Projection zoom lens

Abstract

To obtain a high-performance projection zoom lens that suppresses various aberrations while maintaining a wide angle of view. [Solution] The lens optical system 100 includes a first lens group having negative refractive power, an N-3 lens group having positive refractive power, an N-1 lens group having positive refractive power, and an N lens group having positive refractive power, with the first lens group and the N-1 lens group each including at least one aspherical lens L1..., L17..., and when the focal length of the entire system at the wide-angle end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], the optical system 100 satisfies 20>fw>10, 60>Aw>40, 5.0>(Aw / fw)>2.5, and an optical adjustment system 200 includes a zooming adjustment section Mcz in which the N-3 lens group, the N-2 lens group, and the N-1 lens group all move independently in the optical axis direction Dc from the reduction side to the enlargement side when changing magnification from the wide-angle end to the telephoto end.

Description

Technical Field

[0001] The present invention relates to a projection zoom lens suitable for use in an optical device equipped with a projection optical system such as a projector.

Background Art

[0002] Conventionally, as a projection zoom lens provided in a projection optical system for projecting an image from a projector onto a screen or the like, a zoom lens described in Patent Document 1 proposed by the present applicant is known.

[0003] This zoom lens aims to obtain good image quality through necessary corrections for various aberrations and field curvature, and to balance each performance well and reasonably, such as achieving overall miniaturization, weight reduction, and cost reduction. Specifically, from the telephoto side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, a third lens group having a positive refractive power, a fourth lens group having a positive refractive power, a fifth lens group having a positive or negative refractive power, and a sixth lens group having a positive refractive power are sequentially arranged to form a lens optical system, and an optical adjustment system including a zooming adjustment unit that fixes the first lens group and the sixth lens group and independently moves the second lens group to the fifth lens group in the optical axis direction. Each lens of the fourth lens group is composed of a single lens, and convex lenses and concave lenses are alternately arranged in the optical axis direction.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the conventional zoom lens described in Patent Document 1 also had the following problems to be solved.

[0006] In other words, projection zoom lenses used in projection optics such as projectors generally require high optical performance in terms of brightness, zoom ratio, and wide-angle field of view, in order to enlarge and project optical images onto a screen.

[0007] In particular, with short-focus lenses, it is necessary to reduce various aberrations such as curvature, distortion, and chromatic aberration, and a projection optical system with good telecentricity is required. However, with conventional projection zoom lenses of this type, there has been a challenge in constructing a higher-performance projection zoom lens 1 that secures a wide angle of view and suppresses various aberrations.

[0008] In addition, this type of projection zoom lens is supported in a position that protrudes forward from the front of the projector body, and is equipped with an optical adjustment system that has a lens optical system with numerous lens groups and various adjustment parts such as a zoom adjustment section. Therefore, miniaturization and weight reduction of the entire zoom lens are required. On the other hand, these various requirements are mutually influential, as meeting some requirements may prevent others from being met. Therefore, it is not easy to improve the various lens performance requirements while also ensuring miniaturization and weight reduction. Ultimately, there is also the fundamental challenge of how to realize a high-performance zoom lens while maintaining a good balance in suppressing various aberrations.

[0009] The present invention aims to provide a projection zoom lens that solves the problems present in the background technology described above. [Means for solving the problem]

[0010] To solve the above-mentioned problems, the projection zoom lens 1 according to the present invention is configured by arranging the first lens group to the Nth lens group (N is 6 or 7, the same applies hereinafter) in order from the magnification side E to the reduction side S, and comprises a first lens group having negative refractive power, an N-3 lens group having positive refractive power, an N-1 lens group having positive refractive power, and an Nth lens group having positive refractive power, and each of the first lens group and the N-1 lens group includes at least one aspherical lens L1..., L17... and wide The lens optical system 100 is provided, where the total focal length of the system at the angular end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], satisfying the following conditions: 20>fw>10…[Condition 1], 60>Aw>40…[Condition 2], 5.0>(Aw / fw)>2.5…[Condition 3], and the optical adjustment system 200 is provided, which has a zooming adjustment section Mcz in which the N-3 lens group, the N-2 lens group, and the N-1 lens group all move independently in the optical axis direction Dc from the reduction side to the enlargement side when changing magnification from the wide-angle end to the telephoto end.

[0011] In this case, according to a preferred embodiment of the invention, the first lens group may include at least one concave lens L3 that satisfies the condition νd1 > 70…[Condition Equation 4] when the Abbe number of the d line is νd1. The (N-1) lens group may also include at least one convex lens L16… that satisfies the condition νd2 > 70…[Condition Equation 5] when the Abbe number of the d line is νd2. Furthermore, the Nth lens group may be provided with a convex lens L21… that satisfies the condition nd > 1.8…[Condition Equation 6] at the most narrowed S, when the refractive index of the d line is nd. [Effects of the Invention]

[0012] The projection zoom lens 1 according to the present invention, having such a configuration, produces the following remarkable effects.

[0013] (1) In projection zoom lenses used in projection optical systems such as projectors that project optical images onto a screen, it is possible to construct a high-performance projection zoom lens 1 that has a wide angle of view while suppressing various aberrations. In particular, even in the case of short focal length lenses, by using aspherical lenses, as well as high refractive index glass materials and low dispersion glass materials in appropriate places, it is possible to secure various requirements such as miniaturization and weight reduction, and provide a high-performance projection zoom lens with good telecentricity while suppressing various aberrations such as curvature, distortion, and chromatic aberration required for wide-angle lenses.

[0014] (2) In a preferred embodiment, when the first lens group is constructed, if at least one concave lens L3... that satisfies the Abbe number of the d line νd1 > 70... [Condition Equation 4] is included, then the concave lens L3... with an Abbe number greater than 70 is included, and thus the occurrence of chromatic aberration, especially in the periphery, can be effectively suppressed.

[0015] (3) In a preferred embodiment, when the N-1 lens group is constructed, if at least one convex lens L16... that satisfies the Abbe number of the d line νd2 > 70... [Condition Equation 5] is included, then since the convex lens L16... with an Abbe number greater than 70 is included, the occurrence of chromatic aberration can be suppressed in particular, and fluctuations in chromatic aberration that occur during magnification can be effectively suppressed.

[0016] (4) In a preferred embodiment, when the refractive index of the d line is nd, if a convex lens L21… satisfying nd > 1.8… [condition equation 6] is provided at the most narrowed S, then a convex lens L21 with a refractive index greater than 1.8 is included, and in particular, good aberration characteristics can be ensured while maintaining appropriate telecentricity. [Brief explanation of the drawing]

[0017] [Figure 1] Overall lens configuration diagram of the TELE side of the projection zoom lens in Embodiment 1 of a preferred embodiment of the present invention. [Figure 2]Overall lens configuration diagram showing a comparison of the lens positions on the WIDE side and the TELE side of the projection zoom lens of Example 1, [Figure 3] List of [Conditional Expression 1] - [Conditional Expression 6] in the optical characteristics of the projection zoom lens according to this embodiment, [Figure 4] Longitudinal aberration diagram of the reference distance on the WIDE side of the projection zoom lens of Example 1, [Figure 5] Longitudinal aberration diagram of the reference distance on the TELE side of the projection zoom lens of Example 1, [Figure 6] Overall lens configuration diagrams of the projection zoom lens of Example 2 for (a) the WIDE side and (b) the TELE side, [Figure 7] Longitudinal aberration diagram of the reference distance on the WIDE side of the projection zoom lens of Example 2, [Figure 8] Longitudinal aberration diagram of the reference distance on the TELE side of the projection zoom lens of Example 2, [Figure 9] Overall lens configuration diagrams of the projection zoom lens of Example 3 for (a) the WIDE side and (b) the TELE side, [Figure 10] Longitudinal aberration diagram of the reference distance on the WIDE side of the projection zoom lens of Example 3, [Figure 11] Longitudinal aberration diagram of the reference distance on the TELE side of the projection zoom lens of Example 3,

Mode for Carrying Out the Invention

[0018] Next, preferred embodiments according to the present invention will be given and described in detail based on the drawings.

[0019] In addition, Example 1 and Example 2 in the embodiments are composed of the first lens group G1 to the seventh lens group G7, and Example 3 is composed of the first lens group G1 to the sixth lens group G6. That is, the lens optical system 100 of the present invention is applied to the first lens group to the Nth lens group (N is 6 or 7).

Examples

[0020] First, the lens optical system 100 and optical adjustment system 200 of the projection zoom lens 1 according to Embodiment 1 of this embodiment will be described with reference to Figures 1-5.

[0021] This projection zoom lens 1 is intended for use as a short-focus projection zoom lens in a projector.

[0022] In Figure 1, E represents the magnification side, such as a screen, and S represents the reduction side (reduced conjugate side), which becomes an image display element such as a liquid crystal panel. Therefore, the magnification side E is in front in the direction of the optical axis Dc, and the reduction side S is in the direction of the optical axis Dc.

[0023] As shown in Figure 1, the lens optical system 100 comprises seven lens groups G1, G2, G3, G4, G5, G6, and G7, arranged in order from the magnification side E to the reduction side S, and a prism Pr, as shown in the schematic diagram, is provided on the reduction side S relative to the seventh lens group G7.

[0024] Specifically, the lens system comprises, in order from the magnification side E to the reduction side S, a first lens group G1 having a negative refractive power overall, a second lens group G2 having a positive refractive power overall, a third lens group G3 having a negative refractive power overall, a fourth lens group G4 having a positive refractive power overall, a fifth lens group G5 having a positive refractive power overall, a sixth lens group G6 having a positive refractive power overall, and a seventh lens group G7 having a positive refractive power overall.

[0025] More specifically, the first lens group G1 is composed of the following lenses arranged in order from the magnification side E to the reduction side S: an aspherical lens L1, a negative lens L2 using a negative meniscus lens with a convex surface on the magnification side E, a negative lens L3 using a negative meniscus lens with a convex surface on the magnification side E, a negative lens L4 using a biconcave lens, a negative lens L5 using a biconcave lens, and a positive lens L6 using a biconvex lens. The first lens group G1 has a total of six lenses L1...L6, all of which are single lenses.

[0026] The second lens group G2 is composed of a positive lens L7 using a positive meniscus lens with a convex surface on the reduction side S, arranged in order from the magnification side E to the reduction side S, a cemented lens J1 formed by joining a positive lens L8 using a positive meniscus lens with a convex surface on the reduction side S and a negative lens L9 using a negative meniscus lens with a convex surface on the reduction side S. The second lens group G2 has a total of three lenses L7...L9 and is composed of single lenses and cemented lenses.

[0027] The third lens group G3 consists of a negative lens L10, which uses a negative meniscus lens with a convex surface on the magnification side E. The fourth lens group G4 consists of a positive lens L11, which uses a biconvex lens, and a negative lens L12, which uses a negative meniscus lens with a convex surface on the reduction side S, arranged in order from the magnification side E to the reduction side S. The fourth lens group G4 has a total of two lenses, L11 and L12, both of which are single lenses.

[0028] The fifth lens group G5 is composed of a positive lens L13 using a biconvex lens, arranged in order from the magnification side E to the reduction side S, and a negative lens L14 using a negative meniscus lens with a convex surface on the reduction side S. The fifth lens group G5 has a total of two lenses L13 and L14, both of which are single lenses. The sixth lens group G6 is composed of a negative lens L15 using a biconcave lens, a positive lens L16 using a biconvex lens, and an aspherical lens L17, arranged in order from the magnification side E to the reduction side S. The sixth lens group G6 has a total of three lenses L15, L16, and L17, all of which are single lenses.

[0029] The seventh lens group G7 is composed of, in order from the magnification side E to the reduction side S, a positive lens L18 using a biconvex lens, a cemented lens J2 formed by joining a biconcave lens L19 and a biconvex lens L20, and a positive lens L21 using a biconvex lens. The seventh lens group G7 has a total of four lenses L18, L19, L20, and L21, consisting of two single lenses and one cemented lens J2.

[0030] In the above lens configuration, the first lens group G1 includes at least one concave lens L3…(example: three concave lenses L3, L4, L5) that satisfies [condition 4] when the Abbe number of the d line is νd1. νd1>70 … [Conditional expression 4]

[0031] If the first lens group G1 includes at least one concave lens L3 that satisfies [condition equation 4], it will include a concave lens L3 with an Abbe number of more than 70, and therefore, the occurrence of chromatic aberration, especially at the periphery, can be effectively suppressed.

[0032] Furthermore, the sixth lens group G6 includes at least one convex lens L16 that satisfies [condition 5] when the Abbe number of the d line is νd2. νd2>70 … [Conditional expression 5]

[0033] By including at least one convex lens L16 that satisfies [condition equation 5] in the sixth lens group G6, it includes a convex lens L16 with an Abbe number exceeding 70, which in turn suppresses the occurrence of chromatic aberration and effectively suppresses fluctuations in chromatic aberration that occur during magnification.

[0034] Furthermore, in the seventh lens group G7, a convex lens L21 is provided at the most narrowed side S, where the refractive index of the d line is nd, satisfying [condition 6]. nd > 1.8 … [Condition 6]

[0035] By providing a convex lens L21 that satisfies [condition equation 6] in the seventh lens group G7, it is possible to ensure good aberration characteristics while maintaining appropriate telecentricity, as it includes a convex lens L21 with a refractive index greater than 1.8.

[0036] Then, when the total focal length of the system at the wide-angle end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], the system is configured to satisfy [Condition 1] - [Condition 3]. 20 > fw > 10 … [Condition 1] 60 > Aw > 40 … [Condition 2] 5.0 > [Aw / fw] > 2.5 … [Condition 3]

[0037] On the other hand, the projection zoom lens 1 includes an optical adjustment system 200 having a zoom adjustment section Mcz, as shown in the principle configuration diagram in Figure 2.

[0038] In this case, as shown in Figure 2, the zoom adjustment unit Mcz has the function of having the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 all independently move in the optical axis direction Dc from the reduction side S to the enlargement side E when the zoom is changed from the wide-angle end to the telephoto end. In Figure 2, the movement directions of the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 are indicated by arrows M1, M2, and M3, respectively.

[0039] Table 1a shows the "surface data" (lens data) of the projection zoom lens 1 according to Example 1.

[0040] [Table 1a]

[0041] In Table 1a, the "surface data" indicates the surface number of the lens surface counted from the magnification side E, denoted by i. This surface number i corresponds to the symbol (number) shown in Figure 1. Correspondingly, the radius of curvature R(i), axial spacing D(i), refractive index nd(i), and Abbe number νd(i) of the lens surface are shown. nd(i) and νd(i) are values ​​relative to the d line (587.56 [nm]). The axial spacing D(i) indicates the lens thickness or air space between opposing surfaces. The units for the radius of curvature R(i) and spacing D(i) are [mm]. INFINITY for the radius of curvature R(i) represents a plane. Blank spaces for refractive index nd(i) and Abbe number νd(i) indicate air.

[0042] [Table 1b]

[0043] The "aspheric coefficients" in [Table 1b] are expressed by [Equation 1] in a Cartesian coordinate system (X,Y,Z) where the origin is the center of the surface and the optical axis direction Dc is Z, with ASP being the surface number of the aspheric surface. In [Equation 1], R is the radius of curvature of the center, K is the cone constant, A4, A6, A8, A12... are the aspheric coefficients of the 4th, 6th, 8th, 10th, 12th order, etc., respectively, and H is the distance from the origin on the optical axis. Note that in Table 1, "E" means "×10".

[0044]

number

[0045] Figure 3 shows the condition values ​​in each conditional expression for the projection zoom lens 1 in each embodiment, including Example 1.

[0046] In Example 1, the total focal length fw at the wide-angle end is 14.40 [mm], satisfying [Condition 1] 20>fw>10, the half-angle of view Aw [°] at the wide-angle end is 50.99 [°], satisfying [Condition 2] 60>Aw>40, and (Aw / fw) is 3.541, satisfying [Condition 3] 5.0>(Aw / fw)>2.5. Furthermore, the Abbe numbers νd1 of the d-lines of the three concave lenses L3, L4, and L5 in the first lens group G1 are 70.4 for the concave lens (negative lens) L3, 81.6 for the biconcave lens (negative lens) L4, and 81.6 for the biconcave lens (negative lens) L5, all satisfying [Condition 4] νd1>70. Furthermore, the Abbe number νd2 of the d line of the biconvex lens (positive lens) L16 in the sixth lens group G6 is 95.1, satisfying condition νd2 > 70. Also, the refractive index nd of the d line of the biconvex lens (positive lens) L21 in the seventh lens group G7 is 1.80810, satisfying condition nd > 1.8.

[0047] Figures 1 and 2(b) show the lens positions in the optical axis Dc direction of each lens L1... when the projection zoom lens 1 according to Example 1 is adjusted to the TELE side, and Figure 2(a) shows the lens positions in the optical axis Dc direction of each lens L1... when it is adjusted to the WIDE side.

[0048] Figures 4 and 5 show the longitudinal aberration diagrams of the projection zoom lens 1 according to Example 1 at a reference distance (E=1380mm). Figure 4 shows the WIDE side, and Figure 5 shows the TELE side. Each longitudinal aberration diagram shows, from left to right, spherical aberration (610nm, 550nm, 455nm), astigmatism (550nm), and distortion (550nm). Each scale division (1 division) represents ±0.10mm, ±0.10mm, and ±1.0%.

[0049] As shown in Figures 4 and 5, the projection zoom lens 1 according to Example 1 exhibits excellent aberration characteristics, i.e., good projection performance (optical performance), with no significant distortion in any of the longitudinal aberrations.

[0050] Thus, the projection zoom lens 1 according to this embodiment has as a basic configuration a first lens group G1 having negative refractive power, a fourth lens group G4 having positive refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having positive refractive power, and the first lens group G1 and the sixth lens group G6 each include at least one aspherical lens L1 and L17, and when the focal length of the entire system at the wide-angle end is fw [mm] and the half angle of view at the wide-angle end is Aw [°], then [Conditional Equation 1] - [Conditional Equation 3] By providing a lens optical system 100 that satisfies the requirements, and by providing an optical adjustment system 200 having a zoom adjustment section Mcz in which the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 each move independently in the optical axis direction Dc from the reduction side to the enlargement side when changing magnification from the wide-angle end to the telephoto end, it is possible to construct a high-performance projection zoom lens 1 that has a wide angle of view while suppressing various aberrations, for use in projection optical systems such as projectors that project optical images onto a screen. In particular, even in the case of short focal length lenses, by using aspherical lenses, as well as high refractive index glass materials and low dispersion glass materials in appropriate places, it is possible to secure various requirements such as miniaturization and weight reduction, and provide a high-performance projection zoom lens with good telecentricity while suppressing various aberrations such as curvature, distortion, and chromatic aberration required for wide-angle lenses. [Examples]

[0051] Next, the lens optical system 100 of the projection zoom lens 1 according to Embodiment 2 of this embodiment will be described with reference to Figures 6-8 and 3.

[0052] Figure 6(a) shows the overall lens configuration of the WIDE side of the projection zoom lens in Example 2, and Figure 6(b) shows the overall lens configuration of the TELE side of the projection zoom lens in Example 2.

[0053] As shown in Figures 6(a) and (b), the lens optical system 100 comprises seven lens groups G1, G2, G3, G4, G5, G6, and G7, arranged in order from the magnification side E to the reduction side S, and a prism Pr, as shown in the schematic diagram, is provided on the reduction side S relative to the seventh lens group G7.

[0054] Specifically, the lens system comprises, in order from the magnification side E to the reduction side S, a first lens group G1 having a negative refractive power overall, a second lens group G2 having a positive refractive power overall, a third lens group G3 having a negative refractive power overall, a fourth lens group G4 having a positive refractive power overall, a fifth lens group G5 having a negative refractive power overall, a sixth lens group G6 having a positive refractive power overall, and a seventh lens group G7 having a positive refractive power overall.

[0055] Specifically, the first lens group G1 is composed of the following lenses arranged in order from the magnification side E to the reduction side S: an aspherical lens L1, a negative lens L2 using a negative meniscus lens with a convex surface on the magnification side E, a negative lens L3 using a negative meniscus lens with a convex surface on the magnification side E, a negative lens L4 using a biconcave lens, a negative lens L5 using a biconcave lens, and a positive lens L6 using a positive meniscus lens with a convex surface on the magnification side E. The first lens group G1 has a total of six lenses L1...L6, all of which are single lenses.

[0056] The second lens group G2 is composed of a positive lens L7 using a biconvex lens, a positive lens L8 using a biconvex lens, and a cemented lens J1 formed by joining a negative lens L9 using a negative meniscus lens with a convex surface on the reduction side S, in order from the magnification side E to the reduction side S. The second lens group G2 has a total of three lenses L7...L9 and is composed of single lenses and cemented lenses. The third lens group G3 is composed of a negative lens L10 using a biconcave lens.

[0057] The fourth lens group G4 is composed of a negative lens L11 using a biconvex lens and a negative lens L12 using a negative meniscus lens with a convex surface on the magnifying side E, arranged in order from the magnifying side E to the reducing side S. The fourth lens group G4 has a total of two lenses L11 and L12, both of which are single lenses.

[0058] The fifth lens group G5 consists of a positive lens L13 using a biconvex lens and a negative lens L14 using a biconcave lens. The fifth lens group G5 has a total of two lenses, L13 and L14, both of which are single lenses.

[0059] The sixth lens group G6 is composed of a negative lens L15 using a negative meniscus lens with a convex surface on the reduction side S, a positive lens L16 using a biconvex lens, and an aspherical lens L17. The sixth lens group G6 has a total of three lenses L15, L16, and L17, all of which are single lenses.

[0060] The seventh lens group G7 is composed of, in order from the magnification side E to the reduction side S, a positive lens L18 using a biconvex lens, a cemented lens J2 formed by joining a biconcave lens L19 and a biconvex lens L20, and a positive lens L21 using a biconvex lens. The seventh lens group G7 has a total of four lenses L18, L19, L20, and L21, consisting of two single lenses and one cemented lens J2.

[0061] In the above lens configuration, the first lens group G1 includes at least one concave lens L4…(example: two concave lenses L4, L5) that satisfies [condition 4] such that νd1 > 70 when the Abbe number of the d line is νd1, which is the same as in Example 1. Also, the sixth lens group G6 includes at least one convex lens L16 that satisfies [condition 5] such that νd2 > 70 when the Abbe number of the d line is νd2, which is the same as in Example 1. Furthermore, the seventh lens group G7 is provided with a convex lens L21 that satisfies [condition 6] such that nd > 1.8 when the refractive index of the d line is nd, at the most narrowed side S, which is the same as in Example 1.

[0062] Furthermore, when the total focal length at the wide-angle end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], the conditions [Equation 1] - [Equation 3], namely 20>fw>10 [Equation 1], 60>Aw>40 [Equation 2], and 5.0>[Aw / fw]>2.5 [Equation 3] are satisfied, which is the same as in Example 1.

[0063] Furthermore, as shown in Figures 6(a) and (b), similar to Embodiment 1, the optical adjustment system 200 includes a zooming adjustment section Mcz in which the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6 each move independently in the optical axis direction Dc from the reduction side S to the enlargement side E when the zoom is changed from the wide-angle end to the telephoto end.

[0064] Table 2a shows the "surface data" (lens data) of the projection zoom lens 1 according to Example 2, and Table 2b shows the "aspheric coefficient" of the aspherical lens in the projection zoom lens 1 according to Example 2.

[0065] [Table 2a]

[0066] [Table 2b]

[0067] Furthermore, Figure 3 shows the condition values ​​for each conditional equation of the projection zoom lens 1 in Example 2. In Example 2, the total focal length fw at the wide-angle end is 15.89 [mm], satisfying [Conditional Equation 1] 20>fw>10, the half-angle of view Aw [°] at the wide-angle end is 46.81 [°], satisfying [Conditional Equation 2] 60>Aw>40, and (Aw / fw) is 2.945, satisfying [Conditional Equation 3] 5.0>(Aw / fw)>2.5. In addition, the Abbe numbers νd1 of the d lines of the two concave lenses L4 and L5 in the first lens group G1 are 81.6 for negative lens L4 and 81.6 for negative lens L5, both satisfying [Conditional Equation 4] νd1>70. Furthermore, the Abbe number νd2 of the d line of the biconvex lens (positive lens) L16 in the sixth lens group G6 is 95.1, satisfying condition νd2 > 70. Also, the refractive index nd of the d line of the biconvex lens (positive lens) L21 in the seventh lens group G7 is 1.80810, satisfying condition nd > 1.8.

[0068] As shown in Figures 7 and 8, the projection zoom lens 1 according to Example 2 exhibits excellent aberration characteristics, i.e., good projection performance (optical performance), with no significant distortion in any of the longitudinal aberrations. Thus, the projection zoom lens 1 according to Example 2 can achieve the same effects as Example 1. [Examples]

[0069] Next, the lens optical system 100 of the projection zoom lens 1 according to Embodiment 3 of this embodiment will be described with reference to Figures 9-11 and 3.

[0070] Figure 9(a) shows the overall lens configuration of the WIDE side of the projection zoom lens in Example 3, and Figure 9(b) shows the overall lens configuration of the TELE side of the projection zoom lens in Example 3.

[0071] Specifically, as shown in Figures 9(a) and (b), the system comprises six lens groups G1, G2, G3, G4, G5, and G6, arranged sequentially from the magnification side E to the reduction side S, and the reduction side S relative to the sixth lens group G6 is equipped with a prism Pr as shown in the schematic diagram.

[0072] Specifically, the lens system comprises, in order from the magnification side E to the reduction side S, a first lens group G1 having a negative refractive power overall, a second lens group G2 having a positive refractive power overall, a third lens group G3 having a positive refractive power overall, a fourth lens group G4 having a positive refractive power overall, a fifth lens group G5 having a positive refractive power overall, and a sixth lens group G6 having a positive refractive power overall.

[0073] In this case, the first lens group G1 is composed of the following lenses arranged in order from the magnification side E to the reduction side S: aspherical lens L1, aspherical lens L2, negative lens L3 using a negative meniscus lens with a convex surface on the magnification side E, negative lens L4 using a negative meniscus lens with a convex surface on the magnification side E, cemented lens J1 formed by joining a negative lens L5 using a biconcave lens and a positive lens L6 using a biconvex lens, and negative lens L7 using a biconcave lens. The first lens group G1 has a total of seven lenses L1...L7, and is composed of five single lenses and one cemented lens.

[0074] The second lens group G2 is configured by arranging the following lenses in order from the magnification side E to the reduction side S: a positive lens L8 using a positive meniscus lens with a convex surface on the magnification side E; a positive lens L9 using a biconvex lens; a bonded lens J2 formed by joining a positive lens L10 using a biconvex lens and a negative lens L11 using a negative meniscus lens with a convex surface on the reduction side S; and a negative lens L12 using a negative meniscus lens with a convex surface on the magnification side E.

[0075] The third lens group G3 is composed of a positive lens L13 using a biconvex lens and a negative lens L14 using a biconcave lens, arranged in order from the magnification side E to the reduction side S. The third lens group G3 is composed of two single lenses.

[0076] The fourth lens group G4 is composed of a positive lens L15 using a biconvex lens, arranged in order from the magnification side E to the reduction side S, and a negative lens L16 using a negative meniscus lens with a convex surface on the reduction side S. The fourth lens group G4 has a total of two lenses L15 and L16, both of which are single lenses.

[0077] The fifth lens group G5 is composed of a negative lens L17 using a biconcave lens, a positive lens L18 using a biconvex lens, and an aspherical lens L19, arranged in order from the magnification side E to the reduction side S. The fifth lens group G5 has a total of three lenses L17, L18, and L19, all of which are single lenses.

[0078] The sixth lens group G6 is composed of, in order from the magnification side E to the reduction side S, a positive lens L20 using a positive meniscus lens with a convex surface on the reduction side S, a cemented lens J3 formed by joining a negative lens L21 using a biconcave lens and a positive lens L22 using a biconvex lens, and a positive lens L23 using a biconvex lens. The sixth lens group G6 has a total of four lenses L20, L21, L22, and L23, consisting of three single lenses and one cemented lens J3.

[0079] In the above lens configuration, the first lens group G1 includes at least one concave lens L7 that satisfies [condition 4] such that νd1 > 70 when the Abbe number of the d line is νd1, and the fifth lens group G5 includes at least one convex lens L18 that satisfies [condition 5] such that νd2 > 70 when the Abbe number of the d line is νd2. This is the same as in Example 1. Furthermore, the sixth lens group G6 is provided with a convex lens L23 that satisfies [condition 6] such that nd > 1.8 at the most narrowed side S when the refractive index of the d line is nd.

[0080] Furthermore, when the total focal length at the wide-angle end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], the conditions [Equation 1] - [Equation 3], namely 20>fw>10 [Equation 1], 60>Aw>40 [Equation 2], and 5.0>[Aw / fw]>2.5 [Equation 3] are satisfied, which is the same as in Example 1.

[0081] Furthermore, as shown in Figures 9(a) and (b), the optical adjustment system 200 includes a zooming adjustment section Mcz in which the third lens group G3, the fourth lens group G4, and the fifth lens group G5 each move independently in the optical axis direction Dc from the reduction side S to the enlargement side E when changing magnification from the wide-angle end to the telephoto end.

[0082] Table 3a shows the "surface data" (lens data) of the projection zoom lens 1 according to Example 3, and Table 3b shows the "aspheric coefficient" of the aspherical lens in the projection zoom lens 1 according to Example 3.

[0083] [Table 3a]

[0084] [Table 3b]

[0085] Furthermore, Figure 3 shows the condition values ​​for each conditional equation of the projection zoom lens 1 in Example 3. In Example 3, the total focal length fw at the wide-angle end is 11.99 [mm], satisfying [Conditional Equation 1] 20>fw>10, the half-angle of view Aw [°] at the wide-angle end is 55.24 [°], satisfying [Conditional Equation 2] 60>Aw>40, and (Aw / fw) is 4.609, satisfying [Conditional Equation 3] 5.0>(Aw / fw)>2.5. Also, the Abbe number νd1 of the d line of a single concave lens (negative lens) L7 in the first lens group G1 is 95.1, satisfying [Conditional Equation 4] νd1>70. Furthermore, the Abbe number νd2 of the d line of the biconvex lens (positive lens) L18 in the fifth lens group G5 is 95.1, satisfying [Conditional Equation 5] νd2>70. Furthermore, the refractive index nd of the d-line of the biconvex lens (positive lens) L23 in the sixth lens group G6 is 1.84666, satisfying condition 6, nd > 1.8.

[0086] As shown in Figures 10 and 11, the projection zoom lens 1 according to Example 3 exhibits excellent aberration characteristics, i.e., good projection performance (optical performance), with no significant distortion in any of the longitudinal aberrations. Thus, the projection zoom lens 1 according to Example 3 can achieve the same effects as Example 1.

[0087] Although preferred embodiments, including Examples 1-3, have been described in detail above, the present invention is not limited to these embodiments, and the details of the configuration, shape, materials, quantity, numerical values, etc., can be arbitrarily changed, added, or deleted without departing from the spirit of the present invention.

[0088] For example, in a lens optical system 100, a lens optical system 100 that includes at least one concave lens L3 in the first lens group satisfying νd1 > 70 when the Abbe number of the d line is νd1 [Condition Equation 4], a lens optical system 100 that includes at least one convex lens L16 in the (N-1) lens group satisfying νd2 > 70 when the Abbe number of the d line is νd2 [Condition Equation 5], and a lens optical system 100 that provides a convex lens L21 in the Nth lens group that satisfies nd > 1.8 [Condition Equation 6] on the most narrowed side S when the refractive index of the d line is nd, is not an essential constituent requirement, and does not exclude cases where these conditions Equations 4, 5, and 6 are not satisfied. [Industrial applicability]

[0089] The projection zoom lens according to the present invention can be used as a projection lens, including dedicated lenses or interchangeable lenses, in various optical devices such as projectors. [Explanation of Symbols]

[0090] 1: Projection zoom lens, 100: Lens optics, 200: Optical adjustment system, E: Magnification side, S: Reduction side, fw: Total focal length of the system at the wide-angle end, Aw: Half-angle of view at the wide-angle end, Dc: Optical axis direction, Mcz: Zooming adjustment unit, L3…: Concave lens, L16…: Convex lens, L21…: Convex lens

Claims

1. A projection zoom lens comprising a first lens group to the Nth lens group (N is 6 or 7, the same applies hereinafter) arranged in order from the magnification side to the reduction side, wherein the lens optical system satisfies [Conditional Equation 1] - [Conditional Equation 3] when the focal length of the entire system at the wide-angle end is fw [mm] and the half-angle of view at the wide-angle end is Aw [°], and the projection zoom lens comprises an optical adjustment system having a zoom adjustment section in which the Nth-3 lens group, the Nth-2 lens group, and the Nth-1 lens group all move independently in the optical axis direction from the reduction side to the magnification side when the zoom is changed from the wide-angle end to the telephoto end. 20 > fw > 10 ... [Condition 1] 60 > Aw > 40 ... [Conditional Equation 2] 5.0 > [Aw / fw] > 2.5 ... [Conditional Equation 3]

2. The projection zoom lens according to claim 1, characterized in that the first lens group includes at least one concave lens that satisfies [conditional equation 4] when the Abbe number of the d line is νd1. νd1>70... [Conditional expression 4]

3. The projection zoom lens according to claim 1, characterized in that the N-1 lens group includes at least one convex lens that satisfies [condition 5] when the Abbe number of the d line is νd2. νd2>70... [Conditional expression 5]

4. The projection zoom lens according to claim 1 or 2, characterized in that the N lens group includes a convex lens that satisfies [conditional equation 6] on the most retracted side, when the refractive index of the d line is nd. nd > 1.8 ... [Conditional Equation 6]

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