Natural Focusing and Fine Structure of Light

umbilic�focus �higher�catastrophes �swallowtail�caustic �optical�catastrophes �wave�dislocations �fold�caustic �equiphase�lines �diffraction�catastrophe �initial�wavefront �umbilic�point surface�tension�condition �catastrophe�optics �optical�caustics �caustic�networks �pure�edge�type �paraxial�case �cusp�line �parabolic�umbilic �elliptical�vibration �elliptic�umbilic dislocation�rings �hyperbolic�umbilic �light�caustics �singular�section �phase�screen