Abstract: A structure for responding to incident radiation for directing said radiation in a selected direction with respect to the structure, the structure using at least two outer diffraction elements and an intermediate diffraction element, the diffraction characteristics being selected so that the selected direction remains within relatively limited confines independent of the angles of incidence of the incoming radiation over a selected range thereof.

Abstract: A diffraction grating structure in the form of a substrate having a grating portion at an input surface thereof and a solid portion at an output surface thereof. A plurality of diffracting elements are formed in the grating portion, the diffracting elements having grooves, the depths thereof depending on the wavelength of incoming radiation impinging on the diffraction elements. The diffracting elements are formed at a selected slant angle with reference to a direction orthogonal to the plane of the input surface of the grating portion of the structure. The incoming radiation is redirected through the grating structure in a selected direction so as to be effectively concentrated at a selected spatial region.

Abstract: A diffraction grating responds to incoming radiation incident thereon within a given range of incidence angles and re-directs such incident radiation from the structure in a selected direction within relatively limited confines. A liquid crystal material is positioned in contact with the diffracting surface of said at least one diffraction structure, the liquid crystal material, when inactivated, having a refractive index substantially the same as that of the diffraction structure. Activation means place the liquid crystal material in an activated state so that the refractive index thereof is substantially different from that of the diffraction structure whereby incoming radiation within a given range of incidence angles is transmitted through the structure and exits in the selected direction.