Explication to surveillance system terms

By Published by
. Views . Comments . 2 Votes


Camera Synchronization Modes: Vertical Synchronization, Color Video Compound Signal Synchronization, External Synchronization, Direct Currency Locked and Complete Synchronization
Complete synchronous locked is the best way of synchronizing entirely two precise instruments such as broadcastings and studio vidicons. It can synchronize the horizontal, the vertical, the even or odd district, the color-triggered frequency and phases.
Vertical Synchronization is the simplest mode to synchronize two cameras. With the vertical drive frequency, it can make sure an old video switching or 4-switching instrument of showing several image sources on one monitor. The vertical drive signals generally has the repeated frequency 20/16.7ms (50/60Hz) and pulses with a width 1~3ms.
Color video compound signal means video signal plus color triggered signal. Color Video Compound Signal Synchronization is the synchronization of camera and external color video compound signal. However, it just synchronizes ones of horizontal and vertical but not the color triggered synchronization.
External synchronization is most similar to the video compound signal synchronization. The video signal is synchronized from a camera to another one. The camera with external synchronization can pick up the horizontal and vertical signals from the color video compound signal synchronously.

Achromatic trundling
The video camera with a digital signal processor only produce image trundled in strong color effect while working under the fluorescent light. The image turns into blue from white color, and then changes into pink color and last turns back to the white color. It continues a circulation caused by the AC power source working at a level of 50/60Hz.Different from the candescences can offer stable light, the daylight lamps emit light fluctuating for the change of AC strength and colors in a 8.3ms speed. Traditional camera needs 100~150ms to calculate the white balance, 8.5mslower than the AC. So, for the nonce image, it needs 8 circulation times to get a color trundling in cleanness. 

Back-light compensation 
Back-light compensation can offer ideal exposal of an object in a setting with strong back light, no matter the main object moves to any position on screen, in the centre, up or down and left or right. For an ordinary camera without super-strong dynamic characteristic, only having 1/60s shutter speed and 2.0aperture option as example, it is ineluctable of a bright background or a point light source behind the main object. The average value of all latest light taken from camera decides the exposal grade. It is not a good way to calculate because the aperture is shuttered while the shutter speed rises and the main object is too dark to be seen. To comeover this problem, the back-light compensation is added as an authorized theory to generally use on camera. Image is firstly divide into 6 or rooms (2 rooms is on reiteration), and every room can separately calculate the exposal grade with this added right, for example, the centre part can rise 9 times of other ones, and the object in the centre position can be seen very clearly, since the exposal mainly take the reference of the light grade in the centre to calculate. However, there is a big bug which the object becomes dark if it is moved to other position but the centre, since it is not distinguished and granted a right when it is not in the centre.
F stands for the lens aperture; F pause 2:1 and f3.4mm means that the lens focus is 3.4mm.
Lens F2.0 and f3.4~4 usually have a competitive price, used ordinarily in veneer camera. The aperture of lens F2.0 can collect light as half as what human being eyes can do and lens 3.4ms of 1/4’’CCD has an angle 60degree and of 1/3’’CCD an angle 90 degree, very close to that of human being eyes. Human being eyes have a large visual angle, about 150 degree ~180 degree. Pls note that, F state and f focus are only basic parameters but do not represent good quality.
Super-wide dynamic is a camera image characteristic under a strong comparison. Wide dynamic camera has a dynamic range decuples times larger than the traditional camera with that of only 3:1. The natural light can be arrayed from 120,000Lux to 0.00035Lux in a star night. This comparison is easily seen by human being eyes. Human being eyes can deal with the comparison 1000:1. To a traditional camera, there is a problem for it to deal with this comparison. It just has a comparison capacity of 3:1, getting an inner right exposal only with a 1/60s electronic shutter or higher-class ones, but the outdoor image will be clear away (all in the white).On opposed, when traditional camera gets a perfect outdoor exposal with 1/6000s, it will be eliminated the inner image(all in the dark)

Field depth
The field depth is that when an object is on a clear focus, it is all clear for the scene in the range from a distance before this object to that of the behind. This range is called field depth. It is divided into foreground field depth and behind field depth. The latter one is longer than the former. The field depth is larger, the scene far away from the focus is clearer, contrarily the field depth is small and the scene far is blurring.

Focus is an optical parameter indispensable in all .optical instruments. Theoretically, it is the distance from the focus to the central of lens. For a lens, it is a thing meaning of focus. The length of focus is proportional to the size of imaging. Focus is long and image is big; focus is short and image is small. The lens focus is inversely proportional to the visual angle. Focus is long and the perspective effect is weak; focus is short and the perspective effect is strong. The length of focus is also inversely proportional to the contrast. Focus is long and the contract is small; focus is short and the contract is large. Focusing distance is big and the field depth is long; focusing distance is small and the field depth is short. So, to shoot a distant scene, it is better to choose a lens with a big focusing distance; and, to screen a close shot, it is better to use a lens with a small focusing distance. The focusing distance is measured by unit cm.

There are manual switch and automatic switch. The manual is to choose artificially the channel you want to look; the automatic is to setup the video switching order in advance. The switching time can be adjusted with one button, generally between 1s to 30s. If 24-hour monitoring is not in need, a switch instrument can be added into the control room, connecting its input with camera and the output with monitor. The switch input have pathways of 2, 4,8,12 and 16, and the output is divided into single pathway and double pathway matchable with synchronous switching audio (depending on the type.) 

Video server
Video server is a professional computer instrument for video data compressing, memorizing and processing. It is applied generally n video monitoring, internet educating, IP video meeting, advertisement inserting, video program ordering and so on. The video server employs the compressed formats of M-JPEG, H.261, H.263, MPEG-2, and MPEG-4, etc., to compress and recode the video data under the technology standard for meeting the need of storage and transmission. It has multi- channel outputs and inputs and kinds of audio connecters in formats. It can realize the audio data transmission and share by joining net with matched SCST or FC net connecters. It is composed of audio compressing coder, high capacity storage instrument, input or output channels, internet interface, audio and video interfaces, RS422 serial interfaces, protocol interface, software interface and audio and video crossing matrix, etc., providing fragmentary phase and video processing functions.

Internet camera
Internet camera is a new generation camera of combining the traditional camera and the internet technique. It transmits the image by internet to another internet end. The person in distance can monitor the image without any professional software but only a standard internet browser such as Microsoft IE or Netscape. There is a built-in inserted chip with a real time inserted operation system of internet camera. The video signal digitized from the camera is compressed in high efficiency by the chip, and then transmitted to the web server thought the general internet. The internet user can view the image from the camera directly with the browser and the user granted also can control the Pan & Tilt lens or do something with the system configuration.

Dynamic sensing
The whole monitor picture is divided into several districts. The user can choose any one of them and setup sensitivity with degree from 1 to 20 to the chose district. When something moves, the camera can senses it and take a record. 

Communication interface
Communication interface is brought up about the video and audio input and output in security monitor system. It contains RS-232, RS-485. general interfaces, supporting general internet-joining setting such as PSTN, ISDN and LAN etc., USB2.0 high speed data interface connecting computer for important image backup, and VGA output with line-scan function selectable on your need.

Monitor is the standard output of surveillance system. We can get the image from the camera because of the monitor. There are color monitor and black and white monitor, with sizes of 9, 10, 12, 14, 15, 17, 21 inch etc.. The most usual use is 14inch size. Monitor also has horizontal resolution like camera representing with TV line. In the practical use, it requires that the monitor lines must match to the camera. Besides, there are some monitors with audio input, S-video input, and RGB heft input etc. except of audio input closely relating to monitoring, other inputs most are about the image processing.

Pan & Tilt Heads
Pan & Tilt Heads is an installation platform with AC, movable on directions horizontal and vertical. There are inner pan & tilt heads and outdoor ones. The outdoor pan & tilt heads have better airproof capacity, waterproof, dustproof and big load. You can install them on walls or ceilings with two ways of installing aside and hanging. Pan & tilt heads have the general or dome looks. The dome pan & tilt head is set in a dome shield with characteristics of preventing dust and image inference as well as concealment, artistic look and fast-installation.

Inserted system
Inserted system integrates the operating system and functioning softwares into one computer hardware system. Simply it is to incorporate of system application software and hardware, similar to BTOS, with high responding speed, high degree automatization and short code software, especially suitable for real-time application and multi-task system.

Automatic high speed tracking dome
Automatic high speed tracking dome is combined of photics, electronics, machines, information processing and internet into one system. It is composed of camera lens, dynamical transmission, and movement controlling instrument, basic on high speed collateral processing image analyzing, identifying, compressing and communicating, with kinds functions of video image taking, position controlling, lens direction setting, moving object detecting, identifying and tracking, flame and smoke alarming etc. when moving object go into the dome camera real time monitoring range, with the calculating of difference between former and present image by high speed DSP chip. The object is determined as a moving one when the calculating result reaches a figure and the dome camera sent order automatically to the pan & tilt head for direction adjustment. That dome camera tracks the moving object is in sequence and no need of artificial controlling or computer system supporting. To dispel of the image interference from AC, you can switch to the LL (Line Lock) mode which is a synchronization of locking the camera synchronous pulse with applying AC.

Automatic gain control  
Automatic gain control requires the camera video output signal to the TV transmission regulated standard level. For output of standard video signal under different scene illumination, it is necessary to expand the amplifier gain adjustable in a large range. This kind of adjustment usually finishes in automatism with the detected video signal average level. The circuit of realizing this function is called automatic gain control circuit, for short AGC circuit. With the AGC function, the camera sensitivity can rise under the minimum illumination, but the interference turns in patency for the enlargement of both signal and interference synchronously.

Sound source 
Sound source means the sound-recording carrier or the instrument of playing the sound. The carrier has been recorded sound. With this premise, the acoustics system can revive the sound in carrier. This carrier is the source to the acoustics system. Audio source records and processes the simulating signal which is sequent on time and whose range changes following the time (such as sound wave, the currency in sound system and voltage signals). This simulating signal directly transferred from the sound can be directly magnified by the traditional amplifier with easy and convenient process. Correspondingly, the digital source indirectly records and processes the binary data stream formed with permutation combination of 0 and 1. The simulative sound wave can’t be employed directly by the digital source but have to be transferred into digital signal for recording through the special instrument. When playing, it is necessary to turn the digital signal into the simulative one for magnifying by traditional amplifier. It is obvious that digital source process more complexes but the its advantage is that its Signal-to-Noise ratio and dynamic range is far superb that of the simulative. The effect by digital source is still kept a high quality while time after time copy and transmission, which simulative source can’t reach.

Real-time editing
Real-time editing is to process the original data collected by hard disc camera integrally turning into image file with the standard formats of MPEG-1 or MPEG-2 and saving to the hard disc directly without data-over-stock and data-loss during the process. It is very different from the operation in steps of computer writing which collects the original data first and then processes and transfers these data into standard MPEG-1 or MPEG-2 format image file. It is high required of high operating speed for the whole system otherwise it just can depend on lower the image quality to reach the data quantity.

Super HAD image sensor 
Super HAD image sensor,HAD---Hole Accumulation Diode, is CCD image sensor with electronic image quality upgrading technique. It can rise the CCD sensor performance and strengthen the digital processing function, reducing noise and interference while camera working, making image brighter and clearer with colors. The effect with this function is prominent especially working at night or under scene light inadequate.

White balance  
White balance means that object color changes different from the original because of the coming light color. The image color temperature will be different under different light while shooting. The picture shot under the tungsten filament light is in deflection of orange color. Unlike human being eyes. CCD can’t correct automatically the color variation. So, a white balance correction operation is in need which can amend the error caused by external light, adjusting the color strength of red, green and blue in the whole picture under a reference of the image present particularity.

CODEC of Alterable Code Stream
CODEC---Coder-decoder device
Alterable code stream CODEC can self-regulate the band width according to the variation of data quantity. When the images change fast with rich color, it can get a bigger band width and when the images change slowly with non-rich color, it gets a smaller band width. It can guarantee high quality image while recording as well as a furthest room-saving.

CODEC of Fixed Code Stream 
CODEC---Coder-decoder device
Fixed code stream CODEC offers a fixed band width no matter how big or small the data quantity is. When the images with rich color change fast, it lowers the image quality for narrow band width and the image looks in pause and color distortion. When data quantity is small, there is much band width and it wastes the memory room.

Access Control Technology
Access Control Technology is a new way of access management. It allows persons with the entitled to get into an appointed district, at the same time refuses those without the entitled. The system code keyboard or a reader set aside the door transmits the data read to the local controller affirming admission according to database compiled in advance.  

Write a guide
Explore More
Choose a template

Additional site navigation