Geometrical diffraction and the features in the knife-edge diffraction pattern

It appears that the knife-edge diffraction phenomenon has been well-studied over the past 200 years, but a recent study reported a new feature in its diffraction pattern: the concaveness of diffraction fringes and its reversal of direction from near field to far field. This study presents comprehensive experimental results of diffraction from various types of knife edges. The results show the concaveness of both reflective and passing-through diffraction. Using the approach of diffuse reflection from infinitesimal structure, this paper explains both qualitatively and quantitatively the knife-edge diffraction patterns.