How does autofocus work? - Science Scrapbook 11.11.24

Millions of people now own compact digital cameras and camera phones that will automatically focus on parts of a scene, without having to turn a focus wheel. But how does autofocus work? In this Naked Science Scrapbook we find out how battleship technology has found its way into cameras and why some autofocus cameras use ultrasound to figure out what to focus on...