Reflective Surface Defect Detection Using Linear Transition Patterns
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Solution Overview
Problem
Existing methods for detecting defects on reflective surfaces are complex, requiring extensive calculations and large, uniquely coded patterns, making them slow and difficult to implement, especially for large or highly curved surfaces.
Innovation Solution
A method and device using a camera and data processing unit to detect local defects on reflective surfaces by analyzing the contrast and shape of essentially linear light-dark transitions in reflected patterns, without geometric measurement, allowing for fast and accurate defect localization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical inspection methods are used to detect defects on reflective surfaces, then the inspection process becomes complex and time-consuming, but the detection precision is insufficient due to distorted reflections
Solution Approach 1:
The patent creates a virtual copy of the reflective surface by capturing its reflection in a planar reference surface (mirror). This virtual copy can be digitally processed without the complications of physical optical alignment, allowing precise defect detection through image comparison while simplifying the inspection system architecture.
Solution Approach 2:
The planar reference surface acts as an intermediary between the defect detection system and the curved reflective surface. By capturing reflections in this intermediate planar surface, the system converts complex curved surface reflections into manageable 2D image data that can be processed by standard vision systems.
2Reliability
If multiple inspection systems are deployed to achieve complete coverage, then the detection capability improves, but the inspection time increases significantly
Solution Approach 1:
The patent transitions from physical multi-angle inspection to virtual multi-angle inspection by capturing reflections of the surface from different virtual perspectives in a single planar reference surface. This dimensional transformation allows comprehensive defect coverage without requiring multiple physical inspection passes or systems.
Solution Approach 2:
The system performs preliminary capture of the entire reflective surface in a single planar reference surface, storing all necessary inspection data upfront. This preliminary action enables subsequent defect analysis without requiring additional inspection time, as all surface areas are captured simultaneously rather than sequentially.
3Measurement precision
If traditional image processing methods are applied to curved reflective surfaces, then the processing complexity increases, but the defect detection accuracy decreases due to perspective distortion
Solution Approach 1:
The patent applies local quality transformation by mapping the distorted reflection image to a corrected coordinate system that compensates for the specific curvature characteristics of the reflective surface. This localized correction approach maintains defect detection accuracy while simplifying the overall processing by addressing only the necessary geometric transformations.
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 fast and cost-effective detection of local defects on reflective surfaces, including large or curved surfaces, without the need for complex calibration or large patterns, using a simple pattern and image analysis.
Implementation Method 1
a planar reference surface having a reflective property opposite to the curved reflective surface is set, and a virtual image of the curved reflective surface is obtained through the planar reference surface
Data Source
Figure 1
AI summary
The invention relates to a method for detecting local defects on a reflective surface (13) by means of a device (10), which method reaches a high speed when detecting defects on the reflective surface. The device (10) has at least one pattern (12) for reflection on the reflective surface, at least one camera (1) and a data processing unit (7), wherein: 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.