Basic knowledge of video surveillance

2016-07-13

1. What are the two types of cameras according to imaging components?

It is divided into two types of CCD and CMOS. The advantage of CCD is that the image quality is good and the illumination is low. CMOS is mainly for the use, generally only for the visual intercom, home chat camera.

2, what is the full name of the CCD?

CCD, the English charge coupled device, an abbreviation for a charge-coupled device, is a special semiconductor device that has many of the same photosensitive elements, each of which is called a pixel. CCD is a very important part of the camera, it acts as a light to convert the electric signal, similar to the human eye, so its performance will directly affect the performance of the camera.

3, what is the surface structure of the CCD?

Each of the CCD elements is made up of millions of MOS capacitors, each of which corresponds to a focused lens that converts light from the lens to electrical energy.

4, what is the definition unit of the camera?
TVL, also called TV lines, such as 420-wire, 480-wire.

5. What kinds of video formats are there?

At present, there are three kinds of analog technology in the global color TV system, that is, NTSC (also known as N, or the United States), PAL (also known as PAL or West German, British Standard), China can only use PAL system, SECAM system (also known as SECON or French format).

6. How does interlaced scanning work?

The earliest PAL system, to display 25 frames per second, each frame is composed of 2 fields, odd number field, even number field. An odd field is a scan of an electron beam when scanning an odd line in 1-625 lines, and an even number field indicates that an electron beam scan scans the even lines in 1-625 rows, so that 50 fields per second are scanned. This is an interlaced scan.

7, progressive scan mode is how to operate? Progressive scan is sequentially scanned from line 1th-625 lines, with no parity.

8. What is the lowest illumination unit?
Illuminance units are: Lux, (Lux). Light evenly irradiated objects, the luminous flux on the area of 1 square meters is 1 lumens (the traditional method of measurement is a light-point candle 1 meters away from the amount of light 1 square meters), its illuminance is 1 lux.

9. What is the automatic gain control abbreviation?
AGC Full Name: Auto Gain Control

10, automatic gain control is to meet what conditions?
The video signal amplitude of the CCD output has a standard value: 1vp-p. When the light is too strong or too weak, the video signal will exceed or fall below this intensity. In this case, circuit processing is required to reduce or enhance the video signal to meet the standard values. The function of this TV implementation is automatic gain control. Automatic gain enables brighter video to be illuminated, enabling the camera to achieve a lower illumination level.

11, what is the electronic aperture abbreviation?

The electronic aperture adjusts the light intensity by automatically adjusting the electronic shutter speed through the camera, which is referred to as ELC.

12, the electronic shutter refers to which component of what parameters?

Electronic shutter refers to the speed of the CCD scan, usually from 1/10000 seconds to 1/50 seconds, some can be faster or slower. When the speed is 1/10000 seconds, it means that the time required for the CCD scan to complete an image is 1/10000 seconds. The speed of the scan affects the brightness of the image, the higher the scanning speed, the lower the imaging brightness, the lower the scanning speed, and the higher the imaging brightness. In addition, the scanning speed will affect the high-speed moving object imaging, the object in the high-speed movement of imaging in the low-speed scanning will form a drag image blur, in the high-speed scanning imaging fast, drag shadow reduction, monitoring moving objects preferably choose better light conditions and faster electronic brightness.

13, automatic white balance control abbreviation for what? Why does the camera need white balance?

AWC Full Name: Automatic white balance Control. The reason why the camera needs white balance is because the camera sees white that is different from the white that the human eye sees. White reflects all the colors of the light, when the reflected light is dominated by a certain color (different colors of light with different color temperature), the camera to see the white objects will become this color, resulting in color. The human eye will automatically adapt to the color temperature, allowing us to correctly identify the original colour of the object and the reflected light, even if it reflects only one light. Therefore, the camera needs to process the video, so that the camera can correctly recognize the reflected light and the original color in different color temperature, so that the person seems more acceptable, this process is called white balance. The white balance function of the camera can only be adjusted within a certain temperature range, such as 3200K (incandescent), 6500K or 9300K.

14, automatic tracking white balance control abbreviation for what?
Auto-tracking white balance abbreviated to ATW.

15. What is the backlight compensation abbreviation for?

backlight compensation abbreviation BLC full name: Back light Control 59, backlight compensation is to solve what problem? It is mainly to solve the uneven light in the monitoring area. Especially backlight situation, the backlight part of the screen is black, enable backlight compensation can be dimmed part of the image highlighting.

16. What kinds of synchronization methods are commonly used in cameras?

There are mainly internal synchronization, external synchronization, power synchronization, Kimsan Li cameras and vs synchronization. Used in conjunction with the Kimsan Li matrix. Power sync is when AC power is used, all cameras are synchronized at the frequency of the AC power supply, allowing the camera to be used in fluorescent lighting environments , the working frequency is consistent with the flicker frequency of the light, avoiding the bias color. system synchronization switch is the premise of the system is the camera in a synchronous signal operation, if the matrix in the switch with this synchronization signal as the benchmark, You can achieve a broadcast-level switching effect. In the actual monitoring project to solve the problem is: How to send the synchronization signal to all the cameras and matrices in the system, and to ensure that each camera and matrix, each camera synchronization position is consistent. because a camera with system synchronization places the sync position of VS on the blanking area, so that the matrix switches between vs synchronization, The matrix sends a synchronous signal to the camera through the coaxial video cable, forcing all cameras to synchronize, so that each switching occurs in the presence of the blanking area, completely solve the video switching problem of image jitter, the user simply through the menu set at each video input side overlay vs signal, There is no need to make any changes to the line or hardware.

Basic knowledge of video surveillance