Direct observations of plane wave and spherical wave Pendellösung fringes

By using successive Bragg reflections in a monolithic block of effectively perfect silicon, both plane wave (Ewald type) and spherical wave (Kato type) Pendellösung fringes have been obtained in the same wedge‐shaped crystal. In agreement with the theories, the fringe spacings are the same only at the centre of Bragg reflection and the fringe positions are different in the two cases.