Fast computation of spatial transfer function for ultrasound imaging

2007 ◽  
Vol 121 (5) ◽  
pp. 3083-3083
Author(s):  
Emre H. Guven ◽  
Eric Miller ◽  
Robin Cleveland
Keyword(s):  
Transfer Function ◽  
Ultrasound Imaging ◽  
Fast Computation ◽  
Spatial Transfer Function

scholarly journals Reconstruction of Microscopic Thermal Fields from Oversampled Infrared Images in Laser-Based Powder Bed Fusion

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4859
Author(s):  
Leigh Stanger ◽  
Thomas Rockett ◽  
Alistair Lyle ◽  
Matthew Davies ◽  
Magnus Anderson ◽  
...  
Keyword(s):  
Transfer Function ◽  
Measured Signal ◽  
Powder Bed Fusion ◽  
Validation Data ◽  
Powder Bed ◽  
Spatial Gradients ◽  
Microstructure Modeling ◽  
Thermal Fields ◽  
Significant Difference ◽  
Spatial Transfer Function

This article elucidates the need to consider the inherent spatial transfer function (blur), of any thermographic instrument used to measure thermal fields. Infrared thermographic data were acquired from a modified, commercial, laser-based powder bed fusion printer. A validated methodology was used to correct for spatial transfer function errors in the measured thermal fields. The methodology was found to make a difference of 40% to the measured signal levels and a 174 °C difference to the calculated effective temperature. The spatial gradients in the processed thermal fields were found to increase significantly. These corrections make a significant difference to the accuracy of validation data for process and microstructure modeling. We demonstrate the need for consideration of image blur when quantifying the thermal fields in laser-based powder bed fusion in this work.

scholarly journals An undergraduate experiment to illustrate spatial transfer function concepts in Fourier optics

2020 ◽  
Vol 88 (8) ◽  
pp. 617-624
Author(s):  
Jérôme Salvi ◽  
Gil Fanjoux ◽  
Anne Boetsch ◽  
Remo Giust
Keyword(s):  
Transfer Function ◽  
Fourier Optics ◽  
Function Concepts ◽  
Spatial Transfer Function

The receptive field of the primate P retinal ganglion cell, I: Linear dynamics

1997 ◽  
Vol 14 (1) ◽  
pp. 169-185 ◽  
Author(s):  
Ethan A. Benardete ◽  
Ehud Kaplan
Keyword(s):  
Transfer Function ◽  
Receptive Field ◽  
Ganglion Cells ◽  
Cell Dynamics ◽  
Early Form ◽  
Filter Model ◽  
First Order ◽  
Significant Difference ◽  
Functional Classes ◽  
Spatial Transfer Function

AbstractThe ganglion cells of the primate retina include two major anatomical and functional classes: P cells which project to the four parvocellular layers of the lateral geniculate nucleus (LGN), and M cells which project to the two magnocellular layers. The characteristics of the P-cell receptive field are central to understanding early form and color vision processing (Kaplan et al., 1990; Schiller & Logothetis, 1990). In this and in the following paper, P-cell dynamics are systematically analyzed in terms of linear and nonlinear response properties. Stimuli that favor either the center or the surround of the receptive field were produced on a CRT and modulated with a broadband signal composed of multiple m-sequences (Benardete et al., 1992b; Benardete & Victor, 1994). The first-order responses were calculated and analyzed in this paper (part I). The findings are: (1) The first-order responses of the center and surround depend linearly on contrast. (2) The dynamics of the center and surround are well described by a bandpass filter model. The most significant difference between center and surround dynamics is a delay of approximately 8 ms in the surround response. (3) In the LGN, these responses are attenuated and delayed by an additional 1–5 ms. (4) The spatial transfer function of the P cell in response to drifting sine gratings at three temporal frequencies was measured. This independent method confirmed the delay between the (first-order) responses of the center and surround. This delay accounts for the dependence of the spatial transfer function on the frequency of stimulation.

scholarly journals Spatial and temporal properties of luminosity horizontal cells in the turtle retina.

1983 ◽  
Vol 82 (5) ◽  
pp. 573-598 ◽  
Author(s):  
D Tranchina ◽  
J Gordon ◽  
R Shapley
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Horizontal Cell ◽  
Temporal Frequency ◽  
Horizontal Cells ◽  
Background Illumination ◽  
Cell Responses ◽  
Temporal Properties ◽  
Frequency Transfer ◽  
Spatial Transfer Function

Luminosity horizontal cells in the turtle retina respond approximately linearly to visual stimuli with contrast levels spanning a large part of the physiological range. We characterized the response properties of these cells under conditions of low photopic background illumination by measuring their spatial and temporal frequency transfer functions. Our experimental results indicate in two ways that, under these conditions, feedback from luminosity horizontal cells to cones does not play a major role in the mechanisms underlying the spatial and temporal tuning of horizontal cell responses. First, the shape of the spatial transfer function depended only weakly on the temporal frequency with which it was measured. Second, the shape of the temporal transfer function depended only weakly on the spatial frequency with which it was measured.

Spatial transfer function for the beam emission spectroscopy diagnostic on DIII-D

2006 ◽  
Vol 77 (10) ◽  
pp. 10F110 ◽  
Author(s):  
M. W. Shafer ◽  
R. J. Fonck ◽  
G. R. McKee ◽  
D. J. Schlossberg
Keyword(s):  
Transfer Function ◽  
Emission Spectroscopy ◽  
Spatial Transfer Function

Radiation Damage of Support Films

1981 ◽  
Vol 39 ◽  
pp. 28-29
Author(s):  
H.A. Cohen ◽  
W. Chiu
Keyword(s):  
Transfer Function ◽  
Low Temperatures ◽  
Carbon Support ◽  
Contrast Transfer Function ◽  
Electron Dose ◽  
Imaging Parameters ◽  
Negative Stain ◽  
Phase Corrections ◽  
Two Parameters ◽  
Medium Dose

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

Possible applications of fraunhofer holography in high resolution electron microscopy

1978 ◽  
Vol 36 (1) ◽  
pp. 222-223 ◽  
Author(s):  
N. Bonnet ◽  
M. Troyon ◽  
P. Gallion
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Transfer Function ◽  
Radiation Damage ◽  
High Resolution Electron Microscopy ◽  
Far Field ◽  
Field Region ◽  
Crystalline Materials ◽  
Resolution Electron ◽  
The Ideal

Two main problems in high resolution electron microscopy are first, the existence of gaps in the transfer function, and then the difficulty to find complex amplitude of the diffracted wawe from registered intensity. The solution of this second problem is in most cases only intended by the realization of several micrographs in different conditions (defocusing distance, illuminating angle, complementary objective apertures…) which can lead to severe problems of contamination or radiation damage for certain specimens.Fraunhofer holography can in principle solve both problems stated above (1,2). The microscope objective is strongly defocused (far-field region) so that the two diffracted beams do not interfere. The ideal transfer function after reconstruction is then unity and the twin image do not overlap on the reconstructed one.We show some applications of the method and results of preliminary tests.Possible application to the study of cavitiesSmall voids (or gas-filled bubbles) created by irradiation in crystalline materials can be observed near the Scherzer focus, but it is then difficult to extract other informations than the approximated size.

Ultimate resolution and information in electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 496-497
Author(s):  
D. Van Dyck
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Transfer Function ◽  
Information Transfer ◽  
Communication Channel ◽  
Structural Information ◽  
Information Rate ◽  
Noise Power ◽  
Signal Power ◽  
Imaging Device

An (electron) microscope can be considered as a communication channel that transfers structural information between an object and an observer. In electron microscopy this information is carried by electrons. According to the theory of Shannon the maximal information rate (or capacity) of a communication channel is given by C = B log2 (1 + S/N) bits/sec., where B is the band width, and S and N the average signal power, respectively noise power at the output. We will now apply to study the information transfer in an electron microscope. For simplicity we will assume the object and the image to be onedimensional (the results can straightforwardly be generalized). An imaging device can be characterized by its transfer function, which describes the magnitude with which a spatial frequency g is transferred through the device, n is the noise. Usually, the resolution of the instrument ᑭ is defined from the cut-off 1/ᑭ beyond which no spadal information is transferred.

Analytic integration of contrast transfer functions

1988 ◽  
Vol 46 ◽  
pp. 822-823
Author(s):  
Peter Rez
Keyword(s):  
Wave Function ◽  
Transfer Function ◽  
Transfer Functions ◽  
Spherical Aberration ◽  
Continuous Distribution ◽  
Objective Lens ◽  
Direction Parallel ◽  
Scattering Angle ◽  
Analytic Integration ◽  
Image Position

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is1where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by2where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.

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