Elastic Compensating Pad for Ophthalmic Lens Blocking
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Solution Overview
Problem
Mechanical stresses in ophthalmic lens blanks during the blocking process due to varying layer thicknesses of block materials lead to unintended power errors and deformation, particularly in bifocal and trifocal lenses, resulting in optical imperfections like ripples or 'power bumps' that exceed permitted tolerance ranges.
Innovation Solution
A compensating pad with a main body designed to be elastic, self-adhesive, and conformable, which matches the maximum layer thickness differences of the ophthalmic lens blank, is applied to the lens blank or interposed between the lens and the block piece to ensure a uniformly thick block material layer, reducing mechanical stresses and maintaining the desired curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If block material is applied to hold the ophthalmic lens blank during machining, then the lens blank can be securely mounted and machined, but mechanical stresses occur during curing due to shrinkage behavior causing deformation and power errors
Solution Approach 1:
A compensating pad is introduced as an intermediary element between the ophthalmic lens blank and the block material. This pad serves as a mediator that compensates for shrinkage-induced thickness variations in the block material layer, thereby preventing mechanical stresses and deformation while maintaining secure holding during machining.
Solution Approach 2:
The compensating pad is designed with variable thickness to counteract the non-uniform shrinkage of the block material. By changing the thickness parameter of the pad according to the specific shrinkage pattern, the total thickness of the block material layer becomes uniform, eliminating differential stresses that cause deformation and power errors.
2Stability of the object's composition
If the block material layer has varying thickness due to surface topography differences, then the block material can conform to the lens blank surface, but non-uniform shrinkage causes mechanical stresses and local deformation
Solution Approach 1:
The compensating pad is designed with spatially varying thickness to address local variations in surface topography. Different regions of the pad have different thicknesses tailored to compensate for the specific local shrinkage characteristics, ensuring uniform total thickness across the entire surface while maintaining conformity to the lens blank shape.
3Object-affected harmful factors
If a protective film is applied to the optically active surface before blocking, then the surface is protected during machining, but the film does not compensate for block material thickness variations
Solution Approach 1:
The compensating pad serves as a functional intermediary that the protective film alone cannot provide. While the film protects the surface, the pad actively compensates for thickness variations in the block material layer, addressing both protection and precision requirements through a dedicated compensatory element.
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 compensating pad effectively neutralizes layer thickness differences, achieving uniform shrinkage behavior and minimizing stress-induced deformations, thereby reducing cylinder errors and ensuring the ophthalmic lenses meet optical power tolerance standards.
Implementation Method 1
The compensating pad (40) comprises a main body (41), that is either designed to be elastic, having a maximum thickness corresponding to a maximum layer thickness difference of the ophthalmic lens blank (10)
Implementation Method 2
The compensating pad (40) comprises a main body (41), that is either designed to be elastic... or designed to be elastic abutting on an area directly adjacent to a segment edge
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3C
AI summary
The invention provides a compensating pad (40, 400) for applying to an ophthalmic lens blank (10) to be blocked, or for interposing between an ophthalmic lens blank (10) and a block piece (30). The compensating pad (40, 400) comprises a main body (41, 410), that is designed to be elastic, having a maximum thickness corresponding to a maximum layer thickness difference of the ophthalmic lens blank (10), in order to locally compensate for the layer thickness difference of the blocked ophthalmic lens blank (10).