Projection optical system

Abstract

The 1-2nd lens group is divided into three lens groups which move when focusing is performed during the magnification change. Even in a case in which the second optical group is formed of one mirror, it is possible for a primary image to contain appropriate aberration and to hereby reduce aberration of an image which is finally projected onto a screen through the second optical group.

Claims

1. A projection optical system comprising: in order from a reduction side, a first optical group which is formed of a plurality of lenses and has positive power; and a second optical group which has one reflective surface having a concave aspheric shape, wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, and wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of only two lenses, and F3 lens group formed of one negative lens.

2. The projection optical system according to claim 1, wherein the F3 lens group of the three lens groups configuring the 1-2nd lens group includes one aspheric lens formed of a resin.

3. The projection optical system according to claim 1, wherein the F2 lens group of the three lens groups configuring the 1-2nd lens group includes a biconvex lens and a biconcave lens in this order from the reduction side.

4. The projection optical system according to claim 3, wherein the biconvex lens and the biconcave lens of the F2 lens group form a cemented lens.

5. The projection optical system according to claim 1, wherein, in the 1-2nd lens group, the F1 lens group is configured of at least two positive lenses, the F2 lens group is configured of two lenses of a biconvex lens and a biconcave lens in this order from the reduction side, and the F3 lens group is configured of a resin lens having negative power and having both surfaces being aspheric surfaces.

6. The projection optical system according to claim 1, wherein the 1-1st lens group has an aperture therein, a positive lens, and at least a negative lens disposed on the enlargement side from the aperture in this order from the reduction side, of which the negative lens has at least one surface being an aspheric shape.

7. The projection optical system according to claim 1, wherein the 1-1st lens group includes an aperture therein, at least two sets of cemented lenses of positive lenses and negative lenses disposed on the reduction side from the aperture, and a negative lens having at least one surface being an aspheric shape.

8. The projection optical system according to claim 7, wherein the negative lens is disposed on the reduction side from the aperture disposed in the 1-1st lens group, is a negative meniscus lens and has at least an aspheric surface on a concave surface side.

9. The projection optical system according to claim 1, wherein a numerical aperture on an object side is equal to or more than 0.3.

10. The projection optical system according to claim 1, wherein the reduction side is substantially telecentric.

11. The projection optical system according to claim 1, wherein elements configuring the first optical group and the second optical group all have a rotationally symmetric system.

12. The projection optical system according to claim 1, wherein a range of magnification change is equal to or greater than 1.5 times.

13. The projection optical system according to claim 1, wherein the first optical group forms an intermediate image before the one reflective surface of the second optical group.

14. A projection optical system comprising: in order from a reduction side, a first optical group which is formed of a plurality of lenses and has positive power; and a second optical group which has one reflective surface having a concave aspheric shape, wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, wherein the 1-1st lens group has an aperture therein, a positive lens, and at least a negative lens disposed on the enlargement side from the aperture in this order from the reduction side, of which the negative lens has at least one surface being an aspheric shape, and wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of two lenses, and F3 lens group formed of one negative lens.

15. A projection optical system comprising: in order from a reduction side, a first optical group which is formed of a plurality of lenses and has positive power; and a second optical group which has one reflective surface having a concave aspheric shape, wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, wherein the 1-1st lens group includes an aperture therein, at least two sets of cemented lenses of positive lenses and negative lenses disposed on the reduction side from the aperture, and a negative lens having at least one surface being an aspheric shape, and wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of two lenses, and F3 lens group formed of one negative lens.

16. The projection optical system according to claim 15, wherein the negative lens is disposed on the reduction side from the aperture disposed in the 1-1st lens group, is a negative meniscus lens and has at least an aspheric surface on a concave surface side.

17. A projection optical system comprising: in order from a reduction side, a first optical group which is formed of a plurality of lenses and has positive power; and a second optical group which has one reflective surface having a concave aspheric shape, wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of two lenses, and F3 lens group formed of one negative lens, and wherein a numerical aperture on an object side is equal to or more than 0.3.

18. A projection optical system comprising: in order from a reduction side, a first optical group which is formed of a plurality of lenses and has positive power; and a second optical group which has one reflective surface having a concave aspheric shape, wherein the first optical group is formed to include a 1-1st lens group which is fixed when focusing is performed during the magnification change and has positive power, and a 1-2nd lens group which moves when focusing is performed during the magnification change, is formed of a plurality of lenses, and has positive power as a whole, wherein the 1-2nd lens group is a lens group which individually moves when focusing is performed during the magnification change, and includes three lens groups of a positive F1 lens group formed of at least two lenses, F2 lens group formed of two lenses, and F3 lens group formed of one negative lens, and wherein the reduction side is substantially telecentric.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

(2) FIG. 1 is a diagram showing a schematic configuration of a projector in which a projection optical system of an embodiment is incorporated.

(3) FIG. 2 is a diagram showing light fluxes and a configuration from an object surface to a projection surface in the projection optical system of the embodiment or Example 1.

(4) FIG. 3 is an enlarged diagram showing a part from the object surface to a concave reflective mirror in FIG. 2.

(5) FIG. 4 is a diagram showing a configuration of the projection optical system of Example 1.

(6) FIGS. 5A to 5C are diagrams showing aberration on a reduction side of the projection optical system of Example 1.

(7) FIGS. 6A to 6E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5A.

(8) FIGS. 7A to 7E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5B.

(9) FIGS. 8A to 8E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5C.

(10) FIG. 9 is a diagram showing a configuration of a projection optical system of Example 2.

(11) FIGS. 10A to 10C are diagrams showing aberration on a reduction side of the projection optical system of Example 2.

(12) FIGS. 11A to 11E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10A.

(13) FIGS. 12A to 12E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10B.

(14) FIGS. 13A to 13E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10C.

(15) FIG. 14 is a diagram showing a configuration of a projection optical system of Example 3.

(16) FIGS. 15A to 15C are diagrams showing aberration on a reduction side of the projection optical system of Example 3.

(17) FIGS. 16A to 16E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15A.

(18) FIGS. 17A to 17E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15B.

(19) FIGS. 18A to 18E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15C.

(20) FIG. 19 is a diagram showing a configuration of a projection optical system of Example 4.

(21) FIGS. 20A to 20C are diagrams showing aberration on a reduction side of the projection optical system of Example 4.

(22) FIGS. 21A to 21E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20A.

(23) FIGS. 22A to 22E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20B.

(24) FIGS. 23A to 23E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20C.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(25) Hereinafter, a projection optical system according to an embodiment of the invention will be described in detail with reference to the drawings.

(26) As illustrated in FIG. 1, a projector 2, in which the projection optical system according to an embodiment of the invention is incorporated, includes an optical system section 50 which projects an image light flux, and a circuit device 80 which controls an operation of the optical system section 50.

(27) In the optical system section 50, a light flux source 10 is, for example, an extra-high pressure mercury lamp, and emits light fluxes including an R light flux, a G light flux, and a B light flux. The light flux source 10 may be a discharge light flux source, in addition to an extra-high pressure mercury lamp, or may be a solid-state light flux source, such as an LED or a laser. A first integrator lens 11 and a second integrator lens 12 have a plurality of lens elements arranged in an array. The first integrator lens 11 divides a light flux from the light flux source 10 into a plurality of light fluxes. Each lens element of the first integrator lens 11 condenses the light flux from the light flux source 10 in the vicinity of the lens elements of the second integrator lens 12. The lens elements of the second integrator lens 12 form images of the lens elements of the first integrator lens 11 on the liquid crystal panels 18R, 18G, and 18B in cooperation with a superimposing lens 14. In this configuration, the entire display regions of the liquid crystal panels 18R, 18G, and 18B are illuminated with a light flux from the light flux source 10, in substantially uniform brightness.

(28) A polarization conversion element 13 converts a light flux from the second integrator lens 12 to a predetermined linearly polarized light flux. The superimposing lens 14 superimposes the image of each lens element of the first integrator lens 11 on the display regions of the liquid crystal panels 18R, 18G, and 18B through the second integrator lens 12.

(29) A first dichroic mirror 15 reflects the R light flux incident from the superimposing lens 14 and transmits the G light flux and the B light flux. The R light flux reflected from the first dichroic mirror 15 is incident to the liquid crystal panel 18R serving as an optical modulator through a reflective mirror 16 and a field lens 17R. The liquid crystal panel 18R modulates the R light flux in response to an image signal so as to form an R-color image.

(30) A second dichroic mirror 21 reflects the G light flux from the first dichroic mirror 15 and transmits the B light flux. The G light flux reflected from the second dichroic mirror 21 is incident to the liquid crystal panel 18G serving as an optical modulator through a field lens 17G. The liquid crystal panel 18G modulates the G light flux in response to an image signal to form a G-color image. The B light flux transmitted through the second dichroic mirror 21 is incident to the liquid crystal panel 18B serving as an optical modulator through relay lenses 22 and 24, reflective mirrors 23 and 25, and a field lens 17B. The liquid crystal panel 18B modulates the B light flux in response to an image signal to form a B-color image.

(31) A cross dichroic prism 19 is a prism for light flux composition, combines light fluxes modulated by the liquid crystal panels 18R, 18G, and 18B to form an image light flux, and causes the image light flux to travel to a projection optical system 40.

(32) The projection optical system 40 is a zoom lens for projection, which projects an image light modulated by the liquid crystal panels 18G, 18R, and 18B and combined by the cross dichroic prism 19 onto a screen (not shown) on an enlarged scale.

(33) The circuit device 80 includes an image processing unit 81 to which an external image signal, such as a video signal, is input, a display driving unit 82 which drives the liquid crystal panels 18G, 18R, and 18B provided in the optical system section 50 on the basis of an output of the image processing unit 81, a lens driving unit 83 which operates a driving mechanism (not shown) provided in the projection optical system 40 to adjust a state of the projection optical system 40, and a central control unit 88 which performs overall control of the operations of the circuit portions 81, 82, and 83, and the like.

(34) The image processing unit 81 converts the input external image signal to an image signal including the tone of each color or the like. The image processing unit 81 may perform various image processes, such as distortion correction or color correction, on the external image signal.

(35) The display driving unit 82 can operate the liquid crystal panels 18G, 18R, and 18B on the basis of an image signal output from the image processing unit 81, and can form an image corresponding to the image signal or an image corresponding to an image signal subjected to the image process, on the liquid crystal panels 18G, 18R, and 18B.

(36) The lens driving unit 83 operates under the control of the central control unit 88, and appropriately moves some optical components configuring the projection optical system 40 along an optical axis OA through an actuator AC, thereby it is possible to perform focusing during magnification change in projection of an image on a screen by the projection optical system 40. Further, the lens driving unit 83 can change a vertical position of the image projected on the screen, through adjustment of a tilt at which the entire projection optical system 40 moves vertically perpendicular to the optical axis OA.

(37) Hereinafter, the projection optical system 40 of the embodiment will be specifically described with reference to FIG. 2 and FIG. 3. The projection optical system 40 illustrated in FIG. 2 or the like has the same configuration as the projection optical system 40 of Example 1 to be described below.

(38) The projection optical system 40 of the embodiment projects an image formed on a projection-performed surface of the liquid crystal panel 18G (18R or 18B), onto a screen (not shown). A prism PR corresponding to the cross dichroic prism 19 in FIG. 1 is disposed between the plane of projection optical system 40 and the liquid crystal panel 18G (18R or 18B).

(39) The projection optical system 40 includes a first optical group 40a which is formed of a plurality of lenses and has positive power and a second optical group 40b which is configured of one mirror MR with a reflective surface having a concave aspheric shape. The first optical group 40a is fixed when focusing is performed during the magnification change, and is formed to have a 1-1st lens group 41 having positive power and a 1-2nd lens group 42 which moves when focusing is performed during the magnification change, is formed of a plurality of lens groups, and has positive power as a whole.

(40) The 1-1st lens group 41 has an aperture ST inside thereof and is formed to have a lens group E1 on a reduction side from the aperture ST and a lens group E2 on an enlargement side from the aperture ST.

(41) The 1-2nd lens group 42 has, in order from the reduction side, three lens groups of a positive F1 lens group (hereinafter, lens group F1), which is formed of at least two (in an example in FIG. 3, three) lenses, an F2 lens group (hereinafter, lens group F2) which is formed of two lenses, and an F3 lens group (hereinafter, lens group F3) which is formed of one negative lens. The lens groups F1 to F3 are caused to individually move, for each lens group by the actuator AC, in a direction A1 along the optical axis OA when focusing is performed during magnification change. Further, the actuator AC can cause the lens groups F1 to F3 to move in various modes by performing of the focusing during magnification change and, for example, the groups moving individually may be linked to each other using a cam mechanism or the like.

(42) Hereinafter, the lenses configuring each lens group will be described in order from the reduction side. Of the first optical group 40a, the lens group E1 of the 1-1st lens group 41 has seven lenses L1 to L7 and the lens group E2 thereof has two lenses L8 and L9. The lens group F1 of the 1-2nd lens group 42 has three lenses L10 to L12, the lens group F2 thereof has two lenses L13 and L14, and the lens group F3 thereof has one lens L15. In other words, the first optical group 40a is configured to have 15 lenses L1 to L15 as a whole.

(43) Of the lenses L1 to L7 configuring the lens group E1, the lens L2 as a positive lens and the lens L3 as a negative lens form a cemented lens, and the lens L4 and the lens L5 form a cemented lens. Further, the lens L6 is a negative aspheric glass lens. In other words, the 1-1st lens group 41 has at least two sets of cemented lenses of the positive lenses and the negative lenses on the reduction side from the aperture ST and has a negative lens having at least one surface with aspheric shape formed. Particularly, the lens L6 as the negative lens, on which the aspheric shape is formed, is a negative meniscus lens and has the aspheric surface on at least a concave side. Further, of the lenses configuring the lens group E1, the lenses other than the lens L6 are spherical glass lenses. In addition, the lenses L1 to L7 have a circular shape which is symmetric about the optical axis OA.

(44) For the two lenses L8 and L9 configuring the lens group E2, the lenses L8 is the positive lens and the lens L9 is the negative lens. Particularly, the lens L9 is a negative aspheric glass lens. In other words, the 1-1st lens group 41 has one positive lens and at least one negative lens, in order from the reduction side on the enlargement side from the aperture ST and aspheric shape is formed on one surface of the at least corresponding lens. Further, lens L8 is a spherical glass lens. In addition, the lenses L8 and L9 have a circular shape which is symmetric about the optical axis OA.

(45) Of the lenses L10 to L12 configuring the lens group F1, lens L10 is a positive biconvex lens. In addition, the lens L11 and the lens L12 form a cemented lens, and the cemented lens functions as a positive lens as a whole. In other words, it is also possible to consider that the lens group F1 is configured to have two positive lenses. Further, the lenses L10 to L12 are spherical glass lenses and have a circular shape which is symmetric about the optical axis OA.

(46) Of the lenses L13 and L14 configuring the lens group F2, the lens L13 is a biconvex lens (positive lens), and the lens L14 is a biconcave lens (negative lens). In addition, the lens L13 and the lens L14 form a cemented lens. Further, the lenses L13 and L14 are spherical glass lenses and have a circular shape which is symmetric about the optical axis OA.

(47) One lens L15 configuring the lens group F3 disposed on the farthest enlargement side of the lens groups is a lens (aspheric lens) having negative power with both surfaces subjected to a aspheric surface process and a lens (resin lens) formed of a resin. Further, the lens L15 does not have a circular shape but has a shape in which a part on the upper side (side onto which an image light is projected) is notched from a state of a circle which is symmetric about the optical axis OA.

(48) The second optical group 40b is configured of one mirror MR having a concave aspheric shape and the mirror MR reflects the image light emitted from the first optical group 40a, and thereby projects the image light to a screen.

(49) Further, in the projection optical system 40, all of the lenses L1 to L15 configuring the first optical group 40a have a circular shape which is symmetric about the optical axis OA or a shape with a notched part and the mirror MR configuring the second optical group 40b also has a partially notched shape from a circular shape which is symmetric about the optical axis OA. In other words, elements configuring the first optical group 40a and the second optical group 40b all belong to a rotationally symmetric system. In addition, as shown in FIG. 1, the reduction side in the projection optical system 40 is substantially telecentric. For example, as described above, in a case where light fluxes modulated by the respective liquid crystal panels 18R, 18G, and 18B in the cross dichroic prism 19 are combined into an image light, it is possible to hereby easily absorb variations due to assembly.

(50) Such a short throw projection optical system above has an abnormally short distance to a screen. In the projection optical system 40 described above, an object positioned on a panel surface PI of the liquid crystal panel 18G (18R or 18B), that is, an image on a panel, in the first optical group 40a, is temporarily formed as an image in front of a mirror of the second optical group 40b, is again formed as an image on a screen by one mirror MR configuring the second optical group 40b, and thereby short throw projection is performed in the first optical group 40a. In other words, in this case, the first optical group 40a plays a role of forming a primary image (intermediate image) in front of the mirror MR. In the projection as described above, aberration fluctuation due to focusing during magnification change is greater than a case of general projection, and thus it is common not to have a significantly large range of magnification change. Accordingly, the primary image formed by the first optical group 40a needs to be compatible even in a case where, when an angle of view is abnormally wide and thus projection magnification is changed, the aberration fluctuation is likely to increase. In addition, in the short throw projection optical system, it is easy to increase contrast reduction due to field curvature and astigmatism fluctuation which directly influence on image performance, and distortion due to movement of a focus group is highly likely to be also increased more than in a normal lens system.

(51) In comparison, it is possible to perform effective correction so as to suppress the aberration fluctuation to be small by changing a gap between the lens group including aspheric lens disposed on the first optical group 40a and a aspheric mirror of the second optical group 40b. Since such correction can be performed, in the present embodiment, as described above, the lenses in the 1-2nd lens group 42 are divided into a plurality of three lens groups F1 to F3 and perform movement when focusing is performed during the magnification change. Even in a case where the second optical group 40b is configured of one mirror MR, it is possible to hereby achieve a good image having small aberration, compared to an image of which the primary image has moderate aberration, and which is finally projected on the screen through the second optical group 40b. In other words, in the projector 2 as a proximity type projector, a wide range of magnification change is covered and it is possible to be also applied to an image display element having high resolution.

(52) In the first optical group 40a, when one aspheric lens is included in the lenses configuring the 1-2nd lens group 42 as a focusing group disposed on the enlargement side, there is a concern that a sufficient range of magnification change will not be secured by a design. When two aspheric lenses are included in the 1-2nd lens group 42, it is possible to widen the range of the magnification change; however, in this case, in order to sufficiently widen the range of the magnification change, the shape of each aspheric lens is highly likely to have a highly aspheric shape as a significantly different surface shape from the spherical shape, surface sensitivity or refractive index sensitivity becomes high, further eccentricity sensitivity between surfaces also becomes high, and there is a high possibility that variation in the final lens performance is likely to be increased.

(53) In comparison, in the present embodiment, instead of that one aspheric lens (lens L15) is included in the 1-2nd lens group 42 as the focusing group, a aspheric glass surface (lens L9) is effectively disposed on the enlargement side from the aperture ST in the 1-1st lens group 41, and thereby it is possible to suppress an enhancement in sensitivity by having one aspheric resin lens disposed in the 1-2nd lens group 42 and it is possible to reduce the aberration fluctuation even in a wide range of the magnification change.

(54) In addition, for the aspheric lens (lens L15) of the 1-2nd lens group 42, in order to prevent interference with a light flux reflected from the mirror of the second optical group 40b, not only there is a need to have an atypical shape such as a partially notched circular shape, but also, a aspheric resin-molded surface is normally used because the diameter is relatively increased such that, in the present embodiment, the lens L15 is also a aspheric resin lens having an atypical shape. However, the aspheric resin-molded surface also has lower accuracy than the aspheric glass-molded surface, and thus there is a need to sufficiently reduce sensitivity at the time of the design because the system is likely to be influenced by variations due to surface accuracy or refractive index as described above. Therefore, in the present embodiment, in the F2 lens group disposed on the reduction side (upstream side on an optical path) of the lens L15 (F3 lens group) as a aspheric lens of the 1-2nd lens group 42, a biconvex lens and a biconcave lens are disposed from the reduction side, a convex surface faces the reduction side of the F2 lens group, a concave surface faces the enlargement side, and thereby a light flux incident to the lenses L15 is adjusted to have an appropriate angle and the sensitivity in the lens L15 is suppressed to be reduced.

(55) Further, in the 1-1st lens group 41, if a configuration on the reduction side from the aperture ST has only the spherical lenses, it is considered that it is possible to be applied only to brightness having the F-number of about 1.8, when applied to a wide range of the magnification change. In comparison, in the present embodiment, the aspheric glass surface (lens L6) is appropriately disposed on the reduction side from the aperture ST, and thereby it is possible to achieve an image having less flare and high contrast even at the F-number of about 1.6. Even when the number of (in the present embodiment, 15) lenses is substantially the same as an example in the related art, the numerical aperture on the object side is equal to or more than 0.3, that is, with brightness having the F-number of about 1.6, a range of magnification change of high magnification of 1.5 (further, equal to or more than 1.6) is secured, and performance of sufficient application to the image display element having high resolution is achieved.

EXAMPLE

(56) Hereinafter, a specific example of the projection optical system 40 will be described. Meanings of specifications common in Examples 1 to 4 in the following description are defined as follows.

(57) f Focal Length of Entire system

(58) ω Half Angle of View

(59) Na Numerical Aperture

(60) R Curvature Radius

(61) D Surface Interval in Optical Axis (Lens Thickness in Optical Axis Or Lens Interval in Optical Axis)

(62) Nd Refractive Index of d line

(63) Vd Abbe Number of d line

(64) The aspheric surface is defined by the following polynomial equation (aspheric surface equation).

(65) $z=\frac{{\mathrm{ch}}^2}{1+\sqrt{1-\left(k+1\right)c^2{h}^2}}+A_4{h}^4+A_6{h}^6+A_8{h}^8+A_{10}{h}^{10}+A_{12}{h}^{12}+A_{14}{h}^{14}$
Here,

(66) c: Curvature (1/R)

(67) h: Height From Optical Axis

(68) k: Coefficient Of Conic Of Aspheric Surface

(69) Ai: Coefficient Of Aspheric Surface In High Order Equation

Example 1

(70) Data of lens surfaces of Example 1 is shown in Table 1. Further, OBJ means the panel surface PI and STO means the aperture ST. In addition, a surface having “*” after a surface reference number means a surface having aspheric shape.

(71) TABLE-US-00001 TABLE 1 f 3.753 ω 72.7 NA 0.313 R D Nd Vd OBJ Infinity 9.500 1 Infinity 25.970  1.51633 64.14 2 Infinity 0.000 3 29.749 9.200 1.61800 63.33 4 −90.854  0.200 5 31.147 8.000 1.49700 81.54 6 −46.319  1.200 1.80518 25.42 7 115.301  0.200 8 21.01  10.500  1.48749 70.24 9 −18.367  1.200 1.90366 31.31 10 40.142 0.400 *11 22.722 1.400 1.58913 61.15 *12 14.117 0.300 13 19.166 4.000 1.48749 70.24 14 223.258  0.671 STO Infinity 3.142 16 26.258 4.600 1.84666 23.78 17 −52.237  2.067 *18 −101.023  1.800 1.74320 49.29 *19 20.505 variable interval 20 198.906  4.200 1.64769 33.79 21 −105.554  0.200 22 82.236 10.800  1.62004 36.26 23 −32.21  2.000 1.80518 25.42 24 −127.875  variable interval 25 47.079 11.500  1.58144 40.75 26 −83.369  2.000 1.80518 25.42 27 83.369 variable interval *28 −146.264  2.800 1.53116 56.04 *29 35.005 variable interval *30 −54.303  variable reflective interval surface 31 Infinity

(72) In Table 1 and the following Tables, an exponent of 10 (for example, 1.00×10+18) is described using E (for example, 1.00E+18).

(73) Table 2 shows a aspheric surface coefficient of a lens surface of Example 1.

(74) TABLE-US-00002 TABLE 2 Aspheric Surface Coefficient K A04 A06 A08 A10 A12 A14 11 −1.4162 −3.1275E−04 2.1480E−06 −4.7918E−09 0.0000E+00 0.0000E+00 0.0000E+00 12 −1.9911 −2.5613E−04 2.3305E−06 −9.6210E−09 1.5979E−11 0.0000E+00 0.0000E+00 18 −1.0000 −8.9299E−05 0.0000E+00   0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 19 0.6743 −7.5262E−05 1.0469E−07 −5.4544E−10 0.0000E+00 0.0000E+00 0.0000E+00 28 −104.8836 −1.3716E−05 2.6918E−08 −3.8636E−11 2.1555E−14 −6.2068E−18  0.0000E+00 29 0.0000 −3.3687E−05 4.9222E−08 −7.9903E−11 7.8149E−14 −4.7186E−17  1.2130E−20 30 −0.9865   5.6413E−08 3.8062E−11 −5.3064E−14 1.7923E−17 −3.1309E−21  2.1598E−25

(75) Table 3 shows values of variable intervals 19, 24, 27, 29, and 30 in Table 2 at the projection magnification of 125 times, the projection magnification of 100 times, and the projection magnification of 169 times.

(76) TABLE-US-00003 TABLE 3 Variable Interval 125× 100× 169× 19 13.506 13.945 13.203 24 6.445 4.000 8.916 27 16.200 17.836 14.500 29 110.000 110.369 109.532 30 −501.000 −409.990 −666.138

(77) FIG. 4 is a sectional diagram showing the projection optical system of Example 1. The projection optical system in FIG. 4 corresponds to the projection optical system 40 of Embodiment 1. Further, the lens L15 or the mirror MR having a partially notched shape from a circle in FIG. 3 or the like is depicted intact without a notch in FIG. 4. In FIG. 4, the projection optical system performs enlargement projection of an image on the panel surface PI to the screen at a magnification depending on a distance. In other words, the projection optical system has 15 lenses L1 to L15 of the lenses L1 to L7 configuring the lens group E1 of the 1-1st lens group 41, the lenses L8 and L9 configuring the lens group E2 thereof, the lenses L10 to L12 configuring the lens group F1 of 1-2nd lens group 42, the lenses L13 and L14 configuring the lens group F2 thereof, and the lens L15 configuring the lens group F3 thereof, in this order from the reduction side. For example, as in a case where projection onto a wall surface is changed to projection onto a floor surface, the magnification change occurs due to the change of a projection position (change of projection distance), and the 1-1st lens group 41 is fixed as is when focusing is performed during the magnification change, whereas the lens groups F1 to F3 configuring the 1-2nd lens group 42 individually move.

(78) Further, the respective lenses L1 to L15 will be described in detail. In the 1-1st lens group 41, the lens L1 as a first lens is a positive lens, the lens L2 as a second lens is a positive lens, the lens L3 as a third lens is a negative lens, the lens L2 and the lens L3 form a cemented lens, the lens L4 as a fourth lens is a positive lens, the lens L5 as a fifth lens is a negative lens, the lens L4 and the lens L5 form a cemented lens, the lens L6 as a sixth lens is a negative meniscus lens having both surfaces subjected to a aspheric surface process, the lens L7 as a seventh lens is a positive lens with a convex surface facing the reduction side, L8 and the lens L9 as a ninth lens is a biconcave lens having both surfaces subjected to a aspheric surface process. In addition, in the 1-2nd lens group 42, the lens L10 as a tenth lens is a positive lens, the lens L11 as an eleventh lens is a positive lens, the lens L12 as a twelfth lens is a negative lens, the lens L11 and the lens L12 form a cemented lens, the lens L13 as a thirteenth lens is a positive lens, the lens L14 as a fourteenth lens is a negative lens, the lens L13 and the lens L14 form a cemented lens, and the lens L15 as a fifteenth lens is a negative lens having both surfaces subjected to a aspheric surface process. In addition, the second optical group 40b is configured of one mirror having a concave aspheric surface.

(79) FIG. 5A is a diagram showing aberration (spherical aberration, astigmatism, and distortion) on the reduction side of the projection optical system when the projection magnification of 125 times is performed. FIG. 5B is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 100 times is performed. FIG. 5C is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 169 times (170 times) is performed. In addition, FIGS. 6A to 6E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5A. FIG. 6A is a diagram showing the lateral aberration in a case of the maximum angle of view and FIGS. 6A to 6E are diagrams showing lateral aberration at five levels of the angle of view. Similarly, FIGS. 7A to 7E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5B. FIGS. 8A to 8E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 5C.

Example 2

(80) Data of lens surfaces of Example 2 is shown in Table 4. Further, OBJ means the panel surface PI and STO means the aperture ST. In addition, a surface having “*” after a surface reference number means a surface having aspheric shape.

(81) TABLE-US-00004 TABLE 4 f 3.757 ω 72.7 NA 0.313 R D Nd Vd OBJ Infinity 9.500 1 Infinity 25.970  1.51633 64.14 2 Infinity 0.000 3 34.367 9.200 1.61800 63.33 4 −71.540  0.200 5 29.406 8.000 1.48749 70.24 6 −66.556  1.200 1.80518 25.42 7 79.741 0.200 8 20.625 10.500  1.48749 70.24 9 −19.048  1.200 1.90366 31.31 10 36.555 0.400 *11 20.515 1.400 1.58913 61.15 *12 13.882 0.300 13 19.471 4.000 1.48749 70.24 14 −800.000  0.451 STO Infinity 2.385 16 26.460 4.600 1.84666 23.78 17 −56.596  2.599 *18 −75.346  1.800 1.74320 49.29 *19 21.259 variable interval 20 267.720  2.000 1.80518 25.42 21 39.846 10.800  1.62004 36.26 22 −69.505  0.200 23 82.085 5.800 1.64769 33.79 24 −242.910  variable interval 25 56.357 10.500  1.58144 40.75 26 −93.383  2.000 1.80518 25.42 27 93.383 variable interval *28 −311.142  2.800 1.53116 56.04 *29 33.733 variable interval *30 −53.857  variable reflective interval surface 31 Infinity

(82) Table 5 shows a aspheric surface coefficient of a lens surface of Example 2.

(83) TABLE-US-00005 TABLE 5 Aspheric Surface Coefficient K A04 A06 A08 A10 A12 A14 11 −0.2240 −2.7796E−04 1.8104E−06 −3.7963E−09 0.0000E+00 0.0000E+00 0.0000E+00 12 −2.5184 −1.8785E−04 1.7541E−06 −6.7530E−09 1.1439E−11 0.0000E+00 0.0000E+00 18 −1.0000 −9.0000E−05 0.0000E+00   0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 19 0.2425 −6.1991E−05 1.2108E−07 −3.1167E−10 0.0000E+00 0.0000E+00 0.0000E+00 28 −90.0000   1.7601E−06 −7.2288E−10    6.5613E−12 −1.2369E−14  6.6559E−18 0.0000E+00 29 0.0000 −2.1539E−05 2.1299E−08 −2.5888E−11 1.8274E−14 −9.2287E−18  1.4615E−21 30 −1.0313   4.2586E−08 5.7313E−11 −6.5033E−14 2.1447E−17 −3.6118E−21  2.4248E−25

(84) Table 6 shows values of variable intervals 19, 24, 27, 29, and 30 in Table 5 at the projection magnification of 125 times, the projection magnification of 100 times, and the projection magnification of 169 times.

(85) TABLE-US-00006 TABLE 6 Variable Interval 125× 100× 169× 19 11.780 12.132 11.420 24 8.016 4.000 12.553 27 18.200 21.454 14.500 29 113.000 113.410 112.523 30 −501.000 −408.855 −665.888

(86) FIG. 9 is a sectional diagram showing the projection optical system of Example 2. Further, the lens L15 or the mirror MR having a partially notched shape from a circle in an actual optical system is depicted intact without a notch in FIG. 9. In FIG. 9, the projection optical system performs enlargement projection of an image on the panel surface PI to the screen at a magnification depending on a distance. In other words, the projection optical system has 15 lenses L1 to L15 of the lenses L1 to L7 configuring the lens group E1 of the 1-1st lens group 41, the lenses L8 and L9 configuring the lens group E2 thereof, the lenses L10 to L12 configuring the lens group F1 of 1-2nd lens group 42, the lenses L13 and L14 configuring the lens group F2 thereof, and the lens L15 configuring the lens group F3 thereof, in this order from the reduction side. For example, as in the case where projection onto a wall surface is changed to projection onto a floor surface, the magnification change occurs due to the change of a projection position (change of projection distance), and the 1-1st lens group 41 is fixed as is when focusing is performed during the magnification change, whereas the lens groups F1 to F3 configuring the 1-2nd lens group 42 individually move.

(87) As above, in Example 2, the first optical group 40a is configured to have 15 lenses from the lens L1 (first lens) to the lens L15 (fifteenth lens) numbered from the reduction side, and the first optical group 40a can be divided into the 1-1st lens group 41 which is fixed when focusing is performed during the magnification change, and the 1-2nd lens group 42 which moves when focusing is performed during the magnification change.

(88) More specifically, the 1-1st lens group 41 is configured to include the lens group E1 having the lens L1 formed as a positive lens, the cemented lens of the positive lens L2 and the negative lens L3, the cemented lens of the positive lens L4 and the negative lens L5, the negative lens L6 (negative meniscus lens) having both surfaces subjected to a aspheric surface process with a convex surface facing the reduction side, and the positive lens L7 with a convex surface facing the reduction side, the aperture ST, and the lens group E2 having the lens L8 which is the positive biconvex lens and the biconcave lens L9 having both surfaces subjected to a aspheric surface process, in this order from the reduction side. In other words, a total of nine lenses in lens groups E1 and E2 are sequentially arranged.

(89) The 1-2nd lens group 42 is configured to include the lens group F1 (F1 lens group) having the cemented lens of the negative lens L10, the positive lens L11, and the positive lens L12, the lens group F2 (F2 lens group) having the cemented lens of the positive lens L13 and the negative lens L14, and the lens group F3 (F3 lens group) having the negative lens L15 having both surfaces subjected to a aspheric surface process, from the reduction side, and a total of six lenses in the lens groups F1 to F3 are sequentially disposed. The 1-2nd lens group 42 performs focusing by causing the three lens groups to individually move, when the projection distance is changed and the focusing is performed during the magnification change.

(90) The second optical group 40b is configured of one mirror having a concave aspheric surface.

(91) FIG. 10A is a diagram showing aberration (spherical aberration, astigmatism, and distortion) on the reduction side of the projection optical system when the projection magnification of 125 times is performed. FIG. 10B is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 100 times is performed. FIG. 10C is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 169 times (170 times) is performed. In addition, FIGS. 11A to 11E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10A. FIG. 11A is a diagram showing the lateral aberration in a case of the maximum angle of view and FIGS. 11A to 11E are diagrams showing lateral aberration at five levels of the angle of view. Similarly, FIGS. 12A to 12E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10B. FIGS. 13A to 13E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 10C.

Example 3

(92) Data of lens surfaces of Example 3 is shown in Table 7. Further, OBJ means the panel surface PI and STO means the aperture ST. In addition, a surface having “*” after a surface reference number means a surface having aspheric shape.

(93) TABLE-US-00007 TABLE 7 f 3.753 ω 72.6 NA 0.313 R D Nd Vd OBJ Infinity 9.500 1 Infinity 25.970  1.51633 64.14 2 Infinity 0.000 3 30.324 9.200 1.49700 81.54 4 −71.284  0.200 5 26.206 8.000 1.48749 70.24 6 −334.183  1.200 1.80518 25.42 7 41.952 0.200 8 21.564 10.500  1.51633 64.14 9 −20.465  1.200 1.90366 31.31 10 107.431  0.400 *11 28.721 1.400 1.58913 61.15 *12 17.727 0.300 13 16.458 4.000 1.48749 70.24 14 62.093 3.825 STO Infinity 0.100 16 24.772 4.600 1.80518 25.42 17 −38.760  1.800 1.72000 50.23 18 31.098 3.085 *19 −34.966  1.000 1.80610 40.88 *20 −79.856  variable interval 21 415.184  4.200 1.62004 36.26 22 −91.821  0.200 23 115.177  5.145 1.49700 81.54 24 −142.461  variable interval 25 46.248 11.500  1.58144 40.75 26 −81.203  2.000 1.80518 25.42 27 81.203 variable interval *28 −48.237  2.800 1.53116 56.04 *29 56.594 variable interval *30 −54.610  variable reflective interval surface 31 Infinity

(94) Table 8 shows a aspheric surface coefficient of a lens surface of Example 3.

(95) TABLE-US-00008 TABLE 8 Aspheric Surface Coefficient K A04 A06 A08 A10 A12 A14 11 3.8417 −2.9555E−04 1.7720E−06 −5.4969E−09 0.0000E+00 0.0000E+00 0.0000E+00 12 −1.2392 −2.4315E−04 2.0834E−06 −8.7043E−09 1.2324E−11 0.0000E+00 0.0000E+00 19 1.0000 −6.3421E−05 −2.8492E−07    2.2387E−10 0.0000E+00 0.0000E+00 0.0000E+00 20 0.0000 −1.4309E−05 −5.9025E−08    1.7127E−09 0.0000E+00 0.0000E+00 0.0000E+00 28 −12.8176 −1.7791E−05 3.5018E−08 −5.8774E−11 4.5182E−14 −1.6494E−17  0.0000E+00 29 0.0000 −2.6459E−05 3.8735E−08 −6.4740E−11 6.8251E−14 −4.3252E−17  1.2169E−20 30 −0.9784   5.6039E−08 4.6814E−11 −5.9371E−14 2.0499E−17 −3.6330E−21  2.5799E−25

(96) Table 9 shows values of variable intervals 20, 24, 27, 29, and 30 in Table 8 at the projection magnification of 125 times, the projection magnification of 100 times, and the projection magnification of 169 times.

(97) TABLE-US-00009 TABLE 9 Variable Interval 125× 100× 169× 20 19.369 19.836 19.135 24 6.220 4.000 8.423 27 16.086 17.633 14.500 29 114.000 114.205 113.617 30 −501.000 −410.608 −666.363

(98) FIG. 14 is a sectional diagram showing the projection optical system of Example 3. Further, the lens L15 or the mirror MR having a partially notched shape from a circle in an actual optical system is depicted intact without a notch in FIG. 14. In FIG. 14, the projection optical system performs enlargement projection of an image on the panel surface PI to the screen at a magnification depending on a distance. In other words, the projection optical system has 15 lenses L1 to L15 of the lenses L1 to L7 configuring the lens group E1 of 1-1st lens group 41, the lenses L8 to L10 configuring the lens group E2 thereof, the lenses L11 and L12 configuring the lens group F1 of 1-2nd lens group 42, the lenses L13 and L14 configuring the lens group F2 thereof, and the lens L15 configuring the lens group F3 thereof, in this order from the reduction side. For example, as in the case where projection onto a wall surface is changed to projection onto a floor surface, the magnification change occurs due to the change of a projection position (change of projection distance), and the 1-1st lens group 41 is fixed as is when focusing is performed during the magnification change, whereas the lens groups F1 to F3 configuring the 1-2nd lens group 42 individually move.

(99) As above, in Example 3, the first optical group 40a is configured to have 15 lenses from the lens L1 (first lens) to the lens L15 (fifteenth lens) numbered from the reduction side, and the first optical group 40a can be divided into the 1-1st lens group 41 which is fixed when focusing is performed during the magnification change, and the 1-2nd lens group 42 which moves when focusing is performed during the magnification change.

(100) More specifically, the 1-1st lens group 41 is configured to include the lens group E1 having the lens L1 formed as a positive lens, the cemented lens of the positive lens L2 and the negative lens L3, the cemented lens of the positive lens L4 and the negative lens L5, the negative lens L6 (negative meniscus lens) having both surfaces subjected to a aspheric surface process with a convex surface facing the reduction side, and the positive lens L7 with a convex surface facing the reduction side, the aperture ST, and the lens group E2 which has the cemented lens of the positive lens L8 and the negative lens L9, and the lens L10 as the negative meniscus lens having both surfaces subjected to a aspheric surface process with a convex surface facing the enlargement side, in this order from the reduction side. In other words, a total of ten lenses in lens groups E1 and E2 are sequentially arranged.

(101) The 1-2nd lens group 42 is configured to include the lens group F1 (F1 lens group) having the cemented lens of the positive lens L11 and the positive lens L12, the lens group F2 (F2 lens group) having the cemented lens of the positive lens L13 and the negative lens L14, and the lens group F3 (F3 lens group) having the negative lens L15 having both surfaces subjected to a aspheric surface process, from the reduction side, and a total of five lenses in the lens groups F1 to F3 are sequentially disposed. The 1-2nd lens group 42 performs focusing by causing the three lens groups to individually move, when the projection distance is changed and the focusing is performed during the magnification change.

(102) The second optical group 40b is configured of one mirror having a concave aspheric surface.

(103) FIG. 15A is a diagram showing aberration (spherical aberration, astigmatism, and distortion) on the reduction side of the projection optical system when the projection magnification of 125 times is performed. FIG. 15B is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 100 times is performed. FIG. 15C is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 169 times (170 times) is performed.

(104) In addition, FIGS. 16A to 16E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15A. FIG. 16A is a diagram showing the lateral aberration in a case of the maximum angle of view and FIGS. 16A to 16E are diagrams showing lateral aberration at five levels of the angle of view. Similarly, FIGS. 17A to 17E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15B. FIGS. 18A to 18E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 15C.

Example 4

(105) Data of lens surfaces of Example 4 is shown in Table 10. Further, OBJ means the panel surface PI and STO means the aperture ST. In addition, a surface having “*” after a surface reference number means a surface having aspheric shape.

(106) TABLE-US-00010 TABLE 10 f 3.757 ω 72.7 NA 0.313 R D Nd Vd OBJ Infinity 9.500 1 Infinity 25.910  1.51633 64.14 2 Infinity 0.000 3 28.940 9.600 1.49700 81.54 4 −72.351  0.200 5 28.008 7.600 1.49700 81.54 6 −80.728  1.200 1.80518 25.42 7 84.182 0.200 8 23.162 10.500  1.51633 64.14 9 −18.390  1.200 1.90366 31.31 10 49.861 0.200 *11 22.232 1.400 1.58913 61.15 *12 14.512 0.500 13 18.701 4.000 1.48749 70.24 14 85.780 2.500 STO Infinity 2.657 16 26.255 4.200 1.84666 23.78 17 −72.326  2.805 *18 −285.961  1.800 1.74320 49.29 *19 20.094 variable interval 20 294.948  3.800 1.76182 26.52 21 −185.552  0.200 22 88.771 11.700  1.65412 39.68 23 −32.587  2.000 1.80518 25.42 24 −207.713  variable interval 25 47.462 11.000  1.58144 40.75 26 −286.510  1.907 27 −162.790  2.000 1.80518 25.42 28 86.542 variable interval *29 278.000  2.800 1.53116 56.04 *30 32.790 variable interval *31 −53.401  variable reflective interval surface 32 Infinity

(107) Table 11 shows a aspheric surface coefficient of a lens surface of Example 4.

(108) TABLE-US-00011 TABLE 11 Aspheric Surface Coefficient K A04 A06 A08 A10 A12 A14 11 1.8918 −3.2189E−04 1.7484E−06 −4.3348E−09 0.0000E+00 0.0000E+00 0.0000E+00 12 −1.7155 −2.4569E−04 2.0775E−06 −8.0954E−09 1.6529E−11 0.0000E+00 0.0000E+00 18 −1.0000 −9.0000E−05 0.0000E+00   0.0000E+00 0.0000E+00 0.0000E+00 0.0000E+00 19 −0.5794 −5.2934E−05 1.0377E−07 −1.8067E−10 0.0000E+00 0.0000E+00 0.0000E+00 29 90.0000 −6.9308E−06 2.1311E−08 −4.1442E−11 3.8427E−14 −1.6720E−17  0.0000E+00 30 0.0000 −2.8334E−05 3.9541E−08 −6.2687E−11 5.5340E−14 −2.6577E−17  2.7658E−21 31 −0.9858   1.1080E−07 3.6232E−11 −6.1654E−14 2.2886E−17 −4.2330E−21  3.0644E−25

(109) Table 12 shows values of variable intervals 19, 24, 27, 28, 30, and 31 in Table 11 at the projection magnification of 125 times, the projection magnification of 100 times, and the projection magnification of 169 times.

(110) TABLE-US-00012 TABLE 12 Variable Interval 125× 100× 169× 19 14.163 15.223 13.108 24 7.258 4.000 11.119 28 13.838 15.762 11.500 30 112.362 112.637 111.895 31 −501.000 −412.661 −661.960

(111) FIG. 19 is a sectional diagram showing the projection optical system of Example 4. Further, the lens L15 or the mirror MR having a partially notched shape from a circle in an actual optical system is depicted intact without a notch in FIG. 19. In FIG. 19, the projection optical system performs enlargement projection of an image on the panel surface PI to the screen at a magnification depending on a distance. In other words, the projection optical system has 15 lenses L1 to L15 of the lenses L1 to L7 configuring the lens group E1 of 1-1st lens group 41, the lenses L8 and L9 configuring the lens group E2 thereof, the lenses L10 to L12 configuring the lens group F1 of 1-2nd lens group 42, the lenses L13 and L14 configuring the lens group F2 thereof, and the lens L15 configuring the lens group F3 thereof, in this order from the reduction side. For example, as in the case where projection onto a wall surface is changed to projection onto a floor surface, the magnification change occurs due to the change of a projection position (change of projection distance), and the 1-1st lens group 41 is fixed as is when focusing is performed during the magnification change, whereas the lens groups F1 to F3 configuring the 1-2nd lens group 42 individually move.

(112) As above, in Example 4, the first optical group 40a is configured to have 15 lenses from the lens L1 (first lens) to the lens L15 (fifteenth lens) numbered from the reduction side, and the first optical group 40a can be divided into the 1-1st lens group 41 which is fixed when focusing is performed during the magnification change, and the 1-2nd lens group 42 which moves when focusing is performed during the magnification change.

(113) More specifically, the 1-1st lens group 41 is configured to include the lens group E1 having the lens L1 formed as a positive lens, the cemented lens of the positive lens L2 and the negative lens L3, the cemented lens of the positive lens L4 and the negative lens L5, the negative lens L6 (negative meniscus lens) having both surfaces subjected to a aspheric surface process with a convex surface facing the reduction side, and the positive lens L7 with a convex surface facing the reduction side, the aperture ST, and the lens group E2 which has the positive lens L8 and the negative lens L9, in this order from the reduction side. In other words, a total of nine lenses in lens groups E1 and E2 are sequentially arranged.

(114) The 1-2nd lens group 42 is configured to include the lens group F1 (F1 lens group) having the positive lens L10, the cemented lens of the negative lens L11 and the positive lens L12, the lens group F2 (F2 lens group) having the positive lens L13 and the negative lens L14, and the lens group F3 (F3 lens group) having the negative lens L15 having both surfaces subjected to a aspheric surface process, from the reduction side, and a total of six lenses in the lens groups F1 to F3 are sequentially disposed. The 1-2nd lens group 42 performs focusing by causing the three lens groups to individually move, when the projection distance is changed and the focusing is performed during the magnification change.

(115) The second optical group 40b is configured of one mirror having a concave aspheric surface.

(116) FIG. 20A is a diagram showing aberration (spherical aberration, astigmatism, and distortion) on the reduction side of the projection optical system when the projection magnification of 125 times is performed. FIG. 20B is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 100 times is performed. FIG. 20C is a diagram showing aberration on the reduction side of the projection optical system when the projection magnification of 169 times (170 times) is performed.

(117) In addition, FIGS. 21A to 21E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20A. FIG. 21A is a diagram showing the lateral aberration in a case of the maximum angle of view and FIGS. 21A to 21E are diagrams showing lateral aberration at five levels of the angle of view. Similarly, FIGS. 22A to 22E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20B. FIGS. 23A to 23E are diagrams showing lateral aberration of the projection optical system, which correspond to FIG. 20C.

SUMMARY OF EXAMPLES

(118) In any one of Examples, a simple configuration, in which the lens group F3 (F3 lens group) is one aspheric resin lens, is employed while a wide angle of view is equal to or greater than a half angle of view of 70° at a wide angle end.

(119) The invention is not limited to the embodiments or examples described above and can be performed in various aspects within a range without departing from the gist thereof.

(120) For example, in order to lower the image height to be projected, the F2 lens group formed of the cemented lens may have the non-circular shape, in addition to the lens L15 (F3 lens group) as the aspheric lens.

(121) In addition, in the respective Examples, one or more lenses having substantially no power may be added before and after or between the lenses configuring each lens group.

(122) In addition, a target of enlargement projection by the projection optical system 40 is not limited to the liquid crystal panels 18G, 18R, and 18B, but it is possible for the projection optical system 40 to perform enlargement projection of an image formed by various light flux modulating elements such as a digital micromirror device, in which a micromirror functions as a pixel.

(123) The entire disclosure of Japanese Patent Application No. 2015-013031, filed Jan. 27, 2015 is expressly incorporated by reference herein.