training for advanced research


Glossary terms about Contrast

Referring to the appearance of an image: the extent to which various parts of an image differ in brightness.

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12 pages mention Contrast

Applications and practical uses - what the SEM can do
view bulk material, coatings, sectioned material, foils, even grids prepared for transmission electron microscopy). Image compositional and some bonding differences (through contrast and using backscattered electrons). 
Background information - What is scanning electron microscopy?
This is somewhat surprising at first glance, given the contrast between the simple technology of the LM and the complex electronics, vacuum equipment, voltage supplies and electron optics system of electron microscopes. 
Beam Adjustment
Choose a low magnification to start with and ensure your contrast and brightness are adjusted so you can see an image. 
Electromagnetic lenses, apertures and beam size
Generating an image
This topographical contrast due to the position of the SE detector is a major factor in the "life-like" appearances of SE images. 
Image Capture
To take a photograph you may need to adjust the contrast and brightness against a scale inbuilt in the machine, otherwise you can rely on your eyes. 
Images from electrons
An electron backscatter diffraction pattern (EBSP) EBSP from a quasicrystalline AlMnSi inclusion in an aluminium alloy. (Crystallographic information.) An orientation (channelling) contrast image A duplex steel sample, collected using forescatter detectors mounted on an EBSD detector. 
In order to produce contrast in the image the signal intensity from the beam-specimen interaction must be measured from point-to-point across the specimen surface. 
Perfecting an image - signal processing
In this way we can adjust the signal to change contrast and brightness of our final image. 
Sample preparation
Troubleshooting: edge effect, charging, sample damage
It will also increase BSE and so the image will start to show changes in contrast based on composition. 
Variable Pressure or Low Vacuum scanning electron microscopy (LVSEM)
Backscattered electron imaging (BSE) of nonconductive, uncoated samples can provide information about composition via the contrast of the image: whiter regions have a higher average atomic number than darker regions.