Camera lens selection method

If the camera is compared to the human eye, the lens is like an eyeball, which is directly related to the distance, range and effect of the monitoring object. The selection of lens should consider the following points:

1) The lens size should be equal to or larger than the camera imaging surface size. For example: 1/3 "camera can choose 1/3" ~ 1 "lens in the whole range, but the size of horizontal angle of view is the same. Only using lens larger than 1/3" can make more use of shaping and more accurate The center optical path of the lens is improved, so the image quality and resolution can be improved.

2) Select the appropriate lens focal length. The larger the focal length, the farther the monitoring distance, the smaller the horizontal viewing angle, and the narrower the monitoring range; the smaller the focal length, the closer the monitoring distance, the larger the horizontal viewing angle, the wider the monitoring range. The focal length of the lens can be estimated according to the following formula.

f = A × L / H
(f--lens focal length; A--camera CCD vertical size; L--distance from subject to lens; H--height of subject)

Format 1 inch 2/3 inch 1/2 inch 1/3 inch 1/4 inch

CCD vertical size 9.6? 6.6? 4.8? 3.6? 2.7?

3) Considering the changes of ambient light, light plays a very important role in the image collection effect. Generally speaking, for the environment where the light change is not obvious, we often choose a manual iris lens. After adjusting the iris hand to a more ideal value, it will not move. Automatic iris, can automatically adjust the size of the aperture value according to the change of light and dark to ensure the image quality. However, it should be noted that if the light illumination is not uniform, especially when the contrast between the monitoring target and the background light is large, the effect of using the automatic iris lens is not ideal.

4) Consider the best monitoring scope. Because the focal length of the lens is inversely proportional to the horizontal angle of view, it is impossible to achieve both wide and clear vision at the same time. Each focal length lens can only achieve the best monitoring effect within a certain range, so if the monitoring distance is far and the range is large, it is best to increase the number of cameras, or use an electric zoom lens with the gimbal installation .

5) The lens interface should be consistent with the camera interface. Current cameras and lenses are usually CS-type interfaces. CS-type cameras can be mated with CS-type and C-type lenses. However, when mating with C-type lenses, a matching ring must be added between the lens and the camera. The protective glass of the CCD imaging surface is damaged, causing damage to the CCD camera. C-type cameras cannot be matched with CS-type lenses.