JP2017161845A - Optical system, optical instrument and method for manufacturing optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical system (wide angle lens) that is small and has high optical performance.SOLUTION: An optical system WL includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, in which upon focusing from an infinite distance to a close distance object, the front group G1 and the rear group G2 move to an object side along the optical axis and an interval between the front group G1 and the rear group G2 varies, satisfying a conditional expression of 1.05<X1/X2<4.00. In the expression, X1 represents an amount of movement of the front group G1 upon focusing; and X2 represents an amount of movement of the rear group G2 upon focusing.SELECTED DRAWING: Figure 1

Description

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

  Conventionally, as an optical system used in an optical apparatus such as a digital still camera or a digital video camera, an optical system that is small and can perform good aberration correction by a floating focus method has been proposed (for example, (See Patent Document 1). However, in such an optical system, it is necessary to suppress the displacement of the image plane that occurs during focusing.

JP 2012-128294 A

  The optical system according to the present invention has a front group having a positive refractive power and a rear group having a positive refractive power arranged in order from the object side, and when focusing from infinity to a short distance object, The front group and the rear group move to the object side along the optical axis, the interval between the front group and the rear group changes, and the following conditional expression is satisfied.

1.05 <X1 / X2 <4.00
Where X1: movement amount of the front group at the time of focusing,
X2: Movement amount of the rear group at the time of focusing.

  An optical apparatus according to the present invention is configured by mounting the above optical system.

An optical system manufacturing method according to the present invention is a method for manufacturing an optical system having a front group having a positive refractive power and a rear group having a positive refractive power, which are arranged in order from the object side. When focusing on a short-distance object, the front group and the rear group move to the object side along the optical axis, the interval between the front group and the rear group changes, and the following conditional expression is satisfied As described above, each lens is arranged in a lens barrel.
1.05 <X1 / X2 <4.00
Where X1: movement amount of the front group at the time of focusing,
X2: Movement amount of the rear group at the time of focusing.

It is a figure which shows the lens structure of the optical system which concerns on 1st Example of this embodiment. FIG. 2A is a diagram illustrating various aberrations when the optical system according to the first example is focused at infinity, and FIG. 2B is a diagram illustrating various aberrations when the optical system according to the first example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on 2nd Example of this embodiment. FIG. 4A is a diagram showing various aberrations when the optical system according to the second example is focused at infinity, and FIG. 4B is a diagram showing various aberrations when the optical system according to the second example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on 3rd Example of this embodiment. FIG. 6A is a diagram illustrating various aberrations when the optical system according to the third example is focused at infinity, and FIG. 6B is a diagram illustrating various aberrations when the optical system according to the third example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on 4th Example of this embodiment. FIG. 8A is a diagram showing various aberrations when the optical system according to the fourth example is focused at infinity, and FIG. 8B is a diagram showing various aberrations when the optical system according to the fourth example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on 5th Example of this embodiment. FIG. 10A is a diagram showing various aberrations when the optical system according to the fifth example is focused at infinity, and FIG. 10B is a diagram showing various aberrations when the optical system according to the fifth example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on 6th Example of this embodiment. 12A is a diagram showing various aberrations when the optical system according to the sixth example is focused at infinity, and FIG. 12B is a diagram showing various aberrations when the optical system according to the sixth example is focused at a short distance. FIG. It is a figure which shows the lens structure of the optical system which concerns on the 7th Example of this embodiment. FIG. 14A is a diagram showing various aberrations when the optical system according to the seventh example is focused at infinity, and FIG. 14B is a diagram showing various aberrations when focusing on the short distance of the optical system according to the seventh example. FIG. It is a figure which shows the lens structure of the optical system which concerns on the 8th Example of this embodiment. FIG. 16A is a diagram showing various aberrations when the optical system according to the eighth example is focused at infinity, and FIG. 16B is a diagram showing various aberrations when the optical system according to the eighth example is focused at a short distance. FIG. It is a figure which shows the structure of the camera provided with the optical system which concerns on this embodiment. It is a flowchart which shows the manufacturing method of the optical system which concerns on this embodiment.

  Hereinafter, the optical system and the optical apparatus of the present embodiment will be described with reference to the drawings. As an example of the optical system (wide-angle lens) WL according to the present embodiment, an optical system WL (1) illustrated in FIG. 1 includes a front group G1 having a positive refractive power and a positive refractive power arranged in order from the object side. And a rear group G2. In such an optical system WL (1), when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move to the object side along the optical axis, and the front group G1 and the rear group G2 The interval between and changes.

  The optical system WL according to the present embodiment may be the optical system WL (2) shown in FIG. 3, the optical system WL (3) shown in FIG. 5, or the optical system WL (4) shown in FIG. 9 may be the optical system WL (5) shown in FIG. 11, the optical system WL (6) shown in FIG. 11, the optical system WL (7) shown in FIG. 13, or the optical system WL (8) shown in FIG. . 3, 5, 7, 9, 11, 13, and 15, each group of the optical systems WL (2) to WL (8) includes the optical system WL (1 ).

  As described above, the optical system WL according to the present embodiment is configured to include the front group G1 having a positive refractive power and the rear group G2 having a positive refractive power. At the time of focusing, the front group G1 and the rear group G2 move toward the object side along the optical axis, and the interval between the front group G1 and the rear group G2 changes. With this configuration, it is possible to obtain an optical system that is small and has good optical performance by suppressing displacement of the image plane during focusing.

  Under the above configuration, the optical system WL according to the present embodiment satisfies the following conditional expression (1).

1.05 <X1 / X2 <4.00 (1)
Where X1: the amount of movement of the front group G1 during focusing,
X2: A movement amount of the rear group G2 at the time of focusing.

  Conditional expression (1) is a conditional expression for defining an appropriate range for the amount of movement of the front group G1 and the rear group G2 during focusing. By satisfying conditional expression (1), it is possible to satisfactorily correct field curvature and off-axis aberrations.

If the corresponding value of the conditional expression (1) exceeds the upper limit value, it is necessary to increase the power (refractive power) of the rear group G2, so that it is difficult to correct spherical aberration, coma aberration, and the like. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (1) is preferably 3.50, more preferably 3.00.
It is good.

  If the corresponding value of conditional expression (1) is lower than the lower limit value, it is necessary to weaken the power of the rear group G2, so that the optical performance at the time of focusing on a close range cannot be kept good, and correction of field curvature is performed. Becomes difficult. In order to ensure the effect of the present embodiment, the lower limit value of the conditional expression (1) is preferably 1.10, and more preferably 1.20.

  The optical system WL of the present embodiment preferably satisfies the following conditional expression (2).

0.20 <Bf / f <0.75 (2)
Where Bf: the air equivalent distance on the optical axis from the lens surface closest to the image side to the image plane I in the optical system WL in the infinitely focused state,
f: Focal length of the optical system WL in an infinitely focused state.

  Conditional expression (2) is a conditional expression for defining an appropriate range between the back focus and the focal length of the optical system WL. If the corresponding value of the conditional expression (2) exceeds the upper limit value, the back focus becomes long, so that the telecentricity is maintained, but the entire optical system becomes large, which is not preferable. Further, since the diameter of the front group G1 is increased, it is difficult to correct distortion. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (2) is preferably 0.70, and more preferably 0.60.

  When the corresponding value of the conditional expression (2) is lower than the lower limit, the back focus is short and the exit pupil position is too close to the image plane I, so that shading becomes remarkable, and particularly the resolution around the screen is reduced. Invite. In order to ensure the effect of the present embodiment, the lower limit value of conditional expression (2) is preferably 0.30, and more preferably 0.40.

  In the optical system WL of the present embodiment, it is preferable that the aperture stop S is disposed in the front group G1 or the rear group G2, and the following conditional expression (3) is satisfied.

0.04 <ST1 / TL <0.30 (3)
However, ST1: the distance on the optical axis from the lens surface closest to the object side to the aperture stop S in the optical system WL in an infinitely focused state,
TL: Distance on the optical axis from the lens surface closest to the object side to the image plane I in the optical system WL in an infinitely focused state, and the air conversion distance from the lens surface closest to the image side to the image plane.

  Conditional expression (3) is a conditional expression for defining an appropriate range of the position of the exit pupil from the total length of the optical system WL and the position of the aperture stop S. If the corresponding value of the conditional expression (3) exceeds the upper limit value, the telecentricity is maintained, but as a result, the entire length of the optical system WL becomes long and the entire optical system becomes large, which is not preferable. Also, if the diameter of the front group G1 is to be reduced while the total length of the optical system WL is long, it is difficult to correct off-axis light beams such as distortion. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (3) is preferably 0.25, and more preferably 0.20.

  When the corresponding value of the conditional expression (3) is below the lower limit value, the position of the aperture stop S is displaced to the object side from the appropriate position, so that the light rays cannot be blocked evenly. For this reason, distortion of the point image at the time of narrowing down and peripheral light reduction occur. In order to ensure the effect of the present embodiment, the lower limit value of conditional expression (3) is preferably 0.05, and more preferably 0.06.

  The optical system WL of the present embodiment preferably satisfies the following conditional expression (4).

0.10 <Dinf / Dmod <1.60 (4)
Where Dinf: the air spacing on the optical axis between the front group G1 and the rear group G2 in the infinitely focused state,
Dmod: the air space on the optical axis between the front group G1 and the rear group G2 in the short distance in-focus state.

  Conditional expression (4) is a conditional expression for defining an appropriate range for the interval (air interval) between the front group G1 and the rear group G2. If the corresponding value of the conditional expression (4) exceeds the upper limit value, the distance between the front group G1 and the rear group G2 in the short distance in-focus state is too short, so that the optical performance at the time of close focus can be kept good. This makes it difficult to correct field curvature. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (4) is preferably 1.30, and more preferably 1.10.

  When the corresponding value of the conditional expression (4) is below the lower limit value, the distance between the front group G1 and the rear group G2 in the short distance in-focus state becomes long, so that the telecentricity is maintained, but the diameter of the front group G1 is This is not preferable because it becomes large and the entire optical system becomes large. In addition, it is difficult to correct off-axis light beams such as distortion. In order to ensure the effect of the present embodiment, the lower limit value of conditional expression (4) is preferably 0.15, and more preferably 0.20.

  The optical system WL of the present embodiment preferably satisfies the following conditional expression (5).

0.30 <Y / BL <0.70 (5)
Y: radius of the image circle of the optical system WL,
BL: Distance on the optical axis from the most object-side lens surface to the most image-side lens surface in the infinitely focused optical system WL.

  Conditional expression (5) is a conditional expression for defining an appropriate range for the radius of the image circle (that is, the maximum image height) and the lens thickness of the optical system WL. If the corresponding value of conditional expression (5) exceeds the upper limit value, the lens configuration is thin with respect to the format size of the image sensor, but it becomes difficult to correct various aberrations. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (5) is preferably 0.65, and more preferably 0.60.

  If the corresponding value of conditional expression (5) is less than the lower limit value, the maximum image height of the optical system WL becomes small, and vignetting occurs in the peripheral light flux. Further, since it is necessary to arrange a power and a lens to reduce the incident height of off-axis rays, it is difficult to correct curvature of field, distortion, etc. as a result, which is not preferable. In order to ensure the effect of the present embodiment, the lower limit value of conditional expression (5) is preferably 0.35, and more preferably 0.40.

  The optical system WL of the present embodiment preferably satisfies the following conditional expression (6).

0.80 <TL / (FNO × Bf) <2.70 (6)
Where FNO: F number of the optical system WL in focus at infinity,
Bf: an air equivalent distance on the optical axis from the lens surface closest to the image side to the image plane I in the optical system WL in an infinitely focused state,
TL: Distance on the optical axis from the lens surface closest to the object side to the image plane I in the optical system WL in an infinitely focused state, and the air conversion distance from the lens surface closest to the image side to the image plane.

Conditional expression (6) is a conditional expression that defines an appropriate balance of the overall length of the optical system WL, the back focus, and the F number as a bright single focus lens (wide angle lens). If the corresponding value of conditional expression (6) exceeds the upper limit value, the total length of the optical system WL is too long, which is not preferable. In addition, since the F number of the optical system WL is too small, it is difficult to correct spherical aberration. In order to ensure the effect of the present embodiment, the upper limit value of conditional expression (6) is preferably 2.40, and more preferably 2.20.

  When the corresponding value of the conditional expression (6) is below the lower limit value, the total length of the optical system WL is too short, and it becomes difficult to correct coma and the like. In order to ensure the effect of the present embodiment, the lower limit value of conditional expression (6) is preferably 0.90, and more preferably 0.95.

  In the optical system WL of the present embodiment, it is preferable that the lens disposed closest to the object side of the front group G1 is a negative lens. In an optical system (wide-angle lens) having a Gaussian lens configuration, spherical aberration fluctuates to the minus side when focusing at a short distance, and it is difficult to maintain good optical performance when focusing at a short distance. On the other hand, by disposing the negative lens closest to the object side in the front group G1, the spherical aberration at the time of focusing at a short distance can be changed to the plus side, and as a result, the spherical aberration can be suppressed.

  In the optical system WL of the present embodiment, it is preferable that the object-side lens surface of the negative lens disposed closest to the object side in the front group G1 is a concave surface. By making the object-side lens surface of the most object-side negative lens in the front group G1 concave, the power of the negative lens is increased, so that spherical aberration can be effectively suppressed.

  In the optical system WL of the present embodiment, it is preferable that the image-side lens surface of the lens disposed closest to the image side in the rear group G2 is a convex surface. As a result, the Petzval sum can be appropriately corrected, and the position of the exit pupil sufficiently separated from the image plane I can be secured.

  The optical apparatus according to the present embodiment includes the optical system WL having the above-described configuration. As a specific example, a camera (optical apparatus) provided with the optical system WL will be described with reference to FIG. The camera 1 is a digital camera provided with the optical system WL according to the above-described embodiment as a photographing lens 2 as shown in FIG. In the camera 1, light from an object (subject) (not shown) is collected by the photographing lens 2 and reaches the image sensor 3. Thereby, the light from the subject is picked up by the image pickup device 3 and recorded as a subject image in a memory (not shown). In this way, the photographer can shoot the subject with the camera 1. The camera 1 may be a mirrorless camera or a single lens reflex camera having a quick return mirror. Further, the camera 1 is not limited to a single-lens reflex type camera in which the lens barrel and the camera body main body are detachable. Even if the lens barrel and the camera body main body are an integrated compact type camera. Good. According to such a configuration, by mounting the optical system WL as a photographic lens, it is possible to suppress the displacement of the image plane at the time of focusing, and obtain an optical apparatus that is small and has good optical performance. It becomes possible.

  Next, the method for manufacturing the above-described optical system WL will be outlined with reference to FIG. First, a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power are arranged in order from the object side in the lens barrel (step ST1). When focusing from infinity to a short distance object, the front group G1 and the rear group G2 move to the object side along the optical axis, and the distance between the front group G1 and the rear group G2 changes. (Step ST2). Further, each lens is arranged in the lens barrel so as to satisfy at least the conditional expression (1) (step ST3). According to such a manufacturing method, it is possible to manufacture a small-sized optical system having good optical performance by suppressing the displacement of the image plane during focusing.

Hereinafter, an optical system (wide angle lens) WL according to an example of the present embodiment will be described with reference to the drawings. 1, 3, 5, 7, 9, 11, 13, and 15 show the configurations of the optical systems WL {WL (1) to WL (8)} according to the first to eighth embodiments. It is sectional drawing which shows refractive power distribution. Each cross-sectional view describes the position of each group (along with “infinity” and “near distance”) when focusing from infinity to a near object.

  In FIGS. 1, 3, 5, 7, 9, 11, 13, and 15, each group is represented by a combination of a symbol G and a number, and each lens is represented by a combination of a symbol L and a number. ing. In this case, in order to prevent complications due to an increase in the types and numbers of codes and numbers, the lens groups and the like are represented using combinations of codes and numbers independently for each embodiment. For this reason, even if the combination of the same code | symbol and number is used between Examples, it does not mean that it is the same structure.

  Tables 1 to 8 are shown below. Of these, Table 1 is the first example, Table 2 is the second example, Table 3 is the third example, Table 4 is the fourth example, and Table 5 is the first. 5 Example, Table 6 is 6th Example, Table 7 is 7th Example, Table 8 is a table | surface which shows each item data in 8th Example. In each embodiment, d-line (wavelength λ = 587.6 nm) and g-line (wavelength λ = 435.8 nm) are selected as the aberration characteristic calculation targets.

  In the [Overall Specifications] table, f indicates the focal length of the entire system in the optical system WL in the infinitely focused state, and FNO indicates the F number. 2ω represents an angle of view (the unit is ° (degree), ω is a half angle of view), and Y represents an image height (maximum image height). Bf represents the air-converted distance (back focus) on the optical axis from the lens surface closest to the image side to the image plane I in the optical system WL in the infinite focus state, and TL in the optical system WL in the infinite focus state. The distance (full length) on the optical axis from the lens surface closest to the object side to the image plane I is shown. In TL, the distance from the lens surface closest to the image side to the image plane I in the optical system WL indicates an air conversion distance. In addition, the values of TL and Bf are shown for the infinite focus state and the short distance (closest distance) focus state in [variable interval data] described later.

  X1 represents the amount of movement of the front group G1 during focusing, and X2 represents the amount of movement of the rear group G2 during focusing. Each moving amount is positive in the direction from the object side to the image side. ST1 indicates the distance on the optical axis from the most object side lens surface to the aperture stop S in the infinitely focused optical system WL, and BL indicates the most object side lens surface in the infinitely focused optical system WL. The distance on the optical axis from the lens surface to the most image side lens surface is shown.

In the table of [lens specifications], the surface number indicates the order of the optical surfaces from the object side along the light traveling direction, and R indicates the radius of curvature of each optical surface (the surface where the center of curvature is located on the image side). D is a positive value), D is a surface interval which is a distance on the optical axis from each optical surface to the next optical surface (or image surface), νd is an Abbe number based on the d-line of the material of the optical member, nd indicates the refractive index of the optical member material with respect to the d-line. The curvature radius “∞” indicates a plane or an aperture, and (aperture S) indicates the aperture aperture S. The description of the refractive index of air nd = 1.0000 is omitted. When the lens surface is an aspherical surface, the surface number is marked with * and the radius of curvature R column indicates the paraxial radius of curvature.

In the [Aspherical Data] table, the shape of the aspherical surface shown in [Lens Specifications] is shown by the following equation (a). X (y) is the distance along the optical axis direction from the tangential plane at the apex of the aspheric surface to the position on the aspheric surface at height y (zag amount), and R is the radius of curvature of the reference sphere (paraxial curvature radius) , Κ is the conic constant, and Ai is the i-th aspherical coefficient. “E-n” indicates “× 10 ⁻ⁿ ”. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ . The secondary aspheric coefficient A2 is 0, and the description thereof is omitted.

X (y) = (y ² / R) / {1+ (1−κ × y ² / R ² ) ^1/2 } + A4 × y ⁴ + A6 × y ⁶ + A8 × y ⁸ + A10 × y ¹⁰ + A12 × y ¹² + A14 Xy ¹⁴ ... (a)

  In the table of [Group Data], the start surfaces (most object side surfaces) and focal lengths of the front group G1 and the rear group G2 are shown.

  The table of [variable distance data] shows the surface distance Di to the next surface in the surface number i in which the surface distance is “variable” in the table indicating [lens specifications]. For example, in the first embodiment, surface intervals D8 and D16 at surface numbers 8 and 16 are shown. These values are shown for the infinite focus state and the short distance (closest distance) focus state, respectively.

  The table corresponding to the conditional expressions (1) to (6) shows values corresponding to the conditional expressions (1) to (6).

  Hereinafter, in all the specification values, “mm” is generally used for the focal length f, curvature radius R, surface distance D, and other lengths, etc. unless otherwise specified, but the optical system is proportionally enlarged. Alternatively, the same optical performance can be obtained even by proportional reduction, and the present invention is not limited to this.

  The explanation of the table so far is common to all the embodiments, and the duplicate explanation below will be omitted.

(First embodiment)
A first embodiment will be described with reference to FIGS. FIG. 1 is a diagram illustrating a lens configuration of an optical system according to a first example of the present embodiment. The optical system WL (1) according to the first example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side. The sign (+) or (−) attached to the symbol of each group indicates the refractive power of each group, and this is the same in all the following examples.

  The front group G1 is arranged in order from the object side, the meniscus first negative lens L11 having a convex surface facing the object side, an aperture stop S, a biconcave second negative lens L12, and a biconvex shape. It is composed of a cemented lens composed of a first positive lens L13 and a biconvex second positive lens L14. The first negative lens L11 has an aspheric lens surface on the object side.

  The rear group G2 includes a cemented lens composed of a biconvex first positive lens L21 and a biconcave first negative lens L22, arranged in order from the object side, and a meniscus-shaped first lens with a convex surface facing the image side. A cemented lens including a second positive lens L23, a meniscus second negative lens L24 having a convex surface facing the image side, and a meniscus third positive lens L25 having a convex surface facing the image side. . The third positive lens L25 has an aspheric lens surface on the image side.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (1) according to the first example, when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 1 below lists values of specifications of the optical system according to the first example.

(Table 1)
[Overall specifications]
f = 24.88
FNO = 1.87
2ω = 60.1
Y = 14.25
Bf = 14.687
TL = 44.867
X1 = -2.466
X2 = -1.925
ST1 = 3.701
BL = 30.180
[Lens specifications]
Surface number R D νd nd
1 * 30.8401 1.5000 31.16 1.688930
2 20.5905 2.2008
3 ∞ 2.6833 (Aperture S)
4 -19.3699 0.8001 40.98 1.581440
5 27.7890 3.1806 52.33 1.755000
6 -30.9598 0.1001
7 52.2934 3.2581 40.66 1.883000
8 -32.4827 D8 (variable)
9 36.5887 5.0663 40.66 1.883000
10 -18.9352 0.8001 30.13 1.698950
11 19.9997 4.3541
12 -19.0168 2.0763 46.59 1.816000
13 -13.5233 0.8004 30.13 1.698950
14 -254.9861 0.8000
15 -71.2612 2.0000 40.10 1.851348
16 * -21.9663 D16 (variable)
17 ∞ 2.0000 63.88 1.516800
18 ∞ 0.1000
[Aspherical data]
1st surface κ = 1.0000, A4 = -5.34672E-05, A6 = -6.49809E-08
A8 = -4.57464E-09, A10 = 4.18288E-11, A12 = -1.57370E-13, A14 = 0.00000E + 00
16th surface κ = 1.0000, A4 = 4.49624E-05, A6 = 1.25196E-08
A8 = 3.83338E-09, A10 = -3.15603E-11, A12 = 1.34880E-13, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 24.38
G2 9 916.87
[Variable interval data]
Infinite focus state Short range focus state
f = 24.88 β = −0.1
D0 ∞ 261.29
D8 0.559 1.101
D16 13.268 15.193
Bf (air) 14.687 16.612
TL (air) 44.867 47.332
[Conditional expression values]
Conditional expression (1) X1 / X2 = 1.281
Conditional expression (2) Bf / f = 0.590
Conditional expression (3) ST1 / TL = 0.082
Conditional expression (4) Dinf / Dmod = 0.508
Conditional expression (5) Y / BL = 0.472
Conditional expression (6) TL / (FNO × Bf) = 1.632

  FIG. 2A is a diagram illustrating various aberrations of the optical system according to the first example when focusing on infinity. In each aberration diagram of FIG. 2A, FNO represents an F number, and A represents a half angle of view. The spherical aberration diagram shows the F-number value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum half field angle, and the lateral aberration diagram shows the half field angle value. FIG. 2B is a diagram of various aberrations when the optical system according to Example 1 is in focus at a short distance (closest distance). In each aberration diagram of FIG. 2B, NA represents the numerical aperture, and H0 represents the object height. The spherical aberration diagram shows the numerical aperture value corresponding to the maximum aperture, the astigmatism diagram and the distortion diagram show the maximum object height, and the lateral aberration diagram shows the value of each object height. 2A and 2B, d indicates the d-line (wavelength λ = 587.6 nm), and g indicates 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 aberration diagrams of the following examples, the same reference numerals as those in this example are used, and redundant description is omitted.

  From the respective aberration diagrams, it can be seen that the optical system according to the first example has excellent imaging performance by satisfactorily correcting various aberrations.

(Second embodiment)
2nd Example is described using FIGS. 3-4 and Table 2. FIG. FIG. 3 is a diagram illustrating a lens configuration of an optical system according to the second example of the present embodiment. The optical system WL (2) according to the second example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power arranged in order from the object side.

  The front group G1 is arranged in order from the object side, the meniscus first negative lens L11 having a convex surface facing the object side, an aperture stop S, a biconcave second negative lens L12, and a biconvex shape. It is composed of a cemented lens composed of a first positive lens L13 and a biconvex second positive lens L14. The first negative lens L11 has an aspheric lens surface on the object side.

  The rear group G2 includes a cemented lens composed of a biconvex first positive lens L21 and a biconcave first negative lens L22, arranged in order from the object side, and a meniscus-shaped first lens with a convex surface facing the image side. 2 negative lenses L23 and a meniscus second positive lens L24 having a convex surface facing the image side. The second positive lens L24 has an aspheric lens surface on the image side.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (2) according to the second example, the front group G1 and the rear group G2 move toward the object side along the optical axis with different amounts of movement when focusing from infinity to a short distance object. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 2 below lists values of specifications of the optical system according to the second example.

(Table 2)
[Overall specifications]
f = 24.87
FNO = 1.85
2ω = 60.3
Y = 14.25
Bf = 14.314
TL = 44.835
X1 = -2.548
X2 = -1.927
ST1 = 3.916
BL = 30.521
[Lens specifications]
Surface number R D νd nd
1 * 25.5040 1.5000 31.16 1.688930
2 18.6960 2.4157
3 ∞ 2.6833 (Aperture S)
4 -15.7969 0.8001 38.03 1.603420
5 60.8750 3.0479 52.33 1.755000
6 -24.1051 0.1001
7 57.7654 3.2320 40.66 1.883000
8 -31.5105 D8 (variable)
9 37.6601 5.8206 40.66 1.883000
10 -16.5976 0.7993 30.13 1.698950
11 20.0514 4.7260
12 -17.8284 0.8002 27.57 1.755200
13 -93.7042 1.0000
14 -77.4574 2.2166 40.10 1.851348
15 * -19.9971 D15 (variable)
16 ∞ 2.0000 63.88 1.516800
17 ∞ 0.1000
[Aspherical data]
1st surface κ = 1.0000, A4 = -4.88778E-05, A6 = 2.20240E-08
A8 = -5.16914E-09, A10 = 3.00275E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
15th surface κ = 1.0000, A4 = 4.38327E-05, A6 = 5.96629E-09
A8 = 3.39332E-09, A10 = -8.97554E-12, A12 = -2.19810E-13, A14 = 1.84040E-15
[Group data]
Group Start surface Focal length
G1 1 26.15
G2 9 325.65
[Variable interval data]
Infinite focus state Short range focus state
f = 24.87 β = −0.1
D0 ∞ 261.29
D8 1.379 2.001
D15 12.896 14.823
Bf (air) 14.314 16.241
TL (air) 44.835 47.383
[Conditional expression values]
Conditional expression (1) X1 / X2 = 1.323
Conditional expression (2) Bf / f = 0.576
Conditional expression (3) ST1 / TL = 0.087
Conditional expression (4) Dinf / Dmod = 0.689
Conditional expression (5) Y / BL = 0.467
Conditional expression (6) TL / (FNO × Bf) = 1.593

  FIG. 4A is a diagram illustrating various aberrations of the optical system according to Example 2 when focused on infinity. FIG. 4B is a diagram illustrating various aberrations when the optical system according to Example 2 is in focus at a short distance (closest distance). From the respective aberration diagrams, it can be seen that the optical system according to the second example has excellent imaging performance by properly correcting various aberrations.

(Third embodiment)
A third embodiment will be described with reference to FIGS. FIG. 5 is a diagram showing a lens configuration of an optical system according to the third example of the present embodiment. The optical system WL (3) according to the third example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 is arranged in order from the object side, the meniscus first negative lens L11 having a convex surface facing the object side, an aperture stop S, a biconcave second negative lens L12, and a biconvex shape. It is composed of a cemented lens composed of a first positive lens L13 and a biconvex second positive lens L14. The first negative lens L11 has an aspheric lens surface on the object side.

  The rear group G2 includes, in order from the object side, a cemented lens including a biconvex first positive lens L21 and a biconcave first negative lens L22, and a biconcave second negative lens L23. And a second meniscus positive lens L24 having a convex surface facing the image side. The second positive lens L24 has an aspheric lens surface on the image side.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (3) according to the third example, when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 3 below lists values of specifications of the optical system according to the third example.

(Table 3)
[Overall specifications]
f = 24.47
FNO = 1.80
2ω = 64.7
Y = 15.30
Bf = 14.174
TL = 44.984
X1 = -2.513
X2 = -1.854
ST1 = 3.918
BL = 30.810
[Lens specifications]
Surface number R D νd nd
1 * 33.6258 1.5000 31.16 1.688930
2 21.3183 2.4178
3 ∞ 2.6833 (Aperture S)
4 -18.3419 0.7972 38.03 1.603420
5 52.2261 3.2276 52.33 1.755000
6 -27.2223 0.0975
7 58.8778 3.2618 40.66 1.883000
8 -30.7587 D8 (variable)
9 34.5854 5.7924 40.66 1.883000
10 -17.5323 0.8042 30.13 1.698950
11 19.2264 4.5520
12 -19.3254 0.8777 27.57 1.755200
13 2309.2099 1.0000
14 -141.6693 2.4035 40.10 1.851348
15 * -20.2687 D15 (variable)
16 ∞ 2.0000 63.88 1.516800
17 ∞ 0.1000
[Aspherical data]
1st surface κ = 1.0000, A4 = -5.40060E-05, A6 = -7.45960E-08
A8 = -3.30700E-09, A10 = 2.14440E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
15th surface κ = 1.0000, A4 = 4.41290E-05, A6 = -1.40220E-08
A8 = 3.73110E-09, A10 = -8.21740E-12, A12 = -2.66630E-13, A14 = 2.18070E-15
[Group data]
Group Start surface Focal length
G1 1 25.78
G2 9 319.15
[Variable interval data]
Infinite focus state Short range focus state
f = 24.47 β = −0.1
D0 ∞ 256.93
D8 1.395 2.054
D15 12.755 14.609
Bf (air) 14.174 16.028
TL (air) 44.984 47.497
[Conditional expression values]
Conditional expression (1) X1 / X2 = 1.356
Conditional expression (2) Bf / f = 0.579
Conditional expression (3) ST1 / TL = 0.087
Conditional expression (4) Dinf / Dmod = 0.375
Conditional expression (5) Y / BL = 0.497
Conditional expression (6) TL / (FNO × Bf) = 1.763

  FIG. 6A is a diagram of various aberrations of the optical system according to the third example when focusing on infinity. FIG. 6B is a diagram of various aberrations when the optical system according to Example 3 is in focus at a short distance (closest distance). From the respective aberration diagrams, it can be seen that the optical system according to the third example has excellent imaging performance by properly correcting various aberrations.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. 7 to 8 and Table 4. FIG. FIG. 7 is a diagram showing a lens configuration of an optical system according to the fourth example of the present embodiment. The optical system WL (4) according to the fourth example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 includes, in order from the object side, a biconcave first negative lens L11, a biconvex first positive lens L12, an aperture stop S, and a biconcave second negative lens. The lens includes a cemented lens including L13 and a biconvex second positive lens L14, and a meniscus third negative lens L15 having a convex surface facing the image side. The third negative lens L15 has an aspheric lens surface on the image side.

  The rear group G2 includes, in order from the object side, a cemented lens including a biconvex first positive lens L21 and a biconcave first negative lens L22, and a biconcave second negative lens L23. And a biconvex second positive lens L24. The second positive lens L24 has an aspheric lens surface on the image side.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (4) according to the fourth example, when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 4 below provides values of specifications of the optical system according to the fourth example.

(Table 4)
[Overall specifications]
f = 24.97
FNO = 1.85
2ω = 62.1
Y = 14.25
Bf = 14.318
TL = 44.678
X1 = -3.115
X2 = -2.382
ST1 = 6.433
BL = 30.360
[Lens specifications]
Surface number R D νd nd
1 -23.5865 1.0000 41.51 1.575010
2 32.5087 0.9332
3 20.7551 3.5088 40.66 1.883000
4 -45.6852 1.0000
5 ∞ 2.0111 (Aperture S)
6 -30.3720 0.8000 32.18 1.672700
7 15.9804 3.7857 40.66 1.883000
8 -34.7764 1.0000
9 -23.1553 0.8000 31.16 1.688930
10 * -100.1049 D10 (variable)
11 34.2710 5.2717 40.66 1.883000
12 -13.3880 0.8000 32.18 1.672700
13 31.6442 3.9709
14 -16.5099 0.8000 33.72 1.647690
15 104.7860 0.1000
16 62.8584 4.2211 40.10 1.851348
17 * -21.0915 D17 (variable)
18 ∞ 2.0000 63.88 1.516800
19 ∞ 0.1000
[Aspherical data]
10th surface κ = 1.0000, A4 = 7.09969E-05, A6 = 5.82420E-08
A8 = 3.73981E-09, A10 = -1.74407E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
17th surface κ = 1.0000, A4 = 3.72602E-05, A6 = -2.34539E-08
A8 = 1.32257E-09, A10 = -6.49301E-12, A12 = 0.00000E + 00, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 57.97
G2 11 34.64
[Variable interval data]
Infinite focus state Short range focus state
f = 24.97 β = −0.1
D0 ∞ 263.17
D10 0.358 1.090
D17 12.899 15.281
Bf (air) 14.318 16.700
TL (air) 44.678 47.792
[Conditional expression values]
Conditional expression (1) X1 / X2 = 1.307
Conditional expression (2) Bf / f = 0.573
Conditional expression (3) ST1 / TL = 0.144
Conditional expression (4) Dinf / Dmod = 0.328
Conditional expression (5) Y / BL = 0.469
Conditional expression (6) TL / (FNO × Bf) = 1.687

  FIG. 8A is a diagram of various aberrations of the optical system according to Example 4 when focused on infinity. FIG. 8B is a diagram of various aberrations when the optical system according to Example 4 is in focus at a short distance (closest distance). From the respective aberration diagrams, it can be seen that the optical system according to the fourth example has excellent imaging performance by satisfactorily correcting various aberrations.

(5th Example)
A fifth embodiment will be described with reference to FIGS. 9 to 10 and Table 5. FIG. FIG. 9 is a diagram illustrating a lens configuration of an optical system according to Example 5 of the present embodiment. The optical system WL (5) according to the fifth example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 includes a meniscus negative lens L11 having a convex surface facing the object side and a meniscus positive lens L12 having a convex surface facing the object side, which are arranged in order from the object side.

The rear group G2 has an aperture stop S, a cemented lens including a biconcave first negative lens L21 and a biconvex first positive lens L22, and a convex surface facing the object side, which are arranged in order from the object side. A meniscus second negative lens L23, a cemented lens composed of a biconcave third negative lens L24 and a biconvex second positive lens L25, and a biconcave fourth negative lens L26. ,
And a biconvex third positive lens L27. The second negative lens L23 has an aspheric lens surface on the image side. The fourth negative lens L26 has an aspheric lens surface on the object side. The third positive lens L27 has an aspheric image side lens surface.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (5) according to the fifth example, when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 5 below lists values of specifications of the optical system according to the fifth example.

(Table 5)
[Overall specifications]
f = 30.54
FNO = 2.09
2ω = 53.0
Y = 15.00
Bf = 18.311
TL = 47.320
X1 = -5.716
X2 = -2.286
ST1 = 7.414
BL = 29.009
[Lens specifications]
Surface number R D νd nd
1 55.0636 0.8000 29.57 1.717360
2 22.1561 0.3000
3 23.9630 1.8848 40.66 1.883000
4 643.3073 D4 (variable)
5 ∞ 2.0651 (Aperture S)
6 -42.5194 0.8000 39.21 1.595510
7 9.3595 6.7632 40.66 1.883000
8 -69.0596 0.1121
9 148.4065 0.8000 45.45 1.801387
10 * 34.0456 3.3527
11 -15.0000 0.8371 30.13 1.698950
12 25.5709 4.1237 40.66 1.883000
13 -17.8073 0.5000
14 * -29.1326 1.4823 31.16 1.688930
15 124.3007 1.5000
16 45.4049 2.6878 40.10 1.851348
17 * -96.6279 D17 (variable)
18 ∞ 2.0000 63.88 1.516800
19 ∞ 0.1000
[Aspherical data]
10th surface κ = 1.0000, A4 = 3.93427E-05, A6 = 7.10185E-07
A8 = -1.02837E-08, A10 = 3.49200E-10, A12 = 0.00000E + 00, A14 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -6.65698E-05, A6 = 1.61906E-08
A8 = -7.10032E-09, A10 = 4.59883E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
17th surface κ = 1.0000, A4 = -5.81195E-07, A6 = -3.43147E-08
A8 = 2.90295E-10, A10 = -6.62198E-13, A12 = 0.00000E + 00, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 61.22
G2 5 43.63
[Variable interval data]
Infinite focus state Short range focus state
f = 30.54 β = -0.1
D0 ∞ 334.22
D4 1.000 4.430
D17 16.892 19.178
Bf (air) 18.311 20.597
TL (air) 47.320 53.036
[Conditional expression values]
Conditional expression (1) X1 / X2 = 2.500
Conditional expression (2) Bf / f = 0.600
Conditional expression (3) ST1 / TL = 0.157
Conditional expression (4) Dinf / Dmod = 0.226
Conditional expression (5) Y / BL = 0.517
Conditional expression (6) TL / (FNO × Bf) = 1.236

  FIG. 10A is a diagram of various aberrations of the optical system according to Example 5 when focusing on infinity. FIG. 10B is a diagram illustrating various aberrations when the optical system according to Example 5 is in focus at a short distance (closest distance). From each aberration diagram, it can be seen that the optical system according to the fifth example has excellent imaging performance by satisfactorily correcting various aberrations.

(Sixth embodiment)
A sixth embodiment will be described with reference to FIGS. 11 to 12 and Table 6. FIG. FIG. 11 is a diagram showing a lens configuration of an optical system according to the sixth example of the present embodiment. The optical system WL (6) according to the sixth example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 includes a meniscus negative lens L11 having a convex surface facing the object side and a meniscus positive lens L12 having a convex surface facing the object side, which are arranged in order from the object side.

  The rear group G2 has an aperture stop S, a cemented lens including a biconcave first negative lens L21 and a biconvex first positive lens L22, and a convex surface facing the object side, which are arranged in order from the object side. A meniscus second negative lens L23, a cemented lens composed of a biconcave third negative lens L24 and a biconvex second positive lens L25, and a meniscus second lens having a convex surface facing the image side. 4 negative lens L26, and biconvex third positive lens L27. The second negative lens L23 has an aspheric lens surface on the image side. The fourth negative lens L26 has an aspheric lens surface on the object side. The third positive lens L27 has an aspheric image side lens surface.

An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (6) according to the sixth example, the front group G1 and the rear group G2 move toward the object side along the optical axis with different amounts of movement when focusing from infinity to a short distance object. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 6 below provides values of specifications of the optical system according to the sixth example.

(Table 6)
[Overall specifications]
f = 30.62
FNO = 2.14
2ω = 52.8
Y = 15.00
Bf = 16.576
TL = 46.417
X1 = -5.237
X2 = -2.089
ST1 = 7.304
BL = 29.841
[Lens specifications]
Surface number R D νd nd
1 53.1624 0.8000 29.57 1.717360
2 18.9326 0.3000
3 19.9763 2.0557 40.66 1.883000
4 713.1579 D4 (variable)
5 ∞ 2.0651 (Aperture S)
6 -39.7457 0.8000 39.21 1.595510
7 9.5460 7.0748 40.66 1.883000
8 -64.0501 0.1000
9 200.6575 0.8000 45.45 1.801387
10 * 37.1432 3.8475
11 -15.0000 0.8000 30.13 1.698950
12 24.6832 4.0285 40.66 1.883000
13 -19.2739 0.5000
14 * -25.7603 1.4823 31.16 1.688930
15 -981.1528 1.5000
16 40.1314 2.6878 40.10 1.851348
17 * -189.9800 D17 (variable)
18 ∞ 4.6521 63.88 1.516800
19 ∞ 0.1000
[Aspherical data]
10th surface κ = 1.0000, A4 = 2.83775E-05, A6 = 4.12350E-07
A8 = -2.80992E-09, A10 = 1.77330E-10, A12 = 0.00000E + 00, A14 = 0.00000E + 00
14th surface κ = 1.0000, A4 = -5.97932E-05, A6 = -1.37330E-07
A8 = -5.45235E-09, A10 = 1.92647E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
17th surface κ = 1.0000, A4 = 7.84190E-06, A6 = -5.42053E-08
A8 = 1.93014E-10, A10 = -2.25932E-13, A12 = 0.00000E + 00, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 52.98
G2 5 48.18
[Variable interval data]
Infinite focus state Short range focus state
f = 30.62 β = −0.1
D0 ∞ 335.52
D4 0.999 4.148
D17 13.409 15.498
Bf (air) 16.576 18.665
TL (air) 46.417 51.654
[Conditional expression values]
Conditional expression (1) X1 / X2 = 2.507
Conditional expression (2) Bf / f = 0.541
Conditional expression (3) ST1 / TL = 0.157
Conditional expression (4) Dinf / Dmod = 0.241
Conditional expression (5) Y / BL = 0.503
Conditional expression (6) TL / (FNO × Bf) = 1.309

  FIG. 12A is a diagram of various aberrations of the optical system according to Example 6 when focused on infinity. FIG. 12B is a diagram illustrating various aberrations when the optical system according to Example 6 is in focus at a short distance (closest distance). From each aberration diagram, it can be seen that the optical system according to Example 6 has excellent imaging performance by correcting various aberrations satisfactorily.

(Seventh embodiment)
A seventh embodiment will be described with reference to FIGS. 13 to 14 and Table 7. FIG. FIG. 13 is a diagram showing a lens configuration of an optical system according to the seventh example of the present embodiment. The optical system WL (7) according to the seventh example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 includes a meniscus first negative lens L11 having a convex surface facing the object side, a biconvex positive lens L12, and a biconcave second negative lens L13 arranged in order from the object side. And a cemented lens.

  The rear group G2 includes an aperture stop S, a cemented lens including a biconvex first positive lens L21 and a biconcave first negative lens L22, and a biconcave second, which are arranged in order from the object side. The negative lens L23 and a biconvex second positive lens L24, and a biconvex third positive lens L25. The first positive lens L21 has an aspheric lens surface on the object side. The second negative lens L23 has an aspheric lens surface on the object side. The second positive lens L24 has an aspheric lens surface on the image side.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (7) according to the seventh example, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts when focusing from infinity to a short distance object. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 7 below provides values of specifications of the optical system according to the seventh example.

(Table 7)
[Overall specifications]
f = 31.56
FNO = 2.20
2ω = 47.4
Y = 14.00
Bf = 22.645
TL = 47.455
X1 = -7.006
X2 = -3.117
ST1 = 8.804
BL = 24.810
[Lens specifications]
Surface number R D νd nd
1 59.8248 0.8040 70.32 1.487490
2 14.4329 0.3274
3 16.3422 4.8625 49.26 1.743200
4 -36.6404 0.7989 41.51 1.575010
5 27.5371 D5 (variable)
6 ∞ 0.2959 (Aperture S)
7 * 16.6614 2.5633 40.10 1.851348
8 -39.9032 0.8000 30.13 1.698950
9 16.3607 5.0395
10 * -12.0711 0.8000 31.16 1.688930
11 30.6678 2.2782 40.10 1.851348
12 * -24.1100 1.0000
13 96.5352 3.2292 40.66 1.883000
14 -41.0451 D14 (variable)
15 ∞ 2.0000 64.17 1.516800
16 ∞ 0.1000
[Aspherical data]
7th surface κ = 1.0000, A4 = -2.21170E-05, A6 = -1.02561E-07
A8 = -3.74746E-09, A10 = 1.54704E-11, A12 = 0.00000E + 00, A14 = 0.00000E + 00
10th surface κ = 1.0000, A4 = 4.14903E-04, A6 = 1.73676E-06
A8 = -6.05789E-08, A10 = 7.26224E-10, A12 = 0.00000E + 00, A14 = 0.00000E + 00
12th surface κ = 1.0000, A4 = 2.36538E-04, A6 = 3.42662E-07
A8 = -1.74584E-08, A10 = 1.51803E-10, A12 = 0.00000E + 00, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 200.03
G2 6 32.96
[Variable interval data]
Infinite focus state Short range focus state
f = 31.56 β = −0.1
D0 ∞ 336.06
D5 2.011 5.900
D14 21.226 24.343
Bf (air) 22.645 25.762
TL (air) 47.455 54.460
[Conditional expression values]
Conditional expression (1) X1 / X2 = 2.248
Conditional expression (2) Bf / f = 0.718
Conditional expression (3) ST1 / TL = 0.186
Conditional expression (4) Dinf / Dmod = 0.341
Conditional expression (5) Y / BL = 0.564
Conditional expression (6) TL / (FNO × Bf) = 0.953

  FIG. 14A is a diagram of various aberrations of the optical system according to Example 7 when focused on infinity. FIG. 14B is a diagram illustrating various aberrations when the optical system according to Example 7 is in focus at a short distance (closest distance). From the respective aberration diagrams, it can be seen that the optical system according to the seventh example has excellent imaging performance by properly correcting various aberrations.

(Eighth embodiment)
The eighth embodiment will be described with reference to FIGS. 15 to 16 and Table 8. FIG. FIG. 15 is a diagram showing a lens configuration of an optical system according to the eighth example of the present embodiment. The optical system WL (8) according to the eighth example includes a front group G1 having a positive refractive power and a rear group G2 having a positive refractive power, which are arranged in order from the object side.

  The front group G1 includes, in order from the object side, a biconcave first negative lens L11, a meniscus first positive lens L12 having a convex surface facing the object side, an aperture stop S, and a biconvex shape A cemented lens composed of the second positive lens L13 and the biconcave second negative lens L14, and a cemented lens composed of the biconcave third negative lens L15 and the biconvex third positive lens L16. Is composed of. The first positive lens L12 has an aspheric lens surface on the image side. The second positive lens L13 has an aspheric lens surface on the object side. The third negative lens L15 has an aspheric lens surface on the object side. The third positive lens L16 has an aspheric lens surface on the image side.

  The rear group G2 includes a biconvex positive lens L21.

  An image plane I is disposed on the image side of the rear group G2. A low pass for cutting a spatial frequency higher than the limit resolution of an image pickup device (for example, CCD, CMOS, etc.) disposed on the image plane I in the vicinity of the image plane I between the rear group G2 and the image plane I. A filter FL is arranged. In the optical system WL (8) according to the eighth example, when focusing from infinity to a short distance object, the front group G1 and the rear group G2 move toward the object side along the optical axis with different movement amounts. The interval between the group G1 and the rear group G2 is configured to change (become larger).

  Table 8 below provides values of specifications of the optical system according to the eighth example.

(Table 8)
[Overall specifications]
f = 36.00
FNO = 1.86
2ω = 66.4
Y = 21.60
Bf = 26.266
TL = 67.489
X1 = -10.611
X2 = -7.439
ST1 = 21.099
BL = 41.223
[Lens specifications]
Surface number R D νd nd
1 -55.9752 3.276 32.2 1.67270
2 66.4702 6.696
3 22.3000 4.647 37.2 1.88202
4 * 78.5590 6.480
5 ∞ 1.390 (Aperture S)
6 * 36.8224 7.514 40.1 1.85135
7 -13.1563 1.195 30.1 1.69895
8 28.8627 3.895
9 * -17.3649 0.800 31.2 1.68893
10 41.4253 2.867 37.2 1.88202
11 * -38.8979 D11 (variable)
12 148.1269 2.363 40.7 1.88300
13 -84.7387 D13 (variable)
14 ∞ 1.500 63.9 1.51680
15 ∞ 0.100
[Aspherical data]
4th surface κ = -7.4347, A4 = -2.12039E-06, A6 = -4.62851E-09
A8 = -3.89378E-11, A10 = 1.62537E-13, A12 = 0.00000E + 00, A14 = 0.00000E + 00
6th surface κ = -3.7658, A4 = -3.64787E-05, A6 = -2.46920E-07
A8 = -2.72969E-11, A10 = -1.06678E-11, A12 = 5.40520E-14, A14 = 0.00000E + 00
9th surface κ = -2.4977, A4 = 1.15907E-04, A6 = -6.01456E-08
A8 = 1.13761E-09, A10 = -6.10067E-12, A12 = 0.00000E + 00, A14 = 0.00000E + 00
11th surface κ = -20.0000, A4 = 6.91648E-05, A6 = -6.87359E-08
A8 = -3.48048E-10, A10 = 6.16431E-13, A12 = 0.00000E + 00, A14 = 0.00000E + 00
[Group data]
Group Start surface Focal length
G1 1 63.80
G2 12 61.34
[Variable interval data]
Infinite focus state Short range focus state
f = 36.00 β = -0.2287
D0 ∞ 176.59
D11 0.100 3.271
D13 25.177 32.617
Bf (air) 26.266 33.706
TL (air) 67.489 85.538
[Conditional expression values]
Conditional expression (1) X1 / X2 = 1.426
Conditional expression (2) Bf / f = 0.730
Conditional expression (3) ST1 / TL = 0.313
Conditional expression (4) Dinf / Dmod = 0.031
Conditional expression (5) Y / BL = 0.524
Conditional expression (6) TL / (FNO × Bf) = 1.382

  FIG. 16A is a diagram of various types of aberration when the optical system according to Example 8 is in focus at infinity. FIG. 16B is a diagram illustrating various aberrations when the optical system according to Example 8 is in focus at a short distance (closest distance). From the respective aberration diagrams, it can be seen that the optical system according to the eighth example has excellent imaging performance by satisfactorily correcting various aberrations.

  According to each of the embodiments described above, an optical system that is small and has good optical performance can be realized.

  Here, each said Example has shown one specific example of this invention, and this invention is not limited to these.

  Note that the following contents can be adopted as appropriate as long as the optical performance of the optical system of the present embodiment is not impaired.

  As a numerical example of the optical system of the present embodiment, a two-group configuration including a front group and a rear group has been shown, but the present application is not limited to this, and an optical system having other group configurations (for example, three groups). Can also be configured. Specifically, a configuration in which a lens or a lens group is added to the most object side or the most image plane side of the optical system of the present embodiment may be used.

  In the optical system of the present embodiment, the lens group or the partial lens group is moved so as to have a component in a direction perpendicular to the optical axis, or is rotated and moved (oscillated) in the in-plane direction including the optical axis. An anti-vibration lens group that corrects image blur caused by blur may be used.

  The lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. When the lens surface is a spherical surface or a flat surface, lens processing and assembly adjustment are facilitated, and optical performance deterioration due to errors in processing and assembly adjustment can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in 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 with an aspheric shape on the glass surface. Either is fine. 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 may be replaced by a lens frame without providing a member as an aperture stop.

  Each lens surface may be provided with an antireflection film having a high transmittance in a wide wavelength region in order to reduce flare and ghost and achieve high contrast optical performance. Thereby, flare and ghost can be reduced, and high optical performance with high contrast can be achieved.

G1 Front group G2 Rear group I Image surface S Aperture stop

Claims (11)

A front group having a positive refractive power and a rear group having a positive refractive power, arranged in order from the object side,
When focusing from infinity to a short distance object, the front group and the rear group move to the object side along the optical axis, the interval between the front group and the rear group changes,
An optical system satisfying the following conditional expression:
1.05 <X1 / X2 <4.00
Where X1: movement amount of the front group at the time of focusing,
X2: Movement amount of the rear group at the time of focusing. The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.20 <Bf / f <0.75
Where Bf: the air equivalent distance on the optical axis from the lens surface closest to the image side to the image plane in the optical system in the infinitely focused state,
f: Focal length of the optical system in an infinitely focused state. An aperture stop is disposed in the front group or the rear group,
The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.04 <ST1 / TL <0.30
However, ST1: Distance on the optical axis from the lens surface closest to the object side to the aperture stop in the optical system in the infinitely focused state,
TL: Distance on the optical axis from the lens surface closest to the object side to the image plane in the optical system in the infinitely focused state, and the air-converted distance from the lens surface closest to the image side to the image plane. The optical system according to any one of claims 1 to 3, wherein the following conditional expression is satisfied.
0.10 <Dinf / Dmod <1.60
Where Dinf: the air space on the optical axis between the front group and the rear group in an infinitely focused state,
Dmod: an air space on the optical axis between the front group and the rear group in a short distance in-focus state. The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.30 <Y / BL <0.70
Where Y: radius of the image circle of the optical system,
BL: Distance on the optical axis from the most object side lens surface to the most image side lens surface in the optical system in an infinitely focused state. The optical system according to claim 1, wherein the following conditional expression is satisfied.
0.80 <TL / (FNO × Bf) <2.70
Where FNO: F number of the optical system in focus at infinity,
Bf: air equivalent distance on the optical axis from the lens surface closest to the image side to the image plane in the optical system in the infinitely focused state,
TL: Distance on the optical axis from the most object-side lens surface to the image plane in the optical system in the infinitely focused state, and the distance from the most image-side lens surface to the image plane in terms of air.   The optical system according to any one of claims 1 to 6, wherein the lens disposed closest to the object side in the front group is a negative lens.   The optical system according to claim 7, wherein an object side lens surface of the negative lens disposed closest to the object side of the front group is a concave surface.   9. The optical system according to claim 1, wherein an image-side lens surface of a lens disposed closest to the image side of the rear group is a convex surface.   An optical apparatus configured by mounting the optical system according to claim 1. A method of manufacturing an optical system having a front group having a positive refractive power and a rear group having a positive refractive power, arranged in order from the object side,
When focusing from infinity to a short distance object, the front group and the rear group move to the object side along the optical axis, the interval between the front group and the rear group changes,
To satisfy the following conditional expression,
A method of manufacturing an optical system, wherein each lens is arranged in a lens barrel.
1.05 <X1 / X2 <4.00
Where X1: movement amount of the front group at the time of focusing,
X2: Movement amount of the rear group at the time of focusing.

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