Projection zoom lens and projection-type display apparatus
AssigneeFujinon Corporation
InventorAkiko Nagahara
Life of this patent
Estimating the term…
Abstract
A zoom lens includes, in order from a magnification side, a negative first lens group for focus adjustment adapted to be fixed during power-varying, a positive second lens group adapted to move during power-varying, a negative third lens group, a positive fourth lens group, and a positive fifth lens group, and a positive sixth lens group adapted to be fixed during power-varying, the sixth lens group having a stop arranged nearest to the magnification side. Each lens is a single lens. A ratio of a back focal length of the entire system to a focal length at a wide-angle end of the entire system is larger than 2.5, and Fno. is set constant over the whole region of power-varying.
Claims11
A projection zoom lens comprising, in order from a magnification side:
- a first lens group having negative refractive power adapted to perform focusing with being fixed during power-varying;
- a second lens group having positive refractive power adapted to move during power-varying;
- a third lens group having negative refractive power adapted to move during power-varying;
- a fourth lens group having positive refractive power adapted to move during power-varying;
- a fifth lens group having positive refractive power adapted to move during power-varying;
- and
- a sixth lens group having positive refractive power adapted to be fixed during power-varying and to include a first stop nearest to the magnification side,
- wherein a numerical aperture is set constant over the whole region of power-varying,
- each lens included in the first to sixth groups is a single lens,
- a reduction side is made telecentric, and
- the following conditional expression (1) is satisfied:
- 2.5<Bf/f (1)
- where Bf denotes an air-converted back focal length of the entire system, and
- f denotes a focal length at a wide-angle end of the entire system.
Dependencies are inferred from the claim text.