Night Vision Tutorial

A Quick Introduction to Night Vision and the Night Vision Capabilities of Ahlers Aerospace, Inc.

NVIS, or Night Vision imaging Systems have been in use (mainly by the U.S. and a few other military organizations) for many years. Now they are becoming widespread in many civilian and commercial applications, such as police aviation, and air-ambulance ships. The basic design criteria, which has remained relatively unchanged, is the development of a system that would amplify the existing light (radiation) that is present when an area is illuminated only by starlight. In effect, such a system would allow the user to ‘see in the dark’.

The Technology

In today’s systems, this objective is accomplished by an image tube that passes only light of a wavelength from 630 to 950 nanometers (nm) (near IR). This radiation is collected, amplified electronically and projected onto a phosphor plate situated at the viewing end of the device. The resulting (enhanced) image is then viewed by the observer. Modern ‘generation III or IV’ systems have excellent gain, low distortion and minimal noise, allowing a very detailed image to be visible in almost total darkness.

Because sunlight and most artificial lighting produces large amounts of radiation in the 630 to 950 nm range, it is amplified, along with the starlight, rendering the goggle or viewing apparatus useless. Consequently, for NVIS goggles to be of any practical use, all radiation in these frequencies must be eliminated in the immediate area of use (such as the aircraft cockpit). In an unmodified cockpit, such light sources abound. These must ALL be either modified (filtered) or turned off for NVIS goggles to function effectively.

Filtering objectionable light sources usually employs some type of filter surrounding the source that blocks the transmission of light within the 600 to 930 nm range. The remaining light that is transmitted through the filter is not amplified by the goggles, and is perceived by the eye as green.

Ahlers Offers Experience and Flexibility

Ahlers Aerospace has extensive experience in the modification of vehicular cockpits for use with night vision goggles. Some of the choices we offer to modify unfiltered lighting are:

Bezel and eyebrow conversions and postlights

In this approach, the internal instrument lighting (if present) is disabled, and the instrument is illuminated by an add-on full face bezel or eyebrow or by added postlights that contain the filtered light source. This approach produces good lighting, and is significantly more cost-effective than internal conversions. This approach is also used for MIL compliant conversions, as the light sources are filtered to green A or B requirements. Dial colors, again, are difficult to distinguish with the unaided eye. Some aircraft wiring modifications must be made to bring lighting power to the added equipment.

Internal conversion

This is the all-around best approach, as the lighting source within the instrument or annunciator is filtered to produce compatible light. This approach is normally used to achieve MIL-STD-3009 compliance (green A or Green B). Due to the frequency of the resulting light however, instrument color range markings are not easily discernable during night operations when viewed with the unaided eye.

Dot Matrix, LCD, Flat-Panel

Additionally, Ahlers has the capability to modify most of the dot-matrix, LCD, and flat-panel displays (normally found on communication equipment) to be NVIS compatible. We can also modify most caution panels and annunciators. And we can supply a variety of maplights, floodlights, and hand held flashlights, with filtering to Green A, Green B, or NVIS white.

Options for Non-MIL STD

For applications where MIL STD compliance is not required (such as DO-275 conversions) where the cockpit may be NVIS compatible (‘NVIS friendly’), Ahlers offers an excellent low-cost NVIS ‘white’ conversion. In this approach, each indicator face is covered with a thin add-on bezel that incorporates a proprietary NVIS compatible filter. The advantage to this approach is that there is no modification to either the instrumentation or to the aircraft wiring. The bezels remain attached at all times, and during daytime operation, the color of the filter is such that dial range marking colors are not adversely changed as they are with green A filtering. Daylight readability is excellent though the filter. As this type of filter, by necessity, allows passage of some yellow and red light, the filtered instruments and annunciators are brighter when viewed in the goggle than they would be under green A filtering, but are still held at a level that does not interfere with goggle operation (does not cause gain reduction), nor reduce goggle effectivity for viewing outside the aircraft.

Ahlers has the capability and the knowledge to convert nearly any light source in the cockpit or the aircraft to NVIS compatibility or compliance.