Fluorescence of ceramic color standards.

Fluorescence has been found in color standards available for use in calibration and verification of color measuring instruments. The fluorescence is excited at wavelengths below about 600?nm and emitted above 700?nm, within the response range of silicon photodiodes, but at the edge of the response of most photomultipliers and outside the range commonly scanned in commercial colorimeters. The degree of fluorescence on two of a set of 12 glossy ceramic tiles is enough to introduce significant error when those tiles have been calibrated in one mode of measurement and are used in another.

Analytical solution for integrating sphere spectral efficiency inclusive of atmospheric attenuation.

An analytical solution to the attenuation of flux within an integrating sphere due to spherical integrating source coating, exit port escape, and atmospheric absorption is derived employing a geometric probability distribution of completed sphere transits. This is used to determine the mean number of completed sphere transits and its variance. Equations that provide the attenuation ratios for the three extinction mechanisms are derived using the energy balance and summation of reflection methods.

The effect of UV absorbing sunscreens on the reflectance and the consequent protection of skin.

The in vivo reflectance spectra of Caucasian skin, coated with preparations containing sunscreen vehicle, vehicle with olive oil and vehicle with the UVB and UVA absorbers 2-ethylhexyl-4-methoxycinnamate and 4-t-butyl-4'-methoxydibenzoylmethane were determined. All preparations reduced the reflectance of skin throughout the UVA spectral range (320 to 400 nm), with the sunscreen preparations containing the UVB and UVB plus UVA absorbers reducing the reflectance more than the sunscreen vehicle alone. This phenomenon, which facilitates the penetration of UV radiation to the lower epidermis and dermal layers of skin and therefore lessens sunscreen efficacy, is attributed to optical coupling mediated by refractive index matching of the sunscreen to the upper epidermis.