An improved method for angular-resolved characterization of the optical anisotropy of pyrolytic carbon.

Summary A description is given of an experimental technique that improves the accuracy of the measurement of light extinctions by polarized light microscopy from deposits of pyrolytic carbon. The measurements were performed using a specially developed digital photometric image-analysis procedure providing high spatial and angular resolution of light extinctions over the reflecting optical domains with a high dynamic range of grey levels. The digital image acquisition and data processing are illustrated using circular-shaped pyrolytic carbon matrices of infiltrated carbon fibre felts and planar layers of pyrolytic graphite. The calculated value of the extinction angle for single crystalline graphite is discussed with respect to the experimental values for pyrolytic carbon with different degrees of optical anisotropy. Practical requirements for the accuracy of the method are discussed.