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.

Image quality with Kirkpatrick-Baez microscope in hard X-ray

Abstract: An important diagnosis method--Kirkpatrick-Baez microscope system in ICF experiments was researched. The brief aberration of the Kirkpatrick-Baez microscope was calculated. The main aberration, spherical aberration was analyzed, and the spherical aberration is 94% of the total aberration. The configuration was simulated by the ray tracing method. Resolutions in different fields and mirror-lengths were compared. The model of Kirkpatrick-Baez microscope was made in computer with 10 {mu}m resolution at 8 keV. It was studied about the adjusting tolerance method of Kirkpatrick-Baez microscope. When numerical aperture is 0.0037, the angle error range is -0.087 degree-0.067 degree . (authors)

High-resolution elliptical Kirkpatrick–Baez microscope for implosion higher-mode instability diagnosis

Abstract: High-resolution X-ray imaging diagnosis is a critical method for measuring Rayleigh-Taylor instability growth and hot spot interface morphology in inertial confinement fusion experiments. In this study, we develop a quasi-monochromatic elliptical Kirkpatrick-Baez microscope based on aberration theory, breaking the aberration limit of conventional Kirkpatrick-Baez microscopes. The microscope was characterized in the laboratory for spatial resolution performance and modulation transfer function before being implemented in cavity experiments at the SG-III prototype laser facility. The results demonstrate that the edge-based method achieves a spatial resolution of <2 µm in the central field of view and modulation of 800 lp/mm spatial frequency of >20%.

Adaptive optics for in-orbit spherical aberration correction

Abstract: We investigate the feasibility of using an adaptive mirror for in-orbit aberration corrections. The advantage of an in-situ aberration correction of optical components in the space environment is that the mirror shape can be adjusted in an iterative fashion until the best image is obtained. Using the actuator spacing, corresponding to one-half the Nyquist frequency, the Strehl ratio of the corrected wavefront improves to 0.95 when the mirror is fabricated with 6.5 waves of spherical aberration. The Strehl ratio is decreased to 0.86 when the number of actuators is reduced by a factor of 4, in a 2D adaptive optics model.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Reconstruction of electron exit waves: basic theory and applications

Abstract: With the popularization of field emission gun transmission electron microscopes (FEG-TEM),the information limit and the point resolution become two key important parameters to characterize the resolution ability of the microscopesBecause of the oscillation characteristic of the contrast transfer function,the information between the point resolution and information limit in the high resolution images taken from the FEG-TEM is difficult to interpretReconstruction of electron exit waves from focal series of lattice images extends resolution to near/sub-angstrom values,corrects for dominant aberrations of the objective lens,and allows imaging the atomic structure of crystalline materials directlyThis has enabled us to directly record columns of the light elements carbon,nitrogen and oxygen with sub-angstrom resolutionThis technique establishes the basis of quantitative TEM

3D reconstruction of 2D crystals

Abstract: High Resolution three-dimensional (3D) reconstruction of several proteins has been achieved from two-dimensional (2D) crystals by electron crystallography structure determination. However, for badly ordered 2D crystals, especially non-flat crystals, Fourier-filtering based methods fail, while single particle processing approaches can produce reconstructions of superior resolution by aligning particles in 3D space. We have investigated a single particle processing approach combined with the crystallographic method to generate images centered on the unit cells of 2D crystal images. The implemented software uses the predictive lattice node tracking in 2dx/MRC software to extract particles from the microscope images. These particles are then subjected to a local contrast transfer function (CTF) correction. The tilt geometry obtained in the 2dx software is used to initialize the Euler angles, which along with translations are then refined by a single particle processing approach. Finally, iterative transform algorithms, namely the error reduction algorithm and the hybrid input-output algorithm, are applied to retrieve missing information in the previously obtained 3D reconstruction. Compared with conventional single particle processing for randomly oriented particles, the required computational costs are greatly reduced as the 2D crystals restrict the parameter search space. Preliminary results from a 3D reconstruction of the membrane protein GlpF suggest that the iterative transform process improves 3D resolution.