JP2018138944A - Projection optical system and projection-type image display device - Google Patents

Abstract

To provide a projection optical system capable of suppressing the occurrence of distortion on a projected image plane while suppressing an increase in the number of lenses when an angle of view is increased. A projection optical system 3A includes a reduction-side conjugate surface (liquid crystal panel 18) positioned on the reduction side and a first lens group LU1 that conjugates the intermediate image 30, and an enlargement side positioned on the magnification side of the intermediate image 30. The second lens unit LU2 makes the conjugate surface (screen S) conjugate. The second lens group LU2 has a half angle of view of 60 ° or more, the focal length of the entire lens system is f, the focal length of the second lens group is f2, and the second lens group from the most reduction side surface of the first lens group. The following conditional expressions (1) and (2) are satisfied, where TL is the distance to the most magnified surface and D is the distance between the first lens group and the second lens group. 1.0 <f2 / | f | <2.2 (1) 0.27 <D / TL <0.45 (2) [Selection] FIG.

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 aberration in the projection optical system. Further, in a projection optical system that forms an intermediate image in the middle of the lens system, the overall length of the lens tends to be long. Therefore, as in Patent Document 1, an optical path deflecting means is arranged in the middle of the optical system to make the whole compact. Is required.

  In view of these points, an object of the present invention is to provide a projection optical system that suppresses the occurrence of aberrations that affect performance, such as the placement accuracy of optical path deflection means, and facilitates the placement of optical path deflection means. There is to do. 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 magnification side of the intermediate image. A second lens group having a conjugate plane 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 second lens group is f2, when TL is the distance from the most demagnifying side surface of the first lens group to the most enlarging side surface of the second lens group, and D is the distance between the first lens group and the second lens group, The following conditional expressions (1) and (2) are satisfied.
1.0 <f2 / | f | <2.2 (1)
0.27 <D / TL <0.45 (2)

  Since the present invention satisfies the conditional expression (1), various aberrations can be easily corrected. That is, the first lens group needs to efficiently take in the light flux from the reduction-side conjugate surface and make it incident on the second lens group. Accordingly, it is desirable that the F-number on the reduction side of the first lens group is bright. Here, if the value of the conditional expression (1) exceeds the lower limit, the focal length of the second lens group becomes too close to the focal length of the entire lens system. This makes it necessary to make the F number of the first lens group substantially equal to the F number of the second lens group, making it difficult to correct aberrations. On the other hand, when the value of conditional expression (1) exceeds the upper limit and the focal length of the second lens group is increased, the magnification of the intermediate image is increased. This makes it possible to darken the F-number of the second lens group, which facilitates correction of aberrations. However, if the intermediate image becomes too large, the image circle of the second lens group also increases, and the lens size increases accordingly. Increased and undesirable.

  In addition, since the present invention satisfies the conditional expression (2), various aberrations can be corrected in a well-balanced manner, and an interval can be secured between the first lens group and the second lens group. Therefore, for example, it is possible to arrange the optical path deflecting means between the first lens group and the second lens group to make the projection optical system more compact. That is, when the value of conditional expression (2) exceeds the upper limit, the distance between the first lens group and the second lens group becomes too wide. As a result, since the entire length of the first lens group and the entire length of the second lens group are pressed against the entire lens length, it is difficult to correct various aberrations in a balanced manner. On the other hand, if the value of conditional expression (2) exceeds the lower limit, the distance between the first lens group and the second lens group becomes narrow, and it becomes difficult to dispose the optical path deflecting means between them. 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 distance from the most reduction side surface to the most enlargement side surface of the first lens group is TL1, and the distance from the most enlargement side surface to the most reduction side surface of the second lens group is TL2. In this case, it is desirable to satisfy the following conditional expression (3).
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)

  Conditional expression (3) relates to the total length of the first lens group, the total length of the second lens group, and the distance between the first lens group and the second lens group. If conditional expression (2) is satisfied, the occurrence of various aberrations can be suppressed to a small level. Further, if the conditional expression (3) is satisfied, an interval can be secured between the first lens group and the second lens group. That is, if the value of conditional expression (3) exceeds the lower limit, the total length of the first lens group or the second lens group becomes too short, so that the first lens group or the second lens group is suppressed while suppressing the total length of the entire lens system. It becomes difficult to suppress various generated aberrations to be small. On the other hand, if the value of conditional expression (3) exceeds the upper limit, the distance between the first lens group and the second lens group becomes narrow, and it becomes difficult to dispose the optical path deflecting means between them.

  In the present invention, it is desirable to have two optical path deflecting means for bending the optical path between the first lens group and the second lens group. If the two optical path deflecting units are arranged, for example, the optical path can be deflected by 180 °, so that the projection optical system can be easily made compact. Here, when the optical path deflecting unit is disposed in the middle of the first lens group or in the middle of the second lens group, for example, a plurality of lenses constituting each lens group and the optical path deflecting unit are positioned with high positional accuracy. If not arranged, the optical performance is likely to deteriorate. That is, each lens group constitutes an imaging optical system as a single unit. Therefore, when the optical path deflecting unit is arranged in the middle of each lens group, the optical axis shift or the light is changed before and after the optical path deflecting unit. Shaft tilting (tilt) is likely to occur, and optical performance is likely to deteriorate. On the other hand, if the optical path deflecting unit is arranged between the first lens group and the second lens unit, it is avoided that the positional accuracy of the plurality of lenses constituting each lens group is lowered by the arrangement of the optical path deflecting unit. it can. Therefore, it is possible to avoid the occurrence of a shift of the optical axis or tilting of the optical axis in each lens group, and it is possible to avoid deterioration of the optical performance of each lens group. Further, when the optical path deflecting means is provided in the lens group, the performance deterioration is not proportional to the angle of view, so it is difficult to simply correct the performance deterioration caused by one optical path deflecting means with the other optical path deflecting means. On the other hand, when the optical path deflecting means is provided between the lens groups, the cause of the performance deterioration caused by one of the optical path deflecting means is only the tilt in proportion to the angle of view of the intermediate image plane. By adjusting the means, the optical axes of the first lens group and the second lens group can be easily adjusted.

In the present invention, the two optical path deflecting units include a first optical path deflecting unit disposed between the first lens group and the intermediate image, and between the first optical path deflecting unit and the second lens group. The distance from the most magnified surface of the first lens unit to the paraxial focal position of the intermediate image is d1, and the intermediate image from the most demagnifying surface of the second lens unit. When the distance to the paraxial focal position is d2, it is desirable to satisfy the following conditional expressions (4) and (5).
0.2 <f2 / d2 <0.7 (4)
0.1 <d2 / d1 <0.35 (5)

  Conditional expression (4) relates to the ratio between the focal length of the second lens group and the distance from the reduction-side surface of the second lens group to the paraxial focal position of the intermediate image. If the conditional expression (4) is satisfied, the back focus of the second lens group can be secured while suppressing the total length of the second lens group. Moreover, if the conditional expression (4) is satisfied, the influence of dust or the like attached to the optical path deflecting element can be suppressed. That is, if the value of conditional expression (4) exceeds the lower limit, the back focus of the second lens group becomes too long, and it is difficult to ensure sufficient performance while suppressing the overall length of the second lens group. . On the other hand, when the value of conditional expression (4) exceeds the upper limit, the back focus of the second lens group becomes too short. As a result, when two optical path deflecting units are disposed between the first lens group and the second lens group, the optical path deflecting unit disposed near the second lens group is positioned near the intermediate image. It will be. As a result, it becomes easy to project dust or the like adhering to the optical path deflecting unit onto the enlargement side conjugate plane, and therefore, it is easily affected by dust or the like adhering to the optical path deflecting unit. Here, the intermediate image formed by the first lens group tends to bend toward the reduction side as the image height increases from the vicinity of the optical axis. Therefore, the second optical path deflecting unit is preferably disposed between the intermediate image and the second lens group. However, if the value of the conditional expression (4) exceeds the lower limit, the distance between the intermediate image and the second lens group is increased. Narrow. Accordingly, it is difficult to dispose the second optical path deflecting unit between the intermediate image and the second lens group.

  Conditional expression (5) relates to the ratio of the distance from the first lens group to the intermediate image and the distance from the second lens group to the intermediate image. If the conditional expression (5) is satisfied, the two optical path deflecting units can be arranged efficiently. In other words, if the value of conditional expression (5) exceeds the lower limit, the distance between the intermediate image and the second lens group becomes too short, so the second deflecting means must be arranged between the intermediate image and the first optical path deflecting means. Occurs. Here, if the second deflecting unit is disposed between the intermediate image and the first optical path deflecting unit, it is necessary to provide a gap between the first lens unit and the second lens unit, so that the total lens length becomes long. On the other hand, if the value of conditional expression (5) exceeds the upper limit, the distance between the first lens group and the intermediate image becomes too short. Therefore, it is difficult to secure a space for arranging the optical path deflecting unit between the first lens group and the intermediate image.

In the present invention, the second lens group includes, in order from the magnifying side, a twenty-second lens group composed of three or less negative lenses and one positive lens, and a twenty-first lens group located on the reduction side of these lenses. The 21st lens group has a positive power on the reduction side, the 22nd lens group has a negative power on the enlargement side, and the focal length of the 21st lens group is When f21, it is desirable to satisfy the following conditional expression (6).
0.2 <f2 / f21 <0.5 (6)

  Conditional expression (6) relates to the focal length of the 21st lens group having positive power in the second lens group. If the conditional expression (6) is satisfied, it is possible to satisfactorily correct various aberrations while suppressing the overall length of the second lens group while ensuring the back focus of the second lens group. That is, when the value of conditional expression (6) exceeds the lower limit, the focal length of the 21st lens group becomes too long. As a result, it is easy to ensure the back focus of the second lens group, but it is difficult to keep the total length of the second lens group small. On the other hand, when the value of conditional expression (6) exceeds the upper limit, the focal length of the 21st lens group becomes too short. As a result, it becomes difficult to lengthen the back focus of the second lens group, and the positive power in the second lens group becomes too strong, making it difficult to correct spherical aberration and curvature of field in a balanced manner. .

  In the present invention, the twenty-second lens group includes, in order from the reduction side, one positive lens having a convex surface on the reduction side, and two or less meniscus negative lenses having a convex surface on the enlargement side; And a negative lens having an aspherical shape with aspherical surfaces on both sides, and may be composed of four or less lenses as a whole. 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, the first lens group includes, in order from the reduction side, an eleventh lens group having a positive power and a twelfth lens group including only a positive lens, and the twelfth lens group includes: In order from the reduction side, a meniscus positive lens having a convex surface on the enlargement side, a positive lens having a convex surface on the enlargement side, and a positive lens having a convex surface on the reduction side Can be. In this way, it becomes easy to form an intermediate image. Note that the magnification side of the positive lens with the convex surface facing the reduction side may be convex or concave.

  In the present invention, the first lens group includes an eleventh lens group having a positive power and a twelfth lens group that includes only positive lenses, which are arranged in order from the reduction side. The lens group may be composed of two lenses, a meniscus positive lens having a convex surface facing the enlargement side and a biconvex positive lens, which are arranged in order from the reduction side. This also makes it easy to form an intermediate image.

In the present invention, it is desirable that the following conditional expressions (7) and (8) are satisfied when the focal length of the twelfth lens group is f12.
5 <f12 / | f | <16 (7)
0.2 <f12 / d1 <0.8 (8)

  Conditional expression (7) relates to the ratio of the focal length of the entire lens system to the focal length of the twelfth lens group. If the conditional expression (7) is satisfied, the aberration generated in the twelfth lens group can be suppressed and the enlargement of the twelfth lens group can be suppressed. That is, when the value of conditional expression (7) exceeds the lower limit, the positive power of the twelfth lens group becomes too strong. As a result, it is difficult to reduce the aberration generated in the twelfth lens group. In addition, it is difficult to increase the distance between the first lens group and the second lens group. Accordingly, when two optical path deflecting units are arranged between them, it is difficult to arrange them. On the other hand, if the value of conditional expression (7) exceeds the upper limit, the power of the twelfth lens group becomes too weak, so the angle of the light beam emitted from the twelfth lens group becomes too loose. As a result, the diameter of the lens disposed on the enlargement side of the twelfth lens group is increased, so that the lens system is enlarged.

  Conditional expression (8) relates to the ratio of the distance from the first lens group to the position of the intermediate image and the focal length of the eleventh lens group arranged on the magnification side of the first lens group. If the conditional expression (8) is satisfied, the light beam emitted from the first lens group can be corrected efficiently before entering the second lens group, and an optical path deflecting unit or the like is provided between the first lens group and the second lens group. Can be provided. Further, if the conditional expression (8) is satisfied, an increase in the size of the second lens group can be suppressed. That is, if the value of conditional expression (8) exceeds the lower limit and the distance between the twelfth lens group and the intermediate image becomes too short, the correction effect such as field curvature is reduced. If the value of conditional expression (8) exceeds the upper limit and the positive power of the twelfth lens group becomes too weak, the positive power of the entire first lens group 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 (8) exceeds the lower 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. Therefore, it is difficult to dispose the optical path deflecting unit between the first lens group and the second lens group.

  In the present invention, the two optical path deflecting units disposed between the first lens group and the second lens group 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, an image in which aberration is suppressed can be projected on a screen (enlarged side conjugate surface). Further, since the optical path deflecting element is easily disposed between the first lens group and the second lens group constituting the projection optical system, the projection optical system can be made compact by refracting the optical path of the projection optical system. Can do. 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. 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 21 lenses as a whole.

  The first lens group LU1 is composed of 11 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 reduction side, and a positive third lens having a biconvex shape. Lens L3, biconvex positive fourth lens L4 and biconcave negative fifth lens L5, meniscus positive sixth lens L6 with the convex surface facing the reduction side, biconvex positive seventh lens Lens L7, biconcave negative eighth lens L8, meniscus positive ninth lens L9 with the convex surface facing the enlargement side, biconvex positive tenth lens L10, positive with the convex surface facing the reduction side The eleventh lens L11. The second lens L2 and the third lens L3 are cemented to form a first cemented lens LC1. The fourth lens L4 to the sixth lens L6 are cemented to form a second cemented lens LC2. The seventh lens and the eighth lens are cemented to form a third cemented lens LC3.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens. The eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens unit LU12 includes three positive single lenses, a ninth lens L9 to an eleventh lens L11. A diaphragm STO (not shown) is disposed between the eleventh lens group LU11 and the twelfth lens group LU12.

  The second lens group LU2 is composed of ten lenses. That is, the second lens unit LU2 is composed of a positive twelfth lens L12 having aspheric surfaces on both sides, a meniscus negative thirteenth lens L13 with a convex surface facing the enlargement side, and a biconvex shape in order from the reduction side. A positive 14th lens L14, a biconvex positive 15th lens L15, a biconvex positive 16th lens L16, a biconcave negative 17th lens L17, a meniscus shape with a convex surface facing the reduction side A positive 18th lens L18, a negative 19th lens L19 with an aspheric surface on both sides and a convex surface on the enlargement side, a negative 20th lens L20 with a meniscus shape with a convex surface on the enlargement side, on both sides It consists of a negative 21st lens L21 with an aspherical surface. The sixteenth lens L16 and the seventeenth lens L17 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 enlargement 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 twenty-first lens unit LU21 includes a twelfth lens L12 to a seventeenth lens L17. The twenty-second lens group LU22 includes an eighteenth lens L18 to a twenty-first lens L21. 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 and the second optical path deflecting means are provided between the first lens group LU1 and the second lens group LU2. 32 is arranged. The first optical path deflecting means 31 is located closer to the first lens group LU1 than the second optical path deflecting means 32. In this example, the first optical path deflecting means 31 is located on the first lens group LU1 side with respect to the intermediate image 30, and the second optical path deflecting means 32 is located on the second lens group LU2 side with respect to 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 by the projection optical system 3A, the first focus lens group LF1 including the thirteenth lens L13 to the seventeenth lens L17 and the eighteenth lens with the twenty-first lens L21 fixed. Focusing is performed by moving the second focusing lens unit LF2 including three lenses L18 to L20 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 -3.969
FNo. 1.606
ω 70.9 °

  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. In addition, the axis | shaft upper surface space | interval M1 is the distance of the screen S and the 21st lens L21. The axial top surface distance M2 is a distance between the 21st lens L21 and the second focus lens group LF2 (18th lens L18 to 20th lens L20). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (18th lens L18 to 20th lens L20) and the first focus lens group LF1 (13th lens L13 to 17th lens L17). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the thirteenth lens L13 to the seventeenth lens L17) and the twelfth lens L12. 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
L21 * 1 -59.717 5.000 1.53116 56.04
* 2 32.050 M2
L20 3 40.042 2.000 1.72000 50.23
4 18.211 4.814
L19 * 5 32.114 2.000 1.83220 40.10
* 6 14.307 6.839
L18 7 -183.979 16.293 1.72000 50.23
8 -34.931 M3
L17 9 -14.328 1.200 1.78472 25.68
L16 10 277.599 6.040 1.49700 81.54
11 -15.377 0.200
L15 12 915.154 6.786 1.49700 81.54
13 -24.105 0.100
L14 14 35.615 7.560 1.48749 70.24
15 -120.313 0.200
L13 16 49.901 1.500 1.51633 64.14
17 27.593 M4
L12 * 18 -172.433 8.000 1.53116 56.04
* 19 -16.959 101.500
L11 20 -131.016 6.500 2.00069 25.46
21 -75.606 27.695
L10 22 103.287 9.500 1.61800 63.33
23 -231.586 2.805
L9 24 53.102 6.000 1.85150 40.78
25 90.802 42.304
STO Infinity 0.600
L8 27 -142.212 1.200 1.84666 23.78
L7 28 15.667 6.500 1.61800 63.33
29 -30.027 0.800
L6 30 -22.623 4.500 1.85150 40.78
L5 31 -12.593 1.500 1.78472 25.68
L4 32 24.490 5.000 1.58913 61.15
33 -62.257 9.091
L3 34 101.166 9.500 1.85896 22.73
L2 35 -22.299 1.500 1.74077 27.79
36 -101.370 0.100
L1 37 52.948 4.500 1.78590 44.20
38 -1243.548 1.594
39 Infinity 25.910 1.51680 64.17
40 Infinity 9.477
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 14.624 14.473 14.723
M3 3.956 3.807 4.178
M4 14.888 15.188 14.568

  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 aspherical expression for defining the aspherical shapes of the surface numbers 1 and 2 that are aspherical.

Surface number 1 2
K -0.36929 -10.08221
A03 4.98489E-04 6.46830E-04
A04 -3.48681E-06 -1.25365E-05
A05 -8.32539E-08 -1.14688E-08
A06 5.98523E-10 1.13607E-09
A07 5.73235E-11 -2.52465E-12
A08 -3.55076E-13 6.85359E-14
A09 -2.02500E-14 0.00000E + 00
A10 2.72411E-16 0.00000E + 00

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

Surface number 5 6 18 19
K -0.39406 -0.56862 0.00000 -0.63456
A04 2.18790E-06 7.27930E-05 1.93530E-06 3.66910E-05
A06 -2.33480E-08 4.81640E-07 -5.35940E-08 -1.78550E-08
A08 8.05160E-11 -4.20260E-09 3.17260E-12 -1.72810E-10
A10 -1.69080E-13 3.67280E-11 3.26170E-13 8.04100E-13
A12 0.00000E + 00 2.55140E-30 -2.83270E-16 -5.24770E-16

  In this example, the 22nd lens group LU22 located closest to the screen S includes, in order from the reduction side, a positive lens having a convex surface on the reduction side (18th lens L18) and 2 having a convex surface on the enlargement side. A negative meniscus lens (the 19th lens L19 and the 20th lens L20) and the aspherical negative lens (21st lens L21) having an aspheric surface on both sides. Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  The first lens group LU1 includes an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens, which are arranged in order from the reduction side. Are arranged in order from the reduction side, a meniscus-shaped positive lens having a convex surface on the enlargement side (ninth lens L9), a positive lens having at least a convex surface on the enlargement side (tenth lens L10), and It consists of three lenses, a positive lens (eleventh lens L11) with a convex surface facing the reduction side. Therefore, it is easy to form the intermediate image 30.

Further, the projection optical system 3A satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f2 is the focal length of the second lens unit LU2.
1.0 <f2 / | f | <2.2 (1)
That is, in this example, f2 / | f | = 1.489.

  Conditional expression (1) relates to the ratio between the focal length f of the entire lens system and the focal length f2 of the second lens unit LU2. Since the projection optical system 3A satisfies the conditional expression (1), various aberrations can be easily corrected. That is, the first lens group LU1 needs to efficiently take in the light flux from the liquid crystal panel 18 and make it incident on the second lens group LU2. Accordingly, it is desirable that the F-number on the reduction side of the first lens unit LU1 is bright. Here, if the value of conditional expression (1) exceeds the lower limit and the focal length of the second lens unit LU2 is too close to the focal length of the entire lens system, the F number of the first lens unit LU1 is set to the second lens. Since it is necessary to make the F number of the group LU2 substantially the same, it is difficult to correct aberrations. On the other hand, when the value of the conditional expression (1) exceeds the upper limit and the focal length of the second lens unit LU2 is increased, the magnification of the intermediate image 30 is increased, so that the F number of the second lens unit LU2 can be darkened. . Accordingly, correction of aberration becomes easy.

Further, the projection optical system 3A has a distance TL on the optical axis L from the most reduction side surface of the first lens unit LU1 to the most enlargement side surface of the second lens unit LU2, and the first lens unit LU1 and the first lens unit LU1. When the interval on the optical axis L of the two lens units LU2 is D, the following conditional expression (2) is satisfied.
0.27 <D / TL <0.45 (2)
That is, in this example, D / TL = 0.296.

  Since the projection optical system 3A satisfies the conditional expression (2), it is easy to correct various aberrations, and the first optical path deflection unit 31 and the second optical path deflection are provided between the first lens group LU1 and the second lens group LU2. The space for arranging the means 32 can be confirmed. That is, if the value of conditional expression (2) exceeds the upper limit and the distance between the first lens group LU1 and the second lens group LU2 becomes too wide, the total length of the first lens group LU1 and the second lens with respect to the total lens length. The entire length of the group LU2 is compressed. Therefore, it becomes difficult to correct various aberrations in a balanced manner. On the other hand, if the value of conditional expression (2) exceeds the lower limit, the distance between the first lens group LU1 and the second lens group LU2 becomes narrow, and it becomes difficult to dispose the optical path deflecting means between them.

Further, the projection optical system 3A sets the distance on the optical axis L from the most reduction side surface to the most enlargement side surface of the first lens group LU1 to TL1, and the most enlargement side from the most reduction side surface of the second lens group LU2. When the distance to the surface is TL2, the following conditional expression (3) is satisfied.
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)
That is, in this example, TL1 * TL2 / D ² = 1.382.

  Conditional expression (3) relates to the total length of the first lens group LU1, the total length of the second lens group LU2, and the distance between the first lens group LU1 and the second lens group LU2. Since the projection optical system 3A satisfies the conditional expression (2), it is possible to suppress the occurrence of various aberrations. Further, since the projection optical system 3A satisfies the conditional expression (3), the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are disposed between the first lens group LU1 and the second lens group LU2. You can confirm the space. That is, when the value of conditional expression (3) exceeds the lower limit, the total length of the first lens group LU1 or the second lens group LU2 becomes too short, so that the first lens group LU1 or It becomes difficult to suppress various aberrations that occur in the two-lens group LU2. On the other hand, if the value of the conditional expression (3) exceeds the upper limit, the distance between the first lens group LU1 and the second lens group LU2 becomes narrow, so that it becomes difficult to arrange the optical path deflecting means between them.

The projection optical system 3A has the following condition when the focal length f2 of the second lens unit LU2 and the distance from the most reduced surface of the second lens unit LU2 to the paraxial focal position of the intermediate image 30 are d2. Formula (4) is satisfied.
0.2 <f2 / d2 <0.7 (4)
That is, in this example, f2 / d2 = 0.295.

  Conditional expression (4) relates to the ratio between the focal length of the second lens unit LU2 and the distance from the reduction-side surface of the second lens unit LU2 to the paraxial focal position of the intermediate image 30. Since the projection optical system 3A satisfies the conditional expression (4), it is possible to ensure the back focus of the second lens group LU2 while suppressing the total length of the second lens group LU2. In addition, since the projection optical system 3A satisfies the conditional expression (4), it is possible to suppress the influence of dust attached to the optical path deflecting element. That is, when the value of conditional expression (4) exceeds the lower limit, the back focus of the second lens unit LU2 becomes too long, and it is difficult to ensure sufficient performance while suppressing the overall length of the second lens unit LU2. It becomes. On the other hand, when the value of conditional expression (4) exceeds the upper limit, the back focus of the second lens unit LU2 becomes too short. Thus, when two optical path deflecting units are arranged between the first lens group LU1 and the second lens group LU2, the optical path deflecting unit disposed at a position close to the second lens group LU2 is used for the intermediate image 30. It will be located in the vicinity. As a result, it becomes easy to project dust or the like adhering to the optical path deflecting unit onto the enlargement side conjugate plane, and therefore, it is easily affected by dust or the like adhering to the optical path deflecting unit.

  Here, the intermediate image 30 formed by the first lens group LU1 tends to bend toward the reduction side as the image height increases from the vicinity of the optical axis L. Therefore, as shown in FIG. 3, the second optical path deflecting unit 32 is preferably disposed between the intermediate image 30 and the second lens unit LU2, but when the value of the conditional expression (4) exceeds the lower limit, The interval between the intermediate image 30 and the second lens group LU2 becomes narrow. Accordingly, it is difficult to dispose the second optical path deflecting unit 32 between the intermediate image 30 and the second lens group LU2.

Further, the projection optical system 3A has a distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (intermediate from the most magnified surface of the first lens group LU1 on the optical axis L). (Distance to the image 30) d1, and the distance from the most reduction side surface of the second lens group LU2 to the paraxial focal position of the intermediate image 30 (from the most reduction side surface of the second lens group LU2 on the optical axis L) When the distance to the intermediate image 30 is d2, the following conditional expression (5) is satisfied.
0.1 <d2 / d1 <0.35 (5)
That is, in this example, d2 / d1 = 0.246.

  Conditional expression (5) relates to the ratio between the distance from the first lens group LU1 to the intermediate image 30 and the distance from the second lens group LU2 to the intermediate image 30. Since the projection optical system 3A satisfies the conditional expression (5), the two optical path deflecting units can be arranged efficiently. That is, if the value of the conditional expression (5) exceeds the lower limit, the distance between the intermediate image 30 and the second lens unit LU2 becomes too short, so that the second deflecting unit is located between the intermediate image 30 and the first optical path deflecting unit 31. Need to be placed in Here, if the second deflecting unit is disposed between the intermediate image 30 and the first optical path deflecting unit 31, it is necessary to provide a gap between the first lens unit LU1 and the second lens unit LU2, so that the total lens length becomes long. . On the other hand, when the value of conditional expression (5) exceeds the upper limit, the distance between the first lens unit LU1 and the intermediate image 30 becomes too short. Therefore, it is difficult to secure a space for arranging the optical path deflecting unit between the first lens group LU1 and the intermediate image 30.

Further, the projection optical system 3A satisfies the following conditional expression (6) when the focal length of the second lens unit LU2 is f2 and the focal length of the 21st lens unit LU21 is f21.
0.2 <f2 / f21 <0.5 (6)
That is, in this example, f2 / f21 = 0.256.

  Conditional expression (6) relates to the focal length of the twenty-first lens unit LU21 having positive power in the second lens unit LU2. Since the projection optical system 3A satisfies the conditional expression (6), it is possible to satisfactorily correct various aberrations while suppressing the overall length of the second lens unit LU2 while ensuring the back focus of the second lens unit LU2. That is, when the value of conditional expression (6) exceeds the lower limit, the focal length of the twenty-first lens unit LU21 becomes too long. As a result, it is easy to ensure the back focus of the second lens unit LU2, but it is difficult to keep the overall length of the second lens unit LU2 small. On the other hand, when the value of conditional expression (6) exceeds the upper limit, the focal length of the twenty-first lens unit LU21 becomes too short. As a result, it becomes difficult to lengthen the back focus of the second lens unit LU2, and the positive power in the second lens unit LU2 becomes too strong, making it difficult to correct spherical aberration and field curvature in a balanced manner. It becomes.

The projection optical system 3A satisfies the following conditional expression (7), where f is the focal length of the entire lens system and f12 is the focal length of the twelfth lens unit LU12.
5 <f12 / | f | <16 (7)
That is, in this example, f2 / f21 = 13.187.

  Conditional expression (7) relates to the ratio of the focal length of the entire lens system to the focal length of the twelfth lens unit LU12. Since the projection optical system 3A satisfies the conditional expression (7), it is possible to reduce the aberration generated in the twelfth lens group LU12 and to suppress the enlargement of the twelfth lens group LU12. That is, when the value of conditional expression (7) exceeds the lower limit, the positive power of the twelfth lens unit LU12 becomes too strong. As a result, it is difficult to reduce the aberration generated in the twelfth lens group LU12. On the other hand, if the value of the conditional expression (7) exceeds the upper limit, the power of the twelfth lens unit LU12 becomes too weak, so that the angle of the light beam emitted from the twelfth lens unit LU12 becomes too gentle. As a result, the diameter of the lens disposed on the enlargement side of the twelfth lens group LU12 increases, and the lens system increases in size. Here, if the value of conditional expression (7) exceeds the lower limit, it is difficult to increase the distance between the first lens group LU1 and the second lens group LU2. Therefore, it becomes difficult to arrange two optical path deflecting means between them.

Further, the projection optical system 3A sets the focal length of the twelfth lens group LU12 to f12, and the distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (first on the optical axis L). When the distance from the most magnified surface of the lens group LU1 to the intermediate image 30 is d1, the following conditional expression (8) is satisfied.
0.2 <f12 / d1 <0.8 (8)
That is, in this example, f12 / d1 = 0.642.

  Conditional expression (8) relates to the ratio of the distance from the first lens group LU1 to the position of the intermediate image 30 and the focal length of the eleventh lens group LU11 arranged on the enlargement side of the first lens group LU1. Since the projection optical system 3A satisfies the conditional expression (8), the light beam emitted from the first lens group LU1 can be efficiently corrected before entering the second lens group LU2, and the first lens group LU1 and the second lens can be corrected. A space in which an optical path deflecting unit or the like can be disposed can be provided between the group LU2. Further, since the projection optical system 3A satisfies the conditional expression (8), it is possible to suppress an increase in the size of the second lens unit LU2. That is, if the value of conditional expression (8) exceeds the upper limit and the distance between the twelfth lens unit LU12 and the intermediate image 30 becomes too short, the correction effect such as field curvature is reduced. If the value of conditional expression (8) exceeds the lower limit and the positive power of the twelfth lens unit LU12 becomes too weak, the positive power of the entire first lens unit LU1 becomes weak. As a result, since the relay magnification by the first lens group LU1 is increased, it is necessary to increase the diameter of the second lens group LU2, resulting in an increase in the size of the lens system. On the other hand, if the value of conditional expression (8) exceeds the lower limit and the positive power of the twelfth lens unit LU12 becomes too strong, the distance between the first lens unit LU1 and the intermediate image 30 becomes narrow. Therefore, it becomes difficult to dispose the optical path deflecting means between the first lens group LU1 and the second lens group LU2.

  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 means 31 and the second optical path deflecting means 32 for bending the optical path are provided between the first lens group LU1 and the second lens group LU2. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3A and the projector 1 can be configured compactly.

  Here, when the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are arranged in the middle of the first lens group LU1 or in the middle of the second lens group LU2, for example, the lens groups LU1 and LU2 are arranged. Unless the plurality of lenses constituting each of the optical path deflecting means 31 and 32 are arranged with high positional accuracy, the optical performance is likely to deteriorate. That is, each of the lens groups LU1 and LU2 constitutes an imaging optical system as a single unit. Therefore, when the optical path deflecting units 31 and 32 are arranged in the middle of the plurality of lenses, the optical path deflecting units 31 and 32 are provided. The optical axis L is easily shifted before and after the optical axis L, and the optical axis L is tilted (tilted). On the other hand, in this example, two optical path deflecting means 31 and 32 are arranged between the first lens group LU1 and the second lens group LU2. Accordingly, it is possible to avoid a decrease in the positional accuracy of the plurality of lenses constituting the lens groups LU1 and LU2 due to the arrangement of the optical path deflecting units 31 and 32. Therefore, it is possible to avoid the shift of the optical axis L or the tilt of the optical axis L from occurring inside the lens groups LU1 and LU2, and it is possible to avoid the deterioration of the optical performance of the lens groups LU1 and LU2.

  In this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 disposed between the first lens group LU1 and the second lens group LU2 are supported by a single support member. 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 L <b> 1 to L <b> 11 constituting the first lens group LU <b> 1 are held by the first lens barrel 35. The lenses L12 to L21 constituting the second lens group LU2 are held by the second lens barrel 36. The first optical path deflecting means 31 and the second optical path deflecting means 32 are supported by a hollow support member 37 having a right isosceles triangular shape when viewed from the side. A portion of the support member 37 corresponding to two sides sandwiching a right angle includes a first support portion 37a that supports the first optical path deflecting unit 31 and a second support that supports the second optical path deflecting unit 32 along each side. A portion 37b is provided. In addition, a first abutting portion 37c that abuts the first lens barrel 35 and a second abutting portion 37d that abuts the second lens barrel 36 are provided on one side of the support member 37 that faces the right angle of the right isosceles triangle shape. Is 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 unit 31 and the second optical path deflecting unit 32 are supported by the first optical path deflecting unit 31 supported by the first support part 37a and the second optical path deflecting unit 32 supported by the second support part 37b. The support member 37 is supported with high positional accuracy. Further, since the first contact portion 37c and the second contact portion 37d are provided on the single support member 37, the first lens barrel 35 and the second lens barrel 36 are in contact with these contact portions, respectively. By doing so, it is easy to make the optical axis of the first lens group parallel to the optical axis of the second lens group. Furthermore, since the first support part 37a, the second support part 37b, the first contact part 37c, and the second contact part 37d are provided on the single support member 37, the first lens group LU1, the second lens The 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. Accordingly, it is possible to measure the squareness etc. with the collimator, and it is possible to easily secure the positional accuracy of each of the optical path deflection means 31 and 32.

  Here, when the focal position of the intermediate image 30 coincides with each of the optical path deflecting units 31 and 32, scratches on the reflecting surface of each of the optical path deflecting units 31 and 32, dust adhering to the reflecting surface, etc. are enlarged as they are. There is a risk of projection. On the other hand, in this example, as shown in FIG. 3, each optical path deflection is performed so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of each optical path deflecting means 31, 32 do not overlap. Means 31 and 32 are 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 20 lenses as a whole.

  The first lens group LU1 is composed of 11 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 negative first lens with a convex surface facing the object side. Three lenses L3, a biconvex positive fourth lens L4, a biconcave negative fifth lens L5, an aperture stop STO, a meniscus positive sixth lens L6 with a convex surface facing the enlargement side, a biconcave shape The negative seventh lens L7 and the biconvex positive eighth lens L8, the meniscus positive ninth lens L9 with the convex surface facing the enlargement side, the biconvex positive tenth lens L10, and the reduction side It consists of a positive eleventh lens L11 with a convex meniscus shape. 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. The seventh lens and the eighth lens are cemented to form a third cemented lens LC3.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens. The eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens unit LU12 includes three positive single lenses, a ninth lens L9 to an eleventh lens L11.

  The second lens group LU2 is composed of nine lenses. That is, the second lens unit LU2 includes, in order from the reduction side, a positive twelfth lens L12 having an aspheric surface on both sides, a meniscus positive thirteenth lens L13 with a convex surface on the enlargement side, and a convex surface on the reduction side. 14th lens L14 having a positive meniscus shape, positive 15th lens L15 having a biconvex shape, negative 16th lens L16 having a biconcave shape, and 17th lens having a meniscus shape having a convex surface facing the reduction side L17, a meniscus negative 18th lens L18 having an aspheric surface on both sides and a convex surface on the enlargement side, a meniscus negative 19th lens L19 having a convex surface on the enlargement side, and an aspheric surface on both sides And a negative 20th lens L20. The fifteenth lens L15 and the sixteenth lens L16 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 enlargement 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 twenty-first lens unit LU21 includes a twelfth lens L12 to a sixteenth lens L16. The twenty-second lens group LU22 includes four lenses, a seventeenth lens 17 to a twentieth lens L20. 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 and the second optical path deflecting means are provided between the first lens group LU1 and the second lens group LU2. 32 is arranged. The first optical path deflecting means 31 is located closer to the first lens group LU1 than the second optical path deflecting means 32. In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are located on the first lens group LU1 side with respect to 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, the first focus lens group LF1 including the thirteenth lens L13 to the sixteenth lens L16 and the seventeenth lens with the twentieth lens L20 fixed. Focusing is performed by moving the second focusing lens unit LF2 including three lenses of the 17th to 19th lenses L19 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. 1.606
ω 70.8 °

  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. Note that the shaft upper surface distance M1 is the distance between the screen S and the twentieth lens L20. The axial upper surface distance M2 is a distance between the twentieth lens L20 and the second focus lens group LF2 (the seventeenth lens 17 to the nineteenth lens L19). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (17th lens 17 to 19th lens L19) and the first focus lens group LF1 (13th lens L13 to 16th lens L16). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the thirteenth lens L13 to the sixteenth lens L16) and the twelfth lens L12. 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
L20 * 1 -59.081 5.000 1.53116 56.04
* 2 30.201 M2
L19 3 45.793 2.000 1.59522 67.73
4 17.877 4.756
L18 * 5 27.133 2.000 1.74320 49.29
* 6 12.95 11.717
L17 7 -90.519 9.548 1.75700 47.82
8 -31.880 M3
L16 9 -18.458 1.200 1.85896 22.73
L15 10 255.728 5.207 1.49700 81.54
11 -18.527 0.200
L14 12 -304.149 6.645 1.49700 81.54
13 -20.939 0.100
L13 14 25.657 7.000 1.48749 70.24
15 57.792 M4
L12 * 16 86.250 8.000 1.53116 56.04
* 17 -19.193 108.000
L11 18 -509.113 6.500 2.00069 25.46
19 -108.772 0.100
L10 20 108.064 8.000 1.61800 63.33
21 -542.567 16.224
L9 22 69.520 5.400 1.88300 40.80
23 107.816 39.326
L8 24 31.403 7.000 1.85150 40.78
L7 25 -30.376 1.200 1.84666 23.78
26 17.249 1.273
L6 27 29.919 2.000 1.83400 37.16
28 37.562 1.500
STO 29 Infinity 2.500
L5 30 -20.936 2.703 1.85896 22.73
L4 31 62.369 5.500 1.48749 70.24
32 -23.302 0.100
L3 33 168.498 2.429 1.62588 35.70
L2 34 19.889 9.000 1.61800 63.33
35 -51.213 12.934
L1 36 70.253 6.500 1.85896 22.73
37 -67.231 5.225
38 Infinity 25.910 1.51680 64.17
39 Infinity 9.512
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 twentieth lens L20 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 15.765 15.813 15.701
M3 4.163 4.025 4.324
M4 17.874 17.965 17.777

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

Surface number 1 2
K -0.27775 -7.47508
A03 4.87868E-04 6.20806E-04
A04 -3.34599E-06 -1.22477E-05
A05 -8.35091E-08 -8.86070E-09
A06 4.94577E-10 1.22594E-09
A07 5.64356E-11 -6.18537E-12
A08 -2.91969E-13 6.76329E-14
A09 -1.92313E-14 0.00000E + 00
A10 2.36856E-16 0.00000E + 00

  Next, the fifth surface, the sixth surface, the sixteenth surface, and the seventeenth surface are higher-order aspheric surfaces represented by the even-order aspheric surface expression of Equation 2. The following values are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 5, 6, 16, and 17 that are aspherical surfaces.

Surface number 5 6 16 17
K -1.07910 -0.02236 0.00000 -0.62090
A04 -4.19870E-06 4.41410E-05 8.89980E-07 5.28500E-05
A06 -3.89030E-08 3.26890E-07 -4.56800E-08 -2.69000E-08
A08 7.73470E-11 -3.32120E-09 -5.55130E-11 -1.42540E-10
A10 -5.79970E-14 2.28460E-11 4.23780E-13 8.74340E-13
A12 0.00000E + 00 0.00000E + 00 -6.23540E-16 -4.09370E-16

  In this example, the 22nd lens group LU22 located closest to the screen S includes, in order from the reduction side, a positive lens having a convex surface on the reduction side (17th lens L17) and 2 having a convex surface on the enlargement side. The number of negative meniscus lenses (the 18th lens L18 and the 19th lens L19) and the aspherical negative lens (20th lens L20) with aspherical surfaces on both surfaces. Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  The first lens group LU1 includes an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens, which are arranged in order from the reduction side. Are arranged in order from the reduction side, a meniscus-shaped positive lens having a convex surface on the enlargement side (ninth lens L9), a positive lens having at least a convex surface on the enlargement side (tenth lens L10), and It consists of three lenses, a positive lens (eleventh lens L11) with a convex surface facing the reduction side. Therefore, it is easy to form the intermediate image 30.

Further, the projection optical system 3B satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f2 is the focal length of the second lens unit LU2.
1.0 <f2 / | f | <2.2 (1)
That is, in this example, f2 / | f | = 1.380. Since the projection optical system 3B satisfies the conditional expression (1), various aberrations can be easily corrected.

Further, the projection optical system 3B has a distance TL on the optical axis L from the most reduction side surface of the first lens unit LU1 to the most enlargement side surface of the second lens unit LU2, and the first lens unit LU1 and the first lens unit LU1. When the interval on the optical axis L of the two lens units LU2 is D, the following conditional expression (2) is satisfied.
0.27 <D / TL <0.45 (2)
That is, in this example, D / TL = 0.318. Since the projection optical system 3B satisfies the conditional expression (2), it is easy to correct various aberrations, and the first optical path deflection unit 31 and the second optical path deflection are provided between the first lens group LU1 and the second lens group LU2. The space for arranging the means 32 can be confirmed.

Further, the projection optical system 3B sets the distance on the optical axis L from the most reduction side surface to the most enlargement side surface of the first lens unit LU1 as TL1, and the most enlargement side from the most reduction side surface of the second lens unit LU2. When the distance to the surface is TL2, the following conditional expression (3) is satisfied.
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)
That is, in this example, TL1 * TL2 / D ² = 1.129. Since the projection optical system 3B satisfies the conditional expression (2), it is possible to suppress the occurrence of various aberrations. In addition, since the projection optical system 3B satisfies the conditional expression (3), the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are disposed between the first lens group LU1 and the second lens group LU2. You can confirm the space.

The projection optical system 3B has the following conditions when the focal length f2 of the second lens unit LU2 and the distance from the most reduced surface of the second lens unit LU2 to the paraxial focal position of the intermediate image 30 are d2. Formula (4) is satisfied.
0.2 <f2 / d2 <0.7 (4)
That is, in this example, f2 / d2 = 0.339. Since the projection optical system 3B satisfies the conditional expression (4), it is possible to secure the back focus of the second lens group LU2 while suppressing the total length of the second lens group LU2. In addition, since the projection optical system 3B satisfies the conditional expression (4), it is possible to suppress the influence of dust or the like attached to the optical path deflecting element.

Further, the projection optical system 3B has a distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (intermediate from the most magnified surface of the first lens group LU1 on the optical axis L). (Distance to the image 30) d1, and the distance from the most reduction side surface of the second lens group LU2 to the paraxial focal position of the intermediate image 30 (from the most reduction side surface of the second lens group LU2 on the optical axis L) When the distance to the intermediate image 30 is d2, the following conditional expression (5) is satisfied.
0.1 <d2 / d1 <0.35 (5)
That is, in this example, d2 / d1 = 0.176. Since the projection optical system 3B satisfies the conditional expression (5), a space for arranging the first optical path deflecting means 31 and the second optical path deflecting means 32 is provided between the first lens group LU1 and the second lens group LU2. I can confirm.

The projection optical system 3B satisfies the following conditional expression (6) when the focal length of the second lens unit LU2 is f2 and the focal length of the 21st lens unit LU21 is f21.
0.2 <f2 / f21 <0.5 (6)
That is, in this example, f2 / f21 = 0.240. Since the projection optical system 3B satisfies the conditional expression (6), it is possible to satisfactorily correct various aberrations while suppressing the overall length of the second lens unit LU2 while ensuring the back focus of the second lens unit LU2.

The projection optical system 3B satisfies the following conditional expression (7), where f is the focal length of the entire lens system and f12 is the focal length of the twelfth lens unit LU12.
5 <f12 / | f | <16 (7)
That is, in this example, f2 / f21 = 14.053. Since the projection optical system 3B satisfies the conditional expression (7), it is possible to reduce the aberration generated in the twelfth lens group LU12 and to suppress the enlargement of the twelfth lens group LU12.

Further, the projection optical system 3B sets the focal length of the twelfth lens group LU12 to f12, and the distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (first on the optical axis L). When the distance from the most magnified surface of the lens group LU1 to the intermediate image 30 is d1, the following conditional expression (8) is satisfied.
0.2 <f12 / d1 <0.8 (8)
That is, in this example, f12 / d1 = 0.606. Since the projection optical system 3B satisfies the conditional expression (8), the light beam emitted from the first lens group LU1 can be efficiently corrected before entering the second lens group LU2, and the first lens group LU1 and the second lens can be corrected. A space in which an optical path deflecting unit or the like can be disposed can be provided between the group LU2. Further, since the projection optical system 3B satisfies the conditional expression (8), it is possible to suppress an increase in size of the second lens unit LU2.

  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.

  Furthermore, 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 between the first lens group LU1 and the second lens group LU2. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3B and the projector 1 can be configured compactly.

  Here, when the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are arranged in the middle of the first lens group LU1 or in the middle of the second lens group LU2, for example, the optical performance is deteriorated. In this example, two optical path deflecting units 31 and 32 are disposed between the first lens group LU1 and the second lens group LU2. Accordingly, it is possible to avoid a decrease in the positional accuracy of the plurality of lenses constituting the lens groups LU1 and LU2 due to the arrangement of the optical path deflecting units 31 and 32. Therefore, it is possible to avoid the shift of the optical axis L or the tilt of the optical axis L from occurring inside the lens groups LU1 and LU2, and it is possible to avoid the deterioration of the optical performance of the lens groups LU1 and LU2.

  Also in this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 arranged between the first lens group LU1 and the second lens group LU2 are supported by a single support member shown in FIG. Is done. Therefore, 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 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. Accordingly, it is possible to measure the squareness etc. with the collimator, and it is possible to easily secure the positional accuracy of each of the optical path deflection means 31 and 32.

  Here, when the focal position of the intermediate image 30 coincides with each of the optical path deflecting units 31 and 32, scratches on the reflecting surface of each of the optical path deflecting units 31 and 32, dust adhering to the reflecting surface, etc. are enlarged as they are. There is a risk of projection. On the other hand, in this example, as shown in FIG. 9, each optical path deflection is performed so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of each optical path deflecting means 31, 32 do not overlap. Means 31 and 32 are 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 ten lenses. That is, in order from the reduction side, the first lens unit LU1 has a meniscus positive first lens L1 with a convex surface facing the reduction side, a biconvex positive second lens L2, and a biconvex positive third lens. Lens L3, biconcave negative fourth lens L4, biconvex positive lens F5, meniscus positive sixth lens L6 with the convex surface facing the reduction side, biconvex positive seventh lens Ten lenses of a lens L7, a meniscus negative eighth lens L8 with a convex surface facing the enlargement side, a meniscus positive ninth lens L9 with a convex surface facing the magnification side, and a tenth lens with a biconvex shape and a positive tenth lens It consists of a lens L10. The third lens L3, the fourth lens L4, and the fifth lens L5 are cemented to form the first cemented lens LC1.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens. The eleventh lens group LU11 includes a first lens L1 to an eighth lens L8. The twelfth lens group LU12 is composed of two positive single lenses, a ninth lens L9 and a tenth lens L110.

  The second lens group LU2 is composed of nine lenses. That is, the second lens unit LU2 includes, in order from the reduction side, a meniscus positive eleventh lens having a convex surface on the magnification side, a positive twelfth lens L12 having aspheric surfaces on both sides, and a convex surface on the magnification side. A meniscus positive 13th lens L13 with a facing meniscus shape, a meniscus positive 14th lens L14 with a convex surface facing the reduction side, a biconvex positive 15th lens L15, a biconcave negative 16th lens L16 The lens includes a biconvex positive 17th lens L17, a meniscus negative 18th lens L18 having a convex surface facing the enlargement side, and a negative 19th lens L19 having aspheric surfaces on both sides. The fifteenth lens L15 and the sixteenth lens L16 are cemented to form a second cemented lens LC2.

  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 enlargement 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 21st lens group LU21 is composed of an 11th lens L11 to a 16th lens L16. The twenty-second lens group LU22 includes three lenses, a seventeenth lens 17 to a nineteenth lens L19. 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 and the second optical path deflecting means are provided between the first lens group LU1 and the second lens group LU2. 32 is arranged. The first optical path deflecting means 31 is located closer to the first lens group LU1 than the second optical path deflecting means 32. In this example, the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are located closer to the first lens group LU1 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, the first focus lens group LF1 including the twelfth lens L12 to the sixteenth lens L16 and the seventeenth lens with the nineteenth lens L19 fixed. Focusing is performed by moving the second focusing lens unit LF2 including two lenses of the 17th to 18th lenses 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. 1.896
ω 71.2 °

  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 19th lens L19 and the second focus lens group LF2 (the 17th lens 17 and the 18th lens L18). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (the 17th lens 17 and the 18th lens L18) and the first focus lens group LF1 (the 12th lens L12 to the 16th lens L16). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the twelfth lens L12 to the sixteenth lens L16) and the eleventh lens L11. 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 -101.450 2.771 1.50941 55.87
* 2 22.745 M2
L18 3 25.280 2.000 1.72000 50.23
4 12.132 7.310
L17 5 684.622 2.174 1.65412 39.68
6 -134.912 M3
L16 7 -20.923 1.200 1.84666 23.78
L15 8 91.218 10.500 1.61800 63.33
9 -16.920 0.100
L14 10 -741.007 12.842 1.49700 81.54
11 -26.885 0.100
L13 12 56.061 7.326 1.49700 81.54
13 1728.755 3.528
L12 * 14 -33.942 5.000 1.83220 40.10
* 15 -20.168 M4
L11 16 69.183 5.000 1.84666 23.78
17 108.041 117.000
L10 18 140.761 7.500 1.88300 40.80
19 -118.493 0.100
L9 20 29.650 7.500 1.83400 37.34
21 58.061 13.534
L8 22 1237.809 1.500 1.72825 28.46
23 14.726 7.867
L7 * 24 191.581 3.000 1.69680 55.46
* 25 -54.734 10.900
STO Infinity 15.000
L6 27 -56.004 3.400 1.48749 70.24
28 -22.114 0.100
L5 29 85.481 7.000 1.49700 81.54
L4 30 -16.734 1.200 1.80000 29.84
L3 31 25.268 7.000 1.49700 81.54
32 -48.971 0.100
L2 33 56.168 4.997 1.43875 94.94
34 -120.125 3.991
L1 35 -79.159 5.531 1.85896 22.73
36 -29.202 0.000
37 Infinity 25.910 1.51680 64.17
38 Infinity 9.490
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 that is the distance between the nineteenth lens L19 and the screen S is set to 500 mm as the reference projection distance 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 14.775 14.569 14.921
M3 4.629 4.713 4.498
M4 8.115 8.237 8.101
Here, the first surface and the second surface are higher-order aspheric surfaces represented by the odd-order aspheric expression of Equation 1. The following values are the coefficients of the odd-order aspherical expression for defining the aspherical shapes of the surface numbers 1 and 2 that are aspherical.

Surface number 1 2
K 0.00000 -6.77704
A03 3.42334E-04 7.39447E-04
A04 2.27608E-06 -2.32226E-05
A05 -1.41805E-07 9.48097E-07
A06 1.63897E-09 -2.71785E-09
A07 -2.13699E-11 -4.65611E-10
A08 7.79533E-13 1.51382E-13
A09 0.00000E + 00 0.00000E + 00
A10 0.00000E + 00 0.00000E + 00

  Next, the 14th surface, the 15th surface, the 24th surface, and the 25th surface are higher-order aspherical surfaces represented by the even-order aspherical surface expression of Equation 2. The following values are the coefficients of the even-order aspherical expression for defining the aspherical shapes of the surface numbers 14, 15, 24, and 25 that are aspherical.

Surface number 14 15 24 25
K 0.00000 -0.89461 26.01542 0.81084
A04 2.42000E-05 3.68200E-05 5.33790E-06 -2.36060E-07
A06 2.89930E-10 -5.20250E-09 3.92960E-08 -1.99380E-08
A08 -9.70380E-12 -1.08380E-11 -1.66870E-12 1.85220E-10
A10 0.00000E + 00 0.00000E + 00 2.01090E-12 0.00000E + 00
A12 0.00000E + 00 0.00000E + 00 0.00000E + 00 0.00000E + 00

  In this example, the 22nd lens group LU22 located closest to the screen S includes, in order from the reduction side, a positive lens having a convex surface on the reduction side (17th lens L17) and 2 having a convex surface on the enlargement side. A negative meniscus lens (18th lens L18) and an aspherical negative lens (19th lens L19) having aspheric surfaces on both sides. Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  The first lens group LU1 includes an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens, which are arranged in order from the reduction side. Are two lenses, a meniscus positive lens (ninth lens L9) and a biconvex positive lens (tenth lens L10) arranged in order from the reduction side and having a convex surface facing the enlargement side. Consists of. Therefore, it is easy to form the intermediate image 30.

Furthermore, the projection optical system 3C satisfies the following conditional expression (1), where f is the focal length of the entire lens system and f2 is the focal length of the second lens unit LU2.
1.0 <f2 / | f | <2.2 (1)
That is, in this example, f2 / | f | = 1.898. Since the projection optical system 3C satisfies the conditional expression (1), various aberrations can be easily corrected.

The projection optical system 3C also sets the distance on the optical axis L from the most reduction surface of the first lens unit LU1 to the most enlargement surface of the second lens unit LU2 to TL, and the first lens unit LU1 and the first lens unit LU1. When the interval on the optical axis L of the two lens units LU2 is D, the following conditional expression (2) is satisfied.
0.27 <D / TL <0.45 (2)
That is, in this example, D / TL = 0.384. Since the projection optical system 3C satisfies the conditional expression (2), it is easy to correct various aberrations, and the first optical path deflection unit 31 and the second optical path deflection are provided between the first lens group LU1 and the second lens group LU2. The space for arranging the means 32 can be confirmed.

Further, the projection optical system 3C sets the distance on the optical axis L from the most reduction side surface to the most enlargement side surface of the first lens unit LU1 to TL1, and the most enlargement side from the most reduction side surface of the second lens unit LU2. When the distance to the surface is TL2, the following conditional expression (3) is satisfied.
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)
That is, in this example, TL1 * TL2 / D ² = 0.866. Since the projection optical system 3C satisfies the conditional expression (2), it is possible to suppress the occurrence of various aberrations. Since the projection optical system 3C satisfies the conditional expression (3), the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are disposed between the first lens group LU1 and the second lens group LU2. You can confirm the space.

The projection optical system 3C has the following condition when the focal length f2 of the second lens unit LU2 and the distance from the most reduced surface of the second lens unit LU2 to the paraxial focal position of the intermediate image 30 are d2. Formula (4) is satisfied.
0.2 <f2 / d2 <0.7 (4)
That is, in this example, f2 / d2 = 0.542. Since the projection optical system 3C satisfies the conditional expression (4), it is possible to ensure the back focus of the second lens group LU2 while suppressing the total length of the second lens group LU2. In addition, since the projection optical system 3C satisfies the conditional expression (4), it is possible to suppress the influence of dust or the like attached to the optical path deflecting element.

Further, the projection optical system 3C has a distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (from the most magnified surface of the first lens group LU1 on the optical axis L to the middle). (Distance to the image 30) d1, and the distance from the most reduction side surface of the second lens group LU2 to the paraxial focal position of the intermediate image 30 (from the most reduction side surface of the second lens group LU2 on the optical axis L) When the distance to the intermediate image 30 is d2, the following conditional expression (5) is satisfied.
0.1 <d2 / d1 <0.35 (5)
That is, in this example, d2 / d1 = 0.134. Since the projection optical system 3C satisfies the conditional expression (5), a space for arranging the first optical path deflecting means 31 and the second optical path deflecting means 32 is provided between the first lens group LU1 and the second lens group LU2. I can confirm.

Further, the projection optical system 3C satisfies the following conditional expression (6) when the focal length of the second lens unit LU2 is f2 and the focal length of the 21st lens unit LU21 is f21.
0.2 <f2 / f21 <0.5 (6)
That is, in this example, f2 / f21 = 0.421. Since the projection optical system 3C satisfies the conditional expression (6), it is possible to satisfactorily correct various aberrations while suppressing the overall length of the second lens unit LU2 while ensuring the back focus of the second lens unit LU2.

The projection optical system 3C satisfies the following conditional expression (7), where f is the focal length of the entire lens system and f12 is the focal length of the twelfth lens unit LU12.
5 <f12 / | f | <16 (7)
That is, in this example, f2 / f21 = 8.557. Since the projection optical system 3C satisfies the conditional expression (7), it is possible to reduce the aberration generated in the twelfth lens group LU12 and to suppress the enlargement of the twelfth lens group LU12.

Further, the projection optical system 3C sets the focal length of the twelfth lens group LU12 to f12, and the distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (first on the optical axis L). When the distance from the most magnified surface of the lens group LU1 to the intermediate image 30 is d1, the following conditional expression (8) is satisfied.
0.2 <f12 / d1 <0.8 (8)
That is, in this example, f12 / d1 = 0.329. Since the projection optical system 3C satisfies the conditional expression (8), the light beam emitted from the first lens group LU1 can be efficiently corrected before entering the second lens group LU2, and the first lens group LU1 and the second lens can be corrected. A space in which an optical path deflecting unit or the like can be disposed can be provided between the group LU2. Further, since the projection optical system 3C satisfies the conditional expression (8), it is possible to suppress an increase in size of the second lens group LU2.

  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.

  Furthermore, 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 between the first lens group LU1 and the second lens group LU2. 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.

  Here, when the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are arranged in the middle of the first lens group LU1 or in the middle of the second lens group LU2, for example, the optical performance is deteriorated. In this example, two optical path deflecting units 31 and 32 are disposed between the first lens group LU1 and the second lens group LU2. Accordingly, it is possible to avoid a decrease in the positional accuracy of the plurality of lenses constituting the lens groups LU1 and LU2 due to the arrangement of the optical path deflecting units 31 and 32. Therefore, it is possible to avoid the shift of the optical axis L or the tilt of the optical axis L from occurring inside the lens groups LU1 and LU2, and it is possible to avoid the deterioration of the optical performance of the lens groups LU1 and LU2.

  Also in this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 arranged between the first lens group LU1 and the second lens group LU2 are supported by a single support member shown in FIG. Is done. Therefore, 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 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. Accordingly, it is possible to measure the squareness etc. with the collimator, and 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 each of the optical path deflecting units 31 and 32, scratches on the reflecting surface of each of the optical path deflecting units 31 and 32, dust adhering to the reflecting surface, and the like are directly expanded. There is a risk of projection. On the other hand, in this example, as shown in FIG. 14, each optical path deflection is performed so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of each optical path deflecting means 31, 32 do not overlap. Means 31 and 32 are 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 4)
FIG. 18 is a configuration diagram (ray diagram) of the projection optical system of Example 4. FIG. 19 is a configuration diagram (ray diagram) of the projection optical system when two optical path deflecting means are arranged. As shown in FIG. 18, 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 17 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, a biconcave negative third lens L3, and a reduction side. A meniscus positive fourth lens L4 having a convex surface, a meniscus positive fifth lens L5 having a convex surface on the reduction side, a biconvex positive sixth lens L6, and a biconcave negative seventh lens. The lens L7 includes a positive meniscus eighth lens L8 having a convex surface facing the enlargement side, and a positive ninth lens L9 having a biconvex shape. The second lens L2, the third lens L3, and the fourth lens L4 are cemented to form the first cemented lens LC1.

  The first lens group LU1 includes, in order from the reduction side, an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens. 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 and a ninth lens L9.

  The second lens group LU2 is composed of eight 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 reduction side. Positive 12th lens L12, biconvex positive 13th lens L13, biconcave negative 14th lens L14, biconvex positive 15th lens L15, meniscus shape with convex surface facing the enlargement side It consists of a negative sixteenth lens L16 and a negative seventeenth lens L17 with aspheric surfaces on both sides. The thirteenth lens L13 and the fourteenth lens L14 are cemented to form a second cemented lens LC2.

  The second lens group LU2 includes a 21st lens group LU21 and a 22nd 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 enlargement 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 twenty-first lens unit LU21 includes a tenth lens L10 to a fourteenth lens L14. The twenty-second lens group LU22 includes three lenses of a fifteenth lens 15 to a seventeenth lens L17. The twenty-first lens group LU21 has positive power. The twenty-second lens group LU22 has negative power.

  Here, as shown in FIG. 19, when the projection optical system 3D is made compact, the first optical path deflecting means 31 and the second optical path deflecting means are provided between the first lens group LU1 and the second lens group LU2. 32 is arranged. The first optical path deflecting means 31 is located closer to the first lens group LU1 than the second optical path deflecting means 32. In this example, the first optical path deflecting means 31 is located on the first lens group LU1 side with respect to the intermediate image 30, and the second optical path deflecting means 32 is located on the second lens group LU2 side with respect to 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 3D, the first focus lens group LF1 including the eleventh lens L11 to the lens L14 and the fifteenth lens 15 with the seventeenth lens L17 fixed. Further, focusing is performed by moving the second focusing lens unit LF2 including the two lenses of the sixteenth lens L16 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. 1.904
ω 71.3 °

  The lens data of the projection optical system 3D 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 a distance between the screen S and the seventeenth lens L17. The axial upper surface distance M2 is a distance between the seventeenth lens L17 and the second focus lens group LF2 (the fifteenth lens L15 and the sixteenth lens L16). The axial upper surface distance M3 is a distance between the second focus lens group LF2 (the fifteenth lens L15 and the sixteenth lens L16) and the first focus lens group LF1 (the eleventh lens L11 to the fourteenth lens L14). The axial upper surface distance M4 is a distance between the first focus lens group LF1 (the eleventh lens L11 to the fourteenth lens L14) 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
L17 * 1 -80.885 2.771 1.53116 56.04
* 2 29.891 M2
L16 3 30.101 2.000 1.72916 54.68
4 11.236 5.537
L15 5 177.463 6.173 1.48749 70.24
6 -71.405 M3
L14 7 -18.139 1.200 1.84666 23.78
L13 8 116.404 10.993 1.61800 63.33
9 -18.319 0.555
L12 10 -235.185 12.217 1.49700 81.54
11 -27.471 0.100
L11 12 149.282 10.997 1.49700 81.54
13 -52.152 M4
L10 * 14 -31.652 7.500 1.53116 56.04
* 15 -14.488 126.753
L9 16 93.200 8.500 1.88300 40.76
17 -234.661 5.025
L8 18 32.957 8.000 1.83400 37.16
19 87.206 14.862
L7 20 -147.540 1.500 1.84666 23.78
21 15.216 4.159
L6 * 22 66.248 3.000 1.74320 49.29
23 -60.725 11.739
STO 24 Infinity 13.000
L5 25 -255.530 3.400 1.49700 81.54
26 -22.520 0.100
L4 27 -845.204 5.065 1.48749 70.24
L3 28 -17.667 1.200 1.70154 41.24
L2 29 33.108 4.636 1.48749 70.24
30 -105.822 0.100
L1 31 26.322 7.648 1.43875 94.94
32 -50.949 0.200
33 Infinity 25.910 1.51680 64.17
34 Infinity 9.534
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 that is the distance between the seventeenth lens L17 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 15.753 15.626 15.887
M3 4.201 4.154 4.169
M4 5.704 5.879 5.603

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

Surface number 1 2
K 0.00000 -8.84026
A03 3.35430E-04 5.06641E-04
A04 3.02612E-06 -1.63863E-05
A05 -9.68838E-08 8.89507E-07
A06 -3.01364E-10 -4.46611E-09
A07 -1.85324E-13 -3.26469E-10
A08 6.91803E-13 1.75653E-14
A09 0.00000E + 00 0.00000E + 00
A10 0.00000E + 00 0.00000E + 00

  Next, the 14th surface, the 15th surface and the 22nd surface are higher-order aspherical surfaces represented by the even-order aspherical surface expression of Equation 2. The following values are coefficients of even-order aspherical expressions for defining the aspherical shapes of the surface numbers 14, 15, and 22 that are aspherical.

Surface number 14 15 22
K 0.00000 -0.92625 -1.00000
A04 1.78510E-05 4.02710E-05 1.20580E-05
A06 3.64870E-09 -8.42190E-09 6.61800E-08
A08 -7.66100E-12 -5.07790E-12 -1.13150E-11
A10 0.00000E + 00 0.00000E + 00 2.64720E-12
A12 0.00000E + 00 0.00000E + 00 0.00000E + 00

  In this example, the 22nd lens group LU22 located closest to the screen S includes, in order from the reduction side, a positive lens having a convex surface on the reduction side (15th lens L15) and 2 having a convex surface on the enlargement side. A negative meniscus lens (the sixteenth lens L16), and an aspherical negative lens (a seventeenth lens L17) having aspheric surfaces on both sides. Therefore, it is easy to set the half angle of view of the second lens unit LU2 to 60 ° or more.

  The first lens group LU1 includes an eleventh lens group LU11 having a positive power and a twelfth lens group LU12 including only a positive lens, which are arranged in order from the reduction side. Are two lenses, a meniscus positive lens (eighth lens L8) and a biconvex positive lens (ninth lens L9), which are arranged in order from the reduction side, with the convex surface facing the enlargement side. Consists of. 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 f2 is the focal length of the second lens unit LU2.
1.0 <f2 / | f | <2.2 (1)
That is, in this example, f2 / | f | = 1.794. Since the projection optical system 3D satisfies the conditional expression (1), it is easy to correct various aberrations.

The projection optical system 3D also sets the distance on the optical axis L from the most demagnifying side surface of the first lens unit LU1 to the most enlarging side surface of the second lens unit LU2 as TL, and the first lens unit LU1 and the first lens unit LU1. When the interval on the optical axis L of the two lens units LU2 is D, the following conditional expression (2) is satisfied.
0.27 <D / TL <0.45 (2)
That is, in this example, D / TL = 0.416. Since the projection optical system 3D satisfies the conditional expression (2), it is easy to correct various aberrations, and the first optical path deflection unit 31 and the second optical path deflection are provided between the first lens group LU1 and the second lens group LU2. The space for arranging the means 32 can be confirmed.

Further, the projection optical system 3D sets the distance on the optical axis L from the most reduction side surface to the most enlargement side surface of the first lens unit LU1 as TL1, and the most enlargement side from the most reduction side surface of the second lens unit LU2. When the distance to the surface is TL2, the following conditional expression (3) is satisfied.
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)
That is, in this example, TL1 * TL2 / D ² = 0.490. Since the projection optical system 3D satisfies the conditional expression (2), it is possible to reduce the occurrence of various aberrations. Since the projection optical system 3D satisfies the conditional expression (3), the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are disposed between the first lens group LU1 and the second lens group LU2. You can confirm the space.

The projection optical system 3D has the following condition when the focal length f2 of the second lens unit LU2 and the distance from the most reduced surface of the second lens unit LU2 to the paraxial focal position of the intermediate image 30 are d2. Formula (4) is satisfied.
0.2 <f2 / d2 <0.7 (4)
That is, in this example, f2 / d2 = 0.276. Since the projection optical system 3D satisfies the conditional expression (4), it is possible to ensure the back focus of the second lens group LU2 while suppressing the total length of the second lens group LU2. In addition, since the projection optical system 3D satisfies the conditional expression (4), it is possible to suppress the influence of dust attached to the optical path deflecting element.

Further, the projection optical system 3D has a distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (intermediate from the most magnified surface of the first lens group LU1 on the optical axis L). (Distance to the image 30) d1, and the distance from the most reduction side surface of the second lens group LU2 to the paraxial focal position of the intermediate image 30 (from the most reduction side surface of the second lens group LU2 on the optical axis L) When the distance to the intermediate image 30 is d2, the following conditional expression (5) is satisfied.
0.1 <d2 / d1 <0.35 (5)
That is, in this example, d2 / d1 = 0.255. Since the projection optical system 3D satisfies the conditional expression (5), a space for arranging the first optical path deflecting means 31 and the second optical path deflecting means 32 is provided between the first lens group LU1 and the second lens group LU2. I can confirm.

Further, the projection optical system 3D satisfies the following conditional expression (6) when the focal length of the second lens unit LU2 is f2 and the focal length of the 21st lens unit LU21 is f21.
0.2 <f2 / f21 <0.5 (6)
That is, in this example, f2 / f21 = 0.379. Since the projection optical system 3D satisfies the conditional expression (6), it is possible to satisfactorily correct various aberrations while suppressing the overall length of the second lens unit LU2 while ensuring the back focus of the second lens unit LU2.

The projection optical system 3D satisfies the following conditional expression (7), where f is the focal length of the entire lens system and f12 is the focal length of the twelfth lens unit LU12.
5 <f12 / | f | <16 (7)
That is, in this example, f2 / f21 = 8.784. Since the projection optical system 3D satisfies the conditional expression (7), it is possible to reduce the aberration generated in the twelfth lens group LU12 and to suppress the enlargement of the twelfth lens group LU12.

Further, the projection optical system 3D sets the focal length of the twelfth lens group LU12 to f12, and the distance from the most magnified surface of the first lens group LU1 to the paraxial focal position of the intermediate image 30 (first on the optical axis L). When the distance from the most magnified surface of the lens group LU1 to the intermediate image 30 is d1, the following conditional expression (8) is satisfied.
0.2 <f12 / d1 <0.8 (8)
That is, in this example, f12 / d1 = 0.344. Since the projection optical system 3D satisfies the conditional expression (8), the light beam emitted from the first lens group LU1 can be efficiently corrected before entering the second lens group LU2, and the first lens group LU1 and the second lens can be corrected. A space in which an optical path deflecting unit or the like can be disposed can be provided between the group LU2. Further, since the projection optical system 3D satisfies the conditional expression (8), it is possible to suppress an increase in the size of the second lens unit LU2.

  FIG. 20 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3D is at position 1. FIG. 21 is an aberration diagram (spherical aberration, astigmatism, and distortion) when each lens of the projection optical system 3D is at position 2. FIG. 22 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. 20 to 22, in the projection optical system 3D, spherical aberration, astigmatism, and distortion are corrected satisfactorily.

  Furthermore, 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 between the first lens group LU1 and the second lens group LU2. Thereby, since the optical path can be deflected by 180 °, the projection optical system 3D and the projector 1 can be configured compactly.

  Here, when the first optical path deflecting unit 31 and the second optical path deflecting unit 32 are arranged in the middle of the first lens group LU1 or in the middle of the second lens group LU2, for example, the optical performance is deteriorated. In this example, two optical path deflecting units 31 and 32 are disposed between the first lens group LU1 and the second lens group LU2. Accordingly, it is possible to avoid a decrease in the positional accuracy of the plurality of lenses constituting the lens groups LU1 and LU2 due to the arrangement of the optical path deflecting units 31 and 32. Therefore, it is possible to avoid the shift of the optical axis L or the tilt of the optical axis L from occurring inside the lens groups LU1 and LU2, and it is possible to avoid the deterioration of the optical performance of the lens groups LU1 and LU2.

  Also in this example, the first optical path deflecting means 31 and the second optical path deflecting means 32 arranged between the first lens group LU1 and the second lens group LU2 are supported by a single support member shown in FIG. Is done. Therefore, 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 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. Accordingly, it is possible to measure the squareness etc. with the collimator, and 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 each of the optical path deflecting units 31 and 32, scratches on the reflecting surface of each of the optical path deflecting units 31 and 32, dust adhering to the reflecting surface, etc. are enlarged as they are. There is a risk of projection. On the other hand, in this example, as shown in FIG. 19, each optical path deflection is performed so that the focal position from the on-axis to the maximum image height in the intermediate image 30 and the reflecting surface of each optical path deflecting means 31 and 32 do not overlap. Means 31 and 32 are 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 37 ... support member 37a ... first support part 37b ... second support part 37c ... first contact Part, 37d ... second contact part, L ... optical axis, L1-L21 ... lens, LU1 ... first lens group, LU11 ... 11th lens group, LU12 ... 12th lens group, LU2 ... second lens group, LU21 ... 21st lens group, LU22 ... 22nd lens group, LF1 ... 1st focus lens group, LF2 ... 2nd focus lens group, LC1-LC4 ... cemented lens, M1-M4 ... axial top surface spacing, S ... screen ( Enlarged side conjugate surface).

Claims (11)

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,
The focal length of the entire lens system is f, the focal length of the second lens group is f2, the distance from the most demagnifying side surface of the first lens group to the most enlarging side surface of the second lens group is TL, A projection optical system satisfying the following conditional expressions (1) and (2), where D is the distance between the first lens group and the second lens group:
1.0 <f2 / | f | <2.2 (1)
0.27 <D / TL <0.45 (2) When the distance from the most reduction side surface to the most enlargement side surface of the first lens group is TL1, and the distance from the most reduction side surface to the most enlargement side surface of the second lens group is TL2, The projection optical system according to claim 1, wherein the conditional expression (3) is satisfied.
^{0.3 <TL1 * TL2 / D 2} <1.7 ··· (3)   3. The projection optical system according to claim 1, further comprising two optical path deflecting units for bending an optical path between the first lens group and the second lens group. The two optical path deflecting units include a first optical path deflecting unit disposed between the first lens group and the intermediate image, and a first optical path deflecting unit disposed between the first optical path deflecting unit and the second lens group. 2 deflection means,
The distance from the most enlargement side surface of the first lens group to the paraxial focal position of the intermediate image is d1, and the distance from the most reduction side surface of the second lens group to the paraxial focal position of the intermediate image is d2. The projection optical system according to claim 3, wherein the following conditional expressions (4) and (5) are satisfied.
0.2 <f2 / d2 <0.7 (4)
0.1 <d2 / d1 <0.35 (5) The second lens group includes, in order from the magnifying side, a twenty-second lens group including three or less negative lenses and one positive lens, and a twenty-first lens group positioned on the reduction side of these lenses; Consists of
The twenty-first lens group has positive power;
The twenty-second lens group has negative power;
5. The projection optical system according to claim 1, wherein the following conditional expression (6) is satisfied when a focal length of the twenty-first lens group is f <b> 21.
0.2 <f2 / f21 <0.5 (6)   The twenty-second lens group includes, in order from the reduction side, one positive lens having a convex surface on the reduction side, two or less meniscus negative lenses having a convex surface on the enlargement side, and aspheric surfaces on both sides The projection optical system according to claim 5, wherein the projection optical system includes a negative lens having an aspherical shape to which is provided, and is composed of four or less lenses as a whole. The first lens group includes, in order from the reduction side, an eleventh lens group having a positive power and a twelfth lens group including only a positive lens.
The twelfth lens group includes, in order from the reduction side, a meniscus positive lens having a convex surface on the enlargement side, a positive lens having a convex surface on the enlargement side, and a positive lens having a convex surface on the reduction side, The projection optical system according to claim 1, wherein the projection optical system includes three lenses. The first lens group includes, in order from the reduction side, an eleventh lens group having a positive power and a twelfth lens group including only a positive lens.
The twelfth lens group is composed of two lenses, a meniscus positive lens having a convex surface facing the enlargement side, and a biconvex positive lens, which are arranged in order from the reduction side. The projection optical system according to any one of claims 1 to 6. 9. The projection optical system according to claim 7, wherein the following conditional expressions (7) and (8) are satisfied when the focal length of the twelfth lens group is f12.
5 <f12 / | f | <16 (7)
0.2 <f12 / d1 <0.8 (8)   4. The projection optical system according to claim 3, wherein the two optical path deflecting units disposed between the first lens group and the second lens group are positioned and held by one support member. . A projection optical system according to any one of claims 1 to 10,
An image display element for displaying an image on the reduction-side conjugate plane;
A projection-type image display device comprising:

Images