Optical system, optical device, and method for manufacturing optical system

Abstract

Provided are an optical system, an optical device, and a method for manufacturing an optical system which achieve miniaturization, increase the angle of view, reduce distortion aberration, and ensure a sufficient amount of peripheral light.　An optical system OL used in an optical device such as a camera 1 includes, in order from an object side, a front group G1, an aperture diaphragm S, and a rear group G2. The front group G1 includes, in order from the object side, a meniscus-shaped first negative lens LN1 including a convex surface facing the object side, a meniscus-shaped second negative lens LN2 including a convex surface facing the object side, and a first cemented lens CL1 including a third negative lens LN3 having negative refractive power and a first positive lens LP1 having positive refractive power. The rear group G2 includes a focusing group Gf that moves on an optical axis during focusing, and is configured to satisfy a predetermined conditional expression.

Description

Optical system, optical instrument, and method for manufacturing an optical system

[0001] This invention relates to an optical system, an optical instrument, and a method for manufacturing an optical system.

[0002] In recent years, ultra-wide-angle lenses with large apertures and numerical apertures of less than 2 have been developed (see, for example, Patent Document 1). These lenses tend to use large-diameter aspherical lenses on the object side, and there is a need to achieve both miniaturization of the optical system and performance, as well as to ensure the amount of peripheral light characteristic of ultra-wide-angle lenses.

[0003] Japanese Patent Publication No. 2024-011096

[0004] An optical system according to a first aspect of the present invention has, in order from the object side, a front group, an aperture, and a rear group. The front group has, in order from the object side, a first negative lens with a meniscus shape with a convex surface facing the object side, a second negative lens with a meniscus shape with a convex surface facing the object side, and a first cemented lens consisting of a third negative lens having negative refractive power and a first positive lens having positive refractive power. The rear group has a focusing group that moves along the optical axis when focusing, and satisfies the following condition: 1.60 < ndLN1 < 1.77 where ndLN1 is the refractive index of the medium of the first negative lens with respect to the d line.

[0005] An optical system according to a second aspect of the present invention comprises, in order from the object side, a front group, an aperture, and a rear group, wherein the front group has a first negative lens with a meniscus shape and a convex surface facing the object side, the rear group has a positive refractive power, and the rear group has a focusing group that moves along the optical axis when focusing, and satisfies the following condition: -0.20 < f / f1 < 0.20 where f: focal length of the entire optical system, f1: focal length of the front group

[0006] A method for manufacturing an optical system according to a first aspect of the present invention is a method for manufacturing an optical system having, in order from the object side, a front group, an aperture, and a rear group, wherein, in the front group, in order from the object side, a first negative lens with a meniscus shape with a convex surface facing the object side, a second negative lens with a meniscus shape with a convex surface facing the object side, and a first cemented lens consisting of a third negative lens having negative refractive power and a first positive lens having positive refractive power are arranged, and a focusing group that moves along the optical axis when focusing is arranged in the rear group, and is arranged to satisfy the following condition: 1.60 < ndLN1 < 1.77 where ndLN1: refractive index of the medium of the first negative lens with respect to the d line

[0007] A second aspect of the present invention relates to a method for manufacturing an optical system having, in order from the object side, a front group, an aperture, and a rear group, wherein a first negative lens with a meniscus shape and a convex surface facing the object side is placed on the front group closest to the object, the rear group is arranged to have a positive refractive power, and a focusing group that moves along the optical axis when focusing is placed on the rear group is arranged to satisfy the following condition: -0.20 < f / f1 < 0.20 where, f: focal length of the entire optical system, f1: focal length of the front group

[0008] This is a cross-sectional view showing the lens configuration of the optical system according to the first embodiment when an object at infinity is in focus. This is an aberration diagram of the optical system according to the first embodiment, where (a) shows the case when an object at infinity is in focus and (b) shows the case when an object at close range is in focus. This is a cross-sectional view showing the lens configuration of the optical system according to the second embodiment when an object at infinity is in focus. This is an aberration diagram of the optical system according to the second embodiment, where (a) shows the case when an object at infinity is in focus and (b) shows the case when an object at close range is in focus. This is a cross-sectional view showing the lens configuration of the optical system according to the third embodiment when an object at infinity is in focus. This is an aberration diagram of the optical system according to the third embodiment, where (a) shows the case when an object at infinity is in focus and (b) shows the case when an object at close range is in focus. This is a cross-sectional view showing the lens configuration of the optical system according to the fourth embodiment when an object at infinity is in focus. This is an aberration diagram of the optical system according to the fourth embodiment, where (a) shows the case when an object at infinity is in focus and (b) shows the case when an object at close range is in focus. This is a cross-sectional view showing the lens configuration of the optical system according to the fifth embodiment when an object at infinity is in focus. A diagram of aberrations of the optical system according to the fifth embodiment, where (a) shows the case when an object at infinity is in focus, and (b) shows the case when an object at close range is in focus. A cross-sectional view showing the lens configuration of the optical system according to the sixth embodiment when an object at infinity is in focus. A diagram of aberrations of the optical system according to the sixth embodiment, where (a) shows the case when an object at infinity is in focus, and (b) shows the case when an object at close range is in focus. A cross-sectional view of a camera equipped with the above optical system. A flowchart for explaining the manufacturing method of the above optical system, where (a) shows the first embodiment, and (b) shows the second embodiment.

[0009] Preferred embodiments will be described below with reference to the drawings.

[0010] (First Embodiment) The optical system OL according to the first embodiment, as shown in Figure 1, has, in order from the object side, a front group G1, an aperture (aperture diaphragm S), and a rear group G2. The front group G1 has, in order from the object side, a first negative lens LN1 with a meniscus shape and a convex surface facing the object side, a second negative lens LN2 with a meniscus shape and a convex surface facing the object side, and a first cemented lens CL1 consisting of a third negative lens LN3 with negative refractive power and a first positive lens LP1 with positive refractive power. The rear group G2 has a focusing group Gf that moves along the optical axis when focusing. By configuring it in this way, it is possible to provide an optical system OL that is miniaturized, has a wide angle of view, has little distortion, and has sufficient peripheral light.

[0011] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional expression (1).

[0012] 1.60 < ndLN1 < 1.77 (1) where ndLN1: refractive index of the medium of the first negative lens LN1 with respect to the d line

[0013] Conditional equation (1) defines an appropriate range for the refractive index of the medium of the first negative lens LN1, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (1), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (1), it is more desirable to set the lower limit of conditional equation (1) to 1.61, 1.63, 1.65, and further to 1.67. Also, in order to ensure the effect of conditional equation (1), it is more desirable to set the upper limit of conditional equation (1) to 1.75, 1.74, and further to 1.73.

[0014] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (2).

[0015] 50.00 < νdLN1 < 60.00 (2) where νdLN1: Abbe number of the medium of the first negative lens LN1 with respect to the d line

[0016] Conditional equation (2) defines an appropriate range for the Abbe number of the medium of the first negative lens LN1, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (2), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (2), it is more desirable to set the lower limit of conditional equation (2) to 51.00, 52.00, and even 53.00. Furthermore, in order to ensure the effect of conditional equation (2), it is more desirable to set the upper limit of conditional equation (2) to 58.00, 55.00, and even 54.00.

[0017] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (3).

[0018] 1.50 < ndLN2 < 1.90 (3) where ndLN2: refractive index of the medium of the second negative lens LN2 with respect to the d line

[0019] Conditional equation (3) defines an appropriate range for the refractive index of the medium of the second negative lens LN2, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (3), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (3), it is more desirable to set the lower limit of conditional equation (3) to 1.55, 1.60, 1.65, 1.70, 1.75, and further to 1.80. Also, in order to ensure the effect of conditional equation (3), it is more desirable to set the upper limit of conditional equation (3) to 1.87, 1.85, and further to 1.83.

[0020] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (4).

[0021] 20.00 < νdLN2 < 60.00 (4) where νdLN2: Abbe number of the medium of the second negative lens LN2 with respect to the d line

[0022] Conditional equation (4) defines an appropriate range for the Abbe number of the medium of the second negative lens LN2, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (4), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (4), it is more desirable to set the lower limit of conditional equation (4) to 25.00, 30.00, 35.00, and even 40.00. Furthermore, in order to ensure the effect of conditional equation (4), it is more desirable to set the upper limit of conditional equation (4) to 55.00, 50.00, 45.00, and even 43.00.

[0023] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (5).

[0024] 1.40 < ndLN3 < 1.80 (5) where ndLN3: refractive index of the medium of the third negative lens LN3 with respect to the d line

[0025] Conditional equation (5) defines an appropriate range for the refractive index of the medium of the third negative lens LN3, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (5), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (5), it is more desirable to set the lower limit of conditional equation (5) to 1.45, 1.46, 1.48, and further to 1.49. Also, in order to ensure the effect of conditional equation (5), it is more desirable to set the upper limit of conditional equation (5) to 1.75, 1.70, 1.65, 1.60, 1.55, and further to 1.50.

[0026] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (6).

[0027] 50.00 < νdLN3 < 100.00 (6) where νdLN3: Abbe number of the medium of the third negative lens LN3 with respect to the d line

[0028] Conditional equation (6) defines an appropriate range for the Abbe number of the medium of the third negative lens LN3, which is positioned in the front group G1 of the optical system OL, with respect to the d line. By satisfying this conditional equation (6), miniaturization of the optical system OL can be achieved, and various aberrations, especially chromatic aberration, can be corrected well. In order to ensure the effect of this conditional equation (6), it is more desirable to set the lower limit of conditional equation (6) to 55.00, 60.00, 65.00, 70.00, 75.00, and even 80.00. Furthermore, in order to ensure the effect of conditional equation (6), it is more desirable to set the upper limit of conditional equation (6) to 95.00, 90.00, 85.00, and even 83.00.

[0029] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (7).

[0030] 0.000 < ΔPgFLN3 < 0.050 (7) where ΔPgFLN3: anomalous dispersion of the medium of the third negative lens LN3. Here, the anomalous dispersion ΔPgFLN3 is given by ΔPgFLN3 = PgFLN3 - (0.648327 - 0.0018024 × νdLN3). However, PgFLN3 ≡ (ngLN3 - nFLN3) / (nFLN3 - nCLN3): Partial dispersion ratio of the medium of the third negative lens LN3 ngLN3: Refractive index of the medium of the third negative lens LN3 with respect to the g line nFLN3: Refractive index of the medium of the third negative lens LN3 with respect to the F line nCLN3: Refractive index of the medium of the third negative lens LN3 with respect to the C line νdLN3: Abbe number of the medium of the third negative lens LN3 with respect to the d line

[0031] Conditional equation (7) defines an appropriate range for the anomalous dispersion of the medium of the third negative lens LN3, which is positioned in the front group G1 of the optical system OL.

[0032] Here, the anomalous dispersion "ΔPgF" is expressed as the deviation of the partial dispersion ratio "PgF ≡ (ng - nF) / (nF - nC)" from the normal dispersion "PgF = agF + bgF × νd" and is given by the following equation: ΔPgF = PgF - (agF + bgF × νd) Then, substituting the coefficients "agF = 0.648327" and "bgF = -0.0018024" obtained from the normal dispersion reference glass, it is expressed as follows: ΔPgF = PgF - (0.648327 - 0.0018024 × νd) Note that nC, nF, and ng are the refractive indices for the C line (wavelength λ = 656.3 nm), F line (wavelength λ = 486.1 nm), and g line (wavelength λ = 435.8 nm), respectively, and νd is the Abbe number for the d line (wavelength λ = 587.6 nm).

[0033] By satisfying this condition (7), the optical system OL can be miniaturized, and various aberrations, especially the second-order dispersion of chromatic aberration, can be effectively corrected. To ensure the effectiveness of this condition (7), it is more desirable to set the lower limit of condition (7) to 0.010, 0.015, 0.020, 0.025, 0.030, and even more so to 0.035. Furthermore, to ensure the effectiveness of condition (7), it is more desirable to set the upper limit of condition (7) to 0.045, 0.040, and even more so to 0.038.

[0034] Furthermore, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional equation (8).

[0035] 1.50 < ndLP1 < 1.80 (8) where ndLP1: refractive index of the medium of the first positive lens LP1 with respect to the d line

[0036] Conditional equation (8) defines an appropriate range for the refractive index of the medium of the first positive lens LP1 positioned in the front group G1 of the optical system OL with respect to the d line. By satisfying this conditional equation (8), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (8), it is more desirable to set the lower limit of conditional equation (8) to 1.55, 1.60, and further to 1.65. Also, in order to ensure the effect of conditional equation (8), it is more desirable to set the upper limit of conditional equation (8) to 1.75, and further to 1.73.

[0037] Also, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional expression (9).

[0038] 20.00 < νdLP1 < 40.00 (9) Here, νdLP1: Abbe number with respect to the d line of the medium of the first positive lens LP1

[0039] The conditional expression (9) defines an appropriate range of the Abbe number with respect to the d line of the medium of the first positive lens LP1 disposed in the front group G1 of the optical system OL. By satisfying this conditional expression (9), miniaturization of the optical system OL can be realized, and various aberrations, particularly axial chromatic aberration and lateral chromatic aberration, can be corrected well. In order to ensure the effect of this conditional expression (9), it is more desirable that the lower limit value of the conditional expression (9) is 25.00, and further 28.00. Also, in order to ensure the effect of the conditional expression (9), it is more desirable that the upper limit value of the conditional expression (9) is 35.00, 33.00, and further 31.00.

[0040] Also, it is desirable that the optical system OL according to the first embodiment satisfies the following conditional expression (10).

[0041] ndLP1 + 0.019 × νdLP1 < 2.315 (10) Here, ndLP1: Refractive index with respect to the d line of the medium of the first positive lens LP1 νdLP1: Abbe number with respect to the d line of the medium of the first positive lens LP1

[0042] The conditional expression (10) defines an appropriate relationship between the refractive index and the Abbe number with respect to the d line of the medium of the first positive lens LP1 disposed in the front group G1 of the optical system OL. By satisfying this conditional expression (10), miniaturization of the optical system OL can be realized, and various aberrations, particularly axial chromatic aberration and lateral chromatic aberration, can be corrected well.

[0043] (Second Embodiment) The optical system OL according to the second embodiment, as shown in Figure 1, has, in order from the object side, a front group G1, an aperture (aperture diaphragm S), and a rear group G2. The front group G1 has a first negative lens LN1 with a meniscus shape, with its convex surface facing the object side, at the closest point to the object. The rear group G2 has a focusing group Gf that has positive refractive power and moves along the optical axis when focusing. By configuring it in this way, it is possible to provide an optical system OL that is miniaturized, has a wide angle of view, has little distortion, and has sufficient peripheral light.

[0044] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the following conditional expression (11).

[0045] -0.20 < f / f1 < 0.20 (11) where, f: focal length of the entire optical system OL, f1: focal length of the front group G1

[0046] Conditional equation (11) specifies the ratio of the focal length of the entire optical system OL to the focal length of the front group G1. By satisfying this conditional equation (11), miniaturization of the optical system OL can be achieved while obtaining good optical performance. If the value falls below the lower limit of conditional equation (11), it becomes difficult to correct aberrations caused by the front group G1, and attempting to correct them forcibly will result in an enlarged optical system OL, which is undesirable. In order to ensure the effect of this conditional equation (11), it is more desirable to set the lower limit of conditional equation (11) to -0.18, -0.16, and further to -0.15. Also, if the value exceeds the upper limit of conditional equation (11), it becomes difficult to secure back focus. If the refractive power of the negative lens closest to the object in the rear group G2 is increased in an attempt to forcibly secure back focus, the exit pupil will become closer, resulting in poor matching with the oblique incidence characteristics of the image sensor, which is undesirable as it can cause color shading and other problems. Furthermore, in order to ensure the effect of conditional expression (11), it is more desirable to set the upper limit of conditional expression (11) to 0.15, 0.10, 0.050, 0.025, and even 0.00.

[0047] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (1). The effects of satisfying this condition (1) are as described above.

[0048] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (2). The effects of satisfying this condition (2) are as described above.

[0049] Furthermore, in the optical system OL according to the second embodiment, it is desirable that the front group G1 has a second negative lens LN2 that has a negative refractive power on the image plane side of the first negative lens LN1. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0050] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (3). The effects of satisfying this condition (3) are as described above.

[0051] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (4). The effects of satisfying this condition (4) are as described above.

[0052] Furthermore, in the optical system OL according to the second embodiment, it is desirable that the front group G1 includes a second negative lens LN2 having negative refractive power and a third negative lens LN3 having negative refractive power, located on the image plane side of the first negative lens LN1. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0053] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (5). The effects of satisfying this condition (5) are as described above.

[0054] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (6). The effects of satisfying this condition (6) are as described above.

[0055] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (7). The effects of satisfying this condition (7) are as described above.

[0056] Furthermore, in the optical system OL according to the second embodiment, it is desirable that the front group G1 includes a second negative lens LN2 having negative refractive power, a third negative lens LN3 having negative refractive power, and a first positive lens LP1 having positive refractive power, located on the image plane side of the first negative lens LN1. By configuring it in this way, the number of negative meniscus lenses in the front group G1 of the ultra-wide-angle lens can be reduced, achieving miniaturization, and providing an optical system OL with a wide angle of view, low distortion, and sufficient peripheral illumination.

[0057] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (8). The effects of satisfying this condition (8) are as described above.

[0058] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (9). The effects of satisfying this condition (9) are as described above.

[0059] Furthermore, it is desirable that the optical system OL according to the second embodiment satisfies the above-described condition (10). The effects of satisfying this condition (10) are as described above.

[0060] (Regarding the First and Second Embodiments) Furthermore, in the optical system OL according to the first and second embodiments (hereinafter referred to as "these embodiments"), it is desirable that the front group G1 has a fourth negative lens LN4 that constitutes a negative refractive power lens component LCN on the image plane side of the first positive lens LP1. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0061] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (12).

[0062] 1.55 < ndLN4 < 2.00 (12) where ndLN4: refractive index of the medium of the fourth negative lens LN4 with respect to the d line

[0063] Conditional equation (12) defines an appropriate range for the refractive index of the medium of the fourth negative lens LN4 constituting the optical system OL with respect to the d line. By satisfying this conditional equation (12), miniaturization of the optical system OL can be achieved, and various aberrations, especially coma aberration, can be corrected well. In order to ensure the effect of this conditional equation (12), it is more desirable to set the lower limit of conditional equation (12) to 1.60, 1.65, and further to 1.70. Also, in order to ensure the effect of conditional equation (12), it is more desirable to set the upper limit of conditional equation (12) to 1.95, 1.90, and further to 1.80.

[0064] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (13).

[0065] 15.00 < νdLN4 < 35.00 (13) where νdLN4: Abbe number of the medium of the fourth negative lens LN4 with respect to the d line

[0066] Conditional equation (13) defines an appropriate range for the Abbe number of the medium of the fourth negative lens LN4 constituting the optical system OL with respect to the d line. By satisfying this conditional equation (13), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. Furthermore, in order to ensure the effect of this conditional equation (13), it is more desirable to set the lower limit of conditional equation (13) to 20.00, 22.00, and even 25.00. Also, in order to ensure the effect of conditional equation (13), it is more desirable to set the upper limit of conditional equation (13) to 33.00, 30.00, and even 29.00.

[0067] Furthermore, in the optical system OL according to this embodiment, the lens component LCN positioned on the image plane side of the first positive lens LP1 may be a cemented lens consisting of a fourth negative lens LN4 and a positive lens LP2 bonded to the object side of the fourth negative lens LN4. By using a cemented lens, correction of lateral chromatic aberration and axial chromatic aberration becomes easier.

[0068] Furthermore, in the optical system OL according to this embodiment, it is desirable that the front group G1 has a third positive lens LP3 on the image plane side of the fourth negative lens LN4. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0069] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (14).

[0070] 1.60 < ndLP3 < 1.80 (14) where ndLP3: refractive index of the medium of the third positive lens LP3 with respect to the d line

[0071] Conditional equation (14) defines an appropriate range for the refractive index of the medium of the third positive lens LP3 constituting the optical system OL with respect to the d line. By satisfying this conditional equation (14), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (14), it is even more desirable to set the lower limit of conditional equation (14) to 1.65, and further to 1.70. Also, in order to ensure the effect of conditional equation (14), it is even more desirable to set the upper limit of conditional equation (14) to 1.75.

[0072] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional expression (15).

[0073] 25.00 < νdLP3 < 45.00 (15) where νdLN3: Abbe number of the medium of the third positive lens LP3 with respect to the d line

[0074] Conditional equation (15) defines an appropriate range for the Abbe number of the medium of the third positive lens LP3 constituting the optical system OL with respect to the d line. By satisfying this conditional equation (15), miniaturization of the optical system OL can be achieved, and various aberrations, especially axial chromatic aberration, can be well corrected. In order to ensure the effect of this conditional equation (15), it is more desirable to set the lower limit of conditional equation (15) to 30.00, and even more so to 33.00. Furthermore, in order to ensure the effect of conditional equation (15), it is more desirable to set the upper limit of conditional equation (15) to 40.00, and even more so to 35.00.

[0075] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (16).

[0076] 2.315 < ndLP3 + 0.019 × νdLP3 (16) where, ndLP3: refractive index of the medium of the third positive lens LP3 with respect to the d line νdLN3: Abbe number of the medium of the third positive lens LP3 with respect to the d line

[0077] Conditional equation (16) defines the relationship between the refractive index of the medium of the third positive lens LP3 constituting the optical system OL with respect to the d line and the Abbe number. By satisfying this conditional equation (16), the optical system OL can be miniaturized, and various aberrations, especially axial chromatic aberration, can be corrected well.

[0078] Furthermore, in the optical system OL according to this embodiment, it is desirable that the front group G1 has a second cemented lens CL2 formed by bonding a positive lens LP4 and a negative lens LN5 in order from the object side to the image plane side of the third positive lens LP3. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral illumination. In addition, an optical system OL having this configuration can effectively correct axial chromatic aberration.

[0079] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (17).

[0080] 0.000 < ΔPgFLP4 - ΔPgFLN5 < 0.060 (17) where ΔPgFLP4: anomalous dispersion of the medium of the positive lens LP4 constituting the second cemented lens CL2. Here, the anomalous dispersion ΔPgFLP4 is given by ΔPgFLP4 = PgFLP4 - (0.648327 - 0.0018024 × νdLP4). However, PgFLP4 ≡ (ngLP4 - nFLP4) / (nFLP4 - nCLP4): Partial dispersion ratio of the medium of the positive lens LP4 ngLP4: Refractive index of the medium of the positive lens LP4 with respect to the g line nFLP4: Refractive index of the medium of the positive lens LP4 with respect to the F line nCLP4: Refractive index of the medium of the positive lens LP4 with respect to the C line νdLP4: Abbe number of the medium of the positive lens LP4 with respect to the d line ΔPgFLN5: Anomalous dispersion of the medium of the negative lens LN5 constituting the second cemented lens CL2 Here, the anomalous dispersion ΔPgFLN5 is given by ΔPgFLN5 = PgFLN5 - (0.648327 - 0.0018024 × νdLN5). However, PgFLN5 ≡ (ngLN5 - nFLN5) / (nFLN5 - nCLN5): Partial dispersion ratio of the medium of the negative lens LN5 ngLN5: Refractive index of the medium of the negative lens LN5 with respect to the g line nFLN5: Refractive index of the medium of the negative lens LN5 with respect to the F line nCLN5: Refractive index of the medium of the negative lens LN5 with respect to the C line νdLN5: Abbe number of the medium of the negative lens LN5 with respect to the d line

[0081] Conditional equation (17) defines the difference between the anomalous dispersion of the medium of the positive lens LP4 constituting the second cemented lens CL2 and the anomalous dispersion of the medium of the negative lens LN5. By satisfying this conditional equation (17), miniaturization of the optical system OL can be achieved, and various aberrations, especially the second-order dispersion of chromatic aberration, can be well corrected. In order to ensure the effect of this conditional equation (17), it is more desirable to set the lower limit of conditional equation (17) to 0.005, 0.010, 0.015, and even more preferably to 0.018. Furthermore, in order to ensure the effect of conditional equation (17), it is more desirable to set the upper limit of conditional equation (17) to 0.050, 0.040, 0.030, and even more preferably to 0.020.

[0082] Furthermore, in the optical system OL according to this embodiment, it is desirable that the focusing group Gf has at least one positive lens Lpf and at least one negative lens Lnf. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral illumination.

[0083] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional expression (18).

[0084] 0.10 < f / f2 < 0.50 (18) where, f: focal length of the entire optical system OL, f2: focal length of the rear group G2 when an object at infinity is in focus.

[0085] Conditional equation (18) defines the ratio of the focal length of the entire optical system OL to the focal length of the rear group G2. By satisfying this conditional equation (18), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (18), it is more desirable to set the lower limit of conditional equation (18) to 0.15, 0.20, 0.25, 0.30, and even 0.34. Also, in order to ensure the effect of conditional equation (18), it is more desirable to set the upper limit of conditional equation (18) to 0.45, 0.40, 0.38, and even 0.36.

[0086] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (19).

[0087] 1.20 < ff / f2 < 2.00 (19) where, ff: focal length of the focusing group Gf, f2: focal length of the rear group G2 when an object at infinity is in focus.

[0088] Conditional equation (19) defines the ratio of the focal length of the focusing group Gf to the focal length of the rear group G2. If the value falls below the lower limit of conditional equation (19), the refractive power of the focusing group Gf becomes too strong, which is undesirable because it increases the influence of positioning errors in the optical axis direction and aberration fluctuations during eccentricity. To ensure the effectiveness of conditional equation (19), it is more desirable to set the lower limit of conditional equation (19) to 1.30, and even more so to 1.35. Conversely, if the value exceeds the upper limit of conditional equation (19), the refractive power of the focusing group Gf becomes too weak, requiring a long focus interval (the distance between the front and rear of the focusing group Gf when in focus), which is undesirable because it prevents miniaturization of the rear group G2. To ensure the effectiveness of conditional equation (19), it is more desirable to set the upper limit of conditional equation (19) to 1.90, 1.80, and even more so to 1.70.

[0089] Furthermore, in the optical system OL according to this embodiment, it is desirable that the rear group G2 has a third cemented lens CL3 formed by joining a meniscus-shaped negative lens LN21 with a convex surface facing the object side and a positive lens LP21. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0090] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (20).

[0091] 1.70 < ndLN21 (20) where ndLN21: refractive index of the medium of the negative lens LN21 constituting the third cemented lens CL3 with respect to the d line

[0092] Conditional equation (20) defines an appropriate range for the refractive index of the medium of the negative lens LN21, which constitutes the third cemented lens CL3 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (20), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (20), it is more desirable to set the lower limit of conditional equation (20) to 1.75, 1.80, 1.85, 1.90, 1.95, and even 2.00.

[0093] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional expression (21).

[0094] 0.000 < ΔPgFLP21 (21) where ΔPgFLP21: anomalous dispersion of the medium of the positive lens LP21 constituting the third cemented lens CL3. Here, the anomalous dispersion ΔPgFLP21 is given by ΔPgFLP21 = PgFLP21 - (0.648327 - 0.0018024 × νdLP21). However, PgFLP21 ≡ (ngLP21 - nFLP21) / (nFLP21 - nCLP21): Partial dispersion ratio of the medium of the positive lens LP21 ngLP21: Refractive index of the medium of the positive lens LP21 with respect to the g line nFLP21: Refractive index of the medium of the positive lens LP21 with respect to the F line nCLP21: Refractive index of the medium of the positive lens LP21 with respect to the C line νdLP21: Abbe number of the medium of the positive lens LP21 with respect to the d line

[0095] Conditional equation (21) defines an appropriate range for the anomalous dispersion of the medium of the positive lens LP21 that constitutes the third cemented lens CL3 located in the rear group G2 of the optical system OL. By satisfying this conditional equation (21), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (21), it is more desirable to set the lower limit of conditional equation (21) to 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, and even more so to 0.035.

[0096] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (22).

[0097] 1.40 < ndLP21 < 1.70 (22) where, ndLP21: refractive index of the medium of the positive lens LP21 constituting the third cemented lens CL3 with respect to the d line

[0098] Conditional equation (22) defines an appropriate range for the refractive index of the medium of the positive lens LP21, which constitutes the third cemented lens CL3 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (22), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (22), it is more desirable to set the lower limit of conditional equation (22) to 1.45, 1.47, and further to 1.49. Also, in order to ensure the effect of this conditional equation (22), it is more desirable to set the upper limit of conditional equation (22) to 1.65, 1.60, 1.55, and further to 1.50.

[0099] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (23).

[0100] 50.00 < νdLP21 < 100.00 (23) where, νdLP21: Abbe number of the medium of the positive lens LP21 constituting the third cemented lens CL3 with respect to the d line

[0101] Conditional equation (23) defines an appropriate range for the Abbe number of the medium of the positive lens LP21, which constitutes the third cemented lens CL3 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (23), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (23), it is more desirable to set the lower limit of conditional equation (23) to 55.00, 60.00, 65.00, 70.00, 75.00, and even 80.00. Furthermore, in order to ensure the effect of this conditional equation (23), it is more desirable to set the upper limit of conditional equation (23) to 95.00, 90.00, 85.00, and even 82.00.

[0102] Furthermore, in the optical system OL according to this embodiment, it is desirable that the rear group G2 has a fourth cemented lens CL4 formed by joining a meniscus-shaped positive lens LP22 and a negative lens LN22, with the convex surface facing the image plane. By configuring it in this way, it is possible to achieve miniaturization and provide an optical system OL with a wide angle of view, low distortion, and sufficient peripheral illumination.

[0103] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (24).

[0104] 1.70 < ndLN22 (24) where ndLN22: refractive index of the medium of the negative lens L22 constituting the fourth cemented lens CL4 with respect to the d line

[0105] Conditional equation (24) defines an appropriate range for the refractive index of the medium of the negative lens LN22, which constitutes the fourth cemented lens CL4 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (24), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (24), it is more desirable to set the lower limit of conditional equation (24) to 1.75, 1.80, 1.85, 1.90, 1.95, and even 2.00.

[0106] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (25).

[0107] 0.000 < ΔPgFLP22 (25) where ΔPgFLP22: anomalous dispersion of the medium of the positive lens LP22 constituting the fourth cemented lens CL4. Here, the anomalous dispersion ΔPgFLP22 is given by ΔPgFLP22 = PgFLP22 - (0.648327 - 0.0018024 × νdLP22). However, PgFLP22 ≡ (ngLP22 - nFLP22) / (nFLP22 - nCLP22): Partial dispersion ratio of the medium of the positive lens LP22 ngLP22: Refractive index of the medium of the positive lens LP22 with respect to the g line nFLP22: Refractive index of the medium of the positive lens LP22 with respect to the F line nCLP22: Refractive index of the medium of the positive lens LP22 with respect to the C line νdLP22: Abbe number of the medium of the positive lens LP22 with respect to the d line

[0108] Conditional equation (25) defines an appropriate range for the anomalous dispersion of the medium of the positive lens LP22 that constitutes the fourth cemented lens CL4 located in the rear group G2 of the optical system OL. By satisfying this conditional equation (25), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. Furthermore, in order to ensure the effect of this conditional equation (25), it is more desirable to set the lower limit of conditional equation (25) to 0.005, 0.010, 0.015, 0.020, 0.025, 0.030, and even more so to 0.035.

[0109] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (26).

[0110] 1.70 < ndLP22 (26) where ndLP22: refractive index of the medium of the positive lens LP22 constituting the fourth cemented lens CL4 with respect to the d line

[0111] Conditional equation (26) defines an appropriate range for the refractive index of the medium of the positive lens LP22, which constitutes the fourth cemented lens CL4 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (26), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. Furthermore, in order to ensure the effect of this conditional equation (26), it is more desirable to set the lower limit of conditional equation (26) to 1.75, 1.80, 1.85, 1.90, and even 1.94.

[0112] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (27).

[0113] 15.00 < νdLP22 < 30.00 (27) where, νdLP22: Abbe number of the medium of the positive lens LP22 constituting the fourth cemented lens CL4 with respect to the d line

[0114] Conditional equation (27) defines an appropriate range for the Abbe number of the medium of the positive lens LP22, which constitutes the fourth cemented lens CL4 located in the rear group G2 of the optical system OL, with respect to the d line. By satisfying this conditional equation (27), miniaturization of the optical system OL can be achieved, and good optical performance can be obtained. In order to ensure the effect of this conditional equation (27), it is more desirable to set the lower limit of conditional equation (27) to 16.00, and further to 17.00. Also, in order to ensure the effect of this conditional equation (27), it is more desirable to set the upper limit of conditional equation (27) to 25.00, 20.00, and further to 18.00.

[0115] Furthermore, in the optical system OL according to this embodiment, it is desirable that the focusing group Gf is positioned between the third cemented lens CL3 and the fourth cemented lens CL4. By configuring it in this way, it is possible to achieve miniaturization while providing an optical system OL with a wide angle of view, low distortion, and sufficient peripheral light.

[0116] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (28).

[0117] 45.00° < ω < 70.00° (28) where ω: half-angle of view of the optical system OL

[0118] Conditional equation (28) defines an appropriate range for the half-angle of view of the optical system OL. By satisfying this conditional equation (28), miniaturization of the optical system OL can be achieved while obtaining good optical performance. If the value falls below the lower limit of conditional equation (28), the lens configuration becomes excessive for the specifications required for the optical system OL, making miniaturization of the optical system OL difficult and therefore undesirable. Furthermore, in order to ensure the effect of conditional equation (28), it is more desirable to set the lower limit of conditional equation (28) to 50.00°, 52.00°, 54.00°, 56.00°, and even 57.00°. On the other hand, if the value exceeds the upper limit of conditional equation (28), the load on the negative lenses constituting the front group G1 increases, making it difficult to correct distortion and field curvature, which is also undesirable. Furthermore, in order to ensure the effectiveness of conditional equation (28), it is more desirable to set the upper limit of conditional equation (28) to 65.00°, 64.00°, 62.00°, 60.00°, 59.00°, and even 58.00°.

[0119] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (29).

[0120] 1.00 < Fno < 2.90 (29) where Fno: F number of the optical system OL

[0121] Conditional equation (29) defines an appropriate range for the F-number of the optical system OL. If the F-number falls below the lower limit of conditional equation (29), the optical system OL becomes larger, and forcibly miniaturizing it deteriorates the optical performance, which is undesirable. To ensure the effectiveness of conditional equation (29), it is more desirable to set the lower limit of conditional equation (29) to 1.10, 1.20, 1.30, 1.40, and further to 1.43. Conversely, if the F-number falls above the upper limit of conditional equation (29), the lens configuration becomes excessively large for the specifications required for the optical system OL, making it difficult to miniaturize the optical system OL, which is undesirable. To ensure the effectiveness of conditional equation (29), it is more desirable to set the upper limit of conditional equation (29) to 2.80, 2.50, 2.10, 2.00, 1.90, 1.80, and further to 1.50.

[0122] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (30).

[0123] -0.10 < D < 0.00 (30) where D: distortion at the outermost edge

[0124] Conditional equation (30) defines an appropriate range for the amount of distortion aberration of the optical system OL. Here, the amount of distortion aberration at the outermost edge is the amount of distortion aberration at the maximum image height Ymax, and if Ymax is the actual image height and Ymax' is the ideal image height, it is expressed as D = (Ymax - Ymax') / Ymax'. By satisfying conditional equation (30), it is possible to achieve miniaturization of the optical system OL, and to provide an optical system OL with a wide angle of view, good distortion correction, and sufficient peripheral illumination. If the value falls below the lower limit of conditional equation (30), electronic distortion aberration correction becomes necessary, which is undesirable because it stretches point images when photographing stars, impairing image quality. Furthermore, in order to ensure the effect of conditional equation (30), it is more desirable to set the lower limit of conditional equation (30) to -0.08, -0.06, -0.05, and even -0.45. Furthermore, exceeding the upper limit of conditional equation (30) is undesirable because it becomes difficult to secure sufficient ambient light. In order to ensure the effectiveness of conditional equation (30), it is more desirable to set the upper limit of conditional equation (30) to -0.005, -0.01, -0.02, -0.03, and even -0.035.

[0125] Furthermore, it is desirable that the optical system OL according to this embodiment satisfies the following conditional equation (31).

[0126] 0.50 < BFa / Ymax < 2.00 (31) where, BFa: back focus (air equivalent length) of the optical system OL, Ymax: maximum image height of the optical system OL

[0127] Conditional equation (31) defines the ratio of the back focus to the maximum image height of the optical system OL. By satisfying conditional equation (31), it is possible to achieve miniaturization of the optical system OL while providing an optical system OL with a wide angle of view, low distortion, and sufficient peripheral illumination. If the value falls below the lower limit of conditional equation (31), the optical system OL may physically interfere with the camera body, or it may become difficult to install an optical filter near the lens mount, impairing the functionality of the optical system OL, which is undesirable. Furthermore, in order to ensure the effect of conditional equation (31), it is more desirable to set the lower limit of conditional equation (31) to 0.55, 0.60, 0.65, 0.70, and even 0.75. On the other hand, if the value exceeds the upper limit of conditional equation (31), it becomes necessary to strengthen the power arrangement of the negative lens of the front group G1 in order to secure the back focus, which increases the size of the optical system OL, and is therefore undesirable. Also, forcibly miniaturizing the system will degrade the optical performance, which is undesirable. Furthermore, in order to ensure the effect of conditional equation (31), it is more desirable to set the upper limit of conditional equation (31) to 1.80, 1.60, 1.50, 1.30, 1.00, 0.90, and even 0.80.

[0128] Furthermore, the conditions and configurations described above each produce the effects mentioned above, and it is not limited to those that satisfy all of them. It is possible to obtain the effects described above by satisfying any one of the conditions or configurations, or any combination of any of the conditions or configurations.

[0129] Next, a camera, which is an optical device equipped with the optical system OL according to this embodiment, will be described with reference to Figure 13. This camera 1 is a so-called mirrorless camera with interchangeable lenses, equipped with the optical system OL according to this embodiment as the photographic lens 2. In this camera 1, light from an object (subject) not shown is focused by the photographic lens 2 and forms an image of the subject on the imaging surface of the imaging unit 3 via an OLPF (Optical low pass filter) not shown. Then, the image of the subject is photoelectrically converted by a photoelectric conversion element (image sensor) provided in the imaging unit 3 to generate an image of the subject. This image is displayed in an EVF (Electronic viewfinder) 4 provided in the camera 1. This allows the photographer to observe the subject through the EVF 4.

[0130] Furthermore, when the photographer presses a release button (not shown), the image converted photoelectrically by the imaging unit 3 is stored in a memory (not shown). In this way, the photographer can take a photograph of a subject with the camera 1. Although this embodiment describes an example of a mirrorless camera, the same effects as the camera 1 can be achieved even if the optical system OL according to this embodiment is mounted on a single-lens reflex type camera that has a quick-return mirror in the camera body and observes the subject with a viewfinder optical system.

[0131] The following points may be adopted as appropriate, provided they do not impair optical performance.

[0132] In this embodiment, an optical system OL consisting of two lens groups, front group G1 and rear group G2, is shown. However, the above configuration and conditions can be applied to other group configurations such as three-group or four-group systems. Furthermore, a configuration in which a lens or lens group is added closest to the object, or a configuration in which a lens or lens group is added closest to the image plane, is also acceptable. Specifically, a configuration in which a lens group whose position relative to the image plane is fixed when focusing or changing magnification is considered can be added closest to the image plane. In addition, unless a boundary is specifically specified, a lens group refers to a portion having at least one lens, separated by an air gap that changes when focusing or changing magnification. In addition, a lens component refers to a single lens or a cemented lens formed by joining multiple lenses.

[0133] Furthermore, a focusing group may be formed by moving a single or multiple lens groups, or a partial lens group, along the optical axis to focus from an object at infinity to an object at close range. In this case, the focusing group can also be applied to autofocus and is suitable for motor drive (such as an ultrasonic motor) for autofocus. In particular, it is preferable to make at least a part of the rear group G2 the focusing group, and to fix the position of the other lenses relative to the image plane when focusing. Considering the load on the motor, it is preferable that the focusing group is composed of a single lens or one lens component.

[0134] Alternatively, a vibration-damping group may be used to correct image blur caused by camera shake by moving the lens group or partial lens group so that it has a displacement component perpendicular to the optical axis, or by rotating (oscillating) it in an in-plane direction including the optical axis.

[0135] Furthermore, the lens surface may be formed as a sphere, a plane, or an aspherical surface. A spherical or plane lens surface is preferable because it facilitates lens processing and assembly adjustment, and prevents deterioration of optical performance due to processing and assembly adjustment errors. It is also preferable because the deterioration of image quality is minimal even if the image plane is misaligned. If the lens surface is aspherical, it may be an aspherical surface formed by grinding, a glass molded aspherical surface formed from glass using a mold, or a composite aspherical surface formed by forming resin in an aspherical shape on the surface of glass. The lens surface may also be a diffractive surface, and the lens may be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0136] The aperture diaphragm S is preferably positioned between the front group G1 and the rear group G2, but its function may be substituted by the lens frame instead of providing a separate aperture diaphragm component.

[0137] Furthermore, each lens surface may be coated with an anti-reflective coating that has high transmittance over a wide wavelength range in order to reduce flare and ghosting and achieve high contrast optical performance.

[0138] The general method for manufacturing the optical system OL according to this embodiment will be described below with reference to Figure 14.

[0139] The manufacturing method for the optical system OL according to the first embodiment is as shown in Figure 14(a). First, a front lens group G1, an aperture (aperture diaphragm S), and a rear lens group G2 are prepared in order from the object side (step S100). Next, in the front lens group G1, starting from the object side, a first negative lens LN1 with a meniscus shape and a convex surface facing the object, a second negative lens LN2 with a meniscus shape and a convex surface facing the object, and a first cemented lens CL1 consisting of a third negative lens LN3 having negative refractive power and a first positive lens LP1 having positive refractive power are arranged (step S110). Furthermore, a focusing group Gf that moves along the optical axis when focusing is arranged in the rear lens group G2 (step S120). These lens groups are then arranged to satisfy a predetermined condition (for example, the condition (1) described above) (step S130).

[0140] The manufacturing method for the optical system OL according to the second embodiment is as shown in Figure 14(b). First, a front lens group G1, an aperture (aperture diaphragm S), and a rear lens group G2 are prepared in that order from the object side (step S200). Next, a meniscus-shaped first negative lens LN1 with its convex surface facing the object side is placed on the front lens group G1 (step S210). The rear lens group G2 is then arranged to have a positive refractive power (step S220), and a focusing group Gf that moves along the optical axis when focusing is placed on the rear lens group G2 (step S230). These lens groups are then arranged to satisfy a predetermined condition (for example, the condition (11) described above) (step S240).

[0141] Based on the above, it is possible to provide an optical system, optical instrument, and method for manufacturing an optical system that achieve miniaturization, have an ultra-wide angle, yet exhibit minimal coma aberration even at the edges, a flat image plane, minimal distortion, and sufficient peripheral light.

[0142] The following describes each embodiment based on the drawings. Figures 1, 3, 5, 7, 9, and 11 are cross-sectional views showing the configuration and refractive index distribution of the optical system OL (OL1 to OL6) according to each embodiment.

[0143] In each embodiment, for the aspherical surface, the height in the direction perpendicular to the optical axis is y, the distance along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface (sag amount) is S(y), the radius of curvature of the reference spherical surface (paraxial radius of curvature) is r, the conic constant is K, and the aspherical coefficient of the nth order is An. When this is the case, it is represented by the following formula (a).

[0144] S(y) = (y 2 / r) / {1 + (1 - K × y 2 / r 2 ) 1 / 2} + A4 × y 4 + A6 × y 6 + A8 × y 8 + A10 × y 10 + A12 × y 12 + A14 × y 14 + A16 × y 16 + A18 × y 18 + A20 × y 20 (a)

[0145] Note that in each embodiment, the second-order aspherical coefficient A2 is 0. Also, in the table of each embodiment, an asterisk is attached to the right of the surface number for the aspherical surface. Further, in each embodiment, "E-n" indicates "×10 -n ".

[0146] [First Embodiment] FIG. 1 is a diagram showing the configuration of an optical system OL1 according to the first embodiment. This optical system OL1 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture stop S, and a rear group G2 having a positive refractive power.

[0147] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); and an object The lens component LCN is a bonded negative lens formed by joining a meniscus-shaped positive lens L15 (LP2) with its concave surface facing the body side and a meniscus-shaped negative lens L16 (LN4) with its concave surface facing the object side; a biconvex positive lens L17 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L18 (LP4) with its concave surface facing the object side and a meniscus-shaped negative lens L19 (LN5) with its concave surface facing the object side.

[0148] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a biconcave negative lens L28 with an aspherical shape whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0149] Furthermore, a filter group FL is positioned between the optical system OL1 and the image plane I.

[0150] Furthermore, the optical system OL1 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and the negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0151] Table 1 below lists the specifications of the optical system OL1. In Table 1, f in the overall specifications is the focal length of the entire system, FNO is the F number, ω is the half-angle of view [°], Ymax is the maximum image height, TL is the total optical length, and BF is the back focus, which represents the value when focused at infinity. Here, the back focus BF represents the air-equivalent length of the distance along the optical axis from the lens surface closest to the image plane (30th surface) of the optical system OL to the image plane I. The total optical length TL represents the distance along the optical axis from the lens surface closest to the object (1st surface) of the optical system OL to the lens surface closest to the image plane (30th surface) plus the air-equivalent length of the back focus. Furthermore, in the lens data, the first column m indicates the order (surface number) of the lens surfaces from the object side along the direction of light propagation, the second column r indicates the radius of curvature of each lens surface, the third column d indicates the distance along the optical axis from one optical surface to the next (interplanar spacing), and the fourth column nd and fifth column νd indicate the refractive index and Abbe number for the d line (λ = 587.6 nm). Also, the radius of curvature ∞ indicates a plane, and the refractive index of air of 1.00000 is omitted. In addition, the lens group focal length indicates the starting surface number and focal length of the front group G1, rear group G2, and focusing group Gf.

[0152] Here, the units of focal length f, radius of curvature r, interplanar spacing d, and other lengths listed in all the following specifications are generally "mm," but this is not limited to this, as optical systems can achieve equivalent optical performance even when proportionally enlarged or reduced. Furthermore, the explanations of these symbols and the specifications table are the same in subsequent examples.

[0153] (Table 1) First Example [Overall Specifications] f = 14.392 FNO = 1.456 ω = 57.516 Ymax = 21.700 TL (Air Equivalent Length) = 145.4230 BF (Air Equivalent Length) = 17.0549 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 62.9773 2.0000 1.69343 53.30 2* 16.9520 17.2081 3* 41.1404 2.3384 1.80835 40.55 4* 24.7617 10.4093 5 -69.7981 1.8399 1.49710 81.56 6 23.2498 12.4500 1.69895 30.05 7 -74.5443 2.6118 8 -35.0736 12.2277 1.68430 26.81 9 -20.4337 1.8193 1.75211 25.05 10 -75.6021 0.1000 11 53.3290 7.5196 1.72047 34.71 12 -60.7323 3.7954 13 -84.2913 6.9575 1.55397 71.76 14 -23.2068 1.8000 1.73800 32.33 15 -210.4002 1.0000 16 ∞ 0.5000 Aperture diaphragm S 17 24.7306 2.0000 2.00100 29.12 18 18.1894 9.4557 1.49710 81.56 19 157.4890 d1 20 65.2936 6.8028 1.49710 81.56 21 -34.5623 1.0000 22* 147.2611 3.0001 1.85135 40.10 23* 81.5475 d2 24 190.4240 6.0916 1.49710 81.56 25 -31.8161 0.1000 26 -43.7124 4.8426 1.94594 17.98 27 -21.7108 1.8000 2.00330 28.27 28 -113.6655 1.5831 29* 102.2197 2.5000 1.80610 40.73 30* 55.0755 15.9000 31 ∞ 1.6000 1.51680 64.13 32 ∞ 0.1000 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -226.409 Rear group G2 17 40.428 Focusing group Gf 20 56.957.

[0154] In this optical system OL1, the first, second, third, fourth, 22nd, 23rd, 29th, and 30th surfaces are formed in an aspherical shape. Table 2 below shows the data for the aspherical surfaces, i.e., the cone constant K and the values ​​of each aspherical constant A4 to A20.

[0155] (Table 2) [Aspherical Data] 1st Face K = -6.2272 A4 = 3.5118E-06 A6 = -6.3466E-09 A8 = 9.7085E-12 A10 = -7.2573E-16 A12 = -1.6075E-17 A14 = 2.4400E-20 A16 = -1.7749E-23 A18 = 6.7356E-27 A20 = -1.0613E-30 2nd Face K = 0.3474 A4 = -5.5383E-06 A6 = -2.8130E-08 A8 = 1.3964E-10 A10=-1.0335E-12 A12= 4.2508E-15 A14=-1.0266E-17 A16= 1.4832E-20 A18=-1.1981E-23 A20= 4.1753E-27 3rd side K=-13.1134 A4 =-2.7487E-05 A6 = 1.1771E-07 A8 =-1.6462E-10 A10= 7.9498E-14 A12= 7.5381E-18 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 0.7340 A4 =-4.4942E-05 A6 = 2.4308E-07 A8 =-4.3485E-10 A10= 7.8544E-13 A12=-1.5307E-16 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 22nd page K= 1.0000 A4 =-7.2146E-05 A6 =-2.0664E-07 A8 = 2.1132E-09 A10=-1.2889E-11 A12= 5.8909E-14 A14=-1.4865E-16 A16= 1.5334E-19 A18= 0.0000E+00 A20= 0.0000E+00 23rd side K= 1.0000 A4 =-6.9186E-05 A6 =-1.9590E-07 A8 = 2.3802E-09 A10=-1.2380E-11 A12= 4.2569E-14 A14=-8.5550E-17 A16= 7.4344E-20 A18= 0.0000E+00 A20= 0.0000E+00 29th page K= 1.0000 A4 =-5.6641E-06 A6 =-3.8165E-07 A8 = 1.1873E-09 A10=-1.2893E-12 A12= 1.0380E-14 A14=-6.3838E-17 A16= 9.7584E-20 A18= 0.0000E+00 A20= 0.0000E+00 30th side K= 1.0000 A4 = 9.6732E-06 A6 = -3.5270E-07 A8 = 1.0021E-09 A10 = 3.2339E-12 A12 = -2.5078E-14 A14 = 5.3214E-17 A16 = -3.8626E-20 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0156] Furthermore, in this optical system OL1, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 3 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object. Note that d0 indicates the distance from the lens surface (first surface) closest to the object in the optical system OL1 to the object, f indicates the focal length, and β indicates the magnification. This explanation is the same in subsequent embodiments.

[0157] (Table 3) [Variable interval data] Focused object infinite distance f 14.392 - β - -0.080 d0 ∞ 160.9968 d1 3.0806 1.7955 d2 1.5346 2.8197

[0158] Figure 2 shows the spherical aberration diagram, astigmatism diagram, distortion diagram, chromatic aberration diagram, and coma aberration diagram for the optical system OL1 when focused on an object at infinity and when focused on an object at close range. In each aberration diagram, FNO indicates the F number, NA indicates the numerical aperture, and Y indicates the image height. Note that the spherical aberration diagram shows the F number or numerical aperture value corresponding to the maximum aperture, the astigmatism and distortion diagrams show the maximum image height, and the coma aberration diagrams show the values ​​of each image height. d indicates the d line (λ = 587.6 nm), g indicates the g line (λ = 435.8 nm), F indicates the F line (λ = 486.1 nm), and C indicates the C line (λ = 656.3 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. The same reference numerals as in this embodiment are used in the aberration diagrams of each embodiment shown below. These aberration diagrams show that the optical system OL1 has good aberration correction and excellent imaging performance.

[0159] [Second Embodiment] Figure 3 shows the configuration of the optical system OL2 according to the second embodiment. This optical system OL2 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture diaphragm S, and a rear group G2 having a positive refractive power.

[0160] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); and an object The lens component LCN is a bonded negative lens formed by joining a meniscus-shaped positive lens L15 (LP2) with its concave surface facing the body side and a meniscus-shaped negative lens L16 (LN4) with its concave surface facing the object side; a biconvex positive lens L17 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L18 (LP4) with its concave surface facing the object side and a meniscus-shaped negative lens L19 (LN5) with its concave surface facing the object side.

[0161] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a meniscus-shaped positive lens L28 with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0162] Furthermore, a filter group FL is positioned between the optical system OL2 and the image plane I.

[0163] Furthermore, the optical system OL2 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and the negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0164] Table 4 below lists the specifications of the optical system OL2. Note that the 11th plane represents the ray determination plane.

[0165] (Table 4) Second Example [Overall Specifications] f = 14.420 FNO = 1.461 ω = 57.465 Ymax = 21.700 TL (Air Equivalent Length) = 145.4549 BF (Air Equivalent Length) = 17.0549 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 61.7500 2.0000 1.69343 53.30 2* 17.8991 17.1499 3* 45.1107 2.0204 1.80835 40.55 4* 24.0053 11.4268 5 -63.1475 1.8787 1.49710 81.56 6 23.2498 13.0463 1.69895 30.05 7 -71.4113 3.4573 8 -33.6380 9.9438 1.68430 26.81 9 -19.3614 1.8001 1.75211 25.05 10 -67.4926 -1.5000 11 ∞ 1.6000 12 58.2417 7.6659 1.72047 34.71 13 -52.2751 2.2030 14 -68.1735 6.6078 1.55397 71.76 15 -23.7369 1.8000 1.73800 32.33 16 -178.2193 1.0000 17 ∞ 2.8905 Aperture diaphragm S 18 24.9540 1.9999 2.00100 29.12 19 18.6263 10.5755 1.49710 81.56 20 929.8933 d1 21 78.5260 6.4461 1.49710 81.56 22 -38.7050 1.0000 23* 94.2783 2.7500 1.85135 40.10 24* 59.7858 d2 25 168.0630 5.9088 1.49710 81.56 26 -32.5862 0.1000 27 -41.5657 4.7118 1.94594 17.98 28 -21.4658 2.0963 2.00330 28.27 29 -291.6802 2.5117 30* 371.0296 2.5000 1.80610 40.73 31* 630.9520 15.9000 32 ∞ 1.6000 1.51680 64.13 33 ∞ 0.1000 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -171.802 Rear group G2 18 41.472 Focusing group Gf 21 69.279.

[0166] In this optical system OL2, the first, second, third, fourth, 23rd, 24th, 30th, and 31st surfaces are formed in an aspherical shape. Table 5 below shows the data for the aspherical surfaces, i.e., the cone constant K and the values ​​of each aspherical constant A4 to A20.

[0167] (Table 5) [Aspherical Data] 1st Face K = -6.0537 A4 = 3.9542E-06 A6 = -6.9129E-09 A8 = 9.7402E-12 A10 = -6.1534E-16 A12 = -1.6030E-17 A14 = 2.4377E-20 A16 = -1.7725E-23 A18 = 6.7866E-27 A20 = -1.1080E-30 2nd Face K = 0.2002 A4 = -1.3079E-06 A6 = -1.9773E-08 A8 = 7.1800E-11 A10=-5.0695E-13 A12= 1.8930E-15 A14=-3.8570E-18 A16= 4.3630E-21 A18=-2.3949E-24 A20= 4.1807E-28 3rd side K=-24.9050 A4 =-1.6173E-05 A6 = 7.4600E-08 A8 =-9.6883E-11 A10= 3.8955E-14 A12= 3.9425E-18 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 0.9209 A4 =-4.3519E-05 A6 = 2.8023E-07 A8 =-8.5495E-10 A10= 2.3933E-12 A12=-2.4987E-15 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 Page 23 K= 1.0000 A4 =-7.0711E-05 A6 =-2.3439E-07 A8 = 2.4535E-09 A10=-1.5219E-11 A12= 7.1221E-14 A14=-1.8588E-16 A16= 1.9829E-19 A18= 0.0000E+00 A20= 0.0000E+00 24th side K= 1.0000 A4 =-6.9597E-05 A6 =-2.2260E-07 A8 = 2.5710E-09 A10=-1.3236E-11 A12= 4.6815E-14 A14=-9.8166E-17 A16 = 8.8542E-20 A18 = 0.0000E+00 A20 = 0.0000E+00 30th side K = 1.0000 A4 = 1.7703E-05 A6 = -2.8749E-07 A8 =-6.1335E-10 A10= 8.4409E-12 A12=-2.5304E-14 A14= 3.9994E-17 A16=-5.0835E-20 A18= 0.0000E+00 A20= 0.0000E+00 31st side K= 1.0000 A4 = 3.2654E-05 A6 = -2.3578E-07 A8 = -9.9739E-10 A10 = 1.2508E-11 A12 = -4.4646E-14 A14 = 7.3781E-17 A16 = -5.1364E-20 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0168] Furthermore, in this optical system OL2, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 6 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object.

[0169] (Table 6) [Variable interval data] Focused object infinity near distance f 14.420 - β - -0.084 d0 ∞ 152.0000 d1 3.0094 1.6127 d2 1.8001 3.1967

[0170] Figure 4 shows the spherical aberration, astigmatism, distortion, chromatic aberration, and coma aberration diagrams for the optical system OL2 when focused on an object at infinity and when focused on an object at close range. From these aberration diagrams, it can be seen that the optical system OL2 has good correction for various aberrations and possesses excellent imaging performance.

[0171] [Third Embodiment] Figure 5 shows the configuration of the optical system OL3 according to the third embodiment. This optical system OL3 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture diaphragm S, and a rear group G2 having a positive refractive power.

[0172] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); and an object The lens component LCN is a bonded negative lens formed by joining a meniscus-shaped positive lens L15 (LP2) with its concave surface facing the body side and a meniscus-shaped negative lens L16 (LN4) with its concave surface facing the object side; a biconvex positive lens L17 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L18 (LP4) with its concave surface facing the object side and a meniscus-shaped negative lens L19 (LN5) with its concave surface facing the object side.

[0173] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a meniscus-shaped positive lens L28 with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0174] Furthermore, a filter group FL is positioned between the optical system OL3 and the image plane I.

[0175] Furthermore, the optical system OL3 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and the negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0176] Table 7 below lists the specifications of the optical system OL3. Note that the 11th plane represents the ray determination plane.

[0177] (Table 7) Third Example [Overall Specifications] f = 14.420 FNO = 1.466 ω = 57.465 Ymax = 21.700 TL (Air Equivalent Length) = 145.4542 BF (Air Equivalent Length) = 17.0550 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 61.8866 2.0000 1.67798 54.89 2* 17.8512 17.1225 3* 43.2426 2.2458 1.80835 40.55 4* 23.1261 11.4263 5 -61.9512 2.1017 1.49710 81.56 6 23.2498 13.0172 1.69895 30.13 7 -74.1654 3.5391 8 -33.3201 8.9450 1.71736 29.52 9 -18.6973 1.8356 1.76182 26.58 10 -65.7460 -1.5000 11 ∞ 1.6000 12 58.1825 7.7940 1.72047 34.71 13 -52.1655 2.4978 14 -63.9744 6.6388 1.55397 71.76 15 -23.3273 1.8001 1.73800 32.33 16 -157.2855 1.0026 17 ∞ 2.7974 Aperture diaphragm S 18 24.8646 2.0001 2.00100 29.12 19 18.6101 10.6829 1.49710 81.56 20 533.7779 2.9848 21 75.9398 6.3236 1.49710 81.56 22 -38.4551 1.0000 23* 92.8598 2.7452 1.85135 40.10 24* 59.6236 1.8000 25 188.4857 6.0174 1.49710 81.56 26 -32.0938 0.1000 27 -40.0525 4.8950 1.94594 17.98 28 -21.0681 1.9939 2.00330 28.27 29 -225.2475 2.4925 30* 374.6876 2.4999 1.80610 40.73 31* 1048.9535 14.6592 32 ∞ 1.6000 1.51680 64.13 33 ∞ 1.3409 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -165.424 Rear group G2 18 41.191 Focusing group Gf 21 67.415.

[0178] In this optical system OL3, the first, second, third, fourth, 23rd, 24th, 30th, and 31st surfaces are formed in an aspherical shape. Table 8 shows the data for the aspherical surfaces, i.e., the cone constant K and the values ​​of each aspherical constant A4 to A20.

[0179] (Table 8) [Aspherical Data] 1st Face K = -5.6509 A4 = 3.7805E-06 A6 = -6.8652E-09 A8 = 9.7741E-12 A10 = -5.9055E-16 A12 = -1.6038E-17 A14 = 2.4362E-20 A16 = -1.7731E-23 A18 = 6.7871E-27 A20 = -1.1048E-30 2nd Face K = 0.1744 A4 = -7.7535E-07 A6 = -2.0204E-08 A8 = 7.2656E-11 A10=-5.0658E-13 A12= 1.8944E-15 A14=-3.8549E-18 A16= 4.3615E-21 A18=-2.3978E-24 A20= 4.1575E-28 3rd side K=-23.0378 A4 =-1.5768E-05 A6 = 6.8855E-08 A8 =-7.5663E-11 A10= 7.2647E-15 A12= 2.0171E-17 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 0.9105 A4 =-4.5849E-05 A6 = 2.8919E-07 A8 =-9.1121E-10 A10= 2.6212E-12 A12=-2.8178E-15 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 Page 23 K= 1.0000 A4 =-7.0986E-05 A6 =-2.2171E-07 A8 = 2.1893E-09 A10=-1.2080E-11 A12= 5.0089E-14 A14=-1.1384E-16 A16= 1.0102E-19 A18= 0.0000E+00 A20= 0.0000E+00 24th side K= 1.0000 A4 =-6.9755E-05 A6 =-2.1611E-07 A8 = 2.4552E-09 A10=-1.1958E-11 A12= 3.8621E-14 A14=-7.1738E-17 A16= 5.5096E-20 A18= 0.0000E+00 A20= 0.0000E+00 30th side K= 1.0000 A4 = 1.6837E-05 A6 =-3.3382E-07 A8 = 4.7810E-10 A10=-1.6866E-12 A12= 2.5268E-14 A14=-9.3806E-17 A16= 9.6314E-20 A18= 0.0000E+00 A20= 0.0000E+00 31st side K= 1.0000 A4 = 3.0542E-05 A6 = -2.6009E-07 A8 = -3.2302E-10 A10 = 6.5004E-12 A12 = -1.7295E-14 A14 = 9.4529E-18 A16 = 1.0513E-20 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0180] Furthermore, in this optical system OL3, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 9 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object.

[0181] (Table 9) [Variable interval data] Focused object infinite distance f 14.420 - β - 0.028 d0 ∞ 152.0005 d1 2.9848 1.6003 d2 1.8000 3.1845

[0182] Figure 6 shows the spherical aberration, astigmatism, distortion, chromatic aberration, and coma aberration diagrams for the optical system OL3 when focused on an object at infinity and when focused on an object at close range. From these aberration diagrams, it can be seen that the optical system OL3 has good correction for various aberrations and possesses excellent imaging performance.

[0183] [Fourth Embodiment] Figure 7 shows the configuration of the optical system OL4 according to the fourth embodiment. This optical system OL4 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture diaphragm S, and a rear group G2 having a positive refractive power.

[0184] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object side, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object side, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); a lens component LCN which is a meniscus-shaped negative lens L15 (LN4) with a concave surface facing the object side; a biconvex positive lens L16 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L17 (LP4) with a concave surface facing the object side and a meniscus-shaped negative lens L18 (LN5) with a concave surface facing the object side.

[0185] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a meniscus-shaped positive lens L28 with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0186] Furthermore, a filter group FL is positioned between the optical system OL4 and the image plane I.

[0187] Furthermore, the optical system OL4 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0188] Table 10 below lists the specifications of the optical system OL4. Note that the 10th plane represents the ray determination plane.

[0189] (Table 10) Fourth Example [Overall Specifications] f = 14.293 FNO = 1.461 ω = 57.694 Ymax = 21.700 TL (Air Equivalent Length) = 147.4546 BF (Air Equivalent Length) = 17.0549 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 65.7870 2.0000 1.72903 54.04 2* 17.9152 16.7233 3* 40.2818 2.2315 1.80610 40.73 4* 22.9907 10.7135 5 -63.6310 1.8029 1.49710 81.56 6 23.2498 13.1395 1.71736 29.57 7 -77.2500 3.4787 8 -31.1527 9.5308 1.74000 28.30 9 -79.5501 -1.5000 10 ∞ 1.6000 11 64.4066 7.5553 1.72047 34.71 12 -51.2850 2.0166 13 -75.2485 7.1847 1.55397 71.76 14 -23.0846 1.8000 1.73800 32.33 15 -138.6542 1.1188 16 ∞ 2.6812 Aperture diaphragm S 17 25.1170 1.9997 2.00100 29.12 18 18.6148 10.6227 1.49710 81.56 19 407.4182 2.9616 20 73.6558 6.4683 1.49710 81.56 21 -38.3166 1.0000 22* 81.7188 2.7500 1.85135 40.10 23* 56.2210 1.8000 24 149.2301 6.2119 1.49710 81.56 25 -32.7287 0.1000 26 -43.3189 5.8464 1.94594 17.98 27 -21.4936 1.9900 2.00330 28.27 28 -5797.4178 4.0724 29* -159.2628 2.4999 1.80610 40.73 30* -72.5132 15.9000 31 ∞ 1.6000 1.51680 64.13 32 ∞ 0.1000 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -101.437 Rear group G2 17 40.479 Focusing group Gf 20 64.488.

[0190] In this optical system OL4, the first, second, third, fourth, 22nd, 23rd, 29th, and 30th surfaces are formed in an aspherical shape. Table 11 below shows the data for the aspherical surfaces, i.e., the cone constant K and the values ​​of each aspherical constant A4 to A20.

[0191] (Table 11) [Aspherical Data] 1st Face K = -6.3333 A4 = 3.5324E-06 A6 = -6.8282E-09 A8 = 9.7938E-12 A10 = -6.3448E-16 A12 = -1.6015E-17 A14 = 2.4368E-20 A16 = -1.7743E-23 A18 = 6.8055E-27 A20 = -1.1162E-30 2nd Face K = 0.1404 A4 = -1.3140E-06 A6 = -2.0708E-08 A8 = 7.2664E-11 A10=-5.0642E-13 A12= 1.8941E-15 A14=-3.8535E-18 A16= 4.3609E-21 A18=-2.3995E-24 A20= 4.1545E-28 3rd side K=-18.8406 A4 =-1.2120E-05 A6 = 3.4878E-08 A8 = 1.4491E-11 A10=-8.8219E-14 A12= 5.2582E-17 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 1.0109 A4 =-4.2848E-05 A6 = 2.3850E-07 A8 =-6.8690E-10 A10= 1.9324E-12 A12=-1.6090E-15 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 22nd page K= 1.0000 A4 =-7.2141E-05 A6 =-1.3898E-07 A8 = 9.8775E-10 A10=-3.0885E-12 A12= 7.9648E-15 A14=-2.1252E-18 A16=-2.3445E-20 A18= 0.0000E+00 A20= 0.0000E+00 23rd side K= 1.0000 A4 =-7.2290E-05 A6 =-1.2092E-07 A8 = 1.2236E-09 A10=-3.8150E-12 A12= 6.4072E-15 A14=-2.3119E-19 A16=-1.2513E-20 A18= 0.0000E+00 A20= 0.0000E+00 Page 29 K= 1.0000 A4 = 1.2570E-05 A6 =-3.3601E-07 A8 = 1.8084E-09 A10=-1.6551E-11 A12= 9.0541E-14 A14=-1.9996E-16 A16= 1.2171E-19 A18= 0.0000E+00 A20= 0.0000E+00 30th side K= 1.0000 A4 = 2.7121E-05 A6 = -2.7538E-07 A8 = 1.2982E-09 A10 = -1.1100E-11 A12 = 6.4802E-14 A14 = -1.6225E-16 A16 = 1.3925E-19 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0192] Furthermore, in this optical system OL4, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 12 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object.

[0193] (Table 12) [Variable interval data] Focused object infinity near distance f 14.293 - β - -0.083 d0 ∞ 152.0001 d1 2.9616 1.6000 d2 1.8000 3.1616

[0194] Figure 8 shows the spherical aberration, astigmatism, distortion, chromatic aberration, and coma aberration diagrams for the optical system OL4 when focused on an object at infinity and when focused on an object at close range. From these aberration diagrams, it can be seen that the optical system OL4 has good correction of various aberrations and possesses excellent imaging performance.

[0195] [Fifth Embodiment] Figure 9 shows the configuration of the optical system OL5 according to the fifth embodiment. This optical system OL5 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture diaphragm S, and a rear group G2 having a positive refractive power.

[0196] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); and an object The lens component LCN is a bonded negative lens formed by joining a meniscus-shaped positive lens L15 (LP2) with its concave surface facing the body side and a meniscus-shaped negative lens L16 (LN4) with its concave surface facing the object side; a biconvex positive lens L17 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L18 (LP4) with its concave surface facing the object side and a meniscus-shaped negative lens L19 (LN5) with its concave surface facing the object side.

[0197] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a meniscus-shaped positive lens L28 with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0198] Furthermore, a filter group FL is positioned between the optical system OL5 and the image plane I.

[0199] Furthermore, the optical system OL5 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and the negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0200] Table 13 below lists the specifications of the optical system OL5. Note that the 11th plane represents the ray determination plane.

[0201] (Table 13) Fifth Example [Overall Specifications] f = 14.420 FNO = 1.463 ω = 57.465 Ymax = 21.700 TL (Air Equivalent Length) = 145.4549 BF (Air Equivalent Length) = 17.0548 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 67.3450 2.0000 1.63858 55.18 2* 18.2823 17.3011 3* 44.3637 2.1187 1.80835 40.55 4* 22.4650 11.4393 5 -70.0232 2.2321 1.49710 81.56 6 23.2498 13.1378 1.71736 29.57 7 -86.2022 3.7114 8 -32.7426 8.7407 1.74000 28.30 9 -22.8606 1.9382 1.75211 25.05 10 -66.4447 -1.5000 11 ∞ 1.6000 12 60.1380 7.7571 1.72047 34.71 13 -53.9177 2.2361 14 -65.7493 6.5864 1.55397 71.76 15 -23.0358 1.8012 1.73800 32.33 16 -156.9268 1.0000 17 ∞ 2.8216 Aperture diaphragm S 18 24.7321 1.9996 2.00100 29.12 19 18.5936 10.6287 1.49710 81.56 20 489.6906 2.9922 21 78.0487 6.3164 1.49710 81.56 22 -37.8526 1.0000 23* 96.1964 2.7500 1.85135 40.10 24* 61.6943 1.8000 25 215.6995 5.9065 1.49710 81.56 26 -31.4486 0.1000 27 -39.0880 4.8410 1.94594 17.98 28 -20.8132 2.1129 2.00330 28.27 29 -199.2838 2.5309 30* 574.2964 2.5001 1.80610 40.73 31* -1194.6297 15.9000 32 ∞ 1.6000 1.51680 64.13 33 ∞ 0.0999 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -155.367 Rear group G2 18 40.710 Focusing group Gf 21 66.699.

[0202] In this optical system OL5, the first, second, third, fourth, 23rd, 24th, 30th, and 31st surfaces are formed in an aspherical shape. Table 14 below shows the data for the aspherical surfaces, i.e., the cone constant K and the values ​​of each aspherical constant A4 to A20.

[0203] (Table 14) [Aspherical Data] 1st Face K = -6.4966 A4 = 3.6766E-06 A6 = -6.9404E-09 A8 = 9.8318E-12 A10 = -6.0630E-16 A12 = -1.6041E-17 A14 = 2.4351E-20 A16 = -1.7739E-23 A18 = 6.7912E-27 A20 = -1.1033E-30 2nd Face K = 0.1790 A4 = -8.3215E-07 A6 = -2.0897E-08 A8 = 7.3703E-11 A10=-5.0695E-13 A12= 1.8936E-15 A14=-3.8543E-18 A16= 4.3622E-21 A18=-2.4002E-24 A20= 4.1061E-28 3rd side K=-22.1738 A4 =-1.5035E-05 A6 = 6.3473E-08 A8 =-7.1530E-11 A10= 1.9556E-14 A12= 1.3167E-20 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 0.9475 A4 =-4.1482E-05 A6 = 2.3859E-07 A8 =-6.7268E-10 A10= 1.9129E-12 A12=-2.0026E-15 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 Page 23 K= 1.0000 A4 =-7.0917E-05 A6 =-3.0306E-07 A8 = 4.2125E-09 A10=-3.4119E-11 A12= 1.7746E-13 A14=-4.9901E-16 A16= 5.7972E-19 A18= 0.0000E+00 A20= 0.0000E+00 24th side K= 1.0000 A4 =-7.1425E-05 A6 =-2.4370E-07 A8 = 3.4831E-09 A10=-2.3012E-11 A12= 9.7425E-14 A14=-2.3211E-16 A16= 2.3405E-19 A18= 0.0000E+00 A20= 0.0000E+00 30th side K= 1.0000 A4 = 1.0575E-05 A6 =-2.2328E-07 A8 =-6.3430E-10 A10= 9.5495E-12 A12=-4.6417E-14 A14= 1.2969E-16 A16=-1.7270E-19 A18= 0.0000E+00 A20= 0.0000E+00 31st side K= 1.0000 A4 = 2.6366E-05 A6 = -1.8994E-07 A8 = -6.1327E-10 A10 = 8.2318E-12 A12 = -3.1092E-14 A14 = 5.8316E-17 A16 = -4.9872E-20 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0204] Furthermore, in this optical system OL5, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 15 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object.

[0205] (Table 15) [Variable interval data] Focused object infinity near distance f 14.420 - β - -0.083 d0 ∞ 152.0005 d1 2.9922 1.6000 d2 1.8000 3.1922

[0206] Figure 10 shows the spherical aberration diagram, astigmatism diagram, distortion diagram, chromatic aberration diagram, and coma aberration diagram of the optical system OL5 when focused on an object at infinity and when focused on an object at close range. From these aberration diagrams, it can be seen that the optical system OL5 has good correction of various aberrations and possesses excellent imaging performance.

[0207] [Sixth Embodiment] Figure 11 shows the configuration of the optical system OL6 according to the sixth embodiment. This optical system OL6 is composed of, in order from the object side, a front group G1 having a negative refractive power, an aperture diaphragm S, and a rear group G2 having a positive refractive power.

[0208] The front group G1 consists of, in order from the object side, a meniscus-shaped negative lens L11 (LN1) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a meniscus-shaped negative lens L12 (LN2) with a convex surface facing the object, where the lens surface on the object side and the lens surface on the image side are formed in an aspherical shape; a bonded positive lens CL1 formed by joining a biconcave negative lens L13 (LN3) and a biconvex positive lens L14 (LP1); and an object The lens component LCN is a bonded negative lens formed by joining a meniscus-shaped positive lens L15 (LP2) with its concave surface facing the body side and a meniscus-shaped negative lens L16 (LN4) with its concave surface facing the object side; a biconvex positive lens L17 (LP3); and a bonded negative lens CL2 formed by joining a meniscus-shaped positive lens L18 (LP4) with its concave surface facing the object side and a meniscus-shaped negative lens L19 (LN5) with its concave surface facing the object side.

[0209] The rear group G2 consists of, in order from the object side, a bonded positive lens CL3 formed by joining a meniscus-shaped negative lens L21 (LN21) with a convex surface facing the object side and a meniscus-shaped positive lens L22 (LP21) with a convex surface facing the object side; a biconvex positive lens L23 (LPf); a meniscus-shaped negative lens L24 (LNf) with a convex surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape; a biconvex positive lens L25; a bonded negative lens CL4 formed by joining a meniscus-shaped positive lens L26 (LP22) with a concave surface facing the object side and a meniscus-shaped negative lens L27 (LN22) with a concave surface facing the object side; and a meniscus-shaped positive lens L28 with a concave surface facing the object side, whose object-side and image-side lens surfaces are formed in an aspherical shape.

[0210] Furthermore, a filter group FL is positioned between the optical system OL6 and the image plane I.

[0211] Furthermore, the optical system OL6 is configured to move the focusing group Gf, which consists of the positive lens L23 (LPf) and the negative lens L24 (LNf) of the rear group G2, towards the object along the optical axis when focusing from an object at infinity to an object at close range.

[0212] Table 16 below lists the specifications of the optical system OL6. Note that the 11th plane represents the ray determination plane.

[0213] (Table 16) Sixth Example [Overall Specifications] f = 14.419 FNO = 1.463 ω = 57.466 Ymax = 21.700 TL (Air Equivalent Length) = 145.4448 BF (Air Equivalent Length) = 17.0768 [Lens Data] m r d nd νd Object Surface ∞ d0 1* 67.8514 2.0000 1.62291 58.30 2* 17.7898 16.9465 3* 40.5980 2.0810 1.82098 42.50 4* 21.4050 11.1242 5 -69.0090 2.1838 1.49710 81.56 6 23.2498 13.1693 1.71736 29.57 7 -83.6757 3.8882 8 -31.8623 7.8298 1.76182 26.58 9 -29.1198 1.8013 1.75575 24.71 10 -72.6432 -1.5000 11 ∞ 1.6000 12 60.6931 7.6415 1.72047 34.71 13 -52.1589 2.1987 14 -65.8405 6.6573 1.55397 71.76 15 -22.9922 1.8020 1.73800 32.33 16 -138.1840 1.0593 17 ∞ 2.7407 Aperture diaphragm S 18 24.5335 1.9997 2.00100 29.12 19 18.3563 10.6279 1.49710 81.56 20 416.4809 3.0019 21 79.1620 6.1665 1.49710 81.56 22 -38.3492 1.0000 23* 83.2806 2.7500 1.85135 40.10 24* 57.3724 1.8000 25 223.1383 5.9750 1.49710 81.56 26 -31.3860 0.1000 27 -39.4338 5.2231 1.94594 17.98 28 -20.5801 2.2494 2.00330 28.27 29 -219.7854 3.7509 30* -132.1580 2.5000 1.80610 40.73 31* -77.4298 15.9219 32 ∞ 1.6000 1.51680 64.13 33 ∞ 0.1000 Image plane ∞ [Lens group focal length] Lens group starting plane focal length Front group G1 1 -114.132 Rear group G2 18 40.394 Focusing group Gf 21 66.098.

[0214] In this optical system OL6, the first, second, third, fourth, 23rd, 24th, 30th, and 31st surfaces are formed in an aspherical shape. Table 17 below shows the data for the aspherical surfaces, i.e., the values ​​of the cone constant K and each aspherical constant A4 to A20.

[0215] (Table 17) [Aspherical Data] 1st Face K = -7.3698 A4 = 3.6817E-06 A6 = -6.9224E-09 A8 = 9.7630E-12 A10 = -5.9482E-16 A12 = -1.6032E-17 A14 = 2.4351E-20 A16 = -1.7735E-23 A18 = 6.7692E-27 A20 = -1.0901E-30 2nd Face K = 0.1833 A4 = -5.1830E-07 A6 = -2.3678E-08 A8 = 7.4679E-11 A10=-5.0571E-13 A12= 1.8942E-15 A14=-3.8546E-18 A16= 4.3590E-21 A18=-2.3985E-24 A20= 4.2264E-28 3rd side K=-19.0550 A4 =-1.0710E-05 A6 = 4.2611E-08 A8 =-1.9846E-11 A10=-4.3425E-14 A12= 3.4636E-17 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 4th side K= 0.9344 A4 =-4.3100E-05 A6 = 2.4120E-07 A8 =-7.3642E-10 A10= 2.1353E-12 A12=-2.2201E-15 A14= 0.0000E+00 A16= 0.0000E+00 A18= 0.0000E+00 A20= 0.0000E+00 Page 23 K= 1.0000 A4 =-7.2002E-05 A6 =-2.0528E-07 A8 = 2.1167E-09 A10=-1.2955E-11 A12= 5.7772E-14 A14=-1.3582E-16 A16= 1.2296E-19 A18= 0.0000E+00 A20= 0.0000E+00 24th side K= 1.0000 A4 =-7.1872E-05 A6 =-1.7550E-07 A8 = 2.1072E-09 A10=-1.0735E-11 A12= 3.7193E-14 A14=-7.3160E-17 A16 = 5.8235E-20 A18 = 0.0000E+00 A20 = 0.0000E+00 30th side K = 1.0000 A4 = 1.1092E-05 A6 = -3.0147E-07 A8 = 1.1496E-09 A10=-7.8725E-12 A12= 3.9447E-14 A14=-7.1235E-17 A16= 6.5942E-21 A18= 0.0000E+00 A20= 0.0000E+00 31st side K= 1.0000 A4 = 2.4823E-05 A6 = -2.4117E-07 A8 = 7.8922E-10 A10 = -5.1155E-12 A12 = 3.1317E-14 A14 = -8.1218E-17 A16 = 6.9620E-20 A18 = 0.0000E+00 A20 = 0.0000E+00.

[0216] Furthermore, in this optical system OL6, the on-axial air gap d1 between positive lens L22 and positive lens L23, and the on-axial air gap d2 between negative lens L24 and positive lens L25, change when focusing. Table 18 below shows the variable gaps when focusing on an object at infinity and when focusing on a close-range object.

[0217] (Table 18) [Variable interval data] Focused object infinity near distance f 14.419 - β - -0.084 d0 ∞ 152.0100 d1 3.0019 1.6000 d2 1.8000 3.2019

[0218] Figure 12 shows the spherical aberration, astigmatism, distortion, chromatic aberration, and coma aberration diagrams for the optical system OL6 when focused on an object at infinity and when focused on an object at close range. From these aberration diagrams, it can be seen that the optical system OL6 has good correction of various aberrations and possesses excellent imaging performance.

[0219] [Corresponding Values ​​for Conditional Expressions] The corresponding values ​​for conditional expressions (1) to (31) in the first to sixth embodiments are shown in Table 19 below.

[0220] (Table 19) (1) ndLN1 (2) νdLN1 (3) ndLN2 (4) νdLN2 (5) ndLN3 (6) νdLN3 (7) ΔPgFLN3 (8) ndLP1 (9) νdLP1 (10) ndLP1+0.019×νdLP1 (11) f / f1 (12) ndLN4 (13) νdLN4 (14) ndLP3 (15) νdLP3 (16) ndLP3+0.019×νdLP3 (17) ΔPgFLP4−ΔPgFLN5 (18) f / f2 (19) ff / f2 (20) ndLN21 (21) ΔPgFLP21 (22) ndLP21 (23) νdLP21 (24) ndLN22 (25) ΔPgFLP22 (26) ndLP22 (27) νdLP22 (28) ω (29) Fno (30) D (31) BFa / Ymax First Example Second Example Third Example D -0.040 -0.040 -0.040 ΔPgFLN3 0.037 0.037 0.037 ΔPgFLP4 0.020 0.020 0.020 ΔPgFLN5 0.001 0.001 0.001 ΔPgFLP21 0.369 0.369 0.369 ΔPgFLP22 0.039 0.039 0.039 (1) 1.693 1.693 1.678 (2) 53.30 53.30 54.89 (3) 1.808 1.808 1.808 (4) 40.55 40.55 40.55 (5) 1.497 1.497 1.497 (6) 81.56 81.56 81.56 (7) 0.037 0.037 0.037 (8) 1.699 1.699 1.699 (9) 30.05 30.05 30.13 (10) 2.270 2.270 2.271 (11) -0.064 -0.084 -0.087 (12) 1.752 1.752 1.762 (13) 25.05 25.05 26.58 (14) 1.720 1.720 1.720 (15) 34.71 34.71 34.71 (16) 2.380 2.380 2.380 (17) 0.0192 0.0192 0.0192 (18) 0.356 0.348 0.350 (19) 1.409 1.671 1.637 (20) 2.001 2.001 2.001 (21) 0.369 0.369 0.369 (22) 1.497 1.497 1.497 (23) 81.56 81.56 81.56 (24) 2.003 2.003 2.003 (25) 0.039 0.039 0.039 (26) 1.946 1.946 1.946 (27) 17.98 17.98 17.98 (28) 57.516 57.465 57.465 (29) 1.456 1.461 1.466 (30) -0.040 -0.040 -0.040 (31) 0.786 0.786 0.786 Fourth Example Fifth Example Sixth Example D -0.040 -0.040 -0.040 ΔPgFLN3 0.037 0.037 0.037 ΔPgFLP4 0.020 0.020 0.020 ΔPgFLN5 0.001 0.001 0.001 ΔPgFLP21 0.369 0.369 0.369 ΔPgFLP22 0.039 0.039 0.039 (1) 1.729 1.639 1.623 (2) 54.04 55.18 58.30 (3) 1.806 1.808 1.821 （４）　　　　　　　40.73 　　　40.55 　　　42.50 （５）　　　　　　　 1.497　　　 1.497　　　 1.497 （６）　　　　　　　81.56 　　　81.56 　　　81.56 （７）　　　　　　　 0.037　　　 0.037　　　 0.037 （８）　　　　　　　 1.717　　　 1.717　　　 1.717 （９）　　　　　　　29.57 　　　29.57 　　　29.57 （１０）　　　　　　 2.279　　　 2.279　　　 2.279 （１１）　　　　　　-0.141　　　-0.093　　　-0.126 （１２）　　　　　　 1.740　　　 1.752　　　 1.756 （１３）　　　　　　28.30 　　　25.05 　　　24.71 （１４）　　　　　　 1.720　　　 1.720　　　 1.720 （１５）　　　　　　34.71 　　　34.71 　　　34.71 （１６）　　　　　　 2.380　　　 2.380　　　 2.380 （１７）　　　　　　 0.0192　　　0.0192　　　0.0192 （１８）　　　　　　 0.353　　　 0.354　　　 0.357 （１９）　　　　　　 1.593　　　 1.638　　　 1.636 （２０）　　　　　　 2.001　　　 2.001　　　 2.001 （２１）　　　　　　 0.369　　　 0.369　　　 0.369 （２２）　　　　　　 1.497　　　 1.497　　　 1.497 （２３）　　　　　　81.56 　　　81.56 　　　81.56 （２４）　　　　　　 2.003　　　 2.003　　　 2.003 （２５）　　　　　　 0.039　　　 0.039　　　 0.039 （２６）　　　　　　 1.946　　　 1.946　　　 1.946 （２７）　　　　　　17.98 　　　17.98 　　　17.98 （２８）　　　　　　57.694　　　57.465　　　57.466 （２９）　　　　　　 1.461　　　 1.463　　　 1.463 （３０）　　　　　　-0.040　　　-0.040　　　-0.040 （３１）　　　　　　 0.786　　　 0.786　　　 0.787.

[0221] 1. Camera (Optical Equipment) OL (OL1-OL6) Optical System G1 Front Group S Aperture Diaphragm G2 Rear Group Gf Focusing Group LPf Positive Lens LNf Negative Lens LN1 First Negative Lens LN2 Second Negative Lens CL1 First Bonded Lens LN3 Third Negative Lens LP1 First Positive Lens LCN Lens Components LP2 Positive Lens LN4 Fourth Negative Lens LP3 Third Positive Lens CL2 Second Bonded Lens LP4 Positive Lens LN5 Negative Lens CL3 Third Bonded Lens LN21 Negative Lens LP21 Positive Lens CL4 Fourth Bonded Lens LP22 Positive Lens LN22 Negative Lens

Claims

Starting from the object side, It has a front group, an aperture, and a rear group. The aforementioned group, in order from the object side, is as follows: A first negative lens with a meniscus shape, with its convex surface facing the object, A second negative lens with a meniscus shape, with its convex surface facing the object, It has a first cemented lens consisting of a third negative lens having a negative refractive power and a first positive lens having a positive refractive power, The aforementioned rear group has a focusing group that moves along the optical axis when focusing occurs. An optical system that satisfies the following conditions. 1.60 < ndLN1 < 1.77 however, ndLN1: Refractive index of the medium of the first negative lens with respect to the d line. Starting from the object side, It has a front group, an aperture, and a rear group. The aforementioned front group has a first negative lens with a meniscus shape, which faces the object side, and is located closest to the object. The aforementioned group has a positive refractive power, The aforementioned rear group has a focusing group that moves along the optical axis when focusing occurs. An optical system that satisfies the following conditions. -0.20 < f / f1 < 0.20 however, f: Focal length of the entire optical system f1: Focal length of the front group The optical system according to claim 2, satisfying the following conditional expression. 1.60 < ndLN1 < 1.77 however, ndLN1: Refractive index of the medium of the first negative lens with respect to the d line. An optical system according to any one of claims 1 to 3 that satisfies the following conditional expression. 50.00 < νdLN1 < 60.00 however, νdLN1: Abbe number of the medium of the first negative lens with respect to the d line The front group has a second negative lens having a negative refractive power on the image plane side than the first negative lens, An optical system according to any one of claims 1 to 4 that satisfies the following conditional expression. 1.50 < ndLN2 < 1.90 20.00 < νdLN2 < 60.00 however, ndLN2: Refractive index of the medium of the second negative lens with respect to the d line. νdLN2: Abbe number of the medium of the second negative lens with respect to the d line The aforementioned front group includes a second negative lens having negative refractive power and a third negative lens having negative refractive power, positioned on the image plane side of the first negative lens. An optical system according to any one of claims 1 to 5 that satisfies the following conditional expression. 1.40 < ndLN3 < 1.80 50.00 < νdLN3 < 100.00 0.000 < ΔPgFLN3 < 0.050 however, ndLN3: Refractive index of the medium of the third negative lens with respect to the d line. νdLN3: Abbe number of the medium of the third negative lens with respect to the d line ΔPgFLN3: Abnormal dispersion of the medium of the third negative lens. Here, the anomalous dispersion ΔPgFLN3 is defined as ΔPgFLN3 = PgFLN3 - (0.648327 - 0.0018024 × νdLN3). however, PgFLN3 ≡ (ngLN3 - nFLN3) / (nFLN3 - nCLN3): Partial dispersion ratio of the medium of the third negative lens. ngLN3: Refractive index of the medium of the third negative lens with respect to the g line. nFLN3: Refractive index of the medium of the third negative lens with respect to the F line. nCLN3: Refractive index of the medium of the third negative lens with respect to the C line. νdLN3: Abbe number of the medium of the third negative lens with respect to the d line The aforementioned front group includes, on the image plane side of the first negative lens, a second negative lens having a negative refractive power, a third negative lens having a negative refractive power, and a first positive lens having a positive refractive power. An optical system according to any one of claims 1 to 6 that satisfies the following conditional expression. 1.50 < ndLP1 < 1.80 20.00 < νdLP1 < 40.00 ndLP1+0.019×νdLP1 < 2.315 however, ndLP1: Refractive index of the medium of the first positive lens with respect to the d line. νdLP1: Abbe number of the medium of the first positive lens with respect to the d line The front group has a fourth negative lens on the image plane side of the first positive lens, which constitutes a lens component of negative refractive power. The optical system according to claim 1 or 7, satisfying the following conditional expression. 1.55 < ndLN4 < 2.00 15.00 < νdLN4 < 35.00 however, ndLN4: Refractive index of the medium of the fourth negative lens with respect to the d line. νdLN4: Abbe number of the medium of the fourth negative lens with respect to the d line The optical system according to claim 8, wherein the lens component is a cemented lens comprising the fourth negative lens and a positive lens bonded to the object side of the fourth negative lens. 　 The front group has a third positive lens on the image plane side of the fourth negative lens, The optical system according to claim 8 or 9, satisfying the following conditional expression. 1.60 < ndLP3 < 1.80 25.00 < νdLP3 < 45.00 2.315 <ndLP3+0.019×νdLP3 however, ndLP3: Refractive index of the medium of the third positive lens with respect to the d line. νdLN3: Abbe number of the medium of the third positive lens with respect to the d line The aforementioned front group has a second cemented lens on the image plane side of the third positive lens, in which a positive lens and a negative lens are joined together in order from the object side. The optical system according to claim 10, satisfying the following conditional expression. 0.000 < ΔPgFLP4 - ΔPgFLN5 < 0.060 however, ΔPgFLP4: Abnormal dispersion of the medium of the positive lens constituting the second cemented lens. Here, the anomalous dispersion ΔPgFLP4 is defined as ΔPgFLP4 = PgFLP4 - (0.648327 - 0.0018024 × νdLP4). however, PgFLP4 ≡ (ngLP4 - nFLP4) / (nFLP4 - nCLP4): Partial dispersion ratio of the medium of the positive lens. ngLP4: Refractive index of the medium of the positive lens with respect to the g line. nFLP4: Refractive index of the medium of the positive lens with respect to the F line. nCLP4: Refractive index of the medium of the positive lens with respect to the C line. νdLP4: Abbe number of the medium of the positive lens with respect to the d line ΔPgFLN5: Abnormal dispersion of the medium of the negative lens constituting the second cemented lens. Here, the anomalous dispersion ΔPgFLN5 is defined as ΔPgFLN5 = PgFLN5 - (0.648327 - 0.0018024 × νdLN5). however, PgFLN5 ≡ (ngLN5 - nFLN5) / (nFLN5 - nCLN5): Partial dispersion ratio of the medium of the negative lens. ngLN5: Refractive index of the medium of the negative lens with respect to the g line. nFLN5: Refractive index of the medium of the negative lens with respect to the F line. nCLN5: Refractive index of the medium of the negative lens with respect to the C line. νdLN5: Abbe number of the medium of the negative lens with respect to the d line The optical system according to any one of claims 1 to 11, wherein the focusing group comprises at least one positive lens and at least one negative lens. 　 An optical system according to any one of claims 1 to 12 that satisfies the following conditional expression. 0.10 < f / f2 < 0.50 however, f: Focal length of the entire optical system f2: Focal length of the rear group when the object at infinity is in focus. An optical system according to any one of claims 1 to 13 that satisfies the following conditional expression. 1.20 < ff / f2 < 2.00 however, ff: Focal length of the aforementioned focusing group f2: Focal length of the rear group when the object at infinity is in focus. 　 The aforementioned rear group has a third cemented lens formed by joining a meniscus-shaped negative lens and a positive lens with the convex surface facing the object side. An optical system according to any one of claims 1 to 14 that satisfies the following conditional expression. 1.70 <ndLN21 0.000 < ΔPgFLP21 however, ndLN21: Refractive index of the medium of the negative lens constituting the third cemented lens with respect to the d line. ΔPgFLP21: Abnormal dispersion of the medium of the positive lens constituting the third cemented lens Here, the anomalous dispersion ΔPgFLP21 is defined as ΔPgFLP21 = PgFLP21 - (0.648327 - 0.0018024 × νdLP21). however, PgFLP21 ≡ (ngLP21 - nFLP21) / (nFLP21 - nCLP21): Partial dispersion ratio of the medium of the positive lens ngLP21: Refractive index of the medium of the positive lens with respect to the g line. nFLP21: Refractive index of the medium of the positive lens with respect to the F line. nCLP21: Refractive index of the medium of the positive lens with respect to the C line. νdLP21: Abbe number of the medium of the positive lens with respect to the d line The optical system according to claim 15, satisfying the following conditional expression. 1.40 < ndLP21 < 1.70 50.00 < νdLP21 < 100.00 however, ndLP21: Refractive index of the medium of the positive lens constituting the third cemented lens with respect to the d line. νdLP21: Abbe number of the medium of the positive lens constituting the third cemented lens with respect to the d line The aforementioned rear group includes a third cemented lens formed by joining a meniscus-shaped negative lens and a positive lens with a convex surface facing the object side, and a fourth cemented lens formed by joining a meniscus-shaped positive lens and a negative lens with a convex surface facing the image plane side. An optical system according to any one of claims 1 to 16 that satisfies the following conditional expression. 1.70 <ndLN22 0.000 < ΔPgFLP22 however, ndLN22: Refractive index of the medium of the negative lens constituting the fourth cemented lens with respect to the d line. ΔPgFLP22: Abnormal dispersion of the medium of the positive lens constituting the fourth cemented lens Here, the anomalous dispersion ΔPgFLP22 is defined as ΔPgFLP22 = PgFLP22 - (0.648327 - 0.0018024 × νdLP22). however, PgFLP22 ≡ (ngLP22 - nFLP22) / (nFLP22 - nCLP22): Partial dispersion ratio of the medium of the positive lens. ngLP22: Refractive index of the medium of the positive lens with respect to the g line. nFLP22: Refractive index of the medium of the positive lens with respect to the F line. nCLP22: Refractive index of the medium of the positive lens with respect to the C line. νdLP22: Abbe number of the medium of the positive lens with respect to the d line The optical system according to claim 17, satisfying the following conditional expression. 1.70 < ndLP22 15.00 < νdLP22 < 30.00 however, ndLP22: Refractive index of the medium of the positive lens constituting the fourth cemented lens with respect to the d line. νdLP22: Abbe number of the medium of the positive lens constituting the fourth cemented lens with respect to the d line The optical system according to claim 17 or 18, wherein the focusing group is arranged between the third cemented lens and the fourth cemented lens. 　 An optical system according to any one of claims 1 to 19 that satisfies the following conditional expression. 45.00° < ω < 70.00° however, ω: Half-angle of view of the optical system An optical system according to any one of claims 1 to 20 that satisfies the following conditional expression. 1.00 < Fno < 2.90 however, Fno: F-number of the optical system. An optical system according to any one of claims 1 to 21 that satisfies the following conditional expression. -0.10 < D < 0.00 however, D: Peripheral distortion An optical system according to any one of claims 1 to 22 that satisfies the following conditional expression. 0.50 < BFa / Ymax < 2.00 however, BFa: Back focus (air equivalent length) of the optical system. 　 Ymax: Maximum image height of the optical system 　 An optical instrument having the optical system described in any one of claims 1 to 23. 　 A method for manufacturing an optical system having, in order from the object side, a front group, an aperture, and a rear group, In the front group, starting from the side closest to the object, a first negative lens with a meniscus shape and a convex surface facing the object, a second negative lens with a meniscus shape and a convex surface facing the object, and a first cemented lens consisting of a third negative lens having negative refractive power and a first positive lens having positive refractive power are arranged. In the aforementioned rear group, a focusing group that moves along the optical axis during focusing is arranged. A method for manufacturing an optical system arranged to satisfy the following condition. 1.60 < ndLN1 < 1.77 however, ndLN1: Refractive index of the medium of the first negative lens with respect to the d line. A method for manufacturing an optical system having, in order from the object side, a front group, an aperture, and a rear group, A first negative lens with a meniscus shape, with its convex surface facing the object, is placed in the front group, The aforementioned rear group is arranged to have a positive refractive power, In the aforementioned rear group, a focusing group that moves along the optical axis during focusing is arranged. A method for manufacturing an optical system arranged to satisfy the following condition. -0.20 < f / f1 < 0.20 however, f: Focal length of the entire optical system f1: Focal length of the front group

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