Zoom lens system and projector having the same
AssigneeCanon Kabushiki Kaisha
InventorKen Wada
Life of this patent
Estimating the term…
Abstract
A zoom lens system discloses a zoom lens system which is small in size and exhibits favorable optical performance. The zoom lens system, according to the present invention includes, in order from the front to the rear: a first lens unit having negative optical power; a second lens unit having positive optical power; a third lens unit having positive optical power; a fourth lens unit having positive optical power; and a fifth lens unit having positive optical power. Of these five lens units, at least three lens units move at the time of zooming. Further, the fifth lens unit is provided with a positive lens element having a relatively high refractive index.
Claims10
A zoom lens system comprising, in order from the front to the rear:
- a first lens unit having negative optical power;
- a second lens unit having positive optical power;
- a third lens unit having positive optical power;
- a fourth lens unit having positive optical power;
- and
- a fifth lens unit having positive optical power,
- wherein at least three lens units out of the first lens unit to the fifth lens unit move during zooming, and
- the following condition is satisfied:
- 1.63<N5p<1.85
- where N5p is an average refractive index of a material of each positive lens element possessed by the fifth lens unit.
Dependencies are inferred from the claim text.