The lens is an important part of the monitoring front-end. Its cooperation with the camera determines the effect of the front-end equipment. 

If we have a clear concept of the lens, it can help us choose and match the equipment more appropriately, achieve better effect and reduce the situation of changing equipment. Therefore, the classification and selection of lens is a basic knowledge that monitoring engineers and technicians must understand. 

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The types of cameras used in different occasions can be roughly divided into:

(1) Wide angle lens: the angle of view is above 90 degrees, which is generally used in places with large angle of view such as elevator car and hall;

(2) Nornal lens: the viewing angle is about 30 degrees, which is generally used in walkways, community boundaries and other places;

(3) Telephoto lens: the viewing angle is within 20 degrees, and the focal length is from tens of millimeters to hundreds of millimeters, which is used for long-distance monitoring;

(4) Zoom lens: the focal length range of the lens is variable, which can be changed from wide angle to long focus, and the viewing angle range is wide;

(5) Pinhole lens: used for concealed monitoring.

2 . Determination of lens focal length when selecting a lens, there are five factors to determine the lens standard:

(1) Monitor the size of the site

(2) Size of the subject

(3) Object distance

(4) Focal length

(5) CCD target size.

4. The focal length standard of the lens can be determined by field measurement and calculation. The calculation method is as follows:

u 1/3 ″ CCD F=4.8  ×  L / W or F = 3.6 ×  L / h or: U 1 / 2 ″ CCD f = 6.4 ×  L / W or F = 4.8 ×  L/H

Where W is the width of the subject; H is the height of the subject; L is the distance between the lens and the subject; F is the focal length of the lens.

We should pay attention to such a principle when selecting the lens: that is, the CCD of small-size target can use the lens of large-size target CCD camera, 

the amount of light will become larger, the color will become better, and the image effect will certainly become better. In order to obtain the same viewing angle from 1 / 3 "and 1 / 2" CCD cameras, 

the lens focal length of 1 / 3 "CCD camera must be shortened; Combining various factors, a good camera needs to choose the lens that matches it to make your camera achieve better results.

5.Optical lens, SECULENS, your first choice!