Fresnel Lens Non-Effective Surface Angles Stray Light
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Solution Overview
Problem
Common virtual reality (VR) display apparatuses suffer from stray light due to optical elements that deflect light in unintended directions, degrading image quality and user experience.
Innovation Solution
A VR display apparatus incorporating a Fresnel lens with ring structures featuring optically non-effective surfaces with varying inclined angles, covered with light-absorbing material layers and an anti-reflection layer, to minimize stray light reflections and absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical element (e.g. lens) is disposed between the display and the user's eyes to enable clear imaging on the retina, then the user can see the virtual image clearly, but some surfaces of the optical element reflect light in unintended directions and generate stray light that deteriorates image quality
Solution Approach 1:
The patent applies anti-reflection coatings on the optical element surfaces to convert harmful light reflections into beneficial light transmission. The coatings are designed with specific refractive indices and thicknesses to minimize stray light generation while maintaining clear imaging, directly addressing the contradiction between image clarity and stray light reduction
Solution Approach 2:
The patent modifies the physical parameters of the optical element by varying the inclined angles of optically non-effective surfaces in different areas (central vs. peripheral regions). This parameter change allows different parts of the lens to handle light differently, reducing overall stray light while preserving image quality
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
Effectively reduces stray light generation, enhancing image clarity and user experience by optimizing the design of the Fresnel lens's surfaces and coatings.
Implementation Method 1
an optical element (e.g. lens) is disposed between the display and the user's eyes, and a traveling path of light is changed via refractive power thereof
Implementation Method 2
some surfaces of the optical element are likely to make a portion of the light from the display not to travel in a direction and path that are initially expected, but is reflected toward a direction that is not expected and result in stray light
Data Source
AI summary
A virtual reality display apparatus includes at least one display and at least one optical assembly. The display is configured to provide an image beam to a user's left eye or right eye. The optical assembly is disposed on a transmission path of the image beam. The optical assembly includes a first Fresnel lens which includes a plurality of ring structures surrounding an optical axis thereof. Each of the ring structures has an effective refraction surface and an optically non-effective surface connected to the effective refraction surface and disposed between the optical axis and the effective refraction surface. An average inclined angle of optically non-effective surfaces in a central area of the first Fresnel lens inclined with respect to the optical axis is smaller than an average inclined angle of optically non-effective surfaces in a peripheral area of the first Fresnel lens inclined with respect to the optical axis.