MIL-PRF-29580C
4.5.2.1 Optical density and angular protection. The optical densities shall be measured at all
angles at which incident laser radiation in the specified threat wavelength bands may enter the eye.
The calculation for angular protection shall be for an eye with an 8 mm diameter pupil rotated
± 35° with respect to the user's line of sight through the lens. The eye relief (see 6.4.1) shall be
not greater than 24 mm. The measurements shall be made with a spectrophotometer, a
photometer, lasers of the appropriate wavelengths, or any equivalent method. The densities shall
meet the requirements specified in 3.4.3.1.
4.5.2.2 Transmittance. The photopic and scotopic transmittance of the spectacle lenses shall
be computed as shown in table V or an equivalent method. The spectacle lenses shall meet the
requirements specified in 3.4.3.2.
4.5.2.3 Near-infrared transmittance. The near-infrared transmittance of the spectacle lenses
shall be computed as the average of the spectral transmittances at 50 nm steps in the spectral
region of 800 to 1200 nm. The spectacle lenses shall meet the requirements specified in 3.4.3.3.
4.5.2.4 Erythermal ultraviolet transmittance. The erythermal ultraviolet transmittance of the
spectacle lenses shall be computed by averaging the transmittances at wavelengths of 290, 300,
310, and 320 nm. The spectacle lenses shall meet the requirements specified in 3.4.3.4.
4.5.2.5 Haze. The haze shall be determined in accordance with ASTM-D1003,
Procedure A. The spectacle lenses shall meet the requirements specified in 3.4.3.5.
4.5.2.6 Abrasion resistance. The transmittance and haze of the lenses shall be determined, as
specified in ASTM-D1003, before and after the abrasion test. The surface abrasion test shall be
performed by rubbing with a specially standardized eraser mounted as illustrated on figure 1, and
held approximately normal to the lens. The eraser shall be rubbed across the surface of the lens
from one point to another, over the same path, for 20 complete cycles with a force of 4.4 to
5.5 kg continuously applied. Wherever possible, rubs of about 25 mm length are preferred. After
the rubbing has been completed, the lens shall be thoroughly cleaned to remove dirt, film,
fingermarks, and grease marks using a mild detergent and water, followed by drying with a soft
cloth or lens tissue. The lens shall meet the requirements specified in 3.4.3.6.
4.5.3 Environmental test.
4.5.3.1 General test performance procedure. Before performing the environmental tests, all
the spectacles shall be measured and meet the requirements for lens defects (see 3.4.2.4), optical
density (see 3.4.3.1) and transmittance (see 3.4.3.2). Spectacles shall be placed in an
environmental chamber to allow adequate circulation around the item. The spectacles shall be
placed in the test chamber so that the entire front surface can be photographed from the viewing
port without disturbing the sample. A white light source shall be positioned behind the spectacles
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