1. A detection apparatus for detecting presence or otherwise of an item comprising at least two regions having different optical characteristics, said apparatus comprising: an emitter operative to illuminate a measuring region of said apparatus with electromagnetic radiation; and a detector located and operative to receive electromagnetic radiation reflected from said measuring region of said apparatus and operative to output a signal corresponding to a measured characteristic of said electromagnetic radiation reflected from said measuring region, wherein said apparatus is operative to compare said measured characteristic with a set of pre-defined characteristics, and further wherein if said measured characteristic is consistent with at least one of said pre-defined characteristics, the apparatus is operative to output a signal indicative of presence or otherwise of one of said at least two regions of said item in said measuring region.