Waveguide Optical Device With Reflective Light Coupling
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Solution Overview
Problem
Existing augmented and virtual reality displays face challenges in achieving high efficiency and uniformity of light distribution across the entire display width due to the continuous nature of the pupil replication provided by output gratings.
Innovation Solution
An optical device comprising a waveguide with an input reflective surface, an intermediate diffractive optical element, and an output reflective surface is used to expand and direct light, employing total internal reflection and diffraction to overcome efficiency and uniformity losses associated with traditional output gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If an output grating is used to couple light out of the waveguide, then light can be directed towards the viewer, but efficiency and uniformity of light distribution deteriorate due to continuous pupil replication
Solution Approach 1:
The patent segments the light coupling function by replacing the continuous output grating with discrete reflective elements (mirrors or prisms) positioned at specific locations within the waveguide. These discrete elements reflect light at controlled angles to direct it toward the viewer, eliminating the continuous pupil replication effect of the grating while maintaining efficient light extraction and uniform distribution across the display width.
2Device complexity
If a single input projector is used to provide light across the entire width of the display, then device complexity is reduced, but achieving high efficiency and uniformity becomes difficult
Solution Approach 1:
The patent introduces intermediate reflective elements (mirrors or prisms) as mediators within the waveguide that work in conjunction with the single input projector. These intermediaries redirect and distribute the light from the projector across the entire display width, enabling a single projector to achieve uniform illumination without requiring multiple projectors or complex optical systems.
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 optical device achieves efficient and uniform light expansion without the efficiency losses of traditional output gratings, allowing for wide-screen displays with improved brightness and coverage.
Implementation Method 1
The projected light is totally internally reflected within the waveguide
Implementation Method 2
an intermediate diffractive optical element configured to receive light in the waveguide from a first direction, and provide an expansion of the received light in a second direction perpendicular to the first direction
Implementation Method 3
an output optical element comprising an output reflective surface configured to reflect the expanded light out of the waveguide towards a viewer
Data Source
AI summary
Optical devices and methods for expanding input light and outputting the expanded light include a waveguide and an input optical element to receive light incident on a first side of the waveguide. The input optical element includes an input reflective surface to reflect the received light into the waveguide. An intermediate diffractive optical element receives light in the waveguide from a first direction, and provides an expansion of the received light in a second direction perpendicular to the first direction. An output optical element includes an output reflective surface to reflect the expanded light out of the waveguide towards a viewer. The waveguide guides light along an optical path from the input optical element to the intermediate diffractive optical element and from the intermediate diffractive optical element to the output optical element.