Terahertz continuous wave fan blade nondestructive detection imaging optical path system

Abstract

The application discloses a terahertz continuous wave fan blade nondestructive detection imaging light path system and relates to the technical field of terahertz nondestructive detection. The existing blade nondestructive detection platform based on terahertz can only perform simple frequency switching, which leads to the technical problem that false judgments and missed judgments of non-defective blades are prone to occur in the scanning process. Specifically, the platform performs imaging through terahertz continuous wave scanning through an imaging light path module. In the imaging forward process, a frequency self-adaptive switching unit analyzes deviation results and accurate results in historical scanning, establishes historical scanning abnormal areas, error areas and corresponding invalid / non-adaptive frequency ranges and scene parameters, and realizes self-adaptive optimization of scanning frequency. In the imaging backward process, a defect identification unit distinguishes process defect positions and instantaneous defect positions, analyzes change characteristics of the defect positions in a continuous operation period, and judges a blade defect development trend.

Description

Technical Field

[0001] This invention relates to the field of terahertz nondestructive testing technology, specifically to an imaging optical path system for nondestructive testing of terahertz continuous wave wind turbine blades. Background Technology

[0002] In aerospace, energy and power industries, blades are core and critical components, and their operational safety and reliability directly determine the overall performance of the equipment. During long-term service, blades are prone to defects due to wear, corrosion, fatigue and other factors. If these defects are not detected and addressed in a timely manner, they may lead to serious safety accidents. Therefore, it is crucial to conduct efficient and accurate non-destructive testing on blades. Terahertz waves have advantages such as strong penetration, sensitivity to non-metallic materials and no ionizing radiation, and have been widely used in the field of blade non-destructive testing.

[0003] Currently, in existing technologies:

[0004] Terahertz-based blade non-destructive testing platforms often employ fixed-frequency scanning modes or can only perform simple frequency switching. They lack in-depth mining and utilization of historical scanning data, which can easily lead to problems such as misjudging defective blades as defective blades and missing defective blades during the scanning process, making it difficult to guarantee scanning accuracy.

[0005] Meanwhile, existing detection platforms do not fully consider the impact of environmental parameters (such as electromagnetic interference intensity and temperature fluctuation range) on scanning results during frequency switching. Environmental factors can easily lead to fluctuations in scanning frequency, further reducing scanning accuracy and stability.

[0006] In the defect identification stage, existing technologies can only achieve preliminary location of defects, cannot effectively distinguish between process defects and instantaneous defects, and lack the ability to predict the development trend of defects. This results in a lack of targeted maintenance and repair of blades, making it difficult to achieve preventive maintenance and increasing equipment operation risks and maintenance costs.

[0007] To address the aforementioned technical shortcomings, a solution is proposed. Summary of the Invention

[0008] The purpose of this invention is to solve the problems mentioned above by proposing a terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system.

[0009] The objective of this invention can be achieved through the following technical solutions:

[0010] The terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system includes a non-destructive testing platform, wherein the communication connections of the non-destructive testing platform are as follows:

[0011] The imaging optical path module performs imaging through terahertz continuous wave scanning;

[0012] The frequency adaptive switching unit performs frequency adaptive switching during the terahertz wave scanning phase during imaging execution; the defect identification unit identifies defects based on terahertz imaging after imaging is completed.

[0013] Furthermore, the process of the imaging optical path module is as follows:

[0014] Terahertz waves generated by a terahertz solid source are used as a detection beam. The beam is focused by a front-end TPX lens, so that the terahertz waves are focused on the detection area of ​​the wind turbine blade under test. After the terahertz waves penetrate the detection area, they form a transmitted beam carrying internal structural information. The transmitted beam is then focused and imaged again by a rear-end lens group, forming a transmitted image at the terahertz imaging detector camera.

[0015] Furthermore, the process of the frequency adaptive switching unit is as follows:

[0016] Based on the historical data collection process, the scanning time and the corresponding scanning area of ​​the blade are recorded, and the blade parameters of the blade area are determined, specifically the blade thickness and blade level.

[0017] Simultaneously, based on the scanning time and the corresponding scanning operation results, the scanning results are divided into deviation results and accurate results according to the accuracy rate of the scanning results; deviation results are further divided into defective blades that were scanned but not defective blades.

[0018] Furthermore, using the deviation results as analytical features, the parameters of the scanned blade under the scenario of scanning defects into a defect-free blade are obtained, and the scanning terahertz wave frequency of the blade region is obtained simultaneously; based on multi-scenario statistics, historical scanning abnormal regions are established, and the terahertz wave frequency range of the corresponding regions is obtained and marked as invalid ranges; according to the time period of occurrence of invalid ranges, the environmental parameters within the corresponding time period are extracted, specifically the surrounding electromagnetic interference intensity and temperature fluctuation range; and marked as invalid scenario parameters.

[0019] The parameters of the scanned blade are obtained when the defective blade is not detected, and the scanning terahertz wave frequency of the blade area is obtained simultaneously. Based on the statistics of multiple scenarios, the historical scanning error area is established, and the terahertz wave frequency range of the corresponding area is obtained and marked as the non-adaptation range. According to the time period of the non-adaptation range, the environmental parameters in the corresponding time period are extracted and marked as non-adaptation scenario parameters.

[0020] Furthermore, based on the real-time scanned blade area, the blade parameters are determined, and the blade parameters corresponding to the historical scan abnormal area and historical scan error area are compared. If the parameters do not overlap, it is inferred that the scanning risk of the current scanned blade area is low, and the terahertz wave rated frequency of the current hardware device is used as the output; if the parameters overlap, it is inferred that the scanning risk of the current scanned blade area is high.

[0021] The type of overlapping parameter is determined, and the invalid range or non-fit range is used as the reference standard for setting the terahertz wave frequency. After the frequency range is set, invalid scene parameters and non-fit scene parameters are provided. The floating time of the invalid scene parameter and the time point when the corresponding scanning frequency is in the invalid range are collected according to the historical scanning period. The overlap frequency of the invalid time point is obtained. If the overlap frequency of the invalid time point exceeds the invalid overlap frequency threshold, it is marked as an interference parameter; otherwise, if the overlap frequency of the invalid time point does not exceed the invalid overlap frequency threshold, it is marked as a non-interference parameter.

[0022] The system simultaneously acquires the floating time of parameters in the non-adaptive scenario and the time points when the corresponding scanning frequency is within the non-adaptive range. At the same time, it extracts the overlap frequency of non-adaptive time points. If the non-adaptive time point exceeds the non-adaptive overlap frequency threshold, it is marked as a non-adaptive parameter; if the non-adaptive time point does not exceed the non-adaptive overlap frequency threshold, it is marked as an adaptive parameter.

[0023] Furthermore, based on the real-time output stage within the determined frequency range, environmental parameters are extracted. If interference parameters appear in the real-time collected environmental parameters, environmental control is implemented, and fluctuations within the frequency range are managed. If non-adaptive parameters appear, environmental monitoring is performed, and adjustments are made based on the actual frequency values ​​within the frequency range. This process is repeated to complete adaptive control.

[0024] Furthermore, the process of the defect identification unit is as follows:

[0025] The obtained terahertz imaging is marked as the detection area image; and the detection area image is analyzed to determine the defect location in the detection area image based on the terahertz wave phase fluctuation, thereby obtaining the image defect location distribution map within the blade detection area;

[0026] Collect the boundary of a single image defect location and determine the boundary texture corresponding to the image defect location boundary and the non-image defect location boundary. If the level of the trajectory corresponding to the boundary texture is lower than the set level position, the corresponding image defect location is marked as a process defect location; if the level of the trajectory corresponding to the boundary texture is not lower than the set level position, the corresponding image defect location is marked as an instantaneous defect location.

[0027] Furthermore, based on the image acquisition of the continuous operation cycle, according to the location type in the image defect location distribution map, the shortening rate of the defect-free distance between adjacent process defect locations is obtained, and at the same time, the location extension area after the instantaneous defect location boundary appears at the process defect location is collected.

[0028] If the rate of reduction of the distance between adjacent process defect locations exceeds the distance reduction rate threshold, or if the area of ​​the instantaneous defect location after the process defect location appears exceeds the extension area threshold, it is inferred that there is a defect development trend in the blade detection area during the blade operation phase, generating a defect aggravation signal and sending it to the non-destructive testing platform.

[0029] If the rate of reduction of the distance between adjacent process defect locations does not exceed the distance reduction rate threshold, and the area of ​​extension after the instantaneous defect location boundary appears does not exceed the extension area threshold, it is inferred that there is no defect development trend in the blade detection area during the blade operation phase, and a defect stabilization signal is generated and sent to the non-destructive testing platform.

[0030] Furthermore, after receiving the blades, the non-destructive testing platform performs unified operation and maintenance, with the priority order from high to low being blades with aggravated defects, blades with stable defects, and blades without defects.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] 1. This invention utilizes optimized terahertz wave irradiation and transmission technology to ensure that the terahertz beam can accurately irradiate the key detection area of ​​the wind turbine blade, thereby improving detection accuracy. Existing technologies often suffer from beam scattering or energy loss, which limits the accuracy of detection results. This invention, through precise optical path design and beam adjustment, avoids these problems and ensures that internal defects in the wind turbine blade can be clearly detected.

[0033] Terahertz waves possess strong penetrating power, enabling them to effectively penetrate wind turbine blades and obtain information about their internal structure. Compared to traditional ultrasonic or X-ray detection, terahertz waves cause less damage to materials and can capture more minute structural changes. Existing X-ray or ultrasonic technologies often fail to accurately capture minute defects or non-uniform structures, while this invention provides higher-resolution imaging data, helping engineers detect more detailed internal problems.

[0034] 2. The frequency adaptive switching unit uses historical acquisition processes as data support for adaptive switching of scanning frequency, which changes the current situation where frequency switching lacks historical data reference. It can optimize the scanning frequency according to the actual situation of different blade areas, effectively improve the scanning progress, and improve scanning accuracy. By recording the historical scanning time, corresponding blade area, and blade parameters, the scanning results are divided into deviation results and accurate results according to the accuracy rate. For the two deviation scenarios, historical scanning abnormal areas and error areas are established respectively, and the corresponding invalid / incompatible frequency range and invalid / incompatible scenario parameters are clearly defined. This enables precise positioning of the causes of historical scanning deviations and provides reliable data support for subsequent real-time frequency control.

[0035] By quantitatively analyzing the overlap frequency between environmental parameter fluctuations and frequencies within invalid / incompatible ranges, interference parameters are distinguished from non-interference parameters, and compatible parameters are distinguished from incompatible parameters. Based on this, environmental control and frequency fluctuation adjustment are carried out respectively, effectively reducing the impact of environmental factors on scanning results and ensuring the stability of scanning frequency.

[0036] 3. The defect identification unit determines the defect location and generates a defect location distribution map based on terahertz imaging, achieving precise defect location and providing a clear basis for subsequent defect analysis and maintenance. By collecting the boundary texture of the defect location, it distinguishes between process defect locations and instantaneous defect locations based on the horizontality of the boundary texture trajectory, solving the problem of the inability to effectively distinguish defect types in existing technologies. It can accurately determine the nature of the defect (persistent or temporary), improving the accuracy of defect identification. By tracking and analyzing the image acquisition data within a continuous operating cycle, it obtains key features such as the shortening rate of the defect-free distance between adjacent process defect locations and the extended area after the appearance of process defects at the boundary of instantaneous defect locations. By comparing with corresponding thresholds, it accurately predicts the development trend of blade defects, realizing the transformation from "passive detection" to "active prediction," providing strong support for preventive maintenance. Attached Figure Description

[0037] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0038] Figure 1 This is a schematic diagram of the system composition of the non-destructive testing imaging optical path system in this invention;

[0039] Figure 2 This is a three-dimensional hardware simulation diagram of the imaging optical path module in this invention;

[0040] Figure 3 This is a diagram illustrating the design of the input field of view in the lens design of this invention.

[0041] Figure 4 This is a schematic diagram of the modulation transfer function curve in a real-world scenario according to the present invention. Detailed Implementation

[0042] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0044] Please see Figure 1 As shown, the terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system includes a non-destructive testing platform, which is connected to an imaging optical path module; the non-destructive testing platform serves as a data transmission hub and is connected to a frequency adaptive switching unit and a defect identification unit.

[0045] In this invention, the imaging optical path module uses terahertz waves generated by a terahertz solid-state source as a detection beam. The beam is focused by a front-end TPX lens, so that the terahertz waves are focused on the detection area of ​​the wind turbine blade under test. After the terahertz waves penetrate the detection area, they form a transmitted beam carrying internal structural information. The transmitted beam is then focused and imaged again by a rear-end lens group, and finally a transmitted image is formed at the terahertz imaging detector camera (TeraSense4096), thereby realizing non-destructive detection of structural anomalies such as internal defects, delamination, inclusions or uneven thickness of the wind turbine blade.

[0046] The above technical solution emphasizes that each function is achieved through a well-defined structure and optical path, including terahertz generation, focused illumination, sample transmission, imaging convergence, and signal acquisition and processing.

[0047] Please see Figure 2 As shown, the imaging optical path module of the present invention includes at least the following hardware components:

[0048] 1) Terahertz solid-state source: used to generate continuous or quasi-continuous terahertz radiation;

[0049] 2) TPX Shaping Mirror: Located in front of the terahertz solid source emission end, it is used to converge the terahertz beam and focus the beam onto the area of ​​the wind turbine blade under test.

[0050] 3) Wind turbine blade clamping / positioning mechanism: used to fix the wind turbine blade to be tested and to place the area to be tested near the focal plane of the TPX lens;

[0051] 4) The wind turbine blades under inspection: The area under inspection is the key inspection object in the terahertz wave transmission path;

[0052] 5) Rear-end lens group: Located on the transmission side of the wind turbine blade under test, it is used to collect the terahertz transmitted beam after penetrating the blade and perform secondary focusing / imaging;

[0053] 6) Terahertz camera (Terasense4096): Located at the image plane of the rear lens group, used to acquire transmission imaging data of the probe;

[0054] The terahertz solid-state source, TPX lens, blade detection area, rear lens group, and imaging detector camera are arranged sequentially along the same optical path direction. The clamping / positioning mechanism keeps the wind turbine blade under test stable during the detection process, ensuring the precision and repeatability of the optical path.

[0055] Specifically, the terahertz solid-state source generates a terahertz beam and emits it outward, with the emitted beam being a 0.11 THz continuous wave.

[0056] The TPX lens is positioned between the solid source emission end and the blade. Through its transmission and refraction, it focuses the terahertz beam to form a focal area in space (i.e., the detection focal area). By adjusting the distance between the TPX lens and the blade (which can be achieved by the clamping / positioning mechanism 3 or an independent displacement structure), the detection area of ​​the blade is placed within the focal area to improve the local irradiation energy density and the imaging signal-to-noise ratio.

[0057] When terahertz waves penetrate the area of ​​the blade being detected, the distribution of internal materials, thickness variations, and defects (such as pores, inclusions, delamination, etc.) will absorb, scatter, and modulate the phase / amplitude of the terahertz waves, thus enabling the transmitted beam to carry information related to the internal structure.

[0058] The transmitted light beam enters the rear lens group, which collects the transmitted light beam and forms an image at the detector end. By setting the relative distance between the lens group and the detector camera, the transmitted light beam forms a clear intensity distribution image on the effective imaging surface of the detector, thereby converting the "internal modulation information of the blade" into collectable two-dimensional image data. The terahertz imaging detector camera samples the terahertz radiation intensity distribution at the image plane and outputs pixel matrix data for subsequent display, storage, or defect identification.

[0059] The non-destructive testing platform generates testing instructions and drives the imaging optical path module to perform hardware cooperation to complete terahertz imaging. During the pre-imaging process, the non-destructive testing platform generates a frequency adaptive switching signal and sends it to the frequency adaptive switching unit.

[0060] After receiving the frequency adaptive switching signal, the frequency adaptive switching unit performs frequency switching during the terahertz wave scanning stage. That is, it uses the historical acquisition process as data support to perform adaptive switching of the scanning frequency, which more accurately improves the scanning progress and enhances the scanning accuracy.

[0061] Based on the historical data collection process, the scanning time and the corresponding scanning area of ​​the blade are recorded, and the blade parameters of the blade area, such as blade thickness and blade levelness, are determined.

[0062] Simultaneously, based on the scanning time and the corresponding scanning operation results, the scanning results are divided into deviation results and accurate results according to the accuracy rate of the scanning results; deviation results are further divided into defective blades that were scanned but not defective blades.

[0063] Using the deviation results as analytical features, the parameters of the scanned blade are obtained under the scenario of scanning defects into a defect-free blade, and the scanning terahertz wave frequency of the blade region is obtained simultaneously; based on multi-scenario statistics, historical scanning abnormal regions are established, and the terahertz wave frequency range of the corresponding regions is obtained and marked as invalid ranges; according to the time period of the occurrence of invalid ranges, environmental parameters such as the intensity of surrounding electromagnetic interference and the temperature fluctuation range are extracted and marked as invalid scenario parameters;

[0064] The parameters of the scanned blade are obtained when the defective blade is not detected, and the scanning terahertz wave frequency of the blade area is obtained simultaneously. Based on the statistics of multiple scenarios, the historical scanning error area is established, and the terahertz wave frequency range of the corresponding area is obtained and marked as the non-adaptation range. According to the time period of the non-adaptation range, the environmental parameters in the corresponding time period are extracted and marked as non-adaptation scenario parameters.

[0065] Based on the real-time scanned blade area, the blade parameters are determined, and the blade parameters corresponding to the historical scan abnormal area and historical scan error area are compared. If the parameters do not overlap, it is inferred that the scanning risk of the current scanned blade area is low, and the terahertz wave rated frequency of the current hardware device is used as the output; if the parameters overlap, it is inferred that the scanning risk of the current scanned blade area is high.

[0066] The type of overlapping parameter is determined, and the invalid range or non-fit range is used as the reference standard for setting the terahertz wave frequency. After the frequency range is set, invalid scene parameters and non-fit scene parameters are provided. The floating time of the invalid scene parameter and the time point when the corresponding scanning frequency is in the invalid range are collected according to the historical scanning period. The overlap frequency of the invalid time point is obtained. If the overlap frequency of the invalid time point exceeds the invalid overlap frequency threshold, it is marked as an interference parameter; otherwise, if the overlap frequency of the invalid time point does not exceed the invalid overlap frequency threshold, it is marked as a non-interference parameter.

[0067] The system simultaneously acquires the floating time of parameters in non-adaptive scenarios and the time points when the corresponding scanning frequency is within the non-adaptive range. It also extracts the overlap frequency of non-adaptive time points. If the non-adaptive time point exceeds the non-adaptive overlap frequency threshold, it is marked as a non-adaptive parameter; if the non-adaptive time point does not exceed the non-adaptive overlap frequency threshold, it is marked as an adaptive parameter.

[0068] Based on the real-time output stage of the determined frequency range, environmental parameters are extracted. If interference parameters appear in the real-time collected environmental parameters, environmental control is implemented, and fluctuations in the frequency range are managed. If non-adaptive parameters appear, environmental monitoring is performed, and adjustments are made based on the actual frequency values ​​within the frequency range. This process is repeated to achieve adaptive control and improve the efficiency of blade area scanning.

[0069] During the post-imaging process, the non-destructive testing platform generates a defect identification signal and sends it to the defect identification unit; after receiving the defect identification signal, the defect identification unit performs defect identification based on terahertz imaging.

[0070] The obtained terahertz imaging is marked as the detection area image; and the detection area image is analyzed to determine the defect location in the detection area image based on the terahertz wave phase fluctuation, thereby obtaining the image defect location distribution map within the blade detection area;

[0071] Collect the boundary of a single image defect location and determine the boundary texture corresponding to the image defect location boundary and the non-image defect location boundary. If the level of the trajectory corresponding to the boundary texture is lower than the set level position, the corresponding image defect location is marked as a process defect location; if the level of the trajectory corresponding to the boundary texture is not lower than the set level position, the corresponding image defect location is marked as an instantaneous defect location.

[0072] Based on the image acquisition of the continuous operation cycle, according to the location type in the image defect location distribution map, the shortening rate of the defect-free distance between adjacent process defect locations is obtained, and the location extension area after the instantaneous defect location boundary appears after the process defect location appears is collected.

[0073] If the rate of reduction of the distance between adjacent process defect locations exceeds the distance reduction rate threshold, or if the area of ​​the instantaneous defect location after the process defect location appears exceeds the extension area threshold, it is inferred that there is a defect development trend in the blade detection area during the blade operation phase, generating a defect aggravation signal and sending it to the non-destructive testing platform.

[0074] If the rate of reduction of the distance between adjacent process defect locations does not exceed the distance reduction rate threshold, and the area of ​​position extension after the instantaneous defect location boundary appears does not exceed the extension area threshold, it is inferred that there is no defect development trend in the blade detection area during the blade operation phase, a defect stabilization signal is generated and sent to the non-destructive testing platform.

[0075] After receiving the equipment, the non-destructive testing platform performs unified maintenance and repair on the blades, with the priority order from high to low being blades with worsening defects, blades with stable defects, and blades without defects.

[0076] Example 2

[0077] Based on the hardware operation process of the imaging optical path module, an example from a real-world scenario is given.

[0078] According to the testing requirements, if the crack width is greater than 20mm, the blade is considered to need to be scrapped. This can be understood as the crack width that needs to be detected should be at least 10mm, and it should be detectable at least according to the scrapping standard. Otherwise, the test is considered invalid.

[0079] The parameters of the terahertz camera are as follows: resolution 64×64, pixel size 1.5mm, distance between the terahertz source and the detection imaging system is 6000mm, and the distance between the detection imaging system and the object under test (wind turbine blade) is tentatively designed to be 3000mm.

[0080] According to imaging detection theory:

[0081] ;

[0082] Where: f—focal length of the lens, mm;

[0083] α — Pixel size, mm;

[0084] N – Number of pixels;

[0085] H – Height of the object, mm;

[0086] Due to the large pixel size of the camera, a long focal length lens is required to distinguish details. Considering the size of the device and the research on the camera to be used, this camera is not suitable for detail-resolving imaging. After discussion, it was decided to use a 500mm focal length to first verify the functionality.

[0087] Based on the designed focal length, calculate the number of pixels occupied by this imaging system when imaging a 10mm crack at a distance of 3000mm:

[0088] ;

[0089] According to the principles of imaging detection, 2.2 pixels are barely enough to observe the target. The specific effect will be evaluated based on the actual imaging effect after the system is assembled and adjusted.

[0090] Based on the focal lengths of the camera and lens, the field of view of the imaging system can be calculated as follows:

[0091] ;

[0092] If the distance between the wind turbine blades and the imaging system is 3000mm, then the imaging area size is 580mm × 580mm, calculated as follows:

[0093]

[0094] Lens design:

[0095] Based on the lens focal length and imaging method, a Cooke three-element lens was chosen as the initial structure, with an entrance pupil diameter of 150mm and a wavelength of 30μm. The lens's designed linear field of view is as follows:

[0096] ;

[0097] Then set the maximum input field of view to 7.75°, such as... Figure 3 As shown;

[0098] The zoom system has a focal length of 500mm. An evaluation function is set to optimize the system. The lens material is replaced with TPX, and aberration optimization is performed to obtain the desired result.

[0099] Aberration analysis point plot:

[0100] A dot pattern is formed on the image plane by all the light rays emanating from an on-axis object point and passing through the optical system. Due to aberrations, this results in a blur pattern of varying sizes. Therefore, the dot pattern directly reflects the energy-gathering capability of the optical system. For imaging objective systems, the dot pattern should be small and have good roundness.

[0101] Lens design involves the MTF (Modulation Transfer Function). As an optical transfer function, the MTF reflects the ability of an object to transmit different frequency components. A schematic diagram of the MTF curve can be found here. Figure 4 As shown, the high-frequency range reflects the detail transmission of an object, the mid-frequency range reflects the tonal transmission of an object, and the low-frequency range reflects the contour transmission of an object. For imaging optical systems, the amplitude transfer function (MTF) affects image quality. MTF is the ratio of image modulation degree to object modulation degree, and modulation degree is defined as the difference between the maximum and minimum intensities divided by the sum of the maximum and minimum intensities.

[0102] Example 3

[0103] The mechanical part of this invention mainly revolves around designing mechanical structures suitable for the field of high-altitude exploration, including a quick-release structure for rapid disassembly during high-altitude operations and a waterproof structure for extreme weather conditions:

[0104] The quick-release design is mainly centered around the rapid connection with the drone. This quick-release structure allows for quick connection to the drone, providing a convenient and reliable method for subsequent detection of blade damage. The quick-release structure consists of seven main parts, including a base, quick-release plate side clamps, plate frame-clamping plate, positioning bolts, positioning shaft, spring, and hand-tightening bolts.

[0105] The working principle is mainly through the assembly of the drone connecting plate frame-plate, the non-destructive testing device connecting the base and other components. When using it, the hand-tightening screws must first be loosened. At this time, the quick-release plate cannot be removed. The positioning shaft on the quick-release plate, under the elastic force of the spring, presses the positioning shaft carrying the positioning bolt into the positioning hole on the plate. The positioning shaft protruding outward must be pressed to push the positioning bolt out of the positioning hole. Only then can the plate frame-plate be removed. This ensures that even if the hand-tightening screws are loose, the quick-release plate remains fixed on the base, which can greatly prevent high-altitude accidents.

[0106] The waterproof structure of the device needs to consider several aspects. First, due to the special nature of terahertz waves, the device needs to be in a sealed environment to prevent light from entering. However, terahertz waves need to propagate through waveguides, so the dust and water resistance of the waveguides is a major concern. On the other hand, the device casing itself cannot be manufactured as a single piece, and the frame needs to be assembled by splicing. Therefore, the joints of the frame assembly are another major focus for waterproofing. Finally, the waterproofing of the connectors also needs to be taken into account.

[0107] First, let me introduce the design of the waveguide port's waterproof structure. The waveguide port adopts a multi-layered, multi-layered waterproof structure. The first layer is the fixing plate, which is embedded and tightly attached to the lens ring. The connection is an L-shaped gap. In case of rain or erosion, the L-shaped gap can effectively prevent rainwater from entering. There are two such protective measures at the waveguide port: the fixing plate and the lens ring, and the lens ring and the lens, which form two L-shaped protective barriers. After these two protective barriers, there is an even more rigorous protective barrier, mainly composed of the lens, silicone pad, and front panel. A sealing groove is set at the waveguide port on the front panel. The silicone pad is placed in the groove and squeezed by the lens to form a barrier with excellent sealing effect. This sealing effect can prevent water from entering for a certain period of time even when immersed in water.

[0108] Secondly, waterproofing the frame itself is also very important. The waterproofing of the frame mainly considers the joints. The waterproofing structure at the joints has two aspects: a loop structure and a sealing ring structure. The loop structure itself effectively prevents rainwater from entering, and with the addition of the sealing ring structure, the waterproofing level can reach IP56.

[0109] Finally, there is the issue of the waterproof structure of the connectors. The connectors mainly use bolts, and each bolt is equipped with a waterproof gasket. The threaded connection of the bolt itself can achieve the effect of dust and water protection. After adding the waterproof gasket, the dust and water protection effect can reach the IP56 level.

[0110] In summary, this invention optimizes the optical path design to ensure that the terahertz beam accurately illuminates the critical detection area of ​​the wind turbine blade under test. In this technical solution, the beam focusing, angle adjustment, and transmission process are precisely designed and regulated, avoiding beam scattering, deviation, or energy loss problems that may occur in traditional detection methods. This optimized illumination and transmission technology ensures that the terahertz wave can efficiently and stably penetrate the wind turbine blade and provide a high-quality transmission signal, thereby enhancing the accuracy and reliability of the detection.

[0111] Thresholds, preset values, preset ranges, etc. are set for result comparison and analysis to determine whether they are good or bad. The value of these thresholds is determined by a combination of large-scale model analysis of sample data and human experience. They can also be adjusted appropriately based on seasonal or common-sense influences.

[0112] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system, characterized in that, This includes a non-destructive testing platform, whose communication connections include: The imaging optical path module performs imaging through terahertz continuous wave scanning; The frequency adaptive switching unit performs frequency adaptive switching during the terahertz wave scanning phase of imaging execution; the process of the frequency adaptive switching unit is as follows: Based on the historical data collection process, the scanning time and the corresponding scanning area of ​​the blade are recorded, and the blade parameters of the blade area are determined, specifically the blade thickness and blade level. Simultaneously, based on the scanning time and the corresponding scanning operation results, the scanning results are divided into deviation results and accurate results according to the accuracy rate of the scanning results; deviation results are further divided into defective blades that were scanned but not defective blades. Using the deviation results as analytical features, the parameters of the scanned blade are obtained under the scenario of scanning defects into a defect-free blade, and the scanning terahertz wave frequency of the blade region is obtained simultaneously. Based on the statistics of multiple scenarios, historical scanning abnormal areas are established, and the terahertz wave frequency range of the corresponding areas is obtained and marked as invalid ranges. According to the time period of the occurrence of invalid ranges, the environmental parameters within the corresponding time period are extracted, specifically the surrounding electromagnetic interference intensity and temperature fluctuation range. And mark it as an invalid scene parameter; The parameters of the scanned blade are obtained when the defective blade is not detected, and the scanning terahertz wave frequency of the blade area is obtained simultaneously. Based on the statistics of multiple scenarios, the historical scanning error area is established, and the terahertz wave frequency range of the corresponding area is obtained and marked as the non-adaptation range. According to the time period of the non-adaptation range, the environmental parameters in the corresponding time period are extracted and marked as non-adaptation scenario parameters. Based on the real-time scanned blade area, the blade parameters are determined, and the blade parameters corresponding to the historical scan abnormal area and historical scan error area are compared. If the parameters do not overlap, it is inferred that the scanning risk of the current scanned blade area is low, and the terahertz wave rated frequency of the current hardware device is used as the output; if the parameters overlap, it is inferred that the scanning risk of the current scanned blade area is high. The type of overlapping parameter is determined, and the invalid range or non-fit range is used as the reference standard for setting the terahertz wave frequency. After the frequency range is set, invalid scene parameters and non-fit scene parameters are provided. The floating time of the invalid scene parameter and the time point when the corresponding scanning frequency is in the invalid range are collected according to the historical scanning period. The overlap frequency of the invalid time point is obtained. If the overlap frequency of the invalid time point exceeds the invalid overlap frequency threshold, it is marked as an interference parameter; otherwise, if the overlap frequency of the invalid time point does not exceed the invalid overlap frequency threshold, it is marked as a non-interference parameter. The system simultaneously acquires the floating time of parameters in non-adaptive scenarios and the time points when the corresponding scanning frequency is within the non-adaptive range. It also extracts the overlap frequency of non-adaptive time points. If the non-adaptive time point exceeds the non-adaptive overlap frequency threshold, it is marked as a non-adaptive parameter; if the non-adaptive time point does not exceed the non-adaptive overlap frequency threshold, it is marked as an adaptive parameter. Based on the real-time output stage of the determined frequency range, environmental parameters are extracted. If interference parameters appear in the real-time collected environmental parameters, environmental control is implemented, and fluctuations in the frequency range are managed. If non-adaptive parameters appear, environmental monitoring is performed, and adjustments are made based on the actual frequency value fluctuations within the frequency range. Adaptive regulation is completed sequentially; The defect identification unit identifies defects based on terahertz imaging after imaging is completed.

2. The terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system according to claim 1, characterized in that, The process of the imaging optical path module is as follows: Terahertz waves generated by a terahertz solid source are used as a detection beam. The beam is focused by a front-end TPX lens, so that the terahertz waves are focused on the detection area of ​​the wind turbine blade under test. After the terahertz waves penetrate the detection area, they form a transmitted beam carrying internal structural information. The transmitted beam is then focused and imaged again by a rear-end lens group, forming a transmitted image at the terahertz imaging detector camera.

3. The terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system according to claim 1, characterized in that, The process of the defect identification unit is as follows: The obtained terahertz imaging is marked as the detection area image; and the detection area image is analyzed to determine the defect location in the detection area image based on the terahertz wave phase fluctuation, thereby obtaining the image defect location distribution map within the blade detection area; Collect the boundary of a single image defect location and determine the boundary texture corresponding to the image defect location boundary and the non-image defect location boundary. If the level of the trajectory corresponding to the boundary texture is lower than the set level position, the corresponding image defect location is marked as a process defect location; if the level of the trajectory corresponding to the boundary texture is not lower than the set level position, the corresponding image defect location is marked as an instantaneous defect location.

4. The terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system according to claim 3, characterized in that, Based on the image acquisition of the continuous operation cycle, according to the location type in the image defect location distribution map, the shortening rate of the defect-free distance between adjacent process defect locations is obtained, and the location extension area after the instantaneous defect location boundary appears after the process defect location appears is collected. If the rate of reduction of the distance between adjacent process defect locations exceeds the distance reduction rate threshold, or if the area of ​​the instantaneous defect location after the process defect location appears exceeds the extension area threshold, it is inferred that there is a defect development trend in the blade detection area during the blade operation phase, a defect aggravation signal is generated and sent to the non-destructive testing platform. If the rate of reduction of the distance between adjacent process defect locations does not exceed the distance reduction rate threshold, and the area of ​​extension after the instantaneous defect location boundary appears does not exceed the extension area threshold, it is inferred that there is no defect development trend in the blade detection area during the blade operation phase, and a defect stabilization signal is generated and sent to the non-destructive testing platform.

5. The terahertz continuous wave wind turbine blade non-destructive testing imaging optical path system according to claim 4, characterized in that, After receiving the blades, the non-destructive testing platform performs unified operation and maintenance inspections, with the priority order from high to low being blades with aggravated defects, blades with stable defects, and blades without defects.

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