Compact Beam Scanner with Aperture Reflector for AR Displays
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Solution Overview
Problem
Existing scanning projector displays face challenges with field of view (FOV) reduction due to oblique incidence of light beams on tiltable reflectors, leading to increased size and complexity, as well as optical path length and surface area requirements, which affect the comfort and efficiency of wearable head-mounted displays.
Innovation Solution
A beam scanning method involving a scanning reflector with an aperture and a back reflector that collimates and transmits the scanned beam to a pupil replicating waveguide, allowing normal incidence and reducing the gap between the reflector and input coupler, thereby minimizing the overall size and optimizing the FOV.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If oblique incidence of light beams on tiltable reflectors is used to scan the beam, then the field of view can be covered, but the device size and complexity increase
Solution Approach 1:
Instead of using oblique incidence of light on a tiltable reflector, the patent inverts the approach by using normal incidence on a planar reflector with an aperture. The light beam passes through the aperture, reflects off a stationary planar surface, and exits through the same aperture, eliminating the need for tilting mechanisms while maintaining scanning capability through the aperture geometry.
Solution Approach 2:
The patent extracts the tilting function from the reflector itself and replaces it with a stationary planar reflector combined with an aperture. The scanning function is achieved by the geometric arrangement of the aperture and reflector rather than by mechanical tilting, thereby removing the complexity of tiltable mechanisms.
2Ease of operation
If oblique incidence scanning is used, then beam scanning can be achieved, but the optical path length and surface area requirements increase
Solution Approach 1:
The patent inverts the conventional scanning approach by using normal incidence through an aperture rather than oblique incidence. This shortens the optical path length because the light travels perpendicular to the reflector surface and exits through the same aperture, eliminating the extended path required for oblique incidence geometry.
3Ease of operation
If a larger gap between reflector and input coupler is used, then oblique incidence scanning can be implemented, but the overall device size increases
Solution Approach 1:
The patent inverts the conventional arrangement by placing the aperture in the reflector itself rather than having the reflector separate from the input coupler. This eliminates the need for a large gap between reflector and input coupler, as the aperture is integrated into the reflector structure, thereby reducing the overall device volume.
4Ease of manufacture
If conventional scanning projector display is used, then image display can be achieved, but power loss occurs due to optical losses
Solution Approach 1:
The patent inverts the conventional optical path by using normal incidence through an aperture with a stationary planar reflector. This configuration reduces optical losses because the light travels a shorter path and undergoes fewer reflections and refractions, thereby improving power efficiency while maintaining image display capability.
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 configuration enables a compact and efficient scanning projector display with reduced size and optical losses, maintaining high image quality and user comfort by minimizing the gap between the reflector and input coupler, thus enhancing the field of view and reducing power loss.
Implementation Method 1
The back reflector may be curved to collimate the reflected light beam to produce a collimated scanned beam
Implementation Method 2
a back reflector disposed to reflect light transmitted through the aperture back toward the scanning reflector
Implementation Method 3
The scanning reflector may have an aperture for allowing the light beam to propagate therethrough toward the back reflector
Data Source
AI summary
A display device includes a relay waveguide and a scanner. The scanner is configured to angularly scan image light for coupling into the waveguide, and includes a scanning reflector and a second reflector disposed between the scanning reflector and an input coupler of the waveguide. The scanning reflector has an aperture for the image light to propagate therethrough toward the second reflector. The second reflector is configured to reflect at least a portion of the image light received through the aperture back toward the scanning reflector and to transmit at least a portion of the image light reflected from the scanning reflector toward the input coupler. The arrangement enables a compact design of the display.