Projection optical system and projection display device

Abstract

To provide a projection optical system which has a wide angle of view and a long back focus, and yet is reduced in size and offers good optical performance, and to provide a projection display device equipped with the same.SOLUTION: A projection optical system disclosed herein is for projecting an image on a reduction-side imaging plane onto a magnification-side imaging plane and has a half view angle of 50 degrees or more on the magnification side. When one lens component is assumed to be one single lens or one cemented lens, the projection optical system includes a P lens component representing a lens component with positive power located on the most magnification side among lens components of the projection optical system and an N lens component representing a lens component with negative power located next to the P lens component on the magnification side, and satisfies predetermined conditional expressions.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a projection optical system and a projection display device. [Background technology]

[0002] As optical systems applicable to projection display devices, the optical systems described in Patent Documents 1 and 2 below are known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 195857 [Patent Document 2] International Publication No. 2020 / 110380 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for projection optical systems that have a wide angle of view and a long back focus, while also being compact and maintaining good optical performance. These requirements are becoming higher every year.

[0005] The present disclosure has been made in consideration of the above circumstances, and provides a projection optical system that has a wide angle of view and a long back focus while being compact and maintaining good optical performance, and a projection display device equipped with this projection optical system. [Means for solving the problem]

[0006] A first aspect of the present disclosure is a projection optical system that projects an image on a reduction-side image forming plane onto an enlargement-side image forming plane, the projection optical system having a half angle of view of 50 degrees or more on the enlargement side, and when one lens component is one single lens or one cemented lens, the projection optical system includes a P lens component that is the lens component on the most enlargement side and has positive power, and an N lens component that is a lens component with negative power that is disposed adjacent to the enlargement side of the P lens component, 1 <Zp / Ymax<4 (1) 0.2 <Rpf / Ymax<2.3 (2) 0.2 <Rnr / Ymax<5 (3) 2 <Bf / Ymax<8 (4) 1.35 <Y50 / Y40<1.5 (5) The projection optical system satisfies conditional expressions (1), (2), (3), (4), and (5). Here, Ymax is the maximum image height on the reduction-side image plane. Zp is the distance on the optical axis from the surface of the optical element with the most magnification power in the projection optical system to the most magnification-side lens surface of the P lens component. Rpf is the radius of curvature of the most magnification-side lens surface of the P lens component. Rnr is the radius of curvature of the most reduction-side lens surface of the N lens component. Bf is the reduction-side back focus in air equivalent distance of the projection optical system. Y40 is the image height on the reduction-side image plane for a light ray with a half angle of view of 40 degrees on the magnification side. Y50 is the image height on the reduction-side image plane for a light ray with a half angle of view of 50 degrees on the magnification side. If the projection optical system is a variable magnification optical system, Ymax, Zp, Bf, Y40, and Y50 are the values ​​at the wide-angle end.

[0007] A second aspect of the present disclosure is a projection optical system of the first aspect, which comprises, in order along the optical path from the enlargement side to the reduction side, a first optical system and a second optical system, wherein the second optical system forms an intermediate image between the first and second optical systems at a position conjugate with the reduction side image forming surface, and the first optical system re-images the intermediate image on the enlargement side image forming surface.

[0008] A third aspect of the present disclosure provides a projection optical system according to the first aspect, in which, assuming that the distance on the optical axis between the N lens component and the P lens component is Dnp, and that when the projection optical system is a variable magnification optical system, Dnp is a value at the wide-angle end, 0 <Dnp / Ymax<0.1 (6) Conditional expression (6) expressed as follows is satisfied.

[0009] A fourth aspect of the present disclosure is a projection optical system according to the first aspect, in which, when the radius of curvature of the lens surface of the P lens component on the most reduction side is Rpr, 0<(Rpr+Rpf) / (Rpr-Rpf)<2 (7) Conditional expression (7) expressed as follows is satisfied.

[0010] A fifth aspect of the present disclosure is a projection optical system according to the first aspect, in which, when the larger of the maximum effective diameter of the lens surface of the P lens component on the most enlargement side and the maximum effective diameter of the lens surface of the P lens component on the most reduction side is defined as EDp, 0.5 <EDp / Ymax<2.5 (8) Conditional expression (8) expressed as follows is satisfied.

[0011] A sixth aspect of the present disclosure is a projection optical system according to the first aspect, wherein, when the radius of curvature of the lens surface of the N lens component on the most enlargement side is Rnf, -1<(Rnr+Rnf) / (Rnr-Rnf)<0.5 (9) Condition (9) is satisfied.

[0012] A seventh aspect of the present disclosure is a projection optical system according to the second aspect, wherein the projection optical system is a zoom lens including a moving lens group in the second optical system that moves during magnification variation, 0.2 <dAmax / Ymax<2.5 (10) Conditional formula (10) expressed as follows is satisfied. Here, the group consisting of all lenses on the enlargement side of the moving lens group most on the enlargement side among the moving lens groups included in the projection optical system is referred to as the enlargement-side fixed group. The longest air space between lens surfaces on the optical axis within the enlargement-side fixed group is referred to as dAmax. If the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end.

[0013] An eighth aspect of the present disclosure relates to the projection optical system of the second aspect, in which the projection optical system is a zoom lens, and the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a 2A lens group, a 2B lens group, a 2C lens group, and a 2D lens group, and during magnification variation, the 2A lens group and the 2D lens group are fixed with respect to the reduction-side image plane, and the 2B lens group and the 2C lens group move while changing their mutual spacing. Here, a group in the second optical system whose spacing from adjacent groups in the optical axis direction changes during magnification variation is considered to be one lens group.

[0014] A ninth aspect of the present disclosure is a projection optical system according to the eighth aspect, wherein, when the focal length of the 2B lens group is f2B and the focal length of the 2C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) Condition (11) expressed by the following expression is satisfied.

[0015] A tenth aspect of the present disclosure is a projection optical system according to the first aspect, in which, when the larger of the maximum effective diameter of the enlargement-side surface of the most enlargement-side lens in the projection optical system and the maximum effective diameter of the reduction-side surface of the most enlargement-side lens in the projection optical system is defined as EDL1, and the specific gravity of the most enlargement-side lens in the projection optical system is defined as ρL1, 0.5 <EDL1×ρL1 / Ymax<10 (12) Conditional expression (12) expressed by the following expression is satisfied.

[0016] An eleventh aspect of the present disclosure is the projection optical system of the first aspect, wherein the P lens component is a single lens, and the refractive index of the P lens component with respect to the d-line is 1.65 or more.

[0017] A twelfth aspect of the present disclosure is a projection optical system according to the eleventh aspect, wherein the N lens component is a single lens, and the refractive index of the N lens component with respect to the d-line is 1.65 or less.

[0018] A thirteenth aspect of the present disclosure is the projection optical system of the second aspect, wherein the first optical system includes an aspherical lens.

[0019] A fourteenth aspect of the present disclosure is the projection optical system of the thirteenth aspect, wherein the first optical system includes two aspherical lenses.

[0020] A fifteenth aspect of the present disclosure is a projection optical system according to the thirteenth aspect, in which the lens surface of the first optical system closest to the enlargement side is aspherical, with a concave surface facing the enlargement side in the paraxial region, and with an inflection point where the concave-convex shape changes midway as one moves from the optical axis to the periphery.

[0021] A sixteenth aspect of the present disclosure is the projection optical system of the second aspect, wherein the reduction side is telecentric.

[0022] A seventeenth aspect of the present disclosure is a projection display device including the projection optical system according to any one of the first to sixteenth aspects.

[0023] An eighteenth aspect of the present disclosure is a projection optical system consisting of a first optical system and a second optical system, in that order along the optical path from the enlargement side to the reduction side, wherein the second optical system forms an intermediate image between the first and second optical systems and at a position conjugate with the reduction side image plane, and the first optical system re-images the intermediate image on the enlargement side image plane, and at the most enlargement side of the projection optical system is a focus group which includes six or more lenses and moves along the optical axis to adjust the focus of the entire image plane when the projection distance changes, and the spacing between all lenses in the focus group remains unchanged during focus adjustment.

[0024] A nineteenth aspect of the present disclosure is the projection optical system of the eighteenth aspect, wherein a focus group is disposed within the first optical system.

[0025] A twentieth aspect of the present disclosure provides the projection optical system of the eighteenth aspect, 0.02<(1-βF 2 )×βFr 2 <0.2 (13) Conditional formula (13) expressed as follows is satisfied. Here, the paraxial lateral magnification of the focus group is defined as βF. The combined paraxial lateral magnification of all lenses on the reduction side of the focus group is defined as βFr. When the projection optical system is a variable magnification optical system, βF and βFr are defined as values ​​at the wide-angle end.

[0026] A twenty-first aspect of the present disclosure provides the projection optical system of the eighteenth aspect, 0.1<((1-βF 2 )×βFr 2 ) / ΔtF<0.5 (14) It satisfies conditional expression (14) expressed as follows. Here, βF is the paraxial lateral magnification of the focus group. βFr is the composite paraxial lateral magnification of all lenses on the reduction side of the focus group. Ymax is the maximum image height on the reduction-side image plane. ΔtF is the amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1 x Ymax in the optical axis direction. If the projection optical system is a variable magnification optical system, βF, βFr, Ymax, and ΔtF are the values ​​at the wide-angle end.

[0027] A twenty-second aspect of the present disclosure is the projection optical system of the eighteenth aspect, wherein the focus group includes two or more positive lenses.

[0028] A 23rd aspect of the present disclosure is a projection optical system according to the 18th aspect, wherein the lens surface of the focus group closest to the enlargement side is aspherical, with a concave surface facing the enlargement side in the paraxial region, and with an inflection point where the concave-convex shape changes midway as one moves from the optical axis to the periphery.

[0029] A 24th aspect of the present disclosure is a projection optical system according to the 18th aspect, wherein one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a positive lens, and the other is a negative lens; 0≦dFr12 / Ymax<0.1 (15) Conditional expression (15) expressed as follows is satisfied. Here, the distance on the optical axis between the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is defined as dFr12. The maximum image height on the reduction-side image forming surface is defined as Ymax. If the projection optical system is a variable magnification optical system, Ymax is defined as the value at the wide-angle end.

[0030] A 25th aspect of the present disclosure is directed to the projection optical system of the 18th aspect, wherein a back focus correction group is disposed that adjusts the back focus by moving along the optical axis.

[0031] A 26th aspect of the present disclosure is a projection optical system according to the 18th aspect, wherein the projection optical system is a zoom lens including a moving lens group in the second optical system that moves during magnification variation, 0.2 <dAmax / Ymax<2.5 (10) Conditional formula (10) expressed as follows is satisfied. Here, the group consisting of all lenses on the enlargement side of the moving lens group most on the enlargement side among the moving lens groups included in the projection optical system is referred to as the enlargement-side fixed group. The longest air space between lens surfaces on the optical axis within the enlargement-side fixed group is referred to as dAmax. If the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end.

[0032] A 27th aspect of the present disclosure relates to the projection optical system of the 18th aspect, in which the projection optical system is a zoom lens, and the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a 2A lens group, a 2B lens group, a 2C lens group, and a 2D lens group, and during magnification variation, the 2A lens group and the 2D lens group are fixed with respect to the reduction-side image plane, and the 2B lens group and the 2C lens group move while changing their mutual spacing. Here, a group in the second optical system whose spacing from adjacent groups in the optical axis direction changes during magnification variation is considered to be one lens group.

[0033] A 28th aspect of the present disclosure is a projection optical system according to the 27th aspect, wherein, when the focal length of the 2B lens group is f2B and the focal length of the 2C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) Condition (11) expressed by the following expression is satisfied.

[0034] A twenty-ninth aspect of the present disclosure is a projection display device including the projection optical system according to any one of the eighteenth to twenty-eighth aspects.

[0035] A 30th aspect of the present disclosure is a projection optical system consisting of a first optical system and a second optical system, wherein the second optical system forms an intermediate image between the first and second optical systems and at a position conjugate with the reduction-side image-forming surface, and the first optical system re-images the intermediate image on the enlargement-side image-forming surface, and wherein the projection optical system is provided with a focus group that moves along the optical axis to adjust the focus of the entire image surface when the projection distance changes, and a back-focus correction group that moves along the optical axis to adjust the back-focus, 5 <ZFBr / |f|<20 (16) Conditional formula (16) expressed as follows is satisfied. Here, ZFBr is the distance on the optical axis from the lens surface of the first optical system on the magnification side to the lens surface of the lens surfaces included in the focus group and back focus correction group on the reduction side. The focal length of the projection optical system is f. If the projection optical system is a variable magnification optical system, ZFBr and f are values ​​at the wide-angle end.

[0036] A thirty-first aspect of the present disclosure provides the projection optical system of the thirtieth aspect, 0.02<(1-βFF 2 )×βFFr 2 <0.2 (17) 0.1<|(1-βB 2 )×βBr 2 |<2 (18) Conditional expressions (17) and (18) expressed as follows are satisfied. Here, the paraxial lateral magnification of the focus group is βFF. The composite paraxial lateral magnification of all lenses on the reduction side of the focus group is βFFr. The paraxial lateral magnification of the back focus correction group is βB. The composite paraxial lateral magnification of all lenses on the reduction side of the back focus correction group is βBr. When the projection optical system is a variable magnification optical system, βFF, βFFr, βB, and βBr are values ​​at the wide-angle end.

[0037] A thirty-second aspect of the present disclosure provides the projection optical system of the thirtieth aspect, 0.7<|(1-βB 2 )×βBr 2 | / ΔtB<1.4 (19) Conditional expression (19) expressed as follows is satisfied. Here, the paraxial lateral magnification of the back focus correction group is defined as βB. The composite paraxial lateral magnification of all lenses on the reduction side of the back focus correction group is defined as βBr. The maximum image height on the reduction-side image plane is defined as Ymax. The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the back focus correction group moves 0.1 × Ymax in the optical axis direction is defined as ΔtB. If the projection optical system is a variable magnification optical system, βB, βBr, Ymax, and ΔtB are values ​​at the wide-angle end.

[0038] A thirty-third aspect of the present disclosure provides the projection optical system of the thirtieth aspect, 0.1<((1-βFF 2 )×βFFr 2 ) / ΔtFF<0.5 (20) It satisfies conditional expression (20) expressed as follows. Here, the paraxial lateral magnification of the focus group is βFF. The composite paraxial lateral magnification of all lenses on the reduction side of the focus group is βFFr. The maximum image height on the reduction-side image plane is Ymax. The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1 x Ymax in the optical axis direction is ΔtFF. If the projection optical system is a variable magnification optical system, βFF, βFFr, Ymax, and ΔtFF are values ​​at the wide-angle end.

[0039] A thirty-fourth aspect of the present disclosure is the projection optical system of the thirtieth aspect, wherein the focus group and the back focus correction group are movable independently of each other.

[0040] A thirty-fifth aspect of the present disclosure is the projection optical system of the thirty-first aspect, wherein the projection optical system is a zoom lens including a moving lens group in the second optical system that moves during magnification variation, 0.2 <dAmax / Ymax<2.5 (10) Conditional formula (10) expressed as follows is satisfied. Here, the group consisting of all lenses on the enlargement side of the moving lens group most on the enlargement side among the moving lens groups included in the projection optical system is referred to as the enlargement-side fixed group. The longest air space between lens surfaces on the optical axis within the enlargement-side fixed group is referred to as dAmax. If the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end.

[0041] A 36th aspect of the present disclosure relates to the projection optical system of the 30th aspect, in which the projection optical system is a zoom lens, and the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a 2A lens group, a 2B lens group, a 2C lens group, and a 2D lens group, and during magnification variation, the 2A lens group and the 2D lens group are fixed with respect to the reduction-side image plane, and the 2B lens group and the 2C lens group move while changing their mutual spacing. Here, a group in the second optical system whose spacing from adjacent groups in the optical axis direction changes during magnification variation is considered to be one lens group.

[0042] A thirty-seventh aspect of the present disclosure is a projection optical system according to the thirty-sixth aspect, wherein, when the focal length of the 2B lens group is f2B and the focal length of the 2C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) Condition (11) expressed by the following expression is satisfied.

[0043] A thirty-eighth aspect of the present disclosure is a projection display device including the projection optical system according to any one of the thirtieth to thirty-seventh aspects.

[0044] In this specification, "consisting of" and "consisting of" are intended to mean that, in addition to the listed components, other optical elements than lenses, such as lenses that have substantially no power (refractive power), apertures, masks, filters, cover glasses, flat mirrors, and prisms, as well as mechanical parts such as lens flanges, lens barrels, image sensors, and image stabilization mechanisms, may also be included.

[0045] In this specification, "a group having positive power" means that the group as a whole has positive power, and "a lens component having positive power" means that the lens component as a whole has positive power. Similarly, "a group having negative power" means that the group as a whole has negative power, and "a lens component having negative power" means that the lens component as a whole has negative power. In this specification, the "lens group," "focus group," and "back focus correction group" are not limited to configurations consisting of multiple lenses, and may be configurations consisting of only one lens.

[0046] A compound aspherical lens (a lens in which a lens (for example, a spherical lens) and an aspherical film formed on that lens are integrally constructed and function as a single aspherical lens as a whole) is not considered a cemented lens, but is treated as a single lens. Unless otherwise specified, the radius of curvature, sign of power, and surface shape of lenses including aspherical surfaces are those in the paraxial region. Unless otherwise specified, the "distance on the optical axis" used in the conditional expressions is a geometric distance. The "focal length" used in the conditional expressions is the paraxial focal length. The values ​​used in the conditional expressions are based on the d-line.

[0047] The terms "d-line," "C-line," and "F-line" used in this specification are emission lines, and the wavelength of the d-line is treated as 587.56 nm (nanometers), the wavelength of the C-line as 656.27 nm (nanometers), and the wavelength of the F-line as 486.13 nm (nanometers). [Effects of the Invention]

[0048] According to the present disclosure, it is possible to provide a projection optical system that has a wide angle of view and a long back focus while being compact and maintaining good optical performance, and a projection display device that includes this projection optical system. [Brief explanation of the drawings]

[0049] [Figure 1] 1 is a cross-sectional view showing the configuration and light beams of a projection optical system according to an embodiment, which corresponds to the projection optical system of Example 1. FIG. [Figure 2] FIG. 10 is a diagram for explaining symbols in a conditional expression. [Figure 3] FIG. 2 is a partially enlarged view of the projection optical system of FIG. [Figure 4] FIG. 10 is a diagram for explaining the maximum effective diameter. [Figure 5] FIG. 10 is a diagram for explaining the amount of change in the tangential image plane. [Figure 6] 3A to 3C are diagrams showing various aberrations in the projection optical system of Example 1. [Figure 7] 10 is a cross-sectional view showing the configuration and light beam of a projection optical system according to a second embodiment. [Figure 8] 10A to 10C are diagrams showing various aberrations in the projection optical system of Example 2. [Figure 9] 10 is a cross-sectional view showing the configuration and light beam of a projection optical system according to a third embodiment. [Figure 10] 10A to 10C are diagrams showing various aberrations in the projection optical system of Example 3. [Figure 11] 10 is a cross-sectional view showing the configuration and light beam of a projection optical system according to a fourth embodiment. [Figure 12] 10A to 10C are diagrams showing various aberrations in the projection optical system of Example 4. [Figure 13] 10 is a cross-sectional view showing the configuration and light beam of a projection optical system according to a fifth embodiment. [Figure 14] 10A to 10C are diagrams showing various aberrations in the projection optical system of Example 5. [Figure 15] 10 is a cross-sectional view showing the configuration and light beam of a projection optical system according to a sixth embodiment. [Figure 16] 10A to 10C are diagrams showing various aberrations in the projection optical system of Example 6. [Figure 17] 1 is a schematic configuration diagram of a projection display device according to an embodiment. [Figure 18] FIG. 10 is a schematic configuration diagram of a projection display device according to another embodiment. [Figure 19] FIG. 10 is a schematic configuration diagram of a projection display device according to yet another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0050] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0051] FIG. 1 shows a cross-sectional view of the configuration of a projection optical system according to an embodiment of the present disclosure and light beams. In FIG. 1, the light beams shown are an axial light beam B0 and a light beam Bmax at the maximum half angle of view. In FIG. 1, the left side is the enlargement side, and the right side is the reduction side. The example shown in FIG. 1 corresponds to the projection optical system of Example 1, which will be described later.

[0052] FIG. 1 shows an example in which an optical element PP and a light valve display surface Sim are arranged on the reduction side of the projection optical system, assuming that the projection optical system will be installed in a projection display device. The light valve is a display element that outputs an optical image, and this optical image is displayed as an image on the display surface Sim. The light valve can be, for example, a liquid crystal display element or an image display element such as a DMD (Digital Micromirror Device: registered trademark). The optical element PP is a component that is assumed to be a filter, cover glass, color synthesis prism, etc. The optical element PP is a component that has no power. The material, length, and number of components of the optical element PP can be changed as appropriate, and a configuration in which the optical element PP is omitted is also possible.

[0053] The projection optical system can project an image on a reduction-side image formation surface onto an enlargement-side image formation surface. For example, a projection optical system installed in a projection display device projects an image displayed on a display surface Sim of a display element onto a screen Scr. Specifically, in a projection display device, a light beam imparted with image information on the display surface Sim of a display element is incident on the projection optical system via an optical member PP and projected onto the screen Scr, which is the projection surface, by the projection optical system. In this case, the display surface Sim corresponds to the reduction-side image formation surface, and the screen Scr corresponds to the enlargement-side image formation surface. The display surface Sim and the screen Scr are optically conjugate. Note that in this specification, the "screen Scr" refers to an object onto which the projection image formed by the projection optical system is projected. The screen Scr may be a dedicated screen, or may be a room wall, floor, ceiling, or the exterior wall of a building.

[0054] In this specification, the "enlargement side" refers to the screen Scr side on the optical path, and the "reduction side" refers to the display surface Sim side on the optical path. In this specification, the "enlargement side" and the "reduction side" are determined along the optical path. Furthermore, "adjacent" in relation to the arrangement of components means that they are adjacent in order on the optical path. In the following, to avoid redundant explanation, "in order from the enlargement side to the reduction side along the optical path" may be expressed as "in order from the enlargement side to the reduction side."

[0055] The projection optical system of the present disclosure is configured as a wide-angle optical system with a half angle of view of 50 degrees or more on the magnification side. With this configuration, it is possible to project an image with a wide angle of view. A more preferable configuration is one in which the half angle of view on the magnification side is 55 degrees or more.

[0056] As an example, the projection optical system shown in FIG. 1 comprises, in order from the enlargement side to the reduction side along the optical path, a first optical system G1 and a second optical system G2. The second optical system G2 forms an intermediate image MI between the first optical system G1 and the second optical system G2, at a position conjugate with the display surface Sim (corresponding to the reduction-side image plane). The first optical system G1 re-images the intermediate image MI onto a screen Scr (corresponding to the enlargement-side image plane). In other words, the projection optical system shown in FIG. 1 is a relay optical system with the second optical system G2 as a relay group. When shortening the focal length of the projection optical system to achieve a wide angle, the lens on the enlargement side tends to become large if the required optical performance is to be achieved while maintaining the necessary back focus. By using a relay optical system in which the intermediate image MI is formed internally, it is possible to achieve a compact configuration without increasing the lens diameter, even with a wide angle and long back focus. Note that the intermediate image MI is conceptually indicated by a dotted line in FIG. 1. The shape of the intermediate image MI in FIG. 1 is not necessarily accurate.

[0057] As an example, the projection optical system in Figure 1 is a zoom lens, with the first optical system G1 fixed relative to the reduction-side image plane and the second optical system G2 including a lens group that moves when the magnification is changed. Hereinafter, the lens group that moves when the magnification is changed will be referred to as the "moving lens group." In this way, by configuring the second optical system G2 to include a moving lens group rather than the first optical system G1, which is a wide-angle system, fluctuations in field curvature and distortion when the magnification is changed can be suppressed.

[0058] As an example, each optical system in FIG. 1 is configured as follows: The first optical system G1 is composed of lenses L1a to L1l, in order from the enlargement side to the reduction side. The second optical system G2 is composed of, in order from the enlargement side to the reduction side, a second-order lens group G2A, a second-order lens group G2B, a second-order lens group G2C, and a second-order lens group G2D. The second-order lens group G2A is composed of lenses L2a to L2d, in order from the enlargement side to the reduction side. The second-order lens group G2B is composed of a lens L2e. The second-order lens group G2C is composed of an aperture stop St and lenses L2f to L2i, in order from the enlargement side to the reduction side. The second-order lens group G2D is composed of a lens L2j. Note that the aperture stop St shown in FIG. 1 does not indicate its size or shape, but rather its position in the optical axis direction. This method of illustrating the aperture stop St is similar in other drawings.

[0059] In this specification, a lens group in the second optical system G2 is defined as a group whose distance in the optical axis direction between adjacent groups changes during magnification. That is, a "lens group" is a component of the second optical system G2 that includes at least one lens and is separated by an air gap that changes during magnification. During magnification, the distance between adjacent lenses within a lens group does not change. During magnification, each lens group is moved or fixed individually. A "lens group" may include components other than a lens without power, such as an aperture stop St and / or a plane mirror.

[0060] In the example shown in Figure 1, during magnification, the second-side lens group G2A and the second-side lens group G2D are fixed relative to the reduction-side image plane, while the second-side lens group G2B and the second-side lens group G2C move while varying their relative distance. In this way, configuring the second optical system G2, which is a relay group, as a four-group configuration is advantageous for achieving a zoom lens with a wide angle of view. Generally, the lenses on the magnification and reduction sides of a relay group tend to have larger diameters. Therefore, by fixing the second-side lens group G2A on the magnification side and the second-side lens group G2D on the reduction side during magnification, and making the second-side lens group G2B and the second-side lens group G2C movable, the mechanical mechanism for movement can be made more compact. Furthermore, by fixing the second-side lens group G2D during magnification, fluctuations in telecentricity during magnification can be suppressed. In Figure 1, arrows are drawn below the movable lens groups to indicate the approximate direction of movement of each group when changing magnification from the wide-angle end to the telephoto end.

[0061] In the example of FIG. 1, lenses L1a to L1c of the first optical system G1 are each a single lens with negative power, and lens L1d is a single lens with positive power. In this specification, a "single lens" refers to a single lens that is not cemented. In this specification, a single lens or a cemented lens is referred to as one lens component. Hereinafter, the lens component on the magnification side that has positive power among the lens components included in the projection optical system will be referred to as the "P lens component LP." In addition, the lens component with negative power that is located adjacent to the magnification side of the P lens component LP will be referred to as the "N lens component LN." In the example of FIG. 1, lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN.

[0062] When the P lens component LP is a single lens, the refractive index of the P lens component LP at the d-line is preferably 1.65 or greater. By making the refractive index 1.65 or greater, it becomes easier to ensure the power required of the P lens component LP, which is advantageous for correcting various aberrations, particularly astigmatism. To obtain better characteristics, the refractive index of the P lens component LP at the d-line is more preferably 1.7 or greater, and even more preferably 1.75 or greater.

[0063] When the N lens component LN is a single lens, it is preferable that the refractive index of the N lens component LN at the d-line be 1.65 or less. By setting the refractive index to 1.65 or less, the power of the N lens component LN does not become too strong, which is advantageous for correcting various aberrations, particularly spherical aberration and field curvature. To obtain better characteristics, it is more preferable that the refractive index of the N lens component LN at the d-line be 1.6 or less, and even more preferable that it be 1.57 or less.

[0064] It is preferable that the first optical system G1 includes an aspherical lens. By placing an aspherical lens in the first optical system G1, which is a wide-angle system, it is advantageous for correcting curvature of field and distortion. It is more preferable that the first optical system G1 includes two aspherical lenses. In this case, it is even more advantageous for correcting curvature of field and distortion.

[0065] The lens surface closest to the magnification side of the first optical system G1 is preferably aspherical, with a concave surface facing the magnification side in the paraxial region and an inflection point where the concave / convex shape changes midway from the optical axis toward the periphery. This is advantageous for correcting distortion in wide-angle systems. In this specification, the term "lens surface" refers to a lens surface through which light rays used for imaging pass. An inflection point is a point where the surface shape changes from convex to concave, or from concave to convex, i.e., a point where the sign of the radius of curvature changes. Having an inflection point on the lens surface allows the refractive power of the peripheral portion of the lens to be determined independently of the refractive power in the paraxial region.

[0066] It is preferable that the projection optical system be telecentric on the reduction side. Projection display devices that output high-definition images use a three-plate system, which requires good telecentricity. In recent years, in order to realize small, high-definition projection display devices, the so-called pixel shift system, which shifts pixels to achieve a resolution two or four times the number of pixels of the display element, has become popular, and a telecentric optical system is desirable to ensure the resolution in this case.

[0067] Note that the above-mentioned "telecentric on the reduction side" includes an error that is practically acceptable in the technical field to which the technology of the present disclosure pertains. For example, the error may be within a range in which the angle between the optical axis Z and the chief ray incident on the reduction-side image forming surface when ray tracing is performed from the magnification side to the reduction side is between -3 degrees and +3 degrees. In a system that does not include an aperture stop St, when the light beam is viewed from the magnification side to the reduction side, telecentricity may be determined by using the bisector angle between the upper and lower maximum rays in the cross section of the light beam that converges at a point on the reduction-side image forming surface as a substitute for the chief ray.

[0068] It is preferable that the projection optical system includes a focus group that moves along the optical axis Z to adjust the focus of the entire image surface when the projection distance changes. Here, "the entire image surface" refers to, for example, the entire projected image projected onto the screen Scr. By moving the focus group, it is possible to adjust the position of the conjugate point on the optical axis when the projection distance changes and correct the curvature of field when the projection distance changes. The "adjustment of the position of the conjugate point" mentioned above includes, for example, focusing. By including such a focus group in the projection optical system, it is possible to adjust the focus while maintaining optical performance up to the periphery of the image surface when the projection distance changes.

[0069] As an example, the projection optical system in the example of Figure 1 includes only one focus group, which is made up of lenses L1a to L1i. In Figure 1, parentheses and a hollow double-headed arrow parallel to the optical axis Z are written under the lenses corresponding to the focus group. In the example of Figure 1, the spacing between all lenses in the focus group remains unchanged during the focus adjustment. Note that in the drawings of this application, multiple lenses shown enclosed in a single parentheses accompanying an arrow indicating movement indicate that they move integrally. "Moving integrally" means moving simultaneously in the same direction by the same amount.

[0070] It is preferable that the focus group is located on the most enlarged side within the projection optical system, which allows the group configuration to be simplified.

[0071] It is preferable that the focus group be disposed within the first optical system G1, which is advantageous for correcting tilt of the image plane when the projection distance changes in the ultra-wide-angle lens system.

[0072] To ensure performance when the projection distance changes, it is preferable for the focus group to include six or more lenses. By configuring the focus group with six or more lenses, it becomes easier to ensure performance when the projection distance changes, even if the projection optical system only includes one focus group. For example, the focus group in Figure 1 consists of nine lenses.

[0073] It is preferable that the focus group includes two or more positive lenses, which is advantageous for good correction of field curvature. For example, the focus group in Figure 1 is composed of five negative lenses and four positive lenses.

[0074] It is preferable that the lens surface closest to the magnification side of the focus group be an aspherical surface that faces a concave surface toward the magnification side in the paraxial region and has an inflection point where the concave / convex shape changes midway as one moves from the optical axis toward the periphery, which is advantageous for correcting distortion in wide-angle lens systems.

[0075] It is preferable that one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a negative lens, and the other is a positive lens. This is advantageous for suppressing fluctuations in lateral chromatic aberration during focus adjustment. If one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a negative lens and the other is a positive lens, the negative lens and the positive lens may be cemented together. If a cemented lens including a negative lens and a positive lens is located at the most reduction side of the focus group, this is advantageous for suppressing fluctuations in lateral chromatic aberration during focus adjustment.

[0076] For example, in the example of Fig. 1, the lens L1i, which is the first lens from the reduction side of the focus group, is a negative lens, and the lens L1h, which is the second lens from the reduction side of the focus group, is a positive lens. In the example of Fig. 1, the lens L1i and the lens L1h are cemented together.

[0077] It is preferable that the lens surface of the focus group closest to the reduction side be a concave surface, which is effective in correcting curvature of field during focus adjustment.

[0078] It is preferable that a back focus correction group be disposed within the projection optical system, which adjusts the back focus by moving along the optical axis Z. When an error occurs that causes a uniform focus error from the vicinity of the optical axis to the peripheral parts of the image plane, the back focus correction group can be moved to adjust the focus. Possible causes of the error include errors on the projection optical system side when the projection optical system is mounted on a projection display device and / or errors on the projection display device side, focus error due to temperature, and the influence of gravity. The back focus correction group is not limited to a configuration consisting of multiple lenses, and may be a configuration consisting of only one lens.

[0079] For example, the back focus correction group is made up of lens L1j in the example shown in Fig. 1. In Fig. 1, parentheses and a black double-headed arrow parallel to the optical axis Z are written below the lens corresponding to the back focus correction group.

[0080] Both the focus group and the back focus correction group may be disposed within the projection optical system, which is advantageous for achieving good focus adjustment.

[0081] When both the focus group and the back-focus correction group are disposed in the projection optical system, it is preferable that the focus group and the back-focus correction group are movable independently of each other. By separately adjusting the position of the conjugate point and correcting the field curvature, and by separately adjusting the back focus, it is possible to focus the entire image plane and obtain a good projection image.

[0082] In the projection optical system of the present disclosure, it is preferable that all optical elements having power are refractive elements. In a projection optical system including a reflective optical element having power, the light beam near the optical axis reflected by the reflective surface of the optical element is generally blocked by the projection display device and cannot be used to form a projected image. To avoid this blocking, the center position of the image on the reduction-side image forming surface is shifted from the optical axis Z of the projection optical system, and this shift amount is often large. Therefore, in a projection optical system including a reflective optical element having power, the size of the reflective surface having power tends to be large, making miniaturization often difficult. In contrast, in a projection optical system in which all optical elements having power are refractive, the light beam near the optical axis can also be used to form a projected image, and even if the shift amount is small, it is possible to reduce the shift amount. Reducing the shift amount allows for the miniaturization of each optical element, which leads to the miniaturization of the entire optical system.

[0083] Next, preferred and possible configurations for the conditional expressions of the projection optical system of the present disclosure will be described. In the following description of the conditional expressions, to avoid redundant explanation, the same symbols will be used for elements with the same definitions, and duplicate explanations of the symbols will be omitted. Also, to avoid redundant explanation, the "projection optical system of the present disclosure" will be simply referred to as the "projection optical system" below. When the projection optical system is a variable magnification optical system, all symbols used in the following conditional expressions are values ​​at the wide-angle end.

[0084] It is preferable that the projection optical system satisfy the following conditional formula (1). Here, Ymax is the maximum image height on the reduction-side image plane. Zp is the distance on the optical axis from the surface of the optical element having the most power on the enlargement side of the projection optical system to the lens surface of the P lens component LP on the most enlargement side. Note that the "surface of the optical element having power" refers to, for example, a lens surface, a non-flat mirror surface, a diffractive surface, etc. As an example, FIG. 1 shows the above maximum image height Ymax, and FIG. 2 shows the above distance Zp. FIG. 2 is a diagram for explaining the symbols in each conditional formula for the projection optical system of FIG. 1. By satisfying conditional formula (1), the P lens component LP can be positioned in a position that is effective for miniaturization. 1 <Zp / Ymax<4 (1)

[0085] To obtain better characteristics, the lower limit of conditional expression (1) should preferably be set to 1.5, and more preferably to 1.7, and the upper limit of conditional expression (1) should preferably be set to 3, and more preferably to 2.5.

[0086] It is preferable that the projection optical system satisfy the following conditional expression (2). Here, Rpf is the radius of curvature of the lens surface of the P lens component LP on the most enlargement side. By ensuring that the corresponding value of conditional expression (2) is not below the lower limit, the power of the lens surface of the P lens component LP on the most enlargement side does not become too strong, thereby suppressing the occurrence of aberrations. This is advantageous for correcting various aberrations, particularly spherical aberration and field curvature. By ensuring that the corresponding value of conditional expression (2) is not above the upper limit, the power of the lens surface of the P lens component LP on the most enlargement side does not become too weak, thereby being advantageous for correcting higher-order aberrations. This makes it easier to achieve compactness while appropriately correcting various aberrations. In this specification, "higher order" in relation to aberrations means fifth order or higher. 0.2 <Rpf / Ymax<2.3 (2)

[0087] To obtain better characteristics, the lower limit of conditional expression (2) should preferably be set to 0.5, and more preferably to 0.7, and the upper limit of conditional expression (2) should preferably be set to 2, and more preferably to 1.8.

[0088] It is preferable that the projection optical system satisfy the following conditional expression (3). Here, the radius of curvature of the lens surface of the N lens component LN on the most reduction side is defined as Rnr. By ensuring that the corresponding value of conditional expression (3) is not below the lower limit, the power of the lens surface of the N lens component LN on the most reduction side does not become too strong, and the occurrence of aberrations can be suppressed. This is advantageous for correcting various aberrations, particularly spherical aberration and field curvature. By ensuring that the corresponding value of conditional expression (3) is not above the upper limit, the power of the lens surface of the N lens component LN on the most reduction side does not become too weak, and this is advantageous for correcting higher-order aberrations. This makes it easy to achieve compactness while appropriately correcting various aberrations. 0.2 <Rnr / Ymax<5 (3)

[0089] To obtain better characteristics, the lower limit of conditional expression (3) should preferably be set to 0.5, and more preferably to 0.7, and the upper limit of conditional expression (3) should preferably be set to 3, and more preferably to 2.5.

[0090] It is more preferable that the projection optical system simultaneously satisfy conditional expressions (1), (2), and (3). By arranging the P lens component LP at a position that satisfies conditional expression (1), and by configuring the two lens surfaces that face each other with air as their interface so that the upper limits of conditional expressions (2) and (3) are not exceeded, it becomes advantageous to shorten the overall length of the optical system and reduce the diameter of the lenses, thereby facilitating the miniaturization of the optical system.

[0091] It is preferable that the projection optical system satisfy the following conditional expression (4). Here, the back focus on the reduction side of the projection optical system in terms of the air equivalent distance is defined as Bf. Ensuring that the corresponding value of conditional expression (4) is not equal to or less than the lower limit thereof is advantageous for ensuring a long back focus. Ensuring that the corresponding value of conditional expression (4) is not equal to or greater than the upper limit thereof is advantageous for reducing the overall length of the optical system and the lens diameter. 2 <Bf / Ymax<8 (4)

[0092] In order to obtain better characteristics, the lower limit of conditional expression (4) should preferably be set to 2.5, and more preferably to 2.7. In order to obtain better characteristics, the upper limit of conditional expression (4) should preferably be set to 5, and even more preferably to 4.

[0093] It is preferable that the projection optical system satisfy the following conditional expression (5). Here, Y40 is the image height on the reduction-side image plane of a light ray with a half angle of 40 degrees on the magnification side. Y50 is the image height on the reduction-side image plane of a light ray with a half angle of 50 degrees on the magnification side. As an example, FIG. 2 shows a light beam B40 with a half angle of 40 degrees on the magnification side, the image height Y40 of the light beam B40 on the reduction-side image plane, a light beam B50 with a half angle of 50 degrees on the magnification side, and the image height Y50 of the light beam B50 on the reduction-side image plane. In FIG. 2, the angles between the optical axis Z and the principal rays contained in the light beams B40 and B50 are shown as 40° and 50°, respectively. Projection display devices are required to project distortion-free images, even with ultra-wide-angle projection optical systems. By satisfying conditional expression (5), it becomes easy to project distortion-free images onto the screen Scr in a wide-angle optical system. 1.35 <Y50 / Y40<1.5 (5)

[0094] In order to obtain better characteristics, the lower limit of conditional expression (5) should preferably be set to 1.37, and more preferably to 1.4. In order to obtain better characteristics, the upper limit of conditional expression (5) should preferably be set to 1.46, and even more preferably to 1.44.

[0095] In a configuration in which the half angle of view on the enlargement side is 55 degrees or greater, the projection optical system preferably satisfies the following conditional formula (5A): Here, the image height on the reduction-side image plane of a ray of light with a half angle of view of 55 degrees on the enlargement side is defined as Y55. By satisfying conditional formula (5A), it becomes easier to project an undistorted image onto the screen Scr in a wider-angle optical system. 1.6 <Y55 / Y40<1.8 (5A)

[0096] In order to obtain better characteristics, the lower limit of conditional formula (5A) should preferably be set to 1.65, and more preferably to 1.68.In order to obtain better characteristics, the upper limit of conditional formula (5A) should preferably be set to 1.75, and even more preferably to 1.72.

[0097] It is preferable that the projection optical system satisfy the following conditional expression (6). Here, the distance on the optical axis between the N lens component LN and the P lens component LP is defined as Dnp. FIG. 3 shows a partial enlarged view including lenses L1a to L1d of the projection optical system of FIG. 1, and shows the above-mentioned distance Dnp as an example. Since the N lens component LN and the P lens component LP are separate lens components, Dnp>0. Furthermore, since Ymax>0, the lower limit of conditional expression (6) is Dnp / Ymax>0. Ensuring that the corresponding value of conditional expression (6) is not greater than the upper limit is advantageous for correcting spherical aberration. 0 <Dnp / Ymax<0.1 (6)

[0098] To improve manufacturability, the lower limit of conditional expression (6) should preferably be set to 0.002, and more preferably to 0.004. To obtain better characteristics, the upper limit of conditional expression (6) should preferably be set to 0.05, and even more preferably to 0.03.

[0099] It is preferable that the projection optical system satisfy the following conditional expression (7). Here, the radius of curvature of the lens surface of the P lens component LP on the most reduction side is Rpr. By ensuring that the corresponding value of conditional expression (7) is not equal to or less than the lower limit, it is advantageous for correcting spherical aberration. By ensuring that the corresponding value of conditional expression (7) is not equal to or greater than the upper limit, it is advantageous for correcting astigmatism. 0<(Rpr+Rpf) / (Rpr-Rpf)<2 (7)

[0100] To obtain better characteristics, the lower limit of conditional expression (7) should preferably be set to 0.2, and more preferably to 0.3.To obtain better characteristics, the upper limit of conditional expression (7) should preferably be set to 1, and more preferably to 0.95.

[0101] It is preferable that the projection optical system satisfy the following conditional expression (8). Here, EDp is defined as the larger of the maximum effective diameter of the lens surface of the P lens component LP on the most enlargement side and the maximum effective diameter of the lens surface of the P lens component LP on the most reduction side. As an example, FIG. 3 shows the above maximum effective diameter EDp. Ensuring that the value corresponding to conditional expression (8) is not equal to or smaller than the lower limit is advantageous for ensuring the required F-number. Ensuring that the value corresponding to conditional expression (8) is not equal to or larger than the upper limit is advantageous for placing the P lens component LP near the pupil position, which is advantageous for making the optical system more compact. 0.5 <EDp / Ymax<2.5 (8)

[0102] In order to obtain better characteristics, the lower limit of conditional expression (8) should preferably be set to 1, and more preferably to 1.2. In order to obtain better characteristics, the upper limit of conditional expression (8) should preferably be set to 2, and more preferably to 1.8.

[0103] Here, the "maximum effective diameter" in this specification will be explained with reference to FIG. 4. FIG. 4 is an explanatory diagram. In FIG. 4, the left side is the enlargement side, and the right side is the reduction side. FIG. 4 shows an on-axis ray Xa and an off-axis ray Xb passing through the lens Lx. In the example of FIG. 4, the upper maximum ray of the off-axis ray Xb, ray Xb1, is the outermost ray. Here, "outside" refers to the radially outward direction centered on the optical axis Z, i.e., the side away from the optical axis Z. In this specification, the position of the intersection between this outermost ray and the lens surface is the position Px of the maximum effective diameter. Furthermore, twice the distance from the position Px of the maximum effective diameter to the optical axis Z is the maximum effective diameter ED of the enlargement-side surface of the lens Lx. Note that in the example of FIG. 4, the upper maximum ray of the off-axis ray Xb is the outermost ray, but which ray is the outermost ray varies depending on the optical system.

[0104] It is preferable that the projection optical system satisfy the following conditional expression (9). Here, the radius of curvature of the lens surface of the N lens component LN on the most enlargement side is Rnf. By ensuring that the corresponding value of conditional expression (9) is not equal to or less than the lower limit, it is advantageous for correcting field curvature. By ensuring that the corresponding value of conditional expression (9) is not equal to or greater than the upper limit, it is advantageous for correcting astigmatism. -1<(Rnr+Rnf) / (Rnr-Rnf)<0.5 (9)

[0105] To obtain better characteristics, the lower limit of conditional expression (9) should preferably be set to -0.8, and more preferably to -0.7, and the upper limit of conditional expression (9) should preferably be set to 0.1, and even more preferably to 0.05.

[0106] It is preferable that the projection optical system satisfy the following conditional expression (10). Here, the group consisting of all lenses on the enlargement side of the most enlargement-side moving lens group among the moving lens groups included in the projection optical system is referred to as the enlargement-side fixed group. The longest air distance between lens surfaces on the optical axis within the enlargement-side fixed group is referred to as dAmax. In the example of FIG. 1, the most enlargement-side moving lens group among the moving lens groups included in the projection optical system is the second lens group G2B. In the example of FIG. 1, the enlargement-side fixed group consists of all lenses from lens L1a to lens L2d, and the distance on the optical axis between lens L1l and lens L2a corresponds to the above-mentioned longest air distance dAmax. As an example, FIG. 2 shows the above-mentioned longest air distance dAmax. By ensuring that the corresponding value of conditional expression (10) is not equal to or less than the lower limit, appropriate lens distances can be ensured, which is advantageous for correcting lateral chromatic aberration and field curvature. By ensuring that the corresponding value of conditional expression (10) is not equal to or greater than the upper limit, which is advantageous for shortening the overall length of the optical system. 0.2 <dAmax / Ymax<2.5 (10)

[0107] In order to obtain better characteristics, the lower limit of conditional expression (10) should preferably be set to 0.5, and more preferably to 1. In order to obtain better characteristics, the upper limit of conditional expression (10) should preferably be set to 2, and more preferably to 1.5.

[0108] In a configuration in which the second optical system G2 is composed of, in order from the enlargement side to the reduction side along the optical path, the second-A lens group G2A, the second-B lens group G2B, the second-C lens group G2C, and the second-D lens group G2D, and in which, during magnification, the second-A lens group G2A and the second-D lens group G2D are fixed relative to the reduction-side image plane, and the second-B lens group G2B and the second-C lens group G2C move while varying their mutual spacing, it is preferable that the projection optical system satisfy the following conditional expression (11). Here, the focal length of the second-B lens group G2B is defined as f2B. The focal length of the second-C lens group G2C is defined as f2C. To miniaturize a projection optical system with a wide angle of view and a long back focus, it is preferable to configure the projection optical system so that a positive power is located on the reduction side. Therefore, among the moving lens groups included in the second optical system G2, assigning a stronger moving lens group with a positive power is advantageous for miniaturization. By ensuring that the corresponding value of conditional expression (11) is not equal to or less than the lower limit, it is possible to make the moving lens group with the stronger power among the moving lens groups included in the second optical system G2 have positive power, which is advantageous for size reduction. By ensuring that the corresponding value of conditional expression (11) is not equal to or greater than the upper limit, the absolute value of the power of the second-C lens group G2C does not become too large relative to the power of the second-B lens group G2B, which is advantageous for effective correction of astigmatism. 0 <f2B / |f2C|<0.5 (11)

[0109] In order to obtain better characteristics, it is more preferable to set the upper limit of conditional expression (11) to 0.3, and even more preferable to set it to 0.2.

[0110] It is preferable that the projection optical system satisfy the following conditional expression (12). Here, EDL1 is defined as the larger of the maximum effective diameter of the enlargement-side surface of the most enlargement-side lens in the projection optical system and the maximum effective diameter of the reduction-side surface of the most enlargement-side lens in the projection optical system. As an example, FIG. 3 shows the above-mentioned maximum effective diameter EDL1. The specific gravity of the most enlargement-side lens in the projection optical system is defined as ρL1. Ensuring that the value corresponding to conditional expression (12) is not equal to or smaller than the lower limit is advantageous for correcting distortion. Ensuring that the value corresponding to conditional expression (12) is not equal to or larger than the upper limit can contribute to reducing the weight of the optical system, even in wide-angle optical systems in which the most enlargement-side lens often has the largest lens diameter within the optical system. 0.5 <EDL1×ρL1 / Ymax<10 (12)

[0111] In order to obtain better characteristics, it is more preferable that the lower limit of conditional expression (12) be set to 1, and even more preferable that it be set to 3. In order to obtain better characteristics, it is more preferable that the upper limit of conditional expression (12) be set to 8, and even more preferable that it be set to 6.

[0112] In a configuration in which a back focus correction group that adjusts the back focus by moving along the optical axis Z is disposed within a projection optical system, it is preferable that the projection optical system satisfy at least one of the following conditional expressions (18) and (19). Here, the paraxial lateral magnification of the back focus correction group is defined as βB. The combined paraxial lateral magnification of all lenses on the reduction side of the back focus correction group is defined as βBr. The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the back focus correction group moves 0.1×Ymax in the optical axis direction is defined as ΔtB. βB, βBr, and ΔtB are values ​​when the magnification of the projection optical system is 120x. 0.1<|(1-βB 2 )×βBr 2 |<2 (18) 0.7<|(1-βB 2 )×βBr 2 | / ΔtB<1.4 (19)

[0113] By ensuring that the value corresponding to conditional expression (18) is not equal to or smaller than the lower limit, the amount of movement of the back focus correction group during back focus adjustment can be suppressed, which is advantageous for downsizing the optical system.By ensuring that the value corresponding to conditional expression (18) is not equal to or larger than the upper limit, the amount of change in back focus per amount of movement of the back focus correction group does not become too large, which is advantageous for suppressing strict fine adjustment of back focus.

[0114] In order to obtain better characteristics, the lower limit of conditional expression (18) should preferably be set to 0.2, and more preferably to 0.25. In order to obtain better characteristics, the upper limit of conditional expression (18) should preferably be set to 1.5, and even more preferably to 1.

[0115] Conditional expression (19) is a conditional expression for bringing the entire image plane into focus when focusing is performed to adjust the back focus. By satisfying conditional expression (19), it becomes easy to bring the entire image plane, including both the optical axis and the peripheral areas of the image plane, into focus.

[0116] In order to obtain better characteristics, the lower limit of conditional expression (19) should preferably be set to 0.75, and more preferably to 0.8.In order to obtain better characteristics, the upper limit of conditional expression (19) should preferably be set to 1.3, and even more preferably to 1.2.

[0117] As an example, the change amount ΔtB is shown schematically in Fig. 5 using arrows. In Fig. 5, the optical axis direction is taken horizontally in the figure, and the tangential image plane t0 based on the design values ​​is shown by a solid line, while the tangential image plane tB1 when the back focus correction group moves 0.1 × Ymax in the optical axis direction is shown by a dashed line. ω in Fig. 5 is the half angle of view, and the position corresponding to a half angle of view of 0 degrees is shown by a thin solid line, and the position corresponding to a half angle of view of 50 degrees is shown by a dashed line.

[0118] In a configuration in which a focus group that adjusts the focus of the entire image plane when the projection distance changes by moving along the optical axis Z is disposed within a projection optical system, it is preferable that the projection optical system satisfy at least one of the following conditional expressions (17) and (20). Here, the paraxial lateral magnification of the focus group is defined as βFF. The composite paraxial lateral magnification of all lenses on the reduction side of the focus group is defined as βFFr. The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtFF. βFF, βFFr, and ΔtFF are values ​​when the magnification of the projection optical system is 120x. 0.02<(1-βFF 2 )×βFFr 2 <0.2 (17) 0.1<((1-βFF 2 )×βFFr 2 ) / ΔtFF<0.5 (20)

[0119] By ensuring that the value corresponding to condition (17) is not less than the lower limit, it is advantageous for focusing near the optical axis.By ensuring that the value corresponding to condition (17) is not more than the upper limit, it is advantageous for achieving a good balance between focusing on the optical axis and at the periphery of the image plane.

[0120] In order to obtain better characteristics, the lower limit of conditional expression (17) should preferably be set to 0.03, and more preferably to 0.05.In order to obtain better characteristics, the upper limit of conditional expression (17) should preferably be set to 0.15, and even more preferably to 0.13.

[0121] Conditional expression (20) is a conditional expression for achieving a good balance between focus on the optical axis and the peripheral parts of the image plane when the projection distance changes in a wide-angle lens system. Satisfying conditional expression (20) is advantageous for achieving a good balance between focus on the optical axis and the peripheral parts of the image plane.

[0122] In order to obtain better characteristics, the lower limit of conditional expression (20) should preferably be set to 0.2, and more preferably to 0.25, and the upper limit of conditional expression (20) should preferably be set to 0.4, and even more preferably to 0.35.

[0123] In a configuration in which a focus group that moves along the optical axis Z to adjust the focus of the entire image plane when the projection distance changes, and a back focus correction group that moves along the optical axis Z to adjust the back focus, are arranged in the projection optical system, it is preferable that the projection optical system satisfy both of the above conditional expressions (17) and (18).

[0124] When the focus group includes six or more lenses, is located on the most enlargement side of the projection optical system, and has a configuration in which the spacing between all lenses in the focus group remains unchanged during focus adjustment, it is preferable that the projection optical system satisfy at least one of the following conditional expressions (13) and (14). Here, the paraxial lateral magnification of the focus group is defined as βF. The composite paraxial lateral magnification of all lenses on the reduction side of the focus group is defined as βFr. The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtF. βF, βFr, and ΔtF are values ​​when the enlargement magnification of the projection optical system is 120x. 0.02<(1-βF 2 )×βFr 2 <0.2 (13) 0.1<((1-βF 2 )×βFr 2 ) / ΔtF<0.5 (14)

[0125] By ensuring that the value corresponding to condition (13) is not less than the lower limit, it is advantageous for focusing near the optical axis.By ensuring that the value corresponding to condition (13) is not more than the upper limit, it is advantageous for achieving a good balance between focusing on the optical axis and the peripheral parts of the image plane.

[0126] In order to obtain better characteristics, the lower limit of conditional expression (13) should preferably be set to 0.03, and more preferably to 0.05.In order to obtain better characteristics, the upper limit of conditional expression (13) should preferably be set to 0.15, and even more preferably to 0.13.

[0127] Condition (14) is a condition for achieving a good balance between focus on the optical axis and the periphery of the image plane when the projection distance changes in a wide-angle lens system. Satisfying condition (14) is advantageous for achieving a good balance between focus on the optical axis and the periphery of the image plane.

[0128] In order to obtain better characteristics, the lower limit of conditional expression (14) should preferably be set to 0.2, and more preferably to 0.25, and the upper limit of conditional expression (14) should preferably be set to 0.4, and even more preferably to 0.35.

[0129] In a configuration in which one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a negative lens and the other is a positive lens, it is preferable that the projection optical system satisfy the following conditional expression (15). Here, the distance on the optical axis between the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is dFr12. As an example, the above distance dFr12 is shown in Figure 2. Satisfying conditional expression (15) is advantageous for suppressing fluctuations in lateral chromatic aberration during focus adjustment. 0≦dFr12 / Ymax<0.1 (15)

[0130] In a configuration in which both a focus group and a back-focus correction group are disposed within a projection optical system, the projection optical system preferably satisfies the following conditional expression (16). Here, ZFBr is the distance on the optical axis from the lens surface of the first optical system G1 on the most enlargement side to the lens surface of the focus group and back-focus correction group on the most reduction side among the lens surfaces included in the focus group and back-focus correction group. As an example, FIG. 2 shows the above distance ZFBr. By ensuring that the value corresponding to conditional expression (16) is not equal to or less than the lower limit, it becomes easy to ensure space for disposing both the focus group and the back-focus correction group. By ensuring that the value corresponding to conditional expression (16) is not equal to or greater than the upper limit, the position of the focus group or back-focus correction group will not be too far to the reduction side, which is advantageous for ensuring good operability. 5 <ZFBr / |f|<20 (16)

[0131] In order to obtain better characteristics, it is more preferable to set the lower limit of conditional expression (16) to 7, and even more preferable to set it to 10. In order to obtain better characteristics, it is more preferable to set the upper limit of conditional expression (16) to 19, and even more preferable to set it to 15.

[0132] Preferred and possible configurations, including those related to conditional expressions, can be combined in any combination within a range consistent with the present disclosure, and are preferably selectively adopted as appropriate according to the required specifications. Various modifications are possible within the scope of the spirit of the technology of the present disclosure. For example, in the technology of the present disclosure, the number and shape of lenses included in each group and each optical system may be different from those in the example of FIG. 1. The groups that are fixed during magnification, the moving lens group, the focus group, and the back focus correction group may be different from those in the example of FIG. 1.

[0133] In the example of FIG. 1, the back-focus correction group is disposed on the reduction side of the focus group. More specifically, the back-focus correction group is disposed adjacent to the focus group. However, the technology disclosed herein can also be configured such that the focus group and the back-focus correction group are not adjacent to each other. In that case, the back-focus correction group may be disposed adjacent to the reduction side of the intermediate image MI.

[0134] The back focus correction group may be configured to consist of one lens. More specifically, the back focus correction group may be configured to consist of one positive lens. Alternatively, the back focus correction group may be configured to consist of three lenses. For example, the back focus correction group may be configured to consist of one negative lens and two positive lenses.

[0135] From the above, a projection optical system according to a preferred embodiment of the present disclosure is a projection optical system that projects an image on a reduction-side image plane onto an enlargement-side image plane, and has a half angle of view on the enlargement-side of 50 degrees or more. When one lens component is a single lens or a cemented lens, the projection optical system includes a P lens component LP that is the lens component on the most enlargement side and has positive power among the lens components included in the projection optical system, and an N lens component LN that is a lens component with negative power that is arranged adjacent to the enlargement side of the P lens component LP, and satisfies the above conditional expressions (1), (2), (3), (4), and (5).

[0136] Another preferred embodiment of the projection optical system of the present disclosure is a projection optical system consisting of, in order from the enlargement side to the reduction side along the optical path, a first optical system G1 and a second optical system G2, wherein the second optical system G2 forms an intermediate image MI between the first optical system G1 and the second optical system G2 at a position conjugate with the reduction side image plane, and the first optical system G1 re-images the intermediate image MI on the enlargement side image plane, and at the most enlargement side of the projection optical system is a focus group which includes six or more lenses and moves along the optical axis Z to adjust the focus of the entire image plane when the projection distance changes, and the spacing between all lenses in the focus group remains unchanged during focus adjustment.

[0137] A projection optical system according to yet another preferred aspect of the present disclosure is a projection optical system consisting of, in order from the enlargement side to the reduction side along the optical path, a first optical system G1 and a second optical system G2, wherein the second optical system G2 forms an intermediate image MI between the first optical system G1 and the second optical system G2 at a position conjugate with the reduction-side image forming surface, and the first optical system G1 re-images the intermediate image MI on the enlargement-side image forming surface, and wherein the projection optical system is provided with a focus group that moves along the optical axis Z to adjust the focus of the entire image surface when the projection distance changes, and a back focus correction group that moves along the optical axis Z to adjust the back focus, and satisfies the above conditional expression (16).

[0138] Next, examples of the projection optical system of the present disclosure will be described with reference to the drawings. Note that the reference symbols assigned to each lens, each lens group, and each optical system in the cross-sectional views of each example are used independently for each example to avoid cluttering the explanation and drawings due to an increase in the number of digits in the reference symbols. Therefore, even if common reference symbols are assigned in drawings of different examples, this does not necessarily mean that the configuration is the same.

[0139] [Example 1] The configuration of the projection optical system of Example 1 and a cross-sectional view of the light beam are shown in Figure 1. The illustration method and configuration are as described above, so some overlapping explanations will be omitted here. The projection optical system of Example 1 comprises, in order along the optical path from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order along the optical path from the enlargement side to the reduction side, a secondA lens group G2A having positive power, a secondB lens group G2B having positive power, a secondC lens group G2C having positive power, and a secondD lens group G2D having positive power.

[0140] For the projection optical system of Example 1, basic lens data is shown in Tables 1A and 1B, specifications and variable surface spacing during magnification are shown in Table 2, variable surface spacing during focusing is shown in Table 3, and aspherical coefficients are shown in Table 4. Here, to avoid making one table too long, the basic lens data is shown in two tables, Table 1A and Table 1B. Table 1A shows the first optical system G1, and Table 1B shows the second optical system G2.

[0141] The basic lens data table is written as follows. The Sn column shows the surface number, with the surface on the most magnification side being surface 1 and the numbers increasing by one as you move toward the reduction side. The R column shows the radius of curvature of each surface. The D column shows the surface distance on the optical axis between each surface and the surface adjacent to it on the reduction side. The Nd column shows the refractive index for the d-line of each component element. The νd column shows the Abbe number of each component element based on the d-line. The ED column shows the maximum effective diameter of each surface for the most magnification side lens and the P lens component LP.

[0142] In the table of basic lens data, the sign of the radius of curvature of a surface with a convex shape facing the enlargement side is positive, and the sign of the radius of curvature of a surface with a convex shape facing the reduction side is negative. The column for the surface number of the surface corresponding to the aperture stop St lists the surface number and the term (St). The table of basic lens data also shows the optical element PP. The value in the bottom column of the D column in the table is the distance between the surface on the most reduction side in the table and the display surface Sim. The symbol DD[ ] is used to indicate the variable surface distance when changing magnification, and the surface number on the enlargement side of this distance is entered in the [ ] in the D column.

[0143] Table 2 shows the zoom ratio Zr, absolute value of focal length |f|, back focal length Bf in air equivalent distance, F-number FNo., maximum full angle of view 2ω, and variable surface spacing during zooming, based on the d-line. The [°] in the 2ω column indicates that the unit is degrees. In Table 2, the columns labeled "WIDE," "MIDDLE," and "TELE" show the values ​​for the wide-angle end, mid-focal length state, and telephoto end, respectively.

[0144] In Example 1, when the projection distance changes, focusing is performed by changing the distance between surfaces 17 and 18. Table 3 shows the variable surface distances that are required for focusing at each projection distance. The projection distance is the distance on the optical axis from the magnification-side image plane (corresponding to the screen Scr in Figure 1) to the lens surface on the most magnification side.

[0145] In the basic lens data, the surface numbers of aspherical surfaces are marked with an *, and the value of the paraxial radius of curvature is listed in the column for the radius of curvature of the aspherical surface. In Table 4, the Sn row shows the surface numbers of aspherical surfaces, and the KA and Am rows show the numerical values ​​of the aspherical coefficients for each aspherical surface. Note that m in Am is an integer of 3 or more, and varies depending on the surface. For example, for the first surface in Example 1, m = 3, 4, 5, ... 20. The numerical values ​​of the aspherical coefficients in Table 4, "E±n" (n: integer), are expressed as "×10 ±n KA and Am are aspherical coefficients in the aspherical formula given below. Zd=C×h 2 / {1+(1-KA×C 2 ×h 2 ) 1 / 2}+ΣAm×h m however, Zd: Aspheric depth (length of the perpendicular line drawn from a point on the aspheric surface at height h to a plane perpendicular to the optical axis Z where the vertex of the aspheric surface is in contact) h: Height (distance from optical axis Z to lens surface) C: Reciprocal of paraxial radius of curvature KA, Am: aspherical coefficients In the aspherical formula, Σ means the summation over m.

[0146] In the data in each table, degrees are used as the unit of angle and mm (millimeters) as the unit of length, but since the optical system can be used with proportional enlargement or reduction, other appropriate units can also be used. Also, in each table below, values ​​are listed rounded to a certain number of decimal places.

[0147] [Table 1A]

[0148] [Table 1B]

[0149] [Table 2]

[0150] [Table 3]

[0151] [Table 4]

[0152] FIG. 6 shows aberration diagrams of the projection optical system of Example 1 when the projection distance is 725.7 mm (millimeters). In FIG. 6, the upper row labeled "WIDE" shows aberrations in the wide-angle end state, the middle row labeled "MIDDLE" shows aberrations in the intermediate focal length state, and the lower row labeled "TELE" shows aberrations in the telephoto end state. From left to right, FIG. 6 shows spherical aberration, astigmatism, distortion, and lateral chromatic aberration. In the spherical aberration diagram, aberrations for the d-line, C-line, and F-line are shown by solid lines, long-dashed lines, and short-dashed lines, respectively. In the astigmatism diagram, aberrations for the d-line in the sagittal direction are shown by solid lines, and aberrations for the d-line in the tangential direction are shown by short-dashed lines. In the distortion diagram, aberrations for the d-line are shown by solid lines. In the lateral chromatic aberration diagram, aberrations for the C-line and F-line are shown by long-dashed lines and short-dashed lines, respectively. In spherical aberration diagrams, the F-number value is shown after "FNo.=". In other aberration diagrams, the maximum half angle of view value is shown after "ω=". The horizontal axis of aberration diagrams other than distortion diagrams is in mm (millimeters).

[0153] The symbols, meanings, notation, and illustration methods of each data item related to the above-described Example 1 are basically the same in the following Examples unless otherwise specified, and therefore, redundant explanations will be omitted below. In the cross-sectional views of the following Examples, the screen Scr is not shown.

[0154] [Example 2] FIG. 7 shows a cross-sectional view of the configuration and light beam of the projection optical system of Example 2. The projection optical system of Example 2 comprises, in order from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order from the enlargement side to the reduction side, a second-A lens group G2A having positive power, a second-B lens group G2B having positive power, a second-C lens group G2C having positive power, and a second-D lens group G2D having positive power. During magnification variation, the second-A lens group G2A and the second-D lens group G2D are fixed with respect to the display surface Sim, while the second-B lens group G2B and the second-C lens group G2C move while changing the distance between them.

[0155] The first optical system G1 is composed of, in order from the enlargement side to the reduction side, lenses L1a to L1l. The second-A lens group G2A is composed of, in order from the enlargement side to the reduction side, lenses L2a to L2d. The second-B lens group G2B is composed of a lens L2e. The second-C lens group G2C is composed of, in order from the enlargement side to the reduction side, an aperture stop St and lenses L2f to L2i. The second-D lens group G2D is composed of a lens L2j. Lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN. The focus group is composed of lenses L1a to L1i. The back focus correction group is composed of lens L1j.

[0156] For the projection optical system of Example 2, basic lens data is shown in Tables 5A and 5B, specifications and variable surface spacing during magnification are shown in Table 6, variable surface spacing during focusing is shown in Table 7, aspherical coefficients are shown in Table 8, and each aberration diagram is shown in Fig. 8. Each aberration diagram is for a projection distance of 725.7 mm (millimeters).

[0157] [Table 5A]

[0158] [Table 5B]

[0159] [Table 6]

[0160] [Table 7]

[0161] [Table 8]

[0162] [Example 3] 9 shows a cross-sectional view of the configuration and light beam of the projection optical system of Example 3. The projection optical system of Example 3 comprises, in order from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order from the enlargement side to the reduction side, a second-A lens group G2A having positive power, a second-B lens group G2B having positive power, a second-C lens group G2C having positive power, and a second-D lens group G2D having positive power. During magnification variation, the second-A lens group G2A and the second-D lens group G2D are fixed with respect to the display surface Sim, while the second-B lens group G2B and the second-C lens group G2C move while changing the distance between them.

[0163] The first optical system G1 is composed of, in order from the enlargement side to the reduction side, lenses L1a to L1l. The second-A lens group G2A is composed of, in order from the enlargement side to the reduction side, lenses L2a to L2d. The second-B lens group G2B is composed of a lens L2e. The second-C lens group G2C is composed of, in order from the enlargement side to the reduction side, lens L2f, an aperture stop St, and lenses L2g to L2i. The second-D lens group G2D is composed of a lens L2j. Lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN. The focus group is composed of lenses L1a to L1i. The back focus correction group is composed of lens L1j.

[0164] For the projection optical system of Example 3, basic lens data is shown in Tables 9A and 9B, specifications and variable surface spacing during magnification are shown in Table 10, variable surface spacing during focusing is shown in Table 11, aspherical coefficients are shown in Table 12, and each aberration diagram is shown in Fig. 10. Each aberration diagram is for a projection distance of 725.7 mm (millimeters).

[0165] [Table 9A]

[0166] [Table 9B]

[0167] [Table 10]

[0168] [Table 11]

[0169] [Table 12]

[0170] [Example 4] FIG. 11 shows a cross-sectional view of the configuration and light beams of the projection optical system of Example 4. The projection optical system of Example 4 comprises, in order from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order from the enlargement side to the reduction side, a second-A lens group G2A having positive power, a second-B lens group G2B having positive power, a second-C lens group G2C having negative power, and a second-D lens group G2D having positive power. During magnification variation, the second-A lens group G2A and the second-D lens group G2D are fixed with respect to the display surface Sim, while the second-B lens group G2B and the second-C lens group G2C move while changing the distance between them.

[0171] The first optical system G1 is composed of lenses L1a to L1l, in order from the enlargement side to the reduction side. The second-A lens group G2A is composed of lenses L2a to L2d, in order from the enlargement side to the reduction side. The second-B lens group G2B is composed of lens L2e. The second-C lens group G2C is composed of lens L2f, aperture stop St, and lenses L2g to L2i, in order from the enlargement side to the reduction side. The second-D lens group G2D is composed of lens L2j. Lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN. The focus group is composed of lenses L1a to L1i. The back focus correction group is composed of lenses L2a to L2c.

[0172] For the projection optical system of Example 4, basic lens data is shown in Tables 13A and 13B, specifications and variable surface spacing during magnification are shown in Table 14, variable surface spacing during focusing is shown in Table 15, aspherical coefficients are shown in Table 16, and each aberration diagram is shown in Fig. 12. Each aberration diagram is for a projection distance of 725.7 mm (millimeters).

[0173] [Table 13A]

[0174] [Table 13B]

[0175] [Table 14]

[0176] [Table 15]

[0177] [Table 16]

[0178] [Example 5] FIG. 13 shows a cross-sectional view of the configuration and light beam of the projection optical system of Example 5. The projection optical system of Example 5 comprises, in order from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order from the enlargement side to the reduction side, a second-A lens group G2A having positive power, a second-B lens group G2B having positive power, a second-C lens group G2C having negative power, and a second-D lens group G2D having positive power. During magnification variation, the second-A lens group G2A and the second-D lens group G2D are fixed relative to the display surface Sim, while the second-B lens group G2B and the second-C lens group G2C move while changing the distance between them.

[0179] The first optical system G1 is composed of lenses L1a to L1l, in order from the enlargement side to the reduction side. The second-A lens group G2A is composed of lenses L2a to L2d, in order from the enlargement side to the reduction side. The second-B lens group G2B is composed of lens L2e. The second-C lens group G2C is composed of lens L2f, aperture stop St, and lenses L2g to L2i, in order from the enlargement side to the reduction side. The second-D lens group G2D is composed of lens L2j. Lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN. The focus group is composed of lenses L1a to L1i. The back focus correction group is composed of lenses L2a to L2c.

[0180] For the projection optical system of Example 5, basic lens data is shown in Tables 17A and 17B, specifications and variable surface spacing during magnification are shown in Table 18, variable surface spacing during focusing is shown in Table 19, aspherical coefficients are shown in Table 20, and each aberration diagram is shown in Fig. 14. Each aberration diagram is for a projection distance of 688.0 mm (millimeters).

[0181] [Table 17A]

[0182] [Table 17B]

[0183] [Table 18]

[0184] [Table 19]

[0185] [Table 20]

[0186] [Example 6] FIG. 15 shows a cross-sectional view of the configuration and light beam of the projection optical system of Example 6. The projection optical system of Example 6 comprises, in order from the enlargement side to the reduction side, a first optical system G1 and a second optical system G2. The second optical system G2 comprises, in order from the enlargement side to the reduction side, a second-A lens group G2A having positive power, a second-B lens group G2B having positive power, a second-C lens group G2C having negative power, and a second-D lens group G2D having positive power. During magnification variation, the second-A lens group G2A and the second-D lens group G2D are fixed relative to the display surface Sim, while the second-B lens group G2B and the second-C lens group G2C move while changing the distance between them.

[0187] The first optical system G1 is composed of lenses L1a to L1l, in order from the enlargement side to the reduction side. The second-A lens group G2A is composed of lenses L2a to L2d, in order from the enlargement side to the reduction side. The second-B lens group G2B is composed of lens L2e. The second-C lens group G2C is composed of lens L2f, aperture stop St, and lenses L2g to L2i, in order from the enlargement side to the reduction side. The second-D lens group G2D is composed of lens L2j. Lens L1d corresponds to the P lens component LP, and lens L1c corresponds to the N lens component LN. The focus group is composed of lenses L1a to L1i. The back focus correction group is composed of lenses L2a to L2c.

[0188] For the projection optical system of Example 6, basic lens data is shown in Tables 21A and 21B, specifications and variable surface spacing during magnification are shown in Table 22, variable surface spacing during focusing is shown in Table 23, aspherical coefficients are shown in Table 24, and each aberration diagram is shown in Fig. 16. Each aberration diagram is for a projection distance of 767.9 mm (millimeters).

[0189] [Table 21A]

[0190] [Table 21B]

[0191] [Table 22]

[0192] [Table 23]

[0193] [Table 24]

[0194] For the projection optical systems of Examples 1 to 6, Table 25 shows the values ​​of Ymax, Y55, Y50, Y40, and ρL1, and Table 26 shows the corresponding values ​​of conditional expressions (1) to (20). The corresponding values ​​of conditional expressions (13), (14), and (17) to (20) are values ​​when the magnification of the projection optical system is 120 times. The projection optical system of the present disclosure is intended for use at a magnification of 50 times or more (i.e., a lateral magnification of the entire projection optical system of 0.02 or less). The corresponding values ​​of the examples shown in Table 26 may be used as the upper or lower limits of the conditional expressions to set preferred ranges for the conditional expressions.

[0195] [Table 25]

[0196] [Table 26]

[0197] The projection optical systems of Examples 1 to 6 have a wide angle of view, with a total angle of view of 110 degrees or more at the wide-angle end. The projection optical systems of Examples 1 to 6 have a small F-number, less than 2. Furthermore, the projection optical systems of Examples 1 to 6 have a long back focus, yet are compact, and various aberrations are well corrected, achieving high optical performance.

[0198] Next, a projection display device according to an embodiment of the present disclosure will be described. FIG. 17 is a schematic diagram of a projection display device according to an embodiment of the present disclosure. The projection display device 100 shown in FIG. 17 includes a projection optical system 10 according to an embodiment of the present disclosure, a light source 15, and transmissive display elements 11a-11c as light valves that output optical images corresponding to the respective color lights. The projection display device 100 also includes dichroic mirrors 12 and 13 for color separation, a cross dichroic prism 14 for color synthesis, condenser lenses 16a-16c, and total reflection mirrors 18a-18c for deflecting the optical path. Note that FIG. 17 only shows a schematic representation of the projection optical system 10. An integrator is disposed between the light source 15 and the dichroic mirror 12, but is not shown in FIG. 17.

[0199] White light from light source 15 is separated into three colored light beams (green light, blue light, and red light) by dichroic mirrors 12 and 13, and then passes through condenser lenses 16a to 16c, where the colored light beams are incident on and modulated by transmissive display elements 11a to 11c corresponding to the colored light beams, and then are color-synthesized by cross dichroic prism 14 before being incident on projection optical system 10. Projection optical system 10 projects an optical image based on the modulated light modulated by transmissive display elements 11a to 11c onto screen 105.

[0200] Fig. 18 is a schematic diagram of a projection display device according to another embodiment of the present disclosure. The projection display device 200 shown in Fig. 18 includes a projection optical system 210 according to an embodiment of the present disclosure, a light source 215, and DMD (Digital Micromirror Device: registered trademark) elements 21a to 21c as light valves that output optical images corresponding to the respective color lights. The projection display device 200 also includes TIR (Total Internal Reflection) prisms 24a to 24c for color separation and color synthesis. 18. The projection optical system 210 includes a light source 215 and a polarization separating prism 25, which separates the illumination light from the projection light. 210 is shown only in outline in Fig. 18. An integrator is disposed between the light source 215 and the polarization separating prism 25, but is not shown in Fig. 18.

[0201] White light from light source 215 is reflected by a reflective surface inside polarization separation prism 25, and then separated into three colored light beams (green light, blue light, and red light) by TIR prisms 24a-24c. Each separated colored light beam enters and is modulated by the corresponding DMD elements 21a-21c, travels again in the opposite direction through TIR prisms 24a-24c, and is color-synthesized. Then, it passes through polarization separation prism 25 and enters projection optical system 210. Projection optical system 210 projects an optical image based on the modulated light by DMD elements 21a-21c onto screen 205.

[0202] Fig. 19 is a schematic diagram of a projection display device according to yet another embodiment of the present disclosure. The projection display device 600 shown in Fig. 19 includes a projection optical system 66 according to an embodiment of the present disclosure, a light source 61, and a DMD element 64 as a light valve that outputs an optical image corresponding to each color light. The projection display device 600 also includes a color wheel 62, a light-guiding optical system 63, and a TIR prism 65. Note that Fig. 19 shows the projection optical system 66 only in a simplified manner.

[0203] The color wheel 62 has three color filters (green, blue, and red) arranged on its circumference, and as the color wheel 62 rotates, the filters of each color are inserted sequentially into the optical path. White light from the light source 61 is time-divided into three colored light beams (green light, blue light, and red light) by entering the rotating color wheel 62. After time division, each colored light beam passes through a light-guiding optical system 63 and a TIR prism 65, then enters a DMD element 64 where it is modulated, and then passes through the TIR prism 65 again before entering a projection optical system 66. The projection optical system 66 projects an optical image based on the light modulated by the DMD element 64 onto a screen 67.

[0204] Although the technology of the present disclosure has been described above using embodiments and examples, the technology of the present disclosure is not limited to the above embodiments and examples and can be modified in various ways. For example, the radius of curvature, surface spacing, refractive index, Abbe number, aspherical coefficient, etc. of each lens are not limited to the values ​​shown in the above examples and can take other values.

[0205] Furthermore, the projection display device according to the technology of the present disclosure is not limited to the above configuration. For example, the optical members and light valves used for beam separation or beam combination can be modified in various ways. The light valve is not limited to a configuration in which light from a light source is spatially modulated by an image display element and output as an optical image based on image data. It may also be a configuration in which light output from a self-luminous image display element is output as an optical image based on image data. Examples of self-luminous image display elements include image display elements in which light-emitting elements such as LEDs (Light Emitting Diodes) or OLEDs (Organic Light Emitting Diodes) are two-dimensionally arranged. The light valve is not limited to a three-panel type, but may be a single-panel type. Configuring the light valve to be compatible with a single-panel type allows for the miniaturization of the optical engine.

[0206] The following supplementary items are further disclosed regarding the above embodiments and examples. [Appendix 1] A projection optical system that projects an image on a reduction-side image-forming surface onto an enlargement-side image-forming surface, The half angle of view on the magnification side is 50 degrees or more, When one lens component is one single lens or one cemented lens, the projection optical system includes a P lens component which is the lens component on the most enlargement side and has positive power, and an N lens component which is a lens component with negative power and is disposed adjacent to the enlargement side of the P lens component, The maximum image height on the reduction-side imaging surface is defined as Ymax, Zp is the distance on the optical axis from the surface of the optical element having the most magnification power in the projection optical system to the most magnification lens surface of the P lens component, The radius of curvature of the lens surface of the P lens component closest to the enlargement side is Rpf, The radius of curvature of the lens surface of the N lens component closest to the reduction side is Rnr, The back focus on the reduction side of the projection optical system in terms of air equivalent distance is Bf, The image height of a light ray having a half angle of view of 40 degrees on the enlargement side on the reduction side image forming plane is defined as Y40, The image height of a light ray having a half angle of view of 50 degrees on the enlargement side on the reduction side image forming plane is defined as Y50, If the projection optical system is a variable magnification optical system, then, assuming that Ymax, Zp, Bf, Y40, and Y50 are values ​​at the wide-angle end, 1 <Zp / Ymax<4 (1) 0.2 <Rpf / Ymax<2.3 (2) 0.2 <Rnr / Ymax<5 (3) 2 <Bf / Ymax<8 (4) 1.35 <Y50 / Y40<1.5 (5) A projection optical system that satisfies conditional expressions (1), (2), (3), (4), and (5) expressed as follows: [Appendix 2] The optical system comprises, in order from the magnification side to the reduction side along the optical path, a first optical system and a second optical system, The projection optical system described in Appendix 1, wherein the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with the reduction-side image-forming surface, and the first optical system re-images the intermediate image on the enlargement-side image-forming surface. [Appendix 3] The distance on the optical axis between the N lens component and the P lens component is Dnp, When the projection optical system is a variable magnification optical system, if Dnp is the value at the wide-angle end, 0 <Dnp / Ymax<0.1 (6) 3. The projection optical system according to claim 1, which satisfies conditional expression (6) shown below. [Appendix 4] If the radius of curvature of the lens surface of the P lens component closest to the reduction side is Rpr, then 0<(Rpr+Rpf) / (Rpr-Rpf)<2 (7) 4. The projection optical system according to claim 1, which satisfies conditional expression (7) below. [Appendix 5] When the larger of the maximum effective diameter of the lens surface of the P lens component on the most enlargement side and the maximum effective diameter of the lens surface of the P lens component on the most reduction side is defined as EDp, 0.5 <EDp / Ymax<2.5 (8) 5. The projection optical system according to any one of claims 1 to 4, which satisfies conditional expression (8) shown below. [Appendix 6] When the radius of curvature of the lens surface on the most enlargement side of the N lens component is Rnf, -1<(Rnr+Rnf) / (Rnr-Rnf)<0.5 (9) 6. The projection optical system according to any one of claims 1 to 5, which satisfies conditional expression (9) shown below. [Appendix 7] the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed group is defined as dAmax, When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2 <dAmax / Ymax<2.5 (10) 3. The projection optical system according to claim 2, which satisfies conditional expression (10) shown below. [Appendix 8] the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; The projection optical system described in Appendix 2 or Appendix 7, wherein, during magnification variation, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them. [Appendix 9] The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) 9. The projection optical system according to claim 8, which satisfies conditional expression (11) shown below. [Appendix 10] EDL1 is the larger of the maximum effective diameter of the enlargement-side surface of the most enlargement-side lens in the projection optical system and the maximum effective diameter of the reduction-side surface of the most enlargement-side lens in the projection optical system, If the specific gravity of the lens on the most enlarged side of the projection optical system is ρL1, then 0.5 <EDL1×ρL1 / Ymax<10 (12) 10. The projection optical system according to any one of claims 1 to 9, which satisfies conditional expression (12) shown below. [Appendix 11] the P lens component is a single lens, 11. The projection optical system according to any one of claims 1 to 10, wherein the refractive index of the P lens component with respect to the d-line is 1.65 or more. [Appendix 12] The N lens component is a single lens, 12. The projection optical system according to claim 11, wherein the refractive index of the N lens component with respect to the d-line is 1.65 or less. [Appendix 13] 3. The projection optical system according to claim 2, wherein the first optical system includes an aspherical lens. [Appendix 14] 14. The projection optical system according to claim 13, wherein the first optical system includes two aspherical lenses. [Appendix 15] 15. The projection optical system according to claim 13, wherein the lens surface of the first optical system closest to the enlargement side is an aspheric surface that faces a concave surface toward the enlargement side in the paraxial region and has an inflection point where the concave and convex shape changes midway from on the optical axis to the periphery. [Appendix 16] 16. The projection optical system according to any one of claims 1 to 15, wherein the reduction side is telecentric. [Appendix 17] A projection display device comprising the projection optical system according to any one of Supplementary Note 1 to Supplementary Note 16. [Appendix 18] A projection optical system including, in order from the enlargement side to the reduction side along an optical path, a first optical system and a second optical system, the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with a reduction-side image-forming surface, and the first optical system re-images the intermediate image on an enlargement-side image-forming surface; a focus group including six or more lenses is disposed on the most enlarged side of the projection optical system, and the focus group moves along the optical axis to adjust the focus of the entire image plane when the projection distance changes; The projection optical system in which the distances between all lenses in the focus group remain unchanged during the focus adjustment. [Appendix 19] 19. The projection optical system according to claim 18, wherein the focus group is disposed within the first optical system. [Appendix 20] The paraxial lateral magnification of the focus group is βF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFr, When the projection optical system is a variable magnification optical system, βF and βFr are values ​​at the wide-angle end, 0.02<(1-βF 2 )×βFr 2 <0.2 (13) 20. The projection optical system according to claim 18 or 19, which satisfies conditional expression (13) shown below. [Appendix 21] The paraxial lateral magnification of the focus group is βF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtF, When the projection optical system is a variable magnification optical system, βF, βFr, Ymax, and ΔtF are the values ​​at the wide-angle end, 0.1<((1-βF 2 )×βFr 2 ) / ΔtF<0.5 (14) 21. The projection optical system according to any one of claims 18 to 20, which satisfies conditional expression (14) shown below. [Appendix 22] 22. The projection optical system according to claim 18, wherein the focus group includes two or more positive lenses. [Appendix 23] 23. The projection optical system according to any one of claims 18 to 22, wherein the lens surface of the focus group closest to the enlargement side is an aspheric surface that faces a concave surface toward the enlargement side in the paraxial region and has an inflection point where the concave and convex shape changes midway as it moves from the optical axis to the periphery. [Appendix 24] one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a positive lens, and the other is a negative lens; The distance on the optical axis between the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is defined as dFr12, The maximum image height on the reduction-side imaging surface is defined as Ymax, When the projection optical system is a variable magnification optical system, if Ymax is the value at the wide-angle end, 0≦dFr12 / Ymax<0.1 (15) 24. The projection optical system according to any one of claims 18 to 23, which satisfies conditional expression (15) shown below. [Appendix 25] 25. The projection optical system according to any one of appendix 18 to appendix 24, further comprising a back focus correction group that adjusts the back focus by moving along the optical axis. [Appendix 26] the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed group is defined as dAmax, When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2 <dAmax / Ymax<2.5 (10) 26. The projection optical system according to any one of claims 18 to 25, which satisfies conditional expression (10) shown below. [Appendix 27] the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; 27. The projection optical system according to claim 18, wherein, during magnification change, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them. [Appendix 28] The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) 28. The projection optical system according to claim 27, which satisfies conditional expression (11) shown below. [Appendix 29] A projection display device comprising the projection optical system according to any one of Supplementary Note 18 to Supplementary Note 28. [Appendix 30] A projection optical system including, in order from the enlargement side to the reduction side along an optical path, a first optical system and a second optical system, the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with a reduction-side image-forming surface, and the first optical system re-images the intermediate image on an enlargement-side image-forming surface; a focus group that moves along an optical axis to adjust the focus of the entire image plane when the projection distance changes, and a back focus correction group that moves along the optical axis to adjust the back focus, disposed within the projection optical system; ZFBr is the distance on the optical axis from the lens surface of the first optical system closest to the enlargement side to the lens surface of the lens surfaces included in the focus group and the back focus correction group closest to the reduction side, The focal length of the projection optical system is defined as f, When the projection optical system is a variable magnification optical system, ZFBr and f are the values ​​at the wide-angle end, 5 <ZFBr / |f|<20 (16) A projection optical system that satisfies conditional expression (16) expressed as follows: [Appendix 31] The paraxial lateral magnification of the focus group is βFF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFFr, The paraxial lateral magnification of the back focus correction group is defined as βB, The composite paraxial lateral magnification of all the lenses on the reduction side of the back focus correction group is defined as βBr, In the case where the projection optical system is a variable magnification optical system, when βFF, βFFr, βB, and βBr are values ​​at the wide-angle end, 0.02<(1-βFF 2 )×βFFr 2 <0.2 (17) 0.1<|(1-βB 2 )×βBr 2 |<2 (18) 31. The projection optical system according to claim 30, which satisfies conditional expressions (17) and (18) expressed by the following formula: [Appendix 32] The paraxial lateral magnification of the back focus correction group is defined as βB, The composite paraxial lateral magnification of all the lenses on the reduction side of the back focus correction group is defined as βBr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the back focus correction group moves 0.1×Ymax in the optical axis direction is defined as ΔtB, When the projection optical system is a variable magnification optical system, βB, βBr, Ymax, and ΔtB are the values ​​at the wide-angle end, 0.7<|(1-βB 2 )×βBr 2 | / ΔtB<1.4 (19) 32. The projection optical system according to claim 30 or 31, which satisfies conditional expression (19) shown below. [Appendix 33] The paraxial lateral magnification of the focus group is βFF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFFr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtFF, In the case where the projection optical system is a variable magnification optical system, when βFF, βFFr, Ymax, and ΔtFF are values ​​at the wide-angle end, 0.1<((1-βFF 2 )×βFFr 2 ) / ΔtFF<0.5 (20) 33. The projection optical system according to any one of claims 30 to 32, which satisfies conditional expression (20) shown below. [Appendix 34] 34. The projection optical system according to any one of claims 30 to 33, wherein the focus group and the back focus correction group are movable independently of each other. [Appendix 35] the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed group is defined as dAmax, When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2 <dAmax / Ymax<2.5 (10) 35. The projection optical system according to any one of claims 30 to 34, which satisfies conditional expression (10) shown below. [Appendix 36] the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system is composed of, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; 36. The projection optical system according to claim 30, wherein, during magnification change, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them. [Appendix 37] The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0 <f2B / |f2C|<0.5 (11) 37. The projection optical system according to claim 36, which satisfies conditional expression (11) shown below. [Appendix 38] A projection display device comprising the projection optical system according to any one of Supplementary Note 30 to Supplementary Note 37. [Explanation of symbols]

[0207] 10 Projection optical system 11a to 11c Transmissive display element 12 Dichroic mirror 13 Dichroic mirror 14 Cross dichroic prism 15 light source 16a~16c Condenser Lens 18a~18c Total reflection mirror 21a~21c DMD elements 24a~24c TIR Prism 25 Polarization separation prism 61 Light source 62 Color Wheel 63 Light guide optical system 64 DMD elements 65 TIR Prism 66 Projection optical system 67 screens 100 Projection display device 105 screens 200 Projection display device 205 screens 210 Projection optical system 215 Light source 600 Projection display device B0 On-axis luminous flux B40 luminous flux B50 luminous flux Bmax luminous flux dAmax Maximum air gap dFr12 spacing Dnp Interval ED Maximum Effective Diameter EDL1 Maximum Effective Diameter EDp Maximum Effective Diameter G1 1st optical system G2 2nd optical system G2A 2A lens group G2B 2B lens group G2C 2C lens group G2D 2nd lens group L1a~L2j lenses LN N lens element LP P lens components Lx Lens MI intermediate image PP optical components Px position Scr Screen Sim display surface St aperture stop t0 tangential image plane tB1 Tangential image plane Xa On-axis luminous flux Xb1 ray Xb Off-axis luminous flux Y40 image height Y50 image height Ymax Maximum image height Z optical axis ZFBr distance Zp distance ΔtB change amount

Claims

1. A projection optical system that projects an image on a reduction-side image-forming surface onto an enlargement-side image-forming surface, The half angle of view on the magnification side is 50 degrees or more, When one lens component is one single lens or one cemented lens, the projection optical system includes a P lens component which is the lens component on the most enlargement side and has positive power, and an N lens component which is a lens component with negative power and is disposed adjacent to the enlargement side of the P lens component, The maximum image height on the reduction-side imaging surface is defined as Ymax, Zp is the distance on the optical axis from the surface of the optical element having the most magnification power in the projection optical system to the most magnification lens surface of the P lens component, The radius of curvature of the lens surface of the P lens component closest to the enlargement side is Rpf, The radius of curvature of the lens surface of the N lens component closest to the reduction side is Rnr, The back focus on the reduction side of the projection optical system in terms of air equivalent distance is Bf, The image height of a light ray having a half angle of view of 40 degrees on the enlargement side on the reduction side image forming plane is defined as Y40, The image height of a light ray having a half angle of view of 50 degrees on the enlargement side on the reduction side image forming plane is defined as Y50, When the projection optical system is a variable magnification optical system, when Ymax, Zp, Bf, Y40, and Y50 are values ​​at the wide-angle end, 1<Zp / Ymax<4 (1) 0.2<Rpf / Ymax<2.3 (2) 0.2<Rnr / Ymax<5 (3) 2<Bf / Ymax<8 (4) 1.35<Y50 / Y40<1.5 (5) A projection optical system that satisfies conditional expressions (1), (2), (3), (4), and (5) expressed as follows:

2. The optical system comprises, in order from the magnification side to the reduction side along the optical path, a first optical system and a second optical system, 2. The projection optical system of claim 1, wherein the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with the reduction-side image forming surface, and the first optical system re-images the intermediate image onto the enlargement-side image forming surface.

3. The distance on the optical axis between the N lens component and the P lens component is Dnp, When the projection optical system is a variable magnification optical system, if Dnp is the value at the wide-angle end, 0<Dnp / Ymax<0.1 (6) 2. The projection optical system according to claim 1, which satisfies conditional expression (6) expressed as follows:

4. When the radius of curvature of the lens surface on the most reduction side of the P lens component is Rpr, 0<(Rpr+Rpf) / (Rpr-Rpf)<2 (7) 2. The projection optical system according to claim 1, which satisfies conditional expression (7) expressed as follows:

5. When the larger of the maximum effective diameter of the lens surface of the P lens component on the most enlargement side and the maximum effective diameter of the lens surface of the P lens component on the most reduction side is defined as EDp, 0.5<EDp / Ymax<2.5 (8) 2. The projection optical system according to claim 1, which satisfies conditional expression (8) expressed as follows:

6. When the radius of curvature of the lens surface on the most enlargement side of the N lens component is Rnf, -1<(Rnr+Rnf) / (Rnr-Rnf)<0.5 (9) 2. The projection optical system according to claim 1, which satisfies conditional expression (9) expressed as follows:

7. the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed lens unit is defined as dAmax; When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2<dAmax / Ymax<2.5 (10) 3. The projection optical system according to claim 2, which satisfies conditional expression (10) expressed as follows:

8. the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system comprises, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; 3. The projection optical system according to claim 2, wherein, during magnification variation, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them.

9. The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0<f2B / |f2C|<0.5 (11) 9. The projection optical system according to claim 8, which satisfies conditional expression (11) expressed as follows:

10. EDL1 is the larger of the maximum effective diameter of the enlargement-side surface of the most enlargement-side lens in the projection optical system and the maximum effective diameter of the reduction-side surface of the most enlargement-side lens in the projection optical system, If the specific gravity of the lens on the most enlargement side of the projection optical system is ρL1, then 0.5<EDL1×ρL1 / Ymax<10 (12) 2. The projection optical system according to claim 1, which satisfies conditional expression (12) expressed as follows:

11. the P lens component is a single lens, 2. The projection optical system according to claim 1, wherein the refractive index of the P lens component with respect to the d-line is 1.65 or more.

12. The N lens components are single lenses, 12. The projection optical system according to claim 11, wherein the refractive index of the N lens component with respect to the d-line is 1.65 or less.

13. The projection optical system according to claim 2 , wherein the first optical system includes an aspherical lens.

14. The projection optical system according to claim 13, wherein the first optical system includes two aspherical lenses.

15. 14. The projection optical system according to claim 13, wherein the lens surface of the first optical system closest to the enlargement side is an aspherical surface that faces a concave surface toward the enlargement side in the paraxial region and has an inflection point where the concave and convex shape changes midway as one moves from the optical axis to the periphery.

16. 3. The projection optical system according to claim 2, wherein the reduction side is telecentric.

17. A projection display device comprising the projection optical system according to any one of claims 1 to 16.

18. a projection optical system including, in order from the enlargement side to the reduction side along an optical path, a first optical system and a second optical system, the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with a reduction-side image-forming surface, and the first optical system re-images the intermediate image on an enlargement-side image-forming surface; a focus group including six or more lenses is disposed on the most enlarged side of the projection optical system, and the focus group moves along the optical axis to adjust the focus of the entire image plane when the projection distance changes; The projection optical system in which the distances between all lenses in the focus group remain unchanged during the focus adjustment.

19. The projection optical system according to claim 18 , wherein the focus group is disposed within the first optical system.

20. The paraxial lateral magnification of the focus group is βF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFr, When the projection optical system is a variable magnification optical system, βF and βFr are values ​​at the wide-angle end, 0.02<(1-βF) ２ )×βFr ２ <0.2 (13) 19. The projection optical system according to claim 18, which satisfies conditional expression (13) expressed as follows:

21. The paraxial lateral magnification of the focus group is βF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is defined as βFr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtF, In the case where the projection optical system is a variable magnification optical system, when βF, βFr, Ymax, and ΔtF are values ​​at the wide-angle end, 0.1<((1-βF ２ )×βFr ２ ) / ΔtF<0.5 (14) 19. The projection optical system according to claim 18, which satisfies conditional expression (14) expressed as follows:

22. 19. The projection optical system according to claim 18, wherein the focus group includes two or more positive lenses.

23. The projection optical system of claim 18, wherein the lens surface closest to the magnification side of the focus group is an aspherical surface that faces the magnification side in the paraxial region and has an inflection point where the concave and convex shapes change midway as one moves from the optical axis to the periphery.

24. one of the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is a positive lens, and the other is a negative lens; The distance on the optical axis between the first lens from the reduction side of the focus group and the second lens from the reduction side of the focus group is dFr12, The maximum image height on the reduction-side imaging surface is defined as Ymax, When the projection optical system is a variable magnification optical system, if Ymax is the value at the wide-angle end, 0≦dFr12 / Ymax<0.1 (15) 19. The projection optical system according to claim 18, which satisfies conditional expression (15) expressed as follows:

25. 19. The projection optical system according to claim 18, further comprising a back focus correction group that adjusts the back focus by moving along the optical axis.

26. the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed lens unit is defined as dAmax; When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2<dAmax / Ymax<2.5 (10) 19. The projection optical system according to claim 18, which satisfies conditional expression (10) expressed as follows:

27. the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system comprises, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; 19. The projection optical system according to claim 18, wherein, during magnification variation, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them.

28. The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0<f2B / |f2C|<0.5 (11) 28. The projection optical system according to claim 27, which satisfies conditional expression (11) expressed as follows:

29. A projection display device comprising the projection optical system according to any one of claims 18 to 28.

30. a projection optical system including, in order from the enlargement side to the reduction side along an optical path, a first optical system and a second optical system, the second optical system forms an intermediate image between the first optical system and the second optical system at a position conjugate with a reduction-side image-forming surface, and the first optical system re-images the intermediate image on an enlargement-side image-forming surface; a focus group that moves along an optical axis to adjust the focus of the entire image plane when the projection distance changes, and a back focus correction group that moves along the optical axis to adjust the back focus, disposed within the projection optical system; ZFBr is the distance on the optical axis from the lens surface of the first optical system on the most enlargement side to the lens surface of the lens surfaces included in the focus group and the back focus correction group on the most reduction side, The focal length of the projection optical system is defined as f, When the projection optical system is a variable magnification optical system, ZFBr and f are the values ​​at the wide-angle end, 5<ZFBr / |f|<20 (16) A projection optical system that satisfies conditional expression (16) expressed as follows:

31. The paraxial lateral magnification of the focus group is βFF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is βFFr, The paraxial lateral magnification of the back focus correction group is defined as βB, The composite paraxial lateral magnification of all the lenses on the reduction side of the back focus correction group is defined as βBr, In the case where the projection optical system is a variable magnification optical system, when βFF, βFFr, βB, and βBr are values ​​at the wide-angle end, 0.02<(1-βFF ２ )×βFFr ２ <0.2 (17) 0.1<|(1-βB ２ )×βBr ２ |<2 (18) 31. The projection optical system according to claim 30, which satisfies conditional expressions (17) and (18) expressed as follows:

32. The paraxial lateral magnification of the back focus correction group is defined as βB, The composite paraxial lateral magnification of all the lenses on the reduction side of the back focus correction group is defined as βBr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the back focus correction group moves 0.1×Ymax in the optical axis direction is defined as ΔtB, When the projection optical system is a variable magnification optical system, βB, βBr, Ymax, and ΔtB are the values ​​at the wide-angle end, 0.7<|(1-βB ２ )×βBr ２ | / ΔtB<1.4 (19) 31. The projection optical system according to claim 30, which satisfies conditional expression (19) expressed as follows:

33. The paraxial lateral magnification of the focus group is βFF, The composite paraxial lateral magnification of all the lenses on the reduction side of the focus group is βFFr, The maximum image height on the reduction-side imaging surface is defined as Ymax, The amount of change in the optical axis direction of the tangential image plane at a half angle of view of 50 degrees when the focus group moves 0.1×Ymax in the optical axis direction is defined as ΔtFF, In the case where the projection optical system is a variable magnification optical system, when βFF, βFFr, Ymax, and ΔtFF are values ​​at the wide-angle end, 0.1<((1-βFF ２ )×βFFr ２ ) / ΔtFF<0.5 (20) 31. The projection optical system according to claim 30, which satisfies conditional expression (20) expressed as follows:

34. 31. The projection optical system according to claim 30, wherein the focus group and the back focus correction group are movable independently of each other.

35. the projection optical system is a zoom lens including a moving lens group that moves during magnification change within the second optical system, a group consisting of all lenses on the enlargement side of the movable lens group that is the most enlargement side among the movable lens groups included in the projection optical system is defined as an enlargement-side fixed group; the longest air gap between lens surfaces on the optical axis in the magnification-side fixed lens unit is defined as dAmax; When the projection optical system is a variable magnification optical system, dAmax is the value at the wide-angle end, 0.2<dAmax / Ymax<2.5 (10) 31. The projection optical system according to claim 30, which satisfies conditional expression (10) expressed as follows:

36. the projection optical system is a zoom lens, In the second optical system, when the group whose distance in the optical axis direction from the adjacent group changes during magnification is one lens group, the second optical system comprises, in order from the enlargement side to the reduction side along the optical path, a second-A lens group, a second-B lens group, a second-C lens group, and a second-D lens group; 31. The projection optical system according to claim 30, wherein, during magnification variation, the second-A lens group and the second-D lens group are fixed relative to the reduction-side image plane, and the second-B lens group and the second-C lens group move while changing the distance between them.

37. The focal length of the second lens group B is f2B, When the focal length of the second C lens group is f2C, 0<f2B / |f2C|<0.5 (11) 37. The projection optical system according to claim 36, which satisfies conditional expression (11) expressed as follows:

38. A projection display device comprising the projection optical system according to any one of claims 30 to 37.

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