ac surface discharge on dielectric materials observed by advanced Pockels effect technique

Techniques for visualization and quantification of the latent electric charge image on dielectric materials have been developed using Pockels effect of a BSO (Bi12SiO20) single crystal, a charge coupled device camera recording system, and a computer image processing technique. The Pockels device of the BSO single crystal was used as a transducer to transfer the surface charge density to retard the transmitted light beam. The basic principle of advanced electro‐optical surface charge measurement is described and typical surface charge distributions of positive and negative discharge streamers produced by an ac (50 Hz) high voltage are demonstrated. The measured surface charge images are shown on a computer monitor as three‐dimensional figures.