The "monitoring system" is one of the most widely used systems in security systems. Monitoring systems are generally composed of front-end cameras and back-end software systems. Currently, monitoring systems are widely used in major, medium, and small cities across the country. Many friends in the surveillance industry, especially those who have just entered the industry, have encountered some monitoring problems and have been confused. The following article shares the basics of monitoring and interpretation.
1. What is the meaning of CCTV? —— (Difficulty: Moderate)
A: CCTV is an abbreviation of English Closed Circuit Television, which means closed-circuit television monitoring system.
2. What is the focal length of the lens? —— (Difficulty: Moderate)
A: From the optical principle, the focal length is the distance from the focal point to the center of the lens. The focal length. Such as "f=8-24mm," means that the focal length of the lens is 8-24mm.
3. What is the relationship between focal length and imaging size? —— (Difficulty: Easy)
A: The focal length is proportional to the imaging size. The longer the focal length, the larger the imaging. The shorter the focal length, the smaller the imaging. The focal length of the lens is inversely proportional to the size of the viewing angle, the longer the focal length, the smaller the angle of view, and the shorter the focal length, the larger the angle of view.
4. What is the relationship between the length of focal length and perspective? —— (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 focal length is inversely proportional to the strength of perspective. The longer the focal length is, the weaker the perspective is, and the shorter the focal length is, the stronger the perspective is.
5. What is the camera's back focus adjustment? —— (Difficulty: Easy)
A: When the standard lens is mounted, the image of the subject to be shot is exactly 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 rear focus of the camera.
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 specification is the F value. The smaller the F value, the higher the brightness of the lens. Each time the F value is reduced by the first-order distance, the brightness is increased by twice. The incident light amount of the lens is proportional to the cross-sectional area of ​​the light beam [the square of the effective aperture [D] of the lens], so the image brightness is inversely proportional to the square of the F-number. From this, it is estimated that the brightness is increased twice for each decrease in F-number.
7. What is the aperture of the lens? —— (Difficulty: Easy)
A: The function of the aperture is just like the rainbow of our human eyes. It is mainly used to adjust the amount of light entering the camera, F means the aperture of the lens, and a smaller F value means a larger aperture.
8. What is the depth of field? —— (Difficulty: Easy)
A: When an object is clearly focused, 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 where the focus is quite clear is called the depth of field.
9. What is a wide-angle lens? (Wide Angle)——(Difficulty: Easy)
A: Since the wide-angle lens has a very short focal length, the scene projected onto the film becomes smaller and the angle at which the lens is shot is widened. In addition to shooting more scenes, it is possible to capture wide-angle images in a narrow environment. The viewing angle is more than 90 degrees, the observation range is relatively large, and the near image is deformed.
10. What is a telephoto lens? —— (Difficulty: Easy)
A: Within 20 degrees of view, the focal length can reach 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 imaging.
12. What is optical zoom? —— (Difficulty: Easy)
A: It is based on the optical lens structure to achieve zoom, that is, through the lens movement to zoom in and zoom out the scene to be shot, the larger the optical zoom, the more distant the scene can be shot.
13, what is a three variable lens? —— (Difficulty: Easy)
A: The aperture, focus, and focal length all need to be adjusted.
14, what is a two variable lens? —— (Difficulty: Easy)
A: Usually an auto iris lens, and focus and focus must be adjusted.
15, what is the video driver of 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 that converts the video signal from the camera to control the aperture motor.
16. What is the DC driverno Amp - (difficulty: easy)
A: It uses the DC voltage on the camera to directly control the aperture. This lens contains only a galvo diaphragm motor and there is no amplifier circuit in the camera. The two types of drive products are not interchangeable, but there is now a general-purpose automatic aperture 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, C-type and CS-type. The C-type lens is equipped with a 5-mm ring to adjust the aperture value between the CCD camera and the lens. Type C cameras can be used with Type C cameras, but cameras equipped with CS cannot use Type C lenses.
18. What is an aspheric lens? (Aspherical Lens)——(Difficulty: Easy)
A: The shape of the lens grinding is parabola, quadratic curve, cubic curve or high-order curve, and the correction factors such as lens aberration, chromatic aberration, spherical aberration, etc. are taken into account in the design, and usually one aspherical lens can achieve multiple spheres. The lens corrects the aberration effect, so the number of lenses can be reduced, so that the accuracy of the lens is better, the resolution is better, the color reproduction is more accurate, the light reflection in the lens is reduced, and the lens volume is also reduced accordingly. Aspherical lenses feature high magnification, short object distance, and large aperture. High magnification can simplify the type of lens, short object distance can be used in the occasion of close-range shooting, and large aperture can adapt to dark places, so the application field is becoming wider and wider. Japan's AVENIA aspheric lens product SSV0770, close to 30cm.
19, what is the relative aperture of the lens - (Difficulty: easy)
Answer: In order to control the amount of light flux through the lens, an aperture is set 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. The ratio of D to the focal length f is defined as the relative aperture A, that is, A=D/f, and the relative aperture of the lens is determined. The illuminance of the captured image, like the illuminance of the image, is proportional to the square of the relative aperture of the lens. Generally, it is customary to use F=f/D, which is the reciprocal of the relative light path to indicate the size of the lens aperture. The smaller the value of F, the larger the aperture, the greater the luminous flux reaching the CCD chip. Therefore, 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: The CMOS is called ComplementaryMetal-Oxide Semiconductor and the Chinese translation is Complementary Metal Oxide Semiconductor. The manufacturing technology of CMOS is no different from general computer chips. It is mainly made of semiconductors made of silicon and germanium, which make it possible to coexist on the CMOS with N (band-electricity) and P (band + electricity) grades. In semiconductors, the current generated by these two complementary effects can be recorded and interpreted by the processing chip as an image.
21, what is CCD - (difficulty: easy)
A: The CCD is called the Charge Coupled Device, which translates to "charge-coupled devices." It is made of a high-sensitivity semiconductor material that converts light into electric charge. Therefore, it has the advantages of high sensitivity, anti-glare, small distortion, small size, long life, anti-vibration and so on. The photosensitive element on it is called "pixel". The larger the number of CCD pixels and the larger the size of a single pixel, the clearer the collected images will be.
22. What are the dimensions of the CCD chip? —— (Difficulty: Easy)
A: The image size of a CCD is commonly used. The size of a camera with a smaller 1/2", 1/3", 1/4" size can be made smaller. Under the same optical lens, the larger the imaging size, the larger the field of view. The larger the angle is, the larger the chip size is, the imaging plane size (width X height) diagonal 1/26.4x4.8mm8mm1/34.8x3.6mm6mm.
23, what is a HAD sensor - (Difficulty: more difficult)
A: The HAD (HOLE-ACCUMULATION DIODE) sensor is based on the N-type substrate, P-type, N + 2 polar body surface, plus positive pore accumulation layer, which is SONY unique structure. Due to the design of this positive hole accumulation layer, the dark current problem often found on the surface of the sensor can be solved. In addition, the vertical type tunnel through which electrons can pass is designed on the N-type substrate, so that the aperture ratio is increased, and the sentence is changed, which also increases the sensitivity. In the early 80s, Sony led its use in variable-speed electronic shutter products. Clear images can also be obtained when shooting fast-moving objects.
24, what is SUPERHADCCD - (difficulty: more difficult)
A: The unit area of ​​the CCD is also getting smaller and smaller. The tiny lens technology can no longer enhance the brightness. If the magnification of the amplifier inside the CCD module is increased, the noise will be improved and the image quality will be significantly affected. . Sony furthered the research and development of CCD technology, improved the technology of using tiny lenses in the past, improved the light utilization rate, and developed the technology that optimizes the shape of the lens, the Sony SUPERHADCCD technology. Basically, the design that enhances the luminosity by improving the light use efficiency has laid the foundation for the current CCD basic technology.
25. What is EXVIEW HAD CCD? —— (Difficulty: Easy)
A: The infrared light longer than the visible light wavelength can also be photoelectrically converted in the semiconductor silicon chip. However, until now, the CCD has not been able to collect these photoelectrically converted charges in an effective way into the sensor. For this reason, 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 visible light range is extended to infrared light, allowing the brightness to be greatly improved. With the "EXVIEW HAD CCD" component, high-brightness photographs can also be obtained in a dark environment. In addition, when the photoelectric conversion is performed in the deep layer of the silicon crystal plate, the SMEAR component of the vertical CCD portion may leak out, and the SMEAR component may be collected in the sensor. Therefore, the noise that affects the image quality is also greatly reduced.
26, what is the scanning system, commonly used are those? —— (Difficulty: Easy)
A: The television format refers to the specific systems and technical standards adopted by a country's television system. Specifically speaking, there are currently three television formats in the world. At present, most countries in the world (including most European countries, Africa, Australia and China) adopt the PAL system and adopt a frame rate of 25 fps; the United States, Japan, Canada and other countries adopt It is an NTSC system developed by the National Television Standards Committee (NTSC) and adopts a 30fps frame rate (precisely 29.97fps); another standard SECAM system is mainly used in France, the former Soviet Union and Eastern European countries.
27. What is the working mode of CCD camera? —— (Difficulty: Easy)
A: The image of the subject is focused on the CCD chip through the lens. The CCD accumulates a corresponding proportion of charge according to the light intensity. The charge accumulated by each pixel is moved outward by points under the control of the video timing. After filtering and amplifying, the charge is accumulated. , forming a video signal output. The video signal is connected to the video input of a monitor or television to see the same video image as the original image.
28, what is the camera's pixels? —— (Difficulty: Moderate)
A: Pixels are one of the most important indicators of camera CCDs. In general, higher pixel products have better image quality. But on the other hand, it is not that the higher the pixel, the better. For the same picture, the higher the pixel, the stronger the ability to analyze the image. In order to obtain high-resolution images or pictures, the amount of data it records is also large. Much more, the requirements for storage devices are much higher.
29. What is the resolution of the camera? —— (Difficulty: Moderate)
A: Usually refers to the level of resolution, unless specifically designated as "vertical." The index for evaluating camera resolution is the horizontal resolution, which is the line pair, that is, the number of black and white line pairs that can be distinguished 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 is.
30. What is the camera's vertical resolution? (-(Difficulty: Easy)
A: The number of vertical re solusions is derived from the maximum number of horizontally interactive black and white lines.
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