Waveguide Optical Device for Uniform Wide-Screen Light Expansion
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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 wide screens due to the continuous nature of pupil replication 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, which expands light in two perpendicular directions using total internal reflection and diffraction, allowing for efficient and uniform light output without the limitations of 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 output grating is segmented into discrete reflective elements arranged in an array. Each element independently reflects light from specific regions of the waveguide, replacing the continuous grating structure. This segmentation allows control over light distribution while improving efficiency and uniformity by eliminating continuous pupil replication effects.
Solution Approach 2:
The diffractive output grating is replaced with a reflective optical element system. Instead of using diffraction (a wave-optics phenomenon), the patent employs reflection from discrete elements to redirect light. This substitution simplifies the optical mechanism and improves performance by avoiding the efficiency losses inherent in diffractive gratings.
2Area of stationary object
If a single input projector is used to provide light across the entire width of the display, then device complexity is reduced, but achieving wide-screen coverage and uniform light distribution becomes difficult
Solution Approach 1:
The optical system utilizes the vertical dimension (height of the waveguide) to expand light laterally across the display width. By directing light at angles that cause it to traverse the vertical dimension multiple times through total internal reflection, the system achieves wide horizontal coverage without requiring multiple input projectors or complex lateral expansion optics.
Solution Approach 2:
The waveguide structure serves multiple functions simultaneously: it guides light from the input projector, expands the field of view across the display width, and directs light to the output elements. This multi-functionality eliminates the need for separate optical components for each function, reducing overall device complexity while achieving wide-screen coverage.
3Ease of operation
If traditional output gratings are used for light coupling, then light can be directed out of the waveguide, but construction complexity and manufacturing difficulty increase
Solution Approach 1:
The diffractive grating structure is replaced with a reflective element array that can be more easily manufactured. The reflective elements can be formed as discrete features on the waveguide surface or as separate optical components, simplifying fabrication compared to precision diffractive gratings. This substitution improves ease of manufacture while maintaining light coupling capability.
Solution Approach 2:
The optical mechanism changes from diffraction-based to reflection-based. By altering the fundamental optical parameter (using reflection instead of diffraction), the system achieves easier manufacturing. The reflective elements can be designed with simpler geometries and fabricated using standard optical manufacturing processes, improving ease of production.
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, enabling wide-screen displays with improved brightness and coverage, independent of the light source aspect ratio, and reducing construction complexity.
Implementation Method 1
an input reflective surface configured to reflect the received light into the waveguide
Implementation Method 2
The projected light is totally internally reflected within the waveguide
Implementation Method 3
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 4
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.