Four-Polarisation Camera for Anisotropy Mapping at Three Orientations: Micro-Grain of Olivine

A four-polarisation camera was used to map the absorbance of olivine micro-grains before and after high-temperature annealing (HTA). It is shown that HTA xenoliths at above 1200 °C in O2 flow makes them magnetised. Different modes operation polariscope with polarisation control sample transmission reflection were used. The type assembled for non-transparent samples HTA. optical observation placed on an achromatic, plastic, quarter-wavelength waveplate as a holder. Inspection sample’s birefringence (retardance), well absorbance, undertaken. best fit transmitted intensity or transmittance T (hence, A=−log10T) obtainable using simple only three orientations (from four measured by camera). When light one very low due cross-polarised condition (polariser–analyser arrangement), three-point can be validated T(θ)=Amp×cos(2θ−2θshift)+offset, where amplitude Amp, offset offset, orientation azimuth θshift extracted each pixel via fit.