1. A system comprising: a passive infrared sensor configured to detect infrared radiation emitted by an object; a lens comprising a plurality of lenslets that are arranged in a circular array and such that at least two lenslets of the plurality of lenslets are nonconcentric, wherein different ones of the lenslets are configured to focus the infrared radiation emitted by the object from different directions at different times, and wherein different ones of the lenslets have different lens characteristics to provide focused infrared beams of different intensities to the passive infrared sensor; and a processor coupled to the passive infrared sensor, wherein the processor is configured to estimate a direction of motion of the object based on magnitudes of a signal that is based on detected intensities of the focused infrared beams focused by different ones of the lenslets and received by the passive infrared sensor from different directions at different times, wherein different peaks of the magnitudes of the signal correspond to the different ones of the lenslets and wherein the direction of motion of the object is further estimated based on the different ones of the lenslets to which the peaks of the magnitudes of the signal correspond.