Wide-angle lens system and image -taking device

Abstract

A wide-angle lens system has, from the object side thereof: a first lens element having a negative optical power and having a meniscus shape convex to the object side; a second lens element having a biconcave shape; a third lens element having a biconvex shape; and a fourth lens element having a negative optical power and having a meniscus shape convex to the image side. Alternatively, a wide-angle lens system has, from the object side thereof: a first lens element having a negative optical power; a second lens element having a negative optical power; a third lens element having a positive optical power; and a fourth lens element having a positive optical power.

Description

technical field [0001] The present invention relates to a compact wide-angle lens system, and more particularly to a system capable of providing a total viewing angle of approximately 150 degrees and suitable for use with a solid-state image sensor in digital input devices such as video phones, walkie-talkies, surveillance cameras, vehicle cameras, etc. (such as digital still cameras or digital video cameras) ) wide-angle lens system. Background technique [0002] Many wide-angle lens systems designed as imaging optical systems have been proposed, which can be used in surveillance cameras, vehicle cameras, etc., together with solid-state image sensors. Some of these wide-angle lens systems can provide a total viewing angle of about 150 degrees, and some of them are composed of eight lens elements (see Patent Publication 1 below). [0003] Patent Publication 1: JP-A-2004-102162 [0004] However, the wide-angle lens system disclosed in the aforementioned Patent Publication 1...

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Problems solved by technology

[0004] However, the wide-angle lens system disclosed in the above-mentioned Patent Publication 1 requires an extremely large number (namely, eight) of lens elements, and has a complicated structure and an extremely long overall length

Additionally, all lens elements are glass lens elements, which makes wide-angle lens systems unsatisfactory in terms of cost and weight

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