Imaging optical system

Abstract

To accommodate large image sensors, and considering the weight reduction of the focusing lens which is primarily driven in focusing, we provide an imaging optical system that achieves both a large aperture ratio and good aberration correction. [Solution] An imaging optical system comprising, in order from the object side, a front group GrF with positive refractive power, a first focus group GrFC1 with negative refractive power, a second focus group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power, wherein when focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane, the first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side, satisfying a specific conditional equation.

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. Also, lenses with a large aperture ratio are desired in order to obtain a large size of out-of-focus images and to use a high-speed shutter. On the other hand, in autofocus and video shooting, the lens used for focusing is desired to be lightweight in order to reduce the burden on the actuator. However, when the aperture ratio of the lens is increased, the lens used for focusing also becomes larger, increasing the burden on the actuator and its control. In particular, in a telephoto lens with a large aperture ratio, the lens diameter tends to increase, so reducing the weight of the focusing lens is an important issue.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent documents 1 to 3 disclose imaging optical systems that are compatible with large image sensors and are intended to support autofocus. In patent documents 1 to 3, the weight of the focusing lens has been reduced, and in particular, patent documents 2 to 3 demonstrate the effect of good aberration correction by floating focus. However, the embodiments use imaging optical systems with an F1.8 aperture, and further increasing the aperture ratio would result in an increase in the overall size of the lens system.

[0005] Furthermore, Patent Documents 4 to 5 disclose imaging optical systems with even larger aperture ratios. Patent Documents 4 and 5 reveal the difficulty of achieving both aberration correction and weight reduction of the focusing unit when further increasing the aperture ratio.

[0006] This invention has been made in view of the above 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 achieves both a large aperture ratio and good aberration correction. [Means for solving the problem]

[0007] To solve the above problems, the present invention provides an imaging optical system comprising, in order from the object side, a front group GrF with positive refractive power, a first focus group GrFC1 with negative refractive power, a second focus group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power, wherein when focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane, the first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side, and the following conditional equation is satisfied. (1) 0.20 < LGrF / fF < 1.40 LGrF: Length of the front group GrF along the optical axis in the state of infinity focus. fF: Focal length of the front group GrF when in focus at infinity. [Effects of the Invention]

[0008] 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 achieves both a large aperture ratio and good aberration correction. [Brief explanation of the drawing]

[0009] [Figure 1] This is a lens configuration diagram according to Embodiment 1 of the imaging optical system of the present invention. [Figure 2] This is a longitudinal aberration diagram of the imaging optical system of Example 1 at an infinity shooting distance. [Figure 3] This is a longitudinal aberration diagram of the imaging optical system of Example 1 at a shooting distance of 2.4 m. [Figure 4] This is a longitudinal aberration diagram of the imaging optical system of Example 1 at a shooting distance of 1.1m. [Figure 5] This is a diagram of the lateral aberration of the imaging optical system of Example 1 at an imaging distance of infinity. [Figure 6] This is a lateral aberration diagram of the imaging optical system of Example 1 at a shooting distance of 2.4 m. [Figure 7] This is a lateral aberration diagram of the imaging optical system of Example 1 at a shooting distance of 1.1m. [Figure 8] This is a lens configuration diagram according to Embodiment 2 of the imaging optical system of the present invention. [Figure 9] This is a longitudinal aberration diagram of the imaging optical system of Example 2 at an infinity shooting distance. [Figure 10] This is a longitudinal aberration diagram of the imaging optical system of Example 2 at a shooting distance of 2.4 m. [Figure 11] This is a longitudinal aberration diagram of the imaging optical system of Example 2 at a shooting distance of 1.1m. [Figure 12] This is a diagram of the lateral aberration of the imaging optical system of Example 2 at an imaging distance of infinity. [Figure 13] This is a lateral aberration diagram of the imaging optical system of Example 2 at a shooting distance of 2.4 m. [Figure 14] This is a lateral aberration diagram of the imaging optical system of Example 2 at a shooting distance of 1.1m. [Figure 15] This is a lens configuration diagram according to Embodiment 3 of the imaging optical system of the present invention. [Figure 16] It is a longitudinal aberration diagram of the imaging optical system of Example 3 at an infinite shooting distance. [Figure 17] It is a longitudinal aberration diagram of the imaging optical system of Example 3 at a shooting distance of 2.6 m. [Figure 18] It is a longitudinal aberration diagram of the imaging optical system of Example 3 at a shooting distance of 1.3 m. [Figure 19] It is a lateral aberration diagram of the imaging optical system of Example 3 at an infinite shooting distance. [Figure 20] It is a lateral aberration diagram of the imaging optical system of Example 3 at a shooting distance of 2.6 m. [Figure 21] It is a lateral aberration diagram of the imaging optical system of Example 3 at a shooting distance of 1.3 m. [Figure 22] It is a lens configuration diagram according to Example 4 of the imaging optical system of the present invention. [Figure 23] It is a longitudinal aberration diagram of the imaging optical system of Example 4 at an infinite shooting distance. [Figure 24] It is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of 2.6 m. [Figure 25] It is a longitudinal aberration diagram of the imaging optical system of Example 4 at a shooting distance of 1.3 m. [Figure 26] It is a lateral aberration diagram of the imaging optical system of Example 4 at an infinite shooting distance. [Figure 27] It is a lateral aberration diagram of the imaging optical system of Example 4 at a shooting distance of 2.6 m. [Figure 28] It is a lateral aberration diagram of the imaging optical system of Example 4 at a shooting distance of 1.3 m. [Figure 29] It is a lens configuration diagram according to Example 5 of the imaging optical system of the present invention. [Figure 30] It is a longitudinal aberration diagram of the imaging optical system of Example 5 at an infinite shooting distance. [Figure 31] It is a longitudinal aberration diagram of the imaging optical system of Example 5 at a shooting distance of 2.4 m. [Figure 32] It is a longitudinal aberration diagram of the imaging optical system of Example 5 at a shooting distance of 1.0 m. [Figure 33] It is a lateral aberration diagram of the imaging optical system of Example 5 at an infinite shooting distance. [Figure 34] This is a lateral aberration diagram of the imaging optical system of Example 5 at a shooting distance of 2.4 m. [Figure 35] This is a lateral aberration diagram of the imaging optical system of Example 5 at a shooting distance of 1.0 m. [Figure 36] This is a lens configuration diagram according to Embodiment 6 of the imaging optical system of the present invention. [Figure 37] This is a longitudinal aberration diagram of the imaging optical system of Example 6 at an infinity shooting distance. [Figure 38] This is a longitudinal aberration diagram of the imaging optical system of Example 6 at a shooting distance of 2.0 m. [Figure 39] This is a longitudinal aberration diagram of the imaging optical system of Example 6 at a shooting distance of 1.1m. [Figure 40] This is a diagram of the lateral aberration of the imaging optical system of Example 6 at an infinity shooting distance. [Figure 41] This is a lateral aberration diagram of the imaging optical system of Example 6 at a shooting distance of 2.0 m. [Figure 42] This is a lateral aberration diagram of the imaging optical system of Example 6 at a shooting distance of 1.1m. [Figure 43] This is a lens configuration diagram according to Embodiment 7 of the imaging optical system of the present invention. [Figure 44] This is a longitudinal aberration diagram of the imaging optical system of Example 7 at an infinity shooting distance. [Figure 45] This is a longitudinal aberration diagram of the imaging optical system of Example 7 at a shooting distance of 2.4 m. [Figure 46] This is a longitudinal aberration diagram of the imaging optical system of Example 7 at a shooting distance of 1.1m. [Figure 47] This is a diagram of the lateral aberration of the imaging optical system of Example 7 at an imaging distance of infinity. [Figure 48] This is a lateral aberration diagram of the imaging optical system of Example 7 at a shooting distance of 2.4 m. [Figure 49] This is a lateral aberration diagram of the imaging optical system of Example 7 at a shooting distance of 1.1m. [Figure 50] This is a lens configuration diagram according to Embodiment 8 of the imaging optical system of the present invention. [Figure 51]This is a longitudinal aberration diagram of the imaging optical system of Example 8 at an infinity shooting distance. [Figure 52] This is a longitudinal aberration diagram of the imaging optical system of Example 8 at a shooting distance of 3.3m. [Figure 53] This is a longitudinal aberration diagram of the imaging optical system of Example 8 at a shooting distance of 1.5 m. [Figure 54] This is a diagram of the lateral aberration of the imaging optical system of Example 8 at an infinity shooting distance. [Figure 55] This is a lateral aberration diagram of the imaging optical system of Example 8 at a shooting distance of 3.3m. [Figure 56] This is a lateral aberration diagram of the imaging optical system of Example 8 at a shooting distance of 1.5 m. [Modes for carrying out the invention]

[0010] As can be seen from the lens configuration diagrams shown in Figures 1, 8, 15, 22, 29, 36, 43, and 50, the imaging optical system of the present invention consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves toward the image side, and the second focusing group GrFC2 moves toward the object side.

[0011] In this text, lens components refer to single lenses or cemented lenses formed by joining multiple lenses together.

[0012] To achieve good aberration correction across the entire system, the lenses must be appropriately arranged. The imaging optical system of the present invention has, from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2, and a rear group GrR with positive refractive power. During focusing, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. This group configuration makes it easier to reduce the weight and size of the focusing lens group, and also suppresses the increase in size of the entire lens system.

[0013] The imaging optical system of the present invention is preferably satisfied with the following condition. (1) 0.20 < LGrF / fF < 1.40 LGrF: Length of the front group GrF along the optical axis in the state of infinity focus. fF: Focal length of the front group GrF when in focus at infinity.

[0014] Conditional equation (1) defines the ratio of the length of the front group GrF on the optical axis to the focal length in the infinity focus state as a desirable condition for suppressing the increase in size of the entire lens system and correcting aberrations.

[0015] If the length of the front group GrF exceeds the upper limit of condition (1), it becomes difficult to miniaturize the entire system. If the length of the front group GrF exceeds the lower limit of condition (1), there is no space to arrange the lenses, which increases the refractive power of each lens in the front group GrF, making it difficult to correct aberrations when increasing the aperture ratio.

[0016] Furthermore, regarding the above-mentioned conditional equation (1), it is desirable to set the lower limit to 0.30, and setting the lower limit to 0.40 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 1.10, and setting the upper limit to 0.80 will make the aforementioned effect more certain.

[0017] The imaging optical system of the present invention is preferably satisfied with the following condition. (2) 0.42 < f / fFC2R < 4.00 f: Focal length of the entire lens system when focused at infinity fFC2R: Combined focal length of the second focus group GrFC2 and the rear group GrR when focused at infinity.

[0018] Conditional equation (2) specifies the ratio of the combined focal length of the second focusing group GrFC2 and the rear group GrR to the focal length of the entire system as a preferred condition for increasing the aperture ratio and correcting aberrations.

[0019] If the combined focal length of the second focus group GrFC2 and the rear group GrR exceeds the upper limit of condition (2) and becomes small, the refractive power increases, making it difficult to correct aberrations such as spherical aberration. Also, the image circle shrinks as the light rays converge, making it difficult to use with large image sensors. If the combined focal length of the second focus group GrFC2 and the rear group GrR exceeds the lower limit of condition (2) and becomes large, it becomes difficult to achieve a large aperture ratio.

[0020] Furthermore, regarding the above-mentioned conditional equation (2), it is desirable to set the lower limit to 0.80, and setting the lower limit to 1.00 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 3.00, and setting the upper limit to 2.50 will make the aforementioned effect more certain.

[0021] The imaging optical system of the present invention is preferably satisfied with the following condition. (3) 0.15 < LGrFGrR / LALL < 0.50 LGrFGrR: Length along the optical axis from the image-side surface of the front group GrF to the object-side surface of the rear group GrR in the infinity focus state. LALL: The length along the optical axis from the object-side surface of the front group GrF to the image plane when in the infinity focus state.

[0022] Conditional equation (3) specifies the ratio of the distance from the front group GrF to the rear group GrR to the length of the entire lens system in order to secure the space used for focusing in the entire lens system.

[0023] If the distance between the front group GrF and the rear group GrR exceeds the upper limit of condition (3), the lengths of the front group GrF and the rear group GrR will decrease, making it difficult to arrange the lenses necessary for aberration correction, which is undesirable. In particular, in the front group GrF, the refractive power of each lens must be increased in order to lower the on-axial ray height with a small number of elements, making aberration correction difficult when increasing the aperture ratio. In the rear group GrR, in particular, the refractive power of each lens must be increased in order to suppress the increase in off-axial ray height and to achieve a large aperture ratio, making aberration correction difficult with a small number of elements. If the distance between the front group GrF and the rear group GrR exceeds the lower limit of condition (3), the space used for focusing becomes narrower, which is undesirable because it will increase the minimum focusing distance or increase the aberration fluctuation during focusing.

[0024] Furthermore, regarding the above-mentioned conditional equation (3), it is desirable to set the lower limit to 0.18, and setting the lower limit to 0.22 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.42, and setting the upper limit to 0.35 will make the aforementioned effect more certain.

[0025] The imaging optical system of the present invention is preferably satisfied with the following condition. (4) 50.00 < vdG24 < 102.00 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF.

[0026] (4') 55.00 < vdG24 < 102.00 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF.

[0027] Conditional equations (4) and (4') specify the average Abbe number of the second, third, and fourth positive lenses from the object side in the front group GrF as a condition for chromatic aberration correction of the entire lens system. As the focal length of the entire system increases, chromatic aberration correction in the rear group GrR becomes difficult, so chromatic aberration correction in the front group GrF is important.

[0028] If the average Abbe number exceeds the upper limit of condition (4), the correction of chromatic aberration becomes excessive, which is undesirable. Also, because the refractive index of the material tends to decrease, it becomes difficult to correct various aberrations, including spherical aberration. If the average Abbe number exceeds the lower limit of condition (4), the correction of chromatic aberration becomes insufficient, which is undesirable.

[0029] Furthermore, regarding the above-mentioned conditions (4) and (4'), it is desirable to set the lower limit to 60.00, and setting the lower limit to 70.00 will make the aforementioned effect more certain. Also, setting the upper limit to 96.00 will make the aforementioned effect more certain.

[0030] The imaging optical system of the present invention is preferably satisfied with the following condition. (5) 0.000 < |K2| < 0.370 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

[0031] (5')0.000<|K2|<0.600 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

[0032] Conditional equations (5) and (5') define the focus sensitivity of the second focus group GrFC2 as preferred conditions for aberration correction.

[0033] If the focus sensitivity exceeds the upper limit of condition (5') and becomes large, it becomes difficult to coordinate control for focusing with the first focus group GrFC1, which is undesirable. Furthermore, if the second focus group GrFC2 has negative refractive power, the amount of movement of the first focus group GrFC1 for focusing increases, which is undesirable as it enlarges the entire lens system. Also, if the second focus group GrFC2 has positive refractive power, the positive refractive power of the rear group GrR weakens, which is undesirable as it increases the positive distortion aberration of the entire lens system. If the focus sensitivity exceeds the lower limit of condition (5) and becomes small, the refractive power of the second focus group GrFC2 weakens, which is undesirable as it increases the fluctuation of distortion aberration during focusing.

[0034] Furthermore, setting the lower limit of the above-mentioned condition (5) to 0.010 makes the aforementioned effect more reliable. It is also desirable to set the upper limit to 0.290, and setting the upper limit to 0.200 makes the aforementioned effect even more reliable.

[0035] Furthermore, the aforementioned condition (5') can be made more certain by setting the lower limit to 0.010. It is also desirable to set the upper limit to 0.470. It is even more desirable to set that upper limit to 0.370. It is even more desirable to set that upper limit to 0.290. And by setting that upper limit to 0.200, the aforementioned effect can be made even more certain.

[0036] The imaging optical system of the present invention is preferably satisfied with the following condition. (6)0.107< ΔGr1GrFC1 / Ymax <1.000 ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height

[0037] (6´)0.095< ΔGr1GrFC1 / Ymax <1.000 ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height

[0038] Conditional equations (6) and (6') define the preferred conditions for the arrangement of the first focus group GrFC1, specifying the ratio of the distance between the front group GrF and the first focus group GrFC1 to the maximum image height.

[0039] If the upper limit of condition (6) is exceeded, the distance to the front group GrF becomes large, which is undesirable because the length of the front group GrF becomes shorter, making it difficult to arrange the lenses necessary for aberration correction. If the lower limit of condition (6') is exceeded, the distance to the front group GrF becomes small, which is undesirable because the space required for focusing movement becomes narrower.

[0040] Furthermore, regarding the above-mentioned conditions (6) and (6'), it is desirable to set the lower limit to 0.150, and setting the lower limit to 0.180 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.700, and setting the upper limit to 0.500 will make the aforementioned effect more certain.

[0041] Furthermore, in the imaging optical system of the present invention, it is desirable that the second to fourth positive lenses from the object side within the front group GrF have a positive meniscus shape with a convex surface on the object side.

[0042] Achieving both a large aperture ratio and a compact overall lens system requires rapidly reducing the axial ray height while simultaneously correcting aberrations. The shape of the second to fourth positive lenses from the object side within the front group GrF is a positive meniscus with a convex surface on the object side, which allows for good correction of chromatic aberration and coma aberration when reducing the axial ray height.

[0043] In the imaging optical system of the present invention, it is desirable that the aperture diaphragm S is located on the object side of the first focus group GrFC1 and that the following condition is satisfied. (4') 55.00 < vdG24 < 102.00 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF.

[0044] Because the aperture diaphragm S is located closer to the object than the first focus group GrFC1, it is possible to cut off the on-axial rays during focusing with the aperture diaphragm S, eliminating the need for aperture drive control to adjust exposure. Furthermore, since the aperture diaphragm S mechanism and the focusing actuator mechanism can be separated, it is possible to avoid increasing the size of the product.

[0045] In the imaging optical system of the present invention, it is desirable that the aperture diaphragm S is adjacent to the image side of the front group GrF and that the following condition is satisfied. (5')0.000<|K2|<0.600 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

[0046] By positioning the aperture diaphragm S adjacent to the image side of the front lens group GrF, it becomes possible to cut off axial rays during focusing with the aperture diaphragm S, eliminating the need for aperture drive control for exposure adjustment. Furthermore, integrating the front lens group GrF reduces manufacturing tolerances, thereby reducing variations in optical performance during manufacturing. In addition, the absence of a lens group between the aperture diaphragm S and the focusing group makes it easier to shorten the overall optical length.

[0047] In the imaging optical system of the present invention, it is desirable that the second focus group GrFC2 has a negative refractive power.

[0048] By making the second focus group GrFC2 negative, it becomes easier to increase the focus sensitivity of the first focus group GrFC1 and decrease the focus sensitivity of the second focus group GrFC2. This suppresses the deterioration of focusing accuracy even when momentary errors occur in the coordinated control for focusing due to external factors such as shocks.

[0049] In the imaging optical system of the present invention, it is preferable that the first focus group GrFC1 consists of a single lens.

[0050] The first focusing group, GrFC1, is positioned at a high axial ray height. Therefore, using a single lens element reduces weight, which is advantageous for controlling focusing speed and precision.

[0051] In the imaging optical system of the present invention, it is preferable that the second focus group GrFC2 consists of one or two lenses.

[0052] The second focusing group, GrFC2, is also lighter with fewer lens elements, which is advantageous for controlling focusing speed and accuracy. Furthermore, the second focusing group, GrFC2, is effective in reducing chromatic aberration during focusing, and having only two lenses makes it easier to select materials, thus enhancing this effect.

[0053] In the imaging optical system of the present invention, it is desirable that the rear group GrR has one or more negative lenses on the image side of the positive lens.

[0054] The arrangement of positive and negative lenses within the rear group GrR creates a telephoto-type effect, making it easier to achieve both a shorter overall lens length and a larger aperture ratio.

[0055] The imaging optical system of the present invention is preferably satisfied with the following condition. (7) 0.600 < |K1| < 4.000 |K1|: Focus sensitivity of the first focus group GrFC1 in the infinity focus state. |K1|=|(1-βFC1^2)*((βFC2*βR)^2)| βFC1: Lateral magnification of the first focus group GrFC1 in the infinity focus state. βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

[0056] Conditional equation (7) defines the focus sensitivity of the first focus group GrFC1 as a preferred condition for aberration correction.

[0057] If the focus sensitivity exceeds the upper limit of condition (7), the manufacturing error sensitivity of the first focus group GrFC1 increases, and the variation in astigmatism, especially during eccentricity, becomes larger, which is undesirable. If the focus sensitivity exceeds the lower limit of condition (7), the focusing movement of the first focus group increases, and the overall lens system becomes larger, which is also undesirable.

[0058] Furthermore, regarding the above-mentioned conditional equation (7), it is desirable to set the lower limit to 0.800, and setting the lower limit to 0.900 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 3.400, and setting the upper limit to 2.900 will make the aforementioned effect more certain.

[0059] The imaging optical system of the present invention is preferably satisfied with the following condition. (8) 0.00 < |fFC12 / fFC2| < 0.50 fFC12: Combined focal length of the first focus group GrFC1 to the second focus group GrFC2 when focused at infinity. fFC2: Focal length of the preceding second focus group GrFC2

[0060] Conditional equation (8) specifies a preferred condition for the focus group, which is the ratio of the combined focal length of the first focus group GrFC1 to the second focus group GrFC2 to the focal length of the focus of the second focus group GrFC2.

[0061] If the refractive power of the second focusing group GrFC2 exceeds the upper limit of condition (8) and becomes relatively large, it is undesirable because coordinated control for focusing with the first focusing group GrFC1 becomes difficult. Furthermore, if the second focusing group GrFC2 has negative refractive power, the amount of movement of the first focusing group GrFC1 for focusing increases, and the overall lens system becomes larger, which is undesirable. Also, if the second focusing group GrFC2 has positive refractive power, the positive refractive power of the rear group GrR weakens, and the positive distortion aberration of the entire lens system becomes larger, which is undesirable. If the refractive power of the second focusing group GrFC2 exceeds the lower limit of condition (8) and becomes relatively small, it is undesirable because the fluctuation of distortion aberration during focusing becomes large.

[0062] Furthermore, regarding the above-mentioned conditional equation (8), it is desirable to set the lower limit to 0.01, and setting the lower limit to 0.03 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.33, and setting the upper limit to 0.23 will make the aforementioned effect more certain.

[0063] The imaging optical system of the present invention is preferably satisfied with the following condition. (9) 0.00 < |f / fFC2| < 1.00 f: Focal length of the entire lens system when focused at infinity fFC2: Focal length of the preceding second focus group GrFC2

[0064] Conditional equation (9) specifies the ratio of the focal length of the second focus group GrFC2 to the focal length of the entire system as a preferred condition for the focus group.

[0065] If the refractive power of the second focus group GrFC2 becomes relatively large, exceeding the upper limit of condition (9), it becomes difficult to coordinate control for focusing with the first focus group GrFC1, which is undesirable. Also, if the second focus group has negative refractive power, the amount of movement of the first focus group for focusing increases, making the entire lens system larger, which is undesirable. Also, if the second focus group has positive refractive power, the positive refractive power of the rear group GrR weakens, and the positive distortion aberration of the entire lens system increases, which is undesirable. If the refractive power of the second focus group GrFC2 becomes relatively small, exceeding the lower limit of condition (9), it becomes undesirable because the fluctuation of distortion aberration during focusing increases.

[0066] Furthermore, regarding the above-mentioned conditional equation (9), it is desirable to set the lower limit to 0.02, and setting the lower limit to 0.06 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.90, and setting the upper limit to 0.80 will make the aforementioned effect more certain.

[0067] The imaging optical system of the present invention is preferably satisfied with the following condition. (10) 15.00 <vdGla1<40.00 (11) 0.010 < ΔPgFGla1 < 0.100 vdGla1: Abbe number of the positive lens closest to the object ΔPgFGla1: ΔPgF of the positive lens closest to the object. Here, ΔPgF represents the anomalous dispersion between the g and F lines and is expressed by the following formula. ΔPgF = PgF - 0.64833 + 0.00180νd 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)

[0068] Conditional equations (10) and (11) specify the Abbe number and anomalous dispersion of the positive lens closest to the object as preferred conditions for chromatic aberration correction.

[0069] If the upper limit of condition (10) is exceeded, there will be insufficient secondary color removal, which is undesirable. If the lower limit of condition (10) is exceeded, there will be an excess of secondary color removal, which is also undesirable.

[0070] Exceeding the upper limit of condition (11) is undesirable because it results in excessive secondary color removal. Exceeding the lower limit of condition (11) is undesirable because it results in insufficient secondary color removal.

[0071] Furthermore, it is desirable to set the lower limit of the above-mentioned conditional equation (10) to 17.0. It is also desirable to set the upper limit to 35.00, and setting the upper limit to 30.00 will make the aforementioned effect more certain.

[0072] Furthermore, regarding the above-mentioned conditional equation (11), it is desirable to set its lower limit to 0.015, and setting the lower limit to 0.020 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.050, and setting the upper limit to 0.040 will make the aforementioned effect more certain.

[0073] The imaging optical system of the present invention is preferably satisfied with the following condition. (12) 0.25 < |exp / f| < 1.50 exp: Length from the exit pupil position to the image plane f: Focal length of the entire lens system when focused at infinity

[0074] Conditional equation (12) specifies the ratio of the exit pupil position to the total focal length as a preferred condition for the exit pupil position.

[0075] If the exit pupil position exceeds the upper limit of condition (12) and becomes larger, the lens diameter on the image side becomes larger than the aperture diaphragm S, which is undesirable. If the exit pupil position exceeds the lower limit of condition (12) and becomes smaller, off-axis rays reach the image plane at a steep angle, which is undesirable because it leads to a decrease in sensitivity and peripheral light intensity when an image sensor is used.

[0076] Furthermore, regarding the above-mentioned conditional equation (12), it is desirable to set its lower limit to 0.35, and setting the lower limit to 0.45 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 1.20, and setting the upper limit to 1.00 will make the aforementioned effect even more certain.

[0077] The imaging optical system of the present invention is preferably satisfied with the following condition. (13)0.080<(Y1GrF-Y2GrF) / f<0.300 Y1GrF: On-axis ray height of the object-side surface of the aforementioned group GrF Y2GrF: On-axis ray height of the image-side surface of the front group GrF. f: Focal length of the entire lens system when focused at infinity

[0078] Conditional equation (13) defines a preferred condition for the change in height of the on-axial rays passing through the front group GrF, and specifies the ratio of this change to the focal length of the entire system.

[0079] If the upper limit of condition (13) is exceeded and the axial rays within the front group GrF decrease sharply, the refractive power of the positive lenses within the group increases, leading to larger spherical aberrations and making it difficult to achieve good aberration correction for the entire system. If the lower limit of condition (13) is exceeded and the decrease in axial rays within the front group GrF is small, the diameter of the image lens becomes larger than that of the front group GrF, which is undesirable.

[0080] Furthermore, regarding the above-mentioned conditional equation (13), it is desirable to set its lower limit to 0.090, and setting the lower limit to 0.100 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 0.250, and setting the upper limit to 0.200 will make the aforementioned effect more certain.

[0081] The imaging optical system of the present invention is preferably satisfied with the following condition. (14) 0.75 <f / fF<2.50 f: Focal length of the entire lens system when focused at infinity fF: Focal length of the front group GrF when in focus at infinity.

[0082] Conditional equation (14) defines the ratio of the focal length of the front group GrF 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.

[0083] If the focal length of the front group GrF decreases beyond the upper limit of condition (14), the refractive power of the front group increases, making aberration correction difficult when increasing the aperture ratio. If the focal length of the front group GrF increases beyond the lower limit of condition (14), the refractive power of the front group decreases, making it difficult to miniaturize the entire lens system.

[0084] Furthermore, regarding the above-mentioned conditional equation (14), it is desirable to set its lower limit to 0.95, and setting the lower limit to 1.00 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 2.20, and setting the upper limit to 1.85 will make the aforementioned effect more certain.

[0085] The imaging optical system of the present invention is preferably satisfied with the following condition. (15) 0.70 <f / fR<3.50 f: Focal length of the entire lens system when focused at infinity fR: Focal length of the rear group GrR in the state of infinity focus

[0086] Conditional equation (15) defines the ratio of the focal length of the rear group GrR to the focal length of the entire system at infinity focus as a desirable condition for increasing the aperture ratio and correcting aberrations.

[0087] If the focal length of the rear group GrR decreases beyond the upper limit of condition (15), the refractive power of the rear group GrR increases, making aberration correction difficult when increasing the aperture ratio. If the focal length of the rear group GrR increases beyond the lower limit of condition (15), the refractive power of the rear group GrR decreases, making it difficult to achieve both a large aperture ratio and miniaturization of the entire lens system.

[0088] Furthermore, regarding the above-mentioned conditional equation (15), it is desirable to set its lower limit to 0.90, and even more desirable to set its lower limit to 1.10, and setting its lower limit to 1.30 will make the aforementioned effect more certain. Also, it is desirable to set its upper limit to 3.10, even more desirable to set its upper limit to 2.80, and even more desirable to set its upper limit to 2.50 will make the aforementioned effect more certain.

[0089] The imaging optical system of the present invention is preferably satisfied with the following condition. (16) 1.00 < |f / fFC1| < 4.00 f: Focal length of the entire lens system when focused at infinity fFC1: Focal length of the first focus group GrFC1 in the infinity focus state

[0090] Conditional equation (16) defines a preferred condition for aberration correction, which is the ratio of the focal length of the first focus group GrFC1 to the focal length of the entire system when in focus at infinity.

[0091] If the focal length of the first focus group GrFC1 decreases beyond the upper limit of condition (16), the manufacturing error sensitivity of the first focus group GrFC1 increases, and the variation in astigmatism, especially during eccentricity, becomes larger, which is undesirable. If the focal length of the first focus group GrFC1 increases beyond the lower limit of condition (16), the focusing movement of the first focus group GrFC1 increases, and the overall lens system becomes larger, which is also undesirable.

[0092] Furthermore, regarding the above-mentioned conditional equation (16), it is desirable to set its lower limit to 1.20, and setting the lower limit to 1.40 will make the aforementioned effect more certain. Also, it is desirable to set the upper limit to 3.70, and setting the upper limit to 3.30 will make the aforementioned effect more certain.

[0093] Next, the lens configuration of an embodiment of 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.

[0094] In the [surface data], the surface number is the number of the lens surface or aperture diaphragm S 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), vd is the Abbe number for the d line, and PgF indicates the partial dispersion ratio for the g line (wavelength 435.8 nm) and the F line (wavelength 486.1 nm).

[0095] The asterisk (*) next to the lens surface number indicates that the lens surface is aspherical. BF represents the back focus.

[0096] The (diaphragm) appended to the surface number indicates that an aperture diaphragm S is located at that position. The radius of curvature relative to the plane or aperture diaphragm S is indicated with ∞ (infinity).

[0097] The [Aspherical Data] section shows the values ​​of the coefficients that give the aspherical shape of the lens surface marked with an asterisk (*) in the [Surface Data] section. The aspherical shape 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, ..., and A20 are the 4th, 6th, ..., and 20th order aspherical coefficients, respectively, and the coordinates of the aspherical surface are expressed by the following formula. TIFF2026056718000002.tif19168

[0098] The [Various Data] section shows values ​​such as the zoom ratio and focal length at each focal length state.

[0099] The [Variable Interval Data] section shows the variable interval and BF values ​​for each focal length state.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] Furthermore, in the lens configuration diagrams of each embodiment, the arrows represent the trajectory of the lens group when focusing from infinity to near distance, S is the aperture diaphragm, I is the image plane, and the dashed line passing through the center is the optical axis. [Examples]

[0104] Figure 1 is a lens configuration diagram of the imaging optical system of Embodiment 1 of the present invention.

[0105] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0106] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a positive meniscus lens with its convex surface facing the object and a negative meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a double-sided aspherical positive meniscus lens with its convex surface facing the object.

[0107] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0108] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens composed of a biconvex lens and a biconcave lens, a biconvex lens, and a biconcave lens with aspherical surfaces on both sides.

[0109] The specifications of the imaging optical system in Example 1 are shown below. Numerical Example 1 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 139.1088 4.8329 1.86966 20.02 0.6435 2 242.8613 0.9000 3 92.4653 8.0166 1.43700 95.10 0.5336 4 199.2979 0.1500 5 66.2231 9.2418 1.43700 95.10 0.5336 6 123.1719 0.7000 7 57.9228 11.0967 1.43875 94.93 0.5340 8 149.8268 2.4925 1.90043 37.37 0.5767 9 64.5442 0.1500 10 53.9493 10.9955 1.43875 94.93 0.5340 11 267.3073 0.1500 12 71.7755 1.4510 1.85451 25.15 0.6103 13 38.5925 3.6698 14* 47.4008 6.5576 1.58313 59.46 0.5405 15* 122.7395 5.7746 16 (aperture) ∞ (d16) 17 402.5829 1.0830 1.75500 52.32 0.5473 18 36.5722 (d18) 19 61.6251 1.0000 1.84666 23.78 0.6192 20 29.6300 4.2961 1.72916 54.54 0.5453 21 50.7374 (d21) 22 52.1881 8.9390 1.88100 40.14 0.5700 23 -52.1881 1.0000 1.76634 35.82 0.5792 24 -109.5737 0.7000 25 1000.0000 5.3636 1.94594 17.98 0.6546 26 -57.6051 1.0000 1.76182 26.61 0.6123 27 48.5100 1.9463 28 116.6417 3.1455 2.00069 25.46 0.6136 29 -283.4942 1.2989 30* -72.1371 1.4004 1.58313 59.46 0.5405 31* 250.0000 28.4437 32 ∞ (BF) Image plane ∞ [Aspherical data] Pages 14, 15, 30, and 31 K 1.31969 -0.49418 -9.33638 3.00773 A4 -1.74600E-06 8.00700E-07 1.40182E-06 5.97410E-06 A6 -2.74822E-10 1.89969E-09 6.12079E-09 5.19546E-09 A8 -5.27433E-12 -1.05116E-11 -1.36953E-10 -1.40827E-10 A10 1.14794E-14 3.73574E-14 1.20007E-12 1.36630E-12 A12 -1.96123E-17 -7.53480E-17 -5.23473E-15 -6.38593E-15 A14 1.81911E-20 8.48844E-20 1.15364E-17 1.58507E-17 A16 -1.23654E-23 -4.45989E-23 -8.53231E-21 -1.69005E-20 A18 2.16244E-27 -6.26134E-27 -9.90443E-24 -3.43479E-24 A20 -6.33221E-31 1.29953E-29 1.46825E-26 1.53859E-26 [Various Data] INF 2407mm 1104mm Focal length 131.00 127.10 118.92 F-numbers: 1.46, 1.55, 1.67 Full angle of view 2ω 18.16 16.90 15.35 Image height Y 21.63 21.63 21.63 Lens length 152.55 152.55 152.55 [Variable interval data] INF 2407mm 1104mm d0 ∞ 2254.5496 951.4780 d16 3.2297 7.6457 14.4546 d18 20.3908 15.1920 7.0477 d21 3.1336 3.9164 5.2518 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 93.78 G2 17 -53.35 G3 19 -243.22 G4 22 55.42 [Examples]

[0110] Figure 8 is a lens configuration diagram of the imaging optical system according to Embodiment 2 of the present invention.

[0111] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0112] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a positive meniscus lens with its convex surface facing the object and a negative meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a positive meniscus lens with its convex surface facing the object and an aspherical image side.

[0113] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0114] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a biconvex lens, a negative meniscus lens with its convex surface facing the object, a cemented lens composed of a biconvex lens and a biconcave lens, and a biconcave lens with aspherical surfaces on both sides.

[0115] The specifications of the imaging optical system in Example 2 are shown below. Numerical Example 2 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 99.0044 8.9895 1.66382 27.35 0.6319 2 275.8199 0.9000 3 79.2910 7.8614 1.43875 94.93 0.5340 4 143.0933 0.1500 5 68.2459 7.2074 1.43875 94.93 0.5340 6 106.3373 0.7000 7 57.2459 10.0194 1.43875 94.93 0.5340 8 130.9629 1.4000 1.85451 25.15 0.6103 9 54.6789 0.3469 10 49.1982 10.8741 1.41390 101.00 0.5340 11 230.5091 0.1500 12 73.5987 1.0000 1.61396 44.29 0.5632 13 37.8249 4.1109 14 49.3591 5.2521 1.51633 64.06 0.5333 15* 102.8497 5.6239 16 (aperture) ∞ (d16) 17 358.7567 1.1495 1.79450 45.39 0.5573 18 39.7918 (d18) 19 121.1107 1.0000 1.85451 25.15 0.6103 20 40.4772 4.9578 1.73400 51.05 0.5500 21 147.3183 (d21) 22 56.8875 6.4330 1.83481 42.74 0.5648 23 -105.7080 1.0000 1.64769 33.84 0.5924 24 -614.3093 0.1500 25 710.6759 3.2898 1.75575 24.71 0.6291 26 -140.2399 0.3009 27 281.0978 1.0000 1.77047 29.74 0.5951 28 39.1480 1.0628 29 48.9433 5.2291 2.00069 25.46 0.6136 30 -602.4094 1.0000 1.55298 55.07 0.5447 31 53.4794 3.0188 32 -610.0402 1.0000 1.61881 63.85 0.5417 33* 118.7678 29.0427 34 ∞ (BF) Image plane ∞ [Aspherical data] Pages 15 and 33 K -0.03770 0.64143 A4 1.27138E-06 2.34001E-06 A6 1.65256E-10 1.77383E-08 A8 7.40117E-13 -4.98759E-10 A10 1.25184E-15 7.32541E-12 A12 -2.49360E-17 -6.11841E-14 A14 1.18756E-19 3.06966E-16 A16 -2.74692E-22 -9.14836E-19 A18 3.16561E-25 1.49266E-21 A20 -1.45036E-28 -1.02623E-24 [Various Data] INF 2416mm 1116mm Focal length 131.01 127.63 120.17 F-numbers: 1.46, 1.55, 1.69 Full angle of view 2ω 18.18 16.85 15.24 Image height Y 21.63 21.63 21.63 Lens length 152.52 152.52 152.52 [Variable interval data] INF 2416mm 1116mm d0 ∞ 2263.9811 963.8435 d16 1.9171 6.5360 13.5680 d18 25.2309 17.4773 5.6327 d21 1.1500 4.2847 9.0973 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 96.15 G2 17 -56.42 G3 19 -1226.37 G4 22 70.77 [Examples]

[0116] Figure 15 is a lens configuration diagram of the imaging optical system according to Embodiment 3 of the present invention.

[0117] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0118] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a double-sided aspherical positive meniscus lens with its convex surface facing the object.

[0119] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0120] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens composed of a positive meniscus lens with its concave surface facing the object and a biconcave lens, a biconvex lens, and a biconcave lens with aspherical surfaces on both sides.

[0121] The specifications of the imaging optical system in Example 3 are shown below. Numerical Example 3 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 103.3435 5.5538 1.92286 20.88 0.6390 2 161.0655 0.9000 3 77.0591 9.7648 1.43700 95.10 0.5336 4 168.4322 0.1500 5 52.0438 10.4235 1.43700 95.10 0.5336 6 84.8612 0.7000 7 53.1002 5.1440 1.43700 95.10 0.5336 8 67.7652 0.9117 9 64.9764 1.7957 1.91082 35.25 0.5822 10 37.5703 14.6524 1.43700 95.10 0.5336 11 150.4466 0.3510 12 97.9636 1.3856 1.85451 25.15 0.6103 13 42.5866 2.0107 14* 46.2188 8.0354 1.58313 59.46 0.5405 15* 310.7091 4.1034 16 (aperture) ∞ (d16) 17 184.7642 1.8204 1.80420 46.50 0.5573 18 33.2414 (d18) 19 152.5868 1.0000 1.85451 25.15 0.6103 20 46.7545 2.7991 1.69560 59.05 0.5433 21 109.1983 (d21) 22 51.0087 8.3471 1.78800 47.37 0.5559 23 -46.7892 1.0000 1.94594 17.98 0.6546 24 -76.7937 1.9277 25 -277.9678 5.4917 1.86966 20.02 0.6435 26 -48.6253 1.0000 1.6956 59.05 0.5433 27 41.2579 2.0306 28 83.1598 4.1749 1.84666 23.78 0.6192 29 -145.9364 1.0622 30* -250.0000 1.6475 1.58313 59.46 0.5405 31* 61.2381 25.5768 32 ∞ (BF) Image plane ∞ [Aspherical data] Pages 14, 15, 30, and 31 K 2.02860 -10.00000 -10.00000 0.42030 A4 -3.23272E-06 1.21155E-06 -5.09210E-05 -5.12445E-05 A6 -5.55679E-09 -5.90760E-09 3.05654E-07 3.22572E-07 A8 2.84738E-11 8.73348E-11 -1.31062E-09 -1.30463E-09 A10 -1.60092E-13 -6.26656E-13 4.27910E-12 1.60004E-12 A12 4.89429E-16 2.77445E-15 -1.75667E-14 1.92847E-14 A14 -8.87246E-19 -7.59718E-18 1.02520E-16 -1.40639E-16 A16 8.78396E-22 1.27144E-20 -4.33916E-19 4.48114E-19 A18 -3.76714E-25 -1.19226E-23 9.77391E-22 -7.12996E-22 A20 5.71335E-30 4.85129E-27 -8.91100E-25 4.51224E-25 [Various Data] INF 2613mm 1264mm Focal length 149.94 140.86 129.11 F-number 1.67 1.75 1.85 Full angle of view 2ω 15.89 14.96 13.94 Image height Y 21.63 21.63 21.63 Lens length 152.70 152.70 152.70 [Variable interval data] INF 2613mm 1264mm d0 ∞ 2460.4445 1110.9642 d16 3.2316 7.1273 12.3538 d18 23.0966 16.9897 9.1058 d21 2.6077 4.8189 7.4763 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 89.53 G2 17 -50.67 G3 19 -242.96 G4 22 69.90 [Examples]

[0122] Figure 22 is a lens configuration diagram of the imaging optical system according to Embodiment 4 of the present invention.

[0123] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0124] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a positive meniscus lens with its convex surface facing the object and a negative meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a double-sided aspherical positive meniscus lens with its convex surface facing the object.

[0125] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0126] The rear group GrR consists of a cemented lens of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens of a positive meniscus lens with its concave surface facing the object and a biconcave lens, a biconvex lens, and a biconcave lens with aspherical surfaces on both sides.

[0127] The specifications of the coupled optical system in Example 4 are shown below. Numerical Example 4 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 93.5994 5.6231 1.92286 20.88 0.6390 2 137.1048 0.9000 3 78.0596 9.7674 1.43700 95.10 0.5336 4 173.1160 0.1500 5 53.1074 10.0819 1.43700 95.10 0.5336 6 86.1298 0.7000 7 53.8322 5.5180 1.43700 95.10 0.5336 8 70.9567 1.8385 1.91082 35.25 0.5822 9 39.6300 0.4210 10 37.3994 15.3049 1.43700 95.10 0.5336 11 144.0812 0.1500 12 90.4927 1.4011 1.85451 25.15 0.6103 13 41.2699 2.3601 14* 45.6988 8.7810 1.58313 59.46 0.5405 15* 304.0931 4.4944 16 (aperture) ∞ (d16) 17 174.1348 1.0000 1.78800 47.49 0.5538 18 32.5156 (d18) 19 177.5661 1.0000 1.85451 25.15 0.6103 20 49.9043 2.4637 1.72916 54.67 0.5453 21 101.5570 (d21) 22 47.5761 8.4813 1.78800 47.37 0.5559 23 -47.5761 1.0000 1.94594 17.98 0.6546 24 -79.1616 2.0723 25 -431.8297 3.6105 1.86966 20.02 0.6435 26 -54.7382 1.0000 1.72916 54.09 0.5448 27 43.7207 3.3767 28 105.8545 4.5374 1.84666 23.78 0.6192 29 -88.5583 1.0500 30* -250.0000 1.4272 1.58313 59.46 0.5405 31* 49.5458 25.0127 32 ∞ (BF) Image plane ∞ [Aspherical data] Pages 14, 15, 30, and 31 K 1.79750 -2.36320 -7.77100 -3.04810 A4 -3.52121E-06 8.98550E-07 -9.48206E-05 -9.25107E-05 A6 -1.67709E-09 2.36341E-09 8.34231E-07 8.62111E-07 A8 -4.93188E-12 -1.10409E-11 -5.78560E-09 -6.04752E-09 A10 1.34466E-14 7.84706E-14 3.06961E-11 3.21599E-11 A12 -2.77961E-17 -2.91780E-16 -1.17040E-13 -1.20295E-13 A14 2.16525E-20 6.86137E-19 2.95287E-16 2.91816E-16 A16 1.56068E-23 -8.53334E-22 -4.31117E-19 -4.02949E-19 A18 -3.41168E-26 4.33770E-25 2.61097E-22 2.29755E-22 A20 1.18147E-29 4.23642E-29 2.48386E-26 1.55147E-26 [Various data] INF 2613mm 1260mm Focal length 149.90 140.65 128.85 F number 1.67 1.75 1.85 Full picture angle 2ω 15.94 15.00 13.97 Image height Y 21.63 21.63 21.63 Overall lens length 152.00 152.00 152.00 [Variable interval data] INF 2613mm 1260mm d0 ∞ 2461.5020 1107.8887 d16 2.9010 6.7822 12.0106 d18 23.0721 16.9963 9.1708 d21 2.5000 4.6946 7.2917 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting surface Focal length G1 1 88.95 G2 17 -50.90 G3 19 -207.02 G4 22 67.52

Example

[0128] FIG. 29 is a lens configuration diagram of the imaging optical system according to Example 5 of the present invention.

[0129] From the object side in order, it consists of a front group GrF with positive refractive power, a first focus group GrFC1 with negative refractive power, a second focus group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to a short distance, the front group GrF and the rear group GrR are fixed with respect to the image plane, the first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. The aperture stop S is on the object side of the first focus group GrFC1 and adjacent to the image side of the front group GrF.

[0130] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a double-sided aspherical positive meniscus lens with its convex surface facing the object.

[0131] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0132] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens composed of a plano-convex lens with a flat surface facing the object and a biconcave lens, a cemented lens composed of a biconvex lens and a biconcave lens, and a biconcave lens with aspherical surfaces on both sides.

[0133] The specifications of the imaging optical system in Example 5 are shown below. Numerical Example 5 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 79.2829 4.3754 1.86966 20.02 0.6435 2 113.1682 6.8230 3 66.9474 4.3006 1.43700 95.10 0.5336 4 91.0285 0.1500 5 51.4425 7.5633 1.43700 95.10 0.5336 6 88.8321 0.8857 7 49.9466 10.1229 1.43700 95.10 0.5336 8 195.6781 0.1500 9 102.7611 1.4307 1.85451 25.15 0.6103 10 37.5345 3.4927 11* 45.3817 7.7806 1.58313 59.46 0.5405 12* 213.6895 4.4492 13 (aperture) ∞ (d13) 14 397.0747 1.0723 1.75500 52.32 0.5473 15 39.1975 (d15) 16 68.2668 1.0000 1.85451 25.15 0.6103 17 33.1111 4.8280 1.72916 54.54 0.5453 18 73.6553 (d18) 19 55.4502 9.0071 1.88300 40.81 0.5656 20 -55.4502 1.0000 1.76634 35.82 0.5792 21 -163.5595 0.7000 22 ∞ 2.8973 1.94594 17.98 0.6546 23 -102.8618 1.0000 1.62004 36.30 0.5873 24 41.8335 1.5778 25 67.5281 10.0004 2.00100 29.13 0.5995 26 -141.9230 3.4754 1.85451 25.15 0.6103 27 88.5197 2.4835 28* -250.0000 1.3000 1.58313 59.46 0.5405 29* 175.4586 23.3421 30 ∞ (BF) Image plane ∞ [Aspherical data] Pages 11, 12, 28, and 29 K 1.00180 8.09720 10.00000 -10.00000 A4 -1.77279E-06 8.26044E-07 -1.26766E-06 2.93105E-06 A6 -9.23350E-10 4.54775E-10 -4.47789E-08 -4.36900E-08 A8 -7.82234E-13 -3.20674E-13 8.52528E-10 7.93111E-10 A10 -4.95720E-15 -9.69925E-15 -7.05140E-12 -5.91265E-12 A12 1.70226E-17 4.98971E-17 3.34772E-14 2.53749E-14 A14 -3.51790E-20 -1.13255E-19 -9.26558E-17 -6.33552E-17 A16 4.11257E-23 1.33337E-22 1.34406E-19 8.24720E-20 A18 -3.13486E-26 -8.12482E-26 -6.81711E-23 -3.48857E-23 A20 1.07545E-29 2.09172E-29 -2.06887E-26 -1.54335E-26 [Various data] INF 2402mm 1000mm Focal length 105.01 103.34 98.78 F number 1.46 1.53 1.65 Full picture angle 2ω 22.63 21.36 19.44 Image height Y 21.63 21.63 21.63 Overall lens length 143.06 143.06 143.06 [Variable interval data] INF 2402mm 1000mm d0 ∞ 2258.8035 856.9770 d13 3.4250 6.9548 13.3690 d15 21.9305 16.8372 6.9610 d18 2.5000 4.0635 7.5255 BF 0.0001 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 85.30 G2 14 -57.68 G3 16 -1199.53 G4 19 64.33 [Examples]

[0134] Figure 36 is a lens configuration diagram of the imaging optical system according to Embodiment 6 of the present invention.

[0135] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0136] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a double-sided aspherical positive meniscus lens with its convex surface facing the object.

[0137] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0138] The rear group GrR consists of a lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a three-element cemented lens composed of a biconvex lens, a biconcave lens, and a biconvex lens, a negative meniscus lens with its convex surface facing the object, and a biconcave lens with aspherical surfaces on both sides.

[0139] The imaging optics parameters for Example 6 are shown below. Numerical Example 6 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 95.4797 5.5344 1.86966 20.02 0.6435 2 133.2202 3.0336 3 61.2721 10.3208 1.43875 94.93 0.5340 4 102.0569 0.1500 5 50.4753 10.5422 1.43875 94.93 0.5340 6 85.7739 0.1500 7 63.3681 1.8348 1.85451 25.15 0.6103 8 47.8997 9.7545 1.48071 85.29 0.5362 9 111.7931 0.1500 10 71.4948 1.5001 1.85451 25.15 0.6103 11 41.0099 4.8621 12* 51.5620 6.4423 1.58313 59.46 0.5405 13* 173.4270 4.7640 14 (aperture) ∞ (d14) 15 282.9460 1.1353 1.72916 54.54 0.5453 16 39.6021 (d16) 17 80.6881 1.0000 1.84666 23.78 0.6192 18 32.7041 4.5011 1.88300 40.76 0.5667 19 61.3835 (d19) 20 53.0034 8.5383 1.91082 35.25 0.5833 21 -60.1640 1.0000 1.85451 25.15 0.6103 22 -1320.5297 0.7000 23 268.7319 4.3654 1.94594 17.98 0.6546 24 -85.2300 1.0851 1.80518 25.46 0.6157 25 35.3252 10.0000 2.00100 29.13 0.5995 26 -314.5307 0.1500 27 82.2952 1.0000 1.83400 37.17 0.5786 28 37.6997 5.5244 29* -250.0000 1.3000 1.68948 31.02 0.5987 30* 174.6078 17.0565 31 ∞ (BF) Image plane ∞ [Aspherical data] 12th, 13th, 29th, 30th K 1.92920 -9.39400 10.00000 -3.01790 A4 -3.41133E-06 -1.27223E-07 -4.49428E-05 -3.97507E-05 A6 -5.94524E-10 6.15072E-11 2.86365E-07 2.75666E-07 A8 -1.27268E-11 -5.93579E-13 -1.43619E-09 -1.24380E-09 A10 4.08832E-14 -2.05725E-15 6.06628E-12 5.05384E-12 A12 -8.26804E-17 1.45244E-17 -1.49045E-14 -1.24553E-14 A14 8.10711E-20 -2.95980E-20 1.02833E-17 1.02249E-17 A16 -2.63508E-23 3.07995E-23 2.78454E-20 1.91594E-20 A18 -1.00531E-26 -1.63454E-26 -5.25351E-23 -4.05024E-23 A20 3.03945E-30 5.21606E-30 2.30083E-26 1.49020E-26 [Various Data] INF 2012mm 1100mm Focal length 101.18 99.78 96.96 F-numbers: 1.24, 1.31, 1.39 Full angle of view 2ω 23.59 21.82 20.24 Image height Y 21.63 21.63 21.63 Lens length: 144.45 x 144.45 x 144.45 [Variable interval data] INF 2012mm 1100mm d0 ∞ 1867.7915 955.8456 d14 2.9439 8.2987 13.9994 d16 22.6069 15.1736 7.4213 d19 2.5000 4.5785 6.6301 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 92.68 G2 15 -63.28 G3 17 -433.52 G4 20 53.82 [Examples]

[0140] Figure 43 is a lens configuration diagram of the imaging optical system according to Embodiment 7 of the present invention.

[0141] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with positive refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0142] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a positive meniscus lens with its convex surface facing the object and a negative meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a positive meniscus lens with an aspherical surface facing the object and its convex surface facing the object.

[0143] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0144] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens composed of a biconvex lens and a biconcave lens, a positive meniscus lens with its convex surface facing the object, and a biconcave lens with aspherical surfaces on both sides.

[0145] The specifications of the coupled optical system in Example 7 are shown below. Numerical Example 7 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 117.1854 6.0439 1.66382 27.35 0.6319 2 219.8859 0.9000 3 83.9403 8.9280 1.43875 94.93 0.5340 4 181.6874 0.1500 5 62.7203 9.5014 1.43875 94.93 0.5340 6 110.0951 0.7000 7 56.9619 11.0980 1.43875 94.93 0.5340 8 149.8895 1.4000 1.85451 25.15 0.6103 9 51.4599 1.1486 10 49.6799 10.2920 1.62200 30.66 0.6248 11 164.2884 0.1500 12 58.6208 1.0000 1.78880 28.42 0.6006 13 38.0999 5.0485 14* 51.5388 4.5941 1.51633 64.06 0.5333 15 94.8428 5.8668 16 (aperture) ∞ (d16) 17 224.7265 1.0000 1.74100 52.60 0.5479 18 36.6111 (d18) 19 96.6402 1.0000 1.85451 25.15 0.6103 20 35.6456 5.4861 1.69930 51.11 0.5552 21 195.0162 (d21) 22 59.6636 7.3150 1.90525 35.04 0.5848 23 -67.1153 1.0000 1.68948 31.02 0.5987 24 -138.1863 0.1500 25 230.2066 4.0647 1.75575 24.71 0.6291 26 -103.7723 1.0000 1.80000 29.84 0.6017 27 47.5951 1.2986 28 72.1163 3.6533 2.00069 25.46 0.6136 29 566.2945 1.0892 30* -202.7038 1.2934 1.59201 67.02 0.5358 31* 55.8077 27.9878 32 ∞ (BF) Image plane ∞ [Aspherical data] Pages 14, 30, and 31 K -2.11020 0.00000 0.00000 A4 8.15788E-07 9.53113E-07 2.86068E-06 A6 -7.29072E-10 -4.20498E-10 2.14870E-09 A8 -1.51252E-13 1.85536E-12 -6.10211E-12 A10 -2.09038E-16 -1.04797E-14 2.97471E-14 A12 8.41382E-19 9.22872E-17 5.85940E-17 A14 -2.04017E-21 -4.89598E-19 -6.01301E-19 A16 2.93769E-24 1.54242E-21 1.95077E-21 A18 -2.31344E-27 -2.65755E-24 -3.46125E-24 A20 7.67306E-31 1.92848E-27 2.58654E-27 [Various Data] INF 2414mm 1115mm Focal length 131.00 126.60 117.94 F-number 1.45 1.55 1.68 Full angle of view 2ω 18.24 16.89 15.23 Image height Y 21.63 21.63 21.63 Lens length 152.50 152.50 152.50 [Variable interval data] INF 2414mm 1115mm d0 ∞ 2261.2759 962.6919 d16 1.5021 6.0628 12.9795 d18 26.2477 18.6740 7.2783 d21 1.5912 4.6042 9.0832 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 95.75 G2 17 -59.16 G3 19 1007.85 G4 22 90.07 [Examples]

[0146] Figure 50 is a lens configuration diagram of the imaging optical system according to Embodiment 8 of the present invention.

[0147] The lens consists of, in order from the object side, a front group GrF with positive refractive power, a first focusing group GrFC1 with negative refractive power, a second focusing group GrFC2 with negative refractive power, and a rear group GrR with positive refractive power. When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane, the first focusing group GrFC1 moves towards the image side, and the second focusing group GrFC2 moves towards the object side. The aperture diaphragm S is located closer to the object than the first focusing group GrFC1 and adjacent to the image side of the front group GrF.

[0148] The front group GrF consists of a positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, another positive meniscus lens with its convex surface facing the object, a cemented lens composed of a positive meniscus lens with its convex surface facing the object and a negative meniscus lens with its convex surface facing the object, a positive meniscus lens with its convex surface facing the object, a negative meniscus lens with its convex surface facing the object, and a positive meniscus lens with an aspherical surface facing the object and its convex surface facing the object.

[0149] The first focusing group GrFC1 consists of a negative meniscus lens with its convex surface facing the object. The second focusing group GrFC2 consists of a cemented lens composed of a negative meniscus lens with its convex surface facing the object and a positive meniscus lens with its convex surface facing the object.

[0150] The rear group GrR consists of a cemented lens composed of a biconvex lens and a negative meniscus lens with its concave surface facing the object, a cemented lens composed of a biconvex lens and a biconcave lens, a positive meniscus lens with its convex surface facing the object, and a biconcave lens with aspherical surfaces on both sides.

[0151] The specifications of the imaging optical system in Example 8 are shown below. Numerical Example 8 Unit: mm [Surface data] Face number rd nd vd PgF Object surface ∞ (d0) 1 154.2992 9.3056 1.66382 27.35 0.6319 2 329.5240 3.1026 3 113.6054 11.2659 1.43700 95.10 0.5336 4 215.3201 0.2307 5 87.7193 12.2279 1.43700 95.10 0.5336 6 155.8175 1.0286 7 78.1457 14.8830 1.43700 95.10 0.5336 8 192.5337 1.9131 1.85451 25.15 0.6103 9 65.7184 0.4798 10 60.4053 15.8915 1.62200 30.66 0.6248 11 188.9328 0.1823 12 103.8956 1.3664 1.78880 28.43 0.6009 13 51.0585 6.5781 14* 69.1355 8.2892 1.58313 59.46 0.5405 15 242.7300 6.6998 16 (aperture) ∞ (d16) 17 381.4794 1.4567 1.69680 55.46 0.5426 18 47.7773 (d18) 19 81.3290 1.2671 1.84666 23.78 0.6192 20 42.8285 5.0247 1.75500 52.32 0.5474 21 71.5810 (d21) 22 71.8812 12.5637 1.90366 31.32 0.5948 23 -85.6502 1.4479 1.68430 26.81 0.6232 24 -189.0532 0.1500 25 629.3453 4.3660 1.75575 24.71 0.6291 26 -84.9383 1.3004 1.74077 27.76 0.6078 27 63.3895 1.7491 28 97.4266 4.6585 2.00069 25.46 0.6136 29 351.9216 0.3488 30* 260.3705 1.7000 1.59201 67.02 0.5358 31* 72.2609 40.9191 32 ∞ (BF) Image plane ∞ [Aspherical data] Pages 14, 30, and 31 K -2.45100 0.00000 0.00000 A4 5.77000E-07 -6.47454E-07 1.55838E-07 A6 -1.55961E-10 2.72492E-09 2.42322E-09 A8 1.81718E-17 -1.19788E-12 4.38337E-12 A10 -1.57211E-17 -9.92547E-15 -3.09996E-14 A12 2.08682E-20 8.64616E-17 1.79200E-16 A14 -2.73258E-23 -4.53735E-19 -9.52495E-19 A16 2.12485E-26 1.41399E-21 3.30001E-21 A18 -9.03639E-30 -2.40992E-24 -6.25290E-24 A20 1.61853E-33 1.72989E-27 4.99006E-27 [Various Data] INF 3310mm 1516mm Focal length 180.00 174.09 162.51 F-numbers: 1.45, 1.54, 1.66 Full angle of view 2ω 13.46 12.57 11.49 Image height Y 21.63 21.63 21.63 Lens length 209.50 209.50 209.50 [Variable interval data] INF 3310mm 1516mm d0 ∞ 3100.1185 1306.9229 d16 3.8938 10.2637 20.1102 d18 31.8008 22.8561 9.2206 d21 3.4076 5.9824 9.7715 BF 0.0000 0.0000 0.0000 [Lens group data] Group Starting plane Focal length G1 1 130.19 G2 17 -78.52 G3 19 -516.38 G4 22 87.59

[0152] In all embodiments, the aperture diaphragm S is located between the front group GrF and GrFC1, but the aperture diaphragm S may also be placed inside the front group GrF.

[0153] Furthermore, although not described in the examples, miniaturization and performance improvements may be achieved by using elements such as hybrid aspherical lenses, diffraction gratings, and refractive index distribution lenses. The shape of the aspherical lens may also be gull-wing shaped with inflection points, or it may be a free-form surface.

[0154] 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 1.43 or less or 2.01 or greater may be used, as may materials with an Abbe number νd of 17.0 or less or 101.0 or greater.

[0155] Furthermore, materials with characteristics not described in the examples may be used for miniaturization, weight reduction, and good aberration correction. Liquid lenses or gel lenses may be used to perform minute focusing movements.

[0156] Furthermore, in the embodiment, part or all of the lens group may be moved in a direction substantially perpendicular to the optical axis to provide vibration damping.

[0157] The following is a list of corresponding values ​​for the conditional expressions in each of the above embodiments. [Conditional expression corresponding value] Conditional expression EX1 EX2 EX3 EX4 EX5 EX6 EX7 EX8 (1) 0.64 0.61 0.69 0.71 0.55 0.59 0.64 0.67 (2) 1.74 1.71 1.48 1.44 1.48 1.55 1.57 1.63 (3) 0.26 0.27 0.25 0.25 0.27 0.27 0.28 0.26 (4) 95.04 94.93 95.10 95.10 95.10 91.72 94.93 95.10 (5) 0.096 0.022 0.156 0.182 0.016 0.045 0.045 0.075 (6) 0.315 0.228 0.316 0.318 0.315 0.317 0.245 0.433 (7) 1.825 1.740 2.543 2.563 1.444 1.099 1.716 1.753 (8) 0.16 0.04 0.16 0.18 0.04 0.12 0.06 0.12 (9) 0.54 0.11 0.62 0.72 0.09 0.23 0.13 0.35 (10) 20.02 27.35 20.88 20.88 20.02 20.02 27.35 27.35 (11) 0.031 0.033 0.028 0.028 0.031 0.031 0.033 0.033 (12) 0.63 0.64 0.52 0.51 0.72 0.70 0.59 0.62 (13) 0.160 0.163 0.148 0.149 0.120 0.158 0.161 0.159 (14) 1.40 1.36 1.67 1.69 1.23 1.09 1.37 1.38 (15) 2.36 1.85 2.15 2.22 1.63 1.88 1.45 2.06 (16) 2.46 2.32 2.96 2.95 1.82 1.60 2.21 2.29 (4') 95.04 94.93 95.10 95.10 95.10 91.72 94.93 95.10 (5') 0.096 0.022 0.156 0.182 0.016 0.045 0.045 0.075 (6') 0.315 0.228 0.316 0.318 0.315 0.317 0.245 0.433

[0158] The configuration of the embodiment of the imaging optical system of the present invention has been described above, but various modifications are possible and are not limited to the above-described embodiments and examples. The shapes and numerical values ​​of each part shown in the above numerical examples are all just examples for implementing this technology, and the scope of the present invention should not be interpreted as being limited by these embodiments.

[0159] The above embodiments can take the following configuration. [Section 1] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 has negative refractive power, and the second focus group GrFC2 has negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (1) 0.20 < LGrF / fF < 1.40 LGrF: Length of the front group GrF along the optical axis in the state of infinity focus. fF: Focal length of the front group GrF when in focus at infinity. [Section 2] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 has negative refractive power, and the second focus group GrFC2 has negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (2) 0.42 < f / fFC2R < 4.00 f: Focal length of the entire lens system when focused at infinity fFC2R: Combined focal length of the second focus group GrFC2 and the rear group GrR when focused at infinity. [Section 3] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 has negative refractive power, and the second focus group GrFC2 has negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (3) 0.15 < LGrFGrR / LALL < 0.50 LGrFGrR: Length along the optical axis from the image-side surface of the front group GrF to the object-side surface of the rear group GrR in the infinity focus state. LALL: The length along the optical axis from the object-side surface of the front group GrF to the image plane when in the infinity focus state. [Section 4] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 has negative refractive power, and the second focus group GrFC2 has negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (4) 50.00 < vdG24 < 102.00 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF. [Section 5] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 has negative refractive power, and the second focus group GrFC2 has negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (5) 0.000 < |K2| < 0.370 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. [Section 6] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (5) 0.000 < |K2| < 0.370 (6)0.107< ΔGr1GrFC1 / Ymax <1.000 |K2|: Focus sensitivity of the second focus group GrFC2 in the state of infinity focus. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height [Section 7] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (4') 55.00 < vdG24 < 102.00 (6´)0.095< ΔGr1GrFC1 / Ymax <1.000 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF. ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height [Section 8] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized in that the second to fourth positive lenses from the object side within the front group GrF have a positive meniscus shape with a convex surface on the object side. [Section 9] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. The aperture diaphragm S is located closer to the object than the first focus group GrFC1. An imaging optical system characterized by satisfying the following condition. (4') 55.00 < vdG24 < 102.00 vdG24: The average Abbe number of the second, third, and fourth positive lenses from the object side of the front group GrF. [Section 10] Starting from the object side, the first group GrF of positive refractive powers, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the positive refractive power group GrR, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed relative to the image plane. The first focus group GrFC1 moves towards the image, and the second focus group GrFC2 moves towards the object. The aperture diaphragm S is adjacent to the image side of the front group GrF. An imaging optical system characterized by satisfying the following condition. (5')0.000<|K2|<0.600 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. [Section 11] The imaging optical system according to any one of [Item 6] to [Item 9], characterized in that the second focus group GrFC2 has a negative refractive power. [Section 12] The imaging optical system according to any one of [Clause 1] to [Clause 9] or [Clause 11], characterized in that it comprises an aperture diaphragm S, the aperture diaphragm S being adjacent to the image side of the front group GrF. [Section 13] The imaging optical system according to any one of [Clause 1] to [Clause 7], [Clause 9] to [Clause 12], characterized in that the shape of the second to fourth positive lenses in the front group GrF is a positive meniscus with a convex surface on the object side. [Section 14] The imaging optical system according to any one of [Item 1] to [Item 13], characterized in that the first focus group GrFC1 consists of a single lens. [Section 15] The imaging optical system according to any one of [Item 1] to [Item 14], characterized in that the second focus group GrFC2 consists of one or two lenses. [Section 16] The imaging optical system according to any one of [Clause 1] to [Clause 15], characterized in that the rear group GrR with positive refractive power has one or more negative lenses on the image side of the positive lens. [Section 17] An imaging optical system according to any one of [Item 1] to [Item 16], characterized in that it satisfies the following conditions. (7) 0.600 < |K1| < 4.000 (8) 0.00 < |fFC12 / fFC2| < 0.50 (9) 0.00 < |f / fFC2| < 1.00 (10) 15.00 <vdGla1<40.00 (11) 0.010 < ΔPgFGla1 < 0.100 (12) 0.25 < |exp / f| < 1.50 (13)0.080<(Y1GrF-Y2GrF) / f<0.300 (14) 0.75 <f / fF<2.50 (15) 0.70 <f / fR<3.50 (16) 1.00 < |f / fFC1| < 4.00 |K1|: Focus sensitivity of the first focus group GrFC1 in the infinity focus state. |K1|=|(1-βFC1^2)*((βFC2*βR)^2)| βFC1: Lateral magnification of the first focus group GrFC1 in the infinity focus state. βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. fFC12: Combined focal length of the first focus group GrFC1 to the second focus group GrFC2 when focused at infinity. fFC2: Focal length of the preceding second focus group GrFC2 f: Focal length of the entire lens system when focused at infinity vdGla1: Abbe number of the positive lens closest to the object ΔPgFGla1: ΔPgF of the positive lens closest to the object. Here, ΔPgF represents the anomalous dispersion between the g and F lines and is expressed by the following formula. ΔPgF = PgF - 0.64833 + 0.00180νd 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) exp: Length from the exit pupil position to the image plane Y1GrF: On-axis ray height of the object-side surface of the aforementioned group GrF Y2GrF: On-axis ray height of the image-side surface of the front group GrF. fF: Focal length of the front group GrF when in focus at infinity. fR: Focal length of the rear group GrR in the state of infinity focus fFC1: Focal length of the first focus group GrFC1 in the infinity focus state [Explanation of Symbols]

[0160] GrF front group GrR posterior group GrFC1 First Focus Group GrFC2 Second Focus Group I image plane S Aperture diaphragm

Claims

1. Starting from the object side, the first group of positive refractive powers GrF, The first focus group of negative refractive power GrFC1, the second focus group of negative refractive power GrFC2, It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (1) 0.20<LGrF / fF<1.40 LGrF: Length of the front group GrF along the optical axis in the state of infinity focus. fF: Focal length of the front group GrF in the state of infinity focus

2. Starting from the object side, the first group of positive refractive powers GrF, The first focus group of negative refractive power GrFC1, the second focus group of negative refractive power GrFC2, It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (2) 0.42< f / fFC2R <4.00 f: Focal length of the entire lens system when focused at infinity fFC2R: The combined focal length of the second focus group GrFC2 and the rear group GrR when focused at infinity.

3. Starting from the object side, the first group of positive refractive powers GrF, The first focus group of negative refractive power GrFC1, the second focus group of negative refractive power GrFC2, It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (3) 0.15< LGrFGrR / LALL <0.50 LGrFGrR: Length along the optical axis from the image-side surface of the front group GrF to the object-side surface of the rear group GrR in the infinity focus state. LALL: The length along the optical axis from the object-side surface of the front group GrF to the image plane when in focus at infinity.

4. Starting from the object side, the first group of positive refractive powers GrF, The first focus group of negative refractive power GrFC1, the second focus group of negative refractive power GrFC2, It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (4) 50.00< vdG24 <102.00 vdG24: The average value of the Abbe numbers of the second, third, and fourth positive lenses from the object side of the front group GrF.

5. Starting from the object side, the first group of positive refractive powers GrF, The first focus group of negative refractive power GrFC1, the second focus group of negative refractive power GrFC2, It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (5) 0.000<|K2|<0.370 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

6. Starting from the object side, the first group of positive refractive powers GrF, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (5) 0.000<|K2|<0.370 (6) 0.107<ΔGr1GrFC1 / Ymax<1.000 |K2|: Focus sensitivity of the second focus group GrFC2 in the state of infinity focus. |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height

7. Starting from the object side, the first group of positive refractive powers GrF, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized by satisfying the following condition. (4') 55.00< vdG24 <102.00 (6') 0.095< ΔGr1GrFC1 / Ymax <1.000 vdG24: The average value of the Abbe numbers of the second, third, and fourth positive lenses from the object side of the front group GrF. ΔGr1GrFC1: The length parallel to the optical axis between the position of the on-axial ray height on the image-side face of the front group GrF and the position of the on-axial ray height on the object-side face of the first focus group GrFC1 in the infinity focus state. Ymax: Maximum image height

8. Starting from the object side, the first group of positive refractive powers GrF, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. An imaging optical system characterized in that the second to fourth positive lenses from the object side within the aforementioned front group GrF have a positive meniscus shape with a convex surface on the object side.

9. Starting from the object side, the first group of positive refractive powers GrF, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. The aperture diaphragm S is located closer to the object than the first focus group GrFC1. An imaging optical system characterized by satisfying the following condition. (4') 55.00< vdG24 <102.00 vdG24: The average value of the Abbe numbers of the second, third, and fourth positive lenses from the object side of the front group GrF.

10. Starting from the object side, the first group of positive refractive powers GrF, The first focus group GrFC1 and the second focus group GrFC2 have negative refractive power. It consists of the group GrR with positive refractive power, When focusing from infinity to near distance, the front group GrF and the rear group GrR are fixed with respect to the image plane. The first focus group GrFC1 moves toward the image side, and the second focus group GrFC2 moves toward the object side. The aperture diaphragm S is adjacent to the image side of the front group GrF. An imaging optical system characterized by satisfying the following condition. (5') 0.000<|K2|<0.600 |K2|: Focus sensitivity of the second focus group GrFC2 in the infinity focus state |K2|=|(1-βFC2^2)*(βR^2)| βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state.

11. The imaging optical system according to any one of 6 to 9, characterized in that the second focus group GrFC2 has a negative refractive power.

12. The imaging optical system according to any one of claims 1 to 9, wherein the aperture diaphragm S is adjacent to the image side of the front group GrF.

13. The imaging optical system according to any one of claims 1 to 7 or 9 to 10, characterized in that the shape of the second to fourth positive lenses in the front group GrF is a positive meniscus with an object-side convex surface.

14. The imaging optical system according to any one of claims 1 to 10, characterized in that the first focus group GrFC1 consists of a single lens.

15. The imaging optical system according to any one of claims 1 to 10, characterized in that the second focus group GrFC2 consists of one or two lenses.

16. The imaging optical system according to any one of claims 1 to 10, characterized in that the rear group GrR with positive refractive power has one or more negative lenses on the image side of the positive lens.

17. The imaging optical system according to any one of claims 1 to 10, characterized in that it satisfies the following conditional expression. (7) 0.600<|K1|<4.000 (8) 0.00<|fFC12 / fFC2|<0.50 (9) 0.00<|f / fFC2|<1.00 (10) 15.00<vdGla1<40.00 (11) 0.010<ΔPgFGla1<0.100 (12) 0.25<|exp / f|<1.50 (13) 0.080<(Y1GrF-Y2GrF) / f<0.300 (14) 0.75<f / fF<2.50 (15) 0.70<f / fR<3.50 (16) 1.00< |f / fFC1| <4.00 |K1|: Focus sensitivity of the first focus group GrFC1 in the infinity focus state |K1|=|(1-βFC1^2)*((βFC2*βR)^2)| βFC1: Lateral magnification of the first focus group GrFC1 in the infinity focus state. βFC2: Lateral magnification of the second focus group GrFC2 in the infinity focus state. βR: Lateral magnification of the rear group GR in the infinity focus state. fFC12: The combined focal length of the first focus group GrFC1 and the second focus group GrFC2 when focused at infinity. fFC2: Focal length of the second focus group GrFC2 f: Focal length of the entire lens system when focused at infinity vdGla1: Abbe number of the positive lens closest to the object. ΔPgFGla1: ΔPgF of the positive lens closest to the object. Here, ΔPgF represents the anomalous dispersion between the g and F lines and is expressed by the following formula. ΔPgF=PgF-0.64833+0.00180νd PgF = (ng - nF) / (nF - nC): Partial variance ratio between the g and 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) exp: Length from the exit pupil position to the image plane Y1GrF: On-axis ray height of the object-side surface of the aforementioned group GrF Y2GrF: On-axis ray height of the image-side surface of the front group GrF. fF: Focal length of the front group GrF in the state of infinity focus fR: Focal length of the rear group GrR in the state of infinity focus fFC1: Focal length of the first focus group GrFC1 in the infinity focus state.

Images