Some biological materials observed by a new high-resolution SEM

1987 ◽  
Vol 45 ◽  
pp. 554-555
Author(s):  
K. Tanaka ◽  
A. Mitsushima ◽  
H. Takayama
Keyword(s):  
Endoplasmic Reticulum ◽  
High Resolution ◽  
Electron Probe ◽  
Motor Nerve ◽  
Focal Length ◽  
Biological Materials ◽  
Objective Lens ◽  
Probe Diameter ◽  
Short Focal Length ◽  
Dark Space

Recently we made a high resolution SEM (UHS-T1) with a aid of Hitachi Co. Ltd. It was equipped with a field emission source and the objective lens with short focal length (3.6 mm). The electron probe is estimated to 0.4 nm on calculation, and the probe diameter of 0.5 nm is confirmed by observation in STEM mode. On observation of a biological material (a rat motor nerve cell) which was coated with platinum by an ion sputter coater, the SEM shows 0.5 nm resolution when the width of the dark space criterion was used. In the present study some biological materials are observed with this new SEM. The results are as follows.Specimens were prepared by the aldehyde prefix osmium-DMSO-osmium method. In the specimens, mitochondria, Golgi complex, endoplasmic reticulum and so on, were very clearly observed (Fig.1) in comparison with those observed by ordinary SEM.

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.

Improvements in the electron probe forming capabilities and x-ray hole counts in the Philips TEM

1983 ◽  
Vol 41 ◽  
pp. 376-377
Author(s):  
Richard L. McConville
Keyword(s):  
Field Strength ◽  
Electron Probe ◽  
Spherical Aberration ◽  
Focal Length ◽  
Objective Lens ◽  
Parallel Beam ◽  
Tilt Axis ◽  
X Ray ◽  
Small Probe ◽  
Specimen Height

A second generation twin lens has been developed. This symmetrical lens with a wider bore, yet superior values of chromatic and spherical aberration for a given focal length, retains both eucentric ± 60° tilt movement and 20°x ray detector take-off angle at 90° to the tilt axis. Adjust able tilt axis height, as well as specimen height, now ensures almost invariant objective lens strengths for both TEM (parallel beam conditions) and STEM or nano probe (focused small probe) modes.These modes are selected through use of an auxiliary lens situ ated above the objective. When this lens is on the specimen is illuminated with a parallel beam of electrons, and when it is off the specimen is illuminated with a focused probe of dimensions governed by the excitation of the condenser 1 lens. Thus TEM/STEM operation is controlled by a lens which is independent of the objective lens field strength.

A Slotted Electrode Stigmator for Correction of Short Focal Length Objectives

1967 ◽  
Vol 25 ◽  
pp. 226-227 ◽  
Author(s):  
J. H. Reisner ◽  
J.J Schuler
Keyword(s):  
Focal Plane ◽  
Focal Length ◽  
Image Distortion ◽  
Slot Width ◽  
Objective Lens ◽  
Physical Restraints ◽  
Critical Dimensions ◽  
Short Focal Length ◽  
Magnetic Poles ◽  
Simple Reduction

One of the difficulties which must be overcome in the design of objective lens stigmators is that they necessarily take up space where it is most precious, in the vicinity of the specimen. The space following the specimen is needed for the contrast aperture while the space between magnetic poles in the gap is required for stage mechanism. To go appreciably below the objective back focal plane to position stigmators subjects the image to possible image distortion when correction is large. A further problem is caused by the trend to shorter objective focal lengths, e.g., 1.5 mm, thus further reducing the space available for the stigmator.To adapt the electrostatic stigmator to these physical restraints, a design has been completed which is only 0.75 mm thick and has a free bore diameter of the same size. Its sensitivity is 0.1 micron/volt with 100 kV electrons. The overall diameter is uncritical and may be adapted to the physical requirements of the system. It should be possible to make stigmators of 3 mm thickness with a simple reduction of critical dimensions (thickness and slot width).

A 100 KV Transmission Scanning Microscope

1971 ◽  
Vol 29 ◽  
pp. 22-23
Author(s):  
A. V. Crewe
Keyword(s):  
Focal Length ◽  
Electron Gun ◽  
Objective Lens ◽  
Scanning Microscope ◽  
Parallel Beam ◽  
Condenser Lens ◽  
Focal Length Lens ◽  
Short Focal Length ◽  
Pass Through ◽  
Correction System

A 100 kv transmission scanning microscope is now being constructed which should have a point resolution of 2.5 to 3 Å. The design of this microscope is similar to the design of our existing 30 kv 5 Å microscope, but there are several significant changes which are based upon some difficulties and sources of inflexibility of that microscope.A field emission electron gun of our usual design will be used as the source of electrons, the only difference being that the spacing between the anodes has been increased from 2 to 3 cm. The electron beam will then pass through a condenser lens which will produce a parallel beam of electrons. This parallel beam will then be focused onto the specimen by means of a short focal length lens (approximately 1 mm focal length). The reason for using a condenser lens to produce the parallel beam of electrons is that in the future a quadrupole-octupole correction system will be installed in this section of the microscope in order to attempt to correct the spherical aberrations of the objective lens and thereby improve its resolution.

A Spherical-Aberration Corrector Using Electrontransparent Conducting Foils

1973 ◽  
Vol 31 ◽  
pp. 262-263
Author(s):  
M. G. R. Thomson
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Field Of View ◽  
Objective Lens ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
Short Focal Length ◽  
Successful Approach ◽  
Fifth Order

One of the problems associated with building any aberration-corrected electron microscope objective lens lies in the difficulty of obtaining a sufficiently short focal length. A number of systems have focal lengths in the 1cm. range, and these are more suitable for microprobe work. If the focal length can be made short enough, the chromatic aberration probably does not need to be corrected, and the design is much simplified. A corrector device which can be used with a conventional magnetic objective lens of short focal length (Fig. 1) must either have dimensions comparable to the bore and gap of that lens, or have very large magnetic or electric field gradients. A successful approach theoretically has been to use quadrupoleoctopole corrector units, although these suffer from very large fifth order aberrations and a limited field of view.

State of the development of multipole correctors for a probe-forming system and a high-resolution 200kV TEM

1995 ◽  
Vol 53 ◽  
pp. 596-597
Author(s):  
M. Haider ◽  
J. Zach
Keyword(s):  
High Resolution ◽  
Low Voltage ◽  
Spherical Aberration ◽  
Limiting Factors ◽  
Objective Lens ◽  
Probe Diameter ◽  
Physical Limit ◽  
Low Energies ◽  
Routine Basis ◽  
Electron Microscopes

The development of modern high resolution electron microscopes has shown the emergence of new modern microscopes which are easy to operate and, more importantly, with which one can attain high resolution on a routine basis. However, the physical limit set by the inherent aberrations of electron lenses could not be overcome by simply optimising the geometry of the pole pieces. The only direct way to get rid of the aberrations of the round lenses is to use a corrector with which the resolution limiting aberrations can be compensated.For the observation of uncoated biological surfaces we started a project to develop a Low Voltage Scanning Electron Microscope (LVSEM). The main problem with using low energies is to design electron optics with which one can achieve high resolution in the range of 1 nm at energies of 1 keV and below. Hence, the two main axial aberrations of such a probe forming system: the chromatic and the spherical aberration Cc and C3, respectively, have to be considered as the limiting factors of the probe diameter. Therefore, the compensation of these two aberrations is the best choice as one does not want to run into other limitations if, for example, the geometry of the objective lens is scaled down in order to obtain small aberration coefficients.

High Resolution Scanning Microscopy

1969 ◽  
Vol 27 ◽  
pp. 172-173 ◽  
Author(s):  
A. V. Crewe ◽  
J. Wall
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Focal Length ◽  
Emission Source ◽  
Scanning Microscopy ◽  
Objective Lens ◽  
Scanning Microscope ◽  
Current Point ◽  
Single Objective

We have previously reported on the development of a scanning microscope with a resolution of 20 Å. This instrument has now been improved so that the current point resolution is about 5 Å at 18 Kv.The microscope consists of a field emission gun followed by a single objective lens (see Fig. 1). The gun produces an image (real or virtual) of the field emission source which is then demagnified by the lens. The focal length of this lens has been shortened from 1 mm to 0.6 mm to produce a second beam crossover at the exit of the lens.

Research of the Aerial Camera Lens to Eliminate the Secondary Spectrum

2014 ◽  
Vol 644-650 ◽  
pp. 4076-4079
Author(s):  
Zheng Liang
Keyword(s):  
High Resolution ◽  
Simple Structure ◽  
Focal Length ◽  
Optical Design ◽  
Effective Size ◽  
Optical Material ◽  
Objective Lens ◽  
Topographic Mapping ◽  
Camera Lens

Aerial cameras are widely used in resource surveys, topographic mapping, military reconnaissance and many other fields. This paper introduced the sort of aerial camera, the development in our country and abroad about the theory of secondary spectrum. In order to meet the requirement for simple structure and high-resolution, the optical design of the apochromatism objective lens of aerial camera is achieved by common optical material. Objective’s focal length is 400mm, relative aperture is F/4 and work waveband is 420nm~850nm. Designing results show that the MTF of every field above 0.75 in 60lp/mm and satisfy the requirements of imaging for large frame array CCD whose effective size is 36mm×48mm.

Quadrupole-Octopole and Foil Lens Corrector Systems

1971 ◽  
Vol 29 ◽  
pp. 16-17 ◽  
Author(s):  
M. G. R. Thomson ◽  
E. H. Jacobsen
Keyword(s):  
Spherical Aberration ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Order Effect ◽  
Objective Lens ◽  
Axially Symmetric ◽  
Third Order ◽  
First Order ◽  
Short Focal Length ◽  
Strong Focusing

The theorem due to Scherzer which states, in essence, that a conventional axially symmetric, magnetic or electrostatic lens can never be free from third order spherical aberration is well known. Attempts to circumvent this limitation have been carried out over the past thirty years with little result, but meanwhile the ill effects have been minimized by using magnetic lenses of very short focal length.The most studied alternative is the use of doubly symmetric strong focusing lenses. The first order imaging is performed with three or more quadrupoles, and the third order aberrations corrected with three octopoles. The design by Deltrap for example has no first order effect other than to invert the image, and has a third order spherical aberration coefficient which exactly cancels out that of the magnetic objective lens with which it us used. To avoid chromatic aberration this magnetic objective lens must have a very short focal length (2 mm for 100 kv operation with a resolution of 1 Å), and the overall system then has so much coma that the field of view is limited to 50 Å diameter.

A Combined Conventional and Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 84-85
Author(s):  
P.S. Ong
Keyword(s):  
Magnetic Field ◽  
Electron Microscope ◽  
Focal Length ◽  
Objective Lens ◽  
Pole Piece ◽  
Image Brightness ◽  
Focal Length Lens ◽  
Short Focal Length ◽  
Electron Microscopes ◽  
Scanning Electron

In electron optical instrumentation, it would be generally desirable to have a lens with a short focal length. Both spherical and chromatical aberration decreases with focal length and this will result in a better resolution and image brightness. This consideration has been taken into account in the design of conventional electron microscopes, and the focal length of the objective lens of such instrumentation ranges from a few millimeters to a fraction of a millimeter. A short focal length lens requires that the specimen be located in a magnetic field i.e., within the pole piece gap. This results in (a) a limitation in the size of the specimen and (b) a restriction, to use the microscope to nonmagnetic specimens only.

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