Normal Vector Measurement via Illuminance Difference Stereo
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Solution Overview
Problem
Existing measurement systems for determining normal vectors on a target surface require precise adjustment of light sources and cameras according to a predetermined positional relationship, making them inconvenient and limiting in flexibility and accuracy.
Innovation Solution
A measurement system comprising multiple projectors and cameras that project and capture images to calculate normal vectors without the need for pre-defined positional relationships, using illuminance difference stereo methods to determine vectors and luminance values, allowing for flexible positioning and precise surface analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a predetermined positional relationship between the imaging apparatus and four or more light sources is required, then the measurement precision can be maintained, but the ease of operation deteriorates due to the need for precise adjustment of all light sources and imaging apparatus
Solution Approach 1:
The system uses the imaged sphere itself to automatically determine light source positions and imaging apparatus position through image processing, eliminating the need for manual adjustment. The sphere's known geometry allows the system to self-calibrate by detecting light source positions from the spherical image and calculating relative positions automatically
Solution Approach 2:
The patent changes from fixed predetermined positional relationships to dynamically calculated positions based on image analysis. By using the sphere image to derive light source positions and imaging apparatus position, the system adapts parameters automatically rather than relying on pre-set configurations
2Measurement precision
If four or more light sources are used to maintain measurement accuracy, then the measurement precision improves, but the device complexity increases due to multiple light sources requiring coordination
Solution Approach 1:
The patent extracts the position determination function from manual adjustment and transfers it to automatic image processing. By taking out the positioning task from the mechanical adjustment domain and placing it in the computational domain, the system reduces device complexity while maintaining precision
Solution Approach 2:
The system replaces mechanical positioning and adjustment mechanisms with optical imaging and computational analysis. Instead of mechanically coordinating multiple light sources, the system uses image processing to determine positions, substituting mechanical complexity with computational simplicity
3Measurement precision
If parallelized light sources are used for normal vector measurement, then the measurement precision is maintained, but the adaptability deteriorates due to limitations in strain and defect detection
Solution Approach 1:
The system achieves multi-functionality by using the same spherical imaging setup for multiple detection purposes. The apparatus can detect normal vectors, strain, and various surface defects using the captured sphere image, making the system universal rather than specialized for a single measurement type
Data Source
AI summary
A measurement method includes measuring a normal vector of a measured portion based on a first vector representing a direction from a measured portion to a principal point of a first lens, a second vector representing a direction from the measured portion to a principal point of a second lens, a third vector representing a direction from the measured portion to a principal point of a third lens, a first value representing luminance of the measured portion in a situation in which the first projector projects a fourth image via the first lens, a second value representing the luminance of the measured portion in a situation in which the second projector projects a fifth image via the second lens, and a third value representing the luminance of the measured portion in a situation in which the third projector projects a sixth image via the third lens.