Progressive Addition Lens Surface Smoothing for Reduced Swim Effect
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Solution Overview
Problem
Progressive addition lenses often cause discomfort due to uncontrolled variations in mean power, leading to the 'swim effect' and disorientation for the wearer, particularly in the temporal and nasal sides of the near reference point.
Innovation Solution
A method is employed to determine an improved surface for progressive addition lenses by mixing an initial surface with a smoothed surface using a mixing ratio map, focusing on smoothing mean power undulations while preserving primary viewing zones, utilizing radial-basis-function smoothing techniques and considering astigmatism and mean power distributions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If smoothing techniques are applied to the lens surface to reduce mean power variations, then wearer comfort is improved and swim effect is reduced, but the primary viewing zones may be affected and optical performance may deteriorate
Solution Approach 1:
The patent applies different smoothing intensities to different regions of the lens surface. The mixing ratio map assigns higher smoothing ratios to peripheral regions where mean power variations cause discomfort, while maintaining lower smoothing ratios in primary viewing zones to preserve optical quality. This local differentiation resolves the contradiction by improving comfort in non-critical areas without compromising vision in critical areas.
Solution Approach 2:
The patent applies smoothing selectively rather than uniformly across the entire lens surface. By using a mixing ratio map that applies partial smoothing action only where needed (in peripheral regions with problematic mean power variations), the solution improves wearer comfort while avoiding excessive smoothing that would degrade optical performance in primary viewing zones.
2Object-affected harmful factors
If the lens surface is smoothed to reduce mean power undulations, then the swim effect is minimized, but the primary viewing zones may be altered
Solution Approach 1:
The mixing ratio map implements local quality by assigning region-specific smoothing characteristics. Peripheral regions experiencing swim effect undergo stronger smoothing (higher mixing ratios), while primary viewing zones maintain their original surface characteristics (lower mixing ratios). This spatially varying approach eliminates swim effect in affected areas while preserving the precision required for optimal vision in primary viewing zones.
Solution Approach 2:
The mixing ratio map acts as an intermediary mechanism that mediates between the smoothed surface and the initial lens surface. By controlling the mixing ratio at each point, it allows the smoothed surface to contribute where needed (reducing swim effect) while the initial surface contributes where precision is critical (primary viewing zones), thus resolving the contradiction through controlled combination.
3Ease of operation
If aggressive smoothing is applied to eliminate mean power variations, then wearer disorientation is reduced, but lens design complexity and processing requirements increase
Solution Approach 1:
The patent applies smoothing partially rather than aggressively across the entire surface. The mixing ratio map enables moderate, selective smoothing action only in peripheral regions where mean power variations cause disorientation, avoiding the need for aggressive global smoothing. This reduces wearer disorientation while keeping processing complexity manageable by limiting the scope and intensity of smoothing operations.
Solution Approach 2:
The patent changes the smoothing parameter (mixing ratio) spatially across the lens surface rather than applying a uniform aggressive smoothing parameter. This parameter variation allows gentle smoothing in primary viewing zones and stronger smoothing only where needed, reducing wearer disorientation while avoiding the excessive complexity that would result from uniform aggressive smoothing applied everywhere.
Data Source
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AI summary
Method, for example implemented by computer means, for determining an improved surface adapted for a progressive addition lens, wherein the method comprises: - obtaining an initial surface adapted for the progressive addition lens, - determining a smoothed surface based on the initial surface, - determining a mixing ratio map between the smoothed surface and the initial surface at each point of the initial and smoothed surfaces, the mixing ratio map being determined so as to exclude a primary viewing zone of the initial surface, - determining an improved surface adapted for the progressive addition lens by mixing the initial surface and the smoothed surface on a point-by-point basis using the determined mixing ratio map.