System, method and platform for non-destructive detection precision verification of hidden points on skin

Abstract

The invention relates to a system, method and platform for verifying nondestructive detection precision of hidden points on skin, and belongs to the field of terahertz imaging, and the system comprises a terahertz probe measurement group, a laser interference ranging reference group and a displacement control device; the terahertz probe measurement group is used for transmitting terahertz waves to the terahertz tag and receiving reflected waves so as to obtain the position information of the tag; the laser interference ranging reference group is used for providing a position reference of which the measurement precision is higher than that of the terahertz probe measurement group; and the displacement control device is used for controlling the displacement of the terahertz tag in three dimensions so as to simulate the movement of a hidden point. According to the invention, nanoscale precision reference is provided through the laser interference ranging reference group and far exceeds the millimeter-level precision requirement of a terahertz positioning algorithm, the problem of insufficient reference precision of a verification environment is solved, and a reliable basis is provided for verification of a high-precision algorithm.

Description

Technical Field

[0001] This invention belongs to the field of terahertz imaging, specifically relating to a system, method, and platform for hidden point measurement verification used to test the accuracy of terahertz signal recognition and positioning algorithms. Background Technology

[0002] Terahertz waves, electromagnetic waves with frequencies between 0.1 and 10 THz, fall between microwaves and infrared radiation. They possess advantages such as low photon energy, high penetration, and fingerprint spectral characteristics, demonstrating significant application potential in fields such as security inspection, non-destructive testing, and quality control. Compared to traditional detection techniques like X-rays, terahertz waves do not cause ionizing damage to biological tissues, possessing inherent safety, and are particularly suitable for human body scanning, concealed object detection, and identification of internal defects in non-metallic materials.

[0003] The following mainly describes the advantages and disadvantages of X-ray imaging, ultrasonic imaging, and terahertz imaging in non-destructive testing. X-ray imaging mainly utilizes X-rays to penetrate objects and form images based on differences in density. It has the advantages of high resolution and fast imaging speed, but it carries the risk of ionizing radiation, which poses a potential hazard to biological tissues. Ultrasonic imaging is based on the reflection and propagation characteristics of sound waves in different media. It has the advantages of being radiation-free, providing real-time imaging, and having low equipment costs, but it is greatly affected by coupling agents and has poor penetration ability in gases and metals. Terahertz imaging utilizes the interaction between terahertz waves and matter to form reflection, absorption, or scattering effects. It forms images by analyzing time-domain waveforms or spectra, and has the advantages of being radiation-free and having strong penetration ability in non-polar materials. However, terahertz signals are easily affected by factors such as water vapor absorption, propagation attenuation, and beam splitting, resulting in low signal-to-noise ratio and difficulty in verifying positioning accuracy.

[0004] In terahertz nondestructive testing applications, particularly for detecting hidden points on skin, such as identifying keel distortion under aircraft skin or locating internal defects in industrial materials, the core challenge currently facing technology is how to quantify and evaluate the accuracy of identification and location algorithms. Terahertz signals are susceptible to interference from physical layer factors such as near-field spherical wave effects and signal attenuation in complex real-world scenarios, leading to a reduced system signal-to-noise ratio and affecting the accuracy of location. Most existing terahertz detection systems rely on direct imaging and subjective judgment, lacking standardized and quantifiable verification environments, making it difficult to objectively evaluate algorithm accuracy. More importantly, current technologies cannot provide reliable reference benchmarks at the micrometer or even nanometer level of precision, failing to meet the verification requirements of high-precision terahertz location algorithms and hindering the further development of terahertz technology in the field of high-precision nondestructive testing. Summary of the Invention

[0005] This invention aims to solve the problems of the prior art mentioned above. It proposes a system and method for verifying the accuracy of non-destructive detection of hidden points on skin. The technical solution of this invention is as follows:

[0006] A system for verifying the accuracy of non-destructive detection of concealed points on skin includes: a terahertz probe measurement group, a laser interferometric ranging reference group, and a displacement control device; the terahertz probe measurement group is used to emit terahertz waves to a terahertz tag and receive reflected waves to obtain the tag's position information; the laser interferometric ranging reference group is used to provide a position reference with a measurement accuracy higher than that of the terahertz probe measurement group; the displacement control device is used to control the displacement of the terahertz tag in three dimensions to simulate the movement of the concealed point.

[0007] Furthermore, the terahertz tag comprises a gold film surface layer, a chromium adhesive layer, and a quartz substrate stacked from top to bottom, wherein the thickness of the gold film surface layer is 100 nm, the thickness of the chromium adhesive layer is 20 nm, the thickness of the quartz substrate is 500 μm, and the overall size of the tag is a square structure of 2 mm × 2 mm.

[0008] Furthermore, the laser interferometric ranging reference group includes three SJ6000 laser interferometric rangefinders to achieve nanometer-level measurement accuracy.

[0009] Furthermore, the displacement control device is a three-axis driven displacement stage, which can achieve micron-level precision displacement adjustment in the X, Y, and Z dimensions, and is equipped with a high-precision sample holder for fixing the terahertz label.

[0010] A method for verifying the accuracy of non-destructive detection of concealed points using any of the systems described herein, comprising the following steps:

[0011] (1) Establish a reference coordinate system, including the horizontal XY coordinate system and the vertical Z coordinate system;

[0012] (2) Measure the reference position value of the terahertz tag using a laser interferometric ranging reference set;

[0013] (3) Measure the position value of the terahertz tag using the terahertz probe measurement group;

[0014] (4) Compare the reference position value and the measured position value, calculate the measurement error, and evaluate the positioning accuracy of the terahertz detection system.

[0015] Furthermore, the establishment of the transverse XY coordinate system in step (1) includes: attaching a reference label to the center point of the inner corner of the L-shaped linear reflector, using this point as the origin, and the directions of the two arms of the L-shape as the X-axis and Y-axis to establish a coordinate system.

[0016] Furthermore, the measurement of the laser interferometric ranging reference group in step (2) includes: using two laser interferometers arranged along the X-axis and Y-axis, enabling automatic environmental compensation through linear measurement software, and collecting real-time distance data from the laser source to the reflector to obtain the displacement of the tag.

[0017] Furthermore, the measurement of the terahertz probe measurement group in step (3) includes: after the terahertz wave penetrates the heat insulation tile, it is reflected by the tag and returns to the terahertz probe. By analyzing the time-domain waveforms collected by the terahertz time-domain spectroscopy system before and after the terahertz tag moves, and performing two-dimensional imaging, the measurement coordinates of the terahertz tag before and after moving in the XY coordinate system are obtained respectively. By comparing the terahertz tag coordinates before and after moving, the relative displacement of the hidden point at the center of the tag can be calculated, and the position is converted to the absolute coordinate system.

[0018] Furthermore, the method also includes longitudinal measurement accuracy verification: the displacement of the label in the Z-axis direction is measured by a laser interferometer and compared with the longitudinal distance measured by the terahertz probe to obtain the longitudinal measurement error.

[0019] A terahertz nondestructive testing accuracy verification platform applying any one of the methods described herein includes a computer control unit, a terahertz time-domain spectroscopy system, a laser interferometer system, a three-axis displacement stage, and a coordinate transformation module. The computer control unit coordinates the operation of each subsystem to achieve automated control of the measurement process and data acquisition and processing. The terahertz time-domain spectroscopy system generates and detects terahertz waves. The laser interferometer system provides a high-precision length reference and performs real-time position monitoring and calibration of the displacement stage to ensure scanning positioning accuracy. The three-axis displacement stage carries and drives the sample or probe to perform precise positioning and scanning in three-dimensional space to achieve point-by-point imaging. The coordinate transformation module matches and transforms the position data measured by the laser interferometer with the terahertz spectral data in spatial coordinates to achieve precise spatial positioning of the internal features of the sample.

[0020] The advantages and beneficial effects of this invention are as follows:

[0021] 1. This invention provides a nanometer-level precision reference through a laser interferometric ranging reference set, which far exceeds the millimeter-level precision requirement of terahertz positioning algorithms, solves the problem of insufficient accuracy of the verification environment reference, and provides a reliable foundation for high-precision algorithm verification;

[0022] 2. By designing a dedicated terahertz label and loading obstacles such as heat-insulating tiles, the actual conditions for terahertz beam penetration performance testing were simulated, enhancing the practicality and reliability of the verification environment;

[0023] 3. By adopting a dual verification process of horizontal and vertical dimensions, combined with coordinate system establishment and transformation, a comprehensive evaluation of the terahertz probe measurement results was achieved, forming a complete closed-loop verification system, and providing a standardized and quantifiable testing platform for terahertz identification and positioning algorithms.

[0024] The primary innovation of this invention lies in its system architecture, particularly the introduction of a laser interferometric ranging reference set as the accuracy verification system for the entire platform. This design corresponds to the three orthogonally arranged laser interferometers described in claim 3. Its innovation is not simply about improving measurement accuracy, but rather about constructing a reference benchmark independent of the terahertz detection system, with an accuracy several orders of magnitude higher. This allows for objective and quantitative calibration of the accuracy of the terahertz identification and positioning algorithm. This approach of creatively applying top-tier tools from the field of precision metrology to terahertz detection verification transcends the boundaries of different technical fields and is not a conventional technique in this area. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the verification environment for a preferred embodiment of the present invention.

[0026] Figure 2 This is a flowchart for measuring accuracy verification. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and thoroughly described below with reference to the accompanying drawings. The described embodiments are merely some embodiments of the present invention.

[0028] The technical solution of the present invention to solve the above-mentioned technical problems is:

[0029] This invention designs and implements a system specifically for verifying the accuracy of non-destructive detection of hidden points on skin. At the hardware level, the system constructs an opto-mechatronics integrated architecture centered on a terahertz probe measurement group, a laser interferometric ranging reference group, and a three-axis displacement stage. At the software level, based on a high-precision measurement and control system, it achieves automated synchronous control of tag displacement, terahertz signal acquisition, and laser interferometric measurement. The computer drives the three-axis displacement stage through a motor controller to perform multi-dimensional precision displacement, simulating the actual movement of the hidden point, and simultaneously triggering the terahertz probe and laser interferometer to complete the accurate acquisition and comparison of position data. Regarding the accuracy verification method, this invention proposes a dual verification process, both horizontal and vertical. By establishing a reference coordinate system, coordinate transformation, and error analysis, it achieves an objective quantitative evaluation of the positioning accuracy of the terahertz detection system. This comparison mechanism between a high-precision reference and measured data ensures that the system can achieve reliable verification with micron-level or even nanometer-level accuracy even in complex environments.

[0030] To achieve the above objectives, the present invention adopts the following technical solution: First, a displacement control device drives the terahertz tag to perform micrometer-level precision displacement in the X, Y, and Z dimensions to simulate the movement of a concealed point; then, a laser interferometric ranging reference group is used to measure the reference position value of the tag, providing a nanometer-level precision reference; simultaneously, a terahertz wave is emitted by the terahertz probe measurement group, penetrates the heat insulation tile, and is reflected by the tag to collect the time-domain waveform. The waveform is analyzed, and the relative displacement of the tag is calculated using algorithm imaging; further, the terahertz measurement value is converted to an absolute coordinate system through coordinate transformation; finally, the reference value and the measurement value are compared to calculate the positioning error, thereby evaluating the accuracy of the terahertz detection system.

[0031] Specifically, the terahertz tag adopts a sandwich-like layered configuration, including a 100nm thick gold film surface layer, a 20nm thick chromium adhesion layer, and a 500μm thick quartz substrate, with a square structure of size 2mm×2mm, for efficient reflection of terahertz waves; the laser interferometric ranging reference group uses an SJ6000 laser interferometer to achieve nanometer-level measurement accuracy; the verification process includes lateral measurement accuracy verification and longitudinal measurement accuracy verification. Lateral verification establishes an XY coordinate system and measures the displacement using two orthogonally arranged laser interferometers, while longitudinal verification measures the displacement in the Z-axis direction using one laser interferometer, and performs error analysis in conjunction with the terahertz probe measurement results.

[0032] like Figure 1 As shown, the verification environment is functionally divided into two core modules: the terahertz probe measurement group and the laser interferometric ranging reference group. The computer serves as the control and data processing center of the entire system, responsible for coordinating the operation of each component. A three-axis driven displacement stage is located at the center of the system, with a terahertz tag fixed on its high-precision sample holder. To examine the penetration performance of the terahertz beam, a heat-insulating tile is loaded between the terahertz tag and the probe. During the measurement process, the terahertz wave emitted by the terahertz probe penetrates the heat-insulating tile, is reflected by the tag, penetrates the heat-insulating tile again, and returns to the terahertz probe. The laser interferometric ranging reference group uses three orthogonally arranged SJ6000 laser interferometers, achieving nanometer-level measurement accuracy and providing a reliable reference standard for terahertz measurement results.

[0033] like Figure 2 As shown, the measurement accuracy verification is divided into lateral measurement accuracy verification and longitudinal measurement accuracy verification. Lateral verification establishes an XY reference coordinate system and uses two laser interferometers to measure the displacement in the X and Y directions respectively; longitudinal verification uses one laser interferometer to measure the displacement in the Z-axis direction. The verification process includes five main steps: optical path setup, coordinate establishment, data acquisition, coordinate transformation, and error assessment, forming a complete closed-loop verification system.

[0034] In practical implementation, the terahertz tag is designed as a square structure, measuring 2mm × 2mm, employing a sandwich-like layered configuration. From top to bottom, it consists of a 100nm thick gold film surface layer, a 20nm thick chromium (Cr) adhesion layer, and a 500μm thick quartz substrate. This structure ensures efficient reflection of terahertz waves. The tag is fixed to a high-precision sample holder on a three-axis driven displacement stage. The displacement stage is motor-controlled, enabling micron-level precision displacement adjustment in the X, Y, and Z dimensions to simulate the translational movement of concealed points in practical applications.

[0035] In the lateral measurement accuracy verification experiment, a 2mm reflective label (reference label) was first attached to the center point of the inner corner of the L-shaped linear reflector, and an XY coordinate system was established using this point as the origin. Two laser interferometers were placed along the X / Y axes, ensuring that the laser interferometers, linear interferometer, and linear reflector were on the same axis. Using the linear measurement software with automatic environmental compensation enabled, the acquisition program was run to measure the real-time distance from the laser source to the L-shaped reflector. Then, the label to be tested was attached to the target position, and the measurement data from the laser interferometer was read to obtain the displacement of the label to be tested relative to the reference label.

[0036] In the longitudinal measurement accuracy verification experiment, a 2mm reflective label was adhered to the front surface of a linear reflector. A laser interferometer was fixed behind the linear reflector using a tripod, ensuring optical path collimation. The real-time distance from the laser source to the reflector was measured using linear measurement software. By moving the linear reflector along the Z-axis and reading the measurement data from the laser interferometer, the displacement of the reflective label in the Z-axis direction could be obtained. This displacement was used as a reference value and compared with the longitudinal distance measured by the terahertz probe to calculate the measurement error.

[0037] Experimental results demonstrate that this system can achieve an objective quantitative evaluation of the positioning accuracy of the terahertz detection system. In lateral measurements, the comparison error between the nanometer-precision reference value provided by the laser interferometer and the terahertz measurement value is controlled within the micrometer range; in longitudinal measurements, the system also exhibits good stability and repeatability. Through coordinate system establishment and transformation, a complete verification closed loop is formed, providing a standardized testing platform for terahertz identification and positioning algorithms.

[0038] The specific embodiments of the present invention are not only applicable to the accuracy verification of hidden point detection under aircraft skin, but can also be extended to other industrial scenarios that require high-precision non-destructive testing, such as the location of internal defects in composite materials and the identification of hidden objects in security inspection, etc., and have broad application prospects and promotion value.

[0039] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0040] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0041] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0042] The above embodiments should be understood as illustrative only and not as limiting the scope of protection of the present invention. After reading the description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent changes and modifications also fall within the scope defined by the claims of the present invention.

Claims

1. A system for verifying the accuracy of non-destructive detection of concealed points on skin, characterized in that, include: Terahertz probe measurement group, laser interferometric ranging reference group, and displacement control device; The terahertz probe measurement group is used to emit terahertz waves to the terahertz tag and receive the reflected waves to obtain the tag's position information; the laser interferometric ranging reference group is used to provide a position reference with a measurement accuracy higher than that of the terahertz probe measurement group; the displacement control device is used to control the displacement of the terahertz tag in three dimensions to simulate the movement of the concealed point.

2. The system according to claim 1, characterized in that, The terahertz tag comprises a gold film surface layer, a chromium adhesive layer, and a quartz substrate stacked from top to bottom. The gold film surface layer has a thickness of 100 nm, the chromium adhesive layer has a thickness of 20 nm, the quartz substrate has a thickness of 500 μm, and the overall size of the tag is a square structure of 2 mm × 2 mm.

3. The system according to claim 1, characterized in that, The laser interferometric ranging reference group includes three SJ6000 laser interferometric rangefinders, used to achieve nanometer-level measurement accuracy.

4. The system according to claim 1, characterized in that, The displacement control device is a three-axis driven displacement stage, which can achieve micron-level precision displacement adjustment in the X, Y, and Z dimensions, and is equipped with a high-precision sample holder for fixing terahertz labels.

5. A method for verifying the accuracy of non-destructive detection of concealed points using the system described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Establish a reference coordinate system, including the horizontal XY coordinate system and the vertical Z coordinate system; (2) Measure the reference position value of the terahertz tag using a laser interferometric ranging reference set; (3) Measure the position value of the terahertz tag using the terahertz probe measurement group; (4) Compare the reference position value and the measured position value, calculate the measurement error, and evaluate the positioning accuracy of the terahertz detection system.

6. The method according to claim 5, characterized in that, The step (1) of establishing the horizontal XY coordinate system includes: attaching the reference label to the center point of the inner corner of the L-shaped linear reflector, using this point as the origin, and using the directions of the two arms of the L-shape as the X-axis and Y-axis to establish the coordinate system.

7. The method according to claim 5, characterized in that, The measurement of the laser interferometric ranging reference group in step (2) includes: using two laser interferometers arranged along the X-axis and Y-axis, enabling automatic environmental compensation through linear measurement software, and collecting real-time distance data from the laser source to the reflector to obtain the displacement of the tag.

8. The method according to claim 5, characterized in that, The measurement of the terahertz probe measurement group in step (3) includes: the terahertz wave penetrates the heat insulation tile and is reflected by the tag and returns to the terahertz probe. By analyzing the time-domain waveforms collected by the terahertz time-domain spectroscopy system before and after the terahertz tag moves, and performing two-dimensional imaging, the measurement coordinates of the terahertz tag before and after moving in the XY coordinate system are obtained respectively. By comparing the terahertz tag coordinates before and after moving, the relative displacement of the hidden point at the center of the tag can be calculated, and the position is converted to the absolute coordinate system.

9. The method according to claim 5, characterized in that, The method also includes longitudinal measurement accuracy verification: the displacement of the label in the Z-axis direction is measured by a laser interferometer and compared with the longitudinal distance measured by the terahertz probe to obtain the longitudinal measurement error.

10. A terahertz nondestructive testing accuracy verification platform applying the method of any one of claims 5-9, characterized in that, It includes a computer control unit, a terahertz time-domain spectroscopy system, a laser interferometer system, a three-axis displacement stage, and a coordinate transformation module. The computer control unit coordinates the operation of each subsystem, enabling automated control of the measurement process and data acquisition and processing. The terahertz time-domain spectroscopy system generates and detects terahertz waves. The laser interferometer system provides a high-precision length reference and performs real-time position monitoring and calibration of the displacement stage to ensure scanning positioning accuracy. The three-axis displacement stage carries and moves the sample or probe to perform precise positioning and scanning in three-dimensional space, achieving point-by-point imaging. The coordinate transformation module matches and transforms the spatial coordinates of the position data measured by the laser interferometer with the terahertz spectral data, achieving precise spatial positioning of the internal features of the sample.

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