Soft Contact Lens Inversion Detection via OCT Edge Geometry
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Solution Overview
Problem
Existing contact lens inspection systems are not accurate enough to detect inverted soft contact lenses, leading to incorrect identification and potential discarding of non-defective lenses, and do not integrate well with automated manufacturing lines.
Innovation Solution
The use of optical coherence tomography (OCT) to obtain sectional images of contact lenses, determining cross-sectional edge geometry, and comparing it with predetermined parameters to accurately assess inversion, orientation, and position within a container.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a relatively simple measurement is used to detect inverted contact lenses, then the detection process is fast and easy to implement, but the measurement accuracy decreases leading to incorrect identification of non-inverted lenses as inverted
Solution Approach 1:
The patent transitions from simple 2D image analysis to 3D optical coherence tomography (OCT) imaging. By obtaining cross-sectional images of the contact lens and analyzing the three-dimensional geometry of the lens edge, the system achieves accurate inversion detection without sacrificing speed. The 3D structural information allows differentiation between truly inverted lenses and those that appear inverted due to manufacturing tolerances.
Solution Approach 2:
The patent replaces mechanical measurement methods with optical measurement using OCT technology. Instead of physical contact or simple optical imaging, the system uses low-coherence interferometry to obtain precise cross-sectional images of the lens, enabling non-contact, high-precision geometric analysis that resolves the accuracy-speed contradiction.
2Reliability
If strict quality standards are applied to detect inverted lenses, then the reliability of detection increases, but the loss of non-defective lenses increases due to false positives from manufacturing deviations
Solution Approach 1:
The patent applies local quality analysis by examining specific geometric features of the contact lens edge in cross-section rather than applying uniform strict criteria to the entire lens. By focusing on the local geometry of the lens periphery and comparing it against predetermined parameters, the system achieves reliable inversion detection while tolerating manufacturing variations in other areas.
Solution Approach 2:
The patent changes the measurement parameters from simple 2D image characteristics to 3D geometric parameters of the lens edge cross-section. By measuring parameters such as the curvature radius of the lens periphery and comparing them against predetermined values, the system creates a more nuanced detection criterion that reduces false positives while maintaining high reliability.
3Productivity
If automated manufacturing lines are used to produce contact lenses, then the productivity increases, but the measurement precision decreases due to tolerances in the automated process leading to improper detection results
Solution Approach 1:
The patent implements preliminary action by performing inversion detection before the contact lenses are packaged and distributed. The OCT-based measurement system is integrated into the manufacturing line to identify and separate inverted lenses early in the process, preventing them from reaching customers while allowing the automated manufacturing to continue at high volume without compromising detection precision.
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 method provides high accuracy in detecting inverted contact lenses, enhancing the quality control in manufacturing and ensuring proper orientation before packaging, while being suitable for integration into automated manufacturing lines.
Implementation Method 1
using an optical coherence tomography system to obtain at least one sectional image of at least a part of the contact lens comprising the lens edge
Data Source
AI summary
A method for determining the inversion state of a soft contact lens (1), comprising imaging a soft contact lens having a convex surface (2, 3) and a concave surface (3, 2), a lens center and a lens edge (5) surrounding said soft contact lens (1), the method comprising using an optical coherence tomography system to obtain at least one sectional image of at least a part of the contact lens (1) comprising the lens edge (5), determining a cross-sectional edge geometry of the contact lens (1) extending from the lens edge (5) towards the lens center of the contact lens in the sectional image, the cross-sectional edge geometry corresponding to the convex and concave surface boundaries of the contact lens (1) in the sectional image, selecting a parameter defining the cross-sectional edge geometry of the contact lens (1) imaged and comparing the parameter defining the cross-sectional edge geometry of the contact lens (1) with a predetermined parameter defining a cross-sectional edge geometry of a non-inverted contact lens to determine whether said contact lens (1) is inverted.