In this invention, a correlation data and interpolation data generation circuit generates a vertical correlation signal, a plurality of left-downwardly inclined direction correlation signals, and a plurality of right-downwardly inclined direction correlation signals. The vertical direction correlation...http://www.google.co.uk/patents/US4985764?utm_source=gb-gplus-sharePatent US4985764 - Apparatus for detecting a pixel correlation and generating an interpolation signal for a digital television signal
