Sensitivity Of Human Eye Research Articles

Evaluating the general V(λ), mismatch spectral quality factor index ƒ₁ and the uncertainty of photometers

The general term photometry refers to the measurement of light and its perceived brightness; it can be applied to various purposes, including lighting design, display calibration, and the setting of safety standards. A device used for measuring light is called a light meter or photometer. Ideally, such devices should have a spectral responsivity-that is, they should respond to light in a way which mimics the human eye's sensitivity to different wavelengths. The sensitivity of the human eye is described by the Commission Internationale de l'Éclairage, CIE, luminous efficiency function, V(λ), a plot of the sensitivity of the eye versus wavelength over the visible region, from violet, approximately 380 nm, through red, approximately 780 nm. In practical applications, it is usually preferable to detect light with silicon or selenium photodetectors and measure the electrical current generated. These photodetectors are sensitive to a wide range of wavelengths, including those outside of the visible spectrum: ultraviolet (UV) and infrared (IR). However, due to its nature, the spectral responsivity of silicon and selenium photodetectors is also different from that of the human eye. For example, silicon photodetectors are much more sensitive to infrared radiation, which is imperceptible to human vision. This in turn leads to erroneous light measurements when using the direct raw response of the detector. The spectral quality factor and , indicating the mismatch between the spectral responsivity and the CIE luminous efficiency function V(λ), is the most crucial characteristic of photometers. The general mismatch index , denoted as V(λ), delineates the disparity between a photometer's relative spectral responsivity and the spectral luminous efficiency function for photopic vision, V(λ). It's highly probable that photometers will adopt white light-emitting diode (LED) sources as calibration references going forward. This transition may necessitate refining the general V(λ) mismatch index's definition, possibly through alternative normalization methods for or by introducing a different assessment function for evaluating mismatches . In this research, spectral quality factor for the photometer NIS-2 has been determined with value 3.8%. This percentage value is classified the photometer NIS-2 as medium quality. The uncertainty was determined through a calculation performed using my Microsoft Excel program, and the final value obtained is 0.010.

P‐37: Enhanced Text Display with Balanced Anti‐reflection and Anti‐glare Design

Influences of anti‐reflection (AR) and anti‐glare (AG) components on display performance were studied, especially for the scenario of indoor text reading. Both ambient influence and display clarity were analyzed in search of a cost‐effective combination of the two components. A design method based on human eye sensitivity curves was developed for the optimization of AG component.

Novel green/red oxyfluoride phosphors with excellent optical properties for near-UV excited white light emitting diode

Novel eye-sensitive Ba3Nb2O2F12(H2O)2:Tb3+ green and Ba3Nb2O2F12(H2O)2:Mn4+ red oxyfluoride phosphors with extremely strong absorption in the UV region were designed and synthesized by simple co-precipitation strategy. Particularly, Tb3+ ions were doped in this matrix for the first time, which greatly improves their absorption efficiency in the near ultraviolet region (367 nm) and emits sharp green light (544 nm). In addition, the Ba3Nb2O2F12(H2O)2:Mn4+ red phosphors have strong zero phonon line (ZPL) emission at 625 nm, which is conducive to improving the sensitivity of human eye and color purity. Meanwhile, the optical properties of the red phosphor are significantly enhanced via doping K+ cations as charge compensators. Crystal field environment and nephelauxetic effect of the as-prepared phosphors before and after K+ cation doping were systematically analyzed. Moreover, these synthesized red/green phosphors have good thermal stability and moisture resistance. Remarkably, the as-prepared Ba3Nb2O2F12(H2O)2:5%Mn4+ or K0.9Ba2.1Nb2O2F12(H2O)2:5%Mn4+ red phosphors can be directly mixed with the as-synthesized Ba3Nb2O2F12(H2O)2:13%Tb3+ green phosphor coating on 365 nm near-ultraviolet LED chip to package WLED devices with excellent electroluminescence performance. These findings are conducive to opening an avenue for screening the unique structure of optical materials.

Exploring Different Designs in Thieno[3,4-b]pyrazine-Based Dyes to Enhance Divergent Optical Properties in Dye-Sensitized Solar Cells

Two novel organic sensitizers for Dye-Sensitized Solar Cells (DSSC), called TP1 and TP2, based on the electron-poor thieno[3,4-b]pyrazine (TPz) π-bridge and the electron-rich N,N-bis(4-(hexylthio)phenyl)aniline (TPA) were designed following two different approaches: the classical D-A-π-A design and a symmetric structure with double anchoring functions. Both compounds were prepared exploiting short synthetic pathways based on direct arylation strategies and possibly one-pot desymmetrization. The two novel dyes displayed opposite optical properties: a broad and intense light absorption over the entire visible spectrum for TP1, and a localized absorption that peaked in the center of the visible region for TP2, resulting in a pitch-dark coloration and a green tone, respectively. When assembling the photovoltaic devices, different electrolyte compositions were explored to enhance the optical properties of the dyes. Power conversion efficiencies as high as 5.2% under full sun intensity were recorded for small test devices. The composition of the light transmitted through the TP2-containing transparent DSSC fits well with the human eye sensitivity spectrum, thus fulfilling the transparency requirements for building-integrated photovoltaics (BIPV).

A novel image steganography algorithm based on hybrid machine leaning and its application in cyberspace security

As an important technology in the field of cyberspace security, image steganography is of great strategic significance to the research of image steganography. With the wider application of image steganography technology, there are fewer and fewer cases of image steganography using a single algorithm, and more adaptive steganography of images is used instead. According to the different sensitivities of human eyes to the foreground area and background area of the image, the key to solving this problem is to segment the foreground and background of the carrier image. Aiming at the problem of low maximum embedding capacity of traditional steganography algorithm and poor perception quality of carrier image after steganography, this paper firstly uses adaptive threshold segmentation to process carrier removal image, and divides the image into foreground and background regions. Secondly, in order to improve the embedding capacity, high-capacity steganography is used for pixels in the foreground area of the image, and low-capacity steganography is used for the background area of the image. At the same time, in order to improve the security of the secret information, hybrid machine learning is used to encrypt before the secret information is embedded, and finally BFS (Breadth First Search) is used to complete the steganography of the carrier image. The experimental results show that the PSNR (Peak Signal to Noise Ratio) value of the pictures after steganography by this algorithm is above 52.71 dB, which has high image perception quality. Better protection of confidential information.

High Precision Mesh-Based Drone Image Stitching Based on Salient Structure Preservation and Regular Boundaries

Addressing problems such as obvious ghost, dislocation, and distortion resulting from the traditional stitching method, a novel drone image-stitching method is proposed using mesh-based local double-feature bundle adjustment and salient structure preservation which aims to obtain more natural panoramas.The proposed method is divided into the following steps. First, reducing parallax error is considered from both global and local aspects. Global bundle adjustment is introduced to minimize global transfer error, and then the local mesh-based feature-alignment model is incorporated into the optimization framework to achieve more accurate alignment. Considering the sensitivity of human eyes to linear structure, the global linear structure that runs through the images obtained by segment fusion is introduced to prevent distortions and align matching line segments better. Rectangular panoramas usually have better visual effects. Therefore, regular boundary constraint combined with mesh-based shape-preserving transform can make the results more natural while preserving mesh geometry. Two new evaluation metrics are also developed to quantify the performance of linear structure preservation and the alignment difference of matching line segments. Extensive experiments show that our proposed method can eliminate parallax and preserve global linear structures better than other state-of-the-art stitching methods and obtain more natural-looking stitching results.

Accuracy of Cirrus Detection by Surface-Based Human Observers

Abstract The longest cirrus time series are ground-based, visual observations captured by human observers [synoptic observations (SYNOP)]. However, their reliability is impacted by an unfavorable viewing geometry (cloud overlap) and misclassification due to low cloud optical thickness, especially at night. For the very first time, this study assigns a quantitative value to uncertainty. We validate 15 years of SYNOP observations (2006–20) against data from the cloud lidar flown on board the Cloud–Aerosol Lidar and Infrared Pathfinder (CALIPSO) spacecraft. We develop a dedicated method to match SYNOP reports (with a hemispherical field of view) with lidar samples (along-track profiles). Our evaluation of the human eye’s sensitivity to cirrus revealed that it is moderate, at best. In perfect conditions (daytime with no mid/low-level clouds) the probability of correct detection was 44%–83% (Cohen’s kappa coefficient < 0.6), and this fell to 24%–42% (kappa < 0.3) at night. Lunar illumination improved detection, but only when the moon’s phase exceeded 50%. Cirrus optical depth had a clear impact on detection. When clouds at all levels were considered (i.e., real-life conditions), the reliability of the visual method was moderate to poor: it detected 47%–71% of cirrus (kappa < 0.45) during the day and 28%–43% (kappa < 0.2) at night and decreased with an increasing low/midlevel cloud fraction. These kappa coefficients suggest that agreement with CALIPSO data was close to random. Our findings can be directly applied to estimations of cirrus frequency/trends. Our reported probabilities of detection can serve as a benchmark for other ground-based cirrus detection methods. Significance Statement Cirrus clouds heat the atmosphere, so any increase in their frequency will contribute to climate warming. The longest cirrus time series (including the presatellite era) are surface-based detections by a human observer at a meteorological station. Our study is the first to quantitatively evaluate the reliability of these observations. Our results show that, because of the viewing geometry (cloud overlap) and human eye sensitivity, reliability ranges from moderate at best to very low. Nighttime detections are especially unreliable, as well as those in the presence of low/midlevel cloud. Cirrus frequencies and trends calculated from visual observations should, thus, be considered with caution.

IoT based smart and intelligent smart city energy optimization

With the effective result of IoT architecture in all research areas, we propose IoT framework based energy efficient smart and intelligent street road lighting system that consist of IoT sensor bases smart electric pole with controller for tuning LED lamps. In our work we replace traditional metal halide lamps with mesophic design LED lamps based on human eye sensitivity and it provides significant saving of energy too. Based on the sensor unit information about traffic flow and presence and absence of occupant smart and intelligent decision making module compute intensity level that generate different width pulse using PWM dimming system which triggers LED power switch via DALI controller mounted inside LED Light Controller. For efficient use of sustainable energy resources we use sustainable power systems that consist of PV solar panel units, Battery storage systems and smart electric power grids. For the charging battery system we use MPPT based dynamic battery charging algorithm. From experiment and simulated result, we observe that proposed energy efficient Smart Street lighting saves considerable amount of energy during peak and off peak hours not only at highway roads but at residential and sub-urban pedestrian areas also. It will finally decrease the consumption of energy and carbon emission. We perform comparative result analysis of proposed systems with existing lighting systems based on energy consumption. Our experimentation result also represents the effectiveness of the proposed dynamic battery charging algorithm based on the battery storage PV solar panel system performance.

Theory of speckle suppression in a laser projector based on a long multimode fiber

We analyzed the speckle suppression efficiency of a multimode fiber in a practical laser projector, and developed a theoretical model. Theoretical analysis and simulations indicate that the speckle suppression coefficient can be approximated as a linear function of the square root of the ratio of the numerical aperture of the objective lens and the eye. To suppress the speckle below human eye sensitivity, the objective lens should have a large numerical aperture. The decorrelation uses only the radial direction of the objective lens aperture for speckle suppression and does not consider the azimuthal direction, which can be the focus of future studies. The speckle contrast data obtained in the experiments are consistent with the theoretical results.

Study of photoluminescent and photometric properties of ZnS:Mn2+ quantum dots for white light emission

Abstract In this paper, ZnS, Mn2+-doped ZnS, and ZnS:Mn2+/ZnS core-shell quantum dots (QDs) are successfully prepared by the co-precipitation route at 80 °C in basic aqueous solutions. X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDX), UV–Visible absorption (UV–Vis), photoluminescence (PL), photoluminescence excitation (PLE) spectroscopy and photometric studies were employed to characterize the samples. The QDs have the zinc blende structure, and their CIE (x, y) chromaticity coordinates can be tuned by the Mn2+ impurity and the TGA-Zn2+ concentrations. The overlap between these QDs spectral power and the human eye sensitivity spectra is significantly enhanced with the efficient energy transfer process. The scotopic/photopic (S/P) ratios, the luminous efficacy of optical radiation (LER), and the color correlated temperature (CCT) increase from 0.93 to 1.69, 389.84–706.53 l m/Wotp, and 2782–14,037 K, respectively. As a result, the ZnS:Mn2+ QDs are suitable for the development of tune color components in white thin-film electroluminescent (TFEL) devices as well as light-emitting diodes (LEDs).

Indoor daylighting using Fresnel lens solar-concentrator-based hybrid cylindrical luminaire for illumination and water heating

Abundant availability of sunlight during daytime and the broad spectrum of solar energy has attracted much attention from researchers. The photometric parameters of sunlight such as color coordinates, color rendering index, and color temperature are most appropriate for human vision as compared to artificial light sources. This is due to the fact that visible portion of sunlight is almost uniform and matches perfectly with the human eye sensitivity curve. Further, it is well known that sunlight also has great health benefits. To exploit these advantages, we have developed a solar concentrator system based on a large Fresnel lens and a light guide to transport sunlight indoors. The infrared portion of solar energy is utilized for water heating, and the visible portion of sunlight is transmitted via a plastic optical fiber (POF) bundle which guides sunlight into the rooms. One end of the POF is coupled with a light guide, and another end is coupled with a cylindrical rod-shaped luminaire made up of acrylic. POFs are low cost, flexible, and easily available compared to glass fibers, and therefore are generally used for transporting sunlight indoors. However, the spectral profile of transmitted sunlight does not remain uniform in the visible portion while propagating via long POF. To achieve optimum spectral profile, a blue LED is ingrooved into the cylindrical luminaire. The design of the system, experimental details, thermal efficiency, and photometric parameters such as color coordinates, illuminance, optical efficiency, and spectrum of indoor lighting are reported. The proposed hybrid system will reduce the requirement of electricity consumption during the daytime, improve indoor illumination quality, and be useful for sustainable development.

Development of criteria for determining the color saturation of gemstones

The urgency of the problem is conditioned by spectral methods development providing objectivity and accuracy of gemstones color grading. The purpose of the work: working-out the criteria which allows to determine gemstones saturation based on physicsmathematics patterns and spectral data. Methodology of the research: studying of colored gemstones transmittance spectra, discovery of the regularities and development of physics-mathematics methods for the color saturation grading. Results. The absolute and relative criteria for gemstone saturation grading was suggested as ratio of difference between light transmittance to squared difference between wavelengths at the area of basic chromophore element. Experimental data and allochromatic gemstones saturation calculation examples were presented considering spectral sensitivity of human eye. Summary. Gemstones absorption and transmittance spectra research allows to define tone and saturation gemstone color features. To improve tone and saturation definition accuracy, it is necessary to select standard hue of gemstones for wavelengths scale graduating along with spectral sensitivity of human eye.

Investigation of speckle suppression beyond human eye sensitivity by using a passive multimode fiber and a multimode fiber bundle.

A method of speckle suppression without any active device is expected for pico-projectors. The effectiveness of the passive method of speckle reduction using a single multimode fiber and a multimode fiber bundle was actually measured and theoretically analyzed. The dependences of the speckle contrast and speckle suppression coefficient on the parameters of multimode fiber and projection systems were investigated. Our results shown that the efficiency of speckle suppression was limited because only the radial direction of the objective lens aperture was used. An improvement using both of the radial and azimuthal directions of the objective lens aperture is required.

Ultraefficient Green LEDs Using Quantum Dots in Liquid Matrix

Green spectral range, which has the highest human eye sensitivity, is one of the most fundamental colors in lighting and display. Quantum dots (QDs) offer exceptional optical properties including high quantum yield (QY), strong absorption, and narrow emission linewidths for efficient green-emitting diodes. In this article, we demonstrated QD-based light-emitting diodes (QD-LEDs) that operate at a luminous efficiency (LE) level of 95 lumens per electrical watt, the luminous efficacy of optical radiation of 409 lumens per optical watt, and external quantum efficiency (EQE) of 23.3% in the green spectral region. For that, we synthesized 1-octanethiol-capped CdSe/ZnS QDs with an absolute QY of 91% and integrated them in a liquid matrix that allows conservation of the QD efficiency in device architecture. Our simulations were in agreement with the performance of the fabricated QD-LEDs, and they showed that the QD-LEDs can be further improved to reach LE levels over 250 lm/W.

Spatiotemporal Symmetric Convolutional Neural Network for Video Bit-Depth Enhancement

In contrast to the high sensitivity of human eyes and rapid development of modern display devices in terms of dynamic range, mainstream multimedia sources are generally at relatively lower bit depths (BDs). Therefore, BD enhancement (BDE), which attempts to transform low-BD multimedia sources into high-BD sources, is considered of significant research value. Current BDE algorithms are based on images rather than videos. However, for massive numbers of videos, temporal continuity among frames should be considered. Thus, in this paper, we propose a spatiotemporal symmetric BDE network for videos based on an encoder–decoder network. Consecutive frames are input into five subnets in the encoder, where the convolutional filters in the temporal symmetric subnets share the same weights to achieve lower model complexity. In addition, symmetric skip connections are introduced between the symmetric convolutional/deconvolutional layers of the encoder/decoder to pass features and alleviate the gradient diffusion problem. The experimental results show that our model can efficiently eliminate false contours and chroma distortions. The model significantly outperforms state-of-the-art image BDE algorithms and single-frame baseline models in terms of PSNR and SSIM.

(Invited) Mn4+ r-Line Emission Intensity: The Ways of Its Enhancement

Mn4+-based red phosphors are excellent materials to be used for making white LEDs with warm white light. They can be excited by the blue or ultraviolet light to produce red photoluminescence (PL), which is due to the parity and spin-forbidden 2Eg→4A2g transition. However, in many host materials, the intensity of the 2Eg→4A2g zero-phonon line (R-line) is very weak due to the presence of the inversion center of the crystallographic site occupied by the manganese ions. As a result, the red-shifted Stokes components dominate in the emission spectra of such hosts, but this leads to the decreased overlap of the PL spectra with human eye sensitivity curve and decreased intensity of the phosphor (lower lumen/Watt value). Therefore, finding the recipes of enhancement of the R-line intensity and production of brighter phosphors is an important scientific and technological task. In the present work we establish the key parameters responsible for the energy and the intensity of the Mn4+ R-line. Thorough consideration and analysis of the optical spectra for a large number of the Mn4+-based phosphors allowed to draw the following conclusions: The energetic position of the R-line is determined by the “Mn4+-ligand” bonding covalence. Most phosphors for the solid state lighting can be conditionally divided into fluorides and oxides (where the fluorine or oxygen ions are the Mn4+ nearest neighbors, respectively). In ionic fluorides, the Mn-F bonding covalence is weak, which shifts the R-line to higher energies, with the emission wavelength at about 620 nm. In covalent oxides, the stronger Mn-O bonding covalence lowers the energy of the 2Eg state, moving the emission to about 650 nm.In the host crystals, where the Mn4+ ions are located at the sites without inversion center, the R-line intensity is higher compared with the crystals possessing inversion symmetry at the Mn4+ Absence of the inversion center relaxes the parity section rule, which enhances the R-line intensity. As a result, the phosphor luminosity is increased considerably. The inversion center can be removed by cation co-doping, when different cations in the second coordination sphere around the Mn4+ ion remove the inversion center. As an example, a figure below shows the PL spectra of K2SiF6:Mn4+ and NaKSiF6:Mn4+. In the former case the ideal MnF6 octahedron with the inversion center does not allow for high R-line intensity. It the latter case structural disorder and mixed occupation at the K/Na site results in the presence of different cations in the second coordination sphere. As a result, the intensity of the R-line is increased by several times. Therefore, to get the phosphors with increased luminosity one has to focus on the host materials without inversion center at the dopant sites. If, however, the inversion symmetry exists, it should be broken by additional co-doping that would produce structural disorder around the dopant. Figure 1

Excellent human eye sensitivity matching, high luminous efficacy, high quantum yield and thermal stability of narrow-band red-emitting SrLiAl3N4:Eu2+ phosphor

Here, using the safety raw materials Li3N, Sr3N2 and Eu2O3 instead of LiAlH4, SrH2 and EuF3 (besides AlN), the nitride phosphor SrLiAl3N4:Eu2+ (SLA:Eu2+) was synthesized in the glove box (O2<0.1 ppm, H2O<0.1 ppm) under continuous purified nitrogen flow. It avoids the dangerous synthesis and production environment negative factors caused by the dangerous materials of LiAlH4 and SrH2. The luminescence properties of SLA:Eu2+ with different aid-sintering additives (LiCl and SrF2) were improved, such as red emission (~ 653 nm), narrow full-width at half-maximum (FWHM ~ 50 nm), highly luminous efficacy (23.6 lm/W) and superior thermal property. The narrow band emission of SLA:Eu2+ fits well with the curve of human eye sensitivity and leads to excellent chromatic saturation. Moreover, the white light-emitting-diodes (LEDs) devices have been fabricated by combining a 450 nm blue chip with the commercial LCN630, LCL530 phosphor and as-prepared red-emitting phosphor SLA:0.004Eu2+, 0.1LiCl, 0.3SrF2 which shows a greater color rendering index (Ra) value of 90.3 and low correlated color temperature (CCT) of 2726 K. Importantly, the luminous efficacy, the purity and R9 value increased up to 110.10 lm/W, 62.2% and 55, respectively. The results exhibit the materials with high luminous efficacy, low correlated color temperature and narrow band red emission, delivering the foundation for white LEDs.

(Invited) Red Fluoride Phosphors: A Story of Reliability

Ever since the introduction of the high-brightness blue LED in 1994 [1], research on photoluminescent materials has gained tremendous interest. The combined emission from a blue emitting LED chip and a yellow emitting phosphor yields white light. The first white LEDs (wLEDs) were based on an (In,Ga)N LED chip and the efficient, chemically stable yellow phosphor Y3Al5O12:Ce3+. Despite the high luminous efficacy of the radiation (LER) attainable with this single phosphor wLED, the performance in terms of color rendering is low due to a lack of red emission. Improvement of the color rendering index (CRI) requires an additional emitter in the red spectral region. Therefore, tremendous effort has been spent on the development of red emitting phosphor materials. Red sulfide phosphors such as (Ca,Sr)S:Eu2+ [2] were first investigated. However, the poor chemical stability and strong thermal quenching associated with sulfides led research to new phosphor classes. Due to their high chemical stability and high quantum efficiency, Eu2+ nitride phosphors [3] such as CaAlSiN3:Eu2+ are currently considered as the most suited candidate for wLED applications. Nevertheless, even the Eu2+ doped nitrides possess serious drawbacks. Apart from their higher production cost, they often suffer from broad excitation- and emission bands. Excitation bands extending beyond 500 nm cause reabsorption issues when used in a phosphor blend together with green or yellow phosphors. On the other hand, broad emission bands partially reaching above 650 nm are inefficient as the human eye sensitivity becomes negligible in this spectral region. Several red fluoride phosphors show a saturated red emission band below 650 nm based on the photoluminescence of Mn4+ in an octahedral fluorine coordination. In addition to their optimal optical performance, the low-cost production by means of wet chemical synthesis is an additional benefit. However, trace impurities in the form of impurity phases and secondary Mn valences often occur after synthesis. The present study reveals a strong correlation between purity after synthesis and stability of K2SiF6:Mn4+, a benchmark red fluoride phosphor [4-6]. Recently a two-step precipitation method has gained interest to improve the Mn valence related issue. K2MnF6, is first synthesized as a precursor material, incorporating Mn4+ in a [MnF6]2- coordination complex. In a second step, these complexes are incorporated in a fluoride host by dropwise addition of K2MnF6/KF in 40% HF and SiO2 in 40% HF. Although the chemical yield is higher compared to other chemical routes, such as wet chemical etching, and some improvements in stabilizing the Mn4+ valence state can be expected, careful examination of the purity proves necessary. Combined feedback from in- and ex-situ X-ray diffraction, diffuse reflection spectroscopy, X-ray absorption near edge spectroscopy, thermal gravimetric and differential thermal analysis revealed the presence of impurities after synthesis of K2SiF6:Mn4+. On the one hand, hydrated secondary crystalline phases, such as KMnF4•H2O, K2MnF5•H2O and similar hydrated structures, are easily formed during synthesis. As a result, parasitic absorption due to Mn3+ occurs which limits the attainable quantum efficiency of the as-synthesized impure phosphor. On the other hand, impurities such as KHF2 severely increase the hygroscopic behavior of the phosphor after synthesis. KHF2 is easily hydrolyzed, leading to hydrated KF, an impurity hardly detectable by XRD at room temperature. As a result of water absorption in the impure phosphor, a further reduction of Mn4+ to Mn3+ is observed when the phosphor is placed in high humidity. Nevertheless, detection, identification and elimination of these impurities lead to efficient and high purity K2SiF6:Mn4+, showing good chemical and thermal stability. To further enhance stability, thin protective Al2O3, TiO2 or SiO2 shells were coated using thermally assisted, plasma enhanced or ozone enhanced Atomic Layer Deposition (ALD) and subsequently evaluated. Nakamura, S., M. Senoh, and T. Mukai, High‐power InGaN/GaN double‐heterostructure violet light emitting diodes. Applied Physics Letters, 1993. 62(19): p. 2390-2392. Hu, Y., et al., Preparation and luminescent properties of (Ca1-x,Srx)S:Eu2+ red-emitting phosphor for white LED. Journal of Luminescence, 2005. 111(3): p. 139-145. Li, S., et al., Critical Review—Narrow-Band Nitride Phosphors for Wide Color-Gamut White LED Backlighting. ECS Journal of Solid State Science and Technology, 2017. 7(1): p. R3064-R3078. Sijbom, H.F., et al., K2SiF6:Mn4+ as a red phosphor for displays and warm-white LEDs: a review of properties and perspectives. Optical Materials Express, 2017. 7(9): p. 3332-3365. Murphy, J.E., et al., PFS, K2SiF6:Mn4+: the Red-line Emitting LED Phosphor behind GE's TriGain Technology™ Platform. SID Symposium Digest of Technical Papers, 2015. 46(1): p. 927-930. Paulusz, A.G., Efficient Mn(IV) Emission in Fluorine Coordination. Journal of The Electrochemical Society, 1973. 120(7): p. 942-947.

Problems with signal lighting colours’ recognition

The article presents the main eye hazards caused by excessive eye exposure on optical radiation. The human eye sensitivity spectral distribution in the context of signal colour recognition was discussed. In order to explain the effects of the mechanism of phenomena responsible for the recognition of signal lights colour, a graphical analysis of spectral distributions of signal lights emitted from traditional incandescent sources and LED sources (light emitting diode) was performed. This analysis also takes into account the conditions under which observation of signal lights may take place (daylight and night vision conditions). The conclusions also indicate the further direction of studies on the influence of colour recognition affected by vision conditions, eye sensitivity spectral distribution (including disturbance of colour recognition) and different types of signal light sources.

SPECTRAL SENSITIVITY OF HUMAN VISION TO THE LIGHT PULSES

. In the paper we represent experimental results of the research of human vision sensitivity to pulsed radiation of discrete light emitting diodes (LEDs) of different colors when their dissipated electrical power was the same. We used color components of RGB LED matrix and determined the values of the dissipated power at which resultant LED radiation was perceived as white light. These power values were used to investigate sensitivity of human eye to radiation of each color of RGB matrix. Spectral characteristic of RGB LED under investigation was checked for presence of additional spectral components. The results we obtained give the possibility to develop information systems with concealment of the data transfer process using white light which color components are informative.