Interferometer Reference Fluid Tank Prism Contact Lens Metrology
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Solution Overview
Problem
Current metrology methods are inadequate for accurately measuring soft contact lenses due to their instability and lack of structural support, limiting spatial resolution, sensitivity, and dynamic range, which hinders the characterization of their optical and physical properties.
Innovation Solution
A system utilizing a low coherence light beam interferometry system with a beam splitter, diverger assembly, measurement assembly, reference assembly, and imaging assembly to generate interference patterns for precise measurement of contact lens surfaces, including a cuvette for fluid immersion and a controller for adjusting positions and path lengths, enabling whole lens reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional metrology methods are used to measure soft contact lenses, then the measurement process is simple, but the measurement precision and spatial resolution are insufficient
Solution Approach 1:
The measurement system is divided into separate functional modules: a measurement assembly for holding and measuring the contact lens, and a reference assembly with a reference fluid tank containing a reference prism. This segmentation allows each module to be optimized independently for its specific function while maintaining overall measurement precision.
Solution Approach 2:
A reference fluid tank with a reference prism is introduced as an intermediary element to provide a stable reference path for interferometric measurements. The reference fluid (saline solution) matches the refractive index of the contact lens material, enabling accurate surface profile measurements by compensating for refractive effects.
2Stability of the object's composition
If soft contact lenses are measured in air, then the measurement setup is simple, but the lenses become unstable due to evaporation and lack structural support
Solution Approach 1:
The contact lens is immersed in a fluid (saline solution) within the measurement assembly during measurement. This fluid environment maintains lens stability by preventing evaporation and providing buoyant support, eliminating the need for complex mechanical mounting structures while keeping the lens in its natural hydrated state.
Solution Approach 2:
The measurement environment is changed from air to fluid immersion, which fundamentally alters the physical conditions under which the lens is measured. This parameter change stabilizes the lens by maintaining its hydrated state and providing structural support through buoyancy, allowing accurate measurements without complex mounting.
3Measurement precision
If the contact lens is moved to different positions for measurement, then comprehensive lens characterization is achieved, but the optical path length varies causing measurement errors
Solution Approach 1:
The system uses interferometric feedback to continuously monitor and measure the optical path length differences as the contact lens is repositioned. The reference assembly provides a stable reference path that enables real-time compensation for position changes, allowing the lens to be moved to different locations for comprehensive characterization while maintaining measurement accuracy.
Solution Approach 2:
The reference fluid tank with reference prism acts as an intermediary that provides a stable, known optical path. This reference path serves as a benchmark against which variations in the measurement path can be compared and compensated, enabling accurate measurements even when the lens position changes during comprehensive characterization.
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 system provides robust, flexible, and accurate characterization of contact lens surface properties and thickness profiles, overcoming limitations of existing methods by achieving high spatial resolution and sensitivity, suitable for advanced lens designs.
Implementation Method 1
create an image with an interference pattern from the combined light beam
Implementation Method 2
a beam splitter configured to create a first light beam and a second light beam from the light beam generated by the optics assembly
Implementation Method 3
a diverger assembly including at least one lens configured to propagate the first light beam
Implementation Method 4
the at least one contact lens surface creating a first reflected light beam and the measurement assembly being configured to direct the first reflected light beam towards the beam splitter
Implementation Method 5
a reference assembly configured to receive the second light beam and direct a second reflected light beam to the beam splitter to provide a wavefront reference for measuring the contact lens
Data Source
AI summary
The system and methods are made to apply interferometry to ophthalmic applications. The system makes use of a low-coherence interferometer to obtain a plurality of measurements of a contacts lens. The system and methods characterizes the surface profile of both surfaces of a contact lens, a thickness profiles, and combines these measurements with an index information to reconstruct a complete model of the contact lens.