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you are viewing. Emission points are acceptable if they do
not interfere with the usability of the device.
3. Black Spots.
These are cosmetic blemishes in the image intensifiers or dirt
or debris between the lenses. Black spots are acceptable as
long as they do not interfere with viewing the image. No action
is required if this condition is present unless the spots
interfere with the usability of the device.
4. Fixed-Pattern Noise.
This is usually a cosmetic blemish characterized by a faint
hexagonal (honeycomb) pattern throughout the viewing area
that most often occurs at high light levels or when viewing
very bright lights (See Figure 5-4). This pattern can be seen
in every image intensifier if the light level is high enough. This
condition is acceptable as long as the pattern does not
interfere with viewing the image and usability of the device.
Figure 5-4
Fixed-Pattern Noise
5. Chicken Wire.
An irregular pattern of dark thin lines in the field of view either
throughout the image area or in parts of the image area (See
Figure 5-5). Under the worst-case condition, these lines will form
hexagonal or square-wave shaped lines. This is typically viewed
in high light conditions. No action is required if this condition
5-5
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