Diffractive Multifocal IOL Echelette Geometry for Lower Chromatic Aberration
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Solution Overview
Problem
Conventional multifocal intraocular lenses (IOLs) suffer from chromatic aberration, where different colors of light are focused at different distances, adversely affecting image contrast, particularly for distance vision.
Innovation Solution
A multifocal ophthalmic lens with diffractive structures featuring echelettes of specific step heights that exclude the 0th diffractive order, ensuring optical path lengths are between one and twice the wavelength, thereby reducing chromatic aberration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional multifocal IOLs use diffractive structures with standard echelette step heights, then multiple focal lengths are achieved for improved vision ranges, but chromatic aberration increases causing different colors to focus at different distances
Solution Approach 1:
The patent applies parameter changes by precisely controlling the echelette step height parameter to be between 0.4λ and 0.6λ (where λ is the wavelength of light). This specific parameter range modifies the diffraction characteristics to reduce chromatic aberration while maintaining multiple focal lengths. The optimized step height parameter creates a balance between achieving multiple focuses and minimizing wavelength-dependent focal shifts.
2Object-affected harmful factors
If the echelette step height is made very large, then chromatic aberration is reduced, but the 0th diffractive order is included causing degraded image quality
Solution Approach 1:
The patent optimizes the echelette step height parameter to a specific range (0.4λ to 0.6λ) that simultaneously achieves two objectives: reducing chromatic aberration while excluding the 0th diffractive order. This precise parameter optimization ensures that the step height is large enough to minimize chromatic effects but not so large as to include the 0th order, thereby maintaining image quality.
Solution Approach 2:
The patent replaces the conventional approach of using large step heights to reduce chromatic aberration with a more precise optical design that uses controlled diffraction through optimized echelette geometry. This substitution of the mechanical approach (large physical steps) with an optical design approach (controlled diffraction patterns) achieves the same chromatic reduction without the unwanted 0th order inclusion.
3Manufacturing precision
If the echelette step height is made very small, then image quality is maintained, but chromatic aberration worsens causing different wavelengths to focus at different distances
Solution Approach 1:
The patent identifies an optimal parameter range (0.4λ to 0.6λ) for echelette step height that balances image quality and chromatic aberration reduction. This optimized parameter range is larger than conventional small step heights, enabling sufficient chromatic aberration reduction while maintaining the exclusion of the 0th diffractive order and preserving image quality.
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 lens improves image quality by focusing light of different wavelengths at similar distances, enhancing polychromatic image contrast and overall vision performance.
Implementation Method 1
The ophthalmic lens has an anterior surface, a posterior surface and at least one diffractive structure including a plurality of echelettes. The echelettes have at least one step height of at least one wavelength and not more than two wavelengths in optical path length.
Implementation Method 2
Different colors of light have different wavelengths and, therefore, different foci. As a result, the multifocal IOL focuses light of different colors at different distances from the lens.
Data Source
AI summary
A method and system provide a multifocal ophthalmic device. The ophthalmic lens has an anterior surface, a posterior surface and at least one diffractive structure including a plurality of echelettes. The echelettes have at least one step height of at least one wavelength and not more than two wavelengths in optical path length. The diffractive structure(s) reside on at least one of the anterior surface and the posterior surface. The diffractive structure(s) provide a plurality of focal lengths for the ophthalmic lens.