FMCW Lidar Sideband Filtering for Compact Precision Ranging
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Solution Overview
Problem
Conventional lidar technologies face challenges in achieving high-reliability, long-distance, and high-precision measurements due to limitations in increasing pulse power and reducing pulse width simultaneously, which restricts miniaturization and integration, especially in vehicle-mounted applications.
Innovation Solution
A detection apparatus utilizing a silicon microring modulator for external modulation of a continuous laser beam, combining modulation and wavelength selection to generate symmetric side band signals, enabling miniaturization and improving ranging precision while maintaining narrow linewidth and coherence length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If conventional TOF-based lidar increases pulse power to extend measurement distance, then measurement distance is improved, but pulse width cannot be reduced simultaneously to improve ranging precision
Solution Approach 1:
The patent transitions from pulse-based TOF measurement to continuous wave FMCW measurement, fundamentally changing the operational parameters of the lidar system. This allows independent optimization of measurement distance (through frequency sweep time) and ranging precision (through frequency sweep range) without the mutual constraints present in pulse-based systems
Solution Approach 2:
The patent implements dynamic frequency modulation of the continuous laser beam, where the frequency sweeps linearly over time. This dynamic frequency variation enables the system to achieve both long measurement distances and high ranging precision by controlling the sweep characteristics, unlike static pulse parameters in conventional TOF systems
2Manufacturing precision
If FMCW-based lidar uses lithium niobate modulator or high-precision tunable resonant cavity to perform linear adjustment on optical frequency, then frequency sweep linearity is improved, but volume of the lidar increases and miniaturization becomes difficult
Solution Approach 1:
The patent replaces traditional mechanical or bulk optical components (lithium niobate modulators, tunable resonant cavities) with an integrated photonic circuit implementation. The linear frequency modulation is achieved through on-chip waveguide structures and modulation techniques, eliminating the need for large external components and enabling miniaturization while maintaining frequency sweep linearity
Solution Approach 2:
The patent integrates multiple functional components (laser source, modulator, wavelength selector, detector) into a single photonic integrated circuit chip. This nested integration approach allows the complex FMCW functionality to be contained in a compact form factor, achieving both high frequency sweep linearity and small volume
3Measurement precision
If FMCW-based lidar increases frequency sweep range and frequency sweep time to improve ranging precision and measurement distance, then performance is improved, but requirement for laser linewidth and frequency sweep linearity becomes more stringent
Solution Approach 1:
The patent introduces a wavelength selection module as an intermediary component that filters and selects specific wavelength components from the broadened laser spectrum. This mediator allows the system to tolerate broader laser linewidth while still achieving the required frequency sweep characteristics by selecting only the necessary spectral components, thus relaxing the stringent linewidth requirements
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 reduces system complexity, facilitates miniaturization, and enhances ranging precision and measurement distance by decoupling the modulation module from the light source, utilizing silicon microring modulators with low loss and high efficiency, thereby improving signal-to-noise ratio and integration.
Implementation Method 1
The modulation module is configured to modulate the continuous laser beam from the light source module to obtain a first laser beam including a carrier signal and symmetric side band signals
Implementation Method 2
The first wavelength selection module is configured to allow at least one side band signal in the symmetric side band signals to pass through and prevent the carrier signal from passing through
Data Source
Figure 1~2a
Figure 2b~2c
Figure 3a~3b
AI summary
A detection apparatus, a lidar, a chip, and a terminal device are provided. The detection apparatus may be independently used as a chip, or may be used in a lidar or a terminal device (for example, a vehicle, a smart home device, or an intelligent transportation device). The detection apparatus includes: a light source module (401), configured to emit a continuous laser beam; a modulation module (402), configured to modulate the continuous laser beam from the light source module (401), to obtain a first laser beam including a carrier signal and symmetric side band signals; a first wavelength selection module (403), configured to allow at least one side band signal in the symmetric side band signals to pass through and prevent the carrier signal from passing through, to obtain a second laser beam; and an optical transceiver module (404), configured to: emit the second laser beam to a detection area, and receive a first echo signal for the second laser beam, where the first echo signal includes the at least one side band signal, and a first side band signal in the at least one side band signal included in the first echo signal is used to detect a target. This can reduce a volume of the detection apparatus, and can improve ranging precision in the field such as self-driving, intelligent driving, or mapping.