Holographic Waveguide LIDAR Using Switchable Gratings
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Solution Overview
Problem
Current LIDAR systems are bulky, expensive, and inadequate for providing wide-angle, high-resolution, long-range operation, relying on bulky rotating optics technology.
Innovation Solution
The use of waveguide optics based on switchable grating technology, specifically switchable Bragg gratings, which allow for a compact, lightweight LIDAR system by optimizing the scanning cycle to coincide with the diffracting state of the gratings, eliminating the need for rotating optics and enabling efficient angular resolution without the need for complex optical assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bulky rotating optics technology is used, then LIDAR can achieve wide-angle scanning and high-resolution measurement, but the system becomes extremely bulky and expensive
Solution Approach 1:
The patent replaces bulky mechanical rotating optics with a waveguide-based optical system using switchable gratings. The waveguide contains an array of gratings that can be selectively activated to steer light in different directions, eliminating the need for large rotating mirrors or lenses while achieving the same angular scanning function with a compact, lightweight structure.
Solution Approach 2:
The patent divides the waveguide into multiple segments, each containing a specific grating element. Each grating can be independently controlled to direct light in a particular angular direction. This segmentation allows the system to achieve wide-angle scanning by activating different segments sequentially, replacing the need for a single large rotating optical component.
2Measurement precision
If imaging array technology is used, then LIDAR can provide high-resolution 3D mapping, but the system becomes very expensive
Solution Approach 1:
The patent employs a single detector that sequentially measures different angular positions by utilizing the waveguide's inherent optical path differences. The waveguide structure itself serves to direct light from different angles to the same detector at different times, eliminating the need for expensive multi-element detector arrays while achieving the same spatial resolution through temporal multiplexing.
Solution Approach 2:
The patent uses periodic activation of different grating elements in the waveguide to scan different angular positions. By sequentially activating gratings corresponding to different angles and measuring the reflected light intensity at each position, the system reconstructs a high-resolution 3D map over time, achieving imaging array performance through periodic temporal sampling.
3Weight of stationary object
If switchable gratings are used to reduce system bulk, then the LIDAR becomes compact and lightweight, but achieving wide-angle scanning with high angular resolution becomes more difficult
Solution Approach 1:
The patent utilizes the third dimension (depth/thickness of the waveguide) to encode angular information. By positioning grating elements at different depths and orientations within the waveguide, the system can steer light across a wide angular range in the lateral direction. This dimensional encoding allows compact switchable gratings to achieve scanning capabilities that would otherwise require large lateral optical components.
Solution Approach 2:
The patent employs dynamically switchable grating elements that can be activated in different sequences and combinations to expand the effective scanning angular range. By controlling the timing and pattern of grating activation, the system can adaptively cover different angular sectors, achieving versatile wide-angle scanning capability from a compact fixed-structure waveguide.
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 approach results in a compact, lightweight, and cost-effective LIDAR system capable of providing wide-angle, high-resolution, long-range operation, with the added benefit of being eye-safe and invisible to current night vision technology, while integrating seamlessly with other waveguide devices like displays and eye trackers.
Implementation Method 1
The transmitter waveguide contains a multiplicity of grating elements disposed in at least one grating layer. Each grating element is operative to diffract light into a predefined range of output directions.
Implementation Method 2
The receiver waveguide contains a multiplicity of grating elements disposed in at least one grating layer. Each grating element diffracts light reflected from external points and incident within a predefined angular range into a TIR path to the detector.
Implementation Method 3
When an electric field is applied to the grating via transparent electrodes, the natural orientation of the LC droplets is changed causing the refractive index modulation of the fringes to reduce and the hologram diffraction efficiency to drop to very low levels.
Data Source
AI summary
A holographic waveguide LIDAR comprises a transmitter waveguide coupled to a beam deflector and a receiver waveguide coupled to a detector module. The transmitter waveguide contains an array of grating elements for diffracting a scanned laser beam into a predefined angular ranges. The receiver waveguide contains an array of grating elements for diffracting light reflected from external points within a predefined angular range towards the detector module.