Newton Rings Fringe Analysis via Discrete Chirp Fourier Transform
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Solution Overview
Problem
Existing interferometric measurement methods, such as the fringe centerline method, are sensitive to noise and occlusions in interference fringe patterns, leading to inaccurate estimation of physical parameters like curvature radius and vertex position, and require human intervention which introduces errors.
Innovation Solution
The method employs discrete chirp Fourier transform (DCFT) on signals from Newton's rings fringe patterns to determine chirp rate and frequency parameters, allowing for accurate estimation of physical parameters even in noisy conditions, reducing human error and improving stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the fringe centerline method is used to process interference fringe patterns, then the automation degree is improved, but the measurement precision deteriorates due to sensitivity to noise and occlusions
Solution Approach 1:
The patent transforms the fringe pattern processing from spatial domain to frequency domain by applying Fourier transform. This parameter change in the processing domain allows the method to be insensitive to noise and occlusions while maintaining high automation. The frequency domain representation enables robust extraction of fringe parameters without manual intervention.
Solution Approach 2:
The patent replaces the traditional mechanical/image-processing approach (fringe centerline extraction) with a mathematical transformation approach (Fourier transform). This substitution eliminates the sensitivity to noise and occlusions that plagues the mechanical processing method while maintaining full automation.
2Manufacturing precision
If the ring-counting calculating method is used to measure interference fringe patterns, then the manufacturing precision is improved with simple implementation, but the reliability deteriorates due to human errors from visual fatigue
Solution Approach 1:
The patent replaces manual ring-counting with automated Fourier transform processing. The frequency domain analysis automatically identifies fringe parameters without human intervention, eliminating visual fatigue errors while maintaining the simplicity of the overall measurement process.
Solution Approach 2:
The Fourier transform method enables the system to self-determine fringe parameters automatically. The algorithm independently extracts frequency and phase information from the fringe pattern without requiring human observation or counting, thus improving reliability while keeping the process simple.
3Extent of automation
If traditional Fourier transform is used on interference fringe patterns, then the automation degree is improved, but the measurement precision deteriorates because it cannot accurately estimate parameters when chirp rate is non-zero
Solution Approach 1:
The patent introduces a chirp rate parameter to account for the quadratic phase variation in the fringe pattern. By modifying the standard Fourier transform to include this parameter, the method can accurately handle cases where the fringe frequency varies across the pattern, thereby improving measurement precision while maintaining automation.
Solution Approach 2:
The patent transitions from a static frequency analysis to a dynamic chirp rate analysis. The modified Fourier transform accommodates the dynamic variation in fringe frequency across the pattern, allowing accurate parameter estimation even when the chirp rate is non-zero.
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 high-accuracy estimation of physical parameters with improved error stability, as the parameters are linearly related to the chirp rate and frequency parameters obtained by DCFT, and is not influenced by noise or occlusions in the fringe patterns.
Implementation Method 1
performing a discrete chirp Fourier transform on the first-direction signal to obtain a first magnitude spectrum of an intensity distribution signal of a first-direction pixel set
Implementation Method 2
An interferometric measurement plays an important role in the non-contact measuring methods, and a key point thereof is to analyze and process an interference fringe pattern (for example, a Newton's rings fringe pattern)
Data Source
AI summary
A method, device and electronic apparatus for estimating physical parameters are disclosed. The method includes: reading a Newton's rings fringe pattern obtained by performing an interferometric measurement on a unit to be measured; obtaining the number and length of first-direction signals of the Newton's rings fringe pattern; performing, for each of the first-direction signals, a discrete chirp Fourier transform (DCFT) on the first-direction signal based on each first chirp rate parameter within a range of the length of first-direction signals, to obtain a first magnitude spectrum of an intensity distribution signal in a DCFT domain; determining a first chirp rate parameter and a first frequency parameter corresponding to a first magnitude peak value based on the first magnitude spectrum; and estimating the physical parameters involved in the interferometric measurement at least according to the first chirp rate parameter and first frequency parameter corresponding to the first magnitude peak value. In this way, the physical parameters involved in the interferometric measurement can be estimated with high accuracy and stably.