<title>Rainbow and full-field cylindrical fiber optic holograms</title>

Abstract

Simplified techniques of recording rainbow and full-field cylindrical holograms by using flexible fiber optic light beam delivery systems are described. The method used in recording full-fieId cylindrical holograms is similar to that of the conventional technique, where the object is kept at the centre of a cylinder and the hologram recording film is wrapped around the object forming a cylindrical shape. There are, however, some practical problems in realising these holograms: (a) proper illumination of the object and (b) achievement of a balanced intensity ratio between the object and the reference beams. These problems have conveniently been overcome by employing flexible multiple fiber optic beam delivery systems, where both front and the back sides of the object have been illuminated separately using a practically non-overlapping fiber optic end geometry coupled with an independent reference beam. Rainbow holograms in both one-step and two-step recording geometries have also been successfully realised, where the advantage of flexibility offered by fiber optic beam delivery system is gainfully utilised for providing the desired vertically inclined (overhanging) reference beam. Methods for recording inbuilt reference beam and large size rainbow holograms by the use of optical fibers in the recording geometries are also being studied.