Interferometer for Single-Use Lens Mold Thickness Verification
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Solution Overview
Problem
Existing methods for verifying the geometry of single-use molds for soft contact lenses, particularly toric lenses, are inadequate as they struggle to accurately measure curved surfaces, leading to potential manufacturing defects and inefficiencies in the production process.
Innovation Solution
The use of fiber optic interferometry to measure the thickness profile of the molding cavity in a closed lens mold, allowing for precise determination of the mold's acceptability by comparing measured profiles to predetermined specifications, which can be done non-destructively and efficiently both offline and inline during the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If linear coordinates are used to measure mold geometry, then measurement process is simple, but measurement accuracy on curved surfaces deteriorates
Solution Approach 1:
The patent replaces mechanical coordinate-based measurement systems with optical interferometry. The interferometer uses light waves to measure the thickness profile of the molding cavity, enabling accurate measurement of curved surfaces without the limitations of linear coordinates. This substitution of mechanical measurement with optical measurement resolves the contradiction between measurement simplicity and curved surface accuracy.
2Productivity
If mold geometry is not verified, then production process is faster, but manufacturing precision deteriorates
Solution Approach 1:
The patent implements preliminary verification of the molding cavity geometry using interferometry before lens production begins. By measuring the thickness profile at multiple positions and comparing it to the desired profile, the system ensures that the mold geometry is correct before committing to production, thereby maintaining manufacturing precision without significantly impacting production speed.
Solution Approach 2:
The interferometer creates an optical copy or representation of the molding cavity thickness profile by measuring the interference patterns of light waves. This optical copy allows for verification of the cavity geometry without physical contact or distortion, enabling quality control while maintaining production efficiency.
3Measurement precision
If multiple measurement positions are used, then measurement accuracy improves, but measurement time increases
Solution Approach 1:
The interferometer continuously measures the thickness profile at multiple positions along the molding cavity in a single scanning operation. Rather than performing discrete, sequential measurements that would consume time, the optical measurement system captures the entire thickness profile continuously, maintaining high measurement precision without proportionally increasing measurement time.
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 enables accurate and efficient verification of single-use molds, ensuring conformity to specifications without the need for sample lenses, reducing development time, and detecting issues such as incorrect mating or incomplete closure of mold halves.
Implementation Method 1
The method uses fiber optic interferometry to measure the thickness profile of a molding cavity of the single use mold
Data Source
AI summary
A method for determining whether or not a single use mold is acceptable, comprisesproviding a closed lens mold (1) comprising two lens mold halves, and having a first and a second optical lens molding surface forming a molding cavity (15) and defining a molding cavity thickness therebetween,providing at least one interferometer (3), each having at least one thickness measurement beam (31),providing a lens mold holder (2),positioning the lens mold (1) such that the thickness measurement beam (31) of the interferometer (3) impinges on the lens mold (1) for measurement of the distance between the two molding surfaces surrounding the molding cavity (15),measuring the thickness profile of the molding cavity (15) with the interferometer (3) on at least three positions of the molding cavity (15) of the lens mold (1),comparing the measured thickness profile with a predetermined thickness profile to determine whether or not the lens mold (1) is acceptable.