1. A computational imaging system comprising; an imaging sub-system; a transmissive liquid crystal (LC) element placed in the light path of the imaging sub-system and functioning as the aperture of the imaging sub-system; the LC element comprising a periodically patterned electrode which is patterned according to a periodical modulation function and configured to deliberately blur an intermediate image captured by the imaging sub-system by applying a controllable voltage thereto; and a digital focus processor configured to deconvolute the periodical modulation function to remove the blur away from the intermediate image and determine an all-in-focus real image.