A device and method for three-dimensional (3-D) imaging using a defocusing technique is disclosed. The device comprises a lens having a substantially oblong aperture, a sensor operable for capturing light transmitted from an object through the lens and the substantially oblong aperture, and a processor communicatively connected with the sensor for processing the sensor information and producing a 3-D image of the object. The aperture may have an asymmetrical shape for distinguishing objects in front of versus in back of the focal plane. The aperture may also be rotatable, where the orientation of the observed pattern relative to the oblong aperture is varied with time thereby removing the ambiguity generated by image overlap. The disclosed device further comprises a light projection system configured to project a predetermined pattern onto a surface of the desired object thereby allowing for mapping of unmarked surfaces in three dimensions.