NIGHT VISION TECHNOLOGY BASICS
The first night vision equipment devices were developed for military application during World War II to aid missions in very low-light and night-time conditions. A night vision device gathers available light particles called photons, and through electrical, and chemical process amplifies them to produce usable image in near complete darkness. The resulting image is monochrome green, or black and white.
All night vision equipment devices consist of the four main parts: 1. Objective lens 2. Eyepiece 3. Housing 4. Electron tube or Image Intensifier Tube (IIT). The Image Intensifier Tube is the most important, and performance determining part of a night vision device. After wide-spread use during the Vietnam War, the night vision technology has started to evolve, leading to major breakthroughs.
Each significant performance leap in night vision technology and its capabilities has become known as a “generation”.
NIGHT VISION GENERATIONS
The first night vision devices fielded at the end of the WW II were active, and based on the anode image intensifier tubes with S-1 photocathode. Large infrared spotlights were required to illuminate targets, as the technology at the time did not allow significant light amplification to produce usable low light images.
GENERATION 1 (GEN I)
Developed by the US Army, the Gen 1 night vision devices were derivatives of the Gen 0 active devices, but did not require infrared spotlight to operate. Built around an S-20 photocathode with greater light sensitivity, they relied on ambient light and amplified available light around 1000x.
GENERATION 2 (GEN II)
The second generation night vision devices (Gen 2) represent the major technological breakthrough compared to Gen 0 and Gen 1 night vision devices. The Gen 2 image intensifier tubes are based on micro-channel plate (MCP) – a honeycomb-like wafer designed to trap photons, and increase their number as they pass through it. The Gen 2 also has an S-25 photocathode with greater light sensitivity. These improvement lead to a much brighter night vision image with higher resolution, capable of light amplification around 20,000x, allowing the devices to function in almost complete darkness and moonless nights.
GENERATION 3 (GEN III)
The third generation night vision devices (Gen 3) also use the Micro Channel Plate (MCP) developed for Gen 2. The main advancement found in Gen 3 night vision devices is a gallium arsenide (GaAs) photocathode, which greatly improves light amplification and system resolution. To increase the image intensifier tube useful life, the MCP in Gen 3 is coated with an ion barrier film. The coating, however, reduces the effectiveness of the MCP, as it allows fewer photons to pass through. The ion barrier is also the main reason for the “halo” effect observed during the bright light exposure. The light amplification of the Gen 3 night vision devices is also much greater, at around 30,000–50,000.
GENERATION 3+ PINNACLE /AUTOGATED /FILMLESS (GEN 3 CURRENT PRODUCTION)
The current production Gen 3 night vision image intensifiers built around the same concept of using micro channel plate to amplify available light, originally employed in Gen II image intensifiers. However, today the Gen 3+ night vision image intensifiers have far better performance compared to Gen 2 or early Gen 3 night vision technology.
THE MAIN DIFFERENTIATORS INCLUDE:
Gated Power Supply – Automatically adjusts photocathode voltage to control gain, and adapt to changing light conditions.
Removed Ion Barrier Film – Increases MCP effectiveness, allowing more photons through MCP and reducing image noise.
Even though these technological advancements significantly improve performance of night vision devices, the US Army Night Vision & Electronic Sensors Directorate (governing body) overseeing night vision technology, has not yet designated it as Generation IV.
Therefore, officially, the Gen IV night vision devices don’t exist at this time.
All the night vision generations described above are official US Army night vision designations. Other variants and derivatives of night vision devices designations, typically used in marketing materials for civilian market, are not recognized by NVESD, and oftentimes are misleading on purpose.
FOM – FIGURE OF MERIT
Significant improvements in the Gen 3 night vision technology allowed to produce new Gen 3 night vision devices that would significantly surpass in performance earlier Gen 3 night vision devices. In the early 2000’s US Government has determined that the term “Generation” doesn’t fully describe the performance level of a night vision device for the purpose of export control. Parameters that significantly affect overall performance capability of a night vision image intensifier are the Signal to Noise ratio and the Resolution, measured in line pairs per millimeter.
FOM or the Figure of Merit, is a number calculated by multiplying the Signal-to-noise ratio by the resolution of a night vision image intensifier.FOM number allows quickly estimate general performance level of the specific night vision image intensifier, and consequently the night vision device built around it.
All export licensing decisions are based on the night vision performance level measured in FOM.