Optical system and lens apparatus having the same, imaging apparatus, imaging system

Abstract

To provide an optical system that can reduce a ghost while maintaining a high performance and an extremely wide angle, a lens device having the optical system, an imaging device having the optical system, and an imaging system having the optical system.SOLUTION: The optical system includes a first lens group with a negative refractive power, a diaphragm, and a second lens group with a positive refractive power, the first lens group, the diaphragm, the second lens group being sequentially arranged in the direction from an object to an image. A first lens with a negative refractive power is arranged in the nearest position to an object, and has a protruding meniscus shape on an object side. The distance between the object-side surface of the first lens to the diaphragm on an optical axis and the focal distance of the optical system are properly set.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical system, and a lens apparatus, an image pickup apparatus and an image pickup system including the same. Background Art

[0002] In recent years, there has been a demand for an image pickup apparatus that captures an image with a full angle of view of about 180° in order to capture an ultra-wide-angle image that covers the field of view for use in content that provides a sense of realism such as VR. Patent Document 1 proposes an optical system having an angle of view of approximately 180°. Prior Art Literature Patent Literature

[0003] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2009-058817 Summary of the Invention Problem to be Solved by the Invention

[0004] In an ultra-wide-angle lens as disclosed in Patent Document 1, a negative meniscus lens having a large curvature is often arranged closest to the object side. In this case, ghost light that reaches an image plane after being reflected by another lens on the image side and then reflected by the meniscus lens closest to the object side is likely to occur.

[0005] The present invention can provide an optical system that is ultra-wide-angle and high-performance while being capable of reducing ghost, and a lens apparatus, an image pickup apparatus and an image pickup system including the optical system. Means for Solving the Problem

[0006] A lens device as one aspect of the present invention is a lens device having a first optical system and a second optical system arranged in parallel with the first optical system, wherein the first optical system and the second optical system each consist of a first lens group with negative refractive power, an aperture, and a second lens group with positive refractive power, arranged in order from the object side to the image side, the first lens group having a first lens with negative refractive power positioned closest to the object and a second lens positioned adjacent to the image side of the first lens, the first lens having a meniscus shape convex toward the object side, the distance along the optical axis from the object-side surface of the first lens to the aperture being dG1P, the focal length of the optical system being f, the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens being D12, and the focal length of the first lens group being f1 RG2min is the absolute value of the radius of curvature of the image-side surface of the second lens with the smaller absolute value of the radius of curvature, and L is the distance along the optical axis from the object-side surface of the first lens to the image plane. In that case, 14.2 <dG1P / f<34.5 3. 5 <D12 / f≦4.66 -8.0 <f1 / f<-2.5 4.2 <RG2min / f<16.0 25.0 <L / f<40.0 It is characterized by satisfying the following conditional expression. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical system that is ultra-wide-angle, high-performance, and capable of reducing ghosting, as well as a lens device, imaging device, and imaging system having the same. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of the optical system of Example 1. [Figure 2] This is a longitudinal aberration diagram of the optical system in Example 1. [Figure 3] This is a cross-sectional view of the optical system of Example 2. [Figure 4] This is a longitudinal aberration diagram of the optical system in Example 2. [Figure 5] This is a cross-sectional view of the optical system of Example 3. [Figure 6] This is a longitudinal aberration diagram of the optical system in Example 3. [Figure 7]This is a cross-sectional view of the optical system of Example 4. [Figure 8] This is a longitudinal aberration diagram of the optical system in Example 4. [Figure 9] This is an explanatory diagram of the lens device. [Figure 10] This diagram schematically shows two image circles formed by two optical systems. [Figure 11] This is a schematic diagram of the imaging device. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described in detail below with reference to the drawings. In each drawing, the same reference numeral is used for identical components, and redundant descriptions are omitted.

[0010] Figures 1, 3, 5, and 7 are cross-sectional views of the optical systems of Examples 1 to 4, respectively. In each cross-sectional view, the left side is the object side and the right side is the image side. The optical system of each example is composed of multiple lens groups. Note that the lens groups may include aperture diaphragms.

[0011] The optical system of each embodiment has a first lens group L1 with negative refractive power, an aperture diaphragm SP, and a second lens group L2 with positive refractive power, arranged in order from the object side to the image side. In each cross-sectional view, Li represents the i-th lens group (where i is a natural number) from the object side among the lens groups included in the optical system. IP is the image plane, and when the optical system of each embodiment is used as the imaging optical system of a digital still camera or digital video camera, the imaging surface of a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor is placed on it. When the optical system of each embodiment is used as the imaging optical system of a silver halide film camera, a photosensitive surface corresponding to the film surface is placed on the image plane IP.

[0012] Figures 2, 4, 6 and 8 are longitudinal aberration diagrams of the optical systems of Examples 1 to 4, respectively. In the spherical aberration diagram, Fno is the F-number, and indicates the amount of spherical aberration for the d-line (wavelength 587.6 nm) and the g-line (wavelength 435.8 nm). In the astigmatism diagram, ΔS indicates the amount of astigmatism on the sagittal image plane, and ΔM indicates the amount of astigmatism on the meridional image plane. The distortion diagram indicates the amount of distortion with respect to the d-line. The chromatic aberration diagram indicates the amount of chromatic aberration at the g-line. ω is the half angle of view (°) for imaging.

[0013] Next, a characteristic configuration of the optical system of each example will be described.

[0014] A first lens G1 having negative refractive power is disposed closest to the object side. The first lens G1 has a meniscus shape convex toward the object side. With such a configuration, an ultra-wide-angle optical system can be implemented.

[0015] The optical system of each example satisfies the following conditional expression (1).

[0016] 14.2<dG1P / f<34.5 (1) Here, dG1P is the distance on the optical axis from the object-side surface of the first lens G1 to the stop SP. f is the focal length of the optical system of each example.

[0017] When ghost light reflected by the first lens G1 has an angle with respect to the optical axis, the longer the distance on the optical axis from the first lens G1 to the stop SP, the more the ghost light falls outside the effective diameter of the stop SP and the lens disposed on the object side of the stop SP, making it less likely to reach the image plane IP. When the distance on the optical axis from the first lens G1 to the stop SP becomes shorter by falling below the lower limit value of conditional expression (1), ghost light easily passes through the effective diameter of each lens surface and reaches the image plane IP, which is not preferable. When exceeding the upper limit value of conditional expression (1), the first lens group L1 increases in size, making correction of off-axis aberrations difficult, which is not preferable.

[0018] By having the configuration described above, an ultra-wide-angle, high-performance optical system capable of reducing ghosting can be implemented.

[0019] Furthermore, it is preferable that the numerical range of conditional expression (1) be the numerical range of conditional expression (1a) below.

[0020] 15.8 <dG1P / f<31.2 (1a) Furthermore, it is even more preferable to set the numerical range of condition (1) to the numerical range of condition (1b) below.

[0021] 16.2 <dG1P / f<27.0 (1b) Next, we will describe the conditions that are preferable for the optical systems of each embodiment to satisfy.

[0022] The first lens group L1 includes a second lens G2 positioned adjacent to the image side of the first lens G1, and the optical system of each embodiment preferably satisfies the following condition (2).

[0023] 4.2 <RG2min / f<16.0 (2) Here, RG2min is the absolute value of the radius of curvature of the second lens G2, specifically the object-side and image-side surfaces, of which the absolute value of the radius of curvature is smaller.

[0024] If the curvature of the second lens G2 increases below the lower limit of condition (2), ghost light reflected by the second lens G2 is more likely to reach the effective diameter of the first lens G1. As a result, ghost light reflected between the second lens G2 and the first lens G1 can reach the image plane IP, making it more likely to produce ring-shaped ghosting, which is undesirable. If the curvature of the second lens G2 decreases above the upper limit of condition (2), the refractive power of the second lens G2 decreases, resulting in insufficient correction of distortion and image plane aberration, which is also undesirable.

[0025] The first lens group L1 includes a third lens positioned adjacent to the image side of the second lens, and the optical system of each embodiment preferably satisfies the following condition (3).

[0026] 4.2 <RG3min / f<18.9 (3) Here, RG3min is the absolute value of the radius of curvature of the third lens G3, specifically the object-side and image-side surfaces, of which the absolute value of the radius of curvature is smaller.

[0027] If the curvature of the third lens G3 increases below the lower limit of condition (3), ghost light reflected by the third lens G3 is more likely to reach within the effective diameter of the first lens G1. As a result, ghost light reflected between the third lens G3 and the first lens G1 can reach the surface IP, making it more likely to produce ring-shaped ghosting, which is undesirable. If the curvature of the third lens G3 decreases above the upper limit of condition (3), the refractive power of the third lens G3 decreases, resulting in insufficient correction of distortion and image plane aberration, which is also undesirable.

[0028] The optical system of each embodiment preferably satisfies the following condition (4).

[0029] 4.2 <Rmin / f<16.0 (4) Here, Rmin is the absolute value of the radius of curvature of the smallest absolute value of the radius of curvature among all the object-side and image-side faces of all the lenses included in the first lens group L1, excluding the first lens G1.

[0030] If the curvature of the lenses included in the first lens group L1 becomes larger than the lower limit of condition (4), ghost light reflected by the lenses included in the first lens group L1 is more likely to reach within the effective diameter of the first lens G1. Therefore, ghost light reflected between the lenses included in the first lens group L1 and the first lens G1 can reach the image plane IP, making it more likely for ring-shaped ghosting to occur, which is undesirable. If the curvature of the lenses included in the first lens group L1 becomes smaller than the upper limit of condition (4), the refractive power of the lenses included in the first lens group L1 decreases, resulting in insufficient correction of distortion and image plane aberration, which is also undesirable.

[0031] The optical system of each embodiment preferably satisfies the following condition (5).

[0032] 25.0 <L / f<46.0 (5) Here, L is the distance along the optical axis from the object-side surface of the first lens G1 to the image plane.

[0033] If the distance along the optical axis from the object-side surface of the first lens G1 to the image plane increases, ghost light reflected by the first lens G1, if it is at an angle to the optical axis, will deviate outside the aperture SP and the effective diameter of the lens, making it difficult to reach the image plane IP. If the distance along the optical axis from the object-side surface of the first lens G1 to the image plane decreases below the lower limit of condition (5), ghost light will more easily reach the image plane IP, which is undesirable. If the distance along the optical axis from the object-side surface of the first lens G1 to the image plane increases above the upper limit of condition (5), the first lens group L1 will become larger, making it difficult to correct off-axis aberrations, which is undesirable.

[0034] The optical system of each embodiment preferably satisfies the following condition (6).

[0035] 1.6 < (R1 - R2) / (R1 - R2) < 3.0 (6) Here, R1 is the radius of curvature of the object-side surface of the first lens G1, and R2 is the radius of curvature of the image-side surface of the first lens G1.

[0036] Conditional equation (6) defines the shape factor (lens shape) of the first lens G1. If the radius of curvature of the image-side surface of the first lens G1 falls below the lower limit of conditional equation (6), it is undesirable because ghost light reflected from the image-side surface enters the effective diameter of the lens positioned on the image side of the first lens G1, making ghosting more likely. Also undesirable because the refractive power of the first lens G1 becomes large, and distortion becomes too large. If it exceeds the upper limit of conditional equation (6), it is undesirable because the negative refractive power of the first lens G1 becomes weak, making it difficult to capture ultra-wide-angle light rays.

[0037] The optical system of each embodiment preferably satisfies the following condition (7).

[0038] 3.0 <D12 / f<5.6 (7) Here, D1 is the distance along the optical axis from the image-side surface of the first lens G1 to the object-side surface of the second lens G2.

[0039] If the distance along the optical axis from the image-side surface of the first lens G1 to the object-side surface of the second lens G2 becomes long, ghost light reflected by the second lens G2 is more likely to escape outside the effective diameter of the first lens G1, making it less likely for the ghost light to reach the image plane IP. If it falls below the lower limit of condition (7), ghost light reflected between the second lens G2 and the first lens G1 will reach the image plane IP, making it more likely for ring-shaped ghosts to occur, which is undesirable. If it exceeds the upper limit of condition (7), and the distance along the optical axis from the image-side surface of the first lens G1 to the object-side surface of the second lens G2 becomes long, the height of the off-axis rays passing through the second lens G2 becomes low, making it difficult for the second lens G2 to correct off-axis aberrations, which is undesirable.

[0040] The optical system of each embodiment preferably satisfies the following condition (8).

[0041] -8.0 <f1 / f<-1.0 (8) Here, f1 is the focal length of the first lens group L1.

[0042] If the value falls below the lower limit of condition (8), the negative refractive power of the first lens group L1 increases, causing distortion and field curvature, making it difficult to achieve high performance, which is undesirable. If the value exceeds the upper limit of condition (8), the negative refractive power of the first lens group L1 decreases, making it difficult to capture ultra-wide-angle light rays, which is also undesirable.

[0043] The optical system of each embodiment preferably satisfies the following condition (9).

[0044] 3.2 <f2 / f<8.7 (9) Here, f2 is the focal length of the second lens group L2.

[0045] If the value falls below the lower limit of condition equation (9), the positive refractive power of the second lens group L2 becomes too large, making it difficult to adequately correct the aberrations occurring within the second lens group L2, thus hindering high performance, which is undesirable. If the value exceeds the upper limit of condition equation (9), the positive refractive power of the second lens group L2 becomes too small, making it difficult to correct the aberrations occurring in the first lens group L1, which is also undesirable.

[0046] Furthermore, it is preferable that the numerical ranges of conditional expressions (2) to (9) be the numerical ranges of the following conditional expressions (2a) to (9a).

[0047] 4.3 <RG2min / f<15.5 (2a) 4.5 <RG3min / f<17.5 (3a) 4.3 <Rmin / f<15.5 (4a) 29.0 <L / f<43.0 (5a) 1.7 < (R1 - R2) / (R1 - R2) < 2.7 (6a) 3.2 <D12 / f<5.3 (7a) -7.5 <f1 / f<-2.0 (8a) 3.8 <f2 / f<7.8 (9a) Furthermore, it is even more preferable to set the numerical ranges of conditional expressions (2) to (12) to the numerical ranges of the following conditional expressions (2b) to (9b).

[0048] 4.5 <RG2min / f<13.8 (2b) 5.3 <RG3min / f<16.2 (3b) 4.5 <Rmin / f<13.8 (4b) 31.0 <L / f<40.0 (5b) 1.8 < (R1 - R2) / (R1 - R2) < 2.5 (6b) 3.5 <D12 / f<5.0 (7b) -6.5 <f1 / f<-2.5 (8b) 4.8 <f2 / f<7.0 (9b) Next, the optical systems of each embodiment will be described in detail.

[0049] The optical system of each embodiment has a first lens group L1 with negative refractive power, an aperture SP, and a second lens group L2 with positive refractive power, arranged in order from the object side to the image side. The first lens G1 with negative refractive power is positioned closest to the object, and the first lens G1 has a meniscus shape that is convex toward the object side.

[0050] In the optical systems of Examples 1 to 3, the first lens group L1 includes a first lens G1, a second lens G2, a third lens G3, a fourth lens G4, and a prism Pr1, arranged in order from the object side to the image side.

[0051] In the optical system of Example 4, the first lens group L1 has a first lens G1, a second lens G2, a third lens G3, and a prism Pr1 arranged in order from the object side to the image side.

[0052] In each embodiment, the first lens group L1 includes a prism Pr1, but it does not have to. Also, the prism Pr1 may or may not have refractive power.

[0053] Furthermore, in the optical system of each embodiment, the second lens group L2 includes a prism Pr2.

[0054] The numerical values ​​corresponding to Examples 1 to 4 are shown below.

[0055] In the surface data for each numerical example, r represents the radius of curvature of each optical surface, and d (mm) represents the on-axial spacing (distance along the optical axis) between the m-th 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 νd represents the Abbe number of the optical element. Note that the Abbe number νd of a certain material is given by Nd, NF, and NC, respectively, when the refractive indices at the Fraunhofer lines d-line (587.6 nm), F-line (486.1 nm), and C-line (656.3 nm) are Nd, NF, and NC. νd = (Nd-1) / (NF-NC) It is represented as follows.

[0056] Note that "back focus" is the distance along the optical axis from the final lens surface (the lens surface closest to the image) to the paraxial image plane, expressed in terms of air equivalent length. "Total lens length" is the length obtained by adding the back focus to the distance along the optical axis from the frontmost lens surface (the lens surface closest to the object) to the final surface of the optical system.

[0057] [Numerical Example 1] Unit: mm Surface data Face number rd nd νd 1 31.291 1.90 2.00100 29.1 2 11.855 12.09 3 -45.428 1.05 1.71300 53.9 4 15.009 10.52 5 -35.359 0.85 1.90043 37.4 6 28.556 1.35 7 41.900 3.90 1.60342 38.0 8 -15.226 7.10 9 ∞ 11.37 1.85150 40.8 10 ∞ 6.96 11 (aperture) ∞ 1.74 12 -358.576 0.50 1.75500 52.3 13 10.047 3.13 1.59270 35.3 14 -21.792 0.50 15 ∞ 11.37 1.85150 40.8 16 ∞ 0.50 17 16.882 2.50 1.48749 70.2 18 -143.856 3.78 19 15.011 2.75 1.49700 81.6 20 -44.314 0.59 21 39.517 0.75 2.00069 25.5 22 7.122 5.92 1.49700 81.6 23 -38.109 13.21 Image plane ∞ Various data Focal length 3.21 F-number 2.91 Half-angle of view (degrees): 95.1 Image height 5.25 Lens length: 104.33 BF 13.21 Lens group data Group starting plane focal length L1 1 -9.38 L2 12 18.82 Single lens data Lens starting plane, focal length 1 1 -20.05 2 3 -15.71 3 5 -17.43 4 7 19.00 5 9 0.00 6 12 -12.94 7 13 12.04 8 15 0.00 9 17 31.15 10 19 22.91 11 21 -8.78 12 22 12.62 [Numerical Example 2] Unit: mm Surface data Face number rd nd νd 1 38.234 1.90 2.00100 29.1 2 12.083 14.92 3 -52.303 1.05 2.00100 29.1 4 15.958 3.39 5 -20.211 0.85 1.95375 32.3 6 430.947 2.92 7 251.947 3.90 1.76182 26.5 8 -15.877 11.47 9 ∞ 11.69 1.51633 64.1 10 ∞ 4.58 11 (aperture) ∞ 2.95 12 48.345 0.50 1.77250 49.6 13 8.249 4.33 1.59551 39.2 14 -31.525 0.15 15 ∞ 11.69 1.51633 64.1 16 ∞ 0.50 17 30.953 1.81 1.49700 81.6 18 -27.246 4.52 19 13.258 3.12 1.49700 81.6 20 -18.661 0.76 21 -35.746 0.75 2.00100 29.1 22 7.125 5.17 1.48749 70.2 23 -13.655 13.21 Image plane ∞ Various data Focal length 3.20 F-number 2.91 Half-angle (degrees): 90.0 Image height 5.25 Lens length: 106.12 BF 13.21 Lens group data Group starting plane focal length L1 1 -9.07 L2 12 20.32 Single lens data Lens starting plane, focal length 1 1 -18.31 2 3 -12.12 3 5 -20.22 4 7 19.73 5 9 0.00 6 12 -12.94 7 13 11.44 8 15 0.00 9 17 29.46 10 19 16.12 11 21 -5.88 12 22 10.46 [Numerical Example 3] Unit: mm Surface data Face number rd nd νd 1 31.436 1.90 2.00069 25.5 2 12.088 12.33 3 -49.357 1.05 2.00100 29.1 4 32.411 3.00 5 -112.521 0.85 2.00100 29.1 6 35.545 14.40 7 -202.852 3.90 2.00100 29.1 8 -32.408 13.54 9 ∞ 11.62 1.85150 40.8 10 ∞ 4.23 11 (aperture) ∞ 4.80 12 65.452 0.50 1.71999 50.2 13 8.044 2.90 1.59270 35.3 14 -87.265 0.15 15 ∞ 11.62 1.85150 40.8 16 ∞ 0.50 17 17.805 1.91 1.48749 70.2 18 -43.242 4.87 19 14.578 2.82 1.49700 81.6 20 -35.244 0.78 21 -736.379 0.75 2.00069 25.5 22 7.315 5.03 1.49700 81.6 23 -19.079 13.21 Image plane ∞ Various data Focal length 3.21 F-number 2.91 Half-angle (degrees): 90.1 Image height 5.25 Lens length: 116.66 BF 13.21 Lens group data Group starting plane focal length L1 1 -16.26 L2 12 21.14 Single lens data Lens starting plane, focal length 1 1 -20.64 2 3 -19.42 3 5 -26.91 4 7 38.10 5 9 0.00 6 12 -12.78 7 13 12.57 8 15 0.00 9 17 26.14 10 19 21.15 11 21 -7.23 12 22 11.36 [Numerical Example 4] Unit: mm Surface data Face number rd nd νd 1 34.986 1.90 2.00100 29.1 2 11.822 12.43 3 -30.002 1.05 1.90043 37.4 4 22.685 14.27 5 -37.095 5.04 1.90366 31.3 6 -20.209 18.56 7 ∞ 16.90 1.85150 40.8 8 ∞ 10.00 9 (aperture) ∞ 1.26 10 16.261 0.50 1.90043 37.4 11 8.175 2.45 1.63980 34.5 12 33.379 0.41 13 ∞ 8.54 1.85150 40.8 14 ∞ 2.42 15 64.655 1.72 1.48749 70.2 16 -38.843 5.00 17 11.372 2.91 1.49700 81.6 18 -63.549 0.60 19 33.099 0.75 1.95375 32.3 20 6.951 4.80 1.49700 81.6 21 -37.414 13.21 Image plane ∞ Various data Focal length 3.21 F-number 2.91 Half-angle (degrees): 90.1 Image height 5.25 Lens length: 124.73 BF 13.21 Zoom lens group data Group starting plane focal length L1 1 -18.43 L2 10 20.88 Single lens data Lens starting plane, focal length 1 1 -18.60 2 3 -14.21 3 5 43.03 4 7 0.00 5 10 -18.81 6 11 16:30 7 13 0.00 8 15 50.05 9 17 19.66 10 19 -9.36 11 20 12.23 The various values ​​in each numerical example are summarized in Table 1 below. In each numerical example, the d line is used as the reference wavelength, and the values ​​in Table 1 are those at that reference wavelength.

[0058] [Table 1]

[0059] [Lens device] As shown in Figure 9, the lens device has a first optical system 101 that includes the optical system of each embodiment and a second optical system 102 that includes the optical system of each embodiment and is arranged in parallel with the first optical system 101. As shown in Figure 10, the image circles 201 and 202 formed by the first optical system 101 and the second optical system 102 are arranged side by side on the image sensor 200. [Imaging device] Next, an example of a digital still camera (imaging device) using the optical system of each embodiment as the imaging optical system will be described with reference to Figure 11. In Figure 11, 10 is the camera body, and 11 is the imaging optical system composed of any of the optical systems described in Examples 1 to 4. 12 is a solid-state image sensor (photoelectric conversion element) such as a CCD sensor or CMOS sensor, which is built into the camera body 10 and receives the optical image formed by the imaging optical system 11 and converts it into photoelectric light. The camera body 10 may be a so-called single-lens reflex camera with a quick-turn mirror, or a so-called mirrorless camera without a quick-turn mirror.

[0060] By applying the optical systems of each embodiment to imaging devices such as digital still cameras, it is possible to obtain imaging devices with compact lenses. [Imaging System] Furthermore, an imaging system (surveillance camera system) may be configured that includes the optical system of each embodiment and a control unit that controls the optical system. In this case, the control unit can control the optical system. At this time, the control unit does not need to be integrated with the optical system; the control unit may be configured separately from the optical system. For example, a configuration may be adopted in which a control unit (control device) located at a distance has a transmitting unit that sends control signals (commands) for controlling the optical system. With such a control unit, the optical system can be remotely operated.

[0061] Alternatively, the control unit may be equipped with an operating section such as a controller or buttons for remotely controlling the optical system, thereby enabling the optical system to be controlled in response to user input to the operating section. For example, buttons may be provided as the operating section. In this case, the system should be configured so that when the user presses a button, a signal is sent from the control unit to the optical system.

[0062] Furthermore, the imaging system may have a display unit, such as a liquid crystal panel, that displays information about the optical system. In this case, the user can remotely operate the optical system via the control unit while viewing the information about the optical system displayed on the display unit. In this case, the display unit and the control unit may be integrated, for example, by employing a touch panel.

[0063] Although 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 its gist. [Explanation of Symbols]

[0064] L1 First lens group L2 Second lens group SP aperture diaphragm (aperture) G1 First Lens

Claims

1. The first optical system and A lens device having a second optical system arranged in parallel with the first optical system, The first optical system and the second optical system each consist of a first lens group with negative refractive power, an aperture, and a second lens group with positive refractive power, arranged in order from the object side to the image side. The first lens group comprises a first lens with negative refractive power positioned closest to the object, and a second lens positioned adjacent to the image side of the first lens. The first lens has a meniscus shape that is convex toward the object side, When the distance along the optical axis from the object-side surface of the first lens to the aperture is dG1P, the focal length of the optical system is f, the distance along the optical axis from the image-side surface of the first lens to the object-side surface of the second lens is D12, the focal length of the first lens group is f1, the absolute value of the radius of curvature of the surface with the smaller absolute value of the radius of curvature among the object-side surface and image-side surface of the second lens is RG2min, and the distance along the optical axis from the object-side surface of the first lens to the image plane is L, 14.2<dG1P / f<34.5 3.5<D12 / f≦4.66 -8.0<f1 / f<-2.5 4.2<RG2min / f<16.0 25.0<L / f<40.0 A lens device characterized by satisfying the following conditional equation.

2. The first lens group includes a third lens positioned adjacent to the image side of the second lens. When the absolute value of the radius of curvature of the surface with the smaller absolute value of the radius of curvature among the object-side surface and the image-side surface of the third lens is RG3min, 4.2<RG3min / f<18.9 The lens device according to claim 1, characterized in that it satisfies the following condition.

3. When Rmin is the absolute value of the radius of curvature of the surface with the smallest absolute value of the radius of curvature among all the object-side and image-side surfaces of all the lenses in the first lens group except the first lens, 4.2<Rmin / f<16.0 The lens device according to claim 1 or 2, characterized in that it satisfies the following conditional expression.

4. When the radius of curvature of the object-side surface of the first lens is R1 and the radius of curvature of the image-side surface of the first lens is R2, 1.6<(R1+R2) / (R1-R2)<3.0 A lens device according to any one of claims 1 to 3, characterized in that it satisfies the following conditional expression.

5. When the focal length of the second lens group is f2, 3.2<f2 / f<8.7 A lens device according to any one of claims 1 to 4, characterized in that it satisfies the following conditional expression.

6. A lens device according to any one of claims 1 to 5, An imaging device characterized by having a first optical system and an image sensor that receives an image formed by the second optical system.

7. An imaging system characterized by comprising a lens device according to any one of claims 1 to 5, and a control unit for controlling the first optical system and the second optical system.

8. The imaging system according to claim 7, characterized in that the control unit is configured separately from the first optical system and the second optical system, and has a transmitting unit that transmits control signals for controlling the first optical system and the second optical system.

9. The imaging system according to claim 7 or 8, characterized in that the control unit is configured separately from the first optical system and the second optical system, and has an operating section for operating the first optical system and the second optical system.

10. The imaging system according to any one of claims 7 to 9, characterized in that it has a display unit for displaying information relating to the first optical system and the second optical system.

Images