RGB‐Color Image Analysis for Determination of Birefringence of Micro‐Films and Columnar Coatings

The birefringence analysis of thin approximate to 1 mu$\approx 1\hspace*{3.33333pt}\umu $m SiO2 films deposited via evaporation at a glancing angle of 70 circle$\hspace*{3.33333pt}{70}<^>{\circ}$ to the normal on resist pillar arrays on Si and nanopatterned SiO2 substrates is carried out by spectral and color (red-green-blue [RGB]) imaging modes. Retardance and birefringence of the films deposited over flat and structured regions can be distinguished with only approximate to 1% difference between neighboring regions for the visible spectral range using RGB numerical analysis of images. The Michel-Levy color map is used for color rendering of birefringence to make quantitative measurements by numerical RGB color filtering. It is shown that by using lambda/2$\lambda /2$ at 530 nm waveplate inserted at pi/4$\pi /4$ angle to the cross polarizer-analyzer setup, the range of changes in chromaticity xy-coordinates expands approximately twice upon angular rotation of a birefringent sample. This facilitates a better signal-to-noise determination of birefringence. The proposed method with lambda/2$\lambda /2$-plate color shifting can be directly used to determine birefringence from step-like spectral features in reflection and transmission polariscopy. Direct measurement of birefringence (Delta n=0.023${\Delta}n=0.023$) and retardance of SiO2 chevron film is carried out using Berek compensator as a benchmark.