Matrix Photodetector Research Articles

Зависимость величины сигнала от смещения функции рассеяния точки, вписанной в четыре пиксела матрицы

An algorithm has been developed for calculating changes in the signal level of a matrix pixel when the point scattering function is shifted at an angle of 45º relative to the joining point of 4 matrix pixels. In the initial state of the point spread function, the point is inscribed in four pixels. The spectral sensitivity of a pixel is constant within the pixel area. The distribution of pixel irradiance in the point spread function in the form of uniform irradiance is considered. Method. The calculation is based on the method of dividing the point spread function on each pixel of the matrix into separate areas for which the signal is calculated. The displacement of the point scattering function by Δx along the X axis and by Δy along the Y axis is taken in a form normalized to the radius of the spot. To create a two-dimensional graph of the dependence of the pixel signal on the displacement of the point scattering function along the X, Y axes, we introduce the relative displacement of the point scattering function η. Main results. An algorithm has been developed for calculating changes in the signal level of a matrix pixel when the point scattering function is shifted relative to the matrix pixels for the case of pixel irradiation in the lens scattering circle in the form of uniform irradiance. The dependence of the normalized matrix pixel signal on the relative displacement of the point scattering function η at an angle of 45º has been plotted for the above case of irradiation. Practical significance. Matrix photodetectors are widely used in guidance and tracking systems for space objects and astronomical sensors. For a defocused optical system, uniform distribution is used. When the point scattering function shifts relative to the joining point of the four pixels of the matrix, the matrix signal drops, which, with a low signal-to-noise ratio, can lead to a breakdown in tracking or an increase in the error in measuring the angular coordinates of a space object. The results of these studies can be used to model a target guidance system and determine target coordinates.

Application of the Kimmel method for two-layer matrix color separation systems

In this work, interpolation by the Kimmel method is applied for the developed color separation systems based on matrix photodetectors. Author's two-layer receivers with an equal distribution of layers of the visible and infrared spectra over the sensitive surface are given. To compare the interpolation result, it was proposed to use a matrix photodetector with a modified standard RGBG system on RGBIr. This system shows what a multispectral receiver would be like without the use of multilayer silicon technologies. Thus, it was possible to show that the use of two-layer color separation systems simplifies the interpolation algorithm by a factor of two. The developed systems can be useful in various fields of science and technology. The use of such multispectral matrices is necessary especially in agriculture and forestry for monitoring the environment and detecting fire.

Компьютерное моделирование процесса формирования изображений в гиперспектральной системе на базе интерферометра Фабри-Перо

The article deals with the issues of computer simulation of the processes of spectral image formation in a hyperspectral system based on the Fabry-Perot interferometer, designed to work in the visible spectrum. A mathematical model of a hyperspectral system and its main variable parameters for evaluating the obtained characteristics of spectral selectivity are considered. A block diagram illustrating the simulation process is given. The results of computer simulation are presented. The characteristics of spectral selectivity obtained by computer simulation are given, depending on the air-gap distance between the mirror plates of the Fabry-Perot interferometer at a fixed angle of incidence of the radiant flux. The possibility of singlechannel and three-channel registration of spectral responses of the interferometer corresponding to RGB channels of a standard color matrix photodetector is shown. The variants of the structural schemes of the hyperspectral system are analyzed based on the existing compromises between the sensitivity of the system, its spectral selectivity, speed, accuracy, resolution, and complexity of implementation.

Physics of a diffraction-quality optical system, taking into account the range of received radiation

The process of detecting, selecting and measuring the parameters of the movement of the observation object has a pronounced probabilistic nature. This is caused by source emission fluctuations, interference from extended and point natural sources distributed over the field of view at the input of the opto-electronic device and its own noise. As a result, the output information of the optoelectronic device, after processing by the onboard system, is output to the control and navigation system with a certain error that determines the quality of the aircraft’s control and navigation system information. The resolution is estimated depending on the equivalent weight function of the optical system and intermediate links which characterizes spatial distortions introduced into the optical image of an object taking into account the range of radiation received by the matrix photodetector. We obtained an expression that allows us to estimate the potential resolving power of the optoelectronic device taking into account the finite wavelength range of the received radiation and determine the condition under which the receiver can be considered to be spatially continuous. The present paper is devoted to estimation of the resolving power of an optoelectronic device with a matrix photodetector of radiation.

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.

Color distribution functions of multilayer multispectral matrix photodetectors after interpolation

Color distribution functions of multilayer multispectral matrix photodetectors after interpolation

Investigation of optical phenomena in multispectral matrix photodetector based on silicon

A study is presented in the field of development and creation of modernized multi-layer color separation multispectral systems with increased color resolution. The types of structures of the developed patterns of matrix photodetectors based on multilayer silicon with working layers for use in the blue, green, red and infrared spectral ranges are considered. A method for calculating silicon layers in the form of optical films with specified characteristics is proposed. The silicon layers act as both a sensing element and a specific wavelength filter to highlight the blue, green, red and infrared ranges of the spectrum. The reflection and transmission coefficients were calculated for the selected wavelengths at various angles of incidence on the sensor. The Brewster angle for these wavelengths is also calculated. The possible presence of a microlens sensor surface is taken into account. Calculations are presented for cells with four-layer and two-layer structures for various combinations of layers. The dependences of the reflection and transmission coefficients for two-layer and four-layer structures of semiconductor sensors for p- and s-polarization, also for unpolarized light, are obtained. It is shown that the combination of layers in the red and infrared ranges of the spectra has the minimum reflection coefficient and the maximum transmission coefficient. The results obtained can be used in the development of multilayer multispectral systems with registration of infrared radiation. As a result, it is possible to use a pair of red and infrared spectra as the basis of a matrix photodetector pattern, and layers of blue and green spectra as auxiliary ones for building a full-color image.

Investigation of ACS image stabilization of on-board optoelectronic guidance and tracking devices

Introduction. The movement of the carrier and external factors (the effects of the atmosphere, temperature and pressure) degrade significantly the image quality of the servo optoelectronic systems (OES) and the positioning accuracy of the emitting OES. The issues of image quality improvement and the probability of keeping the image of the observation object (OO) on the optical axis of the servo EOS are considered.Materials and Methods. The development of an automatic control system for an optoelectronic device (ACS OED) involved solving a multi-criteria optimization problem taking into account a number of conflicting technical-andeconomic (TE) requirements. The determination of tolerated dynamic errors (TDE) of image stabilization was a key issue in the development of on-board optoelectronic devices (OOED). Lagrange equations of the second kind and the mixed Gilbert method made it possible to obtain a mathematical model of the CO OED. Then, the decomposition of a two-link ACS with nonlinear cross-couplings in the CO was performed. A functional diagram of the image formation model of the OOED was presented. The parameters of the matrix photodetector and the requirements for the dynamic error of the ACS OED, taking into account the permissible MTF of the OED, were listed. The functions of transferring modulation, as well as linear, harmonic and vibrational shift of the image corresponding to the permissible and achieved TDE were visualized. Logarithmic frequency characteristics were created in the Mathcad environment. The two-link control system of the OED with the specified parameters of the CO for the considered movement was presented as two independent azimuth and elevation control channels.Results. The processes of control of the on-board optoelectronic system in the stabilization and tracking modes were described. To study the dynamics of spatial control of the OOEP in accordance with the ACS methodology, a computer simulation model (CSM) of the digital automatic control systems (DACS) of the OED was developed. It was implemented in the Matlab environment and consisted of CSM CO, drives, proportional-integral-derivative (PID) controllers taking into account non-linearities, a central computing device (CCD), a guidance software device, a CSMcarrier that implemented the equations of motion. Harmonic vibrations of the carrier were described. The errors of tracking and stabilization in the tracking mode with an additional control action introduced in the form of a constant speed were determined. The dynamics of spatial control of the OOED was investigated. A computer simulation model of a digital automatic control system of an optoelectronic device, the results of modeling the DACS OED without considering the board movement, and the processes of OED control subject to movement were visualized.Discussion and Conclusions. The stabilization accuracy was calculated for the studied cases. It was established that the stabilization tens of times exceeded the previously stated indicators, and it tens of times reduced the requirements for the convergence of the laser beam and the laser radiation power when developing the optical path of the product in question. The proposed CSM can be used in the development of the on-board optoelectronic systems. In this case, the application of the presented methodology and CSM will help to reduce labor costs and minimize errors.

Comparative Analysis of the Spectral Sensitivity of Three-Color Matrix Photodetectors

Comparative Analysis of the Spectral Sensitivity of Three-Color Matrix Photodetectors

Fourier Analysis of the Spectral Characteristics of a Matrix Photodetector in the Frequency and Time Domain

Fourier Analysis of the Spectral Characteristics of a Matrix Photodetector in the Frequency and Time Domain

Open-source 3D-printed terahertz pulse time-domain holographic detection module.

We present a holographic detection module to measure the spatially resolved distribution of pulsed terahertz field in a single scan by a motorized translation stage, responsible for the time delay. All mounts of the optical elements of the module are easily reproduced by 3D printing and attached to the optical cage system. The latter greatly simplifies the measurement procedure, allowing the experimenter to move and adjust the detection system as a single device. The developed mounts are made universal and can be used in other setups. We have made 3D models available as open-source hardware. The module is based on an electro-optical detection scheme with wide-aperture ZnTe crystal, crossed polarizers, and a matrix photodetector. The validation of its operability was performed with two experiments to measure the spatial distribution of the unperturbed field from the generator and the vortex field formed by the spiral phase plate. Optical vortices with multiple topological charges of 2-4 were detected on spectral components in the range from 0.3 to 1.1 THz. In addition, we have detailed the alignment process of terahertz imaging systems.

Evaluation of the efficiency of the algorithm for determining the angular coordinates of the target by a matrix photodetector

Evaluation of the efficiency of the algorithm for determining the angular coordinates of the target by a matrix photodetector

Method for the numerical evaluation of the color rendering quality of matrix photodetectors

To objectively evaluate the color image of an architectural object when changing its spectral quality and luminance in lighting, it is necessary to ensure its accurate fixation. The measurement of the color coordinates of an object provides the fully capture of its appearance, but this does not allow to get an adequate evaluation of the visual impression without visualizing the lighting scene. This requires a thorough procedure of reproducing the same color coordinates for each point of the image and the object with the same angular coordinates. In this work, an attempt is made to develop a numerical criterion for evaluating the quality of color rendering of the camera as a fixer of color visual impression of the selected scene. The development of a numerical detailed method for evaluation of the quality of color rendering of cameras will allow capturing more reliably such a subjective concept as the correspondence of the visual impression of the real scene and the image file of this scene. The digital format, which contains information about the object, avoids the problems associated with aging of the image. The proposed method of developing ways to numerically evaluate color distortion in photography is considered on the example of digital cameras Nikon D300s, Sony DSC-H5. The described approach for the case of known spectral characteristics allows to unambiguously link the calculated reaction of the camera with the chromaticity coordinates of spectrally pure colors. Modern methods of evaluating the quality of light sources (IES TM-30-15) allow evaluation of the direction of the shift. The proposed indicator – graph E (λi) numerically characterizes the difference between the reaction of the camera and the reaction of the human eye and does not give an idea in which direction there is a difference, conditionally red or blue image compared to the natural scene, but is the simplest and most understandable to the untrained user. It is shown that with an accuracy of measuring spectral characteristics of 1% for the considered example with Nikon D300s, this indicator at different wavelengths is calculated with an uncertainty of not more than 0.002.

A comparative analysis of the frequency spectra of the human eye and a cut diamond in visible light

The paper investigates the frequency characteristics of the spectra of a human eye and a faceted diamond (brilliant). The relevance of the research deals with a large number of modern studies on the use of diamond as a lens of the eye. The results obtained were compared with the averaged data (described in the literature) on the visibility curve of day, evening and night vision of the human eye. The research method is based on the representation of the optical environment of the human eye and diamond in the form of a dynamic link with an input and output. The Gaussian function is used to approximate the spectral curves. The study of the inertial properties of such a link in the time domain is performed by feeding signals to its input in the form of a δ-function or a unit function. The steady-state forced oscillations at the output of the investigated dynamic link are found when a harmonic action is applied to the input. Frequency characteristics discover a relationship between the spectra of the input and output signals, representing the direct Fourier transform of the function of time. It was found that the spectra of the visibility of the human eye and the luminescent radiation of diamond have the properties of ultra-wideband signals. It is shown that the amplification of light takes place in the time domain when the width of the spectrum at its half-maximum does not exceed a certain critical value. This phenomenon also manifests itself in the frequency domain. It was revealed that the dynamic links of diamond and human eyes for day and night vision exhibit amplifying properties. Their comparison in terms of the light amplification factor showed their insignificant difference. The results obtained can find application in the creation of matrix photodetectors and as a standard in identifying a faceted diamond (brilliant) of unknown origin and producing a lens from a diamond.

The laser radiation parameters control method based on the digital video system registration

The paper describes a method of a beam radiation parameters analysis. Such analysis bases on the laser beam registration in the plane of a diffusely reflecting screen and digital processing of the registered image. The algorithm of the laser beam spatial parameters determination is presented and realized programmatically. The experiment was carried out using a digital high-speed video system and a solid-state pulsed periodic laser based on a Cr3+: BeAl2O4 alexandrite crystal. A comparison of the proposed method with a standardized method based on the registration of radiation by a matrix photodetector is presented. The development of measure methods of the laser radiation parameters is necessary due to the appearance of new sources of laser radiation and their use in various applications.

MWIR optoelectronic module based on the Russian 640512 InSb photodetector

Consideration is given to the results of the development of an optoelectronic module based on a Russian cooled matrix photodetector of 640512 elements format, operating
 in the spectral range of 3.6–4.9 microns, based on InSb. The paper describes the basic algorithms used for video image processing, describes the main blocks of the developed device, describes the methods for measuring NETD and spatial resolution, and gives the characteristics of the device.

Small Object Signal Formation Model for Optical System with Matrix Photodetector When Processed by the Laplace Operator

The authors review the formation of a small object signal by an optical system with a matrix photodetector. They develop a mathematical model of signal formation and test it. The authors calculate the signal/noise proportion for various small object signal shapes and amplitudes processed by the Laplace operator.

Growing indium antimonide single crystals with a diameter of 100 mm by the modified Chochralsky method

At present, all over the world there is a tendency to increase the diameters of single crystals of both elementary semiconductors and semiconductor compounds. There are reports indicating the use of single crystals of III-V semiconductors with a diameter of four to six inches. So far, indium antimonide single crystals up to 75 mm in diameter have been obtained in Russia.Indium antimonide is the element base of the broadest field of solid-state electronics — optoelectronics. On its basis, linear and matrix photodetectors are manufactured, operating in the spectral wavelength range of 3-5 microns, which are used as a viewing element in thermal imaging systems.In this work, we selected the thermal growth conditions and obtained indium antimonide single crystals 100 mm in diameter in the crystallographic direction [100]. The solution of this problem has made it possible to significantly increase the yield of suitable photodetectors.Single crystals 100 mm in diameter were grown by the Czochralski method in a two-stage process. The design of the graphite heating unit was enlarged and matched to a working crucible with a diameter of 150 millimeters and a load of 4.5-5 kg.The Van der Pauw method was used to measure the electrical properties of the obtained single crystals, which corresponded to the standard parameters of undoped indium antimonide. Using an optical microscope, the etching pits were counted using the 9-field method. The dislocation density in crystals with a diameter of 100 mm was ≤ 100 cm-2 and corresponded to the values ​for crystals of 50 mm.

Контроль стану кровообігу нижніх кінцівок у хворих на цукровий діабет

Дослідження проблеми ураження нижніх кінцівок у хворих на цукровий діабет (ЦД) набуває все більшого значення у зв’язку зі значним поширенням кількості хворих. Важливим є питання ранньої діагностики діабетичної ангіопатії нижніх кінцівок. У проявах хвороби Рейно й ураження нижніх кінцівок у хворих на ЦД є багато спільного. При хворобі Рейно, як правило, спостерігається спазм дрібних артерій дистальних відділів кінцівок. У хворих на ЦД відбувається порушення магістрального кровотоку в артеріях нижніх кінцівок різного ступеня тяжкості, що також призводить до спазму дрібних артерій дистальних відділів. Впровадження термографічної діагностики дозволяє диференціювати хворобу Рейно від проявів ускладнень ЦД.

Fourier analysis of spectral characteristics of a matrix photodetector in the frequency and time domain

The purpose of this paper is to research the frequency and time characteristics of the photo-detector using the direct and inverse Fourier transform. The spectral characteristics of the matrix photodetector were selected as the object of research. For the channels of the trans-ducer it was found that the frequency spectrum consists of two elementary bands in the form of Gaussian curves. It was revealed that the spectra have super-broadband properties. The impulse (time) characteristic of the spectra is described by the equation in an analytical form, which is in good agreement with the calculation. The rise time of the transient response is 1.8–2.9 fs. The process of absorption of light is significantly influenced by dielectric relaxa-tion of the charge. The results obtained provide important information on the properties of the photodetector in the frequency and time domain.