| 摘要 |
PURPOSE:To widen a tracking operation range effectively at its boundary line and to perform more accurate focus detection and focus control by setting a limit area narrower than the whole or part of a photographic image plane in this area, and tracking a subject within the limit area. CONSTITUTION:When signals indicating positions of boundary lines 30-33 are generated according to the operation of the knob and lock button of a limit area setting means, positions on horizontal lines corresponding to those boundary lines and a specific position on each horizontal scanning line having its upper and lower end on horizontal scanning lines are only selected. For the purpose, the number of scanning lines in one field is counted for the former and horizontal scanning lines having numbers corresponding to positions of boundary lines 32 and 44 set with the knob 42, etc., are selected. Further, a pulse train is generated by multiplying a horizontal synchronizing signal frequency for the latter and pulses with numbers corresponding to the positions of boundary lines 30 and 31 set with the know 40, etc., while counted from the starting end of each horizontal scanning period are only selected. |
