Lens device

Abstract

To perform appropriate color aberration correction by suppressing an influence of a temperature in the entire zoom adjustment area, and to eliminate decrease in a focus deviation and resolution performance at the time of a temperature fluctuation.SOLUTION: A lens device includes: a lens configuration part Mp having a first lens group G1 of negative refractive power, a second lens group G2 of negative refractive power, a third lens group G3 of negative refractive power, a fourth lens group G4 of positive refractive power, a fifth lens group G5 of positive or negative refractive power, a sixth lens group G6 of positive refractive power, and a seventh lens group G7 of positive refractive power in sequence from an expansion side E; and a lens adjustment part Mc for fixing the first lens group G1 and the seventh lens group G7 at the time of a zooming adjustment, moving each of the second lens group G2 to the sixth lens group G6 independently in a light axis direction Dc, and moving only the second lens group G2 in the light axis direction Dc at the time of a focusing adjustment. The lens device includes a first specific positive lens Lx that satisfies predetermined conditions 1 and 2 in a lens group having the largest travel stroke at the time of a zooming adjustment.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 aims to realize a zoom lens for projection having a high zoom ratio, a small F-number, small magnification chromatic aberration, high MTF characteristics, and resolution characteristics, and the display device side is telecentric. Specifically, in order from the wide-angle side, a negative first lens group G1, a positive second lens group G2, a third lens group G3, a fourth lens group G4, a negative fifth lens group G5, a positive or negative sixth lens group G6, and a positive seventh lens group G7 are arranged, and an aperture stop S 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.

[0007] Specifically, in order to correct the chromatic aberration of the lens used, a positive lens formed from a material with a high Abbe number is generally used. However, many of these materials with a high Abbe number have a large negative temperature coefficient of refractive index, and therefore, when the temperature fluctuates, there are problems such as so-called out-of-focus and a decrease in resolution performance.

[0008] In particular, in a lens device with a large zoom ratio, if the lens group that moves significantly during zooming includes a positive lens made of a material with a high Abbe number and a large negative temperature coefficient of refractive index, there will be a large difference in the change in optical performance due to temperature fluctuations between the wide-angle end and the telephoto end, making it difficult to suppress the effects of temperature across the entire zoom range. Conversely, if a material with a low Abbe number is used, it will be impossible to provide sufficient chromatic aberration correction. These effects tend to become more pronounced as the zoom ratio increases.

[0009] SUMMARY OF THE INVENTION An object of the present invention is to provide a lens device that solves the problems present in the background art. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides a lens device 1 including a plurality of lens groups G1... in order from the enlargement side E, the lens group Mp including, in order from the enlargement side E, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive or negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having positive refractive power, and a lens group Mp including, in order from the enlargement side E, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive or negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having positive refractive power, the lens group Mp being configured such that, during zooming adjustment, the first lens group G1 and the seventh lens group G7 are fixed, and the second lens group G2 to the sixth lens group G6 are aligned along the optical axis. and a lens adjustment unit Mc that moves the second lens group G2 independently in the direction Dc and moves only the second lens group G2 in the optical axis direction Dc during focusing adjustment, and the lens group (G4) that has the largest movement stroke during zooming adjustment includes a positive lens (hereinafter referred to as the first specified positive lens) Lx, and the first specified positive lens Lx is formed so as to satisfy vdx>65 (condition 1) and Kx>-1.0 (condition 2) when vdx is the Abbe number for the d-line and Kx is the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40°C (=dn / dT [1E-6 / °C (n: refractive index, T: temperature [°C])]).

[0011] In this case, according to a preferred embodiment of the invention, when configuring the optical system 100, 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, it can be configured to satisfy [ft / fw]>1.55 (condition 3), and when the focal length of the first specified positive lens Lx is fpx, it can be configured to satisfy 0<[fpx / fw]<5 (condition 4). Furthermore, when the refractive indices for the C-line, F-line, and g-line are nCx, nFx, and ngx, respectively, the first specified positive lens Lx is configured so that the anomalous dispersion (ΔPg,F)x, defined as (ΔPg,F)x = Px + [0.001694 × νdx] - 0.6445, where Px is the partial dispersion ratio defined by Px = [ngx - nFx] / [nFx - nCx] and νdx is the Abbe number, satisfies (ΔPg,F)x > 0.005 (condition 5), and when the linear expansion coefficient at -30 to +70°C is αx [1E-7 / °C], it is desirable to configure the first specified positive lens Lx so that αx < 90 (condition 6).

[0012] Furthermore, when constructing the optical system 100, when the Abbe number for the d-line of the positive lens (hereinafter referred to as the second specified positive lens) Ly located furthest on the reduction side S in the lens group G1-G3 located on the enlargement side E relative to the first specified positive lens Lx is νdy and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40°C is Ky, the optical system 100 can be configured to satisfy νdy>65 (condition 7) and Ky>-1.0 (condition 8). Furthermore, when the refractive indices for the C-line, F-line, and g-line are nCy, nFy, and ngy, respectively, it is desirable that this second specified positive lens Ly be configured so that the anomalous dispersion (ΔPg,F)y, defined as (ΔPg,F)y = Py + [0.001694 × νdy] - 0.6445, where Py is defined as Py = [ngy - nFy] / [nFy - nCy] and νdy is the Abbe number, satisfies (ΔPg,F)y > 0.005 (condition 9), and when the linear expansion coefficient at -30 to +70°C is αy [1E-7 / °C], αy < 95 (condition 10).

[0013] On the other hand, the optical system 100 includes a cemented lens J3 formed by cementing a second specified positive lens Ly and a negative lens L10, and is preferably configured to satisfy the following conditions: 0<[fpy / fw]<5 (Condition 11), -0.050<[fw / fB]<-0.005 (Condition 12), where fB is the composite focal length of this cemented lens J3, fpy is the focal length of the second specified positive lens Ly, and fw is the focal length of the entire system at the wide-angle end. The optical system 100 is preferably applied to a projection optical system. [Effects of the Invention]

[0014] The lens device 1 according to the present invention having such a configuration provides the following significant effects.

[0015] (1) By using a positive lens formed from a material with a refractive index temperature coefficient Kx close to 0 or a positive value and a high Abbe number νd, it is possible to suppress the effects of temperature across the entire zoom range while achieving good chromatic aberration correction. This makes it possible to eliminate problems such as focus shift and reduced resolution even when temperature fluctuations occur.

[0016] (2) In a preferred embodiment, when configuring the optical system 100, if 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, and the optical system is configured to satisfy the following condition (condition 3): [ft / fw]>1.55. This is particularly effective in optical systems with large zoom ratios, and enables the above-mentioned excellent correction of chromatic aberration and effectively resolves the problems of focus error and reduced resolution.

[0017] (3) In a preferred embodiment, when constructing the optical system 100, if the focal length of the first specified positive lens Lx is fpx, and the optical system 100 is configured to satisfy 0<[fpx / fw]<5 (condition 4), the ratio of the focal length fpx of the first specified positive lens Lx to the focal length fw of the entire system at the wide-angle end can be kept within an appropriate range, that is, the power of the first specified positive lens Lx can be made relatively large, and therefore the effects of temperature and chromatic aberration on the entire optical system 100 can be sufficiently suppressed.

[0018] (4) In a preferred embodiment, when the refractive indices of the first specified positive lens Lx for the C-line, F-line, and g-line are nCx, nFx, and ngx, respectively, and the partial dispersion ratio Px defined by Px = [ngx - nFx] / [nFx - nCx] and the Abbe number vdx are configured such that the anomalous dispersion (ΔPg,F)x defined as (ΔPg,F)x = Px + [0.001694 × vdx] - 0.6445 satisfies (ΔPg,F)x > 0.005 (condition 5), the Abbe number vd of the first specified positive lens Lx can be set high and the anomalous dispersion can be set significantly on the positive side, thereby enabling chromatic aberration correction to be performed effectively and efficiently.

[0019] (5) In a preferred embodiment, when forming the first specified positive lens Lx, if the linear expansion coefficient at -30 to +70°C is αx [1E-7 / °C], and the first specified positive lens Lx is configured to satisfy αx<90 (condition 6), the linear expansion coefficient of the first specified positive lens Lx can be suppressed to less than 90, thereby reducing the impact of temperature fluctuations on optical performance.

[0020] (6) In a preferred embodiment, when constructing the optical system 100, when the Abbe number for the d-line of the second specified positive lens Ly located on the furthest reduction side S in the lens group G1-G3 located on the enlargement side E relative to the first specified positive lens Lx is νdy and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40°C is Ky, if the optical system is constructed so as to satisfy νdy>65... (condition 7) and Ky>-1.0... (condition 8), the effect of temperature fluctuations on the optical performance of the second specified positive lens Ly can be reduced.

[0021] (7) In a preferred embodiment, when the refractive indices of the second specified positive lens Ly for the C-line, F-line, and g-line are nCy, nFy, and ngy, respectively, and Py is defined by Py=[ngy-nFy] / [nFy-nCy] and the Abbe number νdy is set such that the anomalous dispersion (ΔPg,F)y, defined as (ΔPg,F)y=Py+[0.001694×νdy]-0.6445, satisfies (ΔPg,F)y>0.005 (condition 9), the Abbe number νd of the second specified positive lens Ly can be set high and the anomalous dispersion can be set significantly on the positive side, thereby enabling chromatic aberration correction to be performed effectively and efficiently.

[0022] (8) In a preferred embodiment, when the linear expansion coefficient of the second specified positive lens Ly at -30 to +70°C is αy [1E-7 / °C], by satisfying αy<95... (condition 10), the linear expansion coefficient of the second specified positive lens Ly can be suppressed to less than 95, thereby reducing the impact of temperature fluctuations on optical performance.

[0023] (9) In a preferred aspect, the optical system 100 includes a cemented lens J3 formed by cementing together the second specified positive lens Ly and the negative lens L10, and is configured to satisfy the following conditions: 0<[fpy / fw]<5 (condition 11), −0.050<[fw / fB]<−0.005 (condition 12), where fB is the composite focal length of the cemented lens J3, fpy is the focal length of the second specified positive lens Ly, and fw is the focal length of the entire system at the wide-angle end. In this case, the second specified positive lens Ly, which is disposed near a lens group that has a large movement stroke during zooming, is configured as the cemented lens J3, and the ratio of the composite focal length fB of the cemented lens J3 to the focal length fw of the entire system is made sufficiently small. This enables effective correction of chromatic aberration throughout the entire zoom range without significantly affecting the power of the lens groups that significantly contribute to magnification changes near the cemented lens J3.

[0024] (10) In a preferred embodiment, when optical system 100 is applied to a projection optical system, it is possible to realize an optical system that has a high zoom ratio and exhibits little change in optical performance due to temperature fluctuations, while ensuring sufficient optical performance, particularly for a projector that projects onto a screen (enlarged side E). [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a lens configuration section of a lens device according to a preferred embodiment of the present invention; [Figure 2] FIG. 2 is a functional diagram of the lens adjustment unit of the lens device; [Figure 3] 1 is a diagram showing an optical path of the lens device; [Figure 4] FIG. 2 is a longitudinal aberration diagram of the lens device at a reference distance on the wide side; [Figure 5] FIG. 2 is a longitudinal aberration diagram of the lens device at a reference distance on the telephoto side; [Figure 6] A list of the lens group movement amounts during zoom adjustment of the lens device; [Figure 7] A list of optical characteristics of the lens device; DETAILED DESCRIPTION OF THE INVENTION

[0026] Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0027] First, the configuration of a lens device 1 according to this embodiment will be specifically described with reference to FIGS.

[0028] The lens device 1 shown in the embodiment is a projection lens (zoom lens) used in a projector, and is assumed to be applied to a projection optical system, particularly a projection zoom optical system, as the optical system 100. In this way, by applying the optical system 100 to a projection optical system, it is possible to achieve an optical system with a high zoom ratio and, further, small changes in optical performance due to temperature fluctuations, while ensuring sufficient optical performance for a projector that projects onto a screen.

[0029] In Fig. 1, E indicates the enlargement side, such as a screen, and S indicates the reduction side, which will be an image display element, such as a liquid crystal panel. Therefore, the enlargement side E is in front of the optical axis Dc, and the reduction side S is in back of the optical axis Dc. In Fig. 1, 200 indicates a schematic prism.

[0030] This lens device 1 is equipped with an optical system 100 that broadly includes a lens component Mp and a lens adjustment component Mc. As shown in Fig. 1, the lens component Mp is made up of seven lens groups. That is, the lens component Mp is made up of, in order from the magnification side E, a first lens group G1, a second lens group G2, a third lens group G3, a fourth lens group G4, a fifth lens group G5, a sixth lens group G6, and a seventh lens group G7.

[0031] The first lens group G1 has a negative refractive power as a whole and is composed of four single lenses: a positive meniscus lens L1 having a convex surface facing the magnification side E, negative meniscus lenses L2 and L3 having a convex surface facing the magnification side E, and a biconcave lens L4, in that order from the magnification side E. The second lens group G2 has a positive refractive power as a whole and is composed of two cemented lenses: a cemented lens J1 formed by cementing a positive meniscus lens L5 having a convex surface facing the reduction side S with a negative meniscus lens L6 having a convex surface facing the reduction side S, and a cemented lens J2 formed by cementing a negative meniscus lens L7 having a convex surface facing the magnification side E with a biconvex lens L8.

[0032] The third lens group G3 is composed of a cemented lens J3 formed by cementing a biconvex lens L9 and a biconcave lens L10. In this case, the biconvex lens L9 constitutes a second specific lens Ly, which will be described later. The third lens group G3 is composed of one cemented lens and has negative refractive power as a whole. The fourth lens group G4 is composed of a biconvex lens L11, i.e., a single lens, having positive refractive power. This biconvex lens L11 constitutes a first specific lens Lx, which will be described later.

[0033] Furthermore, the fifth lens group G5 is composed of, from the magnification side E, two single lenses: a biconvex lens L12 and a biconcave lens L13, and has negative refractive power as a whole. The sixth lens group G6 is composed of, from the magnification side E, a cemented lens J4 consisting of a biconcave lens L14 and a biconvex lens L15, and a biconvex lens L16. That is, the sixth lens group G6 is composed of one cemented lens and one single lens, and has positive refractive power as a whole. The seventh lens group G7 is composed of a biconvex lens L17 using a single lens with positive refractive power.

[0034] On the other hand, the lens adjustment unit Mc is configured as shown in Fig. 2. That is, during zoom adjustment, the first lens group G1 and the seventh lens group G7 are fixed, and a zoom adjustment mechanism Mcz is provided that independently moves 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 in the optical axis direction Dc. Fig. 6 specifically shows the movement amounts of each lens group G1-G7 during zoom adjustment by the zoom adjustment mechanism Mcz in the lens device 1 of this embodiment. The lens adjustment unit Mc is also provided with a focusing adjustment mechanism Mcf that moves only the second lens group G2 in the optical axis direction Dc during focusing adjustment.

[0035] The zooming adjustment mechanism Mcz and the focusing adjustment mechanism Mcf can be configured using a known adjustment mechanism that uses a cam barrel (not shown), etc. Therefore, they are not limited to any specific configuration as long as they have the above-mentioned adjustment functions.

[0036] Furthermore, in the above configuration, the lens group with the largest movement stroke during zoom adjustment is the fourth lens group G4, as shown in FIG. 6, and the biconvex lens (positive lens) L11 that constitutes this fourth lens group G4 is configured as the first specified positive lens Lx.

[0037] When the Abbe number for the d-line is νdx and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40° C. is Kx (=dn / dT [1E-6 / ° C.]), the first specified positive lens Lx satisfies the following conditions 1 and 2, namely, νdx>65 … (condition 1) Kx>-1.0 … (condition 2) Form it so as to satisfy the following.

[0038] With this configuration, the refractive index temperature coefficient Kx is close to 0 or has a positive value, and the Abbe number vd is a high value, so that temperature effects can be suppressed throughout the entire zoom range while good chromatic aberration correction can be performed. In other words, even when temperature fluctuations occur, problems such as focus shift and reduced resolution can be eliminated.

[0039] In addition, in the optical system 100, 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 condition 3 is satisfied, that is, [ft / fw]>1.55 … (Condition 3) Even in such an optical system with a large zoom ratio, the above-mentioned chromatic aberration can be corrected satisfactorily, and the problems of focus shift and degradation of resolution performance can be effectively eliminated. In addition, when the focal length of the first specified positive lens Lx is fpx, the following condition 4, i.e., 0<[fpx / fw]<5 … (condition 4) If the optical system 100 is configured to satisfy Condition 4, the ratio of the focal length fpx of the first specified positive lens Lx to the focal length fw of the entire system at the wide-angle end can be kept within an appropriate range, that is, the power of the first specified positive lens Lx can be made relatively large, and therefore the effects of temperature and chromatic aberration on the entire optical system 100 can be sufficiently suppressed.

[0040] Furthermore, when the refractive indices of the first specified positive lens Lx for the C-line, F-line, and g-line are nCx, nFx, and ngx, respectively, the anomalous dispersion (ΔPg,F)x, defined as (ΔPg,F)x=Px+[0.001694×νdx]-0.6445, is determined by the partial dispersion ratio Px, defined by Px=[ngx-nFx] / [nFx-nCx], and the Abbe number νdx, so that the anomalous dispersion (ΔPg,F)x satisfies the following condition 5, i.e., (ΔPg,F)x>0.005 … (Condition 5) If the lens is configured to satisfy condition 5, the Abbe number νd of the first specified positive lens Lx can be set high and the anomalous dispersion can be set large on the positive side, so that chromatic aberration can be corrected effectively. In addition, when forming the first specified positive lens Lx, when the linear expansion coefficient at -30 to +70°C is αx [1E-7 / °C], the lens is configured to satisfy the following condition 6, that is, αx<90 … (Condition 6) With this configuration, the linear expansion coefficient of the first specified positive lens Lx can be suppressed to less than 90, and the influence of temperature fluctuations on optical performance can be reduced.

[0041] Materials with a high Abbe number (νd) and a large positive anomalous dispersion often have a large negative refractive index linear expansion coefficient, and the linear expansion coefficient also tends to be large. For example, the refractive index temperature coefficient at temperatures of 20-40°C is approximately -2.0 to -6.5 (1E-6 / °C), and the linear expansion coefficient at temperatures of -30 to +70°C is approximately 100-140 (1E-7 / °C). When these values ​​are large, the impact of temperature fluctuations on optical performance cannot be ignored. However, by suppressing the refractive index temperature coefficient to -1.0 or higher and the linear expansion coefficient to less than 90, the impact of temperature fluctuations on optical performance can be effectively reduced.

[0042] On the other hand, in the optical system 100, the biconvex lens (positive lens) L9 located on the most reduction side S in the lens group G1-G3 located on the enlargement side E relative to the first specified positive lens Lx is configured as the second specified positive lens Ly.

[0043] When the Abbe number for the d-line is νdy and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40° C. is Ky, the second specified positive lens Ly satisfies the following conditions 7 and 8, namely: νdy>65 … (condition 7) Ky>-1.0 … (condition 8) By forming the second specified positive lens Ly in this manner, it is possible to reduce the influence of temperature fluctuations on the optical performance of the second specified positive lens Ly.

[0044] The second specified positive lens Ly on the enlargement side E, which is located near the fourth lens group G4 and has a large stroke during zoom adjustment, is also susceptible to large differences in the effects of temperature fluctuations between the wide-angle end and the telephoto end, just like the first specified positive lens Lx. Therefore, just like the first specified positive lens Lx described above, the material of the second specified positive lens Ly is designed to suppress changes in its physical properties due to temperature fluctuations. As a result, the effects on the optical performance of the lens device 1 can be further reduced.

[0045] Furthermore, when the refractive indices of the second specified positive lens Ly for the C-line, F-line, and g-line are nCy, nFy, and ngy, respectively, the anomalous dispersion (ΔPg,F)y, defined as (ΔPg,F)y=Py+[0.001694×νdy]−0.6445, where Py is defined as Py=[ngy−nFy] / [nFy−nCy] and νdy is the Abbe number, satisfies the following condition 9, i.e., (ΔPg,F)y>0.005 … (Condition 9) The second specified positive lens Ly is configured to satisfy the following condition 10, where αy [1E-7 / °C] is the linear expansion coefficient of the second specified positive lens Ly at temperatures between -30 and +70°C, i.e., αy<95... (Condition 10) This makes it possible to suppress the linear expansion coefficient of the second specified positive lens Ly to less than 95, thereby reducing the effect of temperature fluctuations on optical performance.

[0046] Materials with a high Abbe number (νd) and a large positive anomalous dispersion often have a large negative refractive index linear expansion coefficient, and the linear expansion coefficient also tends to be large. For example, the refractive index temperature coefficient at temperatures of 20-40°C is approximately -2.0 to -6.5 (1E-6 / °C), and the linear expansion coefficient at temperatures of -30 to +70°C is approximately 100-140 (1E-7 / °C). When these values ​​are large, the impact of temperature fluctuations on optical performance cannot be ignored. However, by suppressing the refractive index temperature coefficient to -1.0 or higher and the linear expansion coefficient to less than 95, the impact of temperature fluctuations on optical performance can be reduced.

[0047] Furthermore, when the second specified positive lens Ly is configured as a cemented lens J3 cemented to the negative lens L10, and when the composite focal length of the cemented lens J3 is fB, the focal length of the second specified positive lens Ly is fpy, and the focal length of the entire system at the wide-angle end is fw, the following conditions 11 and 12 are satisfied, i.e., 0<[fpy / fw]<5 … (Condition 11) -0.050<[fw / fB]<-0.005 … (Condition 12) With this configuration, the second specified positive lens Ly, which is disposed near a lens group that has a large stroke of movement during zooming adjustment, is configured as the cemented lens J3, and the ratio of the combined focal length fB of the cemented lens J3 to the focal length fw of the entire system can be made sufficiently small, so that chromatic aberration can be effectively corrected throughout the entire zoom range without significantly affecting the power of the lens groups that make a significant contribution to magnification change near the cemented lens J3.

[0048] Furthermore, if the focal length fpy of the second specified positive lens Ly is too large relative to the focal length fw of the entire system, that is, if the power of the second specified positive lens Ly is too small, the contribution of the second specified positive lens Ly to the refractive power of the entire optical system 100 will be low, and therefore a sufficient effect in suppressing changes in resolution performance due to temperature fluctuations cannot be expected.

[0049] As described above, the lens device 1 according to this embodiment has a basic configuration including a lens configuration section Mp having, in order from the enlargement side E, a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, a fourth lens group G4 having positive refractive power, a fifth lens group G5 having positive or negative refractive power, a sixth lens group G6 having positive refractive power, and a seventh lens group G7 having positive refractive power; and during zooming adjustment, the first lens group G1 and the seventh lens group G7 are fixed, and the second lens group G2 to the sixth lens group G6 are moved independently in the optical axis direction Dc, and during focusing adjustment, only the second lens group G2 is moved. The optical system 100 includes a lens adjustment unit Mc that moves the lens in the optical axis direction Dc. The lens group with the longest movement stroke during zoom adjustment includes a first specified positive lens Lx. The first specified positive lens Lx is configured to satisfy the following conditions: νdx > 65 (Condition 1) and Kx > -1.0 (Condition 2), where νdx is the Abbe number at the d-line and Kx (= dn / dT [1E-6 / °C]) is the temperature coefficient of the relative refractive index at the d-line at temperatures between 20 and 40°C. Therefore, by using a positive lens formed from a material with a refractive index temperature coefficient Kx near or positive to 0 and a high Abbe number νd, excellent chromatic aberration correction can be achieved while suppressing the effects of temperature throughout the zoom range. This eliminates problems such as focus error and resolution degradation even when temperature fluctuations occur. FIG. 3 shows a ray diagram of the lens device 1.

[0050] Table 1 shows lens data (surface data of the entire lens system) in the lens device 1 according to this embodiment.

[0051] [Table 1]

[0052] The surface data in Table 1 indicates the surface number of the lens surface counted from the magnification side E by i, and this surface number i corresponds to the symbol (number) shown in Figure 1. Correspondingly, the radius of curvature of the lens surface R(i), the thickness and spacing on the optical axis D(i), the refractive index of the lens nd(i), and the Abbe number of the lens νd(i) are shown. nd(i) and νd(i) are values ​​relative to the d-line (587.56 nm). The thickness and spacing D(i) indicates the lens thickness or air space between opposing surfaces. The units for the radius of curvature R(i) and surface spacing D(i) are mm. The infinity value for the radius of curvature R(i) indicates a flat surface. The blank spaces for the refractive index nd(i) and Abbe number νd(i) indicate air.

[0053] Table 2 (a) shows lens data for the "first specified positive lens Lx," and (b) shows lens data for the "second specified positive lens Ly."

[0054] [Table 2]

[0055] FIG. 7 shows the optical characteristics of the lens device 1 according to this embodiment, specifically, the focal length ft of the entire system at the telephoto end, the focal length fw of the entire system at the wide-angle end, the zoom ratio [ft / fw], the total angle of view (wide-angle end) ω, and the back focus bf.

[0056] In Table 2 (a), for the first specified positive lens Lx, νdx is "69.89", which satisfies condition 1 of "νdx>65". Kx is "3.6 [1E-6 / °C]", which satisfies condition 2 of "Kx>-1.0". fpx is "84.07 [mm]", and [fpx / fw] is "3.43", which satisfies condition 4 of "0<[fpx / fw]<5". (ΔPg,F)x is "0.0057", which satisfies condition 5 of "(ΔPg,F)x>0.005". αx is "63 [1E-7 / °C]", which satisfies condition 6 of "αx<90".

[0057] On the other hand, in Figure 7, ft is 39.09 mm and fw is 24.50 mm. Therefore, [ft / fw] is 1.596, which satisfies condition 3: [ft / fw] > 1.55.

[0058] Furthermore, for the second specified positive lens Ly in Table 2(b), νdy is "69.89", which satisfies condition 7, "νdy > 65". Ky is "3.6 [1E-6 / °C]", which satisfies condition 8, "Ky > -1.0". (ΔPg,F)y is "0.0057", which satisfies condition 9, "(ΔPg,F)y > 0.005". αy is "63 [1E-7 / °C]", which satisfies condition 10, "αx < 95". fpy is "49.48 [mm]" and [fpy / fw] is "2.02", which satisfies condition 11, "0 < [fpy / fw] < 5". fB is "-667.43 [mm]" and [fw / fB] is "-0.037", which satisfies condition 12: "-0.050<[fw / fB]<-0.005".

[0059] 4 and 5 show longitudinal aberration diagrams of the lens apparatus 1 according to this embodiment. FIG. 4 shows a longitudinal aberration diagram at a reference distance on the WIDE side (E=3500 mm on the magnification side), and FIG. 5 shows a longitudinal aberration diagram at a reference distance on the TELE side (E=3500 mm on the magnification side). From left to right, each longitudinal aberration diagram shows spherical aberration (656.27 nm, 587.56 nm, 486.13 nm, 435.83 nm), astigmatism (550 nm), and distortion (550 nm). Each scale (1 division) is ±0.05 mm, ±0.05 mm, and ±1.0%.

[0060] As shown in Figures 4 and 5, the lens device 1 according to this embodiment has no significant disturbance in longitudinal aberration on either the WIDE side or the TELE side, and it can be confirmed that good aberration characteristics, i.e., good imaging performance (optical performance), are obtained.

[0061] 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.

[0062] For example, the presence of the lens construction unit Mp and the lens adjustment unit Mc is an essential component, but this does not preclude the use of lens units from the eighth lens unit onward when constructing the lens construction unit Mp. Furthermore, this does not preclude the addition of other adjustment mechanisms, such as an aperture adjustment device, in addition to the lens adjustment unit Mc. Furthermore, while conditions 1 and 2 are essential components of the present invention, conditions 3 to 12 can be adopted as needed. In other words, it is desirable to satisfy all of conditions 3 to 12, but the condition to be satisfied can be any one of the conditions or a selected combination of two or more conditions. Therefore, this does not preclude cases where all of conditions 3 to 12 are not satisfied. [Industrial Applicability]

[0063] 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]

[0064] 1: lens device, 100: optical system, E: magnification side, S: reduction side, Lx: positive lens (first specified positive lens), Ly: positive lens (second specified positive lens), L10: negative lens, J3: cemented lens, 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, Mp: lens construction section, Mc: lens adjustment section, Dc: optical axis direction

Claims

1. The lens device has a plurality of lens groups in order from the magnification side, the lens configuration section being made up of, in order from the magnification side, a first lens group having negative refractive power, a second lens group having positive refractive power, a third lens group having negative refractive power, a fourth lens group having positive refractive power, a fifth lens group having positive or negative refractive power, a sixth lens group having positive refractive power, and a seventh lens group having positive refractive power, and a zoom lens unit that makes the first lens group and the seventh lens group immobile during zoom adjustment, and makes the second lens group to the sixth lens group move independently in the optical axis direction. and a lens adjustment unit that moves only the second lens group in the optical axis direction during focusing adjustment, and that moves only the second lens group in the optical axis direction during focusing adjustment, wherein a positive lens (hereinafter referred to as a first specified positive lens) is included in the lens group with the largest movement stroke during zooming adjustment, and this first specified positive lens is formed to satisfy the following (Condition 1) and (Condition 2) when the Abbe number for the d-line is vdx and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40°C is Kx (= dn / dT [1E-6 / °C]). νdx>65… (Condition 1) Kx>-1.0... (Condition 2)

2. 2. The lens device according to claim 1, wherein the optical system satisfies the following condition 3, where fw is a focal length of the entire system at the wide-angle end and ft is a focal length of the entire system at the telephoto end. [ft / fw]>1.55 ... (Condition 3)

3. 3. The lens device according to claim 1, wherein the optical system satisfies the following condition 4, where fpx is the focal length of the first specified positive lens Lx: 0<[fpx / fw]<5… (Condition 4)

4. The lens device according to claim 1, 2 or 3, characterized in that, when the refractive indices for the C-line, F-line and g-line are nCx, nFx and ngx, respectively, of the first specified positive lens are such that the anomalous dispersion (ΔPg,F)x, defined as (ΔPg,F)x = Px + [0.001694 × νdx] - 0.6445, where Px is a partial dispersion ratio defined by Px = [ngx - nFx] / [nFx - nCx] and νdx is an Abbe number, satisfies the following (Condition 5): (ΔPg,F)x>0.005... (Condition 5)

5. The lens device according to any one of claims 1 to 4, characterized in that the first specified positive lens satisfies the following (Condition 6) when the linear expansion coefficient at -30 to +70°C is αx[1E-7 / °C]. αx<90… (Condition 6)

6. The optical system is a lens device described in any one of claims 1 to 5, characterized in that, when the Abbe number for the d-line of a positive lens (hereinafter referred to as the second specified positive lens) located furthest from the reduction side in a lens group located on the enlargement side relative to the first specified positive lens is νdy and the temperature coefficient of the relative refractive index for the d-line at a temperature of 20-40°C is Ky, the optical system satisfies the following (Condition 7) and (Condition 8). νdy>65… (Condition 7) Ky>-1.0... (Condition 8)

7. The lens device according to claim 6, characterized in that, when the refractive indices for the C-line, F-line, and g-line are nCy, nFy, and ngy, respectively, of the second specified positive lens are such that the anomalous dispersion (ΔPg,F)y, defined as (ΔPg,F)y=Py+[0.001694×νdy]−0.6445, where Py is defined by Py=[ngy−nFy] / [nFy−nCy] and νdy is the Abbe number, satisfies the following (Condition 9): (ΔPg, F)y>0.005 (Condition 9)

8. 8. The lens device according to claim 6, wherein the second specified positive lens satisfies the following condition 10 when the linear expansion coefficient at −30 to +70° C. is αy[1E−7 / ° C.]: αy<95… (Condition 10)

9. 7. The lens device according to claim 6, wherein the optical system includes a cemented lens formed by cementing together the second specified positive lens and a negative lens, and wherein, when a focal length of the cemented lens is fB, a focal length of the second specified positive lens is fpy, and a focal length of the entire system at a wide-angle end is fw, the following conditions 11 and 12 are satisfied: 0<[fpy / fw]<5 (Condition 11) −0.050<[fw / fB]<−0.005 (Condition 12)

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

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