Imaging optical system and imaging device having the same

Abstract

To provide a compact image capturing optical system which offers a wide angle of view and good imaging performance, and to provide an image capturing device.SOLUTION: An optical system provided herein has six or seven lenses comprising a first lens group consisting of a single negative lens, an aperture stop, and a second lens group having positive refractive power arranged in order from the object side to the image side. The most object-side lens surface of the image capturing optical system includes a convex region in a paraxial area and the most image-side lens surface of the image capturing optical system includes a concave region in the paraxial area, while the most object-side lens surface of the second lens group includes a convex region in the paraxial area. The image capturing optical system has at least one convex lens having a refractive index of 1.63 or greater for the d-ray. The image capturing optical system satisfies a conditional expression concerning a distance TD from an apex of the most object-side lens surface to an apex of the most image-side lens surface, and a distance DSP from an apex of the most object-side lens surface to the aperture stop.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical system suitable for digital video cameras, digital still cameras, broadcast cameras, silver halide film cameras, surveillance cameras, vehicle-mounted cameras, and the like. [Background technology]

[0002] In recent years, there has been an increasing need to take beautiful landscape photographs that capture a wide field of view and group photographs that capture the expressions of many people. At the same time, there has also been an increasing demand for smaller cameras to improve portability. To achieve this, there is a demand for compact imaging optical systems that have a wide imaging angle, sufficiently ensure good imaging performance, and are compact. For example, Patent Document 1 discloses an imaging optical system that consists of seven lenses, has a half angle of view of approximately 30 degrees, and an F-number of approximately 2.1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-21340 A Summary of the Invention [Problem to be solved by the invention]

[0004] A high-performance, compact imaging optical system can be provided according to the configuration of Patent Document 1. However, the configuration of Patent Document 1 is particularly insufficient in suppressing spherical aberration and field curvature, and it cannot be said that good imaging performance is necessarily achieved with a compact configuration.

[0005] An object of the present invention is to provide a compact imaging optical system that ensures good imaging performance at a wide angle, and an imaging apparatus having the same. [Means for solving the problem]

[0006] An imaging optical system according to one aspect of the present invention is an imaging optical system consisting of six or seven lenses, the imaging optical system consisting of a first lens group consisting of one negative lens, an aperture stop, and a second lens group having positive refractive power, arranged in this order from the object side to the image side, the lens surface closest to the object side of the imaging optical system including a convex area in the paraxial area, and the lens surface closest to the image side of the imaging optical system Aspherical shape with an inflection point , and a paraxial region including a concave region, and the lens surface of the second lens group closest to the object side includes a convex region in the paraxial region, and the imaging optical system has at least one convex lens having a refractive index of 1.63 or more at the d-line, and in the imaging optical system, a distance from a vertex of the lens surface closest to the object side to a vertex of the lens surface closest to the image side is defined as TD, and a distance from the vertex of the lens surface closest to the object side to the aperture stop is defined as DSP The distance from the aperture stop to the vertex of the lens surface closest to the object in the second lens group is SP1 When 0.05 < DSP / TD < 0.28 0.02 < SP1 / TD < 0.11 The present invention is characterized in that the following conditional expression is satisfied:

[0007] Other objects and features of the present invention will be described in the following embodiments. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an imaging optical system and an imaging device that ensure good imaging performance at a wide angle and are compact. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of a lens of an imaging optical system according to a first embodiment. [Figure 2] 4A and 4B are longitudinal aberration diagrams of the imaging optical system in Example 1 when focused on an object at infinity. [Figure 3] 4A to 4C are longitudinal aberration diagrams of the imaging optical system in Example 1 when focused on an object distance of −0.05 m. [Figure 4] 4A to 4C are diagrams illustrating lateral aberrations of the imaging optical system according to the first embodiment when the object distance is infinity and the imaging optical system is focused on the object. [Figure 5]4A to 4C are diagrams showing lateral aberrations of the imaging optical system in Example 1 when focused on an object at a distance of −0.05 m. [Figure 6] FIG. 10 is a cross-sectional view of a lens of an imaging optical system according to a second embodiment. [Figure 7] 10A and 10B are longitudinal aberration diagrams of the imaging optical system according to Example 2 when focused on an object at infinity. [Figure 8] 10A and 10B are longitudinal aberration diagrams of the imaging optical system in Example 2 when focused on an object distance of −0.2 m. [Figure 9] 10A and 10B are diagrams illustrating lateral aberrations of the imaging optical system according to the second embodiment when the object distance is infinity and the imaging optical system is focused on the object. [Figure 10] 10A and 10B are diagrams illustrating lateral aberration of the imaging optical system according to Example 2 when focused on an object at a distance of −0.2 m. [Figure 11] FIG. 10 is a cross-sectional view of a lens of an imaging optical system according to a third embodiment. [Figure 12] 10A and 10B are longitudinal aberration diagrams of the imaging optical system according to Example 3 when focused on an object at infinity. [Figure 13] 10A and 10B are longitudinal aberration diagrams of the imaging optical system according to Example 3 when focused on an object at a distance of −0.2 m. [Figure 14] 10A and 10B are diagrams illustrating lateral aberrations of the imaging optical system according to Example 3 when the object distance is infinity and the imaging optical system is focused. [Figure 15] 10A and 10B are diagrams illustrating lateral aberration of the imaging optical system according to Example 3 when focused on an object at a distance of −0.2 m. [Figure 16] 1 is a schematic diagram of a main part of an imaging device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of an imaging optical system and an imaging device having the same will be described with reference to the accompanying drawings.

[0011] Fig. 1 is a lens cross-sectional view of the imaging optical system of Example 1 when focused at infinity. Fig. 2 is a longitudinal aberration diagram of the imaging optical system of Example 1 when focused at infinity. Fig. 3 is a longitudinal aberration diagram of the imaging optical system of Example 1 when focused at -0.05 m. Fig. 4 is a lateral aberration diagram of the imaging optical system of Example 1 when focused at infinity. Fig. 5 is a lateral aberration diagram of the imaging optical system of Example 1 when focused at -0.05 m. The optical system of Example 1 is an imaging optical system with a focal length of approximately 6.8 mm, an aperture ratio of approximately 2.8, and a half angle of view of approximately 44 degrees.

[0012] Fig. 6 is a lens cross-sectional view of the imaging optical system of Example 2 when focused at infinity. Fig. 7 is a longitudinal aberration diagram of the imaging optical system of Example 2 when focused at infinity. Fig. 8 is a longitudinal aberration diagram of the imaging optical system of Example 2 when focused at -0.2 m. Fig. 9 is a lateral aberration diagram of the imaging optical system of Example 2 when focused at infinity. Fig. 10 is a lateral aberration diagram of the imaging optical system of Example 2 when focused at -0.2 m. The optical system of Example 2 is an imaging optical system with a focal length of approximately 18.4 mm, an aperture ratio of approximately 2.9, and a half angle of view of approximately 44 degrees.

[0013] Fig. 11 is a lens cross-sectional view of the imaging optical system of Example 3 when focused at infinity. Fig. 12 is a longitudinal aberration diagram of the imaging optical system of Example 3 when focused at infinity. Fig. 13 is a longitudinal aberration diagram of the imaging optical system of Example 3 when focused at -0.2 m. Fig. 14 is a lateral aberration diagram of the imaging optical system of Example 3 when focused at infinity. Fig. 15 is a lateral aberration diagram of the imaging optical system of Example 3 when focused at -0.2 m. The optical system of Example 3 is an imaging optical system with a focal length of approximately 18.4 mm, an aperture ratio of approximately 2.9, and a half angle of view of approximately 44 degrees.

[0014] The imaging optical system of each embodiment is an imaging optical system used in imaging devices such as digital still cameras, digital video cameras, broadcast cameras, silver halide film cameras, surveillance cameras, and vehicle-mounted cameras.

[0015] In each lens cross-sectional view, the left is the object side (front) and the right is the image side (rear). The imaging optical system of each embodiment is composed of multiple lens groups. L1 is the first lens group consisting of lenses with negative refractive power. SP is an F-number determination member (aperture stop) that acts as an aperture stop to determine (limit) the maximum F-number (Fno) light beam. L2 is the second lens group with positive refractive power. IM indicates the image plane, and when the imaging optical system of each embodiment is used as the imaging optical system of a digital video camera or digital still camera, the imaging surface of a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed thereon. When used as the imaging optical system of a silver halide film camera, a photosensitive surface equivalent to the film surface is placed at the image plane IM. OA indicates the optical axis.

[0016] Furthermore, the imaging optical system of each embodiment is configured so that the entire imaging optical system is moved toward the object side during focusing.

[0017] Each longitudinal aberration diagram will be explained below. In the spherical aberration diagram, Fno is the F-number, and shows the amount of spherical aberration for the d-line (wavelength 587.6 nm) and g-line (wavelength 435.8 nm). In the astigmatism diagram, S shows the amount of astigmatism on the sagittal image plane, and M shows the amount of astigmatism on the meridional image plane. In the distortion diagram, the amount of distortion for the d-line is shown. In the chromatic aberration diagram, the amount of chromatic aberration for the g-line is shown. ω is the half angle of view (°).

[0018] Each lateral aberration diagram will now be described. The lateral aberration diagram for each example shows aberration at each image height, and from top to bottom, shows aberration diagrams for the d-line at image heights of 100%, 90%, 70%, 40%, and the center. S represents the sagittal image plane, and M represents the meridional image plane. In each lateral aberration diagram, Fno represents the F-number, and ω represents the half imaging angle of view (°).

[0019] Next, the characteristic configuration of the imaging optical system of each embodiment will be described.

[0020] The imaging optical system in each embodiment consists of six or seven lenses. This configuration allows for both excellent imaging performance and compactness. The imaging optical system is composed of, arranged in order from the object side to the image side, a first lens group L1 consisting of a single negative lens, an aperture stop SP, and a second lens group L2 with positive refractive power. This configuration allows for both a wide-angle and compactness. The lens surface closest to the object in the imaging optical system includes a region in its paraxial region that is convex toward the object side. This configuration allows for suppression of distortion, which occurs particularly when the angle of view is wide. The lens surface closest to the image in the imaging optical system includes a region in its paraxial region that is concave toward the image side. This configuration allows for a short back focus of the imaging optical system, thereby allowing for a compact imaging optical system as a whole. The lens surface closest to the object in the second lens group L2 includes a region in its paraxial region that is convex toward the object side. This configuration allows for particularly good correction of spherical aberration. The imaging optical system also has at least one convex lens with a refractive index of 1.63 or greater at the d-line. This configuration makes it possible to suppress an increase in the so-called Petzval sum, and in particular to effectively correct field curvature.

[0021] Furthermore, in the imaging optical system, when the distance from the vertex of the lens surface closest to the object to the vertex of the lens surface closest to the image is defined as TD and the distance from the vertex of the lens surface closest to the object to the aperture stop SP is defined as DSP, the imaging optical system of each embodiment satisfies the following conditional expression (1):

[0022] 0.05 < DSP / TD < 0.28 …(1) Conditional expression (1) defines the ratio of the distance DSP from the vertex of the lens surface closest to the object to the aperture stop SP to the distance TD from the vertex of the lens surface closest to the object to the vertex of the lens surface closest to the image. Exceeding the upper limit of conditional expression (1) undesirably increases the value of DSP, which makes the entire imaging optical system larger. Falling below the lower limit of conditional expression (1) undesirably reduces the value of DSP, which makes it difficult to correct coma and chromatic aberration of magnification, among other things.

[0023] Furthermore, the convex lens having a refractive index of 1.63 or more at the d-line preferably has a refractive index of 1.66 or more at the d-line.

[0024] Furthermore, it is more preferable that the convex lens having a refractive index of 1.63 or more at the d-line has a refractive index of 1.69 or more at the d-line.

[0025] Furthermore, it is preferable that the numerical range of conditional expression (1) be within the range of the following conditional expression (1a).

[0026] 0.07 < DSP / TD < 0.27 …(1a) It is more preferable that the numerical range of conditional expression (1) be set to the following conditional expression (1b).

[0027] 0.09 < DSP / TD < 0.26 …(1b) Next, conditions that are preferably satisfied in the imaging optical system of each embodiment will be described: It is preferable that the imaging optical system of each embodiment satisfy one or more of the following conditional expressions (2) to (9).

[0028] It is preferable that the imaging optical system of each embodiment satisfies the following conditional expression (2), where BF is the back focus.

[0029] 0.05 < BF / TD < 0.45 …(2) Conditional expression (2) defines the ratio of the back focal length BF to the distance TD from the vertex of the lens surface closest to the object to the vertex of the lens surface closest to the image. Exceeding the upper limit of conditional expression (2) undesirably increases the BF value, which results in an increase in the overall size of the imaging optical system. Falling below the lower limit of conditional expression (2) undesirably decreases the BF value, which results in a risk of interference between the imaging optical system and the imaging surface.

[0030] In the imaging optical system of each embodiment, it is preferable that the following conditional expression (3) be satisfied, where N21P is the refractive index at the d-line of the lens closest to the object in the second lens unit L2.

[0031] 1.60 < N21P < 2.10 …(3) Conditional expression (3) defines the refractive index N21P at the d-line of the lens closest to the object in the second lens group L2. Exceeding the upper limit of conditional expression (3) undesirably increases the value of N21P, sharply limiting the freedom in selecting glass types due to the characteristics of glass materials. Falling below the lower limit of conditional expression (3) undesirably reduces the value of N21P, making correction of spherical aberration in particular difficult.

[0032] It is preferable that the imaging optical system of each embodiment satisfies the following conditional expression (4), where f is the focal length of the imaging optical system.

[0033] 0.30 < f / TD < 0.60 …(4) Conditional expression (4) defines the ratio of the focal length f of the imaging optical system to the distance TD from the vertex of the lens surface closest to the object to the vertex of the lens surface closest to the image. If the upper limit of conditional expression (4) is exceeded, the value of f becomes too large, which is undesirable because it becomes difficult to achieve a wide angle of view for the entire imaging optical system. If the lower limit of conditional expression (4) is exceeded, the value of TD becomes too large, which is undesirable because it results in an increase in the size of the entire imaging optical system.

[0034] In the imaging optical system of each embodiment, it is preferable that the following conditional expression (5) be satisfied, where f1 is the focal length of the first lens unit L1.

[0035] -1.80 < f1 / f < -0.80 …(5) Conditional expression (5) defines the ratio between the focal length f1 of the first lens group L1 and the focal length f of the imaging optical system. If the upper limit of conditional expression (5) is exceeded, the value of f1 becomes too small, which is undesirable because it makes it particularly difficult to correct distortion. If the lower limit of conditional expression (5) is exceeded, the value of f becomes too small, which is undesirable because it makes it particularly difficult to suppress the so-called Petzval sum.

[0036] In the imaging optical system of each embodiment, it is preferable that the following conditional expression (6) be satisfied, where f2 is the focal length of the second lens unit L2.

[0037] 0.60 < f2 / f < 1.10 …(6) Conditional expression (6) defines the ratio of the focal length f2 of the second lens group L2 to the focal length f of the imaging optical system. If the upper limit of conditional expression (6) is exceeded, the value of f becomes too small, which is undesirable because it makes it particularly difficult to suppress the so-called Petzval sum. If the lower limit of conditional expression (6) is exceeded, the value of f2 becomes too small, which is undesirable because it makes it particularly difficult to correct spherical aberration and coma.

[0038] In the imaging optical system of each embodiment, it is preferable to satisfy the following conditional expression (7), where DSP2 is the distance from the aperture stop SP to the vertex of the lens surface closest to the image side.

[0039] 0.08 < DSP / DSP2 < 0.45 …(7) Conditional expression (7) defines the ratio of the distance DSP from the vertex of the lens surface closest to the object to the aperture stop SP to the distance DSP2 from the aperture stop SP to the vertex of the lens surface closest to the image. Exceeding the upper limit of conditional expression (7) undesirably increases the value of DSP, which results in an excessively large overall imaging optical system. Falling below the lower limit of conditional expression (7) undesirably reduces the value of DSP, which makes it particularly difficult to correct coma and chromatic aberration of magnification.

[0040] In the imaging optical system of each embodiment, it is preferable to satisfy the following conditional expression (8), where L12 is the distance from the vertex of the image-side lens surface of the lens closest to the object to the vertex of the object-side lens surface of the lens adjacent to the image-side of the lens closest to the object:

[0041] 0.08 < L12 / TD < 0.40 …(8) Conditional expression (8) defines the ratio of the distance L12 from the vertex of the image-side lens surface of the lens closest to the object to the vertex of the object-side lens surface of the lens adjacent to the image side of the lens closest to the object to the distance TD from the vertex of the object-side lens surface to the vertex of the lens surface closest to the image. Exceeding the upper limit of conditional expression (8) undesirably increases the value of L12, which results in an increase in the overall size of the imaging optical system. Falling below the lower limit of conditional expression (8) undesirably reduces the value of L12, which results in physical difficulty in constructing the aperture stop SP.

[0042] In the imaging optical system of each embodiment, it is preferable that the following conditional expression (9) be satisfied, where SP1 is the distance from the aperture stop SP to the vertex of the lens surface of the second lens unit L2 closest to the object.

[0043] 0.02 < SP1 / TD < 0.11 …(9) Conditional expression (9) defines the ratio of the distance SP1 from the aperture stop SP to the vertex of the lens surface closest to the object in the second lens group L2 to the distance TD from the vertex of the lens surface closest to the object to the vertex of the lens surface closest to the image. Exceeding the upper limit of conditional expression (9) undesirably increases the value of SP1, which makes the entire imaging optical system larger. Falling below the lower limit of conditional expression (9) undesirably decreases the value of SP1, which makes it physically difficult to configure the aperture stop SP.

[0044] It is more preferable that the numerical ranges of the conditional expressions (2) to (9) be within the ranges of the following conditional expressions (2a) to (9a).

[0045] 0.07 < BF / TD < 0.42 …(2a) 1.66 < N21P < 2.06 …(3a) 0.32 < f / TD < 0.56 …(4a) -1.75 < f1 / f < -0.85 …(5a) 0.65 < f2 / f < 1.05 …(6a) 0.10 < DSP / DSP2 < 0.42 …(7a) 0.10 < L12 / TD < 0.36 …(8a) 0.03 < SP1 / TD < 0.10 …(9a) It is more preferable that the numerical ranges of the conditional expressions (2) to (9) be within the ranges of the following conditional expressions (2b) to (9b).

[0046] 0.09 < BF / TD < 0.39 …(2b) 1.72 < N21P < 2.02 …(3b) 0.34 < f / TD < 0.52 …(4b) -1.70 < f1 / f < -0.90 …(5b) 0.70 < f2 / f < 1.00 …(6b) 0.12 < DSP / DSP2 < 0.39 …(7b) 0.12 < L12 / TD < 0.32 …(8b) 0.04 < SP1 / TD < 0.09 …(9b) Next, the configuration that the imaging optical system of each embodiment preferably satisfies will be described.

[0047] In the imaging optical system of each embodiment, it is preferable that the second lens unit L2 has at least one cemented lens including a positive lens and a negative lens. This configuration makes it possible to effectively correct axial chromatic aberration in particular.

[0048] In addition, it is preferable that the lens surface closest to the image side in the imaging optical system of each embodiment has an aspheric surface having an inflection point. By adopting this configuration, it is possible to effectively correct high-order components of field curvature in particular.

[0049] Numerical Examples 1 to 3 corresponding to Examples 1 to 3, respectively, are shown below.

[0050] In the surface data of each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the axial spacing (distance on the optical axis) between the mth surface and the (m+1)th surface. Here, m is the surface number counted from the light incident side. Also, nd represents the refractive index of each optical element with respect to the d-line, and vd represents the Abbe number of the optical element. Note that the Abbe number vd of a certain material is given by the following when the refractive indices at the d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) of the Fraunhofer lines are Nd, NF, and NC, respectively: νd=(Nd-1) / (NF-NC) It is expressed as:

[0051] In each numerical example, d, focal length (mm), F-number, and half angle of view (°) are all values ​​when the optical system of each example is focused on an object at infinity. "Back focus BF" is the distance on the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed as an air-equivalent length. "Total lens length" is the distance on the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final lens surface plus the back focus. "Lens group" is not limited to cases where it is composed of multiple lenses, but also includes cases where it is composed of a single lens.

[0052] If the optical surface is aspherical, an asterisk (*) is added to the right of the surface number. The aspherical shape is expressed as follows: X is the displacement from the vertex of the surface in the optical axis direction, h is the height from the optical axis in the direction perpendicular to the optical axis, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, A10, and A12 are the aspherical coefficients of each order. x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 +A4×h 4 +A6×h 6 +A8×h 8 +A10×h 10 +A12×h 12 ] In addition, "e±XX" in each aspherical coefficient is "×10± XX " means. [Numerical Example 1] Unit: mm Surface Data Surface number rd nd νd 1* 8.966 0.60 1.49710 81.6 2* 3.174 2.79 3 (Aperture) ∞ 0.78 4 10.750 1.50 1.83481 42.7 5 -8.149 0.12 6 11.325 1.66 1.76385 48.5 7 -7.399 0.45 1.85478 24.8 8 6.460 0.95 9* -10.851 1.18 1.53110 55.9 10* -5.329 1.86 11* 6.574 2.06 1.53110 55.9 12* 7.088 (variable) Image plane ∞ Aspheric data Front page K = 0.00000e+000 A 4= 2.31496e-003 A 6=-3.07394e-004 A 8= 1.14999e-005 A10=-2.30540e-007 2nd side K = 0.00000e+000 A 4= 4.06494e-003 A 6=-6.93509e-005 A 8=-2.34204e-005 A10= 1.29123e-006 9th page K = 0.00000e+000 A 4= 1.50275e-003 A 6=-3.23329e-004 A 8= 8.96630e-005 A10=-5.76909e-006 Side 10 K = 0.00000e+000 A 4= 1.08501e-003 A 6=-2.01049e-004 A 8= 7.80864e-005 A10=-2.68774e-006 Page 11 K = 0.00000e+000 A 4=-4.76032e-003 A 6= 6.37123e-005 A 8=-1.68621e-007 A10=-8.18349e-010 A12=-6.12455e-011 Side 12 K = 0.00000e+000 A 4=-4.22718e-003 A 6= 3.22538e-005 A 8=-3.60035e-007 A10=-4.39326e-010 A12=-5.47494e-012 Various data Focal length 6.80 F-number 2.78 Half angle of view (°) 43.99 Image height 6.56 Lens length 17.10 BF 3.14 When focusing on an object distance of infinity When focusing on an object distance of -0.05m d12 3.14 4.68 First lens unit L1: First surface 1, Last surface 2 Second lens unit L2 First surface 4 Last surface 12 Focus lens group First surface 1 Last surface 12 [Numerical Example 2] Unit: mm Surface Data Surface number rd nd νd 1 34.906 1.50 1.48749 70.2 2 7.830 6.98 3 (Aperture) ∞ 2.90 4 19.590 8.11 1.76385 48.5 5 -17.616 0.12 6 -401.975 4.92 1.49700 81.5 7 -9.013 0.80 1.69895 30.1 8 56.210 4.19 9* -20.273 3.15 1.53110 55.9 10* -11.733 2.25 11* 15.093 3.84 1.53110 55.9 12* 14.843 (variable) Image plane ∞ Aspheric data 9th page K = 0.00000e+000 A 4= 2.33482e-004 A 6=-1.06939e-005 A 8= 1.47254e-007 A10=-5.93963e-010 Side 10 K = 0.00000e+000 A 4= 4.16992e-004 A 6=-1.20937e-005 A 8= 1.56418e-007 A10=-4.94880e-010 Page 11 K = 0.00000e+000 A 4=-1.53327e-005 A 6=-6.52980e-006 A 8= 7.63873e-008 A10=-3.78347e-010 A12=6.82184e-013 Side 12 K = 0.00000e+000 A 4=-1.87910e-004 A 6=-2.21562e-006 A 8= 2.30346e-008 A10=-8.73736e-011 A12= 9.03519e-014 Various data Focal length 18.37 F-number 2.88 Half angle of view (°) 43.99 Image height 17.74 Lens length 52.15 BF 13.39 When focusing on an object distance of infinity When focusing on an object distance of -0.2m d12 13.39 15.73 First lens unit L1: First surface 1, Last surface 2 Second lens unit L2 First surface 4 Last surface 12 Focus lens group First surface 1 Last surface 12 [Numerical Example 3] Unit: mm Surface Data Surface number rd nd νd 1 34.906 1.00 1.48749 70.2 2 7.830 4.81 3 (Aperture) ∞ 2.19 4 25.401 1.00 1.53172 48.8 5 14.007 8.95 1.72916 54.7 6 -17.367 0.12 7 -134.819 7.78 1.49700 81.5 8 -8.979 1.00 1.64769 33.8 9 40.466 1.58 10* -36.368 4.47 1.53110 55.9 11* -13.639 0.50 12* 13.338 5.15 1.53110 55.9 13* 14.930 (variable) Image plane ∞ Aspheric data Side 10 K = 0.00000e+000 A 4= 3.15336e-004 A 6=-5.65148e-006 A 8= 6.89939e-008 A10=-3.37091e-010 Page 11 K = 0.00000e+000 A 4= 2.48252e-004 A 6=-6.08036e-006 A 8= 8.94169e-008 A10=-3.72940e-010 Side 12 K = 0.00000e+000 A 4=-1.89846e-004 A 6=-3.35768e-006 A 8= 3.89835e-008 A10=-1.62903e-010 A12= 1.15004e-013 Page 13 K = 0.00000e+000 A 4=-2.32996e-004 A 6=-8.89458e-007 A 8= 9.80151e-009 A10=-2.98976e-011 A12=-6.00623e-015 Various data Focal length 18.38 F-number 2.88 Half angle of view (°) 43.98 Image height 17.74 Lens length 52.13 BF 13.58 When focusing on an object distance of infinity When focusing on an object distance of -0.2m d13 13.58 15.94 First lens unit L1: First surface 1, Last surface 2 Second lens unit L2: First surface 4, Last surface 13 Focus lens group First surface 1 Last surface 13 The various values ​​in each numerical example are summarized in Table 1 below.

[0053] [Table 1]

[0054] [Imaging device] Next, an embodiment of a digital camera (image pickup device) using the image pickup optical system in each embodiment will be described with reference to Fig. 16. Fig. 16 is a schematic diagram of the main part of the image pickup device.

[0055] In Fig. 16, reference numeral 20 denotes a digital camera body, and 21 denotes any one of the imaging optical systems (imaging optical systems) described in each of Examples 1 to 3. 22 denotes a solid-state imaging element (photoelectric conversion element) such as a CCD sensor or CMOS sensor that is built into the digital camera body 20 and receives and photoelectrically converts an optical image (subject image) formed via the imaging optical system 21. 23 denotes storage means (memory) that records information corresponding to the subject image photoelectrically converted by the imaging element 22, and 24 denotes a display element (finder) formed by a liquid crystal display panel or the like, for observing the subject image formed on the imaging element 22. The camera body 20 may be a so-called single-lens reflex camera having a quick-turn mirror, or a so-called mirrorless camera having no quick-turn mirror.

[0056] In this way, by applying the imaging optical system of the present invention to an imaging device such as a digital still camera, it is possible to provide a compact imaging device that ensures good imaging performance at a wide angle.

[0057] Although the preferred embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and examples, and various combinations, modifications, and changes are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0058] L1 First lens group L2 Second lens group SP aperture stop

Claims

1. An imaging optical system consisting of six or seven lenses, the imaging optical system comprises, arranged in order from the object side to the image side, a first lens group consisting of one negative lens, an aperture stop, and a second lens group having positive refractive power; the lens surface of the imaging optical system closest to the object side includes a convex area in a paraxial area, the lens surface of the imaging optical system closest to the image side has an aspherical shape having an inflection point and includes a concave area in a paraxial area, the lens surface of the second lens group closest to the object side includes a convex area in a paraxial area, the imaging optical system includes at least one convex lens having a refractive index of 1.63 or more at the d-line; In the imaging optical system, when TD is the distance from the vertex of the lens surface closest to the object side to the vertex of the lens surface closest to the image side, DSP is the distance from the vertex of the lens surface closest to the object side to the aperture stop, and SP1 is the distance from the aperture stop to the vertex of the lens surface closest to the object side of the second lens group, 0.05 < DSP / TD < 0.28 0.02 < SP1 / TD < 0.11 An imaging optical system characterized by satisfying the following conditional expression:

2. When the back focus of the imaging optical system is BF, 0.05 < BF / TD < 0.45 2. The imaging optical system according to claim 1, wherein the following condition is satisfied:

3. When the refractive index of the lens closest to the object side in the second lens group is N21P at the d-line, 1.60 < N21P < 2.10 3. The imaging optical system according to claim 1, wherein the following condition is satisfied:

4. When the focal length of the imaging optical system is f, 0.30 < f / TD < 0.60 4. The imaging optical system according to claim 1, wherein the following condition is satisfied:

5. When the focal length of the imaging optical system is f and the focal length of the first lens group is f1, -1.80 < f1 / f < -0.80 5. The imaging optical system according to claim 1, wherein the following condition is satisfied:

6. When the focal length of the imaging optical system is f and the focal length of the second lens group is f2, 0.60 < f2 / f < 1.10 6. The imaging optical system according to claim 1, wherein the following condition is satisfied:

7. In the imaging optical system, when the distance from the aperture stop to the vertex of the lens surface closest to the image side is DSP2, 0.08 < DSP / DSP2 < 0.45 7. The imaging optical system according to claim 1, wherein the following condition is satisfied:

8. In the imaging optical system, when the distance from the vertex of the image-side lens surface of the lens closest to the object side to the vertex of the object-side lens surface of the lens adjacent to the image side of the lens closest to the object side is L12, 0.08 < L12 / TD < 0.40 8. The imaging optical system according to claim 1, wherein the following condition is satisfied:

9. 9. The imaging optical system according to claim 1, wherein the second lens group includes a cemented lens set including a positive lens and a negative lens.

10. An imaging optical system consisting of six or seven lenses, the imaging optical system comprises, arranged in order from the object side to the image side, a first lens group consisting of one negative lens, an aperture stop, and a second lens group having positive refractive power; the lens surface of the imaging optical system closest to the object side includes a convex area in a paraxial area, the lens surface of the imaging optical system closest to the image side has an aspherical shape having an inflection point and includes a concave area in a paraxial area, the lens surface of the second lens group closest to the object side includes a convex area in a paraxial area, the imaging optical system includes at least one convex lens having a refractive index of 1.63 or more at the d-line; In the imaging optical system, when the distance from the vertex of the lens surface closest to the object side to the vertex of the lens surface closest to the image side is TD, the distance from the vertex of the lens surface closest to the object side to the aperture stop is DSP, and the refractive index at the d-line of the lens closest to the object side in the second lens group is N21P, 0.05 < DSP / TD < 0.28 1.72 < N21P < 2.02 An imaging optical system characterized by satisfying the following conditional expression:

11. An imaging apparatus comprising: the imaging optical system according to claim 1; and an imaging element that receives an optical image formed through the imaging optical system.

Images