Specular Object Scanner Using Spherical Harmonics Illumination
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Solution Overview
Problem
Current object scanning technologies fail to independently measure diffuse and specular reflectance parameters for each surface point, missing important surface reflectance details and being limited in scanning highly specular and transparent objects.
Innovation Solution
A system using a controllable field of illumination with limited-order Spherical Harmonics and Fourier Series patterns, combined with a rotating arc-shaped light source and multiple cameras, to capture high-resolution reflectance properties, including diffuse and specular albedo, surface orientation, and anisotropy parameters, allowing for high-fidelity geometric modeling of various objects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If exhaustive BRDF measurement using point light sources is used, then complete reflectance field capture is achieved, but a large number of high-dynamic range photographs are required
Solution Approach 1:
The patent transforms the illumination from point sources to extended area light sources with controlled spatial distribution. By changing the lighting parameters from discrete points to continuous area sources with specific geometric arrangements, the system achieves complete reflectance field capture with significantly fewer photographs while maintaining measurement precision.
Solution Approach 2:
The patent segments the illumination field into controlled zones using multiple area light sources positioned at specific locations. This segmentation allows independent control of different illumination regions, enabling comprehensive BRDF measurement without requiring exhaustive point-by-point sampling.
2Loss of time
If BRDF slices from a single viewpoint are used to infer parameters, then measurement time is reduced, but important surface reflectance detail is lost
Solution Approach 1:
The patent transitions from single-viewpoint 2D imaging to multi-viewpoint 3D imaging geometry. By introducing multiple cameras positioned at different viewpoints around the object, the system captures reflectance information from multiple dimensions simultaneously, preserving surface detail while reducing measurement time compared to exhaustive single-viewpoint sampling.
Solution Approach 2:
The patent merges measurements from multiple viewpoints and multiple area light sources into a unified reflectance model. This combination allows the system to infer complete surface reflectance properties by integrating information from limited viewpoints, achieving both time efficiency and detail preservation.
3Quantity of substance
If sparse viewpoint and lighting directions are used with smooth reflectance assumption, then data requirements are reduced, but independent measurement of diffuse and specular reflectance is not achieved
Solution Approach 1:
The patent applies local quality control by using area light sources with specific spatial distributions that create distinct illumination patterns on different regions of the object surface. Each area light source illuminates specific zones with controlled angular characteristics, enabling the system to independently measure diffuse and specular reflectance parameters through the unique spatial-frequency signatures produced by different surface properties.
Solution Approach 2:
The patent uses composite illumination from multiple area light sources with different spatial distributions and angular characteristics. This composite lighting approach creates a rich set of illumination conditions that simultaneously encode both diffuse and specular reflectance information, allowing independent parameter measurement with reduced data requirements compared to uniform lighting.
4Ease of manufacture
If conventional scanning is used on highly specular objects, then standard procedures are followed, but inter-reflections and limited scanning capability occur
Solution Approach 1:
The patent introduces area light sources as intermediaries between the camera and highly specular object surfaces. These extended light sources create distributed illumination that reduces the intensity of direct specular reflections and minimizes inter-reflection effects between multiple surfaces, enabling reliable scanning of highly specular objects while maintaining procedural simplicity.
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 accurate measurement and separation of diffuse and specular reflectance, achieving high-fidelity geometric models and reflectance properties of objects, including translucent and reflective surfaces, with reduced image requirements and minimized inter-reflections.
Implementation Method 1
a light source configured to illuminate the object with a controllable field of illumination
Implementation Method 2
capture high-resolution reflectance properties, including diffuse and specular albedo
Data Source
AI summary
An apparatus to measure surface orientation maps of an object may include a light source that is configured to illuminate the object with a controllable field of illumination. One or more cameras may be configured to capture at least one image of the object. A processor may be configured to process the image(s) to extract the reflectance properties of the object including an albedo, a reflection vector, a roughness, and/or anisotropy parameters of a specular reflectance lobe associated with the object. The controllable field of illumination may include limited-order Spherical Harmonics (SH) and Fourier Series (FS) illumination patterns with substantially similar polarization. The SH and FS illumination patterns are used with different light sources.