Terahertz Thickness Measurement Using Swept-Wavelength Lasers
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Solution Overview
Problem
Current methods for measuring the thickness of non-metallic materials are limited, especially for materials through which light is not transmitted, and existing terahertz wave technologies only focus on generating waves without providing a means for thickness measurement.
Innovation Solution
An apparatus using a wavelength-fixed laser and a wavelength-swept laser to generate a terahertz continuous wave with a high-frequency change, coupled with a data acquisition and calculation system to perform real-time non-contact non-destructive thickness measurement by analyzing the time-domain data of terahertz waves transmitted or reflected from the sample.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical methods are used for thickness measurement, then non-contact measurement is achieved, but materials through which light is not transmitted cannot be measured
Solution Approach 1:
The patent changes the fundamental parameter of the measurement wave from optical frequency to terahertz frequency. Terahertz waves have different penetration characteristics compared to optical waves, allowing them to transmit through opaque non-metallic materials while maintaining non-contact measurement capability. This parameter change enables the system to measure materials that were previously inaccessible to optical methods.
2Adaptability or versatility
If terahertz wave generation is implemented, then measurement of opaque materials is enabled, but thickness measurement functionality is not provided
Solution Approach 1:
The patent introduces time-domain signal analysis as an intermediary mechanism to extract thickness information from terahertz wave interactions with the sample. By analyzing the temporal characteristics of transmitted or reflected terahertz signals, the system converts physical thickness measurements into detectable temporal data patterns, enabling precise measurement of opaque materials.
Solution Approach 2:
The patent replaces traditional optical measurement mechanisms with terahertz wave-based detection. Instead of using light reflection or transmission methods, the system employs terahertz waves that can penetrate opaque materials and analyzes the temporal signature of the transmitted or reflected waves to determine thickness, substituting the measurement mechanism entirely.
3Productivity
If frequency change rate of terahertz wave is increased, then measurement speed is improved, but signal stability may be compromised
Solution Approach 1:
The patent implements periodic frequency sweeping of the terahertz wave source. Instead of continuously varying frequency, the system performs periodic sweeps at controlled rates, allowing the detector to capture signals at specific frequency points. This periodic action enables high measurement speed through rapid sweeping while maintaining signal stability by synchronizing detection with the sweeping cycle and allowing signal accumulation during each period.
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 accurate and efficient real-time thickness measurement of non-conductive materials, improving signal-to-noise ratio and reducing measurement time, suitable for various applications including medical, agricultural, and material evaluation.
Implementation Method 1
a wavelength-fixed laser generating first laser light having a first fixed wavelength λ1; a wavelength-swept laser generating second laser light having a second wavelength λ2 changed from a preset minimum wavelength to a preset maximum wavelength at a high speed
Implementation Method 2
an emitter receiving the first mixed light split from the coupler to output the terahertz wave having a frequency fTHz=|f1−f2| corresponding to a difference between a frequency f1=c/λ1 (c is the speed of light in vacuum) corresponding to the first wavelength λ1 and a frequency f2=c/λ2 corresponding to the second wavelength λ2
Implementation Method 3
a detector receiving the second mixed light split from the coupler and the terahertz wave transmitting or reflected from a sample to generate a photocurrent
Data Source
AI summary
Provided is an apparatus for real-time non-contact non-destructive thickness measurement using a terahertz wave, and more particularly, an apparatus for real-time non-contact non-destructive thickness measurement using a terahertz wave, which is capable of measuring a thickness of a sample by irradiating a terahertz continuous wave, which is generated from a wavelength-fixed laser and a wavelength-swept laser and of which the frequency is changed at a high speed, to the sample and measuring the terahertz wave transmitting or reflected from the sample.