An optical phase grating produces an interference pattern rich in intensity and spatial-frequency information from the external scene. The grating includes an odd number of repeated sets of adjacent horizontal portions, separated by steps, that fill an area that radiates outward from a central region. At a given distance from the central region and within the area of the phase grating, each of the first horizontal portions is of a first width that differs from a second width of the adjacent second horizontal portions. The interference patterns produced by the grating can be processed to extract images and other information of interest about an imaged scene.