Variable magnification projection optical system and projection device

Abstract

To provide a zoom projection optical system which allows for reducing distortion aberration in a peripheral area of a projection image at the wide-angle end, and easily viewing the projection image in a bright environment.SOLUTION: A zoom projection optical system comprises, in order from the magnification side, a first lens group having a negative refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power. When zooming, the first lens group is stationary and the second lens group and third lens group move. The second lens group includes a plurality of lenses having a positive refractive power. All lenses with a positive refractive power in the first lens group and second lens group are made of a glass material having a transmittance greater than 0.98 at a thickness of 10 mm for light with a wavelength of 440 nm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a variable magnification projection optical system and a projection apparatus. [Background technology]

[0002] Patent Document 1 (WO 2014 / 104083) discloses a variable magnification projection optical system consisting of, in order from the magnification side, a first lens group having negative refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, a fourth lens group having negative refractive power, a fifth lens group, and a sixth lens group having positive refractive power. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2014 / 104083 Summary of the Invention [Problem to be solved by the invention]

[0004] In the variable magnification projection optical system of Patent Document 1, the number of lenses included in the second lens group is small. In order to reduce the distortion aberration in the peripheral area of ​​the projected image at the wide-angle end, it is necessary to increase the number of lenses included in the first lens group. However, since the first lens group is arranged on the enlargement side of the second lens group, the diameter of the lens included in the first lens group tends to be larger than the diameter of the lens included in the second lens group. When the lens diameter increases, the thickness of the lens on the optical axis of the variable magnification projection optical system (center thickness of the lens) increases, and the light transmittance of the lens decreases. In a bright environment, it becomes difficult to view the projected image.

[0005] The present disclosure has been made in consideration of these problems, and its purpose is to provide a variable magnification projection optical system and projection device that reduces distortion aberration in the peripheral area of ​​the projected image at the wide-angle end, and enables the projected image to be easily viewed in bright environments. [Means for solving the problem]

[0006] A variable magnification projection optical system according to a first aspect of the present disclosure is for enlarging and projecting an image displayed on an image display surface, and includes, in order from the enlargement side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. During magnification change, the first lens group is fixed, and the second lens group and the third lens group move. The second lens group includes a plurality of lenses having positive refractive power. All of the lenses having positive refractive power in the first lens group and the second lens group are formed of a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0007] A variable magnification projection optical system according to a second aspect of the present disclosure is for enlarging and projecting an image displayed on an image display surface, and includes, in order from the enlargement side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. During magnification change, the first lens group is fixed, and the second lens group and the third lens group move. The second lens group includes a plurality of lenses having positive refractive power. The refractive indexes of all lenses having positive refractive power in the first lens group and the second lens group for the d-line are less than 1.6.

[0008] A variable magnification projection optical system according to a third aspect of the present disclosure is the variable magnification projection optical system according to the first aspect of the present disclosure, in which all of the lenses in the first lens group are formed from a glass material having a transmittance greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0009] A variable magnification projection optical system according to a fourth aspect of the present disclosure is the variable magnification projection optical system according to the second aspect of the present disclosure, in which the refractive index for the d-line of all lenses in the first lens group is less than 1.75.

[0010] A variable magnification projection optical system according to a fifth aspect of the present disclosure is a variable magnification projection optical system according to the first or third aspect of the present disclosure, in which all of the lenses in the first lens group and the second lens group are formed from a glass material having a transmittance greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0011] A variable magnification projection optical system according to a sixth aspect of the present disclosure is the variable magnification projection optical system according to any one of the first to fifth aspects of the present disclosure, wherein the first lens group is made up of seven or less lenses having a refractive power.

[0012] A variable magnification projection optical system according to a seventh aspect of the present disclosure is the variable magnification projection optical system according to any one of the first to sixth aspects of the present disclosure, wherein the second lens group is made up of four or more lenses having refractive power.

[0013] A variable magnification projection optical system according to an eighth aspect of the present disclosure is a variable magnification projection optical system according to any one of the first to seventh aspects of the present disclosure, further comprising at least one lens group that is disposed on the reduction side of the third lens group and moves along the optical axis of the variable magnification projection optical system during magnification variation.

[0014] A variable magnification projection optical system according to a ninth aspect of the present disclosure is the variable magnification projection optical system according to any one of the first to eighth aspects of the present disclosure, wherein the first lens group does not include an aspheric surface.

[0015] A variable magnification projection optical system according to a tenth aspect of the present disclosure is the variable magnification projection optical system according to any one of the first to ninth aspects of the present disclosure, in which the variable magnification projection optical system does not include an aspheric surface.

[0016] A projection device according to the present disclosure includes an image display element having an image display surface, and a variable magnification projection optical system according to any one of the first to ninth aspects of the present disclosure. Effect of the Invention

[0017] According to the variable magnification projection optical system and projection device of the present disclosure, it is possible to reduce distortion in the peripheral area of ​​a projected image at the wide-angle end, and to make the projected image easily visible in a bright environment. [Brief description of the drawings]

[0018] [Figure 1] 1 is a diagram showing the configuration of a variable magnification projection optical system according to a first embodiment. [Diagram 2] FIG. 13 is a diagram showing the configuration of a variable magnification projection optical system according to a second embodiment. [Diagram 3] FIG. 13 is a diagram showing the configuration of a variable magnification projection optical system according to a third embodiment. [Figure 4] FIG. 13 is a diagram showing the configuration of a variable magnification projection optical system according to a fourth embodiment. [Figure 5A] FIG. 2 is a longitudinal aberration diagram at the wide-angle end of Example 1, showing aberrations (spherical aberration, astigmatism, and distortion) at the wide-angle end. [Figure 5B] FIG. 2 is a longitudinal aberration diagram at the telephoto end of Example 1, showing aberrations (spherical aberration, astigmatism, and distortion) at the telephoto end. [Figure 6A] FIG. 11 is a longitudinal aberration diagram at the wide-angle end of Example 2, showing aberrations (spherical aberration, astigmatism, and distortion) at the wide-angle end. [Figure 6B] FIG. 11 is a longitudinal aberration diagram at the telephoto end of Example 2, showing aberrations (spherical aberration, astigmatism, and distortion) at the telephoto end. [Figure 7A] FIG. 11 is a diagram showing longitudinal aberration at the wide-angle end of Example 3, illustrating aberrations (spherical aberration, astigmatism, and distortion) at the wide-angle end. [Figure 7B] FIG. 13 is a longitudinal aberration diagram at the telephoto end of Example 3, showing aberrations (spherical aberration, astigmatism, and distortion) at the telephoto end. [Figure 8A] FIG. 13 is a longitudinal aberration diagram at the wide-angle end of Example 4, showing aberrations (spherical aberration, astigmatism, and distortion) at the wide-angle end. [Figure 8B] FIG. 13 is a longitudinal aberration diagram at the telephoto end of Example 4, showing aberrations (spherical aberration, astigmatism, and distortion) at the telephoto end. [Figure 9] 1 is a schematic diagram showing a projection device according to an embodiment; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] A variable magnification projection optical system and a projection apparatus according to an embodiment of the present disclosure will be described below with reference to the drawings.

[0020] A variable magnification projection optical system according to a first aspect of the present embodiment is for enlarging and projecting an image displayed on an image display screen, and includes, in order from the enlargement side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. During magnification, the first lens group is fixed, and the second and third lens groups move. The second lens group includes a plurality of lenses having positive refractive power. All of the lenses in the first and second lens groups having positive refractive power are formed of a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0021] The enlargement side means the side (so-called front side) of the screen surface (enlargement side image surface) on which the enlarged optical image is projected, along the optical axis of the variable magnification projection optical system, whereas the reduction side means the side (so-called rear side) on which an image display element having an image display surface is disposed, along the optical axis of the variable magnification projection optical system.

[0022] The variable magnification projection optical system of the first aspect of this embodiment includes, in order from the magnification side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Therefore, off-axis light rays are converged in the third lens group and then proceed through the second lens group and the first lens group. The diameters of the lenses included in the first lens group and the second lens group can be reduced. The center thicknesses of the lenses included in the first lens group and the second lens group can be reduced. The transmittance of the lenses included in the first lens group and the second lens group is increased, and the light transmittance of the first lens group and the second lens group is increased. The light transmittance of the variable magnification projection optical system is increased, and the projected image can be easily viewed in a bright environment.

[0023] In the variable magnification projection optical system of the first aspect of this embodiment, the first lens group is fixed during magnification change, so that even if the negative refractive power of the first lens group is increased in order to increase the angle of view of the variable magnification projection optical system, it is possible to reduce fluctuations in aberration during magnification change.

[0024] In the variable magnification projection optical system of the first aspect of this embodiment, the second lens group includes a plurality of lenses having positive refractive power. Therefore, even if the negative refractive power of the first lens group is strengthened to increase the angle of view of the variable magnification projection optical system, the distortion caused by the first lens group can be corrected by the plurality of lenses having positive refractive power included in the second lens group without increasing the number of lenses having positive refractive power included in the first lens group. The distortion in the peripheral area of ​​the projected image at the wide-angle end can be reduced. In addition, the number of lenses in the first lens group, which tends to have a large lens diameter, can be reduced, so that the light transmittance of the first lens group can be increased. The light transmittance of the variable magnification projection optical system is increased, and the projected image can be easily viewed in a bright environment.

[0025] In the variable magnification projection optical system of the first aspect of this embodiment, all lenses having positive refractive power in the first lens group and the second lens group are formed of glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. By forming the lenses having positive refractive power, which tend to have a larger central thickness than lenses having negative refractive power, from a glass material having high transmittance, the light transmittance of the first lens group and the second lens group is increased, and the light transmittance of the variable magnification projection optical system is increased. The projected image can be easily viewed in a bright environment.

[0026] A variable magnification projection optical system according to a second aspect of the present embodiment is for enlarging and projecting an image displayed on an image display surface, and includes, in order from the enlargement side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. During magnification change, the first lens group is fixed, and the second and third lens groups move. The second lens group includes a plurality of lenses having positive refractive power. The refractive index of all lenses having positive refractive power in the first and second lens groups for the d-line (wavelength 587.56 nm) is less than 1.6.

[0027] The variable magnification projection optical system of the second aspect of this embodiment includes, in order from the magnification side, a first lens group having negative refractive power, a second lens group having negative refractive power, and a third lens group having positive refractive power. Therefore, off-axis light rays are converged in the third lens group and then proceed through the second lens group and the first lens group. The diameters of the lenses included in the first lens group and the second lens group can be reduced. The center thicknesses of the lenses included in the first lens group and the second lens group can be reduced. The transmittance of the lenses included in the first lens group and the second lens group is increased, and the light transmittance of the first lens group and the second lens group is increased. The light transmittance of the variable magnification projection optical system is increased, and the projected image can be easily viewed in a bright environment.

[0028] In the variable magnification projection optical system according to the second aspect of this embodiment, the first lens group is fixed during magnification change, so that even if the negative refractive power of the first lens group is increased in order to increase the angle of view of the variable magnification projection optical system, it is possible to reduce fluctuations in aberration during magnification change.

[0029] In the variable magnification projection optical system of the second aspect of this embodiment, the second lens group includes a plurality of lenses having positive refractive power. Therefore, even if the negative refractive power of the first lens group is strengthened to increase the angle of view of the variable magnification projection optical system, the distortion caused by the first lens group can be corrected by the plurality of lenses having positive refractive power included in the second lens group without increasing the number of lenses having positive refractive power included in the first lens group. The distortion in the peripheral area of ​​the projected image at the wide-angle end can be reduced. In addition, the number of lenses in the first lens group, which tends to have a large lens diameter, can be reduced, so that the light transmittance of the first lens group can be increased. The light transmittance of the variable magnification projection optical system is increased, and the projected image can be easily viewed in a bright environment.

[0030] Since the first lens group and the second lens group have negative refractive power, the angle of incidence of off-axis light rays to the lenses having positive refractive power in the first lens group and the second lens group becomes large. In the variable magnification projection optical system of the second aspect of this embodiment, the refractive index of all lenses having positive refractive power in the first lens group and the second lens group with respect to the d-line is smaller than 1.6. Therefore, the angle of incidence of off-axis light rays to the lenses having positive refractive power in the first lens group and the second lens group can be prevented from exceeding the critical angle. The angle of view of the variable magnification projection optical system can be increased, and the projected image can be easily viewed in a bright environment.

[0031] In this embodiment, it is preferable that all lenses in the first lens group are formed from a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0032] This increases the light transmittance of the first lens group, thereby increasing the light transmittance of the variable magnification projection optical system, making it easier to view the projected image in a bright environment.

[0033] In this embodiment, it is preferable that the refractive index of all lenses in the first lens group for the d-line is smaller than 1.75.

[0034] In the variable magnification projection optical system of the second aspect of this embodiment, the refractive index of all lenses having positive refractive power in the first lens group and the second lens group for the d-line is smaller than 1.6. Therefore, the Petzval sum of the variable magnification projection optical system of the second aspect of this embodiment tends to be large. By making the refractive index of all lenses in the first lens group smaller than 1.75 for the d-line, the refractive index of the lenses having negative refractive power in the first lens group and the second lens group can be made small. The Petzval sum of the variable magnification projection optical system is reduced, and the deterioration of the field curvature of the variable magnification projection optical system can be suppressed.

[0035] In this embodiment, it is preferable that all lenses in the first lens group and the second lens group are formed from a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0036] Therefore, the light transmittance of the first lens group and the second lens group increases, and the light transmittance of the variable magnification projection optical system increases, making it easier to view the projected image in a bright environment.

[0037] In this embodiment, it is preferable that the first lens group is made up of seven or less lenses having refractive power.

[0038] Since the number of lenses in the first lens group, which tends to have a large lens diameter, can be reduced, the light transmittance of the first lens group can be increased. This increases the light transmittance of the variable magnification projection optical system, making it easier to view the projected image in bright environments.

[0039] In the present embodiment, the second lens group preferably consists of four or more lenses having refractive power.

[0040] By increasing the number of lenses in the second lens group, which is easier to make the lens diameter smaller than that of the first lens group, the distortion caused by the first lens group can be more effectively corrected by the multiple lenses having positive refractive power included in the second lens group without increasing the number of lenses having positive refractive power included in the first lens group. The distortion in the peripheral area of ​​the projected image at the wide-angle end can be reduced. In addition, since the number of lenses in the first lens group, which tends to have a large lens diameter, can be reduced, the light transmittance of the first lens group can be increased. The light transmittance of the variable magnification projection optical system is increased, making it easier to view the projected image in a bright environment.

[0041] It is preferable that the variable magnification projection optical system of this embodiment further comprises at least one lens group that is disposed on the reduction side of the third lens group and moves along the optical axis of the variable magnification projection optical system during magnification variation.

[0042] Therefore, the moving distance of the second lens group and the moving distance of the third lens group during magnification change can be reduced, and the fluctuation in aberration of the variable magnification projection optical system during magnification change can be reduced.

[0043] In the present embodiment, it is preferable that the first lens group does not include an aspheric surface.

[0044] Therefore, it is possible to realize equivalent aberration performance without using an aspheric surface for the purpose of aberration correction, while reducing the cost of the first lens group, which tends to have a large lens diameter.

[0045] It is preferable that the variable magnification projection optical system of the present embodiment does not include an aspheric surface.

[0046] Therefore, it is possible to reduce the cost of the variable magnification projection optical system while realizing the same aberration performance without using an aspheric surface for the purpose of aberration correction.

[0047] The projection device of the present embodiment includes an image display element having an image display surface, and Magnification projection optical system It is equipped with.

[0048] The projection device of this embodiment is Magnification projection optical system This reduces distortion in the peripheral area of ​​the projected image at the wide-angle end, and makes it possible to easily view the projected image in a bright environment.

[0049] <Specific Optical Configuration of Variable Magnification Projection Optical System of the Embodiment>

[0050] The specific optical configuration of the variable magnification projection optical system ZL according to the first to fourth embodiments will be described with reference to Figures 1 to 4. In each of Figures 1 to 4, "Wide" is a lens cross-sectional view at the wide-angle end, "Tele" is a lens cross-sectional view at the telephoto end, and "AX" represents the optical axis of the variable magnification projection optical system ZL. Both "Wide" and "Tele" are lens cross-sectional views when focusing on an object at infinity.

[0051] The variable magnification projection optical system ZL enlarges and projects an image displayed on an image display surface IM of the image display element 7 (see FIG. 9) at an angle of view of, for example, 80° or more. On the reduction side of the variable magnification projection optical system ZL, a prism PR (for example, a TIR (Total Internal Reflection) prism, a color separation / combination prism, etc.) and a cover glass CG that covers the image display surface IM of the image display element 7 are arranged.

[0052] (First embodiment) 1, the variable magnification projection optical system ZL is substantially composed of a plurality of lens groups having refractive power. For example, the variable magnification projection optical system ZL is substantially composed of six lens groups G1-Gr6 having refractive power. In this specification, the variable magnification projection optical system ZL being substantially composed of a plurality of lens groups having refractive power means that the variable magnification projection optical system ZL is composed of a plurality of lens groups having refractive power, or that the variable magnification projection optical system ZL is composed of a plurality of lens groups having refractive power and other lens groups not having refractive power. The variable magnification projection optical system ZL does not include an aspheric surface.

[0053] The first lens group G1 is the lens group located on the most enlargement side among the lens groups constituting the variable magnification projection optical system and having refractive power. The first lens group G1 has negative refractive power. The first lens group G1 is composed of seven or less lenses having refractive power. The second lens group G2 is the lens group located second from the enlargement side among the lens groups constituting the variable magnification projection optical system and having refractive power. The second lens group G2 has negative refractive power. The second lens group G2 is composed of four or less lenses having refractive power. The second lens group G2 includes a plurality of lenses having positive refractive power. The third lens group G3 is the lens group located third from the enlargement side among the lens groups constituting the variable magnification projection optical system and having refractive power. The third lens group G3 has positive refractive power.

[0054] The fourth lens group G4 is the fourth lens group from the magnification side among the lens groups that constitute the variable magnification projection optical system and have refractive power. The fourth lens group G4 has negative refractive power. The fifth lens group G5 is the fifth lens group from the magnification side among the lens groups that constitute the variable magnification projection optical system and have refractive power. The fifth lens group G5 has positive refractive power. The fifth lens group G5 has an aperture stop ST on the most magnification side of the fifth lens group G5. The sixth lens group G6 is the sixth lens group from the magnification side among the lens groups that constitute the variable magnification projection optical system and have refractive power. The sixth lens group G6 has positive refractive power.

[0055] During magnification change, the interval between two adjacent lens groups among the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 changes. For example, during magnification change, the first lens group G1 and the sixth lens group G6 are fixed, and the second to fifth lens groups G2-G5 move. Specifically, during magnification change from the wide-angle end (W) to the telephoto end (T), the second lens group G2 moves along a locus having a convex shape on the reduction side (U-turn movement), the third lens group G3 moves monotonously to the enlargement side, the fourth lens group G4 moves monotonously to the reduction side, and the fifth lens group G5 moves monotonously to the enlargement side. Since the first lens group G1 and the sixth lens group G6 are fixed during magnification change, the total length of the variable magnification projection optical system does not change due to the magnification change, and the variable magnification mechanism of the variable magnification projection optical system ZL can be simplified.

[0056] When each lens of the first lens group G1 to the sixth lens group G6 in the first embodiment is viewed in terms of a paraxial surface shape, the lenses are configured as follows, in order from the object side:

[0057] The first lens group G1 is made up of seven lenses L11-L17 having refractive power. Specifically, the first lens group G1 is made up of, in order from the magnification side, a negative meniscus lens L11 with a convex surface facing the magnification side, a negative meniscus lens L12 with a convex surface facing the magnification side, a negative meniscus lens L13 with a convex surface facing the magnification side, a biconvex positive lens L14, a negative meniscus lens L15 with a convex surface facing the magnification side, a biconvex positive lens L16, and a negative meniscus lens L17 with a convex surface facing the magnification side. The first lens group G1 does not include an aspheric surface.

[0058] All lenses having positive refractive power in the first lens group G1 (lenses L14 and L16 in this embodiment) are made of a glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, and TAFD5G (all glass materials manufactured by HOYA Corporation).

[0059] The refractive index of all lenses having positive refractive power in the first lens group G1 (lenses L14 and L16 in this embodiment) for the d-line (wavelength 587.56 nm) is less than 1.6. By forming all lenses having positive refractive power in the first lens group G1 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the first lens group G1 for the d-line can be made less than 1.6.

[0060] All the lenses in the first lens group G1 (lenses L11-L17 in this embodiment) are made of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, TAFD5G, E-FD5, E-FD1, BAFD8, and NBFD13 (all glass materials manufactured by HOYA Corporation). All lenses having positive refractive power in the first lens group G1 (lenses L14 and L16 in this embodiment) are formed from a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm, so naturally, all lenses having positive refractive power in the first lens group G1 among all lenses in the first lens group G1 satisfy the condition that the lens is formed from a glass material having a transmittance of greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0061] The refractive index of all lenses in the first lens group G1 (lenses L11-L17 in this embodiment) for the d-line is less than 1.75. By forming all lenses in the first lens group G1 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the first lens group G1 for the d-line can be made less than 1.75. Since the refractive index of all lenses having positive refractive power in the first lens group G1 (lenses L14, L16 in this embodiment) for the d-line is less than 1.6, all lenses having positive refractive power in the first lens group G1 among all lenses in the first lens group G1 naturally satisfy the condition that the refractive index of the lens for the d-line is less than 1.75.

[0062] The second lens group G2 is composed of four lenses L21-L24 having refractive power. The second lens group G2 includes two lenses having positive refractive power. Specifically, the second lens group G2 is composed of, in order from the magnification side, a biconvex positive lens L21, a biconcave negative lens L22, a biconcave negative lens L23, and a biconvex positive lens L24. The second lens group G2 does not include an aspheric surface.

[0063] All lenses having positive refractive power in the second lens group G2 (lenses L21 and L24 in this embodiment) are made of a glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, and TAFD5G (all glass materials manufactured by HOYA Corporation).

[0064] The refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L21 and L24 in this embodiment) for the d-line is smaller than 1.6. By forming all lenses having positive refractive power in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of the first lens group G2 for the d-line can be reduced. 2 Lens group G 2The refractive index of all lenses having a positive refractive power in the range of 1.6 or less can be set to be less than 1.6.

[0065] All the lenses in the second lens group G2 (lenses L21-L24 in this embodiment) are made of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, TAFD5G, E-FD5, E-FD1, BAFD8, and NBFD13 (all glass materials manufactured by HOYA Corporation). All of the lenses having positive refractive power in the second lens group G2 (in this embodiment, lenses L21 and L24) are formed from a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm, so naturally, all of the lenses having positive refractive power in the second lens group G2 among all the lenses in the second lens group G2 satisfy the condition that the lens is formed from a glass material having a transmittance of greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0066] The refractive index of all lenses in the second lens group G2 (lenses L21-L24 in this embodiment) for the d-line is less than 1.75. By forming all lenses in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the second lens group G2 for the d-line can be made less than 1.75. Since the refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L21, L24 in this embodiment) for the d-line is less than 1.6, all lenses having positive refractive power in the second lens group G2 among all lenses in the second lens group G2 naturally satisfy the condition that the refractive index of the lens for the d-line is less than 1.75.

[0067] The third lens group G3 is composed of two lenses L31 and L32 having refractive power. Specifically, the third lens group G3 is composed of, from the enlargement side, a positive meniscus lens L31 with a convex surface facing the reduction side, and a positive meniscus lens L32 with a convex surface facing the enlargement side. The third lens group G3 does not include an aspheric surface.

[0068] The fourth lens group G4 is composed of three lenses L41-L43 having refractive power. Specifically, the fourth lens group G4 is composed of, from the magnification side, a biconcave negative lens L41, a biconcave negative lens L42, and a biconvex positive lens L43. The fourth lens group G4 does not include an aspheric surface.

[0069] The fifth lens group G5 is composed of six lenses L51-L56 having refractive power. Specifically, the fifth lens group G5 is composed of, in order from the enlargement side, a positive meniscus lens L51 with a convex surface facing the reduction side, a negative meniscus lens L52 with a convex surface facing the reduction side, a positive meniscus lens L53 with a convex surface facing the reduction side, a biconvex positive lens L54, a biconcave negative lens L55, and a biconvex positive lens L56. The fifth lens group G5 does not include an aspheric surface.

[0070] The sixth lens group G6 is composed of one lens L61 having refractive power. Specifically, the sixth lens group G6 is composed of a biconvex positive lens L 61 The sixth lens group G6 does not include an aspheric surface.

[0071] (Second embodiment) 2, the variable magnification projection optical system ZL of the second embodiment is configured similarly to the variable magnification projection optical system ZL of the first embodiment (see FIG. 1), but differs from the variable magnification projection optical system ZL of the first embodiment in the following points: In the second embodiment, the fourth lens group G4 is fixed during magnification change; The variable magnification projection optical system ZL of the second embodiment has a wider angle of view than the variable magnification projection optical system ZL of the first embodiment.

[0072] (Third embodiment) 3, the variable magnification projection optical system ZL of the third embodiment is configured similarly to the variable magnification projection optical system ZL of the first embodiment (see FIG. 1), but differs from the variable magnification projection optical system ZL of the first embodiment in the following respects: In the variable magnification projection optical system ZL of the third embodiment, a negative lens L21 that has a flat surface on the enlargement side and a concave surface on the reduction side is added to the most enlargement side of the second lens group G2, and the second lens group G2 is composed of five lenses L21-L25.

[0073] Specifically, the second lens group G2 in the third embodiment is configured as follows, in order from the object side, when each lens is viewed in terms of a paraxial surface shape. The second lens group G2 is composed of five lenses L21-L25 having refractive power. The second lens group G2 includes two lenses having positive refractive power. Specifically, the second lens group G2 is composed of, in order from the enlargement side, a negative lens L21 having a flat surface on the enlargement side and a concave surface on the reduction side, a biconvex positive lens L22, a biconcave negative lens L23, a biconcave negative lens L24, and a biconvex positive lens L25. The second lens group G2 does not include an aspheric surface.

[0074] All lenses having positive refractive power in the second lens group G2 (lenses L22 and L25 in this embodiment) are made of a glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, and TAFD5G (all glass materials manufactured by HOYA Corporation).

[0075] The refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L22 and L25 in this embodiment) for the d-line is smaller than 1.6. By forming all lenses having positive refractive power in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of the first lens group G2 for the d-line can be reduced. 2 Lens group G 2 The refractive index of all lenses having a positive refractive power in the range of 1.6 or less can be set to be less than 1.6.

[0076] All the lenses in the second lens group G2 (lenses L21-L25 in this embodiment) are made of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, TAFD5G, E-FD5, E-FD1, BAFD8, and NBFD13 (all glass materials manufactured by HOYA Corporation). All of the lenses having positive refractive power in the second lens group G2 (in this embodiment, lenses L22 and L25) are formed from a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm, so naturally, all of the lenses having positive refractive power in the second lens group G2 among all the lenses in the second lens group G2 satisfy the condition that the lens is formed from a glass material having a transmittance of greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0077] The refractive index of all lenses in the second lens group G2 (lenses 21-L25 in this embodiment) for the d-line is less than 1.75. By forming all lenses in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the second lens group G2 for the d-line can be made less than 1.75. Since the refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L22, L25 in this embodiment) for the d-line is less than 1.6, all lenses having positive refractive power in the second lens group G2 among all lenses in the second lens group G2 naturally satisfy the condition that the refractive index of the lens for the d-line is less than 1.75.

[0078] (Fourth embodiment) 4, the variable magnification projection optical system ZL of the fourth embodiment is configured similarly to the variable magnification projection optical system ZL of the third embodiment (see FIG. 3), but differs from the variable magnification projection optical system ZL of the third embodiment in the following respects: The first lens group G1 is made up of six lenses L11-L16. The lens L21 of the second lens group G2, which is located on the most enlargement side, is a biconcave negative lens L21.

[0079] Specifically, the first lens group G1 and the second lens group G2 in the fourth embodiment are configured as follows, in order from the object side, when each lens is viewed in terms of a paraxial surface shape.

[0080] The first lens group G1 is composed of six lenses L11-L16 having refractive power. Specifically, the first lens group G1 is composed of, in order from the magnification side, a negative meniscus lens L11 with a convex surface facing the magnification side, a negative meniscus lens L12 with a convex surface facing the magnification side, a negative meniscus lens L13 with a convex surface facing the magnification side, a biconvex positive lens L14, a biconvex positive lens L15, and a biconcave negative lens L16. The first lens group G1 does not include an aspheric surface.

[0081] All lenses having positive refractive power in the first lens group G1 (lenses L14 and L15 in this embodiment) are made of a glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, and TAFD5G (all glass materials manufactured by HOYA Corporation).

[0082] The refractive index of all lenses having positive refractive power in the first lens group G1 (lenses L14 and L15 in this embodiment) for the d-line is less than 1.6. By forming all lenses having positive refractive power in the first lens group G1 from the above-mentioned glass material manufactured by HOYA Corporation, for example, the refractive index of all lenses having positive refractive power in the first lens group G1 for the d-line can be made less than 1.6.

[0083] All the lenses in the first lens group G1 (lenses L11-L16 in this embodiment) are made of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, TAFD5G, E-FD5, E-FD1, BAFD8, and NBFD13 (all glass materials manufactured by HOYA Corporation). All of the lenses having positive refractive power in the first lens group G1 (in this embodiment, lenses L14 and L15) are formed from a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm, so naturally, all of the lenses having positive refractive power in the first lens group G1 among all the lenses in the first lens group G1 satisfy the condition that the lens is formed from a glass material having a transmittance of greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0084] The refractive index of all lenses in the first lens group G1 (lenses L11-L16 in this embodiment) for the d-line is less than 1.75. By forming all lenses in the first lens group G1 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the first lens group G1 for the d-line can be made less than 1.75. Since the refractive index of all lenses having positive refractive power in the first lens group G1 (lenses L14, L15 in this embodiment) for the d-line is less than 1.6, all lenses having positive refractive power in the first lens group G1 among all lenses in the first lens group G1 naturally satisfy the condition that the refractive index of the lens for the d-line is less than 1.75.

[0085] The second lens group G2 is composed of five lenses L21-L25 having refractive power. The second lens group G2 includes two lenses having positive refractive power. Specifically, the second lens group G2 is composed of, in order from the magnification side, a biconcave negative lens L21, a biconvex positive lens L22, a biconcave negative lens L23, a biconcave negative lens L24, and a biconvex positive lens L25. The second lens group G2 does not include an aspheric surface.

[0086] All lenses having positive refractive power in the second lens group G2 (lenses L22 and L25 in this embodiment) are made of a glass material having a transmittance of more than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, and TAFD5G (all glass materials manufactured by HOYA Corporation).

[0087] The refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L22 and L25 in this embodiment) for the d-line is smaller than 1.6. By forming all lenses having positive refractive power in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of the first lens group G2 for the d-line can be reduced. 2 Lens group G 2 The refractive index of all lenses having a positive refractive power in the range of 1.6 or less can be set to be less than 1.6.

[0088] All the lenses in the second lens group G2 (lenses L21-L25 in this embodiment) are made of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm. Examples of such glass materials include FC5, FCD1, PCD4, BSC7, BACD5, TAC8, E-FD2, FF5, NBFD11, TAF1, TAF3, TAFD5G, E-FD5, E-FD1, BAFD8, and NBFD13 (all glass materials manufactured by HOYA Corporation). All of the lenses having positive refractive power in the second lens group G2 (in this embodiment, lenses L22 and L25) are formed from a glass material having a transmittance of greater than 0.98 at a thickness of 10 mm for light having a wavelength of 440 nm, so naturally, all of the lenses having positive refractive power in the second lens group G2 among all the lenses in the second lens group G2 satisfy the condition that the lens is formed from a glass material having a transmittance of greater than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

[0089] The refractive index of all lenses in the second lens group G2 (lenses 21-L25 in this embodiment) for the d-line is less than 1.75. By forming all lenses in the second lens group G2 from the above-mentioned glass material manufactured by HOYA, for example, the refractive index of all lenses having positive refractive power in the second lens group G2 for the d-line can be made less than 1.75. Since the refractive index of all lenses having positive refractive power in the second lens group G2 (lenses L22, L25 in this embodiment) for the d-line is less than 1.6, all lenses having positive refractive power in the second lens group G2 among all lenses in the second lens group G2 naturally satisfy the condition that the refractive index of the lens for the d-line is less than 1.75. EXAMPLES

[0090] The configuration of the variable magnification projection optical system ZL according to the first to fourth embodiments will be described in more detail below with reference to the construction data of the examples. Examples 1 to 4 given here are numerical examples corresponding to the first to fourth embodiments described above, respectively. The configuration diagrams (FIGS. 1 to 4) of the variable magnification projection optical system ZL representing the first to fourth embodiments show the optical configurations (lens arrangement, lens shape, etc.) of the corresponding Examples 1 to 4, respectively.

[0091] In the construction data for each embodiment, the surface data are, from the left column, surface number i, paraxial radius of curvature r (mm), axial surface spacing d (mm), refractive index nd for the d-line (wavelength 587.56 nm), and Abbe number vd for the d-line. Note that SC represents the screen surface, stop represents the aperture stop, and image represents the image display surface.

[0092] As various data of Examples 1-4, the zoom ratio, and the focal length (Fl, mm) of the entire system of the variable magnification projection optical system ZL in each focal length state of the wide-angle end (Wide), the intermediate focal length state (Middle), and the telephoto end (Tele), F-number (Fno.), half angle of view (ω, °), image height (y'max, mm), lens total length (TL, mm), back focus (BF, mm), and variable axial surface interval (variable: di (i: surface number), mm) are shown. In addition, as lens group data, the focal length (mm) of each lens group is shown. Note that the back focus BF is the distance from the final lens surface to the paraxial image surface expressed as the air equivalent length. The lens total length TL is the distance from the lens front surface (the most enlarged side surface of the first lens group G1) to the final lens surface (the most reduced side surface of the sixth lens group G6) plus the back focus BF. In addition, the image height y'max corresponds to half the diagonal length of the image display surface IM.

[0093] Figures 5A to 8 BThe spherical aberration diagrams in show the amount of spherical aberration for the d-line (wavelength 587.56 nm) (shown by a solid line), the amount of spherical aberration for the C-line (wavelength 656.28 nm) (shown by a dashed line), and the amount of spherical aberration for the g-line (wavelength 435.84 nm) (shown by a broken line), each expressed as the deviation (unit: mm) of the focal position in the direction of the optical axis AX from the paraxial image plane. The vertical axis shows the value obtained by normalizing the incidence height to the pupil by its maximum height (i.e., the relative pupil height). B In the astigmatism diagrams of FIG. 5A to FIG. 8, the dashed line T represents the tangential image plane for the d-line, as a deviation (unit: mm) of the focal position in the direction of the optical axis AX from the paraxial image plane, and the solid line S represents the sagittal image plane for the d-line, as a deviation (unit: mm) of the focal position in the direction of the optical axis AX from the paraxial image plane. The vertical axis represents the image height (IMG HT, unit: mm). B In the distortion diagram of FIG. 1, the horizontal axis represents distortion (unit: %) for the d-line, and the vertical axis represents image height (IMG HT, unit: mm).

[0094] Numerical Example 1 Unit: mm Surface Data ird nd vd object(SC) infinity 3800.000 1 106.581 6.500 1.62299 58.12 2 63.433 16.118 3 97.699 5.200 1.72916 54.67 4 51.928 24.530 5 242.462 4.300 1.59282 68.62 6 66.885 15.796 7 248.848 15.788 1.58144 40.89 8 -99.187 6.300 9 191.181 4.123 1.67270 32.17 10 60.687 5.886 11 70.334 25.210 1.51680 64.20 12 -67.549 0.300 13 -524.049 3.000 1.72916 54.67 14 54.291 variable 15 989.335 7.519 1.51680 64.20 16 -51.381 1.857 17 -62.834 2.100 1.80610 33.27 18 110.132 5.877 19 -103.401 2.246 1.59282 68.62 20 101.746 2.708 21 117.780 7.555 1.58144 40.89 22 -84.602 variable 23 -390.397 5.542 1.54072 47.20 24 -74.782 0.769 25 59.464 6.259 1.74330 49.22 26 343.396 variable 27 -91.179 1.800 1.43700 95.10 28 34.024 9.878 29 -71.362 1.604 1.43700 95.10 30 83.948 1.294 31 56.653 5.688 1.56732 42.84 32 -72.825 variable 33 (stop) infinity 23.800 34 -43.788 6.025 1.43700 95.10 35 -26.929 2.765 36 -24.924 1.800 1.80420 46.50 37 -49.585 0.858 38 -351.166 5.757 1.43700 95.10 39 -48.772 1.462 40 129.382 8.077 1.43700 95.10 41 -52.148 1.374 42 -259.563 2.000 1.80610 40.73 43 47.611 2.645 44 54.167 8.694 1.43700 95.10 45 -76.885 variable 46 81.437 5.892 1.61997 63.88 47 -333.642 13.500 48 infinity 70.000 1.51680 64.20 49 infinity 4.000 50 infinity 3.000 1.48749 70.44 51 infinity 1.500 image infinity Various data Zoom ratio 1.46 Wide Middle Tele Fl 13.115 16.121 19.127 Fno. 2.354 2.425 2.490 ω 41.693 35.807 31.248 y'max 11.650 11.650 11.650 TL 429.225 429.203 429.184 BF 67.225 67.203 67.184 d14 30.335 32.948 29.249 d22 20.934 9.092 3.356 d26 4.751 16.737 27.004 d32 33.084 21.150 12.014 d45 6.000 15.177 23.480 Lens Group Data Group (plane) focal length 1 ( 1- 14) -54.978 2 ( 15- 22) -131.885 3 ( 23- 26) 61.107 4 ( 27- 32) -118.103 5 ( 33- 45) 169.316 6 ( 46- 51) 106.162

[0095] Numerical Example 2 Unit: mm Surface Data ird nd vd object(SC) infinity 3800.000 1 107.210 6.500 1.62299 58.12 2 62.359 15.750 3 95.185 5.200 1.72916 54.67 4 51.122 23.976 5 222.503 4.300 1.59282 68.62 6 65.774 15.616 7 266.825 15.299 1.58144 40.89 8 -97.746 6.300 9 184.501 3.900 1.67270 32.17 10 60.532 5.877 11 70.322 24.966 1.51680 64.20 12 -66.665 0.300 13 -530.147 3.000 1.72916 54.67 14 54.117 variable 15 973.821 7.621 1.51680 64.20 16 -51.054 1.848 17 -62.473 2.100 1.80610 33.27 18 108.891 6.261 19 -95.303 2.361 1.59282 68.62 20 117.009 2.714 21 134.391 7.654 1.58144 40.89 22 -79.139 variable 23 -570.068 5.676 1.54072 47.20 24 -81.618 4.377 25 60.963 6.287 1.74330 49.22 26 481.042 variable 27 -95.349 1.800 1.43700 95.10 28 33.073 8.783 29 -70.043 1.600 1.43700 95.10 30 85.656 1.194 31 55.035 5.642 1.56732 42.84 32 -76.211 variable 33 (stop) infinity 23.482 34 -45.852 6.041 1.43700 95.10 35 -27.383 2.773 36 -25.258 1.800 1.80420 46.50 37 -51.545 1.050 38 -283.941 5.776 1.43700 95.10 39 -47.115 1.321 40 127.283 8.082 1.43700 95.10 41 -52.227 1.414 42 -245.814 2.000 1.80610 40.73 43 47.646 2.649 44 54.324 8.631 1.43700 95.10 45 -78.499 variable 46 76.417 5.993 1.61997 63.88 47 -383.554 13.500 48 infinity 70.000 1.51680 64.20 49 infinity 4.000 50 infinity 3.000 1.48749 70.44 51 infinity 1.500 image infinity Various data Zoom ratio 1.46 Wide Middle Tele Fl 13.111 16.115 19.120 Fno. 2.346 2.424 2.490 ω 41.737 35.876 31.321 y'max 11.650 11.650 11.650 TL 429.226 429.199 429.184 BF 67.226 67.199 67.184 d14 28.411 29.840 26.476 d22 22.016 9.889 3.653 d26 4.675 15.373 24.973 d32 32.987 22.456 13.668 d45 6.000 16.532 25.319 Lens Group Data Group (plane) focal length 1 ( 1- 14) -55.137 2 ( 15- 22) -134.342 3 ( 23- 26) 61.664 4 ( 27- 32) -112.294 5 ( 33- 45) 177.224 6 ( 46- 51) 103.297

[0096] Numerical Example 3 Unit: mm Surface Data ird nd vd object(SC) infinity 3800.000 1 107.961 6.500 1.62299 58.12 2 63.012 16.130 3 97.716 5.200 1.72916 54.67 4 51.627 23.623 5 198.650 4.300 1.59282 68.62 6 67.006 15.763 7 262.938 15.397 1.58144 40.89 8 -99.819 6.300 9 192.621 3.900 1.67270 32.17 10 60.224 5.869 11 69.713 25.005 1.51680 64.20 12 -67.218 0.300 13 -506.317 3.000 1.72916 54.67 14 54.644 variable 15 infinity 2.500 1.49700 81.61 16 258.251 3.775 17 191.145 8.483 1.51680 64.20 18 -52.042 1.899 19 -63.124 2.100 1.80610 33.27 20 100.730 6.445 21 -92.181 2.219 1.59282 68.62 22 126.471 2.627 23 142.856 7.402 1.58144 40.89 24 -83.590 variable 25 -651.420 5.728 1.54072 47.20 26 -77.174 3.180 27 62.457 6.321 1.74330 49.22 28 614.290 variable 29 -91.827 1.800 1.43700 95.10 30 33.223 9.085 31 -69.012 1.601 1.43700 95.10 32 88.747 1.192 33 55.969 5.658 1.56732 42.84 34 -74.304 variable 35 (stop) infinity 23.791 36 -45.630 6.055 1.43700 95.10 37 -27.250 2.755 38 -25.217 1.800 1.80420 46.50 39 -51.423 1.104 40 -252.790 5.670 1.43700 95.10 41 -47.734 1.215 42 113.932 8.190 1.43700 95.10 43 -53.039 1.380 44 -272.111 2.000 1.80610 40.73 45 46.953 2.642 46 53.365 8.693 1.43700 95.10 47 -78.197 variable 48 81.410 5.907 1.61997 63.88 49 -330.390 13.500 50 infinity 70.000 1.51680 64.20 51 infinity 4.000 52 infinity 3.000 1.48749 70.44 53 infinity 1.500 image infinity Various data Zoom ratio 1.46 Wide Middle Tele Fl 13.113 16.118 19.123 Fno. 2.353 2.425 2.490 ω 41.715 35.811 31.251 y'max 11.650 11.650 11.650 TL 429.225 429.203 429.186 BF 67.225 67.203 67.186 d14 22.145 24.285 20.709 d24 21.301 9.926 4.230 d28 4.553 16.065 25.954 d34 33.496 21.907 12.948 d47 6.000 15.313 23.654 Lens Group Data Group (plane) focal length 1 ( 1- 14) -55.870 2 ( 15- 24) -118.362 3 ( 25- 28) 59.560 4 ( 29- 34) -113.275 5 ( 35- 47) 169.970 6 ( 48- 53) 105.935

[0097] Numerical Example 4 Unit: mm Surface Data ird nd vd object(SC) infinity 3800.000 1 112.890 6.500 1.62299 58.12 2 63.068 18.977 3 120.349 5.200 1.72916 54.67 4 59.947 20.429 5 209.639 4.300 1.59282 68.62 6 69.702 16.703 7 1517.502 13.003 1.58144 40.89 8 -97.910 23.938 9 1045.425 14.198 1.51680 64.20 10 -74.463 0.300 11 -5265.796 3.000 1.72916 54.67 12 52.869 variable 13 -1627.519 2.500 1.49700 81.61 14 160.916 2.980 15 49.859 11.345 1.51680 64.20 16 -83.131 1.970 17 -120.761 2.100 1.80610 33.27 18 46.905 7.943 19 -143.608 2.200 1.59282 68.62 20 174.189 2.341 21 99.143 6.745 1.58144 40.89 22 -193.655 variable 23 85687.816 6.749 1.54072 47.20 24 -81.222 13.905 25 69.670 6.045 1.74330 49.22 26 -5194.753 variable 27 -84.762 1.800 1.43700 95.10 28 36.165 9.563 29 -71.338 1.600 1.43700 95.10 30 74.847 1.504 31 57.510 5.556 1.56732 42.84 32 -75.992 variable 33 (stop) infinity 23.945 34 -51.907 5.167 1.43700 95.10 35 -28.243 2.819 36 -25.918 1.800 1.80420 46.50 37 -55.299 1.330 38 -239.255 5.388 1.43700 95.10 39 -51.034 1.122 40 92.414 8.406 1.43700 95.10 41 -54.526 1.201 42 -483.006 2.000 1.80610 40.73 43 43.678 3.337 44 51.078 8.814 1.43700 95.10 45 -81.064 variable 46 102.319 5.813 1.61997 63.88 47 -193.965 13.500 48 infinity 70.000 1.51680 64.20 49 infinity 4.000 50 infinity 3.000 1.48749 70.44 51 infinity 1.500 image infinity Various data Zoom ratio 1.46 Wide Middle Tele Fl 13.115 16.121 19.127 Fno. 2.355 2.422 2.490 ω 41.635 35.792 31.250 y'max 11.650 11.650 11.650 TL 429.231 429.208 429.186 BF 67.231 67.208 67.186 d12 18.577 23.293 19.958 d22 24.786 11.372 5.060 d26 4.441 16.088 25.528 d32 23.594 12.373 4.219 d45 6.067 14.339 22.699 Lens Group Data Group (plane) focal length 1 ( 1- 12) -51.324 2 ( 13- 22) -139.667 3 ( 23- 26) 60.734 4 ( 27- 32) -106.549 5 ( 33- 45) 160.528 6 ( 46- 51) 108.862

[0098] Table 1 shows the values ​​for each example. [Table 1]

[0099] <Projection device> A projection device 1 according to an embodiment will be described with reference to Fig. 9. As shown in Fig. 9, the projection device 1 includes a light source 3, an illumination optical system 5, a reflecting mirror 6, a prism PR, a cover glass CG, an image display element 7, a variable magnification projection optical system ZL, an actuator 8, and a control unit 9. The variable magnification projection optical system ZL is any one of the variable magnification projection optical systems ZL according to the first to fourth embodiments.

[0100] The light source 3 is, for example, a white light source such as a xenon lamp, or a laser light source. The image display element 7 is, for example, a digital micromirror device (DMD) or a liquid crystal display element (LCD). A cover glass CG is provided on an image display surface IM of the image display element 7. The actuator 8 can move a movable lens group for zooming or focusing along an optical axis AX of the variable magnification projection optical system ZL. The control unit 9 controls the projection device 1. The control unit 9 controls, for example, the image display element 7 and the actuator 8. The control unit 9 controls the actuator to move a movable lens group for zooming or focusing.

[0101] Illumination light emitted from the light source 3 is incident on the image display element 7 via the illumination optical system 5, the reflecting mirror 6, and the prism PR. The image display element 7 modulates the illumination light and reflects the image light. The prism PR is, for example, a TIR prism or a color separation / combining prism. The variable magnification projection optical system ZL enlarges and projects the image light formed by the image display element 7 onto the screen surface SC. On the optical axis AX of the variable magnification projection optical system ZL, the distance between the variable magnification projection optical system ZL and the screen surface SC is, for example, 1 m or more and 3 m or less.

[0102] The movable lens group may be moved manually without using the actuator 8. In addition, when the image display element 7 is a self-luminous image display element, the light source 3, the illumination optical system 5, and the reflecting mirror 6 may be omitted.

[0103] Although the embodiments and examples have been described, the embodiments and examples disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present disclosure is defined by the claims, and it is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0104] 1 projection device, 3 light source, 5 illumination optical system, 6 reflecting mirror, 7 image display element, 8 actuator, 9 control unit, L11, L12, L13, L14, L15, L16, L17, L21, L22, L23, L24, L25, L31, L32, L41, L42, L43, L51, L52, L53, L54, L55, L56, L61 lens, AX optical axis, CG cover glass, G1 first lens group, G2 second lens group, G3 third lens group, G4 fourth lens group, G5 fifth lens group, G6 sixth lens group, IM image display surface, PR prism, SC screen surface, ZL variable magnification projection optical system.

Claims

1. A variable magnification projection optical system that enlarges and projects an image displayed on an image display surface, comprising: The variable magnification projection optical system includes, in order from the magnification side, a first lens group having negative refractive power; a second lens group having negative refractive power; a third lens group having a positive refractive power, During magnification change, the first lens group is fixed, and the second lens group and the third lens group are moved, the second lens group includes a plurality of lenses having positive refractive power; all lenses having positive refractive power in the first lens group and the second lens group are formed of a glass material having a transmittance greater than 0.989 at a thickness of 10 mm for light having a wavelength of 440 nm.

2. 2. The variable magnification projection optical system according to claim 1, wherein all lenses in said first lens group are formed from a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

3. 3. The variable magnification projection optical system according to claim 1, wherein all lenses in the first lens group and the second lens group are formed of a glass material having a transmittance of more than 0.97 at a thickness of 10 mm for light having a wavelength of 440 nm.

4. 4. The variable magnification projection optical system according to claim 1, wherein the first lens group is made up of seven or less lenses having a refractive power.

5. 5. The variable magnification projection optical system according to claim 1, wherein the second lens group is made up of four or more lenses having a refractive power.

6. 6. The variable magnification projection optical system according to claim 1, further comprising at least one lens group that is disposed on the reduction side of the third lens group and moves along an optical axis of the variable magnification projection optical system during magnification variation.

7. The variable magnification projection optical system according to claim 1 , wherein the first lens group does not include an aspheric surface.

8. The variable magnification projection optical system according to claim 1 , wherein the variable magnification projection optical system does not include an aspheric surface.

9. an image display element having the image display surface; A projection apparatus comprising the variable magnification projection optical system according to claim 1 .

Images