This study focuses on optical OFDM in a rolling shutter based VLC for further high-speed data rates. Because an image sensor is employed, DCO-OFDM suffers from poor error performance owing to its high PAPR. To address this problem, we propose a polarity-separated transmission, in which the bipolar OFDM signal is separated into positive and negative parts and transmitted by two LEDs simultaneously. Polarity-separated transmission is expected to double the grayscale range and improve error performance because it reconstructs the original bipolar signal by combining the received signals from two LEDs. We experimentally evaluate the SER of DCO-OFDM and polarity-separated transmissions.