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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TL;DR: Quantitative modeling for high-resolution (phase contrast) gas cell environmental transmission electron microscopy (ETEM) imaging is presented and extension of the approach to the aberration-corrected ETEM is discussed.
Abstract: Quantitative modeling for high-resolution (phase contrast) gas cell environmental transmission electron microscopy (ETEM) imaging is presented in this paper. Concepts of pre-specimen scattering object (PreSO) and post-specimen scattering object (PoSO) are introduced to explain electron scattering caused by gas and window membranes associated with the gas environmental cell (E-cell). PreSO preserves the structural phase information and the effect can be evaluated by averaging the contrast transfer functions (CTFs) over random electron scattering. PoSO is treated as information loss and the unscattered electrons play a major role in determining the ETEM image quality. The theoretical model is compared and matched well with our systematic gas ETEM experimental results under various gas pressures. Extension of our approach to the aberration-corrected ETEM is discussed.
18 citations
TL;DR: A linear approximation for the multi-pass contrast transfer function (CTF) is developed to explain how the resolution depends on the number of passes through the sample.
18 citations
TL;DR: It is demonstrated that obstruction of low-resolution features is significantly reduced by lowering the acceleration voltage of the microscope, and computational approaches to correct BPP images for SSB contrast and to compensate for mechanical drift of the BPP are presented.
17 citations
TL;DR: The effects of defocus and primary spherical aberration on the images of a straight edge in a confocal microscope are investigated and one can improve the quality of the edge images, particularly the sharpness, by slightly reducing the aperture size of the objective and the collection lenses.
Abstract: The effects of defocus and primary spherical aberration on the images of a straight edge in a confocal microscope are investigated. When the aberrations are small, the sharpness of the edge image may be enhanced. But the images are degraded if the aberrations become strong in the system. In the latter case, one can improve the quality of the edge images, particularly the sharpness, by slightly reducing the aperture size of the objective and the collection lenses. This result is qualitatively verified by experimental results.
17 citations
TL;DR: In this article, the light distribution in the point image is rigorously derived in terms of an integral over angular coordinates involving the eikonal function about a reference surface at infinity.
Abstract: The notion that the optical contrast transfer function is a useful tool for assessing the performance of image-forming instruments has been accepted generally for some time and is now well established. This paper discusses one method of making the transition from ray-trace data to the evaluation of this important function. First, the light distribution in the point image is rigorously derived in terms of an integral over angular coordinates involving the eikonal function about a reference surface at infinity. Then, the ray-trace procedure is developed in the language of refraction and translation matrices culminating in matrix elements which are simply related to the eikonal coefficients of wave optics. Finally, the numerical evaluation of the contrast transfer function in amplitude and phase from these eikonal coefficients is presented, and the paper ends with an example showing the off-axis transfer function for line structures oriented at various azimuths. All calculations are carried out to fifth order in the eikonal coefficients, and emphasis is placed on the usefulness of this approach on relatively slow, low-capacity computing machines.
17 citations