[en] Results of the study produced the following conclusions: higher line density gratings could be produced immediately by superimposing existing gratings (after reducing wire widths); unwanted higher orders could be reduced by chemical treatment of existing ''deep groove'' gratings; symmetric phase gratings could be produced immediately by plating with a low absorption material instead of with gold; symmetric phase plates (gratings) can be etched with existing equipment (a combination of two would focus beam on a spot, with up to 16% efficiency); to improve performance, eventually one should manufacture asymmetric phase gratings, and ''tailor'' the contours of absorption gratings; in the longrun, probably ''shingle gratings'' will offer the best performance; and the conjectured ''Impossibility Theorem'' may limit the performance of gratings, no mater how they are constructed