Position Of Light Source Research Articles

Astrometric search for ultralight dark matter

Precision astrometry offers a way to probe new physics. By measuring the angular position of light sources at unprecedented precision, astrometry could probe minuscule fluctuations of underlying spacetime. This work explores the possibility of probing ultralight dark matter candidates using precision astrometry. Through the coherent and stochastic density fluctuations over the scale of its wavelength, ultralight dark matter perturbs the propagation of light and the geodesics of the observer and source, leading to unique time-dependent signatures in the angular position of background light sources. With detector specifications similar to the current and future astrometry observations, such as Gaia and the Roman Space Telescope, it is shown that the ultralight scalar dark matter of mass 10−18–10−16 eV could be probed when its density near the Solar System is about a few thousand times larger than the nominal dark matter density measured on a much larger kpc scale. This sensitivity is comparable to current pulsar timing array observations at a similar mass range. Explicit expressions for the angular deflection induced by most generic metric perturbations are derived and its gauge invariance is explicitly checked at the linear order. Published by the American Physical Society 2024

Development of a smartphone-based colorimetric detection for quantification of vitamin C in dietary supplements and skin care products

This research project presents a development of an assay tool for quantification of vitamin C in dietary supplements and skin care products. The proposed method was developed based on decolorization of acidic potassium permanganate (KMnO4) by vitamin C through a redox reaction, with subsequent colorimetric detection by using digital imaging. The imaging was carried out using smartphone camera and free-downloaded RGB color detector application. To obtain optimal conditions, influential parameters such as light source position installed inside a 19 cm × 46 cm × 10 cm lightbox, reagent concentrations, and reaction time were studied. To the best conditions, good linearity (r2 > 0.99) in the range 1–70 mg vitamin C/L was obtained. Relative standard deviation was less than 3.9% indicating high precision. The proposed method was validated by quantification of vitamin C content in 15 sample solutions using the proposed method in comparison with the reference iodometric titration method. The results obtained from those two methods were not significantly different using paired t-test at confidence level of 95% (texp=0.41, tcrit=2.14). The results indicated that utilizing smartphone camera with free-downloaded color detector application is possible as an alternative analysis tool for determination of vitamin C.

Stability of Intensity Imbalance between Left‐ and Right‐Circulation Modes in GaN Hexagonal Microdisk

The mechanisms underlying the stability of the intensity imbalance between the left‐ and right‐circulating lasing modes in a GaN hexagonal microdisk resonator are investigated. Finite‐difference time‐domain simulations reveal that the imbalance is determined by the position of the point light source (seed light for lasing) inside the resonator. The coupling mechanism between the resonance modes and light from the source is clarified using numerical calculations. In addition, it is confirmed that light is highly coupled with one of the circulation modes when the source is placed off the bilateral symmetry axis of the mode near the side of the resonator, without any influence of the polarization of the source. The results indicate that the imbalance of the lasing modes observed in the experiments is determined by the position of the seed light near the side of the resonator, which must be spontaneous emission from impurities or defects, such as donor–acceptor pairs, donor‐bounded excitons, basal plane stacking faults, or the transition of free electrons in the conduction band to acceptor levels et al.

Subject-specific information enhances spatial accuracy of high-density diffuse optical tomography.

Functional near-infrared spectroscopy (fNIRS) is a widely used imaging method for mapping brain activation based on cerebral hemodynamics. The accurate quantification of cortical activation using fNIRS data is highly dependent on the ability to correctly localize the positions of light sources and photodetectors on the scalp surface. Variations in head size and shape across participants greatly impact the precise locations of these optodes and consequently, the regions of the cortical surface being reached. Such variations can therefore influence the conclusions drawn in NIRS studies that attempt to explore specific cortical regions. In order to preserve the spatial identity of each NIRS channel, subject-specific differences in NIRS array registration must be considered. Using high-density diffuse optical tomography (HD-DOT), we have demonstrated the inter-subject variability of the same HD-DOT array applied to ten participants recorded in the resting state. We have also compared three-dimensional image reconstruction results obtained using subject-specific positioning information to those obtained using generic optode locations. To mitigate the error introduced by using generic information for all participants, photogrammetry was used to identify specific optode locations per-participant. The present work demonstrates the large variation between subjects in terms of which cortical parcels are sampled by equivalent channels in the HD-DOT array. In particular, motor cortex recordings suffered from the largest optode localization errors, with a median localization error of 27.4 mm between generic and subject-specific optodes, leading to large differences in parcel sensitivity. These results illustrate the importance of collecting subject-specific optode locations for all wearable NIRS experiments, in order to perform accurate group-level analysis using cortical parcellation.

Design of Photoelectric Positioning System and Realization of Its Positioning Mathematical Equation

The research of photoelectric positioning system based on wireless data transmission is a multidisciplinary research direction. In the design of photoelectric positioning system, the LED used for light sensing is selected as the light source, and the AC/DC isolated LED driving circuit based on AP3706 is designed. When designing photoelectric conversion circuit, considering the influence of noise interference on detection accuracy, a capacitor is added and connected in parallel with the feedback capacitor. In order to improve the detection accuracy, reduce the relative error of the four-channel signal processing process and maintain the consistency of the four channels, a noninverting amplifier circuit composed of four operational amplifiers LM324 amplifier chips is adopted in this study. NewMsg-RF2401 module is used for wireless data transmission. The system control module adopts ADμC841 single chip microcomputer as the control core. According to the characteristics of this single chip microcomputer, the corresponding ADC module input drive circuit and control-data transmission interface circuit are designed. While designing the hardware of the system, it is necessary to calculate the positioning position. In this study, a positioning mathematical equation is proposed, which can obtain the position of the moving target in the geographical area under the wireless transmission network. In the experiment, firstly, the implementation process of the positioning mathematical equation is described, and then the performance of the proposed positioning mathematical equation is compared with that of the random positioning equation and the binary positioning equation. The results show that more messages can be transmitted by using the positioning mathematical equation proposed in this study. Based on this, it is used in the positioning system designed in this study, which is unfolded under the condition of constant background light, adjusts the position of the movable light source and determines the position coordinates. According to the horizontal and vertical displacement of the light source detected by the system, the positioning error is less than 0.1%, which is in line with the design expectation.

The Reviewed of Ray Tracing Technology Optimization

The technology of ray tracing is a graphics rendering technique that enables the simulation of realistic lighting effects, including accurate shadows, reflections, and refractions. The fundamental principle of ray tracing technology lies in the emission of one or more rays from the camera, which traverse along the path intersecting with objects within the scene. Subsequently, it computes the color and intensity of light based on object materials and light source positions, ultimately amalgamating these rays into a synthesized final image. Ray tracing technology enhances the authenticity and precision of graphics, albeit at the expense of substantial computational overhead and resource consumption, necessitating optimization for improved rendering efficiency and performance. The present paper provides a comprehensive overview of various optimization techniques employed in ray tracing technology, encompassing spatial acceleration structures, importance sampling, differential rendering, noise reduction, among others. Through rigorous experimentation and analysis, the advantages, disadvantages, and applicable scenarios of these methods are thoroughly examined.

A novel three-dimensional surface reconstruction method for fabric appearance evaluation

Traditional fabric appearance evaluation method mainly relies on subjective and manual operation, which is not uniform and time-consuming. In this paper, one set of self-developed 3D reconstruction system and method based on photometric stereo is proposed for objective fabric appearance evaluation. A photometric stereo image acquisition system equipped with multi-directional lighting sources is developed for the 3D surface reconstruction. Lighting and camera calibration is conducted to obtain the position of light sources and the intrisic parameters of digital camera. Our experimental results show that 3D fabric surface could be reconstructed effectively based on photometric stereo vision method, it has the potential to be used for fabric appearance evaluation.

Evolution of Fetal Cardiac Imaging over the Last 20 Years

The purpose of this article is to describe the evaluation of a variety of congenital heart diseases (CHDs) using three-dimensional (3D) ultrasound with different software, such as Cristal Vue, Realistic Vue, LumiFlow, and Spatiotemporal Image Correlation (STIC), with HDlive and HDlive Flow Silhouette modes. These technologies provide realistic images of the fetal heart and cardiac vessels using a fixed virtual light source that allows the operator to freely select a better light source position to enhance the cardiovascular anatomical details. In addition, Fetal Intelligent Navigation Echocardiography (FINE) technology, also known as “5D Heart” or “5D”, is a technology that enables the automatic reconstruction of the nine standard fetal echocardiographic views and can alert non-specialists to suspected CHD. Through the use of artificial intelligence, an ultrasound machine is able to perform automatic anatomical and functional measurements. In addition, hese technologies enable the reconstruction of fetal cardiac structures in realistic images, improving the depth perception and resolution of anatomic cardiac details and blood vessels compared to those of standard two-dimensional (2D) ultrasound.

Effect of inclination angle and light source position on water temperature profile and productivity of solar still: an indoor experiment

Solar stills are generally used to obtain fresh and clean water from saline, brackish, and wastewater using solar energy. Many factors affect the performance of solar still, such as solar radiation, altitude, top cover inclination angle, etc. In this research, indoor solar still experiments have been carried out with different top cover inclination angles and light source positions with 7 hours of operating time. This research aims to study the effect of those two variables on water temperature profile and productivity of solar still. Halogen lamp was used as artificial light source. Three light source positions were selected based on the yearly solar azimuth and elevation angles data of Yogyakarta, Indonesia. The selected inclination angles were 20°, 30°, and 40°. Results demonstrated that light source position which related to incident angle of light at the top cover of solar still affected the water temperature profile in solar still. The water temperature profile decreased considerably when the angle of incident light was higher than 40°. Condensate productivity can be increased by using higher inclination angle of solar still top cover and highest condensate productivity of 518.75 mL/m2 can be obtained by using 40° of inclination angle. However, water temperature profile which affected by light source position must be taken into consideration when using higher inclination angle. Lower water temperature profile caused the decreasing of condensate productivity.

Light Source Modules for Defect Detection on Highly Reflective Metallic Surfaces

High strength and highly reflective metal sheets are widely applied in industry; industrial requirements for defect detection are extremely demanding, particularly in the aviation and automotive industries. Classifying and recognizing surface defects on steel plate surfaces is highly challenging. Currently, defect detection is still inspected visually by personnel. However, given the high temperatures at inspection sites and the high risks in the operating environments, machine vision inspection systems are expected to replace manual inspection processes eventually. Therefore, this study developed an automated defect detection system that reduces the high reflectivity of examined objects. The light sources emitted light rays to the rays diffused and reflected multiple times inside the hemispherical cover to produce uniform illumination. Subsequently, image processing was conducted to highlight defect features on the stainless-steel plates. Relatively favorable light source positions were identified, which reduced the difficulty of class identification, the omission rate in defect detection to be decreased, and frequently encountered reflection problems in the automated optical inspection of metallic products to be overcome.

A real-time IR navigation system for pleural photodynamic therapy with a 3D surface acquisition system.

Photodynamic therapy (PDT) has been used intraoperatively to treat patients with malignant pleural mesothelioma. For the efficiency of PDT, it is crucial to deliver light doses uniformly. The current procedure utilizes eight light detectors placed inside the pleural cavity to monitor the light. An updated navigation system, combined with a novel scanning system, is developed to provide real-time guidance for physicians during pleural PDT to improve light delivery. The scanning system consists of two handheld three-dimensional (3D) scanners to capture the pleural cavity's surface topographies quickly and precisely before PDT so that the target surface can be identified for real-time light fluence distribution calculation during PDT. An algorithm is developed to further process the scanned volume to denoise for accurate light fluence calculation and rotate the local coordinate system into any desired direction for a clear visualization during the real-time guidance. The navigation coordinate system is registered to the patient coordinate system utilizing at least three markers to track the light source point position within the pleural cavity throughout the treatment. During PDT, the light source position, the scanned pleural cavity, and the light fluence distribution for the cavity's surface will be displayed in 3D and 2D, respectively. For validation, this novel system is tested using phantom studies with a large chest phantom and 3D-printed lung phantoms of different volumes based on a personal CT scan, immersed in a liquid tissue-simulating phantom with different optical properties, and treated with eight isotropic detectors and the navigation system.

Turning carpets into multi-image switchable displays

In this study, we propose a method that repurposes household carpets as dynamic visual displays. Our living environment is permeated with carpets and other fibrous materials, some of which can be given traces of different shades by raising their fibers. By manipulating this property for individual fibers, it is possible to (1) present animated expressions that continuously switch between multiple images by changing appropriate light source positions, and (2) create viewpoint-dependent images. We implemented software that enables the user to input images and hardware that physically controls the direction in which the fibers rise. Our technology has the advantage of being adaptable to existing cloth materials, and capable of redrawing images many times.

An evacuation model considering the phototactic behavior of panic pedestrians under limited visual field

In the emergency evacuation process, pedestrians affected by their panic will have evacuation behavior that rushes toward the light. To study the impact of panic pedestrian phototactic behavior on the evacuation process, a multi-model coupled cellular automata model is proposed. First, a heterogeneous model of emotional contagion based on the OCEAN model and the SIS model is established, which considers the influence of individual characteristics such as personality, gender, and age on emotional contagion, and the increase and decay of pedestrian emotion are also correlated with their location. Next, the “guidance field”, “orienteering field”, “herding field” and “phototactic field” are introduced to build an extended cellular automata model, pedestrians in different areas have different movement modes, and pedestrians with different emotional states in the same area also differ. Finally, the phototactic behavior of pedestrians in evacuation is reproduced by simulation, and the effects of factors such as emotional threshold, information transfer, visual field distance, light source position, and multiple light sources interference on the evacuation process are discussed. The results show that whether phototactic behavior is favorable or unfavorable to evacuation depends on the position of the light source. When the light source is located at the exit can guide pedestrians to escape, while located in other places will trigger local congestion. Increases in the emotional threshold, information transfer, and visual field distance can effectively mitigate the adverse effects of phototactic behavior. Additionally, the light sources in other positions will cause some interference with the light sources at the exit when multiple light sources exist, prolonging the evacuation time. Our research can provide some guidance for designing building structures and developing evacuation strategies in emergency situations.

The XY-Scanner for Absolute End-to-End Calibration of Fluorescence Detectors

The precise determination of the energy scale is a key part of experiments in astroparticle physics. At the Pierre Auger Observatory, the energy scale is set by the calorimetric measurement of extensive air showers with fluorescence detectors. Thus, the absolute end-to-end calibration of the fluorescence detectors is of utmost importance. In the past, this calibration was performed by illuminating the whole optical system of a fluorescence telescope with a large-scale extended uniform light source of the same diameter as the telescope aperture. However, handling difficulties, excessive manpower requirements, and degradation of such a source led to the need for a different approach for the absolute end-to-end calibration. The fundamental idea of the novel approach is to significantly reduce the geometrical size of the calibration light source, which is a near-UV LED source implemented in a portable integrating sphere with specifically designed interior. This light source is moved over the aperture by a rail mechanism with two independent linear stages named the XY-Scanner. Calibration data are evaluated from a series of light source positions instead of illuminating the entire aperture at once. The absolute photometric determination of the light source emission intensity is performed in a dedicated laboratory setup with a measurement uncertainty of 3.5 %. The XY-Scanner mechanics installed at the aperture gives also the opportunity to install other, devices for instance a narrow, collimated beam source to investigate local impurities of the telescopes. This contribution gives an overview of this novel XY-Scanner calibration method and presents preliminary results and discusses plans for the future.

Preliminary Characterization of Robust Detection Method of Solar Cell Array for Optical Wireless Power Transmission with Differential Absorption Image Sensing

In an optical wireless power transmission (OWPT) system, position and size of the photovoltaic device (PV) should be accurately determined from the light source position. Even though the detection of PV for OWPT has been studied and reported in some literature, the methods reported thus far are not so robust against varying background illumination. This study aims to solve such problems utilizing an image sensor which generates a differential absorption image from two wavelength images. Unnecessary background illumination presented in the two images is subtracted in the differential image. The differential image of the Si substrate target, which simulates PV, was detected by this sensor from a 104.5 cm distance. Signal illumination intensity was less than 1 μW/cm2 on the target, and detection accuracy was 3.1% for the diameter of the substrate and about 6.3% for the area. The system level requirement is derived, and they were verified by these results. The detection range of this sensor is shown to be expandable at the cost of, for example, increasing the receiver diameter of the image sensor or controlling the transmitter beam’s divergence. With the simple experiment apparatus, preliminary results of performance assessment were obtained and issues for performance improvement and potential of this image sensor were recognized.

Error Analysis of Photometric Stereo with Near Quasi‐Point Lights

AbstractThe shape recovery quality of photometric stereo is sensitive to complicated error factors under close range lighting of quasi‐point lights. However, the error performance of photometric stereo under this practical scenario is still obscure. This paper presents a comprehensive error analysis of photometric stereo with near quasi‐point lights (NQPL‐PS). Five main error factors are identified under this scenario and their corresponding analytical formulations are introduced. Statistic computation and experiments are used to validate the theoretical formulations and inspect the relationships between normal inaccuracies and each type of discrepancies. In addition, the impacts of multiple system parameters of an NQPL‐PS configuration on the normal estimation error are also studied. In order to evaluate the relative importance of various error factors, a probability‐based evaluation criterion is proposed, which focuses on the error performance over the state space and the error space, rather than the simple comparison of the values of normal inaccuracy. The assessment results show that the non‐uniformity of illuminants, and the calibration error in the position of light sources hold the dominant places among those five error factors. This paper provides insights for the accuracy improvement and system design of NQPL‐PS.

Importance of light source position in exposure sequence for optimization of coloration and yield of red winter lettuce

Winter production of greenhouse crops in northern countries is totally dependent on supplementary lighting. The aim of this study was to investigate the effect of the light source (high-pressure vapor lamps (HPS), light-emitting diodes (LED), or a combination) and their distribution in time on growth and coloration of red winter lettuce (Lactuca sativa L. cv. ‘Carmoli’). The used energy associated to each of the light treatments was also evaluated. The number of leaves, fresh and dry weight were significantly higher for plants treated only with HPS lights, whereas the red pigmentation was enhanced in plants grown only under LEDs. The lower yield under LEDs was associated with a significantly lower leaf temperature compared to plants grown under HPS lights. One week at the end of the growth period under LEDs was enough to achieve a satisfactory red color, while not compromising plant yield. The energy use efficiency was increased by nearly 50% in the LED-only treatment despite the lower plant yield compared to the HPS-only treatment. These results demonstrate that supplemental light quality can be strategically used by improving the light source position in exposure sequence to enhance the growth and coloration of winter lettuce.

Antenatal diagnosis of congenital heart disease by 3D ultrasonography using spatiotemporal image correlation with HDlive Flow and HDlive Flow silhouette rendering modes.

This pictorial review describes the assessment of a great variety of types of congenital heart disease by three-dimensional ultrasonography with spatiotemporal image correlation using HDlive and the HDlive Flow silhouette rendering mode. These technologies provide fetal heart surface patterns by using a fixed virtual light source that propagates into the tissues, permitting a detailed reconstruction of the heart structures. In this scenario, ultrasound operators can freely select a better light source position to enhance the anatomical details of the fetal heart. HDlive and the HDlive Flow silhouette rendering mode improve depth perception and the resolution of anatomic cardiac details and blood vessel walls compared to standard two-dimensional ultrasonography.

Geometric system analysis of ILMD-based LID measurement systems using Monte-Carlo simulation

Imaging Luminance Measuring Device (ILMD) based luminous intensity distribution measurement systems are an established method for measuring the luminous intensity distribution (LID) of light sources in the far field. The advantage of this system is the high-resolution acquisition of a large angular range with one image. For the uncertainty budget, the mathematical description of the system can be divided into photometric and geometric contributions. In the following, we will present a Monte-Carlo approach to analyse the geometric contributions which are the uncertainty of measurement direction and measurement distance. Therefore, we set up a geometric system description based on kinematic transformations that describes the connection between detector and light source position. To consider all relevant input quantities we simulate the adjustment and measurement process. Finally, an analysis of the geometric input parameters is shown.

Research on Stability of Gray Value of Excited-State Fluorescent Oil Film Based on Variable Light Vector Angle

In global skin-friction measurement of aircraft, the fluorescent oil film method can characterize the distribution of skin friction well. However, in an actual wind tunnel test, the wing of the aircraft will inevitably produce corresponding vibrations due to the influence of wind, which will change the relative position between fluorescent oil film and UV (ultraviolet) excitation light source (position fixed). This also directly affects gray value imaging of fluorescent oil films. Based on this, a mathematical model is established to judge the stability of the gray value of fluorescent oil film in this vibrational environment; then, the model can be solved to obtain the vibrational range constraint that enables the gray value of fluorescent oil film to be stabilized. In order to simplify the calculation process, the light vector angle is used to describe the constraint, which also makes the results more intuitive. Through experimental analysis and demonstration, the prediction accuracy of this model can reach 95.61%, which has certain practical engineering application significance.