JP2018180042A - Zoom lens and image capturing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which is more compact and light-weight as a whole and offers macro shooting capability.SOLUTION: A zoom lens that solves the above problem consists of n lens groups comprising a positive first lens group G1 and a negative second lens group G2 in order from the object side, and a negative n-th lens group (G4) and a positive (n-1)th lens group (G3) in order from the image side. When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the n-th lens group are kept stationary while the second lens group G2 and the (n-1)th lens group are moved along an optical axis such that a distance between the first lens group G1 and the second lens group G2 increases and a distance between the (n-1)th lens group and the n-th lens group decreases. Shifting of focus from an object at infinity to an object at a short distance is accomplished by moving the second lens group toward the image side. The zoom lens satisfies predetermined conditions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens and an imaging device, and more particularly to a zoom lens and an imaging device that are compact and lightweight and have a focusing function.

  In a zoom lens or the like for a conventional single-lens reflex camera, there is a need to secure a long flange back with respect to a focal length in order to dispose an optical element or the like related to an optical finder. Therefore, a lens group having a positive refractive power is disposed in the rear lens group disposed on the image side among the lens groups constituting the zoom lens, and lens design is performed so as to easily secure the back focus. I was securing the flange back. However, in recent years, with the spread of digital still cameras and the like that capture images with a live view image displayed on a liquid crystal screen provided on the back surface of the imaging device main body or the like in order to miniaturize the imaging device main body. Imaging devices that are not provided are becoming widely used. For this reason, the zoom lens which does not require a long flange back is also increasing (for example, refer to "patent documents 1"-"patent document 3"), and miniaturization of a zoom lens is called for. Among such small-sized zoom lenses, zoom lenses suitable for moving image shooting have been proposed, such as those in which the focusing group is miniaturized, and those in which a vibration reduction lens necessary for camera shake correction is provided.

  In particular, in order to continuously perform autofocus at high speed during moving image shooting, etc., out-of-focus state → focusing while vibrating (wobbling) some lens groups (focusing group) in the optical axis direction at high speed Focused state → Create an out-of-focus state, detect the signal component of the frequency band with a partial image area from the output signal of the imaging device, find the optimal position of the focusing group to be in focus, A method of repeating a series of operations such as moving the focusing group can be considered. When introducing such wobbling, in zoom lens design, it is necessary to be careful that the size of the image corresponding to the subject changes during wobbling. Such a zooming action at the time of focusing is caused by a change in focal length of the entire lens system as the focusing group moves in the optical axis direction at the time of wobbling. For example, when performing live view shooting, if the magnification change due to wobbling is large, the user may feel discomfort. It is known that in order to reduce this feeling of incongruity, it is effective to focus on the lens group behind the stop. Also, in order to introduce wobbling and realize high-speed autofocus, downsizing and weight reduction of the focusing group are essential conditions.

  As described above, in addition to the need to miniaturize the zoom lens itself in accordance with the recent miniaturization of the image pickup apparatus main body and the shortening of the flange back, it is possible to drive the focusing group at high speed. It is desired to reduce the outer diameter as much as possible and to reduce the weight.

  In the anti-vibration lens group as well, it is desirable to reduce the outer diameter of the anti-vibration lens group as well as to lighten the influence of image deterioration due to camera shake and to reduce the load on the anti-vibration drive system. It is rare.

  Here, Patent Document 1 discloses a zoom lens of a four-group configuration connected to an eyepiece portion of an endoscope. In the zoom lens, at the time of zooming from the wide-angle end to the telephoto end, the first lens unit and the fourth lens unit are fixed in the optical axis direction, and the second lens unit and the third lens unit are moved closer to each other. . In this configuration, when focusing from an infinite distance object to a close distance object, it is conceivable to move the second lens unit or the third lens unit to the image side. However, in the zoom lens, the distance between the second lens group and the third lens group is insufficient, and the second lens group or the third lens group can not be made into a focusing group. Therefore, in the zoom lens, the first lens group fixed at the time of zooming is set as a focusing group, and focusing is performed by moving the first lens group. In the zoom lens, it is not preferable to provide a focusing group separately from the variable power group, because the drive mechanism is increased in size and the zoom lens unit is reduced in size and weight.

  The zoom lens disclosed in Patent Document 2 realizes the high zoom ratio, the large aperture ratio, and the miniaturization by the four-group configuration. However, in the zoom lens, the third lens unit having the same diameter as the other lens units is used as the focusing unit, and the downsizing and weight reduction of the focusing unit are insufficient. In addition, the distance between the aperture stop and the third lens unit is insufficient, and the amount of movement of the third lens unit at the time of focusing can not be secured particularly at the telephoto end, and focusing on a short distance object Will be difficult. Therefore, proximity imaging is difficult.

  Patent Document 3 discloses a zoom lens for an exposure apparatus capable of securing a required variable magnification ratio by a four-group configuration. However, in Example 1, the second lens group, the third lens group, and the fourth lens group are moved in the optical axis direction at the time of zooming, and the number of movable groups moved at the time of zooming is large. It is not preferable in order to reduce the size and weight of the zoom lens unit. On the other hand, in the second embodiment, only the second lens group and the third lens group are moved during zooming, and the fourth lens group is fixed in the optical axis direction, which is preferable in terms of downsizing of the drive mechanism. However, since the lateral magnification at the telephoto end of the fourth lens group which is the final lens group is small, in order to realize a zoom lens having a high zoom ratio, the total optical length from the first lens group to the third lens group is shortened. I can not do it. Therefore, when the fourth lens unit is used as a moving unit or a fixed unit, it is difficult to reduce the size and weight of the zoom lens unit.

Japanese Patent Application Laid-Open No. 11-125770 Patent No. 4-281419 gazette JP, 2002-207167, A

  By the way, conventionally, in a solid-state imaging device that receives an optical image and converts it into an electrical image signal, there is a limitation for efficiently capturing incident light with an on-chip micro lens etc. It has been desired to ensure the telecentricity of the light flux incident on the solid-state imaging device by enlarging the exit pupil by a certain degree or more. However, in recent solid-state imaging devices, there are improvements in the aperture ratio and advances in design freedom of on-chip microlenses, and the restriction on the exit pupil required on the lens side has decreased. For this reason, conventionally, various proposals have been made for arranging a lens group having positive refractive power behind a zoom lens to ensure telecentricity, but in recent years this has not been the case. For this reason, even when oblique incidence of light flux to the solid-state image sensor is caused by disposing a lens group having negative refractive power behind the zoom lens, peripheral light reduction (shading) due to a mismatch of the pupil with the on-chip micro lens etc. ) Has become less noticeable. Further, even if the distortion is large to some extent and is conventionally noticeable, it is also possible to correct by image processing as the software and camera system progress and improve.

  Therefore, an object of the present invention is to provide a zoom lens capable of proximity imaging while achieving downsizing and weight reduction as a whole.

  In order to solve the above problems, the zoom lens according to the present invention is composed of n lens groups (where n is a natural number of 4 or more) and includes, from the object side, a first lens group having positive refractive power. A second lens group having negative refractive power, and an nth lens group having negative refractive power and an n-1th lens group having positive refractive power in this order from the image side, and the wide-angle end The first lens group and the n-th lens group are fixed in the optical axis direction during zooming from the telephoto end to the telephoto end, and the distance between the first lens group and the second lens group is wide. The second lens group and the n-1st lens group are moved in the optical axis direction so that the distance between the 1st lens group and the nth lens group becomes narrow, and an infinite distance object to a close distance object At the time of focusing, one lens group other than the first lens group and the n-th lens group is arranged in the optical axis direction. Focusing by moving, characterized by satisfying the following condition.

(1) 0.40 ≦ m 2 / mn 1 ≦ 3.00
However,
m2: moving amount of the second lens unit at the time of zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side)
mn-1: moving amount of the (n-1) -th lens unit at the time of zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side)

  Further, in order to solve the above problems, an imaging device according to the present invention includes the zoom lens, and an imaging element that converts an optical image formed by the zoom lens to an electrical signal on the image side thereof. It is characterized by

  According to the present invention, it is possible to provide a zoom lens capable of proximity imaging while achieving downsizing and weight reduction as a whole.

It is a figure which shows the lens structural example of the variable magnification optical system of Example 1 of this invention. The upper part is a lens block diagram at the wide angle end, and the lower part is a lens block diagram at the telephoto end. They are spherical aberration, astigmatism, and a distortion aberration at the time of the farthest point object focusing in the wide-angle end state of the variable magnification optical system of Example 1 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point at an intermediate focus position of the variable magnification optical system according to Example 1 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point in the telephoto end state of the variable magnification optical system according to Example 1 of the present invention. FIG. 6 is a lateral aberration diagram of the zoom optical system of the first embodiment of the present invention at the telephoto end. It is a figure which shows the lens structural example of the variable magnification optical system of Example 2 of this invention. The upper part is a lens block diagram at the wide angle end, and the lower part is a lens block diagram at the telephoto end. They are spherical aberration, astigmatism, and a distortion aberration at the time of the farthest point object focusing in the wide-angle end state of the variable magnification optical system of Example 2 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point at an intermediate focus position of the variable magnification optical system according to the second embodiment of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point in the telephoto end state of the variable magnification optical system according to Example 2 of the present invention. FIG. 7 is a lateral aberration diagram of the zoom optical system of the second embodiment of the present invention at the telephoto end. It is a figure which shows the lens structural example of the variable magnification optical system of Example 3 of this invention. The upper part is a lens block diagram at the wide angle end, and the lower part is a lens block diagram at the telephoto end. They are spherical aberration, astigmatism, and distortion at the time of the farthest point object focusing in the wide-angle end state of the variable magnification optical system of Example 3 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point at an intermediate focus position of the variable magnification optical system according to Example 3 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point in the telephoto end state of the variable magnification optical system according to Example 3 of the present invention. FIG. 7 is a lateral aberration diagram of the zoom optical system of the third embodiment of the present invention at the telephoto end. It is a figure which shows the lens structural example of the variable magnification optical system of Example 4 of this invention. The upper part is a lens block diagram at the wide angle end, and the lower part is a lens block diagram at the telephoto end. They are spherical aberration, astigmatism, and a distortion at the time of the farthest point object focusing in the wide-angle end state of the variable magnification optical system of Example 4 of this invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point at an intermediate focus position of the variable magnification optical system according to Example 4 of the present invention. They are spherical aberration, astigmatism, and a distortion aberration at the time of the farthest point object focusing in the state of the telephoto end of the variable magnification optical system of the fourth embodiment of the present invention. FIG. 13 is a lateral aberration diagram in a telephoto end state of the variable magnification optical system of Example 4 of the present invention. It is a figure which shows the lens structural example of the variable magnification optical system of Example 5 of this invention. The upper part is a lens block diagram at the wide angle end, and the lower part is a lens block diagram at the telephoto end. They are spherical aberration, astigmatism, and a distortion aberration at the time of the farthest point object focusing in the wide-angle end state of the variable magnification optical system of Example 5 of the present invention. They are spherical aberration, astigmatism, and distortion at the time of focusing on the farthest point at an intermediate focus position of the variable magnification optical system of the fifth embodiment of the present invention. They are spherical aberration, astigmatism, and a distortion aberration at the time of the most distant point object focusing in the telephoto end state of the variable magnification optical system of Example 5 of this invention. FIG. 13 is a lateral aberration diagram in a telephoto end state of the variable magnification optical system of Example 5 of the present invention. It is a schematic diagram which shows an example of the imaging device of this invention.

  Hereinafter, embodiments of a zoom lens and an imaging device according to the present invention will be described.

1. Zoom lens 1-1. Optical System Configuration The zoom lens comprises n (where n is a natural number of 4 or more) lens groups, and has a first lens group having positive refractive power and negative refractive power in order from the object side. The second lens group is provided, and an n-th lens group having negative refractive power and an n-1st lens group having positive refractive power are sequentially provided from the image side, and the air gap between the lens groups is changed It is a zoom lens that changes magnification by making When zooming from the wide-angle end to the telephoto end, the first lens unit and the n-th lens unit are fixed units fixed in the optical axis direction, and the second lens unit and the n-1st lens unit are fixed in the optical axis direction It is a movable group to be moved. In addition, by moving one lens group other than the first lens group and the n-th lens group in the optical axis direction, an object at infinity is brought into focus from a near distance object. The zoom lens may include at least four lens units of the first lens unit, the second lens unit, the n-1st lens unit, and the nth lens unit, and the second lens unit and the nth lens unit Another fixed group and / or a movable group may be provided between the -1 lens group.

  In the zoom lens, the first lens unit disposed closest to the object side during zooming and the nth lens unit disposed closest to the image are fixed in the optical axis direction during zooming and focusing. The optical total length of the zoom lens does not change during zooming and focusing. The zoom lens is housed in a lens barrel and configured as a lens unit. If the total optical length is fixed, the length of the lens barrel that accommodates the zoom lens can also be fixed, so the lens barrel structure can be simplified, and the entire zoom lens can be miniaturized. . Therefore, with the lens unit as a sealed structure, it is easy to prevent dust, dirt, water, and the like from intruding into the lens unit.

  In addition, since the entire optical length of the zoom lens does not change at the time of zooming and focusing, it is easy to maintain the distance to the subject even when shooting a close subject, and the front lens of the zoom lens on the subject Contact can be prevented.

   Furthermore, in the zoom lens, at least two movable groups of the second lens group and the (n-1) -th lens group may be provided. If there are at least two movable groups, the magnification change ratio can be changed continuously by moving the two movable groups in the optical axis direction during zooming.

  At the time of focusing, the zoom lens performs focusing by moving one lens group other than the first lens group and the n-th lens group in the optical axis direction. As described above, the first lens unit and the nth lens unit are fixed units. Therefore, if focusing is achieved by moving these lens groups in the optical axis direction at the time of focusing, the drive mechanism for focusing becomes complicated, and the reduction and weight reduction of the entire zoom lens can not be achieved. In the zoom lens, by setting the focusing group to one lens group other than the first lens group and the n-th lens group, the size and weight of the entire zoom lens can be reduced.

  Then, at the time of focusing, it is preferable to perform focusing by moving any one of the at least two movable groups. The optical configuration of the zoom lens can be simplified by using the lens unit that moves at the time of zooming as the focusing unit that moves at the time of focusing. Furthermore, in the zoom lens, it is more preferable to set the second lens group as a focusing group and to move the second lens group to the image side to focus when focusing from an infinite distance object to a close distance object. Here, since the second lens group has a negative refracting power and has a lens group having a positive refracting power on the image side, the lens outer diameter is larger than that of the n-1th lens group having a positive refracting power. It is easy to make Therefore, by using the second lens unit as the focusing unit, the focusing unit can be reduced in size and weight, and the load on the drive mechanism can be reduced. From these things, size reduction and weight reduction of a drive mechanism can be achieved, and further size reduction and weight reduction of the said lens unit can be implement | achieved.

  In the zoom lens having the above configuration, for example, the n-th lens unit can be moved in the vertical direction with respect to the optical axis, and the n-th lens unit can be moved in the perpendicular direction with respect to the optical axis. For example, the image blur generated at the time of imaging may be corrected. That is, the nth lens group may be configured as a so-called anti-vibration group. In the present invention, the vibration reduction group is not limited to the nth lens group, and any lens group from the first lens group to the nth lens group may be used as the vibration reduction group. For example, if a lens group having a small outer diameter (such as a second lens group) is employed as a vibration reduction group, the outer diameter of the zoom lens can be reduced.

  In the zoom lens, n is a natural number of 4 or more. The upper limit value of n is not particularly limited, but when the number of n increases, it becomes difficult to achieve size reduction and weight reduction of the zoom lens. From this point of view, n is preferably 6 or less, and more preferably 5 or less. As described above, the zoom lens may have at least two movable groups, and most preferably n = 4.

1-2. Operation (1) Scaling Operation Next, the scaling operation will be described. In the zoom lens, at the time of zooming, the first lens unit and the nth lens unit are fixed, and at least the second lens unit and the n−1th lens unit are movable. At the time of zooming from the wide-angle end to the telephoto end, the distance between the first lens group and the second lens group is wide, and the distance between the n-1st lens group and the nth lens group is narrow. The group and the (n-1) th lens group are respectively moved in the optical axis direction. That is, the second lens unit and the (n-1) th lens unit move to the image side. By configuring in this manner, it is possible to suppress an increase in the radial direction of the (n-1) -th lens unit even when the light flux diverged by the second lens unit directly enters the (n-1) -th lens unit. It becomes easy to achieve size reduction and weight reduction of a drive mechanism. Further, by moving the second lens unit and the (n-1) th lens unit in this manner during zooming, it is possible to suppress an increase in the overall optical length of the zoom lens.

  On the other hand, when the n-1th lens group is moved so that the distance between the n-1th lens group and the nth lens group becomes wide during zooming from the wide angle end to the telephoto end, the n-1st lens group at the wide angle end It is necessary to arrange the first lens unit close to the nth lens unit. In this case, at the wide angle end, the luminous flux emitted from the second lens group passes through a long distance and enters the (n-1) th lens group. Therefore, unless there is a lens group having a strong positive refractive power between the second lens group and the (n-1) -th lens group, it is necessary to increase the outer diameter of the lens constituting the (n-1) -th lens group . Therefore, this leads to an increase in size and weight of the n-1st lens group which is a movable group, a load on a drive mechanism for moving the n-1th lens group in the optical axis direction is increased, and the lens unit is miniaturized And it is unpreferable in aiming at weight reduction. Further, assuming that, at the time of zooming from the wide angle end to the telephoto end, both lens groups are moved so that the distance between the second lens group and the (n-1) th lens group becomes narrow, The distance to the (n-1) -th lens unit becomes short. In such a configuration, focusing from an infinite distance object to a near distance object is usually performed by moving the second lens unit to the image side or moving the (n-1) th lens unit to the object side. . When the distance between the second lens unit and the (n-1) th lens unit at the telephoto end is short, the moving amount of the second lens unit or the (n-1) th lens unit can not be secured at the time of focusing. In order to secure the moving amount of the second lens unit or the n-1st lens unit at the time of focusing, it is necessary to secure the distance between the second lens unit and the n-1th lens unit at the telephoto end. Thus, the overall optical length of the zoom lens is undesirably increased.

(2) Focusing Operation In the case of focusing from an infinite distance object to a near distance object, the zoom lens focuses by moving the second lens unit to the image side. By making the zooming operation as described above and moving the second lens group at the time of focusing in this manner, it is possible to secure the amount of movement of the second lens group at the time of focusing while achieving downsizing of the entire optical length. Therefore, the shortest imaging distance can be shortened even at the telephoto end, and a zoom lens capable of close-up imaging can be obtained.

1-3. Conditional Expressions Next, conditions that the zoom lens should or should be satisfied will be described.

1-3-1. Conditional expression (1)
The zoom lens satisfies the following conditions.

(1) 0.40 ≦ m 2 / mn 1 ≦ 3.00
However,
m2: moving amount of the second lens unit during zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side)
mn-1: moving amount of the (n-1) -th lens unit at the time of zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side)

  Conditional expression (1) defines the ratio of the amount of movement of the second lens unit in the optical axis direction during zooming and the amount of movement of the (n−1) th lens unit in the optical axis direction during zooming. . When the conditional expression (1) is satisfied, the ratio of the moving amounts of the second lens unit and the (n-1) th lens unit at the time of zooming becomes within an appropriate range, and while realizing a high zooming ratio, It is possible to suppress an increase in the overall optical length. Further, in this case, it is possible to suppress an increase in the overall optical length while securing the amount of movement of the second lens unit at the time of focusing.

  On the other hand, when the numerical value of the conditional expression (1) becomes smaller than the lower limit value, the moving amount of the second lens unit with respect to the moving amount of the (n-1) th lens unit becomes too small. In such a case, it is difficult to obtain a zoom lens having a large zoom ratio. On the other hand, when the numerical value of the conditional expression (1) exceeds the upper limit value, the moving amount of the second lens unit with respect to the moving amount of the (n-1) th lens unit becomes too large. Therefore, in order to secure the amount of movement of the second lens group at the time of focusing, it is necessary to secure the distance between the second lens group and the (n-1) th lens group at the telephoto end. Thus, the overall optical length of the zoom lens is undesirably increased.

  In order to obtain the above effect, the lower limit value of conditional expression (1) is more preferably 0.50, and still more preferably 0.55. The upper limit is more preferably 2.00, still more preferably 1.80, still more preferably 1.60, still more preferably 1.40, and 1.20. It is even more preferred that

1-3-2. Conditional expression (2)
It is preferable that the zoom lens satisfies the following conditions.
(2) 1.00 ≦ bnt ≦ 3.00
However,
bnt: Lateral magnification of the nth lens group when focusing on an infinite object at telephoto end

  Conditional expression (2) defines the range of the lateral magnification of the n-th lens unit at the time of focusing on an infinity object at the telephoto end. By satisfying the conditional expression (2), it becomes easy to make the zoom lens a bright optical system with a small F number, and spherical aberration can be corrected well. In addition, it is also effective in reducing the size of the zoom lens.

  On the other hand, when the numerical value of the conditional expression (2) becomes smaller than the lower limit value, the lateral magnification of the nth lens group at the time of focusing on an infinite object at the telephoto end is too small. The focal length of the system constituted by the lens units up to the lens unit becomes long, and the total optical length becomes long, which is not preferable in order to miniaturize the zoom lens. On the other hand, if the value of the conditional expression (2) exceeds the upper limit value, the lateral magnification of the nth lens group at the time of focusing on an infinite object at the telephoto end becomes too large, making it difficult to reduce the F number. It is not preferable because a bright optical system can not be realized.

  In order to obtain the above effects, the lower limit value of conditional expression (2) is more preferably 1.10, still more preferably 1.20, and still more preferably 1.30. The upper limit value of conditional expression (2) is more preferably 2.60, further preferably 2.40, still more preferably 2.20, and 2.00 more More preferred.

1-3-3. Conditional expression (3)
It is preferable that the zoom lens satisfies the following conditions.

(3) 0.30 ≦ | f 2 | // (fw × ft) ≦ 1.00
However,
f2: Focal length of the second lens group fw: Focal length of the whole zoom lens system when focusing on an infinite object at the wide angle end ft: Focal length of the whole zoom lens system when focusing on an infinite object at the telephoto end

  Here, “√ (fw × ft)” means the effective focal length of the zoom lens (the focal length of the zoom lens at the intermediate focal length position). Conditional expression (3) defines the ratio of the focal length of the second lens unit to the effective focal length. When conditional expression (3) is satisfied, the refractive power of the second lens unit is appropriate, and it is easy to achieve downsizing and weight reduction of the focusing group, and to easily realize quick autofocus. Become. In addition, since aberration variation caused by the movement of the second lens group can be made within an appropriate range, it becomes easy to realize good optical performance with a small number of lenses.

  On the other hand, when the numerical value of the conditional expression (3) becomes smaller than the lower limit value, the refractive power of the second lens unit becomes strong, so that the aberration fluctuation caused by the movement of the second lens unit during zooming or focusing becomes growing. In order to realize good optical performance, it is necessary to increase the number of lenses for aberration correction. Therefore, it becomes difficult to reduce the size and weight of the second lens unit, and the load on the drive mechanism increases, and it becomes difficult to realize quick autofocus. On the other hand, when the numerical value of the conditional expression (3) exceeds the upper limit value, the refractive power of the second lens unit is weak, and the moving amount of the second lens unit at the time of zooming is increased to realize a high zoom ratio. The amount of movement of the second lens group at the time of focusing also increases. Therefore, the entire optical length of the zoom lens becomes long, and it becomes difficult to reduce the size and weight of the zoom lens.

  In order to obtain the above effect, the lower limit value of the conditional expression (3) is more preferably 0.34, and still more preferably 0.38. The upper limit value is more preferably 0.80, and still more preferably 0.65.

1-3-4. Conditional expression (4)
It is preferable that the zoom lens satisfies the following conditions.
(4) bt ≦ − 0.80
However,
bt: Maximum imaging magnification at the telephoto end of the whole zoom lens system

  Conditional expression (4) defines the maximum imaging magnification at the telephoto end of the zoom lens, that is, the upper limit of the imaging magnification at the shortest imaging distance of the zoom lens. At this time, the imaging magnification refers to the ratio of the height of the image plane (image height) to the height of the subject, and when the conditional expression (4) is satisfied, the zoom lens The zoom lens can be formed to have a size of 0.8 times or more the actual size of the image), and the zoom lens can be a macro lens with a short shortest imaging distance.

  In order to obtain the above effect, the upper limit value of conditional expression (4) is more preferably −0.90, and still more preferably −1.00. It is also preferable to set conditional expression (4) to bt <−0.80, bt <−0.90, and bt <−1.00. There is no particular optical meaning to set the lower limit value of the conditional expression (4), but the lower limit value can be about -10.0, or about -5.0. If the lower limit value of the conditional expression (4) is less than −10.0 or less than −5.0, the amount of movement of the focus group becomes large, so the optical total length of the zoom lens becomes long, which is not preferable.

1-3-5. Conditional expression (5)
It is preferable that the zoom lens satisfies the following conditions.

(5) 0.10 mn-1 / ((fw x ft) 2.00
However,
fw: Focal length of the whole zoom lens system when focusing on an infinite object at the wide angle end ft: Focal length of the whole zoom lens system when focusing on an infinite object at the telephoto end

  Conditional expression (5) defines the ratio of the amount of movement of the (n−1) -th lens unit at the time of zooming and the effective focal length of the zoom lens. By satisfying the conditional expression (5), downsizing and weight reduction of the (n-1) th lens unit which is a movable unit at the time of zooming can be achieved, and a load on the drive mechanism can be reduced. Therefore, the lens unit can be reduced in size and weight. Further, the amount of movement of the (n-1) -th lens unit at the time of zooming can be set within an appropriate range, and an increase in the overall optical length of the zoom lens can be suppressed.

  On the other hand, when the value of the conditional expression (5) is less than the lower limit, the refractive power of the (n-1) th lens group becomes strong, so that the aberration fluctuation accompanying the movement of the (n-1) th lens group during zooming is large. Become. In order to realize good optical performance, it is necessary to increase the number of lenses for aberration correction. Therefore, it becomes difficult to reduce the size and weight of the (n-1) -th lens unit, and the load on the drive mechanism increases. On the other hand, when the numerical value of the conditional expression (5) exceeds the upper limit, the refractive power of the (n-1) th lens unit is weak, and to achieve a high zoom ratio, the movement amount of the n-1 lens group at the time of zooming Need to increase. Therefore, the entire optical length of the zoom lens becomes long, and it becomes difficult to reduce the size and weight of the zoom lens.

  In order to obtain the above effect, the lower limit value of the conditional expression (5) is more preferably 0.12, and still more preferably 0.14. The upper limit value of conditional expression (5) is more preferably 1.80, more preferably 1.60, still more preferably 1.40, and still more preferably 1.20. Preferably, it is 1.00.

1-3-6. Conditional expression (6)
It is preferable that the zoom lens satisfies the following conditions.
(6) 0.20 ≦ fnf / | (fw × ft) ≦ 1.20
However,
fn: Focal length of the nth lens group fw: Focal length of the whole zoom lens system when focusing on an infinite object at the wide angle end ft: Focal length of the whole zoom lens system when focusing on an infinite object at the telephoto end

  Conditional expression (6) defines the ratio of the focal length of the nth lens group to the effective focal length of the zoom lens. When the conditional expression (6) is satisfied, various aberrations generated in the n-th lens unit can be reduced. Therefore, the nth lens group is configured to be movable in the vertical direction with respect to the optical axis, and the image blur is corrected by moving the nth lens group in the vertical direction with respect to the optical axis as a vibration reduction group. When configured, it is possible to reduce decentering coma, decentering astigmatism, and decentering chromatic aberration when the nth lens group is moved in a direction perpendicular to the optical axis. Therefore, good optical performance can be obtained with a small number of lenses during image stabilization, and the zoom lens can be miniaturized even when the image stabilization function is provided. In addition, since the amount of movement in the direction perpendicular to the optical axis of the nth lens group can be made within an appropriate range at the time of image stabilization, it is also possible to suppress an increase in the diameter of the lens barrel that accommodates the zoom lens. it can.

  On the other hand, when the numerical value of the conditional expression (6) is less than the lower limit value, the refractive power of the nth lens group becomes too strong, and it becomes difficult to use the nth lens group as a vibration reduction group. That is, decentering comatic aberration, decentering astigmatism and decentering chromatic aberration when the nth lens group is moved in a direction perpendicular to the optical axis become large. Therefore, in order to maintain good optical performance, a large number of lenses are required for aberration correction. Therefore, the increase in the number of lenses causes the n-th lens unit to be large and heavy, which is not preferable for downsizing the zoom lens. In addition, when the vibration isolation group becomes heavy, the drive mechanism for driving the vibration isolation group also becomes large, which is not preferable. On the other hand, if the numerical value of the conditional expression (6) exceeds the upper limit value, the refractive power of the nth lens group becomes too weak. Therefore, in order to secure the image stabilization correction angle, the optical axis of the nth lens group at the time of image stabilization It is necessary to increase the amount of movement in the vertical direction with respect to. Therefore, in this case, the diameter of the lens barrel that accommodates the zoom lens needs to be increased, which is not preferable in order to miniaturize the lens unit.

  In order to obtain the above effect, the lower limit value of the conditional expression (6) is more preferably 0.30, and still more preferably 0.40. The upper limit value of conditional expression (6) is more preferably 1.00, still more preferably 0.90, and still more preferably 0.80.

2. Imaging Device Next, an imaging device according to the present invention will be described. An image pickup apparatus according to the present invention is characterized by comprising the above-mentioned zoom lens and an image pickup element for converting an optical image (object image) formed by the zoom lens on the image side thereof into an electric signal. Here, although the imaging device etc. is not particularly limited, the zoom lens according to the present invention is suitable for a solid imaging device with a high resolution and a large image height, so that the solid imaging device has a resolution of full hi-vision or higher. Is more preferable, the resolution is 4 K or more, and more preferably 8 K or more.

  The imaging device may be configured as a digital still camera that acquires a still image, or may be configured as a digital video camera that acquires a moving image. In the zoom lens, the above configuration and the like can be adopted, and focusing can be performed quickly by setting the second lens unit as a focusing unit. For example, when an imaging device provided with the zoom lens according to the present invention is connected to the eyepiece of the observation optical system, the subject image can be enlarged and displayed on the display device while appropriately changing the observation magnification and the observation field of view. The details of the subject can be observed well.

  The imaging device may be a lens-fixed imaging device in which the zoom lens is fixed to a housing, or may be a lens-interchangeable imaging device in which the zoom lens is configured to be removable. .

3. Observation Image Display System Next, an observation image display system to which the zoom lens and the imaging device according to the present invention can be preferably applied will be described.

  First, the observation optical system will be described. An observation optical system generally includes an objective lens system and an eyepiece lens system, and an optical system configured to form a primary subject image (real image) by the objective lens system and to substantially collimate it by the eyepiece lens system. It is a system. The observer can observe the subject image through the eyepiece. In some observation optical systems, a relay lens system is disposed between the objective lens system and the eyepiece lens system, and the overall lens length is extended by the relay lens system to form a plurality of intermediate subject images. .

  In the present invention, the eyepiece portion of the observation optical system mainly refers to a lens barrel portion in which an eyepiece lens system is accommodated, and generally refers to a part or a portion called an eyepiece lens or an eyepiece.

  Specific examples of the observation optical system include a microscope, a rigid endoscope (rigid endoscope), and the like. The zoom lens can be suitably used by being connected to the eyepieces of these observation optical systems. Below, the case where it connects and uses for the eyepiece part of an endoscope, especially a rigid endoscope, is mentioned as an example, and is demonstrated.

  The rigid endoscope generally comprises a thin cylindrical insertion portion inserted into the narrow portion, and an eyepiece portion connected to the insertion portion, the objective lens system is accommodated in the insertion portion, and the eyepiece portion The eyepiece system is accommodated as described above. In the case of a rigid endoscope used in the medical field, the insertion portion is inserted into the body through a hole or the like made in the patient's body, and the eyepiece is placed outside the body. In order to secure the length of the insertion portion, the relay lens system may be accommodated together with the objective lens system in the insertion portion, or a relay portion in which the relay lens system is accommodated between the insertion portion and the eyepiece. It may be connected. To realize a rigid endoscope image display system for displaying an object image acquired by the rigid endoscope on a display device such as a monitor by connecting an imaging device including the zoom lens, an imaging device, etc. to an eyepiece of the rigid endoscope. Can.

  However, the zoom lens is not limited to a mode in which the zoom lens is connected to the eyepiece portion of the rigid scope, and can be connected to the eyepiece portions of various observation optical systems such as a microscope. By connecting to the eyepiece, an observation image display system similar to the above can be realized.

  As described above, in the aspect of being connected to the eyepiece of the observation optical system, in the zoom lens, the imaging visual field (observation angle of view) is continuously adjusted by adjusting the moving amount of each movable group, etc. The observation magnification of the affected area can be arbitrarily changed. Therefore, at the time of endoscopic surgery etc. using a rigid endoscope image display system, according to the progress of surgery, expansion observation of a diseased part, partial observation, etc. can be performed arbitrarily. At that time, it is not necessary to change the distance between the tip of the insertion portion of the rigid endoscope (more precisely, the tip of the objective lens) and the affected part (object), that is, the working distance of the rigid endoscope. Therefore, while the tip of the insertion portion of the rigid endoscope is disposed at a position not interfering with the surgical instrument etc., it is possible to adjust to the required viewing field and observation magnification required according to the progress of the surgery. Furthermore, since there is no need to provide a magnification changing mechanism on the rigid endoscope side, the optical configuration of the rigid endoscope can be simplified, and enlargement of the rigid endoscope, in particular, enlargement of the insertion portion can be suppressed. Here, the zooming mechanism refers to a movable group provided to change the magnification of the object image, and a driving mechanism such as a cam for moving the movable group in the optical axis direction.

  It is preferable that such a rigid endoscope image display system has an image processing unit that electrically processes image data related to an optical image generated by a zoom lens. The image processing unit may be provided in the imaging device main body, or may be provided in a control device (for example, a personal computer or the like) that controls the image display operation of the display device.

  In the zoom lens according to the present invention, when attempting to obtain a small-sized, high-resolution optical system while achieving a high zoom ratio, distortion of the image shape is likely to occur. Therefore, in the observation image display system, by providing an image processing unit that electrically processes the distortion of the image shape to the image data, an observation object image with little distortion of the image shape is output to an image output device or the like. be able to. The image processing unit corrects the image data by correlating the correction data with the storage unit in which the correction data for correcting the distortion of the image shape is stored in advance, the image data acquired by the observation imaging apparatus, and the correction data. It is preferable to include an arithmetic processing unit (CPU) or the like.

  Here, it is preferable that the image processing unit electrically processes data related to distortion among image data related to an optical image formed by the zoom lens. If it is possible to electrically process data relating to distortion in the image processing unit, the observation subject image can be obtained even if the second lens group of the zoom lens is formed of a lens of a small diameter and strong refractive power is arranged. It can be displayed on an image output device etc. without distortion.

  Further, it is preferable that the image processing unit electrically processes data relating to lateral chromatic aberration among image data relating to an optical image formed by the zoom lens. If it is possible to electrically process data relating to lateral chromatic aberration in the image processing unit, it is possible to display an object image with small chromatic aberration on an image output device or the like. Therefore, it is possible to reduce the number of lenses constituting the zoom lens, and to miniaturize the zoom lens.

  Next, the present invention will be specifically described by showing examples. However, the present invention is not limited to the following examples. The optical system in each of the following embodiments is an observation optical system as an imaging optical system used in an imaging apparatus (optical apparatus) such as a digital camera or a video camera, and in particular, performs internal observation of a microscope or a narrow space. The present invention can be preferably applied to an observation imaging apparatus for Further, in each lens sectional view, the left side in the drawing is the observation subject side (object side), and the right side is the image side.

  Embodiments of the zoom lens according to the present invention will be described with reference to the drawings. FIG. 1 is a view showing an example of the lens configuration of the zoom lens according to the first embodiment. An upper stage is a lens block diagram in a wide-angle end state, and a lower stage is a lens block diagram in a telephoto end state.

  As shown in FIG. 1, in the zoom lens according to Example 1, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive index are arranged in order from the object side. It comprises a third lens group G3 having a force and a fourth lens group G4 having a negative refractive power. The zoom lens is used by being connected to an eyepiece of a rigid endoscope (not shown). The specific lens configuration of each lens group is as shown in FIG. Further, in FIG. 1, “S” shown on the object side of the first lens group G1 indicates a virtual diaphragm position when the eyepiece of the rigid endoscope is connected. In addition, "CG" refers to cover glass, low pass filter, infrared filter and so on. “I” is an image plane, and indicates an imaging surface of a solid-state imaging device such as a CCD sensor or a CMOS sensor, a film surface of a silver salt film, or the like. These points are the same as in the lens cross-sectional views shown in the other embodiments, so the description will be omitted below.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed in the optical axis direction, and the second lens group G2 and the third lens group G3 have different loci on the image side Move to At the time of focusing from an infinite distance object to a close distance object, the second lens group G2 moves to the image side. In addition, the fourth lens group G4 is configured to be movable in a direction perpendicular to the optical axis, and by moving the fourth lens group G4 in a direction perpendicular to the optical axis, camera movement or the like occurs during imaging. Image blur can be corrected.

  In the zoom lens of Embodiment 1, the third lens unit is the (n-1) th lens unit, and the fourth lens unit is the nth lens unit.

  FIGS. 2 to 4 show longitudinal aberration diagrams of spherical aberration, astigmatism and distortion, respectively, at infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state of the zoom lens according to the first embodiment. . In the spherical aberration diagram, the vertical axis represents the f-number (indicated by FNO in the figure), the solid line represents d-line (wavelength λ = 587.56 nm), the short broken line represents g-line (wavelength λ = 435.84 nm), and the long broken line represents C It is a characteristic of a line (wavelength λ = 656.27 nm). In the astigmatism diagram, the vertical axis represents the angle of view (W in the figure), the solid line represents the sagittal plane (S in the figure), and the broken line the characteristics of the meridional plane (M in the figure). is there. In the distortion aberration diagram, the vertical axis represents the angle of view (indicated by W in the figure). However, these are the characteristics of the zoom lens itself, and the characteristics when the zoom lens is used alone without being connected to the eyepiece of the rigid endoscope. The same applies to the lateral aberration described next. In each of the lateral aberration diagrams, dec represents the movement amount of the vibration reduction group.

  FIG. 5 is a lateral aberration diagram of the zoom lens of Embodiment 1 at the telephoto end. In each lateral aberration diagram shown in FIG. 5, the three aberration diagrams positioned on the left side as viewed in the drawing correspond to the basic state in which no camera shake correction is performed at the telephoto end (vibration correction amount 0 deg). Further, three aberration diagrams positioned on the right side in the drawing correspond to a camera shake correction state at the telephoto end where the fourth lens unit as the vibration reduction unit is moved by a predetermined amount in the direction perpendicular to the optical axis.

  Of the lateral aberration diagrams in the basic state, the upper row shows the lateral aberration at the image point of 70% of the maximum image height, the middle row shows the lateral aberration at the axial image point, and the lower row shows the horizontal aberration at the image point of -70% of the maximum image height Correspond to each. Of the horizontal aberration diagrams in the camera shake correction state, the upper row shows the horizontal aberration at the image point of 70% of the maximum image height, the middle row shows the horizontal aberration at the axial image point, and the lower row shows the horizontal image at the -70% image point of the maximum image height. Each corresponds to the aberration. In each lateral aberration diagram, the horizontal axis represents the distance from the chief ray on the pupil plane, the solid line represents the d-line, the short broken line the g-line, and the long broken line the C-line. Further, with respect to the zoom lens, an angle change amount by moving the anti-vibration group in the direction perpendicular to the optical axis by a predetermined amount at the time of camera shake correction is 0.3 degrees. The amount of movement of the vibration reduction group at that time is 0.836 mm.

  As apparent from FIG. 5, it is understood that the symmetry of the transverse aberration at the on-axis image point is good. In addition, when the lateral aberration at the + 70% image point and the lateral aberration at the −70% image point are compared in a basic state, the degree of curvature is small and the inclination of the aberration curve is almost equal. It can be seen that the aberration is small. This means that sufficient imaging performance is obtained even in the camera shake correction state. Also, at any zoom position, it is possible to perform sufficient shake correction for the shake correction angle up to 0.3 ° without reducing the imaging characteristics. Furthermore, it is possible to make the shake correction angle even larger than 0.3 ° by further increasing the movement amount of the vibration reduction group in the direction perpendicular to the optical axis. These points are the same as in the other embodiments described later.

  Next, lens data of Numerical Example 1 to which specific numerical values are applied in the present Example 1 is shown in Table 1. The lens data shown in Table 1 are as follows. The "surface number" indicates the order of the lens surfaces counted from the object side. “R” indicates the radius of curvature of the lens surface, “d” indicates the lens thickness or the distance on the optical axis of the lens surfaces adjacent to each other, “nd” indicates the refractive index for the d-line, and “vd” The Abbe number for d line is shown. Also, “∞” described in the column of “r” means that the radius of curvature is ∞ (infinity). Further, a column described as "dn (where n is a plane number)" such as "d5" described in the column "d" indicates that it is a variable interval at the time of zooming. The unit of length in each table is all "mm" and the unit of angle of view is all "°".

  Table 2 shows various data of the zoom lens. Table 2 shows the “focal length”, “F number”, “half angle of view”, “full lens length (optical total length)”, “back focus” of the zoom lens at the wide angle end, intermediate focal length position, and telephoto end. The variable interval on the optical axis at the time of zooming shown in Table 1 (in focus at infinity) "dn" is shown. Table 2 also shows the zoom ratio and the image height of the zoom lens.

  Table 3 shows the “starting surface” and “focal length” of each lens unit constituting the zoom lens, “configuration length” corresponding to the length on the optical axis from the starting surface to the end surface of each lens unit, and The "movement amount" on the optical axis of each lens unit at the time of magnification is shown. However, the sign is positive for movement toward the image side.

  Table 4 shows the lateral magnifications of the respective lens units at the wide-angle end, the intermediate focal length position, and the telephoto end, together with the front surfaces of the respective lens units.

  Table 5 shows the maximum imaging magnification at the telephoto end of the zoom lens and the variable interval on the optical axis at the time of focusing of the nearest point object at the telephoto end. The closest point object means an object at the shortest imaging distance position of the zoom lens.

  Table 26 shows the numerical values of the conditional expression (1) to the conditional expression (6) of the zoom lens.

  The matters relating to these drawings and tables are the same as in the other embodiments, and thus the description thereof will be omitted below.

(1) Configuration of Optical System FIG. 6 is a cross-sectional view showing an example of the lens configuration of a zoom lens according to a second embodiment of the present invention. As shown in FIG. 6, in the zoom lens according to the second embodiment, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive index are arranged in order from the object side. It comprises a third lens group G3 having a force and a fourth lens group G4 having a negative refractive power. The zoom lens is used by being connected to an eyepiece of a rigid endoscope (not shown). The specific lens configuration of each lens group is as shown in FIG. The third lens group G3 is an n-1th lens group, and the fourth lens group G4 is an nth lens group.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed in the optical axis direction, and the second lens group G2 and the third lens group G3 have different loci on the image side Move to At the time of focusing from an infinite distance object to a close distance object, the second lens group G2 moves to the image side. In addition, the fourth lens group G4 is configured to be movable in a direction perpendicular to the optical axis, and by moving the fourth lens group G4 in a direction perpendicular to the optical axis, camera movement or the like occurs during imaging. Image blur can be corrected. The movement amount of the vibration control group is 0.779 mm when the angle change amount by moving the vibration control group by a predetermined amount in the direction perpendicular to the optical axis at the time of camera shake correction is 0.3 degrees.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 6 shows surface data of the zoom lens, Table 7 shows various data, Table 8 shows data on each lens group constituting the zoom lens, and Table 9 shows lateral magnification of each lens group, etc. Table 10 shows the maximum imaging magnification and the like at the telephoto end of the zoom lens. Table 26 shows the numerical values of the conditional expression (1) to the conditional expression (6) of the zoom lens.

  FIGS. 7 to 9 show spherical aberration, astigmatism and distortion at the time of infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state of the zoom lens according to the second embodiment, respectively. FIG. 10 shows a lateral aberration diagram of the zoom lens of Embodiment 2 at the telephoto end.

(1) Configuration of Optical System FIG. 11 is a sectional view showing an example of the lens configuration of a zoom lens according to a third embodiment of the present invention. As shown in FIG. 11, in the zoom lens according to Example 3, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive index are arranged in order from the object side. It comprises a third lens group G3 having a force and a fourth lens group G4 having a negative refractive power. The zoom lens is used by being connected to an eyepiece of a rigid endoscope (not shown). The specific lens configuration of each lens group is as shown in FIG. The third lens group G3 is an n-1th lens group, and the fourth lens group G4 is an nth lens group.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed in the optical axis direction, and the second lens group G2 and the third lens group G3 have different loci on the image side Move to At the time of focusing from an infinite distance object to a close distance object, the second lens group G2 moves to the image side. In addition, the fourth lens group G4 is configured to be movable in a direction perpendicular to the optical axis, and by moving the fourth lens group G4 in a direction perpendicular to the optical axis, camera movement or the like occurs during imaging. Image blur can be corrected. The amount of movement of the vibration control group is 0.640 mm when the angle change amount by moving the vibration control group by a predetermined amount in the direction perpendicular to the optical axis at the time of camera shake correction is 0.3 degrees.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 11 shows surface data of the zoom lens, Table 12 shows various data, Table 13 shows data on each lens group constituting the zoom lens, and Table 14 shows lateral magnification and the like of each lens group. Table 15 shows the maximum imaging magnification and the like at the telephoto end of the zoom lens. Table 26 shows the numerical values of the conditional expression (1) to the conditional expression (6) of the zoom lens.

  FIGS. 12 to 14 respectively show spherical aberration, astigmatism and distortion at the time of infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state of the zoom lens according to the third embodiment. FIG. 15 shows a lateral aberration diagram of the zoom lens of Embodiment 3 at the telephoto end.

(1) Configuration of Optical System FIG. 16 is a sectional view showing an example of the lens configuration of a zoom lens according to a fourth embodiment of the present invention. As shown in FIG. 16, in the zoom lens according to the fourth embodiment, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive index are arranged in order from the object side. It comprises a third lens group G3 having a force and a fourth lens group G4 having a negative refractive power. The zoom lens is used by being connected to an eyepiece of a rigid endoscope (not shown). The specific lens configuration of each lens group is as shown in FIG. The third lens group G3 is an n-1th lens group, and the fourth lens group G4 is an nth lens group.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed in the optical axis direction, and the second lens group G2 and the third lens group G3 have different loci on the image side Move to At the time of focusing from an infinite distance object to a close distance object, the second lens group G2 moves to the image side. In addition, the fourth lens group G4 is configured to be movable in a direction perpendicular to the optical axis, and by moving the fourth lens group G4 in a direction perpendicular to the optical axis, camera movement or the like occurs during imaging. Image blur can be corrected. The amount of movement of the vibration control group is 1.416 mm when the angle change amount by moving the vibration control group by a predetermined amount in the direction perpendicular to the optical axis during hand movement correction is 0.3 degrees.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 16 shows surface data of the zoom lens, Table 17 shows various data, Table 18 shows data on each lens group constituting the zoom lens, Table 19 shows lateral magnification of each lens group, etc. Table 20 shows the maximum imaging magnification and the like at the telephoto end of the zoom lens. Table 26 shows the numerical values of the conditional expression (1) to the conditional expression (6) of the zoom lens.

  FIGS. 17 to 19 show spherical aberration, astigmatism and distortion at the time of infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state of the zoom lens according to the fourth embodiment, respectively. FIG. 20 shows a lateral aberration diagram of the zoom lens of Embodiment 4 at the telephoto end.

(1) Configuration of Optical System FIG. 21 is a sectional view showing an example of the lens configuration of a zoom lens according to a fifth embodiment of the present invention. As shown in FIG. 21, in the zoom lens according to Example 5, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive index are arranged in order from the object side. The third lens group G3 having a force, the fourth lens group G4 having a positive refractive power, and the fifth lens group G4 having a negative refractive power. The zoom lens is used by being connected to an eyepiece of a rigid endoscope (not shown). The specific lens configuration of each lens group is as shown in FIG.
The fourth lens group G4 is an n-1th lens group, and the fifth lens group G5 is an nth lens group.

  When zooming from the wide-angle end to the telephoto end, the first lens group G1 and the fourth lens group G4 are fixed in the optical axis direction, and the second lens group G2, the third lens group G3 and the fourth lens group G4 It moves to the image side with different trajectories. At the time of focusing from an infinite distance object to a close distance object, the second lens group G2 moves to the image side. The fifth lens group G5 is configured to be movable in a direction perpendicular to the optical axis. By moving the fifth lens group G5 in a direction perpendicular to the optical axis, the fifth lens group G5 is generated during imaging such as camera shake. Image blur can be corrected. The amount of movement of the vibration control group is 0.823 mm when the angle change amount by moving the vibration control group by a predetermined amount in the direction perpendicular to the optical axis during hand movement correction is 0.3 degrees.

(2) Numerical Example Next, a numerical example to which a specific numerical value of the zoom lens is applied will be described. Table 21 shows surface data of the zoom lens, Table 22 shows various data, Table 23 shows data on each lens group constituting the zoom lens, and Table 24 shows lateral magnification of each lens group, etc. Table 25 shows the maximum imaging magnification and the like at the telephoto end of the zoom lens. Table 26 shows the numerical values of the conditional expression (1) to the conditional expression (6) of the zoom lens.

  FIGS. 21 to 23 show spherical aberration, astigmatism and distortion at the time of infinity focusing in the wide-angle end state, the intermediate focal length state and the telephoto end state of the zoom lens according to the fifth embodiment, respectively. FIG. 25 shows a lateral aberration diagram of the zoom lens of the fifth embodiment at the telephoto end.

(Example of imaging apparatus)
Next, an embodiment of an imaging device according to the present invention will be described. The imaging device 10 according to the present invention is connected to the rigid endoscope 20 and used. The imaging device 10 includes a lens unit that accommodates the zoom lens 11 according to the present invention, and an imaging device main body 12 to which the lens unit is detachably attached. In the lens unit, for example, the zoom lens according to any one of the first to fifth embodiments can be accommodated. In the first lens group G1 of each embodiment, the flat plates (surface numbers 1 and 2) disposed closest to the object side are cover glasses, and the cover glass on the object side (eyepiece) Prevent the ingress of dust, dirt and water from the department side). In the zoom lens, the lens disposed closest to the image side and the housing of the lens unit are sealed, and dust, water, etc. from the image side are prevented from entering the lens unit housing. . An imaging element 13 (I) is disposed in the imaging device body 12, and a cover glass (CG) is disposed on the object side of the imaging element 13. A display device 14 such as a liquid crystal monitor is provided on the back side of the imaging device body.

  The rigid mirror 20 includes, in order from the object side, a lens barrel 21 in which an objective lens system (not shown), a relay lens system (not shown), and an eyepiece lens system (not shown) are accommodated, a light source 22, and an illumination optical system. It has 23 and. The lens barrel portion 21 is formed to be elongated in the entire optical length direction, and the object side thereof corresponds to the insertion portion described above, and is inserted into, for example, the body of a patient. The image side of the lens barrel 21 corresponds to the above-described eyepiece, and a doctor or the like can observe the inside of a patient, that is, an affected area or the like through the eyepiece. In addition, a lens unit is connected to the eyepiece unit. The light source 22 is provided outside the lens barrel 21 and near the eyepiece. The illumination optical system 23 transmits the illumination light from the light source 22 to the object side of the lens barrel 21 and illuminates the affected area and the like. Although not shown in FIG. 26, the imaging apparatus main body 11 is connected to a personal computer or the like provided with the above-mentioned image processing unit via the communication connection means, and the rigid mirror 20 and the imaging apparatus are displayed on a display device such as a personal computer. A rigid endoscope image (observation image) of an affected area or the like acquired according to 10 may be displayed. In addition, the image pickup apparatus main body or a personal computer connected to the image pickup apparatus main body and a personal computer etc. at a remote place are connected via communication connection means such as the Internet, and a display area at a remote place The rigid endoscope image of may be displayed. With such a configuration, the rigid endoscope image display system (observation image display system) can be realized.

  In the embodiment of the imaging device, the imaging device 10 and the rigid mirror 20 are connected freely. In the embodiment of the imaging device, the lens unit accommodating the variable magnification optical system 11 is exchangeably attached to the imaging device main body 12. However, the imaging device according to the present invention is not limited to these modes, and the lens unit and the imaging device main body 12 may be integrally (not separably) configured, or the imaging device 10 and the rigid endoscope Of course, 20 may be integrated.

  According to the present invention, it is possible to provide a zoom lens capable of proximity imaging while achieving downsizing and weight reduction as a whole.

G1 ... first lens group G2 ... second lens group G3 ... third lens group G4 ... fourth lens group G5 ... fifth lens group F ... focusing group VC · · · Anti-vibration group S: virtual aperture position 10: imaging device 11: zoom lens 12: imaging device main body 13: imaging device 14: display device 20: rigid mirror (observation Optical system)
21 ··· Lens barrel 22 ··· Light source 23 · · · Illumination optical system

Claims (8)

It consists of n lens groups (where n is a natural number of 4 or more),
From the object side, it comprises a first lens group having a positive refractive power and a second lens group having a negative refractive power,
A zoom that includes an n-th lens unit having a negative refractive power and an n-1st lens unit having a positive refractive power in order from the image side, and performs zooming by changing an air space between the lens units A lens,
When zooming from the wide-angle end to the telephoto end, the first lens unit and the n-th lens unit are fixed in the optical axis direction, and the distance between the first lens unit and the second lens unit is wide. Moving the second lens group and the n-1st lens group in the optical axis direction such that the distance between the n-1th lens group and the nth lens group becomes narrow;
During focusing from an infinite distance object to a near distance object, focusing is performed by moving one lens unit other than the first lens unit and the nth lens unit in the optical axis direction,
A zoom lens characterized by satisfying the following conditions.
(1) 0.40 ≦ m 2 / mn 1 ≦ 3.00
However,
m2: moving amount of the second lens unit at the time of zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side)
mn-1: moving amount of the (n-1) -th lens unit at the time of zooming from the wide-angle end to the telephoto end (the sign is positive with respect to the movement to the image side) The zoom lens according to claim 1, wherein the following conditions are satisfied.
(2) 1.00 ≦ bnt ≦ 3.00
However,
bnt: Lateral magnification of the n-th lens unit when focusing on an infinite object at the telephoto end The zoom lens according to claim 1, wherein the following condition is satisfied.
(3) 0.30 ≦ | f 2 | // (fw × ft) ≦ 1.00
However,
f2: Focal length of the second lens group fw: Focal length of the entire zoom lens system when focusing on an infinite object at the wide-angle end ft: Focal length of the entire zoom lens system when focusing on an infinite object at the telephoto end The zoom lens according to any one of claims 1 to 3, which satisfies the following conditions.
(4) bt ≦ − 0.80
However,
bt: Maximum imaging magnification at the telephoto end of the whole zoom lens system The zoom lens according to any one of claims 1 to 4, wherein the following conditions are satisfied.
(5) 0.10 mn-1 / ((fw x ft) 2.00
However,
fw: Focal length of the whole zoom lens system when focusing on an infinite object at the wide angle end ft: Focal length of the whole zoom lens system when focusing on an infinite object at the telephoto end The zoom lens according to any one of claims 1 to 5, wherein the following conditions are satisfied.
(6) 0.20 ≦ fnf / | (fw × ft) ≦ 1.20
However,
fn: Focal length of the nth lens group fw: Focal length of the entire zoom lens system when focusing on an infinite object at the wide-angle end ft: Focal length of the entire zoom lens system when focusing on an infinite object at the telephoto end   The zoom lens according to any one of claims 1 to 6, wherein when focusing from an infinite distance object to a close distance object, the second lens unit is moved to the image side to focus.   A zoom lens according to any one of claims 1 to 7, and an image pickup device for converting an optical image formed by the zoom lens to an electrical signal on the image side thereof. Imaging device.

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