JP4631872B2 - Zoom lens and optical apparatus having the same - Google Patents

Description

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

  Conventionally, for example, a digital still camera or a video camera that records a subject image using a solid-state imaging device such as a CCD or CMOS is generally equipped with a zoom lens.

  However, in many zoom lenses, as the focal length in the telephoto end state increases, the total length of the lens system increases, and the lens outer diameter of the lens unit closest to the object increases, resulting in a large lens barrel member. This has resulted in inconvenience in portability.

  Therefore, when the digital still camera is carried, the portability is improved by storing the lens group in the camera body with the distance between the lens groups narrowed so that the distance between the lens groups is minimized.

  Furthermore, in order to reduce the thickness of the digital still camera in the retracted state, it has been considered to use partial barrels and reduce the length of each partial barrel. However, it has been impossible to make the thickness smaller than the length of each partial barrel.

  Nowadays, portability when carrying a digital still camera is very important, and in order to reduce the size, thickness, and weight of the camera body, the zoom lens, which is a photographic lens, has been reduced in size and weight. It has been.

  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 mounting such a zoom lens, it does not protrude from the camera body when shifting from the storage state to the use state, and is excellent in portability even in the use state. In addition, it greatly contributes to miniaturization and thinning of the camera. Furthermore, since the movable part exists inside the camera body, there is no movable part on the surface, which is effective for applications such as waterproofing, drip-proofing, and dustproofing.

A conventional zoom lens that can bend an optical path includes 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. A positive, negative, positive four group type zoom lens composed of a fourth lens group having power is disclosed (for example, see Patent Document 1).
JP 2003-302576 A

  However, in the disclosed example of Patent Document 1, the air gap between the second lens group, the third lens group, and the fourth lens group is effectively varied during zooming, which contributes to downsizing. Since the three lens groups are moved, there is a problem that the number of movable lens groups increases and the movable mechanism becomes complicated.

  The present invention has been made in view of the above problems, and provides a zoom lens having excellent imaging performance with a small and simple movable mechanism suitable for an optical apparatus in which a place where the zoom lens is disposed is limited. To do. Also provided is an optical device comprising the zoom lens.

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 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 The zoom lens is characterized in that the distance between the first lens group and the fourth lens group is reduced, and the first lens group includes a negative lens and satisfies the following conditions.
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative lens

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

Further, according to the present invention, 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 in order from the object side along the optical axis. And a fourth lens group having a positive refractive power. The first lens group includes a negative lens, and the negative lens satisfies the following condition and is in a wide-angle end state. When the focal length changes from the telephoto end state to the telephoto end state, the first lens group is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, and the second lens The second lens group and the fourth lens group are along the optical axis so that the distance between the third lens group and the third lens group is decreased, and the distance between the third lens group and the fourth lens group is decreased. The zoom lens zooming method is characterized in that the zoom lens moves.
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative lens

Further, according to the present invention, 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 in order from the object side along the optical axis. When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group is formed 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 and the fourth lens The first lens group includes a negative lens, and the negative lens satisfies the following condition, and moves the second lens group toward the object side to move closer to an object at infinity. A focus adjustment method for a zoom lens characterized by focusing on a distance object is proposed. To.
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative lens

  According to the present invention, there is provided a bent zoom lens having excellent imaging performance with a small and simple movable mechanism, which is suitable for an optical apparatus in which a place where the zoom lens is disposed is limited, and the zoom lens. An optical device can be provided.

  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 shows a front view and FIG. 1B shows a rear view. 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) of the photographing lens is opened and light from a subject (not shown) is condensed by the photographing lens 2. The image is formed 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 In this configuration, the distance from the fourth lens group is reduced.

  The first lens group has an action of bending the optical path by approximately 90 degrees and an action of converging the light flux. Further, when the focal length changes from the wide-angle end state to the telephoto end state, the first lens group is always fixed. As described above, the first lens group having the largest weight among the lens groups constituting the zoom lens is not moved, so that the structure can be simplified.

  The second lens group functions to enlarge the image of the subject formed by the first lens group, and as the focal length changes from the wide-angle end state to the telephoto end state, the first lens group and the second lens group The focal length is changed by increasing the magnification by increasing the interval.

  The third lens group has a function of converging 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 sine condition, The Petzval sum is well corrected.

  The fourth lens group has a function of further converging the light beam converged by the third lens group, and when changing the focal length from the wide-angle end state to the telephoto end state, the distance between the third lens group and the fourth lens group. It is possible to suppress the fluctuation of the image plane with respect to the change of the focal length by actively changing.

  With this configuration, a zoom lens having a small size and excellent imaging performance can be achieved.

In order to reduce the size of the zoom lens according to the embodiment of the present invention, it is preferable that the first lens group includes a negative lens, and the negative lens satisfies the following conditional expression (1).
nd1> 1.900 (1)
Here, nd1 is the refractive index of the d-line (wavelength λ = 587.6 nm) of the negative lens.

  Conditional expression (1) is a conditional expression that defines the refractive index of the negative lens in the first lens group. Exceeding the lower limit value of conditional expression (1) is not preferable because the effective diameter and the outer diameter of the negative lens in the first lens group become large and the entire zoom lens becomes large. As a result, the thickness of the camera body is also affected, making it impossible to reduce the size. Further, coma and distortion are deteriorated, which is not preferable.

  In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (1) to 1.910. In order to further secure the effect of the present invention, it is more preferable to set the lower limit of conditional expression (1) to any one of 1.920, 1.930, and 1.940. There may be a plurality of negative lenses that satisfy the conditional expression (1).

In order to reduce the size of the zoom lens according to the embodiment of the present invention, it is desirable that the negative lens of the first lens group satisfies the following conditional expression (2).
νd1 <20.50 (2)
Where νd1 is the Abbe number of the d-line of the negative lens.

  Conditional expression (2) defines the Abbe number of the negative lens in the first lens group. When the upper limit value of conditional expression (2) is exceeded, chromatic aberration generated by the first lens unit alone becomes large, and it becomes difficult to correct it satisfactorily.

  In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (2) to 20.30. In order to further secure the effect of the present invention, it is more preferable to set the upper limit of conditional expression (2) to 20.00 or 19.80.

  In the zoom lens according to the embodiment of the present invention, the third lens group corrects spherical aberration generated by the third lens group alone, and corrects the exit pupil position as far as possible from the image plane. It is desirable that the lens is composed of a single lens having a refractive power of 1 and a cemented lens having a negative refractive power, and in order from the object side along the optical axis, a positive lens having a convex surface facing the object side, and a convex surface facing the object side It is desirable that the lens is composed of a cemented lens having a negative refractive power, a positive lens having a negative surface and a negative lens having a concave surface facing the image side.

  The positive lens with the convex surface facing the object side converges the off-axis light beam so that it does not move away from the optical axis, thereby reducing the lens diameter.

  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. It is desirable that the lens is composed of a single lens having a refractive power of 1 and a cemented lens having a negative refractive power, and in order from the object side along the optical axis, a positive lens having a convex surface facing the object side, and a convex surface facing the object side It is desirable that the lens is composed of a cemented lens having a negative refractive power, a positive lens having a negative surface and a negative lens having a concave surface facing the image side.

  The positive lens with the convex surface facing the object side converges the off-axis light beam so that it does not move away from the optical axis, thereby reducing the lens diameter. 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.

In addition, it is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (3).
0.5 <f4 / f3 <1.1 (3)
Here, f3 is the focal length of the third lens group, and f4 is the focal length of the fourth lens group.

  Conditional expression (3) is a conditional expression for defining an optimum focal length ratio range of the third lens group and the fourth lens group.

  If the upper limit of conditional expression (3) is exceeded, the refractive power of the third lens group becomes relatively weak, making it difficult for the third lens group to efficiently contribute to zooming. A high zoom ratio of about 3 times or more cannot be secured. Further, since the refractive power of the fourth lens group becomes relatively strong, coma and astigmatism generated in the fourth lens group become too large, and the object of the present invention is to obtain excellent optical performance. It can no longer be achieved.

  If the lower limit of conditional expression (3) is not reached, the refractive power of the third lens group becomes relatively strong, and the variation in field curvature that occurs in the third lens group during zooming becomes large. . In addition, the refractive power of the fourth lens group becomes relatively weak, the amount of movement increases during zooming, and fluctuations in coma and astigmatism generated in the fourth lens group become large. As a result, it becomes difficult to suppress degradation of performance in the entire zoom range from the wide-angle end state to the telephoto end state.

  In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (3) to 1.0. 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 0.95. In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (3) to 0.55. In order to further secure the effect of the present invention, it is more preferable to set the lower limit of conditional expression (3) to 0.60.

  In the zoom lens according to the embodiment of the present invention, the negative lens of the first lens group is a negative meniscus lens having a convex surface directed toward the object side in order to balance further high performance and downsizing. The first lens group is preferably composed of, in order from the object side along the optical axis, a negative meniscus lens, an optical path bending optical element, and a positive lens having a convex surface facing the object side.

  By having the first lens group configured as described above, it is possible to simplify the structure, and it is possible to satisfactorily correct spherical aberration and coma generated by the first lens group alone with a minimum number of components.

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> 1.800 (4)
Here, ndp is the refractive index of the d-line of the right-angle prism.

  Conditional expression (4) is a conditional expression that defines an appropriate refractive index range of the right-angle prism for the purpose of bending the optical path. 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 lower limit of conditional expression (4) is exceeded, the shape of the right-angle prism becomes large, and the entire zoom lens becomes undesirably large. 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 as 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 1.820. 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 1.830.

  In the zoom lens according to the embodiment of the present invention, it is preferable that at least one lens in the first lens group is an aspherical lens. By disposing an aspheric lens in the first lens group, it is possible to satisfactorily correct coma and astigmatism variations that occur when the focal length changes from the wide-angle end state to the telephoto end state. Furthermore, it can contribute to the reduction in the outer diameter of the first lens group.

  In the zoom lens according to the embodiment of the present invention, the second lens unit has a concave surface directed toward the image side in order from the object side along the optical axis in order to balance further higher performance and downsizing. It is desirable that the lens is composed of a negative lens and a cemented lens having negative refractive power of a negative lens having a concave surface facing the object side and a positive lens.

  By configuring the second lens group as described above, it is possible to satisfactorily correct coma and lateral chromatic aberration generated by the second lens group alone with a simple configuration.

  In the zoom lens according to the embodiment of the present invention, it is desirable to dispose at least one aspheric lens in the second lens group in order to further improve the performance. Here, by arranging an aspherical lens in the second lens group, it is possible to satisfactorily correct coma variation that occurs when the focal length changes from the wide-angle end state to the telephoto end state.

It is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (5).
0.8 <(− f2) / fw <1.3 (5)

  Conditional expression (5) is a conditional expression for defining an appropriate focal length range of the second lens group.

  If the upper limit of conditional expression (5) is exceeded, the refractive power of the second lens group will increase, and coma and astigmatism generated by the second lens group alone will become too large, resulting in performance changes during close-up shooting. Becomes large and is not preferable. As a result, it becomes difficult to shorten the shortest shooting distance.

  If the lower limit of conditional expression (5) is not reached, the refractive power of the second lens group will be weakened, and the amount of movement during focus adjustment will increase, and the drive system members and the like necessary for movement will increase in size. Therefore, there is a risk of interference with other members. In addition, spherical aberration deteriorates when trying to reduce the size. As a result, it becomes impossible to save space when storing in the camera body.

  In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (5) to 1.25. In order to further secure the effect of the present invention, it is more preferable to set the upper limit of conditional expression (5) to 1.20. In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (5) to 0.85. In order to further secure the effect of the present invention, it is more preferable to set the lower limit of conditional expression (5) to 0.90.

  In the zoom lens according to the embodiment of the present invention, it is desirable to adjust the focus from an infinitely distant object to a close object by moving the second lens group to the object side along the optical axis. In the zoom lens of the present invention, the air distance between the first lens group and the second lens group is close to the second lens group in the wide-angle end state. Since the feeding amount is very small, it is possible to avoid interference between the lens and the mechanical parts that support the lens. Further, the amount of extension of the second lens group can be secured from the wide-angle end state to the telephoto end state, and so-called macro photography is possible.

  On the other hand, it is conceivable to adjust the focus from an object at infinity to an object at a short distance with the fourth lens group. It will be difficult to ensure. Further, in the telephoto end state, it is not preferable to increase the air gap between the third lens unit and the fourth lens unit because the spherical aberration and the field curvature in the telephoto end state are increased.

In addition, it is desirable that the zoom lens according to the embodiment of the present invention satisfies the following conditional expression (6).
1.5 <f1 / (− f2) <4.0 (6)
Here, f1 is the focal length of the first lens group, and f2 is the focal length of the second lens group.

  Conditional expression (6) is a conditional expression for defining an appropriate range for the focal length ratio between the first lens group and the second lens group.

  If the upper limit of conditional expression (6) is exceeded, the refractive power of the first lens group becomes relatively weak, and the lens outer diameter of the entire first lens group becomes large, making it impossible to contribute to downsizing. End up. Further, since the refractive power of the second lens group becomes relatively strong, the occurrence of coma aberration cannot be suppressed, and high optical performance cannot be obtained.

  If the lower limit value of conditional expression (6) is not reached, the refractive power of the first lens group becomes relatively strong, which is advantageous for miniaturization, but the spherical aberration and the fluctuation of the field curvature during zooming. Is undesirably large. In addition, since the refractive power of the second lens group becomes relatively weak, the second lens group cannot efficiently contribute to zooming, and the amount of movement necessary for zooming cannot be secured.

  In order to secure the effect of the present invention, it is preferable to set the upper limit of conditional expression (6) to 3.5. In order to further secure the effect of the present invention, it is more preferable to set the upper limit of conditional expression (6) to 3.0. In order to secure the effect of the present invention, it is preferable to set the lower limit of conditional expression (6) to 1.7. In order to further secure the effect of the present invention, it is more preferable to set the lower limit of conditional expression (6) to 2.0.

  In the zoom lens according to the embodiment of the present invention, it is desirable to dispose at least one aspheric lens in the third lens group in order to further improve the performance. By disposing an aspheric lens in the third lens group, it is possible to satisfactorily correct spherical aberration and coma aberration fluctuations that occur when the focal length changes from the wide-angle end state to the telephoto end state.

  In the zoom lens according to the embodiment of the present invention, it is desirable to dispose at least one aspheric lens in the fourth lens group in order to further improve the performance. By disposing an aspherical lens in the fourth lens group, it is possible to satisfactorily correct the variation in field curvature that occurs when the focal length changes from the wide-angle end state to the telephoto end state.

The zoom lens zooming method according to the embodiment of the present invention includes a first lens group having an optical path bending optical element having a positive refractive power and a negative refractive power in order from the object side along the optical axis. Is composed of a second lens group having a positive refractive power, a fourth lens group having a positive refractive power, and the first lens group includes a negative lens. When the focal length changes from the wide-angle end state to the telephoto end state, the following conditional expression (1) is satisfied, the first lens group and the third lens group are fixed with respect to the image plane, and the first lens The second lens so that the distance between the second 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. It is desirable that the group and the fourth lens group move along the optical axis.
nd1> 1.900 (1)
Here, nd1 is the refractive index of the d-line of the negative lens.

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

In addition, the zoom lens focus adjusting method according to the embodiment of the present invention includes a first lens group having an optical path bending optical element and having a positive refractive power in order from the object side along the optical axis, and a 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. The distance between the third lens group and the fourth lens group is reduced, and the first lens group includes a negative lens. The negative lens satisfies the following conditional expression (1), and the second lens group is A focus that adjusts the focus from an infinite object to a near object by moving it to the object side along the optical axis. Adjustment method is desirable.
nd1> 1.900 (1)
Here, nd1 is the refractive index of the d-line of the negative lens.

  By adopting such a focus adjustment method, it is possible to avoid interference of the lens or mechanical parts supporting the lens by using the second lens group with a small lens extension amount during focus adjustment. Further, the amount of extension of the second lens group can be ensured from the wide-angle end state to the telephoto end state, and so-called macro photography can be made possible.

  The zoom lens according to the embodiment of the present invention is a blur detection system that detects a blur of a lens system in order to prevent a shooting failure due to an image blur caused by a camera shake or the like that is likely to occur in a high-magnification zoom lens. And the driving means are combined with the lens system, and the whole or a part of one of the lens groups constituting the lens system is decentered with respect to the optical axis as a shift lens group. It is possible to correct image blur by driving a shift lens group by driving means and shifting an image on the image plane so as to correct image blur (fluctuation in image plane position) caused by lens system blur. Is possible. As described above, 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 drawings.

  FIG. 3 is a diagram illustrating the state of movement of each lens group in the refractive power distribution of the zoom lens according to each embodiment of the present invention and the change in the focal length state from the wide-angle end state W to the telephoto end state T. 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 negative meniscus lens L21 having an aspheric surface on the image surface I side and a convex surface facing the object side, a biconcave negative lens, and a convex surface on the object side This is composed of a cemented lens L22 having a negative refractive power formed by bonding with a positive meniscus lens facing the lens.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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 side, and a bonding of a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L42 having a negative refractive power made of a combination.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

  Further, 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 pickup device (not shown), and the image pickup device is composed of a CCD, a CMOS, or the like (the same applies to the following embodiments).

  The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state W to the telephoto end state T.

  Table 1 below lists values of specifications of the zoom lens according to the first example. In the table, “f” in “Overall specifications” indicates the focal length, and F.F. NO represents the F number, 2ω represents the angle of view (unit: degree), and Bf represents the back focus. 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 = 587.6 nm). 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. The “conditional expression corresponding value” indicates a value corresponding to each conditional expression.

  In addition, the focal length f, the radius of curvature r, the surface interval d, 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. The above reference numerals are the same in other embodiments, and the description thereof is omitted.

(Table 1)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 13.00 to 18.35
F.NO = 3.23 to 3.88 to 4.36
2ω = 63.45 to 31.73 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 25.0000 0.80 1.92286 18.90
2 10.1687 2.92
3 0.0000 8.00 1.83481 42.71
4 0.0000 0.20
* 5 16.5591 2.59 1.77377 47.18
6 -26.6813 (d6)
7 43.1399 1.00 1.80610 40.88
* 8 9.6052 1.42
9 -10.6311 0.70 1.78800 47.37
10 9.2523 1.54 1.92286 18.90
11 139.6780 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.9234 1.32 1.69350 53.20
14 -27.4529 0.20
15 11.7142 1.57 1.65160 58.55
16 -6.2105 0.70 1.83481 42.71
17 7.4146 (d17)
18 10.0252 1.55 1.58913 61.16
* 19 -11.6786 0.10
20 6.5080 2.28 1.48749 70.23
21 -18.1248 0.75 1.79504 28.54
22 5.7167 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.4495 + 4.2291 × 10 ^-5 -1.2508 × 10 ^-7 + 3.0136 × 10 ^-9 -4.1299 × 10 ^-11
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 1.4000 × 10 ^-3 -3.9508 × 10 ^-5 + 1.3308 × 10 ^-6 -4.6579 × 10 ^-9
[13th page]
κ C4 C6 C8 C10
+0.3527 + 1.7586 × 10 ^-5 + 1.2242 × 10 ^-5 -8.6518 × 10 ^-7 + 5.7865 × 10 ^-8
[19th page]
κ C4 C6 C8 C10
+5.6263 + 7.1091 × 10 ^-4 + 1.4030 × 10 ^-5 -1.5418 × 10 ^-7 + 2.2411 × 10 ^-8

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 13.0000 18.3500
d6 1.3806 6.0114 7.8333
d11 7.5027 2.8719 1.0500
d17 5.2220 2.5639 1.1150
d22 5.6760 8.3341 9.7830
Bf 0.5900 0.5900 0.5900

"Values for conditional expressions"
(1) nd1 = 1.92286
(2) νd1 = 18.90
(3) f4 / f3 = 0.74169
(4) ndp = 1.83481
(5) (−f2) /fw=1.13206
(6) f1 / (− f2) = 2.65137

  FIG. 5 is a diagram showing 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 = 13.00 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm).

  In each aberration diagram, FNO indicates an F number, and A indicates 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. Further, 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 said code | symbol is the same also in other Examples, and abbreviate | omits description.

  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. 6 is a diagram illustrating a lens configuration of the zoom lens according to the second embodiment of the present invention developed along the optical axis.

  In FIG. 6, 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 negative meniscus lens L21 having an aspheric surface on the image plane I side and a convex surface facing the object side, a biconcave negative lens, and a biconvex shape It is composed of a cemented lens L22 having a negative refractive power formed by bonding with a positive lens.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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 side, and a bonding of a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L42 having a negative refractive power made of a combination.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

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

  The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state W to the telephoto end state T.

  Table 2 below provides values of 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 12.42 to 18.35
F.NO = 3.29 to 3.89 to 4.40
2ω = 63.45 to 33.16 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 37.3815 0.80 1.92286 18.90
2 11.4743 2.50
3 0.0000 9.00 1.80420 46.50
4 0.0000 0.20
* 5 15.6194 2.52 1.77377 47.18
6 -26.0835 (d6)
7 33.9415 0.90 1.82080 42.71
* 8 8.3923 1.47
9 -9.3559 0.70 1.80400 46.57
10 10.5119 1.31 1.92286 18.90
11 -104.7189 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.2921 1.40 1.69350 53.20
14 -24.0200 0.15
15 12.7408 1.68 1.65160 58.55
16 -4.9883 0.70 1.83481 42.71
17 7.2495 (d17)
18 9.8677 1.86 1.58913 61.16
* 19 -11.3223 0.10
20 7.1768 2.06 1.49700 81.54
21 -21.5501 0.80 1.79504 28.54
22 5.9728 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.2861 + 2.7530 × 10 ^-5 -1.9665 × 10 ^-7 + 6.3806 × 10 ^-10 -1.9119 × 10 ^-12
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 2.0979 × 10 ^-3 -9.3712 × 10 ^-5 + 4.3205 × 10 ^-6 -6.7633 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.4009 + 7.1395 × 10 ^-5 + 1.4244 × 10 ^-5 -4.5095 × 10 ^-7 + 6.1718 × 10 ^-8
[19th page]
κ C4 C6 C8 C10
-9.0000 -4.4999 × 10 ^-4 + 3.2020 × 10 ^-5 -1.0016 × 10 ^-6 + 1.0650 × 10 ^-8

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.4200 18.3500
d6 1.3518 5.5097 7.5388
d11 7.2370 3.0791 1.0500
d17 5.2070 2.6787 1.1000
d22 5.8964 8.4247 10.0034
Bf 0.6000 0.6000 0.6000

"Values for conditional expressions"
(1) nd1 = 1.92286
(2) νd1 = 18.90
(3) f4 / f3 = 0.76620
(4) ndp = 1.80420
(5) (−f2) /fw=1.08310
(6) f1 / (− f2) = 2.52762

  FIG. 7 is a diagram of various aberrations in the infinitely focused state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the second example, and (a) is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm).

  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. 8 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. 8, 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 negative meniscus lens L21 having an aspheric surface on the image plane I side and a convex surface facing the object side, a biconcave negative lens, and a biconvex shape It is composed of a cemented lens L22 having a negative refractive power formed by bonding with a positive lens.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

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

  The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and is fixed with respect to the image plane during zooming from the wide-angle end state W to the telephoto end state T.

  Table 3 below provides values of 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 12.42 to 18.35
F.NO = 3.46 to 4.03 to 4.40
2ω = 63.45 to 33.21 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 37.2624 0.90 1.92286 18.90
2 11.1482 2.45
3 0.0000 9.00 1.83481 42.71
4 0.0000 0.20
* 5 15.1979 2.57 1.77377 47.18
6 -25.3799 (d6)
7 41.2336 0.90 1.82080 42.71
* 8 8.4256 1.50
9 -9.2831 0.70 1.78800 47.37
10 12.0522 1.30 1.92286 18.90
11 -68.6250 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.6045 1.45 1.69350 53.20
14 -34.1354 0.15
15 10.6131 1.87 1.65160 58.55
16 -5.3841 0.70 1.83481 42.71
17 7.0835 (d17)
18 10.0717 1.99 1.58913 61.16
* 19 -10.9249 0.10
20 7.5031 2.19 1.48749 70.23
21 -11.3937 0.80 1.79504 28.54
22 6.7316 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-5.8159 + 1.8991 × 10 ^-4 -2.5581 × 10 ^-6 + 2.9511 × 10 ^-8 -2.0089 × 10 ^-10
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 2.0520 × 10 ^-3 -8.7500 × 10 ^-5 + 3.6741 × 10 ^-6 -4.7536 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.4028 +8.0 510 × 10 ^-5 + 1.5444 × 10 ^-5 -9.1869 × 10 ^-7 + 7.2852 × 10 ^-8
[19th page]
κ C4 C6 C8 C10
-9.0000 -5.8178 × 10 ^-4 + 3.4645 × 10 ^-5 -1.1500 × 10 ^-6 + 1.5550 × 10 ^-8

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.4200 18.3500
d6 1.3774 5.6717 7.9738
d11 7.6464 3.3521 1.0500
d17 4.4527 2.2134 1.1000
d22 5.6029 7.8422 8.9556
Bf 0.5999 0.6000 0.6000

"Values for conditional expressions"
(1) nd1 = 1.92286
(2) νd1 = 18.90
(3) f4 / f3 = 0.79595
(4) ndp = 1.83481
(5) (−f2) /fw=1.10029
(6) f1 / (− f2) = 2.422205

  FIG. 9 is a diagram showing 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). FIG. 9A is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm).

  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. 10 is a diagram illustrating a lens configuration of the zoom lens according to the fourth example 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 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 L21 having an aspheric surface on the image plane I side, a biconcave negative lens, and a biconvex positive lens. This is composed of a cemented lens L22 having a negative refractive power made up of these two lenses.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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, which is formed by bonding together.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

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

  The aperture stop S is disposed between the second lens group G2 and the third lens group G3, and is fixed with respect to the image plane I during zooming from the wide-angle end state W to the telephoto end state T.

  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 12.42 to 18.35
F.NO = 3.46 to 4.04 to 4.41
2ω = 63.44 to 33.20 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 33.7718 0.80 1.94595 17.98
2 11.7461 2.50
3 0.0000 9.00 1.83481 42.71
4 0.0000 0.20
* 5 13.9344 2.60 1.77377 47.18
6 -27.5986 (d6)
7 -61.3807 0.90 1.82080 42.71
* 8 8.9234 1.40
9 -12.0258 0.80 1.81600 46.62
10 11.6524 1.35 1.94595 17.98
11 -97.7336 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.7058 1.50 1.68863 52.85
14 -25.9720 0.15
15 13.8124 1.90 1.65160 58.55
16 -4.5044 0.80 1.83481 42.71
17 9.1795 (d17)
18 10.2475 2.15 1.58913 61.16
* 19 -10.8582 0.10
20 6.9779 2.15 1.48749 70.23
21 -13.5284 0.80 1.79504 28.54
22 5.9758 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.5628 + 5.9482 × 10 ^-5 -5.0922 × 10 ^-7 + 3.3737 × 10 ^-9 -3.2731 × 10 ^-11
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 1.6926 × 10 ^-3 -5.7910 × 10 ^-5 + 6.6386 × 10 ^-7 + 9.8033 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.4479 + 1.1451 × 10 ^-4 + 2.1327 × 10 ^-5 -1.1862 × 10 ^-6 + 1.2675 × 10 ^-7
[19th page]
κ C4 C6 C8 C10
-9.0000 -5.6183 × 10 ^-4 + 3.8657 × 10 ^-5 -1.1222 × 10 ^-6 + 2.5253 × 10 ^-9

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.4198 18.3496
d6 1.3281 5.1577 7.2028
d11 6.9247 3.0950 1.0500
d17 4.7633 2.4074 1.2377
d22 5.7268 8.0827 9.2525
Bf 0.5998 0.5997 0.5997

"Values for conditional expressions"
(1) nd1 = 1.94595
(2) νd1 = 17.98
(3) f4 / f3 = 0.85941
(4) ndp = 1.83481
(5) (−f2) /fw=0.97891
(6) f1 / (− f2) = 2.5823

  FIG. 11 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 fourth example, and (a) is a wide-angle end state (f = 6.49 mm). (B) shows various aberrations in the intermediate focal length state (f = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm).

  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.

(5th Example)
FIG. 12 is a diagram illustrating a lens configuration of the zoom lens according to the fifth example developed along the optical axis.

  In FIG. 12, 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 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 negative meniscus lens L21 having a convex surface facing the object side and an aspheric surface on the image surface I side, a biconcave negative lens, and a convex surface facing the object side. This is composed of a cemented lens L22 having a negative refractive power formed by bonding with a positive meniscus lens facing the lens.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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, which is formed by bonding together.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

  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.

  Table 5 below provides values of specifications of the zoom lens according to the fifth example.

(Table 5)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 13.00 to 18.35
F.NO = 3.25 to 3.92 to 4.44
2ω = 63.46 to 31.68 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 30.0000 0.80 1.92286 18.90
2 10.8266 2.76
3 0.0000 10.50 1.88300 40.76
4 0.0000 0.20
* 5 17.6854 2.54 1.77377 47.18
6 -24.9579 (d6)
7 49.4226 1.00 1.80610 40.88
* 8 10.1943 1.32
9 -11.0741 0.70 1.77250 49.60
10 8.9104 1.40 1.92286 18.90
11 66.6471 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 8.0543 1.33 1.69350 53.20
14 -23.6288 0.10
15 14.5229 1.55 1.65160 58.55
16 -5.8631 0.70 1.83481 42.71
17 8.2446 (d17)
18 9.6258 2.04 1.58913 61.16
* 19 -11.5184 0.10
20 6.9573 2.15 1.48749 70.23
21 -18.4789 0.80 1.79504 28.54
22 5.7682 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.8966 + 3.3740 × 10 ^-5 -2.5195 × 10 ^-7 + 2.9256 × 10 ^-9 -2.3805 × 10 ^-11
[Eighth side]
κ C4 C6 C8 C10
-8.9802 + 1.2224 × 10 ^-3 -3.6939 × 10 ^-5 + 1.5818 × 10 ^-6 -1.8716 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.3629 + 2.1443 × 10 ^-5 + 9.5031 × 10 ^-6 -4.2244 × 10 ^-7 + 3.9902 × 10 ^-8
[19th page]
κ C4 C6 C8 C10
+5.7565 + 7.8405 × 10 ^-4 + 1.7280 × 10 ^-5 -2.5355 × 10 ^-7 + 2.9997 × 10 ^-8

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.9997 18.3499
d6 1.3662 5.9198 7.7019
d11 7.3857 2.8321 1.0500
d17 5.4454 2.6465 1.1000
d22 6.1696 8.9684 10.5150
Bf 0.5900 0.5900 0.5900

"Values for conditional expressions"
(1) nd1 = 1.92286
(2) νd1 = 18.90
(3) f4 / f3 = 0.71550
(4) ndp = 1.88300
(5) (−f2) /fw=1.14409
(6) f1 / (− f2) = 2.49132

  FIGS. 13 to 15 are graphs showing various aberrations of the zoom lens according to the fifth example in the infinite focus state with respect to the d-line (λ = 587.6 nm), and FIG. 13 shows the wide-angle end state (f = 6. 49 shows various aberrations in the intermediate focal length state (f = 13.00 mm), and FIG. 15 shows various aberrations in the telephoto end state (f = 18.35 mm).

  As is apparent from each aberration diagram, the zoom lens according to the fifth 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.

(Sixth embodiment)
FIG. 16 is a diagram illustrating a lens configuration of the zoom lens according to the sixth example developed along the optical axis.

  In FIG. 16, 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 negative meniscus lens L21 having a convex surface on the object side and an aspheric surface on the image plane I side, a biconcave negative lens, and a biconvex shape. It is composed of a cemented lens L22 having a negative refractive power formed by bonding with a positive lens.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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 side, and a bonding of a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L42 having a negative refractive power made of a combination.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

  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.

  Table 6 below provides values of specifications of the zoom lens according to the sixth example.

(Table 6)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 13.00 to 18.35
F.NO = 3.28 to 3.89 to 4.40
2ω = 63.45 to 33.20 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 24.5000 0.80 1.92286 18.90
2 9.9772 2.95
3 0.0000 8.50 1.83481 42.71
4 0.0000 0.20
* 5 16.6000 2.63 1.77377 47.18
6 -24.8401 (d6)
7 74.7674 1.00 1.82080 42.71
* 8 9.4961 1.39
9 -10.0785 0.70 1.78800 47.37
10 11.0108 1.35 1.92286 18.90
11 -140.1574 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.2743 1.39 1.69350 53.20
14 -26.2141 0.15
15 13.0403 1.59 1.65160 58.55
16 -5.7472 0.70 1.83481 42.71
17 7.0000 (d17)
18 9.8799 1.69 1.58913 61.16
* 19 -11.2538 0.10
20 6.8394 2.19 1.48749 70.23
21 -15.4997 0.80 1.79504 28.54
22 6.0883 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 0.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.5215 + 3.9133 × 10 ^-5 -1.9315 × 10 ^-7 + 3.1162 × 10 ^-9 -3.5747 × 10 ^-11
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 1.4631 × 10 ^-3 -4.9164 × 10 ^-5 + 2.1048 × 10 ^-6 -2.6229 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.3110 + 4.3394 × 10 ^-5 + 1.0663 × 10 ^-5 -4.6198 × 10 ^-7 + 4.5396 × 10 ^-8
[19th page]
κ C4 C6 C8 C10
-1.7610 + 1.0693 × 10 ^-4 + 6.5769 × 10 ^-6 -2.4528 × 10 ^-7 + 8.6823 × 10 ^-10

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.4200 18.3500
d6 1.3733 5.6158 7.7020
d11 7.3787 3.1362 1.0500
d17 5.0253 2.6114 1.1000
d22 5.9477 8.3616 9.8730
Bf 0.6000 0.6000 0.6000

"Values for conditional expressions"
(1) nd1 = 1.92286
(2) νd1 = 18.90
(3) f4 / f3 = 0.70338
(4) ndp = 1.83481
(5) (−f2) /fw=1.11448
(6) f1 / (− f2) = 2.571707

  FIGS. 17 to 19 are graphs showing various aberrations of the zoom lens according to Example 6 in the infinite focus state with respect to the d-line (λ = 587.6 nm), and FIG. 17 shows the wide-angle end state (f = 6. 49 shows various aberrations in the intermediate focal length state (f = 12.42 mm), and FIG. 19 shows various aberrations in the telephoto end state (f = 18.35 mm).

  As is apparent from each aberration diagram, the zoom lens according to the sixth 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.

(Seventh embodiment)
FIG. 20 is a diagram illustrating a lens configuration of the zoom lens according to the seventh example developed along the optical axis.

  In FIG. 20, 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 L21 having an aspheric surface on the image plane I side, a biconcave negative lens, and a biconvex positive lens. This is composed of a cemented lens L22 having a negative refractive power made up of these two lenses.

  The third lens group G3 is formed by sticking, in order from the object side along the optical axis, a biconvex positive lens L31 having an aspheric surface on the object side, and a biconvex positive lens and a biconcave negative lens. It is composed of a cemented lens L32 having a negative refractive power made of a combination.

  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, which is formed by bonding together.

  Further, the focus adjustment from the object at infinity to the object at a short distance is performed by moving the second lens group G2 to the object side along the optical axis.

  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.

  Table 7 below provides values of specifications of the zoom lens according to the seventh example.

(Table 7)
"Overall specifications"
Wide-angle end state Intermediate focal length state Telephoto end state
f = 6.49 to 12.42 to 18.35
F.NO = 3.48 to 4.07 to 4.44
2ω = 63.43 to 33.20 to 22.52

"Lens data"
Surface number Curvature radius Surface spacing Refractive index Abbe number
1 29.3816 0.85 1.94595 17.98
2 10.9980 2.45
3 0.0000 9.00 1.83481 42.71
4 0.0000 0.20
* 5 14.0983 2.60 1.77377 47.18
6 -26.4642 (d6)
7 -64.2210 0.90 1.82080 42.71
* 8 9.3699 1.40
9 -12.3854 0.80 1.81600 46.62
10 10.6993 1.35 1.94595 17.98
11 -299.4574 (d11)
12 0.0000 0.50 (Aperture stop S)
* 13 7.7797 1.45 1.68863 52.85
14 -22.4777 0.20
15 14.8768 1.90 1.64000 60.09
16 -4.8081 0.80 1.83481 42.71
17 9.2275 (d17)
18 9.8310 2.15 1.58913 61.16
* 19 -11.1803 0.10
20 7.1100 2.15 1.48749 70.23
21 -13.1759 0.80 1.79504 28.69
22 6.0262 (d22)
23 0.0000 0.65 1.54437 70.51
24 0.0000 1.40
25 0.0000 0.50 1.51633 64.14
26 0.0000 (Bf)

"Aspherical data"
[Fifth side]
κ C4 C6 C8 C10
-1.5628 + 5.9061 × 10 ^-5 -4.2880 × 10 ^-7 + 6.8266 × 10 ^-10 + 2.1560 × 10 ^-11
[Eighth side]
κ C4 C6 C8 C10
-9.0000 + 1.4768 × 10 ^-3 -4.2970 × 10 ^-5 + 3.4527 × 10 ^-7 + 8.8838 × 10 ^-8
[13th page]
κ C4 C6 C8 C10
+0.4479 + 4.1008 × 10 ^-5 + 2.5708 × 10 ^-5 -2.5079 × 10 ^-6 + 1.8686 × 10 ^-7
[19th page]
κ C4 C6 C8 C10
-9.0000 -4.8117 × 10 ^-4 + 3.5584 × 10 ^-5 -1.1993 × 10 ^-6 + 1.2638 × 10 ^-8

"Variable interval data"
Wide-angle end state Intermediate focal length state Telephoto end state
f 6.4900 12.4198 18.3496
d6 1.3281 5.1578 7.2028
d11 7.0747 3.2450 1.2000
d17 4.7632 2.4074 1.2377
d22 4.6997 7.0555 8.2252
Bf 0.5997 0.5997 0.5997

"Values for conditional expressions"
(1) nd1 = 1.94595
(2) νd1 = 17.98
(3) f4 / f3 = 0.85941
(4) ndp = 1.83481
(5) (−f2) /fw=0.97868
(6) f1 / (− f2) = 2.5823

  FIGS. 21 to 23 are graphs showing various aberrations of the zoom lens according to the seventh example in the infinite focus state with respect to the d-line (λ = 587.6 nm), and FIG. 21 is a wide angle end state (f = 6. 49 shows various aberrations in the intermediate focal length state (f = 12.42 mm), and FIG. 23 shows various aberrations in the telephoto end state (f = 18.35 mm).

  As is apparent from each aberration diagram, the zoom lens according to the seventh 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.

  As described above, according to the present invention, the zoom lens is suitable for a video camera, a digital still camera, etc. using a solid-state imaging device, and used when a place where the zoom lens is disposed is limited. Therefore, it is possible to realize a small zoom lens having excellent imaging performance.

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

  It should be noted that the four-group lens system of the present embodiment can be made into a five-group lens system by adding one lens group closest to the image plane side. In this case, as the added fifth lens group, both a lens having a positive refractive power and a lens having a negative refractive power can be adopted. The fifth lens group to be added may be fixed or movable during zooming. In the five-group lens system, at least one of the third lens group and the fifth lens group may be shifted in a direction substantially orthogonal to the optical axis as a shift lens group.

  Alternatively, a single lens group, a plurality of lens groups, or a partial lens group may be moved in the optical axis direction to be a focusing lens group that performs focusing from an object at infinity to a near object. 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). In particular, the second lens group or the fourth lens group is preferably a focusing lens group.

  In the zoom lens of this embodiment, the third lens group is a shift lens group, but another lens group or a partial group may be a shift lens group. In the zoom lens of this embodiment, since the third lens group is a fixed group during zooming, the third lens group is preferably a shift lens group, but the second lens group may be a shift lens group. The shift lens group only needs to have at least two single lenses, and preferably has one cemented lens obtained by cementing two single lenses.

  The lens surface may be an aspherical surface. The aspherical surface may be any one of an aspherical surface by grinding, a glass mold aspherical surface in which glass is formed into an aspherical shape, and 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.

  The above-described embodiment is merely an example, and is not limited to the above-described configuration and shape, and can be appropriately modified and changed within the scope of the present invention.

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 the 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 the wide-angle end state W to the 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. 7A is a diagram illustrating various aberrations of the zoom lens according to the first example in the infinite focus state with respect to 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 = 13.00 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm). 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. 9A is a diagram illustrating various aberrations of the zoom lens according to the second example in the infinite focus state with respect to 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 = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm). 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. 9A 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. (B) shows various aberrations in the intermediate focal length state (f = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm). 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. 7A is a diagram illustrating various aberrations of the zoom lens according to the fourth example in the infinite focus state 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 = 12.42 mm), and (c) shows various aberrations in the telephoto end state (f = 18.35 mm). It is a figure which expands and shows the lens structure of the zoom lens concerning 5th Example of this application along an optical axis. FIG. 11 shows various aberration diagrams in the wide-angle end state (f = 6.49 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the fifth example. FIG. 11 shows various aberration diagrams in the intermediate focal length state (f = 13.00 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the fifth example. FIG. 11 shows various aberration diagrams in the telephoto end state (f = 18.35 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the fifth example. It is a figure which expands and shows the lens structure of the zoom lens concerning 6th Example of this application along an optical axis. FIG. 11 shows various aberration diagrams in the wide-angle end state (f = 6.49 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the sixth example. FIG. 10 shows various aberration diagrams in the intermediate focal length state (f = 12.42 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the sixth example. FIG. 12 shows various aberration diagrams in the telephoto end state (f = 18.35 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the sixth example. It is a figure which expands and shows the lens structure of the zoom lens concerning 7th Example of this application along an optical axis. FIG. 11 shows various aberration diagrams in the wide-angle end state (f = 6.49 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the seventh example. FIG. 11 shows various aberration diagrams in the intermediate focal length state (f = 12.42 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the seventh example. FIG. 18 shows various aberration diagrams in the telephoto end state (f = 18.35 mm) in the infinite focus state with respect to the d-line (λ = 587.6 nm) of the zoom lens according to the seventh example.

Explanation of symbols

G1 First lens group G2 Second lens group G3 Third lens group G4 Fourth lens group P Optical path bending optical element (right angle prism)
FL filter group S Aperture stop I Image plane

Claims (22)

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 is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, An interval between the second lens group and the third lens group is reduced, and an interval between the third lens group and the fourth lens group is reduced;
The first lens group includes a negative lens;
A zoom lens satisfying the following conditions:
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative lens   The zoom lens according to claim 1, wherein the third lens group is fixed with respect to the image plane when the focal length changes from the wide-angle end state to the telephoto end state.   The zoom lens according to claim 1, wherein the third lens group includes at least one cemented lens. The zoom lens according to claim 1, wherein the negative lens satisfies the following conditional expression.
nd1> 1.94
However,
nd1: refractive index of d-line of the negative lens   The third 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 side. 5. The zoom lens according to claim 1, wherein the zoom lens includes a cemented lens having a refractive power of 1 to 4.   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 side. The zoom lens according to claim 1, wherein the zoom lens includes a cemented lens having a refractive power of 5. The zoom lens according to claim 1, wherein the following condition is satisfied.
0.5 <f4 / f3 <1.1
However,
f3: focal length of the third lens group f4: focal length of the fourth lens group   The zoom lens according to claim 1, wherein the following condition is satisfied.
0.5 <f4 / f3 <1.0
However,
f3: focal length of the third lens group
f4: focal length of the fourth lens group   The zoom lens according to claim 1, wherein the following condition is satisfied.
0.5 <f4 / f3 <0.95
However,
f3: focal length of the third lens group
f4: focal length of the fourth lens group The negative lens of the first lens group is a negative meniscus lens having a convex surface facing the object side,
The first lens group includes, in order from the object side along the optical axis, the negative meniscus lens, the optical path bending optical element, and a positive lens having a convex surface facing the object side. The zoom lens according to any one of 1 to 9 . The optical path bending optical element is a right angle prism;
The zoom lens according to any one of claims 1 to 10, characterized in that the following condition is satisfied.
ndp> 1.800
However,
ndp: refractive index of d-line of the right-angle prism The zoom lens according to any one of claims 1 to 11 , wherein the first lens group includes at least one aspherical lens. The second lens group includes, in order from the object side along the optical axis, a negative lens having a concave surface facing the image side, a negative lens having a negative refractive power and a negative lens having a concave surface facing the object side. the zoom lens according to claim 1, any one of 12, characterized in that they are composed of. Wherein at least the zoom lens according to any one of claims 1 to 13, characterized in that it comprises one aspherical lens in the second lens group. The zoom lens according to any one of claims 1 to 14, characterized in that the following condition is satisfied.
0.8 <(− f2) / fw <1.3
However,
fw: focal length of the entire zoom lens system in the wide-angle end state f2: focal length of the second lens group The zoom according to any one of claims 1 to 15 , wherein the second lens group is moved toward the object side along the optical axis to perform focus adjustment from an object at infinity to a short-distance object. lens. The zoom lens according to any one of claims 1 to 16, characterized in that the following condition is satisfied.
1.5 <f1 / (− f2) <4.0
However,
f1: Focal length of the first lens group f2: Focal length of the second lens group Wherein at least the zoom lens according to any one of claims 1 to 17, characterized in that it comprises one aspherical lens in the third lens group. The zoom lens according to any one of claims 1 to 18 , wherein the fourth lens group includes at least one aspherical lens. An optical apparatus comprising the zoom lens according to any one of claims 1 to 19 . 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 first lens group includes a negative lens, and the negative lens satisfies the following conditions:
When the focal length changes from the wide-angle end state to the telephoto end state, the first lens group is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, The second lens group and the fourth lens group are light so that 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 zoom lens zooming method characterized by moving along an axis.
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative 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 is fixed with respect to the image plane, the distance between the first lens group and the second lens group increases, An interval between the second lens group and the third lens group is reduced, and an interval between the third lens group and the fourth lens group is reduced;
The first lens group includes a negative lens, and the negative lens satisfies the following conditions:
A focus adjustment method for a zoom lens, wherein the second lens group is moved to the object side along the optical axis to perform focus adjustment from an object at infinity to a near object.
nd1> 1.900
νd1 <20.50
However,
nd1: refractive index of d-line of the negative lens νd1: Abbe number of d-line of the negative lens

Images