Search results for "WAVELENGTH"
showing 10 items of 741 documents
Determining the efficiency of optical sources using a smartphone's ambient light sensor
2017
This work reports the use of a smartphone’s ambient light sensor as a valuable tool to study and characterize the efficiency of an optical source. Here, we have measured both luminous efficacy and efficiency of several optical sources (incandescent bulb and halogen lamp) as a function of the electric power consumed and the distance to the optical detector. The illuminance of LEDs as a function of the distance to the optical detector is characterized for different wavelength emissions. Analysis of the results confirms an inverse-square law of the illuminance with the detector–source distance and shows good agreement with values obtained by classical experiments. This experience will trigger …
Disorder-induced single-mode transmission.
2017
Localized states trap waves propagating in a disordered potential and play a crucial role in Anderson localization, which is the absence of diffusion due to disorder. Some localized states are barely coupled with neighbours because of differences in wavelength or small spatial overlap, thus preventing energy leakage to the surroundings. This is the same degree of isolation found in the homogeneous core of a single-mode optical fibre. Here we show that localized states of a disordered optical fibre are single mode: the transmission channels possess a high degree of resilience to perturbation and invariance with respect to the launch conditions. Our experimental approach allows identification…
Modelling the appearance of chromatic environment using hyperspectral imaging
2013
Color of objects is a spectral composition of incident light source, reflection properties of the object itself, and spectral tuning of the eye. Light sources with different spectral characteristics can produce metameric representation of color; however most variable in this regard is vision. Pigments of color vision are continuously bleached by different stimuli and optical density of the pigment is changed, while continuous conditions provide an adaptation and perception of white. Special cases are color vision deficiencies which cover almost 8 % of male population in Europe. Hyperspectral imaging allows obtaining the spectra of the environment and modelling the performance of the dichrom…
Investigation of the Na2O/Ag2O ratio on the synthesis conditions and properties of the 80TeO2–10ZnO–[(10−x)Na2O–xAg2O] glasses
2019
International audience; Properties of the tellurite glasses 80TeO2–10ZnO–[(10−x)Na2O–xAg2O] are investigated as a function of the substitution ratio x between Na2O and Ag2O. One observe that the variation of glass transition temperature decreases monotonously with x and that surface crystallization mechanism is favored. The assignment of the Raman bands and their relation with the underlying glass structure is discussed. While both Na2O and Ag2O oxides act as glass network modifiers, their progressive equimolar substitution does not lead to a meaningful evolution in the structure of the TZ[Na10-xAgx] glass. The refractive index and the cut-off wavelength are found to increase with x. The co…
Atmospheric turbidity and its spectral extinction
1955
The indices of the wavelength dependency of the haze extinction which were currently determined from measurements of solar radiation and visibility at Mainz, show pronounced seasonal variations. The summer values are in general definitely higher than in winter. There is no connection with the scatter light types of the sky-light or with the meteorological situation.
Derivation of the physical parameters of the jet in S5 0836+710 from stability analysis
2019
A number of extragalactic jets show periodic structures at different scales that can be associated with growing instabilities. The wavelengths of the developing instability modes and their ratios depend on the flow parameters, so the study of those structures can shed light on jet physics at the scales involved. In this work, we use the fits to the jet ridgeline obtained from different observations of S5 B0836$+$710 and apply stability analysis of relativistic, sheared flows to derive an estimate of the physical parameters of the jet. Based on the assumption that the observed structures are generated by growing Kelvin-Helmholtz (KH) instability modes, we have run numerical calculations of s…
Optical-sectioning improvement in two-color excitation scanning microscopy
2004
We present a new beam-shaping technique for two-color excitation fluorescence microscopy. We show that by simply inserting a properly designed shaded-ring filter in the illumination beam of smaller wavelength, it is possible to improve the effective optical sectioning capacity of such microscopes by 23%. Such an improvement is obtained at the expense of only a very small increasing of the overall energy in the point-spread-function sidelobes. The performance of this technique is illustrated by a numerical imaging simulation.
Optical properties of the low-molecular amorphous azochromophores and their application in holography
2015
The films based on the low-molecular amorphous azochromophore 2-(3-(4-((4- (Ethyl(2-(trityloxy)ethyl)amino)phenyl)diazenyl)styryl)-5,5-dimethylcyclohex-2-enylidene) malononitrile (IWK-2M) were prepared. The optical properties of the material, such as transmittance and reflection spectra of the film, sensitivity to polarization holographic recording by two wavelengths (405 and 532 nm) were studied. The direct relief formation during the polarization holographic recording was explored, relief depth dependence on exposure and record beam intensity was investigated. The holographic matrix on this material base was produced without chemical etching process; the replication of holographic image w…
Full field of view super-resolution imaging via two static masks
2008
The usage of two static gratings for obtaining super resolved imaging dates back to the work by Bachl and Lukosz in 1967. However, in that approach, a severe reduction in the field of view was the necessary condition for improving the resolution. In this paper we present two approaches that are also based upon two static gratings but without the need to sacrifice in the field of view. The key idea for not paying with the field of view is performed in two ways: First, by using white light illumination that averages the ghost images obtained outside the region of interest since the positions of those images are wavelength dependent. Second, by using two random functions for the encoding and t…
Photochemical Size Reduction of CdSe and CdSe/ZnS Semiconductor Nanoparticles Assisted by nπ* Aromatic Ketones
2009
A novel effect of n pi* aromatic ketones on the quantum dots optical properties is reported. By controlling experimental conditions such as time of irradiation, presence of air in the media, hydrogen donor capacity of the solvent, and irradiation wavelength, core and core-shell CdSe QDs can be resized as convenient.