Night vision devices have been in service for over half a century and has changed the face of modern combat forever. With Night Vision the modern warfighter or law enforcement professional can today, move, shoot and communicate effectively in complete darkness, giving him/her a distinct advantage over their “night blind” enemies. Operators can use it for, surveillance, navigation, vehicle operation, precise shooting or to covertly approach a target area just to name a few examples.
“There are two main types of Night Vision; light amplification and thermal enhancement. Most units are of the light amplification variety.”
UNDERSTANDING LIGHT
Light consists of particles known as photons and the flow of those particles as a wave. The amount of energy in a light wave is related to its Wavelength: Shorter wavelengths have more energy (violet) and longer wavelengths have less (red).
ELECTROMAGNETIC SPECTRUM
Infrared light, the Night Vision portion of the spectrum and can be split into three categories:
Near Infrared
Closest to visible light, has wavelengths that range from 0.7 to 1.3 microns. Used by a variety of electronic devices, such as remote controls.
Mid Infrared
Mid IR has wavelengths ranging from 1.3 to 3 microns. Used by a variety of electronic devices, such as remote controls.
Thermal Infrared
Thermal IR occupies the largest part of the infrared spectrum with wavelengths ranging from 3 microns to over 30 microns.
The main difference in the three infrared categories is that Thermal IR is actually emitted by an object instead of reflected off it. This stems from what is happening at an atomic level. After the electrons in an atom achieve a high energy orbit (once they are heated), they eventually return to their ground state. This is achieved by releasing energy in the form of Photons – a particle of light. The photon emitted has a very specific wavelength (color) that depends on the state of the electron’s energy when the photon is released. Anything that is alive uses energy and therefore, generates heat. Many inanimate objects also generate heat, firing off photons in the Thermal Infrared Spectrum. Objects that become very hot will begin to emit photons in the visible light spectrum, such as a flame. Thermal imaging takes advantage of this infrared emission.
THE TWO TYPES OF NIGHT VISION
Light Amplification
Light amplification technology is also known as image enhancement. This technology relies on a special tube, called an Image Intensifier Tube, which converts photons into electrons back again to amplify infrared and visible light.
Thermal Imaging
All objects emit infrared energy. The amount of infrared energy emitted is proportional to the amount of heat an object or organism produces. Thermal imagers sense this infrared energy and provide a thermal signature of a scene.
Light Amplification
HOW LIGHT AMPLIFICATION WORKS
Infrared light, the Night Vision portion of the spectrum and can be split into three categories:
1
An Objective Lens captures ambient and near-infrared light.
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The light is funneled to the Image Intensifier Tube which runs on 5,000 volts of battery power.
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Light energy (photons) pass through a Photocathode, which converts them to electric energy (electrons).
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The electrons move on to the Microchannel Plate (MCP) where they are multiplied by a factor of thousands via a chain reaction caused by collision with the microchannel walls.
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The electrons exit the Microchannel Plate and hit a screen coated with Phosphors. The energy of the electrons cause the phosphors to reach an excited state, releasing photons. The phosphors create the green image on the screen that characterizes modern night vision.
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The green image is viewed by the operator through the Ocular Lens. The ocular lens allows for the magnification and focus of the image.
CLASSIFICATIONS
GEN 0
The original night vision system created by the United States Army was first used in combat during the Battle of Okinawa in 1945 during World War II and later in the Korean War. These scopes required a secondary source of projected infrared light. Now is considered obsolete for modern tactical application.
GEN 1
Marked by the introduction of Passive Infrared, these are the “Starlight Scopes” of the 1960’s used during the Vietnam War. Generation 1 units do not require a source of projected infrared light. They do not work well on cloudy or moonless nights and are now considered “toys” and are not recomended for tactical application.
GEN 2
Developed in the 1970’s, these systems mark a major improvement in image intesifier technology due to the addition of the Microchannel Plate to the image-intensifier tube. G en 2 units are widely used in tactical applications today, with Gen2+ units offering images comparable to Gen3.
GEN 3
The most current generation of night vision; developed in the 1980’s, it is widely issued and used by US warfighters and elite law enforcement units. Gen3 systems have improved resolution and sensitivity due to a Gallium Arsenide Photocathode, which is extremely efficient in converting photons into electrons and enables detection of objects at greater distance under much darker conditions. These systems are considered to be the best option for today’s modern conflicts.
GEN 3 PINNACLE
PINNACLE© is a proprietary thin film technology, only available from ITT Technologies that enhances Generation 3 image intensifier technology. It allows much more light to be let through while maintaining a long tube life. One drawback however is that it lets in too much light causing street lights and headlights to be problematic. The Gen3 Omni VII package, fixes this with a series of improvements which eliminate the temporary blindness caused by exposure to light too bright for the night vision device and drastically reduce the halo effect around distant light sources.
GEN 4
Primarily used as a marketing term, as no true "Generation 4" has been designated by the military. Previously, it was believed that Filmless technology would become designated as "Generation 4," however, modern Unfilmed tubes have retained the "Gen. 3" designation. Some advanced Generation 2 architecture units have also been referred to as "Generation 4," "4th Gen.," or "4G" by their manufacturers.
OMNI
The US Army procures night vision devices through multi-year/multi-product contracts referred to as “Omnibus” – or “OMNI.” For each successive OMNI contract, ITT has provided Gen3 devices with increasingly higher performance. Therefore, Gen3 devices may further be defined as OMNI 3,4,5, etc. The current Omnibus contract as of 2010, is OMNI VIII.
PERFORMANCE ATTRIBUTES
Sensitivity
Also known as Photo-response, is the image tube’s ability to detect available light and is usually measured in microamperes per lumen (uA/lm).
Signal to Noise
Plays a key role in night vision performance. The role of the Micro-channel Plate, it is the unit’s ability to transfer a strong signal from input to output and is usually referenced as a ratio, 19:1 for example.
Resolution
The unit’s ability to resolve detail in the image. Measured in line pairs per millimeter (lp/mm), higher resolution produces a cleaner image.
DETECTION RANGES
| DETECTION RANGE | FULL MOON | QTR MOON | STARLIGHT | OVERCAST |
| (6′ MAN with 1x Mag.) | (0.1 lux) | (0.01 lux) | (0.001 lux) | (0.0001 lux) |
| GEN 3 | 890 YDS | 850 YDS | 601 YDS | 220 YDS |
| GEN 2 | 690 YDS | 650 YDS | 430 YDS | 160 YDS |
| WITHOUT NV | 250 YDS | 50 YDS |
IMPORTANT CHARACTERISTICS
Textures, Light & Dark
Objects that appear light during the day, but have a dull surface may appear darker than (normally) dark objects with highly reflective surfaces. For example: A shiny dark-colored jacket may appear brighter than a light-colored jacket with a dull surface.
Depth Perception
Night vision does not present normal depth perception. The naked eye has an approximate 190 degree field of view. Most night vision goggles have only a 40 degree field of view. This is somewhat tempered by the advent of the night vision monocular which keeps one eye free, reducing the tunnel-like view. This greatly increases overall depth perception and situational awareness since the unaided eye can maintain peripheral vision. Even so, depth perception is somewhat limited, which can hamper the operator’s ability to navigate cluttered terrain and perform simple tasks that require hand/eye coordination. Distance estimation is also degraded, requiring much training for high speed driving while using night vision.
Fog And Rain
Night vision is very responsive to reflective ambient light; therefore, the light reflecting off fog or heavy rain causes much more light to go toward the night vision unit and may degrade its performance.
Honeycomb
This is a faint hexagonal pattern which is the result of the manufacturing process.
Black Spots
A few black spots throughout the image area are inherent characteristics of all night vision technology. These spots remain constant and should not increase in size or number.
Thermal Imaging
HOW LIGHT THERMAL IMAGING WORKS
1
A special lens focuses infrared light that is emitted by all objects.
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This focused light is then scanned by a phased array of infrared detector elements that create a detailed temperature pattern called a Thermogram.
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Once the signal processing unit sends the information to the display it appears as various colors depending on the intensity of the infrared emission. Most thermal imaging devices can sense temperatures ranging from -4 degrees Fahrenheit (-20 degrees Celsius) to 3,000 F (2,000 C), and scan at a rate of 30 times per second. This type of imaging is able to detect people and vehicles in near-absolute darkness with little or no ambient lighting.
CLASSIFICATIONS
UN-COOLED
Un-Cooled is the most common type of thermal imaging device. The infrared detector elements are contained in a unit that operates at room temperature. This types of system is completely quiet, activates immediately and has the battery built right in.
CRYOGENICALLY COOLED
More expensive and more susceptible to damage, Cryogenically Cooled Thermal Imaging Devices have elements sealed inside a container that cools them. to below 32 F (zero C). The advantage of this system is much higher resolution and sensitivity, Cryogenically-cooled systems can “see” a difference as small as 0.2 F (0.1 C) from more than 1,000 ft (300m) away, this is enough to tell if a person is holding a gun at that distance. Unlike traditional image-enhancement night vision technology, thermal imaging is great for detecting people and vehicles in near-absolute darkness with little or no ambient lighting.
