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Glossary terms about Aperture

Aperture
In electron microscopy: a minute hole in a strip of metal that is placed in the path of the electron beam in order to restrict or limit electron progress down the machine column. An aperture stops off-axis or off-energy electrons.


21 pages mention Aperture

Alignment
 
Astigmatism
The apertures introduced into the lens may disturb the field if they are not precisely centered around the axis. 
Chromatic aberration
 
Electron column
The electron column is made up of the gun assembly at the top, a column filled with a set of electromagnetic lenses, the sample port and airlock, and a set of apertures that can be moved in and out of the path of the beam. 
Electron gun
 
Focus/stigmation
Micrograph quality is affected by aperture size, focus, stigmation, and use of image collection software. 
Frequently asked questions
 
Image appearance
When strong diffraction conditions are achieved, the image will appear darker as more electrons are scattered outside of the objective aperture
Image capture
 
Image types
In the bright field image the objective aperture is used to select the unscattered electron beam. 
Images from electrons
 
Imaging mode setup
The first component to consider is apertures. 
Lenses: electromagnetic lenses
 
Machine operating procedures
The GIF comes standard with a 2kx2k slow scan CCD (GIF LS2002 CCD), a bright field (BF), dark field (DF), and high-angle annular dark field (HAADF) STEM detectors are all located just above the entrance aperture for the GIF. 
Machine settings
 
Resolution
Note: The term nsinα is named numerical aperture
Spherical aberration
 
The Eucentric Position
 
Using the JEM-1010 Transmission Electron Microscope for physical science material
If there isn’t any light, ensure the camera is out (press red light on camera control); check that the magnification is not extremely high; or possibly a grid bar is blocking the beam. To find your sample on the grid, press LOW MAG (right hand console) and move out the objective aperture by turning silver lever to the right and you will see the full grid. 
Using the JEM-1010 Transmission Electron Microscope for thin resin sections of biological material
If there isn't any light, ensure the camera is out (press red light on camera control); check that the magnification is not extremely high; or possibly a grid bar is blocking the beam. To find your sample on the grid, press LOW MAG and move out the objective aperture by turning the silver lever to the right and you will see the full grid. 
What content is right for me?
bright field). how to use the apertures (both the condenser and objective) to enhance contrast [see