High Illumination Conditions Research Articles

Integrated Active Quenching Circuit for high-rate and distortionless SPAD-based time-resolved fluorescence applications.

Time-Correlated Single Photon Counting (TCSPC) is a pivotal technique in low-light-detection applications, renowned for its exceptional sensitivity and bandwidth, widely used in Fluorescence Lifetime Imaging Microscopy (FLIM) and quantum optics. Despite its features, TCSPC is significantly hindered by the pile-up effect, which may distort measurements at high photon-detection rates. Overcoming pile-up is challenging, with traditional solutions often involving complex post-processing or multichannel systems, complicating the TCSPC setup and limiting performance. A breakthrough to overcome this issue is matching the photodetector dead time to an integer multiple of the laser period, obtaining a distortionless histogram even at high illumination conditions. Building on this concept, we present an Active Quenching Circuit (AQC) developed in high-voltage 150 nm technology, achieving unprecedented control over the Single Photon Avalanche Diode (SPAD) dead time. Our design compensates for Process, Voltage, and Temperature (PVT) variations, ensuring ultra precise and robust dead time tuning. The presented AQC achieves a dead-time resolution of 50 ps suitable for time-resolved experiments within a selectable range of laser frequencies from 20 to 100 MHz, maintaining close-to- ideal linearity in dead-time control. Experimental validations through fluorescence measurements reveal a distortion as low as 0.43% under elevated count-rate conditions, highlighting the efficacy of our circuit in overcoming the pile-up limitation.

Pain-induced effects on the pupillary light response under high and low illumination conditions.

The present study investigated the impact of two different light intensities on the pain-modulated pupillary light response (PLR). Additionally, it aimed to demonstrate parasympathetic and sympathetic influences on PLR parameters in response to pain, as predicted by functional models. A total of 24 participants were included in a randomized, repeated-measures design. The PLR was measured in response to both dark and bright light stimuli within two test cycles. Pain was induced using the cold pressor test (CPT), which involved immersing participants' feet in ice water. PLR measurements were taken during baseline and ice-water immersion within each test cycle. The assessed PLR parameters included initial diameter (INIT), latency (LAT), amplitude (AMP), and re-dilation time (ReDIL25). Along with these parameters, heart rate (HR) and pain ratings were also computed and analyzed. The CPT caused moderate pain in participants, and the resulting PLR parameters were found to be congruent with the expected parasympathetic and sympathetic nervous system activities. Although the luminance of the stimulus did influence PLR parameters, no interaction with pain exposure was found. The results showed that different aspects of pain experienced by an individual, as modulated through the sympathetic and parasympathetic nervous systems, are visible in their pupillary reactions to light. Notably, within the range used in the current study, light intensity did not significantly affect the pain-related PLR effects.

Light environment affects the efficiency of surgical suture training

BackgroundSuture knotting is the basis of surgical skills. In the process of surgical skills learning, the surrounding environment, especially the light, will affect the efficiency of learning. This study investigated the effect of optical environment on the learning of stitching and knotting skills.MethodsA total of 44 medical students were randomly divided into four groups and participated in the study of suture knotting in four different optical environments. During the process, we assess objective pressure level by testing salivary amylase activity Likert scale and objective structured clinical examination (OSCE) was used to estimate the subjective psychological state and overall skill mastery in surgical suturing respectively.ResultsUnder high illumination conditions (700 lx), the salivary amylase activity of the high color temperature group (6000 K) was significantly higher than that of the low color temperature group (4000 K) (p < 0.0001). Similarly, under low illumination (300 lx), the salivary amylase activity of the high color temperature group was also significantly higher than that of the low color temperature group (p < 0.05). The student under high illumination conditions (700 lx) and the low color temperature (6000 K) have an autonomy score between 37–45, which is significantly higher compared to the other three groups (p < 0.0001). Group 2 has an average OSCE score of 95.09, which were significantly higher than those of the other three groups (p < 0.05).ConclusionHigh illumination combined with low color temperature is considered as the optimal training conditions, promoting trainees' optimism, reducing stress levels, and enhancing learning efficiency. These results highlight the pivotal role of light environment in improving the quality and efficiency of surgical skills training.

Impact of Correlated Color Temperature on Visitors’ Perception and Preference in Virtual Reality Museum Exhibitions

From the perspective of psychophysiological evaluation, this paper provides a theoretical reference for the lighting settings of museums. In order to study the impact of correlated color temperature (CCT) on visitors' perception and preference in museum exhibitions, an experiment was conducted in the ergonomics laboratory of Nanjing Forestry University. We invited 50 participants to visit the virtual reality museum exhibitions with different CCTs, built by Autodesk 3D's Max 2017. Specific psychophysiology variables-eye movement, electrodermal activity (EDA), and heart rate variability (HRV)-and the perception and preference of participants were collected. The results indicated that the association of CCT with eye movement, HRV, and some perceptual dimensions was significant. Under high illumination conditions with different CCTs, the pupil diameter and warmth decreased with the increase in CCT, but the comfort and pleasure scores increased first and then decreased. The CCT scenes sorted by LF/HF ratio from high to low were 4500 K, 6000 K, and 3000 K, which was consistent with the results of preference ranking. The LF/HF ratio showed significant sex differences and major discrepancies.

Analysis of infrared nanojets with self-focusing nonlinearities

We present a numerical study of the linear and nonlinear diffraction and focusing properties of dielectric metasurfaces consisting of silicon microcylinder arrays resting on a silicon substrate. Upon diffraction, such structures lead to the formation of near-field intensity profiles that are reminiscent of photonic nanojets and propagate in a similar fashion. The generation and propagation of these photonic jets were analyzed under high intensity mid-infrared illumination conditions for which the third-order optical nonlinearity of silicon leads to pronounced self-focusing effects. The illumination wavelength of 3388 nm was selected to be below the two-photon absorption edge. Our results indicate that the Kerr nonlinear effect enhances light concentration throughout the generated photonic jet with an increase in intensity of about 20% compared to the linear regime for the power levels considered in this work. In all cases, the transverse beamwidth remains subwavelength, and the nonlinear effect reduces the full width half maximum size by 100 nm for both electric field intensity and the longitudinal Poynting vector.

Cocrystal of Apixaban-Quercetin: Improving Solubility and Bioavailability of Drug Combination of Two Poorly Soluble Drugs.

Drug combinations have been the hotspot of the pharmaceutical industry, but the promising applications are limited by the unmet solubility and low bioavailability. In this work, novel cocrystals, consisting of two antithrombotic drugs with poor solubility and low bioavailability in vivo, namely, apixaban (Apx) and quercetin (Que), were developed to discover a potential method to improve the poor solubility and internal absorption of the drug combination. Compared with Apx, the dissolution behavior of Apx–Que (1:1) and Apx–Que–2ACN (1:1:2) was enhanced significantly, while the physical mixture of the chemicals failed to exhibit the advantages. The dissolution improvements of Apx–Que–2ACN could be explained by the fact that the solid dispersion-like structure and column-shaped cage of Que accelerated the access of the solvent to the inner layer of Apx. The fracture of the hydrogen bonds of Apx, which was the joint of the adjacent Que chains, facilitated the break-up of the structures. Besides, the bioavailability of Apx–Que was increased compared with the physical mixture and Apx, and Apx–Que remained stable in high temperature and illumination conditions. Therefore, a drug–drug cocrystal of two antithrombotic agents with poor solubility was developed, which exhibited greatly improved solubility, bioavailability and superior stability, indicating a novel method to overcome the shortages of drug combination.

Design of Very High Resolution Satellite Telescopes Part II: Comprehensive Performance Assessment

In Part I [1] , a Korsch-based optical telescope design of a very high resolution earth observation satellite with a ground sampling distance of 25 cm is presented. In this part II, a system performance evaluation of the Korsch optical design employing a time-delay and integration charge-coupled device is investigated. Several key performance metrics are assessed, including the system modulation transfer function (MTF), absolute signal-to-noise ratio (SNR), differential SNR, noise equivalent change of reflectance, and cutoff resolution. The level of the national imagery interpretability rating scales (NIIRS) for measuring the image quality is also predicted. The system MTF has been computed, involving optics, detector, platform, orbit, atmosphere, and target illumination conditions. The SNR has been analyzed at different target albedos, solar, and satellite zenith angles. A new strategy for expressing the system evaluation based on the low- and high-illumination conditions is adopted; providing the operational ranges of such metrics. The assessment shows that for the high- and low-illumination conditions, the predictable performance of the proposed telescope gives promising results and provides an acceptable image quality.

Face Recognition for Varying Illumination and Different Optical Zoom Using a Combination of Binary and Geometric Features

Preservation of image features caused by binary conversion is a difficult task under variation of illumination conditions. Several binary conversion-based methods have used an adaptive thresholding technique to improve their performance under illumination variation conditions because of its robustness. However, the performances of existing methods were still limited under high differences illumination conditions especially for uncontrolled lighting sources. In addition, various length of face-to-camera distance gives significant problem affect for the performance of face recognition method. It happens when various images are available for the same person with different length face-to-camera distances due to the appearance of varying facial features of the same person. Therefore, this study proposed to combine the strength normalization and feature-based method to build an illumination distribution model to overcome this problem. With the proposed method the illumination model will fit with variation of illumination conditions in a whole image to generate an adaptive threshold for a novel columnar binary conversion method. The proposed method consists of five main stages, starting with eye area detection using the developed Viola–Jones algorithm. Next, the iris is detected using the Circular Hough Transform (CHT) method and will convert it into binary using the proposed Columnar Binary Conversion (CBC) method to preserve the appearance of the facial features under the illumination variation. Then, the proposed Facial Feature Region Normalization (FFRN) method is performed to improve the effects of different optical zooms for the classification step. The classification is conducted based on the similarity measurement between the extracted normalised binary face region and the dataset that must be converted into their equivalent normalised binary images. The proposed method is evaluated on two different smartphone databases, namely as Smartphone Face Video (SFV) and MOBIO. The performance results showed the outperformance of the proposed method.

Automatic detection of calving events from time-lapse imagery at Tunabreen, Svalbard

Abstract. Calving is an important process in glacier systems terminating in the ocean, and more observations are needed to improve our understanding of the undergoing processes and parameterize calving in larger-scale models. Time-lapse cameras are good tools for monitoring calving fronts of glaciers and they have been used widely where conditions are favourable. However, automatic image analysis to detect and calculate the size of calving events has not been developed so far. Here, we present a method that fills this gap using image analysis tools. First, the calving front is segmented. Second, changes between two images are detected and a mask is produced to delimit the calving event. Third, we calculate the area given the front and camera positions as well as camera characteristics. To illustrate our method, we analyse two image time series from two cameras placed at different locations in 2014 and 2015 and compare the automatic detection results to a manual detection. We find a good match when the weather is favourable, but the method fails with dense fog or high illumination conditions. Furthermore, results show that calving events are more likely to occur (i) close to where subglacial meltwater plumes have been observed to rise at the front and (ii) close to one another.

Impact of microalgae culture conditions over the capacity of copper nanoparticle biosynthesis

The biosynthesis of metallic nanoparticles (NPs) has been previously reported using a variety of organic molecules produced by microalgae. However, the results obtained could vary due to the metabolic responses that microalgae have to different culture conditions which could affect the characteristics of the produced nanoparticles. In the present report, copper nanoparticle formation was evaluated by the microalgae Chlorella kessleri, Dunaliella tertiolecta, and Tetraselmis suecica, developed under combined conditions of low (L−) and high (L+) illumination, with low (S−) and high salinity (S+). The illumination was 12 h:12 h light/dark. NP formation was evaluated 72 h after exposure to copper salt. Cupric oxide (CuO) NPs were detected spectrophotometrically in both the culture media (extracellular NPs) and cells (intracellular NPs) of Ch. kessleri with absorbance in the range of 200 to 235 nm. Metallic copper NPs (Cun) were detected with an absorbance between 540 and 560 nm in treatments with cells of C. kessleri and D. tertiolecta which were grown in L+S−, while T. suecica cells showed Cun NPs formations in L−S−, L−S+, and L+S−. The size difference of the NPs was measured by scanning electron microscopy (SEM), in treatments with cells of C. kessleri, ranging in size from 15 to 25 nm (L−S−) and 55 to 65 nm (L+S−). In treatments with culture media, sizes from 35 to 45 nm (L−S−) of NPs were obtained. Differences in the biosynthesis of Cu-based NPs are possible, depending on the culture conditions and the strain of microalgae to be utilized.

Nanophotonics of higher-plant photosynthetic membranes

The thylakoid membrane inside chloroplasts hosts the light-dependent reactions of photosynthesis. Its embedded protein complexes are responsible for light harvesting, excitation energy transfer, charge separation, and transport. In higher plants, when the illumination conditions vary, the membrane adapts its composition and nanoscale morphology, which is characterized by appressed and non-appressed regions known as grana and stroma lamellae, respectively. Here we investigate the nanophotonic regime of light propagation in chloroplasts of higher plants and identify novel mechanisms in the optical response of the thylakoid membrane. Our results indicate that the relative contributions of light scattering and absorption to the overall optical response of grana strongly depend on the concentration of the light-harvesting complexes. For the pigment concentrations typically found in chloroplasts, the two mechanisms have comparable strengths, and their relative value can be tuned by variations in the protein composition or in the granal diameter. Furthermore, we find that collective modes in ensembles of grana significantly increase light absorption at selected wavelengths, even in the presence of moderate biological disorder. Small variations in the granal separation or a large disorder can dismantle this collective response. We propose that chloroplasts use this mechanism as a strategy against dangerously high illumination conditions, triggering a transition to low-absorbing states. We conclude that the morphological separation of the thylakoid membrane in higher plants supports strong nanophotonic effects, which may be used by chloroplasts to regulate light absorption. This adaptive self-organization capability is of interest as a model for novel bioinspired optical materials for artificial photosynthesis, imaging, and sensing.

Brightness guided preprocessing for automatic cold steel weapon detection in surveillance videos with deep learning

The automatic detection of cold steel weapons handled by one or multiple persons in surveillance videos can help reducing crimes. However, the detection of these metallic objects in videos faces an important problem: their surface reflectance under medium to high illumination conditions blurs their shapes in the image and hence makes their detection impossible. The objective of this work is two-fold: (i) To develop an automatic cold steel weapon detection model for video surveillance using Convolutional Neural Networks(CNN) and (ii) strengthen its robustness to light conditions by proposing a brightness guided preprocessing procedure called DaCoLT (Darkening and Contrast at Learning and Test stages). The obtained detection model provides excellent results as cold steel weapon detector and as automatic alarm system in video surveillance.

Pulsed time‐of‐flight pixel with on‐chip 20 klux background light suppression in standard CMOS technology

SummaryA novel time‐of‐flight pixel designed in 0.18‐μm standard CMOS technology with an indirect pulsed technique is presented. This design is capable of operating in ambients with high levels of background light, since a novel in‐pixel background suppression circuit makes it robust up to 20 klux of ambient light. In addition to this, the pixel incorporates an adaptive number of accumulations circuit that selects the optimum number of accumulations for each situation at pixel level, avoiding saturation even under high illumination conditions.

Influence of knockout of At4g20990 gene encoding α-CA4 on photosystem II light-harvesting antenna in plants grown under different light intensities and day lengths.

Effect of knockout of the At4g20990 gene encoding α-carbonic anhydrase 4 (α-CA4) in Arabidopsis thaliana in plants grown in low light (LL, 80μmol photons m-2s-1) or in high light (HL, 400μmol photons m-2s-1) under long (LD, 16h) or short (SD, 8h) day length was studied. In α-CA4 knockout plants, under all studied conditions, the non-photochemical quenching was lower; the decrease was more pronounced under HL. This pointed to α-CA4 implication in the processes leading to energy dissipation in PSII antenna. In this context the content of major antenna proteins Lhcb1 and Lhcb2 was lower in α-CA4 knockouts than in wild-type (WT) plants under all growth conditions. The expression level of lhcb2 gene was also lower in mutants grown under LD, LL and HL in comparison to WT. At the same time, this level was higher in mutants grown under SD, LL and it was the same under SD, HL. Overall, the data showed that the knockout of the At4g20990 gene affected both the contents of proteins of PSII light-harvesting complex and the expression level of genes encoding these proteins, with peculiarities dependent on day length. These data together with the fact of a decrease of non-photochemical quenching of leaf chlorophyll a fluorescence in α-CA4-mut as compared with that in WT plants implied that α-CA4 participates in acclimation of photosynthetic apparatus to light intensity, possibly playing important role in the photoprotection. The role of this CA can be especially important in plants growing under high illumination conditions.

INFLUENCE OF THE TOPOGRAPHIC CORRECTION STRATEGY ON THE LAND COVER CLASSIFICATION: A SPECTRAL APPROACH

Topographic correction methods applied to orbital imagery have been evaluated by several authors. The evaluation criteria have been based on the correlation decreasing between shade and reflectance at different spectral bands or, in some cases, it has included the performance of digital classifiers trying to separate specifi c land cover types. Some topographic correction methods include sampling procedures based on the original image to be corrected and results are dependent on how they are conducted. The influence of the topographic correction on the land cover types spectral characterization is frequently neglected although it is relevant, specially in "quantitative remote sensing" in which empirical or physical relations between radiometric data and biophysical or geophysical data are explored. The objective here was to evaluate the classification results achieved from original and topographic corrected images using the C-correction method exploring two sampling procedures. The infl uence of the spectral characterization of some land cover types was also evaluated. Results indicated that pixels under high and low illumination conditions presented bigger spectral dynamics, specially in the infrared spectral region (near and SWIR). Topographic correction based on a single land cover class (vegetation) did not present better classifi cation result when compared to that classifi cation based on the original images. Sampling procedures based on diff erent land cover classes presented lower mapping accuracy and low matching level with the other classification results.

Detection of soybean aphids in a greenhouse using an image processing technique

Soybean aphid (Aphis glycines) is one of the most important insect pests of soybeans in North America. Insecticide application is performed if the aphids count exceeds the economic threshold of 250 per plant. Precise estimates of aphid densities are needed for field conditions to maximize insecticide application efficiency. The current method of identifying and counting aphids on a plant is a labor-intensive and time consuming process. The objective of this study was to use image processing technique to detect and count different sized soybean aphids on a soybean leaf. The trials were conducted with soybean plants grown in a greenhouse. Three sets of data were collected on different dates using replicate plants from 4 soybean varieties infested with a range of aphid densities. Images of infested soybean trifoliate leaves were captured with different cameras under 2 different illumination conditions with different cameras used across the different data sets. The images captured were processed in MATLAB™ R2014a software using the Image Processing Toolbox to identify and count aphids. In order to evaluate the accuracy of the algorithm, the aphids counted with the sensing system were compared to a count generated manually by a trained expert. The algorithm counting with SONY™ camera images correlated (r2=0.96) very well with manual counts. The misclassification percentage was low for most cameras with different resolutions under high illumination conditions. The results also showed that images captured with an inexpensive regular digital camera gave satisfactory results under high illumination conditions.

Hydrogenated Amorphous Silicon Thin-Film Transistor-Based Optical Pixel Sensor With High Sensitivity Under Ambient Illumination

This letter develops an optical pixel sensor that is based on hydrogenated amorphous silicon thin-film transistors. Exploiting the photo sensitivity of the photo TFTs and combining different color filters, the proposed sensor can sense an optical input signal of a specified color under high ambient illumination conditions. Measurements indicate that the proposed pixel sensor effectively reacts to the optical input signal under light intensities from 873 to 12,910 lux, proving that the sensor is highly reliable under strong ambient illumination.

Wide range temperature dependence of analytical photovoltaic cell parameters for silicon solar cells under high illumination conditions

Several attempts have been made to investigate the PV cell parameters’ dependence on temperature under normal illumination conditions, although there is no report available in the literature providing information about this dependence in the case of high illumination conditions. We therefore investigate analytically the dependence on temperature of five PV cell parameters of Si solar cells under high illumination conditions. The obtained performance parameters under illumination intensities of 10 and 15 suns were, respectively: the short circuit current density, Jsc values increased by 5.38% and 2.86%; the open circuit voltage, Voc values, on the other hand, decreased approximately by 16.87% and 17.75%; the obtained fill factor, FF losses were 5.84% and 5.34%, and the overall losses in efficiency, η were approximately 17.52% and 19.91%. The losses resulting from the series resistance and surface charge recombination are reduced with an increase in temperature within the 298–353K range, whereas the losses caused by the shunt resistance and reverse saturation current are increased. The reverse saturation current density increases by 3583% and 5988% under illumination intensities of 10 and 15 suns (1sun=1kW/m2), respectively. The analytically predicted values of Voc, FF, and η showed good agreement with the experimentally measured values for the several values of Pin and T.

Adaptive fusion algorithm of heterogeneous sensor networks under different illumination conditions

This paper presents an adaptive fusion method used in heterogeneous sensor networks, which consist of infrared sensors and visible sensors. A fuzzy system is applied to classify the imaging illumination conditions. We select three image quality evaluation parameters as the inputs of the fuzzy system, and the system’s output will determine the fusion weights of the two kinds of images. It means that the classification results are used to guide the fusion process. An adaptive fusion scheme according to blended basis functions is used to fuse the images. Our adaptive fusion rule is compared with the weighted average fusion scheme in the experiments under both high illumination conditions as well as low illumination conditions. The simulation results on the Matlab platform verify that our adaptive fusion algorithm has better applicability to different illumination environments when compared with the fixed weights fusion algorithm.

Intensity dependency of photovoltaic cell parameters under high illumination conditions: An analysis

Previously, an analytical method was developed to extract the photovoltaic (PV) cell parameters, such as the shunt resistance, Rsh, series resistance, Rs, diode ideality factor, n, and reverse saturation current density, J0, through the use of the single current density–voltage (J–V) characteristics under high illumination conditions. Accurate knowledge of the PV cell parameters under different illumination conditions is of vital importance to PV design and performance. Although several attempts have been made to examine the dependency of the PV cell parameters on the illumination intensity Pin, there are no reports on the dependence of the PV cell parameters on Pin under high illumination conditions. In this regards, dependency of the analytically-predicted PV cell parameters on Pin of Si solar cells with various structures has been investigated. The analytically-predicted values of Rsh and Rs decreased with increasing Pin. The rate of change in Rsh, however, was higher than that of Rs. The decrease in Rsh may be due to light induced degradation of PV cells. The decrease in Rs values might be due to an increase in the conductivity of the active region. On the other hand, n and J0 increased with increasing Pin. This increase in n and J0 might have a savior effect, reducing the curve factor CF and hence the performance of the PV cell. The rate change in all PV cell parameters was higher at lower Pin values than at the higher Pin values. The theoretically computed values of the open circuit voltage Voc, curve factor CF and efficiency η using this method showed good agreement with the experimentally measured values at various Pin.The performance of the PV systems is dependent on the product of the Jsc, Voc and CF. Therefore, it is important to determine the optimal value of Pin to achieve the maximum output power (minimum losses due to Rsh, Rs, n and J0) from a PV system. By doing so, the cost per peak watt of solar energy can be minimized by enhancing the performance of PV systems.