Dynamic Illumination for Transparent Object Defect Detection
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Solution Overview
Problem
Current optical inspection methods for translucent or transparent objects fail to reliably detect both high-contrast and low-contrast defects on objects moving at high speed, requiring multiple inspection stations and increasing production costs.
Innovation Solution
A method and device that control a light source to produce alternating dark and light zones with discontinuous spatial variation, allowing for the detection of both high-contrast and low-contrast defects using a single inspection station by varying light intensity and using a series of independently controlled elementary light sources or a controlled liquid crystal screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform extended light source is used for inspection, then high-contrast defects can be detected, but low-contrast defects cannot be detected due to insufficient contrast
Solution Approach 1:
The patent applies periodic action by using a light source that alternates between uniform illumination and patterned illumination (such as striped or dotted patterns). This periodic switching allows the system to detect both high-contrast defects (during uniform illumination) and low-contrast defects (during patterned illumination), as the patterned light creates enhanced contrast through moiré effects or local intensity variations that reveal subtle refractive defects.
Solution Approach 2:
The patent changes the illumination parameters by varying the spatial distribution of light intensity. The light source transitions from a uniform intensity distribution to a patterned distribution with specific frequencies and orientations. This parameter change enables the system to adapt to different defect types, as the patterned illumination creates optical effects that amplify the contrast of low-contrast defects while maintaining the ability to detect high-contrast defects during uniform illumination phases.
2Measurement precision
If a test pattern light source is used to detect low-contrast defects, then low-contrast defects can be detected, but high-contrast defects cannot be correctly detected in the black band regions
Solution Approach 1:
The system uses periodic switching between test pattern illumination and uniform illumination. During test pattern illumination, low-contrast defects are detected through pattern distortion analysis. During uniform illumination phases, high-contrast defects are detected without the interference of pattern artifacts. This periodic alternation ensures both defect types are reliably detected without the limitations of continuous patterned illumination.
Solution Approach 2:
The illumination system is made dynamic by allowing real-time switching between different illumination modes (uniform and patterned). This dynamic capability enables the system to adapt the illumination type based on the specific inspection requirements, ensuring optimal detection conditions for both low-contrast and high-contrast defects within the same inspection cycle.
3Reliability
If multiple inspection stations are used to detect both high-contrast and low-contrast defects, then detection reliability is improved, but production line congestion increases and inspection cost rises
Solution Approach 1:
The patent merges the functions of multiple inspection stations into a single integrated station. By combining uniform illumination capabilities and patterned illumination capabilities in one station, the system can detect both high-contrast and low-contrast defects without requiring objects to pass through separate inspection stations sequentially. This merging eliminates production line congestion and reduces inspection costs while maintaining comprehensive defect detection coverage.
Solution Approach 2:
The inspection station is designed with multi-functionality, capable of performing both high-contrast defect detection and low-contrast defect detection using a single light source that can switch between illumination modes. This universal design eliminates the need for specialized inspection stations for different defect types, improving productivity by allowing continuous inspection at a single location while maintaining high reliability for detecting both defect categories.
4Device complexity
If a single light source with variations is used to detect both defect types, then device complexity is reduced, but very weakly contrasting refracting defects remain undetected
Solution Approach 1:
The single light source performs periodic switching between uniform illumination and patterned illumination modes. The patterned illumination uses specific patterns (stripes, dots, or other geometric configurations) that create enhanced optical effects for very weakly contrasting defects. This periodic action allows the simple single-source system to achieve high measurement precision for weak defects during patterned phases while maintaining low device complexity through the use of a single controllable light source.
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 the simultaneous detection of high-contrast and low-contrast defects on transparent or translucent objects moving at high speed, reducing inspection costs and congestion on production lines while maintaining detection performance for both defect types.
Implementation Method 1
The camera produces an image thanks to the light passing through the objects. This principle of lighting is said by transmission.
Implementation Method 2
Other less marked refracting defects such as air bubbles, surface folds or local variations in thickness of the transparent material cause, under these observation conditions, insufficient contrast in the image to be able to be detected.
Data Source
Figure 1~2D
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AI summary
The invention relates to an in-line optical method of inspecting transparent or translucent objects (2) running at high speed between a light source (3) and means (4) for taking images of the objects and for analyzing the images taken, so as to detect defects in the objects. According to the invention the method consists: in controlling the single light source (3) so that said source produces in succession two types of illumination for each object running past said source, the first type being a homogenous illumination whereas the second type is formed from alternate dark zones and light zones with a discontinuous spatial variation; in taking images of each running object when each of them is illuminated in succession by the two types of illumination; and in analyzing the images taken with the illuminations of the first and second types for the purpose of detecting high-contrast defects and low-contrast defects respectively.