Triangular Prism Optical Element for Near-Eye Display Beam Expansion
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Solution Overview
Problem
Current multi-focal display architectures for head-mounted or near-to-eye displays face challenges such as low efficiency, excessive heat dissipation, and large footprint due to the use of classical micro-projection units with LEDs and reflective spatial light modulators, which also result in a vergence-accommodation conflict leading to visual fatigue.
Innovation Solution
The implementation of an optical element comprising a stack of layers arranged as a right triangular prism, where every second layer is of a first type and every other second layer is of a second type, to expand and uniform a beam of light efficiently, thereby reducing the size and heat of the image projector unit while maintaining high brightness and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If classical micro-projection units with LEDs and reflective spatial light modulators are used, then the multi-focal display architecture can be implemented, but the system dissipates excessive heat and has low efficiency
Solution Approach 1:
The patent replaces the mechanical/optical scanning system with a static waveguide-based display architecture. Instead of using moving mirrors or liquid crystal shutters to direct light to different focal planes, the invention uses fixed waveguides with embedded diffraction gratings to steer light, eliminating mechanical components that generate heat and improve overall system efficiency.
Solution Approach 2:
The patent introduces waveguides as intermediary optical elements between the light source and the user's eye. These waveguides act as mediators that efficiently transport light through total internal reflection and controlled coupling, reducing energy loss and heat generation compared to direct LED-to-modulator coupling in traditional systems.
2Use of energy by moving object
If LEDs with large emission angles are used, then the light source can be compact, but it is hard to gather and transmit light efficiently
Solution Approach 1:
The patent applies local quality by using directionally selective light coupling at specific locations within the waveguide. Instead of attempting to collect light from all directions, the system uses localized coupling regions with precise angular acceptance to efficiently capture light from compact LED sources while maintaining small overall device volume.
Solution Approach 2:
The patent transitions from three-dimensional light collection to two-dimensional planar waveguide propagation. By confining light to propagate within the plane of thin waveguide layers, the system efficiently directs light from compact sources without requiring large collection angles, thus maintaining both small size and high efficiency.
3Reliability
If the aperture of the projection lens is stepped down to ensure sufficient depth of field, then the depth of focus is improved, but the overall light throughput is worsened
Solution Approach 1:
The patent replaces the traditional projection lens with a waveguide-based optical system that uses total internal reflection and diffraction gratings to control light propagation. This substitution eliminates the need to compromise aperture size for depth of field, as the waveguide architecture inherently provides the necessary optical path length and focusing control without blocking light throughput.
4Adaptability or versatility
If multiple transparent displays are used in multi-focal architecture, then the vergence-accommodation conflict is mitigated, but the footprint of the image projector unit becomes large
Solution Approach 1:
The patent implements nesting by integrating multiple focal plane functionalities within a single compact waveguide structure. Instead of requiring separate projection paths for each focal plane, the invention embeds multiple diffraction grating layers within the waveguide, allowing light to be directed to different focal planes through sequential or simultaneous grating interactions, thus reducing the overall projector footprint.
Solution Approach 2:
The patent merges multiple optical functions (light guiding, focal plane selection, and image projection) into a single integrated waveguide assembly. By combining these functions that would traditionally require separate components and large footprints, the system achieves multi-focal capability in a compact form factor suitable for near-eye displays.
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
This solution effectively expands and uniformizes the light beam, reducing the projector's footprint and heat dissipation while maintaining high brightness and efficiency, thus addressing the limitations of current multi-focal display architectures and enhancing user experience by reducing visual fatigue.
Implementation Method 1
the stack of layers forms a right triangular prism in which a surface of the input facet forms a first side of the right triangular prism and a surface of the output facet forms a second side of the right triangular prism
Implementation Method 2
plurality of layers of a first type and plurality of layers of a second type, wherein the plurality of layers of the first type and the second type are arranged as a stack of layers
Implementation Method 3
the stack of layers forms a right triangular prism
Data Source
AI summary
An optical element for expanding and uniforming a beam of light. The optical element includes a plurality of layers of a first type and plurality of layers of a second type arranged as a stack of layers. The stack of layers includes an input facet for receiving a beam of light and an output facet to output expanded and uniformed beam of light. The stack of layers forms a right triangular prism having a first side and a second side of a same width.