Specular reflectance of cold-rolled aluminum surfaces

The specular reflectance of cold-rolled aluminum surface is studied using a fiber optic system. An approximation for the determination of surface roughness is presented.     

On the effective field and optical constants of alkali halides containingF colour centres

Summary The Onsager and Lorentz local fields ofF colour centres are compared and their change as a function of angular frequency and temperature is also considered. The change of these fields is proportional to the change of the refractive index produced byF centres. Some approximations about the explicit temperature dependence of the refractive-index change are also presented.

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Riassunto I campi locali di Onsager e Lorentz diF centri di colore sono confrontati e si considera il loro cambiamento in funzione della frequenza angolare e della temperatura. Il cambiamento di questi campi è proporzionale al cambiamento dell'indice di rifrazione prodotto daF centri. Si presentano anche alcune approssimazioni riguardo alla esplicita dipendenza dalla temperatura del cambiamento dell'indice di rifrazione.

     

Complex refractive index of turbid liquids

We present a multifunction spectrophotometer for the measurement of light reflection from thick and transmission from very thin turbid liquid samples. Moreover, we present a method to get the complex refractive index of such turbid liquids. As an example of the high performance of the device and the method, we present data on inks that are used in offset printing.     

Terahertz absorption spectra of commonly used antimalarial drugs

Optical Review - Terahertz (THz) spectra from the pure forms [i.e. the active pharmaceutical ingredients (APIs)] of four commonly used antimalarial drugs are reported. The well-defined spectral...     

Dispersion Theory for Two-phase Layered-Geometry Nanocomposites

A dispersion theory for linear optical properties of two-phase layered-geometry nanocomposites is presented. Generalized dispersion relations and sum rules are stated using the results from complex analysis. The concept of Lorentzian linear susceptibility is exploited in theoretical treatment of the effective linear susceptibility of the nanocomposite. The meromorphism of total reflectance in the case of effective meromorphic nonlinear susceptibility was observed.     

On all-optical laser cleaning and inspection of contaminated concave metal surfaces

A technique for all-optical laser cleaning and surface quality monitoring of concave metal surfaces is suggested. Contaminated pharmaceutical punches from a tablet compression machine were cleaned using high-energy laser pulses. Image information obtained from a diffractive-optical-element-based sensor was used in inspection of the surface quality change of the concave punches due to laser cleaning. Alternative method for mechanical cleaning of punches is introduced, which is based on simultaneous laser cleaning and surface quality inspection of the punches.     

Far infrared (THz) absorption spectra for the quantitative differentiation of calcium carbonate crystal structures: Exemplified in mixtures and in paper coatings

In this paper, far-infrared (FIR) spectroscopic techniques have been employed to detect different calcium carbonate crystal concentrations in powder mixtures. We have compared absorption spectral features of both pure and mixtures of natural ground calcium carbonate (GCC) and synthetic precipitated calcium carbonate (PCC). It is evident that the absorbance data differentiate clearly and unequivocally between calcite and aragonite in the spectral range of 2–18 THz. Also, from the absorbance measurement of two sets of mixtures, we have revealed a linear relationship between the ratio of some selected absorbance peaks of the mixtures and concentration of a particular pigment within the mixture. This innovative technique could be a novel, practicable technique for quality control or for analyzing coating and/or filler pigments and extenders in the paper making and printing industries. Finally, we have proven in the case of paper that, surface roughness and print color play no role as far as the locations and magnitudes of the absorbance spectral features are concerned.     

Measurement of the refractive index of highly turbid media: comment

We comment on the recent Letter by Calhoun et al. [Opt. Lett. 35, 1224 (2010)]. We wish to correct their statement about the order of the magnitude of the absorption coefficient of inks that we have we studied. In addition, we consider the inconsistency of their theoretical model with the experimental data obtained for milk and milk-cream samples.     

Detection of Refractive Index Change of Liquids by Diffractive Element talrd Sensor

Refractive index change of liquids was detected using a temperature compensated prism cavity together with a diffractive optical element fabricated by electron beam lithography. Small changes of refractive index could be detected from image data of the sensor.     

Scanning of skin gloss by a diffractive optical element-based handheld glossmeter

Skin specular gloss (referred to as “gloss’’) determination is important in dermatology and cosmetic industry as it gives an indication of the skin health and beauty. Its accurate determination is, therefore, necessary. Commercially available glossmeters typically employ large incidence angle geometry, large illumination area, and fixed point measurements making them impractical regarding measurement of curved and complex non-planar objects or surfaces as well as low gloss regime such as the skin. In this study, we have demonstrated the novel application of a diffractive optical element-based handheld glossmeter with scanning capability, overcoming the disadvantages of conventional glossmeters, in the accurate determination of skin gloss and gloss profile for different skin types under different measurement conditions. Different parts of the body (back of the hands, the inner part of the arm and the forehead) of four volunteers with light, dark and intermediate skin types were scanned (also in different directions) to obtain the skin gloss profile and the statistical average skin gloss. Additionally, the skin surface was modified by arm extension and scanned as well. Our preliminary results showed that the statistical average skin gloss reading increased with the increasing lightness of skin. Areas with higher sebaceous glands (forehead) showed higher gloss reading than the other body parts (inner arm and back of the hand). However, the roughness of the skin surface decreased the statistical average skin gloss reading. The handheld scanning skin glossmeter allows for the accurate determination of skin gloss with sensitivity to small variation in the skin surface roughness with high repeatability.