A panoramic scanning infrared detection system, method, and application for pipe cracks.

Abstract

This invention discloses a panoramic ring-scan infrared detection system, method, and application for pipe cracks. It includes a photothermal excitation acquisition system and a reflection scanning system arranged along the inner axis of the pipe. The photothermal excitation acquisition system shapes a laser beam into a ring-shaped spot via a fiber optic coupler and projects it onto the reflection scanning system. The reflection scanning system reflects the projected ring-shaped spot through a conical reflector, forming a circumferential scanning ring laser on the inner wall of the pipe's curved surface, creating a dynamic scanning heat flux on the pipe's curved surface structure. By acquiring the dynamic temperature field of the circumferential curved surface inside the tested pipe, circumferential ring-scan infrared detection of defects in the pipe's curved surface structure is achieved. This invention integrates mechanical movement, laser shaping, and the principle of a conical reflector to achieve efficient, integrated, non-contact online detection of the circumferential curved surface structure of pipes, significantly improving the detection capability and efficiency of pipe curved surface structures and expanding the applicability of laser infrared detection to anisotropic structures.

Description

Technical Field

[0001] This invention relates to the field of non-contact photothermal infrared non-destructive testing technology, specifically to a panoramic ring-scan infrared detection system, method, and application for pipe cracks. Background Technology

[0002] Pipelines are widely used in energy fields such as water supply, oil, and heating. They are an important component of special equipment and infrastructure. Under complex stress and chemical corrosion environments, they are prone to cracking, which affects mechanical properties and poses a serious threat to safety. Therefore, efficient full-coverage inspection and accurate crack defect evaluation are required.

[0003] Currently, automated visual inspection based on video probes is widely used in pipe inspection, offering advantages such as high efficiency, speed, and system miniaturization. However, it lacks the capability to detect damage inside the pipe wall. Existing eddy current and ultrasonic testing methods, along with corresponding online inspection technologies, are applied to pipe inspection. However, issues such as near-contact testing methods (eddy current and ultrasonic testing) and surface blind spots (ultrasonic testing) pose significant challenges to inspection coverage and efficiency in long-distance, high-volume inspections. Furthermore, the diverse applications for pipes of different materials, diameters, and sizes also significantly increase the complexity and cost of the mechanical control systems for these methods.

[0004] Infrared nondestructive testing (NDT) technology, due to its non-contact, long-distance, and large-area detection characteristics, is widely used in key fields such as aerospace, defense, shipbuilding, and energy. Especially in damage and defect assessment, active infrared detection offers higher sensitivity and signal-to-noise ratio. However, current technologies still struggle to achieve efficient online inspection of pipelines across the entire circumference. Laser infrared (LIIR) detection uses high-energy focusing and flexibly shaped, precisely controllable dynamic lasers as the thermal excitation source. Spatially modulated LIIR detection methods are suitable for detecting circumferentially distributed curved surface cracks within pipelines. To achieve efficient and accurate detection of circumferentially distributed pipeline damage, in-depth research is needed on the heat conduction and heat wave diffusion laws of pipeline curved surface structures, particularly in LIIR detection, where quantitative research on curved surface cracks in pipelines remains insufficient. Summary of the Invention

[0005] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide a panoramic ring-scan infrared detection system, method, and application for pipe cracks. This invention generates a scanning ring laser through a coupling design of mechanical movement and laser shaping, and uses a conical reflector to reflect the laser, forming a full-circumferential dynamic ring-scanning laser thermal excitation mode within the pipe. Similarly, the principle of the conical reflector is utilized to achieve infrared thermal imaging detection of the pipe's full-circumferential curved surface, solving the problem of efficient and comprehensive detection of surface and subsurface defects in the curved structure within the pipe.

[0006] The present invention is achieved through the following technical solution.

[0007] One aspect of the present invention provides a panoramic circumferential scanning infrared detection system for pipe cracks, comprising a photothermal excitation acquisition system and a reflection scanning system arranged along the inner axis of the pipe;

[0008] The photothermal excitation acquisition system is equipped with a laser fiber connected to a laser, a fiber optic coupler barrel connected to the laser fiber, a first-axis conical mirror and a convex lens located inside the fiber optic coupler barrel, and a second-axis conical mirror located inside a movable lens; it is used to project the annular light spot shaped by the fiber optic coupler barrel, which is guided by the laser fiber, onto the reflection scanning system.

[0009] The reflective scanning system is equipped with a conical reflector inside the pipe, which reflects the annular light spot projected by the photothermal excitation acquisition system through the conical reflector to form a full-circumferential scanning ring laser on the inner wall of the curved surface of the pipe, thereby forming a dynamic scanning heat flow on the curved surface structure of the pipe.

[0010] By acquiring the dynamic temperature field of the entire circumferential curved surface inside the tested pipeline, full-circumferential ring laser scanning infrared detection of defects in the pipeline's curved surface structure can be achieved.

[0011] As a preferred method, a small infrared thermal imager positioned above the lens barrel of the fiber optic coupler is used to collect the dynamic temperature field of the entire circumferential curved surface inside the pipe under test, thereby realizing the full circumferential ring laser scanning infrared detection of defects in the curved surface structure of the pipe.

[0012] Preferably, the movable lens can move back and forth along its own axis.

[0013] Preferably, the axial conical lens, the convex lens, and the optical fiber coupler are all coaxial inside the lens barrel.

[0014] Preferably, the cone angle of the cone-shaped reflector is at least greater than 90°.

[0015] Preferably, the photothermal excitation acquisition system and the reflection scanning system maintain a fixed distance.

[0016] Another aspect of the present invention provides a detection method for a panoramic scanning infrared detection system for pipe cracks, comprising:

[0017] The photothermal excitation acquisition system and the reflection scanning system are fixed in the center inside the tube, and the rotatable lens of the photothermal excitation acquisition system is coaxially set with the center of the conical reflector of the reflection scanning system.

[0018] The control computer synchronously starts a small infrared thermal imager for sampling and a laser generator to produce laser light to a laser fiber.

[0019] The Bessel beam introduced by the laser fiber enters the inside of the fiber coupler tube, passes through the first axis conical mirror, the convex lens and the second axis conical mirror in succession, and is shaped into a ring-shaped light spot. It is reflected by the conical reflector and generates a static ring laser beam along the tube axis to irradiate the inner wall of the curved surface of the tube.

[0020] Adjust the distance d between the convex lens and the second-axis conical mirror to adjust the diameter R of the annular light spot projected onto the conical reflector;

[0021] Adjust the numerical aperture NA of the second-axis conical mirror to control the width D of the ring of a full-circumferential scanning ring laser irradiating the inner wall of the pipe;

[0022] The photothermal excitation acquisition system and the reflection scanning system work together to move and scan along the pipeline axis, while the rotary full-circumferential linear scanning laser performs dynamic scanning and thermal excitation heating on the inner wall of the pipeline.

[0023] A small infrared thermal imager acquires the transient temperature field of the curved surface structure inside the pipe through the infrared reflection light path of the conical reflector, and transmits the data back to the control computer, realizing the full-circumferential ring laser scanning infrared detection of defects in the overall curved surface structure of the pipeline.

[0024] Preferably, the relationship between the distance d between the convex lens and the second-axis conical mirror and the diameter R of the annular light spot projected onto the conical mirror satisfies the following condition:

[0025] Keeping the cone angle α of the first-axis conical mirror, the cone angle θ of the conical mirror, and the focal length f of the convex lens constant, and fixing the numerical aperture NA of the second-axis conical mirror, the distance d between the convex lens and the second-axis conical mirror is proportional to the diameter R of the annular spot of the conical mirror; then the annular width D of the full-circumference scanning ring laser remains unchanged.

[0026] The numerical aperture NA of the second-axis conical mirror and the ring width D of the adjusted full-circumferential scanning ring laser must satisfy the following conditions:

[0027] Keeping the cone angle α of the first-axis conical mirror, the cone angle θ of the conical reflector, and the focal length f of the convex lens constant, and fixing the distance d between the convex lens and the second-axis conical mirror, the numerical aperture NA of the second-axis conical mirror is inversely proportional to the ring width D of the circumferential scanning ring laser. Then the ring spot diameter R of the conical reflector remains unchanged.

[0028] Preferably, the thermally excited laser wavelength is 980-1064nm, and the infrared thermal imager acquisition wavelength is 7-14μm.

[0029] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0030] 1. A high-power fiber laser is shaped into a ring scanning spot by a ring beam shaping lens group probe (fiber coupler lens barrel, two axial conical mirrors, convex lens, and movable lens). The ring scanning spot is coaxially irradiated by the conical reflector and then divided and reflected onto the curved surface of the inner wall of the pipe, thus achieving full circumferential ring scanning thermal excitation.

[0031] 2. A small infrared thermal imager is used to acquire circumferential defect temperature detection images of the pipe's inner wall reflected by a conical reflector, thereby enabling circumferential detection and acquisition of curved structures.

[0032] 3. By controlling the photothermal excitation acquisition system and the reflective scanning system to perform a centered scan along the pipeline axis, efficient non-contact ring-scan photothermal infrared detection is achieved. This detection system only needs to perform a single scan inside the inspected pipeline to obtain multiple pieces of information about defects on the inner wall.

[0033] The panoramic ring-scan infrared detection system for pipe cracks, as described in this invention, has the advantages of being easy to implement, easy to operate, highly practical, efficient in detection, and low in cost. It can be widely used in the detection of defects and damage in water supply, oil, and heating pipelines. Attached Figure Description

[0034] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, do not constitute an undue limitation of the invention. In the drawings:

[0035] Figure 1 This invention presents a schematic diagram of a panoramic circumferential scanning infrared detection system for pipe cracks.

[0036] Figure 2(a) is a diagram of the laser ring scanning probe system in this invention;

[0037] Figure 2(b) is a schematic diagram of the ring-scanning laser reflection optical path in this invention;

[0038] Figure 3 This is a schematic diagram of the tube curve structure model in this invention;

[0039] Figure 4(a) is a schematic diagram of defect detection from the perspective of the tube axis in this invention;

[0040] Figure 4(b) is a schematic diagram of local magnified defect detection from the perspective of the tube axis in this invention;

[0041] Figure 5 This is a schematic diagram of the temperature lines spanning the defect in this invention.

[0042] In the figure: 1. Miniature infrared thermal imager; 2. Fiber optic coupler lens tube; 3. Fiber optic cable; 4. First-axis conical mirror; 5. Convex lens; 6. Movable lens; 7. Second-axis conical mirror; 8. Ring spot; 9. Conical reflector; 10. Ring laser; 11. In-tube centering scanning mechanism; 12. Photothermal excitation acquisition system; 13. Reflection scanning system; 14. Surface defects. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0044] like Figure 1 As shown in the figure, an embodiment of the present invention provides a panoramic circumferential scanning infrared detection system for pipe cracks, including a photothermal excitation acquisition system 12 and a reflection scanning system 13 arranged along the inner axis direction A of the pipe. The photothermal excitation acquisition system 12 and the reflection scanning system 13 move together along the pipe axis direction A. The full-circumferential scanning ring laser will form a full-circumferential scanning ring laser 10 on the inner wall of the pipe and form a dynamic scanning heat flow on the curved surface structure of the pipe, thereby realizing efficient full-circumferential infrared non-destructive detection of defects 14 in the curved surface structure of the pipe.

[0045] As shown in Figure 2(a), the photothermal excitation acquisition system 12 includes a small infrared thermal imager 1, a fiber optic coupler tube 2, a laser fiber 3, and a movable lens 6. The laser fiber 3 is connected to the incident end of the fiber optic coupler tube 2, and the movable lens 6 is connected to the exit end. A first-axis conical mirror 4 and a convex lens 5 are disposed inside the fiber optic coupler tube 2. The first-axis conical mirror 4, the convex lens 5, and the fiber optic coupler tube 2 are coaxial. A second-axis conical mirror 7 is located inside the movable lens 6. The small infrared thermal imager 1 is positioned above the fiber optic coupler tube 2.

[0046] like Figure 1 As shown, the reflective scanning system 13 includes an in-tube centering scanning mechanism 11 and a cone reflector 9. The cone reflector 9 is installed in the tube through the in-tube centering scanning mechanism 11. The cone reflector 9 is coaxial with the movable lens 6. The annular light spot 8 emitted from the movable lens 6 is projected onto the cone surface of the cone reflector 9.

[0047] The detection principle of the method of the present invention is as follows: During the annular scanning detection inside the pipe, the Bessel beam guided by the laser fiber 3 is shaped into a two-dimensional focused annular spot 8 by the first axis conical mirror 4, the convex lens 5 and the second axis conical mirror 7. The annular spot 8 is divided and projected onto the inner wall of the curved surface of the pipe by the conical reflector 9 to form a full-circumferential scanning annular laser 10. Then, together with the photothermal excitation acquisition system 12 and the reflection scanning system 13, they move and scan along the pipe axis direction A. The full-circumferential scanning annular laser will form a full-circumferential scanning annular laser 10 on the inner wall of the pipe and form a dynamic scanning heat flow on the curved surface structure of the pipe. The defects 14 on the upper surface and subsurface of the curved surface structure will hinder the diffusion mode of the dynamic scanning heat flow, thereby forming a local temperature rise with defect thermal characteristics on the surface. The small infrared thermal imager 1 also acquires the dynamic temperature field of the entire circumferential curved surface inside the pipe under test by reflection through the conical reflector 9; further, by unfolding the planar infrared image of the conical reflection and identifying and quantitatively analyzing the thermal characteristic signals of defects in the image, the detection of defects in this area is realized; the photothermal excitation acquisition system 12 and the reflection scanning system 13 are at a fixed distance and move together along the pipe axis direction A for scanning, and the infrared detection image video sequence of the defects is stitched together, thus realizing online non-destructive testing and full imaging detection of the overall structure of the pipe curved surface, thereby realizing efficient full circumferential infrared non-destructive testing of defects in the pipe curved surface structure.

[0048] The following is combined with Figures 1 to 3 The present invention will be further described in detail with reference to specific embodiments.

[0049] This invention provides a panoramic circumferential infrared detection method for pipe cracks, comprising the following steps:

[0050] Step 1: As Figure 1 As shown, the photothermal excitation acquisition system 12 and the reflection scanning system 13 of the full-circumference ring laser scanning infrared detection system are fixed in the center inside the tube, and the movable lens 6 of the photothermal excitation acquisition system and the conical reflector 9 of the reflection scanning system are kept coaxially aligned.

[0051] Step 2: Complete the settings on the control computer to enable the synchronous control system to synchronously start the small infrared thermal imager 1 for sampling and the laser generator to generate laser input to the laser fiber 3.

[0052] Step 3: The Bessel beam introduced by the laser fiber 3 enters the interior of the fiber coupler tube 2, passing successively through the first-axis conical mirror 4, the convex lens 5, and the second-axis conical mirror 7, finally forming a ring-shaped light spot 8. The shaped ring-shaped light spot 8 is reflected by the conical reflector 9, generating a stationary ring laser beam 10 along the tube axis, which illuminates the inner wall of the curved surface of the tube, as shown in Figure 2(a). The cone angle of the conical reflector 9 should be at least greater than 90°, and its mirror surface should be able to efficiently reflect the laser wavelength and the wavelength collected by the infrared thermal imager to ensure an effective infrared imaging optical path angle and laser reflection projection angle.

[0053] Step 4: By adjusting the distance d between the convex lens 5 and the second-axis conical mirror 7, the diameter R of the annular spot 8 projected onto the conical reflector 9 can be adjusted. By adjusting the numerical aperture (NA) of the second-axis conical mirror 7, the width D of the annular ring of the circumferential scanning laser 10 irradiating the inner wall of the pipe can be controlled, thereby controlling the mode of dynamic excitation heat flow, as shown in Figure 2(b).

[0054] The relationship between the distance d between the convex lens 5 and the second-axis conical mirror 7 and the diameter R of the annular light spot 8 satisfies the following condition:

[0055] While keeping the axial cone angle α of the first axial cone mirror 4, the axial cone angle θ of the cone mirror 9, and the focal length f of the convex lens 5 constant, the numerical aperture NA of the second axial cone mirror 7 is fixed. The distance d between the convex lens 5 and the second axial cone mirror 7 is directly proportional to the diameter R of the annular spot of the cone mirror 9; the larger d is, the larger R is; the smaller d is, the smaller R is; then the annular width D of the full-circumference scanning annular laser 10 remains unchanged.

[0056] The numerical aperture NA of the second-axis conical mirror 7 and the annular width D of the adjusted full-circumferential scanning ring laser 10 shall satisfy the following conditions:

[0057] While keeping the axial cone angle α of the first axial cone mirror 4, the axial cone angle θ of the cone mirror 9, and the focal length f of the convex lens 5 constant, the distance d between the convex lens 5 and the second axial cone mirror 7 is fixed. The numerical aperture NA of the second axial cone mirror 7 is inversely proportional to the ring width D of the full-circumference scanning ring laser 10. The larger NA is, the smaller D is, and the smaller NA is, the larger D is. Then the ring spot diameter R of the cone mirror 9 remains unchanged.

[0058] Step 5: Control the photothermal excitation acquisition system 12 and the reflection scanning system 13 to move and scan along the pipe axis direction A. The circumferential scanning ring laser 10 will dynamically scan and heat the inner wall of the pipe. The dynamic circumferential scanning ring laser 10 will mainly generate dynamic heat flow that diffuses along the surface. When it encounters crack defects on the curved inner wall, there is a significant temperature difference on both sides of the surface crack perpendicular to the surface of the object being measured. At the same time, the thermal excitation of the dynamic circumferential scanning ring laser 10 includes heat flow that diffuses along the pipe thickness. When it encounters debonding or thinning defects on the subsurface, it will cause a local temperature rise at the defect.

[0059] Step 6: While the laser performs scanning thermal excitation, the small infrared thermal imager 1 acquires circumferential imaging of the transient temperature field of the curved surface structure inside the pipe through the infrared reflection path of the conical reflector 9 and transmits the data back to the control computer. Since the thermal excitation laser wavelength (980-1064nm) is completely different from and far apart from the infrared thermal imager's acquisition wavelength (7-14μm), the two reflection paths do not interfere with each other. The infrared imaging detection structure will fully reflect the temperature changes on the curved surface of the pipe's inner wall. By unfolding the circular detection image from the conical reflection imaging, performing quantitative detection and analysis, and stitching the detection results together, full coverage detection of surface and subsurface defects 14 of the overall curved surface structure of the pipe is achieved.

[0060] The following is combined with Figures 3 to 5 The present invention will be further described in detail with reference to specific embodiments.

[0061] Establish a pipe curvature structure model using finite element simulation software, such as Figure 3 As shown, the tubular structure is made of structural steel with a density of 7850 kg / m³. 3 The isotropic thermal conductivity is 60.5 W / m·℃, and the specific heat constant pressure is 434 J / kg·℃. The dimensional parameters of the tube bend structure model are: outer radius 110 mm, inner radius 100 mm, and length 250 mm. One axial transverse and one longitudinal defect are pre-embedded in the tube bend structure; specific parameters are shown in Table 1. The purpose of establishing this model is to simulate the heat conduction process of a real tube bend structure after annular laser excitation, to demonstrate the application of this invention in this embodiment.

[0062] Table 1. Parameters of axial and longitudinal defects embedded in the tube bend structure.

[0063]

[0064] In this embodiment, to ensure the realism of the numerical simulation, a 1mm mesh size is selected to divide the model into meshes based on the size parameters of the tube curved structure model.

[0065] In this embodiment, to meet the requirements for detecting defects in the tube bend structure, a laser wavelength of 1064nm is selected, with a laser power of approximately 25W and a heat flux density of 2×10⁻⁶. 5 The laser beam has a power density (W / m) and a laser spot radius of 6 mm. The first axial cone has a cone angle of 140°, the convex lens has a focal length of 50 mm, and the second axial cone has a cone angle of 140°. The conical reflector is a single-sided reflector with a cone angle of 100°. The 6 mm laser spot passes through the first axial cone, the convex lens, and the second axial cone, finally forming a ring-shaped spot with a width of 4 mm. This ring-shaped spot is reflected by the conical reflector, producing a stationary 4 mm wide ring laser beam along the pipe axis that illuminates the inner wall of the curved pipe surface. Therefore, a 4 mm wide ring laser is chosen in the numerical simulation to simulate and excite the curved pipe structure model.

[0066] In this embodiment, in order to satisfy the requirement that the photothermal excitation acquisition system and the reflection scanning system move together along the pipe axis and to ensure the continuity of the temperature cloud map during numerical simulation, the present invention selects the forward speed of the ring laser as 6 mm / s.

[0067] In this embodiment, the inner surface temperature characteristic data of the curved tube structure is directly extracted using a software data acquisition module to simulate the data reflected by the conical reflector in real-world conditions using a small infrared thermal imager. The dynamic, circumferentially scanning ring laser primarily generates dynamic heat flow that diffuses along the surface. When it encounters the obstruction of a pre-embedded crack defect on the inner wall of the curved surface, a significant temperature difference exists on both sides of the pre-embedded crack defect perpendicular to the surface of the object being measured, as shown in Figure 4(a). A magnified temperature cloud map of the defect area is shown in Figure 4(b), and a temperature line diagram spanning the defect is shown in Figure 4(b). Figure 5 As shown in the figure. The results show that a significant fault-like temperature difference was formed on both sides of the crack, with a maximum difference of approximately 20℃. This significant temperature difference can be clearly captured and imaged by a small infrared thermal imager, forming clear and distinct infrared detection features. This method can detect the entire inner surface of the pipe over a length of 157,000 mm. 2 The area only requires a single 40-second scan.

[0068] As can be seen from the above embodiments, this invention fully utilizes the dynamic heat flow signal and damage characteristics of circumferential ring-scanning laser excitation, employing ring-shaped scanning laser and reflective circumferential thermal excitation and imaging detection to ultimately achieve full-coverage infrared non-destructive testing of pipe curved surface structures. The method proposed in this invention is simple, with distinct technical features and significant detection characteristic signals. It exhibits high reliability and efficiency for detecting pipe curved structures, providing an effective approach for efficient online inspection of pipeline-type special equipment. This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make substitutions and modifications to some technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. An infrared detection system for panoramic scanning of pipe cracks, characterized in that, This includes a photothermal excitation acquisition system and a reflective scanning system arranged along the inner axis of the pipeline; The photothermal excitation acquisition system is equipped with a laser fiber connected to a laser, a fiber optic coupler barrel connected to the laser fiber, a first-axis conical mirror and a convex lens located inside the fiber optic coupler barrel, and a second-axis conical mirror located inside a movable lens. The photothermal excitation acquisition system is used to project the annular spot of laser light shaped by the fiber optic coupler barrel, which is guided by the laser fiber, onto the reflection scanning system. The reflective scanning system is equipped with a conical reflector inside the pipe, which reflects the annular light spot projected by the photothermal excitation acquisition system through the conical reflector to form a full-circumferential scanning ring laser on the inner wall of the curved surface of the pipe, thereby forming a dynamic scanning heat flow on the curved surface structure of the pipe. The Bessel beam introduced by the laser fiber enters the inside of the fiber coupler tube, passes through the first axis conical mirror, the convex lens and the second axis conical mirror in succession, and is shaped into a ring-shaped light spot. It is reflected by the conical reflector and generates a static ring laser beam along the tube axis to irradiate the inner wall of the curved surface of the tube. Adjust the distance d between the convex lens and the second-axis conical mirror to adjust the diameter R of the annular light spot projected onto the conical reflector; Adjust the numerical aperture NA of the second-axis conical mirror to control the ring width D of a full-circumferential scanning ring laser irradiating the inner wall of the pipe; By acquiring the dynamic temperature field of the entire circumferential curved surface inside the tested pipeline, full-circumferential ring laser scanning infrared detection of defects in the pipeline's curved surface structure can be achieved.

2. The infrared detection system for panoramic scanning of pipe cracks according to claim 1, characterized in that, By using a small infrared thermal imager positioned above the lens barrel of the fiber optic coupler to acquire the dynamic temperature field of the entire circumferential curved surface inside the pipe under test, the full circumferential ring laser scanning infrared detection of defects in the curved surface structure of the pipe can be achieved.

3. The infrared detection system for panoramic scanning of pipe cracks according to claim 1, characterized in that, The movable lens can move back and forth along its own axis.

4. The infrared detection system for panoramic scanning of pipe cracks according to claim 1, characterized in that, The axial conical lens, the convex lens, and the optical fiber coupler are all coaxial inside the lens barrel.

5. The infrared detection system for panoramic scanning of pipe cracks according to claim 1, characterized in that, The cone angle of the cone-shaped mirror is greater than .

6. The infrared detection system for panoramic scanning of pipe cracks according to claim 1, characterized in that, The photothermal excitation acquisition system and the reflective scanning system maintain a fixed distance.

7. A detection method for an infrared detection system for panoramic scanning of pipe cracks as described in any one of claims 1-6, characterized in that, include: The photothermal excitation acquisition system and the reflection scanning system are fixed in the center inside the tube, and the rotatable lens of the photothermal excitation acquisition system is coaxially set with the center of the conical reflector of the reflection scanning system. The control computer synchronously starts a small infrared thermal imager for sampling and a laser generator to produce laser light to a laser fiber. The Bessel beam introduced by the laser fiber enters the inside of the fiber coupler tube, passes through the first axis conical mirror, the convex lens and the second axis conical mirror in succession, and is shaped into a ring-shaped light spot. It is reflected by the conical reflector and generates a static ring laser beam along the tube axis to irradiate the inner wall of the curved surface of the tube. Adjust the distance d between the convex lens and the second-axis conical mirror to adjust the diameter R of the annular light spot projected onto the conical reflector; Adjust the numerical aperture NA of the second-axis conical mirror to control the ring width D of a full-circumferential scanning ring laser irradiating the inner wall of the pipe; The photothermal excitation acquisition system and the reflection scanning system work together to move and scan along the pipeline axis, while the rotary full-circumferential linear scanning laser performs dynamic scanning and thermal excitation heating on the inner wall of the pipeline. A small infrared thermal imager acquires the transient temperature field of the curved surface structure inside the pipe through the infrared reflection light path of the conical reflector, and transmits the data back to the control computer, realizing the full-circumferential ring laser scanning infrared detection of defects in the overall curved surface structure of the pipeline.

8. The infrared detection method for panoramic scanning of pipe cracks according to claim 7, characterized in that, The relationship between the distance d between the convex lens and the second-axis conical mirror and the diameter R of the annular light spot projected onto the conical mirror should satisfy the following condition: Maintain the axis-cone angle of the first axis conic mirror Conical reflector axis cone angle With the focal length f of the convex lens remaining constant and the numerical aperture NA of the second-axis cone mirror fixed, the distance d between the convex lens and the second-axis cone mirror is proportional to the diameter R of the annular spot of the cone mirror; therefore, the annular width D of the full-circumferential scanning ring laser remains constant. The numerical aperture NA of the second-axis conical mirror and the ring width D of the adjusted full-circumferential scanning ring laser must satisfy the following conditions: Maintain the axis-cone angle of the first axis conic mirror Conical reflector axis cone angle With the focal length f of the convex lens remaining constant, and the distance d between the convex lens and the second-axis cone mirror fixed, the numerical aperture NA of the second-axis cone mirror is inversely proportional to the ring width D of the circumferential scanning ring laser. Therefore, the diameter R of the ring spot of the cone mirror remains constant.

9. The infrared detection method for panoramic scanning of pipe cracks according to claim 7, characterized in that, The thermally excited laser wavelength is 980-1064nm, and the infrared thermal imager acquires wavelengths of 7~14μm.

10. The application of the infrared detection system for panoramic scanning of pipe cracks as described in any one of claims 1-6 in the detection of defects and damage in water supply, oil and heating pipelines.

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