Zoom lens and imaging device equipped with zoom lens

Abstract

a first optical element group having a lens group and an optical element that bends the optical axis, arranged in this order from the object side to the image side; a second optical element group having negative refractive power; and a third optical element group having positive refractive power, wherein the lens group has positive refractive power and is located closer to the object side than the optical element, and the second optical element group and the third optical element group are configured to be movable along the optical axis so that the zoom lens changes magnification from a wide-angle end to a telephoto end.

Description

[Technical Field]

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

[0002] 2. Description of the Related Art Conventionally, various zoom lenses equipped with an optical element that bends the optical axis have been known.

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

[0004] This zoom lens has a small dimension in the direction of incidence of light rays from an object (i.e., it is thin), but the F-number at the wide-angle end is about F28, so it cannot be said that the aperture is sufficiently large.

[0005] In addition, in the zoom lens described in WO2021 / 085154A1, a prism is disposed on the object side of the lens group, i.e., the prism is disposed closest to the object. In this zoom lens, although the dimension in the direction of light incidence can be reduced, a sufficient size cannot be ensured for the maximum diameter of the first lens group, which is calculated by the focal length (EFL) / F-number, making it difficult to achieve a large aperture. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2007-34064 [Patent Document 2] International Publication No. WO2021 / 085154A1 Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a zoom lens that can be placed in a thin imaging device, has a large aperture, and is capable of telephoto shooting, and an imaging device equipped with the zoom lens. [Means for solving the problem]

[0008] The zoom lens according to the present invention comprises: Arranged in order from the object side to the image side, a first optical element group having a lens group including at least one lens and an optical element that bends the optical axis; a second optical element group including at least one lens and having negative refractive power; a third optical element group including at least one lens and having a positive refractive power; the lens group has positive refractive power and is disposed 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 so that the zoom lens can vary its magnification between a wide-angle end and a telephoto end.

[0009] In the zoom lens, When the focal length of the first lens group is f1 and the focal length of the entire optical system when focused on infinity at the telephoto end is ft, 0.5≦f1 / ft≦6 may be satisfied.

[0010] In addition, in the zoom lens, 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 D12 and the distance on the optical axis from the surface of the first optical element group closest to the object side to an image plane is TTL, 0.2≦D12 / TTL≦0.7 may be satisfied.

[0011] In addition, in the zoom lens, When the focal length of the third optical element group is f3, the focal length of the entire optical system when focusing on infinity at the wide-angle end is fw, and the focal length of the entire optical system when focusing on infinity at the telephoto end is ft, 0.2≦f3 / √(fw×ft)≦1.1 may be satisfied.

[0012] In addition, in the zoom lens, When the focal length of the second optical element group is f2 and the focal length of the entire optical system when focused on infinity at the telephoto end is ft, 0.2≦|f2 / ft|≦1.0 may be satisfied.

[0013] In addition, in the zoom lens, The second optical element group and the third optical element group may have a maximum effective diameter h23 of 9 mm or less within a range through which a light ray passes.

[0014] In addition, in the zoom lens, The distance on the optical axis from the surface of the first optical element group closest to the object to the image plane may be 40 mm or less.

[0015] Moreover, the zoom lens is Equipped with an aperture that adjusts the amount of light passing through, The diaphragm may be disposed between the image-side surface of the optical element in the first optical element group and the surface closest to the object in the third optical element group.

[0016] Moreover, the zoom lens is At least one surface of at least one lens in the third optical element group may be aspherical.

[0017] In addition, in the zoom lens, At least one lens in the third optical group may be made of plastic.

[0018] Furthermore, the imaging device according to the present invention comprises: Any of the zoom lenses listed above; an image sensor that is disposed at the image plane position of the zoom lens and converts the formed optical image into an electrical signal; [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an imaging device according to this embodiment. [Figure 2] FIG. 2 is a lens configuration diagram of a zoom lens provided in the imaging device. [Figure 3] FIG. 3 is a lens configuration diagram of the zoom lens of Example 1, showing the wide-angle end and the telephoto end. [Figure 4] FIG. 4 is a longitudinal aberration diagram of the zoom lens when focused on infinity at the wide-angle end. [Figure 5] FIG. 5 is a longitudinal aberration diagram of the zoom lens when focused on infinity at the telephoto end. [Figure 6] FIG. 6 is a lens configuration diagram of a zoom lens according to the second embodiment, showing the wide-angle end and the telephoto end. [Figure 7] FIG. 7 is a longitudinal aberration diagram of the zoom lens when focused on infinity at the wide-angle end. [Figure 8] FIG. 8 is a longitudinal aberration diagram of the zoom lens when focused on infinity at the telephoto end. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0021] The imaging device according to this embodiment is capable of capturing an image of a target object (object), such as a digital camera, a smartphone, or a tablet device, and the imaging device described below is, for example, a smartphone.

[0022] 1, imaging device 100 includes a zoom lens (optical system) 1 disposed so that at least a portion thereof is built into imaging device body 101, and an image sensor (imaging element) 5 disposed at an imaging position (image plane position) of zoom lens 1. Specifically, imaging device 100 includes imaging device body 101, zoom lens (optical system) 1, image sensor 5, and a display unit 102 such as an LCD screen that displays imaging (image) data output from image sensor 5. Imaging device 100 also includes a control unit (arithmetic unit) 103 that controls each component and performs arithmetic processing on signals from image sensor 5 and the like, and a power supply 104.

[0023] The image sensor 5, which is placed at the imaging plane of the zoom lens 1, is an element that converts the optical image formed by the zoom lens 1 into an electrical signal (image capture data), and the image sensor 5 in this embodiment is a CMOS image sensor. Note that, because the imaging plane of the zoom lens 1 and the light receiving surface of the image sensor 5 are placed at the same position, hereinafter the image sensor (more specifically, the light receiving surface of the image sensor) may also be referred to as the image plane 5.

[0024] As shown in FIG. 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 this 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, in this order from the object side to the image side along the optical axis C, the first optical element group G1, the second optical element group G2, the third optical element group G3, and an optical filter (an IR filter in this embodiment). The zoom lens 1 also includes an aperture (aperture device) 7 located at a predetermined position on the optical axis C and a protective glass 8 located on the object side of the first optical element group G1. The aperture 7 of this embodiment is located 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 during zooming and focusing.

[0025] The second optical element group G2 and the third optical element group G3 are configured to be movable along the optical axis C so that the zoom lens 1 can vary the magnification between the wide-angle end and the telephoto end (see FIG. 3).

[0026] The first optical element group G1 has 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 and is arranged closer to the object than the reflective optical element 15. In the first optical element group G1 of this embodiment, the lens group 10 includes one lens (first lens) 11, and the reflective optical element 15 is a prism made of glass having a reflective surface 15a that reflects incident light rays and bends the light rays (optical axis C). In FIG. 2, the reflective optical element (prism) 15 is represented by a square. This is also true in FIGS. 3 and 6.

[0027] The second optical element group G2 includes at least one lens and has negative refractive power. The second optical element group G2 of this embodiment includes two lenses (second lens 21 and third lens 22). The third optical element group G3 includes at least one lens and has positive refractive power. The third optical element group G3 of this embodiment includes five lenses (fourth lens 31 to eighth lens 35).

[0028] The zoom lens 1 also has a lens barrel 16 that holds each of the optical element groups G1 to G3. The lens barrel 16 of this embodiment includes a bending portion 16A that receives light rays (light from an object) and bends the optical axis C of the incident light rays, and a main body portion 16B that is built into the image capture device body 101. The bending portion 16A is where the first optical element group G1 is arranged, and the main body portion 16B is where the second optical element group G2 and the third optical element group G3 are arranged.

[0029] 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 include groups that are configured with only one optical element (lens, etc.). That is, 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).

[0030] Here, when the focal length of the first optical element group is f1 and the focal length of the entire optical system when focused on infinity at the telephoto end is ft, the zoom lens 1 may satisfy the following conditional expression (1): 0.5≦f1 / ft≦6 (1) The focal length of the entire optical system when focused at infinity at the telephoto end is 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 focused at infinity at the wide-angle end is the focal length of the entire optical system when zoomed to the wide-angle end and focused at infinity.

[0031] If the value of f1 / ft is less than the lower limit (0.5), the positive refractive power of the first optical element group G1 will be too strong, reducing the distance between the first lens 11 and the second optical element group G, making it impossible to ensure space for arranging the reflective optical element 15 for bending the optical axis C. On the other hand, if the value of f1 / ft is greater than the upper limit (6), the positive refractive power of the first optical element group G1 will be too weak, increasing the dimension (total length) of the optical system (zoom lens) 1 along the optical axis C at the telephoto end, making it difficult to make the zoom lens 1 compact. In other words, by satisfying the above conditional expression (1) in the zoom lens 1, it is possible to achieve a balance between ensuring space for arranging the reflective optical element 15 and reducing the dimension of the zoom lens 1 along the optical axis C.

[0032] From the viewpoint 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 satisfy the following conditional expression (1a). 1≦f1 / ft≦5 (1a)

[0033] Furthermore, in this zoom lens 1, when the distance on the optical axis C from the surface closest to the object (the surface closest to the object of the first lens 11) 11a of the first optical element group G1 to the surface closest to the object (the surface closest to the object of the second lens 21) 21a of the second optical element group G2 is defined as D12, and the distance on the optical axis C from the surface closest to the object of the first optical element group G1 11a to the image plane 5 is defined as TTL, the zoom lens 1 may satisfy the following conditional expression (2): 0.2≦D12 / TTL≦0.7 (2)

[0034] If the value of D12 / TTL is smaller 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, making it impossible to ensure space for arranging the reflective optical element 15. On the other hand, if the value of D12 / TTL is larger 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, making it impossible to compact the dimensions of the zoom lens 1 along the optical axis C. In other words, by satisfying the above conditional expression (2) in the zoom lens 1, it is possible to achieve a balance between ensuring space for arranging the reflective optical element 15 and compacting the dimensions of the zoom lens 1 along the optical axis C.

[0035] From the viewpoint 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 satisfy the following conditional expression (2a). 0.25≦D12 / TTL≦0.65 (2a)

[0036] Furthermore, in this zoom lens 1, when the focal length of the third optical element group G3 is f3, the focal length of the entire zoom lens (optical system) when focusing on infinity at the wide-angle end is fw, and the focal length of the entire zoom lens (optical system) when focusing on infinity at the telephoto end is ft, the zoom lens 1 may satisfy the following conditional expression (3): 0.2≦f3 / √(fw×ft)≦1.1 (3)

[0037] The above conditional expression (3) defines 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, among the optical element groups G1 to G3 that make up the zoom lens 1, the third optical element group G3 is the main group. Therefore, when the third optical element group G3 falls within an appropriate range of refractive power, that is, when the above conditional expression (3) is satisfied in the zoom lens 1, the magnification ratios of the second optical element group G2 and the third optical element group G3 become appropriate, and performance from the wide-angle end to the telephoto end becomes optimal.

[0038] Specifically, when the value of f3 / √(fw×ft) is smaller 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, resulting in larger fluctuations in field curvature, spherical aberration, etc., and larger fluctuations in performance from the wide-angle end to the telephoto end, making it difficult to ensure good performance over the entire range from the wide-angle end to the telephoto end.On the other hand, when the value of f3 / √(fw×ft) is larger than the upper limit (1.1), the refractive power of the third optical element group G3 becomes weaker, increasing the dimension of the zoom lens 1 along the optical axis C and weakening the correction of spherical aberration, making it difficult to configure a zoom lens (optical system) 1 with a fast F-number.

[0039] It is more preferable that the zoom lens 1 satisfy the following conditional expression (3a). 0.25≦f3 / √(fw×ft)≦1.0 (3a)

[0040] Furthermore, in this zoom lens 1, when the focal length of the second optical element group G2 is f2 and the focal length of the entire zoom lens (optical system) when focusing on infinity at the telephoto end is ft, the zoom lens 1 may satisfy the following conditional expression (4): 0.2≦|f2 / ft|≦1.0 (4)

[0041] Conditional expression (4) defines the ratio between the focal length f2 of the second optical element group G2 and the focal length ft of the entire zoom lens (optical system) when focusing on infinity at the telephoto end. In the zoom lens 1 of this embodiment, when changing magnification 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 move along the optical axis C as a magnification changing group on different trajectories so as to reduce the distance between them. Furthermore, due to the relationship between the movement amount of the zooming groups (magnification changing groups) G2 and G3 when changing magnification and the refractive power (1 / focal length) of the zooming groups G2 and G3, if the zooming groups G2 and G3 exceed a certain range of refractive power, the zoom lens 1 will not be compact and will not achieve high performance.

[0042] Specifically, if the value of |f2 / ft| is greater than the upper limit (1.0), the refractive power of the second optical element group G2 becomes too weak, and the amount of movement during magnification change becomes large, which increases the overall length (dimension along the optical axis C) of the zoom lens 1 in order to ensure the desired magnification change, making it difficult to make the zoom lens 1 compact. On the other hand, if 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, which increases fluctuations in things like field curvature during magnification change, upsetting the overall balance of performance.

[0043] From the viewpoint of compactness and high performance, it is more preferable that the zoom lens 1 satisfy the following conditional expression (4a): 0.3≦|f2 / ft|≦0.9 (4a)

[0044] In this zoom lens 1, the maximum effective diameter h23 of the light ray passing range in the second optical element group G2 and the third optical element group G3 may be 9 mm or less.

[0045] This configuration makes it possible to realize a compact size suitable for use in portable imaging devices such as smartphones. In the zoom lens 1 of this embodiment, the maximum effective diameter h23 of the light ray passage range in the second optical element group G2 and the third optical element group G3 is the outer diameter of the fourth lens 31.

[0046] In this zoom lens 1, the distance on the optical axis C from the surface 11a of the first optical element group G1 closest to the object to the image plane 5 may be 40 mm or less.

[0047] Even with this configuration, a compact size that can be used in a portable imaging device 100 such as a smartphone can be achieved.

[0048] In this zoom lens 1, at least one surface of at least one lens (fourth lens 31 to eighth lens 35) in the third optical element group G3 may be aspherical.

[0049] In this way, making at least one surface of at least one of the lenses 31 to 35 in the third optical element group G3 aspherical is advantageous for improving the performance of the zoom lens 1. In particular, making at least one surface of a lens having positive refractive power aspherical can significantly improve the effect of correcting spherical aberration.

[0050] In this zoom lens 1, at least one lens (fourth lens 31 to eighth lens 35) in the third optical element group G3 may be made of plastic.

[0051] With this configuration, the cost and weight of the zoom lens 1 can be reduced.

[0052] The zoom lens 1 described above can be installed in a slim imaging device 100, has a large aperture, and is capable of telephoto shooting.

[0053] In the zoom lens 1 of this embodiment, a first optical element group G1 having positive refractive power, a second optical element group G2 having negative refractive power, and a third optical element group G3 having positive refractive power are arranged in this order from the object side. By weakening the contribution of the first optical element group G1 to the refractive power of the entire zoom lens 1 system and adopting a weak telephoto configuration with positive refractive power, a large-aperture telephoto zoom lens 1 is obtained.

[0054] Furthermore, 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 move toward each other on the optical axis C as a zooming group, thereby keeping the image plane position constant.

[0055] In the zoom lens 1 of this embodiment, the second optical element group G2 moves in one direction from the object side to the image side when changing magnification from the wide-angle end to the telephoto side, but the second optical element group G2 may be configured to move toward the object side halfway when changing magnification from the wide-angle end to the telephoto side. 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 changing magnification.

[0056] In the zoom lens 1 of this embodiment, the first optical element group G1 is fixed with respect 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.

[0057] Furthermore, in the zoom lens 1 of this embodiment, the first optical element group G1 having positive refractive power includes a first lens 11 having positive refractive power and a reflective optical element 15 having a reflecting surface 15a such as a prism. In this manner, the zoom lens 1 is configured so that the light beam (optical axis C) is bent (bent by 90° in the example of this embodiment) in the first optical element group G1. Therefore, by arranging the zoom lens 1 so that the overall length direction of the zoom lens (optical system) 1 (the dimension along the optical axis C of the portion closer to the image plane than the reflective optical element 15) coincides with the length direction of the image pickup device (smartphone) 100 (the up-down direction in FIG. 1), the dimension of the image pickup device (smartphone) 100 in the effective diameter direction of the zoom lens 1 (the left-right direction in FIG. 1), i.e., the thickness of the image pickup device 100, can be reduced.

[0058] Furthermore, by using a lens having positive refractive power as the first lens 11, the light rays that pass through the first lens 11 converge while traveling through the second optical element group G2, and the effective diameter of each optical element group G2, G3 on the image side of the reflective optical element 15 can be reduced, i.e., the thickness of the imaging device (smartphone) 100 can be more effectively reduced.

[0059] The zoom lens 1 and the imaging device 100 including the zoom lens 1 of the present invention are not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, or part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, part of the configuration of one embodiment can be deleted.

[0060] In the zoom lens 1 of the above embodiment, the diaphragm 7 is disposed on the object side of the third optical element group G3, but this configuration is not limiting. The diaphragm 7 may be disposed between the image-side surface 15b of the reflective optical element 15 in the first optical element group G1 and the surface 31a of the third optical element group G3 closest to the object. With this configuration, by limiting the width of light rays incident on the third optical element group G3, it is possible to ensure the amount of light during magnification change and also suppress fluctuations in the performance of the zoom lens 1.

[0061] Furthermore, the reflective optical element 15 of the zoom lens 1 of the above embodiment is configured by a prism, and the optical axis (optical path) C is bent by the reflective surface 15a within the prism, but is not limited to this configuration. The reflective optical element 15 may also be a reflective mirror or the like.

[0062] Next, Examples 1 and 2 of the imaging device of the present invention will be described. In each of the following Examples, the same reference numerals are used for components corresponding to those of the zoom lens 1 of the above-described embodiment. In the tables of each of the following Examples, r is the radius of curvature, d is the lens thickness or lens spacing, Nd is the refractive index for the d-line, and Vd is the Abbe number based on the d-line. The surface profile of the aspherical shape is given, for example, by the following equation 1:

number

[0063] Each longitudinal aberration diagram shows, from left to right, spherical aberration (SA (mm)), astigmatism (AST (mm)), and distortion (DIS (%)). In each spherical aberration diagram, the vertical axis represents the F-number (denoted as FNO in the diagram), with the solid line representing the d-line, the dashed line representing the F-line, and the dashed-dotted line representing the C-line characteristics. In each astigmatism diagram, the vertical axis represents the angle of view, with the solid line representing the sagittal plane characteristics and the dashed-dotted line representing the meridional plane characteristics. In each distortion diagram, the vertical axis represents the angle of view.

[0064] Table 1 also shows various data for each of Examples 1 and 2 below. [Table 1]

[0065] [Example 1] FIG. 3 is a lens configuration diagram showing the positions of lenses 11, 15, 21, 22, and 31-35 constituting the zoom lens 1 of the first embodiment at the wide-angle end and the telephoto end. Specifically, the zoom lens 1 of the first embodiment includes, from the object side to the image side, a first optical element group G1 having positive refractive power, a second optical element group G2 having negative refractive power, and a third optical element group G3 having positive refractive power. In this zoom lens 1, incident light passes through the first optical element group G1, causing its optical axis C to be bent 90 degrees, and then passes through the second and third optical element groups G2 and G3 to form an image on the imaging surface of an image sensor 5 such as a CMOS. A UV / IR cut filter 6 that adjusts the wavelength of incident light is disposed between the third optical element group G3 and the image sensor (imaging surface) 5.

[0066] In this zoom lens 1, the first optical element group G1 includes, from the object side, a first lens 11 (lens group 10) having positive refractive power and a prism (reflective optical element) 15 that bends the optical path. The second optical element group G2 includes, 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 in the second optical element group G2 are concave. The third optical element group G3 includes, from the object side, a diaphragm 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 in the third optical element group G3 is convex.

[0067] In addition, this zoom lens 1 exhibits a zoom function by moving the second optical element group G2 and the third optical element group G3 in the direction of the optical axis C. In addition, in the zoom lens 1, focus adjustment (focusing) from infinity to close range is performed by moving the second optical element group G2 along the optical axis C at each zoom position. In addition, in the zoom lens 1, vibration correction is performed by shifting the third optical element group G3 in a planar direction perpendicular to the optical axis C in response to vibrations applied to the zoom lens 1. Alternatively, in the zoom lens 1, vibration correction may be performed by shifting the image sensor (imaging surface) 5 in a planar direction perpendicular to the optical axis C in response to the vibrations.

[0068] Fig. 4 is a diagram of longitudinal aberration when focusing at infinity at the wide-angle end, and Fig. 5 is a diagram of longitudinal aberration when focusing at infinity at the telephoto end. 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 position data for the focus group when focusing at an object distance of 500 mm, and Table 6 shows group data for the zoom lens.

[0069] [Table 2] [Table 3] [Table 4] [Table 5] [Table 6]

[0070] [Example 2] FIG. 6 is a lens configuration diagram showing the positions of lenses 11, 15, 21, 22, and 31-37 constituting a zoom lens 1A of the first embodiment at the wide-angle end and the telephoto end. Specifically, the zoom lens 1A of the second embodiment includes, from the object side to the image side, a first optical element group G1 having positive refractive power, a second optical element group G2 having negative refractive power, and a third optical element group G3 having positive refractive power. In this zoom lens 1A, incident light passes through the first optical element group G1, causing its optical axis C to be bent 90 degrees. The incident light then passes through the second and third optical element groups G2 and G3 to form an image on the imaging surface of an image sensor 5, such as a CMOS. A UV / IR cut filter 6 for adjusting the wavelength of incident light is disposed between the third optical element group G3 and the image sensor (imaging surface) 5.

[0071] In this zoom lens 1A, the first optical element group G1 includes, from the object side, a first lens 11 (lens group 10) having positive refractive power and a prism (reflective optical element) 15 that bends the optical path. The second optical element group G2 includes, from the object side, a second lens 21 having positive refractive power, a third lens 22 having negative refractive power, and a diaphragm 7. The object-side and image-side surfaces of the third lens 22 of the second optical element group G2 are concave. The third optical element group G3 includes, 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 in the third optical element group G3 is a convex surface.

[0072] In addition, this zoom lens 1A exhibits a zoom function by moving the second optical element group G2 and the third optical element group G3 in the direction of the optical axis C. In addition, in the zoom lens 1A, focus adjustment (focusing) from infinity to close range is performed by moving the second optical element group G2 along the optical axis C at each zoom position. In addition, in the zoom lens 1A, vibration correction is performed by shifting the third optical element group G3 in a planar direction perpendicular to the optical axis C in response to vibrations applied to the zoom lens 1. Alternatively, in the zoom lens 1, vibration correction may be performed by shifting the image sensor (imaging surface) 5 in a planar direction perpendicular to the optical axis C in response to the vibrations.

[0073] Fig. 7 shows longitudinal aberration diagrams when focusing on infinity at the wide-angle end, and Fig. 8 shows longitudinal aberration diagrams when focusing on infinity at the telephoto end. 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 on infinity, Table 10 shows position data for the focus group when focusing at an object distance of 500 mm, and Table 11 shows group data for the zoom lens.

[0074] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11]

[0075] In order to express the present invention, the present invention has been properly and sufficiently described above through the embodiments with reference to the drawings, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims. [Explanation of symbols]

[0076] 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 closest to the object in the first optical element group) 15: Reflective optical element (prism) 15a: Reflective surface 15b: Image side surface of the reflecting optical element 16: Telescope tube 16A: Bent part 16B: Main body 21: Second lens 21a: Object-side surface of the second lens (the surface closest to the object in the second optical element group) 22: Third lens 31-38: 4th to 11th lenses 31a: Surface closest to the object in the third optical element group 100: Imaging device 101: Imaging device body 102: Display section 103: Control unit (arithmetic unit) 104: Power supply C: Optical axis G1: First optical element group G2: Second optical group G3: Third optical element group

Claims

1. Arranged in order from the object side to the image side, a first optical element group having a lens group including at least one lens and an optical element that bends the optical axis; a second optical element group including at least one lens and having negative refractive power; a third optical element group including at least one lens and having a positive refractive power; the lens group has positive refractive power and is disposed 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 an optical axis so that the zoom lens changes magnification between a wide-angle end and a telephoto end.

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

3. When a distance on the optical axis from the surface of the first optical element group closest to the object side to a surface of the second optical element group closest to the object side is defined as D12, and a distance on the optical axis from the surface of the first optical element group closest to the object side to an image plane is defined as TTL, 0.2≦D12 / TTL≦0.7 3. The zoom lens according to claim 1, wherein the following is satisfied:

4. When the focal length of the third optical element group is f3, the focal length of the entire optical system when focusing on infinity at the wide-angle end is fw, and the focal length of the entire optical system when focusing on infinity at the telephoto end is ft, 0.2≦f3 / √(fw×ft)≦1.1 4. The zoom lens according to claim 1, wherein the following is satisfied:

5. When the focal length of the second optical element group is f2 and the focal length of the entire optical system when focusing on infinity at the telephoto end is ft, 0.2≦|f2 / ft|≦1.0 5. The zoom lens according to claim 1, wherein the following is satisfied:

6. 6. The zoom lens according to claim 1, wherein a maximum effective diameter h23 of a light beam passing range in the second optical element group and the third optical element group is 9 mm or less.

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

8. Equipped with an aperture that adjusts the amount of light passing through, 8. The zoom lens according to claim 1, wherein the diaphragm is disposed between an image-side surface of the optical element in the first optical element group and a surface of the third optical element group closest to the object side.

9. 9. The zoom lens according to claim 1, wherein at least one surface of at least one lens in the third optical element group is aspherical.

10. 10. The zoom lens according to claim 1, wherein at least one lens in the third optical element group is made of plastic.

11. The zoom lens according to any one of claims 1 to 10, an image sensor that is disposed at an image plane position of the zoom lens and converts a formed optical image into an electrical signal.

Images