Phase Contrast Lens Inspection System for Defect Detection
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Solution Overview
Problem
Current inspection methods for ophthalmic lenses, such as bright-field and dark-field imaging, are inadequate in accurately detecting defects like tears, peripheral ruptures, and inclusions, leading to unnecessary rejection of non-defective lenses due to hypersensitivity of phase contrast methods.
Innovation Solution
Combining phase contrast imaging with bright-field imaging to enhance defect detection by translating refractive index differences into intensity differences, using a phase plate to separate background light from scattered light and cause destructive interference, resulting in a darker specimen image that highlights defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase contrast imaging is used alone, then defect detection sensitivity is improved, but false rejection rate increases due to hypersensitivity to cosmetic flaws
Solution Approach 1:
The patent combines phase contrast imaging with bright-field imaging to create a hybrid inspection system. The phase contrast component detects refractive index variations and subtle defects, while the bright-field component provides a stable reference for cosmetic appearance. By merging these two imaging modes, the system achieves both high defect detection sensitivity and reduced false rejection of cosmetic flaws.
Solution Approach 2:
The system dynamically adjusts imaging parameters by switching between phase contrast and bright-field modes based on the inspection needs. Phase contrast is activated when subsurface defects or refractive index variations need detection, while bright-field is used for cosmetic evaluation. This parameter changing approach allows optimal detection sensitivity without permanent hypersensitivity to cosmetic variations.
2Measurement precision
If multiple imaging methods are combined, then inspection accuracy is improved, but system complexity increases
Solution Approach 1:
The inspection system is designed with multi-functional imaging capabilities that can operate in different modes (phase contrast, bright-field, and combined) using a single integrated platform. The optical system includes a phase plate that can be inserted or removed to switch between imaging modes, allowing one system to perform multiple inspection functions without requiring separate dedicated devices for each imaging method.
3Difficulty of detecting and measuring
If phase contrast imaging is used, then refractive index differences are translated into intensity differences improving defect visibility, but cosmetic flaws are enhanced excessively
Solution Approach 1:
The bright-field imaging acts as an intermediary that moderates the hypersensitive response of phase contrast imaging to cosmetic flaws. While phase contrast translates refractive index differences into intensity differences for improved defect visibility, the concurrent bright-field imaging provides a neutral reference that prevents cosmetic variations from being over-emphasized. The combined evaluation of both imaging modes allows differentiation between genuine defects and cosmetic variations.
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
The combined imaging method provides a more accurate inspection system that effectively identifies size accuracy, surface defects, tears, and inclusions, reducing false rejections and improving production yield and wearer comfort.
Implementation Method 1
phase contrast imaging with bright-field imaging to enhance defect detection by translating refractive index differences into intensity differences, using a phase plate to separate background light from scattered light and cause destructive interference
Implementation Method 2
using a phase plate to separate background light from scattered light and cause destructive interference, resulting in a darker specimen image that highlights defects
Data Source
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AI summary
The present invention relates to an inspection system for the automatic inspection of ophthalmic lenses, preferably in an automated lens manufacturing line. The inspection system provides a phase contrast imaging unit and an inspection method using said phase contrast imaging unit designed to recognize defective lenses with an improved degree of reliability but that does not falsely sort out perfect lenses.