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: This work investigates the feasibility of using an adaptive mirror for in-orbit aberration corrections using a two-dimensional adaptive optics model and finds that the Strehl ratio of the corrected wave front improves.
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 of the Nyquist frequency, the Strehl ratio of the corrected wave front improves to 0.95 when the mirror is fabricated with 6.5 waves of spherical aberration. The Strehl ratio decreases to 0.86 when the number of actuators is reduced by a factor of 4, in a two-dimensional adaptive optics model.
16 citations
Journal Article•
TL;DR: A contrast transfer function (CTF) of print is introduced and it is found that the CTF of print can be expressed by a simple function of the MTF of paper, MTF paper (ω): CTF print (ω) = [1 + MTFpaper (ω)]/2.
Abstract: Image quality of print is dependent on the paper characteristics. However, there are relatively few studies on the imaging characteristics of paper. In a previous report, we introduced a new method for measuring the modulation transfer function (MTF) of paper. In this report, a contrast transfer function (CTF) of print is introduced. We find that the CTF of print, CTF print (ω), can be expressed by a simple function of the MTF of paper, MTF paper (ω): CTF print (ω) = [1 + MTF paper (ω)]/2. The CTF of print predicted by the function was approximately same as the measured CTF of print.
16 citations
TL;DR: In this paper, the spherical aberration of electrostatic lenses can be corrected for the aperture angle of up to 60° by introducing spherical meshes, based on the capability of stigmatic imaging by a spherical refractive surface in light optics.
Abstract: The spherical aberration of electrostatic lenses can be corrected for the aperture angle of up to 60° by introducing spherical meshes. The principle of correction is based on the capability of stigmatic imaging by a spherical refractive surface in light optics. The electrostatic potential distribution around a mesh required for the correction was studied using the analytical expression of the general solution of the Laplace equation, and the amount of aberration was determined by ray tracing. It is shown that the sign of spherical aberration at a virtual image produced by the field near the mesh can be made positive or negative, according to the position of the object and the degree of deformation of the electrostatic field from spherical symmetry when retreating from the mesh surface. It thus becomes possible to cancel the spherical aberration of a focusing field which follows the field near the mesh, and a total lens field without spherical aberration is realized. The possibility of canceling the spherical aberration is verified in a practical design example of an extraction lens for electron spectrometers, which may increase the sensitivity to much higher than that obtained with conventional lenses.
16 citations
TL;DR: In this article, lines of diffraction contrast have been observed near the interfaces of epitaxial layers of III-V compounds in transmission electron microscope samples cut perpendicular to the growth plane.
16 citations
TL;DR: This work introduces a technique for merging the information from both images, including signal to noise ratio weighting, contrast transfer function correction, and optional Weiner filtration, which produces a composite image with reduced contrastTransfer function artifacts and optimized contrast.
16 citations