A transimpedance preamplifier using a feedforward approach for robust rejection of DC photogenerated currents

The preamplifier proposed in this paper is designed to extract weak variable photogenerated signals from a high-level continuous background ensuring low noise and high transimpedance gain. An efficient cancellation of the DC component directly at the photodetector output, exploiting a feedforward approach, allows us to properly amplify the variable signal components of interest avoiding saturation of the preamplifier. Furthermore, the large transimpedance gain allows for minimizing the effects of the noise introduced by the following stages on the signal processing chain. In the paper, we present the proposed approach and a possible circuit realization with a signal AC/DC ratio as small as 1/1000 ensuring low noise, high gain, and a considerable bandwidth. The realized preamplifier offers a Noise Equivalent Power NEP ≃ 1.12 nW, an in-band transimpedance gain of 4.4 MΩ, and a wide bandwidth from about 1 Hz up to 100 kHz, making it suitable for use in several applications both in biomedical and industrial fields

A method for estimating object detection probability, lateral resolution, and errors in 3D-LiDARs

3D-LiDARs are nowadays used for many applications, the success of which certainly depends on the processing of the LiDAR output—the point cloud, PC,—but it also inexorably depends on the quality of the PC data. In this study, we propose an experimental method aimed at allowing estimating the errors and deformations that will statistically affect the LiDAR output — the PC. Taking advantage of the fact that LiDARs sample the surrounding space by observing it along divergent lines, hereinafter referred to as rays, this study proposes a simple method based on the experimental determination of the ray detection probability — the probability that a single ray detects the hit object, or a fraction of it, by adding a point in the point cloud. All other probabilities of interest are derived from such a probability. The proposed method also allows highlighting unexpected errors such as cross-talk. As will be shown by the examples given, due to cross-talk, small objects may be deformed and enlarged on a significantly greater number of points in the PC. Likewise, objects angularly separated by an angle greater than the angular resolution declared by the manufacturer may unexpectedly result in a continuum of points. Such errors may compromise the ability to perform very important tasks such as detection, classification, and tracking of dynamic and static objects, as well as the partition of the scene into drivable and non-drivable regions and the path planning around generic obstacles in 3D space

Assessment of Natural Resources Use for Sustainable Development - DPSIR Framework for Case Studies in Portsmouth and Thames Gateway, U.K.

This chapter reports on the uses of the DPSIR framework to assess the sustainability of the intertidal environments within the two UK case study areas, Portsmouth and Thames Gateway. It focuses on statutory conservation areas dominated by intertidal habitats. Two are located in Portsmouth (Portsmouth and Langstone Harbours) and four in the Thames Gateway (Benfleet Marshes, South Thames Estuary, Medway Estuary and the Swale in the Thames Gateway). Based on the reduction of a number of pressures and impacts observed in recent decades and the improvement of overall environmental quality, all six SSSIs are considered to be sustainable in the short and medium term. In the future, it is possible that the impacts of climate change, especially sea-level rise, might result in further reduction in the area and/or quality of intertidal habitats. Further integration between conservation and planning objectives (both for urban development and management of flood risk) at local level is needed to support the long-term sustainability of intertidal habitats

LiDARs detected signal and Target distance estimation: measurement errors from Target reflectance and multiple echos

The use of LiDARs in automotive is increasingly widespread. In order to operate in a critical environment such as that of mobility, these systems must offer increasingly high performance. In particular, the ability to estimate the position of objects regardless of their reflectance and presence of diffusing backgrounds is a very sought-after feature by manufacturers. In commercial systems various strategies are used to make the measurement as insensitive as possible to these effects, however, it is not possible to fully compensate for the measurement errors caused by them. In this paper, we propose two simple experimental setups to verify the presence of these measurement errors in two scenarios. Moreover, we report the performance of a commercial LiDAR (MRS 6000 by Sick) using certified reflectance standards (Spectralon (R) Diffuse Reflectance Standards, by Labsphere). For this LiDAR, the results obtained show that a logarithmic variation of the reflectance of the target of 1.26-log at a target distance 2.4 m provides incompatible measurements. Furthermore, the presence of a background at a distance shorter than 11 cm, 12 cm and 13 cm respectively with 50 %, 75 % and 99 % reflectance also provides incompatible measurements for a target distance of 1.3 m from the LiDAR

Analysis, Quantification, and Discussion of the Approximations Introduced by Pulsed 3-D LiDARs

Light detection and rangings (LiDARs) are considered essential for the environmental sensing required by most advanced driver assistance system (ADAS), including autonomous driving. This has led to significant investments resulted in the availability of countless measuring systems that are increasingly performing and less expensive. Nevertheless, the extremely high speed of light still leads to a nonnegligible quantization error in the direct time-of-flight (ToF) measure at the base of pulsed LiDARs-the leading technology for automotive applications. Hence, pulsed 3-D LiDARs analyze the surrounding by approximating and deforming it on concentric spheres whose radii are quantized with a quantization step that, for most commercial systems, is on the order of some centimeters. The deformation and error introduced by such quantization can thus he significant. In this study, we point out the approximations and assumptions intrinsic to 3-D LiDARs and propose a measurement procedure that, through the analysis of the fine variations of the target position, allows an accurate investigation of the axial resolution and error-probably among the few limitations still affecting this technology. To the best of our knowledge, this is the first study focused on the detailed analysis of the quantization error in 3-D LiDARs. The proposed method has been tested on one of the most popular 3-D LiDARs, namely the MRS 6000 by Sick. The obtained results revealed for the MRS 6000 a quantization step of about 6 cm (ToF quantization of about 0.4 ns) and an axial error normally distributed with experimental standard deviation of about 30 mm

Comparison of VLP-16 and MRS-1000 LiDAR systems with absolute interferometer

Nowadays, LiDARs hold a relevant place in providing the environmental sensing required by most ADAS. Promoted by such increasing demand, many new manufacturers are emerging and, new LiDARs are continuously made available on the market. If, on the one hand, the availability of LiDARs with increasing performance and reducing cost has brought significant benefits also promoting the spread of such measuring systems in other areas such as industrial controls and agriculture, on the other, it has made it more difficult to extricate in the immense set of LiDARs present on the market today. In response to this growing need for standards and methods capable of comparing the various LiDARs, many international standards and scientific publications are being produced on the subject. In this paper, we continue our work on LiDARs characterization, focusing our attention on comparing the performances of two of the must popular systems - namely, the MRS 1000 by Sick and the VLP 16 by Velodyne. Starting from the analysis of the warm-up time and stability, such a comparison focused on analyzing the axial error of both systems. Such errors have been estimated by exploiting a custom rail system and an absolute interferometer. The obtained results revealed warm-up times of a few tens of minutes and maximum absolute axial errors of a few centimeters in the range [1.5,21] m

Human adipose stromal cells (ASC) for the regeneration of injured cartilage display genetic stability after in vitro culture expansion

Mesenchymal stromal cells are emerging as an extremely promising therapeutic agent for tissue regeneration due to their multi-potency, immune-modulation and secretome activities, but safety remains one of the main concerns, particularly when in vitro manipulation, such as cell expansion, is performed before clinical application. Indeed, it is well documented that in vitro expansion reduces replicative potential and some multi-potency and promotes cell senescence. Furthermore, during in vitro aging there is a decrease in DNA synthesis and repair efficiency thus leading to DNA damage accumulation and possibly inducing genomic instability. The European Research Project ADIPOA aims at validating an innovative cell-based therapy where autologous adipose stromal cells (ASCs) are injected in the diseased articulation to activate regeneration of the cartilage. The primary objective of this paper was to assess the safety of cultured ASCs. The maintenance of genetic integrity was evaluated during in vitro culture by karyotype and microsatellite instability analysis. In addition, RT-PCR array-based evaluation of the expression of genes related to DNA damage signaling pathways was performed. Finally, the senescence and replicative potential of cultured cells was evaluated by telomere length and telomerase activity assessment, whereas anchorage-independent clone development was tested in vitro by soft agar growth. We found that cultured ASCs do not show genetic alterations and replicative senescence during the period of observation, nor anchorage-independent growth, supporting an argument for the safety of ASCs for clinical use

A simple method for the preliminary analysis and benchmarking of automotive LiDARs in fog

The vast multitude of LiDAR systems currently available on the market makes the need for methods to compare their performances increasingly high. In this study, we focus our attention on the development of a method for the analysis of the effects induced by the fog, one of the main challenges for Advanced Driver Assist Systems (ADASs) and autonomous driving. Large experimental setups capable of reconstructing adverse weather conditions on a large scale in a controlled and repeatable way are certainly the best test conditions to analyze and compare LiDARs performances in the fog. Nonetheless, such large plants are extremely expensive and complex, therefore only available in a few sites in the world. In this study, we thus propose a measurement method, a data analysis procedure and, an experimental setup that are extremely simple and inexpensive to implement. The achievable results are reasonably less accurate than those obtainable with large plants. Nevertheless, the proposed method can allow to easily and quickly obtain a preliminary estimate of the performance in the presence of fog and a rapid benchmarking of different LiDAR systems

Potentialities of the combined use of underwater fluorescence imagery and photogrammetry for the detection of fine-scale changes in marine bioconstructors

Marine communities are facing both natural disturbances and anthropogenic stressors. Bioconstructor species are endangered by multiple large-scale and local pressures and the early identification of impacts and damages is a primary goal for preserving coral reefs. Taking advantage of the recent development in underwater photogrammetry, the use of photogrammetry and fluorimetry was coupled to design, test and validate in laboratory a multi-sensor measuring system that could be potentially exploited in open water by SCUBA divers for assessing the health status of corals and detecting relevant biometric parameters with high accuracy and resolution. The approach was tested with fragments of the endemic coral Cladocora caespitosa, the sole zooxanthellate scleractinian reef-builder in the Mediterranean. The most significant results contributing to the scientific advancement of knowledge were: 1) the development of a cost-effective, flexible and easy-to-use approach based on emerging technologies; 2) the achievement of a sub-centimetric resolution for measuring relevant biometric parameters (polyp counting, colony surface areas and volumes); 3) set up of a reliable and repeatable strategy for multi-temporal analyses capable of quantifying changes in coral morphology with sub-centimeter accuracy; 4) detect changes in coral health status at a fine scale and under natural lighting through autofluorescence analysis. The novelty of the present research lies in the coupling of emerging techniques that could be applied to a wide range of 3D morphometrics, different habitats and species, thus paving the way to innovative opportunities in ecological research and more effective results than traditional in-situ measurements. Moreover, the possibility to easily modify the developed system to be installed on an underwater remotely operated vehicle further highlights the possible concrete impact of the research for ecological monitoring and protection purposes