We present an overview of our research effort on volume holographic digital data storage. Innovations, developments, and new insights gained in the design and operation of working storage platforms, novel optical components and techniques, data coding and signal processing algorithms, systems tradeoffs, materials testing and tradeoffs, and photon-gated storage materials are summarized.

Holographic data storage

A lithographic apparatus configured to project a patterned beam of radiation onto a target portion of a substrate is disclosed. The apparatus includes a first radiation dose detector and a second radiation dose detector, each detector comprising a secondary electron emission surface configured to receive a radiation flux and to emit secondary electrons due to the receipt of the radiation flux, the first radiation dose detector located upstream with respect to the second radiation dose detector viewed with respect to a direction of radiation transmission, and a meter, connected to each detector, to detect a current or voltage resulting from the secondary electron emission from the respective electron emission surface.

Lithographic apparatus, and device manufacturing method

We propose a volume holographic data storage scheme that employs counterpropagating reference and image beams and wavelength multiplexing for page differentation. This method is compared with that based on angular multiplexing. A reduction in holographic cross talk is predicted. Further cross-talk reduction that is due to sidelobe suppression is observed in experiments by using photorefractive crystals and the proposed orthogonal data storage.

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Optical data storage by using orthogonal wavelength-multiplexed volume holograms

Combinations, called matrices with memories, of matrix materials with remotely addressable or remotely programmable recording devices that contain at least one data storage unit are provided. The matrix materials are those that are used in as supports in solid phase chemical and biochemical syntheses, immunoassays and hybridization reactions. The data storage units are preferably non-volatile antifuse memories. By virtue of this combination, molecules and biological particles, such as phage and viral particles and cells, that are in proximity or in physical contact with the matrix combination can be labeled by programming the memory with identifying information and can be identified by retrieving the stored information. Combinations of matrix materials, memories, and linked molecules and biological materials are also provided. The combinations have a multiplicity of applications, including combinatorial chemistry, isolation and purification of target macromolecules, capture and detection of macromolecules for analytical purposes, selective removal of contaminants, enzymatic catalysis, chemical modification and other uses.

Remotely programmable matrices with memories

Automatic PCB Inspection Algorithms

A multidimensional optical storage medium is provided for storing a plurality of holographic images representative of data. An interrogation network generates a search argument including a target data field to be simultaneously searched for over at least a segment of the optical storage medium. The interrogation network couples the search argument into the optical storage medium and extracts a set of address fields at which data fields in the storage medium that match the target data field of the search argument are stored.

Content addressable optical data storage system

An improved interferometer measuring system that corrects for errors in the determination of the position of a measurement reflector along a measurement path due to the presence of an atmosphere (e.g. atmospheric turbulence) along the path is disclosed. The system includes a two-wavelength interferometer for measuring the atmosphere and a basic length interferometer for a basic measurement of a change in position of the measurement reflector. A calibration procedure for correcting the basic measurements made by the basic length interferometer uses first and second correction coefficients related to the average refractivity of the atmosphere and the change in the refractivity of the atmosphere, respectively. The coefficients can be determined by interferometric measurements or from a combination of interferometric measurements and data from an atmospheric sensor(s), including a humidity sensor. The two-wavelength interferometer can include a pulsed laser source, a compact reference path element, and path length adjustment element. An algorithm is disclosed for efficiently determining the phase difference between the two beams of the two-wavelength interferometer. Beam combining techniques and apparatus for combining the beams of the two-wavelength interferometer and the basic length measurement interferometer while preserving the polarization of the laser beams are also disclosed. The data obtained from the two-wavelength interferometer can be corrected, based on measurements made by the basic length interferometer, for aging due to the movement of the reflecting mirror subsequent to measurement of the atmosphere by the two-wavelength interferometer.

Interferometer with air turbulence compensation

Image comparison is accomplished by forming a composite image composed of a reference image and a test image. A two-dimensional image spectrum is generated from the composite image and then is whitened by setting the magnitude of every point of the two-dimensional image spectrum to a uniform level. A phase-only image of the composite image is then constructed, and values of the phase-only image exceeding a predetermined threshold are detected as an indication of the location of a difference between the reference and test images.

Image comparison system

Apparatus for storage and retrieval of digital data includes a multidimensional holographic storage medium for storing phase holographic images representative of the digital data. Selected regions of the medium are independently addressable by a beam of light. The storage medium is a spectral hole burning material having absorption regions independently addressable by selected frequencies of light, and includes selectively bleached absorption structures forming frequency channels. An external electric field of selected voltage can be applied to the storage medium to induce Stark effect broadening of the spectral holes, so that at a given frequency of light, a different phase hologram can be stored for each of a plurality of voltages, whereby multiple phase holograms can be stored for each frequency of light. Alternatively, physical stress can be applied to the storage medium to induce a stress field and associated broadening.

Optical memory method and apparatus utilizing frequency channeling and Stark effect

The present invention generally provides systems and methods for detection of agents of interest in a bulk quantity of matter, which also contains clutter and other constituents that typically interfere with the detection of one or more agents of interest. A detection system of the invention generally contains a collection subsystem for obtaining a bulk sample, an interrogation subsystem for generating one or more analytical signals representative of the composition of the bulk sample, and an analytical subsystem according to the teachings of the invention that implements the methods and algorithms of the invention for analyzing the sample analytical signals to determine whether one or more agents of interest are present, e.g., at quantities above a certain threshold, in the bulk sample.

Philip D. Henshaw

Papers

Content addressable optical data storage system

Interferometer with air turbulence compensation

Image comparison system

Optical memory method and apparatus utilizing frequency channeling and Stark effect

Agent detection in the presence of background clutter