JP2007298832A - Zoom lens and optical device equipped therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact zoom lens having excellent image forming performance considering that it is used when a zoom lens arranging spot is limited, and an optical device equipped therewith. <P>SOLUTION: The zoom lens is constituted of: a first lens group G1 equipped with an optical path bending optical element P and having positive refractive power; a second lens group G2 having negative refractive power; a third lens group G3 having positive refractive power; and a fourth lens group G4 having positive refractive power in order from an object side along an optical axis. When a focal distance is changed from a wide angle end state to a telephoto end state, the first lens group and the third lens group are fixed relative to an image surface, and the second lens group and the fourth lens group move along the optical axis. The third lens group is constituted of a cemented lens L31 comprising a positive lens turning its convex surface to the object side and a negative lens turning its concave surface to an image side and having positive refractive power in order from the object side along the optical axis, and satisfies a predetermined condition. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a small zoom lens suitable for a video camera, a digital still camera, or the like using a solid-state imaging device.

  Conventionally, portability when carrying a digital still camera or the like is emphasized, and in order to reduce the size, thickness, and weight of the camera body, the zoom lens that is a photographing lens has been reduced in size and weight.

  Accordingly, a zoom lens has been devised that includes an optical element that can bend the optical path approximately 90 degrees in a part of the lens system. By installing such a zoom lens, the lens does not protrude from the camera body when shifting from the stored state to the use state, and it is excellent in portability even in the use state, making the camera smaller and thinner. It contributes greatly. In addition, since the movable part is present inside the camera body, there is no movable part on the surface, which is effective for applications such as waterproof, drip-proof and dust-proof.

As such a zoom lens, 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 refraction in order from the object side. There is disclosed a positive, negative, positive and negative five-group type zoom lens composed of a fourth lens group having power and a fifth lens group having negative refractive power (see, for example, Patent Document 1).
JP 2005-84283 A

  However, in the disclosed example of Patent Document 1, the lens group constituting the lens system is configured with five positive, negative, positive, and negative. Although it is possible to improve the performance by configuring the lens system with a large number of lens groups, there is a problem that it becomes difficult to shorten the overall length due to the accumulation of the thickness of each lens group.

  The present invention has been made in view of the above problem, and provides a zoom lens having excellent imaging performance that is small and has excellent imaging performance in consideration of use when a place where the zoom lens is disposed is limited. With the goal.

In order to solve the above-described problems, the present invention provides, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, and a second lens group having a negative refractive power. And a third lens group having a positive refractive power and a fourth lens group having a positive refractive power, and when the focal length changes from the wide-angle end state to the telephoto end state, the first lens group And the third lens group are fixed with respect to the image plane, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased. The distance between the third lens group and the fourth lens group decreases, and the third lens group has a positive lens having a convex surface facing the object side and a concave surface facing the image side in order from the object side along the optical axis. Consists of a cemented lens with positive refractive power and a negative lens facing Providing a zoom lens, characterized by foot.
nd3p> nd3n
νd3p> νd3n
Where nd3p is the refractive index of the d-line of the positive lens in the third lens group, nd3n is the refractive index of the d-line of the negative lens in the third lens group, and νd3p is the refractive index of the third lens group. The Abbe number of d-line of the positive lens, νd3n, is the Abbe number of d-line of the negative lens in the third lens group.

  Further, according to the present invention, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power And a fourth lens group having positive refractive power, and when the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group Is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group In the wide-angle end state, when focusing on a close object, the second lens group moves to the object side up to a predetermined shooting distance, and the predetermined lens distance is reduced. When focusing on an object closer than the shooting distance, the fourth lens group is Providing a zoom lens, characterized by moving the.

  In addition, the present invention provides an optical device including the zoom lens.

Further, according to the present invention, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power And a fourth lens group having a positive refractive power, and the third lens group includes a positive lens with a convex surface facing the object side in order from the object side along the optical axis. The first lens is composed of a cemented lens having a positive refractive power with a negative lens having a concave surface facing the image side, satisfies the following conditions, and changes the focal length from the wide-angle end state to the telephoto end state. The group and the third lens group are fixed with respect to the image plane, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased. The third lens group and the fourth lens group are reduced in distance so that the distance between the third lens group and the fourth lens group is reduced. Wherein a lens group fourth lens group provides a focal distance adjustment method characterized by moving along the optical axis.
nd3p> nd3n
νd3p> νd3n
Where nd3p is the refractive index of the d-line of the positive lens in the third lens group, nd3n is the refractive index of the d-line of the negative lens in the third lens group, and νd3p is the refractive index of the third lens group. The Abbe number of d-line of the positive lens, νd3n, is the Abbe number of d-line of the negative lens in the third lens group.

  Further, according to the present invention, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power And a fourth lens group having positive refractive power, and when the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group Is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group Zoom lens in which the distance between the first lens group and the fourth lens group is reduced, and when focusing on a short-distance object, either the second lens group or the fourth lens group up to a predetermined shooting distance Moves to the object side and the shooting distance is closer than the predetermined shooting distance. When performing the focusing on the object, the lens group that did not movable during focusing to the predetermined object distance is to provide a focusing method of the zoom lens, characterized in that moves toward the object side.

  Further, according to the present invention, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a positive refractive power And a fourth lens group having positive refractive power, and when the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group Is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group In the wide-angle end state, when focusing on a close object, the second lens group moves to the object side up to a predetermined shooting distance. When focusing on an object that is closer than the predetermined shooting distance, Serial fourth lens group to provide a focusing method of the zoom lens, characterized by moving toward the object side.

  According to the present invention, it is possible to provide a small zoom lens having excellent imaging performance in consideration of use when a place where the zoom lens is disposed is limited.

  Hereinafter, embodiments of the present invention will be described.

  1A and 1B show an electronic still camera that is an optical device equipped with a zoom lens according to an embodiment of the present invention, which will be described later. FIG. 1A is a front view, and FIG. FIG. 2 is a cross-sectional view taken along line A-A ′ in FIG. 1A, and shows an outline of the arrangement of zoom lenses according to an embodiment of the present invention to be described later.

  1 and 2, the electronic still camera 1 according to the present invention is configured such that when a power button (not shown) is pressed, a shutter (not shown) that covers the photographing lens 2 is opened, and the photographing lens 2 removes an object from a subject (not shown). The light is collected and imaged on the image sensor C arranged on the image plane I. The subject image formed on the imaging device C is displayed on the liquid crystal monitor 3 disposed behind the electronic still camera 1. The photographer determines the composition of the subject image while looking at the liquid crystal monitor 3, and then presses the release button 4 to photograph the subject image with the image sensor C, and records and saves it in a memory (not shown).

  The photographic lens 2 is composed of a zoom lens 2 according to an embodiment of the present invention to be described later, and light incident from the front of the electronic still camera 1 is approximately 90 degrees downward by a prism P in the zoom lens 2 to be described later. Since it is deflected (downward in FIG. 2), the electronic still camera 1 can be thinned.

  The electronic still camera 1 also zooms the auxiliary light emitting unit 5 that emits auxiliary light when the subject is dark and the zoom lens 2 that is the photographing lens 2 from the wide-angle end state (W) to the telephoto end state (T). A wide (W) -tele (T) button 6 and a function button 7 used for setting various conditions of the electronic still camera 1 are arranged.

  In this way, an electronic still camera 1 that is an optical device incorporating a zoom lens 2 according to an embodiment of the present invention to be described later is configured.

  Next, a zoom lens according to an embodiment of the present invention will be described.

  The zoom lens according to the embodiment of the present invention includes, in order from the object side along the optical axis, a first lens group having an optical path bending optical element and having a positive refractive power, and a second lens group having a negative refractive power. And a third lens group having a positive refractive power and a fourth lens group having a positive refractive power, and when the focal length changes from the wide-angle end state to the telephoto end state, The third lens group is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens group The distance from the fourth lens group is reduced.

  The first lens group has a function of bending the optical path by approximately 90 degrees and a function of converging the light flux. When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group is always fixed, and is the largest of the lens groups, and there is no need to move the heavy lens group structurally. It can be simplified.

  The second lens group functions to enlarge the image of the subject formed by the first lens group, and widens the distance between the first lens group and the second lens group from the wide-angle end state toward the telephoto end state. Thus, the enlargement ratio is increased and the focal length is changed.

  The third lens group acts to converge the light beam expanded by the second lens group, and in order to achieve high performance, the third lens group is composed of a plurality of lens groups, and spherical aberration and sign condition, It is desirable that the Petzval sum be corrected well.

  The fourth lens group has a function of further converging the light beam converged by the third lens group, and the distance between the third lens group and the fourth lens group is positively changed when the focal length is changed. The fluctuation of the image plane with respect to the change of the focal length can be suppressed.

  By configuring the zoom lens in this way, it is possible to achieve a small zoom lens having excellent imaging performance, which is suitable for an optical apparatus in which a place where the zoom lens is disposed is limited.

In addition, it is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expressions (1) and (2) in order to achieve small size and high performance based on the above configuration.
nd3p> nd3n (1)
νd3p> νd3n (2)
Where nd3p is the refractive index of the d-line of the positive lens in the third lens group, nd3n is the refractive index of the d-line of the negative lens in the third lens group, and νd3p is the d-line of the positive lens in the third lens group. Abbe number, νd3n, is the Abbe number of the d-line of the negative lens in the third lens group.

  Conditional expressions (1) to (2) are conditional expressions that define combinations of optical material characteristics of the positive lens and the negative lens in the third lens group.

  If the conditions of the conditional expressions (1) to (2) are not satisfied, the axial chromatic aberration and the lateral chromatic aberration generated by the third lens group alone become large, and it becomes difficult to maintain good performance. As a result, it becomes impossible to improve the performance of the zoom lens.

In addition, it is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (3) in order to reduce the size and improve the performance.
TL / Ymax <12 (3)
However, TL is the total length along the optical axis from the lens surface closest to the object side of the first lens group to the image plane, and Ymax is the maximum image height.

  Conditional expression (3) is a conditional expression for defining an appropriate total length for balancing downsizing and high performance.

  If the conditional expression (3) is not satisfied, the total length becomes large, and the balance between miniaturization and high performance cannot be achieved. As a result, the total length of the lens becomes large, which is contrary to the intention of the present invention. Moreover, since spherical aberration deteriorates, it is not preferable.

  In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (3) to 11.8. In order to further secure the effect of the present invention, it is more preferable to set the upper limit of conditional expression (3) to 11.7.

In the zoom lens according to the embodiment of the present invention, it is preferable that the optical path bending optical element is a right-angle prism and satisfies the following conditional expression (4).
ndp> 1.83 (4)
Where ndp is the refractive index of the right-angle prism.

  Conditional expression (4) is a conditional expression that defines an appropriate refractive index range of the right-angle prism. The right-angle prism can deflect the optical path by total reflection and reduce the light loss, and can make the optical system compact.

  If the conditional expression (4) is not satisfied, the shape of the right-angle prism becomes large and the entire zoom lens becomes large, which is not preferable. In addition, coma and lateral chromatic aberration generated in the first lens group are deteriorated. As a result, the thickness of the camera body is also affected, making it impossible to reduce the size. In addition to the right-angle prism, a mirror, an optical fiber, or the like can be used for the optical path bending optical element.

  In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (4) to 1.84. In order to further secure the effect of the present invention, it is more preferable to set the lower limit of conditional expression (4) to 1.85.

  In the zoom lens according to the embodiment of the present invention, it is desirable that the second lens group and the fourth lens group are used in combination when focusing on a short-distance object in order to further reduce the size. When focusing on an object at a short distance, either the second lens group or the fourth lens group moves to the object side up to a predetermined shooting distance, and the object closer to the shooting distance than the predetermined shooting distance. When focusing, it is desirable that the lens group that has not been moved when focusing to a predetermined shooting distance moves to the object side.

  With such a configuration, the group interval between the first lens unit and the second lens unit in the infinite focus state in the wide-angle end state and the group interval between the third lens unit and the fourth lens group in the telephoto end state are set. It is possible to minimize the total length of the lens system. In addition, it is possible to shorten the shooting distance when shooting a short-distance object, and to enable macro shooting and the like.

  On the other hand, when the focusing group is a single lens group, the focusing group can be moved only to the point where the lens or mechanical parts that hold the lens interfere with each other. This is contrary to the intention of the invention of downsizing.

  In the zoom lens according to the embodiment of the present invention, in order to further reduce the size, the second lens group and the fourth lens group are used in combination when focusing on a short-distance object in the wide-angle end state. In the wide-angle end state, when focusing on an object at a short distance, the second lens group moves to the object side up to a predetermined shooting distance, and the object closer to the shooting distance than the predetermined shooting distance. When performing focusing, it is desirable that the fourth lens group be moved to the object side.

  With such a configuration, it is possible to minimize the group distance between the first lens group and the second lens group in the infinitely focused state at the wide-angle end state, and to reduce the overall length of the lens system. Is possible. In addition, it is possible to reduce the shooting distance when shooting a short-distance object, and it is possible to perform macro shooting and the like.

  On the other hand, when the focusing group is a single lens group, the focusing group can be moved only to the point where the lens or mechanical parts that hold the lens interfere with each other. This is contrary to the intention of the invention of downsizing.

  The zoom lens according to the embodiment of the present invention includes, in order from the object side along the optical axis, a first lens group that includes an optical path bending optical element and has positive refractive power, and a second lens that has negative refractive power. When the focal length changes from the wide-angle end state to the telephoto end state, the first lens is composed of a lens group, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The group and the third lens group are fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, the distance between the second lens group and the third lens group decreases, and the third lens When the distance between the first lens group and the fourth lens group is reduced, and when focusing on a short-distance object in the wide-angle end state, the second lens group moves to the object side until a predetermined shooting distance, and a predetermined shooting distance is reached. When focusing on an object at a shorter distance than the fourth lens group, the fourth lens unit moves toward the object side. Growth is desirable.

  With this configuration, it is possible to minimize the group distance between the first lens group and the second lens group in the infinite state at the wide-angle end state, and it is possible to reduce the overall length of the lens system. is there. In addition, it is possible to reduce the shooting distance when shooting a short-distance object, and it is possible to perform macro shooting and the like.

  On the other hand, when the focusing group is a single lens group, the focusing group can be moved only to the point where the lens or mechanical parts that hold the lens interfere with each other. This is contrary to the intention of the invention of downsizing.

  Further, in the zoom lens according to the embodiment of the present invention, in order to balance high performance and miniaturization, the second lens group has a negative surface with a concave surface facing the object side in order from the object side along the optical axis. It is desirable that the lens is composed of a cemented lens having a negative refractive power between the lens and the positive lens. By making the second lens group a cemented lens having a negative refractive power, it is possible to satisfactorily correct axial chromatic aberration and lateral chromatic aberration generated by the second lens group alone.

  In the zoom lens according to the embodiment of the present invention, it is desirable that the most object-side surface in the second lens group is an aspherical surface in order to balance higher performance and smaller size. By arranging an aspherical surface on the most object side surface in the second lens group, it is possible to satisfactorily correct coma and astigmatism fluctuations that occur when the focal length changes from the wide-angle end state to the telephoto end state. it can.

  Further, in the zoom lens according to the embodiment of the present invention, the fourth lens group corrects spherical aberration generated by the fourth lens group alone and corrects the exit pupil position as far as possible from the image plane. A positive lens having a convex surface facing the image side and a positive lens having a convex surface facing the object side, in order from the object side along the optical axis. A cemented lens having a negative refractive power between the lens and a negative lens having a concave surface facing the image side is desirable.

  By reducing the off-axis light flux by the biconvex positive lens of the fourth lens group so that it is not separated from the optical axis, the lens diameter can be reduced. Further, since the fourth lens group as a whole has a positive refractive power, the exit pupil position can be moved away from the image plane, which is suitable for an optical system using a solid-state imaging device as a light receiving element.

The zoom lens focal length adjustment method according to the embodiment of the present invention includes, in order from the object side along the optical axis, a first lens group that includes an optical path bending optical element and has positive refractive power, and negative refraction. A second lens group having a power, a third lens group having a positive refractive power, and a fourth lens group having a positive refractive power. The third lens group is formed from the object side along the optical axis. In order, it is composed of a cemented lens having a positive refractive power of a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side, and satisfies the following conditional expressions (1) and (2): When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group increases. The distance between the second lens group and the third lens group decreases, and the third lens group and the fourth lens group A fourth lens group group second lens so that the distance is reduced have a way of moving along the optical axis is desirable.
nd3p> nd3n (1)
νd3p> νd3n (2)
Where nd3p is the refractive index of the d-line of the positive lens in the third lens group, nd3n is the refractive index of the d-line of the negative lens in the third lens group, and νd3p is the d-line of the positive lens in the third lens group. Abbe number, νd3n, is the Abbe number of the d-line of the negative lens in the third lens group.

  By adopting such a focal length varying method, it is possible to reduce the number of movable lens groups and to simplify the drive mechanism.

  Further, the zoom lens focusing method according to the embodiment of the present invention includes, in order from the object side along the optical axis, a first lens group that includes an optical path bending optical element and has positive refractive power, and negative refractive power. A second lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When the focal length changes from the wide-angle end state to the telephoto end state, The first lens group and the third lens group are fixed with respect to the image plane, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased. A zoom lens in which the distance between the third lens group and the fourth lens group is reduced, and when focusing on a short-distance object, either the second lens group or the fourth lens group is used up to a predetermined shooting distance. Either of them moves to the object side, and the shooting distance is closer than the specified shooting distance. When performing the focusing on the body, how a lens group that did not movable during focusing to a predetermined object distance is moved to the object side is desirable.

  By adopting such a focusing method, the distance between the first lens group and the second lens group in the infinitely focused state in the wide-angle end state, and the third lens group and the fourth lens group in the telephoto end state. The group interval can be minimized, and the total length of the lens system can be reduced. In addition, it is possible to shorten the shooting distance when shooting a short-distance object, and to enable macro shooting and the like.

  Further, the zoom lens focusing method according to the embodiment of the present invention includes, in order from the object side along the optical axis, a first lens group that includes an optical path bending optical element and has positive refractive power, and negative refractive power. A second lens group having a positive refractive power, a fourth lens group having a positive refractive power, and a fourth lens group having a positive refractive power. When the focal length changes from the wide-angle end state to the telephoto end state, The first lens group and the third lens group are fixed with respect to the image plane, the distance between the first lens group and the second lens group is increased, and the distance between the second lens group and the third lens group is decreased. A zoom lens in which the distance between the third lens group and the fourth lens group is reduced, and in the wide-angle end state, when focusing on a short-distance object, the second lens group is an object up to a predetermined shooting distance. When focusing on an object that is closer than the specified shooting distance, How the fourth lens group moves to the object side is desirable.

  By adopting such a focusing method, the distance between the first lens group and the second lens group in the infinitely focused state in the wide-angle end state, and the third lens group and the fourth lens group in the telephoto end state. The group interval can be minimized, and the total length of the lens system can be reduced. In addition, it is possible to reduce the shooting distance when shooting a short-distance object, thereby enabling macro shooting and the like.

  In the zoom lens according to the present invention, it is desirable to dispose at least one aspheric lens in each of the first to fourth lens groups.

  For example, by arranging an aspheric lens in the first lens group, it is possible to satisfactorily correct coma aberration aberration fluctuations that occur when the focal length changes from the wide-angle end state to the telephoto end state. It can also contribute to the downsizing of the first lens group.

  In addition, by arranging an aspheric lens in the second lens, it is possible to satisfactorily correct coma and astigmatism fluctuations that occur when the focal length changes from the wide-angle end state to the telephoto end state.

  In addition, by arranging an aspheric lens in the third lens group, it is possible to satisfactorily correct variations in spherical aberration and coma generated by the third lens group alone, and to minimize performance degradation during lens shift. It is possible to correct the curvature of field.

  Further, by arranging an aspheric lens in the fourth lens group, it is possible to satisfactorily correct the variation in spherical aberration that occurs in the fourth lens group alone.

  Further, in the zoom lens of the present invention, in order to prevent a shooting failure due to an image blur caused by a camera shake or the like which is likely to occur in a high-magnification zoom lens, a blur detection system for detecting a blur of the lens system and a driving unit are provided. By combining the lens system and decentering all or part of one of the lens groups constituting the lens system as a shift lens group, image blur caused by the blur of the lens system detected by the blur detection system ( The image blur can be corrected by driving the shift lens group by the driving means and shifting the image so as to correct the fluctuation of the image plane position. Thus, the zoom lens of the present invention can function as a so-called vibration-proof optical system.

(Example)
Embodiments of the zoom lens according to the embodiment of the present invention will be described below with reference to the accompanying drawings.

  FIG. 3 is a diagram illustrating a state of movement of each lens unit in a refractive power distribution of the zoom lens according to each embodiment of the present invention and a change in a focal length state from a wide-angle end state (W) to a telephoto end state (T). It is.

  As shown in FIG. 3, the zoom lens according to each embodiment of the present invention includes a first lens group G1 having a positive refractive power and a second lens having a negative refractive power in order from the object side along the optical axis. The lens group G2 includes a third lens group G3 having a positive refractive power, a fourth lens group G4 having a positive refractive power, and a filter group FL including a low-pass filter and an infrared cut filter. . When the focal length state changes from the wide-angle end state W to the telephoto end state T (that is, zooming), the first lens group G1 and the third lens group G3 are fixed with respect to the image plane I, and the first lens group A configuration in which the distance between G1 and the second lens group G2 increases, the distance between the second lens group G2 and the third lens group G3 decreases, and the distance between the third lens group G3 and the fourth lens group G4 decreases. It is.

In each embodiment, the height of the aspheric surface in the direction perpendicular to the optical axis is y, and the distance (sag amount) along the optical axis from the tangential plane of the apex of each aspheric surface to each aspheric surface at height y. Is S (y), the radius of curvature of the reference sphere (paraxial radius of curvature) is r, the conic constant is κ, and the nth-order aspherical coefficient is Cn, it is expressed by the following equation.
S (y) = (y ² / r) / {1+ (1−κ × y ² / r ² ) ^1/2 }
+ C4 × y ⁴ + C6 × y ⁶ + C8 × y ⁸ + C10 × y ¹⁰

  In each embodiment, the secondary aspheric coefficient C2 is zero. In the table of each example, an aspherical surface is marked with * on the left side of the surface number.

(First embodiment)
FIG. 4 is a diagram illustrating a lens configuration of the zoom lens according to the first embodiment of the present invention developed along the optical axis.

  In FIG. 4, the first lens group G1 includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface facing the object side, a right-angle prism P intended to bend the optical path by approximately 90 degrees, It is composed of a biconvex positive lens L12 having an aspheric surface on the object side.

  The second lens group G2 includes, in order from the object side along the optical axis, a biconcave negative lens having a concave surface on the object side and an aspheric surface on the object side, and a positive meniscus lens having a concave surface on the image plane I side. This is composed of a cemented lens L21 having a negative refractive power, which is formed by bonding together.

  The third lens group G3 has, in order from the object side along the optical axis, a positive refractive power joint formed by bonding a biconvex positive lens having an aspheric surface on the object side and a biconcave negative lens. It is composed of a lens L31.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens L41 having an aspheric surface on the image plane I side, a biconvex positive lens, and a biconcave negative lens. This is composed of a cemented lens L42 having a negative refractive power made up of these two lenses.

  The filter group FL includes a low-pass filter, an infrared cut filter, and the like.

  The image plane I is formed on an image sensor (not shown), and the image sensor is composed of a CCD, a CMOS, or the like. The configuration of the image plane I is the same for each of the following examples, and the description thereof will be omitted.

  The aperture stop S is disposed closest to the object side of the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  In the wide-angle end state, when focusing on an object at a short distance, the second lens group G2 moves toward the object up to a predetermined shooting distance, and focuses on an object at a closer distance than the predetermined shooting distance. When performing the above, the fourth lens group G4 moves to the object side.

  Table (1) below lists the values of the specifications of the zoom lens according to the first example of the present invention. In the table, “f” in “Overall specifications” indicates the focal length, and F.F. NO represents the F number, and 2ω represents the angle of view (unit: degree). In the “lens data”, the surface number indicates the order of the lens surfaces from the object side along the direction in which the light beam travels, the surface interval indicates the surface interval of each lens surface, and the refractive index and Abbe number indicate the d-line (λ Bf indicates the back focus. The radius of curvature of 0.0000 indicates a plane, and the refractive index of air of 1.0000 is omitted. “Aspherical data” indicates the surface number, the conical coefficient κ, and the values of the aspherical coefficients C4 to C10. “Variable interval data” indicates the focal length f, each variable interval, and the value of the back focus Bf. “Focus data” indicates the amount of movement Δ2 of the second lens group G2 and the amount of movement Δ4 of the fourth lens group G4 when focusing on the shooting distances of 0.3 m and 0.1 m in the wide-angle end state. The sign is positive when moving to the object side with the positions of the second lens group G2 and the fourth lens group G4 in the infinitely focused state as the origin. The “conditional expression corresponding value” indicates a value corresponding to each conditional expression.

  In addition, the focal length f, the radius of curvature, the surface interval, and other length units listed in all the following specification values are generally “mm”, but the optical system is proportionally enlarged or reduced. However, the same optical performance can be obtained, and the present invention is not limited to this. Moreover, the said code | symbol is the same also in another Example, and subsequent description is abbreviate | omitted.

(Table 1)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 10.37 to 18.40
F.NO = 3.38 to 3.89 to 4.91
2ω = 62.93 to 39.56 to 22.40

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 18.0000 0.70 1.92286 18.90
2 7.7804 2.15
3 0.0000 8.50 1.88300 40.76
4 0.0000 0.17
* 5 17.8716 2.20 1.76802 49.23
6 -16.6457 (d6)
* 7 -12.4031 0.70 1.80139 45.46
8 5.4198 1.22 1.92286 18.90
9 9.7839 (d9)
10 0.0000 0.25 (Aperture stop S)
* 11 4.9041 1.55 1.85026 32.35
12 -12.5495 0.80 1.76182 26.52
13 4.8718 (d13)
14 7.4644 2.00 1.58913 61.14
* 15 -9.0541 0.09
16 7.9720 2.25 1.51633 64.14
17 -5.3173 0.70 1.90366 31.31
18 8.7191 (d18)
19 0.0000 0.56 1.54437 70.51
20 0.0000 0.35
21 0.0000 0.43 1.51633 64.14
22 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-0.1746 -1.5223 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
-6.2703 -2.7741 × 10 ^-5 + 0.0000 × 10 ^-0 + 1.5818 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
+1.0680 -8.8558 × 10 ^-4 -2.2718 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[15th page]
κ C4 C6 C8 C10
-0.3211 + 1.7947 × 10 ^-4 + 5.5035 × 10 ^-6 -8.1580 × 10 ^-7 + 0.0000 × 10 ^-0

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 10.3700 18.4000
d6 1.0149 3.7207 6.2865
d9 6.0247 3.3189 0.7531
d13 4.8042 3.1241 0.7036
d18 5.7847 7.4674 9.8853
Bf 0.5125 0.5125 0.5125

"Focus data"
Shooting distance 0.3m 0.1m
Δ2 0.3005 0.3005
Δ4 0.0000 0.4793

"Values for conditional expressions"
Ymax = 3.75
(1) (nd3p> nd3n) → (1.85026> 1.76182)
(2) (νd3p> νd3n) → (32.35> 26.52)
(3) TL / Ymax = 11.40461
(4) ndp = 1.88300

  FIG. 5 is a diagram illustrating various aberrations in the infinitely focused state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the first example, and (a) is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 6 shows various conditions in the short-distance focusing state (shooting distance 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the first example. It is an aberration diagram.

  In each aberration diagram, FNO denotes an F number, NA denotes a numerical aperture, H0 denotes an object height, and A denotes a half angle of view (unit: degree). In the aberration diagrams showing astigmatism, the solid line shows the sagittal image plane, and the broken line shows the meridional image plane. In the aberration diagrams showing the spherical aberration, the solid line shows the spherical aberration, and the broken line shows the sine condition (sine condition). In addition, the meaning of said code | symbol is the same also in another Example, and subsequent description is abbreviate | omitted.

  As is apparent from each aberration diagram, the zoom lens according to the first example has excellent imaging performance with various aberrations corrected well in each focal length state from the wide-angle end state to the telephoto end state. I understand.

(Second embodiment)
FIG. 7 is a diagram showing a lens configuration of the zoom lens according to the second embodiment of the present invention developed along the optical axis.

  In FIG. 7, the first lens group G1 includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a right-angle prism P intended to bend the optical path by approximately 90 degrees, It is composed of a biconvex positive lens L12 having an aspheric surface on the object side.

  The second lens group G2 includes, in order from the object side along the optical axis, a biconcave negative lens having a concave surface on the object side and an aspheric surface on the object side, and a positive meniscus lens having a concave surface on the image plane I side. This is composed of a cemented lens L21 having a negative refractive power, which is formed by bonding together.

  The third lens group G3 includes, in order from the object side along the optical axis, a cemented lens L31 having a positive refractive power formed by bonding a convex meniscus positive lens having an aspheric surface on the object side and a negative meniscus lens. It is configured.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens L41 having an aspheric surface on the image plane I side, a biconvex positive lens, and a biconcave negative lens. This is composed of a cemented lens L42 having a negative refractive power made up of these two lenses.

  The filter group FL includes a low-pass filter, an infrared cut filter, and the like.

  The aperture stop S is disposed closest to the object side of the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

In the wide-angle end state, when focusing on an object at a short distance, the second lens group G2 moves toward the object up to a predetermined shooting distance, and focuses on an object at a closer distance than the predetermined shooting distance. When performing the above, the fourth lens group G4 moves toward the object side. Table 2 below lists the values of the specifications of the zoom lens according to the second example.

(Table 2)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 10.37 to 18.40
F.NO = 3.37 to 3.87 to 4.89
2ω = 63.53 to 39.53 to 22.40

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 18.0000 0.70 1.92286 18.90
2 7.6680 2.15
3 0.0000 8.50 1.88300 40.76
4 0.0000 0.17
* 5 17.6844 2.20 1.76802 49.23
6 -16.6506 (d6)
* 7 -13.3278 0.70 1.80139 45.46
8 5.0053 1.22 1.92286 18.90
9 9.1455 (d9)
10 0.0000 0.30 (Aperture stop S)
* 11 4.9030 1.55 1.85049 40.19
12 183.9440 0.80 1.71736 29.52
13 4.8561 (d13)
14 7.2630 2.00 1.51633 64.06
* 15 -8.0017 0.09
16 6.9440 2.25 1.51633 64.14
17 -5.6543 0.70 1.90366 31.31
18 8.2901 (d18)
19 0.0000 0.56 1.54437 70.51
20 0.0000 0.35
21 0.0000 0.43 1.51633 64.14
22 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-0.1454 -1.1936 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
-6.1412 + 1.8170 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[11th page]
κ C4 C6 C8 C10
+1.0851 -8.3586 × 10 ^-4 -2.3842 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[15th page]
κ C4 C6 C8 C10
-0.4028 + 1.8495 × 10 ^-4 + 7.3128 × 10 ^-6 -8.0261 × 10 ^-7 + 0.0000 × 10 ^-0

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 10.3700 18.4000
d6 1.1713 3.8771 6.4429
d9 5.9731 3.2673 0.7015
d13 4.6953 3.0153 0.5948
d18 5.8218 7.5018 9.9223
Bf 0.5125 0.5125 0.5125

["Focus data"
Shooting distance 0.3m 0.1m
Δ2 0.3005 0.3005
Δ4 0.0000 0.4796

"Values for conditional expressions"
Ymax = 3.75
(1) (nd3p> nd3n) → (1.85049> 1.71736)
(2) (νd3p> νd3n) → (40.19> 29.52)
(3) TL / Ymax = 11.42676
(4) ndp = 1.88300

  FIG. 8 is a diagram showing various aberrations of the zoom lens according to the second example in the state of focusing on infinity with respect to the d-line (λ = 587.6 nm), and (a) is a wide angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 9 shows various zoom lens conditions in the short-distance focusing state (shooting distance: 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the second example. It is an aberration diagram.

  As is apparent from each aberration diagram, the zoom lens according to the second example has excellent imaging performance with various aberrations corrected well in each focal length state from the wide-angle end state to the telephoto end state. I understand.

(Third embodiment)
FIG. 10 is a diagram illustrating a lens configuration of the zoom lens according to the third embodiment of the present invention developed along the optical axis.

  In FIG. 10, the first lens group G1 includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, and an optical device such as a right-angle prism intended to bend the optical path by approximately 90 degrees. It comprises an element P and a biconvex positive lens L12 having an aspheric surface on the object side.

  The second lens group G2 includes, in order from the object side along the optical axis, a biconcave negative lens having a concave surface facing the object side and an aspheric surface on the object side, and a positive meniscus lens facing the concave surface to the image surface I side. It is comprised from the cemented lens L21 of the negative refractive power which consists of pasting.

  The third lens group G3 includes, in order from the object side along the optical axis, a cemented lens L31 having a positive refractive power that is formed by bonding a positive meniscus lens having an aspheric surface on the object side and a negative meniscus lens. Yes.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens L41 having an aspheric surface on the image plane I side, a biconvex positive lens, and a biconcave negative lens. It is composed of a cemented lens L42 having a negative refractive power made by bonding.

  The filter group FL includes a low-pass filter, an infrared cut filter, and the like.

  The aperture stop S is disposed closest to the object side of the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

In the wide-angle end state, when focusing on an object at a short distance, the second lens group G2 moves toward the object up to a predetermined shooting distance, and focuses on an object at a closer distance than the predetermined shooting distance. When performing the above, the fourth lens group G4 moves toward the object side. Table 3 below lists the values of the specifications of the zoom lens according to the third example.

(Table 3)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 10.37 to 18.40
F.NO = 3.38 to 3.88 to 4.88
2ω = 62.48 to 39.57 to 22.40

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 18.3000 0.70 1.92286 18.90
2 7.5480 2.15
3 0.0000 8.50 1.88300 40.76
4 0.0000 0.15
* 5 17.3829 2.20 1.76802 49.23
6 -16.6404 (d6)
* 7 -13.9802 0.70 1.80139 45.46
8 4.8168 1.25 1.92286 18.90
9 8.8070 (d9)
10 0.0000 0.20 (Aperture stop S)
* 11 4.8355 1.55 1.82080 42.71
12 228.2363 0.80 1.68893 31.07
13 4.8222 (d13)
14 7.0317 2.00 1.51633 64.06
* 15 -8.1981 0.10
16 7.0716 2.25 1.51633 64.14
17 -5.6943 0.70 1.90366 31.31
18 8.2741 (d18)
19 0.0000 0.55 1.54437 70.51
20 0.0000 0.35
21 0.0000 0.50 1.51633 64.14
22 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-0.1774 -4.2434 × 10 ^-6 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
-3.5035 + 1.2078 × 10 ^-4 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
+1.1259 -8.9755 × 10 ^-4 -3.1350 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[15th page]
κ C4 C6 C8 C10
-0.4981 + 2.1235 × 10 ^-4 + 1.1198 × 10 ^-5 -8.7385 × 10 ^-6 + 0.0000 × 10 ^-0

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 10.3700 18.3999
d6 1.4323 4.1381 6.7039
d9 6.0359 3.3301 0.7643
d13 4.7725 3.0924 0.6719
d18 5.7844 7.4644 9.8850
Bf 0.4762 0.4762 0.4762

"Focus data"
Shooting distance 0.3m 0.1m
Δ2 0.3008 0.3008
Δ4 0.0000 0.4820

"Values for conditional expressions"
Ymax = 3.75
(1) (nd3p> nd3n) → (1.82080> 1.68893)
(2) (νd3p> νd3n) → (42.71> 31.07)
(3) TL / Ymax = 11.50703
(4) ndp = 1.88300

  FIG. 11 is a diagram illustrating various aberrations of the zoom lens according to the third example in the infinite focus state with respect to the d-line (λ = 587.6 nm), and FIG. 11A is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 12 shows various values in the short-distance focusing state (shooting distance 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the third example. It is an aberration diagram.

As is apparent from each aberration diagram, the zoom lens according to the third example has excellent imaging performance with various aberrations corrected well in each focal length state from the wide-angle end state to the telephoto end state. I understand.
[Fourth embodiment]
FIG. 13 is a diagram illustrating a lens configuration of a zoom lens according to a fourth example of the present invention developed along the optical axis.

  In FIG. 13, the first lens group G1 includes, in order from the object side along the optical axis, a negative meniscus lens L11 having a convex surface directed toward the object side, a right-angle prism P intended to bend the optical path by approximately 90 degrees, It is composed of a biconvex positive lens L12 having an aspheric surface on the object side.

  The second lens group G2 includes, in order from the object side along the optical axis, a biconcave negative lens having a concave surface facing the object side and an aspheric surface on the object side, and a positive meniscus lens facing the concave surface to the image surface I side. It is comprised from the cemented lens L21 of the negative refractive power which consists of pasting.

  The third lens group G3 has, in order from the object side along the optical axis, a positive refractive power joint formed by bonding a biconvex positive lens having an aspheric surface on the object side and a biconcave negative lens. It is composed of a lens L31.

  The fourth lens group G4 includes, in order from the object side along the optical axis, a biconvex positive lens L41 having an aspheric surface on the image plane I side, a biconvex positive lens, and a biconcave negative lens. This is composed of a cemented lens L42 having a negative refractive power made up of these two lenses.

  The filter group FL includes a low-pass filter, an infrared cut filter, and the like.

  The aperture stop S is disposed closest to the object side of the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state to the telephoto end state.

  In the wide-angle end state, when focusing on an object at a short distance, the second lens group G2 moves toward the object up to a predetermined shooting distance, and focuses on an object at a closer distance than the predetermined shooting distance. When performing the above, the fourth lens group G4 moves to the object side.

  Table 4 below provides values of specifications of the zoom lens according to the fourth example.

(Table 4)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 10.37 to 18.40
F.NO = 3.36 to 3.86 to 4.88
2ω = 61.90-39.51-22.42

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 18.3000 0.70 1.92286 18.90
2 7.5044 2.15
3 0.0000 8.50 1.88300 40.76
4 0.0000 0.17
* 5 17.0792 2.20 1.76802 49.23
6 -16.8871 (d6)
* 7 -15.5610 0.70 1.80139 45.46
8 4.6036 1.22 1.92286 18.90
9 8.2225 (d9)
10 0.0000 0.25 (Aperture stop S)
* 11 4.8923 1.55 1.83441 37.28
12 -53.6767 0.80 1.75520 27.51
13 5.1812 (d13)
14 7.0547 2.00 1.51633 64.06
* 15 -7.9717 0.09
16 7.2115 2.25 1.51633 64.14
17 -5.6683 0.70 1.90366 31.31
18 8.2994 (d18)
19 0.0000 0.56 1.54437 70.51
20 0.0000 0.35
21 0.0000 0.43 1.51633 64.14
22 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-0.1618 -2.3527 × 10 ^-6 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[Seventh side]
κ C4 C6 C8 C10
-4.1303 + 1.4320 × 10 ^-4 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[11th page]
κ C4 C6 C8 C10
+1.1273 -8.8815 × 10 ^-4 -3.0706 × 10 ^-5 + 0.0000 × 10 ^-0 + 0.0000 × 10 ^-0
[15th page]
κ C4 C6 C8 C10
-0.6270 + 2.3810 × 10 ^-4 + 1.1479 × 10 ^-5 -8.0287 × 10 ^-7 + 0.0000 × 10 ^-0

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 10.3700 18.4000
d6 1.4836 4.1894 6.7552
d9 6.0107 3.3049 0.7390
d13 4.7932 3.1132 0.6926
d18 5.8002 7.4803 9.9008
Bf 0.5125 0.5125 0.5125

"Focus data"
Shooting distance 0.3m 0.1m
Δ2 0.3009 0.3009
Δ4 0.0000 0.4824

"Values for conditional expressions"
Ymax = 3.75
(1) (nd3p> nd3n) → (1.83441> 1.75520)
(2) (νd3p> νd3n) → (37.28> 27.51)
(3) TL / Ymax = 11.552708
(4) ndp = 1.88300

  FIG. 14 is a diagram of various aberrations of the zoom lens according to the fourth example in the state of focusing on infinity with respect to the d-line (λ = 587.6 nm), and (a) is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 15 shows various values in the short-distance focusing state (shooting distance: 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the fourth example. It is an aberration diagram.

  As is apparent from each aberration diagram, the zoom lens according to the fourth example has excellent imaging performance with various aberrations corrected well in each focal length state from the wide-angle end state to the telephoto end state. I understand.

  According to the present invention, it is possible to realize a small zoom lens having excellent imaging performance, which is suitable when a place where a zoom lens such as a video camera or a digital still camera using a solid-state image sensor is disposed is limited. be able to.

  The contents described below can be appropriately adopted as long as the optical performance is not impaired.

  In each embodiment, a four-group configuration is shown, but the present invention can also be applied to other group configurations such as a five-group configuration.

  The focusing lens group can also be applied to autofocus, and is also suitable for driving a motor for autofocus (such as an ultrasonic motor).

  Alternatively, the lens group or the partial lens group may be vibrated in a direction perpendicular to the optical axis so as to correct an image blur caused by camera shake. In particular, the second or fourth lens group is preferably an anti-vibration lens group.

  The lens surface may be an aspherical surface. The aspherical surface may be any of an aspherical surface by grinding, a glass mold aspherical surface in which a glass is formed into an aspherical shape, or a composite aspherical surface in which a resin is formed in an aspherical shape on the glass surface.

  Further, each lens surface is provided with an antireflection film having a high transmittance over a wide wavelength range, and flare and ghost can be reduced to achieve high optical performance with high contrast.

  In addition, in order to explain the present invention in an easy-to-understand manner, the configuration requirements of the embodiment have been described, but it goes without saying that the present invention is not limited to this.

1 shows an electronic still camera that is an optical device equipped with a zoom lens according to an embodiment of the present invention, where (a) shows a front view and (b) shows a rear view. It is sectional drawing along the A-A 'line of Fig.1 (a), and has shown the outline | summary of arrangement | positioning of the zoom lens concerning embodiment of this invention. It is a figure which shows the mode of movement of each lens group in the refractive power distribution of the zoom lens concerning each Example of this invention, and the change of the focal distance state from a wide-angle end state (W) to a telephoto end state (T). It is a figure which expands and shows the lens structure of the zoom lens concerning 1st Example of this invention along an optical axis. FIG. 6 is a diagram illustrating various aberrations of the zoom lens according to the first example in the infinite focus state with respect to the d-line (λ = 587.6 nm), where (a) illustrates various aberrations in the wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 6 is a diagram illustrating various aberrations of the zoom lens according to the first example in the short-distance focusing state (shooting distance: 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm). . It is a figure which expands and shows the lens structure of the zoom lens concerning 2nd Example of this invention along an optical axis. FIG. 10 is a diagram illustrating various aberrations of the zoom lens according to the second example in the infinite focus state with respect to the d-line (λ = 587.6 nm), where (a) illustrates various aberrations in the wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 11 is a diagram illustrating various aberrations of the zoom lens according to Example 2 in a short-distance focusing state (shooting distance: 0.1 m) in a wide-angle end state (f = 6.49 mm) with respect to d line (λ = 587.6 nm). . It is a figure which expands and shows the lens structure of the zoom lens concerning 3rd Example of this invention along an optical axis. FIG. 7A is a diagram illustrating various aberrations of the zoom lens according to the third example in the infinite focus state with respect to the d-line (λ = 587.6 nm), and FIG. 9A illustrates various aberrations in the wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 11 is a diagram illustrating various aberrations of the zoom lens according to the third example in the short-distance focusing state (shooting distance: 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm). . It is a figure which expands and shows the lens structure of the zoom lens concerning 4th Example of this invention along an optical axis. FIG. 12A is a diagram illustrating various aberrations of the zoom lens according to the fourth example in the state of focusing on infinity with respect to the d-line (λ = 587.6 nm), and (a) illustrates various aberrations in the wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 10.37 mm), and (c) shows various aberrations in the telephoto end state (f = 18.40 mm). FIG. 11 is a diagram illustrating various aberrations in the short-distance focusing state (shooting distance: 0.1 m) in the wide-angle end state (f = 6.49 mm) with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the fourth example. .

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group P Right angle prism FL filter group S Aperture stop I Image surface

Claims (13)

A first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group Increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group decreases,
The third lens group includes, in order from the object side along the optical axis, a cemented lens having a positive refractive power of a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side,
A zoom lens satisfying the following conditions:
nd3p> nd3n
νd3p> νd3n
However,
nd3p: refractive index of the d-line of the positive lens in the third lens group nd3n: refractive index of the d-line of the negative lens in the third lens group νd3p: d of the positive lens in the third lens group Abbe number of line νd3n: Abbe number of d line of the negative lens in the third lens group The zoom lens according to claim 1, wherein the following condition is satisfied.
TL / Ymax <11.6
However,
TL: Total length Ymax along the optical axis from the lens surface closest to the object side to the image plane of the first lens group: Maximum image height The optical path bending optical element is a right angle prism;
The zoom lens according to claim 1, wherein the zoom lens satisfies the following condition.
ndp> 1.83
However,
ndp: refractive index of d-line of the right-angle prism When focusing on an object at a short distance, one of the second lens group and the fourth lens group moves to the object side up to a predetermined shooting distance,
When focusing on an object closer to the shooting distance than the predetermined shooting distance, the lens group that did not move when focusing to the predetermined shooting distance moves to the object side. The zoom lens according to claim 1. In the wide-angle end state, when focusing on an object at a short distance, the second lens group moves to the object side up to a predetermined distance,
5. The apparatus according to claim 1, wherein the fourth lens group moves toward the object side when focusing on an object having a shooting distance closer than the predetermined shooting distance. 6. Zoom lens. A first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group Increases, the distance between the second lens group and the third lens group decreases, the distance between the third lens group and the fourth lens group decreases,
In the wide-angle end state, when focusing on a short-distance object, the second lens group moves to the object side up to a predetermined shooting distance,
The zoom lens, wherein when focusing on an object closer than the predetermined shooting distance, the fourth lens group moves toward the object side.   The second lens group includes a cemented lens having negative refractive power of a negative lens and a positive lens having a concave surface facing the object side in order from the object side along the optical axis. The zoom lens according to any one of 1 to 6.   The zoom lens according to any one of claims 1 to 7, wherein a surface closest to the object side in the second lens group is an aspherical surface.   The fourth lens group includes, in order from the object side along the optical axis, a positive lens having a convex surface facing the object side, a positive lens having a convex surface facing the object side, and a negative lens having a concave surface facing the image surface side. The zoom lens according to any one of claims 1 to 8, wherein the zoom lens is configured by a cemented lens having negative refractive power.   An optical device comprising the zoom lens according to any one of claims 1 to 9. A first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
The third lens group includes, in order from the object side along the optical axis, a cemented lens having a positive refractive power of a positive lens having a convex surface facing the object side and a negative lens having a concave surface facing the image side, The following conditions are satisfied,
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group Increases, the distance between the second lens group and the third lens group decreases, and the distance between the third lens group and the fourth lens group decreases. A focal length adjustment method, wherein the lens group moves along the optical axis.
nd3p> nd3n
νd3p> νd3n
However,
nd3p: refractive index of the d-line of the positive lens in the third lens group nd3n: refractive index of the d-line of the negative lens in the third lens group νd3p: d of the positive lens in the third lens group Abbe number of line νd3n: Abbe number of d line of the negative lens in the third lens group A first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group A zoom lens in which the distance between the second lens group and the third lens group decreases and the distance between the third lens group and the fourth lens group decreases,
When focusing on an object at a short distance, one of the second lens group and the fourth lens group moves to the object side up to a predetermined shooting distance,
When focusing on an object closer to the shooting distance than the predetermined shooting distance, the lens group that did not move when focusing to the predetermined shooting distance moves to the object side. Zoom lens focusing method. A first lens group having an optical path bending optical element and having a positive refractive power, a second lens group having a negative refractive power, and a third lens group having a positive refractive power in order from the object side along the optical axis. And a fourth lens group having a positive refractive power,
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the third lens group are fixed with respect to the image plane, and the distance between the first lens group and the second lens group A zoom lens in which the distance between the second lens group and the third lens group decreases and the distance between the third lens group and the fourth lens group decreases,
In the wide-angle end state, when focusing on a short-distance object, the second lens group moves to the object side up to a predetermined shooting distance,
A focusing method for a zoom lens, wherein the fourth lens group moves to the object side when focusing on an object closer than the predetermined shooting distance.

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