Abstract: The effective coherence length of a single-frequency, solid-state laser is limited to reduce spurious, secondary holograms in conjunction with a holographic recording. The wavelength of the laser is varied or ‘scanned’ with high precision over a very small wavelength range. In an embodiment, the temperature of the laser's resonant cavity optical bench is altered, causing the dimension of the cavity to change and the emission wavelength to move in a controlled manner. The changing wavelength is monitored at high resolution, and a feedback control loop updates the temperature set-point to keep the monitored laser wavelength moving at a desired rate of change through a desired range. As the wavelength of the laser is scanned, the phase of the holographic interference pattern is locked at a position of maximum coherence/contrast within the holographic film aperture.

Abstract: A method and apparatus for encapsulating optical elements, particularly dichromated gelatin (DGC) holographic optical elements (HOEs), exhibits a very high degree of environmental integrity. In broad terms, the optical element is disposed between opposing plates, and a metal seal soldered to the edge(s) of the plates to seal the optical element therewithin. In the preferred embodiment, the metalization includes chrome and nickel, or alloys thereof, followed by gold or platinum. The metallization is preferably applied using a low-temperature process such as vacuum deposition or sputtering. The metal seal may be in the form of a foil or wire. One or both of the plates are compatible with wavelengths of interest, and the technique may be used in transmissive and reflective configurations.

Abstract: An online system for permitting users in a data network to manage inventories of their collectibles (including antiques) includes a database of collectibles, user inventory files, user information files, a database of needed items and items available for sale, and a server-based task for managing and searching the database of needed items and items available for sale. The database of collectibles includes object classes indexed by primary classes and subclasses, and user inventory files storing inventories of instances of the object classes, including instances that each user has, instances that each user would like to sell, and instances that each user would like to buy. Users may access their respective inventories by inspecting, editing, and adding the instances to the user inventories; obtaining valuations of instances in their inventories; and insuring instances in their inventories.

Abstract: A method and apparatus for encapsulating optical elements, particularly dichromated gelatin (DGC) holographic optical elements (HOEs), exhibits a very high degree of environmental integrity. In broad terms, the optical element is disposed between opposing plates, and a metal seal soldered to the edge(s) of the plates to seal the optical element therewithin. In the preferred embodiment, the metalization includes chrome and nickel, or alloys thereof, followed by gold or platinum. The metallization is preferably applied using a low-temperature process such as vacuum deposition or sputtering. The metal seal may be in the form of a foil or wire. One or both of the plates are compatible with wavelengths of interest, and the technique may be used in transmissive and reflective configurations.

Abstract: Polarization-dependent losses (PDL) are balanced in an optical system through the use of a weak polarizer placed in an optical path so as to compensate for the static PDL of the rest of the system. The weak polarizer comprises an interface or a layer of material having a different refractive index in the operating wavelength band, placed in the optical path at an angle to provide a desired level of PDL compensation. The geometry and indices of the two material are deliberately chosen to compensate for PDL elsewhere in the system. One implementation of the invention involves the use glass and air as the two materials, either in the form of a prism or a glass plate. The invention may alternatively take the form of a weak polarizer adhered to, or sandwiched between, a block of optical material such as glass. Preferably, a material having an index close to that of glass would be used in such a case, such as a polymer.