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Fixed focus, zoom lens selection
- Apr 14, 2018 -

The selection of fixed focus and zoom lenses depends on the size of the monitored scene range and the clarity of the scene of the scene being monitored.

 

When the lens specification (the lens size is generally divided into 1/3′′, 1/2′′, and 2/3′′, etc.), the relationship between the focal length of the lens and the angle of field of the lens is: the longer the lens focal length, the field of view of the lens The smaller the angle is (see Figure 1), the relationship between the lens size and the field of view of the lens in the case of a fixed focal length of the lens: the larger the lens size, the larger the field of view of the lens. It can be seen that in the case that the lens object distance is constant, as the lens focal length becomes larger, the screen area of the monitored scene seen on the end monitor of the system is smaller, but the picture details become clearer; With the increase of the lens specification, the screen area of the monitored scene seen on the end monitor of the system increases, but the details of the screen become more and more blurred, and the CS interface lens is used under the premise of a fixed lens focal length and focal length. The field of view will be greater than the field of view of the Type C interface lens.

The angle of view of the lens can be divided into the horizontal angle of view of the image and the vertical angle of view of the image, and the horizontal angle of view of the image is larger than the vertical angle of view of the image. Usually, the field of view angle we are referring to generally refers to the image horizontal field of view of the lens. . In narrow monitored environments such as elevator cars, narrow rooms should use short-focus wide-angle or ultra-wide-angle prime lenses, such as the optional lens size 1/2′′, CS interface, lens focal length of 3.6mm or 2.6mm The lens, the lens field of view angle is not less than 99 ° or 127 °, which for the camera in a small space in the general elevation of about 2.5m, the camera's field of view angle range is sufficient to cover the entire close range of small monitored space. According to the actual situation in the field, choose a manual zoom lens such as the Nissan Computar T2Z2814CS-2 lens. This lens is a 1/3′′ CS type manual iris lens, and its focal length is 2 times adjustable (manual focus). The focusing range is 2.8 to 6.0 mm, and the field of view angle varies from 96° to 47.2°. This type of lens is ideal for use in narrow, monitored environments. When used, it can be easily and flexibly monitored according to actual needs. The "point" or "face" of the scene is monitored.


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