Specular Surface Defect Detection via Column-by-Column Intensity Analysis
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Solution Overview
Problem
Current methods for inspecting glossy or high-gloss surfaces, such as alloy wheels, are inefficient due to limited spatial resolution and sensitivity to small local defects, relying on time-consuming and subjective visual examinations or contactless methods with limited throughput and resolution.
Innovation Solution
A device and method using a line projector to emit a light fan beam pattern onto a detection face by reflection from the specular surface, allowing for automatic detection of surface defects by evaluating the pattern's global intensity maximum in a column-by-column manner, potentially using ultraviolet or extreme ultraviolet light for high-resolution imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If visual examination by human examiners is used to inspect specular surfaces, then surface defects can be detected, but the inspection process becomes time-consuming and costly
Solution Approach 1:
The patent replaces manual visual examination with an automated optical measurement system using deflectometry. A camera captures images of a projected stripe pattern reflected from the specular surface, and a computer automatically evaluates the images to detect surface defects. This substitution eliminates human fatigue and subjectivity while enabling continuous automated inspection, thereby improving both reliability and productivity.
Solution Approach 2:
The system creates an optical copy of the surface geometry by projecting a stripe pattern and capturing its reflection. The deflectometry method generates a digital representation of the surface shape and defects through the captured stripe pattern images, enabling automated analysis without direct human observation of the actual surface.
2Ease of manufacture
If laser light-slit method is used for optical scanning, then surfaces with diffuse scattering can be measured, but the spatial resolution is limited and sensitivity to small local defects is reduced
Solution Approach 1:
The patent changes the fundamental measurement parameters by using deflectometry instead of laser triangulation. The stripe pattern projection and camera-based capture enable higher spatial resolution and sensitivity to small local inclination changes. The system achieves improved measurement precision while maintaining broad applicability to various surface types including specular surfaces that reflect light in a predictable manner.
3Measurement precision
If deflectometry method with sequential picture capture is used, then highly reflecting surfaces can be sensed with good resolution, but data transmission rate limits throughput to maximum of 100 pictures/s
Solution Approach 1:
The patent extracts only the essential measurement information from the captured stripe pattern images using efficient image evaluation algorithms. Instead of transmitting and processing complete high-resolution images, the system extracts relevant surface geometry data and defect information, reducing data transmission requirements and enabling higher throughput while maintaining measurement precision.
Solution Approach 2:
The system performs preliminary image processing and evaluation directly at the capture stage, preparing the data for subsequent analysis. By pre-processing the stripe pattern images to extract surface information before transmission, the system reduces the computational burden and data transmission requirements, thereby increasing overall testing throughput.
4Area of stationary object
If mechanical repositioning of the object or metrological arrangement is used for step-wise positioning, then complete surface coverage is achieved, but the process becomes costly and slow
Solution Approach 1:
The patent uses a line projector to emit a light fan beam pattern that covers an extended area of the detection face simultaneously. This dimensional approach allows parallel measurement of multiple surface points in a single capture, eliminating the need for sequential mechanical repositioning while achieving complete surface coverage.
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 continuous, automatic inspection of specular surfaces with enhanced sensitivity to small defects and improved resolution, reducing the need for mechanical repositioning and increasing testing throughput.
Implementation Method 1
illuminator configured to project a pattern onto the detection face by reflection via the at least partially specular surface
Data Source
AI summary
Among a device and a method for sensing at least partially specular surfaces, the device includes a detection face and an illuminator configured to project a pattern onto the detection face by reflection via the at least partially specular surface.