Diffraction Fresnel diffraction:ifa source s and the viewing screen are each a finite distance from an intermediate object,the resulting diffraction pattern is called fresnel diffraction(菲涅尔衍射） 。 Diffraction Fresnel diffraction：if a source s and the viewing screen are each a finite distance from an intermediate object, the resulting diffraction pattern is called fresnel diffraction(菲涅尔衍射）。 P