1. A system comprising: a passive infrared sensor configured to detect infrared radiation emitted by an object; a lens comprising a plurality of lenslets, 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 detected intensities of infrared beam focused by different ones of the lenslets and received by the passive infrared sensor from different directions at different times.