Thin Waveguide Imager for Low-Diffraction Near-Eye Displays
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Solution Overview
Problem
Existing head-mounted displays (HMDs) are bulky, unbalanced, and uncomfortable due to their large size and weight, and traditional waveguides suffer from diffraction effects causing color dispersion and ghost images, making them unsuitable for curved substrates and real-world object visibility.
Innovation Solution
The use of low-mode waveguides, including a low-mode waveguide with an in-coupler, 1xN splitter, phase shifters, and a slab waveguide portion with a FOV expander and hologram, allows for precise light distribution and control, enabling 2D image formation in an angular domain without significant color gamut reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional waveguides are used in HMDs, then light can be propagated through the waveguide, but diffraction effects cause color dispersion and ghost images, reducing image quality
Solution Approach 1:
The waveguide is divided into multiple linear waveguides arranged in an array, with each waveguide receiving a portion of the input light through a 1xN splitter. This segmentation allows independent control of light paths and reduces diffraction artifacts by distributing light across multiple guided modes rather than relying on a single traditional waveguide path.
Solution Approach 2:
Different regions of the waveguide structure are assigned different functions: the input region contains the in-coupler and splitter, the middle region contains phase shifters for temporal control, and the output region contains emitters and slab waveguide. This local differentiation optimizes each region's performance while minimizing overall diffraction effects.
2Reliability
If a large number of optical components are used to improve optical performance, then image quality improves, but the device becomes bulky, heavy, and uncomfortable to wear
Solution Approach 1:
Multiple optical functions (splitting, phase shifting, beam steering, and image formation) are merged into a single integrated waveguide structure. The 1xN splitter, phase shifters, linear waveguide array, and slab waveguide portion work together as one unified system, eliminating the need for separate bulky optical components while maintaining high optical performance.
Solution Approach 2:
The waveguide structure performs multiple functions simultaneously: it splits light, controls phase, steers beams, and forms images all within the same optical path. This multi-functionality reduces the number of separate components needed, thereby reducing overall device weight and complexity.
3Reliability
If conventional waveguide structures are used, then light propagation is achieved, but the device complexity increases due to the need for precise component alignment and integration
Solution Approach 1:
The splitter, phase shifters, and waveguide array are integrated into a single monolithic structure where light propagation efficiency is maintained through unified design. This integration reduces alignment complexity compared to assembling separate components, as the relative positions are fixed during fabrication rather than requiring post-assembly alignment.
4Adaptability or versatility
If traditional HMD designs are used, then display functionality is provided, but the field of view is limited and image clarity is reduced due to diffraction effects
Solution Approach 1:
The invention transitions from conventional 2D display geometry to a 3D angular domain representation by using an array of linear waveguides with controlled phase delays. This dimensional transformation enables expanded field of view while maintaining image clarity through precise spatial and angular control of light propagation paths.
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 compact, efficient, and comfortable HMD by reducing diffraction artifacts and improving image clarity, allowing for precise light control and expanded field of view, suitable for both virtual and augmented reality applications.
Implementation Method 1
an oblique-angle redirector for redirecting an image light beam provided by a light engine in a direction oblique to an optical axis of the image light beam
Implementation Method 2
a low-mode waveguide including a core layer and a first cladding layer disposed over the core layer... propagating the redirected image light beam in a propagation direction substantially parallel to the substrate
Implementation Method 3
N phase shifters each coupled to a particular one of the N linear waveguides for delaying image light portions propagating therein by a controllable amount
Implementation Method 4
a slab waveguide portion coupled to the array of N linear waveguide emitters for propagating therein the delayed image light portions emitted by corresponding emitters of the array of N linear waveguide emitters
Data Source
Figure 1A~1C
Figure 2
Figure 3~4A
AI summary
A device for providing a 1D line of an image is disclosed. The device is based on a thin slab waveguide coupled to a beam redirecting device such as a tiltable mirror MEMS scanner, a waveguide-based phased array, or a waveguide-based optical switch switching image light between waveguides of a waveguide array coupled to a collimating element formed in the low-mode slab waveguide. The image may be formed by scanning a collimated beam propagating in the slab waveguide, or by forming the 1D singular distribution of brightness at a same time. The device may be used in a near-eye display for forming a 2D image in angular domain.