Three-dimensional virtual images for security applications

Three-dimensional images may be produced by a number of methods, the earliest being integral photography. The basic concept involves exposing a photographic emulsion to light scattered from an object through a fly's eye lens to produce an array of micro-images, one behind each lenslet. An observer viewing the composite image through the lenslet array sees a three-dimensional representation of the object. Over the past 5 years, 3M has applied laser technology to the creation of three-dimensional virtual images using the integral photography approach. The virtual images made by this process can be observed by a viewer with the unaided eye in either reflected or transmitted light. The images display large movement as an observer's viewing perspective changes and have a distinct on/off-viewing angle beyond which the image cannot be seen. The fidelity of the virtual images requires maintaining the registration of the substrate lenslets and the micro-images produced by the laser imaging process. This makes the images difficult to copy or modify and an ideal, cost-effective candidate for an overt security feature.