JP2012230340A - Optical system, imaging apparatus having the same, and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact optical system having a small number of lenses, and achieving high performance, and to provide an imaging apparatus having the optical system and a manufacturing method of the optical system.SOLUTION: An optical system OS to be mounted on a single-lens reflex camera 1 or the like includes, in order from an object side along an optical axis, a front group GF, an aperture stop S, and a rear group GR having a positive refractive power. The front group GF includes, in order from the object side, a first positive lens component LF1, a second positive lens component LF2, and a negative lens component LF3. The rear group GR includes, in order from the object side, a negative lens component LR1 in which a negative lens LRn1 with its concave surface facing the object side and a positive lens LRp1 are joined, a first positive lens component LR2 in which a positive lens LRp2 and a negative lens LRn2 are joined, and a second positive lens component LR3.

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 front group, an aperture stop, and a rear group having a positive refractive power. Has, in order from the object side, a first positive lens component, a second positive lens component, and a negative lens component, and the rear group in order from the object side is a positive lens and a positive lens with a concave surface facing the object side. A negative lens component in which the lens is cemented, a first positive lens component in which the positive lens and the negative lens are cemented, and a second positive lens component, wherein the following conditional expression is satisfied: To do.
0.000 <nRP-nRN <0.350
-1.00 <(rp2 + rp1) / (rp2-rp1) <1.00
However,
nRP: refractive index with respect to d-line of medium of positive lens constituting negative lens component in rear group nRN: refractive index with respect to d-line of medium of negative lens constituting negative lens component in rear group rp1: in rear group The radius of curvature of the surface closest to the object side of the first positive lens component rp2: The radius of curvature of the surface closest to the image side of the first positive lens component in the rear group

Such an optical system preferably satisfies the following conditional expression.
2.0 <fF2 / f0 <10.0
However,
fF2: focal length of the second positive lens component in the front group f0: focal length of the entire system when focusing on infinity

Such an optical system preferably satisfies the following conditional expression.
0.001 <fR / fF <1.500
However,
fF: Focal length of the front group when focusing on infinity fR: Focal length of the rear group when focusing on infinity

Such an optical system preferably satisfies the following conditional expression.
0.2 <fR2 / f0 <4.0
However,
fR2: focal length of the first positive lens component in the rear group f0: focal length of the entire system when focusing on infinity

Such an optical system preferably satisfies the following conditional expression.
2.5 <(− fR1) / f0 <40
However,
fR1: Focal length of the negative lens component in the rear group f0: Focal length of the entire system when focusing on infinity

  In such an optical system, the front group preferably has at least one aspheric surface.

  In such an optical system, the rear group preferably has at least one aspheric surface.

  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 is an optical system manufacturing method including a front group, an aperture stop, and a rear group having a positive refractive power in order from the object side along the optical axis. Then, as the front group, a first positive lens component, a second positive lens component, and a negative lens component are arranged in order from the object side, and a concave surface is directed to the object side in order from the object side as the rear group. A negative lens component in which a negative lens and a positive lens are cemented, a first positive lens component in which a positive lens and a negative lens are cemented, and a second positive lens component are disposed, and the following conditional expression is satisfied: It is characterized by that.
0.000 <nRP-nRN <0.350
-1.00 <(rp2 + rp1) / (rp2-rp1) <1.00
However,
nRP: refractive index with respect to d-line of medium of positive lens constituting negative lens component in rear group nRN: refractive index with respect to d-line of medium of negative lens constituting negative lens component in rear group rp1: in rear group The radius of curvature of the surface closest to the object side of the first positive lens component rp2: The radius of curvature of the surface closest to the image side of the first positive lens component in the rear group

  According to the present invention, it is possible to provide a high-performance optical system that is small in size, has a small number of components, an image pickup apparatus having the optical system, and a method for manufacturing the optical system.

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. 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 the present embodiment includes a front group GF, an aperture stop S, and a rear group GR having a positive refractive power in order from the object side along the optical axis. Configured. Further, the front group GF includes a first positive lens component LF1, a second positive lens component LF2, and a negative lens component LF3 in order from the object side, and the rear group GR is in order from the object side to the object side. A negative lens component LR1 in which a negative lens LRn1 and a positive lens LRp1 having a concave surface are cemented to each other, a first positive lens component LR2 in which a positive lens LRp2 and a negative lens LRn2 are cemented, and a second positive lens component LR3, , And is configured. 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.

  This optical system OS basically deteriorates coma aberration, especially sagittal coma aberration, which is a defect of so-called Gaussian type, xenota type optical system represented by positive and negative signs, and chromatic aberration, curvature of field and astigmatism. It is improved without letting it. The conditions for configuring such an optical system OS will be described below.

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

0.000 <nRP-nRN <0.350 (1)
However,
nRP: refractive index of medium of positive lens LRp1 constituting negative lens component LR1 in rear group GR with respect to d-line nRN: refractive index of medium of negative lens LRn1 constituting negative lens component LR1 of rear group GR with respect to d-line

  Conditional expression (1) defines a difference in refractive index with respect to the d-line (wavelength λ = 587.6 nm) between the medium of the positive lens LRp1 and the medium of the negative lens LRn1 constituting the negative lens component LR1 in the rear group GR. It is. If this condition is not met, the setting of the optimum value for the Petzval sum is impaired, and as a result, the field curvature deteriorates.

  When the value exceeds the upper limit value of the conditional expression (1), 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. Further, the ability to correct spherical aberration is also reduced, and it is not preferable because it is impossible to select a glass material for optimal chromatic aberration. When the upper limit value of conditional expression (1) is set to 0.300, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of the conditional expression (1) is set to 0.200, the effect of the present application can be exhibited more. In addition, by suppressing the upper limit value of conditional expression (1) to 0.170, the effect of the present application can be maximized.

  Further, when the lower limit of conditional expression (1) is not reached, the difference in refractive index becomes remarkably small, and the refractive index of the negative lens LRn1 becomes larger than the refractive index of the positive lens LRp1. In this case, the positive and negative refractive indexes are reversed, and it is difficult to keep the Petzval sum small. Therefore, the Petzval sum deviates greatly from the optimum value, and as a result, the correction of curvature of field and the correction of astigmatism are deteriorated. If the lower limit value of conditional expression (1) is set to 0.020, it is advantageous for correction of various aberrations such as field curvature and astigmatism. Further, when the lower limit value of the conditional expression (1) is set to 0.035, the effect of the present application can be further exhibited. Further, by setting the lower limit value of conditional expression (1) to 0.05, 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).

-1.00 <(rp2 + rp1) / (rp2-rp1) <1.00 (2)
However,
rp1: radius of curvature of the surface closest to the object side of the first positive lens component LR2 in the rear group GR rp2: radius of curvature of the surface closest to the image side of the first positive lens component LR2 in the rear group GR

  Conditional expression (2) is a condition that defines the overall shape factor of the first positive lens component LR2 in the rear group GR. This condition is greatly related to correction of spherical aberration and coma. Here, the conditional expression (2) being set within ± 1 means that the overall shape factor of the first positive lens component LR2 indicates a biconvex shape. By maintaining this shape, it is possible to correct spherical aberration and to correct coma.

  When the upper limit of conditional expression (2) is exceeded, the first positive lens component LR2 has a positive meniscus shape that exceeds the plano-convex shape with the convex surface facing the object side and the convex surface toward the object side. This shape is not preferable because the correction of spherical aberration deteriorates and the correction of astigmatism also deteriorates. In addition, manufacturing sensitivity such as eccentricity increases, which is not preferable. If the upper limit value of conditional expression (2) is set to 0.75, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of the conditional expression (2) is set to 0.70, the effect of the present application can be exhibited more. Further, by suppressing the upper limit value of conditional expression (2) to 0.60, the effect of the present application can be maximized.

  When the lower limit of conditional expression (2) is not reached, the first positive lens component LR2 has a positive meniscus shape that exceeds the planoconvex shape with the convex surface facing the image side and the convex surface toward the image side. In this case, correction of spherical aberration, sagittal coma aberration, and meridional coma aberration deteriorates, which is not preferable. In addition, manufacturing sensitivity such as eccentricity increases, which is not preferable. If the lower limit value of conditional expression (2) is set to −0.7, it is advantageous for correcting various aberrations. Moreover, when the lower limit value of the conditional expression (2) is set to −0.42, the effect of the present application can be exhibited more. Moreover, the effect of the present application can be maximized by setting the lower limit value of conditional expression (2) to −0.40.

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

2.0 <fF2 / f0 <10.0 (3)
However,
fF2: focal length of the second positive lens component LF2 in the front group GF f0: focal length of the entire system when focusing on infinity

  Conditional expression (3) defines the focal length of the second positive lens component LF2 of the front group GF. The front group GF of the optical system OS according to the present embodiment has a positive / negative configuration, and defines an optimum refractive power of the second positive lens component LF2 at the intermediate portion.

  If the upper limit value of conditional expression (3) is exceeded, it means that the refractive power of the second positive lens component LF2 becomes weak. In this case, correction of field curvature and astigmatism deteriorates, which is not preferable. When the upper limit value of conditional expression (3) is set to 9.0, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of conditional expression (3) is set to 8.0, the effect of the present application can be exhibited more. Further, by suppressing the upper limit value of conditional expression (3) to 7.0, the effect of the present application can be maximized.

  Further, when the lower limit value of conditional expression (3) is not reached, it means that the refractive power of the second positive lens component LF2 becomes strong. In that case, correction of coma aberration, spherical aberration, and distortion is deteriorated as a result, which is not preferable. If the lower limit value of conditional expression (3) is set to 2.5, it is advantageous for correction of various aberrations such as spherical aberration. Further, when the lower limit value of the conditional expression (3) is set to 3.0, the effect of the present application can be exhibited more. Further, when the lower limit value of the conditional expression (3) is set to 3.8, the effect of the present application can be further exhibited. Further, by setting the lower limit value of conditional expression (3) to 4.0, 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).

0.001 <fR / fF <1.500 (4)
However,
fF: Focal length of front group GF when focusing on infinity fR: Focal length of rear group GR when focusing on infinity

  Conditional expression (4) defines the focal length ratio between the front group GF and the rear group GR constituting the optical system OS according to this embodiment, in other words, the magnitude relationship between the refractive powers of the front group GF and the rear group GR. It is a condition.

  When the upper limit value of conditional expression (4) is exceeded, the focal length of the rear group GR is greater than that of the front group GF. In other words, the refractive power of the rear group GR is weaker than that of the front group GF, and focusing on the front group GF indicates that the refractive power of the front group GF is significantly stronger than that of the rear group GR. In this case, the balance of correction of field curvature, astigmatism, and coma is lost, which is not preferable. If the upper limit value of conditional expression (4) is set to 1.000, various aberrations can be corrected. Further, when the upper limit value of the conditional expression (4) is set to 0.550, the effect of the present application can be exhibited more. Further, by suppressing the upper limit value of conditional expression (4) to 0.350, the effects of the present application can be maximized.

  When the lower limit value of conditional expression (4) is not reached, the focal length of the rear group GR becomes smaller than that of the front group GF. In other words, the refractive power of the rear group GR is significantly stronger than that of the front group GF, and focusing on the front group GF indicates that the refractive power of the front group GF is weaker than that of the rear group GR. In this case, spherical aberration and coma are particularly deteriorated, which is not preferable. When the lower limit value of conditional expression (4) is set to 0.010, the above-mentioned various aberrations can be corrected more favorably. Moreover, when the lower limit value of the conditional expression (4) is set to 0.030, the effect of the present application can be exhibited more. Moreover, by setting the lower limit value of conditional expression (4) to 0.070, 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).

0.2 <fR2 / f0 <4.0 (5)
However,
fR2: focal length of the first positive lens component LR2 in the rear group GR f0: focal length of the entire system when focusing on infinity

  Conditional expression (5) is a condition that defines the relationship between the focal lengths of the first positive lens component LR2 having a biconvex shape as a whole in the rear group GR, in other words, the refractive power. The rear group GR of the optical system OS according to the present embodiment has a negative positive / positive configuration, and defines an optimum refractive power of the biconvex first positive lens component LR2 at the intermediate portion.

  When the value exceeds the upper limit value of the conditional expression (5), it means that the focal length of the first positive lens component LR2 becomes extremely long and the positive refractive power becomes weak. In this case, correction of field curvature and astigmatism deteriorates, which is not preferable. When the upper limit value of conditional expression (5) is set to 3.0, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of the conditional expression (5) is set to 2.0, the effect of the present application can be exhibited more. Moreover, the effect of the present application can be maximized by suppressing the upper limit value of conditional expression (5) to 1.7.

  On the other hand, if the lower limit value of conditional expression (5) is not reached, it means that the focal length of the first positive lens component LR2 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 (5) to 0.5 is advantageous for correcting various aberrations such as spherical aberration. Further, when the lower limit value of the conditional expression (5) is set to 0.7, the effect of the present application can be exhibited more. Further, by setting the lower limit value of conditional expression (5) to 1.0, 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 (6).

2.5 <(− fR1) / f0 <40 (6)
However,
fR1: focal length of the negative lens component LR1 in the rear group GR f0: focal length of the entire system when focusing on infinity

  Conditional expression (6) is a condition that defines the focal length of the negative lens component LR1 in which the negative lens LRn1 having the concave surface facing the object side in the rear group GR and the positive lens LRp1 are cemented. The rear group GR of the optical system OS according to the present embodiment has a negative positive configuration, and defines the optimum refractive power of the negative lens component LR1 on the object side.

  If the upper limit value of conditional expression (6) is exceeded, it means that the absolute value of the focal length of the negative lens component LR1 is significantly increased and the negative refractive power is weakened. In this case, the correction capability of spherical aberration and coma aberration is lowered, which is not preferable. If the upper limit value of conditional expression (6) is set to 30, the above-described correction of various aberrations becomes more advantageous. Further, when the upper limit value of conditional expression (6) is set to 25, the effect of the present application can be further exhibited. Further, by suppressing the upper limit value of conditional expression (6) to 20, 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 absolute value of the focal length of the negative lens component LR1 is remarkably reduced and the negative 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 (6) to 3.0 is advantageous for correcting various aberrations such as spherical aberration. Further, when the lower limit value of the conditional expression (6) is set to 4.0, the effect of the present application can be exhibited more. Further, by setting the lower limit value of conditional expression (6) to 6.9, the effect of the present application can be maximized.

  The front group GF preferably has at least one aspheric surface, which is advantageous for correcting spherical aberration and coma corresponding to a large aperture. The rear group GR preferably has at least one aspheric surface. Similarly, the rear group GR is advantageous for correcting spherical aberration and coma corresponding to a large aperture. 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 the optical system OS according to the present embodiment, the first positive lens component LF1, the second positive lens component LF2, and the negative lens component LF3 that constitute the front group GF, and the second positive lens component that constitutes the rear group GR. The LR 3 is composed of a single lens as shown in FIG. 1, but may be composed of a cemented lens in which two or more single lenses are cemented.

  FIG. 5 is 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 optical system OS described above. 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. 5 may be one that holds the photographing lens 2 in a detachable manner or may be molded 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, the optical system OS having the two-group configuration is shown, but the above-described configuration conditions and the like can be applied to other group configurations such as the third group, the fourth group, and the like. Further, a configuration in which a lens or a lens group is added to the most object side, or a configuration in which a lens or a lens group is added to the most image side may be used. The lens group is a portion having at least one lens separated by the aperture stop S as described above, or at least one piece separated by an air interval that changes at the time of zooming or focusing. The part which has a lens is shown.

  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 front group GF or a rear focus using the rear group GR 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 rear group GR 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. In the manufacturing method of the optical system OS, the front group GF, the aperture stop S, and the rear group GR having a positive refractive power are arranged in this order from the object side along the optical axis. Specifically, in the present embodiment, for example, as the front group GF, in order from the object side, a biconvex aspherical positive lens (first positive lens component) LF1, and a positive meniscus lens (first lens) with a convex surface facing the object side. 2 positive lens components) LF2 and a negative meniscus lens (negative lens component) LF3 having a convex surface facing the object side (step S100), an aperture stop S (step S200), and the rear group GR as an object In order from the side, a negative lens component LR1 in which a biconcave lens LRn1 and a biconvex lens LRp1 are cemented, a first positive lens component LR2 in which a biconvex lens LRp2 and a negative meniscus lens LRn2 with a concave surface facing the object side are cemented, and A biconvex aspherical positive lens (second positive lens component) LR3 is arranged (step S300). At this time, the negative lens component LR1 and the first positive lens component LR2 constituting the rear group GR satisfy the conditional expression (1) and the conditional expression (2) described above.

  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 and 3 show the configuration of the optical system OS (OS1, OS2) 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 (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 right 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, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power. The front group GF includes, in order from the object side, a first positive lens component LF1 composed of an aspherical positive lens having a biconvex lens shape, a second positive lens component LF2 composed of a positive meniscus lens having a convex surface facing the object side, and the object side. And a negative lens component LF3 composed of a negative meniscus lens having a convex surface facing the surface. The rear group GR includes, in order from the object side, a negative lens component LR1 in which a biconcave lens (a negative lens having a concave surface facing the object side) LRn1 and a biconvex lens (positive lens) LRp1 are cemented, and a biconvex lens (positive lens). LRp2 is composed of a first positive lens component LR2 in which a negative meniscus lens (negative lens) LRn2 having a concave surface facing the object side is cemented, and a second positive lens component LR3 composed of a biconvex aspherical positive lens. ing.

  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 back focus Bf is the most image side lens of the optical system OS1. This represents the distance on the optical axis from the surface (fifteenth surface) 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. The surface numbers 1 to 15 shown in Table 1 correspond to the numbers 1 to 15 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. 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 = F1.210
ω = 20.83 °
Y = 21.6
TL = 97.9986
Bf = 37.9986

[Lens data]
m rd νd nd
1 * 68.8166 7.0000 49.53 1.744430
2 -294.0348 0.1000
3 38.2098 10.0000 46.63 1.816000
4 39.7292 4.2000
5 285.9607 1.5000 31.06 1.688930
6 28.2115 7.0000
7 0.0000 7.0000 Aperture stop S
8 -28.6407 1.7000 29.52 1.717360
9 58.9495 9.5000 46.63 1.816000
10 -42.9396 0.1000
11 141.1289 6.5000 49.61 1.772500
12 -52.9259 1.3000 52.32 1.517420
13 -380.3063 0.1000
14 * 201.4725 4.0000 49.61 1.772500
15 -104.4312 Bf

[Lens focal length]
Lens group Start surface Focal length Front group 1 339.4386
Rear group 8 41.6343

  In the optical system OS1 according to the first example, the lens surfaces of the first surface and the fourteenth 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 A8.

(Table 2)
κ A4 A6 A8
1st surface 0.6729 -5.61406E-07 -9.97203E-11 -2.12831E-13
14th surface 10.6153 -9.55365E-07 -2.33540E-11 0.00000E + 00

  Table 3 below shows values corresponding to the conditional expressions for the optical system OS1 according to the first example. In Table 3, nRP is the refractive index of the medium of the positive lens LRp1 constituting the negative lens component LR1 in the rear group GR with respect to the d-line, and nRN is the negative lens LRn1 constituting the negative lens component LR1 in the rear group GR. Refractive index with respect to the d-line of the medium, rp1 is the radius of curvature of the most object side surface of the first positive lens component LR2 in the rear group GR, and rp2 is the most image side surface of the first positive lens component LR2 in the rear group GR , F0 is the focal length of the entire system, fF2 is the focal length of the second positive lens component LF2 in the front group GF, fF is the focal length of the front group GF when focused at infinity, and fR is focused at infinity. At that time, the focal length of the rear group GR, fR1 represents the focal length of the negative lens component LR1 in the rear group GR, and fR2 represents the focal length of the first positive lens component LF2 in the rear group GR. The description of these symbols is the same in the following embodiments.

(Table 3)
(1) nRP-nRN = 0.09864
(2) (rp2 + rp1) / (rp2-rp1) = 0.458
(3) fF2 / f0 = 5.3326
(4) fR / fF = 0.1227
(5) fR2 / f0 = 1.4964
(6) (−fR1) /f0=11.2062

  Thus, the optical system OS1 according to the first example satisfies all the conditional expressions (1) to (6).

  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. The optical system OS2 includes, in order from the object side, a front group GF having a positive refractive power, an aperture stop S, and a rear group GR having a positive refractive power. The front group GF includes, in order from the object side, a first positive lens component LF1 composed of an aspherical positive lens having a biconvex lens shape, a second positive lens component LF2 composed of a positive meniscus lens having a convex surface facing the object side, and the object side. And a negative lens component LF3 composed of a negative meniscus lens having a convex surface facing the surface. The rear group GR includes, in order from the object side, a negative lens component LR1 in which a biconcave lens (a negative lens having a concave surface facing the object side) LRn1 and a biconvex lens (positive lens) LRp1 are cemented, and a biconvex lens (positive lens). LRp2 is composed of a first positive lens component LR2 in which a negative meniscus lens (negative lens) LRn2 having a concave surface facing the object side is cemented, and a second positive lens component LR3 composed of a biconvex aspherical positive lens. ing.

  Table 4 below lists values of specifications of the optical system OS2 according to the second example. The surface numbers 1 to 15 shown in Table 4 correspond to the numbers 1 to 15 shown in FIG.

(Table 4)
[Overall specifications]
f = 58.0216
FNO = F1.217
ω = 20.83 °
Y = 21.6
TL = 97.9972
Bf = 37.9972

[Lens data]
m rd νd nd
1 * 68.6463 7.0000 49.53 1.744430
2 -284.0624 0.1000
3 38.3363 10.0000 46.63 1.816000
4 40.0410 4.2000
5 513.0081 1.5000 31.06 1.688930
6 28.3928 7.0000
7 0.0000 7.0000 Aperture stop S
8 -30.5598 1.7000 28.46 1.728250
9 51.9885 9.5000 40.77 1.883000
10 -50.3917 0.1000
11 157.5857 6.5000 49.61 1.772500
12 -59.9955 1.3000 52.32 1.517420
13 -137.9000 0.1000
14 * 266.2953 4.0000 49.61 1.772500
15 -107.7468 Bf

[Lens focal length]
Lens group Start surface Focal length Front group 1 400.8473
Rear group 8 41.2837

  In the optical system OS2 according to the second example, the lens surfaces of the first surface and the fourteenth surface 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 A8.

(Table 5)
κ A4 A6 A8
1st surface 0.6729 -5.61406E-07 -9.97203E-11 -2.12831E-13
14th surface 6.1738 -1.03841E-06 -3.16075E-10 0.00000E + 00

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

(Table 6)
(1) nRP-nRN = 0.15475
(2) (rp2 + rp1) / (rp2-rp1) = − 0.06662
(3) fF2 / f0 = 5.2311
(4) fR / fF = 0.130
(5) fR2 / f0 = 1.3536
(6) (−fR1) /f0=17.0128

  As described above, the optical system OS2 according to the second example satisfies all the conditional expressions (1) to (6).

  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.

  According to each of the above-described embodiments, it has a comprehensive angle of about 2ω = 41.6 °, and further has a large aperture F1.2, 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 OS1 and OS2 shown in the above embodiments in the camera 1 described above. Moreover, each said Example has shown the specific example of this invention, and this invention is not limited to these.

OS (OS1, OS2) Optical system GF Front group LF1 First positive lens component LF2 Second positive lens component LF3 Negative lens component S Aperture stop GR Rear group LR1 Negative lens component LRn1 Negative lens LRp1 Positive lens LR2 First positive lens component LRp2 Positive lens LRn2 Negative lens LR3 Second positive lens component 1 SLR camera (imaging device)

Claims (9)

In order from the object side along the optical axis,
The front group,
An aperture stop,
A rear group having a positive refractive power,
The front group is in order from the object side,
A first positive lens component;
A second positive lens component;
A negative lens component,
The rear group is in order from the object side,
A negative lens component in which a negative lens having a concave surface facing the object side and a positive lens are cemented, and
A first positive lens component in which a positive lens and a negative lens are cemented;
A second positive lens component,
An optical system satisfying the following conditional expression:
0.000 <nRP-nRN <0.350
-1.00 <(rp2 + rp1) / (rp2-rp1) <1.00
However,
nRP: refractive index with respect to d-line of medium of the positive lens constituting the negative lens component in the rear group nRN: refractive index with respect to d-line of medium of the negative lens constituting the negative lens component in the rear group rp1: radius of curvature of the most object side surface of the first positive lens component in the rear group rp2: radius of curvature of the most image side surface of the first positive lens component in the rear group The optical system according to claim 1, wherein the following conditional expression is satisfied.
2.0 <fF2 / f0 <10.0
However,
fF2: focal length of the second positive lens component in the front 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.
0.001 <fR / fF <1.500
However,
fF: focal length of the front group when focused at infinity fR: focal length of the rear group when focused at infinity The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.2 <fR2 / f0 <4.0
However,
fR2: focal length of the first positive lens component in the rear 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.
2.5 <(− fR1) / f0 <40.0
However,
fR1: focal length of the negative lens component in the rear group f0: focal length of the entire system when focusing on infinity   The optical system according to claim 1, wherein the front group has at least one aspheric surface.   The optical system according to claim 1, wherein the rear group has at least one aspheric surface.   An imaging apparatus comprising the optical system according to claim 1. In order from the object side along the optical axis, a manufacturing method of an optical system having a front group, an aperture stop, and a rear group having a positive refractive power,
As the front group, in order from the object side, a first positive lens component, a second positive lens component, and a negative lens component are arranged,
As the rear group, in order from the object side, a negative lens component in which a negative lens having a concave surface facing the object side and a positive lens are cemented, a first positive lens component in which a positive lens and a negative lens are cemented, Two positive lens components,
An optical system manufacturing method satisfying the following conditional expression:
0.000 <nRP-nRN <0.350
-1.00 <(rp2 + rp1) / (rp2-rp1) <1.00
However,
nRP: refractive index with respect to d-line of medium of the positive lens constituting the negative lens component in the rear group nRN: refractive index with respect to d-line of medium of the negative lens constituting the negative lens component in the rear group rp1: radius of curvature of the most object side surface of the first positive lens component in the rear group rp2: radius of curvature of the most image side surface of the first positive lens component in the rear group

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