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

Abstract

The present invention provides an optical system comprising, in order from the object side, a first lens group, an aperture stop, and a rear group, the rear group having a first cemented lens comprising a positive lens and a negative lens, the optical system being configured so as to satisfy the following conditional expressions at the same time: 0.350 lt; bf / result; 0.700, 1.350 lt, 0.700, 1.350 lt; tL / result; 2.000, 0.050 lt, 0.050 lt; np1-Nn1lt, and Np1-Nn1lt; 0.400 where Bf is the back focal length in terms of air, y is the maximum image height, TL is the distance from the lens surface closest to the object side to the image surface, 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] The present disclosure relates to an optical system, an optical device, and a method for manufacturing the optical system. Background Art

[0002] Conventionally, there are disclosed optical systems used in optical devices such as photographic cameras, electronic still cameras, and video cameras (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-054078 Summary of the invention

[0006] The optical system disclosed in the present invention is composed of a first lens group, an aperture stop, and a rear group in order from the object side, the rear group having a first cemented lens composed of a positive lens and a negative lens, and the optical system satisfies the following conditional expressions at the same time: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. Np1: refractive index of the positive lens constituting the first cemented lens, Nn1: refractive index of the negative lens constituting the first cemented lens.

[0007] The optical system disclosed in the present invention is composed of a first lens group, an aperture stop, and a rear group in order from the object side, the rear group having a first cemented lens composed of a positive lens and a negative lens, and the optical system satisfies the following conditional expressions at the same time: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 1.500 < tp1 / tn1 < 7.000 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. tp1: the center thickness of the positive lens constituting the first cemented lens, tn1: The center thickness of the negative lens constituting the first cemented lens.

[0008] The optical system disclosed in the present invention is composed of a first lens group, an aperture stop, and a rear group in order from the object side, the rear group has a first cemented lens composed of a positive lens and a negative lens, the first lens group has a positive lens arranged on the most object side, and the optical system satisfies the following conditional expressions at the same time: 1.000 < f / y < 1.600 0.025 < t1 / f < 0.080 in, f: focal length of the entire optical system, y: maximum image height, t1: The center thickness of the lens closest to the object side.

[0009] The present invention discloses a method for manufacturing an optical system, wherein the optical system is composed of a first lens group, an aperture stop, and a rear lens group in order from the object side, wherein the rear lens group has a first cemented lens composed of a positive lens and a negative lens, and each lens is arranged in such a way that the optical system satisfies the following conditional expressions at the same time: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. 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

[0010] Figure 1 It is a cross-sectional view of the optical system of the first embodiment when an object at infinity is in focus.

[0011] Figure 2 1 and 10 are diagrams showing various aberrations of the optical system of the first embodiment when an object at infinity is in focus.

[0012] Figure 3 It is a cross-sectional view of the optical system of the second embodiment when an object at infinity is in focus.

[0013] Figure 4 1 and 10 are diagrams showing various aberrations of the optical system of the second embodiment when an object at infinity is in focus.

[0014] Figure 5It is a cross-sectional view of the optical system of the third embodiment when an object at infinity is in focus.

[0015] Figure 6 These are diagrams showing various aberrations of the optical system of Example 3 when an object at infinity is in focus.

[0016] Figure 7 It is a cross-sectional view of the optical system of the fourth embodiment when an object at infinity is in focus.

[0017] Figure 8 These are diagrams showing various aberrations of the optical system of Example 4 when an object at infinity is in focus.

[0018] Fig. 9 It is a cross-sectional view of the optical system of the fifth embodiment when an object at infinity is in focus.

[0019] Fig.10 These are diagrams showing various aberrations of the optical system of Example 5 when an object at infinity is in focus.

[0020] Fig.11 It is a schematic diagram of a camera including the optical system of this embodiment.

[0021] Fig.12 This is a flowchart schematically showing a method for manufacturing the optical system according to the present embodiment. DETAILED DESCRIPTION

[0022] Hereinafter, an optical system, an optical device, and a method for manufacturing an optical system according to an embodiment of the present application will be described.

[0023] The optical system of this embodiment is composed of a first lens group, an aperture stop, and a rear group in order from the object side. The rear group has a first cemented lens composed of a positive lens and a negative lens. The optical system satisfies the following conditional expressions at the same time.

[0024] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface Np1: Refractive index of the positive lens constituting the first cemented lens Nn1: Refractive index of the negative lens constituting the first cemented lens

[0025] In the optical system of this embodiment, the rear group includes the first cemented lens, so that chromatic aberration can be corrected well and the Petzval sum can be maintained at an appropriate value, thereby making it possible to correct field curvature well.

[0026] Conditional expression (1) specifies the ratio of the back focus to the maximum image height in air conversion length. The optical system of this embodiment satisfies conditional expression (1), thereby ensuring a back focus of an appropriate length for configuring necessary filters between the optical system and the image plane, while appropriately correcting various aberrations.

[0027] In the optical system of this embodiment, when the value of conditional expression (1) exceeds the upper limit, the back focus becomes too long, and the total length of the optical system increases. In addition, in the optical system, when the total length is shortened by shortening the length other than the back focus, it is difficult to properly correct various aberrations.

[0028] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (1) to 0.700. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (1) to 0.691, and further to 0.550.

[0029] In the optical system of this embodiment, when the value of conditional expression (1) is below the lower limit, the back focus becomes too short, making it difficult to arrange filters in front of the image sensor, and the quality of the image signal output from the image sensor decreases.

[0030] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (1) to 0.350. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (1) to 0.369, and further to 0.400.

[0031] Conditional expression (2) specifies the ratio of the distance from the lens surface closest to the object to the image plane (optical total length) to the maximum image height. The optical system of this embodiment satisfies conditional expression (2), thereby suppressing the increase in the total length of the optical system, suppressing the shadow in the imaging element, and appropriately correcting various aberrations.

[0032] In the optical system of the present embodiment, when the value of conditional expression (2) exceeds the upper limit, the total length of the optical system increases, and the optical system becomes larger.

[0033] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (2) to 2.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (2) to 1.843, and further to 1.820.

[0034] In the optical system of the present embodiment, when the value of conditional expression (2) is lower than the lower limit, the incident angle of light to the image sensor increases, causing shadows and making it difficult to correct various aberrations.

[0035] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (2) to 1.350. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (2) to 1.400, and further to 1.600.

[0036] Conditional expression (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 including the first cemented lens satisfying conditional expression (3).

[0037] In the optical system of the present embodiment, when the value of conditional expression (3) exceeds the upper limit, the refractive power on the cemented surface of the first cemented lens becomes too strong, and various aberrations are generated greatly.

[0038] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (3) to 0.400. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (3) to 0.350, and further to 0.300.

[0039] In the optical system of this embodiment, when the value of conditional expression (3) is lower than the lower limit, the Petzval sum cannot be appropriately corrected by the first cemented lens, and it is difficult to suppress field curvature in the entire optical system.

[0040] In the optical system of this embodiment, by setting the lower limit of conditional expression (3) to 0.050, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit of conditional expression (3) to 0.060, and further to 0.070.

[0041] In an optical system that satisfies conditional expressions (1), (2), and (3) at the same time, it is possible to suppress the increase in the total length of the optical system, ensure a back focus of appropriate length, suppress shadows in the imaging element, and appropriately correct various aberrations.

[0042] The optical system of this embodiment is composed of a first lens group, an aperture stop, and a rear group in order from the object side. The rear group has a first cemented lens composed of a positive lens and a negative lens. The optical system satisfies the following conditional expressions at the same time.

[0043] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface tp1: Center thickness of the positive lens constituting the first cemented lens tn1: Center thickness of the negative lens constituting the first cemented lens

[0044] Conditional expression (4) specifies the ratio of the center thickness of the positive lens constituting the first joint lens to the center thickness of the negative lens constituting the first joint lens. The optical system of this embodiment satisfies conditional expression (4), thereby being able to appropriately correct various aberrations while suppressing the increase in the total length of the optical system.

[0045] In the optical system of this embodiment, when the value of conditional expression (4) exceeds the upper limit, the thickness on the optical axis of the positive lens constituting the first cemented lens becomes too large, and the total length of the optical system increases.

[0046] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (4) to 7.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (4) to 6.000, and further to 5.000.

[0047] In the optical system of this embodiment, when the value of conditional expression (4) is lower than the lower limit, the refractive power of the positive lens constituting the first cemented lens cannot be sufficiently strong, and it is difficult to correct various aberrations such as chromatic aberration and Petzval sum.

[0048] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (4) to 1.500. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (4) to 1.800, and further to 3.000.

[0049] In an optical system that satisfies conditional expressions (1), (2), and (4) at the same time, it is possible to suppress the increase in the total length of the optical system, ensure an appropriate length of back focus, suppress shadows in the imaging element, and appropriately correct various aberrations.

[0050] The optical system of this embodiment is composed of a first lens group, an aperture stop and a rear group in sequence from the object side. The rear group has a first combined lens composed of a positive lens and a negative lens. The first lens group has a positive lens arranged on the closest object side. The optical system simultaneously satisfies the following conditional expressions.

[0051] (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 in, f: focal length of the entire optical system y: maximum image height t1: The center thickness of the lens closest to the object side

[0052] Conditional expression (5) defines the ratio of the focal length of the entire optical system to the maximum image height. The optical system of this embodiment satisfies conditional expression (5) and can appropriately correct spherical aberration and coma at the same time while suppressing an increase in the total length of the optical system.

[0053] In the optical system of this embodiment, when the value of conditional expression (5) exceeds the upper limit, the focal length of the optical system becomes too long, and the total length of the optical system increases. In addition, when the total length of the optical system is to be shortened, it is difficult to appropriately correct various aberrations.

[0054] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (5) to 1.600. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (5) to 1.550, and further to 1.500.

[0055] In addition, in the optical system of the present embodiment, when the value of conditional expression (5) is lower than the lower limit value, the difference between the deviation angle of the on-axis light beam and the deviation angle of the off-axis light beam for the lens closest to the object side becomes larger, making it difficult to simultaneously correct the spherical aberration caused by the on-axis light beam and the coma caused by the off-axis light beam.

[0056] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (5) to 1.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (5) to 1.100, and further to 1.200.

[0057] Conditional expression (6) specifies the ratio of the center thickness of the lens closest to the object to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (6), thereby being able to properly correct coma while arranging the exit pupil at an appropriate position.

[0058] In the optical system of this embodiment, when the value of conditional expression (6) exceeds the upper limit, the thickness of the positive lens arranged on the most object side becomes too thick, and since the position of the aperture stop is close to the image plane, it is difficult to arrange the exit pupil at an appropriate position.

[0059] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (6) to 0.080. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (6) to 0.075, and further to 0.070.

[0060] In the optical system of the present embodiment, when the value of conditional expression (6) is below the lower limit, the thickness of the positive lens arranged on the most object side becomes too thin, making it difficult to correct coma aberration.

[0061] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (6) to 0.025. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (6) to 0.030, and further to 0.035.

[0062] In an optical system that satisfies both conditional expressions (5) and (6), the exit pupil can be arranged at an appropriate position while suppressing an increase in the total length of the optical system, and spherical aberration and coma can be appropriately corrected simultaneously.

[0063] In addition, in the optical system of the present embodiment, it is preferable that the optical system satisfies the following conditional expression.

[0064] (7) 3.000 < νdp1-νdn1 < 30.000 in, νdp1: Abbe number of the positive lens constituting the first cemented lens based on the d line νdn1: Abbe number of the negative lens constituting the first cemented lens based on the d line

[0065] Conditional expression (7) defines the difference in Abbe number based on the d-line in the positive lens and the negative lens constituting the first cemented lens. The optical system of this embodiment satisfies conditional expression (7), thereby being able to appropriately correct chromatic aberration by the first cemented lens.

[0066] In the optical system of the present embodiment, when the value of conditional expression (7) exceeds the upper limit, correction of chromatic aberration by the first cemented lens becomes excessive.

[0067] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (7) to 30.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (7) to 25.000, and further to 20.000.

[0068] In the optical system of the present embodiment, when the value of conditional expression (7) is lower than the lower limit, correction of chromatic aberration by the first cemented lens becomes too small.

[0069] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (7) to 3.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (7) to 4.500, and further to 5.000.

[0070] In the optical system of the present embodiment, it is preferable that the rear group is composed of a positive lens and a negative lens and has a second cemented lens different from the first cemented lens.

[0071] In the optical system of this embodiment, by having such a configuration, it is possible to appropriately correct the chromatic aberration of magnification.

[0072] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0073] (8) 1.000 < f / y < 1.380 f: focal length of the entire optical system

[0074] Conditional expression (8) specifies the ratio of the focal length of the entire optical system to the maximum image height. The optical system of this embodiment satisfies conditional expression (8), thereby being able to appropriately correct spherical aberration and coma at the same time while appropriately correcting chromatic aberration of magnification through the first and second cemented lenses.

[0075] In the optical system of the present embodiment, when the value of conditional expression (8) exceeds the upper limit value, chromatic aberration of magnification cannot be appropriately corrected by the first cemented lens and the second cemented lens.

[0076] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (8) to 1.380. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (8) to 1.330, and further to 1.280.

[0077] In addition, in the optical system of the present embodiment, when the value of conditional expression (8) is lower than the lower limit, the difference between the deflection angle of the on-axis light beam and the deflection angle of the off-axis light beam for the lens closest to the object side becomes larger, making it difficult to appropriately correct spherical aberration and coma at the same time.

[0078] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (8) to 1.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (8) to 1.100, and further to 1.200.

[0079] In the optical system of the present embodiment, it is preferred that, in the first cemented lens and the second cemented lens, a negative lens is arranged on the object side for the cemented lens arranged on the object side, and a negative lens is arranged on the image side for the cemented lens arranged on the image side.

[0080] In the optical system of the present embodiment, in the cemented lens, by arranging a negative lens on the object side where the on-axis light beam is thicker, various aberrations, especially spherical aberration, can be effectively corrected. In addition, by making the first cemented lens and the second cemented lens have a symmetrical shape, various aberrations, especially coma, can be effectively corrected.

[0081] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0082] (9) -0.030 < fc1 / fc2 < 1.000 in, fc1: The combined focal length of the first cemented lens and the second cemented lens that is located on the object side fc2: The combined focal length of the first cemented lens and the second cemented lens that is disposed on the image plane side

[0083] Conditional formula (9) specifies the ratio of the composite focal length of the first and second combined lenses disposed on the object side to the composite focal length of the first and second combined lenses disposed on the image side. The optical system of this embodiment satisfies conditional formula (9), thereby suppressing the increase in the total length of the optical system while suppressing the generation of spherical aberration.

[0084] In the optical system of this embodiment, when the value of conditional expression (9) exceeds the upper limit, the refractive power of the first and second cemented lenses arranged on the image plane side increases, and the total length of the optical system becomes too long.

[0085] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (9) to 1.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (9) to 0.960, and further to 0.930.

[0086] In the optical system of this embodiment, when the value of conditional expression (9) is lower than the lower limit, the refractive power of the cemented lens arranged on the image plane side of the first cemented lens and the second cemented lens increases, causing spherical aberration.

[0087] In the optical system of this embodiment, by setting the lower limit value of conditional expression (9) to -0.030, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (9) to -0.020, and further to -0.010.

[0088] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0089] (10) 0.050 < Np2-Nn2 < 0.400 in, Np2: Refractive index of the positive lens constituting the second cemented lens Nn2: Refractive index of the negative lens constituting the second cemented lens

[0090] Conditional expression (10) specifies the ratio of the refractive index of the positive lens constituting the second cemented lens to 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 satisfying conditional expression (10).

[0091] In the optical system of the present embodiment, when the value of conditional expression (10) exceeds the upper limit, the refractive power on the cemented surface of the second cemented lens becomes too strong, and large aberrations occur.

[0092] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (10) to 0.400. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (10) to 0.350, and further to 0.300.

[0093] In the optical system of the present embodiment, when the value of conditional expression (10) is lower than the lower limit, the Petzval sum cannot be appropriately corrected by the second cemented lens, and field curvature occurs.

[0094] In the optical system of this embodiment, by setting the lower limit value of conditional expression (10) to 0.050, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (10) to 0.060, and further to 0.070.

[0095] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0096] (11) 3.000 < νdp2-νdn2 < 30.000 in, νdp2: Abbe number of the positive lens constituting the second cemented lens based on the d line νdn2: Abbe number of the negative lens constituting the second cemented lens based on the d line

[0097] Conditional expression (11) specifies the difference between the Abbe number of the positive lens constituting the second cemented lens based on the d-line and the Abbe number of the negative lens constituting the second cemented lens based on the d-line. The optical system of this embodiment satisfies conditional expression (11), thereby being able to appropriately correct chromatic aberration through the second cemented lens.

[0098] In the optical system of the present embodiment, when the value of conditional expression (11) exceeds the upper limit value, the correction of chromatic aberration by the second cemented lens becomes excessive.

[0099] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (11) to 30.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (11) to 25.000, and further to 20.000.

[0100] In the optical system of the present embodiment, when the value of conditional expression (11) is lower than the lower limit, correction of chromatic aberration by the second cemented lens becomes too small.

[0101] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the lower limit value of conditional expression (11) to 3.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit value of conditional expression (11) to 4.500, and further to 5.000.

[0102] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0103] (12) 0.550 < (ΣΔPzi) / ΔPz < 1.400 in, ΣΔPzi: The sum of the Petzval sum of each of at least one cemented lens composed of a positive lens and a negative lens and 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

[0104] Conditional formula (12) specifies the ratio of the sum of the Petzval sum of each of the cemented lenses composed of a positive lens and a negative lens and included in the rear group and the sum of the Petzval sum of the entire optical system and the reciprocal of the focal length of the entire optical system to the sum of the Petzval sum of the entire optical system. In conditional formula (12), the numerator represents the correction power of the Petzval sum in the cemented lens, and the denominator represents the correction power of the Petzval sum in the entire optical system. The optical system of this embodiment satisfies conditional formula (12), so that the image curvature can be appropriately corrected by the cemented lens.

[0105] In the optical system of the present embodiment, when the value of conditional expression (12) exceeds the upper limit value, correction of the field curvature by the cemented lens becomes excessive.

[0106] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (12) to 1.400. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (12) to 1.200, and further to 1.100.

[0107] In the optical system of the present embodiment, when the value of conditional expression (12) is lower than the lower limit, correction of the field curvature by the cemented lens becomes too small.

[0108] In the optical system of this embodiment, by setting the lower limit of conditional expression (12) to 0.550, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit of conditional expression (12) to 0.800, and further to 0.950.

[0109] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0110] (13) 0.525 < ΣD / TL < 0.967 in, ΣD: The distance from the lens surface closest to the object to the lens surface closest to the image plane TL: The distance from the lens surface closest to the object to the image surface

[0111] Conditional expression (13) specifies the ratio of the distance from the lens surface closest to the object side to the lens surface closest to the image side to the distance from the lens surface closest to the object side to the image plane. The optical system of this embodiment satisfies conditional expression (13), thereby ensuring a back focal length of appropriate length while arranging the lenses required for correcting various aberrations.

[0112] In the optical system of the present embodiment, when the value of conditional expression (13) exceeds the upper limit, the back focus becomes too short, making it difficult to arrange filters and the like in front of the image sensor.

[0113] In the optical system of this embodiment, by setting the upper limit value of conditional expression (13) to 0.967, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred that the upper limit value of conditional expression (13) is set to 0.850, and further set to 0.775.

[0114] In the optical system of the present embodiment, when the value of conditional expression (13) is lower than the lower limit, it is difficult to arrange lenses required for correcting various aberrations.

[0115] In the optical system of this embodiment, by setting the lower limit value of conditional expression (13) to 0.525, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (13) to 0.600, and further to 0.675.

[0116] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0117] (14) 0.050 < dL1_St / TL < 0.167

[0118] in, dL1_St: The distance from the lens surface closest to the object to the aperture stop TL: The distance from the lens surface closest to the object to the image surface

[0119] Conditional expression (14) specifies the ratio of the distance from the lens surface closest to the object to the aperture stop to the distance from the lens surface closest to the object to the image plane. The optical system of this embodiment satisfies conditional expression (14), thereby being able to appropriately correct spherical aberration while suppressing shadows in the imaging element.

[0120] In the optical system of this embodiment, when the value of conditional expression (14) exceeds the upper limit, the exit pupil position approaches the image plane, and a shadow is generated in the image sensor.

[0121] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (14) to 0.167. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (14) to 0.145, and further to 0.130.

[0122] In the optical system of the present embodiment, when the value of conditional expression (14) is lower than the lower limit, the aberration cannot be sufficiently corrected by the optical system in front of the aperture stop, and it is difficult to correct the spherical aberration.

[0123] In the optical system of this embodiment, by setting the lower limit of conditional expression (14) to 0.050, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit of conditional expression (14) to 0.055, and further to 0.070.

[0124] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0125] (15) 0.750 < TL / f < 1.600 in, TL: The distance from the lens surface closest to the object to the image surface f: focal length of the entire optical system

[0126] Conditional expression (15) specifies 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. The optical system of this embodiment satisfies conditional expression (15), thereby suppressing the increase in the total length of the optical system, suppressing the shadow in the imaging element, and appropriately correcting various aberrations.

[0127] In the optical system of this embodiment, when the value of conditional expression (15) exceeds the upper limit, the total length of the optical system becomes too large. In addition, the focal length is too short relative to the total length, and the focal length of each group becomes short, making it difficult to correct coma and spherical aberration.

[0128] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (15) to 1.600. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (15) to 1.500, and further to 1.450.

[0129] In the optical system of this embodiment, when the value of conditional expression (15) is below the lower limit, the total length of the optical system becomes too small, making it difficult to properly arrange the lenses for correcting various aberrations. In addition, the exit pupil position is close to the image plane, causing a shadow in the imaging element.

[0130] In the optical system of this embodiment, by setting the lower limit of conditional expression (15) to 0.750, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit of conditional expression (15) to 0.900, and further to 1.100.

[0131] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0132] (16) 0.590 < TLs / TL < 1.333 in, TLs: distance from the aperture stop surface to the image surface TL: The distance from the lens surface closest to the object to the image surface

[0133] Conditional expression (16) specifies the ratio of the distance from the aperture stop surface to the image plane to the distance from the lens surface closest to the object side to the image plane. The optical system of this embodiment satisfies conditional expression (16), thereby being able to suppress shadows in the imaging element while appropriately correcting spherical aberration.

[0134] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (16) to 1.333. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (16) to 1.150, and further to 0.950.

[0135] In the optical system of the present embodiment, when the value of conditional expression (16) is lower than the lower limit, the exit pupil position is close to the image plane, and a shadow is generated in the image sensor.

[0136] In the optical system of this embodiment, by setting the lower limit value of conditional expression (16) to 0.590, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (16) to 0.625, and further to 0.750.

[0137] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0138] (17) 0.700 < f1 / f < 5.000 in, f1: Focal length of the first lens group f: focal length of the entire optical system

[0139] Conditional expression (17) specifies the ratio of the focal length of the first lens unit to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (17), thereby suppressing the increase in the total length of the optical system and suppressing the occurrence of various aberrations such as spherical aberration and coma.

[0140] In the optical system of this embodiment, when the value of conditional expression (17) exceeds the upper limit, the positive refractive power of the first lens unit becomes weak, and thus the total length of the optical system becomes too long.

[0141] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (17) to 5.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (17) to 4.800, and further to 4.650.

[0142] In the optical system of this embodiment, when the value of conditional expression (17) is lower than the lower limit, the positive refractive power of the first lens unit becomes too strong, and various aberrations such as spherical aberration and coma are likely to occur.

[0143] In the optical system of this embodiment, by setting the lower limit of conditional expression (17) to 0.700, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferable to set the lower limit of conditional expression (17) to 1.000, and further to 1.400.

[0144] In the optical system of the present embodiment, the first lens group preferably includes one or two lenses.

[0145] In the optical system of this embodiment, when the first lens group has three or more lenses, the total length of the optical system increases. In addition, since the position of the aperture stop surface is close to the image plane, the exit pupil becomes short, and a shadow is easily generated in the imaging element.

[0146] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0147] (18) 0.010 < D1 / TL < 0.150 in, D1: The distance from the lens surface closest to the object side of the first lens group to the lens surface closest to the image side of the first lens group TL: The distance from the lens surface closest to the object to the image surface

[0148] Conditional expression (18) specifies the ratio of the distance from the lens surface closest to the object side of the first lens group to the lens surface closest to the image plane side of the first lens group to the distance from the lens surface closest to the object side to the image plane. The optical system of this embodiment satisfies conditional expression (18), thereby being able to appropriately correct coma while suppressing an increase in the total length of the optical system.

[0149] In the optical system of this embodiment, when the value of conditional expression (18) exceeds the upper limit, the thickness of the first lens unit increases, so the total length of the optical system becomes too long.

[0150] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (18) to 0.150. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (18) to 0.130, and further to 0.110.

[0151] In the optical system of the present embodiment, when the value of conditional expression (18) is less than the lower limit, the thickness of the first lens unit becomes small, making it difficult to correct coma aberration.

[0152] In the optical system of this embodiment, by setting the lower limit value of conditional expression (18) to 0.010, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (18) to 0.020, and further to 0.025.

[0153] In addition, the optical system of the present embodiment is preferably composed of 6 or more and 9 or less lenses.

[0154] When the optical system of the present embodiment is composed of more than 9 lenses, the total thickness of the lenses increases, and the total length of the optical system increases. In addition, when the optical system of the present embodiment is composed of less than 6 lenses, it is difficult to properly correct each aberration.

[0155] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0156] (19) 0.025 < t1 / ΣD < 0.080 in, t1: The center thickness of the lens closest to the object side ΣD: The distance from the lens surface closest to the object to the lens surface closest to the image plane

[0157] Conditional expression (19) specifies the ratio of the center thickness of the lens closest to the object side to the distance from the lens surface closest to the object side to the lens surface closest to the image plane side. The optical system of this embodiment satisfies conditional expression (19), thereby being able to appropriately correct coma while suppressing shadows in the imaging element.

[0158] In the optical system of this embodiment, when the value of conditional expression (19) exceeds the upper limit, the center thickness of the lens closest to the object side becomes larger and the position of the aperture stop surface is closer to the image plane, so the exit pupil becomes shorter and shadows are easily generated in the shooting element.

[0159] In the optical system of this embodiment, by setting the upper limit value of conditional expression (19) to 0.080, the effect of this embodiment can be obtained more reliably. In order to obtain the effect of this embodiment more reliably, it is preferable to set the upper limit value of conditional expression (19) to 0.070.

[0160] In the optical system of the present embodiment, when the value of conditional expression (19) is below the lower limit, the center thickness of the lens closest to the object becomes small, making it difficult to correct coma aberration.

[0161] In the optical system of this embodiment, by setting the lower limit value of conditional expression (19) to 0.025, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (19) to 0.030, and further to 0.035.

[0162] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0163] (20) -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 in, rR1: The radius of curvature of the object side lens surface closest to the image plane rR2: The radius of curvature of the image-side lens surface of the lens closest to the image plane

[0164] Conditional expression (20) defines the shape factor of the lens closest to the image plane. The optical system of the present embodiment can appropriately suppress the occurrence of field curvature by satisfying conditional expression (20).

[0165] In the optical system of this embodiment, when the value of conditional expression (20) exceeds the upper limit, the incident angle to the object-side lens surface of the lens closest to the image plane becomes large, and field curvature is likely to occur.

[0166] In the optical system of this embodiment, by setting the upper limit value of conditional expression (20) to -1.500, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (20) to -1.800, and further to -2.000.

[0167] In the optical system of this embodiment, when the value of conditional expression (20) is lower than the lower limit, the incident angle to the image-side lens surface of the lens closest to the image plane becomes large, and field curvature is likely to occur.

[0168] In the optical system of this embodiment, by setting the lower limit value of conditional expression (20) to -4.500, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (20) to -4.000, and further to -3.000.

[0169] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0170] (21) 0.130 < tR / ΣD < 0.350 in, tR: The center thickness of the lens closest to the image plane ΣD: The distance from the lens surface closest to the object to the lens surface closest to the image plane

[0171] Conditional expression (21) specifies 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 side to the lens surface closest to the image plane. The optical system of this embodiment satisfies conditional expression (21), thereby suppressing the increase in the total length of the optical system while suppressing the shadow in the imaging element.

[0172] In the optical system of this embodiment, when the value of conditional expression (21) exceeds the upper limit value, the total length of the optical system becomes too large.

[0173] In the optical system of this embodiment, by setting the upper limit value of conditional expression (21) to 0.350, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred that the upper limit value of conditional expression (21) is set to 0.300, and further set to 0.270.

[0174] In addition, in the optical system of this embodiment, when the value of conditional expression (21) is lower than the lower limit, the center thickness of the lens closest to the image plane becomes smaller and the positive optical focal length becomes weaker, so the position of the exit pupil is close to the image plane, and shadows are easily generated in the imaging element.

[0175] In the optical system of this embodiment, by setting the lower limit value of conditional expression (21) to 0.130, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred that the lower limit value of conditional expression (21) is set to 0.150, and further set to 0.180.

[0176] In addition, in the optical system of the present embodiment, it is preferred that the rear group comprises, in order from the object side, a second lens group, a third lens group having negative optical focal length, and a fourth lens group, the third lens group comprising, on the side closest to the object, a negative meniscus lens which is arranged on the image plane side relative to the aperture stop and has a concave surface facing the object side, and is arranged on the side closest to the image plane, and the fourth lens group consists of positive lenses.

[0177] In the optical system of this embodiment, by having such a configuration, it is possible to correct field curvature well while lengthening the distance between the exit pupil and the image plane.

[0178] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0179] (22) 0.300 < (-f3) / f < 2.200 in, f3: Focal length of the third lens group f: focal length of the entire optical system

[0180] Conditional expression (23) specifies the ratio of the focal length of the third lens group to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (22), thereby being able to appropriately correct various aberrations such as coma in the sagittal direction and field curvature while suppressing the increase in the total length of the optical system.

[0181] In the optical system of this embodiment, when the value of conditional expression (22) exceeds the upper limit, the total length of the optical system becomes too large. In addition, it is difficult to set the exit pupil at an appropriate position.

[0182] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (22) to 2.200. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (22) to 1.600, and further to 1.300.

[0183] In the optical system of this embodiment, when the value of conditional expression (22) is below the lower limit, the refractive power of the third lens unit becomes too large, making it difficult to correct various aberrations such as coma in the sagittal direction and field curvature.

[0184] In the optical system of this embodiment, by setting the lower limit value of conditional expression (22) to 0.300, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (22) to 0.450, and further to 0.750.

[0185] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0186] (23) 0.450 < f4 / f < 2.300

[0187] in,

[0188] f4: Focal length of the 4th lens group

[0189] f: focal length of the entire optical system

[0190] Conditional expression (23) defines the ratio of the focal length of the fourth lens unit to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (23), thereby suppressing the shadow on the image sensor and suppressing the increase in the total length of the optical system.

[0191] In the optical system of this embodiment, when the value of conditional expression (23) exceeds the upper limit, the position of the exit pupil is close to the image plane, and shadows are likely to be generated in the image sensor. In addition, it is difficult to correct the Petzval sum.

[0192] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (23) to 2.300. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (23) to 1.680, and further to 1.500.

[0193] In the optical system of the present embodiment, when the value of conditional expression (23) is lower than the lower limit, the total length of the optical system becomes too large.

[0194] In the optical system of this embodiment, by setting the lower limit value of conditional expression (23) to 0.450, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (23) to 0.650, and further to 1.000.

[0195] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0196] (24) 0.286 < (-f3) / f4 < 2.000 in, f3: Focal length of the third lens group f4: Focal length of the 4th lens group

[0197] Conditional expression (24) specifies the ratio of the focal length of the third lens group to the focal length of the fourth lens group. The optical system of this embodiment satisfies conditional expression (24), thereby being able to appropriately correct various aberrations such as field curvature and coma by the third lens group and the fourth lens group.

[0198] In the optical system of this embodiment, when the value of conditional expression (24) exceeds the upper limit, the refractive power of the third lens unit becomes too strong, making it difficult to correct various aberrations such as field curvature and coma.

[0199] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (24) to 2.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (24) to 1.500, and further to 1.350.

[0200] In the optical system of this embodiment, when the value of conditional expression (24) is lower than the lower limit, the refractive power of the fourth lens unit becomes too strong, making it difficult to correct various aberrations such as field curvature and coma.

[0201] In the optical system of this embodiment, by setting the lower limit value of conditional expression (24) to 0.286, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (24) to 0.350, and further to 0.600.

[0202] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0203] (25) 0.300 < f2 / f < 2.000 in, f2: Focal length of the second lens group f: focal length of the entire optical system

[0204] Conditional expression (25) specifies the ratio of the focal length of the second lens group to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (25), thereby being able to satisfactorily correct field curvature and coma aberration without color fluctuation.

[0205] In the optical system of the present embodiment, when the value of conditional expression (25) exceeds the upper limit, the Petzval sum cannot be maintained at an appropriate value, and it is difficult to correct the field curvature well.

[0206] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (25) to 2.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (25) to 1.800, and further to 1.500.

[0207] In the optical system of the present embodiment, when the value of conditional expression (25) is lower than the lower limit, it is difficult to suppress the occurrence of deviation in coma aberration for each color.

[0208] In the optical system of this embodiment, by setting the lower limit value of conditional expression (25) to 0.300, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (25) to 0.500, and further to 0.700.

[0209] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0210] (26) 1.500 < (r312+r311) / (r312-r311) < 7.000 in, r311: The radius of curvature of the object-side lens surface of the lens closest to the object in the third lens group r312: The radius of curvature of the image-side lens surface of the lens closest to the object in the third lens group

[0211] Conditional expression (26) defines the shape factor of the lens closest to the object side of the third lens unit. The optical system of this embodiment can appropriately suppress the occurrence of field curvature by satisfying conditional expression (26).

[0212] In the optical system of this embodiment, when the value of conditional expression (26) is higher than the upper limit or lower than the lower limit, the deflection angle of the off-axis light beam becomes too large, so that field curvature is likely to occur.

[0213] In the optical system of this embodiment, the effect of this embodiment can be obtained more reliably by setting the upper limit value of conditional expression (26) to 7.000. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the upper limit value of conditional expression (26) to 5.000, and further to 3.000.

[0214] In the optical system of this embodiment, by setting the lower limit value of conditional expression (26) to 1.500, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (26) to 1.700, and further to 2.000.

[0215] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0216] (27) 0.150 < d3 / f < 0.750 in, d3: The distance from the aperture stop to the lens surface closest to the object side of the third lens group f: focal length of the entire optical system

[0217] Conditional expression (27) specifies the ratio of the distance from the aperture stop to the lens surface of the third lens group closest to the object side to the focal length of the entire optical system. The optical system of this embodiment satisfies conditional expression (27), thereby suppressing the increase in the total length of the optical system while suppressing the shadow in the imaging element.

[0218] In the optical system of this embodiment, when the value of conditional expression (27) exceeds the upper limit value, the total length of the optical system becomes too large.

[0219] In the optical system of this embodiment, by setting the upper limit value of conditional expression (27) to 0.750, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred that the upper limit value of conditional expression (27) is set to 0.700, and further set to 0.650.

[0220] In the optical system of the present embodiment, when the value of conditional expression (27) is lower than the lower limit, the position of the exit pupil is close to the image plane, and a shadow is likely to be generated in the image sensor.

[0221] In the optical system of this embodiment, by setting the lower limit value of conditional expression (27) to 0.150, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (27) to 0.200, and further to 0.250.

[0222] In addition, in the optical system of the present embodiment, it is preferable that the following conditional expression is satisfied.

[0223] (28) 0.400 < dL1_Gr3 / ΣD < 0.900 in, dL1_Gr3: The distance from the lens surface closest to the object to the lens surface closest to the object of the third lens unit ΣD: The distance from the lens surface closest to the object to the lens surface closest to the image plane

[0224] Conditional expression (28) specifies the ratio of the distance from the lens surface closest to the object side to the lens surface closest to the object side of the third lens group to the distance from the lens surface closest to the object side to the lens surface closest to the image plane side. The optical system of this embodiment satisfies conditional expression (28), thereby suppressing the increase in the total length of the optical system while suppressing the shadow in the imaging element.

[0225] In the optical system of this embodiment, when the value of conditional expression (28) exceeds the upper limit value, the total length of the optical system becomes too large.

[0226] In the optical system of this embodiment, by setting the upper limit value of conditional expression (28) to 0.900, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred that the upper limit value of conditional expression (28) is set to 0.850, and further set to 0.800.

[0227] In the optical system of this embodiment, when the value of conditional expression (28) is lower than the lower limit, the position of the exit pupil is close to the image plane, and a shadow is likely to be generated in the image sensor.

[0228] In the optical system of this embodiment, by setting the lower limit value of conditional expression (28) to 0.400, the effect of this embodiment can be obtained more reliably. In addition, in order to obtain the effect of this embodiment more reliably, it is preferred to set the lower limit value of conditional expression (28) to 0.450, and further to 0.500.

[0229] According to the above structure, it is possible to realize a compact optical system having excellent imaging performance.

[0230] The optical device of this embodiment has the optical system having the above-mentioned structure, thereby realizing an optical device having excellent optical performance.

[0231] The manufacturing method of the optical system of the present embodiment is that the optical system is composed of a first lens group, an aperture stop and a rear group in sequence from the object side, and the rear group has a first joined lens composed of a positive lens and a negative lens. In the manufacturing method of the optical system, each lens is arranged in such a way that the optical system simultaneously satisfies the following conditional expressions.

[0232] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface Np1: Refractive index of the positive lens constituting the first cemented lens Nn1: Refractive index of the negative lens constituting the first cemented lens

[0233] The manufacturing method of the optical system of the present embodiment is that the optical system is composed of a first lens group, an aperture stop and a rear group in sequence from the object side, and the rear group has a first joined lens composed of a positive lens and a negative lens. In the manufacturing method of the optical system, each lens is arranged in such a way that the optical system simultaneously satisfies the following conditional expressions.

[0234] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface tp1: The thickness of the positive lens constituting the first cemented lens on the optical axis tn1: The thickness of the negative lens constituting the first cemented lens on the optical axis

[0235] The manufacturing method of the optical system of the present embodiment is that the optical system is composed of a first lens group, an aperture stop and a rear group in sequence from the object side, and the rear group has a first joined lens composed of a positive lens and a negative lens. In the manufacturing method of the optical system, each lens is arranged in such a way that the optical system simultaneously satisfies the following conditional expressions.

[0236] (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 in, f: focal length of the entire optical system y: maximum image height t1: The center thickness of the positive lens located closest to the object side

[0237] By using this method for manufacturing an optical system, an optical system with good optical performance can be manufactured.

[0238] (Numerical Example)

[0239] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings.

[0240] (First embodiment)

[0241] Figure 1 It is a cross-sectional view of the optical system of the first embodiment when an object at infinity is in focus.

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

[0243] The first lens group G1 is composed of a positive meniscus lens L1 having a convex surface facing the object side.

[0244] The second lens group G2 is composed of the following lenses in sequence from the object side: a cemented positive lens composed of a biconcave negative lens L2 and a biconvex positive lens L3, a cemented positive lens composed of a biconvex positive lens L4 and a biconcave negative lens L5, and a meniscus-shaped positive lens L6 with the concave surface facing the object side.

[0245] The third lens group G3 is composed of a negative meniscus lens L7 having a concave surface facing the object side.

[0246] The fourth lens group G4 is composed of a positive lens L8 of a meniscus shape with a concave surface facing the object side. The positive lens L8 is formed by providing a resin layer on the surface on the object side of a glass lens body. The positive lens L8 is a composite aspheric lens in which the surface on the object side of the resin layer is an aspheric surface. In the [lens parameters] described later, surface number 14 represents the surface on the object side of the resin layer, surface number 15 represents the surface on the image side of the resin layer and the surface on the object side of the lens body (the surface where the resin layer and the lens body are bonded), and surface number 16 represents the surface on the image side of the lens body. In the present embodiment, the composite aspheric lens is regarded as one aspheric lens. Therefore, the surface with surface number 14 is equivalent to the object side lens surface of the positive lens L8, and the sum of the surface intervals of surface number 14 and surface number 15 is equivalent to the center thickness of the positive lens L8.

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

[0248] In the optical system of this embodiment, focusing is performed by moving the entire optical system along the optical axis. In the optical system of this embodiment, when focusing on a close object from a state focused on infinity, the optical system moves 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 are equivalent to the rear group. In addition, the cemented positive lens composed of the negative lens L2 and the positive lens L3 is equivalent to the first cemented lens, and the cemented positive lens composed of the positive lens L4 and the negative lens L5 is equivalent to the second cemented lens.

[0250] Table 1 below shows the values ​​of the parameters of the optical system of this embodiment. In [Lens Parameters] in Table 1, m represents the order of the optical surface from the object side, r represents the radius of curvature, d represents the surface interval, n(d) represents the refractive index for the d line (wavelength 587.6nm), and νd represents the Abbe number for the d line. The radius of curvature r=∞ represents a plane. In addition, in [Lens Parameters], the optical surface with "*" is represented as an aspherical surface.

[0251] In [Aspherical surface data], m represents the optical surface corresponding to the aspherical surface data, K represents the cone constant, and A4 to A18 represent the aspherical surface coefficients.

[0252] When the height perpendicular to the optical axis is y, the distance along the optical axis from the tangent plane of each aspheric surface at the height y to each aspheric surface (the amount of depression) is S(y), the radius of curvature of the reference spherical surface (paraxial radius of curvature) is r, the cone constant is K, and the n-order aspheric coefficient is An, the aspheric surface is represented by the following formula (a). In addition, in each embodiment, the quadratic aspheric coefficient A2 is 0. In addition, "En" represents "×10 -n ”.

[0253] (a) S(y) = (y 2 / r) / { 1 + (1-K×y 2 / r 2 ) 1 / 2} + A4×y 4 + A6×y 6 + A8×y 8 +A10×y 10 +A12×y 12 + A14×y 14 +A16×y 16 + A18×y 18

[0254] In [Overall Parameters] in Table 1, f represents the focal length of the entire optical system, F.NO represents the F value of the optical system, ω represents the half field angle (degrees), Y represents the maximum image height, and TL represents the distance from the lens surface closest to the object to the image plane when focusing on an object at infinity.

[0255] In "Back Focus" in Table 1, Bf represents the back focus of the optical system in terms of air conversion length.

[0256] The focal length f, the radius of curvature r, and other lengths described in Table 1 are expressed in “mm.” However, even if the optical system is scaled up or scaled down, the same optical performance can be obtained, and therefore the present invention is not limited thereto.

[0257] The symbols in Table 1 described above are also used in tables of other examples described later.

[0258] (Table 1)

[0259] [Lens parameters]

[0260] [Aspherical surface data]

[0261] [Overall parameters]

[0262] [Focal length data for each group]

[0263] [Back focus]

[0264] Figure 21 and 10 are diagrams showing various aberrations of the optical system of the first embodiment when an object at infinity is in focus.

[0265] In each aberration diagram, FNO represents the F value, and Y represents the image height. In detail, the value of the F value corresponding to the maximum aperture is shown in the spherical aberration diagram, the maximum value of the image height is shown in the astigmatism diagram and the distortion diagram, and the value of each image height is shown in the coma diagram. d represents the d line, and g represents the g line (wavelength 435.8nm). In the astigmatism diagram, the solid line represents the sagittal image plane, and the dotted line represents the meridional image plane. In the aberration diagrams of other embodiments described later, the same symbols as those of the aberration diagrams of this embodiment are also used.

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

[0267] (Second embodiment)

[0268] Figure 3 It is a cross-sectional view of the optical system of the second embodiment when an object at infinity is in focus.

[0269] The optical system of this embodiment comprises, from the object side, a first lens group G1 with positive optical power, an aperture stop S, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power.

[0270] The first lens group G1 is composed of a positive meniscus lens L1 having a convex surface facing the object side.

[0271] The second lens group G2 is composed, in order from the object side, of a positive lens formed by a biconcave negative lens L2 and a biconvex positive lens L3, a 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.

[0272] The third lens group G3 is composed of a negative meniscus lens L7 having a concave surface facing the object side.

[0273] The fourth lens group G4 is composed of a positive lens L8 of a meniscus shape with a concave surface facing the object side. The positive lens L8 is formed by providing a resin layer on the object side surface of a glass lens body. The positive lens L8 is a composite aspheric lens in which the object side surface of the resin layer is an aspheric surface. In the [lens parameters] described later, surface number 14 represents the object side surface of the resin layer, surface number 15 represents 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 bonded), and surface number 16 represents the image side surface of the lens body. The surface numbered 14 is equivalent to the object side lens surface of the positive lens L8, and the sum of the surface intervals between the surface numbers 14 and 15 is equivalent to the center thickness of the positive lens L8.

[0274] An imaging element (not shown) composed of a CCD or a CMOS or the like is arranged on the image plane I.

[0275] In the optical system of this embodiment, focusing is performed by moving the entire optical system along the optical axis. In the optical system of this embodiment, when focusing on a close object from a state focused on infinity, the optical system moves from the image plane side to the object side.

[0276] In the optical system of this embodiment, the second lens group G2, the third lens group and the fourth lens group are equivalent to the rear group. In addition, the cemented positive lens of the negative lens L2 and the positive lens L3 is equivalent to the first cemented lens, and the cemented positive lens of the positive lens L4 and the negative lens L5 is equivalent to the second cemented lens.

[0277] Table 2 below shows the values ​​of the parameters of the optical system of this embodiment.

[0278] (Table 2)

[0279] [Lens parameters]

[0280] [Aspherical surface data]

[0281] [Overall parameters]

[0282] [Focal length data for each group]

[0283] [Back focus]

[0284] Figure 4 1 and 10 are diagrams showing various aberrations of the optical system of the second embodiment when an object at infinity is in focus.

[0285] As can be seen from the aberration diagrams, the optical system of this embodiment appropriately corrects various aberrations and has high optical performance.

[0286] (Third embodiment)

[0287] Figure 5 It is a cross-sectional view of the optical system of the third embodiment when an object at infinity is in focus.

[0288] The optical system of this embodiment comprises, from the object side, a first lens group G1 with positive optical power, an aperture stop S, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power.

[0289] The first lens group G1 is composed of a positive meniscus lens L1 having a convex surface facing the object side.

[0290] The second lens group G2 is composed, in order from the object side, of a positive lens formed by a biconcave negative lens L2 and a biconvex positive lens L3, a 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.

[0291] The third lens group G3 is composed of a negative meniscus lens L7 having a concave surface facing the object side.

[0292] The fourth lens group G4 is composed of a positive lens L8 of a meniscus shape with a concave surface facing the object side. The positive lens L8 is formed by providing a resin layer on the object side surface of a glass lens body. The positive lens L8 is a composite aspheric lens in which the object side surface of the resin layer is an aspheric surface. In the [lens parameters] described later, surface number 14 represents the object side surface of the resin layer, surface number 15 represents 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 bonded), and surface number 16 represents the image side surface of the lens body. The surface numbered 14 is equivalent to the object side lens surface of the positive lens L8, and the sum of the surface intervals between the surface numbers 14 and 15 is equivalent to the center thickness of the positive lens L8.

[0293] An imaging element (not shown) composed of a CCD or a CMOS or the like is arranged on the image plane I.

[0294] In the optical system of this embodiment, focusing is performed by moving the entire optical system along the optical axis. In the optical system of this embodiment, when focusing on a close object from a state focused on infinity, the optical system moves from the image plane side to the object side.

[0295] In the optical system of this embodiment, the second lens group G2, the third lens group and the fourth lens group are equivalent to the rear group. In addition, the cemented positive lens of the negative lens L2 and the positive lens L3 is equivalent to the first cemented lens, and the cemented positive lens of the positive lens L4 and the negative lens L5 is equivalent to the second cemented lens.

[0296] Table 3 below shows the values ​​of the parameters of the optical system of this embodiment.

[0297] (Table 3)

[0298] [Lens parameters]

[0299] [Aspherical surface data]

[0300] [Overall parameters]

[0301] [Focal length data for each group]

[0302] [Back focus]

[0303] Figure 6 These are diagrams showing various aberrations of the optical system of Example 3 when an object at infinity is in focus.

[0304] As can be seen from the aberration diagrams, the optical system of this embodiment appropriately corrects various aberrations and has high optical performance.

[0305] (Fourth embodiment)

[0306] Figure 7 It is a cross-sectional view of the optical system of the fourth embodiment when an object at infinity is in focus.

[0307] The optical system of this embodiment comprises, from the object side, a first lens group G1 with positive optical power, an aperture stop S, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power.

[0308] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L1 having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side.

[0309] The second lens group G2 is composed, from the object side, in sequence: a positive lens composed of a meniscus-shaped positive lens L3 with its concave surface facing the object side and a negative lens L4 with its concave surface facing the object side, and a negative lens composed of a meniscus-shaped positive lens L5 with its concave surface facing the object side and a biconcave negative lens L6.

[0310] The third lens group G3 is composed of a negative meniscus lens L7 having a concave surface facing the object side.

[0311] The fourth lens group G4 is composed of a positive lens L8 of a meniscus shape with a concave surface facing the object side. The positive lens L8 is formed by providing a resin layer on the object side surface of a glass lens body. The positive lens L8 is a composite aspheric lens in which the object side surface of the resin layer is an aspheric surface. In the [lens parameters] described later, surface number 14 represents the object side surface of the resin layer, surface number 15 represents 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 bonded), and surface number 16 represents the image side surface of the lens body. The surface numbered 14 is equivalent to the object side lens surface of the positive lens L8, and the sum of the surface intervals between the surface numbers 14 and 15 is equivalent to the center thickness of the positive lens L8.

[0312] An imaging element (not shown) composed of a CCD or a CMOS or the like is arranged on the image plane I.

[0313] In the optical system of this embodiment, focusing is performed by moving the entire optical system along the optical axis. In the optical system of this embodiment, when focusing on a close object from a state focused on infinity, the optical system moves from the image plane side to the object side.

[0314] In the optical system of this embodiment, the second lens group G2, the third lens group and the fourth lens group are equivalent to the rear group. In addition, the positive lens L3 and the negative lens L4 are connected to the first connected lens, and the positive lens L5 and the negative lens L6 are connected to the second connected lens.

[0315] Table 4 below shows the values ​​of the parameters of the optical system of this embodiment.

[0316] (Table 4)

[0317] [Lens parameters]

[0318] [Aspherical surface data]

[0319] [Overall parameters]

[0320] [Focal length data for each group]

[0321] [Back focus]

[0322] Figure 8 These are diagrams showing various aberrations of the optical system of Example 4 when an object at infinity is in focus.

[0323] As can be seen from the aberration diagrams, the optical system of this embodiment appropriately corrects various aberrations and has high optical performance.

[0324] (Fifth embodiment)

[0325] Fig. 9 It is a cross-sectional view of the optical system of the fifth embodiment when an object at infinity is in focus.

[0326] The optical system of this embodiment includes, from the object side, a first lens group G1 with negative optical power, an aperture stop S, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power.

[0327] The first lens group G1 is composed of, in order from the object side, a positive meniscus lens L1 having a convex surface facing the object side, and a negative meniscus lens L2 having a convex surface facing the object side.

[0328] The second lens group G2 is composed of a cemented positive lens of a biconvex positive lens L3 and a biconcave negative lens L4.

[0329] The third lens group G3 is composed of, in order from the object side, a meniscus-shaped negative lens L5 having a concave surface facing the object side and a biconcave negative lens L6.

[0330] The fourth lens group G4 is composed of a positive lens L7 of a meniscus shape with a concave surface facing the object side. The positive lens L7 is formed by providing a resin layer on the surface on the object side of a glass lens body. The positive lens L7 is a composite aspheric lens in which the surface on the object side of the resin layer is an aspheric surface. In the [lens parameters] described later, surface number 13 represents the surface on the object side of the resin layer, surface number 14 represents the surface on the image side of the resin layer and the surface on the object side of the lens body (the surface where the resin layer and the lens body are bonded), and surface number 15 represents the surface on the image side of the lens body. The surface numbered 13 is equivalent to the object side lens surface of the positive lens L7, and the sum of the surface intervals between the surface numbers 13 and 14 is equivalent to the center thickness of the positive lens L7.

[0331] An imaging element (not shown) composed of a CCD or a CMOS or the like is arranged on the image plane I.

[0332] In the optical system of this embodiment, focusing is performed by moving the entire optical system along the optical axis. In the optical system of this embodiment, when focusing on a close object from a state focused on infinity, the optical system moves from the image plane side to the object side.

[0333] 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. In addition, the cemented positive lens of the positive lens L3 and the negative lens L4 corresponds to the first cemented lens.

[0334] Table 5 below shows the values ​​of the parameters of the optical system of this embodiment.

[0335] (Table 5)

[0336] [Lens parameters]

[0337] [Aspherical surface data]

[0338] [Overall parameters]

[0339] [Focal length data for each group]

[0340] [Back focus]

[0341] Fig.10 These are diagrams showing various aberrations of the optical system of Example 5 when an object at infinity is in focus.

[0342] As can be seen from the aberration diagrams, the optical system of this embodiment appropriately corrects various aberrations and has high optical performance.

[0343] According to the above-described embodiments, an optical system having excellent optical performance can be realized.

[0344] The conditional expressions corresponding to the values ​​of the respective embodiments are shown below.

[0345] Bf is the back focal length in terms of air conversion 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 disposed closest to the object side. νdp1 is the Abbe number of the positive lens constituting the first cemented lens based on the d-line, and νdn1 is the Abbe number of the negative lens constituting the first cemented lens based on the d-line. F is the focal length of the entire optical system. fc1 is the composite focal length of the cemented lens disposed on the object side of the first cemented lens and the second cemented lens, and fc2 is the composite focal length of the cemented lens disposed on the image 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 of the positive lens constituting the second cemented lens based on the d-line, and νdn2 is the Abbe number of the negative lens constituting the second cemented lens based on the d-line. ΣΔPzi is the sum of the Petzval sum of each cemented lens and the reciprocal of the synthetic focal length of the cemented lens for at least one cemented lens composed of a positive lens and a negative lens and included in the rear group, 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 side to the lens surface closest to the image side. dL1_St is the distance from the lens surface closest to the object side to the aperture stop. TLs is the distance from the aperture stop surface to the image surface. 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 side of the first lens group to the lens surface closest to the image side of the first lens group. ΣD is the distance from the lens surface closest to the object side to the lens surface closest to the image side. rR1 is the radius of curvature of the object side lens surface of the lens closest to the image side, and rR2 is the radius of curvature of the image side lens surface of the lens closest to the image side. tR is the center thickness of the lens closest to the object side. r311 is the radius of curvature of the object side lens surface of the lens closest to the object side of the third lens group, and r312 is the radius of curvature of the image side lens surface of the lens closest to the object side of the third lens group. d3 is the distance from the aperture stop to the lens surface closest to the object side of the third lens group. dL1_Gr3 is the distance from the lens surface closest to the object to the lens surface closest to the object of the third lens unit.

[0346] [Conditional value]

[0347] The above-mentioned embodiments are specific examples of the present invention, and the present invention is not limited thereto. The following contents can be appropriately adopted within the range that the optical performance of the optical system according to the embodiment of the present application is not impaired.

[0348] Next, according to Fig.11 A camera including the optical system according to the present embodiment will be described.

[0349] Fig.11 It is a schematic diagram of a camera including the optical system of this embodiment.

[0350] The camera 1 is a so-called mirrorless camera of an interchangeable lens type that includes the optical system of the first embodiment as a photographic lens 2 .

[0351] In the camera 1, light from an object (subject) not shown is collected by the photographic lens 2 and reaches the imaging element 3. The imaging element 3 converts the light from the subject into image data. The image data is displayed on the electronic viewfinder 4. Thus, the photographer whose eyes are located at the eye point EP can observe the subject.

[0352] Furthermore, when the photographer presses a release button (not shown), the image data is stored in a memory (not shown). Thus, the photographer can take a picture of a subject using the camera 1 .

[0353] Here, the optical system of the first embodiment mounted on the camera 1 as the photographic lens 2 is an optical system having good optical performance. Therefore, the camera 1 can achieve good optical performance. In addition, even if a camera is configured to mount the optical system of the second to fifth embodiments as the photographic lens 2, the same effect as the camera 1 can be achieved.

[0354] Finally, according to Fig.12 The outline of the method for manufacturing the optical system according to the present embodiment will be described. Fig.12 This is a flowchart schematically showing a method for manufacturing the optical system according to the present embodiment.

[0355] Fig.12 The optical system manufacturing method of the present embodiment shown includes the following steps S11 to S13.

[0356] Step S11: Prepare the first lens group, the aperture stop and the rear lens group.

[0357] Step S12: The rear group is provided with a first cemented lens.

[0358] Step S13: Make the optical system satisfy the following conditional expressions simultaneously.

[0359] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (3) 0.050 < Np1-Nn1 < 0.400 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface Np1: Refractive index of the positive lens constituting the first cemented lens Nn1: Refractive index of the negative lens constituting the first cemented lens

[0360] In a modified example, it is also possible to replace Fig.12 Instead of step S13 in the method for manufacturing the optical system shown in the figure, step S23 shown below is executed.

[0361] Step S23: Make the optical system satisfy the following conditional expressions simultaneously.

[0362] (1) 0.350 < Bf / y < 0.700 (2) 1.350 < TL / y < 2.000 (4) 1.500 < tp1 / tn1 < 7.000 in, Bf: Back focal length in air conversion length y: maximum image height TL: The distance from the lens surface closest to the object to the image surface tp1: The thickness of the positive lens constituting the first cemented lens on the optical axis tn1: The thickness of the negative lens constituting the first cemented lens on the optical axis

[0363] In other variations, it is also possible to replace Fig.12 Instead of step S13 in the method for manufacturing the optical system shown in the figure, step S33 shown below is executed.

[0364] Step S33: Make the optical system satisfy the following conditional expressions simultaneously.

[0365] (5) 1.000 < f / y < 1.600 (6) 0.025 < t1 / f < 0.080 in, f: focal length of the entire optical system y: maximum image height t1: The center thickness of the positive lens located closest to the object side

[0366] According to these methods for manufacturing an optical system of the present embodiment, it is possible to manufacture an optical system having good imaging performance.

[0367] Although a four-group structure is shown as an embodiment of the optical system of this embodiment, this embodiment is not limited to the four-group structure, and may also be other group structures (e.g., a five-group structure, etc.). Specifically, the optical system of this embodiment may also have a structure in which lenses or optical components are added to the object side or the image plane side of the optical system of the embodiment.

[0368] The optical system of this embodiment may also include an anti-shake lens group, which corrects image shake caused by hand shake by moving in a manner having a component in a direction perpendicular to the optical axis. The anti-shake lens group may be a lens group or a partial lens group composed of one or more lens components included in the lens group.

[0369] In the optical system of this embodiment, when focusing, the entire optical system, any one lens group, multiple lens groups, or part of the lens groups may be moved in the optical axis direction. For example, when focusing from an infinitely distant object to a close object, the lens group arranged on the object side relative to the aperture stop and the lens group arranged on the image side relative to the aperture stop may be moved toward the object side by different amounts.

[0370] In the optical system of this embodiment, the lens surface may be formed by a spherical surface or a flat surface, or may be formed by an aspherical surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment become easy, and the degradation of optical performance caused by errors in processing and assembly adjustment is prevented, so it is preferred. In addition, when the lens surface is a spherical surface or a flat surface, the degradation of the image rendering performance when the image plane is offset is small, so it is preferred.

[0371] When the lens surface is an aspheric surface, the aspheric surface can also be formed by grinding glass or glass molding using a mold having an aspheric shape, or can be formed on a resin surface bonded to the glass surface. In addition, in the optical system of this embodiment, the lens surface can also be a diffraction surface, and the lens can also be a refractive index distribution lens (GRIN lens) or a plastic lens.

[0372] In the optical system of this embodiment, the aperture stop is preferably arranged between the first lens group and the second lens group. However, instead of providing an independent component as the aperture stop, a lens frame or the like may be used to replace the aperture stop.

[0373] It should be understood that those skilled in the art can add various changes, substitutions, and modifications to the present invention without departing from the spirit and scope of the present disclosure.

[0374] Description of symbols

[0375] S Aperture stop

[0376] I Image plane

[0377] 1. Camera

[0378] 2 Camera Lenses

[0379] 3. Camera elements

Claims

1. An optical system, wherein: The optical system is composed of a first lens group, an aperture stop, and a rear lens group in order from the object side. The rear group has a first cemented lens consisting of a positive lens and a negative lens. The optical system satisfies the following conditions at the same time: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. Np1: the refractive index of the positive lens constituting the first cemented lens, Nn1: refractive index of the negative lens constituting the first cemented lens.

2. An optical system, wherein: The optical system is composed of a first lens group, an aperture stop, and a rear lens group in order from the object side. The rear group has a first cemented lens consisting of a positive lens and a negative lens. The optical system satisfies the following conditions at the same time: 0.350 < Bf / y < 0.700 1. 350 < TL / y < 2.000 1.500 < tp1 / tn1 < 7.000 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. tp1: the center thickness of the positive lens constituting the first cemented lens, tn1: The center thickness of the negative lens constituting the first cemented lens.

3. An optical system, wherein: The optical system is composed of a first lens group, an aperture stop, and a rear lens group in order from the object side. The rear group has a first cemented lens consisting of a positive lens and a negative lens. The first lens group includes a positive lens disposed closest to the object side. The optical system satisfies the following conditions at the same time: 1.000 < f / y < 1.600 0.025 < t1 / f < 0.080 in, f: focal length of the entire optical system, y: maximum image height, t1: The center thickness of the lens closest to the object side.

4. The optical system according to any one of claims 1 to 3, wherein: The optical system satisfies the following conditional formula: 3.000 < νdp1-νdn1 < 30.000 in, νdp1: Abbe number of the positive lens constituting the first cemented lens based on the d-line, νdn1: Abbe number of the negative lens constituting the first cemented lens with respect to the d-line.

5. The optical system according to any one of claims 1 to 3, wherein: The rear group is composed of a positive lens and a negative lens, and has a second cemented lens different from the first cemented lens.

6. The optical system according to claim 5, wherein: The optical system satisfies the following conditional formula: 1.000 < f / y < 1.380 f: The focal length of the entire optical system.

7. The optical system according to claim 5 or 6, wherein: In the first cemented lens and the second cemented lens, a negative lens is arranged on the object side for the cemented lens arranged on the object side, and a negative lens is arranged on the image side for the cemented lens arranged on the image side.

8. An optical system according to any one of claims 5 to 7, wherein: The optical system satisfies the following conditional formula: -0.030 < fc1 / fc2 < 1.000 in, fc1: the combined focal length of the first cemented lens and the second cemented lens, whichever is disposed on the object side. fc2: A combined focal length of the first cemented lens and the second cemented lens, the cemented lens disposed on the image plane side.

9. The optical system according to any one of claims 5 to 8, wherein: The optical system satisfies the following conditional formula: 0.050 < Np2-Nn2 < 0.400 in, Np2: the refractive index of the positive lens constituting the second cemented lens, Nn2: refractive index of the negative lens constituting the second cemented lens.

10. The optical system according to any one of claims 5 to 9, wherein: The optical system satisfies the following conditional formula: 3.000 < νdp2-νdn2 < 30.000 in, νdp2: Abbe number of the positive lens constituting the second cemented lens based on the d-line, νdn2: Abbe number of the negative lens constituting the second cemented lens based on the d-line.

11. The optical system according to any one of claims 1 to 10, wherein: The optical system satisfies the following conditional formula: 0.550 < (ΣΔPzi) / ΔPz < 1.400 in, ΣΔPzi: the sum of the Petzval sum of each of at least one cemented lens composed of a positive lens and a negative lens and included in the rear group and the sum of 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.

12. The optical system according to any one of claims 1 to 11, wherein: The optical system satisfies the following conditional formula: 0.525 < ΣD / TL < 0.967 in, ΣD: The distance from the lens surface closest to the object to the lens surface closest to the image plane. TL: The distance from the lens surface closest to the object to the image surface.

13. The optical system according to any one of claims 1 to 12, wherein: The optical system satisfies the following conditional formula: 0.050 < dL1_St / TL < 0.167 in, dL1_St: The distance from the lens surface closest to the object to the aperture stop. TL: The distance from the lens surface closest to the object to the image surface.

14. The optical system according to any one of claims 1 to 13, wherein: The optical system satisfies the following conditional formula: 0.750 < TL / f < 1.600 in, TL: The distance from the lens surface closest to the object to the image surface. f: The focal length of the entire optical system.

15. The optical system according to any one of claims 1 to 14, wherein: The optical system satisfies the following conditional formula: 0.700 < f1 / f < 5.000 in, f1: focal length of the first lens group, f: The focal length of the entire optical system.

16. The optical system according to any one of claims 1 to 15, wherein: The optical system satisfies the following conditional formula: 0.010 < D1 / TL < 0.150 in, D1: the distance from the lens surface of the first lens group closest to the object side to the lens surface of the first lens group closest to the image plane side, TL: The distance from the lens surface closest to the object to the image surface.

17. An optical system according to any one of claims 1 to 16, wherein: The optical system satisfies the following conditional formula: 0.025 < t1 / ΣD < 0.080 in, t1: The center thickness of the lens closest to the object side, ΣD: The distance from the lens surface closest to the object side to the lens surface closest to the image side.

18. An optical system according to any one of claims 1 to 17, wherein: The optical system satisfies the following conditional formula: -4.500 < (rR2+rR1) / (rR2-rR1) < -1.500 in, rR1: The radius of curvature of the object side lens surface closest to the image plane, rR2: The radius of curvature of the image-side lens surface of the lens closest to the image plane.

19. An optical system according to any one of claims 1 to 18, wherein: The optical system satisfies the following conditional formula: 0.130 < tR / ΣD < 0.350 in, tR: The center thickness of the lens closest to the image plane, ΣD: The distance from the lens surface closest to the object side to the lens surface closest to the image side.

20. The optical system according to any one of claims 1 to 19, wherein: The rear group includes, 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 unit includes, on the most object side, a negative meniscus lens disposed on the image plane side relative to the aperture stop and having a concave surface facing the object side, and disposed on the most object side. The fourth lens group is composed of positive lenses.

21. The optical system of claim 20, wherein: The optical system satisfies the following conditional formula: 0.300 < (-f3) / f < 2.200 in, f3: focal length of the 3rd lens group, f: The focal length of the entire optical system.

22. An optical system according to claim 20 or 21, wherein: The optical system satisfies the following conditional formula: 0.450 < f4 / f < 2.300 in, f4: focal length of the 4th lens group, f: The focal length of the entire optical system.

23. An optical system according to any one of claims 20 to 22, wherein: The optical system satisfies the following conditional formula: 0.286 < (-f3) / f4 < 2.000 in, f3: focal length of the 3rd lens group, f4: focal length of the fourth lens group.

24. An optical system according to any one of claims 20 to 22, wherein: The optical system satisfies the following conditional formula: 0.300 < f2 / f < 2.000 in, f2: focal length of the second lens group, f: The focal length of the entire optical system.

25. An optical system according to any one of claims 20 to 24, wherein: The optical system satisfies the following conditional formula: 1.500 < (r312+r311) / (r312-r311) < 7.000 in, r311: the radius of curvature of the object-side lens surface of the lens closest to the object side of the third lens group, r312: The radius of curvature of the image-side lens surface of the lens closest to the object side of the third lens group.

26. An optical system according to any one of claims 20 to 25, wherein: The optical system satisfies the following conditional formula: 0.400 < dL1_Gr3 / ΣD < 0.900 in, dL1_Gr3: the distance from the lens surface closest to the object to the lens surface closest to the object of the third lens group, ΣD: The distance from the lens surface closest to the object side to the lens surface closest to the image side.

27. An optical device comprising the optical system according to any one of claims 1 to 26.

28. A method for manufacturing an optical system, The optical system is composed of the first lens group, the aperture stop, and the rear lens group in order from the object side. The rear group has a first cemented lens composed of a positive lens and a negative lens, wherein: The lenses are arranged in such a way that the optical system satisfies the following conditional expressions at the same time: 0.350 < Bf / y < 0.700 1.350 < TL / y < 2.000 0.050 < Np1-Nn1 < 0.400 in, Bf: back focal length in air conversion length, y: maximum image height, TL: The distance from the lens surface closest to the object to the image surface. Np1: the refractive index of the positive lens constituting the first cemented lens, Nn1: refractive index of the negative lens constituting the first cemented lens.

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