Adjustable light source for low light level with nearly constant correlated color temperature

Low light level (LLL) calibration becomes more and more important since the rapid growth of remote sensing. The spectral radiance at normal higher light levels can be calibrated with good accuracy, while LLL spectral radiance cannot. If an adjustable light source can be designed at nearly constant correlated color temperature (CCT) covering several orders of magnitude, low light level spectral radiance can be obtained with the help of a photodetector. Whether or not the spectral distribution of an integrating sphere based light source is nearly constant is investigated. By adjusting the diameter of the variable aperture between the integrating sphere and tungsten lamp, the spectral radiance can be varied over 6 orders of magnitude. However, the relative spectrum in the red region increases notably when the spectral radiance is decreased to 1/100000. If the spectral radiance is decreased further, the spectral difference can be more than 300% and CCT decreases more than 250 K. By using baffles and another integrating sphere, low light level radiation source at nearly constant spectral distribution is obtained. The variation of CCT is less than 50 K over 6 orders of magnitude.

A Method for the Reduction of Out-of-Band Measurement Errors in Multi-band Instruments using Synthetic Source Distributions

A method to reduce multi-band sensor measurement biases due to finite out-of-band response is described. The method takes advantage of the fact that out-of-band measurement errors cancel if the calibration source and the measured source have the same spectral distributions—independent of their spectral distributions or the magnitude of a sensor band’s out-of-band response. Using a known spectral responsivity, a synthetic, arbitrary source spectral distribution can replace a realized spectral distribution in the measurement equation and the signal can be calculated rather than measured. Given the freedom to select any arbitrary distribution for the synthetic source, the efficacy of the approach depends on the fidelity of the replication of the measured spectrum by the synthetic source spectrum. To illustrate the method, an example application is given of top-of-the-atmosphere measurements of water-leaving radiance by multi-band filter radiometers on celestial Earth-viewing sensors.

THE STUDY OF HOMOGENEOUS AND HETEROGENEOUS SENSITIZED CRYSTALS OF CADMIUM SULFIDE. PART IV. FEATURES OF THE REVERSE PHOTOEXCITATION METHOD

For the first time, a reverse method of studying the spectral distribution curves of the photocurrent was applied, which allows to separate the contribution of equilibrium and non-equilibrium carriers. This publication is a continuation of the reviews [1-3]. In order to preserve the generality of the work, the numbering of sections is selected to be general. Numbers of formulas and figures are presented in sections. References to literature in each review are given individually. Cadmium sulfide crystals are used in our research as a convenient model material. The results obtained on them and the constructed models are also applied to other semiconductor substances.

INVESTIGATION OF THE INFLUENCE OF CORRELATED COLOR TEMPERATURE OF LED illuminatorS AS A FACTOR OF SAFETY LIGHTING OF HIGHWAYS FOR DIFFICULT WEATHER CONDITIONS

A investigation of the dependence of relative horizontal illumination level and brightness of the most common types of road surface in Ukraine when using LED illuminators with different spectral distribution of radiation in the presence of aerial aerosols of different optical densities (strong, moderate, weak fog and haze) is performed. Mathematical models of LED illuminators with correlated color temperature Tcc = (2200÷8400) K in the visible range of the spectrum λ = (380÷780) nm have been created. Their use together with the selected model of the spectral dependence of the scattering index β (λ) (Ferdinandоv’s model) of the atmospheric environment with the presence of aqueous aerosols, which cause a limited meteorological range of visibility MOR = (0.1÷3) km, showed a slight (1%) advantage in creation of illumination from lamps of a warm spectrum of radiation (TCC = 2200 K) in comparison with cold (Tcc = 8400 K) for cases of strong fogs with MOR = 100 m. Calculations involving the analysis of mathematical modeling of the spectral distribution of the reflection coefficients for two types of road surface (new and worn asphalt) proved that when using warm spectrum illuminators the brightness of the most common in Ukraine old asphalt pavement in the conditions of MOR = 100 m by 5% exceeds the corresponding value of the cold spectrum emitters. This difference gradually decreases as visibility is improved due to the weaker spectral dependence of β (λ) and at MV = 3 km is 4.5%. The advantage of using warm spectrum illuminators will be significantly enhanced for the case of estimating the brightness of the coverage over long distances, for example, airfield runways, which will significantly improve flight safety.

CREATING A SENSE OF THE UNUSUAL WITH CHROMATIC LIGHT

Due to the influence of COVID-19, there is a need to create an environment where people can relax and feel special in a separated space. Therefore, in this study, we will clarify the psychological changes that occur when people are surrounded by an unusual environment. This study prepared eight LED lighting colours: red, orange, yellow, green, blue, light blue, purple, and white. The room was illuminated, and the participants were asked to evaluate their impressions using the SD method on a 7-point scale. As a result of impression evaluation, red gave a warm impression, yellow gave a bright impression, blue gave a cold impression, and purple gave a mature impression, just like the psychological effects of colours. Green gave an artificial impression that was different from the psychological effects of the other colours. From these results, we can conclude that impressions do not correlate with colour symbolism when the entire room is illuminated with coloured light. In the future, we will clarify the relationship between wavelength and impression by studying the spectral distribution of each light source.

PHOTOELECTRIC PROPERTIES OF MnIn2S4 SINGLE CRYSTALS

The spectral distribution of the photoconductivity and the temperature dependence of the photocurrent of MnIn2S4 single crystals are investigated. The intrinsic, impurity photoconductivity and a maximum at an energy of 2.69 eV, which is associated with the intracenter transition of Mn2+ ions (6A1→4A1), are revealed in the photoconductivity spectrum. The region of the wavelengths of 600–1000 nm appears with an excess of manganese in the crystals and is caused by a donor defect. At temperatures of 80—145 K, the increase in the photocurrent is associated with the thermal depletion of the adhesion levels. The activation energy of the adhesion levels is determined.

On the empirical spectral distribution for certain models related to sample covariance matrices with different correlations

Given [Formula: see text], we study two classes of large random matrices of the form [Formula: see text] where for every [Formula: see text], [Formula: see text] are iid copies of a random variable [Formula: see text], [Formula: see text], [Formula: see text] are two (not necessarily independent) sets of independent random vectors having different covariance matrices and generating well concentrated bilinear forms. We consider two main asymptotic regimes as [Formula: see text]: a standard one, where [Formula: see text], and a slightly modified one, where [Formula: see text] and [Formula: see text] while [Formula: see text] for some [Formula: see text]. Assuming that vectors [Formula: see text] and [Formula: see text] are normalized and isotropic “in average”, we prove the convergence in probability of the empirical spectral distributions of [Formula: see text] and [Formula: see text] to a version of the Marchenko–Pastur law and the so-called effective medium spectral distribution, correspondingly. In particular, choosing normalized Rademacher random variables as [Formula: see text], in the modified regime one can get a shifted semicircle and semicircle laws. We also apply our results to the certain classes of matrices having block structures, which were studied in [G. M. Cicuta, J. Krausser, R. Milkus and A. Zaccone, Unifying model for random matrix theory in arbitrary space dimensions, Phys. Rev. E 97(3) (2018) 032113, MR3789138; M. Pernici and G. M. Cicuta, Proof of a conjecture on the infinite dimension limit of a unifying model for random matrix theory, J. Stat. Phys. 175(2) (2019) 384–401, MR3968860].

Modeling electron transfer from the barrier in InAs/GaAs quantum dot-well structure

We study single electron tunnelling from the barrier in the binary InAs/GaAs quantum structure including quantum well (QW) and quantum dot (QD). The tunneling is described in the terms of localized/delocalized states and their spectral distribution. The modeling is performed by using the phenomenological efective potential approach for InAs/GaAs heterostructures. The results for the two and three-dimensional models are presented. We focus on the efect of QD-QW geometry variations. The relation to the PL experiments is shown.