Background Illumination Conditions Research Articles

Observation of meteors from space with the Mini-EUSO detector on board the International Space Station

Context. Observations of meteors in the Earth’s atmosphere offer a unique tool for determining the flux of meteoroids that are too small to be detected by direct telescopic observations. Although these objects are routinely observed from ground-based facilities, such as meteor and fireball networks, space-based instruments come with notable advantages and have the potential to achieve a broad and uniform exposure. Aims. In this paper, we describe the first observations of meteor events with Mini-EUSO, a very wide field-of-view telescope launched in August 2019 from the Baikonur cosmodrome and installed on board the Russian Zvezda module of the International Space Station. Mini-EUSO can map the night-time Earth in the near-UV range (290-130 nm) with a field of view equal to 44° × 44° and a spatial resolution of about 4.7 km at an altitude of 100 km from the ground. The detector saves triggered transient phenomena with a sampling frequency of 2.5 µs and 320 µs, as well as a continuous acquisition at 40.96 ms scale that is suitable for meteor observations. Methods. We designed two dedicated and complementary trigger methods, together with an analysis pipeline able to estimate the main physical parameters of the observed population of meteors, such as the duration, horizontal speed, azimuth, and absolute magnitude. To compute the absolute flux of meteors from Mini-EUSO observations, we implemented a simulation framework able to estimate the detection efficiency as a function of the meteor magnitude and the background illumination conditions. Results. The instrument detected 24 thousand meteors within the first 40 data-taking sessions from November 2019 to August 2021, for a total observation time of approximately 6 days with a limiting absolute magnitude of +6. Our estimation of the absolute flux density of meteoroids in the range of mass between 10−5 kg to 10−1 kg was found to be comparable to other results available in the literature. Conclusions. The results of this work prove the potential for space-based observations to increase the statistics of meteor observations achievable with instruments operating on the ground. The slope of the mass distribution of meteoroids sampled with Mini-EUSO suggests a mass index of either s = 2.09 ± 0.02 or s = 2.31 ± 0.03, according to two different methodologies for the computation of the pre-atmospheric mass starting from the luminosity of each event.

Deep-learning blurring correction of images obtained from NIR single-pixel imaging.

In challenging scenarios characterized by low-photon conditions or the presence of scattering effects caused by rain, fog, or smoke, conventional silicon-based cameras face limitations in capturing visible images. This often leads to reduced visibility and image contrast. However, using near-infrared (NIR) light within the range of 850-1550nm offers the advantage of reduced scattering by microparticles, making it an attractive option for imaging in such conditions. Despite NIR's advantages, NIR cameras can be prohibitively expensive. To address this issue, we propose a vision system that leverages NIR active illumination single-pixel imaging (SPI) operating at 1550nm combined with time of flight operating at 850nm for 2D image reconstruction, specifically targeting rainy conditions. We incorporate diffusion models into the proposed system to enhance the quality of NIR-SPI images. By simulating various conditions of background illumination and droplet size in an outdoor laboratory scenario, we assess the feasibility of utilizing NIR-SPI as a vision sensor in challenging outdoor environments.

Investigation of the Optical Communication Channel Throughput of an Information Receiver in the Form of a Silicon Photomultiplier Tube under Conditions of Background Illumination

Investigation of the Optical Communication Channel Throughput of an Information Receiver in the Form of a Silicon Photomultiplier Tube under Conditions of Background Illumination

Investigation of the optical communication channel throughput of an information receiver in the form of a silicon photomultiplier tube under conditions of background illumination

Investigation of the optical communication channel throughput of an information receiver in the form of a silicon photomultiplier tube under conditions of background illumination

Deep UV Sensors Enabling Solar-Blind Flame Detectors for Large-Area Applications

Large-area compatible, solar-blind deep-ultraviolet sensors based on active pixels are demonstrated with CMOS amplifiers based on poly-Si thin-film transistors and Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> thin-film photoresistors. The active pixel configuration sensor enables approximately 40X higher responsivity compared to a discrete sensor, and the CMOS inverter amplifier exhibits a gain of 210 V/V. The Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> -based sensors were integrated on the same substrate depositing the films using magnetron sputtering at room temperature, ensuring its compatibility with large-area applications. The responsivity of discrete Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> sensors was evaluated at different wavelengths in the deep-ultraviolet and visible ranges, and showed a maximum responsivity of 51 A/W for a wavelength of 232 nm, with a deep-ultraviolet to visible light rejection ratio of approximately 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The active pixel sensor was implemented as flame detector resulting in an output voltage signal of up to 2 V when the system was exposed to a flame under regular background illumination conditions.

Energy-Efficient Image Recognition System for Marine Life

This article focuses on designing an energy-efficient image recognition system for marine monitoring. One of the main challenges of an underwater imaging system is the strict power consumption constraints due to the limited on-site resources. Considering the need for continuous operation in different water turbidity levels and background illumination conditions, an energy-efficient approach is needed for the effective utilization of the resources. In this work, we propose a recognition framework that will adaptively adjust the system parameters, such as camera frame rate and LED illumination level, based on the environmental conditions to optimize the energy consumption while ensuring a high recognition accuracy. The first part of the proposed decision system contains the convolutional neural network (CNN)-based animal recognition block which is used for obtaining the confidence level for a single frame. The second part is the adaptive decision block that dynamically changes the system parameters and combines the results of the recognition block for multiple frames based on the environmental conditions. In our experiments, we have used nearly 8000 underwater images for training and testing the single frame recognition block and used nearly 200 different video sequences for training and testing the adaptive decision block. Based on measurements of a hardware framework composed of a Raspberry Pi 3 Model B, a Pi NoIR Camera v2.1, and 850 nm LEDs, the proposed system achieves up to 92.7% energy savings with a comparable recognition performance by dynamically changing the frame rate and emitted light intensity based on water turbidity and background illumination level.

An open-source high-speed infrared videography database to study the principles of active sensing in freely navigating rodents.

BackgroundActive sensing is crucial for navigation. It is characterized by self-generated motor action controlling the accessibility and processing of sensory information. In rodents, active sensing is commonly studied in the whisker system. As rats and mice modulate their whisking contextually, they employ frequency and amplitude modulation. Understanding the development, mechanisms, and plasticity of adaptive motor control will require precise behavioral measurements of whisker position.FindingsAdvances in high-speed videography and analytical methods now permit collection and systematic analysis of large datasets. Here, we provide 6,642 videos as freely moving juvenile (third to fourth postnatal week) and adult rodents explore a stationary object on the gap-crossing task. The dataset includes sensory exploration with single- or multi-whiskers in wild-type animals, serotonin transporter knockout rats, rats received pharmacological intervention targeting serotonergic signaling. The dataset includes varying background illumination conditions and signal-to-noise ratios (SNRs), ranging from homogenous/high contrast to non-homogenous/low contrast. A subset of videos has been whisker and nose tracked and are provided as reference for image processing algorithms.ConclusionsThe recorded behavioral data can be directly used to study development of sensorimotor computation, top-down mechanisms that control sensory navigation and whisker position, and cross-species comparison of active sensing. It could also help to address contextual modulation of active sensing during touch-induced whisking in head-fixed vs freely behaving animals. Finally, it provides the necessary data for machine learning approaches for automated analysis of sensory and motion parameters across a wide variety of signal-to-noise ratios with accompanying human observer-determined ground-truth.

Deep Raman spectroscopy for the non-invasive standoff detection of concealed chemical threat agents

Deep Raman spectroscopy has been utilized for the standoff detection of concealed chemical threat agents from a distance of 15m under real life background illumination conditions. By using combined time and space resolved measurements, various explosive precursors hidden in opaque plastic containers were identified non-invasively. Our results confirm that combined time and space resolved Raman spectroscopy leads to higher selectivity towards the sub-layer over the surface layer as well as enhanced rejection of fluorescence from the container surface when compared to standoff spatially offset Raman spectroscopy. Raman spectra that have minimal interference from the packaging material and good signal-to-noise ratio were acquired within 5s of measurement time. A new combined time and space resolved Raman spectrometer has been designed with nanosecond laser excitation and gated detection, making it of lower cost and complexity than picosecond-based laboratory systems.

Identification of POMC processing products in single melanotrope cells by matrix-assisted laser desorption/ionization mass spectrometry

The use of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) in identifying proopiomelanocortin (POMC) processing products in melanotrope cells of the pituitary intermediate lobe of Xenopus laevis was explored. Mass spectra were obtained with such a high sensitivity of detection that the peptides could be identified in a single melanotrope cell. In addition to known POMC processing products of the Xenopus melanotrope cell, t he presence of previously unidentified POMC-derived peptides was demonstrated. Together these POMC processing products accounted for the entire length of the POMC precursor. Furthermore, Xenopus possesses two genes for POMC and the sensitivity and accuracy of the MALDI-MS technique allowed identification of processing products of both the POMC A and POMC B gene. In addition, differences were obtained between the mass spectra of melanotrope cells from Xenopus laevis adapted to different conditions of background illumination. These results show that MALDI-MS is a valuable tool in the study of the expression of peptides in single (neuroendocrine) cells.

Rapid, Blue‐Light Induced Transpiration in Avena

AbstractThe transpiration responses of primary Avena leaves to blue‐light pulses were investigated. Only light with wave length shorter than 524 nm can produce the rapid transpiration response. The action spectrum has a maximum around 450 nm. The rapid transpiration response induced by blue‐light pulses successively disappeared in long‐term experiments if the plant was kept in darkness between the pulses. However, if visible light was given to the plant between the pulses, the rapid response was restored.The magnitude of the rapid transpiration response was investigated under different conditions of background illumination and blue‐light exposure. Saturation of the response was obtained with an irradiation level of 1.5–2 mW.cm−2 (5 min pulses) and with a pulse duration of 4 min (pulse irradiance 2 mW.cm−2). A pulse duration of 3 s was sufficient to produce a significant rapid response at an irradiation level of 2 mW.cm−2.

Experimental determination of the maximum permissible exposure to picosecond laser pulses of 1.06 μ wavelength

The maximum permissible (from the point of view of safety) exposure to laser radiation pulses of 1.06 μ wavelength was determined experimentally. In the case of 100 psec pulses under conditions of moderate background illumination (pupil diameter 5.5 mm) the safe energy density on the cornea of the human eye was Hs=1.5×10−5J/cm2. In the case of a train of thirteen 100-psec pulses separated by intervals of 10 nsec the corresponding value, obtained under the same background illumination conditions, was Hs=2.6×10−5J/cm2.

The effects of fluorescent and incandescent illumination upon repetitive behaviors in autistic children

Repetitive behaviors of six autistic children were observed under two conditions of background illumination. During two sessions, the room was illuminated by fluorescent light and during two other sessions, by equal intensity incandescent light. Subjects spent significantly more time engaged in repetitive behavior under fluorescent light. Previous research suggested that these findings were related to the flickering nature of fluorescent ilumination. Practical and theoretical implications were discussed. Further experimentation was suggested to assess relationships between flickering illumination and arousal.

Single Photon Detection and Timing in the Lunar Laser Ranging Experiment

The goals of the Lunar Laser Ranging Experiment lead to the need for the measurement of a 2.5 sec time interval to an accuracy of a nanosecond or better. The systems analysis which included practical retroreflector arrays, available laser systems, and large telescopes led to the necessity of single photon detection. Operation under all background illumination conditions required auxiliary range gates and extremely narrow spectral and spatial filters in addition to the effective gate provided by the time resolution. Nanosecond timing precision at relatively high detection efficiency was obtained using the RCA C31000F photomultiplier and Ortec 270 constant fraction of pulse-height timing discriminator. The timing accuracy over the 2.5 sec interval was obtained using a digital interval with analog vernier ends. Both precision and accuracy are currently checked internally using a triggerable, nanosecond light pulser. Future measurements using sub-nanosecond laser pulses will be limited by the time resolution of single photon detectors.

EFFECTS OF INTERMITTENT VISUAL INPUT DISRUPTION, FLICKER-RATE, AND WORK TIME ON TRACKING PERFORMANCE AND ACTIVATION LEVEL.

The effects of flicker-rate (0 to 24 cps) on rotary tracking performance and physiological “indicants” of activation level were studied under two conditions of background illumination (illuminated and non-illuminated). During the illuminated condition the target was visible between flashes (continuously), whereas during the non-illuminated condition it was visible only during the flash. Muscle tension of the neck and forearm flexor muscles, skin conductance, and heart rate were used as indicants of activation level. Tracking performance varied significantly with flicker-rate and illumination level. During the illuminated condition, performance decreased then increased as flicker-rate increased, the low point being at about 9 cps. During the non-illuminated background condition, performance increased rapidly as flicker-rate was increased up to 9 cps. Further increases had relatively slight effects on tracking performance. The physiological indicants remained essentially constant when flicker-rate was varied, indicating no change in activation level. The performance data were interpreted in terms of a “psychological moment” model.