Zoom lens

Abstract

The invention relates to a zoom lens. The zoom lens comprises a first lens group having positive refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power and a fourth lens group having positive refractive power arranged in order from the object side to the image side along the optical axis, wherein the second lens group and the fourth lens group reciprocally move along the optical axis during zooming, from the object side to the image side along the optical axis, a first lens of the first lens group is set as a negative refractive power lens, and a first lens of the second lens group is set as a negative refractive power lens. The zoom lens is advantaged in that the FNO reaches the star level, the image side F number reaches 1.0-1.4, the lens is enabled to get enough light, the signal-to-noise ratio is reduced with sufficient illumination, so a clear image is obtained, an aperture value of the zoom lens is nearly constant in the zoom process, and that brightness of frames does not change as the focal length changes during zooming is guaranteed.

Description

technical field [0001] The invention relates to the technical field of optical imaging, in particular to a zoom lens. Background technique [0002] In the field of security monitoring, small-volume zoom lenses are widely used because of their variable focal lengths. Specifically, in the field of security monitoring, zoom lenses generally need to have the following characteristics: 1. Different monitoring places require lenses with different field of view (focal length), and the field of view of the lens can be increased to expand the surveillance range; 2. The security lens should be It can still meet the requirements of use in low-light environments such as night vision; 3. The security lens should also have a large zoom ratio, which can adapt to all-weather monitoring needs such as daytime, dusk and night. 4. Reasonable temperature compensation design ensures that the lens can maintain the same resolution as normal temperature without refocusing when the lens is in a high...

AI Technical Summary

Problems solved by technology

It is difficult for the existing large-aperture zoom lenses to achieve confocal performance of visible light and infrared light bands, small temperature drift, and large zoom magnification at the same time, which makes it difficult for existing security lenses to have all the above characteristics at the same time. Resolution requires the use of glass aspheric lenses, which greatly increases the cost

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