Oblique projection optical system
First Claim
1. An oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising:
- in order along a projection optical path from a secondary image surface side,only one curved reflective surface; and
a lens unit having a plurality of lens elements,wherein the curved reflective surface has a portion having a positive optical power and a portion having a negative optical power, andwherein, given that a principal ray emitted from a center of the primary image surface and passing through a center of an aperture stop is a central principal ray, the curved reflective surface includes at an intersection thereof with the central principal ray a direction having a positive optical power and a direction having a negative optical power.
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Abstract
In an oblique projection optical system for performing enlargement projection from a primary image surface on the reduction side to a secondary image surface on the enlargement side, at least one reflective surface having an optical power is provided, and, assuming that of the aforementioned surfaces, the reflective surface located on the most secondary image surface side in the optical path is a first curved reflective surface, the first curved reflective surface has a portion having a positive optical power and a portion having a negative optical power.
24 Citations
22 Claims
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1. An oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising:
- in order along a projection optical path from a secondary image surface side,
only one curved reflective surface; and a lens unit having a plurality of lens elements, wherein the curved reflective surface has a portion having a positive optical power and a portion having a negative optical power, and wherein, given that a principal ray emitted from a center of the primary image surface and passing through a center of an aperture stop is a central principal ray, the curved reflective surface includes at an intersection thereof with the central principal ray a direction having a positive optical power and a direction having a negative optical power. - View Dependent Claims (2, 3, 4)
- in order along a projection optical path from a secondary image surface side,
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5. An oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising:
- in order along a projection optical path from a secondary image surface side,
only one curved reflective surface; and a lens unit having a plurality of lens elements, wherein the curved reflective surface has a portion having a positive optical power and a portion having a negative optical power, wherein at least one rotation-symmetric optical element is provided which has an optical power and whose rotation-symmetric shape is formed at least partly with either of the curved reflective surface or a refractive surface of the lens unit, and wherein, given that a direction normal to the primary image surface is an Xo direction, that an image shorter-side direction of the primary image surface is a Yo direction, and that an XoYo plane including a center of the primary image surface is a PXoYo plane, a rotation center axis of said at least one rotation-symmetric optical element lies within an optical extension plane of the PXoYo plane and also is not parallel to an optical extension direction of the Xo direction. - View Dependent Claims (6, 7, 8)
- in order along a projection optical path from a secondary image surface side,
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9. An oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising:
- in order along a projection optical path from a secondary image surface side,
only one curved reflective surface; and a lens unit having a plurality of lens elements, wherein the curved reflective surface has a portion having a positive optical power and a portion having a negative optical power, wherein a maximum value of an angle of incidence that is formed by a principal ray of a projected beam with respect to the secondary image surface is 65 degrees or more, and wherein conditional formula (3) below is fulfilled;
1.05<
(α
max/α
min)<
3
(3)where α
max represents the maximum value (in degrees) of the angle of incidence that is formed by the principal ray of the projected beam with respect to the secondary image surface, andα
min represents a minimum value (in degrees) of the angle of incidence that is formed by the principal ray of the projected beam with respect to the secondary image surface.- View Dependent Claims (10, 11, 12, 13, 14, 15)
where CoR1Zmax represents a curvature of the curved reflective surface in the Zi direction near a region where the beam RaysXiYiθ
max is reflected on the curved reflective surface on the optical extension plane of the PXiYi plane, andCoR1Zmin represents a curvature of the curved reflective surface in the Zi direction near a region where the beam RaysXiYiθ
min is reflected on the curved reflective surface on the optical extension plane of the PXiYi plane.
- in order along a projection optical path from a secondary image surface side,
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11. The oblique projection optical system according to claim 10,
wherein conditional formula (5) below be fulfilled: -
(CoR1Zmin−
CoR1Ymin)/(CoR1Zmax−
CoR1Ymax)>
1
(5)where CoR1Ymax represents a curvature of the curved reflective surface in the Yi direction near the region where the beam RaysXiYiθ
max is reflected on the curved reflective surface on the optical extension plane of the PXiYi plane, andCoR1Ymin represents a curvature of the curved reflective surface in the Yi direction near the region where the beam RaysXiYiθ
min is reflected on the curved reflective surface on the optical extension plane of the PXiYi plane.
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12. The oblique projection optical system according to claim 9,
wherein, given that a direction normal to the secondary image surface is an Xi direction, that an image shorter-side direction of the secondary image surface is a Yi direction, that an XiYi plane including a center of the secondary image surface is a PXiYi plane, and, that, of beams on the PXiYi plane that reach the secondary image surface, the beam having a principal ray which forms a largest angle with the Xi direction when incident on the secondary image surface is RaysXiYiθ - max and the beam having a principal ray which forms a smallest angle with the Xi direction when incident on the secondary image surface is RaysXiYiθ
min, a shape of an effective optical region of the curved reflective surface on an optical extension plane of the PXiYi plane is a concave having a positive optical power at a region where the beam RaysXiYiθ
max is reflected and is a convex having a negative optical power at a region where the beam RaysXiYiθ
min is reflected.
- max and the beam having a principal ray which forms a smallest angle with the Xi direction when incident on the secondary image surface is RaysXiYiθ
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13. The oblique projection optical system according to claim 12,
wherein, given that a principal ray emitted from a center of the primary image surface and then passing through a center of an aperture stop is a central principal ray, and that a curvature on a line where the optical extension plane of the PXiYi plane and the curved reflective surface intersect each other is CoR1Y, a point at which a sign of the curvature CoR1Y is reversed is located closer to the region where the beam RaysXiYiθ - min is reflected than the intersection of the central principal ray and the curved reflective surface.
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14. The oblique projection optical system according to claim 9,
wherein, given that a direction normal to the secondary image surface is an Xi direction, that an image shorter-side direction of the secondary image surface is a Yi direction, that an XiYi plane including a center of the secondary image surface is a PXiYi plane, that a direction normal to the primary image surface is an Xo direction, that an image shorter side direction of the primary surface is a Yo direction, and that an XoYo plane including a center of the primary image surface is a PXoYo plane, an optical extension plane of the PXoYo plane and an optical extension plane of the PXiYi plane are on the same plane. -
15. The oblique projection optical system according to claim 9, farther comprising:
a flat reflective surface, for bending the projection optical path such that a direction normal to the secondary image surface and an image longer-side direction of the primary image surface are parallel to each other, that is arranged between the lens unit and the curved reflective surface.
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16. An image projection apparatus comprising:
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an image display device that forms an image to be projected; a light source; an illumination optical system that guides light from the light source to the image display device; and an oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising;
in order along a projection optical path from a secondary image surface side,only one curved reflective surface; and a lens unit having a plurality of lens elements, wherein the curved reflective surface has a portion having a positive optical power and a portion having a negative optical power, wherein a maximum value of an angle of incidence that is formed by a principal ray of a projected beam with respect to the secondary image surface is 65 degrees or more, and wherein conditional formula (3) below is fulfilled;
1.05<
(α
max/α
min)<
3
(3)where α
max represents the maximum value (in degrees) of the angle of incidence that is formed by the principal ray of the projected beam with respect to the secondary image surface, andα
min represents a minimum value (in degrees) of the angle of incidence that is formed by the principal ray of the projected beam with respect to the secondary image surface,wherein the image display device is positioned on the primary image surface.
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17. An oblique projection optical system for performing enlargement projection from a primary image surface on a reduction side to a secondary image surface on an enlargement side, the oblique projection optical system comprising:
- in order along a projection optical path from a secondary image surface side,
a first curved reflective surface; a second curved reflective surface; a third curved reflective surface having a negative optical power; and a fourth curved reflective surface having a positive optical power, wherein the first curved reflective surface has a portion having a positive optical power and a portion having a negative optical power. - View Dependent Claims (18, 19, 20, 21, 22)
- in order along a projection optical path from a secondary image surface side,
Specification