Chromatic Range Sensor Thickness Measurement via Transform Processing
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Solution Overview
Problem
Chromatic range sensors face measurement errors when determining the thickness of thin workpieces due to merging wavelength peaks, especially in the blue part of the Z range, which affects accuracy and signal detection.
Innovation Solution
A chromatic range sensor system employing a confocal optical path with axial chromatic dispersion and transform processing, such as Fourier transform processing, to accurately determine workpiece thickness by analyzing output spectral profile data and isolating wavelength peaks, even for thin workpieces with overlapping peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If chromatic range sensors are used to measure thin workpieces, then measurement capability is provided, but measurement precision deteriorates due to merging wavelength peaks
Solution Approach 1:
The patent introduces transform processing (Fourier transform, wavelet transform, or other signal processing techniques) as an intermediary method to analyze the spectral profile data. This processing technique acts as a mediator that can extract accurate thickness information even when wavelength peaks merge, thereby resolving the contradiction between maintaining measurement capability and preserving measurement precision for thin workpieces.
2Device complexity
If traditional peak isolation methods are used, then simple processing is provided, but measurement reliability deteriorates for thin workpieces with overlapping peaks
Solution Approach 1:
The patent transforms the measurement approach by changing the processing parameters and methods. Instead of relying on simple peak isolation, it employs transform processing that analyzes the spectral data in transformed domains (frequency domain, time-frequency domain), enabling reliable thickness measurement for thin workpieces while maintaining reasonable processing complexity through established mathematical transforms.
3Length of stationary object
If measurement is performed at closer distances (blue Z range), then measurement range is improved, but measurement precision deteriorates due to peak merging
Solution Approach 1:
The patent moves the analysis from the wavelength domain to transformed domains (frequency domain, time-frequency domain) using signal processing techniques. This dimensional transformation allows the system to resolve overlapping peaks by analyzing their characteristics in the transformed space, thereby maintaining measurement precision across the full measurement range including the blue Z range where peak merging occurs.
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
The system achieves accurate thickness measurements with less than 10% error for workpieces as thin as 5 microns, improving measurement precision across a range of distances and reducing errors associated with peak merging.
Implementation Method 1
an optical element having axial chromatic aberration, also referred to as axial or longitudinal chromatic dispersion, may be used to focus a broadband light source such that the axial distance to the focus varies with the wavelength
Implementation Method 2
A spectrometer-type detector measures the signal level for each wavelength, in order to determine the surface height
Implementation Method 3
The processing to determine the thickness comprises utilization of transform processing, such as utilization of Fourier transform processing
Data Source
AI summary
A chromatic range sensor (CRS) system is provided that determines a workpiece thickness and includes an optical pen, an illumination source, a wavelength detector and a processing portion. The optical pen includes an optics portion providing axial chromatic dispersion, the illumination source is configured to generate multi-wavelength light and the wavelength detector includes a plurality of pixels distributed along a measurement axis. In operation, the optical pen inputs a spectral profile from the illumination source and outputs corresponding radiation to first and second workpiece surfaces of a workpiece (e.g., which may be transparent) and outputs reflected radiation to the wavelength detector which provides output spectral profile data. The processing portion processes the output spectral profile data to determine a thickness of the workpiece. In various implementations, the processing to determine the thickness may not rely on determining a distance to the workpiece and/or may utilize transform processing, etc.