A visible region of interest (ROI) extraction method based on region expansion is proposed. It is a method that is combined with a new reverse realization of calibration based on homography. The proposed method extracts the ROI automatically and successfully and simultaneously calibrates the distortion caused by the stereoscopic camera system. It is a practical and easy method because it does not require any extra processing before display. It can be used to discard the confusing margin of the synthesized image of several parallax images and reduce the data amount needed to be processed and encoded. Here, real-time capturing, transmitting, and three-dimensional displaying systems are demonstrated to verify its effectiveness and feasibility.