Camera cover selection

In order to ensure the reliability of the operation of the camera and the lens and prolong its service life, it is necessary to equip the camera with a cover with various special protective measures, called a protective cover. In addition, the protective cover can prevent human damage to the camera and lens as much as possible. Similar to the PTZ equipment, the protective cover is generally divided into general-purpose and special-purpose types, and can be divided into indoor type and outdoor type.
First, the universal protective cover
The indoor enclosure must be able to protect the camera and lens from dust, foreign matter and corrosive gases, and at the same time be able to match the installation site to prevent vandalism. Interior guards are typically made of painted or anodized aluminum, painted steel, brass or plastic. If plastic is used, fire resistant or flame retardant type should be used. The shield must be strong enough that the mounting interface must be secure and the window should be clear and transparent with safety glass or plastic (polycarbonate). The electrical connections are designed to be easy to install and maintain.
The camera's operating temperature is -5 ° C ~ 45 ° C, and the most suitable temperature is 0 ° C ~ 30 ° C, otherwise it will affect the image quality, and even damage the camera. Therefore, the outdoor protective cover should be adapted to various climatic conditions, such as wind, rain, snow, frost, low temperature, exposure, sand and the like. Outdoor shields may be configured with different locations such as sunshields, interior/external fans, heaters/defroaches, wipers, washers, etc.
First, the outdoor enclosure is highly sealed to prevent rain from entering. At the same time, the inlet should be opened under the protective cover to prevent rainwater from flowing down the cable into the protective cover. A wiper should also be installed in front of the shield to clean up the accumulated rain and dirt in time so that the camera can pass through the glass and capture clear images. A defroster in front of the hood or on the glass melts the window when it is frosted or snowy.
Secondly, the protective cover should be equipped with a heater, which is heated in a low temperature environment to raise the internal temperature of the protective cover to ensure the normal operation of the camera/lens; the internal or external fan can circulate the air inside the cover and reduce the temperature inside the protective cover. In the place where there is less wind and less rain, consider installing a washer so that the window glass can be cleaned at any time with the wiper to ensure image monitoring.
The auxiliary equipment control function of the outdoor type shield has two kinds of automatic control and manual control. For example, the heater/defroster and the fan are automatically activated or turned off by the temperature sensor inside the shield, and like a wiper, a washer, etc. The action is achieved by the controller through the operation of the control device.
Outdoor shrouds are typically made of aluminum, coated steel, stainless steel or plastic that can be used in outdoor environments. The manufacturing material must be able to withstand the irradiation of ultraviolet rays, otherwise the aging phenomenon such as cracking, fading, and strength reduction will occur soon. Stainless steel shrouds should be used in environments where helmets are required to be durable, highly safe, and resistant to vandalism; properly treated aluminum shrouds are also a good performance shroud. There are three treatment methods: polyurethane baking varnish, anodizing , anodizing and painting. Aluminum or steel mutual aid should not be used in corrosive atmospheres; stainless steel or special plastic shields should be used in salt spray environments.
In addition, in order to increase the safety performance of the protective cover and prevent human damage, many protective covers are also equipped with a tamper switch, and an alarm signal will be issued once the protective cover is opened.
There are many types of protective covers in the monitoring system, and generally can be divided into rectangular shields, wall or ceiling shields, ball shields, corner shields, and slope shields according to their shapes.
(a) rectangular shield
Rectangular shrouds are the most common shields for surveillance systems, and are low cost, rugged, versatile, and aesthetically pleasing. The indoor rectangular shield does not require special anti-rust treatment. Generally, it is painted or anodized aluminum, steel or high-impact plastic such as polyvinyl chloride (PVC), engineering plastic (ABS) or polycarbonate. Materials such as Lexan.
The opening structure of the rectangular protective cover has a top cover detachable type, a front and rear cover disassembling type, a slide pull-out type, a top cover strut type, a hinge suspension type, a top cover sliding type, etc., and various structural forms are installed and overhauled. Easy maintenance.
(2) Ball type shield
Ball-type shields are available in both hemispherical and global versions. Most of the outdoor applications use global domes. In indoor applications, hemispheres or global shields are selected depending on the site environment. Global shields are typically mounted with brackets or ceiling mounts, and hemispherical shields are most commonly ceiling mounted and ceiling mounted.
There are three types of plastic domes that provide scene light for the inside of the hood: transparent, coated (translucent aluminum or chrome) and brown. A transparent dome is often used when the dome is only used to protect the camera and lens without the need to conceal the camera's pointing. The transparent dome has minimal light loss (10% to 15%). If you want to hide the camera's pointing for additional security, you will need a coated or brown dome. After the light passes through the coated dome, it decays by about two f-stops (about 75% of the attenuation). The brown dome is relatively good, and the light attenuation is only about 1 f-stop, about 50%.
Unlike the flat plastic or glass used in rectangular shroud windows, the excellent optical quality and light transmission properties of all the domes give the image a degree of optical distortion, and the high quality spherical shield has little optical distortion. The axis of the camera must be perpendicular to the circumscribed plane of the point at which the dome is intersected. The distortion is at least uniform. The main effect is that the focal length of the lens changes slightly. This change is generally not noticeable or not annoying, otherwise the image There will be horizontal or vertical stretching, especially if the pan/tilt is installed in the dome. When the camera is rotated frequently, the distortion of the image is easily found. Therefore, optical distortion is an important indicator for testing the dome.
The outdoor dome is also similar to the rectangular shield. In addition to the sealing protection level to meet the outdoor environment, the interior is equipped with fans, heaters and other devices to compensate for changes in the outdoor ambient temperature. Since the dome can not be installed like a rectangular shield, it is generally equipped with a rain-proof device or the like to prevent excessive rain from dripping through the lower dome to form water stains, and also has a certain shading effect. .
(three) corner cover
The corner shield is a shield designed for interior corners (the junction of two walls and ceiling). Generally installed in a small room or hall, elevator car, stairwell or prison cell.
The camera is tilted into the corner guard and points to the surveillance area under the ceiling. The viewing window of the shield is perpendicular to the lens axis. There is also a special angle cover. The camera is pointed above the ceiling in the protective cover. The front of the camera is equipped with a front reflector, which can reflect the scene under the ceiling to the camera. The position of the mirror can be adjusted up and down, left and right. Change the field of view of the camera. Since the scene image of the mirror is an inverted image, the camera must be installed upside down.
(four) embedded shield
The built-in shield is usually on the ceiling and wall, partially exposed and partially enclosed. This type of shield is suitable for applications where a more concealed installation is required.

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