JP2014139699A - Image forming optical system and imaging apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming optical system which is advantageous for sound insulation and protection against dust and is easy to reduce a radial direction and easy to secure optical performance and to provide an imaging apparatus using the image forming optical system.SOLUTION: The image forming optical system comprises, in order from an object side to an image surface side, a first lens group having positive refractive power, a second lens group having positive or negative refractive power, and a third lens group having positive refractive power and includes an aperture stop arranged between the object side surface of the first lens group and the object side surface of the second lens group. A lens closest to the object side in the first lens group and a lens closest to an image side in the third lens group are always fixed, the second lens group comprises one negative lens component, and the negative lens component is a single lens. Only the second lens group is moved on an optical axis, in focusing from a long distance to a close distance and the third lens group comprises a front sub-lens group having positive refractive power, arranged on the object side and a rear sub-lens group having negative refractive power, arranged on the image side, with the largest axial air space in the third lens group interposed therebetween.

Description

  The present invention relates to an optical system used in an imaging apparatus or the like, and particularly relates to an imaging optical system suitable for a single focus interchangeable lens in a mirrorless type camera and an imaging apparatus using the imaging optical system.

  2. Description of the Related Art Conventionally, there has been known an imaging optical system that keeps the entire length constant, adopts an inner focus method, and is advantageous for dustproofing and soundproofing during a focusing operation. The imaging optical systems disclosed in Patent Document 1 and Patent Document 2 are, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, an aperture stop, and a positive refractive power. The first lens group and the third lens group are always fixed, and the second lens group having negative refractive power is moved to the image side during focusing from a long distance to a short distance. Thereby, an imaging optical system having favorable optical performance while being advantageous for dustproof and soundproofing.

JP-A-11-160617 JP-A-2005-321574

  However, the imaging optical systems disclosed in Patent Literature 1 and Patent Literature 2 have a configuration in which a first lens group and a movable second lens group during focusing are arranged on the object side of the aperture stop. The distance between the first lens group and the aperture stop is large, and as a result, the diameter of the first lens group is large.

  The present invention has been made in view of the above-described problems, and provides an imaging optical system that is advantageous for soundproofing and dustproofing, can easily suppress the radial direction, and easily secure optical performance, and an imaging apparatus using the same. It is intended to do.

  In order to solve the above problems, an imaging optical system according to the present invention is as follows.

In order from the object side to the image plane side, the first lens group includes a first lens group having a positive refractive power, a second lens group having a positive or negative refractive power, and a third lens group having a positive refractive power. An aperture stop disposed between the object side surface of the second lens group and the object side surface of the second lens group, and the most object side lens in the first lens group and the most image side lens in the third lens group are always The second lens group is composed of one negative lens component, the negative lens component is a single lens, and only the second lens group moves along the optical axis during focusing from a long distance to a short distance, The third lens group includes a front sub lens group having a positive refractive power disposed on the object side and a rear sub lens having a negative refractive power disposed on the image side with the largest on-axis air gap in the third lens group interposed therebetween. Preferably it consists of a group.

  Hereinafter, the reason and effect | action which took such a structure are demonstrated.

  Dustproofness is achieved by using an inner focus type imaging optical system in which the most object side lens and the most image side lens of the imaging optical system are always fixed, and only the second lens group is moved in the optical axis direction during focusing. This is advantageous for ensuring soundproofing.

  By disposing the aperture stop closer to the object side than the second lens group, the effective diameter of the first lens group that most affects the size of the imaging optical system can be reduced, and the radial size of the optical system can be reduced. It becomes easy to make it smaller.

  In addition, by suppressing the radial size of the first lens group, it is easy to reduce the axial thickness of the first lens group having positive refractive power. This is advantageous for downsizing the imaging optical system and improves portability.

  On the other hand, considering the weight reduction of the imaging optical system, the securing of the moving range of the second lens group for focusing from a long distance to a close object, and aberration correction, the third lens group is separated from the aperture stop. become. At this time, since the aperture stop is closer to the object side than the second lens unit, the third lens unit having a positive refractive power is further away from the aperture stop. At this time, in order to perform correction including distortion, it is preferable that the third lens group has a configuration that considers both on-axis aberrations and off-axis aberrations.

  In the present invention, the object side is a front sub-lens group having positive refractive power across the largest axial air interval in the third lens group, and the image side of the axial air interval is a rear sub-lens group having negative refractive power. It is said.

  As described above, the sub-lens group having negative refractive power is arranged on the image side in the third lens group having positive refractive power, thereby maintaining the function of canceling the axial aberration in the front sub-lens group having positive refractive power. On the other hand, increasing the off-axis ray incident height is advantageous for securing a function of canceling off-axis aberrations (particularly distortion).

  Therefore, the above-described configuration is advantageous for soundproofing and dustproofing, and provides an imaging optical system that is advantageous for downsizing and ensuring optical performance.

  In the above-described invention, it is preferable that at least one of the following configurations is further satisfied.

  It is preferable that the first lens group and the third lens group are always fixed.

  Since a structure for moving the first lens group and the third lens group is not required, the mechanical configuration can be simplified, which is preferable.

Further, it is preferable that the rear sub lens group in the third lens group satisfies the following conditional expression (1).
−10 <f3r / f3G <−0.05 (1)
However,
f3r is a focal length of the rear sub lens group,
f3G is a focal length of the third lens group.

  By securing the negative refractive power of the rear sub-lens group so as not to fall below the lower limit of conditional expression (1), it becomes more advantageous for correction of on-axis aberrations and off-axis aberrations (particularly distortion aberration). In addition, the imaging optical system as a whole becomes a telephoto type, which leads to shortening of the overall length of the optical system.

  Overcorrection can be suppressed by appropriately suppressing the negative refractive power of the rear sub lens unit so as not to exceed the upper limit of conditional expression (1). In addition, the exit pupil is easily separated from the image plane, which is advantageous for reducing shading.

The imaging optical system according to any one of claims 1 to 3, wherein the second lens group satisfies the following conditional expression (2).
It is preferable.
0.1 <| f / f2G | <5.0 (2)
However,
f is a focal length of the imaging optical system,
f2G is a focal length of the second lens group.

  By securing a positive or negative refractive power so as not to fall below the lower limit of conditional expression (2), the focusing function can be secured.

  By appropriately suppressing the refractive power of the focusing lens group so as not to exceed the upper limit of conditional expression (2), it is advantageous for reducing the weight of the second lens group and reducing aberration fluctuations during movement of the second lens group.

Moreover, it is preferable that the axial distance between the front sub lens group and the rear sub lens group in the third lens group satisfies the following conditional expression (3).
0.01 <D3Gfr / f3G <0.5 (3)
However,
D3Gfr is the axial distance between the front sub lens group image side surface and the rear sub lens group object side surface in the third lens group,
f3G is a focal length of the third lens group.

  It is advantageous for correction of both on-axis aberrations and off-axis aberrations by appropriately securing the distance between the two sub lens groups so as not to fall below the lower limit of conditional expression (3) and to exceed the upper limit.

Moreover, it is preferable that the axial distance between the second lens group and the third lens group satisfies the following conditional expression (4).
0.22 <D2G3G / D1Gf3G <0.8 (4)
However,
D2G3G is the axial distance between the second lens group image side surface and the third lens group object side surface;
D1Gf3G is an axial distance between the first lens group object side surface and the third lens group object side surface.

  By securing an on-axis distance between the second lens group and the third lens group so as not to fall below the lower limit value of conditional expression (4), it is easy to cancel off-axis aberrations that occur in the first lens group. Become. This is also advantageous for reducing the weight of the imaging optical system.

  By appropriately restraining the axial distance between the second lens group and the third lens group so as not to exceed the upper limit of the conditional expression (4), it becomes easy to make the imaging optical system small, particularly as an interchangeable lens. When used, it is advantageous for downsizing.

  In addition, it is preferable that the axial distance between the second lens group and the third lens group is the largest of the axial air distances in the imaging optical system when focusing on the farthest distance.

  Ensuring an axial distance between the second lens group and the third lens group is advantageous for correcting off-axis aberrations. In particular, when the second lens group has a negative refractive power, the movement space of the second lens group is secured, and the close distance can be easily reduced.

  Next, the second lens group that performs focusing will be described.

  The second lens group preferably comprises two or less lenses.

  The lens group that moves during focusing can be reduced in weight, which is advantageous for reducing power consumption, improving AF speed, and accuracy during wobbling and focusing operations.

  Further, it may be any of the following.

  It is preferable that the second lens unit is composed of one negative lens component and moves to the image side during focusing from a long distance to a short distance.

  However, the lens component is a lens body in which only the object side surface and the image side surface are in contact with air, and means a single lens or a cemented lens. This is advantageous for reducing the weight of the second lens group.

  Furthermore, it is preferable that the negative lens component is a single lens. This is even more advantageous for weight reduction.

Furthermore, it is preferable that the negative lens component of the second lens group satisfies the following conditional expression (5).
−0.99 <SF <0.99 (5)
However,
SF = (R1 + R2) / (R1-R2),
R1 is a paraxial radius of curvature of the object-side lens surface of the negative lens component,
R2 is the radius of curvature of the image side lens surface of the negative lens component
It is.

  By preventing the absolute value of the curvature of the object-side lens surface of the negative lens component from becoming large so as not to fall below the lower limit of conditional expression (5), it becomes easy to suppress fluctuations in coma during focusing. The negative refractive power of the lens surface on the object side of the negative lens component is ensured so as not to exceed the upper limit of conditional expression (5), thereby contributing to aberration correction in the first lens group.

  In addition, it is preferable that the second lens group includes a single positive lens component and moves to the object side during focusing from a long distance to a short distance. However, the lens component is a lens body in which only the object side surface and the image side surface are in contact with air, and means a single lens or a cemented lens. This is advantageous for reducing the weight of the second lens group.

  The positive lens component is preferably a single lens. This is further advantageous for reducing the weight of the imaging optical system.

  In addition, it is preferable that the second lens group includes only two lenses, a negative lens and a positive lens. This is advantageous mainly for correcting chromatic aberration in the second lens group.

  Moreover, it is preferable that the negative lens and the positive lens in the second lens group are cemented. Thereby, it becomes easy to suppress the influence on the image due to the eccentricity of the lens.

  Furthermore, it is preferable that the second lens group includes only two negative lenses. Thereby, the negative refractive power can be shared by a plurality of negative lenses, which is mainly advantageous in reducing coma.

  In addition, it is preferable that the second lens group includes two lenses, a single lens having a convex surface facing the object side and a biconcave lens in order from the object side to the image side. As a result, higher-order aberrations that cannot be corrected by the biconcave lens can be corrected by the meniscus lens, which is advantageous in securing performance.

Further, it is preferable that the axial distance from the object side surface of the first lens group to the image side surface of the third lens group satisfies the following conditional expression (6).
0.68 <LTL / TL <0.90 (6)
However,
LTL is the axial distance from the object side surface of the first lens group to the image side surface of the third lens group,
TL is the sum of the back focus expressed by the LTL and the air conversion distance.

  By securing an axial distance from the first lens group object side surface to the third lens group image side surface so as not to fall below the lower limit of conditional expression (6), the third lens group can be brought closer to the image plane, and the imaging optical system This is advantageous for downsizing and ensuring optical performance. By separating the rear sub lens unit from the image plane so as not to exceed the upper limit of conditional expression (6), the incident angle on the image plane can be suppressed, which is advantageous in reducing shading.

  Further, when performing moving image shooting or high-speed AF, it is preferable that the focusing lens group is light. For this reason, the following should be performed for the aperture stop.

  It is preferable that the brightness stop is disposed on the image side of the first lens group. The focusing lens group is disposed in the vicinity of the aperture stop while reducing the size of the first lens group, which is advantageous for reducing the size and weight of the focusing lens group.

  Further, it is preferable that the brightness stop is always fixed together with the first lens group. Since the aperture stop does not move during the focusing operation, the weight of the moving member during focusing can be reduced. Therefore, it is advantageous for reducing power consumption, improving AF speed, and accuracy during AF operation (wobbling operation) during moving image shooting and high-speed AF operation.

  Furthermore, it is preferable that the first lens group has the following configuration.

  The first lens group preferably includes two positive lenses and at least one negative lens disposed on the object side of the brightness stop.

  Sharing a positive refractive power among a plurality of positive lenses and using a negative lens is advantageous in correcting spherical aberration, coma aberration, and chromatic aberration.

  The first lens group preferably includes a lens component having a positive refractive power and a cemented lens component having a positive lens and a negative lens and having a convex surface facing the object side in order from the object side to the image side. However, the lens component is a lens body in which only the object side surface and the image side surface are in contact with air, and means a single lens or a cemented lens.

  Sharing positive refractive power between the object side lens component and the image side lens component on the object side surface and using a negative lens for the image side lens component is advantageous for correcting spherical aberration, coma aberration, and chromatic aberration.

  Further, the third lens group preferably has the following configuration.

  It is preferable that the front sub lens group in the third lens group includes two lenses, and the rear sub lens group in the third lens group includes one lens component having a negative refractive power.

  Constructing the front sub-lens group with a plurality of lenses is advantageous in reducing aberrations by sharing the positive refractive power or canceling out aberrations. Further, the rear sub lens group is made into one lens component, which is advantageous for weight reduction.

  The front sub lens group in the third lens group preferably includes two positive lens components. Constructing the front sub-lens group with a plurality of lens components is advantageous in reducing aberrations by sharing the positive refractive power.

Furthermore, it is preferable that the effective diameters of the first lens group and the aperture stop satisfy the following conditional expression (7).
0.5 <ES / E1Gf <0.95 (7)
However,
ES is the effective diameter of the aperture stop,
E1Gf is the effective diameter of the object side surface of the first lens group,
When the effective diameter changes, it is the effective diameter at the time of full aperture.

  By making sure that the lower limit of conditional expression (7) is not exceeded, the first lens unit can be downsized. By preventing the aperture stop from being closer to the object side so as not to exceed the upper limit of conditional expression (7), it becomes easy to suppress the occurrence of barrel distortion.

In addition, it is preferable that the distance between the object-side lens surface and the image-side lens surface across the space in which the aperture stop is disposed satisfies the following conditional expressions (8) and (9).
0.03 <DSon_ax / f <0.19 (8)
0.03 <DSoff_ax / f <0.19 (9)
However,
DSon_ax is the distance on the optical axis between the lens surface on the object side and the lens surface on the image side that sandwiches the space where the aperture stop is disposed, and is the minimum value when the distance on the optical axis changes ,
DSoff_ax is a distance measured in the direction of the optical axis at the position where the maximum ray height of each of the lens surface on the object side and the lens surface on the image side across the space where the aperture stop is disposed, and is measured in the optical axis direction. Minimum value if the distance changes,
f is a focal length of the imaging optical system.

  A brightness diaphragm driving mechanism when the aperture size of the brightness diaphragm is made variable by securing a space in which the brightness diaphragm is arranged so as not to fall below the lower limit values of the conditional expressions (8) and (9). This is advantageous for securing the space for placement. It is advantageous for shortening the overall length by appropriately suppressing the space where the aperture stop is disposed so as not to exceed the upper limit values of the conditional expressions (8) and (9).

  These imaging optical systems are effective when used in an imaging apparatus such as a digital camera because the exit pupil is easily separated from the image plane and the performance is easily improved.

  An imaging apparatus having an imaging optical system and an imaging element having an imaging surface that is disposed on the image side of the imaging optical system and converts an optical image into an electrical signal. An imaging optical system is preferable.

  Unless otherwise specified, each of the above-described configurations is a configuration in which the farthest distance is in focus. It is more preferable that a plurality of the above-described configurations are satisfied simultaneously.

  Furthermore, in each conditional expression, it is preferable that the lower limit and / or the upper limit be further reduced to ensure the effect.

For conditional expression (1), it is more preferable to set the lower limit to −5.0, more preferably to −1.6.
More preferably, the upper limit value is -0.1, more preferably -0.15.

For conditional expression (2), it is more preferable to set the lower limit value to 0.4, more preferably 0.7.
More preferably, the upper limit value is 3.5 or even 2.5.

For conditional expression (3), it is more preferable to set the lower limit to 0.015, more preferably 0.017.
More preferably, the upper limit value is 0.35, more preferably 0.25.

For conditional expression (4), it is more preferable to set the lower limit value to 0.24, more preferably 0.25.
It is more preferable that the upper limit value is 0.7, further 0.6.

For conditional expression (5), it is more preferable to set the lower limit value to −0.85, more preferably to −0.7.
More preferably, the upper limit value is 0.85, more preferably 0.7.

For conditional expression (6), it is more preferable to set the lower limit value to 0.7, further 0.72.
More preferably, the upper limit value is 0.85, more preferably 0.81.

For conditional expression (7), it is more preferable to set the lower limit value to 0.55, more preferably 0.6.
It is more preferable that the upper limit value be 0.9 or 0.84.

For conditional expression (8), it is more preferable to set the lower limit value to 0.04, more preferably 0.05.
More preferably, the upper limit value is 0.17, more preferably 0.15.

In conditional expression (9), the lower limit value is more preferably 0.04, and even more preferably 0.05.
More preferably, the upper limit value is 0.17, more preferably 0.15.

  According to the present invention, it is possible to provide an imaging optical system that is advantageous for soundproofing and dustproofing and is easy to secure optical performance while being small in size. Furthermore, it is possible to provide an imaging apparatus using such an imaging optical system.

2 is a cross-sectional view of the optical system of Example 1. FIG. 6 is a cross-sectional view of an optical system according to Example 2. FIG. 6 is a sectional view of an optical system according to Example 3. FIG. 6 is a sectional view of an optical system according to Example 4. FIG. 10 is a cross-sectional view of an optical system according to Example 5. FIG. 10 is a cross-sectional view of an optical system according to Example 6. FIG. 10 is a cross-sectional view of an optical system according to Example 7. FIG. 10 is a sectional view of the optical system according to Example 8. FIG. 10 is a sectional view of an optical system according to Example 9. FIG. 10 is a sectional view of the optical system according to Example 10. FIG. FIG. 6 is a diagram illustrating various aberrations of the optical system of Example 1 in an infinitely focused state. FIG. 6 is a diagram illustrating various aberrations of the optical system of Example 2 in an infinitely focused state. FIG. 6 is a diagram illustrating various aberrations of the optical system according to Example 3 in an infinitely focused state. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 4 in an infinitely focused state. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 5 in a focused state at infinity. FIG. 12 is a diagram illustrating various aberrations of the optical system according to Example 6 in a focused state at infinity. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 7 in a focused state at infinity. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 8 in a focused state at infinity. FIG. 10 is a diagram illustrating various aberrations of the optical system according to Example 9 in a focused state at infinity. FIG. 11 is a diagram illustrating various aberrations of the optical system according to Example 10 in an infinitely focused state. It is sectional drawing of the lens interchangeable camera which used the wide angle lens of this invention as an interchangeable lens. It is a front perspective view which shows the external appearance of the digital camera by this invention. It is a rear view of the digital camera of FIG. It is a cross-sectional view of the digital camera of FIG. FIG. 23 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 22.

  Examples 1 to 10 of the present invention will be described. 1-10 is sectional drawing of the optical system of each Example. In addition, in each figure, five parallel plates change the pixel pitch from the object side while keeping the dust-proof filter F1 that splashes dust away by ultrasonic vibration, the IR-cut filter F2 with IR cut coating, and the flange back constant. The adjustment parallel plate F3, the low-pass filter F4, and the cover glass C that cancel the change in the thickness of the low-pass filter accompanying the above.

  FIG. 1 is a sectional view of the optical system according to the first embodiment. FIG. 1A is a cross-sectional view of the optical system at the time of focusing on infinity according to the first embodiment, and FIG.

  As shown in FIG. 1, the optical system of Example 1 includes a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens having a positive refractive power in order from the object side to the image side. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a positive meniscus lens L11 having a convex surface directed toward the object side, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconcave negative lens L22.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 2 is a sectional view of the optical system according to the second embodiment. 2A is a cross-sectional view of the optical system when focusing on infinity according to the second embodiment, and FIG. 2B is a cross-sectional view of the optical system when focusing close to the second embodiment.

  As shown in FIG. 2, the optical system according to the second embodiment includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a positive refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned at the 1st lens group G1.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, a positive meniscus lens L12 with a convex surface facing the object side, a negative meniscus lens L13 with a convex surface facing the object side, and a biconcave negative lens L14. And an aperture stop S and a positive meniscus lens L15 having a convex surface facing the image side.

  The second lens group G2 is composed of a positive meniscus lens L21 having a convex surface directed toward the object side.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a cemented lens SU31 of a biconcave negative lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a negative meniscus lens L33 having a convex surface directed toward the image side.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the object side with respect to focusing from infinity to the close.

  FIG. 3 is a sectional view of the optical system according to the third embodiment. 3A is a cross-sectional view of the optical system at the time of focusing on infinity according to the third embodiment, and FIG. 3B is a cross-sectional view of the optical system at the time of focusing close to the third embodiment.

  As shown in FIG. 3, the optical system of Example 3 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconcave negative lens L22.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a positive meniscus lens L31 having a convex surface directed toward the image side, and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 4 is a sectional view of the optical system of Example 4. 4A is a cross-sectional view of the optical system at the time of focusing on infinity according to the fourth embodiment, and FIG. 4B is a cross-sectional view of the optical system at the time of focusing close to the fourth embodiment.

  As shown in FIG. 4, the optical system of Example 4 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side and a negative meniscus lens L22 having a convex surface facing the object side.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 5 is a sectional view of the optical system of Example 5. 5A is a cross-sectional view of the optical system at the time of focusing on infinity according to the fifth embodiment, and FIG. 5B is a cross-sectional view of the optical system at the time of focusing close to the fifth embodiment.

  As shown in FIG. 5, the optical system of Example 5 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconcave negative lens L22.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 6 is a sectional view of the optical system according to the sixth embodiment. 6A is a cross-sectional view of the optical system at the time of focusing on infinity according to the sixth embodiment, and FIG. 6B is a cross-sectional view of the optical system at the time of focusing close to the sixth embodiment.

  As shown in FIG. 6, the optical system of Example 6 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a positive meniscus lens L21 having a convex surface facing the object side and a negative meniscus lens L22 having a convex surface facing the object side.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 7 is a sectional view of the optical system according to the seventh embodiment. 7A is a cross-sectional view of the optical system at the time of focusing on infinity according to Example 7, and FIG. 7B is a cross-sectional view of the optical system at the time of focusing close to Example 7 of the present invention.

  As shown in FIG. 7, the optical system of Example 7 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a biconcave negative lens 21 and a cemented lens SU21 including a positive meniscus lens L22 having a convex surface directed toward the object side.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a positive meniscus lens L32 having a convex surface directed toward the object side. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 8 is a sectional view of the optical system according to the eighth embodiment. FIG. 8A is a cross-sectional view of the optical system at the time of focusing on infinity according to the eighth embodiment, and FIG.

  As shown in FIG. 8, the optical system according to the eighth embodiment includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes, in order from the object side, a negative meniscus lens L21 having a convex surface directed toward the object side, and a biconcave negative lens L22.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 9 is a sectional view of the optical system according to Example 9. 9A is a cross-sectional view of the optical system at the time of focusing on infinity according to Example 9, and FIG. 9B is a cross-sectional view of the optical system at the time of focusing close to Example 9 of FIG.

  As shown in FIG. 9, the optical system according to the ninth embodiment includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, a biconvex positive lens L12, a negative meniscus lens L13 having a convex surface facing the image side, and a cemented lens SU11 of a biconcave negative lens L14.

  The second lens group G2 includes one biconcave negative lens L21.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

  FIG. 10 is a sectional view of the optical system according to Example 10. FIG. 10A is a cross-sectional view of the optical system at the time of focusing on infinity according to the tenth embodiment, and FIG.

  As shown in FIG. 10, the optical system of Example 10 includes, in order from the object side to the image side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a first lens group having a positive refractive power. It consists of three lens groups G3. Moreover, it has the aperture stop S arrange | positioned between the 1st lens group G1 and the 2nd lens group G2.

  The first lens group G1 includes, in order from the object side, a biconvex positive lens L11, and a cemented lens SU11 of a biconvex positive lens L12 and a biconcave negative lens L13.

  The second lens group G2 includes one biconcave negative lens L21.

  The third lens group G3 includes a front sub lens group G3F having a positive refractive power and a rear sub lens group G3R having a negative refractive power. The front sub lens group G3F includes a biconvex positive lens L31 and a biconvex positive lens L32. The rear sub lens group G3R includes a biconcave negative lens L33.

  The first lens group G1 and the third lens group G3 are always fixed. The second lens group G2 moves toward the image side with respect to focusing from infinity to the close.

Below, the numerical data of Examples 1-10 are shown. In the numerical data of Examples 1 to 10, r is the radius of curvature of the lens surface, d is the lens thickness and air spacing, nd and νd are the refractive index and Abbe number at the d-line (λ = 587.6 nm), and f is Focal length, Fno is an F number, ω is a half field angle (°), fb (in air) is an air-converted back focus, and IH is an image height.

Numerical example 1
Unit mm

Surface data surface number r d nd νd
1 37.765 3.43 1.81600 46.62
2 4789.512 0.10
3 22.665 5.15 1.59282 68.63
4 -68.251 1.00 2.00069 25.46
5 360.227 1.33
6 (Aperture) ∞ d6
7 108.885 1.00 1.59270 35.31
8 21.893 1.78
9 -67.118 0.99 1.51823 58.90
10 17.207 d10
11 67.696 2.46 1.77250 49.60
12 -50.277 0.10
13 39.865 3.67 1.59282 68.63
14 -32.036 3.54
15 -27.971 1.00 1.59270 35.31
16 102.879 8.99
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.38 2.21
d10 10.16 9.33

Various data
f 39.52 39.26
Fno 1.84 1.83
2ω (angle of view (°)) 31.41 30.00

fb (in air) 13.72
Total length (in air) 50.80
IH 11.15

Each group focal length first lens group 25.33
Second lens group -16.32
Third lens group 25.46

Distance between objects at close focus 85cm

Numerical example 2
Unit mm

Surface data surface number r d nd νd
1 48.872 3.96 1.81600 46.62
2 -590.823 0.10
3 21.656 3.50 1.60311 60.64
4 35.232 2.46
5 140.222 1.00 1.64769 33.79
6 17.832 5.47
7 -22.616 1.00 1.58144 40.75
8 89.969 2.05
9 (Aperture) ∞ 2.01
10 -178.438 3.03 1.77250 49.60
11 -25.617 d11
12 22.919 3.50 1.45650 90.27
13 328.581 d13
14 -127.951 3.20 1.80000 29.84
15 67.776 3.43 1.77250 49.60
16 -34.180 6.45
17 -16.934 1.00 1.51742 52.43
18 -33.850 8.99
19 ∞ 0.65 1.51633 64.14
20 ∞ 0.85
21 ∞ 0.82 1.54424 70.86
22 ∞ 0.76 1.51300 61.08
23 ∞ 1.08 1.54424 70.86
24 ∞ 0.45
25 ∞ 0.80 1.50700 63.38
26 ∞ 0.75
Image plane ∞

Infinity close
d11 3.73 0.29
d13 11.88 15.33

Various data
f 44.78 44.52
Fno 1.84 1.82
2ω (angle of view (°)) 28.07 26.38

fb (in air) 13.73
Total length (in air) 71.50
IH 11.15

Each group focal length first lens group 237.50
Second lens group 53.78
Third lens group 387.12

Distance between objects at close focus 85cm

Numerical example 3
Unit mm

Surface data surface number r d nd νd
1 34.809 3.78 1.81600 46.62
2 -907.405 0.10
3 26.975 4.19 1.59282 68.63
4 -106.315 1.00 2.00069 25.46
5 80.103 1.90
6 (Aperture) ∞ d6
7 32.930 1.00 1.59270 35.31
8 20.677 2.43
9 -46.936 0.99 1.51633 64.14
10 19.852 d10
11 -933.621 1.94 1.77250 49.60
12 -44.683 0.10
13 32.400 3.85 1.59282 68.63
14 -37.244 6.17
15 -30.511 1.00 1.63980 34.46
16 162.770 8.99
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.39 2.69
d10 11.60 10.29

Various data
f 44.23 43.80
Fno 1.84 1.82
2ω (angle of view (°)) 28.21 26.74

fb (in air) 13.72
Total length (in air) 55.17
IH 11.15

Each group focal length first lens group 31.39
Second lens group -20.73
Third lens group 29.24

Distance between objects at close focus 85cm

Numerical example 4
Unit mm

Surface data surface number r d nd νd
1 71.959 2.27 1.81600 46.62
2 -2188.347 0.10
3 44.474 4.55 1.59282 68.63
4 -56.489 1.00 1.80518 25.42
5 278.334 1.65
6 (Aperture) ∞ d6
7 14.646 2.19 1.90366 31.32
8 16.586 2.18
9 40.144 0.99 1.81600 46.62
10 15.230 d10
11 91.406 2.27 1.77250 49.60
12 -62.593 0.20
13 24.430 4.297 1.59282 68.63
14 -70.331 3.18
15 -47.825 1.00 1.59270 35.31
16 20.749 8.99
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.38 5.98
d10 21.38 16.78

Various data
f 46.81 46.28
Fno 1.84 1.82
2ω (angle of view (°)) 26.85 25.30

fb (in air) 13.72
Total length (in air) 62.36
IH 11.15

Each group focal length first lens group 53.22
Second lens group -55.12
Third lens group 41.74

Distance between objects at close focus 85cm

Numerical example 5
Unit mm

Surface data surface number r d nd νd
1 41.881 4.04 1.81600 46.62
2 -585.377 0.10
3 30.078 4.81 1.59282 68.63
4 -105.483 1.00 2.00069 25.46
5 124.383 1.76
6 (Aperture) ∞ d6
7 49.317 1.00 1.59270 35.31
8 28.403 2.24
9 -65.163 0.99 1.51742 52.43
10 21.202 d10
11 61.511 3.13 1.77250 49.60
12 -58.914 0.10
13 50.956 3.37 1.59282 68.63
14 -57.226 7.18
15 -34.734 1.00 1.85026 32.27
16 114.221 8.98
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.38 2.89
d10 16.58 15.07

Various data
f 49.00 48.03
Fno 1.84 1.81
2ω (angle of view (°)) 25.53 24.20

fb (in air) 13.71
Total length (in air) 62.40
IH 11.15

Each group focal length first lens group 33.52
Second lens group -23.99
Third lens group 35.65

Numerical example 6
Unit mm

Surface data surface number r d nd νd
1 62.734 2.67 1.81600 46.62
2 -695.249 0.10
3 39.109 4.43 1.59282 68.63
4 -77.930 1.00 1.84666 23.78
5 117.525 2.43
6 (Aperture) ∞ d6
7 15.591 2.13 1.80518 25.42
8 16.298 3.24
9 88.222 1.00 1.64000 60.08
10 17.346 d10
11 101.936 2.19 1.77250 49.60
12 -64.487 0.10
13 27.238 4.08 1.59282 68.63
14 -67.099 4.39
15 -49.982 1.00 1.85026 32.27
16 27.903 8.99
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.39 5.32
d10 18.75 14.83

Various data
f 48.89 48.08
Fno 1.84 1.81
2ω (angle of view (°)) 25.73 24.18

fb (in air) 13.73
Total length (in air) 62.63
IH 11.15

Each group focal length first lens group 50.75
Second lens group -45.86
Third lens group 40.97

Distance between objects at close focus 85cm

Numerical example 7
Unit mm

Surface data surface number r d nd νd
1 42.023 3.30 1.81600 46.62
2 -565.225 0.10
3 41.851 4.49 1.59282 68.62
4 -71.032 1.00 2.00069 25.46
5 120.818 2.10
6 (Aperture) ∞ d6
7 -263.487 1.00 1.51742 52.43
8 18.674 3.00 1.80518 25.42
9 20.594 d9
10 60.394 3.04 1.81600 46.62
11 -45.960 0.10
12 26.632 4.91 1.59282 68.62
13 115.266 4.04
14 -65.825 1.00 1.74077 27.79
15 26.799 9.00
16 ∞ 0.65 1.51633 64.14
17 ∞ 0.85
18 ∞ 0.82 1.54424 70.86
19 ∞ 0.76 1.51300 61.08
20 ∞ 1.08 1.54424 70.86
21 ∞ 0.45
22 ∞ 0.80 1.50700 63.38
23 ∞ 0.75
Image plane ∞

Infinity close
d6 1.91 5.27
d9 21.41 18.06

Various data
f 46.63 46.22
Fno 1.84 1.83
2ω (angle of view (°)) 26.99 25.11

fb (in air) 13.73
Total length (in air) 65.14
IH 11.15

Each group focal length first lens group 44.59
Second lens group -40.31
Third lens group 39.95

74cm distance between objects in close-up focus

Numerical example 8
Unit mm

Surface data surface number r d nd νd
1 39.785 3.75 1.81600 46.62
2 -986.669 0.10
3 27.350 4.56 1.59282 68.63
4 -110.314 1.00 2.00069 25.46
5 126.007 1.71
6 (Aperture) ∞ d6
7 49.880 1.00 1.59270 35.31
8 25.474 2.24
9 -59.709 0.99 1.51742 52.43
10 19.810 d10
11 96.391 2.81 1.77250 49.60
12 -61.003 0.10
13 43.033 4.00 1.59282 68.63
14 -40.931 6.64
15 -32.349 1.00 1.74950 35.28
16 143.481 8.99
17 ∞ 0.65 1.51633 64.14
18 ∞ 0.85
19 ∞ 0.82 1.54424 70.86
20 ∞ 0.76 1.51300 61.08
21 ∞ 1.08 1.54424 70.86
22 ∞ 0.45
23 ∞ 0.80 1.50700 63.38
24 ∞ 0.75
Image plane ∞

Infinity close
d6 1.38 2.65
d10 13.91 12.64

Various data
f 46.71 45.92
Fno 1.84 1.81
2ω (angle of view (°)) 26.73 25.41

fb (in air) 13.72
Total length (in air) 58.90
IH 11.15

Each group focal length first lens group 30.82
Second lens group -21.30
Third lens group 32.72

Distance between objects at close focus 85cm

Numerical example 9
Unit mm

Surface data surface number r d nd νd
1 50.728 3.63 1.81600 46.62
2 -296.362 0.10
3 28.253 5.23 1.59282 68.62
4 -77.351 1.00 1.84666 23.78
5 -6928.538 1.00 1.59270 35.31
6 34.493 3.44
7 (Aperture) ∞ d7
8 -98.588 0.99 1.49700 81.54
9 22.343 d9
10 102.097 2.78 1.75500 52.32
11 -54.433 0.10
12 30.424 3.96 1.59282 68.63
13 -69.822 5.79
14 -43.217 1.00 1.68893 31.07
15 36.958 8.98
16 ∞ 0.65 1.51633 64.14
17 ∞ 0.85
18 ∞ 0.82 1.54424 70.86
19 ∞ 0.76 1.51300 61.08
20 ∞ 1.08 1.54424 70.86
21 ∞ 0.45
22 ∞ 0.80 1.50700 63.38
23 ∞ 0.75
Image plane ∞

Infinity close
D7 1.96 9.05
d9 18.82 11.73

Various data
f 46.95 45.75
Fno 1.84 1.80
2ω (angle of view (°)) 26.83 22.63

fb (in air) 13.72
Total length (in air) 63.51
IH 11.15

Each group focal length first lens group 44.18
Second lens group -36.55
Third lens group 36.76

40cm distance between objects in close-up focus

Numerical example 10
Unit mm

Surface data surface number r d nd νd
1 38.210 4.85 1.81600 46.62
2 -696.429 0.10
3 38.546 6.04 1.59282 68.62
4 -69.680 1.00 2.00069 25.46
5 79.121 2.20
6 (Aperture) ∞ d6
7 -84.999 0.79 1.49700 81.54
8 22.376 d8
9 183.082 2.05 1.81600 46.62
10 -53.617 0.10
11 30.944 4.65 1.59282 68.62
12 -71.308 7.41
13 -41.882 1.00 1.72151 29.23
14 40.015 8.94
15 ∞ 0.65 1.51633 64.14
16 ∞ 0.85
17 ∞ 0.82 1.54424 70.86
18 ∞ 0.76 1.51300 61.08
19 ∞ 1.08 1.54424 70.86
20 ∞ 0.45
21 ∞ 0.80 1.50700 63.38
22 ∞ 0.75
Image plane ∞

Infinity close
d6 1.89 7.21
d8 19.64 14.32

Various data
f 47.46 46.79
Fno 1.84 1.82
2ω (angle of view (°)) 26.64 23.20

fb (in air) 13.68
Total length (in air) 65.37
IH 11.15

Each group focal length first lens group 44.81
Second lens group -35.55
Third lens group 36.65

50cm distance between objects in close-up focus

  FIGS. 11 to 20 are graphs showing various aberrations of the optical systems of Examples 1 to 10. FIGS. In each drawing, (a) shows various aberrations in the infinite focus state, and (b) shows various aberrations in the closest focus state. Spherical aberration and lateral chromatic aberration are numerical values at respective wavelengths of 435.8 nm (g line: one-dot chain line), 587.6 nm (d line: solid line), and 656.3 nm (C line: wavy line). Astigmatism, the solid line indicates the sagittal image plane, and the dotted line indicates the meridional image plane. FNO represents the F number, and IH represents the image height.

Next, the values of conditional expressions (1) to (9) in the above embodiments will be shown.

Conditional Example Example 1 Example 2 Example 3 Example 4 Example 5
(1) -1.45 -0.17 -1.37 -0.58 -0.88
(2) -2.42 0.83 -2.13 -0.85 -2.04
(3) 0.14 0.02 0.21 0.08 0.20
(4) 0.39 0.27 0.41 0.57 0.49
(5)--1.15---
(6) 0.73 0.81 0.75 0.78 0.78
(7) 0.61 0.63 0.70 0.83 0.71
(8) 0.07 0.09 0.07 0.06 0.06
(9) 0.07 0.07 0.09 0.14 0.07

Conditional Example Example 6 Example 7 Example 8 Example 9 Example 10
(1) -0.65 -0.64 -1.07 -0.78 -0.77
(2) -1.07 -1.16 -2.19 -1.28 -1.33
(3) 0.11 0.10 0.20 0.16 0.20
(4) 0.50 0.56 0.45 0.52 0.54
(5)---0.63 0.58
(6) 0.78 0.79 0.77 0.78 0.79
(7) 0.80 0.76 0.71 0.66 0.67
(8) 0.08 0.09 0.07 0.11 0.09
(9) 0.14 0.07 0.07 0.07 0.06

  FIG. 21 is a cross-sectional view of a single-lens mirrorless camera as an electronic image pickup apparatus using a lens of the present invention and using a small CCD or CMOS as an image pickup device. In FIG. 21, 1 is a single-lens mirrorless camera, 2 is a photographic lens system disposed in a lens barrel, 3 is a lens barrel mount that allows the photographic lens system 2 to be detachably attached to the single-lens mirrorless camera 1, Type mounts and bayonet type mounts are used. In this example, a bayonet type mount is used. Reference numeral 4 denotes an image sensor surface, and 5 denotes a back monitor.

  As the taking lens system 2 of the single-lens mirrorless camera 1 having such a configuration, for example, the lens of the present invention shown in the first to tenth embodiments is used.

  According to the present invention as described above, as an interchangeable lens suitable for a single-lens mirrorless type digital camera, various aberrations such as distortion, chromatic aberration, and curvature of field are well corrected, and a small number of compact lenses that ensure telecentricity. It becomes possible to provide a simple optical system.

  22 to 24 are conceptual diagrams of the configuration of another imaging apparatus according to the present invention in which a lens is incorporated in the photographing optical system 41. FIG. 22 is a front perspective view showing the appearance of the digital camera 40, FIG. 23 is a rear view thereof, and FIG. 24 is a schematic cross-sectional view showing the configuration of the digital camera 40.

  In this example, the digital camera 40 includes a photographic optical system 41 positioned on the photographic optical path 42, a finder optical system 43 positioned on the finder optical path 44, a shutter button 45, a pop-up flash 46, a liquid crystal display monitor 47, and the like. In addition, when a shutter button 45 disposed on the upper portion of the camera 40 is pressed, photographing is performed through the photographing optical system 41, for example, the lens of the first embodiment, in conjunction therewith. The object image formed by the photographing optical system 41 is formed on the image pickup surface (photoelectric conversion surface) of the CCD 49 as an image pickup element provided in the vicinity of the image forming surface. The object image received by the CCD 49 is displayed as an electronic image on the liquid crystal display monitor 47 provided on the back of the camera or the finder image display element 54 via the processing means 51. Further, the processing means 51 is connected to a recording means 52 so that a photographed electronic image can be recorded.

  The recording unit 52 may be provided separately from the processing unit 51, or may be configured to perform recording and writing electronically using a flexible disk, a memory card, an MO, or the like. Further, it may be configured as a silver salt camera in which a silver salt film is arranged in place of the CCD 49.

  Further, a finder eyepiece lens 59 is disposed on the finder optical path 44. The object image displayed on the finder image display element 54 is magnified by the finder eyepiece lens 59 and adjusted to a diopter that is easy for the observer to see, and is guided to the observer eyeball E. A cover member 50 is disposed on the exit side of the finder eyepiece lens 59.

  FIG. 25 is a block diagram showing the internal circuitry of the main part of the digital camera 40. In the following description, the processing unit 51 includes, for example, the CDS / ADC unit 24, the temporary storage memory 17, the image processing unit 18, and the like, and the storage unit 52 includes, for example, the storage medium unit 19 and the like.

  As shown in FIG. 25, the digital camera 40 is connected to the operation unit 12, the control unit 13 connected to the operation unit 12, and the control signal output port of the control unit 13 via buses 14 and 15. An imaging drive circuit 16, a temporary storage memory 17, an image processing unit 18, a storage medium unit 19, a display unit 20, and a setting information storage memory unit 21 are provided.

  The temporary storage memory 17, the image processing unit 18, the storage medium unit 19, the display unit 20, and the setting information storage memory unit 21 are configured to be able to input or output data with each other via the bus 22. The imaging drive circuit 16 is connected with a CCD 49 and a CDS / ADC unit 24.

  The operation unit 12 includes various input buttons and switches, and is a circuit that notifies the control unit of event information input from the outside (camera user) via these input buttons and switches. The control unit 13 is a central processing unit composed of, for example, a CPU, and has a built-in program memory (not shown). The control unit 13 is input by a camera user via the operation unit 12 according to a program stored in the program memory. This circuit controls the entire digital camera 40 in response to the instruction command.

  The CCD 49 receives an object image formed via the photographing optical system 41 according to the present invention. The CCD 49 is an image pickup element that is driven and controlled by the photographing drive circuit 16 and converts the light amount of each pixel of the object image into an electrical signal and outputs it to the CDS / ADC unit 24.

  The CDS / ADC unit 24 amplifies the electric signal input from the CCD 49 and performs analog / digital conversion, and temporarily generates the raw video data (Bayer data, hereinafter referred to as RAW data) that has just been subjected to the amplification and digital conversion. It is a circuit that outputs to the memory 17.

  The temporary storage memory 17 is a buffer made of, for example, SDRAM or the like, and is a memory device that temporarily stores the RAW data output from the CDS / ADC unit 24. The image processing unit 18 reads out the RAW data stored in the temporary storage memory 17 or the RAW data stored in the storage medium unit 19, and performs various corrections including distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs image processing electrically.

  The storage medium unit 19 detachably mounts a card-type or stick-type recording medium made of, for example, a flash memory, and RAW data transferred from the temporary storage memory 17 to the card-type or stick-type flash memory. It is a control circuit of an apparatus that records and holds image data processed by the image processing unit 18.

  The display unit 20 includes a liquid crystal display monitor 47 and a finder image display element 54, and is a circuit that displays an image, an operation menu, and the like on the liquid crystal display monitor 47 and the finder image display element 54. The setting information storage memory unit 21 stores a ROM unit in which various image quality parameters are stored in advance, and an image quality parameter selected by an input operation of the operation unit 12 among the image quality parameters read from the ROM unit. RAM section is provided. The setting information storage memory unit 21 is a circuit for controlling input / output to / from these memories.

  According to the present invention, the digital camera 40 configured in this manner is compact with a small number of components, in which various aberrations such as chromatic aberration and curvature of field are corrected well, and telecentricity is ensured while performing distortion correction to some extent. An imaging apparatus using a wide-angle optical system can be provided.

  The present invention may be applied not only to a so-called compact digital camera that photographs a general subject as described above, but also to a surveillance camera or the like that requires a wide angle of view.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group G3F ... Front sub lens group G3R ... Rear sub lens group S ... Brightness stop I ... Image plane 1 ... Interchangeable lens camera 2 ... Shooting lens system DESCRIPTION OF SYMBOLS 3 ... Mount part 4 ... Image pick-up element surface 5 ... Back monitor 12 ... Operation part 13 ... Control part 14, 15 ... Bus 16 ... Imaging drive circuit 17 ... Temporary memory 18 ... Image processing part 19 ... Storage medium part 20 ... Display part 21 ... Setting information storage memory unit 22 ... Bus 24 ... CDS / ADC unit 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 43 ... Viewfinder optical system 44 ... Viewfinder optical path 45 ... Shutter button 46 ... Pop-up strobe 47 ... LCD monitor 49 ... CCD
DESCRIPTION OF SYMBOLS 50 ... Cover member 51 ... Processing means 52 ... Recording means 54 ... Image display element 59 for finder ... Eyepiece for finder

Claims (18)

In order from the object side to the image plane side,
A first lens unit having positive refractive power;
A second lens group having positive or negative refractive power;
It consists of a third lens group with positive refractive power,
An aperture stop disposed between the object side surface of the first lens group and the object side surface of the second lens group;
The most object side lens in the first lens group and the most image side lens in the third lens group are always fixed,
The second lens group comprises one negative lens component;
The negative lens component is a single lens;
During focusing from a long distance to a short distance, only the second lens group moves along the optical axis,
The third lens group includes a front sub lens group having a positive refractive power disposed on the object side and a rear sub lens having a negative refractive power disposed on the image side with the largest axial air space in the third lens group interposed therebetween. An imaging optical system comprising a lens group. 2. The imaging optical system according to claim 1, wherein the first lens group and the third lens group are always fixed. The imaging optical system according to claim 1, wherein the rear sub lens group in the third lens group satisfies the following conditional expression (1).
−10 <f3r / f3G <−0.05 (1)
However,
f3r is a focal length of the rear sub lens group,
f3G is a focal length of the third lens group. The imaging optical system according to any one of claims 1 to 3, wherein the second lens group satisfies the following conditional expression (2).
0.1 <| f / f2G | <5.0 (2)
However,
f is a focal length of the imaging optical system,
f2G is a focal length of the second lens group. 5. The axial distance between the front sub-lens group and the rear sub-lens group in the third lens group satisfies the following conditional expression (3): 5. The imaging optical system according to any one of the above.
0.01 <D3Gfr / f3G <0.5 (3)
However,
D3Gfr is the axial distance between the front sub lens group image side surface and the rear sub lens group object side surface in the third lens group,
f3G is a focal length of the third lens group. 6. The axial distance between the second lens group and the third lens group satisfies the following conditional expression (4), according to any one of claims 1 to 5: The imaging optical system described.
0.22 <D2G3G / D1Gf3G <0.8 (4)
However,
D2G3G is the axial distance between the second lens group image side surface and the third lens group object side surface;
D1Gf3G is an axial distance between the first lens group object side surface and the third lens group object side surface. The axial distance between the second lens group and the third lens group at the time of focusing on the farthest distance is the largest of the axial air distances in the imaging optical system. The imaging optical system according to any one of claims 1 to 6. The imaging optical system according to any one of claims 1 to 7 , wherein the negative lens component of the second lens group satisfies the following conditional expression (5).
−0.99 <SF <0.99 (5)
However,
SF = (R1 + R2) / (R1-R2),
R1 is a paraxial radius of curvature of the object-side lens surface of the negative lens component,
R2 is the radius of curvature of the image side lens surface of the negative lens component
It is. Any one of claims 1 to 8, characterized in that the axial distance from the object side surface of the first lens group to the image side surface of the third lens group satisfies the conditional expression (6) below The imaging optical system described in 1.
0.68 <LTL / TL <0.90 (6)
However,
LTL is the axial distance from the object side surface of the first lens group to the image side surface of the third lens group,
TL is the sum of the back focus expressed by the LTL and the air conversion distance. An imaging optical system according to any one of claims 1 to 9, wherein the aperture stop is disposed on the image side of the first lens group. An imaging optical system according to any one of claims 1 to 10, wherein the aperture stop is always fixed with the first lens group. The said 1st lens group has two positive lenses arrange | positioned at the object side of the said aperture stop, and at least 1 negative lens, The one of Claim 1 thru | or 11 characterized by the above-mentioned. The imaging optical system described. The first lens group is in order from the object side to the image side.
13. The connection according to claim 1 , comprising: a lens component having a positive refractive power; and a cemented lens component having a positive lens and a negative lens and having a convex surface facing the object side. Image optics. The front sub lens group in the third lens group has two lenses,
The imaging optical system according to any one of claims 1 to 13 , wherein the rear sub-lens group in the third lens group includes one lens component having a negative refractive power. The imaging optical system according to claim 1 , wherein the front sub lens group in the third lens group includes two positive lens components. Furthermore, the imaging optical system according to any one of 15 claims 1 effective diameter of the diaphragm the said brightness and the first lens group satisfies the following condition (7).
0.5 <ES / E1Gf <0.95 (7)
However,
ES is the effective diameter of the aperture stop,
E1Gf is the effective diameter of the object side surface of the first lens group,
When the effective diameter changes, it is the effective diameter at the time of full aperture. The distance between the object-side lens surface and the image-side lens surface across the space in which the aperture stop is disposed satisfies the following conditional expressions (8) and (9): The imaging optical system according to any one of 1 to 16 .
0.03 <DSon_ax / f <0.19 (8)
0.03 <DSoff_ax / f <0.19 (9)
However,
DSon_ax is the distance on the optical axis between the lens surface on the object side and the lens surface on the image side that sandwiches the space where the aperture stop is disposed, and is the minimum value when the distance on the optical axis changes ,
DSoff_ax is a distance measured in the direction of the optical axis at the position where the maximum ray height of each of the lens surface on the object side and the lens surface on the image side across the space where the aperture stop is disposed, and is measured in the optical axis direction. Minimum value if the distance changes,
f is a focal length of the imaging optical system. The imaging optical system according to any one of claims 1 to 17 ,
And an imaging device having an imaging surface disposed on the image side of the imaging optical system and converting an optical image into an electrical signal.

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