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US 2001/0055162 A1Published application
Zoom lens system
AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorTakashi Enomoto
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AssigneeAsahi Kogaku Kogyo Kabushiki Kaisha
InventorTakashi Enomoto
Estimating the term…
A two-lens-group zoom lens system includes a positive first lens group and a negative second lens group in this order from the object, and zooming is performed by varying the distance between the first and the second lens groups. The positive first lens group includes a negative first lens element, a plastic-made second lens element having at least one aspherical surface, and a positive third lens element in this order from the object. The zoom lens system satisfies the following conditions: 3.5<fT/f1G<4.5 (1) −4.7<fT/f2G<−3.7 (2) 63<νDL3 (3) wherein fT designates the focal length of the entire zoom lens system at the long focal length extremity; f1G designates the focal length of the positive first lens group; f2G designates the focal length of the negative second lens group; and νdL3 designates the Abbe number with respect to the positive third lens element in the positive first lens group.
A zoom lens system in which a positive first lens group and a negative second lens group are provided in this order from the object, and zooming is performed by varying the distance between said positive first lens group and said negative second lens group, wherein said positive first lens group comprises a negative first lens element, a plastic-made second lens element having at least one aspherical surface, and a positive third lens element in this order from the object, said zoom lens system satisfies the following conditions:
A zoom lens system in which a positive first lens group and a negative second lens group are provided in this order from the object, and zooming is performed by varying the distance between said positive first lens group and said negative second lens group, wherein said positive first lens group consists of a negative first lens element having a concave object side surface, a plastic second lens element having at least one aspherical surface, and a positive third lens element, in this order from the object, and said zoom lens system satisfies the following conditions:
A zoom lens system in which a positive first lens group and a negative second lens group are provided in this order from the object, and zooming is performed by varying the distance between said positive first lens group and said negative second lens group, wherein said positive first lens group comprises a negative first lens element having a concave object side surface, a plastic negative second lens element having at least one aspherical surface, and a positive third lens element, in this order from the object, and said zoom lens system satisfies the following conditions:
Dependencies are inferred from the claim text.