Reflective Surface Defect Detection Using Light-Dark Transitions
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Solution Overview
Problem
Existing deflectometry methods for detecting defects on reflective surfaces are complex, requiring extensive calculations, multiple images, large patterns, and time-consuming calibration, especially for large or highly curved surfaces.
Innovation Solution
A method and device using a pattern with line-shaped light-dark transitions, a camera, and a data processing unit to evaluate image data for local defects without geometric measurement, allowing for fast and accurate defect detection on reflective surfaces, including partially transparent ones like vehicle windscreens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If extensive algorithms are used to decode patterns and reconstruct surface geometry, then measurement precision is improved, but productivity deteriorates due to significantly reduced evaluation speed
Solution Approach 1:
The patent extracts only the essential information needed for defect detection - specifically the positions and orientations of light-dark transitions - rather than performing full surface geometry reconstruction. This selective extraction of critical data maintains sufficient measurement precision for defect detection while dramatically reducing computational complexity and improving evaluation speed
Solution Approach 2:
Instead of reconstructing the complete surface geometry and then detecting defects, the patent inverts the approach by directly detecting defects through light-dark transition analysis without full geometric reconstruction. This reverses the traditional workflow to achieve faster evaluation while maintaining defect detection capability
2Measurement precision
If multiple images or large area-coded patterns are used to resolve coding, then measurement precision is improved, but device complexity worsens due to requirements for multiple cameras or complex pattern production
Solution Approach 1:
The patent segments the pattern into distinct light and dark regions with clearly defined transitions, where each transition contains localized orientation information. This segmentation allows a single camera to capture sufficient data for defect detection without requiring multiple images or complex area-coded patterns, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The pattern is designed with local quality variations through light-dark transitions that encode orientation information at specific locations. Each transition region provides localized surface orientation data, enabling precise defect detection without requiring global pattern coverage or multiple imaging systems, thus simplifying the overall device configuration
3Measurement precision
If large plane mirrors are used for calibration, then measurement precision is improved, but loss of time increases due to considerable calibration effort, especially for large or highly curved surfaces
Solution Approach 1:
The patent uses a digitally generated virtual pattern that can be copied and displayed on any suitable surface (screen, display panel) rather than requiring physical calibration mirrors. This digital copying approach eliminates the need for large plane mirrors and complex physical calibration setups, significantly reducing calibration time while maintaining measurement precision through software-based reference frame establishment
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 rapid and efficient localization of defects with reduced computational effort, suitable for large or curved surfaces, by analyzing light-dark transitions in image data without the need for surface geometry measurement.
Implementation Method 1
a pattern 12 for reflection on the reflective surface 13
Data Source
AI summary
A method for detecting local defects on a reflective surface with a device having at least one pattern for reflection on the reflective surface, at least one camera and a data processing unit. The pattern has at least one substantially linear light-dark transition, the positioning and orientation of the camera are known, the camera captures the pattern reflected on the surface and generates image data of the reflected pattern which are transmitted by the camera to the data processing unit, and the data processing unit determines local defects on the surface on the basis of an evaluation of at least one property of the at least one light-dark transition in the image data of the reflected pattern. Also a device and a computer program.