Transparent Object Inspection Using Dark-Field Defect Imaging
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Solution Overview
Problem
Existing methods for inspecting transparent objects are inefficient and prone to human error, as defects within the transparent structure are difficult to detect accurately due to variations in defect appearance based on illumination and camera orientation, especially when using bright backgrounds.
Innovation Solution
An inspection system utilizing one or more imaging units, light sources, and dark backgrounds arranged around an inspection position, where light sources illuminate the object from one side and imaging units capture images from the opposite side through a dark background, detecting defects by identifying scattered light indicative of defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If bright background with camera is used to capture defects in transparent objects, then defects can be visualized, but measurement precision deteriorates due to inaccurate identification of opaque marks produced by impurities and defects
Solution Approach 1:
The patent inverts the traditional bright background approach by using a dark background instead. The imaging unit captures light that has passed through the transparent object against a dark background, making defects visible as bright spots rather than dark opaque marks. This inversion resolves the contradiction by eliminating the ambiguity between impurities and defects that occurs on bright backgrounds.
Solution Approach 2:
The patent utilizes changes in light intensity and color properties to distinguish defects from the transparent object. By using a dark background, defects appear as bright spots with specific color characteristics, while the transparent object remains dark. This color and intensity differentiation enables precise measurement and identification of defects without the confusion present in bright background methods.
2Ease of operation
If manual inspection is used, then flexibility is maintained, but productivity deteriorates due to human error and inspection time
Solution Approach 1:
The patent implements automated optical inspection where the imaging unit and computing unit work together to automatically detect and identify defects without human intervention. The system self-performs the inspection function, capturing images, processing data, and identifying defects autonomously. This resolves the contradiction by maintaining operational simplicity while dramatically increasing productivity and eliminating human error.
Solution Approach 2:
The patent replaces manual mechanical inspection with an automated optical and computational system. Instead of human eyes and hands examining objects, the system uses imaging units to capture light patterns and computing units to analyze them automatically. This substitution resolves the contradiction by maintaining ease of operation through automated functionality while achieving high-speed inspection capable of processing large quantities of objects.
3Reliability
If illumination patterns are used to identify irregularities, then defect detection is enabled, but device complexity increases due to multiple light sources and imaging units required
Solution Approach 1:
The patent employs a single imaging unit that performs multiple functions: capturing light transmitted through the transparent object, detecting defects as bright spots, and providing data for defect identification. The dark background serves multiple purposes by providing contrast, eliminating ambient light interference, and enabling clear visualization of defects. This multi-functionality reduces device complexity while maintaining reliable defect detection capability.
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 efficient, automatic, and accurate detection of defects in transparent objects, suitable for large quantities, with minimal human intervention, by using dark field imaging to distinguish scattered light from defects against a dark background.
Implementation Method 1
The light sources are configured to emit light to illuminate the transparent object at least from a first side of the object
Implementation Method 2
The at least one imaging unit is configured and arranged relative to the inspection position to capture one or more images of the transparent object from a second side of the transparent object
Implementation Method 3
The scattered light, being deflected from a defect in the transparent object, is indicative of said defect
Data Source
AI summary
An inspection system for detecting defects in a transparent object, the system comprising at least one imaging unit, one or more light sources and at least one dark background that are arranged around an inspection position for inspection of the transparent object. The light sources are configured emit light to illuminate the transparent object at least from a first side of the object when the object is positioned at the inspection position. The imaging unit is configured and arranged relative to the inspection position to capture one or more images of the transparent object from a second side of the object when the object is positioned at the inspection position, and configured to generate image data. The dark background is arranged so that the inspection position lies between the at least one imaging unit and the at least one dark background.