Don’t Fear The Night
- ight vision devices have been in service for over half a century and have changed the face of modern combat forever. 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. Night vision is employed in many facets of the tactical arts. Operators use it to covertly approach a target area, surveillance, navigation, vehicle operation, and precise shooting to name a few. Night vision has drastically increased the safety and operational capabilities of the modern warfighter. Night vision technology can be categorized into two main areas: light amplificaiton and thermal enhancement. Most night vision units are of the light amplificaiton variety.
- Light amplification technology is also known as image enhancement. This technology relies on a special tube, called an Image Intensifier Tube, which collects and amplifies infrared and visible light. Basically, the tube converts photons into electrons and back again.
How it works:
- The optic’s conventional Objective Lens captures ambient and some near-infrared light.
- The gathered light is funneled to the Image Intensifier Tube. This battery-powered system outputs a high voltage of about 5,000 volts to the image-tube components.
- The light energy (photons) pass through the Photocathode, which converts them to electric energy (electrons).
- The electrons continue through the tube to the Microchannel Plate (MCP) where they are multiplied by a factor of thousands. The MCP is a tiny glass disc that has millions of microscopic holes (microchannels), made using fiber-optic technology. The MCP is contained in a vacuum with metal electrodes on either side. Each microchannel is about 45 times longer than it is wide. The travelling electrons are accelerated into the MCP as they hit the first electrode, hurtling them through the microchannels by the 5,000-volt burst being sent between the electrode pair. As the electrons pass through the microchannels, they cause thousands more electrons to be released in each channel in a process called Cascaded Secondary Emission. Basically, the original electrons collide with the sides of the channels, exciting atoms and causing other electrons to be released. The newly-released electrons also collide with the sides of the microchannels, creating a chain reaction of thousands more electrons being released. While only a few electrons entered the MCP, thousands leave it by time they make their way through. The microchannels are created at a slight angle (about 5-8 degree bias) to encourage electron collisions and reduce both ion and direct-light feedback from the phosphors on the output side.
- The electrons exit the Microchannel Plate and hit a screen coated with Phosphors. The electrons maintain their position in relation to the channel they passed through. Since they stay in the same alignment as the original photons that entered the tube, they provide a perfect image upon exiting. 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.
- The green image is viewed by the operator through the Ocular Lens. The ocular lens allows for the magnification and focus of the image.
The level of performance relates to Technology Generation. The higher the Gen#, the better the performance. Performance levels are largely based ont he amount of available light necessary to produce a clear image.
- Generation 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. It was first suited for individual use in the form of the M3 Carbine; an M2 Carbine fitted with a mount designed to accept an infrared sight, the T-120. Before then, Generation 0 systems were mounted on tanks. Gen0 systems rely on Active Infrared, meaning that a projection unit called an IR Iluminator is attached to the device. The unit projections a beam of near-infrared light in the same way a flashlight projections visible light. The near-infrared light is invisible to the naked eye and reflects off objects, bouncing back to the lens of the night vision device. Gen0 systems use an Anode in conjunction with a Cathode to accelerate the electrons. While revolutionary in its day, this approach of electron acceleration distorts the image and greatly decreases the life of the tube. This technology was quickly duplicated by hostile nations and allowed enemy combatants to easily see the projected infrared beam like a becon. Generation 0 night vision is considered obsolete for modern tactical application.
- Generation 1 – The introduction of Passive Infrared marked the advent of Gen1 night vision devices. These are the “Starlight Scopes” of the 1960’s used during the Vietnam War. The most widely-issued Starlight Scopes were the AN/PVS-1 and AN/PVS-2. Generation 1 night vision devices use ambient light provided by the moon and stars to augment the normal amounts of reflected infrared in the environment and are built by connecting three image intensifier tubes in a series. The major innovation is that, unlike Gen0, Generation 1 units do not require a source of projected infrared light. Their main limitation is that they do not work well on cloudy or moonless nights. Gen1 systems use an Anode in conjunction with a Cathode, so like the previous Gen0, Gen1 units suffer from image distoration and short tube life. Many of the inexpensive night vision units offered on the market (including the Russian systems which are often mislabeled as higher generation) use Generation 1 technology. Crude by today’s standards, Generation 1 units can be considered “toys” and are not recomended for tactical application.
- Generation 2 – Developed in the 1970’s, Gen2 night vision systems mark a major improvement in image intesifier technology. Gen 2 units offer improved resolution and performance over the earlier Generation 1 and are considered to be much more reliable. Usability is greatly increased in that Gen2 systems can be made small enough for head-mounting; the first of which was the AN/PVS-5 (still in use today). The increase in sensitivity of Generation 2 night vision units is due to the addition of the Microchannel Plate to the image-intensifier tube. The MCP increases the number of electrons rather than simply accelerating the original ones, offering a significantly-less distorted and brighter image than the previous gen, while providing a 2,000 hour tube life. Generation 2 units are widely used in tactical applications today, with Gen2+ units offering images comperable with the later Gen3.
- Generation 3 – Generation 3 is the most current generation of night vision, developed in the 1980’s, and is widely issued and used by US warfighters and elite law enforcement units. The most widely recognized Gen3 units are the PVS-7 Night Vision Goggles and the PVS-14 Night Vision Monocular, though Gen3 tubes are present in many other units. There are no substantial changes in the underlying technology from Gen2, but Gen3 systems have even better resolution and sensitivity. This is because the Photocathode is made using Gallium Arsenide, which is extremely efficient in converting photons into electrons and enables detection of objects at greater distance under much darker conditions. The Microchannel Plate is also coated with an Ion Barrier to dramatically increase the life of the tube to 10,000 hours as demonstrated by actual testing and not extrapolation. Generation 3 night vision systems are considered to be the best option for today’s modern conflicts.
- Generation 4 – A strong debate rages in certain circles regarding the existance of Generation 4 night vision systems. The short answer is: yes, they do exist. However, the explanation as to why it is not in service is a bit more complicated. Development of Gen4 technology began in response to a request from the US Army in 1998 for a tube that had no ion barrier or protective coating on the Microchannel Plate. The new systems would be dubbed “Gen4” and were based on preliminary tests revealing that a filmless tube would increase performance by 20%. The problem is the cost with which this “upgrade” came. Testing revealed immediate degredation of the tube because there was, now, no protection of the Photocathode from the harmful ions generated during normal tube operations. These Gen4 tubes were, also, not meeting the 10,000 hour tube life requirement of standard Gen3 devices.
ITT and Litton, the two foremost manufacturers of PVS-14’s, began development of their Gen4 systems to meet the Army’s new Omni V Procurement Contract. During their development process, ITT found that the answer was not to remove the protective film, but to thin it. This new microfilm (10,000 times thinner than a human hair) provides the protection of the tube needed to meet the 10,000 hour tube life requirement while offering Gen4 performance. This new tube has become the system by which all other night vision units are judged. But, since it still contains a protective film, it cannot, honestly, be classified as Generation 4 (even though it provides better all-around performance). So, Generation 4 technology does exist, but it is not practical for field use.
- Generation 3 Pinnacle – PINNACLE© is a proprietary thin film technology, only available from ITT Technologies that represents an enhancement to Generation 3 image intensifier technology. To understand PINNACLE© it is important to understand film technology in Gen3 tubes and why it is needed. Light energy, or “photons” strikes the photocathode (the first surface in a Gen3 tube) causing electrons to be emitted out the other side, towards the Microchannel Plate (MCP). When they strike, they knock even more electrons out of other atoms, causing them to be positively charged (positive ions). The electrons pass through the MCP, continually multiplying and get converted back into photons for your eye to see as they pass through the phosphor screen. But, the positive ions created at the MCP travel in the opposite direction of the electrons and head back to the photocathode, striking it with significant force which can lead to damage. Suffice to say, Gen3 tubes are more sensitive to this damage than Gen2 and require protective film barrier of Aluminum Oxide to get the life needed out of the tube. The Aluminum Oxide film is placed over the MCP to absorb the positive electrons before they can travel back to the photocathode to damage it. However, this film only allows about 50% of the electrons through, reducing the sensitivity, and represents the standard Gen3 tube. The government requested Gen4, the goal of which, was to remove the film to allow 100% transfer. However, this severely cut the tube life and was deemed unacceptable. So, ITT produced a tube with a thinner film that would allow more transfer of electrons than the standard Gen3 tube. Since it also allows more transfer of the damaging positive ions, ITT reduces the electrostatic fields around the MCP/ Photocathode. So, in laymen’s terms, much more light is let through. This, however, causes another problem.On its own, a thin-filmed tube lets in too much light, so excessive light such as street lights and head lights are a big problem. So, as part of the Gen3 Omni VII package, PINNACLE© tubes contain an advanced autogated power supply, improved MCP hole size, a more sensitive photocathode, and other 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. The user can stay on mission and in the fight because his/her vision is not bloomed out. Initially, PINNACLE© tubes were only put into MILSPEC units. Night Quest and Night Enforcer units did not get PINNACLE© tubes. Eventually, ITT stopped making the dual battery configuration PVS-14 and consolidated their commercial and law enforcement lines into the Night Enforcer line. At this time, the Night Enforcer used a standard ITT Gen3 Autogated tube, while the MILSPEC AN/PVS-14 got PINNACLE© tubes. The Night Enforcers built during this period can be identified by their label which has the model number “ITTE-NEPVS-14-11.” These Night Enforcers had the same body housing and features of the AN/PVS-14, minus the PINNACLE© tube. It wasn’t long before ITT consolidated production yet again and made the decision to only produce Gen3 PINNACLE© Autogated tubes and put them in all their PVS-14’s. This really only affected the Night Enforcer line and represents the Night Enforcer model available today. The latest and greatest Night Enforcer PVS-14 has a label that reads: “ITTE-NEPVS-14-17.” This is how to identify a PINNACLE© Night Enforcer. Of course, all current production AN/PVS-14’s have had PINNACLE© tubes since they were released. The difference in item numbers is critical because there were a lot of tactical gear retailers that offered PVS-14’s along with other gear. Not quite knowing the difference, they purchased ITTE-NEPVS-14-11’s with non-PINNACLE© tubes. These became less desirable when PINNACLE© was made available to the masses in the form of the ITTE-NEPVS-14-17. Now, we see a lot of tactical gear sellers trying to off-load their older Night Enforcers at lower prices with customers who don’t understand the differences buying them.
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 (see range detection chart below). Therefore, Gen3 devices may further be defined as OMNI 3,4,5, etc. The current Omnibus contract as of 2006, is OMNI VII.
While organization by Generation is a classifiable way of categorizing night vision devices, individual units are evaluated by their specific performance attributes. These are divided into three main areas.
- Sensitivity, or Photo-response, is the image tube’s ability to detect available light and is usually measured in microamperes per lumen (uA/lm). The latest generation night vision devices have excellent sensitivity and do not require added IR illumination. Some manufacturers who use lesser-quality tubes, will add IR illuminators to their products to “boost” the perceived performance in low light areas. These units are to be avoided for any tactical work since they require an IR illuminator to achieve acceptable performance. The IR light can be detected by adversaries using night vision and can compromise the operator’s position.
- Signal To Noise plays a key role in night vision performance. 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. Signal to noise is the role of the Micro-channel Plate in Gen2 and 3 night vision systems.
- Resolution is the unit’s ability to resolve detail in the image. Measured in line pairs per millimeter (lp/mm), higher resolution produces a cleaner image. Some manufacturers put magnified optics in their systems to give the illusion of higher-resolving systems. However, this sacrifices field-of-view and can give the operator a disproportionate idea of their environment if they are relying on the night vision unit for navigation purposes. Some units give the option of higher magnification, but it is not necessary for effective function of the system. The highest possible resolution is required for accurate target discrimination aiding in preventing blue-on-blue and blue-on-white incidents.
This chart is based on night vision systems with a 1x lens. Recognition range will increase when greater magnification is used.
Night Vision 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 through night vision units. For example: a shiney dark-colored jacket may appear brighter than a light-colored jacket with a dull surface.
- 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; therfore, the light reflecting off fog or heavy rain causes much more light to go toward the night vision unit and may degrade its performance.
- This is a faint hexagonal pattern which is the result of the manufacturing process.
- 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.