Source: http://www.google.com/patents/US7048388?dq=6,373,753
Timestamp: 2015-05-24 06:04:59
Document Index: 500735034

Matched Legal Cases: ['Art 3', 'Art 1', 'art 11', 'art 11', 'art 11', 'art 11', 'art 11']

Patent US7048388 - Projection optical system, magnification projection optical system ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system. An intermediate image surface of the projected object surface is positioned...http://www.google.com/patents/US7048388?utm_source=gb-gplus-sharePatent US7048388 - Projection optical system, magnification projection optical system, magnification projection apparatus, and image projection apparatusAdvanced Patent SearchPublication numberUS7048388 B2Publication typeGrantApplication numberUS 10/771,523Publication dateMay 23, 2006Filing dateFeb 5, 2004Priority dateFeb 6, 2003Fee statusPaidAlso published asUS7441908, US7631975, US7637618, US7637621, US7922341, US7938545, US20040156117, US20060126032, US20080304019, US20090015801, US20090015910, US20090021703, US20100039625, US20110038039, USRE45258Publication number10771523, 771523, US 7048388 B2, US 7048388B2, US-B2-7048388, US7048388 B2, US7048388B2InventorsAtsushi Takaura, Kazuhiro Fujita, Nobuo SakumaOriginal AssigneeRicoh Company, Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (53), Non-Patent Citations (6), Referenced by (52), Classifications (27), Legal Events (3) External Links: USPTO, USPTO Assignment, EspacenetProjection optical system, magnification projection optical system, magnification projection apparatus, and image projection apparatus
US 7048388 B2Abstract
A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system. An intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as the final image on the projection surface via the reflecting mirrors, which include at least one anamorphic polynomial free-formed surface having different vertical and lateral powers. A light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface and the transmission dioptric system is decentered with respect to a normal of the projected object surface, the transmission refractive elements prevented from being decentered with respect to each other.
1. A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein:
an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors;
the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers;
a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and
the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other.
2. The projection optical system as claimed in claim 1, wherein:
the reflection dioptric system includes first and second reflecting mirrors arranged in an order described from upstream to downstream on a downstream side of the transmission dioptric system;
the intermediate image surface of the projected object surface is positioned between the first and second reflecting mirrors; and
the first reflecting mirror includes an axially symmetric reflecting surface having negative power, and the second reflecting mirror includes an anamorphic polynomial free-form surface having different vertical and lateral powers.
3. The projection optical system as claimed in claim 1, comprising an anamorphic polynomial free-form surface having different vertical and lateral powers in the transmission dioptric system as a part correcting an aspect ratio of the intermediate image of the projected object surface.
4. The projection optical system as claimed in claim 1, wherein an NA in the transmission dioptric system is greater on an upstream side thereof than on the downstream side thereof.
5. The projection optical system as claimed in claim 1, wherein the intermediate image surface is tilted and curved with respect to a principal ray of a light beam emitted from a center of the projected object surface.
6. The projection optical system as claimed in claim 1, wherein a principal ray emitted from a center of the projected object surface and a principal ray emitted from a margin of the projected object surface are parallel to each other in a last surface of the transmission dioptric system.
7. The projection optical system as claimed in claim 1, wherein magnification of the intermediate image falls in a range of 1 to 5.
8. The projection optical system as claimed in claim 1, wherein magnification of projection is 40� or higher.
9. The projection optical system as claimed in claim 8, wherein an angle of projection to the projection surface is 5� or greater.
10. A projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein:
the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other at a group unit level.
11. The projection optical system as claimed in claim 10, wherein:
12. The projection optical system as claimed in claim 10, comprising an anamorphic polynomial free-form surface having different vertical and lateral powers in the transmission dioptric system as a part correcting an aspect ratio of the intermediate image of the projected object surface.
13. The projection optical system as claimed in claim 10, wherein an NA in the transmission dioptric system is greater on an upstream side thereof than on the downstream side thereof.
14. The projection optical system as claimed in claim 10, wherein the intermediate image surface is tilted and curved with respect to a principal ray of a light beam emitted from a center of the projected object surface.
15. The projection optical system as claimed in claim 10, wherein a principal ray emitted from a center of the projected object surface and a principal ray emitted from a margin of the projected object surface are parallel to each other in a last surface of the transmission dioptric system.
16. The projection optical system as claimed in claim 10, wherein magnification of the intermediate image falls in a range of 1 to 5.
17. The projection optical system as claimed in claim 10, wherein magnification of projection is 40� or higher.
18. The projection optical system as claimed in claim 17, wherein an angle of projection to the projection surface is 5� or greater.
19. An image projection apparatus magnifying an image displayed on a projected object surface and projecting the magnified image on a projection surface by a projection optical system, wherein:
the projection optical system guides and projects a light beam from the projected object surface onto the projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors;
20. The image projection apparatus as claimed in claim 19, wherein the image projection apparatus is of a front projector type.
21. The image projection apparatus as claimed in claim 19, wherein the image projection apparatus is of a rear projector type, comprising a folding mirror folding back an imaging optical path.
22. An image projection apparatus magnifying an image displayed on a projected object surface and projecting the magnified image on a projection surface by a projection optical system, wherein:
23. The image projection apparatus as claimed in claim 22, wherein the image projection apparatus is of a front projector type.
24. The image projection apparatus as claimed in claim 22, wherein the image projection apparatus is of a rear projector type, comprising a folding mirror folding back an imaging optical path.
Japanese Examined Patent Application
Publication No. 6-91641 (Prior Art 3) discloses an image projection apparatus that is a video projector. The first mirror surface of the imaging optical system of the video projector has a convex shape so as to reduce the thickness of the video projector.
The image projection methods of Prior Art 1 and 3 perform image formation using only one or more reflecting mirrors to magnify and project a single light valve image on a screen. Therefore, these image projection methods enjoy the merit of no generation of chromatic aberration in principle. In the case of displaying images of red, green, and blue separately, using three light valves instead of a single light valve, and combining the separate images on a screen, the intervention of a color combining part such as a cross prism or a Philips prism is necessary, thus resulting in the generation of chromatic aberration at the time of combining colors. However, the imaging optical system composed of only reflecting surfaces cannot correct chromatic aberration.
One or more of the above-described objects of the present invention are achieved by a projection optical system for use in an image projection apparatus illuminating a light valve forming an image in accordance with a modulating signal with illumination light from a light source, the projection optical system including first and second optical systems arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream side of the light valve, wherein the first optical system includes at least one dioptric system and has positive power; the second optical system includes at least one reflecting surface having power and has positive power; and the image formed by the light valve is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected.
One or more of the above objects of the present invention are also achieved by an image projection apparatus that illuminates a light valve forming an image in accordance with a modulating signal with illumination light from a light source, the image projection apparatus including: a projection optical system, the projection optical system including first and second optical systems arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream side of the light valve, wherein the first optical system includes at least one dioptric system and has positive power; the second optical system includes at least one reflecting surface having power and has positive power; and the image formed by the light valve is formed as an intermediate image in the optical path, and the intermediate image is magnified and projected by the projection optical system.
One or more of the above objects of the present invention are also achieved by a magnification projection optical system that guides a light beam from an image display panel to a screen in an upstream-downstream direction, projects the light beam from a direction inclined to a normal of the screen, and forms on the screen a magnified version of an image displayed on the image display panel, the magnification projection optical system including: a reflection optical system; and a transmission optical system, wherein the reflection optical system includes a plurality of reflecting surfaces having power and includes at least one rotationally asymmetric reflecting surface.; and the transmission optical system includes a transmitting surface having refractive power and includes at least one aspheric surface.
One or more of the above objects of the present invention are also achieved by a projection optical system, including: a first optical system including at least one dioptric system and having positive power; and a second optical system including one or more reflecting surfaces having power, the second optical system having positive power as a whole, wherein the first and second optical systems are arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream side of an object surface; an object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image; and in respect to an optical axis of an optical element positioned at a furthest upstream end of the first optical system and having refractive power, at least one of other optical elements is shifted or tilted.
One or more of the above objects of the present invention are also achieved by a projection optical system, including: a first optical system including at least one dioptric system and having positive power; and a second optical system including one or more reflecting surfaces having power, the second optical system having positive power as a whole, wherein the first and second optical systems are arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream side of an object surface; an object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image; and in the first optical system, with respect to an optical axis of one of optical elements of the first optical system, which one is positioned at a furthest upstream end of the first optical system and has refractive power, the other optical elements are prevented from being tilted.
One or more of the above objects of the present invention are also achieved by an image projection apparatus that, by a projection optical system, guides a light beam from an image display panel to a screen and forms on the screen a final version of the image displayed on the image display panel, wherein: the projection optical system includes: a first optical system including at least one dioptric system and having positive power; and a second optical system including one or more reflecting surfaces having power, the second optical system having positive power as a whole; the first and second optical systems are arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream side of an object surface; an object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image; and with respect to an optical axis of an optical element positioned at a furthest upstream end of the first optical system and having refractive power, at least one of other optical elements is shifted or tilted.
One or more of the above objects of the present invention are also achieved by an image projection apparatus that, by a projection optical system, guides a light beam from an image display panel to a screen and forms on the screen a final version of the image displayed on the image display panel, wherein: the projection optical system includes: a first optical system including at least one dioptric system and having positive power; and a second optical system including one or more reflecting surfaces having power, the second optical system having positive power as a whole; the first and second optical systems are arranged along an optical path defining an upstream-downstream direction in an order described from upstream to downstream on a downstream end of an object surface; an object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image; and in the first optical system, with respect to an optical axis of one of optical elements of the first optical system, which one is positioned at a furthest upstream end of the first optical system and has refractive power, the other optical elements are prevented from being tilted.
One or more of the above objects of the present invention are also achieved by a projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein: the transmission dioptric system includes a plurality of transmission refractive elements; substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system; an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors; the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers; a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other.
One or more of the above objects of the present invention are also achieved by a projection optical system guiding and projecting a light beam from a projected object surface onto a projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors, wherein: the transmission dioptric system includes a plurality of transmission refractive elements; substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system; an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors; the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers; a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other at a group unit level.
One or more of the above objects of the present invention are also achieved by an image projection apparatus magnifying an image displayed on a projected object surface and projecting the magnified image on a projection surface by a projection optical system, wherein: the projection optical system guides and projects a light beam from the projected object surface onto the projection surface in an upstream-downstream direction through a transmission dioptric system and a reflection dioptric system of one or two reflecting mirrors; the transmission dioptric system includes a plurality of transmission refractive elements; substantial telecentricity is provided from the projected object surface up to a first surface of the transmission dioptric system; an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors; the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers; a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other.
an intermediate image surface of the projected object surface is positioned closer to the reflection dioptric system than to the transmission dioptric system, and an intermediate image on the intermediate image surface is formed as a final image on the projection surface via the reflecting mirrors; the reflecting mirrors include at least one anamorphic polynomial free-form surface having different vertical and lateral powers; a light beam from the reflection dioptric system to the projection surface is guided at an angle to a normal of the projection surface; and the transmission dioptric system is decentered with respect to a normal of the projected object surface, and the transmission refractive elements of the transmission dioptric system are prevented from being decentered with respect to each other at a group unit level.
FIG. 8 is an enlarged view of a projection optical system of the image projection apparatus of FIG. 7 according to the present invention.;
Referring to FIG. 1, the image projection apparatus includes a light valve 15, which is a liquid crystal panel in this embodiment. The light valve 15 is hereinafter referred to simply as a panel 15. The image projection apparatus further includes a light source 10 composed of a light emitting part 11 and an illumination optical system 12. The light emitting part 11 is composed of a lamp and a reflector. A light beam from the light emitting part 11 is illumination light in the illumination optical system 12. The illumination light from the light source 10 illuminates the panel 15.
The first optical system 17 has positive power as a whole. As shown in FIG. 2, the intermediate image Iint formed by the first optical system 17 is an inverted version of the image formed on the panel 15. The intermediate image Iint is preferably a one to several times magnified image of the image on the panel 15. If the intermediate image Iint is a reduced image the second optical system 19 is required to have high enlarging magnification so that the first and second optical systems 17 and 19 as a whole obtain a displayed image of high magnification. This makes it difficult to realize a balance between aberration correction and high magnification.
According to the configuration of FIGS. 1 and 2, each light beam forming the intermediate image Iint by the first optical system 17 is reflected by the second optical system 19 to have its optical path folded-back so that an image is projected in the direction opposite to the direction in which the light beam forming the intermediate image Iint travels.
Ri' (mm)
Ti' (mm)
The optical arrangement of FIG. 4 is drawn differently from that of FIG. 3 for convenience of description. As is apparent from the above-described data, however, the optical arrangement of FIG. 4 is substantially equal to that of FIG. 3. In the optical arrangement of FIG. 4, the curvature of the exit surface of the first optical system 17B and the curvature of the reflecting surface of the second optical system 19B are different from those of the firsthand second optical systems 17A and 19A, respectively.
The above-described matter may be implemented by providing, on the light valve side of the intermediate image (the side upstream of the intermediate image in the upstream-downstream direction from the panel 15 to the screen 21) in the optical path of the first and second optical systems, an optical element having negative power for bringing the position at which the intermediate image is formed close to the reflecting surface having positive power of the second optical system.
The projection optical system slightly increases in size to move the position of the intermediate image Iint away from the light valve 15. However, by forming the above-described negative-power optical element of a reflecting mirror, it is possible to employ a layout folding back an optical path, thereby reducing the size of the entire optical system.
In the case of replacing the transmission liquid crystal panel employed as the panel 15 with a reflection liquid crystal light valve, efficient illumination can be performed by splitting an illumination optical path and a projection optical path using a polarization beam splitter.
Referring to FIG. 6, the reference ray of a group of light beams traveling from an image display panel 1 (hereinafter referred to simply as a panel 1) toward a screen 2 is made incident thereon at a predetermined angle to the normal (perpendicular) of the screen 2. The reference ray is the principal ray of a light beam guided from the center of the panel 1 to the screen 2. The reference ray is the principal ray of a light beam guided from the center of the panel 1 to the screen 2.
The panel 1 is a reflection liquid crystal panel, and is illuminated with linearly polarized illumination light via a polarization beam splitter 1A. Light beams modulated by the panel 1 become imaging light beams through the polarization beam splitter 10A. The image display panel may be a lightbulb such as a transmission or reflection liquid crystal panel or a DMD.
It is desirable to provide the transmission optical system 3 with light beam condensing action. In this embodiment, a magnification effect load-is reduced in the transmission optical system 3 so as to prevent particularly the aperture of a lens on the downstream side from becoming larger in size. Accordingly, the entire or a substantial portion of the magnification effect as a magnification projection optical system is assumed by the reflection optical system.
A diaphragm 9 is provided on the upstream side of the reflecting surface 4 on the downstream side of the transmission optical system 3. An image I9 of the diaphragm 9 is formed with negative reducing magnification in an imaging optical path by the reflecting surfaces 4 through 7 on the downstream side of the diaphragm 9. That is, the image 19 of reducing magnification of the diaphragm 9 is formed as an inverted image between the reflecting surface 7 and the rotationally asymmetric reflecting surface 8 by the action of the reflecting surfaces 4 through 7 of the reflection optical system.
The imaging light beams form the intermediate image of the panel 1 in the optical path inside the reflection optical system. Like the image 19 of the diaphragm 9, the intermediate image is a real image of negative magnification and an inverted image. In the embodiment of FIG. 6, the intermediate image of the panel 1 is formed in the vicinity of the reflecting surface 7. That is, the intermediate image of the panel 1 is formed by the transmission optical system 3 and the reflecting surfaces 4 through 6.
The position of, the diaphragm 9 is not limited to the position of FIG. 6. The diaphragm 9 may be provided between surfaces in the transmission optical system 3, for instance. In this case, part of the transmission optical system 3 contributes to the formation of the image I9 of the diaphragm 9.
As the object displaying an image to be projected, one configured to illuminate the light valve 15 with a light beam from the light emitting part 11 formed of the lamp and the reflector through the illumination optical system 12, as described with reference to FIG. 1, may be employed. Specifically, a halogen lamp, a xenon lamp, a metal halide lamp, or a super-high pressure mercury lamp is suitable as the light emitting part 11. An integrator optical system that makes the intensity of the light beam reflected from the reflector to have directivity uniform with respect to the light valve 15 may be employed as the illumination optical system 12.
As the above-described object, a type of object that performs optical path splitting with respect to a DMD panel using an oblique incidence optical system or a total reflection prism may be employed. A type of image display device illuminated with light from an external light source, such as a light valve such as a liquid crystal panel, a DMD, or a film slide, may also be employed as the above-described object. An object of a self-luminous type, such as a two-dimensional arrangement of light-emitting diodes, an LED array, an EL array, or a plasma display, may also be employed.
The projection optical system shown in FIGS. 7 and 8 includes the positive-power first optical system 71 including at least one dioptric system (such as the lens 711) and the second optical system 72 having positive power as a whole and including at least one reflecting surface having power (such as the reflecting surface 721). The first and second optical systems 71 and 72 are provided in the order described from the object surface side so that an object image is formed temporarily as an intermediate image, and thereafter, is formed as a final image. In the first optical system 71, with respect to the optical axis of the lens (optical element) 711, positioned furthest on the object side (closest to the object) and having refractive power, the other optical elements, or the lenses 712 through 716 and the reflecting surfaces 721 and 722, are shifted or tilted. That is, a shift or tilt is caused in units of optical elements. The dioptric system may include a light transmitting type element performing diffraction.
The transmission dioptric system 120 includes the lenses (transmission refractive elements) 121 through 127. It is substantially telecentric from the projected object surface up to the first surface (the object-side surface of the lens 121) of the transmission dioptric system 120 as shown in FIG. 10. The intermediate image surface of the projected object surface is positioned between the reflecting mirrors 131 and 132 of the reflection dioptric system 130. An intermediate image on the intermediate image surface is re-formed as a final image on the projection surface via the second reflecting mirror 132. The transmission refractive element means a general optical element performing refraction of light at the interface of a light transmitting medium, and is typically a lens. Alternatively, the transmission refractive element may be a light transmitting element performing diffraction.
Embodiment 1 is a specific embodiment of the image projection apparatus and the projection optical system of FIGS. 7 and 8. That is, Embodiment 1 includes the first optical system 71 having positive power and including at least one dioptric system and the second optical system 72 including at least one reflecting surface having power and having positive power as a whole. The first and second optical systems 71 and 72 are arranged in the order described from upstream to downstream on the downstream side of the object surface. An object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image. The optical elements 712 through 716, 721, and 722 are shifted or tilted with respect to the optical axis of the optical element 711 having refractive power, which is positioned at the furthest upstream end of the first optical system 71.
The magnification of the intermediate image is approximately 3�.
Z = X2 � x 2 + Y2 � y 2 + X2Y � x 2 y + Y3 � y 3 + X4 � x 4 + X2Y2 � x 2 y 2 + Y4 � y 4 + X4Y � x 4 y + X3Y2 � x 3 y 2 + Y5 � y 5 + X6 � x 6 + X4Y2 � x 4 y 2 + X2Y4 � x 2 y 4 + Y6 � y 6 + ⋯ where X2, Y2, X2Y, Y3, X2Y2, etc. are coefficients, letting the vertical directions be the Y directions, the lateral directions be the X directions, and the depth of the curved surface be the Z directions. The vertical (upward and downward) directions and the lateral (rightward and leftward) directions are considered based on the projected image. The coefficients of the polynomial free-form surface are shown in Table 2.
The image surface (screen) of the final image is a plane surface parallel to the rightward and leftward directions of FIG. 7. There is a great difference in angle of incidence to the screen between a lower position (closer to the object) and a higher position (remoter from the object) of the image height. Therefore, the projected image tends to be narrowed downward and distorted. In this embodiment, distortion on the final image surface is corrected by inversely setting the distortion of the intermediate image.
Z=c�r 2/[1+√{1−(1+k)c 2 r 2 }]+Ar 4 +Br 6 +Cr 8
where Z is an axial depth, c is a paraxial radius of curvature, r is the distance from an optical axis in a direction perpendicular thereto, k is a conic constant, and A, B, and C-are higher-order aspheric coefficients. The same applies to the following embodiments.
Embodiment 5 has the same optical configuration as Embodiment 3 (FIG. 13) but has different data.
As described above, each of Embodiments 1 through 5 includes a positive-power first optical system including at least one dioptric system and a second optical system having positive power as a whole, the second optical system including at least one reflecting surface having power. The first and second optical systems are arranged in the order described from upstream to downstream on the downstream side of an object. An object image is temporarily formed as an intermediate image, and thereafter, is formed as a final image. With respect to the optical axis of an optical element that is positioned furthest on the object side in the first optical system and has refractive power, one or more of the other optical elements are shifted or tilted. In Embodiments 3 through 5, with respect to the optical axis of the optical element (lens) 911, positioned furthest on the object side in the first optical system and having refractive power, the other optical elements 912 through 915 of the first optical system 91 are not tilted.
In Embodiments 3 and 4, the first optical system 91 is composed of two or more groups. Of the two or more groups, the lens 913, forming a group as a doublet is shifted.
In each of Embodiments 1 through 5, at least one of the reflecting surfaces included in the second optical system is a free-form surface. Of the reflecting surfaces included in the second optical system, the reflecting surface positioned furthest on the side of the position at which the final image is formed is a free-form surface. Further, in Embodiments 1 through 5, the reflecting surface having positive power and reflecting a light beam made incident on the second optical system first is rotationally symmetric. In Embodiments 1 and 3 through 5, the rotationally symmetric reflecting surface is a spherical reflecting surface.
MTF performance and distortion on a screen by the projection optical system of Embodiment 6 are 5.60% or higher and 2% or lower, respectively, at a frequency of 0.5 c/mm.
−0.5Y 91.2%
−0.1Y 92.6%
In the transmission dioptric system, an NA (=0.143) on the projected object surface side is greater than an NA (=0.01) on the intermediate image surface side. The magnification of the intermediate image M1 (=1.5) falls within the range of 1 to 5. The magnification of projection (=75�) is 40� or higher. The angle of projection to a projection surface θ (=11 degrees) is 5 degrees or greater.
In the case of forming the transmission dioptric system, its NA on the projected object surface side (hereinafter, an NA1) is determined by the orientation distribution characteristics of an illumination system, while its NA on the intermediate image surface side (hereinafter, an NA2) is changeable by the arrangement and the configuration of the transmission dioptric system. In order to increase magnification of projection, it is effective to increase the power of the reflection dioptric system. This, however, reduces the focal length of the reflection dioptric system on its image or downstream side so that the focal point of light beams is shifted to the reflecting mirror side of the reflection dioptric system. As a result, only a small-size final image can be formed. That is, magnification is reduced. In order to eliminate this disadvantage, the NA2 of light beams incident on the reflection dioptric system was focused on. As a result, it was determined that making the NA2 smaller than the NA1 had a remarkable effect in increasing the projection optical system magnification.
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EventsDateCodeEventDescriptionNov 15, 2013FPAYFee paymentYear of fee payment: 8Oct 21, 2009FPAYFee paymentYear of fee payment: 4May 4, 2004ASAssignmentOwner name: RICOH COMPANY, LTD., JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TAKAURA, ATSUSHI;FUJITA, KAZUHIRO;SAKUMA, NOBUO;REEL/FRAME:015295/0605Effective date: 20040127RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services