| 摘要 |
An optical system having a wide angle of view for forming an optical image of a photographic subject on light-receiving surfaces of an imaging element that converts the optical image into an electrical signal comprises a first lens having a negative optical power and a group of lenses each having a positive optical power, which are serially disposed from an object side. The first lens comprises at least one aspherical surface, and has a concave surface centered around an optical axis in vicinity of the optical axis on an image-side surface thereof. Further, an optical entire length T (mm) of the entire system, half angle of view theta, and focal distance f<SUB>tot </SUB>(mm) of the entire system satisfy the following conditional expressions. <?in-line-formulae description="In-line Formulae" end="lead"?>10 mm<Txsin theta<30 mm <?in-line-formulae description="In-line Formulae" end="tail"?> <?in-line-formulae description="In-line Formulae" end="lead"?>7<T/F<SUB>tot</SUB><20 <?in-line-formulae description="In-line Formulae" end="tail"?> Thereby, the wide-angle optical system achieving a wide angle of view, reducing the optical entire length and capable of favorably correcting an aberration can be obtained. An image pickup device comprising the wide-angle optical system can be provided in a compact size, however, is still capable of photographing a wide region. Therefore, the image pickup device is suitable for monitor cameras such as an in-vehicle camera and a security camera.
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