Rotating Waveguide Expander for Large AR Eye Box
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Solution Overview
Problem
Existing virtual display devices face challenges in enlarging the eye box without the need for large and costly out-coupling elements, which are difficult to manufacture.
Innovation Solution
A display apparatus with a rotating expander device that includes a waveguide plate and diffractive elements, allowing for a large eye box by rotating smaller out-coupling elements to cover a larger display area, utilizing a motor to rotate the expander device and enhance the exit pupil.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of out-coupling element is increased to enlarge the eye box, then the eye box size is improved, but the manufacturing difficulty and cost increase
Solution Approach 1:
The expander device is made rotatable about an optical axis, transforming a static large out-coupling element into a dynamic system where smaller out-coupling elements sweep through a circular path. This dynamic motion creates a large effective display area without requiring large individual out-coupling elements, thus resolving the contradiction between eye box size and manufacturing ease
Solution Approach 2:
The invention transitions from a two-dimensional planar arrangement to a three-dimensional circular sweeping path. By rotating the expander device, the out-coupling elements trace a circular trajectory, effectively utilizing the third dimension (rotation) to expand the display area beyond the physical size of the out-coupling elements themselves
2Area of stationary object
If the size of out-coupling element is increased to enlarge the display area, then the display area is improved, but the manufacturing cost increases
Solution Approach 1:
The rotatable expander device allows smaller, less expensive out-coupling elements to generate a large display area through rotational motion. The effective display area is determined by the circular path swept by the out-coupling elements rather than the size of the elements themselves, reducing manufacturing cost while maintaining large display area
Solution Approach 2:
The rotational motion creates multiple instantaneous positions of the out-coupling elements, effectively copying the optical function across a larger area. Each position along the circular path contributes to the overall display area, allowing a small element to serve the function of a much larger static element
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 provides a large eye box with reduced manufacturing costs and improved image quality by using smaller, easier-to-produce out-coupling elements, enabling a larger display area without visually detectable flickering.
Implementation Method 1
a diffractive expander device to extend exit pupil of the optical engine
Implementation Method 2
an in-coupling element to form first guided light and second guided light by diffracting the input light into the waveguide plate
Implementation Method 3
a first out-coupling element to form output light by diffracting the first guided light out of the waveguide plate, and a second out-coupling element to form output light by diffracting the second guided light out of the waveguide plate
Data Source
AI summary
A display apparatus for displaying a virtual image (VIMG1) includes a rotating expander device (EPE1) to form light beams (B3P0,R,B3P1,R) of output light (OUT1) by expanding light beams (B0P0,R,B0P1,R) of input light (IN1), the expander device (EPE1) includes: a waveguide plate (SUB1), an in-coupling element (DOE1) to form first guided light (B1a) and second guided light (B1c) by coupling input light (IN1) into the waveguide plate (SUB1), a first out-coupling element (DOE3a) to form output light (OUT1) by coupling the first guided light (B1a) out of the waveguide plate (SUB1), and a second out-coupling element (DOE3c) to form output light (OUT1) by coupling the second guided light (B1c) out of the waveguide plate (SUB1). The in-coupling element (DOE1) has a first input grating vector (V1a) and a second input grating vector (V1c), and an angle (α1ac) between the first and second input grating vectors is between 60° and 120°.