Abstract

An optical sight was designed incorporating an edge-illuminated hologram and a remotely located He–Ne laser. The hologram projects a virtual image of a reticle at infinity and is illuminated by a laser through a fiber-optics lightguide. Edge illuminated holograms have several advantages over front illumination: laser light not diffracted by the hologram remains inside the glass plate and is not scattered by surface contamination, and sunlight is not diffracted into the viewers’ eyes. Edge illumination allows the sight to be compact with large exit aperture. Edge-illuminated hologram recording presents a number of unique problems. Recording in ordinary holographic plates results in low diffraction efficiency and low-contrast images. Preprocessing of the plates to reduce silver-halide content improves the results. Exact refractive-index matching between the photographic plate, emulsion, and cover plate is needed to avoid excessive surface reflections. Photographs of the sight module and projected reticle are shown.

© 1985 Optical Society of America