A 3-D depth camera system, such as in a motion capture system, tracks an object such as a human in a field of view using an illuminator, where the field of view is illuminated using multiple diffracted beams. An image sensing component obtains an image of the object using a phase mask according to a double-helix point spread function, and determines a depth of each portion of the image based on a relative rotation of dots of light of the double-helix point spread function. In another aspect, dual image sensors are used to obtain a reference image and a phase-encoded image. A relative rotation of features in the images can be correlated with a depth. Depth information can be obtained using an optical transfer function of a point spread function of the reference image.