Fixed-Pattern Noise (FPN)

A faint hexagonal (honeycomb) pattern throughout the image area that most often occurs under high-light conditions. This pattern is inherent in the structure of the microchannel plate and can be seen in virtually all Gen 2 and Gen 3 systems if the light level is high enough. Footlambert(fL) A unit of brightness equal to one footcandle at a distance of one foot.