Fully Automated Measurement of the Modulation Transfer Function of Charge-Coupled Devices above the Nyquist Frequency

Broek, Wouter Van den; Aert, Sandra Van; Dyck, D. Van

doi:10.1017/s1431927611012633

Cited by 20 publications

(11 citation statements)

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“…In our current experiments, we confirm that the one-dimensional Fourier amplitude spectra of empty images are fitted quite well by a single Lorentzian function [5]. While the fitting is never perfect, and the accuracy varies between cameras, a single Lorentzian function is in all cases within a few percent of the experimental data.…”

Section: Discussionsupporting

confidence: 78%

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Ranking TEM cameras by their response to electron shot noise

et al. 2013

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We demonstrate two ways in which the Fourier transforms of images that consist solely of randomly distributed electrons (shot noise) can be used to compare the relative performance of different electronic cameras. The principle is to determine how closely the Fourier transform of a given image does, or does not, approach that of an image produced by an ideal camera, i.e. one for which single-electron events are modeled as Kronecker delta functions located at the same pixels where the electrons were incident on the camera. Experimentally, the average width of the single-electron response is characterized by fitting a single Lorentzian function to the azimuthally averaged amplitude of the Fourier transform. The reciprocal of the spatial frequency at which the Lorentzian function falls to a value of 0.5 provides an estimate of the number of pixels at which the corresponding line-spread function falls to a value of 1/e. In addition, the excess noise due to stochastic variations in the magnitude of the response of the camera (for single-electron events) is characterized by the amount to which the appropriately normalized power spectrum does, or does not, exceed the total number of electrons in the image. These simple measurements provide an easy way to evaluate the relative performance of different cameras. To illustrate this point we present data for three different types of scintillator-coupled camera plus a silicon-pixel (direct detection) camera.

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Section: Discussionsupporting

confidence: 78%

“…Multiplication of this ratio by the independently-determined detective quantum efficiency, DQE(0), produces the desired DQE(s) [1–4]. More recently, a similar approach has been developed that uses images of two-dimensional, opaque objects rather than a straight edge [5]. …”

Section: Introductionmentioning

confidence: 99%

Ranking TEM cameras by their response to electron shot noise

et al. 2013

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“…The MTF of the CCD camera's scintillator was measured using the method described by Thust [7,20]. For this purpose, a series of shadow images of the microscope's beam blanker was taken, from times the camera's Nyquist frequency, treating aliasing artifacts by suitable aliasing masks.…”

Section: Determination Of the Mtfmentioning

confidence: 99%

Comparison of intensity and absolute contrast of simulated and experimental high-resolution transmission electron microscopy images for different multislice simulation methods

et al. 2013

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confidence: 99%

“…Detector performances can be assessed by the measurement of the effective gain, the conversion factor, the point spread or modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) [1,2]. Defective pixels can also be listed as outliers in a lookup table.…”

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Optimization of the Data Acquisition and Processing using a Prior Knowledge of the Camera Characteristics: an EFTEM Case Study

Lucas¹,

Hébert²

2014

Microsc Microanal

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In transmission electron microscopy (TEM), electrons are nowadays traditionally detected using a charged-coupled device (CCD) in the case of indirect detection trough a scintillator via an optical fiber coupling, or more recently using complementary metal-oxide semiconductor (CMOS) with direct detection. In both cases the "true" image is unfortunately degraded by the non-ideal point spread function (PSF) of the detector leading to a blurring of the signal and the addition of stochastic noise components such as dark-current noise or readout-noise.Detector performances can be assessed by the measurement of the effective gain, the conversion factor, the point spread or modulation transfer function (MTF), the noise power spectrum (NPS) and the detective quantum efficiency (DQE) [1,2]. Defective pixels can also be listed as outliers in a lookup table. On-site characterization of the detector performance can be useful for several reasons. First of all, it allows us to verify the specifications provided by the manufacturers of the devices, to compare the relative performance of different detectors and to estimate their degradation over time. Secondly it can help to optimize the data acquisition strategy for a given problem, for instance low dose experiments or high-resolution imaging. Finally this information can be used as prior knowledge for data processing algorithms.In this work energy filtered transmission electron microscopy (EFTEM) has been used to illustrate the benefits of the knowledge of the characteristics of the detection system. EFTEM is useful technique to investigate the chemistry of materials at the nanometric scale. However such a technique is often limited by long exposition times and weak signals, in particular at high-energy losses. Images corresponding to different energy losses are sequentially recorded on the camera device, resulting in a 3-dimensional dataset {x, y, E} for which each image plane {x, y} is convolved with the PSF of the camera and each spectrum {E} with the resolution response function of the spectrometer.This works aims in a first step to measure the noise and contrast transfer characteristics of the Gatan US1000 camera used in our JEOL 2200FS TEM microscope in order to improve our EFTEM acquisitions. The recently developed silhouette method [2] is used for the determination of the CCD MTF. In a seconds step this works tries to apply multivariate statistical approaches such as principal component analysis [3,4] and algorithms based on statistics in order to perform the denoising of the data as well as the improvement of its spatial or spectral resolution by deconvolution techniques. The prior knowledge of the (quasi-poissonian) noise model and the MTF of the camera are embedded in the deconvolution algorithms in order to perform the regularization of the solutions in a realistic way.The data processing procedure is demonstrated on a simulated dataset providing a ground truth for exploring the applications, limits and eventual pitfalls of the algorithms under known noise levels an...

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Fully Automated Measurement of the Modulation Transfer Function of Charge-Coupled Devices above the Nyquist Frequency

Cited by 20 publications

References 12 publications

Ranking TEM cameras by their response to electron shot noise

Ranking TEM cameras by their response to electron shot noise

Comparison of intensity and absolute contrast of simulated and experimental high-resolution transmission electron microscopy images for different multislice simulation methods

Optimization of the Data Acquisition and Processing using a Prior Knowledge of the Camera Characteristics: an EFTEM Case Study

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