Annular aperture diffracted energy distribution for an extended source.

The annular aperture diffracted energy distribution in the image plane for an extended incoherent source has been calculated and tabulated for source sizes up to five times the size of the Airy disk and for annular aperture ratios up to 0.5. It is shown that for a scanning instrument an increase in the instantaneous field of view from one to two times the Rayleigh limit degrades the effective resolution by a factor significantly less than two.