JP6744797B2 - Projection optical system, projection device, and imaging device - Google Patents

Description

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

2. Description of the Related Art Projectors (hereinafter, also referred to as “projectors”) that project an original image displayed on an image display device such as a liquid crystal display device or a DMD (digital micromirror device) as a magnified image on a projection surface such as a screen have come close. Widely used.

In a projection optical system that projects a magnified image of an original image, the original image and the magnified image have a conjugate relationship, the original image is displayed on the reduction-side conjugate surface, and the magnified image is formed on the magnification-side conjugate surface. It

As such a projection optical system, after imaging light beams from the original image on the reduction-side conjugate surface are sequentially formed on the optical path leading to the enlargement-side conjugate surface as a first intermediate image and a second intermediate image, There is known a projection optical system that forms an enlarged image on a conjugate surface on the enlargement side (Patent Documents 1 to 4 and the like).

According to the present invention, the image-forming light flux from the original image on the reduction-side conjugate surface is sequentially formed as a first intermediate image and a second intermediate image on the optical path leading to the enlargement-side conjugate surface, and then the enlargement-side conjugate image is formed. The objective is to realize a novel projection optical system that forms an enlarged image on the 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 the optical path from the reduction side to the enlargement side, and from the original image on the conjugate plane on the reduction side. The image-forming light flux of is imaged as a first intermediate image and a second intermediate image sequentially on the optical path reaching the enlargement-side conjugate surface, and then is formed as an enlarged image on the enlargement-side conjugate surface. In the optical system, the first intermediate image is formed on the reduction side of the second optical group, the second intermediate image is formed between the second optical group and the third optical group, The first optical group includes a first lens group, an optical path separating optical unit, and a reflecting optical unit, and the optical path separating optical unit reflects the image forming light beam from the original image as an incident image forming light beam. The first lens group has a function of separating the optical path of the reflected imaging light flux reflected by the reflection optical means and directed toward the enlargement side from the optical path of the incident imaging light flux while being directed to the optical means side. , A portion between the optical path separating optical means and the reflecting optical means is made common to the incident image forming light beam and the reflective image forming light beam, and the second optical group is connected from the first optical group. The image forming apparatus includes a second lens group that forms the second intermediate image having the first intermediate image as an object on the enlargement side of the second optical group by the image light flux, and the third optical group includes the second optical group. The concave mirror has a function of reflecting the image-forming light flux from the group toward the conjugate surface on the enlargement side and forming the enlarged image with the second intermediate image as an object .

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

3 is a diagram showing the configuration of a projection optical system of Example 1. FIG. FIG. 6 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in Example 1. FIG. 7 is a diagram showing coma aberration at a projection distance of 700 mm in Example 1. 6 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 1000 mm in Example 1. FIG. 6 is a diagram showing coma aberration at a projection distance of 1000 mm in Example 1. FIG. It is a figure which shows the structure of the projection optical system of Example 2. FIG. 7 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in Example 2. FIG. 9 is a diagram showing coma aberration at a projection distance of 700 mm in Example 2. It is a figure which shows the structure of the projection optical system of Example 3. FIG. 10 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in Example 3. FIG. 9 is a diagram showing coma aberration at a projection distance of 700 mm in Example 3. It is a figure which shows the structure of the projection optical system of Example 4. FIG. 9 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in Example 4. FIG. 13 is a diagram showing coma aberration at a projection distance of 700 mm in Example 4. It is a figure which shows the structure of the projection optical system of Example 5. 16 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in Example 5. FIG. FIG. 16 is a diagram showing coma aberration at a projection distance of 700 mm in Example 5. It is a figure which shows the structure of another form of the projection optical system of Example 5. It is a figure which shows the structure of another form of the projection optical system of Example 5. FIG. 5 is a diagram showing an example of an optical path in which a rectangular display element is arranged and used in the projection optical system of Example 1. It is a figure which shows another embodiment of a projection optical system as an explanatory view only about a characteristic part.

Embodiments will be described below.
FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, and FIG. 19 show seven examples of embodiments of the projection optical system. In order to avoid complication, common reference numerals are used in these figures.
In these figures, reference numeral G1 indicates the first optical group, reference numeral G2 indicates the second optical group, and reference numeral G3 indicates the third optical group.
Reference numeral MD indicates an image display element. In the embodiments 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 respectively included in the “original image”. Is displayed as. In the figure, three liquid crystal panels are drawn together for the sake of convenience.

Reference symbol P indicates a prism for color combination. Lights from the original images of the three liquid crystal panels are color-synthesized by the prism P to be “imaging light flux from the original image” and enter the projection optical system.
Reference numeral SPD indicates "optical path separating optical means", reference numeral IM1 indicates "first intermediate image", and reference numeral IM2 indicates "second intermediate image". Further, reference numeral RFD indicates “reflection optical means”.
Regarding the optical path separating optical unit 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 “reduction side conjugate surface”.
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 enlargement side of the optical path separation optical means SPD". The 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. Further, 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 splitting optical means SPD is in the form of a right-angle prism, and the lower left portion in the figure 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 "transmissive surface".
When the image-forming light flux from the original image (color-synthesized by the prism P) enters the optical path separating optical means SPD, it is reflected by the reflecting surface toward the reflecting optical means RFD.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD. The first lens group includes eight lenses, seven lenses arranged between the optical path separating optical means SPD and the reflecting optical means RFD, and one lens PFL arranged on the enlargement side of the optical path separating optical means SPD. It is composed of a lens.
The reflection optical means RFD is a plane mirror, the reflection surface of which matches the aperture stop S.
The second optical group G2 is arranged on the most magnifying side of the magnifying lens PFL in the first optical group G1 and is composed of three lenses.
The third optical group G3 is composed of a "concave mirror" arranged on the enlargement side of the second optical group G2.
That is, the image-forming light flux from the image display surface of the image display element MD (image-forming light flux from the original image) is reflected by the reflecting surface R1 of the optical path separating optical means SPD, and becomes an "incident image-forming light flux", which is reflected optics. After being incident on the means RFD and being reflected, it becomes a “reflected image-forming light flux”, which is transmitted through the “transmissive surface” of the optical path separating optical means SPD, transmitted through the lens PFL, and after forming the first intermediate image IM1. , The second intermediate image IM2 is formed through the second optical group G2.
After that, the enlarged image of the original image is formed on the conjugate plane (generally a screen) on the enlargement side, which is reflected by the third optical group G3 and is not shown in FIG.

As described above, in the projection optical system according to the embodiment shown in FIG. 1, 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 image-forming light flux from the image display surface of the image display element MD, which is the conjugate surface on the reduction side, is sequentially formed as the first intermediate image IM1 and the second intermediate image IM2 on the optical path leading to the conjugate surface on the enlargement side. It is a projection optical system that forms an image and then forms an enlarged image on the conjugate plane on the enlargement side.
The first optical group G1 has a first lens group, an optical path separating optical means SPD, and a reflecting optical means RFD having a reflecting surface for reflecting the image forming light flux from the optical path separating optical means SPD side to the second optical group G2 side. The optical path splitting optical means SPD has an optical path of an incident image forming light flux traveling from the original image to 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 flux.
At least a part of the first lens group (a portion formed by seven lenses arranged between the optical path separation optical unit SPD and the reflection optical unit RFD) has a "incident imaging light flux and a reflection 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 of the embodiment shown in FIG. 6 is similar to that of the embodiment shown in FIG.
A first optical group G1, a second optical group G2, and a third optical group G3 are sequentially arranged on the optical path from the reduction side to the enlargement side, and the image-forming light flux from the original image on the reduction-side conjugate surface is This is a projection optical system that sequentially forms images as a first intermediate image IM1 and a second intermediate image IM2 on an optical path leading to the enlargement-side conjugate surface, and then forms an enlarged image on the enlargement-side conjugate surface.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. The optical path splitting optical means SPD has an optical path of an incident image forming light flux traveling from the original image to the reflecting optical means RFD and a reflective image forming light flux reflected by the reflecting optical means RFD toward the second optical group G2. It has the function of separating from the optical path of.
The optical path splitting optical means SPD has a right-angle prism shape like the optical path splitting optical means SPD in the embodiment of FIG. 1, and a lower left portion in the figure from the intersection of the optical axes AX1 and AX2 on the diagonal slope. The reflection surface R1 is formed, and the upper right portion of the intersection is a "transmission surface".
The reflective optical means RFD is also a plane mirror like the reflective optical means RFD in the embodiment of FIG. 1, and its reflective surface matches the aperture stop S.
At least a part of the first lens group (seven lenses arranged between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image forming light beam and the reflective image forming light beam, The third optical group G3 has a concave mirror located on the enlargement side of the second intermediate image G2.

On the other hand, in the projection optical system of which the embodiment is 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 image-forming light flux from the original image on the reduction-side conjugate surface is sequentially formed as a first intermediate image IM1 and a second intermediate image IM2 on the optical path leading to the enlargement-side conjugate surface, and then the expansion-side image IM2. This is a projection optical system that forms an enlarged image on the conjugate plane.
The first optical group G1 includes a first lens group, an optical path separating optical means SPD, and a reflecting optical means RFD having a reflecting surface for reflecting the image forming light flux from the optical path separating optical means side to the second optical group side. The optical path splitting optical means SPD has the optical path of the incident image-forming light flux traveling from the original image to the reflecting optical means RFD and the reflective image-forming light flux reflected by the reflecting optical means RFD toward the second optical group G2. It has the function of separating from the optical path.
At least a part of the first lens group is “shared by the incident imaging light flux and the reflection imaging light flux”, 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 according to the embodiment 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 extending from the reduction side to the enlargement side. The image forming light flux from the original image on the side conjugate surface is sequentially formed on the optical path reaching the enlargement side conjugate surface as a first intermediate image IM1 and a second intermediate image IM2, and then on the enlargement side conjugate surface. It is a projection optical system that forms an enlarged image.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. Is configured. The optical path splitting optical means SPD is, like the one shown in FIGS. 1 and 6, a right-angled prism shape, and the lower left portion in the figure is the reflection 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 "transmissive surface", and the optical path of the incident image-forming light flux from the original image to 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 and image-forming light flux directed toward.
At least a part of the first lens group (six lenses arranged between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image-forming light beam and the reflective image-forming 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 “reflection surface which also serves as the aperture stop S” of the reflection optical means RFD is concave and has a refractive power.

The projection optical system of 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 extending from the reduction side to the enlargement side. The image forming light flux from the original image on the side conjugate surface is sequentially formed on the optical path reaching the enlargement side conjugate surface as a first intermediate image IM1 and a second intermediate image IM2, and then on the enlargement side conjugate surface. It is a projection optical system that forms an enlarged image.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. Is configured. The optical path splitting optical means SPD is, like the one shown in FIGS. 1 and 6, a right-angle prism shape, has a reflecting surface R1 and a "transmissive surface", and has an optical path of an incident image-forming light flux from the original image toward the reflecting optical means RFD. And the optical path of the reflected image-forming light flux which is reflected by the reflective optical means RFD and goes to the second optical group G2.
At least a part of the first lens group (seven lenses arranged between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image-forming light beam and the reflective image-forming 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 is different 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 of the first lens system on which the incident image-forming light flux is finally incident. The reflective film also serves 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 image-forming light flux formed with the reflection film is finally incident” which also serves as the aperture stop may be a flat surface.

The projection optical system according to the embodiment 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 extending from the reduction side to the enlargement side. The image forming light flux from the original image on the side conjugate surface is sequentially formed on the optical path reaching the enlargement side conjugate surface as a first intermediate image IM1 and a second intermediate image IM2, and then on the enlargement side conjugate surface. It is a projection optical system that forms an enlarged image.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. Is configured. The optical path splitting optical means SPD is a plane mirror having a reflecting surface equivalent to the reflecting surface R1 in the optical path splitting optical means in FIG. Has a function of separating from the optical path of the reflected image-forming light flux that is reflected by and goes toward the second optical group G2.
As in the embodiment shown in FIG. 1, the reflection optical means RFD is a plane mirror, the reflection surface of which matches the aperture stop S.
At least a part of the first lens group (7 lenses disposed between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image-forming light beam and the reflective image-forming 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 showing the embodiment in FIG. 15, the first lens group is “7 lenses arranged between the optical path separating optical means SPD and the reflecting optical means RFD”, and an enlargement of the optical path separating optical means SPD. It is composed of two lenses arranged on the side.

The projection optical system of which the embodiment is shown 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 extending from the reduction side to the enlargement side. The image forming light flux from the original image on the side conjugate surface is sequentially formed on the optical path reaching the enlargement side conjugate surface as a first intermediate image IM1 and a second intermediate image IM2, and then on the enlargement side conjugate surface. It is a projection optical system that forms an enlarged image.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. Is configured. The optical path splitting optical means SPD is the same plane mirror as the optical path splitting optical means of FIG. 15, and the optical path of the incident image-forming light flux from the original image toward the reflecting optical means RFD and the second optical group G2 reflected by the reflecting optical means RFD. It has a function of separating the optical path of the reflected and image-forming light flux directed toward.
In the embodiment shown in FIG. 18, the imaging light flux from the original image is directly incident on the reflection optical means RFD as an incident imaging light flux, and the reflection imaging light flux reflected by the reflection optical means RFD is an optical path separation optical path. It is reflected by the means SPD and goes toward the second optical group side.
As in the embodiment shown in FIG. 1, the reflection optical means RFD is a plane mirror, the reflection surface of which matches the aperture stop S.
At least part of the first lens group (seven lenses arranged between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image-forming light beam and the reflective image-forming 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 “7 lenses arranged between the optical path separating optical means SPD and the reflecting optical means RFD”, and an expansion of the optical path separating optical means SPD. It is composed of two lenses arranged on the side.

The projection optical system according to the embodiment shown in FIG. 19 is configured such that the plane mirror, which is the optical path separation optical means SPD in the embodiment shown in FIG. 18, is “rotated counterclockwise” in the plane of FIG. Angle formed by AX1 and optical axis AX2: θAX is an example configured to be “angle smaller than 90 degrees”.
Therefore, 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 extending from the reduction side to the enlargement side. Imaged light fluxes from the original image on the conjugate plane are sequentially formed as a first intermediate image IM1 and a second intermediate image IM2 on the optical path reaching the enlargement side conjugate plane, and then the enlarged image is formed on the enlargement side conjugate plane. Is a projection optical system for forming an image.
The first optical group G1 includes a first lens group, an optical path separating optical unit SPD, and a reflecting optical unit RFD having a reflecting surface that reflects an image forming light beam from the optical path separating optical unit side to the second optical group G2 side. Is configured. The optical path splitting optical means SPD is the same plane mirror as the optical path splitting optical means of FIG. 15, and the optical path of the incident image-forming light flux from the original image toward the reflecting optical means RFD and the second optical group G2 reflected by the reflecting optical means RFD. It has a function of separating the optical path of the reflected and image-forming light flux directed toward.
The image forming light beam from the original image is directly incident on the reflecting optical means RFD as an incident image forming light beam, and the reflected image forming light beam reflected by the reflecting optical means RFD is reflected by the optical path separating optical means SPD to be the second optical element. Head towards the flock.
As in the embodiment shown in FIG. 1, the reflection optical means RFD is a plane mirror, the reflection surface of which matches the aperture stop S.
At least part of the first lens group (seven lenses arranged between the optical path separating optical unit SPD and the reflecting optical unit RFD) is shared by the incident image-forming light beam and the reflective image-forming 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 separating optical means SPD and the reflecting optical means RFD” and two lenses arranged on the enlargement side of the optical path separating optical means SPD. ing.

As described above, seven optical arrangements of the projection optical system of the present invention are illustrated, 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 splitting optical means SPD can be replaced with those shown in FIGS. 15, 18, and 19.
The optical path separating optical means reflects one of "a portion to be an incident image-forming light flux and a portion to be the reflective image-forming light flux" out of the image-forming light flux from the original image on the reduction-side conjugate surface, and the other. By "passing", the optical paths of these two imaging light fluxes are separated, and the optical path separating optical means SPD in each of the above-described embodiments has such a configuration.
The optical path splitting optical means can also be configured to "have a polarization combining means, a polarization splitting means, and a retardation plate" as in the example described later. Further, the optical path splitting optical means SPD can be configured by a “half mirror”.
Further, 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 reflective film can be formed on the "lens surface on which the incident image-forming light flux is finally incident" of the first lens group to form a reflective optical means, but it is not formed when the reflective film is formed. Also in this case, the “lens surface on which the incident image-forming light flux is finally incident” can be a curved surface or a flat surface.

The size of the magnified image formed on the conjugate plane on the magnifying side is changed by changing the projection distance from the third optical group to the conjugate surface (screen or the like) on the magnifying side, but when the projection optical system has a wide angle of view. The field curvature and the distortion are likely to increase with respect to the variation of the projection distance.

Although various methods are possible for focusing (focusing) the magnified image on the "conjugate surface (screen or the like) on the magnifying side", in the above-described embodiments, a plurality of second optical systems G2 are provided. It is configured to have (three) lenses, and it is possible to perform focusing by moving one or more lenses forming the second optical group G2 in the optical axis direction.
The second optical group G2 is close to the exit side of the image-forming light flux and is easily accessible. By moving one or more lens groups in the second optical group, the focus and the curvature of the image plane are kept good. Matching is possible.
The projection optics are also preferably "substantially telecentric" on the reduction side.

The projection optical system of 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 image-forming light flux on the optical path from the reduction-side conjugate surface to the enlargement-side conjugate surface at the original image position, and “2Ym” is on the mirror surface of the concave mirror of the third optical group. It is the maximum effective diameter.
“Lr” is the distance on the optical axis between the reflecting surface of the reflecting optical means and the lens surface of the second optical group that is closest to the expansion side, and “Lm” is the third surface of the second optical group and the lens surface that is closest to the expansion side. It is the distance on the optical axis from the concave mirror surface of the optical group.
“ ΘAX ” is the 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.

Parameter of condition (1): If Ym/Yi becomes smaller, the maximum effective diameter of the light beam on the mirror surface of the concave mirror becomes smaller, 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 chief ray density of each image height on the mirror surface of the concave mirror becomes excessive, and it becomes difficult to suppress various aberrations such as distortion mainly corrected by the concave mirror. easy.
If the parameter of condition (1): Ym/Yi exceeds the upper limit, the concave mirror of the third optical group tends to be large, and it tends to be difficult to configure the projection optical system compactly.
When the parameter of condition (2): Lm/Lr is small, Lm may be small and Lr may be large, but the distance: Lm is a certain amount as a 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 of condition (2): Lm/Lr exceeds the lower limit, the lengths (Lr+Lm) on the optical axis of the first optical group and the second optical group increase, and the projection optical system tends to increase in size.
If the parameter of condition (2): Lm/Lr exceeds the upper limit, the lengths 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 the optical performance Is difficult to maintain. Further, if the increase in the lengths 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 becomes large, and at the same time, the concave mirror also tends to become large, and the projection optical system is compact. It tends to be difficult to realize.
Further, by satisfying the condition (3), it is possible to achieve a reasonable optical arrangement.

In the projection optical system showing the embodiment 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 arranged on the reduction side of the first intermediate image IM1 or at the “position including the first intermediate image IM1 (in the case of the embodiment of FIG. 1)”.
Like the projection optical system of the present invention, the image-forming light flux from the original image on the reduction-side conjugate surface is sequentially formed as the first intermediate image IM1 and the second intermediate image IM2 on the optical path leading to the enlargement-side conjugate surface. After that, in the projection optical system that forms an enlarged image on the conjugate plane on the enlargement side, the second intermediate image IM2 is an “object (object point)” in the image formation of the concave mirror of the third optical group.
Then, 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 magnified image on the conjugate plane on the magnifying side, it is preferable that the second intermediate image IM2 be a “good image”. If the second intermediate image IM2 is not a good image, the mirror shape of the concave mirror tends to have a complicated shape in order to form a good magnified image. In order to form a good second intermediate image IM2, it is preferable that the first intermediate image is a “good image”.

In each of the embodiments described above, the lens PFL on the most magnifying side of the first optical group G1 is arranged on the reduction side of the first intermediate image IM1 or at the “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 chief 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. ..
As described above, from the viewpoint of “arranging 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 "common to the incident image-forming light beam and the reflected image-forming light beam", and this common part is a so-called "folding optical system". It has become. Thus, by forming a part of the first lens group as the “folding back optical system”, it is possible to realize a good first intermediate image while reducing the number of lenses forming the first lens group.

Moreover, by making a part of the first lens group 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.
By forming a part of the first lens group as a folding optical system, the first lens group can have a “structure close to a symmetrical equal-magnification optical system”, and the reflecting optical means: the reflecting surface of the RFD is an aperture stop. Can be set to. Further, as in the embodiment shown in FIG. 12, the number of parts can be reduced by forming a reflection film on the last lens surface on which the incident image-forming light beam enters to form the reflection optical means RFD.
In addition, since the first optical group G1 has a “structure close to that of a unity-magnification optical system”, the reflection optical means: RFD can be a plane mirror having a reflection surface as a flat surface, which makes the projection optical system easy to assemble. be able to. Alternatively, the degree of freedom in design is improved by making the reflecting surface of the reflection optical means: RFD curved, and the performance of the projection optical system can be improved.

By mounting such a projection optical system, a projection device having excellent projection performance can be realized. FIG. 20 shows one embodiment of the projection device. This projection apparatus uses the projection optical system PRS of the present invention, and an image display element MD arranged on the reduction-side conjugate plane (similarly to FIG. 1, etc., three liquid crystal panels are combined into one for convenience. The image displayed on the screen SC is formed on the screen SC which is the conjugate surface on the enlargement side.
Further, by mounting the projection optical system of the present invention and disposing the image pickup element at the conjugate point on the reduction side, it is possible to realize an image pickup apparatus capable of picking up an image on the conjugate surface on the enlargement side.

"Example"
Five specific examples of the projection optical system will be given below.
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. In addition, a conjugate surface (screen or the like) on the enlargement side of the screen or the like onto which the enlarged image is projected is shown as an “image surface”.

"R" represents the radius of curvature of each surface (including the surface of the aperture stop S and the prism P for color combination) (paraxial radius of curvature for an aspherical surface), and "D" on the optical axis. Represents the surface spacing of. The unit of length is "mm".
Surface spacing: D is displayed by "reversing the sign before and after the reflecting surface". “Nd and νd” indicates the “refractive index and Abbe number for d line” of the material of each lens.
The “focal length” is the focal length of the projection optical system at the d-line (in each embodiment, the projection distance is a value at 700 mm), “NA” is the numerical aperture on the reduction side, and “object height” is It 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 displacement amount in the optical axis direction: Z, the paraxial radius of curvature: R, the conic constant: K, the aspherical surface of the nth degree, with the intersection point with the optical axis as the origin. As a coefficient: An, a well-known equation 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 R, K, and An. The aspherical surface is represented by adding "* mark" 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 RD 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 Transparent 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 of the three lenses constituting the second optical group G2 in the optical axis direction.

"Aspherical data"
The data of the aspherical surface are given below.
Surface 36
K=2.915703 A4=5.62046E-05 A6=-1.18034E-06 A8=2.24920E-08
A10=-2.37010E-10 A12=9.49591E-13
Surface 37
K=-0.863225 A4=2.52066E-04 A6=-8.03667E-07 A8=7.18714E-09
A10=-2.41923E-10 A12=2.36632E-12
Surface 38
K=-0.636376 A4=-4.45113E-05 A6=2.53876E-06 A8=2.40648E-08
A10=1.89421E-09 A12=-1.73584E-11
Surface 39
K=-1.569243 A4=1.93658E-04 A6=-1.00718E-05 A8=3.45432E-07
A10=-5.88910E-09 A12=5.88827E-11
Surface 40
K=-0.679846 A4=-7.25686E-05 A6=-6.06854E-06 A8=3.02542E-07
A10=-7.49194E-09 A12=6.51695E-11
Surface 41
K=-2.552383 A4=-4.14707E-04 A6=1.11392E-05 A8=-7.69006E-08
A10=-3.31496E-09 A12=6.54793E-11
42nd surface
K=3.245191 A4=-5.01414E-04 A6=1.12614E-06 A8=1.34021E-07
A10=-7.01951E-09 A12=8.79689E-11
Surface 43
K=-1.638918 A4=-4.35977E-05 A6=-2.67086E-06 A8=1.23500E-07
A10=-3.92457E-09 A12=4.42236E-11
Surface 44
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 magnifying side): Variable surface intervals for 1000 mm and 700 mm are 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 value of conditional expression"
(1) Ym/Yi=1.99
(2) Lm/Lr=0.37
(3) θAX=90°.

FIG. 2 shows the spherical aberration, astigmatism, and distortion of the projection optical system of Example 1 at a projection distance of 700 mm, and FIG. 3 shows the coma. 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.
Aberrations are shown with a wavelength of 532 nm being green light as a representative, and aberrations of wavelengths of 638 nm and 450 nm of red and blue lights are also shown in the spherical aberration diagram and coma aberration diagram. In the diagram of astigmatism, S indicates the aberration of the sagittal image, and M indicates the aberration of the meridional image.
The spherical aberration, astigmatism, and distortion at a projection distance of 1000 mm in Example 1 are shown in FIG. 4, and coma is shown in FIG. 5, following FIGS. 2 and 3, respectively.

"Example 2"
Example 2 is a specific example of the projection optical system shown as an embodiment in FIG.
Surface number RD 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 Transparent 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 closest to the reduction side in the optical axis direction among the three lenses forming the second optical group G2.

"Aspherical data"
The data of the aspherical surface are given below.
Surface 34
K=1.603407 A4=6.62499E-05 A6=-1.47855E-06 A8=2.13965E-08
A10=-1.61087E-10 A12=3.04660E-13
Surface 35
K=-16.185981 A4=1.37057E-04 A6=-2.00047E-06 A8=2.34483E-08
A10=-1.88936E-10 A12=6.14870E-13
Surface 36
K=-0.861684 A4=1.60081E-04 A6=-4.15035E-06 A8=2.11338E-07
A10=-5.58538E-09 A12=7.82222E-11
Surface 37
K=-1.275659 A4=2.13278E-04 A6=-7.81789E-06 A8=2.11280E-07
A10=-3.44166E-09 A12=3.20992E-11
Surface 38
K=-1.368834 A4=-7.65177E-05 A6=-1.14321E-05 A8=1.55813E-07
A10=-1.29025E-09 A12=9.12296E-12
Surface 39
K=-1.887530 A4=-4.10972E-04 A6=2.51109E-06 A8=-1.14759E-07
A10=-8.20290E-10 A12=3.33966E-11
Surface 40
K=3.612239 A4=-5.44430E-04 A6=9.39714E-07 A8=8.94005E-08
A10=-7.43024E-09 A12=-1.10566E-12
Surface 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 surface
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 intervals for 1000 mm and 700 mm are 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 value of conditional expression"
(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 of 700 mm of the projection optical system of Example 2, and FIG. 8 shows a diagram of coma.

"Example 3"
Example 3 is a specific example of the projection optical system shown as an embodiment in FIG.
Surface number RD 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 Transparent 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 integrally.
The reflecting surface (R17) of the reflecting optical means RFD is a concave spherical surface.

"Aspherical data"
The data of the aspherical surface are given below.
33rd surface
K=-28.096426 A4=-6.77425E-05 A6=-5.90182E-07 A8=2.94466E-08
A10=-3.06620E-10 A12=1.04612E-12
Surface 34
K=-1.670922 A4=4.80203E-05 A6=-1.44409E-06 A8=1.39862E-07
A10=-3.08812E-09 A12=3.68637E-11
Surface 35
K=-1.803642 A4=2.62605E-04 A6=-6.98860E-06 A8=2.32598E-07
A10=-4.33412E-09 A12=4.51871E-11
Surface 36
K=-3.660291 A4=-1.36764E-04 A6=-6.18455E-06 A8=1.48461E-07
A10=-5.25541E-09 A12=5.84470E-11
Surface 37
K=-2.861026 A4=-4.65468E-04 A6=5.22020E-06 A8=-1.25681E-07
A10=-9.52226E-10 A12=3.62857E-11
Surface 38
K=2.168481 A4=-3.93818E-04 A6=1.32053E-06 A8=3.46782E-08
A10=-2.00594E-09 A12=2.01621E-11
Surface 39
K=-1.557297 A4=-6.74713E-05 A6=-2.59035E-06 A8=7.47685E-08
A10=-1.67863E-09 A12=1.09976E-11
Surface 40
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 intervals for 1000 mm and 700 mm are 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 value of conditional expression"
(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.

"Example 4"
Example 4 is a specific example of the projection optical system whose embodiment is shown in FIG.
Surface number RD 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 Transparent 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 ∞
Focusing is performed by displacing one of the three lenses forming the second optical group G2 on the most reduction side in the optical axis direction, as in the first and second embodiments.
As the optical path splitting optical means SPD in the first optical group, a prismatic one is used as in the first to third embodiments, but it is attached to the prism P.
The reflection optical means RFD is formed as a reflection film on the last lens surface (16th surface) on which the incident image-forming light flux enters.

"Aspherical data"
The data of the aspherical surface are given below.
Surface 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 surface
K=-15.730675 A4=1.36967E-04 A6=-2.17077E-06 A8=2.42200E-08
A10=-1.76205E-10 A12=5.19923E-13
33rd surface
K=-0.823506 A4=1.35284E-04 A6=-4.93090E-06 A8=2.39756E-07
A10=-6.53768E-09 A12=8.70535E-11
Surface 34
K=-1.287323 A4=2.18563E-04 A6=-7.97156E-06 A8=2.01418E-07
A10=-3.23617E-09 A12=3.00384E-11
Surface 35
K=-2.092687 A4=-1.17823E-04 A6=-1.06700E-05 A8=1.98389E-07
A10=-2.12011E-09 A12=-1.87671E-12
Surface 36
K=-2.167473 A4=-4.53662E-04 A6=2.77479E-06 A8=-8.28418E-08
A10=-1.42869E-10 A12=9.64186E-12
Surface 37
K=2.814082 A4=-5.85877E-04 A6=1.47679E-06 A8=7.18255E-08
A10=-7.28339E-09 A12=4.64457E-11
Surface 38
K=-1.313465 A4=-6.71534E-05 A6=-2.16340E-06 A8=3.88675E-08
A10=-5.92669E-10 A12=-3.70224E-11
Surface 39
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 intervals for 1000 mm and 700 mm are 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 value of conditional expression"
(1) Ym/Yi=1.73
(2) Lm/Lr=0.39
(3) θAX=90°
FIG. 13 is a diagram showing spherical aberration, astigmatism, and distortion at a projection distance of 700 mm in the projection optical system of Example 4, and FIG. 14 is a diagram showing coma.

1, FIG. 6, FIG. 9 and FIG. 12 showing the configurations of the projection optical systems of Examples 1 to 4 mentioned above are all “object height” which is the maximum ray height of the original image on the image display surface. FIG. 6 is a diagram in which each of the optical elements includes a ray group of FIG. Generally, in a projector, the shape of the image display surface of the image display element that displays the original image is rectangular, so the "optical path separation optical means SPD" in the lens configuration diagram shown in two dimensions is drawn larger than it is in actual use. Has been.

"Example 5"
Example 5 is a specific example of the projection optical system whose embodiment is shown in FIG.
Surface number RD 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 "plane mirror" is used as the optical path splitting optical means SPD and is arranged so that the incident image-forming light beam and the reflected image-forming light beam to the reflection optical means RFD do not interfere with each other. Focusing is performed by displacing the lens on the most reduction side of the three lenses forming the second optical group G2 and displacing the two lenses on the enlargement side as a unit, as in the case of the third embodiment. ing.

"Aspherical data"
The data of the aspherical surface are given below.
Surface 37
K=-0.429722 A4=2.14785E-04 A6=-2.24509E-06 A8=1.99647E-08
A10=-9.55644E-11 A12=1.79738E-13
Surface 38
K=-4.945603 A4=1.37493E-04 A6=2.67595E-06 A8=1.97759E-08
A10=-8.36109E-10 A12=8.55167E-12
Surface 39
K=-4.186418 A4=3.31687E-04 A6=-6.07612E-06 A8=3.16769E-07
A10=-6.32160E-09 A12=6.90243E-11
Surface 40
K=-14.671774 A4=-1.73473E-04 A6=-1.91202E-06 A8=1.99566E-07
A10=-1.46132E-08 A12=2.45877E-10
Surface 41
K=-5.738160 A4=-4.92591E-04 A6=8.28085E-06 A8=-2.01226E-07
A10=-2.76139E-09 A12=1.11235E-10
42nd surface
K=2.045825 A4=-7.14286E-04 A6=7.58939E-06 A8=-1.06669E-07
A10=-2.41779E-09 A12=3.42255E-11
Surface 43
K=-1.184088 A4=-8.13286E-05 A6=-2.65166E-06 A8=1.06600E-07
A10=-3.21074E-09 A12=7.19981E-12
Surface 44
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 intervals for 1000 mm and 700 mm are 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 value of conditional expression"
(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.

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 is good over a wide projection distance from a long distance to a short distance. It maintains excellent optical performance.

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

Although the drawings showing the configurations of Examples 1 to 5 all show only the light rays within the plane of the paper, the display element MD of the original image of the projector is arranged as a rectangle long horizontally (horizontally). The case is general. In the example of the projector shown in FIG. 20, the projection optical system of Example 1 is used and shown as a stereoscopic view together with the light rays emitted from the four corner points of the image display element.

As described above, the projection optical system of the present invention appropriately supports 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, and the like. It is possible and is not limited to the one shown in the embodiment.
In each of the embodiments described above with reference to FIGS. 1, 6, 9, 12, 15, 18, and 19, the imaging light flux of “oblique rays” is used. That is, in each of the embodiments, the image-forming light beam from the reduction-side conjugate surface is incident on the prism P while being displaced from the "reduction-side optical axis AX1 of the optical path separation optical unit SPD". This is because the optical path splitting optical means (SPD) reflects one of the part to be the incident image-forming light beam and the part to be the reflective image-forming light beam and allows the other to pass therethrough, thereby forming both of these image-forming light beams. It depends on what is to separate the optical path of.

However, the present invention is not limited to this, and the principal ray at the center of the image-forming light flux from the conjugate plane on the reduction side matches the optical axis AX1 on the reduction side of the optical path separating optical means SPD, and the principal ray of the reflected imaging light flux is on the enlargement side. It is also possible to make it coincide with the optical axis AX2 of.
An example of this case is shown in FIG. 21 in an explanatory view of only the main part.
In FIG. 21, reference sign P1 is a “color combining prism”, reference sign S1 is a “wavelength selection 1/2λ phase difference plate” that gives a phase difference in a specific wavelength range, reference sign P2 is a “wideband polarization beam splitter”, and reference sign S2 is A "broadband 1/4 lambda retarder" is shown.
Further, reference numeral L10 is a portion of the first lens group of the first optical group, which is disposed between the broadband ¼λ phase difference plate S2 and the reflection optical means RFD, that is, “incident image formation light flux and reflection image formation”. It is a lens system part shared with the light flux."

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

The image forming lights R(S) and B(S) emitted from these light sources and formed into an image forming light flux by the image display element are “S polarized light” with respect to the polarizing film of the prism P1 as shown in FIG. ], and is reflected by the polarizing film toward the polarizing beam splitter P2.
On the other hand, the imaging light G(P) that has become an imaging light flux 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 image forming lights R(S), G(P), and B(S) are color-synthesized.
In FIG. 21, for simplification of description, the light rays of these three colors are drawn separately from each other, but in reality, they are combined so that the central light rays of the respective image forming light fluxes match.
The color-combined image forming lights R(S), G(P), and B(S) are incident on the wavelength selection 1/2λ phase difference plate S1. The wavelength selection ½λ retardation plate S1 allows the image forming lights R(S) and B(S) to pass therethrough as they are, but the image forming light G(P) rotates its polarization direction by 90 degrees. Then, the light is transmitted as the imaging light G(S). As the “wavelength selection 1/2λ retardation plate” that imparts a phase difference to such a specific wavelength region, a commercially available color select (trade name, manufactured by Colorlink Japan Co., Ltd.) can be used.
The image forming lights R(S), G(S), and B(S) whose polarization directions are aligned by the wavelength selection 1/2λ phase difference plate S1 are incident on the broadband polarization beam splitter P2 and are directed to the reflection optical means RFD side. It is reflected toward, enters the broadband ¼λ retardation plate S2, is changed from S-polarized light into circularly polarized light, is transmitted through the lens system portion L10 as an incident image-forming light beam, and is incident on and reflected by the reflection optical means RFD.
The reflected image-forming light flux reflected by the reflection optical means RFD passes through the lens system portion L10 and the broadband ¼λ phase difference plate S2 as shown in FIG. The reflected image-forming light fluxes R(P), G(P), and B(P) are transmitted through the broadband polarization beam splitter P2.
The wideband 1/4λ phase difference plate S2 may be arranged between the lens system portion L10 and the reflection optical means RFD. In this case, since the wideband 1/4λ phase difference plate S2 is arranged near the aperture stop, it is small. can do.

A commercially available retardation plate (product number: WPQW-VIS-4M manufactured by Sigma Optical Co., Ltd.) can be used as the broadband ¼λ retardation plate S2, and a broadband deflection beam splitter ( A product number: PBSW-10-3/7) manufactured by Sigma Koki Co., Ltd. can be used.
In this way, the optical path of the incident image-forming light flux traveling from the original image to the reflective optical means RFD and the optical path of the reflective image-forming light flux reflected by the reflective optical means to the second optical group are separated. At this time, both the light beam center of the incident image-forming light beam directed to the reflection optical means RFD and the light beam center of the reflected image-forming light beam reflected by the reflection optical means RFD are both on the optical axis of the lens system portion L10 (that is, in the projection optical system). Optical axis).
In the embodiment shown in FIG. 21, the color synthesizing prism P1, the broadband polarization beam splitter P2, the wavelength selection ½λ phase difference plate S1 and the broadband ¼λ phase difference plate S2 constitute “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 by 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 device, and imaging device can be realized.
[1]
A first optical group (G1), a second optical group (G2), and a third optical group G3) are sequentially arranged on the optical path from the reduction side to the enlargement side, and the original image on the conjugate plane on the reduction side is formed. Of the imaging light flux of 1 is sequentially formed as a first intermediate image (IM1) and a second intermediate image (IM2) on the optical path reaching the enlargement-side conjugate surface, and then enlarged on the enlargement-side conjugate surface. A projection optical system for forming an image, wherein the first intermediate image (IM2) is formed on the reduction side of the second optical group (G2), and the second intermediate image (IM2) is the second optical image. An image is formed between the group (G2) and the third optical group (G3), and the first optical group (G1) includes a first lens group, an optical path separating optical unit (SPD), and a reflecting optical unit ( RFD), the optical path splitting optical means (SPD) directs the imaging light flux from the original image to the reflection optical means (RFD) side as an incident imaging light flux, and by the reflection optical means. The first lens group has a function of separating the optical path of the reflected image-forming light flux reflected and traveling toward the enlargement side from the optical path of the incident image-forming light beam, and the first lens group is provided between the optical-path separating optical means and the reflective optical means. Is shared by the incident image-forming light flux and the reflected image-forming light flux, and the second optical group uses the image-forming light flux from the first optical group as the first intermediate image. The second optical group has a second lens group that forms an image of the two intermediate images on the enlargement side of the second optical group, and the third optical group forms the image-forming light flux from the second optical group on the conjugate plane on the enlargement side. A projection optical system that is a concave mirror that reflects toward the second intermediate image and has the function of forming the enlarged image with the second intermediate image as an object (Examples 1 to 5, FIGS. 1, 6, 9, 12, and 15). , FIG. 18, FIG. 19).

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

[3]
The projection optical system according to [1] or [2],
Distance on the optical axis between the reflecting surface of the reflecting optical means and the lens surface of the second optical group that is closest to the magnification: Lr, the lens surface of the second optical group, and the concave mirror surface of the third optical group On the optical axis: Lm, the condition:
(2) 0.25 <Lm/Lr <0.55
A projection optical system that satisfies the conditions (Examples 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 magnifying side of the first lens group is a positive lens (PFL) and the reduction side or the first intermediate image (IM1). 1. Projection optical system arranged at a position including one intermediate image (Examples 1 to 5, FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19).

[5]
The projection optical system according to [4], wherein the positive lens (PFL) on the most magnification side of the first lens group has at least one aspherical surface. , FIG. 9, FIG. 12, FIG. 15, FIG. 18, and 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 image-forming light flux is an aperture stop. 1 to 5, FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG.

[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 image-forming light flux is the incident image-forming light flux of the first lens group. Is a projection optical system formed on the lens surface on which is finally incident (Example 4 FIG. 12).

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

[9]
The projection optical system according to any one of [1] to [6], wherein the reflection optical means (RFD) has a flat reflecting surface for reflecting the incident image-forming 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) has a plurality of lenses, and one or more of the plurality of lenses are moved in the optical axis direction. And a projection optical system for focusing on the enlargement side conjugate surface (Examples 1 to 5, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 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, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19).

[12]
The projection optical system according to any one of [1] to [10], wherein the angle between the optical axis on the reduction side of the optical path separation optical means (SPD) and the optical axis on the enlargement side of the optical path separation optical means: θAX is a condition:
(3) 45° ≤ θAX ≤ 90°
A projection optical system satisfying the conditions (Examples 1 to 5, FIG. 1, FIG. 6, FIG. 9, FIG. 12, FIG. 15, FIG. 18, FIG. 19, FIG. 21).

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

[14]
The projection optical system according to [13], wherein the optical path separating optical means includes a polarization combining means (P1), a polarization separating means (P2), and retardation plates (S1, S2) (FIG. 21).

[15]
A projection device equipped with the projection optical system according to any one of [1] to [14] (FIG. 20).

[16]
An image pickup apparatus, which is equipped with the projection optical system according to any one of [1] to [14], and which picks up an image formed on the reduction side of an object on the enlargement side by an image pickup means.

Although the preferred embodiments of the invention have been described above, the invention is not limited to the specific embodiments described above, and the invention described in the scope of claims unless otherwise specified. Various modifications and changes can be made 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 enumeration of the suitable effects resulting from the invention, and the effects according to the invention are not limited to "the effects 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 separation optical means
AX1 Optical axis of image-forming light beam on reduction side of optical path separation optical means
AX2 Optical path of the image-forming light beam on the enlargement side of the optical path separating optical means
RFD reflection optical means
PFL The first lens on the most magnifying side of the first optical group
Prism for P color composition
MD image display device

Japanese Patent No. 5728202 Japanese Patent No. 5767614 Patent No. 5960579 JP, 2015-200829, A

Claims (16)

A first optical group, a second optical group, and a third optical group are sequentially arranged on an optical path extending from the reduction side to the enlargement side, and an imaging light flux from the original image on the conjugate plane on the reduction side is expanded. A projection optical system that sequentially forms images as a first intermediate image and a second intermediate image on an optical path reaching the side conjugate surface, and then forms an enlarged image on the enlargement side conjugate surface,
The first intermediate image is formed on the reduction side of the second optical group, the second intermediate image is formed between the second optical group and the third optical group,
The first optical group includes a first lens group, an optical path separating optical unit, and a reflecting optical unit,
The optical path separating optical means directs the image-forming light beam from the original image as an incident image-forming light beam toward the reflecting optical means side, and at the same time, reflects the image-forming light beam reflected by the reflecting optical means toward the enlargement side. Has a function of separating the optical path from the optical path of the incident image-forming light beam,
In the first lens group, a portion between the optical path separation optical unit and the reflection optical unit is shared by the incident imaging light flux and the reflection imaging light flux.
The second optical group is a second lens group that forms the second intermediate image having the first intermediate image as an object on the magnifying side of the second optical group by the imaging light flux from the first optical group. Have
The third optical group reflects the image-forming light flux from the second optical group toward the conjugate surface on the enlargement side, and has a concave mirror having a function of forming the enlarged image with the second intermediate image as an object. projection optical system is. The projection optical system according to claim 1, wherein
The maximum effective diameter of the image-forming light flux on the optical path from the conjugate surface on the reduction side to the conjugate surface on the enlargement side at the original image position: 2Yi, and the maximum effective diameter on the mirror surface of the concave mirror: 2Ym are conditions:
(1) 1.5 <Ym/Yi <5.0
Projection optical system that satisfies the requirements. The projection optical system according to claim 1 or 2, wherein
Distance on the optical axis between the reflecting surface of the reflecting optical means and the lens surface of the second optical group that is closest to the magnification: Lr, the lens surface of the second optical group, and the concave mirror surface of the third optical group On the optical axis: Lm, the condition:
(2) 0.25 <Lm/Lr <0.55
Projection optical system that satisfies the requirements. The projection optical system according to any one of claims 1 to 3,
A projection optical system in which the most magnifying side of the first lens group is a positive lens, and is arranged at a reduction side of the first intermediate image or at a position including the first intermediate image. The projection optical system according to claim 4,
The positive lens closest to the magnification in the first lens group is a projection optical system having at least one aspherical surface. The projection optical system according to any one of claims 1 to 5,
A projection optical system in which the reflection surface of the reflection optical means that reflects the incident image-forming light flux is an aperture stop. The projection optical system according to any one of claims 1 to 6,
A projection optical system in which the reflection surface of the reflection optical means for reflecting the incident image-forming light flux is formed on a lens surface of the first lens group on which the incident image-forming light flux finally enters. The projection optical system according to any one of claims 1 to 7,
A projection optical system of the first lens group, wherein the reflective surface of the reflective optical means that reflects the incident image-forming light flux is a curved surface. The projection optical system according to any one of claims 1 to 7,
A projection optical system in which the reflection surface of the reflection optical means of the first lens group that reflects the incident image-forming light flux is a flat surface. The projection optical system according to any one of claims 1 to 9,
The projection optical system in which the second optical group has a plurality of lenses, and at least one of the plurality of lenses is moved in the optical axis direction to perform focusing on the conjugate surface on the enlargement side. The projection optical system according to any one of claims 1 to 10,
A 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 separating optical means and the optical axis on the enlargement side of the optical path separating optical means is a condition:
(3) 45° ≤ θAX ≤ 90°
A projection optical system characterized in that The projection optical system according to any one of claims 1 to 12,
The optical path splitting optical means reflects one of the part to be the incident image-forming light beam and the part to be the reflective image-forming light beam and allows the other to pass therethrough, so that the optical paths of these two image-forming light beams are passed. A projection optical system that performs separation. The projection optical system according to claim 13,
A projection optical system in which the optical path separating optical means includes a polarized light combining means, a polarized light separating means, and a retardation plate. A projection device comprising the projection optical system according to claim 1. An imaging device, which is equipped with the projection optical system according to any one of claims 1 to 14, and which captures an image formed on the reduction side of an object on the enlargement side by an imaging means.

Images