Zoom lens system
AssigneeMinolta Camera Kabushiki Kaisha
InventorsHideki Nagata, Soh Ohzawa, Hiroyuki Matsumoto, Masakuni Tai
Life of this patent
Estimating the term…
Abstract
A zoom lens system of the invention is double telephoto type zoom lens system having a positive/negative/positive/negative refractive power arrangement. During zooming from the wide angle side toward the telephoto side, the first through fourth lens units move such that the distance between the first and second lens units increases and the distance between the third and fourth lens units decreases. The refractive power of the first lens unit and the refractive power of the fourth lens unit are appropriately prescribed so that an adequate back focal lens distance is preserved.
Claims13
A zoom lens system, comprising from an object side:
- a first lens unit having a positive refractive power;
- a second lens unit having a negative refractive power;
- a third lens unit having a positive refractive power;
- and
- a fourth lens unit having a negative refractive power,
- wherein the first through fourth lens units move such that the distance between the first and second lens units increases and the distance between the third and fourth lens units decreases during zooming from the wide angle toward the telephoto end of the zoom range, and
- wherein following conditions are fulfilled:
- -0.3<.phi.1/.phi.4<-0.1
- where
- .phi.1 represents the refractive power of the first lens unit, and
- .phi.4 represents the refractive power of the fourth lens unit.
A zoom lens system, comprising from an object side:
- a first lens unit having a positive refractive power;
- a second lens unit having a negative refractive power;
- a third lens unit having a positive refractive power;
- and
- a fourth lens unit having a negative refractive power,
- wherein the first through fourth lens units move such that the distance between the first and second lens units increases and the distance between the third and fourth lens units decreases during zooming from the wide angle toward the telephoto end of the zoom range,
- wherein the third lens unit consists of from the object side a front lens unit having a negative refractive power and a rear lens unit having a positive refractive power and the front lens unit includes a positive lens and a negative lens, and
- wherein following conditions are fulfilled:
- <
- T3
- .nu.+<.nu.-
- where
- T3 represents the distance between front lens unit and the rear lens unit,
- .nu.+ represents Abbe number of the positive lens of front lens unit, and
- .nu.- represents Abbe number of the negative lens of front lens unit.
Dependencies are inferred from the claim text.