Diffractive Multifocal Lens Asymmetric Groove Design
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Solution Overview
Problem
Conventional diffractive multifocal lenses face challenges in efficiently distributing diffraction efficiency across orders and optimizing their phase structure, leading to complex machining processes and potential errors due to high variability and sensitivity to errors like fluctuation and vibration.
Innovation Solution
A method is introduced to control diffraction efficiency by varying the inclinations and depth of the diffraction phase structure, using a Gaussian function for smoothing to simplify the phase structure and improve machinability, allowing for the integration of lost efficiency into the phase portion, thereby enhancing overall efficiency and reducing glare and light scattering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a conventional diffractive multifocal lens structure (saw-toothed blazed groove or rectangular binary diffraction structure) is used, then the lens is light in weight and can be made thin, but glare is generated due to high wavelength dependency, inducing high dispersibility
Solution Approach 1:
The patent modifies the diffraction structure parameters by using asymmetric triangular groove profiles with optimized inclination angles (first inclination different from second inclination) and controlled depth ratios. This parameter optimization reduces wavelength dependency effects, thereby minimizing glare and dispersibility while maintaining the lightweight and thin lens characteristics
2Ease of manufacture
If the phase structure is optimized for actually machining a lens, then machining becomes feasible, but desired efficiency is not obtained due to fluctuation and vibration caused by error
Solution Approach 1:
The patent incorporates error compensation mechanisms by designing the diffraction structure with built-in tolerance margins. The asymmetric triangular groove design and optimized depth parameters provide a buffer against machining fluctuations and vibrations, ensuring that desired diffraction efficiency is maintained even when minor machining errors occur
3Manufacturing precision
If a designed phase structure with extremely detailed structure is used, then diffraction efficiency control is improved, but additional steps are required and machining becomes extremely difficult
Solution Approach 1:
The patent divides the diffraction structure into two main segments: asymmetric triangular groove profiles for primary diffraction control and rounded corners for secondary optimization. This segmentation allows each component to be machined separately with standard techniques, avoiding the need for complex multi-step processes while achieving the desired diffraction efficiency distribution
4Device complexity
If conventional diffraction structures are used, then the lens structure is simple, but it is difficult to change phase structure and efficiently distribute efficiency in each order to desired values
Solution Approach 1:
The patent introduces adjustable parameters in the asymmetric triangular groove design, including first and second inclination angles and depth ratios. These dynamic parameters allow the phase structure to be modified to achieve different diffraction efficiency distributions for various orders, providing versatility while maintaining relatively simple lens construction
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 approach enables efficient control of diffraction efficiency across multiple orders, simplifies the machining process, and reduces glare and light scattering, resulting in improved contrast sensitivity and optical performance for multifocal lenses.
Implementation Method 1
A diffractive multifocal lens having a plurality of focuses is used as a general optical element
Data Source
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AI summary
There is provided a diffractive multifocal lens, wherein a diffraction phase structure of a diffraction pattern has a structure expressed by the following formula: φξ={p1ξ,0≤ξ<wp2ξ-0.5-qπ,w≤ξ<1-wp1ξ-1,1-w≤ξ≤1 wherein ζ indicates a position in a radial direction of the lens in one period of the diffraction pattern, and φ (ζ) indicates a value (radian) of a phase shift amount of light passing through the position of ζ from the phase of light passing through a reference plane.