Imaging lens and imaging device

Abstract

This imaging lens comprises a first lens group, an aperture stop, and a second lens group that are disposed in order from an object side to an image side. The first lens group comprises, in order from the object side to the image side, a fist negative meniscus lens having an aspherical shape on both sides or one side with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens having negative refractive power or a unit having a negative-positive arrangement in order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side from focusing on an infinite-distance object to focusing on a short-distance object. The imaging lens satisfies conditional expression (1) and conditional expression (2). (1): 40.00 < νdL1 < 96.00, (2): -10.0 < fL1 / f < -2.0 where νdL1 is the Abbe number at the d line of the first negative meniscus lens, fL1 is the focal length of the first meniscus lens, and f is the focal length of the entire system at the time of infinite-distance focusing.

Description

Technical Field

[0006] , ,

[0005] , , ,

[0001] This technology relates to the technical field of an imaging lens including a first lens group and a second lens group arranged in order from the object side to the image side, and an imaging device using such an imaging lens.

Background Art

[0002] In digital cameras and the like, there is a demand for a function capable of taking pictures with a wide angle of view for landscape and indoor photography, and various imaging lenses with increased aperture have been proposed (see, for example, Patent Document 1 and Patent Document 2).

[0003] However, an optical system having a wide angle of view and high resolution from the center to the periphery of the screen tends to have deteriorated magnification chromatic aberration, coma aberration, sagittal coma flare, etc. In addition, with the recent increase in pixel count in digital cameras and the like, strict correction of various aberrations has been required for the optical systems used.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Disclosure of the Invention

Problems to be Solved by the Invention

[0005] Conventionally proposed retrofocus type imaging devices are relatively easy to widen the angle of view while securing the flange back, and since the lens existing on the object side most is a strong negative lens, it is necessary to use a glass material with a high refractive index. Also, generally, the higher the refractive index of the glass material, the smaller the Abbe number. Therefore, it is difficult to correct magnification chromatic aberration well.

[0006] In Patent Document 1, various aberrations associated with increasing the aperture are corrected by using a Gaussian-type configuration for the rear group, which is symmetrical to the aperture diaphragm. On the other hand, because the object side needs to have a strong negative refractive power, lenses with negative refractive power on the object side have a small Abbe number. Therefore, this configuration is disadvantageous for correcting chromatic aberration.

[0007] Furthermore, in Patent Document 2, a retrofocus type is employed to achieve a large aperture wide-angle lens while ensuring sufficient flange back distance. However, the front group has a negative refractive power on the object side relative to the aperture diaphragm, while the positive refractive power is on the image side. However, because the refractive power arrangement is asymmetrical across the aperture diaphragm, distortion and chromatic aberration tend to occur more easily.

[0008] Therefore, the objective of this imaging lens and imaging device is to provide a wide-angle lens that enables a larger aperture while correcting various aberrations. [Means for solving the problem]

[0009] The imaging lens according to this technology consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group comprises a positive lens group that moves from the image side to the object side when focusing from an object at infinity to a nearby object, and the first lens group is fixed when focusing from an object at infinity to a nearby object. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1) and (2), Conditional expressions (6), (8), and (9) It satisfies the condition. (1) 40.00 < νdL1 < 85.00 (2)-10.0 <fL1 / f<-2.0 (6)3<|fG1 / fG2| (8)-1.5 <fG2 / fLA<-0.2 (9) 0.3 <BF / f<2.5 however, νdL1: Abbe number of the d-line of the first negative meniscus lens fL1: Focal length of the first negative meniscus lens f: Focal length of the entire system at infinite focus fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. BF: Back focus Let it be so.

[0010] As a result, the negative refractive power is divided on the object side, and the Abbe number and the negative refractive power of the first negative meniscus lens are optimized. Furthermore, during focus drive, the first lens group, which has a large volume and weight relative to the entire system, is not moved in the optical axis direction.

[0011] The imaging lens according to another aspect of the present technology includes a first lens group, an aperture stop, and a second lens group arranged in order from the object side to the image side. The first lens group includes, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and having a convex surface facing the object side, a second negative meniscus lens having a convex surface facing the object side, and a single lens having a negative refractive power or a unit having a negative-positive arrangement in order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an infinite object to a close object. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. Satisfies the following conditional expressions (1), conditional expression (2), conditional expression (5), Conditional expressions (6), (8), and (9) and satisfies. (1) 40.00 < νdL1 < 85.00 (2) -10.0 < fL1 / f < -2.0 (5) 1.5 < fG2F / f < 8.5 (6)3<|fG1 / fG2| (8)-1.5 <fG2 / fLA<-0.2 (9) 0.3 <BF / f<2.5 However, νdL1: Abbe number of the d-line of the first negative meniscus lens fL1: Focal length of the first negative meniscus lens f: Focal length of the entire system at infinite focus fG2F: Focal length of the positive lens group in the second lens group fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. BF: Back focus Let it be so.

[0012] As a result, the negative refractive power on the object side is divided, and the Abbe number and negative refractive power of the first negative meniscus lens are optimized. In addition, the focal length of the positive lens group, which functions as the focusing group, is optimized.

[0025] The imaging device according to the present technology includes an imaging lens and an imaging element that converts an optical image formed by the imaging lens into an electrical signal. The imaging lens includes a first lens group, an aperture stop, and a second lens group arranged in order from the object side to the image side. The first lens group includes, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and a convex surface facing the object side, a second negative meniscus lens having a convex surface facing the object side, and a single lens having a negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an infinite object to a near-distance object. The first lens group is fixed when focusing from an infinite object to a near-distance object. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. Satisfy the following conditional expressions (1) and conditional expression (2). Conditional expressions (6), (8), and (9) Satisfy. (1) 40.00 < νdL1 < 85.00 (2) -10.0 < fL1 / f < -2.0 (6)3<|fG1 / fG2| (8)-1.5 <fG2 / fLA<-0.2 (9) 0.3 <BF / f<2.5 However, νdL1: Abbe number of the d-line of the first negative meniscus lens fL1: Focal length of the first negative meniscus lens f: Focal length of the entire system at infinity focus fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. BF: Back focus Let it be so.

[0026] As a result, in the imaging lens, the negative refractive power is divided on the object side, and the Abbe number and negative refractive power of the first negative meniscus lens are optimized. Furthermore, during focus drive, the first lens group, which has a large volume and weight relative to the entire system, is not moved in the optical axis direction.

[0027] Other imaging devices relating to this technology include an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal, the imaging lens consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side, the first lens group includes, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side, the second lens group includes a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance, The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1), (2), and (5) Conditional expressions (6), (8), and (9) It satisfies the condition. (1) 40.00 < νdL1 < 85.00 (2)-10.0 <fL1 / f<-2.0 (5) 1.5 <fG2F / f<8.5 (6)3<|fG1 / fG2| (8)-1.5 <fG2 / fLA<-0.2 (9) 0.3 <BF / f<2.5 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity fG2F: Focal length of the positive lens group in the second lens group. fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. BF: Back focus Let's assume that.

[0028] As a result, in the imaging lens, the negative refractive power is divided on the object side, and the Abbe number and negative refractive power of the first negative meniscus lens are optimized. In addition, the focal length of the positive lens group that functions as the focusing group is optimized.

[0029] Another imaging lens relating to this technology consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side, the first lens group having, in order from the object side to the image side, a first negative meniscus lens with a convex surface facing the object side and a second negative meniscus lens with a convex surface facing the object side, the first lens group having a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having a negative refractive power closest to the object side of the positive lens to the lens closest to the object side of the positive lens, The lens unit is composed of a lens different from the second negative meniscus lens, The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance, and the distance from the image plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus, and the following conditions (3), (4), and (5) apply. Conditional expression (7) And condition (9') is satisfied. (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 (5) 1.5 <fG2F / f<8.5 (7) 0.30 <fL1 / fL2<2.50 (9′)0.3 <BF / f<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens BF: Back focus Let's assume that.

[0030] This makes it easier for the upper rays of the off-axis field of view to pass through the center of the lens and the lower rays to pass through the periphery of the lens, and also optimizes the refractive power of a positive lens with an aspherical shape on one or both sides, and the distance from the positive lens with an aspherical shape on one or both sides to the aperture diaphragm. Furthermore, the focal length of the positive lens group, which functions as the focusing group, is optimized. In addition, the overall length is shortened.

[0043] Another imaging device relating to this technology comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal, wherein the imaging lens consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side, wherein the first lens group has, in order from the object side to the image side, a first negative meniscus lens with a convex surface facing the object side and a second negative meniscus lens with a convex surface facing the object side, wherein the first lens group has a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having a negative refractive power closest to the object side of the positive lens to the lens closest to the object side of the positive lens, The lens unit is composed of a lens different from the second negative meniscus lens, The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance, and the distance from the image plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus, and the following conditions (3), (4), and (5) apply. Conditional expression (7) And condition (9') is satisfied. (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 (5) 1.5 <fG2F / f<8.5 (7) 0.30 <fL1 / fL2<2.50 (9′)0.3 <BF / f<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens BF: Back focus Let's assume that.

[0044] As a result, in the imaging lens, the upper rays of the off-axis field of view are more likely to pass through the center of the lens and the lower rays are more likely to pass through the periphery of the lens, and the refractive power of the positive lens having an aspherical shape on both sides or one side, and the distance from the positive lens having an aspherical shape on both sides or one side to the aperture diaphragm are optimized. Furthermore, the focal length of the positive lens group, which functions as the focusing group, is optimized. In addition, the overall length is shortened. [Brief explanation of the drawing]

[0045] [Figure 1] Figures 2 to 31, along with this figure, show embodiments of the imaging lens and imaging device of this technology. This figure shows the lens configuration of the first embodiment of the imaging lens. [Figure 2] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the first embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 3] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the first embodiment. [Figure 4] This figure shows the lens configuration of the second embodiment of the imaging lens. [Figure 5] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the second embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 6] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the second embodiment. [Figure 7] This figure shows the lens configuration of the third embodiment of the imaging lens. [Figure 8] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the third embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 9] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the third embodiment. [Figure 10]This figure shows the lens configuration of the fourth embodiment of the imaging lens. [Figure 11] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the fourth embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 12] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the fourth embodiment. [Figure 13] This figure shows the lens configuration of the fifth embodiment of the imaging lens. [Figure 14] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the fifth embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 15] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the fifth embodiment. [Figure 16] This is a diagram showing the lens configuration of the sixth embodiment of the imaging lens. [Figure 17] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the sixth embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 18] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the sixth embodiment. [Figure 19] This is a diagram showing the lens configuration of the seventh embodiment of the imaging lens. [Figure 20] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the seventh embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 21] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the seventh embodiment. [Figure 22] This figure shows the lens configuration of the eighth embodiment of the imaging lens. [Figure 23] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the eighth embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 24] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the eighth embodiment. [Figure 25] This figure shows the lens configuration of the ninth embodiment of the imaging lens. [Figure 26] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the ninth embodiment, showing spherical aberration, astigmatism, and distortion. [Figure 27] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the ninth embodiment. [Figure 28] This figure shows the lens configuration of the tenth embodiment of the imaging lens. [Figure 29] This is a longitudinal aberration diagram in a numerical example where specific numerical values ​​are applied to the 10th embodiment, and it shows spherical aberration, astigmatism, and distortion aberration. [Figure 30] This is a lateral aberration diagram in a numerical example where specific numerical values ​​are applied to the tenth embodiment. [Figure 31] This is a block diagram showing an example of an imaging device. [Modes for carrying out the invention]

[0046] The following describes the configuration for implementing this imaging lens and imaging device.

[0047] [Composition of imaging lens] The imaging lens of this technology consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group comprises a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance, and satisfies the following conditions (1) and (2). (1) 40.00 < νdL1 < 96.00 (2)-10.0 <fL1 / f<-2.0 however, νdL1: Abbe number of the d line of the first negative meniscus lens fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity Let's assume that.

[0048] The first lens group acts as a wide converter in the entire optical system, ensuring a wide field of view while maintaining sufficient back focus. The first lens group has a first negative meniscus lens with its convex surface facing the object side. Because the first lens group acts as a wide converter, it needs to have a retrofocus type refractive power arrangement, with negative refractive power on the object side and positive refractive power on the image side. In this case, by arranging the first negative meniscus lens with an aspherical shape that reduces the conic coefficient with respect to the aperture, it becomes possible to effectively correct distortion and field curvature, as well as miniaturize the first lens group.

[0049] Furthermore, the first lens group comprises, in order from the object side to the image side, a first negative meniscus lens with its convex surface facing the object side, a second negative meniscus lens with its convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive sequence from the object side to the image side. Since the first lens group plays the role of a wide converter, it is necessary to have a retrofocus type refractive power arrangement with negative refractive power on the object side and positive refractive power on the image side. By dividing the negative lens on the object side into a unit consisting of the first negative meniscus lens and the second negative meniscus lens, the negative refractive power can be divided, making it possible to effectively correct various aberrations such as distortion and field curvature.

[0050] Conditional equation (1) specifies the Abbe number of the first negative meniscus lens to be within a desirable range in order to effectively correct chromatic aberration.

[0051] If the value falls below the lower limit of condition (1), the Abbe number of the first negative meniscus lens becomes small, making it difficult to adequately correct chromatic aberration.

[0052] On the other hand, if the upper limit of condition (1) is exceeded, the Abbe number of the first negative meniscus lens increases, and generally, the refractive index tends to decrease. As a result, the refractive index of the first negative meniscus lens decreases, and its refractive power weakens, making it difficult to adequately correct distortion and field curvature.

[0053] Therefore, by satisfying condition (1) with the imaging lens, the Abbe number of the first negative meniscus lens is optimized, and chromatic aberration, distortion, and field curvature can be effectively corrected.

[0054] Furthermore, setting the upper limit of condition (1) to 85.00 can suppress distortion and field curvature, which is preferable.

[0055] Furthermore, setting the lower limit of condition (1) to 48.00 can suppress chromatic aberration, which is preferable.

[0056] Conditional equation (2) defines a preferred range for the first negative meniscus lens, which acts as a wide converter for the first lens group and is closest to the object, in order to increase the angle of view while performing good aberration correction.

[0057] If the value falls below the lower limit of condition (2), the negative refractive power of the first negative meniscus lens relative to the total refractive power of the system becomes weak. As a result, the first lens group, which acts as a wide converter, cannot share the negative refractive power between the first negative meniscus lens and the second negative meniscus lens unit, making it difficult to correct various aberrations such as distortion and field curvature.

[0058] On the other hand, if the upper limit of condition (2) is exceeded, the refractive power of the first negative meniscus lens becomes stronger relative to the refractive power of the entire system. This results in an extremely strong negative refractive power of the first negative meniscus lens, which is undesirable because it worsens distortion and astigmatism.

[0059] Therefore, by satisfying condition (2) with the imaging lens, the negative refractive power of the first negative meniscus lens is optimized, and distortion, field curvature, and astigmatism can be effectively corrected.

[0060] Furthermore, setting the lower limit of condition (2) to -6.5 is preferable, as it can suppress distortion and field curvature.

[0061] According to this imaging lens technology, by using a glass material with a high Abbe number in the lens that has an aspherical surface and the negative refractive power closest to the object, it is possible to provide a wide-angle lens that enables a large aperture while effectively correcting various aberrations, including chromatic aberration.

[0062] [Another imaging lens configuration] Another imaging lens of this technology consists of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side. The first lens group has, in order from the object side to the image side, a first negative meniscus lens with a convex surface facing the object side and a second negative meniscus lens with a convex surface facing the object side. The first lens group has positive lenses with an aspherical shape on both sides or one side, and a lens unit consisting of a lens with negative refractive power closest to the object side of the positive lens to the lens closest to the object side of the positive lens. The second lens group has a group of positive lenses that moves from the image side to the object side when focusing from an object at infinity to an object at close range, and satisfies the following conditions (3) and (4). (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group dLP: Distance from the object-side surface to the image plane of the positive lens in the first lens group. dS: Distance from the aperture diaphragm to the image plane Let's assume that.

[0063] By positioning a positive lens with an aspherical shape on one or both sides of the first lens group near the aperture diaphragm where the marginal rays of the on-axis field of view are high, spherical aberration can be effectively corrected. Furthermore, by positioning this positive lens near the aperture diaphragm, the upper rays of the off-axis field of view pass through the center of the lens and the lower rays pass through the periphery of the lens, thus enabling effective correction of coma aberration.

[0064] The first lens group has a lens unit comprising lenses with negative refractive power closest to the object side of a positive lens having an aspherical shape on one or both sides, and lenses closest to the object side of this positive lens. By arranging the lens unit on the object side of the positive lens having an aspherical shape on one or both sides in this way, it becomes possible to enhance the correction effect of spherical aberration.

[0065] If the value falls below the lower limit of condition (3), the refractive power of the positive lens with an aspherical shape on one or both sides becomes extremely strong compared to the lens unit, resulting in a deterioration of spherical aberration in the entire system. Furthermore, near the aperture, the refractive power of the positive lens with an aspherical shape on one or both sides becomes too strong, causing the light rays incident on the second lens group to converge more, resulting in larger fluctuations in spherical aberration during focusing.

[0066] On the other hand, if the upper limit of condition (3) is exceeded, the refractive power of a positive lens with an aspherical shape on one or both sides becomes extremely weak, and the effect of the aspherical lens is weakened, making it impossible to adequately correct aberrations such as spherical aberration.

[0067] Therefore, by satisfying condition (3) of the imaging lens, the refractive power of the positive lens having an aspherical shape on both sides or one side is optimized, which suppresses fluctuations in spherical aberration during focusing and allows for good correction of various aberrations such as spherical aberration.

[0068] Furthermore, setting the lower limit of condition (3) to -35.00 can suppress chromatic aberration, which is preferable.

[0069] If the upper limit of condition (4) is exceeded, the distance from the positive lens, which has an aspherical shape on both sides or one side, to the aperture diaphragm becomes too large. As a result, when marginal rays of the axial angle of view enter this positive lens, the rays do not spread sufficiently, making it impossible to properly correct aberrations such as spherical aberration.

[0070] On the other hand, if the value falls below the lower limit of condition (4), the distance from the positive lens, which has an aspherical shape on both sides or one side, to the aperture diaphragm becomes too short, causing the lens structure to become unusable.

[0071] Therefore, by satisfying condition (4) of the imaging lens, the distance from the positive lens having an aspherical shape on both sides or one side to the aperture diaphragm is optimized, allowing for good correction of various aberrations such as spherical aberration and enabling the lens structure to be properly configured.

[0072] Furthermore, setting the upper limit of condition (4) to 1.50 allows for better correction of various aberrations such as spherical aberration, which is preferable.

[0073] Furthermore, by setting the upper limit of conditional equation (4) to 1.40, various aberrations such as spherical aberration can be corrected even more effectively, which is preferable.

[0074] With another imaging lens based on this technology, by appropriately defining the focal length of each lens in the first lens group, it is possible to provide a wide-angle lens that enables a large aperture while effectively correcting various aberrations, including chromatic aberration.

[0075] [Configuration of an imaging lens according to one embodiment] In an imaging lens according to one embodiment of this technology (including other aspects of this technology; the same applies hereinafter in "imaging lens"), it is desirable that the following condition (5) is satisfied. (5) 1.5 <fG2F / f<8.5 however, fG2F: Focal length of the positive lens group in the second lens group f: Total focal length of the system when focused at infinity Let's assume that.

[0076] Conditional equation (5) is a conditional equation for appropriately setting the focal length of the positive lens group that functions as the focusing group in the second lens group.

[0077] If the value falls below the lower limit of condition (5), the refractive power of the positive lens group becomes too strong, resulting in large aberrations in the positive lens group that cannot be adequately corrected for spherical aberration and other aberrations.

[0078] On the other hand, if the upper limit of condition (5) is exceeded, the refractive power of the positive lens group becomes too weak, resulting in insufficient focus sensitivity and a longer focus stroke, making it difficult to miniaturize the imaging lens.

[0079] Therefore, by satisfying condition (5) with the imaging lens, the focal length of the positive lens group that functions as the focusing group is optimized, allowing for good correction of various aberrations such as spherical aberration, and shortening the focusing stroke, thereby enabling miniaturization of the imaging lens.

[0080] Furthermore, by setting the upper limit of condition (5) to 6.5, the focus stroke can be shortened and the device can be made smaller, which is preferable.

[0081] Furthermore, setting the lower limit of condition (5) to 2.5 makes it possible to suppress various aberrations such as spherical aberration, which is more preferable.

[0082] In an imaging lens according to one embodiment of this technology, it is desirable that the following condition (6) is satisfied. (6)3<|fG1 / fG2| however, fG1: Focal length of the first lens group fG2: Focal length of the second lens group Let's assume that.

[0083] Conditional equation (6) is a conditional equation for appropriately setting the ratio of refractive powers between the first lens group and the second lens group.

[0084] The first lens group acts as a wide converter in the entire optical system, increasing the angle of view while ensuring sufficient back focus. By making the incident light from the first lens group afocal to the second lens group, spherical aberration fluctuations during focusing can be suppressed.

[0085] Furthermore, setting the lower limit of condition (6) to 4 can suppress various aberrations such as spherical aberration, which is preferable.

[0086] In an imaging lens according to one embodiment of this technology, it is desirable that the following condition (7) is satisfied. (7) 0.30 <fL1 / fL2<2.50 however, fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens Let's assume that.

[0087] The first lens group acts as a wide converter, and by dividing the negative lens on the object side into a unit consisting of a first negative meniscus lens and a second negative meniscus lens, the negative refractive power can be divided, making it possible to correct various aberrations such as distortion and field curvature. Furthermore, the second negative meniscus lens must have a refractive power that is somewhat higher than that of the first negative meniscus lens.

[0088] If the value falls below the lower limit of condition (7), the refractive power of one of the negative meniscus lenses (the first or second negative meniscus lens) weakens, making it impossible to correct distortion and field curvature.

[0089] On the other hand, if the upper limit of condition (7) is exceeded, the refractive power of the first negative meniscus lens weakens, making it difficult to adequately correct chromatic aberration with the first negative meniscus lens.

[0090] Therefore, by satisfying condition (7) of the imaging lens, the refractive powers of the first negative meniscus lens and the second negative meniscus lens are optimized, allowing for good correction of distortion and field curvature, while the first negative meniscus lens also effectively corrects chromatic aberration.

[0091] Furthermore, setting the upper limit of condition (7) to 1.55 can suppress chromatic aberration, which is preferable.

[0092] Furthermore, setting the lower limit of condition (7) to 0.40 can suppress distortion and field curvature, which is preferable.

[0093] In an imaging lens according to one embodiment of this technology, it is desirable that the following condition (8) is satisfied. (8)-1.5 <fG2 / fLA<-0.2 however, fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. Let's assume that.

[0094] In order to shorten the flange back and reduce the overall length, a negative refractive force is required in the second lens group, and condition (8) is a condition for appropriately setting the ratio between the second lens group and the negative air lens in the second lens group.

[0095] If the value falls below the lower limit of condition (8), the refractive power of the negative air lens in the second lens group becomes too strong relative to the second lens group, making it difficult to correct aberrations such as spherical aberration that occur in the negative air lens.

[0096] On the other hand, if the upper limit of condition (8) is exceeded, the refractive power of the negative air lens in the second lens group becomes weaker than that of the second lens group, making it difficult to shorten the flange back and miniaturize the lens.

[0097] Therefore, by satisfying condition (8) of the imaging lens, the refractive power of the negative air lens relative to the second lens group is optimized, allowing for good correction of various aberrations such as spherical aberration, and also enabling miniaturization of the imaging lens by shortening the flange back.

[0098] Furthermore, setting the lower limit of conditional equation (8) to -1.2 can suppress various aberrations such as spherical aberration, which is preferable.

[0099] In an imaging lens according to one embodiment of this technology, the distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus, and it is desirable that the following condition (9) is satisfied. (9) 0.3 <BF / f<2.5 however, BF: Back focus f: Total focal length of the system when focused at infinity Let's assume that.

[0100] If the upper limit of condition (9) is exceeded, the back focus becomes too long, making it impossible to shorten the overall length.

[0101] On the other hand, if the value falls below the lower limit of condition (9), it becomes difficult to secure a sufficient distance between the image plane and the lens closest to the image, resulting in reduced manufacturability.

[0102] Therefore, by satisfying condition (9) of the imaging lens, the back focus can be shortened and the overall length shortened, thereby enabling miniaturization of the imaging lens.

[0103] Furthermore, by setting the upper limit of condition (9) to 1.55, the back focus can be shortened and the overall length can be reduced, which is preferable.

[0104] Furthermore, setting the lower limit of condition (9) to 0.4 is preferable because it ensures a sufficient distance between the image plane and the lens closest to the image, thereby improving manufacturability.

[0105] In an imaging lens according to one embodiment of this technology, it is desirable that the following condition (10) is satisfied. (10) 2.3 <SL1<4.6 however, SL1: Specific gravity of the first negative meniscus lens [g / cm²] Let's assume that.

[0106] The specific gravity of glass materials generally has a positive correlation with the refractive index, with a tendency for the refractive index to increase as the specific gravity increases. Conditional equation (10) is an equation for appropriately setting the specific gravity of the first negative meniscus lens in order to reduce the weight of the lens.

[0107] If the value falls below the lower limit of condition (10), the refractive index of the first negative meniscus lens becomes too small, and the negative refractive power of the first negative meniscus lens weakens, making it impossible for the first negative meniscus lens to properly correct distortion and field curvature. On the other hand, if the value exceeds the upper limit of condition (10), the specific gravity of the first lens group, which occupies the majority of the volume in the entire system, becomes too high, making it difficult to lighten the lenses in the entire system.

[0108] Therefore, by satisfying the condition equation (10) of the imaging lens, the refractive index of the first negative meniscus lens is optimized, allowing for good correction of distortion and field curvature, as well as reducing the overall weight of the lenses.

[0109] In an imaging lens according to one embodiment of this technology, it is desirable that the first lens group be fixed when focusing from an object at infinity to an object at a close distance.

[0110] The first lens group has a large volume and weight relative to the entire system, which is disadvantageous for increasing the speed of focus drive.

[0111] Therefore, because the first lens group is fixed when focusing from an object at infinity to an object at a close distance, the first lens group, which has a large volume and weight relative to the entire system, does not move in the optical axis direction during focus driving, thus enabling faster focus driving.

[0112] [Examples of numerical values ​​for imaging lenses] The following describes specific embodiments of the imaging lens of this technology and numerical examples in which specific numerical values ​​are applied to these embodiments, with reference to the drawings and tables.

[0113] The meanings of the symbols used in the following tables and explanations are as follows.

[0114] "r" represents the paraxial radius of curvature of the i-th surface, "d" represents the axial spacing (thickness of the lens center or air gap) between the i-th surface and the (i+1)-th surface, "nd" represents the refractive index of the lens, etc., at the d-line (λ=587.6nm) starting from the i-th surface, and "νd" represents the Abbe number of the lens, etc., at the d-line starting from the i-th surface.

[0115] Regarding "r", "∞" indicates that the surface is a plane. Regarding "d", "variable" indicates that the interval is variable.

[0116] Aspherical surfaces are marked with an asterisk (*) to the right of the surface number, and aperture diaphragms are marked with the word "diaphragm" to the right of the surface number.

[0117] "κ" is the conic constant (conic constant), and "A4", "A6", "A8", "A10", and "A12" represent the 4th, 6th, 8th, 10th, and 12th order aspherical coefficients, respectively.

[0118] In the following tables showing aspherical coefficients, etc., "En" represents the base-10 exponential notation, i.e., "10 to the power of minus n". For example, "0.12345E-05" represents "0.12345 × (10 to the power of minus five)".

[0119] Some imaging lenses used in each embodiment have an aspherical lens surface. The aspherical shape is defined by the following equation 1, where "x" is the distance in the optical axis direction from the vertex of the lens surface (sag), "y" is the height in the direction perpendicular to the optical axis (image height), "c" is the paraxial curvature at the vertex of the lens (reciprocal of the radius of curvature), "κ" is the conic constant (conic constant), and "A4", "A6", ... are the 4th, 6th, ... aspherical coefficients, respectively.

[0120]

number

[0121] Figures 1, 4, 7, 10, 13, 16, 19, 22, 25, and 28 show the lens configuration at infinity for each embodiment.

[0122] Figures 2, 5, 8, 11, 14, 17, 20, 23, 26, and 29 show the spherical aberration diagrams, astigmatism diagrams, and distortion diagrams for each embodiment at infinity and the closest approach position.

[0123] Figures 3, 6, 9, 12, 15, 18, 21, 24, 27, and 30 show the lateral aberration diagrams for each embodiment at infinity and the closest focusing position. The left column shows the lateral aberration (meridional coma aberration) with a tangential beam, and the right column shows the lateral aberration (sagittal coma aberration) with a sagittal beam.

[0124] <First Embodiment> Figure 1 shows the lens configuration of the imaging lens 1 in the first embodiment of this technology.

[0125] The imaging lens 1 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0126] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0127] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0128] The first lens group G1 consists of seven lenses composed of six lens components.

[0129] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative lens L13 with concave surfaces on both sides, and a positive meniscus lens L14 with a convex surface facing the image side.

[0130] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative lens L13 is an aspherical lens with an aspherical shape formed on both sides.

[0131] The second lens group G2 consists of seven lenses composed of six lens components.

[0132] The six lenses from positive lens L8 to negative lens L13 are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios in the front and back directions, separated by an air gap formed in the second lens group G2.

[0133] Furthermore, the air gap between negative lenses L12 and L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0134] Table 1 shows the lens data for Numerical Example 1, in which specific numerical values ​​were applied to the imaging lens 1.

[0135] [Table 1]

[0136] Table 2 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 1.

[0137] [Table 2]

[0138] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative lens L13 and the positive meniscus lens L14 change. Table 3 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 1.

[0139] [Table 3]

[0140] Table 4 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 of the aspheric surface in Numerical Example 1, along with the cone constant κ.

[0141] [Table 4]

[0142] Table 5 shows the focal lengths of each lens group in Numerical Example 1.

[0143] [Table 5]

[0144] Figure 2 is the longitudinal aberration diagram of numerical example 1, and Figure 3 is the transverse aberration diagram of numerical example 1. In Figure 2, in spherical aberration, the solid line shows the value of the d line (587.56 nm), the dotted line shows the value of the c line (656.27 nm), and the dashed line shows the value of the g line (435.84 nm). In astigmatism, the solid line shows the value of the sagittal image plane of the d line, and the dashed line shows the value of the meridioanal image plane of the d line. In distortion aberration, the value of the d line is shown. In Figure 3, the solid line shows the value of the d line, the dotted line shows the value of the c line, and the dashed line shows the value of the g line, and Y' is the image height on the imaging plane.

[0145] With the above configuration, the imaging lens 1 achieves a large aperture of F-number 1.85 while also being compact.

[0146] Furthermore, from the various aberration diagrams, it is clear that Numerical Example 1 has good correction of various aberrations and possesses excellent imaging performance.

[0147] <Second Embodiment> Figure 4 shows the lens configuration of the imaging lens 2 in the second embodiment of this technology.

[0148] The imaging lens 2 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0149] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive meniscus lens L4 with its convex surface facing the object side, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0150] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L3 and positive meniscus lens L4 are bonded together to form a cemented lens, which is configured as a unit with negative and positive lenses arranged sequentially from the object side to the image side. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0151] The first lens group G1 consists of seven lenses composed of five lens components.

[0152] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, and a negative lens L13 with concave surfaces on both sides.

[0153] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative lens L13 is an aspherical lens with an aspherical shape formed on both sides.

[0154] The second lens group G2 consists of six lenses composed of five lens components.

[0155] The six lenses from positive lens L8 to negative lens L13 are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios in the front and back directions, separated by an air gap formed in the second lens group G2.

[0156] Furthermore, the air gap between negative lenses L12 and L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0157] Table 6 shows the lens data for Numerical Example 2, in which specific numerical values ​​were applied to the imaging lens 2.

[0158] [Table 6]

[0159] Table 7 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 2.

[0160] [Table 7]

[0161] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative lens L13 and the image plane IMG change. Table 8 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 2.

[0162] [Table 8]

[0163] Table 9 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 for the aspheric surface in Numerical Example 2, along with the cone constant κ.

[0164] [Table 9]

[0165] Table 10 shows the focal lengths of each lens group in numerical example 2.

[0166] [Table 10]

[0167] Figure 5 is the longitudinal aberration diagram for numerical example 2, and Figure 6 is the transverse aberration diagram for numerical example 2. In Figure 5, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion, the value of the d line is shown. In Figure 6, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0168] With the above configuration, the imaging lens 2 achieves a large aperture of F-number 2.06 while also being compact.

[0169] Furthermore, from the various aberration diagrams, it is clear that numerical example 2 has good correction of various aberrations and possesses excellent imaging performance.

[0170] <Third Embodiment> Figure 7 shows the lens configuration of the imaging lens 3 in the third embodiment of this technology.

[0171] The imaging lens 3 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0172] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0173] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0174] The first lens group G1 consists of seven lenses composed of six lens components.

[0175] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative meniscus lens L13 with a convex surface facing the image side, and a positive lens L14 with convex surfaces on both sides.

[0176] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative meniscus lens L13 is an aspherical lens with aspherical shapes formed on both sides.

[0177] The second lens group G2 consists of seven lenses composed of six lens components.

[0178] The six lenses, from the positive lens L8 to the negative meniscus lens L13, are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios across the air gap formed in the second lens group G2.

[0179] Furthermore, the air gap between the negative lens L12 and the negative meniscus lens L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0180] Table 11 shows the lens data for numerical example 3, in which specific numerical values ​​were applied to the imaging lens 3.

[0181] [Table 11]

[0182] Table 12 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 3.

[0183] [Table 12]

[0184] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative meniscus lens L13 and the positive lens L14 change. Table 13 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 3.

[0185] [Table 13]

[0186] Table 14 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 of the aspheric surface in Numerical Example 3, along with the cone constant κ.

[0187] [Table 14]

[0188] Table 15 shows the focal lengths of each lens group in numerical example 3.

[0189] [Table 15]

[0190] Figure 8 is the longitudinal aberration diagram for numerical example 3, and Figure 9 is the transverse aberration diagram for numerical example 3. In Figure 8, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion, the value of the d line is shown. In Figure 9, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0191] With the above configuration, the imaging lens 3 achieves a large aperture of F-number 1.85 while also being compact.

[0192] Furthermore, from the various aberration diagrams, it is clear that numerical example 3 has good correction of various aberrations and possesses excellent imaging performance.

[0193] <Fourth Embodiment> Figure 10 shows the lens configuration of the imaging lens 4 in the fourth embodiment of this technology.

[0194] The imaging lens 4 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0195] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive meniscus lens L4 with its convex surface facing the object side, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0196] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L3 and positive meniscus lens L4 are bonded together to form a cemented lens, which is configured as a unit with negative and positive lenses arranged sequentially from the object side to the image side. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0197] The first lens group G1 consists of seven lenses composed of five lens components.

[0198] The second lens group G2 is composed of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative lens L13 with concave surfaces on both sides, and a positive meniscus lens L14 with its convex surface facing the image side.

[0199] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative lens L13 is an aspherical lens with aspherical surfaces formed on both sides.

[0200] The second lens group G2 is composed of seven lenses and six lens components.

[0201] The six lenses from the positive lens L8 to the negative lens L13 are configured as a positive lens group G2F that moves from the image side to the object side when focusing on an object from infinity to a close - distance object. However, during focusing, the front and rear may be moved at different movement ratios across the air gap formed in the second lens group G2.

[0202] Also, the air gap between the negative lens L12 and the negative lens L13 functions as the most strongly negative air lens LA in the refractive power of the second lens group G2.

[0203] Table 16 shows the lens data of Numerical Example 4 in which specific numerical values are applied to the imaging lens 4.

[0204]

Table 16

[0205] Table 17 shows the focal length f, F - number Fno, semi - angle of view ω, image height Y, and overall optical length L of Numerical Example 4.

[0206]

Table 17

[0207] When focusing between infinity and the closest distance (250 mm), the distance between the aperture stop S and the positive lens L8 and the distance between the negative lens L13 and the positive meniscus lens L14 change. Table 18 shows the variable distances at infinity and the closest distance for each surface interval in Numerical Example 4.

[0208]

Table 18

[0209] Table 19 shows the aspherical coefficients A4, A6, A8, A10, A12 of the 4th, 6th, 8th, 10th, and 12th orders in Numerical Example 4 together with the conic constant κ.

[0210]

Table 19

[0211] [[ID=Z4]]The focal lengths of each lens group in Numerical Example 4 are shown in Table 20.

[0212]

Table 20

[0213] Figure 11 is the longitudinal aberration diagram of Numerical Example 4, and Figure 12 is the lateral aberration diagram of Numerical Example 4. In Figure 11, for spherical aberration, the solid line indicates the value of the d-line (587.56 nm), the dotted line indicates the value of the c-line (656.27 nm), the dashed-dotted line indicates the value of the g-line (435.84 nm), for astigmatism, the solid line indicates the value of the sagittal image plane of the d-line, the dashed line indicates the value of the meridional image plane of the d-line, and for distortion, the value of the d-line is shown. In Figure 12, the solid line indicates the value of the d-line, the dotted line indicates the value of the c-line, the dashed-dotted line indicates the value of the g-line, and Y′ is the image height on the imaging plane.

[0214] With the above configuration, the imaging lens 4 realizes a large aperture of F-number 2.11 and is miniaturized.

[0215] Furthermore, from the various aberration diagrams, it is clear that numerical example 4 has good correction of various aberrations and possesses excellent imaging performance.

[0216] <Fifth Embodiment> Figure 13 shows the lens configuration of the imaging lens 5 in the fifth embodiment of this technology.

[0217] The imaging lens 5 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0218] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive meniscus lens L4 with its convex surface facing the object side, a negative lens L5 with concave surfaces on both sides, a positive meniscus lens L6 with its convex surface facing the object side, and a positive lens L7 with convex surfaces on both sides.

[0219] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L3 and positive meniscus lens L4 are bonded together to form a cemented lens, which is configured as a unit with negative and positive lenses arranged sequentially from the object side to the image side. The negative lens L5 and positive meniscus lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive meniscus lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0220] The first lens group G1 consists of seven lenses composed of five lens components.

[0221] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive meniscus lens L9 with its convex surface facing the image side, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative lens L13 with concave surfaces on both sides, and a positive meniscus lens L14 with its convex surface facing the image side.

[0222] The positive meniscus lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative lens L13 is an aspherical lens with aspherical surfaces formed on both sides.

[0223] The second lens group G2 is composed of seven lenses and six lens components.

[0224] The six lenses from the positive lens L8 to the negative lens L13 are configured as a positive lens group G2F that moves from the image side to the object side when focusing on an object from infinity to a close distance. However, during focusing, the front and rear may be moved at different movement ratios with the air gap formed in the second lens group G2.

[0225] Also, the air gap between the negative lens L12 and the negative lens L13 functions as the most powerful negative air lens LA in the refractive power of the second lens group G2.

[0226] Table 21 shows the lens data of Numerical Example 5 in which specific numerical values are applied to the imaging lens 5.

[0227]

Table 21

[0228] Table 22 shows the focal length f, F-number Fno, semi-aperture angle ω, image height Y, and overall optical length L of Numerical Example 5.

[0229]

Table 22

[0230] When focusing between infinity and the closest distance (250 mm), the distance between the aperture stop S and the positive lens L8 and the distance between the negative lens L13 and the positive meniscus lens L14 change. Table 23 shows the variable intervals at infinity and the closest distance for each surface interval in Numerical Example 5.

[0231] [Table 23]

[0232] Table 24 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 for the aspheric surface in Numerical Example 5, along with the cone constant κ.

[0233] [Table 24]

[0234] Table 25 shows the focal lengths of each lens group in numerical example 5.

[0235] [Table 25]

[0236] Figure 14 is the longitudinal aberration diagram for numerical example 5, and Figure 15 is the transverse aberration diagram for numerical example 5. In Figure 14, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion aberration, the value of the d line is shown. In Figure 15, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0237] With the above configuration, the imaging lens 5 achieves a large aperture of F-number 2.47 while also being compact.

[0238] Furthermore, from the various aberration diagrams, it is clear that numerical example 5 has excellent image-forming performance, with various aberrations being well corrected.

[0239] <Sixth Embodiment> Figure 16 shows the lens configuration of the imaging lens 6 in the sixth embodiment of this technology.

[0240] The imaging lens 6 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0241] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative meniscus lens L3 with its convex surface facing the object side, a positive meniscus lens L4 with its convex surface facing the object side, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0242] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0243] The first lens group G1 consists of seven lenses composed of six lens components.

[0244] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, and a negative meniscus lens L13 with a convex surface facing the image side.

[0245] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative meniscus lens L13 is an aspherical lens with aspherical shapes formed on both sides.

[0246] The second lens group G2 consists of six lenses composed of five lens components.

[0247] The six lenses, from the positive lens L8 to the negative meniscus lens L13, are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios across the air gap formed in the second lens group G2.

[0248] Furthermore, the air gap between the negative lens L12 and the negative meniscus lens L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0249] Table 26 shows the lens data for numerical example 6, in which specific numerical values ​​were applied to the imaging lens 6.

[0250] [Table 26]

[0251] Table 27 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 6.

[0252] [Table 27]

[0253] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative meniscus lens L13 and the image plane IMG change. Table 28 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 6.

[0254] [Table 28]

[0255] Table 29 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 for the aspheric surface in Numerical Example 6, along with the cone constant κ.

[0256] [Table 29]

[0257] Table 30 shows the focal lengths of each lens group in numerical example 6.

[0258] [Table 30]

[0259] Figure 17 is the longitudinal aberration diagram for numerical example 6, and Figure 18 is the transverse aberration diagram for numerical example 6. In Figure 17, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion, the value of the d line is shown. In Figure 18, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0260] With the above configuration, the imaging lens 6 achieves a large aperture of F-number 1.85 while also being compact.

[0261] Furthermore, from the various aberration diagrams, it is clear that numerical example 6 has excellent image-forming performance, with various aberrations being well corrected.

[0262] <Seventh Embodiment> Figure 19 shows the lens configuration of the imaging lens 7 in the seventh embodiment of this technology.

[0263] The imaging lens 7 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0264] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0265] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0266] The first lens group G1 consists of seven lenses composed of six lens components.

[0267] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative meniscus lens L13 with a convex surface facing the image side, and a positive lens L14 with convex surfaces on both sides.

[0268] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative meniscus lens L13 is an aspherical lens with aspherical shapes formed on both sides.

[0269] The second lens group G2 consists of seven lenses composed of six lens components.

[0270] The six lenses, from the positive lens L8 to the negative meniscus lens L13, are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios across the air gap formed in the second lens group G2.

[0271] Furthermore, the air gap between the negative lens L12 and the negative meniscus lens L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0272] Table 31 shows the lens data for numerical example 7, in which specific numerical values ​​were applied to the imaging lens 7.

[0273] [Table 31]

[0274] Table 32 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 7.

[0275] [Table 32]

[0276] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative meniscus lens L13 and the positive lens L14 change. Table 33 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 7.

[0277] [Table 33]

[0278] Table 34 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 of the aspheric surface in Numerical Example 7, along with the cone constant κ.

[0279] [Table 34]

[0280] Table 35 shows the focal lengths of each lens group in numerical example 7.

[0281] [Table 35]

[0282] Figure 20 is the longitudinal aberration diagram for numerical example 7, and Figure 21 is the transverse aberration diagram for numerical example 7. In Figure 20, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion, the value of the d line is shown. In Figure 21, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0283] With the above configuration, the imaging lens 7 achieves a large aperture of F-number 1.85 while also being compact.

[0284] Furthermore, from the various aberration diagrams, it is clear that numerical example 7 has excellent image-forming performance, with various aberrations being well corrected.

[0285] <Eighth Embodiment> Figure 22 shows the lens configuration of the imaging lens 8 in the eighth embodiment of this technology.

[0286] The imaging lens 8 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0287] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0288] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0289] The first lens group G1 consists of seven lenses with seven lens components.

[0290] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a positive lens L9 with convex surfaces on both sides, a negative lens L10 with concave surfaces on both sides, a positive lens L11 with convex surfaces on both sides, a negative lens L12 with concave surfaces on both sides, a negative lens L13 with concave surfaces on both sides, and a positive meniscus lens L14 with a convex surface facing the image side.

[0291] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative lens L13 is an aspherical lens with an aspherical shape formed on both sides.

[0292] The second lens group G2 consists of seven lenses composed of six lens components.

[0293] The six lenses from positive lens L8 to negative lens L13 are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios in the front and back directions, separated by an air gap formed in the second lens group G2.

[0294] Furthermore, the air gap between negative lenses L12 and L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0295] Table 1 shows the lens data for numerical example 8, in which specific numerical values ​​were applied to the imaging lens 8.

[0296] [Table 36]

[0297] Table 37 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 8.

[0298] [Table 37]

[0299] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative lens L13 and the positive meniscus lens L14 change. Table 38 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 8.

[0300] [Table 38]

[0301] Table 39 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 of the aspheric surface in Numerical Example 8, along with the cone constant κ.

[0302] [Table 39]

[0303] Table 40 shows the focal lengths of each lens group in numerical example 8.

[0304] [Table 40]

[0305] Figure 23 is the longitudinal aberration diagram for numerical example 8, and Figure 24 is the transverse aberration diagram for numerical example 8. In Figure 23, in spherical aberration, the solid line represents the value of the d line (587.56 nm), the dotted line represents the value of the c line (656.27 nm), and the dashed line represents the value of the g line (435.84 nm). In astigmatism, the solid line represents the value of the sagittal image plane of the d line, and the dashed line represents the value of the meridioanal image plane of the d line. In distortion, the value of the d line is shown. In Figure 24, the solid line represents the value of the d line, the dotted line represents the value of the c line, and the dashed line represents the value of the g line, with Y' being the image height on the imaging plane.

[0306] With the above configuration, the imaging lens 8 achieves a large aperture of F-number 1.86 while also being compact.

[0307] Furthermore, from the various aberration diagrams, it is clear that numerical example 8 has excellent image-forming performance, with various aberrations being well corrected.

[0308] <Ninth Embodiment> Figure 25 shows the lens configuration of the imaging lens 9 in the ninth embodiment of this technology.

[0309] The imaging lens 9 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0310] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive lens L6 with convex surfaces on both sides, and a positive lens L7 with convex surfaces on both sides.

[0311] The first negative meniscus lens L1 and positive lens L7 are aspherical lenses with aspherical shapes formed on both sides. The negative lens L5 and positive lens L6 are bonded together to form a cemented lens, and the negative lens L5 and positive lens L6 constitute the lens unit LN. The positive lens L7 is configured as a positive lens LP with aspherical shapes formed on both sides.

[0312] The first lens group G1 consists of seven lenses composed of six lens components.

[0313] The second lens group G2 consists of, in order from the object side to the image side, a bilaterally convex positive lens L8, a bilaterally convex positive lens L9, a bilaterally concave negative lens L10, a bilaterally convex positive lens L11, a bilaterally concave negative lens L12, a bilaterally concave negative lens L13, and a bilaterally convex positive lens L14.

[0314] The positive lens L9 and the negative lens L10 are bonded together to form a cemented lens. The negative meniscus lens L13 is an aspherical lens with aspherical shapes formed on both sides.

[0315] The second lens group G2 consists of seven lenses composed of six lens components.

[0316] The six lenses, from the positive lens L8 to the negative meniscus lens L13, are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios across the air gap formed in the second lens group G2.

[0317] Furthermore, the air gap between the negative lens L12 and the negative meniscus lens L13 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0318] Table 41 shows the lens data for Numerical Example 1, in which specific numerical values ​​were applied to the imaging lens 9.

[0319] [Table 41]

[0320] Table 42 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and optical length L for numerical example 1.

[0321] [Table 42]

[0322] During focusing between infinity and the closest focusing distance (250mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative meniscus lens L13 and the positive meniscus lens L14 change. Table 43 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 1.

[0323] [Table 43]

[0324] Table 44 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 of the aspheric surface in Numerical Example 1, along with the cone constant κ.

[0325] [Table 44]

[0326] Table 45 shows the focal lengths of each lens group in Numerical Example 1.

[0327] [Table 45]

[0328] Figure 26 is the longitudinal aberration diagram of numerical example 1, and Figure 27 is the transverse aberration diagram of numerical example 1. In Figure 26, in spherical aberration, the solid line shows the value of the d line (587.56 nm), the dotted line shows the value of the c line (656.27 nm), and the dashed line shows the value of the g line (435.84 nm). In astigmatism, the solid line shows the value of the sagittal image plane of the d line, and the dashed line shows the value of the meridioanal image plane of the d line. In distortion aberration, the value of the d line is shown. In Figure 27, the solid line shows the value of the d line, the dotted line shows the value of the c line, and the dashed line shows the value of the g line, and Y' is the image height on the imaging plane.

[0329] With the above configuration, the imaging lens 9 achieves a large aperture of F-number 1.85 while also being compact.

[0330] Furthermore, from the various aberration diagrams, it is clear that Numerical Example 1 has good correction of various aberrations and possesses excellent imaging performance.

[0331] <Tenth Embodiment> Figure 28 shows the lens configuration of the imaging lens 10 in the tenth embodiment of this technology.

[0332] The imaging lens 10 consists of a first lens group G1 having positive refractive power, an aperture diaphragm S, and a second lens group G2 having positive refractive power, all arranged in order from the object side to the image side.

[0333] The first lens group G1 consists of, in order from the object side to the image side, a first negative meniscus lens L1 with its convex surface facing the object side, a second negative meniscus lens L2 with its convex surface facing the object side, a negative lens L3 with concave surfaces on both sides, a positive lens L4 with convex surfaces on both sides, a negative lens L5 with concave surfaces on both sides, a positive meniscus lens L6 with its convex surface facing the object side, and a positive lens L7 with convex surfaces on both sides.

[0334] The first negative meniscus lens L1 and negative lens L3 are aspherical lenses with aspherical shapes formed on both sides. Negative lens L5 and positive lens L6 are bonded together to form a cemented lens.

[0335] The first lens group G1 consists of seven lenses composed of six lens components.

[0336] The second lens group G2 consists of, in order from the object side to the image side, a positive lens L8 with convex surfaces on both sides, a negative lens L9 with concave surfaces on both sides, a positive lens L10 with convex surfaces on both sides, a negative lens L11 with concave surfaces on both sides, a positive lens L12 with convex surfaces on both sides, a negative lens L13 with concave surfaces on both sides, a negative meniscus lens L14 with a convex surface facing the image side, and a negative meniscus lens L15 with a convex surface facing the image side.

[0337] The positive lens L8 and the negative lens L9 are bonded together to form a cemented lens, and the positive lens L10 and the negative lens L11 are also bonded together to form a cemented lens. The negative lens L14 is an aspherical lens with an aspherical shape formed on both sides.

[0338] The second lens group G2 consists of eight lenses composed of six lens components.

[0339] The seven lenses from positive lens L8 to negative lens L14 are configured as a positive lens group G2F that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. However, during focusing, the lenses may be moved at different ratios in the front and back directions, separated by an air gap formed in the second lens group G2.

[0340] Furthermore, the air gap between negative lenses L13 and L14 functions as the negative air lens LA with the strongest refractive power in the second lens group G2.

[0341] Table 46 shows the lens data for numerical example 10, in which specific numerical values ​​were applied to the imaging lens 10.

[0342] [Table 46]

[0343] Table 47 shows the focal length f, F-number Fno, half-angle of view ω, image height Y, and total optical length L for numerical example 10.

[0344] [Table 47]

[0345] During focusing between infinity and the closest focusing distance (190mm), the distance between the aperture diaphragm S and the positive lens L8, and the distance between the negative lens L14 and the negative meniscus lens L15 change. Table 48 shows the variable distances of each plane at infinity and the closest focusing distance in numerical example 10.

[0346] [Table 48]

[0347] Table 49 shows the 4th, 6th, 8th, 10th, and 12th order aspheric coefficients A4, A6, A8, A10, and A12 for the aspheric surface in Numerical Example 10, along with the cone constant κ.

[0348] [Table 49]

[0349] Table 50 shows the focal lengths of each lens group in numerical example 10.

[0350] [Table 50]

[0351] Figure 29 is the longitudinal aberration diagram of numerical example 10, and Figure 30 is the transverse aberration diagram of numerical example 10. In Figure 29, in spherical aberration, the solid line shows the value of the d line (587.56 nm), the dotted line shows the value of the c line (656.27 nm), and the dashed line shows the value of the g line (435.84 nm). In astigmatism, the solid line shows the value of the sagittal image plane of the d line, and the dashed line shows the value of the meridioanal image plane of the d line. In distortion aberration, the value of the d line is shown. In Figure 30, the solid line shows the value of the d line, the dotted line shows the value of the c line, and the dashed line shows the value of the g line, and Y' is the image height on the imaging plane.

[0352] With the above configuration, the imaging lens 10 achieves a large aperture of F-number 2.06 while also being compact.

[0353] Furthermore, from the various aberration diagrams, it is clear that numerical example 10 has excellent image-forming performance, with various aberrations being well corrected.

[0354] [Values ​​in the imaging lens condition formula] The following explains the values ​​in the conditional formula for the imaging lens of this technology.

[0355] Table 51 shows the values ​​of conditional equations (1) to (10) in numerical examples 1 to 10 for imaging lenses 1 to 10.

[0356] [Table 51]

[0357] As is clear from Table 51, imaging lenses 1 to 10 are configured to satisfy conditions (1) to (10).

[0358] [Configuration of the imaging device] The imaging device of this technology consists of a first lens group, an aperture diaphragm, and a second lens group, arranged sequentially from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group comprises a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance, and satisfies the following conditions (1) and (2). (1) 40.00 < νdL1 < 96.00 (2)-10.0 <fL1 / f<-2.0 however, νdL1: Abbe number of the d line of the first negative meniscus lens fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity Let's assume that.

[0359] Therefore, in this imaging device, similar to the imaging lens of this technology, by arranging a first negative meniscus lens having an aspherical shape that reduces the conic coefficient with respect to the aperture in the imaging lens, it becomes possible to correct distortion and field curvature well, and to miniaturize the first lens group.

[0360] Furthermore, similar to the imaging lens of this technology, by dividing the negative lens on the object side of the imaging lens into a unit consisting of a first negative meniscus lens and a second negative meniscus lens, the negative refractive force can be divided, making it possible to effectively correct various aberrations such as distortion and field curvature.

[0361] Furthermore, in the imaging device, by satisfying the condition (1) of the imaging lens, the Abbe number of the first negative meniscus lens is optimized, and chromatic aberration, distortion, and field curvature can be effectively corrected.

[0362] Furthermore, in the imaging device, by satisfying condition (2) with respect to the imaging lens, the negative refractive power of the first negative meniscus lens is optimized, and distortion, field curvature, and astigmatism can be effectively corrected.

[0363] As described above, this imaging device provides a wide-angle lens that enables a large aperture while effectively correcting various aberrations, including chromatic aberration, by using a glass material with a high Abbe number in the lens that has multiple aspherical surfaces and the negative refractive power closest to the object.

[0364] [Another imaging lens configuration] Another imaging lens of this technology comprises an imaging lens consisting of a first lens group, an aperture diaphragm, and a second lens group arranged sequentially from the object side to the image side, the first lens group having a first negative meniscus lens with a convex surface facing the object side and a second negative meniscus lens with a convex surface facing the object side, arranged sequentially from the object side to the image side, the first lens group having a positive lens with an aspherical shape on both sides or one side, and a lens unit consisting of a lens with negative refractive power closest to the object side of the positive lens to the lens closest to the object side of the positive lens, and the second lens group having a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at close range, satisfying the following conditions (3) and (4). (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group dLP: Distance from the object-side surface to the image plane of the positive lens in the first lens group. dS: Distance from the aperture diaphragm to the image plane Let's assume that.

[0365] Therefore, in another imaging device of this technology, similar to another imaging lens of this technology, by arranging the positive lens aperture diaphragm, which has an aspherical shape on both sides or one side of the first lens group, near the diaphragm, the upper rays of the off-axis field of view pass through the center of the lens and the lower rays pass through the periphery of the lens, thereby enabling good correction of coma aberration.

[0366] Furthermore, another imaging device using this technology, similar to another imaging lens using this technology, can enhance the correction effect of spherical aberration by arranging the lens unit on the object side of a positive lens having an aspherical shape on both sides or one side in the imaging lens.

[0367] Furthermore, in the imaging device, by satisfying the condition (3) of the imaging lens, the refractive power of the positive lens having an aspherical shape on both sides or one side is optimized, which suppresses fluctuations in spherical aberration during focusing and allows for good correction of various aberrations such as spherical aberration.

[0368] Furthermore, in an imaging device, if the imaging lens satisfies condition (4), the distance from the positive lens having an aspherical shape on both sides or one side to the aperture diaphragm is optimized, allowing for good correction of various aberrations such as spherical aberration and enabling the construction of an appropriate lens structure.

[0369] As described above, with this imaging device, by appropriately defining the focal lengths of each lens in the first lens group, it is possible to provide a wide-angle lens that enables a large aperture while effectively correcting various aberrations, including chromatic aberration.

[0370] [One embodiment of an imaging device] Figure 31 shows a block diagram of a digital still camera according to one embodiment of the imaging device of this technology.

[0371] The imaging device (digital still camera) 100 includes an image sensor 15 having a photoelectric conversion function that converts captured light into electrical signals, a camera signal processing unit 20 that performs signal processing such as analog-to-digital conversion of captured image signals, and an image processing unit 30 that performs recording and playback processing of image signals. The imaging device 100 also includes a display unit 40 that displays captured images, a R / W (reader / writer) 50 that writes and reads image signals to and from the memory 90, a CPU (Central Processing Unit) 60 that controls the entire imaging device 100, an input unit 70 for various switches and other inputs that can be operated by the user, and a lens drive control unit 80 that controls the driving of the imaging lens 1 (including imaging lenses 2 to 10).

[0372] The camera signal processing unit 20 performs various signal processing on the output signal from the image sensor 15, including conversion to a digital signal, noise reduction, image quality correction, and conversion to luminance and chromatic difference signals.

[0373] The image processing unit 30 performs compression encoding, decompression and decoding of image signals based on a predetermined image data format, as well as conversion processing of data specifications such as resolution.

[0374] The display unit 40 has the function of displaying various data such as the user's operation status to the input unit 70 and captured images.

[0375] The R / W 50 writes image data encoded by the image processing unit 30 to the memory 90 and reads image data recorded in the memory 90.

[0376] The CPU 60 functions as a control processing unit that controls each circuit block provided in the imaging device 100, and controls each circuit block based on instruction input signals from the input unit 70, etc.

[0377] The input unit 70 outputs an instruction input signal to the CPU 60 in response to user operations.

[0378] The lens drive control unit 80 controls a motor (not shown) or the like that drives the lens group based on a control signal from the CPU 60.

[0379] Memory 90 is, for example, a removable semiconductor memory that can be inserted into a slot connected to R / W 50. Alternatively, memory 90 may not be removable from a slot and may be integrated into the imaging device 100.

[0380] The operation of the imaging device 100 will be described below.

[0381] In the standby state for shooting, under the control of the CPU 60, the captured image signal is output to the display unit 40 via the camera signal processing unit 20 and displayed as a camera-through image.

[0382] When an image is captured based on an instruction input signal from the input unit 70, the captured image signal is output from the camera signal processing unit 20 to the image processing unit 30, where it is compressed and encoded, and converted into digital data in a predetermined data format. The converted data is output to the R / W 50 and written to the memory 90.

[0383] Focusing is performed by the lens drive control unit 80 moving the focus lens group based on a control signal from the CPU 60.

[0384] When playing back image data recorded in memory 90, the R / W 50 reads out predetermined image data from memory 90 in response to an operation on the input unit 70, and after decompression and decoding processing is performed by the image processing unit 30, a playback image signal is output to the display unit 40 and the playback image is displayed.

[0385] In this technology, "imaging" refers to a series of processes, some or all of which include the following: photoelectric conversion, which converts the light captured by the image sensor 15 into an electrical signal; conversion of the output signal from the image sensor 15 into a digital signal by the camera signal processing unit 20, noise reduction, image quality correction, conversion to brightness and color difference signals; compression encoding, decompression and decoding of the image signal based on a predetermined image data format by the image processing unit 30, and conversion of data specifications such as resolution; and writing the image signal to the memory 90 by the R / W 50.

[0386] In other words, "imaging" may refer only to the photoelectric conversion process that converts the light captured by the image sensor 15 into an electrical signal, or it may refer to the process from the photoelectric conversion process that converts the light captured by the image sensor 15 into an electrical signal to the conversion of the output signal from the image sensor 15 into a digital signal by the camera signal processing unit 20, noise reduction, image quality correction, conversion to brightness and color difference signals, etc., and then the image processing unit 30 This may refer to the compression coding, decompression and decoding of image signals based on a predetermined image data format, as well as the conversion of data specifications such as resolution. It may also refer to the photoelectric conversion process that converts the light captured by the image sensor 15 into an electrical signal, followed by the conversion of the output signal from the image sensor 15 to a digital signal by the camera signal processing unit 20, noise reduction, image quality correction, conversion to brightness and chromatic difference signals, and the compression coding, decompression and decoding of image signals based on a predetermined image data format, as well as the conversion of data specifications such as resolution by the image processing unit 30. It may also refer to the writing of the image signal to the memory 90 by the R / W 50. The order of each process in the above process may be changed as appropriate.

[0387] Furthermore, in this technology, the imaging device 100 may be configured to include only some or all of the image sensor 15, camera signal processing unit 20, image processing unit 30, and R / W 50 that perform the above processing.

[0388] [others] In the imaging lens and imaging apparatus of this technology, other optical elements such as lenses without refractive power may be arranged in addition to the first lens group G1 and the second lens group G2. In this case, the lens configuration of the imaging lens of this technology is substantially a two-group lens configuration consisting of the first lens group G1 and the second lens group G2.

[0389] Although the above example shows the application of the imaging device to a digital still camera, the scope of application of the imaging device is not limited to digital still cameras. It can be widely applied to digital video cameras, camera sections of digital input / output devices in mobile terminals such as mobile phones with built-in cameras, and so on.

[0390] [This technology] This technology can also be configured as follows:

[0391] <1> It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The following conditions (1) and (2) must be satisfied. Imaging lens. (1) 40.00 < νdL1 < 96.00 (2)-10.0 <fL1 / f<-2.0 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity Let's assume that.

[0392] <2> The following condition (5) is satisfied. The aforementioned <1> The imaging lens described above. (5) 1.5 <fG2F / f<8.5 however, fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity Let's assume that.

[0393] <3> The following condition (6) is satisfied. The aforementioned <1> or the above <2> The imaging lens described above. (6)3<|fG1 / fG2| however, fG1: Focal length of the first lens group fG2: Focal length of the second lens group Let's assume that.

[0394] <4> The following condition (7) is satisfied. The aforementioned <1> From the above <3> The imaging lens listed in any of the following. (7) 0.30 <fL1 / fL2<2.50 however, fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens Let's assume that.

[0395] <5> The following condition (8) is satisfied. The aforementioned <1> from the above <4> The imaging lens listed in any of the following. (8)-1.5 <fG2 / fLA<-0.2 however, fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. Let's assume that.

[0396] <6> The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following condition (9) is satisfied. The aforementioned <1> from the above <5> The imaging lens listed in any of the following. (9) 0.3 <BF / f<2.5 however, BF: Back focus f: Total focal length of the system when focused at infinity Let's assume that.

[0397] <7> The following condition (10) is satisfied. The aforementioned <1> from the above <6> The imaging lens listed in any of the following. (10) 2.3 <SL1<4.6 however, SL1: Specific gravity of the first negative meniscus lens [g / cm²] Let's assume that.

[0398] <8> The first lens group is fixed when focusing from an object at infinity to an object at a close distance. The aforementioned <1> from the above <7> The imaging lens listed in any of the following.

[0399] <9> The system comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal. The aforementioned imaging lens is It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The following conditions (1) and (2) must be satisfied. Imaging device. (1) 40.00 < νdL1 < 96.00 (2)-10.0 <fL1 / f<-2.0 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity Let's assume that.

[0400] <10> It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens with its convex surface facing the object side, and a second negative meniscus lens with its convex surface facing the object side. The first lens group comprises a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having negative refractive power closest to the object side of the positive lens, from the lens closest to the object side of the positive lens to the lens closest to the object side of the positive lens. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The following conditions (3) and (4) are satisfied. Imaging lens. (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane Let's assume that.

[0401] <11> The following condition (5) is satisfied. The aforementioned <10> The imaging lens described above. (5) 1.5 <fG2F / f<8.5 however, fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity Let's assume that.

[0402] <12> The following condition (6) is satisfied. The aforementioned <10> or the above <11> The imaging lens described above. (6)3<|fG1 / fG2| however, fG1: Focal length of the first lens group fG2: Focal length of the second lens group Let's assume that.

[0403] <13> The following condition (7) is satisfied. The aforementioned <10> from the above <12> The imaging lens listed in any of the following. (7) 0.30 <fL1 / fL2<2.50 however, fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens Let's assume that.

[0404] <14> The following condition (8) is satisfied. The aforementioned <10> from the above <13> The imaging lens listed in any of the following. (8)-1.5 <fG2 / fLA<-0.2 however, fG2: Focal length of the second lens group fLA: The focal length of the negative air lens with the strongest refractive power in the second lens group. Let's assume that.

[0405] <15> The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following condition (9) is satisfied. The aforementioned <10> from the above <14> The imaging lens listed in any of the following. (9) 0.3 <BF / f<2.5 however, BF: Back focus f: Total focal length of the system when focused at infinity Let's assume that.

[0406] <16> The following condition (10) is satisfied. The aforementioned <10> from the above <15> The imaging lens listed in any of the following. (10) 2.3 <SL1<4.6 however, SL1: Specific gravity of the first negative meniscus lens [g / cm²] Let's assume that.

[0407] <17> The first lens group is fixed when focusing from an object at infinity to an object at a close distance. The aforementioned <10> from the above <16> The imaging lens listed in any of the following.

[0408] <18> The system comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal. The aforementioned imaging lens is It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens with its convex surface facing the object side, and a second negative meniscus lens with its convex surface facing the object side. The first lens group comprises a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having negative refractive power closest to the object side of the positive lens, from the lens closest to the object side of the positive lens to the lens closest to the object side of the positive lens. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The following conditions (3) and (4) are satisfied. Imaging device. (3)-35.00 <fLN / fLP<-1.05 (4) 1.00 <dLP / dS<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane Let's assume that. [Explanation of Symbols]

[0409] 1-10 Imaging Lenses 100 Imaging device G1 First Lens Group G2 Second Lens Group L1 First Negative Meniscus Lens L2 Second Negative Meniscus Lens L3 lens LN Lens Unit LP (Long-Limited Focal Lens) G2F positive lens group S Aperture diaphragm

Claims

1. It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The first lens group is fixed when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1), (2), (6), (8), and (9) must be satisfied. Imaging lens. (1) 40.00<νdL1<85.00 (2) -10.0<fL1 / f<-2.0 (6) 3<|fG1 / fG2| (8) -1.5<fG2 / fLA<-0.2 (9) 0.3<BF / f<2.5 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: Focal length of the negative air lens with the strongest refractive power in the second lens group. BF: The aforementioned back focus Let's assume that.

2. It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1), (2), (5), (6), (8), and (9) are satisfied. Imaging lens. (1) 40.00<νdL1<85.00 (2) -10.0<fL1 / f<-2.0 (5) 1.5<fG2F / f<8.5 (6) 3<|fG1 / fG2| (8) -1.5<fG2 / fLA<-0.2 (9) 0.3<BF / f<2.5 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity fG2F: Focal length of the positive lens group in the second lens group. fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: Focal length of the negative air lens with the strongest refractive power in the second lens group. BF: The aforementioned back focus Let's assume that.

3. The following condition (5) is satisfied. The imaging lens according to claim 1. (5) 1.5<fG2F / f<8.5 however, fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity Let's assume that.

4. The following condition (7) is satisfied. The imaging lens according to claim 1 or claim 2. (7) 0.30<fL1 / fL2<2.50 however, fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens Let's assume that.

5. The following condition (10) is satisfied. The imaging lens according to claim 1 or claim 2. (10) 2.3<SL1<4.6 however, SL1: Specific gravity of the first negative meniscus lens [g / cm²] Let's assume that.

6. The system comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal. The aforementioned imaging lens is It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The first lens group is fixed when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1), (2), (6), (8), and (9) must be satisfied. Imaging device. (1) 40.00<νdL1<85.00 (2) -10.0<fL1 / f<-2.0 (6) 3<|fG1 / fG2| (8) -1.5<fG2 / fLA<-0.2 (9) 0.3<BF / f<2.5 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: Focal length of the negative air lens with the strongest refractive power in the second lens group. BF: The aforementioned back focus Let's assume that.

7. The system comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal. The aforementioned imaging lens is It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens having an aspherical shape on both sides or one side and with a convex surface facing the object side, a second negative meniscus lens with a convex surface facing the object side, and a single lens with negative refractive power or a unit arranged in a negative-positive order from the object side to the image side. The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (1), (2), (5), (6), (8), and (9) are satisfied. Imaging device. (1) 40.00<νdL1<85.00 (2) -10.0<fL1 / f<-2.0 (5) 1.5<fG2F / f<8.5 (6) 3<|fG1 / fG2| (8) -1.5<fG2 / fLA<-0.2 (9) 0.3<BF / f<2.5 however, νdL1: Abbe number of the d line of the first negative meniscus lens. fL1: Focal length of the first negative meniscus lens f: Total focal length of the system when focused at infinity fG2F: Focal length of the positive lens group in the second lens group. fG1: Focal length of the first lens group fG2: Focal length of the second lens group fLA: Focal length of the negative air lens with the strongest refractive power in the second lens group. BF: The aforementioned back focus Let's assume that.

8. It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens with its convex surface facing the object side, and a second negative meniscus lens with its convex surface facing the object side. The first lens group comprises a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having negative refractive power closest to the object side of the positive lens, from the lens closest to the object side of the positive lens to the lens closest to the object side of the positive lens. The lens unit is composed of a lens different from the second negative meniscus lens, The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (3), (4), (5), (7), and (9') are satisfied. Imaging lens. (3) -35.00<fLN / fLP<-1.05 (4) 1.00<dLP / dS<1.55 (5) 1.5<fG2F / f<8.5 (7) 0.30<fL1 / fL2<2.50 (9') 0.3<BF / f<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens BF: The aforementioned back focus Let's assume that.

9. The following condition (6) is satisfied. The imaging lens according to claim 8. (6) 3<|fG1 / fG2| however, fG1: Focal length of the first lens group fG2: Focal length of the second lens group Let's assume that.

10. The following condition (8) is satisfied. The imaging lens according to claim 8. (8) -1.5<fG2 / fLA<-0.2 however, fG2: Focal length of the second lens group fLA: Focal length of the negative air lens with the strongest refractive power in the second lens group. Let's assume that.

11. The following condition (10) is satisfied. The imaging lens according to claim 8. (10) 2.3<SL1<4.6 however, SL1: Specific gravity of the first negative meniscus lens [g / cm²] Let's assume that.

12. The first lens group is fixed when focusing from an object at infinity to an object at a close distance. The imaging lens according to claim 8.

13. The system comprises an imaging lens and an image sensor that converts the optical image formed by the imaging lens into an electrical signal. The aforementioned imaging lens is It consists of a first lens group, an aperture diaphragm, and a second lens group, arranged in order from the object side to the image side. The first lens group comprises, in order from the object side to the image side, a first negative meniscus lens with its convex surface facing the object side, and a second negative meniscus lens with its convex surface facing the object side. The first lens group comprises a positive lens having an aspherical shape on both sides or one side, and a lens unit composed of a lens having negative refractive power closest to the object side of the positive lens, from the lens closest to the object side of the positive lens to the lens closest to the object side of the positive lens. The lens unit is composed of a lens different from the second negative meniscus lens, The second lens group has a positive lens group that moves from the image side to the object side when focusing from an object at infinity to an object at a close distance. The distance from the image-plane side surface of the lens closest to the image in the second lens group to the image plane is defined as the back focus. The following conditions (3), (4), (5), (7), and (9') are satisfied. Imaging device. (3) -35.00<fLN / fLP<-1.05 (4) 1.00<dLP / dS<1.55 (5) 1.5<fG2F / f<8.5 (7) 0.30<fL1 / fL2<2.50 (9') 0.3<BF / f<1.55 however, fLN: Focal length of the lens unit fLP: Focal length of the positive lens in the first lens group. dLP: Distance from the object-side surface of the positive lens in the first lens group to the image plane. dS: Distance from the aperture diaphragm to the image plane fG2F: Focal length of the positive lens group in the second lens group. f: Total focal length of the system when focused at infinity fL1: Focal length of the first negative meniscus lens fL2: Focal length of the second negative meniscus lens BF: The aforementioned back focus Let's assume that.

Images