Multilayer Diffractive Optical Element Stabilization
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Solution Overview
Problem
Existing optical elements using diffractive and refractive surfaces face challenges in maintaining high diffraction efficiency and resistance to environmental changes, particularly due to changes in refractive index and absorption caused by ultraviolet light, leading to flare and degradation of optical properties.
Innovation Solution
A multilayer diffractive optical element is manufactured using a method that includes a precursor of an energy curable resin with fine particles of transparent conductive materials like ITO, where the material is cured by light irradiation and then subjected to heat treatment, followed by additional light irradiation (post light irradiation) to stabilize the optical properties, and a layer with low oxygen permeability is applied to prevent oxygen diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dispersion material containing fine particles of transparent conductive material like ITO is used to achieve high diffraction efficiency and low dispersion, then the optical element shows high diffraction efficiency over the whole visible region, but the refractive index changes in use environment causing degradation of optical properties
Solution Approach 1:
The patent applies preliminary action by performing heat treatment and post light irradiation on the dispersion material containing ITO fine particles before the optical element is put into use. The heat treatment is conducted at 60°C to 150°C for 1 hour to 48 hours, which pre-stabilizes the refractive index by reducing the number of charge carriers in the ITO. This preliminary stabilization prevents subsequent refractive index changes during actual use, thereby maintaining high diffraction efficiency without requiring changes to the optical element structure.
Solution Approach 2:
The patent applies parameter changes by modifying the physical and chemical parameters of the dispersion material through controlled heat treatment and light irradiation. Specifically, the temperature parameter is controlled during heat treatment (60°C to 150°C), and the light irradiation dose is controlled to achieve the desired stabilization effect. These parameter changes reduce the charge carrier concentration in ITO, thereby stabilizing the refractive index while preserving the high diffraction efficiency and low dispersion characteristics of the material.
2Reliability
If transparent conductive material fine particles are used to achieve low dispersion characteristics, then high diffraction efficiency is obtained, but oxygen diffusion causes change in optical properties over time
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the harmful effect of oxygen diffusion into a beneficial stabilization process. Instead of simply preventing oxygen contact, the patent utilizes controlled heat treatment in the presence of oxygen to modify the ITO fine particles. The heat treatment causes oxygen to interact with the ITO surface, reducing charge carriers and stabilizing the refractive index. Thus, what could be harmful (oxygen exposure) becomes beneficial (refractive index stabilization) when applied under controlled conditions.
3Reliability
If conventional glass materials with different dispersion characteristics are used to correct chromatic aberration, then chromatic aberration can be reduced, but the number of lenses and device complexity increase
Solution Approach 1:
The patent applies composite materials by creating a dispersion material that combines a binder resin with fine particles of transparent conductive material like ITO. This composite material exhibits both low dispersion characteristics and high transparency, allowing a single optical element to achieve chromatic aberration correction that previously required multiple lenses made from different glass materials. The composite structure enables one material to perform the function of multiple conventional materials, thereby reducing device complexity while maintaining optical performance.
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 method effectively stabilizes the refractive index and transmission at long wavelengths, maintaining high diffraction efficiency and resistance to environmental changes, thereby enhancing the optical element's performance and longevity.
Implementation Method 1
a precursor of an energy curable resin with fine particles of transparent conductive materials like ITO, where the material is cured by light irradiation
Implementation Method 2
subjected to heat treatment, followed by additional light irradiation (post light irradiation) to stabilize the optical properties
Implementation Method 3
a diffractive optical element having a diffraction grating... one light ray incident on a diffractive optical element is divided into plural light rays of different orders by a diffraction function
Implementation Method 4
in a refractive optical system using the refraction of light, lenses formed from glass materials having different dispersion characteristics are used together in combination
Data Source
AI summary
A method for manufacturing an optical element includes the steps of: providing a first material including a precursor of a first energy curable resin which contains fine particles of a transparent conductive material on a transparent substrate, curing the first material by light irradiation, and performing a heat treatment on the cured first material. In the method described above, the cured first material processed by the heat treatment is again processed by light irradiation.