Application of multilayers to VUV and x-ray astronomy

The progress of multilayers makes it possible to fabricate a normal incidence telescope with high angular resolution and wide field of view in the wavelength region 30-300A, though the sensitive wavelength region is limited by the Bragg condition. The sensitive energy region of a grazing incidence telescope is drastically extended up to 100keV by means of depth-graded multilayers which satisfy the Bragg condition in the broad energy band. A multilayer coated grating is also useful dispersive element with high efficiency and spectral resolution in the 1-300A region. This development is expected to open up a new field in astronomical imaging and spectroscopic observations, which are not accessible by present telescopes.