What is night vision for helicopter pilots, and how helpful is it in the aviation industry? Let’s face it — we are a species of the light. Once it gets dark, we no longer can see as we could in daylight. This decline in visual acuity has been with us as long as we have walked the earth. The inability to see well in the dark has also restricted our ability to fly helicopters at night safely until recently.

In January 1999, a night-vision imaging system (NVIS) was introduced to commercial aviation for the first time. The FAA issued an STC allowing night-vision goggles (NVG) to be used by a helicopter operator providing EMS. And so it began; the night was no longer restricted to flying safely in the dark.

The advantages that NVIS technology brings to helicopter operations are numerous. It improves flight crew situational awareness and reduces the probability of a collision with terrain or artificial obstructions. It increases safety significantly when flying in the dark, and safety is what it is all about.

Development of Image Intensifier Systems

The foundation of image intensifier systems technology was laid during World War II when the Allied forces and the German Wehrmacht were engaged in a race to produce infrared image converters.

These elementary versions of NVDs, called “black light sniper devices” by the Allies, were used in spectral ranges in the visible light’s vicinity, which is why they’d rather be classified as “near infrared devices” from modern day’s point of view, however, the basic principle was already similar with today’s NVDs.

From a military perspective, the new technology had one decisive disadvantage: The devices represented infrared searchlights, i.e., active reflection systems, which were rendered useless when the enemy forces were equipped with the same technology.

Consequently, there came a need to develop passive systems that could work without the conspicuous infrared searchlights. This was achieved by Vladimir Zworykin, who had the idea of developing a photoelectric image converter even before the World War II’s outbreak; even though he had it patented as early as 1935, he only realized it during the 1950s.

The result exceeded all expectations. The amplification effect, later labeled ‘image intensification’ (I.I., later known as I2), was incredibly potent. It amplified the light reflected at night by the moon and stars to create a monochrome image, utilizing the wavelength of the phosphorus in the image tube. The concept of an ambient light intensifier turned real. However, it was to take another decade until this technology became marketable.

The first gen of NVDs meeting wartime requirements (GEN-1 NVD) was operated in Vietnam in 1964 when the US troops’ military leaders realized that their troops were facing an enemy that mostly used individual military actions under cover of darkness for reasons of nominal and material inferiority and specific local knowledge.

Thus, the Vietnam conflict was among the great driving forces for the development of powerful NVDs satisfying wartime requirements. Consequently, a 2nd and a 3rd generation of image intensifiers (GEN-2/GEN-3 NVD) were successively introduced to the market, which essentially was marked by increased luminescence or sensitivity and a longer service life.

Even so, the applications were limited to hand-held night telescopes and weapon-mounted telescopic sights for a long time, thus being used by ground forces only. However, there was never any doubt that the air forces also had a great interest in adapting to the new technology. NVDs would permit flying under VMC pr visual meteorological conditions, and all pilots, then and now, would prefer this to fly under IMC or instrument meteorological conditions, aside from the fact that certain missions can’t be flown under IMC.

Nevertheless, this required that binocular vision was maintained and freedom of hands was guaranteed, resulting in the necessity to develop a binocular lens and to install it on the pilots’ helmet systems. This, however, took some time.

The US Air Force used the first binocular helmet-mounted displays (HMDs) at the beginning of the 1970s. They were based on 2nd-generation image intensifiers and were designated “aviator’s night vision imaging system” (ANVIS). Most NVDs for pilots commonly used in modern times are based on advancements of this prototype.

Understanding Optoelectronic Image Enhancement

Older night vision gear relies on optoelectronic image enhancement tech. It utilizes an arrangement of optical lenses and a unique electronic vacuum tube to grab and boost the visible and infrared light bouncing off objects nearby.

The system’s first objective lens captures the faint visible light reflected from the subject and some light from the low end of the infrared spectrum. Like all light, this light is made of small particles called photons.

Light particles travel through the lens and enter an image-intensifier tube, which enhances images. This special electronic vacuum tube has two components and is powered by small AA or N-cell batteries.

The tube’s first part is known as the photocathode. This component turns the incoming photons into electrons. As you may remember from science class, neutrons, photons, and electrons are all very small particles that make the components of an atom. Neutrons and photons combine to create the atom’s nucleus—electrons swirl around the nucleus and carry an electrical charge.

Freshly generated electrons move into the next section of the vacuum tube, the microchannel plate (MCP). This MCP is a compact glass disc with millions of minuscule holes, increasing the electron quantity and, in turn, magnifying the electrical signal by several thousand times.

As the electrons exit the end of the image intensifier tube, they hit a phosphor-coated screen. When the screen’s phosphors are struck, they illuminate, forming a bright green image surpassing the faint light that passes through the objective lens. Using an ocular lens, you observe the phosphor image, adjust the focus, and, if needed, enlarge the image.

Why isn’t this conventional night vision image in color? Transforming photons into electrons is part of the process. This removes color details from the image, turning the initial colored light into a black-and-white picture. The choice of green phosphors is deliberate. Green is the most comfortable color to see for longer durations in low-light conditions.

What Is Night Vision For Helicopter Pilots And How Do Helicopter Pilots Fly At Night?

A night-vision device (NVD), also known as a night-vision goggle (NVG) and night optical/observation device (NOD), is an optoelectronic device that enables images to be produced in light levels approaching total darkness. Night vision has two classes: Night Vision Goggles (NVGs) take in small amounts of visible and near-infrared light reflected from the targets, magnify it using high-resolution image intensifier tubes, and a project that is on display. Thermal IR cameras detect negligible differences in Heat (also called infrared, or thermal, energy) – as little as 0.01°C – and show them as shades of grey in black and white television video but usually with relatively low resolution. The image produced is often monochrome, e.g., shades of green.

NVDs are normally used by the military and law enforcement agencies but are accessible to civilian users. The term often refers to a complete unit, which includes an image intensifier tube, a protective and generally water-resistant housing, and some mounting system. Many NVDs include optical components such as sacrificial lenses, telescopic lenses, or mirrors. An NVD might have an IR illuminator, making it an active rather than a passive night-vision device.

Night vision devices are becoming important equipment for night flying, night driving, night surveillance, wildlife observation, and search-and-rescue missions.

Flying with NVDs

Vision is one of pilots’ most important information sources during their flight. Hence, an above-average vision is one of the basic prerequisites for qualifying for the pilot profession. However, vision has much more than most pilot candidates know during their initial examination. Vital as a central vision of 100% is that without peripheral vision, it wouldn’t be possible to properly assess climb and descent rates or recognize environmental obstacles.