1. An iris camera for capturing one or more images of irises of a user, the iris camera comprising: a lens; two image sensors for capturing one or more images produced by the lens, the two image sensors being spaced-apart, each one of the two spaced-apart image sensors being adapted and positioned to capture an image of a different iris of the user; a processor for analyzing the degree of focus of successive images captured by the sensors 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, the proximity sensor being positioned between the two spaced-apart image sensors; wherein the processor is arranged to use 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.