Reported in this paper is the first application, to our knowledge, of a low-coherence optical local oscillator signal source to the live electrooptic imaging (LEI) scheme, where high frequency electric field (EF) distributions are visualized in real time. A fiber-optic super luminescent diode (SLD) in conjunction with a LiNbO_3 Mach–Zehnder modulator (MZM) was found to work well for the real-time imaging of gigahertz-range EF distributions with high suppression of interference pattern image noises (IPINs), which have long been a problem to be solved. While the SLD-based LEI system works up to the MZM bandwidth (10 GHz), IPINs caused by microscopic defects in an electrooptic sensor appear, suggesting a limitation given by the SLD coherence length.