White Light Interferometer Noise Suppression via Adaptive Signal Processing
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Solution Overview
Problem
Conventional shape measuring apparatuses using white light interferometers are susceptible to noise, leading to unstable and inaccurate measurements due to large signal swells on the baseline, especially influenced by the surface characteristics of the sample.
Innovation Solution
A shape measuring apparatus with a wideband light source, an optical system for generating an interfering light intensity distribution image, and an adaptive signal processing block using RLS algorithms to suppress noise and accurately detect peak positions, incorporating a peak detection block for precise measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional white light interferometer measurement is used, then the measurement process is simple, but the measurement results are unstable and inaccurate due to noise influence
Solution Approach 1:
The patent implements an adaptive signal processing block that uses feedback mechanisms to continuously adjust signal processing parameters. The system processes interfering light intensity sequences through multiple signal generating units, weighting units, and adaptive signal processing blocks that refine measurements in real-time, thereby improving both accuracy and stability of measurement results
Solution Approach 2:
The patent introduces an intermediary signal processing system between the optical measurement and final results. This includes signal generating units, weighting units, and adaptive signal processing blocks that act as intermediaries to filter noise and extract accurate measurement data from the interfering light intensity sequences
2Measurement precision
If adaptive signal processing with multiple signal generating units is used, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the signal processing function into multiple distinct units: signal generating units, weighting units, signal adding units, signal subtracting units, and adaptive signal processing blocks. Each unit performs a specific function in the signal processing chain, making the complex processing task manageable and modular while improving measurement accuracy
3Device complexity
If weighted average calculation is used for peak detection, then arithmetic processing is simplified, but noise influence increases leading to baseline swells
Solution Approach 1:
The patent replaces simple weighted average calculation with an adaptive feedback-based signal processing system. The adaptive signal processing blocks continuously adjust processing parameters based on feedback from the interfering light intensity sequences, effectively suppressing noise and baseline swells while maintaining reasonable processing complexity
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 apparatus achieves stable and accurate measurement results by effectively eliminating noise and improving the signal-to-noise ratio, significantly reducing baseline fluctuations and missing data, thereby enhancing measurement stability.
Implementation Method 1
the white light applied from a white light source to an object to be measured and reflected by the object to be measured is made to interfere with the white light applied from the white light source to a reference face and reflected by the reference face
Data Source
AI summary
A shape measuring apparatus includes: an optical system configured to guide a light from a light source having a wideband spectrum to an object to be measured and a reference face; an imaging unit configured to image the interfering light intensity distribution image output from the optical system; an optical path length difference changing unit configured to change the optical path length difference; and an arithmetic processing unit configured to obtain the peak value of an interfering light intensity sequence indicating the change in the interfering light intensity due to the change in the optical path length difference at each measurement position of the interfering light intensity distribution images stored in the image storing unit, and configured to obtain the peak value as the position in the direction of the optical axis at each measurement position of the object to be measured.