Diffractive Optical Element Resolving Wavelength Dependence
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Solution Overview
Problem
Conventional diffractive optical elements suffer from significant wavelength dependence in diffraction efficiency, leading to unnecessary diffracted light and image degradation, especially when used in wide wavelength bands, and face challenges in moldability and temperature stability due to material limitations.
Innovation Solution
A diffractive optical element comprising a substrate with a diffraction grating pattern made of a resin-based composite material containing inorganic particles, paired with a coating film of a similar resin-based composite material, optimized for refractive index and Abbe's number differences to reduce wavelength dependence and enhance moldability, with an antireflection film for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a diffractive optical element with a blaze-like diffraction grating pattern is used to achieve high diffraction efficiency, then the first-order diffraction efficiency can reach approximately 100% for a specific wavelength, but the wavelength dependence of diffraction efficiency becomes remarkable, causing unnecessary diffracted light and image degradation
Solution Approach 1:
The invention changes the material parameters by using a resin-based composite material containing inorganic particles with specific refractive index and Abbe's number. This material parameter change allows the diffraction grating depth to be reduced while maintaining high diffraction efficiency across a wider wavelength range, thereby reducing wavelength dependence and minimizing unnecessary diffracted light.
Solution Approach 2:
The invention employs a composite material consisting of a resin base and dispersed inorganic particles. This composite structure enables tailored optical properties, specifically achieving the desired refractive index and Abbe's number combination that reduces wavelength dependence of diffraction efficiency while maintaining high diffraction efficiency, thus resolving the contradiction between energy utilization and harmful diffraction.
2Ease of manufacture
If glass or conventional resin materials are used for the substrate and coating film, then the diffractive optical element can be manufactured, but the moldability is poor and the diffraction grating depth must be increased, making manufacturing difficult
Solution Approach 1:
The invention changes the material parameters by selecting a resin-based composite with specific refractive index and Abbe's number that enables shallower diffraction grating depths. This parameter optimization improves moldability and manufacturing precision, as shallower gratings are easier to manufacture with higher precision using conventional molding techniques.
Solution Approach 2:
The invention applies local quality optimization by carefully selecting the refractive index and Abbe's number of the composite material to achieve the desired optical performance with reduced diffraction grating depth. This localized material property optimization enables both ease of manufacture and high manufacturing precision.
3Reliability
If the diffraction grating depth is increased to reduce wavelength dependence, then the optical performance may improve, but the manufacturing difficulty increases and moldability deteriorates
Solution Approach 1:
The invention fundamentally changes the material parameters by using a resin-based composite with specifically selected refractive index and Abbe's number. This parameter change enables the achievement of low wavelength dependence with reduced diffraction grating depth, thereby improving both reliability and ease of manufacture simultaneously.
Solution Approach 2:
The use of composite materials with tunable optical properties allows optimization of the refractive index and Abbe's number to reduce wavelength dependence without increasing diffraction grating depth. This composite material approach resolves the contradiction between reliability and manufacturing ease.
4Adaptability or versatility
If conventional materials are used without inorganic particles, then the material selection is limited and manufacturing costs are higher, but the refractive index and Abbe's number cannot be optimized to reduce wavelength dependence
Solution Approach 1:
The invention uses composite materials containing inorganic particles dispersed in a resin matrix. This composite structure provides a wide range of material selection by varying the type, size, and concentration of inorganic particles, enabling optimization of refractive index and Abbe's number to reduce wavelength dependence while maintaining manufacturing feasibility.
Solution Approach 2:
The invention utilizes parameter changes in the composite material composition to achieve the desired refractive index and Abbe's number. By adjusting the inorganic particle content and properties, the material can be optimized for reduced wavelength dependence, expanding material selection adaptability while improving optical reliability.
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 reduced wavelength dependence of diffraction efficiency, improved moldability, and enhanced optical performance, including better MTF properties and reduced color aberration, while allowing for easier manufacturing and reduced manufacturing costs.
Implementation Method 1
a diffractive optical element having diffraction grating rings on its surface (e.g. aspherical lens) is capable of reducing lens aberrations such as field curvature and chromatic aberration
Implementation Method 2
n(λ) represents a refractive index and is a function of wavelength
Data Source
AI summary
A diffractive optical element that can be molded readily, an imaging apparatus incorporating the diffractive optical element, and a method for manufacturing the diffractive optical element are provided. A diffractive optical element (10) includes a substrate (11) that is made of a first material containing a resin and has a surface (11a, 11b) on which a diffraction grating pattern (12a, 12b) is formed, and a coating film (13a, 13b) that is made of a second material containing a resin and is disposed so as to be in contact with a portion of the diffraction grating pattern (12a, 12b), and at least one material selected from the first material and the second material is a composite material containing inorganic particles.