Common Path Interferometer Surface Measurement
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Solution Overview
Problem
Existing surface measurement technologies face challenges in achieving high-precision and rapid distance measurements across various surface geometries and profiles, with limitations in accuracy due to interactions between laser radiation and surface angles, leading to measurement errors and uncertainties.
Innovation Solution
The use of a frequency-modulated laser source with a fiber ring laser and a common path interferometer, combined with algorithmic corrections for perpendicular beam deviations and adaptive scanning guidance, allows for high-precision measurements by accounting for surface tilts and irregularities, reducing systematic errors and enhancing measurement reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a frequency-modulated laser source with common path interferometer is used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent introduces a common path interferometer as an intermediary optical system that mediates between the laser source and the surface being measured. This interferometer compensates for angular dependencies and surface tilts by providing a reference beam path that shares common optical components, thereby maintaining high measurement precision while managing the complexity through intelligent optical design
Solution Approach 2:
The patent employs frequency modulation of the laser source as a parameter change technique. By modulating the laser frequency and using Fourier transform analysis, the system achieves high precision distance measurements by transforming the measurement into the frequency domain, where angular dependencies can be algorithmically corrected
2Measurement precision
If algorithmic corrections for perpendicular beam deviations are applied, then measurement precision is improved, but loss of time increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing correction factors for angular dependencies and surface tilts in lookup tables. During measurement, the system quickly retrieves and applies these pre-computed corrections rather than performing complex real-time calculations, thereby maintaining high precision while minimizing processing time
Solution Approach 2:
The patent replaces complex real-time mechanical/optical alignment adjustments with algorithmic corrections based on Fourier transform analysis of the frequency-modulated signal. This substitution of computational methods for physical adjustments achieves high precision without the time loss associated with iterative mechanical alignment
3Measurement precision
If adaptive scanning guidance is used to maintain perpendicular beam impact, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements feedback control in the scanning system by continuously monitoring the angular position of the probe relative to the surface normal and adjusting the scanning trajectory in real-time. This feedback mechanism ensures perpendicular beam impact is maintained throughout the measurement process, achieving high precision while using computationally efficient control algorithms
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 and rapid surface measurements with minimal dependence on surface shape, reducing measurement uncertainties and achieving reliable distance information across diverse surface geometries without additional measurement components.
Implementation Method 1
a frequency-modulated laser source (1) for generating at least one laser beam
Implementation Method 2
interferometrically measuring the distance from a reference point to the surface (7)
Data Source
Figure 1~2
Figure 3~5c
Figure 5d~5h
AI summary
In a method for gauging surfaces (7``), in which a frequency-modulated laser beam is generated, the laser beam is emitted onto the surface as measuring radiation (MS), the measuring radiation (MS) backscattered from the surface (7``) is received and the distance between a reference point and the surface (7``) is measured interferometrically, wherein the measuring radiation (MS) is emitted and received while the surface to be gauged is being scanned, and a measuring arm and a reference interferometer arm with a partially common beam path are used, deviations from the essentially perpendicular impingement of the measuring radiation (MS) on the surface (7``) are taken into account algorithmically during distance measurement and/or are avoided or reduced during scanning by controlling the emission of the measuring radiation (MS).