Aspheric Lens Assembly for AR Eyebox Expansion
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Solution Overview
Problem
Existing augmented reality display technologies have a limited eyebox and are bulky due to the need for a large waveguide thickness to achieve sufficient exit dimensions, leading to reduced user immersion and increased device size and weight.
Innovation Solution
A lens assembly comprising a display panel and multiple lenses, where the N-th lens has an exit surface with a length-to-width ratio greater than 3:1, and includes aspheric surfaces to reduce aberrations, allowing for a larger eyebox and improved imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large waveguide thickness is used to achieve sufficient exit dimensions, then the exit dimensions are improved, but the device size and weight increase
Solution Approach 1:
The optical system is segmented into multiple functional lens groups (first lens group for image formation, second lens group for beam expansion, third lens group for field of view adjustment). This segmentation allows each group to perform its specific function efficiently, achieving sufficient exit dimensions without requiring a large waveguide thickness, thereby reducing device weight while maintaining performance.
Solution Approach 2:
The patent transitions from a single-dimension waveguide thickness approach to a multi-dimensional lens system configuration. By using multiple lenses with different focal lengths and positions arranged in sequence, the system achieves the required exit dimensions through spatial arrangement in multiple dimensions rather than increasing waveguide thickness, thus reducing overall device size and weight.
2Area of stationary object
If a large waveguide thickness is used to achieve sufficient exit dimensions, then the exit dimensions are improved, but the device size increases
Solution Approach 1:
The optical system is segmented into multiple functional lens groups (first lens group for image formation, second lens group for beam expansion, third lens group for field of view adjustment). This segmentation allows each group to perform its specific function efficiently, achieving sufficient exit dimensions without requiring a large waveguide thickness, thereby reducing device weight while maintaining performance.
Solution Approach 2:
The patent transitions from a single-dimension waveguide thickness approach to a multi-dimensional lens system configuration. By using multiple lenses with different focal lengths and positions arranged in sequence, the system achieves the required exit dimensions through spatial arrangement in multiple dimensions rather than increasing waveguide thickness, thus reducing overall device size and weight.
3Device complexity
If conventional lens designs are used, then the structure is simple, but the eyebox is limited and imaging quality is reduced
Solution Approach 1:
The optical system is segmented into multiple functional lens groups (first lens group for image formation, second lens group for beam expansion, third lens group for field of view adjustment). This segmentation allows each group to perform its specific function efficiently, achieving sufficient exit dimensions without requiring a large waveguide thickness, thereby reducing device weight while maintaining performance.
Solution Approach 2:
The patent employs aspheric surfaces on the lenses instead of simple spherical surfaces. The aspheric profiles (including even and odd aspheric terms in the surface equations) enable better correction of optical aberrations, improving imaging quality and expanding the eyebox while maintaining a manageable structural complexity through precise surface shaping.
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 lens assembly provides a larger eyebox, reduces aberrations, and achieves excellent imaging quality, enhancing user immersion and reducing the size and weight of augmented reality devices.
Implementation Method 1
a lens assembly, comprising a display panel and N number of lenses; wherein the N number of lenses comprises a first lens having a receiving surface configured to receive image light from the display panel and an N-th lens having an exit surface through which the image light exits
Implementation Method 2
the exit surface is a first even aspheric surface... the first even aspheric surface satisfies the following function: wherein Z stands for a shortest distance between a respective point on the first even aspheric surface to a plane tangent to the first even aspheric surface at a vertex of the even aspheric surface; c stands for a curvature of the even aspheric surface; k stands for a quadratic surface coefficient; r stands for a shortest distance between the respective point on the first even aspheric surface to an optical axis of the lens assembly
Data Source
AI summary
A lens assembly is provided. The lens assembly includes a display panel and N number of lenses. The N number of lenses includes a first lens having a receiving surface configured to receive image light from the display panel and an N-th lens having an exit surface through which the image light exits, N≥2. On a side where the image light exits the N-th lens, the N-th lens has a length and a width. A ratio of the length to the width is greater than 3:1.