Holograms that are predominantly in use today as replicable devices for display, security, or packaging can generally be divided into two categories: either surface relief rainbow holograms, which include three dimensional images and intricate grating patterns, or reflection type volume holograms. The Aztec structure is a special surface relief device that combines aspects of both of these types. Its fabrication by holographic means requires techniques of both surface and volume holograms, and thus it is technically more difficult to make than either separately. The structure is deeper than the standard surface relief hologram, and its profile has the characteristic of several well defined steps, such that, when viewed on edge, resemble a stepped pyramid. Thus, replication of the Aztec structure requires special high resolution techniques to faithfully record the submicron features of the stepped profile, and thus is more difficult to manufacture. The visual characteristics of the Aztec structure are similar to the volume hologram, in that single colors, rather than rainbow colors, can be viewed. Also, a combination of single colors can be encoded into a single master, yielding unique visual effects.
