Optical system, virtual image display device, and head-mounted display
An optical system includes: a first optical portion, on which image light from an image display element is incident; a light guide configured to guide the image light incident from the first optical portion; and a second optical portion configured to direct the image light guided in the light guide to an object. The first optical portion has an anamorphic surface having: a first shape in a first direction; and a second shape in a second direction different from the first direction, the first shape being different from the second shape. The first optical portion forms an intermediate image of the image light.
1. An optical system, comprising:
a first optical portion, on which image light from an image display element is incident, the first optical portion having an anamorphic surface having:
a first shape in a first direction; and
a second shape in a second direction different from the first direction, the first shape being different from the second shape, the first optical portion to form an intermediate image of the image light;
a light guide to guide the image light incident from the first optical portion;
a second optical portion to direct the image light guided in the light guide to an object; and
a partial reflector between the first optical portion and the second optical portion, the partial reflector to:
transmit the image light guided in the light guide, from a first side of the partial reflector, in which the first optical portion is disposed; and
reflect the image light guided in the light guide, from a second side of the partial reflector to direct the image light to the object, the first side being different from the second side,
wherein the second optical portion reflects the image light transmitted through the partial reflector back to the partial reflector.
2. The optical system according to claim 1 , further comprising multiple partial reflectors including the partial reflector,
wherein the multiple partial reflectors are spaced apart from each other in an optical axis direction.
3. The optical system according to claim 1 ,
wherein the second optical portion has a reflection surface that is an anamorphic surface that reflects the image light transmitted through the partial reflector back to the partial reflector.
4. The optical system according to claim 3 ,
wherein the optical system satisfies a formula:
−0.9 <TL max/ R max<−0.3
where
TLmax is a distance (mm) between an image-forming position, at which the intermediate image is formed, and the reflection surface in an optical axis direction, in a cross-sectional plane in which an absolute value of a magnification of the intermediate image becomes maximum; and
Rmax is a paraxial radius of curvature of the reflection surface in the cross-sectional plane.
5. The optical system according to claim 3 ,
wherein the optical system satisfies a formula:
−0.7 <TL min/ R min<−0.1
where
TLmin is a distance (mm) between an image-forming position, at which the intermediate image is formed, and the reflection surface in an optical axis direction in a cross-sectional plane in which an absolute value of a magnification of the intermediate image becomes minimum; and
Rmin is a paraxial radius of curvature of the reflection surface in the cross-sectional plane.
6. The optical system according to claim 3 ,
wherein the optical system satisfies a formula:
0.3 <TL min/ TL max<0.9
where
TLmax is a distance (mm) between an image-forming position, at which the intermediate image is formed, and the reflection surface in an optical axis direction in a cross-sectional plane in which an absolute value of a magnification of the intermediate image becomes maximum; and
TLmin is a distance (mm) between the image-forming position and the reflection surface in a cross-sectional plane in which an absolute value of the magnification of the intermediate image becomes minimum.
7. The optical system according to claim 1 ,
wherein the optical system satisfies a formula:
0.4<βmin/βmax<0.95
where
βmin is a minimum absolute value of a magnification of the intermediate image, and
βmax is the maximum absolute value of the magnification of the intermediate image.
8. The optical system according to claim 1 ,
wherein the optical system satisfies a formula:
0.5<βmin<2.0
where
βmin is a minimum absolute value of a magnification of the intermediate image.
9. The optical system according to claim 1 ,
wherein the first optical portion includes an aperture stop on an optical path of the image light.
10. A virtual image display device comprising:
the optical system according to claim 1 ; and
the image display element to emit image light to the optical system.
11. A head-up display comprising the virtual image display device according to claim 10 .
12. An optical system, comprising:
a first optical portion, on which image light from an image display element is incident, the first optical portion having an anamorphic surface having:
a first shape in a first direction; and
a second shape in a second direction different from the first direction, the first shape being different from the second shape, the first optical portion configured to form an intermediate image of the image light;
a light guide configured to guide the image light incident from the first optical portion; and
a second optical portion configured to direct the image light guided in the light guide to an object,
wherein the second optical portion has an anamorphic surface.
13. The optical system according to claim 12 , wherein:
the second optical portion has an anamorphic surface.
14. The optical system according to claim 12 ,
wherein the optical system satisfies a formula:
0.4<βmin/βmax<0.95
where
βmin is a minimum absolute value of a magnification of the intermediate image, and
βmax is a maximum absolute value of the magnification of the intermediate image.
15. The optical system according to claim 12 ,
wherein the optical system satisfies a formula:
0.5<βmin<2.0
where
βmin is a minimum absolute value of a magnification of the intermediate image.
16. The optical system according to claim 12 , wherein:
the first optical portion includes an aperture stop on an optical path of the image light.
17. A virtual image display device comprising:
the optical system according to claim 12 ; and
the image display element to emit image light to the optical system.
18. A head-up display comprising the virtual image display device according to claim 17 .
19. An optical system, comprising:
a first optical portion, on which image light from an image display element is incident, the first optical portion having an anamorphic surface having:
a first shape in a first direction; and
a second shape in a second direction different from the first direction, the first shape being different from the second shape, the first optical portion to form an intermediate image of the image light;
a light guide to guide the image light incident from the first optical portion; and
a second optical portion to direct the image light guided in the light guide to an object,
wherein:
the light guide has a lowest thickness in the first direction, and
a magnification of the intermediate image in the first direction has a minimum absolute value.
20. The optical system according to claim 19 , wherein:
the second optical portion has an anamorphic surface.