Waveguide Optical System for Compact AR Displays
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Solution Overview
Problem
Wearable display apparatuses for augmented reality face challenges in achieving a wide angle of view and high resolution due to the mismatch between the diameter of light output from a laser scanning projector and the thickness of the waveguide, resulting in dark portions in the image and increased size when using separate optical systems to enlarge the light diameter.
Innovation Solution
An optical system comprising a waveguide with a transmissive reflective layer and additional waveguides and reflective layers that split and refract light to minimize dark portions without enlarging the light diameter, allowing for a compact wearable display apparatus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the thickness of the waveguide is reduced to match the small diameter of light from the laser scanning projector, then the waveguide can accommodate the light input, but dark portions appear in the output image
Solution Approach 1:
The waveguide is divided into multiple waveguides (first waveguide, second waveguide, third waveguide) with different thicknesses. Each waveguide receives light at different positions and guides it to the output, ensuring that the combined output covers the entire output surface without dark portions, while each individual waveguide maintains a thickness suitable for its specific light input diameter.
2Illumination intensity
If a separate optical system (beam expander) is used to enlarge the diameter of light incident on the waveguide, then the light diameter matches the waveguide thickness, but the size of the wearable display apparatus increases
Solution Approach 1:
Instead of enlarging the light diameter in the horizontal dimension using a beam expander, the solution transitions to the vertical dimension by stacking multiple waveguides of different thicknesses. This allows the system to accommodate the small diameter light from the laser scanning projector without requiring horizontal expansion, thus maintaining a compact apparatus size while eliminating dark portions in the output image.
3Volume of moving object
If the waveguide thickness is made equal to the light diameter, then the apparatus remains compact, but dark portions appear in the image when the light diameter is smaller than the waveguide thickness
Solution Approach 1:
Each waveguide is assigned a specific thickness matched to the local light diameter it receives. The first waveguide has a thickness matching the light diameter at its input position, the second waveguide has a different thickness for its light input, and so on. This local optimization ensures that each waveguide efficiently guides its specific light input without creating dark portions, while the combination of multiple waveguides provides uniform overall output brightness.
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 effectively reduces dark portions in the image and maintains a compact size for wearable display apparatuses by optimizing light guidance within the waveguide structure, enhancing the user's field of view without the need for additional optical components.
Implementation Method 1
a transmissive reflective layer provided on a top surface of the first waveguide and configured to reflect some light incident thereon and to transmit come light incident thereon
Implementation Method 2
an out-coupler provided on one of the first waveguide and the second waveguide and configured to emit light incident thereon to an outside
Implementation Method 3
a first waveguide configured to guide light; causing light incident on the first waveguide to be totally internally reflected within the first waveguide and thereby incident on the transmissive reflective layer
Implementation Method 4
an in-coupler provided on the first waveguide and configured to guide light output by the light source into the first waveguide
Data Source
AI summary
An optical system is provided which includes a light source which outputs light; a first waveguide; a transmissive reflective layer provided on a top surface of the first waveguide and configured to reflect some light and transmit the remaining light incident thereon; a second waveguide provided on a top surface of the transmissive reflective layer; an in-coupler provided on the first waveguide and configured to allow the light output by the light source to enter the first waveguide; and an out-coupler provided on one of the first waveguide and the second waveguide and configured to emit light from the optical system.