Study on spherical aberration in the laser optical system

2021 ◽  
Author(s):  
Heng Jiang ◽  
Chengyu Li ◽  
Xiangjin Wang
Keyword(s):  
Optical System ◽  
Spherical Aberration

Atomic Resolution in Crystal Aperture Stem

1990 ◽  
Vol 48 (1) ◽  
pp. 236-237
Author(s):  
J T Fourie
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Three Dimensional ◽  
Transmission Function ◽  
Optical Systems ◽  
Bragg Angle ◽  
Electron Optical System ◽  
Intimate Contact ◽  
Diffraction Effects ◽  
Design Aspect

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.

scholarly journals Current Status of the Astrometric Capabilities of the Hubble Space Telescope Fine Guidance Sensors

1991 ◽  
Vol 127 ◽  
pp. 68-76
Author(s):  
W.H. Jefferys ◽  
G.F. Benedict ◽  
R.L. Duncombe ◽  
O.G. Franz ◽  
L.W. Fredrick ◽  
...  
Keyword(s):  
Optical System ◽  
Reference Frames ◽  
Optical Axis ◽  
Hubble Space Telescope ◽  
Current Knowledge ◽  
Spherical Aberration ◽  
Radial Distance ◽  
Current Status ◽  
Space Telescope ◽  
Wavefront Error

AbstractThe Fine Guidance Sensors (FGSs) are the instrument of choice for most astrometric measurements with the Hubble Space Telescope (HST). The observed amount of spherical aberration in the Ritchey Chretien optical system does not affect positional measurements with perfectly aligned FGSs because they are interferometers. The FGSs combine wavefronts from points in the exit pupil with other points which are at the same radial distance from the optical axis. Asymmetric aberrations such as coma and astigmatism do affect the measured positions. The current knowledge of the HST wavefront error, the FGS operation and the implications for milliarcsecond relative astrometry are discussed. It is still planned to use the HST to tie the HIPPARCOS and VLBI Reference Frames together at the few milliarcsecond level.

Information and Metrology-Driven Optimisation of Wavefront Error in Telescope-Detected Radiation

2020 ◽  
pp. 37-51
Author(s):  
V.V. Sychev ◽  
A.I. Klem
Keyword(s):  
Wave Front ◽  
Uniform Distribution ◽  
Optical System ◽  
Software Package ◽  
Spherical Aberration ◽  
Space Telescope ◽  
Exit Pupil ◽  
Wavefront Error

The paper presents a solution to an information and metrology problem concerning minimising the wave-front error of telescope-detected radiation. As an example, we used aberration computation and simulation describing the optical system of the space telescope installed in the Millimetron observatory. We show that many factors that affect a space telescope decrease the quality of the image obtained. It is necessary to eliminate the effects of the distortion-generating factors and reduce their contribution to the total wavefront error. As the dimensions of the collecting aperture in telescopes increase, the factors that distort the wavefront of the radiation detected by the telescope begin to significantly affect the quality of the image obtained. We consider the ways of decreasing the effects of the distortion-generating factors caused by aberrations in the optical system. One of the solutions to this problem is to select a rational configuration of the space telescope optical system. In order to minimise the aberration, we used the Zemax 13 Release 2 SP4 Premium software package to simulate the optical system, to analyse and optimise it so as to diminish the scattering spot in the exit pupil. We achieved this goal by decreasing the spherical aberration and ensuring a more uniform distribution of it over the field. We used the data obtained to estimate the admissible dimensions of the misalignment spot

scholarly journals Полнопольный оптический когерентный томограф на базе микропрофилометра МИИ-4 с использованием микрообъективов с воздушной иммерсией

2019 ◽  
Vol 127 (8) ◽  
pp. 347
Author(s):  
А.С. Абдурашитов ◽  
О.В. Гришин ◽  
А.А. Намыкин ◽  
В.В. Тучин
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Turbid Media ◽  
Reference Channel ◽  
Dynamic Adjustment ◽  
Technical Solutions

A modernized Linnik micro profilometer (MII-4) is introduced for the tomographic studies of transparent and relatively turbid media using air-immersion objectives. The construction of the reference channel in standard MII-4 is reworked by adding the dynamic adjustment of reference arm length to compensate for the effect of the divergence between focal and coherent volumes, as well as spherical aberration arising from the focusing of the optical system into the deeper layers of an object without using immersion. An analysis of existing technical solutions for the reference arm is done, their main disadvantages are indicated. All stages are described including assembling and adjusting the system. The device was able to perform a tomographic studies transparent and turbid layered objects.

scholarly journals On a theory of the second order longitudinal spherical aberra­tion for a symmetrical optical system

1920 ◽  
Vol 97 (683) ◽  
pp. 196-198
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Empirical Method ◽  
Second Order ◽  
Point Of View ◽  
Axial Plane ◽  
First Order ◽  
Usual Theory ◽  
Semi Empirical

1. The object of this investigation is to establish a formula for the longitudinal spherical aberration of rays which traverse a symmetrical optical system in an axial plane that shall be capable of fairly easy computation for any combination of lenses, and at the same time shall be accurate to the second order and free from certain important difficulties of convergency which occur in certain neighbourhoods when we attempt to use for the longitudinal aberration the method of aberration of successive orders. From the point of view of the optical designer, the usual theory of aberrations, which, for all practical purposes, is largely restricted to the first order, is known to give an unsatisfactory approximation. In practice, the designer adopts a semi-empirical method of tracing a number of rays through the system by means of the trigonometrical equations, a method which is laborious and lengthy, and which can at best give only incomplete informa­tion and very limited guidance for effecting improvements.

Image diffractionnelle due à une pupille aberrante non-uniforme

1985 ◽  
Vol 63 (2) ◽  
pp. 275-281 ◽  
Author(s):  
Jean-Eudes Villeneuve ◽  
Subhash C. Biswas ◽  
Albéric Boivin
Keyword(s):  
Optical System ◽  
Spherical Aberration ◽  
Graphical Form ◽  
Analytical Expressions ◽  
Elegant Solution

The problem of diffraction by a nonuniform pupil exhibiting residual aberrations has been studied theoretically. A simple and elegant solution of the problem has been obtained. This solution is valid for the case where a circularly symmetrical pupil filter is used in conjunction with an optical system having spherical aberration, primary coma, curvature, or distorsion. The analytical expressions of that solution can be evaluated numerically with remarkable simplicity. Results for a few optimum apodizers and primary coma are presented in graphical form and discussed.

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