Showing papers on "Night vision published in 2020"

Organic photodiodes and phototransistors toward infrared detection: materials, devices, and applications

Abstract: Because of their advantages, including easy tunability of optical and electrical properties by tailoring the molecular structure, flexibility, and compatibility with a low-temperature fabricating process, the use of organic semiconductors (OSCs) as active layers has shown strong competitiveness as candidates for use in next-generation high-sensitivity organic photodetectors (OPDs). Infrared (IR) OPDs that are sensitive to illumination at wavelengths higher than 780 nm have been rapidly developed in recent years driven by potential applications such as remote control, night vision, and imaging as well as biomedical monitoring. In this review, after a brief illustration of the mechanisms, we summarize the recent advances in high-performance IR organic photodiodes (OPDIs) and organic phototransistors (OPTs). We will highlight the state-of-the-art protocols for constructing qualified IR OPDs, including new OSCs with excellent photoelectric properties, optimization of active-layer-fabrication processes, and novel device architectures. Thereafter, we will discuss the IR organic light detector as a platform for integrated applications, such as health monitoring, spectrometric analysis, and electronic eyes. This review aims to provide readers with a deeper understanding of the design of future IR OPDs and IR-OPD-based integrated practices.

2D materials beyond graphene toward Si integrated infrared optoelectronic devices.

Abstract: Since the discovery of graphene in 2004, it has become a worldwide hot topic due to its fascinating properties. However, the zero band gap and weak light absorption of graphene strictly restrict its applications in optoelectronic devices. In this regard, semiconducting two-dimensional (2D) materials are thought to be promising candidates for next-generation optoelectronic devices. Infrared (IR) light has gained intensive attention due to its vast applications, including night vision, remote sensing, target acquisition, optical communication, etc. Consequently, the generation, modulation, and detection of IR light are crucial for practical applications. Due to the van der Waals interaction between 2D materials and Si, the lattice mismatch of 2D materials and Si can be neglected; consequently, the integration process can be achieved easily. Herein, we review the recent progress of semiconducting 2D materials in IR optoelectronic devices. Firstly, we introduce the background and motivation of the review. Then, the suitable materials for IR applications are presented, followed by a comprehensive review of the applications of 2D materials in light emitting devices, optical modulators, and photodetectors. Finally, the problems encountered and further developments are summarized. We believe that milestone investigations of IR optoelectronics based on 2D materials beyond graphene will emerge soon, which will bring about great industrial revelations in 2D material-based integrated nanodevice commercialization.

Light-emitting diodes: brighter NIR-emitting phosphor making light sources smarter.

Abstract: A brighter near-infrared (NIR) phosphor is achieved by inhibiting the oxidation of Cr3+ and reducing the surface defects of phosphor particles, enabling the realization of smarter and more sensitive light sources for night vision.

Broadband near-infrared emission of La3Ga5GeO14:Tb3+,Cr3+ phosphors: energy transfer, persistent luminescence and application in NIR light-emitting diodes

Abstract: A La3Ga5GeO14:Tb3+,Cr3+ near-infrared phosphor with high efficiency was prepared by a high-temperature solid-state method. The synthesized samples were analyzed by X-ray diffraction (XRD), diffuse reflectance spectroscopy, photoluminescence spectroscopy (PL&PLE), fluorescence decay curves and temperature dependent photoluminescence spectroscopy. Due to the highly efficient energy transfer from Tb3+ to Cr3+ ions, at an excitation wavelength of 373 nm, all La3Ga5GeO14:Tb3+,Cr3+ samples show strong emission bands in the range of 400–1300 nm, and the optimal doping concentration is under the conditions of x = 2.5 mol% and y = 1.4 mol%. In addition, the La2.975Ga4.986GeO14:0.025Tb3+,0.014Cr3+ phosphor showed excellent thermal stability, and the emission intensity at 423 K maintained 62% of the original value at 298 K. NIR pc-LED devices were prepared by combining a La2.975Ga4.986GeO14:0.025Tb3+,0.014Cr3+ phosphor with a 460 nm blue light emitting chip. Photoluminescence with a total output power of 3.018 mW could be achieved at a driving current of 160 mA, indicating the potential application in night vision lighting.

Ultralow-Transition-Energy Organic Complex on Graphene for High-Performance Shortwave Infrared Photodetection

Abstract: Room-temperature, high-sensitivity, and broadband photodetection up to the shortwave infrared (SWIR) region is extremely significant for a wide variety of optoelectronic applications, including contamination identification, thermal imaging, night vision, agricultural inspection, and atmospheric remote sensing. Small-bandgap semiconductor-based SWIR photodetectors generally require deep cooling to suppress thermally generated charge carriers to achieve increased sensitivity. Meanwhile, the photogating effect can provide an alternative way to achieve superior photosensitivity without the need for cooling. The optical photogating effect originates from charge trapping of photoinduced carriers at defects or interfaces, resulting in an extremely high photogain (106 or higher). Here, a highly sensitive SWIR hybrid photodetector, fabricated by integrating an organic charge transfer complex on a graphene transistor, is reported. The organic charge transfer complex (tetrathiafulvalene-chloranil) has an exceptional low-energy intermolecular electronic transition down to 0.5 eV, with the aim of achieving efficient SWIR absorption for wavelengths greater than 2 µm. The photogating effect at the organic complex and graphene interface enables an extremely high photogain and a high detectivity of ≈1013 Jones, along with a response time of 8 ms, at room temperature for a wavelength of 2 µm.

Asymmetric electrode incorporated 2D GeSe for self-biased and efficient photodetection.

Abstract: 2D layered germanium selenide (GeSe) with p-type conductivity is incorporated with asymmetric contact electrode of chromium/Gold (Cr/Au) and Palladium/Gold (Pd/Au) to design a self-biased, high speed and an efficient photodetector. The photoresponse under photovoltaic effect is investigated for the wavelengths of light (i.e. ~220, ~530 and ~850 nm). The device exhibited promising figures of merit required for efficient photodetection, specifically the Schottky barrier diode is highly sensitive to NIR light irradiation at zero voltage with good reproducibility, which is promising for the emergency application of fire detection and night vision. The high responsivity, detectivity, normalized photocurrent to dark current ratio (NPDR), noise equivalent power (NEP) and response time for illumination of light (~850 nm) are calculated to be 280 mA/W, 4.1 × 109 Jones, 3 × 107 W-1, 9.1 × 10-12 WHz-1/2 and 69 ms respectively. The obtained results suggested that p-GeSe is a novel candidate for SBD optoelectronics-based technologies.

Making of Night Vision: Object Detection Under Low-Illumination

Abstract: Object detection has so far achieved great success. However, almost all of current state-of-the-art methods focus on images with normal illumination, while object detection under low-illumination is often ignored. In this paper, we have extensively investigated several important issues related to the challenge low-illumination detection task, such as the importance of illumination on detection, the applicabilities of illumination enhancement on low-illumination object detection task, and the influences of illumination balanced dataset and model's parameters initialization, etc. We further have proposed a Night Vision Detector (NVD) with specifically designed feature pyramid network and context fusion network for object detection under low-illuminance. Through conducting comprehensive experiments on a public real low-illuminance scene dataset ExDARK and a selected normal-illumination counterpart COCO*, we on one hand have reached some valuable conclusions for reference, on the other hand, have found specific solutions for low-illumination object detection. Our strategy improves detection performance by 0.5%~2.8% higher than basic model on all standard COCO evaluation criterions. Our work can be taken as effective baseline and shed light to future studies on low-illumination detection.

Homeostatic plasticity in the retina is associated with maintenance of night vision during retinal degenerative disease.

Abstract: Neuronal plasticity of the inner retina has been observed in response to photoreceptor degeneration. Typically, this phenomenon has been considered maladaptive and may preclude vision restoration in the blind. However, several recent studies utilizing triggered photoreceptor ablation have shown adaptive responses in bipolar cells expected to support normal vision. Whether such homeostatic plasticity occurs during progressive photoreceptor degenerative disease to help maintain normal visual behavior is unknown. We addressed this issue in an established mouse model of Retinitis Pigmentosa caused by the P23H mutation in rhodopsin. We show robust modulation of the retinal transcriptomic network, reminiscent of the neurodevelopmental state, and potentiation of rod - rod bipolar cell signaling following rod photoreceptor degeneration. Additionally, we found highly sensitive night vision in P23H mice even when more than half of the rod photoreceptors were lost. These results suggest retinal adaptation leading to persistent visual function during photoreceptor degenerative disease.

Network Architecture of Gap Junctional Coupling among Parallel Processing Channels in the Mammalian Retina

Abstract: Gap junctions are ubiquitous throughout the nervous system, mediating critical signal transmission and integration, as well as emergent network properties. In mammalian retina, gap junctions within the Aii amacrine cell-ON cone bipolar cell (CBC) network are essential for night vision, modulation of day vision, and contribute to visual impairment in retinal degenerations, yet neither the extended network topology nor its conservation is well established. Here, we map the network contribution of gap junctions using a high-resolution connectomics dataset of an adult female rabbit retina. Gap junctions are prominent synaptic components of ON CBC classes, constituting 5%-25% of all axonal synaptic contacts. Many of these mediate canonical transfer of rod signals from Aii cells to ON CBCs for night vision, and we find that the uneven distribution of Aii signals to ON CBCs is conserved in rabbit, including one class entirely lacking direct Aii coupling. However, the majority of gap junctions formed by ON CBCs unexpectedly occur between ON CBCs, rather than with Aii cells. Such coupling is extensive, creating an interconnected network with numerous lateral paths both within, and particularly across, these parallel processing streams. Coupling patterns are precise with ON CBCs accepting and rejecting unique combinations of partnerships according to robust rulesets. Coupling specificity extends to both size and spatial topologies, thereby rivaling the synaptic specificity of chemical synapses. These ON CBC coupling motifs dramatically extend the coupled Aii-ON CBC network, with implications for signal flow in both scotopic and photopic retinal networks during visual processing and disease.SIGNIFICANCE STATEMENT Electrical synapses mediated by gap junctions are fundamental components of neural networks. In retina, coupling within the Aii-ON CBC network shapes visual processing in both the scotopic and photopic networks. In retinal degenerations, these same gap junctions mediate oscillatory activity that contributes to visual impairment. Here, we use high-resolution connectomics strategies to identify gap junctions and cellular partnerships. We describe novel, pervasive motifs both within and across classes of ON CBCs that dramatically extend the Aii-ON CBC network. These motifs are highly specific with implications for both signal processing within the retina and therapeutic interventions for blinding conditions. These findings highlight the underappreciated contribution of coupling motifs in retinal circuitry and the necessity of their detection in connectomics studies.

Deep Learning Thermal Image Translation for Night Vision Perception

Abstract: Context enhancement is critical for the environmental perception in night vision applications, especially for the dark night situation without sufficient illumination. In this article, we propose a thermal image translation method, which can translate thermal/infrared (IR) images into color visible (VI) images, called IR2VI. The IR2VI consists of two cascaded steps: translation from nighttime thermal IR images to gray-scale visible images (GVI), which is called IR-GVI; and the translation from GVI to color visible images (CVI), which is known as GVI-CVI in this article. For the first step, we develop the Texture-Net, a novel unsupervised image translation neural network based on generative adversarial networks. Texture-Net can learn the intrinsic characteristics from the GVI and integrate them into the IR image. In comparison with the state-of-the-art unsupervised image translation methods, the proposed Texture-Net is able to address some common challenges, e.g., incorrect mapping and lack of fine details, with a structure connection module and a region-of-interest focal loss. For the second step, we investigated the state-of-the-art gray-scale image colorization methods and integrate the deep convolutional neural network into the IR2VI framework. The results of the comprehensive evaluation experiments demonstrate the effectiveness of the proposed IR2VI image translation method. This solution will contribute to the environmental perception and understanding in varied night vision applications.

Low frequency noise-dark current correlations in HgCdTe infrared photodetectors.

Abstract: In this paper, low frequency noise and dark current correlation is investigated as a function of reverse bias and temperature for short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR) HgCdTe homo-junction photodetectors. Modelling of dark current-voltage characteristics shows that the detectors have ohmic-behavior under small reverse bias, thus enabling further analysis of 1/f noise-current dependences with the empirical square-law relation (SI ∼ I2) at different temperature regions. It is found that for the SWIR and MWIR devices, the total 1/f noise spectral density at arbitrary temperatures can be modelled by the sum of shunt and generation-recombination noise as SI(T,f)=[αSHISH2(T)+αG−RIG−R2(T)]/f, with no contribution from the diffusion component observed. On the other hand, for the LWIR device the diffusion component induced 1/f noise that cannot be overlooked in high temperature regions, and a 1/f noise-current correlation of SI(T,f)={αs[IDIFF2(T)+IG−R2(T)]+αSHISH2(T)}/f is proposed, with a shared noise coefficient of αs ≅ 1 × 10−9 which is close to that calculated for shunt noise. The 1/f noise-current correlation established in this work can provide a powerful tool to study the low frequency noise characteristics in HgCdTe-based photodetectors and to help optimizing the “true” detectivity of devices operating at low frequency regime.

Progress in and Outlook for Cryogenic Microcooling

Abstract: Semiconductor-based devices in various fields such as night vision, space exploration, medical inspection, telecommunication, among others could benefit from operating at cryogenic temperatures. Besides, cryogenic temperatures also can offer some unique capabilities to superconducting devices, which are not available at ambient temperature. However, existing cryocoolers are oversized in terms of size and cooling power. Widespread use of these electronic devices requires cryocoolers that are small, low cost, low interference, and reliable. This review presents an overview of cooling cycles and discusses the opportunities and difficulties when adopting these cycles for realizing cryogenic temperatures above 1 K in microscale. It is found by comparison that, at present, fluid-based cryocoolers are more suitable for miniaturization. Concerning the miniaturization of fluid-based cryocoolers, emphasis is put on the effect that scaling has on the gross and net cooling power and on various parasitic losses, the microscale manufacturing technologies, and the state of the art of microcoolers. Some aspects that remain to be further developed for widespread use of cryogenic microcooling, are considered at the end of this review.

Embedded Night-Vision System for Pedestrian Detection

Abstract: Assistive vision-based solutions for the driver extend the capabilities of human vision and support safe travel. Unfortunately, their widespread usage is generally limited to expensive cars. Interestingly, a high price is most likely a derivative of the costs incurred in the research instead of the value of hardware components. In the article we show that a mobile system for pedestrian detection in severe lighting conditions can be build using state of the art algorithms and widely available hardware. The proposed night-vision system for pedestrian detection processes thermal images using a proprietary ODROID XU4 microcomputer under Ubuntu MATE operating system. We applied a cascade object detector for the task of human silhouette detection in context of thermal imagery and contrasted the results with the state of the art deep learning approach. The experiments conducted prove effectiveness of the proposed solution.

Validation of a Vision-Guided Mobility Assessment for RPE65-Associated Retinal Dystrophy.

Abstract: Purpose To validate a vision-guided mobility assessment for individuals affected by RPE65-associated retinal dystrophy (RPE65-RD). Methods In this comparative cross-sectional study, 29 subjects, comprising 19 subjects with RPE65-RD and 10 normally-sighted subjects undertook three assessments of mobility: following a straight line, navigating a simple maze, and stepping over a sidewalk "kerb." Performance was quantified as the time taken to complete each assessment, number of errors made, walking speed, and percent preferred walking speed, for each assessment. Subjects also undertook assessments of visual acuity, contrast sensitivity, full-field static perimetry, and age-appropriate quality of life questionnaires. To identify the most relevant metric to quantify vision-guided mobility, we investigated repeatability, as well as convergent, discriminant, and criterion validity. We also measured the effect of illumination on mobility. Results Walking speed through the maze assessment best discriminated between RPE65-RD and normally-sighted subjects, with both convergent and discriminant validity. Walking speed also approached statistical significance when assessed for criterion validity (P = 0.052). Subjects with RPE65-RD had quantifiably poorer mobility at lower illumination levels. A relatively small mean difference (-0.09 m/s) was identified in comparison to a relatively large repeatability coefficient (1.10 m/s). Conclusions We describe a novel, quantifiable, repeatable, and valid assessment of mobility designed specifically for subjects with RPE65-RD. The assessment is sensitive to the visual impairment of individuals with RPE65-RD in low illumination, identifies the known phenotypic heterogeneity and will furthermore provide an important outcome measure for RPE65-RD. Translational relevance This assessment of vision-guided mobility, validated in a dedicated cohort of subjects with RPE65-RD, is a relevant and quantifiable outcome measure for RPE65-RD.

Recent Progress in Emerging Near-Infrared Emitting Materials for Light-Emitting Diode Applications

Abstract: In view of the wide applications of near-infrared (NIR) light in night vision, security, medicine, sensors, telecommunications, and military applications, and the scarcity of high-efficiency NIR-emitting materials, development of alternative NIR-emitting materials is urgently required. In this review, we focus on three kinds of emerging NIR-emitting materials used in light-emitting diodes (LEDs), namely organic materials, inorganic quantum dot (QD) materials, and organic–inorganic hybrid perovskite materials; the corresponding devices are organic LEDs, QD LEDs, and perovskite LEDs. The advantages and disadvantages of the three kinds of materials are discussed, some representative works are reviewed, and a brief outlook for these materials is provided.

A hybridized local and charge transfer excited state for solution-processed non-doped green electroluminescence based on oligo(p-phenyleneethynylene)

Abstract: We herein report a new highly efficient green emissive hot-exciton molecule, 1,4-bis((4′-diphenylamino-3-cyano-[1,1′-biphenyl]-4-yl)ethynyl)-2,5-bis(2-ethylhexyloxy)benzene (2EHO-TPA-CNPE) that consists of an extended D′–π′–A–π–D–π–A–π′–D′ molecular π-system with diphenylamino end units (D′) and ethynylene/phenylene spacers (π/π′). The new molecule exhibits high photoluminescence (PL) quantum efficiencies (ΦPL = 0.95 (solution) and 0.45 (spin-coated neat thin-film)), and a strong PL solvatochromic behavior revealing significant changes in excited state energies/characteristics (locally excited (LE) → hybridized local and charge transfer (HLCT) → charge-transfer (CT)) depending on solvent polarity. Highly efficient (radiative exciton yield (ηr) = 50–59% ≫ 25%) green-emitting OLEDs were fabricated in a conventional device architecture by employing (non-)doped thin-films reaching a maximum current efficiency (CEmax) of 12.0 cd A−1 and a maximum external quantum efficiency (EQEmax) of 5.5%. The emission profile of the non-doped OLED has CIE 1976 (u′, v′) chromaticity coordinates of (0.10, 0.55) corresponding to a night vision imaging system (NVIS) compatible Green A region. 2EHO-TPA-CNPE-based OLED devices of industrial relevance were also fabricated by ink-jet printing the emissive layer and by fabricating an inverted architecture, which possessed respectable device performances of 2.4–6.1 cd A−1. The solid-state solvation effect in OLED devices yields HLCT electronic behavior resulting in high ηr's, which is confirmed by TDDFT to originate from energetically/spatially favorable reverse intersystem crossings (RISCs) (T2/3 → S1). As a unique observation, delayed fluorescence due to this RISC was evident in the PL decay lifetime measurement with a ns-scale lifetime of ∼10 ns. These results clearly allow a better understanding of the structure–photophysical property–electroluminescence relationships in this new class of oligo(p-phenyleneethynylene)-based hot-exciton molecules, and it could open up new opportunities for high-performance solution-processed optoelectronic/sensing applications.

Ignoring correlated activity causes a failure of retinal population codes.

Abstract: From starlight to sunlight, adaptation alters retinal output, changing both the signal and noise among populations of retinal ganglion cells (RGCs). Here we determine how these light level-dependent changes impact decoding of retinal output, testing the importance of accounting for RGC noise correlations to optimally read out retinal activity. We find that at moonlight conditions, correlated noise is greater and assuming independent noise severely diminishes decoding performance. In fact, assuming independence among a local population of RGCs produces worse decoding than using a single RGC, demonstrating a failure of population codes when correlated noise is substantial and ignored. We generalize these results with a simple model to determine what conditions dictate this failure of population processing. This work elucidates the circumstances in which accounting for noise correlations is necessary to take advantage of population-level codes and shows that sensory adaptation can strongly impact decoding requirements on downstream brain areas. To see during day and night, the retina adapts to a trillion-fold change in light intensity. The authors show that an accurate read-out of retinal signals over this intensity range requires that brain circuits account for changing noise correlations across populations of retinal neurons.

Nightly selection of resting sites and group behavior reveal antipredator strategies in giraffe.

Abstract: This study presents the first findings on nocturnal behavior patterns of wild Angolan giraffe. We characterized their nocturnal behavior and analyzed the influence of ecological factors such as group size, season, and habitat use. Giraffe were observed using night vision systems and thermal imaging cameras on Okapuka Ranch, Namibia. A total of 77 giraffe were observed during 24 nights over two distinct periods-July-August 2016 (dry season) and February-March 2017 (wet season). Photoperiod had a marked influence on their activity and moving behavior. At dusk, giraffe reduced the time spent moving and increasingly lay down and slept at the onset of darkness. Body postures that likely correspond to rapid eye movement (REM) sleep posture (RSP) were observed 15.8 ± 18.3 min after giraffe sat down. Season had a significant effect with longer RSP phases during the dry season (dry: 155.2 ± 191.1 s, n = 79; wet: 85.8 ± 94.9 s, n = 73). Further analyses of the influence of social behavior patterns did not show an effect of group size on RSP lengths. When a group of giraffe spent time at a specific resting site, several individuals were alert (vigilant) while other group members sat down or took up RSP. Simultaneous RSP events within a group were rarely observed. Resting sites were characterized by single trees or sparse bushes on open areas allowing for good visibility in a relatively sheltered location.

Connectomic analysis reveals an interneuron with an integral role in the retinal circuit for night vision.

Abstract: Night vision in mammals depends fundamentally on rod photoreceptors and the well-studied rod bipolar (RB) cell pathway. The central neuron in this pathway, the AII amacrine cell (AC), exhibits a spatially tuned receptive field, composed of an excitatory center and an inhibitory surround, that propagates to ganglion cells, the retina's projection neurons. The circuitry underlying the surround of the AII, however, remains unresolved. Here, we combined structural, functional and optogenetic analyses of the mouse retina to discover that surround inhibition of the AII depends primarily on a single interneuron type, the NOS-1 AC: a multistratified, axon-bearing GABAergic cell, with dendrites in both ON and OFF synaptic layers, but with a pure ON (depolarizing) response to light. Our study demonstrates generally that novel neural circuits can be identified from targeted connectomic analyses and specifically that the NOS-1 AC mediates long-range inhibition during night vision and is a major element of the RB pathway.

Neuro-ophthalmologic Findings in Visual Snow Syndrome.

Abstract: Background and purpose The findings of ophthalmic examinations have not been systematically investigated in visual snow syndrome. This study reviewed the abnormal neuro-ophthalmologic findings in a patient cohort with symptoms of visual snow syndrome. Methods We retrospectively reviewed 28 patients who were referred for symptoms of visual snow to a tertiary referral hospital from November 2016 to October 2019. We defined the findings of best corrected visual acuity (BCVA), visual field testing, pupillary light reflex, contrast sensitivity, full-field and multifocal electroretinography, and optical coherence tomography. Results Twenty patients (71%) were finally diagnosed as visual snow syndrome. Their additional visual symptoms included illusionary palinopsia (61%), enhanced entoptic phenomenon (65%), disturbance of night vision (44%), and photophobia (65%). A history of migraine was identified in ten patients (50%). The mean BCVA was less than 0.1 logarithm of the minimum angle of resolution, and electrophysiology showed normal retinal function in all patients. Contrast sensitivity was decreased in two of the seven patients tested. Medical treatment was applied to five patients which all turned out to be ineffective. Among the eight patients who were excluded, one was diagnosed with rod-cone dystrophy and another with idiopathic intracranial hypertension. Conclusions Neuro-ophthalmologic findings are mostly normal in patients with visual snow syndrome. Retinal or neurological diseases must be excluded as possible causes of visual snow.

Highly Doped Upconversion Nanoparticles for In Vivo Applications Under Mild Excitation Power.

Abstract: One of the major challenges in using upconversion nanoparticles (UCNPs) is to improve their brightness. This is particularly true for in vivo studies, as the low power excitation is required to prevent the potential photo toxicity to live cells and tissues. Here, we report that the typical NaYF4:Yb0.2,Er0.02 nanoparticles can be highly doped, and the formula of NaYF4:Yb0.8,Er0.06 can gain orders of magnitude more brightness, which is applicable to a range of mild 980 nm excitation power densities, from 0.005 W/cm2 to 0.5 W/cm2. Our results reveal that the concentration of Yb3+ sensitizer ions plays an essential role, while increasing the doping concentration of Er3+ activator ions to 6 mol % only has incremental effect. We further demonstrated a type of bright UCNPs 12 nm in total diameter for in vivo tumor imaging at a power density as low as 0.0027 W/cm2, bringing down the excitation power requirement by 42 times. This work redefines the doping concentrations to fight for the issue of concentration quenching, so that ultrasmall and bright nanoparticles can be used to further improve the performance of upconversion nanotechnology in photodynamic therapy, light-triggered drug release, optogenetics, and night vision enhancement.

Psychophysiological response in night and instrument helicopter flights.

Abstract: Instrument and night flights are sources of mishaps: they produce stressful contexts to aircrews in which operability can be affected. This study aimed to analyse the effect of night and instrument flights in cortical arousal, autonomic modulation, muscle strength, and stress perception. 23 people were analysed (8 helicopter pilots, 4 helicopter mechanics - Spanish Air Forces - and 11 controls) before and after instrument and night flight exposition. Lactate and perceived exertion rose after flights. Anxiety was higher in instrument than in night flights. Pilots had a higher sense of anxiety before a flight compared to mechanics, although mechanics experienced a higher raise of heart rate during flight, with lower heart rate variability. Breath capacity was affected in pilots. Cortical arousal was more affected in unexperienced than in experienced aircrew during flights. These data suggest differences in their previous training. Practitioner summary: Night and instrument helicopter flights produced a different psychophysiological response of aircrew. These results could help to design specific training for aircrew that usually face instrument and night manoeuvres. Specific training based on high-intensity interval training integrated with reverse periodisation could improve their preparation. Abbreviations: BMI: body mass index; BOS: blood oxygen saturation; BT: body temperature; CA: cognitive anxiety; CFFT: critical flicker fusion threshold; ES: effect size; FEV1: forced expiratory volume in 1 second; FVC: forced vital capacity; HF: high frequency; HR: heart rate; HRV: heart rate variability; HIS: isometric handgrip strength; LF: low frequency; NVG: night vision googles; PEF: peak expiratory flow; pNN50: proportion of differences between R-R intervals higher than 50 ms; RMSSD: square root of the mean of the sum of the squared differences between adjacent normal R-R intervals; RPE: rated of perceived exertion; SA: somatic anxiety; SC: self confidence; STAI: state trait anxiety inventory.

Study on the improvement of the 20-inch microchannel plate photomultiplier tubes for neutrino detector

Abstract: The 20-inch MCP-PMT employs microchannel plates (MCP) as the electron multiplier unlike the traditional photomultiplier tubes (PMTs) with the dynode structure According to the performance requirements for 20-inch PMTs to be used in the Hyper-Kamiokande (Hyper-K) project, North Night Vision Technology Co, Ltd (NNVT) developed a novel 20-inch MCP-PMT based on the modification of the 20-inch MCP-PMT used for the Jiangmen Underground Neutrino Observatory by optimizing the design of the focusing electrode structure, the fabrication of the photocathode, and the other processes The performance of the new NNVT 20-inch MCP-PMTs was evaluated and compared with respect to time resolution and noise It was found that the transit time spread of the novel type is lower than 4 ns and the dark count rate is lower than 15 kHz Compared to the previous model, the novel 20-inch MCP-PMT presents enhanced performance for time resolution and noise that is promising for its use in high-energy physics applications such as neutrino detection

Night Vision Surveillance: Object Detection using Thermal and Visible Images

Abstract: Surveillance has become an important task in recent time mainly due to the increasing of crime rates. The existing research on surveillance for day time has achieved better performance by detecting and tracking objects using deep learning algorithms. However, it is difficult to achieve the same performance for night vision mainly due to low illumination and/or bad weather situation. One of the important tasks in surveillance is object detection which results in both class and location of the detected object with clear boundary of the objects from the image. We propose an efficient object detection module using fusion of thermal and visible images. Fusion module consists of encoder-decoder network in which encoder uses depthwise convolution to extracts efficient features from the given thermal and visible images. Then after, fused image is reconstructed using convolutional layers and final map is utilized in object detection algorithm (i.e., mask RCNN). The proposed method shows the effectiveness of utilization of pre-processing module i.e., fusion in object detection algorithm. Here, it is observed that the proposed method performs better for night vision when images are trained carefully with various features. Moreover, proposed method performs better on real time night vision images having no illumination condition.

Refractive, visual, and subjective quality of vision outcomes for very high myopia LASIK from - 10.00 to - 13.50 diopters

Abstract: To evaluate laser-assisted in situ keratomileusis (LASIK) outcomes, subjective quality of vision (QoV) and patient satisfaction in eyes with very high myopia (VHM) above − 1000 diopters (D) Consecutive myopic and myopic-astigmatism eyes with spherical equivalent (SEQ) ranging between − 1000 to − 1350 D underwent LASIK with the WaveLight® Allegretto Wave® Eye-Q 400 Hz excimer laser Treatment accuracy, efficacy, safety, stability, cylinder vectors, and higher-order aberrations were evaluated, together with subjective QoV and night vision disturbances (NVDs) 114 eyes had a preoperative SEQ of − 1102 ± 081 D, with a median follow-up of 24 months A total of 72, 84, and 94% of eyes were within ± 050, ± 075 and ± 100 D of intended SEQ (R2 = 071) The efficacy index was 093 ± 020, with 51 and 81% of eyes achieving 20/20 and 20/25 The astigmatism correction index was 095 ± 033 The safety index was 105 ± 012 The average myopic regression was − 051 ± 038 D Preoperative QoV scores improved significantly postoperatively (75 ± 08 vs 91 ± 07; P < 0001), with less NVDs (P < 0001) Total, spherical and coma root mean square (RMS) postoperative ocular higher-order aberrations were 107 ± 034, 067 ± 025, and 070 ± 040 μm Very high myopia LASIK between − 1000 to − 1350 D is safe and results in good visual outcomes, with high patient satisfaction and a significant improvement in patient-reported QoV after surgery Appropriately selected patients within this very high myopia group can be included as LASIK candidates

Recent Trends on Object Detection and Image Classification: A Review

Abstract: The area, object detection has seen a drastic development of algorithms and techniques over the past years. The arrival of deep learning has boosted the improvement in accuracy and performance of systems. This paper is a brief survey of several works developed so far in the field of image classification and object detection and a relative study of different methods. Survey is divided in three sub areas as Machine Learning based approach, Deep Learning based approach and object detection for night vision applications. A comparative table with the discussed works is also given.