FMCW Lidar Imaging with Parallel Detector Arrays for Fast Scene Ranging
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Solution Overview
Problem
Conventional lidar systems face challenges in achieving high frame rates, high sensitivity, and resilience to ambient noise, particularly in methods like time-of-flight (TOF) and frequency modulated continuous wave (FMCW), which are limited by mechanical scanning and ambient light interference.
Innovation Solution
A solid-state lidar system using an array of detectors and lenses to concurrently receive and process frequency modulated coherent signals, allowing for simultaneous scanning in multiple directions, with each detector mixing a local oscillator signal with return signals to generate RF beat signals for range determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional mechanical devices (articulated mirrors, rotating mirrors, gimbals) are used for scanning, then the system can cover the entire scene, but the scan rate is limited, reliability decreases, and system cost increases
Solution Approach 1:
The patent replaces mechanical scanning devices (articulated mirrors, rotating mirrors, gimbals) with a solid-state photonic integrated circuit system. The scanning function is achieved through electrical control of light propagation paths within the photonic circuit, eliminating moving mechanical parts and thereby increasing scan rate and reliability while reducing system cost.
2Speed
If direct time-of-flight method is used, then high frame rates can be achieved, but sensitivity is low and resilience to ambient noise is poor
Solution Approach 1:
The patent employs frequency modulated continuous wave (FMCW) technology where the optical frequency is dynamically modulated over time. This dynamic frequency modulation allows the system to achieve both high frame rates and high sensitivity by enabling coherent detection that can distinguish weak return signals from ambient noise through frequency discrimination.
Solution Approach 2:
The patent changes the optical frequency parameter over time in a controlled manner (frequency modulation). By sweeping the optical frequency and detecting the frequency shift of return signals, the system achieves high sensitivity to distance changes while maintaining high frame rates, overcoming the limitations of direct TOF methods.
3Measurement precision
If FMCW method with coherent detection is used, then sensitivity is improved and resilience to ambient noise is greatly reduced, but frame rate decreases due to point-by-point scanning
Solution Approach 1:
The patent segments the optical detection function into multiple parallel photodetectors integrated on the photonic integrated circuit. Each photodetector can independently detect light from different spatial directions simultaneously, enabling parallel processing of multiple scan points and thereby achieving high frame rates while maintaining the sensitivity benefits of coherent detection.
Solution Approach 2:
The photonic integrated circuit is designed to perform multiple functions: frequency modulation, beam scanning in multiple directions, and coherent detection, all within a single integrated platform. This multi-functionality allows the system to achieve both high sensitivity through coherent detection and high frame rates through parallel multi-directional scanning capabilities.
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 high frame rates, high sensitivity, and strong resilience to ambient noise, enabling improved detection range and resolution with reduced scanning delays and lower power consumption.
Implementation Method 1
wherein the LO signal interferes with the one of the return signals
Implementation Method 2
each detector of the array is configured to receive and mix the local oscillator signal with a corresponding return signal of each detector thereby generating a radio frequency (RF) beat signal
Data Source
Figure 1
Figure 2
Figure 3~5
AI summary
A system for determining a range of a scene is presented. The system includes an optical source to generate an input signal and a first optical coupler to tap a predetermined portion of the input signal as a LO signal. The system includes an emitting unit to transmit a remaining portion of the input signal as an output signal onto the scene, and an imaging unit to receive return signals from the scene. The imaging unit includes an array of detectors coupled to one or more lenses. A position of each detector is associated with a unique direction of the return signals. Also, the lenses may receive and direct the return signals onto the detectors. Further, each detector of the array is configured to mix the LO signal with a corresponding return signal thereby generating a RF beat signal that is further processed to determine the range of the scene.