Zoom lens and image pickup device

Abstract

The present disclosure relates to a zoom lens and an image pickup apparatus. A zoom lens includes, in order from the object side to the image side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, an intermediate group including two or more lens units, and a rear group including one or more lens units and having a positive refractive power. The first lens unit does not move for zooming. During zooming, the second lens unit moves, and the distance between each adjacent lens unit varies. Among all the lens units of the zoom lens, the second lens unit moves the largest amount of movement during zooming, and has the largest zoom ratio between the wide-angle end and the telephoto end. A predetermined condition is satisfied.

Description

Technical Field

[0001] The embodiments relate to zoom lenses and image pickup devices. Background Technology

[0002] Zoom lenses used in image acquisition devices such as surveillance cameras, digital still cameras, video cameras, and broadcast cameras are expected to have wider angles of view and smaller size. Japanese Patent Application Publications No. 2012-047813 and No. 2014-109761 each disclose a negative lead type zoom lens as a small zoom lens with a wide angle of view.

[0003] It is also required that the zoom lens described above has high optical performance capable of obtaining images with high image quality (such as 8K quality). Summary of the Invention

[0004] This disclosure provides, for example, a zoom lens that offers advantages such as wide viewing angle, small size, and high optical performance.

[0005] According to one aspect of the embodiment, a zoom lens, from the object side to the image side, sequentially includes a first lens unit having negative refractive power, a second lens unit having positive refractive power, an intermediate group comprising two or more lens units, and a rear group comprising one or more lens units and having positive refractive power. The first lens unit does not move for zooming. During zooming, the second lens unit moves, and the distance between adjacent lens units changes. Among all the lens units of the zoom lens, the second lens unit moves the largest amount of movement during zooming and has the largest zoom ratio between the wide-angle and telephoto ends. A predetermined condition is met.

[0006] An image acquisition device including a zoom lens also constitutes another aspect of the embodiment.

[0007] Other features of this disclosure will become clear from the following description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0008] Figure 1 It is a cross-sectional view of the zoom lens based on Example 1.

[0009] Figures 2A to 2C It is based on the aberration diagrams of the zoom lens in Example 1 at the wide-angle end, intermediate zoom position, and telephoto end.

[0010] Figure 3 It is a cross-sectional view of the zoom lens based on Example 2.

[0011] Figures 4A to 4C This is an aberration diagram of the zoom lens in Example 2 at the wide-angle end, intermediate zoom position, and telephoto end.

[0012] Figure 5 It is a cross-sectional view of the zoom lens based on Example 3.

[0013] Figures 6A to 6C It is based on the aberration diagrams of the zoom lens in Example 3 at the wide-angle end, intermediate zoom position, and telephoto end.

[0014] Figure 7 It is a cross-sectional view of the zoom lens based on Example 4.

[0015] Figures 8A to 8C It is based on the aberration diagrams of the zoom lens in Example 4 at the wide-angle end, intermediate zoom position, and telephoto end.

[0016] Figure 9 It is a cross-sectional view of the zoom lens based on Example 5.

[0017] Figures 10A to 10C It is based on the aberration diagrams of the zoom lens in Example 5 at the wide-angle end, intermediate zoom position, and telephoto end.

[0018] Figure 11 It is a cross-sectional view of the zoom lens based on Example 6.

[0019] Figures 12A to 12C It is based on the aberration diagrams of the zoom lens at the wide-angle end, the intermediate zoom position, and the telephoto end in Example 6.

[0020] Figure 13 This is an illustration of an image pickup device including a zoom lens according to any one of Examples 1 to 6. Detailed Implementation

[0021] A description of embodiments of the present disclosure will now be given with reference to the accompanying drawings.

[0022] First, before specifically describing Examples 1 through 6, the commonalities of the examples will be described. The zoom lenses according to the various examples are used as image-collecting lenses for various image-collecting devices such as digital still cameras, video cameras, broadcast cameras, surveillance cameras, and silver halide film cameras. The image-collecting lenses may be interchangeable with respect to the image-collecting device or may be provided integrally with the image-collecting device. The zoom lenses according to the various examples can also be used as projection optics systems for image projection devices (projectors).

[0023] The zoom lenses in the various examples are negative-guided zoom lenses, comprising, from the object side to the image side, a first lens unit with negative refractive power, a second lens unit with positive refractive power, an intermediate group comprising two or more lens units, and a rear group comprising one or more lens units with positive refractive power. Because the negative first lens unit and the positive second lens unit are arranged on the object side, the zoom lenses in the various examples are advantageous for a wide angle of view.

[0024] A "lens unit" is one or more lenses that move as a whole during zoom (magnification change) between the wide-angle and telephoto ends. That is, the distances between adjacent lens units change during zoom. A lens unit may include an aperture stop. The wide-angle and telephoto ends represent zoom states with the maximum and minimum angles of view (shortest focal length), respectively, where the individual lens units moving during zoom are located at one end and the other end of a mechanically or controllably movable range along the optical axis.

[0025] In the zoom lenses according to the various examples, during zooming, the first lens unit does not move (is fixed), the second lens unit and at least one intermediate lens unit move, and the distances between adjacent lens units change. Since zooming is performed by the second lens unit and the lens unit on the image side of the second lens unit, changes in the image plane caused by zooming and various aberration fluctuations during zooming can be corrected.

[0026] In all examples, zooming is primarily performed by the second lens unit. That is, when assuming that the magnification change rate (zoom ratio) of the lens unit is the absolute value obtained by dividing the lateral magnification of the lens unit at the telephoto end by the lateral magnification of the lens unit at the wide-angle end, the magnification change rate of the second lens unit is the largest among all lens units.

[0027] During zooming, at least one intermediate lens unit (hereinafter also referred to as the "focusing lens unit") moves primarily to correct for changes in the image plane. The focusing lens unit also moves during focusing on the object at various distances from infinity to the closest distance. Intermediate lens units, in addition to the focusing lens unit, include lens units that move during zooming to more accurately correct for aberration fluctuations.

[0028] The rear group with positive refractive power corrects the lateral chromatic aberration that occurs in the first lens unit where the off-axis beam is at a high height, and reduces the angle at which the ray enters the image plane.

[0029] In each example, during zooming between the wide-angle and telephoto ends, the second lens unit moves the most among the individual lens units that move during zooming. Here, the "movement" of the second lens unit is the absolute value of the difference between the positions of the lens surface at the wide-angle and telephoto ends within the second lens unit.

[0030] In each example, the second lens unit includes at least one positive lens and at least one negative lens. In the case where the second lens unit includes a cemented lens in which the positive and negative lenses are cemented together, the positive and negative lenses are assumed to be uncemented single lenses. The zoom lenses according to each example satisfy the following inequalities (1) and (2), where f2p represents the shortest focal length among the focal lengths of the positive lenses included in the second lens unit, f2n represents the shortest focal length among the focal lengths of the negative lenses included in the second lens unit, and f2 represents the focal length of the second lens unit.

[0031] 0.65 ≤ f2p / f2 ≤ 2.00 (1)

[0032] -0.85 ≤ f2n / f2 < 0 (2)

[0033] If f2p / f2 is less than the lower limit of inequality (1), then the refractive power of the second lens unit is too small, causing the amount of movement of the second lens unit during zooming to increase, making it difficult to reduce the size of the zoom lens. If f2p / f2 is greater than the upper limit of inequality (1), then the refractive power of the second lens unit is too large to properly correct aberrations.

[0034] The upper limit of inequality (2) is determined by the fact that the refractive power of the second lens unit is positive and f2n is a negative focal length. If f2n / f2 is less than the lower limit of inequality (2), then the optical power of the negative lens included in the second lens unit is too small to correct various aberrations, especially spherical aberration and coma. By reducing the aberrations of the second lens unit, which serves as the main zoom unit, aberration fluctuations during zooming can be further reduced.

[0035] With the above configuration and satisfying the conditions of inequalities (1) and (2), zoom lenses become advantageous for wide viewing angles, small size and support for high-resolution optical performance.

[0036] The numerical ranges of inequalities (1) and (2) can be set as follows.

[0037] 0.68≤f2p / f2≤1.50(1a)

[0038] -0.80≤f2n / f2<0(2a)

[0039] The numerical ranges of inequalities (1) and (2) can be set as follows.

[0040] 0.72≤f2p / f2≤0.90(1b)

[0041] -0.76≤f2n / f2<0(2b)

[0042] According to the various examples, the zoom lens can satisfy at least one of the following inequalities (3) to (9).

[0043] The focal lengths f2p and f2n can satisfy the following inequality (3).

[0044] -2.00 ≤ f2p / f2n ≤ -0.95 (3)

[0045] If f2p / f2n does not satisfy the numerical range of inequality (3), then various aberrations caused by the second lens unit, especially spherical aberration and coma, may worsen.

[0046] In addition, the following inequality (4) can be satisfied, where m2 represents the amount of movement of the second lens unit between the wide-angle end and the telephoto end, and m3 represents the amount of movement of the third lens unit between the wide-angle end and the telephoto end. The third lens unit is included in the intermediate group and is deployed at a position adjacent to the second lens unit on the image side.

[0047] 1.0 < m² / m³ ≤ 2.5 (4)

[0048] The aperture stop can be set in the second lens unit or the third lens unit, while satisfying the condition of inequality (4). In this case, the height change of the beam in the second lens unit during zooming can be reduced, making it easier to reduce aberration fluctuations during zooming.

[0049] As a negative-guided zoom lens suitable for widening the field of view, the zoom lens according to each example can satisfy the following inequality (5), where f1 represents the focal length of the first lens unit.

[0050] -0.85 ≤ f1 / f2 ≤ -0.55 (5)

[0051] If f1 / f2 is less than the lower limit of inequality (5), then the negative refractive power of the first lens unit may be too weak to widen the viewing angle well. If f1 / f2 is greater than the upper limit of inequality (5), then the negative refractive power of the first lens unit may be too strong to correct on-axis chromatic aberration well.

[0052] To correct on-axis chromatic aberration, the first lens unit may include at least one positive lens and may satisfy the following inequalities (6) and (7), where vd1p represents the Abbe number of at least one positive lens relative to the d-line, and θgF1p represents the partial dispersion ratio of the positive lens relative to the g-line and F-line.

[0053] νd1p ≤ 40 (6)

[0054] θgF1p+0.00162×νd1p-0.64146 ≤ 0.006 (7)

[0055] Since the first lens unit has negative refractive power, at least one positive lens in the first lens unit can have high dispersion that satisfies inequality (6) in order to correct on-axis chromatic aberration. Furthermore, when considering the secondary spectrum, inequality (7) can be satisfied. The Abbe number νd1p is expressed by the following formula, where nd, nF, and nC represent the refractive indices of the positive lens (the material of the positive lens) relative to the d-line (wavelength 587.6 nm), F-line (wavelength 486.1 nm), and C-line (wavelength 656.3 nm), respectively.

[0056] νd1p=(nd-1) / (nF-nC)

[0057] The partial dispersion ratio θgF1p is expressed by the following formula, where ng, nF, and nC represent the refractive indices of the positive lens relative to the g line (wavelength 435.8 nm), the F line, and the C line, respectively.

[0058] θgF1p=(ng-nF) / (nF-nC)

[0059] The positive lens in the first lens unit can be cemented to the negative lens to correct on-axis chromatic aberration.

[0060] The following inequality (8) can be satisfied, where Ndp represents the maximum refractive index of at least one positive lens with positive refractive power in the latter group.

[0061] 1.85 ≤ Ndp (8)

[0062] If Ndp is below the lower limit of the numerical range of inequality (8), then the curvature of each surface of the positive lens is too large, resulting in an increase in various aberrations.

[0063] The Abbe number νdp of the positive lens with the largest refractive index in the rear group relative to the d line can satisfy the following inequality (9).

[0064] νdp ≤ 25 (9)

[0065] The correction effect can be improved by satisfying the condition of inequality (9) in the latter group of the correction of lateral color difference.

[0066] Furthermore, the intermediate group may include at least one lens unit with negative refractive power. By using this negative lens unit as the focusing lens unit, the amount of movement of the focusing lens unit during focusing can be reduced, and the size of the zoom lens can be further reduced.

[0067] The numerical ranges of inequalities (3) to (9) can be set as follows.

[0068] -1.90≤f2p / f2n≤-0.97(3a)

[0069] 1.0 <m2 / m3≤2.2(4a)

[0070] -0.80≤f1 / f2≤-0.56(5a)

[0071] νd1p≤39(6a)

[0072] θgF1p+0.00162×νd1p-0.64146≤0.004(7a)

[0073] 1.90≤Ndp(8a)

[0074] νdp≤23(9a)

[0075] The numerical ranges of inequalities (3) to (9) can be set as follows.

[0076] -1.80≤f2p / f2n≤-0.98(3b)

[0077] 1.0 <m2 / m3≤1.9(4b)

[0078] -0.76≤f1 / f2≤-0.57(5b)

[0079] νd1p≤38(6b)

[0080] θgF1p+0.00162×νd1p-0.64146≤0.002(7b)

[0081] 1.95≤Ndp(8b)

[0082] νdp≤21(9b)

[0083] The following are descriptions of Examples 1 through 6. Figure 1 , Figure 3 , Figure 5 , Figure 7 , Figure 9 and Figure 11Examples 1 through 6 illustrate the configuration of zoom lenses at the wide-angle end. Each of the zoom lenses according to Examples 1 through 4, from the object side to the image side, sequentially includes a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, an intermediate group including a third lens unit B3 with positive refractive power and a fourth lens unit B4 with negative refractive power, and a fifth lens unit B5 with positive refractive power as the rear group. The zoom lens according to Example 5 includes a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, an intermediate group including a third lens unit B3 with positive refractive power, a fourth lens unit B4 with positive refractive power and a fifth lens unit B5 with negative refractive power, and a sixth lens unit B6 with positive refractive power as the rear group. The zoom lens according to Example 6 includes a first lens unit B1 with negative refractive power, a second lens unit B2 with positive refractive power, an intermediate group including a third lens unit B3 with negative refractive power, a fourth lens unit B4 with positive refractive power and a fifth lens unit B5 with negative refractive power, and a sixth lens unit B6 with positive refractive power as the rear group.

[0084] In the various figures, AP represents an aperture stop. In each of Examples 1 to 5, the second lens unit B2 includes the aperture stop AP, and in Example 6, the third lens unit B3 includes the aperture stop AP.

[0085] DP stands for a glass block, such as a cover glass and a low-pass filter, set in an image sensor, such as a CCD sensor or a CMOS sensor. IM stands for image plane, and the image pickup plane of an image sensor is deployed on the image plane IM. In silver halide film cameras, the film surface (photosensitive surface) of the silver halide film is deployed on the image plane IM.

[0086] In each example, the first lens unit B1 includes a positive lens LP1. The second lens unit B2 includes a positive lens LP2 with the shortest focal length among the positive lenses included in the second lens unit B2 and a negative lens LN2 with the shortest focal length among the negative lenses included in the second lens unit B2. The rear group includes a positive lens LP3 with the maximum refractive power among the positive lenses included in the rear group.

[0087] In the various accompanying figures, arrows are shown below each lens unit that moves during zooming, indicating the trajectory of that lens unit during zooming from the wide-angle end to the telephoto end. In each of Examples 1 to 4, the second lens unit B2, the third lens unit B3, and the fourth lens unit B4 move toward the object side during zooming from the wide-angle end to the telephoto end. In each of Examples 5 and 6, the second lens unit B2, the third lens unit B3, the fourth lens unit B4, and the fifth lens unit B5 move toward the object side during zooming from the wide-angle end to the telephoto end.

[0088] Each of the fourth lens unit B4 in Examples 1 to 4 and the fifth lens unit B5 in Examples 5 and 6 moves to compensate for the change in the image plane during zooming. Solid and dashed lines are illustrated below each of these lens units in the accompanying drawings, indicating the movement trajectory of the lens unit during zooming when focusing on an object at infinity and a near object, respectively. The fourth lens unit B4 in Examples 1 to 4 and the fifth lens unit B5 in Examples 5 and 6 move as a focusing lens unit during focusing. Specifically, each of these lens units moves towards the image side during focusing from an object at infinity to a near object.

[0089] Tables 1 through 6 provide numerical examples corresponding to Examples 1 through 6, respectively. In each numerical example, f represents the focal length (mm), Fno represents the F-number, and ω represents the half angle of view (°).

[0090] Surface number i indicates the order of the surfaces counting from the object side. r represents the radius of curvature (mm) of the i-th surface from the object side, d represents the lens thickness or air distance (mm) between the i-th and (i+1)-th surfaces, and n represents the refractive index of the optical material between the i-th and (i+1)-th surfaces relative to the d-line. ν represents the Abbe number of the optical material between the i-th and (i+1)-th surfaces relative to the d-line.

[0091] An asterisk (*) next to a surface number indicates that the surface has an aspherical shape. The shape of an aspherical surface is expressed by the following equation, where z represents the displacement (sag) from the surface vertex in the direction of the optical axis, y represents the height from the optical axis in the direction perpendicular to the optical axis, assuming the direction of light propagation is positive, r represents the paraxial radius of curvature, k represents the conic constant, and Bj (j = 1 to 16) represents the aspherical coefficient.

[0092]

[0093] In the various tables, "E±x" represents "10". ±x All unspecified coefficients are 0.

[0094] Table 7 summarizes the values ​​corresponding to the above inequalities (1) to (9) in numerical examples 1 to 6.

[0095] Figure 2A , Figure 4A , Figure 6A , Figure 8A , Figure 10A and Figure 12AExamples of longitudinal aberrations (spherical aberration, astigmatism, distortion, and chromatic aberration) at the wide-angle end are shown in numerical examples 1 through 6. Figure 2B , Figure 4B , Figure 6B , Figure 8B , Figure 10B and Figure 12B The longitudinal aberrations at intermediate zoom positions are illustrated according to numerical examples 1 to 6, and Figure 2C , Figure 4C , Figure 6C , Figure 8C , Figure 10C and Figure 12C The longitudinal aberrations at the telephoto end are illustrated according to numerical examples 1 through 6. In each spherical aberration diagram, Fno represents the F-number, the solid line represents the spherical aberration relative to the d-line, the double-dotted line represents the spherical aberration relative to the C-line, and the single-dotted line represents the spherical aberration relative to the g-line. The separation at the bottom indicates the axial chromatic aberration. In each astigmatism diagram, the solid line S represents the sagittal image plane, and the dashed line M represents the meridional image plane. The various distortion diagrams illustrate the distortion relative to the d-line. In each chromatic aberration diagram, the double-dotted line represents the lateral chromatic aberration relative to the C-line, and the single-dotted line represents the lateral chromatic aberration relative to the g-line. ω represents the half angle of view (°).

[0096] The zoom lens configurations in Examples 1 to 6 are merely examples, and the number of lenses in each lens unit, the number of aspherical lenses, or the number of lens units included in the intermediate group can be varied. Furthermore, each of the zoom lenses according to Examples 1 to 6 is a zoom lens having a lens unit arrangement from the object side of negative, positive, positive, negative, and positive; a lens unit arrangement of negative, positive, positive, positive, negative, and positive; or a lens unit arrangement of negative, positive, negative, positive, negative, and positive, but other lens unit arrangements can be used.

[0097] Table 1 (Numerical Example 1)

[0098]

[0099]

[0100] Table 2 (Numerical Example 2)

[0101]

[0102]

[0103] Table 3 (Numerical Example 3)

[0104]

[0105]

[0106] Table 4 (Numerical Example 4)

[0107]

[0108]

[0109] Table 5 (Numerical Example 5)

[0110]

[0111]

[0112] Table 6 (Numerical Examples)

[0113]

[0114]

[0115] Table 7

[0116]

[0117] Image pickup device

[0118] Figure 13 An example is illustrated using a zoom lens according to any one of Examples 1 to 6 as an image pickup device (surveillance camera) in an imaging optical system. Figure 13 In the figures, reference numeral 16 indicates an imaging optical system including a zoom lens according to any one of Examples 1 to 6. Reference numeral 11 indicates a camera body. Reference numeral 12 indicates an image sensor, such as a CCD sensor and a CMOS sensor, for capturing (photoelectric conversion) an image of an object formed by the imaging optical system 16. Reference numeral 13 indicates a recording medium for recording image information generated based on the signal output from the image sensor 12. Reference numeral 14 indicates a cable serving as a transmission unit for transmitting image information to an external device.

[0119] By applying a zoom lens according to any one of Examples 1 to 6 to an image acquisition device such as a surveillance camera, a small and wide-angle image acquisition device with good optical performance capable of supporting high resolution can be realized.

[0120] The image acquisition device using any of the zoom lenses according to Examples 1 to 6 is not limited to a surveillance camera, and the zoom lens according to any of Examples 1 to 6 can also be used in another image acquisition device such as a video camera and a digital still camera. In addition to the zoom lens, the image acquisition device may also include image processing circuitry that electrically corrects aberrations.

[0121] While the invention has been described with reference to exemplary embodiments, it should be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the appended claims should be given the broadest interpretation to cover all such modifications and equivalent structures and functions.

Claims

1. A zoom lens, wherein the lens unit in the zoom lens is composed of the following components from the object side to the image side: A first lens unit with negative refractive power; A second lens unit with positive refractive power; The intermediate group, from the object side to the image side, is composed of a third lens unit with positive refractive power and a fourth lens unit with negative refractive power, or from the object side to the image side, it is composed of a third lens unit with positive refractive power, a fourth lens unit with positive refractive power, and a fifth lens unit with negative refractive power, or from the object side to the image side, it is composed of a third lens unit with negative refractive power, a fourth lens unit with positive refractive power, and a fifth lens unit with negative refractive power; and The rear group consists of a single lens unit and has positive refractive power. The first lens unit remains stationary for zooming. During zooming, the second lens unit moves and the distance between adjacent lens units changes. Among all the lens units of the zoom lens, the second lens unit moves the most during zooming and has the largest zoom ratio between the wide-angle and telephoto ends. The following inequalities are satisfied: 0.65 ≤ f2p / f2 ≤ 2.00 -0.85 ≤ f2n / f2 < 0 Where f2p represents the shortest focal length among at least one positive lens in the second lens unit, f2n represents the shortest focal length among at least one negative lens in the second lens unit, and f2 represents the focal length of the second lens unit.

2. The zoom lens according to claim 1, wherein the following inequality is satisfied: -2.00 ≤ f2p / f2n ≤ -0.

95.

3. The zoom lens according to claim 1, wherein the intermediate group includes a third lens unit adjacent to the second lens unit, and The following inequalities are satisfied: 1.0 < m² / m³ ≤ 2.5 Where m2 represents the amount of movement of the second lens unit between the wide-angle end and the telephoto end, and m3 represents the amount of movement of the third lens unit between the wide-angle end and the telephoto end.

4. The zoom lens according to claim 3, wherein the second lens unit or the third lens unit includes an aperture stop.

5. The zoom lens according to claim 1, wherein the following inequality is satisfied: -0.85 ≤ f1 / f2 ≤ -0.55 Where f1 represents the focal length of the first lens unit.

6. The zoom lens according to claim 1, wherein the first lens unit comprises a positive lens satisfying the following inequality: νd1p ≤ 40 θgF1p+0.00162×νd1p-0.64146 ≤ 0.006 Where νd1p represents the Abbe number of the positive lens relative to the d line, and θgF1p represents the partial dispersion ratio of the positive lens relative to the g and F lines.

7. The zoom lens of claim 6, wherein the positive lens in the first lens unit is cemented to the negative lens.

8. The zoom lens according to claim 1, wherein the following inequality is satisfied: 1.85 ≤ Ndp Where Ndp represents the refractive index of at least one of the positive lenses in the latter group that has the maximum refractive index relative to the d-line.

9. The zoom lens according to claim 8, wherein the following inequality is satisfied: νdp ≤ 25 Where νdp represents the Abbe number relative to the d-line of the positive lens with the largest refractive index included in the latter group.

10. The zoom lens of claim 1, wherein the intermediate group comprises a lens unit that is movable to focus and has negative refractive power.

11. An image acquisition device, comprising: The zoom lens according to any one of claims 1 to 10; as well as An image sensor is configured to capture an image formed by a zoom lens.

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