Barrel and Pincushion

2021 ◽  
pp. 100-102
Author(s):  
Stephen R. Wilk
Keyword(s):  
Optical System ◽  
Negative Sign ◽  
Positive Coefficient ◽  
Optical Aberrations ◽  
Barrel Distortion

One of the five basic optical aberrations is Distortion. Whether the Distortion aberration has a positive or negative sign determines whether it is described as “Pincushion” or “Barrel” distortion. The origin of the term “Barrel” distortion is obvious—the image of a square object produced by an optical system with negative distortion resembles a classic “barrel” shape. But one with a positive coefficient produces a shape that is not that of the pincushions of my acquaintance. What kinds of pincushions inspired the name of this characteristic aberration, and who came up with it?

Fisheye Lens Distortion Calibration Based on the Lens Charactetic Curves

2014 ◽  
Vol 519-520 ◽  
pp. 636-639
Author(s):  
Bao Long Zhang ◽  
Shao Jing Zhang ◽  
Wei Qi Ding ◽  
Hui Shuang Shi
Keyword(s):  
Optical System ◽  
Characteristic Curve ◽  
Calibration Method ◽  
Lens Distortion ◽  
Wide Angle ◽  
Forming Process ◽  
Fisheye Lens ◽  
Large Scope ◽  
Wide Angle Lens ◽  
Barrel Distortion

The fisheye lens is a kind of ultra wide angle lens, which can produce a big super-wide-angle lens distortion. In order to cover a large scope of light, barrel distortion is artificially added to the optical system. However, in some cases this distortion is not allowed, then it requires calibrations of those distortions. Most of the traditional distortion calibration method uses target plane calibration to do it. This paper discusses the way of design fisheye lens, through which we can know the forming process of distortion clearly. Based on this paper, a simple and effective calibration method can be understood. Different from common camera calibration method, the proposed calibration method can avoid the error occurring in the process of calibrating test, that directly use the lens’ characteristic curve. Through multiple sets of experimental verifications, this method is effective and feasible.

scholarly journals Space Variant PSF – Deconvolution of Wide-Field Astronomical Images

10.14311/1023 ◽  
2008 ◽  
Vol 48 (3) ◽  
Author(s):  
M. Řeřábek
Keyword(s):  
Optical System ◽  
Imaging System ◽  
Real Data ◽  
Wavefront Aberration ◽  
Wide Field ◽  
Optical Aberrations ◽  
Optical Aberration ◽  
Transfer Characteristics ◽  
Astronomical Images ◽  
Space Variant

The properties of UWFC (Ultra Wide-Field Camera) astronomical systems along with specific visual data in astronomical images contribute to a comprehensive evaluation of the acquired image data. These systems contain many different kinds of optical aberrations which have a negatively effect on image quality and imaging system transfer characteristics, and reduce the precision of astronomical measurement. It is very important to figure two main questions out. At first: In which astrometric depend on optical aberrations? And at second: How optical aberrations affect the transfer characteristics of the whole optical system. If we define the PSF (Point Spread Function) [2] of an optical system, we can use some suitable methods for restoring the original image. Optical aberration models for LSI/LSV (Linear Space Invariant/Variant) [2] systems are presented in this paper. These models are based on Seidel and Zernike approximating polynomials [1]. Optical aberration models serve as suitable tool for estimating and fitting the wavefront aberration of a real optical system. Real data from the BOOTES (Burst Observer and Optical Transient Exploring System) experiment is used for our simulations. Problems related to UWFC imaging systems, especially a restoration method in the presence of space variant PSF are described in this paper. A model of the space variant imaging system and partially of the space variant optical system has been implemented in MATLAB. The “brute force” method has been used for restoration of the testing images. The results of different deconvolution algorithms are demonstrated in this paper. This approach could help to improve the precision of astronomic measurements. 

scholarly journals Adaptive Optics for Visual Simulation

ISRN Optics ◽  
2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Enrique Josua Fernández
Keyword(s):  
Adaptive Optics ◽  
Optical System ◽  
State Of The Art ◽  
Neural Adaptation ◽  
Current Paper ◽  
Visual Simulation ◽  
Optical Aberrations ◽  
Current State ◽  
Ocular Aberrations ◽  
Visual Testing

A revision of the current state-of-the-art adaptive optics technology for visual sciences is provided. The human eye, as an optical system able to generate images onto the retina, exhibits optical aberrations. Those are continuously changing with time, and they are different for every subject. Adaptive optics is the technology permitting the manipulation of the aberrations, and eventually their correction. Across the different applications of adaptive optics, the current paper focuses on visual simulation. These systems are capable of manipulating the ocular aberrations and simultaneous visual testing though the modified aberrations on real eyes. Some applications of the visual simulators presented in this work are the study of the neural adaptation to the aberrations, the influence of aberrations on accommodation, and the recent development of binocular adaptive optics visual simulators allowing the study of stereopsis.

Image Distortion in the Reconstruction of Periodic Images: Effect and Correction

1980 ◽  
Vol 38 ◽  
pp. 684-685
Author(s):  
Jon Rigden ◽  
J.W. Wiggins
Keyword(s):  
Electron Micrographs ◽  
Image Distortion ◽  
Field Of View ◽  
Dimensional Structure ◽  
Two Dimensional ◽  
Missing Information ◽  
Optical Aberrations ◽  
Radial Distortion ◽  
Single Number ◽  
Barrel Distortion

There are two electron optical aberrations which are commonly ignored because they are unimportant, even ignored, in most electron micrographs. These aberrations are radial distortion - also known as pincushion or barrel distortion, depending on the sign - and spiral distortion, an effect which never occurs in light optics. They are both illustrated in Figure 1. Since these distortions are generally uninteresting, microscope manufacturers do not provide substantial information about their instruments. Typically, either there is no information at all, or a single number related to the distortion constant is provided with no indication as to where in the field of view it was measured or at what magnification, although both items are needed to actually assess the distortion constant. Taking the most optimistic view of the missing information, one can still determine that radial distortion is a major factor in limiting the resolution attained by Unwin and Henderson in their reconstruction of the two-dimensional structure of bacteriorhodopsin.

MODELING AND PERFORMANCE EVALUATION OF OPTICAL SYSTEMS USING SKEW RAY TRACING

2007 ◽  
Vol 31 (2) ◽  
pp. 143-156
Author(s):  
Te-Tan Liao ◽  
Jing-Fung Lin
Keyword(s):  
Ray Tracing ◽  
Optical System ◽  
Monochromatic Light ◽  
Merit Function ◽  
Optical Systems ◽  
Optical Aberrations ◽  
Algebra Approach ◽  
Homogeneous Transformation Matrix ◽  
Overall Performance ◽  
And Performance

This paper applies a computational geometric algebra approach based on a 4 x 4 homogeneous transformation matrix to model optical systems and to evaluate their performance. In the proposed approach, the directions of the refracted/reflected rays at each boundary in the optical system are determined using skew ray tracing based upon Snell’s law. The differential changes in the image coordinates caused by optical aberrations are derived for both polychromatic and monochromatic light by applying a sensitivity analysis approach. Finally, a merit function is constructed comprising five individual defect items in order to evaluate the overall performance of a generic optical system. The proposed analytical approach provides a comprehensive and robust approach for the modeling and evaluation of optical systems.

scholarly journals Computer Simulation for the Effects of Optical Aberrations on Solar Images Using Karhunen-Loeve polynomials

2021 ◽  
pp. 2463-2473
Author(s):  
Raaid Noffi Hassan ◽  
Huda Shaker Ali ◽  
Wafaa Hikmat Wadee
Keyword(s):  
Wave Front ◽  
Adaptive Optics ◽  
Optical System ◽  
Solar Surface ◽  
Phase Error ◽  
Circular Aperture ◽  
Initial State ◽  
Optical Aberrations ◽  
Wave Aberration ◽  
Aperture Function

     Numerical simulations were carried out to evaluate the effects of different aberrations modes on the performance of optical system, when observing and imaging the solar surface. Karhunen-Loeve aberrations modes were simulated as a wave front error in the aperture function of the optical system. To identify and apply the appropriate rectification that removes or reduces various types of aberration, their attribute must be firstly determined and quantitatively described. Wave aberration function is well suitable for this purpose because it fully characterizes the progressive effect of the optical system on the wave front passing through the aperture. The Karhunen-Loeve polynomials for circular aperture were used to describe wave front deviations and to predict the initial state of adaptive optics corrections. The results showed that increasing the aberration modes causes an increase in the blurring of the observed image. Also, we conclude that the optical phase error is increased significantly when aperture’s radii are increased.

Study of Thermal Deformations Induced Optical Aberrations for Al2O3Mirror in an Optical System

2012 ◽  
Vol 39 (10) ◽  
pp. 1002001
Author(s):  
周琼 Zhou Qiong ◽  
姜宗福 Jiang Zongfu ◽  
习锋杰 Xi Fengjie
Keyword(s):  
Optical System ◽  
Optical Aberrations ◽  
Thermal Deformations

scholarly journals V. A new treatment of optical aberrations

1913 ◽  
Vol 212 (484-496) ◽  
pp. 149-185 ◽  
Keyword(s):  
Optical System ◽  
Geometrical Optics ◽  
Optical Image ◽  
Numerical Calculations ◽  
Refractive Indices ◽  
Optical Aberrations ◽  
Before And After ◽  
New Treatment ◽  
Axial System

The method developed by Gauss in his ‘Dioptrische Untersuchungen’ is probably the most powerful, as well as the readiest, method in geometrical optics. It has in effect hitherto been restricted to systems in which the relations of original and emergent rays are strictly linear, or, in optical language, those in which the aberrations can be neglected. It is true that Seidel bases his celebrated discussion of aberrations upon Gauss's method, but he soon modifies it and replaces its system of co-ordinates and characteristic steps by others. The following pages show how the method may be extended and retained throughout the discussion of the aberrations of any co-axial system. They will be found to throw light upon the general relation­ ships of the well-known Petzval condition and Abbe Sine condition, to furnish a ready method of describing, analysing and measuring the faults of an optical image, and to be particularly adapted to numerical calculations, to the order to which these are necessary for telescopic objectives. It will be convenient to state here the essentials of the method in the form in which they will be used later. Let O xyz , O 'x'y'z' be rectangular axes in the original and emergent media, of which the refractive indices are µ, µ' , respectively. O x , O' x ' are the axes of the optical system. Take the equations of any ray before and after its passage through the system in the respective forms y = β x + b , z = γ x + c , and ...........(1) y' = β' x '+ b ', z ' = γ x '+ c ', then, provided there is a strict linear correspondence as well as symmetry about the axis, we may put b ' = gb + h β, c ' = gc + h γ , ......................(2) β, = kb + l β, γ' = kc + l γ , where g, h, k, l are constants involving the curvatures of the refracting surfaces, the distances between them and the refractive indices; also gl - hk = μ/μ'.

A Field Emission System For Transmission Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 298-299
Author(s):  
Michel Troyonal ◽  
Huei Pei Kuoal ◽  
Benjamin M. Siegelal
Keyword(s):  
Electron Microscope ◽  
Field Emission ◽  
Optical System ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Electron Optical System ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

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