220.127.116.11 Objective T-number - on-axis. The effective T-number will be
determined by flooding the image plane of the periscope objective with a known
luminosity and measuring the illumination of the projected image on a target
placed in front of the periscope. A luminous source providing a diffuse
luminosity of approximately 100 foot lamberts over a circular area 1.0 inch in
diameter shall be positioned in the image tube cavity by means of a suitable
adapter. A reticle shall be mounted between the luminous source and the
objective lens and positioned to provide a sharply focused image at a distance
of 10.0 feet from the entrance window of the head assembly. The reticle pat-
tern shall be as indicated in Figure 11. Luminance measurements shall be made
from a magnesium oxide target placed within the center cross mark of the reti-
cle image at 10.0 feet. The objective T-number shall not exceed the value
specified in 18.104.22.168.
22.214.171.124 Objecive T-number - off-axis. Perform this test aS in
126.96.36.199. The objective T-Number shall be measured at the 4 peripheral cross
marks of the reticle image. The objective T-numbers shall not exceed the
value specified in 188.8.131.52.
184.108.40.206 Resolution - unity power system. The test for resolution shall
be performed utilizing an auxilliary telescope conforming to the requirements
of 3.10.6, and a resolving power chart on a wall target or positioned in a
collimator. The resolving power target shall represent the angular subtense
for the minutes of arc specified. Construction of the target shall conform to
the USAF 1951 Resolution Pattern in accordance with MIL-STD-150. The target
shall be illuminated by diffuse light from a 2870° ± 100% tungsten lamp.
The target shall have the detectable line structure and proper line count when
observed through the telescope positioned at the exit aperture of the unit
power system. Resolution shall meet the requirements of 3.10.6.
4.6.9 Image intensifier tube, Government furnished. Each Goverment fur-
nished image tube shall be subjected to the following verification inspections
prior to insertion into the periscope:
220.127.116.11 Physical defects. Prior to energizing the tube it shall be sub-
jetted to a visual and tactile examination. The tube shall show no evidence
of physical defects as specified in 18.104.22.168. The image tube shall than be
positioned on the testtng equipment specified in 22.214.171.124.3 and energized.
Visually examine the energized screen. The energized screen shall conform to
the requirements of 126.96.36.199.
188.8.131.52 Operational defects. Position the image tube on the fixture
specified in 184.108.40.206.3 shall not evidence any audible or visible
defect identified in 220.127.116.11.
18.104.22.168 Luminance gain, center resolution and image alinement. The
examination and tests for these characteristics shall be in accordance with
MIL-I-55340. The image tube shall conform to the requirements of 22.214.171.124
through 126.96.36.199 inclusive.
4.6.10 Optical characteristics with image tube installed. The condi-
tions, and positioning of the periscope for these tests shall be as specified
in 4.6.8, except that the Image tube shall be installed in the periscope. The
test equipment specified in 4.S.188.8.131.52 shall be utilized to energize the
oscillator and reticle projector of the periscope.