An imaging system includes a positionable device configured to axially shift an image plane, wherein the image plane is generated from photons emanating from an object and passing through a lens, a detector plane positioned to receive the photons of the object that pass through the lens, and a computer programmed to characterize the lens as a mathematical function, acquire two or more elemental images of the object with the image plane of each elemental image at different axial positions with respect to the detector plane, determine a focused distance of the object from the lens, based on the characterization of the lens and based on the two or more elemental images acquired, and generate a depth map of the object based on the determined distance.