A lens unit includes a lens barrel for receiving at least one lens and a motor arranged to displace the lens barrel between various positions. Displacement of the lens barrel is proportional to an electrical signal applied to the motor. A first conductor is fixed to the lens barrel and is arranged to make electrical contact with a second conductor when the lens barrel is at an initial position. A processor is arranged to detect a change in the electrical contact, to determine an electrical signal at the time of the change and to generate an electrical signal corresponding to the desired displacement.