TECHNICAL FIELD

The present disclosure relates to a projection lens system that projects an image of a reduction side into a magnification side, and an image projection device including the projection lens system.

BACKGROUND ART

PTL 1 discloses an optical system for successfully correcting chromatic aberrations and reducing a shift in focus position due to a temperature change in an image projection device and an imaging device. In the optical system of PTL 1, at least two positive lenses in which the Abbe number, anomalous dispersion property, rate of change in refractive index with respect to temperature changes, and the like are set in appropriate ranges are disposed closer to the reduction side than a diaphragm. As a result, the shift in the focus position caused by the change in refractive index due to the temperature change can be reduced, while the axial chromatic aberration is successfully corrected by increasing the width of an axial light flux. PTL 1 describes that a lamp used as a light source is a cause of high temperature in the image projection device.

CITATION LIST

Patent Literature

PTL 1: Unexamined Japanese Patent Publication No. 2011-053663

SUMMARY

The present disclosure provides a projection lens system and an image projection device that can improve the image quality of an image when the brightness of the image projection device is increased.

A projection lens system according to the present disclosure is a lens system that projects an image of a reduction side into a magnification side in an image projection device, a back glass being disposed on the reduction side. The projection lens system includes one or more negative lenses. Each of the one or more negative lenses has a surface on the reduction side and a surface on the magnification side. Each of the one or more negative lenses satisfies following condition (1) in the surface on the reduction side or the surface on the magnification side. All of the one or more negative lenses satisfy following conditions (2) and (3),
|h/H|<2.0  (1)
Tn≥98.5%  (2)
Dn/Db≤0.05  (3)

where

h indicates a height of a most off-axis principal ray,

H indicates a height of an axial ray passing through a highest pupil position,

Tn indicates a transmittance of light having a wavelength of 460 nm when a lens material of the one or more negative lenses has a thickness of 10 mm,

Dn indicates a thickness of the one or more negative lenses on an optical axis, and

Db indicates a total thickness of the back glass.

An image projection device according to the present disclosure includes the projection lens system described above and an image forming element. The image forming element forms an image.

According to the projection lens system and the image projection device according to the present disclosure, it is possible to improve the image quality of an image when the brightness of the image projection device is increased.

