Progressive-Addition Lens Asymmetric Reference Point Alignment
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Solution Overview
Problem
Aspherically designed progressive-addition lenses often exhibit differences between measured and prescribed addition powers due to the asymmetric distribution of surface powers on the lens back surface, leading to confusion during lens inspection and selection based on wearer prescriptions.
Innovation Solution
The progressive-addition lens design includes a progressive surface and an aspherically designed surface formed of an aspherical or atoroidal surface, where the reference point of the aspherically designed surface is positioned vertically below the prism reference point of the progressive surface and above the near design reference point, ensuring that the measured distance and addition powers align with their prescribed values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an aspherically designed surface is used to correct aberrations, then optical performance is improved, but the measured addition power deviates from the prescribed value
Solution Approach 1:
The patent applies asymmetry by intentionally designing the aspherically designed surface with asymmetric power distribution. The asymmetric addition power distribution is concentrated in the lower half of the lens, which compensates for the asymmetric measurement error caused by the aspherical back surface. This asymmetric design allows the measured addition power to align with the prescribed value while maintaining aberration correction performance.
2Reliability
If asymmetric power distribution is used to correct aberrations, then optical quality is improved, but lens inspection becomes confusing
Solution Approach 1:
The patent applies local quality by concentrating the asymmetric addition power distribution specifically in the lower half of the lens rather than distributing it uniformly. This localized asymmetric design corrects aberrations in the peripheral regions while maintaining accurate addition power measurement at the lower visual axis, thereby simplifying lens inspection without compromising optical quality.
3Reliability
If aspherical surface is used for aberration correction, then lens performance is improved, but measured power differs from prescribed power
Solution Approach 1:
The patent applies preliminary action by pre-calculating and pre-distributing the asymmetric addition power during the lens design and manufacturing process. The asymmetric power distribution is built into the aspherically designed surface before the lens is completed, ensuring that the measured power automatically aligns with the prescribed power without requiring post-manufacturing adjustments.
Data Source
Figure 1A~1B
Figure 2~4
Figure 5A~5C
AI summary
In a progressive-addition lens having a progressive surface on one side and an aspherical or atoroidal surface on the other side, the lens shape is designed so that a high degree of aberration correction can be carried out on the periphery of the lens and the distance power and addition power of the lens acting on the eye of a wearer substantially correspond to the distance power and addition power measured by a lens meter. A progressive-addition lens includes a progressive surface and an aspherically designed surface formed of an aspherical or atoroidal surface, and the reference point of the aspherically designed surface is located in the vertical direction of the lens below a prism reference point of the progressive surface and above a near design reference point.