![]() ![]() From a processing standpoint, the method is not optimal, as the complete wavefield spectrum matrix has to be multiplied with a phase factor matrix at each step. The phase shift migration (PSM) algorithm works by migrating the recorded wavefield in small steps, and creating a focused image line/plane at each depth (using the "exploding reflector model"). One major advantage of this approach is that the wavefield is easily extrapolated between media with different wave velocities, enabling multi-layer imaging (very relevant for immersion ultrasound imaging). With Fourier-domain processing, it is possible to extrapolate a sampled pulse-echo wavefield in both space and time ("wavefield migration"). Fourier-domain processing is very common for synthetic aperture radar and sonar, but in the field of ultrasound, the time-domain "delay-and-sum" approach still dominates. The main focus of the algorithms is on Fourier-domain synthetic aperture processing of ultrasound data. Bottom drilled holes in PMMA and aluminium blocks See the thesis.pdf file under the 'docs' folder for further details. The original figure numbering and captions have been included for context. The following images are taken from the thesis to illustrate some of the applications of the algorithms in the toolbox. The name of the toolbox is an abbreviation of "Synthetic APerTure UltraSound". The toolbox could also represent a collection of reference methods against which new algorithms are compared. The data sets included in the toolbox will hopefully be useful in the development of new algorithms for similar measurement geometries. The toolbox is meant to help people who are new to the field and are looking to make implementations of published algorithms. As with so many things, "the devil is in the details" when it comes practical implementation of synthetic aperture algorithms. The PhD thesis is included in the "docs" folder, and can also be downloaded from. Skjelvareid, as a collection of algorithms developed during his work as a PhD candidate. The toolbox was originally written by Martin H. The details of this process is described in the PhD thesis included in the toolbox. Conceptually, this is done by treating the raw images as measurements of a wave field, and using the wave equation to manipulate the wave field into a focused image. The algorithms in the Synaptus toolbox take such raw, unfocused images as input and processes them to create focused images. Examples of such images are given in the "Example raw and focused images" section below. Due to the divergence of the transducer beams, the echoes from scattering objects are "smeared" laterally, making the images unfocused and hard to interpret. A similar measurement can be performed using an array of multiple transducers. By moving the transducer laterally relative to the object under study, it is possible to create a 2- or 3-dimensional image of the object. A measurement at a single point in space thus produces a 1-dimensional "depth profile". A backscattered "echo" is created when the waves interact with an object or layer with different physical properties than the propagating medium, e.g. ![]() Such data is produced by a transducer that transmits waves into a propagating medium, and records backscattered waves from within the medium. The core functionality of the toolbox is to create focused images from raw (unfocused) pulse-echo data. The toolbox focuses on algorithms implemented in the Fourier domain, and on imaging in multilayered structures (e.g. It was originally developed for ultrasonic imaging for non-destructive testing, but can be applied for similar imaging modes (e.g. Synaptus is a Matlab/Octave toolbox for synthetic aperture or array imaging. Available through Mathworks File Exchange: Summary
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