Abstract: A three-dimensional (3D) scanner includes a light source, an optical detector, a reference reflector, and a 3D aperture structure having side walls and an aperture, the aperture sized to pass a first portion of the light reflected by the reference reflector, the side walls sized to block a second portion of the light reflected by the reference reflector. The 3D scanner further includes a tilted optical bandpass filter to block ambient background light without creating cavity reflections that might cause errors in measured distance.