Optical system and imaging device

Abstract

This provides a new technology that allows for improved focusing performance by retrofitting existing imaging devices. [Solution] The optical system according to this disclosure has an optical element that, when combined with another optical system located closer to the object, forms an overall optical system that focuses on the other optical system. The optical element moves along the optical axis when focusing between a first object distance and a second object distance that is shorter than the first. The optical system satisfies specific conditions expressed by a specific formula.

Description

Technical Field

[0001] The present invention relates to an optical system and an imaging device.

Background Art

[0002] Imaging measures equipped with solid-state imaging devices such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor) have rapidly spread in a wide range of fields such as single-lens reflex cameras, digital still cameras, video cameras, or surveillance cameras. Along with this, the demand for lenses compatible with solid-state imaging devices has been expanding. In recent years, the number of pixels and sensitivity of solid-state imaging devices have been increasing, and high-resolution lenses are required. In addition, the miniaturization and spread of imaging devices have progressed, and the imaging lens is desired to be miniaturized, lightweight, and inexpensive. In addition, an imaging device that focuses only during any close-up shooting other than at infinity is required, and an imaging device that performs ranging to focusing in a short time is required.

[0003] For such an imaging device, there is known an imaging device that improves the speed of the focusing operation by attaching and using an attachment lens device so as to be interposed between a master lens having no wobbling function and a camera body (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] On the other hand, when enhancing focusing performance after the use of an imaging device, there may be limitations imposed by the imaging device being used. For example, in the case of a surveillance camera with a camera built into the casing, the space available for later enhancing focusing performance may be limited. Thus, optical systems that may be added to enhance focusing performance are required to accommodate the limitations of the imaging device, and there is a need for new optical systems that satisfy these requirements.

[0006] One aspect of the present invention aims to provide a novel technology that can improve the focusing performance of an existing imaging device by retrofitting it. [Means for solving the problem]

[0007] To solve the above problems, an optical system according to one aspect of the present invention is an optical system having an optical element, and when it is combined with another optical system located closer to the object to form an overall optical system, the optical system focuses on the other optical system, When focusing between a first object distance and a second object distance that is shorter than the first, the optical element moves along the optical axis and satisfies the following equation. 0.001 <Lb / La<2.0 (1) 0.001 < Bmin / Bmax (2) however La: Total length of the entire optical system when in focus Lb: Distance along the optical axis from the vertex of the lens surface closest to the object in the optical element of the overall optical system to the image plane. Bmax: Maximum magnification of the entire optical system. Bmin: Minimum magnification of the entire optical system

[0008] Furthermore, in order to solve the above problems, an imaging device according to one aspect of the present invention includes an overall optical system comprising the above-mentioned optical system and another optical system arranged on the object side of the optical system, and an image sensor that receives light from the image formed by the overall optical system. [Effects of the Invention]

[0009] According to one aspect of the present invention, a new technology is available that can improve the focusing performance of an existing imaging device by retrofitting it. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram schematically shows the optical configuration of the optical system in Example 1. [Figure 2] This figure shows the longitudinal aberration of the optical system of Example 1 when it is in focus at infinity. [Figure 3] This figure shows the longitudinal aberration of the optical system of Example 1 when the first object is in focus at a distance of 5m. [Figure 4] This figure shows the longitudinal aberration of the optical system in Example 1 when the second object distance is 1m and the system is in focus. [Figure 5] This diagram schematically shows the optical configuration of the optical system in Example 2. [Figure 6] This figure shows the longitudinal aberration of the optical system of Example 2 when it is in focus at infinity. [Figure 7] This figure shows the longitudinal aberration of the optical system in Example 2 when the first object is in focus at a distance of 5m. [Figure 8] This figure shows the longitudinal aberration of the optical system in Example 2 when the second object distance is 1m and the system is in focus. [Figure 9] This diagram schematically shows the optical configuration of the optical system in Example 3. [Figure 10] This figure shows the longitudinal aberration of the optical system of Example 3 when it is in focus at infinity. [Figure 11] This figure shows the longitudinal aberration of the optical system in Example 3 when the first object is in focus at a distance of 5m. [Figure 12] This figure shows the longitudinal aberration of the optical system in Example 3 when the second object distance is 1m and the system is in focus. [Figure 13] This diagram schematically shows the optical configuration of the optical system in Example 4. [Figure 14] This figure shows the longitudinal aberration of the optical system of Example 4 when it is in focus at infinity. [Figure 15]This is a diagram showing the longitudinal aberration when focusing at a first object distance of 5 m, which is the optical system of Example 4. [Figure 16] This is a diagram showing the longitudinal aberration when focusing at a second object distance of 1 m, which is the optical system of Example 4. [Figure 17] This is a diagram schematically showing an example of the configuration of an imaging device according to an embodiment of the present invention. [Figure 18] This is a perspective view schematically showing the appearance of an example of an imaging device according to an embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0011] [Optical System] The optical system according to the embodiment of the present invention has an optical member, and when constituting an entire optical system with another optical system disposed on the object side of the optical system, the other optical system is focused. By the optical system of this embodiment having the above configuration, it satisfies the following formula, and it is possible to realize good optical performance of the entire optical system while suppressing an excessive increase in the overall optical length of the entire optical system.

[0012] In this embodiment, the "another optical system" is an optical system that forms an image in cooperation with the optical system of this embodiment, and is, for example, an optical system already provided in the imaging device. It is preferable that the other optical system does not have a focusing function from the viewpoint of expressing the focusing function by the optical system of this embodiment and making such a focusing effect more prominent. It is preferable that the other optical system has a focusing function from the viewpoint of being able to further enhance the focusing function of the entire optical system by strengthening the focusing function of the other optical system.

[0013] In this embodiment, the "entire optical system" means an optical system constituted by the optical system of this embodiment and the above-mentioned another optical system. In the entire optical system, the optical system of this embodiment is disposed on the image plane side of the other optical system. That is, the optical system of this embodiment is located on the most image plane side in the entire optical system.

[0014] [Optical Configuration of the Optical System] [Optical Member] The optical system of this embodiment includes optical elements. In this embodiment, "optical elements" means optical elements and groups thereof that enable the overall optical system to focus at different object distances within the overall optical system. An example of such optical elements is a group of lenses including a specific lens. Note that "group of lenses" means a collection of lenses that further includes one of the above-mentioned specific lenses or other lenses. The group of lenses moves along the optical axis when the overall optical system is in focus. During movement, the spacing between the optical elements constituting the group of lenses in the optical axis direction remains constant, and the entire group of optical elements constituting the group of lenses moves.

[0015] The optical element described above moves along the optical axis when focusing between a first object distance and a second object distance that is shorter than the first object distance. The "first object distance" refers to the longest shooting distance in the entire optical system. The "second object distance" refers to the shortest shooting distance in the entire optical system. In this embodiment, the movement of the optical element along the optical axis when focusing between the first and second object distances reduces the overall weight of the focusing group in the entire optical system, and enables further speed improvements in focusing due to the movement of the optical element. The "focusing group" is a general term for the lens group that moves when focusing in the entire optical system. For example, if only the optical system of this embodiment moves when focusing in the entire optical system, then it refers to the lens group that constitutes the optical system of this embodiment.

[0016] As mentioned above, the optical component may include a group of lenses. Including a group of lenses in the optical component is preferable from the viewpoint of improving the focusing performance of the optical system of this embodiment, and, if necessary, other optical performance, because it can include lenses with various characteristics.

[0017] Furthermore, the optical component may consist of a single lens. Having the optical component consist of a single lens is preferable from the viewpoint of reducing the weight of the optical system in this embodiment.

[0018] The lenses constituting the optical components can be appropriately determined within a range that allows for the achievement of the desired focus. Examples of such lenses include single lenses, bonded lenses formed by bonding the lens surfaces of multiple single lenses together with an adhesive, and composite lenses formed by integrating a single lens with a resin material without an air gap. Examples of single lenses include convex lenses, concave lenses, meniscus lenses, spherical lenses, and aspherical lenses.

[0019] Furthermore, the optical component may have a lens surface closest to the object that is concave relative to the object. Having a concave lens surface closest to the object is preferable from the viewpoint of correcting field curvature.

[0020] <Opening diaphragm> The optical component is preferably positioned on the object side of the aperture diaphragm in the overall optical system. The aperture diaphragm may be present in another optical system as described above, or it may be present in the optical system of this embodiment. If the optical system of this embodiment has an aperture diaphragm, the aperture diaphragm is positioned on the image plane side of the optical component.

[0021] The aperture diaphragm is a component that defines the diameter of the light beam and defines the F-number of another optical system or the overall optical system. Positioning the aperture diaphragm closer to the object is preferable from the viewpoint of reducing the ray angle of the light of the image in the overall optical system and reducing the diameter of the lens on the image plane side.

[0022] The optical system of this embodiment may further include other components besides the optical elements described above, to the extent that the effects of the present invention are obtained. Examples of such other components include liquid lenses.

[0023] [Optical properties of the optical system] The optical system of this embodiment preferably satisfies one or more of the following equations. Each equation will be explained below.

[0024] The optical system of this embodiment preferably satisfies the following equation. 0.001 <Lb / La<2.0 (1) however La: Total length of the entire optical system Lb: Distance along the optical axis from the vertex of the lens surface closest to the object in the overall optical system to the image plane.

[0025] Equation 1 defines the ratio of the total optical length to the position of the focusing group from the image plane. It is preferable for Lb / La to be within the above range, as this reduces the overall weight of the focusing group in the entire optical system and enables faster focusing.

[0026] From the viewpoint of effectively correcting optical performance, it is preferable that Lb / La be greater than 0.01 and more preferably greater than 0.05. Furthermore, from the viewpoint of suppressing the overall optical length, it is preferable that Lb / La be less than 1.0 and even more preferably 0.3 or less. Lb / La can be appropriately adjusted, for example, by varying the minimum focusing distance depending on the situation.

[0027] Furthermore, it is preferable that the optical system of this embodiment satisfies the following equation. 0.001 < Bmin / Bmax (2) however Bmax: Maximum magnification of the entire optical system Bmin: Minimum magnification of the entire optical system

[0028] Equation 2 defines the range in which the focusing group can be moved by detecting the shooting distance. It is preferable for βmin / Bmax to be within the above range, as this reduces the overall weight of the focusing group in the entire optical system and enables faster focusing.

[0029] From the viewpoint of suppressing optical performance, a Bmin / Bmax ratio of 0.050 or higher is more preferable, and a ratio of 0.100 or higher is even more preferable. Furthermore, from the viewpoint of suppressing optical performance, a Bmin / Bmax ratio of 1.000 or lower may be acceptable. The Bmin / Bmax ratio can be adjusted, for example, by changing the imaging range.

[0030] Furthermore, it is preferable that the optical system of this embodiment satisfies the following equation. |t / f|<1.0 (3) however t: Thickness of the optical element of the focusing group along the optical axis f: Focal length of the optical elements in the focusing group

[0031] Equation 3 defines the relationship between the thickness of the optical elements in the focusing group and the focal length of the focusing group. It is preferable for |t / f| to be within the above range, as this reduces the overall weight of the focusing group in the entire optical system and enables faster focusing.

[0032] From the viewpoint of ensuring a manufacturable thickness for the optical elements of the focusing group, |t / f| is more preferably 0.001 or greater, and even more preferably 0.002 or greater. Also, from the viewpoint of suppressing the overall optical length of the optical system, |t / f| may be 0.5 or less. |t / f| can be adjusted, for example, by varying the minimum or maximum shooting distance.

[0033] Furthermore, it is preferable that the optical system of this embodiment satisfies the following equation. -15.0 <La / ra<-0.1 (4) however La: Total length of the entire optical system ra: Radius of curvature of the lens surface closest to the object in the optical component.

[0034] Equation 4 defines the total optical length and the radius of curvature on the object side of the focusing group. It is preferable for La / ra to be within the above range from the viewpoint of effectively suppressing the optical performance in the imaging range.

[0035] From the viewpoint of suppressing the overall optical length of the optical system, La / ra is preferably greater than -15.0, more preferably -10.0 or higher, and even more preferably -5.0 or higher. Furthermore, from the viewpoint of effectively suppressing the optical performance of the imaging range, La / ra is preferably less than -0.1, more preferably -0.5 or lower, and even more preferably -0.7 or lower. La / ra can be appropriately adjusted, for example, by varying the imaging range.

[0036] Furthermore, it is preferable that the optical system of this embodiment satisfies the following equation. 0.85 < |βA| < 1.25 (5) however βA: Lateral magnification of the optical element when focused at infinity

[0037] Equation 5 defines the lateral magnification of the optical element. It is preferable for |βA| to be within the above range from the viewpoint of effectively suppressing the optical performance in the imaging range.

[0038] From the viewpoint of suppressing optical performance in the shooting range, |βA| is preferably greater than 0.85, more preferably 0.95 or greater, and even more preferably 1.00 or greater. Also, from the viewpoint of suppressing the amount of movement when the focusing group moves within the shooting range, |βA| is preferably less than 1.25, more preferably 1.22 or less, and even more preferably 1.20 or less. |βA| can be appropriately adjusted, for example, by changing the focal length of the overall optical system.

[0039] Furthermore, if the optical component includes a lens group having two or more lenses, βA is the lateral magnification at the telephoto end when the optical component is in focus at infinity.

[0040] The optical system of this embodiment can be appropriately designed experimentally or by computer simulation, depending on the above-mentioned conditions, the optical characteristics of another optical system cooperating with it, and the focusing performance newly required of the other optical system.

[0041] In focusing using the optical system of this embodiment, the position of the optical element at the time of focus may be corrected by referring to the input value of the control unit of the imaging device, in order to improve accuracy. Alternatively, if there is a sensor that measures the distance to the object (subject) separately from the imaging device, the position of the optical element at the time of focus may be corrected by referring to the input value of the sensor. The control of the position correction of the optical element at the time of focus, referring to the input value of the sensor, may be performed by the control unit of the imaging device, or by a separate control unit for controlling the focusing of the optical system. Controlling the focusing of the optical system by the separate control unit according to the input value of the sensor is preferable from the viewpoint of convenience, because when the optical system of this embodiment is retrofitted to another optical system, the focus can be precisely controlled with only the retrofitted configuration.

[0042] [Imaging device] An imaging device according to an embodiment of the present invention comprises the aforementioned overall optical system and an image sensor that receives the image formed by the overall optical system. The overall optical system includes the optical system of this embodiment described above and another optical system arranged on the object side of the optical system. An example of the configuration of the imaging device according to this embodiment is schematically shown in Figure 17.

[0043] As shown in Figure 17, the imaging device 1 comprises a main body 2, a first lens barrel 3, and a second lens barrel 4. The main body 2 has an image sensor on the optical axis OA. The image sensor is, for example, a CCD or CMOS, and includes an image plane I in the image sensor and has a cover glass CG. The main body 2 has a body mount that can be detachably connected to either the first lens barrel 3 or the second lens barrel 4.

[0044] The first lens barrel 3 is positioned closest to the object and has multiple lenses L1 to L12 and an aperture diaphragm S on the optical axis OA. The aperture diaphragm is positioned between lens L6 and lens L7.

[0045] The second telescope tube 4 is positioned between the first telescope tube 3 and the main body 2. The second telescope tube 4 has a lens L13 on the optical axis OA. The lens L13 is a concave meniscus lens and is positioned so as to be concave towards the object. The lens L13 is also positioned to be movable along the axial direction of the second telescope tube 4.

[0046] The second lens barrel 4 has a lens mount at its image plane end that is detachably connected to the body mount of the main body 2, and a body mount at its object end. The first lens barrel 3 also has a lens mount at its image plane end. The main body 2 and the second lens barrel 4 are connected by the body mount of the main body 2 and the lens mount on the image plane side of the second lens barrel 4, and the second lens barrel 4 and the first lens barrel 3 are connected by the body mount on the object side of the second lens barrel 4 and the lens mount on the image plane side of the second lens barrel 4. In this way, the first lens barrel 3 can be attached to the main body 2, and the second lens barrel 4 is configured to be interposed between the first lens barrel 3 and the main body 2.

[0047] The second lens barrel 4 moves from the object side to the image plane side when focusing occurs. When focusing occurs, the object distance of the entire optical system becomes longer than before focusing. In this embodiment, for example, the object distance of the entire optical system when focusing occurs corresponds to the first object distance, and the object distance of the entire optical system before focusing corresponds to the second object distance.

[0048] In the imaging device 1, which consists of the first lens barrel 3 and the main body 2, if the subject cannot be focused by the imaging device itself, the lens L13 of the second lens barrel 4 will focus, thus bringing the subject into focus. In this way, the focusing performance of the imaging device 1 is further enhanced by the retrofittable second lens barrel 4.

[0049] Figure 18 schematically shows the external appearance of the imaging device 1. In Figure 18, a distance measuring sensor 5 is externally attached to the object-side end of the first lens barrel 3. The distance measuring sensor 5 measures the distance to the subject. The detected value from the distance measuring sensor 5 can be used to control the movement position of the lens L13 in the second lens barrel 4 when focusing.

[0050] 〔summary〕 A first aspect of the present invention is an optical system having an optical element, which, when combined with another optical system located closer to the object, forms an overall optical system that focuses on the other optical system, wherein the optical element moves along the optical axis when focusing between a first object distance and a second object distance that is shorter than the first, and satisfies the following equation. The first aspect can be retrofitted to existing imaging devices to improve focusing performance, and is effective from the viewpoint of reducing the weight of the entire focusing group in the overall optical system, and from the viewpoint of achieving faster focusing. 0.001 <Lb / La<0.3 (1) 0.001 < Bmin / Bmax (2) however La: Total length of the entire optical system when in focus Lb: Distance along the optical axis from the vertex of the lens surface closest to the object in the overall optical system to the image plane. Bmax: Maximum magnification of the entire optical system Bmin: Minimum magnification of the entire optical system

[0051] A second aspect of the present invention is that, in the first aspect, the optical component includes a group of lenses. The second aspect is even more effective from the viewpoint of improving the optical properties of the optical system.

[0052] A third aspect of the present invention is that, in the first aspect, the optical element is composed of a single lens. The third aspect is even more effective in terms of reducing the weight of the optical system and increasing the speed of the drive during focusing.

[0053] A fourth aspect of the present invention is that, in any of the first to third aspects, the optical system satisfies the aforementioned equation 3. The fourth aspect is even more effective from the viewpoint of reducing the overall weight of the focusing group in the overall optical system and achieving faster focusing.

[0054] A fifth aspect of the present invention is that, in any of the first to fourth aspects, the optical system satisfies the aforementioned equation 4. The fifth aspect is even more effective in terms of effectively suppressing the optical performance within the photographable range.

[0055] A sixth aspect of the present invention is that, in any of the first to fifth aspects, the optical system satisfies the aforementioned equation 5. The sixth aspect is even more effective in terms of effectively suppressing the optical performance within the photographable range.

[0056] A seventh aspect of the present invention is an imaging device having (1) an overall optical system including an optical system of any of the first to sixth aspects and another optical system arranged on the object side of the optical system, and (2) an image sensor that receives an image formed by the overall optical system. The seventh aspect makes it possible to improve the focusing performance by retrofitting the optical system of this aspect to an existing imaging device consisting of another optical system and an image sensor, and is effective from the viewpoint of reducing the weight of the entire focusing group in the overall optical system and from the viewpoint of achieving faster focusing.

[0057] The optical system according to the present invention, as described above, can improve the focusing performance of imaging devices used in various applications with a simple configuration, thereby further enhancing the versatility of imaging devices. This invention, which achieves such effects, is expected to contribute to the further expansion of technologies using imaging devices, and is anticipated to contribute to achieving, for example, United Nations Sustainable Development Goal (SDG) 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."

[0058] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Examples]

[0059] Examples of the present invention are described below.

[0060] In the following embodiments, the optical configuration of the optical system is illustrated. In the diagram of the optical configuration, GA represents the first lens group, GB represents the second lens group, S represents the aperture diaphragm, CG represents the cover glass, I represents the image sensor, and L represents the lens. In each embodiment, lens group GB is configured to be detachably positioned between lens group GA and the image sensor.

[0061] Furthermore, the aberrations of the optical system are illustrated for each embodiment. The longitudinal aberration diagrams shown in each figure represent, from left to right, spherical aberration (mm), astigmatism (mm), and distortion (%), respectively.

[0062] In the diagram showing spherical aberration, the vertical axis represents the ratio to the maximum aperture (F-number), and the horizontal axis represents the amount of defocus (mm). The dotted line shows the spherical aberration of the optical system with light of the g line (wavelength λ=435.84nm), the solid line shows the spherical aberration of the d line (wavelength λ=587.56nm), and the dashed line shows the spherical aberration of light of the C line (wavelength λ=656.27nm).

[0063] In the diagram showing astigmatism, the vertical axis represents image height (mm) and the horizontal axis represents defocus amount (mm). The solid line represents the sagittal image plane (S) relative to the d line, and the dotted line represents the meridional image plane (T) relative to the d line.

[0064] In the diagram showing distortion, the vertical axis represents image height (mm), and the horizontal axis represents percentage.

[0065] Furthermore, the lens data for the optical system in each embodiment is shown in a table. In the table, "r" represents the radius of curvature, and "d" represents the lens thickness or lens spacing. Also, "Nd" represents the refractive index for the d line (wavelength λ = 587.56 nm), and "νd" represents the Abbe number for the d line. The symbol "S" in the table represents the aperture. "INF" means infinity. In the "d" column, indications such as "D(23)" indicate that the spacing of the lens surfaces on the term axis is a variable spacing that changes when in focus.

[0066] Furthermore, various data for the optical system are shown in tables for each embodiment (e.g., Table 2 in Embodiment 1). The values ​​in the tables indicate the values ​​for each item at the lens position when the lens is focused at infinity.

[0067] Furthermore, the object distance data for each embodiment is shown in a table. The values ​​in the table indicate the values ​​for each item at the lens position when the lens is focused at infinity. For example, in Table 3, the INF value for D23 indicates the lens position when the lens is focused at infinity, the value of 5.0 mm indicates the lens position when the lens is focused at infinity, and the value of 1.0 mm indicates the lens position when the lens is focused at infinity. Similarly, in Table 3, the INF value for D25 indicates the lens position when the lens is focused at infinity, the value of 5.0 mm indicates the lens position when the lens is focused at infinity, and the value of 1.0 mm indicates the lens position when the lens is focused at infinity.

[0068] [Example 1] Figure 1 is a schematic diagram showing the optical configuration of the optical system of Example 1 when focused at infinity. Figure 2 is a diagram showing the longitudinal aberration of the optical system of Example 1 when focused at infinity. Figure 3 is a diagram showing the longitudinal aberration of the optical system of Example 1 when focused at a first object distance of 5m. Figure 4 is a diagram showing the longitudinal aberration of the optical system of Example 1 when focused at a second object distance of 1m.

[0069] The optical system of Example 1 has, in order from the object side, lens group GA and lens group GB.

[0070] The lens group GA has a positive refractive power and consists of, in order from the object side, a concave meniscus lens L1, a concave meniscus lens L2, a concave meniscus lens L3, a biconvex lens L4, a convex meniscus lens L5, a biconvex lens L6, a cemented lens formed by a biconvex lens L7 and a biconcave lens L8, a cemented lens formed by a biconcave lens L9 and a biconvex lens L10, a biconvex lens L11, and a biconvex lens L12.

[0071] The lens group GB has negative refractive power and is composed of a concave meniscus lens L13. In the optical system of Example 1, focusing from an object at infinity to an object at close range is achieved by moving the lens group GB in the direction of the arrow in the figure (towards the image plane).

[0072] Table 1 shows the lens data for the optical system of Example 1. In Table 1, surface numbers 1 to 23 are the surface numbers of the lenses in lens group GA, and surface numbers 24 and 25 are the surface numbers of lens group GB. Surface number 13 represents the aperture. Surface numbers 26 and 27 represent the cover glass (CG), and surface number 28 represents the image plane.

[0073] [Table 1] Lens data Face number rd Nd νd 1 25.2837 2.5000 1.8467 23.78 2 14.6423 3.3167 3 53.7258 1.2000 1.5182 58.96 4 16.3372 4.6659 5 -35.9517 3.0000 1.6730 38.26 6 -144.0646 0.2000 7 108.6731 5.0000 1.9229 20.88 8 -43.7999 6.5133 9 99.9088 2.2618 1.4875 70.44 10 501.6323 1.5000 11 23.9272 4.9343 1.4970 81.61 12 -31.2471 5.8388 13 S INF 1.5000 14 25.0413 2.3892 1.5503 75.50 15 -12.8261 1.0000 1.6200 36.30 16 14.0547 3.1754 17 -8.4423 1.0000 1.7847 25.68 18 41.4020 3.8930 1.5928 68.62 19 -11.3853 0.2000 20 143.0846 3.3628 1.5928 68.62 21 -22.3510 0.2000 22 80.3428 3.0894 1.9229 20.88 23 -48.8527 D(23) 24 -60.0000 1.0000 1.5350 55.71 25 -100.0000 D(25) 26 INF 0.7500 1.5168 64.20 27 INF 1.0000 28 INF

[0074] Furthermore, various data for the optical system of Example 1 are shown in Table 2, and the object distance data for the optical system of Example 1 is shown in Table 3.

[0075] [Table 2] Various Data Focal length (mm) 17.0789 FNo 3.03 Half-angle (°): 27.7 Image height (mm) 8.900

[0076] [Table 3] Object distance Object distance INF 5.0m 1.0m D 23 2.2585 2.6575 4.3104 D 25 15.7756 15.3767 13.7237

[0077] [Example 2] Figure 5 is a schematic diagram showing the optical configuration of the optical system of Example 2 when focused at infinity. Figure 6 is a diagram showing the longitudinal aberration of the optical system of Example 2 when focused at infinity. Figure 7 is a diagram showing the longitudinal aberration of the optical system of Example 2 when focused at a first object distance of 5m. Figure 8 is a diagram showing the longitudinal aberration of the optical system of Example 2 when focused at a second object distance of 1m.

[0078] The optical system of Example 2 has, in order from the object side, lens group GA and lens group GB.

[0079] The lens group GA has a positive refractive power and consists of, in order from the object side, a concave meniscus lens L1, a concave meniscus lens L2, a concave meniscus lens L3, a biconvex lens L4, a convex meniscus lens L5, a biconvex lens L6, a cemented lens formed by a biconvex lens L7 and a biconcave lens L8, a cemented lens formed by a biconcave lens L9 and a biconvex lens L10, a biconvex lens L11, and a biconvex lens L12.

[0080] The lens group GB has negative refractive power and is composed of a concave meniscus lens L13. In the optical system of Example 2, focusing from an object at infinity to an object at close range is achieved by moving the lens group GB in the direction of the arrow in the figure (towards the image plane).

[0081] Table 4 shows the lens data for the optical system of Example 2. In Table 4, surface numbers 1 to 23 are the surface numbers of the lenses in lens group GA, and surface numbers 24 and 25 are the surface numbers of lens group GB. Surface number 13 represents the aperture. Surface numbers 26 and 27 represent the cover glass (CG), and surface number 28 represents the image plane.

[0082] [Table 4] Lens data Face number rd Nd νd 1 25.2837 2.5000 1.8467 23.78 2 14.6423 3.3167 3 53.7258 1.2000 1.5182 58.96 4 16.3372 4.6659 5 -35.9517 3.0000 1.6730 38.26 6 -144.0646 0.2000 7 108.6731 5.0000 1.9229 20.88 8 -43.7999 4.5830 9 99.9088 2.2618 1.4875 70.44 10 501.6323 1.5000 11 23.9272 4.9343 1.4970 81.61 12 -31.2471 5.8388 13 S INF 1.5000 14 25.0413 2.3892 1.5503 75.50 15 -12.8261 1.0000 1.6200 36.30 16 14.0547 3.1754 17 -8.4423 1.0000 1.7847 25.68 18 41.4020 3.8930 1.5928 68.62 19 -11.3853 0.2000 20 143.0846 3.3628 1.5928 68.62 21 -22.3510 0.2000 22 80.3428 3.0894 1.9229 20.88 23 -48.8527 D(23) 24 -35.8388 1.0000 1.5350 55.71 25 -117.9621 D(25) 26 INF 0.7500 1.5168 64.20 27 INF 1.0000 28 INF

[0083] Furthermore, various data for the optical system of Example 2 are shown in Table 5, and the object distance data for the optical system of Example 2 is shown in Table 6.

[0084] [Table 5] Various Data Focal length (mm) 19.3923 FNo 3.44 Half-angle (°): 24.6 Image height (mm) 8.900

[0085] [Table 6] Object distance Object distance INF 5.0m 1.0m D 23 4.1843 4.3681 5.0968 D 25 15.7802 15.5964 14.8677

[0086] [Example 3] Figure 9 is a schematic diagram showing the optical configuration of the optical system of Example 3 when focused at infinity. Figure 10 is a diagram showing the longitudinal aberration of the optical system of Example 3 when focused at infinity. Figure 11 is a diagram showing the longitudinal aberration of the optical system of Example 3 when focused at a first object distance of 5m. Figure 12 is a diagram showing the longitudinal aberration of the optical system of Example 3 when focused at a second object distance of 1m.

[0087] The optical system of Example 3 has, in order from the object side, lens group GA and lens group GB.

[0088] The lens group GA has a positive refractive power and consists of, in order from the object side, a biconvex lens L1, a convex meniscus lens L2, a concave meniscus lens L3, a cemented lens formed from a biconvex lens L4 and a biconcave lens L5, a biconcave lens L6, a convex meniscus lens L7, and a biconvex lens L8.

[0089] The lens group GB has negative refractive power and is composed of a concave meniscus lens L9. In the optical system of Example 3, focusing from an object at infinity to an object at close range is achieved by moving the lens group GB in the direction of the arrow in the figure (towards the image plane).

[0090] Table 7 shows the lens data for the optical system of Example 3. In Table 7, surface numbers 1 to 16 are the surface numbers of the lenses in lens group GA, and surface numbers 17 and 18 are the surface numbers of lens group GB. Surface number 7 represents the aperture. Surface numbers 19 and 20 represent the cover glass (CG), and surface number 21 represents the image plane.

[0091] [Table 7] Lens data Face number rd Nd νd 1 62.4373 4.0000 1.5168 64.20 2 2456.5636 0.1500 3 19.8616 5.7939 1.7292 54.67 4 33.1214 0.9105 5 52.4685 1.2000 1.5927 35.45 6 16.8903 11.6463 7 S INF 2.0000 8 22.0300 6.0100 1.8348 42.72 9 -52.8763 1.0000 1.6889 31.16 10 28.8198 3.9494 11 -20.9361 1.0000 1.6477 33.84 12 32.5345 1.5394 13 -61.3684 4.2304 1.7292 54.67 14 -27.5414 0.1500 15 47.1007 3.7500 1.8042 46.50 16 -47.1007 D(16) 17 -35.8224 1.0000 1.5350 55.71 18 -61.6781 D(18) 19 0.0000 1.0000 1.5168 64.20 20 0.0000 1.0000 21 0.0000

[0092] Furthermore, various data for the optical system of Example 3 are shown in Table 8, and the object distance data for the optical system of Example 3 is shown in Table 9.

[0093] [Table 8] Various Data Focal length (mm) 53.4058 FNo 3.28 Half-angle (°): 9.3 Image height (mm) 8.800

[0094] [Table 9] Object distance Object distance INF 5.0m 1.0m D 16 3.2610 5.4061 16.7920 D 18 18.4114 16.2664 4.8805

[0095] [Example 4] Figure 13 is a schematic diagram showing the optical configuration of the optical system of Example 4 when focused at infinity. Figure 14 is a diagram showing the longitudinal aberration of the optical system of Example 4 when focused at infinity. Figure 15 is a diagram showing the longitudinal aberration of the optical system of Example 4 when focused at a first object distance of 5m. Figure 16 is a diagram showing the longitudinal aberration of the optical system of Example 4 when focused at a second object distance of 1m.

[0096] The optical system of Example 4 has, in order from the object side, lens group GA and lens group GB.

[0097] The lens group GA has a positive refractive power and consists of, in order from the object side, a biconvex lens L1, a convex meniscus lens L2, a concave meniscus lens L3, a cemented lens formed from a biconvex lens L4 and a biconcave lens L5, a biconcave lens L6, a convex meniscus lens L7, and a biconvex lens L8.

[0098] The lens group GB has negative refractive power and is composed of a concave meniscus lens L9. In the optical system of Example 4, focusing from an object at infinity to an object at close range is achieved by moving the lens group GB in the direction of the arrow in the figure (towards the image plane).

[0099] Table 10 shows the lens data for the optical system of Example 4. In Table 10, surface numbers 1 to 16 are the surface numbers of the lenses in lens group GA, and surface numbers 17 and 18 are the surface numbers of the attachment lens group GB. Surface number 7 represents the aperture. Surface numbers 19 and 20 represent the cover glass (CG), and surface number 21 represents the image plane.

[0100] [Table 10] Lens data Face number rd Nd νd 1 62.4373 4.0000 1.5168 64.20 2 2456.5636 0.1500 3 19.8616 5.7939 1.7292 54.67 4 33.1214 0.9105 5 52.4685 1.2000 1.5927 35.45 6 16.8903 9.7314 7 S INF 2.0000 8 22.0300 6.0100 1.8348 42.72 9 -52.8763 1.0000 1.6889 31.16 10 28.8198 3.9494 11 -20.9361 1.0000 1.6477 33.84 12 32.5345 1.5394 13 -61.3684 4.2304 1.7292 54.67 14 -27.5414 0.1500 15 47.1007 3.7500 1.8042 46.50 16 -47.1007 D(16) 17 -24.5241 1.0000 1.5350 55.71 18 -143.1114 D(18) 19 INF 1.0000 1.5168 64.20 20 INF 1.0000 21 INF Furthermore, various data for the optical system of Example 4 are shown in Table 11, and the object distance data for the optical system of Example 4 is shown in Table 12.

[0101] [Table 11] Various Data Focal length (mm) 61.5751 FNo 3.76 Half-angle (°): 8.0 Image height (mm) 8.800

[0102] [Table 12] Object distance Object distance INF 5.0m 1.0m D 16 8.0445 9.0644 13.4340 D 18 15.9945 14.9746 10.6050

[0103] Table 13 shows the values ​​of each parameter in each embodiment. Table 14 shows the numerical values ​​of each formula in each embodiment. In the notes in the tables below, "INF" indicates the lens position when focused at infinity, and "MOD" indicates the lens position when focused at the shortest focusing distance.

[0104] [Table 13] Example 1 Example 2 Example 3 Example 4 Remarks La 81.5247 81.5247 72.0023 72.4539 Lb 18.5256 18.5302 21.4114 18.9945 INF Lb 16.4737 17.6177 7.8805 13.605 MOD Bmin 0.0034 0.0039 0.0106 0.0122 Bmax 0.0167 0.0189 0.0501 0.058 t 1 1 1 1 f 17.0789 19.3923 53.4051 61.5944 La 81.5247 81.5247 72.0023 72.4539 ra -60 -35.8388 -35.8224 -24.5241 βA 1.0667 1.1869 1.1335 1.3281 INF βA 1.0585 1.1737 1.0350 1.1758 MOD

[0105] [Table 14] Example 1 Example 2 Example 3 Example 4 Remarks Lb / La 0.2272 0.2273 0.2974 0.2622 INF Lb / La 0.2021 0.2161 0.1094 0.1878 MOD Bmin / Bmax 0.2036 0.2063 0.2116 0.2103 |t / f| 0.0035 0.0103 0.0062 0.0181 La / ra -1.3587 -2.2748 -2.0100 -2.9544 βA 1.0667 1.1869 1.1335 1.3281 INF βA 1.0585 1.1737 1.0350 1.1758 MOD [Explanation of Symbols]

[0106] 1. Imaging device 2 Main unit 3 First barrel 4 Second barrel 5. Distance measuring sensor

Claims

1. An optical system having an optical element, which, when combined with another optical system located closer to the object, forms an overall optical system that focuses on the other optical system, An optical system in which the optical element moves along the optical axis when focusing between a first object distance and a second object distance that is shorter than the first object distance, and which satisfies the following equation. 0.001<Lb / La<2.0 (1) 0.001<Bmin / Bmax (2) however La: Total length of the entire optical system when in focus Lb: Distance along the optical axis from the vertex of the lens surface closest to the object in the optical element of the overall optical system to the image plane. Bmax: Maximum magnification of the entire optical system. Bmin: Minimum magnification of the overall optical system.

2. The optical system according to claim 1, wherein the optical element includes a group of lenses.

3. The optical system according to claim 1, wherein the optical element is composed of a single lens.

4. The optical system according to claim 1, satisfying the following formula. |t / f|<1.0 (3) however t: Thickness of the optical member along the optical axis f: Focal length of the optical element

5. The shape of the lens surface of the optical element closest to the object is concave relative to the object, and The optical system according to claim 1, satisfying the following formula. -15.0<La / ra<-0.1 (4) however ra: Radius of curvature of the lens surface closest to the object in the optical element.

6. The optical system according to claim 1, satisfying the following formula. 0.85<|βA|<1.25 (5) however βA: Lateral magnification of the optical element when focused at infinity.

7. An imaging device comprising an overall optical system including the optical system described in any one of claims 1 to 6 and the other optical system disposed on the object side of the optical system, and an image sensor that receives an image formed by the overall optical system.

Images