| 摘要 |
1,241,990. Diffraction gratings. F. W. KANTOR. Oct.24, 1968 [Oct. 25, 1967], No.50609/68. Heading G2J. An optical grating comprises a substrate 76 having a serrated surface comprising a plurality of ridges 78 with corresponding surfaces 81 of each ridge inclined acutely with respect to an imaginary surface 82 joining the peaks of the ridges, a plurality of built-up layers 80 on each of said corresponding surfaces and terminating at a terminal surface, extending across the layers 80, and the terminal edges of selected ones of the layers being recessed from the terminal surface. The terminal surface may be flat and may be parallel to imaginary surface 82. In one embodiment the corresponding surfaces of the ridges 83 Fig. 10 are curved, the curvatures being such that the spacing between terminal edges of alternate layers is graduated and the device focuses incident radiation. The grating may act either as a zone plate or as a fresnel lens. The recesses in the terminal edges are formed by etching. Some examples of materials are given; e.g. silicon oxide and aluminium layers; iron-magnesium layers (especially for use with X-rays). Suitable substrates may be glass or epoxy resin. Preferably the substrate is transparent to radiation and the layers opaque, the layers being cut down to the peaks of the ridges to form a terminal surface joining all said peaks. |
