Infra-red laser shield

Abstract

A method of making a holographic optical element is disclosed. The method comprises the steps of determining the separation between interference pattern planes tangent to surfaces separated by a desired distance which achieves desired optical properties at a given first wavelength and angular orientation of light in a hologram disposed on a curved surface of first shape corresponding to the shape of a curved holographic element. The angular characteristics of exposure to achieve of this separation of planes in a planar analog of the desired curved holographic element is determined. The angles of exposure of interfering light rays to achieve this separation of planes in the planar analog by exposure of a sensitive substantially planar surface at a second wavelength in order to achieve the desired separation of planes and angular characteristics are determined. A source is constructed having the desired angular exposure characteristics and having a wavelength equal to the second wavelength, the source being constructed using a pair of source sets which are activated in sequence to make the desired interference pattern while shading parts of the substrate. An interference pattern is recorded in a photosensitive substantially planar film disposed on a substantially planar substrate using the constructed source. The interference pattern is developed. The developed interference pattern acts as a transmission hologram. The sensitive film with the interference pattern recorded in it is removed from the substantially planar substrate, the developing being done before removal of the sensitive layer in order that the removal may be carried out in a lighted area. The removed sensitive layer is the adhered to a substrate having the first shape, the removed layer being stretched and bent for adhesion to the substrate.