Covert security television surveillance.

#Hidden

Hidden security television surveillance.

Mikhail Yuryevich Arsenyev

HIDDEN SECURITY TELEVISION SURVEILLANCE

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Source: Special Equipment magazine

Technical means of surveillance have a long history.

Before the advent of television systems, the most common were systems for the covert acquisition of visual information based on photographic technology.

Miniature cameras appeared in the first half of the last century.

MINOLTA achieved particular success in this area, producing a number of models that became classics.

The main disadvantages of photographic equipment for use in this area were:

• it did not have the ability to record and transmit the movement of the subject at a distance;
• it could not take pictures in complete darkness (except for cases of using special film sensitive to infrared radiation);
• did not provide in most cases the ability to remotely control the complex;
• had a limited operating time without reloading the cassette;
• it was impossible to obtain an image of the subject in real time;
• the photographic equipment had a fairly complex mechanical design, which resulted in low reliability and the possibility of breakage or jamming of the mechanism at the most inopportune moment;
• there was a constant risk of getting a poor-quality photograph due to incorrectly selected exposure, film overexposure and other unpredictable accidents.

All of the above-mentioned shortcomings created significant difficulties during work. Cinematography, while solving the problem of obtaining a moving image, was more cumbersome, and most importantly, noisier.

Therefore, it was not widely used in practice. An important step in the development of surveillance equipment was the appearance of relatively small-sized television cameras in the 70s. The first cameras were based on electronic vacuum devices.

The advantages of television surveillance over photographic surveillance are obvious:

• the ability to automate the system, and, consequently, remote control of the complex;
• transmission of movement in real time;
• the ability to record on a video recorder;
• the ability to wire and wirelessly transmit a television signal at a distance.

The spread of CCD-based TV cameras in the 1980s dramatically reduced the size and increased the reliability of TV surveillance systems.

An additional advantage of CCD cameras was their significant sensitivity in the infrared (IR) range.

This made it possible to ensure high-quality shooting even in complete darkness, using infrared illumination. A significant advantage of such shooting is that the object in most cases does not suggest the possibility of shooting in the dark.

Mass production of television cameras in the 90s led to a sharp reduction in their cost. This made television systems available to most enterprises and organizations, as well as individuals. Television equipment began to be widely used to control technological processes in production, to study hard-to-reach places, to equip robotic systems, for underwater filming, and of course — for surveillance.

By the method of surveillance, television systems can be divided into open and covert surveillance systems.

The undoubted advantages of open surveillance systems are the ease of installation and the possibility of using high-quality, large-sized television cameras and high-aperture lenses, which means obtaining high-resolution images in the widest range of illumination. In addition, the obvious presence of a television surveillance system at the facility disciplines potential offenders and thus reduces the number of petty thefts, especially in stores.

One should not forget about increasing the prestige of a company that can afford to install a surveillance system. However, with an open installation there is a high probability of theft or breakage of the camera itself.

This probability can be significantly reduced by using a hidden camera installation. If a potential thief or hooligan does not know about the camera, he will not be able to steal or break it. Of course, a hidden installation requires higher qualifications and is more labor-intensive than an open one, but the confidence in the safety of the equipment is worth it.

Typical tasks of hidden systems include:

• Video surveillance in stores to combat theft by both customers and staff. For such systems, it is advisable to use combined systems that include open and hidden video cameras. Open cameras will scare off small thieves, but will not be able to combat theft by staff, since store employees, who are well aware of the viewing angles of these cameras, will find a way to avoid these sectors. In the event of an open attack on a store, open video cameras are also ineffective, since they will most likely be immediately disabled by the criminals. In these cases, hidden video cameras will give the maximum effect. It is desirable that only security personnel and the management of the enterprise know their location. In addition, a hidden video surveillance system will help document cases of extortion and blackmail both by representatives of organized crime and by individual unscrupulous employees of government and supervisory authorities. In subsequent legal proceedings, such video recording can play a vital role.
• Video surveillance in various industries to combat theft by personnel. Unfortunately, theft is common in most Russian enterprises, both state and private. Sometimes the amount of regularly stolen goods becomes so large that it wipes out all the profits of the enterprise and makes the management seriously think about solving the problem. One effective solution is to install a completely hidden or combined video surveillance system. For example, in places where theft is possible, it makes sense to install hidden cameras, and open ones along the perimeter of the fence, in inaccessible places. There are many known cases where after installing such a system at an enterprise, theft significantly decreased or stopped altogether. However, as with equipping a store, an important condition for the effectiveness of the system is that the employees do not know the specific places where the hidden cameras are installed.
• Video surveillance in apartments. Usually aimed at preventing theft, robbery, and hooliganism. The situation is complicated by the fact that in the absence of the owners of the house, the probability of theft of an openly installed camera approaches 100%. The only way to protect a video camera is to install it hidden inside a wall or entrance door. One of the most common options for disguising a camera is the phenomenon of Russian video surveillance called a “video peephole.” For more information on video peepholes, see “Special Equipment,” No. 2, 2000.
• Video surveillance in cottage and summer cottage communities. In this case, the task is complicated by the fact that the owners of many houses do not live there permanently, and in winter, most summer cottage communities are practically deserted. In these conditions, thieves have a lot of time not only to steal property, but also to disable security systems. Of course, in this case, only a completely hidden surveillance system can be effective, and even the internal parts of the system (for example, a VCR, monitor, power supply, etc.) must also be placed in a hiding place. Recently, systems with image and alarm signal transmission via a telephone line have become popular. Signals can be received on the homeowner's computers and (or) on the control panel of an off-site or private security service.

Figure 1 shows a typical diagram of a television surveillance system based on two television cameras.

MON – monitor;
VM – video tape recorder;
BU – control unit;
BP – power supply;
MU – masking device;
IKP – infrared illumination unit;
TK1 – television camera No. 1 with lens;
TK2 – television camera No. 2 with lens;
ME – masking elements.

The main part of any covert surveillance system is a camouflage device (MD). MD is an object in which television cameras are placed (in our case, TK1 and TK2).

By type, MD systems are divided into stationary, insertable, and portable.

Stationary products are mainly located in furniture, walls, ceilings and doors of buildings and structures. Rooms equipped in this way are usually the best viewed and listened to, since when installing equipment it is possible to take into account the specific situation (location of furniture and windows, direction of sunlight, shape and geometric dimensions of the room, height of ceilings, etc.).

You can make a hidden cable line in the walls and get the highest quality “picture” at the output.

In addition, in this case, the developer is usually not constrained by strict restrictions regarding the dimensions and weight of the product, since the walls of the buildings have a significant thickness and sufficient load-bearing capacity.

This circumstance allows the use of:

• TV cameras and optics with the best characteristics;
• high-power infrared illumination;
• network power supplies, the most capacious batteries, etc.

Thus, stationary surveillance systems usually have higher technical characteristics compared to portable and insertable products.

The main disadvantages of stationary systems are:

• complexity of installation, which means a long installation time;
• the impossibility of quickly changing the composition or parameters of the system (replacing cameras, lenses, changing the field of view, etc.);
• high probability of the object leaving the observation zone;
• the difficulty of using such systems in the absence of control over the equipped room.

The items being brought in are placed in such furnishings that can be brought in, rearranged, and taken out of the room.

If as a MUany electrical appliance is used, then when connected to the power grid, it can be used to power the equipment. This allows the continuous operation time of the product to be practically unlimited.

Installation of such a product usually takes much less time than a stationary system.

However, in the process of manufacturing the brought-in product, it is difficult to take into account all the features of the room in which it will subsequently be located. The video signal from the system is usually transmitted wirelessly. This somewhat reduces the reliability of the connection, but increases the mobility of the system.

Such MU can be rotated or moved without any dismantling.

The disadvantages of brought-in MU include:

• forced small dimensions of television equipment, and, consequently, deterioration of their characteristics compared to stationary systems;
• impossibility of changing the camera's field of view during observation, and, consequently, a high probability of the object leaving the observation zone;
• forced small dimensions of the battery, and, consequently, a shorter autonomous operation time of the complex;
• the difficulty of creating such a product without the MU (for example, a household appliance) losing its functionality.

Wearable MU are usually the most labor-intensive products to manufacture. In this case, the equipment is placed in bags, boxes, packages, suitcases of various types, etc. The wearable product is intended for shooting «hand-held».

This allows such products to be used for documenting video information in rapidly changing conditions. These are the most mobile surveillance systems.

They allow you to quickly change the field of view of the TV camera, reliably control the complex without using remote control, quickly replace the batteries and cassettes of the portable video recorder, which is usually located inside the MU itself.

Disadvantages of wearable systems:

• strict restrictions on the dimensions and weight of the equipment, and, consequently, high labor intensity of development and production, relatively low characteristics of television cameras and small capacity of batteries, leading to the need for their frequent replacement;
• inability to use mains power supply;
• image shake when shooting handheld (if the camera does not have an electronic or optical image stabilizer).

It should be remembered that according to the RF Government Resolutions No. 214 of 10.03.00 and No. 770 of 01.07.96, the development and use of most systems based on portable and wearable MU (namely, based on household items) is the exclusive prerogative of law enforcement agencies.

The MU in Fig. 1 contains TK1 and TK2 television cameras (their number can vary from 1 to 16 or more depending on the specific task). Color and black-and-white cameras are often used. In this case, the color camera usually works in good lighting conditions, and the black-and-white camera — in the dark.

It is also possible to use several cameras with different fields of view.

The above-mentioned RF Government Resolutions impose restrictions on the sensitivity of television cameras, namely, on television cameras “operating at low illumination of the object (0.01 lux or less) or at low illumination on the receiving element of 0.0001 lux or less.”

Most miniature body cameras have lower sensitivity and, therefore, can be used not only by law enforcement agencies. Table 1 lists the main characteristics of some miniature box cameras.

Table 1.

TV cameras are placed behind masking elements (ME). ME, as their name suggests, are used to camouflage television cameras. It is clear that high quality camouflage is one of the main requirements when developing a covert surveillance system. This issue has previously received little attention in specialized literature, so I consider it necessary to cover it in more detail.

There are three main types of ME:

1. Small-diameter hole.

This type of ME involves the use of a television camera with a pin-hole lens. Such lenses have a small entrance pupil and provide shooting through a hole with a diameter of about 1 mm or less.

As practice shows, it is possible to detect such a hole on a dark background with careful installation only after a long, painstaking study of the surface. An important characteristic of a “pin-hole” lens is the pupil removal, that is, the distance from the place where you can install the diaphragm with a minimum opening to the front edge of the lens.

Naturally, the greater this distance, the easier it is to mount the camera. Cheap single-lens lenses with a small entrance pupil, which are supplied with most TV cameras, do not have any pupil removal at all, and, strictly speaking, cannot be called “pin-hole”. In addition, they often have plastic lenses instead of glass.

This means less resistance to aggressive environments, abrasives, daylight, temperature changes, etc.

Technical data for some lenses are given in Table 2.

Table 2.

The main disadvantage of this method of camouflage is the decrease in sensitivity of the TV camera due to the lower aperture ratio of pin-hole lenses compared to conventional lenses. Some restrictions are also imposed on the angle of view of the cameras (there are practically no pin-hole lenses with a focal length of less than 3 mm).

The image obtained with cheap single-lens lenses has significantly less clarity in the corners than in the center.

In addition, pin-hole lenses usually do not have an auto diaphragm. This makes it difficult for the camera to operate with large differences in illumination on the object.

However, the latter drawback can be somewhat alleviated by using an electronic shutter, the range of which is quite wide in modern camera models.

Certain problems arise when using short-focus pin-hole lenses with color television cameras.

These lenses have a small backscatter, meaning they need to be moved almost right up to the CCD matrix, and most color TV cameras have a thick corrective filter in front of the matrix, which interferes with focusing. You can get out of this situation by using special lenses with a built-in filter or thin film filters.

At the same time, the use of cameras with a small lens aperture has become the most widespread due to its versatility (a small aperture can be made in almost any surface).

It should be noted that only lenses with a small entrance aperture without pupil removal are permitted for widespread use.

2. A light filter in the form of a translucent plate.

The material for such a light filter is ordinary or organic glass with a certain transmission coefficient.

The value of this coefficient, i.e. the optical density of the filter, is determined by a compromise between the quality of camera masking (the most dense filter) and maintaining good camera sensitivity (the most transparent filter).

This method of masking allows the use of high-aperture lenses with an auto diaphragm, which is an undoubted advantage compared to the first type of ME, however, the filter always reduces the sensitivity and resolution of the camera.

When using color cameras, to avoid color distortion, the filter should be neutral gray. The disadvantages of this ME include the fact that the presence of a filter on the MUis not always acceptable and can often arouse unnecessary suspicion.

3. A fine mesh (less than 1 mm).

This ME is somewhat similar to a light filter and has similar advantages and disadvantages. Camouflage requirements — the finest mesh with the minimum ratio between the area of ​​the holes and the area of ​​the mesh material.

To obtain a high-quality image, the requirements are directly opposite. As in the case of a light filter, it is necessary to seek some compromise. It should be remembered that in the case of using television cameras with automatic focusing, this function should be disabled, since the camera may focus not on the object of observation, but on the grid. In addition, the presence of a grid on the MU, as well as a light filter, must be somehow justified.

When developing systems with ME in the form of a light filter or grid, a mandatory condition is the absence of light sources inside the MU, as well as low light reflectivity of the internal parts of the system. This means that all units should be black and matte if possible.

The lens shine is a particular problem. Often, denser filters and grids have to be installed to mask it, that is, to sacrifice the sensitivity of the camera.

The greatest difficulty in installing TV cameras behind all these ME is the case of a non-orthogonal direction of the TV camera in relation to the ME, since in this case the lens inevitably moves away from the ME, which means a sharp deterioration in image quality.

In the first case, the use of conical lenses can help, and in the second and third cases, only mechanical modification of the lens housing can help.

Figure 2 shows examples of such an installation.

Fig. 2

The part of the high-aperture lens housing that has to be removed when using ME in the form of a filter or grid is painted black. Because of the above problem, rotating platforms, and therefore lenses with a zoom lens, are rarely used for covert surveillance. In principle, such systems are only possible when using ME in the form of a filter or grid, but its size in this case increases sharply.

An additional unmasking factor in this case is the noise of the operating rotating platform.

In addition, the cost of one TV camera, a high-quality lens with an auto-iris and zoom, a large thermal housing for its installation and a rotating platform with a remote control significantly exceeds the total cost of four small-sized TV cameras for outdoor installation and a quad for simultaneously displaying four images on a monitor screen and a VCR.

Such a system with several TV cameras has a number of important advantages over a single-camera system:

• The fields of view of several television cameras more densely “cover” the observed area, and their partial mutual overlap makes the system more reliable, since the failure or destruction of one television camera does not lead to a large loss of information.
• The system can record video in autonomous mode, without an operator. Moreover, all four images are always recorded. When using one camera on a rotating platform, there is a high probability that the operator, “running in” with the lens to one point, ignores other places. Simply put, while the security guard is staring intently at a pretty girl “accidentally” passing by, bags have long been carried out of the neighboring window. In this case, the most important event may remain unrecorded at all and the money spent on television surveillance can be considered wasted.
• The absence of moving parts (rotating platforms, motorized lenses, etc.) increases the reliability of the system.
• The ease of installation of small-sized cameras allows you to do without hiring highly qualified specialists.

The main disadvantage of small-sized television cameras is the lack of an automatic diaphragm in the lenses.

However, modern models have a highly efficient electronic shutter (typical minimum exposure time is 1/100,000 second) that allows observation in almost the same range of illumination as in the case of inexpensive lenses with an auto diaphragm, since the range of change in the relative aperture of most of them is relatively small.

The way out of this situation is a careful choice of the installation location and the direction of the camera's viewing.

It is desirable that bright objects, such as the sun, sky, lanterns, spotlights, various glare surfaces, etc., do not fall into the camera's field of view.

It should be noted that a number of countries have established the production of special materials for the manufacture of ME. Thus, the company Sonic Communications (International) Ltd. (Great Britain) offers the material MONOVISION based on stainless steel foil to solve such problems. Any pattern can be printed on the substrate.

In addition to the patterns “under the tree”, “under the plastic”, “branded” stickers and information labels are made (Fig. 3).

This is the main advantage of MONOVISION over light filters and grids. MONOVISION has high optical characteristics.

	Description: Ford logo Color: Blue/white Size: 43x113x1 mm
	Description: Info. “Flammable” label Color: Red/black Size: 90x90x1 mm

Fig. 3

For shooting in complete darkness, an infrared illumination unit IRP is used. The disadvantages of using such illumination are some defocusing of cameras in the infrared range (ideally, the cameras should be rebuilt when the illumination is turned on, which is almost impossible during covert surveillance) and the main unmasking factor of IRP — significant thermal heating.

In addition, the sensitivity of television cameras in the infrared region is significantly lower than in the visible region. Most television cameras are practically insensitive to radiation with a wavelength longer than 1 µm, and powerful emitters with a shorter wavelength can often be detected by the dark-adapted eye by the dark red glow of the emitters.

Color television cameras are generally insensitive to infrared radiation due to the previously mentioned corrective light filter in front of the CCD matrix. Masking IRP also presents a certain problem.

Here are two examples of camouflage for infrared illumination sources:

• A bolt-shaped emitter (LEDs are located in the bolt head and covered with a round light filter). The power of the product is low, but such camouflage allows it to be used quite universally, in various situations. The disadvantage is the need for good heat dissipation, i.e. the bolt must be screwed into metal with sufficient mass and surface. It is recommended to improve the thermal contact between the bolt and the radiator with a special heat-conducting paste.
• An emitter made in the form of a plate for placing an apartment number. The plate is a metal base on which IR diodes are mounted and a light filter made of organic glass is glued to it. The emitter is installed on the door. The apartment number digits are attached (or applied in one way or another) to the surface of the plate. An additional radiator is not needed in this case, since the area of ​​the plate is sufficient for normal operation even when installed on heat-insulating material (leatherette, wood, etc.). The radiation power of the plate significantly exceeds the IR bolt (see Table 3). IR plates are often made with a hole in the metal base for the lens of a television camera placed behind the plate. This allows the TV camera and ICP to be installed behind one ME (plate light filter).

Table 3.

The illumination range is standardized for a TV camera with a sensitivity of 0.1 lux.

For more information on IR illumination, see “Special Equipment”, No. 1, 2000.

The equipment is powered by a power supply BP. It often combines a network power supply and a battery.

When the mains voltage is present, the battery is recharged, and when the voltage is lost, the system switches to it. Naturally, the larger the capacity (and, accordingly, the dimensions) of the battery, the longer the autonomous operation time of the system. Both serial uninterruptible power supplies and specially manufactured ones can be used.

In simpler systems, either a mains source or a battery is used.

The system shown in Fig. 1 is controlled by the control unit CU.

It can switch video signals, turn on and off TV cameras and lighting, etc. If there is a telemetry channel, it becomes possible to display information about the current state of the system (for example, data on the battery charge, illumination at the site, the number of the operating camera, etc.).

For this, liquid crystal screens and LED indicators are usually used.

Control of the MU units and transmission of the video signal is carried out via a wired or wireless channel.

If possible, naturally, the simplest and most reliable transmission via cable is used.

The use of special equipment for wireless transmission of video signals is permitted only to law enforcement agencies, so we will only provide a brief description of some possible methods.

The most common, traditional method is radio transmission.

Advantages of the radio channel:

• relative ease of installation when using antennas with a circular radiation pattern;
• no need for direct visibility between the transmitter and receiver.

Disadvantages of the radio channel:

• high probability of direction finding and interception of information (in the absence of signal encoding);
• difficulty in installing effective narrow-beam antennas;
• possibility of communication failure during observation due to interference;
• significant consumption of powerful transmitters, leading to an increase in the weight and dimensions of the power supply (mainly the battery).

Another option for wireless communication is the use of an optical communication channel. In this case, the signal transmitter is a light-emitting element, such as a semiconductor infrared laser.

The main advantage of this transmission method is the difficulty of intercepting information due to the narrow beam pattern.

In addition, radio interference does not affect transmission in this case. The disadvantage of this method is the possibility of interruption of communication due to disruption of direct visibility between the transmitter and receiver, unstable transparency of the atmosphere. This means that rain or fog can make signal transmission impossible.

Of course, communication will also be interrupted if the line between the receiver and the transmitter is blocked by some object. This method of transmission has not yet found wide application.

The VM video recorder is used to record images. Usually, small-sized video recorders manufactured by SONY are used. Their main characteristics are summarized in Table 4.

Table 4.

The most promising, apparently, is recording audio and video information on small-sized solid-state storage devices. However, this recording technology is not yet widely used. Currently, small-sized, “pocket” personal computers are sometimes used as such storage devices.

A VCR may include a monitor in the form of a liquid crystal display (see Table 4).

In inexpensive household systems, a regular TV is sometimes used instead of a monitor.

The product discussed above is a typical version of a television surveillance system. In many cases, it is possible to exclude or add individual units and move them from one part of the system to another, but the basic scheme usually remains unchanged.

In conclusion, it should be noted that television surveillance technology is becoming increasingly widespread. Security television often helps document various crimes and helps identify and catch offenders.

It plays a certain role in the fight against terrorism in public places (in particular, in stores, subways, train stations, etc.) and on city streets. The objectivity of the “electronic eye” allows you to confirm or refute witness testimony, and sometimes do without it altogether.

The use of television surveillance in everyday life brings our homes to a higher level of security and comfort.