188.8.131.52 Nine power system.
a. With the tube installed there shall be no more than six (6)
particules of dirt (or foreign matter) appearing on the screen image when
viewing from the eyepiece end of the periscope. The maximum apparent dimen-
sion of any particle shall not exceed the reticle line width. In addition,
the minimum separation between particles shall represent 10 mils in object
space. (Excluding the image tube surface.)
b. With the image tube removed and a light source inserted in the
tube cavity, there shall be not evidence of condensates, grease, fingerprints,
fractures or adhesive separations when viewing the glass components from the
objective and eyepiece end of the periscope. In addition, when viewing from
the objective end, the total number of dirt (or foreign) particles on the
glass surfaces (combined) shall not exceed four (4). The maximum apparent
dimension of any particle shall be 0.025 inches.
3.11.3 Resolution - nine power system. The nine power system shall be
capable of resolving the following values (for the axis specified when obser-
ving a resolution target having the background luminance in foot lamberts
(ft-1) and the contrast specified. Contrast (for the purpose of this require-
ment) is defined as the difference in density between the dark lines and the
black and clear)
High 1.0 or greater
1.5 x 10 ft-1
Low 0.20 ± 0.5
6 X 10-5ft-1
RT is the minimum on axis resolution requirement for the image intensifier
tube. The mandatory functional requirements of the Image Intensifier Assembly
type 7854A are specified in MIL-I-55340.
3.11.4 Contrast transfer. The following values (for the axis specified)
shall be met with 2870° ± 100°K radiance, modulated at the special fre-
quency (angular spacing) indicated, incident to the entrance aperture of the
periscope. UT is them minimum contrast transfer value obtained from the
image intensified tube assembly installed in the periscope being tested.