Catadioptric Lens Folder for Wide-FoV Sharp Near-Eye Imaging
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Solution Overview
Problem
Existing Near Eye Display (NED) and Head Mounted Display (HMD) devices face challenges in providing a wide field of view (FoV) while maintaining a compact form factor and ensuring sharp image quality across a broad range of eye positions, particularly in virtual and augmented reality applications.
Innovation Solution
The implementation of a catadioptric lens with a catadioptric folder that includes a semi-reflective surface and a reflective polarizer, combined with a Quarter Wave Plate (QWP) retarder, allows for a wide FoV of up to 170 degrees horizontally and 160 degrees vertically, while maintaining a compact design and supporting sharp image acuity through a monotonically decreasing inter-surface distance configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide field of view is implemented in NED/HMD devices, then the visual coverage and user immersion are improved, but the device size and complexity increase
Solution Approach 1:
The optical system is divided into multiple lens elements (first lens element, second lens element, third lens element) with specific functional assignments. Each element contributes to different aspects of light manipulation, allowing the system to achieve wide FoV while distributing the optical complexity across manageable segments rather than requiring a single large complex lens.
Solution Approach 2:
The patent employs a nested arrangement where lens elements are positioned in sequence along the optical path, with each subsequent element building upon the optical function of the previous ones. The reflective polarizer and QWP retarder are integrated within the lens structure, creating a compact nested configuration that maximizes optical functionality within minimal space.
2Device complexity
If a compact form factor is maintained, then the device portability and usability are improved, but the field of view and image quality deteriorate
Solution Approach 1:
The patent utilizes the optical path folding technique where light travels in multiple dimensions rather than a straight line. The reflective polarizer folds the optical path back on itself, effectively increasing the optical length and FoV capability within a compact physical footprint. This dimensional manipulation allows wide-angle viewing without proportionally increasing device size.
Solution Approach 2:
The patent achieves compactness by carefully controlling and optimizing specific parameters: the inter-surface distance is set to 0.5mm-2.0mm, the central thickness of lens elements is optimized, and the refractive indices are selected within specific ranges. These parameter optimizations allow the system to maintain small physical dimensions while preserving optical performance.
3Device complexity
If a compact lens design is used, then the device size is reduced, but the image sharpness and contrast across broad eye positions deteriorate
Solution Approach 1:
Each lens element is designed with specific local optical properties: the first lens element has positive refractive power with specific curvature radii, the second lens element has negative refractive power, and the third lens element has positive refractive power. The reflective polarizer and QWP retarder are positioned at specific locations with precise optical characteristics. This local optimization of each component's properties ensures sharp image quality across the wide FoV while maintaining compact dimensions.
Solution Approach 2:
The patent employs composite optical structures combining different materials and optical properties: refractive lens elements made from optical materials with specific refractive indices, reflective polarizing materials, and birefringent QWP retarder materials. This composite approach allows each material to contribute its strengths, achieving superior image quality and polarization control within a compact form factor.
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 catadioptric lens achieves a wide FoV and improved image sharpness and contrast, enhancing user immersion and performance in virtual and augmented reality environments without compromising the device's compactness or usability.
Implementation Method 1
a catadioptric lens with a catadioptric folder that includes a semi-reflective surface
Implementation Method 2
a reflective polarizer
Implementation Method 3
a Quarter Wave Plate (QWP) retarder
Data Source
AI summary
For example, a catadioptric lens may configured to direct light from a display to an eye of a user. The catadioptric lens may include a catadioptric folder configured to fold an optical path of the catadioptric lens. For example, the catadioptric folder may include a first surface including a semi-reflective surface; a second surface including a reflective polarizer surface, the second surface opposite to the first surface; and a retarder between the first surface and the second surface, the retarder configured to convert a polarization of the light in a path between the first surface and the second surface. For example, the first and second surfaces may be configured such that, over at least 10% of the catadioptric folder, an inter-surface distance of the catadioptric folder is monotonically decreasing with a distance from a central axis of the catadioptric lens.