Optical Interferometry for Thin-Film Material Strength and Cracking
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Solution Overview
Problem
Existing methods for determining the strength limit and degree of deformation of thin-film materials in flexible electronic systems are inadequate in accurately measuring material cracking and deformation beyond the elastic range, particularly in non-contact, non-destructive ways.
Innovation Solution
The method employs optical interferometry with a diffraction grating sensor, modulating the laser beam with a periodic frequency to isolate signals from external interference, and using a semi-transparent mirror to focus the central interference fringe for precise intensity measurement, allowing for the determination of material strength limits and degree of cracking through analysis of beam intensity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional contact methods are used to measure deformation of thin-film materials, then measurement can be performed, but the method is destructive and cannot accurately measure material cracking beyond the elastic range
Solution Approach 1:
The patent replaces mechanical contact measurement methods with optical interferometry. A diffraction grating sensor is applied to the substrate surface, and optical interference patterns are used to measure deformation and detect microcracks in thin-film materials without physical contact, enabling non-destructive measurement beyond the elastic range
Solution Approach 2:
The patent introduces a diffraction grating as an intermediary sensor element applied to the substrate surface. This grating acts as a mediator that converts mechanical deformation into optical interference patterns, allowing indirect measurement of strain and crack detection without direct contact with the thin-film material
2Ease of operation
If optical interferometry with diffraction grating is used for non-contact measurement, then non-contact measurement capability is achieved, but external interference factors affect measurement precision
Solution Approach 1:
The patent applies periodic modulation to the laser beam at a specific frequency (e.g., 1 kHz). This periodic action creates a modulated optical signal that can be distinguished from external interference through frequency filtering, thereby maintaining measurement precision in the presence of environmental disturbances
Solution Approach 2:
The patent employs feedback through phase-sensitive detection and signal processing. The modulated signal from the diffraction grating is processed using lock-in amplification or Fourier filtering techniques, which provide feedback-based noise rejection and enhance the signal-to-noise ratio for precise deformation measurement
3Measurement precision
If laser beam intensity measurement is used to determine material strength limit, then strength limit determination is achieved, but the measurement is affected by background light and external interference
Solution Approach 1:
The patent uses periodic modulation of the laser beam at a known frequency to encode the measurement signal. By detecting only the modulated component at this specific frequency, the system can distinguish the true signal from background light and external interference, enabling accurate intensity measurement for strength limit determination
Solution Approach 2:
The patent converts the potential harm of external light interference into a benefit by using frequency modulation. The modulated signal approach allows the system to operate in environments with background light, as the frequency-encoded signal can be selectively extracted from the total light spectrum, turning the presence of background light into a non-issue
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 approach enables accurate, non-contact measurement of material strength limits and deformation, identifying the onset of microcracks with high precision, essential for assessing the reliability of thin-film materials in flexible electronic systems.
Implementation Method 1
a diffraction grating which is illuminated with radiation including at least two frequencies to produce an interference pattern
Implementation Method 2
the interference of the portion of the beam of light reflected and superimposed at the boundary surfaces of the transparent film
Implementation Method 3
a non-contact method that uses wave reflection on a surface
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
The method consists in measuring the intensity of the beam passing through the tested material before and after deformation, introducing modulation of the primary laser beam with a periodic function of a given frequency that allows to obtain in the detection path a signal independent of external interference factors, then the AC signal from the detector is amplified and filtered using a Fourier filter or phase-sensitive amplifier, and then the signal is transmitted to the data logger, while during the measurement the intensity of the central interference fringe falling on the photosensitive matrix decreases by directing the central fringe directly to the photo recorder using a semi-transparent mirror, as a result of which data on changes in the intensity of light passing through the sample is obtained. As a result of applying the above measurement steps, identification of the strength limit of the tested material is obtained.