Optical system and optical apparatus

Abstract

An optical system (OL) has, in order from an object side along an optical axis, a first lens group (G1) having a positive refractive power, a second lens group (G2), a third lens group (G3), and a fourth lens group (G4). When focusing from an infinite distance object to a close distance object, the second lens group (G2) and the third lens group (G3) move along the optical axis with different trajectories from each other, and the second lens group (G2) and the third lens group (G3) are composed of three or less lenses in total.

Description

Technical Field

[0001] This invention relates to optical systems, optical devices, and methods for manufacturing optical systems. Background Technology

[0002] Previously, optical systems suitable for digital still cameras or video cameras have been disclosed (for example, see Patent Document 1). In such optical systems, it is required to maintain excellent optical performance from focusing at infinity to focusing at close range.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2019-194630 Summary of the Invention

[0006] The optical system of the first invention has a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially along the optical axis from the object side. The first lens group has positive optical power. When focusing from an object at infinity to a closer object, the second lens group and the third lens group move along the optical axis along different trajectories from each other. The second lens group and the third lens group together consist of three or fewer lenses.

[0007] The optical system of the second invention has a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially along the optical axis from the object side. The first lens group has positive optical power. When focusing from an object at infinity to a closer object, the second lens group and the third lens group move along the optical axis along different trajectories from each other. The optical system satisfies the following condition:

[0008] 0.010 < (Δx2A + Δx3A) / D1 < 0.200

[0009] Wherein, Δx2A: the absolute value of the movement of the second lens group when focusing from an object at infinity to a closer object.

[0010] Δx3A: The absolute value of the movement of the third lens group when focusing from an object at infinity to a closer object.

[0011] D1: The length on the optical axis of the first lens group.

[0012] The optical device of the present invention is configured to include the above-described optical system.

[0013] The present invention discloses a method for manufacturing an optical system having a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially along the optical axis from the object side. The first lens group has positive optical power, and each lens is arranged in the lens barrel in the following manner: when focusing from an object at infinity to a closer object, the second lens group and the third lens group move along the optical axis along different trajectories from each other, and the second lens group and the third lens group together consist of three or fewer lenses. Attached Figure Description

[0014] Figure 1 This is a diagram showing the lens structure of the optical system of the first embodiment.

[0015] Figure 2 (A) Figure 2 (B) are aberration diagrams of the optical system of the first embodiment when focusing at infinity and when focusing at close range.

[0016] Figure 3 This is a diagram showing the lens structure of the optical system of the second embodiment.

[0017] Figure 4 (A) Figure 4 (B) are aberration diagrams of the optical system of the second embodiment when focusing at infinity and when focusing at close range.

[0018] Figure 5 This is a diagram showing the lens structure of the optical system of the third embodiment.

[0019] Figure 6 (A) Figure 6 (B) are aberration diagrams of the optical system of the third embodiment when focusing at infinity and when focusing at close range.

[0020] Figure 7 This is a diagram showing the lens structure of the optical system of the fourth embodiment.

[0021] Figure 8 (A) Figure 8 (B) are aberration diagrams of the optical system of the fourth embodiment when focusing at infinity and when focusing at close range.

[0022] Figure 9 This is a diagram showing the lens structure of the optical system of the fifth embodiment.

[0023] Figure 10 (A) Figure 10 (B) are aberration diagrams of the optical system of the fifth embodiment when focusing at infinity and when focusing at close range.

[0024] Figure 11This is a diagram showing the structure of a camera equipped with an optical system according to various embodiments.

[0025] Figure 12 This is a flowchart illustrating the manufacturing method of the optical system according to various embodiments. Detailed Implementation

[0026] The preferred embodiments of the present invention will be described below. First, according to... Figure 11 A camera (optical device) having an optical system with each embodiment will be described. For example... Figure 11 As shown, the camera 1 consists of a main body 2 and a camera lens 3 mounted on the main body 2. The main body 2 includes an image sensor 4, a main control unit (not shown) for controlling the operation of the digital camera, and an LCD screen 5. The camera lens 3 includes an optical system OL consisting of multiple lens groups and a lens position control mechanism (not shown) for controlling the position of each lens group. The lens position control mechanism consists of a sensor for detecting the position of the lens groups, a motor for moving the lens groups back and forth along the optical axis, and a control circuit for driving the motor.

[0027] Light from the subject is focused by the optical system OL of the camera lens 3 and reaches the image plane I of the image sensor 4. The light from the subject reaching the image plane I is photoelectrically converted by the image sensor 4 and recorded as digital image data in a memory (not shown). The digital image data recorded in the memory can be displayed on the LCD screen 5 according to user operation. Furthermore, this camera can be a mirrorless camera or a single-lens reflex camera with a quick-return mirror. Figure 11 The optical system OL shown schematically illustrates the optical system of the camera lens 3, but the lens structure of the optical system OL is not limited to this structure.

[0028] Next, the optical system of the first embodiment will be described. For example... Figure 1 As shown, the optical system OL (1), as an example of the optical system (photographic lens) OL in the first embodiment, is configured to have a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 arranged sequentially along the optical axis from the object side. The first lens group G1 has positive optical power. When focusing from an object at infinity to a closer object, the second lens group G2 and the third lens group G3 move along the optical axis along different trajectories from each other. In addition, the second lens group G2 and the third lens group G3 together consist of three or fewer lenses.

[0029] According to the first embodiment, an optical system with excellent optical performance from infinity focusing to close-range focusing, and an optical device equipped with the optical system, can be obtained. The optical system OL of the first embodiment may also be... Figure 3The optical system OL(2) shown can also be Figure 5 The optical system OL(3) shown can also be Figure 7 The optical system OL(4) shown can also be Figure 9 The optical system OL(5) shown is illustrated.

[0030] Next, the optical system of the second embodiment will be described. For example... Figure 1 As shown, the optical system OL (1), as an example of the optical system (photographic lens) OL in the second embodiment, is configured to have a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 arranged sequentially along the optical axis from the object side. The first lens group G1 has a positive optical power. When focusing from an object at infinity to a closer object, the second lens group G2 and the third lens group G3 move along the optical axis along different trajectories from each other.

[0031] Under the above structure, the optical system OL of the second embodiment satisfies the following conditional expression (1).

[0032] 0.010<(Δx2A+Δx3A) / D1<0.200…(1)

[0033] Where, Δx2A: the absolute value of the movement of the second lens group G2 when focusing from an object at infinity to a closer object.

[0034] Δx3A: The absolute value of the movement of the third lens group G3 when focusing from an object at infinity to a closer object.

[0035] D1: Length on the optical axis of lens group G1 (first lens group)

[0036] According to the second embodiment, an optical system with excellent optical performance from infinity focusing to close-range focusing, and an optical device equipped with such an optical system, can be obtained. The optical system OL of the second embodiment may also be... Figure 3 The optical system OL(2) shown can also be Figure 5 The optical system OL(3) shown can also be Figure 7 The optical system OL(4) shown can also be Figure 9 The optical system OL(5) shown is illustrated.

[0037] Condition (1) specifies an appropriate relationship between the sum of the movement of the second lens group G2 and the third lens group G3 during focusing and the length on the optical axis of the first lens group G1. By satisfying condition (1), aberration variations during focusing from an object at infinity to a closer object can be suppressed.

[0038] When the corresponding value of conditional expression (1) is lower than the lower limit, the movement of the second lens group G2 and the third lens group G3 during focusing decreases, resulting in a tendency for the optical power of the second lens group G2 and the third lens group G3 to increase, making it difficult to suppress aberration changes during focusing. By setting the lower limit of conditional expression (1) to 0.015, 0.020, 0.025, 0.030, 0.035, 0.040, and further setting it to 0.042, the effect of this embodiment can be obtained more reliably.

[0039] When the corresponding value of conditional expression (1) is higher than the upper limit value, the first lens group G1 becomes shorter, thus tending to increase the optical power of the first lens group G1, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the upper limit value of conditional expression (1) to 0.175, 0.160, 0.150, 0.125, 0.115, 0.110, and further setting it to 0.100, the effect of this embodiment can be obtained more reliably.

[0040] The optical system OL of the first and second embodiments preferably satisfies the following condition (2).

[0041] -0.20<Δx² / f²<0.00…(2)

[0042] Where Δx2: the amount of movement of the second lens group G2 when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -).

[0043] f2: Focal length of the second lens group G2

[0044] Condition (2) specifies the appropriate relationship between the amount of movement of the second lens group G2 during focusing and the focal length of the second lens group G2. By satisfying condition (2), aberration variations during focusing from an object at infinity to a closer object can be suppressed.

[0045] When the corresponding value of conditional expression (2) is lower than the lower limit, the optical power of the second lens group G2 used for focusing becomes stronger, making it difficult to suppress aberration changes during focusing. In addition, the amount of movement of the second lens group G2 used for focusing increases, resulting in an increase in the overall length of the optical system OL. In order to suppress the increase in the overall length of the optical system OL, it is necessary to shorten the first lens group G1 and enhance the optical power of the first lens group G1, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the lower limit of conditional expression (2) to -0.18, -0.15, -0.13, -0.10, -0.09, and further setting it to -0.08, the effects of each embodiment can be obtained more reliably.

[0046] When the corresponding value of condition (2) reaches the upper limit, it is difficult to ensure the optical power or movement of the second lens group G2 for focusing, which is not preferable. By setting the upper limit of condition (2) to -0.01, and further to -0.02, the effects of each embodiment can be obtained more reliably.

[0047] The optical system OL of the first and second embodiments preferably satisfies the following condition (3).

[0048] -0.20<Δx3 / f3<0.00…(3)

[0049] Where Δx3: the amount of movement of the third lens group G3 when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -).

[0050] f3: Focal length of the third lens group G3

[0051] Condition (3) specifies the appropriate relationship between the amount of movement of the third lens group G3 and the focal length of the third lens group G3 during focusing. By satisfying condition (3), aberration variations during focusing from an object at infinity to a closer object can be suppressed.

[0052] When the corresponding value of conditional expression (3) is lower than the lower limit, the optical power of the third lens group G3, which is used for focusing, becomes stronger, making it difficult to suppress aberration changes during focusing. In addition, the amount of movement of the third lens group G3, which is used for focusing, increases, resulting in an increase in the overall length of the optical system OL. In order to suppress the increase in the overall length of the optical system OL, it is necessary to shorten the first lens group G1 and increase the optical power of the first lens group G1, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the lower limit of conditional expression (3) to -0.18, -0.16, and further to -0.15, the effects of each embodiment can be obtained more reliably.

[0053] When the corresponding value of condition (3) reaches the upper limit, it is difficult to ensure the optical power or movement of the third lens group G3 for focusing, which is not preferable. By setting the upper limit of condition (3) to -0.01, the effects of each embodiment can be obtained more reliably.

[0054] The optical system OL of the first and second embodiments preferably satisfies the following condition (4).

[0055] 1.00 <f2 / (-f3)<4.00…(4)

[0056] Where f2 is the focal length of the second lens group G2.

[0057] f3: Focal length of the third lens group G3

[0058] Condition (4) specifies the appropriate relationship between the focal length of the second lens group G2 and the focal length of the third lens group G3. By satisfying condition (4), aberration variations when focusing from an object at infinity to a closer object can be suppressed.

[0059] When the corresponding value of conditional expression (4) is lower than the lower limit, the optical power of the second lens group G2, which is used for focusing, becomes stronger, making it difficult to suppress aberration changes during focusing. By setting the lower limit of conditional expression (4) to 1.05, 1.10, 1.15, 1.20, 1.25, 1.30, and further setting it to 1.35, the effects of each implementation method can be obtained more reliably.

[0060] When the corresponding value of conditional expression (4) is higher than the upper limit value, the optical power of the third lens group G3, which is used for focusing, becomes stronger, making it difficult to suppress aberration changes during focusing. By setting the upper limit value of conditional expression (4) to 3.80, 3.50, 3.25, 3.00, 2.85, 2.80, 2.75, and further setting it to 2.70, the effects of each implementation method can be obtained more reliably.

[0061] The optical system OL of the first and second embodiments preferably satisfies the following conditional expression (5).

[0062] -3.00<Δx2 / Δx3<-0.20…(5)

[0063] Where Δx2: the amount of movement of the second lens group G2 when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -).

[0064] Δx3: The amount of movement of the third lens group G3 when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is +, and the sign of the movement towards the object is -).

[0065] Condition (5) specifies the appropriate relationship between the amount of movement of the second lens group G2 and the amount of movement of the third lens group G3 during focusing. By satisfying condition (5), various aberrations such as axial chromatic aberration or spherical aberration can be well corrected.

[0066] When the corresponding value of conditional expression (5) is lower than the lower limit, the movement of the second lens group G2, which is used for focusing, increases, thereby increasing the overall length of the optical system OL. In order to suppress the increase in the overall length of the optical system OL, it is necessary to shorten the first lens group G1 and enhance the optical power of the first lens group G1, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the lower limit of conditional expression (5) to -2.85, -2.70, -2.60, -2.50, -2.45, and further setting it to -2.40, the effects of each implementation method can be obtained more reliably.

[0067] When the corresponding value of conditional expression (5) is higher than the upper limit, the movement of the third lens group G3, which is used for focusing, increases, resulting in an increase in the overall length of the optical system OL. In order to suppress the increase in the overall length of the optical system OL, it is necessary to shorten the first lens group G1 and enhance the optical power of the first lens group G1, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the upper limit of conditional expression (5) to -0.25, -0.30, -0.35, -0.40, -0.45, and further setting it to -0.50, the effects of each implementation method can be obtained more reliably.

[0068] In the optical system OL of the first and second embodiments, it is preferable that the fourth lens group G4 has an image stabilization group that can move in a manner having a displacement component perpendicular to the optical axis in order to correct image jitter, and has a negative optical power. This suppresses aberration variations during image jitter correction.

[0069] In the optical system OL of the first and second embodiments, it is preferable that the image stabilization group consists of two or more lenses. This allows for the suppression of aberration variations during image shake correction.

[0070] The optical system OL of the first and second embodiments preferably satisfies the following condition (6).

[0071] -8.50 <f1 / fVR<-3.00…(6)

[0072] Where f1 is the focal length of the first lens group G1.

[0073] fVR: Focal length of the image stabilization group

[0074] Condition (6) specifies the appropriate relationship between the focal length of the first lens group G1 and the focal length of the image stabilization group. By satisfying condition (6), aberration variations during image shake correction can be suppressed.

[0075] When the corresponding value of conditional expression (6) is lower than the lower limit, the optical power of the image stabilization group becomes stronger, making it difficult to suppress aberration changes when correcting image shake. By setting the lower limit of conditional expression (6) to -8.25, -8.10, -8.00, -7.85, -7.70, -7.50, -7.30, and further setting it to -7.25, the effects of each implementation method can be obtained more reliably.

[0076] When the corresponding value of conditional expression (6) is higher than the upper limit value, the optical power of the first lens group G1 becomes stronger, making it difficult to correct various aberrations such as axial chromatic aberration or spherical aberration. By setting the upper limit value of conditional expression (6) to -3.15, -3.30, -3.50, -3.65, -3.80, -4.00, -4.10, -4.20, and further setting it to -4.25, the effects of each implementation method can be obtained more reliably.

[0077] The optical system OL of the first and second embodiments preferably satisfies the following condition (7).

[0078] 0.45 < β2 < 0.80…(7)

[0079] Where β2: the magnification of the second lens group G2 when focusing on an object at infinity.

[0080] Condition (7) specifies an appropriate range for the magnification of the second lens group G2 when focusing on an object at infinity. By satisfying condition (7), variations in aberrations, primarily spherical aberration, during focusing can be suppressed.

[0081] When the corresponding value of condition (7) is lower than the lower limit, it is difficult to suppress the variation of various aberrations during focusing. By setting the lower limit of condition (7) to 0.46, 0.47, 0.48, and further setting it to 0.49, the effects of each implementation method can be obtained more reliably.

[0082] When the corresponding value of condition (7) is higher than the upper limit, it is difficult to suppress the variation of various aberrations during focusing. By setting the upper limit of condition (7) to 0.78, 0.75, 0.73, and further to 0.70, the effects of each implementation method can be obtained more reliably.

[0083] The optical system OL of the first and second embodiments preferably satisfies the following condition (8).

[0084] 0.20<1 / β3<0.50…(8)

[0085] Where β3: the magnification of the third lens group G3 when focusing on an object at infinity.

[0086] Condition (8) specifies an appropriate range for the magnification of the third lens group G3 when focusing on an object at infinity. By satisfying condition (8), variations in aberrations, primarily spherical aberration, during focusing can be suppressed.

[0087] When the corresponding value of conditional expression (8) is lower than the lower limit, it is difficult to suppress the variation of various aberrations during focusing. By setting the lower limit of conditional expression (8) to 0.22, 0.24, 0.25, and further setting it to 0.26, the effects of each implementation method can be obtained more reliably.

[0088] When the corresponding value of conditional expression (8) is higher than the upper limit value, it is difficult to suppress the variation of various aberrations during focusing. By setting the upper limit value of conditional expression (8) to 0.48, 0.46, 0.45, and further setting it to 0.44, the effects of each implementation method can be obtained more reliably.

[0089] The optical system OL of the first and second embodiments preferably satisfies the following condition (9).

[0090] {β2+(1 / β2)} -2 <0.25…(9)

[0091] Where β2: the magnification of the second lens group G2 when focusing on an object at infinity.

[0092] Condition (9) specifies an appropriate range for the magnification of the second lens group G2 when focusing on an object at infinity. By satisfying condition (9), it is possible to suppress variations in various aberrations such as spherical aberration, distortion, and coma during focusing and reduce the amount of movement of the focusing group.

[0093] The corresponding value of condition (9) is preferably within the range of condition. For example, if the lower limit of condition (9) is set to 0.10, 0.12, 0.14, or further set to 0.15, the effects of each implementation method can be obtained more reliably.

[0094] When the corresponding value of conditional expression (9) is higher than the upper limit, it is difficult to suppress the variation of various aberrations during focusing. By setting the upper limit of conditional expression (9) to 0.24, and further setting it to 0.23, the effects of each implementation method can be obtained more reliably.

[0095] The optical system OL of the first and second embodiments preferably satisfies the following conditional expression (10).

[0096] {β3+(1 / β3)} -2 <0.18…(10)

[0097] Where β3: the magnification of the third lens group G3 when focusing on an object at infinity.

[0098] Condition (10) specifies an appropriate range for the magnification of the third lens group G3 when focusing on an object at infinity. By satisfying condition (10), it is possible to suppress variations in various aberrations such as spherical aberration, distortion, and coma during focusing and reduce the amount of movement of the focusing group.

[0099] The corresponding value of condition (10) is preferably within the range of condition. For example, if the lower limit of condition (10) is set to 0.03 and further set to 0.05, the effects of each implementation method can be obtained more reliably.

[0100] When the corresponding value of conditional expression (10) is higher than the upper limit value, it is difficult to suppress the variation of various aberrations during focusing. By setting the upper limit value of conditional expression (10) to 0.16, 0.15, and further to 0.14, the effects of each implementation method can be obtained more reliably.

[0101] In the optical system OL of the first and second embodiments, it is preferable that the first lens group G1 has a positive lens (L15) that satisfies the following conditional formulas (11) to (13).

[0102] ndL1+(0.01425×νdL1)<2.12…(11)

[0103] νdL1<35.00…(12)0.702<θgFL1+(0.00316×νdL1)…(13)

[0104] Where ndL1: the refractive index of the positive lens for the d-line.

[0105] νdL1: Abbe number of the positive lens relative to the d-line.

[0106] θgFL1: The relative partial dispersion of the positive lens, defined by the following formula when the refractive index of the positive lens for the g line is set as ngL1, the refractive index of the positive lens for the F line is set as nFL1, and the refractive index of the positive lens for the C line is set as nCL1.

[0107] θgFL1=(ngL1-nFL1) / (nFL1-nCL1)

[0108] In addition, the Abbe number νdL1 of the positive lens, with reference to the d-line, is defined by the following formula.

[0109] νdL1=(ndL1-1) / (nFL1-nCL1).

[0110] Condition (11) specifies the appropriate relationship between the refractive index of the positive lens in the first lens group G1 relative to the d-line and the Abbe number of the positive lens relative to the d-line. By satisfying condition (11), it is possible to perform good correction of reference aberrations such as spherical aberration and coma, as well as correction of primary chromatic aberration (achromatic aberration).

[0111] When the corresponding value of condition (11) is higher than the upper limit value, for example, the petrogram becomes smaller, making it difficult to correct for image plane curvature, which is therefore not preferred. By setting the upper limit value of condition (11) to 2.11, 2.10, 2.09, 2.08, 2.07, and further to 2.06, the effects of each implementation can be obtained more reliably.

[0112] The lower limit of condition (11) can also be set to 1.83. When the corresponding value of condition (11) is lower than this lower limit, the correction of reference aberration and color difference becomes excessive, which is not preferred. By setting the lower limit of condition (11) to 1.85, 1.90, 1.95, and further to 1.98, the effects of each implementation method can be obtained more reliably.

[0113] Condition (12) specifies the appropriate range of the Abbe number of the positive lens in the first lens group G1, with the d-line as the reference. By satisfying condition (12), it is possible to perform good correction of reference aberrations such as spherical aberration and coma, as well as correction of primary chromatic aberration (achromatic aberration).

[0114] When the corresponding value of conditional expression (12) is higher than the upper limit value, it is difficult to correct axial chromatic aberration, for example, in a lens group where the positive lens is positioned on the image plane side, and therefore it is not preferred. By setting the upper limit value of conditional expression (12) to 32.50, 32.00, 31.50, 31.00, 30.50, 30.00, and further setting it to 29.50, the effects of each embodiment can be obtained more reliably.

[0115] Alternatively, the lower limit of conditional expression (12) can be set to 18.00. When the corresponding value of conditional expression (12) is lower than this lower limit, the correction of reference aberration and color difference becomes excessive, which is not preferred. By setting the lower limit of conditional expression (12) to 18.50, 19.00, 19.50, and further to 20.00, the effects of each implementation method can be obtained more reliably.

[0116] Condition (13) appropriately specifies the aberrant dispersion of the positive lens in the first lens group G1. By satisfying condition (13), in addition to primary achromatic correction, secondary spectra can be well corrected in chromatic aberration correction.

[0117] When the corresponding value of condition (13) is lower than the lower limit, the abnormal dispersion of the positive lens becomes smaller, making it difficult to correct chromatic aberration. By setting the lower limit of condition (13) to 0.704, 0.708, 0.710, 0.712, and further to 0.715, the effects of each implementation method can be obtained more reliably.

[0118] The upper limit of condition (13) can also be set to 0.900. When the corresponding value of condition (13) is higher than this upper limit, the color difference correction becomes excessive, which is not preferred. By setting the upper limit of condition (13) to 0.880, 0.850, 0.825, and further to 0.800, the effects of each implementation method can be obtained more reliably.

[0119] The optical system OL of the first and second embodiments preferably has lenses (L12, L13) that satisfy the following condition (14). In addition, in order to distinguish it from other lenses, a lens that satisfies condition (14) is sometimes called a specific lens.

[0120] 80.00<νdL2…(14)

[0121] Where, νdL2: Abbe number of a specific lens relative to the d-line.

[0122] Condition (14) specifies the appropriate range of the Abbe number of a particular lens based on the d-line. By satisfying condition (14), axial chromatic aberration and magnification chromatic aberration can be well corrected.

[0123] When the corresponding value of condition (14) is lower than the lower limit, it is difficult to correct the axial color difference and magnification color difference. By setting the lower limit of condition (14) to 81.00, 81.80, 82.50, 84.00, 85.50, 87.00, and further setting it to 90.00, the effects of each implementation method can be obtained more reliably.

[0124] The upper limit of condition (14) can also be set to 110.00. When the corresponding value of condition (14) is higher than this upper limit, the correction of axial color difference and magnification color difference becomes excessive, which is not preferred. By setting the upper limit of condition (14) to 107.50, 105.00, 102.50, 100.00, and further setting it to 98.00, the effects of each embodiment can be obtained more reliably.

[0125] The optical system OL of the first and second embodiments preferably satisfies the following conditional expression (15).

[0126] 3.50°<2ω<8.50°…(15)

[0127] Where 2ω: the full field of view of the optical system OL

[0128] Condition (15) specifies an appropriate range of the full field of view of the optical system OL. By satisfying condition (15), a telephoto optical system with a long focal length can be obtained, which is therefore preferred. By setting the lower limit of condition (15) to 3.80°, and further to 4.00°, the effects of each embodiment can be obtained more reliably. In addition, by setting the upper limit of condition (15) to 8.00°, 7.50°, 7.00°, and further to 6.50°, the effects of each embodiment can be obtained more reliably.

[0129] In the optical system OL of the first and second embodiments, it is preferable that, when focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis towards the object side, and the third lens group G3 moves along the optical axis towards the image plane side. This allows for effective correction of aberrations during focusing from an object at infinity to a closer object. Furthermore, it enables efficient use of the space of the optical system OL, maintaining good optical performance while minimizing the overall length of the optical system OL.

[0130] In the optical system OL of the first and second embodiments, the second lens group G2 consists of a single lens. This makes the second lens group G2 lighter, enabling high-speed focusing from objects at infinity to objects at close range. Furthermore, since it is not necessary to reduce the lens diameter for the sake of lightweight focusing, the optical power of, for example, the first lens group G1 will not become excessively strong, allowing for good correction of various aberrations such as axial chromatic aberration and spherical aberration.

[0131] In the optical system OL of the first and second embodiments, it is preferable that the third lens group G3 is composed of a single lens component. This makes the third lens group G3 lighter, thus enabling high-speed focusing from an object at infinity to a closer object. Furthermore, since it is not necessary to reduce the lens diameter for the sake of lightweight focusing groups, the optical power of, for example, the first lens group G1 will not become excessively strong, and various aberrations such as axial chromatic aberration and spherical aberration can be well corrected. In each embodiment, the lens component refers to a single lens or a combined lens.

[0132] The optical system OL of the first and second embodiments preferably has an aperture stop (S) disposed on the image plane side relative to the second lens group G2. Therefore, since the aperture is disposed in the optical system OL where the beam diameter is smaller, the outer diameter of the lens barrel can be miniaturized.

[0133] Furthermore, it is preferable that the aperture (aperture stop S) is positioned on the image plane side relative to the third lens group G3. Therefore, since the aperture is positioned in the optical system OL where the beam diameter decreases, the outer diameter of the lens barrel can be miniaturized.

[0134] In the optical system OL of the first and second embodiments, the second lens group G2 is a first focusing lens group that moves during focusing, and the first focusing lens group can have either positive or negative optical power. Furthermore, the third lens group G3 is a second focusing lens group that moves during focusing, and the second focusing lens group can also have either positive or negative optical power.

[0135] In the optical system OL of the first and second embodiments, the second lens group G2 is the first focusing lens group that moves during focusing, and the third lens group G3 is the second focusing lens group that moves during focusing. Alternatively, one or more lenses with positive or negative optical power may be provided between the first focusing lens group and the second focusing lens group.

[0136] Next, refer to Figure 12 The manufacturing method of the optical system OL according to the first embodiment will be summarized. First, a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 with positive optical power are arranged sequentially along the optical axis from the object side (step ST1). Next, the second lens group G2 and the third lens group G3 are configured such that when focusing from an object at infinity to a closer object, they move along the optical axis along different trajectories (step ST2). In addition, each lens is arranged in the lens barrel such that the second lens group G2 and the third lens group G3 consist of three or fewer lenses in total. According to this manufacturing method, an optical system with excellent optical performance from focusing at infinity to focusing at close range can be manufactured. Next, similar to the case of the first embodiment, refer to... Figure 12 The manufacturing method of the optical system OL according to the second embodiment will be summarized. First, a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 with positive optical power are arranged sequentially along the optical axis from the object side (step ST1). Next, the second lens group G2 and the third lens group G3 are configured such that, when focusing from an object at infinity to a closer object, they move along the optical axis along different trajectories from each other (step ST2). In addition, each lens is arranged in the lens barrel in a manner that at least satisfies the above-described condition (1). According to this manufacturing method, an optical system with excellent optical performance from focusing at infinity to focusing at close range can be manufactured.

[0137] Example

[0138] Hereinafter, the optical system OL of each embodiment will be described with reference to the accompanying drawings. Figure 1 , Figure 3 , Figure 5 , Figure 7 , Figure 9 The optical system shown is one of embodiments 1 to 5.

[0139] A cross-sectional view of the structure and power distribution of OL{OL(1)~OL(5)}. In the cross-sectional views of the optical systems OL(1)~OL(5) in embodiments 1 to 5, arrows are used along with the word "focus" to indicate the direction of movement along the optical axis of the second and third lens groups when focusing on an object from infinity to a closer distance. In addition, arrows are used along with the word "image stabilization" to indicate the direction of movement of a portion of the fourth lens group when it corrects image shake as an image stabilization group.

[0140] In these Figure 1 , Figure 3 , Figure 5 , Figure 7 , Figure 9 In this embodiment, lens groups are represented by a combination of the symbol G and numbers, and individual lenses are represented by a combination of the symbol L and numbers. To prevent excessive complexity due to the increased variety and number of symbols and numbers, a separate combination of symbols and numbers is used to represent lens groups, etc., for each embodiment. Therefore, even if the same combination of symbols and numbers is used across embodiments, it does not necessarily mean that they are identical structures.

[0141] Tables 1 through 5 are shown below. Table 1 shows the parameter data in the first embodiment, Table 2 shows the parameter data in the second embodiment, Table 3 shows the parameter data in the third embodiment, Table 4 shows the parameter data in the fourth embodiment, and Table 5 shows the parameter data in the fifth embodiment. In each embodiment, the d-line (wavelength λ = 587.6 nm) and the g-line (wavelength λ = 435.8 nm) are selected as the objects for calculating aberration characteristics.

[0142] In the [Overall Parameters] table, f represents the focal length of the entire lens system, FNO represents the F-number, 2ω represents the field of view (in degrees, ω is the half field of view), and Y represents the image height. TL represents the distance along the optical axis from the front of the lens to the rear surface of the lens plus Bf when focusing at infinity. Bf represents the distance along the optical axis from the rear surface of the lens to the image plane I when focusing at infinity (back focal length). Additionally, in the [Overall Parameters] table, fVR represents the focal length of the image stabilization group. Δx2 represents the amount of movement of the second lens group when focusing from an object at infinity to a closer object. Δx3 represents the amount of movement of the third lens group when focusing from an object at infinity to a closer object. Furthermore, regarding the movement of the lens groups, the sign of the movement towards the image plane is +, and the sign of the movement towards the object is -. β2 represents the magnification of the second lens group when focusing on an object at infinity. β3 represents the magnification of the third lens group when focusing on an object at infinity.

[0143] In the [Lens Parameters] table, the surface number indicates the order of the optical surfaces from the object side along the direction of light travel; R represents the radius of curvature of each optical surface (the surface with the center of curvature on the image side is positive); D represents the distance on the optical axis from each optical surface to the next optical surface (or image surface), i.e., the surface spacing; nd represents the refractive index of the optical component material with respect to the d-line; νd represents the Abbe number of the optical component material with respect to the d-line; and θgF represents the relative partial dispersion of the optical component material. "∞" for the radius of curvature indicates a plane or opening; (aperture S) indicates the aperture stop S. The refractive index of air, nd = 1.00000, is omitted.

[0144] Let ng be the refractive index of the material of the optical component relative to the g line (wavelength λ = 435.8 nm), let nF be the refractive index of the material of the optical component relative to the F line (wavelength λ = 486.1 nm), and let nC be the refractive index of the material of the optical component relative to the C line (wavelength λ = 656.3 nm). Then, the relative partial dispersion θgF of the material of the optical component is defined by the following equation (A).

[0145] θgF=(ng-nF) / (nF-nC)…(A)

[0146] In the [Variable Interval Data] table, the plane interval at plane number i, where the plane interval is (Di), is shown in the [Lens Parameters] table. In the [Variable Interval Data] table, f represents the focal length of the entire lens system, and β represents the magnification.

[0147] The table in [Lens Group Data] shows the initial plane (the plane closest to the object) and focal length of each lens group.

[0148] In all parameter values ​​below, the focal length f, radius of curvature R, interplanar spacing D, and other lengths will generally be expressed in "mm" unless otherwise specified. However, the same optical performance can be obtained even if the optical system is scaled up or down, so it is not limited to this.

[0149] The descriptions of the tables up to this point are the same in all embodiments, and repeated descriptions are omitted below.

[0150] (First Embodiment)

[0151] use Figures 1-2 Table 1 describes the first embodiment. Figure 1 This is a diagram illustrating the lens structure of the optical system of the first embodiment. The optical system OL(1) of the first embodiment consists of a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power, arranged sequentially along the optical axis from the object side. When focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis to the object side, and the third lens group G3 moves along the optical axis to the image side, with the spacing between adjacent lens groups changing. In addition, during focusing, the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane I. An aperture stop S is disposed between the third lens group G3 and the fourth lens group G4. The symbols (+) or (-) attached to the designation of each lens group indicate the optical power of each lens group, which is the same in all the following embodiments.

[0152] The first lens group G1 consists of a combined lens consisting of a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a biconvex positive lens L13, a biconcave negative lens L14, a biconvex positive lens L15, and a biconcave negative lens L16 arranged sequentially along the optical axis from the object side, and a positive meniscus lens L17 with its convex surface facing the object side.

[0153] The second lens group G2 consists of a positive meniscus lens L21 with its convex surface facing the object. The third lens group G3 consists of a negative meniscus lens L31 with its convex surface facing the object. In other words, the second lens group G2 and the third lens group G3 together consist of two lenses.

[0154] The fourth lens group G4 consists of a concave negative lens L41, a conjoined lens formed by combining a positive meniscus lens L42 (concave side facing the object) and a concave negative lens L43, a biconvex positive lens L44, a biconvex positive lens L45, a conjoined lens formed by combining a negative meniscus lens L46 (convex side facing the object) and a biconvex positive lens L47, and a concave negative lens L48, arranged sequentially along the optical axis from the object side. An optical filter FL is positioned between the positive lens L45 and the negative meniscus lens L46 (of the conjoined lens) in the fourth lens group G4. An image plane I is positioned on the image side of the fourth lens group G4.

[0155] In this embodiment, the negative lens L41 of the fourth lens group G4, together with the positive meniscus lens L42 and the negative lens L43, constitutes an image stabilization group that can move in a direction perpendicular to the optical axis to correct for displacement of the imaging position (image jitter on image plane I) caused by hand tremors, etc. The positive lens L15 of the first lens group G1 is equivalent to a positive lens that satisfies the above-described conditions (11) to (13). The positive meniscus lens L12, positive lens L13, and positive meniscus lens L17 of the first lens group G1, the positive meniscus lens L21 of the second lens group G2, and the negative lens L43 of the fourth lens group G4 are equivalent to lenses (specific lenses) that satisfy the above-described condition (14).

[0156] Table 1 below shows the values ​​of the parameters of the optical system of the first embodiment.

[0157] (Table 1)

[0158] [Overall Parameters]

[0159]

[0160] [Lens Parameters]

[0161]

[0162]

[0163] [Variable Interval Data]

[0164]

[0165] [Lens Group Data]

[0166]

[0167] Figure 2 (A) is a diagram of aberrations when the optical system of the first embodiment is focused at infinity. Figure 2(B) is an aberration diagram of the optical system of the first embodiment during close-range focusing. In the aberration diagrams during infinity focusing, FNO represents the F-value and Y represents the image height. In the aberration diagrams during close-range focusing, NA represents the numerical aperture and Y represents the image height. Additionally, the spherical aberration diagram shows the F-value or numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and distortion diagram show the maximum image height, and the coma diagram shows the values ​​of each image height. d represents the d-line (wavelength λ = 587.6 nm), and g represents the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, solid lines represent the sagittal image plane, and dashed lines represent the meridional image plane. Furthermore, the same symbols as in this embodiment are used in the aberration diagrams of the embodiments shown below, and repeated descriptions are omitted.

[0168] As can be seen from the various aberration diagrams, the optical system of the first embodiment effectively corrects various aberrations throughout the entire region from focusing at infinity to focusing at close range, and has excellent imaging performance.

[0169] (Second Embodiment)

[0170] use Figures 3-4 Table 2 illustrates the second embodiment. Figure 3 This is a diagram illustrating the lens structure of the optical system of the second embodiment. The optical system OL(2) of the second embodiment consists of a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power, arranged sequentially along the optical axis from the object side. When focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis to the object side, and the third lens group G3 moves along the optical axis to the image side, with the spacing between adjacent lens groups changing. Furthermore, during focusing, the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane I. An aperture stop S is positioned between the third lens group G3 and the fourth lens group G4.

[0171] The first lens group G1 consists of a combined lens consisting of a biconvex positive lens L11, a positive meniscus lens L12 with its convex surface facing the object side, a biconvex positive lens L13, a biconcave negative lens L14, a biconvex positive lens L15, and a biconcave negative lens L16 arranged sequentially along the optical axis from the object side, and a positive meniscus lens L17 with its convex surface facing the object side.

[0172] The second lens group G2 consists of a biconvex positive lens L21. The third lens group G3 consists of a concave positive meniscus lens L31 facing the object side and a biconcave negative lens L32, forming a conjoined lens (with negative optical power). In other words, the second lens group G2 and the third lens group G3 consist of a total of three lenses.

[0173] The fourth lens group G4 consists of a combined lens formed by joining a positive meniscus lens L41 (concave side facing the object) and a biconcave negative lens L42, arranged sequentially along the optical axis from the object side; a biconcave negative lens L43; a biconvex positive lens L44; a biconvex positive lens L45 and a negative meniscus lens L46 (concave side facing the object); a biconvex positive lens L47; and a negative meniscus lens L48 (concave side facing the object). An image plane I is positioned on the image side of the fourth lens group G4.

[0174] In this embodiment, the positive meniscus lens L41 and negative lenses L42 and L43 of the fourth lens group G4 constitute an image stabilization group that can move in a direction perpendicular to the optical axis to correct for displacement of the imaging position (image jitter on image plane I) caused by hand tremors, etc. The positive lens L15 of the first lens group G1 is equivalent to a positive lens that satisfies the above-described conditions (11) to (13). The positive meniscus lens L12, positive lens L13 and positive meniscus lens L17 of the first lens group G1 are equivalent to lenses (specific lenses) that satisfy the above-described condition (14).

[0175] Table 2 below shows the values ​​of the parameters of the optical system of the second embodiment.

[0176] (Table 2)

[0177] [Overall Parameters]

[0178]

[0179] [Lens Parameters]

[0180]

[0181]

[0182] [Variable Interval Data]

[0183]

[0184] [Lens Group Data]

[0185]

[0186] Figure 4 (A) is a diagram of aberrations when the optical system of the second embodiment is focused at infinity. Figure 4 (B) is an aberration diagram of the optical system of the second embodiment during close-range focusing. As can be seen from the aberration diagram, the optical system of the second embodiment effectively corrects aberrations throughout the entire region from infinity focusing to close-range focusing, and has excellent imaging performance.

[0187] (Third Embodiment)

[0188] use Figures 5-6 Table 3 illustrates the third embodiment. Figure 5 This diagram illustrates the lens structure of the optical system of the third embodiment in its infinity-focusing state. The optical system OL(3) of the third embodiment comprises a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power, arranged sequentially along the optical axis from the object side. When focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis towards the object side, and the third lens group G3 moves along the optical axis towards the image side, with the spacing between adjacent lens groups changing. Furthermore, during focusing, the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane I. An aperture stop S is positioned between the third lens group G3 and the fourth lens group G4.

[0189] The first lens group G1 is a combined lens consisting of a positive meniscus lens L11 with its convex surface facing the object side, a positive meniscus lens L12 with its convex surface facing the object side, a biconvex positive lens L13, a biconcave negative lens L14, a biconvex positive lens L15, and a biconcave negative lens L16 arranged sequentially along the optical axis from the object side, and a positive meniscus lens L17 with its convex surface facing the object side.

[0190] The second lens group G2 consists of a positive meniscus lens L21 with its convex surface facing the object. The third lens group G3 consists of a negative meniscus lens L31 with its convex surface facing the object. In other words, the second lens group G2 and the third lens group G3 together consist of two lenses.

[0191] The fourth lens group G4 consists of a combined lens formed by combining a biconvex positive lens L41, a biconvex positive lens L42, and a biconcave negative lens L43, arranged sequentially along the optical axis from the object side; a combined lens formed by combining a biconcave negative lens L44, a biconvex positive lens L45, a biconvex positive lens L46, and a biconcave negative lens L47; a biconvex positive lens L48; and a negative meniscus lens L49 with its concave surface facing the object side. An image plane I is positioned on the image side of the fourth lens group G4.

[0192] In this embodiment, the positive lens L42, negative lenses L43, and negative lens L44 of the fourth lens group G4 constitute an image stabilization group that can move in a direction perpendicular to the optical axis to correct for displacement of the imaging position (image jitter on image plane I) caused by hand tremors, etc. The positive lens L15 of the first lens group G1 is equivalent to a positive lens that satisfies the above-described conditions (11) to (13). The positive meniscus lens L12, positive lens L13, and positive meniscus lens L17 of the first lens group G1 are equivalent to lenses (specific lenses) that satisfy the above-described condition (14).

[0193] Table 3 below shows the values ​​of the parameters of the optical system of the third embodiment.

[0194] (Table 3)

[0195] [Overall Parameters]

[0196]

[0197] [Lens Parameters]

[0198]

[0199]

[0200] [Variable Interval Data]

[0201]

[0202] [Lens Group Data]

[0203]

[0204] Figure 6 (A) is a diagram of aberrations when the optical system of the third embodiment is focused at infinity. Figure 6 (B) is an aberration diagram of the optical system of the third embodiment during close-range focusing. As can be seen from the aberration diagram, the optical system of the third embodiment effectively corrects aberrations throughout the entire region from infinity focusing to close-range focusing, and has excellent imaging performance.

[0205] (Example 4)

[0206] use Figures 7-8 Table 4 illustrates the fourth embodiment. Figure 7This diagram illustrates the lens structure of the optical system of the fourth embodiment in its infinity-focusing state. The optical system OL(4) of the fourth embodiment comprises a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with negative optical power, arranged sequentially along the optical axis from the object side. When focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis towards the object side, and the third lens group G3 moves along the optical axis towards the image side, with the spacing between adjacent lens groups changing. Furthermore, during focusing, the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane I. The aperture stop S is disposed within the fourth lens group G4.

[0207] The first lens group G1 is a combined lens consisting of a positive meniscus lens L11 with its convex surface facing the object side, a biconvex positive lens L12, a biconvex positive lens L13, a biconcave negative lens L14, a positive meniscus lens L15 with its concave surface facing the object side, a negative meniscus lens L16 with its convex surface facing the object side, and a positive meniscus lens L17 with its convex surface facing the object side, arranged sequentially along the optical axis from the object side.

[0208] The second lens group G2 consists of a positive meniscus lens L21 with its convex surface facing the object. The third lens group G3 consists of a negative meniscus lens L31 with its convex surface facing the object. In other words, the second lens group G2 and the third lens group G3 together consist of two lenses.

[0209] The fourth lens group G4 consists of a combined lens arranged along the optical axis from the object side, consisting of a biconvex positive lens L41, a biconvex positive lens L42 and a biconcave negative lens L43 (forming a combined lens), a biconcave negative lens L44, a biconvex positive lens L45, a biconvex positive lens L46 and a negative meniscus lens L47 with its concave surface facing the object side, a biconvex positive lens L48 and a negative meniscus lens L49 with its concave surface facing the object side, and a negative meniscus lens L50 with its concave surface facing the object side. An aperture stop S is positioned between the positive lens L41 and the positive lens L42 (of the combined lens) in the fourth lens group G4. An image plane I is positioned on the image side of the fourth lens group G4. An optical filter FL is positioned between the negative meniscus lens L50 and the image plane I in the fourth lens group G4.

[0210] In this embodiment, the positive lens L42, negative lenses L43, and negative lens L44 of the fourth lens group G4 constitute an image stabilization group that can move in a direction perpendicular to the optical axis to correct for displacement of the imaging position (image jitter on image plane I) caused by hand tremors, etc. The positive meniscus lens L15 of the first lens group G1 is equivalent to a positive lens that satisfies the above-described conditions (11) to (13). The positive lenses L12, L13, and L17 of the first lens group G1, and the negative meniscus lens L49 of the fourth lens group G4 are equivalent to lenses (specific lenses) that satisfy the above-described condition (14).

[0211] Table 4 below shows the values ​​of the parameters of the optical system of the fourth embodiment.

[0212] (Table 4)

[0213] [Overall Parameters]

[0214]

[0215] [Lens Parameters]

[0216]

[0217]

[0218] [Variable Interval Data]

[0219]

[0220]

[0221] [Lens Group Data]

[0222]

[0223] Figure 8 (A) is a diagram of aberrations when the optical system of the fourth embodiment is focused at infinity. Figure 8 (B) is an aberration diagram of the optical system of the fourth embodiment during close-range focusing. As can be seen from the aberration diagram, the optical system of the fourth embodiment effectively corrects aberrations throughout the entire region from infinity focusing to close-range focusing, and has excellent imaging performance.

[0224] (5th embodiment)

[0225] use Figures 9-10 Table 5 illustrates the fifth embodiment. Figure 9This diagram illustrates the lens structure of the optical system of the fifth embodiment in its infinity-focusing state. The optical system OL(5) of the fifth embodiment comprises a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power, arranged sequentially along the optical axis from the object side. When focusing from an object at infinity to a closer object, the second lens group G2 moves along the optical axis towards the object side, and the third lens group G3 moves along the optical axis towards the image side, with the spacing between adjacent lens groups changing. Furthermore, during focusing, the first lens group G1 and the fourth lens group G4 are fixed relative to the image plane I. An aperture stop S is positioned between the third lens group G3 and the fourth lens group G4.

[0226] The first lens group G1 is a combined lens consisting of a positive meniscus lens L11 with its convex surface facing the object side, a positive meniscus lens L12 with its convex surface facing the object side, a biconvex positive lens L13, a biconcave negative lens L14, a biconvex positive lens L15, and a biconcave negative lens L16 arranged sequentially along the optical axis from the object side, and a positive meniscus lens L17 with its convex surface facing the object side.

[0227] The second lens group G2 consists of a positive meniscus lens L21 with its convex surface facing the object. The third lens group G3 consists of a negative meniscus lens L31 with its convex surface facing the object. In other words, the second lens group G2 and the third lens group G3 together consist of two lenses.

[0228] The fourth lens group G4 consists of a combined lens arranged sequentially along the optical axis from the object side: a biconvex positive lens L41, a biconvex positive lens L42 and a biconcave negative lens L43, a biconcave negative lens L44, a negative meniscus lens L45 with its convex surface facing the object side and a biconvex positive lens L46, a biconvex positive lens L47 and a biconcave negative lens L48, and a biconvex positive lens L49 and a biconcave negative lens L50. An image plane I is positioned on the image side of the fourth lens group G4.

[0229] In this embodiment, the positive lens L42, negative lens L43, and negative lens L44 of the fourth lens group G4 constitute an image stabilization group that can move in a direction perpendicular to the optical axis to correct for displacement of the imaging position (image jitter on image plane I) caused by hand tremors, etc. The positive lens L15 of the first lens group G1 is equivalent to a positive lens that satisfies the above-described conditions (11) to (13). The positive meniscus lens L12, positive lens L13, and positive meniscus lens L17 of the first lens group G1, the positive meniscus lens L21 of the second lens group G2, and the negative lens L43 of the fourth lens group G4 are equivalent to lenses (specific lenses) that satisfy the above-described condition (14).

[0230] Table 5 below shows the values ​​of the parameters of the optical system of the fifth embodiment.

[0231] (Table 5)

[0232] [Overall Parameters]

[0233]

[0234]

[0235] [Lens Parameters]

[0236]

[0237]

[0238] [Variable Interval Data]

[0239]

[0240] [Lens Group Data]

[0241]

[0242] Figure 10 (A) is a diagram of aberrations when the optical system of the fifth embodiment is focused at infinity. Figure 10 (B) is an aberration diagram of the optical system of the fifth embodiment during close-range focusing. As can be seen from the aberration diagram, the optical system of the fifth embodiment effectively corrects aberrations throughout the entire region from infinity focusing to close-range focusing, and has excellent imaging performance.

[0243] Next, a table of [corresponding values ​​of conditional expressions] is shown below. In this table, the values ​​corresponding to each conditional expression (1) to (15) are summarized for all embodiments (1 to 5).

[0244] Condition (1) 0.010 < (Δx2A + Δx3A) / D1 < 0.200

[0245] Condition (2) -0.20 < Δx² / f² < 0.00

[0246] Condition (3) -0.20 < Δx³ / f³ < 0.00

[0247] Conditional expression (4)1.00 <f2 / (-f3)<4.00

[0248] Condition (5) -3.00 < Δx² / Δx³ < -0.20

[0249] Conditional expression (6)-8.50 <f1 / fVR<-3.00

[0250] Condition (7) 0.45 < β2 < 0.80

[0251] Condition (8) 0.20 < 1 / β3 < 0.50

[0252] Condition (9) {β² + (1 / β²)} -2 <0.25

[0253] Condition (10){β3+(1 / β3)} -2 <0.18

[0254] Conditional expression (11)ndL1+(0.01425×νdL1)<2.12

[0255] Condition (12)νdL1<35.00

[0256] Condition (13) 0.702 < θgFL1 + (0.00316 × νdL1)

[0257] Condition (14) 80.00 < νdL2

[0258] Condition (15) 3.50° < 2ω < 8.50°

[0259] [Conditional values] (Examples 1-3)

[0260]

[0261]

[0262] [Conditional values] (Examples 4-5)

[0263] According to the above embodiments, it is possible to realize an optical system with excellent optical performance from infinity focusing to close-range focusing, and with a long focal length and brightness.

[0264] The above embodiments illustrate specific examples of the invention of this application, but the invention of this application is not limited to these.

[0265] The following can be appropriately adopted within the range that does not impair the optical performance of the optical system of this embodiment.

[0266] Although four structures are shown as an example of the optical system in this embodiment, this application is not limited to this, and other structures (e.g., five groups) can also be constructed. Specifically, it is also possible to add a lens or lens group to the optical system in this embodiment on the side closest to the object or the side closest to the image plane, or to add a lens or lens group between the second lens group (first focusing lens group) and the third lens group (second focusing lens group). In addition, a lens group refers to a portion having at least one lens that is separated by the air gap that changes during focusing.

[0267] Although an embodiment of the optical system described herein shows a structure with image stabilization, this application is not limited to this and may also include a structure without image stabilization.

[0268] The lens surface can be formed from a spherical or flat surface, or from an aspherical surface. When the lens surface is spherical or flat, lens processing and assembly adjustments become easier, preventing degradation of optical performance caused by errors in processing and assembly adjustments, and therefore this is preferred. Furthermore, there is less degradation in rendering performance when the image plane is offset, and this is also preferred.

[0269] When the lens surface is aspherical, the aspherical surface can be any of the following: a ground aspherical surface, a glass-molded aspherical surface formed by molding glass into an aspherical shape using a mold, or a composite aspherical surface formed by molding resin onto the glass surface into an aspherical shape. Additionally, the lens surface can also be a diffractive surface, and the lens can be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0270] Although the aperture stop is preferably positioned between the third lens group and the fourth lens group, or within the fourth lens group, it is also possible to omit the component that serves as the aperture stop and to use the lens frame instead.

[0271] In order to reduce glare and ghosting and achieve high contrast optical performance, an antireflective coating with high transmittance in a wide wavelength range can also be applied to each lens surface.

[0272] Label Explanation

[0273] G1 Lens Group 1 G2 Lens Group 2

[0274] G3 is the third lens group, and G4 is the fourth lens group.

[0275] I Image Plane S Aperture Stop

Claims

1. An optical system, wherein, The optical system consists of a first lens group, a second lens group, a third lens group, and a fourth lens group arranged sequentially along the optical axis from the object side. The first lens group has positive optical power. When focusing from an object at infinity to a closer object, the second lens group and the third lens group move along the optical axis along different trajectories from each other. The first lens group has three individual lenses, which are arranged continuously from the object side toward the image side and have positive optical power. The second lens group and the third lens group together consist of no more than three lenses. The fourth lens group has an image stabilization group that can move with a displacement component perpendicular to the optical axis to correct image jitter, and has negative optical power. The optical system satisfies the following condition: -3.00 < Δx² / Δx³ ≤ -0.22 -8.50 <f1 / fVR<-4.25 0.20<1 / β3≤0.42 Wherein, Δx2: the amount of movement of the second lens group when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -). Δx3: The amount of movement of the third lens group when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is +, and the sign of the movement towards the object is -). f1: The focal length of the first lens group fVR: The focal length of the image stabilization group. β3: Magnification of the third lens group when focusing on an object at infinity.

2. The optical system according to claim 1, wherein, The optical system satisfies the following condition: -0.20 < Δx² / f² < 0.00 Wherein, Δx2: the amount of movement of the second lens group when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -). f2: The focal length of the second lens group.

3. The optical system according to claim 1, wherein, The optical system satisfies the following condition: -0.20 < Δx³ / f³ < 0.00 Wherein, Δx3: the amount of movement of the third lens group when focusing from an object at infinity to a closer object (the sign of the movement towards the image plane is set to +, and the sign of the movement towards the object is set to -). f3: The focal length of the third lens group.

4. The optical system according to claim 1, wherein, The optical system satisfies the following condition: 1.00 <f2 / (-f3)<4.00 Where, f2: the focal length of the second lens group. f3: The focal length of the third lens group.

5. The optical system according to claim 1, wherein, The image stabilization system consists of two or more lenses.

6. The optical system according to claim 1, wherein, The optical system satisfies the following condition: 0.45<β2<0.80 Wherein, β2: the magnification of the second lens group when focusing on an object at infinity.

7. The optical system according to claim 1, wherein, The optical system satisfies the following condition: {β2+(1 / β2)} -2 <0.25 Wherein, β2: the magnification of the second lens group when focusing on an object at infinity.

8. The optical system according to claim 1, wherein, The optical system satisfies the following condition: {β3+(1 / β3)} -2 <0.18 Wherein, β3: the magnification of the third lens group when focusing on an object at infinity.

9. The optical system according to claim 1, wherein, The first lens group has a positive lens that satisfies the following condition: ndL1+(0.01425×νdL1)<2.12 νdL1<35.00 0.702 < θgFL1 + (0.00316 × νdL1) Wherein, ndL1: the refractive index of the positive lens for the d-line. νdL1: The Abbe number of the positive lens relative to the d-line. θgFL1: The relative partial dispersion of the positive lens, defined by the following formula when the refractive index of the positive lens for the g line is set to ngL1, the refractive index of the positive lens for the F line is set to nFL1, and the refractive index of the positive lens for the C line is set to nCL1. θgFL1=(ngL1-nFL1) / (nFL1-nCL1).

10. The optical system according to claim 1, wherein, The optical system has a lens that satisfies the following condition: 80.00<νdL2 Wherein, νdL2: the Abbe number of the lens with respect to the d-line.

11. The optical system according to claim 1, wherein, The optical system satisfies the following condition: 3.50° < 2ω < 8.50° Wherein, 2ω: the full field of view of the optical system.

12. The optical system according to claim 1, wherein, When focusing from an object at infinity to a closer object, the second lens group moves along the optical axis to the object side, and the third lens group moves along the optical axis to the image plane side.

13. The optical system according to claim 1, wherein, The second lens group consists of one lens.

14. The optical system according to claim 1, wherein, The third lens group consists of one lens component.

15. The optical system according to claim 1, wherein, The optical system has an aperture that is positioned on the image plane side relative to the second lens group.

16. The optical system according to claim 15, wherein, The aperture is positioned on the image plane side compared to the third lens group.

17. An optical device configured to have the optical system described in any one of claims 1 to 16.

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