JP7277309B2 - Zoom lenses and optics - Google Patents

Description

The present invention relates to a zoom lens used in optical equipment including imaging devices such as surveillance cameras, digital cameras, and video cameras, and interchangeable lens devices.

2. Description of the Related Art In imaging devices such as surveillance cameras, there is a demand for lenses that are compact and have high optical performance not only for visible light but also for near-infrared light. Patent Documents 1 and 2 disclose a two-group zoom lens composed of a negative lens group and a positive lens group in order from the object side to the image side.

Japanese Patent Application Laid-Open No. 2001-330773 JP 2004-309865 A

However, the zoom lenses disclosed in Patent Documents 1 and 2 do not sufficiently correct chromatic aberration for near-infrared light.

The present invention provides a compact zoom lens capable of satisfactorily correcting chromatic aberration for visible light and near-infrared light, and an optical apparatus having the zoom lens.

A zoom lens as one aspect of the present invention comprises a first lens group having negative refractive power and a second lens group having positive refractive power, which are arranged in order from the object side to the image side. The spacing between the first and second lens groups changes during zooming. The second lens group includes a first lens having a positive or negative refractive power disposed closest to the object side, and a refracting lens having a sign opposite to that of the first lens disposed adjacent to the image side of the first lens. It includes a second lens having power, and at least two positive lenses and one negative lens arranged closer to the image than the second lens. The second lens group includes at least two sets of cemented lenses, and the two sets of cemented lenses have refractive powers with different signs. The focal length of the first lens group is f1; the focal length of the second lens group is f2; Let β2w be the lateral magnification of the lens group at the wide-angle end, β2t be the lateral magnification of the second lens group at the telephoto end , fG2cp be the focal length of the cemented lens with positive refractive power among the two cemented lenses, and negative refraction. Let fG2cn be the focal length of the cemented lens with power . At this time,
-1.30≤f1/f2≤-0.65
15≦νn1≦31
2.0≤β2t/β2w≤6.0
0.70≦|fG2cp/fG2cn|≦1.30
It is characterized by satisfying the following conditions. An optical apparatus using the above zoom lens also constitutes another aspect of the present invention.

According to the present invention, it is possible to realize a compact zoom lens capable of satisfactorily correcting chromatic aberration for visible light and near-infrared light.

1 is a lens cross-sectional view at the wide-angle end of a zoom lens that is Embodiment 1 of the present invention. FIG. 4A and 4B are aberration diagrams at the wide-angle end of the zoom lens of Example 1. FIG. 4A and 4B are aberration diagrams at an intermediate zoom position of the zoom lens of Example 1. FIG. 4A and 4B are aberration diagrams at the telephoto end of the zoom lens of Example 1. FIG. FIG. 5 is a cross-sectional view of the zoom lens at the wide-angle end that is Embodiment 2 of the present invention. FIG. 10 is an aberration diagram at the wide-angle end of the zoom lens of Example 2; FIG. 10 is an aberration diagram at an intermediate zoom position of the zoom lens of Example 2; FIG. 10 is an aberration diagram at the telephoto end of the zoom lens of Example 2; FIG. 5 is a cross-sectional view of a zoom lens at the wide-angle end that is Embodiment 3 of the present invention. FIG. 10 is an aberration diagram at the wide-angle end of the zoom lens of Example 3; FIG. 11 is an aberration diagram at an intermediate zoom position of the zoom lens of Example 3; FIG. 10 is an aberration diagram at the telephoto end of the zoom lens of Example 3; FIG. 5 is a cross-sectional view of a zoom lens at the wide-angle end that is Embodiment 4 of the present invention. FIG. 11 is an aberration diagram at the wide-angle end of the zoom lens of Example 4; FIG. 11 is an aberration diagram at an intermediate zoom position of the zoom lens of Example 4; FIG. 11 is an aberration diagram at the telephoto end of the zoom lens of Example 4; 5A and 5B are a cross-sectional view and an external view showing a surveillance camera of Example 5 in which the zoom lens of each Example is used together with a dome cover; 6A and 6B are a cross-sectional view and an external view showing a surveillance camera of Example 6 using the zoom lens of each Example together with a flat plate cover; 4A and 4B are diagrams showing movement of lens groups during zooming in the zoom lens of each embodiment. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIGS. 1, 3, 5 and 7 show lens cross sections of zoom lenses according to Example 1, Example 2, Example 3 and Example 4 of the present invention, respectively. Imaging devices include surveillance cameras, digital cameras, video cameras, and the like. Note that the zoom lens of each embodiment may be used in an interchangeable lens device (optical device) detachably with respect to an imaging device.

First, common items of each embodiment will be described. In each drawing, the left side is the subject side (object side), and the right side is the image side. The wide-angle end and the telephoto end refer to zoom positions when the lens group that moves during zooming is positioned at both mechanical ends of the movable range.

As shown in the above drawings, the zoom lens of each embodiment includes a first lens unit L1 having negative refractive power and a second lens unit L2 having positive refractive power, which are arranged in order from the object side to the image side. It is a two-group zoom lens consisting of During zooming, the first lens unit L1 and the second lens L2 move independently of each other along the optical axis, as shown in FIG.

Specifically, when zooming from the wide-angle end to the telephoto end, the first lens unit L1 moves from the object side to the image side, and the second lens unit L2 moves from the image side to the object side, as indicated by solid arrows in each figure. move to the side. In this way, the first lens group L1 and the second lens group L2 move so that the distance between them changes during zooming. The solid-line arrow and broken-line arrow for the first lens unit L1 denote movement trajectories for correcting image plane fluctuations during zooming from the wide-angle end to the telephoto end when focusing on an infinity object and a short-distance object, respectively. showing.

When focusing from an infinite distance object to a short distance object, the first lens unit L1 moves from the image side to the object side as indicated by an arrow F in each figure. An arrow F indicates the movement of the first lens unit L1 during focusing from an infinity object to a close object at the telephoto end.

SP is an aperture stop, which is arranged between the first lens group L1 and the second lens group L2. It is preferable that the aperture stop SP be stationary (fixed) during zooming. As a result, there is no need to provide a mechanism for driving the aperture stop SP during zooming, and the size of the zoom lens can be reduced. On the other hand, moving the aperture stop SP during zooming increases the degree of freedom in setting the movement trajectories of the first and second lens units L1 and L2 that move during zooming.

G is an optical block corresponding to an optical filter, a faceplate, or the like. IP is an image plane, and when a zoom lens is used as an imaging optical system, the image plane IP is the imaging plane of a solid-state imaging device (photoelectric conversion device) such as a CCD sensor or a CMOS sensor, or the film plane of a film camera. is placed.

The zoom lens of each embodiment has a configuration capable of satisfactorily correcting chromatic aberration with respect to visible light (g-line to C-line) and near-infrared light (C-line to t-line) while being compact. In particular, as shown in FIG. 11, the configuration of the second lens unit L2 in which the on-axis light flux and the off-axis light flux overlap makes it possible to satisfactorily correct axial chromatic aberration and lateral chromatic aberration.

2A, 2B, 2C, 4A, 4B, 4C, 6A, 6B, 6C and 8A, 8B, 8C are, respectively, Example 1, Example 2, Example 3 and FIG. 11 is an aberration diagram of the zoom lens of Example 4; Of the aberration diagrams, A is the aberration diagram at the wide-angle end, B is the aberration diagram at the intermediate zoom position, and C is the aberration diagram at the telephoto end. In the spherical aberration diagrams, Fno is the F number and ω is the half angle of view (°). In the spherical aberration diagram, the amount of spherical aberration for the d-line (wavelength 587.6 nm), g-line (wavelength 435.8 nm), C-line (wavelength 656.3 nm) and t-line (wavelength 1,013.98 nm) is indicated by a solid line, It is indicated by a two-dot chain line, a one-dot chain line and a broken line. In the astigmatism diagrams, S indicates the amount of astigmatism (solid line) on the sagittal image plane, and M indicates the amount of astigmatism (broken line) on the meridional image plane. The distortion diagram shows the amount of distortion with respect to the d-line. The chromatic aberration chart shows the amount of chromatic aberration at the g-line, C-line and t-line.

In each embodiment, the second lens unit L2 includes a first lens having a positive or negative refractive power that is arranged closest to the object side, and the first lens unit that is arranged adjacent to the image side of the first lens. A second lens having refractive power opposite in sign to the lens. That is, when the first lens is the positive lens G2p1, the second lens is the negative lens G2n1, and when the first lens is the negative lens G2p1, the second lens is the positive lens G2p1. Further, the second lens group L2 includes at least two positive lenses and one negative lens on the image side of the second lenses (G2p1, G2n1).

In the zoom lens of each embodiment, the focal length of the first lens group L1 is f1, the focal length of the second lens group L2 is f2, and the first lens and the second lens have a negative refractive power. νn1 is the Abbe number of the lens (negative lens) G2n1 having power with reference to the d-line, β2w is the lateral magnification of the second lens unit L2 at the wide-angle end, and β2t is the lateral magnification of the second lens unit L2 at the telephoto end. , the following conditional expressions (1) to (3) are satisfied.
-1.30≤f1/f2≤-0.65 (1)
15≦νn1≦31 (2)
2.0≤β2t/β2w≤6.0 (3)
Conditional expression (1) indicates a condition for appropriately setting the relationship between the second lens group L2 responsible for zooming and the first lens group L1 responsible for image plane correction. If f1/f2 exceeds the upper limit of conditional expression (1), the refractive power (power) of the second lens unit L2 responsible for zooming becomes too weak, or the power of the first lens unit L1 responsible for image plane correction becomes too weak. becomes too strong. If the power of the second lens unit L2 becomes too weak, the amount of movement of the second lens unit L2 during zooming becomes large, making it impossible to reduce the size of the zoom lens. If the power of is too strong, the chromatic aberration of magnification increases, which is not preferable.

If f1/f2 falls below the lower limit of conditional expression (1), the power of the second lens group L2 becomes too strong or the power of the first lens group L1 becomes too weak. If the power of the second lens unit L2 becomes too strong, it becomes difficult to correct spherical aberration. This is not preferable because the zoom lens cannot be miniaturized.

Conditional expression (2) indicates the condition that high-dispersion glass is used as the material of the first or second lens G2n1 having negative refractive power at a position effective for correcting chromatic aberration. The second lens group L2 as a whole has positive power, but has a positive lens G2p1 and a negative lens G2n1 within the second lens group L2. In this case, effective chromatic aberration correction is performed by causing the negative lens G2n1 to produce chromatic aberration opposite to the chromatic aberration produced by the positive lens G2p1. It is desirable that the negative lens G2n1 be arranged near the diaphragm SP. This is because axial chromatic aberration can be effectively corrected by arranging the negative lens G2n1 at a position where the F-number luminous flux diameter becomes large.

If νn1 exceeds the upper limit of conditional expression (2), chromatic aberration correction becomes insufficient, which is not preferable. If νn1 is less than the lower limit of conditional expression (2), chromatic aberration correction becomes excessive, which is not preferable.

Conditional expression (3) indicates a condition regarding the lateral magnification of the second lens unit L2. Since the second lens group L2 is responsible for zooming, by appropriately setting the lateral magnification ratio (variable magnification ratio) at the wide-angle end and the telephoto end, a zoom that enables imaging at a magnification that meets the imaging purpose. You can get lenses.

If β2t/β2w exceeds the upper limit of conditional expression (3), the amount of movement of the second lens unit L2 must be increased in order to obtain the necessary zoom ratio, and the zoom lens cannot be made compact. , unfavorable. If β2t/β2w is less than the lower limit of conditional expression (3), it is not possible to sufficiently change the angle of view as a zoom lens, which is not preferable.

In each embodiment, the positive lens G2p1 and the negative lens G2n1 are each composed of a single lens, but they may be cemented together to form a cemented lens.

It is more preferable to set the numerical ranges of the conditional expressions (1) to (3) to the numerical ranges of the following conditional expressions (1a) to (3a).
-1.10≤f1/f2≤-0.68 (1a)
19≦νn1≦28 (2a)
2.2≤β2t/β2w≤4.5 (3a)
It is more preferable to set the numerical ranges of the conditional expressions (1) to (3) to the numerical ranges of the following conditional expressions (1b) to (3b).
-1.00≤f1/f2≤-0.75 (1b)
21≦νn1≦26 (2b)
2.5≤β2t/β2w≤4.0 (3b)
Also, the zoom lens of each embodiment preferably satisfies at least one of the following conditional expressions (4) to (10).

In the second lens unit L2, an air lens is formed by an air gap between the first lens and the second lens (positive lens G2p1 and negative lens G2n1), and the radius of curvature of the object-side surface of the air lens is Rs1, Let Rs2 be the radius of curvature of the image-side surface. At this time,
0.10≦|(Rs1−Rs2)/(Rs1+Rs2)|≦0.65 (4)
It is preferable to satisfy the following conditions.

Conditional expression (4) indicates a condition for good aberration correction while maintaining a bright F-number. In particular, since a brighter (smaller) F-number increases spherical aberration, a good spherical aberration correction effect is obtained by giving the air lens a shape that increases its power at a position where the F-number luminous flux diameter increases.
If |(Rs1−Rs2)/(Rs1+Rs2)| exceeds the upper limit of conditional expression (4), the effect of the air lens becomes large and spherical aberration correction becomes excessive. This is not preferable because the effect of an air lens cannot be obtained and spherical aberration correction is insufficient.

The first lens unit L1 is composed of a negative meniscus lens arranged from the object side to the image side, a biconcave negative lens, and a positive lens having a convex surface on the object side. Let νd1p be the Abbe number, and nd1p be the refractive index for the d-line of the positive lens in the first lens unit L1. At this time,
15≦νd1p≦25 (5)
1.90≦nd1p≦2.25 (6)
It is preferable to satisfy the following conditions.

Conditional expressions (5) and (6) are obtained by appropriately setting the material properties (dispersion) of the positive lens in the first lens unit L1, and the negative meniscus lens and the biconcave lens located on the object side in the first lens unit L1. Conditions for correcting lateral chromatic aberration generated in a negative lens using a positive lens are shown. If vd1p exceeds the upper limit of conditional expression (5), correction of chromatic aberration of magnification becomes insufficient, and if it falls below the lower limit of conditional expression (5), chromatic aberration correction becomes excessive, which is not preferable. When nd1p exceeds the upper limit of conditional expression (6), the balance of the Petzval sum of the entire lens system is affected and field curvature increases. This is not preferable because it increases the size of one lens unit L1.

The second lens group L2 includes at least two sets of cemented lenses, the two sets of cemented lenses are given refractive powers with different signs, and one of the two sets of cemented lenses having positive refractive power is selected. Let fG2cp be the focal length, and fG2cn be the focal length of the cemented lens having negative refractive power. At this time,
0.70≦|fG2cp/fG2cn|≦1.30 (7)
It is preferable to satisfy the following conditions.

Conditional expression (7) indicates a condition for performing chromatic aberration correction more appropriately. By employing a cemented lens, it becomes possible to correct lateral chromatic aberration and axial chromatic aberration more satisfactorily. In addition, by employing at least two pairs of cemented lenses and making their power signs different from each other, chromatic aberration of not only visible light but also near-infrared light can be satisfactorily corrected without increasing coma and astigmatism. be able to.
If |fG2cp/fG2cn| exceeds the upper limit of conditional expression (7), the power of the cemented lens with positive power becomes too weak, and correction of spherical aberration, coma, and the like becomes insufficient, which is not preferable. If |fG2cp/fG2cn| is less than the lower limit of conditional expression (7), the power of the cemented lens with positive power becomes too strong, and particularly spherical aberration increases, which is not preferable.

In the second lens unit L2, νd2p is the Abbe number of one of the at least two positive lenses arranged closer to the image side than the first lens and the second lens (the positive lens G2p1 and the negative lens G2n1) with respect to the d-line. do. At this time,
75≦νd2p≦100 (8)
It is preferable to satisfy the following conditions.

Conditional expression (8) eliminates axial chromatic aberration from visible light to near-infrared by using low-dispersion glass as the material of the positive lens that the second lens unit L2 has on the image side of the positive lens G2p1 and the negative lens G2n1. Conditions for better correction are shown. If vd2p exceeds the upper limit of conditional expression (8), it will be difficult to obtain glass that satisfies it, and if it falls below the lower limit of conditional expression (8), chromatic aberration correction will be insufficient, which is not preferable.

Let M1 be the amount of movement of the first lens unit L1 during zooming from the wide-angle end to the telephoto end. At this time,
0.75≦|M1/f1|≦1.45 (9)
It is preferable to satisfy the following conditions.

Conditional expression (9) indicates the relationship between the amount of movement of the first lens unit L1 during zooming and the focal length (power). If |M1/f1| exceeds the upper limit of conditional expression (9), the amount of movement of the first lens unit L1 during zooming becomes too large, making it difficult to reduce the size of the zoom lens. If |M1/f1| falls below the lower limit of conditional expression (9), the amount of movement of the first lens unit L1 during zooming becomes too small, and it becomes necessary to increase the power of the first lens unit L1. This is not preferable because it increases aberrations such as surface curvature.

Let M2 be the amount of movement of the second lens unit L2 during zooming from the wide-angle end to the telephoto end. At this time,
0.50≦|M2/f2|≦0.95 (10)
It is preferable to satisfy the following conditions.

Conditional expression (10) indicates the relationship between the amount of movement of the second lens unit L2 during zooming and the focal length (power). If |M2/f2| exceeds the upper limit of conditional expression (10), the amount of movement of the second lens unit L2 during zooming becomes too large, making it difficult to reduce the size of the zoom lens. If |M2/f2| falls below the lower limit of conditional expression (10), the amount of movement of the second lens unit L2 during zooming becomes too small, and it becomes necessary to increase the power of the second lens unit L2. Aberrations increase, which is not preferable for securing a bright F-number.

The shape of the negative lens G2n1, which is the first or second lens in the second lens group L2, may be a meniscus shape or a biconcave shape. However, in order not to overcorrect chromatic aberration, a meniscus shape that does not easily have negative power is more preferable. Further, when the radius of curvature of the object-side surface of the meniscus-shaped negative lens G2n1 is Rn1, and the radius of curvature of the image-side surface is Rn2,
0.12≦|(Rn1−Rn2)/(Rn1+Rn2)|≦0.60 (11)
It is preferable to have a shape that satisfies the following conditions. It is more preferable to set the numerical ranges of the conditional expressions (4) to (11) to the numerical ranges of the following conditional expressions (4a) to (10a).
0.13≦|(Rs1−Rs2)/(Rs1+Rs2)|≦0.55 (4a)
16≤νd1p≤23 (5a)
1.93≦Nd1p≦2.15 (6a)
0.75≦|fG2cp/fG2cn|≦1.15 (7a)
78≦νd2p≦98 (8a)
0.80≦|M1/f1|≦1.40 (9a)
0.55≦|M2/f2|≦0.85 (10a)
0.15≦|(Rn1−Rn2)/(Rn1+Rn2)|≦0.55 (11a)
It is more preferable to set the numerical ranges of the conditional expressions (4) to (10) to the numerical ranges of the following conditional expressions (4b) to (10b).
0.15≦|(Rs1−Rs2)/(Rs1+Rs2)|≦0.50 (4b)
17≦νd1p≦21 (5b)
1.94≦Nd1p≦2.10 (6b)
0.80≦|fG2cp/fG2cn|≦1.10 (7b)
80≦νd2p≦96 (8b)
0.95≦|M1/f1|≦1.30 (9b)
0.60≦|M2/f2|≦0.75 (10b)
0.20≦|(Rn1−Rn2)/(Rn1+Rn2)|≦0.50 (11b)
Next, a specific optical configuration of each embodiment will be described. In the following description, a plurality of lenses forming each of the first and second lens groups L1 and L2 are arranged in order from the object side to the image side.

In the zoom lens of Example 1, the first lens unit L1 is composed of an object-side convex meniscus negative lens G11, a biconcave negative lens G12, and an object-side convex meniscus positive lens G13.

The second lens unit L2 includes a biconvex positive lens G21 (G2p1), an image-side convex meniscus negative lens G22 (G2n1), a biconvex positive lens G23, a biconvex positive lens G24, and a biconcave lens. It is composed of a shaped negative lens G25, a biconvex positive lens G26, and a meniscus negative lens G27 convex to the image side. The lenses G24, G25 and the lenses G26, G27 each form a cemented lens. Chromatic aberration is well corrected by providing a difference in Abbe's number and refractive index in each cemented lens.

As the negative lens G22, a glass having a small Abbe's number, which is a relatively high-dispersion system, is used as a negative lens. This has the effect of canceling the chromatic aberration that occurs in the positive lens in the second lens group.

In the zoom lens of Example 2, the configuration of the first lens group L1 is the same as that of Example 1. FIG.

The second lens unit L2 includes a meniscus negative lens G21 (G2n1) convex to the object side, a biconvex positive lens G22 (G2p1), a positive meniscus lens G23 convex to the object side, and a biconvex positive lens G24. , a biconcave negative lens G25, a biconvex positive lens G26, and a meniscus negative lens G27 convex toward the image side. The lenses G24, G25 and the lenses G26, G27 each form a cemented lens.

In the zoom lens of Example 3, the configurations of the first lens group L1 and the second lens group L2 are the same as those of Example 1.

In the zoom lens of Example 4, the configuration of the first lens group L1 is the same as that of Example 1. FIG.

The second lens unit L2 includes a biconvex positive lens G21 (G2p1), a biconcave negative lens G22 (G2n1), a biconvex positive lens G23, an object-side convex negative meniscus lens G24, and an object-side lens. It is composed of a convex positive lens G25, a biconvex positive lens G26, and a negative meniscus lens G27 convex to the image side. The lenses G24 and G25 and the lenses G26 and G27 respectively constitute cemented lenses.

With the configuration of each of the above embodiments, it is possible to realize a compact zoom lens capable of satisfactorily correcting chromatic aberration.

In addition, in the zoom lens of each embodiment, the shape and the number of lenses may be changed. Further, image blurring due to vibration such as camera shake may be corrected by moving some lenses or lens groups with respect to the optical axis.

FIG. 9 shows a cross section (A) and an external appearance (B) of a surveillance camera as Example 5 of the present invention using the zoom lens of each example together with a dome cover 15 . Also, FIG. 10 shows a cross section (A) and an external view (B) of a monitoring camera as Example 6 of the present invention in which the zoom lens of each example is used together with a flat plate cover 17 .

Each cover is a transparent cover made of a plastic material such as polymethylmethacrylate (PMMA) or polycarbonate (PC), and has a thickness of several millimeters. When these covers 15 and 17 are used, it is desirable to construct the zoom lens in consideration of the influence of the focal length and material of the covers to satisfactorily correct various aberrations.

Further, IS is a solid-state imaging device arranged on the image plane of the zoom lens. The solid-state imaging device IS captures a subject image formed by the zoom lens and generates an image signal.

FIG. 9(B) shows the monitoring camera shown in FIG. 9(A). The camera body 10 is attached to the indoor ceiling.

FIG. 10B shows the surveillance camera shown in FIG. 10A. The camera body 11 accommodates a lens section 16 having a zoom lens and a solid-state imaging device 12 for capturing an object image formed by the lens section 16 . An image signal from the solid-state imaging device 12 is recorded in the memory section 13 or transmitted to the outside via the network cable 14 .

By using the zoom lens of each embodiment, each of the monitoring cameras described above can obtain a high-quality image in which chromatic aberration is well corrected.

Numerical Examples 1 to 4 corresponding to Examples 1 to 4, respectively, are shown below. In each numerical example, each surface of the zoom lens is given a surface number i (i is a natural number). The two surfaces closest to the image side are planes corresponding to the optical block G. FIG. r is the radius of curvature of each surface (mm), d is the lens thickness or distance (air gap) (mm) on the optical axis between the surface with surface number i and the surface with surface number (i+1), and nd is each surface is the refractive index for the d-line of the material of the optical member having νd is the Abbe number of the material of the optical member having each surface with respect to the d-line. The Abbe number νd of a certain material is given by
νd = (Nd-1)/(NF-NC)
is represented by

Focal length (mm), F-number and half angle of view (°) are values when the optical system is focused on an object at infinity. The total lens length is the length obtained by adding the back focus BF to the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object side) to the final surface (the lens surface closest to the image side) of the optical system. Back focus BF is the distance from the final surface of the optical system to the image plane.

The "*" attached to the surface number means that the surface has an aspherical shape. The aspheric shape has the x-axis in the direction of the optical axis, the h-axis in the direction perpendicular to the optical axis, the positive direction in which light travels, R being the paraxial radius of curvature, k being the conic constant, and A4, A6 and A8 being the aspheric surfaces. When used as a coefficient, it is represented by the following formula. The aspheric coefficient "ex" means 10 ^-x .

x=(h ² /R)/[1+{1−(1+k)(h/R) ² } ^1/2 +A4×h ⁴ +A6×h ⁶
+A8× ^h8
Table 1 summarizes the values corresponding to the above-described conditional expressions (1) to (11) in Numerical Examples 1 to 4.

[Numerical Example 1]
Plane data
Face number rd nd νd
1 21.502 0.90 1.90366 31.3
2 7.788 4.46
3 -21.565 0.60 1.63854 55.4
4 10.725 1.54
5 14.781 2.20 1.95906 17.5
6 52.785 (variable)
7 (aperture) ∞ (variable)
8 20.494 2.15 1.69680 55.5 (G2p1)
9 -16.032 0.45
10 -10.043 0.50 1.84666 23.8 (G2n1)
11 -23.647 0.15
12 8.305 2.60 1.49700 81.5
13 -47.741 0.15
14 16.925 2.05 1.95906 17.5
15 -528.565 0.45 1.75520 27.5
16 6.07 0.59
17 11.21 4.30 1.67790 55.3
18 -4.398 0.50 1.90366 31.3
19 -16.019 (Variable)
20 ∞ 0.50 1.51633 64.1
Image plane ∞

Various data
Zoom ratio 2.8
wide-angle medium-telephoto
Focal length 3.4 6.46 9.52
F number 1.88 2.41 3.40
Half angle of view 46.64 29.13 20.72
Image height 3.6 3.6 3.6
Lens length (in air) 49.86 41.13 40.34
BF (in air) 6.74 10.35 13.95

Spacing Wide Medium Telephoto
d6 11.32 2.59 1.80
d7 8.22 4.61 1.00
d19 4.16 7.77 11.38

Focal length of each group
1-8.66
2 10.22

[Numerical Example 2]
Plane data
Face number rd nd νd
1 17.745 0.90 1.90366 31.3
2 7.783 4.90
3 -23.958 0.60 1.65160 58.5
4 9.736 1.61
5 13.108 2.20 1.95906 17.5
6 32.139 (variable)
7 (aperture) ∞ (variable)
8 17.04 0.50 1.84666 23.8 (G2n1)
9 9.977 0.45
10 14.613 2.15 1.69680 55.5 (G2p1)
11 -43.49 0.15
12 7.413 2.60 1.49700 81.5
13 86.404 1.44
14 32.059 2.05 1.95906 17.5
15 -33.121 0.45 1.76182 26.5
16 6.133 0.37
17 7.598 5.02 1.61405 55.0
18 -4.90 0.50 1.90366 31.3
19 -11.919 (variable)
20 ∞ 0.50 1.51633 64.1
Image plane ∞

Various data
Zoom ratio 2.8
wide-angle medium-telephoto
Focal length 3.4 6.46 9.52
F number 1.88 2.36 3.35
Half angle of view 46.64 29.13 20.72
Image height 3.6 3.6 3.6
Lens length (in air) 52.88 43.94 43.26
BF (in air) 6.76 10.67 14.57

Spacing Wide Medium Telephoto
d6 11.62 2.68 2.00
d7 8.61 4.71 0.80
d19 3.90 7.81 11.72

Focal length of each group
1-8.50
2 10.85

[Numerical Example 3]
Plane data
Face number rd nd νd
1 19.243 0.90 1.90366 31.3
2 7.737 5.06
3 -20.062 0.60 1.63854 55.4
4 11.653 1.57
5 15.945 2.20 1.95906 17.5
6 57.508 (variable)
7 (aperture) ∞ (variable)
8 25.167 2.19 1.71999 50.2 (G2p1)
9 -13.963 0.45
10 -9.848 0.50 1.85478 24.8 (G2n1)
11 -23.397 0.15
12 8.597 3.10 1.43700 95.1
13 -34.024 0.15
14 23.993 2.23 1.95906 17.5
15 -28.772 0.45 1.76182 26.5
16 6.681 0.49
17 9.42 4.89 1.62041 60.3
18 -4.90 0.50 1.90366 31.3
19 -13.785 (variable)
20 ∞ 0.50 1.51633 64.1
Image plane ∞

Various data
Zoom ratio 2.8
wide-angle medium-telephoto
Focal length 3.4 6.45 9.50
F number 1.78 2.23 3.00
Half angle of view 46.64 29.16 20.75
Image height 3.6 3.6 3.6
Lens length (in air) 52.86 43.45 42.47
BF (in air) 6.80 10.51 14.23

Spacing Wide Medium Telephoto
d6 12.39 2.98 2.00
d7 8.23 4.52 0.80
d19 4.06 7.77 11.49

Focal length of each group
1-8.80
2 10.72

[Numerical Example 4]
Plane data
Face number rd nd νd
1 48.046 0.90 1.90366 31.3
2 10.503 3.41
3 -40.332 0.60 1.6968 55.5
4 11.586 2.86
5 19.066 2.20 1.94595 18.0
6 74.008 (variable)
7 (aperture) ∞ (variable)
*8 15.83 1.83 1.7645 49.1 (G2p1)
9 -190.123 0.27
10 -72.654 0.45 1.85896 22.7 (G2n1)
11 57.777 0.15
12 10.681 2.65 1.497 81.5
13 -20.85 1.80
14 15.393 0.50 1.60342 38.0
15 5.00 2.61 1.497 81.5
16 6.849 0.70
17 12.29 4.30 1.6935 50.8
18 -5.704 0.50 1.91082 35.3
19 -28.483 (variable)
20 ∞ 0.50 1.51633 64.1
Image plane ∞

aspherical data
8th side
K = 0.00000e+000 A4=-1.39180e-004 A6=-6.84237e-007
A8=-9.98469e-009

Various data
Zoom ratio 2.92
wide-angle medium-telephoto
Focal length 3.59 7.04 10.49
F number 1.84 2.4 3.33
Half angle of view 45.08 27.09 18.95
Image height 3.6 3.6 3.6
Lens length (in air) 53.80 42.60 41.30
BF (in air) 5.34 9.19 13.04

Spacing Wide Medium Telephoto
d6 14.37 3.17 1.86
d7 8.37 4.52 0.67
d19 3.05 6.90 10.75

Focal length of each group
1-9.94
2 11.1

[Imaging system]
Note that an imaging system (surveillance camera system) including the zoom lens of each embodiment and a control unit that controls the zoom lens may be configured. In this case, the controller can control the zoom lens so that each lens group moves as described above during zooming and focusing. At this time, the controller does not need to be configured integrally with the zoom lens, and the controller may be configured separately from the zoom lens. For example, a configuration in which a control unit (control device) disposed far from a driving unit that drives each lens of a zoom lens includes a transmission unit that transmits a control signal (command) for controlling the zoom lens is adopted. may According to such a controller, the zoom lens can be remotely controlled.

Further, by providing an operation unit such as a controller and buttons for remotely operating the zoom lens in the control unit, the zoom lens may be controlled according to the user's input to the operation unit. For example, an enlargement button and a reduction button are provided as an operation unit, and the control unit controls the zoom lens so that when the user presses the enlargement button, the magnification of the zoom lens increases, and when the user presses the reduction button, the magnification of the zoom lens decreases. A signal may be sent to the driving section of the .

The imaging system may also have a display unit such as a liquid crystal panel that displays information (movement state) regarding zooming of the zoom lens. The information about the zoom of the zoom lens is, for example, the zoom magnification (zoom state) and the movement amount (movement state) of each lens group. In this case, the user can remotely operate the zoom lens via the operation unit while viewing information about the zoom of the zoom lens displayed on the display unit. At this time, the display unit and the operation unit may be integrated by adopting a touch panel or the like.

Each embodiment described above is merely a representative example, and various modifications and changes can be made to each embodiment in carrying out the present invention.

L1 First lens group L2 Second lens group IP Image plane G2p1 Positive lens G2n1 Negative lens

Claims (12)

Arranged in order from the object side to the image side,
a first lens group having negative refractive power;
and a second lens group having a positive refractive power,
the distance between the first and second lens groups changes during zooming,
The second lens group includes a first lens having a positive or negative refractive power disposed closest to the object side, and a sign opposite to the first lens disposed adjacent to the image side of the first lens. and at least two positive lenses and one negative lens arranged closer to the image side than the second lens,
The second lens group includes at least two sets of cemented lenses, and the two sets of cemented lenses have refractive powers with different signs,
f1 is the focal length of the first lens group; f2 is the focal length of the second lens group; νn1, β2w is the lateral magnification of the second lens group at the wide-angle end, β2t is the lateral magnification of the second lens group at the telephoto end , and the focal point of the cemented lens having positive refractive power among the two sets of cemented lenses When the distance is fG2cp and the focal length of the cemented lens having negative refractive power is fG2cn ,
-1.30≤f1/f2≤-0.65
15≦νn1≦31
2.0≤β2t/β2w≤6.0
0.70≦|fG2cp/fG2cn|≦1.30
A zoom lens characterized by satisfying the following condition. In the second lens group, an air lens is formed by an air gap between the first lens and the second lens,
When the radius of curvature of the object-side surface of the air lens is Rs1 and the radius of curvature of the image-side surface of the air lens is Rs2,
0.10≦|(Rs1−Rs2)/(Rs1+Rs2)|≦0.65
2. The zoom lens according to claim 1, which satisfies the following condition: The first lens group is composed of a meniscus negative lens arranged from the object side to the image side, a negative lens having concave surfaces on the object side and the image side, and a positive lens having a convex surface on the object side. ,
When the Abbe number of the positive lens of the first lens group with respect to the d-line as a reference is νd1p, and the refractive index of the positive lens of the first lens group with respect to the d-line is nd1p,
15≤νd1p≤25
1.90≦nd1p≦2.25
3. The zoom lens according to claim 1, wherein the following condition is satisfied. In the second lens group, when the Abbe number of one of the at least two positive lenses arranged on the image side of the second lens with respect to the d-line as a reference is νd2p,
75≦νd2p≦100
4. The zoom lens according to any one of claims 1 to 3 , wherein the following condition is satisfied. Having an aperture stop between the first lens group and the second lens group,
5. The zoom lens according to claim 1 , wherein said aperture stop is stationary during zooming. When the amount of movement of the first lens group during zooming from the wide-angle end to the telephoto end is M1,
0.75≦|M1/f1|≦1.45
6. The zoom lens according to any one of claims 1 to 5 , wherein the following condition is satisfied. When the amount of movement of the second lens group during zooming from the wide-angle end to the telephoto end is M2,
0.50≦|M2/f2|≦0.95
7. The zoom lens according to any one of claims 1 to 6, wherein the following condition is satisfied. a zoom lens according to any one of claims 1 to 7;
An optical apparatus comprising an imaging element for imaging a subject image formed by the zoom lens. An imaging system comprising: the zoom lens according to any one of claims 1 to 7 ; and a control unit that controls the zoom lens during zooming. 10. The imaging system according to claim 9 , wherein the control section is configured separately from the zoom lens, and has a transmission section that transmits a control signal for controlling the zoom lens. 11. The imaging system according to claim 9 , wherein the control section is configured separately from the zoom lens, and has an operation section for operating the zoom lens. 12. The imaging system according to any one of claims 9 to 11 , further comprising a display section for displaying information about zooming of said zoom lens.

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