Optical system and imaging device

Abstract

To provide a compact and lightweight optical system and imaging device for cameras, which are becoming increasingly smaller. [Solution] The optical system consists of a first lens group and a rear group having multiple lens groups, in order from the object side. When focusing, the spacing between adjacent lens groups changes. The rear group has a first focus group having a negative refractive power that moves when focusing, and a second focus group having a negative refractive power that moves when focusing. Between the first and second focus groups, there is at least one lens group P having a positive refractive power. Lens group P has a subgroup PN that has a negative refractive power closest to the object, and satisfies a predetermined conditional equation. The imaging device comprises the optical system and an image sensor.

Description

Technical Field

[0001] The present invention relates to an optical system and an imaging device. Specifically, for example, it relates to an optical system and an imaging device suitable for an imaging optical system of digital input / output devices such as a digital still camera or a digital video camera using a solid-state imaging device or the like.

Background Art

[0002] In recent years, imaging devices using solid-state imaging devices such as digital still cameras have become widespread. Along with this, the optical system has been improved in performance and miniaturized, and small imaging device systems have been rapidly spreading. Furthermore, in an optical system capable of close-up photography with a high magnification, high optical performance is required from infinity to the closest distance. Therefore, a so-called floating method has been adopted in which aberration variation is suppressed by moving a plurality of lens groups during focusing.

[0003] Patent Document 1 and Patent Document 2 are inventions of a macro lens composed of a first lens group to a fifth lens group of positive, negative, positive, negative, positive, and floating in the second lens group and the fourth lens group.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in an optical system adopting the floating method, when the weight of each focus group required during focusing becomes large, it leads to an increase in the size of the optical system and the lens barrel.

[0006] In the optical systems described in Patent Documents 1 and 2, the second lens group has a large number of lenses and is heavy, resulting in insufficient miniaturization and weight reduction. Furthermore, the image-side lens group of the focusing group is large, resulting in insufficient miniaturization and weight reduction of the product as a whole.

[0007] Therefore, the objective of the present invention is to provide a compact optical system and imaging device that have high optical performance from infinity to very close distances.

[0008] To solve the above problems, the optical system according to the present invention is: Starting from the object side, it consists of a first lens group and a rear group having multiple lens groups. When focusing, the spacing between adjacent lens elements changes. The aforementioned rear group comprises a first focus group having a negative refractive force that moves when focusing, and a second focus group having a negative refractive force that moves when focusing. Between the first focus group and the second focus group, there is a lens group P having at least one positive refractive power. The lens group P has a subgroup PN that has the most negative refractive power on the object side, It is characterized by satisfying the following conditional expression. 0.3 < |fP / fPN|···(1) 0.05 <|(1-βf1×βf1)×βf1r×βf1r| / Fno <2.0 ····(2) however, fP: Focal length of the lens group P fPN: Focal length of the subgroup PN βf1: Horizontal magnification when the first focus group is in focus at infinity. βf1r: Horizontal magnification at infinity for all lenses positioned on the image side of the first focus group. Fno: F number when the entire system is open at infinity focus.

[0009] Furthermore, in order to solve the above-mentioned problems, the imaging device according to the present invention is characterized by comprising the optical system and an image sensor that converts the optical image formed by the optical system into an electrical signal.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a small-sized optical system and an imaging device while having high optical performance from infinity to the closest distance.

Brief Description of the Drawings

[0011] [Figure 1] It is a cross-sectional view of the optical system of Example 1 of the present invention. [Figure 2] It is a diagram of various aberrations when the optical system of Example 1 is focused at infinity. [Figure 3] It is a diagram of various aberrations when the optical system of Example 1 is focused at the closest distance. [Figure 4] It is a cross-sectional view of the optical system of Example 2 of the present invention. [Figure 5] It is a diagram of various aberrations when the optical system of Example 2 is focused at infinity. [Figure 6] It is a diagram of various aberrations when the optical system of Example 2 is focused at the closest distance. [Figure 7] It is a cross-sectional view of the optical system of Example 3 of the present invention. [Figure 8] It is a diagram of various aberrations when the optical system of Example 3 is focused at infinity. [Figure 9] It is a diagram of various aberrations when the optical system of Example 3 is focused at the closest distance. [Figure 10] It is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0012] Hereinafter, embodiments of the optical system and the imaging device according to the present invention will be described. However, the optical system and the imaging device described below are one aspect of the optical system and the imaging device according to the present invention, and the optical system and the imaging device according to the present invention are not limited to the following aspects.

[0013] 1. Optical System 1-1. Optical Configuration The optical system according to the present invention is composed of, in order from the object side, a first lens group having positive or negative refractive power, and a rear group having multiple lens groups. The rear group has a first focus group having negative refractive power that moves in the optical axis direction when focusing, and a second focus group having negative refractive power that moves in the optical axis direction when focusing, and has at least one lens group P having positive refractive power between the first focus group and the second focus group. Miniaturization of the optical system can be achieved by appropriately configuring the lens group P. (1) First lens group The behavior of the first lens group is not limited during focusing, but it is more preferable for the optical system to be fixed relative to the image plane. Furthermore, it is preferable for the first lens group to have at least one positive lens, as this makes it easier to suppress chromatic aberration and achieve good optical performance. It is even more preferable to have at least two positive lenses. Furthermore, it is preferable for the first focusing group to have the positive lens on the image side in order to suppress aberration fluctuations during focusing. Furthermore, it is preferable for the first lens group to have at least one negative lens, as this makes it easier to suppress chromatic aberration and obtain good optical performance. Furthermore, it is preferable for the first lens group to have at least one cemented lens of a positive and a negative lens, as this makes it easier to suppress chromatic aberration and reduce the sensitivity of each lens. Alternatively, it is preferable for the lens group to have positive refractive power, as this makes it easier to suppress various aberrations and achieve miniaturization.

[0014] Here, a "lens group" consists of one or more adjacent lenses, and the distance between adjacent lens groups along the optical axis changes when focusing. If a single lens group consists of multiple lenses, the distance along the optical axis between each lens in that lens group is assumed not to change when focusing.

[0015] (2) Rear group The rear group is composed of multiple lens groups, and its specific configuration is not particularly limited as long as it has a first focusing group, a second focusing group, and lens group P. There may be a lens group between the first focusing group and lens group P, and a lens group may be formed between the second focusing group and lens group P. Furthermore, a lens group may be formed on the image side of the second focusing group. The lens group positioned on the image side of the second focusing group may be a lens group that is fixed with respect to the image plane when focusing.

[0016] (3) First focus group The first focus group is a group of lenses with negative refractive power, and has one or more negative refractive powers As long as it has the necessary lenses, its specific configuration is not particularly limited. The first focusing group may have one or more lenses with positive refractive power and one or more lenses with negative refractive power. Furthermore, it is preferable for the optical system and lens barrel to be miniaturized if the first focusing group consists of a single lens component (single lens component), which is either a single lens or a cemented lens made by bonding two or more lenses together. It is also preferable that the first focusing group has a concave surface on the object side.

[0017] (4) Second focus group The first focus group is a group of lenses with negative refractive power, and has one or more negative refractive powers As long as it has the necessary lenses, its specific configuration is not particularly limited. The second focusing group may have one or more lenses with positive refractive power and one or more lenses with negative refractive power. Furthermore, it is preferable for the first focusing group to consist of a single lens component (single lens component), which is either a single lens or a cemented lens made by bonding two or more lenses together, in order to miniaturize the optical system and lens barrel. It is also preferable for the second focusing group to have a concave surface on the object side.

[0018] (5) Lens group P The lens group P is positioned between the first and second focusing groups and has a positive refractive power. By appropriately setting the power of the negative subgroup PN, which is positioned closest to the object within the lens group P, miniaturization of the optical system and lens barrel can be achieved. The configuration is not particularly limited except for that of the subgroup PN. It is preferable that the lens group P is fixed with respect to the image plane when focusing.

[0019] (6) Subgroup PN The subgroup PN is positioned closest to the object in the lens group P and has negative power. Its lens configuration is not particularly limited, but it is preferable that it consists of negative lenses and negative lenses in order from the object side, or negative lenses and positive lenses in order from the object side, or negative lenses, positive lenses and positive lenses in order from the object side, or negative lenses, positive lenses and negative lenses in order from the object side, or negative lenses, negative lenses and positive lenses in order from the object side, or negative lenses, negative lenses and negative lenses in order from the object side. Furthermore, it is more preferable from the viewpoint of miniaturizing the optical system and lens barrel to consist of one lens component (single lens component) which is a single lens or a cemented lens made by bonding two or more lenses together. From the viewpoint of aberration correction, it is preferable that the subgroup PN has at least one positive lens.

[0020] (7) Aperture diaphragm In this optical system, the arrangement of the aperture diaphragm is not particularly limited. However, the aperture diaphragm referred to here is the aperture diaphragm that defines the diameter of the optical system, that is, the aperture diaphragm that defines Fno of the optical system. However, it is preferable to place the aperture diaphragm in the rear group in order to miniaturize the aperture unit. Furthermore, if the rear group includes a lens group with negative refractive power, it is preferable to place the aperture diaphragm on the object side of the lens group with negative refractive power. In order to cancel out negative distortion and negative field curvature that occur in the front group, it is sufficient to generate aberrations in the same direction before and after the aperture diaphragm. Therefore, by placing the aperture diaphragm on the image side of the first lens group and on the object side of the lens group with negative refractive power in the rear group, aberrations can be efficiently canceled out before and after the aperture diaphragm, which is preferable in order to obtain an optical system with high optical performance.

[0021] The aperture diaphragm is more preferably positioned between the first and second focusing groups, and more preferably positioned before, after, or within the lens group P. This configuration enables good aberration correction in the close-focus state, making it possible to construct a high-performance optical system.

[0022] (8) Other lenses The rear group may have lenses on the image side of the second focusing group. From the viewpoint of aberration correction, it is preferable to have at least one positive lens on the image side of the second focusing group. More preferably, it is preferable to have at least two positive lenses. Furthermore, from the viewpoint of aberration correction, it is preferable to have the positive lens on the image side of the optical system. It is also preferable to have a lens with negative refractive power on the image side of the second focusing group.

[0023] 1-2.Operation (1) Focus The specific operation of the optical system is not particularly limited, as long as at least the first and second focusing groups move along the optical axis when focusing from infinity to near distance. For example, when focusing from infinity to near distance, it is preferable that the first and second focusing groups move toward the image side along the optical axis, respectively. Furthermore, when focusing from infinity to near distance, it is more preferable that the first and second focusing groups move along the optical axis by different amounts. This configuration makes it possible to have higher optical performance from infinity to near distance. Furthermore, when focusing from infinity to near distance, it is more preferable that the amount of optical axis movement relative to the image plane of the second focusing group is greater than that of the first focusing group. This configuration makes it possible to have even higher optical performance from infinity to near distance. Furthermore, it is more preferable to have an additional lens group that moves when focusing from infinity to near distance, in addition to the first and second focusing groups. This configuration makes it possible to have higher optical performance from infinity to near distance.

[0024] 1-3. Conditional expression The optical system should employ the configuration described above and, moreover, satisfy at least one of the following conditional equations.

[0025] 1-3-1. Conditional expression (1) 0.3 < |fP / fPN|····(1) however, fP: Focal length of lens group P, fPN: Focal length of the subgroup PN

[0026] The above conditional equation (1) defines the power of the subgroup PN within the lens group P. By satisfying conditional equation (1), spherical aberration and coma aberration that occur when the weight of the first focusing group is reduced can be effectively corrected.

[0027] Conversely, if the value of condition (1) falls below the lower limit, spherical aberration and coma aberration will not be adequately corrected, making it difficult to achieve high optical performance.

[0028] To obtain the above effect, the lower limit of condition (1) is more preferably 0.6, and even more preferably 0.8 or higher. The upper limit of condition (1) is more preferably 3.0, more preferably 2.0, and even more preferably 1.5. When adopting these preferred lower or upper limits, the inequality sign (<) in condition (1) may be replaced with an equality sign (≦). The same principle applies to other conditional expressions.

[0029] 1-3-2. Conditional expression (2) 0.05 <|(1-βf1×βf1)×βf1r×βf1r| / Fno <2.0 ····(2) however, βf1: Horizontal magnification when the first focus group is focused at infinity. βf1r: Horizontal magnification at infinity for all lenses positioned on the image side from the first focus group. Fno: The maximum aperture F-number of the optical system when focused at infinity.

[0030] Conditional equation (2) defines the focus sensitivity of the first focus group. Here, focus sensitivity refers to the amount of change in the image plane in response to the amount of focus movement. By satisfying conditional equation (2), both miniaturization and high performance can be achieved.

[0031] Conversely, if the value of condition (2) falls below the lower limit, the amount of focus shift increases, resulting in a larger optical system and lens barrel. On the other hand, if the value of condition (2) is above the upper limit, the amount of focus shift can be reduced, which is advantageous for miniaturizing the optical system and lens barrel, but the sensitivity becomes too high, making it difficult to control the focusing operation.

[0032] To obtain the above effect, the lower limit of conditional equation (2) is preferably 0.1, more preferably 0.3, and even more preferably 0.6. Furthermore, the upper limit of conditional equation (2) is preferably 1.8, and more preferably 1.6.

[0033] 1-3-3. Conditional expression (3) 0.05 <|(1-βf2×βf2)×βf2r×βf2r| / Fno <2.0 ····(3) however, βf2: Horizontal magnification when the second focus group is focused at infinity. βf2r: Horizontal magnification at infinity focus for all lenses positioned on the image side from the second focus group onwards.

[0034] Conditional equation (3) defines the focus sensitivity of the second focus group. By satisfying conditional equation (3), it is possible to achieve both miniaturization and high performance.

[0035] Conversely, if the value of condition (3) falls below the lower limit, the amount of focus movement increases, resulting in a larger optical system and lens barrel. On the other hand, if the value of condition (3) is above the upper limit, the amount of focus movement can be reduced, which is advantageous for miniaturizing the optical system and lens barrel, but the sensitivity becomes too high, making it difficult to control the focusing operation.

[0036] To obtain the above effect, the lower limit of conditional equation (3) is preferably 0.1, more preferably 0.3, and even more preferably 0.6. Furthermore, the upper limit of conditional equation (3) is preferably 1.8, and more preferably 1.6.

[0037] 1-3-4. Conditional expression (4) 0.1 < fP / f < 2.0 ····(4) however, f: Focal length of the optical system when focused at infinity

[0038] Conditional equation (4) defines the lens group P. By satisfying conditional equation (4), it is possible to achieve both miniaturization and high performance.

[0039] Conversely, if the value of conditional equation (4) falls below the lower limit, various aberrations increase, requiring a larger size for correction. On the other hand, if the value of conditional equation (4) exceeds the upper limit, the converging effect of the P group weakens, resulting in a larger optical system.

[0040] To obtain the above effect, the lower limit of conditional equation (4) is preferably 0.15, more preferably 0.2, and even more preferably 0.25. Furthermore, the upper limit of conditional equation (4) is preferably 0.9, and more preferably 0.7.

[0041] 1-3-5. Conditional expression (5) -1.0 <ff1 / f< -0.1 ····(5) however, ff1: Focal length of the first focus group f: Focal length of the optical system when focused at infinity

[0042] Conditional equation (5) defines the power of the first focus group. By satisfying conditional equation (5), it is possible to achieve both miniaturization and high performance.

[0043] In contrast, if the value of condition (5) falls below the lower limit, the amount of focus shift increases, resulting in a larger size. On the other hand, if the value of condition (5) exceeds the upper limit, various aberrations increase, and the optical system becomes larger in order to correct them.

[0044] To obtain the above effect, the lower limit of conditional equation (5) is preferably -0.9, more preferably -0.8, and even more preferably -0.7. Furthermore, the upper limit of conditional equation (5) is preferably -0.2, and more preferably -0.3.

[0045] 1-3-6. Conditional expression (6) -1.0 <ff2 / f< -0.1 ····(6) however, ff2: Focal length of the second focus group f: Focal length of the optical system when focused at infinity

[0046] Conditional equation (6) defines the power of the second focus group. By satisfying conditional equation (6), it is possible to achieve both miniaturization and high performance.

[0047] In contrast, if the value of condition (6) falls below the lower limit, the amount of focus shift increases, resulting in a larger size. On the other hand, if the value of condition (6) exceeds the upper limit, various aberrations increase, and the optical system becomes larger in order to correct them.

[0048] To obtain the above effect, the lower limit of conditional equation (6) is preferably -0.9, more preferably -0.8, and even more preferably -0.7. Furthermore, the upper limit of conditional equation (6) is preferably -0.2, and more preferably -0.3.

[0049] 1-3-7. Conditional expression (7) 0.05 <f1 / f<1.0 ····(7) however, f1: Focal length of the first lens group f: Focal length of the optical system when focused at infinity

[0050] Conditional equation (7) defines the power of the first lens group. By satisfying conditional equation (7), it is possible to achieve both miniaturization and high performance.

[0051] Conversely, if the value of condition (7) falls below the lower limit, various aberrations increase, and the optical system becomes larger to compensate for them. On the other hand, if the value of condition (7) exceeds the upper limit, the total optical length increases, resulting in a larger optical system.

[0052] To obtain the above effect, the lower limit of conditional equation (7) is preferably 0.1, more preferably 0.2, and even more preferably 0.3. Furthermore, the upper limit of conditional equation (7) is preferably 0.9, and more preferably 0.8.

[0053] 1-3-8. Conditional expression (8) -1.0 <m1 / ff1< -0.2 ····(8a) -1.0 <m2 / ff2< -0.2 ····(8b) however, m1: Amount of movement of the first focus group when focusing from infinity to the closest distance. m2: The amount of movement of the second focus group when focusing from infinity to the closest distance. ff1: Focal length of the first focus group ff2: Focal length of the second focus group Note that the direction of movement from the object to the image is considered positive.

[0054] Conditional equations (8a) and (8b) define the ratio of the power of the first and second focus groups to the amount of movement required for focusing from infinity to the closest distance. By satisfying conditions (8a) and (8b) simultaneously, miniaturization and high performance can be achieved at the same time.

[0055] In contrast, when the values ​​of conditional equations (8a) and (8b) fall below the lower limit, the amount of focus shift increases, resulting in a larger optical system. On the other hand, when the values ​​of conditional equations (8a) and (8b) exceed the upper limit, various aberrations increase, and the optical system becomes larger in order to correct them.

[0056] To obtain the above effect, the lower limit of conditional equation (8a) is preferably -0.8, more preferably -0.6, and even more preferably -0.5. Furthermore, the upper limit of conditional equation (8a) is preferably -0.21, and more preferably -0.22.

[0057] To obtain the above effect, the lower limit of conditional equation (8b) is preferably -0.8, more preferably -0.6, and even more preferably -0.5. Furthermore, the upper limit of conditional equation (8b) is preferably -0.22, and more preferably -0.24.

[0058] 2. Imaging device Next, the imaging device according to the present invention will be described. The imaging device according to the present invention is characterized by comprising the optical system according to the present invention and an image sensor that converts the optical image formed by the optical system into an electrical signal. Preferably, the image sensor is provided on the image side of the optical system.

[0059] There are no particular limitations on the image sensor, and solid-state image sensors such as CCD (Charge Coupled Device) sensors and CMOS (Complementary Metal Oxide Semiconductor) sensors can also be used. The imaging device according to the present invention is suitable for imaging devices using such solid-state image sensors, such as digital cameras and video cameras. Furthermore, the imaging device can be applied to various imaging devices such as single-lens reflex cameras, mirrorless cameras, digital still cameras, surveillance cameras, in-vehicle cameras, and drone cameras. These imaging devices may be interchangeable-lens imaging devices or fixed-lens imaging devices in which the lens is fixed to the housing. In particular, the optical system according to the present invention is suitable for the optical system of imaging devices equipped with large image sensors such as full-frame sensors. Because the optical system is generally small, lightweight, and has high optical performance, high-quality images can be obtained even when used as an optical system for such imaging devices.

[0060] Figure 10 is a schematic diagram showing an example of the configuration of an imaging device according to this embodiment. As shown in Figure 10, the imaging device 1 has a camera 2 and a lens 3 that can be attached to or removed from the camera 2. The imaging device 1 is one embodiment of an imaging device. The camera 2 has a CCD sensor 21 as an image sensor and a cover glass 22. The CCD sensor 21 is positioned in the camera 2 at a location where the optical axis of the lens in the lens 3 attached to the camera 2 is the central axis. The camera 2 may have an IR cut filter or the like instead of the cover glass 22. Also, the camera 2 may have a CMOS sensor instead of the CCD sensor 21.

[0061] Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples. [Examples]

[0062] (1) Optical configuration Figure 1 shows a cross-sectional view of the lens of the optical system of Example 1. As shown in Figure 1, the optical system consists of a first lens group G1 having positive refractive power and a rear group having multiple lens groups, in order from the object side. The rear group consists of a second lens group G2 (first focus group) having negative refractive power, a third lens group G3 (lens group P) having positive refractive power, a fourth lens group (second focus group) having negative refractive power, and a fifth lens group having positive refractive power, in order from the object side.

[0063] When focusing from infinity to close range, the first focusing group moves towards the image, and the second focusing group also moves towards the image. The configuration of each lens group is described below.

[0064] The first lens group G1 consists of, in order from the object side, a biconvex lens, a biconcave lens, a cemented lens formed by joining a biconvex lens and a negative meniscus lens with its concave surface facing the object side, a biconvex lens, and a biconcave lens.

[0065] The second lens group G2 consists of biconcave lenses.

[0066] The third lens group G3 consists, in order from the object side, of an aperture diaphragm, a cemented lens formed by joining a biconvex lens and a biconcave lens, a positive meniscus lens with a concave surface on the object side, and a biconvex lens. Here, subgroup PN consists of the cemented lens closest to the object.

[0067] The fourth lens group G4 consists, in order from the object side, of a cemented lens formed by joining a positive meniscus lens with a concave surface on the object side and a biconcave lens.

[0068] The fifth lens group G5 consists of, in order from the object side, a biconvex lens, a biconcave lens, and a positive meniscus lens with a convex surface on the object side.

[0069] In Figure 1, "I" represents the image plane, specifically the imaging surface of a solid-state image sensor such as a CCD sensor or CMOS sensor, or the film surface of a silver halide film. A cover glass (CG) or similar is provided on the object side of the image plane. This is the same principle as in the cross-sectional lens diagrams shown in other embodiments, and therefore will not be explained further.

[0070] (2) Numerical Examples Next, we will describe a numerical example in which specific numerical values ​​of the optical system are applied. Below, we show the "Lens Data," "Specifications Table," "Variable Interval," and "Lens Group Data." The values ​​of each conditional expression (Table 1) are shown together after Example 3.

[0071] In the "Lens Data" section, "Surface Number" indicates the order of the lens surfaces counted from the object side, "R" is the radius of curvature of the lens surface, "D" is the lens thickness or air gap on the optical axis, "Nd" is the refractive index at the d line (wavelength λ=587.56nm), and "ABV" is the Abbe number at the d line. In the "Surface Number" column, "STOP" following the surface number indicates that the surface is an aperture diaphragm. In the "D" column, "D(9)", "D(11)", etc., indicate that the spacing of the lens surfaces on the optical axis is a variable spacing that changes during magnification. Also, "0.0000" in the radius of curvature column means infinity, indicating that the lens surface is flat.

[0072] In the "Specifications Table," "f" is the focal length of the optical system, "Fno" is the F-number, "ω" is the half-angle of view, and "Y" is the image height. The values ​​shown are for infinity focus and close focus (MOD), respectively.

[0073] In the "Variable Interval" section, the values ​​for infinity focus and close-up focus are shown, respectively. The same applies to other embodiments. Here, the shooting distance refers to the distance from the image plane.

[0074] Since the items in each of these tables are the same as those in the tables shown in other examples, we will omit further explanation below.

[0075] Furthermore, Figures 2 and 3 show the longitudinal aberration diagrams of the optical system when focusing on an object at infinity and when focusing on a close-up object. The longitudinal aberration diagrams shown in each figure, from left to right, represent spherical aberration (mm), astigmatism (mm), and distortion (%), respectively. In the spherical aberration diagram, the solid line represents the spherical aberration at line C (wavelength 656.27 nm), the dashed line represents the spherical aberration at line d (wavelength 587.56 nm), and the dashed line represents the spherical aberration at line F (wavelength 486.13 nm). In the astigmatism diagram, the vertical axis is the half-angle of view (ω) and the horizontal axis is defocus, with the solid line representing the sagittal image plane (S) at line d and the dashed line representing the meridional image plane (T) at line d. In the distortion diagram, the vertical axis is the half-angle of view (ω) and the horizontal axis is distortion. These matters are the same in the aberration diagrams shown in other embodiments, so the explanation is omitted below.

[0076] (Lens data) Face number RD Nd ABV 1 100.1350 4.3798 1.92119 23.96 2 -98.6318 1.7173 3 -75.3119 1.1000 1.58913 61.25 4 26.9027 5.3372 5 60.8824 7.3949 1.59282 68.62 6 -27.0778 1.0000 1.85451 25.15 7 -108.4941 0.2000 8 48.0920 6.0449 1.59282 68.62 9 -53.7047 D(9) 10 -124.3739 0.9000 1.59349 67.00 11 41.8731 D(11) 12STOP 0.0000 2.0000 13 -4147.1302 3.3000 1.49700 81.61 14 -42.1546 0.8000 1.80809 22.76 15 50.4880 2.0585 16 -2099.2589 2.9563 1.89286 20.36 17 -56.7699 0.2000 18 49.6082 5.2402 1.75500 52.32 19 -49.6082 D(19) 20 -105.2889 2.3000 1.86966 20.02 21 -41.7558 0.8000 1.69680 55.53 22 35.9595 D(22) 23 42.7870 6.0298 1.43700 95.10 24 -42.7870 15.1674 25 -30.1667 1.0000 1.71300 53.94 26 58.2877 0.8918 27 35.8576 4.8483 1.48749 70.44 28 284.4302 19.4558 29 0.0000 2.5000 1.51633 64.14 30 0.0000 1.0000 Image plane 0.0000

[0077] (Specifications table) INF MOD f 87.3000 38.8752 Fno 2.9093 5.8166 ω 14.0522 8.1250 Y 21.633 21.633

[0078] (Variable interval) Shooting distance INF 227.4085 D(9) 2.1000 15.5002 D(11) 18.5258 5.1255 D(19) 2.1000 17.1003 D(22) 17.6506 2.6500

[0079] (Lens group data) Group Surface number Focal length G1 1-9 47.3434 G2 10-11 -52.6768 G3 13-19 38.6246 G4 20-22 -42.2133 G5 23-28 228.7960 [Examples]

[0080] (1) Optical configuration Figure 4 shows a cross-sectional view of the lens of the optical system of Example 2. As shown in Figure 4, the optical system consists of a first lens group G1 having positive refractive power and a rear group having multiple lens groups, in order from the object side. The rear group consists of a second lens group G2 (first focusing group) having negative refractive power, a third lens group G3 (lens group P) having positive refractive power, a fourth lens group (second focusing group) having negative refractive power, and a fifth lens group having positive refractive power, in order from the object side.

[0081] When focusing from infinity to close range, the first focusing group F1 moves towards the image, and the second focusing group F2 also moves towards the image. The configuration of each lens group is described below.

[0082] The first lens group G1 consists of, in order from the object side, a biconvex lens, a biconcave lens, a cemented lens formed by joining a biconvex lens and a negative meniscus lens with its concave surface facing the object side, a biconvex lens, and a biconcave lens.

[0083] The second lens group G2 is also composed of biconcave lenses.

[0084] The third lens group G3 consists, in order from the object side, of an aperture diaphragm, a cemented lens formed by joining a biconcave lens and a biconvex lens, a positive meniscus lens with a concave surface on the object side, and a biconvex lens. Here, subgroup PN consists of the cemented lens closest to the object.

[0085] The fourth lens group G4 consists, in order from the object side, of a cemented lens formed by joining a positive meniscus lens with a concave surface on the object side and a biconcave lens.

[0086] The fifth lens group G5 consists of, in order from the object side, a biconvex lens, a biconcave lens, and a positive meniscus lens with a convex surface on the object side.

[0087] (2) Numerical Examples Next, we will show a numerical example in which specific values ​​of the optical system are applied. Furthermore, Figures 5 and 6 show the longitudinal aberration diagrams of the optical system when focusing on an object at infinity and when focusing on a close distance.

[0088] (Lens data) Face number RD Nd ABV 1 71.5589 4.1210 1.92119 23.96 2 -219.5042 0.2004 3 -293.7763 1.3000 1.49700 81.61 4 26.5081 8.6424 5 58.0026 6.4801 1.49700 81.61 6 -33.2115 1.0000 1.92286 20.88 7 -79.1808 0.2000 8 42.0817 5.3301 1.49700 81.61 9 -68.0747 D(9) 10 -87.1892 1.0000 1.59349 67.00 11 36.2811 D(11) 12STOP 0.0000 1.8241 13 -119.2121 1.0000 1.85451 25.15 14 34.6920 4.5239 1.43700 95.10 15 -116.3563 2.0044 16 -141.1644 2.4170 1.92286 20.88 17 -59.1152 0.2000 18 61.2811 4.9001 1.75500 52.32 19 -48.4537 D(19) 20 -93.9014 2.0000 1.92286 20.88 21 -49.8638 1.0000 1.67790 55.35 22 41.6734 D(22) 23 85.7772 5.0026 1.59349 67.00 24 -46.2418 15.9953 25 -31.0227 1.2491 1.75500 52.32 26 79.6879 0.2000 27 39.4153 4.9393 1.73400 51.47 28 99.6712 21.7980 29 0.0000 2.5000 1.51633 64.14 30 0.0000 1.0000 Image plane 0.0000

[0089] (Specifications table) INF MOD F 87.1571 40.3979 Fno 2.9100 5.8200 ω 13.9280 7.7952 Y 21.633 21.633

[0090] (Variable interval) Shooting distance INF 226.4085 D (9) 2.0000 14.4077 D(11) 16.1682 3.7606 D(19) 1.7339 17.6759 D(22) 19.1433 3.2013

[0091] (Lens group data) Group Surface number Focal length G1 1-9 44.3441 G2 10-11 -43.0385 G3 13-19 38.3126 G4 20-22 -46.8480 G5 23-28 215.7390 [Examples]

[0092] (1) Optical configuration Figure 7 shows a cross-sectional view of the lens of the optical system of Example 3. As shown in Figure 7, the optical system consists of a first lens group G1 having positive refractive power and a rear group having multiple lens groups. The rear group is composed of, in order from the object side, a second lens group G2 (first focus group) having negative refractive power, a third lens group G3 (lens group P) having positive refractive power, a fourth lens group (second focus group) having negative refractive power, and a fifth lens group having negative refractive power.

[0093] When focusing from infinity to close range, the first focusing group F1 moves towards the image, and the second focusing group also moves towards the image. The configuration of each lens group is described below.

[0094] The first lens group G1 consists of, in order from the object side, a biconvex lens, a bonded lens formed by joining a positive meniscus lens with a convex surface facing the object side and a negative meniscus lens with a convex surface facing the object side, a bonded lens formed by joining a negative meniscus lens with a concave surface facing the object side and a biconvex lens, a biconvex lens, a biconvex lens, and a biconvex lens.

[0095] The second lens group G2 consists of biconcave lenses.

[0096] The third lens group G3 consists of, in order from the object side, an aperture diaphragm, a negative meniscus lens with a convex surface on the object side, a positive meniscus lens with a concave surface on the object side, and a biconvex lens. Here, subgroup PN consists of the negative meniscus lens closest to the object.

[0097] The fourth lens group G4 consists, in order from the object side, of a cemented lens formed by joining a positive meniscus lens with a concave surface on the object side and a biconcave lens.

[0098] The fifth lens group G5 consists of a biconvex lens, a biconcave lens, and a biconvex lens, in that order from the object side.

[0099] (2) Numerical Examples Next, we will show a numerical example in which specific values ​​of the optical system are applied. Furthermore, Figures 8 and 9 show the longitudinal aberration diagrams of the optical system when focusing on an object at infinity and when focusing on a close distance.

[0100] (Lens data) Face number RD Nd ABV 1 328.0375 2.3837 1.84666 23.78 2 -443.5133 0.2000 3 46.4243 4.3180 1.92286 20.88 4 384.4079 1.3000 1.49700 81.61 5 22.9260 8.1557 6 -64.2191 1.0000 1.84666 23.78 7 30.5205 6.5259 1.49700 81.61 8 -53.1204 0.2140 9 146.9022 2.6972 1.95375 32.32 10 -211.4652 0.2000 11 30.4009 6.7703 1.49700 81.61 12 -68.7349 D(12) 13 -98.1191 1.0000 1.80420 46.50 14 40.1255 D(14) 15STOP 0.0000 1.2000 16 175.5201 0.8000 1.92286 20.88 17 45.8212 4.8715 18 -1753.0653 3.5427 1.91082 35.25 19 -51.2594 0.2371 20 49.0287 6.0726 1.59282 68.62 21 -45.4303 D(21) 22 -93.6428 2.0000 1.92286 20.88 23 -51.4215 1.0000 1.65160 58.54 24 43.8768 D(24) 25 -205.9687 3.2710 1.57501 41.50 26 -37.7312 15.1693 27 -28.0849 1.0000 1.80420 46.50 28 93.9401 0.2000 29 46.5640 5.4341 1.59282 68.62 30 -112.0570 20.3384 31 0.0000 2.5000 1.51633 64.14 32 0.0000 1.0000 Image plane 0.0000

[0101] (Specifications table) INF MOD F 87.2985 40.7664 Fno 2.9100 5.8200 ω 13.7866 78.2947 Y 21.633 21.633

[0102] (Variable interval) Shooting distance INF 219.9901 D(13) 2.1560 12.6172 D(15) 14.8866 4.4255 D(22) 2.0000 16.9999 D(25) 19.5559 4.5559

[0103] (Lens group data) Group Surface number Focal length G1 1-12 41.8265 G2 13-14 -35.2992 G3 16-21 32.4073 G4 22-24 -51.1001 G5 25-30 -351.0320

[0104] [Table 1] Example 1 Example 2 Example 3 Conditional expression (1) | fP / fPN| 0.910 0.584 0.481 Conditional expression (2) |(1-βf1×βf1)×βf1r×βf1r| / Fno 1.124 1.301 1.492 Conditional expression (3) |(1-βf2×βf2)×βf2r×βf2r| / Fno 1.413 1.236 1.492 Conditional expression (4) fp / f 0.442 0.437 0.371 Conditional expression (5) ff1 / f -0.603 -0.493 -0.404 Conditional expression (6) ff2 / f -0.537 -0.535 -0.585 Conditional expression (7) f1 / f 0.542 0.506 0.479 Conditional expression (8a) m1 / ff1 -0.254 -0.287 -0.296 Conditional expression (8b) m2 / ff2 -0.320 -0.340 -0.294 Conditional expression (9) β -1.0 -1.0 -1.0

[0105] [summary] An optical system according to a first aspect of the present invention is Starting from the object side, it consists of a first lens group and a rear group having multiple lens groups. When focusing, the spacing between adjacent lens groups changes. The aforementioned rear group comprises a first focus group having a negative refractive force that moves when focusing, and a second focus group having a negative refractive force that moves when focusing. Between the first focus group and the second focus group, there is a lens group P having at least one positive refractive power, The lens group P has a subgroup PN that has the most negative refractive power on the object side, The following equation may also be satisfied. 0.3 < |fP / fPN|···(1) 0.05 <|(1-βf1×βf1)×βf1r×βf1r| / Fno <2.0 ····(2) however, fP: Focal length of the lens group P fPN: Focal length of the subgroup PN βf1: Horizontal magnification when the first focus group is in focus at infinity. βf1r: Horizontal magnification at infinity for all lenses positioned on the image side of the first focus group. Fno: The maximum aperture F-number of the optical system when focused at infinity.

[0106] An optical system according to a second aspect of the present invention, in the first aspect, The following equation may also be satisfied. 0.05 <|(1-βf2×βf2)×βf2r×βf2r| / Fno <2.0 ····(3) however, βf2: Horizontal magnification when the second focus group is in focus at infinity. βf2r: Horizontal magnification at infinity for all lenses positioned on the image side of the second focus group.

[0107] An optical system according to a third aspect of the present invention is, in the first or second aspect, The following equation may also be satisfied. 0.1 < fP / f < 2.0 ····(4) however, f: Focal length of the optical system when focused at infinity

[0108] The optical system according to the fourth aspect of the present invention is, in the first to third aspects, The following equation may also be satisfied. -1.0 <ff1 / f< -0.1 ····(5) however, ff1: Focal length of the first focus group f: Focal length of the optical system when focused at infinity

[0109] The optical system according to the fifth aspect of the present invention is, in the first to fourth aspects, The following equation may also be satisfied. -1.0 <ff2 / f< -0.1 ····(6) however, ff2: Focal length of the second focus group f: Focal length of the optical system when focused at infinity

[0110] The optical system according to the sixth aspect of the present invention is, in the first to fifth aspects, The first lens group has a positive refractive power, The following equation may also be satisfied. 0.05 <f1 / f<1.0 ····(7) however, f1: Focal length of the first lens group f: Focal length of the optical system when focused at infinity

[0111] The optical system according to the seventh aspect of the present invention is, in the first to sixth aspects, The first and second focus groups move toward the image when focusing from infinity to close range. The following equation may also be satisfied. -1.0 <m1 / ff1< -0.2 ····(8a) -1.0 <m2 / ff2< -0.2 ····(8b) however, m1: Amount of movement of the first focus group when focusing from infinity to the closest distance. m2: The amount of movement of the second focus group when focusing from infinity to the closest distance. ff1: Focal length of the first focus group ff2: Focal length of the second focus group Note that the direction of movement from the object to the image is considered positive.

[0112] The optical system according to the eighth aspect of the present invention is, in the first to seventh aspects, The aforementioned subgroup PN may consist of a single lens or a cemented lens formed by bonding two or more lenses together.

[0113] The optical system according to the ninth aspect of the present invention, in the first to eighth aspects, The first focusing group may consist of a single lens or a cemented lens formed by bonding two or more lenses together.

[0114] The optical system according to the tenth aspect of the present invention, in the first to ninth aspects, The second focusing group may consist of a single lens or a cemented lens formed by bonding two or more lenses together.

[0115] An imaging device according to the eleventh aspect of the present invention may include an optical system according to the first to tenth aspects, and an image sensor provided on the image side of the optical system, which converts the optical image formed by the optical system into an electrical signal.

[0116] The optical systems and imaging devices described in the above embodiments and examples are one aspect of the optical system and imaging device according to the present invention, and correspond to the optical systems and imaging devices according to the first to tenth embodiments and the eleventh embodiment. The optical systems and imaging devices of each of the above embodiments provide the same effects and benefits as those described in the above embodiments and examples. The optical systems and imaging devices according to the present invention are not limited to the optical systems and imaging devices described in the embodiments and examples, and can be appropriately modified within the scope of the optical systems and imaging devices of each of the above embodiments.

[0117] [Industrial applicability]

[0118] The optical system according to the present invention can be suitably applied as an imaging optical system in imaging devices such as film cameras, digital still cameras, and digital video cameras. [Explanation of symbols]

[0119] G1 ···First lens group G2 ···Second lens group G3 ···Third lens group G4 ···4th lens group G5 ···5th lens group F1 ···First focus lens group F2 ···Second focus lens group P ···Lens group P CG ···Cover glass I...image plane 2 ···Camera 3...lens S ···Opening diaphragm 21 ···CCD sensor OR CMOS sensor 22 ···Cover glass IP...Image plane

Claims

1. Starting from the object side, it consists of a first lens group and a rear group having multiple lens groups. The aforementioned rear group comprises a first focus group having a negative refractive force that moves when focusing, and a second focus group having a negative refractive force that moves when focusing. Between the first focus group and the second focus group, there is a lens group P having at least one positive refractive power, The lens group P has a subgroup PN that has the most negative refractive power on the object side, An optical system that satisfies the following conditions. 0.3 < | fP / fPN |...(1) 0.05 <|(1-βf1×βf1)×βf1r×βf1r| / Fno ＜２．０ ・・・・（２） however, fP: Focal length of the lens group P fPN: Focal length of the subgroup PN βf1: Horizontal magnification when the first focus group is in focus at infinity. βf1r: Lateral magnification at infinity for all lenses positioned on the image side of the first focus group. Fno: The maximum aperture F-number of the optical system when focused at infinity.

2. The optical system according to claim 1, satisfying the following conditional expression. 0.05 <|(1-βf2×βf2)×βf2r×βf2r| / Fno ＜２．０ ・・・・（３） however, βf2: Lateral magnification when the second focus group is in focus at infinity. βf2r: Lateral magnification at infinity for all lenses positioned on the image side of the second focus group.

3. The optical system according to claim 1, satisfying the following conditional expression. 0.1 < fP / f < 2.0 (4) however, f: Focal length of the optical system when focused at infinity

4. The optical system according to claim 1, satisfying the following conditional expression. -1.0 <ff1 / f< -0.1 (5) however, ff1: Focal length of the first focus group f: Focal length of the optical system when focused at infinity

5. The optical system according to claim 1, satisfying the following conditional expression. -1.0 <ff2 / f< -0.1 (6) however, ff2: Focal length of the second focus group f: Focal length of the optical system when focused at infinity

6. The first lens group has a positive refractive power, The optical system according to claim 1, satisfying the following conditional expression. 0.05<f1 / f<1.0 (7) however, f1: Focal length of the first lens group f: Focal length of the optical system when focused at infinity

7. The first and second focus groups move toward the image when focusing from infinity to close range. The optical system according to claim 1, satisfying the following conditional expression. -1.0 <m1 / ff1< -0.2 (8a) -1.0 <m2 / ff2< -0.2 (8b) however, m1: Amount of movement of the first focus group when focusing from infinity to the closest distance. m2: Amount of movement of the second focus group when focusing from infinity to the closest distance. ff1: Focal length of the first focus group ff2: Focal length of the second focus group Note that the direction of movement from the object to the image is considered positive.

8. The optical system according to claim 1, wherein the subgroup PN is composed of a single lens or a cemented lens formed by bonding two or more lenses together.

9. The optical system according to claim 1, wherein the first focus group is composed of a single lens or a cemented lens formed by bonding two or more lenses together.

10. The optical system according to claim 1, wherein the second focus group is composed of a single lens or a cemented lens formed by bonding two or more lenses together.

11. An imaging device comprising an optical system according to any one of claims 1 to 10, and a solid-state image sensor that converts an optical image formed by the optical system into an electrical signal.

Images