Camera-Based Illumination Measurement Using Albedo Decoupling
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Solution Overview
Problem
Current methods for measuring and evaluating spatial and temporal illuminance in indoor environments suffer from low spatial resolution, especially in large architectural spaces with varying daylight, and require expertise and are costly, making it inconvenient to achieve uniform illumination.
Innovation Solution
A camera-based system using RGB and 3D-depth sensors to measure albedo values and geometrical form factors, facilitating real-time illumination measurement and simulation through a constrained radiosity model, which can handle multiple light sources and areas with higher spatial resolution without prior knowledge of the environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct measurement with conventional luxmeters is used, then measurement accuracy is improved, but spatial resolution deteriorates and measurement cost increases
Solution Approach 1:
The patent uses a camera to capture an image of the scene, creating a visual copy of the illumination distribution. Each pixel in the captured image corresponds to a specific spatial location, allowing simultaneous measurement of illumination across multiple points. This copying approach transforms a point-by-point measurement process into a parallel area measurement, resolving the contradiction between measurement accuracy and spatial resolution.
2Manufacturing precision
If camera-based measurements are used, then spatial resolution is improved, but measurement accuracy deteriorates due to lack of albedo information
Solution Approach 1:
The patent performs preliminary action by capturing a reference image under known illumination conditions (or using pre-stored albedo data) before measuring the actual scene. This preliminary capture of surface reflectivity characteristics allows the system to later compensate for albedo variations when measuring illumination, thereby maintaining measurement accuracy while achieving high spatial resolution through camera-based methods.
Solution Approach 2:
The patent introduces albedo (surface reflectivity) as an intermediary parameter that mediates between the captured image intensity and the actual illumination. By modeling the relationship as Image Intensity = Illumination × Albedo, and either measuring or estimating albedo separately, the system can solve for illumination accurately. This intermediary approach enables the decoupling of surface properties from lighting conditions, resolving the accuracy issue in camera-based measurements.
3Reliability
If conventional light-planning tools are used, then illumination simulation is improved, but device complexity and expertise requirements increase
Solution Approach 1:
The patent replaces complex mechanical measurement systems (conventional luxmeters requiring manual positioning) and sophisticated software simulation tools with a simplified camera-based optical measurement system. By using the camera's inherent parallel imaging capability combined with radiometric calibration, the system achieves accurate illumination measurement without requiring complex mechanical positioning systems or expert-level software operation, thus reducing device complexity while maintaining reliability.
Data Source
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AI summary
A method of measuring illumination of an environment (A) comprises:- capturing (e.g. via an RGB-D camera arrangement 12) images of an illuminated (L) environment (A), - extracting (10) from the image captured light emittance values M(x,t) (or R(x,t)) as well as albedo values Ρ(x) of surface areas ("patches") across the environment (A),- computing (10) illumination values E(x,t) of surface areas across the environment (A) as a function of the emittance values M(x,t) and the albedo values Ρ(x).