1, camera selection
The camera is the main part of the camera, and its function is to observe and collect information. The performance and installation mode of the camera are important factors that determine the quality of the system. At present, the light tube camera has been eliminated, referred to as CCD camera. Its main performance and technical parameters are as follows:
1) color: There are two kinds of cameras: black-and-white cameras and color cameras. Usually, the horizontal resolution of black-and-white camera is higher than that of color camera, and black-and-white camera is more sensitive than color camera, which is more suitable for places with insufficient light and dark light at night. Black and white cameras are cheaper than color cameras. The color image is easy to distinguish the color of clothes from the scene, which is convenient to obtain and distinguish the real-time information of the scene in time.
2) Definition: There are two kinds of definitions: horizontal definition and vertical definition. Vertical definition is limited by TV system, and there is a maximum limit. Because all TV signals in China are PAL system, the vertical resolution of PAL system is 400 lines. Therefore, the definition of a camera is generally expressed by horizontal definition. Horizontal definition refers to the measurement of the horizontal detail definition of TV images by human eyes, which is expressed by TV line TVL.
At present, the horizontal resolution of black-and-white cameras should be above 500 lines, and color cameras should be above 400 lines.
3) Illuminance: The luminous flux received per unit illumination area is called illuminance. Lux (lux) is the illuminance when the light beam with nominal brightness (lumen) is uniformly incident on the lm2 area. The sensitivity of the camera is expressed by the minimum illumination, that is, the camera aims at a specific test card. When the aperture of the lens is 0.4, adjust the illumination of the light source, and measure the amplitude of the video signal at the output end with an oscilloscope as 10% of the rated value. At this time, the measured illuminance of the test card is the lowest illuminance of the camera. Therefore, in fact, the illumination of the subject should be about 10 times of the lowest illumination to obtain a clearer image.
At present, the lowest illumination of black and white cameras is generally selected. When the relative aperture is F/ 1.4, the minimum illumination should be less than 0. 1Lux. Select the minimum illumination of the color camera. When the relative aperture is F/ 1.4, the minimum illumination should be less than 0.2Lux.
3) Synchronization: The camera is required to have power synchronization and external synchronization signal interface. For power synchronization, all cameras are powered by the AC in-phase power supply of the monitoring center, so that the phase of the camera's on-site synchronization signal is synchronized with the commercial power, thus realizing the synchronization mode in phase with the camera's synchronization signal.
For external synchronization, it is necessary to configure a synchronization signal generator to realize forced synchronization, synchronize the working modes of line frequency, field frequency and frame frequency signals used for scanning of TV system, composite blanking signal and synchronization signal provided by peripheral signal generator.
Only when the system is synchronized, the image will not scroll when the time sequence is switched, and the quality of recording and playback can be improved.
4) Power supply: Generally, camera power supplies include 220V AC, 24V AC, 12V DC. The camera power supply can be selected according to the site conditions, but it is recommended to use safe low voltage. When the voltage of 12V DC is selected for power supply, the requirements of camera power synchronization are often not met, and the external synchronization method must be adopted to achieve the purpose of system synchronous switching.
5) Automatic gain control (AGC): In the case of low brightness, the automatic gain function can improve the intensity of image signals to obtain clear images. At present, the minimum illuminance of CCD camera on the market is a parameter under this condition.
6) Automatic white balance: When the white balance of the color camera is normal, the color of the subject can be truly restored. The automatic white balance of color camera is to realize its automatic adjustment.
7) Electronic brightness control: Some CCD cameras can use electronic shutter to adjust the exposure time of CCD image sensor according to the brightness of incident light, so that automatic aperture lens is not needed when the light changes greatly. When using electronic brightness control, the depth of field of the subject is smaller than when using automatic aperture lens.
8) Backlight compensation: Under the condition that only the backlight can be installed, the image of the object photographed by ordinary camera will be darker, so choose a camera with backlight compensation to obtain a clearer image.
2, lens selection
Lenses are classified by function and operation:
1) A camera shooting static objects can choose a fixed focal length lens, and when shooting dynamic objects with changing viewing angles, it can choose a variable focal length lens. The choice of lens focal length depends on the size of the field of view and the distance from the lens to the monitoring target.
F=A × L/B
Where f refers to the focal length (mm);
A-image field and image width (mm);
L—— the distance from the lens to the monitored target;
B—— visual field height (L and B use the same measurement unit).
2) When choosing the focal length of the lens, the size of the camera image sensor must be considered. There are four types: 2/3 ",1/2", 1/3 "and 1/4". These four modes have the azimuth ratio of 3X4 in both vertical X and horizontal dimensions, and the cameras in the four modes correspond to a certain lens. For example, the viewing angle range of the 16mm lens used in the dedicated 1/2 "camera is exactly the same as that of the 12mm lens used in the 1/3" camera. And so on.
3) For monitoring areas with large depth of field and wide field of view and dynamic scenes that need to be monitored, panoramic pan-tilt camera and electric zoom lens with automatic aperture of more than 6 times are generally used.
4) When using charge coupled devices (CCD), you should generally choose an automatic aperture lens, and you can choose a manual variable aperture lens when the indoor illumination is constant or does not change much. The camera lens in the elevator car should choose a wide-angle lens with a horizontal field of view greater than 70 according to the size of the car.
5) With the need of miniaturization, the size of the lens needs to be reduced. In addition to the standard C interface of camera lens, Cs interface is also introduced. Because the Cs interface is 5mm shorter than the C interface and the distance between the lens and the photosensitive part is reduced, the Cs interface system is small and light, and the Cs interface lens is cheaper. A Cs interface camera can be equipped with a Cs interface lens or a C interface lens with a 5mm spacer. C-interface camera can only be equipped with C-interface lens, not Cs-interface lens.
6) The camera lens should aim at the monitoring target from the light source direction to avoid backlight. The focal length of the lens and the size of the camera target surface determine the viewing angle. The smaller the focal length, the larger the field of view, the larger the focal length and the smaller the field of view. If you want to consider clarity, you can use an electric zoom lens, which can be adjusted at any time as needed.
7) luminous flux: the luminous flux of the lens is measured by the ratio of the focal length of the lens to the luminous flux aperture (aperture), which is generally expressed by F. In the case of little light change, it is not necessary to change the aperture after adjusting to a suitable size, and a manual aperture lens can be used. When the aperture line changes greatly, such as outdoors, an automatic aperture lens is generally needed.
3. Front-end system configuration table
No. Product Name Product Model Unit Quantity Remarks
transfer system
There is always a certain distance between the monitoring site and the control center. From the monitoring site to the control center, it is necessary to transmit the image signal and the control signal of the control center to the site, so the transmission system includes two parts: video signal and control signal transmission.
1, video signal transmission
Generally speaking, coaxial cable is used to transmit video baseband signals, but optical cable can also be used to transmit TV signals and balance cable pairs, that is, telephone cable can be used for transmission. Because the cable can shield external electrostatic field and electromagnetic wave, it can reduce crosstalk and transmission loss. But when the cable is used as a long-distance transmission medium, it will affect the unbalanced low-frequency ground current, and sometimes there will be high-frequency interference. The signal transmission bandwidth is 50 Hz ~ 4 MHz. When the transmission distance is less than 200m, the influence of attenuation can generally be ignored when transmitting with coaxial cable. When the transmission distance exceeds 200m, the cable attenuation is large. In order to transmit signals with different frequencies in the whole bandwidth, cable compensation amplifier must be used. In some cases where wiring is very difficult, wireless transmission methods such as microwave directional transmission can be used, but it takes up frequency resources and needs to be approved by the Radio Management Committee.
2. Control signal transmission
For CCTV, the commonly used control methods are direct control, coding control and coaxial video control. Direct control is rarely used at present because there are too many cables. Coding control is to digitize (modulate) all control commands, transmit them, then demodulate them to the control equipment, and restore them to direct control quantities, which can save cables. This method has long transmission distance and is widely used in engineering at present. Coaxial video control means that control signals and video signals are transmitted by coaxial cable through frequency division or video signal blanking period, but the price is more expensive.
3, pipeline trench laying
In order to prevent electromagnetic interference and interference from external power supply and frequency conversion elevator, the cable should be laid in a well-grounded metal tube or metal bridge, and the cable should be protected.
4, transmission system configuration table
No. Product Name Product Model Unit Quantity Remarks
control system
Analog control system
1, video matrix switcher
In order to switch and control multi-channel video input signals and multi-channel video output signals, a switching matrix can be formed by electronic switches, so that any input can be switched to any output. The design should meet the necessary video input/output capability and be easy to expand. In addition to the main control keyboard, CCTV system can also set up sub-control keyboards as needed.
2. Duplex multi-picture video processor
Multi-channel video signals can be combined into an image, so that multi-channel camera signals can be watched on one monitor at the same time. The commonly used 16 picture splitter, also known as multi-picture video processor, is another use of duplex. A video recorder records multiple video signals at the same time, which has the function of single-channel playback, that is, you can choose any one of the multiple video signals recorded at the same time to play back on the monitor.
3. Multi-picture splitter
Through video digital processing, multiple pictures are merged into a divided picture, and a multi-picture divider appears. There are 4 picture splitters, 9 picture splitters and 16 picture splitters. In this way, with a monitor, a video recorder can monitor and record 4, 9, 16 pictures at the same time. Multi-picture splitters are usually divided into three categories:
Simplex image processor: simply monitor an image and record the segmented image.
Duplex image processor: while monitoring single image and divided image, it can record.
Full duplex image processor: It can play back the recorded signal while monitoring and recording.
4. Video distributor
A video signal can be distributed to multiple video outputs at the same time.
5.3.3.2 Digital Image Monitoring System
Video signal transmission through coaxial cable is called traditional analog signal transmission mode. In this way, the video signal has little attenuation in a short distance (for example, about 200m). If it exceeds 200m, the video signal must be compensated and amplified. The traditional CCTV monitoring system is more suitable for use in buildings or small geographical areas.
Digital monitoring system is a combination of computer network technology, multimedia technology and closed-circuit television technology, which is suitable for long-distance transmission of multi-channel video and audio signals. In fact, it is to digitize analog signals, compress and encode them, and transmit video images through computer networks and digital multimedia technologies.
Digital monitoring system organically combines computer network technology, multimedia technology and image monitoring technology, and can transmit high-definition and high-synchronization image signals. It is a brand-new security TV system and has become a powerful tool for modern building management.
Digital image monitoring system can realize remote image monitoring, organically connect monitoring points scattered all over the country through computer network, and enhance the overall security and automatic management ability of image monitoring by using multimedia technology.
At present, many companies use special compression methods and dynamic storage technology to ensure image quality. Data compression and image and sound synthesis are all completed by hardware, and real-time monitoring of 16 can be realized on one system. It can store 16 signals at the same time, and the video image does not lose frames. Dynamic storage technology ensures the continuity and high definition of monitoring images.
5.3.3.3 Digital Hard Disk Video System
1, the function of digital monitoring hard disk video system
Digital hard disk video recording is the latest and best digital image recording equipment in the field of security TV system. It can digitally compress, record and archive all the pictures taken by the camera in the monitoring system in real time, and can randomly retrieve the recorded images according to any retrieval requirements. Due to the adoption of digital recording technology, the anti-attenuation and anti-interference ability of recorded images can be greatly enhanced, so no matter how many times of retrieval or video playback, the clarity of played images will not be affected. However, after repeated retrieval and playback, the video recorded by traditional analog methods will have certain attenuation in image quality and cause a decline in signal-to-noise ratio. When it is necessary to copy the stored image, the digitally recorded image does not have the problem of copy deterioration, while the image recorded in analog mode will deteriorate every time it is copied.
Digital hard disk video recording system is a new generation of hard disk video recording system for monitoring images, which integrates computer network, multimedia intelligence and monitoring TV. The system not only realizes the local digital image monitoring and management, but also realizes the remote transmission of monitoring images, which strengthens the overall security management. In this system, all the image data are stored in digital form. Compared with the traditional analog signal system, the printed photos have higher definition and realism, and the data transmission is more reliable and faster. The system is based on modular design. Each module includes: signal acquisition module, monitoring module, image recording module, remote access module and central control module. The whole system is easy to maintain and install.
Because the computer system is equipped with digital hard disk video recording, the information can be freely transmitted to the range that the network can reach, so the display of monitoring images is no longer limited to the traditional image switching mode, and the controlled images can be monitored at any authorized place as required, so that the system has strong security management ability. The monitoring images are stored in a large-capacity disk array with high compression rate through the image recording module, which can be accessed and retrieved quickly at any time. In other words, multi-channel images of multiple cameras (up to 16 at present) can be displayed on one monitor in real time. At the same time, all images can be recorded in its built-in hard disk drive for playing, searching and conversion, and images can be backed up to an external hard disk. All operations can be completed on the remote control, thus getting rid of the Windows operating system and avoiding the crash. Compared with the traditional tape recording method, it is simple, reliable and has higher playback quality. All records can be kept for a long time, and the reuse rate is extremely high. It can also be transcribed into a CD for archiving. The hard disk configuration is larger than 40G, and the dynamic video can be saved for about one month or even longer.
2. The main characteristics of digital monitoring hard disk video recording system
(1) High efficiency and durability, saving maintenance cost.
Digital hard disk video greatly enhances the anti-attenuation and anti-interference ability of recorded images, and can be recorded, played back and retrieved repeatedly, without distortion or damage, with high efficiency and durability, and saves a lot of maintenance costs. Compared with traditional video storage, it is easy to be damaged after long-term use and has great advantages.
(2) Compatible with existing security TV system equipment.
On the basis of the existing security TV system configuration equipment, only the old video recorder and multi-screen video processor are replaced, and other equipment configured by the system can still be retained.
(3) Adopt special compressed storage technology.
Special compression storage technology is adopted to meet the requirements of high activity dynamic definition video recording and efficient compression storage. At present, some adopt standard MPEG compression storage technology, and some adopt D-TEG coding compression mode to achieve high compression ratio.
(4) High-speed search and clear still images.
Because the system uses hard disk to store images, the system can provide fast search function and high-definition still images. Image resolution can generally reach: 752X 582 or 640X480 pixels. Video recording speed: 25 frames per second. Playback speed: 25 frames per second. Before recording and playback, it can be accurate to year/month/day/hour/minute/second, and the color, brightness, contrast and color saturation of each picture can be adjusted independently.
(5) Strong confidentiality.
The traditional TV monitoring system uses tape to record real-time images, but once it is mastered by criminals, it provides criminals with opportunities to destroy evidence, replace or erase the contents of video tapes and other technical crimes, because anyone can do various operations as long as they have access to video recorders. In the digital TV monitoring system, the image playback is controlled by computer programs, and the operations such as image archiving, playback and status setting are strictly controlled by passwords. If the operator does not know the password or their password authority does not include the above operations, even the operator cannot know the content of the recorded image. In addition, because the hard disk video is used, there is no need to change the storage medium, so the hard disk is difficult to be taken away by anyone, or it can't be played back after being taken away, which is extremely confidential.
5.3.3.4 control system configuration table
No. Product Name Product Model Unit Quantity Remarks
display system
1, display and record
Display and recording equipment is generally installed in the security control room, which is mainly composed of black and white/color monitor, video recorder and video processing equipment.
1) black and white/color special display
Generally, the equipment that reproduces images from camera video signals requires that the horizontal resolution of black and white monitors should be greater than 600 lines, and that of color monitors should be greater than 350 lines.
2) video recorder
It is the recording and playback equipment of the monitoring system. Generally, time-lapse video recorders are used. With 180min ordinary video tape, it can be recorded for more than 24 hours, even up to 480h and 960h, and the remote control function of the video recorder can be automatically operated through the control signal. For the camera and video recording system linked with the safety alarm system, it is appropriate to configure the corresponding delay video recorder separately. At present, you can use digital CD burning and computer hard disk burning.
2. Display the system configuration table
No. Product Name Product Model Unit Quantity Remarks
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