JP2010175628A - Macro lens and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact macro lens which has high performance and a bright F number of 2.8 or less, and to provide a camera having the macro lens. <P>SOLUTION: The macro lens has a two-group configuration composed of a first lens group and a second lens group and is configured such that when focusing from the infinity to a proximity position is performed, the first lens group is moved to an object side rather than the second lens group and each lens group is extended in the same direction. The first lens group comprises, in order from the object side, a positive first lens L1 having a convex shape on the object side, a negative second lens L2 having a concave shape on an image surface side, a positive third lens, a positive fourth lens, a negative fifth lens, sixth and seventh lenses being a negative-and-positive cemented lens having a concave shape on the object side, a positive eighth lens, and a positive ninth lens. The second lens group comprises two or more lenses. The macro lens satisfies a conditional expression of -7.0<fo1/fo2<-1.8, wherein fo1 is the focal length of the first lens L1 and fo2 is the focal length of the second lens L2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a macro lens that can be incorporated as a photographic lens in a digital camera, video camera, surveillance camera, portable information terminal, or the like, or applicable to a reading optical system and the like, and a camera equipped with the macro lens.

  While taking lenses used in general cameras set the reference for aberration correction at infinity, macro lenses capable of close-up photography correct aberrations in the optical system based on the object distance when approaching. Yes.

  In recent years, digital cameras have been widely used in place of silver-salt film type cameras, and there have been various demands for digital cameras by users, and digital cameras rich in individuality have become widespread. Among them, the improvement in convenience when carrying is high priority as a technical problem to be solved, and in order to realize this, the miniaturization of camera lenses and the pursuit of convenience are continued. In parallel with this, technological development for higher performance and higher functionality is also being carried out.

  As a conventional lens for a digital camera, for example, there is one disclosed in Patent Document 1. Further, as high performance lenses, there are macro lenses disclosed in Patent Document 2, Patent Document 3, Patent Document 4, and the like.

  The lens described in Patent Document 1 has a configuration in which six lenses are divided into two groups. This lens realizes a large aperture and is bright (small F-number) and high performance, but is a short focus lens and is not a macro lens.

  The lenses described in Patent Document 2 and Patent Document 3 are retrofocus-type macro lenses that employ a floating mechanism that independently moves at least two lenses during focusing. This lens, for example, has an open F number of 2.8 and can maintain high performance from an infinite focus position to a close-join focus position. However, it is necessary to take a long back focus. Is not enough.

  The lens described in Patent Document 4 is a large-diameter Gaussian macro lens having an F-number of 2.8, for example, but is not sufficient in terms of performance today.

  The present invention has been made in view of the above-described prior art, and is provided with a macro lens that is small, has high performance, and has a bright F number of 2.8 or less, and the macro lens as a photographing lens. It aims at providing the camera which can obtain a quality image.

The present invention is a macro lens having a two-group configuration in which a first lens group and a second lens group are arranged in order from the object side, and focuses on an object at a close position from a state in which an object at infinity is in focus. When in focus, the first lens group moves more to the object side than the second lens group, and the moving direction of each lens group is extended in the same direction for both the first lens group and the second lens group. The first lens group includes, in order from the object side, a first lens having a positive refractive index convex on the object side, a second lens having a negative refractive index having a concave shape on the image side, and positive refraction. A third lens having a positive power, a fourth lens having a positive refractive power, a fifth lens having a negative refractive power, and sixth and seventh cemented lenses having a negative shape and a negative refractive power on the object side. From the lens, the eighth lens having a positive refractive power, and the ninth lens having a positive refractive power The second lens group is composed of two or more lenses. When the focal length of the first lens is fo1 and the focal length of the second lens is fo2, the following conditional expression (1) is satisfied. This is the main feature.
−7.0 <fo1 / fo2 <−1.8 (1)

According to the present invention, in addition to the above-described configuration, the most object-side lens and the most image-side lens of the second lens group are configured by a combination of negative and positive, or positive and negative refractive power, When the focal length of the lens on the object side is Fif and the focal length of the lens on the image plane side is Fie, the following conditional expression (2) is satisfied.
-1.4 <Fif / Fie <-0.8 (2)

In addition to the above configuration, the present invention is characterized in that the following conditional expression (3) is satisfied when the focal length of the first lens unit is Fo and the focal length of the entire lens at infinity is Fz. .
0.5 <Fo / Fz <2.0 (3)

The present invention is also a two-group macro lens in which a first lens group and a second lens group are arranged in order from the object side. When focusing, the first lens group is moved more to the object side than the second lens group, and the moving direction of each lens group is extended in the same direction for both the first lens group and the second lens group. When the maximum photographing magnification is β, the following conditional expression (4) is satisfied.
β <−0.5 (4)

  The camera according to the present invention includes the macro lens configured as described above as a photographing lens.

According to the present invention, it is possible to provide a high-performance macro lens that is small and has a small (bright) F number.
Exceeding the upper limit of conditional expression (1) is advantageous for shortening the overall length of the lens, but high-order spherical aberration and coma aberration increase, making it difficult to achieve high performance. On the other hand, when the lower limit of conditional expression (1) is exceeded, spherical aberration increases and the total length tends to be long, and it is difficult to achieve miniaturization and high performance of the macro lens.

  By satisfying conditional expression (2), a macro lens having high performance and a small F number (bright) can be obtained. If the lower limit of conditional expression (2) is not reached, axial chromatic aberration increases, so that the optical performance at the center is lowered and it is difficult to achieve high performance. If the upper limit of conditional expression (2) is exceeded, coma and chromatic aberration of magnification will increase, and peripheral performance will deteriorate, making it difficult to achieve high performance.

  By satisfying conditional expression (3), a small and high performance macro lens can be obtained. If the upper limit of conditional expression (3) is exceeded, the variation in spherical aberration and coma tends to increase, making it difficult to achieve high performance. If the lower limit of conditional expression (3) is not reached, the back focus increases and the total length increases, making it difficult to reduce the size.

  By satisfying conditional expression (4), a small and high performance macro lens can be obtained. The present invention is a lens capable of close-up shooting from shooting magnification β = 0 to at least β = −0.5. When the upper limit of conditional expression (4) is exceeded, the lens is moved to the object side during macro shooting. As the amount increases, the total lens length during macro photography increases, and various aberrations, particularly lateral chromatic aberration and axial chromatic aberration, further increase.

FIG. 3 is an optical arrangement diagram showing a first example of a macro lens according to the present invention. It is an aberration curve figure at the time of infinity focusing in the 1st example of the above-mentioned macro lens. It is an aberration curve figure at the time of 1/2 time focusing in 1st Example of the said macro lens. It is an optical arrangement | positioning figure which shows 2nd Example of the macro lens which concerns on this invention. It is an aberration curve figure at the time of infinity focusing in the 2nd example of the above-mentioned macro lens. It is an aberration curve figure at the time of 1/2 time focusing in 2nd Example of the said macro lens. It is an optical arrangement | positioning figure which shows 3rd Example of the macro lens which concerns on this invention. It is an aberration curve figure at the time of infinity focusing in the 3rd example of the above-mentioned macro lens. It is an aberration curve figure at the time of 1/2 time focusing in 3rd Example of the said macro lens.

  Embodiments of the macro lens according to the present invention will be described below with reference to the drawings.

  FIG. 1 shows a first embodiment of a macro lens according to the present invention, and shows the position of each lens at infinity. The macro lens according to the above example has a two-group configuration in which a first lens group and a second lens group are arranged in order from the object side (left side in FIG. 1). The first lens group includes, in order from the object side, a first lens L1 having a positive refractive power convex toward the object side, a second lens L2 having a negative refractive index having a concave shape on the image side, and the object side A third lens L3 having a positive convex refractive power and a fourth lens L4 having a positive refractive power convex on the object side, and a fifth lens L5 having a negative refractive power concave on the image plane side, A sixth cemented lens L6 that is a concave cemented lens on the object side and has negative refractive power, a seventh lens L7 that is convex and has positive refractive power on the object side, and a positive refractive power that is convex on the image side. And an eighth lens L8 having a positive refractive power convex toward the image plane side.

  The second lens group includes a tenth lens L10 having a positive refractive power and an eleventh lens L11 having a negative refractive power, and a back insertion glass is disposed behind the tenth lens L10. An optical stop Stop is disposed between the fifth lens L5 and the sixth lens L6. The arrows in the figure represent the movement of the first lens group and the second lens group for focusing on a close object, that is, macro photography, from the state of focusing on an object at infinity as shown in the figure. Is. The direction of movement of the first lens group and the second lens group is the same direction, and in this embodiment, the first lens group and the second lens group are zoomed out by moving them out so that an operation mode capable of macro photography is obtained. It is configured. In addition, the first lens group moves more to the object side than the second lens group. When the macro shooting state is set to focus on an object at infinity, the movement is opposite to the above movement.

Numbers are sequentially given from “1” to “24” to each surface from the object side surface of the first lens L1 to the image side surface of the back insertion glass in the above embodiment. The joint surface of the sixth lens L6 and the seventh lens L7 is represented by a surface number “13”. The surface number “11” indicates the surface of the optical aperture. When the radius of each surface is R, the thickness or space between each surface is D, the refractive index of each optical element, that is, the lens and the back insertion glass is Nd, and the dispersion rate is Vd, these specific numerical values are shown in Table 1. Shown in
The focal length f and FN0. Is as follows.
f = 33.2 mm
FNo. = 1.80

Table 1

Table 2 shows the amount of change between the lens movable portion, that is, the first lens group and the second lens group. In this embodiment, since the first lens group and the second lens group move as described above, the distance D18 between the first lens group and the second lens group and the distance D22 between the second lens group and the back insertion glass change. To do. In Table 2, “INF” indicates a focus at infinity, and “−1 / 2x” indicates a focus at 1/2 times.


Table 2

Here, the meanings of symbols in each embodiment are as follows.
f: focal length of the entire lens (= Fz)
FNo. : F number (Lens brightness)
R: radius of curvature D: surface spacing Nd: refractive index Vd: Abbe number fo1: focal length of the first lens L1 fo2: focal length of the second lens L2 Fif: focal length of the lens closest to the object in the second lens group Fie : Focal length of the lens closest to the image plane in the second lens group Fo: Focal length of the first lens group β: Maximum magnification

The coefficients of the conditional expressions in the first embodiment are as follows.
fo1 = 50.2
fo2 = −23.8
Fif = 42.4
Fie = -41.9
Fo = 42.6
Fz = 33.2 (= f)
fo1 / fo2 = −2.1
Fif / Fie = −1.0
Fo / Fz = 1.3
β = −0.5
Therefore, the numerical values of “fo1 / fo2” in the conditional expression (1), “Fif / Fie” in the conditional expression (2), and “Fo / Fz” in the conditional expression (3) in each of the above-described embodiments are the same. It is within the range of numerical values specified by the conditional expression.

  FIG. 2 shows spherical aberration, astigmatism, distortion aberration, and coma aberration when focusing on infinity in the above example. FIG. 3 shows the spherical aberration, astigmatism, distortion aberration, and coma aberration when focusing on 1/2 of the above embodiment. In the diagram showing spherical aberration, the broken line represents the sine condition. In the diagram showing astigmatism, the solid line represents sagittal and the broken line represents meridional.

  According to the macro lens according to the above embodiment, a small and bright macro lens can be obtained such that the focal length f of the entire lens is f = 33.2 mm and the F number is 1.80, and FIGS. As can be seen, various aberrations at the time of focusing on infinity and at the time of 1/2 magnification can be suppressed.

  FIG. 4 shows a second embodiment of the macro lens according to the present invention, and shows the position of each lens at infinity. The macro lens according to the second example has substantially the same configuration as that of the first example, and has a two-group configuration in which the first lens group and the second lens group are arranged in order from the object side. The first lens group includes, in order from the object side, a first lens L1 having a positive refractive power convex toward the object side, a second lens L2 having a negative refractive index having a concave shape on the image side, and the object side A third lens L3 having a positive convex refractive power and a fourth lens L4 having a positive refractive power convex on the object side, and a fifth lens L5 having a negative refractive power concave on the image plane side, A sixth cemented lens L6 that is a concave cemented lens on the object side and has negative refractive power, a seventh lens L7 that is convex and has positive refractive power on the object side, and a positive refractive power that is convex on the image side. And an eighth lens L8 having a positive refractive power convex toward the image plane side.

  The second lens group includes a tenth lens L10 having a positive refractive power and an eleventh lens L11 having a negative refractive power, and a back insertion glass is disposed behind the tenth lens L10. An optical stop Stop is disposed between the fifth lens L5 and the sixth lens L6. The arrows in the figure represent the movement of the first lens group and the second lens group for focusing on a close object, that is, macro photography, from the state of focusing on an object at infinity as shown in the figure. Is. The direction of movement of the first lens group and the second lens group is the same direction, and in this embodiment, the first lens group and the second lens group are zoomed out by moving them out so that an operation mode capable of macro photography is obtained. It is configured. In addition, the first lens group moves more to the object side than the second lens group. When the macro shooting state is set to focus on an object at infinity, the movement is opposite to the above movement.

Numbers “1” to “24” are assigned to the respective surfaces. When the radius of each surface is R, the thickness or interval between each surface is D, the refractive index of each optical element, that is, the lens and the back insertion glass is Nd, and the dispersion is Vd, these specific numerical values are shown in Table 3. Shown in
The focal length f and FN0. Is as follows.
f = 33.0mm
FNo. = 1.80
Table 3

Table 4 shows the amount of change in the lens movable portion, that is, the first lens group and the second lens group. In this embodiment, the distance D18 between the first lens group and the second lens group and the distance D22 between the second lens group and the back insertion glass are changed. “INF” indicates that the focus is at infinity, and “−1 / 2x” indicates that the focus is ½ times.
Table 4

The coefficients of the conditional expression in the second embodiment are as follows.
fo1 = 147.9
fo2 = -30.2
Fif = 46.2
Fie = -39.7
Fo = 39.1
Fz = 33.0 (= f)
fo1 / fo2 = −4.9
Fif / Fie = −1.2
Fo / Fz = 1.2
β = −0.5
Therefore, the numerical values of “fo1 / fo2” in the conditional expression (1), “Fif / Fie” in the conditional expression (2), and “Fo / Fz” in the conditional expression (3) in each of the above-described embodiments are the same. It is within the range of numerical values specified by the conditional expression.

  FIG. 5 shows spherical aberration, astigmatism, distortion aberration, and coma aberration when focusing on infinity in the above example. FIG. 6 shows spherical aberration, astigmatism, distortion aberration, and coma aberration when the ½ magnification of the above embodiment is in focus. In the diagram showing spherical aberration, the broken line represents the sine condition. In the diagram showing astigmatism, the solid line represents sagittal and the broken line represents meridional.

  According to the macro lens according to the above embodiment, a small and bright macro lens can be obtained such that the focal length f of the entire lens is f = 33.0 mm and the F number is 1.8, and FIGS. As can be seen, various aberrations at the time of focusing on infinity and at the time of 1/2 magnification can be suppressed.

  FIG. 7 shows a third embodiment of the macro lens according to the present invention, and shows the position of each lens at infinity. The macro lens according to the third example has almost the same configuration as the first and second examples, and has a two-group configuration in which the first lens group and the second lens group are arranged. The first lens group also includes the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, and the seventh lens, which are configured in the same manner as each lens in the above-described embodiment. The lens includes a lens L7, an eighth lens L8, and a ninth lens L9. The second lens group is also composed of a tenth lens L10 and an eleventh lens L11, and a back insertion glass is arranged behind the second lens group. An optical stop Stop is disposed between the fifth lens L5 and the sixth lens L6.

  The arrows indicate the direction of movement of the first lens group and the second lens group when shifting from the state of focusing on an object at infinity to the macro photographing state. The first lens group and the second lens group are both extended so that zooming can be performed and an operation mode capable of macro photography is obtained. In addition, the first lens group moves more to the object side than the second lens group. When the macro shooting state is set to focus on an object at infinity, the movement is opposite to the above movement.

Numbers “1” to “24” are assigned to each surface, the radius of each surface is R, the thickness or distance between each surface is D, the refractive index of each optical element, that is, the lens and the back insertion glass is Nd, and the dispersion Table 5 shows these specific numerical values when the rate is Vd.
The focal length f and FN0. Is as follows.
f = 33.0mm
FNo. = 1.8
Table 5

Table 6 shows the amount of change in the lens movable portion, that is, the first lens group and the second lens group. The distance D18 between the first lens group and the second lens group and the distance D22 between the second lens group and the back insertion glass are changed. “INF” indicates that the focus is at infinity, and “−1 / 2x” indicates that the focus is ½ times.
Table 6

The coefficients of the conditional expression in the third embodiment are as follows.
fo1 = 195.3
fo2 = -30.2
Fif = 47.0
Fie = -37.4
Fo = 37.8
Fz = 33.0 (= f)
fo1 / fo2 = −6.5
Fif / Fie = −1.3
Fo / Fz = 1.1
β = −0.5
Therefore, the numerical values of “fo1 / fo2” in the conditional expression (1), “Fif / Fie” in the conditional expression (2), and “Fo / Fz” in the conditional expression (3) in each of the above-described embodiments are the same. It is within the range of numerical values specified by the conditional expression.

  FIG. 8 shows spherical aberration, astigmatism, distortion aberration, and coma aberration when focusing on infinity according to the above example. FIG. 9 shows spherical aberration, astigmatism, distortion aberration, and coma aberration when focusing on 1/2 of the above example. In the diagram showing spherical aberration, the broken line represents the sine condition. In the diagram showing astigmatism, the solid line represents sagittal and the broken line represents meridional.

  According to the macro lens according to the above embodiment, a small and bright macro lens can be obtained such that the focal length f of the entire lens is f = 33.0 mm and the F number is 1.8, and FIGS. As can be seen, various aberrations at the time of focusing on infinity and at the time of 1/2 magnification can be suppressed.

  In any of the embodiments, the second lens group is composed of two lenses. However, the second lens group is not limited to such a configuration, and may be composed of three or more lenses. . In any case, the lens closest to the object side and the lens closest to the image plane in the second lens group are configured by a combination of negative and positive, or positive and negative refractive power, and the focal length of the lens on the object side is defined as Fif. As long as the focal length of the lens on the image plane side is Fie, it is sufficient if it satisfies the conditional expression (2).

  The camera according to the present invention includes the macro lens according to the above embodiment as a photographing lens. Therefore, according to the camera of the present invention, it is possible to obtain a high-quality captured image by suppressing various aberrations when focusing on infinity and focusing on 1/2 times. Further, by providing a small and bright macro lens as a photographic lens, it is possible to obtain a camera that is small and convenient for carrying and can shoot in a relatively dark place.

L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 8th lens L9 9th lens

JP 2006-349920 A JP 2008-20656 A Japanese Patent No. 3800420 Japanese Patent Laid-Open No. 62-195617

Claims (5)

A macro lens having a two-group configuration in which a first lens group and a second lens group are arranged in order from the object side,
When focusing on an object at a close position from the state of focusing on an object at infinity, the first lens group moves more toward the object side than the second lens group, and the direction in which each lens group moves is changed. The first lens group and the second lens group are configured to extend in the same direction,
The first lens group includes, in order from the object side, a first lens having a positive refractive index that is convex on the object side, a second lens having a negative refractive index that is concave on the image side, and a positive refractive power A third lens having positive refractive power, a fifth lens having negative refractive power, a fifth lens having negative refractive power, and sixth and seventh lenses that are negative and positive cemented lenses having a concave shape on the object side. , An eighth lens having a positive refractive power, a ninth lens having a positive refractive power,
The second lens group is composed of two or more lenses,
A macro lens satisfying the following conditional expression (1), where the focal length of the first lens is fo1 and the focal length of the second lens is fo2.
−7.0 <fo1 / fo2 <−1.8 (1) 2. The macro lens according to claim 1, wherein the most object side lens and the most image plane side lens of the second lens group are configured by a combination of negative and positive, or positive and negative refractive power, and the object side. A macro lens characterized by satisfying the following conditional expression (2), where Fif is the focal length of the lens and Fie is the focal length of the lens on the image plane side.
-1.4 <Fif / Fie <-0.8 (2) 3. The macro lens according to claim 1, wherein the following conditional expression (3) is satisfied when the focal length of the first lens group is Fo and the focal length of the entire lens at infinity is Fz. lens.
0.5 <Fo / Fz <2.0 (3) A macro lens having a two-group configuration in which a first lens group and a second lens group are arranged in order from the object side,
When focusing on an object at a close position from the state of focusing on an object at infinity, the first lens group moves more toward the object side than the second lens group, and the direction in which each lens group moves is changed. The first lens group and the second lens group are configured to extend in the same direction,
A macro lens characterized by satisfying the following conditional expression (4) where β is a maximum photographing magnification.
β <−0.5 (4)   A camera comprising the macro lens according to claim 1 as a photographic lens.

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