scholarly journals An Optical Interference Suppression Scheme for TCSPC Flash LiDAR Imagers

2019 ◽  
Vol 9 (11) ◽  
pp. 2206 ◽  
Author(s):  
Lucio Carrara ◽  
Adrian Fiergolski
Keyword(s):  
Interference Suppression ◽  
Time Of Flight ◽  
Integration Time ◽  
Maximum Deviation ◽  
Lidar Signal ◽  
Random Delay ◽  
Optical Interference ◽  
Worst Case ◽  
Flash Lidar ◽  
Autonomous Vehicle Navigation

This paper describes an optical interference suppression scheme that allows flash light detection and ranging (LiDAR) imagers to run safely and reliably in uncontrolled environments where multiple LiDARs are expected to operate concurrently. The issue of optical interference is a potential show-stopper for the adoption of flash LiDAR as a technology of choice in multi-user application fields such as automotive sensing and autonomous vehicle navigation. The relatively large emission angle and field of view of flash LiDAR imagers make them especially vulnerable to optical interference. This work illustrates how a time-correlated single-photon counting LiDAR can control the timing of its laser emission to reduce its statistical correlation to other modulated or pulsed light sources. This method is based on a variable random delay applied to the laser pulse generated by LiDAR and to the internal circuitry measuring the time-of-flight. The statistical properties of the pseudorandom sequence of delays determines the effectiveness of LiDAR resilience against unintentional and intentional optical interference. For basic multi-camera operation, a linear feedback shift register (LFSR) was used as a random delay generator, and the performance of the interference suppression was evaluated as a function of sequence length and integration time. Direct interference from an identical LiDAR emitter pointed at the same object was reduced up to 50 dB. Changing integration time between 10 ms and 100 ms showed a marginal impact on the performance of the suppression (less than 3 dB deviation). LiDAR signal integrity was characterized during suppression, obtaining a maximum relative deviation of the measured time-of-flight of 0.1%, and a maximum deviation of measurements spread (full-width half-maximum) of 3%. The LiDAR signal presented an expected worst-case reduction in intensity of 25%.

Adaptive interference suppression for CDMA systems with a worst-case error criterion

2000 ◽  
Vol 48 (1) ◽  
pp. 284-289 ◽  
Author(s):  
S. Nagaraj ◽  
S. Gollamudi ◽  
S. Kapoor ◽  
Yih-Fang Huang ◽  
J.R. Deller
Keyword(s):  
Interference Suppression ◽  
Error Criterion ◽  
Worst Case ◽  
Cdma Systems ◽  
Adaptive Interference Suppression

scholarly journals Detection of atmospheric gaseous amines and amides by a high resolution time-of-flight chemical ionization mass spectrometer with protonated ethanol reagent ions

2016 ◽  
Author(s):  
Lei Yao ◽  
Ming-Yi Wang ◽  
Xin-Ke Wang ◽  
Yi-Jun Liu ◽  
Hang-Fei Chen ◽  
...  
Keyword(s):  
High Resolution ◽  
Mass Spectrometer ◽  
Chemical Ionization ◽  
Time Of Flight ◽  
Integration Time ◽  
High Time Resolution ◽  
Ionization Mass ◽  
Industrial Emissions ◽  
Resolution Time ◽  
Ambient Measurements

Abstract. Amines and amides are important atmospheric organic-nitrogen compounds but high time resolution, highly sensitive, and simultaneous ambient measurements of these species are rather sparse. Here, we present the development of a high resolution time-of-flight chemical ionization mass spectrometer (HR-ToF-CIMS) method utilizing protonated ethanol as reagent ions to simultaneously detect atmospheric gaseous amines (C1 to C6) and amides (C1 to C6). This method possesses sensitivities of 5.6–19.4 Hz pptv−1 for amines and 3.8–38.0 Hz pptv−1 for amides under total reagent ion signals of ~ 0.32 MHz, and detection limits of 0.10–0.50 pptv for amines and 0.29–1.95 pptv for amides at 3σ of the background signal for a 1-min integration time, respectively. Controlled characterization in the laboratory indicates that relative humidity has significant influences on detection of amines and amides, whereas the presence of organics has no obvious effects. Ambient measurements of amines and amides utilizing this method were conducted from 25 July 2015 to 25 August 2015 in urban Shanghai, China. While the concentrations of amines ranged from a few pptv to hundreds of pptv, concentrations of amides varied from tens of pptv to a few ppbv. Among the C1- to C6-amines, the C2-amines were the dominant species with concentrations up to 130 pptv. For amides, the C3-amides (up to 8.7 ppb) were the most abundant species. The diurnal profiles of amines and amides suggest that in addition to the secondary formation of amides in the atmosphere, industrial emissions could be important sources of amides in urban Shanghai. During the campaign, photo-oxidation of amines and amides might be a main loss pathway for them in day time, and wet deposition was also an important sink.

scholarly journals Robust adaptive beamforming with enhancing the interference suppression capability

2019 ◽  
Vol 8 ◽  
Author(s):  
Linxian Liu ◽  
Yang Li
Keyword(s):  
Performance Optimization ◽  
Signal To Noise Ratio ◽  
Interference Suppression ◽  
Adaptive Beamforming ◽  
Training Data ◽  
Worst Case ◽  
Diagonal Loading ◽  
Steering Vector ◽  
Robust Adaptive Beamforming ◽  
Robust Adaptive

AbstractThe steering vector mismatch causes signal self-nulling for adaptive beamforming when the training data contain the desired signal component. To prevent signal self-nulling, many beamformers use robust technology, which is usually equivalent to the diagonal loading approach. Unfortunately, the diagonal loading approach achieves better signal enhancement at the cost of losing its interference suppression capability, especially at high input signal-to-noise ratio. In this paper, a novel robust adaptive beamforming method is developed to improve the interference suppression capability. The proposed beamformer is based on the worst-case performance optimization technology with a new estimated steering vector and a special set parameter. Firstly, a subspace which is orthogonal to the interference's steering vector is obtained by using the interference-plus-noise covariance matrix; then a new steering vector which is orthogonal to each interference's steering vector is estimated; finally, the beamformer's weight is solved with the worst-case performance optimization technology with a special set parameter. Theoretical analysis of the interference suppression principle is analyzed in detail, and some simulation results are presented to evaluate the performance of the proposed beamformer.

Modeling of a sensitive time-of-flight flash LiDAR system

2016 ◽  
Author(s):  
V. Fathipour ◽  
S. Wheaton ◽  
W. E. Johnson ◽  
H. Mohseni
Keyword(s):  
Time Of Flight ◽  
Lidar System ◽  
Flash Lidar

Time-of-flight depth image enhancement using variable integration time

2013 ◽  
Author(s):  
Sun Kwon Kim ◽  
Ouk Choi ◽  
Byongmin Kang ◽  
James Dokyoon Kim ◽  
Chang-Yeong Kim
Keyword(s):  
Image Enhancement ◽  
Time Of Flight ◽  
Depth Image ◽  
Integration Time ◽  
Variable Integration

scholarly journals Distance Error Correction in Time-of-Flight Cameras Using Asynchronous Integration Time

Sensors ◽  
2020 ◽  
Vol 20 (4) ◽  
pp. 1156
Author(s):  
Eu-Tteum Baek ◽  
Hyung-Jeong Yang ◽  
Soo-Hyung Kim ◽  
Gueesang Lee ◽  
Hieyong Jeong
Keyword(s):  
Error Correction ◽  
Time Of Flight ◽  
Correction Method ◽  
Integration Time ◽  
Depth Information ◽  
Optical Noise ◽  
Depth Sensor ◽  
Distance Map ◽  
Distance Error ◽  
Depth Sensors

A distance map captured using a time-of-flight (ToF) depth sensor has fundamental problems, such as ambiguous depth information in shiny or dark surfaces, optical noise, and mismatched boundaries. Severe depth errors exist in shiny and dark surfaces owing to excess reflection and excess absorption of light, respectively. Dealing with this problem has been a challenge due to the inherent hardware limitations of ToF, which measures the distance using the number of reflected photons. This study proposes a distance error correction method using three ToF sensors, set to different integration times to address the ambiguity in depth information. First, the three ToF depth sensors are installed horizontally at different integration times to capture distance maps at different integration times. Given the amplitude maps and error regions are estimated based on the amount of light, the estimated error regions are refined by exploiting the accurate depth information from the neighboring depth sensors that use different integration times. Moreover, we propose a new optical noise reduction filter that considers the distribution of the depth information biased toward one side. Experimental results verified that the proposed method overcomes the drawbacks of ToF cameras and provides enhanced distance maps.

scholarly journals Laboratory Demonstration of the Local Oscillator Concept for the Event Horizon Imager

2021 ◽  
pp. 2150010
Author(s):  
V. Kudriashov ◽  
M. Martin-Neira ◽  
E. Lia ◽  
J. Michalski ◽  
P. Kant ◽  
...  
Keyword(s):  
Black Hole ◽  
Special Interest ◽  
Integration Time ◽  
Analysis Tool ◽  
Allan Deviation ◽  
Worst Case ◽  
The Third ◽  
Coherent Integration ◽  
Calibration Methods ◽  
Frequency Transfer

Black hole imaging challenges the third-generation space VLBI, the Very Long Baseline Interferometry, to operate on a 500[Formula: see text]GHz band. The coherent integration time needed here is 450[Formula: see text]s though the available space oscillators cannot offer more than 10[Formula: see text]s. Self-calibration methods might solve this issue in an interferometer formed by three antenna/satellite systems, but the need for the third satellite increases the mission costs. A frequency transfer is of special interest to alleviate both performance and cost issues. A concept of two-way optical frequency transfer is examined to investigate its suitability to enable space-to-space interferometry, in particular, to image the “shadows” of black holes from space. The concept, promising on paper, has been demonstrated by tests. The laboratory test set-up is presented and the verification of the temporal stability using standard analysis tool as TimePod has been passed. The resulting Allan Deviation is dominated by the 1/[Formula: see text] phase noise trend since the frequency transfer timescale of interest is shorter than 0.2[Formula: see text]s. This trend continues into longer integration times, as proven by the longest tests spanning over a few hours. The Allan Deviation between derived 103.2[Formula: see text]GHz oscillators is [Formula: see text]/[Formula: see text] within 10[Formula: see text][Formula: see text][Formula: see text]s that degrades twice towards the longest delay of 0.2[Formula: see text]s. The worst case satisfies the requirement with a margin of 11 times. The obtained coherence in the range of 0.997[Formula: see text]0.9998 is beneficial for space VLBI at 557[Formula: see text]GHz. The result is of special interest to future science missions for black hole imaging from space.

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