Zoom lens

Abstract

To provide a middle-focus projection zoom lens with a high zoom ratio, which offers nice and stable performance by suppressing variations in chromatic aberration and astigmatism, in particular.SOLUTION: A zoom lens provided herein includes: a lens optical system 100 comprising a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having positive refractive power, an N-th lens group G6 (G7) with positive refractive power located on the most reduction side S, and an (N-1)th lens group G5 (G6) comprising one cemented lens Js, arranged in order from the magnification side E to the reduction side S; and an optical adjustment system 200 configured to designate the first lens group G1 and the N-th lens groups G6 (G7) as a stationary lens group and designate the second lens group G2 through the (N-1)th lens group G5 (G6) as a movable lens group configured such that each of the lens groups G2, G3, G4, G5 (G6) independently moves along an optical axis Dc while zooming. The zoom lens is set up to satisfy a [conditional expression 1] and a [conditional expression 2].SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a 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 zoom lens provided in a projection optical system that projects an image from a projector onto a screen or the like, the zoom lens described in Patent Document 1 proposed by the present applicant has been known.

[0003] The zoom lens of Patent Document 1 aims to balance each performance well and reasonably, such as ensuring the required brightness, obtaining good image quality by correcting various aberrations and field curvature as required, and 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 negative refractive power, a fourth lens group having a positive refractive power, a fifth lens group having at least two cemented lenses, and a sixth lens group having a positive refractive power are sequentially arranged to form a lens optical system. The first lens group and the sixth lens group are fixed, and a zoom adjustment unit that independently moves the second lens group to the fifth lens group in the optical axis direction, and an optical adjustment system including a focusing adjustment unit that moves the first lens group in the optical axis direction are provided. The total length of the lens optical system (assuming the distance from the lens surface on the telephoto side of the lens arranged on the most telephoto side of the first lens group to the image plane on the wide-angle side is T when projecting at the reference distance, and the focal length of the entire system on the wide-angle side is fw), and it is set to satisfy 5.0 < [T / fw] < 8.0.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the zoom lens described above also had the following problems to be solved.

[0006] That is, this type of zoom lens used in a projector or the like enlarges and projects an optical image onto a distant screen. Therefore, for the zoom lens to be used, while ensuring the required brightness, the required zoom ratio and angle of view are required, and good image quality is required by necessary corrections for various aberrations such as spherical aberration, distortion aberration, and chromatic aberration, and field curvature. In addition, the zoom lens is supported in a state of protruding forward from the front surface of the projector body, and has an optical adjustment system including a lens optical system composed of a relatively large number of lens groups and various adjustment parts such as a zooming adjustment part. Therefore, miniaturization, weight reduction, and cost reduction of the entire zoom lens are also required.

[0007] On the other hand, since each of these required performances has a mutually conflicting relationship such that if some performance items are enhanced, other performance items are impaired, in addition to enhancing each required performance, how to balance each required item well is an important issue for the zoom lens. The zoom lens of Citation Document 1 was also made with the aim of solving this problem, and it is possible to balance each performance well and reasonably, such as ensuring the required brightness, obtaining good image quality, and achieving miniaturization, weight reduction, and cost reduction of the whole.

[0008] However, in a high-magnification and medium-focus projection zoom lens, there were quite a few fluctuations in various aberrations such as spherical aberration, coma aberration, and field curvature. In particular, regarding the fluctuations in chromatic aberration and astigmatism, there was room for further improvement from the viewpoint of suppressing these fluctuations and ensuring good and stable performance.

[0009] An object of the present invention is to provide a zoom lens that solves the problems existing in such background art.

Means for Solving the Problems

[0010] In order to solve the above-described problems, when constructing a zoom lens 1 in which a total of six or seven lens groups G1 - G6 (G7) from the first lens group G1 located on the most enlarged side E to the Nth lens group (N is 6 or 7) located on the most reduced side S are sequentially arranged, from the enlarged side E to the reduced side S, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, an Nth lens group G6 (G7) having a positive refractive power located on the most reduced side S, and an (N - 1)th lens group G5 (G6) having one cemented lens Js, a lens optical system 100 including the above, and during zooming adjustment, the first lens group G1 and the Nth lens group G6 (G7) are used as fixed lens groups, and each lens group G2, G3, G4, G5 (G6) from the second lens group G2 to the (N - 1)th lens group G5 (G6) is used as a movable lens group that independently moves in the direction of the optical axis Dc. The overall focal length on the wide-angle side is fw [mm], and the overall focal length on the telephoto side is ft [mm]. It is characterized in that it is set to satisfy the [conditional formula 1] of 1.5 < [ft / fw] < 2.0 and the [conditional formula 2] of 40 < fw < 50.

[0011] In this case, according to a preferred embodiment of the invention, the cemented lens Js is formed by cementing a positive lens L19 (L20, L14) and a negative lens L18 (L21, L13). When the refractive index of the positive lens L19 (L20, L14) at the d-line is nda, the refractive index of the negative lens L18 (L21, L13) at the d-line is ndb, the Abbe number of the positive lens L19 (L20, L14) at the d-line is νda, and the Abbe number of the negative lens L18 (L21, L13) at the d-line is νdb, it is desirable to set them to satisfy the [conditional expression 3] of nda < ndb and the [conditional expression 4] of νdb < νda. Also, the movable lens group can set the movement amount M2 of the third lens group G3 to be the largest movement amount among each movable lens group. On the other hand, when the refractive index at the d-line of the positive lens located on the reduction side S from the cemented lens Js is ndx, the lens optical system 100 can include one or more positive lenses L20, L21 (L22, L15) that satisfy the [conditional expression 5] of 1.8 < ndx. On the other hand, the first lens group G1 includes two or more negative lenses L2..., and each of the negative lenses L2... can be set to satisfy the [conditional expression 6] of ndc < 1.5 and the [conditional expression 7] of 70 < νdc when the refractive index at the d-line is ndc and the Abbe number at the d-line is νdc.

Effect of the Invention

[0012] According to the zoom lens 1 according to the present invention having such a configuration, the following remarkable effects can be obtained.

[0013] (1) From the wide-angle side E to the telephoto side S, a lens optical system 100 including a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, an Nth lens group G6 (G7) having a positive refractive power located on the most telephoto side S, and an (N - 1)th lens group G5 (G6) having a single cemented lens Js; and an optical adjustment system 200 in which, during zooming adjustment, the first lens group G1 and the Nth lens group G6 (G7) are fixed lens groups, and each lens group G3, G4, G5 (G6) from the second lens group G2 to the (N - 1)th lens group G5 (G6) is a movable lens group that moves independently in the direction of the optical axis Dc. When the overall focal length on the wide-angle side is fw [mm] and the overall focal length on the telephoto side is ft [mm], it is set to satisfy 1.5 < [ft / fw] < 2.0 (conditional expression 1) and 40 < fw < 50 (conditional expression 2). Therefore, while ensuring the required zoom ratio and brightness, good image quality can be obtained, and miniaturization, weight reduction, and cost reduction of the whole can be achieved. Each performance can be balanced well and reasonably, and in a high-magnification medium-focus projection zoom lens, fluctuations in various aberrations such as spherical aberration, coma aberration, and field curvature, especially fluctuations in chromatic aberration and astigmatism, can be suppressed, thereby ensuring good and stable performance.

[0014] (2) In a preferred embodiment, when constructing the cemented lens Js, it is composed of the cementing of a positive lens L19... and a negative lens L18.... When the refractive index of the positive lens L19... at the d-line is nda, the refractive index of the negative lens L18... at the d-line is ndb, the Abbe number of the positive lens L19... at the d-line is νda, and the Abbe number of the negative lens L18... at the d-line is νdb, if it is set to satisfy nda < ndb (conditional expression 3) and νdb < νda (conditional expression 4), an optimal cemented lens Js that satisfies the preferred conditions can be constructed. Therefore, in particular, fluctuations in chromatic aberration and astigmatism can be suppressed.

[0015] (3) In a preferred embodiment, when constructing the movable lens group, if the movement amount M2 of the third lens group G3 is set to be the largest movement amount among each movable lens group, fluctuations such as field curvature associated with the movement of the lens group during magnification change (zooming) can be suppressed.

[0016] (4) In a preferred embodiment, if one or more positive lenses L20, L21 (L22, L15) that satisfy the conditional expression 5 of 1.8 < ndx (where ndx is the refractive index in the d-line) are included in the positive lens located on the reduction side S from the cemented lens Js in the lens optical system 100, appropriate telecentricity can be maintained, and thus good aberration characteristics can be ensured.

[0017] (5) In a preferred embodiment, the first lens group G1 includes two or more negative lenses L2..., and each of the negative lenses L2... satisfies the conditional expression 6 of ndc < 1.5 and the conditional expression 7 of 70 < νdc (where ndc is the refractive index in the d-line and νdc is the Abbe number in the d-line). By setting them in this way, appropriate refractive index and Abbe number in the first lens group G1 can be ensured, and thus chromatic aberration and spherical aberration can be reduced to obtain good optical performance.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

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Figure 7

Figure 8

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Figure 10

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Figure 12

Figure 13

Figure 14

Mode for Carrying Out the Invention

[0019] Next, preferred embodiments according to the present invention will be given and described in detail with reference to the drawings.

Example

[0020] First, the zoom lens 1 according to Example 1 of this embodiment will be described with reference to FIGS. 1-4, 13 and 14.

[0021] First, the configuration of the lens optical system 100 of the zoom lens 1 according to Example 1 will be described with reference to FIGS. 1 and 2.

[0022] Note that this zoom lens 1 is assumed to be applied to a projection lens used in a projector, that is, a projection zoom optical system.

[0023] In FIG. 1, E indicates the enlarged side such as a screen, and S indicates the reduced side (reduced conjugate side) that becomes an image display element such as a liquid crystal panel. Therefore, the enlarged side E is in front of the optical axis Dc direction, and the reduced side S is behind the optical axis Dc direction.

[0024] As shown in Fig. 1, the lens optical system 100 includes a total of seven groups, namely, the first lens group G1 to the seventh lens group G7, arranged in order from the magnification side E to the reduction side S. That is, the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, the sixth lens group G6, and the seventh lens group G7. On the reduction side S with respect to the seventh lens group G7, it includes the prism Pb shown in the schematic diagram.

[0025] The first lens group G1 has a negative refractive power as a whole. In order from the magnification side E to the reduction side S, it is composed of a positive lens L1 using a positive meniscus lens with a convex surface on the magnification side E, 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 negative meniscus lens with a convex surface on the magnification side E, and a negative lens L5 using a biconcave lens. Each of the lenses L1, L2, L3, L4, and L5 is a single lens.

[0026] The first lens group G1 includes two or more (four in Example 1) negative lenses L2, L3, L4, and L5. When the refractive index at the d-line is ndc and the Abbe number at the d-line is νdc for each of these negative lenses L2, L3, L4, and L5, ndc < 1.5 …〔Conditional formula 6〕 70 < νdc …〔Conditional formula 7〕 They are set to satisfy the above conditions. By including two or more negative lenses L2... in the first lens group G1 and setting each of these negative lenses L2... to satisfy the conditional formula 6 of ndc < 1.5 and the conditional formula 7 of 70 < νdc when the refractive index at the d-line is ndc and the Abbe number at the d-line is νdc, appropriate refractive index and Abbe number in the first lens group G1 can be ensured, so that chromatic aberration and spherical aberration can be reduced and good optical performance can be obtained.

[0027] On the other hand, the second lens group G2 has a positive refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a positive lens L6 using a biconvex lens and a cemented lens J1 in which a negative lens L7 using a negative meniscus lens having a convex surface on the reduction side S is cemented, a negative lens L8 using a biconcave lens, and a positive lens L9 using a biconvex lens. Each of the lenses L8 and L9 is a single lens.

[0028] The third lens group G3 has a positive refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a positive lens L10 using a biconvex lens and a negative lens L11 using a negative meniscus lens having a convex surface on the magnification side E. The fourth lens group G4 has a positive refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a positive lens L12 using a biconvex lens, a negative lens L13 using a negative meniscus lens having a convex surface on the reduction side S, a negative lens L14 using a negative meniscus lens having a convex surface on the magnification side E, and a positive lens L15 using a biconvex lens. The fifth lens group G5 has a negative refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a positive lens L16 using a positive meniscus lens having a convex surface on the magnification side E and a negative lens L17 using a biconcave lens.

[0029] Furthermore, the sixth lens group G6 has a positive refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a cemented lens Js in which a negative lens L18 using a biconcave lens and a positive lens L19 using a biconvex lens are cemented and a positive lens L20 using a biconvex lens. The positive lens L20 is a single lens.

[0030] In this case, when constructing the cemented lens Js, let the refractive index of the positive lens L19 at the d-line be nda, the refractive index of the negative lens L18 at the d-line be ndb, the Abbe number of the positive lens L19 at the d-line be νda, and the Abbe number of the negative lens L18 at the d-line be νdb. nda < ndb …〔Conditional expression 3〕 νdb < νda …〔Conditional expression 4〕 It is set to satisfy the above conditions. By setting in this way, an optimal cemented lens Js that satisfies the suitable conditions can be constructed, and in particular, fluctuations in chromatic aberration and spherical aberration can be suppressed.

[0031] Also, the seventh (Nth) lens group G7 serves as the final lens group. The seventh lens group G7 has a positive refractive power as a whole and is composed of a single positive lens L21. Specifically, it is composed of a positive lens L21 using a positive meniscus lens having a convex surface on the magnification side E.

[0032] In addition, the lens optical system 100 includes one or more (two in Example 1) positive lenses L20 and L21 that satisfy [Conditional Expression 5] in a positive lens located on the reduction side S with respect to the cemented lens Js. When the refractive index in the d-line is ndx. By configuring in this way, since appropriate telecentricity can be maintained, there is an advantage that good aberration characteristics can be ensured. 1.8 < ndx … [Conditional Expression 5]

[0033] In the lens optical system 100 having the above configuration, further, when the overall focal length on the wide-angle side is fw [mm] and the overall focal length on the telephoto side is ft [mm], 1.5 < [ft / fw] < 2.0 … [Conditional Expression 1] 40 < fw < 50 … [Conditional Expression 2] It is set to satisfy.

[0034] On the other hand, the zoom lens 1 includes an optical adjustment system 200. FIG. 2 shows an explanatory diagram of the movement state of the optical adjustment system 200 in the zoom lens 1 of Example 1. FIG. 2(a) shows an overall lens configuration diagram showing the lens positions on the WIDE side, and FIG. 2(b) shows an overall lens configuration diagram showing the lens positions on the TELE side.

[0035] The optical adjustment system 200 is configured such that, during zooming adjustment, the first lens group G1 and the seventh lens group G7 are fixed lens groups, and each of the lens groups G2 to G6 from the second lens group G2 to the sixth lens group G6 is an independent movable lens group that moves in the direction of the optical axis Dc. In FIG. 2, M1, M2, M3, M4, and M5 respectively indicate the movement amounts when each of the lens groups G2, G3, G4, G5, and G6 is moved between the WIDE side and the TELE side.

[0036] In this case, when configuring the movable lens group, the movement amount M2 of the third lens group G3 is set to be the largest movement amount among the movable lens groups as shown in Fig. 13(c). By setting it in this way, fluctuations such as field curvature associated with the movement of the lens group during variable magnification (zooming) can be suppressed.

[0037] [Table 1] shows the lens data (surface data) of the zoom lens 1 according to Example 1.

[0038]

Table 1

[0039] The surface data in [Table 1] is indicated by (i) for the surface number of the lens surface counted from the telephoto side E, and this surface number (i) corresponds to the reference numerals (numbers) shown in Fig. 1. Correspondingly, the radius of curvature R(i) of the lens surface, the on-axis surface interval D(i), the refractive index nd(i) of the lens, and the Abbe number νd(i) of the lens are shown respectively. nd(i) and νd(i) are numerical values for the d-line (587.56 [nm]). The on-axis surface interval D(i) indicates the lens thickness or air space between opposite surfaces. Note that the units of the radius of curvature R(i) and the surface interval D(i) are [mm]. INFINITY of the radius of curvature R(i) represents a plane. The blanks for the refractive index nd(i) and the Abbe number νd(i) indicate that it is air.

[0040] Fig. 13 shows the respective numerical values of (a) [conditional expression 1] [conditional expression 2], (b) [conditional expression 3] [conditional expression 4], and (c) the movement amount [mm] of the movable lens group in the zoom lens 1 according to Example 1, and Fig. 14 shows the respective numerical values of (d) [conditional expression 5] and (e) [conditional expression 6] [conditional expression 7].

[0041] As shown in Fig. 13(a), the full-system focal length fw [mm] on the wide-angle side is "43.81", the full-system focal length ft [mm] on the telephoto side is "86.10", and "ft / fw" is "1.965", so it satisfies the [conditional expression 1] of "1.5 < [ft / fw] < 2.0" and also satisfies the [conditional expression 2] of "40 < fw < 50". Also, as shown in Fig. 13(b), the nda of the positive lens L19 is "1.48749" and the ndb of the negative lens L18 is "1.78880", so "1.48749 < 1.78880", which satisfies the [conditional expression 3] of "nda < ndb". Also, the νda of the positive lens L19 is "70.2" and the νdb of the negative lens L18 is "28.4", so "28.4 < 70.2", which satisfies the [conditional expression 4] of "νdb < νda". Also, as shown in Fig. 13(c), the movement amount M2 [mm] of the third lens group G3 is "70.00", which is the largest among the movement amounts M1 - M5.

[0042] Furthermore, as shown in Fig. 14(d), the ndx of the positive lens L20 is "1.80810" and the ndx of the positive lens L21 is "1.80420", each satisfying the [conditional expression 5] of "1.8 < ndx". Also, as shown in Fig. 14(e), for the first lens group G1, the ndc of the negative lens L2 is "1.48749" and the ndc of the negative lenses L3 - L5 is "1.49700" respectively, satisfying the [conditional expression 6] of "ndc < 1.5". Also, the νdc of the negative lens L2 is "70.2" and the νdc of the negative lenses L3 - L5 is "81.6" respectively, satisfying the [conditional expression 7] of "70 < νdc".

[0043] Figs. 3 and 4 show the longitudinal aberration diagrams of the zoom lens 1 according to Example 1. Fig. 3 shows the longitudinal aberration at the reference distance OBJ(E) = 6450 mm on the WIDE side, and Fig. 4 shows the longitudinal aberration at the reference distance OBJ(E) = 6450 mm on the TELE side. Each longitudinal aberration diagram shows, from the left, spherical aberration (610 nm, 550 nm, 455 nm), astigmatism (550 nm), and distortion (550 nm). Each scale graduation (one graduation) is ±0.10 mm, ±0.10 mm, ±1.0%. It can be confirmed that the zoom lens 1 according to Example 1 has good aberration characteristics, that is, projection performance (optical performance) without significant disturbances in any longitudinal aberration.

[0044] Thus, the zoom lens 1 according to this embodiment (Example 1) basically includes, from the wide-angle side E to the telephoto side S, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, a seventh lens group G7 (the Nth lens group G7) having a positive refractive power located on the most telephoto side S, an (N - 1)th lens group G6 having a single cemented lens Js, a lens optical system 100, and during zooming adjustment, the first lens group G1 and the seventh lens group G7 (the Nth lens group G7) are used as fixed lens groups, and each lens group G2, G3, G4, G5, G6 from the second lens group G2 to the sixth lens group G6 (the (N - 1)th lens group G6) is used as a movable lens group that moves independently in the direction of the optical axis Dc. When the overall focal length on the wide-angle side is fw [mm] and the overall focal length on the telephoto side is ft [mm], it is set to satisfy the [conditional formula 1] of 1.5 < [ft / fw] < 2.0 and the [conditional formula 2] of 40 < fw < 50. Therefore, while ensuring the required zoom ratio and brightness, good image quality can be obtained, and miniaturization, weight reduction, and cost reduction of the whole can be achieved. Each performance can be balanced well and reasonably, and in a high-magnification medium-focus projection zoom lens, by suppressing fluctuations in various aberrations such as spherical aberration, coma aberration, and field curvature, especially fluctuations in chromatic aberration and astigmatism, good and stable performance can be ensured.

Example

[0045] Next, the zoom lens 1 according to Example 2 of the present embodiment will be described with reference to FIGS. 5-8, 13 and 14.

[0046] First, the configuration of the lens optical system 100 of the zoom lens 1 according to Example 2 will be described with reference to FIGS. 5 and 6 (FIG. 14). FIG. 5 shows an overall lens configuration diagram showing the lens positions on the WIDE side of the zoom lens 1.

[0047] Similar to Example 1, the lens optical system 100 according to Example 2 includes seven lens groups G1 to G7, namely, the first lens group G1 to the seventh lens group G7, arranged in order from the telephoto side E to the wide side S as shown in FIGS. 5 and 6.

[0048] The first lens group G1 has a negative refractive power as a whole, and the basic lens configuration is the same as that of the first lens group G1 in Example 1, but there are the following differences. That is, in Example 1, a negative meniscus lens with a convex surface on the telephoto side E was used for the negative lens L4, while in Example 2, a biconcave lens is used as the negative lens L4.

[0049] In addition, the first lens group G1 in Example 1 includes four negative lenses L2, L3, L4, and L5 that satisfy [Conditional Expression 6] and [Conditional Expression 7], while the first lens group G1 in Example 2 includes three negative lenses L2, L3, and L4 that satisfy [Conditional Expression 6] and [Conditional Expression 7] as shown in FIG. 14(e), which is different.

[0050] On the other hand, the second lens group G2 has a positive refractive power as a whole, and is configured by arranging, in order from the telephoto side E to the wide side S, a cemented lens J1 formed by cementing a positive lens L6 using a positive meniscus lens with a convex surface on the wide side S and a negative lens L7 using a negative meniscus lens with a convex surface on the wide side S, a negative lens L8 using a biconcave lens, and a positive lens L9 using a positive meniscus lens with a convex surface on the telephoto side E.

[0051] The third lens group G3 has a positive refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, positive lenses L10 and L11 using biconvex lenses, and a negative lens L12 using biconcave lenses. The fourth lens group G4 has a positive refractive power as a whole, and is configured by a positive lens L13 using a single biconvex lens. The fifth lens group G5 has a negative refractive power as a whole, and is configured by a cemented lens J2 in which a negative lens L14 using a biconcave lens arranged on the magnification side E and a positive lens L15 using a biconvex lens arranged on the reduction side are cemented together.

[0052] Furthermore, the sixth lens group G6 has a negative refractive power as a whole, and is configured by arranging, in order from the magnification side E to the reduction side S, a negative lens L16 using a negative meniscus lens having a convex surface on the reduction side S, positive lenses L17 and L18 using biconvex lenses, a negative lens L19 using biconcave lenses, a positive lens L20 using biconvex lenses, and a cemented lens Js in which a negative lens L21 using a negative meniscus lens having a convex surface on the reduction side S are cemented together. In this case, when configuring the cemented lens Js, it is set so as to satisfy the above-mentioned [conditional expression 3] and [conditional expression 4].

[0053] Also, the seventh (the Nth) lens group G7 is the final lens group. The seventh lens group G7 has a positive refractive power as a whole, and is configured by a single positive lens L22, specifically, a positive lens L22 using a biconvex lens. In this case, it is set so as to satisfy the above-mentioned [conditional expression 5]. In addition, when configuring the lens optical system 100, it is set so as to satisfy the above-mentioned [conditional expression 1] and [conditional expression 2].

[0054] On the other hand, FIG. 6 shows an overall lens configuration diagram showing the lens positions on the TELE side of the zoom lens 1. In Example 2, the illustration of the optical adjustment system is omitted, but like Example 1, it includes the optical adjustment system 200 shown in FIG. 2. That is, during zooming adjustment, the first lens group G1 and the seventh lens group G7 are fixed lens groups, and each of the lens groups G2 to G6 from the second lens group G2 to the sixth lens group G6 is provided with a movable lens group that independently moves in the direction of the optical axis Dc. In FIG. 6, P2e indicates the lens position of the third lens group G3 on the WIDE side of the zoom lens 1 (see FIG. 5), P2 indicates the lens position of the third lens group G3 on the TELE side, and M2 indicates the movement amount of the third lens group G3. The movement amount M2 of this third lens group G3 is set to be the largest movement amount among the movable lens groups, as shown in FIG. 13(c).

[0055] [Table 2] shows the lens data (surface data) of the zoom lens 1 according to Example 2.

[0056]

Table 2

[0057] FIG. 13 shows the respective numerical values of (a) [conditional expression 1] [conditional expression 2], (b) [conditional expression 3] [conditional expression 4], and (c) the movement amount [mm] of the movable lens group in the zoom lens 1 according to Example 2, and FIG. 14 shows the respective numerical values of (d) [conditional expression 5], (e) [conditional expression 6] [conditional expression 7].

[0058] As shown in Fig. 13(a), the overall focal length fw [mm] on the wide-angle side is "45.98", the overall focal length ft [mm] on the telephoto side is "90.55", and "ft / fw" is "1.969", so it satisfies the [conditional expression 1] of "1.5 < [ft / fw] < 2.0" and also satisfies the [conditional expression 2] of "40 < fw < 50". Also, as shown in Fig. 13(b), since the nda of the positive lens L20 is "1.62299" and the ndb of the negative lens L21 is "1.67300", it becomes "1.62299 < 1.67300", satisfying the [conditional expression 3] of "nda < ndb", and since the νda of the positive lens L20 is "58.1" and the νdb of the negative lens L18 is "38.3", it becomes "58.1 < 38.3", satisfying the [conditional expression 4] of "νdb < νda". Also, as shown in Fig. 13(c), the movement amount M2 [mm] of the third lens group G3 is "75.81", which is the largest among the movement amounts M1 - M5.

[0059] Furthermore, as shown in Fig. 14(d), the ndx of the positive lens L22 is "1.80810", satisfying the [conditional expression 5] of "1.8 < ndx". Also, as shown in Fig. 14(e), for the negative lens L2 of the first lens group G1, the ndc is "1.49700", and for the negative lenses L3 and L4, the ndc is "1.43700" respectively, satisfying the [conditional expression 6] of "ndc < 1.5", and the νdc of the negative lens L2 is "81.6", and the νdc of the negative lenses L3 and L4 is "95.1" respectively, satisfying the [conditional expression 7] of "70 < νdc".

[0060] On the other hand, Figs. 7 and 8 show the longitudinal aberration diagrams of the zoom lens 1 according to Example 2. Fig. 7 shows the longitudinal aberration at the reference distance OBJ(E) = 6528 mm on the WIDE side, and Fig. 8 shows the longitudinal aberration at the reference distance OBJ(E) = 6528 mm on the TELE side. As shown in Figs. 7 and 8, it can be confirmed that the zoom lens 1 according to Example 2 has good aberration characteristics without large disturbances in any longitudinal aberration, and the same operational effects as in Example 1 can be obtained.

Example

[0061] Next, the zoom lens 1 according to Example 3 of the present embodiment will be described with reference to FIGS. 9-14.

[0062] First, the configuration of the lens optical system 100 of the zoom lens 1 according to Example 3 will be described with reference to FIGS. 9 and 10 (FIG. 14). FIG. 9 shows an overall lens configuration diagram showing the lens positions on the WIDE side of the zoom lens 1.

[0063] As shown in FIGS. 9 and 10, the lens optical system 100 according to Example 3 includes six lens groups G1 to G6 (the Nth lens group G6), arranged in order from the telephoto side E to the wide-angle side S, namely, the first lens group G1, the second lens group G2, the third lens group G3, the fourth lens group G4, the fifth lens group G5, and the sixth lens group G6.

[0064] The first lens group G1 has a negative refractive power as a whole, and includes, in order from the telephoto side E to the wide-angle side S, a positive lens L1 using a positive meniscus lens having a convex surface on the telephoto side E, a negative lens L2 using a negative meniscus lens having a convex surface on the telephoto side E, a negative lens L3 using a negative meniscus lens having a convex surface on the telephoto side E, and a negative lens L4 using a biconcave lens.

[0065] As shown in FIG. 14(e), the first lens group G1 includes two or more (two in Example 3) negative lenses L2 and L4, and each of the negative lenses L2 and L4 is set to satisfy the above [conditional expression 6] and [conditional expression 7] when the refractive index at the d line is ndc and the Abbe number at the d line is νdc.

[0066] The second lens group G2 has a positive refractive power as a whole, and includes, in order from the telephoto side E to the wide-angle side S, a cemented lens J1 formed by cementing a positive lens L5 using a positive meniscus lens having a convex surface on the wide-angle side S and a negative lens L6 using a negative meniscus lens having a convex surface on the wide-angle side S, and a biconvex lens L7.

[0067] The third lens group G3 has a positive refractive power as a whole, and is composed of a cemented lens J3 formed by cementing a positive lens L8 using a biconvex lens and a negative lens L9 using a negative meniscus lens having a convex surface on the reduction side S in order from the enlargement side E to the reduction side S. The fourth lens group G4 has a negative refractive power as a whole, and is configured by arranging a cemented lens J4 formed by cementing a positive lens L10 using a positive meniscus lens having a convex surface on the reduction side S and a negative lens L11 using a biconcave lens, and a positive lens L12 using a biconvex lens in order from the enlargement side E to the reduction side S.

[0068] Furthermore, the fifth lens group G5 (the (N - 1)th lens group G5) has a positive refractive power as a whole, and is composed of a cemented lens Js formed by cementing a negative lens L13 using a biconcave lens and a positive lens L14 using a biconvex lens, and a positive lens L15 using a biconvex lens in order from the enlargement side E to the reduction side S. In this case, when configuring the cemented lens Js, it is set to satisfy the above-mentioned [conditional formula 3] and [conditional formula 4].

[0069] Also, the sixth (the Nth) lens group G6 is the final lens group. The sixth lens group G6 has a positive refractive power as a whole, and is composed of a single positive lens L16, specifically, a positive lens L16 using a biconvex lens. In this case, it is set to satisfy the above-mentioned [conditional formula 5]. In addition, when configuring the lens optical system 100, it is set to satisfy the above-mentioned [conditional formula 1] and [conditional formula 2].

[0070] On the other hand, FIG. 10 shows an overall lens configuration diagram showing the lens positions on the TELE side of the zoom lens 1. In Example 3, the illustration of the optical adjustment system is omitted, but similar to Example 1, it is provided with the optical adjustment system 200 shown in FIG. 2, but is different in the following points.

[0071] That is, at the time of zoom adjustment, the first lens group G1 and the sixth (the Nth) lens group G6 are set as fixed lens groups, and each of the lens groups G2 to G5 (the N-1th lens group G5) from the second lens group G2 is configured as a movable lens group that moves independently in the direction of the optical axis Dc. In FIG. 10, P2e indicates the lens position of the third lens group G3 on the WIDE side of the zoom lens 1 (see FIG. 9), P2 indicates the lens position of the third lens group G3 on the TELE side, and M2 indicates the moving amount of the third lens group G3. As shown in FIG. 13(c), the moving amount M2 of the third lens group G3 is set to be the largest among the moving amounts of each movable lens group.

[0072] [Table 3] shows the lens data (surface data) of the zoom lens 1 according to Example 3.

[0073]

Table 3

[0074] FIG. 13 shows the respective numerical values of (a) [conditional expression 1] [conditional expression 2], (b) [conditional expression 3] [conditional expression 4], and (c) the moving amount [mm] of the movable lens group in the zoom lens 1 according to Example 3, and FIG. 14 shows the respective numerical values of (d) [conditional expression 5] and (e) [conditional expression 6] [conditional expression 7].

[0075] As shown in Fig. 13(a), the overall focal length fw [mm] on the wide-angle side is "40.00", the overall focal length ft [mm] on the telephoto side is "63.73", and "ft / fw" is "1.593", so it satisfies the [conditional formula 1] of "1.5 < [ft / fw] < 2.0" and also satisfies the [conditional formula 2] of "40 < fw < 50". Also, as shown in Fig. 13(b), since the nda of the positive lens L14 is "1.48749" and the ndb of the negative lens L13 is "1.68893", it becomes "1.48749 < 1.68893", satisfying the [conditional formula 3] of "nda < ndb". Also, since the νda of the positive lens L14 is "70.4" and the νdb of the negative lens L13 is "31.2", it becomes "70.4 < 31.2", satisfying the [conditional formula 4] of "νdb < νda". Also, as shown in Fig. 13(c), the movement amount M2 [mm] of the third lens group G3 is "47.65", which is the largest among the movement amounts M1 - M4.

[0076] Furthermore, as shown in Fig. 14(d), the ndx of the positive lens L15 is "1.80518", satisfying the [conditional formula 5] of "1.8 < ndx". Also, as shown in Fig. 14(e), for the first lens group G1, the ndc of the negative lens L2 is "1.48749" and the ndc of the negative lens L4 is "1.49700", satisfying the [conditional formula 6] of "ndc < 1.5". Also, the νdc of the negative lens L2 is "70.4" and the νdc of the negative lens L4 is "81.6", satisfying the [conditional formula 7] of "70 < νdc".

[0077] On the other hand, Figs. 11 and 12 show the longitudinal aberration diagrams of the zoom lens 1 according to Example 3. Fig. 11 shows the longitudinal aberration at the reference distance OBJ(E) = 5280 mm on the WIDE side, and Fig. 12 shows the longitudinal aberration at the reference distance OBJ(E) = 5280 mm on the TELE side. As shown in Figs. 11 and 12, it can be confirmed that the zoom lens 1 according to Example 3 has good aberration characteristics without large disturbances in any of the longitudinal aberrations, and the same operational effects as in Example 1 can be obtained.

[0078] Although the preferred embodiments have been described in detail above, the present invention is not limited to such embodiments, and can be arbitrarily changed, added, or deleted in terms of the detailed configuration, shape, material, quantity, numerical value, etc., without departing from the gist of the present invention.

[0079] For example, since the refractive powers of the fourth lens group G4 and the fifth lens group G5 can be positive or negative, either power can be used. Also, when constructing the cemented lens Js, it is desirable to satisfy [conditional expression 3] of nda < ndb and [conditional expression 4] of νdb < νda, but this is not an essential component. Furthermore, for the movable lens group, it is desirable to set the moving amount M2 of the third lens group G3 to be the largest moving amount among the respective movable lens groups, but it does not limit the magnitudes of the moving amounts of the other movable lens groups. Additionally, although it is desirable to satisfy [conditional expression 5], [conditional expression 6], and [conditional expression 7], these are not essential components.

Industrial Applicability

[0080] The zoom lens according to the present invention can be used as a projection lens including a dedicated lens or an interchangeable lens in various optical devices such as projectors.

Explanation of Reference Numerals

[0081] 1: Zoom lens, 100: Lens optical system, 200: Optical adjustment system, E: Enlargement side, S: Reduction side, G1: First lens group, G2: Second lens group, G3: Third lens group, G4: Fourth lens group, G5: Fifth lens group, G6: Sixth lens group, G7: Seventh lens group, G7(G6): Nth lens group, Js: Cemented lens, L2…: Negative lens, L18(L21, L13): Negative lens, L19(L20, L14): Positive lens, L21(L22, L16): Positive lens, Dc: Optical axis Dc, M2: Moving amount of the third lens group

Claims

1. In a zoom lens in which a total of six or seven lens groups from the first lens group located on the most telephoto side to the Nth lens group (N is 6 or 7) located on the most wide-angle side are sequentially arranged, from the telephoto side to the wide-angle 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, an Nth lens group having a positive refractive power located on the most wide-angle side, and an (N - 1)th lens group having one cemented lens, a lens optical system including: and during zooming adjustment, an optical adjustment system in which the first lens group and the Nth lens group are fixed lens groups, and each lens group from the second lens group to the (N - 1)th lens group is a movable lens group that moves independently in the optical axis direction. When the overall focal length on the wide-angle side is fw [mm] and the overall focal length on the telephoto side is ft [mm], it is characterized in that it is set to satisfy [Conditional Expression 1] and [Conditional Expression 2]. 1.5 < [ft / fw] < 2.0... [Conditional Expression 1] 40 < fw < 50... [Conditional Expression 2]

2. The cemented lens is formed by cementing a positive lens and a negative lens. When the refractive index of the positive lens at the d-line is nda, the refractive index of the negative lens at the d-line is ndb, the Abbe number of the positive lens at the d-line is νda, and the Abbe number of the negative lens at the d-line is νdb, the zoom lens according to Claim 1, characterized in that it satisfies [Conditional Expression 3] and [Conditional Expression 4]. nda < ndb... [Conditional Expression 3] νdb < νda... [Conditional Expression 4]

3. The movable lens group is characterized in that the moving amount of the third lens group is set to be the largest moving amount among the movable lens groups in the zoom lens according to Claim 1.

4. The lens optical system includes one or more positive lenses that satisfy [Conditional Expression 5] when the refractive index at the d-line of a positive lens arranged on the wide-angle side of the cemented lens is ndx. The zoom lens according to Claim 1, characterized by this. 1.8 < ndx... [Conditional Expression 5]

5. The first lens group includes two or more negative lenses, and each of the negative lenses satisfies [Conditional Expression 6] and [Conditional Expression 7] when the refractive index at the d-line is ndc and the Abbe number at the d-line is νdc. The zoom lens according to Claim 1, characterized by this. ndc < 1.5... [Conditional Expression 6] 70 < νdc... [Conditional Expression 7]

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