JP2018060131A - Projection optical system, projection apparatus, and imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel projection optical system which forms an image formation light flux from an original image on a conjugate surface on a reduction side as an enlarged image on the conjugate surface on an enlargement side after sequentially forming as a first intermediate image, a second intermediate image on an optical path reaching the conjugate surface on the enlargement side.SOLUTION: A first optical group G1 of a projection optical system includes: a first lens group; optical path separation optical means SPD; and reflection optical means RFD. The optical path separation optical means SPD has a function of separating the optical path of the incident image formation light flux heading from the original image to the reflection optical means from the optical path of the reflection image formation light flux reflected by the reflection optical means and heading to a second optical group G2. The first lens group has at least a portion thereof that is shared for the incident image formation light flux and the reflection image formation light flux. A third optical group G3 has a recessed mirror located on the enlargement side of a second intermediate image IM2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a projection optical system, a projection device, and an imaging device.

  A projection apparatus (hereinafter also referred to as a “projector”) that projects an original image displayed on an image display element such as a liquid crystal display element or DMD (digital micromirror device) on a projection surface such as a screen as an enlarged image has recently been developed. Widely used.

  In a projection optical system that projects an enlarged image of an original image, the original image and the enlarged image are in a conjugate relationship, the original image is displayed on the reduced conjugate plane, and the enlarged image is imaged on the enlarged conjugate plane. The

  As such a projection optical system, an imaging light beam from an original image on the reduction-side conjugate plane is sequentially imaged as a first intermediate image and a second intermediate image on the optical path to the enlargement-side conjugate plane, A projection optical system that forms an image as an enlarged image on a conjugated surface on the enlargement side is known (Patent Documents 1 to 4, etc.).

  In the present invention, an image-forming light beam from an original image on a reduction-side conjugate plane is sequentially formed as a first intermediate image and a second intermediate image on the optical path to the enlargement-side conjugate plane, and then the enlargement-side conjugate. An object is to realize a novel projection optical system that forms an enlarged image on a surface.

  The projection optical system of the present invention is configured by sequentially arranging a first optical group, a second optical group, and a third optical group on an optical path from the reduction side to the enlargement side, and from the original image on the reduction-side conjugate plane. Are projected sequentially on the optical path to the enlargement-side conjugate plane as a first intermediate image and a second intermediate image, and then formed as an enlarged image on the enlargement-side conjugate plane. An optical system, wherein the first optical group includes a first lens group, an optical path separating optical unit, and a reflecting surface that reflects the imaging light beam from the optical path separating optical unit side to the second optical group side. The optical path separating optical means includes: an optical path of an incident imaging light beam from the original image toward the reflective optical means; and the second optical light reflected by the reflective optical means. Having a function of separating the optical path of the reflected imaging light beam toward the group, One lens group is at least partially shared by the incident imaging light beam and the reflected imaging light beam, and the third optical group includes a concave mirror located on the magnification side of the second intermediate image. Have.

  According to the present invention, the imaging light beam from the original image on the reduction-side conjugate plane is sequentially formed as the first intermediate image and the second intermediate image on the optical path to the enlargement-side conjugate plane, and then the enlargement side. It is possible to realize a novel projection optical system that forms an image as an enlarged image on the conjugate plane.

1 is a diagram illustrating a configuration of a projection optical system according to Example 1. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 700 mm of Example 1. FIG. It is a figure which shows the coma aberration in the projection distance of 700 mm of Example 1. FIG. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 1000 mm of Example 1. FIG. It is a figure which shows the coma aberration in the projection distance of 1000 mm of Example 1. FIG. 6 is a diagram illustrating a configuration of a projection optical system of Example 2. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 700 mm of Example 2. FIG. It is a figure which shows the coma aberration in the projection distance of 700 mm of Example 2. FIG. FIG. 6 is a diagram illustrating a configuration of a projection optical system according to Example 3. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 700 mm of Example 3. FIG. It is a figure which shows the coma aberration in the projection distance of 700 mm of Example 3. FIG. FIG. 10 is a diagram illustrating a configuration of a projection optical system according to Example 4. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 700 mm of Example 4. FIG. It is a figure which shows the coma aberration in the projection distance of 700 mm of Example 4. FIG. 10 is a diagram illustrating a configuration of a projection optical system according to Example 5. It is a figure which shows the spherical aberration, astigmatism, and distortion aberration in the projection distance of 700 mm of Example 5. FIG. It is a figure which shows the coma aberration in the projection distance of 700 mm of Example 5. FIG. It is a figure which shows the structure of another form of the projection optical system of Example 5. FIG. It is a figure which shows the structure of another form of the projection optical system of Example 5. FIG. It is a figure which shows an example optical path which has arrange | positioned and used the rectangular display element for the projection optical system of Example 1. FIG. It is a figure which shows another embodiment of a projection optical system as explanatory drawing only about a characteristic part.

Hereinafter, embodiments will be described.
FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, and FIG. 19 show seven embodiments of the projection optical system. In order to avoid complications, the symbols are shared in these drawings.
In these drawings, reference numeral G1 indicates a first optical group, reference numeral G2 indicates a second optical group, and reference numeral G3 indicates a third optical group.
Reference sign MD indicates an image display element. In the embodiment described below, a transmissive three-plate liquid crystal panel is assumed as the image display element MD. That is, three liquid crystal panels for red (R), green (G), and blue (B) are prepared, and the red image component, the green image component, and the blue image component are “original image” on these three liquid crystal panels, respectively. "Is displayed. In the figure, three liquid crystal panels are drawn together for convenience.

Reference symbol P denotes a color composition prism. Light from the original images of the three liquid crystal panels is color-combined by the prism P and becomes “imaging light beam from the original image” and enters the projection optical system.
Reference symbol SPD indicates “optical path separating optical means”, reference symbol IM1 indicates “first intermediate image”, and reference symbol IM2 indicates “second intermediate image”. Further, the symbol RFD indicates “reflection optical means”.
Regarding the optical path separation optical means SPD, the image display element MD side is the “reduction side”, and the first intermediate image IM1 side is the “enlargement side”. Therefore, the image display surface of the image display element MD is the “conjugate surface on the reduction side”.
Reference numeral AX1 indicates “the optical axis on the reduction side of the optical path separation optical means SPD”, and reference numeral AX2 indicates “the optical axis on the expansion side of the optical path separation optical means SPD”. An angle formed by the optical axis AX1 and the optical axis AX2 (clockwise angle from the optical axis AX1 to the optical axis AX2) is an angle: θAX.
In the embodiment shown in FIGS. 1, 6, 9, 12, 15, and 18, the angle θAX is 90 degrees. In the embodiment shown in FIG. 19, the angle θAB is an angle smaller than 90 degrees.

Please refer to FIG.
In the embodiment shown in FIG. 1, the optical path separating optical means SPD is in the form of a right-angle prism, and the lower left portion in the drawing is the reflecting surface R1 from the intersection of the optical axes AX1 and AX2 on the diagonal slope. The upper right part of the intersection is the “transmission surface”.
When an incident light beam (color-combined by the prism P) from the original image is incident on the optical path separation optical means SPD, it is reflected by the reflection surface toward the reflection optical means RFD.
The first optical group G1 includes a first lens group, an optical path separation optical unit SPD, and a reflection optical unit RFD. The first lens group is composed of eight lenses including seven lenses disposed between the optical path separation optical means SPD and the reflection optical means RFD and one lens PFL disposed on the enlargement side of the optical path separation optical means SPD. It is comprised by the lens of.
The reflection optical means RFD is a plane mirror, and its reflection surface coincides with the aperture stop S.
The second optical group G2 is arranged on the enlargement side of the most enlargement side lens PFL in the first lens group G1, and is constituted by three lenses.
The third optical group G3 includes a “concave mirror” disposed on the enlargement side of the second optical group G2.
In other words, the image forming light beam (image forming light beam from the original image) from the image display surface of the image display element MD is reflected by the reflecting surface R1 of the optical path separation optical means SPD to become an “incident image forming light beam”, which is reflected optical. After being incident on the means RFD and reflected, it becomes a “reflected imaging light beam” that passes through the “transmission surface” of the optical path separation optical means SPD, passes through the lens PFL, and forms the first intermediate image IM1. The second intermediate image IM2 is formed through the second optical group G2.
Thereafter, an enlarged image of the original image is formed on an enlargement conjugate surface (generally a screen) that is reflected by the third optical group G3 and not shown in FIG.

As described above, the projection optical system according to the embodiment shown in FIG. 1 sequentially arranges the first optical group G1, the second optical group G2, and the third optical group G3 on the optical path from the reduction side to the enlargement side. The image-forming light beam from the image display surface of the image display element MD that is configured and is a reduction-side conjugate surface is sequentially combined as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the enlargement-side conjugate surface. This is a projection optical system that forms an image as an enlarged image on the enlargement conjugate plane after imaging.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface that reflects an image forming light beam from the optical path separation optical means SPD side to the second optical group G2 side. The optical path separation optical means SPD includes an optical path of an incident imaging light beam directed from the original image toward the reflection optical means RFD, and a reflection image formation reflected by the reflection optical means RFD toward the second optical group G2. It has a function of separating the optical path of the light beam.
At least a part of the first lens group (a part constituted by seven lenses disposed between the optical path separation optical means SPD and the reflection optical means RFD) is “incident imaging light flux and reflected imaging light flux. Is common to all. The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The projection optical system showing the embodiment in FIG. 6 is the same as that in the embodiment shown in FIG.
The first optical group G1, the second optical group G2, and the third optical group G3 are sequentially arranged on the optical path from the reduction side to the enlargement side, and the imaging light beam from the original image on the reduction-side conjugate plane is This is a projection optical system in which the first intermediate image IM1 and the second intermediate image IM2 are sequentially formed on the optical path to the enlargement-side conjugate surface, and then formed as an enlarged image on the enlargement-side conjugate surface.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. The optical path separation optical means SPD includes an optical path of an incident imaging light beam directed from the original image to the reflection optical means RFD, and a reflected imaging light beam reflected by the reflection optical means RFD and directed to the second optical group G2. It has a function of separating the optical path from each other.
The optical path separation optical means SPD is in the form of a right-angled prism like the optical path separation optical means SPD in the embodiment of FIG. 1, and the lower left portion in the figure is more than the intersection of the optical axes AX1 and AX2 on the diagonal slope. The reflection surface is R1, and the upper right part of the intersection is a “transmission surface”.
The reflection optical means RFD is also a plane mirror, similar to the reflection optical means RFD in the embodiment of FIG. 1, and its reflection surface coincides with the aperture stop S.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image G2.

In the projection optical system shown in FIG. 6, the first optical group G1, the second optical group G2, and the third optical group G3 are sequentially arranged on the optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the reduction-side conjugate plane is sequentially formed as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the enlargement-side conjugate plane, and then the enlargement side This is a projection optical system that forms an enlarged image on a conjugate plane.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side to the second optical group side. The optical path separation optical means SPD includes an optical path of an incident imaging light beam directed from the original image to the reflection optical means RFD, and a reflected imaging light flux reflected by the reflection optical means RFD and directed to the second optical group G2. It has a function of separating the optical path.
At least a part of the first lens group is “shared with the incident imaging light beam and the reflected imaging light beam”, and the third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image G2. .

The projection optical system shown in FIG. 9 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes the first lens group G1, the optical path separation optical means SPD, and the reflective optical means RFD having a reflection surface that reflects the image forming light beam from the optical path separation optical means side to the second optical group G2 side. And is configured. The optical path separating optical means SPD is in the form of a right-angled prism similar to that shown in FIGS. 1 and 6, and the lower left portion in the drawing is the reflecting surface R1 from the intersection of the optical axes AX1 and AX2 on the diagonal slope. The upper right part of the intersection is a “transmission surface”, and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD and the second optical group G2 reflected by the reflection optical means RFD. It has a function of separating the optical path of the reflected image-forming light beam traveling toward.
At least a part of the first lens group (six lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD) is shared by the incident imaging light beam and the reflected imaging light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The projection optical system shown in FIG. 9 differs from the projection optical systems shown in FIGS. 1 and 6 in that the “reflecting surface also serving as the aperture stop S” of the reflecting optical means RFD is concave and has a refractive power.

The projection optical system according to the embodiment shown in FIG. 12 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes the first lens group G1, the optical path separation optical means SPD, and the reflective optical means RFD having a reflection surface that reflects the image forming light beam from the optical path separation optical means side to the second optical group G2 side. And is configured. The optical path separation optical means SPD has a right-angle prism shape, similar to that shown in FIGS. 1 and 6, has a reflection surface R1 and a “transmission surface”, and an optical path of an incident imaging light beam from the original image toward the reflection optical means RFD. And the optical path of the reflected imaging light beam reflected by the reflective optical means RFD and traveling toward the second optical group G2.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The projection optical system shown in FIG. 12 differs from the projection optical systems shown in FIGS. 1, 6, and 9 in that the reflection optical means RFD is formed on the lens surface on which the incident imaging light beam is incident last in the first lens system. The reflecting film is also used as an aperture stop. The lens surface also serving as an aperture stop has a concave surface facing the incident side.
The present invention is not limited to this example, and the “lens surface on which the incident imaging light beam on which the reflection film is formed finally enters” that also serves as the aperture stop can be a flat surface.

The projection optical system shown in FIG. 15 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separation optical means SPD is a plane mirror having a reflection surface equivalent to the reflection surface R1 in the optical path separation optical means in FIG. 1, and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD, and the reflection optical means RFD. Has a function of separating the optical path of the reflected imaging light beam reflected by the light toward the second optical group G2.
The reflection optical means RFD is a plane mirror similar to that in the embodiment shown in FIG. 1, and its reflection surface coincides with the aperture stop S.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam. The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
In the projection optical system shown in FIG. 15, the first lens group includes “seven lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD” and the expansion of the optical path separation optical means SPD. And two lenses arranged on the side.

The projection optical system shown in the embodiment in FIG. 18 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separation optical means SPD is the same plane mirror as the optical path separation optical means of FIG. 15, and is reflected by the reflection optical means RFD and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD, and the second optical group G2. It has a function of separating the optical path of the reflected image-forming light beam traveling toward.
In the embodiment shown in FIG. 18, the imaging light beam from the original image is directly incident on the reflection optical means RFD as an incident imaging light beam, and the reflected imaging light beam reflected by the reflection optical means RFD is optical path separation optics. Reflected by the means SPD and directed toward the second optical group.
The reflection optical means RFD is a plane mirror similar to that in the embodiment shown in FIG. 1, and its reflection surface coincides with the aperture stop S.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam. The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
Also in the projection optical system showing the embodiment in FIG. 18, the first lens group is “seven lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD” and the expansion of the optical path separation optical means SPD. And two lenses arranged on the side.

In the projection optical system shown in FIG. 19, the optical axis is obtained by “rotating counterclockwise” the plane mirror which is the optical path separation optical means SPD in the embodiment shown in FIG. This is an example in which the angle formed by AX1 and the optical axis AX2: θAB is “an angle smaller than 90 degrees”.
Accordingly, the projection optical system shown in FIG. 19 is also configured by sequentially arranging the first optical group G1, the second optical group G2, and the third optical group G3 on the optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the conjugate plane is sequentially formed as the first intermediate image IM1 and the second intermediate image IM2 on the optical path to the enlargement conjugate plane, and then the enlarged image is formed on the enlargement conjugate plane. As a projection optical system.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separation optical means SPD is the same plane mirror as the optical path separation optical means of FIG. 15, and is reflected by the reflection optical means RFD and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD, and the second optical group G2. It has a function of separating the optical path of the reflected image-forming light beam traveling toward.
The imaging light beam from the original image is directly incident on the reflection optical means RFD as an incident imaging light beam, and the reflected imaging light beam reflected by the reflection optical means RFD is reflected by the optical path separation optical means SPD and is second optically reflected. Head to the side of the group.
The reflection optical means RFD is a plane mirror similar to that in the embodiment shown in FIG. 1, and its reflection surface coincides with the aperture stop S.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam. The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The first lens group is composed of “seven lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD” and two lenses arranged on the enlargement side of the optical path separation optical means SPD. ing.

In the above, seven examples of the optical arrangement of the projection optical system of the present invention have been described, but the optical arrangement of the projection optical system is not limited to the above seven examples. For example, in the embodiments shown in FIGS. 1, 6, 9, and 12, the optical path separation optical means SPD can be replaced with those shown in FIGS.
The optical path separating optical means reflects one of “the portion to be the incident imaging light beam and the portion to be the reflected imaging light beam” of the imaging light beam from the original image on the reduction-side conjugate plane, and the other. The optical path separation optical means SPD in each of the above-described embodiments is as described above.
The optical path separation optical means may be configured to have “polarization synthesis means, polarization separation means, and phase difference plate” as in an example described later. Further, the optical path separating optical means SPD can be configured by a “half mirror”.
In the embodiment shown in FIGS. 15, 18, and 19, the reflection optical means RFD can be replaced with that shown in FIGS.
As described above, a reflection film can be formed on the “lens surface on which the incident imaging light beam is finally incident” of the first lens group, but it is not formed even when a reflection film is formed. In this case, the “lens surface on which the incident imaging light beam is incident last” can be a curved surface or a flat surface.

  The size of the enlarged image formed on the enlargement-side conjugate surface is changed by changing the projection distance from the third optical group to the enlargement-side conjugate surface (such as a screen), but when the projection optical system has a wide angle of view. The curvature of field and distortion are likely to increase with respect to fluctuations in the projection distance.

Various methods can be used to focus the enlarged image on the “enlarged conjugate surface (screen or the like)”. In each of the embodiments described above, a plurality of second optical systems G2 are provided. Focusing can be performed by moving one or more lenses constituting the second optical group G2 in the direction of the optical axis.
The second optical group G2 is close to the exit side of the imaging light beam and is easily accessible. By moving one or more lens groups in the second optical group, the second optical group G2 is in focus while maintaining good curvature and distortion of the image plane. Can be combined.
The projection optical system is also preferably “substantially telecentric” on the reduction side.

The projection optical system according to the present invention preferably satisfies any one or more of the following conditions (1) to (3).
(1) 1.5 <Ym / Yi <5.0
(2) 0.25 <Lm / Lr <0.55
(3) 45 ° ≦ θAX ≦ 90 °
The meaning of each symbol in the parameters of these conditions (1) to (3) is as follows.
“2Yi” is the maximum effective diameter of the imaging light beam on the optical path from the reduction conjugate plane to the enlargement conjugate plane at the original image position, and “2Ym” is on the mirror surface of the concave mirror of the third optical group. The maximum effective diameter.
“Lr” is the distance on the optical axis between the reflecting surface of the reflecting optical means and the most magnified lens surface of the second optical group, and “Lm” is the most magnified lens surface of the second optical group and the third lens surface. This is the distance on the optical axis from the concave mirror surface of the optical group.
“ΘAB” is an angle between the optical axis on the reduction side of the optical path separation optical means and the optical axis on the enlargement side of the optical path separation optical means.

When the parameter of the condition (1): Ym / Yi is reduced, the maximum effective diameter of the light beam on the mirror surface of the concave mirror is reduced, so that the concave mirror of the third optical system can be easily downsized. However, if the lower limit of the condition (1) is exceeded, the principal ray density of each image height on the mirror surface of the concave mirror becomes excessive, and it becomes difficult to suppress various aberrations including distortion mainly corrected by the concave mirror. easy.
If the parameter (Ym / Yi) of the condition (1) exceeds the upper limit, the concave mirror of the third optical group tends to be large, and it is difficult to make the projection optical system compact.
Condition (2) parameter: When Lm / Lr is small, when Lm is small, Lr may be large, but the distance: Lm is a certain amount of space for forming the second intermediate image Im2. The size is required, and the distance Lr increases as the parameter Lm / Lr decreases while securing this space.

When the parameter (2) of the condition (2): Lm / Lr exceeds the lower limit, the length (Lr + Lm) on the optical axis of the first optical group and the second optical group becomes large, and the projection optical system tends to be long.
Condition (2) parameter: If Lm / Lr exceeds the upper limit, the length of the first optical group and the second optical group on the optical axis can be reduced, but spherical aberration, coma aberration, etc. tend to increase, and optical performance It is likely to be difficult to maintain. In addition, if the increase in the length of the first optical group and the second optical group on the optical axis is suppressed, the distance between the second optical group and the concave mirror increases, and the concave mirror tends to increase at the same time, and the projection optical system is compact. It is likely to be difficult to realize.
In addition, if the condition (3) is satisfied, a reasonable optical arrangement is possible.

In the projection optical system whose embodiments are shown in FIGS. 1, 6, 9, 12, 15, 18, and 19, the lens PFL on the most magnifying side of the first lens group is a positive lens. The positive lens PFL is disposed on the reduction side of the first intermediate image IM1 or “a position including the first intermediate image IM1 (in the case of the embodiment in FIG. 1)”.
As in the projection optical system of the present invention, the imaging light flux from the original image on the reduction-side conjugate plane is sequentially formed as the first intermediate image IM1 and the second intermediate image IM2 on the optical path to the enlargement-side conjugate plane. Then, in the projection optical system that forms an image as an enlarged image on the enlargement-side conjugate plane, the second intermediate image IM2 is an “object (object point)” in the image formation of the concave mirror of the third optical group.
The first intermediate image IM1 is an “object (object point)” in the image formation of the second optical group.
In order to form a good enlarged image on the enlargement-side conjugate plane, the second intermediate image IM2 is preferably a “good image”. If the second intermediate image IM2 is not a good image, the mirror shape of the concave mirror tends to be a complicated shape in order to form a good enlarged image. In order to form a good second intermediate image IM2, the first intermediate image is preferably a “good image”.

In each of the embodiments described above, the most magnified lens PFL of the first lens group G1 is disposed on the reduction side of the first intermediate image IM1 or at a “position including the first intermediate image IM1” as described above. As a result, the shape of the first intermediate image IM1 and the “direction of the principal ray toward the second optical group G2” are adjusted so that the second optical group G2 can easily form a good second intermediate image IM2. .
Thus, from the viewpoint of “adjusting the shape and principal ray direction of the first intermediate image IM1” by the lens PFL, it is preferable that at least one surface of the lens PFL is an aspherical surface.
In the projection optical system of the present invention, as described above, at least a part of the first lens group is “shared with the incident imaging light beam and the reflected imaging light beam”, and this shared part is a so-called “folding optical system”. " As described above, by forming a part of the first lens group as a “folding optical system”, it is possible to realize a good first intermediate image while reducing the number of lenses constituting the first lens group.

In addition, since a part of the first lens group is a “folding optical system”, the length of the first lens group on the optical axis can be shortened, and the optical size of the projection optical system can be made compact.
Since a part of the first lens group is a folded optical system, the first lens group can be made “a configuration close to a symmetric equal-magnification optical system”, and the reflecting optical means: the reflection surface of the RFD is an aperture stop. Can be set to Further, as in the embodiment shown in FIG. 12, the number of components can be reduced by forming a reflective film on the last lens surface on which the incident imaging light beam is incident to form the reflective optical means RFD.
In addition, since the first optical group G1 is “a configuration close to an equal-magnification optical system”, the reflective optical means: RFD can be a plane mirror having a reflective surface as a plane, and the projection optical system is an optical system that can be easily assembled. be able to. Alternatively, the reflection optical means: the reflection surface of the RFD is curved to increase the degree of design freedom, and the performance of the projection optical system can be improved.

By mounting such a projection optical system, it is possible to realize a projection apparatus having excellent projection performance. One embodiment of the projection apparatus is shown in FIG. This projection apparatus uses the projection optical system PRS of the present invention, and the image display elements MD arranged on the reduction-side conjugate plane (similarly in FIG. 1 and the like, three liquid crystal panels are conveniently combined into one sheet). The image displayed in (2) is formed on the screen SC, which is a conjugate plane on the enlargement side.
In addition, by mounting the projection optical system of the present invention and disposing an image sensor at the reduction-side conjugate point, an imaging apparatus that can capture an image on the enlargement-side conjugate plane can be realized.

"Example"
Hereinafter, five specific examples of the projection optical system will be given.
In each embodiment, the surface number is represented by a number counted from the reduction side (original image side) to the enlargement side. The “image display surface of the image display element” on which the original image is displayed is a conjugate surface on the reduction side of the projection optical system, and is displayed as “object surface” in the data. Further, a conjugate plane (screen or the like) on the enlargement side of a screen or the like on which an enlarged image is projected is shown as an “image plane”.

"R" represents the radius of curvature (including the paraxial radius of curvature for an aspherical surface) of each surface (including the surface of the aperture stop S and the prism P for color synthesis), and "D" represents the optical axis. Represents the surface spacing. The unit of length is “mm”.
Surface spacing: D is displayed with “reversing the sign before and after the reflecting surface”. “Nd and νd” indicates “refractive index and Abbe number with respect to d-line” of the material of each lens.
“Focal distance” is the focal length of the projection optical system at the d-line (in each example, a value at a projection distance of 700 mm), “NA” is the numerical aperture on the reduction side, and “object height” is This is the maximum ray height from the optical axis on the image display surface (object surface).
The shape of the aspherical surface is the height from the optical axis: h, the amount of displacement in the optical axis direction: Z, the paraxial radius of curvature: R, the conic constant: K, the nth-order aspherical surface with the intersection with the optical axis as the origin. As a coefficient: An, the following well-known formula Z = (1 / R) · h ² / [1 + √ {1− (1 + K) · (1 / R) ² · h ² }]
+ A4 ・ h ⁴ + A6 ・ h ⁶ + A8 ・ h ⁸ + ・ ・ ・ + An ・ h ⁿ
The shape is specified by giving the above R, K, An. An aspherical surface is represented by adding “*” to the surface number.

"Example 1"
Example 1 is a specific example of the projection optical system shown as an embodiment in FIG.
Surface number R D Nd νd
Object ∞ 3.000
1 ∞ 19.000 1.77250 49.6 Prism P
2 ∞ 1.000
3 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
4 ∞ -16.000 1.77250 49.6 Reflective surface R1
5 ∞ -0.700
6 -178.212 -4.744 1.80518 25.5
7 43.148 -4.738
8 -14.258 -1.670 1.49700 81.6
9 -14.921 -2.664
10 -21.252 -5.506 1.49700 81.6
11 51.706 -0.100
12 50.662 -0.766 1.76181 26.6
13 -11.843 -9.000 1.49700 81.6
14 310.425 -2.321
15 -15.316 -4.187 1.84666 23.8
16 94.401 -1.296
17 56.043 -2.079 1.80000 29.8
18 -12.713 -1.493
19 ∞ 1.493 (Aperture stop S) Reflective optical means RFD
20 -12.713 2.079 1.80000 29.8
21 56.043 1.296
22 94.401 4.187 1.84666 23.8
23 -15.316 2.321
24 310.425 9.000 1.49700 81.6
25 -11.843 0.766 1.76181 26.6
26 50.662 0.100
27 51.706 5.506 1.49700 81.6
28 -21.252 2.664
29 -14.921 1.670 1.49700 81.6
30 -14.258 4.738
31 43.148 4.744 1.80518 25.5
32 -178.212 0.700
33 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
34 ∞ 16.000 1.77250 49.6 Transmission surface
35 ∞ 8.282
36 * 21.591 5.862 1.80420 46.5 Lens PFL
37 * -26.818 (variable)
38 * -7.751 4.500 1.77250 49.6
39 * -7.133 (variable)
40 * 14.185 1.000 1.84666 23.8
41 * 7.579 0.839
42 * 14.688 3.046 1.62299 58.1
43 * -10.176 40.839
44 * -17.716 -700.000 Concave mirror G3
Image plane ∞
Focusing is performed by displacing the lens on the most reduction side among the three lenses constituting the second optical group G2 in the optical axis direction.

"Aspherical data"
The aspherical data are listed below.
36th
K = 2.915703 A4 = 5.62046E-05 A6 = -1.18034E-06 A8 = 2.24920E-08
A10 = -2.37010E-10 A12 = 9.49591E-13
37th page
K = -0.863225 A4 = 2.52066E-04 A6 = -8.03667E-07 A8 = 7.18714E-09
A10 = -2.41923E-10 A12 = 2.36632E-12
38th page
K = -0.636376 A4 = -4.45113E-05 A6 = 2.53876E-06 A8 = 2.40648E-08
A10 = 1.89421E-09 A12 = -1.73584E-11
39th page
K = -1.569243 A4 = 1.93658E-04 A6 = -1.00718E-05 A8 = 3.45432E-07
A10 = -5.88910E-09 A12 = 5.88827E-11
40th page
K = -0.679846 A4 = -7.25686E-05 A6 = -6.06854E-06 A8 = 3.02542E-07
A10 = -7.49194E-09 A12 = 6.51695E-11
41st side
K = -2.552383 A4 = -4.14707E-04 A6 = 1.11392E-05 A8 = -7.69006E-08
A10 = -3.31496E-09 A12 = 6.54793E-11
42nd page
K = 3.245191 A4 = -5.01414E-04 A6 = 1.12614E-06 A8 = 1.34021E-07
A10 = -7.01951E-09 A12 = 8.79689E-11
43rd page
K = -1.638918 A4 = -4.35977E-05 A6 = -2.67086E-06 A8 = 1.23500E-07
A10 = -3.92457E-09 A12 = 4.42236E-11
44th page
K = -0.852265 A4 = 3.50352E-06 A6 = 5.87818E-09 A8 = -4.54047E-11
A10 = 3.04132E-14 A12 = 1.33901E-16 A14 = 5.91253E-20 A16 = -6.15105E-22
A18 = -1.30006E-24 A20 = 3.33841E-27
In the above notation, for example, “3.33841E-27” represents “3.33841 × 10 ⁻²⁷ ”.

"Variable surface spacing"
Projection distance (distance on the optical axis between the reflecting surface of the concave mirror and the conjugate surface on the enlargement side): The variable surface spacing for 1000 mm and 700 mm is shown below.
Projection distance -1000.000 -700.000
D37 8.740 8.763
D39 3.393 3.370
"Various data"
Focal length 5.24
NA 0.23
Object height 10.00
"Parameter values for conditional expressions"
(1) Ym / Yi = 1.99
(2) Lm / Lr = 0.37
(3) θAX = 90 °.

FIG. 2 shows spherical aberration, astigmatism and distortion at a projection distance of 700 mm of the projection optical system of Example 1, and FIG. 3 shows coma aberration. Each aberration diagram shows “a state in which the reduction side is evaluated using the image plane (screen) as an object”. The same applies to the aberration diagrams of the following examples.
The aberration is represented by the wavelength of green light: 532 nm as a representative, but the spherical aberration diagram and coma aberration diagram also show the red and blue light wavelengths: 638 nm and 450 nm. In the figure of astigmatism, S indicates the sagittal image, and M indicates the aberration of the meridional image.
FIG. 4 shows spherical aberration, astigmatism, and distortion aberration at a projection distance of 1000 mm in Example 1, and FIG. 5 shows coma aberration, respectively.

"Example 2"
Example 2 is a specific example of the projection optical system shown as the embodiment in FIG.
Surface number R D Nd νd
Object ∞ 3.000
1 ∞ 19.000 1.77250 49.6 Prism P
2 ∞ 1.000
3 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
4 ∞ -16.000 1.77250 49.6 Reflective surface R1
5 ∞ -1.000
6 -82.443 -2.993 1.89286 20.4
7 117.893 -5.934
8 -26.668 -2.824 1.49700 81.6
9 -79.796 -0.100
10 -22.538 -1.110 1.56883 56.1
11 -25.045 -0.100
12 -17.220 -3.382 1.92119 24.0
13 -11.344 -6.097 1.49700 81.6
14 66.298 -7.500 1.95375 32.3
15 -14.756 -4.407
16 -20.800 -1.891 1.58267 46.4
17 100.614 -3.162
18 ∞ 3.162 (Aperture stop S) Reflective optical means RFD
19 100.614 1.891 1.58267 46.4
20 -20.800 4.407
21 -14.756 7.500 1.95375 32.3
22 66.298 6.097 1.49700 81.6
23 -11.344 3.382 1.92119 24.0
24 -17.220 0.100
25 -25.045 1.110 1.56883 56.1
26 -22.538 0.100
27 -79.796 2.824 1.49700 81.6
28 -26.668 5.934
29 117.893 2.993 1.89286 20.4
30 -82.443 1.000
31 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
32 ∞ 16.000 1.77250 49.6 Transmission surface
33 ∞ 4.190
34 * 19.768 5.283 1.62041 60.3 Lens PFL
35 * -21.937 (variable)
36 * -5.860 5.000 1.62041 60.3
37 * -6.248 (variable)
38 * 11.372 0.619 1.75520 27.5
39 * 6.681 1.026
40 * 14.377 3.021 1.62041 60.3
41 * -10.593 39.845
42 * -14.978 -700.000 Concave mirror G3
Image plane ∞
Focusing is performed by displacing the lens on the most reduction side among the three lenses constituting the second optical group G2 in the optical axis direction.

"Aspherical data"
The aspherical data are listed below.
34th page
K = 1.603407 A4 = 6.62499E-05 A6 = -1.47855E-06 A8 = 2.13965E-08
A10 = -1.61087E-10 A12 = 3.04660E-13
35th page
K = -16.185981 A4 = 1.37057E-04 A6 = -2.00047E-06 A8 = 2.34483E-08
A10 = -1.88936E-10 A12 = 6.14870E-13
36th page
K = -0.861684 A4 = 1.60081E-04 A6 = -4.15035E-06 A8 = 2.11338E-07
A10 = -5.58538E-09 A12 = 7.82222E-11
37th page
K = -1.275659 A4 = 2.13278E-04 A6 = -7.81789E-06 A8 = 2.11280E-07
A10 = -3.44166E-09 A12 = 3.20992E-11
38th page
K = -1.368834 A4 = -7.65177E-05 A6 = -1.14321E-05 A8 = 1.55813E-07
A10 = -1.29025E-09 A12 = 9.12296E-12
39th page
K = -1.887530 A4 = -4.10972E-04 A6 = 2.51109E-06 A8 = -1.14759E-07
A10 = -8.20290E-10 A12 = 3.33966E-11
40th page
K = 3.612239 A4 = -5.44430E-04 A6 = 9.39714E-07 A8 = 8.94005E-08
A10 = -7.43024E-09 A12 = -1.10566E-12
No. 41
K = -1.503654 A4 = -5.15554E-05 A6 = -2.40135E-06 A8 = 6.31180E-08
A10 = -2.66825E-10 A12 = -5.60088E-11
42nd page
K = -1.139257 A4 = 9.49690E-06 A6 = -4.09789E-08 A8 = -1.23159E-11
A10 = 1.00687E-13 A12 = 6.06898E-16 A14 = -9.02169E-19 A16 = -2.03782E-21
A18 = -3.03450E-23 A20 = 9.00292E-26.

"Variable surface spacing"
Projection distance: The variable surface interval for 1000 mm and 700 mm is shown below.
Projection distance -1000.000 -700.000
D35 9.272 9.294
D37 5.743 5.721
"Various data"
Focal length 5.18
NA 0.20
Object height 10.00
"Parameter values for conditional expressions"
(1) Ym / Yi = 1.68
(2) Lm / Lr = 0.37
(3) θAX = 90 °
FIG. 7 shows a diagram of spherical aberration, astigmatism and distortion at a projection distance: 700 mm of the projection optical system of Example 2, and FIG. 8 shows a diagram of coma aberration.

"Example 3"
Example 3 is a specific example of the projection optical system shown as the embodiment in FIG.
Surface number R D Nd νd
Object ∞ 3.000
1 ∞ 19.000 1.77250 49.6 Prism P
2 ∞ 1.000
3 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
4 ∞ -16.000 1.77250 49.6 Reflective surface R1
5 ∞ -2.000
6 73.643 -3.405 1.57135 53.0
7 27.072 -0.100
8 -18.596 -6.987 1.49700 81.6
9 361.909 -0.100
10 -17.174 -5.075 1.60342 38.0
11 -54.030 -1.440
12 207.372 -7.873 1.91082 35.3
13 -7.844 -3.866 1.49700 81.6
14 -31.346 -0.100
15 -15.027 -1.000 1.48749 70.4
16 -16.258 -0.996
17 155.771 0.996 (Aperture stop S) Reflective optical means RFD
18 -16.258 1.000 1.48749 70.4
19 -15.027 0.100
20 -31.346 3.866 1.49700 81.6
21 -7.844 7.873 1.91082 35.3
22 207.372 1.440
23 -54.030 5.075 1.60342 38.0
24 -17.174 0.100
25 361.909 6.987 1.49700 81.6
26 -18.596 0.100
27 27.072 3.405 1.57135 53.0
28 73.643 2.000
29 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
30 ∞ 16.000 1.77250 49.6 Transmission surface
31 ∞ 8.202
32 52.914 3.419 1.91082 35.3 Lens PFL
33 * -15.784 (variable)
34 * -13.020 5.152 1.83481 42.7
35 * -9.533 (variable)
36 * 15.094 0.550 1.84666 23.8
37 * 8.588 2.037
38 * 17.424 3.364 1.59349 67.0
39 * -9.968 (variable)
40 * -18.133 -700.000 Concave mirror G3
Image plane ∞
In the third embodiment, focusing is performed by displacing the lens on the most reduction side among the three lenses constituting the second optical group G2 and displacing the two lenses on the enlargement side as a unit.
The reflecting surface (R17) of the reflecting optical means RFD is a concave spherical surface.

"Aspherical data"
The aspherical data are listed below.
No. 33
K = -28.096426 A4 = -6.77425E-05 A6 = -5.90182E-07 A8 = 2.94466E-08
A10 = -3.06620E-10 A12 = 1.04612E-12
34th page
K = -1.670922 A4 = 4.80203E-05 A6 = -1.44409E-06 A8 = 1.39862E-07
A10 = -3.08812E-09 A12 = 3.68637E-11
35th page
K = -1.803642 A4 = 2.62605E-04 A6 = -6.98860E-06 A8 = 2.32598E-07
A10 = -4.33412E-09 A12 = 4.51871E-11
36th
K = -3.660291 A4 = -1.36764E-04 A6 = -6.18455E-06 A8 = 1.48461E-07
A10 = -5.25541E-09 A12 = 5.84470E-11
37th page
K = -2.861026 A4 = -4.65468E-04 A6 = 5.22020E-06 A8 = -1.25681E-07
A10 = -9.52226E-10 A12 = 3.62857E-11
38th page
K = 2.168481 A4 = -3.93818E-04 A6 = 1.32053E-06 A8 = 3.46782E-08
A10 = -2.00594E-09 A12 = 2.01621E-11
39th page
K = -1.557297 A4 = -6.74713E-05 A6 = -2.59035E-06 A8 = 7.47685E-08
A10 = -1.67863E-09 A12 = 1.09976E-11
40th page
K = -0.872009 A4 = 4.27235E-06 A6 = -9.56036E-10 A8 = -1.42920E-11
A10 = -9.33863E-14 A12 = 2.84688E-16 A14 = -2.32211E-20 A16 = 4.02465E-21
A18 = -2.16771E-23 A20 = 2.84301E-26.

"Variable surface spacing"
Projection distance: The variable surface interval for 1000 mm and 700 mm is shown below.
Projection distance -1000.000 -700.000
D33 8.939 8.970
D35 4.088 4.080
D39 41.748 41.725
"Various data"
Focal length 5.33
NA 0.26
Object height 10.00
"Parameter values for conditional expressions"
(1) Ym / Yi = 1.89
(2) Lm / Lr = 0.41
(3) θAX = 90 °
FIG. 10 shows a diagram of spherical aberration, astigmatism and distortion at a projection distance of 700 mm of the projection optical system of Example 3, and FIG. 11 shows a diagram of coma aberration.

Example 4
Example 4 is a specific example of the projection optical system whose embodiment is shown in FIG.
Surface number R D Nd νd
Object ∞ 3.000
1 ∞ 20.500 1.77250 49.6 Prism P
2 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
3 ∞ -16.000 1.77250 49.6 Reflective surface R1
4 ∞ -1.000
5 -111.998 -3.964 1.89286 20.4
6 59.644 -0.291
7 -20.687 -2.872 1.49700 81.6
8 -37.516 -1.486
9 -17.781 -3.013 1.92119 24.0
10 -11.646 -5.796 1.49700 81.6
11 55.993 -7.000 1.95375 32.3
12 -15.729 -4.115
13 -22.272 -7.000 1.58267 46.4
14 -48.734 -1.548
15 -36.312 -2.417 1.51680 64.2
16 244.089 2.417 1.51680 64.2 (Aperture stop S) Reflective optical means RFD
17 -36.312 1.548
18 -48.734 7.000 1.58267 46.4
19 -22.272 4.115
20 -15.729 7.000 1.95375 32.3
21 55.993 5.796 1.49700 81.6
22 -11.646 3.013 1.92119 24.0
23 -17.781 1.486
24 -37.516 2.872 1.49700 81.6
25 -20.687 0.291
26 59.644 3.964 1.89286 20.4
27 -111.998 1.000
28 ∞ 16.000 1.77250 49.6 Optical path separation optical means SPD
29 ∞ 16.000 1.77250 49.6 Transmission surface
30 ∞ 2.774
31 * 23.465 4.969 1.67790 50.7 Lens PFL
32 * -19.746 (variable)
33 * -6.383 5.000 1.62041 60.3
34 * -6.437 (variable)
35 * 12.168 0.650 1.75520 27.5
36 * 6.714 1.051
37 * 14.087 3.420 1.62041 60.3
38 * -10.353 41.360
39 * -15.695 -700.000 Concave mirror G3
Image plane ∞
As in the first and second embodiments, focusing is performed by displacing one of the three lenses constituting the second optical group G2 closest to the reduction side in the optical axis direction.
As the optical path separation optical means SPD in the first optical group, a prism-shaped one is used as in the first to third embodiments, but is bonded to the prism P.
The reflective optical means RFD is formed as a reflective film on the last lens surface (the 16th surface) on which the incident imaging light beam is incident.

"Aspherical data"
The aspherical data are listed below.
No. 31
K = -0.929159 A4 = 1.07790E-04 A6 = -1.34251E-06 A8 = 1.92303E-08
A10 = -1.41442E-10 A12 = 3.25560E-13
32nd page
K = -15.730675 A4 = 1.36967E-04 A6 = -2.17077E-06 A8 = 2.42200E-08
A10 = -1.76205E-10 A12 = 5.19923E-13
No. 33
K = -0.823506 A4 = 1.35284E-04 A6 = -4.93090E-06 A8 = 2.39756E-07
A10 = -6.53768E-09 A12 = 8.70535E-11
34th page
K = -1.287323 A4 = 2.18563E-04 A6 = -7.97156E-06 A8 = 2.01418E-07
A10 = -3.23617E-09 A12 = 3.00384E-11
35th page
K = -2.092687 A4 = -1.17823E-04 A6 = -1.06700E-05 A8 = 1.98389E-07
A10 = -2.12011E-09 A12 = -1.87671E-12
36th
K = -2.167473 A4 = -4.53662E-04 A6 = 2.77479E-06 A8 = -8.28418E-08
A10 = -1.42869E-10 A12 = 9.64186E-12
37th page
K = 2.814082 A4 = -5.85877E-04 A6 = 1.47679E-06 A8 = 7.18255E-08
A10 = -7.28339E-09 A12 = 4.64457E-11
38th page
K = -1.313465 A4 = -6.71534E-05 A6 = -2.16340E-06 A8 = 3.88675E-08
A10 = -5.92669E-10 A12 = -3.70224E-11
39th page
K = -1.120260 A4 = 9.74773E-06 A6 = -3.71100E-08 A8 = -5.72869E-12
A10 = 5.50651E-14 A12 = 4.84098E-16 A14 = -6.36902E-19 A16 = 4.11658E-22
A18 = -2.54437E-23 A20 = 5.79065E-26.

"Variable surface spacing"
Projection distance: The variable surface interval for 1000 mm and 700 mm is shown below.
Projection distance -1000.000 -700.000
D32 9.177 9.199
D34 5.598 5.576
"Various data"
Focal length 5.14
NA 0.20
Object height 10.00
"Parameter values for conditional expressions"
(1) Ym / Yi = 1.73
(2) Lm / Lr = 0.39
(3) θAX = 90 °
FIG. 13 shows a diagram of spherical aberration, astigmatism and distortion at a projection distance of 700 mm of the projection optical system of Example 4, and FIG. 14 shows a diagram of coma aberration.

  1, 6, 9, and 12 showing the configurations of the projection optical systems of Examples 1 to 4 listed above are all “object height” that is the maximum ray height of the original image on the image display surface. It is the figure drawn by the magnitude | size which each optical element can contain these light beam groups. In general, in a projector, the shape of the image display surface of an image display element that displays an original image is rectangular, so that “optical path separating optical means SPD” in the lens configuration diagram shown two-dimensionally is drawn larger than the actual use state. It is.

"Example 5"
Example 5 is a specific example of the projection optical system whose embodiment is shown in FIG.
Surface number R D Nd νd
Object ∞ 3.000
1 ∞ 20.000 1.77250 49.6 Prism P
2 ∞ 0.000
3 ∞ 16.000 Optical path separation optical means SPD
4 ∞ -16.000
5 ∞ -1.000
6 -62.929 -4.595 1.737999 32.26
7 60.578 -0.100
8 -14.834 -1.330 1.496997 81.61
9 -15.147 -7.447
10 -22.211 -6.951 1.496997 81.61
11 30.538 -0.800 1.7552 27.53
12 -11.507 -4.594 1.53775 74.7
13 -384.765 -7.253
14 -23.026 -3.605 1.805181 25.46
15 30.809 -0.295
16 34.789 -0.800 1.697002 48.52
17 -14.895 -2.230
18 ∞ 2.230 (Aperture stop S) Reflective optical means RFD
19 -14.895 0.800 1.697002 48.52
20 34.789 0.295
21 30.809 3.605 1.805181 25.46
22 -23.026 7.253
23 -384.765 4.594 1.53775 74.7
24 -11.507 0.800 1.7552 27.53
25 30.538 6.951 1.496997 81.61
26 -22.211 7.447
27 -15.147 1.330 1.496997 81.61
28 -14.834 0.100
29 60.578 4.595 1.737999 32.26
30 -62.929 1.000
31 ∞ 16.000 Optical path separation optical means SPD (air)
32 ∞ 16.000
33 ∞ 3.224
34 -24.238 4.500 1.882997 40.77
35 -21.511 0.100
36 152.523 3.365 1.834805 42.72 Lens PFL
37 * -17.138 (variable)
38 * -16.272 5.880 1.8042 46.5
39 * -9.453 (variable)
40 * 20.014 0.800 1.846663 23.78
41 * 7.617 2.027
42 * 14.959 3.147 1.589129 61.25
43 * -10.049 (variable)
44 * -17.384 -700.000
Image plane ∞
In the fifth embodiment, a “planar mirror” is used as the optical path separation optical means SPD, and is arranged so that the incident imaging light beam and the reflected imaging light beam to the reflection optical means RFD do not interfere with each other. Focusing is performed by displacing the lens on the most reducing side among the three lenses constituting the second optical group G2 and displacing the two lenses on the magnifying side together as in the case of the third embodiment. ing.

"Aspherical data"
The aspherical data are listed below.
37th page
K = -0.429722 A4 = 2.14785E-04 A6 = -2.24509E-06 A8 = 1.99647E-08
A10 = -9.55644E-11 A12 = 1.79738E-13
38th page
K = -4.945603 A4 = 1.37493E-04 A6 = 2.67595E-06 A8 = 1.97759E-08
A10 = -8.36109E-10 A12 = 8.55167E-12
39th page
K = -4.186418 A4 = 3.31687E-04 A6 = -6.07612E-06 A8 = 3.16769E-07
A10 = -6.32160E-09 A12 = 6.90243E-11
40th page
K = -14.671774 A4 = -1.73473E-04 A6 = -1.91202E-06 A8 = 1.99566E-07
A10 = -1.46132E-08 A12 = 2.45877E-10
41st side
K = -5.738160 A4 = -4.92591E-04 A6 = 8.28085E-06 A8 = -2.01226E-07
A10 = -2.76139E-09 A12 = 1.11235E-10
42nd page
K = 2.045825 A4 = -7.14286E-04 A6 = 7.58939E-06 A8 = -1.06669E-07
A10 = -2.41779E-09 A12 = 3.42255E-11
43rd page
K = -1.184088 A4 = -8.13286E-05 A6 = -2.65166E-06 A8 = 1.06600E-07
A10 = -3.21074E-09 A12 = 7.19981E-12
44th page
K = -0.851521 A4 = 3.78547E-06 A6 = 7.56716E-09 A8 = -7.39249E-11
A10 = 7.92718E-14 A12 = 2.32744E-16 A14 = 6.84150E-21 A16 = -8.19406E-22
A18 = -3.49332E-24 A20 = 8.39654E-27.

"Variable surface spacing"
Projection distance: The variable surface interval for 1000 mm and 700 mm is shown below.
Projection distance -1000.000 -700.000
D37 11.428 11.464
D39 3.251 3.245
D43 41.278 41.248
"Various data"
Focal length 5.30
NA 0.23
Object height 10.50
"Parameter values for conditional expressions"
(1) Ym / Yi = 1.71
(2) Lm / Lr = 0.37
(3) θAX = 90 °
FIG. 16 shows a diagram of spherical aberration, astigmatism and distortion at a projection distance of 700 mm of the projection optical system of Example 5, and FIG. 17 shows a diagram of coma aberration.

  In each of the projection optical systems of Examples 1 to 5, as shown in each aberration diagram, the concave mirror of the third optical group G3 is small and compact, but good over a wide projection distance from a long distance to a short distance. The optical performance is maintained.

FIG. 15 showing the lens configuration of the fifth embodiment shows a projection optical system having a configuration in which the imaged light beam from the original image is “first deflected” by the reflection surface of the optical path separation element SPD, but is shown in FIG. As described above, the reflected imaging light beam returned by the reflecting optical means RFD may be deflected. As shown in FIG. 19, the condition (3) for the separated incident imaging light beam and reflected imaging light beam is determined. Parameter: θAX may be a value smaller than 90 degrees. In the example shown in FIG. 19, the parameter: θAX is set to 70 degrees. It should be noted that the parameter: θAX does not stay within the paper in actual use.
The projection optical systems of Examples 1 to 5 are all “substantially telecentric on the reduction side”.

  In the figures showing the configurations of the first to fifth embodiments, only the light rays within the paper surface are displayed, but the display element: MD of the original image of the projector is arranged as a long rectangle in the horizontal (horizontal direction). The case is common. In the example of the projector illustrated in FIG. 20, the projection optical system according to the first embodiment is illustrated as a three-dimensional view together with light beams emitted from the four corner points of the image display element.

As described above, the projection optical system according to the present invention appropriately corresponds to the bending direction, angle, and order of the optical path according to the size of the original image displayed on the image display element, the arrangement position, the form of the illumination optical system, etc. Yes, it is not limited to those shown in the examples.
In the embodiments described above with reference to FIGS. 1, 6, 9, 12, 15, 18, and 19, all use an imaging light beam by “oblique light”. That is, in each of the embodiments, the imaging light beam from the conjugate surface on the reduction side is shifted from the “optical axis AX1 on the reduction side of the optical path separation optical means SPD” and enters the prism P. This is because the optical path separation optical means (SPD) reflects one of a portion to be an incident imaging light beam and a portion to be a reflected imaging light beam and allows the other to pass therethrough. This is because the optical path is separated.

However, the present invention is not limited thereto, and the principal ray of the imaging light beam from the conjugate surface on the reduction side coincides with the optical axis AX1 on the reduction side of the optical path separation optical means SPD, and the principal ray of the reflected imaging light beam is the light on the expansion side. It is also possible to match the axis AX2.
One example of this case is shown in FIG.
In FIG. 21, reference numeral P1 is a “color combining prism”, reference numeral S1 is a “wavelength selection 1 / 2λ phase difference plate” that gives a phase difference to a specific wavelength region, reference numeral P2 is a “wideband polarization beam splitter”, and reference numeral S2 is “Broadband 1 / 4λ phase difference plate” is shown.
Reference numeral L10 denotes a portion of the first lens group in the first optical group that is disposed between the broadband ¼λ phase difference plate S2 and the reflective optical means RFD, that is, “incident imaging light flux and reflective imaging. The lens system part shared by the luminous flux.

The color combining prism P1 is a “polarizing prism” in this embodiment, and is generally used in projectors.
As a light source of an illuminating device that illuminates an image display element (not shown), a light source that emits “linearly polarized light” of R (red), G (green), and B (blue) is used.

The imaging light R (S) and B (S) emitted from these light sources and formed into an imaging light beam by the image display element are “S-polarized light” with respect to the polarizing film of the prism P1, as shown in FIG. ”And reflected by the polarizing film toward the polarizing beam splitter P2.
On the other hand, the imaging light G (P) that has become the imaging light beam enters the polarizing film of the prism P1 as “P-polarized light”, passes through the polarizing film, and travels toward the polarizing beam splitter P2.
In this way, the three colors of imaging light R (S), G (P), and B (S) are color-synthesized.
In FIG. 21, the light beams of these three colors are drawn separately from each other for the sake of simplicity, but in actuality, they are combined so that “the central light beams of the respective imaged light beams match”.
The color-combined imaging lights R (S), G (P), and B (S) enter the wavelength selection 1 / 2λ phase difference plate S1. The wavelength selection 1 / 2λ phase difference plate S1 transmits the imaging light R (S) and B (S) in the polarization state as they are, but the imaging light G (P) rotates its polarization direction by 90 degrees. And transmitted as imaging light G (S). A commercially available color select (trade name, manufactured by Color Link Japan Co., Ltd.) can be used as the “wavelength selection 1 / 2λ phase difference plate” that gives a phase difference to such a specific wavelength range.
The imaging lights R (S), G (S), and B (S) whose polarization directions are aligned by the wavelength selection 1 / 2λ retardation plate S1 are incident on the broadband polarization beam splitter P2 and are reflected on the reflection optical means RFD side. And is incident on the broadband 1 / 4λ phase difference plate S2, is changed from S-polarized light to circularly-polarized light, passes through the lens system portion L10 as an incident imaging light beam, and is incident on the reflection optical means RFD and reflected.
As shown in FIG. 21 (b), the reflected imaging light beam reflected by the reflecting optical means RFD is transmitted through the lens system portion L10, transmitted through the broadband 1 / 4λ phase difference plate S2, and from circularly polarized light to P-polarized light. The reflected imaging light fluxes R (P), G (P), and B (P) are transmitted through the broadband polarization beam splitter P2.
The broadband ¼λ phase difference plate S2 may be disposed between the lens system portion L10 and the reflection optical means RFD. In this case, the broadband ¼λ phase difference plate S2 is small because it is disposed near the aperture stop. can do.

As the broadband 1 / 4λ phase difference plate S2, a commercially available phase difference plate (manufactured by Sigma Koki Co., Ltd., product number: WPQW-VIS-4M) can be used. As the broadband polarization beam splitter P2, a broadband deflection beam splitter ( Sigma Koki Co., Ltd. product number: PBSW-10-3 / 7) can be used.
In this way, the optical path of the incident imaging light beam traveling from the original image toward the reflecting optical means RFD and the optical path of the reflected imaging light beam reflected by the reflecting optical means and traveling toward the second optical group are separated. At this time, the light beam center of the incident imaging light beam directed toward the reflection optical means RFD and the light beam center of the reflection imaging light beam reflected by the reflection optical means RFD are both the optical axis of the lens system portion L10 (that is, the projection optical system). It matches the optical axis.
In the embodiment shown in FIG. 21, the color combining prism P1, the broadband polarization beam splitter P2, the wavelength selection 1 / 2λ phase difference plate S1 and the broadband 1 / 4λ phase difference plate S2 constitute the “optical path separation optical means”. doing.
The “optical path separating optical means” shown in FIG. 21 can also be used in the case of “imaging with oblique rays” as in the embodiment described with reference to FIG.

As described above, according to the present invention, the following projection optical system, projection apparatus, and imaging apparatus can be realized.
[1]
An original image on the conjugate plane on the reduction side, which is configured by sequentially arranging the first optical group (G1), the second optical group (G2), and the third optical group (G3) on the optical path from the reduction side to the enlargement side. Are sequentially formed as a first intermediate image (IM1) and a second intermediate image (IM2) on the optical path to the enlargement-side conjugate surface, and then on the enlargement-side conjugate surface. A projection optical system that forms an image as an enlarged image, wherein the first optical group (G1) includes a first lens group, optical path separation optical means (SPD), and the imaging light flux from the optical path separation optical means side. Reflecting optical means (RFD) having a reflecting surface that reflects toward the second optical group side, and the optical path separating optical means (SPD) is incident from the original image toward the reflecting optical means. The optical path of the imaging light beam and the second light reflected by the reflecting optical means A function of separating the optical path of the reflected imaging light beam toward the group, and at least a part of the first lens group is shared by the incident imaging light beam and the reflected imaging light beam, Three optical groups (G3) are projection optical systems having concave mirrors located on the magnification side of the second intermediate image (Examples 1 to 5, FIGS. 1, 6, 9, 12, 15, and 18). , FIG. 19).

[2]
[1] The projection optical system according to [1], wherein the maximum effective diameter of the imaging light beam on the optical path from the reduction-side conjugate surface to the enlargement-side conjugate surface at the original image position: 2Yi, the mirror surface of the concave mirror Maximum effective diameter above: 2Ym, conditions:
(1) 1.5 <Ym / Yi <5.0
(Embodiments 1 to 5, FIGS. 1, 6, 9, 12, 15, 18, and 19).

[3]
The projection optical system according to [1] or [2],
The distance on the optical axis between the reflecting surface of the reflecting optical means and the most magnified lens surface of the second optical group: Lr, the lens surface of the second optical group and the concave mirror surface of the third optical group The distance on the optical axis: Lm is the condition:
(2) 0.25 <Lm / Lr <0.55
(Embodiments 1 to 5, FIGS. 1, 6, 9, 12, 15, 18, and 19).

[4]
The projection optical system according to any one of [1] to [3], wherein the most enlarged side of the first lens group (G1) is a positive lens (PFL), and the first intermediate image (IM1) is reduced. Projection optical system disposed at the side or at a position including the first intermediate image (Examples 1 to 5, FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19).

[5]
In the projection optical system according to [4], in the first lens group (G1), the most magnified positive lens (PFL) has at least one aspheric surface. , FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG.

[6]
The projection optical system according to any one of [1] to [5], wherein the reflection surface of the reflection optical means (RFD) that reflects the incident imaging light beam is an aperture stop (Example) 1-5 FIG.1, FIG.6, FIG.9, FIG.12, FIG.15, FIG.18, FIG.19).

[7]
The projection optical system according to any one of [1] to [6], wherein the reflecting surface of the reflective optical means (RFD) that reflects the incident imaging beam is the incident imaging beam of the first lens group. Is a projection optical system formed on the last incident lens surface (Example 4 in FIG. 12).

[8]
The projection optical system according to any one of [1] to [6], wherein a reflection surface of the first lens group that reflects an incident imaging light beam of the reflection optical means (RFD) is a curved surface. System (Example 3, Example 4 FIG. 9, FIG. 12).

[9]
The projection optical system according to any one of [1] to [6], wherein the reflection optical unit (RFD) has a flat reflecting surface that reflects the incident imaging light beam (Example 1, 2, 5, FIG. 1, FIG. 6, FIG. 15, FIG. 18, FIG.

[10]
The projection optical system according to any one of [1] to [9], wherein the second optical system (G2) includes a plurality of lenses, and moves one or more of the plurality of lenses in the optical axis direction. Thus, a projection optical system that performs focusing on the enlargement conjugate plane (Examples 1 to 5, FIGS. 1, 6, 9, 12, 15, 18, and 19).

[11]
The projection optical system according to any one of [1] to [10], wherein the projection optical system is substantially telecentric on the reduction side (Examples 1 to 5, FIGS. 1, 6, 9, 12, and 12). 15, FIG. 18, FIG. 19).

[12]
The projection optical system according to any one of [1] to [10], wherein an angle between an optical axis on the reduction side of the optical path separation optical means (SPD) and an optical axis on the enlargement side of the optical path separation optical means: θAX is the condition:
(3) 45 ° ≦ θAX ≦ 90 °
(Embodiments 1-5 FIGS. 1, 6, 9, 12, 12, 15, 18, 19, and 21).

[13]
The projection optical system according to any one of [1] to [12], wherein the optical path separation optical means (SPD) includes a portion to be an incident imaging light beam and a portion to be a reflected imaging light beam. A projection optical system that separates the optical paths of these two image-forming light beams by reflecting one and passing the other (Examples 1 to 5, FIGS. 1, 6, 9, 12, and 15). , FIG. 18, FIG. 19).

[14]
[13] The projection optical system according to [13], wherein the optical path separation optical unit includes a polarization beam combining unit (P1), a polarization beam separation unit (P2), and a phase difference plate (S1, S2) (FIG. 21).

[15]
[1] to [14] A projection apparatus (FIG. 20) formed by mounting the projection optical system according to any one of [14].

[16]
An imaging apparatus that includes the projection optical system according to any one of [1] to [14] and captures an image that can be formed on a reduction side of an object on the enlargement side by an imaging unit.

The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the specific embodiments described above, and the invention described in the claims unless otherwise specified in the above description. Various modifications and changes are possible within the scope of the above.
For example, the third optical group G3 can have one or more lenses and mirrors in addition to the concave mirror.
The effects described in the embodiments of the present invention are merely a list of suitable effects resulting from the invention, and the effects of the present invention are not limited to those described in the embodiments.

G1 first optical group
G2 second optical group
G3 third optical group
IM1 first intermediate image
IM2 second intermediate image
SPD optical path separating optical means
AX1 Optical axis of imaging light flux on reduction side of optical path separating optical means
AX2 Optical axis of imaging light beam on the enlargement side of the optical path separating optical means
RFD reflection optical means
Positive lens on the most magnified side of the PFL first optical group
P Color composition prism
MD image display element

Japanese Patent No. 5728202 Japanese Patent No. 5767614 Japanese Patent No. 5960579 Japanese Patent Laid-Open No. 2015-200829

Reference symbol P denotes a color composition prism. Light from the original images of the three liquid crystal panels is color-combined by the prism P and becomes “imaging light beam from the original image” and enters the projection optical system.
Reference symbol SPD indicates “optical path separating optical means”, reference symbol IM1 indicates “first intermediate image”, and reference symbol IM2 indicates “second intermediate image”. Further, the symbol RFD indicates “reflection optical means”.
Regarding the optical path separation optical means SPD, the image display element MD side is the “reduction side”, and the first intermediate image IM1 side is the “enlargement side”. Therefore, the image display surface of the image display element MD is the “conjugate surface on the reduction side”.
Reference numeral AX1 indicates “the optical axis on the reduction side of the optical path separation optical means SPD”, and reference numeral AX2 indicates “the optical axis on the expansion side of the optical path separation optical means SPD”. An angle formed by the optical axis AX1 and the optical axis AX2 is defined as an angle: θAX.
In the embodiment shown in FIGS. 1, 6, 9, 12, 15, and 18, the angle θAX is 90 degrees. In the embodiment shown in FIG. 19, the angle θAX is an angle smaller than 90 degrees.

Please refer to FIG.
In the embodiment shown in FIG. 1, the optical path separating optical means SPD is in the form of a right-angle prism, and the lower left portion in the drawing is the reflecting surface R1 from the intersection of the optical axes AX1 and AX2 on the diagonal slope. The upper right part of the intersection is the “transmission surface”.
When an incident light beam (color-combined by the prism P) from the original image is incident on the optical path separation optical means SPD, it is reflected by the reflection surface toward the reflection optical means RFD.
The first optical group G1 includes a first lens group, an optical path separation optical unit SPD, and a reflection optical unit RFD. The first lens group is composed of eight lenses including seven lenses disposed between the optical path separation optical means SPD and the reflection optical means RFD and one lens PFL disposed on the enlargement side of the optical path separation optical means SPD. It is comprised by the lens of.
The reflection optical means RFD is a plane mirror, and its reflection surface coincides with the aperture stop S.
The second optical group G2 is arranged on the enlargement side of the most enlargement side lens PFL in the first optical group G1, and is composed of three lenses.
The third optical group G3 includes a “concave mirror” disposed on the enlargement side of the second optical group G2.
In other words, the image forming light beam (image forming light beam from the original image) from the image display surface of the image display element MD is reflected by the reflecting surface R1 of the optical path separation optical means SPD to become an “incident image forming light beam”, which is reflected optical. After being incident on the means RFD and reflected, it becomes a “reflected imaging light beam” that passes through the “transmission surface” of the optical path separation optical means SPD, passes through the lens PFL, and forms the first intermediate image IM1. The second intermediate image IM2 is formed through the second optical group G2.
Thereafter, an enlarged image of the original image is formed on an enlargement conjugate surface (generally a screen) that is reflected by the third optical group G3 and not shown in FIG.

The projection optical system shown in FIG. 9 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separating optical means SPD is in the form of a right-angled prism similar to that shown in FIGS. 1 and 6, and the lower left portion in the drawing is the reflecting surface R1 from the intersection of the optical axes AX1 and AX2 on the diagonal slope. The upper right part of the intersection is a “transmission surface”, and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD and the second optical group G2 reflected by the reflection optical means RFD. It has a function of separating the optical path of the reflected image-forming light beam traveling toward.
At least a part of the first lens group (six lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD) is shared by the incident imaging light beam and the reflected imaging light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The projection optical system shown in FIG. 9 differs from the projection optical systems shown in FIGS. 1 and 6 in that the “reflecting surface also serving as the aperture stop S” of the reflecting optical means RFD is concave and has a refractive power.

The projection optical system according to the embodiment shown in FIG. 12 is configured by sequentially arranging a first optical group G1, a second optical group G2, and a third optical group G3 on an optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the side conjugate plane is sequentially imaged as a first intermediate image IM1 and a second intermediate image IM2 on the optical path to the magnification side conjugate plane, and then on the magnification side conjugate plane. This is a projection optical system that forms an image as an enlarged image.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separation optical means SPD has a right-angle prism shape, similar to that shown in FIGS. 1 and 6, has a reflection surface R1 and a “transmission surface”, and an optical path of an incident imaging light beam from the original image toward the reflection optical means RFD. And the optical path of the reflected imaging light beam reflected by the reflective optical means RFD and traveling toward the second optical group G2.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The projection optical system shown in FIG. 12 differs from the projection optical systems shown in FIGS. 1, 6, and 9 in that the reflection optical means RFD is formed on the lens surface on which the incident imaging light beam is incident last in the first lens system. The reflecting film is also used as an aperture stop. The lens surface also serving as an aperture stop has a concave surface facing the incident side.
The present invention is not limited to this example, and the “lens surface on which the incident imaging light beam on which the reflection film is formed finally enters” that also serves as the aperture stop can be a flat surface.

In the projection optical system shown in FIG. 19, the optical axis is obtained by “rotating counterclockwise” the plane mirror which is the optical path separation optical means SPD in the embodiment shown in FIG. An angle formed by AX1 and the optical axis AX2: an example in which θAX is configured to be “an angle smaller than 90 degrees”.
Accordingly, the projection optical system shown in FIG. 19 is also configured by sequentially arranging the first optical group G1, the second optical group G2, and the third optical group G3 on the optical path from the reduction side to the enlargement side. The imaging light flux from the original image on the conjugate plane is sequentially formed as the first intermediate image IM1 and the second intermediate image IM2 on the optical path to the enlargement conjugate plane, and then the enlarged image is formed on the enlargement conjugate plane. As a projection optical system.
The first optical group G1 includes a first lens group, an optical path separation optical means SPD, and a reflection optical means RFD having a reflection surface for reflecting an image forming light beam from the optical path separation optical means side toward the second optical group G2. It is comprised. The optical path separation optical means SPD is the same plane mirror as the optical path separation optical means of FIG. 15, and is reflected by the reflection optical means RFD and the optical path of the incident imaging light beam from the original image toward the reflection optical means RFD, and the second optical group G2. It has a function of separating the optical path of the reflected image-forming light beam traveling toward.
The imaging light beam from the original image is directly incident on the reflection optical means RFD as an incident imaging light beam, and the reflected imaging light beam reflected by the reflection optical means RFD is reflected by the optical path separation optical means SPD and is second optically reflected. Head to the side of the group.
The reflection optical means RFD is a plane mirror similar to that in the embodiment shown in FIG. 1, and its reflection surface coincides with the aperture stop S.
At least a part of the first lens group (seven lenses disposed between the optical path separation optical unit SPD and the reflection optical unit RFD) is shared by the incident imaging light beam and the reflected imaging light beam. The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image IM2.
The first lens group is composed of “seven lenses arranged between the optical path separation optical means SPD and the reflection optical means RFD” and two lenses arranged on the enlargement side of the optical path separation optical means SPD. ing.

The projection optical system according to the present invention preferably satisfies any one or more of the following conditions (1) to (3).
(1) 1.5 <Ym / Yi <5.0
(2) 0.25 <Lm / Lr <0.55
(3) 45 ° ≦ θAX ≦ 90 °
The meaning of each symbol in the parameters of these conditions (1) to (3) is as follows.
“2Yi” is the maximum effective diameter of the imaging light beam on the optical path from the reduction conjugate plane to the enlargement conjugate plane at the original image position, and “2Ym” is on the mirror surface of the concave mirror of the third optical group. The maximum effective diameter.
“Lr” is the distance on the optical axis between the reflecting surface of the reflecting optical means and the most magnified lens surface of the second optical group, and “Lm” is the most magnified lens surface of the second optical group and the third lens surface. This is the distance on the optical axis from the concave mirror surface of the optical group.
“ ΘAX ” is an angle between the optical axis on the reduction side of the optical path separation optical means and the optical axis on the enlargement side of the optical path separation optical means.

In each of the embodiments described above, the most enlarged lens PFL of the first optical group G1 is arranged on the reduction side of the first intermediate image IM1 or at a “position including the first intermediate image IM1” as described above. As a result, the shape of the first intermediate image IM1 and the “direction of the principal ray toward the second optical group G2” are adjusted so that the second optical group G2 can easily form a good second intermediate image IM2. .
Thus, from the viewpoint of “adjusting the shape and principal ray direction of the first intermediate image IM1” by the lens PFL, it is preferable that at least one surface of the lens PFL is an aspherical surface.
In the projection optical system of the present invention, as described above, at least a part of the first lens group is “shared with the incident imaging light beam and the reflected imaging light beam”, and this shared part is a so-called “folding optical system”. " As described above, by forming a part of the first lens group as a “folding optical system”, it is possible to realize a good first intermediate image while reducing the number of lenses constituting the first lens group.

However, the present invention is not limited to this. The principal ray at the center of the imaging light beam from the conjugate surface on the reduction side matches the optical axis AX1 on the reduction side of the optical path separation optical means SPD, and the principal ray of the reflected imaging light beam is on the enlargement side. It is also possible to match the optical axis AX2.
One example of this case is shown in FIG.
In FIG. 21, reference numeral P1 is a “color combining prism”, reference numeral S1 is a “wavelength selection 1 / 2λ phase difference plate” that gives a phase difference to a specific wavelength region, reference numeral P2 is a “wideband polarization beam splitter”, and reference numeral S2 is “Broadband 1 / 4λ phase difference plate” is shown.
Reference numeral L10 denotes a portion of the first lens group in the first optical group that is disposed between the broadband ¼λ phase difference plate S2 and the reflective optical means RFD, that is, “incident imaging light flux and reflective imaging. The lens system part shared by the luminous flux.

The color synthesizing prism P1 is a “ cross dichroic prism” in this embodiment, and is generally used in projectors.
As a light source of an illuminating device that illuminates an image display element (not shown), an apparatus that emits “linearly polarized light” of R (red), G (green), and B (blue) is used.

[4]
The projection optical system according to any one of [1] to [3], wherein the most enlarged side of the first lens group is a positive lens (PFL), and the first intermediate image (IM1) is reduced or 1 is a projection optical system disposed at a position including an intermediate image (Examples 1 to 5, FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19).

[5]
In the projection optical system according to [4], the positive lens (PFL) on the most magnifying side of the first lens group has at least one aspheric surface. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19).

Claims (16)

The first optical group, the second optical group, and the third optical group are sequentially arranged on the optical path from the reduction side to the enlargement side, and the image forming light beam from the original image on the conjugate surface on the reduction side is expanded. A projection optical system that sequentially forms an image as a first intermediate image and a second intermediate image on the optical path to the conjugate surface on the side, and then forms an image as an enlarged image on the conjugate surface on the enlargement side,
The first optical group includes a first lens group, an optical path separating optical unit, and a reflective optical unit having a reflecting surface that reflects the imaging light beam from the optical path separating optical unit side to the second optical group side. Comprising
The optical path separation optical means separates the optical path of the incident imaging light beam from the original image toward the reflection optical means and the optical path of the reflected imaging light beam reflected by the reflection optical means and toward the second optical group. Has function,
The first lens group is at least partially shared by the incident imaging light beam and the reflected imaging light beam,
The third optical group is a projection optical system having a concave mirror located on the enlargement side of the second intermediate image. The projection optical system according to claim 1,
The maximum effective diameter at the original image position: 2Yi and the maximum effective diameter on the mirror surface of the concave mirror: 2Ym of the imaging light beam on the optical path from the reduction-side conjugate surface to the enlargement-side conjugate surface are:
(1) 1.5 <Ym / Yi <5.0
Projection optical system that satisfies The projection optical system according to claim 1 or 2,
The distance on the optical axis between the reflecting surface of the reflecting optical means and the most magnified lens surface of the second optical group: Lr, the lens surface of the second optical group and the concave mirror surface of the third optical group The distance on the optical axis: Lm is the condition:
(2) 0.25 <Lm / Lr <0.55
Projection optical system that satisfies The projection optical system according to any one of claims 1 to 3,
A projection optical system in which the most enlargement side of the first lens group is a positive lens, and is disposed on the reduction side of the first intermediate image or at a position including the first intermediate image. The projection optical system according to claim 4,
A projection optical system in which at least one of the positive lenses on the most magnified side of the first lens group is an aspherical surface. The projection optical system according to any one of claims 1 to 5,
A projection optical system in which a reflecting surface of the reflecting optical means for reflecting the incident imaging light beam is an aperture stop. The projection optical system according to any one of claims 1 to 6,
A projection optical system in which the reflecting surface of the reflecting optical means for reflecting the incident imaging light beam is formed on a lens surface of the first lens group on which the incident imaging light beam is finally incident. A projection optical system according to any one of claims 1 to 7,
The projection optical system of the said 1st lens group whose said reflective surface which reflects the said incident imaging light beam of the said reflection optical means is a curved surface. A projection optical system according to any one of claims 1 to 7,
The projection optical system of the said 1st lens group whose said reflective surface of the said reflective optical means that reflects the said incident imaging light beam is a plane. The projection optical system according to any one of claims 1 to 9,
The second optical system includes a plurality of lenses, and one or more of the plurality of lenses are moved in the optical axis direction to perform focusing on the enlargement-side conjugate surface. A projection optical system according to any one of claims 1 to 10,
Projection optical system that is almost telecentric on the reduction side. The projection optical system according to any one of claims 1 to 11,
The angle: θAX between the optical axis on the reduction side of the optical path separation optical means and the optical axis on the enlargement side of the optical path separation optical means is a condition:
(3) 45 ° ≦ θAX ≦ 90 °
A projection optical system characterized by satisfying The projection optical system according to any one of claims 1 to 12,
The optical path separating optical means reflects one of the portion to be the incident imaging light beam and the portion to be the reflected imaging light beam and passes the other, thereby allowing the optical paths of both the imaging light beams to be reduced. A projection optical system that performs separation. The projection optical system according to claim 13,
A projection optical system in which the optical path separation optical means includes a polarization beam combining means, a polarization separation means, and a phase difference plate.   The projection apparatus formed by mounting the projection optical system of any one of Claims 1-14.   An image pickup apparatus that mounts the projection optical system according to any one of claims 1 to 14 and picks up an image that can be formed on a reduction side of an object on the enlargement side by an image pickup unit.

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