Aspherical Watch Crystal Lens for Wide-Angle Readability
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Solution Overview
Problem
Traditional timepiece optical solutions fail to provide optimal reading visibility when the wearer is offset from the timepiece, limiting the angular range of clear reading to approximately 10°, making them inefficient for varied observer positions.
Innovation Solution
An optical device with an aspherical lens is positioned between the indicator and the observer, featuring a surface shape defined by a specific equation with non-zero asphericity coefficients, enhancing readability by increasing the angular range of visibility through optimization algorithms like Latin hypercube sampling and genetic algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional spherical lens is used to enlarge the indication, then the reading is optimized vertically above the lens, but the angular range of clear reading is limited to approximately 10°
Solution Approach 1:
The patent applies an aspherical lens surface instead of a traditional spherical surface. The aspherical surface is defined by mathematical equations with asphericity coefficients (k, α4, α6, α8) that control the curvature variation across the lens surface. This curved surface design redirects light rays to maintain focus over a wider angular range, expanding visibility from 10° to approximately 30° while preserving reading clarity through optimized optical path control.
2Adaptability or versatility
If the lens shape is modified to increase angular range, then visibility over broader angles is achieved, but distortion of the indication may increase
Solution Approach 1:
The patent systematically varies multiple optical parameters including the conic constant (k) and higher-order asphericity coefficients (α4, α6, α8) to optimize the lens performance. By adjusting these parameters within specific ranges, the design achieves a balance between expanding the angular field of view and controlling optical distortion. The parameter optimization ensures that magnification remains consistent across different viewing angles while minimizing image deformation.
3Adaptability or versatility
If a complex aspherical surface with multiple coefficients is used, then the angular range and readability are significantly improved, but the manufacturing complexity increases
Solution Approach 1:
The aspherical surface is defined by a systematic mathematical formulation using standard optical coefficients (k, α4, α6, α8) that can be directly input into modern lens design and manufacturing software. This parametric approach allows computational optimization of the surface shape while maintaining compatibility with contemporary precision manufacturing techniques such as computer-controlled grinding and polishing, thereby managing fabrication complexity through digital modeling.
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 aspherical lens design significantly increases the angular range of clear visibility by up to 100% compared to traditional solutions, minimizing distortion and maintaining readability across a broader range of observer positions.
Implementation Method 1
An optical device with an aspherical lens is positioned between the indicator and the observer... The aspherical lens design significantly increases the angular range of clear visibility
Data Source
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AI summary
Timepiece crystal, in particular watch crystal, characterized in that it comprises an optical device comprising at least one lens intended to magnify an indication provided by a timepiece, said lens comprising at least one aspherical face comprising at least one section passing through a vertical plane comprising an optical axis of vertical direction z, of which at least one contour can be defined by the following equation: zr=r2R1+1−1−κr2R2+α4r4+α6r6+⋯ where R is the nominal radius of curvature, k is the taper constant, and α (4,6,...) is (are) one (or more) asphericity coefficient(s), and where at least the taper constant k and/or at least one asphericity coefficient is non-zero.