Carousel Cuvette Interferometer for Ophthalmic Lens Wavefront Testing
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Solution Overview
Problem
Current metrology techniques for evaluating optical lenses lack the combination of spatial resolution, high sensitivity, and large dynamic range needed to accurately measure advanced lens types, limiting their ability to provide precise visual acuity and comfort for contact lens wearers.
Innovation Solution
The use of a Mach-Zehnder interferometer with lenses submerged in a saline solution within a cuvette, employing reverse raytracing to generate theoretical wavefronts and account for induced aberrations, allowing for the measurement of a wide range of ophthalmic lenses without null optics, thereby increasing dynamic range and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current metrology techniques (focimeters, moire deflectometry) are used for lens evaluation, then the measurement process is simple and direct, but the spatial resolution, sensitivity, and dynamic range are insufficient for advanced lens types
Solution Approach 1:
The measurement system is segmented into multiple independent cuvettes arranged in a carousel, each capable of holding and positioning lenses at specific angular positions. This segmentation allows the complex measurement task to be divided into multiple simpler sequential measurements as lenses are rotated into the measurement position one at a time.
Solution Approach 2:
A liquid medium (saline solution) is introduced as an intermediary between the lens and the measurement system. This liquid immersion medium matches the refractive index of the lens material, eliminating refraction effects at the air-lens interface and enabling direct wavefront measurement without complex null optics or alignment procedures.
2Measurement precision
If lenses are measured in air using conventional methods, then the setup is straightforward, but the dynamic range and sensitivity are limited
Solution Approach 1:
A liquid medium (saline solution) is introduced as an intermediary between the lens and the measurement system. This liquid immersion medium matches the refractive index of the lens material, eliminating refraction effects at the air-lens interface and enabling direct wavefront measurement without complex null optics or alignment procedures.
Solution Approach 2:
The refractive index parameter of the measurement environment is changed from air (n≈1.0) to liquid immersion medium (n≈1.33), which matches the lens material refractive index. This parameter change eliminates refraction effects and extends the dynamic range of measurable lens powers while simplifying the optical system.
3Productivity
If multiple lenses are measured sequentially using a single measurement position, then the equipment is simpler, but the measurement time increases
Solution Approach 1:
The measurement system is segmented into multiple independent cuvettes arranged in a carousel, each capable of holding and positioning lenses at specific angular positions. This segmentation allows the complex measurement task to be divided into multiple simpler sequential measurements as lenses are rotated into the measurement position one at a time.
Solution Approach 2:
Lenses are pre-positioned in their respective cuvettes within the carousel before measurement begins. The carousel is pre-loaded with multiple lenses, and the system automatically rotates to bring each lens into the measurement position in sequence, eliminating manual intervention and reducing measurement time.
4Reliability
If advanced lens designs with higher visual correction are produced, then visual acuity and comfort for wearers improve, but the measurement precision requirements increase beyond current metrology capabilities
Solution Approach 1:
A liquid medium (saline solution) is introduced as an intermediary between the lens and the measurement system. This liquid immersion medium matches the refractive index of the lens material, eliminating refraction effects at the air-lens interface and enabling direct wavefront measurement without complex null optics or alignment procedures.
Solution Approach 2:
The mechanical alignment and positioning systems required in conventional air-based metrology are replaced with a liquid immersion measurement system. The liquid medium provides automatic optical alignment by matching refractive indices, eliminating the need for complex mechanical adjustment mechanisms and improving measurement precision for advanced lens designs.
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 precise measurement of lens characteristics such as diameter, circularity, relative thickness, defects, and ophthalmic prescription, effectively addressing the limitations of existing metrology techniques by providing high spatial resolution and dynamic range.
Implementation Method 1
The present invention involves obtaining information utilized to evaluate a wide range of ophthalmic lens types by measuring the transmitted wavefront of the lens
Implementation Method 2
measuring the transmitted wavefront of the lens... evaluate a wide range of ophthalmic lens types
Data Source
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AI summary
Modified MZ (Mach-Zender) interferometers are utilized to analyze the transmitted, aspherical wavefront of an ophthalmic lens by mounting the lens in a cuvette having a rotatable carousel that can hold multiple lenses. Fresh, temperature controlled, saline solution is circulated about the lenses, and the cuvette is positioned in a vertical test arm of the interferometer configuration. Reverse raytracing is utilized to remove aberrations induced into the wavefront as it is imaged from immediately behind the lens to the detector of the interferometer.