Topic
Contrast transfer function
About: Contrast transfer function is a research topic. Over the lifetime, 934 publications have been published within this topic receiving 26533 citations.
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01 Jan 2002
TL;DR: Comparisons and conversion methods between the ISO 16067-1 SFR and a common MTF/CTF method and how to relate measurements made using the two methods are reported.
Abstract: With the advent of the ISO standard 16067-1 Spatial Frequency Response for Electronic Desktop Scanners it becomes useful to compare established methods, such as Modulation Transfer Function or Contrast Transfer Function (MTF/CTF) to the new standard method. This facilitates communication between companies, vendors, OEM suppliers and end users as to the actual performance being provided or specified. However, when making a change in measurement method in an established field, it is important to understand the relationship between prior measurement methods and the one being adopted. This is required to provide clear migration paths for vendors, manufacturers and reviewers from the old method to the new, while preserving the knowledge inherent in the body of data available from prior measurements. This paper reports comparisons and conversion methods between the ISO 16067-1 SFR and a common MTF/CTF method and how to relate measurements made using the two methods. A number of consumer class desktop scanners with different optical systems are compared when operated at the optical sampling rate (ppi) as well as lower and higher sample rates (ppi). Preliminary results indicate a good correlation is found between the methods though different conversion factors must be used for different sampling rates.
23 May 2022
TL;DR: In this paper , a new method is developed for 3D reconstruction of multi-material objects using propagation-based X-ray phase contrast tomography (PB-CT) with phase retrieval via the contrast transfer function (CTF) formalism.
Abstract: A new method is developed for three-dimensional (3D) reconstruction of multi-material objects using propagation-based X-ray phase-contrast tomography (PB-CT) with phase retrieval via the contrast transfer function (CTF) formalism. The approach differs from conventional PB-CT algorithms that apply phase retrieval on individual two-dimensional (2D) projections. Instead, this method involves performing phase retrieval to the CT-reconstructed volume in 3D. The CTF formalism is further extended to the cases of partially-coherent illumination and strongly absorbing samples. Simulated results demonstrate that the proposed post-reconstruction CTF method provides fast and stable phase retrieval, producing results equivalent to conventional pre-reconstruction 2D CTF phase retrieval. Moreover, it is shown that application can be highly localised to isolated objects of interest, without a significant loss of quality, thus leading to increased computational efficiency. Combined with the extended validity of the CTF to greater propagation distances, this method provides additional advantages over approaches based on the transport-of-intensity equation.
TL;DR: In this paper, a practical method for the Wiener filter is explained by using a HREM image of multiply twinned Ag particle, and the other techniques are also demonstrated with various images.
Abstract: Two kinds of image processing techniques can be applied to the high resolution electron microscope (HREM) images : one in the real space (averaging of periodic images) and the other in the Fourier space. There are several methods in the latter, such as ring masking, window masking and a CTF (contrast transfer function) compensation using the Wiener filter.The Wiener filter is extremely useful for the HREM image processing, because the filter can improve the CTF, and thus provide improve images. The image contrast can partially be reversed and that in the high frequency region can be enhanced by the Wiener filter. A practical method for the Wiener filter is explained by using a HREM image of multiply twinned Ag particle. An application is shown with a high temperature superconducting material, and the other techniques are also demonstrated with various images.