Coded aperture

Coded apertures or coded-aperture masks are grids, gratings, or other patterns of materials opaque to various wavelengths of electromagnetic radiation.

However, the energy of hard X-rays and γ-rays is too high to be reflected or refracted, and simply passes through the lenses and mirrors of optical telescopes.

The pinhole camera is the most basic form of such a modulation imager, but its disadvantage is low throughput, as its small aperture allows through little radiation.

The coded aperture imaging technique is one of the earliest forms of computational photography and has a strong affinity to astronomical interferometry.

[3] Different mask patterns exhibit different image resolutions, sensitivities and background-noise rejection, and computational simplicities and ambiguities, aside from their relative ease of construction.