<p>An object detection apparatus and a method for calibrating an object detection apparatus. The apparatus comprises a housing provided with a light source and a light detector. The light source directs a beam of light towards the light detector. The housing has a base which is provided with a datum surface. The light beam has a defined distance and angle from the datum base. The method for calibrating an object detection apparatus involves setting threshold levels for light intensity received at the light detector. The apparatus has two modes of operation. The invention also includes an adapter for an object detection apparatus which detects the presence of an object by obstructing a light path.</p>
