MIL-PRF-22885H
4.7.36 Sunlight readability (when specified) (see 3.1 and 3.41). A light source of 3,000 degrees to 5,000 degrees
Kelvin color temperature shall be directed at an angle of φ1 = 15 degrees ±2 degrees to the normal of a diffuse
reflectance standard (pressed barium sulphate or PTFE powder (polytetrafluorethylene resin), (see figure 10). The
size of the light source shall be limited so that θ < 20 degrees. A photometer shall be positioned at an angle of φ2 =
15 degrees ±2 degrees to the normal of the reflectance standard. The light source shall be adjusted to produce
10,000 foot candles illumination on the reflectance standard as measured by the photometer. The reflectance
standard shall then be removed and replaced by the viewing surfaces of the display to be tested. Using this test
configuration, the luminance of the legend, both illuminated and nonilluminated, plus that of the adjacent background
areas, shall be measured. Three luminance readings per legend character shall be taken (see figure 9). From these
readings, the following contrast ratios can be calculated for each character:
B2 - B1
The ON / BACKGROUND contrast CL =
B1
The OFF / BACKGROUND contrast CUL = B3 - B1
B1
B1 = Average background luminance
B2 = Average character luminance, lighted
B3 = Average character luminance, unlighted
The test shall be repeated with φ1 and φ2 = 30 degrees ±2 degrees. Normal production units shall be tested. The
sample units shall have two lines of characters which utilize at least three-fourths of the maximum horizontal length of
the legend. The contrast readings for the characters with the highest and lowest average contrast on each unit shall
be reported.
4.7.37 NVIS compatibility (see 3.42) (when specified, see 3.1). The test procedure for measuring luminance,
chromaticity and spectral radiance shall be in accordance with MIL-L-85762 for illuminated controls (for NVIS green A
and B), caution signals (for NVIS yellow), and warning signals (for NVIS red).
4.7.38 Stray lights (when specified) (see 3.1 and 3.43). When switches are tested for stray lights, a photometric
measurement shall be made on stray light areas as determined from visual inspection. To determine stray light
emitted at acute angles to the display face, a flat-white neutrally reflecting surface of 85 percent ±5 percent reflecting
shall be placed perpendicular to the front face and parallel to the top edge (horizontally) at a distance of 1 inch (25.4
mm) from the switch. A minimum of five (above display, upper third, center of display, lower third, and below display)
sets of brightness-readings shall be made. The brightness readings shall be made perpendicular to the reflecting
surface at a distance of 1 inch (25.4 mm) in front of the display (or at any point on the reflecting surface that appears
to be reflecting stray light from the display). The reflecting surface shall then be positioned parallel to a side edge
and at least five more sets of readings shall be made in the same manner as the above. All readings shall fall within
the limits specified in 3.43.
4.7.39 Field of view (see 3.44). The switches shall be mounted in a vertical position with the character(s)
displayed on the screen. Unless otherwise specified (see 3.1), the screen shall be viewed from a distance of 3 feet,
at all angles up to 40 degrees to a line perpendicular to the viewing surface.
5. PACKAGING
5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in the contract or order
(see 6.2). When actual packaging of materiel is to be performed by DoD personnel, these personnel need to contact
the responsible packaging activity to ascertain requisite packaging requirements. Packaging requirements are
maintained by the Inventory Control Point's packaging activity within the Military Department or Defense Agency, or
within the Military Department's System Command. Packaging data retrieval is available from the managing Military
Department's or Defense Agency's automated packaging files, CD-ROM products, or by contacting the responsible
packaging activity.
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