Zoom lens and imaging device

Abstract

This invention provides a zoom lens that includes resin lenses, is compact and lightweight, yet offers wide-angle, large-aperture, and high magnification ratio performance, and maintains good optical performance even under temperature changes. [Solution] The zoom lens has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group including one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses with negative refractive power and one or more positive resin lenses with positive refractive power. The focal length of the first lens group, the focal length of the second lens group, the combined focal length of the one or more negative resin lenses, and the combined focal length of the one or more positive resin lenses are appropriately set.

Description

Technical Field

[0001] The present invention relates to a zoom lens and an imaging device.

Background Art

[0002] Conventionally, as a wide-angle zoom lens that is small and can efficiently secure a magnification ratio, a negative-lead type zoom lens having a lens group having negative and positive refractive powers in order from the object side, and a rear group disposed on the image side thereof is known.

[0003] In order to improve the optical performance of the zoom lens and achieve miniaturization, there is a method of using an aspherical lens made of a resin material (resin lens) that is easier to manufacture a more complex aspherical shape instead of an aspherical lens made of glass.

[0004] Patent Document 1 and Patent Document 2 disclose a negative-lead type zoom lens having a negative first lens group, a positive second lens group, and a rear group in order from the object side as a small wide-angle zoom lens using a resin lens.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the zoom lens of Patent Document 1, since the refractive power of the resin lens disposed near the aperture where the light beam diameter tends to be large is strong, the variation in spherical aberration particularly when the temperature changes is large, and there is a problem from the viewpoint of increasing the aperture diameter.

[0007] In the zoom lens described in Patent Document 2, the negative resin lens in the first lens group raises concerns about fluctuations in field curvature during temperature changes, posing a challenge in terms of further widening the angle of view.

[0008] The present invention aims to provide a zoom lens that includes a resin lens, is small and lightweight, yet offers wide-angle, large-aperture, and high magnification ratio performance, and can achieve good optical performance even under temperature changes. [Means for solving the problem]

[0009] To achieve the above objective, a zoom lens according to one aspect of the present invention has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group including one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses with a negative refractive power and one or more positive resin lenses with a positive refractive power. When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the combined focal length of the one or more negative resin lenses is fpn, and the combined focal length of the one or more positive resin lenses is fpp, 0.1 < |f1 / f2| < 1.0 -1.72 <fpn / fpp<-0.58 It is characterized by satisfying the following conditions.

[0010] Another embodiment of the present invention is a zoom lens having, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group including one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses having negative refractive power and one or more positive resin lenses having positive refractive power. When the combined focal length of the one or more resin negative lenses is fpn and the combined focal length of the one or more resin positive lenses is fpp, -1.72 <fpn / fpp<-0.58 Characterized by satisfying the following conditions.

Advantages of the Invention

[0011] According to the present invention, there is provided a zoom lens including a resin lens, which is small and lightweight, and can obtain good optical performance even with temperature changes at a wide angle, large aperture, and high magnification ratio.

Brief Description of the Drawings

[0012] [Figure 1] It is a cross-sectional view at the wide-angle end when the zoom lens of Numerical Example 1 is focused at infinity. [Figure 2] It is an aberration diagram at the wide-angle end when the zoom lens of Numerical Example 1 is focused at infinity. [Figure 3] It is an aberration diagram at the intermediate focal length when the zoom lens of Numerical Example 1 is focused at infinity. [Figure 4] It is an aberration diagram at the telephoto end when the zoom lens of Numerical Example 1 is focused at infinity. [Figure 5] It is a cross-sectional view at the wide-angle end when the zoom lens of Numerical Example 2 is focused at infinity. [Figure 6] It is an aberration diagram at the wide-angle end when the zoom lens of Numerical Example 2 is focused at infinity. [Figure 7] It is an aberration diagram at the intermediate focal length when the zoom lens of Numerical Example 2 is focused at infinity. [Figure 8] It is an aberration diagram at the telephoto end when the zoom lens of Numerical Example 2 is focused at infinity. [Figure 9] It is a cross-sectional view at the wide-angle end when the zoom lens of Numerical Example 3 is focused at infinity. [Figure 10] It is an aberration diagram at the wide-angle end when the zoom lens of Numerical Example 3 is focused at infinity. [Figure 11] It is an aberration diagram at the intermediate focal length when the zoom lens of Numerical Example 3 is focused at infinity. [Figure 12] It is an aberration diagram at the telephoto end when the zoom lens of Numerical Example 3 is focused at infinity. [Figure 13] This is a cross-sectional view of the zoom lens of numerical example 4 at the wide-angle end when it is focused at infinity. [Figure 14] This is an aberration diagram of the zoom lens of numerical example 4 at the wide-angle end when focused at infinity. [Figure 15] This is an aberration diagram of the zoom lens of numerical example 4 at infinity focus and at intermediate focal lengths. [Figure 16] This is an aberration diagram of the zoom lens of numerical example 4 at the telephoto end when it is focused at infinity. [Figure 17] (A) and (B) are diagrams illustrating embodiments of the imaging device of the present invention. [Figure 18] (A) and (B) are diagrams illustrating embodiments of the imaging device of the present invention. [Modes for carrying out the invention]

[0013] In recent years, the use of wide-angle lenses and high-resolution image sensors has made it possible to obtain detailed information even from a wide range of subjects. However, to enlarge the subject and obtain even more detailed information, a zoom lens is desirable. Generally, wide-angle lenses tend to have a larger front element diameter (located on the object side), and increasing the number of lens elements on the object side to improve aberrations also tends to increase the overall length. Therefore, miniaturization is desirable for wide-angle zoom lenses.

[0014] Conventionally, negative-lead type zoom lenses have been known as compact wide-angle zoom lenses that can efficiently secure a wide zoom ratio. These lenses have lens groups with negative and positive refractive powers in order from the object side to the image side, and a rear group positioned on the image side. One way to improve the optical performance and miniaturize these zoom lenses is to use aspherical lenses (resin lenses) made of resin materials, which are easier to manufacture with more complex aspherical shapes, instead of aspherical lenses made of glass.

[0015] Resin materials generally have a larger coefficient of thermal expansion and a greater temperature dependence of their refractive index compared to glass. The present invention aims to provide a zoom lens that includes a resin lens and is small and lightweight, yet can achieve wide-angle, large-aperture, and high magnification ratio performance even when exposed to changes in ambient temperature, and an imaging device having the same.

[0016] The zoom lens of the present invention has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group including one or more lens groups, and is configured to be suitable for a wide-angle zoom lens. In addition, the spacing between adjacent lens groups changes when the magnification is changed. The zoom lens of the present invention, when the focal length of the first lens group is f1 and the focal length of the second lens group is f2, 0.1 < |f1 / f2| < 1.0 ···(1) The conditions are met.

[0017] If the value exceeds the upper limit of condition (1), the absolute value of the refractive power of the first lens group decreases, which is undesirable because it narrows the angle of view at the wide-angle end. If the value falls below the lower limit of condition (1), the absolute value of the refractive power of the first lens group increases, which is undesirable because it worsens the field curvature, especially at the wide-angle end.

[0018] The first lens group includes resin lenses, which include resin lenses with negative refractive power (hereinafter also referred to as negative resin lenses) and resin lenses with positive refractive power (hereinafter also referred to as positive resin lenses). By including a resin negative lens and a resin positive lens in the first lens group, fluctuations in focus and field curvature can be canceled out by both even when temperature changes occur.

[0019] Furthermore, in wide-angle zoom lenses, the diameter of the light beam passing through the first lens group becomes smaller, which helps to minimize spherical aberration fluctuations due to temperature changes in the resin lens, making it easier to achieve a larger aperture. In wide-angle zoom lenses, the first lens group becomes larger as the angle of view widens and the light beam passes through it. However, since resin lenses generally have a lower specific gravity and are lighter than glass lenses, using resin lenses in the first lens group contributes to reducing the weight of the zoom lens.

[0020] The zoom lens of the present invention, when the combined focal length of one or more negative resin lenses included in the first lens group is fpn and the combined focal length of one or more positive resin lenses included in the first lens group is fpp, -1.72 <fpn / fpp<-0.58 ···(2) The conditions are met.

[0021] Here, fpn is defined as the number of resin negative lenses included in the first lens group, N (a positive integer), and the focal length of each resin negative lens included in the first lens group, fpn_i (a positive integer from 1 to N).

number

number

[0022] If the range is outside the range of condition (2), it is undesirable because it is difficult to effectively cancel out the fluctuations in focus and field curvature of the resin negative lens and resin positive lens included in the first lens group during temperature changes. The temperature change in this invention is assumed to range from approximately -20°C to +70°C, centered around the ambient temperature (+25°C). However, the assumed temperature change can be appropriately modified depending on the application, and the effects of this invention remain effective in such cases as well.

[0023] The objectives of the present invention have been achieved as described above, but a more desirable configuration of the present invention will now be described. The resin lens of the present invention has an aspherical shape, and when its refractive index is Nd and its Abbe number is νd, Nd-0.00015×(νd-50) 2 <1.56 ···(3) It is desirable to satisfy the following conditions. If the range falls outside the range of condition (3), it becomes practically impossible to select a suitable resin material for the resin lens, which is undesirable.

[0024] When the Abbe number of the resin negative lens with the smallest absolute value of focal length among the resin negative lenses included in the first lens group is νdn1, 31 < νdn1 < 75 ···(4) It is desirable to satisfy the following conditions. If the upper limit of condition (4) is exceeded, it becomes practically impossible to select a suitable material for the resin lens, which is undesirable. If the lower limit of condition (4) is fallen below, the negative resin lens having a negative refractive power with the same sign as the refractive power of the first lens group will have high dispersion, leading to a deterioration of chromatic aberration, which is also undesirable.

[0025] When the Abbe number of the resin positive lens with the smallest focal length among the resin positive lenses included in the first lens group is νdp1, 15 < νdp1 < 27 ... (5) It is desirable to satisfy the following conditions.

[0026] If the upper limit of condition (5) is exceeded, the positive resin lens, which has a positive refractive power opposite to the negative refractive power of the first lens group, will have low dispersion, leading to a deterioration of chromatic aberration, which is undesirable. If the lower limit of condition (5) is fallen below, it will be practically impossible to select a suitable resin material for the resin lens, which is also undesirable.

[0027] Furthermore, it is desirable that the following condition (6) be satisfied. 0.8 <fpn / f1<5.0 ···(6) If the upper limit of condition (6) is exceeded, the absolute value of the refractive power of the resin negative lens included in the first lens group becomes small, making it difficult to widen the angle, which is undesirable. If the lower limit of condition (6) is exceeded, the absolute value of the refractive power of the resin negative lens included in the first lens group becomes large, leading to deterioration of image field curvature, which is also undesirable.

[0028] Furthermore, it is desirable that the following condition (7) be satisfied. -6.5 <fpp / f1<-1.0 ···(7) If the value exceeds the upper limit of condition (7), the refractive power of the resin positive lens included in the first lens group becomes large, resulting in excessive correction of various aberrations, which is undesirable. If the value falls below the lower limit of condition (7), the refractive power of the resin positive lens included in the first lens group becomes small, resulting in insufficient correction of various aberrations, which is also undesirable.

[0029] When D1 is the sum of the thicknesses of all lenses in the first lens group, including glass and resin lenses, along the optical axis, and Dp1 is the sum of the thicknesses of all resin lenses included in the first lens group along the optical axis, 0.4 <Dp1 / D1≦1.0 ···(8) It is desirable to satisfy the following conditions.

[0030] The upper limit of condition (8) corresponds to the case where the first lens group consists only of resin lenses. If it falls below the lower limit of condition (8), the proportion of glass lenses included in the first lens group increases, which is undesirable because it increases the weight of the first lens group.

[0031] When changing magnification from the wide-angle end to the telephoto end, the first lens group moves in a convex trajectory toward the image side, and the second lens group moves monotonically toward the object side, and when the maximum amount of movement of the second lens group is M2wt, 0.20 < |f2 / M2wt| < 1.00 ···(9) It is desirable to satisfy the following conditions.

[0032] If the upper limit of condition (9) is exceeded, the refractive power of the second lens group weakens, or the amount of movement of the second lens group decreases, making it difficult to achieve high magnification, which is undesirable. If the lower limit of condition (9) is exceeded, the refractive power of the second lens group becomes stronger, leading to deterioration of spherical aberration and coma aberration, which is undesirable. Alternatively, the amount of movement of the second lens group increases, which is undesirable because it increases the overall length of the zoom lens.

[0033] When the air-equivalent distance from the image-side lens surface of the subsequent lens group to the image plane is defined as the back focus, and the back focus is denoted as BF, 0.05 <BF / f2<0.60 ···(10) It is desirable to satisfy the following conditions.

[0034] If the value exceeds the upper limit of condition (10), the back focus becomes large, making it difficult to miniaturize the entire lens system, which is undesirable. If the value falls below the lower limit of condition (10), the refractive power of the second lens group becomes small, making it difficult to achieve high magnification. Alternatively, the back focus becomes too small, making it difficult to increase the focal length at the telephoto end, which is also undesirable.

[0035] Furthermore, it is even more desirable to specify the numerical ranges for conditional expressions (1) to (10) as shown in the following conditional expressions (1a) to (10a). 0.3 < |f1 / f2| < 1.0 ···(1a) -1.58 <fpn / fpp<-0.63 ···(2a) Nd-0.00015×(νd-50) 2 <1.55 ···(3a) 33 < νdn1 < 65 ···(4a) 16 < νdp1 < 26 ···(5a) 0.9 <fpn / f1<4.6 ···(6a) -6.0 <fpp / f1<-1.6 ···(7a) 0.5 <Dp1 / D1≦1.0 ···(8a) 0.35<|f2 / M2wt|<0.85 (9a) 0.10 <BF / f2<0.55 ···(10a)

[0036] Furthermore, it is even more desirable to specify the numerical ranges of the conditional expressions (1a) to (10a) as shown in the following conditional expressions (1b) to (10b). 0.5 < |f1 / f2| < 1.0 ···(1b) -1.42 <fpn / fpp<-0.70 ···(2b) Nd-0.00015×(νd-50) 2 <1.545 ···(3b) 35 < νdn1 < 60 ···(4b) 17 < νdp1 < 25 ···(5b) 1.0 <fpn / f1<4.2 ···(6b) -5.5 <fpp / f1<-2.2 ···(7b) 0.6 <Dp1 / D1≦1.0 ···(8b) 0.50<|f2 / M2wt|<0.75 (9b) 0.15 <BF / f2<0.45 ···(10b) Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. [Examples]

[0037] Figure 1 shows a cross-sectional view of the zoom lens of Example 1 at the wide-angle end when focused at infinity. In the cross-sectional view of the zoom lens, the left side corresponds to the object side and the right side corresponds to the image side. In the lens cross-sectional view of Figure 1, L1 to L4 are the first to fourth lens groups, respectively, SP is the aperture diaphragm, P is a glass block such as the faceplate or low-pass filter of the CCD, and I is the image plane.

[0038] The arrows in Figure 1 show the trajectories of each lens group during zooming from the wide-angle end to the telephoto end. Furthermore, for lens groups moving for focusing, solid arrows show the trajectory during zooming from the wide-angle end to the telephoto end when focused at infinity, while dashed arrows show the trajectory during zooming from the wide-angle end to the telephoto end when focused at close range. The arrow F in the optical axis direction in Figure 1 indicates the direction of movement of the focusing lens group during focusing from infinity to close range. These are also true for other embodiments described later.

[0039] The zoom lens of Example 1 has, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a fourth lens group L4 with positive refractive power.

[0040] The spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves in a convex trajectory toward the image, the second lens group L2 moves toward the object, the third lens group L3 moves toward the object, and the fourth lens group L4 does not move. When focusing from infinity to close range, the third lens group L3 moves towards the image. In the zoom lens of Example 1, the subsequent lens group consists of a third lens group L3 and a fourth lens group L4.

[0041] The first lens group L1 consists of, in order from the object side to the image side, a negative lens, a meniscus negative lens with a convex surface on the object side, a resin meniscus negative lens with a convex surface on the image side (resin negative lens LN1), and a resin positive lens (resin positive lens LP1). The second lens group L2 consists of, in order from the object side to the image side, a positive lens, a cemented lens of a positive and a negative lens, and a positive lens. The third lens group L3 consists of, in order from the object side to the image side, a cemented lens of a negative lens and a positive lens. The fourth lens group L4 consists of a single positive lens.

[0042] Both sides of the resin negative lens LN1 and both sides of the resin positive lens LP1 are aspherical. In addition, both sides of the positive lens located closest to the object in the second lens group are also made of aspherical surfaces.

[0043] The second lens group L2 includes an aperture diaphragm SP that moves as a single unit. The aperture diaphragm SP may maintain a constant diameter during zooming, or it may change according to the zooming position.

[0044] Figures 2, 3, and 4 show the aberration diagrams for the numerical example 1 corresponding to Example 1 at the wide-angle end, intermediate focal length, and telephoto end. In each aberration diagram, d and g represent the d line and g line, respectively. In the astigmatism diagram, M and S represent the meridional image plane and sagittal image plane, respectively. The chromatic aberration diagram is indicated by the g line. As is clear from each aberration diagram, each aberration is well corrected.

[0045] Numerical Values ​​Corresponding to Example 1 Table 1 shows the numerical values ​​corresponding to conditional equations (1), (2), (4) to (10) in Example 1, and Table 2 shows the relationship with the numerical values ​​corresponding to conditional equation (3). The zoom lens of Example 1 satisfies conditional equations (1) to (10), and while being small and lightweight, it achieves wide-angle, large-aperture, and high magnification ratio optical performance even with changes in ambient temperature. [Examples]

[0046] Figure 5 shows a cross-sectional view of the zoom lens of Example 2 at the wide-angle end when focused at infinity. The zoom lens of Example 2 has, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a fourth lens group L4 with positive refractive power.

[0047] The spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves in a convex trajectory toward the image, the second lens group L2 moves toward the object, the third lens group L3 moves toward the object, and the fourth lens group L4 does not move. When focusing from infinity to close range, the third lens group L3 moves towards the image. In the zoom lens of Example 2, the subsequent lens group consists of a third lens group L3 and a fourth lens group L4.

[0048] The first lens group L1 consists of, in order from the object side to the image side, a convex meniscus negative lens on the object side, a resin negative lens (resin negative lens LN1), a concave resin plano-concave negative lens on the object side (resin negative lens LN2), and a resin positive lens (resin positive lens LP1). The second lens group L2 consists of, in order from the object side to the image side, a positive lens, a cemented lens of a convex meniscus positive lens on the object side and a convex meniscus negative lens on the object side, and a positive lens. The third lens group L3 consists of, in order from the object side to the image side, a cemented lens of a negative lens and a convex meniscus positive lens on the object side. The fourth lens group L4 consists of a single positive lens.

[0049] Both sides of the resin negative lens LN1, both sides of the resin negative lens LN2, and both sides of the resin positive lens LP1 are aspherical. In addition, both sides of the positive lens located closest to the object in the second lens group are also made of aspherical surfaces.

[0050] The second lens group L2 includes an aperture diaphragm SP that moves as a single unit. The aperture diaphragm SP may maintain a constant diameter during zooming, or it may change according to the zooming position.

[0051] Figures 6, 7, and 8 show the aberration diagrams for the numerical example 2, corresponding to Example 2, at the wide-angle end, intermediate focal length, and telephoto end. As is clear from each aberration diagram, each aberration has been well corrected. Table 1 shows the numerical values ​​corresponding to conditional equations (1), (2), and (4) to (10) in Numerical Example 2, and Table 2 shows the relationship with the numerical values ​​corresponding to conditional equation (3). The zoom lens of Example 2 satisfies conditional equations (1) to (10), and while being small and lightweight, it achieves wide-angle, large-aperture, and high magnification ratio optical performance even with changes in ambient temperature. [Examples]

[0052] Figure 9 shows a cross-sectional view of the zoom lens of Example 3 at the wide-angle end when focused at infinity. The zoom lens of Example 3 has, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, a third lens group L3 with negative refractive power, and a fourth lens group L4 with positive refractive power.

[0053] The spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves in a convex trajectory toward the image, the second lens group L2 moves toward the object, the third lens group L3 moves toward the object, and the fourth lens group L4 does not move. When focusing from infinity to close range, the third lens group L3 moves towards the image. In the zoom lens of Example 3, the subsequent lens group consists of a third lens group L3 and a fourth lens group L4.

[0054] The first lens group L1 consists of, in order from the object side to the image side, a negative lens, a resin meniscus negative lens with a convex image side (resin negative lens LN1), a resin meniscus negative lens with a convex image side (resin negative lens LN2), a resin meniscus positive lens with a convex object side (resin positive lens LP1), and a resin meniscus positive lens with a convex object side (resin positive lens LP2). The second lens group L2 consists of, in order from the object side to the image side, a positive lens, a cemented lens of a meniscus positive lens with a convex object side and a meniscus negative lens with a convex object side, and a meniscus positive lens with a convex image side. The third lens group L3 consists of a cemented lens of a negative lens and a positive lens, in order from the object side to the image side. The fourth lens group L4 consists of a single positive lens.

[0055] Both sides of the resin negative lens LN1, both sides of the resin negative lens LN2, both sides of the resin positive lens LP1, and both sides of the resin positive lens LP2 are aspherical. In addition, both sides of the positive lens located closest to the object in the second lens group are also made of aspherical surfaces.

[0056] The second lens group L2 includes an aperture diaphragm SP that moves as a single unit. The aperture diaphragm SP may maintain a constant diameter during zooming, or it may change according to the zooming position.

[0057] Figures 10, 11, and 12 show the aberration diagrams for the numerical example 3 corresponding to Example 3 at the wide-angle end, intermediate focal length, and telephoto end. As is clear from each aberration diagram, each aberration has been well corrected. Table 1 shows the numerical values ​​corresponding to conditional equations (1), (2), and (4) to (10) in Numerical Example 3, and Table 2 shows the relationship with the numerical values ​​corresponding to conditional equation (3). The zoom lens of Example 3 satisfies conditional equations (1) to (10), and while being small and lightweight, it achieves wide-angle, large-aperture, and high magnification ratio optical performance even with changes in ambient temperature. [Examples]

[0058] Figure 13 shows a cross-sectional view of the zoom lens of Example 4 at the wide-angle end when focused at infinity. The zoom lens of Example 4 has, in order from the object side to the image side, a first lens group L1 with negative refractive power, a second lens group L2 with positive refractive power, and a third lens group L3 with positive refractive power.

[0059] The spacing between adjacent lens groups changes during zooming. When zooming from the wide-angle end to the telephoto end, the first lens group L1 moves in a convex trajectory toward the image, the second lens group L2 moves toward the object, and the third lens group L3 does not move. During focusing from infinity to close range, the first lens group L1 moves toward the object. In the zoom lens of Example 4, the subsequent lens group consists only of the third lens group L3.

[0060] The first lens group L1 consists of a negative lens, a resin negative lens (resin negative lens LN1), and a resin positive lens (resin positive lens LP1), arranged from the object side to the image side. The second lens group L2 consists of a positive lens, a cemented lens of a positive and a negative lens, a positive lens, and a negative lens, arranged from the object side to the image side. The third lens group L3 consists of a single meniscus positive lens with a convex surface on the object side.

[0061] Both sides of the resin negative lens LN1 and both sides of the resin positive lens LP1 are aspherical. In addition, both sides of the positive lens located closest to the object in the second lens group are also made of aspherical surfaces.

[0062] Adjacent to the object side of the second lens group L2 is an aperture diaphragm SP that moves integrally with the second lens group L2. The aperture diaphragm SP may maintain a constant aperture diameter during zooming, or it may change according to the zooming position.

[0063] Figures 14, 15, and 16 show the aberration diagrams for the numerical example 4, corresponding to Example 4, at the wide-angle end, intermediate focal length, and telephoto end. As is clear from each aberration diagram, each aberration has been well corrected. Table 1 shows the numerical values ​​corresponding to conditional equations (1), (2), and (4) to (10) in Numerical Example 4, and Table 2 shows the relationship with the numerical values ​​corresponding to conditional equation (3). The zoom lens of Example 4 satisfies conditional equations (1) to (10), and while being small and lightweight, it achieves wide-angle, large-aperture, and high magnification ratio optical performance even with changes in ambient temperature.

[0064] In the zoom lens of the present invention, focusing is performed by the movement of the third lens group L3 in Examples 1 to 3, and by the movement of the first lens group L1 in Example 4, along the optical axis. However, the present invention is not limited to this, and focusing may be performed by the movement of other lens groups along the optical axis.

[0065] Numerical Examples 1 to 4 corresponding to Examples 1 to 4 of the present invention are described below. In each numerical example, ri is the radius of curvature of the i-th surface from the object side, di is the distance between the i-th surface and the (i+1)-th surface (lens thickness or air gap), and ndi and vdi are the refractive index and Abbe number of the optical medium between the i-th surface and the (i+1)-th surface, respectively. The Abbe number νd is given by nF, nd, and nC for the Fraunhofer lines F, d, and C, respectively. νd=(nd-1) / (nF-nC) It is defined by the following formula.

[0066] Aspherical shape is defined as having the X-axis in the direction of the optical axis, the h-axis perpendicular to the optical axis, and the direction of light propagation as positive, with R being the paraaxial radius of curvature and the aspherical coefficients being K, A4, A6, and A8,

number

[0067] (Numerical Example 1) Unit: mm Surface data Face number rd nd vd 1 -568.205 0.71 1.69680 55.5 2 7.932 3.17 3 99.514 0.60 1.49700 81.5 4 19.919 2.40 5* -14.998 0.60 1.53500 56.0 6* 1000.000 0.17 7* 22.818 1.97 1.68040 18.1 8* -222.181 (variable) 9* 11.426 3.26 1.58313 59.4 10* -21.453 1.26 11 (aperture) ∞ 0.24 12 10.020 2.50 1.77250 49.6 13 -904.335 0.60 1.85478 24.8 14 6.964 1.17 15 28.098 1.64 1.77250 49.6 16 -21.256 (variable) 17 -24.535 1.05 1.65412 39.7 18 7.478 2.25 1.49700 81.5 19 -674.296 (variable) 20 22.927 1.64 2.00100 29.1 21 -30.420 2.15 22 ∞ 0.80 1.51633 64.1 23 ∞ 1.00 Image plane ∞ Aspherical data 5th page K = 1.81638e-01 A4=-1.08221e-04 A6=-1.92183e-06 Side 6 K = 0.00000e+00 A4=-1.99792e-04 A6= 8.22688e-07 Side 7 K =-1.22720e+01 A4=-4.54753e-05 A6= 1.29115e-06 A8=-1.35601e-08 Side 8 K = 0.00000e+00 A4=-7.47636e-05 A6= 3.90334e-07 9th page K =-2.48342e+00 A4= 8.49071e-05 A6=-9.91019e-08 Side 10 K = 3.40232e+00 A4= 1.53928e-04 A6= 1.64757e-07 Various data Zoom ratio 4.90 Wide-angle, Medium, Telephoto Focal length 3.42 9.92 16.79 F-numbers: 1.44, 2.52, 3.61 Half-angle 65.55 18.47 10.93 Image height 3.20 3.20 3.20 Lens length: 51.40 x 45.10 x 51.37 BF 3.68 3.68 3.68 d 8 19.50 3.75 0.57 d16 1.09 4.96 7.21 d19 1.90 7.49 14.69 Zoom lens group data Group starting plane focal length 1 1 -8.53 2 9 10.47 3 17 -21.18 4 20 13.26

[0068] (Numerical Example 2) Unit: mm Surface data Face number rd nd vd 1 150.000 0.73 1.69680 55.5 2 8.231 3.75 3* -211.667 0.75 1.50940 56.0 4* 28.070 2.32 5* -9.674 0.60 1.53110 56.0 6* ∞ 0.17 7* 15.160 2.32 1.65010 21.5 8* -174.587 (variable) 9* 10.923 3.30 1.58313 59.4 10* -22.764 0.17 11 (aperture) ∞ 1.30 12 9.680 2.53 1.77250 49.6 13 303.788 0.60 1.85478 24.8 14 6.583 1.18 15 23.150 1.69 1.77250 49.6 16 -22.421 (variable) 17 -24.449 0.60 1.65412 39.7 18 7.060 1.74 1.49700 81.5 19 184.185 (variable) 20 23.778 1.61 2.00100 29.1 21 -31.075 2.16 22 ∞ 0.80 1.51633 64.1 23 ∞ 1.00 Image plane ∞ Aspherical data 3rd page K = 0.00000e+00 A4= 8.21923e-05 A6=-2.81062e-06 Side 4 K =-1.31100e+00 A4=-2.84691e-04 A6=-3.48288e-06 5th page K=-1.98188e-01 A4= 1.75964e-05 A6= 2.25796e-06 Side 6 K = 0.00000e+00 A4= 1.39728e-04 A6= 3.62327e-06 Side 7 K =-4.52253e+00 A4=-7.69787e-05 A6= 1.76512e-06 A8=-1.44456e-08 Side 8 K = 0.00000e+00 A4= 1.79645e-05 A6=-7.71590e-07 9th page K =-2.25110e+00 A4= 9.14792e-05 A6=-2.76302e-07 Side 10 K = 9.57846e-01 A4= 1.26455e-04 A6=-4.29958e-07 Various data Zoom ratio 4.90 Wide-angle, Medium, Telephoto Focal length 3.43 10.06 16.84 F-numbers: 1.44, 2.52, 3.61 Half-angle 62.06 18.13 10.87 Image height 3.20 3.20 3.20 Lens length: 51.77 x 45.28 x 51.75 BF 3.69 3.69 3.69 d 8 19.60 3.61 0.57 d16 1.09 4.22 5.64 d19 2.05 8.41 16.50 Zoom lens group data Group starting plane focal length 1 1 -8.72 2 9 10.32 3 17 -19.19 4 20 13.66

[0069] (Numerical Example 3) Unit: mm Surface data Face number rd nd vd 1 -7689.495 0.70 1.72916 54.7 2 7.315 4.85 3* -29.911 1.05 1.53110 56.0 4* -149.245 0.57 5* -13.163 0.60 1.53500 56.0 6* ∞ 0.20 7* 83.112 1.27 1.63910 23.5 8* 3079.217 0.20 9* 13.442 1.80 1.63910 23.5 10 * 44.221 (variable) 11* 11.121 3.44 1.58313 59.4 12* -16.657 0.25 13 (aperture) ∞ 0.50 14 9.361 3.03 1.69680 55.5 15 159.470 0.50 1.85478 24.8 16 6.473 1.31 17 -26.362 0.97 1.73400 51.5 18 -12.706 (variable) 19 -13.125 0.50 1.53172 48.8 20 5.963 3.08 1.49700 81.5 21 -36.619 (variable) 22 16.298 2.23 1.80400 46.5 23 -23.371 3.42 24 ∞ 0.80 1.51633 64.1 25 ∞ 1.00 Image plane ∞ Aspherical data 3rd page K = 0.00000e+00 A4=-1.87301e-04 A6=-7.32065e-06 Side 4 K = 0.00000e+00 A4=-5.32448e-04 A6=-3.42855e-06 5th page K = 2.37230e+00 A4= 3.60500e-04 A6= 2.31463e-06 Side 6 K = 0.00000e+00 A4= 3.53194e-04 A6=-6.16619e-06 A8= 3.78923e-08 Side 7 K = 1.34722e+01 A4= 8.37701e-04 A6=-9.44798e-06 A8= 2.05914e-07 Side 8 K = 0.00000e+00 A4= 5.34200e-04 A6=-2.95975e-06 A8= 2.92007e-07 9th page K =-1.18979e+00 A4=-4.52929e-04 A6=-3.09304e-07 A8= 1.17231e-07 Side 10 K =-2.76840e+01 A4=-1.17225e-04 A6=-3.22471e-06 A8= 3.52725e-08 Page 11 K =-3.16270e+00 A4= 1.50880e-04 A6=-1.18837e-06 Side 12 K=-9.70262e-01 A4= 1.34863e-04 A6=-8.94521e-07 Various data Zoom ratio 4.00 Wide-angle, Medium, Telephoto Focal length 3.46 8.47 13.86 F-numbers: 1.44, 2.52, 3.61 Half-angle 62.22 21.97 13.43 Image height 3.20 3.20 3.20 Lens length: 51.61 x 46.62 x 51.58 BF 4.95 4.95 4.95 d10 17.97 4.30 0.57 d18 0.60 7.34 14.38 d21 1.03 2.98 4.62 Zoom lens group data Group starting plane focal length 1 1 -8.94 2 11 11.56 3 19 -31.88 4 22 12.25

[0070] (Numerical Example 4) Unit: mm Surface data Face number rd nd vd 1 -289.204 0.69 1.59522 67.7 2 8.343 4.99 3* -12.671 0.60 1.56650 37.6 4* 15.890 0.30 5* 18.419 2.31 1.65010 21.5 6* -27.507 (variable) 7 (aperture) ∞ -0.51 8* 10.181 3.25 1.58313 59.4 9* -23.140 0.32 10 9.630 2.70 1.49700 81.5 11 -1081.986 0.60 1.85478 24.8 12 7.786 4.10 13 16.687 2.45 1.80400 46.5 14 -14.097 2.75 15 -8.755 0.60 1.65412 39.7 16 52.860 (Variable) 17 10.355 1.78 1.72916 54.7 18 102.529 0.77 19 ∞ 0.80 1.51000 60.0 20 ∞ 1.00 Image plane ∞ Aspherical data 3rd page K = 6.56455e-01 A4= 3.56193e-05 A6=-2.36203e-07 Side 4 K =-7.76934e+00 A4=-8.27252e-05 A6=-1.67574e-06 5th page K =-1.92708e+00 A4=-1.52276e-04 A6= 2.40892e-07 A8=-2.55575e-08 Side 6 K = 6.52217e+00 A4= 1.12654e-05 A6=-6.27984e-08 A8=-8.66070e-09 Side 8 K = 6.28051e-02 A4=-1.57380e-04 A6=-4.47976e-07 A8= 1.74913e-09 9th page K =-1.47837e+01 A4=-2.96584e-05 A6= 1.36628e-06 Various data Zoom ratio 4.91 Wide-angle, Medium, Telephoto Focal length 3.76 11.11 18.47 F-numbers: 1.44, 2.51, 3.61 Half-angle 55.22 16.37 9.75 Image height 3.20 3.20 3.20 Lens length: 50.53 x 44.09 x 50.61 BF 2.30 2.30 2.30 d 6 20.86 4.57 1.25 d16 0.45 10.30 20.14 Zoom lens group data Group starting plane focal length 1 1 -10.65 2 7 11.14 3 17 15.67

[0071] [Table 1]

[0072] Table 2 shows the relationship between conditional equation (3) and the various numerical values ​​of the resin lens in each numerical example. [Table 2] As described above, each embodiment makes it possible to realize a large-aperture, compact zoom lens with a wide angle, high magnification ratio, and good optical performance throughout the entire zoom range.

[0073] (Imaging device) Next, an embodiment of an imaging device (surveillance camera) using the zoom lens of the present invention as the imaging optical system will be described with reference to Figures 17 and 18. In Figures 17 and 18(A), 16 is a photographic optical system composed of any of the zoom lenses described in Examples 1 to 4. 17 in Figure 17(A) and 15 in Figure 18(A) are covers that protect the photographic optical system 16. In Figure 17(B), 11 is the surveillance camera body, and 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the camera body and receives the subject image formed by the imaging optical system 16.

[0074] 13 is a memory that records information corresponding to the subject image converted photoelectrically by the solid-state image sensor 12. 14 is a network cable for transferring the subject image converted photoelectrically by the solid-state image sensor 12. Figure 18(B) shows an example of this imaging device being used as a surveillance camera when a dome-shaped cover 15 is attached and mounted on the ceiling. 10 is the part not covered by the dome-shaped cover 15.

[0075] By applying the imaging device of the present invention to optical equipment such as surveillance cameras, it is possible to realize compact optical equipment with high optical performance. The imaging device is not limited to surveillance cameras; it can also be used with video cameras, digital cameras, and other similar devices. Furthermore, by using an electronic image sensor such as a CCD, the output image quality can be further improved by electronically correcting aberrations. Although preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its gist.

[0076] This embodiment includes the following configuration. (Composition 1) The lens system has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group containing one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses with a negative refractive power and one or more positive resin lenses with a positive refractive power. When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the combined focal length of the one or more negative resin lenses is fpn, and the combined focal length of the one or more positive resin lenses is fpp, 0.1 < |f1 / f2| < 1.0 -1.72 <fpn / fpp<-0.58 A zoom lens characterized by satisfying the following conditions. (Configuration 2) The resin lens included in the first lens group includes an aspherical surface, and when the refractive index is Nd and the Abbe number is νd, Nd-0.00015×(νd-50) 2 <1.56 A zoom lens according to configuration 1, characterized by satisfying the following conditions. (Composition 3) When the Abbe number of the resin negative lens with the smallest absolute value of focal length among the one or more resin negative lenses is denoted as νdn1, 31<νdn1<75 A zoom lens according to configuration 1 or 2, characterized by satisfying the following conditions. (Composition 4) When the Abbe number of the resin positive lens with the smallest focal length among the one or more resin positive lenses is denoted as νdp1, 15<νdp1<27 A zoom lens according to any one of configurations 1 to 3, characterized by satisfying the following conditions. (Composition 5) 0.8 <fpn / f1<5.0 A zoom lens according to any of configurations 1 to 4, characterized by satisfying the following conditions. (Composition 6) -6.5 <fpp / f1<-1.0 A zoom lens described in any of configurations 1 to 5, characterized by satisfying the following conditions. (Composition 7) When D1 is the sum of the lengths of all lenses in the first lens group along the optical axis, and Dp1 is the sum of the lengths of the resin lenses in the first lens group along the optical axis, 0.4 <Dp1 / D1≦1.0 A zoom lens according to any one of configurations 1 to 6, characterized by satisfying the following conditions. (Composition 8) When changing magnification from the wide-angle end to the telephoto end, the first lens group moves in a convex trajectory toward the image side, and the second lens group moves monotonically toward the object side, and when the maximum amount of movement of the second lens group is M2wt, 0.20 < |f2 / M2wt| < 1.00 A zoom lens described in any of configurations 1 to 7, characterized by satisfying the following conditions. (Composition 9) When the back focus is set to BF, 0.05 <BF / f2<0.60 A zoom lens according to any of configurations 1 to 8, characterized by satisfying the following conditions. (Composition 10) The zoom lens according to any one of configurations 1 to 9, characterized in that the subsequent lens group is composed of a group of lenses with negative refractive power and a group of lenses with positive refractive power, in order from the object side to the image side. (Composition 11) The zoom lens according to any one of configurations 1 to 9, characterized in that the subsequent lens group is composed of a single lens group with positive refractive power. (Composition 12) The lens system has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group containing one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses having negative refractive power and one or more positive resin lenses having positive refractive power. When the combined focal length of the one or more resin negative lenses is fpn and the combined focal length of the one or more resin positive lenses is fpp, -1.72 <fpn / fpp<-0.58 A zoom lens characterized by satisfying the following conditions. (Composition 13) An imaging device characterized by having a zoom lens as described in any of configurations 1 to 12, and an image sensor that receives the image formed by the zoom lens. [Explanation of Symbols]

[0077] L1 First lens group L2 Second lens group L3 Third lens group (successor lens group) L4 4th lens group (successor lens group)

Claims

1. The lens system has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group containing one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes a resin negative lens with a negative refractive power of 1 or more, and a resin positive lens with a positive refractive power of 1 or more. When the focal length of the first lens group is f1, the focal length of the second lens group is f2, the combined focal length of the one or more negative resin lenses is fpn, and the combined focal length of the one or more positive resin lenses is fpp, 0.1<|f1 / f2|<1.0 -1.72<fpn / fpp<-0.58 A zoom lens characterized by satisfying the following conditions.

2. The resin lens included in the first lens group includes an aspherical surface, and when the refractive index is Nd and the Abbe number is νd, Nd-0.00015×(νd-50) ２ <1.56 The zoom lens according to claim 1, characterized by satisfying the following conditions.

3. When the Abbe number of the resin negative lens with the smallest absolute value of focal length among the one or more resin negative lenses is denoted as νdn1, 31 < νdn1 < 75 The zoom lens according to claim 1, characterized by satisfying the following conditions.

4. When the Abbe number of the resin positive lens with the smallest focal length among the one or more resin positive lenses is denoted as νdp1, 15 < νdp1 < 27 The zoom lens according to claim 1, characterized by satisfying the following conditions.

5. 0.8<fpn / f1<5.0 The zoom lens according to claim 1, characterized by satisfying the following conditions.

6. -6.5<fpp / f1<-1.0 The zoom lens according to claim 1, characterized by satisfying the following conditions.

7. When D1 is the sum of the lengths of all lenses in the first lens group along the optical axis, and Dp1 is the sum of the lengths of the resin lenses in the first lens group along the optical axis, 0.4<Dp1 / D1≦1.0 The zoom lens according to claim 1, characterized by satisfying the following conditions.

8. When changing magnification from the wide-angle end to the telephoto end, the first lens group moves in a convex trajectory toward the image side, and the second lens group moves monotonically toward the object side, and when the maximum amount of movement of the second lens group is M2wt, 0.20<|f2 / M2wt|<1.00 The zoom lens according to claim 1, characterized by satisfying the following conditions.

9. When the back focus is set to BF, 0.05<BF / f2<0.60 The zoom lens according to claim 1, characterized by satisfying the following conditions.

10. The zoom lens according to claim 1, characterized in that the subsequent lens group is composed of a group of lenses with negative refractive power and a group of lenses with positive refractive power, in order from the object side to the image side.

11. The zoom lens according to claim 1, characterized in that the subsequent lens group is composed of a single lens group with positive refractive power.

12. The lens system has, in order from the object side to the image side, a first lens group with negative refractive power, a second lens group with positive refractive power, and a subsequent lens group containing one or more lens groups. The spacing between adjacent lens groups changes during zooming. The first lens group includes one or more negative resin lenses having negative refractive power and one or more positive resin lenses having positive refractive power. When the combined focal length of the one or more resin negative lenses is fpn and the combined focal length of the one or more resin positive lenses is fpp, -1.72<fpn / fpp<-0.58 A zoom lens characterized by satisfying the following conditions.

13. An imaging device characterized by having a zoom lens according to any one of claims 1 to 12 and an image sensor that receives an image formed by the zoom lens.

Images