Lens device

Abstract

To reduce aberration related to field curvature, and reduce the entire lens device and further reduce costs without complicating a mechanism of the lens device.SOLUTION: A lens device comprises: a lens optical system 100 that has a first lens group G1 in which a first front lens group G1F and a first rear lens group G1R are arranged from an enlargement side E, and the first front lens group G1F includes an aspherical lens Ls having both aspherical lens surfaces, and which has negative refractive power, a fourth lens group G4 having positive refractive power, and a seventh lens group G7 having positive refractive power; and an optical adjustment system 200 that has a zooming adjustment unit Mcz that makes the first lens group G1 and the seventh lens group G7 stationary and moves a second lens group G2 to a sixth lens group G6 independently in a direction of an optical axis Dc, and a focusing adjustment unit Mcf that independently moves the first front lens group G1F and the first rear lens group G1R in the direction of the optical axis Dc.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lens device suitable for use in a projection optical system provided in a projector or the like.

Background Art

[0002] Conventionally, as a lens device provided with a projection optical system (projection lens) for projecting an image from a projector onto a screen or the like, a zoom lens for projection described in Patent Document 1 and a projection optical system described in Patent Document 2 are known.

[0003] The zoom lens for projection of Patent Document 1 has a high zoom ratio, a small F number, small magnification chromatic aberration, high MTF characteristics, and resolution characteristics, and aims to realize a zoom lens for projection in which the display device side is telecentric. Specifically, in order from the wide-angle side, a negative first lens group, a positive second lens group, a third lens group, a fourth lens group, a negative fifth lens group, a positive or negative sixth lens group, and a positive seventh lens group are arranged, and an aperture stop is arranged between the fourth and fifth lens groups. When zooming, the second to sixth lens groups move, and when zooming from the wide-angle end to the telephoto end, the distances between the first and second lens groups, the first and third lens groups, and the first and fourth lens groups all decrease. The focal length of the entire system at the wide-angle end: fw, the focal length of the first lens group: fl, the focal length of the second lens group: f2, the focal length of the third lens group: f3, and the focal length of the fourth lens group: f4 are configured to satisfy 1.3 < |f| / fw < 1.9, 0.6 < f2 / f3 < 3.5, and 0.4 < f4 / f3 < 3.7.

[0004] Furthermore, the projection optical system of Patent Document 2 aims to provide a projection optical system that has a simple configuration and is capable of adjusting the field curvature appropriately. Specifically, when constructing the projection optical system, it has a first lens whose power on the optical axis and the power in the meridional section of the outermost periphery are different from each other, a second lens adjacent to the first lens, and a diaphragm arranged at a position where the off-axis chief ray intersects with the optical axis, and is configured so that the field curvature of the projected image can be adjusted by changing the distance between the first lens and the second lens in the optical axis direction, and further configured so as to satisfy a predetermined conditional formula. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-200454 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-126036 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional lens devices, including the above-mentioned projection zoom lens and projection optical system, have the following problems to be solved.

[0007] That is, with this type of lens device, even if focusing adjustment is performed on the center of the optical axis, a problem occurs in which the image becomes blurred on peripheral surfaces away from the optical axis. For this reason, in conventional technology, it was necessary to provide a separate adjustment mechanism that changes the spacing between lenses in the front lens group located on the enlargement side of the projection optical system, specifically, to provide a separate adjustment lens or adjustment lens group that moves in the optical axis direction, in order to correct the field curvature that fluctuates during focusing adjustment.

[0008] Moreover, when the installation space for the optical system is limited, the focusing adjustment mechanism and the image plane correction mechanism will be arranged closer to each other, which will cause complication in the mechanism of the lens device and become a bottleneck in reducing the size and cost of the entire lens device. Therefore, there are still further problems to be solved.

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

Means for Solving the Problems

[0010] In order to solve the above-mentioned problems, when constructing the lens device 1 composed of arranging seven lens groups G1, G2, G3, G4, G5, G6, G7 from the wide-angle side E to the telephoto side S in order, from the wide-angle side E to the telephoto side S in order, it consists of the first front lens group G1F and the first rear lens group G1R. The first front lens group G1F includes at least one aspherical lens Ls in which both the lens surface on the wide-angle side E (i = 1) and the lens surface on the telephoto side S (i = 2) are formed as aspherical surfaces. At the same time, two negative lenses L2 and L3 are arranged in the first rear lens group G1R, and the lens device 1 has a first lens group G1 having a negative refractive power as a whole, a fourth lens group G4 having a positive refractive power as a whole, a fifth lens group G5 having a negative refractive power as a whole, a sixth lens group G6 having a negative refractive power as a whole, and a seventh lens group G7 having a positive refractive power as a whole. It is provided with a zooming adjustment unit Mcz that makes the second lens group G2 to the sixth lens group G6 move independently in the direction of the optical axis Dc, and when focusing, makes the first front lens group G1F and the first rear lens group G1R move independently in the same direction along the optical axis Dc, widens the distance between the first front lens group G1F and the first rear lens group G1R when focusing on the near-distance side, and narrows the distance between the first front lens group G1F and the first rear lens group G1R when focusing on the far-distance side. The lens optical system 100 is provided with a focusing adjustment unit Mcf that moves as described above, and when the total angle of view at the wide-angle end is faw, it satisfies the [conditional formula 1] of "55° < faw < 75°".

[0011] In this case, according to a preferred embodiment of the invention, it is desirable that the lens optical system 100 satisfy the conditional formula 2 of "[ft / fw]<2.5," where fw is the overall focal length at the wide-angle end and ft is the overall focal length at the telephoto end. The lens device 1 is optimally suited for use in a projection optical system. [Effects of the Invention]

[0012] The lens device 1 according to the present invention having such a configuration provides the following significant effects.

[0013] (1) A lens optical system 100 is provided in which a first front lens group G1F and a first rear lens group G1R are arranged in order from the enlargement side E to the reduction side S, and the first front lens group G1F includes at least one aspherical lens Ls whose lens surface on both the enlargement side E and the reduction side S is formed as an aspherical surface, and the lens optical system 100 includes a first lens group G1 having a negative refractive power as a whole, a fourth lens group G4 having a positive refractive power as a whole, and a seventh lens group G7 having a positive refractive power as a whole, and the first lens group G1 and the seventh lens group G7 are fixed. The lens device is configured with an optical adjustment system 200 having a zoom adjustment unit Mcz that moves the second lens group G2 to the sixth lens group G6 independently in the direction of the optical axis Dc, and a focusing adjustment unit Mcf that moves the first front lens group G1F and the first rear lens group G1R independently in the direction of the optical axis Dc. This makes it possible to reduce aberrations related to field curvature without providing a separate image plane correction mechanism, and also makes it possible to reduce the size and cost of the entire lens device without introducing mechanical complexity into the lens device.

[0014] (2) When constructing the focusing adjustment unit Mcf, the first front lens group G1F and the first rear lens group G1R are moved in the same direction during focusing. Also, when focusing on the near - distance side, the distance between the first front lens group G1F and the first rear lens group G1R is increased, and when focusing on the far - distance side, the distance between the first front lens group G1F and the first rear lens group G1R is decreased. Therefore, it is possible to simultaneously correct the field curvature during focusing. That is, by increasing the distance between the first front lens group G1F and the first rear lens group G1R when focusing on the near - distance side, the field curvature in the (+) direction at the peripheral image height can be reduced. And by decreasing the distance between the first front lens group G1F and the first rear lens group G1R when focusing on the far - distance side, the field curvature in the (-) direction at the peripheral image height can be reduced.

[0015] (3) When constructing the lens optical system 100, when the full - angle of view at the wide - angle end is faw, since it is configured to satisfy the [conditional formula 1] of "55° < faw < 75°", the full - angle of view faw at which the correction effect of the aspherical lens Ls on the field curvature based on the combined use of the functions of the aspherical lens Ls and the focusing adjustment unit Mcf in the first lens group G1 is reduced can avoid angles less than 55° and angles exceeding 75°. Thereby, a good correction effect on the field curvature can be ensured.

[0016] (4) When constructing the first lens group G1, it is composed of a first front lens group G1F including an aspherical lens Ls and a first rear lens group G1R arranged with two negative lenses L2 and L3 in order from the enlargement side E to the reduction side S. Therefore, the first lens group G1 located on the most enlarged side E in the lens device 1 can be constructed with a small number of lens elements. This can contribute to the weight reduction of the lens device 1 which is relatively long in the direction of the optical axis Dc. In particular, it can effectively reduce various aberrations including the field curvature generated during focusing and contribute to the improvement of the overall image quality.

[0017] (5) In a preferred embodiment, when the lens optical system 100 is configured to satisfy Conditional Expression 2, "[ft / fw]<2.5," where fw is the focal length of the entire system at the wide-angle end and ft is the focal length of the entire system at the telephoto end, the spacing between the first front lens group G1F and the first rear lens group G1R changes, thereby making it possible to reduce field curvature during focusing from the wide-angle end to the telephoto end, even when the zoom ratio is large.

[0018] (6) In a preferred embodiment, when the lens device 1 is used in a projection optical system, it is possible to achieve a high zoom ratio and a wide angle of view while ensuring sufficient optical performance, particularly in a projector that projects onto a screen, and it is also possible to effectively eliminate field curvature that occurs during focusing. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram showing the overall lens configuration of a lens device according to a first embodiment of the present invention; [Figure 2] FIG. 2 is a diagram showing the principle of an optical adjustment system in the lens device of the first embodiment; [Figure 3] FIG. 2 is a diagram showing an optical path of the lens device according to the first embodiment; [Figure 4] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a reference distance on the WIDE side; [Figure 5] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a reference distance on the TELE side; [Figure 6] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a close distance on the WIDE side; [Figure 7] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a close distance on the TELE side; [Figure 8] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a long distance on the WIDE side; [Figure 9] FIG. 2 is a longitudinal aberration diagram of the lens device of Example 1 at a long distance on the TELE side; [Figure 10] FIG. 10 is a diagram showing the principle of an optical adjustment system in the lens device of the second embodiment; [Figure 11] FIG. 3 is a diagram showing an optical path of the lens device according to the second embodiment; [Figure 12] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a reference distance on the WIDE side; [Figure 13] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a reference distance on the TELE side; [Figure 14] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a close distance on the WIDE side; [Figure 15] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a close distance on the TELE side; [Figure 16] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a long distance on the WIDE side; [Figure 17] FIG. 10 is a longitudinal aberration diagram of the lens device of Example 2 at a long distance on the TELE side; [Figure 18] Optical characteristics table of the lens device according to the embodiment DETAILED DESCRIPTION OF THE INVENTION

[0020] Next, preferred embodiments of the present invention will be described in detail with reference to the drawings. [Example]

[0021] First, the configuration of a lens optical system 100 of a lens device 1 according to Example 1 of this embodiment will be described with reference to FIG.

[0022] It is assumed that the lens device 1 is applied to a projection lens (zoom lens) used in a projector, i.e., a projection optical system, particularly a projection zoom optical system. Thus, by applying the lens device 1 to a projection optical system (projection zoom optical system), it is possible to achieve a high zoom ratio and a wide angle of view while ensuring sufficient optical performance, particularly for a projector that projects onto a screen, and to effectively eliminate field curvature that occurs during focusing. In FIG. 1, E (OBJ) indicates the enlargement side of a screen or the like, and S (IMG) indicates the reduction side (reduction conjugate side) that serves as an image display element such as a liquid crystal panel. Therefore, the enlargement side E is located in front of the optical axis Dc, and the reduction side S is located behind the optical axis Dc.

[0023] As shown in Figure 1, the lens optical system 100 has seven lens groups G1, G2, G3, G4, G5, G6, and G7 arranged in order from the enlargement side E to the reduction side S, from the first lens group G1 to the seventh lens group G7, and has a prism Pb shown in the schematic diagram on the reduction side S of the seventh lens group G7.

[0024] The first lens group G1 is composed of, from the enlargement side E to the reduction side S, a foremost lens L1 constituting the first front lens group G1F, and two negative lenses L2 and L3 constituting the first rear lens group G1R. Specifically, the negative meniscus lens L2 has a convex surface on the enlargement side E, and the biconcave lens L3. In this case, the first lens group G1 has negative refractive power as a whole. The foremost lens L1 is composed of a single aspherical lens Ls, and both the lens surface on the enlargement side E (i=1) and the lens surface on the reduction side S (i=2) are formed aspherical. The forming conditions (aspherical coefficients) of the aspherical lens Ls are shown in Table 1b, which will be described later.

[0025] In this way, by constructing the first lens group G1 from three single lenses L1, L2, and L3, the first lens group G1, which is located on the magnification side E of the lens device 1, can be constructed using a small number of lenses, which contributes to reducing the weight of the lens device 1, which is relatively long in the direction of the optical axis Dc, and in particular, it can effectively reduce various aberrations, including field curvature, that occur during focusing, contributing to improving the overall quality of the image.

[0026] The second lens group G2 is composed of two single lenses: a biconvex lens L4 located on the enlargement side E and a biconcave lens L5 located on the reduction side S. The third lens group G3 is composed of a single lens using the biconvex lens L4. In this manner, the second lens group G2 and the third lens group G3 can each be configured to have negative or positive refractive power overall. Therefore, each lens group G2 and G3 is not limited or restricted by specific optical conditions, i.e., whether the refractive power is positive or negative, thereby increasing the design freedom of the lens optical system 100.

[0027] On one side, on the reduction side S of the third lens group G3, there is provided a fourth lens group G4 composed of a single lens using a biconvex lens L7. Therefore, this fourth lens group G4 has a positive refractive power as a whole. Further, with respect to the fourth lens group G4, on the reduction side S, there is provided a fifth lens group G5 using a cemented lens J1. This cemented lens J1 is configured by cementing a biconcave lens L8 located on the enlargement side E and a biconvex lens L9 located on the reduction side S.

[0028] On the reduction side S of the fifth lens group G5, there is provided a sixth lens group G6. This sixth lens group G6 includes, in order from the enlargement side E to the reduction side S, a cemented lens J2 and a biconvex lens L12. The cemented lens J2 is configured by cementing a biconcave lens L10 located on the enlargement side E and a biconvex lens L11 located on the reduction side S, and the biconvex lens L12 is composed of a single lens. The fifth lens group G5 and the sixth lens group G6 can be configured to have a negative or positive refractive power as a whole, respectively. Therefore, since each of the lens groups G5 and G6 is not limited or restricted by a specific optical condition, that is, whether the refractive power is on the positive side or the negative side, the design freedom of the lens optical system 100 can be increased. The seventh lens group G7 includes a biconvex lens L13 using a single lens. Therefore, this seventh lens group G7 has a positive refractive power as a whole.

[0029] Also, when configuring this lens optical system 100, when the full angle of view at the wide-angle end is faw, it is configured to satisfy the following [Conditional Expression 1]. 55° < faw < 75° … [Conditional Expression 1]

[0030] By configuring according to this condition, the full angle of view faw at which the correction effect on the field curvature of the aspherical lens Ls based on the combined use of the functions of the aspherical lens Ls and the focusing adjustment unit Mcf in the first lens group G1 is reduced can avoid angles less than 55° and angles exceeding 75°, so that a good correction effect on the field curvature can be ensured.

[0031] Furthermore, when the focal length of the entire system at the wide-angle end is fw and the focal length of the entire system at the telephoto end is ft, the following [Conditional Expression 2] is satisfied. [ft / fw]<2.5 … [Condition 2] If configured under this condition, even when the zoom ratio is large, the distance between the first front lens group G1F and the first rear lens group G1R changes, making it possible to reduce the curvature of field during focusing from the wide-angle end to the telephoto end.

[0032] On the other hand, the lens device 1 is equipped with a zoom adjustment unit Mcz and a focusing adjustment unit Mcf, the basic configuration of which is shown in Fig. 2. In this case, the zoom adjustment unit Mcz has the function of immobilizing the first lens group G1 and the seventh lens group G7, and independently moving the second lens group G2 to the sixth lens group G6 in the direction of the optical axis Dc.

[0033] The focusing adjustment unit Mcf also has the function of moving the first front lens group G1F and the first rear lens group G1R independently in the direction of the optical axis Dc. More specifically, the focusing adjustment unit Mcf is configured to move the first front lens group G1F and the first rear lens group G1R in the same direction during focusing, and to widen the space between the first front lens group G1F and the first rear lens group G1R during focusing on the close distance side, and narrow the space between the first front lens group G1F and the first rear lens group G1R during focusing on the long distance side.

[0034] With this configuration, it is possible to simultaneously correct field curvature during focusing. That is, by widening the distance between the first front lens group G1F and the first rear lens group G1R during focusing on the close distance side, it is possible to reduce field curvature in the (+) direction at the peripheral image height, and by narrowing the distance between the first front lens group G1F and the first rear lens group G1R during focusing on the long distance side, it is possible to reduce field curvature in the (-) direction at the peripheral image height. Note that FIG. 3 shows an optical path diagram of the lens device 1 according to Example 1.

[0035] Furthermore, [Table 1a] shows the lens data (surface data) of the lens device 1, and [Table 1b] shows the aspherical data (aspherical coefficients) and focus interval of the aspherical lens Ls.

[0036] [Table 1a]

[0037] [Table 1b]

[0038] In the surface data in Table 1a, i indicates the surface number of the lens surface counted from the magnification side E. This surface number i corresponds to the symbol (number) shown in Figure 1. Correspondingly, the radius of curvature R(i), on-axis surface spacing D(i), lens refractive index nd(i), and lens Abbe number νd(i) are also shown. nd(i) and νd(i) are values ​​relative to the d-line (587.56 nm). On-axis surface spacing D(i) indicates the lens thickness or air space between opposing surfaces. The radius of curvature R(i) and surface spacing D(i) are measured in mm. The surface number E indicates the image position on the magnification side, and S indicates the image position on the reduction side. The "infinity" symbol in the radius of curvature R(i) indicates a flat surface. Blank spaces for the refractive index nd(i) and Abbe number νd(i) indicate air.

[0039] The aspherical coefficients in Table 1b are expressed by Equation 1 in a Cartesian coordinate system (X, Y, Z) with the origin at the center of the surface and Z along the optical axis Dc, where S1 (i=1) and S2 (i=2) are the aspherical surface numbers. In Equation 1, R is the central radius of curvature, A4, A6, A8, A10, etc. are the aspherical coefficients for the fourth, sixth, eighth, tenth, etc. orders, respectively, and H is the distance from the origin on the optical axis. In Table 1b, "E" means "power of 10." Regarding the focus distance in Table 1b, for example, the reference distance "(i)=2-3" indicates the distance D(i) [mm] between surface numbers (i)=2 and (i)=3, and "(i)=6-7" indicates the distance D(i) [mm] between surface numbers (i)=6 and (i)=7.

[0040] [Number]

[0041] (a) and (b) of FIG. 18 show the optical characteristics of the lens device 1 according to Example 1. As shown in (a), the F-number of Example 1 is "2.2" in WIDE and "3.2" in TELE. Also, the image height is "12.2 [mm]" both in WIDE and TELE.

[0042] Also, as shown in (b), the full angle of view faw at the wide-angle end of the lens device 1 according to Example 1 is "67.6 [°]", which satisfies the [conditional expression 1] of "55° < faw < 75°". Furthermore, since the full focal length fw at the wide-angle end is "18.4 [mm]" and the full focal length ft at the telephoto end is "38.7 [mm]", ft / fw is "2.10", which satisfies the [conditional expression 2] of "[ft / fw] < 2.5".

[0043] FIGS. 4 - FIG. 9 show the longitudinal aberration diagrams of the lens device 1 according to Example 1. FIG. 4 is the longitudinal aberration diagram at the reference distance (WIDE side, E = 2920 mm), FIG. 5 is the longitudinal aberration diagram at the reference distance (TELE side, E = 2920 mm), FIG. 6 is the longitudinal aberration diagram at the short distance (WIDE side, E = 2050 mm), FIG. 7 is the longitudinal aberration diagram at the short distance (TELE side, E = 2050 mm), FIG. 8 is the longitudinal aberration diagram at the long distance (WIDE side, E = 8760 mm), and FIG. 9 is the longitudinal aberration diagram at the long distance (TELE side, E = 8760 mm), respectively. Each longitudinal aberration diagram shows spherical aberration (610 nm, 550 nm, 460 nm), astigmatism (550 nm), and distortion (550 nm) from the left side. Each scale graduation (one graduation) is ±0.05 mm, ±0.05 mm, ±1.0%.

[0044] As shown in FIGS. 4 - FIG. 9, it can be confirmed that for the lens device 1 according to Example 1, any longitudinal aberration has no significant disturbance and good aberration characteristics, that is, projection performance (optical performance) is obtained. [Example]

[0045] Next, the configuration of the lens optical system 100 of the lens device 1 according to Example 2 of this embodiment will be described with reference to FIGS.

[0046] 10 and 11, the same components and functional parts as those in Figures 1 to 3 are denoted by the same reference numerals to clarify the configuration. Therefore, the basic configuration and functions of Example 2 are basically the same as those of Example 1.

[0047] As shown in Figure 10, the lens optical system 100 of Example 2 has seven lens groups G1, G2, G3, G4, G5, G6, and G7, from the first lens group G1 to the seventh lens group G7, arranged in order from the enlargement side E to the reduction side S, and has a prism Pb, shown in a schematic diagram, on the reduction side S of the seventh lens group G7.

[0048] The first lens group G1 is composed of, from the enlargement side E to the reduction side S, a foremost lens L1 constituting the first front lens group G1F, and two negative lenses L2 and L3 constituting the first rear lens group G1R. Specifically, the negative meniscus lenses L2 and L3 have a convex surface on the enlargement side E. In this case, the first lens group G1 has negative refractive power as a whole. The foremost lens L1 is composed of a single aspherical lens Ls, and both the lens surface on the enlargement side E (i=1) and the lens surface on the reduction side S (i=2) are formed aspherical. The forming conditions (aspherical coefficients) of the aspherical lens Ls are shown in Table 2b, which will be described later.

[0049] The second lens group G2 is composed of a biconvex lens L4 that uses one single lens. The third lens group G3 is composed of two single lenses: a biconcave lens L5 located on the enlargement side E, and a positive meniscus lens L6 located on the reduction side S and having a convex surface facing the enlargement side E. The second lens group G2 and the third lens group G3 can each be configured to have negative or positive refractive power overall.

[0050] On the other hand, on the reduction side S relative to the third lens group G3, there is a fourth lens group G4 composed of a single lens using a biconvex lens L7. Therefore, this fourth lens group G4 has positive refractive power overall. Furthermore, on the reduction side S relative to the fourth lens group G4, there is a fifth lens group G5 using a cemented lens J1. This cemented lens J1 is composed of a biconcave lens L8 located on the enlargement side E and a biconvex lens L9 located on the reduction side S cemented together.

[0051] The reduction side S of the fifth lens group G5 is equipped with a sixth lens group G6. This sixth lens group G6 includes, in order from the enlargement side E to the reduction side S, a cemented lens J2 and a biconvex lens L12. The cemented lens J2 is formed by cementing a biconcave lens L10 located on the enlargement side E to a biconvex lens L11 located on the reduction side S, and the biconvex lens L12 is formed from a single lens. The fifth lens group G5 and the sixth lens group G6 can each be configured to have negative or positive refractive power overall. The seventh lens group G7 includes a biconvex lens L13 using a single lens. Therefore, this seventh lens group G7 has positive refractive power overall.

[0052] In configuring this lens optical system 100, the aforementioned [Conditional Formula 1] and [Conditional Formula 2] must be satisfied, just like in Example 1. Also, like Example 1, Example 2 is provided with a zoom adjustment unit Mcz and a focusing adjustment unit Mcf, and the zoom adjustment unit Mcz has the function of keeping the first lens group G1 and the seventh lens group G7 immobile and independently moving the second lens group G2 to the sixth lens group G6 in the direction of the optical axis Dc.

[0053] Furthermore, the focusing adjustment unit Mcf has a function of independently moving the first front lens group G1F and the first rear lens group G1R in the direction of the optical axis Dc. That is, more specifically, when focusing, the first front lens group G1F and the first rear lens group G1R are moved in the same direction, and when focusing on the near - distance side, the distance between the first front lens group G1F and the first rear lens group G1R is widened, and when focusing on the far - distance side, the distance between the first front lens group G1F and the first rear lens group G1R is narrowed. Note that FIG. 11 shows the optical path diagram of the lens device 1 according to Embodiment 2.

[0054] Also, [Table 2a] shows the lens data (surface data) of the lens device 1, and [Table 2b] shows the aspherical data (aspherical coefficients) of the aspherical lens Ls and the focus interval.

[0055]

Table 2a

[0056]

Table 2b

[0057] Figures (a) and (b) of FIG. 18 show the optical characteristics of the lens device 1 according to Embodiment 2. As shown in (a), the F - number of Embodiment 2 is the same as that of Embodiment 1, being "2.2" for WIDE and "3.2" for TELE. Also, the image height of the lens device 1 according to Embodiment 2 is the same as that of Embodiment 1, being "12.2 [mm]" for both WIDE and TELE.

[0058] Also, as shown in (b), the full - angle of view faw at the wide - angle end of the lens device 1 according to Embodiment 2 is "68.4 [°]", satisfying the [conditional expression 1] of "55° < faw < 75°". Furthermore, the overall focal length fw at the wide - angle end is "18.1 [mm]", and the overall focal length ft at the telephoto end is "38.5 [mm]", so ft / fw is "2.13", satisfying the [conditional expression 2] of "[ft / fw] < 2.5".

[0059] 12 to 17 show longitudinal aberration diagrams of the lens apparatus 1 according to Example 2. Fig. 12 shows longitudinal aberration diagrams at a reference distance (WIDE side, E=3504 mm), Fig. 13 shows longitudinal aberration diagrams at a reference distance (TELE side, E=3504 mm), Fig. 14 shows longitudinal aberration diagrams at a close distance (WIDE side, E=2640 mm), Fig. 15 shows longitudinal aberration diagrams at a close distance (TELE side, E=2640 mm), Fig. 16 shows longitudinal aberration diagrams at a long distance (WIDE side, E=12000 mm), and Fig. 17 shows longitudinal aberration diagrams at a long distance (TELE side, E=12000 mm). Each longitudinal aberration diagram shows, from left to right, spherical aberration (610 nm, 550 nm, 460 nm), astigmatism (550 nm), and distortion (550 nm). Each scale division (1 division) is ±0.05mm, ±0.05mm, ±1.0%.

[0060] As shown in Figures 12 to 17, the lens device 1 of Example 2 has slightly inferior longitudinal aberrations compared to the various aberrations of the lens device 1 of Example 1 (Figures 4 to 9), but it can be confirmed that good aberration characteristics, i.e., projection performance (optical performance), are obtained.

[0061] Therefore, the lens device 1 according to this embodiment has a basic configuration in which a first front lens group G1F and a first rear lens group G1R are arranged in that order from the enlargement side E to the reduction side S, and the first front lens group G1F includes at least one aspherical lens Ls whose lens surfaces on both the enlargement side E and the reduction side S are formed aspherical, and the lens device 1 is provided with a lens optical system 100 having a first lens group G1 having negative refractive power as a whole, a fourth lens group G4 having positive refractive power as a whole, and a seventh lens group G7 having positive refractive power as a whole; The optical adjustment system 200 has a zoom adjustment unit Mcz that keeps the first lens group G1 and the seventh lens group G7 stationary and moves the second lens group G2 to the sixth lens group G6 independently in the direction of the optical axis Dc, and a focusing adjustment unit Mcf that moves the first front lens group G1F and the first rear lens group G1R independently in the direction of the optical axis Dc. Therefore, it is possible to reduce aberrations related to field curvature without providing a separate image plane correction mechanism, and it is possible to reduce the size and cost of the entire lens device without introducing mechanical complexity into the lens device.

[0062] Although the preferred embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the detailed configuration, shape, material, quantity, numerical values, etc. can be changed, added, or deleted as desired within the scope that does not deviate from the gist of the present invention.

[0063] For example, while the lens optical system 100 is configured with seven lens groups G1-G7, adding additional lens groups to form eight or more lens groups G1... is not excluded. Similarly, while the first lens group G1 is preferably configured with a first front lens group G1F including an aspherical lens Ls and a first rear lens group G1R including two negative lenses L2 and L3, other configurations are not excluded as long as the first front lens group G1F includes at least one aspherical lens Ls with both lens surfaces on the magnification side E formed aspherical and has negative refractive power overall. Furthermore, while it is desirable for the lens optical system 100 to satisfy Conditional Expression 2, "[ft / fw]<2.5," this is not a required component. Furthermore, while the lens apparatus 1 is optimal for use in a projection optical system, other applications are not excluded. [Industrial Applicability]

[0064] The lens device according to the present invention can be used as a dedicated lens or a projection lens (projection zoom lens) including an interchangeable lens in various optical devices such as a projector. [Explanation of symbols]

[0065] 1: lens device, 100: lens optical system, 200: optical adjustment system, E: magnification side, S: reduction side, G1: first lens group, G1F: first front lens group, G1R: first rear 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, (i=1): lens surface, (i=2): lens surface, Ls: aspherical lens, L2: negative lens, L3: negative lens, Dc: optical axis, Mcz: zooming adjustment section, Mcf: focusing adjustment section, faw: total angle of view at wide-angle end, fw: total system focal length at wide-angle end, ft: total system focal length at telephoto end

Claims

1. The present invention provides a lens device comprising seven lens groups, from a first lens group to a seventh lens group, arranged in order from the magnification side to the reduction side, the seventh lens group being arranged in order from the magnification side to the reduction side, the seventh lens group being arranged in order from the magnification side to the reduction side, the first front lens group and the first rear lens group being arranged in the first front lens group, the first rear lens group including at least one aspherical lens having aspherical surfaces on both the magnification side and the reduction side, and two negative lenses being arranged in the first rear lens group, the seventh lens group having a negative refractive power as a whole, a fourth lens group having a positive refractive power as a whole, a fifth lens group having a negative refractive power as a whole, a sixth lens group having a negative refractive power as a whole, and a seventh lens group having a positive refractive power as a whole. and an optical adjustment system having a zoom adjustment unit that keeps the first lens group and the seventh lens group stationary and moves the second to sixth lens groups independently in the direction of the optical axis, and a focusing adjustment unit that moves the first front lens group and the first rear lens group independently in the same direction along the optical axis during focusing, so as to increase the spacing between the first front lens group and the first rear lens group when focusing to a close distance side and decrease the spacing between the first front lens group and the first rear lens group when focusing to a long distance side, wherein the lens optical system satisfies the following [Conditional Expression 1] when a total angle of view at the wide-angle end is defined as faw. 55°<faw<75°… [Conditional expression 1]

2. 2. The lens device according to claim 1, wherein the lens optical system satisfies the following conditional expression 2, where fw is an overall focal length at the wide-angle end and ft is an overall focal length at the telephoto end. [ft / fw]<2.5 ... [Conditional Formula 2]

3. 3. The lens device according to claim 1, wherein the optical system is applied to a projection optical system.

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