Progressive Multifocal Lens Design for Aberration Control
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Solution Overview
Problem
Progressive multifocal ophthalmic lenses often cause optical aberrations and discomfort due to uneven power distribution and astigmatism, affecting both static and dynamic vision.
Innovation Solution
A progressive multifocal lens design with specific surface and optical characteristics, including defined mean sphere and cylinder values, and adherence to surface and optical conditions that ensure a smooth transition between distance, intermediate, and near vision zones, reducing aberrations and improving comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a progressive multifocal lens is designed to provide multiple vision zones (distance, intermediate, near), then the versatility of the lens is improved, but optical aberrations and astigmatism increase causing wearer discomfort
Solution Approach 1:
The patent applies local quality by defining specific optical characteristics for different zones of the lens. Each vision zone (distance, intermediate, near) has optimized power distribution and astigmatism control parameters tailored to its specific function, rather than applying a uniform design across the entire lens surface.
Solution Approach 2:
The patent implements dynamics through the progressive transition between vision zones. The optical power and astigmatism values change continuously and progressively from the distance zone through the intermediate zone to the near zone, creating a dynamic optical field that adapts to the wearer's viewing distance without abrupt transitions.
2Adaptability or versatility
If the lens surface is made complex to accommodate multiple focal points, then the functionality for presbyopia correction is improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes by systematically varying optical parameters (power, astigmatism, axis orientation) across different zones of the lens surface. These parameters are precisely controlled and defined for each zone, allowing complex optical functionality to be achieved through controlled parameter variation rather than geometric complexity alone.
3Ease of operation
If the progression length is extended to provide smoother transitions between zones, then the ease of operation is improved, but the lens area required increases
Solution Approach 1:
The patent applies partial action by implementing the full progressive transition only in the vertical meridian where it is most needed for natural viewing movements, while controlling astigmatism and power distribution in horizontal and diagonal directions to maintain compact lens dimensions. This selective application of progressive design achieves smooth transitions without requiring excessive lens area.
Data Source
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AI summary
The invention relates to a finished or semi-finished lens which comprises: a disc containing all the points of the lens that have the same abscissa and the same ordinate as points located within a circle in the reference plane having a diameter of 30 millimetres and centred on the prism reference point; a progression length of less than 14.5 millimetres; a first specific point having a cylinder value equal to the maximum cylinder value of all the points of the lens located in the nasal area and in the disc; and a second specific point having a cylinder value equal to the maximum cylinder value of all the points of the lens located in the temporal area and in the disc; a first ratio between: the maximum gradient of the cylinder for the points of the lens that have the same abscissa and the same ordinate as the points located on segments connecting the mounting cross to the first and second specific points, and surface addition of less than 0.095 per millimetre; and a second ratio between: the maximum cylinder value of the first and second specific points, and surface addition of no more than 0.85. The invention enhances the comfort of the wearer.