Double-Sided Progressive Lens Curvature Control
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Solution Overview
Problem
Progressive-power lenses often cause discomfort due to image distortion and fluctuation, especially in the transition from the progressive portion to the near portion, with negative dioptric power lenses exhibiting vertical image elongation, and existing solutions do not adequately address these issues.
Innovation Solution
A double-sided progressive-power lens design where the surface power is adjusted on both the object-side and eyeball-side surfaces to achieve a desired addition power, with the eyeball-side surface having a negative addition power and the object-side surface having a positive addition power, ensuring that the horizontal direction curvature is greater than the vertical direction curvature in the progressive and near portions to balance image magnification and reduce distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the addition power becomes larger, then the near vision power is improved, but discomfort such as fluctuation, distortion, and blurring is increased
Solution Approach 1:
The patent changes the curvature parameters of the progressive surface by controlling the ratio between vertical curvature (CT) and horizontal curvature (CY). Specifically, it sets CT/CY ≤ 0.8 in the progressive portion and CT/CY ≤ 0.6 in the near portion, which modifies the optical path and reduces distortion while maintaining the required addition power for near vision.
Solution Approach 2:
The patent applies different curvature characteristics to different regions of the lens. The distance portion, progressive portion, and near portion each have specifically controlled curvature ratios, allowing optimal optical performance in each zone while minimizing overall distortion and fluctuation effects.
2Measurement precision
If the progressive-power lens is fitted with optimal distance portion performance, then distance vision is improved, but the near portion position is necessarily set and optimal fitting in the near portion cannot be performed independently
Solution Approach 1:
The patent introduces asymmetric curvature control by differentiating between vertical (CT) and horizontal (CY) curvature components. By controlling their ratio differently in various lens zones, it creates an asymmetric optical design that allows independent optimization of both distance and near portion fitting parameters.
3Object-affected harmful factors
If the horizontal direction curvature is increased in the progressive and near portions, then image distortion is reduced, but the lens design complexity is increased
Solution Approach 1:
The patent simplifies the design complexity by establishing clear quantitative criteria for curvature control (CT/CY ≤ 0.8 in progressive portion, CT/CY ≤ 0.6 in near portion). These parameter specifications provide a straightforward design guideline that reduces distortion without requiring overly complex design procedures.
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 effectively reduces image distortion and fluctuation by ensuring equal vertical and horizontal magnifications in the distance portion and increasing horizontal magnification in the progressive and near portions, improving image clarity and reducing eye fatigue during near work.
Implementation Method 1
a progressive-power lens includes an object-side surface and an eyeball-side surface... vertical direction curvature CT and horizontal direction curvature CY... horizontal direction curvature CY is larger than the vertical direction curvature CT
Data Source
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AI summary
A progressive-power lens has one surface which satisifies the following expressions CYDP=CTDP where CT(DP) denotes a vertical direction curvature at the distance reference point, CY(DP) denotes a horizontal direction curvature, CY(P) denotes a horizontal direction curvature at a point on the principal meridian which is located further on the near portion than the progressive start point, and CT(P) denotes a vertical direction curvature at the point.