Subzonal Multifocal Diffractive Lens Design for Astigmatism Correction
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Solution Overview
Problem
Conventional multifocal diffractive lenses in ophthalmology have limited design freedom due to segmented Fresnel zones of equal areas, which restricts the ability to optimize energy allocation among multiple foci and correct astigmatism effectively.
Innovation Solution
The subzonal multifocal diffractive (SMUD) lens design, where each Fresnel zone is divided into subzones with independent phase profiles and arbitrary projected areas, allowing for more flexible energy distribution and astigmatism correction through a toric refractive surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional Fresnel zones of equal areas are used, then the lens structure is simple and manufacturing is easier, but the design freedom is limited and energy allocation among multiple foci cannot be optimized
Solution Approach 1:
Each Fresnel zone is divided into multiple subzones with different optical paths, allowing independent control of light distribution to multiple foci. This segmentation enables flexible energy allocation while maintaining the overall Fresnel zone structure for manufacturability.
Solution Approach 2:
Different subzones within each Fresnel zone are assigned different optical characteristics (different optical paths to different foci), creating local variations in optical quality. This allows optimization of energy distribution to specific foci while maintaining simplicity in other regions.
2Reliability
If sharp edges are formed at zone boundaries to create desired optical path differences, then diffraction output is achieved, but manufacturing precision requirements increase
Solution Approach 1:
By dividing zones into subzones with gradual optical path transitions, the abrupt sharp edges are replaced with more gradual transitions that are easier to manufacture while maintaining the required diffraction effects through controlled optical path differences.
3Productivity
If multiple subzones with independent phase profiles are implemented, then energy allocation among foci is optimized, but device complexity increases
Solution Approach 1:
The lens is segmented into subzones with independent phase profiles, allowing each subzone to contribute differently to multiple foci. This segmentation enables optimized energy allocation while the repetitive modular structure keeps manufacturing complexity manageable.
Solution Approach 2:
Each subzone is designed to contribute to multiple foci simultaneously, making the lens structure multi-functional. This universal approach allows a single lens design to serve multiple imaging purposes without requiring separate optical elements for each focus.
4Measurement precision
If conventional bifocal or trifocal designs are used, then clear images at specific distances are achieved, but astigmatism correction is limited
Solution Approach 1:
Different subzones are assigned different optical paths targeting different foci, allowing local optimization for both distance-specific imaging and astigmatism correction. This local quality variation enables simultaneous achievement of clear images at multiple distances and correction of astigmatic aberrations.
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 design enhances the ability to achieve desired optical outputs with improved diffraction efficiency and astigmatism correction, enabling sharper images at multiple focal distances while minimizing glare and halos in dim conditions.
Implementation Method 1
Diffractive lenses have been used in ophthalmology for several decades. Conventional diffractive lenses are segmented into zones of equal areas, which are usually referred to as Fresnel zones. Sharp edges are formed at the zone boundaries to create desired optical path differences immediately across zone boundaries to achieve desired diffraction output.
Implementation Method 2
Conventional diffractive lenses are segmented into zones of equal areas, which are usually referred to as Fresnel zones.
Implementation Method 3
The phase profile of each subzone is independent of all other subzones within the same zone, and a phase step is formed at the edge of each subzone. The phase profile is a thickness profile or a refractive index profile, which changes with radius r from an inner edge to an outer edge of each subzone.
Data Source
AI summary
The apparatus and design method of a subzonal multifocal diffractive (SMUD) lens is described herein. The apparatus includes a plurality of annular concentric zones. Each zone are further divided into at least two subzones, where the division of the subzones is arbitrary, but the division is consistent with respect to radius squared r2 across all zones. The subzone phase profile is independent with each other within the same zone, and can be optimized to achieve a desired splitting ratio among all foci.