Edge Positioning via Fresnel Diffraction Profile Analysis
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Solution Overview
Problem
Existing methods for determining the position of an object's edge, particularly in strands with coherent light, face challenges in measurement accuracy and speed due to computational intensity and interference from diffraction fringes, especially when measuring transparent or very thin strands.
Innovation Solution
A method involving coherent light illumination, recording spatial intensity curves of diffraction fringes, and comparing them with periodic reference intensity curves, either differentiated or integrated over a square location axis, to determine the object's edge position, allowing for high accuracy and robustness against disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the correlation method is used to determine geometric shadow boundaries by comparing measured diffraction fringes with a reference diffraction pattern, then measurement accuracy is improved, but computational time increases significantly
Solution Approach 1:
The patent extracts and evaluates only the characteristic feature points (local maxima, minima, and zeros) from the complete diffraction fringe pattern, rather than processing the entire intensity curve. This selective extraction maintains measurement accuracy while dramatically reducing computational complexity and processing time.
Solution Approach 2:
Instead of performing a complete correlation analysis across the entire diffraction pattern, the method applies partial action by focusing computation only on identifying and evaluating specific characteristic feature points. This partial processing approach achieves sufficient measurement accuracy without the excessive computational burden of full pattern correlation.
2Productivity
If characteristic feature points of diffraction fringes are evaluated to determine edge position, then evaluation speed is improved, but measurement reliability deteriorates when feature points are disturbed by interference
Solution Approach 1:
The patent merges three different evaluation methods (local maxima/minima evaluation, zero-crossing evaluation, and correlation method) into a unified system. By combining multiple approaches, the system maintains high evaluation speed while improving reliability through cross-validation and selection of the most robust method for each measurement situation.
Solution Approach 2:
The method dynamically changes evaluation parameters by selecting different feature points and evaluation strategies based on the quality and characteristics of the measured diffraction fringes. When interference is detected, the system adjusts which parameters (feature points) are evaluated or switches to alternative methods, maintaining reliability under varying conditions.
3Measurement precision
If Fourier transformation is applied to sinusoidal diffraction fringe models, then measurement accuracy is improved, but sensitivity to signal quality and interference increases
Solution Approach 1:
The patent applies partial action by using Fourier transformation only on selected segments or specific frequency components of the diffraction signal, rather than transforming the entire signal. This selective application maintains measurement accuracy for the relevant components while reducing the amplification of noise and interference that occurs with full-signal transformation.
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 reliable and fast measurement of object positions and diameters, even in conditions prone to interference, with enhanced accuracy and reduced computational complexity, suitable for transparent or thin strands.
Implementation Method 1
Due to the coherent, monochromatic radiation of the light source, diffraction fringes are generated at the geometric shadow boundaries of the strand
Implementation Method 2
recording the spatial intensity curve of at least one diffraction fringe with at least one single-line or multi-line optical sensor
Data Source
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AI summary
The invention relates to a method for determining the position of at least one edge of an object, in particular of a strand, comprising steps of: illuminating the object using light from at least one coherent light source, diffraction borders being generated on both geometric boundaries of the shadow formed by the object. In one embodiment, the intensity profiles are first differentiated according to the location. Each differentiated intensity profile can either be plotted on a quadratic position axis and compared to a periodic reference intensity profile, or be directly compared to a reference intensity profile that results from a periodic function. In a second embodiment, the intensity profiles are compared to a reference intensity profile that results from a periodic function, if this function has a period length with a substantially inversely linear dependency on the location, and if the function is integrated over the location.