What is a Security Camera?

There are many types of video cameras, waterproof digital video cameras, and the basic principles of their work are the same: convert optical image signals into electrical signals for storage or transmission. When we photograph an object, the light reflected on this object is collected by the camera lens, so that it is focused on the light-receiving surface of the imaging device (such as the target surface of the camera tube), and then the light is converted into electrical energy by the imaging device. "Video Signal". The photoelectric signal is very weak. It needs to be amplified by a preamp circuit, and then processed and adjusted by various circuits. The final standard signal can be recorded on a recording medium such as a video recorder, or transmitted through a transmission system or sent to a monitor. show.

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There are many types of video cameras, waterproof digital video cameras, and the basic principles of their work are the same: the optical image signal is converted into

1. Photoconductive camera tube: lead oxide tube, selenium arsenic tellurium tube.

2. Solid-state photoelectric sensor CCD: The development trend is regardless of the broadcast level or business level.

1. Identifying the imaging element <br /> The imaging element is like the human retina and is the core component of the camera. At present, China does not have the ability to manufacture. Most of the cameras on the market use chips produced by Japanese companies such as Sony, Sharp, and Panasonic. South Korea also has the ability to produce them, but the quality is slightly lower. The more common imaging element is a CCD (also CMOS). The main differences between CCDs are color, size and brand.
(1) The CCD chip can be divided into color and black and white according to color. Color is suitable for identifying the details of the scene, such as the color of clothing or the scene. Black and white are suitable for low-light areas and areas where lighting equipment cannot be installed at night, and the price is low.
(2) The CCD chip can be divided into the following sizes according to the size of the target surface:
The size of the CCD target surface is directly related to the size of the camera's viewing angle, and also has a certain degree of contrast, which has nothing to do with sharpness. The larger the CCD chip size, the wider the viewing angle, and the higher the price. Most of the chips used are 1 / 3-inch and 1 / 4-inch with high cost performance.
(3) The mainstream brands of CCD chips are as follows:
Many businesses on the market claim to use Sony CCDs, but secretly use SHARPCCDs to steal beams and change columns. Standard or promised goods are used to send samples, but low-end replacement or mixed shipments are used. This is also something to pay attention to when purchasing. Products must be checked in place, especially when the purchase price is significantly lower than the normal market price. But usually a "tear-not-guaranteed" sticker is affixed to the camera, which makes many engineering companies worry. We recommend that you buy big brands and purchase them from authorized regular dealers. In addition, you can also randomly disassemble the batch to check the brand and size of the CCD.
2.Identify the authentic HD camera

1. The PSTN phone mode is widely used to connect to external networks, which is cheap and practical, but the transmission speed is not very fast, and sometimes transmission error conditions occur, and data needs to be resent. When downloading files, the maximum speed can reach 56kbit / s, but when uploading files, the maximum speed is 33.6 kbit / s.

2. ISDN telephone mode has a high usage rate in many countries, with a maximum transmission speed of 128 kbit / s.

3.xDSL mode Xdsl mode includes: ADSL, HDSL, IDSL and VDSL, etc., which are becoming more and more popular. Telecommunications service companies and ISP vendors both provide xDSL transmission modes. As long as you pay a fixed monthly fee, you can connect to the Internet.
Different ISP vendors have different standard speeds, and there are differences in upload and download speeds. The download speed is usually about 1Mbit / s and the upload speed is about 250Kbit / s.

4.Cable Modem
Cable television transmission is a popular service in densely populated metropolitan areas. The speed varies from region to region, and the speed will vary depending on how many users are using the service around. Generally the maximum speed is 1Mbit / s.

5. T 1 connection is provided by the Internet ISP manufacturer. You can connect to the Internet as needed by paying a fixed monthly fee. This line is more popular in units with high line usage rates such as company line numbers or Internet cafes. The connection speed is 1.5 Mbit / s.

There are two main standards for 6.10 Mbit Ethernet; 10BaseT using twisted pair and 10Base2 using coaxial cable (RG-58). Because 10Base2 is a bit unreliable, if there is an interruption anywhere on the cable, the entire network will stop working, so it is not often used. General transmission capacity can use 50% of 10 Mbit / s.

7. The main standard of 100 Mbit Ethernet is 100BaseT, which can use about 50% of 100Mbit / s capacity; if there is a switch, 100% of capacity can be used.

8. 1000 Mbit (GB) Ethernet is used in the backbone network of the building. The main standard is 1000BaseT, which can use about 50% of the capacity of 1000Mbit / s; if there is a switch, 100% of the capacity can be used.

9. Mobile phones (GSM, CDMA, CDPD, TDMA)
Mobile phone mode is a good way to connect a remote camera (such as a camera for traffic monitoring) without a phone line. Its transmission speed is low, but it can meet the needs of still images. The general communication speed range is 5-20Kbit / s.

10. Wireless Network (IEEE 802.11)
Since cables are not needed, wireless networks are becoming more popular. There are many standards for high-speed wireless communication. The maximum communication speed is usually -11Mbit / s; the actual actual speed is generally 1Mbit / s.

11. Wireless network (Bluetooth)
Bluetooth wireless communication is an increasingly popular standard with a maximum speed of 720 Kbit / s and a typical actual speed of 500Kbit / s.

Recommendations for selecting connection lines The telephone mode is suitable for applications that do not require high-speed transmission. · XDSL is suitable for office or store residence. · Mobile phone or wireless network is suitable for remote camera. · 100Mbit Ethernet is recommended in buildings.

Camera Selection Guide

The TV surveillance system uses remote-control cameras, lenses, electric pan-tilt heads and other equipment to directly watch everything happening in the monitored place and target on the monitor. And the information content of the image of the monitored place and target can be transmitted to the recorder for recording.

Camera: convert the optical signal of the subject into an electrical signal, and then send it to the transmission part of the system for transmission.

The camera should choose CCD black and white, color camera. The horizontal resolution of black and white cameras is 400 lines, and the horizontal resolution of color cameras is 270 lines. The signal-to-noise ratio requires 46dB. Cameras with different sensitivity should be selected according to the illuminance of the surveillance target. The minimum ambient illuminance of the surveillance target should be 10 times higher than the minimum illuminance of the camera. When remote control is required, a remote lens device with optical focus, aperture opening, and zoom can be selected. The camera can be a small-sized, light-weight, charge-coupled device (CCD) camera that is convenient for field installation and maintenance. According to the working environment, the corresponding camera protective cover should be selected. The protective cover can be set with a temperature control system and a remote wiper as required. The supporting device for fixing the camera on a specific location can use a camera bracket or a pan / tilt head. When a camera needs to monitor multiple scenes in different directions, it should be equipped with an automatic focusing device and a remote electric pan / tilt. When the camera needs to be hidden, it can be installed in the ceiling or wall, and the lens can be a pinhole or prism lens. For the anti-theft system, additional external sensors and system combinations can be installed for linkage alarm. System equipment for monitoring underwater targets should use high-sensitivity camera tubes, closed pressure-resistant, waterproof protective sleeves, and water leakage alarm devices. The setting position, camera direction and lighting conditions of the camera shall meet the following requirements:

(1) The camera should be installed near the surveillance target where it is not vulnerable to external damage. The installation position should not affect the operation of field equipment and normal activities of personnel. The installation height should be 2.5 ~ 5m from the ground; the outdoor should be 3.5 ~ 10m from the ground, and it should not be lower than 3.5m.

(2) The camera in the elevator car shall be installed on the top of the elevator car, diagonally to the elevator operator, and shall be able to monitor the panorama in the elevator car.

(3) The camera lens should avoid direct light, to ensure that the target surface of the camera tube is not damaged. In the field of view of the lens, there must be no objects blocking the surveillance target.

(4) The camera lens should be aimed at the monitoring target from the direction of the light source, and avoid backlight installation; when backlight installation is required, the contrast of the surveillance area should be reduced.

Cameras: There are two types of cameras: color cameras and black and white cameras. Camera target surface specifications are: 1 inch, 1/2 inch, 2/3 inch, 1/3 inch and so on.

Camera construction and installation

(1) The camera should be installed near the surveillance target where it is not easily damaged by the outside world. Installation height: 2.5 ~ 5m from the ground indoor; 3.5 ~ 10m from the ground outdoors, no less than 3.5m.

(2) The camera in the elevator car should be installed on the top of the elevator at the opposite corner of the elevator operator; the optical axis of the camera should be at a 45 ° angle to the two walls of the elevator and 45 ° to the ceiling of the elevator.

(3) The camera lens should be directed at the surveillance target in the direction of the light source.

(4) The camera lens should avoid direct light, to ensure that the target surface of the camera tube is not damaged; there must be no objects blocking the surveillance target in the field of view of the lens.

Specific methods can refer to the 97 × 700 intelligent building weak electrical engineering design and construction atlas.

Four points of the camera

First, the maximum aperture

The true value of the maximum aperture is reflected in increasing the amount of light entering in low light conditions to achieve the best exposure combination. Shooting landscapes generally does not require the ability of the lens to blur. In addition, except for very dark places, the lens caliber is generally not too demanding. However, when the 70-200mm zoom lens is equipped with a 2x teleconverter to make the telephoto focal length 400mm and use AF autofocus, it is best to choose a lens with a maximum aperture of F2.8. A large aperture is useful for accurate focusing in dark conditions. Shooting people with large-aperture lenses can take pictures with natural light even when the light is weak. In addition, a lens with a large maximum aperture can bring a fast shutter speed, so sports photography also needs a large-aperture lens.

Another reason to require a large lens aperture is to be able to blur the background freely and to ensure the quality of blur. When the maximum aperture of F1.4 is reduced to F2, both the imaging quality and the blurring quality of the background are stronger than the maximum aperture of F2. Therefore, it is of great value to reduce the aperture of a large aperture lens by one stop, and any photographer must be good at using this feature of the lens.

Second, the focal length

The first thing to pay attention to when choosing a lens is the focal length of the lens. The focal length is actually a matter of viewing angle. In addition, the user must make it clear, what is the main purpose of my lens purchase? For shooting landscapes or people. As we all know, a wide-angle lens should be used for landscapes, and a telescope lens should be used for people. Therefore, you must first determine the focal length of the lens you want to buy according to the purpose of photography.

The best focal length for shooting landscapes is 24mm wide-angle focal length and 200mm telephoto focal length (both based on 35mm specifications, the same below). When the wide-angle focal length of the standard zoom lens evolves from 28mm to 24mm, the viewing angle becomes wider, and the range of objects that can be accommodated is greatly expanded. Generally speaking, the maximum aperture required for shooting landscapes is not too high. If you are mainly shooting landscapes, a wide-angle focal length of 24mm is basically sufficient when you choose a zoom lens. As for the telephoto focal length, it must be at least 200mm. If the telephoto focal length is 300mm or 400mm, it is more ideal, and the degree of freedom will be greatly improved. The telephoto focal length of traditional zoom lenses is mostly 300mm, which is 450mm when used on digital SLRs, and the focal length has been increased by 1.5 times, which makes people feel more happy. This is the value of digital SLRs. The wide-angle focal length of the digital ultra-wide-angle lens produced is generally up to 12mm, which is equivalent to 18mm in the 35mm format, which is nearly 1.5 times larger than the 28mm focal length in the 35mm format, thereby greatly widening the left and right ranges of the landscape scene.

The best focal length for shooting people is 85mm. According to the 35mm standard, the lens is basically selected based on the 85mm focal length. The portrait shot at 85mm focal length is basically close to the picture taken by a medium-format camera. Not only is the distance suitable, but the human face appears very natural, and the distance between the camera and the subject can basically be maintained at the usual speaking distance. The 85mm focal length can also blur the background to highlight people. In order to obtain a good blurring effect, a lens with a maximum aperture should be selected. The 85mm focal length is about 135mm on a digital SLR. Although the distance of the shot is slightly weaker, it is basically not a big deal, so the focal length of the person's lens should be at least about 85mm.

For shooting flowers, a 100mm macro lens is enough for a traditional SLR. The 100mm macro lens can be used for equal magnification photography, which can take flowers very large. However, when equal magnification photography or near equal magnification photography, due to long focal length and shallow depth of field, it is prone to shake, so anti-shake measures should be considered when shooting. From this point of view, the 50mm macro lens is easier to use on digital SLRs.

Third, close-up capability

The close-up capability of the lens is another important choice after the focal length and maximum aperture. This is the same whether it is a wide-angle lens, a standard lens, or a telescope lens. So, how close is the proper close-up capability?

First of all, let's talk about the wide-angle lens for shooting landscapes. The close-up capability has almost nothing to do with wide-angle lenses. However, when shooting flower scenery with a wide landscape as the background, it is often necessary to make the flowers larger. It seems very important.

The existing 50mm standard lens has a close-up capability of about 45cm, which is basically satisfactory for use. However, when using the shortest shooting distance for a large-caliber standard lens, there is often a large aberration due to the lens extension, which causes low image quality. Be prepared for this when purchasing and using it.

If the telescope lens is used to shoot landscapes, there is not much demand for close-up capabilities. However, if it is used to shoot people or flowers, the close-up ability of the lens is very important.

Fourth, expressiveness

When choosing a lens, many people first pay attention to the sharpness of this lens. The purpose of the photo determines what sharpness is required. High-quality high-quality lenses are mainly used by professional photographers. If it is just general photography, there is no need to spend a lot of money to buy high-quality high-quality lenses. In addition, the imaging sharpness of the lens is also directly related to the aperture size. When a lens is reduced by one or two stops from the maximum aperture, the imaging sharpness will be greatly improved.

Distortion is an optical phenomenon caused by the optical performance of the lens. It is impossible for each lens to be free of distortion. The manufacturers have corrected the distortion when producing the lens, and strive to control the distortion to a minimum. Generally speaking, there are mainly three types of lens distortions: barrel-type distortions that easily occur at the wide-angle end of zoom lenses, pincushion-type distortions that occur easily at the telephoto end, and bucket-type distortions that occur after the wide-angle-end barrel distortion is corrected. As far as the status quo of the lens is concerned, the most prominent problem is barrel distortion at the wide-angle end. When purchasing, you should choose a style with small barrel distortion as much as possible.

During backlight photography, due to the strong sunlight or other strong light sources repeatedly reflecting on the mirror surface, halo and flare will be formed on the screen. This small part of the light that forms the halo and flare will not only not be imaged on the screen, but will also cause random reflections in the mirror to reduce the image quality. To prevent this, a hood must be used for backlit photography. The excellent lens has adopted the process of completely preventing halos and flares during the manufacturing process, and the contrast is very good even when shooting against backlight.

Camera debugging method

1. Turn on the camera's automatic electronic shutter function

2. Use the controller to maximize the lens aperture

3 Aim the camera at an object 30 meters away and adjust the focus to infinity (most lenses are facing the lens and the front

(The focus adjustment ring rotates clockwise to the end)

4 Use the controller to adjust the lens zoom to push the scene farthest, and adjust the back intercept of the lens to make the scene clearest

5. Use the controller to adjust the lens zoom to pull the scene to, and fine-tune the lens focus to make the scene most clear

6. Repeat 4-5 steps several times until the scene is always clear during the lens zoom

CCD cameras can be roughly divided into the following categories:

Divided by camera resolution

The image is above 380,000 dots, color resolution is greater than or equal to 480 lines, black and white resolution, and high resolution above 600 lines.

Divided by camera sensitivity

(1) Ordinary type: The illumination required for normal work is 1 ~ 3 LUX (lux)

(2) Moonlight type: The illumination required for normal work is about 0.1 LUX

(3) Starlight type: The illumination required for normal work is below 0.01 LUX

(4) Infrared illumination type: In principle, it can be zero illumination and use infrared light source for imaging.

Divided by the size of the CCD target surface of the imaging element

(1) 2 / 3in target surface size is 8.8mm wide x 6.6mm high, 11mm diagonal

(2) 1 / 2in target surface size is 6.4mm wide x 4.8mm high, 8mm diagonal

(3) 1 / 3in target surface size is 4.8mm wide x 3.6mm high, 6mm diagonal

(4) 1 / 5in is under development and no official product has been launched yet

Camera infrared

Features :

1 · 1/3 SONY CCD

Infrared camera

· High definition infrared color camera

2 · Use 12 imported IR LED lights, project the light source at different angles to make the image clearer

3. Infrared is automatically turned on when the light is below 10 Lux; the shooting distance is more than 15 meters

4 · Imported lens sheet, water-proof gas affects the image

5 · Flat wall installation / 90 degree installation

Infrared camera technology is divided into passive infrared camera technology and active infrared camera technology. Passive infrared camera technology uses the principle that any object has infrared light emission above absolute zero (-273 ° C). Due to the strong infrared light emitted by the human body and heating objects, the red light emitted by other non-heating objects is weak. Therefore, special infrared cameras can be used for night monitoring. Passive infrared camera technology is not used in night vision systems because the equipment is costly and cannot reflect the surrounding environment. Active infrared camera technology uses a special "infrared lamp" to artificially generate infrared radiation, which produces infrared light that is invisible to the human eye and can be captured by ordinary cameras, radiates "illumination" of scenes and environments, uses ordinary low-light CCD black and white cameras or uses "daylight Color auto-black-and-white camera at night or infrared low-light color camera to feel the surrounding environment

Infrared light reflected back to achieve night vision.

Light is an electromagnetic wave whose wavelength ranges from a few nanometers (1nm = 10-9m) to about 1 millimeter (mm). What the human eye sees is only a part of it. We call it visible light. The wavelength range of visible light is from 380nm to 780nm. The wavelength of visible light is divided into red, orange, yellow, green, cyan, blue, and purple light. The wavelength is shorter than that of purple light. It is called ultraviolet light, and wavelengths longer than infrared light are called infrared light.

Infrared camera is a camera device that integrates a camera, a protective cover, an infrared lamp, and a power supply and cooling unit. The basic principle of night vision is to use ordinary CCD black and white cameras to feel the spectral characteristics of infrared light (that is, visible light and infrared light), and use infrared light as a "light source" for night vision imaging.

Explosion-proof camera

Explosion-proof camera

product name:

Class B carbon steel (30m-80m) explosion-proof infrared camera

Parameter characteristics:

Class B or C explosion-proof, color 420 line or 480 line, 30m-80 infrared light automatically turn on, 1/3 "SONY Exview CCD, optional lens focal length, special carbon steel stainless steel optional, IP65, built-in heat sink 220V power supply (36 and 8 infrared lights)

Explosion-proof cameras are equipped with nano stealth wiper function (non-stick water, non-stick oil, repellent dust)

Application:

Suitable for petrochemical, mine, military, medicine, ammunition depot, explosive depot, oil depot, ship, drilling platform, gas station, fireworks production, food processing storage, oil tanker, tanker, small warehouse, explosion-proof elevator monitor