5-5
you are viewing. Emission points are acceptable if they do
not in ter fer e wit h th e usa bil ity of th e de vic e.
3. Bla ck S pots .
These are cosmetic blemishes in the image intensifiers or dirt
or debris be tween the l enses. Bl ack spots a re accept able as
long as they do not interfere with viewing the image. No action
is requi red if t his con dition is pres ent unl ess the spots
inter fer e wi th th e us abi lit y of t he d evic e.
4. Fix ed- Pat ter n Noi se.
This is usuall y a co smetic blemi sh cha racter ized by a fain t
hexagonal (h oneycomb) pattern thr oughout th e viewing a rea
that mo st oft en occ urs a t high light levels or wh en vi ewing
very brigh t lights ( See Figur e 5-4). This patt ern can be seen
in every im age inte nsifier if the li ght level is high e nough. This
conditio n is acc eptabl e as lon g as th e patte rn does not
inte rf er e w it h v ie wi ng th e i mag e a nd us ab il it y o f t he de vi ce .
Figur e 5- 4
Fixed -Pa tte rn N oise
5. Chi cken Wir e.
An irregular pat tern of dark thin l ines in the fiel d of view either
throughout t he image area or in parts o f the image ar ea (See
Fig ur e 5 - 5) . U n de r t he w or st - ca se c on di t io n, th e se li ne s wi ll fo r m
hexagonal or square-wave shaped lines. This is typically viewed
in hi gh li gh t co nd it io ns . No action is required if this condition