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

Abstract

This optical system comprising a first lens group, an aperture diaphragm, and a rear group in the stated order from an object side, the rear group having a first doublet lens comprising a positive lens and a negative lens, is configured so as to satisfy all of the following conditions: 0.350 < Bf / y < 0.700, 1.350 < TL / y < 2.000, and 0.050 < Np1 – Nn1 < 0.400, where Bf is the back focal distance as an air conversion length, y is the maximum image height, TL is the distance from the lens surface closest to the object to the image plane, NP1 is the refractive index of the positive lens constituting the first doublet lens, and Nn1 is the refractive index of the negative lens constituting the first doublet lens.

Description

[Technical Field]

[0001] The present disclosure relates to an optical system, an optical instrument, and a method for manufacturing an optical system. [Background technology]

[0002] BACKGROUND ART Conventionally, optical systems for use in optical devices such as photographic cameras, electronic still cameras, and video cameras have been proposed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-054078 Summary of the Invention

[0004] The optical system of the present disclosure comprises, in order from the object side, a first lens group, an aperture stop, and a rear group. The rear group has a first cemented lens composed of a positive lens and a negative lens, and satisfies both of the following conditional expressions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: Refractive index of the positive lens that makes up the first cemented lens Nn1: Refractive index of the negative lens that makes up the first cemented lens

[0005] The optical system of the present disclosure comprises, in order from the object side, a first lens group, an aperture stop, and a rear group. The rear group has a first cemented lens composed of a positive lens and a negative lens, and satisfies both of the following conditional expressions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 1.500 < tp1 / tn1 < 7.000 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane tp1: Center thickness of the positive lens that makes up the first cemented lens tn1: Center thickness of the negative lens that makes up the first cemented lens

[0006] The optical system of the present disclosure comprises, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group having a first cemented lens consisting of a positive lens and a negative lens, the first lens group having a positive lens arranged closest to the object side, and satisfying both of the following conditional expressions: 1.000 < f / y < 1.600 0.025 < t1 / f < 0.080 however, f: focal length of the entire optical system y: Maximum image height t1: Center thickness of the lens closest to the object

[0007] The method for manufacturing an optical system according to the present disclosure is a method for manufacturing an optical system including, in order from the object side, a first lens group, an aperture stop, and a rear group, where the rear group has a first cemented lens consisting of a positive lens and a negative lens, and the lenses are arranged so as to satisfy both of the following conditional expressions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: Refractive index of the positive lens that makes up the first cemented lens Nn1: Refractive index of the negative lens that makes up the first cemented lens [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a cross-sectional view of the optical system of the first example when focusing on an object at infinity. [Figure 2] 4A to 4C are diagrams showing various aberrations in the optical system of Example 1 when focusing on an object at infinity. [Figure 3] FIG. 10 is a cross-sectional view of the optical system of the second example when focusing on an object at infinity. [Figure 4] 10A to 10C are diagrams illustrating various aberrations in the optical system of Example 2 when focusing on an object at infinity. [Figure 5] FIG. 10 is a cross-sectional view of the optical system of the third example when focusing on an object at infinity. [Figure 6] 10A to 10C are diagrams illustrating various aberrations in the optical system of Example 3 when focusing on an object at infinity. [Figure 7] FIG. 10 is a cross-sectional view of the optical system of the fourth example when focusing on an object at infinity. [Figure 8] 10A to 10C are diagrams showing various aberrations in the optical system of Example 4 when focusing on an object at infinity. [Figure 9] FIG. 10 is a cross-sectional view of the optical system of the fifth example when focusing on an object at infinity. [Figure 10] 10A to 10C are diagrams illustrating various aberrations in the optical system of Example 5 when focusing on an object at infinity. [Figure 11] FIG. 1 is a schematic diagram of a camera equipped with the optical system of the present embodiment. [Figure 12] 1 is a flowchart showing an outline of a method for manufacturing an optical system according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] An optical system, an optical device, and a method for manufacturing an optical system according to embodiments of the present application will be described below.

[0010] The optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture stop, and a rear group. The rear group has a first cemented lens consisting of a positive lens and a negative lens, and satisfies both of the following conditional expressions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: Refractive index of the positive lens that makes up the first cemented lens Nn1: Refractive index of the negative lens that makes up the first cemented lens

[0011] The optical system of this embodiment has the rear group first cemented lens, which makes it possible to effectively correct chromatic aberration, maintain the Petzval sum at an appropriate value, and effectively correct field curvature.

[0012] Conditional expression (1) defines the ratio between the back focus and the maximum image height in terms of the air-equivalent length. By satisfying conditional expression (1), the optical system of this embodiment can appropriately correct various aberrations while ensuring a back focus of an appropriate length that allows necessary filters to be arranged between the optical system and the image plane.

[0013] In the optical system of this embodiment, if the value of conditional expression (1) exceeds the upper limit, the back focal length becomes too long, increasing the overall length of the optical system. Furthermore, if the overall length of the optical system is reduced by reducing the length of any element other than the back focal length, it becomes difficult to appropriately correct various aberrations.

[0014] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (1) to 0.700. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (1) to 0.691, or even 0.550.

[0015] Furthermore, in the optical system of this embodiment, if the value of conditional formula (1) falls below the lower limit, the back focus becomes too short, making it difficult to place filters in front of the image sensor, and the quality of the image signal output from the image sensor decreases.

[0016] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (1) to 0.350. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (1) to 0.369, or even 0.400.

[0017] Conditional expression (2) defines the ratio between the distance from the lens surface closest to the object to the image plane (total optical length) and the maximum image height. By satisfying conditional expression (2), the optical system of this embodiment can suppress an increase in the total length of the optical system, while suppressing shading at the image sensor and appropriately correcting various aberrations.

[0018] In the optical system of this embodiment, if the value of conditional expression (2) exceeds the upper limit, the overall length of the optical system becomes long, and the optical system becomes large.

[0019] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (2) to 2.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (2) to 1.843, and more preferably 1.820.

[0020] Furthermore, in the optical system of this embodiment, if the value of conditional expression (2) falls below the lower limit, the angle of incidence of light rays onto the image sensor increases, causing shading and making it difficult to correct various aberrations.

[0021] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (2) to 1.350. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (2) to 1.400, or even 1.600.

[0022] Conditional expression (3) defines the difference between the refractive index of the positive lens that constitutes the first cemented lens and the refractive index of the negative lens that constitutes the first cemented lens. By having a first cemented lens that satisfies conditional expression (3), the optical system of this embodiment can appropriately suppress the occurrence of various aberrations.

[0023] In the optical system of this embodiment, if the value of conditional expression (3) exceeds the upper limit, the refractive power at the cemented surface of the first cemented lens becomes too strong, causing large aberrations.

[0024] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (3) to 0.400. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (3) to 0.350, and more preferably 0.300.

[0025] Furthermore, in the optical system of this embodiment, if the value of conditional expression (3) falls below the lower limit, the Petzval sum cannot be appropriately corrected by the first cemented lens, making it difficult to suppress curvature of field in the entire optical system.

[0026] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (3) to 0.050. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (3) to 0.060, or even 0.070.

[0027] In an optical system that satisfies all of conditional expressions (1), (2), and (3), an increase in the overall length of the optical system is suppressed, an appropriate back focal length is ensured, shading at the image sensor is suppressed, and various aberrations can be appropriately corrected.

[0028] The optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture stop, and a rear group. The rear group has a first cemented lens consisting of a positive lens and a negative lens, and satisfies both of the following conditional expressions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane tp1: Center thickness of the positive lens that makes up the first cemented lens tn1: Center thickness of the negative lens that makes up the first cemented lens

[0029] Conditional expression (4) defines the ratio between the center thickness of the positive lens constituting the first cemented lens and the center thickness of the negative lens constituting the first cemented lens. By satisfying conditional expression (4), the optical system of this embodiment can appropriately correct various aberrations while suppressing an increase in the overall length of the optical system.

[0030] In the optical system of this embodiment, if the value of conditional expression (4) exceeds the upper limit, the thickness on the optical axis of the positive lens constituting the first cemented lens becomes too large, and the overall length of the optical system becomes large.

[0031] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (4) to 7.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (4) to 6.000, and more preferably 5.000.

[0032] Furthermore, in the optical system of this embodiment, if the value of conditional expression (4) falls below the lower limit, the refractive power of the positive lens constituting the first cemented lens cannot be made sufficiently strong, making it difficult to correct various aberrations such as chromatic aberration and Petzval sum.

[0033] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (4) to 1.500. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (4) to 1.800, or even 3.000.

[0034] In an optical system that satisfies all of conditional expressions (1), (2), and (4), it is possible to suppress an increase in the overall length of the optical system, ensure an appropriate back focal length, suppress shading at the image sensor, and appropriately correct various aberrations.

[0035] The optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group having a first cemented lens consisting of a positive lens and a negative lens, the first lens group having a positive lens arranged closest to the object side, and satisfies both of the following conditional expressions: (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 however, f: focal length of the entire optical system y: Maximum image height t1: Center thickness of the lens closest to the object

[0036] Conditional expression (5) defines the ratio between the focal length of the entire optical system and the maximum image height. By satisfying conditional expression (5), the optical system of this embodiment can appropriately correct both spherical aberration and coma while suppressing an increase in the overall length of the optical system.

[0037] In the optical system of this embodiment, if the value of conditional expression (5) exceeds the upper limit, the focal length of the optical system becomes too long, and the overall length of the optical system becomes large. Furthermore, if an attempt is made to shorten the overall length of the optical system, it becomes difficult to appropriately correct various aberrations.

[0038] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (5) to 1.600. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (5) to 1.550, and more preferably 1.500.

[0039] Furthermore, in the optical system of this embodiment, if the value of conditional expression (5) falls below the lower limit, the difference between the deflection angle of the on-axis light beam and the deflection angle of the off-axis light beam with respect to the lens closest to the object becomes large, making it difficult to simultaneously correct the spherical aberration caused by the on-axis light beam and the coma caused by the off-axis light beam.

[0040] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (5) to 1.000. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (5) to 1.100, or even 1.200.

[0041] Conditional expression (6) defines the ratio between the center thickness of the lens closest to the object and the focal length of the entire optical system. By satisfying conditional expression (6), the optical system of this embodiment can appropriately correct coma while positioning the exit pupil at an appropriate position.

[0042] In the optical system of this embodiment, if the value of conditional expression (6) exceeds the upper limit, the thickness of the positive lens located closest to the object becomes too thick, and the position of the aperture stop becomes close to the image plane, making it difficult to position the exit pupil at an appropriate position.

[0043] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (6) to 0.080. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (6) to 0.075, and more preferably 0.070.

[0044] Furthermore, in the optical system of this embodiment, if the value of conditional expression (6) falls below the lower limit, the thickness of the positive lens positioned closest to the object becomes too thin, making it difficult to correct coma.

[0045] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (6) to 0.025. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (6) to 0.030, and more preferably 0.035.

[0046] In an optical system that satisfies both conditional expressions (5) and (6), an increase in the overall length of the optical system is suppressed, the exit pupil is positioned at an appropriate position, and both spherical aberration and coma can be appropriately corrected.

[0047] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (7) 3.000 < νdp1-νdn1 < 30.000 however, νdp1: Abbe number based on the d-line of the positive lens that makes up the first cemented lens νdn1: Abbe number of the negative lens that makes up the first cemented lens, based on the d-line

[0048] Conditional expression (7) defines the difference in Abbe number, based on the d-line, between the positive lens and the negative lens constituting the first cemented lens. By satisfying conditional expression (7), the optical system of this embodiment can appropriately correct chromatic aberration by the first cemented lens.

[0049] In the optical system of this embodiment, if the value of conditional expression (7) exceeds the upper limit, the correction of chromatic aberration by the first cemented lens becomes excessive.

[0050] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (7) to 30,000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (7) to 25,000, or even 20,000.

[0051] In the optical system of this embodiment, if the value of conditional expression (7) is below the lower limit, the correction of chromatic aberration by the first cemented lens will be insufficient.

[0052] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (7) to 3.000. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (7) to 4.500, or even 5.000.

[0053] In the optical system of this embodiment, it is preferable that the rear group includes a positive lens and a negative lens, and has a second cemented lens different from the first cemented lens.

[0054] With the optical system of this embodiment having such a configuration, lateral chromatic aberration can be appropriately corrected.

[0055] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (8) 1.000 < f / y < 1.380 f: focal length of the entire optical system

[0056] Conditional expression (8) defines the ratio between the focal length of the entire optical system and the maximum image height. By satisfying conditional expression (8), the optical system of this embodiment can appropriately correct both spherical aberration and coma while appropriately correcting chromatic aberration of magnification with the first cemented lens and the second cemented lens.

[0057] In the optical system of this embodiment, if the value of conditional expression (8) exceeds the upper limit, chromatic aberration of magnification cannot be appropriately corrected by the first cemented lens and the second cemented lens.

[0058] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (8) to 1.380. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (8) to 1.330, or preferably 1.280.

[0059] Furthermore, in the optical system of this embodiment, if the value of conditional expression (8) falls below the lower limit, the difference between the deflection angle of the on-axis light beam and the deflection angle of the off-axis light beam with respect to the lens closest to the object becomes large, making it difficult to appropriately correct both spherical aberration and coma aberration.

[0060] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (8) to 1.000. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (8) to 1.100, or even 1.200.

[0061] In the optical system of the present embodiment, it is preferable that of the first cemented lens and the second cemented lens, the cemented lens arranged on the object side has a negative lens arranged on the object side, and that the cemented lens arranged on the image plane side has a negative lens arranged on the image plane side.

[0062] In the optical system of this embodiment, by arranging the negative lens on the object side of the cemented lens where the axial light beam is thicker, it is possible to effectively correct various aberrations, particularly spherical aberration. Also, by making the first cemented lens and the second cemented lens symmetrical, it is possible to effectively correct various aberrations, particularly coma.

[0063] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (9) -0.030 < fc1 / fc2 < 1.000 however, fc1: The composite focal length of the first cemented lens and the second cemented lens, whichever is closer to the object fc2: The composite focal length of the first cemented lens and the second cemented lens, whichever is located closer to the image plane

[0064] Conditional expression (9) defines the ratio between the composite focal length of the cemented lens of the first cemented lens and the second cemented lens that is located closer to the object side and the composite focal length of the cemented lens of the first cemented lens and the second cemented lens that is located closer to the image plane side. By satisfying conditional expression (9), the optical system of this embodiment can suppress the occurrence of spherical aberration while suppressing an increase in the overall length of the optical system.

[0065] In the optical system of this embodiment, if the value of conditional expression (9) exceeds the upper limit, the refractive power of the cemented lens located on the image plane side of the first cemented lens or the second cemented lens becomes large, and the overall length of the optical system becomes too large.

[0066] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit value of conditional expression (9) to 1.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (9) to 0.960, and more preferably 0.930.

[0067] In the optical system of this embodiment, when the value of conditional expression (9) is below the lower limit, object The refractive power of the cemented lens placed on the side becomes large, causing spherical aberration.

[0068] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (9) to -0.030. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (9) to -0.020, or even -0.010.

[0069] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (10) 0.050 < Np2-Nn2 < 0.400 however, Np2: Refractive index of the positive lens that makes up the second cemented lens Nn2: Refractive index of the negative lens that makes up the second cemented lens

[0070] Condition (10) satisfies the relationship between the refractive index of the positive lens constituting the second cemented lens and the refractive index of the negative lens constituting the second cemented lens. difference The optical system of this embodiment has a second cemented lens that satisfies conditional expression (10), and thus can appropriately correct the Petzval sum.

[0071] In the optical system of this embodiment, if the value of conditional expression (10) exceeds the upper limit, the refractive power at the cemented surface of the second cemented lens becomes too strong, causing large aberrations.

[0072] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (10) to 0.400. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (10) to 0.350, and more preferably 0.300.

[0073] Furthermore, in the optical system of this embodiment, if the value of conditional expression (10) falls below the lower limit, the second cemented lens cannot adequately correct the Petzval sum, and curvature of field occurs.

[0074] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (10) to 0.050. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (10) to 0.060, or even 0.070.

[0075] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (11) 3.000 < νdp2-νdn2 < 30.000 however, νdp2: Abbe number based on the d-line of the positive lens that makes up the second cemented lens νdn2: Abbe number based on the d-line of the negative lens that makes up the second cemented lens

[0076] Conditional expression (11) defines the difference between the Abbe number, based on the d-line, of the positive lens constituting the second cemented lens and the Abbe number, based on the d-line, of the negative lens constituting the second cemented lens. By satisfying conditional expression (11), the optical system of this embodiment can appropriately correct chromatic aberration by the second cemented lens.

[0077] In the optical system of this embodiment, if the value of conditional expression (11) exceeds the upper limit, the correction of chromatic aberration by the second cemented lens becomes excessive.

[0078] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit value of conditional expression (11) to 30,000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit value of conditional expression (11) to 25,000, or even 20,000.

[0079] Furthermore, in the optical system of this embodiment, if the value of conditional expression (11) is below the lower limit, the correction of chromatic aberration by the second cemented lens will be insufficient.

[0080] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the lower limit of conditional expression (11) to 3.000. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (11) to 4.500, or even 5.000.

[0081] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (12) 0.550 < (ΣΔPzi) / ΔPz < 1.400 however, ΣΔPzi: The sum of the Petzval sum of at least one cemented lens in the rear group, which is made up of a positive lens and a negative lens, and the reciprocal of the composite focal length of the cemented lens. ΔPz: The sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system

[0082] Conditional expression (12) defines the ratio of the sum of the Petzval sum of at least one cemented lens included in the rear group, the cemented lens being composed of a positive lens and a negative lens, and the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the cemented lens to the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system. In conditional expression (12), the numerator represents the corrective power of the Petzval sum of the cemented lens, and the denominator represents the corrective power of the Petzval sum of the entire optical system. By satisfying conditional expression (12), the optical system of this embodiment can appropriately correct field curvature using the cemented lens.

[0083] In the optical system of this embodiment, if the value of conditional expression (12) exceeds the upper limit, the correction of field curvature by the cemented lens becomes excessive.

[0084] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (12) to 1.400. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (12) to 1.200, or even 1.100.

[0085] Furthermore, in the optical system of this embodiment, if the value of conditional expression (12) falls below the lower limit, the correction of field curvature by the cemented lens will be insufficient.

[0086] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (12) to 0.550. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (12) to 0.800, or even 0.950.

[0087] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (13) 0.525 < ΣD / TL < 0.967 however, ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane TL: Distance from the lens surface closest to the object to the image plane

[0088] Conditional expression (13) defines the ratio between the distance from the lens surface closest to the object to the lens surface closest to the image plane and the distance from the lens surface closest to the object to the image plane. By satisfying conditional expression (13), the optical system of this embodiment can ensure an appropriate back focal length while enabling the arrangement of lenses necessary to correct various aberrations.

[0089] In the optical system of this embodiment, if the value of conditional expression (13) exceeds the upper limit, the back focus becomes too short, making it difficult to place filters in front of the image sensor.

[0090] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit of conditional expression (13) to 0.967. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit of conditional expression (13) to 0.850, or more preferably 0.775.

[0091] Furthermore, in the optical system of this embodiment, if the value of conditional expression (13) falls below the lower limit, it becomes difficult to arrange the lenses necessary to correct various aberrations.

[0092] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (13) to 0.525. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (13) to 0.600, and more preferably 0.675.

[0093] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (14) 0.050 < dL1_St / TL < 0.167 however, dL1_St: Distance from the lens surface closest to the object to the aperture stop TL: Distance from the lens surface closest to the object to the image plane

[0094] Conditional expression (14) defines the ratio between the distance from the lens surface closest to the object to the aperture stop and the distance from the lens surface closest to the object to the image plane. By satisfying conditional expression (14), the optical system of this embodiment can appropriately correct spherical aberration while suppressing shading at the image sensor.

[0095] In the optical system of this embodiment, if the value of conditional expression (14) exceeds the upper limit, the exit pupil position becomes close to the image plane, causing shading at the image sensor.

[0096] In the optical system of this embodiment, the effect of this embodiment can be more reliably achieved by setting the upper limit of conditional expression (14) to 0.167. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (14) to 0.145, and more preferably 0.130.

[0097] Furthermore, in the optical system of this embodiment, if the value of conditional expression (14) falls below the lower limit, the optical system before the aperture stop cannot sufficiently correct aberrations, making it difficult to correct spherical aberrations.

[0098] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (14) to 0.050. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (14) to 0.055, and more preferably 0.070.

[0099] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (15) 0.750 < TL / f < 1.600 however, TL: Distance from the lens surface closest to the object to the image plane f: focal length of the entire optical system

[0100] Conditional expression (15) defines the ratio of the distance from the lens surface closest to the object to the image plane to the focal length of the entire optical system. By satisfying conditional expression (15), the optical system of this embodiment can suppress an increase in the overall length of the optical system, suppress shading at the image sensor, and appropriately correct various aberrations.

[0101] In the optical system of this embodiment, if the value of conditional expression (15) exceeds the upper limit, the overall length of the optical system becomes too long. Also, the focal length becomes too short for the overall length, and the focal length of each lens group becomes short, making it difficult to correct coma and spherical aberration.

[0102] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit of conditional expression (15) to 1.600. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit of conditional expression (15) to 1.500, or even 1.450.

[0103] Furthermore, in the optical system of this embodiment, if the value of conditional expression (15) is below the lower limit, the overall length of the optical system becomes too short, making it difficult to appropriately position lenses for correcting various aberrations. Also, the exit pupil position becomes close to the image plane, causing shading at the image sensor.

[0104] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the lower limit of conditional expression (15) to 0.750. In order to further ensure the effect of this embodiment, it is preferable to set the lower limit of conditional expression (15) to 0.900, or even 1.100.

[0105] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (16) 0.590 < TLs / TL < 1.333 however, TLs: Distance from the aperture stop to the image plane TL: Distance from the lens surface closest to the object to the image plane

[0106] Conditional expression (16) defines the ratio between the distance from the aperture stop surface to the image plane and the distance from the lens surface closest to the object to the image plane. By satisfying conditional expression (16), the optical system of this embodiment can appropriately correct spherical aberration while suppressing shading at the image sensor.

[0107] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (16) to 1.333. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (16) to 1.150, or more preferably 0.950.

[0108] Furthermore, in the optical system of this embodiment, if the value of conditional expression (16) falls below the lower limit, the exit pupil position becomes close to the image plane, causing shading at the image sensor.

[0109] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (16) to 0.590. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (16) to 0.625, or even 0.750.

[0110] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (17) 0.700 < f1 / f < 5.000 however, f1: focal length of the first lens group f: focal length of the entire optical system

[0111] Conditional expression (17) defines the ratio between the focal length of the first lens group and the focal length of the entire optical system. By satisfying conditional expression (17), the optical system of this embodiment can suppress the occurrence of various aberrations such as spherical aberration and coma while suppressing an increase in the overall length of the optical system.

[0112] In the optical system of this embodiment, if the value of conditional expression (17) exceeds the upper limit, the positive refractive power of the first lens group becomes weak, and the overall length of the optical system becomes too long.

[0113] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit of conditional expression (17) to 5.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (17) to 4.800, or even 4.650.

[0114] Furthermore, in the optical system of this embodiment, if the value of conditional expression (17) falls below the lower limit, the positive refractive power of the first lens group becomes too strong, and various aberrations such as spherical aberration and coma tend to occur.

[0115] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (17) to 0.700. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (17) to 1.000, or even 1.400.

[0116] In the optical system of this embodiment, it is preferable that the first lens group has one or two lenses.

[0117] In the optical system of this embodiment, when the first lens group has three or more lenses, the overall length of the optical system increases. Also, since the aperture stop plane is positioned closer to the image plane, the exit pupil becomes shorter, making shading more likely to occur at the image sensor.

[0118] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (18) 0.010 < D1 / TL < 0.150 however, D1: The distance from the lens surface in the first lens group closest to the object to the lens surface in the first lens group closest to the image plane TL: Distance from the lens surface closest to the object to the image plane

[0119] Conditional expression (18) defines the ratio between the distance from the lens surface in the first lens group closest to the object to the lens surface in the first lens group closest to the image plane and the distance from the lens surface closest to the object to the image plane. By satisfying conditional expression (18), the optical system of this embodiment can appropriately correct coma while suppressing an increase in the overall length of the optical system.

[0120] In the optical system of this embodiment, if the value of conditional expression (18) exceeds the upper limit, the thickness of the first lens group increases, and the overall length of the optical system becomes too large.

[0121] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (18) to 0.150. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (18) to 0.130, and more preferably 0.110.

[0122] Furthermore, in the optical system of this embodiment, if the value of conditional expression (18) falls below the lower limit, the thickness of the first lens group becomes small, making it difficult to correct coma.

[0123] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (18) to 0.010. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (18) to 0.020, or even 0.025.

[0124] Moreover, the optical system of this embodiment is preferably made up of six or more and nine or less lenses.

[0125] If the optical system of this embodiment is configured with more than nine lenses, the total lens thickness increases, and the overall length of the optical system increases. Also, if the optical system of this embodiment is configured with fewer than six lenses, it becomes difficult to appropriately correct various aberrations.

[0126] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (19) 0.025 < t1 / ΣD < 0.080 however, t1: Center thickness of the lens closest to the object ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

[0127] Conditional expression (19) defines the ratio of the center thickness of the lens closest to the object to the distance from the lens surface closest to the object to the lens surface closest to the image plane. By satisfying conditional expression (19), the optical system of this embodiment can appropriately correct coma while suppressing shading at the image sensor.

[0128] In the optical system of this embodiment, if the value of conditional expression (19) exceeds its upper limit, the central thickness of the lens closest to the object becomes large and the position of the aperture stop surface becomes closer to the image plane, which shortens the exit pupil and makes shading more likely to occur at the image sensor.

[0129] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (19) to 0.080. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (19) to 0.070.

[0130] Furthermore, in the optical system of this embodiment, if the value of conditional expression (19) falls below the lower limit, the center thickness of the lens closest to the object becomes small, making it difficult to correct coma.

[0131] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (19) to 0.025. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (19) to 0.030, and more preferably 0.035.

[0132] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (20) -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, rR1: Radius of curvature of the object-side lens surface of the lens closest to the image plane rR2: Radius of curvature of the lens surface closest to the image plane

[0133] Conditional expression (20) defines the shape factor of the lens closest to the image plane. By satisfying conditional expression (20), the optical system of this embodiment can appropriately suppress the occurrence of field curvature.

[0134] In the optical system of this embodiment, if the value of conditional expression (20) exceeds the upper limit, the angle of incidence on the object-side lens surface of the lens closest to the image plane becomes large, making field curvature more likely to occur.

[0135] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (20) to -1.500. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (20) to -1.800, or even -2.000.

[0136] Furthermore, in the optical system of this embodiment, if the value of conditional expression (20) is below the lower limit, the angle of incidence on the image-side lens surface of the lens closest to the image side becomes large, making it more likely that curvature of field will occur.

[0137] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (20) to -4.500. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (20) to -4.000, or even -3.000.

[0138] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (21) 0.130 < tR / ΣD < 0.350 however, tR: Center thickness of the lens closest to the image plane ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

[0139] Conditional expression (21) defines the ratio of the center thickness of the lens closest to the image plane to the distance from the lens surface closest to the object plane to the lens surface closest to the image plane. By satisfying conditional expression (21), the optical system of this embodiment can suppress shading at the image sensor while suppressing an increase in the overall length of the optical system.

[0140] In the optical system of this embodiment, if the value of conditional expression (21) exceeds the upper limit, the overall length of the optical system becomes too large.

[0141] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (21) to 0.350. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (21) to 0.300, and more preferably 0.270.

[0142] Furthermore, in the optical system of this embodiment, if the value of conditional expression (21) falls below the lower limit, the central thickness of the lens closest to the image plane will be small and the positive refractive power will be weak, so the position of the exit pupil will be close to the image plane and shading will be more likely to occur at the image sensor.

[0143] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (21) to 0.130. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (21) to 0.150, or even 0.180.

[0144] Furthermore, in the optical system of this embodiment, it is preferable that the rear group comprises, in order from the object side, a second lens group, a third lens group having negative refractive power, and a fourth lens group, the third lens group having, closest to the object side, a negative meniscus lens with its concave surface facing the object side that is located closer to the image plane than the aperture stop, and the fourth lens group is composed of a positive lens.

[0145] With the optical system of this embodiment, by having such a configuration, it is possible to effectively correct field curvature while increasing the distance between the exit pupil and the image plane.

[0146] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (22) 0.300 < (-f3) / f < 2.200 however, f3: focal length of the third lens group f: focal length of the entire optical system

[0147] Conditional Expression ( 22 ) defines the ratio between the focal length of the third lens group and the focal length of the entire optical system. By satisfying conditional expression (22), the optical system of this embodiment can appropriately correct various aberrations, such as sagittal coma and field curvature, while suppressing an increase in the overall length of the optical system.

[0148] In the optical system of this embodiment, if the value of conditional expression (22) exceeds the upper limit, the overall length of the optical system becomes too long, and it becomes difficult to set the exit pupil at an appropriate position.

[0149] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (22) to 2.200. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (22) to 1.600, or more preferably 1.300.

[0150] Furthermore, in the optical system of this embodiment, if the value of conditional expression (22) falls below the lower limit, the refractive power of the third lens group becomes too strong, making it difficult to correct various aberrations such as sagittal coma and field curvature.

[0151] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (22) to 0.300. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (22) to 0.450, or even 0.750.

[0152] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (23) 0.450 < f4 / f < 2.300 however, f4: focal length of the fourth lens group f: focal length of the entire optical system

[0153] Conditional expression (23) defines the ratio between the focal length of the fourth lens group and the focal length of the entire optical system. By satisfying conditional expression (23), the optical system of this embodiment can suppress shading at the image sensor while preventing an increase in the overall length of the optical system.

[0154] In the optical system of this embodiment, if the value of conditional expression (23) exceeds the upper limit, the position of the exit pupil becomes close to the image plane, making it easier for shading to occur at the image sensor and also making it difficult to correct the Petzval sum.

[0155] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit of conditional expression (23) to 2.300. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit of conditional expression (23) to 1.680, or more preferably 1.500.

[0156] Furthermore, in the optical system of this embodiment, if the value of conditional expression (23) falls below the lower limit, the overall length of the optical system becomes too large.

[0157] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (23) to 0.450. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (23) to 0.650, or even 1.000.

[0158] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (24) 0.286 < (-f3) / f4 < 2.000 however, f3: focal length of the third lens group f4: focal length of the fourth lens group

[0159] Conditional expression (24) defines the ratio between the focal length of the third lens group and the focal length of the fourth lens group. By satisfying conditional expression (24), the optical system of this embodiment can appropriately correct various aberrations such as field curvature and coma by the third lens group and the fourth lens group.

[0160] In the optical system of this embodiment, if the value of conditional expression (24) exceeds the upper limit, the refractive power of the third lens group becomes too strong, making it difficult to correct various aberrations such as curvature of field and coma.

[0161] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit of conditional expression (24) to 2.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (24) to 1.500, and more preferably 1.350.

[0162] Furthermore, in the optical system of this embodiment, if the value of conditional expression (24) falls below the lower limit, the refractive power of the fourth lens group becomes too strong, making it difficult to correct various aberrations such as curvature of field and coma.

[0163] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (24) to 0.286. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (24) to 0.350, or even 0.600.

[0164] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (25) 0.300 < f2 / f < 2.000 however, f2: focal length of the second lens group f: focal length of the entire optical system

[0165] Conditional expression (25) defines the ratio between the focal length of the second lens group and the focal length of the entire optical system. By satisfying conditional expression (25), the optical system of this embodiment can effectively correct curvature of field and effectively correct coma so that it does not vary from color to color.

[0166] In the optical system of this embodiment, if the value of conditional expression (25) exceeds the upper limit, the Petzval sum cannot be maintained at an appropriate value, making it difficult to satisfactorily correct the curvature of field.

[0167] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (25) to 2.000. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (25) to 1.800, or even 1.500.

[0168] Furthermore, in the optical system of this embodiment, if the value of conditional expression (25) falls below the lower limit, it becomes difficult to suppress the coma aberration for each color so that it does not vary.

[0169] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (25) to 0.300. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (25) to 0.500, or even 0.700.

[0170] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (26) 1.500 < (r312+r311) / (r312-r311) < 7.000 however, r311: Radius of curvature of the object-side lens surface of the lens closest to the object in the third lens group r312: Radius of curvature of the image-side lens surface of the lens closest to the object in the third lens group

[0171] Conditional expression (26) defines the shape factor of the lens in the third lens group closest to the object. By satisfying conditional expression (26), the optical system of this embodiment can appropriately suppress the occurrence of curvature of field.

[0172] In the optical system of this embodiment, if the value of conditional expression (26) exceeds the upper limit or falls below the lower limit, the deflection angle becomes too large for off-axis light beams, making field curvature more likely to occur.

[0173] In the optical system of this embodiment, the effect of this embodiment can be further ensured by setting the upper limit of conditional expression (26) to 7.000. In order to further ensure the effect of this embodiment, it is preferable to set the upper limit of conditional expression (26) to 5.000, or even 3.000.

[0174] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (26) to 1.500. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (26) to 1.700, or even 2.000.

[0175] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (27) 0.150 < d3 / f < 0.750 however, d3: Distance from the aperture stop to the lens surface in the third lens group closest to the object f: focal length of the entire optical system

[0176] Conditional expression (27) defines the ratio of the distance from the aperture stop to the lens surface in the third lens group closest to the object to the focal length of the entire optical system. By satisfying conditional expression (27), the optical system of this embodiment can suppress shading at the image sensor while suppressing an increase in the overall length of the optical system.

[0177] In the optical system of this embodiment, if the value of conditional expression (27) exceeds the upper limit, the overall length of the optical system becomes too large.

[0178] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (27) to 0.750. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (27) to 0.700, or more preferably 0.650.

[0179] Furthermore, in the optical system of this embodiment, if the value of conditional expression (27) falls below the lower limit, the position of the exit pupil becomes close to the image plane, making shading more likely to occur at the image sensor.

[0180] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (27) to 0.150. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (27) to 0.200, or even 0.250.

[0181] In the optical system of this embodiment, it is preferable to satisfy the following conditional expression: (28) 0.400 < dL1_Gr3 / ΣD < 0.900 however, dL1_Gr3: distance from the lens surface closest to the object to the lens surface closest to the object in the third lens group ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

[0182] Conditional expression (28) defines the ratio between the distance from the lens surface closest to the object to the lens surface closest to the object in the third lens group and the distance from the lens surface closest to the object to the lens surface closest to the image plane. By satisfying conditional expression (28), the optical system of this embodiment can suppress shading at the image sensor while suppressing an increase in the overall length of the optical system.

[0183] In the optical system of this embodiment, if the value of conditional expression (28) exceeds the upper limit, the overall length of the optical system becomes too large.

[0184] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the upper limit value of conditional expression (28) to 0.900. In order to make the effect of this embodiment more certain, it is preferable to set the upper limit value of conditional expression (28) to 0.850, and more preferably 0.800.

[0185] Furthermore, in the optical system of this embodiment, if the value of conditional expression (28) falls below the lower limit, the position of the exit pupil becomes close to the image plane, making shading more likely to occur at the image sensor.

[0186] In the optical system of this embodiment, the effect of this embodiment can be made more certain by setting the lower limit of conditional expression (28) to 0.400. In order to make the effect of this embodiment more certain, it is preferable to set the lower limit of conditional expression (28) to 0.450, or even 0.500.

[0187] With the above configuration, it is possible to realize an optical system that is small in size and has good imaging performance.

[0188] The optical device of this embodiment has the optical system configured as described above, which makes it possible to realize an optical device with excellent optical performance.

[0189] The method for manufacturing an optical system according to this embodiment is a method for manufacturing an optical system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, where the rear group has a first cemented lens composed of a positive lens and a negative lens, and the lenses are arranged so as to satisfy both of the following conditional expressions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: Refractive index of the positive lens that makes up the first cemented lens Nn1: Refractive index of the negative lens that makes up the first cemented lens

[0190] The method for manufacturing an optical system according to this embodiment is a method for manufacturing an optical system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, where the rear group has a first cemented lens composed of a positive lens and a negative lens, and the lenses are arranged so as to satisfy both of the following conditional expressions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane tp1: Thickness of the positive lens in the first cemented lens on the optical axis tn1: Thickness of the negative lens that makes up the first cemented lens on the optical axis

[0191] The method for manufacturing an optical system according to this embodiment is a method for manufacturing an optical system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, where the rear group has a first cemented lens composed of a positive lens and a negative lens, and the lenses are arranged so as to satisfy both of the following conditional expressions: (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 however, f: focal length of the entire optical system y: Maximum image height t1: Center thickness of the positive lens located closest to the object

[0192] By using such a method for manufacturing an optical system, an optical system having good optical performance can be manufactured.

[0193] (Numerical example) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0194] (First Example) FIG. 1 is a cross-sectional view of the optical system of the first embodiment when focusing on an object at infinity.

[0195] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power.

[0196] The first lens group G1 is made up of a positive meniscus lens L1 with its convex surface facing the object side.

[0197] The second lens group G2 consists of, in order from the object side, a cemented positive lens consisting of a biconcave negative lens L2 and a biconvex positive lens L3, a cemented positive lens consisting of a biconvex positive lens L4 and a biconcave negative lens L5, and a meniscus positive lens L6 with its concave surface facing the object side.

[0198] The third lens group G3 is made up of a negative meniscus lens L7 with its concave surface facing the object side.

[0199] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object side. The positive lens L8 is constructed by providing a resin layer on the object-side surface of a glass lens body. The positive lens L8 is a composite aspherical lens in which the object-side surface of the resin layer is aspherical. In the "Lens Specifications" described below, surface number 14 indicates the object-side surface of the resin layer, surface number 15 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the resin layer and the lens body are cemented), and surface number 16 indicates the image-side surface of the lens body. In this embodiment, the composite aspherical lens is treated as a single aspherical lens. Therefore, the surface with surface number 14 corresponds to the object-side lens surface of the positive lens L8, and the sum of the surface spacings of surface numbers 14 and 15 corresponds to the center thickness of the positive lens L8.

[0200] On the image plane I, an image pickup element (not shown) made up of a CCD, a CMOS, or the like is disposed.

[0201] The optical system of this embodiment focuses by moving the entire optical system along the optical axis. When the optical system of this embodiment is focused on an object at close range from an infinity focused state, it is moved from the image plane side to the object side.

[0202] In the optical system of this embodiment, the second lens group G2, the third lens group, and the fourth lens group correspond to the rear group, the cemented positive lens consisting of the negative lens L2 and the positive lens L3 corresponds to the first cemented lens, and the cemented positive lens consisting of the positive lens L4 and the negative lens L5 corresponds to the second cemented lens.

[0203] Table 1 below lists the specifications of the optical system of this example. In the [Lens specifications] in Table 1, m is the order of the optical surface counted from the object side, r is the radius of curvature, d is the surface spacing, n(d) is the refractive index for the d-line (wavelength 587.6 nm), and vd is the Abbe number for the d-line. A radius of curvature of r=∞ indicates a flat surface. Additionally, in the [Lens specifications], an optical surface marked with an "*" is an aspherical surface.

[0204] In the [aspherical surface data], m indicates the optical surface corresponding to the aspherical surface data, K indicates the conic constant, and A4 to A18 indicate the aspherical surface coefficients.

[0205] The aspherical surface is expressed by the following formula (a), where y is the height in the direction perpendicular to the optical axis, S(y) is the distance (amount of sag) along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface, r is the radius of curvature (paraxial radius of curvature) of the reference spherical surface, K is the conic constant, and An is the n-th order aspherical coefficient. In each example, the second order aspherical coefficient A2 is 0. Also, "En" is expressed as "×10 -n " indicates.

[0206] (a) S(y) = (y 2 / r) / { 1 + (1-K×y 2 / r 2 ) 1 / 2} + A4×y 4 + A6×y 6 + A8×y8 + A10×y 10 + A12×y 12 + A14×y 14 + A16×y 16 + A18×y 18

[0207] In the [Overall Specifications] section of Table 1, f is the focal length of the entire optical system, F.NO is the F-number of the optical system, ω is the half angle of view (degrees), Y is the maximum image height, and TL is the distance from the lens surface closest to the object to the image plane when focusing on an object at infinity.

[0208] In the [Back Focus] section of Table 1, Bf indicates the back focus in terms of the air-equivalent length of the optical system.

[0209] The units of focal length f, radius of curvature r, and other lengths listed in Table 1 are "mm." However, this is not limited to this, as the same optical performance can be obtained even when the optical system is proportionally enlarged or reduced.

[0210] The symbols in Table 1 described above will be used in the same manner in tables of other embodiments described later.

[0211] (Table 1) [Lens specifications] mrdn(d) νd * 1) 11.70227 1.270 1.58913 61.1 2) 13.38340 1.620 3> ∞ 1.590 (aperture stop) 4) -37.93400 0.700 1.59270 35.3 5) 11.35394 2.800 1.88300 40.7 6) -46.90284 0.310 7) 58.38846 3.870 1.81600 46.6 8) -8.93495 0.700 1.62004 36.4 9) 39.69665 2.920 *10) -9.52831 1.100 1.58313 59.5 *11) -9.47003 2.170 12) -9.36192 1.000 1.75520 27.6 13) -25.39515 0.710 *14) -45.86660 0.100 1.56093 36.6 15) -59.69914 6.530 1.88300 40.7 16) -18.98009 Bf [Aspherical surface] m 1) 10) 11) 14) K 1.0000 0.2964 1.0000 1.0000 A4 -6.30E-05 -1.07E-04 1.94E-04 4.28E-05 A6 -1.02E-06 1.09E-05 9.62E-06 -3.34E-07 A8 -1.93E-08 -1.04E-07 1.86E-08 1.25E-09 A10 -6.74E-09 -3.79E-09 -3.20E-12 A12 1.76E-10 3.78E-11 3.14E-15 A14 8.59E-14 A16 -9.66E-14 A18 1.31E-15 [All Yuan] f 26.78 F.No. 2.90 ω 40.30 Y 21.05 TL 38.15 [Focus distance of each group] Group initial focal distance G1 1 123.54 G2 4 20.55 G3 12 -20.18 G4 14 31.47 [Back focus] When focusing on infinity When focusing on a short distance object Bf 10.760 15.873

[0212] FIG. 2 is a diagram showing various aberrations of the optical system of the first example when focusing on an object at infinity.

[0213] In each aberration diagram, FNO indicates the F-number, and Y indicates the image height. More specifically, spherical aberration diagrams indicate the F-number value corresponding to the maximum aperture, astigmatism diagrams and distortion diagrams indicate the maximum image height, and coma diagrams indicate the value of each image height. d indicates the d-line, and g indicates the g-line (wavelength 435.8 nm). In astigmatism diagrams, the solid line indicates the sagittal image plane, and the dashed line indicates the meridional image plane. The same symbols as those used in the aberration diagrams of this embodiment are used in the aberration diagrams of other embodiments described below.

[0214] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0215] (Second Example) FIG. 3 is a cross-sectional view of the optical system of the second embodiment when focusing on an object at infinity.

[0216] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power.

[0217] The first lens group G1 is made up of a positive meniscus lens L1 with its convex surface facing the object side.

[0218] The second lens group G2 consists of, in order from the object side, a cemented positive lens of a biconcave negative lens L2 and a biconvex positive lens L3, a cemented positive lens of a biconvex positive lens L4 and a biconcave negative lens L5, and a meniscus negative lens L6 with its concave surface facing the object side.

[0219] The third lens group G3 is made up of a negative meniscus lens L7 with its concave surface facing the object side.

[0220] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object side. The positive lens L8 is constructed by providing a resin layer on the object-side surface of a glass lens body. The positive lens L8 is a hybrid aspherical lens in which the object-side surface of the resin layer is aspherical. In the Lens Specifications section described below, surface number 14 indicates the object-side surface of the resin layer, surface number 15 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the resin layer and the lens body are cemented), and surface number 16 indicates the image-side surface of the lens body. Surface number 14 corresponds to the object-side lens surface of the positive lens L8, and the sum of the surface spacings of surface numbers 14 and 15 corresponds to the center thickness of the positive lens L8.

[0221] On the image plane I, an image pickup element (not shown) made up of a CCD, a CMOS, or the like is disposed.

[0222] The optical system of this embodiment focuses by moving the entire optical system along the optical axis. When the optical system of this embodiment is focused on an object at close range from an infinity focused state, it is moved from the image plane side to the object side.

[0223] In the optical system of this embodiment, the second lens group G2, the third lens group, and the fourth lens group correspond to the rear group, the cemented positive lens formed by the negative lens L2 and the positive lens L3 corresponds to the first cemented lens, and the cemented positive lens formed by the positive lens L4 and the negative lens L5 corresponds to the second cemented lens.

[0224] Table 2 below lists the specifications of the optical system of this example.

[0225] (Table 2) [Lens specifications] mrdn(d) νd * 1) 10.67194 1.037 1.82098 42.5 2) 12.50984 1.628 3> ∞ 1.687 (aperture stop) 4) -60.66908 0.700 1.59270 35.3 5) 10.07412 2.912 1.88300 40.7 6) -113.20557 0.639 7) 88.89249 3.144 1.88300 40.7 8) -8.19957 0.700 1.71736 29.6 9) 59.76467 2.873 *10) -12.75253 1.100 1.82098 42.5 11) -14.76677 2.007 12) -8.77600 1.100 1.68376 37.6 13) -17.99477 0.638 *14) -36.55640 0.100 1.56093 36.6 15) -42.98427 5.955 1.84850 43.8 16) -17.28034 Bf [Aspherical surface] m 1) 10) 14) K 1.0000 0.2964 1.0000 A4 -4.34E-05 -2.20E-04 3.68E-05 A6 3.34E-08 -4.66E-06 -1.50E-07 A8-2.62E-08 2.34E-07 1.39E-10 A10 -1.44E-08 A12 3.40E-10 A14 -3.50E-12 [All Yuan] f 26.78 F.No. 2.90 ω 40.30 Y 21.05 TL 36.67 [Focus distance of each group] Group initial focal distance G1 1 70.54 G2 4 26.69 G3 12 -26.33 G4 14 32.68 [Back focus] When focusing on infinity When focusing on a short distance object Bf 10.454 15.521

[0226] FIG. 4 is a diagram showing various aberrations of the optical system of the second example when focusing on an object at infinity.

[0227] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0228] (Third Example) FIG. 5 is a cross-sectional view of the optical system of the third embodiment when focusing on an object at infinity.

[0229] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power.

[0230] The first lens group G1 is made up of a positive meniscus lens L1 with its convex surface facing the object side.

[0231] The second lens group G2 consists of, in order from the object side, a cemented positive lens of a biconcave negative lens L2 and a biconvex positive lens L3, a cemented positive lens of a biconvex positive lens L4 and a biconcave negative lens L5, and a meniscus negative lens L6 with its concave surface facing the object side.

[0232] The third lens group G3 is made up of a negative meniscus lens L7 with its concave surface facing the object side.

[0233] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object side. The positive lens L8 is constructed by providing a resin layer on the object-side surface of a glass lens body. The positive lens L8 is a hybrid aspherical lens in which the object-side surface of the resin layer is aspherical. In the Lens Specifications section described below, surface number 14 indicates the object-side surface of the resin layer, surface number 15 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the resin layer and the lens body are cemented), and surface number 16 indicates the image-side surface of the lens body. Surface number 14 corresponds to the object-side lens surface of the positive lens L8, and the sum of the surface spacings of surface numbers 14 and 15 corresponds to the center thickness of the positive lens L8.

[0234] On the image plane I, an image pickup element (not shown) made up of a CCD, a CMOS, or the like is disposed.

[0235] The optical system of this embodiment focuses by moving the entire optical system along the optical axis. When the optical system of this embodiment is focused on an object at close range from an infinity focused state, it is moved from the image plane side to the object side.

[0236] In the optical system of this embodiment, the second lens group G2, the third lens group, and the fourth lens group correspond to the rear group, the cemented positive lens formed by the negative lens L2 and the positive lens L3 corresponds to the first cemented lens, and the cemented positive lens formed by the positive lens L4 and the negative lens L5 corresponds to the second cemented lens.

[0237] Table 3 below lists the specifications of the optical system of this example.

[0238] (Table 3) [Lens specifications] mrdn(d) νd * 1) 9.53357 1.234 1.84737 43.7 2) 11.38114 1.618 3> ∞ 1.824 (aperture stop) 4) -32.65502 0.700 1.59270 35.3 5) 11.50292 2.500 1.85108 40.1 6) -57.90288 0.554 7) 162.74756 4.035 1.85108 40.1 8) -7.11488 0.700 1.70461 29.8 9) 86.79392 3.674 10) -6.26321 1.100 1.58286 59.5 11) -7.61044 2.220 12) -9.63075 1.100 1.77002 31.4 13) -12.85267 0.100 14) -35.01849 0.050 1.56093 36.6 15) -49.83022 4.810 1.88300 40.7 16) -20.81236 Bf [Aspherical surface] m 1) 6) 7) 10) 11) 14) K 1.0000 1.0000 1.0000 0.7304 0.7541 1.0000 A4 -1.27E-05 1.09E-04 1.24E-05 4.58E-04 4.96E-04 5.10E-05 A6 3.13E-07 1.33E-07 -6.29E-07 1.28E-05 6.00E-06 -1.80E-07 A8 -1.19E-08 -2.59E-08 -6.17E-08 2.27E-08 2.18E-07 2.62E-10 A10 2.87E-09 -8.22E-09 A12 -1.91E-10 9.94E-11 A14 3.13E-12 -3.49E-13 [All Yuan] f 26.78 F.No. 2.90 ω 40.20 Y 21.05 TL 36.68 [Focal length data for each group] Group starting plane focal length G1 1 53.05 G2 4 39.61 G3 12 -58.60 G4 14 44.64 [Back focus] When focusing on infinity When focusing on a short distance object Bf 10.455 15.515

[0239] FIG. 6 is a diagram showing various aberrations of the optical system of the third example when focusing on an object at infinity.

[0240] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0241] (Fourth Example) FIG. 7 is a cross-sectional view of the optical system of the fourth embodiment when focusing on an object at infinity.

[0242] The optical system of this embodiment has, in order from the object side, a first lens group G1 having positive refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power.

[0243] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L1 with a convex surface facing the object side, and a negative meniscus lens L2 with a convex surface facing the object side.

[0244] The second lens group G2 consists of, in order from the object side, a cemented positive lens consisting of a meniscus positive lens L3 with a concave surface facing the object side and a meniscus negative lens L4 with a concave surface facing the object side, and a cemented negative lens consisting of a meniscus positive lens L5 with a concave surface facing the object side and a biconcave negative lens L6.

[0245] The third lens group G3 is made up of a negative meniscus lens L7 with its concave surface facing the object side.

[0246] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object side. The positive lens L8 is constructed by providing a resin layer on the object-side surface of a glass lens body. The positive lens L8 is a hybrid aspherical lens in which the object-side surface of the resin layer is aspherical. In the Lens Specifications section described below, surface number 14 indicates the object-side surface of the resin layer, surface number 15 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the resin layer and the lens body are cemented), and surface number 16 indicates the image-side surface of the lens body. Surface number 14 corresponds to the object-side lens surface of the positive lens L8, and the sum of the surface spacings of surface numbers 14 and 15 corresponds to the center thickness of the positive lens L8.

[0247] On the image plane I, an image pickup element (not shown) made up of a CCD, a CMOS, or the like is disposed.

[0248] The optical system of this embodiment focuses by moving the entire optical system along the optical axis. When the optical system of this embodiment is focused on an object at close range from an infinity focused state, it is moved from the image plane side to the object side.

[0249] In the optical system of this embodiment, the second lens group G2, the third lens group, and the fourth lens group correspond to the rear group, the cemented positive lens of the positive lens L3 and the negative lens L4 corresponds to the first cemented lens, and the cemented negative lens of the positive lens L5 and the negative lens L6 corresponds to the second cemented lens.

[0250] Table 4 below lists the specifications of the optical system of this example.

[0251] (Table 4) [Lens specifications] mrdn(d) νd 1) 13.45109 1.290 2.00100 29.1 2) 21.21240 0.591 3) 2035.86690 0.700 1.78472 25.6 4) 48.46055 0.798 5> ∞ 1.622 (aperture stop) * 6) -1428.55530 2.259 1.85108 40.1 7) -9.49007 1.191 1.78472 25.6 8) -23.19148 0.450 9) -59.94728 3.500 1.88300 40.7 10) -7.48584 0.900 1.59270 35.3 11) 23.19209 5.633 12) -7.56291 1.100 1.66382 27.4 13) -15.31415 0.100 *14) -52.50435 0.050 1.56093 36.6 15) -52.50435 6.616 1.88300 40.7 16) -17.80787 Bf [Aspherical data] m 6) 14) K 1.0000 1.0000 A4 -2.16E-04 -1.19E-05 A6 2.74E-06 1.34E-08 A8 -1.55E-07 -1.59E-11 A10 3.48E-13 [Overall specifications] f 25.75 F.No 2.90 ω 41.70 Y 20.70 TL 36.46 [Focal length data for each group] Group starting plane focal length G1 1 67.07 G2 6 25.70 G3 12 -23.86 G4 14 28.00 [Back focus] When focusing on infinity When focusing on a short distance object Bf 9.655 14.259

[0252] FIG. 8 is a diagram showing various aberrations of the optical system of the fourth example when focused on an object at infinity.

[0253] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0254] (Fifth Example) FIG. 9 is a cross-sectional view of the optical system of the fifth embodiment when focusing on an object at infinity.

[0255] The optical system of this embodiment has, in order from the object side, a first lens group G1 having negative refractive power, an aperture stop S, a second lens group G2 having positive refractive power, a third lens group G3 having negative refractive power, and a fourth lens group G4 having positive refractive power.

[0256] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L1 with a convex surface facing the object side, and a negative meniscus lens L2 with a convex surface facing the object side.

[0257] The second lens group G2 is composed of a cemented positive lens consisting of a biconvex positive lens L3 and a biconcave negative lens L4.

[0258] The third lens group G3 is composed of, in order from the object side, a negative meniscus lens L5 with its concave surface facing the object side, and a negative biconcave lens L6.

[0259] The fourth lens group G4 consists of a meniscus-shaped positive lens L7 with its concave surface facing the object side. The positive lens L7 is constructed by providing a resin layer on the object-side surface of a glass lens body. The positive lens L7 is a hybrid aspherical lens in which the object-side surface of the resin layer is aspherical. In the Lens Specifications section described below, surface number 13 indicates the object-side surface of the resin layer, surface number 14 indicates the image-side surface of the resin layer and the object-side surface of the lens body (the surface where the resin layer and the lens body are cemented), and surface number 15 indicates the image-side surface of the lens body. The surface with surface number 13 corresponds to the object-side lens surface of the positive lens L7, and the sum of the surface spacings of surface numbers 13 and 14 corresponds to the center thickness of the positive lens L7.

[0260] On the image plane I, an image pickup element (not shown) made up of a CCD, a CMOS, or the like is disposed.

[0261] The optical system of this embodiment focuses by moving the entire optical system along the optical axis. When the optical system of this embodiment is focused on an object at close range from an infinity focused state, it is moved from the image plane side to the object side.

[0262] In the optical system of this embodiment, the second lens group G2, the third lens group, and the fourth lens group correspond to the rear group, and the cemented positive lens of the positive lens L3 and the negative lens L4 corresponds to the first cemented lens.

[0263] Table 5 below lists the specifications of the optical system of this example.

[0264] (Table 5) [Lens specifications] mrdn(d) νd 1) 10.42781 2.079 1.78518 48.0 2) 26.35580 0.555 3) 89.59998 0.700 1.59270 35.3 4) 16.01165 1.285 5> ∞ 2.266 (aperture stop) 6) 19.55988 2.668 1.90265 35.7 7) -21.03161 0.700 1.80809 22.7 8) 29.74775 4.939 * 9) -14.09688 1.000 1.80610 40.7 10) -21.74529 0.106 11) -42.10327 1.947 1.58313 59.5 *12) 75.75753 1.376 *13) -37.52464 0.082 1.56093 36.6 14) -48.69243 6.896 1.88300 40.7 15) -18.36826 Bf [Aspherical data] m 9) 12) 13) K 1.0000 1.0000 1.0000 A4 -6.83E-04 -3.24E-04 1.12E-04 A6 4.71E-06 3.00E-06 -1.06E-06 A8 -4.40E-07 -2.57E-08 2.73E-09 A10 1.09E-08 8.87E-11 A12 -1.88E-10 [Overall specifications] f 31.98 F.No 2.90 ω 35.00 Y 21.70 TL 37.16 [Focal length data for each group] Group starting plane focal length G1 1 45.30 G2 6 39.25 G3 9 -24.08 G4 13 32.96 [Back focus] When focusing on infinity When focusing on a short distance object Bf 10.555 18.297

[0265] FIG. 10 is a diagram showing various aberrations of the optical system of the fifth embodiment when focused on an object at infinity.

[0266] From each aberration diagram, it can be seen that the optical system of this example appropriately corrects various aberrations and has high optical performance.

[0267] According to the above-described embodiments, an optical system having good optical performance can be realized.

[0268] The values ​​corresponding to the conditional expressions in each example are shown below.

[0269] Bf is the back focal length in air equivalent length, y is the maximum image height, and TL is the distance from the lens surface closest to the object to the image plane. Np1 is the refractive index of the positive lens in the first cemented lens, and Nn1 is the refractive index of the negative lens in the first cemented lens. tp1 is the central thickness of the positive lens in the first cemented lens, and tn1 is the central thickness of the negative lens in the first cemented lens. t1 is the central thickness of the positive lens located closest to the object. νdp1 is the Abbe number of the positive lens in the first cemented lens, referenced to the d-line, and νdn1 is the Abbe number of the negative lens in the first cemented lens, referenced to the d-line. f is the focal length of the entire optical system. fc1 is the composite focal length of the cemented lens located closest to the object, between the first cemented lens and the second cemented lens, and fc2 is the composite focal length of the cemented lens located closest to the image plane, between the first cemented lens and the second cemented lens. Np2 is the refractive index of the positive lens in the second cemented lens, and Nn2 is the refractive index of the negative lens in the second cemented lens. νdp2 is the Abbe number of the positive lens constituting the second cemented lens, referenced to the d-line, and νdn2 is the Abbe number of the negative lens constituting the second cemented lens, referenced to the d-line. ΣΔPzi is the sum of the Petzval sum of at least one cemented lens in the rear group, each cemented lens consisting of a positive lens and a negative lens, and the reciprocal of the composite focal length of the cemented lens. ΔPz is the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system. ΣD is the distance from the lens surface closest to the object to the lens surface closest to the image plane. dL1_St is the distance from the lens surface closest to the object to the aperture stop. TLs is the distance from the aperture stop surface to the image plane. f1 is the focal length of the first lens group, f2 is the focal length of the second lens group, f3 is the focal length of the third lens group, and f4 is the focal length of the fourth lens group. D1 is the distance from the lens surface in the first lens group closest to the object to the lens surface in the first lens group closest to the image. ΣD is the distance from the lens surface closest to the object to the lens surface closest to the image. rR1 is the radius of curvature of the lens surface closest to the object of the lens closest to the image, and rR2 is the radius of curvature of the lens surface closest to the image. tR is the center thickness of the lens closest to the object.r311 is the radius of curvature of the object-side lens surface of the lens closest to the object in the third lens group, and r312 is the radius of curvature of the image-side lens surface of the lens closest to the object in the third lens group. d3 is the distance from the aperture stop to the lens surface closest to the object in the third lens group. dL1_Gr3 is the distance from the lens surface closest to the object to the lens surface closest to the object in the third lens group.

[0270] [Conditional expression corresponding value] Conditional Expression Example 1 2 3 4 5 (1) Bf / y 0.511 0.497 0.497 0.466 0.486 (2) TL / y 1.812 1.742 1.742 1.761 1.712 (3) Np1-Nn1 0.290 0.290 0.258 0.066 0.095 (4) tp1 / tn1 4.000 4.160 3.571 1.897 3.811 (5),(8) f / y 1.272 1.272 1.272 1.244 1.474 (6) t1 / f 0.047 0.039 0.046 0.050 0.065 (7) νdp1-νdn1 5.400 5.400 4.800 14.500 13.000 (8) fc1 / fc2 0.706 0.678 0.918 -0.019 (10) Np2-Nn2 0.196 0.166 0.146 0.290 (11) νdp2-νdn2 10.200 11.100 10.300 5.400 (12) (ΣΔPzi) / (ΔPz) 1.062 0.990 0.866 0.880 0.589 (13) ΣD / TL 0.718 0.715 0.715 0.735 0.716 (14) dL1_St / TL 0.076 0.073 0.078 0.093 0.124 (15) TL / f 1.425 1.369 1.369 1.416 1.162 (16) TLs / TL 0.924 0.927 0.922 0.907 0.876 (17) f1 / f 4.613 2.634 1.981 2.605 1.417 (18) D1 / TL 0.033 0.028 0.034 0.071 0.090 (19) t1 / ΣD 0.046 0.040 0.047 0.048 0.078 (20) (rR2+rR1) / (rR2-rR1) -2.412 -2.793 -3.930 -2.026 -2.918 (21) tR / ΣD 0.242 0.231 0.185 0.249 0.262 (22) (-f3) / f 0.754 0.983 2.188 0.927 0.753 (23) f4 / f 1.175 1.220 1.667 1.087 1.031 (24) (-f3) / f4 0.641 0.806 1.313 0.852 0.731 (25) f2 / f 0.767 0.997 1.479 0.998 1.227 (26) (r312+r311) / (r312-r311) 2.168 2.904 6.978 2.951 4.686 (27) d3 / f 0.603 0.589 0.646 0.604 0.331 (28) dL1_Gr3 / ΣD 0.696 0.703 0.769 0.706 0.571

[0271] The above examples are merely illustrative of the present invention, and the present invention is not limited thereto. The following content can be appropriately adopted within the scope that does not impair the optical performance of the optical system of the embodiment of the present application.

[0272] Next, a camera equipped with the optical system of this embodiment will be described with reference to FIG. FIG. 11 is a schematic diagram of a camera equipped with the optical system of this embodiment.

[0273] The camera 1 is a so-called mirrorless camera with interchangeable lenses, which has the optical system according to the first embodiment as the photographic lens 2.

[0274] In camera 1, light from an object (subject) (not shown) is collected by photographic lens 2 and reaches image sensor 3. Image sensor 3 converts the light from the subject into image data. The image data is displayed on electronic viewfinder 4. This allows a photographer with their eye positioned at eyepoint EP to observe the subject.

[0275] Furthermore, when the photographer presses a release button (not shown), the image data is stored in a memory (not shown). In this way, the photographer can use the camera 1 to photograph a subject.

[0276] Here, the optical system of the first embodiment mounted on the camera 1 as the photographic lens 2 is an optical system with good optical performance. Therefore, the camera 1 can achieve good optical performance. Note that even if a camera is constructed with the optical system of the second to fifth embodiments mounted on the photographic lens 2, the same effects as those of the camera 1 can be achieved.

[0277] Finally, an outline of the method for manufacturing the optical system of this embodiment will be explained with reference to Fig. 12. Fig. 12 is a flow chart showing an outline of the method for manufacturing the optical system of this embodiment.

[0278] The method for manufacturing the optical system of this embodiment shown in FIG. 12 includes the following steps S11 to S13.

[0279] Step S11: The first lens group, the aperture stop, and the rear lens group are prepared.

[0280] Step S12: The rear group is configured to have a first cemented lens.

[0281] Step S13: The optical system is set to satisfy both of the following conditions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: Refractive index of the positive lens that makes up the first cemented lens Nn1: Refractive index of the negative lens that makes up the first cemented lens

[0282] In a modified example, step S23 shown below may be executed instead of step S13 in the method for manufacturing an optical system shown in FIG.

[0283] Step S23: The optical system is set to satisfy both of the following conditions: (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane tp1: Thickness of the positive lens in the first cemented lens on the optical axis tn1: Thickness of the negative lens that makes up the first cemented lens on the optical axis

[0284] In another modification, step S33 shown below may be executed instead of step S13 in the method for manufacturing an optical system shown in FIG.

[0285] Step S33: The optical system is set to satisfy both of the following conditions: (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 however, f: focal length of the entire optical system y: Maximum image height t1: Center thickness of the positive lens located closest to the object

[0286] According to these manufacturing methods for the optical system of this embodiment, an optical system having good imaging performance can be manufactured.

[0287] Although a four-group configuration has been shown as an example of the optical system of this embodiment, this embodiment is not limited to a four-group configuration and other group configurations (for example, a five-group configuration, etc.) are also possible. Specifically, the optical system of this embodiment may have a configuration in which a lens or optical member is added to the optical system of the example closest to the object or closest to the image plane.

[0288] The optical system of this embodiment may have an anti-vibration lens group that corrects image blur caused by camera shake by moving the lens group so as to have a component perpendicular to the optical axis. The anti-vibration lens group may be a lens group or a partial lens group consisting of one or more lens components included in the lens group.

[0289] In the optical system of this embodiment, the entire optical system, any one lens group, multiple lens groups, or a portion of the lens groups may be moved in the optical axis direction during focusing. For example, during focusing from an object at infinity to a close object, the lens group located closer to the object than the aperture stop and the lens group located closer to the image plane than the aperture stop may be moved toward the object by different amounts.

[0290] In the optical system of this embodiment, the lens surface may be spherical or flat, or may be aspherical. A spherical or flat lens surface is preferred because it facilitates lens processing and assembly adjustment, and prevents degradation of optical performance due to errors in processing and assembly adjustment. Furthermore, a spherical or flat lens surface is preferred because it minimizes degradation of imaging performance when the image plane is misaligned.

[0291] When the lens surface is aspherical, the aspherical surface may be formed by grinding glass or by glass molding using a mold having an aspherical shape, or may be formed on the surface of a resin bonded to the surface of the glass. In addition, in the optical system of this embodiment, the lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

[0292] In the optical system of this embodiment, it is preferable that the aperture stop be located between the first lens group and the second lens group, but instead of providing an independent component as the aperture stop, the frame of the lens or the like may serve that role.

[0293] It should be understood that those skilled in the art can make various changes, substitutions, and alterations thereto without departing from the spirit and scope of the present disclosure. [Explanation of symbols]

[0294] S aperture stop I image plane 1 camera 2. Shooting lens 3. Image sensor

Claims

1. It consists of, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group includes a first cemented lens composed of a positive lens and a negative lens, and a second cemented lens composed of a positive lens and a negative lens, the second cemented lens being different from the first cemented lens, An optical system that satisfies both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 0.550 < (ΣΔPzi) / ΔPz < 0.880 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens ΣΔPzi: the sum of the Petzval sum of at least one cemented lens included in the rear group, the cemented lens being made up of a positive lens and a negative lens, and the reciprocal of the composite focal length of the cemented lens ΔPz: the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system

2. An optical system as described in claim 1, which satisfies the following conditional expression. 0.050 < dL1_St / TL < 0.167 however, dL1_St: Distance from the lens surface closest to the object to the aperture stop

3. An optical system according to claim 1 or 2, which satisfies the following conditional expression: 0.700 < f1 / f < 5.000 however, f1: focal length of the first lens group f: focal length of the entire optical system

4. An optical system according to claim 1 or 2, which satisfies the following conditional expression: -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, rR1: Radius of curvature of the object-side lens surface of the lens closest to the image plane rR2: Radius of curvature of the lens surface closest to the image plane

5. An optical system as described in claim 1 or 2, wherein the lens in the rear group closest to the image plane is a positive lens of meniscus shape with its concave surface facing the object side.

6. A lens system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group includes a first cemented lens composed of a positive lens and a negative lens, and a second cemented lens composed of a positive lens and a negative lens, the second cemented lens being different from the first cemented lens, An optical system that satisfies both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 0.050 < dL1_St / TL < 0.167 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens dL1_St: Distance from the lens surface closest to the object to the aperture stop

7. An optical system as described in claim 6, which satisfies the following conditional expression. 0.700 < f1 / f < 5.000 however, f1: focal length of the first lens group f: focal length of the entire optical system

8. An optical system according to claim 6 or 7, which satisfies the following conditional expression: -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, rR1: Radius of curvature of the object-side lens surface of the lens closest to the image plane rR2: Radius of curvature of the lens surface closest to the image plane

9. An optical system as described in claim 6 or 7, wherein the lens in the rear group closest to the image plane is a positive lens of meniscus shape with its concave surface facing the object side.

10. A lens system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group includes a first cemented lens composed of a positive lens and a negative lens, and a second cemented lens composed of a positive lens and a negative lens, the second cemented lens being different from the first cemented lens, An optical system that satisfies both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 0.700 < f1 / f < 5.000 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens f1: focal length of the first lens group f: focal length of the entire optical system

11. An optical system according to claim 10, which satisfies the following conditional expression: -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, rR1: Radius of curvature of the object-side lens surface of the lens closest to the image plane rR2: Radius of curvature of the lens surface closest to the image plane 12. An optical system as described in claim 10 or 11, wherein the lens in the rear group closest to the image plane is a positive meniscus lens with its concave surface facing the object side.

13. A lens system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, the first lens group is made up of one lens, the rear group includes a first cemented lens composed of a positive lens and a negative lens, and a second cemented lens composed of a positive lens and a negative lens, the second cemented lens being different from the first cemented lens, An optical system that satisfies both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens rR1: Radius of curvature of the object-side lens surface of the lens closest to the image plane rR2: Radius of curvature of the lens surface closest to the image plane 14. The optical system of claim 13, wherein the lens in the rear group closest to the image plane is a positive meniscus lens with its concave surface facing the object side.

15. A lens system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group includes a first cemented lens composed of a positive lens and a negative lens, and a second cemented lens composed of a positive lens and a negative lens, the second cemented lens being different from the first cemented lens, the lens element in the rear group closest to the image plane is a positive meniscus lens element with its concave surface facing the object side, An optical system that satisfies both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens

16. 16. The optical system according to claim 1, wherein the following condition is satisfied: 3.000 < νdp1-νdn1 < 30.000 however, νdp1: Abbe number of the positive lens constituting the first cemented lens, based on the d-line νdn1: Abbe number of the negative lens constituting the first cemented lens, based on the d-line

17. 16. The optical system according to claim 1, wherein the following condition is satisfied: 1.000 < f / y < 1.380 f: focal length of the entire optical system

18. 16. The optical system according to claim 1, wherein of the first cemented lens and the second cemented lens, the cemented lens arranged on the object side has a negative lens arranged on the object side, and the cemented lens arranged on the image plane side has a negative lens arranged on the image plane side.

19. 16. The optical system according to claim 1, wherein the following condition is satisfied: -0.030 < fc1 / fc2 < 1.000 however, fc1: composite focal length of the first cemented lens and the cemented lens of the second cemented lens that is located closer to the object side fc2: composite focal length of the first cemented lens and the second cemented lens, whichever is closer to the image plane

20. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.050 < Np2-Nn2 < 0.400 however, Np2: the refractive index of the positive lens constituting the second cemented lens Nn2: refractive index of the negative lens constituting the second cemented lens

21. 16. The optical system according to claim 1, wherein the following condition is satisfied: 3.000 < νdp2-νdn2 < 30.000 however, νdp2: Abbe number of the positive lens constituting the second cemented lens, based on the d-line νdn2: Abbe number of the negative lens constituting the second cemented lens, based on the d-line

22. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.525 < ΣD / TL < 0.967 however, ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane TL: Distance from the lens surface closest to the object to the image plane

23. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.750 < TL / f < 1.600 however, TL: Distance from the lens surface closest to the object to the image plane f: focal length of the entire optical system

24. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.010 < D1 / TL < 0.150 however, D1: distance from the lens surface of the first lens group closest to the object to the lens surface of the first lens group closest to the image plane TL: Distance from the lens surface closest to the object to the image plane

25. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.025 < t1 / ΣD < 0.080 however, t1: Center thickness of the lens closest to the object ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

26. 16. The optical system according to claim 1, wherein the following condition is satisfied: 0.130 < tR / ΣD < 0.350 however, tR: Center thickness of the lens closest to the image plane ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

27. the rear group comprises, in order from the object side, a second lens group, a third lens group having negative refractive power, and a fourth lens group; the third lens group includes, at a position closest to the object side, a negative meniscus lens arranged closest to the image side among negative meniscus lenses arranged closer to the image side than the aperture stop and having a concave surface facing the object side, 16. The optical system according to claim 1, wherein the fourth lens group is made up of a positive lens.

28. 28. The optical system according to claim 27, wherein the following condition is satisfied: 0.300 < (-f3) / f < 2.200 however, f3: focal length of the third lens group f: focal length of the entire optical system

29. 28. The optical system according to claim 27, wherein the following condition is satisfied: 0.450 < f4 / f < 2.300 however, f4: focal length of the fourth lens group f: focal length of the entire optical system

30. 28. The optical system according to claim 27, wherein the following condition is satisfied: 0.286 < (-f3) / f4 < 2.000 however, f3: focal length of the third lens group f4: focal length of the fourth lens group

31. 28. The optical system according to claim 27, wherein the following condition is satisfied: 0.300 < f2 / f < 2.000 however, f2: focal length of the second lens group f: focal length of the entire optical system

32. 28. The optical system according to claim 27, wherein the following condition is satisfied: １．５００ ＜ (r312+r311) / (r312-r311) ＜ ７．０００ however, r311: radius of curvature of the object-side lens surface of the lens closest to the object side in the third lens group r312: radius of curvature of the image-side lens surface of the lens closest to the object in the third lens group

33. 28. The optical system according to claim 27, wherein the following condition is satisfied: 0.400 < dL1_Gr3 / ΣD < 0.900 however, dL1_Gr3: distance from the lens surface closest to the object to the lens surface closest to the object in the third lens group ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane

34. An optical instrument comprising the optical system according to any one of claims 1, 6, 10, 13 and 15.

35. It consists of, in order from the object side, a first lens group, an aperture stop, and a rear group, a manufacturing method for an optical system including a first cemented lens including a positive lens and a negative lens, and a second cemented lens including a positive lens and a negative lens and different from the first cemented lens, A method for manufacturing an optical system in which each lens is arranged so as to satisfy both of the following conditions: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 0.550 < (ΣΔPzi) / ΔPz < 0.880 however, Bf: Back focus in air equivalent length y: Maximum image height TL: Distance from the lens surface closest to the object to the image plane Np1: the refractive index of the positive lens constituting the first cemented lens Nn1: refractive index of the negative lens constituting the first cemented lens ΣΔPzi: the sum of the Petzval sum of at least one cemented lens included in the rear group, the cemented lens being made up of a positive lens and a negative lens, and the reciprocal of the composite focal length of the cemented lens ΔPz: the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system

Images