Light Detection And Ranging Applications Research Articles

Time division multiplexing based multi-spectral semantic camera for LiDAR applications

The recent progress in the development of measurement systems for autonomous recognition had a substantial impact on emerging technology in numerous fields, especially robotics and automotive applications. In particular, time-of-flight (TOF) based light detection and ranging (LiDAR) systems enable to map the surrounding environmental information over long distances and with high accuracy. The combination of advanced LiDAR with an artificial intelligence platform allows enhanced object recognition and classification, which however still suffers from limitations of inaccuracy and misidentification. Recently, multi-spectral LiDAR systems have been employed to increase the object recognition performance by additionally providing material information in the short-wave infrared (SWIR) range where the reflection spectrum characteristics are typically very sensitive to material properties. However, previous multi-spectral LiDAR systems utilized band-pass filters or complex dispersive optical systems and even required multiple photodetectors, adding complexity and cost. In this work, we propose a time-division-multiplexing (TDM) based multi-spectral LiDAR system for semantic object inference by the simultaneous acquisition of spatial and spectral information. By utilizing the TDM method, we enable the simultaneous acquisition of spatial and spectral information as well as a TOF based distance map with minimized optical loss using only a single photodetector. Our LiDAR system utilizes nanosecond pulses of five different wavelengths in the SWIR range to acquire sufficient material information in addition to 3D spatial information. To demonstrate the recognition performance, we map the multi-spectral image from a human hand, a mannequin hand, a fabric gloved hand, a nitrile gloved hand, and a printed human hand onto an RGB-color encoded image, which clearly visualizes spectral differences as RGB color depending on the material while having a similar shape. Additionally, the classification performance of the multi-spectral image is demonstrated with a convolution neural network (CNN) model using the full multi-spectral data set. Our work presents a compact novel spectroscopic LiDAR system, which provides increased recognition performance and thus a great potential to improve safety and reliability in autonomous driving.

Pyroelectric-Accelerated Perovskite Photodetector for Picosecond Light Detection and Ranging.

Light detection and ranging (LiDAR) is indispensable in applications such as unmanned aerial vehicles, autonomous driving, and biomimetic robots. However, the precision and available distance of LiDAR are constrained by the speed and sensitivity of the photodetector, necessitating the use of expensive and energy-consuming avalanche diodes. To address these challenges, in this study, a pyroelectricity-based acceleration strategy with 2D-(graded 3D) perovskite heterojunction is proposed to achieve a record high speed (27.7 ns with an active area of 9 mm2, and 176 ps with an active area of 0.2 mm2) and high responsivity (0.65 A W-1) at zero bias. This success is attributed to the unique mechanism where the electrons from the pyroelectric effect at the Cl-rich 2D/3D interface directly recombine with excess holes during light-dark transitions, breaking speed limitations related to carrier mobility and capacitive effect. Furthermore, the introduced pyroelectric effect significantly enhances the photoresponse, resulting in a self-powered external quantum efficiency exceeding 100%. The study also demonstrates precise position detection at the centimeter level. In conclusion, this research presents a pioneering approach for developing high-speed photodiodes with exceptional sensitivity, mitigating energy and cost concerns in LiDAR applications.

Thermal Behavior of Biaxial Piezoelectric MEMS-Scanners

This paper presents the thermal behavior of non-resonant (quasi-static) piezoelectric biaxial MEMS scanners with Bragg reflectors. These scanners were developed for LIDAR (LIght Detection And Ranging) applications using a pulsed 1550 nm laser with an average power of 2 W. At this power, a standard metal (gold) reflector can overheat and be damaged. The Bragg reflector developed here has up to 24 times lower absorption than gold, which limits heating of the mirror. However, the use of such a reflector involves a technological process completely different from that used for gold and induces, for example, different final stresses on the mirror. In view of the high requirements for optical power, the behavior of this reflector in the event of an increase in temperature needs to be studied and compared with the results of previous studies using gold reflectors. This paper shows that the Bragg reflector remains functional as the temperature rises and undergoes no detrimental deformation even when heated to 200 °C. In addition, the 2D-projection model revealed a 5% variation in optical angle at temperatures up to 150 °C and stability of 2D scanning during one hour of continuous use at 150 °C. The results of this study demonstrate that a biaxial piezoelectric MEMS scanner equipped with Bragg reflector technology can reach a maximum temperature of 150 °C, which is of the same order of magnitude as can be reached by scanners with gold reflectors.

Study experimental time resolution limits of recent ASICs at Weeroc with different SiPMs and scintillators

Medical applications, such as Positron Emission Tomography (PET), and space applications, such as Light Detection and Ranging (LIDAR), are in need of highly specialized ASICs. Weeroc, in collaboration with different partners, is highly involved in developing a new generation of front-end ASICs. In the context of a joined LIDAR project among Weeroc, CNES, and Airbus, Weeroc is working on the development of Liroc, an ASIC for space LIDAR application. Weeroc is also working on advancing ASICs for medical applications with Radioroc under development and intended to be used for PET applications. This study experimentally evaluates the time resolution limits of these ASICs in different configurations, with some of the most recent silicon photomultiplier (SiPM) technologies available on the market, coupled to different scintillation crystals. The best single-photon time resolution (SPTR) was achieved using FBK NUV-HD SiPMs with an FWHM of 90 ps with Liroc and 73 ps with Radioroc. Furthermore, the coincidence time resolution (CTR) of Radioroc was studied with different crystal sizes. Using a large LYSO:Ce,Ca crystal of (3 × 3 × 20 mm3) with Broadcom Near UltraViolet-Metal in Trench (NUV-MT) yields a CTR of 127 ps (FWHM). The best CTR of Radioroc was determined to 83 ps (FWHM) with Broadcom NUV-MT SiPMs coupled to LYSO:Ce,Ca (2 × 2 × 3 mm3)) from Taiwan Applied Crystal (TAC).

Smartphone-Based LiDAR Application for Easy and Accurate Wound Size Measurement.

The accurate assessment of wound size is a critical step in advanced wound care management. This study aims to introduce and validate a Light Detection and Ranging (LiDAR) technique for measuring wound size. Twenty-eight wounds treated from December 2022 to April 2023 at the Chungnam National University Hospital were analyzed. All the wounds were measured using three techniques: conventional ruler methods, the LiDAR technique, and ImageJ analysis. Correlation analysis, linear regression, and Bland-Altman plot analysis were performed to validate the accuracy of the novel method. The measurement results (mean ± standard deviation) obtained using the ruler method, LiDAR technique, and ImageJ analysis were 112.99 ± 110.07 cm2, 73.59 ± 72.97 cm2, and 74.29 ± 72.15 cm2, respectively. The Pearson correlation coefficient was higher for the LiDAR application (0.995) than for the conventional ruler methods (mean difference, -5.0000 cm2), as was the degree of agreement (mean difference, 38.6933 cm2). Wound size measurement using LiDAR is a simple and reliable method that will enable practitioners to conveniently assess wounds with a flattened and irregular shape with higher accuracy. However, non-flattened wounds cannot be assessed owing to the technical limitations of LiDAR.

Evaluation of Residual Stress in MEMS Micromirror Die Surface Mounting Process and Shock Destructive Reliability Test

Light Detection and Ranging (LiDAR) devices based on Micro-Electro-Mechanical Systems (MEMS) micromirrors have been promising sensors for automatic driving owing to the advantages of MEMS devices. The packaging plays a vital role in the reliability of MEMS micromirror but introduces the residual stress from the surface mounting process. The shock reliability of micromirrors is influenced by residual stress. In this work, the residual stress from the surface mounting process are investigated through resonant frequency tests. The frequency drift can be 718 Hz and -281 Hz under the residual stress of 107.0 MPa and -25.0 MPa respectively. As the difference of CTE rises, the residual stress proportionally increases but decreases with the thickness of the substrate. In addition, a higher curing temperature can introduce a more significant stress level. The dynamic response in shock environment under different residual stress are analyzed. Drop fall experiments verify the theoretical conclusions that the stiffness hardening effect can improve the shock level tolerance. The tensile stress levels of 41.7 MPa and 107.0 MPa are corresponding to 100 g and 200 g respectively. The influences of residual stress on frequency drift and reliability need to be considered seriously and simultaneously during the packaging design for MEMS micromirrors. This work provides a deep insight into commercial applications of MEMS-based LiDAR in autonomous driving.

Biaxial Piezoelectric MEMS Mirrors with Low Absorption Coating for 1550 nm Long-Range LIDAR.

This paper presents the fabrication and characterization of a biaxial MEMS (MicroElectroMechanical System) scanner based on PZT (Lead Zirconate Titanate) which incorporates a low-absorption dielectric multilayer coating, i.e., a Bragg reflector. These 2 mm square MEMS mirrors, developed on 8-inch silicon wafers using VLSI (Very Large Scale Integration) technology are intended for long-range (>100 m) LIDAR (LIght Detection And Ranging) applications using a 2 W (average power) pulsed laser at 1550 nm. For this laser power, the use of a standard metal reflector leads to damaging overheating. To solve this problem, we have developed and optimised a physical sputtering (PVD) Bragg reflector deposition process compatible with our sol-gel piezoelectric motor. Experimental absorption measurements, performed at 1550 nm and show up to 24 times lower incident power absorption than the best metallic reflective coating (Au). Furthermore, we validated that the characteristics of the PZT, as well as the performance of the Bragg mirrors in terms of optical scanning angles, were identical to those of the Au reflector. These results open up the possibility of increasing the laser power beyond 2W for LIDAR applications or other applications requiring high optical power. Finally, a packaged 2D scanner was integrated into a LIDAR system and three-dimensional point cloud images were obtained, demonstrating the scanning stability and operability of these 2D MEMS mirrors.

Phase-Modulated Continuous-Wave Coherent Ranging Method and Anti-Interference Evaluation

Light detection and ranging (LiDAR) has been applied in many areas because of its excellent performance. An easily achievable, cost-effective, and high-performance ranging method is a major challenge of LiDAR. Meanwhile, with the increasing applications of LiDAR, numerous LiDARs can be made to operate simultaneously, and potential interference is inevitable. Therefore, immunity against interference is paramount in LiDAR systems. In this paper, we demonstrated a ranging method referred to as phase-modulated continuous-wave (PhMCW). A detection range of 50 m and a ranging error of 2.2 cm are achieved. A one-dimensional scanning LiDAR system that is capable of detecting targets at 28 m is built, demonstrating the validation of the PhMCW method. Moreover, we propose a quantitative method for evaluating the anti-interference capability of lidar systems. The p-values of the Ljung–Box test were 0.0589 and 0.6327 for ToF and coherent LiDAR interferences, respectively, indicating that the PhMCW system is immune to interference. The proposed method can be applied to all types of LiDAR systems, regardless of the ranging method or beam-steering technique used.

A dToF Ranging Sensor with Accurate Photon Detector Measurements for LiDAR Applications.

Direct time-of-flight (dToF) ranging sensors based on single-photon avalanche diodes (SPADs) have been used as a prominent depth-sensing devices. Time-to-digital converters (TDCs) and histogram builders have become the standard for dToF sensors. However, one of the main current issues is the bin width of the histogram, which limits the accuracy of depth without TDC architecture modifications. SPAD-based light detection and ranging (LiDAR) systems require new methods to overcome their inherent drawbacks for accurate 3D ranging. In this work, we report an optimal matched filter to process the raw data of the histogram to obtain high-accuracy depth. This method is performed by feeding the raw data of the histogram into the different matched filters and using the Center-of-Mass (CoM) algorithm for depth extraction. Comparing the measurement results of different matched filters, the filter with the highest depth accuracy can be obtained. Finally, we implemented a dToF system-on-chip (SoC) ranging sensor. The sensor is made of a configurable array of 16 × 16 SPADs, a 940 nm vertical-cavity surface-emitting laser (VCSEL), an integrated VCSEL driver, and an embedded microcontroller unit (MCU) core to implement the best matched filter. To achieve suitably high reliability and low cost, the above-mentioned features are all packaged into one module for ranging. The system resulted in a precision of better than 5 mm within 6 m with 80% reflectance of the target, and had a precision better than 8 mm at a distance within 4 m with 18% reflectance of the target.

Comparative Analysis of SLAM Algorithms for Mechanical LiDAR and Solid-State LiDAR

With the advancement of light detection and ranging (LiDAR) technology in recent years, various new types of LiDAR have emerged, and the price of LiDAR equipment has gradually decreased. At present, low-cost solid-state LiDARs are gradually occupying the market. To evaluate the performance of two LIDARs for simultaneous localization and mapping. This study investigated the application of solid-state LiDAR and mechanical LiDAR in localization and mapping systems and comparatively analyzed their advantages and disadvantages. We selected some classic open-source algorithms [such as LiDAR odometry and mapping (A-LOAM)] to evaluate the performance of mechanical LiDAR and solid-state LiDAR in localization. The experimental data are adopted from some representative open-source data (such as KITTI data) and real data collected by Shenzhen University. The results showed that the localization accuracy of solid-state LiDAR was lower than that of mechanical LiDAR when the mobile robot moved to the corner and faced square to the wall at close range. Moreover, the localization accuracy of solid-state LiDAR was the same as or even higher than that of mechanical LiDAR when the mobile robots had small changes in the field of view (FOV) and the mobile robot moved along straight lines or other tracks.

Applications of LiDAR in Agriculture and Future Research Directions

Light detection and ranging (LiDAR) sensors have accrued an ever-increasing presence in the agricultural sector due to their non-destructive mode of capturing data. LiDAR sensors emit pulsed light waves that return to the sensor upon bouncing off surrounding objects. The distances that the pulses travel are calculated by measuring the time for all pulses to return to the source. There are many reported applications of the data obtained from LiDAR in agricultural sectors. LiDAR sensors are widely used to measure agricultural landscaping and topography and the structural characteristics of trees such as leaf area index and canopy volume; they are also used for crop biomass estimation, phenotype characterisation, crop growth, etc. A LiDAR-based system and LiDAR data can also be used to measure spray drift and detect soil properties. It has also been proposed in the literature that crop damage detection and yield prediction can also be obtained with LiDAR data. This review focuses on different LiDAR-based system applications and data obtained from LiDAR in agricultural sectors. Comparisons of aspects of LiDAR data in different agricultural applications are also provided. Furthermore, future research directions based on this emerging technology are also presented in this review.

A Mixed Calibration Method of Time-to-Digital Converter for LiDAR Applications

This brief presents a mixed calibration method of time-to-digital converter (TDC) for Light Detection and Ranging (LiDAR) applications, which is primarily implemented by a feedback loop consisting of VCRO-based TDC, double-digital-to-analog converter (DDAC), encoder, sampling circuit, LSB-first algorithm (LSBFA) block, and analog buffer. Based on the external input frequency control code (FCC), the method automatically adjusts the DDAC output to control TDC. To ensure that the DDAC output meets the accuracy requirements, a voltage coverage strategy is proposed, which is implemented by an external code controlling the R-2R array. Furthermore, after the chip operation is stable, a voltage trimming approach is presented to avoid introducing drastic switching activity, which is implemented using an error comparator and an LSBFA block. The peak-to-peak INL and DNL of TDC are 1.81 LSB and 0.44 LSB, respectively.

A 40-ps Resolution Robust Continuous Running VCRO-Based TDC for LiDAR Applications

This brief presents a robust continuous running voltage-controlled ring oscillator-based (VCRO-based) time to digital converter (TDC) for Light Detection and Ranging (LiDAR) applications. A robust two-counter method with a hybrid structure counter is proposed to avoid any sampling errors due to metastability and delay accumulation. To reduce the TDC dead time, a two-interleaved sampling channel is adopted. Compared to the prior methods, the proposed structure is free from sampling errors. The proposed TDC has been fabricated in 180-nm CMOS technology. Measurement results show that the error rate is negligible. The peak-to-peak INL and DNL are of 2.08 LSB and 0.46 LSB, respectively.

Monitoring Critical Infrastructure Using 3D LiDAR Point Clouds

Monitoring critical infrastructure is of great importance for resilience against current and emerging hazards. In Canada, at the national level, critical infrastructure is strategically classified into the following 10 sectors: energy and utilities, finance, food, transportation, government, information and communication technology, health, water, safety, and manufacturing. Many of these critical infrastructures may be effectively monitored using emerging technologies such as light detection and ranging (LiDAR). LiDAR technology enables active remote sensing from airborne and terrestrial systems. Accordingly, LiDAR can be used in a wide range of applications related to the monitoring of critical infrastructure to promote resilience. This survey provides a comprehensive, and structured literature overview of LiDAR technology currently available for commercial and research use, and also provides a detailed review of the relevant applications of LiDAR for critical infrastructure monitoring. Several LiDAR-based applications in areas of critical infrastructure such as terrestrial and air transportation, gas, oil, and water pipelines, energy generation and distribution, and security are discussed. A summary of the LiDAR data sets that are currently available for use is also presented.

A GaN–Si hybrid integrated driver for narrow-pulse and high-current LiDAR applications

Light detection and ranging (LiDAR) is the most important active remote sensing tool and is widely used in civilian and military fields. There are a number of methods to drive laser diodes; the most common circuit topologies are capacitor-discharge resonant circuits. However, the performance of the silicon (Si)-based switching device limits the development of Light detection and ranging, such as the large figure of merit (FOM) and the stray inductance. Although different methods have been reported to resolve these problems, there are still great challenges in reducing the pressure on Light detection and ranging driver design. Hence, this work presents a gallium nitride (GaN)–Si hybrid integrated driver for a Light detection and ranging system. In the circuit, the switching power device uses GaN instead of a Si-based device, because GaN enables much better performance for pulsed-laser operation due to its near-ideal switching performance. Furthermore, a GaN push–pull driver stage between the GaN power device and the Si-based driver integrated circuit (IC) was innovatively introduced, which is integrated in the same chip with the GaN power device, thereby effectively reducing the parasitic parameters of the signal chain and enhancing the system reliability. The design and implementation of the Si-based IC and GaN IC are based on 0.18 µm 80–120 V Bipolar-CMOS-DMOS (BCD) technology and 0.5 µm p-GaN technology, respectively. The experimental results suggest that the proposed driver circuit output pulse width is 12.6 ns, and it can normally operate at 10 MHz with turn-on/turn-off delay is 11.94 ns. In addition, the driver was capable of generating approximately 8.25 A current pulses through a low ohmic load with a pulse width of approximately 12.4 ns. This work plays a vital role in promoting the development of information equipment and aerospace equipment such as precise ranging, high-efficiency power supplies, and high-speed motors.

A Linear-Array Receiver AFE Circuit Embedded 8-to-1 Multiplexer for Direct ToF Imaging LiDAR Applications

To increase the light detection and ranging (LiDAR) system spatial resolution, the multiple photodetectors are typically deployed in the receiver. An equivalent linear-array receiver with multiplexing operation scheme is presented for the direct time of flight (dToF) LiDAR applications. In particular, the analog front-end (AFE) circuit of the proposed receiver mainly consists of eight transimpedance preamplifiers (preTIAs), a dummy preTIA, a post amplifier (PA) with an 8-to-1 multiplexer, an analog output buffer and a timing discriminator. The proposed AFE circuit, which achieves a transimpedance gain of ~106 dB <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> , a bandwidth of ~220 MHz, an equivalent input-referred noise current of ~5.1 pA/Hz0.5 and a channel switchover time of 6 ns, was fabricated in a 65 nm standard CMOS technology. The associated DC power consumption is 137 mW with a power supply of 2.5 V. The total area of the proposed AFE circuit, which includes the circuit core, bias circuits and I/O PADs, is approximately equal to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.2\times 1.2$ </tex-math></inline-formula> mm2.

A 50-ps Gated VCRO-Based TDC With Compact Phase Interpolators for Flash LiDAR

This article describes a small footprint, low power gated voltage-controlled ring oscillator (VCRO)-based Time-To-Digital converter (TDC) for Flash Light Detection and Ranging (LiDAR) applications. A group of compact local phase interpolators (PIs) are used to improve the resolution, which is highly area-saving and compatible with in-pixel TDC structure. A non-reset operation mode is introduced to increase the linearity by taking advantage of the dynamic element matching (DEM) property. The proposed TDC has been fabricated in a 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> HV-CMOS technology in a 32 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times32$ </tex-math></inline-formula> array, achieving a resolution of 50 ps. A Phase Lock Loop (PLL) is adopted to track the process, voltage, and temperature (PVT) variations and make the resolution tunable. A power-saving analog buffer is used to distribute the stable control voltage to all the in-pixel TDCs. Measurements show a good linearity performance and array uniformity (a deviation of only 0.89 ps), making it suitable for Flash LiDAR applications.

Synthesis of LiDAR-Detectable True Black Core/Shell Nanomaterial and Its Practical Use in LiDAR Applications.

Light detection and ranging (LiDAR) sensors utilize a near-infrared (NIR) laser with a wavelength of 905 nm. However, LiDAR sensors have weakness in detecting black or dark-tone materials with light-absorbing properties. In this study, SiO2/black TiO2 core/shell nanoparticles (SBT CSNs) were designed as LiDAR-detectable black materials. The SBT CSNs, with sizes of 140, 170, and 200 nm, were fabricated by a series of Stöber, TTIP sol-gel, and modified NaBH4 reduction methods. These SBT CSNs are detectable by a LiDAR sensor and, owing to their core/shell structure with intrapores on the shell (ca. 2–6 nm), they can effectively function as both color and NIR-reflective materials. Moreover, the LiDAR-detectable SBT CSNs exhibited high NIR reflectance (28.2 R%) in a monolayer system and true blackness (L* < 20), along with ecofriendliness and hydrophilicity, making them highly suitable for use in autonomous vehicles.

Two-dimensional silicon optical phased array with large field of view.

Optical phased array (OPA) is a promising beam steering component for light detection and ranging (LiDAR) systems. For most LiDAR applications, two-dimensional (2D, lateral and longitudinal) beam steering with large field of view is required. To achieve large lateral and longitudinal field of view, waveguide with nonuniform spacing and broadband tunable laser source is commonly utilized, resulting in complex structure and high cost. Here, a 2D OPA with large field of view is proposed and demonstrated on the silicon-on-insulator platform. Assisted by an improved optical antenna and polarization switch, lateral and longitudinal steering range could be both significantly improved. The experimental results show the steering ranges are 99.24° × 15.62° and 96.48° × 16.08° for transverse electric mode and transverse magnetic mode, respectively. The proposed scheme provides a promising approach to realize the integrated OPA with large field of view.

Review on the Application of Airborne LiDAR in Active Tectonics of China: Dushanzi Reverse Fault in the Northern Tian Shan

High-resolution topographic data are fundamental for active tectonics studies. Within the last 2 decades, the airborne light detection and ranging (LiDAR) system provided a solution for the accurate and efficient acquisition of detailed geomorphic features. The use of LiDAR data for the identification of microstructural and geomorphic features, fault zone activity analysis, and earthquake disaster assessment remains challenging and has been the focus of active tectonics studies. Based on the LiDAR data of Dushanzi anticline–a reverse fault zone in Xinjiang, China, our group carried out a significant number of active tectonic research studies. By reviewing the specific content of these works, we summarized the main application of LiDAR for a specific structure, the Dushanzi Reverse Fault in the northern Tianshan. In addition, other applications of LiDAR in active tectonics are summarized in this paper. These studies show that high-resolution LiDAR data facilitate detailed studies of the fault activity and paleoseismicity. We hope more researchers can realize the advantages of LiDAR technology in active tectonics research and apply LiDAR technology into their own practical work, so as to promote the development of active tectonics research.