On 2D Focusing of X rays Bragg-diffracted by a biaxially bent crystal

2D focusing of an X-ray wave Bragg-diffracted by a biaxially bent crystal is considered in terms of quasi-back diffraction scattering in the meridional plane. Analytical expressions for the focusing geometrical condition in the meridional plane and for the spatial distribution of the wave intensity in the same plane in the neighborhood of the point source image are derived. They differ from those currently available from the theory.