JP2007212847A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens constituted so that aberration fluctuation arising when a camera shake correction lens group is shifted in a direction vertical to an optical axis is reduced, and to provide an imaging apparatus using the zoom lens. <P>SOLUTION: The zoom lens is constituted of four groups, that is, positive, negative, positive and positive groups arranged in order from an object side. The third lens group comprises a fixed negative group and a positive group which is made movable in the direction vertical to the optical axis so as to correct the movement of an image by the deviation of the optical axis. The negative group has at least a biconcave lens and biconvex lens, and also, at least one surface is an aspherical surface A. The positive group comprises two lenses, convex and concave lenses, and at least one surface is an aspherical surface B. Against spherical aberration at a wide-angle end, the shape of the aspherical surface A is set so that the spherical aberration of the whole system may be inclined to an over-side when the aspherical surface A is replaced with the paraxial spherical surface, and also, against the spherical aberration at the wide-angle end, the shape of the aspherical surface B is set so that the aberration of the whole system is inclined to the under-side when the aspherical surface B is replaced with the paraxial spherical surface. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. Specifically, the present invention relates to a zoom lens that is suitable for a camera that receives light by an image sensor such as a video camera or a digital still camera, and has an optical camera shake correction function, and an image pickup apparatus using the zoom lens.

  As a zoom lens suitable for a video camera, a digital still camera, or the like that records a subject image with an image sensor, for example, a positive / negative positive / positive four-group zoom lens is known.

  The positive / negative / positive / positive four-group zoom lens includes, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, and positive refraction. The fourth lens group having a force is arranged, the first lens group and the third lens group are fixed in the optical axis direction, and the second lens group moves on the optical axis, so that the zooming action is mainly performed. Thus, the fourth lens group moves on the optical axis, thereby performing an action to compensate for a change in image plane position caused by the movement of the second lens group and a focusing action. Specifically, what was described in patent document 1 is known.

  By the way, in an optical system with a large zoom ratio, the angle of view in the telephoto end state becomes narrow, and there has been a problem that image blurring occurs greatly even with minute camera shake.

  An optical camera shake correction system is known as a camera shake correction method for correcting image blur due to camera shake or the like.

  The optical image stabilization system includes a lens shift system that shifts a part of the lens system in a direction perpendicular to the optical axis, or a variable apex angle prism that changes the apex angle of a prism arranged immediately before the lens system, etc. The method is known. However, since the variable apex angle prism is arranged on the object side of the largest first lens group in the lens system, there is a problem in that the size is reduced when the drive system is included.

  The lens shift type optical system is based on, for example, a detection system that detects camera shake due to camera shake, a control system that gives a correction amount to the lens position based on a signal output from the detection system, and an output from the control system. By combining with a shift drive system that drives the shift lens, it is possible to function as an optical camera shake correction system that corrects image blur due to camera shake by lens shift by the drive system.

  As these lens shift type optical systems, for example, those described in Patent Document 2, Patent Document 3, or Patent Document 4 are known.

  The zoom lenses described in these patent documents shift the image by shifting the entire third lens group arranged in the vicinity of the aperture stop or a part of the lens in a direction substantially perpendicular to the optical axis. Is possible.

  Since the third lens group is a lens group fixed in the optical axis direction, a shift drive system larger in the radial direction than the lens diameter can be fixed in the optical axis direction, which is suitable for downsizing the entire system.

  In the zoom lens described in Patent Document 4, the image is shifted by shifting the entire third lens group.

  In the zoom lens described in Patent Document 3, the third lens group includes a positive subgroup and a negative subgroup, and the image is shifted by shifting the positive subgroup.

  In the zoom lens described in Patent Document 2, the third lens group includes a negative subgroup and a positive subgroup, and the image is shifted by shifting the positive subgroup.

JP-A-62-215225 JP 2002-244037 A JP 2003-228001 A JP 2003-295057 A

  However, the conventional lens shift type optical system has a problem in the balance between miniaturization and high performance.

  For example, when the entire third lens unit is shifted as in the zoom lens described in Patent Document 4, there is a problem that it is difficult to achieve both a reduction in the diameter of the first lens unit and an increase in performance.

  In the conventional positive / negative positive / positive 4 group zoom lens, the axial light beam emitted from the third lens group is close to parallel light, and the variation of the axial aberration due to the mutual eccentricity between the third lens group and the fourth lens group is small. Since the off-axis aberration changes greatly, the zoom lens according to Patent Document 4 strongly converges the light beam emitted from the third lens group.

  As a result, the off-axis light beam passing through the fourth lens group approaches the optical axis, and it becomes impossible to satisfactorily correct the coma variation due to the change in the angle of view. For this reason, in order to achieve high performance, it is necessary to weaken the refractive power of the second lens group and to separate the off-axis light beam passing through the first lens group and the second lens group from the optical axis. It was difficult to achieve both a smaller diameter and higher performance.

  In the zoom lens described in Patent Document 3, the third lens group is composed of two partial groups, that is, a positive partial group and a negative partial group, so that the on-axis light beam emitted from the positive partial group is converged, negative Since the on-axis light beam exiting the partial group can be configured in a state close to parallel light, both high performance and a reduction in the lens diameter of the first lens group can be achieved.

  However, there is a problem that it is difficult to shorten the overall length of the lens.

  In the zoom lens according to Patent Document 3, the lateral magnification of the lens unit disposed on the image side of the positive subgroup in the third lens group exceeds 1 ×, so that the positive subgroup is slightly displaced in the optical axis direction. In this case, the image plane position is greatly displaced in the optical axis direction.

  In the zoom lens according to Patent Document 2, the third lens group is composed of a negative subgroup and a positive subgroup, and the positive subgroup is composed of three lenses, but the lens 3 having a larger effective diameter than the negative subgroup. Since the weight of the sheet is heavy, there has been a problem that the drive device for moving the positive subgroup at high speed for camera shake correction is increased in size and power consumption is increased.

  In view of the above-mentioned problems, the present invention reduces the weight of a shift lens group for correcting camera shake, corrects various aberrations in a well-balanced manner in the entire zoom range of the entire system, and the shift lens group is perpendicular to the optical axis. It is an object of the present invention to provide a zoom lens capable of correcting camera shake that can sufficiently suppress aberration fluctuations when shifted in the direction, and an imaging apparatus using the zoom lens.

  A zoom lens according to an embodiment of the present invention includes a first lens group that is positioned in order from the object side and always has a positive refractive power, and a negative refractive power that moves in the direction of the optical axis and mainly performs zooming. A second lens group that has a positive refractive power that is fixed during zooming and focusing, and a positive lens that moves in the optical axis direction and corrects and focuses the fluctuation of the image plane position due to zooming. The third lens group is composed of a negative part group that is always fixed and has a negative refractive power, and is movable in a direction perpendicular to the optical axis and is capable of moving an image due to blurring of the optical axis. A negative subgroup having at least a biconcave lens and a biconvex lens and having at least one aspherical surface, the positive subgroup being a convex lens and a concave lens. When it consists of two pieces of The aspherical surface of the negative subgroup is compared with the spherical aberration curve at the wide-angle end in the reference state in which at least one surface is formed of an aspherical surface and the positive subgroup shares the optical axis with the negative subgroup. The shape of the aspheric surface of the negative subgroup is set so that the spherical aberration curve of the entire system when it is replaced with the paraxial spherical surface is inclined to the over side, and the spherical aberration curve at the wide angle end in the reference state is set. The shape of the aspherical surface of the positive subgroup is set so that the spherical aberration curve of the entire system when the aspherical surface of the positive subgroup is replaced with its paraxial spherical surface is inclined downward.

  In addition, an imaging apparatus according to an embodiment of the present invention includes the zoom lens according to the above-described embodiment of the present invention, and an imaging element that converts an optical image formed by the zoom lens into an electrical signal.

  In the present invention, camera shake correction is possible, the camera shake correction shift lens group can be reduced in weight, various aberrations can be corrected in a balanced manner in the entire zoom range in the entire system, and The aberration variation when the shift lens group is shifted in the direction perpendicular to the optical axis can be suppressed sufficiently small.

  The best mode for carrying out the zoom lens and the imaging apparatus of the present invention will be described below with reference to the drawings.

  The zoom lens according to the present invention includes a first lens group that is positioned in order from the object side and has a positive refractive power, and a second lens that has a negative refractive power that moves in the optical axis direction and mainly performs zooming. A third lens group having a positive refractive power that is fixed during zooming and focusing, and a first lens group having a positive refractive power that moves in the optical axis direction and corrects and focuses fluctuations in image plane position due to zooming. The third lens group is composed of a negative part group that is always fixed and has a negative refractive power, and a positive lens that can move in a direction perpendicular to the optical axis and correct image movement due to optical axis blurring. The negative subgroup includes at least a biconcave lens and a biconvex lens, and at least one surface is aspherical. The positive subgroup includes a convex lens and a concave lens. And at least one side With respect to the spherical aberration curve at the wide-angle end in the reference state where the positive subgroup shares an optical axis with the negative subgroup, the aspherical surface of the negative subgroup is changed to a paraxial spherical surface. The shape of the aspherical surface of the negative portion group is set so that the spherical aberration curve of the entire system when replaced is inclined to the over side, and the positive subgroup is set with respect to the spherical aberration curve at the wide-angle end in the reference state. The shape of the aspherical surface of the positive subgroup is set so that the spherical aberration curve of the entire system when the aspherical surface is replaced with the paraxial spherical surface is inclined downward.

  Here, the inclination of the spherical aberration curve to the over side means that the rays of the annular zone converge on the side farther from the lens as the effective aperture increases, and the spherical aberration curve to the under side. Inclination means that the rays of the zonal converge on the side closer to the lens as the effective aperture increases.

  As described above, it is possible to reduce the weight of the movable lens group for camera shake correction, that is, the shift lens group, by configuring the positive part group in the third lens group with two lenses. In the prior art, if all the lens surfaces of the third lens group having a positive refractive power as a whole are composed of only spherical surfaces, the under-side spherical aberration is positive with the negative subgroup in the third lens group. It has been considered that it is important that the aspherical surfaces arranged in the subgroups work so as to suppress the aberration generated in each lens group. In order to mitigate aberration deterioration when the positive subgroup is decentered (shifted) in a direction perpendicular to the optical axis in order to correct camera shake, an over spherical surface generated from the aspherical surface of the positive subgroup. It is important to increase the aberration to an excessive amount, and from the aspherical surface of the fourth lens group, it is overloaded to correct aberrations of the entire system and reduce aberration fluctuations accompanying the movement of the fourth lens group. The spherical aberration on the side is greatly generated. In the zoom lens of the present invention, in order to cancel out the spherical aberration on the over side, an aspherical surface in which the spherical aberration on the under side is generated is introduced into the negative subgroup, so that the positive subgroup and the optical axis are As a result, it is possible to correct various aberrations in the entire zoom range in the entire system in a reference state sharing the same, and to suppress aberration fluctuations sufficiently when the positive subgroup is decentered.

  When a plurality of surfaces of the negative subgroup are aspherical surfaces, the shape of the spherical aberration curve may be inclined to the over side when all the surfaces are simultaneously replaced with the respective paraxial spherical surfaces. The same effect may not be obtained by replacing only one individual surface with a spherical surface. Further, when a plurality of surfaces of the positive subgroup are aspherical surfaces, the shape of the spherical aberration curve may be inclined to the under side when all the surfaces are replaced with the respective paraxial spherical surfaces at the same time. The same effect may not be obtained by replacing only one individual surface with a spherical surface.

In a zoom lens according to an embodiment of the present invention, fw is a focal length at the wide-angle end of the entire lens system, FN is an open F number at the wide-angle end of the entire lens system, and SAA is a negative lens disposed in the third lens group. The value of the spherical aberration of the entire lens system at the open F number at the wide-angle end when the aspherical surface of the subgroup is replaced with its paraxial spherical surface, SAB is the aspherical surface of the positive subgroup disposed in the third lens group Where the paraxial spherical surface is replaced with the value of the spherical aberration of the entire lens system at the open F number at the wide angle end, and f32 is the focal length of the positive subgroup arranged in the third lens group, and the following conditions It is desirable to satisfy formulas (1) and (2).
(1) -2 <SAB · FN ² · fw / f32 <−0.1
(2) -0.9 <SAA / SAB <-0.003
Conditional expressions (1) and (2) define the shape that provides the best effect of the aspheric surfaces provided in the negative and positive subgroups of the third lens group.

  If the upper limit of conditional expression (1) is exceeded, it becomes difficult to sufficiently suppress aberration fluctuations when the positive subgroup is decentered. Conversely, if the lower limit is exceeded, the field curvature generated from the positive subgroup is large. Thus, it becomes difficult to correct the various aberrations of the entire system in a balanced manner.

  Also, if the lower limit of conditional expression (2) is not reached, the aspherical surface provided in the negative subgroup cannot sufficiently exert its effect. Therefore, when the total aberrations are balanced, the aspherical surface provided in the negative subgroup is provided in the positive subgroup. As a result, it becomes impossible to sufficiently strengthen the effect of the aspheric surface, and as a result, the suppression of aberration fluctuations when the positive subgroup is decentered is weakened. On the other hand, if the upper limit of conditional expression (2) is exceeded, the spherical aberration of the entire system increases to the under side, making correction difficult.

More preferably, the numerical ranges of “SAB · FN ² · fw / f32” and “SAA / SAB” are set as in the following conditional expressions (1a) and (2a).
(1a) −1.5 <SAB · FN ² · fw / f32 <−0.25
(2a) -0.75 <SAA / SAB <-0.0075
In the zoom lens according to the embodiment of the present invention, f31 is a focal length of the negative portion group disposed in the third lens group, and S2 is an air space between the second lens group and the third lens group at the telephoto end. It is desirable that the following conditional expressions (3) and (4) are satisfied.
(3) | S2 / f31 | ≦ 0.15
(4) S2 / f32 ≦ 0.2
Conditional expressions (3) and (4) define conditions for making the refractive power arrangement of the negative and positive subgroups in the third lens group more appropriate. For example, a long back focus may be required due to the necessity of inserting a color separation optical system that separates imaging light into a plurality of color components and receives each color component by a separate imaging device. In such a case, it is necessary to sufficiently spread the light beam diverging and exiting from the second lens group at the wide-angle end, and then entering the fourth lens group via the third lens group. If the refractive power (reciprocal of the focal length) of the two lens groups is increased to increase the divergence, it becomes difficult to correct variations in aberrations due to zooming. Therefore, the divergence is further increased in the negative subgroup. It is preferable that the light bundle is sufficiently spread and sent to the fourth lens group after approaching the parallel light bundle in the positive part group. At this time, if the stop is disposed between the second lens group and the negative subgroup, the negative subgroup and the positive subgroup must be brought close to each other. In order to increase the refractive power, it is necessary to increase the refractive power of the negative subgroup, and as a result, it becomes difficult to correct various aberrations generated from the negative subgroup. In order to solve the above-described problem, a stop is disposed between the negative subgroup and the positive subgroup in the third lens group, and the negative subgroup is located within the range where it does not interfere with the second lens group at the telephoto end. In addition to being arranged close to each other and widening the aperture space, the negative subgroup can be made incident on the positive subgroup after sufficiently expanding the beam bundle with a relatively weak refractive power. In the positive part group, it is preferable that the incident light bundle is sent to the fourth lens group as a parallel light bundle or a convergent light bundle. In the conditional expressions (3) and (4), there is a possibility that the lower limit of the conditional expressions (3) and (4) is as close as possible to the point where the lenses of the second lens group and the negative part group hit each other at the telephoto end.

More preferably, the numerical ranges of “| S2 / f31 |” and “S2 / f32” are set as in the following conditional expressions (3a) and (4a).
(3a) 0.02 <| S2 / f31 | <0.07
(4a) 0.03 <S2 / f32 <0.1
In the zoom lens according to an embodiment of the present invention, it is preferable that the first lens group includes one concave lens and at least two convex lenses positioned in order from the object side. Thereby, an optimum lens configuration of the first lens group is obtained. It should be noted that a three-lens configuration of a cemented lens of a concave meniscus lens and a convex lens with a convex surface facing the object side and a convex lens may be used, or a four-lens configuration in which a single convex lens is added to the image side of the three-lens configuration. . In addition, the concave meniscus lens and the convex lens having a convex surface facing the object side as the cemented lens are separated without being cemented when the lens outer diameter is large and the difference in linear expansion coefficient between them is large. May be. The three-lens configuration is excellent in cost reduction, and the four-lens configuration is more effective in widening the angle and increasing the magnification than in the three-lens configuration, and reducing the secondary spectrum of chromatic aberration at the telephoto end. I can expect.

  In the zoom lens according to an embodiment of the present invention, the first lens group includes a concave lens positioned in order from the object side, a partial system close to an afocal system by a convex lens, one concave lens, and at least two convex lenses. preferable. By configuring the first lens group in this way, it becomes an optimal configuration when further widening the angle compared to a case where it is configured by one concave lens and at least two convex lenses positioned in order from the object side, By making the object side two lenses close to an afocal system composed of a concave lens and a convex lens, the focal length of the first lens group is shortened so that the image side principal point is generated behind the first lens group, The second lens group and subsequent lens groups can be widened and have good aberration correction without imposing much burden on widening the angle.

  In the zoom lens according to an embodiment of the present invention, it is preferable that the second lens group includes two concave lenses and one convex lens positioned in order from the object side. This provides an optimal lens configuration for the second lens group. The minimum lens configuration may be a three-lens configuration of two concave lenses and one convex lens, and the second concave lens and convex lens may be arranged separately or may be a cemented lens. In addition, one concave lens may be added on the image side to form a four lens configuration. The three-sheet configuration is excellent in cost reduction, and the four-sheet configuration can be expected to have a wider angle and higher magnification than the three-sheet configuration.

  In a zoom lens according to an embodiment of the present invention, it is preferable that the negative subgroup in the third lens group is composed of a biconcave lens and a biconvex lens that are sequentially positioned from the object side, and the most image side surface is an aspherical surface. . This gives an example of the configuration of the negative subgroup in the third lens group. The biconcave lens and the biconvex lens may be arranged separately or may be configured as a cemented lens. In order to reduce the sensitivity of the aberration to the error, it is preferable to use a cemented lens. The aspherical surface has a displacement in a direction in which the depth increases with increasing distance from the optical axis with respect to the depth of the paraxial spherical surface.

  Note that when the Abbe numbers of the concave lens and the convex lens are νn and νp, respectively, νn> νp.

  In a zoom lens according to an embodiment of the present invention, it is preferable that the negative subgroup in the third lens group is composed of a biconcave lens and a biconvex lens arranged in order from the object side, and the most object side surface is an aspherical surface. . This gives another example of the configuration of the negative subgroup in the third lens group, and the biconcave lens and the biconvex lens may be arranged separately or may be configured as a cemented lens. In order to reduce the sensitivity of the aberration to the eccentricity error, it is preferable to use a cemented lens. The aspherical surface has a displacement in a direction in which the depth becomes shallower with increasing distance from the optical axis with respect to the depth of the paraxial spherical surface.

  Note that when the Abbe numbers of the concave lens and the convex lens are νn and νp, respectively, νn> νp.

  The zoom lens according to an embodiment of the present invention includes a negative subgroup in the third lens group that includes a biconcave lens sequentially located from the object side, a biconvex lens, and a concave meniscus lens having a convex surface facing the image side. The side surface is preferably an aspherical surface. This gives yet another example of the negative subgroup in the third lens group, and the biconcave lens, biconvex lens, and concave meniscus lens may be arranged separately or configured as a cemented lens. In order to reduce the sensitivity of aberrations to decentration errors, it is preferable to use a cemented lens. The aspherical surface has a displacement in a direction in which the depth increases with increasing distance from the optical axis with respect to the depth of the paraxial spherical surface.

  The biconcave lens is a lens n1, the biconvex lens is a lens p, a concave meniscus lens having a convex surface facing the image side is a lens n2, the Abbe number of each lens is νn1, νp, νn2, and the Abbe number of the concave lens The average value is νn = (νn1 + νn2) / 2, and νn> νp.

  Achromatic conditions are set for the positive subgroup in the third lens group so that lateral aberrations do not fluctuate greatly when decentered (shifted in the direction perpendicular to the optical axis), so axial chromatic aberration is corrected. The fourth lens group is overcorrected with respect to axial chromatic aberration when the fourth lens group mainly corrects the lateral chromatic aberration of magnification, and the positive subgroup in the third lens group. As a result of preferentially correcting chromatic aberrations other than axial chromatic aberration with the fourth lens group, axial chromatic aberration is overcorrected. Therefore, in order to balance axial chromatic aberration, in the three configuration examples, the negative subgroup in the third lens group satisfies the above condition (νn> νp) and selects a medium in the direction of color development. The axial chromatic aberration is corrected well.

  A feature of the zoom lens of the present invention is that the positive subgroup in the third lens group is composed of a convex lens and a concave lens in order from the object side. The zoom lens according to an embodiment of the present invention includes the positive subgroup. However, it consists of a cemented lens of a biconvex lens and a concave lens positioned in order from the object side, and the surface closest to the object side is an aspherical surface. As a result, the sensitivity of aberration to the eccentric error between the biconvex lens and the concave lens can be reduced.

  In the zoom lens according to an embodiment of the present invention, it is preferable that the fourth lens group includes one concave lens and two convex lenses, and at least one surface is aspherical. In order to achieve both long back focus and high performance, the light beam spreads at the wide-angle end and spherical aberration and coma are likely to occur, and astigmatism is likely to occur due to the high principal ray height. Therefore, in the fourth lens group, in order to suppress the aberration generated from the positive lens group, the positive refractive power is dispersed to two or more convex lenses to suppress the occurrence of aberrations, and by arranging one concave lens. The effect of canceling various aberrations generated from the convex lens is exhibited. The aspherical surface of the positive subgroup in the third lens group is set for the purpose of alleviating aberration fluctuations due to decentration during camera shake correction, and the aspherical surface of the negative subgroup in the third lens group is the positive surface group. Since the shape is set in a direction that mainly cancels the spherical aberration generated from the aspherical surface of the subgroup, only the aspherical surface of the negative subgroup and the aspherical surface of the positive subgroup balance the various aberrations of the entire system. In addition, aberration variations caused by the movement of the fourth lens group cannot be corrected. Therefore, it is necessary to alleviate various aberrations generated from the positive refractive power of the fourth lens group by making any at least one surface of the fourth lens group an aspherical surface. As the aspherical shape of the fourth lens group that fulfills the above-mentioned purpose, the spherical aberration curve when the aspherical surface is replaced with its paraxial spherical surface is inclined to the under side with respect to the spherical aberration curve at the wide-angle end in the reference state. The shape is set as follows.

  In the zoom lens according to an embodiment of the present invention, it is preferable that the fourth lens group includes a convex lens and a cemented lens of a concave lens and a convex lens that are sequentially arranged from the object side. As a result, moderate back focus and extremely high imaging performance can be obtained, and the positive refracting power is divided in half, and the convex lens on the image side having a higher principal ray height is achromatic, and a wide angle is obtained. This is a configuration suitable for correcting lateral chromatic aberration.

  In the zoom lens according to an embodiment of the present invention, it is preferable that the fourth lens group includes a cemented lens and a convex lens of a concave lens and a convex lens positioned in order from the object side. Thereby, a longer back focus can be obtained. That is, by arranging a concave lens closest to the object side of the fourth lens group and arranging a positive refractive power closer to the image, the image-side principal point is close to the final surface of the fourth lens group, or a space on the image side. By adopting a so-called retrofocus type refracting power arrangement that is generated in the above, it is possible to achieve both long back focus and high performance.

  In the zoom lens according to an embodiment of the present invention, it is preferable that the fourth lens group includes two lenses, a concave lens and a convex lens, which are sequentially arranged from the object side. As a result, it is possible to reduce the number of lenses by reducing the number of lenses while obtaining a long back focus similar to that in the three embodiments. The sensitivity to aberration when the decentration error occurs in the two lenses constituting this fourth lens group is very high, but the concave lens image side surface is a flat surface and the effective diameter of the glass mold aspherical convex lens. If a flat part is provided outside, a parallel ring-shaped spacer is sandwiched between the planes, and the adhesive core is adjusted and adhered by observing the transmission core, etc. It is possible to keep the yield of the resolving power at the time of assembling well while keeping the core error small.

  Next, specific embodiments of the zoom lens according to the present invention and numerical examples in which specific numerical values are applied to the embodiments will be described.

  The aspherical shape in each numerical example is defined by the following equation (1).

  Here, “xi” is the depth of the aspherical surface of the i-th surface, “H” is the height from the optical axis, “ri” is the radius of curvature of the i-th surface, and “Ak” is the k-th order aspherical coefficient. And

  FIG. 1 shows the lens configuration of a first embodiment of the zoom lens according to the present invention, which has the configuration of the invention of claim 1 and the effects associated therewith, and more specifically, the first lens in order from the object side. The group Gp1 includes a cemented lens of a concave lens 101 and a convex lens 102, a convex lens 103, and a convex meniscus lens 104 having a convex surface facing the object side. The second lens group Gp2 includes a concave lens 201, a concave lens 202, a biconvex lens 203, and a concave lens 204. The negative lens group Gp31, which is always fixed to the third lens group Gp3, is composed of a biconcave lens 311, a biconvex lens 312, and a concave meniscus lens 313 having a convex surface facing the image side. The image side surface 313 is an aspherical surface A, and is positioned on the image side of the negative subgroup Gp31 with the stop S interposed therebetween. The positive subgroup Gp32 movable in the direction perpendicular to the upper surface is composed of a biconvex lens 321 and a concave lens 322. The object side surface of the biconvex lens 321 is an aspherical surface B. The fourth lens group Gp4 is a junction of the concave lens 401 and the convex lens 402. A parallel plane plate P composed of a color separation prism, an optical low-pass filter, and the like is disposed between the fourth lens group Gp4 and the imaging element IM.

  Table 1 shows values of specifications of Numerical Example 1 in which specific numerical values are applied to the first embodiment. The optical elements in each of the following specification tables indicate the reference numerals given to the optical elements in the drawings showing the lens configuration of each embodiment, the surface number i indicates the i-th surface from the object side, and the radius of curvature r represents the paraxial radius of curvature of the surface, surface separation d represents the axial top surface separation between the i-th surface and the (i + 1) -th surface, and the refractive index nd represents the d-line (λ = 587.6 of the surface). nm), the Abbe number νd indicates the value for the d-line of the surface, and the radius of curvature ∞ indicates that the surface is a plane.

The image-side surface A (18th surface) of the optical element 313, the object-side surface B (20th surface) of the optical element 321, and both surfaces (27th surface and 28th surface) of the optical element 403 are aspherical. ing. Table 2 shows the aspheric coefficients of these surfaces. In Table 2 and the following tables showing aspheric coefficients, “e-i” represents an exponential expression with a base of 10, that is, “10- ⁱ ”. For example, “0.26029E-05” represents “ 0.26029 × 10 ⁻⁵ ”.

  A distance d7 between the first lens group Gp1 and the second lens group Gp2, a distance d14 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. And the distance d28 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Therefore, the values at the wide angle end (f = 1.000), intermediate focal length (f = 5.085), and telephoto end (f = 11.667) of each interval are shown in Table 3 together with the focal length, F number, and angle of view 2ω (degrees). Show.

  In FIG. 2, in the reference state in which the positive subgroup Gp32 in the third lens group Gp3 shares the optical axis with the negative subgroup Gp1 and the other lens groups Gp1, Gp2, Gp4, the aspheric surface A, the aspheric surface B Spherical aberration amounts SAA and SAB when the diaphragm is opened at the wide angle end when each is replaced by its paraxial spherical surface.

  3 to 5 are graphs showing various aberrations in the infinite focus state in Numerical Example 1, FIG. 3 is a wide-angle end state (f = 1.000), FIG. 4 is an intermediate focal length state (f = 5.085), FIG. 5 shows various aberration diagrams in the telephoto end state (f = 11.667).

  3 to 5, the solid line in the spherical aberration curve is the d line, the broken line is the g line, the alternate long and short dash line indicates the spherical aberration in the C line, the solid line in the astigmatism curve is sagittal, and the broken line is meridional. Indicates the image plane.

  In addition, the positive subgroup Gp32 in the third lens group Gp3 is decentered in the direction perpendicular to the optical axis, so that the tilt angle formed with the optical axis when the principal ray toward the center of the screen enters the first lens group Gp1. FIG. 6 shows transverse aberration curves of meridional and sagittal at the telephoto end when the angle (hereinafter referred to as camera shake correction angle) is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 7 shows the lens configuration of the second embodiment 2 of the zoom lens of the present invention. The main difference from the first embodiment is that the positive subgroup Gp32 in the third lens group Gp3 is different from the biconvex lens 321. It consists of a cemented lens with a concave lens 322, and the object side surface of the biconvex lens 321 is an aspherical surface B. Other configurations are almost the same as those in the first embodiment. Compared to the first embodiment, by using the two lenses 321 and 322 as a cemented lens, the effect of reducing the sensitivity of the influence of the relative decentering error between the biconvex lens 321 and the concave lens 322 on the aberration. There is.

  Table 4 shows values of specifications of Numerical Example 2 in which specific numerical values are applied to the second embodiment.

  The image-side surface A (18th surface) of the optical element 313, the object-side surface B (20th surface) of the optical element 321, and both surfaces (26th surface and 27th surface) of the optical element 403 are aspherical. ing. Therefore, Table 5 shows the aspheric coefficients of these surfaces.

  A distance d7 between the first lens group Gp1 and the second lens group Gp2, a distance d14 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. The distance d22 and the distance d27 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Accordingly, Table 6 shows the values at the wide-angle end (f = 1.000), the intermediate focal length (f = 6.143), and the telephoto end (f = 14.165) for each interval together with the focal length, F number, and angle of view 2ω (degrees). Show.

  8 to 10 are graphs showing various aberrations in the infinite focus state in Numerical Example 2. FIG. 8 is a wide-angle end state (f = 1.000), FIG. 9 is an intermediate focal length state (f = 6.143), and FIG. 10 shows various aberration diagrams in the telephoto end state (f = 14.765).

  The solid line in the spherical aberration curves in FIGS. 8 to 10 is the d line, the broken line is the g line, the alternate long and short dash line is the spherical aberration in the C line, the solid line in the astigmatism curve is sagittal, and the broken line is meridional. Indicates the image plane.

  Further, FIG. 11 shows transverse aberration curves of meridional and sagittal at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 12 shows the lens configuration of the third embodiment of the zoom lens according to the present invention. The main difference from the second embodiment is that the negative subgroup Gp31 in the third lens group Gp3 is composed of a cemented lens of a biconcave lens 311 and a biconvex lens 312, and the image side surface of the biconvex lens 312 is It is a point which is an aspherical surface A, and other configurations are substantially the same as those of the second embodiment. By reducing the number of components of the negative subgroup Gp31, there is an effect of cost reduction as compared with the second embodiment.

  Table 7 shows the values of specifications of Numerical Example 3 in which specific numerical values are applied to the third embodiment.

  The image-side surface A (17th surface) of the optical element 312, the object-side surface B (19th surface) of the optical element 321, and both surfaces (25th and 26th surfaces) of the optical element 403 are configured as aspherical surfaces. ing. Therefore, Table 8 shows the aspheric coefficients of these surfaces.

  A distance d7 between the first lens group Gp1 and the second lens group Gp2, a distance d14 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. The distance d21 and the distance d26 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Accordingly, Table 9 shows the values at the wide-angle end (f = 1.000), the intermediate focal length (f = 6.291), and the telephoto end (f = 14.823) of each interval together with the focal length, F number, and angle of view 2ω (degrees). Show.

  FIGS. 13 to 15 are graphs showing various aberrations in the infinite focus state in Numerical Example 3, FIG. 13 is a wide-angle end state (f = 1.000), FIG. 14 is an intermediate focal length state (f = 6.291), FIG. 15 shows various aberration diagrams in the telephoto end state (f = 14.823).

  In FIG. 13 to FIG. 15, the solid line in the spherical aberration curve indicates the d-line, the broken line indicates the g-line, the alternate long and short dash line indicates the spherical aberration in the C-line, the solid line in the astigmatism curve indicates the sagittal, and the broken line indicates the meridional. Indicates the image plane.

  Further, FIG. 16 shows transverse aberration curves of meridional and sagittal at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 17 shows the lens configuration of a fourth embodiment of the zoom lens according to the present invention. The main difference from the third embodiment is the aspheric surface A of the negative subgroup Gp31 in the third lens group Gp3. Is the point on the object side surface of the biconcave lens 311, and the rest of the configuration is substantially the same as in the third embodiment. In the third embodiment, in order to make the biconvex lens 312 of the negative subgroup Gp31 into an aspherical lens, it is necessary to make a glass material having a relatively small Abbe number with a glass mold. There are few kinds of glass materials with a small Abbe number, which may be a great design restriction. In addition, the aspherical surface may be realized by means of forming a thin aspherical layer of ultraviolet curable resin on the surface of the spherical glass instead of a glass mold, but glass having a small Abbe number generally has a low ultraviolet transmittance, In some cases, the aspherical resin layer cannot be cured by irradiating ultraviolet rays through glass. In the fourth embodiment, by making the biconcave lens 311 using a glass material having a relatively large Abbe number an aspherical surface, the number of types of glass material suitable for the glass mold is increased, and the degree of design freedom is increased. Since a glass material having a large number has a relatively high transmittance of ultraviolet rays, a glass material suitable for production can be selected even when an aspherical surface is formed by an ultraviolet curable resin instead of a glass mold.

  Table 10 shows the values of specifications of Numerical Example 4 in which specific numerical values are applied to the fourth embodiment.

  The object-side surface A (15th surface) of the optical element 311, the object-side surface B (19th surface) of the optical element 321, and both surfaces (25th and 26th surfaces) of the optical element 403 are configured as aspherical surfaces. ing. Table 11 shows the aspheric coefficients of these surfaces.

  A distance d7 between the first lens group Gp1 and the second lens group Gp2, a distance d14 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. The distance d21 and the distance d26 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Accordingly, Table 12 shows the values at the wide angle end (f = 1.000), the intermediate focal length (f = 6.350), and the telephoto end (f = 14.769), together with the focal length, F number, and angle of view 2ω (degrees). Show.

  18 to 20 are graphs showing various aberrations in the infinite focus state in Numerical Example 4. FIG. 18 is a wide-angle end state (f = 1.000), FIG. 19 is an intermediate focal length state (f = 6.350), and FIG. 20 shows various aberration diagrams in the telephoto end state (f = 14.769).

  In FIG. 18 to FIG. 20, the solid line in the spherical aberration curve indicates the d-line, the broken line indicates the g-line, the alternate long and short dash line indicates the spherical aberration in the C-line, the solid line in the astigmatism curve indicates the sagittal, and the broken line indicates the meridional. Indicates the image plane.

  Further, FIG. 21 shows transverse aberration curves of meridional and sagittal at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 22 shows the lens configuration of the fifth embodiment of the zoom lens according to the present invention. The main difference from the third embodiment is that a color separation prism or the like is used even if the back focus is relatively short. The configuration of the fourth lens group Gp4, which is preferable when the arrangement holds, is provided, and the configuration other than the fourth lens group Gp4 is substantially the same as that of the third embodiment. The fourth lens group Gp4 includes, in order from the object side, a convex lens 401 having a convex surface facing the object side, and a cemented lens of a concave meniscus lens 402 having a concave surface facing the image side and a biconvex lens 403. Is an aspherical surface.

  Table 13 shows the values of specifications of Numerical Example 5 in which specific numerical values are applied to the fifth embodiment.

  The image-side surface A (17th surface) of the optical element 312, the object-side surface B (19th surface) of the optical element 321, and the object-side surface (22nd surface) of the optical element 401 are composed of aspherical surfaces. Yes. Therefore, Table 14 shows the aspheric coefficients of these surfaces.

  A distance d7 between the first lens group Gp1 and the second lens group Gp2, a distance d14 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. The distance d21 and the distance d26 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Accordingly, Table 15 shows the values at the wide angle end (f = 1.000), the intermediate focal length (f = 6.072), and the telephoto end (f = 14.832) of each interval together with the focal length, F number, and angle of view 2ω (degrees). Show.

  23 to 25 show various aberration diagrams of the numerical example 5 in the infinitely focused state, FIG. 23 is a wide angle end state (f = 1.000), FIG. 24 is an intermediate focal length state (f = 6.072), FIG. 25 shows various aberration diagrams in the telephoto end state (f = 14.832).

  In FIG. 23 to FIG. 25, the solid line in the spherical aberration curve indicates the d-line, the broken line indicates the g-line, the alternate long and short dash line indicates the spherical aberration in the C-line, the solid line in the astigmatism curve indicates sagittal, and the broken line indicates meridional. Indicates the image plane.

  Further, FIG. 26 shows meridional and sagittal lateral aberration curves at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 27 shows the lens configuration of a sixth embodiment of the zoom lens according to the present invention. The main difference from the second embodiment is that the first lens group Gp1 is changed from a four-lens configuration to a three-lens configuration. In addition, the second lens group Gp2 is changed from a four-lens configuration to a three-lens configuration to reduce the cost. The other configurations are substantially the same as those of the second embodiment.

  Table 16 shows the values of specifications in Numerical Example 6 in which specific numerical values are applied to the sixth embodiment.

  The image side surface A (15th surface) of the optical element 313, the object side surface B (17th surface) of the optical element 321 and both surfaces (23rd surface, 24th surface) of the optical element 403 are aspherical. ing. Therefore, Table 17 shows the aspheric coefficients of these surfaces.

  A distance d5 between the first lens group Gp1 and the second lens group Gp2, a distance d11 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. The distance d19 and the distance d24 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Therefore, Table 18 shows the values at the wide-angle end (f = 1.000), the intermediate focal length (f = 6.275), and the telephoto end (f = 11.610) of each interval together with the focal length, F number, and angle of view 2ω (degrees). Show.

  28 to 30 are graphs showing various aberrations in the infinite focus state in Numerical Example 6. FIG. 28 shows the wide-angle end state (f = 1.000), FIG. 29 shows the intermediate focal length state (f = 6.275), and FIG. 30 shows various aberration diagrams in the telephoto end state (f = 11.610).

  In FIG. 28 to FIG. 30, the solid line in the spherical aberration curve indicates the d-line, the broken line indicates the g-line, the alternate long and short dash line indicates the spherical aberration in the C-line, the solid line in the astigmatism curve indicates sagittal, and the broken line indicates meridional. Indicates the image plane.

  Further, FIG. 31 shows transverse aberration curves of meridional and sagittal at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  FIG. 32 shows the lens configuration of a seventh embodiment 7 of the zoom lens according to the present invention. The main difference from the third embodiment is the first lens group Gp1 in the third embodiment. The corresponding partial system is GP12, and the first lens group Gp1 is configured by adding a partial system Gp11 close to the afocal system including a concave lens and a convex lens to the object side of the partial system Gp12, and widening of the angle is achieved. This is because the four lens group Gp4 has a two-lens configuration of a concave lens and a convex lens for cost reduction, and the other configurations are substantially the same as those in the third embodiment.

  Table 19 shows the values of specifications of Numerical Example 7 in which specific numerical values are applied to the seventh embodiment.

  The image-side surface A (21st surface) of the optical element 312, the object-side surface B (23rd surface) of the optical element 321, and both surfaces (28th surface and 29th surface) of the optical element 402 are aspherical surfaces. ing. Accordingly, Table 20 shows the aspheric coefficients of these surfaces.

  A distance d11 between the first lens group Gp1 and the second lens group Gp2, a distance d18 between the second lens group Gp2 and the third lens group Gp3, and a distance between the third lens group Gp3 and the fourth lens group Gp4. And the distance d29 between the fourth lens group Gp4 and the plane-parallel plate P change during zooming. Therefore, the values at the wide angle end (f = 1.000), intermediate focal length (f = 5.061), and telephoto end (f = 11.625) of each interval are shown in Table 21 together with the focal length, F number, and angle of view 2ω (degrees). Show.

  FIGS. 33 to 35 are graphs showing various aberrations in the infinite focus state in Numerical Example 7, FIG. 33 is a wide-angle end state (f = 1.000), FIG. 34 is an intermediate focal length state (f = 5.061), FIG. 35 shows various aberration diagrams in the telephoto end state (f = 11.625).

  33 to 35, the solid line in the spherical aberration curve is the d-line, the broken line is the g-line, the alternate long and short dash line is the spherical aberration in the C-line, the solid line in the astigmatism curve is sagittal, and the broken line is the meridional Indicates the image plane.

  Further, FIG. 36 shows lateral aberration curves of meridional and sagittal at the telephoto end when the camera shake correction angle is 0.5 °. In this transverse aberration curve, the solid line indicates the value at the d line, the broken line indicates the value at the g line, and the alternate long and short dash line indicates the value at the C line.

  Table 22 shows values corresponding to the conditional expressions (1) to (4) of the numerical examples 1 to 7.

  Each numerical example satisfies the conditional expressions (1) to (4) and has excellent optical characteristics as shown in each aberration curve described above, and the camera shake correction angle is set to 0.5 °. As shown in the transverse aberration curve at the time, there is little aberration fluctuation at the time of camera shake correction.

  FIG. 37 shows an embodiment of the imaging apparatus of the present invention.

  The imaging apparatus 10 includes a zoom lens 20 and includes an imaging element 30 that converts an optical image formed by the zoom lens 20 into an electrical signal. For example, a device using a photoelectric conversion device such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) can be used as the image pickup device 30. The zoom lens according to the present invention can be applied to the zoom lens 20, and in FIG. 37, the lens group of the zoom lens 1 according to the first embodiment shown in FIG. It is. Of course, not only the zoom lens 1 according to the first embodiment, but also the zoom lenses 2 to 7 according to the second to seventh embodiments and other embodiments than those shown in the present specification. The zoom lens of the present invention configured as follows can be used.

  The electrical signal formed by the image sensor 30 is sent to the control circuit 50 by the video separation circuit 40, and the video signal is sent to the video processing circuit. The signal sent to the video processing circuit is processed into a form suitable for the subsequent processing, and is subjected to various processes such as display by a display device, recording on a recording medium, and transfer by a communication means.

  For example, an operation signal from the outside such as an operation of a zoom button is input to the control circuit 50, and various processes are performed according to the operation signal. For example, when a zooming command by the zoom button is input, the driving units 61 and 71 are operated via the driver circuits 60 and 70 to set the respective lens groups Gp2 and Gp4 to a predetermined state in order to obtain a focal length state based on the command. Move to position. Position information of the lens groups Gp2 and Gp4 obtained by the sensors 62 and 72 is input to the control circuit 50 and is referred to when command signals are output to the driver circuits 60 and 70. Further, the control circuit 50 checks the focus state based on the signal sent from the video separation circuit 40 and operates the drive unit 71 via the driver circuit 70 so as to obtain the optimum focus state. The position of the four lens group Gp4 is controlled.

  The imaging device 10 has a camera shake correction function. For example, when a shake detection unit 80, for example, a gyro sensor detects a shake of the image sensor 30 due to a press of a shutter release button, a signal from the shake detection unit 80 is input to the control circuit 50. A shake correction angle for compensating for shake of the image due to shake is calculated. In order to set the positive subgroup Gp32 of the third lens group Gp3 to a position based on the calculated shake correction angle, the drive unit 91 is operated via the driver circuit 90 so that the positive subgroup Gp32 is perpendicular to the optical axis. Move in any direction. The position of the positive subgroup Gp32 is detected by a sensor 92, and the positional information of the positive subgroup Gp32 obtained by the sensor 92 is input to the control circuit 50 and a command signal is sent to the driver circuit 90. To be referenced.

  The imaging device 10 described above can take various forms as a specific product. For example, the present invention can be widely applied as a camera unit of a digital input / output device such as a digital still camera, a digital video camera, a mobile phone incorporating a camera, and a PDA (Personal Digital Assistant) incorporating a camera.

  The above-described embodiments and numerical examples of the zoom lens of the present invention are examples of the embodiments for achieving the present invention, and the lenses that are cemented lenses in each lens group are arranged separately. On the contrary, it is possible as a design matter to use a cemented lens that is separated and arranged. In addition, the first lens group Gp1 and the second lens group Gp2 whose number is reduced as in the sixth embodiment, the third lens group Gp3 in the first to fifth embodiments, and the third lens group Gp3 in the first to fifth embodiments. A combination of the fourth lens group Gp4 is also possible as a design matter.

  In addition, the specific shapes and numerical values of the respective parts shown in the respective embodiments and numerical examples described above are merely examples of the implementation performed in carrying out the present invention. The technical scope of the invention should not be limitedly interpreted.

It is a figure which shows the lens structure of 1st Embodiment of this invention zoom lens. It is a figure which shows the characteristic of the aspherical shape used for the negative part group and positive part group in a 3rd lens group. 4 to 6 show various aberration diagrams of Numerical Example 1 in which specific numerical values are applied to the first embodiment of the zoom lens according to the present invention. This diagram shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 2nd Embodiment of this invention zoom lens. 9 to 11 show various aberration diagrams of Numerical Example 2 in which specific numerical values are applied to the second embodiment of the zoom lens according to the present invention. This diagram shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 3rd Embodiment of this invention zoom lens. FIGS. 14 to 16 show various aberration diagrams of Numerical Example 3 in which specific numerical values are applied to the third embodiment of the zoom lens according to the present invention. FIG. 14 shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 4th Embodiment of the zoom lens of this invention. FIGS. 19 to 21 show various aberration diagrams of Numerical Example 4 in which specific numerical values are applied to the fourth embodiment of the zoom lens according to the present invention. FIG. 19 shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 5th Embodiment of this invention zoom lens. FIG. 24 to FIG. 26 show various aberration diagrams of Numerical Example 5 in which specific numerical values are applied to the fifth embodiment of the zoom lens of the present invention. FIG. 24 shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 6th Embodiment of this invention zoom lens. FIG. 29 to FIG. 31 show various aberration diagrams of Numerical Example 6 in which specific numerical values are applied to the sixth embodiment of the zoom lens according to the present invention. FIG. 29 shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a figure which shows the lens structure of 7th Embodiment of this invention zoom lens. FIG. 34 to FIG. 36 show various aberration diagrams of Numerical Example 7 in which specific numerical values are applied to the seventh embodiment of the zoom lens according to the present invention. This diagram shows spherical aberration and astigmatism in the wide-angle end state. It shows aberration and distortion. It shows spherical aberration, astigmatism and distortion in the intermediate focal length state. It shows spherical aberration, astigmatism and distortion in the telephoto end state. It is a figure which shows lateral aberration at the time of a camera-shake correction angle of 0.5 degree in a telephoto end. It is a block diagram which shows an example of implementation of this invention imaging device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Zoom lens, 2 ... Zoom lens, 3 ... Zoom lens, 4 ... Zoom lens, 5 ... Zoom lens, 6 ... Zoom lens, 7 ... Zoom lens, Gp1 ... 1st lens group, Gp11 ... Sub system near afocal Gp2 ... second lens group, Gp3 ... third lens group, Gp31 ... negative subgroup, Gp32 ... positive subgroup, Gp4 ... fourth lens group, A ... aspherical surface of negative subgroup, B ... non-positive subgroup Spherical surface, 10 ... imaging device, 20 ... zoom lens, 30 ... imaging element, 50 ... control circuit (camera shake control unit), 80 ... camera shake detection means (camera shake detection unit), 91 ... drive unit (camera shake drive unit)

Claims (18)

A first lens group that is positioned in order from the object side and has a positive refractive power that is always fixed, a second lens group that has a negative refractive power that moves in the optical axis direction and mainly performs zooming, and zooming and focusing In this case, the third lens unit is fixed and has a positive refractive power, and the fourth lens unit has a positive refractive power that moves in the direction of the optical axis and corrects and focuses the fluctuation of the image plane position due to zooming. ,
The third lens group includes a negative part group that is always fixed and has a negative refractive power, and a positive part that has a positive refractive power that can move in a direction perpendicular to the optical axis and correct image movement due to optical axis blurring. A group of
The negative subgroup includes at least a biconcave lens and a biconvex lens, and at least one surface is an aspheric surface.
The positive subgroup consists of two lenses, a convex lens and a concave lens, and at least one surface is formed of an aspheric surface,
The entire system when the aspherical surface of the negative subgroup is replaced with its paraxial spherical surface for the spherical aberration curve at the wide-angle end in the reference state where the positive subgroup shares the optical axis with the negative subgroup The shape of the aspherical surface of the negative subgroup is set so that the spherical aberration curve of the negative subgroup is inclined to the over side, and the aspherical surface of the positive subgroup is set to the spherical aberration curve at the wide-angle end in the reference state. A zoom lens, wherein the shape of the aspherical surface of the positive subgroup is set so that the spherical aberration curve of the entire system when tilted to a paraxial spherical surface is inclined to the under side. The zoom lens according to claim 1, wherein the following conditional expressions (1) and (2) are satisfied.
(1) -2 <SAB · FN ² · fw / f32 <−0.1
(2) -0.9 <SAA / SAB <-0.003
However,
fw: focal length at the wide-angle end of the entire lens system FN: open F-number SAA at the wide-angle end of the entire lens system: the aspherical surface of the negative subgroup arranged in the third lens group is replaced with its paraxial spherical surface The value of the spherical aberration of the entire lens system at the open F-number at the wide-angle end SAB: at the wide-angle end when the aspherical surface of the positive subgroup arranged in the third lens group is replaced with its paraxial spherical surface The value of the spherical aberration of the entire lens system at the open F-number f32: the focal length of the positive subgroup disposed in the third lens group. The zoom lens according to claim 1, wherein the following conditional expressions (3) and (4) are satisfied.
(3) | S2 / f31 | ≦ 0.15
(4) S2 / f32 ≦ 0.2
However,
f31: Focal length S2 of the negative sub-group disposed in the third lens group: Air distance between the second lens group and the third lens group at the telephoto end. The zoom lens according to any one of claims 1 to 3, wherein the first lens group includes one concave lens and at least two convex lenses positioned in order from the object side. The first lens group includes a partial system close to an afocal system including a concave lens and a convex lens positioned in order from the object side, one concave lens, and at least two convex lenses. The zoom lens according to any one of the above. The zoom lens according to any one of claims 1 to 3, wherein the second lens group includes two concave lenses and one convex lens positioned in order from the object side. The zoom according to any one of claims 1 to 3, wherein the negative subgroup includes a biconcave lens and a biconvex lens arranged in order from the object side, and a surface closest to the image side is the aspheric surface. lens. The zoom according to any one of claims 1 to 3, wherein the negative subgroup includes a biconcave lens and a biconvex lens arranged in order from the object side, and a surface closest to the object side is the aspheric surface. lens. 2. The negative portion group includes a biconcave lens, a biconvex lens, a concave meniscus lens having a convex surface facing the image side, and the most aspheric surface on the image side. The zoom lens according to claim 3. The positive part group is composed of a cemented lens of a biconvex lens and a concave lens positioned in order from the object side, and the most object side surface is the aspherical surface. The described zoom lens. The zoom lens according to any one of claims 1 to 3, wherein the fourth lens group includes one concave lens and two convex lenses, and at least one surface is an aspherical surface. The zoom lens according to any one of claims 1 to 3, wherein the fourth lens group includes a convex lens and a cemented lens of a concave lens and a convex lens positioned in order from the object side. 4. The zoom lens according to claim 1, wherein the fourth lens group includes a cemented lens of a concave lens and a convex lens and a convex lens that are sequentially arranged from the object side. The zoom lens according to any one of claims 1 to 3, wherein the fourth lens group includes two lenses, a concave lens and a convex lens, which are sequentially positioned from the object side. An image pickup apparatus including a zoom lens and an image pickup element that converts an optical image formed by the zoom lens into an electrical signal,
The zoom lens includes a first lens group that is positioned in order from the object side and has a positive refracting power that is always fixed, and a second lens group that has a negative refracting power that moves in the optical axis direction and mainly performs zooming. And a third lens group having a positive refractive power that is fixed during zooming and focusing, and a fourth lens group having a positive refractive power that moves in the optical axis direction and corrects and focuses the fluctuation of the image plane position due to zooming. Consisting of a lens group,
The third lens group includes a negative part group that is always fixed and has a negative refractive power, and a positive part that has a positive refractive power that can move in a direction perpendicular to the optical axis and correct image movement due to optical axis blurring. A group of
The negative subgroup includes at least a biconcave lens and a biconvex lens, and at least one surface is an aspheric surface.
The positive subgroup consists of two lenses, a convex lens and a concave lens, and at least one surface is formed of an aspheric surface,
The entire system when the aspherical surface of the negative subgroup is replaced with its paraxial spherical surface for the spherical aberration curve at the wide-angle end in the reference state where the positive subgroup shares the optical axis with the negative subgroup The shape of the aspherical surface of the negative subgroup is set so that the spherical aberration curve of the negative subgroup is inclined to the over side, and the aspherical surface of the positive subgroup is set to the spherical aberration curve at the wide-angle end in the reference state. An imaging device, wherein the shape of the aspherical surface of the positive subgroup is set so that the spherical aberration curve of the entire system when inclined to a paraxial spherical surface is inclined to the underside. The image pickup apparatus according to claim 15, wherein the following conditional expressions (1) and (2) are satisfied.
(1) -2 <SAB · FN ² · fw / f32 <−0.1
(2) -0.9 <SAA / SAB <-0.003
However,
fw: focal length at the wide-angle end of the entire lens system FN: open F-number SAA at the wide-angle end of the entire lens system: the aspherical surface of the negative subgroup arranged in the third lens group is replaced with its paraxial spherical surface The value of the spherical aberration of the entire lens system at the open F-number at the wide-angle end SAB: at the wide-angle end when the aspherical surface of the positive subgroup arranged in the third lens group is replaced with its paraxial spherical surface The value of the spherical aberration of the entire lens system at the open F-number f32: the focal length of the positive subgroup disposed in the third lens group. The imaging apparatus according to claim 15 or 16, wherein the following conditional expressions (3) and (4) are satisfied.
(3) | S2 / f31 | ≦ 0.15
(4) S2 / f32 ≦ 0.2
However,
f31: Focal length S2 of the negative sub-group disposed in the third lens group: Air distance between the second lens group and the third lens group at the telephoto end. A camera shake detection unit that detects a shake of the image sensor and a shake correction angle for correcting an image shake due to the shake of the image sensor detected by the camera shake detection unit are calculated, and a positive lens in the third lens group in the zoom lens is calculated. A camera shake control unit that sends a correction signal for shifting the subgroup in a direction substantially perpendicular to the optical axis by an amount corresponding to the shake correction angle, and the positive subgroup is substantially perpendicular to the optical axis based on the correction signal. An image pickup apparatus according to any one of claims 15 to 17, further comprising: a camera shake driving unit that shifts in any direction.

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