An overview of lidar imaging systems for autonomous vehicles

Lidar imaging systems are one of the hottest topics in the optronics industry. The need to sense the surroundings of every autonomous vehicle has pushed forward a race dedicated to deciding the final solution to be implemented. However, the diversity of state-of-the-art approaches to the solution brings a large uncertainty on the decision of the dominant final solution. Furthermore, the performance data of each approach often arise from different manufacturers and developers, which usually have some interest in the dispute. Within this paper, we intend to overcome the situation by providing an introductory, neutral overview of the technology linked to lidar imaging systems for autonomous vehicles, and its current state of development. We start with the main single-point measurement principles utilized, which then are combined with different imaging strategies, also described in the paper. An overview of the features of the light sources and photodetectors specific to lidar imaging systems most frequently used in practice is also presented. Finally, a brief section on pending issues for lidar development in autonomous vehicles has been included, in order to present some of the problems which still need to be solved before implementation may be considered as final. The reader is provided with a detailed bibliography containing both relevant books and state-of-the-art papers for further progress in the subject.Peer ReviewedPostprint (published version

Development of high-speed imaging techniques for C. elegans nervous system studies

We report high-speed imaging techniques for C. elegans nervous systems studies. We introduce C. elegans, the main model organism in this dissertation, and neuroscientific and biomedical studies using C. elegans involving calcium imaging, nerve regeneration, and drug screening. We review technologies including confocal microscopy and microfluidic devices used in the neuroscientific and biomedical studies We discuss development of a high-speed laser scanning confocal microscope capable of flexible control of imaging conditions, fast imaging speed, and large field-of-view. We provides the design principles used in the development of the confocal microscope including the optical, electrical, and software implementation, and the details of the confocal microscope we built based on the design principles. We present the performance characterization of the confocal microscope, then a few sample images obtained with the confocal microscope. We present development of time-lapse volumetric confocal imaging of whole animal C. elegans Ca²⁺ dynamics. We provide the design of the time-lapse volumetric confocal imaging system including a microfluidic device to accommodate the whole animal within the field-of-view of the imaging system. We examine the feasibility of the volumetric confocal imaging of a whole animal, and demonstrate imaging of the whole animal C. elegans neurons’ response to NaCl within a 630 × 150 × 25 μm³ volume at 2 Hz rate. We report a high-throughput automated imaging platform for C. elegans nerve regeneration study. We describe the design of the automated imaging platform and the automation flow, and characterizes the performance of the platform. The imaging platform can obtain high-resolution 3D confocal images of 20 animals in 10 minutes. We show sample images of C. elegans anterior lateral microtubule nerve regeneration examples acquired via the automated imaging platform. We demonstrate a planar laser activated neuronal scanning platform (PLANS), a high-throughput animal examination system for drug screening. We explain the construction of PLANS involving the optics, the microfluidic device, and the electronics. The PLANS system can scan an animal in less than 5 ms with a spatial sampling resolution of 3 μm FWHM. We show sample scanning results of a Huntington’s disease model of C. elegans. We summarize the studies discussed in this dissertation, and suggest relevant future research to follow up on the studies.Electrical and Computer Engineerin

Fiber-Bragg-Grating-Based Sensor System to Measure Battery State of Charge Based on a Machine Learning Model

Real-time monitoring of the state of charge (SOC) of the batteries used in a wide variety of applications is becoming increasingly important, especially given the impetus by the current targets towards “net-zero”. In this research, an advanced approach was used involving fiber Bragg grating (FBG)-based sensors that were developed and implemented for the measurement of the key parameters required to ensure optimum battery performance. In this work, one of the biggest challenges to assess (and then map) the data from the sensor system developed is tackled in order to better understand the key parameters of the battery in an efficient and improved way. It is well known that the relationship between the changes in the resonance wavelength of the FBGs used in the sensor system, arising due to change in the electrical parameters of the battery, is complex and dependent on several different factors. In this work, this effect was evaluated by coupling the sensor data to a data-driven regression model approach that was developed for the measurement of the SOC of the batteries used, and this was obtained directly and conveniently from the FBG data. In this comprehensive study, FBG-based sensors were fabricated and then installed onto the battery, which then was subjected to a range of charging–discharging cycles, following which the electrical parameters of the battery were estimated from recorded data using a black-box machine learning (ML) model. Data-driven regression algorithms were employed for the training of the black-box model. The efficiency of the estimation of the SOC of the battery from the FBG-based sensor data was found to be high, at 99.62% (R2 values of Estimated SOC and True SOC line), creating a very satisfactory result for this key measurement. Thus, the work shows the robustness of the FBG-based sensor system combined with the neural network algorithm as an effective way to evaluate the electrical parameters of the battery, which is particularly important, as no physical/electrochemical/electrical model of the system is thus required

Atherosclerosis is associated with a decrease in cerebral microvascular blood flow and tissue oxygenation

Chronic atherosclerosis may cause cerebral hypoperfusion and inadequate brain oxygenation, contributing to the progression of cognitive decline. In this study, we exploited two-photon phosphorescence lifetime microscopy to measure the absolute partial pressure of oxygen (PO2) in cortical tissue in both young and old LDLR-/-, hApoB100+/+ mice, spontaneously developing atherosclerosis with age. Capillary red-blood-cell (RBC) speed, flux, hematocrit and capillary diameter were also measured by two-photon imaging of FITC-labelled blood plasma. Our results show positive correlations between RBC speed, flux, diameter and capillary-adjacent tissue PO2. When compared to the young mice, we observed lower tissue PO2, lower RBC speed and flux, and smaller capillary diameter in the old atherosclerotic mice. The old mice also exhibited a higher spatial heterogeneity of tissue PO2, and RBC speed and flux, suggesting a less efficient oxygen extraction

Neocortical Layer 4 to Layer 2/3 Sensory Information Processing Investigated with Digital-Light-Projection Neuronal Photostimulation

The mammalian brain forms neuronal networks and microcircuits with cell-type- and anatomical-specific synaptic connections. Despite great advances in elucidating the cellular physiology of the nervous system, little is known about the computational processes occurring at the level of neuronal microcircuits. Much success has been reported in describing the synaptic input patterns of many brain regions and cell types using photostimulation systems; however, these systems are severely limited in their ability to study the integration of synaptic input from multiple synchronous or temporally correlated presynaptic locations. Here we describe a system that allows the generation of arbitrary 2-D stimulus patterns with thousands of independently controlled sites to manipulate the activity of populations of neurons with high spatial and temporal precision. The PC-controlled Digital-Light-Processing (DLP) based system updates the 780,000 parallel photostimulation beams, or pixels, at a maximum rate of 13 kHz. With the currently used projection objective, the pixel sizes at the plane of focus are 7.3 µm2 . The high-power UV laser source used in this system provides a light flux density sufficient for bins of 8x8 pixels (21.6 µm x 21.6 µm) with dwell times as low 3 ms to reliably induce action potentials in 2.5 mM MNI-caged glutamate. At these settings the effective diameter of a glutamate uncaging site is \u3c 86 µm, which is equivalent to most other UV photostimulation rigs. With DLP photostimulation, sub-threshold responses and action potentials can be synchronously induced at thousands of sites over a 2.76 mm x 2.07 mm area, a capability unmatched by any other current system. This DLP-based system has the unique capability to investigate normal and diseased circuit properties by investigating neuronal responses to spatiotemporally complex activity patterns. This technique was used to investigate the temporal integration of synaptic input in the whisker barrel cortex of mice. The neocortex is organized into layers, with neuronal networks and circuits formed by layer-specific connections. While the anatomical organization of these circuits has been well characterized, the information processing and coding performed by these ensembles is poorly understood. A key component of this investigation concerns the transmission and transformation of the neuronal representation from one neuronal pool to the next. In the rodent somatosensory barrel cortex, histologically-distinguishable “barrels” in layer 4 (L4) receive principal input from a single whisker. L4 projects to layer II/III (L2/3), where the circuit diverges to multiple postsynaptic targets. Using the DLP-photostimulation system, we modulated the synchronicity of action potentials in L4 cells while recording from L2/3 in an acute slice preparation. This data shows that synchronous activity in L4 neurons is highly effective at eliciting strong spiking responses in L2/3 pyramidal cells, while asynchronous L4 activity fails to drive L2/3 to action-potential threshold. Pharmacological manipulation of the slice-bathing solution has suggested that this phenomenon is AMPA-receptor dependent and modulated by NMDA receptor activity. Intracellular pharmacological manipulations suggest that postsynaptic conductances also play a role in the nonlinear L2/3 synaptic integration of L4 activity

Development of swept, confocally-aligned planar excitation (SCAPE) microscopy for high-speed, volumetric imaging of biological tissue

With the wide-spread adoption of exogenous fluorescent indicators – and more recently genetically encoded fluorescent proteins – over the past two decades, there exists a diverse chemical toolkit with which to probe biological systems. Individual cell types and sub-cellular compartments can be targeted in an increasingly wide range of model organisms. However, imaging these samples is often an exercise in balancing the needs of any given experiment against the constraints of the chosen imaging technology. For example, a volume of brain tissue is host to neurons, glia, vascular compartments and red blood cells that all occupy discrete locations in 3D space, but must work together to support healthy organ function. Single-cell activity on the order of milliseconds can trigger downstream processes that unfold over the course of multiple seconds or even minutes. The development of a technique capable of providing depth-resolved, volumetric imaging with scalable spatiotemporal resolution is crucial to developing a proper understanding of such biological systems. Bottlenecks in the throughput of existing technologies stem from a combination of inefficient illumination and volume acquisition strategies, and insufficient sensor read-out speeds. Light sheet microscopy is a promising solution, but individual designs tend to be highly specialized to specific types of samples and do not easily adapt to a wide range of experimental settings. In this thesis, I detail my work in developing swept, confocally-aligned planar excitation (SCAPE) microscopy from a first-generation prototype into a versatile, easy-to-reproduce, easy-to-use system for high-speed, 3D imaging. The first chapter introduces the challenges of designing optical systems capable of high-speed, volumetric imaging. An introduction to design choices faced in the construction of fluorescence microscopes, and current approaches to 3D imaging are discussed. The second chapter describes the progression from the 1st to 2nd generation SCAPE system. Improvements made through ray-tracing models and an enhanced optomechanical design are described, and results from this system in a number of model organisms are presented. The third chapter presents results from a range of biological applications to which SCAPE microscopy has been applied. Work in imaging the zebrafish heart to demonstrate the system’s improved imaging speed, the C. elegans to show the system’s resolution, and finally a number of examples of large field-of-view and high-resolution structural imaging are all described. Finally, the fourth chapter concludes with an overview of the work that lies ahead to both further develop of SCAPE microscopy, as well as to bring the existing system’s strengths to bear in a wider range of environments

Optical Coherence Tomography and Its Non-medical Applications

Optical coherence tomography (OCT) is a promising non-invasive non-contact 3D imaging technique that can be used to evaluate and inspect material surfaces, multilayer polymer films, fiber coils, and coatings. OCT can be used for the examination of cultural heritage objects and 3D imaging of microstructures. With subsurface 3D fingerprint imaging capability, OCT could be a valuable tool for enhancing security in biometric applications. OCT can also be used for the evaluation of fastener flushness for improving aerodynamic performance of high-speed aircraft. More and more OCT non-medical applications are emerging. In this book, we present some recent advancements in OCT technology and non-medical applications