Shared-Resonator LiDAR with Dual Lasers for Speckle Noise Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lidar systems face challenges in increasing the signal-to-noise ratio (SNR) due to signal degradation from atmospheric particles like rain, snow, and fog, and noise from speckle patterns, which are detrimental to their performance, especially at longer ranges.
Innovation Solution
A multiple laser, single optical resonator lidar system is developed, utilizing two lasers optically coupled to a common electrooptic resonator, where one laser operates at a different wavelength than the other to reduce speckle noise and adjust power levels based on environmental conditions, with a controller managing the operation of the lasers to optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single laser is used in the lidar system, then the device complexity is low, but the signal-to-noise ratio is degraded due to speckle noise
Solution Approach 1:
The patent divides the single laser source into multiple laser sources (first laser and second laser) operating at different wavelengths. This segmentation allows the system to reduce speckle noise through wavelength diversity while maintaining manageable device complexity by using a shared optical resonator and control system.
Solution Approach 2:
The patent employs a composite approach by combining multiple lasers with different wavelengths (e.g., 1550nm and 1064nm) that are optically coupled to a common electrooptic resonator. This composite configuration leverages the advantages of each wavelength while mitigating the speckle noise problem through their combined operation.
2Reliability
If the laser power level is increased to improve signal detection, then the signal-to-noise ratio improves, but the speckle noise increases proportionally
Solution Approach 1:
The patent changes the wavelength parameter by using multiple lasers operating at different wavelengths (e.g., 1550nm and 1064nm). This parameter change allows the system to maintain high power levels for improved signal detection while reducing speckle noise through wavelength diversity, as the speckle patterns at different wavelengths do not correlate perfectly.
Solution Approach 2:
The patent converts the harmful speckle noise effect into a beneficial feature by using wavelength diversity. The speckle patterns generated by different wavelengths are uncorrelated, and when combined, they average out the noise while preserving the signal, effectively converting the harmful coherence effect into a noise-reduction mechanism.
3Length of stationary object
If the detection range is increased, then the lidar can detect更远 targets, but the signal degradation from atmospheric particles increases
Solution Approach 1:
The patent changes the operational wavelength parameter to optimize performance for different atmospheric conditions and ranges. By selecting appropriate wavelengths (e.g., 1550nm for eye safety and atmospheric transmission, 1064nm for other conditions), the system can extend detection range while maintaining signal quality by choosing wavelengths that are less affected by atmospheric absorption and scattering.
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
This configuration enhances the SNR by reducing speckle noise and adjusting power levels according to environmental conditions, improving the system's performance in adverse weather and extending its detection range effectively.
Implementation Method 1
the optical resonator is formed of an electrooptic material. Moreover, the first laser and the second laser are optically injection locked to the optical resonator. The lidar system further includes a modulator configured to apply a time-varying voltage to the optical resonator. The time-varying voltage can control modulation of an optical property of the electrooptic material (e.g., index of refraction)
Implementation Method 2
A FMCW lidar system can include a laser source that generates a frequency modulated optical signal that includes a continuous series of optical chirps
Implementation Method 3
A direct TOF lidar system emits an optical signal that includes short pulses of light, such that the pulses of light can reflect off a target in an environment
Implementation Method 4
The noise received by the lidar system commonly includes speckle, which is associated with coherence of a laser
Data Source
AI summary
Various technologies described herein pertain to multiple laser, single optical resonator lidar systems. A lidar system includes a single optical resonator optically coupled to at least a first laser and a second laser. The optical resonator is formed of an electrooptic material. The first laser and the second laser are optically injection locked to the optical resonator. Moreover, a modulator applies a time-varying voltage to the optical resonator to control modulation of an optical property of the electrooptic material, which causes the first laser to generate a first frequency modulated optical signal comprising a first series of optical chirps and/or the second laser to generate a second frequency modulated optical signal comprising a second series of optical chirps. Further, front end optics transmits at least a portion of the first frequency modulated optical signal and/or the second frequency modulated optical signal into an environment from the lidar system.