Overlapping Waveguide Plates for Near-Eye Display Field Angle
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Solution Overview
Problem
Conventional near-eye display technologies face challenges in achieving an ultrathin and lightweight structure with a large field angle and sufficient exit pupil diameter, leading to limitations in user experience due to smaller eye movement range and presence of stray light.
Innovation Solution
A planar waveguide optical element with multiple overlapping waveguide plates and strategically placed partially reflective surfaces, optimized for total internal reflection and beam-splitting, to enhance field angle and exit pupil diameter while minimizing thickness and stray light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional rotationally-symmetric multiple-plates systems are used, then optical properties are maintained, but the system becomes thick and heavy
Solution Approach 1:
The optical system is segmented into multiple waveguide plates with different functions. Each plate has specific beam-split surfaces at different positions and angles, allowing the system to achieve complex optical functions while maintaining thinness. The segmentation enables independent optimization of each plate's thickness and optical path.
Solution Approach 2:
The invention transitions from conventional single-plate or simple multi-plate systems to a multi-dimensional waveguide structure. Multiple waveguide plates are arranged in different spatial dimensions with beam-split surfaces at various angles, creating a three-dimensional optical path that achieves large field angle and thin profile simultaneously.
2Area of stationary object
If free-form curved surface prisms and diffractive optical elements are used, then great field angle and ultrathin structure are achieved, but exit pupil diameter and eye movement range become smaller
Solution Approach 1:
Different regions of the waveguide plates have different local optical properties. Beam-split surfaces are strategically positioned at different locations with different orientations and reflectivities, creating localized optical functions that collectively achieve large exit pupil and wide field angle. Each local region is optimized for its specific function in the overall optical path.
Solution Approach 2:
The multi-plate waveguide system performs multiple optical functions simultaneously. Each waveguide plate serves both as a light transmission medium and as a beam-splitting element, while also contributing to field angle expansion and exit pupil formation. This multi-functionality eliminates the need for separate optical components.
3Object-affected harmful factors
If planar waveguide with beam-split surface array is used, then thickness is reduced, but field angle is limited to 40° due to ghost image and stray light
Solution Approach 1:
The invention converts the potential harmful effect of multiple beam-split surfaces into a beneficial feature. By carefully designing the arrangement, angles, and reflectivities of beam-split surfaces across multiple waveguide plates, the system uses what could be stray light paths to expand the field angle while maintaining image quality. The controlled stray light paths are actually utilized to achieve wider viewing angles.
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 a larger field angle, increased exit pupil diameter, and reduced stray light, resulting in an improved user experience with a lighter and thinner near-eye display apparatus.
Implementation Method 1
transmitting light coupled into the waveguide plates in a predetermined direction by means of total internal reflection
Implementation Method 2
at least one partially reflective surface respectively located inside each of the waveguide plates, and arranged within a space between the main surfaces as a beam-split surface at a characteristic angles with the main surfaces
Data Source
AI summary
A light-weight and ultrathin waveguide optical element having a large field of view includes two or more layers of waveguide plates provided to be overlapped with each other. Within each layer of the waveguide plate are included multiple reflective surfaces with different reflectivity, such that light transmitted through the waveguide plate has a substantially uniform distribution of intensity in a predetermined area when exiting from the waveguide plate. The waveguide optical element is ultrathin such that it can be directly mounted into a spectacle frame. Use of the waveguide optical element with a projection optical assembly can improve user experience as well as display effect with good contrast.