Thermal imaging.
Thermal imaging
Modern security television systems are used at a wide variety of facilities, so there is a need to improve their tactical and technical characteristics. This can be done through the use of thermal imaging equipment and the intellectualization of video signal processing through the use of digital technologies. An example of the use of thermal imaging equipment is the Rossi-MegoSense complex (ROSSI concern)
The main elements of modern security television systems are: television (TV) camera; motion detector; multiplexer. These systems can be improved by using thermal imaging equipment (TIE) and intellectualization of video signal processing by using digital technologies.
Unlike TV cameras on charge-coupled devices (CCD matrices) or TV cameras coupled with image intensifiers (IBI), thermal imaging uses a completely different source of information, inaccessible to the naked human eye. This is the radiation of heated bodies, independent of the level of illumination and time of day. This radiation is processed and converted into a visible image, and since thermal energy radiation is inherent in all bodies without exception, then with the help of TPV devices it is possible to observe all bodies and objects in the spectral range of wavelengths of 3-5 and 8-14 μm, the temperature of which is of interest for the protection of objects: weakly heated (living objects and technical equipment) with a temperature of about 300 K and strongly heated – about 1000 K [1].
The spectral range of the TPV equipment is more favorable than the visible and near IR ranges [2], as a result of which the observation range of TV cameras in conditions of fog, rain, snowfall, local illumination is sharply reduced. In this regard, TPV devices are less vulnerable, which determines their greater range, since the particles of fog and haze are smaller than the operating wavelength of this equipment.
| Fig. 1 shows the characteristics of atmospheric transmission from the wavelength of radiation [3]. The advantages of the thermal imaging range are obvious, which is explained by the significantly lower absorption effect of the molecules of H2O, CO and CO2 contained in the lower layers of the atmosphere. as well as ozone – in the upper layers. |
Fig. 1. Characteristics of atmospheric transmission on a 2000 m long route at a temperature of +15C and humidity of 40% |
Advantages of thermal imaging equipment
Thermal imaging devices for observing objects at night and during the day, as well as in poor visibility conditions, have the following fundamental advantages over traditional surveillance devices:
• the ability to observe around the clock (and the range of vision increases in the dark):
• passive operating principle:
• detection of vehicle tracks:
• the ability to recognize small objects (people) against the background of large and medium ones, as well as control the dynamics of the situation in the observation zone.
Modern TPV devices can detect a person at a distance of 1-5 km. The limiting factor for the widespread introduction of TPV devices in security systems is their high cost. Leading foreign companies strive to reduce the cost due to the modular principle of constructing equipment and the use of matrix uncooled microbolometers. One of the leading manufacturers of TPV equipment is FUR SYSTEMS AGEMA (Sweden).
The main parameters of TPV surveillance devices are:
• type of radiation receiver (these can be uncooled matrices on microbolometers or cooled multi-element receivers on MCT (cadmium-mercury-tellurium) compounds):
• number of image elements (the typical value is 320×240 elements);
• temperature sensitivity «0.1°C and spectral range (3-5 or 8-14 μm);
• video output with standard video signal parameters.
Rossi-MegaSense Complex
Currently, the ROSSI concern is developing a complex based on the Rossi-MegaSense computer system for recognizing moving objects [4] and TPV and TV surveillance devices. The complex is designed to solve problems of security, surveillance, registration and access control. It identifies object contours and tracks them and actually emulates the neural mechanism of human vision, which allows to significantly reduce sensitivity to external sources of interference (shadows, glare, snow, rain, fog). The complex has up to 4 or up to 8 channels for inputting video signals into the computer, and each channel has independent settings for such parameters as the number of detection zones, their location, and size. For each zone, you can set the size of the objects being monitored, the sensitivity threshold to the speed of movement of objects, and the need to monitor small objects. The RossiMegaSense complex using TPV includes the following technical means:
• personal computer IBM PC Pentium II 400MG, RAM 64 Mb, HDD 2.5 Gb:
• operating system – 32 bit Microsoft Windows – 95 or Windows NT:
• thermal imaging or television cameras with a standard video signal at the output.
Complex capabilities
In addition to the main advantages of thermal imaging equipment, this complex has the following capabilities:
• round-the-clock operation;
• high resistance to natural (rain, snow, shadows) and artificial (headlights, glare) interference;
• adjustment to objects of specified sizes;
• zone masking;
• storing frames from any event on any channel with a time and date stamp;
• controlled JPEG – image compression;
• viewing recorded frames in playback, rewind, step, and real-time modes;
• image processing;
• creating an archive;
• voice messages for events of control zone violation;
• control of remote actuators.
Taking into account the listed points, we can assume the areas of application of this complex:
• protection of fuel and energy complex facilities, chemical industry;
• environmental control over harmful man-made emissions into water and air; • protection of complex extended areas;
• prevention of illegal entry of objects into the controlled territory;
• search and rescue operations related to disasters, accidents and search for people, equipment in hard-to-reach places:
• early detection of large fires.
LITERATURE
1. Lloyd J. Thermal imaging systems. Moscow: Mir, 1978.
2. Handbook of lasers. – In 2 volumes/Translated from English under the editorship of A.M. Proklov. — M.: Sovetskoe Radio, 1978.
3. Orlov V.A., Petrov V.I. Observation devices at night and in limited visibility. — M.: Voenizdat, 1989.
4. Rossi-MegaSense-8 television surveillance system//CncTeMbi for security, communications and telecommunications. — 1999. No. 4. P. 66-67.
