Abstract: A method for indicating an overload condition of a data storage system, comprises the steps of: defining one or more load indexes, wherein each of the load indexes has an overload threshold; and if one of the load indexes has met its respective overload threshold, providing an indicator of the overload condition of the storage system, else, monitoring the load indexes.

Abstract: The hologram card generates a hologram image in response to an illumination light beam. The hologram card comprises a substrate of a first plastic material having a first refractive index. The substrate has a contoured surface. The contoured surface is formed to include localized topological features constituting a diffractive optical element. The diffractive optical element is structured to generate a hologram image when illuminated by the illumination light beam. The hologram card also comprises a protective layer of a second plastic material having a second refractive index that differs from the first refractive index by less than 0.2. The protective layer covers the contoured surface of the substrate. The protective layer is chemically bonded to, and directly contacts, at least the topological features constituting the diffractive optical element.

Abstract: An illumination system that comprises a light source, and, disposed in an optical path between the light source and the surface, converging imaging optics, and a diffractive array generator. The diffractive array generator preferably includes a two-dimensional periodic array of multi-level topological features.