MIL-PRF-1/1049H
TABLE I. Testing and inspection - Continued.
9/ The radiation source and filter specified in 1/ shall be used. The source shall be adjusted to produce a .750 inch (19.05 mm)
diameter circle image on the center of the photocathode. The amount of radiation incident on the photocathode (prior to interposing
the filter) shall be 0.01 ± 0.0005 lux. The 5819 or 1P21 photomultiplier shall be adjusted to give 227 microamperes of anode
current. The radiation from the source shall then be excluded from the photocathode and the brightness shall be read in terms of
anode current (LB) of the photomultiplier tube. The ratio of conversion index to background (CI/B) = 1.00/LB.
10/ After the completion of the vibration, shock, and temperature tests specified, the resolution pattern described on figure 2 shall be
focused on the photocathode and the image of the pattern observed on the screen of the tube with a 10 power microscope. The
microscope shall be aligned with the geometric axis of the tube (which shall be the center line of the 1.680 inch (42.69 mm)
diameters at each end of the tube as shown on figure 1) and it shall be focused for best resolution of the test pattern image. W ith
the microscope focused and aligned with the tube operating at normal voltage, a test spot shall then be projected on the center (tube
axis) of the photocathode and the image of the spot shall be observed on the screen. The center of the test spot image shall fall on
the screen within a 0.045 inch (1.14 mm) radius circle concentric with the tube axis. Following the alignment test, the position of the
center of this image shall be recorded. After application of electrical shock, resulting from 10 cycles of alternate periods of 15
seconds with and 10 seconds without application of the rated tube voltage, the center of the above image shall not displace more
than 0.0025 inch (0.064 mm) in any direction from its initially recorded position.
11/ This test shall be performed with a 10 power or greater microscopic monocular; a tungsten radiation source and infrared filter (which
need not be the source and filter specified in 1/), a resolution test pattern, and a condenser lens system to project the resolution test
pattern upon the image tube photocathode. The test pattern shall be placed between the radiation source and the filter and shall be
focused on the photocathode for best equal resolution of line sets in the central area of the image tube screen. The input radiation
level shall be adjusted by the operator to obtain best contrast of the resolution patterns. The image shall be resolved when all lines
in each resolution group can be counted. The resolution test pattern shall be projected 1:1 on the photocathode of the tube.
(Projection other than 1:1 may be used provided the chart size is such that the projected image on the photocathode meets the
requirements of 12/ or 13/, as applicable.)
12/ The resolution pattern for this test, shown on figure 2, shall consist of 3 groups (marked 12, 50, and 12). In the center resolution
group, marked 50, each set of lines shall have 8 black lines with a minimum length-to-width ratio of 15 to 1. In the peripheral
groups, marked 12, each set of lines shall have 5 black lines with a minimum length-to-width ratio of 5 to 1. The width of each black
line and the distance between the black lines in the group marked 50 shall be 0.00039 inch (0.0099 mm). The width of each black
line and the distance between the black lines in the two groups marked 12 shall be 0.0016 inch (0.041 mm). The arrangement and
orientation of the groups and the sets of lines in each group shall be as shown on figure 2.
13/ Magnification is defined as the ratio of the separation of the two image points to the separation of corresponding object points; the
latter being located on a diameter and equidistant from the tube axis. Paraxial magnification is obtained only if the object points are
very close to the tube axis. Center magnification (Cmx) is a close approximation to paraxial magnification and shall be measured
with a nominal chordal separation of object points of 20 ± 0.4 percent of the useful minimum cathode diameter. The object points
shall be projected on the photocathode with nominal monochromatic visible light.
14/ A second magnification measurement shall be made to determine the percentage of distortion. The procedure used to determine
the center magnification (see 13/) shall be used except for the spacing of the points or lines on the photocathode which shall have a
separation of 80 ± 0.4 percent of the useful minimum cathode diameter. Percentage distortion shall be determined by the following
formula:
M 2 - M1
D=
x 100
M1
W here: D = Percentage distortion.
M1 = Magnification obtained in center magnification test.
M2 = Second magnification determined as above.
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