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