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3.5 Operation for Image Observation
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(5) Histogram display
A histogram of the corrent image can be shown.
To show histogram, select Show Histogram from Image menu.
This function periodically calculates and displays a histogram of the displayed image.
Fig. 3.5-17 Histogram
3.5.5 Focus and Astigmatism Correction
Focus and astigmatism correction can be done manually and automatically.
Focus Monitor mode is available for manual focusing.
(1) General method for focusing and astigmatism correction
Focusing and astigmatism corrections are related to each other and need to be repeated
alternately. Use the following process to complete adjustments.
(a) Focus the image. When there is no astigmatism, the sharpest image is obtained at the
best-focus point.
When there is astigmatism, the image looks like its stretching in one direction at an over focused
or under-focused condition, and uniformly focused at the best-focus point.
No image drift
Fig. 3.5-18 Adjusting the Focus