Optical sensing system using liquid crystal cells and a corner cube prism coated with dye films for simultaneous detection of an electric field and decomposition products of SF6

We have developed a multisensing system for simultaneously detecting an electric field and a small quantity of decomposition products generated from an electric discharge in SF6. The sensor head consists of a twisted nematic (TN) liquid crystal (LC) cell, sandwiched between two cholesteric LC cells and a corner cube prism coated with thin dye films. The electric field can be detected as changes in retardations induced in the TN LC cells by an electric field at a wavelength of a selective reflection band of the cholesteric LC. Simulated and experimental results for the relationship between the sensitivity to the electric field and the thickness of the TN LC cell are discussed. The decomposition products can also be detected as spectral changes of methyl orange dye films deposited on the surfaces of the corner cube prism at different wavelength regions outside the selective reflection band.