Explosive detection device based on high-collimation laser irradiation optical beam expanding system

Abstract

The invention discloses an explosive detection device based on a high-collimation laser irradiation optical beam expanding system. The explosive detection device comprises a fixed base, and a carbon dioxide laser, a first-stage light beam expanding system and a second-stage light beam expanding system are installed on the fixed base; a light beam emitted by the carbon dioxide laser enters the first-stage light beam expansion system, and an exit pupil of the first-stage light beam expansion system is an entrance pupil of the second-stage light beam expansion system; light beams emitted by the secondary light beam expansion system form detection laser beams, and a detection station is further installed and used for placing an object to be detected; the fixed base is also provided with an infrared camera and a visible light camera, and the infrared camera and the visible light camera are used for shooting the object to be detected; the system further comprises an image analysis system, and the infrared camera and the visible light camera are connected with the image analysis system and carry out signal transmission. In the invention, the explosive detection device based on the high-collimation laser irradiation optical beam expanding system can be widely applied to safety inspection of explosives.

Description

Technical Field

[0001] The present invention relates to the technical field related to explosive detection equipment, and in particular to an explosive detection device based on a high-collimation laser irradiation optical beam expansion system. Background Art

[0002] Security inspections in public places, such as subway stations, train stations, airports, docks and other places with large traffic and complex backgrounds, urgently need real-time and rapid detection of hidden explosives. Explosive detection equipment can better ensure people's travel safety.

[0003] At present, laser Raman spectroscopy detection technology and terahertz spectroscopy detection technology are usually used to conduct experimental research on explosives. However, the detection distance achieved by the above detection technologies is relatively short, and the manufacturing cost is relatively high. In 2009, Michal R. Papantonakis, Chris Kendziora and others from the US Naval Laboratory used quantum cascade lasers and infrared thermal imaging technology to conduct a series of experimental studies on trace explosives by taking advantage of the selective absorption of laser wavelengths by explosives, and detected and distinguished trinitrotoluene TNT and RDX under certain conditions. However, the verification methods used are all based on principle experimental systems, in which the target detection area borne by the laser beam expansion system is less than 60mm in diameter, which cannot meet the requirements of large detection area, long working distance, and rapid detection for explosive security inspections in public places such as passenger stations. Summary of the invention

[0004] In order to solve the technical problems existing in the background technology, the present invention proposes an explosive detection device based on a high-collimation laser irradiation optical beam expansion system.

[0005] The present invention discloses an explosive detection device based on a high-collimation laser irradiation optical beam expansion system, comprising a fixed base, on which a carbon dioxide laser, a primary beam expansion system, and a secondary beam expansion system are arranged;

[0006] The light beam emitted by the carbon dioxide laser enters the primary light beam expansion system, and the exit pupil of the primary light beam expansion system serves as the entrance pupil of the secondary light beam expansion system;

[0007] The light beam emitted by the secondary beam expansion system forms a detection laser beam, and a detection station is also provided, on which an object to be detected is placed;

[0008] The fixed base is also provided with an infrared camera and a visible light camera, and the infrared camera and the visible light camera are used to photograph the object to be detected;

[0009] It also includes an image analysis system, and the infrared camera and the visible light camera are connected to the image analysis system and transmit the images they capture to the image analysis system.

[0010] In a preferred embodiment, the magnification of the primary beam expansion system is 4 times, and the magnification of the secondary beam expansion system is 23 times.

[0011] In a preferred embodiment, the first-stage beam expansion system includes a positive lens and a negative lens, and the focal length ratio of the positive lens and the negative lens is 4 times.

[0012] As a further optimized solution of the present invention, the first-stage beam expansion system includes a positive lens and a negative lens, and the spherical aberration coefficient expression of the first-stage beam expansion system is:

[0013]

[0014] Where: S1 is the spherical aberration coefficient, n is the refractive index of the lens material, l is the object intercept of the on-axis light, and u is the object angle between the on-axis light and the optical axis;

[0015] The primary beam expansion system should meet the following requirements:

[0016]

[0017] Among them, h1 is the semi-aperture of the positive lens, h2 is the semi-aperture of the negative lens, is the focal power of the positive lens, is the focal power of the negative lens, and β is the magnification of the beam expansion system.

[0018] The optical power of the lens is expressed as follows:

[0019]

[0020] Where n is the refractive index of the lens material, r1 and r2 are the radii of curvature of the front and back surfaces of the lens, and d is the axial center thickness of the lens.

[0021] In a preferred embodiment, the positive lens is a plano-convex lens, and the negative lens is a plano-concave lens.

[0022] As a further optimized solution of the present invention, the beam waist of the carbon dioxide laser is the entrance pupil of the primary beam expansion system, and the beam passes through the negative lens and then the positive lens.

[0023] In a preferred embodiment, the secondary beam expansion system is an off-axis Cassegrain system.

[0024] As a further optimized solution of the present invention, the surface shapes of the primary mirror and the secondary mirror of the Cassegrain system are generally quadratic surfaces, and the expressions thereof are as follows:

[0025]

[0026] Wherein, r is the distance from a point on the quadratic surface to the optical axis, c is the curvature of the vertex of the quadratic surface, and k is the conic coefficient. If k = 0, it represents a spherical surface; if -1 < k < 0, it represents an ellipsoidal surface; if k = -1, it represents a parabolic surface; if k < -1, it represents a hyperbolic surface.

[0027] As a further optimized solution of the present invention, the primary mirror is an off-axis ellipsoidal surface, and the secondary mirror surface type is selected as a spherical surface.

[0028] As a further optimized solution of the present invention, in order to adjust the distance between the primary mirror and the secondary mirror, a frame is further installed on the fixed base, a moving mechanism is installed on the frame, the secondary mirror is installed on the moving end of the moving mechanism, and the moving mechanism drives the secondary mirror to move in the horizontal direction to realize the adjustment of the distance between the secondary mirror and the primary mirror. The moving mechanism is located above the primary mirror.

[0029] In the optical system, it is necessary to align the primary mirror and the secondary mirror to achieve a better beam expansion effect. Therefore, as a further optimized solution of the present invention, it further includes a rotating plate installed on the moving end of the moving mechanism. The secondary mirror is installed on the rotating plate, and the rotating plate can rotate horizontally relative to the moving mechanism;

[0030] It further includes a mounting plate. The mounting plate is vertically rotatably installed on the moving end of the moving mechanism through a vertical shaft, and the rotating plate is installed on the mounting plate, which further facilitates the adjustment of the relative position between the secondary mirror and the primary mirror.

[0031] Preferably, it further includes a pre-tightening mechanism. The pre-tightening mechanism is installed on the moving end of the moving mechanism and is used to apply a pre-tightening force to the vertical shaft and the rotating plate. When the pre-tightening mechanism is not in contact with the vertical shaft and the rotating plate, the vertical shaft and the rotating plate can rotate relative to the frame by a relatively large angle under a certain force. When the pre-tightening mechanism applies a pre-tightening force to the vertical shaft and the rotating plate, the vertical shaft and the rotating plate rotate relative to the frame by a relatively small amplitude under a certain force.

[0032] Specifically, the pre-tightening mechanism includes an adjusting rod installed on the moving end of the moving mechanism. The position of the adjusting rod in the vertical direction can be adjusted, and the bottom of the adjusting rod has a first elastic tightening member that抵触 the rotating part of the rotating plate relative to the mounting plate; it further includes a sliding rod that is horizontally slidably installed on the moving end of the moving mechanism. The sliding rod has a second elastic tightening member that抵触 the vertical shaft. During the vertical movement of the adjusting rod, the sliding rod is squeezed to move horizontally so that the second elastic tightening member抵触 the vertical shaft. Specifically, the adjusting rod can be installed on the moving end of the moving mechanism by a threaded method in the prior art, and the adjusting rod is rotated to realize the lifting of the adjusting rod in the vertical direction.

[0033] In the present invention, the disclosed explosive detection device based on a high-collimation laser irradiation optical beam expansion system can irradiate the detection area at a distance of 2 meters with a 160mm diameter light spot within 4 seconds, and monitor and warn in real time and mark the location, size, geometric shape and other characteristics of contaminated explosives such as TNT and RDX, and can be widely used in the security inspection of explosives.

[0034] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the present invention;

[0036] Figure 2 It is a partial enlarged view of the primary beam expansion system of the present invention;

[0037] Figure 3 It is a partial enlarged view of the two-stage beam expansion system of the present invention;

[0038] Figure 4 It is a light path diagram of the first-level beam expansion system of the present invention;

[0039] Figure 5 The RMS wave aberration distribution diagram of the first-level beam expansion system of the present invention;

[0040] Figure 6 is the diffraction modulation transfer function MTF of the first-order beam expansion system of the present invention;

[0041] Figure 7 is a light path diagram of the two-stage beam expansion system of the present invention;

[0042] Figure 8 is the RMS wave aberration distribution diagram of the two-stage beam expansion system of the present invention;

[0043] Fig. 9 is the diffraction modulation transfer function MTF of the two-stage beam expansion system of the present invention;

[0044] Fig.10 An optical path diagram of a beam expansion system of the present invention with an additional ideal lens (the ideal lens is not a part of the device of the present invention);

[0045] Fig.11 is a light path diagram of the beam expansion system of the present invention;

[0046] Fig.12 is the RMS wave aberration distribution diagram of the beam expansion system of the present invention;

[0047] Fig.13 is the diffraction modulation transfer function MTF of the beam expansion system of the present invention;

[0048] Fig.14 This is the illumination distribution diagram of the beam expansion system obtained by simulation when the input beam is a fundamental mode Gaussian beam with a divergence angle of 2.3 mrad and a beam waist diameter of 1.8 mm, after passing through the beam expansion system, a receiver is set at the position of 2000 mm;

[0049] Fig.15 An illumination distribution diagram of a gradient filter used in the simulation of the present invention;

[0050] Fig.16 The illumination distribution diagram of the simulation of the present invention after adding a gradient filter;

[0051] Fig.17 This is a photo of a light spot with a diameter greater than 160 μm formed by the beam expansion system of the present invention;

[0052] Fig.18 Schematic diagram of the secondary mirror installation structure of the second embodiment of the present invention;

[0053] Fig.19 It is a partial enlarged view of the adjusting rod part in the second embodiment of the present invention;

[0054] In the figure: 1. fixed base; 2. carbon dioxide laser; 3. primary beam expansion system; 30. positive lens; 31. negative lens; 4. secondary beam expansion system; 40. primary mirror; 41. secondary mirror; 5. object to be detected; 6. infrared camera; 7. visible light camera; 8. image analysis system; 9. gradient filter; 10. rotating plate; 11. annular groove; 12. frame; 13. moving mechanism; 14. mounting plate; 15. vertical axis; 16. adjusting rod; 160. adjusting part; 161. connecting part; 1600. adjusting inclined plane; 17. first elastic fastening member; 18. sliding rod; 19. second elastic fastening member; 20. locking mechanism. DETAILED DESCRIPTION

[0055] The preferred embodiments of the present invention are described in detail below, and examples of the preferred embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements with the same or similar functions. The preferred embodiments described below by the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0056] Embodiment 1

[0057] like Figure 1-3The explosive detection device shown is based on a high-collimation laser irradiation optical beam expansion system. The diameter of the irradiated area of ​​the detected target of the present invention is greater than 160mm, and its working distance is greater than 2000mm. The output beam divergence angle is less than 25μrad. The design adopts a 100W power adjustable CO2 laser (laser output beam waist diameter 1.8mm). The system includes a fixed base 1, on which a carbon dioxide laser 2, a primary beam expansion system 3, and a secondary beam expansion system 4 are arranged. The primary beam expansion system 3 and the secondary beam expansion system 4 form a beam expansion system;

[0058] The 10.6 μm wavelength of the carbon dioxide laser is used as the working wavelength of the laser beam expansion system, the output power of the carbon dioxide laser is 100 W (its power is continuously adjustable), and the main technical parameters of the carbon dioxide laser are: the beam waist diameter is 1.8 mm, the far-field divergence angle is 2.3 mrad, the light beam emitted by the carbon dioxide laser 2 enters the primary beam expansion system 3, and the exit pupil of the primary beam expansion system 3 is the entrance pupil of the secondary beam expansion system 4; in this embodiment, the primary beam expansion system 3 adopts an inverted Galilean telescope system, and the secondary beam expansion system adopts an off-axis Cassegrain system;

[0059] The light beam emitted by the secondary beam expansion system 4 forms a detection laser beam, and a detection station is also provided, on which the object to be detected 5 is placed;

[0060] The fixed base 1 is also provided with an infrared camera 6 and a visible light camera 7, which are used to photograph the object to be detected 5. The distances between the infrared camera 6 and the visible light camera 7 and the object to be detected 5 are equal. The infrared camera 6 is a small-volume, large-array, high-resolution, and easy-to-integrate infrared camera; the visible light camera 7 is a digital high-definition camera;

[0061] It also includes an image analysis system 8. The infrared camera 6 and the visible light camera 7 are connected to the image analysis system 8 and transmit the images they capture to the image analysis system 8. The image analysis system 8 software is a detection software developed in C++ language and runs on a computer system with a human-computer interaction interface.

[0062] The present invention can achieve a working distance (the distance from the object to be detected 5 to the infrared camera 6 and the optical camera) greater than 2000 mm, a detection target area diameter greater than 160 mm, a light beam divergence angle less than 25 μrad, and a detection time less than 4 s, so that the device can meet the technical requirements of an engineering prototype of explosive laser detection.

[0063] In a preferred embodiment, the magnification of the first-level beam expansion system 3 is 4 times, and the magnification of the second-level beam expansion system 4 is 23 times. The inverted Galilean telescope system of the first-level beam expansion system 3 adopts a two-single-lens design. The first-level beam expansion system 3 includes a positive lens 30 and a negative lens 31, and the focal length ratio of the positive lens 30 and the negative lens 31 is 4 times.

[0064] The main aberration of the laser beam expansion system is spherical aberration. According to the third-order aberration theory, the PW method can be used to solve the initial structural parameters of the positive lens 30 and the negative lens 31. The expression of the spherical aberration coefficient is:

[0065]

[0066] Where: S1 is the spherical aberration coefficient, n is the refractive index of the lens material, l is the object intercept of the on-axis light, and u is the object angle between the on-axis light and the optical axis;

[0067] The primary beam expansion system 3 is an aphotic system and should satisfy the following expression:

[0068]

[0069] Wherein, h1 is the semi-aperture of the positive lens 30, h2 is the semi-aperture of the negative lens 31, is the focal power of the positive lens 30, is the focal power of the negative lens 31, β is the magnification of the beam expansion system;

[0070] The optical power of the lens is expressed as follows:

[0071]

[0072] Where n is the refractive index of the lens material, r1 and r2 are the radii of curvature of the front and back surfaces of the lens, and d is the axial center thickness of the lens.

[0073] The positive lens 30 is a plano-convex lens, the negative lens 31 is a plano-concave lens, and the lens material is ZnSe. The surface curvature radius and axial center thickness of the positive lens 30 and the negative lens 31 can be calculated. The laser beam waist is used as the entrance pupil of the first-level beam expansion system 3. The axial distance between the entrance pupil and the negative lens 31 is set to 10mm. The negative lens 31 is a plano-concave lens, the positive lens 30 is a plano-convex lens, and the output beam diameter is 7.2mm. Aberration balance and optimization design are performed.

[0074] The design results are that the concave curvature radius of the negative lens 31 is 12.618 mm, the center thickness is 2 mm, the convex curvature radius of the positive lens 30 is 50.47 mm, the center thickness is 4 mm, and the axial spacing between the two lenses is 24.39 mm.

[0075] As a further optimized solution of the present invention, the waist of the carbon dioxide laser 2 is the entrance pupil of the primary beam expansion system 3. The beam passes through the negative lens 31 and then through the positive lens 30, as Figure 4 is the optical path diagram of the primary beam expansion system 3. An ideal lens is added behind the positive lens 30 to analyze the imaging quality of the system. The RMS wave aberration of the beam expansion system can be obtained on the focal plane of the ideal lens as follows Figure 5 shown, and the diffraction modulation transfer function MTF is as follows Figure 6 shown.

[0076] In the preferred embodiment, the secondary beam expansion system 4 is an off-axis Cassegrain system, which can greatly reduce the cost, and the reflecting mirror can fold the optical path to make the system structure more compact. The off-axis design can achieve unobstructed light to reduce energy loss.

[0077] The surface shapes of the primary mirror 40 and the secondary mirror 41 of the Cassegrain system are generally quadratic surfaces, and their expressions are as follows:

[0078]

[0079] where r is the distance from a point on the quadratic surface to the optical axis, c is the curvature at the vertex of the quadratic surface, and k is the conic coefficient. If k = 0, it represents a spherical surface; if -1 < k < 0, it represents an ellipsoidal surface; if k = -1, it represents a parabolic surface; if k < -1, it represents a hyperbolic surface.

[0080] In order to minimize the optical tube length as much as possible, the relative aperture of the primary mirror 40 is selected to be 1 / 2. Then it can be known that its focal length is greater than 320 mm. According to the Gaussian optical formula, the vertex curvature radius of the primary mirror 40 can be calculated to be greater than 640 mm. According to the beam expansion magnification of 23 times, the surface radius of the secondary mirror 41 can be calculated to be approximately 28 mm.

[0081] In order to reduce the cost, the surface shape of the secondary mirror 41 is selected as a spherical surface, and the primary mirror 40 is selected as an off-axis ellipsoidal surface, which reduces the processing difficulty of the secondary mirror 41. Taking the above preliminary design parameters as input parameters, the CODEV optical design software is used for aberration balancing and optimization design. The designed off-axis reflective optical system is as Figure 7 shown. An ideal lens is added behind the primary mirror 40 to analyze the imaging quality of the system. The RMS wave aberration of the beam expansion system can be obtained on the focal plane of the ideal lens as follows Figure 8 shown, and the diffraction modulation transfer function MTF is as follows Fig. 9 shown.

[0082] The combination of the primary beam expansion system and the secondary beam expansion system is to keep the radius of curvature, thickness and lens spacing of the lens in the primary beam expansion system unchanged, and the radius of curvature, surface parameters and the spacing between the two mirrors of the reflector of the secondary beam expansion system as variables. The exit pupil of the primary beam expansion system 3 is the entrance pupil of the secondary beam expansion system. The optimization results are as follows Fig.10 , Fig.11 As shown, an ideal lens is added behind the primary mirror 40 in order to analyze the imaging quality of the system. The RMS wave aberration distribution of the beam expansion system can be obtained on the focal plane of the ideal lens as follows: Fig.12 As shown, the diffraction modulation transfer function MTF is as follows Fig.13 shown.

[0083] The above RMS wave aberration and diffraction modulation transfer function MTF both show that the aberration of the beam expansion system is well corrected. After the laser passes through the beam expansion system, the spot diameter at a working distance of 2000mm is greater than 169mm, and the beam divergence angle is 25μrad.

[0084] Depend on Fig.13 It can be seen from the diffraction modulation transfer function MTF that the MTF value in the sagittal direction is lower than the MTF value in the meridional direction. This is due to the off-axis of the primary mirror 40 and the secondary mirror 41 of the secondary beam expansion system. The greater the off-axis amount, the greater the separation of the MTF values ​​in the sagittal direction and the meridional direction. This will affect the illumination uniformity of the laser illumination area. In this way, the illumination distribution is simulated in the CODE_V software using the beam expansion system designed above. The input beam is assumed to be a fundamental mode Gaussian beam with a divergence angle of 2.3 mrad and a waist diameter of 1.8 mm. After passing through the beam expansion system, a receiver is set at a position of 2000 mm. The relative illumination distribution is simulated as shown in the figure. Figure 14-16 As shown in the figure, it can be seen that the diameter of the lighting area is greater than 160 mm, which meets the technical requirements; however, since the secondary beam expansion system is upward off-axis, the illumination of the upper part of the lighting area becomes relatively small.

[0085] The solution to this problem is to design a gradient filter 9 (as shown below Figure 14-16 As shown), the light intensity transmittance distribution is complementary to the illumination distribution of the area to be compensated, so that the uneven illumination distribution can be effectively compensated. The simulation results are as follows Fig.16 As shown, it can be seen that the basic compensation Fig.14 The inclined distribution of illumination.

[0086] The present invention manufactures a prototype according to the above parameters. The configuration parameters of the experimental prototype are: the laser power is set to 10W, the irradiation time is 4s; the infrared image is configured as black and white temperature mapping; the detection distance is 2m. The test image is obtained as follows Fig.17As shown in the figure, the laser beam expansion system forms a spot larger than 160mm, and the irradiated target surface temperature is 32.3℃ on average. The irradiated spot temperature is relatively uniform, which can be widely used in explosive security inspection. Through experimental verification, the device can irradiate the target area with a 160mm spot at a distance of 2 meters within 4 seconds, monitor and warn in real time, and mark the location, size, geometric shape and other characteristics of contaminated explosives such as TNT and RDX, which can be widely used in explosive security inspection.

[0087] Embodiment 2

[0088] like Figure 18-19 As shown, the difference between this embodiment and the above-mentioned embodiment is that: it also includes a rotating plate 10, a frame 12 and a moving mechanism 13. The frame 12 is installed on the fixed base 1, and the moving mechanism 13 is installed on the frame 12. The rotating plate 10 is installed on the moving frame for transverse rotation, and the secondary mirror 41 is installed on the rotating plate 10. It should be noted that the moving mechanism 13 can be an electric cylinder, an air cylinder, a screw slider transmission mechanism or other mechanism that can drive the plate-like component to move horizontally. In this embodiment, the moving mechanism 13 is a screw slider mechanism, and the rotating plate 10 is installed on the sliding block of the screw slider mechanism. The angle of the secondary mirror 41 relative to the primary mirror 40 is adjusted by rotating the rotating plate 10.

[0089] In some embodiments, preferably, a mounting plate 14 is also included, and the mounting plate 14 is mounted on the moving end of the moving mechanism 13 through a vertical axis 15. The vertical axis 15 can rotate vertically relative to the moving end of the moving mechanism 13. When the moving mechanism 13 is a screw slider mechanism, the vertical axis 15 is vertically rotated and installed on the sliding block. The rotating plate 10 is laterally rotated and installed on the mounting plate 14. The vertical angle of the secondary mirror 41 installed on the rotating plate 10 relative to the primary mirror 40 can be adjusted by rotating the vertical axis 15.

[0090] In some embodiments, preferably, a pre-tightening mechanism is also included, which is installed at the moving end of the moving mechanism 13. The pre-tightening mechanism is used to apply a pre-tightening force to the vertical axis 15 and the rotating plate 10. Specifically, the angle adjustment of the secondary mirror 41 is divided into coarse angle adjustment and fine angle adjustment. When the pre-tightening mechanism is not tightly pressed against the vertical axis 15 and the rotating plate 10, the vertical axis 15 and the rotating plate 10 can rotate to a relatively large angle relative to the frame 12 under a certain force. After the pre-tightening mechanism applies a pre-tightening force to the vertical axis 15 and the rotating plate 10, the vertical axis 15 and the rotating plate 10 can rotate to a relatively small amplitude relative to the frame 12 under a certain force.

[0091] As a further optimized solution of the present invention, the pre-tightening mechanism includes an adjusting rod 16 installed at the moving end of the moving mechanism 13, and the position of the adjusting rod 16 in the vertical direction can be adjusted. The bottom of the adjusting rod 16 has a first elastic tightening member 17 that contacts the rotating part of the rotating plate 10 relative to the mounting plate 14. The first elastic tightening member 17 is made of rubber. Preferably, the first elastic tightening member 17 is conical, and the outer diameter of the first elastic tightening member 17 gradually decreases from top to bottom. The axis of the first elastic tightening member 17 is in the same vertical plane as the axis of rotation of the rotating plate 10 relative to the mounting plate 14 and intersects vertically, and the axis of the first elastic tightening member 17 is vertically downward and perpendicular to the axis of rotation of the rotating plate 10 relative to the mounting plate 14. Preferably, an annular groove 11 is opened on the rotating plate 10, and the annular groove 11 The width is smaller than the maximum outer diameter of the first elastic clamping member 17. When the first elastic clamping member 17 moves downward, the first elastic clamping member 17 extends into the annular groove 11 and contacts the outer wall or bottom of the annular groove 11 to achieve resistance to the rotating plate 10. The side of the adjusting rod 16 has an adjusting slope 1600, and the adjusting slope 1600 is gradually inclined from top to bottom away from the vertical axis 15. The moving end of the moving mechanism 13 is laterally slidably installed with a sliding rod 18. The end of the sliding rod 18 is a second elastic clamping member 19 that resists the vertical axis 15. The second elastic clamping member 19 can be made of rubber material, and the end that slides away from the vertical axis 15 resists the adjusting slope 1600. When the adjusting rod 16 moves downward, the rotating plate 10 and the vertical axis 15 can be pre-tightened at the same time.

[0092] Specifically, the adjustment rod 16 includes an adjustment portion 160 and a connection portion 161. The connection portion 161 is vertically rotatably mounted on the adjustment portion 160. The adjustment portion 160 is threadedly mounted on the moving end of the moving mechanism 13. The connection portion 161 is driven to move downward by rotating the adjustment portion 160, and the connection portion 161 does not rotate. The first elastic abutting member 17 is mounted below the connection portion 161, and the upper portion of the connection portion 161 is provided with an adjustment inclined surface 1600 which is gradually inclined from top to bottom away from the rotation axis. When the connection portion 161 moves downward, the inclined surface abuts against the sliding rod 18 so that the second elastic abutting member 19 abuts against the vertical shaft 15. Of course, the vertical shaft 15 can also be provided with an annular groove like the rotating plate 10. The end of the second elastic abutting member 19 is conical and opposite to the annular groove. The width of the annular groove is smaller than the maximum outer diameter of the second elastic abutting member 19, so as to further increase the limiting and fixing of the vertical shaft 15.

[0093] As a further optimized solution of the present invention, it also includes a locking mechanism 20, which is used to fix the vertical axis 15 and the rotating plate 10 relative to the frame 12. The locking mechanism 20 can be a fixing pin or a fixing screw in the prior art, and the fixing pin for fixing the vertical axis 15 is installed between the vertical axis 15 and the moving end of the moving mechanism 13, and the axis of the fixing pin is parallel to the axis of the vertical axis 15; the fixing pin for fixing the rotating plate 10 is installed between the mounting plate 14 and the rotating plate 10, and the axis of the fixing pin is parallel to the axis of rotation of the rotating plate 10 relative to the mounting plate 14.

[0094] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0095] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0096] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0097] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0098] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. An explosive detection device based on a high-collimation laser irradiation optical beam expansion system, characterized in that: It comprises a fixed base (1), on which a carbon dioxide laser (2), a primary beam expansion system (3), and a secondary beam expansion system (4) are arranged; The beam waist of the light beam emitted by the carbon dioxide laser (2) is the entrance pupil of the primary light beam expansion system (3), and the exit pupil of the primary light beam expansion system (3) is the entrance pupil of the secondary light beam expansion system (4); The light beam emitted by the secondary light beam expansion system (4) forms a detection laser beam, and a detection station is also provided, on which the object to be detected (5) is placed; The fixed base (1) is also provided with an infrared camera (6) and a visible light camera (7), and the infrared camera (6) and the visible light camera (7) are used to photograph the object to be detected (5); It also includes an image analysis system (8), the infrared camera (6) and the visible light camera (7) are connected to the image analysis system (8), and the images captured by the infrared camera (6) and the visible light camera (7) are transmitted to the image analysis system (8).

2. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 1 is characterized in that: The magnification of the primary beam expansion system (3) is 4 times, and the magnification of the secondary beam expansion system (4) is 23 times.

3. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 2 is characterized in that: The primary beam expansion system (3) comprises a positive lens (30) and a negative lens (31), and the focal length ratio of the positive lens (30) and the negative lens (31) is 4 times.

4. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 1 is characterized in that: The primary beam expansion system (3) comprises a positive lens (30) and a negative lens (31).

5. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 4 is characterized in that: The positive lens (30) is a plano-convex lens, and the negative lens (31) is a plano-concave lens.

6. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 5 is characterized in that: The beam waist of the carbon dioxide laser (2) is the entrance pupil of the primary beam expansion system (3), and the beam passes through the negative lens (31) and then the positive lens (30).

7. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 1 is characterized in that: The secondary beam expansion system (4) is an off-axis Cassegrain system.

8. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 7 is characterized in that: The primary mirror (40) is an off-axis ellipsoidal surface, and the secondary mirror (41) is a spherical surface.

9. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 7, characterized in that: A frame is also installed on the fixed base, a moving mechanism is installed on the frame, and the secondary mirror is installed at the moving end of the moving mechanism. The secondary mirror is driven to move in the horizontal direction by the moving mechanism to adjust the distance between the secondary mirror and the primary mirror.

10. The explosive detection device based on a high-collimation laser irradiation optical beam expansion system according to claim 9, characterized in that: It also includes a mounting plate, which is mounted on the moving end of the moving mechanism by vertical rotation via a vertical axis; It also includes a rotating plate mounted on the mounting plate, the secondary mirror is mounted on the rotating plate, and the rotating plate can be laterally rotated relative to the moving mechanism.

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