Finished Lens Thickness Curve for Sharp Edge Prevention
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Solution Overview
Problem
The manufacturing of optical lenses often results in sharp edges that are prone to cracking, chipping, damage polishing tools, and cause handling difficulties, leading to cosmetic defects and increased rejection rates.
Innovation Solution
A method to calculate a finished lens shape by determining thickness curves and curvature profiles without relying on frame shape data, ensuring a minimal edge thickness and optimizing the lens geometry to eliminate sharp edges, using computer-aided methods to define a prescription and peripheral parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the back surface of the lens blank is machined to fulfill the prescription, then the optical performance is improved, but sharp edges are formed at the outer perimeter
Solution Approach 1:
The patent applies preliminary action by calculating and determining the thickness curve and curvature profile before the actual machining process. The method predicts the finished lens shape and identifies potential sharp edges in advance, allowing preventive measures to be taken during the machining process to avoid forming sharp edges while still fulfilling the prescription requirements.
Solution Approach 2:
The patent changes parameters by introducing a thickness curve and curvature profile as additional control parameters beyond the standard prescription. By adjusting these parameters during the machining process, the method maintains the required optical performance while modifying the outer perimeter shape to eliminate sharp edges.
2Weight of moving object
If the outer perimeter thickness is reduced to meet design requirements, then the lens weight is reduced, but sharp edges and recesses are formed
Solution Approach 1:
The patent changes the thickness distribution parameter by introducing a controlled thickness curve that maintains minimum thickness requirements at the outer perimeter. This allows weight reduction in the central optical zones while preventing excessive thinning at the edges that would create sharp edges and compromise edge strength.
Solution Approach 2:
The patent applies local quality by differentiating the thickness requirements across different zones of the lens. The central optical zones can have thinner sections for weight reduction, while the outer perimeter zones maintain sufficient thickness to avoid sharp edges, with each zone optimized for its specific function.
3Strength
If the lens is machined to a complex shape to avoid sharp edges, then edge strength is improved, but manufacturing complexity increases
Solution Approach 1:
The patent reduces manufacturing complexity by performing preliminary calculations to determine the optimal thickness curve and curvature profile before machining. This upfront planning allows the complex shape adjustments needed to avoid sharp edges to be systematically determined, simplifying the actual machining process rather than requiring complex real-time adjustments.
Solution Approach 2:
The patent implements feedback by using the calculated thickness curve and curvature profile to guide the machining process. The predetermined parameters provide continuous reference values during manufacturing, ensuring that the lens shape evolves correctly to avoid sharp edges while maintaining edge strength, thereby simplifying quality control.
4Adaptability or versatility
If frame shape data is used to determine lens shape, then the lens fits the frame, but the manufacturing process becomes constrained
Solution Approach 1:
The patent applies preliminary action by calculating the thickness curve and curvature profile based on the lens blank characteristics and prescription requirements, independent of frame shape data. This preliminary determination of lens geometry provides a standardized base that can then be adapted to various frames, maintaining manufacturing flexibility while ensuring frame compatibility through subsequent edging processes.
Data Source
AI summary
A finished lens with a predetermined shape, including one front face, one back face and a perimeter corresponding to the shape, including a prescription part on the lens that together with the front face fulfills prescription data of a wearer and a peripheral part on the lens, the prescription part being delimited by a thickness curve and the peripheral part extending from the thickness curve towards an outer edge of the lens, the thickness curve corresponding to a value of thickness less than or equal to a predetermined thickness requirement.