and the maximum laser energy density appears inside the plastic. Therefore, by controlling the laser power, the inner layer of the plastic can be melted before the outer layer, and plastic laser welding without damage to the plastic surface and without adding absorbent to the welding surface can be achieved. At the same time, by using a large numerical aperture focusing method, a light spot of tens of microns can be designed, and this tiny light spot can be used in welding occasions of tiny devices.

Description

Technical Field

[0001] The invention belongs to the field of laser welding, and in particular relates to an M-type short-focus infrared laser lens, which can be used for precision welding of thermoplastic plastics. Background Art

[0002] At present, there are various laser welding equipment and corresponding laser lenses for plastic welding on the market. The light sources of these equipment are mostly near-infrared lasers (wavelength ≤ 1200 nm). Plastics do not absorb lasers in this band strongly. When welding, absorbents must be coated on the plastic welding surface or filled inside the plastic to perform effective welding. Laser welding in this band will cause plastic products to be contaminated, welding quality is unstable, efficiency is low, and cost is high. Since these problems are caused by the properties of the laser and plastic themselves and have nothing to do with the laser lens, the current near-infrared lens cannot solve the above problems.

[0003] In recent years, domestic and foreign markets have introduced new solutions for mid-infrared laser welding of thermoplastics (wavelength ≥ 1600nm). Since plastics have not only a certain transmittance to lasers in this band, but also a relatively suitable absorption rate (20-40%, 1mm thick), lasers in this band can directly weld optically translucent plastics without absorbents. This method avoids problems such as absorbent pollution, unstable welding quality, and low efficiency.

[0004] In summary, the laser lenses currently on the market have the following obvious defects:

[0005] (1) The lens cannot adapt to mid-infrared lasers. The lens material has a strong absorption of mid-infrared lasers. Under high laser power, the lens surface is easily damaged by heat, and the laser transmittance is low.

[0006] (2) Due to the intrinsic absorption (volume absorption) of plastics and the Gaussian distribution of laser beams, the conventional focusing method is used to focus the mid-infrared laser and then weld it. The welding effect is not good, and the problem of plastic surface damage has not been solved. Therefore, the mid-infrared laser is also limited in the field of plastic laser welding. In addition, the focusing effect of conventional lenses on mid-infrared lasers is not good, and the laser cannot be effectively focused inside the plastic. In addition to the essential reasons for the selective absorption of plastics, the reasons are: First, the laser is not effectively shaped before focusing. The laser before focusing is a Gaussian beam. The energy density of the Gaussian beam is high in the center and low at the edge, which is not conducive to the effective and uniform absorption of laser energy in the focused area; second, the numerical aperture (NA) of the focus is not large enough, and the laser beam cannot be quickly focused into a very small light spot.

[0007] (3) The focus spot of the lenses currently on the market is relatively large (over 1 mm), and the lenses cannot be used in situations where tiny devices are welded, such as microfluidics, microchips, and micro-optical devices. Summary of the invention

[0008] The technical problem to be solved by the present invention is how to achieve damage-free welding when using mid-infrared laser for plastic welding, and how to achieve infrared welding on tiny plastic products, so as to expand the application of mid-infrared laser in the field of plastic welding.

[0009] In order to solve the above technical problems, the present invention provides an M-type short-focus infrared laser lens, comprising:

[0010] An initial beam expansion assembly, used for expanding a Gaussian laser beam having a first diameter into a collimated Gaussian laser beam having a second diameter, wherein the second diameter is larger than the first diameter;

[0011] A shaping component, used for shaping the collimated Gaussian laser beam into a first collimated M-type beam;

[0012] A secondary beam expansion component, used for performing secondary beam expansion and spherical aberration elimination processing on the first collimated M-type beam to obtain a second collimated M-type beam;

[0013] The focusing objective lens assembly is used to focus the second collimated M-type light beam within a preset short distance.

[0014] Furthermore, the shaping component is a flat-conical lens; the initial beam expansion component, the secondary beam expansion component, and the focusing objective lens component are implemented based on a spherical lens.

[0015] Furthermore, the initial beam expansion assembly includes a first biconcave lens, a second biconcave lens, and a plano-convex lens placed in sequence along the optical path; the first biconcave lens and the second biconcave lens are used to expand the Gaussian laser beam with a first diameter twice to obtain a Gaussian laser beam with a second diameter; the plano-convex lens is used to collimate the Gaussian laser beam with the second diameter to obtain the collimated Gaussian laser beam with the second diameter.

[0016] Furthermore, the secondary beam expansion assembly includes a plano-concave lens, a first positive meniscus lens, a second positive meniscus lens and a biconvex lens which are sequentially placed along the optical path; the first positive meniscus lens and the second positive meniscus lens are both bent in the direction of optical path propagation; the first collimated M-type light beam is injected from the concave surface of the plano-concave lens and emitted from its plane, and the plano-concave lens is used to amplify the first collimated M-type light beam again; the first positive meniscus lens, the second positive meniscus lens and the biconvex lens sequentially converge the first collimated M-type light beam that has been amplified again three times to obtain a second collimated M-type light beam.

[0017] Furthermore, the focusing objective lens assembly includes a first plano-convex lens, a first negative meniscus lens, a second plano-convex lens, a third positive meniscus lens, and a fourth positive meniscus lens, which are arranged in sequence along the light path direction; the first plano-convex lens, the first negative meniscus lens, the second plano-convex lens, the third positive meniscus lens, and the fourth positive meniscus lens converge the second collimated M-type light beam five times in sequence; wherein, the second collimated M-type light beam enters from the convex surface of the first plano-convex lens and is emitted from its plane; the first negative meniscus lens bends in the direction of light path propagation, the third positive meniscus lens bends in the opposite direction of light path propagation, and the fourth positive meniscus lens bends in the opposite direction of light path propagation; the second collimated M-type light beam enters from the convex surface of the second plano-convex lens and is emitted from its plane.

[0018] Furthermore, the shaping component is a flat-conical lens; the initial beam expansion component, the secondary beam expansion component, and the focusing objective lens component are implemented based on an aspherical lens.

[0019] Furthermore, the initial beam expansion component is a biconcave lens.

[0020] Furthermore, the secondary beam expansion assembly includes a third plano-convex lens and a fourth plano-convex lens placed in sequence along the optical path direction; the third plano-convex lens and the fourth plano-convex lens collimate the first collimated M-type light beam and expand it; the first collimated M-type light beam enters from the convex surface of the third plano-convex lens and emits from its plane; the first collimated M-type light beam enters from the plane of the fourth plano-convex lens and emits from its convex surface to obtain the second collimated M-type light beam.

[0021] Furthermore, the focusing objective lens assembly includes a fifth plano-convex lens, and the second collimated M-type light beam enters from its convex surface and exits from its planar surface.

[0022] Furthermore, the aspheric surface shapes of the third plano-convex lens, the fourth plano-convex lens, and the fifth plano-convex lens meet the following formula:

[0023]

[0024] Among them, x is the distance vector height from the fixed point of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R, R is the radius of curvature; k is the cone coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface.

[0025] In the M-type short-focus infrared laser lens provided by the present invention, after the Gaussian laser beam is expanded and shaped, the lens can output an M-type beam with a large numerical aperture, which can be focused inside the plastic, and the maximum laser energy density appears inside the plastic. Therefore, by controlling the laser power, the inner layer of the plastic can be melted before the outer layer, and plastic laser welding can be achieved without damaging the plastic surface and without adding absorbent to the welding surface. At the same time, by using a large numerical aperture focusing method, a light spot of tens of microns can be designed, and this tiny light spot can be used in welding occasions of tiny devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the optical structure of an M-type short-focus infrared laser lens provided in the first embodiment of the present invention;

[0027] Figure 2 is a specific optical structure diagram of an M-type short-focus infrared laser lens provided in a second embodiment of the present invention;

[0028] Figure 3 yes Figure 2 The energy density distribution diagram of the collimated M-type beam in the M-type short-focus infrared laser lens shown;

[0029] Figure 4 yes Figure 2 The energy density distribution curve of the collimated M-type light beam in the M-type short-focus infrared laser lens shown;

[0030] Figure 5 It is a specific optical structure diagram of the M-type short-focus infrared laser lens provided in the third embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] Figure 1 The optical structure principle of the M-type short-focus infrared laser lens provided by the first embodiment of the present invention is shown. Figure 1 The M-type short-focus infrared laser lens in this embodiment includes an initial beam expansion component 1, a shaping component 2, a secondary beam expansion component 3 and a focusing lens component 4. Figure 1 The order in is arranged sequentially along the light path.

[0033] The initial beam expander assembly 1 is used to expand a Gaussian laser beam with a first diameter into a collimated Gaussian laser beam with a second diameter, where the second diameter is greater than the first diameter. After the Gaussian laser beam with the first diameter passes through the initial beam expander assembly 1, a collimated Gaussian laser beam with an enlarged beam diameter can be obtained. The collimated laser beam with a large diameter is beneficial for subsequent beam shaping.

[0034] The shaping assembly 2 is used to shape the collimated Gaussian laser beam into a first collimated M-shaped beam. The M-shaped beam (M-Shape) means that the laser spot slides uniformly in a certain direction, and the integrated energy is evenly distributed, that is, a narrow straight line with evenly distributed energy is formed, and the M-shaped spot is more conducive to subsequent laser energy concentration.

[0035] The secondary beam expander assembly 3 is used to perform secondary beam expansion and spherical aberration elimination on the first collimated M-shaped beam to obtain a second collimated M-shaped beam. The second collimated M-shaped beam obtained after secondary beam expansion and spherical aberration elimination is beneficial for subsequent laser focusing design.

[0036] The focusing objective lens assembly 4 is used to focus the second collimated M-shaped beam within a preset short distance. The preset short distance can be designed according to specific conditions and realized by using optical devices with appropriate focal lengths. During welding, the focusing position needs to be controlled inside the plastic to be welded, so that the inner layer of the plastic melts first before the outer layer, so that the plastic surface will not be damaged during welding, and no absorbent needs to be used on the welding surface.

[0037] In the M-type short-focus infrared laser lens provided by the first embodiment of the present invention, after the Gaussian laser beam is expanded and shaped, the lens can output an M-shaped beam with a large numerical aperture. This beam can be focused inside the plastic, and the maximum laser energy density appears inside the plastic. Therefore, by controlling the laser power, the inner layer of the plastic can be melted before the outer layer, realizing plastic laser welding without damage to the plastic surface and without adding absorbent to the welding surface. At the same time, by using the method of focusing with a large numerical aperture, a spot of dozens of micrometers can be designed, and this tiny spot can be used for welding of micro-devices.

[0038] The above initial beam expander assembly 1, secondary beam expander assembly 3, and focusing objective lens assembly 4 can be realized based on spherical lenses or aspherical lenses. The following is described in two embodiments.

[0039] In Figure 1 on the basis of Figure 2 Fig. shows the specific optical structure of the M-type short-focus infrared laser lens provided by the second embodiment of the present invention. The initial beam expander assembly 1, secondary beam expander assembly 3, and focusing objective lens assembly 4 are all realized by using spherical lenses.

[0040] Among them, the initial beam expansion assembly 1 includes a first biconcave lens 11, a second biconcave lens 12 and a plano-convex lens 13 which are sequentially placed along the optical path. The first biconcave lens 11 and the second biconcave lens 12 are used to magnify a Gaussian laser beam having a first diameter into a Gaussian laser beam having a second diameter. Specifically, the first biconcave lens 11 is used to expand the Gaussian laser beam having the first diameter for the first time, and the second biconcave lens 12 is used to expand the Gaussian laser beam after the first expansion for the second time to obtain a Gaussian laser beam having the second diameter. For a single biconcave lens, the larger the radius of curvature or the farther the distance, the higher the magnification, but the larger the size. Considering that the limited space distance inside the lens is not suitable for placing a biconcave lens with a large radius of curvature, and the cost of a biconcave lens with a large radius of curvature is also quite high, the present embodiment uses two biconcave lenses to magnify twice to make up for the defect of insufficient magnification of a biconcave lens, so as to achieve the desired target magnification. In addition, the two biconcave lenses share the magnification function, which can also effectively reduce the spherical aberration of the optical system.

[0041] The materials of the first biconcave lens 11 and the second biconcave lens 12 are both fused silica glass F-Silica, and the curvature radius of the two curved surfaces of the two are both 2.884 mm, and the center thickness is 2 mm. The function is to amplify the laser with a smaller diameter. The plano-convex lens 13 is used to collimate the Gaussian laser beam with the second diameter to obtain the collimated Gaussian laser beam with the second diameter. The material of the plano-convex lens 13 can be selected from fused silica glass F-Silica, the curvature radius of the curved surface is 8.6 mm, and the center thickness is 4 mm.

[0042] The shaping component 2 is implemented by a flat-conical lens. The material of the flat-conical lens is fused quartz glass F-Silica, the taper is 97.6°, the center thickness is 7 mm, and its function is to convert the collimated Gaussian beam into a collimated M-type beam. The M-type spot is more conducive to the subsequent laser energy gathering.

[0043] The secondary beam expansion assembly 3 includes a plano-concave lens 31, a first positive meniscus lens 32, a second positive meniscus lens 33 and a biconvex lens 34 which are sequentially placed along the optical path. The first collimated M-type light beam is incident from the concave surface of the plano-concave lens 31 and is emitted from its plane. The material of the plano-concave lens 31 is fused silica glass F-Silica, the radius of curvature of the curved surface is 12.5 mm, and the center thickness is 2 mm. It is used to amplify the first collimated M-type light beam again, which is beneficial for focusing the laser into a small spot later. The first positive meniscus lens 32 is bent in the direction of optical path propagation. The material is N-BK7, the radius of curvature of the curved surface on both sides are 62.821 mm and 43.68 mm respectively, and the center thickness is 15 mm. It is used to converge the incident first collimated M-type light beam after the amplification. The second positive meniscus lens 33 is bent in the direction of light propagation, and is made of N-BK7. The curvature radii of the two sides are 187.703 mm and 74.47 mm respectively, and the center thickness is 15 mm. It is used to converge the first collimated M-type light beam after the first convergence for the second time. The biconvex lens 34 is made of N-BK7. The curvature radii of the two sides are 734.5 mm and 146.909 mm respectively, and the center thickness is 15 mm. It is used to converge the first collimated M-type light beam after the second convergence for the third time. The light beam after the third convergence is emitted as the second collimated M-type light beam. The energy density distribution of the second collimated M-type light beam is shown as follows: Figure 3 As shown, the energy density distribution curve is Figure 4 shown.

[0044] The focusing objective lens assembly 4 includes a first plano-convex lens 41, a first negative meniscus lens 42, a second plano-convex lens 43, a third positive meniscus lens 44, and a fourth positive meniscus lens 45, which are sequentially placed along the optical path. The second collimated M-type light beam is injected from the convex surface of the first plano-convex lens 9 and emitted from its plane, which is used to converge the second collimated M-type light beam for the first time. The material of the first plano-convex lens 9 can be SF6, the radius of curvature of the curved surface is 310 mm, and the center thickness is 8 mm. The first negative meniscus lens 42 is bent in the direction of optical path propagation, and is used to converge the second collimated M-type light beam emitted by the first plano-convex lens 9 for the second time. The material of the first negative meniscus lens 42 can be N-BK7, the radii of curvature of the curved surfaces on both sides are 143.466 mm and 671.14 mm respectively, and the center thickness is 5 mm. The second collimated M-type light beam enters from the convex surface of the second plano-convex lens 43 and is emitted from its plane, and is used to converge the second collimated M-type light beam emitted by the first negative meniscus lens 42 for the third time. The material of the second plano-convex lens 43 can be SF6, and the curvature radius of the curved surface is 310 mm, and the center thickness is 12 mm. The bending direction of the third positive meniscus lens 44 is opposite to the propagation direction of the optical path, and is used to converge the second collimated M-type light beam emitted by the second plano-convex lens 43 for the fourth time. The material can be SF6, and the curvature radius of the curved surface on both sides is 95.012 mm and 59 mm, respectively, and the center thickness is 12.5 mm. The bending direction of the fourth positive meniscus lens 45 is opposite to the propagation direction of the optical path, and is used to converge the second collimated M-type light beam emitted by the third positive meniscus lens 44 for the fifth time. The material can be SF6, and the curvature radius of the curved surface on both sides is 53.6 mm and 40.3 mm, respectively, and the center thickness is 11 mm.

[0045] The second embodiment adopts the method of combining spherical lenses. The processing cost of spherical lenses is low, and this solution can be used for small-scale production. However, if too many lenses are used, the overall laser transmittance is not high (about 20%) due to the reflection and absorption of laser by the lenses.

[0046] Therefore, in order to improve the overall transmittance of the lens, the M-type short-focus infrared laser lens provided in the third embodiment of the present invention uses an aspherical lens group to replace the spherical lens group in the second embodiment. Figure 5 As shown, in the third embodiment, the initial beam expansion component 1, the secondary beam expansion component 3, and the focusing objective lens component 4 are all implemented based on aspherical lenses.

[0047] Reference Figure 5 The initial beam expansion component is realized by a biconcave lens 10. The material is fused silica glass F-Silica, the curvature radius of both sides is 2.884 mm, and the center thickness is 2 mm.

[0048] The shaping component is implemented by a flat cone lens 20, the material is fused silica glass F-Silica, the taper is 100°, and the center thickness is 10.33 mm. The secondary beam expansion component includes a third plano-convex lens 35, a fourth plano-convex lens 36, a third plano-convex lens 35, and a fourth plano-convex lens 36, which are placed in sequence along the optical path. Specifically, the first collimated M-type light beam is collimated and expanded, and the first collimated M-type light beam is incident from the convex surface of the third plano-convex lens 35 and emitted from its plane; the first collimated M-type light beam is incident from the plane of the fourth plano-convex lens 36 and emitted from its convex surface to obtain a second collimated M-type light beam.

[0049] The focusing objective lens assembly is implemented by a fifth plano-convex lens 40. The second collimated M-type light beam enters from the convex surface of the fifth plano-convex lens 40 and exits from the plane thereof, so as to focus the second collimated M-type light beam inside the plastic to be welded.

[0050] The aspheric surface shapes of the third plano-convex lens 35, the fourth plano-convex lens 36, and the fifth plano-convex lens 40 conform to the following formula:

[0051]

[0052] Among them, x is the distance vector height from the fixed point of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R (R is the radius of curvature), k is the cone coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface.

[0053] The materials, curvature radius, thickness and conic coefficient of the third plano-convex lens 35, the fourth plano-convex lens 36 and the fifth plano-convex lens 40 are shown in the following table:

[0054]

[0055] The overall laser transmittance of the aspheric lens solution is ≥40%, which is suitable for large-scale production.

[0056] The value of the numerical aperture NA of an infrared laser lens is generally between 0 and 1, which is proportional to the light-gathering ability of the lens. The larger the value of the numerical aperture NA, the better the light-gathering effect of the lens. However, under the premise of considering the transmittance or total thickness of the lens, the larger the value of the numerical aperture NA, the more difficult it is to design and process the lens. When it exceeds 0.5, the lens design is already difficult. Through experiments, it was found that regardless of whether a spherical lens or an aspherical lens is used, after selecting the parameters provided in the second and third embodiments above, the value of the numerical aperture NA can reach 0.65, which can achieve good focusing of mid-infrared lasers with a wavelength greater than 1600nm inside the plastic.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An M-type short-focus infrared laser lens, It is characterized in that include: An initial beam expansion component is implemented based on a spherical lens and is used to expand a Gaussian laser beam with a first diameter into a Gaussian laser beam with a second diameter, wherein the second diameter is greater than the first diameter; comprising a first biconcave lens, a second biconcave lens and a plano-convex lens sequentially placed along the optical path; the first biconcave lens and the second biconcave lens are used to expand the Gaussian laser beam with the first diameter twice to obtain a Gaussian laser beam with the second diameter; the plano-convex lens is used to collimate the Gaussian laser beam with the second diameter to obtain the collimated Gaussian laser beam with the second diameter; A shaping component, used for shaping the Gaussian laser beam of the second diameter into a first collimated M-type beam; A secondary beam expansion component, implemented based on a spherical lens, is used to perform secondary beam expansion and spherical aberration elimination processing on the first collimated M-type light beam to obtain a second collimated M-type light beam; it includes a plano-concave lens, a first positive meniscus lens, a second positive meniscus lens and a biconvex lens placed in sequence along the optical path direction; the plano-concave lens is used to amplify the first collimated M-type light beam again; the first positive meniscus lens, the second positive meniscus lens and the biconvex lens sequentially converge the first collimated M-type light beam that has been amplified again three times to obtain a second collimated M-type light beam; A focusing objective lens assembly is implemented based on a spherical lens and is used to focus the second collimated M-type light beam within a preset short distance; it includes a first plano-convex lens, a first negative meniscus lens, a second plano-convex lens, a third positive meniscus lens, and a fourth positive meniscus lens, which are sequentially placed along the light path; the first plano-convex lens, the first negative meniscus lens, the second plano-convex lens, the third positive meniscus lens, and the fourth positive meniscus lens sequentially converge the second collimated M-type light beam five times.

2. The M-type short-focus infrared laser lens as claimed in claim 1, It is characterized in that The shaping component is a flat-conical lens.

3. The M-type short-focus infrared laser lens as claimed in claim 1, It is characterized in that The first positive meniscus lens and the second positive meniscus lens are both bent in the direction of light path propagation; The first collimated M-type light beam enters from the concave surface of the plano-concave lens and exits from the planar surface thereof.

4. The M-type short-focus infrared laser lens as claimed in claim 1, It is characterized in that The second collimated M-type light beam is incident from the convex surface of the first plano-convex lens and emitted from its plane; the first negative meniscus lens bends in the direction of light propagation, the third positive meniscus lens bends in the opposite direction of light propagation, and the fourth positive meniscus lens bends in the opposite direction of light propagation; the second collimated M-type light beam is incident from the convex surface of the second plano-convex lens and emitted from its plane.

5. An M-type short-focus infrared laser lens, It is characterized in that include: An initial beam expansion component, implemented based on an aspheric lens, for expanding a Gaussian laser beam having a first diameter into a Gaussian laser beam having a second diameter, wherein the second diameter is greater than the first diameter; A shaping component, used for shaping the Gaussian laser beam of the second diameter into a first collimated M-type beam; A secondary beam expansion component, implemented based on an aspheric lens, is used to perform secondary beam expansion and spherical aberration elimination processing on the first collimated M-type light beam to obtain a second collimated M-type light beam; comprising a third plano-convex lens and a fourth plano-convex lens sequentially placed along the optical path direction; the third plano-convex lens and the fourth plano-convex lens collimate and expand the first collimated M-type light beam; A focusing objective lens assembly, implemented based on an aspherical lens, comprises a fifth plano-convex lens, for focusing the second collimated M-type light beam within a preset short distance; The aspheric surface shapes of the third plano-convex lens, the fourth plano-convex lens, and the fifth plano-convex lens meet the following formula: Among them, x is the distance vector height from the fixed point of the aspheric surface when the aspheric surface is at a height of h along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R, R is the radius of curvature; k is the cone coefficient; Ai is the correction coefficient of the i-th order of the aspheric surface.

6. The M-type short-focus infrared laser lens as claimed in claim 5, It is characterized in that The shaping component is a flat-conical lens.

7. The M-type short-focus infrared laser lens as claimed in claim 5, It is characterized in that The initial beam expansion component is a biconcave lens.

8. The M-type short-focus infrared laser lens as claimed in claim 5, It is characterized in that The first collimated M-type light beam enters from the convex surface of the third plano-convex lens and is emitted from its plane; the first collimated M-type light beam enters from the plane of the fourth plano-convex lens and is emitted from its convex surface to obtain the second collimated M-type light beam.

9. The M-type short-focus infrared laser lens as claimed in claim 8, It is characterized in that The second collimated M-type light beam enters from the convex surface of the fifth plano-convex lens and exits from the planar surface thereof.

Images