JP2013186458A - Inner focus lens system and imaging apparatus including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inner focus lens system having a focus lens group in which various aberrations are corrected sufficiently and video imaging is also taken into consideration, and an imaging apparatus including the same.SOLUTION: An inner focus lens system includes, in order from an object side, a positive first lens group, an aperture stop, and a positive second lens group. The first lens group includes, in order from the object side, a negative first lens component, a positive second lens component, and a positive third lens component. At least one of the second lens component and the third lens component is a cemented lens component. In a state where the position of the first lens group and the position of the aperture stop are fixed, the second lens group is integrally moved to the object side, so as to perform focusing operation from an infinity object to a short-distance object, to achieve a predetermined configuration.

Description

The present invention relates to an inner focus lens system that performs a focusing operation by moving a lens group other than the most object side lens group. In addition, the present invention relates to an imaging apparatus such as a digital camera or a video camera provided with such an inner focus lens system.
More preferably, the present invention relates to an inner focus lens system that is used in an interchangeable lens system and that is preferable for a small-sized wide-angle lens that enables moving image shooting, and an imaging apparatus using the same.

Conventionally, interchangeable lenses for digital cameras are required to be downsized, ensure telecentricity, and have a large aperture. In recent years, a technology for correcting distortion to some extent by an electrical signal has been proposed due to technical progress of electronic image pickup devices in recent years. In aberration correction, it is not necessary to pay close attention to distortion correction.
In recent years, an interchangeable lens corresponding to a moving image shooting function of a camera body has been studied even in an interchangeable lens digital camera.
With conventional cameras for still image shooting, the objective was to cut off an instant shooting opportunity, so it is only necessary to focus on the target subject at the moment of shooting after deciding on the composition, and there is a need for a function for that purpose. It was done. Specifically, a so-called phase difference type autofocus (AF) function is employed, and the AF method has both the speed and accuracy of the focusing operation.
However, in video shooting, some professional video cameras are focused by a skilled cameraman with manual focus (MF). However, many consumer video cameras always use an AF system according to the subject distance. It is necessary to keep in focus. As a method for this, a contrast AF method (so-called hill-climbing method) using an image sensor is employed.
Furthermore, in order to maintain the in-focus state, the change in contrast of the captured image is measured by always moving the wobbling lens group by a minute amount around the optical axis direction of the in-focus position (called wobbling). If it is determined that the in-focus state has changed, the focus lens group is appropriately moved to operate again to focus again. Since this wobbling function requires a very high speed operation in accordance with the frame rate, the lens group used for wobbling is required to be reduced in weight.
The wobbling lens group is always moved, but the moving range is within the depth of focus. Accordingly, the focus shift during wobbling is controlled so that it cannot be recognized. However, when the change in image magnification is large, the image always appears to fluctuate, which is very unnatural. Accordingly, it is an important requirement to keep the magnification change during wobbling small.
Cameras capable of shooting moving images often have a recording function. When the autofocus operation is performed, noise is recorded if the sound generated from the interchangeable lens itself is loud. Therefore, in a lens system that supports the movie shooting function, it is possible to reduce the number of groups (focus lens group and aperture stop) that move during the focusing operation in order to sufficiently reduce the sound generated during autofocusing. Desired.
Patent Documents 1 and 2 propose an imaging lens system used for a camera with F2.1 or less and an angle of view of 60 ° or more.
Patent Documents 3, 4, and 6 propose an inner focus type inner focus lens system using a positive second lens group. Further, Patent Document 6 proposes an inner focus lens system in which fluctuations in optical performance during focusing operation are corrected by moving the two focus lens groups differently.
In the case of the lens system described in Patent Document 3, the focus lens group is reduced in weight compared to a lens system in which the entire lens system is extended and focused because of the inner focus type with the second lens group having a positive refractive power. Has been. In the case of the lens systems described in Patent Documents 4, 5, and 6, a large aperture of F1.4 and telecentricity can be secured. In addition, because of the rear focus type inner focus, the focus lens group is reduced in weight as compared with the entire extension type imaging lens system.

JP 2000-32490 A JP 2004-101880 A Japanese Patent Laid-Open No. 08-313803 Japanese Patent Laid-Open No. 06-308385 JP 2009-086221 A JP 2010-066432 A

  However, in the lens systems described in Patent Documents 1 and 2, there is no description about the focusing operation. In the lens systems described in Patent Documents 3 to 6, the aperture stop moves together with the focus lens group during the focusing operation. During the focusing operation, the weight of the unit related to the aperture stop is added to the focus lens group, so that the load for performing the focusing operation and wobbling is large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. A focus lens in which various aberrations such as spherical aberration and sagittal coma are satisfactorily corrected even when sufficient brightness and angle of view are ensured, and in consideration of moving image shooting. An object of the present invention is to provide an inner focus lens system having a group.
Furthermore, it aims at providing the imaging device provided with such a lens system.

In view of the above problems, the basic configuration of the inner focus lens system of the present invention is:
From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
Have
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
At least one of the second lens component and the third lens component is a cemented lens component;
A focusing operation from an object at infinity to a near object is performed by moving the second lens group integrally to the object side in a state where the position of the first lens group and the position of the aperture stop are fixed. Basic configuration.

The basic configuration of the inner focus lens system of the present invention is different from the retrofocus type in which the lens system before the aperture stop has negative refractive power and the lens system after the aperture stop has positive refractive power. The first lens unit, which is a lens system before the stop, has positive refractive power. With this configuration, the light ray height on the image side can be suppressed to be lower than that of the aperture stop, which is advantageous for downsizing the second lens unit having a positive refractive power after the aperture stop.
For this reason, since the second lens group can be reduced in weight, using the second lens group as a lens group for wobbling or focusing operation is advantageous for speeding up the operation.
In addition, regarding the configuration of the first lens group, the first lens group is negatively refracted in order from the object side in order to achieve a wide angle of view while satisfactorily correcting spherical aberration and sagittal coma flare by increasing the aperture. The first lens component has a positive power, the second lens component has a positive refractive power, and the third lens component has a positive refractive power. By disposing the first lens component having a negative refractive power on the object side, it is easy to ensure the back focus even when the angle of view is widened.
In particular, since the first lens unit has positive refracting power when the lens component has only negative refracting power and only positive refracting power in order from the object side, the first lens unit has a positive refracting power. Ingredient power is too strong. In this case, spherical aberration when the aperture is increased and sagittal coma flare when the angle of view is increased are likely to be large, and it is difficult to correct these in the first lens group.
Therefore, in the present invention, a plurality of positive lens components including a second lens component having a positive refracting power and a third lens component having a positive refracting power are arranged in the first lens group, so that spherical aberration and sagittal coma flare can be favorably corrected. Making it possible.
Further, by using at least one of the second lens component having a positive refractive power and the third lens component having a positive refractive power as a cemented lens component, it becomes possible to satisfactorily correct curvature of field and chromatic aberration.
In addition, by moving the second lens group to the object side with the position of the first lens group and the position of the aperture stop fixed, it is advantageous for reducing the operation sound during the focusing operation.

In such a basic configuration of the inner focus lens system, the present invention of the first aspect satisfies the following configuration.
The second lens group includes, in order from the object side to the image side, a fourth lens component having a negative refractive power and a fifth lens component having a positive refractive power.
The following conditional expressions (1) and (2) are satisfied.
1.0 ≦ f2 / f ≦ 1.7 (1)
| F / EXP | ≦ 0.43 (2)
However,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
EXP is the distance on the optical axis from the exit pupil position of the inner focus lens system to the paraxial image plane at the time of focusing on an object at infinity, and represents the sign when the exit pupil is closer to the object side than the paraxial image plane. It is defined as minus.

  Regarding the configuration of the second lens group, it is desirable to have a fourth lens component having a negative refractive power and a fifth lens component having a positive refractive power in order from the object side in order to correct spherical aberration and chromatic aberration. This is also preferable in order to reduce aberration fluctuations accompanying the focusing operation.

Conditional expression (1) specifies a preferable ratio of the focal length of the second lens group to the focal length of the entire lens system. It is possible to make appropriate the size of the entire lens system and the aberration variation when focusing on a short-distance object.
Suppressing the refractive power of the second lens group so as not to fall below the lower limit value of conditional expression (1) is advantageous in reducing aberration fluctuations when focusing on a short distance object, particularly fluctuations in field curvature and coma aberration. Become.
By ensuring sufficient refractive power of the second lens group so as not to exceed the upper limit value of conditional expression (1), the amount of movement of the second lens group when focusing on a short-distance object can be reduced. This is advantageous for downsizing.

Conditional expression (2) defines a preferable ratio of the focal length of the entire system to the distance on the optical axis from the exit pupil position of the entire inner focus lens system to the paraxial image plane when focusing on an object at infinity. It is.
Do not exceed the upper limit value of conditional expression (2), and the incident angle of the light beam that passes through the center of the aperture stop and reaches the imaging surface in the light beam with the maximum field angle (that is, off-axis emitted from the lens system) It is preferable that the emission angle of the light beam is appropriate.
When the exit angle of the light beam reaching the imaging surface is suppressed, the telecentricity on the image side is improved. In an image pickup device for a digital camera (for example, CCD, CMOS, etc.), it is preferable because a decrease in peripheral light amount and color shading can be reduced.

In the basic configuration of the inner focus lens system described above, the present invention of the second aspect satisfies the following configuration.
From the object side to the image side,
The first lens group, the aperture stop, the second lens group, the third lens group;
The total number of lens groups is 3,
The second lens group includes a fourth lens component having a negative refractive power and a fifth lens component having a positive refractive power in order from the object side to the image side.
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group I do.

  By arranging the third lens group whose position is fixed, it is easy to reduce the operation sound during the focusing operation of the second lens group. In addition, this is advantageous in reducing aberrations that could not be corrected by the first and second lens groups. If the third lens group is a lens group having a positive refractive power, it is advantageous for separating the exit pupil from the paraxial image plane. If the third lens group is a lens group having a negative refractive power, it is advantageous for correcting off-axis aberrations such as field curvature. The powerless lens group is advantageous for reducing the weight of the third lens group.

In the basic configuration of the inner focus lens system described above, the third aspect of the present invention satisfies the following configuration.
From the object side to the image side,
The first lens group, the aperture stop, the second lens group, a third lens group;
The total number of lens groups is 3,
The second lens component and the third lens component are both cemented lens components;
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group And
The above conditional expression (1) is satisfied.

By disposing two cemented lens components having positive refractive power in the first lens group, the function of correcting aberrations can be shared by each cemented lens component, which is advantageous in reducing various aberrations of the first lens group.
Arranging the third lens group having a fixed position is advantageous in reducing the operation sound during the focusing operation.
The technical significance of conditional expression (1) is as described above.

In the basic configuration of the inner focus lens system described above, the present invention of the fourth aspect satisfies the following configuration.
From the object side to the image side,
The first lens group, the aperture stop, the second lens group, a third lens group having a negative refractive power;
The total number of lens groups is 3,
The second lens component and the third lens component are both cemented lens components;
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group And
The following conditional expression (7) is satisfied.
1.01 <f23 / f2 ≦ 2.0 (7)
However,
f2 is a focal length of the second lens group,
f23 is a combined focal length of the second lens group and the third lens group at the time of focusing on an object at infinity.

This configuration is advantageous for reducing various aberrations of the first lens group.
By disposing the fixed third lens group having negative refractive power, sufficient positive refractive power of the second lens group can be secured, which is advantageous for reducing the amount of movement for the focusing operation. In addition, it is possible to easily reduce aberration fluctuations accompanying the focusing operation, in particular, spherical aberration and field curvature fluctuations that are easily noticeable when the aperture is increased. The size of the second lens group and the amount of movement during the focusing operation can be reduced, which is advantageous for achieving both a reduction in size and an increase in aperture.
This is also advantageous for reducing the operation sound during the focusing operation.
Conditional expression (7) specifies a preferable ratio of the combined focal length of the second lens group and the third lens group to the focal length of the second lens group. This is a preferable conditional expression for appropriately suppressing various aberrations of the entire system during focusing.
By ensuring that the positive refractive power of the second lens group of the lens system behind the aperture stop is sufficiently ensured so as not to fall below the lower limit value of the conditional expression (7), the second value during the focusing operation is obtained. It is easy to suppress an increase in the amount of movement of the lens group, which is advantageous for downsizing.
By setting so as not to exceed the upper limit value of conditional expression (7) and appropriately suppressing the positive refractive power of the second lens unit of the lens system behind the aperture stop, This is advantageous for correction of spherical aberration and curvature of field of the entire lens system when focusing on a short distance object, and correction of spherical aberration and coma.

In the basic configuration of the inner focus lens system described above, the present invention of the fifth aspect satisfies the following configuration.
From the object side to the image side,
The first lens group, the aperture stop, the second lens group, a third lens group;
The total number of lens groups is 3,
The second lens component and the third lens component are both cemented lens components;
The second lens group consists of two or three lenses,
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group Is to do.

This configuration is advantageous for reducing various aberrations of the first lens group.
In addition, the weight of the second lens group that moves during the focusing operation can be reduced.
By disposing the fixed third lens group having negative refractive power, it is advantageous in reducing the operation sound and various aberrations during the focusing operation.

  The above-described inventions may be combined with each other. Moreover, you may incorporate a part of component requirement into the component requirement of another invention.

  More preferably, any of the inner focus lens systems described above satisfies one or more of the following constituent requirements at the same time.

It is preferable that the F number is 2 or less and the half angle of view is 30 ° or more.
The present invention has an advantageous configuration for aberration correction and focusing operation, and it is preferable that the brightness and the angle of view be ensured because of performance.

It is preferable that the following conditional expression (5) is satisfied.
2 ≦ TL / f ≦ 4 (5)
However,
TL is the distance on the optical axis from the lens surface on the most object side of the inner focus lens system to the paraxial image plane.
If there is a parallel plate between the inner focus lens system and the image, replace the parallel plate with the air-converted optical path length (= (length on the optical axis of the parallel plate) / (refractive index of the parallel plate)). To do.

Conditional expression (5) specifies a preferable distance on the optical axis from the lens surface closest to the object side to the paraxial image plane with respect to the focal length of the entire system of the inner focus lens system. This is to make it more advantageous to achieve both.
By ensuring the total length of the lens system so that it does not fall below the lower limit of conditional expression (5), the refractive power of the first and second lens units can be reduced moderately, and the increase in the number of lenses and the increase in the number of aspheric surfaces are suppressed. However, it is possible to satisfactorily correct aberrations in each lens group. Therefore, it is advantageous for the wobbling or focusing operation by reducing the cost and the weight of the focus lens group. Moreover, the influence on the aberration at the time of decentering of the first and second lens groups can be reduced, which is preferable.
It is preferable to reduce the size in use so as not to exceed the upper limit value of conditional expression (3).

It is preferable that the following conditional expression (6) is satisfied.
0.3 ≦ CSD1 / f ≦ 1.0 (6)
However,
CSD1 is the total sum of the thicknesses on the optical axis of all the cemented lens components constituting the first lens group.

Conditional expression (6) specifies a preferable ratio of the total thickness of all the cemented lens components constituting the first lens group on the optical axis with respect to the focal length of the entire system of the inner focus lens system. This is advantageous in reducing both the overall system size and correcting various aberrations.
By making sure that the lower limit of conditional expression (6) is not exceeded, the entrance pupil can be more easily located on the object side, which is advantageous for downsizing and cost reduction of the first lens component. It also becomes easy to reduce the fall of the field curvature to the plus side.
The weight of the cemented lens component and the total length of the lens system are suppressed by appropriately suppressing the distance on the optical axis of the cemented lens component constituting the first lens group so as not to exceed the upper limit value of conditional expression (6). It is done. It is easy to reduce the negative curvature of the field curvature.

  When the second lens component is a cemented lens component in which a negative lens and a positive lens are cemented, the refractive index of the negative lens of the cemented lens component is made lower than the refractive index of the positive lens so that the Petzval sum can be controlled easily. Mainly, it becomes easy to correct the curvature of field.

  When the third lens component is a cemented lens component in which a positive lens and a negative lens are cemented, the chromatic aberration can be easily corrected mainly by making the positive lens of the cemented lens component have a lower dispersion than the negative lens.

Both the second lens component and the third lens component in the first lens group are preferably cemented lens components.
Each cemented lens component can share the aberration correction function, which is advantageous in reducing various aberrations of the first lens group.

The first lens group preferably has at least one aspheric surface.
If an attempt is made to increase the angle of view and brightness while shortening the overall length and reducing the size, the refractive power of the first lens component closest to the object increases, and spherical aberration, field curvature, and distortion are likely to occur. The above-described configuration is preferable because it is possible to achieve both downsizing and correction of various aberrations such as spherical aberration and curvature of field.

The number of lenses constituting the second lens group is preferably 3 or less.
The focus lens group is reduced in weight. Thereby, for example, a load of a motor or the like for moving the focus lens group is reduced. Accordingly, it is possible to reduce the operation sound when the motor main body is miniaturized and the wobbling is performed with the focus lens group, which is preferable because it is a small inner focus lens system having a mechanism suitable for moving image shooting.

  When the second lens group is composed of three or less lenses, it is possible to achieve both miniaturization and correction of aberration by adopting a configuration including a negative lens, one lens, or two positive lenses in order from the object side to the image side. It is advantageous and preferable.

The second lens group preferably has at least three aspheric surfaces.
With the above-described configuration, it is possible to satisfactorily correct sagittal coma that is conspicuous due to spherical aberration, curvature of field, and a large aperture generated in the second lens group. It is preferable because aberration variation accompanying the focusing operation can be reduced.

A third lens group having negative refractive power is disposed on the image side of the second lens group;
It is preferable that the conditional expression (7) is satisfied.
The technical significance is as described above.

  A third lens group consisting of a single negative lens is disposed on the image side of the second lens group, and the position of the third lens group is fixed during focusing from an object at infinity to a near object. Preferably there is.

By adopting the above-described configuration, it is easy to reduce aberration fluctuations during focusing, particularly spherical aberration and field curvature fluctuations that are easily noticeable when the aperture is increased while securing the refractive power of the second lens group. Become.
The size of the second lens group and the amount of movement during the focusing operation can be reduced, which is advantageous for achieving both a reduction in size and an increase in aperture.
The third lens group is preferably a single negative lens in order to secure the back focus.
A fixed third is fixed during focusing operation between the noise source such as the operating sound of the aperture stop during movie shooting and the operating sound of the focus lens group and the sound pickup part (microphone) of the camera body near the image plane. The presence of the lens group can also play a role close to a sound insulation wall, which is advantageous and preferable for noise reduction.

It is preferable that the number of lenses constituting the second lens group is two.
The focus lens group is reduced in weight. Therefore, for example, the load on the motor for moving the focus lens group is reduced, and the operation sound when the motor body is reduced in size and wobbling is also reduced. This is advantageous for a small lens system having a mechanism suitable for moving image shooting.

The second lens group preferably has at least two aspheric surfaces.
This is advantageous for correcting spherical aberration and field curvature generated in the second lens group. This is advantageous in reducing the occurrence of aberrations when focusing on an object at a short distance.

A third lens group having a positive refractive index is disposed on the image side of the second lens group;
You may comprise so that the following conditional expressions (8) may be satisfied.
0.5 ≦ f23 / f2 <1.0 (8)
However,
f23 is a combined focal length of the second lens group and the third lens group at the time of focusing on an object at infinity.

This is advantageous for ensuring telecentricity on the image side of the entire lens system.
Conditional expression (8) specifies a preferable ratio of the combined focal length of the second lens group and the third lens group to the focal length of the second lens group.
By ensuring the positive refractive power of the second lens group so as not to fall below the lower limit value of conditional expression (8), the amount of movement of the second lens group during the focusing operation can be reduced, and the size can be reduced. preferable.
It is advantageous for securing the back focus by appropriately suppressing the positive refractive power of the second lens group so as not to exceed the upper limit value of conditional expression (8). This is also advantageous in reducing spherical aberration and field curvature when focusing on a short distance object in the entire lens system.

  A third lens group including one positive lens having at least one aspheric surface is disposed on the image side of the second lens group, and the third lens group performs a focusing operation from an object at infinity to a near object. In this case, the position is preferably fixed.

The aspherical positive lens in the third lens group can correct aberrations that could not be corrected by the first and second lens groups. Further, by giving the third lens group positive refracting power, the positive refracting power of the second lens group can be kept low. This leads to a reduction in the number of positive lenses in the second lens group and weight reduction of the second lens group. This is advantageous for reducing the load on the motor for focusing operation.
In addition, between the noise source such as the aperture stop sound during movie shooting and the focus lens group operation sound and the sound collection part (microphone) of the camera body near the image plane, the By interposing the three lens groups, the third lens group can have a role of a sound insulation wall.

It is preferable that the following conditional expressions (3) and (4) are satisfied in an infinite object focused state.
| (100 × (y1′−y1) / y1) | <0.30 (3)
| (100 × (y0.7′−y0.7) /y0.7) | <0.30 (4)
However,
y1 is the maximum image height on the imaging surface,
y0.7 is 0.7 times the maximum image height y1,
y1 ′ is the image of y1 when focused at infinity when the second lens group is moved with respect to an object at infinity and a defocus amount of Δs is generated from the image plane when focused at infinity. A ray height at a position where the principal ray having the same angle of view as the shooting angle of view that reaches the height intersects the imaging surface;
y0.7 ′ is the y0 when the infinite focus is obtained when the second lens group is moved with respect to the object at infinity and a defocus amount of Δs is generated from the image plane at the infinite focus. A ray height at a position where a principal ray having the same angle of view as the shooting angle of view leading to an image height of 7 intersects the imaging surface;
Δs is 8 * maximum image height y1 / 1000,
The units of y1, y0.7, y1 ′, y0.7 ′, and Δs are all mm.

In an inner focus lens system suitable for moving image shooting, it is necessary to realize a focusing method that takes into account the high-speed operation of the focus lens group (and wobbling in moving image shooting), and the focus lens group must be made lighter. . Therefore, in the present invention, focusing operation (and wobbling) is performed by the second lens group.
With such a configuration, it is preferable that the inner focus lens system of the present invention has a smaller change in image magnification during focusing operation (and wobbling during moving image shooting) as compared with a conventional lens. Although the amount of change in image magnification varies depending on the height of the image, it is preferable to reduce the amount of change not only for a specific image height but also for the entire screen.
Conditional expressions (3) and (4) are conditional expressions for that purpose, and define the condition of the image magnification change amount with respect to the defocus amount. Here, although it depends on the value of the defocus amount Δs on the image plane, here, the calculation is performed with the defocus amount corresponding to the allowable depth. In general, the permissible depth can be expressed by F number * permissible circle of confusion, but in the present invention, F number = 8, permissible circle of confusion = maximum image height (y1) in consideration of actual use conditions. / 1000.
In order not only to satisfy one of conditional expressions (3) and (4) but also to reduce the amount of change in the entire screen, it is preferable to satisfy both expressions (3) and (4). By satisfying both equations, the change in image magnification can be kept small even at other image heights. By avoiding exceeding the upper limits of conditional expressions (3) and (4), it is possible to reduce the apparent magnification change, which is preferable.

The image pickup apparatus of the present invention includes any one of the above-described inner focus lens systems and an image pickup element that converts an image formed by the inner focus lens system into an electric signal.
An imaging device that takes advantage of the above-described inner focus lens system can be provided.

  Each of the above-described configurations may satisfy a plurality at the same time.

  The above conditional expressions (1), (5) to (8) are preferable because the lower limit value or the upper limit value is set as follows so that the respective functions can be ensured more reliably.

For conditional expression (1),
The lower limit value is preferably 1.05, more preferably 1.1.
The upper limit is preferably 1.65, and more preferably 1.6.
For conditional expression (5),
The lower limit is preferably 2.4, and more preferably 2.8.
The upper limit is preferably 3.6, and more preferably 3.2.
For conditional expression (6),
The lower limit is preferably set to 0.32, more preferably 0.4, and further to 0.5.
It is preferable to set the upper limit value to 0.9, more preferably 0.8.
For conditional expression (7),
The lower limit is preferably 1.15, more preferably 1.3.
The upper limit is preferably 1.85, more preferably 1.7.
Conditional expression (8)
The lower limit is preferably 0.6, and more preferably 0.7.
It is preferable to set the upper limit value to 0.9, more preferably 0.8.

The above-described inner focus lens system may satisfy a plurality of configurations at the same time. This is preferable in obtaining a good inner focus lens system and an imaging apparatus.
Moreover, the combination of a preferable structure is arbitrary.

According to the present invention, it is possible to provide an inner focus lens system in which various aberrations are satisfactorily corrected even when sufficient brightness and angle of view are secured, and which is advantageous for moving image shooting.
Furthermore, an imaging device provided with such a lens system can be provided.

It is a figure showing the lens sectional view at the time of infinity object focusing of Example 1 of the inner focus lens system of the present invention. It is the same figure as FIG. 1 of Example 2 of the inner focus lens system of this invention. It is the same figure as FIG. 1 of Example 3 of the inner focus lens system of this invention. It is the same figure as FIG. 1 of Example 4 of the inner focus lens system of this invention. It is the same figure as FIG. 1 of Example 5 of the inner focus lens system of this invention. FIG. 6 is an aberration diagram for Example 1 when focusing on an object at infinity, at a magnification of −1/30, and an object-image distance of 250 mm. FIG. 6 is an aberration diagram for Example 2 upon focusing on an object at infinity, at a time of −1/30, and an object-image distance of 250 mm. FIG. 10 is an aberration diagram for Example 3 upon focusing on an object at infinity, at a time of −1/30, and an object-image distance of 250 mm. FIG. 12 is an aberration diagram for Example 4 when an object at infinity is in focus, at a time of −1/30, and an object-image distance of 250 mm. FIG. 10 is an aberration diagram for Example 5 upon focusing on an object at infinity, at a time of −1/30, and an object-image distance of 250 mm. It is sectional drawing of the lens interchangeable camera which used the inner focus lens system by this invention as an interchangeable lens. It is a front perspective view which shows the external appearance of the digital camera by this invention. FIG. 13 is a rear perspective view of the digital camera of FIG. 12. FIG. 13 is a configuration block diagram of an internal circuit of a main part of the digital camera of FIG. 12.

  Embodiments of an inner focus lens system and an imaging apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

  The following embodiment is a bright inner focus lens system having an angle of view of 60 ° or more and an F number of 2 or less. Further, this inner focus lens system is suitably used for a photographing lens of a camera such as a digital still camera.

  Examples 1 to 5 of the inner focus lens system of the present invention will be described below. FIGS. 1 to 5 show lens cross-sectional views when focusing on an object at infinity according to Examples 1 to 5, respectively. 1 to 5, the first lens group is indicated by G1, the aperture stop is indicated by S, the second lens group is indicated by G2, the third lens group is indicated by G3, the parallel plate is indicated by C, and the image plane is indicated by I. In FIGS. 1 to 5, a filter (dust removal filter, infrared cut filter, low-pass filter) and a cover glass that protects the imaging surface are illustrated as one optically equivalent parallel plate C.

  As shown in FIG. 1, the inner focus lens system of Embodiment 1 includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. And a third lens group G3 having a negative refractive power.

  During the focusing operation from an object at infinity to a near object, the first lens group G1 is stationary, the aperture stop S is stationary, the second lens group G2 is moved to the object side, and the third lens group G3 is stationary. doing.

In order from the object side, the first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side, a biconcave negative lens L2, a biconvex positive lens L3, a biconvex positive lens L4, and a convex surface on the image side. And a negative meniscus lens L5. Here, the biconcave negative lens L2 and the biconvex positive lens L3 are cemented, and the biconvex positive lens L4 and the negative meniscus lens L5 are cemented.
The second lens group G2 includes a biconcave negative lens L6, a positive meniscus lens L7 having a convex surface directed toward the image side, and a biconvex positive lens L8.
The third lens group G3 includes a negative meniscus lens L9 having a convex surface directed toward the image side.

  The aspheric surfaces are used for a total of six surfaces including both surfaces of the negative meniscus lens L1, both surfaces of the positive meniscus lens L7, and both surfaces of the biconvex positive lens L8.

  As shown in FIG. 2, the inner focus lens system of Example 2 includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. And a third lens group G3 having a negative refractive power.

  During the focusing operation from an object at infinity to a near object, the first lens group G1 is stationary, the aperture stop S is stationary, the second lens group G2 is moved to the object side, and the third lens group G3 is stationary. doing.

In order from the object side, the first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side, a negative meniscus lens L2 having a convex surface directed toward the image side, and a positive meniscus lens L3 having a convex surface directed toward the image side. And a biconvex positive lens L4 and a negative meniscus lens L5 having a convex surface facing the image side. Here, the negative meniscus lens L2 and the positive meniscus lens L3 are cemented, and the biconvex positive lens L4 and the negative meniscus lens L5 are cemented.
The second lens group G2 includes a biconcave negative lens L6, a biconvex positive lens L7, and a biconvex positive lens L8.
The third lens group G3 includes a negative meniscus lens L9 having a convex surface directed toward the image side.

  The aspheric surfaces are used for a total of six surfaces including both surfaces of the negative meniscus lens L1, both surfaces of the biconvex positive lens L7, and both surfaces of the biconvex positive lens L8.

  As shown in FIG. 3, the inner focus lens system of Example 3 includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. And a third lens group G3 having a negative refractive power.

  During the focusing operation from an object at infinity to a near object, the first lens group G1 is stationary, the aperture stop S is stationary, the second lens group G2 is moved to the object side, and the third lens group G3 is stationary. doing.

In order from the object side, the first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side, a biconcave negative lens L2, a biconvex positive lens L3, a biconvex positive lens L4, and a convex surface on the image side. And a negative meniscus lens L5. Here, the biconcave negative lens L2 and the biconvex positive lens L3 are cemented, and the biconvex positive lens L4 and the negative meniscus lens L5 are cemented.
The second lens group G2 includes a biconcave negative lens L6, a biconvex positive lens L7, and a biconvex positive lens L8. Here, the biconcave negative lens L6 and the biconvex positive lens L7 are cemented.
The third lens group G3 includes a negative meniscus lens L9 having a convex surface directed toward the image side.

  The aspheric surfaces are used for a total of five surfaces including both surfaces of the negative meniscus lens L1, the image side surface of the biconvex positive lens L7, and both surfaces of the biconvex positive lens L8.

  As shown in FIG. 4, the inner focus lens system of Example 4 includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. And a third lens group G3 having a positive refractive power.

  During the focusing operation from an object at infinity to a near object, the first lens group G1 is stationary, the aperture stop S is stationary, the second lens group G2 is moved to the object side, and the third lens group G3 is stationary. doing.

In order from the object side, the first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side, a biconcave negative lens L2, a biconvex positive lens L3, a biconvex positive lens L4, and a biconcave negative lens. L5. Here, the biconcave negative lens L2 and the biconvex positive lens L3 are cemented, and the biconvex positive lens L4 and the biconcave negative lens L5 are cemented.
The second lens group G2 includes a negative meniscus lens L6 having a convex surface facing the image side, and a positive meniscus lens L7 having a convex surface facing the image side.
The third lens group G3 includes a positive meniscus lens L8 having a convex surface directed toward the object side.

  The aspheric surfaces are used for a total of six surfaces including both surfaces of the negative meniscus lens L1, both surfaces of the positive meniscus lens L7, and both surfaces of the positive meniscus lens L8.

  As shown in FIG. 5, the inner focus lens system of Example 5 includes, in order from the object side, a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power. It consists of and.

  During the focusing operation from the object at infinity to the object at a short distance, the first lens group G1 is stationary, the aperture stop S is stationary, and the second lens group G2 is moved to the object side.

In order from the object side, the first lens group G1 includes a negative meniscus lens L1 having a convex surface directed toward the object side, a biconcave negative lens L2, a biconvex positive lens L3, a biconvex positive lens L4, and a convex surface on the image side. And a negative meniscus lens L5. Here, the biconcave negative lens L2 and the biconvex positive lens L3 are cemented, and the biconvex positive lens L4 and the negative meniscus lens L5 are cemented.
The second lens group G2 includes a biconcave negative lens L6, a biconvex positive lens L7, and a positive meniscus lens L8 having a convex surface directed toward the object side.

  The aspheric surfaces are used for a total of six surfaces including both surfaces of the negative meniscus lens L1, both surfaces of the biconvex positive lens L7, and both surfaces of the positive meniscus lens L8.

  Below, the numerical data of each said Example are shown. Symbols are the above, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, nd is the refractive index of the d-line of each lens, and νd is the Abbe number of each lens. The focal length is the focal length of the entire system, FNO. Is the F number, ω is the half angle of view, f1, f2,... Are the focal lengths of the lens groups. The total length is obtained by adding back focus to the distance from the lens front surface to the lens final surface. The back focus is an air-converted distance from the last lens surface to the paraxial image plane.

  Further, regarding the in-focus state, when focusing on an object at infinity at infinity, when focusing on an object when the magnification is -1/30 when focusing on an object at infinity, an object image When the distance is 250 mm, the object is focused when the distance between the object images is 250 mm. Note that the state where the object is focused on a short distance object includes, for example, a state where the object-image distance is 250 mm.

The aspherical shape is expressed by the following equation, where x is an optical axis with the light traveling direction being positive, and y is a direction orthogonal to the optical axis.
x = (y ² / R) / [1+ {1− (K + 1) (y / R) ² } ^1/2 ]
^{+ A4y 4 + A6y 6 + A8y} 8 + A10y 10 + A12y 12
Here, R is a paraxial radius of curvature, K is a conical coefficient, and A4, A6, A8, A10, and A12 are fourth, sixth, eighth, tenth, and twelfth aspheric coefficients, respectively. In the aspheric coefficient, “e−n” (n is an integer) indicates “10 ⁻ⁿ ”.

Numerical example 1
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * 78.023 1.200 1.58313 59.38
2 * 12.292 5.003
3 -18.812 1.100 1.53172 48.84
4 58.171 2.930 1.91082 35.25
5 -43.861 0.180
6 24.158 5.129 1.81600 46.62
7 -14.317 1.000 1.74077 27.79
8 -38.509 1.980
9 (Aperture) ∞ Variable
10 -12.438 0.800 1.75211 25.05
11 213.210 0.982
12 * -22.884 1.946 1.53071 55.69
13 * -22.293 0.180
14 * 21.690 5.867 1.74320 49.34
15 * -13.755 variable
16 -35.647 1.100 1.78472 25.68
17 -133.991 10.773
18 ∞ 4.082 1.51633 64.14
19 ∞ 0.745
Image plane (imaging plane) ∞

Aspheric data 1st surface K = 10.2000
A4 = -2.1010e-05, A6 = -3.8353e-08, A8 = -5.99837e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Second side K = -0.7352
A4 = 5.2811e-05, A6 = 2.2610e-07, A8 = 3.1098e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Surface 12 K = 7.9739
A4 = 4.3114e-04, A6 = -1.4535e-05, A8 = 3.3449e-07, A10 = -3.1459e-09, A12 = 0.0000e + 00
Side 13 K = 1.8512
A4 = -7.5849e-06, A6 = -4.3260e-06, A8 = 1.6146e-07, A10 = -1.9473e-09, A12 = 0.0000e + 00
Surface 14 K = -9.0536
A4 = -1.6030e-04, A6 = 3.6904e-06, A8 = -3.3598e-08, A10 = 1.2306e-10, A12 = 0.0000e + 00
15th surface K = -1.3862
A4 = 4.6338e-07, A6 = -5.9155e-07, A8 = 1.2569E-08, A10 = -4.7985e-11, A12 = 0.0000e + 00

In-focus state
At infinity Magnification-1 / 30x When object distance is 250mm
d9 6.1845 5.6476 4.8998
d15 2.3539 2.8908 3.6386

Various data focal length 17.27
FNO. 1.716
Half angle of view ω 34.47
Statue height 10.82
Total length (in air) 52.15
Exit pupil position EXP -45.28

Each group focal length
f1 f2 f3
24.56 19.98 -62.20

Numerical example 2
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * 672.764 1.200 1.58313 59.38
2 * 16.711 4.714
3 -12.947 1.100 1.54814 45.79
4 -432.247 4.334 1.91082 35.25
5 -21.509 0.186
6 24.129 4.649 1.81600 46.62
7 -18.446 1.000 1.75211 25.05
8 -78.574 1.800
9 (Aperture) ∞ Variable
10 -12.323 0.800 1.69895 30.13
11 28.592 0.189
12 * 28.656 3.102 1.58313 59.38
13 * -31.177 0.191
14 * 65.852 4.544 1.74320 49.34
15 * -13.653 variable
16 -41.556 1.100 1.59270 35.31
17 -128.726 10.777
18 ∞ 4.082 1.51633 64.14
19 ∞ 0.745
Image plane (imaging plane) ∞

Aspherical data first surface K = 8.8093
A4 = 1.8357e-06, A6 = -1.1413e-07, A8 = 7.5561e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Second side K = 1.5404
A4 = -2.0055e-05, A6 = -3.9708e-07, A8 = 1.2835e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
12th surface K = -0.3143
A4 = -3.3034e-06, A6 = 1.0907e-07, A8 = 4.3753e-09, A10 = -9.3945e-11, A12 = 0.0000e + 00
Side 13 K = 5.3634
A4 = -2.4805e-05, A6 = 1.6341e-06, A8 = 6.4643e-09, A10 = -2.77691e-10, A12 = 0.0000e + 00
14th surface K = -1.2397
A4 = -7.8775e-05, A6 = 1.2639e-06, A8 = -8.1684e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
15th surface K = -0.4603
A4 = 3.1115e-05, A6 = -3.5940e-07, A8 = 4.6142e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00

In-focus state
At infinity Magnification-1 / 30x When object distance is 250mm
d9 7.2228 6.5331 5.5776
d15 1.9178 2.6075 3.5630

Various data focal length 17.31
FNO. 1.716
Half angle of view ω 35.21
Statue height 10.82
Total length (in air) 52.26
Exit pupil position EXP -46.03

Each group focal length
f1 f2 f3
24.46 24.07 -104.03

Numerical Example 3
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * 670.392 1.200 1.58313 59.38
2 * 14.739 4.985
3 -13.171 1.100 1.56732 42.82
4 701.582 3.031 1.91082 35.25
5 -21.642 0.187
6 22.931 4.752 1.81600 46.62
7 -19.343 1.000 1.75211 25.05
8 -67.331 1.782
9 (Aperture) ∞ Variable
10 -12.518 0.800 1.68893 31.07
11 19.337 3.286 1.58313 59.38
12 * -35.600 0.239
13 * 48.560 5.252 1.74320 49.34
14 * -13.158 Variable
15 -44.201 1.100 1.59270 35.31
16 -717.676 10.832
17 ∞ 4.082 1.51633 64.14
18 ∞ 0.745
Image plane (imaging plane) ∞

Aspherical data first surface K = 10.0016
A4 = 9.8615e-06, A6 = -2.3574e-07, A8 = 1.1769e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Second side K = 1.1120
A4 = -2.1754e-05, A6 = -4.8981e-07, A8 = -1.9711e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
12th surface K = 4.5711
A4 = -2.1910e-05, A6 = 1.9461e-06, A8 = 6.5052e-09, A10 = -1.7209e-10, A12 = 0.0000e + 00
Side 13 K = -10.0646
A4 = -8.44836e-05, A6 = 1.2594e-06, A8 = -5.7141e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
14th surface K = -0.4054
A4 = 2.8349E-05, A6 = -4.6349E-07, A8 = 3.2328e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00

In-focus state
At infinity Magnification-1 / 30x When object distance is 250mm
d9 7.1972 6.6121 5.7877
d14 2.0857 2.6708 3.4951

Various data focal length 17.30
FNO. 1.716
Half angle of view ω 34.61
Statue height 10.82
Total length (in air) 52.27
Exit pupil position EXP -47.32

Each group focal length
f1 f2 f3
25.82 21.87 -79.52

Numerical Example 4
Unit mm

Surface data surface number rd nd νd
Object ∞ ∞
1 * 95.024 1.200 1.58313 59.38
2 * 13.513 5.068
3 -71.965 1.200 1.48749 70.23
4 21.803 7.006 1.81600 46.62
5 -33.442 0.100
6 14.535 4.862 1.88300 40.76
7 -177.157 1.000 1.75211 25.05
8 12.147 3.440
9 (Aperture) ∞ Variable
10 -8.735 0.800 1.80810 22.76
11 -15.311 0.100
12 * -290.634 4.451 1.69350 53.21
13 * -10.555 variable
14 * 30.203 1.980 1.69350 53.21
15 * 52.211 10.247
16 ∞ 4.082 1.51633 64.14
17 ∞ 0.745
Image plane (imaging plane) ∞

Aspheric data 1st surface K = 0.0000
A4 = -5.2502e-05, A6 = 2.7523e-07, A8 = -1.4442e-09, A10 = 3.1965e-12, A12 = 0.0000e + 00
Second side K = 0.0000
A4 = -5.8074e-05, A6 = 1.0050e-07, A8 = -1.4253e-09, A10 = -4.3917e-12, A12 = 0.0000e + 00
Surface 12 K = 0.0000
A4 = -1.2958e-05, A6 = -2.1446e-07, A8 = 4.8507e-09, A10 = -5.1657e-11, A12 = 0.0000e + 00
Side 13 K = 0.0000
A4 = 9.8165e-05, A6 = -7.0310e-08, A8 = 8.0196e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Surface 14 K = 0.0000
A4 = -6.9535e-05, A6 = -3.99837e-07, A8 = 2.1679e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Surface 15 K = 0.0000
A4 = -9.7490e-05, A6 = -2.4776e-07, A8 = 1.5980e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00

In-focus state
At infinity Magnification-1 / 30x When object distance is 250mm
d9 7.3155 6.2141 4.4824
d13 0.9417 2.0430 3.7747

Various data focal length 18.26
FNO. 1.75
Half angle of view ω 31.59
Statue height 10.82
Total length (in air) 53.15
Exit pupil position EXP -44.29

Each group focal length
f1 f2 f3
45.84 28.17 99.65

Numerical Example 5
Unit mm
Surface data surface number rd nd νd
Object ∞ ∞
1 * 142.191 1.200 1.58313 59.38
2 * 15.032 5.733
3 -15.778 1.100 1.56732 42.82
4 58.325 3.994 1.91082 35.25
5 -25.921 0.184
6 24.363 5.011 1.81600 46.62
7 -21.082 1.000 1.75211 25.05
8 -159.512 1.941
9 (Aperture) ∞ Variable
10 -10.169 0.800 1.72825 28.46
11 102.914 0.175
12 * 36.885 5.590 1.69350 53.21
13 * -10.274 0.177
14 * 19.178 1.475 1.74320 49.34
15 * 24.283 variable
16 ∞ 4.082 1.51633 64.14
17 ∞ 0.745
Image plane (imaging plane) ∞

Aspherical data first surface K = 10.0030
A4 = -1.6787e-05, A6 = 4.5076e-08, A8 = -1.5736e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Second side K = 0.4209
A4 = -2.4817e-05, A6 = -1.5085e-07, A8 = 2.2831e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
Surface 12 K = 6.7117
A4 = 2.0816e-06, A6 = -7.3508e-07, A8 = -3.8039e-10, A10 = 0.0000e + 00, A12 = 0.0000e + 00
13th surface K = -0.3163
A4 = 5.9359e-05, A6 = 5.8371e-07, A8 = -9.8457e-09, A10 = 0.0000e + 00, A12 = 0.0000e + 00
14th surface K = -8.4854
A4 = -6.6200e-05, A6 = 1.6437e-06, A8 = -2.1208e-08, A10 = 0.0000e + 00, A12 = 0.0000e + 00
15th page K = -9.6526
A4 = -1.4229e-04, A6 = 2.7594e-06, A8 = -2.4235e-08, A10 = 0.0000e + 00, A12 = 0.0000e + 00

In-focus state At infinity Magnification-1 / 30x At object distance 250mm d9 7.9116 7.0837 6.0134
d15 12.4816 13.3094 14.3797

Various data focal length 16.51
FNO. 1.716
Half angle of view ω 35.49
Statue height 10.82
Total length (in air) 52.21
Exit pupil position EXP -48.88

Each group focal length
f1 f2
27.79 27.33

  The aberration diagrams of Examples 1 to 5 are shown in FIGS. 6 to 10, respectively.

  In these aberration diagrams, (a), (b), (c), and (d) are spherical aberration (SA), astigmatism (AS), distortion aberration (DT), and lateral chromatic aberration at infinity, respectively. (CC) is shown.

  (E), (f), (g), and (h) are spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration at a magnification of −1/30, respectively. (CC) is shown.

  Also, (i), (j), (k), and (l) are respectively spherical aberration (SA), astigmatism (AS), distortion (DT), and lateral chromatic aberration (at a distance between object images of 250 mm). CC).

  The spherical aberration and lateral chromatic aberration are 587.56 nm (d line: solid line), 435.84 nm (g line: two-dot chain line), 486.13 nm (F line: one-dot chain line), 656.27 nm (C line: dotted line). The numerical value in each wavelength is shown. Astigmatism, the solid line represents the sagittal image plane and the dotted line represents the meridional image plane. In each figure, “FNO” indicates the F number, “IH” indicates the maximum image height, and the unit of the horizontal axis is percent (%) of distortion only, and the other is mm.

The values corresponding to each conditional expression in each example are shown below.
Conditional Example 1 Example 2 Example 3 Example 4 Example 5
(1) 1.16 1.39 1.26 1.54 1.65
(2) 0.38 0.38 0.37 0.41 0.34
(3) 0.27 0.27 0.24 0.14 0.27
(4) 0.21 0.21 0.19 0.05 0.20
(5) 3.02 3.02 3.02 2.91 3.16
(6) 0.59 0.64 0.57 0.77 0.67
(7) 1.60 1.37 1.46 0.75 ──
(8) 1.60 1.37 1.46 0.75 ──

FIG. 11 is a cross-sectional view of a single lens mirrorless camera as an electronic imaging apparatus. In FIG. 11, reference numeral 1 denotes a single-lens mirrorless camera, 2 denotes a photographic lens system disposed in the lens barrel, and 3 denotes a lens barrel mounting portion that allows the photographic lens system 2 to be attached to and detached from the single-lens mirrorless camera 1. As the mount unit 3, a screw type mount, a bayonet type mount, or the like is used.
In this example, a bayonet type mount is used. Reference numeral 4 denotes an image sensor surface, and 5 denotes a back monitor. A small CCD or CMOS is used as the image sensor.

  As the photographing lens system 2 of the single-lens mirrorless camera 1, for example, the inner focus lens system of the present invention shown in the first to fifth embodiments is used.

  12 and 13 are conceptual diagrams of the configuration of the imaging apparatus according to the present invention. FIG. 12 is a front perspective view showing the appearance of a digital camera 40 as an image pickup apparatus, and FIG. 13 is a rear perspective view of the same. The photographic optical system 41 of the digital camera 40 uses the inner focus lens system of the present invention.

The digital camera 40 of this embodiment includes a photographing optical system 41 positioned on the photographing optical path 42, a shutter button 45, a liquid crystal display monitor 47, and the like. When the shutter button 45 disposed on the upper part of the digital camera 40 is pressed, In conjunction with this, photographing is performed through the photographing optical system 41, for example, the inner focus lens system of the first embodiment. An object image formed by the photographing optical system 41 is formed on an image sensor (photoelectric conversion surface) provided in the vicinity of the imaging surface.
The object image received by the image sensor is displayed on the liquid crystal display monitor 47 provided on the back of the camera as an electronic image by the processing means. In addition, the photographed electronic image can be recorded in a recording unit.

  FIG. 14 is a block diagram showing an internal circuit of a main part of the digital camera 40. In the following description, the processing means described above is configured by, for example, the CDS / ADC unit 24, the temporary storage memory 17, the image processing unit 18, and the like, and the storage unit is configured by the storage medium unit 19 or the like.

  As shown in FIG. 14, 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 can mutually input and output data via the bus 22. In addition, a CCD 49 and a CDS / ADC unit 24 are connected to the imaging drive circuit 16.

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

  The CCD 49 is an image pickup device that is driven and controlled by the image pickup drive circuit 16, converts the light amount of each pixel of the object image formed via the image pickup optical system 41 into an electric signal, and outputs the electric signal to the CDS / ADC unit 24.

  The CDS / ADC unit 24 amplifies the electrical signal input from the CCD 49 and performs analog / digital conversion, and raw video data (Bayer data, hereinafter referred to as RAW data) obtained by performing the amplification and digital conversion. Is output to the temporary storage memory 17.

  The temporary storage memory 17 is a buffer made of, for example, SDRAM, and is a memory device that temporarily stores 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 includes distortion correction based on the image quality parameter designated by the control unit 13. It is a circuit that performs various image processing electrically.

  The storage medium unit 19 is detachably mounted with a card-type or stick-type recording medium made of, for example, a flash memory, and the RAW data transferred from the temporary storage memory 17 or the image processing unit 18 to these flash memories. Image-processed image data is recorded and held.

  The display unit 20 includes a liquid crystal display monitor 47 and the like, and displays captured RAW data, image data, an operation menu, and the like. The setting information storage memory unit 21 includes a ROM unit that stores various image quality parameters in advance, and a RAM unit that stores image quality parameters read from the ROM unit by an input operation of the operation unit 12.

  The digital camera 40 configured in this manner employs the inner focus lens system of the present invention as the photographing optical system 41, so that a high resolution image can be obtained without degrading the image quality while having a wide angle of view and a small size. An imaging device that is advantageous to obtain can be obtained.

  As described above, the inner focus lens system and the imaging apparatus according to the present invention are useful for obtaining a good image, particularly a moving image, with sufficiently secured brightness and angle of view.

G1 ... 1st lens group G2 ... 2nd lens group G3 ... 3rd lens group S ... Brightness stop C ... Parallel plate I ... Image plane 1 ... Single-lens mirrorless camera 2 ... Shooting lens system 3 ... Mount part 4 of a lens barrel Image pickup device surface 5 Back monitor 12 Operation unit 13 Control units 14 and 15 Bus 16 Image pickup drive circuit 17 Temporary storage memory 18 Image processing unit 19 Storage medium unit 20 Display unit 21 Setting information storage Memory unit 22 ... Bus 24 ... CDS / ADC unit 40 ... Digital camera 41 ... Shooting optical system 42 ... Shooting optical path 45 ... Shutter button 47 ... LCD monitor 49 ... CCD

Claims (25)

From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
Have
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
At least one of the second lens component and the third lens component is a cemented lens component;
In a state where the position of the first lens group and the position of the aperture stop are fixed, the second lens group is moved integrally to the object side to perform a focusing operation from an object at infinity to a near object,
The second lens group includes, in order from the object side to the image side, a fourth lens component having a negative refractive power and a fifth lens component having a positive refractive power.
An inner focus lens system characterized by satisfying the following conditional expressions (1) and (2):
1.0 ≦ f2 / f ≦ 1.7 (1)
| F / EXP | ≦ 0.43 (2)
However,
f is the focal length of the entire imaging lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
EXP is a distance on the optical axis from the exit pupil position of the imaging lens system to the paraxial image plane at the time of focusing on an object at infinity, and is a sign when the exit pupil is on the object side from the paraxial image plane. It is defined as minus. From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
Having a third lens group;
The total number of lens groups is 3,
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
At least one of the second lens component and the third lens component is a cemented lens component;
The second lens group includes a fourth lens component having a negative refractive power and a fifth lens component having a positive refractive power in order from the object side to the image side.
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group An inner focus lens system characterized by From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
Having a third lens group;
The total number of lens groups is 3,
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
The second lens component and the third lens component are both cemented lens components;
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group And
An inner focus lens system characterized by satisfying the following conditional expression (1):
1.0 ≦ f2 / f ≦ 1.7 (1)
However,
f is the focal length of the entire imaging lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
It is. From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
A third lens unit having a negative refractive power;
The total number of lens groups is 3,
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
The second lens component and the third lens component are both cemented lens components;
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group And
An inner focus lens system that satisfies the following conditional expression (7):
1.01 <f23 / f2 ≦ 2.0 (7)
However,
f2 is a focal length of the second lens group,
f23 is a combined focal length of the second lens group and the third lens group at the time of focusing on an object at infinity. From the object side to the image side,
A first lens group having a positive refractive power;
Brightness aperture,
A second lens group having a positive refractive power;
Having a third lens group;
The total number of lens groups is 3,
When a lens block in which only two surfaces of the object side surface and the image side surface are in contact with air in the optical path is a lens component,
The first lens group includes, in order from the object side to the image side, a first lens component having a negative refractive power, a second lens component having a positive refractive power, and a third lens component having a positive refractive power.
The second lens component and the third lens component are both cemented lens components;
The second lens group consists of two or three lenses,
Focusing operation from an infinitely distant object to a close object by moving the second lens group integrally to the object side while fixing the positions of the first lens group, the aperture stop and the third lens group An inner focus lens system characterized by 6. The inner focus lens system according to claim 1, wherein the F number is 2 or less and the half angle of view is 30 degrees or more. The inner focus lens system according to any one of claims 1 to 6, wherein the following conditional expression (5) is satisfied.
2 ≦ TL / f ≦ 4 (5)
However,
TL is the distance on the optical axis from the lens surface on the most object side of the inner focus lens system to the paraxial image plane,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
It is. The inner focus lens system according to claim 1, wherein the following conditional expression (6) is satisfied.
0.3 ≦ CSD1 / f ≦ 1.0 (6)
However,
CSD1 is a sum of thicknesses on the optical axis of all cemented lens components constituting the first lens group,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
It is. The second lens component is a cemented lens component in which a negative lens and a positive lens are cemented, and the refractive index of the negative lens of the second lens component is lower than the refractive index of the positive lens of the second lens component. The inner focus lens system according to any one of claims 1 to 8, wherein The third lens component is a cemented lens component in which a positive lens and a negative lens are cemented, and the dispersion of the positive lens in the third lens group is lower than the dispersion of the negative lens in the third lens component. The inner focus lens system according to any one of claims 1 to 9. 11. The inner focus lens system according to claim 1, wherein both the second lens component and the third lens component in the first lens group are cemented lens components. 11. The inner focus lens system according to any one of claims 1 to 11, wherein the first lens group has at least one aspherical surface. The inner focus lens system according to any one of claims 1 to 12, wherein the number of lenses constituting the second lens group is three or less. The inner focus lens system according to any one of claims 1 to 13, wherein the second lens group has at least three aspheric surfaces. A third lens group having negative refractive power is disposed on the image side of the second lens group;
The inner focus lens system according to any one of claims 1 to 14, wherein the following conditional expression (7) is satisfied.
1.01 <f23 / f2 ≦ 2.0 (7)
However,
f2 is a focal length of the second lens group,
f23 is a combined focal length of the second lens group and the third lens group at the time of focusing on an object at infinity. A third lens group consisting of a single negative lens is arranged on the image side of the second lens group, and the position of the third lens group is fixed during focusing from an object at infinity to a near object. The inner focus lens system according to claim 1, wherein the inner focus lens system is provided. The inner focus lens system according to any one of claims 1 to 16, wherein the number of lenses constituting the second lens group is two. The inner focus lens system according to any one of claims 1 to 17, wherein the second lens group has at least two aspheric surfaces. A third lens group having a positive refractive index is disposed on the image side of the second lens group;
The inner focus lens system according to claim 1, wherein the following conditional expression (8) is satisfied.
0.5 ≦ f23 / f2 <1.0 (8)
However,
f2 is a focal length of the second lens group,
f23 is a combined focal length of the second lens group and the third lens group at the time of focusing on an object at infinity. A third lens group comprising one positive lens having at least one aspherical surface on the image side of the second lens group;
The position of the third lens group is fixed during a focusing operation from an object at infinity to an object at a short distance, according to any one of claims 1, 2, 3, 5, and 19. Inner focus lens system. The inner focus lens system according to any one of claims 1 to 20, wherein the following conditional expressions (3) and (4) are satisfied in an infinitely focused object state.
| (100 × (y1′−y1) / y1) | <0.30 (3)
| (100 × (y0.7′−y0.7) /y0.7) | <0.30 (4)
However,
y1 is the maximum image height on the imaging surface,
y0.7 is 0.7 times the maximum image height y1,
y1 ′ is the image of y1 when focused at infinity when the second lens group is moved with respect to an object at infinity and a defocus amount of Δs is generated from the image plane when focused at infinity. A ray height at a position where the principal ray having the same angle of view as the shooting angle of view that reaches the height intersects the imaging surface;
y0.7 ′ is the y0 when the infinite focus is obtained when the second lens group is moved with respect to the object at infinity and a defocus amount of Δs is generated from the image plane at the infinite focus. A ray height at a position where a principal ray having the same angle of view as the shooting angle of view leading to an image height of 7 intersects the imaging surface;
Δs is 8 * maximum image height y1 / 1000,
The units of y1, y0.7, y1 ′, y0.7 ′, and Δs are all mm. The second lens component is the cemented lens component;
The second lens group includes one negative lens, one or two positive lenses in order from the object side,
The inner focus lens system according to claim 2, wherein the following conditional expression (1) is satisfied.
1.0 ≦ f2 / f ≦ 1.7 (1)
However,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
It is. The inner focus lens system according to claim 2 or 22, wherein the following conditional expressions (1) and (6 ') are satisfied.
1.0 ≦ f2 / f ≦ 1.7 (1)
0.32 ≦ CSD1 / f ≦ 1.0 (6 ′)
However,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
CSD1 is the total sum of the thicknesses on the optical axis of all the cemented lens components constituting the first lens group. The third lens group has a positive refractive power;
The inner focus lens system according to any one of claims 2, 22, and 23, wherein the following conditional expression (1 ') is satisfied.
1.1 ≦ f2 / f ≦ 1.7 (1 ′)
However,
f is the focal length of the entire inner focus lens system when focusing on an object at infinity,
f2 is a focal length of the second lens group,
It is. An image pickup apparatus comprising: the inner focus lens system according to any one of claims 1 to 24; and an image pickup element that converts an image formed by the inner focus lens system into an electric signal.

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