Advancements for Improving Signal-to-Noise Ratio in LiDAR Systems

A technique to reduce background light interference in LiDAR. The technique uses an opaque material with a small aperture behind the lens. Light is focused through the aperture onto a waveguide. A mirror reflects the light towards an array of detectors. This selectively filters out background light not aimed through the aperture.

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Coaxial LiDAR system for improved light collection efficiency to improve signal-to-noise ratio and range of LiDAR detection. The coaxial LiDAR system uses a non-reciprocal polarization rotator (like a Faraday rotator) to convert the polarization of the outgoing scanning beam so it is orthogonal to the polarization of the reflected return beam. This allows a polarization beam splitter to separate the two beams and direct the return beam to the photodetector.

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FMCW LiDAR system that uses a coherent receiver in the reference optical path to improve target detection. The coherent receiver includes a 90° optical hybrid that extracts the full complex beat signal. Combining the outputs of the optical hybrid suppresses the negative image of the beat frequency. This improves the linear phase noise estimation of the optical source and boosts the target signal-to-noise ratio.

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A method and system to compensate for phase noise in LiDAR and radar systems. It involves using an interferometer with two paths: a measurement path and a compensation path. The measurement path goes to the target and back. The compensation path has a delay line to match the round-trip time. The outputs of the two paths are compared to measure the target distance. The key is that the compensation path is delayed by a time longer than the round-trip time. This compensates for phase noise by subtracting the delayed interference signal from the measurement path. The delay is longer than the round-trip time to capture the phase noise. By selecting the appropriate delay length, the system can compensate for phase noise at different target distances.

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A LiDAR device that uses a collimator to generate parallel laser beams from non-parallel beams reflected off a rotating scanner. The collimator actively synchronizes and changes its properties as the scanner rotates to properly collimate the non-parallel beams into parallel beams. This allows using a smaller and faster rotating scanner while still achieving high spatial resolution and signal-to-noise ratio when scanning smaller objects. The active synchronization involves changing the refractive index of the collimator using phase change materials and electrodes.

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A LiDAR system that can reduce noise-light interference from sunlight when using a wavelength-tunable optical phased array (OPA) light source. The system uses an active device to adjust the filter to match the OPA's current wavelength, rather than using a fixed band-pass filter. This allows tuning the OPA without increasing noise-light.

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Steering a light pulse along an optical path and detecting the scattered light to determine a distance to the object. The system uses an array detector where only a subset of detector segments are activated based on the pulse steering direction. This allows steering consecutive pulses to different locations while binocularly collecting the scattered light using a smaller detector subset. Selecting the detector segments that receive the light scattered from the steering direction, can optimize the detection efficiency and reduce background noise compared to using a full detector array.

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LiDAR apparatus and method that accurately detects the flight time of laser pulses for ranging in noisy environments. It converts received signals into unipolar signals and analyzes their correlation with reference signals to identify the exact flight time point. This enables robust ranging even when signals are weak or corrupted by noise. If correlation peaks are not detectable, it increases the reference signal intensity or averages multiple measurements to enhance the signals over the noise.

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Frequency Modulated Continuous Wave (FMCW) LiDAR sensor that eliminates noise caused by a DC offset between the reference and return laser signals. The FMCW LiDAR system uses two lasers - one for the ranging signal and one for the local oscillator signal. The local oscillator signal is offset from the ranging signal by a predetermined frequency. This non-zero offset eliminates the DC component when the reference and return signals are mixed, reducing noise caused by self-mixing and other factors.

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LiDAR system for remote spectroscopy of a target, such as atmospheric gases, using frequency combs. The LiDAR transmits two combs of laser light frequencies towards the target, which reflect. A local comb is mixed with the returns to generate beat signals. The beat signals are processed to find third-beat signals at a specific frequency difference. The third beat signals contain spectroscopic information about the target matter. This allows remote spectroscopy of atmospheric gases, etc.

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Removing noise from LIDAR data caused by sunlight to improve object recognition. The noise removal apparatus predicts the direction and position of the sun based on GPS and image data. It then identifies a region of interest in the LIDAR data corresponding to the sun's location and removes noise points in that region. By selectively filtering out sunlight-induced noise, the apparatus aims to improve detection accuracy without losing actual object data.

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Scanning LIDAR systems that avoid errors caused by external light sources like ambient light or other LIDAR systems. It uses a modulated laser pulse that is distinguishable from ambient light and other LIDAR systems. The LIDAR system includes a pulsed laser that emits a modulated optical pulse. The modulation can be frequency, amplitude, phase or code modulation. The LIDAR system also includes a receiver to detect the modulated laser pulse reflections. The receiver filters out non-modulated light sources, like ambient light or other LIDAR systems, using the modulation frequency or code.

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Reducing noise in lidar systems caused by laser reflection from an internal absorption member. The lidar system has a rotating mirror that changes the laser direction between reflections from a reflector and an absorber. By comparing lidar return signals with and without absorber reflection, the system can estimate and subtract the absorber reflection noise from the lidar output signal.

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A LiDAR system with descan compensation to mitigate signal losses due to descan in fast scanning LiDAR systems. The technique involves intentionally decentering the local oscillator (LO) signal from the optical axis on the second lens to increase the overlap with the target return signal at the detector. This offsets the LO signal to compensate for spatial misalignment caused by fast scanning mirror speeds that can reduce mixing efficiency.

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A solid-state scanning mechanism for LIDAR chips that allows wide-angle scanning without moving parts. The LIDAR chip has an optical switch to direct the outgoing beam into different waveguides, and a redirection component that receives the beam from any waveguide and redirects it. The beam direction can be steered by changing the switch setting to different waveguides.

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A LIDAR system that uses cross-polarized light to determine target material and orientation, and reduce speckle noise. The system sends out a co-propagating, cross-polarized beam towards the target. The detectors measure the returned signals. By comparing the signal strengths from the detectors, the system can determine target properties like reflectivity and orientation. This is possible because different materials reflect polarized light differently. The cross-polarized beam also mitigates speckle noise compared to traditional LIDAR beams.

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Ranging operation in LiDAR systems that leverages the dynamic range of the receiver to enable accurate distance and reflectivity measurements across a wide range of target distances and reflectivities. The method involves transmitting two signals with carefully chosen levels and a time gap. This allows at least one of the reflected signals to fall within the linear dynamic range of the receiver. The received signals are identified and compared to determine distance and reflectivity.

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Improving the range accuracy of a lidar system for autonomous vehicles by using a hybrid digitization technique. The lidar system sends pulses of light towards objects, then receives and digitizes the reflected pulses. To optimize range accuracy across short and long distances, it samples the received analog sensor data at a lower rate for weak pulses, and at a higher rate for stronger pulses. This extracts timing data more accurately from the weak pulses, while still using the full amplitude data from the stronger pulses.

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A lidar imaging method and system using a Gm-APD array sensor to improve image quality under strong background noise conditions. The method involves acquiring two sets of cumulative lidar detection data with the target in and out of the lidar's range gate. Comparing the statistical histograms of these sets allows determination of the target's range interval. Then, an imaging algorithm is applied only within this interval to suppress noise from other ranges. This improves range information recovery and target-background contrast in lidar images.

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A LIDAR chip that enables low-cost and high performance LIDAR systems for applications like autonomous vehicles and augmented reality. The chip uses low-loss, low-noise, high-power waveguides and phased array steering to improve LIDAR performance. It also has integrated components for monitoring, calibration, and attenuation to enable accurate and reliable LIDAR operation.

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