Imaging lens

Abstract

The pickup lens employing the present invention includes a first lens group (11) having negative power, a diaphragm (12), a second lens group (13) having positive power, and a third lens group (14) having negative power, which are arranged in this order from the side of a subject. When varying optical power, in the pickup lens (1), the first lens group (11) is fixed, and the second lens group (13) is moved along the optical axis together with the diaphragm (12), and the third lens group (14) is moved along the optical axis to correct movement of the image point due to variation of optical power.

Description

technical field [0001] The present invention relates to an imaging lens, and more particularly, to an imaging lens with a variable focal power and a structure of at least three lens groups. [0002] This application claims priority from Japanese Patent Application No. 2002-295292 filed on October 8, 2002, the entire contents of which are incorporated herein by reference. Background technique [0003] Until now, there has been provided a photoelectric conversion device such as a C-MOS (Complementary Metal Oxide Semiconductor) or a CCD (Charge Coupled Device) as an imaging device that converts light from an imaging lens into an electronic signal to output the electronic signal thus generated. The camera unit is widely used in various information devices. [0004] Among those information equipment, a portable small information equipment intended for mobile use is desired to make its imaging lens and imaging device smaller while maintaining high imaging performance of its imagi...

AI Technical Summary

Problems solved by technology

[0008] For the imaging lens disclosed in Japanese Patent Application Laid-Open No. 2002-55278, the overall length is too long when built in information equipment, and when changing the optical power, the first lens group is moved, which leads to complicated mechanical design, and difficult to achieve low cost

In such an imaging lens, since the lens group close to the object to be captured is moved and the lens holder is pulled out from the main device body for zooming, there is a fear that the information device may be damaged by falling, colliding or bumping into other objects

[0009] On the other hand, even the imaging lens disclosed in Japanese Patent Application Laid-Open No. 2002-72095 is ideal in terms of collision avoidance from the viewpoint of fixing the lens group close to the object to be captured when the power is changed. Yes, since the last lens group is positive, it is difficult to reduce the back focus, which makes it difficult to miniaturize information equipment

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