Zoom lens system

Inactive Publication Date: 2005-01-20
NIKON CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is made in view of the aforementioned problems and has an object to provide a zoom lens system suitable for a image gathering system using a solid-state imaging device, having a zoom ratio of about three, a small total lens length, and superb optical performance.
Since the first lens group is composed only of a negative lens element and a positive lens element, and the third lens group is composed of a single lens element, it becomes easy to assemble and adjust the first and third lens groups, so it helps to lower the manufacturing cost.
Moreover, when the state of lens group positions varies from the wide-angle end state to the telephoto end state, the third lens group is fixed. Accordingly, the zooming mechanism can be simplified.

Problems solved by technology

However, the zoom lens system proposed in Japanese Patent Application Laid-Open No. 10-293253 has drawbacks such as relatively large number of lens elements composing each lens group, relatively large total lens length, and higher manufacturing costs.
Accordingly, it has a drawback that the diameter of the lens system inevitably becomes large when the system is made to have a wider angle of view.
As a result, the lens system has a drawback that the whole lens system becomes large.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

FIG. 1 is a sectional view showing a zoom lens system according to Example 1 of the present invention together with the movement of each lens group upon zooming. The arrows indicate the movement of each lens group from the wide-angle end state (WIDE) to the telephoto end state (TELE). In the other Examples the same representation is applied.

A zoom lens system according to Example 1 is composed of, in order from the object, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power with an aperture stop S, and a third lens group G3 having positive refractive power.

The third lens group G3 is fixed and the first lens group G1 and the second lens group G2 are moved. In this lens construction, when the state of lens group positions varied from the wide-angle end state (WIDE) to the telephoto end state (TELE), a distance between the first lens group G1 and the second lens group G2 decreases, and a distance between the second lens gr...

example 2

FIG. 3 is a sectional view showing a zoom lens system according to Example 2 of the present invention together with the movement of each lens group upon zooming.

A zoom lens system according to Example 2 is composed of, in order from the object, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power with an aperture stop S, and a third lens group G3 having positive refractive power.

The third lens group G3 is fixed and the first lens group G1 and the second lens group G2 are moved. In this lens construction, when the state of lens group positions varied from the wide-angle end state (WIDE) to the telephoto end state (TELE), a distance between the first lens group G1 and the second lens group G2 decreases, and a distance between the second lens group G2 and the third lens group G3 increases.

The first lens group G1 is composed of, in order from the object, a double concave negative lens L11, and a positive meniscus lens L12 ...

example 3

FIG. 5 is a sectional view showing a zoom lens system according to Example 3 of the present invention together with the movement of each lens group upon zooming.

A zoom lens system according to Example 3 is composed of, in order from the object, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power with an aperture stop S, and a third lens group G3 having positive refractive power.

The third lens group G3 is fixed and the first lens group G1 and the second lens group G2 are moved. In this lens construction, when the state of lens group positions is varied from the wide-angle end state (WIDE) to the telephoto end state (TELE), a distance between the first lens group G1 and the second lens group G2 decreases, and a distance between the second lens group G2 and the third lens group G3 increases.

The first lens group G1 is composed of, in order from the object, a double concave negative lens L11, and a positive meniscus lens L...

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Abstract

The invention provides a zoom lens system suitable for an image gathering system using a solid-state imaging device, having a zoom ratio of about three, a small lens length, and superb optical performance. The zoom lens system includes, in order from an object, a first lens group having negative refractive power, a second lens group having positive refractive power, and a third lens group having positive refractive power. The first lens group consists only of a negative lens and a positive lens. The second lens group includes at least two positive lenses and at least one negative lens. The third lens group consists of one lens. Zooming from a wide-angle end state to a telephoto end state is conducted by decreasing a distance between the first and second lens groups, increasing a distance between the second and third lens groups, and fixing the third lens group. Given conditions are satisfied.

Description

This application claims the benefit of Japanese Patent application No. 2002-255077 which is hereby incorporated by reference. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact zoom lens system and, in particular, to a zoom lens system designed specially to be compact with its whole optical system, being suitable for such as a digital still camera. 2. Related Background Art In an image gathering system using a solid-state imaging device, in order to arrange a low-pass filter or a color correction filter, a lens system having a relatively long back focal length is required. Moreover, a lens system having a good telecentricity on an image side is required. In these days, compactness and low cost are also required to a lens system in addition to satisfying these requirements. These lens systems described above have been proposed, for example, in Japanese Patent Application Laid-Open No. 10-293253 and in Japanese Patent Application Lai...

Claims

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Application Information

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IPC IPC(8): G02B15/163G02B13/18G02B15/177
CPCG02B15/177G02B15/143507
InventorMIZUGUCHI, KEIKOSHIBAYAMA, ATSUSHI
OwnerNIKON CORP