JP2018138945A - Projection optical system and projection type image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical system that can suppress an increase in size of the entire lens system, while reducing aberration.SOLUTION: A projection optical system 3A comprises: a first lens group LU1 that conjugates a reduction-side conjugate plane (liquid crystal panel 18) located on a reduction side and an intermediate image 30; and a second lens group LU2 that conjugates the intermediate image 30 and an enlargement-side conjugate plane (screen S) located on an enlargement side. The second lens group LU2 has a half angle of view of 60° or more; when the focal distance of the entire lens system is f, the focal distance of the first lens group LU1 is f1, and the interval between the first lens group LU1 and second lens group LU2 is D, the following conditional expressions (1) and (2) are satisfied. (1) 0.01<f/f1<0.1 (f<0, f1<0); (2) -1.2<D/f1<-0.2.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a projection optical system suitable for incorporation in a projection image display apparatus that projects an enlarged image of an image display element, and a projection image display apparatus including the projection optical system.

  Projection optical systems for ultra-short focus projectors that can project a large screen from a relatively small space or from a distance close to the screen use ultra-wide-angle lenses that consist only of conventional lenses and curved reflection mirrors. It has been broken.

  However, the conventional super-wide-angle lens has a limit of up to about 60 ° half field angle, and an optical system using a mirror can handle a half field angle of 70 ° or more. There is a disadvantage that the position must be set far away from the optical axis. As an alternative optical system capable of dealing with a half angle of view of 70 ° or more, an optical system has been proposed in which an intermediate image is formed by a relay optical system, and the intermediate image is further projected onto a screen.

  Here, an optical system that can be incorporated in a projection-type image display device such as a projector is described in Patent Document 1. The optical system of this document forms an intermediate image of an image of the image display element inside the optical system when it is incorporated in a projection type image display device, and re-images it on a screen. That is, the optical system of the same document includes a first lens unit that conjugates an image (reduction-side conjugate surface) of an image display element located on the reduction side and an intermediate image, and a screen (enlargement side) located on the intermediate image and the enlargement side. And a second lens group that conjugates the conjugate plane). The first lens group serves as a relay optical system that forms an intermediate image from an image arranged at the reduction-side conjugate position, and the second lens group is an enlargement optical system that magnifies and projects the intermediate image formed by the relay optical system. Play a role. In this document, optical path deflecting means for bending the optical path is provided in the middle of the first lens group.

U.S. Pat. No. 7,0097,865

  In recent projectors, sufficient brightness of the projection screen is required so that the contrast can be sufficiently high even in a bright place, and image display elements have also been improved in definition. Accordingly, the projection optical system is required to have a high resolution while having sufficient brightness.

  In such an optical system, since the image of the image display element is enlarged and projected, it is required to suppress the occurrence of aberration in the projection optical system. In addition, in a projection optical system that forms an intermediate image in the middle of the lens system, the total lens length tends to be long. Therefore, as in Patent Document 1, an optical path deflecting unit is arranged in the middle of the optical system to make the whole compact. It is demanded.

  In view of these points, the object of the present invention is to provide a sufficient space for disposing the optical path deflecting means inside the optical system, while suppressing aberrations that affect performance such as the disposition accuracy of the optical path deflecting means. An object of the present invention is to provide a projection optical system capable of suppressing an increase in the size of the entire lens system. It is another object of the present invention to provide a projection type image display apparatus incorporating such a projection optical system.

In order to solve the above-described problems, a projection optical system according to the present invention includes a reduction-side conjugate surface located on the reduction side, a first lens group that conjugates the intermediate image, and an enlargement side located on the enlargement side A second lens group having a conjugate surface as a conjugate, and the second lens group has a half angle of view of 60 ° or more, the focal length of the entire lens system is f, and the focal length of the first lens group is f1, When the distance between the first lens group and the second lens group is D, the following conditional expressions (1) and (2) are satisfied.
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
−1.2 <D / f1 <−0.2 (2)

  Conditional expression (1) of the present invention relates to the ratio between the focal length of the entire lens system and the focal length of the first lens unit. Since this invention satisfy | fills conditional expression (1), it can suppress that the whole lens system enlarges, suppressing astigmatism. That is, when the value of conditional expression (1) exceeds the lower limit, the focal length of the first lens group becomes long and the power becomes too weak. In this case, the light beam emitted from the first lens group approaches telecentricity. As a result, the imaging magnification of the intermediate image increases, and the second lens group increases in size as the imaging magnification increases. On the other hand, if the value of conditional expression (1) exceeds the upper limit, the focal length of the first lens group becomes short and the power becomes too strong. As a result, each lens power in the first lens group increases and astigmatism increases, so that a flat image surface cannot be obtained. When the value of conditional expression (1) exceeds the upper limit, the F number covered by the second lens group becomes too bright, and the burden on the second lens group becomes large.

  Conditional expression (2) of the present invention relates to the ratio between the distance between the first lens group and the second lens group and the focal length of the first lens group. Since the present invention satisfies the conditional expression (2), it is possible to secure an interval between the first lens group and the second lens group while suppressing an increase in the size of the projection optical system. Here, if a space can be secured between the first lens group and the second lens group, for example, an optical path deflecting unit is disposed between the first lens group and the second lens group, and the projection optical system is A compact configuration is possible. That is, when the value of conditional expression (2) exceeds the upper limit, the distance between the first lens group and the lens group of the second lens group becomes too wide, so that the total length of the lens system becomes long. Further, if the value of conditional expression (2) exceeds the upper limit, it is necessary to increase the lens diameter on the reduction side of the second lens group, so that the second lens group is enlarged. On the other hand, when the value of conditional expression (2) exceeds the lower limit, the distance between the first lens group and the second lens group becomes too narrow, so that the optical path deflecting means is provided between the first lens group and the second lens group. It becomes difficult to arrange etc. The interval between the two lens groups is the distance on the optical axis of the two lens groups, and the interval between the two lenses is the distance on the optical axis of the two lenses.

In the present invention, the first lens group includes an eleventh lens group including a plurality of lenses and a twelfth lens group including at least one positive lens, which are sequentially arranged from the reduction side. When the focal length of the 12 lens units is f12, it is desirable to satisfy the following conditional expression (3).
−2.0 <f12 / f1 <−0.5 (3)

  Conditional expression (3) relates to the ratio between the focal length of the twelfth lens group and the focal length of the first lens group. If conditional expression (3) is satisfied, the light beam can be efficiently relayed from the first lens group to the second lens group, and an image with sufficient contrast can be obtained on the enlargement side conjugate surface. That is, when the value of conditional expression (3) exceeds the lower limit, the focal length of the twelfth lens group becomes long, and the positive power becomes too weak. In this case, since the light beam emitted from the first lens group approaches telecentricity, the second lens group also needs to be brought close to telecentric accordingly, and light rays are efficiently relayed from the first lens group to the entrance pupil of the second lens group. It becomes difficult to do. On the other hand, if the value of conditional expression (3) exceeds the upper limit, the focal length of the twelfth lens group becomes short and the positive power becomes too strong. As a result, coma and astigmatism generated in the twelfth lens group increase, making it difficult to obtain an image with sufficient contrast on the magnification-side conjugate surface. As a result, the number of constituent elements of the twelfth lens group is increased. That is not preferable.

In the present invention, a first optical path deflecting unit disposed between the eleventh lens group and the twelfth lens group, and a second optical path disposed between the first lens group and the second lens group. When the distance between the eleventh lens group and the twelfth lens group is D1, it is preferable that the following conditional expression (4) is satisfied.
0.5 <D1 / D <2.0 (4)

  Conditional expression (4) indicates that the distance between the eleventh lens group and the twelfth lens group in which the first optical path deflecting unit is disposed, and the first lens group and the second lens group in which the second optical path deflecting unit is disposed. Related to the ratio of spacing. If the conditional expression (4) is satisfied, the arrangement of the first optical path deflecting unit and the second optical path deflecting unit becomes easy. That is, when the value of conditional expression (4) exceeds the upper limit, the distance between the eleventh lens group and the twelfth lens group becomes too narrow. Therefore, it becomes difficult to arrange the first optical path deflecting means between them. On the other hand, when the value of conditional expression (4) exceeds the lower limit, the distance between the first lens group and the second lens group becomes too narrow. Therefore, it is difficult to make a space for arranging the second optical path deflecting unit.

In the present invention, it is desirable that the following conditional expression (5) is satisfied, where d1 is the distance from the most magnified surface of the twelfth lens group to the paraxial focal position of the intermediate image.
0.2 <d1 / f12 <0.8 (5)

  That is, if the twelfth lens group includes at least one positive lens, it is easy to form an intermediate image. Here, conditional expression (5) relates to the ratio between the distance from the most magnified surface of the twelfth lens group to the paraxial focal position of the intermediate image and the focal length of the twelfth lens group. If the conditional expression (5) is satisfied, it is possible to correct the curvature of field satisfactorily and to suppress an increase in the size of the second lens group. If the conditional expression (5) is satisfied, the second optical path deflecting unit can be easily arranged. That is, when the value of conditional expression (5) exceeds the lower limit, the distance between the twelfth lens group and the intermediate image becomes too short, so that the correction effect such as field curvature is reduced. If the value of conditional expression (5) exceeds the lower limit and the positive power of the twelfth lens group becomes too weak, the positive power of the first lens group also becomes weak. As a result, since the relay magnification of the first lens group is increased, it is necessary to increase the diameter of the second lens group, resulting in an increase in the size of the second lens group. On the other hand, if the value of conditional expression (5) exceeds the upper limit and the positive power of the twelfth lens group becomes too strong, the distance between the first lens group and the intermediate image becomes narrow accordingly. Therefore, it is difficult to arrange the second optical path deflecting unit.

In the present invention, the twelfth lens group is a positive lens in which the most magnified lens has a convex surface facing the reduction side, and when the radius of curvature of the convex surface is R, the following conditional expression (6) is satisfied. It is desirable to do.
0.3 <| R | / f12 <1.5 (6)

  Conditional expression (6) relates to the ratio between the radius of curvature of the convex surface on the reduction side of the most magnified lens in the twelfth lens group and the focal length of the twelfth lens group. If the conditional expression (6) is satisfied, the field curvature can be corrected satisfactorily and the occurrence of coma and astigmatism can be suppressed. In other words, if the value of conditional expression (6) exceeds the upper limit, the curvature radius of the convex surface on the reduction side of the lens on the most magnifying side of the twelfth lens group becomes too large, so that it is not easy to correct field curvature. On the other hand, when the value of conditional expression (6) exceeds the lower limit, the radius of curvature of the convex surface on the reduction side of the lens on the most enlargement side of the twelfth lens group becomes too small, and coma and astigmatism deteriorate.

  In the present invention, the second lens group includes a twenty-second lens group composed of three or less negative lenses and one positive lens in order from the magnification side, and a twenty-first lens located on the reduction side of those lenses. And the twenty-first lens group has a positive power, and the twenty-second lens group has a negative power. If it does in this way, it will become easy to make the half angle of view of the 2nd lens group into 60 degrees or more.

  In the present invention, it is desirable that only one lens is disposed between the first optical path deflecting unit and the second optical path deflecting unit. In this way, it is possible to arrange the lenses with higher positional accuracy than in the case where a plurality of lenses are arranged between the first optical path deflecting unit and the second optical path deflecting unit.

  In the present invention, the two optical path deflecting means may be supported by a single support member. In this way, the two optical path deflecting means can be supported with high positional accuracy.

  Next, a projection type image display apparatus according to the present invention includes the above-described projection optical system and an image display element that displays an image on the reduction-side conjugate plane.

  According to the present invention, since astigmatism is suppressed in the projection optical system, an image with little distortion can be projected onto the screen (enlarged side conjugate surface). Further, the enlargement of the projection optical system is suppressed, and it is easy to arrange the optical path deflecting element inside the projection optical system. Therefore, it is easy to make the projection optical system compact by refracting the optical path by the optical path deflecting element. Therefore, it is easy to miniaturize the projection type image display apparatus.

It is a figure which shows schematic structure of a projection type image display apparatus provided with the projection optical system of this invention. 1 is a configuration diagram of a projection optical system of Embodiment 1. FIG. FIG. 3 is a configuration diagram when the optical path of the projection optical system of Example 1 is bent. FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 1; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 2; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 3; It is explanatory drawing of the supporting member which supports two optical path deflection | deviation means. FIG. 6 is a configuration diagram of a projection optical system of Example 2. FIG. 10 is a configuration diagram when the optical path of the projection optical system of Example 2 is bent. FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 1; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 2; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 3; FIG. 6 is a configuration diagram of a projection optical system of Example 3. FIG. 10 is a configuration diagram when the optical path of the projection optical system of Example 3 is bent. FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 1; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 2; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 3; FIG. 10 is a configuration diagram of a projection optical system according to a modification of Example 3. FIG. 6 is a configuration diagram of a projection optical system of Example 4. FIG. 10 is a configuration diagram when the optical path of the projection optical system of Example 4 is bent. FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 1; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 2; FIG. 6 is an aberration diagram of the projection optical system when each lens is at position 3;

  Hereinafter, a projection optical system according to an embodiment of the present invention and a projection image display apparatus including the same will be described in detail with reference to the drawings.

(Projection type image display device)
FIG. 1 is a schematic configuration diagram of a projector including the projection optical system of the present invention. As shown in FIG. 1, a projector (projection-type image display device) 1 includes an image light generation optical system 2 that generates image light to be projected onto a screen S, a projection optical system 3 that expands and projects image light, And a control unit 4 that controls the operation of the image light generation optical system 2.

(Image light generation optical system and control unit)
The image light generation optical system 2 includes a light source 10, a first integrator lens 11, a second integrator lens 12, a polarization conversion element 13, and a superimposing lens 14. The light source 10 is composed of, for example, an ultrahigh pressure mercury lamp, a solid light source, or the like. The first integrator lens 11 and the second integrator lens 12 each have a plurality of lens elements arranged in an array. The first integrator lens 11 splits the light flux from the light source 10 into a plurality of parts. Each lens element of the first integrator lens 11 condenses the light beam from the light source 10 in the vicinity of each lens element of the second integrator lens 12.

  The polarization conversion element 13 converts light from the second integrator lens 12 into predetermined linearly polarized light. The superimposing lens 14 superimposes an image of each lens element of the first integrator lens 11 on a display area of a liquid crystal panel 18R, a liquid crystal panel 18G, and a liquid crystal panel 18B, which will be described later, via the second integrator lens 12.

  The image light generation optical system 2 includes a first dichroic mirror 15, a reflection mirror 16, a field lens 17R, and a liquid crystal panel 18R. The first dichroic mirror 15 reflects the R light that is a part of the light beam incident from the superimposing lens 14 and transmits the G light and the B light that are a part of the light beam incident from the superimposing lens 14. The R light reflected by the first dichroic mirror 15 enters the liquid crystal panel 18R via the reflection mirror 16 and the field lens 17R. The liquid crystal panel 18R is an image display element. The liquid crystal panel 18R modulates the R light according to the image signal to form a red image.

  Further, the image light generation optical system 2 includes a second dichroic mirror 21, a field lens 17G, and a liquid crystal panel 18G. The second dichroic mirror 21 reflects the G light that is part of the light beam from the first dichroic mirror 15 and transmits the B light that is part of the light beam from the first dichroic mirror 15. The G light reflected by the second dichroic mirror 21 enters the liquid crystal panel 18G via the field lens 17G. The liquid crystal panel 18G is an image display element. The liquid crystal panel 18G modulates the G light according to the image signal to form a green image.

  The image light generation optical system 2 includes a relay lens 22, a reflection mirror 23, a relay lens 24, a reflection mirror 25, a field lens 17B, and a liquid crystal panel 18G. The B light transmitted through the second dichroic mirror 21 enters the liquid crystal panel 18B via the relay lens 22, the reflection mirror 23, the relay lens 24, the reflection mirror 25, and the field lens 17B. The liquid crystal panel 18B is an image display element. The liquid crystal panel 18B forms a blue image by modulating the B light according to the image signal.

  The liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18B surround the cross dichroic prism 19 from three directions. The cross dichroic prism 19 is a light combining prism, and generates image light by combining light modulated by the liquid crystal panels 18R, 18G, and 18B.

  Here, the cross dichroic prism 19 constitutes a part of the projection optical system 3. The projection optical system 3 projects the image light synthesized by the cross dichroic prism 19 (images formed by the liquid crystal panels 18R, 18G, and 18B) on the screen S in an enlarged manner.

  The control unit 4 includes an image processing unit 6 to which an external image signal such as a video signal is input, and a display that drives the liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18B based on the image signal output from the image processing unit 6. And a drive unit 7.

  The image processing unit 6 converts an image signal input from an external device into an image signal including a gradation of each color. The display driving unit 7 operates the liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18 based on the image signals of the respective colors output from the image processing unit 6. Thereby, the image processing unit 6 displays an image corresponding to the image signal on the liquid crystal panel 18R, the liquid crystal panel 18G, and the liquid crystal panel 18G.

(Projection optics)
Next, the projection optical system 3 will be described. Below, Examples 1-4 are demonstrated as a structural example of the projection optical system 3 mounted in the projector 1. FIG.

Example 1
FIG. 2 is a configuration diagram (ray diagram) of the projection optical system according to the first embodiment. FIG. 3 is a configuration diagram (ray diagram) of the projection optical system when two optical path deflecting units are arranged. As shown in FIG. 2, the projection optical system 3A of the present example includes a first lens group LU1 that conjugates the liquid crystal panel 18 (18R, 18G, 18B), which is a reduction-side conjugate surface, and the intermediate image 30, and an intermediate image. 30 and a second lens unit LU2 that conjugates the screen S that is a magnification side conjugate surface. The first lens group LU1 serves as a relay optical system that forms an intermediate image 30 from the image on the liquid crystal panel 18 disposed at the reduction-side conjugate position, and the second lens group LU2 is an intermediate image formed by the relay optical system. It functions as a magnifying optical system that magnifies and projects 30. The projection optical system 3A is composed of 19 lenses as a whole.

  The first lens group LU1 is composed of nine lenses. That is, the first lens unit LU1 includes, in order from the reduction side, a positive first lens L1 having a biconvex shape, a second lens L2 having a meniscus shape having a convex surface facing the enlargement side, and a positive first lens having a biconvex shape. Three lenses L3 and a biconcave negative fourth lens L4, a meniscus positive fifth lens L5 with a convex surface facing the enlargement side, a biconcave negative sixth lens L6, a biconvex positive positive first lens 7 lens L7, meniscus positive 8th lens L8 with convex surface facing the enlargement side, and biconvex positive 9th lens L9. The third lens L3 and the fourth lens L4 are cemented to form the first cemented lens LC1. The sixth lens L6 and the seventh lens L7 are cemented to form a second cemented lens LC2. A stop STO is disposed between the fourth lens L4 and the fifth lens L5.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 composed of a plurality of lenses and a twelfth lens group LU12 composed of at least one positive lens. In the present example, the eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens group LU12 includes a ninth lens L9.

  The second lens group LU2 is composed of ten lenses. That is, in order from the reduction side, the second lens unit LU2 includes, in order from the reduction side, a positive tenth lens L10 having an aspheric surface on both sides, a meniscus negative eleventh lens L11 with a convex surface on the enlargement side, and a biconvex positive shape. A biconvex positive lens 13, a biconvex positive 14th lens L 14, a biconcave negative 15th lens L 15, a biconvex positive 16th lens L 16, Meniscus negative 17th lens L17 with aspheric surfaces on both sides and convex surface on the enlargement side, meniscus negative 18th lens L18 with convex surfaces on the enlargement side, negative surfaces with aspheric surfaces on both sides No. 19 lens L19. The fourteenth lens L14 and the fifteenth lens L15 are cemented to form a third cemented lens LC3.

  The second lens group LU2 is composed of a twenty-first lens group LU21 and a twenty-second lens group LU22 in order from the reduction side. The 22nd lens group LU22 is composed of three or less negative lenses and one positive lens in order from the magnification side. The twenty-first lens group LU21 includes a lens closer to the intermediate image 30 than the twenty-second lens group LU22. In this example, the 22nd lens group LU22 includes three negative lenses (17th lens L17, 18th lens L18, 19th lens L19) and 1 positive lens (16th lens L16) in order from the enlargement side. ). Accordingly, the twenty-first lens unit LU21 includes the tenth lens L10 to the fifteenth lens L15. The twenty-first lens group LU21 has positive power. The twenty-second lens group LU22 has negative power.

  Here, as shown in FIG. 3, when the projection optical system 3A is made compact, the first optical path deflecting means 31 is arranged between the eleventh lens group LU11 and the twelfth lens group LU12, and the first A second optical path deflecting unit 32 is disposed between the lens group LU1 and the second lens group LU2. In this example, the second optical path deflecting unit 32 is located closer to the first lens group LU1 (reduction side) than the intermediate image 30. In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 deflect the optical axis L in the vertical direction twice, and the optical path is inverted by 180 °. Each of the optical path deflecting means 31 and 32 is a mirror having a surface coated with a reflective material such as aluminum.

  When the projection size on the screen S is changed by the projection optical system 3A, as shown in FIG. 2, the first focus lens including the tenth lens L10 to the fifteenth lens L15 with the nineteenth lens L19 fixed. Focusing is performed by moving the group LF1 and the second focusing lens group LF2 including three lenses of the sixteenth lens L16 to the eighteenth lens L18 in the optical axis L direction.

Next, when the focal length is f, the F number is FNo., And the maximum field angle (half field angle) is ω,
The data of the projection optical system 3A is as follows.
f -3.960
FNo. 1.601
ω 71.0 °

  The lens data of the projection optical system 3A is as follows. The lens column is a symbol assigned to each lens in FIGS. Surfaces marked with * are aspheric surfaces. R is a radius of curvature. d is the axial top surface spacing (mm) (lens thickness or lens spacing). nd is a refractive index. νd is the Abbe number. The axial upper surface distance M1 is the distance between the screen S and the nineteenth lens L19. The axial upper surface distance M2 is a distance between the nineteenth lens L19 and the second focus lens group LF2 (the sixteenth lens L18 to the nineteenth lens L18). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (the 16th lens L18 to the 19th lens L18) and the first focus lens group LF1 (the 10th lens L10 to the 15th lens L15). The axial top surface distance M4 is a distance between the first focus lens group LF1 (the tenth lens L10 to the lens L15) and the ninth lens L9. The axial top surface spacing M1 varies depending on the projection size, and the axial top surface spacings M2, M3, and M4 vary due to focusing when the projection size is changed.

Lens Surface number R d nd νd
S Infinity M1
L19 * 1 -66.453 5.000 1.53116 56.04
* 2 19.447 M2
L18 3 32.287 2.000 1.72916 54.68
4 16.619 7.507
L17 * 5 49.974 2.000 1.83220 40.10
* 6 12.169 11.821
L16 7 49.040 10.948 1.83400 37.16
8 -40.271 M3
L15 9 -152.174 1.200 1.84666 23.78
L14 10 22.382 12.000 1.49700 81.54
11 -23.642 0.200
L13 12 41.613 10.000 1.49700 81.54
13 -46.190 0.100
L12 14 159.238 6.500 1.61800 63.33
15 -51.763 0.200
L11 16 46.720 2.000 1.85896 22.73
17 25.262 8.026
L10 * 18 -33.452 5.030 1.53116 56.04
* 19 -14.023 M4
L9 20 619.069 11.000 1.90366 31.31
21 -80.008 92.003
L8 22 58.273 6.400 2.00069 25.46
23 297.623 18.638
L7 24 29.184 7.217 1.69350 53.20
L6 25 -65.074 1.200 1.84666 23.78
26 22.156 2.500
L5 27 35.000 2.986 1.59522 67.73
28 62.934 4.662
STO 29 Infinity 5.677
L4 30 -32.854 1.200 1.84666 23.78
L3 31 28.745 8.804 1.49700 81.54
32 -21.608 0.100
L2 * 33 23.506 3.000 1.76450 49.10
* 34 19.920 12.313
L1 35 80.495 8.000 1.84666 23.78
36 -41.543 6.893
37 Infinity 25.910 1.51680 64.17
38 Infinity 9.504
OBJ Infinity 0.016

The axis top surface spacings M1, M2, M3, and M4 when focusing is performed by changing the projection size are as follows. The position of each lens after focusing when the axial upper surface distance M1 which is the distance between the 21st lens L21 and the screen S is set to the reference projection distance of 500 mm is the position 1, and the axial upper surface distance M1 is closer to the reference projection distance. The position of each lens when 411 mm is set as position 2, and the position of each lens when the axial top surface distance M1 is set to 662 mm far from the reference projection distance is set as position 3.
Position 1 Position 2 Position 3
M1 500.000 411.800 662.000
M2 7.859 7.867 7.863
M3 3.994 3.936 4.058
M4 60.614 60.664 60.546

  Here, the first surface and the second surface are higher-order aspheric surfaces represented by odd-order aspherical expressions including odd-order aspheric coefficients. Equation 1 below is an odd-order aspheric equation. The lower values of Equation 1 are the coefficients of the odd-order aspheric equation for defining the aspheric shapes of the surface numbers 1 and 2 that are aspheric.

Surface number 1 2
K -32.60112 -5.59829
A03 3.99196E-04 6.97995E-04
A04 -3.67230E-06 -1.26941E-05
A05 -1.10353E-07 8.40418E-08
A06 2.61331E-09 -4.39118E-09
A07 5.23713E-11 0.00000E + 00
A08 -1.01909E-12 0.00000E + 00
A09 -2.23695E-14 0.00000E + 00
A10 5.19866E-16 0.00000E + 00

  Next, the fifth surface, the sixth surface, the eighteenth surface, the nineteenth surface, the thirty-third surface, and the thirty-fourth surface are higher-order aspherical surfaces represented by even-order aspherical expressions including even-ordered aspherical coefficients. is there. Expression 2 below is an even-order aspheric expression. The lower values of Equation 2 are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 5, 6, 18, 19, 33, and 34 that are aspherical.

Surface number 5 6 18 19
K 1.96239 -0.57989 0.00000 -0.18120
A04 6.32900E-06 1.53370E-04 3.26830E-05 1.00070E-04
A06 -1.31490E-07 -2.72430E-07 -5.74200E-07 -1.92660E-07
A08 3.35460E-10 4.83950E-09 1.97640E-09 9.03450E-10
A10 -3.51960E-13 -2.42130E-11 -5.33310E-12 2.77500E-12
A12 0.00000E + 00 0.00000E + 00 -8.96370E-16 2.06420E-16
Surface No. 33 34
K 0.00000 0.00000
A04 -1.61910E-05 -1.53960E-05
A06 -9.50520E-08 -1.31450E-07
A08 4.26990E-10 5.16950E-10
A10 -2.01700E-13 -3.68340E-13
A12 -6.13720E-29 1.00680E-27

  In this example, the 22nd lens group LU22 located closest to the screen S includes one positive lens (16th lens L16) and 3 negative lenses (17th lens L17, 18th lens L18 and 19th lens L19). Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  In the first lens group LU1, the twelfth lens group LU12 located on the intermediate image 30 side is a positive lens (the ninth lens L9). Therefore, it is easy to form the intermediate image 30.

Furthermore, the projection optical system 3A satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f1 is the focal length of the first lens unit LU1.
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
That is, in this example, f / f1 = 0.053.

  Conditional expression (1) relates to the ratio between the focal length f of the entire lens system and the focal length f1 of the first lens unit LU1. Since the projection optical system 3A satisfies the conditional expression (1), an increase in the size of the entire lens system can be suppressed while suppressing astigmatism. That is, when the value of conditional expression (1) exceeds the upper limit, the focal length of the first lens unit LU1 becomes short and the power becomes too strong. As a result, each lens power in the first lens unit LU1 increases and astigmatism increases, so that a flat image surface cannot be obtained. On the other hand, if the value of conditional expression (1) exceeds the lower limit, the focal length of the first lens unit LU1 becomes long and the power becomes too weak. In this case, the light beam emitted from the first lens group LU1 approaches telecentricity. As a result, the imaging magnification of the intermediate image increases, and the second lens group LU2 increases in size as the imaging magnification increases. Here, when the value of the conditional expression (1) exceeds the upper limit, the F number covered by the second lens group LU2 becomes too bright, so that the burden on the second lens group LU2 increases.

The projection optical system 3A satisfies the following conditional expression (2), where f1 is the focal length of the first lens group LU1, and D is the distance between the first lens group LU1 and the second lens group LU2. . The distance D is the distance between the first lens group LU1 and the second lens group LU2 on the optical axis L.
−1.2 <D / f1 <−0.2 (2)
That is, in this example, D / f1 = −0.807.

  Conditional expression (2) relates to the ratio between the distance D between the first lens group LU1 and the second lens group LU2 and the focal length f1 of the first lens group LU1. Since the projection optical system 3A satisfies the conditional expression (2), an interval can be secured between the first lens group LU1 and the second lens group LU2 while suppressing an increase in size of the projection optical system. Therefore, the projection optical system 3A can be configured more compactly by arranging the second optical path deflecting means 32 between the first lens group LU1 and the second lens group LU2. That is, when the value of conditional expression (2) exceeds the upper limit, the distance D between the first lens unit LU1 and the lens unit of the second lens unit LU2 becomes too wide, so that the total length of the lens system is increased. When the value of conditional expression (2) exceeds the upper limit, it is necessary to increase the lens diameter on the reduction side of the second lens group LU2, and thus the second lens group LU2 is enlarged. On the other hand, when the value of the conditional expression (2) exceeds the lower limit, the distance between the first lens group LU1 and the second lens group LU2 becomes too narrow, and therefore, between the first lens group LU1 and the second lens group LU2. It is difficult to dispose the second optical path deflecting means 32 in the second position.

Further, the projection optical system 3A satisfies the following conditional expression (3) when the focal length of the twelfth lens group LU12 is f12 and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. desirable. The distance D1 is a distance on the optical axis L between the eleventh lens group LU11 and the twelfth lens group LU12.
−2.0 <f12 / f1 <−0.5 (3)
That is, in this example, f12 / f1 = −1.045.

  Conditional expression (3) relates to the ratio between the focal length f12 of the twelfth lens group and the focal length f1 of the first lens group LU1. Since the projection optical system 3A satisfies the conditional expression (3), the light beam can be efficiently relayed from the first lens unit LU1 to the second lens unit LU2, and an image with sufficient contrast can be obtained on the screen S (enlarged side conjugate surface). Can do. That is, when the value of conditional expression (3) exceeds the lower limit, the focal length of the twelfth lens unit LU12 becomes long, and the positive power becomes too weak. In this case, since the light beam emitted from the first lens group LU1 approaches telecentricity, the second lens group LU2 also needs to be brought close to telecentric accordingly. It will be difficult to relay efficiently. On the other hand, when the value of conditional expression (3) exceeds the upper limit, the focal length of the twelfth lens unit LU12 becomes short, and the positive power becomes too strong. As a result, coma and astigmatism generated in the twelfth lens group LU12 increase, making it difficult to obtain an image with sufficient contrast on the screen S (enlargement side conjugate surface). As a result, the twelfth lens group This is not preferable because the number of LU 12 is increased.

Further, the projection optical system 3A has the following conditional expression (D) when the distance between the first lens group LU1 and the second lens group LU2 is D and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. 4) is satisfied.
0.5 <D1 / D <2.0 (4)
That is, in this example, D1 / D = 1.518.

  Conditional expression (4) indicates that the distance D1 between the eleventh lens group LU11 and the twelfth lens group LU12 in which the first optical path deflecting unit 31 is disposed, the first lens group LU1 in which the second optical path deflecting unit 32 is disposed, and the first lens group LU1. This relates to the ratio of the distance D between the two lens units LU2. Since the projection optical system 3A satisfies the conditional expression (4), the arrangement of the first optical path deflecting unit 31 and the second optical path deflecting unit 32 is facilitated. That is, when the value of conditional expression (4) exceeds the upper limit, the distance D1 between the eleventh lens group LU11 and the twelfth lens group LU12 becomes too narrow. Therefore, it becomes difficult to arrange the first optical path deflecting means 31 between them. On the other hand, when the value of conditional expression (4) exceeds the lower limit, the distance D between the first lens group LU1 and the second lens group LU2 becomes too narrow. Accordingly, it is difficult to make a space for arranging the second optical path deflecting unit 32.

Further, the projection optical system 3A has the following when the distance from the most magnified surface of the twelfth lens group LU12 to the paraxial focal position of the intermediate image 30 is d1, and the focal length of the twelfth lens group LU12 is f12. Conditional expression (5) is satisfied.
0.2 <d1 / f12 <0.8 (5)
That is, in this example, d1 / f12 = 0.602.

  Conditional expression (5) relates to the ratio between the distance d1 from the most magnified surface of the twelfth lens unit LU12 to the paraxial focal position of the intermediate image 30 and the focal length f12 of the twelfth lens unit LU12. Since the projection optical system 3A satisfies the conditional expression (5), it is possible to correct the curvature of field satisfactorily and to suppress an increase in the size of the second lens unit LU2. Further, since the projection optical system 3A satisfies the conditional expression (5), the second optical path deflecting unit 32 can be easily arranged. That is, when the value of conditional expression (5) exceeds the lower limit, the distance between the twelfth lens unit LU12 and the intermediate image 30 becomes too short, and the correction effect such as field curvature is reduced. If the value of conditional expression (5) exceeds the lower limit and the positive power of the twelfth lens group LU12 becomes too weak, the positive power of the first lens group LU1 also becomes weak. As a result, the relay magnification of the first lens group LU1 is increased, so that the diameter of the second lens group LU2 needs to be increased, leading to an increase in size of the second lens group LU2. On the other hand, if the value of conditional expression (5) exceeds the upper limit and the positive power of the twelfth lens group LU12 becomes too strong, the distance between the first lens group LU1 and the intermediate image 30 becomes narrow accordingly. Therefore, it becomes difficult to arrange the second optical path deflecting means 32.

The projection optical system 3A is a positive lens in which the most magnified lens (the ninth lens L9) of the twelfth lens unit LU12 has a convex surface facing the reduction side. Conditional expression (6) is satisfied.
0.3 <| R | / f12 <1.5 (6)
That is, in this example, | R | /f12=1.020.

  Conditional expression (6) relates to the ratio between the radius of curvature R of the convex surface on the reduction side of the most magnified lens (the ninth lens L9) of the twelfth lens group LU12 and the focal length f12 of the twelfth lens group LU12. Since the projection optical system 3A satisfies the conditional expression (6), it is possible to satisfactorily correct the field curvature and to suppress the occurrence of coma and astigmatism. That is, if the value of conditional expression (6) exceeds the upper limit, the curvature radius of the convex surface on the reduction side of the ninth lens L9 becomes too large, so that it is not easy to correct field curvature. On the other hand, when the value of conditional expression (6) exceeds the lower limit, the radius of curvature of the convex surface on the reduction side of the ninth lens L9 becomes too small, and coma and astigmatism deteriorate.

  FIG. 4 is an aberration diagram (spherical aberration, astigmatism and distortion) when each lens of the projection optical system 3A is at position 1. FIG. 5 is an aberration diagram (spherical aberration, astigmatism and distortion aberration) when each lens of the projection optical system 3A is at position 2. FIG. FIG. 6 is an aberration diagram (spherical aberration, astigmatism and distortion) when each lens of the projection optical system 3A is at position 3. As shown in FIGS. 4 to 6, in the projection optical system 3A, spherical aberration, astigmatism and distortion are corrected satisfactorily.

  Furthermore, in this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 for bending the optical path are provided in the middle of the projection optical system 3A. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3A and the projector 1 can be configured compactly.

  Further, in this example, the second optical path deflecting unit 32 is disposed between the first lens group LU1 and the intermediate image 30. Here, the image plane of the intermediate image 30 formed by the first lens group LU1 is curved toward the reduction side as it approaches the peripheral portion. Accordingly, the size of the second optical path deflecting unit 32 can be reduced by arranging the second optical path deflecting unit 32 between the paraxial focal positions of the first lens group LU1 and the intermediate image 30.

  Further, in the projection optical system 3A, only one lens (the ninth lens L9) of the first lens group LU1 is disposed between the first optical path deflecting unit 31 and the second optical path deflecting unit 32. Therefore, as compared with the case where a plurality of lenses are arranged between the first optical path deflecting unit 31 and the second optical path deflecting unit 32, each lens constituting the projection optical system 3A can be arranged with high positional accuracy. Further, no optical path deflecting means is disposed in the middle of the second lens group LU2. Accordingly, the positional accuracy of the plurality of lenses constituting the second lens group LU2 is not lowered by the arrangement of the optical path deflecting means, and deterioration of the optical performance in the second lens group LU2 can be avoided.

  Here, in this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 are supported by a single support member together with the twelfth lens group LU12. FIG. 7 is an explanatory diagram of a support structure that supports the first lens group LU1, the second lens group LU2, the first optical path deflecting unit 31, and the second optical path deflecting unit 32.

  As shown in FIG. 7, in this example, the lenses L1 to L8 constituting the eleventh lens group LU11 of the first lens group LU1 are held by the first lens barrel 35. The lenses L10 to L19 constituting the second lens group LU2 are held by the second lens barrel 36. The twelfth lens group LU12, the first optical path deflecting means 31, and the second optical path deflecting means 32 of the first lens group LU1 are supported by a hollow support member 37 having an isosceles right triangle shape when viewed from the side. . That is, in the portion corresponding to the two sides sandwiching the right angle in the support member 37, the first support part 37a that supports the first optical path deflecting unit 31 and the second optical path deflecting unit 32 that supports the second optical path deflecting unit 32 along each side. 2 support portions 37b. Further, a third support portion 37c that removably supports the twelfth lens group LU12 is provided between the first support portion 37a and the second support portion 37b of the support member 37. The support member 37 has a first abutting portion 37d with which the first lens barrel 35 abuts on one side of the support member 37 facing the right angle of the right isosceles triangle shape, and a second abutting portion 37e with which the second lens barrel 36 abuts. And are provided.

  Here, the first support part 37 a and the second support part 37 b are provided on a single support member 37. Accordingly, the first optical path deflecting means 31 and the second optical path deflecting means 32 are supported by the first optical path deflecting means 31 supported by the first support portion 37a and the second optical path deflecting means 32 supported by the second support portion 37b. Is supported on the support member 37 with high positional accuracy. The first contact portion 37d and the second contact portion 37e are provided on a single support member 37. Accordingly, by bringing the first lens barrel 35 and the second lens barrel 36 into contact with these contact portions, respectively, the optical axis of the eleventh lens group LU11 and the optical axis of the second lens group LU2 are made parallel. Is easy. Furthermore, since the first support portion 37a, the second support portion 37b, the third support portion 37c, the first contact portion 37d, and the second contact portion 37e are provided on the single support member 37, the eleventh lens The group LU11, the twelfth lens group LU12, the second lens group LU2, the first optical path deflecting unit 31, and the second optical path deflecting unit 32 can be arranged with high positional accuracy.

  In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are mirrors, and the distance between the mirrors is short. Furthermore, since the twelfth lens group LU12 is detachably supported by the third support portion 37c, if the twelfth lens group LU12 is detached from the support member 37, the first optical path deflecting means 31 and the second optical path deflecting means are collimated. Measurements such as 32 squareness can be made. Therefore, it is possible to easily secure the positional accuracy of each of the optical path deflecting means 31 and 32.

  Here, when the focal position of the intermediate image 30 coincides with the second optical path deflecting unit 32, scratches on the reflecting surface of the second optical path deflecting unit 32, dust adhering to the reflecting surface, and the like are enlarged and projected as they are. There is a risk that On the other hand, in this example, as shown in FIG. 3, the second optical path deflecting unit is configured so that the focal position from the on-axis to the maximum image height in the intermediate image 30 does not overlap the reflecting surface of the second optical path deflecting unit 32. 32 is arranged. Therefore, it can be avoided that dust or the like adhering to the reflecting surface is enlarged and projected as it is.

  A prism or the like can be used as the first optical path deflecting unit 31 and the second optical path deflecting unit 32. In this example, the optical axis L is deflected twice in the vertical direction, but the optical axis L may be deflected in an arbitrary direction.

(Example 2)
FIG. 8 is a configuration diagram (ray diagram) of the projection optical system according to the second embodiment. FIG. 9 is a configuration diagram (ray diagram) of the projection optical system when two optical path deflecting means are arranged. As shown in FIG. 8, the projection optical system 3B of this example includes a first lens unit LU1 that conjugates the liquid crystal panel 18 (18R, 18G, 18B), which is a reduction-side conjugate surface, and the intermediate image 30, and an intermediate image. 30 and a second lens unit LU2 that conjugates the screen S that is a magnification side conjugate surface. The first lens group LU1 serves as a relay optical system that forms an intermediate image 30 from the image on the liquid crystal panel 18 disposed at the reduction-side conjugate position, and the second lens group LU2 is an intermediate image formed by the relay optical system. It functions as a magnifying optical system that magnifies and projects 30. The projection optical system 3B is composed of 18 lenses as a whole.

  The first lens group LU1 is composed of eight lenses. That is, the first lens unit LU1 includes, in order from the reduction side, a biconvex positive first lens L1, a biconvex positive second lens L2, a meniscus negative third with a convex surface facing the enlargement side. Lens L3, biconcave negative fourth lens L4, biconvex positive fifth lens L5, meniscus positive sixth lens L6 with a convex surface on the enlargement side, meniscus with convex surface on the enlargement side The shape includes a positive seventh lens L7 and a biconvex positive eighth lens L8. The second lens L2 and the third lens L3 are cemented to form a first cemented lens LC1. The fourth lens L4 and the fifth lens L5 are cemented to form a second cemented lens LC2. A diaphragm STO is disposed between the third lens L3 and the fourth lens L4.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 composed of a plurality of lenses and a twelfth lens group LU12 composed of at least one positive lens. In the present example, the eleventh lens group LU11 includes a first lens L1 to a seventh lens L7. The twelfth lens group LU12 includes an eighth lens L8.

  The second lens group LU2 is composed of ten lenses. That is, the second lens unit LU2 includes, in order from the reduction side, a positive ninth lens L9 with aspheric surfaces on both sides, a meniscus negative tenth lens L10 with a convex surface on the enlargement side, and a biconvex positive shape. 11th lens L11, biconvex positive 12th lens L12, biconvex positive 13th lens L13, biconcave negative 14th lens L14, meniscus positive with convex toward the reduction side The fifteenth lens L15, a meniscus negative 16th lens L16 with aspheric surfaces on both sides and a convex surface on the enlargement side, a meniscus negative 17th lens L17 with a convex surface on the enlargement side, It comprises a negative eighteenth lens L18 with a spherical surface. The thirteenth lens L13 and the fourteenth lens L14 are cemented to form a third cemented lens LC3.

  The second lens group LU2 is composed of a twenty-first lens group LU21 and a twenty-second lens group LU22 in order from the reduction side. The 22nd lens group LU22 is composed of three or less negative lenses and one positive lens in order from the magnification side. The twenty-first lens group LU21 includes a lens closer to the intermediate image 30 than the twenty-second lens group LU22. In this example, the 22nd lens group LU22 includes three negative lenses (18th lens L18, 17th lens L17, 16th lens L16) and 1 positive lens (15th lens L15) in order from the enlargement side. ). Accordingly, the twenty-first lens unit LU21 includes the ninth lens L9 to the fourteenth lens L14. The twenty-first lens group LU21 has positive power. The twenty-second lens group LU22 has negative power.

  Here, as shown in FIG. 9, when the projection optical system 3B is made compact, the first optical path deflecting means 31 is disposed between the eleventh lens group LU11 and the twelfth lens group LU12, and the first A second optical path deflecting unit 32 is disposed between the lens group LU1 and the second lens group LU2. In this example, the second optical path deflecting unit 32 is located closer to the first lens group LU1 (reduction side) than the intermediate image 30. In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 deflect the optical axis L in the vertical direction twice, and the optical path is inverted by 180 °. Each of the optical path deflecting means 31 and 32 is a mirror having a surface coated with a reflective material such as aluminum.

  When the projection size on the screen S is changed by the projection optical system 3B, as shown in FIG. 8, the first focus lens including the tenth lens L10 to the fourteenth lens L14 with the eighteenth lens L18 fixed. Focusing is performed by moving the group LF1 and the second focus lens group LF2 including three lenses of the fifteenth lens L15 to the seventeenth lens L17 in the optical axis L direction.

Next, when the focal length is f, the F number is FNo., And the maximum field angle (half field angle) is ω,
The data of the projection optical system 3B is as follows.
f -3.960
FNo. 1.600
ω 71.1 °

  The lens data of the projection optical system 3B is as follows. The lens column is a symbol assigned to each lens in FIGS. Surfaces marked with * are aspheric surfaces. R is a radius of curvature. d is the axial top surface spacing (mm) (lens thickness or lens spacing). nd is a refractive index. νd is the Abbe number. The shaft upper surface distance M1 is the distance between the screen S and the eighteenth lens L18. The axial upper surface distance M2 is a distance between the eighteenth lens L18 and the second focus lens group LF2 (the fifteenth lens L15 to the seventeenth lens L17). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (15th lens L15 to 17th lens L17) and the first focus lens group LF1 (10th lens L10 to 14th lens L14). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the tenth lens L10 to the fourteenth lens L14) and the ninth lens L9. The axial top surface spacing M1 varies depending on the projection size, and the axial top surface spacings M2, M3, and M4 vary due to focusing when the projection size is changed.

Lens Surface number R d nd νd
S Infinity M1
L18 * 1 -42.033 5.000 1.53116 56.04
* 2 24.256 M2
L17 3 29.808 2.000 1.72916 54.68
4 16.046 6.043
L16 * 5 28.988 2.000 1.83220 40.10
* 6 11.686 6.769
L15 7 -163.705 10.466 1.80100 34.97
8 -34.607 M3
L14 9 -40.802 1.200 1.78472 25.68
L13 10 31.300 9.666 1.49700 81.54
11 -18.242 0.200
L12 12 73.820 10.712 1.49700 81.54
13 -28.015 0.100
L11 14 34.853 8.813 1.59522 67.73
15 -115.164 0.200
L10 16 110.934 2.000 1.85896 22.73
17 27.896 M4
L9 * 18 -56.555 5.435 1.53116 56.04
* 19 -15.232 60.389
L8 20 404.883 8.000 1.90366 31.31
21 -118.131 66.854
L7 22 84.279 8.000 1.91082 35.25
23 1692.347 36.757
L6 24 32.212 3.500 2.00069 25.46
25 35.984 13.352
L5 * 26 50.064 7.000 1.61881 63.85
L4 27 -25.282 1.200 1.76182 26.52
28 47.881 4.414
STO 29 Infinity 3.398
L3 30 324.879 2.000 1.84666 23.78
L2 31 21.504 6.573 1.53775 74.70
32 -54.485 20.871
L1 33 68.761 6.200 1.85896 22.73
34 -57.434 3.202
35 Infinity 25.910 1.51680 64.17
36 Infinity 9.316
OBJ Infinity 0.020

The axis top surface spacings M1, M2, M3, and M4 when focusing is performed by changing the projection size are as follows. The position of each lens after focusing when the axial upper surface distance M1 which is the distance between the 21st lens L21 and the screen S is set to the reference projection distance of 500 mm is the position 1, and the axial upper surface distance M1 is closer to the reference projection distance. The position of each lens when 411 mm is set as position 2, and the position of each lens when the axial top surface distance M1 is set to 662 mm far from the reference projection distance is set as position 3.
Position 1 Position 2 Position 3
M1 500.000 411.800 662.000
M2 7.799 7.809 7.789
M3 7.179 7.105 7.266
M4 7.477 7.542 7.402

  Here, the first surface and the second surface are higher-order aspheric surfaces represented by an odd-order aspheric expression (equation 1) including odd-order aspheric coefficients. The following values are the coefficients of the odd-order aspheric expression for defining the aspheric shapes of the surface numbers 1 and 2 that are aspheric.

Surface number 1 2
K -16.72607 -10.77675
A03 4.83689E-04 8.16544E-04
A04 -5.52256E-06 -1.55624E-05
A05 -1.61485E-07 1.86725E-08
A06 4.13161E-09 -4.98178E-10
A07 6.27958E-11 -1.35272E-11
A08 -1.38019E-12 0.00000E + 00
A09 -2.74522E-14 0.00000E + 00
A10 6.04501E-16 0.00000E + 00

  Next, the fifth, sixth, eighteenth, nineteenth, and twenty-sixth surfaces are higher-order aspherical surfaces represented by an even-order aspherical expression (equation 2) that includes even-ordered aspherical coefficients. It is. The following values are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 5, 6, 18, 19, and 26 that are aspherical.

Surface number 5 6 18 19 26
K -0.79003 -0.33575 0.00000 -0.88832 -1.00000
A04 -2.84890E-06 1.18290E-04 2.77450E-05 8.61370E-05 -1.93250E-06
A06 -1.29090E-07 -1.66290E-07 -1.72210E-07 -1.10320E-07 9.16630E-10
A08 5.00360E-10 7.29830E-10 5.00150E-10 3.99930E-10 3.14440E-11
A10 -7.19920E-13 2.86600E-11 -8.93730E-13 3.43730E-13 0.00000E + 00
A12 0.00000E + 00 0.00000E + 00 -5.12910E-17 -1.71880E-15 0.00000E + 00

  In this example, the 22nd lens group LU22 located closest to the screen S includes one positive lens (15th lens L15) and 3 negative lenses (16th lens L16, 17th lens L17 and 18th lens L18). Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  In the first lens group LU1, the twelfth lens group LU12 located on the intermediate image 30 side is a positive lens (eighth lens L8). Therefore, it is easy to form the intermediate image 30.

Furthermore, the projection optical system 3B satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f1 is the focal length of the first lens unit LU1.
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
That is, in this example, f / f1 = 0.048. Since the projection optical system 3B satisfies the conditional expression (1), an increase in the size of the entire lens system can be suppressed while suppressing astigmatism.

The projection optical system 3B satisfies the following conditional expression (2), where f1 is the focal length of the first lens group LU1, and D is the distance between the first lens group LU1 and the second lens group LU2. .
−1.2 <D / f1 <−0.2 (2)
That is, in this example, D / f1 = −0.732. Since the projection optical system 3B satisfies the conditional expression (2), an interval can be secured between the first lens group LU1 and the second lens group LU2 while suppressing an increase in the size of the projection optical system 3B. Therefore, the projection optical system 3B can be configured more compactly by arranging the second optical path deflecting means 32 between the first lens group LU1 and the second lens group LU2.

Further, the projection optical system 3B satisfies the following conditional expression (3) when the focal length of the twelfth lens group LU12 is f12 and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. Is desirable.
−2.0 <f12 / f1 <−0.5 (3)
That is, in this example, f12 / f1 = −1.228. Since the projection optical system 3B satisfies the conditional expression (3), the light beam can be relayed efficiently from the first lens unit LU1 to the second lens unit LU2, and an image with sufficient contrast can be obtained on the magnification-side conjugate surface.

Further, the projection optical system 3B has the following conditional expression (D) when the distance between the first lens group LU1 and the second lens group LU2 is D and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. 4) is satisfied.
0.5 <D1 / D <2.0 (4)
That is, in this example, D1 / D = 1.107. Since the projection optical system 3B satisfies the conditional expression (4), the arrangement of the first optical path deflecting unit 31 and the second optical path deflecting unit 32 is facilitated.

Further, the projection optical system 3B has the following when the distance from the most magnified surface of the twelfth lens unit LU12 to the paraxial focal position of the intermediate image 30 is d1, and the focal length of the twelfth lens unit LU12 is f12. Conditional expression (5) is satisfied.
0.2 <d1 / f12 <0.8 (5)
That is, in this example, d1 / f12 = 0.441. Since the projection optical system 3B satisfies the conditional expression (5), it is possible to correct the curvature of field satisfactorily and to suppress an increase in the size of the second lens unit LU2. Further, since the projection optical system 3B satisfies the conditional expression (5), the second optical path deflecting unit 32 can be easily arranged.

The projection optical system 3B is a positive lens in which the most magnified lens (eighth lens L8) of the twelfth lens unit LU12 has a convex surface directed toward the reduction side. Conditional expression (6) is satisfied.
0.3 <| R | / f12 <1.5 (6)
That is, in this example, | R | /f12=1.167. Since the projection optical system 3B satisfies the conditional expression (6), it is possible to satisfactorily correct the curvature of field and to suppress the occurrence of coma and astigmatism.

  FIG. 10 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3B is at position 1. FIG. 11 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3B is at position 2. FIG. 12 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3B is at position 3. As shown in FIGS. 10 to 12, in the projection optical system 3B, spherical aberration, astigmatism and distortion are corrected satisfactorily.

  In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 for bending the optical path are provided in the middle of the projection optical system 3B. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3B and the projector 1 can be configured compactly.

  Further, in this example, the second optical path deflecting unit 32 is disposed between the first lens group LU1 and the intermediate image 30. Here, the image plane of the intermediate image 30 formed by the first lens group LU1 is curved toward the reduction side as it approaches the peripheral portion. Accordingly, the size of the second optical path deflecting unit 32 can be reduced by arranging the second optical path deflecting unit 32 between the paraxial focal positions of the first lens group LU1 and the intermediate image 30.

  In the projection optical system 3B, only one lens (eighth lens L8) of the first lens group LU1 is disposed between the first optical path deflecting unit 31 and the second optical path deflecting unit 32. Therefore, as compared with the case where a plurality of lenses are arranged between the first optical path deflecting unit 31 and the second optical path deflecting unit 32, each lens constituting the projection optical system 3B can be arranged with high positional accuracy. Further, in the projection optical system 3B, no optical path deflecting unit is disposed in the middle of the second lens group LU2. Accordingly, the positional accuracy of the plurality of lenses constituting the second lens group LU2 is not lowered by the arrangement of the optical path deflecting means, and deterioration of the optical performance in the second lens group LU2 can be avoided.

  Here, also in this example, the twelfth lens group LU12, the first optical path deflecting means 31, and the second optical path deflecting means 32 are supported by a single support member 37 shown in FIG. 7, and the eleventh lens group LU11. The first lens barrel 35 for holding the second lens barrel 36 and the second lens barrel 36 for holding the second lens group LU2 are in contact with the support member 37. Therefore, the eleventh lens group LU11, the twelfth lens group LU12, the second lens group LU2, the first optical path deflecting means 31, and the second optical path deflecting means 32 can be arranged with high positional accuracy.

  In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are mirrors, and the distance between the mirrors is short. Furthermore, since the twelfth lens group LU12 is detachably supported by the third support portion 37c, if the twelfth lens group LU12 is detached from the support member 37, the first optical path deflecting means 31 and the second optical path deflecting means are collimated. Measurements such as 32 squareness can be made. Therefore, it is possible to easily secure the positional accuracy of each of the optical path deflecting means 31 and 32.

  Further, when the focal position of the intermediate image 30 coincides with the second optical path deflecting unit 32, scratches on the reflecting surface of the second optical path deflecting unit 32, dust adhering to the reflecting surface, etc. are enlarged and projected as they are. There is a risk of end. On the other hand, in this example, as shown in FIG. 9, the second optical path deflecting unit is arranged so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of the second optical path deflecting unit 32 do not overlap. 32 is arranged. Therefore, it can be avoided that dust or the like adhering to the reflecting surface is enlarged and projected as it is.

  A prism or the like can be used as the first optical path deflecting unit 31 and the second optical path deflecting unit 32. In this example, the optical axis L is deflected twice in the vertical direction, but the optical axis L may be deflected in an arbitrary direction.

(Example 3)
FIG. 13 is a configuration diagram (ray diagram) of the projection optical system according to the third embodiment. FIG. 14 is a configuration diagram (ray diagram) of the projection optical system when two optical path deflecting units are arranged. As shown in FIG. 13, the projection optical system 3C of this example includes a first lens group LU1 that conjugates the liquid crystal panel 18 (18R, 18G, 18B), which is a reduction-side conjugate surface, and the intermediate image 30, and an intermediate image. 30 and a second lens unit LU2 that conjugates the screen S that is a magnification side conjugate surface. The first lens group LU1 serves as a relay optical system that forms an intermediate image 30 from the image on the liquid crystal panel 18 disposed at the reduction-side conjugate position, and the second lens group LU2 is an intermediate image formed by the relay optical system. It functions as a magnifying optical system that magnifies and projects 30. The projection optical system 3C is composed of 19 lenses as a whole.

  The first lens group LU1 is composed of nine lenses. That is, the first lens unit LU1 includes, in order from the reduction side, a positive first lens L1 having a biconvex shape, a negative second lens L2 having a meniscus shape having a convex surface facing the enlargement side, and a positive first lens having a biconvex shape. 3 lenses L3, biconcave negative fourth lens L4, meniscus positive fifth lens L5 with convex surface facing the enlargement side, biconcave negative sixth lens L6, biconvex positive positive first lens 7 lens L7, meniscus positive eighth lens L8 with the convex surface facing the enlargement side, and meniscus positive ninth lens L9 with the convex surface facing the reduction side. The third lens L3 and the fourth lens L4 are cemented to form the first cemented lens LC1. The sixth lens L6 and the seventh lens L7 are cemented to form a second cemented lens LC2. A stop STO is disposed between the fourth lens L4 and the fifth lens L5.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 composed of a plurality of lenses and a twelfth lens group LU12 composed of at least one positive lens. In the present example, the eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens group LU12 includes a ninth lens L9.

  The second lens group LU2 is composed of ten lenses. In other words, the second lens unit LU2 has, in order from the reduction side, a positive tenth lens L10 having an aspheric surface on both sides, a biconvex positive eleventh lens L11, and a meniscus shape with a convex surface facing the enlargement side. Negative 12th lens L12, biconvex positive 13th lens L13, biconvex positive 14th lens L14, biconcave negative 15th lens L15, biconvex positive 16th lens L16 A negative 17th lens L17 with a meniscus shape with an aspheric surface on both sides and a convex surface on the enlargement side, a negative 18th lens L18 with a meniscus shape with a convex surface on the enlargement side, and an aspheric surface on both sides It consists of a negative nineteenth lens L19. The eleventh lens L11 and the twelfth lens L12 are cemented to form a third cemented lens LC3. The fourteenth lens L14 and the fifteenth lens L15 are cemented to form a fourth cemented lens LC4.

  The second lens group LU2 is composed of a twenty-first lens group LU21 and a twenty-second lens group LU22 in order from the reduction side. The 22nd lens group LU22 is composed of three or less negative lenses and one positive lens in order from the magnification side. The twenty-first lens group LU21 includes a lens closer to the intermediate image 30 than the twenty-second lens group LU22. In this example, the 22nd lens group LU22 includes three negative lenses (19th lens L19, 18th lens L18, 17th lens L17) and 1 positive lens (16th lens L16) in order from the enlargement side. ). Accordingly, the twenty-first lens unit LU21 includes the tenth lens L10 to the fifteenth lens L15. The twenty-first lens group LU21 has positive power. The twenty-second lens group LU22 has negative power.

  Here, as shown in FIG. 14, when the projection optical system 3C is made compact, the first optical path deflecting means 31 is disposed between the eleventh lens group LU11 and the twelfth lens group LU12, and the first A second optical path deflecting unit 32 is disposed between the lens group LU1 and the second lens group LU2. In this example, the second optical path deflecting unit 32 is located closer to the first lens group LU1 (reduction side) than the intermediate image 30. In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 deflect the optical axis L in the vertical direction twice, and the optical path is inverted by 180 °. Each of the optical path deflecting means 31 and 32 is a mirror having a surface coated with a reflective material such as aluminum.

  When the projection size on the screen S is changed by the projection optical system 3C, as shown in FIG. 13, the first focus lens including the eleventh lens L11 to the fifteenth lens L15 with the nineteenth lens L19 fixed. Focusing is performed by moving the group LF1 and the second focusing lens group LF2 including three lenses of the sixteenth lens L16 to the eighteenth lens L18 in the optical axis L direction.

Next, when the focal length is f, the F number is FNo., And the maximum field angle (half field angle) is ω,
The data of the projection optical system 3C is as follows.
f -3.960
FNo. 1.606
ω 71.0 °

  The lens data of the projection optical system 3C is as follows. The lens column is a symbol assigned to each lens in FIGS. 13 and 14. Surfaces marked with * are aspheric surfaces. R is a radius of curvature. d is the axial top surface spacing (mm) (lens thickness or lens spacing). nd is a refractive index. νd is the Abbe number. The axial upper surface distance M1 is the distance between the screen S and the nineteenth lens L19. The axial upper surface distance M2 is a distance between the nineteenth lens L19 and the second focus lens group LF2 (the sixteenth lens L16 to the eighteenth lens L18). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (the 16th lens L16 to the 18th lens L18) and the first focus lens group LF1 (the 11th lens L11 to the 15th lens L15). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the eleventh lens L11 to the fifteenth lens L15) and the tenth lens L10. The axial top surface spacing M1 varies depending on the projection size, and the axial top surface spacings M2, M3, and M4 vary due to focusing when the projection size is changed.

Lens Surface number R d nd νd
S Infinity M1
L19 * 1 -22.342 5.000 1.53116 56.04
* 2 367.977 M2
L18 3 31.262 2.000 1.88300 40.80
4 16.852 8.770
L17 5 155.893 2.000 1.61800 63.33
6 12.270 8.191
L16 7 64.595 10.466 1.92286 20.88
8 -64.534 M3
L15 9 -30.507 1.200 1.80000 29.84
L14 10 24.153 10.500 1.61800 63.33
11 -21.719 0.200
L13 12 68.911 10.558 1.49700 81.54
13 -26.721 0.100
L12 14 52.585 2.000 1.85896 22.73
L11 15 21.861 11.067 1.49700 81.54
16 -43.040 M4
L10 * 17 -17.734 8.311 1.53116 56.04
* 18 -13.535 58.389
L9 19 -1571.490 8.000 1.80440 39.59
20 -72.016 60.236
L8 21 71.831 7.500 1.85026 32.27
22 324.392 59.198
L7 23 26.215 9.500 1.85150 40.78
L6 24 -26.527 1.200 1.80000 29.84
25 18.068 1.650
L5 * 26 34.959 3.476 1.83441 37.28
* 27 2458.719 1.500
STO 28 Infinity 2.213
L4 29 -20.006 1.500 1.72825 28.46
L3 30 20.997 7.500 1.49700 81.54
31 -20.219 13.687
L2 32 150.784 2.000 1.68893 31.16
33 43.700 2.016
L1 34 62.210 8.500 1.84666 23.78
35 -33.913 0.300
36 Infinity 25.910 1.51680 64.17
37 Infinity 9.521
OBJ Infinity

The axis top surface spacings M1, M2, M3, and M4 when focusing is performed by changing the projection size are as follows. The position of each lens after focusing when the axial upper surface distance M1 which is the distance between the 21st lens L21 and the screen S is set to the reference projection distance of 500 mm is the position 1, and the axial upper surface distance M1 is closer to the reference projection distance. The position of each lens when 411 mm is set as position 2, and the position of each lens when the axial top surface distance M1 is set to 662 mm far from the reference projection distance is set as position 3.
Position 1 Position 2 Position 3
M1 500.000 411.800 662.000
M2 8.049 8.075 8.038
M3 4.615 4.563 4.668
M4 3.198 3.224 3.156

  Here, the first surface and the second surface are higher-order aspheric surfaces represented by an odd-order aspheric expression (equation 1) including odd-order aspheric coefficients. The following values are the coefficients of the odd-order aspheric expression for defining the aspheric shapes of the surface numbers 1 and 2 that are aspheric.

Surface number 1 2
K -17.37145 -90.00000
A03 5.24385E-04 1.26431E-03
A04 -5.49051E-06 -1.39007E-05
A05 -1.84378E-07 -2.74660E-07
A06 3.44216E-09 -3.44368E-09
A07 8.62800E-11 -1.93469E-11
A08 -1.40501E-12 3.26864E-12
A09 -2.88489E-14 0.00000E + 00
A10 5.60575E-16 0.00000E + 00

  Next, the 17th surface, the 18th surface, the 26th surface, and the 27th surface are higher-order aspherical surfaces represented by an even-order aspherical expression (equation 2) including an even-ordered aspherical coefficient. The following values are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 17, 18, 26, and 27 that are aspherical.

Surface No. 17 18 26 27
K 0.00000 -0.95526 1.31550 0.00000
A04 1.15290E-04 1.04400E-04 2.86100E-06 9.81450E-06
A06 2.95970E-08 1.98450E-07 6.62170E-08 9.36070E-08
A08 -8.12790E-10 -6.73910E-10 -3.42980E-11 -2.91180E-10
A10 1.96700E-12 -4.28890E-14 0.00000E + 00 0.00000E + 00
A12 -1.42320E-15 0.00000E + 00 0.00000E + 00 0.00000E + 00

  In this example, the 22nd lens group LU22 located closest to the screen S includes one positive lens (16th lens L16) and 3 negative lenses (17th lens L17, 18th lens L18 and 19th lens L19). Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  In the first lens group LU1, the twelfth lens group LU12 located on the intermediate image 30 side is a positive lens (the ninth lens L9). Therefore, it is easy to form the intermediate image 30.

Further, the projection optical system 3C satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f1 is the focal length of the first lens unit LU1.
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
That is, in this example, f / f1 = 0.064. Since the projection optical system 3C satisfies the conditional expression (1), it is possible to suppress an increase in the size of the entire lens system while suppressing astigmatism.

The projection optical system 3C satisfies the following conditional expression (2), where f1 is the focal length of the first lens group LU1, and D is the distance between the first lens group LU1 and the second lens group LU2. .
−1.2 <D / f1 <−0.2 (2)
That is, in this example, D / f1 = −0.937. Since the projection optical system 3C satisfies the conditional expression (2), an interval can be secured between the first lens group LU1 and the second lens group LU2 while suppressing an increase in the size of the projection optical system 3C. Therefore, the projection optical system 3C can be configured more compactly by arranging the second optical path deflecting means 32 between the first lens group LU1 and the second lens group LU2.

Further, the projection optical system 3C satisfies the following conditional expression (3) when the focal length of the twelfth lens group LU12 is f12 and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. Is desirable.
−2.0 <f12 / f1 <−0.5 (3)
That is, in this example, f12 / f1 = −1.494. Since the projection optical system 3C satisfies the conditional expression (3), the light flux can be relayed efficiently from the first lens unit LU1 to the second lens unit LU2, and an image with sufficient contrast can be obtained on the enlargement side conjugate surface.

Further, the projection optical system 3C has the following conditional expression (D) when the distance between the first lens group LU1 and the second lens group LU2 is D and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. 4) is satisfied.
0.5 <D1 / D <2.0 (4)
That is, in this example, D1 / D = 1.032. Since the projection optical system 3C satisfies the conditional expression (4), the arrangement of the first optical path deflecting unit 31 and the second optical path deflecting unit 32 is facilitated.

Further, the projection optical system 3C has the following when the distance from the most magnified surface of the twelfth lens group LU12 to the paraxial focal position of the intermediate image 30 is d1, and the focal length of the twelfth lens group LU12 is f12. Conditional expression (5) is satisfied.
0.2 <d1 / f12 <0.8 (5)
That is, in this example, d1 / f12 = 0.410. Since the projection optical system 3C satisfies the conditional expression (5), it is possible to correct the curvature of field satisfactorily and to suppress an increase in the size of the second lens unit LU2. Further, since the projection optical system 3C satisfies the conditional expression (5), the second optical path deflecting unit 32 can be easily arranged.

The projection optical system 3C is a positive lens in which the most magnified lens (eighth lens L8) of the twelfth lens unit LU12 has a convex surface facing the reduction side, and when the curvature radius of the convex surface is R, Conditional expression (6) is satisfied.
0.3 <| R | / f12 <1.5 (6)
That is, in this example, | R | /f12=0.773. Since the projection optical system 3C satisfies the conditional expression (6), it is possible to satisfactorily correct the curvature of field and to suppress the occurrence of coma and astigmatism.

  FIG. 15 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3C is at position 1. FIG. 16 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3C is at position 2. FIG. 17 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3C is at position 3. As shown in FIGS. 15 to 17, in the projection optical system 3C, spherical aberration, astigmatism and distortion are corrected satisfactorily.

  In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 for bending the optical path are provided in the middle of the projection optical system 3C. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3C and the projector 1 can be configured in a compact manner.

  Further, in this example, the second optical path deflecting unit 32 is disposed between the first lens group LU1 and the intermediate image 30. Here, the image plane of the intermediate image 30 formed by the first lens group LU1 is curved toward the reduction side as it approaches the peripheral portion. Accordingly, the size of the second optical path deflecting unit 32 can be reduced by arranging the second optical path deflecting unit 32 between the paraxial focal positions of the first lens group LU1 and the intermediate image 30.

  In the projection optical system 3C, only one lens (eighth lens L8) of the first lens group LU1 is disposed between the first optical path deflecting unit 31 and the second optical path deflecting unit 32. Therefore, as compared with the case where a plurality of lenses are arranged between the first optical path deflecting unit 31 and the second optical path deflecting unit 32, each lens constituting the projection optical system 3C can be arranged with high positional accuracy. In the projection optical system 3C, no optical path deflecting unit is disposed in the middle of the second lens group LU2. Accordingly, the positional accuracy of the plurality of lenses constituting the second lens group LU2 is not lowered by the arrangement of the optical path deflecting means, and deterioration of the optical performance in the second lens group LU2 can be avoided.

  Here, also in this example, the twelfth lens group LU12, the first optical path deflecting means 31, and the second optical path deflecting means 32 are supported by a single support member 37 shown in FIG. 7, and the eleventh lens group LU11. The first lens barrel 35 for holding the second lens barrel 36 and the second lens barrel 36 for holding the second lens group LU2 are in contact with the support member 37. Therefore, the eleventh lens group LU11, the twelfth lens group LU12, the second lens group LU2, the first optical path deflecting means 31, and the second optical path deflecting means 32 can be arranged with high positional accuracy.

  In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are mirrors, and the distance between the mirrors is short. Furthermore, since the twelfth lens group LU12 is detachably supported by the third support portion 37c, if the twelfth lens group LU12 is detached from the support member 37, the first optical path deflecting means 31 and the second optical path deflecting means are collimated. Measurements such as 32 squareness can be made. Therefore, it is possible to easily secure the positional accuracy of each of the optical path deflecting means 31 and 32.

  Further, when the focal position of the intermediate image 30 coincides with the second optical path deflecting unit 32, scratches on the reflecting surface of the second optical path deflecting unit 32, dust adhering to the reflecting surface, etc. are enlarged and projected as they are. There is a risk of end. On the other hand, in this example, as shown in FIG. 14, the second optical path deflecting unit is configured so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of the second optical path deflecting unit 32 do not overlap. 32 is arranged. Therefore, it can be avoided that dust or the like adhering to the reflecting surface is enlarged and projected as it is.

  A prism or the like can be used as the first optical path deflecting unit 31 and the second optical path deflecting unit 32. In this example, the optical axis L is deflected twice in the vertical direction, but the optical axis L may be deflected in an arbitrary direction.

(Modification of Example 3)
FIG. 18 is a configuration diagram (ray diagram) of a modification of the projection optical system 3C. As shown by an imaginary line in FIG. 13, the projection optical system 3C ′ according to the modification is composed of a twelfth lens group LU12 of the first lens group LU1 in the projection optical system 3C, two lenses, an eighth lens L8 and a ninth lens L9. This is a positive lens. The eleventh lens group LU11 in the projection optical system 3C is a first lens L1 to a seventh lens L7. Therefore, in the projection optical system 3C ′, as shown in FIG. 18, the first optical path is between the eleventh lens group LU11 and the twelfth lens group LU12 (that is, between the seventh lens L7 and the eighth lens L8). A deflecting unit 31 is disposed, and a second optical path deflecting unit 32 is disposed between the first lens group LU1 and the second lens group LU2.

  Also in this example, no optical path deflecting unit is arranged in the middle of the second lens group LU2. Accordingly, the positional accuracy of the plurality of lenses constituting the second lens group LU2 is not lowered by the arrangement of the optical path deflecting means, and deterioration of the optical performance in the second lens group LU2 can be avoided.

  Further, the projection optical system 3C ′ of this example satisfies all of the conditional expressions (1) to (6). Therefore, the same effect as that of the projection optical system 3C can be obtained.

  In the projection optical system 3C ′ in which the twelfth lens group LU12 is two positive lenses, an eighth lens L8 and a ninth lens L9, the focal length f12 of the twelfth lens group LU12 is different from that of the projection optical system 3C. To become. Further, the distance D1 between the eleventh lens group LU11 and the twelfth lens group LU12 is a distance on the optical axis between the seventh lens L7 and the eighth lens L8 as shown by an imaginary line in FIG. This is different from the optical system 3C. Therefore, in the projection optical system 3C ′, the values of the conditional expressions (3) to (6) are different from those of the projection optical system 3C.

Here, the value of the conditional expression (3) is as follows and satisfies the condition.
−2.0 <f12 / f1 = −1.494 <−0.5 (3)
The value of conditional expression (4) is as follows and satisfies the condition.
0.5 <D1 / D = 1.014 <2.0 (4)
The value of conditional expression (5) is as follows and satisfies the condition.
0.2 <d1 / f12 = 0.542 <0.8 (5)
The value of conditional expression (6) is as follows and satisfies the condition.
0.3 <| R | /f12=1.022 <1.5 (6)

  In the projection optical system 3C ′ of the present example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 perform the deflection of the optical axis L in the vertical direction by 2 degrees to reverse the optical path by 180 °. The lens length of the eleventh lens group LU11 can be made shorter than the lens length of the second lens group LU2. Further, the optical axis of the eleventh lens group LU11 and the optical axis of the second lens group LU2 can be separated in the vertical direction. As a result, as shown in FIG. 18, when the liquid crystal panel 18 is disposed below the optical axis of the second lens group LU2, or when the liquid crystal panel 18 is disposed above the optical axis of the second lens group LU2, etc. The projection light of the projection optical system 3C ′ (projection light emitted from the second lens group LU2 can easily be prevented from interfering with the main body portion on which the liquid crystal panel 18 is mounted in the projector 1).

(Example 4)
FIG. 19 is a configuration diagram (ray diagram) of the projection optical system according to the third embodiment. FIG. 20 is a configuration diagram (ray diagram) of the projection optical system when two optical path deflecting means are arranged. As shown in FIG. 19, the projection optical system 3D of this example includes a first lens unit LU1 that conjugates the liquid crystal panel 18 (18R, 18G, 18B), which is a reduction-side conjugate surface, and the intermediate image 30, and an intermediate image. 30 and a second lens unit LU2 that conjugates the screen S that is a magnification side conjugate surface. The first lens group LU1 serves as a relay optical system that forms an intermediate image 30 from the image on the liquid crystal panel 18 disposed at the reduction-side conjugate position, and the second lens group LU2 is an intermediate image formed by the relay optical system. It functions as a magnifying optical system that magnifies and projects 30. The projection optical system 3D is composed of 19 lenses as a whole.

  The first lens group LU1 is composed of nine lenses. That is, the first lens unit LU1 includes, in order from the reduction side, a biconvex positive first lens L1, a biconvex positive second lens L2, and a meniscus positive third lens with a convex surface facing the reduction side. Lens L3, meniscus negative fourth lens L4 with convex surface facing the reduction side, biconcave negative fifth lens L5, biconvex shape positive sixth lens L6, meniscus with convex surface facing the enlargement side It consists of a positive seventh lens L7 in shape, a plano-convex positive eighth lens L8 with a convex surface facing the enlargement side, and a biconvex positive ninth lens L9. The third lens L3 and the fourth lens L4 are cemented to form the first cemented lens LC1. The fifth lens L5 and the sixth lens L6 are cemented to form a second cemented lens LC2. A stop STO is disposed between the fourth lens L4 and the fifth lens L5.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 composed of a plurality of lenses and a twelfth lens group LU12 composed of at least one positive lens. In the present example, the eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens group LU12 includes a ninth lens L9.

  The second lens group LU2 is composed of ten lenses. That is, the second lens group LU2 includes, in order from the reduction side, a positive tenth lens L10 having an aspheric surface on both sides, a biconcave negative eleventh lens L11, and a biconvex positive twelfth lens L12. A biconvex positive lens 13, a biconvex positive 14th lens L 14, a biconcave negative 15th lens L 15, a biconvex positive 16th lens L 16, and aspherical surfaces on both sides A negative 17th lens L17 having a meniscus shape with a convex surface facing the enlargement side, a negative 18th lens L18 with a meniscus shape having a convex surface facing the magnification side, and a negative 19th lens L19 having aspheric surfaces on both sides Consists of. The eleventh lens L11 and the twelfth lens L12 are cemented to form a third cemented lens LC3. The fourteenth lens L14 and the fifteenth lens L15 are cemented to form a fourth cemented lens LC4.

  The second lens group LU2 is composed of a twenty-first lens group LU21 and a twenty-second lens group LU22 in order from the reduction side. The 22nd lens group LU22 is composed of three or less negative lenses and one positive lens in order from the magnification side. The twenty-first lens group LU21 includes a lens closer to the intermediate image 30 than the twenty-second lens group LU22. In this example, the 22nd lens group LU22 includes three negative lenses (19th lens L19, 18th lens L18, 17th lens L17) and 1 positive lens (16th lens L16) in order from the enlargement side. ). Accordingly, the twenty-first lens unit LU21 includes the tenth lens L10 to the fifteenth lens L15. The twenty-first lens group LU21 has positive power. The twenty-second lens group LU22 has negative power.

  Here, as shown in FIG. 20, when the projection optical system 3D is made compact, the first optical path deflecting means 31 is arranged between the eleventh lens group LU11 and the twelfth lens group LU12, and the first A second optical path deflecting unit 32 is disposed between the lens group LU1 and the second lens group LU2. In this example, the second optical path deflecting unit 32 is located closer to the first lens group LU1 (reduction side) than the intermediate image 30. In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 deflect the optical axis L in the vertical direction twice, and the optical path is inverted by 180 °. Each of the optical path deflecting means 31 and 32 is a mirror having a surface coated with a reflective material such as aluminum.

  When changing the projection size on the screen S with the projection optical system 3D, as shown in FIG. 19, the first focus lens including the eleventh lens L11 to the fifteenth lens L15 with the nineteenth lens L19 fixed. Focusing is performed by moving the group LF1 and the second focusing lens group LF2 including three lenses of the sixteenth lens L16 to the eighteenth lens L18 in the optical axis L direction.

Next, when the focal length is f, the F number is FNo., And the maximum field angle (half field angle) is ω,
The data of the projection optical system 3D is as follows.
f -3.960
FNo. 1.599
ω 71.1 °

  The lens data of the projection optical system 3D is as follows. The lens column is a symbol given to each lens in FIGS. 19 and 20. Surfaces marked with * are aspheric surfaces. R is a radius of curvature. d is the axial top surface spacing (mm) (lens thickness or lens spacing). nd is a refractive index. νd is the Abbe number. The axial upper surface distance M1 is the distance between the screen S and the nineteenth lens L19. The axial upper surface distance M2 is a distance between the nineteenth lens L19 and the second focus lens group LF2 (the sixteenth lens L16 to the eighteenth lens L18). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (the 16th lens L16 to the 18th lens L18) and the first focus lens group LF1 (the 11th lens L11 to the 15th lens L15). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the eleventh lens L11 to the fifteenth lens L15) and the tenth lens L10. The axial top surface spacing M1 varies depending on the projection size, and the axial top surface spacings M2, M3, and M4 vary due to focusing when the projection size is changed.

Lens Surface number R d nd νd
S Infinity M1
L19 * 1 -23.687 5.000 1.53116 56.04
* 2 49.492 M2
L18 3 36.137 2.000 1.72916 54.68
4 19.120 7.431
L17 * 5 33.246 2.000 1.83220 40.10
* 6 14.200 11.429
L16 7 164.406 10.466 1.80 100 34.97
8 -44.222 M3
L15 9 -32.496 1.200 1.74950 35.33
L14 10 31.812 10.500 1.49700 81.54
11 -20.209 0.200
L13 12 104.522 12.416 1.49700 81.54
13 -27.938 0.100
L12 14 40.996 11.149 1.49700 81.54
L11 15 -50.668 2.000 1.85896 22.73
16 59.511 M4
L10 * 17 -301.240 9.713 1.53116 56.04
* 18 -16.241 58.389
L9 19 1238.564 7.500 2.00069 25.46
20 -120.581 77.760
L8 21 84.533 8.000 1.90043 37.37
22 Infinity 35.754
L7 23 47.387 4.000 1.85478 24.80
24 105.975 6.121
L6 25 23.358 6.174 1.76866 45.83
L5 26 -62.364 1.200 1.84666 23.78
27 15.715 4.431
STO 28 Infinity 5.360
L4 29 -17.642 1.200 1.84666 23.78
L3 30 -110.522 4.794 1.49700 81.54
31 -17.392 0.100
L2 32 60.110 3.102 1.49700 81.54
33 -293.973 10.505
L1 34 51.531 6.000 1.85896 22.73
35 -78.171 0.200
36 Infinity 25.910 1.51680 64.17
37 Infinity 9.536
OBJ Infinity

The axis top surface spacings M1, M2, M3, and M4 when focusing is performed by changing the projection size are as follows. The position of each lens after focusing when the axial upper surface distance M1 which is the distance between the 21st lens L21 and the screen S is set to the reference projection distance of 500 mm is the position 1, and the axial upper surface distance M1 is closer to the reference projection distance. The position of each lens when 411 mm is set as position 2, and the position of each lens when the axial top surface distance M1 is set to 662 mm far from the reference projection distance is set as position 3.
Position 1 Position 2 Position 3
M1 500.000 411.800 662.000
M2 4.212 4.142 4.309
M3 5.156 5.040 5.289
M4 9.029 9.214 8.798

  Here, the first surface and the second surface are higher-order aspheric surfaces represented by an odd-order aspheric expression (equation 1) including odd-order aspheric coefficients. The following values are the coefficients of the odd-order aspheric expression for defining the aspheric shapes of the surface numbers 1 and 2 that are aspheric.

Surface number 1 2
K -12.63509 -35.35501
A03 4.39772E-04 8.10560E-04
A04 -3.83844E-06 -1.68494E-05
A05 -1.45770E-07 4.38550E-08
A06 2.23492E-09 0.00000E + 00
A07 6.81484E-11 0.00000E + 00
A08 -8.57808E-13 0.00000E + 00
A09 -2.28038E-14 0.00000E + 00
A10 3.93789E-16 0.00000E + 00

  Next, the fifth surface, the sixth surface, the seventeenth surface, and the eighteenth surface are higher-order aspheric surfaces represented by an even-order aspherical expression (equation 2) including an even-order aspherical coefficient. The following values are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 5, 6, 17, and 18 that are aspherical.

Surface number 5 6 17 18
K -1.54227 -0.72945 0.00000 -0.59104
A04 -4.48250E-06 8.40840E-05 1.32870E-05 5.56830E-05
A06 -7.10270E-08 8.70120E-08 -6.27930E-08 -7.62620E-09
A08 2.53960E-10 -2.00890E-09 1.84340E-10 -2.01520E-10
A10 -2.86560E-13 1.48150E-11 9.04170E-14 1.37850E-12
A12 0.00000E + 00 0.00000E + 00 -5.48580E-16 -1.85370E-15

  In this example, the 22nd lens group LU22 located closest to the screen S includes one positive lens (16th lens L16) and 3 negative lenses (17th lens L17, 18th lens L18 and 19th lens L19). Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  In the first lens group LU1, the twelfth lens group LU12 located on the intermediate image 30 side is a positive lens (the ninth lens L9). Therefore, it is easy to form the intermediate image 30.

Further, the projection optical system 3D satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f1 is the focal length of the first lens unit LU1.
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
That is, in this example, f / f1 = 0.030. Since the projection optical system 3D satisfies the conditional expression (1), an increase in the size of the entire lens system can be suppressed while suppressing astigmatism.

The projection optical system 3D satisfies the following conditional expression (2), where f1 is the focal length of the first lens group LU1, and D is the distance between the first lens group LU1 and the second lens group LU2. .
−1.2 <D / f1 <−0.2 (2)
That is, in this example, D / f1 = −0.448. Since the projection optical system 3D satisfies the conditional expression (2), an interval can be secured between the first lens group LU1 and the second lens group LU2 while suppressing an increase in the size of the projection optical system 3D. Therefore, the projection optical system 3D can be configured more compactly by arranging the second optical path deflecting means 32 between the first lens group LU1 and the second lens group LU2.

Further, the projection optical system 3D satisfies the following conditional expression (3) when the focal length of the twelfth lens group LU12 is f12 and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. Is desirable.
−2.0 <f12 / f1 <−0.5 (3)
That is, in this example, f12 / f1 = −0.838. Since the projection optical system 3D satisfies the conditional expression (3), the light beam can be relayed efficiently from the first lens unit LU1 to the second lens unit LU2, and an image with sufficient contrast can be obtained on the magnification-side conjugate surface.

The projection optical system 3D has the following conditional expression (D) when the distance between the first lens group LU1 and the second lens group LU2 is D and the distance between the eleventh lens group LU11 and the twelfth lens group LU12 is D1. 4) is satisfied.
0.5 <D1 / D <2.0 (4)
That is, in this example, D1 / D = 1.332. Since the projection optical system 3D satisfies the conditional expression (4), the arrangement of the first optical path deflecting unit 31 and the second optical path deflecting unit 32 is facilitated.

Further, the projection optical system 3D has the following when the distance from the most magnified surface of the twelfth lens unit LU12 to the paraxial focal position of the intermediate image 30 is d1, and the focal length of the twelfth lens unit LU12 is f12. Conditional expression (5) is satisfied.
0.2 <d1 / f12 <0.8 (5)
That is, in this example, d1 / f12 = 0.351. Since the projection optical system 3D satisfies the conditional expression (5), it is possible to correct the curvature of field satisfactorily and to suppress an increase in the size of the second lens unit LU2. Further, since the projection optical system 3D satisfies the conditional expression (5), the second optical path deflecting unit 32 can be easily arranged.

The projection optical system 3D is a positive lens in which the most magnified lens (eighth lens L8) of the twelfth lens group LU12 has a convex surface facing the reduction side. Conditional expression (6) is satisfied.
0.3 <| R | / f12 <1.5 (6)
That is, in this example, | R | /f12=1.104. Since the projection optical system 3D satisfies the conditional expression (6), it is possible to satisfactorily correct the curvature of field and to suppress the occurrence of coma and astigmatism.

  FIG. 21 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3D is at position 1. FIG. 22 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3D is at position 2. FIG. 23 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3D is at position 3. As shown in FIGS. 21 to 23, in the projection optical system 3D, spherical aberration, astigmatism, and distortion are corrected satisfactorily.

  In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 for bending the optical path are provided in the middle of the projection optical system 3D. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3D and the projector 1 can be configured compactly.

  Further, in this example, the second optical path deflecting unit 32 is disposed between the first lens group LU1 and the intermediate image 30. Here, the image plane of the intermediate image 30 formed by the first lens group LU1 is curved toward the reduction side as it approaches the peripheral portion. Accordingly, the size of the second optical path deflecting unit 32 can be reduced by arranging the second optical path deflecting unit 32 between the paraxial focal positions of the first lens group LU1 and the intermediate image 30.

  In the projection optical system 3D, only one lens (the ninth lens L9) of the first lens group LU1 is disposed between the first optical path deflecting unit 31 and the second optical path deflecting unit 32. Therefore, as compared with the case where a plurality of lenses are arranged between the first optical path deflecting unit 31 and the second optical path deflecting unit 32, each lens constituting the projection optical system 3D can be arranged with high positional accuracy. In the projection optical system 3D, no optical path deflecting unit is disposed in the middle of the second lens group LU2. Accordingly, the positional accuracy of the plurality of lenses constituting the second lens group LU2 is not lowered by the arrangement of the optical path deflecting means, and deterioration of the optical performance in the second lens group LU2 can be avoided.

  Here, also in this example, the twelfth lens group LU12, the first optical path deflecting means 31, and the second optical path deflecting means 32 are supported by a single support member 37 shown in FIG. 7, and the eleventh lens group LU11. The first lens barrel 35 for holding the second lens barrel 36 and the second lens barrel 36 for holding the second lens group LU2 are in contact with the support member 37. Therefore, the eleventh lens group LU11, the twelfth lens group LU12, the second lens group LU2, the first optical path deflecting means 31, and the second optical path deflecting means 32 can be arranged with high positional accuracy.

  In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are mirrors, and the distance between the mirrors is short. Furthermore, since the twelfth lens group LU12 is detachably supported by the third support portion 37c, if the twelfth lens group LU12 is detached from the support member 37, the first optical path deflecting means 31 and the second optical path deflecting means are collimated. Measurements such as 32 squareness can be made. Therefore, it is possible to easily secure the positional accuracy of each of the optical path deflecting means 31 and 32.

  Further, when the focal position of the intermediate image 30 coincides with the second optical path deflecting unit 32, scratches on the reflecting surface of the second optical path deflecting unit 32, dust adhering to the reflecting surface, etc. are enlarged and projected as they are. There is a risk of end. On the other hand, in this example, as shown in FIG. 20, the second optical path deflecting unit is configured so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of the second optical path deflecting unit 32 do not overlap. 32 is arranged. Therefore, it can be avoided that dust or the like adhering to the reflecting surface is enlarged and projected as it is.

  A prism or the like can be used as the first optical path deflecting unit 31 and the second optical path deflecting unit 32. In this example, the optical axis L is deflected twice in the vertical direction, but the optical axis L may be deflected in an arbitrary direction.

DESCRIPTION OF SYMBOLS 1 ... Projector (projection type image display apparatus), 2 ... Image light production | generation optical system, 3 * 3A-3D ... Projection optical system, 4 ... Control part, 6 ... Image processing part, 7 ... Display drive part, 10 ... Light source, DESCRIPTION OF SYMBOLS 11 ... 1st integrator lens, 12 ... 2nd integrator lens, 13 ... Polarization conversion element, 14 ... Superimposing lens, 15 ... Dichroic mirror, 16 ... Reflection mirror, 17R * 17G * 17B ... Field lens, 18R * 18G * 18B ... Liquid crystal panel (reduction-side conjugate surface), 19: cross dichroic prism, 21: dichroic mirror, 22 ... relay lens, 23 ... reflection mirror, 24 ... relay lens, 25 ... reflection mirror, 30 ... intermediate image, 31 ... first optical path Deflection means, 32 ... second optical path deflection means, 35 ... first lens barrel, 36 ... second lens barrel, 37 ... support member, 37a ... first support section, 3 b ... 2nd support part, 37c ... 3rd support part, 37d ... 1st contact part, 37e ... 2nd contact part, L ... Optical axis, L1-L21 ... Lens, LU1 ... 1st lens group, LU11 ... Eleventh lens group, LU12 ... 12th lens group, LU2 ... second lens group, LU21 ... 21st lens group, LU22 ... 22nd lens group, LF1 ... first focus lens group, LF2 ... second focus lens group LC1-LC4: cemented lens, M1-M4: axial top surface spacing, S: screen (enlarged side conjugate surface).

Claims (9)

A first lens group that conjugates a reduction-side conjugate surface located on the reduction side and an intermediate image, and a second lens group that conjugates the intermediate image and an enlargement-side conjugate surface located on the magnification side;
The second lens group has a half angle of view of 60 ° or more,
When the focal length of the entire lens system is f, the focal length of the first lens group is f1, and the distance between the first lens group and the second lens group is D, the following conditional expressions (1) and (2 ) Satisfying the above).
0.01 <f / f1 <0.1 (f <0, f1 <0) (1)
−1.2 <D / f1 <−0.2 (2) The first lens group includes an eleventh lens group composed of a plurality of lenses and a twelfth lens group composed of at least one positive lens, which are arranged in order from the reduction side.
The projection optical system according to claim 1, wherein the following conditional expression (3) is satisfied when a focal length of the twelfth lens group is f12.
−2.0 <f12 / f1 <−0.5 (3) First optical path deflecting means disposed between the eleventh lens group and the twelfth lens group;
Second optical path deflecting means disposed between the first lens group and the second lens group;
Have
The projection optical system according to claim 2, wherein the following conditional expression (4) is satisfied, where D1 is an interval between the eleventh lens group and the twelfth lens group.
0.5 <D1 / D <2.0 (4) The following conditional expression (5) is satisfied, where d1 is a distance from the most magnified surface of the twelfth lens group to the paraxial focal position of the intermediate image. Projection optical system.
0.2 <d1 / f12 <0.8 (5) The twelfth lens group is a positive lens in which the most magnified lens has a convex surface on the reduction side,
5. The projection optical system according to claim 2, wherein when the radius of curvature of the convex surface is R, the following conditional expression (6) is satisfied.
0.3 <| R | / f12 <1.5 (6) The second lens group includes a twenty-second lens group including three or less negative lenses and one positive lens in order from the magnification side, and a twenty-first lens group located on the reduction side of these lenses. Become
The twenty-first lens group has positive power;
The projection optical system according to claim 1, wherein the twenty-second lens group has a negative power.   4. The projection optical system according to claim 3, wherein only one lens is arranged between the first optical path deflecting unit and the second optical path deflecting unit.   The projection optical system according to claim 3 or 7, wherein the two optical path deflecting units are supported by a single support member. A projection optical system according to any one of claims 1 to 8,
An image display element for displaying an image on the reduction-side conjugate plane;
A projection-type image display device comprising:

Images