Multifocal Lens Phase Structure for Lower Chromatic Aberration
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Solution Overview
Problem
Existing multifocal lenses suffer from chromatic aberration and visual acuity issues, particularly under mesopic and scotopic illumination conditions, and exhibit unwanted light scattering due to sharp transition regions on the diffractive surface.
Innovation Solution
A multifocal lens with concentric diffractive zones defined by a piecewise function that includes three phase terms, where the gradients are negative and quadratically dependent on the radial distance, and a smoothed version of this function is used to minimize chromatic aberration and light scattering, enhancing visual acuity across different vision distances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a diffractive multifocal lens with annular diffraction pattern is used, then good optical properties are achieved, but chromatic aberration and visual acuity issues persist
Solution Approach 1:
The lens is divided into multiple concentric diffractive zones with different phase structures. Each zone is designed with specific phase terms (parabolic, linear, and constant components) that segment the light into different diffraction orders, creating multiple focal points while reducing chromatic aberration through the combined effect of refractive and diffractive powers.
Solution Approach 2:
The patent modifies the phase function parameters by introducing three distinct phase terms with specific gradients (p1, p2, p3) and constants (q2, q3). By optimizing these parameters, the lens achieves reduced chromatic aberration and improved visual acuity across different vision distances, transforming the optical performance through parameter optimization.
2Manufacturing precision
If sharp transition regions are present on the diffractive surface, then diffractive zones are well-defined, but unwanted light scattering effects occur
Solution Approach 1:
The patent applies different phase structures to different local regions of the lens surface. The piecewise function assigns specific parabolic, linear, and constant phase terms to different radial zones, creating locally optimized phase profiles that reduce light scattering while maintaining precise zone definition through the combination of refractive and diffractive elements.
3Adaptability or versatility
If multiple diffractive zones are implemented, then trifocal range is achieved, but device complexity increases
Solution Approach 1:
The lens design integrates multiple functions into a single optical element. The concentric diffractive zones with three-phase structures simultaneously provide distance, intermediate, and near vision correction, eliminating the need for multiple separate lenses or additional corrective glasses. The unified phase function design simplifies the overall system while achieving multifocality.
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 lens reduces chromatic aberration and light scattering, providing high visual acuity for far, intermediate, and near vision, minimizing dysphotopsia effects, and improves manufacturability by smoothing the phase shift function.
Implementation Method 1
a diffractive multifocal lens having an annular diffraction pattern for exhibiting a light diffraction effect, which is formed concentrically repeatedly on a surface of the lens
Implementation Method 2
The lens can lead to a reduction of potential dysphotopsia effects under mesopic and scotopic illumination conditions
Data Source
AI summary
The invention relates to a multifocal lens 1 having several concentric diffractive zones 7, 8, 9, 10 on a lens surface 2, wherein in each diffractive zone a diffraction phase structure is defined, which is expressible by the following function or by a smoothed version of the function:ϕ(ξ)=2π×{p1ξ,0≤ξ<w1p2ξ+q2,w1≤ξ<w2p3ξ+q3,w2≤ξ<1,wherein ξ indicates a position within the respective diffractive zone in a radial direction, φ(ξ) indicates a phase shift experienced by light passing through the position indicated by ξ, w1 and w2 define a spatial partitioning of the respective diffractive zone in the radial direction, p1, p2 and p3 indicate gradients and q2 and q3 are constants. The position ξ depends quadratically on a radial distance to the center of the lens surface and is normalized with respect to the radial width of the respective diffractive zone and the gradients p1, p2 and p3 are negative.