JP5641393B2 - Lens system and optical equipment - Google Patents

Description

The present invention relates to a lens system and an optical apparatus suitable for an interchangeable lens for a single lens reflex camera, a copying lens, and the like.

  Conventionally, many so-called Gaussian lens systems have been proposed as lens systems used for interchangeable lenses for single-lens reflex cameras, copying lenses, and the like.

JP-A-2-230208

In the conventional lens system, not be said to have a sufficiently high optical performance.

The present invention has been made in view of such problems, various aberrations are favorably corrected, and an object thereof is to provide a lens system and an optical apparatus having a high optical performance.

In order to achieve the above object, a lens system according to the present invention includes a first lens group having a positive refractive power and a second lens group having a positive refractive power arranged in order from the object side along the optical axis. A stop is disposed between the first lens group and the second lens group, and there is at least one aspherical lens, and the second lens group is the most object in the second lens group. A first lens component having a negative refractive power located on the object side and a second lens component having a positive refractive power located on the image side, with an air gap formed on the side interposed therebetween, The first lens component is a cemented lens composed of a negative lens and a positive lens, the radius of curvature of the image-side lens surface of the first lens component is r21R, and the object-side lens surface of the second lens component The curvature radius of r2F is r22F, and the focal length of the second lens component is f22. When the focal length of the entire lens system is f (however, when the corresponding surface is an aspherical surface, it is calculated by a paraxial radius of curvature), the following formula 1.169 ≦ (r21R + r22F) / (r21R−r22F ) <12.0 and 1.121 ≦ f22 / f <2.0.

  In the lens system of the present invention, when the focal length of the lens disposed closest to the image side of the second lens group is f2L and the focal length of the entire lens system is f, the following expression 0.5 <f2L It is preferable to satisfy the condition of /f<1.5.

  In the lens system of the present invention, it is preferable that at least one aspherical lens is provided in the second lens group.

  In the lens system of the present invention, it is preferable that the aspheric lens is a composite aspheric lens made of a composite of a glass material and a resin material.

  In the lens system of the present invention, when the refractive index at the d-line of the resin material constituting the composite aspherical lens is na, the following formula 1.450 <na <1.800 is satisfied. preferable.

  An optical apparatus of the present invention has any of the lens systems described above.

According to the present invention, it is possible to provide a lens system and an optical apparatus having high optical performance in which various aberrations are favorably corrected.

It is the figure which showed sectional drawing of the lens system which concerns on 1st Example. FIG. 4A is a diagram illustrating various aberrations of the lens system according to Example 1. FIG. 9A is a diagram illustrating various aberrations in an infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 2nd Example. FIG. 6A is a diagram illustrating various aberrations of the lens system according to Example 2. FIG. 9A is a diagram illustrating various aberrations in an infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 3rd Example. FIG. 6A is a diagram illustrating various aberrations of the lens system according to Example 3, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 4th Example. FIG. 6A is a diagram illustrating various aberrations of the lens system according to Example 4, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 5th Example. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 5, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 6th Example. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 6, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 7th Example. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 7, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed sectional drawing of the lens system which concerns on 8th Example. FIG. 9A is a diagram illustrating various aberrations of the lens system according to Example 8, wherein FIG. 9A illustrates various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. -1/30) is a diagram showing various aberration diagrams. It is the figure which showed the structure of the optical apparatus (camera) provided with the lens system which concerns on this embodiment. It is a flowchart for demonstrating the manufacturing method of the lens system which concerns on this embodiment.

  Hereinafter, the lens system according to the present embodiment will be described with reference to the drawings. As shown in FIG. 1, the lens system according to the present embodiment includes a first lens group G1 having a positive refractive power, an aperture S, and a positive refractive power, which are arranged in order from the object side along the optical axis. The configuration having the second lens group G2 has a so-called Gaussian refractive power arrangement, which corrects distortion aberration well, and corrects spherical aberration and curvature of field.

  In a Gauss type lens system having no aspherical surface, negative spherical aberration is corrected well, but sagittal coma aberration is not sufficiently corrected. Therefore, in the lens system of the present embodiment, by having at least one aspheric lens having a width as large as the lens end, it is possible to efficiently correct negative spherical aberration, and at the same time, sagittal coma aberration is reduced. It is possible to suppress.

  Furthermore, in the lens system according to the present embodiment, the second lens group G2 includes a first lens component located on the object side with an air gap formed closest to the object side in the second lens group G2. (Corresponding to the lens L21 in FIG. 1) and a second lens component located on the image side (corresponding to the lens L22 in FIG. 1), and the radius of curvature of the image side lens surface of the first lens component is r21R. Where the radius of curvature of the object-side lens surface of the second lens component is r22F, the focal length of the second lens component is f22, and the focal length of the entire lens system is f (provided that the corresponding surface is not In the case of forming a spherical surface, it is calculated by the paraxial radius of curvature), and the following conditional expressions (1) and (2) are satisfied.

1.0 ≦ (r21R + r22F) / (r21R−r22F) <12.0 (1)
0.8 <f22 / f <2.0 (2)

  The conditional expression (1) is a conditional expression related to coma aberration, field curvature, and astigmatism. If this conditional expression (1) exceeds the upper limit value, the Petzval sum decreases and the astigmatic difference increases. Further, the shape of the coma aberration tends to be an outer coma, and the imaging performance is deteriorated. Conversely, if conditional expression (1) is below the lower limit, the Petzval sum increases, and astigmatism and field curvature cannot be corrected. In addition, the shape of the coma aberration tends to be an inner coma, and the imaging performance deteriorates.

  In order to secure the effect of the present embodiment, it is desirable to set the upper limit value of conditional expression (1) to 7.0.

  The conditional expression (2) is a conditional expression related to field curvature. When this conditional expression (2) exceeds the upper limit value, the Petzval sum increases positively, and astigmatism and field curvature cannot be corrected, and the imaging performance deteriorates. On the contrary, when the conditional expression (2) is below the lower limit value, a good Petzval sum can be obtained, but the astigmatism difference increases and the imaging performance deteriorates.

  In order to secure the effect of the present embodiment, it is desirable to set the upper limit value of conditional expression (2) to 1.5. In order to further secure the effect of the present embodiment, it is desirable to set the lower limit value of conditional expression (2) to 1.0.

  In the lens system according to the present embodiment, when the focal length of the lens arranged closest to the image side of the second lens group G2 is f2L and the focal length of the entire lens system is f, the following conditional expression (3 ) Is preferably satisfied.

  0.5 <f2L / f <1.5 (3)

  The conditional expression (3) is a conditional expression for securing a suitable back focus and realizing high optical performance. If this conditional expression (3) exceeds the upper limit value, the back focus becomes relatively long with respect to the focal length of the entire lens system, and the lens system is separated from the symmetry, making it difficult to correct distortion. The optical performance deteriorates. Conversely, if conditional expression (3) is below the lower limit, the back focus is relatively short with respect to the focal length of the lens system, and a suitable lens system cannot be obtained. In addition, it becomes difficult to correct curvature of field.

  In order to secure the effect of this embodiment, it is desirable to set the upper limit value of conditional expression (3) to 1.0. In order to further secure the effect of the present embodiment, it is desirable to set the lower limit value of conditional expression (3) to 0.7.

  In the lens system of the present embodiment, it is preferable that at least one aspheric lens is provided in the second lens group G2. With this configuration, it is possible to correct negative spherical aberration and sagittal coma and to achieve high optical performance.

  In the lens system of this embodiment, the aspherical lens is preferably a composite aspherical lens made of a composite of a glass material and a resin material. With this configuration, spherical aberration and coma can be favorably corrected.

  In the lens system of the present embodiment, it is preferable that the following conditional expression (4) is satisfied, where na is the refractive index at the d-line of the resin material constituting the composite aspherical lens.

  1.450 <na <1.800 (4)

  The conditional expression (4) is a conditional expression that defines an appropriate range of the refractive index of the resin material of the composite aspherical lens in order to obtain high optical performance. If the upper limit of conditional expression (4) is exceeded, the refractive index of the resin material of the composite aspherical lens becomes excessively high, and the resin material that easily changes in temperature and moisture absorbs excessive effects such as temperature and humidity. Accordingly, the aberration greatly fluctuates with these changes, it becomes difficult to correct spherical aberration and coma aberration, and high optical performance cannot be realized. On the other hand, if the lower limit of conditional expression (4) is not reached, the refractive index of the resin material of the composite aspherical lens becomes excessively small, and the amount of aspherical deviation from the mother sphere in order to sufficiently obtain the effect of the aspherical surface. Need to be larger. As a result, in resin materials that are subject to temperature changes and moisture absorption changes, the thickness of the resin material of the composite aspherical lens varies greatly between the optical axis and the lens periphery in proportion to the amount of aspherical deviation. As the humidity changes, the aberration fluctuates greatly, making it difficult to correct spherical aberration and coma, making it impossible to achieve high optical performance.

  In order to secure the effect of the present embodiment, it is desirable to set the upper limit of conditional expression (4) to 1.650. In order to further secure the effect of the present embodiment, it is desirable to set the lower limit of conditional expression (4) to 1.500.

  FIG. 17 is a schematic cross-sectional view of a digital single-lens reflex camera CAM (optical apparatus) provided with the lens system having the above configuration as a photographic lens 1. In the digital single-lens reflex camera CAM shown in FIG. 17, light from an object (subject) (not shown) is collected by the photographing lens 1 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.

  Further, when a release button (not shown) is pressed by the photographer, the quick return mirror 3 is retracted out of the optical path, and light of an object (subject) (not shown) condensed by the photographing lens 1 is captured on the image sensor 7. Form an image. 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 photograph an object (subject) with the camera CAM. Note that the camera CAM illustrated in FIG. 17 may be one that holds the photographing lens 1 in a detachable manner or may be molded integrally with the photographing lens 1. The camera CAM may be a so-called single-lens reflex camera or a compact camera that does not have a quick return mirror or the like.

  Next, a manufacturing method of the lens system having the above configuration will be described with reference to FIG. First, each lens (for example, lenses L11 to L23 in FIG. 1) is assembled in a cylindrical barrel (step S1). When assembling the lenses into the lens barrel, the lenses may be incorporated into the lens barrel one by one in the order along the optical axis, or a part or all of the lenses may be integrally held by the holding member and then assembled with the lens barrel member. Good. Next, after each lens is incorporated in the lens barrel, it is confirmed whether an object image is formed in a state where each lens is incorporated in the lens barrel, that is, whether the centers of the lenses are aligned (step) S2). Subsequently, various operations of the lens system are confirmed (step S3). Examples of various operations include a focusing operation in which a lens (for example, the entire lens system in FIG. 1) that focuses from an object at infinity to a short-distance object moves along the optical axis direction, at least some of the lenses ( For example, a camera shake correction operation for moving at least a part of the second lens group G2 in FIG. 1 so as to have a component in a direction perpendicular to the optical axis may be mentioned. Note that the order of confirming the various operations is arbitrary.

  Hereinafter, each example according to the present embodiment will be described with reference to the drawings. Tables 1 to 8 are shown below, but these are tables of specifications in the first to eighth examples. In [Overall specifications], f is the focal length of the entire lens system, FNO is the F number, ω is the half angle of view (unit: degree), and TL is the object side surface of the lens arranged closest to the object side. The total lens length from the first to the image plane I is shown. In [Lens data], the surface number is the order of the lens surfaces from the object side along the direction in which the light beam travels, r is the radius of curvature of each lens surface, and d is the next optical surface from each optical surface (or The distance between surfaces on the optical axis to the image plane), nd represents the refractive index with respect to the d-line (wavelength 587.6 nm), and νd represents the Abbe number with respect to the d-line. In the table, the description of the refractive index “1.00000” of air is omitted. In [Variable interval data], R represents a photographing distance, that is, a distance (unit: m) from the object to the image plane I, β represents a photographing magnification, and Bf represents a back focus. In [Each Group Focal Length Data], the initial surface and focal length of each group are shown. In [Conditional Expression], values corresponding to the conditional expressions (1) to (4) are shown.

In [Aspherical data], the shape of the aspherical surface shown in [Lens data] is shown by the following equation (a). That is, y is the height in the direction perpendicular to the optical axis, and S (y) is the distance (sag amount) along the optical axis from the tangent plane at the apex of the aspheric surface to the position on the aspheric surface at height y. When the radius of curvature of the reference spherical surface (paraxial radius of curvature) is r, the conic coefficient is κ, and the n-th aspherical coefficient is An, the following equation (a) is given. E-n represents ^x10 -n. For example, 1.234E-05 = 1.234 × 10 ⁻⁵ .

S (y) = (y ² / r) / {1+ (1−κ · y ² / r ² ) ^1/2 }
+ A4 × y ⁴ + A6 × y ⁶ (a)

  In the table, “mm” is generally used as the focal length f, radius of curvature r, surface interval d, and other length units. However, since the optical system can obtain the same optical performance even if it is proportionally enlarged or reduced, the unit is not limited to “mm”, and other appropriate units can be used.

  The description of the above table is the same in other examples, and the description thereof is omitted.

(First embodiment)
A first embodiment will be described with reference to FIGS. 1 and 2 and Table 1. FIG. As shown in FIG. 1, the lens system according to the first example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 has a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b arranged in order from the object side along the optical axis, and a convex surface on the image side. A compound aspherical lens L22 comprising a positive meniscus glass lens facing and a resin layer provided on the object side lens surface of the glass lens and having an aspheric surface on the surface opposite to the lens. The second lens component in Item 1) and a biconvex lens L23.

  The image plane I is formed on an image sensor (not shown), and the image sensor is composed of a CCD, a CMOS, or the like. (The description of the image plane I is the same in the following embodiments.)

  Table 1 below lists specifications of the lens system according to the first example. In addition, the surface numbers 1-15 in Table 1 respond | correspond to the surfaces 1-15 shown in FIG.

(Table 1)
[Overall specifications]
f = 51.60
FNo = 1.85
ω = 23.07
TL = 76.16397 (when infinite) to 77.90701 (when projected)

[Lens data]
Surface number r d nd νd
1 40.0000 4.7000 1.83481 42.73
2 381.8864 0.3000
3 24.1500 2.9000 1.80400 46.60
4 33.0000 1.5000
5 79.4297 1.4000 1.67270 32.19
6 18.6247 5.9000
7 0.0000 5.3000 (Aperture stop)
8 -21.0783 1.1000 1.69895 30.13
9 48.0712 3.2000 1.80400 46.60
10 -160.0000 1.9000
* 11 -115.0000 0.1000 1.55389 38.09 (Aspherical surface, resin layer)
12 -115.0000 3.6000 1.77250 49.62
13 -34.3596 0.1000
14 435.5383 4.0000 1.80400 46.60
15 -40.1003 (Bf)

[Aspherical data]
11th surface κ = 0.0000, A4 = -4.1755E-06, A6 = -2.0235E-09

[Variable interval data]
Infinite focus state Short range focus state R ∞ 1.72
β 0.0 1/30
Bf 40.16397 41.90701

[Each group focal length data]
Group Start surface Focal length G1 1 130.24595
G2 8 49.74685

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R-r22F) = 6.111
Conditional expression (2) f22 / f = 1.205
Conditional expression (3) f2L / f = 0.888
Conditional expression (4) na = 1.55389

  It can be seen from the table of specifications shown in Table 1 that the conditional expressions (1) to (4) are satisfied in the lens system according to the first example.

  2A and 2B are graphs showing various aberrations of the first embodiment. FIG. 2A is a diagram showing various aberrations in an infinite focus state (shooting magnification β = 0.0), and FIG. 2B is a close-up focus state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  In each aberration diagram, FNO represents an F number, A represents a light incident angle (unit: degree), NA represents a numerical aperture, and HO represents an object height (unit: mm). Further, d indicates various aberrations with respect to the d-line (wavelength 587.6 nm), g indicates various aberrations with respect to the g-line (wavelength 435.8 nm), and those not described indicate various aberrations with respect to the d-line. In the astigmatism diagram, the solid line indicates the sagittal image plane, and the broken line indicates the meridional image plane. The coma diagram shows the meridional coma aberration for the d-line and the g-line at each incident angle or the object height, the broken line on the right side from the origin indicates the sagittal coma generated in the meridional direction with respect to the d-line, and the broken line on the left side from the origin. Represents the sagittal coma generated in the sagittal direction with respect to the d-line. The explanation of the above aberration diagrams is the same in the other examples, and the explanation is omitted.

  As is apparent from each aberration diagram, it can be seen that the lens system according to Example 1 has various optical aberrations corrected and high optical performance.

(Second embodiment)
The second embodiment will be described with reference to FIGS. 3 and 4 and Table 2. FIG. As shown in FIG. 3, the lens system according to the second example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 has a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b arranged in order from the object side along the optical axis, and a convex surface on the image side. A compound aspherical lens L22 comprising a positive meniscus glass lens facing and a resin layer provided on the object side lens surface of the glass lens and having an aspheric surface on the surface opposite to the lens. The second lens component in Item 1) and a biconvex lens L23.

  Table 2 below lists specifications of the lens system according to the second example. In addition, the surface numbers 1-15 in Table 2 respond | correspond to the surfaces 1-15 shown in FIG.

(Table 2)
[Overall specifications]
f = 51.60
FNo = 1.85
ω = 23.06
TL = 75.46398 (when infinite) to 77.18384 (when projected)

[Lens data]
Surface number r d nd νd
1 41.4455 4.4000 1.83481 42.72
2 436.2147 0.1000
3 23.5000 3.0000 1.80400 46.58
4 31.9799 1.6000
5 72.5066 1.3000 1.67270 32.11
6 18.6402 5.9000
7 0.0000 5.3000 (Aperture stop)
8 -21.3881 1.1000 1.69895 30.13
9 41.4568 3.2000 1.80400 46.58
10 -352.2422 1.8000
* 11 -113.8699 0.1000 1.55389 38.09 (Aspherical surface, resin layer)
12 -113.8699 3.5000 1.80400 46.58
13 -35.9305 0.1000
14 312.3862 3.9000 1.80400 46.58
15 -38.2693 (Bf)

[Aspherical data]
11th surface κ = 0.0000, A4 = -4.4243E-06, A6 = -3.2750E-09

[Variable interval data]
Infinite focus state Short range focus state R ∞ 1.72
β 0.0 1/30
Bf 40.16398 41.88384

[Each group focal length data]
Group Start surface Focal length G1 1 122.89764
G2 8 50.91118

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R−r22F) = 1.955
Conditional expression (2) f22 / f = 1.240
Conditional expression (3) f2L / f = 0.826
Conditional expression (4) na = 1.55389

  From the table of specifications shown in Table 2, it can be seen that the conditional expressions (1) to (4) are satisfied in the lens system according to the second example.

  4A and 4B are graphs showing various aberrations of the second example. FIG. 4A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. 4B is a short-range focus state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it can be seen that the lens system according to Example 2 has various optical aberrations corrected and high optical performance.

(Third embodiment)
A third embodiment will be described with reference to FIGS. 5 and 6 and Table 3. FIG. As shown in FIG. 5, the lens system according to the third example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 has a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b arranged in order from the object side along the optical axis, and a convex surface on the image side. A compound aspherical lens L22 comprising a positive meniscus glass lens facing and a resin layer provided on the object side lens surface of the glass lens and having an aspheric surface on the surface opposite to the lens. And a biconvex lens L23 in which an aspherical surface is formed on the image side lens surface.

  Table 3 below lists specifications of the lens system according to the third example. In addition, the surface numbers 1-15 in Table 3 respond | correspond to the surfaces 1-15 shown in FIG.

(Table 3)
[Overall specifications]
f = 51.60
FNo = 1.85
ω = 22.99
TL = 75.26421 (when infinite) to 76.98419 (when projected)

[Lens data]
Surface number r d nd νd
1 42.0000 4.5000 1.83481 42.72
2 447.9130 0.1000
3 23.5000 3.0000 1.80400 46.58
4 32.5000 1.2500
5 65.7613 1.3000 1.67270 32.11
6 18.7699 5.9000
7 0.0000 5.3000 (Aperture stop)
8 -21.1460 1.1000 1.69895 30.13
9 48.5018 2.7500 1.80400 46.58
10 -1539.0914 1.8000
* 11 -120.0000 0.1000 1.55389 38.09 (Aspherical surface, resin layer)
12 -120.0000 3.8000 1.77250 49.61
13 -33.0270 0.1000
* 14 303.4237 4.1000 1.80400 46.58 (Aspherical)
15 -39.3434 (Bf)

[Aspherical data]
11th surface κ = 0.000, A4 = -3.4030E-06, A6 = -1.2487E-09

14th surface κ = 0.000, A6 = -1.1491E-11

[Variable interval data]
Infinite focus state Short range focus state R ∞ 1.72
β 0.0 1/30
Bf 40.16421 41.88419

[Each group focal length data]
Group Start surface Focal length G1 1 111.08380
G2 8 53.13000

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R−r22F) = 1.169
Conditional expression (2) f22 / f = 1.121
Conditional expression (3) f2L / f = 0.844
Conditional expression (4) na = 1.55389

  It can be seen from the table of specifications shown in Table 3 that the conditional expressions (1) to (4) are satisfied in the lens system according to the third example.

  FIGS. 6A and 6B are graphs showing various aberrations of the third example. FIG. 6A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it can be seen that the lens system according to the third example has various optical aberrations corrected and high optical performance.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. 7 and 8 and Table 4. FIG. As shown in FIG. 7, the lens system according to the fourth example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 has a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b arranged in order from the object side along the optical axis, and a convex surface on the image side. A compound aspherical lens L22 comprising a positive meniscus glass lens facing and a resin layer provided on the object side lens surface of the glass lens and having an aspheric surface on the surface opposite to the lens. The second lens component in Item 1) and a biconvex lens L23.

  Table 4 below lists specifications of the lens system according to the fourth example. In addition, the surface numbers 1-15 in Table 4 respond | correspond to the surfaces 1-15 shown in FIG.

(Table 4)
[Overall specifications]
f = 51.60
FNo = 1.79
ω = 23.04
TL = 74.26413 (when infinite) to 75.98397 (when projected)

[Lens data]
Surface number r d nd νd
1 35.3612 4.4000 1.88300 40.77
2 180.3711 0.1000
3 25.7131 3.0000 1.83481 42.72
4 35.7739 1.3000
5 66.7298 1.2000 1.71736 29.52
6 18.3543 6.0000
7 0.0000 5.3000 (Aperture stop)
8 -20.0000 1.1000 1.75520 27.51
9 99.6345 2.5000 1.80400 46.58
10 -138.9486 2.0000
* 11 -76.7808 0.1000 1.55389 38.09 (Aspherical surface, resin layer)
12 -76.7808 3.0000 1.78800 47.38
13 -30.4743 0.1000
14 274.8017 4.0000 1.83481 42.72
15 -38.0635 (Bf)

[Aspherical data]
11th surface κ = 0.0000, A4 = -3.8621E-06, A6 = 1.2233E-10

[Variable interval data]
Infinite focus state Short range focus state R ∞ 1.72
β 0.0 1/30
Bf 40.16413 41.88397

[Each group focal length data]
Group Start surface Focal length G1 1 113.18227
G2 8 51.94840

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R-r22F) = 3.470
Conditional expression (2) f22 / f = 1.207
Conditional expression (3) f2L / f = 0.781
Conditional expression (4) na = 1.55389

  It can be seen from the table of specifications shown in Table 4 that the conditional expressions (1) to (4) are satisfied in the lens system according to the fourth example.

  8A and 8B are graphs showing various aberrations of the fourth example. FIG. 8A is a diagram showing various aberrations in the infinitely focused state (shooting magnification β = 0.0), and FIG. 8B is a short-range focused state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it can be seen that the lens system according to the fourth example has various optical aberrations corrected and high optical performance.

(5th Example)
The fifth embodiment will be described with reference to FIGS. 9 and 10 and Table 5. FIG. As shown in FIG. 9, the lens system according to the fifth example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 includes a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b, which are arranged in order from the object side along the optical axis, and an object side lens surface. A positive meniscus lens L22 (second lens component in claim 1) which is an aspherical surface and has a convex surface facing the image side, a biconvex lens L23, and a biconvex lens L24 are configured.

  Table 5 below lists specifications of the lens system according to Example 5. In addition, the surface numbers 1-16 in Table 5 respond | correspond to the surfaces 1-16 shown in FIG.

(Table 5)
[Overall specifications]
f = 51.60
FNo = 1.85
ω = 23.05
TL = 77.06402 (when infinite) to 78.80311 (when projected)

[Lens data]
Surface number r d nd νd
1 37.3000 4.4000 1.83481 42.72
2 300.5542 0.1000
3 24.5000 2.9000 1.83481 42.72
4 30.9227 1.3000
5 64.2355 1.3000 1.68893 31.06
6 18.9457 5.9000
7 0.0000 5.3000 (Aperture stop)
8 -20.6094 1.1000 1.69895 30.13
9 38.5017 2.9000 1.77250 49.61
10 -269.9764 1.9000
* 11 -97.2397 3.6000 1.85135 40.04 (Aspherical)
12 -33.8205 0.1000
13 407.6013 2.6000 1.80400 46.58
14 -5362.1017 0.5000
15 1158.2078 3.0000 1.77250 49.61
16
-38.4663 (Bf)

[Aspherical data]
11th surface κ = 0.000, A4 = -2.7883E-06, A6 = -3.8369E-09

[Variable interval data]
Infinite focusing state Short focusing state R ∞ 1.74
β 0.0 1/30
Bf 40.16402 41.90311

[Each group focal length data]
Group Start surface Focal length G1 1 116.97308
G2 8 51.19371

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R-r22F) = 2.126
Conditional expression (2) f22 / f = 1.150
Conditional expression (3) f2L / f = 0.935

  From the table of specifications shown in Table 5, it can be seen that the conditional expressions (1) to (3) are satisfied in the lens system according to the fifth example.

  10A and 10B are graphs showing various aberrations of the fifth example. FIG. 10A is a diagram showing various aberrations in the infinitely focused state (shooting magnification β = 0.0), and FIG. 10B is a short-range focused state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it can be seen that the lens system according to Example 5 has various optical aberrations corrected and high optical performance.

(Sixth embodiment)
A sixth embodiment will be described with reference to FIGS. 11 and 12 and Table 6. FIG. As shown in FIG. 11, the lens system according to the sixth example has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, a biconvex lens L11, a negative meniscus lens L12 having a convex surface on the image side, a positive meniscus lens L13 having a convex surface on the object side, And a negative meniscus lens L14 having a concave surface facing the image side.

  The second lens group G2 includes a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b, which are arranged in order from the object side along the optical axis, and an object side lens surface. A positive meniscus lens L22 (second lens component in claim 1) which is an aspherical surface and has a convex surface directed to the image side, and a biconvex lens L23.

  Table 6 below provides specification values of the lens system according to Example 6. In addition, the surface numbers 1-16 in Table 6 respond | correspond to the surfaces 1-16 shown in FIG.

(Table 6)
[Overall specifications]
f = 51.60
FNo = 1.80
ω = 23.02
TL = 77.06418 (when infinite) to 78.77765 (when projected)

[Lens data]
Surface number r d nd νd
1 43.6955 4.4000 1.88300 40.77
2 -880.0755 0.7000
3 -147.9752 2.0000 1.88300 40.77
4 -235.4993 0.1000
5 25.0406 3.0000 1.83481 42.72
6 31.4071 1.5000
7 77.3387 1.2000 1.71736 29.52
8 20.4873 6.0000
9 0.0000 5.3000 (Aperture stop)
10 -20.0000 1.1000 1.75520 27.51
11 58.2122 2.5000 1.80400 46.58
12 -146.5114 2.0000
* 13 -89.1564 3.0000 1.85135 40.04 (Aspherical)
14 -32.6904 0.1000
15 299.5251 4.0000 1.83481 42.72
16 -36.9303 (Bf)

[Aspherical data]
13th surface κ = 0.000, A4 = -3.2500E-06, A6 = -6.2453E-10

[Variable interval data]
Infinity focusing state Short-distance focusing state R ∞ 1.71
β 0.0 1/30
Bf 40.16418 41.87765

[Each group focal length data]
Group Start surface Focal length G1 1 129.42495
G2 10 48.82961

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R−r22F) = 4.109
Conditional expression (2) f22 / f = 1.147
Conditional expression (3) f2L / f = 0.767

  It can be seen from the table of specifications shown in Table 6 that the conditional expressions (1) to (3) are satisfied in the lens system according to the sixth example.

  12A and 12B are graphs showing various aberrations of the sixth example. FIG. 12A is a diagram showing various aberrations in the infinitely focused state (shooting magnification β = 0.0), and FIG. 12B is a short-range focused state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it can be seen that the lens system according to Example 6 has various optical aberrations corrected and high optical performance.

(Seventh embodiment)
A seventh embodiment will be described with reference to FIGS. 13 and 14 and Table 7. FIG. As shown in FIG. 13, the lens system according to the seventh example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, and includes a positive meniscus lens L11 having a convex surface on the object side, a positive meniscus lens L12 having a convex surface on the object side, and a concave surface on the image side. And a negative meniscus lens L13 directed.

  The second lens group G2 includes a cemented lens L21 (first lens component in claim 1) composed of a biconcave lens L21a and a biconvex lens L21b, which are arranged in order from the object side along the optical axis, and an object side lens surface. A positive meniscus lens L22 (second lens component in claim 1) which is an aspherical surface and has a convex surface directed to the image side, and a biconvex lens L23.

  Table 7 below provides specification values of the lens system according to Example 7. The surface numbers 1 to 14 in Table 7 correspond to the surfaces 1 to 14 shown in FIG.

(Table 7)
[Overall specifications]
f = 51.60
FNo = 1.86
ω = 23.06
TL = 70.86471 (when infinite) to 72.56010 (when projected)

[Lens data]
Surface number r d nd νd
1 40.0000 4.7000 1.83481 42.73
2 320.2167 0.3000
3 24.1500 2.9000 1.80400 46.60
4 33.0000 1.5000
5 75.2087 1.4000 1.67270 32.19
6 18.4804 5.9000
7 0.0000 d7 (variable) (aperture stop)
8 -21.4080 1.1000 1.69895 30.13
9 32.9830 3.2000 1.80400 46.60
10 -154.0000 2.0000
* 11 -125.0000 3.6000 1.85135 40.04 (Aspherical)
12 -37.8007 0.1000
13 1843.2441 4.0000 1.80400 46.60
14 -39.1647 (Bf)

[Aspherical data]
11th surface κ = 0.0000, A4 = -3.6998E-06, A6 = -1.7387E-09

[Variable interval data]
Infinite focus state Short range focus state
d7 5.30 5.70
R ∞ 1.70
β 0.0 1/30
Bf 40.16471 41.86010

[Each group focal length data]
Group Start surface Focal length G1 1 135.26038
G2 8 49.55684

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R−r22F) = 9.621
Conditional expression (2) f22 / f = 1.211
Conditional expression (3) f2L / f = 0.925

  From the table of specifications shown in Table 7, it can be seen that the conditional expressions (1) to (3) are satisfied in the lens system according to the seventh example.

  FIGS. 14A and 14B are graphs showing various aberrations of the seventh example. FIG. 14A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. 14B is a close-up focus state (shooting magnification). Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from each aberration diagram, it is understood that the lens system according to Example 7 has various optical aberrations corrected and high optical performance.

(Eighth embodiment)
The eighth embodiment will be described with reference to FIGS. 15 and 16 and Table 8. FIG. As shown in FIG. 15, the lens system according to the eighth example has a first lens group G1 having a positive refractive power, an aperture stop S, and a positive refraction, which are arranged in order from the object side along the optical axis. And a second lens group G2 having power.

  The first lens group G1 is arranged in order from the object side along the optical axis, a positive meniscus lens L11 having a convex surface facing the object side, a positive meniscus lens L12 having a convex surface facing the object side, and a convex surface facing the object side. It has a positive meniscus lens L13 directed to it and a negative meniscus lens L14 having a concave surface directed to the image side.

  The second lens group G2 has a cemented lens L21 (first lens component in claim 1), which is arranged in order from the object side along the optical axis, and includes a biconcave lens L21a and a biconvex lens L21b, and a convex surface facing the image side. A compound aspherical lens L22 comprising a positive meniscus glass lens and a resin layer provided on the object side lens surface of the glass lens and having an aspherical surface formed on the surface opposite to the lens. 2) and a biconvex lens L23.

  Table 8 below lists specifications of the lens system according to Example 8. The surface numbers 1 to 17 in Table 8 correspond to the surfaces 1 to 17 shown in FIG.

(Table 8)
[Overall specifications]
f = 51.60
FNo = 1.86
ω = 22.97
TL = 75.36324 (when infinite) to 77.10462 (when projected)

[Lens data]
Surface number r d nd νd
1 351.5819 1.0000 1.83481 42.72
2 417.5699 0.1000
3 37.8725 4.0000 1.83481 42.72
4 275.0973 0.1000
5 23.9000 2.8000 1.83481 42.72
6 31.2851 1.4000
7 65.8376 1.3000 1.68893 31.06
8 18.6190 5.9000
9 0.0000 5.3000 (Aperture stop)
10 -20.7925 1.1000 1.69895 30.13
11 44.6623 2.8000 1.80400 46.58
12 -191.3408 1.8000
* 13 -97.7291 0.1000 1.55389 38.09 (Aspherical surface, resin layer)
14 -97.7291 3.8000 1.80400 46.58
15 -34.3000 0.1000
16 733.5980 3.6000 1.80400 46.58
17 -37.9712 (Bf)

[Aspherical data]
13th surface κ = 0.0000, A4 = -5.0532E-06, A6 = -1.3389E-09

[Variable interval data]
Infinite focusing state Short focusing state R ∞ 1.74
β 0.0 1/30
Bf 40.16324 41.90462

[Each group focal length data]
Group Start surface Focal length G1 1 115.96322
G2 10 52.49924

[Conditional expression]
Conditional expression (1) (r21R + r22F) / (r21R-r22F) = 3.088
Conditional expression (2) f22 / f = 1.240
Conditional expression (3) f2L / f = 0.872
Conditional expression (4) na = 1.55389

  From the table of specifications shown in Table 8, it can be seen that the conditional expressions (1) to (4) are satisfied in the lens system according to Example 8.

  FIGS. 16A and 16B are graphs showing various aberrations of the eighth embodiment. FIG. 16A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. Each aberration diagram at β = -1 / 30) is shown.

  As is apparent from the respective aberration diagrams, it is understood that the lens system according to Example 8 has various optical aberrations corrected and high optical performance.

  In the above-described embodiment, the following description can be appropriately adopted as long as the optical performance is not impaired.

  Although the two-group configuration is shown in the above embodiment, the present invention can also be applied to other group configurations such as a third group. 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 refers to a portion having at least one lens separated by an air interval that changes during zooming.

  In addition, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. The focusing lens group can be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor). In particular, it is preferable that the entire system is a focusing lens group.

  In addition, the lens group or the partial lens group is moved so as to have a component perpendicular to the optical axis, or rotated (swinged) in the in-plane direction including the optical axis to correct image blur caused by camera shake. An anti-vibration lens group may be used. In particular, it is preferable that at least a part of the second lens group G2 is a vibration-proof lens group.

  Each lens surface may be formed as a spherical surface, a flat surface, or an aspheric surface. In addition, 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 processing and assembly adjustment errors can be prevented. Further, even when the image plane is deviated, it is preferable because there is little deterioration in drawing performance. On the other hand, when the lens surface is aspherical, this aspherical surface is an aspherical surface by grinding, a glass mold aspherical surface made of glass with an aspherical shape, and a composite type in which resin is formed on the glass surface in an aspherical shape Any aspherical surface may be used. Each 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 between the first lens group G1 and the second lens group G2. 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.

  In the present embodiment, it is preferable that the first lens group G1 has two positive lens components and one negative lens component. In addition, in order from the object side, it is preferable to arrange the lens components in the order of positive and negative with an air gap interposed.

  In the present embodiment, it is preferable that the second lens group G2 has two positive lens components and one negative lens component. In addition, in order from the object side, it is preferable to dispose the lens components in the order of negative and positive with an air gap interposed.

  In addition, in order to make this invention intelligible, although demonstrated with the component requirement of embodiment, it cannot be overemphasized that this invention is not limited to this.

  As described above, according to the present invention, it is possible to provide a lens system having high optical performance in which various aberrations including coma are corrected well, an optical apparatus including the lens system, and a manufacturing method.

G1 First lens group G2 Second lens group S Aperture stop I Image plane CAM Digital SLR camera (optical equipment)

Claims (6)

In a lens system having a first lens group having a positive refractive power and a second lens group having a positive refractive power, arranged in order from the object side along the optical axis,
A diaphragm is disposed between the first lens group and the second lens group;
Having at least one aspheric lens,
The second lens group is located on the image side with a first lens component having a negative refractive power located on the object side with an air gap formed closest to the object side in the second lens group. A second lens component having a positive refractive power,
The first lens component is a cemented lens composed of a negative lens and a positive lens,
The radius of curvature of the image side lens surface of the first lens component is r21R, the radius of curvature of the object side lens surface of the second lens component is r22F, and the focal length of the second lens component is f22, When the focal length of the entire lens system is f (however, when the corresponding surface is aspherical, it is calculated by the paraxial radius of curvature). 12.0
1.121 ≦ f22 / f <2.0
A lens system that satisfies the following conditions. When the focal length of the lens disposed closest to the image side of the second lens group is f2L, and the focal length of the entire lens system is f, the following expression 0.5 <f2L / f <1.5
The lens system according to claim 1, wherein the following condition is satisfied.   The lens system according to claim 1, wherein at least one aspheric lens is provided in the second lens group.   The lens system according to claim 1, wherein the aspheric lens is a composite aspheric lens made of a composite of a glass material and a resin material. When the refractive index at the d-line of the resin material constituting the composite aspheric lens is defined as na, the following formula 1.450 <na <1.800
The lens system according to claim 4, wherein the following condition is satisfied.   An optical apparatus having the lens system according to claim 1.

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