Photodiode Matrix Research Articles

ДОСЛІДЖЕННЯ ЧИСЛОВОЇ ВИПАДКОВОЇ ПОСЛІДОВНОСТІ, ЩО ОДЕРЖАНА З ВЕБ КАМЕРИ

The investigation object of this paper is a random numbers sequence (RNS) obtained from a single frame of a webcam, which can be practically used as a source of chaos for a hardware RNS generator. The problem under consideration was to calculate the primary statistical characteristics of the RNS obtained from the webcam frame and compare them with the crypto-resistance requirements. The obtained statistics confirmed the hypothesis of a high level of chaos using a webcam. In successive frames from image capture (40 milliseconds gap), the photodiode matrix records changes that are not visible to the human eye. Even in absolute darkness , 60% of the changes in the brightness values of the matrix pixels are recorded. Which is 10% higher than the software engineering crypto-resistance requirements for the avalanche effect parameter. This is probably explained by the chaos that accompanies the stochastic interaction of photons of light with the atoms of the material of the sensor. Thus, it is possible to speak about a high level of chaos in the generated RNS. The peculiarity of the research is that for the purity of the experiment, frame generation was carried out in total darkness (approx. luminosity 10-4 lux), and a uniformly illuminated (luminosity 200 lux) white surface. Testing the web camera under extreme conditions gives a complete picture of the unpredictability and chaos of RNS generation. The primary investigation of the statistics of the generated RNS showed a good compliance with some crypto-resistance requirements. The method built on this property allows designing an affordable hardware RNS generator in laboratory conditions without the involvement of special equipment.

Radiotherapy delivery error detection with electronic portal imaging device (EPID)-based in vivo dosimetry.

Radiotherapy delivery error detection with electronic portal imaging device (EPID)-based in vivo dosimetry.

A methodical approach to determining the damage characteristics of cyclically loaded samples of metal structures

The article deals with an actual task of developing engineering methods for predicting the durability of modern long-life machines should be based on the methodology for determining the degree of fatigue damage to materials and structural elements. In the development of such a methodology, the work proposes to use modern optical and computer tools that allow analyzing the parameters of the deformed surface of metal structure samples and, on this basis, to estimate the residual resource of the metal structure. The purpose of the article was to substantiate a methodical approach for determining the limit state of damage using photometric analysis of the topography of the micro-deformed surface of cyclically loaded metal structure samples. To analyze the fatigue damage characteristics of metals and alloys, an experimental information system was developed based on the method of coherent optical scanning of the deformed surface of metal structure samples with a resolution of 0.2 μm/px. The obtained specklograms of the photodiode matrix, corresponding to the two-dimensional image of the micro-deformed surface of the sample in shades of gray 0-255, were computer analyzed. This made it possible to construct diagrams of the kinetics of the process of accumulation of the amplitude of the deformation microrelief of the surface of the laboratory samples for the studied steels St 45 and St 20. It is shown that the kinetics of speckle brightness obtained in the work by the correlation method, which corresponds to the evolution of the accumulation of fatigue damage on the surface of the studied structural steel samples, is characterized by a nonlinear function, which is consistent with the results of deformation microrelief studies obtained by other methods. The proposed methodology for analyzing the discrete distribution of specklogram brightness can be used to predict the onset of the limit state of a metal structure before failure due to fatigue

A Large Area GEMPix detector for treatment plan verification in hadron therapy

Quality Assurance in hadron therapy is crucial to ensure a safe and accurate dose delivery to the patients. This requires fast and reliable detectors with high spatial resolution. A first LaGEMPix prototype that combines a triple Gas Electron Multiplier and a highly pixelated readout based on a matrix of organic photodiodes coated on an oxide thin film transistor backplane has been built. The first version of the LaGEMPix has proven to have a limited spatial resolution, mainly attributed to the isotropic emission of the scintillation photons within the GEM holes. To improve the spatial resolution and confirm our predictions of the role of the photons, we built a new version of the detector with a reduced gap between the last GEM foil and the readout. Experimental results acquired using different methods and experimental set-ups show that the spatial resolution significantly improved with the new design.

INVESTIGATION OF AN OPTOELECTRONIC SYSTEM FOR DETECTING SMALL-SIZED AND INCONSPICUOUS OBJECTSUNDER THE INFLUENCE OF GEOMETRIC NOISE OF A MATRIX PHOTODETECTOR

The basis for reducing the accuracy of obtaining coordinate and non-coordinate information in an optical-electronic system with a matrix photo detector is geometric noise caused by uneven sensitivity and topology of the photodiode matrix. The presented mathematical model of a matrix photodetector based on the geometric array of photodiodes takes into account the main geometric parameters of the topology of the photodiode matrix. The questions of the accuracy of determining coordinates for small-sized and hardly noticeable light objects comparable to the size of a raster by the method of continuous wavelet transforms of signals from a photodiode array are considered. The possibility of geometric noise filtering by the method of continuous wavelet transform is shown by excluding from the scalogram the range of wavelet transform scales corresponding to the period of the geometric raster. It is shown that the algorithms of continuous wavelet transforms provide an increase in the accuracy of extracting the information component of small-sized and inconspicuous objects observed by an optoelectronic system with a matrix photodetector. A software prototype in the NI LabVIEW application development environment is presented. A technique has been developed for carrying out computational experiments to estimate the accuracy of determining the coordinate depending on the position of a small-sized light object relative to the topological raster of a matrix photodetector, as well as to estimate the detection sensitivity at a given noise level of photodiodes. An assessment of the accuracy of obtaining coordinate and non-coordinate information by a matrix photodetector under the influence of geometric noise has been carried out. It has been established that the filtering of geometric noise provides an increase in the detectivity of the optoelectronic system for detecting small-sized and inconspicuous light objects by more than one and a half times.

PRINCIPLES &FUNCTIONS OF CONVENTIONALS & DIGITAL X-RAYS IMAGING SYSTEMS IN DIAGNOSIS

Digital radiography (DR) is an advanced form of x-ray inspection which produces a digital radiographic image instantly on a computer. This technique uses x-ray sensitive plates to capture data during object examination, which is immediately transferred to a computer without the use of an intermediate cassette. The incident x-ray radiation is converted into an equivalent electric charge and then to a digital image through a detector sensor. Compared to other imaging devices, flat panel detectors, also known as digital detector arrays (DDAs) provide high quality digital images. They can have better signal-to-noise ratio and improved dynamic range, which, in turn, provides high sensitivity for radiographic applications. Flat panel detectors work on two different approaches, namely, indirect conversion and direct conversion. Indirect conversion flat panel detectors have a scintillator layer which converts x-ray photons to photons of visible light and utilise a photo diode matrix of amorphous silicon to subsequently convert the light photons into an electrical charge. This charge is proportional to the number and energy of x-ray photons interacting with the detector pixel and therefore the amount and density of material that has absorbed the x-rays. Direct conversion flat panel detectors use a photo conductor like amorphous selenium (a-Se) or Cadmium telluride (Cd-Te) on a multi-micro electrode plate, providing the greatest sharpness and resolution. The information on both types of detectors is read by thin film transistors. In the direct conversion process, when x-ray photons impact over the photo conductor, like amorphous Selenium, they are directly converted to electronic signals which are amplified and digitised. As there is no scintillator, lateral spread of light photons is absent here, ensuring a sharper image. This differentiates it from indirect construction.

Beam-Steered Optical Wireless Communication for Industry 4.0

By means of narrow 2D-steerable infrared beams, interference-free individual wireless connections to densely-spaced devices in industry 4.0 settings can be made. Beam steering by fiber-fed passive diffractive beam steering modules and wavelength-tunable transceivers located in a separate controller location enable readily scalable connectivity to many devices and their nomadic mobility. To accommodate the dynamics in industry 4.0 settings, self-calibrating localization of the devices by means of retro-reflecting corner cube foils and beam scanning is demonstrated, and a low-complexity broadband wide field-of-view optical wireless receiver is presented, based on a matrix of photodiodes.

Very Fast RP–UHPLC–PDA Method for Identification and Quantification of the Cannabinoids from Hemp Oil

In recent years, hemp oils have become ubiquitous in health products on the European market. As the trend continues to grow and more cannabinoids are researched for their therapeutic benefits, more academic and industrial interests are drawn to this direction. Cannabidiol, Δ9-tetrahydrocannabinol, and their acidic forms remain the most examined cannabinoids in hemp and cannabis oils, in the case of cannabidiol due to its proven health implications in numerous articles, and in the case of Δ9-tetrahydrocannabinol, due to the legislation in the European area. These oils sold on the internet contain a wide range of cannabinoids that could demonstrate their effects and benefits. As a result of these claims, we developed a robust and rapid method that can identify and quantify 10 of the most common cannabinoids found in hemp oils: cannabivarin, cannabidiolic acid, cannabigerolic acid, cannabigerol, cannabidiol, cannabinol, Δ9-tetrahydrocannabinol, Δ8-tetrahydrocannabinol, cannabichromene, and tetrahydrocannabinolic acid in less than 11 min, with reverse-phase–high-performance liquid chromatography–photodiode matrix system (RP–UHPLC–PDA) equipped with C18 column, eluting in a gradient using water and acetonitrile with formic acid as mobile phases. The quantification of 9 sample products presented in different matrixes was performed using a calibration curve obtained by analyzing standard solutions from a 10-cannabinoid-mix-certified reference standard. The developed method demonstrated the ability to identify and quantify the main cannabinoids in hemp oil and is a useful tool for pharmaceutical professionals.

Characterization with X-rays of a Large-Area GEMPix Detector with Optical Readout for QA in Hadron Therapy

Quality Assurance (QA) in hadron therapy is crucial to ensure safe and accurate dose delivery to patients. This can be achieved with fast, reliable and high-resolution detectors. In this paper, we present a novel solution that combines a triple Gas Electron Multiplier (GEM) and a highly pixelated readout based on a matrix of organic photodiodes fabricated on top of an oxide-based thin-film transistor backplane. The first LaGEMPix prototype with an active area of 60 × 80 mm2 was developed and characterized using low energy X-rays. The detector comprises a drift gap of 3.5 mm, a triple-GEM stack for electron amplification, and a readout featuring 480 × 640 pixels at a 126 µm pitch. Here, we describe the measurements and results in terms of spatial resolution for various experimental configurations. A comparison with GAFCHROMIC® films and the GEMPix detector used in the charge readout mode was performed to better understand the contribution to the spatial resolution from both the electron diffusion and the isotropic emission of photons. The measurements were compared to Monte Carlo simulations, using the FLUKA code. The simulation predictions are in good agreement with the GEMPix results. Future plans with respect to applications in hadron therapy are discussed.

Ways to improve the parameters of optical gas sensors of ammonia based on polyaniline

The possibility to improve the parameters of the optical ammonia sensors on the basis of polyaniline (PANI) has been investigated. Basing on the analysis of the PANI optical absorption spectra the possibility of a significant increase in sensitivity and selectivity of the ammonia sensors is shown using the additional measurement of optical absorption at wavelengths 800 nm (to increase sensitivity) and 720 nm (to increase selectivity). As measurement of the gas-stimulated changes has been carried out both in the visible region of the spectrum at 600 nm and in the infra-red region at 800 nm, the manufacture of the sensory elements may be realized without difficulty. It has been stated that the sensitivity to ammonia of the thin PANI films increases almost twice at the expense of simultaneous measurements of the optical absorption increase in the visible spectrum and its decrease in the nearest infra-red spectrum and the absolute values of summation of these measurements. The isobestic point of the gas-stimulated changes absence in optical absorption of PANI near 720 nm can be used as a reference point for the ammonia presence, which increases the gas sensor selectivity. We propose the method of detecting the analyte with the optical gas sensor on optoelectronic pairs with the mobile matrix of LEDs and photodiodes, and also the possibility of simultaneous registration of the parallel optocouples independent signals.

Objective assessment of task performance: a comparison of two FFDM detectors using an anthropomorphic breast phantom.

Current digital mammography systems primarily employ one of two types of detectors: indirect conversion, typically using a cesium-iodine scintillator integrated with an amorphous silicon photodiode matrix, or direct conversion, using a photoconductive layer of amorphous selenium (a-Se) combined with thin-film transistor array. The goal of this study was to evaluate a methodology for objectively assessing image quality to compare human observer task performance in detecting microcalcification clusters and extended mass-like lesions achieved with different detector types. The proposed assessment methodology uses a novel anthropomorphic breast phantom fabricated with ink-jet printing. In addition to human observer detection performance, standard linear metrics such as modulation transfer function, noise power spectrum, and detective quantum efficiency (DQE) were also measured to assess image quality. An Analogic Anrad AXS-2430 a-Se detector used in a commercial FFDM/DBT system and a Teledyne Dalsa Xineos-2329 with CMOS pixel readout were evaluated and compared. The DQE of each detector was similar over a range of exposures. Similar task performance in detecting microcalcifications and masses was observed between the two detectors over a range of clinically applicable dose levels, with some perplexing differences in the detection of microcalcifications at the lowest dose measurement. The evaluation approach presented seems promising as a new technique for objective assessment of breast imaging technology.

Photovoltaic Sub-Module With Optical Sensor for Angular Measurements of Incident Light

This paper presents a photovoltaic (PV) sub-module with an optical sensor for angular measurements of incident light. The optical sensor is a CMOS microdevice for accurate tracking of the solar incident angle for application on PV systems. This microdevice was designed in 0.7- ${\mu }\text{m}$ CMOS and is composed by a matrix of photodiodes and the respective read-out circuits. A set of microstructures on metal with the widths of 5 and 10 $ {\mu }\text{m}$ was fabricated on the top of the photodiodes to allow the measuring of angles on a wide range of illuminations and for calibration purposes. The measurements done in the laboratory and in real-field open environments confirmed the suitability to track with good precision the maximum sun’s incident angle in the range [0°, 180°], only limited by the servomotor to rotate the system. This PV sub-module measures 12 cm $\times10$ cm $\times4$ cm and presents a total power consumption of 265 mW, when supplied by 5 V. These features combined with the low cost of this PV sub-module bring excellent prospects for its installation on PV cells to achieve a maximum efficiency in the solar to electric energy conversion. To finish, this PV sub-module costs less than $130, opening good perspectives for its popularization.

Vertical Optical Coupling Structure Based on Polymer for Small Size and High-Speed Photodetectors

This letter presents a new collective and passive thin-film 3D vertical optical coupling structure, which is fabricated based on SU-8 polymer. This technology compensates for the alignment errors of the present passive optical coupling solutions. The structure is collectively manufactured on a matrix of small-sized photodiodes on wafer level to vertically couple with a single-mode optical fiber. The proposed structure shows a coupling efficiency between the 10- $\mu \text{m}$ active area diameter photodetector and single-mode fiber of 94% and a 1-dB alignment tolerance of $\pm 9~\mu \text{m}$ at 1550 nm. Its wafer-level mass-production capability and manufacturing process simplicity make this novel coupling approach a potential solution for short- and long-range optical communication applications.

Novel wearable-type biometric devices based on skin tissue optics with multispectral LED–photodiode matrix

In this study, we examined the possibility of using a multispectral skin photomatrix (MSP) module as a novel biometric device. The MSP device measures optical patterns of the wrist skin tissue. Optical patterns consist of 2 × 8 photocurrent intensities of photodiode arrays, which are generated by optical transmission and diffuse reflection of photons from LED light sources with variable wavelengths into the wrist skin tissue. Optical patterns detected by the MSP device provide information on both the surface and subsurface characteristics of the human skin tissue. We found that in the 21 subjects we studied, they showed their unique characteristics, as determined using several wavelengths of light. The experimental results show that the best personal identification accuracy can be acquired using a combination of infrared light and yellow light. This novel biometric device, the MSP module, exhibited an excellent false acceptance rate (FAR) of 0.3% and a false rejection rate (FRR) of 0.0%, which are better than those of commercialized biometric devices such as a fingerprint biometric system. From these experimental results, we found that people exhibit unique optical patterns of their inner-wrist skin tissue and this uniqueness could be used for developing novel high-accuracy personal identification devices.

OCC-ID: New Broadcasting Service-Based Cloud Model and Image Sensor Communications

In recent decades, the main data traffic of mobile communication is based on the RF technology. Even though the efficiency from optimization for utilization or reuse is applied, there is a limitation of increased traffic demand of RF communication. Visible light communication (VLC) is a new technology that can cooperate with RF to address this limitation. The standard for VLC was published in 2011 as IEEE 802.15.7, which defined the specifications for the MAC layer and the PHY layer. This standard was one of the first for this technology. The decoded operation from emitting light at the receiver in IEEE 802.15.7 is mainly based on the photodetector. However, with the development of image sensors (matrix of photodiodes) on smart devices, the amendment of IEEE 802.15.7 specification is considered. The extension will focus mainly on image sensor communications, named optical camera communications (OCC). In this paper, we analyze the performance of a camera communications system based on different types of image sensor architecture. Then, we suggest OCC-ID, a new application for broadcasting service using camera communications and the cloud model. The proposed architecture is a typical deployment scenario of camera communications.

Cherenkov luminescence measurements with digital silicon photomultipliers: a feasibility study.

BackgroundA feasibility study was done to assess the capability of digital silicon photomultipliers to measure the Cherenkov luminescence emitted by a β source. Cherenkov luminescence imaging (CLI) is possible with a charge coupled device (CCD) based technology, but a stand-alone technique for quantitative activity measurements based on Cherenkov luminescence has not yet been developed. Silicon photomultipliers (SiPMs) are photon counting devices with a fast impulse response and can potentially be used to quantify β-emitting radiotracer distributions by CLI.MethodsIn this study, a Philips digital photon counting (PDPC) silicon photomultiplier detector was evaluated for measuring Cherenkov luminescence. The PDPC detector is a matrix of avalanche photodiodes, which were read one at a time in a dark count map (DCM) measurement mode (much like a CCD). This reduces the device active area but allows the information from a single avalanche photodiode to be preserved, which is not possible with analog SiPMs. An algorithm to reject the noisiest photodiodes and to correct the measured count rate for the dark current was developed.ResultsThe results show that, in DCM mode and at (10–13) °C, the PDPC has a dynamic response to different levels of Cherenkov luminescence emitted by a β source and transmitted through an opaque medium. This suggests the potential for this approach to provide quantitative activity measurements. Interestingly, the potential use of the PDPC in DCM mode for direct imaging of Cherenkov luminescence, as a opposed to a scalar measurement device, was also apparent.ConclusionsWe showed that a PDPC tile in DCM mode is able to detect and image a β source through its Cherenkov radiation emission. The detector’s dynamic response to different levels of radiation suggests its potential quantitative capabilities, and the DCM mode allows imaging with a better spatial resolution than the conventional event-triggered mode. Finally, the same acquisition procedure and data processing could be employed also for other low light levels applications, such as bioluminescence.Electronic supplementary materialThe online version of this article (doi:10.1186/s40658-015-0134-z) contains supplementary material, which is available to authorized users.

Suppression of Instabilities in Thermal Plasma Jet by Additional Arc Current Modulation

Arc current in a dc thermal plasma torch was modulated by superimposed ac current with frequency 15 kHz. The plasma jet optical radiation was recorded by a matrix of fast photodiodes. The analysis of records using standard deviations and 3-D phase portraits has shown that the fluctuations in the plasma jet in the frequency range under 5 kHz were suppressed.

Correlating Mobility and Interaction of Transcription Factors by SPIM-FCS

In single plane illumination microscopy (SPIM) an image of a two-dimensional slice of a sample is formed by illumination with a laser beam focused in only one dimension. Thus, fluorescence fluctuations may be observed simultaneously in all voxels of this 2D slice, thereby obtaining diffusion and transport coefficients as well as concentrations of fluorescently labeled biomolecules, creating a “mobility map” of the observed cell.By combining SPIM with fluorescence correlation and cross-correlation spectroscopy (FCS/FCCS), direct information on the strength of molecular interactions can be obtained. We built a dual color SPIM-FCCS with two laser wavelengths for illumination and dual-channel detection through either an EMCCD camera or an ultrafast avalanche photodiode matrix detector, with wavelength splitting optics to image the two colour channels simultaneously. This system offers a time resolution in the range of 105 frames/sec.Here we demonstrate that SPIM-FCS/FCCS possesses the sensitivity to detect and quantify protein-protein interactions in live cells by characterizing the interaction of the subunits of heterodimeric transcription factors, c-Fos/c-Jun and IQGAP/cdc42. The protein-protein interaction clearly shows up in the cross-correlation amplitude. Analysis of the spatial distribution of diffusion coefficients of the fluorescent proteins and of their cross-correlation amplitude shows that formation of the heterodimer is correlated with regions of decreased mobility, probably related to DNA binding.

Study of Two-Phase Cryogenic Avalanche Detector Characteristics in Argon with Optical Readout Based on Matrix of Geiger-Mode Avalanche Photodiodes

In this article the operation of a two-phase cryogenic avalanche detector (CRAD) in Ar with optical readout using combined multiplier based on thick gas electronic multipliers (THGEMs) and a matrix of Geiger-mode avalanche photodiodes (GAPD) has been studied. The successful operation of such a detector when irradiated by x-ray photons with the average energy of 20 keV was demonstrated. The yield of such combined multiplier amounted at about 100 photoelectrons at THGEM avalanche gain of 160. In addition, the spatial resolution of the detector was measured; it turned out to be 1 mm

A high precision tracking system based on a hybrid strategy designed for concentrated sunlight transmission via fibers

This paper investigates a high precision tracking system that adopts the coordinate calculation algorithm and a photosensitive sensor. This system is designed to satisfy the precision requirement in sun tracking for a concentrated sunlight transmitting system via optical fibers. This system is based on a two-stage tracking process, which consists of a coarse adjustment based on the coordinate calculation algorithm and a fine adjustment using a specially designed photosensitive sensor. The core of the photosensitive sensor is a photodiode matrix that could exactly detect the position of the sunlight focal spot via lens focusing. A predictive control process based on the running trend of sun traces will begin once the fine adjustment is completed. The tracking process is steady and accurate because of the predictability of sun traces based on the coordinate calculation algorithm and the acuteness of the photodiode matrix. The highest tracking precision depends on the compactness of the photodiode matrix and has no limits in the accuracy of the coordinate calculation algorithm. The proposed system can track the sun's focal spot with a position precision of less than 0.3 mm, which is the space between the adjacent photodiodes. The tracking angle precision is determined by the ratio of the position resolution of the photodiode matrix to the focal length, and reaches 0.1°.