Circular Scratch Inspection Using Second-Derivative Image Analysis
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Solution Overview
Problem
Conventional flaw inspection apparatuses are unable to detect circular scratches around holes formed in workpieces, which can occur during machining processes.
Innovation Solution
A circular scratch inspection apparatus comprising a camera, illumination devices that emit light at specific angles to avoid direct reflection, and an image processor that generates second-derivative images and curves to determine the presence of circular scratches by analyzing the number of threshold crossings along radially extending ruler lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional flaw inspection apparatus uses diagonal lighting to capture reflected light from flaws, then it can detect flaws on workpiece surface, but it cannot distinguish circular scratches from other flaw types
Solution Approach 1:
The inspection system segments the analysis by introducing multiple illumination devices positioned at different angles, allowing separate capture of regular reflection patterns and irregular flaw reflections. This segmentation enables the system to distinguish circular scratches from other flaws by analyzing the specific reflection patterns captured from different directions.
Solution Approach 2:
The invention adds a dimensional aspect to flaw inspection by incorporating angular information through multiple illumination sources. Instead of single-direction lighting, the system uses lighting from multiple angles to create a multi-dimensional characterization of surface features, enabling differentiation of circular scratches based on their unique reflection geometry.
2Object-affected harmful factors
If illumination device emits light diagonally onto workpiece surface, then regular reflection is avoided from reaching camera, but circular scratches cannot be differentiated from other flaws
Solution Approach 1:
The system applies local quality differentiation by using multiple illumination devices positioned at specific angles relative to the camera and workpiece. Each illumination device provides localized lighting information from a different direction, allowing the system to characterize the local reflection properties of surface features and identify circular scratches based on their unique angular reflection signature.
Solution Approach 2:
The invention changes the illumination parameter by introducing multiple lighting angles instead of a single diagonal direction. This parameter change allows the system to capture how different surface features reflect light from various angles, providing additional discriminatory information to distinguish circular scratches from other flaw types while still avoiding direct regular reflection into the camera.
3Ease of operation
If single illumination direction is used to avoid direct reflection, then camera can capture flaw reflections, but system lacks capability to determine circular scratch presence
Solution Approach 1:
The system merges multiple illumination devices with different angular positions into a unified inspection system. By combining the information from multiple lighting directions, the system achieves circular scratch detection capability while maintaining a relatively simple operational setup. The merged data from multiple angles provides the additional information needed for accurate circular scratch identification.
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 accurate detection of circular scratches on workpiece surfaces around holes by differentiating between regular and irregular reflections, providing a reliable inspection method for machining flaws.
Implementation Method 1
the light that is reflected regularly on the workpiece surface is not directly incident on the camera
Implementation Method 2
the light that is reflected irregularly on flaws on the workpiece surface is directly incident on the camera
Data Source
AI summary
A circular scratch inspection apparatus includes: a camera capturing an image of a workpiece surface around a hole; illumination device emitting light to the workpiece surface around the hole, the light being reflected on the workpiece surface is not directly incident on the camera; and image processor. The image processor: generates a second-derivative image by performing secondary differentiation on luminance values in an actual image obtained by the camera; generates a second-derivative curve for each of a plurality of ruler lines, extending radially from the hole center and are set in an inspection target region on the workpiece surface; counts a first reference number of times for each ruler line; calculates a first reference total number of times; and determines presence or absence of a circular scratch by using the first reference total number of times.