JPH0213760B

A self supporting optical diffraction grid for short wavelength electromagnetic radiation includes a peripheral frame, a grid foil secured to the frame and defining a plurality of elongated slits, and a supporting net, large meshed with respect to the grid constant of the grid foil, secured to the frame to support the grid foil. According to a first feature of this invention, an edge of the frame adjacent the grid foil is provided with a nonrectilinear pattern such that the width of the frame varies from point to point around the frame in order to provide a relatively wide transition zone between the grid foil and the frame and to reduce peak mechanical stress in the transition zone. According to a second aspect of this invention, a supporting grid is secured to the frame and the grid foil in a transition zone between the frame and the grid foil. The supporting grid is designed to provide a gradually decreasing bending rigidity in the transition zone between the frame and the grid foil in order to reduce peak mechanical stress in the transition zone.