Raster Reflectometry for Partially Reflective Surface Shape Reconstruction
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Solution Overview
Problem
Existing methods for detecting the three-dimensional shape of optically partially reflecting surfaces are limited by the need for model assumptions and require knowledge of the distance between the surface and the measurement system, making them unreliable for complex objects with unknown geometry.
Innovation Solution
A method using raster reflectometry that decouples deflectometric measurement sensitivity from surface point position, employing 'shape from shading' techniques and deflectance and reflectance measurements to reconstruct surface geometry without requiring multiple viewing directions or distance knowledge, utilizing a spatially resolving sensor unit and programmable light sources for directed light pattern projection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional grid reflection methods are used to measure reflective surfaces, then measurement can be performed on smooth surfaces, but the method becomes unreliable and ambiguous for complex surfaces of unknown geometry due to underdetermined differential equations
Solution Approach 1:
The patent introduces a known reference surface (calibration object) as an intermediary between the measurement system and the unknown surface. By first measuring the reference surface with known geometry, the system establishes a baseline that eliminates the underdetermination problem. This intermediary allows subsequent measurements of unknown surfaces to be performed reliably without requiring model assumptions about the surface geometry.
Solution Approach 2:
The patent performs a preliminary measurement step using a reference surface with known geometry before measuring the unknown surface. This preliminary action establishes the calibration data and system parameters needed to make the subsequent measurement of the unknown surface unambiguous and reliable, eliminating the need for model assumptions during the actual measurement.
2Adaptability or versatility
If the distance between the measurement system and the surface is unknown, then the system cannot resolve the underdetermined equations, but requiring distance knowledge limits the method's applicability to surfaces where distance can be measured
Solution Approach 1:
The reference surface acts as an intermediary that encodes distance information indirectly. By measuring the reference surface at known positions and comparing with measurements of the unknown surface, the system can determine surface geometry without requiring direct distance measurement, thus maintaining measurement precision while increasing adaptability.
Solution Approach 2:
The patent creates an optical copy of the reference surface pattern through the unknown surface. By analyzing how the known reference pattern is distorted when reflected off or transmitted through the unknown surface, the system can reconstruct the unknown surface geometry without needing to know the absolute distance, as the distortion itself contains the geometric information.
3Adaptability or versatility
If model assumptions are made about surface smoothness to enable measurement, then measurement can proceed on simple surfaces, but the assumptions limit the method's ability to measure complex surfaces with arbitrary geometry
Solution Approach 1:
The reference surface with known geometry serves as an intermediary that provides ground truth data for calibration. This eliminates the need to make model assumptions about the unknown surface, as the system can directly compare measurements against the known reference to unambiguously reconstruct any surface geometry without relying on smoothness assumptions.
Solution Approach 2:
The patent changes the measurement parameters by using a known reference surface to establish calibration data. This parameter change (from unknown to known reference) allows the system to handle arbitrary surface geometries without model assumptions, as the reference provides the necessary constraints to make the reconstruction problem well-posed.
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
Enables high-resolution, unambiguous surface shape reconstruction from a single image recording configuration, overcoming ambiguity in scanning reflectometry and allowing measurement of surfaces of any shape without distance knowledge, with measurement accuracy limited only by sensor resolution.
Implementation Method 1
at least one light pattern is imaged over a surface to be examined which is at least partially reflected in a directed manner on the surface
Implementation Method 2
scattered or diffusely reflected light components of a light source that illuminates the surface largely homogeneously are detected
Data Source
AI summary
The method involves forming a light pattern over a surface that is to be determined, where the light pattern is partially reflected in the surface. The light pattern is detected by an imaging and/or spatial sensor unit and is evaluated in a way of image evaluation. A reflected light portion directed to the surface and diffused reflected light portion of a light source that homogenously illuminate the surface, are detected and evaluated. The reflected light portion is produced in a grid reflectrometric deflection measurement. An independent claim is also included for a device for determining a shape of an optical partially reflective surface.