Security systems / | Choosing camera video surveillance systems |
The camera - image source object selected for surveillance or protection. We all know how much of CCTV camera depends on which is the basic element of these systems. Properly selected camera provides high image quality, and this is the main, though not the only requirement to obtain the necessary image on the screen of the operator surveillance system.
The role of the camera in an analog surveillance system is obvious and requires no special explanation. But digital video surveillance and recording, which are now becoming the dominant role of the camcorder is no less, and perhaps even more important. No, even the most intelligent software is impossible to improve the poor quality of the image obtained with the incorrect data for the selected operating conditions of the camcorder. In this case, important information would be lost irretrievably. And if you take into account the subsequent compression of the video and a low pace, which provides further information loss and reduced quality (depending on the algorithm and compression), it becomes evident that the professional digital video surveillance role of the camcorder can not be underestimated in any case.
As a rule, the choice of camera experts in the field of CCTV prefer high quality images; design patterns (good to choose from) and a minimum set of video cameras needed for the task. However, the right choice of the camcorder does not solve all problems. It should not be forgotten that improper installation can negate the camera " No " all the advantages of the chosen model.
There are many practical recommendations (of which will be discussed below) for installing the camera, depending on specific site conditions. But one can say with certainty: the protection of an object - a task for professionals, and it must be solved at the professional level. This deficit this solution may be carried out in several stages, but, nevertheless, its implementation must be at a high level. This solution is only possible if the use of high-quality equipment. In the context of reality avaricious pays twice and thus jeopardize the safety of the facility.
They are designed in accordance with modern concepts of image quality and manufactured using the latest technologies. The last two years have shown significant development opportunities of equipment used in the field of television. Even faster development of new digital technologies processing, transmission and storage of large volumes of high-quality video. Therefore, the average image quality and minimum set of video cameras have ceased to hold the sophisticated user. And companies supplying equipment to the market CCTV, have something to offer them.
Currently, the CCTV market a wide range of models in which it is difficult to understand the uninitiated user. The range of tasks that are able to deal with these camcorders is very wide. From the simple, such as visual observation came a guest, to complex, such as remote access to the cameras of any object via the Internet. In each case, depending on the task (observation of the territory, protection of the territory; identification of the offending site and further monitoring of the situation with a high information content), it is necessary to find a compromise between a set of required parameters, the ability to choose the model and its cost, especially in confined budget. We will try to familiarize readers with the modern market of video cameras, and fields of application.
Classification cameras
Based on the requirements of the customer almost immediately you can accurately decide which place a protected area must be visible on the screen. This condition tells you the type of video camera in accordance with the following qualifier.
All the CCTV cameras can be divided into fixed and manageable, which, in turn, depending on the operating conditions referred to cameras for indoor and outdoor use cameras.
The stationary camera for rooms can be divided into standard (without built-in lens); cylindrical and dome, which has a lens with a fixed aperture, or lens with auto iris (auto-iris).
Figure 1. A stationary video camera standard design without built-in lens WV-CP470 (Panasonic) |
Figure 2. The stationary cylindrical camcorder lens EZ-120 (EverFocus) |
Figure 3. Fixed Dome Camera with built-in lens with auto iris WV-CF224 (Panasonic) |
Figure 4. Fixed Dome Camera with built-in lens with auto iris SCC-B5351 (Samsung) |
The stationary camera for outdoor use are installed in housings, which is complemented by a power supply, a heating system and the internal volume of the glass.
Figure 5. ThermoJacket for outdoor camera installation standard design (Computar) |
Figure 6. Modern stationary street cameras WV-CW370 (Panasonic) |
Managed (with the possibility to remotely change the position of the line of sight to the two-coordinate system) camera on a design can be divided into standard, built on the basis of two-coordinate turrets and housings with a video camera (to date, it for a variety of specifications, outdated decision), and the dome.
Figure 7. Modern high speed dome camera for indoor installation WV-CS850 (Panasonic) |
Figure 8. Modern speed dome outdoor installation WV-CW860 (Panasonic) |
Both cameras are intelligent, integrated and easily manageable.
Components of the camera :
- conversion circuit board with the signal obtained with the installed CCD, a composite video signal;
- On the lens mount, CS, M12;
- camera power supply (internal or external);
- housing (rectangular or dome shape);
- Additional built-in or external function modules (transmitters video lightning protection devices, etc.).
The first video camera (in the 30s) were made on the basis of glass tubes coated with a photosensitive phosphor on the inner surface of the glass. They are called to hand the phone, and they work on the principle based on the photoelectric effect. When the CCTV, there are two types of tubes: vidicon nyuvikony. Operation of all transmission tubes is based on the principle of the scanning electron beam coating inside the tube under the action of the electromagnetic field. Video cameras on the basis of the tube nyuvikon were more sensitive, expensive and can only be used with lenses with auto iris.
If the analogy with television tubes used in televisions, it is possible to identify a number of features that do not exist in the current matrix, based on CCD technology - large size video cameras; a high-precision, poorly protected from external influences, the deflection system; the need for a high voltage; short service life of the phosphor coating; the presence of strong geometric distortion.
At first microelectronic technology is not allowed to create a picture element (pixel) in the charge-coupled device (CCD) is smaller than the electron beam, resulting in camcorders that are based on tubes. As a result, the resolution cameras built on the basis of CCD, remained very low. In the 70s, when it became clear that the charge-coupled devices are very sensitive to light, rapid development of CCD technology. Today it has reached a high level. Now we get a matrix, which allows not only receive a very high resolution, but also demonstrate a high sensitivity due to the reduction of losses at the stage of converting light (photons) into a standard video stream.
In the present conditions of the CCD are made by several companies that are leaders and specialized in the production of chips for television cameras. Such companies have their own production and research laboratories, small enough - Panasonic , Samsung , Sony , Sharp and some others. Usually, cameras are based on the matrix produced by these companies, and the circuit studs that are able to either save the baseline signal obtained matrix or worsen it, very much. Thus, the image quality depends not only on a single CCD, but also on the level of circuitry realized end camera manufacturer.
The additional deterioration of image quality make the lenses used in the composition of the camera. The CCTV lenses are used with fixed and varifocal (varifocal lenses). A detailed description of the factors that affect the quality of the optics - too broad question, and full coverage is beyond the scope of this article. In this connection it suffices to point out that the quality of the lens will depend upon such factors as the type of glass, mechanical components, the design, manufacturing technology.
All the lenses produced by the process can be divided iris control - manual and automatic. The auto iris lens control is performed automatically: depending on the level of luminous flux incident on the array, changing the relative aperture of the lens through which it passes. Iris control is through the servo amplifier. There is one feature of the control system with auto iris lens aperture. Lenses with ARD are divided into two subgroups. In the first subgroup of iris control is carried out video signal - VD (video drive), and the second subgroup iris controlled by DC signals - DD (direct drive).
The difference between the two subgroups is that the lenses belonging to the second subset of semiconductor elements iris control amplifier disposed on the board camera. This feature of the construction of the control circuit diaphragm imposes certain requirements for compatibility, the lenses and video cameras, produced by different manufacturers. But at the same time, the lenses with iris control DC cheaper. Today, when manufacturers trying to compete in the market by introducing additional functions in the camcorder, you can select any lens aperture control. From a practical point of view it makes sense to give priority to well-known manufacturers of this type of equipment (depending on the task) - Panasonic, Ernitec, Computar, Canon, Avenir or Tokina.
By the camera power supply is not subject to special requirements, but the choice of improperly it can affect the output parameters of the camera. For its power is used mainly standard (transformer) power supply (corresponding to the power consumption of the camcorder) with an input voltage of 220 (24)/50 Hz and output stabilized voltage 9 V or 12 V (with a ripple of 10 mV). This power supply, depending on the model of camera can be external or built into the camcorder body. Built-in power, of course, the best option in terms of supply, as It manufactured and tested at the plant, where final assembly. But these camcorders are not always convenient to use when it comes to applying another voltage or when solving design problems (lack of visibility of cable communication lines, stealth installed video cameras, no place for a successful installation, etc.). Then apply power to the remote blocks elements of the stabilization of the output voltage. This is a very important thing, which many people forget, because the lack of stabilization of the supply voltage with low ripple (the variable component of the output voltage with a frequency of 50 Hz) is very often the reason for interference in the video signal of your camcorder or unstable.
Let me remind you once again that the camcorder can be divided into several design types — rectangular, cylindrical and spherical. The rectangular chambers are supplied without lens, and spherical and cylindrical lens has a built-in fixed or auto iris, which is a complete solution and simplifies the user experience. Not always sticking out in all directions, the wires of different colors and eye-catching arm arrange demanding customer. Believe me, you do not have to blush and make excuses, if you go to these simple questions creatively.
General recommendations depending on the operating conditions
lighting
Good lighting - an important condition for high-quality video, especially in the color supplement. The light sources may be natural and artificial origin. The sun is the major natural source of light. The color temperature of the light reflected from the earth's surface varies from 6000 K to 20,000 K, depending on the time of the reflection and refraction of light as it passes through the atmosphere. With a low color temperature can take on a red hue, and high - blue. Artificial light sources - heated metal filament or glow gas - produce different color temperatures depending on the source. For right choice of source of artificial lighting is necessary to know the spectral energy of the light source, the human eye and CCD. Detailed description in this article cause makes no sense, but the general recommendation is definitely required.
Tungsten Filament about 3/4 of the energy is radiated in the infrared region in the form of heat radiation. Such artificial light sources and infrared illuminators are suitable to work with cameras that have a heightened sensitivity in the infrared region in black and white. For natural color color cameras, it is desirable to obtain the illumination from fluorescent or halogen lamps. But this condition is necessary only in the absence of natural light conditions. At night most color camera switches to black and white mode, for which the choice of lighting has been described above. With proper design locations cameras light source must not fall into the lens. For this camera, it is desirable to set as high as possible off the ground and directed into the same direction as the light source of the flow, but not forward.