LiDAR Echo Waveform Reconstruction via Phase-Shifted Mixing
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Solution Overview
Problem
Current LiDAR systems face limitations in channel density due to high bandwidth requirements and spatial resolution, with direct ToF systems being limited by large silicon area needs and indirect ToF systems having limited distance measurement capabilities and susceptibility to errors from multiple reflections.
Innovation Solution
A method and system for generating a time domain echo waveform using a triggered source of pulsed electromagnetic radiation, phase-shifted mixing signals, and signal reconstruction to support higher channel density and range measurement capabilities, while resolving multiple reflections and propagation paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct ToF systems use high bandwidth signal processing to achieve high spatial resolution and support multiple channels, then measurement precision and productivity are improved, but device complexity and area of stationary object increase due to large silicon area requirements
Solution Approach 1:
The patent replaces direct time-of-flight measurement with a synthetic aperture radar-like approach using phase-shifted mixing signals. Instead of directly measuring flight time with high bandwidth electronics, the system uses phase-modulated continuous wave signals and signal processing to achieve virtual time-domain resolution, substituting complex high-speed electronics with lower bandwidth signal processing.
Solution Approach 2:
The patent transforms the measurement from direct time domain to frequency domain using phase modulation and mixing. By measuring phase differences at multiple frequencies and reconstructing the time domain waveform synthetically, the system achieves time resolution without requiring correspondingly high bandwidth hardware, effectively moving the complexity from the hardware dimension to the signal processing dimension.
2Device complexity
If indirect ToF systems use phase-stepped sampling to reduce bandwidth requirements and support more channels, then device complexity is reduced, but measurement precision deteriorates due to limited distance measurement capabilities and susceptibility to multiple reflection errors
Solution Approach 1:
The patent divides the measurement process into multiple phase-stepped samples at different frequencies, then reconstructs the complete time domain waveform by combining these segmented measurements. This allows the system to achieve high resolution through computational synthesis rather than direct high-bandwidth measurement, reducing hardware complexity while maintaining precision.
Solution Approach 2:
The patent introduces phase-modulated mixing signals as intermediaries between the emitted light and the detected echo. By using phase-shifted local oscillator signals to mix with the received echo, the system translates time domain information into phase domain measurements, which can be processed with lower bandwidth while preserving measurement accuracy.
3Measurement precision
If LiDAR systems increase channel density to improve spatial resolution, then measurement precision is improved, but device complexity increases due to bandwidth requirements and silicon area constraints
Solution Approach 1:
The patent implements a universal signal processing architecture where a single detector and processing unit can handle multiple virtual channels through synthetic aperture techniques. By using phase-shifted mixing and waveform reconstruction, the system achieves multi-channel capability without requiring proportionally more physical detectors or bandwidth, making the system scalable without linearly increasing complexity.
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 enables LiDAR systems to support greater range measurements with lower bandwidth requirements, improving spatial resolution and reducing errors from multiple reflections, effectively combining the benefits of direct and indirect ToF systems.
Implementation Method 1
an electromagnetic radiation detector cell, the electromagnetic radiation detector cell generating a plurality of stored electrical measurements in response to electromagnetic radiation incident thereupon
Data Source
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AI summary
A method of generating a time domain echo waveform comprises: a triggered source of pulsed electromagnetic radiation (108) emitting (202) a plurality of electromagnetic radiation pulses (132). A plurality of reflected pulses (134) irradiates an electromagnetic radiation detector cell (116), the detector (116) generating a plurality of stored electrical measurements in response thereto. The method also comprises generating a time-varying mixing signal and respectively applying (204, 206) phase-shifted variations thereof to the detector (116) while generating the plurality of electrical measurements. A signal pre-processor (126) reads out (210) the plurality of electrical measurements from the detector (116). A signal reconstruction unit (128) and then generates (300, 302, 500, 502) a spectrum (404, 604) in respect of the electrical measurements and a spectrum (406, 606) of the mixing signal. The signal reconstruction unit (126) generates a reconstruction signal spectrum (408) by deconvolving (304, 504) the spectrum (404, 604) of the stored electrical measurements using the spectrum (406, 606) of the mixing signal and then generates the echo waveform by converting (306, 506) the reconstruction signal spectrum (408) to the time domain.