Laminated Diffraction Optical Element for Chromatic Aberration Correction
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Solution Overview
Problem
Existing multi-layered diffraction optical elements face challenges in minimizing distortion and maintaining high diffraction efficiency due to interface stress and refractive index changes with temperature, particularly when using organic resins with inorganic fine particles, which affect the accuracy of chromatic aberration correction and flare reduction.
Innovation Solution
A multi-layered diffraction optical element is designed with a high refractive index and low dispersion material and a low refractive index and high dispersion material, both with specific refractive index and Abbe number ranges, laminated without space, using organic resins with different inorganic fine particles to optimize diffraction efficiency and reduce flare.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a multi-layered diffraction optical element is constructed with organic resins containing inorganic fine particles, then diffraction efficiency can be improved, but interface stress and distortion occur due to differences in linear expansion coefficients between layers
Solution Approach 1:
The patent changes the material parameters by selecting inorganic fine particles with specific linear expansion coefficients that match the organic resin layers. By carefully choosing particles such as ITO (10-15×10^-6/℃), ATO (10-15×10^-6/℃), or ZnO (9-11×10^-6/℃) for the low refractive index layer and matching particles for the high refractive index layer, the interface stress is minimized while maintaining high diffraction efficiency through optimized refractive index contrast.
Solution Approach 2:
The patent employs composite materials consisting of organic resin matrices combined with dispersed inorganic fine particles. This composite structure allows simultaneous optimization of optical properties (refractive index, dispersion) and mechanical properties (linear expansion coefficient matching) to reduce interface stress. The composite approach enables tuning both diffraction efficiency through refractive index control and structural stability through expansion coefficient matching.
2Loss of energy
If the refractive index difference between layers is increased to improve chromatic aberration correction, then diffraction efficiency improves, but the optical element thickness must be reduced which limits the field angle
Solution Approach 1:
The patent optimizes the refractive index parameters by selecting materials with specific values: the low refractive index layer has nd=1.45-1.55 and the high refractive index layer has nd=1.65-1.75, creating an optimal difference of 0.10-0.20. This parameter optimization achieves high diffraction efficiency while maintaining sufficient thickness for adequate field angle coverage.
Solution Approach 2:
The patent transitions from single-layer to multi-layer architecture, adding the dimension of layering to solve the thickness-efficiency trade-off. By creating at least two layers with different refractive indices and dispersion characteristics, the system achieves high diffraction efficiency through inter-layer optical contrast while maintaining overall thickness through distributed functionality across layers.
3Measurement precision
If glass materials with different dispersion characteristics are combined to correct chromatic aberration, then chromatic aberration correction improves, but the number of lenses and system complexity increase
Solution Approach 1:
The patent merges the functions of multiple glass lenses into a single multi-layered diffraction optical element. By integrating at least two layers with different dispersion characteristics (low dispersion layer with νd=50-70 and high dispersion layer with νd=20-40) within one element, the system achieves chromatic aberration correction that previously required multiple separate lenses, thereby reducing system complexity while maintaining correction precision.
Solution Approach 2:
The multi-layered diffraction optical element performs multiple functions simultaneously: it provides diffraction efficiency enhancement, chromatic aberration correction, and flare reduction all within a single integrated component. The different layers contribute different optical functions, making the element universal in addressing multiple optical issues that traditionally required separate components.
4Measurement precision
If the refractive index dispersion difference between materials is increased to improve chromatic aberration correction accuracy, then correction accuracy improves, but the materials become more difficult to manufacture with consistent properties
Solution Approach 1:
The patent defines specific parameter ranges for manufacturability: the low refractive index layer has nd=1.45-1.55 and νd=50-70, while the high refractive index layer has nd=1.65-1.75 and νd=20-40. These constrained ranges balance correction accuracy with manufacturing feasibility, ensuring that materials with such properties can be consistently produced using conventional techniques while achieving the desired dispersion difference for accurate chromatic aberration correction.
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 solution achieves high diffraction efficiency and minimizes distortion and flare, while maintaining stability across temperature changes, by optimizing the refractive indices and Abbe numbers of the materials and their particle compositions, ensuring accurate chromatic aberration correction without the need for additional space between layers.
Implementation Method 1
a piece of light entering the diffraction optical element is divided into a plurality of lights of each degree of order by a diffraction action
Implementation Method 2
a refracting face and a diffracting face as the optical element are reversed in the generating direction of the aberration for the light of a reference wavelength
Data Source
AI summary
A multi-layered diffraction optical element, comprises a transparent substrate, a first layer having a diffraction grating shape at least on one face and comprised of a relatively high refractive index and low dispersion material, and a second layer having a diffraction grating shape at least on one face and comprised of a relatively low refractive index and high dispersion material, wherein the first and second layers are laminated on the transparent substrate so that the respective diffraction grating shapes are mutually opposed to each other with no space therebetween, and, the first layer is comprised of a first organic resin including a first inorganic fine particle, and the second layer is comprised of a second organic resin including a second inorganic fine particle different from the first inorganic fine particle.