A television receiver display system for displaying, within a main image produced from a first video signal, one or more secondary images produced from a second video signal. Successive frames or fields of picture data of the second video signal are stored in an image memory, and successive lines of...http://www.google.com.hk/patents/US4796089?utm_source=gb-gplus-share專利 US4796089 - Television receiver display apparatus having multi-image display capability
