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.

The relations between the axial aberrations of photographic lenses and their optical transfer functions.

Abstract: The wave aberration of a photographic lens can be represented for an axial image point by means of three coefficients. The usual values of these coefficients are studied. The optical transfer function (OTF) is computed from the wave aberration by means of an analog computer and represented as a function of the size and the shape of the wave aberration. The influence of stopping down the aperture on the image quality is investigated.

The spherical X-ray wave focusing by a bent crystal in the Johann scheme

Abstract: The focusing of a spherical X-ray beam during the Bragg reflection from a bent crystal in the Johann scheme is considered. It is demonstrated that, with an allowance for the spherical aberration of the beam, the wave intensity in the focus is determined by the square modulus of Airy’s function.

Simultaneous Dual-Color Fluorescence Microscope: A Characterization Study

Abstract: Background: High spatial resolution and geometric accuracy is crucial for chromosomal analysis of clinical cytogenetic applications. High resolution and rapid simultaneous acquisition of multiple fluorescent wavelengths can be achieved by utilizing concurrent imaging with multiple detectors. However, such class of microscopic systems functions differently from traditional fluorescence microscopes. Objective: To develop a practical characterization framework to assess and optimize the performance of a high resolution and dual-color fluorescence microscope designed for clinical chromosomal analysis. Methods: A dual-band microscopic imaging system utilizes a dichroic mirror, two sets of specially selected optical filters, and two detectors to simultaneously acquire two fluorescent wavelengths. The system’s geometric distortion, linearity, the modulation transfer function, and the dual detectors’ alignment were characterized. Results: Experiment results show that the geometric distortion at lens periphery is less than 1%. Both fluorescent channels show linear signal responses, but there exists discrepancy between the two due to the detectors’ non-uniform response ratio to different wavelengths. In terms of the spatial resolution, the two contrast transfer function curves trend agreeably with the spatial frequency. The alignment measurement allows quantitatively assessing the cameras' alignment. A result image of adjusted alignment is demonstrated to show the reduced discrepancy by using the alignment measurement method. Conclusions: In this paper, we present a system characterization study and its methods for a specially designed imaging system for clinical cytogenetic applications. The presented characterization methods are not only unique to this dual-color imaging system but also applicable to evaluation and optimization of other similar multi-color microscopic image systems for improving their clinical utilities for future cytogenetic applications.

A new spherical aberration coefficient C 4 for the Gaussian laser beam

Abstract: Laser beam quality is related to the aberration effect. Quartic phase aberration, more commonly known as spherical aberration, can result from aberrated optical components such as beam expanding telescopes, focusing or collimating lenses, or other conventional optical elements. In general, any kind of quartic aberration will lead to increased far field beam spread, degraded laser beam focusability and increased values of the beam quality. Currently, a well established quality parameter for laser beams is the M 2 factor which is proportional to the coefficient of quartic phase aberration denoted C 4 . In many recent papers, authors used C 4 given in geometrical optics approach to evaluate the laser beam quality M 2 which belongs to the Gaussian beam optics and the two disciplines are not to be confused. In this paper, we present a new mathematical set for the spherical aberration coefficient C 4 , especially for Gaussian beams in the context of Gaussian beam optics. A numerical analysis of a set of lenses is done to show the importance of the new C 4 .