Spectacle Lens Tilt Angle Design for Optical Error Reduction
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Solution Overview
Problem
Spectacle lenses in wraparound frames often suffer from dioptric power errors, astigmatic aberrations, and prismatic errors due to inappropriate tilting of the optical concave surface, leading to eyestrain in users.
Innovation Solution
A method for designing spectacle lenses with a spherical optical convex surface and an optically curved concave surface, where the lens tilt angle is determined using a design reference point and parameters like inter-pupil distance, edged lens width, and front bend angle to ensure proper mounting and minimize errors, with the option of an aspherical concave surface for further reduction of errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the spectacle lens is mounted using only the outer shape of the spectacle frame as a reference, then the mounting process is simple, but the optical concave surface forms an inappropriate angle with respect to the spectacle frame, causing dioptric power errors, astigmatic aberration, and prismatic error
Solution Approach 1:
The patent applies preliminary action by pre-calculating the lens tilt angle θ using the formula that incorporates frame parameters (front bend angle, bridge width, lens width) and optical parameters (front surface power, center thickness). This preliminary calculation is performed before the actual mounting process, allowing the lens to be positioned at the correct angle from the outset, thereby avoiding mounting errors while keeping the process straightforward.
Solution Approach 2:
The patent replaces the traditional mechanical trial-and-error mounting approach with a mathematical calculation system. By substituting physical adjustment with a formula-based determination of the lens tilt angle, the system achieves precise optical alignment without requiring complex mechanical adjustment mechanisms or extensive manual intervention.
2Adaptability or versatility
If the optical concave surface is prescribed for different eyesight corrections, then the lens can accommodate various prescriptions, but the optical concave surface tilts relative to the appropriate angle, causing eyestrain
Solution Approach 1:
The patent applies parameter changes by incorporating multiple variables into the lens tilt angle calculation formula, including frame parameters (front bend angle α, bridge width L, lens width W) and optical parameters (front surface power D1, center thickness d). By changing and considering these parameters together, the system maintains reliable optical performance across different prescriptions and frame types.
Solution Approach 2:
The patent applies dynamics by making the lens tilt angle θ a dynamic value that adjusts according to the specific combination of frame parameters and optical parameters. Rather than using a fixed tilt angle, the system calculates the appropriate angle based on the actual parameters of each lens-frame combination, ensuring optimal performance for varying prescriptions.
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
This method effectively reduces dioptric power errors, astigmatic aberrations, and prismatic errors, preventing eyestrain by ensuring the optical concave surface is mounted at the appropriate angle, regardless of prescription, and allows for more accurate determination of the lens tilt angle through calculation and simulation.
Implementation Method 1
light that enters from the object side refracts at the optical convex surface and linearly travels in the lens
Implementation Method 2
the light retracts again at the optical concave surface and enters a pupil of a user
Data Source
AI summary
A method for designing a spectacle lens that includes an optical convex surface on an object side of the spectacle lens and an optical concave surface on an eye side of the spectacle lens and is mounted in a spectacle frame in a manner tilting with respect to a forward sight line, the optical convex surface being spherical, the optical concave surface being optically curved according to a prescription, the method including: defining a design reference point at an intersection of the optical concave surface and the forward sight line; and determining an angle formed by a tangent line at the design reference point and a perpendicular plane perpendicular to the forward sight line as a lens tilt angle θ with which the spectacle lens is mounted in the spectacle frame.