NVIS Keyboards: Backlighting That Works With Night Vision

If you have ever looked through a pair of night vision goggles at an ordinary backlit keyboard, you will know the problem straight away. What looks like a gentle glow to the naked eye turns into a bright smear across the goggle image. Keys disappear, the screen behind them washes out, and the operator either flips the goggles up or turns the backlight off and types blind.

That is why NVIS keyboards exist. They are not a niche curiosity. For anyone fitting out a helicopter, a military vehicle, a patrol boat or a night-time drone ground station, the keyboard lighting is part of the night vision system whether you planned for it or not.

This guide explains what NVIS actually means, what the different "Green" ratings are, and which keyboards we recommend when night vision is in the picture.

Why normal backlighting is a problem for night vision

Night vision goggles work by amplifying very small amounts of light, including near-infrared light that the human eye cannot see. As Winmate's NVIS guide puts it, the intensifier tube boosts faint light "including some near-infrared light that would otherwise be invisible to the human eye".

Most standard LEDs, especially red, amber and white ones, put out energy in exactly the wavelengths the goggles are most sensitive to. To you it is a dim key light. To the goggles it is a floodlight. Grayhill's explanation of NVIS compatibility sums up the effect well: even small amounts of incompatible light can make the goggle image bloom or wash out, reduce contrast and hide critical information.

The usual workaround is to switch the backlight off. That works until someone needs to find the F7 key in a dark cockpit at 3am.

What MIL-STD-3009 and NVIS Green A and B mean

The standard that governs this is MIL-STD-3009, the US military standard for lighting, displays and illuminated components used with night vision imaging systems. It sets limits on how much energy a light source can emit in the wavelengths goggles are sensitive to, along with colour and brightness requirements.

It defines several NVIS colours. The two you will see on keyboards are:

• NVIS Green A: a softer, less saturated green intended for general illumination, such as panel and console lighting.
• NVIS Green B: a more saturated green intended for indicators, with better intensity and readability in daylight.

There are also other NVIS colours, such as Red and White, for warnings and charts, according to Grayhill. Most NVIS keyboards, including the iKey range, use Green B.

Compliance is tested properly, not judged by eye. This overview of NVIS testing explains that spectral radiance, measured with a high precision spectroradiometer in a dark room, is the primary measurement used to judge NVIS compatibility. When a supplier says a keyboard is NVIS compliant, it is reasonable to ask which colour and class it was tested to.

A quick note on goggle classes

Goggles themselves come in classes. Class A goggles are incompatible with red cockpit lighting, while Class B are designed to work with certain types of red lighting and filtered displays, which is why Class B is common in modern cockpits (Winmate). If you are integrating into an aircraft, find out which goggles the crew use before you specify the lighting.

Where NVIS keyboards are needed

• Aircraft and helicopter cockpits, where the crew fly on goggles and every illuminated surface has to be compatible.
• Military vehicles, including command vehicles and armoured vehicles with mission computers.
• Naval and patrol craft, where bridge lighting is kept low at night.
• Law enforcement and border security, particularly surveillance work at night.
• Drone ground stations used for night operations, where the operator may switch between the screen and goggles.

iKey says its NVIS keyboards have been third party tested and approved for NVIS Green B compliance, and lists installations in tanks, aircraft, submarines and helicopters.

The NVIS keyboards we recommend

iKey SL-88-NV: compact and widely used

The iKey SL-88-NV is the one we sell most for night vision work. It is a compact, sealed keyboard with NVIS-compliant Green B backlighting, designed to eliminate the bloom effect of normal LEDs. From the SL-88-NV data sheet:

• NVIS Green B backlighting
• NEMA 4X rated and 100% humidity resistant
• Operating temperature of -40°C to +70°C
• Shock tested to 50g and vibration tested from 20 Hz to 2 kHz
• Keys rated for 10 million cycles
• USB or PS/2, with a 1.2 m coiled cable

iKey SLK-880-FSR: fully submersible with a pointer

If the keyboard needs a built-in pointing device and has to survive being dunked, the SLK-880-FSR is a very tough option. It meets IP68, has a conductive plastic case, an integrated force sensing resistor pointer, and adjustable green backlighting that is also available in an NVIS compatible configuration. It is designed to meet MIL-STD-461 for electromagnetic compatibility.

iKey SLK-101-8L: full size with eight brightness levels

For a full-size layout with a numeric pad, the SLK-101-8L has eight levels of green backlighting and is also available in an NVIS compatible configuration. It is NEMA 4X rated and designed to meet MIL-STD-461.

Wearable and OEM options

• The AK-39-NV is an arm-worn keyboard with six levels (including off) of adjustable Green B backlighting and an FSR pointer, for dismounted users.
• The TMLT-890-OEM is a very thin OEM keyboard designed to meet MIL-461E, with adjustable green backlighting and optional NVIS Green B, for integrators building rugged laptops and consoles.
• The RUGGED RKB-M66KP-AC-BL-DWP is a 12-key IP67 panel mount keypad with an NVIS-compliant backlight, useful for control panels where you only need a few keys.

Practical buying tips

• Check the dimming range, not just the colour. Even a compliant backlight can be too bright for some crews. Adjustable levels, ideally down to off, make a real difference.
• Red is not the same as NVIS. Red backlighting is great for preserving natural night vision, but it is not designed for goggles. If goggles are in use, specify NVIS Green.
• Look at everything else that lights up. An NVIS keyboard next to an unfiltered screen or a bright status LED will not solve the problem on its own.
• Ask for the variant code. Several iKey models are "available in an NVIS configuration", which means you need to order that specific version rather than the standard one.
• Think about EMC at the same time. Most platforms that need NVIS also care about electromagnetic interference, so a keyboard designed to MIL-STD-461 is usually the sensible choice.
• Check the cable and connector early. Military platforms often need specific connectors or cable lengths, and OEM versions give you more freedom there.

NVIS variants are usually built to order, so it pays to get the part number right first time. Our supply and support partner Rugged Limited, with 25 years in rugged keyboards, can help confirm the right variant for your platform.

Talk to us before you specify

NVIS requirements vary a lot between platforms, and it is much easier to get the keyboard right before the console is built than afterwards. If you are working on an aircraft, vehicle, vessel or ground station that will be used with night vision, send us the details and we will put together a quote. We usually reply within 24 hours.

You can also browse our keyboards for defence, aerospace and vehicles or the full iKey range.