442 results about "Phase unwrapping" patented technology

A method for computing a depth map of a scene in a structured light imaging system including a time-of-flight (TOF) sensor and a projector is provided that includes capturing a plurality of high frequency phase-shifted structured light images of the scene using a camera in the structured light imaging system, generating, concurrently with the capturing of the plurality of high frequency phase-shifted structured light images, a time-of-flight (TOF) depth image of the scene using the TOF sensor, and computing the depth map from the plurality of high frequency phase-shifted structured light images wherein the TOF depth image is used for phase unwrapping.

A system and computer-implemented method for determining properties of a subsurface region of interest from seismic data is disclosed. In an embodiment, the method includes obtaining seismic data representative of the subsurface region and an initial earth property model for the subsurface region, performing forward modeling using the initial earth property model to create modeled seismic data with similar acquisition specifications as the actual seismic data, transforming the modeled and actual seismic data to a temporal Fourier frequency domain to create frequency domain modeled and actual seismic data wherein the frequency domain modeled and actual seismic data include an amplitude portion and a phase portion, measuring the misfit between the frequency domain modeled seismic data and frequency domain actual seismic data to produce frequency domain residual seismic data, performing phase unwrapping of the phase portion of certain observed frequency components of the frequency domain residual seismic data to create an unwrapped residual phase portion, and inverting the unwrapped residual phase portion to determine desired properties of the subsurface region of interest, wherein the inverting minimizes an objective function defined to measure the misfit. The method may also include phase extrapolation. Additionally, the method may include a second inverting step using the result of the first inverting step as a starting model. The system includes a data source, a user interface, and a processor configured to execute computer modules designed to perform the method.

Provided is a synthesis system of a time-of-flight (ToF) camera and a stereo camera for reliable wide range depth acquisition and a method therefor. The synthesis system may estimate an error per pixel of a depth image, may calculate a value of a maximum distance multiple per pixel of the depth image using the error per pixel of the depth image, a left color image, and a right color image, and may generate a reconstructed depth image by conducting phase unwrapping on the depth image using the value of the maximum distance multiple per pixel of the depth image.

The present invention discloses a low signal-to-noise ratio short preamble burst signal demodulation system and method. A burst signal detection module detects in real time whether a received signal includes an MPSK signal, if the received signal includes the MPSK signal, an initial position and an ending position of the MPSK signal are offered; then, a coarse frequency synchronization and time synchronization module realizes time synchronization point tracing and coarse frequency offset correction of the signal according to the preamble of the burst signal and the initial position of the MPSK signal; then, sampling timing synchronization and fine frequency offset compensation and phase offset correction are respectively performed by a timing synchronization module and a fine frequency synchronization module on the signal; and finally, a phase unwrapping and de-mapping module completes phase unwrapping and bit decoding. According to the method, time synchronization of the demodulation system is before timing sampling synchronization, a parameter estimation module is reused, while the processing time is not increased, the accuracy of coarse frequency estimation and time synchronization is greatly improved, and hardware resource consumption is reduced greatly.

A stereo-phase-based absolute three-dimensional (3D) shape measurement method is provided that requires neither phase unwrapping nor projector calibration. This proposed method can be divided into two steps: (1) obtain a coarse disparity map from the quality map; and (2) refine the disparity map using local phase information. Experiments demonstrated that the proposed method could achieve high-quality 3D measurement even with extremely low-quality fringe patterns. The method is particular well-suited for a number of different applications including in mobile devices such as phones.

The invention relates to high-precision detection of complex optical curved-surface parts with large-curvature surface shapes, and aims to provide a high-precision detection method for the complex curved-surface parts with large curvature surface shapes, such as optical curved-surface parts, which has the advantages of rapidity, non-contact and no damage to part surfaces and surface layers. The technical scheme adopted by the invention is that the invention provides a grating projection rapid non-contact measurement method and device for high-reflectance free-form curved-surface parts, and the method comprises the following steps that: three degree-of-freedom motion of a measured object is realized with the help of a precision motion control system; coded grating fringes are projected onto the surface of the measured object by using a grating projection device; phase distribution information of the surface of the measured object is obtained from a deformed fringe pattern by using a digital phase shifting technology and a phase unwrapping algorithm; reference phase distribution information is obtained by using a virtual reference surface technology; and three-dimensional morphological information of a measuring area of the surface of the measured object is recovered according to a corresponding relation between phase deviation information and the gradient of the surface of the measured object. The grating projection rapid non-contact measurement method and device are mainly applied to the measurement of the optical curved-surface parts.

A system and computer-implemented method for inverting data from an area of interest to determine physical properties of the area of interest is disclosed. The method includes transforming the data into a Fourier frequency domain to obtain frequency domain data wherein the frequency domain data includes an amplitude portion and a phase portion, performing phase unwrapping of the phase portion of the frequency domain data to generate an unwrapped phase portion, and inverting the unwrapped phase portion to determine the physical properties of the area of interest. The method may also extrapolate the phase. The data inverted may be, for example, seismic data or synthetic aperture radar data. The system includes a data source, a user interface, and a processor configured to execute computer modules designed to execute the method.

The invention belongs to the field of 3D contour measurement on object surface. The main technical features comprise: (1) projecting gratings with different frequencies to the object surface to obtain multiple phase diagrams; (2) unwrapping the phase diagrams with frequency synthesis method to obtain high-precision unwrapped phase; (3) matting corresponding points to external polar line with the unwrapped phase and calculating 3D contour of the object surface; and (4) in order to make the calculation result more reliable, using modulation degree as reliable reference of phase unwrapping and masking the phase with modulation degree less than the set threshold. The invention has the advantages of simple structure, non-contact, high precision, high speed, and easy implementation.

The invention discloses a high-adaptability three-dimensional measuring method based on color structured light in a three-dimensional scanning system. The method comprises the following steps of: coding according to the Gray coding principle by use of 6 pure colors; performing sinusoidal modulation of three components R, G and B at the same time to obtain a color grating for projection; designing an auxiliary grating according to the color grating; projecting the designed color grating and auxiliary grating to a measured object; performing superposition operation of the collected two grating deformation diagrams to obtain the reflectivity of each pixel; compensating the grating deformation diagrams according to the reflectivity of each pixel; performing color image division of the compensated grating deformation diagrams; decoding the divided image to obtain corresponding phase period information; graying the compensated grating deformation diagrams and obtaining the wrapped phase value of each pixel by Fourier transform; realizing phase unwrapping according to the decoded phase period information of each pixel; and finally, realizing three-dimensional reconstruction according to the corresponding relationship between the phase and the object height information.

A mining area surface subsidence synthetic aperture radar interferometry monitoring and calculating method belongs to mining area surface subsidence monitoring and calculating method. The method comprises the following steps: having format conversion, calibration, pre-filtering and interference to interferometric synthetic aperture radar (InSAR) data to obtain an InSAR interference phase, eliminating flat ground effect, an terrain phase and orbit errors of the interference phase by means of precise orbit data and an external dynamic effect model (DEM), obtaining phase values which only contain deformation information of a ground surface after filtering to residual phases, on the condition of large deformation gradient, through phase unwrapping, obtaining deflection of the edge of a mining subsidence basin, fusing the deflection with a few ground measured data, reversely deducing probability integral method parameters of the subsidence basin through a genetic algorithm, calculating sinking values of an arbitrary point of the whole surface subsidence basin through required probability integral method parameters and geological mining data, and therefore mining subsidence deformation field is produced. The mining area surface subsidence synthetic aperture radar interferometry monitoring and calculating method has the advantages of being high in monitoring accuracy, large in monitoring range, convenient to operate, low in cost and large in technical content.

The invention discloses a phase error compensation method applied to grating three-dimensional projection measurement. The method includes the following steps: generating sine grating stripes; collecting grating stripes that are modulated by the surface of an object; pre-processing images; carrying out phase unwrapping through a phase shift method on the basis of the pre-processed stripe images; projecting a grey-scale image with a single gray value onto the surface of a standard white board; mapping regional results in the step (5) onto a target surface of a projector through an obtained ideal phase; establishing regional correction models for different regions according to the regional results; projecting the sine grating stripes onto the object; solving an initial phase through a phaseshift method, compensating the phase on the basis of established regional error compensation, and solving an actual phase; and through calibrated camera parameters and a solved absolute phase, calculating three-dimensional coordinate information of a to-be-measured object through a spatial intersection method. The method overcomes phase errors and measurement errors caused by Gamma non-linearity.

The invention discloses a distributed ultrahigh-speed disturbance quantitative detection method. Ultrahigh-speed disturbance detection can be realized through a time division multiplexing method; and phase demodulation is carried out through phase demodulation methods such as Hilbert transformation and orthogonal transformation so as to be able to realize real-time detection on the disturbance position, frequency and amplitude. The invention further discloses a distributed ultrahigh-speed disturbance quantitative detection device, which comprises a pulse generator, a laser, a first coupler, a pulse modulator, an erbium-doped optical fiber amplifier, a circulator, an optical fiber sensing unit, a second coupler, a balance detector, a band-pass filter, a power amplifier and a data acquisition card. According to the invention, the repetition frequency of detecting light pulses is improved through a time division multiplexing technology, so that a reflecting grating based phi-OTDR system is enabled to realize ultrahigh-speed disturbance detection; and real-time detection for the disturbance position, frequency and amplitude is realized through the phase demodulation method by using a coherent detection structure and combining a phase unwrapping algorithm.

An embodiment of the present invention realizes an interference measurement apparatus which can obtain an interference image to be used for obtaining three-dimensional information of a subject which dynamically changes. An interference measurement apparatus of the present invention, which captures an interference image formed by the reference light beam and the object light beam which has reached the image-capturing element via a subject, the interference measurement apparatus includes: a laser light source; a beam splitter which splits a laser beam into a reference light beam and an object light beam; and an image-capturing element; a polarization splitting section which splits the object light beam into two types of object light beams which are different in polarization direction so that an angular difference is caused between respective propagation directions of the two types of object light beams; and a polarizer array device which allows (i) the reference light beam and (ii) the two types of object light beams which have reached the polarizer array device via the subject to pass through the polarizer array device (30), the polarizer array device in which a plurality of first polarizer regions and a plurality of second polarizer regions are arranged, and each of the plurality of first polarizer regions and each of the plurality of second polarizer regions respectively allowing light components which are different in polarization direction. This makes it possible to obtain, by one-time image capturing, a plurality of interference patterns required for phase unwrapping.

The invention provides 16-step dual-frequency grating phase shift profilometry capable of absolute phase unwrapping in the three-dimensional sensor technology. The invention is characterized by usingcomputers to design codes to generate 16 dual-frequency grating patterns, using a digital light projector to image the grating patterns on the surface of an object instantaneously in sequence, using apick-up device to record the deforming fringe pattern of the object, subsequently using the functional relationship between the gratings with two frequencies, using the absolute phase unwrapping method to directly realize phase unwrapping of point to point in the whole field range and having no relation with the path for phase unwrapping, effectively inhibiting accumulative error diffusion, usingphase measuring profilometry to process the deforming fringes, accurately restoring the three-dimensional shape of the object and obtaining such digital information as deformation of the object and the like by further analyzing the data processing results. The method can be used for measurement study of the characteristics of the object surface with the characteristic of diffuse reflection. The method has the advantages of high measurement precision and strong adaptability to the surface topography of the object, etc.

The invention discloses a time phase unwrapping method based on double frequency three-gray-scale sinusoidal grating fringe projection. The method comprises the steps that two sets and five ideal double-frequency sinusoidal grating fringes are generated by utilizing a computer, then three-gray-scale sinusoidal grating fringes corresponding to the ideal double-frequency sinusoidal grating fringes are generated by adopting the three-gray-scale space pulse width modulation technology, under condition that that a projector keeps the defocusing state, the five three-gray-scale sinusoidal grating fringes are projected to the surface of an object to be measured, two sets of wrapped phase images are solved, wherein the five double-frequency fringes comprise the two sets of wrapped phase images, the fringe order corresponding to the wrapped phase is solved, and unwrapping of the wrapped phase is achieved. The time phase unwrapping method based on the double frequency three-gray-scale sinusoidal grating fringe projection improves measurement precision and measurement speed.

Disclosed is a three-dimensional imaging method for a Polarimetric Interferometric Synthetic Aperture Radar (Pol-In-SAR) based on the polarimetric data integration, which belongs to the Polarimetric radar Interferometric measurement data processing technology field. The data is read in and two scattering vectors k1 and k2 are structured to each scattering unit; eigenvalue decomposition is performed on the matrix K1 K1-K2 K2 and three eigenvalues are obtained: Lambada1>0, Lambada1>0 and Lambada3=0; values of formula(1) can be respectively calculated so as to determine which condition the value belongs to; if in condition 1, w=w<(1)> can be calculated according to formula (6); if in condition 2, w=w<(2)> can be calculated according to formula (14); and then Phi[s]=arg(wk1k2w)can be calculated. An enhanced complex image can be obtained according to formula 3); the matrix Omega12=> is calculated; and then Phi[m]=arg(w[Omega12]w) can be calculated according to formula 22). The flat-earth effect is removed on the obtained whole phase map (single view or multi-view); and phase unwrapping is performed by using branch-cut algorithm. The invention has wide application range, and the calculating time is smaller than that of the interference optimization method; and the integrated phase quality is better than that of interference optimization method, the phase quality can be always enhanced despite the original signal level, thereby establishing a fine basis for generating accurate digital elevation model (DEM) in the future.

The invention discloses a DIXON water-fat separation method in magnetic resonance imaging. The method comprises the following steps: a) in the magnetic resonance scanning process, three different echo signals including the first echo signal S1, the second echo signal S2 and the third echo signal S3 are acquired, wherein the water-fat signal procession phase difference of the first echo signal S1 and the third echo signal S3 is 2npi, and n is a natural number; b) the acquired k space signals are converted into image signals through Fourier transform; c) effective image signal pixels are extracted in a image domain, the phase diagram of the effective image signal pixel composite signal is extracted, and phase unwrapping is performed on the phase diagram to obtain a static magnetic field distribution diagram delta B0; d) and the water image and the fat image in the echo signals are separated by utilizing the static magnetic field distribution diagram delta B0. According to the DIXON water-fat separation method provided in the invention, the echo time can be set flexibly according to a magnetic resonance imaging sequence and application requirements, so not only data can be processed by applying the conventional DIXON algorithm, and but also the limitation on imaging sequence parameter setting can be reduced at the same time.

The invention discloses an expansion method of an interference phase of multi-baseline interference synthetic aperture radar. The process is that a SAR imaging processing is carried out respectively to M echo data received by a satellite; any one of the images after the SAR imaging processing is selected as a main image; by using the main image as a reference, a rough registration is carried out respectively to other images through a correlation method so as to obtain M-1 roughly-registered SAR images; A roughly-registered SAR image is used for constructing an optimum weighted joint data vector jx (i, w); a covariance matrix Cov (i, w) is estimated according to the optimum weighted joint data vector and resolved characteristically so as to obtain a cost function; the interference phase phi corresponding to the minimum value of the output power of the cost function is used as the deployment result of the interference phase; the above-mentioned relevant process is repeated respectively to each of pixels to obtain the expansion result of the interference phase of the entire image. The expansion method disclosed by the invention has the advantages of small calculating amount and accurate expansion of the interference phase when the SAR image registration accuracy is bad, thereby being used for the reconstruction of a ground three-dimensional terrain with high resolution and high precision and the detection of a ground moving target.

A system and computer-implemented method for inverting data from an area of interest to determine physical properties of the area of interest is disclosed. The method includes transforming the data into a Fourier frequency domain to obtain frequency domain data wherein the frequency domain data includes an amplitude portion and a phase portion, performing phase unwrapping of the phase portion of the frequency domain data to generate an unwrapped phase portion of unwrapped data, extrapolating the unwrapped phase portion to create extrapolated unwrapped data, and inverting the extrapolated unwrapped data to determine the physical properties of the area of interest. The data inverted may be, for example, seismic data or synthetic aperture radar data. The system includes a data source, an user interface, and a processor configured to execute computer modules designed to implement the method.

The embodiment of the invention provides a subway subgrade structure monitoring method and device based on foundation InSAR. The method comprises the steps of using a radar sensor for repeatedly observing a target area on a linear scanning slide rail, and obtaining a synthetic aperture radar SAR image in about 10 seconds; matching image elements representing the same object in the target region inthe two SAR images to the same position, carrying out image registration; subjecting an interference image pair after image registration to conjugate multiplication (as shown in the description) to obtain an interference phase graph; carrying out noise filtering processing on the obtained coherent graph gamma; carrying out phase unwrapping on the coherent graph gamma subjected to noise filteringprocessing; carrying out atmospheric correction on the coherent image gamma subjected to phase unwrapping to obtain a deformation graph of the target area; carrying out geocoding on the deformation graph of the target area under the radar coordinate system, projecting to the geographic coordinate system, and obtaining a geographic coded deformation graph. High-precision and continuous deformationmonitoring of the whole area of the subway elevated and roadbed structure can be implemented under the extreme weather conditions or long distances (4Km) range.

The invention relates to a phase sensitive optical time domain reflection fiber sensing system positioning method, which comprises the steps of collecting beat frequency data signals corresponding to multitime light pulses; obtaining a backward diffusion light phase matrix phi; determining an extraneous vibration disturbance position Y; selecting a position X1, a position Z1, a position X2 and a position Z2 that have no phase disturbance before and after the extraneous vibration disturbance position Y; phase unwrapping the X1, Z1, X2 and Z2 at the corresponding column phase in the backward diffusion light phase matrix phi; and then expanding the phase change to a scope of -infinity to +infinity. If the phase of the position is the same while time passing by before and after the phase disturbance position, the phase disturbance is determined to be a false alarm; otherwise, the phase disturbance is determined to be a real extraneous vibration event. The problem of introducing a fault abnormal phase because of polarization fading or interference fading in a phi-OTDR system application is solved; a high rate of false alarm because of fading is reduced; and an accurate positioning of a real extraneous disturbance event is realized. The method is simple and practical in a normal phi-OTDR fiber distributed sensing system.

The invention relates to a phase package-removing method for color stripe code which solves n(x, y) in phi(x, y)=phi(x, y)+2pin(x, y) by using color stripe code striped graph and carries phase unwrapping along a direction perpendicular to stripe arrangement on the basis of obtaining a principle phase of phase shift measurement. Compared with conventional phase package-removing method, the phase package-removing method of present invention simplifies operation, greatly increases data processing efficiency and shortens data processing time. Due to employing a color coding technology in the phase package-removal, the method reduces influence of environment interference light source, and improves anti-interference capability of image process. Because the width of the color code stripe can be arbitrarily regulated, the method is adapted for measuring objects with large inclination angle relative to projection optical axis and discontinuous surface. By combining a color More stripe phase shift measurement method and the color code phase package-removing method, the invention can measure not only static three dimensional object appearance, but also dynamic three dimensional object appearance.

The invention provides a free-moving type three-dimensional scanning method, belongs to the field of optical detection, and relates to a full three-dimensional skeleton surveying method, a handheld measuring device and a multi-angle splicing method based on texture, the curvature of surface and normal directions. Mobile handheld high-precision three-dimensional scanning is a problem of the scanning field, according to the free-moving type three-dimensional scanning method, a three-frequency color fringe projection method is utilized to project three-frequency color fringes of 1 : 4 :12 to the surface of a tested object through a projection device, and a camera is used for shooting a deformed fringe pattern in a single-frame exposure mode. On one hand, a three-frequency phase unwrapping method is adopted by the deformed fringe pattern to calculate out high-frequency carrier frequency to unwrap a phase, and system calibration parameters are used for obtaining a three-dimensional point cloud of the tested object; on the other hand, a texture pattern of the surface of the tested object can be recovered through the deformed fringe pattern. Handheld scanning has a higher requirement for multi-angle splicing, and by means of the free-moving type three-dimensional scanning method, non-mark splicing of multi-angle point clouds is achieved according to the color texture characteristics, measurement of the curvature of surface and restraint of the normal directions.

The invention discloses an airborne SAR (synthetic aperture radar) imaging method suitable for a large squint angle. The method comprises the following steps of: (1) establishing an echo signal model; (2) performing signal imaging by the steps of: (2-1) performing distance fast Fourier transform and azimuth fast Fourier transform on a point target signal; (2-2) performing distance inverse Fouriertransform and performing accurate treatment on the phase of the signal; (2-3) multiplying the result by a Chirpscaling factor; (2-4) performing distance Fourier transform; (2-5) multiplying the result by a distance compensation factor; (2-6) performing distance inverse Fourier transform; (2-7) multiplying the result by an azimuth compensation factor; and (2-8) performing azimuth inverse Fourier transform to obtain a compressed SAR image signal. In the method, by imaging the point target under a large squint angle, a good peak-sidelobe ratio and an integral-sidelobe ratio can be obtained; a relatively high spatial resolution can be obtained in the distance direction and azimuth direction by use of the SAR pulse compression technology and the synthetic aperture technology; and moreover, themethod performs distance relocation correction in a time domain, simplifies an echo signal distance model, reduces the two-dimensional coupling quantity, adopts accurate phase unwrapping, realizes accurate correction of the signal and has a relatively high processing speed.

The invention discloses a continuous variable-angle digital holographic metrology method and a continuous variable-angle digital holographic metrology device for complicated face type and belongs to the technical field of photoelectric measurement. The device comprises a laser, an optical fiber beam splitter, an optical fiber phase shifter, a precision angle deflection device, an off-axis paraboloid calibrator, a collimating lens group, a light combining prism, an optical fiber, a charge coupled device (CCD) camera, a computer and the like. The invention is characterized in that a precision angle deflection structure in a system can precisely change the direction of reference light in a multi-angle mode; when an angle is changed, a hologram which is generated by interference of the reference light and object light can be changed; and a wrapped phase value of an object at each angle is obtained by controlling the optical fiber phase shifter and using a phase shifting method; cosines of the wrapped phase values are added to obtain a function, and peak search is performed, so the height information of each point of the object can be obtained. The invention has the advantages that all points of the object to be measured are separately measured in the measurement process, a phase unwrapping step is eliminated, and face type parameters of the object which has complicated shape and is interrupted can be measured.

The SAR Point Cloud Generation System processes synthetic aperture radar (SAR) data acquired from multiple spatially separated SAR apertures in such a manner as to be able to calculate accurate three-dimensional positions of all of the scatterers within the imaged scene. No spatial averaging is applied thus preserving the high resolution of the original SAR data, and no phase unwrapping processes are required. The effects of height ambiguities are significantly reduced in the SAR Point Cloud Generation System. The SAR Point Cloud Generation System also self-filters against mixed-height pixels that can lead to incorrect height estimates. The system estimates scatterer height by a maximization of an Interferometric Response Function.

The invention provides a phase unwrapping method based on malposition fringes in a three-dimensional scanning system, mainly relating to the reverse engineering; the three-dimensional scanning systemis used for carrying out phase unwrapping according to the malposition fringes; according to the needs, four grating phase shifting pictures with 90-degree phase shifting are designed, and a malposition fringe grating is designed according to the coding requirements for designing the malposition fringes, and the four grating phase shifting pictures are respectively projected to an object to be measured, and then a CCD is used for back-shooting to a computer. According to the four phase shifting pictures, a folding phase shifting picture with phase value which is in a range from -Pi to Pi is obtained by a phase shifting method; the difference of the malposition fringe pictures and the four phase shifting pictures are made respectively, so as to obtain four fringe differential pictures, thefringe characteristics of all positions in the malposition fringe grating are determined by zero fringe information in the differential pictures, and then the coding information of the malposition fringes is combined again, so as to determine the order of each single-cycle fringe in the malposition fringes, which is obtained by the CCD and guide the folding phase to be unwrapped. The whole computing process does not depend on routes, thereby having good real-time performance.

The invention discloses a temporal difference radar interference method applicable to large-gradient ground surface settlement monitoring. According to the whole technical scheme, the method comprises the steps of short-time base line difference interference pattern screening, discrete point phase unwrapping, shape changing component modeling and calculation based on short-time base line difference interference patterns, shape changing component reliability testing, difference interference pattern phase gradient correction, iteration of the processes so as to ensure correctness of shape changing component calculation, and shape changing time sequence modeling and calculation based on corrected difference interference patterns. The problem that shape changing phase ambiguity calculation is difficult or fails due to the fact that shape changes and phase gradients are large in an original temporal difference radar interference technology is solved, finally the purpose of correctly extracting the large-gradient ground surface shape changing speed and the shape changing time sequence is achieved, the effect of decreasing the number of synthetic aperture radar images needed by large-gradient shape changing modeling and calculation is achieved, and the temporal difference radar interference application economic cost is reduced.

In a nuclear magnetic resonance tomography apparatus and a method for the operation thereof, on the basis of the 3-point Dixon method, spin collectives having different chemical shifts are separated by means of information maximization despite great field inhomogeneities. The unwrapping of the phases is implemented over interconnected pixel regions (phase unwrapping) proceeds initially only in regions with high signal amplitude and the regions of lower amplitudes are only successively acquired by increments. These are then assigned to the respectively correct spin type, such as fat or water.