Improvements relating to automatic target following apparatus

3. Automatic target following apparatus comprising A. SENSING MEANS FOR DERIVING A VIDEO SIGNAL REPRESENTING A TARGET, B. MEANS FOR STORING SIGNAL ELEMENTS FROM A FRAME OF SAID VIDEO SIGNAL, C. MEANS FOR COMPARING SIGNAL ELEMENTS FROM A SUBSEQUENT FRAME OF SAID VIDEO SIGNAL WITH THE STORED SIGNAL ELEMENTS WITH DIFFERENT RELATIVE PHASE SHIFTS TO DETECT DEVIATION FROM A DESIRED POINT OF VIEW OF THE TARGET, D. SAID COMPARING MEANS INCLUDING MEANS FOR DERIVING A PLURALITY OF CORRELATION SIGNALS DEPENDENT ON THE CORRELATIONS OF THE SIGNAL ELEMENTS FROM SAID SUBSEQUENT FRAME AND SAID STORED SIGNAL ELEMENTS WITH DIFFERENT RELATIVE PHASE SHIFTS, E. MEANS FOR DERIVING A GUIDANCE SIGNAL FOR THE APPARATUS RESPONSIVE TO THE LARGEST OF SAID CORRELATION SIGNALS, F. MEANS FOR DETECTING A DECLINE IN THE CORRELATION OF SIGNAL ELEMENTS FROM SAID SUBSEQUENT FRAME WITH SAID STORED SIGNAL ELEMENTS, AND G. MEANS FOR UPDATING SAID STORED SIGNAL ELEMENTS WHEN THE DECLINE EXCEEDS A PRE-ARRANGED LIMIT, THEREBY TO ALLOW FOR CHANGES IN THE RELATIVE SIZE OF THE TARGET WITH APPROACH OF THE APPARATUS THERETO.