1. A 3D scanning apparatus configured to image a physical entity, said apparatus comprising: a radiation projector for projecting a plurality of radiation stripes onto said physical entity; a detector for detecting said striped radiation received from said physical entity; and a data storage device for storing said received radiation as a pixellated bitmap image comprising a plurality of rows; said apparatus characterised in that said physical entity, said radiation projector and said detector are geometrically arranged to constrain the number of times that each said received stripe is permitted to occur in a pixel row of said bitmap, said geometrical constraint determining an occlusion classification comprising a plurality of stored types of occlusions and said apparatus additionally comprising an occlusion type processing means for detecting said types of occlusions in said received image data.