Modular Concepts in the Design of Electron Optical Systems

1970 ◽  
Vol 28 ◽  
pp. 362-363
Author(s):  
J.R. Fairbanks
Keyword(s):  
Optical System ◽  
Practical Approach ◽  
Optical Systems ◽  
Objective Lens ◽  
Scientific Instruments ◽  
High Quality ◽  
Condenser Lens ◽  
The Third ◽  
Instrument Maker ◽  
Electron Microscopes

A practical approach to the design of complex machinery is to standardize parts as much as possible. This approach is equally valid for the design of scientific instruments such as electron microscopes, provided there is no sacrifice in performance for the completed instrument. As an example, the illustration shows modular parts used elsewhere in an electron optical column, which are organized by design in this particular case to perform as a second condenser lens.Consider the upper polepiece. This modular piece is used in nine other places in the column; once in the lower condenser as shown, twice in the upper condenser, twice in the objective lens, twice in the second projector, twice in the third projector, and once in the first projector. Since all the polepieces are identical, they are all of the highest quality needed in the most critical lens, the objective. The optical system thus benefits from standardized high quality lenses, (which ultimately is the user's benefit), and the instrument maker benefits from the economy of making pieces in replicate.

Method of calculating the aberrations of soft X-ray and vacuum ultraviolet optical systems

2019 ◽  
Vol 26 (5) ◽  
pp. 1558-1564
Author(s):  
Yiqing Cao ◽  
Zhijuan Shen ◽  
Zhixia Zheng
Keyword(s):  
Optical System ◽  
Vacuum Ultraviolet ◽  
Optical Systems ◽  
Third Order ◽  
Order Accuracy ◽  
X Ray ◽  
Plane Symmetric ◽  
The Third ◽  
Aberration Theory ◽  
Ray Coordinates

Based on the the third-order aberration theory of plane-symmetric optical systems, this paper studies the effect on aberrations of the second-order accuracy of aperture-ray coordinates and the extrinsic aberrations of this kind of optical system; their calculation expressions are derived. The resultant aberration expressions are then applied to calculate the aberrations of two design examples of soft X-ray and vacuum ultraviolet (XUV) optical systems; images are compared with ray-tracing results using SHADOW software to validate the aberration expressions. The study shows that the accuracy of the aberration expressions is satisfactory.

Divergent-beam holography with a 200keV FE TEM

1991 ◽  
Vol 49 ◽  
pp. 678-679
Author(s):  
Xiao Zhang ◽  
David Joy
Keyword(s):  
Optical System ◽  
Photographic Film ◽  
Objective Lens ◽  
Electron Wave ◽  
Transmission Electron ◽  
High Resolution Images ◽  
Phase Data ◽  
Electron Microscopes ◽  
Complete Amplitude ◽  
Commercial Field

A hologram, first described and named by Gabor (1949), permits a medium such as photographic film, which responds only to intensity, to store the complete amplitude and phase information which characterizes an electron wavefront. The hologram is formed by allowing some fraction of a coherent electron wave which has interacted with a specimen to interact again with original incident wave so as to generate an interference pattern. If the hologram is then itself illuminated by a coherent light source and optical system which mimic the original electron-optical system then a pair of images -one real and the other virtual -can be reconstructed and viewed. Because the hologram contains both the amplitude and the phase data of the wavefront, errors and distortions in either component due to aberrations in the objective lens can be corrected by optical manipulates before the image is reconstructed. With the advent of commercial field emission transmission electron microscopes capable of generating both high resolution images and highly coherent electron beams, these holographic techniques are now available as practical tools to improve TEM performance as well as to create new modes of images (Tonomura 1987).

Dreidimensional abbildende Elektronenmikroskope II. Theorie elektronenoptischer Systeme mit gekrümmter Achse / Three-dimensionally Imaging Electron Microscopes II. Theory of Electron-optical Systems with a Curved Axis

1978 ◽  
Vol 33 (11) ◽  
pp. 1361-1377 ◽  
Author(s):  
E. Plies ◽  
D. Typke
Keyword(s):  
Electromagnetic Field ◽  
Electromagnetic Fields ◽  
Optical Axis ◽  
Optical Systems ◽  
Integral Expression ◽  
The Third ◽  
Space Charges ◽  
Single Section ◽  
Electron Microscopes ◽  
Aberration Theory

An imaging and aberration theory of electron- or ion-optical systems composed of arbitrary stationary electromagnetic fields without space charges and currents in the beam-occupied region is developed. It follows the theory of systems with a straight optical axis as formulated by H. Rose. The electromagnetic field is expanded into plane multipoles about the arbitrarily curved and twisted axis. In the expansion of the eikonal, all terms are given which are needed for the calculation of the image aberrations up to the third rank (rank = Seidelian order + power of disturbing potentials + power of the chromatic deviation). For the image aberrations of the second rank, an integral expression is given, from which the single aberration integrals may be derived. Systems with single-section symmetry are treated in more detail.

scholarly journals Effective Optical System Assembly Using Ultra-Precise Manufactured References

2020 ◽  
Vol 14 (4) ◽  
pp. 644-653
Author(s):  
Andreas Gebhardt ◽  
Matthias Beier ◽  
Erik Schmidt ◽  
Thomas Rendel ◽  
Ute Gawronski ◽  
...  
Keyword(s):  
Optical System ◽  
Laser Diodes ◽  
Optical Component ◽  
Machining Process ◽  
Optical Systems ◽  
Active Components ◽  
High Quality ◽  
Diamond Machining ◽  
Position And Orientation ◽  
Aspherical Lenses

The present work demonstrates that exactly manufactured references for joining, mounting, and metrology purposes are crucial in the effective assembly of high-quality optical systems. Based on the alignment turning of spherical and aspherical lenses, the proposed approach can be transferred to non-rotational symmetric elements such as prisms, active components (e.g., laser diodes), and freeform mirrors. The complexity of the optical component decides whether on-machine metrology or specific measurement setups need to be used to determine the position and orientation of the references with respect to the optical function. The resulting correction data are considered during the machining process. The subsequent correction cycle realizes mounting and metrology references down to sub-micron precision using diamond-machining techniques. This approach facilitates the assembly of demanding optical systems and even freeform arrangements in a predictable and passive manner. Different machining setups as well as the corresponding metrology approaches are demonstrated, and results are presented for representative components. The effectiveness of the approach is discussed using rotationally symmetrical lens systems and a snap-together freeform mirror system.

Design of objective lens for 200-kV high-resolution electron microscopes

1983 ◽  
Vol 41 ◽  
pp. 314-315
Author(s):  
K. Tsuno ◽  
T. Honda ◽  
Y. Harada ◽  
M. Naruse
Keyword(s):  
Optical Properties ◽  
Computer Technology ◽  
Axial Magnetic Field ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Resolution Electron ◽  
Correction Of Astigmatism ◽  
Three Stages ◽  
Electron Microscopes ◽  
Stage 1

Developement of computer technology provides much improvements on electron microscopy, such as simulation of images, reconstruction of images and automatic controll of microscopes (auto-focussing and auto-correction of astigmatism) and design of electron microscope lenses by using a finite element method (FEM). In this investigation, procedures for simulating the optical properties of objective lenses of HREM and the characteristics of the new lens for HREM at 200 kV are described.The process for designing the objective lens is divided into three stages. Stage 1 is the process for estimating the optical properties of the lens. Firstly, calculation by FEM is made for simulating the axial magnetic field distributions Bzc of the lens. Secondly, electron ray trajectory is numerically calculated by using Bzc. And lastly, using Bzc and ray trajectory, spherical and chromatic aberration coefficients Cs and Cc are numerically calculated. Above calculations are repeated by changing the shape of lens until! to find an optimum aberration coefficients.

The Reduction of Chromatic Aberrations Due to Instrumental Instabilities

1971 ◽  
Vol 29 ◽  
pp. 14-15
Author(s):  
J. S. Lally ◽  
R. Evans
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Usual Practice ◽  
Voltage Electron ◽  
Short Focal Length ◽  
Chromatic Aberrations ◽  
Electron Microscopes

One of the instrumental factors often limiting the resolution of the electron microscope is image defocussing due to changes in accelerating voltage or objective lens current. This factor is particularly important in high voltage electron microscopes both because of the higher voltages and lens currents required but also because of the inherently longer focal lengths, i.e. 6 mm in contrast to 1.5-2.2 mm for modern short focal length objectives.The usual practice in commercial electron microscopes is to design separately stabilized accelerating voltage and lens supplies. In this case chromatic aberration in the image is caused by the random and independent fluctuations of both the high voltage and objective lens current.

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).

Description of a New High Resolution Scanning Transmission EM

1972 ◽  
Vol 30 ◽  
pp. 418-419
Author(s):  
Michael Beer ◽  
J. W. Wiggins ◽  
David Woodruff ◽  
Jon Zubin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Energy Dispersive Spectrometer ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Condenser Lens ◽  
Transmission Electron ◽  
Pattern Size ◽  
Scanning Transmission ◽  
Under Construction

A high resolution scanning transmission electron microscope of the type developed by A. V. Crewe is under construction in this laboratory. The basic design is completed and construction is under way with completion expected by the end of this year.The optical column of the microscope will consist of a field emission electron source, an accelerating lens, condenser lens, objective lens, diffraction lens, an energy dispersive spectrometer, and three electron detectors. For any accelerating voltage the condenser lens function to provide a parallel beam at the entrance of the objective lens. The diffraction lens is weak and its current will be controlled by the objective lens current to give an electron diffraction pattern size which is independent of small changes in the objective lens current made to achieve focus at the specimen. The objective lens demagnifies the image of the field emission source so that its Gaussian size is small compared to the aberration limit.

7-beam lattice images of (110) oriented Ge

1978 ◽  
Vol 36 (1) ◽  
pp. 290-291
Author(s):  
J.R. Parsons ◽  
C.W. Hoelke
Keyword(s):  
Image Features ◽  
Objective Lens ◽  
Lattice Plane ◽  
Lattice Image ◽  
Crystalline Defects ◽  
Transmission Electron ◽  
Lattice Images ◽  
Electron Microscopes ◽  
Structural Aspects ◽  
Beam Lattice

The direct imaging of a crystal lattice has intrigued electron microscopists for many years. What is of interest, of course, is the way in which defects perturb their atomic regularity. There are problems, however, when one wishes to relate aperiodic image features to structural aspects of crystalline defects. If the defect is inclined to the foil plane and if, as is the case with present 100 kV transmission electron microscopes, the objective lens is not perfect, then terminating fringes and fringe bending seen in the image cannot be related in a simple way to lattice plane geometry in the specimen (1).The purpose of the present work was to devise an experimental test which could be used to confirm, or not, the existence of a one-to-one correspondence between lattice image and specimen structure over the desired range of specimen spacings. Through a study of computed images the following test emerged.

Transmission Scanning Electron Microscopy and Energy Analysis with the Siemens ELMISKOP 101

1972 ◽  
Vol 30 ◽  
pp. 450-451
Author(s):  
H. M. Thieringer
Keyword(s):  
Objective Lens ◽  
Transmission Microscopy ◽  
Image Recording ◽  
Mode Of Operation ◽  
Scanning Transmission ◽  
Electron Microscopes ◽  
And Performance ◽  
Convergent Beam ◽  
Ray Path ◽  
Beam Diffraction

It has repeatedly been show that with conventional electron microscopes very fine electron probes can be produced, therefore allowing various micro-techniques such as micro recording, X-ray microanalysis and convergent beam diffraction. In this paper the function and performance of an SIEMENS ELMISKOP 101 used as a scanning transmission microscope (STEM) is described. This mode of operation has some advantages over the conventional transmission microscopy (CTEM) especially for the observation of thick specimen, in spite of somewhat longer image recording times.Fig.1 shows schematically the ray path and the additional electronics of an ELMISKOP 101 working as a STEM. With a point-cathode, and using condensor I and the objective lens as a demagnifying system, an electron probe with a half-width ob about 25 Å and a typical current of 5.10-11 amp at 100 kV can be obtained in the back focal plane of the objective lens.

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