Zoom lens and imaging device having the same

Abstract

To provide a high-magnification zoom lens with high optical performance. [Solution] A zoom lens comprising a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged in order from the object side to the image side, wherein the distance between adjacent lens groups changes during zooming, the first lens group remains stationary with respect to the image plane during zooming from the wide-angle end to the telephoto end, the fourth lens group has at least three lenses, and when the lateral magnification at the wide-angle end of the second lens group is β2w and the lateral magnification at the wide-angle end of the third lens group is β3w, a predetermined conditional equation is satisfied.

Description

Technical Field

[0001] The disclosure of this specification relates to a zoom lens and an imaging device having the same, and is suitable for imaging devices such as digital cameras, video cameras, TV cameras, surveillance cameras, etc.

Background Art

[0002] In recent years, in zoom lenses mounted on network cameras, video cameras, etc., a zoom lens that is small and has a wide angle of view has been required. In Patent Document 1, a zoom lens including a positive first lens group, a negative second lens group, a positive third lens group, and a positive fourth lens group is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] For zoom lenses mounted on network cameras, etc., high magnification is required. In order to achieve both high magnification and high optical performance of the zoom lens, it is necessary to appropriately set the configuration of each lens group.

Means for Solving the Problems

[0005] A zoom lens as one aspect of the present invention comprises a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged sequentially from the object side to the image side, wherein the distance between adjacent lens groups changes during zooming, and when zooming from the wide-angle end to the telephoto end, the first lens group remains stationary with respect to the image plane, the fourth lens group has at least three lenses, and when the lateral magnification at the wide-angle end of the second lens group is β2w and the lateral magnification at the wide-angle end of the third lens group is β3w, 0.060 ≤ β2w × β3w ≤ 0.150 It is characterized by satisfying the following conditional expression.

[0006] Furthermore, a zoom lens as one aspect of the present invention comprises a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged in order from the object side to the image side, wherein the distance between adjacent lens groups changes during zooming, and the first lens group remains stationary with respect to the image plane during zooming from the wide-angle end to the telephoto end, and the fourth lens group has a cemented lens consisting of a positive lens and a negative lens.

[0007] Furthermore, an imaging device equipped with the above-mentioned zoom lens also constitutes another aspect of the present invention. [Effects of the Invention]

[0008] This allows us to provide high-magnification zoom lenses with superior optical performance. [Brief explanation of the drawing]

[0009] [Figure 1] Cross-sectional view of the zoom lens in Example 1 [Figure 2] Aberration diagrams of the zoom lens of Example 1 at (A) wide-angle end, (B) intermediate focal length 1, (C) intermediate focal length 2, (D) intermediate focal length 3, and (E) telephoto end. [Figure 3] Cross-sectional view of the zoom lens in Example 2 [Figure 4]Aberration diagrams of the zoom lens of Example 2 at (A) wide-angle end, (B) intermediate focal length 1, (C) intermediate focal length 2, (D) intermediate focal length 3, and (E) telephoto end. [Figure 5] Cross-sectional view of the zoom lens in Example 3 [Figure 6] Aberration diagrams of the zoom lens of Example 3 at (A) wide-angle end, (B) intermediate focal length 1, (C) intermediate focal length 2, (D) intermediate focal length 3, and (E) telephoto end. [Figure 7] Schematic diagram of the imaging device [Modes for carrying out the invention]

[0010] Embodiments disclosed herein will be described below with reference to the drawings. Note that the drawings may be drawn to a different scale than the actual dimensions for convenience. Furthermore, in each drawing, the same reference numeral is used for identical components, and redundant descriptions are omitted.

[0011] In this specification, a lens group is a collection of lenses that move or are fixed together with respect to the image plane during zooming between the wide-angle and telephoto ends. That is, the distance between adjacent lens groups changes during zooming. Each lens group may also include an aperture diaphragm.

[0012] Furthermore, in this specification, the wide-angle end and telephoto end refer to the zoom state when the lens group that moves during zooming is located at both ends of the range that is mechanically or controllably movable in the optical axis direction. Intermediate focal length 1 refers to the zoom state when the focus group that moves during zooming is mechanically or controllably located closest to the image in the optical axis direction. Intermediate focal length 2 refers to the zoom state at a zoom position where the maximum zoom ratio when zooming from the wide-angle end to the telephoto end is approximately Z / 2. Intermediate focal length 3 refers to the zoom state when the focus group that moves during zooming is mechanically or controllably located closest to the object in the optical axis direction.

[0013] Figures 1, 3, and 5 are cross-sectional views of the zoom lens B0 of Examples 1 to 3 at the wide-angle end, respectively. In each cross-sectional view, the left side is the object side and the right side is the image side. The zoom lenses of each embodiment are suitable for imaging devices such as digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and in-vehicle cameras.

[0014] In each cross-sectional view, Bi represents the i-th lens group counting from the object side, and Lim represents the m-th lens from the object side among the lenses constituting the i-th lens group Bi. AP is the aperture diaphragm. G is a glass block such as the cover glass, low-pass filter, infrared cut filter, or optical element that has virtually no refractive power for the image sensor. IM is the image plane, and when the zoom lens of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the image plane of a solid-state image sensor such as a CCD sensor or CMOS sensor or a photoelectric conversion element is positioned there.

[0015] In each cross-sectional view, arrows indicate the movement trajectory of each lens group when zooming from the wide-angle end to the telephoto end. Below the focus group, solid and dashed arrows are shown, indicating the movement trajectory to correct image plane fluctuations associated with zooming from the wide-angle end to the telephoto end when focused on an object at infinity (hereinafter referred to as the infinity focus state) and when focused on a close-up object, respectively. Furthermore, below the lens group that moves in the optical axis direction during focusing, a solid arrow with "FC" indicates the direction of movement of the lens group when focusing from infinity to the closest point.

[0016] Figures 2, 4, and 6 are longitudinal aberration diagrams of zoom lens B0 of Examples 1 to 3, respectively. In each longitudinal aberration diagram, the spherical aberration diagram, astigmatism diagram, distortion diagram, and chromatic aberration diagram are shown from left to right. Furthermore, in each longitudinal aberration diagram, (A) shows the longitudinal aberration diagram at the wide-angle end, (B) at intermediate focal length 1, (C) at intermediate focal length 2, (D) at intermediate focal length 3, and (E) at the telephoto end.

[0017] In each longitudinal aberration diagram, Fno represents the F-number, and ω represents the paraxial half angle [°].

[0018] In the spherical aberration diagram, the solid line indicates the spherical aberration amount at the d-line (wavelength 587.6 nm), the two-dot chain line indicates the spherical aberration amount at the g-line (wavelength 435.8 nm), and the one-dot chain line indicates the spherical aberration amount at the C-line (wavelength 656.3 nm). Also, in the spherical aberration diagram, the long dashed line indicates the spherical aberration amount at the F-line (wavelength 486.1 nm). In the astigmatism diagram, the solid line S indicates the astigmatism amount with respect to the d-line on the sagittal image plane, and the dashed line M indicates the astigmatism amount with respect to the d-line on the meridional image plane. In the distortion diagram, the solid line indicates the distortion with respect to the d-line. In the chromatic aberration diagram, the two-dot chain line indicates the chromatic aberration amount with respect to the g-line, the one-dot chain line indicates the chromatic aberration amount with respect to the C-line, and the dashed line indicates the chromatic aberration amount with respect to the F-line. Note that the astigmatism diagram and the chromatic aberration diagram show the aberration amounts when the central ray of the light beam at the aperture position is taken as the chief ray.

[0019] Next, the characteristic configurations of the zoom lens B0 in each embodiment will be described.

[0020] The zoom lens of each embodiment consists of a first lens group B1 with positive refractive power, a second lens group B2 with negative refractive power, a third lens group B3 with positive refractive power, and a fourth lens group B4 with positive refractive power, which are arranged in order from the object side to the image side. By having the third lens group B3 and the fourth lens group B4 with positive refractive power, it is possible to effectively correct the axial chromatic aberration, particularly at the telephoto end.

[0021] In zooming from the wide-angle end to the telephoto end, the first lens group B1 is stationary with respect to the image plane.

[0022] By keeping the first lens group B1 stationary during zooming, the overall length of the zoom lens B0 is not changed, and the eccentricity of the first lens group B1 caused by manufacturing errors during zooming is suppressed, thereby reducing variations in aberrations due to eccentricity. Furthermore, by moving the second lens group B2, the third lens group B3, and the fourth lens group B4 along the optical axis during zooming, aberrations can be effectively corrected by utilizing the spacing between each lens group.

[0023] In the zoom lens B0 of each embodiment, the fourth lens group B4 includes at least three lenses. This makes it possible to effectively correct various aberrations, particularly spherical aberration and coma aberration at the wide-angle end, and field curvature throughout the entire zoom range.

[0024] By satisfying the above configuration, it is possible to realize a high-magnification zoom lens B0 with high optical performance.

[0025] Next, we will describe the conditions that the zoom lens B0 of each embodiment preferably satisfies.

[0026] The zoom lens B0 of each embodiment preferably satisfies one or more of the following conditional expressions (1) to (13). In each conditional expression, the numerical values ​​are expressed as follows.

[0027] Let β2w be the lateral magnification of the second lens group B2 at the wide-angle end, β2t be the lateral magnification of the second lens group B2 at the telephoto end, and β3w be the lateral magnification of the third lens group B3 at the wide-angle end.

[0028] Let TL be the total optical length of zoom lens B0 at the wide-angle end, and D23w be the air distance on the optical axis between the second lens group B2 and the third lens group B3 at the wide-angle end.

[0029] Let νdp be the Abbe number of the material of the positive lens Gp included in the first lens group B1, θgFp be the partial dispersion ratio, and ΔθgFp be the anomalous partial dispersion. However, the anomalous partial dispersion is expressed as ΔθgFp = θgFp + 0.0011 × νdp.

[0030] Let Ndn be the refractive index of the negative lens Gn material included in the first lens group B1 with respect to the d line, and let νdn be the Abbe number.

[0031] Let the focal length of the first lens group B1 be f1, the focal length of the second lens group B2 be f2, the focal length of the third lens group B3 be f3, and the focal length of the fourth lens group B4 be f4.

[0032] Let D1 be the thickness of the first lens group B1 along the optical axis. The thickness in each lens group is the distance along the optical axis from the object-side lens surface of the lens closest to the object to the lens in the group to the image-side lens surface of the lens closest to the image.

[0033] Let m4_max be the difference between the position of the fourth lens group on the optical axis when it is moved furthest towards the object and its position on the optical axis when it is moved furthest towards the image. However, the movement of each lens group is considered positive when it moves from the object side to the image side.

[0034] Let fw be the focal length and bfw be the back focus at the wide-angle end of zoom lens B0. The back focus is the air-equivalent distance from the image-side lens surface of the lens closest to the image among the lenses included in zoom lens B0 to the image plane IM. 0.060 ≤ β2w × β3w ≤ 0.150 (1) 0.40 <D23w / TL<0.55 (2) 65.00 < νdp < 105.00 (3) 0.613 < ΔθgFp < 0.655 (4) 1.60 <Ndn<2.10 (5) 2.19 <Ndn+0.0167×νdn<2.46 (6) 0.10 <D1 / f1<0.35 (7) 0.10 < |f2 / f1| < 0.30 (8) 1.50 < |β2t| < 4.00 (9) 1.50 < |f3 / f2| < 4.00 (10) 0.40 <f3 / f4<1.00 (11) 0.05 <m4_max / TLt<0.25 (12) 0.01 <bfw / fw<0.25 (13)

[0035] Conditional equation (1) defines the appropriate range for the lateral magnification β2w of the second lens group B2 and the lateral magnification β3w of the third lens group B3 at the wide-angle end. If the upper limit of equation (1) is exceeded, the lateral magnification of either the second lens group B2 or the third lens group B3 at the wide-angle end becomes too large. This is undesirable because it results in insufficient magnification of the second lens group B2 or the third lens group, making it difficult to increase the magnification of the zoom lens B0. If the lower limit of equation (1) is exceeded, the refractive power of either the second lens group B2 or the third lens group B3 becomes too strong, making it difficult to correct various aberrations such as spherical aberration, coma aberration, and field curvature, which is also undesirable.

[0036] Condition (2) defines the ratio of the air gap on the optical axis between the second lens group B2 and the third lens group B3 to the total optical length TL at the wide-angle end. Here, the total optical length is the distance on the optical axis from the object-side lens surface to the image plane IM of the lens positioned closest to the object in the zoom lens B0. If the ratio exceeds the upper limit of condition (2), the air gap on the optical axis between the second lens group B2 and the third lens group B3 at the wide-angle end becomes too large, making it difficult to secure the necessary thickness of each lens group for good aberration correction, which is undesirable. If the ratio falls below the lower limit of condition (2), the air gap on the optical axis between the second lens group B2 and the third lens group B3 at the wide-angle end becomes too small, making it difficult to achieve high magnification, which is also undesirable.

[0037] Conditional equation (3) specifies the appropriate Abbe number range for the positive lens Gp included in the first lens group B1. In conditional equation (3), the refractive index with respect to the g line is ng, the refractive index with respect to the F line is nF, the refractive index with respect to the C line is nC, and the partial dispersion ratio θgF = ng - nF / nF - nC.

[0038] If the upper limit of condition (3) is exceeded, it is undesirable because it reduces the degree of freedom in the material of the positive lens Gp in order to achieve the desired optical performance. If the lower limit of condition (3) is exceeded, the dispersion of the material of the positive lens Gp becomes too large, which is undesirable because it increases axial chromatic aberration, especially at the telephoto end.

[0039] Conditional equation (4) defines the appropriate range of partial dispersion ratio for the positive lens Gp. Exceeding the upper limit of conditional equation (4) is undesirable because it reduces the degree of freedom in the material of the positive lens Gp to achieve the desired optical performance. Exceeding the lower limit of conditional equation (4) is also undesirable because the partial dispersion ratio of the positive lens Gp becomes too small, increasing the second-order spectrum of axial chromatic aberration, especially at the telephoto end.

[0040] Conditional equation (5) specifies an appropriate range for the refractive index of the negative lens Gn material included in the first lens group B1 with respect to the d line. Exceeding the upper limit of conditional equation (5) is undesirable because it severely limits the choice of glass material. Exceeding the lower limit of conditional equation (5) is undesirable because the refractive index of the negative lens Gn becomes too weak, requiring an increase in the curvature of the lens surface to maintain the refractive power of the lens, thereby increasing various aberrations.

[0041] Conditional equation (6) specifies an appropriate range for the Abbe number of the negative lens Gn. Exceeding the upper limit of conditional equation (6) is undesirable because it results in excessive correction of axial chromatic aberration at the telephoto end. Exceeding the lower limit of conditional equation (6) is also undesirable because it increases the secondary spectrum of axial chromatic aberration at the telephoto end.

[0042] Conditional equation (7) defines an appropriate range for the thickness of the first lens group B1 with respect to its focal length. The thickness of the first lens group B1 is the distance along the optical axis from the object-side lens surface of the lens L11, which is positioned closest to the object, to the image-side lens surface of the lens positioned closest to the image. Exceeding the upper limit of conditional equation (7) is undesirable because it makes the first lens group B1 too thick, causing the zoom lens L0 to become larger in the optical axis direction. Exceeding the lower limit of conditional equation (7) is undesirable because it makes it difficult to secure the necessary thickness of the first lens group B1 for good aberration correction.

[0043] Conditional equation (8) specifies an appropriate range for the ratio of the focal length of the second lens group B2 to the focal length of the first lens group B1. Exceeding the upper limit of conditional equation (8) is undesirable because the refractive power of the second lens group B2 becomes too weak, requiring an increase in the curvature of the lens surface to maintain the refractive power, thus increasing various aberrations. Exceeding the lower limit of conditional equation (8) is also undesirable because the refractive power of the second lens group B2 becomes too strong, making it difficult to correct various aberrations such as field curvature.

[0044] Conditional equation (9) defines an appropriate range for the lateral magnification of the second lens group B2 at the telephoto end. Exceeding the upper limit of conditional equation (9) is undesirable because it increases the amount of movement of the second lens group B2 too much, making miniaturization difficult. Exceeding the lower limit of conditional equation (9) is also undesirable because it decreases the lateral magnification of the second lens group B2 too much, making high magnification difficult.

[0045] Conditional equation (10) defines an appropriate range for the ratio of the focal length of the third lens group B3 to the focal length of the second lens group B2. Exceeding the upper limit of conditional equation (10) is undesirable because the refractive power of the third lens group B3 becomes too weak, making it difficult to obtain the desired zoom ratio. Exceeding the lower limit of conditional equation (10) is also undesirable because the refractive power of the third lens group B3 becomes too strong, resulting in strong spherical aberration and coma aberration.

[0046] Conditional equation (11) specifies an appropriate range for the ratio of the focal length of the third lens group B3 to the focal length of the fourth lens group B4. Exceeding the upper limit of conditional equation (11) is undesirable because it results in excessive refractive power of the fourth lens group B4, causing strong spherical aberration, coma aberration, field curvature, etc. Exceeding the upper limit of conditional equation (11) is undesirable because it results in excessive refractive power of the fourth lens group B4, making miniaturization difficult.

[0047] Conditional equation (12) defines the ratio of the maximum movement of the fourth lens group B4 to the total optical length of the zoom lens B0 at the telephoto end. If the ratio exceeds the upper limit of conditional equation (12), the movement of the fourth lens group B4 becomes too large, which is undesirable because it forces the zoom lens B0 to become larger in the optical axis direction in order to accommodate the movement of the fourth lens group. If the ratio falls below the lower limit of conditional equation (12), the refractive power of the fourth lens group B4 becomes too strong in order to obtain the desired zoom ratio, which is undesirable because it causes strong spherical aberration, coma aberration, field curvature, etc.

[0048] Conditional equation (13) shows the appropriate relationship between the focal length at the wide-angle end and the back focus at the wide-angle end. If the value exceeds the upper limit of conditional equation (13), the back focus becomes too long, which is undesirable because it causes the zoom lens B0 to become larger in the optical axis direction. If the value falls below the lower limit of conditional equation (13), the back focus becomes too short, which is undesirable because it causes lenses and optical elements positioned near the image plane to come too close to the image plane.

[0049] Furthermore, it is more preferable to set the numerical ranges of conditional expressions (1) to (13) as shown in the following conditional expressions (1a) to (13a). 0.070≦β2w×β3w≦0.145 (1a) 0.45 <D23w / TL<0.53 (2a) 70.00 < νdp < 104.00 (3a) 0.617 < ΔθgFp < 0.650 (4a) 1.65 <Ndn<2.00 (5a) 2.23 <Ndn+0.0167×νdn<2.35 (6a) 0.15 <D1 / f1<0.33 (7a) 0.13 < |f2 / f1| < 0.25 (8a) 1.70 < |β2t| < 3.70 (9a) 1.70 < |f3 / f2| < 3.70 (10a) 0.45 <f3 / f4<0.95 (11a) 0.07 <m4_max / TLt<0.20 (12a) 0.05 <bfw / fw<0.20 (13a)

[0050] Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (1) to (13) as shown in the following conditional expressions (1b) to (13b). 0.080≦β2w×β3w≦0.140 (1b) 0.47 <D23w / TL<0.51 (2b) 74.00 < νdp < 102.00 (3b) 0.620 < ΔθgFp < 0.646 (4b) 1.70 <Ndn<1.90 (5b) 2.26 <Ndn+0.0167×νdn<2.30 (6b) 0.20 <D1 / f1<0.28 (7b) 0.15 < |f2 / f1| < 0.28 (8b) 2.00 < |β2t| < 3.50 (9b) 1.70 < |f3 / f2| < 3.70 (10b) 0.45 <f3 / f4<0.95 (11b) 0.07 <m4_max / TLt<0.20 (12b) 0.05 <bfw / fw<0.20 (13b)

[0051] Next, we will describe the preferred configurations that the zoom lens B0 of each embodiment should satisfy.

[0052] In the zoom lens B0 of each embodiment, it is preferable that the fourth lens group B4 moves in a trajectory that is convex toward the image side when zooming from the wide-angle end to the telephoto end, and then moves in a trajectory that is convex toward the object side. This reduces the width of the optical axis direction in which the fourth lens group B4 moves during zooming, making it possible to achieve high magnification while making the zoom lens smaller in the optical axis direction.

[0053] In the zoom lens B0 of each embodiment, it is preferable that the image-side lens surface of the lens closest to the image in the fourth lens group B4 is convex toward the image side. This reduces the angle of incidence of off-axis rays onto the image plane, thereby suppressing color shading and the like. In addition, reflected light from the cover glass near the image plane is less likely to enter the image plane, thus suppressing ghosting, flare, and the like.

[0054] In the zoom lens B0 of each embodiment, it is preferable that the first lens group B1 has two or more positive lenses arranged adjacent to each other. By sharing the positive refractive power of the first lens group B1 among two or more positive lenses, the curvature of the lens surface of each lens can be reduced, thereby suppressing the occurrence of spherical aberration and coma aberration. Furthermore, in order to further enhance the above effect, it is even more preferable that the first lens group B1 has three or more positive lenses arranged continuously from the object side to the image side.

[0055] In the zoom lens B0 of each embodiment, it is preferable that the second lens group B2 includes three or more negative lenses. In a high-magnification zoom lens, a strong negative refractive force is required on the object side of the zoom lens B0 in order to reduce the amount of movement of each lens group during zooming and shorten the overall length. By sharing this strong negative refractive force among three or more negative lenses, the refractive force per negative lens can be reduced, thereby suppressing distortion and field curvature.

[0056] In the zoom lens B0 of each embodiment, it is preferable that the fourth lens group B4 has a cemented lens consisting of a positive lens and a negative lens. This allows for good correction of aberrations such as field curvature.

[0057] In the zoom lens B0 of each embodiment, vibration isolation can be achieved by moving any entire lens group or a part thereof as a vibration isolation group so as to include a component perpendicular to the optical axis, or by rotating it in a plane direction including the optical axis. In this case, it is preferable to move any entire lens group or a part thereof, which is positioned closer to the image than the first lens group B1, so as to include a component perpendicular to the optical axis, in order to perform vibration isolation. In particular, it is preferable to move any entire third lens group B3 or a part thereof so as to include a component perpendicular to the optical axis, in order to perform vibration isolation.

[0058] Next, the zoom lenses B0 of Examples 1 to 3 will be described in detail. Note that for each example's zoom lens B0, the same configuration as that of Example 1's zoom lens B0 will be omitted from the explanation, and the differences from Example 1 will be described primarily. In each of the following examples, the lenses constituting each lens group are arranged in the order described, from the object side to the image side.

[0059] [Example 1] The zoom lens B0 of Example 1 is composed of a first lens group B1 with positive refractive power, a second lens group B2 with negative refractive power, a third lens group B3 with positive refractive power, and a fourth lens group B4 with positive refractive power, arranged in order from the object side to the image side.

[0060] In the zoom lens B0 of Example 1, the first lens group B1 consists of a cemented lens of negative lens L11 and positive lens L12, and a positive lens L13. The second lens group B2 consists of negative lenses L21, L22, L23, and positive lens L24. The third lens group B3 consists of positive lenses L31, L33, and negative lens L32. The fourth lens group B4 consists of a positive lens L41 and a cemented lens of negative lens L42 and positive lens L43. The aperture diaphragm AP is fixed to the image plane.

[0061] In the zoom lens B0 of Example 1, the positive lens L12 corresponds to the positive lens Gp that satisfies conditions (3) and (4). Also, the negative lens L11 corresponds to the negative lens Gn that satisfies conditions (5) and (6).

[0062] In the zoom lens B0 of Example 1, the fourth lens group B4 moves in a trajectory that is convex toward the image side when zooming from the wide-angle end to the telephoto end, and then moves in a trajectory that is convex toward the object side.

[0063] In the zoom lens B0 of Example 1, the image-side lens surface of the positive lens 43, which is positioned closest to the image in the fourth lens group B4, is convex towards the image side.

[0064] [Example 2] Figure 3 is a cross-sectional view of the zoom lens B0 of Example 2. Figure 4 is a longitudinal aberration diagram of the zoom lens B0 of Example 2 at (A) the wide-angle end, (B) intermediate focal length 1, (C) intermediate focal length 2, (D) intermediate focal length 3, and (E) the telephoto end.

[0065] In the zoom lens B0 of Embodiment 2, the first lens group B1 consists of a cemented lens of negative lens L11 and positive lens L12, and a positive lens L13. The second lens group B2 consists of a negative lens L21, a cemented lens of positive lens L22 and negative lens L23, and a cemented lens of negative lens L24 and positive lens L25. The third lens group B3 consists of a positive lens L31, a positive lens L33, and a negative lens L32. The fourth lens group B4 consists of a negative lens L41, a positive lens L42, and a cemented lens of negative lens L43 and positive lens L44.

[0066] In the zoom lens B0 of Example 2, the second lens group B2 has two cemented lenses. This allows for good correction of fluctuations in axial chromatic aberration during focusing.

[0067] [Example 3] Figure 5 is a cross-sectional view of the zoom lens B0 of Example 3. Figure 6 is a longitudinal aberration diagram of the zoom lens B0 of Example 3 at (A) the wide-angle end, (B) intermediate focal length 1, (C) intermediate focal length 2, (D) intermediate focal length 3, and (E) the telephoto end.

[0068] In the zoom lens B0 of Embodiment 3, the first lens group B1 consists of a cemented lens of negative lens L11 and positive lens L12, positive lens L13, and positive lens L14. The second lens group B2 consists of negative lens L21, negative lens L22, negative lens L23, and positive lens L24. The third lens group B3 consists of positive lens L31, negative lens L32, and a cemented lens of positive lens L33 and negative lens L34. The fourth lens group B4 consists of positive lens L41, and a cemented lens of negative lens L42 and positive lens L43.

[0069] In the zoom lens B0 of Example 3, positive lenses L12, L13, and L14 correspond to positive lenses Gp that satisfy conditions (3) and (4), respectively. Furthermore, negative lens L11 corresponds to negative lens Gn that satisfies conditions (5) and (6). By having multiple positive lenses Gp that satisfy conditions (3) and (4), various aberrations, such as axial chromatic aberration at the telephoto end, can be effectively corrected.

[0070] In the zoom lens B0 of Example 3, the first lens group B1 has three positive lenses L12 to L14 arranged continuously from the object side to the image side. As a result, the positive refractive power of the first lens group B1 can be shared among the three positive lenses, thereby reducing the curvature of the lens surface of each lens and suppressing the occurrence of spherical aberration and coma aberration.

[0071] Next, the numerical examples 1 to 3 corresponding to Examples 1 to 3 are shown. In each numerical example, the surface number i indicates the order of the surfaces when counted from the object side. r is the radius of curvature (mm) of the i-th surface from the object side, d is the lens thickness or air gap on the optical axis between the i-th and (i+1)-th surfaces (mm), and nd is the refractive index of the optical material at the d-line between the i-th and (i+1)-th surfaces. νd is the Abbe number with respect to the d-line of the optical material between the i-th and (i+1)-th surfaces. θgF is the partial dispersion ratio of the optical material between the i-th and (i+1)-th surfaces.

[0072] BF represents the back focus (mm) mentioned above. The overall length of the lens is the distance along the optical axis from the lens surface closest to the object (frontmost) of the zoom lens B0 to the image plane.

[0073] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd θgF 1 53.617 1.33 1.85478 24.8 0.6122 2 33.080 5.98 1.49700 81.5 0.5375 3 ∞ 0.20 4 34.890 3.12 1.72916 54.7 0.5444 5 125.829 (variable) 6 191.705 0.71 1.89190 37.1 0.5780 7 9.108 4.01 8 727.114 0.50 1.89190 37.1 0.5780 9 30.801 1.51 10 -44.041 0.50 1.77250 49.6 0.5520 11 36.399 0.20 12 20.570 2.25 1.95906 17.5 0.6598 13 -1034.721 (variable) 14 (aperture) ∞ (variable) 15* 10.617 3.27 1.58313 59.5 0.5423 16* 149.448 4.32 17 24.442 0.50 1.85025 30.1 0.5979 18 8.661 2.84 19 13.144 2.71 1.49700 81.5 0.5375 20 -30.973 (variable) 21 47.425 1.13 1.95375 32.3 0.5905 22 -61.520 0.85 23 -13.359 0.56 1.67300 38.3 0.5757 24 12.692 3.64 1.59522 67.7 0.5442 25 -12.596 (variable) 26 ∞ 0.85 1.55900 70.0 27 ∞ 1.60 Image plane ∞ Aspherical data Page 15 K = 0.00000e+00 A 4=-3.61292e-05 A 6=-1.00899e-06 A 8= 4.01004e-08 A10=-9.88969e-10 A12= 5.57760e-12 Page 16 K = 0.00000e+00 A 4= 4.61405e-05 A 6=-1.61542e-06 A 8= 8.24948e-08 A10=-2.08853e-09 A12= 1.63703e-11 Various data Zoom ratio 23.60 Wide-angle, Intermediate 1, Intermediate 2, Intermediate 3, Telephoto Focal length 3.80 7.09 15.47 34.44 89.10 F-numbers: 1.85, 2.31, 2.99, 3.67, 4.12 Half-angle 40.13 24.33 11.60 5.35 2.07 Image height 2.88 3.20 3.20 3.20 3.20 Lens length 107.00 107.00 107.00 107.00 107.00 BF 1.60 1.60 1.60 1.60 1.60 d 5 0.94 7.27 16.77 26.26 32.59 d13 33.25 26.92 17.42 7.93 1.60 d14 18.64 11.96 5.37 3.47 3.37 d20 2.38 12.72 16.51 12.70 19.43 d25 9.20 5.53 8.33 14.04 7.41 Zoom lens group data Group starting plane focal length B1 1 49.71 B2 6 -8.72 B3 15 23.10 B4 21 34.76

[0074] [Numerical Example 2] Unit: mm Surface data Face number rd nd νd θgF 1 45.862 1.42 1.85478 24.8 0.6122 2 32.866 6.94 1.43387 95.1 0.5394 3 897.831 0.20 4 40.739 3.16 1.72916 54.1 0.5448 5 135.082 (variable) 6 135.753 0.64 2.05090 26.9 0.6052 7 9.144 4.62 8 -22.848 3.51 1.95906 17.5 0.6598 9 -9.330 0.50 1.80000 29.8 0.6017 10 33.438 0.21 11 30.081 0.50 1.49700 81.5 0.5375 12 18.679 -0.00 13 18.546 2.00 2.05090 26.9 0.6052 14 127.148 (variable) 15 (aperture) ∞ (variable) 16* 9.287 3.84 1.73077 40.5 0.5728 17* 48.519 1.48 18 17.590 0.50 2.05090 26.9 0.6052 19 6.960 0.80 20 8.445 3.69 1.43875 94.7 0.5340 21 -34.759 (variable) 22 -16.758 0.50 1.61800 63.3 0.5426 23 19.724 0.30 24 35.915 0.97 1.56732 42.8 0.5731 25 -223.375 0.20 26 17.629 0.50 2.05090 26.9 0.6052 27 10.314 3.33 1.75500 52.3 0.5474 28 -20.644 (variable) 29 ∞ 0.85 1.55900 70.0 30 ∞ 1.60 Image plane ∞ Aspherical data Page 16 K = 0.00000e+00 A 4=-3.02934e-05 A 6=-3.25290e-07 A 8=-2.41915e-09 A10= 1.94054e-10 A12=-8.49319e-12 Page 17 K = 0.00000e+00 A 4= 6.58964e-05 A 6=-1.02624e-06 A 8= 7.26145e-08 A10=-2.39387e-09 A12= 1.90459e-11 Various data Zoom ratio 23.60 Wide-angle, Intermediate 1, Intermediate 2, Intermediate 3, Telephoto Focal length 3.79 6.64 14.70 34.72 89.57 F-numbers: 1.85, 2.31, 2.99, 3.67, 4.12 Half-angle 40.43 25.86 12.18 5.30 2.05 Image height 2.85 3.20 3.20 3.20 3.20 Lens length 110.60 110.60 110.60 110.60 110.60 BF 1.60 1.60 1.60 1.60 1.60 d 5 0.80 8.28 19.51 30.73 38.21 d14 39.01 31.53 20.30 9.08 1.60 d15 15.22 11.02 5.62 3.61 3.29 d21 2.00 10.33 13.24 6.72 11.89 d28 11.30 7.16 9.65 18.18 13.34 Zoom lens group data Group starting plane focal length B1 1 56.44 B2 6 -9.03 B3 16 20.98 B4 22 41.56

[0075] [Numerical Example 3] Unit: mm Surface data Face number rd nd νd θgF 1 67.466 1.49 1.73800 32.3 0.5900 2 36.501 6.13 1.41390 101.0 0.5340 3 477.072 0.20 4 54.301 2.44 1.49700 81.5 0.5375 5 164.715 0.20 6 35.047 3.16 1.53775 74.7 0.5392 7 197.225 (variable) 8 315.501 0.71 1.90525 35.0 0.5848 9 9.355 4.14 10 -179.931 0.50 1.89190 37.1 0.5780 11 32.678 1.73 12 -34.573 0.50 1.72916 54.7 0.5444 13 54.922 0.20 14 24.723 2.35 1.95906 17.5 0.6598 15 -109.253 (variable) 16 (aperture) ∞ (variable) 17* 9.616 3.67 1.58313 59.5 0.5423 18* 46.642 2.56 19 31.248 0.50 1.74100 52.6 0.5479 20 7.922 1.57 21 10.913 4.40 1.43875 94.7 0.5340 22 -13.340 0.50 2.00100 29.1 0.5997 23 -19.366 (variable) 24 29.509 1.24 2.00100 29.1 0.5997 25 -82.847 0.42 26 -22.786 0.93 1.73800 32.3 0.5900 27 16.015 6.71 1.49700 81.5 0.5375 28 -15.763 (variable) 29 ∞ 0.85 1.55900 70.0 30 ∞ 1.60 Image plane ∞ Aspherical data Page 17 K = 0.00000e+00 A 4=-3.24884e-05 A 6=-1.08981e-06 A 8= 3.39988e-08 A10=-7.84480e-10 A12=-2.65322e-14 Side 18 K = 0.00000e+00 A 4= 2.48025e-05 A 6=-1.46785e-06 A 8= 8.62328e-08 A10=-2.68380e-09 A12= 2.14951e-11 Various data Zoom ratio 31.60 Wide-angle, Intermediate 1, Intermediate 2, Intermediate 3, Telephoto Focal length 3.86 8.43 17.65 41.18 122.13 F-number 1.85 3.45 3.45 5.05 5.05 Half-angle 39.57 21.18 10.22 4.47 1.52 Image height 2.88 3.20 3.20 3.20 3.20 Lens length 121.60 121.60 121.60 121.60 121.60 BF 1.60 1.60 1.60 1.60 1.60 d 7 0.90 4.28 17.79 27.93 34.69 d15 35.35 31.97 18.46 8.32 1.57 d16 23.79 6.92 3.37 3.20 3.25 d23 1.77 22.11 17.19 13.11 23.90 d28 11.12 7.64 16.11 20.36 9.52 Zoom lens group data Group starting plane focal length B1 1 50.93 B2 8 -8.89 B3 17 28.48 B4 24 33.00

[0076] The various values ​​in each numerical example are summarized in Table 1 below.

[0077] [Table 1]

[0078] [Imaging device] Next, with reference to Figure 7, embodiments of a video camera using a zoom lens according to each embodiment disclosed herein as the imaging optical system will be described.

[0079] In Figure 7, 10 represents the video camera body, 11 represents the imaging optical system composed of one of the zoom lenses B0 according to each embodiment of this specification, and 12 represents an image sensor such as a CCD that receives the subject image from the imaging optical system 11. Furthermore, 13 represents a recording means for recording the subject image received by the image sensor 12, and 14 represents a viewfinder for observing the subject image displayed on an unillustrated display element. The display element is composed of a liquid crystal panel or the like, and displays the subject image formed on the image sensor 12.

[0080] By applying the zoom lens B0 disclosed herein to an imaging device such as a video camera, an imaging device with high magnification and high optical performance can be realized.

[0081] Furthermore, by using an electronic image sensor such as a CCD, it becomes possible to electronically correct aberrations, thereby further improving the image quality of the output image.

[0082] 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.

[0083] Furthermore, the disclosures herein include the following configurations.

[0084] (Composition 1) A zoom lens consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged sequentially from the object side to the image side, wherein the distance between adjacent lenses changes during zooming. During zooming from the wide-angle end to the telephoto end, the first lens group remains stationary with respect to the image plane. The fourth lens group has at least three lenses, When the lateral magnification at the wide-angle end of the second lens group is β2w and the lateral magnification at the wide-angle end of the third lens group is β3w, 0.060 ≤ β2w × β3w ≤ 0.150 A zoom lens characterized by satisfying the following conditional equation.

[0085] (Configuration 2) A zoom lens consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged sequentially from the object side to the image side, wherein the distance between adjacent lenses changes during zooming. During zooming from the wide-angle end to the telephoto end, the first lens group remains stationary with respect to the image plane. The fourth lens group is a zoom lens characterized by having a cemented lens consisting of a positive lens and a negative lens.

[0086] (Composition 3) When the total optical length of the zoom lens is TL, and the air distance between the second and third lens groups on the optical axis at the wide-angle end is D23w, 0.40 <D23w / TL<0.55 A zoom lens according to configuration 1 or 2, characterized by satisfying the following conditional expression.

[0087] (Composition 4) The first lens group has a positive lens Gp, When the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, 65.00 < νdp < 105.00 0.613 < ΔθgFp < 0.655 ×νdp A zoom lens according to any one of configurations 1 to 3, characterized in that it satisfies the following conditional expression.

[0088] (Composition 5) The first lens group has a negative lens Gn, When the refractive index of the negative lens material Gn with respect to the d line is Ndn and the Abbe number is νdn, 1.60 <Ndn<2.10 ×νdn<2.46 A zoom lens according to any one of configurations 1 to 4, characterized in that it satisfies the following conditional expression.

[0089] (Composition 6) When the focal length of the first lens group is f1 and the thickness of the first lens group along the optical axis is D1, 0.10 <D1 / f1<0.35 A zoom lens according to any one of configurations 1 to 5, characterized in that it satisfies the following conditional expression.

[0090] (Composition 7) When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, 0.10 < |f2 / f1| < 0.30 A zoom lens according to any one of configurations 1 to 6, characterized by satisfying the following conditional expression.

[0091] (Composition 8) When the lateral magnification at the telephoto end of the second lens group is β2t, 1.50 < |β2t| < 4.00 A zoom lens according to any one of configurations 1 to 7, characterized by satisfying the following conditional expression.

[0092] (Composition 9) When the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 1.50 < |f3 / f2| < 4.00 A zoom lens according to any one of configurations 1 to 8, characterized by satisfying the following conditional expression.

[0093] (Composition 10) When the focal length of the third lens group is f3 and the focal length of the fourth lens group is f4, 0.40 <f3 / f4<1.00 A zoom lens according to any one of configurations 1 to 9, characterized by satisfying the following conditional expression.

[0094] (Composition 11) The zoom lens according to any one of configurations 1 to 10, characterized in that the fourth lens group moves in a trajectory that is convex toward the image side, and then moves in a trajectory that is convex toward the object side, when zooming from the wide-angle end to the telephoto end.

[0095] (Composition 12) When the difference between the position on the optical axis when the fourth lens group is moved furthest toward the object and the position on the optical axis when the fourth lens group is moved furthest toward the image is _max, and the focal length of the fourth lens group is f4, _max / f4<0.25 A zoom lens according to any one of configurations 1 to 11, characterized by satisfying the following conditional expression.

[0096] (Composition 13) The zoom lens according to any one of configurations 1 to 12, characterized in that the image-side lens surface of the lens positioned closest to the image in the fourth lens group is convex toward the image side.

[0097] (Composition 14) When the total focal length of the zoom lens system at the wide-angle end is fw, and the back focus of the zoom lens at the wide-angle end is bfw, 0.01 <bfw / fw<0.25 A zoom lens according to any one of configurations 1 to 13, characterized by satisfying the following conditional expression.

[0098] (Composition 15) The zoom lens according to any one of configurations 1 to 14, characterized in that the first lens group has a cemented lens consisting of a positive lens and a negative lens.

[0099] (Composition 16) The zoom lens according to any one of configurations 1 to 15, characterized in that the fourth lens group has a cemented lens consisting of a positive lens and a negative lens.

[0100] (Composition 17) The zoom lens according to any one of configurations 1 to 16, characterized in that the first lens group has two or more positive lenses arranged adjacent to each other.

[0101] (Composition 18) The zoom lens according to any one of configurations 1 to 17, characterized in that the second lens group has three or more negative lenses.

[0102] (Composition 19) A zoom lens according to any one of configurations 1 to 18, characterized in that the first lens group consists of three lenses, the second lens group consists of four lenses, the third lens group consists of three lenses, and the fourth lens group consists of three lenses.

[0103] (Composition 20) A zoom lens according to any one of configurations 1 to 19, characterized in that the first lens group consists of three lenses, the second lens group consists of five lenses, the third lens group consists of three lenses, and the fourth lens group consists of four lenses.

[0104] (Composition 21) A zoom lens according to any one of configurations 1 to 20, characterized in that the first lens group consists of four lenses, the second lens group consists of four lenses, the third lens group consists of four lenses, and the fourth lens group consists of three lenses.

[0105] (Composition 22) An imaging device characterized by having a zoom lens according to any one of configurations 1 to 21, and an image sensor that receives the image formed by the zoom lens. [Explanation of Symbols]

[0106] B1 First lens group B2 Second lens group B3 Third lens group B4 4th lens group IM image plane AP aperture diaphragm G Glass Block

Claims

1. A zoom lens consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged sequentially from the object side to the image side, wherein the spacing between adjacent lens groups changes during zooming. During zooming from the wide-angle end to the telephoto end, the first lens group remains stationary with respect to the image plane. The fourth lens group has at least three lenses, When the lateral magnification at the wide-angle end of the second lens group is β2w and the lateral magnification at the wide-angle end of the third lens group is β3w, 0.060 ≤ β2w × β3w ≤ 0.150 A zoom lens characterized by satisfying the following conditional equation.

2. When the total optical length of the zoom lens is TL, and the air distance between the second and third lens groups on the optical axis at the wide-angle end is D23w, 0.40<D23w / TL<0.55 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

3. The first lens group has a positive lens Gp, When the Abbe number of the material of the positive lens Gp is ​​νdp, the partial dispersion ratio is θgFp, and the anomalous partial dispersion is ΔθgFp, 65.00<νdp<105.00 0.613<ΔθgFp<0.655 ΔθgFp=θgFp+0.0011×νdp The zoom lens according to claim 1, characterized in that it satisfies the following condition.

4. The first lens group has a negative lens Gn, When the refractive index of the negative lens Gn material with respect to the d line is Ndn and the Abbe number is νdn, 1.60<Ndn<2.10 2.19<Ndn+0.0167×νdn<2.46 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

5. When the focal length of the first lens group is f1 and the thickness of the first lens group along the optical axis is D1, 0.10<D1 / f1<0.35 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

6. When the focal length of the first lens group is f1 and the focal length of the second lens group is f2, 0.10<|f2 / f1|<0.30 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

7. When the lateral magnification at the telephoto end of the second lens group is β2t, 1.50<|β2t|<4.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

8. When the focal length of the second lens group is f2 and the focal length of the third lens group is f3, 1.50<|f3 / f2|<4.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

9. When the focal length of the third lens group is f3 and the focal length of the fourth lens group is f4, 0.40<f3 / f4<1.00 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

10. The zoom lens according to claim 1, characterized in that the fourth lens group moves in a trajectory that is convex toward the image side, and then moves in a trajectory that is convex toward the object side, when zooming from the wide-angle end to the telephoto end.

11. When the difference between the position on the optical axis when the fourth lens group is moved furthest toward the object and the position on the optical axis when the fourth lens group is moved furthest toward the image is m4_max, and the focal length of the fourth lens group is f4, 0.05<m4_max / f4<0.25 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

12. The zoom lens according to claim 1, characterized in that the image-side lens surface of the lens positioned closest to the image in the fourth lens group is convex toward the image side.

13. When the total focal length of the zoom lens at the wide-angle end is fw, and the back focus of the zoom lens at the wide-angle end is bfw, 0.01<bfw / fw<0.25 The zoom lens according to claim 1, characterized in that it satisfies the following condition.

14. The zoom lens according to claim 1, characterized in that the first lens group has a cemented lens consisting of a positive lens and a negative lens.

15. The zoom lens according to claim 1, characterized in that the fourth lens group has a cemented lens consisting of a positive lens and a negative lens.

16. The zoom lens according to claim 1, characterized in that the first lens group has two or more positive lenses arranged adjacent to each other.

17. The zoom lens according to claim 1, characterized in that the second lens group has three or more negative lenses.

18. The zoom lens according to claim 1, characterized in that the first lens group consists of three lenses, the second lens group consists of four lenses, the third lens group consists of three lenses, and the fourth lens group consists of three lenses.

19. The zoom lens according to claim 1, characterized in that the first lens group consists of three lenses, the second lens group consists of five lenses, the third lens group consists of three lenses, and the fourth lens group consists of four lenses.

20. The zoom lens according to claim 1, characterized in that the first lens group consists of four lenses, the second lens group consists of four lenses, the third lens group consists of four lenses, and the fourth lens group consists of three lenses.

21. A zoom lens consisting of a first lens group with positive refractive power, a second lens group with negative refractive power, a third lens group with positive refractive power, and a fourth lens group with positive refractive power, arranged sequentially from the object side to the image side, wherein the spacing between adjacent lens groups changes during zooming. During zooming from the wide-angle end to the telephoto end, the first lens group remains stationary with respect to the image plane. The fourth lens group is a zoom lens characterized by having a cemented lens consisting of a positive lens and a negative lens.

22. An imaging device characterized by having a zoom lens according to any one of claims 1 to 21 and an image sensor that receives light from an image formed by the zoom lens.

Images