1. A 3-D depth camera system, comprising: (a) an illuminator, the illuminator comprising: (i) at least one collimated light source which provides a collimated light beam; (ii) a diffractive optical element which receives the collimated light beam, and creates a plurality of diffracted light beams which illuminate a field of view including a human target; (b) an image sensor which provides a detected image of the human target using reflections of the diffracted light beams from different portions of the human target, the image sensor includes a phase mask which adjusts the detected image so that a point spread function of each of the reflections of the diffracted light beams from the human target is imaged as a double helix; and (c) at least one processor associated with the image sensor which determines depth information of the different portions of the human target, and in response to the depth information, distinguishes motion of the human target in the field of view.