Zoom optical system and shooting device

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive variable power optical system having a compact size and a small F value and having high optical performance with favorably corrected chromatic aberration.SOLUTION: This variable power optical system comprises, in order from an object side, a positive first lens group G1 that is fixed when varying power, a second lens group G2 varying the power by moving along an optical axis Z, an aperture that is fixed when varying the power, a positive third lens group G3 that is fixed when varying the power, and a positive fourth lens group G4 that corrects and focuses an image plane position when varying the power. The second lens group G2 is disposed with, in order from the object side, a negative lens, a positive meniscus lens having a concave surface facing the object side, a biconcave lens, and a positive lens. The variable power optical system is configured to satisfy a prescribed conditional expression related to a focal length of the second lens group G2, the Abbe number of the positive meniscus lens of the second lens group G2, and a moving distance of the second lens group G2 when varying the power from the wide end to the tele end.

Description

technical field [0001] The present invention relates to a variable magnification optical system and an imaging device. More specifically, it relates to a variable magnification optical system that can be used in video cameras, electronic still cameras, etc., and is especially suitable for use as a surveillance camera, and a device equipped with the variable magnification optical system. camera device. Background technique [0002] Currently, CCTV (Closed- circuit Television) with zoom optical system. In this variable power optical system for CCTV, in terms of the four-group configuration, there are many advantages such as the simplification of the lens barrel and the variable power mechanism and the ease of operation, and many have been proposed (for example, refer to the following patent documents 1 to 1). 4). [0003] Patent Document 1: JP-A-2003-98434 [0004] Patent Document 2: JP-A-2004-325566 [0005] Patent Document 3: JP-A-2006-113387 [0006] Patent Document 4...

AI Technical Summary

Problems solved by technology

However, in the CCTV field, since the differentiation of CCTV cameras and mounting lenses is advancing, it is difficult to apply the above-mentioned technology in the field of digital cameras, and as a result, it is necessary to suppress the occurrence of color bleeding by the lens system itself.

[0010] In the conventionally known devices described in Patent Documents 1 to 3, the correction of chromatic aberration is insufficient, or the F value is too large when used as a CCTV at the wide-angle end.

In addition, in the device described in Patent Document 4, since the first lens group is composed of four pieces, the outer diameter of the first lens group is large, and the movement amount of the second lens group is relatively large, so it is relatively small and low in cost. difficulty

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