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Own the Night – Thermal Imagers

From the archives: RECOIL Magazine Issue 14, September/October 2014

Thermal Imagers Are Finally Coming Within Reach

“Get to da chopper!” Who doesn’t love the classic Schwarzenegger film Predator, with the iconic alien creature that has infrared vision and only sees differences in temperature? The ex-Governator is eventually able to best the alien, in part by masking his body heat. Well, you too can see like a Predator, with the help of a thermal imager.

Thermal imagers are comprised of infrared imaging systems that detect infrared radiation, deduce the temperature of objects in view, and produce images of it. The warmer an object, the more radiation it emits — thus a thermal imager allows you to see temperature variations. As a result, warm-blooded animals (whether the multi-legged or two-legged kind) are easily viewed through the imager and appear quite distinct against the surrounding environment, which usually has a different thermal signature. The benefits of this are quite clear, whether you are hunting, conducting surveillance or security, on duty, or deployed. It even has industrial and medical applications, to detect heat leaks, fires, and other clinical indications.

However, this decidedly badass and useful technology has always been extremely expensive due to the cost of the components needed, from the germanium lenses needed to pass the required infrared wavelengths to the specialized sensors and electronics. In recent years, prices have continued to creep lower and lower, finally bringing these products into reach (sort of) for consumers.

Keep in mind that thermal imagers have more in common with digital video cameras than traditional riflescopes or binoculars. Whereas a traditional scope has a number of lens elements through which you view your target, thermal imagers have lens elements in front of a sensor (microbolometer, to be exact), and a display on which you can view the image from the sensor — just like your Handycam. These are digital systems in which the image data is read from the sensor and shown on the display, as opposed to traditional night vision that are typically analog systems, amplifying available light. Several of the models featured in this article can output a video feed or even allow you to take screen shots of what you’re viewing through the imager.

N-Vision TC35 mounted in front of a Leupold Mark 6 1-6x scope, on a Seekins Precision Battlefield 16-inch with stainless match barrel in .300 BLK and a 15-inch Seekins SP3R handguard. FLIR RS64 on a BCM upper with 14.5-inch mid-length Enhanced Light Weight Fluted barrel and BCM KMR handguard. IR Defense IR Hunter IRH640-35 on a Carbon Arms upper with 18-inch stainless Nordic barrel and 15-inch Carbon Feather handguard.

N-Vision TC35 mounted in front of a Leupold Mark 6 1-6x scope, on a Seekins Precision Battlefield 16-inch with stainless match barrel in .300 BLK and a 15-inch Seekins SP3R handguard. FLIR RS64 on a BCM upper with 14.5-inch mid-length Enhanced Light Weight Fluted barrel and BCM KMR handguard. IR Defense IR Hunter IRH640-35 on a Carbon Arms upper with 18-inch stainless Nordic barrel and 15-inch Carbon Feather handguard.

TYPES OF THERMAL IMAGERS

For our purposes, thermal imagers are generally available in the following forms:

Handheld units: These models are meant to be used like a monocular, for observation not targeting.

Dedicated riflescopes: Dedicated thermal riflescopes are rated to withstand recoil and mount directly to a weapon. Note that they operate only in thermal mode, so unless you have an offset-mounted secondary optic, you cannot use the weapon normally when the thermal unit is in play.

Clip-on units: Clip-on thermals attach in front of a regular day scope to provide thermal capabilities only when needed. They can also often be used as standalone thermal scopes or handheld units when detached. Clip-on units offer more versatility, but are more costly.

PHOTO COURTESY OF IR DEFENSE

PHOTO COURTESY OF IR DEFENSE

For those who require targeting capability, choosing between a dedicated thermal scope and a clip-on unit depends on your budget and intended applications. If you can foot the bill, clip-ons allow you to leverage your investment in several ways. But keep in mind that when used in front of a day scope, you’re putting about 2 pounds of weight on the front of your rifle. This may come part and parcel for military personnel in prime physical condition who require the flexibility to add or remove thermal capability as needed on their primary weapon without affecting its zero. For an orthodontist who’s looking to enjoy a nighttime hunt — well, if he can afford thermals in the first place, he might not mind having a lighter, dedicated rig.

Speaking of zeros, dedicated thermal scopes require some extra effort in this regard. Since they only function in thermal mode, you must zero them using a target that you can see through the scope; you can’t just use a piece of paper — disposable hand warmers or frozen water bottles are commonly used (though not overly precise). You can also use steel targets, and there are even some specialized thermal targets (e.g. from IR Defense and MGM Targets), designed to present a more precise thermal signature for zeroing. Whether using dedicated or clip-on units, be sure to confirm your zero through the thermals before relying on them for any serious use.

Low-power traditional riflescopes tend to work the best with clip-on thermals. Remember that the imager goes in front of the scope, so you will essentially be looking through your scope at a video screen. As a result, 1x is usually the most versatile setting — otherwise you’ll just be zooming in to look closely at the middle of the actual display. Zoom in too far and you’ll start seeing individual pixels. You can use red-dot sights, but in our experience it doesn’t work as well. A red-dot sight simply superimposes its reticle on the target; there’s infinite eye relief. It’s essentially like looking through a window, so when you have a clip-on thermal in front of a red-dot, you’re basically looking at the thermal’s display from quite some distance away from where you’d normally want your eye to be — as a result, you generally can’t see the entire display. A traditional riflescope, on the other hand, focuses its image and has a specific eye relief where you need to be to view it clearly; as such you’ll have a better view of the thermal display.

WHAT TO LOOK FOR

Some key characteristics of thermal imagers include the following:

Sensor Resolution: Typical sensor resolutions are approximately 240×180 and 320×240 pixels, with premium models available with 640×480 sensors. As with digital cameras, the greater the resolution, the more visual detail and more usable field of view that is available. So lower resolution sensors will generate more “pixelated” images with less detail. Really, the only reason to go with lower resolutions is cost. Note that the sensors in these products detect radiation in the long-wave infrared bands (LWIR).

RECP-140900-THERMALS-reference01

Focal length/field of view: Just as with a digital camera, the type of lens (i.e. wide-angle or telephoto) and size of the sensor determines what you see on the display, such as how much of the scene in front of you. You can’t necessarily directly compare focal length specifications from one product to another, so we suggest looking at the field of view for each imager (usually expressed in degrees). There’s no right answer here — depending on your particular application, you might want a wide field of view, or you might want a narrower one to allow you to see more detail at longer distances. You can often choose between models from the same manufacturer with different lens elements in front of the sensor to optimize for your needs.

Refresh Rate: This represents the number of times per second that the image is refreshed — e.g. 9Hz is nine times per second and 30Hz is 30 times per second. 9Hz is less expensive (and also exempt from ITAR restrictions, of note for those who wish to take them overseas), but results in a choppy view. If you go to a movie theater, for instance, you’ll usually be seeing the film projected at 24 frames per second. So, 30Hz systems are much better for serious use where you need to track movement or you’re moving yourself — e.g. quickly moving game, scanning, duty use, etc. 60Hz systems are also available, but get more expensive and are typically sought after for applications like recording the video feed or vehicle work where the higher frame rate of 60 times per second helps with fast-moving action.

Power source: Some units use internal rechargeable batteries; others use standardized replaceable batteries such as CR123 or lithium AA. Internal rechargeable batteries present the usual pros and cons — convenient and cost-effective, until you realize right before a big hunt that you forgot to plug it in or if you’ve had to use it heavily in the field and would benefit from being able to swap in fresh batteries. However, they can pack greater battery life into a compact package. In any case, all manufacturers try to make their units as efficient as possible to increase run time.

PHOTO COURTESY OF FLIR

PHOTO COURTESY OF FLIR

Magnification: It’s important to understand the difference between optical and digital magnification. Optical zoom uses lenses to magnify the image, just like your trusty ACOG or Nightforce scope. Digital zoom simply blows up the digital image on the display, making the already limited number of pixels appear larger — so 2x digital zoom actually decreases your image quality by half. With the high cost of germanium lenses, the products we’re looking at in these price ranges only have digital zoom capability.

Processing capability: Since thermal imagers are digital systems, they are essentially small computing systems. Better processing capability to process, enhance and display data from the sensor provides better results.

Tactical Night Vision Company (TNVC) is a leading provider of night vision solutions; its director of operations, Chip Lasky, gets to play with all the coolest gear since he works with a wide variety of manufacturers. He advises that the first three characteristics (resolution, field of view, and refresh rate) are the most important to determine first to match up with your budget and intended use. He also strongly urges consumers to stick with reputable brands, with “pennywise, pound foolish” being his mantra here.

USING THERMALS

Despite what you may have seen in Hollywood films, these thermal imagers usually provide a black and white image, sometimes with color highlights — based on the detected temperatures. Since there’s really only one dimension of information being displayed (the temperature), the temperature value is translated into a shade of gray between white and black. Users can select between hotter temperatures showing up as white or black — hence the commonly used terminology of “white hot” or “black hot.” Prevailing conditions will determine which is easier to use (e.g. desert versus snow). Color highlights can be added with some models to make it easier to quickly see hot spots, but the underlying data is basically the same — so once you get the hang of things you may find yourself staying in black and white mode.

PHOTO COURTESY OF FLIR

PHOTO COURTESY OF FLIR

What you see through a thermal imager is differences and variations in temperature. We humans are not accustomed to viewing the world in this manner, so it really does take some time to get comfortable and be able to more quickly interpret what you’re seeing. It’s actually pretty easy to “get lost” in the thermals — and end up misinterpreting distances, objects, and animals (or people). Jim Smith (owner of Spartan Tactical and a 20-year veteran who served in the U.S. Army Rangers and the elite Delta) trains military, law enforcement, and civilians. “In general, end users should train or practice at least 15 to 30 hours with thermals before using them for an armed engagement or a hunt,” advises Smith. He describes students in his night hunting courses losing perspective of distance and size, subsequently thinking a jackrabbit up close is a hog farther away. Or worse, mistaking a deer for a hog — taking the wrong game could be very bad news where you live, turning your hog eradication expedition into an illegal poaching trip, so don’t take this lightly.

Given the lack of visual details on objects when temperatures do not vary too much, Lasky advises that thermals are outstanding for detection, but more challenging to use for identification. Still, in the dark of night, it is hard to beat thermals when you are concerned with warm-blooded creatures. For safety and security, it’s much easier to scan your property with thermals to determine if anyone’s out there. Hiding from thermals is much more difficult than from traditional night vision (NV) devices — you can pick out a person on the edge of a wood line with regular NV, but as they withdraw back into the woods you’ll need thermal. For hunting, Smith estimates that his students are several times more effective with thermals than image-intensifying NV (whether in-line or lasers). For example, a bobcat moving very slowly is extremely difficult to see with NV, but simple to detect with thermals. Additionally, thermal scopes are valuable for follow up; if you wound an animal, you can pretty quickly find its blood trail.

PHOTO COURTESY OF IR DEFENSE

PHOTO COURTESY OF IR DEFENSE

Environmental conditions can affect the performance of thermal imagers. Angelo Brewer, sales and distribution manager for FLIR, explains that “humidity is the No. 1 factor that can cause issues,” since water blocks infrared energy. “High humidity, dense fog, falling snow, or a heavy rain can all cause challenges.” Extremely hot conditions can decrease the variance in temperature between objects of interest and the background, making it more difficult to distinguish them. Mammals also sweat and can then appear cooler. Again, the more time you spend behind thermals, the more you will learn how to quickly interpret what you see.

A quick reminder as well on another potential misconception — thermal imagers do not work through glass. If you were hoping to stand inside your home and scan your surroundings from behind your locked doors and windows, think again. You’ll just see reflections of yourself and large blobs of gray. The same applies for looking into or out of vehicles.

Once you try a thermal imager, you’ll find yourself intoxicated by the capabilities they provide. So sell that old Ford Focus and get yourself some thermals instead! Following are some examples of products currently on the market.

HANDHELD THERMAL IMAGERS

eotech-x320-thermal-imager

Make and Model:
EOTech X320
Focal Length / Field of View:
25mm / 12 deg
Refresh Rate:
30Hz
Sensor Resolution:
320 x 240 pixels
Display Resolution:
320 x 240 pixels
Digital Zoom:
1x, 2x, 4x
Batteries / Battery Life:
2x AA / 6 hrs (lithium) or 2 hrs (alkaline)
Dimensions:
5.25 x 4.5 x 2 in
Weight:
0.77 pounds
Warranty:
3 years
MSRP:
$3,799
URL:
www.eotechinc.com
Notes:
The only thermal imager from EOTech that is remotely affordable, the X320 provides a lot of practicality and ruggedness in a compact package. It floats, is waterproof to 1 meter, and is rated to survive a 2-meter drop. Controls on the device conform to the KISS principle, with only a click wheel to control brightness and a few options and a manual focus knob. The focus knob is very stiff (due to waterproofing), but it allows you to manually dial in focus for a crisp image. However, there’s no diopter adjustment, and other settings must be configured utilizing the included PC software. There’s an on-screen display with estimated temperature readout, and you can select white hot, black hot, or three other temperature-based colorization options. It utilizes an L-3 core and also has video out.

flir-ps24-and-ps32r-thermal-imagers
Make and Model:
FLIR PS24
Focal Length / Field of View:
19mm / 24 deg
Refresh Rate:
9Hz
Sensor Resolution:
240 x 180 pixels
Display Resolution:
320 x 240 pixels
Digital Zoom:
1x
Batteries / Battery Life:
Internal rechargeable Li-Ion (USB) / 5 hrs
Dimensions:
6.7 x 2.3 x 2.4 in
Weight:
0.78 pounds
Warranty:
2 years
MSRP:
$1,999
URL:
www.flir.com

Make and Model:
FLIR PS32R
Focal Length / Field of View:
35mm / 13 deg
Refresh Rate:
9Hz
Sensor Resolution:
320 x 240 pixels
Display Resolution:
640 x 480 pixels
Digital Zoom:
1x, 2x
Batteries / Battery Life:
Internal rechargeable Li-Ion (USB) / 5 hrs
Dimensions:
6.7 x 2.3 x 2.4 in
Weight:
0.77 pounds
Warranty:
2 years
MSRP:
$3,999
URL:
www.flir.com
Notes:
FLIR has a storied history in this category, pioneering thermal imagers since the 1970s. In fact, its cores are in all of the products on these pages except two. A few years ago, FLIR introduced the PS Scout line of thermal imagers, to offer consumers the opportunity to purchase thermals without mortgaging their homes. The teardrop-shaped and very portable PS units are a nice entry point to the world of thermals. Pushbutton controls are on top, along with a handy small LED light. It has white-hot, black-hot, and four coloration modes, as well as FLIR’s proprietary image enhancement processing. Choppiness due to the 9Hz frame rate is definitely noticeable, though, and can be distracting depending on the task at hand. There’s a diopter adjustment, and it has fixed focus, which is convenient for quick scanning but the resulting images were not always as crisp as the other units with manual focus. The units are sealed against dust, drop test rated to 1 meter, and waterproof to 1 meter (IP67 rating).

pulsar-hd38s-thermal-imager

Make and Model:
Pulsar HD38S
Focal Length / Field of View:
38mm / 14.4 deg
Refresh Rate:
30Hz
Sensor Resolution:
384 x 288 pixels
Display Resolution:
640 x 480 pixels
Digital Zoom:
1x, 2x (effective 2.1x, 4.2x)
Batteries / Battery Life:
4x AA, 5 hrs
Dimensions:
7.9 x 3.4 x 2.3 in
Weight:
0.96 pounds
Warranty:
3 years
MSRP:
$4,560
URL:
www.pulsarnv.com
Notes:
The Pulsar HD38S is built around a French sensor from ULIS. The display has a slight sepia tone to it and has three different image processing modes to emphasize contrast and detail. It has white-hot and black-hot modes. There are pushbuttons on top and a click wheel to navigate through an on-screen menu system. It has a base optical magnification of 2.1x, which can be doubled with digital zoom. The manual focus knob allows you to dial in a crisp image. It also has diopter adjustment and video out capabilities. As a handheld imager, it’s a bit chunkier and heavier than the others, and also slower to power up. It comes with two easily swappable battery containers that each hold four AA batteries and is water resistant (IPX4 rating). Optional rechargeable external battery packs are available.

DEDICATED THERMAL SCOPES

flir-rs24-and-rs64-2-16x-thermal-imagers-and-gun

Make and Model:
FLIR RS24
Focal Length / Field of View:
13mm / 20 deg
Refresh Rate:
30Hz
Sensor Resolution:
240 x 180 pixels
Display Resolution:
640 x 480 pixels
Digital Zoom:
1x
Batteries / Battery Life:
Internal rechargeable Li-Ion (USB) / 4 hrs
Dimensions:
8 x 3.3 x 2.9 in
Weight:
1.79 pounds
Warranty:
3 years, 10 years on sensor
MSRP:
$3,499
URL:
www.flir.com

Make and Model:
FLIR RS64 (2-16x)
Focal Length / Field of View:
60mm / 10 deg
Refresh Rate:
30Hz
Sensor Resolution:
640 x 512 pixels
Display Resolution:
640 x 480 pixels
Digital Zoom:
1x, 2x, 4x, 8x (effective 2x, 4x, 8x, 16x)
Batteries / Battery Life:
Internal rechargeable Li-Ion (USB) / 4 hrs
Dimensions:
8.5 x 3.3 x 2.9 in
Weight:
2.1 pounds
Warranty:
3 years, 10 years on sensor
MSRP:
$8,999
URL:
www.flir.com
Notes:
FLIR has a range of dedicated thermal sights to fit your needs, from the RS24 to the RS64 2-16x — with 13mm, 19mm, 35mm and 60mm lenses, three different sensor sizes, and some selections with 60Hz frame rates. Seeing that big piece of bulbous germanium on the RS64 should already have you bracing for its price. Some have fixed focus and the top end variants have a manual focus adjustment; there’s also a diopter adjustment on the eyepiece and a rubber protective casing. Pushbutton controls are on top, with an on-screen menu system. The image can be viewed in white-hot, black-hot, or various color modes. There are three reticles to choose from and four color selections. Most models have video-out capability as well. The scopes are recoil rated to .30 caliber and waterproof to 1 meter (IPX7 rating). With a base optical magnification of 2x on the RS64, you can crank up the digital zoom all the way to an effective magnification of 16x. The RS units are on stout LaRue ACOG-pattern, quick-detach mounts.

ir-defense-ur-hunter-urh640-35-thermal-imager

Make and Model:
IR Defense IR Hunter IRH640-35
Focal Length / Field of View:
35mm / 18 deg
Refresh Rate:
30Hz
Sensor Resolution:
640 x 512 pixels
Display Resolution:
800 x 600 pixels
Digital Zoom:
1x, 2x, 4x, 8x (effective 1.5x, 3x, 6x, 12x)
Batteries / Battery Life:
2x CR123 / 3.5 hours
Dimensions:
7.4 x 2.9 x 3.1 in
Weight:
2.2 pounds
Warranty:
3 years
MSRP:
$7,995
URL:
www.irdefense.com, www.irhunter.com
Notes:
New to the market, but designed by a veteran of the thermal and night vision industry, the IR Hunter is chock full of well thought out features and functionality. It has a FLIR core and a wonderfully large AMLCD display. Three control knobs with nice tactile feedback provide a refreshingly intuitive user interface utilizing on-screen menus. They control zoom, sharpness, brightness, reticle adjustments, calibration and other settings including image enhancement processing. You can choose between white hot, black hot, and several color modes, as well as three different reticle designs and colors. It has a diopter adjustment and a shuttered rubber eye cup that closes when not in use to prevent light leakage from the display. It has video out capability, and you can also save image captures to internal memory (about 10 to 30 images depending on resolution) and download them later. With a base optical magnification of 1.5x, you can crank up the digital zoom all the way to an effective magnification of 12x. The scope is rated to withstand recoil up to a .50 BMG and waterproof to 1 meter, and our test unit was secured to a LaRue ACOG-pattern quick detach mount. IR Defense also plans to offer a collimating conversion kit to allow the scope to be used as a clip-on unit (it’s actually compatible specifically with the ELCAN SpecterDR sight without any conversion required). There are a variety of models from a baseline variant with a 168 x 128 pixel sensor at $3,995 to the one featured here.

CLIP-ON THERMALS

n-vision-tc35-thermal-imager

Make and Model:
N-Vision TC35
Focal Length / Field of View:
35mm / 13 deg
Refresh Rate:
30Hz (60Hz optional)
Sensor Resolution:
324 x 256 pixels
Display Resolution:
800 x 600 pixels
Digital Zoom:
1x, 2x, 4x
Batteries / Battery Life:
2x CR123A / 4 hours
Dimensions:
6.6 x 3.4 x 3.7 in
Weight:
2.1 pounds
Warranty:
1 year
MSRP:
$8,098
URL:
www.nvisionoptics.com
Notes:
The N-Vision TC35 feels like you could drive nails with it (naturally, it’s rated for .50 BMG). Featuring a FLIR core, it’s fully collimated to be used as a clip-on in front of a day scope, but can also be mounted as a dedicated thermal scope or even detached to use handheld (threaded rubber eyecup included). When used standalone though, the perceived size of the display (even though high resolution) is somewhat small. 60Hz frame rate is available as an upgrade for additional cost. The TC35 has very sturdy construction with pushbutton controls on its side to control calibration, brightness, zoom, reticle, zeroing, and other settings. It has white-hot and black-hot modes. We did see some distortion in the image when panning, which N-Vision noted was unusual but was unable to diagnose prior to press time. You can also take photos, save them to internal memory (up to approximately 400), and download them to your computer later. In addition, it can output video. The unit is sealed against dust and waterproof (IP68 rating).

SOURCES

FLIR | www.flir.com
Spartan Tactical | www.spartantactical.com
Tactical Night Vision Company | www.tnvc.com

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