Imaging optical system

Abstract

To accommodate large image sensors, and considering the reduction in the weight of the focusing lens which is primarily driven during focusing, we provide an imaging optical system with a reduced overall optical length. [Solution] By arranging a front group GF with positive refractive power and a rear group GR with positive refractive power in order from the object side, and having a first rear group GR1 with negative refractive power that moves during focusing, and a second rear group GR2 with positive refractive power on the image side of the first rear group GR1, it becomes easier to lighten and miniaturize the focusing lens group, and it is possible to suppress the increase in size of the entire lens system.

Description

Technical Field

[0001] The present invention relates to an imaging optical system suitable for a photographing lens used in an imaging device such as a still camera or a video camera.

Background Art

[0002] In recent years, cameras employing large-sized imaging elements have become widespread in imaging devices such as digital still cameras and video cameras.

[0003] In a photographing lens used in an imaging device, a lens with a large aperture ratio is desired to obtain a large-sized defocused image and to use a high-speed shutter.

[0004] Also, for high-speed autofocus and autofocus with good tracking performance, the lens used for focusing is desired to be lightweight in order to reduce the burden on the actuator.

[0005] However, when the photographing lens has a larger aperture ratio, the lens group used for focusing also becomes larger, increasing the burden on the actuator and making high-speed focusing and focusing with good tracking performance difficult.

[0006] As an imaging optical system corresponding to a large-sized imaging element and assuming autofocus, for example, Patent Documents 1 to 3 are disclosed.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] The optical systems described in Patent Documents 1 and 2 do not adequately reduce the weight of the focusing lens group, partly because the lenses that are mainly driven during focusing are composed of multiple elements. As a result, the actuator is subjected to a heavy load during autofocus control.

[0009] The optical systems described in Patent Documents 2 and 3 have a relatively long optical length, which affects the size of the product.

[0010] This invention has been made in view of these circumstances, and aims to provide an imaging optical system that can accommodate large image sensors, takes into consideration the weight reduction of the focusing lens which is mainly driven in focusing, and reduces the overall optical length. [Means for solving the problem]

[0011] To achieve the above objective, the imaging optical system according to the present invention consists of a front group GF with positive refractive power and a rear group GR with positive refractive power, in order from the object side, with a first front group GF1 with negative refractive power on the object side of the front group GF, and within the first front group GF1, in order from the object side, a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the air surface on the image side, and a lens component GF13 with negative refractive power that faces the air surface on the object side, and a second front group GF2 with a cemented lens and positive refractive power on the image side of the front group GF, the second front group GF2 consisting of 5 or fewer lenses, and the rear group GR with negative refractive power at the object side. The lens has a first rear group GR1, and when focusing from infinity to near distance, the distance on the object side of the first rear group GR1 increases and the distance on the image side decreases. The first rear group GR1 has a second rear group GR2 with positive refractive power on the image side, and the second rear group GR2F has a front second rear group GR2F with positive refractive power on the object side of the second rear group GR2, and the front second rear group GR2F has a cemented lens with positive refractive power, and the second rear group GR2R has a rear second rear group GR2R with negative refractive power on the image side of the second rear group GR2, and the rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has two or more lenses, and the aperture diaphragm S is adjacent to the object side or image side of the first rear group GR1. Note that lens components refer to a single lens or a cemented lens formed by joining two or more single lenses.

[0012] Furthermore, in order to achieve the above objective, the imaging optical system according to the present invention consists of a front group GF with positive refractive power and a rear group GR with positive refractive power, in order from the object side, the first front group GF1 with negative refractive power overall on the object side of the front group GF, the first front group GF1 with positive refractive power lens component GF11, the negative refractive power lens component GF12 with a concave surface facing the air surface on the image side and the negative refractive power lens component GF13 with a concave surface facing the air surface on the object side, in order from the object side, the second front group GF2 with a cemented lens and positive refractive power overall on the image side of the front group GF, the second front group GF2 consists of 5 or fewer lenses, and the rear group GR has the most object The lens has a first rear group GR1 which is a single lens with negative refractive power on one side, and when focusing from infinity to near distance, the distance on the object side of the first rear group GR1 increases and the distance on the image side decreases, and on the image side of the first rear group GR1 there is a second rear group GR2 which has positive refractive power, and on the object side of the second rear group GR2 there is a front second rear group GR2F which has positive refractive power, and on the image side of the second rear group GR2 there is a rear second rear group GR2R which has negative refractive power, and the rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has two or more lenses, and there is an aperture diaphragm S adjacent to the object side or image side of the first rear group GR1, and the following condition is satisfied. (1) 1.40 < fGR / f < 20.00 fGR: Focal length of the rear group GR when in focus at infinity. f: Focal length of the entire system at infinity focus The term "lens component" refers to either a single lens or a cemented lens formed by joining two or more single lenses.

[0013] Furthermore, in order to achieve the above objective, the imaging optical system according to the present invention consists of a front group GF with positive refractive power and a rear group GR with positive refractive power, in order from the object side, the first front group GF1 with negative refractive power overall on the object side of the front group GF, the first front group GF1 with positive refractive power lens component GF11, the lens component GF12 with negative refractive power that faces the air surface on the image side, and the lens component GF13 with negative refractive power that faces the air surface on the object side, in order from the object side, the second front group GF2 with positive refractive power overall on the image side of the front group GF, and the first rear group GR1 with negative refractive power at the object side of the rear group GR, focusing from infinity to near distances During operation, the distance between the object side of the first rear group GR1 increases, and the distance between the image side decreases. The first rear group GR1 has a second rear group GR2 with positive refractive power on the image side, and the second rear group GR2 consists of 5 to 7 lenses. Within the second rear group GR2, there is a front second rear group GR2F with positive refractive power on the object side, and the front second rear group GR2F has a cemented lens with positive refractive power. Within the second rear group GR2, there is a rear second rear group GR2R with negative refractive power on the image side, and the rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has 2 or more lenses. The first rear group GR1 has an aperture diaphragm S adjacent to either the object side or the image side, and satisfies the following condition. (1) 1.40 < fGR / f < 20.00 fGR: Focal length of the rear group GR when in focus at infinity. f: Focal length of the entire system at infinity focus The term "lens component" refers to either a single lens or a cemented lens formed by joining two or more single lenses.

[0014] Furthermore, in order to achieve the above objective, the imaging optical system according to the present invention consists of a front group GF with positive refractive power and a rear group GR with positive refractive power, in order from the object side, with a first front group GF1 having negative refractive power overall on the object side of the front group GF, and within the first front group GF1 having, in order from the object side, a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the image-side air surface with a concave surface, and a lens component GF13 with negative refractive power that faces the object-side air surface, and a second front group GF2 having a cemented lens and positive refractive power overall on the image side of the front group GF, the second front group GF2 consisting of 5 or fewer lenses, and the first rear group GR1, which is a single lens with negative refractive power, located furthest to the object side of the rear group GR. Furthermore, when focusing from infinity to near distance, the distance on the object side of the first rear group GR1 increases and the distance on the image side decreases, the image side of the first rear group GR1 has a second rear group GR2 with positive refractive power, the second rear group GR2 consists of 5 to 7 lenses, the object side of the second rear group GR2 has a front second rear group GR2F with positive refractive power, the front second rear group GR2F has a cemented lens with positive refractive power, the image side of the second rear group GR2 has a rear second rear group GR2R with negative refractive power, the rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has 2 or more lenses, and the aperture diaphragm S is adjacent to the object side or image side of the first rear group GR1, and the following condition is satisfied. (1) 1.40 < fGR / f < 20.00 fGR: Focal length of the rear group GR when in focus at infinity. f: Focal length of the entire system at infinity focus The term "lens component" refers to either a single lens or a cemented lens formed by joining two or more single lenses. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide an imaging optical system that can accommodate large image sensors, takes into consideration the weight reduction of the focusing lens which is mainly driven in focusing, and reduces the overall optical length. [Brief explanation of the drawing]

[0016] [Figure 1]It is a lens configuration diagram according to Example 1 of the imaging optical system of the present invention. [Figure 2] It is a lens configuration diagram according to Example 2 of the imaging optical system of the present invention. [Figure 3] It is a lens configuration diagram according to Example 3 of the imaging optical system of the present invention. [Figure 4] It is a lens configuration diagram according to Example 4 of the imaging optical system of the present invention. [Figure 5] It is a lens configuration diagram according to Example 5 of the imaging optical system of the present invention. [Figure 6] It is a lens configuration diagram according to Example 6 of the imaging optical system of the present invention. [Figure 7] It is a lens configuration diagram according to Example 7 of the imaging optical system of the present invention. [Figure 8] It is a lens configuration diagram according to Example 8 of the imaging optical system of the present invention. [Figure 9] It is a lens configuration diagram according to Example 9 of the imaging optical system of the present invention. [Figure 10] It is a longitudinal aberration diagram of the imaging optical system of Example 1 at an infinite shooting distance. [Figure 11] It is a longitudinal aberration diagram of the imaging optical system of Example 1 at a shooting distance of 1.0 m. [Figure 12] It is a longitudinal aberration diagram of the imaging optical system of Example 2 at an infinite shooting distance. [Figure 13] It is a longitudinal aberration diagram of the imaging optical system of Example 2 at a shooting distance of 1.0 m. [Figure 14] It is a longitudinal aberration diagram of the imaging optical system of Example 3 at an infinite shooting distance. [Figure 15] It is a longitudinal aberration diagram of the imaging optical system of Example 3 at a shooting distance of 1.0 m. [Figure 16] It is a longitudinal aberration diagram of the imaging optical system of Example 4 at an infinite shooting distance. [Figure 17] It is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of 1.0 m. [Figure 18] It is a longitudinal aberration diagram of the imaging optical system of Example 5 at an infinite shooting distance. [Figure 19]This is a longitudinal aberration diagram of the imaging optical system of Example 5 at a shooting distance of 1.0 m. [Figure 20] This is a longitudinal aberration diagram of the imaging optical system of Example 6 at an infinity shooting distance. [Figure 21] This is a longitudinal aberration diagram of the imaging optical system of Example 6 at a shooting distance of 1.0 m. [Figure 22] This is a longitudinal aberration diagram of the imaging optical system of Example 7 at an infinity shooting distance. [Figure 23] This is a longitudinal aberration diagram of the imaging optical system of Example 7 at a shooting distance of 1.0 m. [Figure 24] This is a longitudinal aberration diagram of the imaging optical system of Example 8 at an infinity shooting distance. [Figure 25] This is a longitudinal aberration diagram of the imaging optical system of Example 8 at a shooting distance of 1.0 m. [Figure 26] This is a longitudinal aberration diagram of the imaging optical system of Example 9 at an infinity shooting distance. [Figure 27] This is a longitudinal aberration diagram of the imaging optical system of Example 9 at a shooting distance of 1.0 m. [Figure 28] This is a diagram of the lateral aberration of the imaging optical system of Example 1 at an infinity shooting distance. [Figure 29] This is a lateral aberration diagram of the imaging optical system of Example 1 at a shooting distance of 1.0 m. [Figure 30] This is a diagram of the lateral aberration of the imaging optical system of Example 2 at an imaging distance of infinity. [Figure 31] This is a lateral aberration diagram of the imaging optical system of Example 2 at a shooting distance of 1.0 m. [Figure 32] This is a diagram of the lateral aberration of the imaging optical system of Example 3 at an infinity shooting distance. [Figure 33] This is a lateral aberration diagram of the imaging optical system of Example 3 at a shooting distance of 1.0 m. [Figure 34] This is a diagram of the lateral aberration of the imaging optical system of Example 4 at an imaging distance of infinity. [Figure 35] This is a lateral aberration diagram of the imaging optical system of Example 4 at a shooting distance of 1.0 m. [Figure 36] This is a diagram of the lateral aberration of the imaging optical system of Example 5 at an infinity shooting distance. [Figure 37] This is a lateral aberration diagram of the imaging optical system of Example 5 at a shooting distance of 1.0 m. [Figure 38] This is a diagram of the lateral aberration of the imaging optical system of Example 6 at an infinity shooting distance. [Figure 39] This is a lateral aberration diagram of the imaging optical system of Example 6 at a shooting distance of 1.0 m. [Figure 40] This is a diagram of the lateral aberration of the imaging optical system of Example 7 at an imaging distance of infinity. [Figure 41] This is a lateral aberration diagram of the imaging optical system of Example 7 at a shooting distance of 1.0 m. [Figure 42] This is a diagram of the lateral aberration of the imaging optical system of Example 8 at an infinity shooting distance. [Figure 43] This is a lateral aberration diagram of the imaging optical system of Example 8 at a shooting distance of 1.0 m. [Figure 44] This is a diagram of the lateral aberration of the imaging optical system of Example 9 at an infinity shooting distance. [Figure 45] This is a lateral aberration diagram of the imaging optical system of Example 9 at a shooting distance of 1.0 m. [Modes for carrying out the invention]

[0017] As can be seen from the lens configuration diagrams shown in Figures 1, 2, 3, 4, 5, 6, 7, 8, and 9, the imaging optical system of the present invention consists of a front group GF with positive refractive power and a rear group GR with positive refractive power, in order from the object side. The object side of the front group GF has a first front group GF1 with negative refractive power as a whole. The first front group GF1 has, in order from the object side, a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the air surface on the image side, and a lens component GF13 with negative refractive power that faces the air surface on the object side. The image side of the front group GF has a cemented lens and a second front group GF2 with positive refractive power as a whole. The second front group GF2 consists of 5 or fewer lenses, and the rear group GR has a negative refractive power closest to the object. The lens has a first rear group GR1 which is a single lens with refractive power. When focusing from infinity to near distance, the distance on the object side of the first rear group GR1 increases, and the distance on the image side decreases. The image side of the first rear group GR1 has a second rear group GR2 with positive refractive power, which consists of 5 to 7 lenses. Within the second rear group GR2, on the object side, there is a front second rear group GR2F with positive refractive power, which is a cemented lens with positive refractive power. Within the second rear group GR2, on the image side, there is a rear second rear group GR2R with negative refractive power, which is a negative lens with a concave surface facing the air surface on the image side and has two or more lenses. The lens has an aperture diaphragm S adjacent to the object side or image side of the first rear group GR1. In this text, lens components refer to single lenses or cemented lenses formed by joining multiple lenses.

[0018] The reason for adopting the aforementioned configuration is explained below. In order to achieve good aberration correction of the entire system, it is necessary to arrange the lenses appropriately. By arranging the front group GF with positive refractive power and the rear group GR with positive refractive power from the object side, and by having the first rear group GR1 with negative refractive power that moves during focusing, and the second rear group GR2 with positive refractive power on the image side of the first rear group GR1, it becomes easier to lighten and miniaturize the focusing lens group, and the overall size of the lens system can be suppressed.

[0019] The configuration employs a first front group GF1 with an overall negative refractive power on the object side and a second front group GF2 with an overall positive refractive power on the image side within the front group GF, thereby suppressing the increase in positive distortion aberration.

[0020] The first front group GF1 has a configuration in which, starting from the object side, it has a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the air surface on the image side with a concave surface, and a lens component GF13 with negative refractive power that also faces the air surface on the object side with a concave surface. This configuration makes the lens diameter on the image side smaller than that of lens component GF11, and allows for a balance between distortion aberration and Petzval sum between lens components GF12 and GF13.

[0021] The second front group GF2, with its cemented lens configuration, facilitates control over axial chromatic aberration correction. Furthermore, considering aberration correction and preventing an increase in the overall lens length, it is appropriate for the second front group GF2 to be composed of five or fewer lenses.

[0022] The rear group GR has a first rear group GR1 with negative refractive power at the object side. When focusing from infinity to near distance, the spacing of the first rear group GR1 increases on the object side and decreases on the image side. This configuration facilitates good aberration correction during focusing. Furthermore, by making the first rear group GR1 a single lens with negative refractive power, the weight of the focusing lens, which is mainly driven during focusing, is reduced. In addition, by appropriately setting the focal length of each lens group, it is possible to fix parts of the front group GF and rear group GR during focusing, which is suitable for reducing the weight of the moving parts during focusing.

[0023] By adopting a configuration in which the image side of the first rear group GR1 within the rear group GR has a second rear group GR2 with positive refractive power, it is possible to increase the aperture ratio of the lens while keeping the F number small. Furthermore, considering aberration correction and preventing an increase in the overall length of the lens, it is appropriate for the second rear group GR2 to consist of 5 to 7 lenses.

[0024] By having a front second rear group GR2F with positive refractive power on the object side and a rear second rear group GR2R with negative refractive power on the image side within the second rear group GR2, it is possible to reduce the lens diameter of the rear group GR while simultaneously securing a wide image circle that can accommodate large image sensors.

[0025] The front second rear group GR2F has a cemented lens, which effectively corrects axial chromatic aberration and lateral chromatic aberration. The rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side, and has two or more lenses, which ensures a wide image circle and improves the correction of aberrations such as astigmatism.

[0026] By having an aperture diaphragm S adjacent to the object side or image side of the first rear group GR1, the light beam at the maximum field of view can pass through the center of the aperture diaphragm. If the light beam at the maximum field of view does not pass through the center of the aperture diaphragm, a rapid decrease in light intensity occurs when the aperture is stopped down, which is undesirable.

[0027] Furthermore, the imaging optical system of the present invention is more effective when it includes the following configuration.

[0028] The lens component GF11 with positive refractive power, the lens component GF12 with negative refractive power (with its concave surface facing the air surface on the image side), and the lens component GF13 with negative refractive power (with its concave surface facing the air surface on the object side) should each preferably be a single lens to prevent the lens system from becoming excessively large.

[0029] Furthermore, the second front group GF2 should ideally consist of three to four elements in order to achieve both good aberration correction and prevent the lens system from becoming excessively large.

[0030] Furthermore, when focusing from infinity to close distance, it is desirable that the front group GF be fixed to the image plane in order to reduce the weight of the focusing lens.

[0031] Furthermore, if there are no constraints on the focusing actuator, it is not necessary to fix part or all of the front group GF or part or all of the second rear group GR2 when focusing from infinity to near distance. In particular, part or all of the second rear group GR2 may be moved. This allows for better aberration correction during focusing.

[0032] The imaging optical system of the present invention is preferably satisfied with the following condition. (1) 1.40 < fGR / f < 20.00 fGR: Focal length of the rear group GR when in focus at infinity. f: Focal length of the entire system at infinity focus

[0033] Conditional equation (1) defines the ratio of the focal length of the rear group GR to the focal length of the entire system at infinity focus, as a desirable condition for suppressing the increase in size of the entire lens system and correcting aberrations.

[0034] When the upper limit of condition (1) is exceeded and the refractive power of the rear group GR decreases, the reduction effect of the rear group GR decreases, making it difficult to achieve both a large aperture ratio that reduces the F number and the suppression of an increase in the overall size of the lens system.

[0035] If the refractive power of the rear group GR increases beyond the lower limit of condition (1), the aberrations generated in the rear group GR will increase, which is undesirable.

[0036] Furthermore, by limiting the lower limit of the above-mentioned conditional equation (1) to 1.80 and the upper limit to 4.80, the aforementioned effect can be made more certain.

[0037] Furthermore, it is desirable that the imaging optical system of the present invention satisfies the following condition. (2) -1.00 < fL23 / fGF < -0.15 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF

[0038] Conditional equation (2) specifies the ratio of the combined focal length of lens component GF12 and lens component GF13 to the focal length of the front group GF as a preferred condition for suppressing the enlargement of the entire lens system and suppressing positive distortion aberration.

[0039] When the upper limit of condition (2) is exceeded and the combined refractive power of lens component GF12 and lens component GF13 becomes large, it becomes difficult to suppress the increase in size of the entire lens system, especially the increase in the height of the rays passing through the second front group GF2.

[0040] When the lower limit of condition (2) is exceeded and the refractive powers of lens components GF12 and GF13 decrease, the negative distortion aberration in the combined system of lens components GF12 and GF13 decreases. As a result, the positive distortion aberration generated in the front group GF increases, making it difficult to suppress the positive distortion aberration of the entire lens system.

[0041] Furthermore, by limiting the lower limit of the above-mentioned conditional equation (2) to -0.66 and the upper limit to -0.25, the aforementioned effect can be made more certain.

[0042] Furthermore, it is desirable that the imaging optical system of the present invention satisfies the following condition. (3)0.71<(1-βR2F)*(βR2R)<2.50 βR2F: Horizontal magnification of the front second rear group GR2F in the infinity focus state. βR2R: Lateral magnification of the rear second group GR2R in the infinity focus state.

[0043] Conditional equation (3) specifies the lateral magnification of the front second rear group GR2F and the rear second rear group GR2R as conditions for suppressing the enlargement of the rear group GR2 and ensuring a wide image circle.

[0044] If the upper limit of condition (3) is exceeded, and the lateral magnification of the front second rear group GR2F decreases or the lateral magnification of the rear second rear group GR2R increases, the effect of the negative refractive power of the rear second rear group GR2R becomes greater, and the height of the rays passing through the second rear group GR2 increases, which is undesirable.

[0045] When the lower limit of condition (3) is exceeded, and the lateral magnification of the front second rear group GR2F becomes large or the lateral magnification of the rear second rear group GR2R becomes small, the effect of the negative refractive power of the rear second rear group GR2R weakens, making it difficult to obtain a wide image circle.

[0046] Furthermore, by limiting the lower limit of the above-mentioned condition (3) to 0.88 and the upper limit to 1.92, the aforementioned effect can be made more certain.

[0047] Furthermore, it is desirable that the imaging optical system of the present invention satisfies the following condition. (4) 0.45 < D_GR / D_GF < 1.50 D_GR: Length along the optical axis from the object-side face to the image-side face of the rear group GR. D_GF: Length along the optical axis from the object-side face to the image-side face of the front group GF.

[0048] Conditional equation (4) specifies the ratio of the lengths of the rear group GR and the front group GF along the optical axis as a condition for suppressing an increase in the overall size of the lens system.

[0049] When the upper limit of condition (4) is exceeded, and the length of the rear group GR along the optical axis increases while the length of the front group GF decreases, the ray height passing through the rear group GR, especially the ray height passing through the front second rear group GR2F, increases, making it difficult to suppress the increase in the overall size of the lens system.

[0050] When the lower limit of condition (4) is exceeded, and the length of the rear group GR along the optical axis decreases while the length of the front group GF increases, the height of the light rays passing through the front group GF increases, making it difficult to suppress the increase in the overall size of the lens system.

[0051] Furthermore, by limiting the lower limit of the above-mentioned conditional equation (4) to 0.64 and the upper limit to 1.28, the aforementioned effect can be made more certain.

[0052] Furthermore, it is desirable that the imaging optical system of the present invention satisfies the following condition. (5) 0.75 <fGF / f<2.00 (6)-2.0<(1-βR1^2)*(βR2^2)<-0.33 fGF: Focal length of the front group GF in the state of infinity focus f: Focal length of the entire system at infinity focus βR1: Horizontal magnification of the first rear group GR1 in the infinity focus state. βR2: Horizontal magnification of the second rear group GR2 in the infinity focus state.

[0053] Conditional equation (5) specifies the ratio of the focal length of the front group GF to the focal length of the entire system as a desirable condition for suppressing the increase in the size of the entire lens system and correcting aberrations.

[0054] When the upper limit of condition (5) is exceeded and the refractive power of the front group GF decreases, the height of the light rays passing through the first front group GF1 increases, making it difficult to suppress the increase in size of the entire lens system.

[0055] When the refractive power of the front group GF increases beyond the lower limit of condition (5), the aberrations generated in the front group GF become larger, which is undesirable.

[0056] Furthermore, by limiting the lower limit of the above-mentioned conditional equation (5) to 0.85 and the upper limit to 1.50, the aforementioned effect can be made more certain.

[0057] Conditional equation (6) specifies the lateral magnification of the first rear group GR1 and the second rear group GR2 with respect to the focus sensitivity of the first rear group GR1, as a desirable condition for suppressing the enlargement of the entire lens system and correcting aberrations.

[0058] When the upper limit of condition (6) is exceeded and the focus sensitivity of the first rear group GR1 decreases, the amount of focus shift increases, making it difficult to suppress the increase in the overall size of the lens system.

[0059] When the lower limit of condition equation (6) is exceeded and the focus sensitivity of the first rear group GR1 increases, the eccentricity sensitivity of the first rear group GR1 increases, which is undesirable because it increases the aberration variation caused by manufacturing errors.

[0060] Furthermore, by limiting the lower limit of the above-mentioned conditional equation (6) to -1.40 and the upper limit to -0.40, the aforementioned effect can be made more certain.

[0061] Next, the lens configuration of an embodiment relating to the imaging optical system of the present invention will be described. In the following description, the lens configuration will be described in order from the object side to the image side. [Examples]

[0062] Figure 1 is a lens configuration diagram of the imaging optical system of Embodiment 1 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fourteenth lenses.

[0063] The first front group GF1 consists of a biconvex lens GF11, a biconcave lens GF12, and a biconcave lens GF13.

[0064] The second front group GF2 consists of a biconvex lens with aspherical surfaces on both sides, a cemented lens with positive refractive power consisting of a biconvex lens and a negative meniscus lens with a concave surface facing the object, and another biconvex lens.

[0065] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0066] The front second rear group GR2F consists of a positive refractive power cemented lens made up of a biconvex lens and a negative meniscus lens with its concave surface facing the object, and a biconvex lens.

[0067] The rear second group GR2R consists of a negative refractive power cemented lens made up of a biconvex lens and a biconcave lens, and a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object side.

[0068] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0069] Figure 2 is a lens configuration diagram of the imaging optical system of Embodiment 2 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fourteenth lenses.

[0070] The first front group GF1 consists of a biconvex lens GF11, a biconcave lens GF12, and a biconcave lens GF13.

[0071] The second front group GF2 consists of a biconvex lens, a biconvex lens with aspherical surfaces on both sides, and a cemented lens with positive refractive power, which is a biconvex lens and a negative meniscus lens with a concave surface facing the object.

[0072] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0073] The front second rear group GR2F consists of a positive refractive power cemented lens and a biconvex lens, which are composed of a positive meniscus lens with a concave surface facing the object and a negative meniscus lens with a concave surface facing the object.

[0074] The rear second group GR2R consists of a biconcave lens, a biconvex lens, and a biconcave lens with double-sided aspheric surfaces.

[0075] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0076] Figure 3 is a lens configuration diagram of the imaging optical system of Embodiment 3 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to sixth lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the seventh lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the eighth to tenth lenses and a rear second rear group GR2R with negative refractive power from the eleventh to thirteenth lenses.

[0077] The first group GF1 consists of a positive meniscus lens GF11 with its convex side facing the object, a biconcave lens GF12, and a biconcave lens GF13.

[0078] The second front group GF2 consists of a double-sided aspherical biconvex lens and a cemented lens with positive refractive power, which is made up of a biconvex lens and a negative meniscus lens with a concave surface facing the object.

[0079] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0080] The front second rear group GR2F consists of a positive refractive power cemented lens made up of a biconvex lens and a negative meniscus lens with its concave surface facing the object, and a biconvex lens.

[0081] The rear second group GR2R consists of a cemented lens with negative refractive power, comprising a positive meniscus lens with a concave surface facing the object side and a biconcave lens, and a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object side.

[0082] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0083] Figure 4 is a lens configuration diagram of the imaging optical system of Embodiment 4 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to the third lens and a second front group GF2 with positive refractive power from the fourth to the seventh lens. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to the eleventh lens and a rear second rear group GR2R with negative refractive power from the twelfth to the fourteenth lens.

[0084] The first group GF1 consists of a biconvex lens GF11, a biconcave lens GF12, and a negative meniscus lens GF13 with its concave surface facing the object.

[0085] The second front group GF2 consists of a double-sided aspherical biconvex lens and a three-element cemented lens with positive refractive power, composed of a biconvex lens, a biconcave lens, and a biconvex lens.

[0086] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0087] The front second rear group GR2F consists of a bonded lens with positive refractive power, comprising a biconvex lens and a biconcave lens, and a biconvex lens.

[0088] The rear second group GR2R consists of a negative meniscus lens with a convex surface facing the object, a positive meniscus lens with a convex surface facing the object, and a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object.

[0089] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0090] Figure 5 is a lens configuration diagram of the imaging optical system of Embodiment 5 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fourteenth lenses.

[0091] The first group GF1 consists of a positive meniscus lens GF11 with a convex surface facing the object, a negative meniscus lens GF12 with an aspherical surface on the image side and a convex surface facing the object, and a negative meniscus lens GF13 with a concave surface facing the object.

[0092] The second front group GF2 consists of a double-sided aspherical biconvex lens and a three-element cemented lens with positive refractive power, composed of a biconvex lens, a biconcave lens, and a biconvex lens.

[0093] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0094] The front second rear group GR2F consists of a bonded lens with positive refractive power, comprising a biconvex lens and a biconcave lens, and a biconvex lens.

[0095] The rear second group GR2R consists of a negative meniscus lens with a convex surface facing the object, a biconvex lens, and a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object.

[0096] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0097] Figure 6 is a lens configuration diagram of the imaging optical system of Embodiment 6 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fourteenth lenses.

[0098] The first group GF1 consists of a positive meniscus lens GF11 with its convex side facing the object, a biconcave lens GF12, and a biconcave lens GF13.

[0099] The second front group GF2 consists of a biconvex lens with aspherical surfaces on both sides, a cemented lens with positive refractive power consisting of a biconvex lens and a negative meniscus lens with a concave surface facing the object, and another biconvex lens.

[0100] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0101] The front second rear group GR2F consists of a positive refractive power cemented lens made up of a biconvex lens and a negative meniscus lens with its concave surface facing the object, and a biconvex lens.

[0102] The rear second group GR2R consists of a bonded lens with negative refractive power composed of a biconvex lens and a biconcave lens, and a negative meniscus lens with both sides aspherical and the concave side facing the object.

[0103] The aperture diaphragm S is adjacent to the image side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, the front second rear group GR2F moves toward the object side, and the front group GF, aperture diaphragm S, and rear second rear group GR2R are fixed relative to the image plane. A flare-cutting diaphragm FC is positioned between the front group GF and the first rear group GR1. [Examples]

[0104] Figure 7 is a lens configuration diagram of the imaging optical system of Embodiment 7 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to the third lens and a second front group GF2 with positive refractive power from the fourth to the seventh lens. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to the eleventh lens and a rear second rear group GR2R with negative refractive power from the twelfth to the fourteenth lens.

[0105] The first front group GF1 consists of a biconvex lens GF11, a biconcave lens GF12, and a biconcave lens GF13.

[0106] The second front group GF2 consists of a biconvex lens with aspherical surfaces on both sides, a cemented lens with negative refractive power consisting of a biconvex lens and a biconcave lens, and a biconvex lens.

[0107] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0108] The front second rear group GR2F consists of a positive refractive power cemented lens made up of a biconvex lens and a negative meniscus lens with its concave surface facing the object, and a biconvex lens.

[0109] The rear second group GR2R consists of a cemented lens with negative refractive power, comprising a positive meniscus lens with a concave surface facing the object side and a biconcave lens, and a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object side.

[0110] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0111] Figure 8 is a lens configuration diagram of the imaging optical system of Embodiment 8 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fourteenth lenses.

[0112] The first group GF1 consists of GF11, a positive meniscus lens with its convex side facing the object; GF12, a biconcave lens with aspherical surfaces on both sides; and GF13, a negative meniscus lens with its concave side facing the object.

[0113] The second front group GF2 consists of a biconvex lens with aspherical surfaces on both sides, a cemented lens with positive refractive power consisting of a biconvex lens and a negative meniscus lens with a concave surface facing the object, and a positive meniscus lens with a concave surface facing the object.

[0114] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0115] The front second rear group GR2F consists of a bonded lens with positive refractive power, comprising a biconvex lens and a biconcave lens, and a biconvex lens.

[0116] The rear second group GR2R consists of a negative meniscus lens with its convex surface facing the object, a biconvex lens, and a biconcave lens with aspherical surfaces on both sides.

[0117] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, while the front group GF, aperture diaphragm S, and second rear group GR2 remain fixed relative to the image plane. [Examples]

[0118] Figure 9 is a lens configuration diagram of the imaging optical system of Embodiment 9 of the present invention. Starting from the object side, it consists of a front group GF with positive refractive power and a rear group GR with positive refractive power. The front group GF consists of a first front group GF1 with negative refractive power from the first to third lenses and a second front group GF2 with positive refractive power from the fourth to seventh lenses. The rear group GR consists of a first rear group GR1 with negative refractive power from the eighth lens and a second rear group GR2 with positive refractive power. The second rear group GR2 consists of a front second rear group GR2F with positive refractive power from the ninth to eleventh lenses and a rear second rear group GR2R with negative refractive power from the twelfth to fifteenth lenses.

[0119] The first front group GF1 consists of a biconvex lens GF11, a biconcave lens GF12, and a biconcave lens GF13.

[0120] The second front group GF2 consists of a biconvex lens with aspherical surfaces on both sides, a cemented lens with positive refractive power consisting of a biconvex lens and a negative meniscus lens with a concave surface facing the object, and another biconvex lens.

[0121] The first rear group GR1 consists of a negative meniscus lens with double-sided aspherical surfaces and a convex surface facing the object.

[0122] The front second rear group GR2F consists of a bonded lens with positive refractive power, comprising a biconvex lens and a biconcave lens, and a biconvex lens.

[0123] The rear second group GR2R consists of a negative refractive power cemented lens made up of a biconvex lens and a biconcave lens, a negative meniscus lens with an aspherical surface on the image side and a concave surface facing the object side, and a biconvex lens.

[0124] The aperture diaphragm S is adjacent to the object side of the first rear group GR1. When focusing from infinity to near distance, the first rear group GR1 moves toward the image side, and the 9th to 14th lenses, which are part of the second rear group GR2, move toward the object side as a single unit, while the front group GF, aperture diaphragm S, and the 15th lens, which is part of the second rear group GR2, remain fixed relative to the image plane.

[0125] The following shows specific numerical data for each embodiment of the imaging optical system of the present invention described above.

[0126] In the [surface data], the surface number is the number of the lens surface or aperture diaphragm counted from the object side, r is the radius of curvature of each surface, d is the spacing between each surface, nd is the refractive index for the d line (wavelength 587.56 nm), and vd is the Abbe number for the d line.

[0127] The asterisk (*) next to the lens surface number indicates that the lens surface is aspherical. BF represents the back focus.

[0128] The (diaphragm) appended to the surface number indicates that an aperture diaphragm is located at that position. The radius of curvature relative to the plane or aperture diaphragm is indicated with ∞ (infinity). The refractive index of air, n=1.0000, is omitted from the description.

[0129] The [Aspherical Data] section shows the coefficient values ​​that give the aspherical shape of the lens surface marked with an asterisk (*) in the [Surface Data] section. The shape of the aspherical surface is defined as follows, where y is the displacement from the optical axis in the direction perpendicular to the optical axis, z is the displacement (sag) in the direction of the optical axis from the intersection of the aspherical surface and the optical axis, r is the radius of curvature of the reference sphere, K is the conic coefficient, and A4, A6, A8, A10, A12, A14, A16, and A20 are the 4th, 6th, 8th, 10th, 12th, 14th, 16th, and 20th order aspherical coefficients, respectively, and the coordinates of the aspherical surface are expressed by the following formula.

[0130] TIFF2026069648000002.tif19168

[0131] The [Various Data] section shows values ​​such as focal length at infinity and at a shooting distance of 1.0m.

[0132] The [Variable Interval Data] section shows the variable interval and BF values ​​at shooting distances of infinity and 1.0m.

[0133] The [Lens Group Data] shows the number of the object-side surface in each lens group and the combined focal length of the entire group.

[0134] In addition, for all the specifications listed below, the units of focal length f, radius of curvature r, lens plane spacing d, and other lengths are millimeters (mm) unless otherwise specified. However, since equivalent optical performance can be obtained in both proportional magnification and proportional reduction in the optical system, this is not the only unit of measurement.

[0135] Furthermore, in the aberration diagrams corresponding to each embodiment, d, g, and C represent the d line, g line, and C line, respectively, and △S and △M represent the sagittal image plane and meridional image plane, respectively.

[0136] Numerical Example 1 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 75.1052 8.0761 1.92286 20.88 2 -663.2678 3.2104 3 -221.0442 1.3000 1.51742 52.15 4 28.0267 12.2601 5 -43.0741 1.2859 1.80518 25.46 6 150.8870 1.0283 7* 89.2900 7.4823 1.76450 49.10 8* -55.1739 0.5621 9 76.0950 10.9740 1.59282 68.62 10 -36.3741 1.2000 1.69895 30.05 11 -419.5413 0.1500 12 249.5104 5.3632 1.88300 40.80 13 -67.6164 2.3076 14 (aperture) ∞ (d14) 15* 89.3570 1.8779 1.59201 67.02 16* 26.4444 (d16) 17 143.6922 10.0848 1.75500 52.32 18 -21.2474 0.9000 1.85451 25.15 19 -220.4492 0.1500 20 78.1343 5.6421 2.00100 29.13 21 -59.5828 0.1500 22 202.6288 3.5861 1.94595 17.98 23 -80.8939 1.0025 1.62004 36.30 24 32.3684 6.7925 25 -35.5202 2.1000 1.68948 31.02 26* -68.5557 (BF) Image plane ∞ [Aspherical data] 7th side 8th side 15th side 16th side K -2.02050 0.31820 0.00000 0.00000 A4 -2.80220E-06 1.14230E-06 -3.00787E-05 -3.28460E-05 A6 -1.95380E-09 -1.63190E-09 1.93193E-07 1.86930E-07 A8 3.31270E-11 1.28480E-11 -1.11198E-09 -9.29090E-10 A10 -2.64290E-13 -8.06900E-14 4.90017E-12 2.53160E-12 A12 1.27320E-15 3.81260E-16 -1.69805E-14 -2.79790E-15 A14 -3.54970E-18 -1.11810E-18 4.46514E-17 0.00000E+00 A16 5.35560E-21 1.86670E-21 -7.37293E-20 0.00000E+00 A18 -3.32250E-24 -1.26950E-24 5.31567E-23 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 26 sides K 0.00000 A4 1.02840E-05 A6 6.27260E-09 A8 -7.05150E-11 A10 1.82840E-12 A12 -1.69670E-14 A14 7.80240E-17 A16 -1.73940E-19 A18 1.46540E-22 A20 0.00000E+00 [Various Data] INF 1.0m Focal length 48.72 48.72 F-number 1.45 1.52 Full angle of view 2ω 46.49 44.14 Image height Y 21.63 21.63 Lens length 127.18 127.18 [Variable interval data] INF 1.0m d0 ∞ 872.8250 d14 3.5500 6.7551 d16 16.8119 13.6068 BF 19.3272 19.3272 [Lens group data] Group starting plane focal length GF 1 50.05 GR 15 156.95 GF1 1 -35.58 GF2 7 25.47 fL23 3 -19.52 GR1 15 -64.16 GR2 17 55.68 GR2F 17 30.90 GR2R 22 -50.72

[0137] Numerical Example 2 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 88.7443 7.4997 1.92286 20.88 2 -486.5499 4.7623 3 -182.4795 1.3000 1.58913 61.25 4 34.6675 10.7085 5 -37.4210 1.3000 1.80809 22.76 6 174.2475 1.4390 7 112.4119 5.2450 1.91082 35.25 8 -127.7717 0.6000 9* 102.0446 8.3337 1.77250 49.50 10* -54.8989 0.1500 11 107.9672 9.1589 1.59282 68.62 12 -43.2065 1.0000 1.78472 25.72 13 -102.1583 2.1000 14 (aperture) ∞ (d14) 15* 250.0000 1.8000 1.58913 61.25 16* 42.5408 (d16) 17 -168.8771 7.4744 1.88100 40.14 18 -21.1768 0.9000 1.86966 20.02 19 -69.9640 0.1500 20 66.1086 6.0059 1.94595 17.98 21 -67.3344 0.1500 22 -227.2101 1.0000 1.68893 31.16 23 33.3785 2.3977 24 71.8547 3.6595 1.88100 40.14 25 -319.8569 2.4185 26* -250.0000 1.8000 1.68948 31.02 27* 57.2290 (BF) Image plane ∞ [Aspherical data] 9 sides 10 sides 15 sides 16 sides K 0.00000 0.00000 0.00000 0.00000 A4 -2.67850E-06 5.43710E-07 5.22540E-06 8.86300E-06 A6 -1.09310E-09 3.91500E-09 2.41200E-08 -1.16040E-08 A8 4.72050E-11 -1.14770E-11 -7.98510E-10 -7.29710E-11 A10 -3.70060E-13 -3.80630E-14 6.43600E-12 -1.36560E-12 A12 1.37700E-15 3.52690E-16 -2.52950E-14 2.13510E-14 A14 -2.48500E-18 -8.62750E-19 4.73800E-17 -9.75560E-17 A16 1.76560E-21 7.34330E-22 -3.10640E-20 1.53220E-19 A18 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 Pages 26 and 27 K 0.00000 0.00000 A4 -7.43810E-05 -6.92450E-05 A6 3.43010E-07 3.37940E-07 A8 -1.22530E-09 -1.12310E-09 A10 2.56200E-12 1.99800E-12 A12 -2.49650E-15 -3.72850E-16 A14 2.46200E-18 -3.08460E-18 A16 -5.16270E-21 1.94640E-21 A18 0.00000E+00 0.00000E+00 A20 0.00000E+00 0.00000E+00 [Various Data] INF 1.0m Focal length 50.05 50.15 F-number 1.45 1.52 Full angle of view 2ω 45.16 43.03 Image height Y 21.63 21.63 Lens length 127.75 127.75 [Variable interval data] INF 1.0m d0 ∞ 872.2509 d14 3.6790 7.9540 d16 21.5582 17.2832 BF 21.1588 21.1588 [Lens group data] Group starting plane focal length GF 1 54.10 GR 15 118.95 GF1 1 -32.20 GF2 7 24.30 fL23 3 -19.08 GR1 15 -87.30 GR2 17 62.06 GR2F 17 27.75 GR2R 22 -41.40

[0138] Numerical Example 3 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 68.0502 8.5778 1.92286 20.88 2 1569.0366 4.7551 3 -537.7676 1.3000 1.54072 47.23 4 28.1621 13.7334 5 -38.7639 2.7101 1.80809 22.76 6 241.1693 1.4336 7* 90.3799 7.8070 1.77250 49.46 8* -49.5250 0.5878 9 60.9250 11.5078 1.59282 68.62 10 -41.8288 1.2000 1.85451 25.15 11 -51.5737 2.3674 12 (aperture) ∞ (d12) 13* 290.0912 1.8184 1.58913 61.25 14* 35.4881 (d14) 15 241.3681 9.7460 1.75500 52.32 16 -20.2421 1.3161 1.85451 25.15 17 -59.4882 0.1500 18 70.7891 5.5758 2.00100 29.14 19 -63.1252 0.1500 20 -134.5747 2.8052 1.94595 17.98 21 -51.7386 1.0000 1.61310 44.36 22 32.2294 6.4206 23 -33.7452 1.8000 1.68948 31.02 24* -70.1254 (BF) Image plane ∞ [Aspherical data] Sides 7, 8, 13, and 14 K 0.00000 0.00000 0.00000 -0.87010 A4 -3.42640E-06 1.51540E-06 1.04110E-05 1.69850E-05 A6 -4.97440E-09 -2.63640E-09 -1.61390E-07 -2.21990E-07 A8 4.80050E-11 2.24030E-11 1.79950E-09 3.03870E-09 A10 -2.87480E-13 -1.49810E-13 -1.48400E-11 -2.82590E-11 A12 1.08570E-15 6.48600E-16 7.73910E-14 1.54240E-13 A14 -2.24580E-18 -1.45890E-18 -2.30090E-16 -4.31410E-16 A16 1.97720E-21 1.36470E-21 3.37650E-19 4.27750E-19 A18 0.00000E+00 0.00000E+00 -1.66890E-22 1.80660E-22 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 24 sides K 0.00000 A4 9.31340E-06 A6 4.02570E-09 A8 4.09730E-11 A10 -1.15050E-13 A12 -4.91250E-16 A14 4.45600E-18 A16 -8.37690E-21 A18 0.00000E+00 A20 0.00000E+00 [Various Data] INF 1.0m Focal length 50.16 50.06 F-number 1.46 1.53 Full angle of view 2ω 45.30 42.98 Image height Y 21.63 21.63 Lens length 128.11 128.11 [Variable interval data] INF 1.0m d0 ∞ 871.8854 d12 3.0633 6.5074 d14 18.4962 15.0521 BF 19.7930 19.7930 [Lens group data] Group starting plane focal length GF 1 51.35 GR 13 169.07 GF1 1 -36.84 GF2 7 25.11 fL23 3 -19.46 GR1 13 -68.82 GR2 15 59.30 GR2F 15 24.56 GR2R 20 -31.89

[0139] Numerical Example 4 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 90.3441 5.9880 1.94595 17.98 2 -978.6659 3.1207 3 -179.0756 1.3000 1.64000 60.08 4 28.3916 13.0475 5 -31.0951 3.9107 1.75211 25.05 6 -356.6993 1.0738 7* 355.3381 8.9538 1.76450 49.10 8* -36.4910 0.3000 9 68.9540 8.8456 1.59282 68.62 10 -50.9247 1.6970 1.68948 31.02 11 53.8935 7.5363 1.88100 40.14 12 -85.4552 2.3097 13 (aperture) ∞ (d13) 14* 80.2709 1.8167 1.59201 67.02 15* 26.5921 (d15) 16 59.5236 11.7625 1.75500 52.32 17 -20.8425 0.9000 1.84666 23.78 18 517.2277 0.1500 19 93.2033 5.5361 1.94595 17.98 20 -50.0712 0.1500 21 47.2820 1.7473 1.91650 31.60 22 26.5653 2.4133 23 67.0044 2.4120 1.65160 58.55 24 257.8427 3.7246 25 -32.0895 2.1000 1.68948 31.02 26* -72.1682 (BF) Image plane ∞ [Aspherical data] Sides 7, 8, 14, and 15 K -4.98410 -0.10240 0.00000 0.00000 A4 -3.18030E-06 7.21760E-07 -2.24570E-05 -2.50430E-05 A6 4.45740E-09 5.45430E-09 8.67990E-08 9.82070E-08 A8 -7.31370E-11 -1.07650E-10 -2.23390E-10 -4.01330E-10 A10 7.82720E-13 1.01690E-12 -5.09550E-13 8.01270E-13 A12 -4.60850E-15 -5.48980E-15 4.79570E-15 -6.15220E-16 A14 1.53060E-17 1.69500E-17 -9.58020E-18 0.00000E+00 A16 -2.65700E-20 -2.75930E-20 -5.02510E-22 0.00000E+00 A18 1.87560E-23 1.83710E-23 1.42950E-23 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 26 sides K 0.00000 A4 9.09770E-06 A6 -2.91700E-08 A8 6.86320E-10 A10 -6.93320E-12 A12 4.65170E-14 A14 -1.96300E-16 A16 4.77180E-19 A18 -5.06910E-22 A20 0.00000E+00 [Various Data] INF 1.0m Focal length 37.66 37.85 F number 1.45 1.50 Overall picture angle 2ω 60.47 58.08 Image height Y 21.63 21.63 Overall lens length 130.06 130.06 [Variable interval data] INF 1.0m d0 ∞ 869.9415 d13 3.5500 5.9300 d15 16.3220 13.9420 BF 19.3908 19.3908 [Lens group data] Group Starting surface Focal length GF 1 43.81 GR 14 119.xx GF1 1 -27.22 GF2 7 25.49 fL23 3 -17.99 GR1 14 -68.03 GR2 16 51.76 GR2F 16 30.58 GR2R 21 -51.58

[0140] Numerical example 5 Unit: mm [Surface data] Surface number r d nd vd Object surface ∞ (d0) 1 68.0291 4.7902 1.94595 17.98 2 183.3290 1.2848 [[ID=6xx]]3 562.7748 1.9834 1.64000 60.08 4* xx.4620 17.g11 5 -28.8049 10.2015 1.75211 25.05<0xx0924>6 -133.2546 1.0000 7* 356.4622 6.3635 1.76450 49.10 <000xx926> Note: There are some unclear or potentially incorrect values in the original text (marked as xx in the translation), which should be double-checked with the original source for accurate translation.8* -39.5979 0.3000 9 83.1922 6.8198 1.59282 68.62 10 -57.9071 1.2000 1.68948 31.02 11 426.5651 4.0564 1.88100 40.14 12 -73.5879 2.5093 13 (aperture) ∞ (d13) 14* 61.3137 1.8035 1.59201 67.02 15* 26.7858 (d15) 16 52.4254 12.3511 1.75500 52.32 17 -20.4868 0.9000 1.84666 23.78 18 222.0634 0.5814 19 113.3346 5.5582 1.94595 17.98 20 -43.3589 0.1500 21 109.4207 1.0000 1.91650 31.60 22 29.2928 1.4503 23 46.6272 5.1346 1.65160 58.55 24 -102.1800 2.9028 25 -28.6790 2.1000 1.68948 31.02 26* -76.9651 (BF) Image plane ∞ [Aspherical data] 4 sides 7 sides 8 sides 14 sides K 0.00000 -2.08090 -0.16620 0.00000 A4 -1.38260E-06 -4.01510E-06 2.18700E-07 -2.23700E-05 A6 -1.55910E-09 2.46110E-09 7.76070E-09 9.18600E-08 A8 -5.96950E-13 4.81530E-11 -7.83330E-11 -1.64170E-10 A10 -2.84560E-15 -4.72270E-13 5.16680E-13 -2.14290E-12 A12 0.00000E+00 2.29970E-15 -2.01780E-15 1.62870E-14 A14 0.00000E+00 -5.37730E-18 5.15270E-18 -5.22540E-17 A16 0.00000E+00 4.65350E-21 -8.38370E-21 8.16890E-20 A18 0.00000E+00 2.24170E-25 6.36020E-24 -4.77230E-23 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 Surface 15, Surface 26 K 0.00000 0.00000 A4 -2.53240E-05 1.03460E-05 A6 1.20920E-07 -1.10140E-07 A8 -5.59660E-10 2.10640E-09 A10 1.08990E-12 -2.25300E-11 A12 -6.37850E-16 1.49600E-13 A14 0.00000E+00 -5.94690E-16 A16 0.00000E+00 1.29660E-18 A18 0.00000E+00 -1.18960E-21 A20 0.00000E+00 0.00000E+00 [Various Data] [[ID=​​​​​​ Image height Y 21.63 21.63 Lens length 130.18 130.18 [Variable interval data] INF 1.0m d0 ∞ 869.8249 d13 3.3500 5.2773 d15 15.1045 13.1772 BF 19.3886 19.3886 [Lens group data] Group starting plane focal length GF 1 39.06 GR 14 85.33 GF1 1 -24.59 GF2 7 27.26 fL23 3 -17.99 GR1 14 -81.94 GR2 16 49.26 GR2F 16 30.39 GR2R 21 -57.63

[0141] Numerical Example 6 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 72.9489 7.6280 1.92286 20.88 2 1307.2933 5.7831 3 -403.0741 1.3001 1.51742 52.15 4 26.8708 11.3892 5 -46.4591 1.2000 1.80518 25.46 6 160.2242 1.0629 7* 94.2083 6.6462 1.76450 49.10 8* -59.7149 0.3000 9 69.7391 11.2935 1.59282 68.62 10 -35.0659 1.2005 1.69895 30.05 11 -221.0181 0.2888 12 4527.5352 4.4755 1.88300 40.80 13 -65.2089 0.5723 14 ∞ (d14) 15* 75.1130 1.8039 1.59201 67.02 16* 26.4606 (d16) 17 (aperture) ∞ (d17) 18 105.4622 9.3946 1.75500 52.32 19 -23.3182 1.0226 1.85451 25.15 20 -268.2222 0.3275 21 82.9121 5.2260 2.00100 29.13 22 -65.3303 (d22) 23 102.3394 4.3311 1.94595 17.98 24 -149.9009 1.4305 1.62004 36.30 25 27.6349 7.2354 26* -34.9931 2.1000 1.68948 31.02 27* -67.5918 (BF) Image plane ∞ [Aspherical data] 7th side 8th side 15th side 16th side K -4.26280 0.23430 0.00000 0.00000 A4 -1.44960E-06 2.26790E-06 -2.30990E-05 -2.66800E-05 A6 -2.14550E-08 -2.00320E-08 9.83790E-08 1.02030E-07 A8 2.78270E-10 2.31930E-10 -3.41670E-10 -3.95640E-10 A10 -2.14030E-12 -1.69870E-12 6.52730E-13 8.96090E-13 A12 9.86310E-15 7.60860E-15 9.73120E-17 -8.90150E-16 A14 -2.65730E-17 -2.01180E-17 -3.55250E-18 0.00000E+00 A16 3.84810E-20 2.87390E-20 7.94250E-21 0.00000E+00 A18 -2.29920E-23 -1.69610E-23 -6.79120E-24 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 Pages 26 and 27 K 0.14770 0.00000 A4 -4.40340E-07 9.17330E-06 A6 4.30490E-09 2.00900E-09 A8 0.00000E+00 5.20260E-11 A10 0.00000E+00 8.78910E-13 A12 0.00000E+00 -1.14060E-14 A14 0.00000E+00 5.70140E-17 A16 0.00000E+00 -1.29440E-19 A18 0.00000E+00 1.04800E-22 A20 0.00000E+00 0.00000E+00 [Various Data] INF 1.0m Focal length 49.19 48.57 F-number 1.45 1.50 Full angle of view 2ω 45.84 43.17 Image height Y 21.63 21.63 Lens length 127.18 127.18 [Variable interval data] INF 1.0m d0 ∞ 872.8249 d14 4.1695 6.6501 d16 12.8580 10.3774 d17 4.3999 3.9086 d22 0.1746 0.6659 BF 19.5614 19.5614 [Lens group data] Group starting plane focal length GF 1 56.79 GR 15 139.50 GF1 1 -37.05 GF2 7 26.39 fL23 3 -20.70 GR1 15 -69.97 GR2 18 54.36 GR2F 18 31.60 GR2R 23 -50.23

[0142] Numerical Example 7 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 84.9130 7.7554 1.92286 20.88 2 -1685.2853 4.6778 3 -568.1612 1.3000 1.51742 52.15 4 38.5510 11.4686 5 -54.0944 1.2000 1.80518 25.46 6 130.2785 1.0000 7* 74.2196 7.9966 1.77250 49.46 8* -68.9659 0.3000 9 54.8660 8.8731 1.59282 68.62 10 -107.1055 1.2000 1.69895 30.05 11 46.5887 0.8090 12 53.9137 7.4653 1.87071 40.73 13 -123.4183 2.3098 14 (aperture) ∞ (d14) 15* 116.1759 1.8000 1.59201 67.02 16* 26.5637 (d16) 17 63.5302 9.8745 1.75500 52.32 18 -24.3201 0.9000 1.85451 25.15 19 -671.2612 0.1500 20 134.0303 4.7942 2.00100 29.14 21 -58.6131 0.1500 22 -253.8728 6.1713 1.94595 17.98 23 -39.7060 1.0000 1.62004 36.30 24 46.6034 6.1027 25 -34.0112 2.1000 1.68948 31.02 26* -67.2177 (BF) Image plane ∞ [Aspherical data] 7th side 8th side 15th side 16th side K 2.34280 0.49970 0.00000 0.00000 A4 -3.07940E-06 5.61550E-07 -2.98970E-05 -3.34735E-05 A6 5.19990E-09 5.83800E-09 2.04170E-07 2.03451E-07 A8 -5.37000E-11 -6.80190E-11 -1.06540E-09 -9.75119E-10 A10 3.42430E-13 4.69240E-13 3.67960E-12 2.44774E-12 A12 -1.39390E-15 -1.99810E-15 -9.04230E-15 -2.46144E-15 A14 3.53590E-18 5.13820E-18 1.81850E-17 0.00000E+00 A16 -5.00280E-21 -7.22580E-21 -2.81370E-20 0.00000E+00 A18 3.03050E-24 4.28910E-24 2.17140E-23 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 26 sides K 0.00000 A4 9.71400E-06 A6 -1.89190E-08 A8 4.14060E-10 A10 -4.14540E-12 A12 2.52760E-14 A14 -9.12350E-17 A16 1.77770E-19 A18 -1.43030E-22 A20 0.00000E+00 [Various Data] INF 1.0m Focal length 59.30 59.00 F-number 1.46 1.54 Full angle of view 2ω 39.19 36.39 Image height Y 21.63 21.63 Lens length 130.18 130.18 [Variable interval data] INF 1.0m d0 ∞ 869.8249 d14 3.8086 8.0334 d16 17.8047 13.5799 BF 19.1636 19.1636 [Lens group data] Group starting plane focal length GF 1 57.76 GR 15 207.18 GF1 1 -48.40 GF2 7 28.20 fL23 3 -25.63 GR1 15 -58.61 GR2 17 55.92 GR2F 17 31.89 GR2R 22 -52.35

[0143] Numerical Example 8 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 74.3034 5.9525 1.94595 17.98 2 541.3409 1.7336 3* -215.0633 2.0000 1.62041 60.29 4* 19.0369 20.6057 5 -21.6637 1.2000 1.80518 25.42 6 -38.6064 1.0000 7* 908.2424 7.3073 1.76450 49.10 8* -35.5942 0.3000 9 388.5351 10.0452 1.59282 68.62 10 -26.8383 1.2000 1.68948 31.02 11 -79.0350 0.1500 12 -361.3194 4.7058 1.77250 49.50 13 -50.1089 2.0000 14 (aperture) ∞ (d14) 15* 62.0664 1.8000 1.59201 67.02 16* 24.1217 (d16) 17 41.9074 13.4116 1.75500 52.32 18 -20.0674 0.9000 1.85451 25.15 19 158.3291 0.1500 20 66.6532 5.7061 1.94595 17.98 21 -49.7128 0.1500 22 94.5380 1.0000 1.91650 31.60 23 39.3530 2.2865 24 2515.3405 3.8684 1.63858 55.18 25 -42.7395 0.7271 26* -40.9289 2.1000 1.78880 28.43 27* 153.9057 (BF) Image plane ∞ [Aspherical data] 3 sides 4 sides 7 sides 8 sides K 0.00000 0.00000 -5.00000 -1.06350 A4 -5.20740E-07 -6.99760E-06 -3.08590E-06 -9.28940E-07 A6 6.15910E-09 -1.37820E-08 -1.15750E-09 5.21600E-09 A8 -9.68200E-12 9.45230E-12 4.72350E-11 -5.52630E-11 A10 9.79740E-15 -1.23060E-13 -1.29630E-13 4.02920E-13 A12 -4.49080E-18 0.00000E+00 3.60730E-16 -1.17150E-15 A14 0.00000E+00 0.00000E+00 0.00000E+00 1.78030E-18 A16 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A18 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 Pages 15, 16, 26, and 27 K 0.00000 0.00000 0.00000 0.00000 A4 -5.03920E-05 -5.65710E-05 -1.17290E-05 1.01780E-05 A6 3.25480E-07 3.07560E-07 5.23730E-09 -4.85930E-08 A8 -1.97530E-09 -1.41370E-09 0.00000E+00 1.20500E-09 A10 1.12240E-11 3.86660E-12 0.00000E+00 -1.19370E-11 A12 -5.62410E-14 -4.97080E-15 0.00000E+00 6.55060E-14 A14 2.04710E-16 0.00000E+00 0.00000E+00 -1.71140E-16 A16 -4.39870E-19 0.00000E+00 0.00000E+00 8.47100E-20 A18 4.02610E-22 0.00000E+00 0.00000E+00 2.99670E-22 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 [Various Data] INF 1.0m Focal length 28.50 28.69 F-number 1.46 1.49 Full angle of view 2ω 77.91 75.68 Image height Y 21.63 21.63 Lens length 130.18 130.18 [Variable interval data] INF 1.0m d0 ∞ 869.8250 d14 3.5500 5.1971 d16 14.9563 13.3092 BF 21.3691 21.3691 [Lens group data] Group starting plane focal length GF 1 37.37 GR 15 104.25 GF1 1 -22.93 GF2 7 26.48 fL23 3 -15.99 GR1 15 -67.84 GR2 17 47.50 GR2F 17 27.54 GR2R 22 -42.97

[0144] Numerical Example 9 Unit: mm [Surface data] Face number rd nd vd Object surface ∞ (d0) 1 76.7761 7.7070 1.92286 20.88 2 -1624.9734 4.4042 3 -251.2618 1.3000 1.51742 52.15 4 28.5784 11.9042 5 -42.7193 1.2997 1.80518 25.46 6 142.6614 1.0000 7* 82.0680 7.7144 1.76450 49.10 8* -55.0808 0.5903 9 84.0428 10.0952 1.59282 68.62 10 -39.1476 1.2000 1.69895 30.05 11 -297.1291 0.1500 12 260.0547 5.2836 1.88300 40.80 13 -68.9618 2.3099 14 (aperture) ∞ (d14) 15* 87.2645 1.8480 1.59201 67.02 16* 26.2986 (d16) 17 95.3063 10.3678 1.75500 52.32 18 -21.6129 0.9000 1.85451 25.15 19 1499.4953 0.1500 20 73.1569 5.6388 2.00100 29.13 21 -59.7051 0.1500 22 171.5596 3.8708 1.94595 17.98 23 -73.1915 1.0000 1.62004 36.30 24 31.5389 7.0830 25 -32.8950 2.1000 1.68948 31.02 26* -71.2226 (d26) 27 276.5199 1.2926 1.51680 64.20 28 -9086.9382 (BF) Image plane ∞ [Aspherical data] 7th side 8th side 15th side 16th side K -2.19350 0.08330 0.00000 0.00000 A4 -2.53630E-06 1.78030E-06 -2.69610E-05 -3.07190E-05 A6 -7.46810E-09 -8.19760E-09 1.75680E-07 1.61370E-07 A8 1.30620E-10 1.12520E-10 -1.22670E-09 -8.44330E-10 A10 -1.16320E-12 -9.19600E-13 7.58970E-12 2.49720E-12 A12 5.82010E-15 4.25700E-15 -3.78360E-14 -3.16360E-15 A14 -1.63530E-17 -1.10020E-17 1.29700E-16 0.00000E+00 A16 2.41490E-20 1.48050E-20 -2.55150E-19 0.00000E+00 A18 -1.45680E-23 -8.01800E-24 2.11370E-22 0.00000E+00 A20 0.00000E+00 0.00000E+00 0.00000E+00 0.00000E+00 26 sides K 0.00000 A4 1.04690E-05 A6 1.88770E-09 A8 4.51440E-11 A10 3.02320E-13 A12 -4.92990E-15 A14 2.29920E-17 A16 -3.97460E-20 A18 1.14250E-23 A20 0.00000E+00 [Various Data] INF 1.0m Focal length 48.72 48.57 F-number 1.45 1.52 Full angle of view 2ω 46.76 44.56 Image height Y 21.63 21.63 Lens length 127.18 127.18 [Variable interval data] INF 1.0m d0 ∞ 872.8250 d14 3.8937 6.3984 d16 16.3114 13.0914 d26 1.2000 1.9153 BF 16.4104 16.4104 [Lens group data] Group starting plane focal length GF 1 50.47 GR 15 168.00 GF1 1 -34.80 GF2 7 25.13 fL23 3 -19.69 GR1 15 -64.31 GR2 17 55.85 GR2F 17 32.06 GR2R 22 -53.42

[0145] Furthermore, a list of corresponding values ​​for the conditional expressions in each of these examples is shown.

[0146] Conditional expression EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 EX9 (1) 3.221 2.377 3.371 3.183 2.991 2.836 3.494 3.657 3.448 (2) -0.390 -0.353 -0.379 -0.411 -0.461 -0.364 -0.444 -0.428 -0.390 (3) 1.177 1.210 1.475 1.236 1.206 1.243 1.198 1.436 1.145 (4) 0.928 0.958 0.919 0.879 0.877 0.957 0.941 0.837 0.986 (5) 1.027 1.081 1.024 1.163 1.369 1.154 0.974 1.311 1.036 (6) -0.859 -0.687 -0.846 -0.687 -0.483 -0.698 -0.982 -0.563 -0.847

[0147] As described above, embodiments of the present invention have been shown, but the following can be appropriately adopted as long as they do not impair the optical performance of the imaging optical system of this embodiment. For example, miniaturization and performance improvements may be made by using hybrid aspherical lenses, diffraction gratings, or refractive index distributed lenses as lens elements. The shape of the aspherical lens may also be gull-wing shaped with inflection points, or it may be a free-form surface.

[0148] Furthermore, although the examples include descriptions of refractive index and Abbe number, these are not limited to specific numerical ranges. Materials with a refractive index nd of 1.45 or less or 2.00 or more may be used, as may materials with an Abbe number νd of less than 17.0 or 95.0 or more.

[0149] Furthermore, materials with distinctive optical properties may be used to achieve miniaturization, weight reduction, and good aberration correction. As a specific example, ΔPgF could be defined and its range specified as follows, but in this invention, the present invention is not limited to any value as long as it is effective for miniaturization, weight reduction, and good aberration correction. ΔPgF = PgF - 0.64833 + 0.00180νd:g, anomalous partial dispersion between F lines PgF = (ng - nF) / (nF - nC): g, partial variance ratio between F lines ng: Refractive index for the g line (wavelength λ = 435.84 nm) nF: Refractive index for the F line (wavelength λ = 486.13 nm) nC: Refractive index for the C line (wavelength λ = 656.27 nm) [Explanation of Symbols]

[0150] GF front group GR rear group GF1 First Group GF2 Second Front Group GR1 1st rear group GR2 Second rear group GR2F Front second rear group GR2R rear 2nd rear group GF11 lens component GF11 GF12 lens component GF12 GF13 lens component GF13 I image plane S Aperture diaphragm FC Flare Cut Aperture

Claims

1. Starting from the object side, the group consists of the front group GF with positive refractive powers and the back group GR with positive refractive powers. Within the aforementioned front group GF, the object side has a first front group GF1 with an overall negative refractive power. Within the first front group GF1, in order from the object side, there is a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the air surface on the image side with a concave surface, and a lens component GF13 with negative refractive power that faces the air surface on the object side with a concave surface. The image side of the aforementioned front group GF has a cemented lens and a second front group GF2 which has a positive refractive power overall. The second front group GF2 consists of five or fewer lenses. The rear group GR has a first rear group GR1, which is a single lens with negative refractive power, at the object side. When focusing from infinity to near distance, the object-side spacing of the first rear group GR1 increases, and the image-side spacing decreases. The first rear group GR1 has a second rear group GR2 with positive refractive power on the image side, The object side of the second rear group GR2 has a front second rear group GR2F with positive refractive power, The second rear group GR2 has a rear second rear group GR2R with negative refractive power on the image side, The aforementioned rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has two or more lenses. The first rear group GR1 has an aperture diaphragm S adjacent to the object side or the image side, An imaging optical system characterized by satisfying the following condition. (1) 1.40< fGR / f <20.00 fGR: Focal length of the rear group GR in the infinity focus state f: Focal length of the entire system when in focus at infinity The term "lens component" refers to either a single lens or a composite lens formed by joining two or more single lenses.

2. Starting from the object side, the group consists of the front group GF with positive refractive powers and the back group GR with positive refractive powers. Within the aforementioned front group GF, the object side has a first front group GF1 with an overall negative refractive power. Within the first front group GF1, in order from the object side, there is a lens component GF11 with positive refractive power, a lens component GF12 with negative refractive power that faces the air surface on the image side with a concave surface, and a lens component GF13 with negative refractive power that faces the air surface on the object side with a concave surface. Within the aforementioned front group GF, the image side has a second front group GF2 with an overall positive refractive power. Within the aforementioned rear group GR, the first rear group GR1, which has a negative refractive power, is located closest to the object. When focusing from infinity to near distance, the object-side spacing of the first rear group GR1 increases, and the image-side spacing decreases. The first rear group GR1 has a second rear group GR2 with positive refractive power on the image side, The second rear group GR2 consists of 5 to 7 lenses. The object side of the second rear group GR2 has a front second rear group GR2F with positive refractive power, The aforementioned front second rear group GR2F has a cemented lens with positive refractive power. The second rear group GR2 has a rear second rear group GR2R with negative refractive power on the image side, The aforementioned rear second rear group GR2R has a negative lens with a concave surface facing the air surface on the image side and has two or more lenses. An imaging optical system characterized by having an aperture diaphragm S adjacent to the object side or image side of the first rear group GR1, and satisfying the following conditional equation. (1) 1.40< fGR / f <20.00 fGR: Focal length of the rear group GR in the infinity focus state f: Focal length of the entire system when in focus at infinity The term "lens component" refers to either a single lens or a composite lens formed by joining two or more single lenses.

3. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (2) -1.00< fL23 / fGF <-0.15 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF

4. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (3) 0.71<(1-βR2F)*(βR2R)<2.50 βR2F: Lateral magnification of the front second rear group GR2F in the infinity focus state. βR2R: Lateral magnification of the rear second rear group GR2R in the infinity focus state.

5. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (4) 0.45< D_GR / D_GF <1.50 D_GR: Length along the optical axis from the object-side surface to the image-side surface of the rear group GR. D_GF: Length along the optical axis from the object-side surface to the image-side surface of the front group GF.

6. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (5) 0.75<fGF / f<2.00 (6) -2.0<(1-βR1^2)*(βR2^2)<-0.33 fGF: Focal length of the front group GF in the state of infinity focus f: Focal length of the entire system when in focus at infinity βR1: Lateral magnification of the first rear group GR1 in the infinity focus state. βR2: Lateral magnification of the second rear group GR2 in the infinity focus state.

7. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (2) -1.00< fL23 / fGF <-0.15 (3) 0.71<(1-βR2F)*(βR2R)<2.50 (4) 0.45< D_GR / D_GF <1.50 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF βR2F: Lateral magnification of the front second rear group GR2F in the infinity focus state. βR2R: Lateral magnification of the rear second rear group GR2R in the infinity focus state. D_GR: Length along the optical axis from the object-side surface to the image-side surface of the rear group GR. D_GF: Length along the optical axis from the object-side surface to the image-side surface of the front group GF.

8. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (2) -1.00< fL23 / fGF <-0.15 (3) 0.71<(1-βR2F)*(βR2R)<2.50 (5) 0.75<fGF / f<2.00 (6) -2.0<(1-βR1^2)*(βR2^2)<-0.33 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF in the state of infinity focus βR2F: Lateral magnification of the front second rear group GR2F in the infinity focus state. βR2R: Lateral magnification of the rear second rear group GR2R in the infinity focus state. f: Focal length of the entire system when in focus at infinity βR1: Lateral magnification of the first rear group GR1 in the infinity focus state. βR2: Lateral magnification of the second rear group GR2 in the infinity focus state.

9. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (2) -1.00< fL23 / fGF <-0.15 (4) 0.45< D_GR / D_GF <1.50 (5) 0.75<fGF / f<2.00 (6) -2.0<(1-βR1^2)*(βR2^2)<-0.33 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF in the state of infinity focus D_GR: Length along the optical axis from the object-side surface to the image-side surface of the rear group GR. D_GF: Length along the optical axis from the object-side surface to the image-side surface of the front group GF. f: Focal length of the entire system when in focus at infinity βR1: Lateral magnification of the first rear group GR1 in the infinity focus state. βR2: Lateral magnification of the second rear group GR2 in the infinity focus state.

10. The imaging optical system according to claim 1 or 2, characterized in that it satisfies the following conditional expression. (2) -1.00< fL23 / fGF <-0.15 (3) 0.71<(1-βR2F)*(βR2R)<2.50 (4) 0.45< D_GR / D_GF <1.50 (5) 0.75<fGF / f<2.00 (6) -2.0<(1-βR1^2)*(βR2^2)<-0.33 fL23: The combined focal length of the negative refractive power lens component GF12 and the negative refractive power lens component GF13. fGF: Focal length of the front group GF in the state of infinity focus βR2F: Lateral magnification of the front second rear group GR2F in the infinity focus state. βR2R: Lateral magnification of the rear second rear group GR2R in the infinity focus state. D_GR: Length along the optical axis from the object-side surface to the image-side surface of the rear group GR. D_GF: Length along the optical axis from the object-side surface to the image-side surface of the front group GF. f: Focal length of the entire system when in focus at infinity βR1: Lateral magnification of the first rear group GR1 in the infinity focus state. βR2: Lateral magnification of the second rear group GR2 in the infinity focus state.

Images