Diffractive Waveguide FMCW LiDAR for Compact Local Beam Mixing
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Solution Overview
Problem
Existing FMCW LiDAR systems face challenges in efficiently projecting and collecting optical radiation for accurate depth mapping due to issues with optical path alignment, noise interference, and component size, particularly in compact applications like mobile devices.
Innovation Solution
An optical sensing apparatus utilizing a transparent slab with diffractive structures, such as surface relief gratings or metasurfaces, to deflect and project a local beam onto detectors, combining multiple optical functions into a compact design, enhancing signal-to-noise ratio and reducing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional optical components are used for beam deflection and projection in FMCW LiDAR, then optical path alignment and signal quality can be maintained, but the apparatus size and component count increase
Solution Approach 1:
The patent integrates multiple optical functions (beam deflection, projection, and diffraction) into a single transparent slab component containing diffractive structures. This merging of functions reduces the number of separate optical components needed in the FMCW LiDAR system, directly addressing the contradiction by decreasing component count while maintaining optical performance
Solution Approach 2:
The transparent slab with diffractive structures serves multiple purposes simultaneously: it acts as a beam deflector, a projection element, and a diffraction grating. This multi-functionality allows a single component to replace what would traditionally require multiple specialized optical elements, thereby reducing apparatus size and component complexity
2Reliability
If multiple separate optical components are used for local beam generation and projection, then optical path control is simplified, but noise interference and signal-to-noise ratio deteriorate
Solution Approach 1:
By combining the local beam generation and projection functions into the integrated transparent slab, the patent reduces the number of optical interfaces and alignment points where noise and misalignment errors could occur. The unified structure maintains stable optical paths while improving signal quality through consistent beam manipulation
Solution Approach 2:
The diffractive structures within the transparent slab act as intermediary elements that precisely control the local beam path through diffraction. These structured intermediaries provide deterministic beam steering and projection, reducing random noise and improving the reliability of optical path control
3Measurement precision
If conventional optical elements are used for FMCW LiDAR, then optical radiation projection is achieved, but component size and apparatus complexity increase
Solution Approach 1:
The patent employs diffractive structures with specific periodic patterns and optical parameters etched into the transparent slab. By optimizing the diffraction grating parameters (period, depth, orientation), the system achieves precise depth mapping capability in a compact form factor, resolving the contradiction between measurement precision and component size
Solution Approach 2:
The diffractive structures utilize the third dimension (depth/height of the slab) to achieve optical function, rather than requiring large lateral dimensions. The diffraction effect occurs through the thickness of the slab, allowing compact in-plane dimensions while maintaining precise optical control for accurate depth mapping
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 efficient optical radiation projection and collection, improving the accuracy of depth maps by increasing signal overlap and reducing noise, while minimizing the apparatus size and complexity.
Implementation Method 1
The second face includes a first diffractive structure, which is disposed in a first location intercepting the transmit axis and is configured to deflect a part of the FM coherent optical radiation to form a local beam propagating diagonally within the transparent slab
Implementation Method 2
deflect a part of the FM coherent optical radiation to form a local beam propagating diagonally within the transparent slab and reflecting from the second face toward the receive axis
Implementation Method 3
a second diffractive structure, which is disposed in a second location intercepting the receive axis and is configured to deflect and project the reflected local beam onto the array of detectors
Data Source
AI summary
Optical sensing apparatus includes a transmitter, which is configured to emit FM coherent optical radiation toward a target. A receiver alongside the transmitter includes an array of optical detectors. An objective optic focuses optical radiation that is reflected from the target onto the receiver. A transparent slab over the transmitter and the receiver has a first face facing the substrate and an opposing second face, which includes a first diffractive structure intercepting the transmit axis and configured to deflect a part of the FM coherent optical radiation to form a local beam propagating diagonally within the transparent slab and reflecting from the second face toward the receive axis. A second diffractive structure on the second face intercepts the receive axis and projects the reflected local beam onto the array of detectors, whereby the local beam mixes at the array with the optical radiation reflected from the target.