FLIR Infrared Thermal Night Vision versus Image Intensified Night Vision

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FLIR Scout vs PVS-14
At least once a week someone will pick up one of our thermal imagers and say with surprise “Oh, it’s not green inside?” because somewhere along the line they thought all night vision works the same.

There are a number of key differences between the thermal imagers FLIR makes and traditional image-intensified night vision devices (NVDs)

FLIR Thermal image vs I2 Night vision imageFrom a technological standpoint there are very different things happening when you run thermals compared to running an NVD. But there’s also some decisions to be made about what might work best for you, depending on what you are asking your equipment to do.

Night vision intensifiers are amplifying the existing light. This means that the filter inside of them is enhancing light that is barely there and filtering it through a series of photon replicating plates to your eye. There’s a lot more going on in there, but the core idea is that an NVD takes what light you have already and makes more of it.

Thermal imagers on the other hand use a microbolometer to detect the infrared radiation emitted by objects around you. When infrared radiation is focused onto the uncooled detector, the heat absorbed causes changes to the electrical properties of the detector material. These changes can be compared to a base value and used to create a thermal image. The key advantage here is that thermals will highlight and differentiate the environment. Rather than simply brightening the image, they are reading the radiation which produces a full spectrum of different heat sources.

At its most basic, Night vision comes in three common generations, with an auto-gating feature that can be applied to any of them.

Similarly, Thermal imagers come in three common resolutions, also with a high refresh-rate feature that can be applied to any of them.

    FLIR scout BTS

    Thermal Imagers

  • 240×180 Detector is the smallest thermal detector, which means there is a grid of 28800 detection points on the image. These sizes are generally rated for a maximum of 300 yards to detect a man sized heat signature.
  • 320×240 Detector is the standard thermal detector available in the Scout line of imagers. It extends the range out to 500 yards, with a 2X extender, this core is able to push out to 900 yards to detect a man sized target.
  • 640X480 Detector is the enhanced size of a military core. Depending on lens configurations, these units can reach out to a kilometer with their detection ability.
  • 30hz Upgrade: Exportable thermal units refresh their image at 7.5hz, which can cause the image to blur or “ghost” in quick moving situations. The enhanced 30hz refresh rate is only available to US citizens, and results in a much sharper and responsive image. These 30hz units are sold under the FLIR Law Enforcement Line.
    PVS-23 Night vision

    Image Intensifiers

  • Gen 1 night-vision relies heavily on assistance from an IR light. These may appear hazy or cloudy and have a higher noise ratio.
  • Gen 2 units are a much brighter and clearer image than Gen 1. But have a limited depth of field compared to the higher generations. That means adjusting focus when looking close and far.
  • Gen 3 devices are the highest end imagers. These provide the widest depth of field where everything is in focus. Military night vision goggles are sometimes called Generation 4 devices, although the US Army does not use that distinction.
  • Auto-Gating Upgrade: Because night vision devices amplify existing light, they can overexpose when hit by daylight, which in turn can damage parts of the imaging tube. Autogating allows a user to safely move between bright light and dark spaces by rapidly activating and deactivating the enhancement plate when too much light is detected.

So which is better?

That’s a hard question. Most western militaries issue their soldiers with NVGs of some kind, as the ability to conduct operations at night has proven a major advantage in all our recent conflicts. Thermal units have come down dramatically in price, more than 50% in the past ten years. But they are generally still more expensive than common night vision units.

NVD soldierGen 1 nightvision may only cost $300, but it borders on being unusuable with its filmy view and limited range. The starting point for a thermal camera is much higher, $1999 for the FLIR PS24 but you get the full functionality of the technology out of the box.

The prices escalate differently between the technologies though. The LS 64 with a 640X512 detector and running at 30hz is only $5999. That’s compared to an autogated PVS-23 Gen 3 night vision device which comes in at a whopping $8599. There is a massive variation between night vision, anywhere from $300 to $9k. A long distance FLIR unit can cost over ten thousand dollars, but the handheld FLIR units are all within $2k-$8k.

Those expensive long distance thermal units do have the benefit of reaching further than any hand held night vision device. A FLIR BTS unit with a 100mm lens can reach out over a kilometer, while most night vision scopes are only 3X or 5X magnification. There’s nothing in the lineup of traditional nightvision devices that will do long range like the BTS units with their telephoto lenses.

Night vision devices are better for the infantry. Because all these units are sensitive to IR light you can use beacons, friendly indicators, and IR lasers for a variety of tools that are only visible to people wearing nightvision. Thermal units only identify heat, so they don’t care which uniform your wearing, but they can pick out a camouflaged person from their surrounding instantly.

FLIR Scout TS32FLIR units are also easier to pickup and use. Make sure they’re charged, and that’s pretty much all the maintenance they need. There’s no finicky focusing like the first two generations of NVDs, and no light restrictions at all. This means they also aren’t constrained to night-time activities. As an outdoorsman, FLIR can have multiple roles in your pack: As a scanning tool, as a confirmation tool, and as a night navigation unit.

For anyone hunting or looking to remove varmints, the flexibility of FLIR makes it a superior option to regular nightvision. The Armed Forces keep FLIR options in most vehicles and spotter teams because of its superior ability to isolate potential threats and anything of interest in an environment.

From our experience, and what we’ve learned from different people using different technologies, the FLIR units are preferable for most kinds of work taking place at night. NVDs have a limited role when many people are all wearing NV goggles working together, while a thermal image provides a wider range of information to an individual user. But what do you think? Thermal or NVD? Feel free to comment here, or join the discussion on our Facebook page.

If you’ve made up your mind, and are looking for a thermal unit of your own, you can see our entire FLIR line on

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One Comment »

  • 19 September 2012 at 3:43 am
    Nathan Luke said:

    Both of these equipments have their own uses and advantages depending on the situation. If I were to decide, I’d pick both becase they can be used in different situations. There are instances where one is more beneficial to use than the other so you can never tell which is more important. In the military they choose both simply because they won’t leave any situation to chance.

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