JP2009145898A - Zoom lens and imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a zoom lens that has a high zoom ratio, excels in lens diameter reduction and restrains performance degradation, and to provide an imaging apparatus that uses the zoom lens. <P>SOLUTION: The zoom lens includes, in order from the object side, a first lens group G1 having positive refractive power, a second lens group G2 having negative refractive power, and a third lens group G3 having positive refractive power, and a fourth lens group G4 having positive refractive power. When a lens position changes from a wide angle end to a telephoto end, the second lens group moves to an image side, the fourth lens group moves so as to compensate for variation in the position of an image surface, resulting from the movement of the second lens group, the first and third lens groups are fixed, and an aperture diaphragm S is disponed on the object side of the third lens group. The third lens group is composed of a negative part group L31 having negative refractive power, and positive part groups L32 and L33 having positive refractive power, which are disposed on the image side of the negative part group with an air interval between them. The positive sub-groups is shifted in a direction nearly perpendicular to an optical axis x, and thereby an image can be shifted in a direction nearly perpendicular to the optical axis. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a novel zoom lens and an imaging apparatus. More specifically, the present invention relates to a technique for suppressing performance deterioration that occurs at the time of image shift while maintaining a high zoom ratio in a zoom lens capable of correcting camera shake and an imaging apparatus using the zoom lens.

  2. Description of the Related Art Conventionally, as a recording means in a camera, an object image formed on the surface of an image sensor is captured by an image sensor using a photoelectric conversion element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal-Oxide Semiconductor). A method is known in which the light amount of a subject image is converted into an electrical output by a conversion element and recorded.

  With recent advances in microfabrication technology, the central processing unit (CPU) has been increased in speed and the storage medium has been highly integrated, so that large-capacity image data that could not be handled before can be processed at high speed. It has become. In addition, the light receiving elements have also been highly integrated and miniaturized. With the high integration, recording at a higher spatial frequency is possible, and the miniaturization allows the entire camera to be miniaturized.

  However, due to the high integration and miniaturization described above, there has been a problem that the light receiving area of each photoelectric conversion element is narrowed, and the influence of noise increases as the electrical output decreases. In order to prevent this, the amount of light reaching the light receiving element is increased by increasing the aperture ratio of the optical system, or a minute lens element (so-called micro lens array) is arranged immediately before each element. It has been done. The microlens array restricts the exit pupil position of the lens system instead of guiding the light beam reaching between adjacent elements onto the element. That is, when the exit pupil position of the lens system approaches the light receiving element, the angle formed by the chief ray reaching the light receiving element with the optical axis increases, and the off-axis light beam toward the screen periphery forms a large angle with respect to the optical axis. As a result, the light does not reach the light receiving element, leading to insufficient light quantity.

  As a zoom lens suitable for a video camera, a digital still camera, or the like that records a subject image using the photoelectric conversion element described above, 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. A fourth lens group having power is arranged, and when the lens position changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed in the optical axis direction; When the lens group moves toward the image side, a zooming action is performed, and the fourth lens group acts to compensate for variations in the image plane position caused by the movement of the second lens group.

  Specifically, 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.

  2. Description of the Related Art 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 disposed on the object side of the largest first lens group in the lens system, there is a problem in terms of downsizing when including the drive system.

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

  As these lens shift type optical systems, for example, Patent Document 2, Patent Document 3, Patent Document 4, or Patent Document 5 is known.

  In the optical systems disclosed in each of the above patent documents, the image is shifted by shifting the entire third lens group disposed in the vicinity of the aperture stop or a part of the lens in a direction substantially perpendicular to the optical axis. It is possible to make it.

  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 disclosed in Patent Document 5, the image is shifted by shifting the entire third lens group.

  In the zoom lenses disclosed in Patent Document 3 and Patent Document 4, 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 disclosed 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-6-337353 JP 2002-244037 A JP 2003-228001 A JP 2002-162563 A JP 2003-295057 A

  However, the conventional zoom lens described above has the following problems in achieving a high zoom ratio and high performance.

  When shifting the entire third lens group, it is necessary to correct fluctuations in off-axis aberrations that occur when the lens position of the third lens group changes, and at the same time correct fluctuations in various aberrations that occur during camera shake correction. Therefore, the negative distortion generated in the wide-angle end state cannot be corrected satisfactorily, and in order to solve this, it is necessary to weaken the refractive power of the second lens group. The lens diameter of the lens group increases, and the size cannot be reduced sufficiently.

  When shifting the positive subgroup arranged on the object side of the third lens group, the interval before and after the aperture stop cannot be sufficiently widened, and interference with the iris mechanism portion occurs.

  When shifting the positive subgroup arranged on the image side of the third lens group, if the zoom ratio is increased, the shift amount of the positive subgroup becomes very large, and the drive mechanism is enlarged and the structure is complicated. There was a problem source that would cause.

  In view of the above-described problems, the present invention has an object to provide a zoom lens that has a high zoom ratio, is excellent in reducing the diameter of the lens, and can suppress performance deterioration, and an imaging device using the zoom lens. To do.

  In order to solve the above-described problem, the zoom lens of the present invention, in order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, and a third lens having a positive refractive power. When the lens position changes from the wide-angle end state to the telephoto end state, the second lens group moves to the image side. At the same time, the fourth lens group moves so as to compensate for the variation of the image plane position accompanying the movement of the second lens group, and the first lens group and the third lens group are fixed in the optical axis direction, and the aperture stop Is disposed on the object side of the third lens group, and the third lens group is disposed on the image side of the negative partial group with a negative refracting power and spaced apart from the negative side group by an air interval to provide a positive refractive power. And having the positive subgroup substantially perpendicular to the optical axis. The optical axis of the image by shifting the direction are those can be shifted in a direction substantially perpendicular.

  Therefore, in the zoom lens of the present invention, the image is shifted by shifting the positive subgroup of the third lens group, and the performance deterioration during the image shift is suppressed.

  The imaging device of the present invention includes the above-described zoom lens of the present invention.

  The zoom lens according to the present invention has, 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 a positive refractive power. The fourth lens group has four lens groups. When the lens position changes from the wide-angle end state to the telephoto end state, the second lens group moves to the image side, and the fourth lens group The first lens group and the third lens group are fixed in the optical axis direction, and the aperture stop is on the object side of the third lens group. And the third lens group includes a negative sub-group having negative refractive power, and a positive sub-group having positive refractive power arranged at an image interval on the image side of the negative sub-group, The image is obtained by shifting the positive subgroup in a direction substantially perpendicular to the optical axis. Characterized in that it is possible to shift in a direction substantially perpendicular to the optical axis.

  Therefore, in the zoom lens of the present invention, the image is shifted by shifting the positive subgroup of the third lens group, and the performance deterioration during the image shift is suppressed. Further, the size can be reduced.

  The imaging apparatus of the present invention converts an optical image formed by the zoom lens of the present invention into an electrical signal by an imaging element and records it.

  In the invention described in claims 2 and 9, f3n is a focal length of the negative sub-group arranged in the third lens group, and f3 is a focal length of the third lens group, the following conditional expression ( 1) 1.4 <| f3n | / f3 <3 is satisfied.

  In the invention described in claim 3, Rn is the radius of curvature of the lens surface closest to the image side of the negative portion group arranged in the third lens group, and Rp is the positive portion arranged in the third lens group. Since the conditional expression (2) −0.3 <(Rn + Rp) / (Rn−Rp) <0.3 is satisfied as the radius of curvature of the lens surface closest to the object side of the group, when the positive subgroup is shifted It is possible to satisfactorily correct the fluctuation of coma generated in

  In the invention described in claim 4 and claim 5, the negative portion group is composed of two lenses, a positive lens and a negative lens, and the positive portion group is a positive lens, a negative lens, and a positive lens 3. An image side lens of a positive lens composed of a single lens, Rp1 being the radius of curvature of the object side lens surface of the positive lens arranged closest to the image side of the positive subgroup, and Rp2 being the most image side of the positive subgroup. Since the conditional expression (3) 0 <(Rp1 + Rp2) / (Rp1−Rp2) <2 is satisfied as the radius of curvature of the surface, it is possible to satisfactorily correct the coma variation due to the change in the angle of view.

In the invention described in claim 6, f2 is the focal length of the second lens group, fw is the focal length of the entire lens system in the wide-angle end state, and ft is the focal length of the entire lens system in the telephoto end state. Since the conditional expression (4) 0.42 <| f2 | / (fw · ft) ^1/2 <0.5 is satisfied, the fluctuation of off-axis aberration caused by zooming can be corrected more satisfactorily. Can do.

  In the invention according to claim 7, Dt is the distance along the optical axis from the aperture stop to the lens surface closest to the image side of the fourth lens group in the telephoto end state, and Z2 is from the wide-angle end state to the telephoto end state. Conditional expression (5) 0.8 <Dt / Z2 <1.2 is satisfied as the amount of movement of the second lens group when the lens position changes until the lens position is changed. can do.

  In the invention described in claim 10, a shake detection unit for detecting the shake of the image pickup device and a shake correction angle for correcting an image shake due to the shake of the image pickup device detected by the shake detection unit are calculated. Camera shake control means for sending a drive signal to the drive unit so that the positive subgroup of the third lens group is positioned based on the shake correction angle, and the positive subgroup is perpendicular to the optical axis based on the drive signal. Since it has a camera shake drive unit that shifts in the direction, it can correct image shake caused by shake of the image sensor due to camera shake, etc., and obtain a high-quality image in which the in-focus state is good and various aberrations are well corrected be able to.

  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 accompanying drawings.

  The zoom lens according to the present invention has, 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 a positive refractive power. When the lens position state changes from the wide-angle end state where the focal length of the entire lens system is the shortest to the telephoto end state where the focal length is the longest, the first lens group and The three lens groups are fixed in the optical axis direction, the second lens group moves toward the image side to perform a zooming action, and the fourth lens group moves to change the image plane position as the second lens group moves. Compensate and focus at close range.

  The third lens group is composed of a negative subgroup having negative refractive power and a positive subgroup having positive refractive power arranged on the image side, and the positive subgroup is shifted in a direction substantially perpendicular to the optical axis. To shift the image.

With the configuration described above, the following configuration can suppress performance degradation that occurs during image shift while maintaining a high zoom ratio.
(A) An aperture stop is disposed on the object side of the third lens group. (B) The position of the aperture stop for appropriately setting the refractive power of the negative subgroup is extremely important for achieving a balance between high performance and downsizing. It is.

  Since the off-axis light beam that passes through the lens group away from the aperture stop passes away from the optical axis, the lens diameter of each lens group is most likely to be minimized when placed near the center of the lens system. In particular, since the first lens group is farthest from the image plane position and the lens diameter tends to be large, it is desirable that the first lens group be disposed slightly closer to the object side than near the center.

  In addition, since the height of the off-axis light beam passing through the movable lens group changes greatly when the lens position state changes, the axis generated when the lens position state changes using this change in height. Variations in external aberration can be corrected satisfactorily. In particular, if one or more movable lens groups are disposed on the object side and the image side of the aperture stop, aberration correction can be performed more satisfactorily.

  From the above, in the present invention, by disposing the aperture stop on the object side of the third lens group, the lens diameter of the first lens group, which tends to increase the lens diameter, is kept small, and high performance is achieved. be able to.

  In the present invention, by fixing the position of the aperture stop in the optical axis direction, the stop mechanism can be fixed in the optical axis direction, and the lens barrel structure can be simplified.

  In the zoom lens of the present invention, the third lens group is composed of a negative part group and a positive part group. The refractive power of the negative part group is important for reducing the lens diameter.

  When the refractive power of the negative subgroup increases, the off-axis light beam passing through the positive subgroup moves away from the optical axis, so the lens diameter of the positive subgroup increases and the weight increases, resulting in shifting the positive subgroup. This will increase the size and complexity of the shift drive mechanism. At the same time, since the off-axis light beam passing through the fourth lens group is also away from the optical axis, the drive mechanism of the focus group also increases in size and complexity, making it difficult to reduce the size.

  Accordingly, in the present invention, the lens diameter can be appropriately reduced by appropriately setting the focal length of the negative subgroup with respect to the focal length of the third lens group.

From the above viewpoint, it is necessary to satisfy the following conditional expression (1), where f3n is the focal length of the negative subgroup disposed in the third lens group and f3 is the focal length of the third lens group.
(1) 1.4 <| f3n | / f3 <3
Conditional expression (1) defines the focal length of the negative subgroup in the third lens group.

  If the lower limit value of conditional expression (1) is not reached, the refractive power of the positive subgroup increases as described above, so that the principal ray passing through the positive subgroup moves away from the optical axis, causing a shortage of peripheral light quantity. End up.

  On the contrary, when the upper limit value of conditional expression (1) is exceeded, as described above, the off-axis light beam passing through the first lens group is separated from the optical axis, and the shift lens group (the positive subgroup of the third lens group) is moved away. The change in the amount of peripheral light when shifted is increased.

  In the zoom lens of the present invention, it is desirable to set the upper limit value of conditional expression (1) to 2.5 in order to achieve higher performance. If the value of conditional expression (1) exceeds 2.5, the off-axis light beam that passes through the fourth lens group is separated from the optical axis, so that the coma aberration that occurs in the periphery of the screen cannot be corrected more satisfactorily. It becomes difficult to obtain higher optical performance.

In a zoom lens with a high zoom ratio, it is necessary to more appropriately correct coma variation that occurs when the shift lens group is shifted, particularly in the telephoto end state. That means
(C) It is important that the air gap formed between the negative subgroup and the positive subgroup is in an appropriate shape.

  Therefore, in the zoom lens of the present invention, the change in coma aberration is corrected well by reducing the change in the optical path length that occurs when shifting.

  Specifically, by reducing the difference between the radius of curvature of the lens surface closest to the image side of the negative subgroup and the radius of curvature of the lens surface closest to the object side of the positive subgroup, the negative subgroup and the positive subgroup can be reduced. The air gap formed between them is made into an appropriate shape, and the fluctuation of coma aberration is corrected well.

Therefore, in the zoom lens of the present invention, Rn is the radius of curvature of the lens surface closest to the image side of the negative portion group arranged in the third lens group, and Rp is the positive portion group arranged in the third lens group. It is desirable to satisfy the following conditional expression (2) as the radius of curvature of the lens surface closest to the object.
(2) -0.3 <(Rn + Rp) / (Rn-Rp) <0.3
As described above, the conditional expression (2) is a conditional expression that defines the shape of the air gap formed between the negative subgroup and the positive subgroup.

  If the lower limit value of conditional expression (2) is not reached, it will be difficult to satisfactorily correct decentration coma that occurs at the center of the screen when the positive subgroup is shifted. On the other hand, when the upper limit of conditional expression (2) is exceeded, fluctuations in coma generated at the periphery of the screen when the positive subgroup is shifted in the telephoto end state are significantly increased, and good optical performance is obtained. It will disappear.

  In the zoom lens according to the present invention, of the two partial groups constituting the third lens group, the negative partial group includes at least one positive lens and one negative lens, and the positive partial group includes at least two positive lenses. It is desirable to have a lens and one positive lens.

  In order to satisfactorily correct variations in various aberrations that occur when the positive subgroup is shifted, it is necessary to suppress to some extent spherical aberration that occurs independently in each of the negative subgroup and the positive subgroup.

  In the zoom lens of the present invention, as indicated by the conditional expression range of the conditional expression (1), the refractive power of the negative subgroup in the third lens group is weaker than that of the positive subgroup. Since the negative subgroup has a weak refractive power, it is possible to satisfactorily correct the positive spherical aberration generated by the negative subgroup alone in the doublet configuration. The positive subgroup consists of a positive lens, a negative lens, and a positive lens. By adopting a so-called triplet configuration, which is a configuration, negative spherical aberration that occurs in the positive subgroup alone is favorably corrected.

In the zoom lens of the present invention, Rp1 is the radius of curvature of the object-side lens surface of the positive lens disposed closest to the image side of the positive subgroup, Rp2 It is desirable to satisfy the following conditional expression (3) as the radius of curvature of the image side lens surface of the positive lens arranged closest to the image side in the positive subgroup.
(3) 0 <(Rp1 + Rp2) / (Rp1-Rp2) <2
Conditional expression (3) is a conditional expression that defines the shape of the positive lens arranged closest to the image side of the positive subgroup.

  If the lower limit of conditional expression (3) is not reached, the negative curvature of field cannot be corrected satisfactorily, and good imaging performance cannot be obtained up to the periphery of the screen.

  If the upper limit value of conditional expression (3) is exceeded, the inward coma generated at the periphery of the screen cannot be corrected well, and good imaging performance cannot be obtained up to the periphery of the screen.

In the zoom lens according to the present invention, since the second lens group is the only negative lens group, the refractive power of the second lens group can be corrected more satisfactorily to correct the fluctuation of off-axis aberration caused by zooming. Is appropriately set, f2 is the focal length of the second lens group, fw is the focal length of the entire lens system in the wide-angle end state, and ft is the focal length of the entire lens system in the telephoto end state, It is desirable to satisfy the following conditional expression (4).
(4) 0.42 <| f2 | / (fw · ft) 1/2 <0.5
Conditional expression (4) is a conditional expression that defines the focal length of the second lens group.

  When the upper limit value of conditional expression (4) is exceeded, the off-axis light beam passing through the second lens group is further away from the optical axis, and as a result, the coma aberration generated at the peripheral edge of the screen in the wide-angle end state is corrected well. It becomes difficult.

  If the lower limit of conditional expression (4) is not reached, it will be difficult to satisfactorily correct off-axis aberration fluctuations that occur when the lens position changes.

  In the zoom lens of the present invention, in order to reduce the overall length of the lens and reduce the lens diameter of the first lens group, the off-axis light beam that passes through the first lens group is brought closer to the optical axis, particularly in the telephoto end state. ing.

  Although the angle of view changes when the positive subgroup is shifted, especially in the telephoto end state, since the angle of view is narrow, the change in the angle of view is large. As a result, the vignetting due to the lens outer diameter of the first lens group. Is likely to cause a shortage of ambient light. For this reason, in order to reduce the lens diameter of the first lens group, it is important to bring the off-axis light beam passing through the first lens group closer to the optical axis.

  Specifically, in the zoom lens of the present invention, the off-axis light beam passing through the first lens group is brought closer to the optical axis by reducing the angle formed by the principal ray passing through the position of the aperture stop and the optical axis. .

  In the so-called three-imager imaging optical system in which a color separation prism is arranged on the image side of the optical system, an image-side telecentric optical system whose exit pupil position is close to infinity is used in order to color-separate a light beam by a dichroic mirror. Mainly used.

  For this reason, the longer the distance from the aperture stop to the image plane position, the weaker the refractive power of the lens group arranged on the image side than the aperture stop, and as a result, the angle formed by the principal ray and the optical axis is reduced. Can do. When the angle formed by the principal ray and the optical axis becomes small in this way, the off-axis light beam incident on the first lens group approaches the optical axis.

  However, the longer the distance from the aperture stop to the image plane position, the closer the aperture stop is to the object side, and there is no movement space for the second lens group at the time of zooming, and the first lens group and the second lens group. It is necessary to increase the refractive power of the lens, and fluctuations in off-axis aberration that occur when the lens position changes are not suppressed, so that high performance cannot be achieved sufficiently.

Therefore, in the zoom lens according to the present invention, in order to achieve further miniaturization and higher performance at the same time, light from the aperture stop to the most image side lens surface of the fourth lens group in the telephoto end state is set to Dt. The distance along the axis, Z2, is preferably configured to satisfy the following conditional expression (5) as the amount of movement of the second lens group when the lens position changes from the wide-angle end state to the telephoto end state. .
(5) 0.8 <Dt / Z2 <1.2
Conditional expression (5) is a conditional expression that defines the distance from the aperture stop to the fourth lens group in the telephoto end state and the amount of movement of the second lens group.

  If the upper limit value of conditional expression (5) is exceeded, it is difficult to correct the fluctuation of off-axis aberration caused by the second lens group when the lens position changes, and to further improve the performance. turn into.

  On the contrary, when the lower limit value of conditional expression (5) is not reached, the combined focal length of the third lens group and the fourth lens group is shortened, and as a result, the angle formed by the principal ray with respect to the optical axis is increased. It becomes difficult to reduce the lens diameter of the lens group.

  By the way, in the zoom lens according to the present invention, the on-axis light beam emitted from the negative partial group arranged in the third lens group is diverged, that is, the positive partial group arranged in the third lens group. It is desirable to set the lateral magnification to a negative value.

When the lateral magnification of the positive subgroup in the third lens group is βa and the lateral magnification of the fourth lens group is βb, the blur correction coefficient βs and the focus sensitivity βf are βs = (1−βa) βb
βf = (1-βa ² ) βb ²
It is represented by

  In the zoom lens of the present invention, by setting the lateral magnification βa of the positive subgroup to satisfy βa <0, the blur correction coefficient βs is increased and the focus sensitivity βf is decreased, while the zoom ratio is high. The image can be shifted with a small lens shift amount, and the positional accuracy in the optical axis direction can be lowered.

  As the positional accuracy in the optical axis direction increases, it becomes necessary to hold the shift lens group, that is, the positive subgroup in a state of being biased in the optical axis direction, so that the positive subgroup is driven to shift in a direction perpendicular to the optical axis. The mechanism becomes complicated. Therefore, in the present invention, by setting the lateral magnification of the positive subgroup as described above, the positional accuracy in the optical axis direction is lowered, and the lens barrel structure is simplified.

  In the zoom lens of the present invention, in order to further improve the performance, the first lens group is composed of four lenses including a cemented lens of a negative lens and a positive lens arranged in order from the object side, and two positive lenses. Desirably configured.

  In the first lens group, since the axial light beam is incident with a wide light beam diameter particularly in the telephoto end state, negative spherical aberration is likely to occur. In addition, since off-axis light flux is incident away from the optical axis, off-axis aberration is likely to occur.

  In the zoom lens according to the present invention, the negative spherical aberration and the longitudinal chromatic aberration are favorably corrected by disposing a cemented lens of a negative lens and a positive lens on the most object side of the first lens group. In the conventional positive / negative / positive / positive four-group zoom lens, the first lens group is composed of a cemented lens and one positive lens located on the image side. While maintaining the zoom ratio, it is possible to suppress the occurrence of negative spherical aberration in the telephoto end state and to satisfactorily correct the coma variation due to the change in the angle of view, thereby realizing higher optical performance.

  In the zoom lens of the present invention, in order to better correct various aberrations generated in the second lens group and obtain higher optical performance, a negative meniscus lens having a concave surface from the object side to the image side, a negative lens It is desirable that the lens is composed of four lenses arranged in the order of a lens, a positive lens, and a negative lens.

  Since the second lens group is a lens group responsible for the zooming action, it is important to further correct various aberrations generated in the second lens group in order to further improve the performance. In the zoom lens of the present invention, the meniscus negative lens with the concave surface facing the image side arranged closest to the object side in the second lens group causes fluctuations in coma caused by a change in the field angle at the wide-angle end state. Since the triplet lens arranged on the image side plays a role to correct axial aberrations well, the division of roles for aberration correction is clarified, and good imaging performance can be obtained. I am doing so.

  In the zoom lens of the present invention, the performance deterioration due to the eccentricity of the positive lens and the negative lens arranged on the image side of the triplet lens is large. Thus, stable optical quality can be obtained.

  In the zoom lens of the present invention, in order to satisfactorily correct fluctuations of various aberrations accompanying changes in the subject position, the fourth lens group has a positive lens with a convex surface facing the object side and a concave surface facing the image side in order from the object side. It is desirable that the negative lens is directed and the positive lens having a convex surface facing the object side is arranged.

  By adopting a triplet configuration for the fourth lens group, it is possible to simultaneously correct off-axis aberrations and on-axis aberrations, and to satisfactorily correct variations in various aberrations that occur when the subject position changes.

  In the zoom lens of the present invention, it is desirable to use a glass material having high anomalous dispersion for the first lens group in order to suppress the occurrence of chromatic aberration more favorably.

  In particular, among the lenses constituting the first lens group, the positive lens in the cemented lens is made of a glass material having a high anomalous dispersion, thereby favorably correcting the secondary dispersion generated at the center of the screen in the telephoto end state. Can do.

  Also, any one of the two positive lenses arranged on the image side of the first lens group is made of a low dispersion glass material having an Abbe number exceeding 65, and this occurs at the periphery of the screen in the telephoto end state. It is possible to satisfactorily correct the lateral chromatic aberration. By using both of the two positive lenses as a low dispersion glass material, it is possible to correct lateral chromatic aberration more satisfactorily.

  In the zoom lens of the present invention, higher optical performance can be realized by using an aspheric lens. In particular, by introducing an aspherical surface into the final lens group, the central performance can be further improved. Further, by using an aspheric lens for the second lens group, it is possible to satisfactorily correct coma variation due to the angle of view generated in the wide-angle end state.

  Furthermore, it goes without saying that higher optical performance can be obtained by using a plurality of aspheric surfaces.

  It is of course possible to arrange a low-pass filter on the image side of the lens system in order to prevent the occurrence of moire fringes or an infrared cut filter according to the spectral sensitivity characteristics of the light receiving element.

  Hereinafter, each embodiment and numerical example of the zoom lens of the present invention will be described.

  In each embodiment, an aspherical surface is used, but the aspherical shape is expressed by the following equation (1).

here,
y: height from the optical axis x: sag amount c: curvature κ: conic constants A, B,...: aspheric coefficient.

  FIG. 1 shows the refractive power distribution of the zoom lens of the present invention. In order from the object side, a first lens group G1 having a positive refractive power, a second lens group G2 having a negative refractive power, and a positive refractive power. The third lens group G3 and the fourth lens group G4 having positive refractive power are arranged, and the telephoto end state (T) shown in the lower part of FIG. 1 from the wide-angle end state (W) shown in the upper part of FIG. During zooming, the air gap between the first lens group G1 and the second lens group G2 increases, and the air gap between the second lens group G2 and the third lens group G3 decreases. The second lens group G2 moves to the image side (see the solid line in the middle stage). At this time, the first lens group G1 and the third lens group G3 are fixed (see the middle broken line), and the fourth lens group G4 corrects the variation of the image plane position accompanying the movement of the second lens group G2. And move to the object side when focusing on a short distance (see the solid line in the middle).

  FIG. 2 is a diagram showing a lens configuration in the first embodiment 1 of the zoom lens according to the present invention. The first lens group G1 includes a cemented lens L11 including a meniscus negative lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, a positive lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The positive lens L13 is directed. The second lens group G2 includes a meniscus negative lens L21 having a concave surface directed toward the image side, a biconcave negative lens L22, and a cemented lens L23 of a biconvex lens and a biconcave lens. The third lens group G3 includes a cemented negative lens L31 including a biconcave lens and a positive lens having a convex surface facing the object side, a cemented lens L32 including a biconvex lens having an aspheric surface on the object side and a negative lens having a concave surface directed to the object side, It is composed of a positive lens L33 having a convex surface facing the image side. The fourth lens group G4 includes a positive lens L41 having a convex surface facing the object side, a cemented lens L42 of a negative lens having an aspheric surface on the object side and a concave surface facing the image side, and a positive lens having a convex surface facing the object side. It is configured.

  In the zoom lens 1 according to the first embodiment, the cemented negative lens L31 disposed in the third lens group G3 forms a negative partial group, and the cemented lens L32 and the positive lens L33 form a positive partial group. Then, it is possible to shift the image in a direction substantially perpendicular to the optical axis x by shifting the positive subgroups L32 and L33 in a direction substantially perpendicular to the optical axis x.

  In the zoom lens 1, a color separation prism PP fixed in the optical axis direction is disposed on the image side of the fourth lens group G4. The aperture stop S is disposed on the object side of the third lens group G3, and is fixed in the optical axis direction together with the third lens group G3 when the lens position changes.

  Table 1 below shows values of specifications of Numerical Example 1 in which specific numerical values are applied to the zoom lens 1 according to the first embodiment. The surface number in the specification table of this numerical example 1 and each numerical example described later indicates the i-th surface counted from the object side, the radius of curvature indicates the radius of curvature of the optical surface of the i-th surface, The surface separation is the axial top surface separation between the i-th optical surface and the (i + 1) -th optical surface from the object side, and the refractive index is d-line (λ = 587.6) of a glass material having the i-th optical surface on the object side. nm), and the Abbe number represents the Abbe number with respect to the d-line of the glass material having the i-th optical surface on the object side. Di indicates that the surface interval is a variable interval, curvature radius 0 indicates that the surface is a flat surface, and Bf indicates that the surface interval is a back focus.

  In the zoom lens 1, when the lens position changes from the wide-angle end state to the telephoto end state, the distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the aperture stop S The distance D14 between the third lens group G3 and the fourth lens group G4, and the distance D28 between the fourth lens group G4 and the color separation prism PP are changed. Therefore, Table 2 shows the values in the wide-angle end state, the intermediate focal length state between the wide-angle end and the telephoto end, and the telephoto end state in the numerical value example 1 in the focal length f, F number FNo. And the angle of view 2ω.

  In the zoom lens 1, the 19th surface and the 24th surface are aspherical. Therefore, Table 3 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D of the aspheric surfaces in Numerical Example 1 together with the conic constant κ. In Table 3 and the following table showing aspheric coefficients, “E-i” represents an exponential expression with a base of 10, that is, “10-i”. For example, “0.12345E-05” represents “ 0.12345 × 10-5 ”.

  Table 4 shows the corresponding values of the conditional expressions (1), (2), (3), (4), and (5) of the numerical example 1.

  FIGS. 3 to 5 show various aberration diagrams in the infinite focus state of Numerical Example 1, FIG. 3 is a wide angle end state (f = 1.000), FIG. 4 is an intermediate focal length state (f = 9.430), FIG. 5 shows various aberrations in the telephoto end state (f = 21.047).

  3 to 5, the solid line in the spherical aberration diagram indicates spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, y represents the image height. In addition, Fno. Indicates the F number, and A indicates the half angle of view.

  6 to 8 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 1, respectively, FIG. 6 is a wide-angle end state (f = 1.000), and FIG. FIG. 8 is a lateral aberration diagram in the intermediate focal length state (f = 9.430), and FIG. 8 in the telephoto end state (f = 21.047).

  From each aberration diagram, it is clear that Numerical Example 1 has excellent imaging performance with various aberrations corrected well.

  FIG. 9 is a diagram showing a lens configuration in the second embodiment 2 of the zoom lens according to the present invention. The first lens group G1 includes a cemented lens L11 including a meniscus negative lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, a positive lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The positive lens L13 is directed. The second lens group G2 includes a meniscus negative lens L21 having a concave surface directed toward the image side, a biconcave negative lens L22, and a cemented lens L23 of a biconvex lens and a biconcave lens. The third lens group G3 includes a cemented negative lens L31 including a biconcave lens and a positive lens having a convex surface facing the object side, a cemented lens L32 including a biconvex lens having an aspheric surface on the object side and a negative lens having a concave surface directed to the object side, It is composed of a positive lens L33 having a convex surface facing the image side. The fourth lens group G4 includes a positive lens L41 having an aspheric convex surface facing the object side, and a cemented lens L42 of a negative lens having a concave surface facing the image side and a positive lens having a convex surface facing the object side. .

  In the zoom lens 2 according to the second embodiment, the cemented negative lens L31 disposed in the third lens group G3 forms a negative partial group, and the cemented lens L32 and the positive lens L33 form a positive partial group. Then, it is possible to shift the image in a direction substantially perpendicular to the optical axis x by shifting the positive subgroups L32 and L33 in a direction substantially perpendicular to the optical axis x.

  In the zoom lens 2, a color separation prism PP fixed in the optical axis direction is disposed on the image side of the fourth lens group G4. The aperture stop S is disposed on the object side of the third lens group G3, and is fixed in the optical axis direction together with the third lens group G3 when the lens position changes.

  Table 5 below shows values of specifications of Numerical Example 2 in which specific numerical values are applied to the zoom lens 2 according to the second embodiment.

  In the zoom lens 2, when the lens position changes from the wide-angle end state to the telephoto end state, the distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the aperture stop S The distance D14 between the third lens group G3 and the fourth lens group G4, and the distance D28 between the fourth lens group G4 and the color separation prism PP are changed. Accordingly, Table 6 shows the values in the wide-angle end state, the intermediate focal length state between the wide-angle end and the telephoto end, and the telephoto end state in the numerical value example 2 in Table 6, and the focal length f, F number FNo. And the angle of view 2ω.

  In the zoom lens 2, the 19th surface and the 24th surface are aspherical. Therefore, Table 7 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D of the aspheric surfaces in Numerical Example 2 together with the conic constant κ.

  Table 8 shows values corresponding to the conditional expressions (1), (2), (3), (4), and (5) of the numerical example 2.

  FIGS. 10 to 12 show various aberration diagrams in the infinite focus state in Numerical Example 2, FIG. 10 is a wide angle end state (f = 1.000), FIG. 11 is an intermediate focal length state (f = 8.860), FIG. 12 shows various aberrations in the telephoto end state (f = 21.057).

  10 to 12, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, y represents the image height. In addition, Fno. Indicates the F number, and A indicates the half angle of view.

  FIGS. 13 to 15 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 2, respectively, FIG. 13 shows the wide-angle end state (f = 1.000), and FIG. FIG. 15 is a transverse aberration diagram in the intermediate focal length state (f = 8.860), and FIG. 15 in the telephoto end state (f = 21.057).

  From each aberration diagram, it is clear that Numerical Example 2 has excellent imaging performance with various aberrations corrected well.

  FIG. 16 is a diagram showing a lens configuration of the zoom lens according to the third embodiment of the present invention. The first lens group G1 includes a cemented lens L11 including a meniscus negative lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, a positive lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The positive lens L13 is directed. The second lens group G2 includes a meniscus negative lens L21 having a concave surface directed toward the image side, a biconcave negative lens L22, and a cemented lens L23 of a biconvex lens and a biconcave lens. The third lens group G3 includes a cemented negative lens L31 including a biconcave lens and a positive lens having a convex surface facing the object side, a cemented lens L32 including a biconvex lens having an aspheric surface on the object side and a negative lens having a concave surface directed to the object side, It is composed of a positive lens L33 having a convex surface facing the image side. The fourth lens group G4 includes a positive lens L41 having an aspheric convex surface facing the object side, and a cemented lens L42 of a negative lens having a concave surface facing the image side and a positive lens having a convex surface facing the object side. .

  In the zoom lens 3 according to the third embodiment, the cemented negative lens L31 disposed in the third lens group G3 forms a negative partial group, and the cemented lens L32 and the positive lens L33 form a positive partial group. Then, it is possible to shift the image in a direction substantially perpendicular to the optical axis x by shifting the positive subgroups L32 and L33 in a direction substantially perpendicular to the optical axis x.

  In the zoom lens 3, a color separation prism PP fixed in the optical axis direction is disposed on the image side of the fourth lens group G4. The aperture stop S is disposed on the object side of the third lens group G3, and is fixed in the optical axis direction together with the third lens group G3 when the lens position changes.

  Table 9 below shows values of specifications of Numerical Example 3 in which specific numerical values are applied to the zoom lens 3 according to the third embodiment.

  In the zoom lens 3, when the lens position changes from the wide-angle end state to the telephoto end state, the distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, the aperture stop S, The distance D14 between the third lens group G3 and the fourth lens group G4, and the distance D28 between the fourth lens group G4 and the color separation prism PP are changed. Therefore, Table 10 shows the values in the wide-angle end state, the intermediate focal length state between the wide-angle end and the telephoto end, and the telephoto end state in the numerical example 3 in Table 10. And the angle of view 2ω.

  In the zoom lens 3, the 19th surface and the 24th surface are aspherical. Therefore, Table 11 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspherical coefficients A, B, C, and D together with the conic constant κ in the numerical example 3.

  Table 12 shows the corresponding values of the conditional expressions (1), (2), (3), (4), and (5) of the numerical example 3.

  FIGS. 17 to 19 show various aberration diagrams in the infinite focus state in Numerical Example 3, FIG. 17 is a wide angle end state (f = 1.000), FIG. 18 is an intermediate focal length state (f = 9.196), FIG. 12 shows various aberrations in the telephoto end state (f = 21.061).

  In each aberration diagram of FIGS. 17 to 19, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, y represents the image height. In addition, Fno. Indicates the F number, and A indicates the half angle of view.

  20 to 22 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 3, respectively, FIG. 20 is a wide-angle end state (f = 1.000), and FIG. FIG. 22 is a lateral aberration diagram in the intermediate focal length state (f = 9.196) and FIG. 22 in the telephoto end state (f = 21.061).

  From the respective aberration diagrams, it is clear that Numerical Example 3 has excellent imaging performance with various aberrations corrected well.

  FIG. 23 is a diagram showing a lens configuration of the zoom lens according to the fourth embodiment of the present invention. The first lens group G1 includes a cemented lens L11 including a meniscus negative lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, a positive lens L12 having a convex surface facing the object side, and a convex surface facing the object side. The positive lens L13 is directed. The second lens group G2 includes a meniscus negative lens L21 having a concave surface directed toward the image side, a biconcave negative lens L22, and a cemented lens L23 of a biconvex lens and a biconcave lens. The third lens group G3 includes a cemented negative lens L31 including a biconcave lens and a positive lens having a convex surface facing the object side, a cemented lens L32 including a biconvex lens having an aspheric surface on the object side and a negative lens having a concave surface directed to the object side, The fourth lens group G4 includes a positive lens L41 having a convex surface directed toward the image side and a convex surface facing the object side, and both surfaces formed of aspheric surfaces, and a negative lens and an object having a concave surface directed toward the image side It is comprised by the cemented lens L42 with the positive lens which turned the convex surface to the side.

  In the zoom lens 4 according to the fourth embodiment, the cemented negative lens L31 disposed in the third lens group G3 forms a negative partial group, and the cemented lens L32 and the positive lens L33 form a positive partial group. Then, it is possible to shift the image in a direction substantially perpendicular to the optical axis x by shifting the positive subgroups L32 and L33 in a direction substantially perpendicular to the optical axis x.

  In the zoom lens 4, a color separation prism PP fixed in the optical axis direction is disposed on the image side of the fourth lens group G4. The aperture stop S is disposed on the object side of the third lens group G3, and is fixed in the optical axis direction together with the third lens group G3 when the lens position changes.

  Table 13 below shows values of specifications of Numerical Example 4 in which specific numerical values are applied to the zoom lens 4 according to the fourth embodiment.

  In the zoom lens 4, when the lens position changes from the wide-angle end state to the telephoto end state, the distance D7 between the first lens group G1 and the second lens group G2, the second lens group G2, and the aperture stop S The distance D14 between the third lens group G3 and the fourth lens group G4, and the distance D28 between the fourth lens group G4 and the color separation prism PP are changed. Accordingly, Table 14 shows the respective values in the wide-angle end state, the intermediate focal length state between the wide-angle end and the telephoto end, and the telephoto end state in the numerical value example 4 in Table 14. And the angle of view 2ω.

  In the zoom lens 4, the 19th surface, the 24th surface, and the 25th surface are aspherical surfaces. Therefore, Table 15 shows the fourth-order, sixth-order, eighth-order, and tenth-order aspheric coefficients A, B, C, and D of the aspheric surfaces in Numerical Example 4 together with the conic constant κ.

  Table 16 shows corresponding values of the conditional expressions (1), (2), (3), (4), and (5) of the numerical example 4.

  FIGS. 24 to 26 show various aberration diagrams of Numerical Example 4 in the infinitely focused state, FIG. 24 is a wide-angle end state (f = 1.000), FIG. 25 is an intermediate focal length state (f = 8.896), FIG. 26 shows various aberrations in the telephoto end state (f = 19.496).

  24 to 26, the solid line in the spherical aberration diagram indicates the spherical aberration, the solid line in the astigmatism diagram indicates the sagittal image plane, and the broken line indicates the meridional image plane. In the coma aberration diagram, y represents the image height. In addition, Fno. Indicates the F number, and A indicates the half angle of view.

  27 to 29 show lateral aberration diagrams in the lens shift state corresponding to 0.5 degrees in the infinitely focused state in Numerical Example 4, respectively, FIG. 27 is the wide-angle end state (f = 1.000), and FIG. FIG. 29 is a lateral aberration diagram in the intermediate focal length state (f = 8.896), and FIG. 29 in the telephoto end state (f = 19.496).

  From the respective aberration diagrams, it is clear that Numerical Example 4 has excellent imaging performance with various aberrations corrected well.

  FIG. 30 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 20 according to the present invention can be applied to the zoom lens 20. In FIG. 30, 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 4 according to the second to fourth embodiments and other embodiments than those shown in this specification. The zoom lens of the present invention configured as follows can be used.

  The electrical signal formed by the image pickup device 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 drive units 61 and 71 are operated via the driver circuits 60 and 70 to set each lens group GR2 and GR4 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 GR2 and GR4 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. 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 GR4 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 subgroups L32 and L33 of the third lens group GR3 to positions based on the calculated shake correction angle, the drive unit 91 is operated via the driver circuit 90, so that the positive subgroups L32 and L33 are changed. Move in a direction perpendicular to the optical axis. The positions of the positive subgroups L32 and L33 are detected by a sensor 92, and the positional information of the positive subgroups L32 and L33 obtained by the sensor 92 is input to the control circuit 50, and a command signal is sent to the driver circuit 90. Referenced when sending.

  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.

  It should be noted that 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, and the present invention is thereby limited. The technical scope of the invention should not be limitedly interpreted.

It is a figure which shows refractive power arrangement | positioning of this invention zoom lens. It is a figure which shows the lens structure of 1st Embodiment of this invention zoom lens. FIGS. 4 to 8 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. Aberration, distortion and coma are shown. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state of 0.5 degrees in the wide-angle end state. The lateral aberration in the lens shift state of 0.5 degrees in the intermediate focal length state is shown. 3 shows lateral aberration in a lens shift state of 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of 2nd Embodiment of this invention zoom lens. FIGS. 11 to 15 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. Aberration, distortion and coma are shown. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state of 0.5 degrees in the wide-angle end state. The lateral aberration in the lens shift state of 0.5 degrees in the intermediate focal length state is shown. 3 shows lateral aberration in a lens shift state of 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of 3rd Embodiment of this invention zoom lens. FIGS. 18 to 22 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. This diagram shows spherical aberration and astigmatism in the wide-angle end state. Aberration, distortion and coma are shown. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state of 0.5 degrees in the wide-angle end state. The lateral aberration in the lens shift state of 0.5 degrees in the intermediate focal length state is shown. 3 shows lateral aberration in a lens shift state of 0.5 degrees in the telephoto end state. It is a figure which shows the lens structure of 4th Embodiment of the zoom lens of this invention. FIG. 25 to FIG. 29 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. 25 shows spherical aberration and astigmatism in the wide-angle end state. Aberration, distortion and coma are shown. It shows spherical aberration, astigmatism, distortion and coma in the intermediate focal length state. It shows spherical aberration, astigmatism, distortion and coma in the telephoto end state. This shows lateral aberration in a lens shift state of 0.5 degrees in the wide-angle end state. The lateral aberration in the lens shift state of 0.5 degrees in the intermediate focal length state is shown. 3 shows lateral aberration in a lens shift state of 0.5 degrees in the telephoto end state. It is a block diagram which shows embodiment of the imaging device of this invention.

DESCRIPTION OF SYMBOLS 1 ... Zoom lens, 2 ... Zoom lens, 3 ... Zoom lens, 4 ... Zoom lens, G1 ... 1st lens group, G2 ... 2nd lens group, G3 ... 3rd lens group, G4 ... 4th lens group, S ... Aperture stop, x ... optical axis, L31 ... negative subgroup, L32 / L33 ... positive subgroup, 10 ... imaging device, 20 ... zoom lens, 30 ... imaging element, 50 ... control circuit (camera shake control means), 80 ... camera shake Detection means, 90 (driver circuit), 91 (drive unit)...

Claims (10)

4 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 a fourth lens group having a positive refractive power. When the lens position changes from the wide-angle end state to the telephoto end state, the second lens group moves to the image side, and the fourth lens group moves the second lens group. The first lens group and the third lens group are fixed in the direction of the optical axis.
An aperture stop is disposed on the object side of the third lens group,
The third lens group includes a negative subgroup having a negative refractive power, and a positive subgroup having a positive refractive power that is disposed on the image side of the negative subgroup at an air interval,
A zoom lens capable of shifting an image in a direction substantially perpendicular to the optical axis by shifting the positive subgroup in a direction substantially perpendicular to the optical axis. The zoom lens according to claim 1, wherein the following conditional expression (1) is satisfied.
(1) 1.4 <| f3n | / f3 <3
However,
f3n: focal length of the negative sub-group arranged in the third lens group f3: focal length of the third lens group. The zoom lens according to claim 1, wherein the following conditional expression (2) is satisfied.
(2) -0.3 <(Rn + Rp) / (Rn-Rp) <0.3
However,
Rn: radius of curvature of the lens surface closest to the image side of the negative sub-group arranged in the third lens group Rp: radius of curvature of the lens surface closest to the object side of the positive sub-group arranged in the third lens group . The negative group is composed of two lenses, a positive lens and a negative lens,
The positive subgroup is composed of three lenses, a positive lens, a negative lens, and a positive lens,
The zoom lens according to claim 1, wherein the following conditional expression (3) is satisfied.
(3) 0 <(Rp1 + Rp2) / (Rp1-Rp2) <2
However,
Rp1: the radius of curvature of the object side lens surface of the positive lens arranged closest to the image side of the positive subgroup Rp2: the radius of curvature of the image side lens surface of the positive lens arranged closest to the image side of the positive subgroup. The negative group is composed of two lenses, a positive lens and a negative lens,
The positive subgroup is composed of three lenses, a positive lens, a negative lens, and a positive lens,
The zoom lens according to claim 3, wherein the following conditional expression (3) is satisfied.
(3) 0 <(Rp1 + Rp2) / (Rp1-Rp2) <2
However,
Rp1: the radius of curvature of the object side lens surface of the positive lens arranged closest to the image side of the positive subgroup Rp2: the radius of curvature of the image side lens surface of the positive lens arranged closest to the image side of the positive subgroup. The zoom lens according to claim 1, wherein the following conditional expression (4) is satisfied.
(4) 0.42 <| f2 | / (fw · ft) ^1/2 <0.5
However,
f2: focal length of the second lens unit fw: focal length of the entire lens system in the wide-angle end state ft: focal length of the entire lens system in the telephoto end state The zoom lens according to claim 1 or 5, wherein the following conditional expression (5) is satisfied.
(5) 0.8 <Dt / Z2 <1.2
However,
Dt: distance along the optical axis from the aperture stop to the most image side lens surface of the fourth lens group in the telephoto end state Z2: second lens group when the lens position changes from the wide-angle end state to the telephoto end state The amount of movement. An imaging apparatus comprising a zoom lens and an image sensor that converts an optical image formed by the zoom lens into an electrical signal,
The 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 a first lens group having a positive refractive power. When the lens position changes from the wide-angle end state to the telephoto end state, the second lens group moves to the image side and the fourth lens group is the second lens group. The first lens group and the third lens group are fixed in the optical axis direction, and the aperture stop is located on the object side of the third lens group. The third lens group includes a negative subgroup having a negative refractive power, and a positive subgroup having a positive refractive power that is disposed on the image side of the negative subgroup with an air gap therebetween. By shifting the positive subgroup in a direction almost perpendicular to the optical axis, An image pickup apparatus that can be shifted in a direction substantially perpendicular to the axis. The imaging device according to claim 8, wherein the following conditional expression (1) is satisfied.
(1) 1.4 <| f3n | / f3 <3
However,
f3n: focal length of the negative sub-group arranged in the third lens group f3: focal length of the third lens group. Camera shake detecting means for detecting shake of the image sensor;
A shake correction angle for correcting image shake due to shake of the image sensor detected by the shake detection means is calculated, and a drive signal is shaken so that the positive subgroup of the third lens group is positioned based on the shake correction angle. Camera shake control means for sending to the drive unit;
The imaging apparatus according to claim 8, further comprising: a camera shake driving unit that shifts the positive subgroup in a direction perpendicular to the optical axis based on the drive signal.

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