Transmission-type high-power laser emission system

Abstract

The invention discloses a transmission-type high-power laser emission system, and relates to the technical field of high-power laser systems, a laser incident end of the system is connected with a high-power fiber laser and is used for accessing a laser beam, and a laser emergent end is used for converging the laser beam to a target position. The system comprises a laser emission lens group, an emission lens cone, a focusing motor and a control circuit board, the laser emission lens group is arranged in the emission lens cone and comprises a laser emission eyepiece group and a laser emission objective lens group, the laser emission eyepiece group is located at an incidence end, the laser emission objective lens group is located at a laser emission end, and the focusing motor is located in the laser emission lens cone. The focusing motor is used for moving the laser emission eyepiece group through the mechanical connecting piece to realize system focusing, and the control circuit board is used for controlling the focusing motor to rotate for focusing according to a focusing signal; according to the technical scheme, the system is simple in structure, the temperature stability is relatively high, and the long-distance light beam directivity convergence function of high-power laser can be achieved.

Description

Technical Field

[0001] The present application relates to the technical field of high-power laser systems, and in particular to a transmission-type high-power laser emission system. Background Art

[0002] Since the high-energy laser system has the advantages of long transmission distance, high hit accuracy, fast steering speed, and high cost-effectiveness, combined with its advantage of being easily equipped on various platforms such as sea, land, and air, it has become the most promising new concept weapon developed at home and abroad. The basic working principle of the high-energy laser system is to use high-power laser to directly damage the target. The beam control launch system has become its core component. It is usually required that the launch system can not only direct the high-power laser to be launched and converged to the target in the far field to achieve damage, but also be able to track the target within a certain distance. However, the fixed-focus optical system cannot achieve continuous focusing, especially when tracking a moving target, the spot cannot reach the average power density of the damage threshold, resulting in a long damage time. Therefore, the continuous focus high-power laser launch optical system is applied to the high-energy laser system, which not only has a higher average power density at the far-field target focus, but also can maintain the stability of the power density of the focused spot during the rapid movement of the target.

[0003] In recent years, various research institutions have conducted certain research on high-power laser launch systems. Existing research mainly analyzes and compares different optical systems used in high-power laser technology. When the action distance is far and energy concentration is required, a focusing launch system is generally used. The focusing launch system can be divided into two structural types: a transmission launch system and a reflection launch system. Existing literature mainly focuses on the reflection launch focusing system. For example, Suzhou University uses a primary and secondary off-axis double-reflection structure to simulate and analyze the focusing effect of a target at 1km; Beijing Institute of Technology uses a refractive secondary beam expansion optical system to achieve focusing within a range of 0.5 to 5km; China Air-to-Air Missile Research Institute has conducted a detailed analysis of the parameter design and focusing characteristics of the Cassegrain coaxial zoom launch system; Hefei University of Technology combines the Cassegrain system with a lens group to change the distance between the Cassegrain system and the lens group to adjust the focus, so that the laser is focused on the moving target. The existing reflective system has a large output aperture and no chromatic aberration, but the reflective system is very sensitive to thermal deformation of structural parts during laser transmission, and the temperature stability is not high. It is impossible to avoid the problem of excessive temperature rise of the system under working conditions. When the system temperature rises too high, it is difficult to control the focusing accuracy, and thus it is unable to meet the needs of target damage within a certain range (such as drones). Summary of the invention

[0004] The purpose of this application is to provide a transmission-type high-power laser emission system, which solves the problems of low temperature stability and poor system reliability existing in the prior art.

[0005] The technical solution of the present application is: to provide a transmission-type high-power laser emission system, which comprises a laser input end and a laser output end, wherein the laser input end is connected to the output connector of the high-power fiber laser and is used to receive the laser beam emitted by the fiber laser, and the laser output end is used to converge the laser beam to a target position;

[0006] The transmission-type high-power laser emission system comprises a laser emission lens group, an emission lens barrel, a focusing motor and a control circuit board;

[0007] The laser emission mirror group is arranged inside the emission mirror tube, and the laser emission mirror group includes a laser emission eyepiece group and a laser emission objective lens group, the laser emission eyepiece group is located at the laser incident end, the laser emission objective lens group is located at the laser emission end, and the diameter of the laser emission eyepiece group is smaller than the diameter of the laser emission objective lens group;

[0008] The laser emission eyepiece group includes two concave lenses, the concave surfaces of the two concave lenses are arranged opposite to each other, and the laser emission eyepiece group is used to expand the incident laser beam to increase the divergence angle of the laser beam so that the laser beam is evenly propagated to the laser emission objective lens group;

[0009] The laser emission objective lens group includes three convex lenses, the convex surfaces of the three convex lenses face the direction of laser emission, and the laser emission objective lens group is used to uniformly converge the expanded laser beam to the target position;

[0010] The focusing motor is arranged outside the emitting lens barrel near the laser emitting eyepiece group, and is used to adjust the position of the laser emitting eyepiece group to achieve system focal length adjustment;

[0011] The control circuit board is used for receiving a focus input signal and controlling a focus motor to perform focus adjustment according to the focus input signal.

[0012] Further, the laser emitting eyepiece group includes a first laser emitting eyepiece and a second laser emitting eyepiece in sequence along the optical path direction;

[0013] The object side of the first laser emission eyepiece is convex, with a radius of curvature of 500.3 mm, and the image side of the first laser emission eyepiece is concave, with a radius of curvature of -77.9 mm;

[0014] The object side surface of the second laser emitting eyepiece is a concave surface with a curvature radius of -88.4 mm, and the image side surface of the second laser emitting eyepiece is a plane.

[0015] Further, the focal length of the first laser emitting eyepiece is -202 mm, and the focal length of the second laser emitting eyepiece is -193 mm;

[0016] The distance between the first laser emitting eyepiece and the second laser emitting eyepiece is 10 mm.

[0017] Further, the laser emitting objective lens group includes a first laser emitting objective lens, a second laser emitting objective lens and a third laser emitting objective lens in sequence along the optical path direction;

[0018] The object side of the first laser emission objective lens is a concave surface with a curvature radius of -500.3 mm, and the image side of the first laser emission objective lens is a convex surface with a curvature radius of 380.9 mm;

[0019] The object side of the second laser emission objective lens is a concave surface with a radius of curvature of -859 mm, and the image side of the first laser emission objective lens is a convex surface with a radius of curvature of 423.8 mm;

[0020] The object side surface of the third laser emission objective lens is a plane, and the image side surface of the third laser emission objective lens is a convex surface with a curvature radius of 621 mm.

[0021] Further, the focal length of the first laser emission objective lens is 3292 mm, the focal length of the second laser emission objective lens is 1796 mm, and the focal length of the third laser emission objective lens is 1355 mm;

[0022] The distance between the first laser emitting objective lens and the second laser emitting objective lens is 8.75 mm; the distance between the second laser emitting objective lens and the third laser emitting objective lens is 2 mm.

[0023] Furthermore, the distance between the laser emission eyepiece group and the laser emission objective lens group ranges from 470 mm to 471.5 mm, and the corresponding focusing position of the transmission-type high-power laser emission system ranges from 2 km to 0.3 km, wherein the larger the distance between the laser emission eyepiece group and the laser emission objective lens group, the closer the focusing position of the system is, and the smaller the distance between the laser emission eyepiece group and the laser emission objective lens group, the farther the focusing position of the system is.

[0024] Furthermore, the focusing motor is connected to the laser emitting eyepiece group through a mechanical connector, and is used to move the laser emitting eyepiece group through the mechanical connector, change the relative position between the laser emitting eyepiece group and the laser emitting objective lens group, and realize system focal length adjustment; the control circuit board is arranged on the emitting lens barrel, and the control circuit board is electrically connected to the focusing motor.

[0025] Furthermore, an aperture stop is provided at the laser incident end, and the aperture stop is located on a side of the laser emitting eyepiece group close to the optical fiber laser.

[0026] Furthermore, each lens in the laser emission eyepiece group and the laser emission objective lens group is made of the same high-purity fused quartz material, and the refractive index of the material is between 1.45 and 1.46.

[0027] The technical solution of the present application also provides an application of a transmission-type high-power laser emission system in achieving target damage, and the application includes the following steps:

[0028] S1: Determine the target position to be damaged and align the laser output end of the system to the target position;

[0029] S2: Determine the range of the system focus position according to the distance of the target position and the predetermined maximum spot size, and calculate the system equivalent focal length range that can damage the target according to the range of the focus position, which specifically includes the following steps:

[0030] The target position is taken as the closest focus position F 1 , according to the predetermined maximum spot size L 2 and the closest focus position F 1 Calculate the farthest focus position F 2 :

[0031]

[0032] Where, L 1 is the width of the laser beam emitted by the system, and the range of the system focus position is (F 1 ,F 2 ); According to the range of focus position (F 1 ,F 2 ) Calculate the equivalent focal length range of the system. The relationship between the equivalent focal length and the focus position is:

[0033]

[0034] Based on the relationship between the equivalent focal length and the focus position, the range of the focus position (F 1 ,F 2 ) corresponding to the equivalent focal length range;

[0035] S3: Based on the calculated focal length range, adjusting the position of the laser emission eyepiece group by using a focusing motor so that the focal length value of the system is within the focal length range;

[0036] S4: Use a fiber laser to emit a laser beam, so that the emitted laser beam converges to a target position to damage the target.

[0037] The beneficial effects of this application are:

[0038] First, the technical solution in the present application adopts a transmission-type laser emission system to realize the convergence and focusing of the optical fiber laser output light in the far field. The main working elements are the lenses in the laser emission eyepiece group and the laser emission objective lens group, wherein the eyepiece group includes two concave lenses with opposite concave surfaces, and the objective lens group includes three convex lenses with convex surfaces facing the light output direction. The width of the eyepiece group is smaller than that of the objective lens group. The two-piece concave lenses can increase the divergence angle of the light beam so that the light beam is evenly propagated to the objective lens group. The three-piece convex lenses can evenly converge the expanded light beam to the target position. The design of expanding the light beam first and then focusing it can improve the far-field quality of the laser beam and avoid the light beam from being emitted. The internal focusing of the shooting lens tube solves the problem of excessive temperature rise of the system due to concentrated laser energy, reduces the impact of high temperature on each lens, and improves the stability of the system; in addition, the material selected for each lens is pure fused quartz with excellent optical properties, which makes the laser launch system have better thermal stability; the technical solution in the present application has a spacing range of 470mm to 471.5mm between the eyepiece group and the objective lens group, and the corresponding system focusing position range is 2km to 0.3km. The technical solution in the present application can realize the directivity and convergence function of high-power laser on long-distance light beams, and can achieve damage to long-distance targets when the average power density of the focus reaches the damage threshold.

[0039] In the prior art, the reflective laser emission system will form a focusing point inside the lens barrel when transmitting the laser, and there is a problem of excessive temperature rise of the system due to the concentration of laser energy. The reflective laser emission system is very sensitive to thermal deformation of structural parts during laser transmission, and has low temperature stability. When the system temperature rises too high, it is difficult to control the focusing accuracy, and the power density of the focused light spot at the target position cannot be kept continuous and stable, thereby failing to meet the demand for target damage within a certain range. The technical solution in the present application uses a lens to achieve laser far-field focusing. There is no focusing point inside the lens barrel when transmitting the laser, which avoids the problem of excessive temperature rise of the system due to the concentration of laser energy, and can keep the power density of the focused light spot continuous and stable. When the equipment platform environment is harsh, the temperature stability is relatively high, and it has great practical application value.

[0040] Second, the technical solution of the laser emission system in this application uses a five-piece lens. The system structure is relatively simple and takes into account factors such as aberration correction and axial distance adjustment of the lens. The five-piece lens is set to reduce the production cost, while avoiding the problem of scattered light spots formed by the lens and poor focusing effect of light energy. The light intensity drop in the entire field of view is minimal, the overall brightness of the light spot image is high, and target damage can be achieved. The lens material uses the same fused quartz material, which improves the stability and transmittance of the system and is easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The advantages of the above and / or additional aspects of the present application will become apparent and easily understood in the description of the embodiments in conjunction with the following drawings, in which:

[0042] Figure 1 is a schematic diagram of the overall structure of a transmission-type high-power laser emission system according to an embodiment of the present application;

[0043] Figure 2 is a schematic structural diagram of a laser emission mirror assembly according to an embodiment of the present application;

[0044] Figure 3 is the divergence angle of the transmission-type high-power laser emission system according to one embodiment of the present application;

[0045] Figure 4 is a wavefront diagram of a transmission-type high-power laser emission system according to an embodiment of the present application;

[0046] Figure 5 This is a diagram showing the effect of using physical optics to track a high-power laser beam focused at a position of 0.3 km according to an embodiment of the present application;

[0047] Figure 6 This is a diagram showing the effect of using physical optics to track a high-power laser beam focused at a position of 2 km according to an embodiment of the present application.

[0048] Among them, 1-laser emitting lens group, 11-laser emitting eyepiece group, 111-first laser emitting eyepiece, 112-second laser emitting eyepiece, 12-laser emitting objective lens group, 121-first laser emitting objective lens, 122-second laser emitting objective lens, 123-third laser emitting objective lens, 2-emitting lens barrel, 3-focusing motor, 4-control circuit board. DETAILED DESCRIPTION

[0049] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0050] In the following description, many specific details are elaborated to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present application is not limited to the specific embodiments disclosed below.

[0051] like Figure 1 to Figure 2As shown, this embodiment provides a transmissive high-power laser emitting system, which includes a laser incident end and a laser output end. The laser incident end is connected to the output connector of the high-power fiber laser and is used to receive the laser beam emitted by the fiber laser. The laser output end is used to converge the laser beam emitted by the fiber laser to a target position.

[0052] In this embodiment, the end of the transmission-type high-power laser emission system for receiving the laser is used as its laser incident end, that is, Figure 1 The right end of the laser incident end is used to connect with the optical fiber output interface of the optical fiber laser; the end used to emit laser in the transmission-type high-power laser emission system is used as its laser output end, that is, Figure 1 The left end of the laser output end is used to focus the laser beam to a preset target position.

[0053] The transmission type high power laser emission system is composed of a laser emission lens group 1, an emission lens barrel 2, a focusing motor 3 and a matching control circuit board 4.

[0054] The laser emitting lens group 1 is arranged inside the emitting lens barrel 2, and the laser emitting lens group 1 includes a laser emitting eyepiece group 11 and a laser emitting objective lens group 12. The laser emitting eyepiece group 11 is located at the laser incident end inside the emitting lens barrel 2, and the laser emitting objective lens group 12 is located at the laser exit end inside the emitting lens barrel 2.

[0055] The laser emission eyepiece group 11 is used to expand the incident laser beam to increase the divergence angle of the laser beam so that the laser beam is evenly propagated to the laser emission objective lens group 12. The laser emission objective lens group 12 is used to evenly converge the expanded laser beam to the target position; the diameter of each lens in the laser emission eyepiece group 11 is smaller than the diameter of each lens in the laser emission objective lens group 12. The optical path of the laser beam in each lens of the laser emission lens group 1 is as follows: Figure 2 As shown, the laser emission eyepiece group 11 diffuses the incident laser, so that the divergence angle of the laser beam increases, and evenly propagates to the position of the laser emission objective lens group 12, and the laser emission objective lens group 12 then evenly converges the expanded laser beam to the target position.

[0056] The laser emitting eyepiece group 11 is composed of a first laser emitting eyepiece 111 and a second laser emitting eyepiece 112, wherein the first laser emitting eyepiece 111 and the second laser emitting eyepiece 112 are both concave lenses, and the concave surfaces of the two concave lenses are arranged adjacent to each other.

[0057] Specifically, the first laser emitting eyepiece 111 and the second laser emitting eyepiece 112 are arranged in sequence according to the optical path direction (the optical path direction is the direction of the laser light beam from the incident end to the exit end), the object side surface of the first laser emitting eyepiece 111 (the object side surface is the side close to the optical fiber laser) is a convex surface, and the image side surface (the image side surface is the side away from the optical fiber laser) is a concave surface, that is, the surface with a small curvature radius in the first laser emitting eyepiece 111 faces the laser emission end of the emitting lens barrel 2; the object side surface of the second laser emitting eyepiece 112 is a concave surface, and the image side surface is a plane, that is, the surface with a small curvature radius in the second laser emitting eyepiece 112 faces the laser incident end of the emitting lens barrel 2.

[0058] The laser emitting objective lens group 12 consists of a first laser emitting objective lens 121, a second laser emitting objective lens 122 and a third laser emitting objective lens 123, wherein the first laser emitting objective lens 121, the second laser emitting objective lens 122 and the third laser emitting objective lens 123 are all convex lenses, and the three convex lenses are arranged in a continuous arrangement.

[0059] Specifically, the first laser emitting objective lens 121, the second laser emitting objective lens 122 and the third laser emitting objective lens 123 are arranged in sequence according to the direction of the optical path. The object side surface of the first laser emitting objective lens 121 is a concave surface, and the image side surface is a convex surface, that is, the surface with a small curvature radius in the first laser emitting objective lens 121 faces the laser incident end of the emitting lens barrel 2; the object side surface of the second laser emitting objective lens 122 is a concave surface, and the image side surface is a convex surface, and the surface with a small curvature radius in the second laser emitting objective lens 122 faces the laser incident end of the emitting lens barrel 2; the object side surface of the third laser emitting objective lens 123 is a plane, and the image side surface is a convex surface, and the surface with an infinite curvature radius (that is, a plane) in the third laser emitting objective lens 123 faces the laser incident end of the emitting lens barrel 2, that is, its convex surface faces the laser exit end.

[0060] In this embodiment, the laser emission eyepiece group 11 can diverge the passing light beam through two concave lenses, increase the diameter of the light beam at the laser emission objective lens group 12, improve the far-field quality of the laser beam, and avoid the light beam focusing inside the emission lens barrel 2, thereby avoiding the problem of excessive temperature rise of the system due to laser energy concentration, reducing the impact of high temperature on each lens, and improving system stability.

[0061] The parameters of the first laser emission eyepiece 111 are: focal length f = -202 mm; object side curvature radius R1 = 500.3 mm; image side curvature radius R2 = -77.9 mm (negative value indicates concave surface);

[0062] The parameters of the second laser emission eyepiece 112 are: focal length f = -193 mm; object side curvature radius R1 = -88.4 mm; image side curvature radius R2 = infinity (the curvature radius is infinite, that is, the side is a plane);

[0063] The parameters of the first laser emission objective lens 121 are: focal length f = 3292 mm; object side curvature radius R1 = -500.3 mm; image side curvature radius R2 = 380.9 mm;

[0064] The parameters of the second laser emission objective lens 122 are: focal length f = 1796 mm; object side curvature radius R1 = -859 mm; image side curvature radius R2 = 423.8 mm;

[0065] The parameters of the third laser emission objective lens 123 are: focal length f = 1355 mm; object side curvature radius R1 = infinity; image side curvature radius R2 = 621 mm;

[0066] The distance between the first laser emitting eyepiece 111 and the second laser emitting eyepiece 112 is 10 mm; the distance between the first laser emitting objective lens 121 and the second laser emitting objective lens 122 is 8.75 mm; the distance between the second laser emitting objective lens 122 and the third laser emitting objective lens 123 is 2 mm.

[0067] In this embodiment, all of the above-mentioned lens materials are of the same type, including the first laser emitting eyepiece 111, the second laser emitting eyepiece 112, the first laser emitting objective lens 121, the second laser emitting objective lens 122, and the third laser emitting objective lens 123, and the refractive index of these lenses is between 1.45 and 1.46.

[0068] The distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12 ranges from 470mm to 471.5mm, and the corresponding focusing position of the transmission type high power laser emission system ranges from 2km to 300m, wherein, the larger the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12, the closer the focusing position of the transmission type high power laser emission system, and the smaller the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12, the farther the focusing position of the transmission type high power laser emission system.

[0069] In the present embodiment, the first laser emitting eyepiece 111 and the second laser emitting eyepiece 112 are both concave lenses, which can increase the divergence angle of the incident laser beam and expand the beam so that the divergent laser beam is evenly irradiated to the laser emitting objective lens group 12. The first laser emitting objective lens 121, the second laser emitting objective lens 122 and the third laser emitting objective lens 123 are all convex lenses, which can focus the divergent laser beam to the target position to form a clear focus. Among them, expanding the light beam through the eyepiece first can avoid the problem of unclear focusing point and unclear laser spot at the target position caused by too small a light beam. The expanded laser light beam has a larger spot size, so that the objective lens can produce a clear focus when focusing, instead of forming an unclear spot due to excessive concentration of the light beam. The expansion of the laser light beam can reduce the spot size and position error during focusing, thereby improving the accuracy of focusing.

[0070] Each lens in the laser emission mirror group 1 is made of high-purity fused quartz; the specific material can be quartz glass JGS1, Corning 7980, Corning 7979, Ohara low OH value quartz or other quartz glass of the same grade.

[0071] Each lens in the laser emission mirror group 1 is provided with an optical coating material for increasing the transmittance of the lens and reducing the reflectivity of the lens. The coating material can be magnesium fluoride (MgF 2 ), silicon dioxide (SiO 2 ) or calcium fluoride (CaF 2 ) etc. to reduce the impact of reflected light on the focusing quality of the system.

[0072] An aperture diaphragm is set at the laser incident end of the emitting lens barrel 2, and the aperture diaphragm is located on the side of the laser emitting eyepiece group 11 close to the fiber laser, and the aperture diaphragm is set at the exit beam waist of the fiber laser. Setting the aperture diaphragm can prevent other stray light from entering the system from the laser incident end and affecting the focusing quality of the system.

[0073] In this embodiment, the aperture stop in the emitting lens barrel 2 is located 40 mm away from the side of the laser emitting eyepiece group 11, and the diameter of the aperture stop is set to 33 mm.

[0074] In this embodiment, the operating band range of the transmission-type high-power laser emitting system is 1080±10nm. The operating band range usually depends on the transmittance of the optical elements used and the choice of materials. Each lens made of high-purity fused quartz can meet the requirement of an operating band range of 1080±10nm; the laser beam expansion ratio is 6.5 (that is, the transmission-type high-power laser emitting system enlarges the diameter / beam width of the input laser beam by 6.5 times).

[0075] In this embodiment, the laser emission lens group 1 is a structure composed of a transmission eyepiece and a transmission objective lens, wherein the transmission objective lens can move back and forth along the axis inside the emission lens barrel 2 under the control of the focusing motor 3 to achieve focusing, so that the transmission high-power laser emission system can perform directionality focusing on laser beams at different distances.

[0076] The focusing motor 3 is installed on one side of the emitting lens barrel 2 near the laser emitting eyepiece group 11. The focusing motor 3 is connected to the laser emitting eyepiece group 11 through a mechanical connector. The focusing motor 3 is used to drive the laser emitting eyepiece group 11 to move back and forth along the axis inside the emitting lens barrel 2 through the mechanical connector, thereby changing the relative position between the laser emitting eyepiece group 11 and the laser emitting objective lens group 12, realizing system focal length adjustment, and thus realizing adjustment of the focusing position of the laser beam.

[0077] In this embodiment, while the distance between the first laser emitting eyepiece 111 and the second laser emitting eyepiece 112, and the distance between the first laser emitting objective lens 121, the second laser emitting objective lens 122 and the third laser emitting objective lens 123 remain unchanged, the adjustable distance between the laser emitting eyepiece group 11 and the laser emitting objective lens group 12 is used as the equivalent adjustable focal length of the transmission type high power laser emitting system.

[0078] In this embodiment, the focusing motor 3 can be a stepper motor or a servo motor, etc. The focusing motor 3 can be connected to the laser emitting eyepiece group 11 through mechanical connectors such as a screw, a lead screw, and a gear system. These mechanical connectors can transmit the rotational motion of the focusing motor 3 to the laser emitting eyepiece group 11, so that the laser emitting eyepiece group 11 can be moved; these mechanical connectors all adopt existing structures, such as a screw mechanical connector, the screw and the rotating shaft of the focusing motor 3 are connected through a coupling, and the nut is connected to the laser emitting eyepiece group 11, and the motor drives the screw to rotate to complete the front and back focusing; the mechanical connectors such as the lead screw and the gear system are all existing structures and will not be repeated here.

[0079] The control circuit board 4 is mounted on the transmitting lens barrel 2 and is electrically connected to the focusing motor 3. The control circuit board 4 is used to receive a focusing input signal and convert the input signal into a motor control instruction, and accurately controls the rotation of the focusing motor 3 through the motor control instruction to achieve focusing.

[0080] In this embodiment, the focus input signal received by the control circuit board 4 comes from a superior controller or a user interface. After the user inputs the required focal length, the control circuit board 4 can perform focus adjustment according to the received focus input signal.

[0081] The transmitting lens barrel 2 is also provided with mechanical interfaces for connecting with external elevation components and sighting components. The external elevation components and sighting components are fixedly connected with the transmitting lens barrel 2 via these mechanical interfaces.

[0082] It should be noted that for the transmission-type high-power laser emission system, the following points need to be considered during the design and production, including: 1) Avoid strong residual reflected laser returning to the system; 2) Avoid the appearance of stray light spots with concentrated energy inside the lens; 3) The refractive index of the lens material is uniform and stable, without scratches, low roughness, and the heat absorption and thermal expansion coefficient of the material are small; 4) The material and design of the coating need to increase the transmittance as much as possible; 5) The overall system has high transmittance to the laser, reducing light absorption, while dissipating heat to the mechanical housing and performing heat dissipation treatment; 6) Comprehensively consider the complexity of processing and assembly, as well as the focusing method and accuracy.

[0083] According to the above requirements, in this embodiment, high-purity fused quartz material is used to make each lens in the laser emission mirror group 1. The high-purity fused quartz material has the advantages of low thermal expansion coefficient, high thermal conductivity, small stress deformation, etc. It is not easy to deform when irradiated by laser, and can quickly transfer heat energy to the mechanical shell of the system for heat dissipation, which is beneficial to improve the stability of the system; since the laser spectrum band range is relatively narrow (the working band is 1080±10nm), each lens in the laser emission mirror group 1 does not require additional chromatic aberration correction, and can be made of the same material; other materials, such as CaF2 material, can better correct chromatic aberration as a positive lens, but the cost is very high, and the risk of damage during processing is high, which will cause waste of expensive materials. The dispersion of K9 material and molten quartz is similar, which is not helpful for chromatic aberration correction. Therefore, in this embodiment, high-purity fused quartz material is used as the material of each lens in the laser emission mirror group 1, which can save costs and improve the high temperature resistance and stability of the system.

[0084] The problem of returning laser and internal stray light of the system needs to be avoided during design, and the quality of the lens needs to be tested after the design is completed. In this embodiment, the laser emission mirror group of the high-power laser emission system adopts a Galilean structural design, which can avoid the problem of wavefront error caused by air ionization or thermal deflection of light caused by internal light focusing. First of all, if you want to avoid internal stray light, you need to avoid the situation where the convergence point of a single reflection is located on the surface or inside of the lens. Specifically, the ghost image of the system cannot be focused on the surface and inside of all lenses, but focuses on the area between the eyepiece group 11 and the objective lens group 12, so that the heat can be transferred to the outside of the emission system through the high thermal conductivity shell. At the same time, it is also necessary to avoid excessive lens focal length (here, the focal length threshold can be set so that the focal length of the lens is less than the threshold); in this embodiment, when setting each lens, the above problems can be solved by accurately controlling the curvature parameters and positions of each lens to avoid the generation of internal stray light; among them, since the laser power density from the aperture to the eyepiece group is the highest, water cooling can be added to the eyepiece group when used. Secondly, with regard to the problem of return light, on the one hand, a material with high light transmittance and low reflectivity is selected when coating the lens to reduce its lens reflectivity. On the other hand, in order to prevent collimated or focused reflected light from reaching the entrance pupil of the system lens, an aperture stop is provided at the entrance pupil of the system lens (i.e., the laser incident end of the emitting lens barrel 2), and the aperture stop is provided at the exit beam waist of the fiber laser, which can prevent other collimated or focused reflected light from reaching the entrance pupil of the system lens and improve the focusing quality of the system.

[0085] The settings of each lens in the laser emission lens group 1 not only improve the system stability and transmittance, but also take into account factors such as aberration correction and lens axial distance. In this embodiment, each lens uses a spherical design, on this basis, the aperture and size of the system are set to the minimum value within the allowable range of the design, so as to control the processing cost and weight. In addition, the roughness of the spherical lens can be better than that of the aspherical lens, which can increase the damage threshold of the lens. The three-piece emission lens has a large light spot dispersion, and the power density outside the field of view will decrease by about 50%. The four-piece design and the three-piece design have little change, which can optimize the image quality, control the dispersion spot to a smaller area, and the full field of view power density will drop to about 70-80%. The five-piece design can further improve the image quality, reduce the aberration except chromatic aberration to a smaller extent, so that the full field of view power density only drops to about 90% on the axis. The image quality will be better if the number of pieces continues to increase, but it will lead to an increase in cost, transmittance, heat dissipation, and installation requirements. In this embodiment, a five-piece lens is provided, which can reduce the power density drop within the field of view, make the light intensity distribution more uniform, and reduce the cost, increase the laser transmittance, reduce the heat dissipation difficulty, and reduce the installation and adjustment requirements. Since the laser power density at the eyepiece is higher, the number of lenses should be reduced as much as possible to reduce the heat dissipation difficulty, so the eyepiece is set to two pieces and the objective lens is set to three pieces.

[0086] Considering the focusing method and accuracy, the focusing amount should not be too large or too small. The focusing amount is set to 1.5mm.

[0087] This embodiment also provides an application of a transmission-type high-power laser emission system in achieving target damage. The transmission-type high-power laser emission system is used to focus the laser beam so that the average power density at the target position reaches the damage threshold, thereby achieving target damage. The specific process is as follows:

[0088] S1: Determine the target position to be damaged and align the laser output end of the system to the target position;

[0089] Use external detection equipment to determine the position of the target that needs to be damaged. Based on the feedback from the sighting and observation components, use the external pitch component to adjust the position of the transmission-type high-power laser emission system so that its laser output end is aligned with the target position.

[0090] S2: Determine the range of the system focus position according to the distance of the target position and the predetermined maximum spot size, and calculate the system equivalent focal length range that can damage the target according to the range of the focus position, which specifically includes the following steps:

[0091] The distance between the system and the target position is taken as the closest focus position F 1 , according to the predetermined maximum spot size L 2 and the closest focus position F 1 Calculate the farthest focus position F2 , farthest focus position F 2 The expression is:

[0092]

[0093] Where, L 1 is the width of the laser beam emitted by the system, and the range of the system focus position is (F 1 ,F 2 ), unit is km.

[0094] In this embodiment, the width of the laser beam emitted by the system can be obtained by measurement (such as using a laser beam analyzer or detector to directly measure the laser beam emitted by the system), and the distance between the system and the target position can be measured by an external distance measuring device.

[0095] Depending on the focus position range (F 1 ,F 2 ) calculates the system equivalent focal length range, which is expressed as:

[0096]

[0097] Where D is the equivalent focal length of the system (i.e., the distance between the laser emitting eyepiece group 11 and the laser emitting objective lens group 12), F is the focusing position of the laser beam, and its unit is km, α 1 , β 1 and γ 1 is the coefficient when the equivalent focal length is in the range [470.0,470.9], α 2 , β 2 and γ 2 is the coefficient when the equivalent focal length is in the range of (470.9,471.5], α 1 =1.6667, β 1 =-1569.5,γ 1 =369500.3333,α 2 =0.9167, β 3 =-864.2,γ 2 =203684.3708.

[0098] Based on the relationship between the equivalent focal length and the focus position, the range (F 1 ,F 2 ) corresponds to the equivalent focal length range.

[0099] In this embodiment, the predetermined maximum spot size L is set. 2 When the power of the optical laser is large, the maximum spot size L is required. 2Relatively large, when the power of the light laser is small, the maximum spot size L is predetermined 2 Relatively small, so that the predetermined maximum spot size L 2 The corresponding average power density value (power density refers to the power per unit area) is greater than or equal to the damage threshold (that is, the power density that can cause damage to the target).

[0100] According to the predetermined average power density value, the maximum laser spot size that can damage the target is determined, wherein the predetermined average power density value is greater than or equal to the damage threshold, and the maximum laser spot size is expressed as:

[0101]

[0102] Wherein, φ is the maximum laser spot size (i.e., the width or diameter of the spot), in meters (km); LP is the total power of the laser, in watts (W); and LPD is a predetermined average power density value. In this embodiment, a circular area formed by irradiating a laser beam to the surface of a target object is set. The total power LP of the laser can be obtained from the specific high-power fiber laser used, and the output power of the high-power fiber laser is the total power of the laser.

[0103] S3: Based on the calculated focal length range, the position of the laser emission eyepiece group 11 is adjusted by using the focusing motor 3 so that the focal length value of the transmission type high power laser emission system is within the focal length range;

[0104] Specifically, any value within the focal length range is selected as the focal length value, and the focal length value is used as the input of the control circuit board 4. The control circuit board 4 is used to control the focusing motor 3 to adjust the position of the laser emission eyepiece group 11, and the focal length of the transmission high-power laser emission system is adjusted to the focal length value.

[0105] S4: Use a fiber laser to emit a laser beam, so that the emitted laser beam converges to a target position to damage the target.

[0106] In this embodiment, the control circuit board 4 in the transmission-type high-power laser emission system is used to drive the focusing motor 3 to adjust the focal length, so that the laser spot size at the target position is required to be smaller than a preset value, thereby making the average power density at the target position reach the damage threshold, thereby achieving the purpose of damaging the target.

[0107] In this embodiment, the transmission-type high-power laser emission system can achieve the functions of far-field focusing of the high-power laser beam at different positions and damaging the target by adjusting the position of the laser emission eyepiece group 11 forward and backward.

[0108] Example: Use fiber laser to input high power laser, the input power is 14kW, the working wavelength is 1080nm, M 2The factor is about 7 (a factor used to measure the spatial coherence and quality of the beam. The M of an ideal Gaussian beam 2 is 1, while the M of the actual beam 2 >1 means the beam deviates from the ideal Gaussian characteristic), the input laser waist diameter is 22mm, the incident laser divergence angle (i.e. the divergence angle of the laser beam during transmission) is 2θ=430μrad, μrad is micro-radians. According to the relationship between the maximum laser spot size and power density, it can be calculated that the spot size (i.e. the diameter of the spot) needs to be less than 130mm in order for the average power density of the spot to reach the damage threshold.

[0109] Table 1

[0110] Focal length / mm 470.0 470.2 470.5 470.9 471.5 Focus position / km 2.0 1.5 1 0.5 0.3

[0111] The transmission-type high-power laser emission system in the application was tested, and focusing was achieved by adjusting the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12. The distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12 is the equivalent focal length of the system. The corresponding relationship between the system equivalent focal length and the focusing position is shown in Table 1.

[0112] It can be seen from Table 1 that when the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12 increases, the focal length increases, and the focus position becomes closer. When the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12 decreases, the focal length decreases, and the focus position becomes farther. For example, when the distance between the laser emission eyepiece group 11 and the laser emission objective lens group 12 is 470 mm, the transmission-type high-power laser emission system achieves the focusing of the laser beam at a position of 2 km. When the laser emission eyepiece group 11 is focused 1.5 mm away from the laser emission objective lens group 12 as a whole, the transmission-type high-power laser emission system achieves the focusing of the laser beam at 0.3 km. The focusing amount is set to 1.5 mm, which can take into account both the focusing accuracy and the control difficulty.

[0113] The wavefront diagram of the laser emitted by the system is as follows Figure 4 As shown; the divergence angle of the system is Figure 3 As shown, the divergence angle of the first group of lasers is a divergence angle (OBJ) of 0.0000 degrees (DEG), the divergence angle of the second group of lasers is a divergence angle of 0.1400 degrees, and the divergence angle of the third group of lasers is a divergence angle of 0.2000 degrees.

[0114] The transmission-type high-power laser emission system in this application is used to focus the laser beam to a predetermined position, and the high-energy laser emitted by the system is simulated using a physical optics method. The simulation results are shown in FIG. Figure 5 to Figure 6 As shown, the physical optics simulation method used here can better simulate the actual diffusion and energy distribution of the light beam in the far field. Figure 5To illustrate the effect of using physical optics to track a high-power laser beam focused at 0.3 km, Figure 6 This is the effect of using physical optics to track a high-power laser beam focused at a position of 2 km. The energy density distribution of the beam at different focusing positions can be seen in the figure. The vertical axis (V / m) in the figure is 2 It represents the square of the electric field intensity (the energy density distribution is obtained by summing the square values ​​of the field intensity in the entire area), which reflects the energy distribution of the light beam in space. The horizontal axis represents the position coordinate on the cross section, in m, and shows the distribution of the light beam energy density on the cross section. The beam diameter of the laser at 0.3 km (usually the beam diameter is defined as the 1 / e drop to the highest energy) is about 40 mm, and the beam diameter of the laser at 2 km is about 130 mm, which meets the damage requirements.

[0115] The steps in this application can be adjusted in order, combined, and deleted according to actual needs.

[0116] The units in the device of the present application can be combined, divided and deleted according to actual needs.

[0117] Although the present application is disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and are not intended to limit the application of the present application. The scope of protection of the present application is defined by the appended claims and may include various modifications, alterations and equivalents made to the invention without departing from the scope and spirit of the present application.

Claims

1. A transmission type high power laser emission system, characterized in that: The transmission-type high-power laser emission system comprises a laser input end and a laser output end, wherein the laser input end is connected to the output connector of the high-power fiber laser and is used to receive the laser beam emitted by the fiber laser, and the laser output end is used to converge the laser beam to the target position; The transmission-type high-power laser emission system comprises a laser emission lens group (1), an emission lens barrel (2), a focusing motor (3) and a control circuit board (4); The laser emission lens group (1) is arranged inside the emission lens barrel (2), and the laser emission lens group (1) comprises a laser emission eyepiece group (11) and a laser emission objective lens group (12), the laser emission eyepiece group (11) is located at the laser incident end, the laser emission objective lens group (12) is located at the laser emission end, and the diameter of the laser emission eyepiece group (11) is smaller than the diameter of the laser emission objective lens group (12); The laser emission eyepiece group (11) comprises two concave lenses, the concave surfaces of the two concave lenses are arranged opposite to each other, and the laser emission eyepiece group (11) is used to expand the incident laser beam to increase the divergence angle of the laser beam, so that the laser beam is evenly propagated to the laser emission objective lens group (12); The laser emission objective lens group (12) comprises three convex lenses, the convex surfaces of the three convex lenses face the direction of laser emission, and the laser emission objective lens group (12) is used to uniformly converge the expanded laser beam to a target position; The focus motor (3) is arranged outside the emitting lens barrel (2) and close to the laser emitting eyepiece group (11), and is used to adjust the position of the laser emitting eyepiece group (11) to achieve system focal length adjustment; The control circuit board (4) is used to receive a focus input signal and control the focus motor (3) to perform focus adjustment according to the focus input signal.

2. The transmission-type high-power laser emitting system according to claim 1, characterized in that: The laser emitting eyepiece set (11) comprises a first laser emitting eyepiece (111) and a second laser emitting eyepiece (112) in sequence along the optical path direction; The object side surface of the first laser emitting eyepiece (111) is a convex surface with a radius of curvature of 500.3 mm, and the image side surface of the first laser emitting eyepiece (111) is a concave surface with a radius of curvature of -77.9 mm; The object side surface of the second laser emitting eyepiece (112) is a concave surface with a curvature radius of -88.4 mm, and the image side surface of the second laser emitting eyepiece (112) is a flat surface.

3. The transmission-type high-power laser emitting system as claimed in claim 2, characterized in that: The focal length of the first laser emitting eyepiece (111) is -202 mm, and the focal length of the second laser emitting eyepiece (112) is -193 mm; The distance between the first laser emitting eyepiece (111) and the second laser emitting eyepiece (112) is 10 mm.

4. The transmission-type high-power laser emitting system according to claim 1, characterized in that: The laser emitting objective lens group (12) comprises, in sequence along the optical path direction, a first laser emitting objective lens (121), a second laser emitting objective lens (122) and a third laser emitting objective lens (123); The object side surface of the first laser emitting objective lens (121) is a concave surface with a radius of curvature of -500.3 mm, and the image side surface of the first laser emitting objective lens (121) is a convex surface with a radius of curvature of 380.9 mm; The object side surface of the second laser emitting objective lens (122) is a concave surface with a radius of curvature of -859 mm, and the image side surface of the first laser emitting objective lens (121) is a convex surface with a radius of curvature of 423.8 mm; The object side surface of the third laser emitting objective lens (123) is a plane, and the image side surface of the third laser emitting objective lens (123) is a convex surface with a curvature radius of 621 mm.

5. The transmission-type high-power laser emitting system as claimed in claim 4, characterized in that: The focal length of the first laser emitting objective lens (121) is 3292 mm, the focal length of the second laser emitting objective lens (122) is 1796 mm, and the focal length of the third laser emitting objective lens (123) is 1355 mm; The distance between the first laser emitting objective lens (121) and the second laser emitting objective lens (122) is 8.75 mm; the distance between the second laser emitting objective lens (122) and the third laser emitting objective lens (123) is 2 mm.

6. The transmission-type high-power laser emitting system according to claim 1, characterized in that: The distance between the laser emission eyepiece group (11) and the laser emission objective lens group (12) ranges from 470 mm to 471.5 mm, and the corresponding focusing position of the transmission-type high-power laser emission system ranges from 2 km to 0.3 km, wherein the larger the distance between the laser emission eyepiece group (11) and the laser emission objective lens group (12), the closer the focusing position of the system is, and the smaller the distance between the laser emission eyepiece group (11) and the laser emission objective lens group (12), the farther the focusing position of the system is.

7. The transmission-type high-power laser emitting system according to claim 1, characterized in that: The focusing motor (3) is connected to the laser emitting eyepiece group (11) via a mechanical connector, and is used to move the laser emitting eyepiece group (11) via the mechanical connector, change the relative position between the laser emitting eyepiece group (11) and the laser emitting objective lens group (12), and achieve system focal length adjustment; the control circuit board (4) is arranged on the emitting lens barrel (2), and the control circuit board (4) is electrically connected to the focusing motor (3).

8. The transmission-type high-power laser emitting system according to claim 1, characterized in that: An aperture stop is provided at the laser incident end, and the aperture stop is located on a side of the laser emission eyepiece group (11) close to the optical fiber laser.

9. The transmission-type high-power laser emitting system according to claim 1, characterized in that: Each lens in the laser emission eyepiece group (11) and the laser emission objective lens group (12) is made of the same high-purity fused quartz material, and the refractive index of the material is between 1.45 and 1.

46.

10. An application of the transmission-type high-power laser emission system as claimed in any one of claims 1 to 9 in achieving target damage, characterized in that: The application includes the following steps: S1: Determine the target position to be damaged and align the laser output end of the system to the target position; S2: Determine the range of the system focus position according to the distance of the target position and the predetermined maximum spot size, and calculate the system equivalent focal length range that can damage the target according to the range of the focus position, which specifically includes the following steps: The target position is taken as the closest focus position F1, and the farthest focus position F2 is calculated according to the predetermined maximum spot size L2 and the closest focus position F1: Where L1 is the width of the system's output laser beam, and the range of the system's focal position is (F1, F2). The system's equivalent focal length range is calculated based on the range of the focal position (F1, F2), and the relationship between the equivalent focal length and the focal position is: Based on the relationship between the equivalent focal length and the focus position, an equivalent focal length range corresponding to the focus position range (F1, F2) is obtained; S3: Based on the calculated focal length range, the position of the laser emission eyepiece group (11) is adjusted using a focusing motor (3) so that the focal length value of the system is within the focal length range; S4: Use a fiber laser to emit a laser beam, so that the emitted laser beam converges to a target position to damage the target.

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