Optical system and image pickup apparatus including the same

Abstract

To obtain an optical system which is compact as a whole and has high optical performance while having a wide angle of view exceeding an imaging angle of view of 180 ° in order to enable omnidirectional photographing with a single eye.SOLUTION: Provided is an optical system having an intermediate image, comprising a first optical system having a plurality of lens elements arranged on the object side of an intermediate image forming position and a second optical system having a plurality of lens elements arranged on the image side of the intermediate image forming position, wherein the following conditional expression is satisfied when the paraxial lateral magnification of the second optical system is β 2 and the imaging angle of view of the optical system having the intermediate image is ω [°] when the optical system having the intermediate image forming position is in focus at infinity: -1.60 <β 2 <-1.01 (1) 180 <2 ω <280 (2) SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an optical system and an imaging device having the same. [Background technology]

[0002] There is a demand for an imaging device that can provide a field of view of nearly 360 degrees, such as omnidirectional imaging. As such an imaging device, a method is known in which the imaging device has multiple optical systems and stitches together images captured by each optical system (stitching process) (Patent Document 1).

[0003] To meet such needs with a single lens without using multiple optical systems, a compact optical system with a wide angle of view exceeding 180 degrees is required. A fisheye lens with intermediate imaging has been disclosed as an optical system with a wide angle of view exceeding 180 degrees (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5839135 specification [Patent Document 2] Patent No. 7045611 specification Summary of the Invention [Problem to be solved by the invention]

[0005] An imaging device that has multiple optical systems and stitches together images captured by each optical system to obtain an omnidirectional image requires an image sensor for each optical system, resulting in high costs. Furthermore, errors in the image sensors can cause color and brightness differences in the captured images. Therefore, correcting these differences creates a burden when performing stitching. Furthermore, incorporating multiple optical systems increases the number of lenses, resulting in higher costs.

[0006] Lenses with a wide angle of view exceeding 180 degrees tend to have a large front lens diameter. To mitigate this, it is effective to use a system with intermediate imaging. However, unless appropriate conditions are specified, it is difficult to achieve sufficient miniaturization of both the overall length and diameter.

[0007] An object of the present invention is to provide an optical system that has a small overall system size and high optical performance, using a lens with a wide imaging angle of view exceeding 180 degrees, suitable for omnidirectional imaging. [Means for solving the problem]

[0008] In order to achieve the above object, an optical system according to one aspect of the present invention is an optical system having an intermediate image, which comprises a first optical system having a plurality of lens elements arranged on the object side of the intermediate image position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate image position, and is characterized in that, when the optical system having an intermediate image is focused at infinity, the paraxial lateral magnification of the second optical system is β2 and the imaging angle of view of the optical system having an intermediate image is ω [°], the optical system is characterized in that it satisfies the following conditional expression: -1.60<β2<-1.01 (1) 180<2ω<280 (2)

[0009] In addition, another aspect of the present invention provides an optical system having an intermediate image, which comprises a first optical system having a plurality of lens elements arranged on the object side of the intermediate image position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate image position, and which is characterized in that, when the optical system having intermediate image formation is focused at infinity, the paraxial lateral magnification of the second optical system is β2 and the imaging angle of view of the optical system having intermediate image formation is ω [°], the optical system is characterized in that it satisfies the following conditional formula: β2<-1.01 (1d) 180<2ω·····(2d) [Effects of the Invention]

[0010] According to the present invention, an optical system can be obtained that has a wide imaging angle of view exceeding 180 degrees, yet is compact overall and has high optical performance. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a lens of an optical system according to a first embodiment. [Figure 2] 3A to 3C are aberration diagrams of the optical system of Example 1. [Figure 3] FIG. 10 is a cross-sectional view of a lens of an optical system according to a second embodiment. [Figure 4] 10A to 10C are aberration diagrams of the optical system of Example 2. [Figure 5] FIG. 10 is a cross-sectional view of a lens of an optical system according to a third embodiment. [Figure 6] 10A and 10B are aberration diagrams of the optical system of Example 3 when focused at infinity. DETAILED DESCRIPTION OF THE INVENTION

[0012] First, let us explain the drawings. Figure 1 is a cross-sectional view of an optical system. O denotes the optical axis. LM denotes the intermediate imaging position. The intermediate imaging position is the intersection of the object paraxial ray and the optical axis O when focusing on an object at infinity. L1 denotes the first optical system. The first optical system is made up of multiple lens elements arranged on the object side of the intermediate imaging position M. L2 denotes the second optical system. The second optical system is made up of multiple lens elements arranged on the image side of the intermediate imaging position M. SP denotes the aperture stop. IP denotes the image plane.

[0013] FIG. 2 shows aberration diagrams when focused at infinity. In the spherical aberration diagram, the vertical axis Fno represents the F-number. The vertical axis ω for astigmatism, distortion, and chromatic aberration represents the half angle of view. The half angle of view represents the half angle of view calculated by actual ray tracing. The horizontal axis represents the amount of each aberration. In the spherical aberration diagram, d represents the d-line (wavelength 587.56 nm) and g represents the g-line (wavelength 435.835 nm). In the astigmatism diagram, S represents the sagittal image plane at the d-line and M represents the meridional image plane at the d-line. Distortion aberration is shown for the d-line. The projection method used in the entire optical system of each embodiment of the present invention is equidistant projection. In the chromatic aberration diagram, g represents the g-line. Note that the projection method in the entire optical system of the present invention is not limited to equidistant projection.

[0014] Next, a method for obtaining an optical system that has a wide imaging angle of view exceeding 180 degrees, yet is compact overall and has high optical performance will be described.

[0015] An optical system according to one aspect of the present invention is an optical system having intermediate imaging, and includes, in order from the object side to the image side, a first optical system having a plurality of lens elements arranged closer to the object than an intermediate imaging position, and a second optical system having a plurality of lens elements arranged closer to the image than the intermediate imaging position, wherein when the optical system having intermediate imaging is focused at infinity, the paraxial magnification of the second optical system is β2 and the imaging angle of view of the optical system having intermediate imaging is ω [°], -1.60<β2<-1.01 (1) 180<2ω<280 (2) The present invention is characterized in that the following condition is satisfied.

[0016] In addition, an optical system according to another aspect of the present invention is an optical system having an intermediate image, comprising, in order from the object side to the image side, a first optical system having a plurality of lens elements arranged closer to the object than an intermediate image position, and a second optical system having a plurality of lens elements arranged closer to the image than the intermediate image position, wherein when the optical system having an intermediate image is focused at infinity, the paraxial magnification of the second optical system is β2 and the imaging angle of view of the optical system having an intermediate image is ω [°], β2<-1.01 (1d) 180<2ω·····(2d) The present invention is characterized in that the following condition is satisfied.

[0017] Here, the intermediate image position is defined as the point where the paraxial ray of an object intersects with the optical axis when the object is focused at infinity.

[0018] When measuring the imaging angle of view, the imaging angle of view in the image height range is obtained by multiplying the short side of the sensor of the imaging device by 0.916 and rounding the value to the nearest whole number. For example, when measuring using a full-size sensor with a long side of the sensor of 36 mm and a short side of 24 mm, the imaging angle of view measured at an image range of 22 mm is used. The imaging half angle of view of the optical system of the present invention is described in the examples.

[0019] When measuring the imaging angle of view, the range where the peripheral light amount is 30% or more is considered to be the imaging angle of view.

[0020] By using an optical system with intermediate imaging, it becomes easy to reduce the size of the first optical system in the radial direction even when the imaging angle of view is wide, exceeding 180 degrees.

[0021] Conditions (1) and (1d) are conditions for obtaining an optical system that has a wide angle of view exceeding 180 degrees, yet is compact and has high optical performance. The paraxial lateral magnification β2 of the second optical system refers to the lateral magnification when a paraxial image formed by the first optical system is used as an object of the second optical system and the object is imaged on the paraxial image plane of the entire optical system. In order to achieve a compact optical system, β2 must be smaller than −1. By making β2 smaller than −1, the paraxial object height of the second optical system is smaller than the height of the paraxial image plane of the second optical system (the paraxial image plane of the entire optical system), making it easier to miniaturize the second optical system. Furthermore, the height of the paraxial image plane formed by the first optical system is also smaller than the height of the paraxial image plane formed by the second optical system, making it easier to miniaturize the first optical system.

[0022] If the upper limit of conditional formula (1) or (1d) is exceeded and the paraxial lateral magnification β2 of the second optical system becomes too large, the paraxial object height of the second optical system becomes larger than the height of the paraxial image plane of the second optical system, making it difficult to obtain an optical system with a compact overall system.

[0023] Conditions (2) and (2d) are conditions for obtaining an omnidirectional imaging device with a nearly 360-degree field of view that exceeds the imaging angle of 180 degrees and is within a range where the imaging device is unlikely to be captured in the image. If the imaging angle of view narrows by exceeding the lower limit of condition (2) or (2d), it becomes impossible to obtain a nearly omnidirectional wide field of view.

[0024] Each embodiment is configured to have the above configuration and an optical system with intermediate imaging that satisfies conditional expressions (1) and (2), or conditional expressions (1d) and (2d). This results in an optical system that has a wide imaging angle of view exceeding 180 degrees, yet is compact overall and has high optical performance.

[0025] Preferably, the lower limits should be set as in conditional expressions (1) and (2).

[0026] If the paraxial lateral magnification β2 of the second optical system becomes small by going below the lower limit of conditional expression (1), the magnification of the object in the second optical system becomes large. Therefore, by exceeding the lower limit of conditional expression (1), it becomes easier to correct various aberrations.

[0027] If the upper limit of conditional expression (2) is exceeded, the imaging angle of view will become wider. Therefore, if the upper limit of conditional expression (1) is not exceeded, it becomes easier to make the entire system compact.

[0028] Preferably, the range of conditional expression (1) or (1d) should be set as follows: -1.50<β2<-1.07 (1a)

[0029] It is more preferable to set the range of conditional expression (1a) as follows: -1.40<β2<-1.10 (1b)

[0030] It is preferable to set the range of conditional expression (2) as follows: 182<2ω<270···(2a)

[0031] It is more preferable to set the range of conditional expression (2a) as follows: 185<2ω<265···(2b)

[0032] It is preferable to set the range of conditional expression (2d) as follows: 182<2ω≦360···(2c)

[0033] It is more preferable to set the range of conditional expression (2c) as follows: 185<2ω<330···(2e)

[0034] It is more preferable to set the range of conditional expression (2e) as follows: 190<2ω<300···(2f)

[0035] In each embodiment, it is more preferable to satisfy the following conditions.

[0036] The distance on the optical axis from the vertex of the object-side surface of the lens closest to the object in an optical system having intermediate image formation to the intermediate image formation position is defined as LM, and the total length of the lens in the optical system having intermediate image formation is defined as TL. In this case, it is advisable to set the distance LM on the optical axis to the intermediate image formation position so as to satisfy the following conditional expression: 0.25 <LM / TL<0.55···(3)

[0037] Conditional expression (3) is a conditional expression that makes it easier to obtain a compact optical system. If the lower limit of conditional expression (3) is exceeded, LM, the distance on the optical axis to the intermediate image position, becomes too short, making it difficult to reduce the size of the second optical system. If the upper limit of conditional expression (3) is exceeded, LM, the distance on the optical axis to the intermediate image position, becomes too long, making it difficult to reduce the size of the first optical system.

[0038] It is preferable to set conditional expression (3) as follows: 0.30 <LM / TL<0.50···(3a)

[0039] It is more preferable to set conditional expression (3a) as follows: 0.32 <LM / TL<0.45···(3b)

[0040] In the first optical system, the refractive index at the d-line (587.56 nm) is defined as Nd1. In this case, it is preferable to set the refractive index Nd1 so that three or more lenses constituting the first optical system, including the lens closest to the object, satisfy the following conditional expression: 1.90 <Nd1<2.40···(4)

[0041] Conditional formula (4) is a conditional formula that makes it easy to obtain a wide angle of view and high optical performance. If the lower limit of conditional formula (4) is exceeded, the refractive index of the lenses that make up the first optical system becomes too low, making it difficult to achieve a wide angle of view while also achieving good aberration correction. This is because as the angle of view becomes wider, the refractive power of each lens, particularly the lens closest to the object, becomes stronger, causing increased aberrations. If the upper limit of conditional formula (4) is exceeded, the refractive index becomes too high, making it difficult to manufacture the glass.

[0042] It is preferable to set conditional expression (4) as follows: 1.95 <Nd1<2.30···(4a)

[0043] It is more preferable to set conditional expression (3a) as follows: 2.00 <Nd1<2.20···(4b)

[0044] In the second optical system, the refractive index at the d-line (587.56 nm) is defined as Nd2. In this case, it is preferable to set the refractive index Nd2 so that two or more lenses constituting the second optical system satisfy the following conditional expression: 1.90 <Nd2<2.40···(5)

[0045] Conditional formula (5) is a conditional formula that makes it easier to obtain high optical performance. If the lower limit of conditional formula (5) is exceeded, the refractive index of the lenses that make up the second optical system becomes too low, making it difficult to achieve good aberration correction. This is because aberrations occur when the image formed by the first optical system is enlarged at the paraxial magnification defined by conditional formula (1). If the upper limit of conditional formula (5) is exceeded, the refractive index becomes too high, making it difficult to manufacture the glass.

[0046] It is preferable to set conditional expression (5) as follows: 1.95 <Nd2<2.30···(5a)

[0047] It is more preferable to set conditional expression (3a) as follows: 2.00 <Nd2<2.20···(5b)

[0048] In the second optical system, starting from the lens closest to the image, the lens group having a negative composite focal length is designated as group 2b, the focal length of group 2b is designated as f2b, and the focal length of the entire optical system having an intermediate image is designated as f. In this case, it is advisable to set the focal length f2b of group 2b so as to satisfy the following conditional expression: -40.0 <f2b / |f|<-10.0···(6)

[0049] Conditional expression (6) is a conditional expression that makes it easy to achieve high optical performance while maintaining a wide angle of view. For example, when the imaging angle of view is wide, exceeding 200 degrees, the negative refractive power of the lens closest to the object in an optical system with intermediate image formation becomes strong. Providing negative refractive power to the 2b group is effective in correcting various aberrations, such as astigmatism and field curvature, that occur in this lens. If the focal length of the 2b group becomes too long, as a result of exceeding the lower limit of conditional expression (6), the 2b group will not be able to sufficiently correct aberrations, making it difficult to achieve high optical performance. If the focal length of the 2b group becomes too short, as a result of exceeding the upper limit of conditional expression (6), the aberrations that occur in the 2b group will increase, making it difficult to achieve high optical performance.

[0050] It is preferable to set conditional expression (6) as follows: -30.0 <f2b / |f|<-15.0···(6a)

[0051] It is more preferable to set conditional expression (3a) as follows: -28.0 <f2b / |f|<-20.0···(6b)

[0052] The distance on the optical axis between the 2b group and the image plane of the optical system having the intermediate image is defined as LB. In this case, it is preferable to set the distance LB on the optical axis so as to satisfy the following conditional expression: 0.01 <LB / TL<0.30···(7)

[0053] Conditional expression (7) is a conditional expression that facilitates the miniaturization of the optical system. For example, in the case of a wide angle of view exceeding 200 degrees, the negative refractive power of the lens closest to the object in the optical system with intermediate image formation becomes strong. As mentioned above, it is effective to give the 2b group negative refractive power to correct various aberrations such as astigmatism and field curvature that occur in this lens. To facilitate the miniaturization of the optical system, it is effective to position the 2b group close to the image plane of the optical system with intermediate image formation. If the lower limit of conditional expression (7) is exceeded, the axial distance LB becomes too short, and the lens becomes too close to the image plane of the optical system with intermediate image formation. This may make it difficult to configure a mechanical mechanism when using this optical system in an interchangeable lens system, for example. If the axial distance LB becomes too long, exceeding the upper limit of conditional expression (7), it becomes difficult to miniaturize the entire optical system with intermediate image formation.

[0054] It is preferable to set conditional expression (7) as follows: 0.04 <LB / TL<0.25···(7a)

[0055] It is more preferable to set conditional expression (3a) as follows: 0.05 <LB / TL<0.10···(7b)

[0056] In the first optical system, the group 1a is a group having multiple lens elements that is located closer to the object side than the first intersection point of the most off-axis chief ray and the optical axis, counting from the object side, and the focal length of group 1a is f1a. In this case, it is advisable to set the focal length f1a of group 1a so as to satisfy the following conditional expression: -4.50 <f1a / |f|<-0.50···(8)

[0057] Conditional expression (8) is a conditional expression that makes it easier to obtain a wide angle of view and high optical performance. If the focal length f1a of the 1a group becomes too long, exceeding the lower limit of conditional expression (8), it becomes difficult to obtain a wide angle of view. If the focal length f1a of the 1a group becomes too short, exceeding the upper limit of conditional expression (8), various aberrations such as curvature of field that occur in the 1a group increase, making it difficult to obtain high optical performance.

[0058] It is preferable to set conditional expression (8) as follows: -3.50 <f1a / |f|<-0.60···(8a)

[0059] It is more preferable to set conditional expression (3a) as follows: -1.50 <f1a / |f|<-0.70···(8b)

[0060] The focal length of the first optical system is defined as f1. In this case, it is preferable to set the focal length f1 of the first optical system so as to satisfy the following conditional expression. 0.50 <f1 / |f|<1.2···(9)

[0061] Conditional expression (9) is a conditional expression that makes it easier to obtain a wide angle of view and high optical performance. If the focal length f1 of the first optical system becomes too short by exceeding the lower limit of conditional expression (9), various aberrations such as curvature of field that occur in the first group increase, making it difficult to obtain high optical performance. If the focal length f1 of the first optical system becomes too long by exceeding the upper limit of conditional expression (9), it becomes difficult to obtain a wide angle of view.

[0062] It is preferable to set conditional expression (9) as follows: 0.60 <f1 / |f|<1.1···(9a)

[0063] It is more preferable to set conditional expression (3a) as follows: 0.70 <f1 / |f|<1.0···(9b)

[0064] The focal length of the second optical system is defined as f2. In this case, it is preferable to set the focal length f2 of the second optical system so as to satisfy the following conditional expression. 5.0 <f2 / |f|<25.0···(10)

[0065] Conditional expression (10) is a conditional expression that makes it easier to achieve compactness and high optical performance. If the focal length f2 becomes too short, exceeding the lower limit of conditional expression (10), various aberrations such as spherical aberration and coma will occur in the second optical system, making it difficult to achieve high optical performance. If the focal length f2 becomes too long, exceeding the upper limit of conditional expression (10), the overall length of the second optical system will increase, making it difficult to achieve compactness.

[0066] It is preferable to set conditional expression (10) as follows: 8.0 <f2 / |f|<23.0···(10a)

[0067] It is more preferable to set conditional expression (3a) as follows: 12.0 <f2 / |f|<20.0···(10b)

[0068] In the first optical system, the group having multiple lens elements that are not part of the group 1a is called group 1b, and the focal length of group 1b is set to f1b. In this case, it is preferable to set the focal length f1b of group 1b so that the following conditional expression is satisfied: 1.60 <f1b / |f|<5.00···(11)

[0069] Conditional expression (11) is a conditional expression that makes it easier to achieve compactness and high optical performance. If the lower limit of conditional expression (11) is exceeded and the focal length f1b becomes too short, various aberrations such as spherical aberration and coma occur in the 1b lens unit, making it difficult to achieve high optical performance. If the upper limit of conditional expression (11) is exceeded and the focal length f1b becomes too long, the overall length of the 1b lens unit becomes large, making it difficult to achieve compactness.

[0070] It is preferable to set conditional expression (11) as follows: 1.80 <f1b / |f|<3.50···(11a)

[0071] It is more preferable to set conditional expression (3a) as follows: 2.00 <f1b / |f|<3.00···(11b) [Example]

[0072] Example 1 is an optical system with a focal length of -6.57 mm, an F-number of 2.91, and an intermediate image with a half angle of view of 95.7 degrees. For distortion correction, an equidistant projection method is used. The entire optical system is composed of a first optical system L1 having multiple lens elements positioned closer to the object than the intermediate image position, a second optical system L2 having multiple lens elements positioned closer to the image than the intermediate image position, and an aperture stop.

[0073] The first optical system L1 is composed of, in order from the object side, a negative meniscus lens convex toward the object side, a negative meniscus lens convex toward the object side, a biconcave negative lens, a biconvex positive lens, a biconvex positive lens, an aperture stop, a cemented lens consisting of a negative meniscus lens convex toward the object side and a biconvex positive lens, a biconvex positive lens, a biconvex negative lens, a biconcave positive lens, a negative meniscus lens convex toward the image side, and a positive lens surface convex toward the object side. This configuration facilitates achieving a wide angle of view and correcting various aberrations such as field curvature. Furthermore, by forming an intermediate image using the first optical system L1 and making the height of its paraxial image plane smaller than the height of the paraxial image plane of the entire optical system, it is easy to achieve a compact optical system as a whole.

[0074] The second optical system L2 is composed of, in order from the object side, a positive lens surface convex toward the image side, a positive meniscus lens surface convex toward the image side, a cemented lens consisting of a biconvex positive lens and a biconcave negative lens, a cemented lens consisting of a negative meniscus lens surface convex toward the object side and a biconvex positive lens, a biconvex positive lens, and a positive meniscus lens surface convex toward the object side. This configuration satisfies conditional formula (1), with a paraxial magnification of -1.3 for the second optical system when focusing on an object at infinity, and also makes it easy to correct various aberrations such as spherical aberration and coma. [Example]

[0075] Example 2 is an optical system with a focal length of -5.15 mm, an F-number of 2.91, and an intermediate image with a half angle of view of 125 degrees. For distortion correction, an equidistant projection method is used. The entire optical system is composed of a first optical system L1 having multiple lens elements positioned closer to the object than the intermediate image position, a second optical system L2 having multiple lens elements positioned closer to the image than the intermediate image position, and an aperture stop.

[0076] The first optical system L1 is composed of, in order from the object side, a negative meniscus lens convex toward the object side, a negative meniscus lens convex toward the object side, a negative meniscus aspherical lens convex toward the object side, a biconvex positive lens, a cemented lens consisting of a negative meniscus lens convex toward the object side and a biconvex positive lens, a biconvex positive lens, a biconvex positive lens, a biconvex negative lens, and a biconvex positive lens. This configuration makes it easy to obtain a wide angle of view and correct various aberrations such as field curvature. In addition, by forming an intermediate image using the first optical system L1 and making the height of its paraxial image plane smaller than the height of the paraxial image plane of the entire optical system, it is easy to obtain a compact optical system as a whole.

[0077] The second optical system L2 is composed of, in order from the object side, a negative meniscus lens convex toward the object side, a biconvex positive lens, a positive meniscus lens convex toward the image side, a cemented lens consisting of a biconvex positive lens and a negative meniscus lens convex toward the image side, an aperture stop, a cemented lens consisting of a negative meniscus lens convex toward the object side and a biconvex positive lens, a biconvex positive lens, and a negative meniscus lens convex toward the object side. This configuration satisfies conditional formula (1), setting the paraxial magnification of the second optical system at infinity to -1.21, and makes it easy to correct various aberrations such as spherical aberration and coma. [Example]

[0078] Example 3 is an optical system with a focal length of -4.97 mm, an F-number of 2.91, and an intermediate image with a half angle of view of 130 degrees. For distortion correction, an equidistant projection method is used. The entire optical system is composed of a first optical system L1 having multiple lens elements positioned closer to the object than the intermediate image position, a second optical system L2 having multiple lens elements positioned closer to the image than the intermediate image position, and an aperture stop.

[0079] The first optical system L1 is composed of, in order from the object side, a negative meniscus lens convex toward the object side, a negative meniscus lens convex toward the object side, a negative meniscus aspherical lens convex toward the object side, a positive meniscus lens convex toward the image side, a cemented lens consisting of a negative meniscus lens convex toward the object side and a biconvex positive lens, a biconvex positive lens, a biconvex positive lens, a biconvex negative lens, and a biconvex positive lens. This configuration makes it easy to obtain a wide angle of view and correct various aberrations such as field curvature. In addition, by forming an intermediate image using the first optical system L1 and making the height of its paraxial image plane smaller than the height of the paraxial image plane of the entire optical system, it is easy to obtain a compact optical system as a whole.

[0080] The second optical system L2 is composed of, in order from the object side, a negative meniscus lens convex toward the object side, a biconvex positive lens, a positive meniscus lens convex toward the image side, a cemented lens consisting of a biconvex positive lens and a negative meniscus lens convex toward the image side, an aperture stop, a cemented lens consisting of a negative meniscus lens convex toward the object side and a biconvex positive lens, a biconvex positive lens, and a negative meniscus lens convex toward the object side. This composition satisfies conditional formula (1), setting the paraxial magnification of the second optical system at -1.20 when focusing on an object at infinity, and makes it easy to correct various aberrations such as spherical aberration and coma.

[0081] Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments and various modifications and variations are possible within the scope of the present invention. For example, aberrations may be corrected by image processing. Furthermore, components such as a low-pass filter or an IR cut filter may be placed in front of the image plane as needed.

[0082] Numerical data for each example is shown below.

[0083] In each embodiment, i indicates the order counted from the object side in the order in which the optical axis O passes, ri indicates the radius of curvature of the ith optical surface (ith surface), and di indicates the axial distance along the optical axis between the ith surface and the (i+1)th surface. Also, ndi and vdi are the refractive index and Abbe number of the material of the ith optical member for the d-line, respectively. The aspherical shape is when the X-axis is in the direction of the optical axis, the H-axis is perpendicular to the optical axis, the direction of travel of the ray is positive, R is the paraxial radius of curvature, k is the conic constant, and A4, A6, A8, and A10 are the respective aspherical coefficients. x=(h 2 / R) / [1+{1-(1+k)(h / R) 2} 1 / 2 ]+A4·h 4 +A6·h 6 +A8·h 8 +A10·h 10 It is expressed by the following formula.

[0084] * denotes a surface having an aspherical shape.

[0085] "ex" is 10 -x This means:

[0086] BF is the back focus in air.

[0087] Table 1 shows the relationship between the parameters for each of the above-mentioned conditional expressions and the numerical data for each conditional expression. [Example]

[0088] Unit: mm Surface Data Surface number rd nd vd Effective diameter 1 26.795 1.54 2.00069 25.5 28.90 2 8.476 4.89 16.44 3 17.565 1.29 1.80810 22.8 15.83 4 7.936 6.86 12.49 5 -9.450 1.29 1.59522 67.7 11.13 6 16.128 1.51 11.90 7 35.081 5.89 2.00100 29.1 12.77 8 -21.484 0.20 13.68 9 77.545 5.34 1.89190 37.1 13.29 10 -216.973 3.49 12.26 11 (Aperture) ∞ 1.65 10.87 12 79.290 1.29 1.73800 32.3 11.07 13 12.489 5.87 1.59522 67.7 11.08 14 -17.054 13.01 11.47 15 12.788 7.56 1.59522 67.7 17.35 16 -26.958 0.30 15.98 17 -24.938 1.54 1.85478 24.8 15.60 18 11.627 1.77 14.18 19 23.690 7.68 2.00100 29.1 14.80 20 -29.107 1.75 15.47 21 -13.102 1.03 1.73800 32.3 15.38 22 -37.669 0.55 16.49 23 38.068 11.40 18.37 24 -28.255 30.79 18.40 25 -731.909 4.68 2.00069 25.5 18.35 26 -48.830 0.20 18.40 27 21.724 4.93 1.43875 94.7 17.32 28 -33.823 1.29 1.66565 35.6 16.21 29 237.786 13.64 15.36 30 169.212 1.29 2.00100 29.1 13.87 31 17.621 4.36 1.43875 94.7 13.63 32 -28.007 0.20 14.05 33 38.349 2.74 1.48749 70.2 14.15 34 -514.091 0.29 13.99 35 21.999 4.56 1.48749 70.2 13.79 36 59.042 36.61 12.64 Image plane ∞ Various data Focal length -6.57 F-number 2.91 Half angle of view [°] 95.7 Image height 11.00 Lens length 193.27 BF 36.61 Entrance pupil position 7.85 Exit pupil position -14.40 Front principal point position 0.43 Back principal point position 43.18 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 5.05 76.30 12.64 -5.56 L1a 1 -20.30 28.80 -8.01 -68.99 L1b 12 21.77 42.35 14.85 -43.85 L2 24 57.29 68.96 166.95 -95.23 Single lens data Lens starting surface focal length 1 1 -12.93 2 3 -19.05 3 5 -9.83 4 7 14.04 5 9 64.60 6 12 -20.25 7 13 13.08 8 15 15.69 9 17 -9.10 10 19 14.07 11 21 -27.72 12 23 23.98 13 25 52.11 14 27 30.99 15 28 -44.40 16 30 -19.73 17 31 25.39 18 33 73.32 19 35 69.14 [Example]

[0089] Unit: mm Surface Data Surface number rd nd vd Effective diameter 1 36.248 2.50 2.00069 25.5 60.00 2 19.130 10.52 37.20 3 20.917 1.29 1.80810 22.8 24.71 4 7.952 5.98 14.95 5* 28.810 0.90 1.58313 59.4 12.94 6 5.314 3.07 9.22 7 96.702 5.15 1.88300 40.8 9.22 8 -93.984 2.66 9.03 9 23.129 1.29 1.85478 24.8 8.52 10 10.811 9.66 1.59522 67.7 8.09 11 -11.405 0.20 13.25 12 17.000 4.52 1.59522 67.7 14.93 13 -160.889 0.26 14.62 14 29.877 6.07 1.59522 67.7 14.30 15 -276.427 3.53 12.56 16 -11.560 1.54 1.85478 24.8 11.32 17 18.525 2.11 12.28 18 32.174 4.51 2.00100 29.1 15.97 19 -28.392 2.25 16.92 20 29.452 1.03 1.73800 32.3 18.40 21 16.763 0.26 18.35 22 17.066 11.69 1.72916 54.7 18.05 23 -164.612 31.65 18.40 24 -262.519 4.84 2.00069 25.5 17.97 25 -41.691 7.59 18.08 26 25.475 5.26 1.43875 94.7 18.12 27 -26.475 1.29 1.66565 35.6 17.68 28 -68.326 4.20 17.49 29 (Aperture) ∞ 14.05 15.99 30 981.640 1.29 2.00100 29.1 11.54 31 13.326 4.87 1.43875 94.7 11.85 32 -22.657 0.20 13.51 33 21.783 9.94 1.48749 70.2 15.35 34 -71.774 10.30 16.75 35 33.931 3.20 1.48749 70.2 18.49 36 21.576 13.50 18.14 Image plane ∞ Aspheric data 5th page K = 0.00000e+00 A 4=-7.47091e-04 A 6= 6.23343e-06 A 8= 1.45562e-08 A10=-2.33660e-10 Various data Focal length -5.15 F-number 2.91 Half angle of view [°] 125 Image height 11.00 Lens length 193.13 BF 13.50 Entrance pupil position 14.78 Exit pupil position -37.25 Front principal point position 9.11 Back principal point position 18.65 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 4.25 65.74 18.80 -3.49 L1a 1 -4.87 29.39 11.44 -10.94 L1b 9 11.69 33.69 6.61 -21.13 L2 20 77.75 111.64 140.50 -158.38 L2b 35 -132.83 3.20 6.46 4.11 Single lens data Lens starting surface focal length 1 1 -43.67 2 3 -16.61 3 5 -11.33 4 7 54.67 5 9 -24.95 6 10 11.13 7 12 26.08 8 14 45.64 9 16 -8.14 10 18 15.65 11 20 -54.60 12 22 21.80 13 24 48.99 14 26 30.53 15 27 -65.74 16 30 -13.50 17 31 19.95 18 33 35.52 19 35 -132.83 [Example]

[0090] Unit: mm Surface Data Surface number rd nd vd Effective diameter 1 35.588 2.50 2.00069 25.5 60.00 2 19.253 9.66 37.44 3 21.341 1.29 1.80810 22.8 26.39 4 8.516 6.55 16.00 5* 46.057 0.90 1.58313 59.4 13.31 6 5.331 3.19 9.26 7 -3121.984 5.15 1.88300 40.8 9.22 8 -45.328 2.83 9.03 9 23.333 1.29 1.85478 24.8 8.16 10 10.646 10.38 1.59522 67.7 9.05 11 -11.636 0.20 14.29 12 17.114 4.09 1.59522 67.7 15.89 13 -224.823 0.26 15.52 14 26.932 6.55 1.59522 67.7 15.03 15 -136.644 2.93 12.75 16 -11.851 1.54 1.85478 24.8 11.52 17 16.067 2.45 12.20 18 28.907 4.47 2.00100 29.1 16.41 19 -32.837 1.84 17.25 20 35.729 1.03 1.73800 32.3 18.39 21 16.721 0.26 18.38 22 16.910 12.06 1.72916 54.7 18.20 23 -70.851 31.72 18.40 24 -279.831 4.74 2.00069 25.5 16.10 25 -41.961 5.48 16.96 26 26.671 4.95 1.43875 94.7 17.11 27 -24.528 1.29 1.66565 35.6 16.72 28 -62.717 2.20 16.58 29 (Aperture) ∞ 16.63 15.79 30 274.787 1.29 2.00100 29.1 12.40 31 13.274 5.34 1.43875 94.7 12.78 32 -23.751 0.40 14.61 33 21.492 10.49 1.48749 70.2 17.11 34 -63.724 8.67 18.35 35 33.448 3.09 1.48749 70.2 19.28 36 21.130 13.50 18.75 Image plane ∞ Aspheric data 5th page K = 0.00000e+00 A 4=-6.36716e-04 A 6= 6.62496e-06 A 8=-1.14994e-08 A10=-7.44905e-11 Various data Focal length -4.97 F-number 2.91 Imaging half angle [°] 130 Image height 11.00 Lens length 191.19 BF 13.50 Entrance pupil position 14.72 Exit pupil position -43.73 Front principal point position 9.32 Back principal point position 18.47 Lens group data Group starting plane Focal length Lens length Front principal point position Rear principal point position L1 1 4.14 66.22 18.66 -3.39 L1a 1 -5.11 29.23 11.19 -11.81 L1b 9 11.91 34.16 6.86 -20.83 L2 20 86.56 109.63 157.59 -176.92 L2b 35 -128.24 3.09 6.15 3.89 Single lens data Lens starting surface focal length 1 1 -45.39 2 3 -18.36 3 5 -10.42 4 7 52.05 5 9 -24.03 6 10 11.31 7 12 26.89 8 14 38.37 9 16 -7.78 10 18 15.94 11 20 -43.59 12 22 19.87 13 24 48.84 14 26 30.01 15 27 -61.34 16 30 -13.97 17 31 20.30 18 33 34.35 19 35 -128.24

[0091] [Table 1]

[0092] The disclosure of each embodiment includes the following configuration.

[0093] (Configuration 1) The optical system with intermediate imaging comprises a first optical system having a plurality of lens elements arranged on the object side of the intermediate imaging position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate imaging position, and is characterized in that the optical system with intermediate imaging satisfies the following conditional formula when the paraxial lateral magnification of the second optical system at infinity focusing is β2 and the imaging angle of view of the optical system with intermediate imaging is ω [°]. -1.60<β2<-1.01 180<2ω<280

[0094] (Configuration 2) The optical system with intermediate imaging described in configuration 1 is characterized in that, when the distance on the optical axis from the object-side vertex of the lens closest to the object in the optical system with intermediate imaging to the intermediate imaging position is LM and the total lens length of the optical system with intermediate imaging is TL, the following conditional expression is satisfied: 0.25 <LM / TL<0.55

[0095] (Configuration 3) The optical system with intermediate imaging according to configuration 1, wherein, in the first optical system, when the refractive index at the d-line (587.56 nm) is Nd1, three or more lenses constituting the first optical system, including the lens closest to the object, satisfy the following conditional expression: 1.90 <Nd1<2.40

[0096] (Configuration 4) The optical system with intermediate imaging according to configuration 1 or 2, characterized in that, when the refractive index of the second optical system at the d-line (587.56 nm) is Nd2, two or more lenses constituting the second optical system satisfy the following conditional expression: 1.90 <Nd2<2.40

[0097] (Configuration 5) The optical system with intermediate imaging according to any one of configurations 1 to 3, wherein in the second optical system, the lens group having a negative composite focal length is group 2b, starting from the lens arranged closest to the image, the focal length of group 2b is f2b, and the focal length of the entire optical system with intermediate imaging is f, the following conditional expression is satisfied: -40.0 <f2b / |f|<-10.0

[0098] (Configuration 6) The optical system with intermediate image formation according to configuration 5, wherein the following condition is satisfied, where LB is the distance on the optical axis between the 2b group and the image plane of the optical system with intermediate image formation: 0.01 <LB / TL<0.30

[0099] (Configuration 7) The optical system with intermediate imaging according to any one of configurations 1 to 6, wherein when in the first optical system, a group having a plurality of lens elements that is located closer to the object side than the first intersection point of the most off-axis chief ray and the optical axis from the object side is designated as group 1a and the focal length of group 1a is designated as f1a, the following conditional expression is satisfied: -4.50 <f1a / |f|<-0.50

[0100] (Configuration 8) 8. The optical system with intermediate imaging according to any one of configurations 1 to 7, wherein the following conditional expression is satisfied when the focal length of the first optical system is f1: 0.50 <f1 / |f|<1.2

[0101] (Configuration 9) 9. The optical system with intermediate imaging according to any one of configurations 1 to 8, wherein the following conditional expression is satisfied when the focal length of the second optical system is f2: 5.0 <f2 / |f|<25.0

[0102] (Configuration 10) 10. The optical system with intermediate imaging according to any one of configurations 1 to 9, wherein, in the first optical system, when a group having a plurality of lens elements that do not constitute group 1a is group 1b and the focal length of group 1b is f1b, the optical system with intermediate imaging according to any one of configurations 1 to 9 is characterized in that the following conditional expression is satisfied: 1.60 <f1b / |f|<5.00

[0103] (Configuration 11) An optical system with intermediate imaging, comprising a first optical system having a plurality of lens elements arranged on the object side of the intermediate imaging position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate imaging position, wherein the optical system with intermediate imaging is characterized in that, when the paraxial lateral magnification of the second optical system is β2 and the imaging angle of view of the optical system with intermediate imaging is ω [°], the optical system with intermediate imaging satisfies the following conditional expression: β2<-1.01 180<2ω

[0104] (Configuration 12) The optical system with intermediate imaging described in configuration 11 is characterized in that, when the distance on the optical axis from the object-side vertex of the lens closest to the object in the optical system with intermediate imaging to the intermediate imaging position is LM and the total lens length of the optical system with intermediate imaging is TL, the following conditional expression is satisfied. 0.25 <LM / TL<0.55

[0105] (Configuration 13) 13. The optical system with intermediate imaging according to configuration 11 or 12, wherein, in the first optical system, when the refractive index at the d-line (587.56 nm) is Nd1, three or more lenses constituting the first optical system, including the lens closest to the object, satisfy the following conditional expression: 1.90 <Nd1<2.40

[0106] (Configuration 14) 14. An optical system with intermediate imaging according to any one of configurations 11 to 13, characterized in that, when the refractive index at the d-line (587.56 nm) in the second optical system is Nd2, two or more lenses constituting the second optical system satisfy the following conditional expression: 1.90 <Nd2<2.40

[0107] (Configuration 15) The optical system with intermediate imaging according to any one of configurations 11 to 14, characterized in that, in the second optical system, the lens group having a negative composite focal length is group 2b, starting from the lens arranged closest to the image, the focal length of group 2b is f2b, and the focal length of the entire optical system with intermediate imaging is f, the following conditional expression is satisfied: -40.0 <f2b / |f|<-10.0

[0108] (Configuration 16) 16. The optical system with intermediate image formation according to configuration 15, wherein the following condition is satisfied, where LB is the distance on the optical axis between the 2b group and the image plane of the optical system with intermediate image formation: 0.01 <LB / TL<0.30

[0109] (Configuration 17) 17. The optical system with intermediate imaging according to any one of configurations 11 to 16, wherein in the first optical system, when a group having a plurality of lens elements arranged closer to the object side than the first intersection point of the most off-axis chief ray and the optical axis from the object side is designated as group 1a, and the focal length of group 1a is designated as f1a, the optical system with intermediate imaging according to any one of configurations 11 to 16 is characterized in that the following conditional expression is satisfied: -4.50 <f1a / |f|<-0.50 (Configuration 18) 18. The optical system with intermediate imaging according to any one of configurations 11 to 17, wherein the following condition is satisfied when the focal length of the first optical system is f1: 0.50 <f1 / |f|<1.2

[0110] (Configuration 19) 19. The optical system with intermediate imaging according to any one of configurations 11 to 18, wherein the following condition is satisfied when the focal length of the second optical system is f2: 5.0 <f2 / |f|<25.0

[0111] (Configuration 20) 19. The optical system with intermediate imaging according to any one of configurations 11 to 19, wherein, in the first optical system, when a group having a plurality of lens elements that do not constitute group 1a is group 1b and the focal length of group 1b is f1b, the optical system with intermediate imaging according to any one of configurations 11 to 19 is characterized in that the following conditional expression is satisfied: 1.60 <f1b / |f|<5.00

[0112] (Configuration 21) 21. An optical system with intermediate imaging according to any one of configurations 11 to 20, characterized in that the following conditional expression is satisfied: 180<2ω≦360

[0113] (Configuration 22) 22. An optical system with intermediate imaging according to any one of configurations 11 to 21, characterized in that the following conditional expression is satisfied: -1.60<β2<-1.01

[0114] (Configuration 23) 23. An imaging device comprising: an optical system having an intermediate image formation according to any one of configurations 1 to 22; and an imaging element for acquiring an image formed by the optical system. [Explanation of symbols]

[0115] O optical axis C most off-axis chief ray LM intermediate imaging position L1 1st optical system L1a Group 1a L1b Group 1b L2 2nd optical system L2b Group 2b SP aperture stop IP image plane

Claims

1. The optical system with intermediate imaging comprises a first optical system having a plurality of lens elements arranged on the object side of the intermediate imaging position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate imaging position, and is characterized in that, when the optical system with intermediate imaging is focused at infinity, the paraxial lateral magnification of the second optical system is β2 and the imaging angle of view of the optical system with intermediate imaging is ω [°], the optical system with intermediate imaging satisfies the following conditional expression: ―１．６０＜β２＜－１．０１ 180<2ω<280

2. The optical system with intermediate image formation described in claim 1, characterized in that when the distance on the optical axis from the object-side vertex of the lens closest to the object in the optical system with intermediate image formation to the intermediate image formation position is LM and the total lens length of the optical system with intermediate image formation is TL, the following conditional expression is satisfied. 0.25<LM / TL<0.55

3. 2. The optical system with intermediate imaging according to claim 1, wherein, in the first optical system, when a refractive index at the d-line (587.56 nm) is defined as Nd1, three or more lenses constituting the first optical system, including the lens closest to the object, satisfy the following conditional expression: 1.90<Nd1<2.40

4. 2. The optical system with intermediate imaging according to claim 1, wherein, when the refractive index at the d-line (587.56 nm) in the second optical system is Nd2, two or more lenses constituting the second optical system satisfy the following conditional expression: 1.90<Nd2<2.40

5. 2. The optical system with intermediate imaging according to claim 1, wherein, in the second optical system, the lens group having a negative composite focal length is the 2b group, starting from the lens arranged closest to the image, the focal length of the 2b group is f2b, and the focal length of the entire optical system with intermediate imaging is f, the following conditional expression is satisfied: -40.0<f2b / |f|<-10.0

6. 6. The optical system with intermediate image formation according to claim 5, wherein the following condition is satisfied, where LB is the distance on the optical axis between the 2b-th group and the image plane of the optical system with intermediate image formation: 0.01<LB / TL<0.30

7. 2. The optical system with intermediate imaging according to claim 1, wherein, in the first optical system, when a group 1a is defined as a group having a plurality of lens elements that is located closer to the object side than the first intersection point of the most off-axis chief ray and the optical axis from the object side, and when a focal length of the group 1a is defined as f1a, the following conditional expression is satisfied: -4.50<f1a / |f|<-0.50

8. 2. The optical system with intermediate imaging according to claim 1, wherein the following condition is satisfied when the focal length of the first optical system is f1: 0.50<f1 / |f|<1.2

9. 2. The optical system with intermediate imaging according to claim 1, wherein the following condition is satisfied when the focal length of the second optical system is f2: 5.0<f2 / |f|<25.0

10. 2. The optical system with intermediate imaging according to claim 1, wherein, in the first optical system, when a group having a plurality of lens elements that are not part of the group 1a is designated as group 1b and the focal length of group 1b is designated as f1b, the following conditional expression is satisfied: 1.60<f1b / |f|<5.00

11. An optical system with intermediate imaging, comprising a first optical system having a plurality of lens elements arranged on the object side of the intermediate imaging position, and a second optical system having a plurality of lens elements arranged on the image side of the intermediate imaging position, wherein the optical system with intermediate imaging is characterized in that, when the paraxial lateral magnification of the second optical system is β2 and the imaging angle of view of the optical system with intermediate imaging is ω [°], the optical system with intermediate imaging satisfies the following conditional expression: β２＜－１．０１ 180<2ω

12. The optical system with intermediate imaging described in claim 11, characterized in that the following conditional expression is satisfied, where LM is the distance on the optical axis from the object-side vertex of the lens closest to the object in the optical system with intermediate imaging to the intermediate imaging position, and TL is the total lens length of the optical system with intermediate imaging. 0.25<LM / TL<0.55

13. 12. The optical system with intermediate imaging according to claim 11, characterized in that, when the refractive index at the d-line (587.56 nm) in the first optical system is Nd1, three or more lenses constituting the first optical system, including the lens closest to the object, satisfy the following conditional expression: 1.90<Nd1<2.40

14. 12. The optical system with intermediate imaging according to claim 11, characterized in that, when the refractive index at the d-line (587.56 nm) in the second optical system is Nd2, two or more lenses constituting the second optical system satisfy the following conditional expression: 1.90<Nd2<2.40

15. 12. The optical system with intermediate imaging according to claim 11, wherein, in the second optical system, the lens group having a negative composite focal length is the 2b group, starting from the lens arranged closest to the image, the focal length of the 2b group is f2b, and the focal length of the entire optical system with intermediate imaging is f, the following conditional expression is satisfied: -40.0<f2b / |f|<-10.0

16. 16. The optical system with intermediate image formation according to claim 15, wherein the following condition is satisfied, where LB is the distance on the optical axis between the 2b-th group and the image plane of the optical system with intermediate image formation: 0.01<LB / TL<0.30

17. 12. The optical system with intermediate imaging according to claim 11, wherein, in the first optical system, when a group having a plurality of lens elements arranged closer to the object side than the first intersection point of the most off-axis chief ray and the optical axis from the object side is defined as group 1a, and the focal length of group 1a is defined as f1a, the following conditional expression is satisfied: -4.50<f1a / |f|<-0.50

18. 12. The optical system with intermediate imaging according to claim 11, wherein the following condition is satisfied when the focal length of the first optical system is f1: 0.50<f1 / |f|<1.2

19. 12. The optical system with intermediate imaging according to claim 11, wherein the following condition is satisfied when the focal length of the second optical system is f2: 5.0<f2 / |f|<25.0

20. 12. The optical system with intermediate imaging according to claim 11, wherein, in the first optical system, when a group having a plurality of lens elements that are not part of the group 1a is designated as group 1b and the focal length of group 1b is designated as f1b, the following conditional expression is satisfied: 1.60<f1b / |f|<5.00

21. 12. The optical system with intermediate imaging according to claim 11, wherein the following condition is satisfied: 180<2ω≦360

22. 22. The optical system with intermediate imaging according to claim 21, wherein the following condition is satisfied: －１．６０＜β２＜－１．０１

23. 23. An imaging apparatus comprising: an optical system having an intermediate image formation according to claim 1; and an imaging element for acquiring an image formed by the optical system.

Images