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US 7,405,886 B2Granted
Zoom lens device
AssigneeAsia Optical Co., Inc.
InventorYu-Min Chang
Life of this patent
Estimating the term…
Abstract
A zoom lens device includes, in sequence from an object side to an imaging side, a negative first lens group, a positive second lens group, and a positive third lens group. When the zoom lens device is moved from a wide-angle condition to a telephoto condition, the second lens group moves towards the object side while the first lens group moves firstly towards the imaging side and then towards the object side to thereby reducing the distance between the first and second lens groups. The third lens group moves only when the zoom lens devices focuses.
Claims19
A zoom lens device comprising, from an object side to an image side:
- a negative first lens group;
- a positive second lens group;
- and
- a positive third lens group;
- with no intervening lenses between the first second and third lens groups;
- and
- wherein the second lens group comprises four lenses having a closest-to-object-side lens having an object-side surface that is aspheric and a closest-to-image-side lens having an image-side surface that is aspheric;
- wherein the second lens group has an overall focal length fG2 and the closest-to-image-side lens of the second lens group has a focus length fL6, which satisfy the following condition:
- 2.10
- ≤
- f
- L
-
-
- 6
- f
- G
-
-
- 2
- ≤
- 3.20
- ;
-
- and
- wherein when the zoom lens device varies from a wide-angle condition to a telephoto condition, the second lens group moves towards the object side while the first lens group moves firstly towards the imaging side and then towards the object side, so that the distance between the first and second lens groups is shortened.
23 more elements
Dependencies are inferred from the claim text.