An image pickup frame is divided into a plurality of areas. A contrast at each area is measured. An area where a main subject is located is detected by comparing contrasts at areas. A distance to a subject in the area where the main subject is located is measured. With this range finding technique, even...http://www.google.ca/patents/US5900927?utm_source=gb-gplus-sharePatent US5900927 - Variable target autofocusing and range finder for measuring distance to a subject
