Patent ID: 7075732

Claim:
A zoom optical system, comprising, in order from an object side thereof, a first lens group having a generally negative refracting power and a second lens group having a generally positive refracting power, wherein: said first lens group comprises a negative single lens element including at least one aspheric surface and a positive single lens element with an air separation interposed between said negative single lens element and said positive single lens element, said second lens group comprises four lens elements inclusive of, in order from an object side thereof, a positive lens element, a cemented lens consisting of a positive lens element and a negative lens element and a positive lens element wherein the number of all lens elements is four, and further comprises at least one aspheric surface, and said zoom optical system is operable to vary a spacing between said lens groups for zooming and satisfies the following conditions: 1.1 <|f 1 |/âˆš{square root over ( )}( f W Â·f T )<2.2â€ƒâ€ƒ(1) 70Â°<2Ï‰ W <85Â°â€ƒâ€ƒ(2) 15Â°<2Ï‰ T <24Â°â€ƒâ€ƒ(3) where f W is a focal length of the zoom optical system at a wide-angle end thereof, which satisfies condition (2), f T is a focal length of the zoom optical system at a telephoto end thereof, which satisfies condition (3), f 1 is a focal length of the first lens group, Ï‰ W is a maximum image pickup half angle of view at the wide-angle end, and Ï‰ T is a maximum image pickup half angle of view at the telephoto end.