Progressive Power Lens Toric Surface Design for Image Sway Reduction
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Solution Overview
Problem
Existing progressive power lenses often suffer from image sway due to variations in magnification and distortion, particularly when the line of sight moves, as they do not effectively manage the differences in surface power across the lens, leading to discomfort and reduced visual clarity.
Innovation Solution
A progressive power lens design incorporating toric surfaces on both the object-side and eye-side surfaces, where the surface power in the horizontal direction is greater than in the vertical direction, with specific conditions ensuring that the shifts in surface power are cancelled, thereby reducing image sway and aberrations when the line of sight moves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional progressive surface is attached to the object-side surface, then the object-side surface can be a spherical surface with constant base curve, but image sway and distortion occur due to variations in magnification
Solution Approach 1:
The patent inverts the conventional design by placing the progressive surface on the eye-side surface instead of the object-side surface. This allows the object-side surface to maintain a simple spherical shape with constant base curve for ease of manufacture, while the progressive power distribution is achieved through the eye-side surface, thereby eliminating image sway and distortion.
Solution Approach 2:
The patent transitions the progressive surface from the object-side to the eye-side surface, effectively moving the functional element to another dimension (surface location). This dimensional change allows the object-side surface to remain simple and spherical while achieving progressive multifocal functionality through the eye-side surface configuration.
2Reliability
If progressive surface and toric surface are combined on the eye-side surface, then image sway is reduced, but lens design complexity increases
Solution Approach 1:
The patent merges the progressive surface and toric surface onto the same eye-side surface, combining multiple optical functions (progressive power distribution and astigmatism correction) into a single surface. This integration reduces image sway and provides comprehensive vision correction while managing design complexity through unified surface configuration.
3Ease of operation
If surface power distribution is adjusted to reduce magnification difference, then visual comfort improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent adjusts the surface power distribution parameters on the eye-side surface to optimize magnification characteristics. By carefully controlling the progressive power addition and toric surface parameters, the patent achieves reduced magnification difference between distance and near portions, improving visual comfort while establishing achievable manufacturing precision requirements.
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 significantly reduces image sway and aberrations by stabilizing the angle of view and maintaining clear vision across different portions of the lens, enhancing user comfort and visual clarity.
Implementation Method 1
A progressive power lens design incorporating toric surfaces on both the object-side and eye-side surfaces, where the surface power in the horizontal direction is greater than in the vertical direction, with specific conditions ensuring that the shifts in surface power are cancelled
Data Source
Figure 1~2B
Figure 3A~3C
Figure 4~5
AI summary
A progressive power lens 10 for spectacles has a distance portion 11 and a near portion 12 of different powers. A surface power OMHP in a horizontal direction on an object-side surface along a principal meridian 14 or a vertical reference line passing through a fitting point Pe, a surface power OMVP(y) in a vertical direction of the object-side surface, the absolute value IMHP of a surface power on an eye-side surface, and the absolute value IMVP of a surface power in a vertical direction on the eye-side surface satisfy the following condition. OMHP(y)>OMVP(y) IMHP(y)>IMVP(y) OMHP(y)-OMVP(y)=IMHP(y)-IMVP(y) In the conditions, y is a coordinate along the principal meridian or the vertical reference line.