JP2013019994A - Optical system, imaging device having the optical system, and manufacturing method of the optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small optical system of smaller number of constituent elements, which has high performance and less coma aberration, especially sagittal coma aberration, and spherical aberration, an imaging device having this optical system, and a manufacturing method of the optical system.SOLUTION: The optical system OS mounted in a single lens reflex camera 1 or the like COMPRISES: a first lens group Ga having a positive refractive power; a second lens group Gb having a negative refractive power; a third lens group Gc; and a fourth lens group Gd having a positive refractive power. The first lens group Ga has at least one positive lens component La, the second lens group Gb has a cemented negative lens Lbn formed by cementing a positive lens Lbnp and a negative lens Lbnn and having a convex surface toward the object side, the third lens group Gc has a cemented lens Lc formed by cementing a negative lens Lcn having a concave surface toward the object side and a positive lens Lcp, and the fourth lens group Gd has a cemented positive lens Ldp1 formed by cementing a positive lens Ldpp having a convex surface toward the object side and a negative lens Ldpn having a concave surface toward the image side, and a positive lens component Ldp2.

Description

  The present invention relates to an optical system, an imaging apparatus having the optical system, and a method for manufacturing the optical system.

  Conventionally, many so-called modified Gaussian lenses have been proposed (see, for example, Patent Document 1).

JP 2009-251398 A

  However, the conventional Gaussian lens has insufficient correction of coma, and it has been particularly difficult to improve sagittal coma.

  The present invention has been made in view of such a problem, and is an optical system that is small in size, has a small number of components, has high performance, has low coma aberration, particularly sagittal coma aberration, and spherical aberration, and an imaging apparatus having the optical system. And it aims at providing the manufacturing method of an optical system.

In order to solve the above problems, an optical system according to the present invention includes, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, A third lens group and a fourth lens group having a positive refractive power; the first lens group has at least one positive lens component; and the second lens group includes a positive lens and a negative lens. And a cemented negative lens having negative refractive power with a convex surface facing the object side, and the third lens group includes a cemented lens formed by cementing a negative lens with a concave surface facing the object side and a positive lens. The fourth lens group includes a positive lens having a positive refractive power and a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side, and a positive lens component. And satisfying the following conditional expression.
0.00 <Ncp-Ncn <0.40
0.01 <Dd1 / Dd0 <0.80
However,
Ncp: refractive index with respect to d-line of medium of positive lens in cemented lens in third lens group Ncn: refractive index with respect to d-line of medium of negative lens in cemented lens in third lens group Dd1: fourth lens group The axial air space between the cemented positive lens in the middle and the positive lens component located on the image side Dd0: the length on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the fourth lens group ( Total thickness of the fourth lens group)

In addition, this optical system preferably satisfies the following conditional expression.
0.0 <fd / f0 <5.0
However,
fd: focal length of the fourth lens unit f0: focal length of the entire system when focusing on infinity

In addition, this optical system preferably satisfies the following conditional expression.
0.00 <Ndpp-Ndpn <0.40
However,
Ndpp: Refractive index with respect to d-line of medium of positive lens in cemented positive lens in fourth lens group Ndpn: Refractive index with respect to d-line of medium of negative lens in cemented positive lens in fourth lens group

In addition, this optical system preferably satisfies the following conditional expression.
-1,000 <(rd2-rd1) / (rd2 + rd1) <-0.000
However,
rd1: radius of curvature of the most object side surface of the cemented positive lens in the fourth lens group rd2: radius of curvature of the most image side surface of the cemented positive lens in the fourth lens group

In addition, this optical system preferably satisfies the following conditional expression.
0.0 <(− fbn) / f0 <5.0
However,
fbn: focal length of the composite of the cemented negative lens in the second lens group f0: focal length of the entire system when focusing on infinity

In addition, this optical system preferably satisfies the following conditional expression.
0.0 <fap / f0 <10.0
However,
fap: focal length of the positive lens component located closest to the image side in the first lens group f0: focal length of the entire system when focusing on infinity

  Further, this optical system preferably has an aperture stop for determining the F number between the second lens group and the third lens group, or between the third lens group and the fourth lens group.

  In the optical system, it is preferable that the first lens group or the second lens group has at least one aspheric surface.

  In the optical system, it is preferable that the fourth lens group has at least one aspheric surface.

  In this optical system, the positive lens component in the fourth lens group is preferably a positive lens having a convex surface facing the object side.

  In addition, an imaging apparatus according to the present invention includes any one of the above-described optical systems.

The optical system manufacturing method according to the present invention includes, in order from the object side along the optical axis, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens. And a fourth lens group having a positive refractive power, wherein at least one positive lens component is disposed as the first lens group, and a positive lens is disposed as the second lens group. A lens and a negative lens are cemented, a cemented negative lens having a negative refractive power with a convex surface facing the object side is arranged, and a negative lens with a concave surface facing the object side and a positive lens are cemented as a third lens group And a positive lens having a positive refractive power, in which a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented as a fourth lens group, and a positive lens And satisfying the following conditional expression: .
0.00 <Ncp-Ncn <0.40
0.01 <Dd1 / Dd0 <0.80
However,
Ncp: refractive index with respect to d-line of medium of positive lens in cemented lens in third lens group Ncn: refractive index with respect to d-line of medium of negative lens in cemented lens in third lens group Dd1: fourth lens group The axial air space between the cemented positive lens in the middle and the positive lens component located on the image side Dd0: the length on the optical axis from the lens surface closest to the object side to the lens surface closest to the image side in the fourth lens group ( Total thickness of the fourth lens group)

  According to the present invention, there are provided an optical system that is small in size, has a small number of components, has high performance, and has low coma, particularly sagittal coma and spherical aberration, an imaging apparatus having the optical system, and a method for manufacturing the optical system. be able to.

It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 1st Example. FIG. 6 is a diagram illustrating various aberrations of the optical system according to Example 1 in an infinitely focused state. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 2nd Example. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 2 in a focused state at infinity. It is sectional drawing which shows the lens structure in the infinite point focusing state of the optical system which concerns on 3rd Example. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 3 in an infinitely focused state. A sectional view of a single-lens reflex camera equipped with an optical system is shown. It is a flowchart for demonstrating the manufacturing method of an optical system.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical system OS according to this embodiment includes a first lens group Ga having a positive refractive power and a second lens group having a negative refractive power in order from the object side along the optical axis. Gb, a third lens group Gc, and a fourth lens group Gd having a positive refractive power are configured. The first lens group Ga has at least one positive lens component Lap, and the second lens group Gb has a negative refraction with a positive lens Lbnp and a negative lens Lpnn cemented with a convex surface facing the object side. The third lens group Gc has a cemented negative lens Lc having a concave surface facing the object side and a positive lens Lcp. The fourth lens group Gd has a cemented negative lens Lbn having power. A positive lens Ldpp having a convex surface facing the object side and a negative lens Ldpn having a concave surface facing the image side are cemented, and includes a cemented positive lens Ldp1 having a positive refractive power and a positive lens component Ldp2. In the following description, “lens component” refers to a single lens (lens element) or a cemented lens in which two or more single lenses (lens elements) are cemented.

  The optical system OS according to the present embodiment has coma aberration, particularly sagittal coma aberration, which is a defect of so-called Gaussian type and xenota type optical systems, which are basically represented by positive, negative, positive, negative, chromatic aberration, curvature of field and non-existence. This is an improvement without deteriorating the point aberration. Hereinafter, conditions for configuring such an optical system OS will be described.

  The optical system OS according to the present embodiment desirably satisfies the following conditional expression (1).

0.00 <Ncp-Ncn <0.40 (1)
However,
Ncp: refractive index with respect to d-line of medium of positive lens Lcp in cemented lens Lc in third lens group Gc Ncn: refractive index with respect to d-line of medium of negative lens Lcn in cemented lens Lc in third lens group Gc

  Conditional expression (1) indicates that refraction at the d-line (wavelength λ = 587.6 nm) of the medium of the positive lens Lcp and the negative lens Lcn constituting the cemented lens Lc with the concave surface facing the object side in the third lens group Gc. It is a condition that defines the difference in rate. If this condition is not met, the setting of the optimum Petzval sum is impaired, resulting in a worsening of field curvature.

  If the upper limit value of the conditional expression (1) is exceeded, it means that the refractive index difference is remarkably increased. Even in this case, the Petzval sum is deteriorated from the optimum value, and as a result, the correction of the field curvature is deteriorated. In addition, the ability to correct spherical aberration also decreases, which makes it impossible to select a glass material for optimal chromatic aberration. If the upper limit value of conditional expression (1) is set to 0.35, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of conditional expression (1) is set to 0.30, the above-described correction of various aberrations becomes more advantageous. Moreover, by setting the upper limit value of conditional expression (1) to 0.25, the effect of the present application can be maximized.

  If the lower limit of conditional expression (1) is not reached, the difference in refractive index is remarkably reduced. Finally, the refractive index of the negative lens Lcn becomes larger than the refractive index of the positive lens Lcp. In this case, the positive and negative refractive indexes are reversed, and it is difficult to keep the Petzval sum small. Accordingly, the Petzval sum deviates greatly from the optimum value, and as a result, correction of curvature of field and correction of astigmatism are deteriorated, which is not preferable. If the lower limit value of conditional expression (1) is set to 0.01, it is advantageous for correction of various aberrations such as field curvature and astigmatism. Setting the lower limit of conditional expression (1) to 0.03 is advantageous for correcting various aberrations such as field curvature and astigmatism. Further, by setting the lower limit value of conditional expression (1) to 0.04, the effect of the present application can be maximized.

  Moreover, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (2).

0.01 <Dd1 / Dd0 <0.80 (2)
However,
Dd1: On-axis air space between the cemented positive lens Ldp1 in the fourth lens group Gd and the positive lens component Ldp2 located on the image side Dd0: the lens closest to the image side from the lens surface closest to the object side in the fourth lens group Gd Length on the optical axis to the surface (total thickness of the fourth lens group Gd)

  Conditional expression (2) is a condition that prescribes the optimum on-axis air distance Dd1 between the cemented positive lens Ldp1 in the fourth lens group Gd and the positive lens component Ldp2 located on the image side thereof. The air distance Dd1 is related to the shape and refractive power of the air lens formed by the cemented positive lens Ldp1 and the positive lens component Ldp2. Therefore, setting the on-axis air interval Dd1 to an optimum value is effective in correcting various aberrations.

  When the upper limit value of the conditional expression (2) is exceeded, the axial air distance Dd1 becomes too large, and the refractive power of the convex air lens formed between the cemented positive lens Ldp1 and the positive lens component Ldp2 decreases, Aberration correction capability decreases. Particularly, spherical aberration and coma are deteriorated, which is not preferable. In addition, the rear lens diameter increases and the peripheral light amount decreases, which is not preferable. If the upper limit value of conditional expression (2) is set to 0.70, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (2) is set to 0.60, the above-mentioned correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (2) to 0.50, the effects of the present application can be maximized.

  When the lower limit of conditional expression (2) is not reached, the axial air interval Dd1 becomes too small, and the diameter of the convex air lens formed between the cemented positive lens Ldp1 and the positive lens component Ldp2 is It becomes small by interference. In order to increase the diameter per lens (position where the lens interferes), it is necessary to make the curvature radius of the image side surface of the cemented positive lens Ldp1 and the curvature radius of the object side surface of the positive lens component Ldp2 close to each other. . Accordingly, when the shape of the air lens formed between the cemented positive lens Ldp1 and the positive lens component Ldp2 deviates greatly from the optimum value, correction of various aberrations such as spherical aberration and coma aberration deteriorates, which is not preferable. Note that setting the lower limit of conditional expression (2) to 0.10 is advantageous for correcting various aberrations such as spherical aberration. Setting the lower limit value of conditional expression (2) to 0.25 is advantageous for correcting various aberrations such as spherical aberration. Further, by setting the lower limit value of conditional expression (2) to 0.31, the effect of the present application can be maximized.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (3).

0.0 <fd / f0 <5.0 (3)
However,
fd: focal length of the fourth lens group Gd f0: focal length of the entire system when focusing on infinity

  Conditional expression (3) is a condition that defines the magnitude of the focal length of the fourth lens group Gd, in other words, the magnitude of the refractive power.

  If the upper limit value of the conditional expression (3) is exceeded, it means that the focal length of the fourth lens group Gd becomes extremely long and the positive refractive power becomes weak. In this case, sagittal coma aberration, field curvature, and astigmatism correction are deteriorated, which is not preferable. Further, it is not preferable because it is difficult to secure the back focus. If the upper limit value of conditional expression (3) is set to 4.0, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (3) is set to 2.0, the above-described correction of various aberrations becomes more advantageous. In addition, the effect of the present application can be maximized by setting the upper limit value of conditional expression (3) to 1.0.

  On the other hand, if the lower limit value of conditional expression (3) is not reached, it means that the focal length of the fourth lens group Gd is remarkably shortened and the positive refractive power is remarkably increased. In this case, the correction of spherical aberration, sagittal coma aberration, and meridional coma aberration deteriorates as a result, which is not preferable. Also, the sensitivity to eccentricity increases, which is not preferable. Note that setting the lower limit of conditional expression (3) to 0.1 is advantageous for correcting various aberrations such as spherical aberration. Setting the lower limit of conditional expression (3) to 0.3 is advantageous for correcting various aberrations such as spherical aberration. Further, by setting the lower limit value of conditional expression (3) to 0.4, the effect of the present application can be maximized.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (4).

0.00 <Ndpp-Ndpn <0.40 (4)
However,
Ndpp: refractive index with respect to the d-line of the medium of the positive lens Ldpp in the cemented positive lens Ldp1 in the fourth lens group Gd Ndpn: with respect to the d-line of the medium of the negative lens Ldpn in the cemented positive lens Ldp1 in the fourth lens group Gd Refractive index

  Conditional expression (4) is a condition that defines the difference in refractive index between the positive lens Ldpp in the cemented positive lens Ldp1 and the negative lens Ldpn in the fourth lens group Gd (wavelength λ = 587.6 nm). . If this condition is not met, the setting of the optimum value for the Petzval sum will be impaired, resulting in a worsening of field curvature.

  If the upper limit value of the conditional expression (4) is exceeded, it means that the refractive index difference is remarkably increased. Even in this case, the Petzval sum is deteriorated from the optimum value, and as a result, the correction of the field curvature is deteriorated. In addition, the ability to correct spherical aberration also decreases, which makes it impossible to select a glass material for optimal chromatic aberration. If the upper limit value of conditional expression (4) is set to 0.35, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (4) is set to 0.33, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (4) to 0.30, the effect of the present application can be maximized.

  Further, when the lower limit of conditional expression (4) is not reached, the difference in refractive index becomes remarkably small, and finally the refractive index of the negative lens Ldpn becomes larger than the refractive index of the positive lens Ldpp. In this case, the positive and negative refractive indexes are reversed, and it is difficult to keep the Petzval sum small. Accordingly, the Petzval sum deviates greatly from the optimum value, and as a result, correction of curvature of field and correction of astigmatism are deteriorated, which is not preferable. When the lower limit value of conditional expression (4) is set to 0.01, it is advantageous for correction of various aberrations such as field curvature and astigmatism. Setting the lower limit of conditional expression (4) to 0.03 is advantageous for correcting various aberrations such as field curvature and astigmatism. In addition, by setting the lower limit value of conditional expression (4) to 0.04, the effect of the present application can be maximized.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (5).

-1,000 <(rd2-rd1) / (rd2 + rd1) <− 0.000 (5)
However,
rd1: radius of curvature of the most object side surface of the cemented positive lens Ldp1 in the fourth lens group Gd rd2: radius of curvature of the most image side surface of the cemented positive lens Ldp1 in the fourth lens group Gd

  Conditional expression (5) is a condition that defines the reciprocal of the form factor of the entire cemented positive lens Ldp1 with the concave surface facing the image side in the fourth lens group Gd. This condition is greatly related to correction of spherical aberration and sagittal coma. When the value set in the conditional expression (5) is negative, the shape of the entire cemented positive lens Ldp1 with the concave surface facing the image side is a positive lens component, but the concave surface is formed on the image side. It shows a negative meniscus shape. Due to the presence of an air lens formed between this shape and the positive lens component Ldp2 located on the image side, it is possible to satisfactorily correct sagittal coma, meridional coma, and spherical aberration.

  When the upper limit value of conditional expression (5) is exceeded, the cemented positive lens Ldp1 is greatly changed from the negative meniscus shape to a positive meniscus shape with a convex surface facing the object side, or a negative meniscus shape with a concave surface facing the object side. Become. Regardless of which shape is reached, the correction of sagittal coma and meridional coma is deteriorated, and correction of spherical aberration is also undesirably deteriorated when trying to correct it satisfactorily. If the upper limit value of conditional expression (5) is set to -0.001, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of conditional expression (5) is set to -0.010, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (5) to −0.015, the effect of the present application can be maximized.

  When the lower limit value of conditional expression (5) is not reached, the cemented positive lens Ldp1 is greatly changed from the negative meniscus shape, and is a plano-convex shape with the plane facing the object side or a plano-concave shape with the plane facing the object side Become a shape. For this reason, the above-described air lens also does not exhibit an optimum shape and finally does not exist. Therefore, since the air lens does not maintain the negative meniscus shape, sagittal coma aberration, meridional coma aberration correction, and spherical aberration correction are deteriorated, which is not preferable. If the lower limit value of conditional expression (5) is set to −0.800, it is advantageous for correcting the above-mentioned various aberrations. Setting the lower limit of conditional expression (5) to −0.600 is advantageous for correcting the above-mentioned various aberrations. In addition, the effect of the present application can be maximized by setting the lower limit value of conditional expression (5) to −0.500.

  In addition, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (6).

0.0 <(− fbn) / f0 <5.0 (6)
However,
fbn: focal length of the combined negative lens Lbn in the second lens group Gb f0: focal length of the entire system when focusing on infinity

  Conditional expression (6) is a condition that defines the combined focal length of the cemented negative lens Lbn in the second lens group Gb.

  When the upper limit value of the conditional expression (6) is exceeded, it means that the negative refractive power of the cemented negative lens Lbn is weakened. In this case, correction of field curvature and astigmatism deteriorates, which is not preferable. If the upper limit value of conditional expression (6) is set to 3.8, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (6) is set to 1.8, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit value of conditional expression (6) to 1.3, the effect of the present application can be maximized.

  On the other hand, if the lower limit value of conditional expression (6) is not reached, it means that the negative refractive power of the cemented negative lens Lbn becomes stronger. In that case, correction of coma aberration, spherical aberration, and distortion is deteriorated as a result, which is not preferable. Note that setting the lower limit of conditional expression (6) to 0.1 is advantageous for correcting various aberrations such as spherical aberration. Setting the lower limit of conditional expression (6) to 0.2 is advantageous for correcting various aberrations such as spherical aberration. Further, by setting the lower limit value of conditional expression (6) to 0.4, the effects of the present application can be maximized.

  Moreover, it is desirable that the optical system OS according to the present embodiment satisfies the following conditional expression (7).

0.0 <fap / f0 <10.0 (7)
However,
fap: focal length of the positive lens component Lap located closest to the image side in the first lens group Ga f0: focal length of the entire system when focusing on infinity

  Conditional expression (7) defines the optimum focal length of the positive lens component Lap located closest to the image side in the first lens group Ga.

  When the upper limit value of the conditional expression (7) is exceeded, it means that the refractive power of the positive lens component Lap becomes weak. In this case, correction of spherical aberration is deteriorated, which is not preferable. Moreover, the front ball diameter is increased, which is not preferable. If the upper limit value of conditional expression (7) is set to 7.0, the above-described correction of various aberrations becomes more advantageous. If the upper limit value of conditional expression (7) is set to 3.3, the above-described correction of various aberrations becomes more advantageous. Further, by setting the upper limit of conditional expression (7) to 2.2, the effect of the present application can be maximized.

  Further, when the lower limit value of conditional expression (7) is not reached, it means that the refractive power of the positive lens component Lap is increased. In that case, correction of coma aberration, spherical aberration, and distortion is deteriorated as a result, which is not preferable. Note that setting the lower limit of conditional expression (7) to 0.1 is advantageous for correcting various aberrations such as spherical aberration. Setting the lower limit of conditional expression (7) to 0.2 is advantageous for correcting various aberrations such as spherical aberration. In addition, by setting the lower limit value of conditional expression (7) to 0.4, the effects of the present application can be maximized.

  Further, the optical system OS according to the present embodiment has an F number of the optical system OS between the second lens group Gb and the third lens group Gc, or between the third lens group Gc and the fourth lens group Gd. It is preferable to have an aperture stop S for determining the magnification chromatic aberration and distortion.

  In such an optical system OS, it is preferable that the first lens group Ga or the second lens group Gb has at least one aspherical surface, because correction of downward coma, sagittal coma, and spherical aberration is improved. .

  In such an optical system OS, it is preferable that the fourth lens group Gd has at least one aspherical surface because correction of upper coma, sagittal coma, spherical aberration, distortion and the like is improved.

  It should be noted that having one aspherical surface before and after the aperture stop S is effective in correcting aberrations caused by a large aperture such as spherical aberration, sagittal coma aberration, meridional coma aberration.

  In such an optical system OS, the image-side positive lens component Ldp2 in the fourth lens group Gd is preferably a positive lens having a convex surface directed toward the object side. Combined with the positive lens component (junction positive lens) Ldp1 with the concave surface facing the image side just before, a convex air lens can be made, which is advantageous for correction of spherical aberration and sagittal coma aberration.

  Further, in the optical system OS according to the present embodiment, a positive lens component Lap (including a positive lens component Lapa in a second example described later) that constitutes the first lens group Ga, and a fourth lens group Gd are constructed. The image-side positive lens component Ldp2 is formed of a single lens in FIGS. 1, 3, and 5, but may be formed of a cemented lens in which two or more single lenses are cemented.

  FIG. 7 shows a schematic cross-sectional view of a single-lens reflex camera 1 (hereinafter simply referred to as a camera) as an imaging apparatus including the above-described optical system OS. In this camera 1, light from an object (subject) (not shown) is collected by the taking lens 2 (optical system OS) and focused on the focusing screen 4 via the quick return mirror-3. The light imaged on the focusing screen 4 is reflected a plurality of times in the pentaprism 5 and guided to the eyepiece lens 6. Thus, the photographer can observe the object (subject) image as an erect image through the eyepiece 6.

  When the release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and the light of the object (subject) (not shown) condensed by the taking lens 2 is captured by the image sensor 7. A subject image is formed on the top. Thereby, the light from the object (subject) is captured by the image sensor 7 and recorded as an object (subject) image in a memory (not shown). In this way, the photographer can shoot an object (subject) with the camera 1. The camera 1 shown in FIG. 7 may be one that holds the photographing lens 2 in a detachable manner, or may be formed integrally with the photographing lens 2. Further, the camera 1 may be a so-called single-lens reflex camera, or a compact camera without a quick return mirror or a mirrorless single-lens reflex camera.

  Here, by mounting the above-described optical system OS as the photographing lens 2 on the camera 1, a large-aperture lens with less spherical aberration, sagittal coma flare, field curvature, and coma is realized by its characteristic lens configuration. doing. As a result, the camera 1 can realize an image pickup apparatus that has a large aperture and is capable of wide-angle shooting with less spherical aberration, sagittal coma aberration, field curvature, and meridional coma aberration.

  In addition, the contents described below can be employed as appropriate within a range that does not impair the optical performance.

  In the present embodiment, an optical system OS having a four-group configuration is shown, but the above-described configuration conditions and the like can also be applied to other group configurations such as a fifth group and a sixth group. In addition, a configuration in which a lens or a lens group is added on the most object side, a configuration in which a lens group is added between the lens or the front and rear groups on the most image side, or a configuration in which a lens group is added between each lens group I do not care.

  In this embodiment, the entire (all groups) feed is used to focus on an object at a short distance from an object at infinity. A focusing lens group that performs focusing from an object to a short-distance object may be used. That is, a method using the first lens group Ga or the like, or a rear focus using the third lens group Gc and the fourth lens group Gd may be used. In this case, the focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (using an ultrasonic motor or the like).

  Also, by moving the lens group or partial lens group so that it has a component in the direction perpendicular to the optical axis, or rotating (swinging) in the in-plane direction including the optical axis, image blur caused by camera shake is corrected. An anti-vibration lens group may be used. In particular, it is preferable that at least one of the third lens group Gc and the fourth lens group Gd is an anti-vibration lens group.

  Further, the lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. It is preferable that the lens surface is a spherical surface or a flat surface because lens processing and assembly adjustment are facilitated, and deterioration of optical performance due to errors in processing and assembly adjustment is prevented. Further, even when the image plane is shifted in the optical axis direction, it is preferable because there is little deterioration in the drawing performance. When the lens surface is an aspheric surface, the aspheric surface is an aspheric surface by grinding, a glass mold aspheric surface made of glass with an aspheric shape, or a composite aspheric surface made of resin on the glass surface. Any of the aspherical surfaces may be used. The lens surface may be a diffractive surface, and the lens may be a gradient index lens (GRIN lens) or a plastic lens.

  The aperture stop S is preferably arranged near the center of the optical system OS. However, the role of the aperture stop may be substituted by a lens frame without providing a member as an aperture stop.

  Further, each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength range in order to reduce flare and ghost and achieve high optical performance with high contrast.

  Hereinafter, an outline of a method for manufacturing the optical system OS according to the present embodiment will be described with reference to FIG. The manufacturing method of the optical system OS includes, in order from the object side along the optical axis, a first lens group Ga having a positive refractive power, a second lens group Gb having a negative refractive power, and a third lens group Gc. And a fourth lens group Gd having a positive refractive power. Specifically, at least one positive lens component Lap is arranged as the first lens group Ga (step S100), and as the second lens group Gb, the positive lens Lbnp and the negative lens Lbnn are cemented to the object side. A cemented negative lens Lbn having a negative refractive power facing the convex surface is disposed (step S200), and a cemented lens Lc formed by cementing the negative lens Lcn having a concave surface facing the object side and the positive lens Lcp is used as the third lens group Gc. (Step S300), and as the fourth lens group Gd, a positive lens Ldpp having a convex surface facing the object side and a negative lens Ldpn having a concave surface facing the image side are cemented, and a cemented positive lens having a positive refractive power Ldp1 and positive lens component Ldp2 are arranged (step S400). At this time, each group satisfies the above-described conditional expression (1) and conditional expression (2).

  As described above, according to the optical system OS according to the present embodiment, a small and high-performance lens suitable for an imaging device such as a camera, a printing lens, and a copying lens, and an imaging device using the same. Can be provided.

  Hereinafter, embodiments of the optical system OS will be described with reference to the drawings. 1, 3 and 5 show the configuration of the optical system OS (OS1 to OS3) according to each embodiment.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), r is the radius of curvature of the reference sphere (paraxial radius of curvature), κ is the conic constant, and An is the nth-order aspherical coefficient, and is expressed by the following equation (a). . In the following examples, “E−n” indicates “× 10 ⁻ⁿ ”.

S (y) = (y ² / r) / [1+ {1−κ (y ² / r ² )} ^1/2 ]
+ A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y <sup>10
+ A12 × y 12 + A14 ×</sup> y 14 + A16 × y 16 (a)

  In each embodiment, the secondary aspheric coefficient A2 is zero. In the table of each example, an aspherical surface is marked with * on the left side of the surface number.

[First embodiment]
FIG. 1 is a diagram illustrating a configuration of an optical system OS1 according to the first example. The optical system OS1 includes, in order from the object side along the optical axis, a first lens group Ga including a biconvex lens (positive lens component) Lap having an aspheric surface on the object side surface, and a biconvex lens (positive lens) Lbnp. And a biconcave lens (negative lens) Lbnn, and a second lens group Gb composed of a cemented negative lens Lbn having a negative refractive power with the convex surface facing the object side, an aperture stop S, and a biconcave lens (negative lens) A third lens group Gc composed of a cemented negative lens Lc formed by cementing Lcn and a biconvex lens (positive lens) Lcp, a biconvex lens (positive lens) Ldpp, and a biconcave lens (negative lens) Ldpn are cemented to have a positive refractive power. And a fourth lens group Gd having a positive refractive power as a whole, including a cemented positive lens Ldp1 having a biconvex lens (positive lens component) Ldp2 having an aspherical surface on the object side surface It is. A dummy glass FL corresponding to an optical low-pass filter is disposed between the fourth lens group Gd of the optical system OS1 and the image plane.

  Table 1 below lists values of specifications of the optical system OS1 according to the first example. In the overall specifications of Table 1, f is the focal length, FNO is the F number, ω is the half angle of view (unit: degree), Y is the image height, TL is the total length of the optical system OS1, and Bf is the back focus. Represents each. The total length TL indicates the distance on the optical axis from the most object side lens surface (first surface) of the optical system OS1 to the image plane, and the air conversion back focus Bf is obtained when the dummy glass FL is removed. This represents the distance on the optical axis from the most image side lens surface (14th surface) of the optical system OS1 to the image surface. In the lens data, the first column m indicates the order (surface number) of the optical surfaces from the object side along the traveling direction of the light beam, the second column r indicates the curvature radius of each optical surface, The column d shows the distance (surface interval) on the optical axis from each optical surface to the next optical surface, and the fourth column νd and the fifth column nd show the Ab for the d-line (wavelength λ = 587.6 nm), respectively. Number and refractive index are shown. In addition, the surface numbers 1-16 shown in this Table 1 respond | correspond to the numbers 1-16 shown in FIG. A curvature radius of 0.0000 indicates a plane on the lens surface and an aperture on the aperture stop S. Further, the refractive index of air of 1.0000 is omitted. Further, the surface interval of the final surface (the 16th surface) is a distance on the optical axis to the image surface. The lens group focal length indicates the surface number (starting surface) where each lens group starts and the focal length of each lens group.

  Here, the focal length f, the radius of curvature r, the surface interval d, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or proportional. Since the same optical performance can be obtained even if the image is reduced, the present invention is not limited to this. The description of these symbols and the description of the specification table are the same in the following embodiments.

(Table 1)
[Overall specifications]
f = 58.0216
FNO = F1.452
ω = 20.79
Y = 21.6
TL = 117.10249
Air conversion Bf = 38.72105

[Lens data]
m rd νd nd
* 1 41.7829 12.0000 49.53 1.744430
2 -983.2203 0.3000
3 357.3028 6.0000 82.57 1.497820
4 -283.8317 1.5000 56.00 1.568830
5 22.0816 12.0000
6 0.0000 8.5500 Aperture stop S
7 -28.7533 1.7000 28.38 1.728250
8 82.6638 8.5000 46.59 1.816000
9 -39.5671 0.1000
10 45.7762 10.4000 40.66 1.883000
11 -48.2606 1.6000 33.73 1.647690
12 42.8602 10.0000
* 13 142.6567 5.0500 49.53 1.744430
14 -94.6176 36.0000
15 0.0000 2.0000 63.88 1.516800
16 0.0000 1.4025

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 54.10970
Second lens group 3 -40.91000
Third lens group 7 -1311.04467
Fourth lens group 10 49.55460

  In the optical system OS1 according to the first example, the lens surfaces of the first surface and the thirteenth surface are formed in an aspheric shape. Table 2 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A16.

(Table 2)
κ A4 A6 A8 A10
First surface -1.0836 2.91667E-06 -9.66089E-10 8.91173E-13 -1.43337E-15
A12 A14 A16
0.14883E-17 -0.79488E-21 0.58104E-25

κ A4 A6 A8 A10
13th surface -51.0569 -9.69256E-07 -2.85815E-09 -3.50912E-12 -1.76023E-14
A12 A14 A16
0.64501E-16 -0.76248E-19 0.00000

  Table 3 below shows values corresponding to the conditional expressions for the optical system OS1 according to the first example. However, Ncp is the refractive index with respect to the d-line of the medium of the positive lens Lcp in the cemented lens Lc in the third lens group Gc, and Ncn is d of the medium of the negative lens Lcn in the cemented lens Lc in the third lens group Gc. Dd1 is the axial air space between the cemented positive lens Ldp1 of the fourth lens group Gd and the positive lens component Ldp2 located on the image side thereof, and Dd0 is the lens closest to the object side of the fourth lens group Gd. The length on the optical axis from the surface to the lens surface closest to the image side (total thickness of the fourth lens group Gd), fd is the focal length of the fourth lens group Gd, and f0 is the entire system at the time of focusing on infinity , Ndpp is the refractive index with respect to the d-line of the medium of the positive lens Ldpp in the cemented positive lens Ldp1 in the fourth lens group Gd, and Ndpn is the negative lens in the cemented positive lens Ldp1 in the fourth lens group Gd. To the d line of the Ldpn medium Rd1 is the curvature radius of the most object side surface of the cemented positive lens Ldp1 in the fourth lens group Gd, and rd2 is the curvature of the most image side surface of the cemented positive lens Ldp1 in the fourth lens group Gd. Fbn represents the combined focal length of the cemented negative lens Lbn in the second lens group Gb, and fap represents the focal length of the positive lens component Lap located closest to the image side in the first lens group Ga. The description of these symbols is the same in the following embodiments.

(Table 3)
(1) Ncp-Ncn = 0.08775
(2) Dd1 / Dd0 = 0.3704
(3) fd / f0 = 0.8541
(4) Ndpp-Ndpn = 0.25331
(5) (rd2-rd1) / (rd2 + rd1) =-0.03290
(6) (-fbn) /f0=0.7051
(7) fap / f0 = 0.9326

  Thus, the optical system OS1 according to the first example satisfies all the conditional expressions (1) to (8).

  FIG. 2 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS1 according to the first example. In each aberration diagram, FNO represents an F number, Y represents an image height, and ω represents a half angle of view [unit: degree]. In each aberration diagram, d represents the aberration with respect to the d-line (wavelength λ = 587.6 nm), and g represents the aberration with respect to the g-line (wavelength λ = 435.8 nm). In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, at each half angle of view ω, the solid line represents the meridional coma aberration with respect to the d-line and the g-line, and the broken line on the left side from the origin represents the sagittal coma aberration generated in the meridional direction with respect to the d-line. The broken line represents the sagittal coma generated in the sagittal direction with respect to the d line. The description of this aberration diagram is the same in the following examples. As is apparent from the respective aberration diagrams shown in FIG. 2, in the optical system OS1 according to the first example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Second Embodiment]
FIG. 3 is a diagram illustrating a configuration of the optical system OS2 according to the second embodiment. This optical system OS2 includes, in order from the object side along the optical axis, a positive meniscus lens Lapa having a convex surface facing the object side, and a positive meniscus lens having a convex surface facing the object side and an aspheric surface on the object side surface (Positive lens component) The first lens group Ga made of Lap, the biconvex lens (positive lens) Lbnp, and the biconcave lens (negative lens) Lbnn are cemented and have a negative refractive power having a negative refractive power with the convex surface facing the object side. A second lens group Gb composed of a lens Lbn; an aperture stop S; a third lens group Gc composed of a cemented negative lens Lc formed by cementing a biconcave lens (negative lens) Lcn and a biconvex lens (positive lens) Lcp; A convex lens (positive lens) Ldpp and a biconcave lens (negative lens) Ldpn are cemented, a cemented positive lens Ldp1 having a positive refractive power, and a biconvex lens having an aspherical surface on the object side. It has a (positive lens component) LDP2, a fourth lens group Gd having a positive refractive power as a whole, composed. A dummy glass FL equivalent to an optical low-pass filter is disposed between the fourth lens group Gd of the optical system OS2 and the image plane.

  Table 4 below lists values of specifications of the optical system OS2 according to the second example. In addition, the surface numbers 1-18 shown in this Table 4 respond | correspond to the numbers 1-18 shown in FIG.

(Table 4)
[Overall specifications]
f = 58.0216
FNO = F1.447
ω = 20.78
Y = 21.6
TL = 116.59449
Air conversion Bf = 38.71306

[Lens data]
m rd νd nd
1 48.3691 6.0000 52.34 1.755000
2 64.8757 0.2000
* 3 48.5769 8.0000 49.53 1.744430
4 315.5532 1.0000
5 192.0921 5.0000 82.57 1.497820
6 -177.9144 1.5000 58.82 1.518230
7 22.1903 12.0000
8 0.0000 8.5500 Aperture stop S
9 -25.4714 1.7000 28.38 1.728250
10 74.9213 8.5000 46.59 1.816000
11 -38.2856 0.1000
12 48.9473 8.0000 40.66 1.883000
13 -81.3767 1.6000 33.73 1.647690
14 46.9021 10.0000
* 15 135.5889 5.0500 49.53 1.744430
16 -67.9281 36.0000
17 0.0000 2.0000 63.88 1.516800
18 0.0000 1.3945

[Lens focal length]
Lens group Start surface Focal length 1st lens group 1 58.61368
Second lens group 5 -48.50394
Third lens group 9 -364.73701
Fourth lens group 12 46.87082

  In the optical system OS2 according to the second example, the third and fifteenth lens surfaces are formed in an aspherical shape. Table 5 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A14.

(Table 5)
κ A4 A6 A8 A10
3rd surface -1.6299 2.68345E-06 -8.23800E-10 1.14177E-12 -1.24468E-15
A12 A14 A16
0.14554E-17 -0.10321E-20 0.27667E-24

κ A4 A6 A8 A10
15th surface -60.1023 -6.09416E-08 -8.52690E-10 -4.41425E-12 -2.55685E-14
A12 A14 A16
0.86429E-17 0.22562E-18 0.00000

  Table 6 below shows values corresponding to the conditional expressions for the optical system OS2 according to the second example.

(Table 6)
(1) Ncp-Ncn = 0.08775
(2) Dd1 / Dd0 = 0.40568
(3) fd / f0 = 0.80784
(4) Ndpp-Ndpn = 0.25331
(5) (rd2-rd1) / (rd2 + rd1) =-0.02134
(6) (−fbn) /f0=0.8360
(7) fap / f0 = 1.3125

  Thus, the optical system OS2 according to the second example satisfies all the conditional expressions (1) to (7).

  FIG. 4 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinitely focused state of the optical system OS2 according to the second example. As is apparent from the respective aberration diagrams shown in FIG. 4, in the optical system OS2 according to the second example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

[Third embodiment]
FIG. 5 is a diagram illustrating a configuration of the optical system OS3 according to the third embodiment. The optical system OS3 includes, in order from the object side along the optical axis, a first lens group Ga including a biconvex lens (positive lens component) Lap having an aspheric surface on the object side surface, and a biconvex lens (positive lens) Lbnp. And a biconcave lens (negative lens) Lbnn are cemented, a second lens group Gb comprising a cemented negative lens Lbn having a negative refractive power with the convex surface facing the object side, a biconcave lens (negative lens) Lcn and a biconvex lens ( Positive lens) A third lens group Gc composed of a cemented positive lens Lc that is cemented with Lcp, an aperture stop S, a biconvex lens (positive lens) Ldpp, and a biconcave lens (negative lens) Ldpn are cemented, and positive refraction. A fourth lens group Gd having a positive cemented lens Ldp1 having a positive power and a biconvex lens (positive lens component) Ldp2 having an aspherical surface on the image side. It is. A dummy glass FL corresponding to an optical low-pass filter is disposed between the fourth lens group Gd of the optical system OS3 and the image plane.

  Table 7 below provides values of specifications of the optical system OS3 according to the third example. In addition, the surface numbers 1-16 shown in this Table 7 respond | correspond to the numbers 1-16 shown in FIG.

(Table 7)
[Overall specifications]
f = 58.0216
FNO = F1.4498
ω = 20.89
Y = 21.6
TL = 118.68947
Air conversion Bf = 38.72512

[Lens data]
m rd νd nd
* 1 41.5795 12.0000 49.53 1.744430
2 -813.4478 0.3000
3 244.3063 6.0000 82.57 1.497820
4 -235.8932 1.5000 59.42 1.583130
5 21.4783 18.6829
6 -28.4726 1.7000 28.38 1.728250
7 45.3584 11.0000 46.59 1.816000
8 -39.2591 1.0000
9 0.0000 1.0000 Aperture stop S
10 46.1192 9.5000 40.66 1.883000
11 -58.1813 1.6000 38.03 1.603420
12 41.2425 10.0000
13 86.1329 5.0000 58.12 1.622990
* 14 -174.2894 36.0000
15 0.0000 2.0000 63.88 1.516800
16 0.0000 1.4066

[Lens focal length]
Lens group Start surface Focal length First lens group 1 53.45815
Second lens group 3 -39.67314
Third lens group 6 1460.90741
Fourth lens group 10 53.19978

  In the optical system OS3 according to the third example, the lens surfaces of the first surface and the fourteenth surface are formed in an aspheric shape. Table 8 below shows the aspheric data, that is, the values of the conic constant κ and the aspheric constants A4 to A14.

(Table 8)
κ A4 A6 A8 A10
1st surface -1.1184 2.85351E-06 -1.04658E-09 8.00265E-13 -1.54291E-15
A12 A14 A16
0.14216E-17 -0.58285E-21 0.000000

κ A4 A6 A8 A10
14th surface -0.1123E + 03 1.29475E-06 4.06801E-09 3.95038E-12 1.23421E-14
A12 A14 A16
-0.14579E-15 0.51293E-18 0.00000

  Table 9 below shows values corresponding to the conditional expressions for the optical system OS3 according to the third example.

(Table 9)
(1) Ncp-Ncn = 0.08775
(2) Dd1 / Dd0 = 0.38314
(3) fd / f0 = 0.91692
(4) Ndpp-Ndpn = 0.27958
(5) (rd2-rd1) / (rd2 + rd1) =-0.05582
(6) (-fbn) /f0=0.6838
(7) fap / f0 = 0.9209

  Thus, the optical system OS3 according to the third example satisfies all the conditional expressions (1) to (7).

  FIG. 6 shows various aberration diagrams of spherical aberration, astigmatism, distortion aberration, lateral chromatic aberration, and coma aberration in the infinite focus state of the optical system OS3 according to the third example. As is apparent from each aberration diagram shown in FIG. 6, in the optical system OS3 according to the third example, various aberrations including spherical aberration, sagittal coma, field curvature, astigmatism, and meridional coma are corrected well. It can be seen that it has high optical performance.

  According to each of the above-described embodiments, it has a comprehensive angle of about 2ω = 41.8 °, further has a large aperture of F1.4, and has high performance, spherical aberration, sagittal coma aberration, field curvature, meridional coma aberration. It is possible to realize an optical system OS in which is corrected well.

  Needless to say, the above-described effects can be obtained by mounting the optical systems OS <b> 1 to OS <b> 3 shown in the above embodiments in the above-described camera 1. Moreover, each said Example has shown the specific example of this invention, and this invention is not limited to these.

OS (OS1 to OS3) Optical system Ga First lens group Gb Second lens group Gc Third lens group Gd Fourth lens group Lapa Object-side positive lens component Lap in the first lens group Image side in the first lens group Positive lens component Lbn cemented negative lens Lc in the second lens group cemented lens component Ldp1 in the third lens group cemented positive lens Ldp2 in the fourth lens group positive lens component S on the image side in the fourth lens group Aperture stop 1 Single-lens reflex camera (imaging device)

Claims (12)

In order from the object side along the optical axis,
A first lens group having a positive refractive power;
A second lens group having negative refractive power;
A third lens group;
A fourth lens group having a positive refractive power,
The first lens group has at least one positive lens component;
The second lens group includes a cemented negative lens having a negative refractive power in which a positive lens and a negative lens are cemented and a convex surface is directed to the object side,
The third lens group includes a cemented lens formed by cementing a negative lens with a concave surface facing the object side and a positive lens;
The fourth lens group includes a positive lens having a positive refractive power and a positive lens having a positive refractive power in which a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented. ,
An optical system satisfying the following conditional expression:
0.00 <Ncp-Ncn <0.40
0.01 <Dd1 / Dd0 <0.80
However,
Ncp: refractive index with respect to d-line of medium of the positive lens in the cemented lens in the third lens group Ncn: refractive index with respect to d-line of medium of the negative lens in the cemented lens in the third lens group Dd1: On-axis air space between the cemented positive lens in the fourth lens group and the positive lens component located on the image side Dd0: Lens closest to the image side from the lens surface closest to the object side in the fourth lens group Length on the optical axis to the surface (total thickness of the fourth lens group) The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.0 <fd / f0 <5.0
However,
fd: focal length of the fourth lens group f0: focal length of the entire system when focusing on infinity The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.00 <Ndpp-Ndpn <0.40
However,
Ndpp: refractive index with respect to the d-line of the medium of the positive lens in the cemented positive lens in the fourth lens group Ndpn: with respect to the d-line of the medium of the negative lens in the cemented positive lens in the fourth lens group Refractive index The optical system according to claim 1, wherein the following conditional expression is satisfied.
-1,000 <(rd2-rd1) / (rd2 + rd1) <-0.000
However,
rd1: radius of curvature of the most object side surface of the cemented positive lens in the fourth lens group rd2: radius of curvature of the most image side surface of the cemented positive lens in the fourth lens group The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.0 <(− fbn) / f0 <5.0
However,
fbn: the focal length of the composite of the cemented negative lens in the second lens group f0: the focal length of the entire system when focusing on infinity The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.0 <fap / f0 <10.0
However,
fap: focal length of the positive lens component located closest to the image side in the first lens group f0: focal length of the entire system when focusing on infinity   2. An aperture stop for determining an F-number is provided between the second lens group and the third lens group, or between the third lens group and the fourth lens group. 7. The optical system according to any one of 6.   The optical system according to claim 1, wherein the first lens group or the second lens group has at least one aspheric surface.   The optical system according to claim 1, wherein the fourth lens group has at least one aspheric surface.   The optical system according to claim 1, wherein the positive lens component in the fourth lens group is a positive lens having a convex surface directed toward the object side.   An imaging apparatus comprising the optical system according to claim 1. A first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group, and a fourth lens group having a positive refractive power in order from the object side along the optical axis. And an optical system manufacturing method comprising:
As the first lens group, at least one positive lens component is disposed,
As the second lens group, a positive lens and a negative lens are cemented, and a cemented negative lens having a negative refractive power with a convex surface facing the object side is disposed,
As the third lens group, a cemented lens formed by cementing a negative lens with a concave surface facing the object side and a positive lens is disposed,
As the fourth lens group, a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side are cemented, and a cemented positive lens having positive refractive power and a positive lens component are arranged. ,
An optical system manufacturing method satisfying the following conditional expression:
0.00 <Ncp-Ncn <0.40
0.01 <Dd1 / Dd0 <0.80
However,
Ncp: refractive index with respect to d-line of medium of the positive lens in the cemented lens in the third lens group Ncn: refractive index with respect to d-line of medium of the negative lens in the cemented lens in the third lens group Dd1: On-axis air space between the cemented positive lens in the fourth lens group and the positive lens component located on the image side Dd0: Lens closest to the image side from the lens surface closest to the object side in the fourth lens group Length on the optical axis to the surface (total thickness of the fourth lens group)

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