Waveguide Projection Optics for Lighter Wearable Displays
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Solution Overview
Problem
Current wearable display devices with augmented or virtual reality functions are bulky and heavy due to the use of complex optical systems and precise positioning mechanisms, which are necessary for conventional projection devices with LED modules and DMDs.
Innovation Solution
A projection device that omits DMDs and complex optical systems by using an optical combiner to guide illumination beams directly to an optical waveguide element through a projection lens, with precise positioning achieved by an optical engine main body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a framework with LED module and DMD is used for projection device, then image projection function is achieved, but volume and weight of wearable display device increase
Solution Approach 1:
The patent extracts and removes the DMD (Digital Micromirror Device) from the projection system, replacing it with a direct optical path from light emitting units through optical combiners to the waveguide. This extraction eliminates the need for complex micromirror positioning mechanisms, significantly reducing volume while maintaining image projection capability.
Solution Approach 2:
The optical combiner in the patent serves multiple functions: it combines light from multiple light emitting units, directs light through the waveguide, and eliminates the need for separate DMD and optical path guidance systems. This multi-functionality reduces the overall number of components and volume of the projection device.
2Measurement precision
If DMD and complex optical path guidance system are used, then precise image projection is achieved, but device complexity increases
Solution Approach 1:
The patent removes the DMD and complex optical path guidance system, replacing them with a simplified direct optical path. Image projection precision is maintained through precise positioning of light emitting units and optical combiners, eliminating the need for complex micromirror control mechanisms.
Solution Approach 2:
The patent merges the functions of light emission, optical path guidance, and image projection into a integrated structure where light emitting units directly couple with optical combiners that guide light through the waveguide. This merging eliminates multiple separate components and reduces overall system complexity.
3Manufacturing precision
If precise optical engine system is used to position elements, then imaging accuracy is improved, but weight of wearable display device increases
Solution Approach 1:
The patent extracts and removes the precise optical engine system with its heavy positioning mechanisms. Instead, it uses a simplified structure where light emitting units and optical combiners are positioned with sufficient precision for AR imaging, significantly reducing weight while maintaining adequate imaging accuracy.
Solution Approach 2:
The patent changes the positioning precision requirements from the high-precision DMD level to a coarser level sufficient for AR waveguide coupling. This parameter change allows using lighter positioning structures and mounting mechanisms while still achieving the required imaging quality for augmented reality applications.
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 reduces the volume and weight of the wearable display device, aligning with design requirements for ease of use, while maintaining image projection functionality.
Implementation Method 1
the illumination beam emitted by the at least one light emitting unit is guided by the optical combiner to become the image beam
Implementation Method 2
the illumination beam emitted by the at least one light emitting unit is guided by the optical combiner to become the image beam
Implementation Method 3
the image beam may be directly projected to the optical waveguide element by the projection lens to display an image frame
Data Source
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AI summary
A wearable display device includes an optical waveguide element and a projection device. The projection device includes an optical engine main body, at least one light emitting unit, an optical combiner, and a projection lens. The optical engine main body has at least one positioning structure. The light emitting unit is connected to the optical engine main body and configured to emit an illumination beam. The optical combiner is disposed in the optical engine main body and positioned at the positioning structure, the optical combiner is located on a transmission path of the illumination beam, and the optical combiner is configured to guide the illumination beam to form an image beam. The projection lens is connected to the optical engine main body, and the projection lens is located on a transmission path of the image beam and configured to project the image beam to the optical waveguide element.