High-Index Fresnel Lens with Diffractive Corrector for AR/VR
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Solution Overview
Problem
Conventional Fresnel lenses used in head-mounted displays suffer from diffractions and other optical artifacts, limiting their application in imaging and virtual/augmented reality operations.
Innovation Solution
An optical assembly comprising a Fresnel lens made of high-refractive-index material (n ≥ 1.9) optically coupled with a diffractive optical element to compensate for chromatic aberration, thereby reducing optical artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If Fresnel lenses are used in head-mounted displays, then the size and weight are reduced, but optical artifacts such as diffractions and visibility of Fresnel zone boundaries occur
Solution Approach 1:
A diffractive optical element is introduced as an intermediary component between the Fresnel lens and the image source. This element compensates for chromatic aberration and reduces optical artifacts generated by the Fresnel lens, allowing the system to maintain both weight reduction and improved optical quality
Solution Approach 2:
The optical system uses a composite structure combining Fresnel lens zones with a diffractive optical element. This composite approach integrates the lightweight advantage of Fresnel lenses with the artifact-reduction capability of diffractive optics, resolving the contradiction between weight and optical quality
2Length of moving object
If conventional lenses are replaced with Fresnel lenses, then the thickness and weight are reduced, but chromatic aberration and diffractions increase
Solution Approach 1:
The diffractive optical element serves as a mediator that corrects chromatic aberration introduced by the thin Fresnel lens. This allows the system to achieve the thickness reduction goal while maintaining optical performance through the compensating action of the intermediary element
Solution Approach 2:
The invention changes the optical parameters by introducing a diffractive element with specific diffraction characteristics that counterbalance the chromatic aberration parameters of the Fresnel lens. This parameter adjustment enables thin lens design without sacrificing reliability
3Length of moving object
If Fresnel lenses with narrow zones are used, then the lens can be made thinner, but diffraction effects become more pronounced
Solution Approach 1:
The diffractive optical element converts the harmful diffraction effects into a beneficial correction mechanism. By designing the diffractive structure to produce complementary diffraction patterns, the system transforms the problem of diffraction from narrow Fresnel zones into a solution that reduces overall optical artifacts
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 optical assembly maintains the compactness and light weight of Fresnel lenses while significantly reducing optical artifacts, enhancing the user experience in head-mounted displays for virtual and augmented reality.
Implementation Method 1
The Fresnel lens includes a high-refractive-index material having a refractive index greater than (or equal to) 1.9
Implementation Method 2
Fresnel lenses suffer from diffractions and other optical artifacts associated with Fresnel structures
Implementation Method 3
The diffractive optical element is optically coupled with the Fresnel lens to compensate for chromatic aberration caused by the Fresnel lens
Data Source
AI summary
An optical assembly includes a Fresnel lens and a diffractive optical element. The Fresnel lens includes a high-refractive-index material having a refractive index greater than 1.9. The diffractive optical element is optically coupled with the Fresnel lens to compensate for chromatic aberration caused by the Fresnel lens. A method for imaging light with the optical assembly is also disclosed.