Abstract: Methods and systems are disclosed for detection of agents such as pathogens or toxic substances and, in particular, to methods and systems for determining the most important background constituents to suppress in a sample, e.g., in a bulk aerosol sample, in order to reduce the probability of false alarms and improve the level of detection of potentially harmful airborne agents.

Abstract: Methods and systems are disclosed for detection of agents such as pathogens or toxic substances and, in particular, to methods and systems for determining the most important background constituents to suppress in a sample, e.g., in a bulk aerosol sample, in order to reduce the probability of false alarms and improve the level of detection of potentially harmful airborne agents.

Abstract: Methods and systems are disclosed for selecting a set of interrogation wavelengths from spectral data, the method including the steps of performing a principal coordinate transformation on the spectral data, choosing an objective function which describes the efficiency of the transformation in separating the class of agents from the class of interferents, rank ordering the interrogation wavelengths according to said objective function, and choosing the set of wavelengths with the highest rank. In one preferred embodiment, the objective function is the smallest spectral angle between the class of agents and the class of interferents.

Abstract: 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.

Abstract: 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.

Abstract: The present invention generally provides methods and systems for characterizing texts, for example, for identifying textual documents by language, topic, author, or other attributes. In some embodiments, a method of the invention can include creating an n-gram frequency spectrum for a document under analysis, preferably selecting a subset of the n-gram frequency spectrum, transforming the n-gram frequency spectrum into principal component space, and identifying one or more attributes of the document according to its similarity to (or distinction from) reference documents in the principal component space.

Abstract: The present invention generally provides systems and methods for distribution of radiation among a plurality of optical channels, each of which can include a non-linear optical element. An optical system of the invention can include a source for generating radiation and an optical time-division multiplexer that can deflect, at any given time interval, the radiation into one of a plurality of optical channels.

Abstract: The present invention generally provides systems and methods for distribution of radiation among a plurality of optical channels, each of which can include a non-linear optical element. An optical system of the invention can include a source for generating radiation and an optical time-division multiplexer that can deflect, at any given time interval, the radiation into one of a plurality of optical channels.

Abstract: 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.

Abstract: An improved interferometric measuring system that includes a system for measuring a phase difference between two coherent beams oscillating at substantially the same frequency, and including a phase modulator disposed into optical communication with one of the coherent beams and being adapted to generate a phase modulated beam signal. A beam combiner combines the phase modulated beam signal with the second one of the coherent beams to generate a combined beam signal. A detector element measures the intensity of the combined beam signal and a date processor analyzes the intensity to determine from the harmonic components of the combined beam signal the phase difference between the two coherent beams.

Abstract: 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.

Abstract: 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.

Abstract: Methods and apparatus for writing and reading data provide storage in a volume of memory material consisting of inhomogenously broadened absorption centers such that a beam of electromagnetic radiation controlled to be independently steered and simultaneously shifted in wavelength can access information stored in four independent dimensions, three spatial and one spectral. The memory medium can be utilized to write and read a selectable connection matrix between two completely populated two-dimensional memory planes.

Abstract: 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.

Abstract: Apparatus for steering a principal beam of electromagnetic radiation consisting of a photorefractive material situated such that the principal beam of radiation passes therethrough, the material being photoconductive and having an index of refraction that is variable in response to transverse electro-optical effects; and variable writing means for irradiating the material in a direction orthogonal to the principal beam with two beams which intersect at a variable angle so as to write a diffraction grating in the material and thereby vary the index of refraction of the material, thus steering the principal beam.