General expressions for the intensity distribution in Fraunhofer N-slit diffraction patterns with finite sources both in the form of a uniformly radiating slit and disk have been obtained. By making use of the secondary maxima in the multiple slit patterns and their dependence upon source dimensions it is shown that multiple slits give a limited but useful advantage over double slits for the determination of the angular extent of distant sources. Results indicate an effective increase in resolution of 1/N, N>2. This is verified experimentally.
A. E. SMITH and C. D. HAUSE, "Fraunhofer Multiple Slit Diffraction Patterns with Finite Sources," J. Opt. Soc. Am. 42, 426-430 (1952)