Terahertz Sensor Array for Pipe Wall Thickness and Sagging Detection
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Solution Overview
Problem
Current terahertz measurement methods for extruded plastic tubes are imprecise, particularly when detecting non-ideal effects such as anisotropic defects and deformities like sagging, due to limitations in reflection peak detection and coverage area.
Innovation Solution
A terahertz measurement device with a main sensor and additional sensors having divergent optical axes, allowing for non-perpendicular incidence of terahertz radiation to detect defects and deformities outside the conventional detection plane, enabling precise detection of anisotropic defects and deformities with enhanced coverage area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single THz sensor is used with perpendicular incidence to measure wall thickness, then the measurement setup is simple, but defects with anisotropic reflection characteristics cannot be detected
Solution Approach 1:
The single sensor is segmented into multiple sensor elements (first sensor, second sensor, third sensor) with different optical axis orientations. Each sensor element detects reflections from different spatial directions, enabling comprehensive defect detection while maintaining a relatively simple overall setup.
Solution Approach 2:
The sensor elements are configured with asymmetric orientations relative to the pipe axis. The first sensor has its optical axis perpendicular to the pipe axis, the second sensor is inclined at a first angle, and the third sensor is inclined at a second angle. This asymmetric arrangement enables detection of anisotropic defects that would be invisible to a single perpendicular sensor.
2Reliability
If multiple sensors with different orientations are used to detect anisotropic defects, then defect detection reliability improves, but device complexity increases
Solution Approach 1:
Multiple sensor elements with different orientations are merged into a single integrated sensor unit. This combining approach achieves comprehensive defect detection capability while avoiding the complexity of multiple separate sensor systems, as all sensors share a common mounting structure and measurement coordinate system.
Solution Approach 2:
The sensor system is designed with multi-functionality, where the same sensor unit can detect both wall thickness (via the perpendicular first sensor) and anisotropic defects (via the inclined second and third sensors). This universal design eliminates the need for separate detection systems for different measurement objectives.
3Measurement precision
If THz radiation is focused on the longitudinal axis of the pipe, then wall thickness measurement is accurate, but sagging and deformities cannot be detected
Solution Approach 1:
The detection capability is extended from a single dimension (perpendicular to pipe axis) to multiple dimensions by introducing sensors with inclined optical axes. The second and third sensors provide detection coverage in angular dimensions, enabling identification of sagging and deformities that manifest as spatial variations in reflection patterns across different orientations.
Solution Approach 2:
Different sensor elements are assigned specialized functions based on their orientation. The first sensor optimized for perpendicular incidence provides accurate wall thickness measurement, while the second and third sensors with inclined axes are specifically suited for detecting sagging and deformities. This local optimization of sensor qualities achieves both precise measurement and comprehensive detection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly increases the probability and quality of defect detection, allowing for reliable identification of defects and deformities, including sagging, with minimal equipment and mechanical adjustments, while maintaining high resolution and large-area coverage.
Implementation Method 1
The THz radiation radiated along the optical axis is partially reflected at the boundary surfaces of the tube, so that it is reflected back along the optical axis in the case of vertical incidence and can be detected as a reflection peak in the recorded signal amplitude.
Data Source
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AI summary
The invention relates to a THz measuring device for measuring at least one layer thickness (d) of a test object (1) conveyed along a conveying direction (v), wherein the THz measuring device has: a main THz sensor for emitting a main THz beam (12) along a first optical axis (A1) in a detection plane (E) at right angles to the conveying direction (v) and for receiving THz radiation reflected along the first optical axis (A1) , at least one additional THz sensor for emitting an additional THz beam (14) along a second optical axis (A2), which extends outside the detection plane (E) and/or at an angle to the detection plane (E), for detecting the additional THz radiation reflected back along the second optical axis (A2), an evaluation and control device (16) which picks up a first signal amplitude from the main THz sensor, determines the main reflection peaks in the first signal amplitude (S12) and, from the main reflection peaks, determines a distance and/or layer thickness in the detection plane (E), and picks up a second signal amplitude from the additional THz sensor, determines additional reflection peaks in the second signal amplitude and assigns the additional reflection peaks to faults (32) in or on the test object (1).