MIL-DTL-62422D(AT)
4.5.3.1.5 Reading 3. The filter shall be placed at 80±1.5 degrees incidence with the
polarization vector parallel to the plane of incidence and the transmitted beam energy shall be
measured at one center point only and each edge as shown on figure 1.
4.5.3.1.6 Optical density at two degrees. For each position and orientation, the value of
reading 2 shall be divided into the value of reading 1. The log (base 10) of this quotient shall be
the optical density of the filter at two degrees.
4.5.3.1.7 Optical density at 80 degrees. For each position and orientation, the value of
reading 3 shall be divided into the value of reading 1. The log (base 10) of this quotient shall be
the optical density of the filter at 80 degrees.
B
+ - test point
+A
A - 0.5 inch
B - 0.5 inch
+
centered, 1 inch apart
A +
+
B
NOTE: A & B are the distances from the edge.
FIGURE 1. Optical density measurement points.
Beamsplitter
Filter
Laser
Sample detector
Monitor detector
FIGURE 2. Beamsplitter setup.
4.5.3.2 Optical density (production). All filters shall be tested for compliance with row
A of table 1. Optical density shall be measured at the center of the filter with light incidence
angles of 0±1.5 degrees and 80±1.5 degrees. The energy incident on the filter shall be "P"
polarized with a minimum 100:1 ratio of "P" to "S". The incident light shall have a collimated
beam diameter of 10±3 mm (l/e2). Filters shall be measured using a laser setup as specified in
4.5.3.1.1 or a spectroradiometer setup as specified in 4.5.5. Either system shall be calibrated
over the optical density range of 3 through 4 using NIST calibrated neutral density filters.
Variations from either of the two test setups mentioned above shall be approved by the
contracting officer. If a laser is used for optical density measurements, see 4.5.3.5.
10
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