Color perception under various light sources using spectral numerical models

Author(s):  
Richard Mitanchey ◽  
Marc R. Fontoynont
2006 ◽  
Vol 78 (6) ◽  
pp. 1239-1252 ◽  
Author(s):  
W. W. Stoffels ◽  
A. J. Flikweert ◽  
T. Nimalasuriya ◽  
J. J. A. M. van der Mullen ◽  
G. M. W. Kroesen ◽  
...  

Metal halide lamps are very efficient light sources based on a Hg plasma arc with metal halide salt additions. In spite of their high efficiency, the lamps suffer from several problems, such as color separation and instabilities, which currently hinder large-scale use. These phenomena are caused by a complex interaction of convection and diffusion flows in the plasma. In order to unravel the various contributions, experiments under microgravity have been performed where convection is absent. The experiments confirm the previously held qualitative views, but also provide absolute data on densities and temperatures that will be used to validate numerical models of these lamps.


2018 ◽  
Vol 183 ◽  
pp. 02030
Author(s):  
Vladimir I. Erofeev ◽  
Sergey I. Gerasimov ◽  
Alexey O. Malkhanov

A possible way of study of single waves in solids is discussed. The soliton is one of these waves without shape and parameters varying. Soliton deformation parameters are connected with the elastic moduli of the third order that allows defining values of these moduli by means of the measured solitondeformation parameters in various type waveguides made of the same material. The conditions under which a soliton can exist in a rod are analytically determined. For simultaneous excitation of loading in several wave guides two new energetic photosensitive structures (the mixtures are given) initiated by means of short light impulses of noncoherent light sources are proposed. Conditions of excitation of the waves on the basis of multipoint optical initiation loading impulses are described. As a technique for registration the shadowgraph visualization is proposed. It is discussed, how the problem connected to the use of energetic initiation structures consisting in the power background illumination can be solved. The shadow scheme with the use of a tiny dot explosive light source (Tbr ~41 kK) allows to carry out modelling experiments on research of slabbing actions, jet formations, fluffings, hydrodynamic instability during shock-wave loading of investigated samples, which makes it attractive for determination of parameters in equations-of-state for investigated materials, creation of numerical models and their validation. Some examples showing basic possibility of application of the declared techniques are included.


2020 ◽  
Vol 48 ◽  
pp. 20-26
Author(s):  
A. A. Ryabtseva ◽  
E. E. Grishina ◽  
O. M. Andryukhina ◽  
A. A. Kovrizhkina ◽  
A. S. Andryukhina

Rationale: The emerging new coronavirus infection caused by SARS-CoV-2 has resulted in a pandemic. Its clinical manifestations are highly variable and the death rate is high due to rapid progression to acute respiratory distress syndrome. Identified abnormalities of the eye are mainly related to conjunctival injury during manifestation of the disease.Aim: To study the eye abnormalities in patients who have undergone COVID-19.Materials and methods: Ophthalmological examination was performed in 23 patients (6 [26%] men and 17 [74%] women, median age 42.39 years) at days 44 to 85 after manifestation of COVID-19 infection in the Department of Ophthalmology, MONIKI. In addition to the standard ophthalmological examination, all patients were evaluated with optical coherence tomography (OCT), auto fluorescence, contrast and color sensitivity test with different light sources, and tear production assessment.Results: In the late convalescence period there were complaints of dry eyes and abnormal color perception, with visual acuity being unchanged. The OCT assessment the peripapillary retina identified small hyper-reflective foci in the inner layers.Conclusion: Eye disease in patients after COVID-19 is mainly related to the condition of the eye surface, abnormal color perception and abnormal architectonics of the inner retinal layers, which can persist for a long time during convalescence.


Author(s):  
Leonid B. Kochin ◽  
Andrey I. Antonets ◽  
Alexey A. Fedorov

2019 ◽  
pp. 113-124
Author(s):  
О. М. Яремчук ◽  
А. В. Кулік

Purpose. The determination of the formation features of basic models of color and identification of color in the initial stages (the 18th – 19th centuries) of scientific research of the problem. Methodology of the research is based on historical and cultural method. The source base is the artistic, scientific and technical literature of the studied period and also artefacts. Results. This publication reveals a generalized approach to theoretical developments on color perception and identification, and covers the initial period of color research and the formation of basic models of color (the 18th – 19th centuries). So in the middle of the 17th century I. Newton founded a seven-color ordering model, placing them to a closed color circle. At about the same time, other attempts at color systemization were proposed, such as color identification in the form of tables of existing paints, the work of I. Brennen and R. Waller. Subsequently, Jacob Christoph Le Blon concluded that in order to get results, you could use only three colors, namely red, yellow and blue. Based on this work, M. Harris presented his color circle, J. Lambert – a triangular color pyramid, and Ph.Runge built a color sphere using the principle of the globe. Goethe, contrary to Newton's physical doctrine of colors, conceived another system, it was based on the phenomenological perception of color. According to Goethe and his followers, the colors come from the struggle of "light" and "darkness". A. Schopenhauer took the step that J. Goethe lacked in his thinking: A. Schopenhauer formed a doctrine of color in terms of psychology, noting the enormous role that our brain plays in color perception, and proposing his model of identification by the principle of intensity / extensiveness/quality. for the formal description of the tri-color system of color, forming a mathe-confirmation of T. Young's theory and came to the conclusion that for the comparison of all shades, three light sources were needed and sufficient: in the red, green and blue parts of the spectrum. The perception of other colors is conditioned by the interaction of these constituents. In his work, J. Maxwell proved that all colors come from a mixture of three spectral colors: red, green, and blue. Based on his research, he introduced the first two-dimensional color spectrum visualization system. H. Grassmann's merit is the mathematical representation of the three spectral colors. E. Hering's theory highlights the psychological aspects of color vision: warm sensations occur for white, yellow, and red colors, while cold sensations occur for black, dark blue, and light blue. G. Peano introduced the concept of "color space" as a system of vector space equations.


Perception ◽  
2020 ◽  
Vol 49 (11) ◽  
pp. 1235-1251
Author(s):  
Stacey Aston ◽  
Kristina Denisova ◽  
Anya Hurlbert ◽  
Maria Olkkonen ◽  
Bradley Pearce ◽  
...  

The colors that people see depend not only on the surface properties of objects but also on how these properties interact with light as well as on how light reflected from objects interacts with an individual’s visual system. Because individual visual systems vary, the same visual stimulus may elicit different perceptions from different individuals. #thedress phenomenon drove home this point: different individuals viewed the same image and reported it to be widely different colors: blue and black versus white and gold. This phenomenon inspired a collection of demonstrations presented at the Vision Sciences Society 2015 Meeting which showed how spatial and temporal manipulations of light spectra affect people’s perceptions of material colors and illustrated the variability in individual color perception. The demonstrations also explored the effects of temporal alterations in metameric lights, including Maxwell’s Spot, an entoptic phenomenon. Crucially, the demonstrations established that #thedress phenomenon occurs not only for images of the dress but also for the real dress under real light sources of different spectral composition and spatial configurations.


Author(s):  
A. M. Bradshaw

X-ray photoelectron spectroscopy (XPS or ESCA) was not developed by Siegbahn and co-workers as a surface analytical technique, but rather as a general probe of electronic structure and chemical reactivity. The method is based on the phenomenon of photoionisation: The absorption of monochromatic radiation in the target material (free atoms, molecules, solids or liquids) causes electrons to be injected into the vacuum continuum. Pseudo-monochromatic laboratory light sources (e.g. AlKα) have mostly been used hitherto for this excitation; in recent years synchrotron radiation has become increasingly important. A kinetic energy analysis of the so-called photoelectrons gives rise to a spectrum which consists of a series of lines corresponding to each discrete core and valence level of the system. The measured binding energy, EB, given by EB = hv−EK, where EK is the kineticenergy relative to the vacuum level, may be equated with the orbital energy derived from a Hartree-Fock SCF calculation of the system under consideration (Koopmans theorem).


Author(s):  
C.J. Stuart ◽  
B.E. Viani ◽  
J. Walker ◽  
T.H. Levesque

Many techniques of imaging used to characterize petroleum reservoir rocks are applied to dehydrated specimens. In order to directly study behavior of fines in reservoir rock at conditions similar to those found in-situ these materials need to be characterized in a fluid saturated state.Standard light microscopy can be used on wet specimens but depth of field and focus cannot be obtained; by using the Tandem Scanning Confocal Microscope (TSM) images can be produced from thin focused layers with high contrast and resolution. Optical sectioning and extended focus images are then produced with the microscope. The TSM uses reflected light, bulk specimens, and wet samples as opposed to thin section analysis used in standard light microscopy. The TSM also has additional advantages: the high scan speed, the ability to use a variety of light sources to produce real color images, and the simple, small size scanning system. The TSM has frame rates in excess of normal TV rates with many more lines of resolution. This is accomplished by incorporating a method of parallel image scanning and detection. The parallel scanning in the TSM is accomplished by means of multiple apertures in a disk which is positioned in the intermediate image plane of the objective lens. Thousands of apertures are distributed in an annulus, so that as the disk is spun, the specimen is illuminated simultaneously by a large number of scanning beams with uniform illumination. The high frame speeds greatly simplify the task of image recording since any of the normally used devices such as photographic cameras, normal or low light TV cameras, VCR or optical disks can be used without modification. Any frame store device compatible with a standard TV camera may be used to digitize TSM images.


1954 ◽  
Author(s):  
Beverly Hillmann ◽  
Katherine Connolly ◽  
Dean Farnsworth

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