Optical system, image projection device, and image pickup device

Abstract

The present disclosure is an optical system having an intermediate imaging position which is conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, inside, the optical system comprising: a magnification optical system having a plurality of lens elements located on a position closer to the magnification side than the intermediate imaging position; and a relay optical system having a plurality of lens elements located on a position closer to the reduction side than the intermediate imaging position. A first lens element located on a position closest to the magnification side among the plurality of lens elements in the magnification optical system is an aspherical lens having a negative refractive power, and satisfies the following conditions (1) to (3), 0.0055 < Δpgfn < 0.030 … (1), 53 < vdn < 58 … (2), 0.28 < fp / fr < 1.0 … (3).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an optical system that forms an intermediate image. Furthermore, the present disclosure relates to an image projection apparatus and an image pickup apparatus that use such an optical system. BACKGROUND

[0002] An optical system of an intermediate imaging type has an advantage of a short focal point and enables wide-angle projection of a large screen, but has a tendency that the overall length of the optical system becomes large. Therefore, the optical system becomes heavy, and in a case where a part of the optical system is mounted outside a housing of a main body of an image projection apparatus, the optical system can be inclined with respect to the apparatus main body due to a moment acting on the center of gravity, and the optical performance is reduced.

[0003] In order to reduce the weight of the optical system, use of a synthetic resin lens is assumed instead of a glass lens. The specific gravity of the synthetic resin is smaller than that of the glass, but the thermal conductivity is small and the linear expansion coefficient is large. Therefore, although the optical system can be made light, there is a tendency that local temperature rise, thermal deformation, and increase in optical aberration, particularly chromatic aberration, occur. This tendency is particularly significant in the case of high-brightness projection.

[0004] Patent Literature 1 discloses a wide-angle imaging optical system, and a first lens L1a closest to a magnification conjugate point has the largest aperture. Both surfaces of the first lens L1a are aspherical surfaces, and are very complex shapes, and therefore it is inferred that a synthetic resin lens is used. However, such a complex aspherical surface shape is very sensitive to thermal deformation, and it is expected that deterioration of optical aberration due to temperature rise is significant.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2019-174633 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The present disclosure provides an optical system that can reduce a moment acting on the center of gravity. Furthermore, the present disclosure provides an image projection apparatus and an image pickup apparatus that use such an optical system.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] One embodiment of the present disclosure is an optical system that has an intermediate imaging position that is conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, inside, and the optical system includes:

[0012] The magnification optical system has a plurality of lens elements at a position closer to the magnification side than the intermediate imaging position.

[0013] a relay optical system having a plurality of lens elements positioned at a position closer to the reduction side than the intermediate imaging position,

[0014] a first lens element positioned at a position closest to the magnification side among the plurality of lens elements in the magnification optical system is an aspherical lens having a negative refractive power,

[0015] conditions (1) to (3) below are satisfied,

[0016] 0.0055 < Δpgfn < 0.030... (1)

[0017] 53 < vdn < 58... (2)

[0018] 0.28 < fp / fr < 1.0... (3)

[0019] Here,

[0020] Δpgfn = (ngn - nfn) / (nfn - ncn) - (-2.20599 x 10 -3 vdn + 6.69612 x 10 -1 )

[0021] vdn: Abbe number of the first lens element

[0022] ngn: refractive index with respect to g-line of the first lens element

[0023] nfn: refractive index with respect to F-line of the first lens element

[0024] ncn: refractive index with respect to C-line of the first lens element

[0025] fp: focal length of the magnification optical system

[0026] fr: focal length of the relay optical system at the wide-angle end.

[0027] Further, an image projection device according to the present disclosure includes the optical system described above, and an image forming element that generates an image projected to a screen via the optical system.

[0028] Further, an image pickup device according to the present disclosure includes the optical system described above, and an image pickup element that photoelectrically converts an optical image formed by the optical system.

[0029] -Effects of Invention-

[0030] With the optical system according to the present disclosure, the moment acting on the center of gravity can be reduced, and the influence of heat can be mitigated. Thus, stable optical performance can be maintained even in the case where light of high intensity passes through the lens, for example, in the case of high-brightness projection. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a configuration diagram of an optical path at a wide-angle end of a zoom lens system of Embodiment 1 at an object distance of 1066 mm.

[0032] Figure 2 is a configuration diagram of a wide-angle end of a zoom lens system of Embodiment 1 at an object distance of 1066 mm.

[0033] Figure 3 is a longitudinal aberration diagram of a zoom lens system of Embodiment 1 at an object distance of 1066 mm.

[0034] Figure 4 is a configuration diagram of an optical path at a wide-angle end of a zoom lens system of Embodiment 2 at an object distance of 1066 mm.

[0035] Figure 5 is a configuration diagram of a wide-angle end of a zoom lens system of Embodiment 2 at an object distance of 1066 mm.

[0036] Figure 6 is a longitudinal aberration diagram of a zoom lens system of Embodiment 2 at an object distance of 1066 mm.

[0037] Figure 7 is a configuration diagram of an optical path at a wide-angle end of a zoom lens system of Embodiment 3 at an object distance of 1066 mm.

[0038] Figure 8 is a configuration diagram of a wide-angle end of a zoom lens system of Embodiment 3 at an object distance of 1066 mm.

[0039] Figure 9 is a longitudinal aberration diagram of a zoom lens system of Embodiment 3 at an object distance of 1066 mm.

[0040] Figure 10 is a configuration diagram of an optical path at a wide-angle end of a zoom lens system of Embodiment 4 at an object distance of 1066 mm.

[0041] Figure 11 is a configuration diagram of a wide-angle end of a zoom lens system of Embodiment 4 at an object distance of 1066 mm.

[0042] Figure 12 is a longitudinal aberration diagram of a zoom lens system of Embodiment 4 at an object distance of 1066 mm.

[0043] Figure 13 is a configuration diagram of an optical path of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 5.

[0044] Figure 14 is a configuration diagram of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 5.

[0045] Figure 15 is a longitudinal aberration diagram at an object distance of 1066 mm of the zoom lens system of Example 5.

[0046] Figure 16 is a configuration diagram of an optical path of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 6.

[0047] Figure 17 is a configuration diagram of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 6.

[0048] Figure 18 is a longitudinal aberration diagram at an object distance of 1066 mm of the zoom lens system of Example 6.

[0049] Figure 19 is a configuration diagram of an optical path of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 7.

[0050] Figure 20 is a configuration diagram of a wide-angle end at an object distance of 1066 mm of the zoom lens system of Example 7.

[0051] Figure 21 is a longitudinal aberration diagram at an object distance of 1066 mm of the zoom lens system of Example 7.

[0052] Figure 22 is a block diagram showing one example of an image projection apparatus to which the present disclosure is applied.

[0053] Figure 23 is a block diagram showing one example of an image projection apparatus to which the present disclosure is applied. DETAILED DESCRIPTION

[0054] Hereinafter, the embodiments will be described in detail with appropriate reference to the accompanying drawings. In the drawings, non-essential detailed description can be omitted. For example, detailed description of known matters or repetitive description of substantially the same structure can be omitted. This is to avoid the following description from becoming unnecessarily redundant and to make it easy for those skilled in the art to understand.

[0055] In addition, the applicant provides the accompanying drawings and the following description in order for those skilled in the art to fully understand the present disclosure, and does not intend to limit the subject matter of the claims by these.

[0056] Hereinafter, various embodiments of the optical system disclosed herein will be described. In each embodiment, the optical system is described as a projector (an example of an image projection device) that projects an original image S, which is spatially modulated by an image forming element such as a liquid crystal or a DMD (digital micromirror device), onto a screen based on an image signal. That is, the optical system disclosed herein can be used to enlarge and project an original image S, which is disposed on an image forming element disposed on a reduction side, onto the screen by arranging a screen (not shown) on an extension line of the magnification side.

[0057] Furthermore, the optical system disclosed herein can also be used to focus light emitted from an object located on the extension line of the magnification side and form an optical image of the object on the imaging surface of the imaging element disposed on the reduction side.

[0058] (Implementation Method 1)

[0059] The following uses Figures 1-21 Embodiment 1 of this disclosure will now be described. Here, as an example of an optical system, a zoom lens system will be described.

[0060] Figure 1 , 4 7, 10, 13, 16, and 19 are optical path configuration diagrams showing the wide-angle end of the zoom lens system according to Examples 1 to 7 at an object distance of 1066 mm. Figure 2 , 5 Figures 8, 11, 14, 17, and 20 are configuration diagrams of the wide-angle end of the zoom lens system involved in Examples 1 to 7 at an object distance of 1066 mm. Figure 2 of (a), Figure 5 of (a), Figure 8 of (a), Figure 11 of (a), Figure 14 of (a), Figure 17 of (a), Figure 20 (a) shows the lens configuration at the wide-angle end of the zoom lens system. Figure 2 (b) Figure 5 (b) Figure 8 (b) Figure 11 (b) Figure 14 (b) Figure 17 (b) Figure 20 (b) represents the lens configuration at the middle position of the zoom lens system. Figure 2 (c) Figure 5 (c) Figure 8 (c) Figure 11 (c) Figure 14 (c) Figure 17 (c)Figure 20 (c) represents the lens configuration at the telephoto end of the zoom lens system.

[0061] The wide-angle end represents the shortest focal length (fw) of the entire system. The intermediate position represents the focal length between the wide-angle and telephoto ends. The telephoto end represents the longest focal length (ft) of the entire system. Based on the focal lengths fw and ft at the wide-angle and telephoto ends, the focal length fm at the intermediate position is defined as √(fw × ft).

[0062] The zoom lens system described in Example 1 includes a first lens group G1 to a fourth lens group G4 and an optical element P. The first lens group G1 has positive optical power and includes first lens elements L1 to 15th lens elements L15, and includes surfaces 1 to 30 (refer to the numerical examples described later). The second lens group G2 has positive optical power and includes 16th lens elements L16 to 18th lens elements L18, and includes surfaces 31 to 36. The third lens group G3 has negative optical power and includes 19th lens elements L19 to 22nd lens elements L22, and includes surfaces 37 to 45. The fourth lens group G4 has positive optical power and includes 23rd lens elements L23 to 25th lens elements L25, and includes surfaces 46 to 51. The optical element P includes surfaces 52 and 53.

[0063] The zoom lens system involved in Example 2 includes a first lens group G1 to a fourth lens group G4 and an optical element P. Since it is the same as in Example 1, the description is omitted.

[0064] The zoom lens system described in Example 3 includes a first lens group G1 to a fourth lens group G4 and an optical element P. The first lens group G1 has positive optical power and includes first lens elements L1 to sixteenth lens elements L16, and includes surfaces 1 to 32 (refer to the numerical examples described later). The second lens group G2 has positive optical power and includes 17th lens elements L17 to 19th lens elements L19, and includes surfaces 33 to 38. The third lens group G3 has negative optical power and includes 20th lens elements L20 to 23rd lens elements L23, and includes surfaces 39 to 47. The fourth lens group G4 has positive optical power and includes 24th lens elements L24 to 26th lens elements L26, and includes surfaces 48 to 53. The optical element P includes surfaces 54 to 55.

[0065] The arrow of the broken line illustrated between (a) of each figure and (b) of each figure is a straight line connecting the positions of the first lens group G1 to the fourth lens group G4 in each state of the wide-angle end, the intermediate position, and the telephoto end in order from the upper side in the figure. The wide-angle end and the intermediate position, and the intermediate position and the telephoto end are connected simply by a straight line, and are different from the movement of the actual lens groups G1 to G4. Further, the signs (+), (-) given to the symbols of each lens group G1 to G4 indicate the positive and negative of the power of each lens group G1 to G4.

[0066] The zoom lens system according to Embodiments 1 to 7 can also include, as needed, a focus adjustment lens group that performs focus adjustment when the object distance changes, and an image surface curvature correction lens group that performs correction of image surface curvature aberration after the focus adjustment lens group has performed focus adjustment.

[0067] In each figure, the imaging position on the magnification side (i.e., the magnification conjugate point) is on the left side, and the imaging position on the reduction side (i.e., the reduction conjugate point) is on the right side. Further, in each figure, the straight line written on the most reduction side indicates the position of the original image S, and the optical element P is on the magnification side of the original image S. The optical element P indicates a prism for color separation and color synthesis, an optical filter, a parallel flat glass, a crystal low-pass filter, an infrared cut filter, and the like.

[0068] The zoom lens system according to Embodiments 1 to 7 has, inside, an intermediate imaging position MI that is conjugate to the magnification conjugate point on the magnification side and the reduction conjugate point on the reduction side, respectively. Further, in each figure, the magnification optical system Op is disposed on the magnification side of the intermediate imaging position MI, and the relay optical system Ol is disposed on the reduction side of the intermediate imaging position MI.

[0069] In the zoom lens system according to Embodiments 1 to 7, there are a plurality of air intervals between the first lens element L1 to the twenty-fifth lens element L25 (the twenty-sixth lens element L26) and the optical element P. The magnification optical system Op has the longest air interval along the optical axis inside the magnification optical system. For example, in Embodiments 1 and 2, as shown in Figure 2 , Figure 5 , there is the longest air interval between the tenth lens element L10 and the eleventh lens element L11. In Embodiment 3, as shown in Figure 8 , there is the longest air interval between the eleventh lens element L11 and the twelfth lens element L12. The magnification optical system Op has a front group Opf disposed at a position on the magnification side of the longest air interval, and a rear group Opr disposed at a position on the reduction side of the longest air interval. The front group Opf and the rear group Opr can also have a single or a plurality of lens elements.

[0070] Figure 3 ,Figure 6 , Figure 9 , Figure 12 , Figure 15 , Figure 18 , Figure 21 These are longitudinal aberration diagrams of the zoom lens system described in Examples 1-7 at an object distance of 1066 mm. In each diagram, (a), (b), and (c) represent the longitudinal aberration diagrams at the wide-angle end, the intermediate position, and the telephoto end of the zoom lens system.

[0071] The vertical aberration diagrams, from left to right, represent spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion aberration (DIS (%)). In the spherical aberration diagram, the vertical axis represents the pupil height; the solid line is the d-line, the short dashed line is the F-line, and the long dashed line is the C-line. In the astigmatism diagram, the vertical axis represents the image height; the solid line is the sagittal plane (shown as 's' in the diagram), and the dashed line is the meridional plane (shown as 'm' in the diagram). In the distortion aberration diagram, the vertical axis represents the image height. Furthermore, the distortion aberration diagram represents the distortion aberration for equidistant projections.

[0072] (Example 1)

[0073] like Figure 1 , 2 As shown, the zoom lens system according to Embodiment 1 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a twelfth lens element L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0074] The front group Opf of the magnifying optical system Op includes, from the magnifying side to the reducing side, lens elements L1 to L10 in sequence. Lens element L1 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L2 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L3 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L4 has a biconcave shape. Lens element L5 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L6 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L7 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L8 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L9 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L10 has a positive meniscus shape with its convex surface facing the reducing side.

[0075] The rear group Opr of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes 11th lens element L11 to 12th lens element L12. The 11th lens element L11 has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface facing the magnifying side.

[0076] The relay optical system Ol, from the magnification side to the reduction side, sequentially includes lens elements L13 to L25, numbered 13 to 25. Lens element L13 has a biconcave shape. Lens element L14 has a biconcave shape. Lens element L15 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L16 has a biconvex shape. Lens element L17 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L18 has a biconvex shape. Lens element L19 has a biconvex shape. Lens element L20 has a biconcave shape. Lens element L21 has a biconcave shape. Lens element L22 has a biconvex shape. Lens element L23 has a biconvex shape. Lens element L24 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L25 has a biconvex shape.

[0077] The relay optical system Ol, from the magnification side to the reduction side, sequentially comprises: a first lens group (L13-L15) with negative optical power, a second lens group (L16-L18) with positive optical power, a third lens group (L19-L22) with negative optical power, and a fourth lens group (L23-L25) with positive optical power. During zooming, the first and third lens groups are fixed, while the second and fourth lens groups are displaced along the optical axis.

[0078] As an example, the first lens element L1 corresponds to the first lens element in the claims.

[0079] An intermediate imaging position MI is located between the 12th lens element L12 and the 13th lens element L13. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-angle side of the relay optical system Ol.

[0080] (Example 2)

[0081] like Figure 4 , 5 As shown, the zoom lens system according to Embodiment 2 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a twelfth lens element L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0082] The front group Opf of the magnification optical system Op includes the 1st to 10th lens elements Ll to LlO in order from the magnification side to the reduction side. The 1st lens element Ll has a negative meniscus shape with the convex surface toward the magnification side. The 2nd lens element L2 has a negative meniscus shape with the convex surface toward the magnification side. The 3rd lens element L3 has a negative meniscus shape with the convex surface toward the magnification side. The 4th lens element L4 has a biconvex shape. The 5th lens element L5 has a positive meniscus shape with the convex surface toward the reduction side. The 6th lens element L6 has a positive meniscus shape with the convex surface toward the reduction side. The 7th lens element L7 has a negative meniscus shape with the convex surface toward the reduction side. The 8th lens element L8 has a positive meniscus shape with the convex surface toward the reduction side. The 9th lens element L9 has a positive meniscus shape with the convex surface toward the reduction side. The 10th lens element LlO has a biconvex shape.

[0083] The rear group Opr of the magnification optical system Op includes the 11th and 12th lens elements Ll l and L12 in order from the magnification side to the reduction side. The 11th lens element Ll l has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface toward the magnification side.

[0084] The relay optical system Ol includes the 13th to 25th lens elements L13 to L25 in order from the magnification side to the reduction side. The 13th lens element L13 has a biconcave shape. The 14th lens element L14 has a biconcave shape. The 15th lens element L15 has a biconvex shape. The 16th lens element L16 has a biconvex shape. The 17th lens element L17 has a biconcave shape. The 18th lens element L18 has a biconvex shape. The 19th lens element L19 has a positive meniscus shape with the convex surface toward the magnification side. The 20th lens element L20 has a negative meniscus shape with the convex surface toward the magnification side. The 21st lens element L21 has a biconcave shape. The 22nd lens element L22 has a biconvex shape. The 23rd lens element L23 has a biconvex shape. The 24th lens element L24 has a negative meniscus shape with the convex surface toward the magnification side. The 25th lens element L25 has a biconvex shape.

[0085] The relay optical system Ol includes, in order from the magnification side to the reduction side, a 1st lens group (L13 to L15) having a negative optical power, a 2nd lens group (L16 to L18) having a positive optical power, a 3rd lens group (L19 to L22) having a negative optical power, and a 4th lens group (L23 to L25) having a positive optical power. At zooming, the 1st lens group and the 3rd lens group are fixed, and the 2nd lens group and the 4th lens group are displaced along the optical axis.

[0086] As one example, the 1st lens element Ll corresponds to the 1st lens element in the claims.

[0087] An intermediate imaging position MI is located between the 12th lens element L12 and the 13th lens element L13. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-angle side of the relay optical system Ol.

[0088] (Example 3)

[0089] like Figure 7 , 8 As shown, the zoom lens system according to Embodiment 3 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a thirteenth lens element L13. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0090] The front group Opf of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes lens elements L1 to L11, numbered 1st to 11th. Lens element L1 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L2 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L3 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L4 has a biconcave shape. Lens element L5 has a biconvex shape. Lens element L6 has a biconcave shape. Lens element L7 has a biconvex shape. Lens element L8 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L9 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L10 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L11 has a biconvex shape.

[0091] The rear group Opr of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes lens elements L12 to L13. Lens element L12 has a biconvex shape. Lens element L13 has a positive meniscus shape with the convex surface facing the magnifying side.

[0092] The relay optical system Ol, from the magnification side to the reduction side, sequentially includes lens elements L14 to L26, numbered 14 to 26. Lens element L14 has a biconcave shape. Lens element L15 has a biconcave shape. Lens element L16 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L17 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L18 has a biconvex shape. Lens element L19 has a biconvex shape. Lens element L20 has a biconvex shape. Lens element L21 has a biconcave shape. Lens element L22 has a biconcave shape. Lens element L23 has a biconvex shape. Lens element L24 has a biconvex shape. Lens element L25 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L26 has a biconvex shape.

[0093] The relay optical system Ol, from the magnification side to the reduction side, sequentially comprises: a first lens group (L14–L16) with negative optical power, a second lens group (L17–L19) with positive optical power, a third lens group (L20–L23) with negative optical power, and a fourth lens group (L24–L26) with positive optical power. During zooming, the first and third lens groups are fixed, while the second and fourth lens groups are displaced along the optical axis.

[0094] As an example, the first lens element L1 corresponds to the first lens element in the claims.

[0095] An intermediate imaging position MI is located between the 13th lens element L13 and the 14th lens element L14. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-focus side of the relay optical system Ol.

[0096] (Example 4)

[0097] like Figure 10 , 11 As shown, the zoom lens system according to Embodiment 4 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes first lens elements L1 to twelfth lens elements L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0098] The front group Opf of the magnification optical system Op includes the 1st to 10th lens elements Ll to LlO in this order from the magnification side to the reduction side. The 1st lens element Ll has a negative meniscus shape with the convex surface toward the magnification side. The 2nd lens element L2 has a negative meniscus shape with the convex surface toward the magnification side. The 3rd lens element L3 has a negative meniscus shape with the convex surface toward the magnification side. The 4th lens element L4 has a biconcave shape. The 5th lens element L5 has a positive meniscus shape with the convex surface toward the reduction side. The 6th lens element L6 has a positive meniscus shape with the convex surface toward the reduction side. The 7th lens element L7 has a negative meniscus shape with the convex surface toward the reduction side. The 8th lens element L8 has a positive meniscus shape with the convex surface toward the reduction side. The 9th lens element L9 has a positive meniscus shape with the convex surface toward the reduction side. The 10th lens element LlO has a positive meniscus shape with the convex surface toward the reduction side.

[0099] The rear group Opr of the magnification optical system Op includes the 11th and 12th lens elements Ll l and L12 in this order from the magnification side to the reduction side. The 11th lens element Ll l has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface toward the magnification side.

[0100] The relay optical system Ol includes the 13th to 25th lens elements L13 to L25 in this order from the magnification side to the reduction side. The 13th lens element L13 has a biconcave shape.

[0101] The 14th lens element L14 has a biconcave shape. The 15th lens element L15 has a positive meniscus shape with the convex surface toward the reduction side. The 16th lens element L16 has a positive meniscus shape with the convex surface toward the reduction side. The 17th lens element L17 has a negative meniscus shape with the convex surface toward the reduction side. The 18th lens element L18 has a biconvex shape. The 19th lens element L19 has a biconvex shape. The 20th lens element L20 has a biconcave shape. The 21st lens element L21 has a biconcave shape. The 22nd lens element L22 has a biconvex shape. The 23rd lens element L23 has a biconvex shape. The 24th lens element L24 has a negative meniscus shape with the convex surface toward the magnification side. The 25th lens element L25 has a biconvex shape.

[0102] The relay optical system Ol includes, in this order from the magnification side to the reduction side, a 1st lens group (L13 to L15) having a negative optical power, a 2nd lens group (L16 to L18) having a positive optical power, a 3rd lens group (L19 to L22) having a negative optical power, and a 4th lens group (L23 to L25) having a positive optical power. At zooming, the 1st lens group and the 3rd lens group are fixed, and the 2nd lens group and the 4th lens group are displaced along the optical axis.

[0103] As one example, the 1st lens element Ll corresponds to the 1st lens element in the claims.

[0104] An intermediate imaging position MI is located between the 12th lens element L12 and the 13th lens element L13. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-angle side of the relay optical system Ol.

[0105] (Example 5)

[0106] like Figure 13 , 14 As shown, the zoom lens system according to Embodiment 5 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a twelfth lens element L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0107] The front group Opf of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes lens elements L1 through L10. Lens element L1 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L2 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L3 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L4 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L5 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L6 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L7 has a biconcave shape. Lens element L8 has a biconvex shape. Lens element L9 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L10 has a biconvex shape.

[0108] The rear group Opr of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes 11th lens element L11 to 12th lens element L12. The 11th lens element L11 has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface facing the magnifying side.

[0109] The relay optical system Ol, from the magnification side to the reduction side, sequentially includes lens elements L13 to L25, numbered 13 to 25. Lens element L13 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L14 has a biconcave shape. Lens element L15 has a positive meniscus shape with its convex surface facing the reduction side. Lens element L16 has a biconvex shape. Lens element L17 has a negative meniscus shape with its convex surface facing the reduction side. Lens element L18 has a biconvex shape. Lens element L19 has a biconvex shape. Lens element L20 has a biconcave shape. Lens element L21 has a biconcave shape. Lens element L22 has a biconvex shape. Lens element L23 has a biconvex shape. Lens element L24 has a negative meniscus shape with its convex surface facing the magnification side. Lens element L25 has a biconvex shape.

[0110] The relay optical system Ol, from the magnification side to the reduction side, sequentially comprises: a first lens group (L13-L15) with negative optical power, a second lens group (L16-L18) with positive optical power, a third lens group (L19-L22) with negative optical power, and a fourth lens group (L23-L25) with positive optical power. During zooming, the first and third lens groups are fixed, while the second and fourth lens groups are displaced along the optical axis.

[0111] As an example, the first lens element L1 corresponds to the first lens element in the claims.

[0112] An intermediate imaging position MI is located between the 12th lens element L12 and the 13th lens element L13. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-angle side of the relay optical system Ol.

[0113] (Example 6)

[0114] like Figure 16 , 17 As shown, the zoom lens system according to Embodiment 6 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a twelfth lens element L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0115] The front group Opf of the magnification optical system Op includes the 1st to 10th lens elements Ll to LlO in order from the magnification side to the reduction side. The 1st lens element Ll has a negative meniscus shape with the convex surface toward the magnification side. The 2nd lens element L2 has a negative meniscus shape with the convex surface toward the magnification side. The 3rd lens element L3 has a negative meniscus shape with the convex surface toward the magnification side. The 4th lens element L4 has a negative meniscus shape with the convex surface toward the reduction side. The 5th lens element L5 has a negative meniscus shape with the convex surface toward the reduction side. The 6th lens element L6 has a positive meniscus shape with the convex surface toward the reduction side. The 7th lens element L7 has a negative meniscus shape with the convex surface toward the reduction side. The 8th lens element L8 has a positive meniscus shape with the convex surface toward the reduction side. The 9th lens element L9 has a positive meniscus shape with the convex surface toward the reduction side. The 10th lens element LlO has a biconvex shape.

[0116] The rear group Opr of the magnification optical system Op includes the 11th and 12th lens elements Ll l and L12 in order from the magnification side to the reduction side. The 11th lens element Ll l has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface toward the magnification side.

[0117] The relay optical system Ol includes the 13th to 25th lens elements L13 to L25 in order from the magnification side to the reduction side. The 13th lens element L13 has a negative meniscus shape with the convex surface toward the magnification side. The 14th lens element L14 has a biconcave shape. The 15th lens element L15 has a positive meniscus shape with the convex surface toward the reduction side. The 16th lens element L16 has a positive meniscus shape with the convex surface toward the reduction side. The 17th lens element L17 has a negative meniscus shape with the convex surface toward the reduction side. The 18th lens element L18 has a biconvex shape. The 19th lens element L19 has a biconvex shape. The 20th lens element L20 has a biconcave shape. The 21st lens element L21 has a biconcave shape. The 22nd lens element L22 has a biconvex shape. The 23rd lens element L23 has a biconvex shape. The 24th lens element L24 has a negative meniscus shape with the convex surface toward the magnification side. The 25th lens element L25 has a biconvex shape.

[0118] The relay optical system Ol includes, in order from the magnification side to the reduction side, a 1st lens group (L13 to L15) having a negative optical power, a 2nd lens group (L16 to L18) having a positive optical power, a 3rd lens group (L19 to L22) having a negative optical power, and a 4th lens group (L23 to L25) having a positive optical power. At zooming, the 1st lens group and the 3rd lens group are fixed, and the 2nd lens group and the 4th lens group are displaced along the optical axis.

[0119] As one example, the 1st lens element Ll corresponds to the 1st lens element in the claims.

[0120] An intermediate imaging position MI is located between the 12th lens element L12 and the 13th lens element L13. Furthermore, an aperture A is positioned between the 19th lens element L19 and the 20th lens element L20. An optical element P with zero optical power is positioned on the reduced-angle side of the relay optical system Ol.

[0121] (Example 7)

[0122] like Figure 19 , 20 As shown, the zoom lens system according to Embodiment 7 includes a magnifying optical system Op and a relay optical system Ol. The magnifying optical system Op includes a first lens element L1 to a twelfth lens element L12. The magnifying optical system Op includes a front group Opf and a rear group Opr.

[0123] The front group Opf of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes lens elements L1 to L10. Lens element L1 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L2 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L3 has a negative meniscus shape with its convex surface facing the magnifying side. Lens element L4 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L5 has a negative meniscus shape with its convex surface facing the reducing side. Lens element L6 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L7 has a biconcave shape. Lens element L8 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L9 has a positive meniscus shape with its convex surface facing the reducing side. Lens element L10 has a biconvex shape.

[0124] The rear group Opr of the magnifying optical system Op, from the magnifying side to the reducing side, sequentially includes 11th lens element L11 to 12th lens element L12. The 11th lens element L11 has a biconvex shape. The 12th lens element L12 has a positive meniscus shape with the convex surface facing the magnifying side.

[0125] The relay optical system Ol includes, in order from the magnification side to the reduction side, the 13th lens element L13 to the 25th lens element L25. The 13th lens element L13 has a negative meniscus shape with the convex surface facing the magnification side. The 14th lens element L14 has a biconcave shape. The 15th lens element L15 has a positive meniscus shape with the convex surface facing the reduction side. The 16th lens element L16 has a positive meniscus shape with the convex surface facing the reduction side. The 17th lens element L17 has a negative meniscus shape with the convex surface facing the reduction side. The 18th lens element L18 has a biconvex shape. The 19th lens element L19 has a biconvex shape. The 20th lens element L20 has a biconcave shape. The 21st lens element L21 has a biconcave shape. The 22nd lens element L22 has a biconvex shape. The 23rd lens element L23 has a biconvex shape. The 24th lens element L24 has a negative meniscus shape with the convex surface facing the magnification side. The 25th lens element L25 has a biconvex shape.

[0126] The relay optical system Ol includes, in order from the magnification side to the reduction side, a first lens group (L13 to L15) having a negative refractive power, a second lens group (L16 to L18) having a positive refractive power, a third lens group (L19 to L22) having a negative refractive power, and a fourth lens group (L23 to L25) having a positive refractive power. At the time of zooming, the first lens group and the third lens group are fixed, and the second lens group and the fourth lens group are displaced along the optical axis.

[0127] As one example, the first lens element L1 corresponds to the first lens element in the claims.

[0128] An intermediate imaging position MI is provided between the 12th lens element L12 and the 13th lens element L13. Further, an aperture A is disposed between the 19th lens element L19 and the 20th lens element L20. On the reduction side of the relay optical system Ol, an optical element P having a refractive power of zero is disposed.

[0129] Further, the zoom lens systems according to Embodiments 1 to 7 can include not only lens elements having a refractive power, but also elements having a refractive power of zero or substantially zero, such as mirrors, apertures, masks, glass covers, filters, prisms, wavelength plates, polarizing elements, and the like.

[0130] Next, conditions that can be satisfied by the zoom lens systems according to the present embodiment are described. Further, a plurality of conditions are prescribed for the zoom lens systems according to the respective embodiments, but all of these plurality of conditions can be satisfied, or effects corresponding to the respective conditions can be obtained by satisfying the individual conditions.

[0131] The zoom lens system according to Embodiments 1 to 7 is an optical system having an intermediate imaging position which is conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, and the optical system has:

[0132] a magnification optical system having a plurality of lens elements positioned on the magnification side of the intermediate imaging position; and

[0133] a relay optical system having a plurality of lens elements positioned on the reduction side of the intermediate imaging position,

[0134] a first lens element positioned on the most magnification side among the plurality of lens elements in the magnification optical system is an aspherical lens having a negative refractive power,

[0135] satisfies the following conditions (1) to (3),

[0136] 0.0055 < Δpgfn < 0.030...(1)

[0137] 53 < vdn < 58...(2)

[0138] 0.28 < fp / fr < 1.0...(3)

[0139] wherein

[0140] Δpgfn = (ngn - nfn) / (nfn - ncn) - (-2.20599 x 10 -3 vdn + 6.69612 x 10 -1 )

[0141] vdn: Abbe number of the first lens element

[0142] ngn: refractive index with respect to g-line of the first lens element

[0143] nfn: refractive index with respect to F-line of the first lens element

[0144] ncn: refractive index with respect to C-line of the first lens element

[0145] fp: focal length of the magnification optical system

[0146] fr: focal length of the relay optical system at a wide-angle end.

[0147] Condition (1) is a conditional expression that prescribes the partial dispersion ratio of the g-line and the F-line of the first lens element. By satisfying condition (1), the on-axis chromatic aberration of each wavelength can be well suppressed throughout the entire zoom range from the wide-angle end to the telephoto end. If it is lower than the lower limit value of condition (1), the on-axis chromatic aberration at the wide-angle end becomes large. Further, if it exceeds the upper limit value of condition (1), the on-axis chromatic aberration at the telephoto end becomes large.

[0148] Condition (2) is a conditional expression that prescribes the Abbe number of the first lens element. By satisfying condition (2), the on-axis chromatic aberration can be well suppressed. If it is lower than the lower limit value of condition (2), the on-axis chromatic aberration on the short-wavelength side is excessively generated and becomes large. On the contrary, if it exceeds the upper limit value, the on-axis chromatic aberration on the short-wavelength side is insufficiently generated and becomes large. In order to satisfy both conditions (1) and (2), the first lens element can also be made of synthetic resin.

[0149] Condition (3) is a conditional expression for prescribing the relationship between the combined focal length of the magnification optical system and the relay optical system. By satisfying this, an optical system that is wide-angle and has a small lens diameter can be realized. If it is lower than the lower limit value of the conditional expression (3), the effective diameter of the lens element that is on the magnification side of the intermediate imaging position and closest to the intermediate imaging position becomes excessively large, and the lens becomes heavy. Conversely, if it exceeds the upper limit value, the effective diameter of the lens that is on the most magnification side becomes excessively large, and the lens becomes heavy.

[0150] In addition, by further satisfying at least one of conditions (1A) and (2A) and (3A) below in addition to conditions (1) to (3), more advantageous effects can be obtained.

[0151] 0.0060 < Δpgfn < 0.028... (1A)

[0152] 53.5 < Vd < 57.5... (2A)

[0153] 0.30 < fp / fr < 0.95... (3A)

[0154] Further, the zoom lens system related to Embodiments 1 to 7 can also have a plurality of air spaces between the lens elements,

[0155] the magnification optical system has a magnification optical system front group located at a position on the magnification side of the longest air space along the optical axis within the magnification optical system, and a magnification optical system rear group located at a position on the reduction side of the longest air space,

[0156] satisfies the following conditions (4) and (5),

[0157] 7 < |Ts / fw| < 15... (4)

[0158] 2 < |Tpr / fw| < 7... (5)

[0159] Here,

[0160] Ts: the longest air interval

[0161] fw: focal length of the entire system at the wide angle end

[0162] Tpr: distance from the surface on the magnification side of the rear group of the magnification optical system to the intermediate imaging

[0163] Condition (4) is a conditional expression that prescribes the relationship between the longest air interval within the magnification optical system and the focal length of the entire system at the wide angle end. By satisfying condition (4), the optical system can be wide-angled. If it is below the lower limit of condition (4), the lens of the front group of the magnification optical system becomes heavy. If it exceeds the upper limit of condition (4), the center of gravity of the entire optical system moves toward the magnification side. Further, condition (5) is a conditional expression that prescribes the relationship between the distance from the surface on the magnification side of the rear group of the magnification optical system to the intermediate imaging and the focal length of the entire system at the wide angle end. By satisfying condition (5), the effect of condition (4) can be exerted.

[0164] In addition, in addition to conditions (4) (5), by further satisfying at least one of conditions (4A) and (5A) below, a more advantageous effect can be obtained.

[0165] 7.2 < |Ts / fw| < 12... (4A)

[0166] 3 < |Tpr / fw| < 6.9... (5A)

[0167] Further, the zoom lens system related to Embodiments 1 to 7 can also satisfy condition (7) with respect to all of the plurality of lens elements that satisfy condition (6) among the plurality of lens elements, and with respect to one lens element that does not satisfy both of conditions (6) and (7) among the plurality of lens elements,

[0168] |ym / (fw•tan(ωm))| < 3.0... (6)

[0169] Tg > 300°C... (7)

[0170] Here,

[0171] fw: focal length of the entire system at the wide angle end

[0172] ωm: maximum half field angle at the wide angle end

[0173] ym: height of the chief ray passing through the lens surface at the most telephoto end

[0174] Tg: glass transition point of the lens material.

[0175] Condition (6) is a conditional expression that prescribes the relationship of the height of the chief ray passing through the lens surface at the most telephoto end, the focal length of the entire system at the wide angle end, and the maximum half field angle at the wide angle end. Condition (7) is a conditional expression that prescribes the glass transition point of the lens material. By satisfying both of conditions (6) and (7), deterioration of the lens can be prevented in the case where high intensity light passes through the lens. In addition, ym is calculated with respect to the surface having a lower height of the surface passing through the magnification side and the reduction side of the lens.

[0176] Further, in the zoom lens system according to Embodiments 1 to 7, the first lens element can have a first lens magnification side surface of an aspherical surface toward the magnification side, and a first lens reduction side surface of an aspherical surface toward the reduction side,

[0177] the first lens magnification side surface and the first lens reduction side surface satisfy the following condition (8),

[0178] dZ(r) / dr > 0... (8)

[0179] Here,

[0180] r: distance from the vertex of the surface along the surface perpendicular to the optical axis of the optical system (r > 0)

[0181] Z(r): sag amount of the surface (set to Z = 0 at the vertex (r = 0), set the reduction side displacement as the sign + and the magnification side displacement as the sign - with respect to the vertex).

[0182] Condition (8) is a conditional expression that prescribes that the first derivative dZ(r) / dr of the sag amount Z(r) of the surface is positive. By satisfying condition (8), even in the case where local heat is generated in the first lens element, the shape change based on thermal expansion changes to be the same for the magnification side surface and the reduction side surface of the first lens. As a result, occurrence of image surface curvature and astigmatism can be suppressed.

[0183] Further, the zoom lens system according to Embodiments 1 to 7 can satisfy the following conditional expression (9),

[0184] 0.5 < (L1R1 + L1R2) / (L1R2 - L1R1) < 5.0... (9)

[0185] Here,

[0186] L1R1: central curvature radius of the first lens magnification side surface

[0187] L1R2: central curvature radius of the first lens reduction side surface.

[0188] Condition (9) is a conditional expression that prescribes the molding factor of the first lens element located on the most magnification side in the magnifying optical system. By satisfying condition (9), the curvature of field and the distortion aberration can be corrected, and the effective diameter of the lens can be reduced. If it is lower than the lower limit value of condition (9), the correction of the curvature of field and the distortion aberration is insufficient. Further, if it exceeds the upper limit value, the effective diameter of the lens located on the magnification side than the aspherical lens becomes large.

[0189] In addition, by further satisfying the following condition (9A) in addition to condition (9), more advantageous effects can be obtained.

[0190] 0.8 < (L1R1+L1R2) / (L1R2-L1R1) < 4.7... (9A)

[0191] Further, the zoom lens system related to Embodiments 1 to 7 can also be configured with a second lens element on the demagnification side of the first lens element,

[0192] satisfying the following conditional expression (10),

[0193] 1.2 < |T1 / fw| < 10.0... (10)

[0194] Here,

[0195] T1: air space between the first lens element and the second lens element

[0196] fw: focal length of the entire system at the wide angle end.

[0197] Condition (10) is a conditional expression that prescribes the relationship between the air space between the first lens element and the second lens element and the focal length of the entire system at the wide angle end. By satisfying condition (10), a lens system that is wide angle and small in lens diameter can be achieved. If it is lower than the lower limit of condition (10), the air space between the first lens element and the second lens element becomes too small, and it is difficult to correct the distortion aberration. On the contrary, if it exceeds the upper limit of condition (10), the effective diameter of the first lens element located on the most magnification side becomes large and heavy.

[0198] In addition, by further satisfying the following condition (10A) in addition to condition (10), more advantageous effects can be obtained.

[0199] 1.3 < |CT1 / fw| < 9.5... (10A)

[0200] Further, the zoom lens system related to Embodiments 1 to 7 can also satisfy the following conditional expression (11),

[0201] 10.0 < |f1 / fw| < 16.0... (11)

[0202] f1: focal length of the first lens element

[0203] fw: focal length of the entire system at the wide angle end.

[0204] Condition (11) is a conditional expression that prescribes the relationship between the focal length of the first lens element and the focal length of the entire system at the wide angle end. By satisfying condition (11), a lens system that is wide angle and small in lens diameter can be realized. If the lower limit of condition (11) is not satisfied, the power of the first lens element becomes too weak and cannot properly correct the distortion aberration. Conversely, if the upper limit of condition (11) is exceeded, the effective diameter of the first lens element located at the most magnification side becomes large and heavy.

[0205] In addition, by further satisfying the following condition (11A) in addition to condition (11), a more advantageous effect can be obtained.

[0206] 10.2 < |f1 / fw| < 15.8... (11A)

[0207] Furthermore, the zoom lens system relating to Embodiments 1 to 7 can also satisfy the following conditional expression (12),

[0208] -8.0 < f1 / Ymax < -1.0... (12)

[0209] Here,

[0210] f1: focal length of the first lens element

[0211] Ymax: maximum image height.

[0212] Condition (12) is a conditional expression that prescribes the relationship between the focal length of the first lens element and the maximum image height. By satisfying condition (12), a lens system that is wide angle and small in lens diameter can be realized. If the lower limit of condition (12) is not satisfied, the power of the first lens element becomes too weak and cannot properly correct the distortion aberration. Conversely, if the upper limit of condition (12) is exceeded, the effective diameter of the first lens element located at the most magnification side becomes large and heavy.

[0213] In addition, by further satisfying the following condition (12A) in addition to condition (12), a more advantageous effect can be obtained.

[0214] -7.8 < f1 / Ymax < -1.2... (12A)

[0215] Furthermore, the zoom lens system relating to Embodiments 1 to 7 can also satisfy the following conditional expression (13),

[0216] 1.5 < |f1 / fp| < 10.0... (13)

[0217] Here,

[0218] f1: focal length of the first lens element.

[0219] Condition (13) is a conditional expression that prescribes the relationship between the focal length of the first lens and the focal length of the magnification optical system. By satisfying condition (13), a wide-angle lens system with a small lens diameter can be achieved. If the lower limit of condition (13) is not satisfied, the distortion aberration cannot be properly corrected. If the upper limit of condition (13) is exceeded, the effective diameter of the first lens located on the most magnification side becomes large and heavy.

[0220] In addition, by further satisfying the following condition (13A) in addition to condition (13), more advantageous effects can be obtained.

[0221] 2.0 < |f1 / fp| < 9.8... (13A)

[0222] Further, the zoom lens system according to Embodiments 1 to 7 can also satisfy the following conditional expression (14),

[0223] 1.0 < |L1R1 / L1R2| < 10.0... (14)

[0224] Here,

[0225] L1R1: central curvature radius of the magnification side surface of the first lens

[0226] L1R2: central curvature radius of the demagnification side surface of the first lens.

[0227] Condition (14) is a conditional expression that prescribes the relationship between the central curvature radius of the magnification side surface of the first lens and the central curvature radius of the demagnification side surface of the first lens. If the upper limit of condition (14) is exceeded, the difference in curvature becomes large, and thus the optical power of the lens peripheral portion also becomes strong, and although the aberration correction is effective, the occurrence of the shape error has a large influence on the performance. If the lower limit of condition (14) is not satisfied, the refractive power becomes too strong, and thus the aberration correction becomes insufficient.

[0228] In addition, by further satisfying the following condition (14A) in addition to condition (14), more advantageous effects can be obtained.

[0229] 1.5 < |L1R1 / L1R2| < 9.5... (14A)

[0230] Further, the zoom lens system according to Embodiments 1 to 7 can also satisfy the following conditional expression (15),

[0231] 0.1 < TL1 / Ymax < 5.0... (15)

[0232] Here,

[0233] TL1: central thickness of the first lens element

[0234] Ymax: maximum image height

[0235] Condition (15) is a conditional expression that prescribes the relationship between the central thickness of the first lens element and the maximum image height. Generally, if the image height becomes large, the lens diameter also becomes large. If the upper limit of condition (15) is exceeded, the thickness of the lens becomes too large, and particularly in the peripheral portion of a concave lens, a chromatic aberration of magnification is easily generated. If the lower limit of condition (15) is fallen below, the strength of the lens becomes insufficient, and a shape error is easily generated at the time of incorporation into a lens barrel or the like, and the performance deteriorates.

[0236] In addition, by further satisfying the following condition (15A) in addition to condition (15), a more advantageous effect can be obtained.

[0237] 0.15 < TL1 / Ymax < 4.7... (15A)

[0238] Further, the zoom lens system relating to Embodiments 1 to 7 can also satisfy the following conditional expression (16),

[0239] 4 < L1R1 / Ymax < 10.5... (16)

[0240] Here,

[0241] L1R1: central radius of curvature of the first lens magnification side surface

[0242] Ymax: maximum image height

[0243] Condition (16) is a conditional expression that prescribes the relationship between the central radius of curvature of the first lens magnification side surface and the maximum image height. If the upper limit of condition (16) is exceeded, in order to correct a barrel-shaped aberration, a negative refractive power becomes strong in the vicinity of the most peripheral portion of the lens, and a non-spherical surface shape in which the inflection point is large is easily generated. If the lower limit of condition (16) is fallen below, in order to correct an astigmatism of an intermediate image height, there is a tendency that a negative refractive power becomes strong in a region through which a light ray of the intermediate image height passes, and a non-spherical surface shape in which the inflection point is large is easily generated. Thus, the degree of difficulty of processing of the lens becomes high, and a shape error is easily generated.

[0244] In addition, by further satisfying the following condition (16A) in addition to condition (16), a more advantageous effect can be obtained.

[0245] 5.0 < L1R1 / Ymax < 9.6... (16A)

[0246] Further, the zoom lens system relating to Embodiments 1 to 7 can also be such that, at the time of zooming, the magnification optical system is fixed, and a part or all of the lens elements of the relay optical system are displaced along the optical axis.

[0247] With this configuration, by disposing the zoom mechanism at a position closer to the reduction side than the intermediate imaging position, it is possible to mount the zoom actuating mechanism, such as a cam, a motor, or the like, to the reduction side. Thus, it is possible to make the center of gravity of the lens barrel closer to the reduction side.

[0248] As above, several embodiments were explained as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which appropriate changes, substitutions, additions, omissions, and the like are made.

[0249] Hereinafter, numerical examples of the zoom lens system involved in Embodiments 1 to 7 will be explained. In each numerical example, the unit of length in the table is "mm" and the unit of the field angle is "°". In each numerical example, r is the radius of curvature, d is the interval of surfaces, nd is the refractive index with respect to the d-line, and vd is the Abbe number with respect to the d-line. In each numerical example, the surface with an asterisk is an aspherical surface, and the aspherical surface shape is defined by the following formula.

[0250] [Formula 1]

[0251]

[0252] Here,

[0253] Z: the distance from the tangent plane at the apex of the aspherical surface to the point on the aspherical surface at a height h from the optical axis,

[0254] h: the height from the optical axis,

[0255] r: the radius of curvature at the apex,

[0256] K: the conic constant,

[0257] An: the aspherical surface coefficient of the nth order.

[0258] (Numerical Example 1)

[0259] Regarding the zoom lens system of Numerical Example 1 (corresponding to Embodiment 1), the surface data is shown in Table 1, various data is shown in Table 2, single lens data is shown in Table 3, and zoom lens group data is shown in Table 4 (unit: mm).

[0260] [Table 1]

[0261] Surface Data

[0262]

[0263]

[0264]

[0265] Aspherical surface data

[0266] 1st surface

[0267] K = 0.00000E+00, A3 = -7.25014E-06, A4 = -1.15220E-06, A5 = 2.72823E-08

[0268] A6 = -4.98172E-11, A7 = -3.06439E-12, A8 = 5.81613E-15, A9 = 4.07487E-16

[0269] A10 = -2.69504E-18

[0270] 2nd surface

[0271] K = -1.22715E+00, A3 = 1.40108E-05, A4 = -2.62157E-06, A5 = 7.38521E-09

[0272] A6 = 2.80400E-10, A7 = 2.43598E-14, A8 = -1.40378E-14, A9 = -2.03884E-16

[0273] A10 = 1.80622E-18

[0274] 9th surface

[0275] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.14919E-05, A5 = 0.00000E+00

[0276] A6 = 2.07809E-07, A7 = 0.00000E+00, A8 = -7.30054E-10, A9 = 0.00000E+00

[0277] A10 = 8.85358E-13

[0278] 10th surface

[0279] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.81203E-05, A5 = 0.00000E+00

[0280] A6 = 1.62721E-07, A7 = 0.00000E+00, A8 = 0.00000E+00, A9 = 0.00000E+00

[0281] A10 = 0.00000E+00

[0282] [Table 2]

[0283] Various data

[0284]

[0285] [Table 3]

[0286] Single lens data

[0287]

[0288]

[0289] [Table 4]

[0290] Zoom lens group data

[0291]

[0292]

[0293] Zoom lens group magnification

[0294]

[0295] (Numerical example 2)

[0296] With respect to the zoom lens system of numerical example 2 (corresponding to example 2), the surface data is shown in Table 5, the various data is shown in Table 6, the single lens data is shown in Table 7, and the zoom lens group data (in mm) is shown in Table 8.

[0297] [Table 5]

[0298] Surface data

[0299]

[0300]

[0301]

[0302] Aspherical surface data

[0303] 1st surface

[0304] K = 0.00000E+00, A3 = -2.65067E-06, A4 = 4.62668E-07, A5 = 1.02356E-09

[0305] A6 = -5.81330E-11, A7 = 8.20273E-14, A8 = 6.76604E-15, A9 = 2.18048E-17

[0306] A10 = -5.71783E-19

[0307] Face 2

[0308] K = -9.55907E-01, A3 = 0.00000E+00, A4 = -1.80425E-06, A5 = 0.00000E+00

[0309] A6 = 9.34430E-11, A7 = 0.00000E+00, A8 = 9.19265E-15, A9 = 0.00000E+00

[0310] A10 = -1.18438E-18

[0311] Face 9

[0312] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 4.18656E-06, A5 = 0.00000E+00

[0313] A6 = 4.74295E-08, A7 = 0.00000E+00, A8 = -1.07013E-09, A9 = 0.00000E+00

[0314] A10 = 0.00000E+00

[0315] Face 10

[0316] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.35037E-05, A5 = 0.00000E+00

[0317] A6 = 7.58692E-08, A7 = 0.00000E+00, A8 = -4.25680E-10, A9 = 0.00000E+00

[0318] A10 = 0.00000E+00

[0319] Face 33

[0320] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 9.60708E-06, A5 = 0.00000E+00

[0321] A6 = -8.51152E-09, A7 = 0.00000E+00, A8 = 4.75793E-12, A9 = 0.00000E+00

[0322] A10 = 0.00000E+00

[0323] 34th surface

[0324] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 9.30721E-06, A5 = 0.00000E+00

[0325] A6 = -5.66264E-09, A7 = 0.00000E+00, A8 = 2.36850E-12, A9 = 0.00000E+00

[0326] A10 = 0.00000E+00

[0327] [Table 6]

[0328] Various data

[0329]

[0330]

[0331] [Table 7] Single lens data

[0332]

[0333]

[0334] [Table 8]

[0335] Zoom lens group data

[0336]

[0337] Zoom lens group magnification

[0338]

[0339] (Numerical example 3)

[0340] With respect to the zoom lens system of numerical example 3 (corresponding to example 3), surface data is shown in Table 9, various data is shown in Table 10, single lens data is shown in Table 11, and zoom lens group data is shown in Table 12 (in mm).

[0341] [Table 9]

[0342] Surface data

[0343]

[0344]

[0345]

[0346] Aspherical surface data

[0347] 1st surface

[0348] K = 0.00000E+00, A3 = -4.98082E-05, A4 = 1.02415E-06, A5 = -2.94689E-08

[0349] A6 = 7.04235E-10, A7 = -6.53517E-12, A8 = -1.32511E-14, A9 = 4.97035E-16

[0350] A10 = -1.16266E-18, A11 = 1.10076E-22, A12 = -1.04222E-23, A13 = -7.34121E-26

[0351] A14 = -1.19521E-26, A15 = 5.84967E-29, A16 = -1.36553E-32, A17 = -1.81844E-33

[0352] A18 = -1.06538E-35, A19 = -2.13620E-37, A20 = -9.95976E-39

[0353] 2nd surface

[0354] K = -9.54170E-01, A3 = -1.48327E-05, A4 = -2.41212E-06, A5 = -5.68248E-10

[0355] A6 = 1.08199E-10, A7 = -3.03274E-13, A8 = 3.45630E-15, A9 = 9.09825E-17

[0356] A10 = 4.23242E-18, A11 = -4.76060E-21, A12 = -5.81989E-22, A13 = -8.46992E-24

[0357] A14 = 8.97671E-26, A15 = -4.55046E-28, A16 = -3.81800E-30, A17 = 1.48597E-32

[0358] A18 = 1.41251E-33, A19 = 3.80980E-35, A20 = -4.85676E-37

[0359] [Table 10]

[0360] Various data

[0361]

[0362] [Table 11]

[0363] Single lens data

[0364]

[0365]

[0366] [Table 12]

[0367] Zoom lens group data

[0368]

[0369]

[0370] Zoom lens group magnification

[0371]

[0372] (Numberical example 4)

[0373] With respect to the zoom lens system of the numberical example 4 (corresponding to example 4), the surface data is shown in Table 13, the various data is shown in Table 14, the single lens data is shown in Table 15, and the zoom lens group data is shown in Table 16 (in mm).

[0374] [Table 13]

[0375] Surface data

[0376]

[0377]

[0378]

[0379] Aspherical surface data

[0380] 1st surface

[0381] K = 0.00000E+00, A3 = -5.32341E-06, A4 = -1.08236E-06, A5 = 2.61031E-08

[0382] A6 = -4.27853E-11, A7 = -3.00834E-12, A8 = 5.23078E-15, A9 = 4.08999E-16

[0383] A10 = -2.64786E-18

[0384] 2nd surface

[0385] K = -1.22711E+00, A3 = 1.51511E-05, A4 = -2.64143E-06, A5 = 7.26941E-09

[0386] A6 = 2.79585E-10, A7 = 3.15970E-14, A8 = -1.39833E-14, A9 = -1.99424E-16

[0387] A10 = 1.77284E-18

[0388] 9th surface

[0389] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 1.92717E-05, A5 = 0.00000E+00

[0390] A6 = 1.99778E-07, A7 = 0.00000E+00, A8 = -7.68502E-10, A9 = 0.00000E+00

[0391] A10 = -1.41298E-13

[0392] 10th surface

[0393] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.60433E-05, A5 = 0.00000E+00

[0394] A6 = 1.52935E-07, A7 = 0.00000E+00, A8 = 0.00000E+00, A9 = 0.00000E+00

[0395] A10 = 0.00000E+00

[0396] [Table 14]

[0397] Various data

[0398]

[0399] [Table 15]

[0400] Single lens data

[0401]

[0402]

[0403] [Table 16]

[0404] Zoom lens group data

[0405]

[0406] Zoom lens group magnification

[0407]

[0408]

[0409] (Numerical example 5)

[0410] With respect to the zoom lens system of numerical example 5 (corresponding to example 5), surface data is shown in Table 17, various data is shown in Table 18, single lens data is shown in Table 19, and zoom lens group data is shown in Table 20 (in mm).

[0411] [Table 17]

[0412] Surface data

[0413]

[0414]

[0415]

[0416] Aspherical surface data

[0417] 1st surface

[0418] K = 0.00000E+00, A3 = -1.80686E-05, A4 = -1.24260E-06, A5 = 2.82728E-08

[0419] A6 = -4.68886E-11, A7 = -3.14281E-12, A8 = 3.69704E-15, A9 = 4.05487E-16

[0420] A10 = -2.70992E-18

[0421] 2nd surface

[0422] K = -1.29848E+00, A3 = 9.60558E-06, A4 = -2.58551E-06, A5 = 8.15356E-09

[0423] A6 = 2,89291E-10, A7 = 7.31407E-14, A8 = -1.40654E-14, A9 = -2.05740E-16

[0424] A10 = 1.87867E-18

[0425] 9th surface

[0426] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.17129E-05, A5 = 0.00000E+00

[0427] A6 = 2.20039E-07, A7 = 0.00000E+00, A8 = -6.23863E-10, A9 = 0.00000E+00

[0428] A10 = 1.23212E-12

[0429] 10th surface

[0430] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.79313E-05, A5 = 0.00000E+00

[0431] A6 = 1.44206E-07, A7 = 0.00000E+00, A8 = 0.00000E+00, A9 = 0.00000E+00

[0432] A10 = 0.00000E+00

[0433] [Table 18]

[0434] Various data

[0435]

[0436] [Table 19]

[0437] Single lens data

[0438]

[0439]

[0440] [Table 20]

[0441] Zoom lens group data

[0442]

[0443] Zoom lens group magnification

[0444]

[0445] (Numberical Example 6)

[0446] With respect to the zoom lens system of Numerical Example 6 (corresponding to Example 6), the surface data is shown in Table 21, various data is shown in Table 22, single lens data is shown in Table 23, and zoom lens group data is shown in Table 24 (in mm).

[0447] [Table 21]

[0448] Surface data

[0449]

[0450]

[0451] Aspherical surface data

[0452] 1st surface

[0453] K = 0.00000E+00, A3 = -1.74067E-05, A4 = -8.55706E-07, A5 = 2.47548E-08

[0454] A6 = -5.71120E-11, A7 = -2.95249E-12, A8 = 6.30469E-15, A9 = 4.04186E-16

[0455] A10 = -2.73602E-18

[0456] 2nd surface

[0457] K = -1.29979E+00, A3 = 3.56842E-06, A4 = -2.46793E-06, A5 = 9.34818E-09

[0458] A6 = 2.89223E-10, A7 = -1.38298E-13, A8 = -1.85781E-14, A9 = -2.48923E-16

[0459] A10 = 2.68573E-18

[0460] 9th surface

[0461] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.51303E-05, A5 = 0.00000E+00

[0462] A6 = 1.94136E-07, A7 = 0.00000E+00, A8 = -4.58227E-10, A9 = 0.00000E+00

[0463] A10 = 4.69317E-13

[0464] 10th surface

[0465] K=0.00000E+00, A3=0.00000E+00, A4=2.81131E-05, A5=0.00000E+00

[0466] A6=1.45179E-07, A7=0.00000E+00, A8=0.00000E+00, A9=0.00000E+00

[0467] A10=0.00000E+00

[0468] [Table 22]

[0469] Various data

[0470]

[0471]

[0472] [Table 23]

[0473] Single lens data

[0474]

[0475]

[0476] [Table 24]

[0477] Zoom lens group data

[0478]

[0479] Zoom lens group magnification

[0480]

[0481] (Numerical example 7)

[0482] With respect to the zoom lens system of numerical example 7 (corresponding to example 7), the surface data is shown in Table 25, the various data is shown in Table 26, the single lens data is shown in Table 27, and the zoom lens group data is shown in Table 28 (in mm).

[0483] [Table 25]

[0484] Surface data

[0485]

[0486]

[0487]

[0488] Aspherical surface data

[0489] 1st surface

[0490] K = 0.00000E+00, A3 = -1.52651E-05, A4 = -9.94232E-07, A5 = 2.44429E-08

[0491] A6 = -1.95730E-11, A7 = -3.08842E-12, A8 = 2.25161E-15, A9 = 4.13973E-16

[0492] A10 = -2.55437E-18

[0493] 2nd surface

[0494] K = -1.34729E+00, A3 = 9.87687E-06, A4 = -2.47222E-06, A5 = 9.33782E-09

[0495] A6 = 2.90162E-10, A7 = -1.04007E-13, A8 = -1.82010E-14, A9 = -2.48249E-16

[0496] A10 = 2.59959E-18

[0497] 9th surface

[0498] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.53409E-05, A5 = 0.00000E+00

[0499] A6 = 2.16366E-07, A7 = 0.00000E+00, A8 = -3.24181E-10, A9 = 0.00000E+00

[0500] A10 = 1.24182E-13

[0501] 10th surface

[0502] K = 0.00000E+00, A3 = 0.00000E+00, A4 = 2.70872E-05, A5 = 0.00000E+00

[0503] A6 = 1.50922E-07, A7 = 0.00000E+00, A8 = 0.00000E+00, A9 = 0.00000E+00

[0504] A10 = 0.00000E+00

[0505] [Table 26]

[0506] Various data

[0507]

[0508]

[0509] [Table 27]

[0510] Single lens data

[0511]

[0512]

[0513] [Table 28]

[0514] Zoom lens group data

[0515]

[0516] Zoom lens group magnification

[0517]

[0518] In the following Table 29, the corresponding values of each conditional expression in each numerical example are shown.

[0519] [Table 29]

[0520]

[0521] In the following Table 30, the values of the variables of each conditional expression (1) to (16) in each numerical example are shown.

[0522] [Table 30]

[0523]

[0524] vdn: Abbe number of the 1st lens element

[0525] ngn: Refractive index of the 1st lens element with respect to g-line

[0526] nfn: Refractive index of the 1st lens element with respect to F-line

[0527] ncn: Refractive index of the 1st lens element with respect to C-line

[0528] Ts: Longest air interval

[0529] Tpr: Distance from the surface on the magnifying side of the magnifying optical system rear group to the intermediate imaging

[0530] T1: air space between the 1st lens element and the 2nd lens element

[0531] TL1: center thickness of the 1st lens element

[0532] fp: focal length of the magnification optical system

[0533] fr: focal length of the relay optical system at the wide-angle end

[0534] fw: focal length of the entire system at the wide-angle end

[0535] f1: focal length of the 1st lens element

[0536] ωm: maximum half field angle at the wide-angle end

[0537] ym: height of the chief ray passing through the lens face at the most telephoto end

[0538] L1R1: center curvature radius of the 1st lens magnification side face

[0539] L1R2: center curvature radius of the 1st lens reduction side face

[0540] Ymax: maximum image height

[0541] In Tables 31 to 34 below, the values of |ym / (fw•tan(ωm))| of Condition Expression (16) and Tg of Condition Expression (17) in each numerical example are shown. In addition, the lens material Z330R is a product name of a cyclic olefin polymer (COP) (Zeon Corporation). The lens element L1 can be made of various synthetic resins, and thus lightening can be achieved. The remaining lens elements L2 to L26 are also made of various synthetic resins, and thus lightening can be achieved.

[0542] [Table 31]

[0543]

[0544] [Table 32]

[0545]

[0546] [Table 33]

[0547]

[0548] [Table 34]

[0549]

[0550] (Embodiment 2)

[0551] Hereinafter, using Figure 22An embodiment 2 of the present disclosure will be described. Figure 22 is a block diagram showing an example of an image projection apparatus according to the present disclosure. The image projection apparatus 100 is provided with the optical system 1 disclosed in the embodiment 1, an image forming element 101, a light source 102, a control section 110, and the like. The image forming element 101 includes a liquid crystal, a DMD, or the like, and generates an image projected to a screen SR via the optical system 1. The light source 102 includes an LED (Light Emitting Diode), a laser, or the like, and supplies light to the image forming element 101. The control section 110 includes a CPU, an MPU, or the like, and controls the entire apparatus and each component. The optical system 1 can also be configured as an interchangeable lens which is freely attachable and detachable with respect to the image projection apparatus 100. In this case, the apparatus which takes off the optical system 1 from the image projection apparatus 100 is an example of a main body apparatus.

[0552] The image projection apparatus 100 described above can reduce the moment acting on the center of gravity of the optical system 1, can reduce the influence of heat, and can realize a wide-angle zoom function by the optical system 1 according to the embodiment 1.

[0553] (Embodiment 3)

[0554] Hereinafter, an embodiment 3 of the present disclosure will be described using Figure 23 Figure 23 is a block diagram showing an example of an image projection apparatus according to the present disclosure. The image projection apparatus 100 is provided with the optical system 1 disclosed in the embodiment 1, an image forming element 101, a light source 102, a control section 110, and the like. The image forming element 101 includes a liquid crystal, a DMD, or the like, and generates an image projected to a screen SR via the optical system 1. The light source 102 includes an LED (Light Emitting Diode), a laser, or the like, and supplies light to the image forming element 101. The control section 110 includes a CPU, an MPU, or the like, and controls the entire apparatus and each component. The optical system 1 can also be configured as an interchangeable lens which is freely attachable and detachable with respect to the image projection apparatus 100. In this case, the apparatus which takes off the optical system 1 from the image projection apparatus 100 is an example of a main body apparatus.

[0555] The image projection apparatus 100 described above can reduce the moment acting on the center of gravity of the optical system 1, can reduce the influence of heat, and can realize a wide-angle zoom function by the optical system 1 according to the embodiment 1.

[0556] As described above, the embodiments have been described as the technical disclosure in the present disclosure. The drawings and detailed description are provided for this purpose.

[0557] ​Therefore, in the structural elements described in the drawings and the detailed description, not only structural elements necessary for solving the problems but also structural elements unnecessary for solving the problems are included in order to illustrate the above-described technology. Therefore, these unnecessary structural elements are described in the drawings or the detailed description, but should not be directly recognized as necessary.

[0558] Furthermore, the above-described embodiments are for illustrating the technology in the present disclosure, and thus various changes, substitutions, additions, omissions, and the like can be made within the scope of the claims or the equivalent thereof.

[0559] Industrial Applicability

[0560] The present disclosure can be applied to an image projection device such as a projector, a head-up display, and an imaging device such as a digital still camera, a digital video camera, a monitoring camera in a monitoring system, a Web camera, and a vehicle-mounted camera. In particular, the present disclosure can be applied to an optical system such as a projector, a digital still camera system, and a digital video camera system that requires high image quality.

Claims

1. An optical system having, inside, an intermediate imaging position conjugate to a magnification conjugate point on a magnification side and a reduction conjugate point on a reduction side, respectively, the optical system comprising: a magnification optical system having a plurality of lens elements located at a position closer to the magnification side than the intermediate imaging position; and a relay optical system having a plurality of lens elements located at a position closer to the reduction side than the intermediate imaging position, a first lens element located at a position closest to the magnification side among the plurality of lens elements in the magnification optical system is an aspherical lens having a negative refractive power, the optical system satisfies the following conditions (1) to (3), 0.0055 < Δpgfn < 0.030... (1) 53 < vdn < 58... (2) 0.28 < fp / fr < 1.0... (3) where, vdn: Abbe number of the first lens element, ngn: refractive index with respect to g-line of the first lens element, nfn: refractive index with respect to F-line of the first lens element, ncn: refractive index with respect to C-line of the first lens element, fp: focal length of the magnification optical system, fr: focal length of the relay optical system at a wide angle end, all of the lens elements among the plurality of lens elements satisfying the condition (6) satisfy the condition (7), and one lens element among the plurality of lens elements does not satisfy both of the conditions (6) and (7), |ym / (fw tan(ωm))| < 3.0... (6) Tg > 300°C... (7) where, fw: focal length of the entire system at a wide angle end, ωm: maximum half field angle at a wide angle end, ym: height of a chief ray passing through a lens surface at a telephoto end, Tg: glass transition point of a lens material.

2. The optical system according to claim 1, wherein, between the lens elements, there are a plurality of air intervals, the magnification optical system has a magnification optical system front group located at a position closer to the magnification side than a longest air interval along an optical axis within the magnification optical system, and a magnification optical system rear group located at a position closer to the reduction side than the longest air interval, the optical system satisfies the following conditions (4) and (5), 7 < |Ts / fw| < 15... (4) 2 < |Tpr / fw| < 7... (5) where, Ts: the longest air interval, fw: focal length of the entire system at a wide angle end, Tpr: distance from a surface on a magnification side of the magnification optical system rear group to the intermediate imaging.

3. The optical system according to claim 1, wherein, the first lens element has a first lens magnification side surface of an aspherical surface toward the magnification side, and a first lens reduction side surface of an aspherical surface toward the reduction side, the first lens magnification side surface and the first lens reduction side surface satisfy the following condition (8), dZ(r) / dr > 0... (8) where, r: distance from a vertex of a surface along a surface perpendicular to an optical axis of an optical system, where r > 0. ​ ​ ​ ​ ​ ​ Δpgfn = (ngn - nfn) / (nfn - ncn) - (-2.20599 x 10 -3 + vdn + 6.69612 x 10 -1 ) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Z(r): sag of the surface, where Z=0 is set at the vertex (r=0), and the displacement of the reduced side is set as the sign + and the displacement of the enlarged side is set as the sign - with respect to the vertex.

4. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (9), 0.5 < (L1R1+L1R2) / (L1R2-L1R1) < 5.0... (9) where, L1R1: central radius of curvature of the enlarged side surface of the first lens, L1R2: central radius of curvature of the reduced side surface of the first lens.

5. The optical system according to claim 1, wherein a second lens element is disposed on the reduced side of the first lens element, the following conditional expression (10) is satisfied, 1.2 < |T1 / fw| < 10.0... (10) where, T1: air interval between the first lens element and the second lens element, fw: focal length of the entire system at the wide angle end.

6. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (11), 10.0 < |f1 / fw| < 16.0... (11) f1: focal length of the first lens element, fw: focal length of the entire system at the wide angle end.

7. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (12), -8.0 < f1 / Ymax < -1.0... (12) where, f1: focal length of the first lens element, Ymax: maximum image height.

8. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (13), 1.5 < |f1 / fp| < 10.0... (13) where, f1: focal length of the first lens element.

9. The optical system according to claim 1, wherein the following conditional expression (14) is satisfied, 1.0 < |L1R1 / L1R2| < 10.0... (14) where, L1R1: central radius of curvature of the enlarged side surface of the first lens, L1R2: central radius of curvature of the reduced side surface of the first lens.

10. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (15), 0.1 < TL1 / Ymax < 5.0... (15) where, TL1: central thickness of the first lens element, Ymax: maximum image height.

11. The optical system according to claim 1, wherein the optical system satisfies the following conditional expression (16), 4 < L1R1 / Ymax < 10.5... (16) where, L1R1: central radius of curvature of the enlarged side surface of the first lens, Ymax: maximum image height.

12. The optical system according to claim 1, wherein at the time of zooming, the enlarged optical system is fixed, and a part or all of the lens elements of the relay optical system are displaced along the optical axis.

13. An image projection apparatus, comprising: the optical system according to any one of claims 1 to 12; and an image forming element that generates an image projected to a screen via the optical system.

14. An image pickup apparatus comprising: the optical system according to any one of claims 1 to 12; and an image pickup element that photoelectrically converts an optical image formed by the optical system.

Images