Stereoscopic Inspection of Specular Aeronautical Surfaces
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Solution Overview
Problem
Current non-destructive testing methods for aeronautical parts using stereoscopy are invasive and unsuitable for surfaces with specular reflections, requiring contact or matification, which are time-consuming and introduce measurement biases.
Innovation Solution
A method involving the projection of lighting onto the surface by multiple projectors, detection of specularities, and selective extinction of lighting to acquire stereoscopic images without contact or matification, allowing for the determination of a three-dimensional model by merging images from different lighting conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact measurement method is used, then measurement precision can be achieved, but the method is invasive and measurement speed is limited
Solution Approach 1:
The patent replaces the mechanical contact measurement system with an optical measurement system using stereoscopic cameras. Instead of physically touching the surface with a measuring head, the system uses light to capture surface geometry, thereby eliminating mechanical constraints and significantly increasing measurement speed while maintaining precision.
Solution Approach 2:
The patent creates an optical copy (image) of the surface geometry through stereoscopic photography. By capturing light reflected from the surface and processing these images into a 3D model, the system obtains precise spatial data without physical contact, resolving the contradiction between non-invasive measurement and measurement precision.
2Measurement precision
If structured light projection method is used on specular surfaces, then three-dimensional reconstruction can be performed, but the method fails due to specular reflections
Solution Approach 1:
The patent dynamically adjusts the illumination conditions by controlling the brightness of individual light sources based on detected specularity. When specular reflections are detected in certain regions, the system reduces or eliminates illumination from specific light sources that cause the specularity, thereby eliminating the measurement error while maintaining illumination in other areas.
Solution Approach 2:
The system implements a feedback loop where stereoscopic images are analyzed to detect specular reflections, and this information is used to adjust the illumination pattern. The control unit modifies the state of light sources based on the detected specularity, creating a closed-loop system that adapts to surface properties and eliminates measurement errors caused by specular reflections.
3Measurement precision
If surface matting is performed, then stereoscopic measurement can be performed on specular surfaces, but the process is lengthy and expensive
Solution Approach 1:
The patent replaces the mechanical/chemical matting process with an optical control approach. Instead of physically modifying the surface by depositing powder, the system uses intelligent control of light sources to eliminate specular reflections optically, thereby achieving the same measurement goal without time-consuming surface preparation.
Solution Approach 2:
The system introduces an intermediary control layer between the light source and the surface. By using a control unit that analyzes images and adjusts illumination dynamically, the system mediates the interaction between light and specular surfaces, eliminating the need for direct surface modification while still enabling accurate measurement.
4Measurement precision
If multiple spotlights are used to illuminate specular surfaces, then stereoscopic images can be acquired, but the system complexity increases
Solution Approach 1:
The patent segments the illumination system into individually controllable light sources, where each light source can be independently adjusted based on its effect on specularity. This segmentation allows the system to selectively illuminate different regions with appropriate lighting conditions, reducing the overall complexity compared to using multiple spotlights that cannot be individually controlled.
Solution Approach 2:
The system changes the parameters of existing light sources (brightness, on/off state) based on detected specularity rather than adding more complex lighting hardware. By dynamically adjusting the parameters of standard light sources, the system achieves adaptability to specular surfaces without significantly increasing device complexity.
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 non-invasive, accurate three-dimensional modeling of aeronautical parts with specular surfaces without the need for mechanical contact or powder matification, improving measurement speed and accuracy.
Implementation Method 1
surfaces that exhibit specular reflections, that is, when a ray incident on the surface is reflected along a single direction
Implementation Method 2
the reflected luminance is the same in all directions of the half-space delimited by the surface
Implementation Method 3
acquiring a stereoscopic image of the surface by a first sensor and by a second sensor
Data Source
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AI summary
The invention relates to a method for the non-destructive inspection of an aeronautical part, by means of acquiring stereoscopic images and determining a three-dimensional model of the part, characterised in that it is used to extinguish one or more portions of the lighting of the part, and subsequently acquire a stereoscopic image of the surface by each of the sensors, these steps being performed by projecting a light on the surface by means of at least two projectors positioned in different locations.