THz Sensor System for Non-Contact Paper Quality Measurement
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Solution Overview
Problem
Current in-line quality control systems for paper sheet materials are limited by the need for physical contact with the paper, which can damage the material, and the complexity of extracting relevant quality parameters from THz measurement signals for robust and meaningful results.
Innovation Solution
A non-contact sensor system using THz radiation that emits and detects THz signals, processes them using a physical model to determine parameters like caliper and basis weight, and calculates quality parameters such as moisture and fiber orientation without material-specific calibration, utilizing a processing unit to fit the detected response to a predicted model response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical contact sensors are used to measure paper quality parameters, then measurement capability is improved, but the risk of paper damage increases
Solution Approach 1:
The patent replaces mechanical contact sensors with THz radiation-based non-contact sensors to measure paper quality parameters. The sensor head uses electromagnetic radiation (THz waves) to detect caliper, basis weight, and moisture content without physically touching the paper, thereby eliminating mechanical damage risk while maintaining measurement capability.
2Measurement precision
If beta radiation sensors are used for quality control, then measurement capability is improved, but system complexity and safety requirements increase
Solution Approach 1:
The patent changes the radiation parameter from beta radiation to THz radiation (terahertz frequency range). This parameter change allows for non-contact measurement with improved safety characteristics, as THz radiation does not require the extensive shielding and safety protocols needed for beta radiation, while still providing the necessary measurement capability for paper quality control.
3Object-affected harmful factors
If THz radiation is used for non-contact measurement, then paper damage risk is reduced, but the complexity of extracting quality parameters from measurement signals increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring the sensor head with multiple THz sensors and establishing the measurement geometry before actual measurement. The system is pre-calibrated and the signal processing algorithms are pre-established to extract quality parameters (caliper, basis weight, moisture) from the THz transmission and reflection signals, thereby reducing the operational complexity during actual measurement.
Solution Approach 2:
The patent applies universality by designing a multi-functional sensor head that simultaneously measures multiple paper quality parameters (caliper, basis weight, moisture content) using THz radiation. This multi-functional approach consolidates what would otherwise require multiple separate measurement systems, reducing overall system complexity despite the advanced physics involved.
4Measurement precision
If multiple sensors are used to measure different quality parameters, then measurement comprehensiveness is improved, but device weight and complexity increase
Solution Approach 1:
The patent implements universality by designing a sensor head where multiple THz sensors share a common mounting structure and optical path. The sensor head simultaneously performs multiple measurements (caliper, basis weight, moisture) using the same physical platform, thereby achieving comprehensive quality parameter measurement without proportionally increasing the weight that would result from completely separate sensor systems.
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
Enables robust and reliable determination of paper sheet quality parameters like caliper, basis weight, and moisture from a single THz radiation signal, reducing the risk of paper damage and eliminating the need for calibration data, thus providing a consistent and accurate in-line quality control.
Implementation Method 1
emitter system for emitting THz radiation
Implementation Method 2
detector system for detecting THz radiation
Implementation Method 3
model parameters being indicative of transmission and/or reflection coefficients at interfaces of the paper sheet material with surrounding media
Data Source
Figure 1~2b
Figure 3a~4
Figure 5~6
AI summary
A non-contact sensor system and method for determining paper sheet quality parameters such as caliper, basis weight and sheet moisture based on THz radiation are provided. The method comprises: Emitting, by an emitter system 10, a THz radiation signal 60 towards the paper sheet material 2 such that the THz radiation interacts with the paper sheet material; Detecting, by a detector system 20, a time and/or frequency dependent response 74 of the THz radiation signal 70 having interacted with the paper sheet material 2; Determining model parameters of a physical model by optimizing the model parameters such that a predicted response of the physical model is fitted to the detected response, the model parameters being indicative of transmission and/or reflection coefficients at interfaces of the paper sheet material with surrounding media; and determining, from the determined model parameters, at least some of the paper sheet quality parameters 91.