Refractive index matching for high light transmission composite systems

Transparent optical polymer/filler systems can be produced into complex shapes for a range of applications, such as lenses, shields, and containers. This work used refractive index liquids as a model for polymer matrices to investigate the degree of refractive index match required to maintain high transmission in an inorganic-filled polymer system (cubic calcium fluoride with particle size of 1 to 5 µm) over the visible spectrum. It was determined that in order to achieve a transparent composite (>85% transmission with 10 mm pathlength) with this filler (using literature reported dispersion data), the materials must have a refractive index match within ±0.007 for 1.6 vol.% loading. With a loading of 3.1 vol.%, the matching range required was reduced to approximately ±0.002.

Microscopical Characterization of Glass Fragments

The methods described involve the double variation method of Emmons which uses the optical microscope and measures dispersion of refractive index. The refractive index of match of the glass and one of a known set of carefully standardized liquids is determined by: (1) measuring the temperature of index match of the glass-liquid combination to obtain the refractive index as a function of wavelengths; and (2) measuring the wavelength of index match of the glass-liquid combination to obtain the refractive index as a function of temperature. Method 1 utilizes a hot stage microscope and monochromator. Method 2 utilizes a hot stage microscope and dispersion staining objective. Modifications of method 1 utilize phase contrast, a Schlieren microscope, or an interference microscope to increase the sensitivity of index match.