There was a time not too long ago when most law enforcement agencies viewed night vision systems as expensive luxuries best reserved for use by specialty units. Now that prices have fallen substantially on these tools, law enforcement is just beginning to realize their capabilities. Handheld night vision tools are now used in tactical, aviation, surveillance, search-and-rescue, evidence recovery, and even patrol operations.
“Night vision” is a term that applies to two types of systems: light amplification (I2), which uses image intensifier tubes and optical lenses to help operators see in the dark; and thermal systems, which use infrared sensors to capture images of objects based on their heat signatures. Both have their benefits for law enforcement, but it’s important to understand their limitations.
Matching the Mission
The first thing that any law enforcement agency shopping for night vision must do is establish how the systems will be used. The next step is to research what night vision tools will best help your agency successfully accomplish that mission. For example, thermal systems are excellent for potential threat detection, search and rescue, and evidence recovery but are not the proper tools for surveillance of a drug dealing operation.
The reason thermal systems are not the preferred tool for surveillance of a criminal operation is that you need to be able to capture evidence that identifies the criminals involved. Thermal imagery technology has not yet advanced to the point that it can be used for facial ID. If you need to see faces, I2 night vision is your best tool.
Guy Blocker, field applications and law enforcement business development manager for FLIR Systems, believes one of the best ways to improve safety of patrol officers would be to equip their vehicles with small night vision systems officers can carry on calls.
“If I had the option of getting out of my patrol car with either a thermal scope or an I2 scope rather than take a flashlight, I would take the night vision,” he says. Blocker explains that a thermal or night vision system can help officers detect threats that are not visible with the naked eye and a flashlight. Noptic even makes a thermal threat detection system that mounts onto a patrol vehicle spotlight.
Three Questions to Ask
Blocker, who has more than 30 years of experience using I2 and thermal night vision tools in the military and working with law enforcement agencies, says there are three basic things that every night vision buyer should ask about the systems they are considering: Resolution, Range, and Field of View.
• Resolution for an I2 night vision system is generally measured in line pairs per millimeter. This is the ability to distinguish between dark and light lines, which can be the difference between seeing what the bad guy has in his hand and not seeing it. I2 night vision systems offer resolution quality up to 72 lp/mm. Resolution for thermal systems is measured in pixels, for example, 640 x 480; and a refresh rate, for example, 60 Hz. These should be very familiar resolution specs for anyone who has shopped for an HD TV.
• The range of an I2 night vision system is about the lenses and the amount of light on the target so the only range factor you can control at the time of purchase is the quality of the glass. An I2 system is like a camera lens with an image intensifier tube inside, and just like any camera lens, the quality of the image is determined by the glass. Range for thermal systems is determined by the quality of the infrared sensors. Ask your provider before buying.
• Field of view is just the amount of image you can see measured in degrees. For example, 32 degrees of a total 360. The standard field of view for night vision systems is 40 degrees but some are available with 51 degrees.
Any discussion of I2 systems always comes around to image intensifier tubes. Specifically, there are Generation 2 and Generation 3 tubes, and in the United States they are made by two companies: L3 and Harris, who recently merged. What that merger means for the I2 market remains to be seen. But Blocker says buyers should think of the tube suppliers as “part suppliers who sell the tubes to other companies” for building systems.
The difference between Gen 2 and Gen 3 tubes comes down to two things: performance and pricing. Gen 3 systems can cost a couple thousand dollars more than Gen 2 systems, and agencies need to determine if they are worth the extra expense.
Blocker argues Gen 3 systems are worth the extra expense for law enforcement agencies because of the image quality. “Law enforcement has to have facial recognition and clear identification to justify an arrest or a warrant,” he says. One option is to buy systems built around Gen 3 tubes that failed to meet military specifications (mil-spec). Such mil-spec fallouts can offer savings to buyers and they may have failed because of performance issues that cannot even be detected by the human eye. Before buying, discuss the quality of the tube with the vendor and ask to see the tube manufacturer’s specs on the tube.
Choosing the Color
I2 night vision systems come in the standard shades of green version and in white phosphor, which is black and white. There are advantages and disadvantages to both. Blocker says white phosphor systems have been around for as long as green but they did not catch on with operators because of expense and eye fatigue.
Prices have dropped substantially on white phosphor systems and adjustable gain features have made the eye fatigue issue much less of a concern. The benefit to white phosphor systems is that they allow wearers to see details they didn’t see with green. The primary disadvantage to white phosphor other than price is that it takes a little longer for the user’s eyes to fully adjust to normal conditions after using a white phosphor system.
Digital vs. Analog
One of the biggest differences between thermal and night vision systems is that thermal systems are digital while I2 night vision systems are essentially analog telescopes or binoculars fitted with light amplification electronics. Blocker says he has long anticipated that military researchers would develop a digital alternative to I2 night vision equipment, but that hasn’t happened.
Because they operate so differently it is difficult and expensive to produce equipment that can both amplify available light and provide thermal imaging. However, such systems do exist. FLIR, for example, makes two weapon sights called ADUNS (advanced dual-band universal night sight) that let operators choose between I2 and thermal images or use both simultaneously. For now, such blended systems are probably best left to special units.
Practice with It
Blocker says he’s seen some agencies buy night vision equipment and then lock it away for critical incidents and special operations only. He advises them to work with it as much as possible so that they can learn its capabilities. “Once you buy it you’ve got to take it out and use it. If nothing else, go out in your backyard and see what you can see,” he says. “Find the darkest places in your jurisdictions and see what it can penetrate. Create a training program around it so that all of your people understand what it can do, what it won’t do, and how to overcome its limitations. You can’t just turn it on and expect the world to be lit up.”