45 results about "Spectral window" patented technology

A method for designing non-linear phase 180° spectral-spatial radio frequency pulses that can be used for spectral editing in magnetic resonance spectroscopic imaging. A novel feature of the pulse is a symmetric sweep developed by the spectral profile from the outside edges of the spectral window towards the middle whereby coupled components are tipped simultaneously and over a short interval. Pulses have been designed for lactate editing at 1.5T and 3T. The spectral and spatial spin-echo profiles of the RF pulses can be measured experimentally and altered in an iterative manner. Spectral-spatial radio frequency (SSRF) pulses allow simultaneous selection in both frequency and spatial domains. These pulses are particularly important for clinical and research magnetic resonance spectroscopy (MRS) applications for suppression of large water and lipid resonances.

A semiconductor laser comprises two optical ring resonators, each comprising an optical waveguide electrically pumped to provide optical gain. The two ring resonators have different round-trip optical path lengths, and are coupled to each other through a half-wave optical coupler. The half-wave optical coupler has a predetermined cross-coupling coefficient and a 180-degree cross-coupling phase. The cross-coupling coefficient is substantially less than the self-coupling coefficients in order to achieve an optimal single-mode selectivity of the laser. The first ring resonator has an optical path length such that its resonant wavelengths correspond to a set of discrete operating channels. The second ring resonator has a slightly different length so that only one resonant wavelength coincides with one of the resonant wavelengths of the first ring resonator over the operating spectral window. The lasing action occurs at the common resonant wavelength. In operation, at least a portion of the optical waveguide in each of the first and the second ring resonators are forward biased to provide substantially equal round-trip optical gains. The second ring resonator is tuned by varying the effective refractive index of a portion of the waveguide through an electrical means, resulting in wavelength switching among the set of discrete operating wavelengths as determined by the first ring resonator.

As hydrogen sulfide is toxic and widely present in many oil and gas facilities, it is highly desirable to use an infrared camera to detect the presence of a hydrogen sulfide (H2S) plume from a safe distance. The proposed are an imaging system and method for detecting hydrogen sulfide (H2S) in a safe distance. The imaging system includes an infrared (IR) imager capable of capturing an image of a scene that includes a gas plume, and a narrow bandpass filter installed in the infrared imager. The narrow bandpass filter has a spectral window. A width of the spectral window is in the range of 100 nm to 300 nm. The spectral window is included in a wavelength range between 2.5 μm and 2.8 μm, a wavelength range between 1.5 μm and 2.0 μm, or a wavelength range between 7.0 μm and 10.0 μm.

An apparatus for detecting and determining a source azimuth for gamma radiation includes at least two scintillation crystals at angular offsets and directed toward a common plane of detection, photodetectors adjacent to each of the scintillation crystals for converting the light response of the scintillation crystals into distinct electrical signals, and a digital processing system configured to analyze spectral data from each electrical signal produced for each crystal. The digital processing system monitors a finite number of spectral windows corresponding to a selected set of radioisotopes, and uses one or more of the electrical signals to determine a signal intensity and a likely source azimuth for a detected radioisotope in the plane of detection. Another scintillation crystal directed outside of the common plane of detection may be used for three-dimensional detection. Related methods for detection and location of gamma ray sources are discussed.

The invention provides a system and a method for modulating frequency domain of a block transmission system based on a wave filter set. The method comprises the following: firstly, an inputted serial modulating symbol sequence is divided into D data block sequences, with a length of K for each, the K point orthogonal transformation is performed; secondly, K elements outputted by each orthogonal transformation are respectively mapped to the K subbelts distributed by the system to transmit by the subbelt mapping; thirdly, the D point DFT transformation is performed on the data block with a length of D transmitted on each subbelt, the data block with a length of D*N is expanded in cycle; fourthly, the K data blocks with a length of D*N are respectively multiplied by corresponding spectral window functions on eachbelt to perform the frequency spectrum forming and the data block accumulation so as to form a data block with a length of D*N; and finally, the D*N point inverse Fourier transform to the data block is performed and the cyclic prefix is added to transmit the processed data block, thereby reducing the complexity on the condition of keeping the performance, particularly on the condition that the number of the distributed sub belts is small such as an upstream link circuit.

The invention discloses a stability control device for transmission spectrums of an optical fiber current transducer, and belongs to the technical field of optical fiber transmission. According to the stability control device, the front end of a polarizer is provided with a first optical fiber filter, and the front end of a sensing unit is provided with a second optical fiber filter. According to the invention, the changes in the spectral form and power of optical waves induced by the drifting of a spectral window of an optical device caused by shaft-aligning errors and temperature in the optical fiber current transducer are eliminated, so that the transmission spectrum in the optical fiber current transducer is stable, thereby eliminating integral optical phase shifting errors of a Faraday effect of the sensing unit. A new scheme for optical paths of all-optical-fiber current transducers based on an optical fiber filter provided by the invention solves the problem that in a traditional optical path, a spectral window of an optical device drifts due to temperature drift and difficulty in accurate shaft-aligning among optical fibers or between an optical fiber and a device, eliminates the influence of spectrum fluctuation on error signals, expands the range of a system for tracking direct-current random phase drift, and improves the anti-jamming capability and stability of the system.

A radiation dosimetry apparatus and method use a scintillating optical fiber array for detecting dose levels. The scintillating optical fiber detectors generate optical energy in response to a predetermined type of radiation, and are coupled to collection optical fibers that transmit the optical energy to a photo-detector for conversion to an electrical signal. The detectors may be embedded in one or more modular, water-equivalent phantom slabs. A repeatable connector couples the collection fibers to the photo-detector, maintaining the fiber ends in a predetermined spatial relationship. The detector fibers may be distributed as desired in a three-dimensional detection space, and may be oriented with their longitudinal axes at different orientations relative to a transmission axis of an incident radiation beam. A calibration method uses two measurements in two spectral windows, one with irradiation of the scintillator at a known dose and one with only irradiation of the collection fiber.

A high confinement nonlinear optical fiber is provided along with methods of parametric amplification for use thereof. The nonlinear optical fiber may include a plurality of concentric layers which are configured to provide different guiding regimes to low-frequency and high-frequency components through transverse geometry and refractive index profiling, thus reducing waveguide dispersion. The resulting optical fiber provides a parametric device with phase-matching in any spectral region of interest, such that a fiber optic parametric amplifier (FOPA) implementing the optical fiber can amplify in any spectral window of interest. A narrow-band FOPA configured to minimize phase mismatching is also provided for use with the optical fiber, and may be implemented as a light source or a monochromator.

An improved system for visual inspection of substrates coated with paints and polymers is disclosed. Painted substrates can be inspected for environmental and physical damage such as corrosion and cracks without removing the paint. The present invention provides the ability to maximize paint thickness penetration. This is accomplished with a spectral bandpass filter that rejects reflected light from the coating opaque bands, while allowing light in the paint window to pass to an IR detector such as an IR camera focal plane. The narrow bandpass range enhances the ability for IR imaging to see through thicker paint layers and improves the contrast over standard commercial IR mid-wave cameras. The bandpass may be adjusted to coincide with the full spectral window of the paint, consistent with the ability of the imaging focal plane to detect light in the spectral region.

A Fabry-Perot cavity comprised of three-dimensional photonic crystal structures is disclosed. The self-assembly of purified and highly monodispersed microspheres is one approach to the successful operation of the device for creating highly ordered colloidal crystal coatings of high structural and optical quality. Such colloidal crystal film mirrors offer high reflection with low losses in the spectral window of the photonic band gap that permit Fabry-Perot resonators to be constructed with high resolving power, for example, greater than 1000 or sharp fringes that are spectrally narrower than 1.0 nm. The three-dimensional photonic crystals that constitute the Fabry-Perot invention are not restricted to any one fabrication method, and may include self-assembly of colloids, layer-by-layer lithographic construction, inversion, and laser holography. Such photonic crystal Fabry-Perot resonators offer the same benefits of high reflection and narrow spectral band responses available from the use of multi-layer dielectric coatings. However, the open structure of three-dimensional photonic crystal films affords the unique ability for external media to access the critical reflection layers and dramatically alter the Fabry-Perot spectrum, and provide means for crafting novel laser, sensor, and nonlinear optical devices. This open structure enables the penetration of gas and liquid substances, or entrainment of nano-particles or biological analytes in gases and liquids, to create subtle changes to the colloidal mirror responses that manifest in strong spectral responses in reflection and transmission of the collective Fabry Perot response.

A method for designing non-linear phase 180° spectral-spatial radio frequency pulses that can be used for spectral editing in magnetic resonance spectroscopic imaging. A novel feature of the pulse is a symmetric sweep developed by the spectral profile from the outside edges of the spectral window towards the middle whereby coupled components are tipped simultaneously and over a short interval. Pulses have been designed for lactate editing at 1.5 T and 3 T. The spectral and spatial spin-echo profiles of the RF pulses can be measured experimentally and altered in an iterative manner. Spectral-spatial radio frequency (SSRF) pulses allow simultaneous selection in both frequency and spatial domains. These pulses are particularly important for clinical and research magnetic resonance spectroscopy (MRS) applications for suppression of large water and lipid resonances.

The present invention provides a broadband signal synthesis method based on multi-transmission and multi-reception frequency division radar, comprising the following steps: 1) at the transmission end of the multi-transmission and multi-reception radar, synchronously transmit M subband signals from M transmitting array elements of the transmitting array; 2) At the receiving end of the multi-transmit and multi-receive radar, N receiving array elements in the receiving array receive echo signals, and each receiving array element is provided with M receiving channels to obtain N×M receiving signals corresponding to different frequency bands and different array elements; 3) Perform beamforming processing and matched filtering processing to obtain M narrowband signals, and then add the spectra of the M narrowband signals to obtain a composite broadband signal, and multiply the composite broadband signal by the reciprocal spectral window to obtain the final broadband signal. The present invention effectively overcomes the problem of side lobes generated when a plurality of narrowbands are synthesized into wideband signals. Therefore, the present invention can use a plurality of narrowband transceiving channels to realize high-resolution range images, thereby greatly reducing the performance requirements of imaging radars for wideband devices.

A semiconductor laser comprises two optical cavities, each comprising an optical waveguide bounded by two partially reflecting elements. The two optical waveguides are disposed on a substrate to form a substantially V-shaped geometry with substantially no cross-coupling at the open end and a predetermined cross-coupling at the closed end for achieving an optimal single-mode selectivity of the laser. The first cavity has a length such that its resonant wavelengths correspond to a set of discrete operating channels. The second cavity has a slightly different length so that only one resonant wavelength coincides with one of the resonant wavelengths of the first cavity over the operating spectral window. The lasing action occurs at the common resonant wavelength. In operation, at least a portion of the optical waveguide in each of the first and the second cavities are forward biased to provide substantially equal round-trip optical gains. The second cavity is tuned by varying the effective refractive index of a portion of the waveguide through an electrical means, resulting in wavelength switching among the set of discrete operating wavelengths as determined by the first cavity.

The invention relates to an optical analysis method for distinguishing a substance (2) present on a substrate such as an object or a document, wherein said method includes the step (a) of illuminating said substrate with a primary light beam selected in order to interact with the substance (2) so that the latter transmits, within a secondary light beam in the visible spectrum, a characteristic chromatic radiation that is not directly detectable in the secondary light beam, and a detection step (b) that comprises a selective filtration sub-step (b1) during which the secondary light beam is filtered through a spectral window of the visible spectrum adapted to said characteristic chromatic radiation in order to detect the substance (2) from the environment thereof. The invention can be used for the optical analysis of documents.

A method of imaging the individual components of systems with sparse spectra using magnetic resonance imaging including the steps of a) exciting nuclei of labeled components using a MRI pulse sequence, b) selecting a proper spectral window to avoid / minimize signal overlap of aliased frequency components. In step a) preferably a spiral chemical shift imaging (spCSI) sequence is employed. In a preferred embodiment, hyperpolarized nuclei of 13C are used for labeling in a pyruvate substrate with metabolites of lacatate, alanine, and bicarbonate.

The invention relates to an optical analysis method for distinguishing a substance present on a substrate such as an object or a document, wherein said method includes the step (a) of illuminating said substrate with a primary light beam (F1) selected in order to interact with the substance (2) so that the latter transmits, within a secondary light beam (F2) in the visible spectrum, a characteristic chromatic radiation that is not directly detectable in the secondary light beam, and a detection step (b) that comprises a selective filtration sub-step (b1) during which the secondary light beam is filtered through a spectral window of the visible spectrum adapted to said characteristic chromatic radiation in order to detect the substance (2) from the environment thereof.

A method for acquiring 3D multispectral MRI of a target includes scanning a spectrum of spectral windows with an MRI scanner, wherein each spectral window of the spectrum defines a continuously-differentiable distribution of frequencies around a scan frequency and adjacent scan frequencies are spaced apart by substantially uniform frequency offsets such that adjacent spectral windows substantially uniformly overlap, wherein selected adjacent spectral windows are scanned in consecutive passes, and nearest neighbor spectral windows within each pass are scanned at a maximum temporal spacing within the pass.