Middle- and long-focal-length lens

Abstract

The invention discloses a middle- and long-focal-length lens. A first lens having positive focal power, a second lens having negative focal power, a third lens having negative focal power and a fourth lens having positive focal powder successively distribute on the optical axis of the middle- and long-focal-length lens from an object side to an image side. The middle- and long-focal-length lens satisfies a relational expression: 1.6<EFL / FL<7, wherein EFL is an effective focal length of the middle- and long-focal-length lens, and FL is a distance from the vertex of the lens closest to an image plane of the system to the image plane. According to the middle- and long-focal-length lens, focusing is achieved through a movement of the single-group lens; the middle- and long-focal-length lens has the advantages of less lenses, the small focusing load, the small lens size and low cost; the middle- and long-focal-length lens can guarantee aberration and be in favor of large batch production; and a focusing speed is easy to guarantee.

Description

technical field [0001] The invention relates to the field of optical devices, in particular to a medium-telephoto lens. Background technique [0002] At present, the known mid-telephoto lenses with a picture angle of 20-30 degrees are achieved by moving multiple groups of lenses or a whole group of lenses to achieve focus, and in order to control aberration and length, a large number of lenses are introduced, resulting in many lenses and poor focus. The load is large, and the focusing speed is not guaranteed. At the same time, the lens is large in size and high in cost, causing a great burden to consumers. Contents of the invention [0003] The invention provides a medium-telephoto lens with good imaging effect, high cost performance, single-group lenses for focusing, short length and small volume. [0004] The present invention proposes a medium-telephoto lens whose optical axis is distributed sequentially from the object side to the image side: [0005] a first lens ha...

AI Technical Summary

Problems solved by technology

[0002] At present, the known mid-telephoto lenses with a picture angle of 20-30 degrees use multiple groups of lenses to move or a whole group of lenses to achieve focus, and in order to control the aberration and length, a large number of lenses are introduced, resulting in many lenses and poor focus. The load is heavy, and the focusing speed is not guaranteed. At the same time, the lens is large in size and high in cost, causing a great burden to consumers

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