Measuring instruments
Study of the Earth’s surface objects reflectance characteristics with unmanned aerial vehicles is one of the most actual remote sensing trends. Aim of this work was to develop a method for obtaining of photospectral data using unmanned aerial spectrometry vehicle.
An adaptation of the cameras spatial resolution evaluating technique based on a specialized target photographic fixation was proposed. A method for synchronizing of the camera and spectrometer of the videospectral device was also proposed. It was based on an experiment with spectra and screen images recording. Different colors were sequentially displayed on the screen. The percentage contribution of each of colors to the “mixed” spectra was calculated. So the out-of-sync time estimation became possible. In addition the work proposed the method for combining images and spectra with their merging into photospectral images. The method allows to consider the aircraft displacement when linking the spectrometer field of view to the RGB image. The way for photospectral images combining based on the images key points detectors was also proposed.
Spatial resolutions for 3 aerial vehicle cameras were obtained. The study showed that the spatial resolution decrease of Zenmuse H20T caused by the device carrier movement with a speed of up to 5 m/s can be ignored. The videospectral device camera and spectrometer out-of-sync time was evaluated. An automatic merging of a set of images using key points detection was made. The spectrometry areas were linked to the panoramic image. The reflectance coefficients were obtained for each of the areas in the range of 350–900 nm. The areas to image linking accuracy was 84.9 ± 11.6 %.
A discrepancy between the angular spatial resolution values got experimentally and theoretically was revealed as a result of the cameras spatial resolution evaluating. This indicates the importance of the imaging equipment spatial resolution experimental evaluation. The videospectral device spectrometer and observation camera out-of-sync time evaluation made it possible to correct the data recording time. This led to the timing error standard deviation reduction from 142 ms to 15 ms. The way for the unmanned aerial spectrometry vehicle data obtaining in a photospectral representation was developed. The proposed methods and techniques can be used in similar unmanned systems.
Measuring devices and systems containing sensors that require sinusoidal excitation are widely used in information and measurement technology both in production conditions and in research practice. Examples include various types of metal detectors, eddy current flaw detectors, analyzers of liquid media, electrometers with a dynamic capacitor, etc. The aim of the work was to develop the optimal architecture and algorithms for the operation of intelligent sensors intended for use in measuring systems operating according to the sinusoidal excitation – response scheme.
This paper describes the approach proposed by the authors to the construction of intelligent sensors based on modern microcontrollers, the distinctive feature of which is the continuous generation of sinusoidal excitation and reading responses in the background, as well as setting the readiness flags for data processing in the main process of the microprocessor, which ensures uninterrupted execution of background processes, the main of which is the generation of a sinusoidal excitatory action.
This approach has been tested in the development of charge-sensitive surface mapping systems, such as the Kelvin probe based on a vibrating capacitor, and the surface photo voltage probe for the case of semiconductors.
A prototype of a pulsed diode-pumped laser based on Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) crystal emitting at 1064 nm is presented for use in airborne rangefinders and atmospheric LIDARs without use of expensive production technologies and components.
Actively Q-Switched laser pulse energy was estimated. Spatial characteristics of laser beam and dependence of pulse energy on the pump pulse energy were obtained at room temperature. Results of diodepumped laser pulse energy measurements are provided within 2 min for pulse repetition rates of 1, 4, 12.5, 22 Hz at ambient temperature range from -40 to +60 °C. Laser diode arrays temperature stabilization was achieved by the use of Peltier module with cooling capacity of 30 W.
Pulse energy values not less than 80 mJ were achieved in the studied ranges of ambient temperature and pulse repetition rate. Laser beam divergence at room temperature does not exceed 1.9 mrad.
Methods of measurements, monitoring, diagnostics
In silicon microelectronics, flat metal spirals are formed to create an integrated inductance. However, the maximum specific inductance of such spirals at low frequencies is limited to a value of the order of tens of microhenries per square centimeter. Gyrators, devices based on operational amplifiers with approximately the same specific inductance as spirals, are also used. Despite the fact that such solutions have been introduced into the production of integrated circuits, the task of searching for new elements with high values of specific inductance is relevant. An alternative to coils and gyrators can be the effect of negative differential capacitance (i.e., inductive type impedance), which is observed in barrier structures based on silicon.
The purpose of the work is to study the low-frequency impedance of Schottky diodes (Mo/n-Si) containing defects induced by α-particles irradiation and determination of the parameters of these defects by methods of low-frequency impedance spectroscopy and DLTS (Deep Level Transient Spectroscopy).
Unpackaged Schottky diodes Mo/n-Si (epitaxial layer of 5.5 μm thickness and resistivity of 1 Ohm∙cm) produced by JSC “Integral” are studied. Inductance measurements were carried out on the as manufactured diodes and on the diodes irradiated with alpha particles (the maximum kinetic energy of an αparticle is 5.147 MeV). The impedance of inductive type of the Schottky diodes at the corresponding DC forward current of 10 µA were measured in the AC frequency range from 20 Hz to 2 MHz. DLTS spectra were used to determine the parameters of radiation-induced defects. It is shown that irradiation of diodes with alpha particles produces three types of radiation-induced defects: A-centers with thermal activation energy of E1 ≈ 190 meV, divacancies with activation energies of E2 ≈ 230 meV and E3 ≈ 410 meV, and Ecenters with activation energy of E4 ≈ 440 meV measured relative to the bottom of c-band of silicon.
At present time widespread use of autonomous laser systems supposes reducing of supply energy, consumed by laser sources that are included in their composition and at the same time increasing of their output energy characteristics. The objective of this work was practical confirmation of possibility of laser beam combining in systems based on a ring delay line.
The experimental setup that implements the principle of synchronous laser beam combining scheme on the ring fiber-optic delay line, developed by authors earlier, is made. The schematic diagram of the manufactured setup is presented, its operation principle is described in detail and its composition is considered. It is noted that in order to achieve the objective measurements of electrical signals received from the photodetector of the setup and measurements of the part of laser radiation power removed by the splitter and formed in the fiber-optic path of the setup are performed. Results of measurements are presented as the waveforms of electrical signals from the photodetector and of power values at the output of the splitter. Plots of dependence of the output power and the circulation power on the power of the initial laser beam introduced into the setup are presented.
Analysis of results showed that the laser beam combining occurs in the ring fiber-optic delay line. Besides, it was found that the proposed scheme provides an increase in the power of the initial beam by 1.05…1.11 times.
The prism deflector which is a multifaceted prism with reflective facets is the most common scanning element that allows to quickly fill a wide scanning area with laser radiation pulses along one coordinate. The parameters of a prismatic deflector are related to the characteristics of the laser radiation of the scanned area parameters and of the deflector position, and are also limited by various factors, such as safety requirements or scanning time. The aim of this work was to analyze the relationship between the external operating conditions of a laser scanning system and the internal design parameters of a prism deflector.
A variant of calculating of laser pulses frequency by the number of spots and their overlap coefficient is considered. A method for calculating of a prism deflector characteristics based on external parameters, such as the angle of incidence of radiation to the facet and the width of the Gaussian beam with dimensions that are safe for а human eye is proposed. Рrismatic deflectors parameters are proposed depending on the number of reflecting facets. Dependence of a deflector size on the angle of radiation incidence to the reflecting face is shown.
When designing a prismatic deflector of a laser scanner used to fill a certain scanning area with the required angular size σ by varying such parameters as the number of faces m and the feed angle α it is possible to achieve optimal deflector characteristics and scanning mode for the task.
The main results of the creation of the domestic complex “Vizir” for measuring bidirectional spectropolarization reflection coefficients and brightness of natural and artificial objects were presented in the article. Its purpose, composition and main technical parameters were indicated.
Spectral-polarization studies of the characteristics of samples that simulates objects (pollution) of natural (forest fires) and man-made (oil spills) emergencies were performed with the help of complex “Vizir” using polarizing nozzles under various conditions (angles of illumination, observation, pollution concentration, the time that passed since the contamination, the degree of wood thermal damage). The results of studies made it possible to increase the accuracy of identification of monitoring objects in emergency zones up to two times.
The main provisions of the two developed methods were outlined. The first method was methodology for determination of the controlled parameters of forest fires by means of aviation monitoring, which makes it possible to record the maximum values of the degree of polarization of reflected radiation for coal 30–40 % and for semi-coal 15–20 % in the wavelength range from 0.5 to 0.7 μm. The second one was methodology for determination of the controlled parameters of man-made emergencies with oil spills by means of aviation monitoring, which makes it possible to record the maximum values of the degree of polarization of an oil spill on water: 40–50 % at optimal view angles close to specular in relation to the angle of solar radiation incidence.
The developed methods were introduced into the activities of the Ministry for Emergency Situations of the Republic of Belarus to make the right management decisions to eliminate emergency situations and their consequences.
ISSN 2414-0473 (Online)