Confocal microscopy
Unlike "normal" microscopy, only a spot of a minimum size in the specimen
is illuminated in confocal microscopy. To enable an image to be formed
from this, the specimen must be scanned. The image of the spot is directed
through a pinhole stop in an intermediate image plane. As a result, only
light from the focal plane can reach the detector (a photomultiplier).
All other (out-of-focus) planes are blocked out. This results in an "optical
section". The images are stored electronically and displayed on a monitor.
A series of optical sections can be recorded by moving a motor a slight
distance along the z-axis
each time an image has been recorded, after which the next image is
then also recorded. Such a z-series permits the lectronic reconstruction
of the three-dimensional structure using suitable computer programs. The
procedure, which is restricted to incident-light techniques, has completely
revolutionized fluorescence microscopy in biology in particular.
The Confocal Scan Module is used to produce confocal images in the
eyepiece, with the height of the reflecting specimen being color-coded
in colors using a color-converting optical system. This enables even minute
defects and contamination on wafers to be detected quickly and reliably.
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