1. An iris camera for capturing an image of an iris of a user, the iris camera comprising: a lens; an image sensor for capturing an image produced by the lens; a processor for analysing the degree of focus of successive images produced by the sensor and for controlling a lens position adjustment motor to move the lens to a position where a subsequent captured image potentially has an increased degree of focus; and a proximity sensor for providing an initial measurement of the distance between the lens and the user; wherein the processor is arranged to user the initial distance measurement obtained by the proximity sensor as a starting point for capturing images of the iris to effect a fine-focus adjustment.