Staring LiDAR System Using Diffractive Optical Element
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Solution Overview
Problem
Scanning LiDAR systems require complex optomechanical structures and high optical power due to the need for raster scanning and short integration times, while staring LiDAR systems face non-uniform illumination from diffractive optical elements (DOEs) that waste optical power.
Innovation Solution
A staring LiDAR system utilizing a radiation source, diffractive optical element (DOE), beamsplitter, reflector, and objective optics to diffract the beam into multiple orders, where the zero order is intercepted and used as a local beam for coherent detection, allowing efficient illumination of a wide field-of-view without moving parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If raster scanning is used in LiDAR systems, then field-of-view coverage is achieved, but device complexity and optical power requirements increase
Solution Approach 1:
The patent replaces the mechanical scanning system with a stationary diffractive optical element (DOE) that uses diffraction physics to direct multiple beam orders across the field-of-view. The DOE diffracts the laser beam into multiple angles simultaneously, eliminating the need for moving scanners and reducing mechanical complexity while maintaining wide area coverage.
Solution Approach 2:
The patent segments the single beam into multiple diffracted orders (first order, second order, third order, etc.) that propagate at different angles. Each order covers a specific portion of the field-of-view, allowing simultaneous illumination of multiple areas without mechanical scanning.
2Area of stationary object
If raster scanning with short integration times is used, then field-of-view coverage is achieved, but optical power requirements increase
Solution Approach 1:
The patent achieves continuous illumination of the entire field-of-view simultaneously through multiple diffracted beam orders. Unlike scanning systems that sequentially cover different areas, the DOE enables all areas to be illuminated at the same time, eliminating the need for high peak power during scanning and reducing overall optical power requirements.
3Area of stationary object
If DOE is used for beam diffraction, then field-of-view coverage is improved, but optical power is wasted due to non-uniform illumination
Solution Approach 1:
The patent applies different functional characteristics to different parts of the optical system. The DOE is designed with specific diffraction efficiencies for different orders, and a beam splitter is introduced to redirect the zeroth order. This local optimization ensures that optical power is distributed more uniformly across the field-of-view, reducing waste while maintaining coverage.
4Area of stationary object
If scanning mechanisms are used, then field-of-view coverage is achieved, but system simplicity is reduced
Solution Approach 1:
The patent eliminates mechanical scanning components entirely by using a stationary DOE that achieves field-of-view coverage through optical diffraction. This substitution of mechanical movement with optical physics simplifies the system, removing moving parts while maintaining the ability to illuminate the entire field-of-view.
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 system achieves compact, simple optomechanics with efficient use of optical power, providing uniform illumination and accurate range and velocity measurements across a wide field-of-view without the need for complex scanning mechanisms.
Implementation Method 1
A diffractive optical element (DOE) is configured to diffract the beam into multiple orders, including a zero order, propagating toward the target at different, respective angles
Implementation Method 2
A beamsplitter is positioned to direct the beam toward a target while directing the optical radiation reflected from the target toward the array of optical detectors
Implementation Method 3
Objective optics are configured to image the target onto the array of optical detectors while spreading the local beam across the array
Implementation Method 4
The light reflected from the target is mixed with a sample of the transmitted light (referred to as the local beam or local oscillator (LO)) and detected by a photodetector, such as a balanced photodiode pair
Implementation Method 5
In certain frequency-modulated continuous-wave (FMCW) LiDAR sensing arrangements, a radio-frequency (RF) chirp is applied to modulate the frequency of a beam of coherent light
Implementation Method 6
When the target is moving, the resulting Doppler shift of the reflected light will cause the beat frequency to increase or decrease, depending on the direction of motion
Data Source
AI summary
Range sensing apparatus includes a radiation source, which emits a beam of coherent optical radiation, and an array of optical detectors. A beamsplitter directs the beam toward a target while directing the optical radiation reflected from the target toward the array of optical detectors. A DOE diffracts the beam into multiple orders, including a zero order, propagating toward the target at different, respective angles. A reflector intercepts and reflects at least a part of the zero order toward the beamsplitter, thereby generating a local beam, which is reflected by the beamsplitter toward the array of optical detectors. Objective optics image the target onto the array of optical detectors while spreading the local beam across the array. Processing circuitry extracts a beat signal from electrical signals output by the optical detectors in response to an optical interference between the optical radiation reflected from the target and the local beam.