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Multialkali
The photosensitive coating used on photocathodes for Gen 2 intensifier tubes.
NR
See NVIS radiance
NVG (Night vision goggles)
An older term for head- or helmet-mounted NVIS. Now superseded by NVIS.
NVIS (Night vision imaging system)
A general term to describe night imaging systems containing intensifier tubes sensitive to the visible and near-infrared bands.
NVIS compatible
A display is NVIS compatible if it does not activate the NVIS AGC circuit and interfere with the visibility of the NVIS image.
NVIS radiance (NR)
A non-dimensioned measure of the radiance detected by an NVIS.
Photopic
Refers to the normal response of the human eye in daylight. The photopic or standard observer curve is a bell shaped curve that describes this response.
Radiance
The radiant flux emitted by a light source per unit solid angle and per unit projected area of radiating surface (expressed in watts per steradian per surface unit).
Response
The sensitivity of a light detector to specific wavelengths. The photopic response curve describes the relative sensitivity of the human eye over the visible spectrum. The NVIS response curve describes the sensitivity of that NVIS (expressed in milliamps/watt) over the visible and IR spectrum.
Scotopic
The human eye response under dark-adaptation conditions.
Secure lighting
A form of NVIS- compatible lighting for ground applications defined by the US Army CECOM Secure Lighting Statement of Work.
Spectral radiance
Radiance emitted by a source over a band of the spectrum. It is measured with a spectroradiometer and described by a curve.
Spectroradiometer
A device for measuring the spectral radiance of a display. To calculate NVIS radiance, MIL-L-85762A requires a scan from 450 to 930 nm, the response range of unfiltered Gen 3 NVIS.
Type I
Refers to NVIS with a direct-view image; the view through the goggle eyepiece only includes the NVIS phosphor-screen image. The pilot must glance down to see his instruments.
Type II
Refers to NVIS with a projected image; the addition of a combiner lens to the goggle eyepiece allows the pilot to simultaneously view the NVIS phosphor-screen image and crewstation instrumentation
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