How an image is produced

Producing an Image


 

To produce an image on the screen, the electron beam scans over the area to be magnified and transfers this image to the TV screen. The electron beam stops at 1,000 points as it scans horizontally across the sample and down 1,000 lines vertically. This gives 1,000,000 points of information. The signal read from the electrons coming off each point is transfered to a corresponding point on the TV screen. Since the TV screen also has 1,000 points horizonally and 1,000 lines vertically, there is a 1:1 correspondance between the scan on the specimen and the TV screen. Since the length of the electron beam scan on the specimen is smaller than the length of the TV screen, a magnification is produced equal to the following equation:

 


                 Length of TV scan
Magnification  =  ______________________________
                   Length of Electron Beam Scan

By changing the size of the scan on the sample, the magnification can be changed. The smaller the area of the electron beam scan, the higher the magnification. Obtaining different degrees of magnifications are important in any practical uses of the SEM.

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