1. An image-change detector comprising: a photodetector array of pixels to sense incident light over a wavelength band of interest; a phase grating to induce near-field spatial modulations responsive to a point source, the near-field spatial modulations illuminating a pattern over the photodetector array responsive to the incident light; and logic coupled to the photodetector array to successively poll a subset of the pixels to produce sets of image data, compare the sets of image data, and detect an image change responsive to the comparison of the sets of image data.