Corrective Lens Focal Depth Extension for Night Vision
Solution Overview
Problem
In low illuminance environments, such as at night or in dark places, individuals with aging or fatigued eyes experience difficulty in perceiving contrast and focusing with conventional corrective lenses, including eyeglasses and contact lenses.
Innovation Solution
A design method for corrective lenses that adds a focal depth extension component, represented by Ar^3, to the z-coordinate value of the refractive surface, increasing the focal depth and contrast sensitivity, while optionally incorporating an edge thickness reduction component to manage edge thickness and prevent astigmatism, with constant A set between 1.73×10^-6 and 1.96×10^-5 for optimal effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a focal depth extension component (Ar^3) is added to increase focal depth, then contrast sensitivity in dark places is improved, but edge thickness of the lens increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different lens regions. The focal depth extension component Ar^3 is added to the z-coordinate value of the refractive surface, but an edge thickness reduction component Dr^10 is specifically applied to the edge portion of the lens. This allows the central region to maintain enhanced focal depth for improved contrast sensitivity while the edge region undergoes thickness reduction to compensate for the thickness increase caused by the focal depth extension.
2Reliability
If constant A is increased to enhance focal depth extension effect, then contrast sensitivity improves, but astigmatism occurrence increases
Solution Approach 1:
The patent applies parameter changes by carefully controlling the value of constant A within a specific range (1.73×10^-6 to 1.96×10^-5). This parameter optimization allows the focal depth extension component Ar^3 to provide sufficient contrast sensitivity improvement while limiting the generation of astigmatism. The patent also introduces constant D with a specific range (1.65×10^-17 to 1.88×10^-16) to further fine-tune the balance between focal depth extension and astigmatism suppression.
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 method enhances contrast sensitivity in dark environments by increasing focal depth, allowing better focus on objects both in front of and behind the original focal point, and suppresses astigmatism, providing improved visibility and comfort for middle-aged and elderly users.
Implementation Method 1
a focal depth extension component represented by Ar3 (where r is the distance from the z-axis and A is a constant) is added to the z-coordinate value of a refractive surface determined based on a prescription power
Data Source
AI summary
A corrective lens that can improve contrast sensitivity in a dark place, for example, at night is provided. When an axis in the anteroposterior direction passing through the geometric center of a lens is defined as the z-axis and a direction extending to the rear side of the lens is defined as the positive direction of the z-axis, a focal depth extension component represented by Ar3 (where r is the distance from the z-axis and A is a constant) is added to the z-coordinate value of a refractive surface determined based on a prescription power to increase the focal depth. The focal depth that decreases (shallows) in a dark place is increased to facilitate focusing on a target object located in front of or behind the original focal point. This can improve contrast sensitivity in a dark place.