Surface Image Processing for Arbitrary-Direction Line Detection
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Solution Overview
Problem
Existing techniques struggle to detect linear irregularities on an inspection surface, particularly those extending in arbitrary directions, due to discrete light source arrangements and issues with shadows and specular reflections, which can obscure fine details.
Innovation Solution
The method employs a photometric stereo approach to generate a normal map from captured images, followed by simulating luminance distribution using virtual light sources to detect linear irregularities, allowing for arbitrary light direction settings and overcoming shadow and specular reflection challenges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple light sources are arranged in discrete positions to illuminate the inspection surface, then the inspection system can detect surface irregularities, but linear irregularities extending in arbitrary directions cannot be detected accurately due to shadow and specular reflection issues
Solution Approach 1:
The patent creates a virtual light source that copies the illumination function of physical light sources but without the limitations of physical constraints. By synthesizing a virtual light source positioned at arbitrary locations, the system can generate illumination from any direction without requiring actual physical light sources at those positions, thereby eliminating shadow and specular reflection problems while maintaining detection accuracy
Solution Approach 2:
The patent introduces an image synthesis process as an intermediary between the captured images and the final detection result. This intermediary step reconstructs the inspection surface appearance under virtual light source illumination by processing multiple images captured under different lighting conditions, enabling accurate detection of linear irregularities in arbitrary directions
2Measurement precision
If physical light sources are positioned to illuminate the inspection surface from various angles, then surface features can be highlighted, but shadow and specular reflection obscure fine linear details
Solution Approach 1:
Instead of using physical light sources that create harmful shadows and specular reflections, the patent creates a virtual light source that copies the desired illumination effect through computational processing. The virtual light source allows the system to simulate illumination from any angle without actually introducing the harmful physical phenomena associated with real light sources
Solution Approach 2:
The patent converts the harmful effects of multiple physical light sources (shadows, specular reflections) into a beneficial computational process. By capturing images under controlled lighting conditions and then synthesizing a virtual light source illumination, the system eliminates the harmful effects while retaining the ability to highlight surface features for detection
3Measurement precision
If multiple images are captured under different lighting conditions, then surface irregularities can be detected, but the processing complexity increases and detection of linear features in arbitrary directions remains difficult
Solution Approach 1:
The patent uses image synthesis to create a virtual illumination scenario from captured images, copying the essential information needed for detection without requiring complex processing of multiple lighting conditions. This approach simplifies the detection process while maintaining the ability to detect irregularities
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
This approach enables accurate detection of fine linear irregularities in any direction and on complex surfaces, aligning with human visual perception of surface features.
Implementation Method 1
The method employs a photometric stereo approach to generate a normal map from captured images, followed by simulating luminance distribution using virtual light sources to detect linear irregularities
Data Source
AI summary
A linear feature in an arbitrary direction on an object surface is detected. An image processing apparatus according to the present disclosure generates an image of a target object by lighting using a virtual light source and detects the linear feature included in the target object based on the image.