Non-coplanar BRDF Measurement for Specialty Coatings
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Solution Overview
Problem
Existing devices for measuring the visual appearance of surfaces, such as discrete multi-angle spectrometers and goniospectrophotometers, provide limited detail, are costly, and require significant time, making them unsuitable for accurately measuring directional variations in surface appearance, especially for specialty coatings like pearlescent paints.
Innovation Solution
A method and apparatus for measuring a spatially under-sampled Bidirectional Reflectance Distribution Function (BRDF) by directing light at a surface from discrete non-coplanar illumination directions, capturing reflectance in multiple directions, and processing the data to derive appearance properties that reflect directional variations, using a system with illumination and receiver optics to analyze the surface's physical and compositional features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If discrete multi-angle spectrometers are used to measure surface appearance, then measurement speed is improved, but measurement precision deteriorates due to limited viewing directions and averaging over all angles
Solution Approach 1:
The patent divides the measurement task into separate non-coplanar viewing directions rather than using a limited set of coplanar angles. By segmenting the measurement into distinct spatial directions (e.g., 45° incident at 0°, 45°, 90°, 135° exit angles), the system captures directional variations without requiring complete hemispherical scanning, thus maintaining speed while improving precision.
Solution Approach 2:
The patent transitions from coplanar measurement geometry to non-coplanar geometry by introducing viewing directions that are not confined to a single plane. This dimensional change allows the system to capture out-of-plane reflectance characteristics that are invisible to conventional coplanar devices, thereby improving directional variation detection without proportionally increasing measurement time.
2Measurement precision
If goniospectrophotometers are used to measure complete BRDF, then measurement precision is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts only the essential viewing directions needed to characterize directional appearance variations, rather than measuring the complete hemispherical BRDF. By selecting specific non-coplanar directions that capture the dominant anisotropic effects, the system achieves sufficient precision for specialty coatings without requiring complex scanning mechanisms that cover all possible angles.
Solution Approach 2:
The patent applies partial action by measuring reflectance at a limited but strategically selected set of non-coplanar directions rather than performing exhaustive hemispherical scanning. This partial measurement approach provides adequate characterization for industrial quality control applications while dramatically reducing device complexity and measurement time compared to complete BRDF measurement systems.
3Measurement precision
If parousiameters are used to measure complete BRDF, then measurement detail is improved, but device size increases and sample area is limited
Solution Approach 1:
The patent segments the measurement into discrete non-coplanar directions using fixed optical paths rather than requiring a large hemispherical screen. This segmentation allows the use of a compact device with fixed geometry that can accommodate larger samples while maintaining measurement precision through selective directional sampling.
4Measurement precision
If complete hemispherical scanning is performed to reduce noise, then measurement precision is improved, but measurement time increases making real-time applications impossible
Solution Approach 1:
The patent uses partial action by measuring at a sufficient but limited number of non-coplanar directions to achieve acceptable precision without performing exhaustive hemispherical scanning. This approach provides a practical compromise that enables real-time or near-real-time measurement while maintaining adequate signal quality through strategic direction selection rather than complete angular coverage.
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 allows for rapid, cost-effective measurement of surface appearance properties, capturing directional variations and physical features, enabling accurate characterization of surfaces with complex coatings without the need for extensive scanning, thus improving upon existing technologies.
Implementation Method 1
measuring a spatially under-sampled Bidirectional Reflectance Distribution Function (BRDF) of a surface... directing light at a surface from discrete non-coplanar illumination directions, capturing reflectance in multiple directions
Data Source
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AI summary
An apparatus for measuring a spatially under-sampled Bidirectional Reflcetance Distribution Function (BRDF) of a surface. The apparatus may comprise a first light source directed to illuminate the surface from a first illumination direction, and a plurality of sensors positioned to receive light reflected by the surface. The plurality of sensors may comprise first, second and third sensors positioned to receive light reflected by the surface in first, second and third non-coplanar directions. In various embodiments, the apparatus may also comprise a computer in communication with the plurality of sensors. The computer is configured to convert light sensed by the plurality of sensors into a first appearance property of the surface considering the first, second, and third reflectance directions.