Back Surface Progressive Lens Concave Eye-Side Design
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Solution Overview
Problem
Conventional back surface progressive-power lenses suffer from increased lens thickness and unattractive external appearance due to the need for a convex object-side refractive surface, which also results in image distortion and discomfort for wearers.
Innovation Solution
A back surface progressive-power lens design featuring a concave eye-side refractive surface with a convex region in the near portion, allowing a small-curvature concave surface for the distance portion and a shallow base curve, thereby reducing lens thickness and improving external appearance, while minimizing optical performance degradation through controlled convexity and surface area ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a convex object-side refractive surface is used in a back surface progressive-power lens, then the lens can provide the required power for the distance portion, but the lens thickness increases and external appearance becomes unattractive
Solution Approach 1:
The patent applies local quality by creating a convex region only in the near portion of the eye-side refractive surface, while keeping the distance portion concave. This localized convexity provides the necessary power for the near portion without requiring a universally convex surface, thereby reducing overall lens thickness while maintaining optical performance.
Solution Approach 2:
The patent inverts the conventional approach by making the eye-side refractive surface concave in the distance portion rather than convex. This inversion allows the lens to achieve the required power through the progressive power variation in the near portion while maintaining a thinner overall lens profile.
2Power
If a convex object-side refractive surface is used to provide addition power, then the lens can correct presbyopia, but image distortion increases and wearer comfort decreases
Solution Approach 1:
The patent localizes the convex surface quality to only the near portion of the lens, while maintaining a concave surface in the distance portion. This localized approach allows the lens to provide addition power for near vision without inducing the widespread image distortion that would result from a universally convex surface.
Solution Approach 2:
By inverting the conventional design and making the eye-side surface concave in the distance portion, the patent reduces the overall curvature variation across the lens, thereby minimizing image distortion while still providing the necessary addition power through the progressive power zone in the near portion.
3Shape
If the eye-side refractive surface is made entirely concave, then external appearance is improved, but the lens cannot provide sufficient power for the near portion
Solution Approach 1:
The patent introduces local quality variation by creating a convex region specifically in the near portion of the eye-side refractive surface. This allows the majority of the lens (distance portion) to maintain a concave shape for aesthetic purposes, while the localized convexity in the near portion provides the necessary power for near vision correction.
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 design achieves a thinner, more aesthetically pleasing progressive-power lens with reduced astigmatism and improved optical performance by limiting the convexity and surface area of the convex region, enhancing user comfort and visual acuity.
Implementation Method 1
the eye-side refractive surface including a distance portion having power to view relatively distant objects, a near portion having power to view relatively near objects, and an intermediate portion having power to continuously view intermediate objects
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
An eye-side refractive surface 11 of a distance portion is concave and at least part of an eye-side refractive surface 3 of a near portion is a convex region 31 where one or both of principal meridians of the surface are convex. This provides a back surface progressive-power lens capable of solving disadvantages in terms of lens thickness, external appearance and the like in a back surface progressive-power lens in which the eye-side refractive surface is formed of a progressive-power surface.