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Introduction to NVIS

In the electromagnetic spectrum, our eyes only respond to wavelengths between 400 and 700 nanometers (nm), which we normally experience as colors (figure 1). The less light, however, the less we distinguish color and detail. On a dark night, we lose color perception entirely, and objects become shadowy, somewhat brighter or dimmer shapes

Figure 1. The electromagnetic spectrum, with a focus on the ultraviolet (250-400 nm), visible (400-700 nm), and infrared bands (700-1,500 nm).

There are two ways of improving night vision. The first is to increase the amount of light reaching the eye, as with a telescope or flashlight. The second is through light amplification, by creating a visible, phosphor-screen image from normally imperceptible radiation, as in a night vision imaging system (NVIS) or forward looking infrared (FLIR) camera.

An NVIS usually looks like a pair of goggles or binoculars, is worn by the viewer, and responds to visible and near-infrared wavelengths up to 930 nm. FLIR is built into aircraft, with sensors below the nose cone and a display screen in the crewstation. It responds to long wavelengths in the 800-1600 nm infrared range, forming a visual representation of heat. Compared to NVIS, it has two main disadvantages; it doesn't track well with the pilot's head movements, and it is not real-time imaging. This brochure deals only with NVIS and NVIS-compatible lighting.