Optical system and rear projector
An optical system that projects projection light from an image generating device, onto a screen is provided. The optical system comprises: a lens system on which the projection light from the image generating device is incident; and an aspherical mirror with negative power as a whole that is disposed on an optical path between the lens system and the screen, wherein a curvature of the aspherical mirror in the radial direction changes positive to negative on a way from a center to a periphery thereof.
1. An optical system that projects projection light from an image generating device, onto a screen, the optical system comprising:
a lens system on which the projection light from the image generating device is incident; and
an aspherical mirror with negative power as a whole that is disposed on an optical path between the lens system and the screen, wherein a curvature of the aspherical mirror in the radial direction changes positive to negative on a way from a center to a periphery thereof,
wherein the curvature of the aspherical mirror decreases from the center to the periphery.
2. The optical system according to claim 1 , wherein a lens located at an end of a projection side of the lens system is a meniscus lens that is convex on the projection side.
3. The optical system according to claim 1 , wherein the optical system projects the projection light on the screen at an incident angle of at least 45°.
4. The optical system according to claim 1 , wherein a distance D between an aspherical mirror end of the lens system and the aspherical mirror and a combined focal length f of the lens system satisfy a condition below
1.0 |f|<D< 3.0 |f|.
5. The optical system according to claim 1 , wherein the lens system includes, from a projection side, a front group with negative refractive power, a rear group with positive refractive power, and one of a flat mirror and a prism that bends an optical path between the front group and the rear group.
6. The optical system according to claim 5 , wherein the front group includes, from the projection side, a first lens group, which has a negative refractive power and includes at least a meniscus lens that is convex on the projection side, and a second lens group which has a positive refractive power.
7. A projector comprising:
the optical system according to claim 1 ;
an image generating device; and
a screen entire area thereof being a prism-type Fresnel screen.
8. A rear projector comprising:
the optical system according to claim 1 ;
an image generating device; and
a screen,
wherein the projection light is projected from a rear side of the screen.
9. The rear projector according to claim 8 , wherein entire area of the screen is a prism-type Fresnel screen.
10. An optical system that projects projection light from an image generating device, onto a screen, the optical system comprising:
a lens system on which the projection light from the image generating device is incident; and
an aspherical mirror with negative power as a whole that is disposed on an optical path between the lens system and the screen, wherein a curvature of the aspherical mirror in the radial direction changes positive to negative on a way from a center to a periphery thereof,
wherein a lens located at an end of a projection side of the lens system is a meniscus lens that is convex on the projection side.
11. A projector comprising:
the optical system according to claim 10 ;
an image generating device; and
a screen entire area thereof being a prism-type Fresnel screen.
12. A projector comprising:
the optical system according to claim 10 ;
an image generating device; and
a screen,
wherein the projection light is projected from a rear side of the screen.
13. An optical system that projects projection light from an image generating device, onto a screen, the optical system comprising:
a lens system on which the projection light from the image generating device is incident; and
an aspherical mirror with negative power as a whole that is disposed on an optical path between the lens system and the screen, wherein a curvature of the aspherical mirror in the radial direction changes positive to negative on a way from a center to a periphery thereof,
wherein the lens system includes, from a projection side, a front group with negative refractive power, a rear group with positive refractive power, and one of a flat mirror and a prism that bends an optical path between the front group and the rear group.
14. A projector comprising:
the optical system according to claim 13 ;
an image generating device; and
a screen entire area thereof being a prism-type Fresnel screen.
15. A projector comprising:
the optical system according to claim 13 ;
an image generating device; and
a screen,
wherein the projection light is projected from a rear side of the screen.