Abstract: A standard integral form whose integrated function equals to the product of the screen function and a linear phase-factor, as a general definition of the Fraunhofer diffraction is proposed. The four devices for receiving this field are shown, especially the receiving set-up of image-plane and its advantages is described. Finally this article introduces to the relationship of the Fraunhofer diffraction and the Fourier transform, and corresponding three kinds of the coherent optical information processing system.

Key words: Fraunhofer diffraction, wavefront phase-factor, spatial frequency spectrum