Zoom lens

Abstract

The invention relates to a zoom lens. First, second, third and fourth lens groups are arranged sequentially from an object side to an image side along an optical axis. The refraction capacities of the first, second, third and fourth lens groups are respectively passive, negative, passive and passive. The first and third lens groups are respectively fixed at a preset position, the second lens group moves along the optical axis according to the change of the image magnifying power, and the fourth lens group moves along the optical axis, so that an imaging surface is kept being fixed on an image recorder. The zoom lens is provided with at least four lenses made of plastic materials, so that the weight of the lens is reduced and the lens groups are conveniently driven. The zoom lens has low variation of light incidence quantity and appropriate zooming ratio and also has the advantage of compact volume so as to reduce the overall size of an image extraction device. The focus FN0 of a diaphragm of the zoom lens is changed when different images are extracted and applied.

Description

technical field [0001] The invention relates to a zoom lens, in particular to a zoom lens that can be applied to image capture devices such as digital video cameras (DV), digital cameras (DSC) and the like. Background technique [0002] With the advancement of modern video technology, image devices such as projectors, digital video cameras, and digital cameras have been widely used. One of the core elements of these image devices is a zoom lens, through which optical zooming of the zoom lens can make images with different magnifications be clearly imaged, so the optical quality of the zoom lens is closely related to the quality of image formation. [0003] Among them, US Patent Application No. US2005 / 0099700A1 discloses a compact zoom lens, which has four groups of lenses with refractive powers of positive, negative, positive, and positive. When the zoom lens zooms from the wide-angle end position to the far end position, the first lens group and the third lens group are fi...

AI Technical Summary

Problems solved by technology

However, the technology of moving the second, third, and fourth lens groups is generally insufficient in terms of zoom ratio, and there is a problem that the maximum aperture value is too high or there are too many lenses, so it still cannot solve the problem of miniaturization of the zoom lens. The problem

[0007] In addition, the content disclosed in U.S. Patent No. US7,379,249 uses five lens groups, and the 10 lenses used are all glass materials, so the cost required is relatively high

Furthermore, the FNO disclosed in the above-mentioned known is 2.78 to 4.02, so the amount of light entering the known zoom lens varies greatly, and the ratio of light entering at the wide-angle end to the telephoto end is (4.02 / 2.78) 2 =2.09 times, so it is known that the amount of incoming light at the telephoto end is significantly smaller than that at the telephoto end

[0008] In addition, the content disclosed in U.S. Patent No. US7,453,647 adopts four lens groups, and the nine lenses used are all glass materials, and three of the lens groups are movable, and the total The length is 75.5mm, so the cost required is higher

Furthermore, the above-mentioned known FNO at wide-angle is 2.53-4.72, so the amount of light entering the known zoom lens varies greatly, and the ratio of light entering at the wide-angle end to the telephoto end is (4.72 / 2.53) 2 = 3.48 times, so it is known that the amount of incoming light at the telephoto end is significantly smaller than that at the telephoto end

Images