When faced with the choice of a thermal imager, many are immersed in a sea of numbers and characteristics, trying to choose the best option. But not everyone is free to navigate among the indications and terms. In this article, we have collected all the main parameters of thermal imaging optics that are important and require explanation. Our material will provide comprehensive information on each type of thermal device and will allow you to make a good choice.
What is thermal vision technology?
Thermal imaging technology helps a person to see in the dark with the help of a thermal imaging device. It measures the temperature using sensors assembled in a matrix. The processor of the thermal imager reads the readings, compares them with the standard and displays the relative difference on the screen in the form of a thermogram. The temperature gradation is judged by the intensity of staining of individual areas. Warm areas are clearly visible against a colder background. As a rule, these are people, animals or heated objects. The rest of the objects are not so bright, but quite distinguishable. Thus, the image provides enough information to navigate, even in complete darkness.
Thermal imaging devices are used all year round, 24/7, regardless of rainfall, temperature and light levels. If you need to navigate in fog, rain, snow or among thickets, this is what you need.
It is worth noting that we see a two-dimensional picture on the screen online. It has no depth of space and therefore, it will be difficult to determine the true magnitude and degree of removal of the object. Part of the problem is solved with the help of a rangefinder and night vision optics.
Before you start searching for a thermal imager, you need to clarify your initial data. They relate to existing equipment, working distances, budget, weight and size preference, mounting compatibility, and more. Your answers to these questions allow you to narrow your search down to a few options. It is among them that you need to look for your ideal product. In order to understand how good, it is, we have collected all the main parameters that you need to check before making a choice.
Check list of the most important parameters
Screen matrix resolution
These numbers are responsible for the quality of the image. If you are used to dealing with medium and long distances, then you need to look for a matrix with a resolution of 640 × 480. If you need to work at a great distance, then 1024×768 is best. The minimum that can be considered for short distances is 384×288. Note that a better image is obtained with an OLED display, especially at low temperatures.
Sensor matrix resolution
For target recognition, it is important that the sensor is of good resolution and provides enough information for decoding. This should be taken into account for thermal imagers with a large digital zoom and work at a great distance. 640×480 resolution is the sweet spot for most cases. Anything above is very good and expensive. Anything below can be used for short range shooting.
Focal length
Wide angle lens 6-25mm – at a distance of 1 km provides a field of view greater than 15° and zoomed out. Normal 35-50mm – at a distance of 1 km gives a field of view of 7-15° and gives a normal zoom. 70-200mm telephoto lens – less than 7° field of view and zoomed in.
NETD
We pay attention to it when the background and the target are close in temperature. We are looking for NETD indicators less than 40. The lower, the better the picture.
Impact resistance
We are looking for information about the caliber of cartridges, the return from which thermal imaging optics normally tolerates. This information is not relevant for observational binoculars and monocular.
Zoom
There are optical and digital. The first magnifies very well and allows you to read details, but increases cost. The digital zoom depends on the resolution of the detector. If the detector is sensitive, then it works adequately.
Matrix update frequency
An extremely important parameter, especially for observing and shooting at a fast moving target. The limit to be equaled for the dynamics is -50-60Hz. For heavy traffic, you need more than 100, but most likely this parameter is inherent in professional equipment. For static, 30 Hz is enough.
Protection
The degree of protection depends on the operating conditions. IP66 rating guarantees protection against dust and raindrops. IP67 – Protects against dust, moisture and withstands short-term immersion in water. If you are using a thermal imager near water, IP68 is best.
Material
Composite reinforced materials and aircraft-grade aluminum will keep the thermal imager and not add extra weight. Plastic, powder iron stamped cases will not be durable.
Battery
Rechargeable battery is better than normal. If you work in the cold, keep in mind that the battery capacity is consumed faster than usual. It is very convenient if the device can connect to the power bank via USB.
Additional features
All thermal cameras can record and take pictures. They save files to a memory card, phone memory or wirelessly connect to any digital device. Some gadgets support video streaming.
Thermal scopes
Thermal sights are the most compact and technologically advanced type of thermal imaging equipment. They have a very practical one-time reset function. It allows the use of different guns with the same thermal sight without zeroing, provided that the zeroing procedure has been performed once. Some models can work as a monocular.
Infrared sights are indispensable if rain or fog is expected. They are excellent if you need to hit a target on a sun-drenched snow field or on a water surface full of sun glare. Camouflage under the surrounding landscape does not save from a thermal imaging sight. If the object differs in temperature from the background, it will be detected.
The maximum working distance does not exceed 4000 yards. The thermal imaging sight is equipped with several types of reticle. For better recognition, there is a picture-in-picture function that allows you to increase the center of the target. Often thermal sights have a built-in ballistic calculator, rangefinder, compass, IF illumination and image stabilizer. Do not worry that the shot can damage the optics. IF scopes are designed with recoil in mind. Cartridge calibers are usually indicated in the instructions.
When choosing a thermal imaging sight, you need to pay attention to the presence of optical and digital zoom, especially if you have to work at long distances. Higher optical zoom values will give a better picture when zoomed in. Digital zoom is important only if there is a large resolution of the sensor and screen matrices.
Thermal imaging sights are equipped with a variable or constant zoom. The first is important for fine tuning without fear of losing sight of the target. The second is useful when shooting at a distance known in advance.
If you plan to work on a running target, then you need to monitor the refresh rate of the matrix at least 50-60 Hz.
Thermal binoculars
The purpose of thermal imaging binoculars is to observe vast spaces from a fixed point. Extreme detection point – 6000 feet. This is the most comfortable type of thermal imager for the eyes, since it has the effect of stereo vision.
When choosing thermal imaging binoculars, you should pay attention to the viewing angle. The smaller it is, the farther the binoculars are able to see and vice versa.
When choosing a lens, you should look for high-quality germanium lenses with a multilayer protective coating. The lens diameter depends on your working distances. The larger the lens, the better the picture and the further thermal imaging binoculars see. It is worth noting that binoculars with large lenses are more expensive and heavier than regular ones.
For the correct operation of the binoculars in hot weather, it is necessary to choose the correct NETD sensitivity. The lower this value, the better a warm object can be seen against a warm background. In addition, there are special modes designed for these conditions.
A 4-10x zoom is fine for most distances. If you have a long observation, the binoculars are mounted on a tripod.
Thermal monocular
The thermal imaging monocular is valued for its compactness and light weight. This crumb will not burden the backpack. It’s incredibly convenient and easy to use. If you need to quickly see something, then the monocular is perfect. Many carry it in their pocket or on a belt around their neck. In addition, the monocular can be mounted on a helmet or a special headband.
The thermal imaging monocular is suitable for short to medium working distances. The maximum working distance is about 1.5 km.
A thermal imaging monocular can replace several types of thermal optics. If you have a good optical sight, then you can mount the monocular on the weapon up to the sight. This manipulation allows you to get a thermal imaging sight.
A distinctive feature of the monocular is the absence of a reticle. But the usual sight has its own, so you don’t have to worry. It is worth paying attention to the instructions regarding the caliber of cartridges that it can withstand.
If you’re looking for a low-cost option for IF equipment with superior performance, then a thermal imaging monocular is the perfect candidate. Besides, when observing at night, the operator maintains night vision with the second free eye.
Thermal goggles
Thermal goggles are for observation and movement and are not designed for aiming. They are needed by everyone who wants to have freedom of movement and free hands. For a walk, you should choose a zoom of 1x. But we want to warn you that driving a car with thermal glasses will not work, because the thermal imager does not see through the glass. For the same reason, it is impossible to aim at a conventional optical sight.
With the help of thermal glasses, it is easy to record a video or take a photo. They perfectly interact with all digital media over a wireless network, Wi-Fi or Bluetooth. Some thermal glasses options support live streaming. The glasses need a good battery and the ability to recharge from an external source.
Since the thermal imager cannot be attributed to budget purchases, we recommend that you approach the choice pragmatically and calculate your steps for the future. Think about how the device will complement the equipment you already have at your disposal and how it will behave with what you plan to buy. Do not settle for buying cheap, dubious and obsolete things. The best thermal optics will not lose relevance and will bring satisfaction for many years.