In order to ensure the reliability of camera and lens work, and extend its service life, the camera must be equipped with the outer cover of various special protective measures, which is called a protective cover. In addition, the protective cover can also prevent human damage to the camera and lens. Similar to the yuntai equipment, the protective cover is generally divided into general and special purpose, and can be divided into indoor and outdoor types.

1. Universal protective cover.

The indoor protective cover must be able to protect the camera and lens from dust, impurities and corrosive gases, and to be able to cooperate with the installation site to prevent damage. The interior cover is made of aluminum, painted steel, brass or plastic coated or anodized. If plastic is used, fire resistant or flame retardant type should be used. The protective cover must be strong enough, the installation interface must be firm, the Windows should be clear and transparent safety glass or plastic (polycarbonate). The design position of the electrical connector should be easy to install and maintain.

Camera working temperature is 5 ℃ ~ 45 ℃, and the most suitable temperature is 0 ℃ ~ 30 ℃, otherwise it will affect the image quality and even damage the camera. Therefore, outdoor protective cover should adapt to various weather conditions, such as wind, rain, snow, frost, low temperature, exposure, dust and so on. The outdoor protective cover will be equipped with auxiliary equipment such as sunshade cover, built-in/external fan, heater/defroster, wiper, washer and so on.

First, outdoor protective cover should be sealed to avoid rain. At the same time, the inlet line should be placed under the protective cover, so as to avoid the pouring of rainwater into the protective cover. The windshield wipers should also be installed in front of the shield so that the rainwater and dirt can be cleared in time so that the camera can get clear images through the glass. Remove the defroster from the front or the glass, and melt it when the Windows are frosted and covered with snow.

Secondly, the protective cover should be equipped with a heater, which can be heated in a low temperature environment to improve the internal temperature of the protective cover to ensure the normal work of the camera/lens. The internal or external fan can circulate the air inside the hood and reduce the temperature inside the enclosure. In the area of multi-wind sand and less rain, it is also necessary to consider the configuration of the washer so that it can be combined with wiper to clean the window glass at any time, so as to ensure the image monitoring effect.

Outdoor type shield auxiliary equipment has automatic control and manual control two kinds of control functions, such as heater/defroster, fans are made by shield the internal temperature sensor on or off automatically, while actions, such as the wipers, washer is controlled by the controllers based on the operation of the equipment.

Outdoor enclosures are usually made of aluminum, coated steel, stainless steel or plastic that can be used outdoors. The manufacturing materials must be able to withstand the exposure of ultraviolet rays, otherwise the cracks, discoloration and strength degradation will soon appear. Stainless steel shields should be used in environments where the cover is durable, high in safety, and resistant to man-made damage. The properly treated aluminum shield is also a good protective cover, and there are three kinds of treatment methods: polyurethane baking varnish, anodizing, anodizing and coating. Aluminum or steel should not be used in an environment with corrosive gases. Protective cover made of stainless steel or special plastic shall be used in the salt mist environment.

In addition, to increase the safety performance of the protective cover, prevent man-made damage, and many protective covers are equipped with anti-dismantling switch. Once the protective cover is opened, the alarm signal will be issued.

There are various kinds of protective covers in the monitoring system, which can be divided into rectangular protective cover, wall or ceiling cover, ball cover, Angle cover, slope shield and so on.

Rectangular shield

The rectangular shield is the most common protective cover of the monitoring system, with low cost, strong and durable, varied in size and beautiful style. Indoor type rectangular shield does not need special antirust processing, the use of paint or general anodic oxidation of aluminium, steel, or high impact plastic, such as polyvinyl chloride (PVC), engineering plastic (ABS) or polycarbonate (such as Lexan) materials.

Rectangular shield the open structure of the sealed type, front and back cover open type, with a top slideway draw-out, lid of the lid hinge brace type, suspension type, sliding type, such as various structures are for the purpose of installation, repair and maintenance is convenient.

Ball shield.

There are two types of ball shields, which are semi-spherical and global, and most outdoor applications are global. In indoor applications, a hemispheric or global shield is selected according to the field environment. The global protective cover is usually mounted with a bracket or suction top. The most common type of semi-spherical protective cover is the ceiling type and ceiling mounted installation.

There are three types of plastic spheres that can provide the scene light for the inside lens: transparent, coated (with translucent aluminum or chromium) and tan. A transparent ball cover is often used when the ball cover is only used as a protective camera and lens without the need for a hidden camera. Transparent ball cover has a minimum loss of light (10% to 15%). If you want to hide the camera's direction to obtain additional security effects, you need to choose a coating or a teahouse. Light is reduced by about two f-stops (approximately equivalent to the attenuation of 75%) through the coating sphere, and the tea color sphere is relatively effective. The light attenuation is only about 1 f-stop, about 50%.

With rectangular shield Windows using the excellent optical quality and the plane of the plastic or glass pervious to light performance is different, all ball cap will bring a certain degree of optical distortion to the image, high quality spherical shield of optical distortion is small. The axis of the camera must intersect with the ball cap point perpendicular to the plane, circumscribed such distortion at least is uniform, the main effect is the focal length of the lens to produce small changes, these changes generally is imperceptible or don't other people, otherwise the image will be horizontal or vertical direction tensile, especially in the ball enclosure is equipped with yuntai camera often turns, image distortion is easy to be found. Therefore, optical distortion is an important index to check the ball cover.

The outdoor ball cover is similar to the rectangular shield, except that the seal protection level should meet the outdoor environment, and the internal fan and heater are installed to compensate for the change of outdoor temperature. As the ball cap can't install wipers like rectangular shield, so generally equipped with such as rain eaves or other similar devices, in order to prevent too much rain the next ball dripping, formation water damage, at the same time also has a certain effect of shading.

Angle cover

Corner cover is designed for interior walls (two walls and ceilings). Generally installed in a small room or hall, elevator car, stairwell or prison cell.

The camera tilt is installed in the corner cover, pointing to the monitoring area under the ceiling. The observation window of the shield is perpendicular to the lens axis. Another Angle to shield is special, the camera inside the guard point to the ceiling above, above the camera is equipped with table before the mirror, under the ceiling of the scene can be reflected to the camera, the position of the mirror can be adjusted up and down, to change the camera's field of view. Because the image of the reflector is inverted image, the camera must reverse the installation.

The embedded shield.

The embedded shield is usually in the ceiling and wall, partially exposed, partially hidden. This type of shield is suitable for situations where it is required to be concealed.