The Truth About Thermal Imagers
It is an indisputable fact that optical-electronic devices — the basis of security television systems.
Optical-electronic devices?
Video cameras?
Yes, but they are not the main subject of this article, but thermal imagers that have stepped out of fantastic military plots and have recently become a tangible reality.
When you read articles about security television and its development trends, communicate with partners and customers at exhibitions and seminars, and, in fact, design surveillance systems, then there is no longer any doubt that the era of digital security systems has arrived.
CCTV is gradually being replaced by IPTV, questions arise about the advisability of choosing megapixel video cameras, about placing the intelligent part of video processing directly at the place where the video cameras are installed in order to reduce the constantly transmitted data flow, unload the central server and reduce the amount of information required for constant analysis by the system operator.
All these questions come down to the problems of transferring and storing information. However, the key information is what should be the result of the system's work.
Various methods can be used to obtain information.
For example, if a person has poor eyesight, he buys glasses, asks people with good eyesight to tell him what he does not see or cannot distinguish.
A person needs the most accurate information so that the brain can make “calculations”, make a decision, draw a conclusion with maximum reliability.
You can train your memory, study mathematics and physics, solve logical problems in order to increase the “intellectual capacity” of the brain, but the brain will be powerless if it does not receive the information it needs to work.
If there is too much data, then this is also not very good, since in this case there is no way to quickly rank the information, “separate the wheat from the chaff” and make a decision based on what will be “the bottom line”, that is, relying on knowledge of the essence of the events taking place.
Thus, it can be assumed that where it is necessary to make decisions “here and now”, conclusions made on the basis of the minimum possible number of information sources with maximum reliability will most fully reflect reality!
It is quite obvious that in order to drive a car, a driver, if he does not have 100% vision, needs glasses or contact lenses; if the sun shines in the eyes, you need sunglasses and visors; at night, when you can’t see anything, you can’t do without illuminating the road with headlights.
All these difficulties confirm the banal truth – no matter how experienced the driver is (the “intellectual capacity” of the brain and the database of reactions to events), without the ability to see (in the absence of reliable information), he is powerless.
The same is true for security television systems, and here there is no difference between CCTV and IPTV! The first and most important thing a system needs is “eyes”, without which everything else simply does not make sense!
So, let's turn to the basis of security television systems – optical-electronic devices, in particular video cameras.
A video camera is a device for obtaining images close to those perceived by the human eye. This is both an advantage and a disadvantage of a video camera. Realizing this fact, video camera manufacturers try to look into the world that is not subject to the human eye (signal accumulation to increase sensitivity, IR projectors), and thereby give the operator more valuable information over a certain period of time. There is no escape from nature, a driver in a car without headlights cannot drive at night, a driver without sunglasses or a visor is dangerous on a sunny day.
Sometimes you hear, “we are limited in budget” or “it is too expensive for us”, but the surveillance system created with such an approach to the matter calls into question the efficiency of its work, relevance, information capacity, and even its ability to solve its task. It happens that the customer of the system does not doubt the efficiency of the funds invested in it, since he was simply not provided with the information that he could have received for the same money. He simply does not know what he missed. And this is a problem!
Leafing through the collection of Russian proverbs and sayings compiled by V.P. Zhukov, in which you can always find an expression that accurately describes almost any situation, I found an old proverb with an obsolete continuation: “Your own eye is a diamond (and someone else's is glass)”.
Well said, and quite applicable to our conversation about optical-electronic devices. Among them now is a thermal imager.
A thermal imager?!
When it is mentioned, the movie “Predator” with Arnold Schwarzenegger in the leading role is often recalled.
It should be noted that in this movie, the “observation conditions” of the Predator for a special forces group were more than harsh – the impassable jungles of South America, foliage, fog, night…
The Predator itself took on the “painting” of the jungle. People did not see it, although it itself, guided by thermal radiation, saw everything, although it did not distinguish the color of the special forces’ camouflage, which was absolutely unimportant for it.
This film is science fiction, but thermal imagers have already become an accessible means with powerful capabilities in video surveillance.
A thermal imager is a device that allows you to equally well control the situation (conduct surveillance) day and night in any weather conditions. A thermal imager operates in the thermal, invisible to the human eye, spectral range, and thus it allows you to distinguish what is inaccessible to night vision devices, conventional television cameras and television cameras with infrared illumination.
Infrared radiation through special, usually germanium optics, hits a detector, the sensitive elements of which change their properties, as a result of which the electrical signal taken from them changes.
This signal is then processed by the electronics unit, and the radiation information is converted into a form understandable to the human brain – a pseudo-video image of the thermal pattern received by the receiver is output.
Unlike measuring thermal imagers, security ones do not determine the temperature of objects – they have other tasks that determine the choice of these devices. The decision-making criteria and compliance with these criteria of existing uncooled IR detectors (and therefore systems based on them) are presented in the table.
The numbers in it indicate the weighting factors of the importance of the parameter for a specific application (10 is the maximum importance) and the compliance of these parameters with uncooled technologies.
The importance of parameters for security thermal imagers can be found out by taking as a basis the postulate that a security thermal imager should provide an image of an intruder at the greatest possible distances at the maximum operating temperature range, and the image should be as clear as possible to eliminate false alarms of security systems.
Any video surveillance system needs good “eyes” to work at full capacity. “You can see better from the mountain” – this is said to (or about) the one who is more experienced, knowledgeable in some issues, etc. You can see better to the one who sees more, better and further, despite such various problems as lack of lighting or too much lighting, bad weather, difficult geographical conditions (forest, water areas, etc.).
If there is a defective link, a “hole” in the system, then undesirable actions will be performed through it or, worse, the object will be destroyed: “A claw gets stuck – the whole bird is lost.” If a system is created, it must solve the problem in a comprehensive manner, invariant to negative parameters acting on the system both from the outside and from the inside.
A thermal imager provides a clearer image of the controlled area than the best video camera, but a video camera can also hypothetically cope with the task. Life sometimes poses challenges that were not even imagined during the development of the concept or design of the system.
If a new security system is being designed or an old one is being modernized, then the use of thermal imagers can fit well into the system concept, increase its efficiency and reduce the final cost.
However, it is necessary to adhere to the rules by which a thermal imager should be installed:
• in places with problematic lighting (poor lighting/lighting interferes);
• for inspection of open spaces;
• for monitoring the water surface;
• in combination with a video camera on a rotating device inside the object to monitor the object itself or the adjacent territory;
• for monitoring areas with vegetation;
• along an unlit perimeter.
Let's consider the example of guarding a railway bridge over a river.
Let's assume that we have three different thermal imagers:
No. 1 – a thermal imager with a viewing angle of 180°
№ 2 – a thermal imager with a narrow or wide viewing angle
№ 3 – a system of thermal imagers/camera/rotating device.
In all three cases, the task of protecting the bridge is solved. The approaches to the bridge are covered with 180° thermal imagers.
The first option – wide-angle thermal imagers “look” along the bridge, the second option – narrow-angle thermal imagers are installed, the third option is option № 2, reinforced with two rotating systems.
The second security option is budget-friendly in terms of initial investment, it uses a minimum number of technical means, the first option is average in price, and the third option is the most expensive. The first option covers a larger area of the water surface than the second.
The third option is the most information-intensive, the rotating cameras operate in scanning mode and survey a large area around the bridge, and when a signal is sent by motion detectors from stationary cameras, they automatically capture and track the target that triggered the detector.
The issues of economic efficiency are among the most important.
The calculation of the efficiency of using a thermal imager at a particular facility is made when assessing the criteria of a possible threat or economic losses.
Border guards solve this problem relatively easily (they have statistical data).
According to data for 2005-2006, the average cost of protecting 1 km of the border was approximately 900 thousand rubles.
The efficiency of using thermal imagers worth 450 thousand rubles. and a human detection range of 700-800 m does not raise any doubts.
With the right approach to calculating efficiency, it is necessary to take into account not the initial cost of the system, but the final one, which includes, for example, the cost of electricity, maintenance, downtime and repair, as well as other operating costs.
To this should be added a qualitative assessment of potential threats during periods of “blindness” of a conventional system.
As a rule, the required number of thermal imagers is several times less than that of video surveillance cameras, in addition, when using them there is no need for lighting, and the period of “blindness” tends to zero.
The most thought-out system from the point of view of security economics combines a set of technical means, each of which is technically and economically suitable for its area.
In this case, the total central integral indicator of the efficiency of the funds invested in the system tends to the extreme point and maximum satisfaction of the customer's requests is ensured.
