Spectral Color Research Articles

Maxwell's color box: Retracing the path of color matching experiments

In his 1860 paper On the theory of compound colours, James Clerk Maxwell described an instrument used to obtain a direct comparison between daylight and a mixture of three selected spectral colors. This investigation was part of Maxwell's study of human color vision, color perception, and color representation, and it encompasses his main achievements in the field. The working principle underlying this device provided the basis from which color diagrams have been derived, beginning with the standard chromaticity diagram proposed by the International Commission on Illumination in 1931. We describe a reconstruction of Maxwell's original version of the color box. Constructing and analyzing data obtained with such a replica could serve as a semester project for advanced optics students.

Exploration of modifier based structural and spectroscopic traits of Eu3+ doped boro-tellurite glasses for solar UV photons converting applications

A new series of stable host glass with different modifier cations have been formed with the molar composition15XO + 39B2O3 + 25TeO2 + 10Na2O + 10K2O + 1Eu2O3 (X = Li2, Ca, Sr, Ba, Zn) through traditional glass preparation technique of melt quenching. The effect caused by the incorporation of modifier cations on the radiative assets of Eu3+ ions in the present host glass were inspected through X-ray Diffraction (XRD), Fourier Transformed Infra-Red (FTIR), UV–vis-NIR, photoluminescence and luminescence decay spectral studies at room temperature. The broad diffraction band in the XRD pattern confirms glassy or amorphous nature of the synthesized samples. The functional modes of vibration and structural modules in the prepared glass samples were inspected through FTIR spectra. The 4f − 4f electronic transitions pertaining to the trivalent europium (Eu3+) ions in the new host glasses were scrutinized by UV–vis-NIR absorption studies where in the dominant covalent bonding nature of the Eu3+ ions with its nearby ligands have been confirmed via average nephelauxetic ratio (β) and bonding parameter(δ) values. Optical bandgap (indirect and direct) values were testified to identify the photon energy transparent window and to explore the tendency of the formation of non-bridging oxygens. Luminescence ability of the prepared samples was inspected by exciting at a wavelength of 465 nm. Among the prepared samples, Eu3+ ions emissions were observed and the highest intensity of emission occurred at 612 nm (5D0→7F2) for BTLi:Eu glass. The Judd-Ofelt parameters were estimated and used to evaluate the radiative parameters such as radiative lifetime (τrad), transition probability (A), branching ratio (βR), stimulated emission cross-section (σPE) of all the emissions observed in the produced glasses and the outcomes were equated with the related literature. The colour chromaticity coordinates and colour correlated temperature (CCT) were explored from the emission spectra using CIE 1931 diagram and the CCT values found to lie in the range of 2000–4000 K. The luminescence decay comfortably fitted to the single exponential decay profile which further confirms the non-appearance of energy transfer via mutual interaction amongst Eu3+ ions in all the present glasses. All the observed results indicate the fact that the incorporation of Li+ cations induces more attractive radiative features with 77 % of UV to visible quantum converting efficiency than all other cations used in this contemporary study and among the prepared glasses, BTLi:Eu glass exhibits a better capability in red light emitting electro-optical applications.

Color quality consideration when switching from FL to LED

Color quality consideration when switching from FL to LED

Quantitative study on impact damage of yellow peach based on hyperspectral image information combined with spectral information

Yellow peaches are graded based on their degree of impact damage to reduce economic losses, and the values of mechanical parameters can be used to characterize the degree of impact damage of them. In this paper, the combined hyperspectral image features and spectral features method was proposed to predict the values of mechanical parameters of yellow peaches. A collision device based on the pendulum principle was built to acquire the mechanical parameters which were maximum force, absorbed energy and average pressure. A hyperspectral imaging system was used to acquire the images of the bruised yellow peaches and the spectral information and color characteristics of images were extracted, respectively. The damage areas of yellow peaches were obtained based on the combined principal component analysis (PCA) and threshold segmentation method. Texture features of the characteristic wavelength images were extracted based on the grey-level co-generation matrix (GLCM). The PLSR models of mechanical parameters were built based on spectral information, image information, and spectral information combined with image information, respectively. The results show that the PLSR models based on spectral information combined with image information are best in prediction the values of damage area and maximum force. However, the PLSR models have not achieved satisfactory performance in prediction the values of absorbed energy and average pressure. To improve the performance of PLSR models of absorbed energy and average pressure, the feature wavelengths were selected by CARS, and the correlation analysis was used between image information and mechanical parameters. The PLSR models were built based on feature spectral information, image feature information, and feature spectral information combined with image feature information, respectively. The results show that the accuracy of all mechanical parameters is significantly improved by the PLSR models based on the feature spectral information combined with the image feature information. The prediction set correlation coefficient (RP) and the root mean square error (RMSEP) of the damaged area, absorbed energy, maximum force and average pressure are 0.928 and 86.632 mm2, 0.826 and 1.469 J, 0.924 and 61.765 N, 0.815 and 0.050 MPa, respectively. The results of the study not only provide a theoretical basis for postharvest grading of fruit, but also provide a reference for analyzing the mechanical properties of fruit.

Tunable luminescence from Bi3+ sensitized La2 Zr2 O7 :Eu3+ red nanophosphors for display applications.

Bismuth ion (Bi3+ ) sensitized, europium ion (Eu3+ ) activated La2 Zr2 O7 nanophosphors are prepared successfully by simple wet chemical method. Strong blue emission of singly doped La2 Zr2 O7 with Bi3+ was observed at 310 nm excitation, its wide emission spectrum has a peak maximum at 465 nm ascribed to electronic transition 3 P1 → 1 S0 of Bi3+ . The recorded photoluminescence spectra of y at% Eu3+ codoped La2 Zr2 O7 , when excited at 285 nm, the emission spectrum exhibits maximum peaks at wavelength values 615 nm, 646 nm and 665 nm which are ascribed to 5 D0 → 7 F2 , 5 D0 → 7 F3 and 5 D0 → 7 F4 transitions of Eu3+ respectively. The chromaticity coordinates for the optimized sample were found to be (0.519, 0.329). Sensitizing with Bi3+ can affect the luminescence properties of La2 Zr2 O7 :Eu3+ phosphors. With reference to the change in Eu3+ concentration from Y = 1, 2, 3, 4 and 5%, color tunable luminescence from blue to orange, red of La2 Zr2 O7 :Bi3+ ,Eu3+ phosphors are observed. The lifetime decay values, energy level description and CIE chromatic color coordinates for Bi3+ , Eu3+ in La2 Zr2 O7 :Bi3+ ,Eu3+ codoped sample was discussed. The spectral overlap between sensitizer, activator ions confirms the efficient energy transfer from Bi3+ to Eu3+ in La2 Zr2 O7 :Bi3+ ,Eu3+ codoped sample and is via a dipole-quadruple mechanism.

Detection of wheat Fusarium head blight using UAV-based spectral and image feature fusion.

Infection caused by Fusarium head blight (FHB) has severely damaged the quality and yield of wheat in China and threatened the health of humans and livestock. Inaccurate disease detection increases the use cost of pesticide and pollutes farmland, highlighting the need for FHB detection in wheat fields. The combination of spectral and spatial information provided by image analysis facilitates the detection of infection-related damage in crops. In this study, an effective detection method for wheat FHB based on unmanned aerial vehicle (UAV) hyperspectral images was explored by fusing spectral features and image features. Spectral features mainly refer to band features, and image features mainly include texture and color features. Our aim was to explain all aspects of wheat infection through multi-class feature fusion and to find the best FHB detection method for field wheat combining current advanced algorithms. We first evaluated the quality of the two acquired UAV images and eliminated the excessively noisy bands in the images. Then, the spectral features, texture features, and color features in the images were extracted. The random forest (RF) algorithm was used to optimize features, and the importance value of the features determined whether the features were retained. Feature combinations included spectral features, spectral and texture features fusion, and the fusion of spectral, texture, and color features to combine support vector machine, RF, and back propagation neural network in constructing wheat FHB detection models. The results showed that the model based on the fusion of spectral, texture, and color features using the RF algorithm achieved the best performance, with a prediction accuracy of 85%. The method proposed in this study may provide an effective way of FHB detection in field wheat.

Crystal structure and temperature sensing performance of the novel Sr2Y8(1-x-y)(SiO4)6O2:xCe3+,yTb3+ thermometric phosphors

For the research of the thermometric performance, a series of Sr2Y8(1-x-y) (SiO4)6O2:xCe3+,yTb3+ phosphors were synthesized with the solid-state reaction method at N2/H2 atmosphere. The crystal structure, room and high temperature photoluminescence spectra, luminescence decay, CIE variation, energy transfer and thermometric performance have been investigated. With the ultraviolet light excitation, both the Ce3+ broadband spectrum and Tb3+ line spectra have been observed. With the increase of the Tb3+ concentration, the emission color chromaticity varies from dark blue to bright green for the series of Sr2Y8(1–0.07-y)(SiO4)6O2:0.07Ce3+,yTb3+ phosphors. Under high temperature, the Ce3+ emission intensity quenches faster than that of Tb3+. Based on the different temperature quenching speeds of Ce3+ and Tb3+, the fluorescence intensity ratio technique was used to evaluate the thermometric performance of the series of Sr2Y8(1–0.07-y) (SiO4)6O2:0.07Ce3+,yTb3+ phosphors. During the temperature range of 298–498 K, the maximum relative sensitivity values of the phosphors of yTb = 0.05, 0.08, 0.1, 0.15, 0.2, 0.25 were calculated as 0.65, 0.69, 0.74, 0.71, 0.66, 0.6% K−1, which are much better than the recommended value of 0.30% K−1 for the practical application. The physical mechanisms for the Ce3+/Tb3+ excitation and emission, energy transfer and temperature quenching have been discussed. Sr2Y8(1-x-y) (SiO4)6O2:xCe3+,yTb3+ phosphors are the candidate thermometric probes for the non-contact temperature sensing applications.

Pixel-wise structured light calibration method with a color calibration target.

We propose to use a calibration target with a narrow spectral color range for the background (e.g., from blue) and broader spectral color range for the feature points (e.g., blue + red circles), and fringe patterns matching the background color for accurate phase extraction. Since the captured fringe patterns are not affected by the high contrast of the calibration target, phase information can be accurately extracted without edging artifacts. Those feature points can be clearly "seen" by the camera if the ambient light matches the feature color or without the background color. We extract each calibration pose for three-dimensional coordinate determination for each pixel, and then establish pixel-wise relationship between each coordinate and phase. Comparing with our previously published method, this method significantly fundamentally simplifies and improves the algorithm by eliminating the computational framework estimate smooth phase near high-contrast feature edges. Experimental results demonstrated the success of our proposed calibration method.

Orange-red luminescence features of Eu3+ doped CaAl4O7 phosphors

A series of orange-red emitting Eu3+ doped CaAl4O7 phosphors was synthesized by the citric acid sol gel process using the metal nitrates as precursors. A study of the phosphors according to their X-ray diffraction patterns confirmed the desired phase without any intermediate or precursor compounds. The SEM imaging does not reveal the crystal structure, but it shows a variation of crystalline size within a few micrometers. In the excitation spectrum of CaAl4O7:xEu3+ (x = 0.01–0.11 mol), sharp multiple peaks at 293 nm, 464 nm, and 533 nm which are characteristics of Eu3+ transitions from 7F → 5D were observed. The photoluminescence emission spectra with an excitation wavelength of 464 nm showed characteristic peaks corresponding to the transition of 5D0 → 7F2 at 612 nm and expressed orange-red region of the electromagnetic field. The emission intensity increased as the concentration of Eu3+ increased to 0.05 mol, where it exhibited the highest emission intensity in the series. The intensity ratio results also indicate an intensity drop after a 0.05 concentration of the Eu3+ ion. The full width at half maximum (FWHM) of the synthesized phosphors is expressed as the concentration increase, which leads to a drop in sharpness. The chromaticity properties indicate high color purity of the synthesized phosphor in the orange-red region by the position of the color coordinates at the edge of the CIE color chromaticity diagram.

A spectral reflectance-based approach for formulating color mixing recipes for single- and multi-layered woven structures

The color of yarn dyed woven fabrics comes from a series of different colored yarns mixed in complex ways and various proportions. Thus, predicting the color mixing effect or formulating the recipe is a difficult task which should consider the interaction between colored yarns and structure variations. Color mixing recipes, which are also called color prediction models, for woven fabrics have generally been derived through the two-dimensional modeling of woven structures. In this study, the three-dimensional geometrical and colorimetrical modelings of single-, double-, and three-layered woven fabrics in a wide range of colors were conducted to obtain two types of optimal spectral reflectance-based color prediction models. Through model evaluations, the obtained three-dimensional color prediction models were proved to have much higher predictive accuracy, especially in terms of lightness and chroma predictions, than that of the two-dimensional color prediction models previously developed.

Colour Variation in the Crocodile Lizard (Shinisaurus crocodilurus) and Its Relationship to Individual Quality.

Simple SummaryThis study examines colour variation in the highly endangered crocodile lizard, Shinisaurus crocodilurus. Both males and females vary in the extent to which their throats and venters are red. Their colouration is easily visible to a lizard receiver, and we found evidence that colour signals individual quality. Females with red venters had larger heads while females with red throats had greater bite force. In males, redder individuals were older. Finally, we found links between colour and fitness in males but not females. Aspects of male colouration were linked to reproductive output such that they sired offspring from heavier litters. The potential fitness consequences of colour should be considered in captive breeding and release programs.Colour plays a key role in animal social communication including as an indicator of individual quality. Using spectrophotometry, we examined colour variation in the throat and venter of the crocodile lizard (Shinisaurus crocodilurus), an endangered species native to southern China and northern Vietnam. We detected two broad colour variants, individuals with and without red, for each body region and each sex. A cluster analysis of spectral colour measurements (hue, chroma, luminance) revealed discrete throat and ventral morphs when measured in a single snapshot in time. However, photographic evidence revealed that the amount of red relative to body size increased as they got older. Individuals with red were equally likely to be male or female and throat colour was unrelated to ventral colour. Therefore, it is premature to claim that crocodile lizards have discrete colour morphs. We used visual modelling to show that the throat and venter were easily discriminable to a lizard visual system, suggesting they function in social communication. We also asked whether colour variation signalled individual quality. Females with red throats had greater bite force while males with red throats were older. In addition, females with red venters had larger heads. We also detected differences in morphology linked to colour. Females with red throats had slender bodies and longer tails, while individuals lacking red on their throats were stouter and had shorter tails. Finally, throat and ventral colour were unrelated to reproductive output (litter size and mass) in females. Males with greater ventral luminance contrast sired offspring from litters with greater litter mass (including stillborns), while males with greater ventral chromatic contrast sired offspring whose collective live mass (excluding stillborns) was greater. Males with greater luminance contrast also sired more live offspring (excluding stillborns). Collectively, these results suggest that male ventral colour signals individual quality in males. Conservation initiatives should take colour variation into account when planning future captive breeding and release programs for this endangered species.

Structural, morphological and optoelectronic aspects of YAlO3:Dy3+ doped nanocrystalline materials for NUV energized WLEDs

Cost-effective urea assisted solution combustion (SC) synthetic method was employed to prepare a series of doped YAlO3:xDy3+ (0.01–0.08 mol) phosphors. The resulting powdered samples were comprehensively examined through various structural as well as optical measurements. Rietveld refinement studies concluded that prepared nanomaterials structured into the orthorhombic system having Pbnm (62) space group. Energy dispersive spectral (EDS) analysis was executed to observe the relative proportions of constituent elements in all doped nanophosphors. Transmission electron microscopy (TEM) micrograph indicated the presence of agglomerated particles with the average size in the nano range. Photoluminescence excitation (PLE) spectra showed that the designated phosphors could be excited by near ultraviolet (NUV) energized lighting sources. The strongest emission centred at 576 nm, corresponding to electric dipole (4F9/2 → 6H13/2) transition of Dy(III) ion. Furthermore, characteristics photometric parameters viz. correlated color temperature (CCT), chromaticity coordinates (x and y), and color purity (%) were figure out with the aid of PL data, which strongly endorsed their usage in NUV energized WLEDs applications.

Microencapsulates by spray of Lacticaseibacillus rhamnosus GG from fermented whole or skimmed cow's milk added with Mexican honeysuckle (Justicia spicigera) extract using mesquite gum as carrier agent

This work aimed to evaluate the effect of the addition 5°Bx Mexican honeysuckle (Justicia spicigera) extract (JSE) in spray dried encapsulates of whole and skimmed unfermented and fermented cow's milk with Lacticaseibacillus rhamnosus (LR). All samples were spray dried at 160 °C. Samples were analyzed in physical properties (moisture content, water activity (aw), L∗, a∗, b∗, Hue, Chroma color parameters, particle size), LR content, and bioactive compounds (total anthocyanins (TA), total phenolic content (TPC), and antioxidant capacity (AC) using the DPPH assay). Results showed that the load of LR was in the range 6.79–7.44 Log10 (CFU/mL) cycles after fermentation, lower values were obtained when JSE was added before fermentation. In addition, LR remains after drying in fermented samples but decrease about 1 Log10 (CFU/mL) cycle. LR was 4.46 Log10 (CFU/mL) in the fermented skimmed milk-J. spicigera extract powder. All powders had aw and moisture content below 0.295 and 6.51%, respectively. Color of powders depended on the moment of addition of JSE and fermentation. Powders from fermented milk were pale brownish/orangey/red (Hue = 44.91–59.7) and unfermented and J. spicigera extract-maltodextrin solution (12% w/v) powders were purple (Hue = 314.52–326.68). Higher particle sizes (52.3–104.7 μm) were obtained with whole milk fermented and unfermented powders. On the contrary, skimmed milk and JSE without milk protein had values in the range 15.56–44.0 μm. TPC in powders were higher (16.96–33.81 mg GAE/g powder db) compared with TA (0.27–0.64 mg Peonidin-3,5-diglucoside/g powder db). TPC increased with fermentation and remain after spray drying. The AC and TPCs were highly correlated and had antioxidant capacity of 10.18 mg TE/g powder db. The principal component analysis showed that the type of milk and fermentation separate the powders in four groups, depending on their physical and antioxidant properties. Encapsulated pigments could be used in formulations in the food industry to increase bioactive compounds and pigments in foods.

High stability in color chromaticity of warm White emitting Diode with Dual-Hue SrSi2O2N2:Eu2+,Yb2+ Oxynitridosilicate Phosphorus

<span>In this study, we analyzed and developed a phosphor with a nitridiosilicate based and emitting color changing from green to orange to apply to our white-light-emitting diodes (WLEDs). Eu<sup>2+</sup> and Yb<sup>2+</sup> trap sites of two-doped SrSi<sub>2</sub>O<sub>2</sub>N<sub>2</sub>:Eu<sup>2+</sup>,Yb<sup>2+</sup> (SrYb) nitridosilicate emit a wide emission in the region between green and orange. Through calculating the decompose time of the green-emission power donor, we could determine the converted energy between the active ions. Furthermore, we also analyzed the impact of co-doping with varied active ion ratios on the photoluminescence (PL) characteristics. As the concentration of Yb<sup>2+</sup> increases, the red emission dominates the green. This was because the obtained phoshor's emission depended on the activator ion components. To generate white light, a combination of the acquired phosphor and the InGaN blue LED chip with a 450 nm wavelength was used. With only two steps, we could detect the hue balance management. Firstly, by modifying the Eu<sup>2+</sup> and Yb<sup>2+</sup> concentration, we can conduct a green-to-orange proportion optimization. Following that, the commission onillumination (CIE) coordinates were transformed to [0.4071; 0.3789] from the original position, which was [0.2805; 0.2014] by enhancing the phosphor powder amount. An environment which has a CRI of around 89 is the optimum condition for conducting white light.</span>

Intense green photoluminescence and upconversion-based intrinsic optical bistability in Ho3+/Yb3+ codoped CaSc2O4 and upconversion in Ho3+/Yb3+ codoped CaY2O4 phosphors

The present study details the downshifting, frequency upconversion and intrinsic optical bistability in CaSc2O4:Ho3+/Yb3+ and upconversion in CaY2O4:Ho3+/Yb3+ phosphors synthesized by a complex-based precursor solution method. The X-ray powder diffraction confirms the formation of highly crystalline phosphors with pure orthorhombic phase. Fourier transform infrared studies of synthesized phosphors show vibrational bands due to the presence of Ca–O, Sc–O and Y–O groups. The diffuse reflectance spectra show a number of bands in the UV–vis–NIR regions due to presence of Ho3+ and Yb3+ ions. The values of optical band gap (Eg) are found to be 5.69 eV and 5.58 eV for the Ho3+/Yb3+ codoped CaSc2O4 and CaY2O4 phosphors, respectively. The Ho3+/Yb3+ codoped CaSc2O4 phosphors display intense green downshifting emission upon 454 nm excitations. The lifetime of green luminescence of CaSc2O4:Ho3+/Yb3+ phosphors with varied Yb3+ concentrations have also been measured. The decay curves show a non-exponential nature fitted to the Inokuti-Hirayama model and the energy transfer microscopic parameters have been also calculated. The Ho3+/Yb3+ co-doped CaSc2O4 and CaY2O4 phosphors display intense green alongwith weak blue, red, and near-infrared upconversion (UC) emissions upon 980 nm excitations. The spectral color purity (Sgr) of CaSc2O4:Ho3+(1%)/Yb3+(5%) phosphor is calculated to be 0.78. Importantly, the variation of pump power generates intrinsic optical bistability (IOB) in the CaSc2O4:Ho3+(1%)/Yb3+(5%) phosphor for the green emission, which is not observed in the CaY2O4:Ho3+(1%)/Yb3+(5%) phosphor. Therefore, the Ho3+/Yb3+ co-doped CaSc2O4 phosphor could potentially be used in UC-based devices, optical memory devices, optical gates, optical transistors and switching devices for optical communications.

Spectroscopic characterizations of Dy3+ ions doped phosphate glasses for epoxy-free white LED applications

The present work illustrates a detailed spectroscopic analysis carried out on dysprosium ions doped Zinc Alumino Sodium Phosphate (ZnAlNaP) glasses with chemical composition of (10-x)ZnO–20Al2O3–10Na2O–60P2O5-xDy2O3 (x = 0.1–2.0 mol%). The XRD spectra verified for an un-doped and Dy3+ ions doped ZnAlNaP glasses demonstrate an enormous hump confirming its amorphous behavior. The FT-IR and Raman spectrum recorded for an un-doped ZnAlNaP and ZnAlNaPDy1.0 glass elucidates various functional groups and vibrational modes involved, respectively. The DSC & TGA studies conducted on an un-doped ZnAlNaP glass revealed its thermal stability and overall weight loss. The absorption spectra were used to calculate the optical bandgap for the as-synthesized glasses and were found to be in the range of 2.9 eV–4.7 eV. Photoluminescence (PL) excitation, emission and decay spectral analysis were done to investigate the suitability of the as-synthesized glasses for epoxy-free solid-state lighting (SSL) devices. The PL emission recorded under 350 nm excitation show two significant bands in blue and yellow regions. Temperature-dependent PL studies conducted on ZnAlNaPDy1.0 glass revealed activation energy of 0.212 eV with a 25.6% loss in PL intensity. The CIE color chromaticity coordinates and correlated color temperature (CCT) were calculated from the PL spectral characteristics. All the spectroscopic investigations conducted on the as-synthesized ZnAlNaPDy glasses finally reveal their superior nature for fabricating epoxy-free white-light emitting diodes (w-LEDs).

Effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network material.

To evaluate the effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network (PICN) material. Specimens of 0.5, 1.0, 1.5 mm thicknesses were obtained by sectioning VITA ENAMIC® multiColor (E-MC) High Translucent CAD-CAM blocks (1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT). Spectral reflectance and color coordinates were measured on white and black backgrounds using a spectroradiometer, CIE D65 illuminant and CIE 45°/0° geometry. CIEDE2000 color and translucency differences (ΔE00 and ΔTP00 ) between thicknesses and adjacent layers were evaluated using their respective 50:50% perceptibility and acceptability thresholds (PT00 and AT00 ). In general, ΔE00 between thicknesses for all shades and layers were above AT00 in general. Chroma decreased from cervical to incisal layers with statistically significant differences (p < 0.05), and ΔE00 between sequential layers were above PT00 , for all shades and thicknesses. TP00 decreased from 0.5 to 1.5 mm and increased from cervical to incisal layers for all shades with statically significant translucency differences (p < 0.05). In general, for all thicknesses, TPT00 < ΔTP00 < TAT00 for sequential layers. The gradient in color and translucency of E-MC PICN material was influenced by the thickness of the CAD-CAM block. In addition, color and TP transition values between the layers depends on the thickness and shade. The effect of thickness must be taken into account by dental technicians and dentists when CAD-CAM multicolor PICN materials are used.

Dermoscopy and skin imaging light sources: a comparison and review of spectral power distribution and color consistency.

.Significance: Dermoscopes incorporate light, polarizers, and optical magnification into a handheld tool that is commonly used by dermatologists to evaluate skin findings. Diagnostic accuracy is improved when dermoscopes are used, and some major artificial intelligence (AI) projects have been accomplished using dermocopic images. Color rendering consistency and fidelity are crucial for clinical diagnostics, AI, and image processing applications.Aim: With many devices available on the market, our objective was to measure the emission spectra of various dermoscopes, compare them with other light sources, and illustrate variations in reflected colors from images of a reference sample.Approach: A spectrometer measured the spectral power distribution (SPD) produced by four dermoscope models and three alternate light sources, illustrating differences in the emission spectra. Most dermoscopes use light-emitting diodes (LEDs), which are inconsistent when compared with one another. An LED was compared with halogen, xenon-arc, and daylight sources. Images of a micro ColorChecker were acquired from several sources, and three specific colors were selected to compare in CIELAB color space. Color consistency and color fidelity measured by color rendering index (CRI) and TM-30-18 graphical vectors show variation in saturation and chroma fidelity.Results: A marked degree of variation was observed in both the emission and reflected light coming from different dermoscopes and compared with other sources. The same chromophores appeared differently depending on the light source used.Conclusions: A lack of uniform illumination resulted in inconsistent image color and likely impacted metamerism and visibility of skin chromophores in real-world settings. Artificial light in skin examinations, especially LEDs, may present challenges for the visual separation of specific colors. Attention to LEDs SPD may be important, especially as the field increases dependency on machine/computer vision.

Effect of color characteristics of chromatic colors on visibility in people with low vision

Effect of color characteristics of chromatic colors on visibility in people with low vision

Tuneable blue to orange phosphor from Sm3+ doped ZnAl2O4 nanomaterials

Undoped and Sm3+ doped ZnAl2O4 nanopowders were synthesized using the co-precipitation method and annealed at 750 ℃ for 3.5 h. The aim of this study was to investigate the effect of varying the Sm3+ concentration on the ZnAl2O4 structure, morphology, and optical properties. The X-ray diffraction analysis confirmed that the samples have a face-centred cubic structure. Crystallite size decreased with an increase in Sm3+ concentration. Scanning electron microscopy revealed that the addition of Sm3+ slightly influence the morphology of the samples. Transmission electron microscopy confirmed a slight decrease in particle sizes. Energy-dispersive X-ray spectroscopy analysis confirmed the anticipated elemental composition. Ultraviolet–visible spectroscopy showed an increase in bandgap compared to the host. Photoluminescence analysis indicated that doping with Sm3+ induced defects within ZnAl2O4. The emission peaks observed around 380, 401, 451, 500, and 739 nm are attributed to host material. The emission peaks at 564, 601, and 649 nm correspond to the 5G5/2 → 6H5/2, 6H7/2, and 6H9/2 transition of Sm3+, respectively. The highest luminescence intensity was found for the 0.5 % Sm3+ sample. The CIE colour chromaticity diagram showed that the emission colour could be tuned from bluish to nearly white to orange.