JP7510149B2 - Projection optical system, projector and imaging device - Google Patents

Description

The present invention relates to a projector device and a projection optical system used therein, and further to an imaging device using the projection optical system.

Various reflective projector devices have been proposed in the past that enlarge the projection screen while reducing the projection space. For example, Patent Documents 1 and 2 show a projection optical system for a projector device in which a first optical system made of a refractive optical system and a second optical system including a reflective surface are arranged from an image display element (light valve) toward the projection screen, that is, from the reduction side toward the enlargement side. This type of projection optical system is often configured to include a moving optical system within the refractive optical system that moves in a direction along the main optical axis of the refractive optical system for focusing (focus adjustment) and magnification (zoom).

Recently, there has been a growing demand for larger projection screens, and for this reason, it is desirable for the above-mentioned projection optical system to be able to effectively reduce the occurrence of aberrations even when the magnification is changed, making it possible to project large, high-quality images.

JP 5145486 A Patent No. 5728202

However, the projection optical system used in conventional reflective projector devices still has room for improvement in terms of reducing the occurrence of aberrations that accompany changes in magnification.

The present invention has been made in consideration of the above circumstances, and aims to provide a projector device that can effectively reduce the occurrence of aberrations that accompany changes in magnification, and a projection optical system that can realize such a projector device.

The projection optical system according to the present invention comprises:
A projection optical system that projects a reduced-side image onto an enlarged-side projection surface,
a lens optical system including a plurality of lenses, which forms a first intermediate image and a second intermediate image in this order toward the enlargement side by light incident from the reduction side;
a concave mirror that reflects the second intermediate image;
the lens optical system forms a first intermediate image therein and includes one or more variable magnification groups therein;
a first variable power group among the variable power groups includes a lens adjacent to the enlarged side of the first intermediate image;
It is characterized by the above.

It is desirable that the first variable power group includes a lens disposed on the reduction side of the first intermediate image and adjacent to the first intermediate image.
In this case, the projection optical system further includes a second magnification variable group and a stop disposed on the reduction side of the first intermediate image,
the second variable power group includes a lens adjacent to the stop;
It is desirable.

the lens optical system further includes a third variable power group having a negative power between the second variable power group and the first variable power group,
the second magnification varying group has positive power,
the third zoom group is disposed adjacent to the enlargement side of the second zoom group;
It is desirable.

In addition, in the projection optical system according to the present invention, when changing the magnification from the wide-angle end to the telephoto end, it is desirable that the second variable magnification group moves from the reduction side to the enlargement side, and the third variable magnification group moves from the reduction side to the enlargement side.

In the projection optical system according to the present invention,
The lens optical system includes a plurality of focusing groups,
a fourth zoom group is disposed between the first zoom group and the third zoom group;
This fourth variable magnification group also serves as the first focusing group that moves during focusing.
It is desirable.

Furthermore, it is desirable that a second focusing group be adjacent to the enlargement side of the first zoom group.

the lens surface on the enlargement side of the first focusing group has a convex surface on the enlargement side,
the reduction-side lens surface of the second focusing group has a convex surface on the reduction side;
It is desirable.

the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 1 which is a meniscus lens having a concave lens surface on the reduction side, and a lens 2 which has a concave lens surface on the enlargement side.
The radius of curvature (1R2) of the lens surface on the reduction side of lens 1 and the radius of curvature (2R1) of the lens surface on the enlargement side of lens 2 are expressed by the following formula 1.
0.55 <|1R2|/|2R1|< 1.00 ... Formula 1
It is desirable that the following is satisfied.

When so configured, the first subgroup further includes a series of lenses 3 arranged on the enlargement side of the lens 2, the lenses having a convex shape on the reduction side;
The radius of curvature (1R1) of the lens surface on the enlargement side of the lens 1 and the radius of curvature (3R2) of the lens surface on the reduction side of the lens 3 are expressed by the following formula 2.
0.5 <|1R1|/|3R2|< 6.0 ... Formula 2
It is desirable that the following is satisfied.

The first variable magnification group is made up of a first subgroup and a second subgroup arranged on the reduction side and the enlargement side of the first intermediate image, respectively.
The first small group includes, in order from the reduction side, a lens 2 having a concave lens surface on the enlargement side and a lens 3 having a convex lens surface on the reduction side.
The radius of curvature (2R1) of the lens surface on the enlargement side of the lens 2 and the radius of curvature (3R2) of the lens surface on the reduction side of the lens 3 are expressed by the following formula 3.
0.30 <|2R1|/|3R2|< 0.70 ... formula 3
It is desirable that the following is satisfied.

the first zoom group comprises a first subgroup and a second subgroup arranged on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 1 which is a meniscus lens having a concave lens surface on the reduction side, and a lens 2 which has a concave lens surface on the enlargement side.
The refractive index of lens 1 (L1nd) and the refractive index of lens 2 (L2nd) are expressed by the following formula 4.
0.3<L2nd - L1nd ... Equation 4
It is desirable that the following is satisfied.

the first zoom group comprises a first subgroup and a second subgroup arranged on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 2 having a concave lens surface on the enlargement side and a lens 3 having a convex lens surface on the reduction side.
The Abbe number of lens 2 (L2νd) and the Abbe number of lens 3 (L3νd) are expressed by the following formula 5.
10.0 < L3νd - L2νd ... formula 5
It is desirable that the following is satisfied.

In the projection optical system of the present invention, the focal length f5 of the first variable magnification group and the focal length fw of the entire projection optical system at the wide-angle end are expressed by the following formula 6:
15.0<|f5|/|fw|<20.0 ... Equation 6
It is desirable that the following is satisfied.

In the projection optical system of the present invention, the first variable magnification group comprises a first subgroup and a second subgroup arranged on the reduction side and the enlargement side of the first intermediate image, respectively;
The focal length f5-1 of the first subgroup and the focal length f5-2 of the second subgroup are expressed by the following formula 7.
2.0 < |f5-1|/|f5-2| < 7.0 ... Equation 7
It is desirable that the following is satisfied.

The projection optical system of the present invention further comprises:
a fixed group on the magnification side of the plurality of variable magnification groups;
The fixed group has a triplet lens on the most magnifying side, which is made up of three lenses cemented together.
The three lenses are, from the reduction side, a negative lens, a positive lens, and a negative lens.
It is desirable.

The focal length f7 of the fixed group and the focal length f8 at the wide-angle end of the lens optical system are expressed by the following formula 8.
1.0 < |f7|/|f8| < 2.5 ... Equation 8
It is desirable that the following is satisfied.

The focal length (f) of the triplet of the fixed group and the focal length fw of the entire projection optical system at the wide-angle end are expressed by the following formula 9:
10.0 < |f junction|/|fw| < 25.0 ... Equation 9
It is desirable that the following is satisfied.

The triplet cemented lens in the fixed group is preferably the lens element located on the most magnifying side of the lens optical system.

The projection optical system of the present invention further comprises:
It has multiple magnification variable groups,
The magnification variable group that has the largest ratio of change in focal length of the entire system (f ratio) when each of these magnification variable groups is moved individually from the wide-angle end to the telephoto end is defined as a variator group Vrg, and the remaining magnification variable groups are defined as compensator groups cng. When the focal length of the entire system at the wide-angle end is 1, the amount of change Δcng is the f ratio of the compensator group cng minus 1, the sum of Δcng is sum Δcng, and the ratio of change in focal length during magnification change of the entire projection optical system (zoom ratio) is Zr. Then, sum Δcng and Zr are expressed by the following formula 10.
|sum Δcng|/|Zr| < 0.03 ... Equation 10
It is desirable that the following is satisfied.

The projection optical system of the present invention further comprises:
an optical element having an entrance surface and an exit surface is provided between the lens optical system and the concave mirror;
the lens optical system forms a second intermediate image by focusing the light emitted from the lens optical system on the reduction side of the concave mirror;
The second intermediate image is formed so as to incline toward the reduction side as the image height increases,
At least a portion of the imaging is performed between the exit surface of the optical element and the concave mirror.
It is desirable.

On the other hand, one projector device according to the present invention is equipped with an image display element on the reduction side of the projection optical system of the present invention described above.

The imaging device according to the present invention is also provided with an imaging element at a position that corresponds to the image formation position on the reduction side when light rays are incident from the enlargement side of the projection optical system of the present invention described above.

The projection optical system according to the present invention is configured so that the first variable magnification group, which includes the lens adjacent to the enlarged side of the first intermediate image, moves during magnification. This makes it possible to cause light rays with narrow beam widths, in which the chief rays are separated, to enter the first variable magnification group, and which invert and diverge after imaging. This makes it possible to perform magnification changes with suppressed fluctuations in off-axis aberrations.

In a preferred embodiment, when the first variable magnification group further includes a lens adjacent to the reduction side of the first intermediate image, the lenses in the first variable magnification group that sandwich the intermediate image move together as the same variable magnification group. This allows lenses with high ray heights for the incoming and outgoing light to be used for magnification, which is more advantageous for aberration correction.

In addition, in the preferred embodiment, the lenses sandwiching the first intermediate image are moved as one group, and the space in which the first intermediate image is formed can be sealed by the lenses and lens frame, making it difficult for dirt and dust to get in, thereby making it possible to suppress the reflection of dirt, etc. In other words, if dirt adheres to the lens surface near the position where the first intermediate image is formed, the dirt may be imaged on the projection screen or imaging surface, but this can be prevented.

In addition, the projector device according to the present invention uses a projection optical system that achieves the above-mentioned effects, and therefore can effectively reduce the occurrence of off-axis aberrations that accompany changes in magnification. This also applies to the imaging device according to the present invention.

1 is a cross-sectional view showing the lens configuration of the projection optical system of Example 1 together with the main light beams, in which the upper and lower sides show the states where the magnification variable system is at the wide-angle end and the telephoto end, respectively. FIG. 1 is a diagram showing basic data of optical elements constituting the projection optical system of Example 1. FIG. 1 is a diagram showing aspheric data of optical elements constituting the projection optical system of Example 1. FIG. 1 is a diagram showing free-form surface data of optical elements constituting the projection optical system of Example 1. FIG. 13 is a diagram showing the amount of change in surface spacing of each part in the projection optical system of the first embodiment. FIG. 1 is a diagram showing numerical values related to the focal length of each part in the projection optical system of the first embodiment. FIG. 1 is a diagram showing the focal lengths of the various parts of the projection optical systems of Examples 1 to 3. FIG. 1 is a diagram showing values of formulas 1 to 10 in the projection optical systems of Examples 1 to 3. Graph showing lateral aberration at the wide-angle end of the projection optical system of Example 1 Graph showing lateral aberration at the telephoto end of the projection optical system of Example 1 Graph showing lateral aberration at near point projection of the projection optical system of Example 1 Graph showing lateral aberration when the projection optical system of Example 1 projects a desired point 11 is a cross-sectional view showing the lens configuration of the projection optical system of Example 2 together with the main light beams, in which the upper and lower sides show the states where the magnification variable system is at the wide-angle end and the telephoto end, respectively. FIG. 11 is a diagram showing basic data of optical elements constituting a projection optical system according to a second embodiment of the present invention; FIG. 13 is a diagram showing aspheric data of optical elements constituting the projection optical system of Example 2. FIG. 13 is a diagram showing free-form surface data of optical elements constituting the projection optical system of Example 2. FIG. 11 is a diagram showing the amount of change in surface spacing of each part in the projection optical system according to the second embodiment. FIG. 11 is a diagram showing numerical values related to the focal length of each part in the projection optical system of the second embodiment. Graph showing lateral aberration at the wide-angle end of the projection optical system of Example 2 Graph showing lateral aberration at the telephoto end of the projection optical system of Example 2 Graph showing lateral aberration at near point projection of the projection optical system of Example 2 Graph showing lateral aberration when the projection optical system of Example 2 projects a desired point 11 is a cross-sectional view showing the lens configuration of the projection optical system of Example 3 together with the main light beams, in which the upper and lower sides show the states where the magnification variable system is at the wide-angle end and the telephoto end, respectively. FIG. 13 is a diagram showing basic data of optical elements constituting the projection optical system of Example 3. FIG. 13 is a diagram showing aspheric data of optical elements constituting the projection optical system of Example 3. FIG. 13 is a diagram showing free-form surface data of optical elements constituting the projection optical system of Example 3. FIG. 13 is a diagram showing the amount of change in surface spacing of each part in the projection optical system according to the third embodiment. FIG. 13 is a diagram showing numerical values related to the focal length of each part in the projection optical system of the third embodiment. Graph showing lateral aberration at the wide-angle end of the projection optical system of Example 3 Graph showing lateral aberration at the telephoto end of the projection optical system of Example 3 Graph showing lateral aberration at near point projection of the projection optical system of Example 3 Graph showing lateral aberration when the projection optical system of Example 3 projects a desired point 11 is a cross-sectional view showing the lens configuration of a projection optical system according to a fourth embodiment together with the main light beams, in which the upper and lower sides show the states where the magnification variable system is at the wide-angle end and the telephoto end, respectively. FIG. 13 is a diagram showing basic data of optical elements constituting a projection optical system according to a fourth embodiment. Diagram explaining the position of lateral aberration measurement

The embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of a projection optical system 100 according to one embodiment of the present invention together with the main light beam. This projection optical system 100 is basically composed of a lens optical system G8 and a reflection optical system G9. In FIG. 1, the state in which the lens optical system G8 is at the wide-angle end is shown in the upper part with the notation WIDE, and the state in which the lens optical system G8 is at the telephoto end is shown in the lower part with the notation TELE. In the upper figure, the approximate position of the optical axis Z from the lens optical system G8 to the concave mirror 5 of the reflection optical system G9 is shown by a dashed line. This cross-sectional view is a cross-sectional view of the projection optical system 100 cut along a plane including the optical path of the main ray of the light beam emitted from the center of the effective projection area of the image display surface 1 of the image display element 2 until it reaches the projection screen.

1, the chief ray (near end chief ray) R0 of the light emitted from the position closest to the optical axis Z of the image display surface 1 of the image display element 2 is shown by a dashed line. Above and below this chief ray R0, upper and lower rays are shown by solid lines, which are emitted from the same position as the chief ray R0 and indicate the spread of light emitted at an angle to the chief ray R0. Furthermore, the chief ray R1 of the light emitted from the projection effective area end (the lower end in the figure) of the image display surface 1 is shown by a dashed line, and the upper and lower rays relative to this chief ray R1 are also shown by solid lines. The position where the above chief ray, upper ray, and lower ray intersect is the imaging position, and the first intermediate image IM1 and the second intermediate image IM2 described later are imaged at this position. The above-mentioned methods of displaying the principal rays R0 and R1, as well as the upper and lower rays, are the same in Figures 13, 23, and 33, which will be described later.

In FIG. 1, the image display surface 1 side of the image display element 2 is the reduction side, and the final lens L20 side of the lens optical system G8 is the enlargement side. In the following, the positions within the lens optical system may be described as the enlargement side being the front and the reduction side being the rear, taking into account the traveling direction of the light beam. The projection optical system 100 shown in FIG. 1 corresponds to Example 1, which will be described later.

This projection optical system 100 can be used, for example, mounted in a projector device to project an image displayed on an image display surface 1 of an image display element (light valve) 2, such as a DMD, a transmissive liquid crystal display device, or a reflective liquid crystal display device, onto a screen. In FIG. 1, the image display surface 1 of the image display element 2 is also shown, assuming that the projection optical system 100 is mounted in a projector device.

In the above projector device, a light beam emitted from a light source (not shown) and then given image information on the image display surface 1 is incident on a lens optical system G8 including a refractive optical system through a glass block 3, and a first intermediate image IM1 is formed in the lens optical system G8. The light beam is incident on a concave mirror 5 through a prism 4 from the lens optical system G8, and the first intermediate image IM1 is further imaged as a second intermediate image IM2 between the prism 4 and the concave mirror 5. The second intermediate image IM2 is reflected and enlarged by a reflection optical system G9 consisting of a concave mirror 5, and is enlarged and projected as a projected image on a screen (not shown). Note that in the lens configuration diagrams of FIG. 1 and FIGS. 13, 23, and 33 described later, only the approximate positions of the first intermediate image IM1 and the second intermediate image IM2 are shown (solid line straight lines). The first intermediate image IM1 and the second intermediate image IM2 are real images that are tilted (inclined) toward the rear (reduction side) as they move away from the principal ray R0. The glass block 3 is a color synthesis prism such as a dichroic prism or a TIR prism.

As shown in FIG. 1, the projection optical system 100 is configured by arranging an image display element 2, a glass block 3, a lens optical system G8, a prism 4, and a reflection optical system G9 in that order from the reduction side to the enlargement side. The lens optical system G8 is configured by arranging, in that order from the reduction side to the enlargement side, a first fixed group G1, a magnification group G2, a magnification group G3, a magnification group G4 that also acts as a focusing group (focus group, first focusing group), a magnification group G5, a second focusing group G6 that acts as a focusing group, and a second fixed group G7. Of these lens groups G1 to G7, some groups are moved in the optical axis direction for magnification or focusing, but the drive mechanisms for this are not shown.

The first fixed group G1 is composed of a biconvex lens L1 having positive refractive power (hereinafter simply referred to as "positive"). The variable magnification group G2 is composed of a meniscus lens L2 having negative refractive power (hereinafter simply referred to as "negative"), a positive biconvex lens L3 cemented to the meniscus lens L2, a negative meniscus lens L4 cemented to the lens L3, a positive biconvex lens L5 with aspheric surfaces on both sides, a negative meniscus lens L6, and a positive biconvex lens L7, which are arranged in order from the reduction side to the enlargement side along the optical axis Z.

Note that optical elements such as lenses L1 to L7 that are rotationally symmetric may be positioned with the center of rotational symmetry away from the optical axis Z. The center of such optical elements is on the principal ray R0, which is a straight extension of the optical axis of the image display element 2. The above explanation of "positioned in order from the reduction side to the enlargement side along the optical axis Z" also includes this.

The magnification group G2 is the second magnification group in the present invention, and between the negative meniscus lens L6 and the positive biconvex lens L7 that constitute part of it, a first field stop FS1, an aperture stop AS, and a second field stop FS2 are arranged, in order from the reduction side. The magnification group G3 is the third magnification group in the present invention, and is composed of a negative meniscus lens L8 and a positive biconvex lens L9, in order from the reduction side. The magnification group G4 is the fourth magnification group in the present invention, and is composed of one positive meniscus lens L10.

The magnification variable group G5 is the first magnification variable group in the present invention, and is composed of a first subgroup G5-1 and a second subgroup G5-2 arranged on the reduction side and the enlargement side, respectively, of the first intermediate image IM1. The first subgroup G5-1 is composed of, from the reduction side, a negative meniscus lens L11 whose lens surface on the reduction side is concave and both surfaces are aspheric, a negative meniscus lens L12 whose lens surface on the enlargement side is concave, and a positive biconvex lens L13. On the other hand, the second subgroup G5-2 is composed of, from the reduction side, a negative biconcave lens L14 and a positive meniscus lens L15.

The second focusing group G6 is composed of a positive meniscus lens L16, both of which have free-form surfaces. The second fixed group G7 is composed of, from the reduction side, a positive biconvex lens L17, both of which have aspheric surfaces, a negative meniscus lens L18, a positive biconvex lens L19 cemented to this lens L18, and a negative meniscus lens L20 cemented to this lens L19.

Of the variable magnification groups described above, variable magnification group G2 basically acts as a so-called variator (variable magnification system) that changes the magnification, while variable magnification groups G3, G4, and G5 act as so-called compensators (correction systems) that correct the focus position shift that occurs with magnification.

Next, detailed data of the components in Example 1 according to the embodiment of the present disclosure will be described with reference to FIGS. 2 to 8. First, FIG. 2 shows basic data of the components. In the basic data in FIG. 2, the surface number column shows the surface numbers that increase sequentially toward the enlargement side, with the surface of the component on the most reduced side being numbered 0. Aspheric surfaces of each surface number are marked with *, and free-form surfaces are marked with parentheses (). "OBJ" at the top of the element column indicates the surface of the image displayed on the image display surface 1 of the image display element (light valve) 2, and "IMG" at the bottom indicates the surface of the projected image that is enlarged and projected onto the projection screen. The column for radius of curvature R shows the paraxial radius of curvature of each surface. The sign of the radius of curvature R is positive when the surface shape is convex toward the reduction side, and negative when the surface shape is convex toward the enlargement side. The column for distance shows the distance in the optical axis direction on the optical axis Z between the surface with the surface number and the surface with the next surface number. This value is the value when the projection optical system 100 is set to the wide-angle end, and the value in the optical path from the reduction side toward the concave mirror 5 is treated as a positive value, and the value in the optical path folded back by the concave mirror 5 is treated as a negative value. The value of the effective diameter is twice the effective image height. The above radius of curvature R, interval, and effective diameter are all in mm. The refractive index nd column shows the refractive index of each optical element with respect to the d line (wavelength 587.6 nm), and the Abbe number νd column shows the Abbe number of each optical element with respect to the d line.

Figure 3 shows data relating to aspheric surfaces, including the surface number and aspheric coefficients of the aspheric surface. If X is the coordinate in the optical axis direction, Y is the coordinate perpendicular to the optical axis, the light traveling direction is positive, and Rdy is the paraxial radius of curvature, then the shape of the aspheric surface can be expressed by the following equation using the coefficients Rdy, K, and ARi (i = 3 to 6, 8, 10, 12) shown in Figure 3. Note that "en" means "10 to the nth power."
X = (1/Rdy) ^Y2 /[1+{1-(1+K)(1/Rdy) ^2Y } ^1/2
+ ^ΣARiYi

Fig. 4 shows data on the free curved surfaces with surface numbers 38 and 39. The shape of the free curved surface is expressed by using the coefficients shown in Fig. 4 to define the sag amount Z at coordinates (X, Y) in the following formula (1), which is a polynomial of degree 1 up to ten. In this case, the coordinates (X, Y) are the coordinates in two mutually orthogonal directions in a plane perpendicular to the optical axis, that is, the short side direction and the long side direction of the image display element 2, and (m+n)≦10. Additionally, c is the vertex curvature, k is the conic constant, and Cj is a coefficient of ^the monomial ^XmYn .

Figure 5 shows the surface spacing values (all units are mm) that change depending on the magnification and focus state of the projection optical system 100. In this table, Z1 indicates the case where the projection optical system 100 is set at the wide-angle end and near-point projection (when projected to the closest position within the focus range), Z2 indicates the case where the projection optical system 100 is set at the telephoto end and near-point projection, Z3 indicates the case where the projection optical system 100 is set at the wide-angle end and far-point projection (when projected to the farthest position within the focus range), and Z4 indicates the case where the projection optical system 100 is set at the telephoto end and far-point projection. Here, as with the spacing values in Figure 3, the value in the optical path from the reduction side toward the concave mirror 5 is treated as a positive value, and the value in the optical path folded back by the concave mirror 5 is treated as a negative value. "EFL" in this table indicates the focal length of the entire system of the projection optical system 100 in each magnification and focus state. In this table, the value in the column with a number added to "s" such as s0 and s7 indicates the surface spacing for the surface with the surface number indicated by the number.

Next, FIG. 6 shows data related to the focal lengths of the main magnification groups, namely, the magnification group G2 that acts as the variator (magnification system) mentioned above, and the magnification groups G3, G4, and G5 that act as compensators (correction systems). Here, the magnification groups G3, G4, and G5, which are arranged from the reduction side to the enlargement side, are shown with the names Compensator 1, Compensator 2, and Compensator 3 added, respectively. FIG. 6 also shows other data related to the focal lengths, as will be described later.

In the "focal length" shown in FIG. 6, "WIDE fw" indicates the focal length fw of the projection optical system 100 in the wide-angle end state, and also indicates the focal length of the entire projection optical system 100 after each of the variable magnification groups G2 to G5 is moved from that state individually. "f ratio" indicates the ratio of the focal length that changes before and after the movement of each of the variable magnification groups G2 to G5. "Change amount" indicates the value obtained by subtracting 1 from the f ratio when the focal length fw of the projection optical system 100 in the wide-angle end is set to 1. "Change rate" indicates the ratio between the "change amount" when all the variable magnification groups are moved to change magnification, and the "change amount" when each of the variable magnification groups G2 to G5 is moved individually. In other words, Change rate={(focal length of the projection optical system 100 after change)/(fw-1)}/(zoom ratio-1)
The zoom ratio is the ratio of the change in focal length during magnification change of the projection optical system 100. In this embodiment 1, the zoom ratio Zr is 1.20, and this is the same in embodiments 2 and 3 described below.

As mentioned above, the magnification variable groups G3, G4 and G5 act as compensators. Therefore, these groups are regarded as compensator groups cng, and when the focal length of the entire system at the wide-angle end is 1, the value obtained by subtracting 1 from the f-ratio of the compensator group cng is shown as the amount of change Δcng. Furthermore, the sum of Δcng (the sum of the values in the magnification variable groups G3 to G5) is shown as sum Δcng, and the zoom ratio is shown as Zr. The values of |sum Δcng| and |sum Δcng|/|Zr| are shown in Figure 6.

Data corresponding to the data of Example 1 shown in Figures 2, 3, 4, 5, and 6 described above is shown in Figures 14, 15, 16, 17, and 18 for Example 2, and in Figures 24, 25, 26, 27, and 28 for Example 3. The method of displaying the corresponding data is the same as that described for Figures 2 to 6, so duplicated explanations for Examples 2 and 3 will be omitted.

Next, FIG. 7 shows the focal lengths of lens groups G1 to G8 and reflection optical system G9 when the projection optical system 100 is at the wide-angle end. In this Example 1 and in Examples 2 and 3 described below, a cemented lens made of three lenses cemented together is used in the second fixed group G7, so the focal length of this cemented lens is also shown. FIG. 7 also shows the focal lengths fw, ft of the projection optical system 100 when it is at the wide-angle end and the telephoto end. FIG. 7 also shows the focal length data for the projection optical system 200 of Example 2 and the projection optical system 300 of Example 3 described below.

The configuration of the main parts in this embodiment and the effects of the configuration will be described in detail below. First, the magnification group G5 in the lens optical system G8 will be described in detail. As described above, this magnification group G5 is the first magnification group in the present invention, and is composed of a first subgroup G5-1 and a second subgroup G5-2 arranged on the reduction side and the enlargement side of the first intermediate image IM1, respectively. The first subgroup G5-1 is composed of three lenses including a lens L13 adjacent to the first intermediate image IM1. On the other hand, the second subgroup G5-2 is composed of two lenses including a lens L14 adjacent to the first intermediate image IM1. By configuring the magnification group G5 to include the second subgroup G5-2 as described above and move during magnification, it is possible to make the light beam, which has a narrow light beam width while the principal ray is separated and which is inverted and diverged after image formation, incident on the magnification group G5, thereby making it possible to change magnification while suppressing the fluctuation of off-axis aberrations.

In this embodiment, the zoom group G5 is configured to further include the first small group G5-1 as described above and move during zooming, so that the lenses sandwiching the first intermediate image IM1 move together as the same zoom group. Therefore, lenses with high ray heights for the incident and outgoing light can be used for zooming, which is more advantageous for aberration correction. Furthermore, in this case, by moving the lenses sandwiching the first intermediate image IM1 as one group, the space in which the first intermediate image IM1 is formed can be sealed with the lenses and the lens frame, making it difficult for dirt and dust to enter, and thus making it possible to suppress the reflection of dirt, etc. In other words, if dirt adheres to the lens surface near the imaging position of the first intermediate image IM1, the dirt may be imaged on the projection screen or the imaging surface, but this can be avoided.

Lens optical system G8 also has a magnification group G2 and two field stops FS1, FS2 and an aperture stop AS arranged on the reduction side of the first intermediate image IM1, and the magnification group G2 includes lenses L6 and L7 adjacent to those stops. With this configuration, the magnification group can include a group in which the light beam is separated and a lens group in which it is not separated. This makes it possible to effectively correct off-axis aberrations and on-axis aberrations that occur with magnification. Incidentally, the field stop and aperture stop do not always have to be configured as in this embodiment, and can be increased or decreased, omitted, or added depending on the design. If there is no need to use two field stops, one of them can be omitted.

In addition, in lens optical system G8, the magnification group G2 has positive power, and a magnification group G3 having positive power is arranged adjacent to the magnification group G2 between the magnification group G2 and the magnification group G5. By reversing the power of the magnification group G2 and the magnification group G3 in this way, it becomes possible to compensate for the fluctuation in optical performance (field curvature) caused by the excessive change in focal length by the magnification group G2 with the magnification group G3.

In this embodiment, in the above configuration, when changing magnification from the wide-angle end to the telephoto end, the magnification group G2 moves from the reduction side to the enlargement side, and the magnification group G3 moves from the reduction side to the enlargement side. In this way, by moving the magnification group G2 as a variator and the magnification group G3 as a compensator in the same direction with the signs of their powers reversed, it is possible to reduce the occurrence of aberrations (field curvature) while ensuring the amount of movement of the magnification group G2.

Lens optical system G8 also includes multiple focusing groups, namely the first focusing group and the second focusing group described below. That is, lens optical system G8 has magnification group G2, magnification group G3, magnification group G4, and magnification group G5 arranged from the reduction side to the enlargement side, with magnification group G4 also acting as a focusing group (first focusing group). The second focusing group G6 is made up of a lens group that is fixed when magnifying and is arranged adjacent to the enlargement side of magnification group G5.

As described above, the focusing group G4 is positioned close to the variable magnification group G5 that contains the first intermediate image IM1, and at a position on the reduction side of the first intermediate image IM1, so that off-axis aberrations and on-axis aberrations that occur in the lens system on the reduction side of the first intermediate image IM1 can be effectively corrected. In addition, fluctuations in optical performance (field curvature) that occur in the lens system on the reduction side of the first intermediate image IM1 during magnification can also be effectively corrected.

Furthermore, in this embodiment, the second focusing group G6 is positioned close to the magnification group G5 that contains the first intermediate image IM1 and at a position on the enlargement side of the first intermediate image IM1, so that off-axis aberrations and on-axis aberrations that occur in the lens system on the enlargement side of the first intermediate image IM1 can be effectively corrected. Also, fluctuations in optical performance (field curvature) that occur in the lens system on the enlargement side of the first intermediate image IM1 during magnification can be effectively corrected.

In addition, in this embodiment, the lens surface on the enlargement side of the first focusing group G4 (the lens surface of lens L10) has a convex surface on the enlargement side, and the lens surface on the reduction side of the second focusing group G6 (the lens surface of lens L16) has a convex surface on the reduction side. By facing the convex surfaces of the two focusing groups G4 and G6 towards each other in this way, the aberrations that occur in each group can be cancelled out.

The first subgroup G5-1 of the magnification group G5 includes, from the reduction side, a lens 1 (lens L11) made of a meniscus lens with a concave lens surface on the reduction side, and a lens 2 (lens L12) with a concave lens surface on the enlargement side. The radius of curvature (1R2) of the reduction-side lens surface of the lens 1 and the radius of curvature (2R1) of the enlargement-side lens surface of the lens 2 satisfy the formula 1.
0.55 <|1R2|/|2R1|< 1.00 ... Formula 1
That is, in Example 1, 1R2 and 2R1 are the radii of curvature of the surfaces No. 27 and No. 30 shown in Fig. 2, which are -34.747 mm and 40.194 mm, respectively, so the value of |1R2|/|2R1| is 0.864.

In addition to the values of the formulas where the above formula 1 specifies the lower and upper limits, Figure 8 also shows the values of the formulas where the below-described formulas 2 to 10 specify the lower and/or upper limits. Figure 8 also shows similar values for Example 2 and Example 3.

The lens surface on the reduction side of lens 1 (lens L11)1 and the lens surface on the enlargement side of lens 2 (lens L12) are shaped as described above and both produce a diverging effect, but because they satisfy formula 1, that is, because the radius of curvature 1R2 of lens L11, which has a concave shape, is relatively large (the curvature is gentle), the diverging power of this lens L11 is not excessively large. On the other hand, if |1R2| is large enough that the value of |1R2|/|2R1| is equal to or greater than the upper limit of 1.00, the diverging power becomes too strong, and the error sensitivity of the aspheric surface precision becomes high. On the other hand, if the value of |1R2|/|2R1| is small enough to be equal to or less than the lower limit of 0.55, the balance of coma aberration correction of the upper and lower rays of the peripheral image height becomes poor.

The first subgroup G5-1 further includes a lens 3 (lens L13) arranged on the enlargement side of the lens 2 (lens L12), the lens surface on the reduction side of which has a convex shape, and the radius of curvature (1R1) of the lens surface on the enlargement side of the lens 1 and the radius of curvature (3R2) of the lens surface on the reduction side of the lens 3 satisfy formula 2.
0.5 <|1R1|/|3R2|< 6.0 ... Formula 2
That is, in Example 1, 1R1 and 3R2 are the radii of curvature of the surfaces No. 28 and No. 31 shown in Fig. 2, respectively, which are -250.335 mm and 80.648 mm, and therefore the value of |1R1|/|3R2| is 3.104.

The lens surface on the enlargement side of lens 1 (lens L11)1 and the lens surface on the reduction side of lens 3 (lens L12) both produce a convergence effect, but if the value of |1R1| is small enough that |1R1|/|3R2| is equal to or less than the lower limit of 0.5, the lens system near the first intermediate image IM1 can be reduced, but the error sensitivity of the aspheric surface precision increases. On the other hand, if the value of |1R1| is large enough that |1R1|/|3R2| is equal to or greater than the upper limit of 6.0, the balance of coma aberration correction for the upper and lower rays at the peripheral image height becomes poor.

The first small group G5-1 further includes a lens 2 (lens L12) having a concave lens surface on the enlargement side, and a lens 3 (lens L13) having a convex lens surface on the reduction side and arranged on the enlargement side of the lens 2 (lens L12). The radius of curvature (2R1) of the lens surface on the enlargement side of the lens 2 and the radius of curvature (3R2) of the lens surface on the reduction side of the lens 3 satisfy formula 3.
0.30 <|2R1|/|3R2|< 0.70 ... formula 3
That is, in Example 1, 2R1 and 3R2 are the radii of curvature of the surfaces No. 29 and No. 30 shown in Fig. 2, which are 40.194 mm and 80.648 mm, respectively, so the value of |2R1|/|3R2| is 0.498.

The lens surface on the enlargement side of lens 2, which has the above-mentioned shape, has a diverging effect, and the lens surface on the reduction side of lens 3, which has the above-mentioned shape, has a converging effect to complement the aberration, so it is desirable that the difference between the values of |2R1| and |3R2| is small. If the value of |2R1| is so small that the value of |2R1|/|3R2| is equal to or less than the lower limit of 0.30, the diverging force becomes too strong, and the maximum lens system near the first intermediate image IM1 becomes large. On the other hand, if the value of |2R1| is so large that the value of |2R1|/|3R2| is equal to or more than the upper limit of 0.70, the diverging force becomes too weak, making it difficult to complement the positive aberration occurring on the lens surface on the reduction side of lens 3.

The first small group G5-1 includes, in order from the reduction side, a lens 1 (lens L11) made of a meniscus lens with a concave lens surface on the reduction side, and a lens 2 (lens L12) with a concave lens surface on the enlargement side. The refractive index of the lens 1 (L1nd) and the refractive index of the lens 2 (L2nd) satisfy the formula 4.
0.3<L2nd - L1nd ... Equation 4
That is, in the first embodiment, L2nd and L1nd are the refractive indices of the lenses 12 and 11 shown in FIG. 2, which are 1.892860 and 1.509172, respectively, so that the value of L2nd-L1nd is 0.384.

By defining the relationship between the refractive indices of lens 1 and lens 2 as in formula 4, the refractive index L2nd of lens 2 can be set high and the refractive index L1nd of lens 1 can be set low, so that even if the power of lens 1 becomes weak, it can be compensated for by lens 2. This increases the design freedom of lens 1. As a result, it becomes possible to mold lens 1 from plastic, and an aspheric lens can be arranged as lens 1.

The first small group G5-1 further includes a lens 2 (lens L12) whose enlargement-side lens surface is concave, and a lens 3 (lens L13) whose reduction-side lens surface is convex and arranged on the enlargement side of the lens 2 (lens L12). The Abbe number (L2νd) of the lens 2 and the Abbe number (L3νd) of the lens 3 satisfy formula 5.
10.0 < L3νd - L2νd ... formula 5
That is, in Example 1, L2nd and L1nd are the Abbe numbers of lenses 12 and 13 shown in Figure 2, respectively, which are 20.3614 and 74.7020, so the value of L3νd - L2νd is 54.341. When the difference between the Abbe number (L3νd) of lens 3 and the Abbe number (L2νd) of lens 2 is so small as to be equal to or less than the lower limit of 10.0, the balance of the correction of lateral chromatic aberration is likely to be lost.

In the first embodiment, the focal length f5 of the first magnification variable group G5 as the first magnification variable group and the focal length fw of the entire projection optical system satisfy the formula (6) when the projection optical system 100 is at the wide-angle end.
15.0<|f5|/|fw|<20.0 ... Equation 6
That is, in the first embodiment, as shown in FIG. 7, f5=81.696 mm and fw=-4.524 mm, so the value of |f5|/|fw| is 18.058.

When the value of |f5|/|fw| is small enough to be below the lower limit of 15.0, i.e., when the refractive power of the variable magnification group G5 is large, the lenses in the intermediate portion of the lens optical system G8 can be made smaller, resulting in cost reduction effects, but the occurrence of coma aberration and the like increases. On the other hand, when the value of |f5|/|fw| is large enough to be above the upper limit of 20.0, i.e., when the refractive power of the variable magnification group G5 is small, the diameter of the intermediate portion of the lens optical system G8 becomes large, the imaging position of the first intermediate image IM1 becomes farther away, and the overall length of the lens optical system G8 also becomes longer.

The focal length f5-1 of the first subgroup G5-1 and the focal length f5-2 of the second subgroup G5-2 satisfy the formula (7).
2.0 < |f5-1|/|f5-2| < 7.0 ... Equation 7
That is, in the first embodiment, as shown in FIG. 7, f5-1=741.785 mm and f5-2=122.163 mm, so the value of |f5-1|/|f5-2| is 6.072.

When the value of |f5-1|/|f5-2| is small enough to fall below the lower limit of 2.0, the lenses in the middle of the lens optical system G8 can be made smaller, resulting in cost reductions, but the occurrence of coma aberration and other aberrations increases. On the other hand, when the value of |f5-1|/|f5-2| is large enough to exceed the upper limit of 7.0, the diameter of the middle part of the lens optical system G8 becomes large.

In addition, in the lens optical system G8, the second fixed group G7 is arranged on the enlargement side of the multiple magnification groups G2 to G5 and the second focusing group G6, and a triplet lens consisting of three lenses L18, L19, and L20 is arranged on the most enlargement side of this second fixed group G7, and these lenses L18, L19, and L20 are, in order from the reduction side, a negative lens, a positive lens, and a negative lens. With this configuration, the enlargement side of the lens optical system G8 is a fixed group, so there is no need to move the lens group and the concave mirror 5 at a position with high tolerance sensitivity, making it easier to manufacture the projection optical system and also easier to control the deviation (eccentricity) of the lens position relative to the optical axis during manufacture. In other words, if the enlargement side of the lens optical system G8 is a moving group, a gap is required between the cam barrel and the fixed barrel to the extent that it can move, which becomes a cause of deviation as a backlash, but this embodiment makes it possible to avoid such a situation.

The focal length f7 of the second fixed group G7 and the focal length f8 of the entire lens optical system G8 at the wide-angle end satisfy the formula (8).
1.0 < |f7|/|f8| < 2.5 ... Equation 8
That is, in the first embodiment, as shown in FIG. 7, f7=29.478 mm and f8=-17.712 mm, so the value of |f7|/|f8| is 1.664.

When the value of |f7|/|f8| is small enough to fall below the lower limit of 1.0, the diameter of the concave mirror 5 can be made small, but coma aberration and curvature of field increase. On the other hand, when the value of |f7|/|f8| is large enough to exceed the upper limit of 2.5, the diameter of the concave mirror 5 increases, reducing manufacturability.

Moreover, the focal length (f cemented) of the triplet cemented lens of the second fixed group G7 and the focal length fw of the entire projection optical system at the wide-angle end satisfy Expression 9.
10.0 < |f junction|/|fw| < 25.0 ... Equation 9
That is, in Example 1, as shown in FIG. 7, f-junction=81.75 mm, and fw=-4.524 mm, so the value of |f-junction|/|fw| is 18.07.

When the value of |f-junction|/|fw| is small enough to fall below the lower limit of 10.0, in other words, when the power of the triplet cemented lens is too strong, the diameter of the concave mirror 5 can be made small, but the curvature of field increases. On the other hand, when the value of |f-junction|/|fw| is large enough to exceed the upper limit of 25.0, in other words, when the power of the triplet cemented lens is too weak, the diameter of the concave mirror 5 increases, reducing manufacturability.

The triplet cemented lens of the second fixed group G7 described above is also the lens element located on the most enlargement side of the lens optical system G8. This configuration makes it easier to manufacture the projection optical system, just as when the triplet cemented lens is located on the most enlargement side of the magnification group, and also makes it easier to control the deviation (decentering) of the lens position relative to the optical axis during manufacture.

Furthermore, the projection optical system 100 of this embodiment is provided with multiple magnification variable groups G2 to G5, and the magnification variable group G2 which is the magnification variable group having the largest ratio of change in focal length of the entire system (f ratio) when each of these magnification variable groups G2 to G5 is moved individually from the wide-angle end to the telephoto end is designated as the variator group Vrg, and the other magnification variable groups G3, G4 and G5 are designated as compensator groups cng. When the focal length of the entire system at the wide-angle end is designated as 1, the amount of change Δcng is the f ratio of the compensator group cng minus 1, the sum of Δcng is designated as sum Δcng, and the ratio of change in focal length during magnification of the entire projection optical system (zoom ratio) is designated as Zr, then sum Δcng and Zr satisfy equation 10.
|sum Δcng|/|Zr| < 0.03 ... Equation 10

In other words, in Example 1, as shown in Figure 6, the magnification group G2 with an f-ratio of 1.20 is the variator group Vrg, and the magnification groups G3, G4, and G5 with f-ratios of 0.97, 1.02, and 1.00, respectively, are the compensator group cng. The sum sum Δcng of the f-ratios of the magnification groups G3, G4, and G5, which are the compensator group cng, is 0.011, and since the zoom ratio Zr = 1.20, the value of |sum Δcng|/|Zr| is 0.009.

When the value of |sum Δcng|/|Zr| is large enough to exceed the upper limit of 0.03, the magnification load during zooming on the compensator group cng, which is made up of the variable magnification groups G3, G4, and G5, increases. This reduces the aberration correction capability of the compensator cng, and performance at intermediate zoom positions deteriorates.

In this embodiment, a prism 4, an optical element having an entrance surface and an exit surface, is disposed between the lens optical system G8 and the concave mirror 5. The lens optical system G8 forms a second intermediate image IM2 by imaging the light emitted from the lens optical system G8 on the reduced side of the concave mirror 8, and the second intermediate image IM2 is imaged so that it is tilted toward the reduced side as the image height increases, and at least a portion of the image is formed between the exit surface of the prism 4 and the concave mirror 5. As mentioned above, the second intermediate image IM2 shown by the solid straight line in Figure 1 indicates the imaging position, but in the figure, the second intermediate image IM2 that is actually imaged as described above is shown roughly as a dashed line extending from the solid straight line.

Here, Figures 9 to 12 respectively show the lateral aberration of the projection optical system 100 of Example 1. These Figures 9, 10, 11, and 12, proceeding from the smallest figure number to the largest figure number, show the results of measuring the lateral aberration when the projection optical system 100 is at the wide-angle end, when it is at the telephoto end, when projecting at a near point, and when projecting at a far point (units are mm). In each case, the lateral aberration was measured at five points 1 to 5 on the projection screen. These five points are labeled 1, 2, etc. from the bottom in the left-right center of each aberration diagram. The specific positions of these points 1 to 5 are positions where light reaches after passing through five coordinates (X, Y)=(0,-1.5), (0,-13.702), (7.2575,-1.5), (7.2575,-6.85) and (7.2575,-13.702) on the image display surface 1, where the positions in the direction perpendicular to the paper surface in FIG. 1 and the position in the up-down direction are respectively designated as X and Y, and the position of the optical axis Z is the origin. The positions on these coordinates correspond to points 1, 2, 3, 4 and 5 on the projection screen in the order of description. That is, each coordinate represents the aberration of the projection image projected on one half of the projection display surface in the X direction, and since the aberration of the projection image is symmetrical with respect to the center in the X direction, only one side is shown. The above coordinate positions are in mm. That is, the size of the image display surface 1 is 13.702 mm in the Y direction and 7.2575 x 2 = 14.515 mm in the X direction. Also, in Figure 35, points 1, 2, 3, 4, and 5 on the projection screen are shown as (1), (2), (3), (4), and (5) on relative coordinates (x, y) relative to the position farthest from the optical axis Z as "1."

Transverse aberration measurements were taken in the y and x directions, and the results are indicated with y-FAN and x-FAN. In this example, lens L16 is used, which has a lens surface with a free-form shape that is not rotationally symmetrical, so the measurement results are shown in this manner. However, since the image height is symmetrical in the left-right direction on the projection screen, only the right side of the above five points on the projection screen was measured. Transverse aberration measurements were also taken for light with wavelengths of 620.0 nm, 550.0 nm, and 460.0 nm, and the measurement results for each wavelength are distinguished by different line types on the graph.

As can be seen from Figures 9 to 12, lateral aberration is well suppressed. Similar aberration diagrams are shown in Figures 19 to 22 for the projection optical system 200 of Example 2, which will be described later, and in Figures 29 to 32 for the projection optical system 300 of Example 3, but the relationship between the state of the projection optical system when measuring the lateral aberration and the figure number is the same as above.

Next, a projection optical system 200 according to a second embodiment of the present invention will be described with reference to FIG. 13. In FIG. 13, elements equivalent to those in FIG. 1 described above are given the same numbers, and descriptions of these will be omitted unless particularly necessary (the same applies below). In the projection optical system 200 according to the second embodiment, the basic lens configuration of the lens optical system G8 is the same as that of the lens optical system G8 according to the first embodiment, and it is fundamentally different from the projection optical system 100 according to the first embodiment in that the prism 4 is omitted.

Basic data of the components in this Example 2 is shown in Figure 14. Data of Example 2 corresponding to each data of Example 1 shown in Figures 3, 4, 5 and 6 are shown in Figures 15, 16, 17 and 18, respectively. The method of obtaining and displaying this data is the same as that explained in Example 1. The results of measuring the lateral aberration of the projection optical system 200 in this Example 2 are shown in Figures 19, 20, 21 and 22. The method of obtaining and displaying this lateral aberration is also the same as that explained in Example 1.

As shown in FIG. 8, in Example 2, all of Equations 1 to 10 are satisfied. Therefore, the effects obtained by satisfying Equations 1 to 10 are obtained in the same way as in Example 1. Also, as shown in FIG. 19 to FIG. 22, it can be seen that lateral aberration is well suppressed in Example 2 as well.

Next, a projection optical system 300 according to a third embodiment of the present invention will be described with reference to Fig. 23. Comparing the projection optical system 300 according to the third embodiment with the projection optical system 100 according to the first embodiment, the projection optical system 300 basically differs in that the second focusing group G6 is configured to include, in addition to the lens L16, a cemented lens formed by cementing together a biconvex lens L17 and a biconcave lens L18.

Basic data of the components in this Example 3 is shown in Figure 24. Data of Example 3 corresponding to each data of Example 1 shown in Figures 3, 4, 5 and 6 are shown in Figures 25, 26, 27 and 28, respectively. The method of obtaining and displaying this data is the same as that explained in Example 1. The results of measuring the lateral aberration of the projection optical system 300 in this Example 2 are shown in Figures 29, 30, 31 and 32. The method of obtaining and displaying this lateral aberration is also the same as that explained in Example 1.

As shown in FIG. 8, in this Example 3, all of Equations 1 to 10 are satisfied. Therefore, the effects obtained by satisfying Equations 1 to 10 are obtained in the same way as in Example 1. Also, as shown in FIG. 29 to FIG. 32, it can be seen that lateral aberration is well suppressed in Example 3 as well.

Next, a projection optical system 400 according to a fourth embodiment of the present invention will be described with reference to FIG. 33. Comparing the projection optical system 400 according to the fourth embodiment with the projection optical system 300 according to the third embodiment, the basic difference is that an optical axis offset prism 40 is used instead of the prism 4.

The basic data of the components in this Example 4 is shown in Figure 34, but since the differences from Example 3 are as described above, the basic data up to lens L22 is the same as the basic data of Example 3 shown in Figure 24. Therefore, Figure 34 only shows the basic data related to the elements from the optical axis offset prism 40 onwards, that is, on the magnification side. The optical axis offset prism 40 used in this Example 4 has two total internal reflection surfaces, so data related to those internal total reflection surfaces is also shown.

Although the present invention has been described above by giving embodiments and examples, the projection optical system of the present invention is not limited to the above examples and can be modified in various ways, for example, the radius of curvature, surface spacing, refractive index, and Abbe number of each lens can be appropriately changed. In addition, as shown in FIG. 1, the projection optical system of the above-described examples is provided with an image display element 2 on the reduction side and can be applied to a projector device that projects an image formed on an image display surface 1. However, the projection optical system of the present invention is not limited to this. A projection optical system basically forms an image of light incident from a reduction side conjugate surface (reduction side conjugate surface) on a magnification side conjugate surface (magnification side conjugate surface), but a projection optical system with well-corrected aberrations can form a good image of light incident from the magnification side conjugate surface on the reduction side conjugate surface. Therefore, it is also possible to configure an imaging device by providing an imaging element at a position that becomes the reduction side imaging position when light is incident from the magnification side to the projection optical system of the present invention.

The projector device of the present invention can also be modified in various ways, for example, with respect to the light valves used and the optical components used for light beam separation or light beam combination.

REFERENCE SIGNS LIST 1 Image display surface 2 Image display element 3 Glass block 4 Prism 5 Concave mirror 40 Optical axis offset prism 100, 200, 300, 400 Projection optical system G1 First fixed group G2, G3, G4, G5 Magnification group
G6 2nd focusing group
G7 Second fixed group G8 Lens optical system G9 Reflection optical system IM1 First intermediate image IM2 Second intermediate image L1 to L22 Lens Z Optical axis

Claims (23)

A projection optical system that projects a reduced-side image onto an enlarged-side projection surface,
a lens optical system including a plurality of lenses, which forms a first intermediate image and a second intermediate image in this order toward the enlargement side by light incident from the reduction side;
a concave mirror that reflects the second intermediate image,
the lens optical system includes therein two or more variable magnification groups each of which forms the first intermediate image and which is made up of a lens group that moves in a direction that changes an interval between adjacent lens groups during magnification variation ,
a first variable power group located on the most enlargement side among the variable power groups includes a lens adjacent to the enlargement side of the first intermediate image;
A projection optical system comprising: the first variable magnification group includes a lens disposed on a reduction side of the first intermediate image and adjacent to the first intermediate image;
The projection optical system according to claim 1 . the magnification varying group further includes a second magnification varying group disposed on a reduction side relative to the first intermediate image and a stop;
the second variable magnification group includes a lens adjacent to the aperture stop;
The projection optical system according to claim 2 . the lens optical system includes a third variable power group having a negative power between the second variable power group and the first variable power group,
the second magnification varying unit has a positive power,
the third zoom group is disposed adjacent to the first zoom group on the enlargement side;
The projection optical system according to claim 3 . When changing magnification from the wide-angle end to the telephoto end,
the second zoom group moves from the reduction side to the enlargement side,
the third zoom group moves from the reduction side to the enlargement side;
5. The projection optical system according to claim 4. the lens optical system includes a plurality of focusing groups;
a fourth zoom group is disposed between the first zoom group and the third zoom group;
the fourth variable magnification group also serves as a first focusing group that moves during focusing;
6. The projection optical system according to claim 4. a second focusing group is adjacent to the first zoom group on the enlargement side;
The projection optical system according to claim 6 . the lens surface on the enlargement side of the first focusing group has a convex surface on the enlargement side,
the reduction-side lens surface of the second focusing group has a convex surface on the reduction side;
The projection optical system according to claim 7 . the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 1 which is a meniscus lens having a concave lens surface on the reduction side, and a lens 2 which has a concave lens surface on the enlargement side,
The radius of curvature (1R2) of the lens surface on the reduction side of the lens 1 and the radius of curvature (2R1) of the lens surface on the enlargement side of the lens 2 satisfy Formula 1.
0.55 <|1R2|/|2R1|< 1.00 ... Formula 1
The projection optical system according to claim 2 . the first subgroup further includes a row of lenses 3 arranged on the enlargement side of the lens 2, the lens surface on the reduction side being convex in shape;
The radius of curvature (1R1) of the enlargement-side lens surface of the lens 1 and the radius of curvature (3R2) of the reduction-side lens surface of the lens 3 satisfy Formula 2.
0.5 <|1R1|/|3R2|< 6.0 ... Formula 2
The projection optical system according to claim 9 . the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 2 having a concave lens surface on the enlargement side and a lens 3 having a convex lens surface on the reduction side,
The radius of curvature (2R1) of the enlargement-side lens surface of the lens 2 and the radius of curvature (3R2) of the reduction-side lens surface of the lens 3 satisfy Formula 3.
11. The projection optical system according to claim 2, wherein 0.30<|2R1|/|3R2|<0.70 (Formula 3). the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 1 which is a meniscus lens having a concave lens surface on the reduction side, and a lens 2 which has a concave lens surface on the enlargement side,
The refractive index (L1nd) of the lens 1 and the refractive index (L2nd) of the lens 2 satisfy Formula 4.
0.3<L2nd - L1nd ... Equation 4
The projection optical system according to claim 2 . the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The first small group includes, in order from the reduction side, a lens 2 having a concave lens surface on the enlargement side and a lens 3 having a convex lens surface on the reduction side,
The Abbe number (L2νd) of the lens 2 and the Abbe number (L3νd) of the lens 3 satisfy Formula 5.
10.0 < L3νd - L2νd ... formula 5
The projection optical system according to claim 2 . The focal length f5 of the first variable magnification group and the focal length fw of the entire projection optical system at the wide-angle end satisfy Expression 6.
15.0<|f5|/|fw|<20.0 ... Equation 6
The projection optical system according to claim 1 . the first zoom group includes a first subgroup and a second subgroup disposed on the reduction side and the enlargement side of the first intermediate image, respectively;
The focal length f5-1 of the first subgroup and the focal length f5-2 of the second subgroup satisfy Equation 7.
2.0 < |f5-1|/|f5-2| < 7.0 ... Equation 7
The projection optical system according to claim 2 . a fixed lens unit on the magnification side of the plurality of variable magnification lenses,
The fixed group has a triplet lens formed by cementing three lenses together on the most enlargement side,
The three lenses are, in order from the reduction side, a negative lens, a positive lens, and a negative lens.
The projection optical system according to claim 1 . A focal length f7 of the fixed group and a focal length f8 at a wide-angle end of the lens optical system satisfy Equation 8.
1.0 < |f7|/|f8| < 2.5 ... Equation 8
The projection optical system according to claim 16 . a focal length (f) of the triplet cemented lens of the fixed group and a focal length (f) of the entire projection optical system at the wide-angle end satisfy Expression 9.
10.0 < |f junction|/|fw| < 25.0 ... Equation 9
18. The projection optical system according to claim 16 or 17. The projection optical system according to any one of claims 16 to 18, wherein the triplet cemented lens of the fixed group is a lens element disposed on the most enlarged side of the lens optical system. a plurality of the magnification varying groups;
The variable magnification group that has the largest ratio of change in focal length of the entire system (f ratio) when each of these variable magnification groups is moved individually from the wide-angle end to the telephoto end is defined as a variator group Vrg, and each of the remaining variable magnification groups is defined as a compensator group cng. When the focal length of the entire system at the wide-angle end is 1, the amount of change Δcng is the f ratio of the compensator group cng minus 1, the sum of Δcng is defined as sum Δcng, and the ratio of change in focal length when changing magnification of the entire projection optical system (zoom ratio) is defined as Zr, then
sum Δcng and Zr satisfy formula 10;
|sum Δcng|/|Zr| < 0.03 ... Equation 10
The projection optical system according to claim 1 . an optical element having an entrance surface and an exit surface is provided between the lens optical system and the concave mirror;
the lens optical system forms a second intermediate image by focusing the light emitted from the lens optical system on a reduction side of the concave mirror;
the second intermediate image is formed so as to incline toward the reduction side as the image height increases,
At least a portion of the image is formed between the exit surface of the optical element and a concave mirror.
The projection optical system according to claim 1 . A projector device comprising an image display element on the reduction side of the projection optical system according to any one of claims 1 to 21. When a light beam is incident from the enlargement side of the projection optical system according to any one of claims 1 to 2,
An imaging device having an image sensor at a position that corresponds to an image formation position on the reduction side.