321 results about "Phase gradient" patented technology

A system and method for using magnetic resonance to track a medical device which attenuates interfering MR signals. The system comprises an MR tracking device comprising one or more radiofrequency (RF) tracking coils adapted to receive a magnetic resonance MR response signal from nuclei excited by an RF pulse. Ideally, the RF tracking coil only receives an MR response signal from nuclei in matter in the close vicinity of the tracking device. The tracking device is attached to medical device. The interfering signal tends to emanate from large objects or large volumes that are outside the close vicinity of the tracking device but which are still weakly coupled to the tracking device. A dephasing gradient is applied perpendicular to the readout gradient before the RF response signal is received thereby dephasing the interfering signal emanating from remote nuclei, which strongly attenuates the interfering signal while the MR response signal is substantially unaffected. The system can also detect errors in tracking location by checking the amplitude of the signal from each coil and the detected distance between each coil, and correcting for such errors by ignoring data from coils having low amplitude or location deviating from known location relative to the other coils.

Methods and systems are provided for suppressing speckle and/or diffraction artifacts in coherent structured illumination sensing systems. A coherent radiation pattern forms an interference pattern at an illumination image plane and illuminates an object. Radiation scattered or otherwise emitted by the object is detected to produce a signal, which is integrated in time. Coherent artifact suppression is attained by using a spatial modulator, such as an acousto-optic device, to vary a phase gradient at the illumination image plane during the signal integration time. Various embodiments are provided for purposes including without limitation: preserving the depth of field of the coherent illumination; using the same acousto-optic device for pattern generation and coherent artifact suppression; electronically controlling the effective spatial coherence of the illumination system; and reducing errors due to coherent artifacts in a laser-based three dimensional imaging system.

The present invention generally refers to a correction method for grating-based X-ray differential phase contrast imaging (DPCI) as well as to an apparatus which can advantageously be applied in X-ray radiography and tomography for hard X-ray DPCI of a sample object or an anatomical region of interest to be scanned. More precisely, the proposed invention provides a suitable approach that helps to enhance the image quality of an acquired X-ray image which is affected by phase wrapping, e.g. in the resulting Moiré interference pattern of an emitted X-ray beam in the detector plane of a Talbot-Lau type interferometer after diffracting said X-ray beam at a phase-shifting beam splitter grating. This problem, which is further aggravated by noise in the obtained DPCI images, occurs if the phase between two adjacent pixels in the detected X-ray image varies by more than π radians and is effected by a line integration over the object's local phase gradient, which induces a phase offset error of π radians that leads to prominent line artifacts parallel to the direction of said line integration.

Talbot imaging systems comprising a Talbot element, a phase gradient generating device, a light detector, and a processor. The Talbot element repeats a Talbot image at a distance from the Talbot element. The phase gradient generating device scans the Talbot image at a plane at the distance from the Talbot element by incrementally changing a phase gradient of a light field incident the Talbot element. As the Talbot image is scanned, the light detector captures time varying data associated with light altered by an object located at the distance from the Talbot element. The processor reconstructs an image of the object based on the time-varying light data.

A wavefront measuring system and method for detecting phase aberrations in wavefronts that are reflected from, transmitted through or internally reflected within objects sought to be measured, e.g., optical systems, the human eye, etc. includes placing a reticle in the path of a return beam from the object, and placing a detector at a diffraction pattern self-imaging plane relative to the reticle. The diffraction pattern is analyzed and results in a model of the wavefront phase characteristics. A set of known polynomials is fitted to the wavefront phase gradient to obtain polynomial coefficients that describe aberrations in the object or within the wavefront source being measured.

Systems and methods are described for phase-sensitive magnetic resonance imaging using an efficient and robust phase correction algorithm. A method includes obtaining a plurality of MRI data signals, such as two-point Dixon data, one-point Dixon data, or inversion recovery prepared data. The method further includes implementing a phase-correction algorithm, that may use phase gradients between the neighboring pixels of an image. At each step of the region growing, the method uses both the amplitude and phase of pixels surrounding a seed pixel to determine the correct orientation of the signal for the seed pixel. The method also includes using correlative information between images from different coils to ensure coil-to-coil consistency, and using correlative information between two neighboring slices to ensure slice-to-slice consistency. A system includes a MRI scanner to obtain the data signals, a controller to reconstruct the images from the data signals and implement the phase-correction algorithm, and an output device to display phase sensitive MR images such as fat-only images and/or water-only images.

The invention discloses an array antenna for generating microwave orbital angular momentum based on a phase gradient super-surface. The array antenna is formed by the arrangement of phase shift units (1), each phase shift unit (1) comprises a dielectric plate (3), a metal patch (4) is arranged on the surface of the dielectric plate (3), an upper hole (5) is formed in the middle of the metal patch (4), a metal ground plate (6) is arranged at the bottom of the dielectric plate (3), a lower hole (7) is formed in the middle of the metal ground plate (6), and a metal pipe (8) is arranged at the middle of the dielectric plate (3) and communicates with the upper hole (5) and the lower hole (7). The array antenna has the characteristics of small size, light weight and low cost; meanwhile, the continuous control of the orbital angular momentum in phases of 0 to 2Pi is further achieved, and obvious vortex orbital angular momentum is generated; and moreover, the array antenna has an excellent reflection effect.

The invention discloses a wave plate based on a medium meta-surface, a beam deflector and a difunctional device integrating the wave plate and a focusing lens. The devices work in a communication waveband, silicon is adopted as a dielectric material, and a substrate is made from silicon dioxide. The devices are characterized in that the brick shape of the silicon material serves as the design ofa unit structure, and a plurality of brick-shaped structures conforming to required phase gradient are arranged according to two-dimensional crystal lattice periodicity to form a rectangular array; the thickness of silicon nano-bricks of the unit structures with medium meta-surfaces is 0.9 microns. The transmitted phase difference of an x-line deflection light component and a y-line deflection light component of incident light is controlled by adjusting the length and width of the unit structures while the deflector or the focusing lens is achieved before phase wave control, and accordingly functions of the wave plate are achieved. Compared with existing devices, the devices are simple in structure, and the deflection efficiency is improved to 80%. Compared with existing wave plates and optical devices which are used in a stacked way, processing and manufacturing inconvenience is overcome, and integration and miniaturization of the optical devices are facilitated.

The invention discloses an ultrathin optical lens construction method based on an artificial microstructure super surface. The ultrathin optical lens construction method comprises the following steps that step (1) required working wavelengths are selected within the range from visible light to intermediate infrared wavelength bandwidth of 600nm-20 microns; incident light irradiates to the artificial microstructure super surface, and phase distribution on the artificial microstructure super surface is calculated according to the required positions of emergent focus points; step (2) rotationally symmetrical periodic structures are designed according to a certain period, and concrete phase values are determined through combination of the obtained phase gradient distribution and the periodic structure units on the surface; and step (3) columnar structures of determined height are selected to act as basic units of the artificial microstructure super surface, and corresponding concrete realization structures are designed according to the phase requirement of each basic unit. The effect of an optical lens at the macro level is realized by the micro-nano structures, the optical size is extremely low under the condition of maintaining high transmittance, and the optical lens is a double-plane lens.

The invention discloses a sub-aperture partition PFA (Polar Format Algorithm) radar imaging method, and belongs to the technical field of radar imaging. All apertures are partitioned into a plurality of sub-apertures; the sub-apertures are processed by using PFA to obtain azimuthal low-resolution images; movement error of the sub-aperture images is eliminated by using PGA (Phase Gradient Autofocus) processing; geometric distortion is eliminated through azimuthal up-sampling, space varying filter and geometric correction; partitioned sub-blocks with overlapped images of all the sub-aperture images obtained by the geometric correction are subjected to image registration; finally all the registered sub-aperture images are fused to obtain a final SAR image. The full-aperture data of a large block is partitioned into sub-aperture data of small blocks for processing, so that the imaging processing efficiency is improved; the partitioned sub-blocks with overlapped images are registered during implementation of the sub-aperture image registration, so that the registration of the entire images can be realized better and seamless splicing of the sub-blocks can also be realized after registration.

The invention belongs to the technical field of electromagnetic wave polarization detection, and particularly discloses an efficient microwave polarization detection device based on a photonic spin Hall effect. For the detection device, electromagnetic wave to be detected is decomposed into left-hand circularly polarized beam and right-hand circularly polarized beam through the efficient photonic spin Hall effect, the module values and phases of the left-hand circularly polarized beam and right-hand circularly polarized beam are respectively measured, and backstepping is carried out to obtain the polarization of the electromagnetic wave to be detected. The photonic spin Hall effect is realized through linear geometry Berry phase gradient of total-reflection type meta-surface with a spin structure. Compared with the traditional polarization detection manner (linear polarization loudspeakers opposite to each other are used for directly measuring x component and y component of electromagnetic wave), the efficient microwave polarization detection device has the advantages that higher convenience and quickness are achieved, the errors are few, and the stability is better. The operating frequency of the device is 10-14GHz, and the structure constants of meta-atoms are scaled in equal proportion or redesigned, so that the operating frequency can be applied to other operating frequency ranges.

The invention belongs to the technical field of radar stealth, and particularly relates to a wideband spirally-coding radar cross-section (RCS) reducing metasurface insensitive to polarization and a design method thereof. The metasurface is of a two-dimensional limited size structure and is formed by arranging eight types of linear super-elements having different gradient directions in 8 by 8 according to a spiral sequence, the gradient directions of eight types of linear super-elements are respectively 0 degree, 45 degrees, 90 degrees, 135 degrees, 180 degrees, 225 degrees, 270 degrees and 315 degrees, each linear super-element is of a two-dimensional limited size structure and is formed by six types of artificial electromagnetic structure units having different sizes in 6 by 6 according to linear gradient, the six types of artificial electromagnetic structure units realize 360-degree coverage, the phase gradient is 60 degrees, the spiral sequence is a single spiral circulation arrangement mode from outside to inside, each artificial electromagnetic structure unit is of a rotary symmetric reflection structure and comprises an upper-layer internal closed ring, an external Jerusalem metal structure, an intermediate-layer dielectric plate and a bottom-layer metal copper plate. The RCS reducing metasurface has the excellent characteristics of thin thickness, good robustness, ultra-wideband working and the like and is easy to process.

The invention provides an FFBP SAR imaging-based autofocus method through which accurately focused SAR images can be obtained in eight steps. The method is based on an FFBP frame, phase gradient information of movement error is extracted by using phase difference information of adjacent sub-apertures of point targets, and movement error is estimated through an integration method and compensated to realize autofocus processing of high-accurate SAR images. Compared with conventional methods, the method is not affected by error order. Movement error of any orders can be estimated, and the robustness of autofocus algorithm is substantially improved. Error information is extracted by using phase difference of adjacent sub-apertures, which avoids repeated calculation of a nested overlapping sub-aperture method. Large-scale optimized searching is not required, computational burden is greatly reduced, and imaging time is shortened.

For correcting differential phase image data 52, differential phase image data 52 acquired with radiation at different energy levels is received, wherein the differential phase image data 52 comprises pixels 60, each pixel 60 having a phase gradient value 62a, 62b, 62c for each energy level. After that an energy dependent behavior of phase gradient values 62a, 62b, 62c of a pixel 60 is determined and a corrected phase gradient value 68 for the pixel 60 is determined from the phase gradient values 62a, 62b, 62c of the pixel 60 and a model for the energy dependence of the phase gradient values 62a, 62b, 62c.

A method and objective apparatus are provided for implementing an enhanced phase contrast microscope. A focusing vortex lens, defined by a diffractive spiral zone plate (SZP) lens, is used for the objective for the phase contrast microscope. The SZP lens focuses and imparts a helical phase to incident illumination to image the specimen with spiral phase contrast. The spiral phase contrast microscope is sensitive to phase gradients in all sample axes. Replacing the objective of a microscope with the diffractive SZP lens of the invention immediately provides existing instruments with spiral phase contrast capability.

The invention belongs to the technical field of super-surfaces, specifically an adjustable linear polarization wave beam separator based on a gradient super-surface. The separator takes TGMS units as the basis, enables six TGMS units to sequentially rotate 30 degrees in the clockwise direction, and obtains a TGMS super-unit with a phase gradient. The TGMS super-unit is enabled to carry out two-dimensional periodic extension in x and y orthogonal directions in a horizontal plane, and a microstrip bias line at the lower layer of the TGMS is used for the feed of the TGMS units in each row, thereby obtaining the separator with a plurality of functions. The TGMS units are in a three-layer metal structure, wherein the upper layer consists of a pair of the same metal pasters and an opening microstrip line, wherein the opening at the center of the opening microstrip line is used for loading a PIN diode, the central layer is a metal ground plate and the center consists of two metal columns and circular grooves wrapping the upper column, and the lower layer is a brush structure. The separator greatly improves the conversion efficiency (greater than 89%), and achieves the switching and regulation and control of wave beam separation frequency bands.

Methods and apparatus for characterizing a polymer sample and in preferred embodiments, libraries of polymer samples, in a comprehensive, directly-coupled multi-dimensional liquid chromatography system are disclosed. The first and second dimensions are preferably high-performance liquid chromatography dimensions, such as for example, a first dimension adapted for determining composition (e.g. adapted for mobile-phase gradient elution chromatography, including reverse phase chromatography, adsorption chromatography and the like), and a second dimension adapted for determining molecular weight or particle size (e.g., adapted for size exclusion chromatography, including gel permeation chromatography).

The invention discloses a two-dimensional beam deflection Fabry-Perot resonant cavity antenna. The two-dimensional beam deflection Fabry-Perot resonant cavity antenna comprises a reflection coverage layer, a dielectric substrate, a metasurface structure, a dielectric substrate, a reflection structure, a dielectric substrate, a feeding structure and a support post, wherein the reflection coverage layer comprises reflection units gradually changing in a two-dimensional direction, the metasurface structure comprises a plurality of rectangular patches, the reflection structure is a metal floor etched with a gap, the feeding structure is a microstrip feeding structure, and the support post comprises four nylon posts. The reflection units in 300-degree phase gradient changing are employed, large-angle and two-dimensional beam deflection is achieved within a working frequency band by two-dimensional arrangement of the unit structures, and thus, the problem that the main beam direction of theantenna cannot be adjusted to cause beam directivity during limitation of the antenna installation space is prevented.

General method for extracting source distance information from any kind of received radiation, including electromagnetic and acoustic, without involving round-trip time or phase in any form, and thus more truly passive than existing passive radars. The method exploits the facts that radiation from a real source must comprise wavepackets of nonzero bandwidth, that the individual frequency components of a wavepacket must have consistent phase at the source, and that their instantaneous phases must increase linearly along the path in proportion to the respective frequencies, so that the phase gradient across the components must be proportional to the distance travelled. The invention simplifies over naïve phase gradient measurement by scanning the phase gradient at a controlled rate, thereby converting the gradient into normalized frequency shifts proportional to the scanning rate and the source distance. It mimics the cosmological redshift and acceleration, but at measurable levels over any desired range and even with sound. Potential applications include stealth and “unjammable” radars for the military, ranging capability for emergency services, commodity low-power vehicular and personal radars, simplification and improvements in radar and diagnostic imaging, improved ranging in general all the way from ground to inter-galactic space, “interference-free” communication systems including radio and television receivers, source-distance (or range-division) multiplexing improved cellphone power control and battery life, and continuous, transparent diagnostics for optical fibres, integrated circuits and transmission lines.