3D Point Cloud Reconstruction for Shadowed Reflective Surfaces
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Solution Overview
Problem
Existing 3D measurement methods struggle with uncooperative surfaces, such as very dark, featureless, or highly reflective surfaces, due to limitations in acquiring measurement points and issues with shadowing and light absorption, leading to inefficient and inaccurate 3D surface reconstruction.
Innovation Solution
A method combining photometric stereo and photogrammetric stereo using a system with multiple illumination units and a light pattern projector, controlled to emit light and project images in various orientations, creating metrically scaled 3D point clouds by combining images under different lighting combinations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If light pattern projection methods are used for 3D measurement, then measurement speed is improved, but shadowing occurs with complex topographies and measurement accuracy deteriorates
Solution Approach 1:
The patent divides the illumination into multiple point light sources arranged in specific spatial configurations rather than using a single projected light pattern. This segmentation allows light to arrive from multiple angles simultaneously, ensuring that shadowed areas in one direction are illuminated from other directions, thereby eliminating shadowing problems while maintaining high measurement speed
Solution Approach 2:
The patent transitions from 2D light pattern projection to 3D spatial illumination by arranging point light sources in three-dimensional space around the object. This dimensional change enables comprehensive illumination of complex topographies from multiple angles, resolving the shadowing issue inherent in planar light projection methods
2Area of stationary object
If traditional light projection methods are used on uncooperative surfaces, then measurement coverage is improved, but light absorption by dark surfaces causes measurement failure
Solution Approach 1:
The patent employs multiple point light sources with potentially different wavelengths and intensities, allowing adjustment of illumination parameters to match the reflective properties of different surface types. This parameter flexibility enables reliable measurement of uncooperative surfaces including very dark, featureless, highly reflective, or specular surfaces by optimizing light-surface interaction
3Reliability
If tactile 3D measuring systems are used to measure uncooperative surfaces, then measurement reliability is improved, but measurement time increases significantly
Solution Approach 1:
The patent replaces the mechanical tactile probing system with an optical measurement system using multiple point light sources and a camera. This substitution eliminates the need for physical contact and sequential point-by-point measurement, achieving both high measurement reliability for uncooperative surfaces and rapid data acquisition through parallel optical sensing
4Loss of information
If multiple light sources are used to eliminate shadows, then measurement completeness is improved, but system complexity increases
Solution Approach 1:
The patent designs the multiple point light sources to serve dual functions: they simultaneously provide comprehensive illumination for shadow elimination and enable photometric stereo measurements for surface normal determination. This multi-functionality reduces the need for separate illumination systems and simplifies the overall measurement setup while maintaining measurement completeness
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 efficient, high-quality 3D surface reconstruction of complex and difficult surfaces by minimizing shadows and occlusions, allowing for accurate and dense 3D point cloud generation with improved scale fidelity.
Implementation Method 1
at least three illumination units in the form of point light sources for emitting, in particular multispectral, light onto an object to be detected
Implementation Method 2
The changing pattern is captured by a detector as corresponding image patterns of the object surface at different locations
Data Source
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AI summary
The invention relates to a method for creating, in particular metrically scaled, 3D point clouds, especially three-dimensional (3D) surface reconstructions of objects, with a measuring system comprising: - at least one image sensor (2), in particular a video sensor, - at least three illumination units (4) in the form of point light sources for emitting, in particular multispectral, light onto an object to be detected in the recording area of the at least one image sensor (2), - at least one light pattern projector (3) for projecting a directed random image onto an object to be detected in the recording area of the at least one image sensor (2), - wherein the illumination units (4) are successively controlled to emit light, and/or the at least one light pattern projector (3) is controlled to project a directed random image.- wherein at least one photogrammetric image in the form of a metrically scaled 3D point cloud is created from the at least one image sensor (2) for each projection of a random image by the at least one light pattern projector (3), and - wherein at least one photometric image in the form of a 3D point cloud is created from a sequence of at least three images of the at least one image sensor (2), - wherein the at least three images are created under illumination by different combinations of illumination, and - wherein an illumination combination of illumination by different illumination units (4) which are activated successively, in particular individually or aggregated, and which differ at least in their position, in particular their pose, with respect to the at least one image sensor (2),corresponds to, or at least to provide few shadows for the creation of 3D point clouds of surfaces of measurement objects with complicated topographies and/or difficult surface properties for 3D surface reconstruction.