Defect Inspection Illumination via Half-Mirror Refraction
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Solution Overview
Problem
Existing defect inspection methods for automobile bodies face challenges in forming a clear striped light and dark pattern due to shadow casting from the machine base, making it difficult to determine defects accurately.
Innovation Solution
The method involves using a first striped illumination unit directly irradiating the object and a second striped illumination unit, refracted by a half mirror, to avoid shadow formation, with the second unit being disposed in a through hole or above it to ensure clear pattern formation, and an image capturing unit to analyze the pattern for defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If reflected light passes through a through hole in the machine base to form a light and dark pattern, then the illumination structure is simplified and compact, but a shadow from the machine base is cast within the imaging range, preventing clear pattern formation
Solution Approach 1:
The patent introduces a half mirror positioned at a 45-degree angle to redirect light from a lateral illumination source through the through hole onto the object surface. This spatial rearrangement in three dimensions allows the illumination path to bypass the machine base shadow zone while maintaining the compact through-hole structure, resolving the contradiction between structural simplicity and measurement precision
2Stability of the object's composition
If the machine base structure is maintained with a through hole for illumination, then the device structure is stable and compact, but shadow formation occurs that interferes with image capture
Solution Approach 1:
The half mirror serves as an intermediary optical element that mediates between the lateral light source and the through-hole illumination path. It redirects the light at 45 degrees, allowing the machine base structure to remain stable with its through hole while eliminating the shadow interference by changing the light's trajectory through the intermediate reflective surface
3Reliability
If striped illumination is used to detect protuberances, then painting defects can be detected, but shadow formation from the machine base prevents clear pattern formation in the imaging range
Solution Approach 1:
By positioning the light source laterally and using a half mirror to redirect light through the machine base at a 45-degree angle, the patent creates a three-dimensional illumination path that bypasses the shadow zone. This allows striped illumination to form clear patterns on the object surface, enabling reliable defect detection without shadow interference
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 allows for accurate determination of defects by preventing shadow interference and ensuring a clear striped pattern, enhancing the reliability of image analysis and defect detection.
Implementation Method 1
refracting second striped illumination from a second striped illumination irradiating unit by a half mirror
Data Source
AI summary
A defect inspection apparatus includes a first slit light source together with a machine base in which a through hole is formed. A second slit light source and a half mirror are provided inside the through hole. First slit light from the first slit light source is directly incident on an object to be photographed (for example, an automobile body). On the other hand, second slit light from the second slit light source proceeds in a direction perpendicular to the direction in which the first slit light proceeds, and thereafter, is refracted by the half mirror, led out from the through hole, and made incident on the object to be photographed.