A Laboratory Testbed for Embedded Computer Control

Because periodicity is a major indicator of structural organisation numerous methods have been devised to demonstrate periodicity masked by background “noise” in the electron microscope image (e.g. photographic image reinforcement, Markham et al, 1964; optical diffraction techniques, Horne, 1977; McIntosh,1974). Computer correlation analysis of a densitometer tracing provides another means of minimising "noise". The correlation process uncovers periodic information by cancelling random elements. The technique is easily executed, the results are readily interpreted and the computer removes tedium, lends accuracy and assists in impartiality.A scanning densitometer was adapted to allow computer control of the scan and to give direct computer storage of the data. A photographic transparency of the image to be scanned is mounted on a stage coupled directly to an accurate screw thread driven by a stepping motor. The stage is moved so that the fixed beam of the densitometer (which is directed normal to the transparency) traces a straight line along the structure of interest in the image.

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Defocus ramp correction in spot-scan imaging

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100121053 ◽

1992 ◽

Vol 50 (1) ◽

pp. 130-131

Author(s):

Kenneth H. Downing

Keyword(s):

Computer Control ◽

Three Dimensional ◽

Sufficient Accuracy ◽

Objective Lens ◽

Electron Crystallography ◽

Contrast Transfer Function ◽

Tilt Axis ◽

Specimen Height ◽

The Difference ◽

Envelope Functions

Three-dimensional structures of a number of samples have been determined by electron crystallography. The procedures used in this work include recording images of fairly large areas of a specimen at high tilt angles. There is then a large defocus ramp across the image, and parts of the image are far out of focus. In the regions where the defocus is large, the contrast transfer function (CTF) varies rapidly across the image, especially at high resolution. Not only is the CTF then difficult to determine with sufficient accuracy to correct properly, but the image contrast is reduced by envelope functions which tend toward a low value at high defocus.We have combined computer control of the electron microscope with spot-scan imaging in order to eliminate most of the defocus ramp and its effects in the images of tilted specimens. In recording the spot-scan image, the beam is scanned along rows that are parallel to the tilt axis, so that along each row of spots the focus is constant. Between scan rows, the objective lens current is changed to correct for the difference in specimen height from one scan to the next.

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Applications of CCEM to Environmental Health Problems

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100117558 ◽

1985 ◽

Vol 43 ◽

pp. 102-103

Author(s):

R. J. Lee ◽

J. S. Walker

Keyword(s):

Electron Microscopy ◽

Image Analysis ◽

Environmental Health ◽

Computer Control ◽

External Agent ◽

External Agents ◽

Computer Controlled ◽

Primitive State ◽

Textural Changes ◽

General Aspects

Electron microscopy (EM), with the advent of computer control and image analysis techniques, is rapidly evolving from an interpretative science into a quantitative technique. Electron microscopy is potentially of value in two general aspects of environmental health: exposure and diagnosis.In diagnosis, electron microscopy is essentially an extension of optical microscopy. The goal is to characterize cellular changes induced by external agents. The external agent could be any foreign material, chemicals, or even stress. The use of electron microscopy as a diagnostic tool is well- developed, but computer-controlled electron microscopy (CCEM) has had only limited impact, mainly because it is fairly new and many institutions lack the resources to acquire the capability. In addition, major contributions to diagnosis will come from CCEM only when image analysis (IA) and processing algorithms are developed which allow the morphological and textural changes recognized by experienced medical practioners to be quantified. The application of IA techniques to compare cellular structure is still in a primitive state.

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The Instructional SEM Laboratory at Iowa State University

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164441 ◽

1996 ◽

Vol 54 ◽

pp. 396-397

Author(s):

L. S. Chumbley ◽

M. Meyer ◽

K. Fredrickson ◽

F.C. Laabs

Keyword(s):

Materials Science ◽

Computer Network ◽

Energy Dispersive Spectrometer ◽

Computer Control ◽

State University ◽

Iowa State University ◽

Internet Server ◽

Schematic Layout ◽

Hands On ◽

Improve Instruction

The Materials Science Department at Iowa State University has developed a laboratory designed to improve instruction in the use of the scanning electron microscope (SEM). The laboratory makes use of a computer network and a series of remote workstations in a classroom setting to provide students with increased hands-on access to the SEM. The laboratory has also been equipped such that distance learning via the internet can be achieved.A view of the laboratory is shown in Figure 1. The laboratory consists of a JEOL 6100 SEM, a Macintosh Quadra computer that acts as a server for the network and controls the energy dispersive spectrometer (EDS), four Macintosh computers that act as remote workstations, and a fifth Macintosh that acts as an internet server. A schematic layout of the classroom is shown in Figure 2. The workstations are connected directly to the SEM to allow joystick and computer control of the microscope. An ethernet connection between the Quadra and the workstations allows students seated there to operate the EDS. Control of the microscope and joystick is passed between the workstations by a switch-box assembly that resides at the microscope console. When the switch-box assembly is activated a direct serial line is established between the specified workstation and the microscope via the SEM’s RS-232.

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