Diffractive Optical Element Wavelength Dependency Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing diffractive optical elements with stacked optical members and diffraction gratings at their interfaces face significant wavelength dependency in diffraction efficiency, which cannot be sufficiently reduced by existing methods.
Innovation Solution
The solution involves selecting optical materials and optimizing the inter-material gradient and blaze wavelength to satisfy specific refractive index and dispersion relationships, ensuring the diffraction efficiency is uniformly high across the visible wavelength range by forming a saw-tooth diffraction grating at the interface between the optical members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two optical materials are stacked with a diffraction grating formed at the interface, then diffraction function is achieved, but wavelength dependency of diffraction efficiency cannot be sufficiently reduced
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive indices and blaze wavelengths of the optical materials. Specifically, it defines mathematical relationships between the refractive indices at different wavelengths (λ1, λ2, λ3) and introduces the parameter M = {n1(λ2)−n2(λ2)}/{n1(λ1)−n1(λ3)−n2(λ1)+n2(λ3)} to characterize the material combination. By adjusting these parameters within specific ranges, the wavelength dependency of diffraction efficiency is significantly reduced while maintaining high diffraction performance across the visible spectrum.
2Reliability
If refractive index difference is optimized for specific wavelengths, then diffraction efficiency at those wavelengths improves, but uniformity across entire visible wavelength range deteriorates
Solution Approach 1:
The patent achieves universality by designing an optical material combination that performs uniformly across the entire visible wavelength range (0.400-0.650 μm). Instead of optimizing for a single wavelength, it establishes comprehensive conditions involving multiple wavelengths (λ1=0.486133 μm, λ2=0.587562 μm, λ3=0.656273 μm) simultaneously. The mathematical constraints on refractive indices ensure that the diffraction grating maintains high efficiency across all visible wavelengths, making the optical element universally applicable for white light diffraction applications.
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 significantly reduces wavelength dependency and enhances average diffraction efficiency across the entire visible wavelength range, achieving efficiencies greater than 99% by carefully selecting the materials and grating parameters.
Implementation Method 1
a diffraction grating is formed at an interface between the optical members
Implementation Method 2
n1(λ) is a refractive index of the first optical member for incident light having a wavelength λ; n2(λ) is a refractive index of the second optical member for the incident light having the wavelength λ
Data Source
AI summary
In a diffractive optical element, a first optical member and a second optical member are stacked, and a diffraction grating is formed at an interface between the first and second optical members. The diffractive optical element is configured so that the followings fall within a predetermined range: an inter-material gradient which is a ratio of an amount of change in reference refractive indexes between the first optical member and the second optical member, to an amount of change in principal dispersions between the first optical member and the second optical member; and a blaze wavelength of the diffraction grating.