JP2012220804A - Lens system, optical apparatus, and method for manufacturing lens system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens system favorably correcting various aberrations including coma-aberration, reducing ghost and flare, and having a high imaging performance, an optical apparatus, and a method for manufacturing lens systems.SOLUTION: The lens system includes, in order from an object side: a first lens group G1 having positive refractive power; a second lens group G2 having positive refractive power; an aperture diaphragm S disposed between the first lens group G1 and the second lens group G2; and at least an aspherical lens. The second lens group G2 has a first lens component L21 disposed closest to the object side, and a second lens component L22 disposed in the image side thereof with an air interval interposed therebetween, and satisfies the following conditional expressions: 1.0≤(r21R+r22F)/(r21R-r22F)<12.0 and 0.8<f22/f<2.0. An antireflection film is provided on at least one surface of optical surfaces of the lens components comprising the second lens group Gp, and the antireflection film is configured to include at least one layer formed by using the wet process.

Description

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

  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. In recent years, for such lens systems, not only the aberration performance but also ghost and flare, which are one of the factors that impair the optical performance, have become more demanding. Higher performance is required for the prevention film, and multilayer film design technology and multilayer film formation technology continue to advance to meet the demand (see, for example, Patent Document 2).

JP-A-2-230208 JP 2000-356704 A

  However, the conventional lens system has a large amount of coma and cannot be said to have sufficiently high optical performance. At the same time, there has been a problem that reflected light that becomes ghost or flare is likely to be generated from the optical surface in such a lens system.

  The present invention has been made in view of the above-described problems, and various aberrations including coma are corrected well, ghosts and flares are further reduced, and a lens system, an optical apparatus, and a lens system having high optical performance are manufactured. It aims to provide a method.

In order to solve the above problems, the present invention provides a lens system having a first lens group having a positive refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side along the optical axis. The first lens group is disposed between the first lens group and the second lens group, has at least one aspheric lens, and the second lens group is the first lens disposed closest to the object side. And a second lens component disposed on the image side of the first lens component with an air gap therebetween, satisfying the following conditional expression and constituting the second lens group An antireflection film is provided on at least one of the optical surfaces of the lens, and the antireflection film includes at least one layer formed using a wet process. To do.
1.0 ≦ (r21R + r22F) / (r21R−r22F) <12.0
0.8 <f22 / f <2.0
However,
r21R: radius of curvature of the image-side lens surface of the first lens component,
r22F: radius of curvature of the object-side lens surface of the second lens component,
f22: focal length of the second lens component,
f: Focal length of the entire lens system (however, when the corresponding surface is an aspheric surface, it is calculated with a paraxial radius of curvature).

  The present invention also provides an optical apparatus comprising the lens system.

The present invention is also a method for manufacturing a lens system having a first lens group having a positive refractive power and a second lens group having a positive refractive power, which are arranged in order from the object side along the optical axis. In addition, a diaphragm is disposed between the first lens group and the second lens group, and has at least one aspheric lens, and the second lens group is a first lens disposed closest to the object side. And a second lens component disposed on the image side of the first lens component with an air gap therebetween, satisfying the following conditional expression and constituting the second lens group An antireflection film is provided on at least one of the optical surfaces in the lens, and the antireflection film includes at least one layer formed using a wet process. It is characterized by being incorporated and checking various operations. To provide a method of manufacturing a lens system.
1.0 ≦ (r21R + r22F) / (r21R−r22F) <12.0
0.8 <f22 / f <2.0
However,
r21R: radius of curvature of the image-side lens surface of the first lens component,
r22F: radius of curvature of the object-side lens surface of the second lens component,
f22: focal length of the second lens component,
f: Focal length of the entire lens system (however, when the corresponding surface is an aspheric surface, it is calculated with a paraxial radius of curvature).

  According to the present invention, it is possible to provide a lens system, an optical apparatus, and a manufacturing method of the lens system, in which various aberrations including coma are corrected well, ghosts and flares are further reduced, and high optical performance is provided.

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 sectional drawing which shows the structure of the lens system which concerns on 1st Example, Comprising: It is a figure explaining an example of a mode that the incident light ray reflects in the 1st ghost generating surface and the 2nd ghost generating surface. 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. 9B illustrates the close focus state (shooting distance β = -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. 9B illustrates the close focus state (shooting distance β = -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. 9B illustrates the close focus state (shooting distance β = -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. It is explanatory drawing which shows an example of the layer structure of an antireflection film. It is a graph which shows the spectral characteristic of an antireflection film. It is a graph which shows the spectral characteristics of the antireflection film concerning a modification. It is a graph which shows the incident angle dependence of the spectral characteristic of the antireflection film concerning a modification. It is a graph which shows the spectral characteristic of the anti-reflective film produced with the prior art. It is a graph which shows the incident angle dependence of the spectral characteristic of the anti-reflective film produced with the prior art.

  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) stop S, and a positive lens, which are arranged in order from the object side along the optical axis. By adopting a configuration including the second lens group G2 having refractive power, a so-called Gaussian refractive power arrangement is realized, distortion is corrected well, and spherical aberration and curvature of field are corrected.

  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 has a first lens component L21 disposed closest to the object side and an air space on the image side of the first lens component L21. A second lens component L22 arranged, a second lens component L22 located on the image side, the radius of curvature of the image side lens surface of the first lens component L21 being r21R, and a second Where the radius of curvature of the object side lens surface of the lens component L22 is r22F, the focal length of the second lens component L22 is f22, and the focal length of the entire lens system is f (provided that the corresponding surface is an aspheric surface). In the case of forming, it is calculated by a 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. Also,
The shape of the coma aberration tends to be an outer coma, and the imaging performance deteriorates. Conversely, if conditional expression (1) is below the lower limit, the Petzval sum increases, and astigmatism and field curvature cannot be corrected. Further, the shape of coma aberration tends to be an inner coma, and the imaging performance is deteriorated.

  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, an antireflection film is provided on at least one of the optical surfaces of the lens components constituting the second lens group G2 (in FIG. 1, the biconvex lens of the second lens group G2). The lens surface (surface number 10) on the image surface side in L21b and the object-side lens surface (surface number 11) of the positive meniscus lens L22), and this anti-reflection film has at least a layer formed using a wet process. Contains one layer. If comprised in this way, since the refractive index difference with air can be made small, it becomes possible to reduce reflection of light more and can further reduce a ghost and flare.

  In the lens system according to the present embodiment, the antireflection film is a multilayer film, and the layer formed using the wet process is preferably the outermost layer among the layers constituting the multilayer film. . If comprised in this way, since the refractive index difference with air can be made small, it becomes possible to make reflection of light smaller, and a ghost and flare can further be reduced.

  In the lens system according to the present embodiment, the refractive index nd is 1.30 or less when the refractive index at the d-line (wavelength 587.6 nm) of the layer formed using the wet process is nd. preferable. If comprised in this way, since the refractive index difference with air can be made small, it becomes possible to make reflection of light smaller, and a ghost and flare can further be reduced.

  In the lens system according to the present embodiment, the optical surface provided with the antireflection film is at least one of the optical surfaces in the lens component constituting the second lens group G2, and the optical surface is ( Aperture) A concave surface as viewed from the diaphragm S is preferable. Since a ghost is likely to occur on the concave lens surface as viewed from the aperture stop S, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to the present embodiment, it is preferable that the concave lens surface viewed from the aperture stop is an image surface side lens surface of at least one lens included in the second lens group G2. Since a ghost is likely to occur on the concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

In the lens system according to this embodiment, it is preferable that the concave lens surface viewed from the aperture stop is an object side lens surface of at least one lens included in the second lens group G2. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to the present embodiment, the concave lens surface when viewed from the aperture stop is the lens surface of the lens located second from the aperture stop of the second lens group toward the image plane side. Is preferred. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to the present embodiment, the concave lens surface when viewed from the aperture stop is the lens surface of the lens positioned third from the aperture stop of the second lens group toward the image plane side. Is preferred. Since a ghost is likely to occur on a concave lens surface as viewed from the aperture stop, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to the present embodiment, the optical surface provided with the antireflection film is preferably a concave surface as viewed from the image plane. Since a ghost is likely to occur on a concave lens surface when viewed from the image plane, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to the present embodiment, the concave lens surface when viewed from the image surface is a lens surface of a lens positioned fourth from the aperture stop of the second lens group toward the image surface side. Is preferred. Since a ghost is likely to occur on a concave lens surface as viewed from the image plane, ghosts and flares can be effectively reduced by forming an antireflection film on such an optical surface.

  In the lens system according to this embodiment, the antireflection film is not limited to a wet process, and may be formed by a dry process or the like. At this time, it is preferable that the antireflection film includes at least one layer having a refractive index of d-line of 1.30 or less. Thus, even if the antireflection film is formed by a dry process or the like, the same effect as that obtained when the wet process is used can be obtained. At this time, the layer having a refractive index of 1.30 or less is preferably the most surface layer among the layers constituting the multilayer film.

  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. 18 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. 18, light from an object (subject) (not shown) is collected by the photographing lens 1 and imaged 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. 18 may hold the photographic lens 1 in a detachable manner, or may be molded integrally with the photographic 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, the first lens group G1 and the second lens group G2 are assembled in the lens barrel (step S10). In this incorporation step, each lens is arranged so that the first lens group G1 has a positive refractive power and the second lens group G2 has a positive refractive power.

  Next, the stop S is disposed between the first lens group G1 and the second lens group G2, and at least one aspheric lens is disposed in the present lens system (step S20).

  Subsequently, the second lens group G2 includes a first lens component L21 that is disposed closest to the object side, and a second lens component L22 that is disposed on the image side of the first lens component L21 with an air gap therebetween. The radius of curvature of the image side lens surface of the first lens component L21 is r21R, the radius of curvature of the object side lens surface of the second lens component L22 is r22F, and the focal length of the second lens component L22 Is f22, and f is the focal length of the entire lens system (however, if the corresponding surface is an aspherical surface, it is calculated by the paraxial radius of curvature), the following conditional expressions (1) and (2) Each lens is arranged so as to be satisfied (step S30).

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

  Here, as an example of the lens arrangement in the present embodiment, as shown in FIG. 1, as a first lens group G1, a positive meniscus lens L11 having a convex surface directed toward the object side in order from the object side along the optical axis. A positive meniscus lens L12 having a convex surface facing the object side, and a negative meniscus lens L13 having a concave surface facing the image side. A cemented lens L21 (first lens component) composed of L21a and a biconvex lens L21b, a positive meniscus glass lens having a convex surface facing the image side, and an object side lens surface of the glass lens. A composite aspherical lens L22 (second lens component) composed of a resin layer having an aspherical surface formed on the opposite surface and a biconvex lens L23 are disposed.

  An antireflection film is provided on at least one of the optical surfaces of the lens components constituting the second lens group G2, and the antireflection film includes at least one layer formed using a wet process. Thus, each lens is arranged (step S40).

  According to the manufacturing method according to this embodiment as described above, various aberrations including coma can be corrected well, ghosts and flares can be further reduced, and a lens system having high optical performance can be obtained.

  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.)

  In the first example, an antireflection film to be described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the positive meniscus lens L22 in the second lens group G2. .

  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
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.

  FIG. 3 shows a state where a ghost is generated by the light beam BM incident from the object side in the lens system of the first embodiment. In FIG. 3, when a light beam BM from the object side enters the lens system L as shown, it is reflected by the lens surface (the first ghost generation surface, whose surface number is 11) in the positive meniscus lens L22. Then, the reflected light is reflected again by the image side lens surface (the second ghost generation surface and its surface number is 10) in the biconvex lens L21b, and reaches the image surface I to generate a ghost. The first ghost generation surface 11 and the second ghost generation surface 10 are concave with respect to the aperture stop S, respectively. L22 is a lens positioned third from the aperture stop S toward the image plane side, and L21b is a lens positioned second from the aperture stop S toward the image plane side. A ghost can be effectively reduced by forming an antireflection film corresponding to a wide incident angle in a wider wavelength range on such a surface.

(Second embodiment)
The second embodiment will be described with reference to FIGS. 4 and 5 and Table 2. FIG. As shown in FIG. 4, 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.

  In the second embodiment, an antireflection film described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the positive meniscus lens L22 in the second lens group G2. .

  Table 2 below lists specifications of the lens system according to the second example. The surface numbers 1 to 15 in Table 2 correspond to the surfaces 1 to 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
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.

  FIGS. 5A and 5B are graphs showing various aberrations of the second example. FIG. 5A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. 5B 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. 6 and 7 and Table 3. FIG. As shown in FIG.
The lens system according to the example includes a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power, which are arranged in order from the object side along the optical axis. It is comprised.

  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.

  In the third example, an antireflection film, which will be described later, is formed on the image side lens surface of the biconvex lens L21b and the object side lens surface of the biconvex lens L23 of the second lens group G2.

  Table 3 below lists specifications of the lens system according to the third example. The surface numbers 1 to 15 in Table 3 correspond to the surfaces 1 to 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
12 -120.0000 3.8000 1.77250 49.61
13 -33.0270 0.1000
* 14 303.4237 4.1000 1.80400 46.58
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. 7A and 7B are graphs showing various aberrations of the third example. FIG. 7A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. 7B 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 the third example has various optical aberrations corrected and high optical performance.

(Fourth embodiment)
A fourth embodiment will be described with reference to FIGS. 8 and 9 and Table 4. FIG. As shown in FIG. 8, the lens system according to the fourth example has 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.

In the fourth example, an antireflection film described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the biconvex lens L23 of the second lens group G2.

  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
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.

  FIGS. 9A and 9B are graphs showing various aberrations of the fourth example. FIG. 9A is a diagram showing various aberrations in the infinite focus state (shooting magnification β = 0.0), and FIG. 9B 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 the fourth example has various optical aberrations corrected and high optical performance.

(5th Example)
A fifth embodiment will be described with reference to FIGS. 10 and 11 and Table 5. FIG. As shown in FIG. 10, the lens system according to the fifth example has 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 facing the image side, a biconvex lens L23, and a biconvex lens L24 are configured.

  In the fifth example, an antireflection film, which will be described later, is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the positive meniscus lens L22 in the second lens group G2. .

  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
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.

  FIGS. 11A and 11B are graphs showing various aberrations of the fifth example. FIG. 11A is a diagram illustrating 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 Example 5 has various optical aberrations corrected and high optical performance.

(Sixth embodiment)
A sixth embodiment will be described with reference to FIGS. 12, 13 and Table 6. FIG. As shown in FIG. 12, the lens system according to the sixth example has a first lens group G1 having positive refractive power, an aperture stop S, and 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.

  In the sixth example, an antireflection film described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the positive meniscus lens L22 in the second lens group G2. .

  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
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.

  FIGS. 13A and 13B are graphs showing various aberrations of the sixth example. FIG. 13A is a diagram showing various aberrations in the infinitely focused state (shooting magnification β = 0.0), and FIG. 13B 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. 14 and 15 and Table 7. FIG. As shown in FIG. 14, the lens system according to the seventh 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, 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.

  In the seventh example, an antireflection film to be described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the positive meniscus lens L22 in the second lens group G2. .

  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
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. 15A and 15B are graphs showing various aberrations of the seventh example. FIG. 15A 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 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. 16 and 17 and Table 8. FIG. As shown in FIG. 16, the lens system according to the eighth 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, 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.

  In the eighth example, an antireflection film described later is formed on the image surface side lens surface of the biconvex lens L21b and the object side lens surface of the biconvex lens L23 of the second lens group G2.

  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
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. 17A and 17B are graphs showing various aberrations of the eighth example. FIG. 17A is a diagram illustrating 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.

  Here, an antireflection film (also referred to as a multilayer broadband antireflection film) used in the lens system according to the present embodiment will be described. FIG. 20 is a diagram showing a film configuration of the antireflection film. The antireflection film 101 is composed of seven layers and is formed on the optical surface of the optical member 102 such as a lens. The first layer 101a is formed of aluminum oxide deposited by a vacuum deposition method. Further, a second layer 101b made of a mixture of titanium oxide and zirconium oxide deposited by a vacuum deposition method is further formed on the first layer 101a. Further, a third layer 101c made of aluminum oxide deposited by a vacuum deposition method is formed on the second layer 101b, and titanium oxide and zirconium oxide deposited by a vacuum deposition method are formed on the third layer 101c. A fourth layer 101d made of the mixture is formed. Furthermore, a fifth layer 101e made of aluminum oxide deposited by vacuum deposition is formed on the fourth layer 101d, and titanium oxide and zirconium oxide deposited by vacuum deposition on the fifth layer 101e. A sixth layer 101f made of the mixture is formed.

  Then, a seventh layer 101g made of a mixture of magnesium fluoride and silica is formed on the sixth layer 101f formed in this way by a wet process, and the antireflection film 101 of this embodiment is formed. For the formation of the seventh layer 101g, a sol-gel method which is a kind of wet process is used. The sol-gel method is a method in which a sol obtained by mixing raw materials is made into a non-flowable gel by hydrolysis / polycondensation reaction, etc., and this gel is heated and decomposed to obtain a product, In the production of an optical thin film, a film can be formed by applying an optical thin film material sol on the optical surface of an optical member and forming a gel film by drying and solidifying. The wet process is not limited to the sol-gel method, and a method of obtaining a solid film without going through a gel state may be used.

  Thus, the first layer 101a to the sixth layer 101f of the antireflection film 101 are formed by electron beam evaporation which is a dry process, and the seventh layer 101g which is the uppermost layer is prepared by a hydrofluoric acid / magnesium acetate method. It is formed by the following procedure by a wet process using the prepared sol solution. First, an aluminum oxide layer to be the first layer 101a, a titanium oxide-zirconium oxide mixed layer to be the second layer 101b, a third layer on the lens film formation surface (the optical surface of the optical member 102 described above) in advance using a vacuum deposition apparatus, An aluminum oxide layer to be the layer 101c, a titanium oxide-zirconium oxide mixed layer to be the fourth layer 101d, an aluminum oxide layer to be the fifth layer 101e, and a titanium oxide-zirconium oxide mixed layer to be the sixth layer 101f are formed in this order. And after taking out the optical member 102 from a vapor deposition apparatus, the thing which added the silicon alkoxide to the sol liquid prepared by the hydrofluoric acid / magnesium acetate method is apply | coated by the spin coat method, The magnesium fluoride used as the 7th layer 101g A layer made of a mixture of silica and silica is formed. The reaction formula when prepared by the hydrofluoric acid / magnesium acetate method is shown in the following formula (5).

2HF + Mg (CH ₃ COO) ² → MgF ₂ + 2CH ₃ COOH (5)

  The sol solution used for the film formation is used for film formation after mixing raw materials and subjecting to an autoclave at 140 ° C. for 24 hours at a high temperature and pressure. The optical member 102 is completed by heat treatment at 160 ° C. for 1 hour in the air after the seventh layer 101g is formed. By using such a sol-gel method, the seventh layer 101g is formed by depositing particles having a size of several nm to several tens of nm leaving a void.

  The optical performance of the optical member having the antireflection film 101 formed as described above will be described with reference to spectral characteristics shown in FIG.

The optical member (lens) having the antireflection film according to this embodiment is formed under the conditions shown in Table 9 below. Here, in Table 9, the reference wavelength is λ, and the layers 101a (first layer) to 101g (seventh layer) of the antireflection film 101 when the refractive index (optical member) of the substrate is 1.62, 1.74, and 1.85. The optical film thickness of each layer is determined. In Table 9, aluminum oxide is expressed as Al ₂ O ₃ , a mixture of titanium oxide and zirconium oxide is expressed as ZrO ₂ + TiO ₂ , and a mixture of magnesium fluoride and silica is expressed as MgF ₂ + SiO ₂ .

  FIG. 21 shows the spectral characteristics when light rays are perpendicularly incident on an optical member in which the reference wavelength λ is 550 nm and the optical film thickness of each layer of the antireflection film 101 is designed in Table 9.

  From FIG. 21, it can be seen that the optical member having the antireflection film 101 designed with the reference wavelength λ of 550 nm can suppress the reflectance to 0.2% or less over the entire range of the wavelength of light rays from 420 nm to 720 nm. Further, even in the optical member having the antireflection film 101 whose optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) in Table 9, the spectral characteristics are hardly affected, and the reference wavelength shown in FIG. The spectral characteristics are almost the same as when λ is 550 nm.

(Table 9)
Material Refractive index Optical film thickness Optical film thickness Optical film thickness Medium Air 1.00
7th layer MgF ₂ + SiO ₂ 1.26 0.268λ 0.271λ 0.269λ
6th layer ZrO ₂ + TiO ₂ 2.12 0.057λ 0.054λ 0.059λ
5th layer Al ₂ O ₃ 1.65 0.171λ 0.178λ 0.162λ
4th layer ZrO ₂ + TiO ₂ 2.12 0.127λ 0.13λ 0.158λ
3rd layer Al ₂ O ₃ 1.65 0.122λ 0.107λ 0.08λ
Second layer ZrO ₂ + TiO ₂ 2.12 0.059λ 0.075λ 0.105λ
1st layer Al ₂ O ₃ 1.65 0.257λ 0.03λ 0.03λ
Refractive index of substrate 1.62 1.74 1.85

  Next, a modified example of the antireflection film will be described. This antireflection film consists of five layers, and similarly to Table 9, the optical film thickness of each layer with respect to the reference wavelength λ is designed under the conditions shown in Table 10 below. In this modification, the above-described sol-gel method is used for forming the fifth layer.

  FIG. 22 shows the spectral characteristics when light rays are perpendicularly incident on an optical member having an antireflection film in which the optical film thickness is designed with the refractive index of the substrate being 1.52 and the reference wavelength λ being 550 nm in Table 10. Yes. It can be seen from FIG. 22 that the antireflection film of this modification has a reflectivity of 0.2% or less over the entire wavelength range of 420 nm to 720 nm. In Table 10, even an optical member having an antireflection film in which each optical film thickness is designed with the reference wavelength λ as the d-line (wavelength 587.6 nm) hardly affects the spectral characteristics, and the spectral characteristics shown in FIG. It has almost the same characteristics.

  FIG. 23 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 22 are 30, 45, and 60 degrees, respectively. 22 and 23 do not show the spectral characteristics of the optical member having the antireflection film whose refractive index is 1.46 shown in Table 10, but the refractive index of the substrate is almost equal to 1.52. Needless to say, it has the following spectral characteristics.

(Table 10)
Material Refractive index Optical film thickness Optical film thickness Medium Air 1.00
5th layer MgF ₂ + SiO ₂ 1.26 0.275λ 0.269λ
Fourth layer ZrO ₂ + TiO ₂ 2.12 0.045λ 0.043λ
3rd layer Al ₂ O ₃ 1.65 0.212λ 0.217λ
Second layer ZrO ₂ + TiO ₂ 2.12 0.077λ 0.066λ
1st layer Al ₂ O ₃ 1.65 0.288λ 0.290λ
Refractive index of substrate 1.46 1.52

  For comparison, FIG. 24 shows an example of an antireflection film formed only by a dry process such as a conventional vacuum deposition method. FIG. 24 shows the spectral characteristics when a light beam is perpendicularly incident on an optical member designed with an antireflection film configured under the conditions shown in Table 11 below with a refractive index of 1.52 of the same substrate as in Table 10. FIG. 25 shows the spectral characteristics when the incident angles of the light rays to the optical member having the spectral characteristics shown in FIG. 24 are 30, 45, and 60 degrees, respectively.

(Table 11)
Material Refractive index Optical film thickness Medium Air 1.00
7th layer MgF ₂ 1.39 0.243λ
6th layer ZrO ₂ + TiO ₂ 2.12 0.119λ
5th layer Al ₂ O ₃ 1.65 0.057λ
Fourth layer ZrO ₂ + TiO ₂ 2.12 0.220λ
3rd layer Al ₂ O ₃ 1.65 0.064λ
Second layer ZrO ₂ + TiO ₂ 2.12 0.057λ
1st layer Al ₂ O ₃ 1.65 0.193λ
Refractive index of substrate 1.52

When comparing the spectral characteristics of the optical member having the antireflection film according to this embodiment shown in FIGS. 21 to 23 with the spectral characteristics of the conventional example shown in FIGS. It can be seen that the corner also has a lower reflectivity and has a lower reflectivity over a wider band.

  Next, application examples of the antireflection films shown in Tables 9 and 10 will be described in Examples 1 to 8 of the present application.

  In the lens system of the first example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400 as shown in Table 1, and the resin of the positive meniscus lens L22 of the second lens group G2 Since the refractive index of nd is 1.555389, the anti-reflective film 101 (see Table 9) corresponding to the refractive index of the substrate corresponding to 1.85 is used on the image side lens surface of the biconvex lens L21b, and a positive meniscus lens. By using an anti-reflective coating (see Table 10) with a refractive index of the substrate of 1.52 on the lens surface of the resin on the object side of L22, the reflected light from each lens surface can be reduced, reducing ghosts and flares. can do.

  In the lens system of the second example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400, as shown in Table 2, and the resin of the positive meniscus lens L22 of the second lens group G2 Since the refractive index of nd is 1.555389, an anti-reflective film 101 (see Table 9) corresponding to a refractive index of the substrate corresponding to 1.85 is used on the image side lens surface of the biconvex lens L21b, and a positive meniscus is used. By using an antireflection film (see Table 10) corresponding to a refractive index of the substrate of 1.52 on the lens surface of the resin on the object side in the lens L22, reflected light from each lens surface can be reduced, and ghost and flare can be reduced. Can be reduced.

  In the lens system of the third example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400, as shown in Table 3, and the refractive index of the biconvex lens L23 of the second lens group G2. Since nd = 1.80400, an antireflection film (see Table 9) corresponding to a refractive index of the substrate of 1.85 is used on the image side lens surface of the biconvex lens L21b, and the object side of the biconvex lens L23 is used. By using an antireflection film (see Table 9) corresponding to a refractive index of the substrate of 1.85 on the lens surface, reflected light from each lens surface can be reduced, and ghost and flare can be reduced.

  In the lens system of the fourth example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400, as shown in Table 4, and the refractive index of the biconvex lens L23 of the second lens group G2. Since nd = 1.83481, the antireflection film 101 (see Table 9) corresponding to the refractive index of the substrate corresponding to 1.85 is used on the image side lens surface of the biconvex lens L21b, and the object in the biconvex lens L23 is used. By using an antireflection film 101 (see Table 9) corresponding to the refractive index of the substrate of 1.85 on the side lens surface, the reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. .

  In the lens system of the fifth example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.77250 as shown in Table 5, and the refraction of the positive meniscus lens L22 of the second lens group G2 is. Since the refractive index is nd = 1.85135, an antireflection film 101 (see Table 9) corresponding to a refractive index of the substrate of 1.74 is used on the image side lens surface of the biconvex lens L21b, and the positive meniscus lens L22. By using an antireflection film 101 (see Table 9) having a substrate refractive index of 1.85 on the object-side lens surface of the lens, reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. Can do.

In the lens system of the sixth example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400 as shown in Table 6, and the refraction of the positive meniscus lens L22 of the second lens group G2 is. Since the ratio is nd = 1.85135, the anti-reflective film 101 (see Table 9) corresponding to the refractive index of the substrate corresponding to 1.85 is used on the image side lens surface of the biconvex lens L21b, and the positive meniscus lens L22. By using an antireflection film 101 (see Table 9) having a substrate refractive index of 1.85 on the object-side lens surface of the lens, reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. Can do.

  In the lens system of the seventh example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400 as shown in Table 7, and the refraction of the positive meniscus lens L22 of the second lens group G2 is. Since the ratio is nd = 1.85135, the anti-reflective film 101 (see Table 9) corresponding to the refractive index of the substrate corresponding to 1.85 is used on the image side lens surface of the biconvex lens L21b, and the positive meniscus lens L22. By using an antireflection film 101 (see Table 9) having a substrate refractive index of 1.85 on the object-side lens surface of the lens, reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. Can do.

  In the lens system of the eighth example, the refractive index of the biconvex lens L21b of the second lens group G2 is nd = 1.80400, as shown in Table 8, and the refractive index of the biconvex lens L23 of the second lens group G2. Since nd = 1.80400, an antireflection film 101 (see Table 9) corresponding to a refractive index of the substrate of 1.85 is used on the image side lens surface of the biconvex lens L21b, and the object in the biconvex lens L23 is used. By using an antireflection film 101 (see Table 9) corresponding to the refractive index of the substrate of 1.85 on the side lens surface, the reflected light from each lens surface can be reduced, and ghosts and flares can be reduced. .

  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 be applied to other group configurations such as a three-group configuration. 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 an anti-vibration 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 satisfactorily correct various aberrations including coma, reduce ghosts and flares, and provide a high optical performance lens system, and an optical apparatus and manufacturing method including the lens system. can do.

G1 First lens group G2 Second lens group S Aperture stop I Image plane CAM Digital SLR camera (optical equipment)
101 Antireflection film 101a 1st layer 101b 2nd layer 101c 3rd layer 101d 4th layer 101e 5th layer 101f 6th layer 101g 7th layer 102 Optical member

Claims (16)

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 includes a first lens component arranged closest to the object side, and a second lens component arranged with an air gap on the image side of the first lens component, and While satisfying the conditional expression
An antireflection film is provided on at least one of the optical surfaces of the lens components constituting the second lens group, and the antireflection film is configured to include at least one layer formed using a wet process. A lens system characterized by
1.0 ≦ (r21R + r22F) / (r21R−r22F) <12.0
0.8 <f22 / f <2.0
However,
r21R: radius of curvature of the image-side lens surface of the first lens component,
r22F: radius of curvature of the object-side lens surface of the second lens component,
f22: focal length of the second lens component,
f: Focal length of the entire lens system (however, when the corresponding surface is an aspheric surface, it is calculated with a paraxial radius of curvature). The antireflection film is a multilayer film,
The lens system according to claim 1, wherein the layer formed by the wet process is a layer on the most surface side among the layers constituting the multilayer film.   3. The lens system according to claim 1, wherein nd is 1.30 or less, where nd is a refractive index at a d-line of a layer formed by using the wet process.   The lens system according to any one of claims 1 to 3, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the diaphragm.   5. The lens system according to claim 4, wherein the lens surface that is concave as viewed from the diaphragm is an image surface side lens surface of at least one lens included in the second lens group.   5. The lens system according to claim 4, wherein the concave lens surface as viewed from the diaphragm is an object side lens surface of at least one lens included in the second lens group.   5. The lens according to claim 4, wherein the concave lens surface when viewed from the diaphragm is a lens surface of a lens positioned second from the diaphragm of the second lens group toward the image plane side. system.   5. The lens according to claim 4, wherein the lens surface that is concave when viewed from the diaphragm is a lens surface of a lens that is located third from the diaphragm of the second lens group toward the image plane side. system.   The lens system according to claim 1, wherein the optical surface provided with the antireflection film is a concave lens surface when viewed from the image plane. 10. The lens surface according to claim 9, wherein the lens surface that is concave when viewed from the image surface is a lens surface of a lens that is located fourth from the stop of the second lens group toward the image surface side. Lens system. 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 13, wherein the following condition is satisfied.   An optical apparatus having the lens system according to claim 1. A method of manufacturing 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 includes a first lens component arranged closest to the object side, and a second lens component arranged with an air gap on the image side of the first lens component, and While satisfying the conditional expression
An antireflection film is provided on at least one of the optical surfaces of the lens components constituting the second lens group, and the antireflection film includes at least one layer formed using a wet process. In addition,
A method of manufacturing a lens system, wherein each lens is incorporated into a lens barrel and various operations are confirmed.
1.0 ≦ (r21R + r22F) / (r21R−r22F) <12.0
0.8 <f22 / f <2.0
However,
r21R: radius of curvature of the image-side lens surface of the first lens component,
r22F: radius of curvature of the object-side lens surface of the second lens component,
f22: focal length of the second lens component,
f: Focal length of the entire lens system (however, when the corresponding surface is an aspheric surface, it is calculated with a paraxial radius of curvature).

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