PROJECTION ZOOM LENS AND IMAGE PROJECTION DEVICE

Japanese Patent JP2017173588

A

PROBLEM TO BE SOLVED: To provide a projection zoom lens that offers high axial chromatic aberration performance compatible with high-definition image display elements, and to provide an image projection device having the same.SOLUTION: A projection zoom lens ZL consists of six lens groups having negative, (positive or negative), positive, negative, positive, and positive power arranged in order from a magnification conjugate side. A fourth lens group Gr4 is comprised of at least one positive lens and at least one negative lens, and at least one of the positive lenses of the fourth lens group Gr4 satisfies the following conditional expressions: 0.71≤θg_Fp+0.004×νdp≤0.73, and 15≤νdp≤25, where θg_Fp=(Ng-NF)/(NF-NC) represents a partial dispersion ratio of a lens material, Ng, NF, and NC represent refractive indexes for the g-ray, F-ray, and C-ray, respectively, and νdp represents an Abbe number of the lens material. An air-equivalent back focus BF of the entire projection zoom lens satisfies a conditional expression: 1.0≤BF/Fw≤2.7, where Fw represents a focal length of the entire projection zoom lens at the wide-angle end.SELECTED DRAWING: Figure 1

INOUE KAZUHIKO
IMAI YUSUKE

JP2016059913A

September 28, 2017

March 24, 2016

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KONICA MINOLTA INC

G02B15/20; G02B13/16

Sano patent office

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