Zoom lens and imaging device provided with zoom lens

Abstract

A zoom lens (1) is provided with a first optical element group (G1), a second optical element group (G2), and a third optical element group (G3) arranged in this order from the object side to the image side, the first optical element group (G1) having a lens group (10) and an optical element (15) that bends an optical axis (C), the second optical element group (G2) having a negative refractive power, and the third optical element group (G3) having a positive refractive power. The lens group (10) has a positive refractive power and is disposed closer to the object side than the optical element (15), and the second optical element group (G2) and the third optical element group (G3) are disposed so as to be movable along the optical axis (C), respectively, so that the zoom lens (1) changes magnification from the wide-angle end to the telephoto end.

Description

Zoom lens and imaging device having the same Technical Field

[0001] The present invention relates to a zoom lens including a plurality of optical element groups, and an imaging device including the zoom lens. Background Art

[0002] Conventionally, various zoom lenses including optical elements that bend the optical axis are known.

[0003] For example, the zoom lens described in Japanese Patent Application Laid-Open No. 2007-34064 includes a first lens group, a second lens group, and a third lens group arranged in order from the object side to the image side. The first lens group includes a first lens having negative refractive power and a prism that bends the optical axis. The second lens group includes two lenses, and the third lens group includes three lenses. In the first lens group of this zoom lens, the first lens having negative refractive power is positioned on the object side of the prism.

[0004] This zoom lens can reduce its size in the incident direction of light from an object (ie, reduce its thickness), but its F-number at the wide-angle end is approximately F28, which cannot be considered as a sufficient increase in aperture.

[0005] Furthermore, in the zoom lens described in WO2021 / 085154A1, a prism is positioned on the object side of the lens group, meaning that the prism is positioned closest to the object. While this zoom lens can reduce the size of the incident light beam, it cannot maintain a sufficient size within the maximum diameter of the first lens group, calculated by dividing the focal length (EFL) by the F-number, making it difficult to achieve a larger aperture.

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-34064

[0009] Patent Document 2: International Publication No. WO2021 / 085154A1

[0010] Summary of the Invention

[0011] Problems to be solved by the invention

[0012] Therefore, an object of the present invention is to provide a zoom lens that can be mounted on a thin imaging device and that has a large aperture and is capable of telephoto photography, and an imaging device including the zoom lens.

[0013] Solutions for solving problems

[0014] The zoom lens of the present invention comprises a first optical element group, a second optical element group, and a third optical element group arranged in order from the object side to the image side.

[0015] The first optical element group includes a lens group including at least one lens and an optical element that bends the optical axis.

[0016] The second optical element group includes at least one lens and has negative refractive power,

[0017] The third optical element group includes at least one lens and has positive refractive power,

[0018] The lens group has positive refractive power and is arranged closer to the object side than the optical element.

[0019] The second optical element group and the third optical element group are configured to be movable along the optical axis, respectively, so that the zoom lens changes magnification between a wide-angle end and a telephoto end.

[0020] In the zoom lens,

[0021] When the focal length of the first lens group is defined as f1 and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the following can be satisfied: 0.5≤f1 / ft≤6.

[0022] In addition, in the zoom lens,

[0023] When the distance on the optical axis from the surface of the first optical element group closest to the object side to the surface of the second optical element group closest to the object side is defined as D12, and the distance on the optical axis from the surface of the first optical element group closest to the object side to the image plane is defined as TTL, it can be satisfied that: 0.2≤D12 / TTL≤0.7.

[0024] In addition, in the zoom lens,

[0025] When the focal length of the third optical element group is defined as f3, the focal length of the entire optical system when focusing at infinity at the wide-angle end is defined as fw, and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, it can satisfy: 0.2≤f3 / √(fw×ft)≤1.1.

[0026] In addition, in the zoom lens,

[0027] When the focal length of the second optical element group is defined as f2, and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the following can be satisfied: 0.2≤|f2 / ft|≤1.0.

[0028] In addition, in the zoom lens,

[0029] Furthermore, a maximum effective diameter h23 of a light transmission range in the second optical element group and the third optical element group may be less than or equal to 9 mm.

[0030] In addition, in the zoom lens,

[0031] A distance on the optical axis from a surface of the first optical element group closest to the object to an image plane may be 40 mm or less.

[0032] In addition, the zoom lens may include an aperture for adjusting the amount of light passing therethrough.

[0033] The aperture is arranged between the image-side surface of the optical element of the first optical element group and the object-side surface of the third optical element group.

[0034] In addition, in the zoom lens,

[0035] At least one surface of at least one lens in the third optical element group may be aspherical.

[0036] In addition, in the zoom lens,

[0037] It is also possible that at least one lens in the third optical element group is made of plastic.

[0038] In addition, the imaging device of the present invention comprises:

[0039] Any of the above zoom lenses; and

[0040] The imaging element is arranged at the image plane position of the zoom lens and converts the formed optical image into an electrical signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 is a schematic diagram showing the configuration of an imaging device according to this embodiment.

[0042] FIG. 2 is a diagram showing the lens configuration of a zoom lens included in the imaging device.

[0043] FIG3 is a lens configuration diagram of the zoom lens according to Example 1, showing the lens configuration at the wide-angle end and the telephoto end.

[0044] FIG. 4 is a diagram showing longitudinal aberrations when the zoom lens is focused at infinity at the wide-angle end.

[0045] FIG. 5 is a diagram showing longitudinal aberrations of the zoom lens when focusing at infinity at the telephoto end.

[0046] FIG6 is a lens configuration diagram of the zoom lens according to Example 2, showing the lens configuration at the wide-angle end and the telephoto end.

[0047] FIG. 7 is a diagram showing longitudinal aberrations when the zoom lens is focused at infinity at the wide-angle end.

[0048] FIG. 8 is a diagram showing longitudinal aberrations of the zoom lens when focusing at infinity at the telephoto end. DETAILED DESCRIPTION

[0049] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0050] The imaging device of this embodiment is a device such as a digital camera, a smartphone, or a tablet device that can capture an image of a target (object). The imaging device described below is, for example, a smartphone.

[0051] As shown in Figure 1, a camera 100 includes a zoom lens (optical system) 1, at least a portion of which is internally mounted within a camera body 101; and an image sensor (imaging element) 5, which is positioned at the imaging position (image plane position) of the zoom lens 1. Specifically, the camera 100 includes the camera body 101, the zoom lens (optical system) 1, the image sensor 5, and a display unit 102, such as a liquid crystal display, that displays captured image data output from the image sensor 5. Furthermore, the camera 100 includes a control unit (computing unit) 103 that controls various components and performs computational processing on signals from the image sensor 5 and other components; and a power supply 104.

[0052] The image sensor 5, located on the imaging plane of the zoom lens 1, converts the optical image formed by the zoom lens 1 into an electrical signal (image data). In this embodiment, the image sensor 5 is a CMOS image sensor. Furthermore, because the imaging plane of the zoom lens 1 and the light-receiving surface of the image sensor 5 are located at the same position, the image sensor (more specifically, the light-receiving surface of the image sensor) will sometimes be referred to as the image plane 5 below.

[0053] As also shown in Figure 2, the zoom lens 1 includes at least a first optical element group G1, a second optical element group G2, and a third optical element group G3, arranged in order from the object side to the image side along the optical axis C. Each of these optical element groups G1, G2, and G3 includes at least one optical element, such as a lens. The zoom lens 1 of this embodiment includes the first optical element group G1, the second optical element group G2, the third optical element group G3, and a filter (an IR filter in this embodiment) 6, arranged in order from the object side to the image side along the optical axis C. The zoom lens 1 also includes an aperture (aperture device) 7 positioned at a predetermined position on the optical axis C and a cover glass 8 positioned on the object side of the first optical element group G1. The aperture 7 of this embodiment is positioned on the object side of the third optical element group G3 and moves along the optical axis C together with the third optical element group G3 when changing magnification or focusing.

[0054] The second optical element group G2 and the third optical element group G3 are configured to be movable along the optical axis C, respectively, so that the zoom lens 1 can change the magnification between the wide-angle end and the telephoto end (see FIG. 3 ).

[0055] The first optical element group G1 includes: a lens group 10 including at least one lens, and a reflective optical element (optical element) 15 that bends the optical axis C. The lens group 10 has positive refractive power (optical focal length) and is arranged on the object side closer to the reflective optical element 15. In the first optical element group G1 of this embodiment, the lens group 10 includes a lens (first lens) 11, and the reflective optical element 15 is a prism having a reflective surface 15a that bends the incident light (optical axis C) by reflecting the incident light, and is made of glass. It should be noted that in Figure 2, the reflective optical element (prism) 15 is represented by a quadrilateral. The same is true for Figures 3 and 6.

[0056] The second optical element group G2 includes at least one lens with negative refractive power. The second optical element group G2 of this embodiment includes two lenses (the second lens 21 and the third lens 22). The third optical element group G3 includes at least one lens with positive refractive power. The third optical element group G3 of this embodiment includes five lenses (the fourth lens 31 to the eighth lens 35).

[0057] The zoom lens 1 also includes a lens barrel 16 that holds the optical element groups G1 to G3. The lens barrel 16 of this embodiment includes a curved portion 16A that allows light (light from an object) to enter and bends the optical axis C of the incident light, and a main body 16B that is incorporated into the imaging device body 101. The curved portion 16A is where the first optical element group G1 is located, and the main body 16B is where the second optical element group G2 and the third optical element group G3 are located.

[0058] It should be noted that in the zoom lens 1 of this embodiment, the lens group 10, the second optical element group G2, and the third optical element group G3 are names for convenience, and also include cases where they are composed of only one optical element (lens, etc.). In other words, the lens group 10, the second optical element group G2, and the third optical element group G3 each include at least one lens, etc. (optical element).

[0059] Here, when the focal length of the first optical element group is defined as f1 and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the zoom lens 1 can satisfy the following conditional expression (1). 0.5≤f1 / ft≤6···(1)

[0060] It should be noted that the focal length of the entire optical system when focusing at infinity at the telephoto end refers to the focal length of the entire optical system when zoomed to the telephoto end and focused at infinity. Similarly, the focal length of the entire optical system when focusing at infinity at the wide-angle end refers to the focal length of the entire optical system when zoomed to the wide-angle end and focused at infinity.

[0061] When the value of f1 / ft is less than the lower limit (0.5), the positive refractive power of the first optical element group G1 is too strong, and thus the distance between the first lens 11 and the second optical element group G becomes small. As a result, it is impossible to ensure space for arranging the reflective optical element 15 for bending the optical axis C. On the other hand, when the value of f1 / ft is greater than the upper limit (6), the positive refractive power of the first optical element group G1 is too weak, and thus the dimension (total length) of the optical system (zoom lens) 1 along the optical axis C at the telephoto end becomes large, making it difficult to reduce the size of the zoom lens 1. That is, by satisfying the above-mentioned conditional expression (1) in the zoom lens 1, a balance can be achieved between ensuring space for arranging the reflective optical element 15 and reducing the size of the zoom lens 1 along the optical axis C.

[0062] It should be noted that, from the perspective of ensuring the arrangement space of the reflective optical element 15 and reducing the size of the zoom lens 1 along the optical axis C, it is more preferable that the zoom lens 1 satisfies the following conditional expression (1a). 1≤f1 / ft≤5···(1a)

[0063] Furthermore, in the zoom lens 1, when the distance on the optical axis C from the surface closest to the object side of the first optical element group G1 (the object-side surface of the first lens 11) 11a to the surface closest to the object side of the second optical element group G2 (the object-side surface of the second lens 21) 21a is defined as D12, and the distance on the optical axis C from the surface closest to the object side of the first optical element group G1 11a to the image plane 5 is defined as TTL, the zoom lens 1 can satisfy the following conditional expression (2). 0.2 ≤ D12 / TTL ≤ 0.7 (2)

[0064] When the value of D12 / TTL is less than the lower limit (0.2), the distance between the first lens 11 and the second optical element group G2 in the direction of the optical axis C becomes too small, and it is impossible to ensure space for arranging the reflective optical element 15. On the other hand, when the value of D12 / TTL is greater than the upper limit (0.7), the distance between the first lens 11 and the second optical element group G2 in the direction of the optical axis C becomes too large, and it is impossible to achieve a compact size of the zoom lens 1 along the optical axis C. In other words, by satisfying the above-mentioned conditional expression (2) in the zoom lens 1, a balance can be achieved between ensuring space for arranging the reflective optical element 15 and achieving a compact size of the zoom lens 1 along the optical axis C.

[0065] It should be noted that, from the perspective of ensuring the arrangement space for the reflective optical element 15 and reducing the size of the zoom lens 1 along the optical axis C, it is more preferable that the zoom lens 1 satisfies the following conditional expression (2a): 0.25≤D12 / TTL≤0.65···(2a)

[0066] Furthermore, in the zoom lens 1, when the focal length of the third optical element group G3 is defined as f3, the focal length of the entire zoom lens (optical system) when focusing at infinity at the wide-angle end is defined as fw, and the focal length of the entire zoom lens (optical system) when focusing at infinity at the telephoto end is defined as ft, the zoom lens 1 can satisfy the following conditional expression (3). 0.2 ≤ f3 / √(fw × ft) ≤ 1.1 (3)

[0067] Conditional equation (3) above specifies the ratio of the focal length f3 of the third optical element group G3 to the effective focal length of the zoom lens 1. Furthermore, of the optical element groups G1 to G3 that constitute the zoom lens 1, the third optical element group G3 is the main group. Therefore, by ensuring that the third optical element group G3 is within an appropriate refractive power range, that is, by satisfying conditional equation (3) above in the zoom lens 1, the magnification ratio of the second optical element group G2 and the third optical element group G3 becomes appropriate, achieving optimal performance from the wide-angle end to the telephoto end.

[0068] Specifically, when the value of f3 / √(fw×ft) is less than the lower limit (0.2), the refractive power of the third optical element group G3 becomes stronger, and the refractive power of the second optical element group G2 also becomes stronger. This results in greater fluctuations in field curvature, spherical aberration, and other effects, and significant performance fluctuations from the wide-angle end to the telephoto end, making it difficult to ensure good performance across the entire range from the wide-angle end to the telephoto end. On the other hand, when the value of f3 / √(fw×ft) is greater than the upper limit (1.1), the refractive power of the third optical element group G3 becomes weaker, thereby increasing the size of the zoom lens 1 along the optical axis C and weakening the correction of spherical aberration. This makes it difficult to achieve a zoom lens (optical system) 1 with a bright F value.

[0069] It should be noted that, in the zoom lens 1, it is more preferable to satisfy the following conditional expression (3a): 0.25≤f3 / √(fw×ft)≤1.0···(3a)

[0070] In the zoom lens 1, when the focal length of the second optical element group G2 is defined as f2 and the focal length of the entire zoom lens (optical system) when focusing at infinity at the telephoto end is defined as ft, the zoom lens 1 can satisfy the following conditional expression (4). 0.2 ≤ |f2 / ft| ≤ 1.0···(4)

[0071] Conditional equation (4) specifies the ratio of the focal length f2 of the second optical element group G2 to the focal length ft of the entire zoom lens (optical system) when focusing at infinity at the telephoto end. In the zoom lens 1 of this embodiment, when the magnification is changed from the wide-angle end to the telephoto end, the first optical element group G1 is fixed, and the second optical element group G2 and the third optical element group G3, as zoom groups, move along different trajectories in the direction of the optical axis C with decreasing spacing between them. Furthermore, due to the relationship between the amount of movement of the zoom groups (zoom groups) G2 and G3 when the magnification is changed and the refractive power (1 / focal length) of the zoom groups G2 and G3, if the refractive power of the zoom groups G2 and G3 exceeds a certain range, the zoom lens 1 cannot achieve both compactness and high performance.

[0072] Specifically, when the value of |f2 / ft| exceeds the upper limit (1.0), the refractive power of the second optical element group G2 becomes too weak, and the amount of movement when changing the magnification increases. Therefore, in order to ensure the variable magnification of the zoom lens 1, the total length (the dimension along the optical axis C) increases, which makes it difficult to achieve compactness in the zoom lens 1. On the other hand, when the value of |f2 / ft| is less than the lower limit (0.2), the refractive power of the second optical element group G2 becomes too strong, and fluctuations such as field curvature when changing the magnification increase, resulting in an imbalance in overall performance.

[0073] It should be noted that, from the viewpoint of compactness and high performance, it is more preferable that the zoom lens 1 satisfies the following conditional expression (4a): 0.3 ≤ |f2 / ft| ≤ 0.9 (4a)

[0074] In addition, in the zoom lens 1 , the maximum effective diameter h23 of the light transmission range in the second optical element group G2 and the third optical element group G3 can be 9 mm or less.

[0075] This configuration enables a compact size suitable for use in portable imaging devices such as smartphones. It should be noted that in the zoom lens 1 of this embodiment, the maximum effective diameter h23 of the range through which light rays pass through the second optical element group G2 and the third optical element group G3 is the outer diameter of the fourth lens 31.

[0076] In addition, in the zoom lens 1 , the distance on the optical axis C from the surface 11 a of the first optical element group G1 closest to the object to the image plane 5 can be 40 mm or less.

[0077] This configuration can also realize a compact size of the imaging device 100 that can be used in a portable type such as a smartphone.

[0078] In the zoom lens 1 , at least one surface of at least one lens (the fourth lens 31 to the eighth lens 35 ) in the third optical element group G3 may be an aspherical surface.

[0079] Thus, by making at least one surface of at least one lens 31-35 of the third optical element group G3 aspherical, it is advantageous to improve the performance of the zoom lens 1. In particular, by making at least one surface of a lens having positive refractive power aspherical, the effect of correcting spherical aberration can be significantly achieved.

[0080] In addition, in the zoom lens 1 , at least one lens (the fourth lens 31 to the eighth lens 35 ) in the third optical element group G3 may be made of plastic.

[0081] According to this configuration, the cost and weight of the zoom lens 1 can be reduced.

[0082] The zoom lens 1 described above can be installed in a thin imaging device 100 and can achieve wide-aperture and telephoto photography.

[0083] The zoom lens 1 of this embodiment comprises, in order from the object side, a first optical element group G1 with positive refractive power, a second optical element group G2 with negative refractive power, and a third optical element group G3 with positive refractive power. Furthermore, by reducing the contribution of the first optical element group G1 to the overall refractive power of the zoom lens 1 system, and adopting a weak telephoto configuration with positive refractive power, a large-aperture telephoto zoom lens 1 can be achieved.

[0084] In the zoom lens 1 of this embodiment, the second optical element group G2 having negative refractive power and the third optical element group G3 having positive refractive power as zoom groups are moved toward each other on the optical axis C, thereby maintaining the image plane position.

[0085] It should be noted that in the zoom lens 1 of this embodiment, the second optical element group G2 moves in a single direction, from the object side to the image side, when the magnification is changed from the wide-angle end to the telephoto end. However, the second optical element group G2 may also be configured to move from the middle of the magnification change to the object side when the magnification is changed from the wide-angle end to the telephoto end. Even in this configuration, the third optical element group G3 moves from the image side to the object side in conjunction with the movement of the second optical element group G2 when the magnification is changed.

[0086] In the zoom lens 1 of this embodiment, the first optical element group G1 is fixed relative to the optical axis C. Therefore, the second optical element group G2 is used for focusing and vibration reduction in the zoom lens 1. The third optical element group G3 is also used for focusing and vibration reduction in the zoom lens 1.

[0087] Furthermore, in the zoom lens 1 of this embodiment, the first optical element group G1, which has positive refractive power, includes a first lens 11 having positive refractive power and a reflective optical element 15, such as a prism, having a reflective surface 15a. Thus, the zoom lens 1 is configured such that light (optical axis C) is bent (by 90° in this embodiment) within the first optical element group G1. Therefore, by arranging the zoom lens 1 so that the overall length of the zoom lens (optical system) 1 (the dimension along the optical axis C at a portion closer to the image plane than the reflective optical element 15) coincides with the longitudinal direction (the vertical direction in FIG. 1 ) of the camera (smartphone) 100, the size of the camera (smartphone) 100 in the effective diameter direction (the horizontal direction in FIG. 1 ), that is, the thickness of the camera 100, can be reduced.

[0088] Moreover, by using a lens having positive refractive power as the first lens 11, a structure is configured in which the light passing through the first lens 11 converges while traveling within the second optical element group G2. This can suppress the effective diameter of each optical element group G2, G3 that is closer to the image side than the reflective optical element 15, that is, the thickness of the shooting device (smartphone) 100 can be more effectively suppressed.

[0089] It should be noted that the zoom lens 1 and the imaging device 100 equipped with the zoom lens 1 of the present invention are not limited to the above-described embodiments. Various modifications may be made without departing from the spirit of the present invention. For example, the configuration of one embodiment may be supplemented with the configuration of another embodiment, or a portion of the configuration of one embodiment may be replaced with the configuration of another embodiment. Furthermore, a portion of the configuration of one embodiment may be deleted.

[0090] In the zoom lens 1 of the above embodiment, the aperture 7 is positioned on the object side of the third optical element group G3, but this configuration is not limiting. The aperture 7 may be positioned between the image-side surface 15b of the reflective optical element 15 of the first optical element group G1 and the surface 31a closest to the object side of the third optical element group G3. This configuration limits the width of the light beams incident on the third optical element group G3, ensuring sufficient light intensity when the magnification is changed, while also suppressing fluctuations in the performance of the zoom lens 1.

[0091] In the zoom lens 1 of the above embodiment, the reflecting optical element 15 is formed of a prism and the optical axis (optical path) C is bent by the reflecting surface 15a in the prism, but the present invention is not limited to this structure. The reflecting optical element 15 may also be a reflecting mirror or the like.

[0092] Next, Examples 1 and 2 of the imaging device of the present invention will be described. In the following examples, components corresponding to those of the zoom lens 1 according to the aforementioned embodiment are denoted by the same reference numerals. In the tables of the following examples, r represents the radius of curvature, d represents the lens thickness or the lens spacing, Nd represents the refractive index for the d-line, and Vd represents the Abbe number based on the d-line. The surface profile of an aspherical shape is given, for example, by the following mathematical formula 1.

[0093] Mathematical formula 1

[0094] (Where c is the curvature (1 / r), h is the height (distance) from the optical axis, k is the cone coefficient, and A4, A6, A8, A10, etc. are the aspheric coefficients of each order.)

[0095] The longitudinal aberration diagrams show, from the left, spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In the spherical aberration diagrams, the vertical axis represents the F-number (denoted by FNO in the diagrams), with the solid line representing the d-line characteristics, the dashed line representing the F-line characteristics, and the long-dashed line representing the C-line characteristics. Furthermore, in the astigmatism diagrams, the vertical axis represents the field of view angle, with the solid line representing the sagittal plane characteristics and the long-dashed line representing the meridional plane characteristics. In the distortion diagrams, the vertical axis represents the field of view angle.

[0096] Table 1 shows various data in each of Examples 1 and 2 described below.

[0097] Table 1

[0098] Example 1

[0099] Figure 3 is a lens configuration diagram showing the positions of the lenses 11, 15, 21, 22, and 31-35 that constitute the zoom lens 1 of Example 1 at the wide-angle and telephoto ends. Specifically, the zoom lens 1 of Example 1 includes, in order from the object side to the image side, a first optical element group G1 with positive refractive power, a second optical element group G2 with negative refractive power, and a third optical element group G3 with positive refractive power. In this zoom lens 1, incident light passes through the first optical element group G1, where its optical axis C is bent 90 degrees. It then passes through the second and third optical element groups G2 and G3, forming an image on the imaging surface of an image sensor 5, such as a CMOS image sensor. Furthermore, a UVIR cutoff filter 6 that modulates the wavelength of incident light is positioned between the third optical element group G3 and the image sensor (imaging surface) 5.

[0100] In this zoom lens 1, the first optical element group G1 includes, in order from the object side, a first lens 11 (lens group 10) having positive refractive power and a prism (reflective optical element) 15 for bending the optical path. Furthermore, the second optical element group G2 includes, in order from the object side, a second lens 21 having positive refractive power and a third lens 22 having negative refractive power. The object-side and image-side surfaces of the third lens 22 of the second optical element group G2 are concave. Furthermore, the third optical element group G3 includes, in order from the object side, an aperture 7, a fourth lens 31 having positive refractive power, a fifth lens 32 having positive refractive power, a sixth lens 33 having negative refractive power, a seventh lens 34 having positive refractive power, and an eighth lens 35 having negative refractive power. The object-side surface of the fourth lens 31 of the third optical element group G3 is convex.

[0101] Furthermore, in this zoom lens 1, the second optical element group G2 and the third optical element group G3 each perform a zoom function by moving in the direction of the optical axis C. Furthermore, in the zoom lens 1, at each zoom position, the second optical element group G2 moves along the optical axis C, enabling focus adjustment (focusing) from infinity to extreme close range. Furthermore, in the zoom lens 1, vibration correction is performed by shifting the third optical element group G3 in a direction perpendicular to the optical axis C in response to vibration applied to the zoom lens 1. Alternatively, in the zoom lens 1, vibration correction can be performed by shifting the image sensor (imaging surface) 5 in a direction perpendicular to the optical axis C in response to the aforementioned vibration.

[0102] Figure 4 shows longitudinal aberrations when focusing at infinity at the wide-angle position, and Figure 5 shows longitudinal aberrations when focusing at infinity at the telephoto position. Table 2 below shows surface data for each lens, Table 3 shows aspherical surface data for each lens, Table 4 shows various data when focusing at infinity, Table 5 shows focus group position data when focusing at an object distance of 500mm, and Table 6 shows group data for the zoom lens.

[0103] Table 2

[0104] Polygon data

[0105] ASP is aspherical

[0106] Table 3

[0107] Table 4

[0108] Various data when focusing at infinity

[0109] Table 5

[0110] Focus group position data when focusing at an object distance of 500m

[0111] Table 6

[0112] Zoom lens group data

[0113] Example 2

[0114] Figure 6 is a lens configuration diagram showing the positions of the lenses 11, 15, 21, 22, and 31-37 that make up the zoom lens 1A of Example 1 at the wide-angle and telephoto ends. Specifically, the zoom lens 1A of Example 2 includes, in order from the object side to the image side, a first optical element group G1 with positive refractive power, a second optical element group G2 with negative refractive power, and a third optical element group G3 with positive refractive power. In this zoom lens 1A, incident light passes through the first optical element group G1, where the optical axis C is bent 90 degrees. It then passes through the second and third optical element groups G2 and G3, forming an image on the imaging surface of an image sensor 5, such as a CMOS image sensor. Furthermore, a UVIR cutoff filter 6 that modulates the wavelength of incident light is positioned between the third optical element group G3 and the image sensor (imaging surface) 5.

[0115] In this zoom lens 1A, the first optical element group G1 includes, in order from the object side, a first lens 11 (lens group 10) having positive refractive power and a prism (reflective optical element) 15 for bending the optical path. Furthermore, the second optical element group G2 includes, in order from the object side, a second lens 21 having positive refractive power, a third lens 22 having negative refractive power, and an aperture 7. The object-side and image-side surfaces of the third lens 22 of the second optical element group G2 are concave. Furthermore, the third optical element group G3 includes, in order from the object side, a fourth lens 31 having positive refractive power, a fifth lens 32 having positive refractive power, a sixth lens 33 having negative refractive power, a seventh lens 34 having negative refractive power, an eighth lens 35 having positive refractive power, a ninth lens 36 having negative refractive power, and a tenth lens 38 having positive refractive power. The object-side surface of the fourth lens 31 of the third optical element group G3 is convex.

[0116] Furthermore, in this zoom lens 1A, the second optical element group G2 and the third optical element group G3 each perform a zoom function by moving in the direction of the optical axis C. Furthermore, in the zoom lens 1A, at each zoom position, the second optical element group G2 moves along the optical axis C, enabling focus adjustment (focusing) from infinity to extreme close range. Furthermore, in the zoom lens 1A, vibration correction is performed by shifting the third optical element group G3 in a direction perpendicular to the optical axis C in response to vibration applied to the zoom lens 1. Alternatively, in the zoom lens 1, vibration correction can be performed by shifting the image sensor (imaging surface) 5 in a direction perpendicular to the optical axis C in response to the aforementioned vibration.

[0117] Figure 7 shows longitudinal aberrations when focusing at infinity at the wide-angle position, and Figure 8 shows longitudinal aberrations when focusing at infinity at the telephoto position. Table 7 below shows surface data for each lens, Table 8 shows aspherical surface data for each lens, Table 9 shows various data when focusing at infinity, Table 10 shows focus group position data when focusing at an object distance of 500mm, and Table 11 shows group data for the zoom lens.

[0118] Table 7

[0119] Polygon data

[0120] ASP is aspherical

[0121] Table 8

[0122] Aspheric surface data

[0123] Table 9

[0124] Various data when focusing at infinity

[0125] Table 10

[0126] Focus group position data when focusing at an object distance of 500m

[0127] Table 11

[0128] Zoom lens group data

[0129] To illustrate the present invention, the present invention has been appropriately and fully described above through the embodiments with reference to the accompanying drawings. However, those skilled in the art will recognize that modifications and / or improvements to the above-described embodiments are readily achievable. Therefore, as long as modifications or improvements implemented by those skilled in the art do not depart from the scope of the claims set forth in the claims, such modifications or improvements should be construed as being included within the scope of the claims.

[0130] Explanation of reference numerals: 1, 1A: Zoom lens 5: Image sensor 8: Protective glass 10: Lens group 11: First lens 11a: Object-side surface of the first lens (surface of the first optical element group closest to the object) 15: Reflecting optical element (prism) 15a: Reflecting surface 15b: Image-side surface of the reflecting optical element 16: Lens barrel 16A: Curved portion 16B: Main body 21: Second lens 21a: Object-side surface of the second lens (surface of the second optical element group closest to the object) 22: Third lens 31 to 38: Fourth to eleventh lenses 31a: Surface of the third optical element group closest to the object 100: Imaging device 101: Imaging device main body 102: Display unit 103: Control unit (computing unit) 104: Power supply C: Optical axis G1: First optical element group G2: Second optical element group G3: Third optical element group

Claims

1. A zoom lens, wherein: The zoom lens comprises a first optical element group, a second optical element group, and a third optical element group arranged in order from the object side to the image side. The first optical element group includes a lens group including at least one lens and an optical element that bends the optical axis. The second optical element group includes at least one lens and has negative refractive power, The third optical element group includes at least one lens and has positive refractive power, The lens group has positive refractive power and is arranged closer to the object side than the optical element. The second optical element group and the third optical element group are configured to be movable along the optical axis, respectively, so that the zoom lens changes magnification between a wide-angle end and a telephoto end.

2. The zoom lens according to claim 1, wherein: When the focal length of the first optical element group is defined as f1 and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the following is satisfied: 0.5≤f1 / ft≤6.

3. The zoom lens according to claim 1 or 2, wherein: When the distance on the optical axis from the surface of the first optical element group closest to the object to the surface of the second optical element group closest to the object is defined as D12, and the distance on the optical axis from the surface of the first optical element group closest to the object to the image plane is defined as TTL, the following conditions are satisfied: 0.2≤D12 / TTL≤0.

7.

4. The zoom lens according to any one of claims 1 to 3, wherein: When the focal length of the third optical element group is defined as f3, the focal length of the entire optical system when focusing at infinity at the wide-angle end is defined as fw, and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the following is satisfied: 0.2≤f3 / √(fw×ft)≤1.

1.

5. The zoom lens according to any one of claims 1 to 4, wherein: When the focal length of the second optical element group is defined as f2, and the focal length of the entire optical system when focusing at infinity at the telephoto end is defined as ft, the following is satisfied: 0.2≤|f2 / ft|≤1.

0.

6. The zoom lens according to any one of claims 1 to 5, wherein: The maximum effective diameter h23 of the light transmission range in the second optical element group and the third optical element group is less than or equal to 9 mm.

7. The zoom lens according to any one of claims 1 to 6, wherein: A distance on the optical axis from a surface of the first optical element group closest to the object to an image plane is 40 mm or less.

8. The zoom lens according to any one of claims 1 to 7, wherein: The zoom lens has an aperture that adjusts the amount of light passing therethrough. The aperture is arranged between the image-side surface of the optical element of the first optical element group and the object-side surface of the third optical element group.

9. The zoom lens according to any one of claims 1 to 8, wherein: At least one surface of at least one lens in the third optical element group is aspherical.

10. The zoom lens according to any one of claims 1 to 9, wherein: At least one lens in the third optical element group is made of plastic.

11. A photographing device, wherein: The photographing device comprises: The zoom lens according to any one of claims 1 to 10; and The imaging element is arranged at the image plane position of the zoom lens and converts the formed optical image into an electrical signal.

Images