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

Abstract

The present invention provides an optical system, optical instruments, and a method for manufacturing an optical system that have good imaging performance. [Solution] The optical system is configured to satisfy the following conditions, with the first lens group, the aperture diaphragm, and the rear group being the first cemented lens, which consists of a positive lens and a negative lens, in that order from the object side. 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 However, Bf is the back focus in air equivalent 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 cemented lens, and Nn1 is the refractive index of the negative lens constituting the first cemented lens.

Description

[Technical Field]

[0001] This disclosure relates to optical systems, optical instruments, and methods for manufacturing optical systems. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-054078 [Overview of the Initiative]

[0004] The optical system of this disclosure consists of, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, the rear group having a first cemented lens consisting of a positive lens and a negative lens, and satisfying all 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: Refractive index of the positive lens constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens

[0005] The optical system of this disclosure consists of, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, the rear group having a first cemented lens consisting of a positive lens and a negative lens, and satisfying all of the following conditions. 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 constituting the first cemented lens tn1: Center thickness of the negative lens constituting the first cemented lens

[0006] The optical system of this disclosure consists of a first lens group, an aperture diaphragm, and a rear lens group, in order from the object side, the rear lens group having a first cemented lens consisting of a positive lens and a negative lens, and the first lens group having a positive lens positioned closest to the object, and satisfying the following conditions. 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: The center thickness of the lens closest to the object.

[0007] The present disclosure is a method for manufacturing an optical system comprising, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, wherein 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 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: Refractive index of the positive lens constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens

Brief Description of the Drawings

[0008] [Figure 1] It is a cross-sectional view of the optical system of the first embodiment when focused on an infinitely distant object. [Figure 2] It is a diagram of various aberrations of the optical system of the first embodiment when focused on an infinitely distant object. [Figure 3] It is a cross-sectional view of the optical system of the second embodiment when focused on an infinitely distant object. [Figure 4] It is a diagram of various aberrations of the optical system of the second embodiment when focused on an infinitely distant object. [Figure 5] It is a cross-sectional view of the optical system of the third embodiment when focused on an infinitely distant object. [Figure 6] It is a diagram of various aberrations of the optical system of the third embodiment when focused on an infinitely distant object. [Figure 7] It is a cross-sectional view of the optical system of the fourth embodiment when focused on an infinitely distant object. [Figure 8] It is a diagram of various aberrations of the optical system of the fourth embodiment when focused on an infinitely distant object. [Figure 9] It is a cross-sectional view of the optical system of the fifth embodiment when focused on an infinitely distant object. [Figure 10] It is a diagram of various aberrations of the optical system of the fifth embodiment when focused on an infinitely distant object. [Figure 11] It is a schematic diagram of a camera equipped with the optical system of this embodiment. [Figure 12] It is a flowchart showing an outline of the manufacturing method of the optical system of this embodiment.

Modes for Carrying Out the Invention

[0009] Hereinafter, the optical system, optical device, and manufacturing method of the optical system according to the embodiments of the present application will be described.

[0010] The optical system of this embodiment includes, 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 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 constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens

[0011] The optical system of this embodiment, by having a rear group first cemented lens, can effectively correct chromatic aberration, maintain the Petzval sum at an appropriate value, and effectively correct field curvature.

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

[0013] In the optical system of this embodiment, if the value of condition equation (1) exceeds the upper limit, the back focus becomes too long, and the overall length of the optical system increases. Furthermore, if the overall length is shortened by reducing lengths other than the back focus in the optical system, it becomes difficult to properly correct various aberrations.

[0014] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (1) to 0.700. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (1) to 0.691, and even further to 0.550.

[0015] Furthermore, in the optical system of this embodiment, if the value of condition (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 thus the quality of the image signal output from the image sensor deteriorates.

[0016] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (1) to 0.350. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (1) to 0.369, and even further to 0.400.

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

[0018] In the optical system of this embodiment, if the value of condition equation (2) exceeds the upper limit, the total length of the optical system increases, and the optical system becomes larger.

[0019] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (2) to 2.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (2) to 1.843, and even further to 1.820.

[0020] Furthermore, in the optical system of this embodiment, if the value of condition equation (2) falls below the lower limit, the angle of incidence of light rays to 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 reliable by setting the lower limit of conditional equation (2) to 1.350. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (2) to 1.400, and even further to 1.600.

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

[0023] In the optical system of this embodiment, if the value of condition equation (3) exceeds the upper limit, the refractive force at the bonding surface of the first cemented lens becomes too strong, causing a large amount of aberrations to occur.

[0024] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (3) to 0.400. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (3) to 0.350, and even further to 0.300.

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

[0026] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (3) to 0.050. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (3) to 0.060, and even further to 0.070.

[0027] An optical system that satisfies all three conditions (1), (2), and (3) can suppress an increase in the overall length of the optical system, ensure an appropriate back focus length, suppress shading on the image sensor, and appropriately correct various aberrations.

[0028] The optical system of this embodiment consists of a first lens group, an aperture diaphragm, and a rear group, in order from the object side, and the rear group has a first cemented lens consisting of a positive lens and a negative lens, and satisfies all 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: Center thickness of the positive lens constituting the first cemented lens tn1: Center thickness of the negative lens constituting the first cemented lens

[0029] Conditional equation (4) defines the ratio of the center thickness of the positive lens constituting the first cemented lens to the center thickness of the negative lens constituting the first cemented lens. By satisfying conditional equation (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 condition equation (4) exceeds the upper limit, the thickness of the positive lens constituting the first cemented lens along the optical axis becomes too large, and the overall length of the optical system increases.

[0031] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (4) to 7.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (4) to 6.000, and even further to 5.000.

[0032] Furthermore, in the optical system of this embodiment, if the value of condition equation (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 made more reliable by setting the lower limit of conditional equation (4) to 1.500. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (4) to 1.800, and even further to 3.000.

[0034] An optical system that satisfies all three conditions (1), (2), and (4) can suppress an increase in the overall length of the optical system, ensure an appropriate back focus length, suppress shading on the image sensor, and appropriately correct various aberrations.

[0035] The optical system of this embodiment consists of a first lens group, an aperture diaphragm, and a rear lens group, in order from the object side. The rear lens group has a first cemented lens consisting of a positive lens and a negative lens, and the first lens group has a positive lens positioned closest to the object, and satisfies 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: The center thickness of the lens closest to the object.

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

[0037] In the optical system of this embodiment, if the value of condition equation (5) exceeds the upper limit, the focal length of the optical system becomes too long, and the overall length of the optical system increases. Furthermore, if one attempts to shorten the overall length of the optical system, it becomes difficult to properly correct various aberrations.

[0038] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (5) to 1.600. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (5) to 1.550, and even further to 1.500.

[0039] Furthermore, in the optical system of this embodiment, if the value of condition equation (5) falls below the lower limit, the difference between the deviation angle of the on-axis light beam and the deviation 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 aberration caused by the off-axis light beam.

[0040] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (5) to 1.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (5) to 1.100, and even further to 1.200.

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

[0042] In the optical system of this embodiment, if the value of condition equation (6) exceeds the upper limit, the thickness of the positive lens positioned closest to the object becomes too thick, and the position of the aperture diaphragm approaches the image plane, making it difficult to position the exit pupil in the appropriate location.

[0043] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (6) to 0.080. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (6) to 0.075, and even further to 0.070.

[0044] Furthermore, in the optical system of this embodiment, if the value of condition equation (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 aberration.

[0045] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (6) to 0.025. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (6) to 0.030, and even further to 0.035.

[0046] In an optical system that satisfies both conditions (5) and (6), the overall length of the optical system is suppressed, the exit pupil is positioned appropriately, and both spherical aberration and coma aberration can be properly corrected.

[0047] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (7) 3.000 < νdp1-νdn1 < 30.000 however, νdp1: Abbe number with reference to the d line of the positive lens constituting the first cemented lens. νdn1: Abbe number with reference to the d line of the negative lens constituting the first cemented lens.

[0048] Conditional equation (7) defines the difference in Abbe numbers with respect to the d line between the positive and negative lenses constituting the first cemented lens. By satisfying conditional equation (7), the optical system of this embodiment can appropriately correct chromatic aberration using the first cemented lens.

[0049] In the optical system of this embodiment, if the value of condition equation (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 made more reliable by setting the upper limit of conditional equation (7) to 30.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (7) to 25.000, and even further to 20.000.

[0051] Furthermore, in the optical system of this embodiment, if the value of condition equation (7) falls below the lower limit, the correction of chromatic aberration by the first cemented lens becomes insufficient.

[0052] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (7) to 3.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (7) to 4.500, and even further to 5.000.

[0053] Furthermore, in the optical system of this embodiment, the rear group preferably consists of a positive lens and a negative lens, and has a second cemented lens that is different from the first cemented lens.

[0054] In the optical system of this embodiment, having such a configuration makes it possible to appropriately correct chromatic aberration.

[0055] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (8) 1.000 < f / y < 1.380 f: Focal length of the entire optical system

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

[0057] In the optical system of this embodiment, if the value of condition equation (8) exceeds the upper limit, chromatic aberration cannot be properly 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 reliable by setting the upper limit of conditional equation (8) to 1.380. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (8) to 1.330, and even further to 1.280.

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

[0060] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (8) to 1.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (8) to 1.100, and even further to 1.200.

[0061] Furthermore, in the optical system of this embodiment, it is preferable that the first cemented lens and the second cemented lens, the cemented lens positioned on the object side has a negative lens positioned on the object side, and the cemented lens positioned on the image plane side has a negative lens positioned on the image plane side.

[0062] In the optical system of this embodiment, by positioning the negative lens on the object side with a wider axial light beam in the cemented lens, various aberrations, particularly spherical aberration, can be effectively corrected. Furthermore, by making the first cemented lens and the second cemented lens symmetrical, various aberrations, particularly coma aberration, can be effectively corrected.

[0063] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (9) -0.030 < fc1 / fc2 < 1.000 however, fc1: The combined focal length of the cemented lens positioned on the object side of the first and second cemented lenses. fc2: The combined focal length of the cemented lens located on the image plane side of the first cemented lens and the second cemented lens.

[0064] Conditional equation (9) defines the ratio of the combined focal length of the cemented lens positioned on the object side among the first and second cemented lenses to the combined focal length of the cemented lens positioned on the image plane side among the first and second cemented lenses. By satisfying conditional equation (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 condition equation (9) exceeds the upper limit, the refractive power of the cemented lens located on the image plane side of the first cemented lens and 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 made more reliable by setting the upper limit of conditional equation (9) to 1.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (9) to 0.960, and even further to 0.930.

[0067] Furthermore, in the optical system of this embodiment, if the value of condition equation (9) falls below the lower limit, the refractive power of the cemented lens located on the object side among the first cemented lens and the second cemented lens increases, causing spherical aberration.

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

[0069] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (10) 0.050 < Np2-Nn2 < 0.400 however, Np2: Refractive index of the positive lens constituting the second cemented lens. Nn2: Refractive index of the negative lens constituting the second fused lens.

[0070] Conditional equation (10) defines the difference 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. The optical system of this embodiment can appropriately correct the Petzval sum by having a second cemented lens that satisfies conditional equation (10).

[0071] In the optical system of this embodiment, if the value of condition equation (10) exceeds the upper limit, the refractive force at the bonding surface of the second bonding lens becomes too strong, causing large aberrations.

[0072] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (10) to 0.400. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (10) to 0.350, and even further to 0.300.

[0073] Furthermore, in the optical system of this embodiment, if the value of conditional equation (10) falls below the lower limit, the Petzval sum cannot be properly corrected by the second cemented lens, resulting in field curvature.

[0074] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (10) to 0.050. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (10) to 0.060, and even further to 0.070.

[0075] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (11) 3.000 < νdp2-νdn2 < 30.000 however, νdp2: Abbe number based on the d line of the positive lens constituting the second cemented lens. νdn2: Abbe number with reference to the d line of the negative lens constituting the second fused lens.

[0076] Conditional equation (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 equation (11), the optical system of this embodiment can appropriately correct chromatic aberration using the second cemented lens.

[0077] In the optical system of this embodiment, if the value of condition equation (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 made more reliable by setting the upper limit of conditional equation (11) to 30.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (11) to 25.000, and even further to 20.000.

[0079] Furthermore, in the optical system of this embodiment, if the value of condition equation (11) falls below the lower limit, the correction of chromatic aberration by the second cemented lens becomes insufficient.

[0080] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (11) to 3.000. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (11) to 4.500, and even further to 5.000.

[0081] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (12) 0.550 < (ΣΔPzi) / ΔPz < 1.400 however, ΣΔPzi: The sum of the Petzval sum of each of the positive and negative lenses in at least one cemented lens included in the rear group, and the reciprocal of the combined focal length of that 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 equation (12) defines the ratio of the sum of the Petzval sum of each of the positive and negative lenses included in the rear group to the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system, for each of the at least one cemented lenses included in the rear group. In conditional equation (12), the numerator represents the corrective power of the Petzval sum in the cemented lens, and the denominator represents the corrective power of the Petzval sum in the entire optical system. By satisfying conditional equation (12), the optical system of this embodiment can appropriately correct field curvature using cemented lenses.

[0083] In the optical system of this embodiment, if the value of condition equation (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 reliable by setting the upper limit of conditional equation (12) to 1.400. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (12) to 1.200, and even further to 1.100.

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

[0086] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (12) to 0.550. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (12) to 0.800, and even further to 0.950.

[0087] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (13) defines the ratio of the distance from the lens surface closest to the object to the lens surface closest to the image plane to the distance from the lens surface closest to the object to the image plane. By satisfying conditional equation (13), the optical system of this embodiment can ensure an appropriate back focus while enabling the arrangement of lenses necessary for correcting various aberrations.

[0089] In the optical system of this embodiment, if the value of condition equation (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 reliable by setting the upper limit of conditional equation (13) to 0.967. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (13) to 0.850, and even more preferably to 0.775.

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

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

[0093] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (14) 0.050 < dL1_St / TL < 0.167 however, dL1_St: Distance from the lens surface closest to the object to the aperture diaphragm. TL: Distance from the lens surface closest to the object to the image plane.

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

[0095] In the optical system of this embodiment, when the value of condition equation (14) exceeds the upper limit, the exit pupil position becomes closer to the image plane, causing shading on the image sensor.

[0096] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (14) to 0.167. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (14) to 0.145, and even more preferably to 0.130.

[0097] Furthermore, in the optical system of this embodiment, if the value of condition equation (14) falls below the lower limit, the optical system before the aperture diaphragm cannot adequately correct aberrations, making it difficult to correct spherical aberration.

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

[0099] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (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 equation (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 condition equation (15) exceeds the upper limit, the overall length of the optical system becomes too large. Furthermore, the focal length is too short relative to the overall length, and the focal length of each group becomes short, making it difficult to correct coma aberration and spherical aberration.

[0102] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (15) to 1.600. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (15) to 1.500, and even further to 1.450.

[0103] Furthermore, in the optical system of this embodiment, if the value of condition equation (15) falls below the lower limit, the overall length of the optical system becomes too small, making it difficult to properly arrange the lenses for correcting various aberrations. Also, the exit pupil position becomes closer to the image plane, causing shading on the image sensor.

[0104] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (15) to 0.750. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (15) to 0.900, and even further to 1.100.

[0105] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (16) 0.590 < TLs / TL < 1.333 however, TLs: Distance from the aperture diaphragm to the image plane. TL: Distance from the lens surface closest to the object to the image plane.

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

[0107] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (16) to 1.333. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (16) to 1.150, and even more preferably to 0.950.

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

[0109] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (16) to 0.590. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (16) to 0.625, and even further to 0.750.

[0110] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (17) defines the ratio of the focal length of the first lens group to the focal length of the entire optical system. By satisfying conditional equation (17), the optical system of this embodiment can suppress the increase in the overall length of the optical system while suppressing the occurrence of various aberrations such as spherical aberration and coma aberration.

[0112] In the optical system of this embodiment, if the value of condition equation (17) exceeds the upper limit, the positive refractive power of the first lens group weakens, causing the overall length of the optical system to become excessively large.

[0113] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (17) to 5.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (17) to 4.800, and even further to 4.650.

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

[0115] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (17) to 0.700. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (17) to 1.000, and even more preferably to 1.400.

[0116] Furthermore, 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, if the first lens group has three or more lenses, the overall length of the optical system increases. Also, because the position of the aperture diaphragm surface is closer to the image plane, the exit pupil becomes shorter, making shading more likely to occur on the image sensor.

[0118] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (18) 0.010 < D1 / TL < 0.150 however, D1: Distance from the lens surface closest to the object in the first lens group to the lens surface closest to the image plane in the first lens group. TL: Distance from the lens surface closest to the object to the image plane.

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

[0120] In the optical system of this embodiment, if the value of condition equation (18) exceeds the upper limit, the thickness of the first lens group increases, causing the overall length of the optical system to become excessively large.

[0121] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (18) to 0.150. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (18) to 0.130, and even further to 0.110.

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

[0123] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (18) to 0.010. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (18) to 0.020, and even more preferably to 0.025.

[0124] Furthermore, the optical system of this embodiment is preferably composed of six or more and nine or fewer lenses.

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

[0126] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (19) 0.025 < t1 / ΣD < 0.080 however, t1: The 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 equation (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 equation (19), the optical system of this embodiment can appropriately correct coma aberration while suppressing shading on the image sensor.

[0128] In the optical system of this embodiment, when the value of condition equation (19) exceeds the upper limit, the central thickness of the lens closest to the object increases, bringing the aperture diaphragm closer to the image plane. As a result, the exit pupil becomes shorter, and shading is more likely to occur on the image sensor.

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

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

[0131] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (19) to 0.025. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (19) to 0.030, and even further to 0.035.

[0132] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 of the lens closest to the image plane.

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

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

[0135] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (20) to -1.500. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (20) to -1.800, and even further to -2.000.

[0136] Furthermore, in the optical system of this embodiment, if the value of condition equation (20) falls below the lower limit, the angle of incidence of the lens closest to the image plane to the image plane increases, making image field curvature more likely to occur.

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

[0138] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (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 to the lens surface closest to the image plane. By satisfying conditional equation (21), the optical system of this embodiment can suppress shading on 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 condition equation (21) exceeds the upper limit, the total 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 reliable by setting the upper limit of conditional equation (21) to 0.350. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (21) to 0.300, and even further to 0.270.

[0142] Furthermore, in the optical system of this embodiment, if the value of condition equation (21) falls below the lower limit, the central thickness of the lens closest to the image plane decreases, and the positive refractive power weakens. As a result, the position of the exit pupil becomes closer to the image plane, making shading more likely to occur on the image sensor.

[0143] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (21) to 0.130. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (21) to 0.150, and even more preferably to 0.180.

[0144] Furthermore, in the optical system of this embodiment, the rear group preferably 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 preferably has a negative meniscus lens positioned closest to the image plane, with its concave surface facing the object side, and positioned closer to the image plane than the aperture diaphragm. The fourth lens group preferably consists of positive lenses.

[0145] In the optical system of this embodiment, having such a configuration makes it possible to increase the distance between the exit pupil and the image plane while effectively correcting image field curvature.

[0146] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (22) defines the ratio of the focal length of the third lens group to the focal length of the entire optical system. By satisfying conditional equation (22), the optical system of this embodiment can appropriately correct various aberrations such as sagittal coma aberration 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 condition equation (22) exceeds the upper limit, the overall length of the optical system becomes too large. Furthermore, it becomes difficult to set the exit pupil to an appropriate position.

[0149] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (22) to 2.200. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (22) to 1.600, and even more preferably to 1.300.

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

[0151] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (22) to 0.300. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (22) to 0.450, and even more preferably to 0.750.

[0152] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (23) defines the ratio of the focal length of the fourth lens group to the focal length of the entire optical system. By satisfying conditional equation (23), the optical system of this embodiment can suppress shading on the image sensor while suppressing an increase in the overall length of the optical system.

[0154] In the optical system of this embodiment, if the value of condition equation (23) exceeds the upper limit, the position of the exit pupil becomes closer to the image plane, making shading on the image sensor more likely to occur. Furthermore, correcting the Petzval sum also becomes difficult.

[0155] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (23) to 2.300. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (23) to 1.680, and even further to 1.500.

[0156] Furthermore, in the optical system of this embodiment, if the value of conditional equation (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 reliable by setting the lower limit of conditional equation (23) to 0.450. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (23) to 0.650, and even further to 1.000.

[0158] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (24) defines the ratio of the focal length of the third lens group to the focal length of the fourth lens group. By satisfying conditional equation (24), the optical system of this embodiment can appropriately correct various aberrations such as field curvature and coma aberration using the third and fourth lens groups.

[0160] In the optical system of this embodiment, if the value of condition equation (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 field curvature and coma aberration.

[0161] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (24) to 2.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (24) to 1.500, and even more preferably to 1.350.

[0162] Furthermore, in the optical system of this embodiment, if the value of condition equation (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 field curvature and coma aberration.

[0163] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (24) to 0.286. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (24) to 0.350, and even further to 0.600.

[0164] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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 equation (25) defines the ratio of the focal length of the second lens group to the focal length of the entire optical system. By satisfying conditional equation (25), the optical system of this embodiment can effectively correct field curvature while also effectively correcting coma aberration so that it does not vary by color.

[0166] In the optical system of this embodiment, if the value of conditional equation (25) exceeds the upper limit, it becomes impossible to maintain the Petzval sum at an appropriate value, making it difficult to adequately correct the field curvature.

[0167] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (25) to 2.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (25) to 1.800, and even more preferably to 1.500.

[0168] Furthermore, in the optical system of this embodiment, if the value of condition equation (25) falls below the lower limit, it becomes difficult to suppress variations in coma aberration for each color.

[0169] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (25) to 0.300. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (25) to 0.500, and even more preferably to 0.700.

[0170] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (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-plane lens surface of the lens closest to the object in the third lens group.

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

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

[0173] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the upper limit of conditional equation (26) to 7.000. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (26) to 5.000, and even further to 3.000.

[0174] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (26) to 1.500. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (26) to 1.700, and even further to 2.000.

[0175] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (27) 0.150 < d3 / f < 0.750 however, d3: Distance from the aperture diaphragm to the lens surface of the third lens group closest to the object. f: Focal length of the entire optical system

[0176] Conditional equation (27) defines the ratio of the distance from the aperture diaphragm to the lens surface closest to the object in the third lens group to the focal length of the entire optical system. By satisfying conditional equation (27), the optical system of this embodiment can suppress shading on 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 equation (27) exceeds the upper limit, the total 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 reliable by setting the upper limit of conditional equation (27) to 0.750. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (27) to 0.700, and even further to 0.650.

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

[0180] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (27) to 0.150. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (27) to 0.200, and even further to 0.250.

[0181] Furthermore, it is preferable that the optical system of this embodiment satisfies the following condition. (28) 0.400 < dL1_Gr3 / ΣD < 0.900 however, dL1_Gr3: Distance from the lens surface closest to the object to the lens surface of the third lens group closest to the object. ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane.

[0182] Conditional equation (28) defines the ratio of the distance from the lens surface closest to the object to the lens surface of the third lens group 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 equation (28), the optical system of this embodiment can suppress shading on 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 equation (28) exceeds the upper limit, the total 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 reliable by setting the upper limit of conditional equation (28) to 0.900. Furthermore, in order to make the effect of this embodiment even more reliable, it is preferable to set the upper limit of conditional equation (28) to 0.850, and even further to 0.800.

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

[0186] In the optical system of this embodiment, the effect of this embodiment can be made more reliable by setting the lower limit of conditional equation (28) to 0.400. Furthermore, to make the effect of this embodiment even more reliable, it is preferable to set the lower limit of conditional equation (28) to 0.450, and even further to 0.500.

[0187] With the above configuration, it is possible to realize a compact optical system with good imaging performance.

[0188] The optical instrument of this embodiment has an optical system with the configuration described above. This makes it possible to realize an optical instrument with good optical performance.

[0189] The manufacturing method of the optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, and the rear group is a manufacturing method of an optical system having a first cemented lens consisting of a positive lens and a negative lens, wherein each lens is arranged so as to satisfy the following conditional equations. (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: The distance from the lens surface closest to the object to the image plane. Np1: Refractive index of the positive lens constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens

[0190] The manufacturing method of the optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, and the rear group is a manufacturing method of an optical system having a first cemented lens consisting of a positive lens and a negative lens, wherein each lens is arranged so as to satisfy the following conditional equations. (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 constituting the first cemented lens along the optical axis. tn1: Thickness of the negative lens constituting the first cemented lens along the optical axis.

[0191] The manufacturing method of the optical system of this embodiment comprises, in order from the object side, a first lens group, an aperture diaphragm, and a rear group, and the rear group is a manufacturing method of an optical system having a first cemented lens consisting of a positive lens and a negative lens, wherein each lens is arranged so as to satisfy the following conditional equations. (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 positioned closest to the object.

[0192] By using this method of manufacturing an optical system, it is possible to manufacture an optical system with good optical performance.

[0193] (Examples of numerical values) The embodiments of this application will be described below with reference to the drawings.

[0194] (First embodiment) Figure 1 is a cross-sectional view of the optical system of the first embodiment when an object at infinity is in focus.

[0195] The optical system of this embodiment includes, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm 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 consists of a meniscus-shaped positive lens L1 with its convex surface facing the object.

[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-shaped positive lens L6 with its concave surface facing the object side.

[0198] The third lens group G3 consists of a meniscus-shaped negative lens L7 with its concave surface facing the object.

[0199] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object. 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 later, 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 joined), 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, surface number 14 corresponds to the object-side lens surface of the positive lens L8, and the sum of the interplanar spacings of surface number 14 and surface number 15 corresponds to the center thickness of the positive lens L8.

[0200] An image sensor (not shown), composed of a CCD or CMOS, is arranged on the image plane I.

[0201] In this embodiment, the optical system achieves focus by moving the entire optical system along the optical axis. When the optical system in this embodiment is focused from infinity to a nearby object, 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. Furthermore, 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 in this embodiment. In the [Lens Specifications] column of Table 1, m is the order of the optical surfaces counted from the object side, r is the radius of curvature, d is the interplanar spacing, n(d) is the refractive index for the d line (wavelength 587.6 nm), and νd is the Abbe number for the d line. A radius of curvature r=∞ indicates a plane. In addition, in the [Lens Specifications] column, optical surfaces marked with "*" indicate that they are aspherical.

[0204] In the [Aspherical Data] section, m represents the optical plane corresponding to the aspherical data, K is the cone constant, and A4 to A18 represent the aspherical coefficients.

[0205] An aspherical surface is expressed by the following equation (a), where y is the height perpendicular to the optical axis, S(y) is the distance along the optical axis from the tangent plane of the vertex of each aspherical surface at height y to each aspherical surface (sag), r is the radius of curvature of the reference sphere (paraxial radius of curvature), K is the cone constant, and An is the nth-order aspherical coefficient. In each embodiment, the second-order aspherical coefficient A2 is 0. Also, "En" is "×10 -n This 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] of Table 1, f represents the focal length of the entire optical system, F.NO represents the F-number of the optical system, ω represents the semi-field angle (degrees), Y represents the maximum image height, and TL represents the distance from the lens surface closest to the object side to the image plane when focusing on an object at infinity.

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

[0209] The units of the focal length f, radius of curvature r, and other lengths described in Table 1 are "mm". However, since the optical system can obtain the same optical performance even with proportional magnification or reduction, it is not limited to this. B

[0210] The symbols in Table 1 described above are used in the same way in the tables of other embodiments described later.

[0211] (Table 1) [Lens Specifications] m r d n(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<T 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 focused at infinity When focused on a close object Bf 10.760 15.873

[0212] Figure 2 is a diagram of various aberrations of the optical system of the first embodiment when focused on an object at infinity.

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

[0214] From each aberration diagram, it can be seen that the optical system of the present embodiment appropriately corrects various aberrations and has high optical performance. <00009​​​​​​​​​​​​​​​​​​​The third lens group G3 consists of a meniscus-shaped negative lens L7 with its concave surface facing the object.

[0220] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object. 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 later, 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 joined), 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 interplanar spacings of surface number 14 and surface number 15 corresponds to the center thickness of the positive lens L8.

[0221] An image sensor (not shown), composed of a CCD or CMOS, is arranged on the image plane I.

[0222] In this embodiment, the optical system achieves focus by moving the entire optical system along the optical axis. When the optical system in this embodiment is focused from infinity to a nearby object, 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. Furthermore, the positive lens formed by the bonding of the negative lens L2 and the positive lens L3 corresponds to the first bonded lens, and the positive lens formed by the bonding of the positive lens L4 and the negative lens L5 corresponds to the second bonded lens.

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

[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 diaphragm) 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] Figure 4 shows the aberrations of the optical system of the second embodiment when an object at infinity is in focus.

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

[0228] (Third embodiment) Figure 5 is a cross-sectional view of the optical system of the third embodiment when an object at infinity is in focus.

[0229] The optical system of this embodiment includes, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm 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 consists of a meniscus-shaped positive lens L1 with its convex surface facing the object.

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

[0232] The third lens group G3 consists of a meniscus-shaped negative lens L7 with its concave surface facing the object.

[0233] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object. 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 later, 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 joined), 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 interplanar spacings of surface number 14 and surface number 15 corresponds to the center thickness of the positive lens L8.

[0234] An image sensor (not shown), composed of a CCD or CMOS, is arranged on the image plane I.

[0235] In this embodiment, the optical system achieves focus by moving the entire optical system along the optical axis. When the optical system in this embodiment is focused from infinity to a nearby object, 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. Furthermore, the positive lens formed by the bonding of the negative lens L2 and the positive lens L3 corresponds to the first bonded lens, and the positive lens formed by the bonding of the positive lens L4 and the negative lens L5 corresponds to the second bonded lens.

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

[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 diaphragm) 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 distance 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] Figure 6 shows the aberrations of the optical system of the third embodiment when an object at infinity is in focus.

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

[0241] (Fourth embodiment) Figure 7 is a cross-sectional view of the optical system of the fourth embodiment when an object at infinity is in focus.

[0242] The optical system of this embodiment includes, in order from the object side, a first lens group G1 having positive refractive power, an aperture diaphragm 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 consists of, in order from the object side, a positive lens L1 with a meniscus shape and a convex surface facing the object side, and a negative lens L2 with a meniscus shape and 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 formed by a meniscus-shaped positive lens L3 with its concave surface facing the object and a meniscus-shaped negative lens L4 with its concave surface facing the object, and a cemented negative lens formed by a meniscus-shaped positive lens L5 with its concave surface facing the object and a biconcave negative lens L6.

[0245] The third lens group G3 consists of a meniscus-shaped negative lens L7 with its concave surface facing the object.

[0246] The fourth lens group G4 consists of a meniscus-shaped positive lens L8 with its concave surface facing the object. 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 later, 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 joined), 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 interplanar spacings of surface number 14 and surface number 15 corresponds to the center thickness of the positive lens L8.

[0247] An image sensor (not shown), composed of a CCD or CMOS, is arranged on the image plane I.

[0248] In this embodiment, the optical system achieves focus by moving the entire optical system along the optical axis. When the optical system in this embodiment is focused from infinity to a nearby object, 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. Furthermore, the positive lens formed by the bonding of the positive lens L3 and the negative lens L4 corresponds to the first bonded lens, and the negative lens formed by the bonding of the positive lens L5 and the negative lens L6 corresponds to the second bonded lens.

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

[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 diaphragm) * 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 distance 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] Figure 8 shows the aberrations of the optical system of the fourth embodiment when an object at infinity is in focus.

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

[0254] (Fifth example) Figure 9 is a cross-sectional view of the optical system of the fifth embodiment when an object at infinity is in focus.

[0255] The optical system of this embodiment includes, in order from the object side, a first lens group G1 having negative refractive power, an aperture diaphragm 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 consists of, in order from the object side, a positive lens L1 with a meniscus shape and a convex surface facing the object side, and a negative lens L2 with a meniscus shape and a convex surface facing the object side.

[0257] The second lens group G2 consists of a bonded positive lens formed by a biconvex positive lens L3 and a biconcave negative lens L4.

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

[0259] The fourth lens group G4 consists of a meniscus-shaped positive lens L7 with its concave surface facing the object. 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 composite aspherical lens in which the object-side surface of the resin layer is aspherical. In the [Lens Specifications] described later, 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 joined), and surface number 15 indicates the image-side surface of the lens body. Surface number 13 corresponds to the object-side lens surface of the positive lens L7, and the sum of the interplanar spacings of surface number 13 and surface number 14 corresponds to the center thickness of the positive lens L7.

[0260] An image sensor (not shown), composed of a CCD or CMOS, is arranged on the image plane I.

[0261] In this embodiment, the optical system achieves focus by moving the entire optical system along the optical axis. When the optical system in this embodiment is focused from infinity to a nearby object, 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. Furthermore, the cemented positive lens formed by 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 in this embodiment.

[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 diaphragm) 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 distance 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] Figure 10 shows the aberrations of the optical system of the fifth embodiment when an object at infinity is in focus.

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

[0267] According to each of the above embodiments, an optical system with good optical performance can be realized.

[0268] The corresponding values ​​for each example are shown below.

[0269] Bf is the back focus 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 constituting the first cemented lens, and Nn1 is the refractive index of the negative lens constituting the first cemented lens. tp1 is the center thickness of the positive lens constituting the first cemented lens, and tn1 is the center thickness of the negative lens constituting the first cemented lens. t1 is the center thickness of the positive lens positioned closest to the object. νdp1 is the Abbe number of the positive lens constituting the first cemented lens with respect to the d line, and νdn1 is the Abbe number of the negative lens constituting the first cemented lens with respect to the d line. f is the focal length of the entire optical system. fc1 is the combined focal length of the cemented lens positioned on the object side of the first cemented lens and the second cemented lens, and fc2 is the combined focal length of the cemented lens positioned on the image plane side of the first cemented lens and the second cemented lens. Np2 is the refractive index of the positive lens constituting the second cemented lens, and Nn2 is the refractive index of the negative lens constituting the second cemented lens. νdp2 is the Abbe number with reference to the d line of the positive lens constituting the second cemented lens, and νdn2 is the Abbe number with reference to the d line of the negative lens constituting the second cemented lens. ΣΔPzi is the sum of the Petzval sum of each of the positive and negative lenses included in the rear group and at least one cemented lens, and the reciprocal of the combined focal length of that cemented lens, and 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 diaphragm. TLs is the distance from the aperture diaphragm 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 closest to the object in the first lens group to the lens surface closest to the image plane in the first lens group. ΣD is the distance from the lens surface closest to the object to the lens surface closest to the image plane. rR1 is the radius of curvature of the object-side lens surface of the lens closest to the image plane, and rR2 is the radius of curvature of the image-side lens surface of the lens closest to the image plane. 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 diaphragm to the object-side lens surface of the third lens group. dL1_Gr3 is the distance from the object-side lens surface to the object-side lens surface of the third lens group.

[0270] [Conditional expression corresponding value] Conditional Expression Examples 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 embodiments illustrate specific examples of the present invention, and the present invention is not limited thereto. The following contents can be appropriately adopted as long as they do not impair the optical performance of the optical system of the embodiments of this application.

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

[0273] Camera 1 is a so-called mirrorless camera with interchangeable lenses, equipped with the optical system according to the first embodiment described above as the shooting lens 2.

[0274] In camera 1, light from an unillustrated object (subject) is focused by the photographic lens 2 and reaches the image sensor 3. The image sensor 3 converts the light from the subject into image data. The image data is displayed in the electronic viewfinder 4. This allows the photographer, with their eye positioned at eye point EP, to observe the subject.

[0275] Furthermore, when the photographer presses a shutter release button (not shown), the image data is stored in memory (not shown). In this way, the photographer can take a picture of the subject with camera 1.

[0276] Here, the optical system of the first embodiment, mounted as the photographic lens 2 in camera 1, is an optical system with good optical performance. Therefore, camera 1 can achieve good optical performance. Furthermore, even if a camera is configured with the optical systems of the second to fifth embodiments as the photographic lens 2, the same effect as camera 1 can be achieved.

[0277] Finally, the general outline of the manufacturing method of the optical system of this embodiment will be described based on Figure 12. Figure 12 is a flowchart illustrating the general outline of the manufacturing method of the optical system of this embodiment.

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

[0279] Step S11: Prepare the first lens group, aperture diaphragm, and rear lens group.

[0280] Step S12: Ensure that the rear group has a first cemented lens.

[0281] Step S13: Ensure that the optical system satisfies 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: The distance from the lens surface closest to the object to the image plane. Np1: Refractive index of the positive lens constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens

[0282] In a modified example, step S23 shown below may be performed instead of step S13 in the manufacturing method of the optical system shown in Figure 12.

[0283] Step S23: Ensure that the optical system satisfies 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 constituting the first cemented lens along the optical axis. tn1: Thickness of the negative lens constituting the first cemented lens along the optical axis.

[0284] In other modifications, step S33, as shown below, may be performed instead of step S13 in the manufacturing method of the optical system shown in Figure 12.

[0285] Step S33: Ensure that the optical system satisfies 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 positioned closest to the object.

[0286] According to these manufacturing methods for the optical system of this embodiment, it is possible to manufacture an optical system having good imaging performance.

[0287] Although a four-group configuration is shown as an example of the optical system in this embodiment, this embodiment is not limited to a four-group configuration and can also be configured with other group configurations (for example, a five-group configuration). Specifically, the optical system of this embodiment may have a configuration in which lenses or optical elements are added to the optical system of the embodiment, either on the object side or on the image plane side.

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

[0289] In this embodiment, when focusing, the entire optical system, any one lens group, multiple lens groups, or a partial lens group may move along the optical axis. For example, when focusing from an object at infinity to a nearby object, the lens group positioned on the object side of the aperture diaphragm and the lens group positioned on the image plane side of the aperture diaphragm may each move towards the object by different amounts.

[0290] In the optical system of this embodiment, the lens surface may be formed as a sphere, a plane, or an aspherical surface. A spherical or plane lens surface is preferable because it facilitates lens processing and assembly adjustment, preventing deterioration of optical performance due to processing and assembly errors. Furthermore, a spherical or plane lens surface is preferable because it reduces the deterioration of image rendering 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 a glass mold using a mold having an aspherical shape, or it may be formed on the surface of a resin bonded to the glass surface. In addition, in the optical system of this embodiment, the lens surface may also be a diffractive surface, and the lens may be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0292] In the optical system of this embodiment, the aperture diaphragm is preferably positioned between the first lens group and the second lens group, but instead of providing a separate component for the aperture diaphragm, its role may be substituted by the lens frame or the like.

[0293] Those skilled in the art will understand that various changes, substitutions, and modifications can be made to this disclosure without deviating from its spirit and scope. [Explanation of Symbols]

[0294] S Aperture diaphragm I image plane 1 Camera 2. Shooting lens 3 Image sensor

Claims

1. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The rear group comprises a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is 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: 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 each of the positive and negative lenses included in the rear group, and the reciprocal of the combined 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. The optical system according to claim 1, satisfying 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 diaphragm.

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

5. The optical system according to claim 1 or 2, wherein the lens closest to the image plane in the rear group is a positive lens with a meniscus shape and a concave surface facing the object.

6. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The rear group comprises a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is 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: 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 diaphragm.

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

9. The optical system according to claim 6 or 7, wherein the lens closest to the image plane in the rear group is a positive lens with a meniscus shape and a concave surface facing the object.

10. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The rear group comprises a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is 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: 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. The optical system according to claim 10, satisfying the following conditional expression. -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 however, rR1: Radius of curvature of the lens surface on the object side of the lens closest to the image plane. rR2: Radius of curvature of the lens surface closest to the image plane of the lens closest to the image plane.

12. The optical system according to claim 10 or 11, wherein the lens closest to the image plane in the rear group is a positive lens with a meniscus shape and a concave surface facing the object.

13. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The first lens group consists of a single lens, The rear group comprises a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is 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: 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 lens surface on the object side of the lens closest to the image plane. rR2: Radius of curvature of the lens surface closest to the image plane of the lens closest to the image plane.

14. The optical system according to claim 13, wherein the lens closest to the image plane in the rear group is a positive lens with a meniscus shape and a concave surface facing the object.

15. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The rear group comprises a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is different from the first cemented lens. The lens closest to the image plane in the rear group is a positive lens with a meniscus shape, with its concave surface facing the object. 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: Refractive index of the positive lens constituting the first cemented lens. Nn1: Refractive index of the negative lens constituting the first cemented lens.

16. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 3.000 < νdp1-νdn1 < 30.000 however, νdp1: Abbe number with reference to the d line of the positive lens constituting the first cemented lens. νdn1: Abbe number with reference to the d line of the negative lens constituting the first cemented lens.

17. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 1.000 < f / y < 1.380 f: Focal length of the entire optical system

18. The optical system according to any one of claims 1, 6, 10, 13, or 15, wherein, of the first cemented lens and the second cemented lens, the cemented lens positioned on the object side has a negative lens positioned on the object side, and the cemented lens positioned on the image plane side has a negative lens positioned on the image plane side.

19. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. -0.030 < fc1 / fc2 < 1.000 however, fc1: The combined focal length of the first cemented lens and the cemented lens positioned on the object side of the second cemented lens. fc2: The combined focal length of the first cemented lens and the cemented lens positioned on the image plane side of the second cemented lens.

20. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 0.050 < Np2-Nn2 < 0.400 however, Np2: Refractive index of the positive lens constituting the second cemented lens. Nn2: Refractive index of the negative lens constituting the second cemented lens.

21. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 3.000 < νdp2-νdn2 < 30.000 however, νdp2: Abbe number with reference to the d line of the positive lens constituting the second cemented lens. νdn2: Abbe number with reference to the d line of the negative lens constituting the second cemented lens.

22. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 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. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 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. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 0.010 < D1 / TL < 0.150 however, D1: The 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. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 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. An optical system according to any one of claims 1, 6, 10, 13, or 15, satisfying the following conditional expression. 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 aforementioned rear group consists, in order from the object side, of a second lens group, a third lens group having negative refractive power, and a fourth lens group. The third lens group includes a negative meniscus lens positioned closest to the image plane, which is a negative meniscus lens positioned closer to the image plane than the aperture diaphragm and has a concave surface facing the object side. The optical system according to any one of claims 1, 6, 10, 13, or 15, wherein the fourth lens group comprises positive lenses.

28. The optical system according to claim 27, satisfying the following conditional expression. 0.300 < (-f3) / f < 2.200 however, f3: Focal length of the third lens group f: Focal length of the entire optical system

29. The optical system according to claim 27, satisfying the following conditional expression. 0.450 < f4 / f < 2.300 however, f4: Focal length of the fourth lens group f: Focal length of the entire optical system

30. The optical system according to claim 27, satisfying the following conditional expression. 0.286 < (-f3) / f4 < 2.000 however, f3: Focal length of the third lens group f4: Focal length of the fourth lens group

31. The optical system according to claim 27, satisfying the following conditional expression. 0.300 < f2 / f < 2.000 however, f2: Focal length of the second lens group f: Focal length of the entire optical system

32. The optical system according to claim 27, satisfying the following conditional expression. 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-plane side lens surface of the lens closest to the object in the third lens group.

33. The optical system according to claim 27, satisfying the following conditional expression. 0.400 < dL1_Gr3 / ΣD < 0.900 however, dL1_Gr3: The distance from the lens surface closest to the object to the lens surface of the third lens group closest to the object. ΣD: Distance from the lens surface closest to the object to the lens surface closest to the image plane.

34. An optical instrument having the optical system described in any one of claims 1, 6, 10, 13, or 15.

35. Starting from the object side, it consists of the first lens group, the aperture diaphragm, and the rear group. The method for manufacturing an optical system having a first cemented lens consisting of a positive lens and a negative lens, and a second cemented lens consisting of a positive lens and a negative lens, which is different from the first cemented lens, A method for manufacturing an optical system in which each lens is arranged to satisfy 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: 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 each of the positive and negative lenses included in the rear group, and the reciprocal of the combined 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