Dry goods are coming: 30 introductory terminology for video surveillance systems

The video surveillance system is the most common subsystem in the weak current system. Many friends in the monitoring industry, especially when they first enter the business, have some headaches when they encounter some monitoring problems. The following article shares the basic knowledge of monitoring and answers!

1. What is the meaning of CCTV? - (Difficulty: Medium)

A: CCTV is the abbreviation of English Closed Circuit Television, meaning closed-circuit television monitoring system.

2. What is the focal length of the lens? - (Difficulty: Medium)

A: From the optical principle, the focal length is the distance from the focus to the center of the lens. That is, the focal length. For example, "f=8-24mm," means that the focal length of the lens is 8-24mm.

3. What is the relationship between the length of the focal length and the size of the image size? (Difficulty: Easy)

A: The length of the focal length is proportional to the size of the image. The longer the focal length, the larger the image, and the shorter the focal length, the smaller the image. The focal length of the lens is inversely proportional to the size of the viewing angle. The longer the focal length, the smaller the viewing angle, and the shorter the focal length, the larger the viewing angle.

4. What is the relationship between the length of the focal length and the depth of field? (Difficulty: Easy)

A: The focal length is inversely proportional to the depth of field. The longer the focal length, the smaller the depth of field, and the shorter the focal length, the greater the depth of field. The length of the focal length is inversely proportional to the strength of the tou visual sense. The longer the focal length, the weaker the visual perception, and the shorter the focal length, the stronger the visual perception.

5. What is the camera's back focus adjustment? - (Difficulty: Easy)

A: When installing the standard lens, the image of the subject should be just on the target surface of the CCD image sensor. A fixed lens can be used, and the method of adjusting the position of the ccd is called the camera's back focus adjustment.

6. What is the lens F value? - (Difficulty: Easy)

A: The F value refers to the brightness of the lens. The <1.2> of the <maximum aperture ratio 1:1.2> shown in the lens specifications is the F value. The smaller the F value, the higher the brightness of the lens. Each time the F value is reduced by one step, the brightness is increased by two times. The amount of light incident on the lens is proportional to the area of ​​the beam [the square of the effective aperture [D] of the lens], so the brightness of the image is inversely proportional to the square of the F value. From this calculation, the brightness is increased by twice as much as the F value is reduced by one step.

7. What is the aperture of the lens? - (Difficulty: Easy)

A: The function of the aperture is like the rainbow trout of our human eyes. It is mainly used to adjust the amount of light entering the camera. F is the aperture of the lens. The smaller F value indicates a larger aperture.

8. What is depth of field? - (Difficulty: Easy)

A: When an object is in focus, all scenes from a certain distance in front of the object to a certain distance behind it are also clear. The distance from front to back with a fairly clear focus is called depth of field.

9. What is a wide-angle lens? (Wide Angle) - (Difficulty: Easy)

A: Because the focal length of the wide-angle lens is very short, the scene projected on the film becomes smaller and the angle of the lens is widened. In addition to shooting more scenes, it is possible to shoot a wide angle image in a narrow environment. The viewing angle is above 90 degrees, the viewing range is large, and the near image is deformed.

10. What is a telephoto lens? - (Difficulty: Easy)

A: The viewing angle is less than 20 degrees, and the focal length can reach several tens of millimeters or hundreds of millimeters.

11. What is a zoom lens? - (Difficulty: Easy)

A: The focal length of the lens is continuously variable, and the focal length can be changed from wide angle to telephoto. The longer the focal length, the larger the image.

12. What is optical zoom? - (Difficulty: Easy)

A: It is based on the optical lens structure to achieve zooming. It is to enlarge and reduce the subject to be photographed by moving the lens. The larger the optical zoom factor, the farther the subject can be photographed.

13. What is a three-variable lens? - (Difficulty: Easy)

A: Aperture, focus, and focal length need to be adjusted manually.

14. What is a two-variable lens? - (Difficulty: Easy)

A: Usually it is an auto iris lens, and the focus and focus need to be adjusted manually.

15. What is the video driver for the lens? (Video driver) - (Difficulty: Easy)

A: It sends a video signal and power from the camera to the lens to control the aperture on the lens. This video input lens contains an amplifier circuit to convert the video signal from the camera into the control of the aperture motor.

16. What is the DC driver of the lens (DC driverno Amp) - (Difficulty: Easy)

A: It uses the DC voltage on the camera to directly control the aperture. This lens contains only the galvanometer aperture motor. There is no amplifier circuit in the camera. The two drive models are not interchangeable, but now there is a universal auto iris lens

17. What is the difference between a C-type interface and a CS-type interface? - (Difficulty: Easy)

A: The lens is equipped with two types of C and CS. The C-mounted lens has a 5mm ring for adjusting the aperture value between the CCD camera and the lens. Type C mounted cameras can use CS type lenses, but CS mounted cameras cannot use C type lenses.

18. What is an aspherical lens? (Aspherical Lens) - (Difficulty: Easy)

Answer: The shape of the lens grinding is parabolic, quadratic, cubic or high-order curve, and the correction factor of the lens, such as phase difference, chromatic aberration and spherical aberration, is considered in the design. Usually, an aspherical lens can reach multiple spherical surfaces. The lens corrects the effect of aberrations, so the number of lenses can be reduced, resulting in better lens accuracy, better definition, more accurate color reproduction, reduced light reflection within the lens, and a corresponding reduction in lens volume. The aspherical lens has the characteristics of high magnification, short object distance, and large aperture. The zooming height can simplify the type of lens. The short object distance can be applied to close-range imaging, and the large aperture can be adapted to dark places, so the application field is becoming wider and wider. Japanese AVENIA's aspherical lens product SSV0770, close-up distance up to 30cm

19. What is the relative aperture of the lens - (Difficulty: Easy)

A: In order to control the amount of light flux through the lens, an aperture is placed at the rear of the lens. Assuming that the effective aperture of the aperture is d, due to the relationship of light refraction, the actual effective aperture of the lens is D, which is larger than d, and the ratio of D to focal length f is defined as relative aperture A, ie A=D/f, and the relative aperture of the lens is determined. The illuminance of the image, the illuminance of the image is proportional to the square of the relative aperture of the lens. It is customary to use F=f/D, that is, the reciprocal of the relative optical path to indicate the size of the lens aperture. The smaller the F value, the larger the aperture and the greater the luminous flux reaching the CCD chip. So in the case of the same focal length f, the smaller the F value, the better the lens

20. What is CMOS technology? - (Difficulty: Easy)

A: CMOS is called ComplementaryMetal-OxideSemiconductor, and Chinese translation is a complementary oxidized metal semiconductor. CMOS manufacturing technology is no different from general computer chips, mainly using semiconductors made of two elements, silicon and germanium, to coexist with N (band-to-electric) and P (with +-electric) levels in CMOS. Semiconductor, the current generated by these two complementary effects can be recorded and interpreted as images by the processing chip.

21, what is CCD - (difficulty: easy)

A: The CCD is called Charge Coupled Device, and the Chinese translation is "charge-coupled device". It is made of a high-sensitivity semiconductor material that converts light into electrical charge. Therefore, it has the advantages of high sensitivity, strong glare resistance, small distortion, small volume, long life, and anti-vibration. The photosensitive element on it is called a "pixel." The more the number of CCD pixels, the larger the single pixel size, the clearer the collected image will be.

22. What are the dimensions of the CCD chip? (Difficulty: Easy)

A: The imaging size of the CCD is usually 1/2", 1/3"1/4". The smaller the size of the camera, the smaller the volume can be. Under the same optical lens, the larger the imaging size, the field of view. The larger the angle. The chip size of the imaging surface (width X height) diagonal 1/26.4x4.8mm8mm1/34.8x3.6mm6mm

23. What is a HAD sensor - (Difficulty: Harder)

A: The HAD (HOLE-ACCUMULATION DIODE) sensor is on the surface of the N-type substrate, P-type, N+2 pole body, plus the positive hole accumulation layer, which is the unique structure of SONY. Due to the design of this layer of positive hole accumulation layer, the problem of dark current often on the surface of the sensor can be solved. In addition, a vertical tunnel through which electrons can pass is designed on the N-type substrate, so that the aperture ratio is improved, and in other words, the sensitivity is also improved. In the early 1980s, Sony used it in the variable-speed electronic shutter product to obtain clear images when shooting fast moving objects.

24, what is SUPERHADCCD - (difficulty: more difficult)

A: The unit area of ​​the CCD is getting smaller and smaller. The tiny lens technology can no longer enhance the brightness. If the magnification of the internal amplifier of the CCD module is increased, the noise will be improved and the image quality will be obviously affected. . Sony has further developed the research and development of CCD technology. It has improved the technology of using tiny lenses, improved the light utilization rate, and developed the shape optimization technology of the lens, namely Sony SUPERHADCCD technology. Basically, it is designed to enhance the light utilization efficiency to enhance the brightness, which also lays the foundation for the current CCD basic technology.

25. What is the EXVIEW HAD CCD? - (Difficulty: Easy)

A: Infrared light that is longer than the visible light wavelength can also be photoelectrically converted in a semiconductor silicon chip. However, until now, the CCD cannot collect these photoelectrically converted charges into the sensor in an efficient manner. To this end, Sony's newly developed "EXVIEWHADCCD" technology in 1998 can effectively convert near-infrared light that has not been effectively utilized before into image data. The range of visible light is extended to infrared rays, so that the brightness can be greatly improved. When using the "EXVIEW HAD CCD" component, you can get high-brightness photos in a dark environment. Moreover, when the photoelectric conversion is performed in the deep layer of the silicon crystal plate, the SMEAR component that leaks into the vertical CCD portion can also be collected in the sensor, so the noise that affects the image quality is also greatly reduced.

26, what is the scanning system, what are the commonly used? - (Difficulty: easy)

A: The TV system refers to the specific systems and technical standards adopted by a country's television system. Specifically, there are three TV systems in the world. Currently, most countries in the world (including most European countries, Africa, Australia, and China) adopt PAL system and adopt 25fps frame rate; the United States, Japan, Canada and other countries adopt It is an NTSC system developed by the National Television Standards Committee (NTSC) with a frame rate of 30 fps (precisely 29.97 fps); another system of SECAM is mainly used in France, the former Soviet Union and Eastern European countries.

27. What is the working mode of the CCD camera?——(Difficulty: Easy)

Answer: The image of the subject is focused on the CCD chip through the lens. The CCD accumulates the corresponding proportion of charge according to the intensity of the light. The accumulated charge of each pixel is moved out point by point under the control of video timing. After filtering and amplification processing , forming a video signal output. The video signal is connected to the video input of the monitor or TV to see the same video image as the original image.

28. What is the pixel of the camera? - (Difficulty: Medium)

A: Pixel is one of the important indicators to measure the camera CCD. In general, products with higher pixels have better image quality. On the other hand, the higher the pixel, the better. For the same picture, the higher the pixel, the stronger the ability to parse the image. In order to obtain a high-resolution image or picture, the amount of data recorded is also large. Much more, the requirements for storage devices are much higher

29. What is the resolution of the camera? - (Difficulty: Medium)

A: Usually refers to horizontal resolution, unless "vertical" is specified. The indicator for evaluating camera resolution is the horizontal resolution, which is in pairs, that is, the number of black and white pairs that can be resolved after imaging. Commonly used black and white cameras have a resolution of 380-600 and a color of 330-540. The larger the value, the clearer the image.

30. What is the vertical resolution of the camera? (-(Difficulty: Easy)

A: The vertical resolution (verticalre solusion) is obtained by observing the maximum number of horizontally interactive black and white lines.