Intensity Of Reflected Radiation Research Articles

Plasmons in AlGaN/GaN grating-gate structure probing with 300 K background illumination

We show that terahertz plasmons in AlGaN/GaN grating-gate structures efficiently modulate the reflection of room temperature thermal radiation, leading to spectra that are in agreement with the measurements of plasmon absorption using high-power external sources. For typical samples of a few square millimeters in size, the reflected radiation intensity is relatively weak, and measurements need the use of gate voltage plasmon modulation and lock-in detection techniques. We show that unintentional use of lock-in techniques may lead to artifacts and demonstrate what kind of special precautions need to be taken into account. We show that drain voltage modulation also leads to modulation of the reflected thermal radiation by plasmons. Our results are of key importance for the research on new resonant plasmon-based terahertz sources because of the always present superposition of electrically excited terahertz emission and background radiation reflected from the structures.

Model of diffuse reflection of optical radiation from the surface of biological tissue, implemented on the basis of two-dimensional fractional Brownian motion process

The numerical model of the diffuse reflection of Gaussian beam from the surface of biological tissue is introduced. The two-dimensional fractional Brownian motion (fBm) with the Hurst index H and the scale parameter σ was used for the simulations of the tissue surface relief. For the surfaces described by fixed σ = 0.1 and H = 0.55, H = 0.803 (corresponds to the surface of a banana fruit), H = 0.9, the angular distributions of the reflected radiation intensity were calculated using a Kirchhoff integral approach. The resulting distributions considerably differ from each other. Therefore, the introduced model can be used for the solution of the inverse problem of finding the fBm parameters of tissue surfaces employing the experimentally measured distribution of the reflected radiation intensity.

Optimal calculation method of aircraft infrared physical imaging simulation

In order to meet the needs of high-precision simulation images in the development process of infrared imaging detection system, the infrared physical imaging radiation transmission model for aircraft was established, and the ray tracing method was used to realize the simulation calculation of radiance image. Aiming at the difference between the reflection characteristics of the aircraft skin and the distribution characteristics of the radiation source, an optimization method for skin radiance calculation using direct lighting multi-importance sampling was proposed. Aiming at the characteristics of strong emission ability and weak extinction ability of aircraft exhaust plume, an optimization method for exhaust plume radiance calculation using combining integration was proposed. The correctness and effectiveness of the physical imaging model and calculation optimization method were verified through simulation experiments. The relative error of the skin radiation calculation is better than 0.05%, and the relative error of the tail flame radiation calculation is better than 0.1%. Compared with the traditional ray tracing method, the calculation optimization method has a faster convergence speed and stronger adaptability. Infrared imaging simulation and radiation characteristics analysis of stealth aircraft were carried out. The simulation results show that infrared stealth technology can reduce the radiation intensity in the mid-waveband and long-waveband, and increase the reflected radiation intensity in the short-waveband.

Assessment of the influence of the manufacturing quality of a reflective coating on the angular distribution function of the reflected radiation intensity of laser signaling systems

Assessment of the influence of the manufacturing quality of a reflective coating on the angular distribution function of the reflected radiation intensity of laser signaling systems

Visualizing the Intensity Distribution of a Microwave Field Using a Microstrip Rectenna with a Schottky Diode

A microwave radiation intensity indicator based on an antenna-coupled detector (rectenna), an amplifier, and a semiconductor light-emitting diode was constructed and tested. This device is a hybrid integrated circuit, where a microstrip log-periodic antenna on a dielectric substrate also serves as a mechanical carrier. The possibility of visual determination of the shape of the antenna radiation pattern and the shape of an object based on the reflected radiation intensity was demonstrated experimentally at 10 and 30 GHz.

A Novel Illumination Compensation Technique for Multi-Spectral Imaging in NDVI Detection.

To overcome the dependence on sunlight of multi-spectral cameras, an active light source multi-spectral imaging system was designed and a preliminary experimental study was conducted at night without solar interference. The system includes an active light source and a multi-spectral camera. The active light source consists of four integrated LED (Light Emitting Diode) arrays and adjustable constant current power supplies. The red LED arrays and the near-infrared LED arrays are each driven by an independently adjustable constant current power supply. The center wavelengths of the light source are 668 nm and 840 nm, which are consistent with that of filter lens of the Rededge-M multi-spectral camera. This paper shows that the radiation intensity measured is proportional to the drive current and is inversely proportional to the radiation distance, which is in accordance with the inverse square law of light. Taking the inverse square law of light into account, a radiation attenuation model was established based on the principle of image system and spatial geometry theory. After a verification test of the radiation attenuation model, it can be concluded that the average error between the radiation intensity obtained using this model and the actual measured value using a spectrometer is less than 0.0003 w/m2. In addition, the fitting curve of the multi-spectral image grayscale digital number (DN) and reflected radiation intensity at the 668 nm (Red light) is y = −3484230x2 + 721083x + 5558, with a determination coefficient of R2 = 0.998. The fitting curve with the 840 nm (near-infrared light) is y = 491469.88x + 3204, with a determination coefficient of R2 = 0.995, so the reflected radiation intensity on the plant canopy can be calculated according to the grayscale DN. Finally, the reflectance of red light and near-infrared light can be calculated, as well as the Normalized Difference Vegetation Index (NDVI) index. Based on the above model, four plants were placed at 2.85 m away from the active light source multi-spectral imaging system for testing. Meanwhile, NDVI index of each plant was measured by a Greenseeker hand-held crop sensor. The results show that the data from the two systems were linearly related and correlated with a coefficient of 0.995, indicating that the system in this article can effectively detect the vegetation NDVI index. If we want to use this technology for remote sensing in UAV, the radiation intensity attenuation and working distance of the light source are issues that need to be considered carefully.

Тематические карты в научных исследованиях Луны

The article presents the results of astrophysical studies of the Moon’s reflected and intrinsic radiation. We studied the intensity of the Moon’s infrared radiation and, thus, carried out a detailed research of the brightness temperature of the Moon’s visible disc, estimated the thermal inertia of the coating substance by the rate of its surface cooling, and the degree of the lunar soil fragmentation. Polarimetric, colorimetric and spectrophotometric measurements of the reflected radiation intensity were carried out at different wavelengths. In the article, we present maps prepared based on our measurement results. We conducted theresearch of the unique South Pole – Aitken basin (SPA). The altitude profiles of the Apollo-11 and Zond-8 spacecrafts and the data of laser altimeters of the Apollo-16 and Apollo-15 spacecrafts were used as the main material. Basing upon this data we prepared a hypsometric map of SPA-basing global relief structure. A surface topography map of the Moon’s Southern Hemisphere is given in the article. The topography model of the SPA topography surface shows displacement centers of the altitude topographic rims from the central rim. Basing upon the detailed study of the basin’s topography as well as its “depth-diameter” ratio we suggest that the basin originated from the impact of a giant cometary body from the Orta Cloud. In our works, we consider the Moon as a part of the Earth’s space infrastructure. High growth rates of the Earth’s population, irrational nature management will cause deterioration of scarce natural resources in the near future. In our article, we present maps of the natural resources on the Moon pointing out the most promising regions of thorium, iron, and titanium. Probably in 20 or 40 years a critical mining level of gold, diamonds, zinc, platinum and other vital rocks and metals will be missing on the Earth.

Research on Ground Feature’s Polarized Properties with Multi-Spectral and Multi-Angle AirMSPI Data

Polarization is an important characteristic of electromagnetic wave, and using polarization information to study ground features has been proved to be an effective means. Research on ground feature’s polarized properties is an essential part of earth observation. At present, it is in highly need of accurate polarization sensors globally. AirMSPI , (Airborne Multiangle Spectro-Polarimetric Imager) as a new airborne polarized sensor, can obtain multi-band and multi-angle polarization data, and the spatial resolution can reach to ~10 meters. Using the experimental data of Tracy in the year of 2013, this paper analyzes the varying pattern of DOLP (Degree of Linear Polarization) as well as pBRF(polarized Bidirectional Reflectance Factor) in 470 nm, 660 nm, 865 nm bands and 9 view zenith angles. The result shows that, forward scattering of ground features contains plenty of polarized radiation, and ground features present strong non-lambertian effect near principal plane of incidence. DOLP and pBRF has strong correlation to relative position between incidence and view angle. DOLP reaches the maximum value when two directions are perpendicular while pBRF increases with larger view zenith angle. Because of atmospheric effect, radiance of blue band contains most polarized light. However, red and infrared band can attenuate atmospheric molecular polarization scattering effectively, thus contain more polarization details of ground features. Water, artificial structure, residential area, bare soil and vegetation show distinct polarization characteristics, and can be clearly identified. Due to depolarization effect from multi-scattering effect, DOLP and reflected radiation intensity have highly negative correlation, with correlation coefficient generally more than -0.8. AirMSPI sensor can provide high-quality polarization data, as a strong verification to ground-based and satellite-based polarization data, and support parameters inversion of atmosphere and ground features.

The Monte Carlo method and analytic averaging for estimation of parameters of polarized radiation asymptotics

A problem of estimation of parameters of polarized radiation time asymptotics is considered in the paper. Using the Monte Carlo method, precise estimates of such parameters are obtained for a half-infinite layer of a material based on the calculation of parametric time derivatives. For two variants of such problem: with a matrix of aerosol scattering and with a Rayleigh matrix of molecular scattering, it is shown that polarization does not influence the asymptotics of the reflected radiation intensity determining the ‘back-scattering noise’ in optical probing of material.

Spatial modulation of a light beam reflected from a nonlinear DFB-structure

Spatial reflected radiation dynamics is studied when a powerful light beam propagates through a nonlinear DFB-structure. The spatial reflected radiation characteristics depending on Bragg detuning and input Gaussian beam parameters are investigated using numerical simulations. The spatial spectrum of the reflected radiation modes is analytically found for the input pulse with a quadratic shape. It is shown that the process of formation of the reflected beam spatial profile is determined by the self-influence effects and the nonlinear Bragg detuning value. The reflected radiation intensity has, as a rule, a ring-shaped structure.

Reflection of a nonstationary beam of light from an absorbing medium in the case of grazing incidence

Temporal characteristics of the reflected radiation intensity in the case of a nonstationary light beam incident at grazing angles upon a semi-infinite medium with large-scale scattering centers are investigated. The problem of small-angle light reflection is solved within the Fokker–Planck approximation. An analytical expression for the reflected radiation intensity is obtained. Temporal characteristics of the reflected radiation are investigated in detail for the most important cases of incident beam modulation: δ pulse, a sequence of rectangular pulses of different duty factors, and a harmonically modulated light signal. The transition mode for different grazing angles and parameters of the scattering medium has been investigated explicitly. Thus, for example, the characteristic transition time to the stationary mode is calculated for irradiation of the medium with a steplike light pulse.

Intensity fluctuations during focusing of reflected light in a turbulent atmosphere

An analysis is made of fluctuations in the intensity of reflected laser radiation in the focal plane of a receiving telescope. It is established that when the fluctuations of the wave incident on the reflector reach saturation, the focusing can alter appreciably the level of saturation of the variance of the reflected radiation intensity compared with the variance in the plane of the receiving aperture.

Intensity fluctuations of light in the focal plane of a receiving telescope caused by round-trip propagation through a turbulent atmosphere

The intensity fluctuations in the focal plane of a receiving telescope of radiation reflected in a turbulent atmosphere have been analyzed. It was found that, when fluctuations of an incident wave are saturated, the focusing can significantly modify the variance of the reflected radiation intensity in comparison with the corresponding value in the aperture plane of the receiving telescope.