JP5531207B2 - Zoom lens - Google Patents

Description

  The present invention relates to a zoom lens that forms a subject image on an image sensor such as a CCD sensor or a CMOS sensor.

  In recent years, not only digital still cameras but also small devices such as mobile phones, personal digital assistants, internet cameras, etc., mounting of zoom lenses has begun to be considered as a new added value, and actually mounted devices have also appeared. I'm starting. The zoom lens is an optical system in which a part of lenses and a lens group constituting the lens system move along the optical axis, and can continuously change the photographing magnification. By mounting the zoom lens, the user can enlarge or reduce the subject image to an arbitrary size at the time of shooting.

  When it is assumed that the zoom lens is mounted on a small device, it is desirable that the total length of the zoom lens is as short as possible. However, in a zoom lens, at the time of zooming and focusing, it is necessary to move at least two lens groups among the lens groups constituting the zoom lens, so that a space for moving these lens groups is provided in the zoom lens. Must be secured. This is an obstacle to downsizing the zoom lens.

On the other hand, the number of pixels of an image sensor that captures an object image as an electrical signal is increasing year by year, and zoom lenses are also required to have high performance such as good aberration correction capability and high resolution. In Patent Document 1, a first lens group composed of one lens having negative refractive power, a second lens group composed of two positive and negative lenses and having negative refractive power as a whole, and positive lenses are disclosed. There is described a zoom lens composed of a third lens group having a refractive power of 4 and a fourth lens group having a positive refractive power. This zoom lens can be reduced in size relatively well while keeping the combined focal length at the wide-angle end of the first lens group and the second lens group within a certain range while having a high variable magnification of about 3 times. It is illustrated.
JP 2001-343588 A

  However, although the zoom lens described in Patent Document 1 corrects aberrations relatively well with a small number of lenses, it does not sufficiently satisfy the demands for high performance and miniaturization.

  Note that such demands for high performance and miniaturization are not limited to small devices such as mobile phones. In devices such as digital still cameras, image scaling, in particular optical scaling with little image degradation, is desired. On the other hand, a reduction in thickness for improving portability is also strongly desired.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a high-performance and compact zoom lens that satisfies high image quality.

  In order to solve the above problems, in the present invention, in order from the object side to the image plane side, a first lens group having a negative 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 first lens group includes a lens having a positive refractive power with a positive radius of curvature of the object side surface, and an image. A lens having a negative refracting power in which the radius of curvature of the surface side surface is positive, and an optical path changing member that is disposed closer to the image surface side than these lenses and changes the traveling direction of the incident light. The two lens group includes a lens having a positive refractive power with a positive curvature radius of the object side surface and a lens with a negative refractive power with a negative curvature radius of the object side surface. The lens group includes a lens having a positive refractive power and a lens group having a negative refractive power as a whole. Form was.

  In the zoom lens according to the present invention, in zooming from the wide-angle end to the telephoto end, the first lens group and the fourth lens group are fixed, and the second lens group is moved to the image plane side before the object. The third lens unit is moved to the object side in a straight line.

  According to the above configuration, the lens groups that are moved during zooming and focusing are only two lens groups, the second lens group and the third lens group. Of these, the second lens group is composed of two positive and negative lenses. For this reason, the lateral chromatic aberration and distortion generated in the first lens group are corrected well by the two positive and negative lenses in the second lens group. In addition, in zooming from the wide-angle end to the telephoto end, the second lens group temporarily moves to the image plane side and then moves to the object side. Therefore, the movement locus becomes concave on the object side. According to the zoom lens of the present invention, the space to be secured for moving the lens group can be minimized as compared with the zoom lens of the type in which the second lens group is moved linearly or parabolically. It becomes possible.

  Further, in the zoom lens according to the present invention, a lens having a positive refractive power that makes the curvature radius of the object-side surface positive, and a curvature radius of the surface on the image plane side are more positive on the object side than the optical path changing member. Since two positive and negative lenses having a negative refractive power are arranged, the chromatic aberration of magnification and distortion (especially distortion occurring at the wide angle end) are caused by the two positive and negative lenses constituting the first lens group. Will be corrected better. Therefore, by adopting such a configuration as a zoom lens, both high performance and small size can be achieved.

  In the zoom lens having the above configuration, the optical path changing member may be a prism that reflects incident light and bends the optical path. By applying the prism, a bent (L type) zoom lens can be configured. In particular, a small portable device such as a mobile phone has a very limited space in which a zoom lens can be mounted. According to the present invention, the thickness of a device on which a zoom lens is mounted can be greatly reduced.

  In the zoom lens having the above-described configuration, the first lens unit is configured such that one cemented lens is disposed closer to the object side than the optical path changing member, and this cemented lens has an image with a positive radius of curvature on the object side surface. It is desirable that the lens has a negative radius of curvature of the surface side surface and a lens having a negative radius of curvature of the object side surface and a positive radius of curvature of the image side surface.

  Alternatively, as the configuration of the first lens group, two lenses having both the radius of curvature of the object-side surface and the radius of curvature of the image-side surface are arranged closer to the object side than the optical path changing member. You may do it.

  Furthermore, as a configuration of the first lens group, a first lens having a negative refractive power, a second lens having a positive refractive power, and an optical path changing member are arranged in order from the object side to the image plane side. It is desirable to configure. As described above, by arranging the first lens having negative refractive power at the position closest to the object side, the photographing field angle of the zoom lens can be increased. In particular, in recent years, not only single focus lenses but also zoom lenses have been strongly demanded to widen the shooting angle of view. Such widening of the angle improves the added value of the zoom lens and also increases the performance of the zoom lens.

In the zoom lens having the above configuration, when the focal length of the lens having positive refractive power in the first lens group is f1p and the focal length of the lens having negative refractive power in the first lens group is f1n, the following conditions are satisfied. It is desirable to satisfy Formula (1).
| F1n / f1p | <0.8 (1)

  Conditional expression (1) is a condition for suppressing chromatic aberration and distortion within a favorable range over the entire zooming range. Outside the range defined by conditional expression (1), the refractive power of a lens having positive refractive power in the first lens group becomes relatively strong, so that distortion at the wide-angle end can be corrected well. Although it can be done, the axial chromatic aberration has a short wavelength with respect to the reference wavelength in the negative direction (object side), and is insufficiently corrected. On the other hand, off-axis lateral chromatic aberration is overcorrected because the short wavelength is in the positive direction with respect to the reference wavelength. As a result, it becomes difficult to obtain good imaging performance.

In the zoom lens configured as described above, it is desirable that the following conditional expression (2) is satisfied, where f1 is the focal length of the first lens group and f2 is the focal length of the second lens group.
0.2 <f2 / f1 <1.0 (2)

  Conditional expression (2) is a condition for suppressing various aberrations within a favorable range over the entire zooming range while reducing the size of the zoom lens. When the upper limit “1.0” is exceeded, the refractive power of the second lens group becomes relatively weak, and the amount of movement of the second lens group during zooming or focusing increases. For this reason, the fluctuation amount of various aberrations becomes large, and it becomes difficult to suppress various aberrations within a favorable range over the entire zooming range. On the other hand, when the value falls below the lower limit “0.2”, the refractive power of the second lens group becomes relatively strong. Therefore, in order to secure the angle of view at the wide-angle end, the diameter of the lens constituting the first lens group. Therefore, it is difficult to reduce the size of the zoom lens.

In the zoom lens configured as described above, it is preferable that the following conditional expression (3) is satisfied, where f1 is the focal length of the first lens group and f3 is the focal length of the third lens group.
0.05 <| f3 / f1 | <0.5 (3)

  Conditional expression (3) is a condition for prescribing the movement mode of the second lens unit and maintaining off-axis imaging performance at a constant level in the entire zooming range. By satisfying the conditional expression (3), the position on the optical axis of the second lens group at the wide angle end and the position on the optical axis of the second lens group at the telephoto end substantially coincide with each other in zooming. That is, by satisfying this conditional expression (3), the distance between the first lens group and the second lens group becomes a substantially constant value at the wide-angle end and the telephoto end, and the zoom lens can be suitably downsized.

  Here, if the upper limit “0.5” in conditional expression (3) is exceeded, the refractive power of the first lens group becomes relatively strong, so that the second lens group moves greatly toward the object side at the telephoto end. This makes it difficult to reduce the size of the zoom lens. In addition, it is difficult to suppress on-axis chromatic aberration, off-axis magnification chromatic aberration, and off-axis coma aberration within a favorable range. On the other hand, below the lower limit “0.05”, the refractive power of the first lens group becomes relatively weak, the diameter of the lens constituting the first lens group becomes large, and the second lens group at the telephoto end becomes In this case, it is difficult to reduce the size of the zoom lens because it moves greatly to the image plane side.

In the zoom lens configured as described above, when the combined focal length at the wide angle end of the first lens group, the second lens group, the third lens group, and the fourth lens group is fw, and the focal length of the third lens group is f3. It is desirable that the following conditional expression (4) is satisfied.
1.0 <f3 / fw <2.0
(4)

  Conditional expression (4) is a condition for defining the size of the entire zoom lens and the refractive power of each lens group. When the upper limit “2.0” is exceeded, the refractive power of the third lens group becomes weak and effective in correcting each aberration, but it is difficult to reduce the size and weight of the zoom lens. On the other hand, when the value is below the lower limit “1.0”, the refractive power of the third lens unit that moves during zooming becomes strong, which is advantageous for downsizing of the zoom lens. It is difficult to keep the balance of curvature of field and curvature of field within a certain range. In addition, since the radius of curvature of the lenses constituting each lens group becomes a small value, the processability of the lenses deteriorates, and the cost of the zoom lens increases.

In the zoom lens having the above configuration, when the focal length of the lens having positive refractive power in the third lens group is f3p and the combined focal length of the lens group having negative refractive power in the third lens group is f3n, It is desirable to satisfy the conditional expression (5).
0.1 <| f3p / f3n | <1.0 (5)

  Conditional expression (5) is a condition for further reducing the size of the zoom lens and keeping the balance of various aberrations such as spherical aberration and coma aberration within a certain range over the entire zooming range. When the upper limit “1.0” is exceeded, the refractive power of the lens group having negative refractive power in the third lens group becomes relatively strong, so that axial chromatic aberration is overcorrected, and the wide-angle end and It becomes difficult to keep the balance between spherical aberration and coma at the telephoto end within a certain range. In addition, since the radius of curvature of the lenses constituting the third lens group becomes a small value, the processability of the lenses deteriorates, leading to an increase in the cost of the zoom lens. On the other hand, when the value is below the lower limit “0.1”, the refractive power of a lens having a positive refractive power in the third lens group becomes relatively strong, so that it is difficult to reduce the size of the zoom lens.

In the zoom lens having the above configuration, when the Abbe number of the lens having positive refractive power in the first lens group is νd1p and the Abbe number of the lens having negative refractive power in the first lens group is νd1n, the following conditions are satisfied. It is desirable to satisfy Formula (6).
| Νd1n−νd1p | <30 (6)

  Conditional expression (6) is a condition for suppressing on-axis chromatic aberration and off-axis lateral chromatic aberration within a favorable range in a well-balanced manner over the entire zooming range. Outside the range defined by conditional expression (6), axial chromatic aberration is undercorrected, and off-axis lateral chromatic aberration is overcorrected, making it difficult to obtain good imaging performance.

  According to the zoom lens of the present invention, it is possible to provide a high-performance and compact zoom lens that satisfies high image quality.

1 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 1 according to a first embodiment that embodies the present invention. FIG. 6 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Example 1 of the same numerical value. FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position of the zoom lens according to Numerical Example 1; FIG. 3 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 1; FIG. 6 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Example 1 of the same numerical value. FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 2. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 2; FIG. 6 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 2; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 2; FIG. 10 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 3 according to a second embodiment that embodies the present invention. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 3; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 3; FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 4. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 4; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 4; FIG. 6 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 5. FIG. 12 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing lateral aberration at an intermediate position in the zoom lens according to Numerical Example 5; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 5; FIG. 12 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 5; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 5; 10 is a cross-sectional view of each lens at a wide-angle end, an intermediate position, and a telephoto end of a zoom lens according to Numerical Example 6. FIG. FIG. 10 is an aberration diagram showing lateral aberration at the wide-angle end of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the wide-angle end of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing lateral aberration at the intermediate position of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing spherical aberration, astigmatism, and distortion at an intermediate position of the zoom lens according to Numerical Example 6; FIG. 10 is an aberration diagram showing lateral aberration at the telephoto end of the zoom lens according to Numerical Example 6; FIG. 11 is an aberration diagram showing spherical aberration, astigmatism, and distortion at the telephoto end of the zoom lens according to Numerical Example 6;

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 and FIG. 8 show lens cross-sectional views of zoom lenses corresponding to Numerical Examples 1 and 2 of the present embodiment. Each drawing also shows a lens cross-sectional view at the wide-angle end, a lens cross-sectional view at an intermediate position between the wide-angle end and the telephoto end, and a lens cross-sectional view at the telephoto end. Since any of the numerical examples has the same basic lens configuration, the lens configuration of the present embodiment will be described with reference to the lens cross-sectional view of Numerical Example 1.

  The zoom lens according to the present embodiment has a four-group configuration. As shown in FIG. 1, in order from the object side to the image surface side, the first lens group G1 having negative refractive power and the negative refractive power. A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are arranged. A filter 10 is disposed between the fourth lens group G4 and the image plane IM of the image sensor. This filter 10 can be omitted.

  In the zoom lens according to the present embodiment, the first lens group G1 and the fourth lens group G4 are fixed, and the second lens group G2 and the third lens group G3 are configured to be movable along the optical axis X. The In this configuration, when zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the object side after moving to the image plane side, and the third lens group G3 moves to the object side along the optical axis X. Will be moved to. That is, the second lens group G2 moves along the optical axis X so that its movement locus is concave toward the object side, and the third lens group G3 has its movement locus in a direction approaching the second lens group G2. It moves along the optical axis X so as to be linear.

  Thus, in the zoom lens according to the present embodiment, zooming is performed by the movement of the third lens group G3, and focusing and back focus are adjusted by the movement of the second lens group G2. The image point is kept constant over the entire area.

  In the zoom lens configured as described above, the first lens group G1 includes, in order from the object side, the first lens L1 having a positive refractive power, the second lens L2 having a negative refractive power, and the incident light to reflect the optical path. It is comprised from the prism P (optical path changing member) bent at right angles. The first lens L1 is formed in a shape in which the radius of curvature of the object side surface is positive and the radius of curvature of the image side surface is negative, that is, a shape that becomes a biconvex lens in the vicinity of the optical axis X. The second lens L2 is formed in a shape in which the radius of curvature of the object side surface is negative and the radius of curvature of the image side surface is positive, that is, a shape that becomes a biconcave lens in the vicinity of the optical axis X. In the first lens L1 and the second lens L2, the image side surface of the first lens L1 and the object side surface of the second lens L2 are cemented to form one cemented lens.

  Note that the configuration of the one cemented lens constituting the first lens group G1 is not limited to the configuration shown in the present embodiment. A first lens L1 having a negative refractive power and a second lens L2 having a positive refractive power are arranged in order from the object side, and the first lens L1 and the second lens L2 are joined to form a single piece. A lens may be configured. Further, the shape of each of the first lens L1 and the second lens L2 is not limited to the shape in the present embodiment. A meniscus lens in which the first lens L1 and the second lens L2 are shaped so that both the radius of curvature of the object-side surface and the radius of curvature of the image-side surface are positive, that is, a convex surface facing the object side in the vicinity of the optical axis X. The first lens L1 and the second lens L2 may be cemented to form a single cemented lens.

  In the present embodiment, the prism P is applied as the optical path changing member. In this way, by applying the prism P as the optical path changing member, a bent (L type) zoom lens can be configured. In particular, in a small portable device such as a mobile phone, a space in which a zoom lens can be mounted is very limited, and there is often no design margin in the thickness direction of the device. If the present invention is embodied as a bent zoom lens, the thickness of the device can be greatly reduced, which contributes to the reduction in size and thickness of the portable device.

  The optical path changing member is not limited to the prism P of the present embodiment. For example, a flat mirror may be disposed behind the second lens L2, and the optical path may be bent at a right angle by reflecting incident light from the second lens L2 by this mirror (optical path changing member). Further, when it is relatively easy to secure a space for mounting the zoom lens, a lens may be applied as the optical path changing member. By applying a lens as the optical path changing member, various aberrations can be corrected more satisfactorily. In short, various optical path changing members can be applied as long as they are optical members, and any one of prisms, mirrors, and lenses, or a combination thereof can be applied as appropriate. For convenience, in each lens cross-sectional view of FIGS. 1 and 8, the prism P is represented as a parallel plane plate equivalent to its optical path length.

  The second lens group G2 includes, in order from the object side, a third lens L3 having a positive refractive power and a fourth lens L4 having a negative refractive power. The third lens L3 is formed in a shape in which the curvature radius of the object side surface is positive and the curvature radius of the image side surface is negative, that is, a shape that becomes a biconvex lens in the vicinity of the optical axis X. The shape of the third lens L3 is not limited to a shape that becomes a biconvex lens in the vicinity of the optical axis X, and may be any shape as long as the radius of curvature of the object side surface is positive. The shape of the third lens L3 is a shape in which the curvature radius of the object side surface and the curvature radius of the image side surface are both positive, that is, a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X. Shape may be sufficient.

  The fourth lens L4 is formed in a shape in which the radius of curvature of the object side surface is negative and the radius of curvature of the image side surface is positive, that is, a shape that becomes a biconcave lens in the vicinity of the optical axis X. Note that the shape of the fourth lens L4 is not limited to a shape that becomes a biconcave lens in the vicinity of the optical axis X, and may be any shape as long as the radius of curvature of the object side surface is negative. The shape of the fourth lens L4 is a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are negative, that is, a meniscus lens having a concave surface facing the object side in the vicinity of the optical axis X. Shape may be sufficient.

  Further, the arrangement of the third lens L3 and the fourth lens L4 in the second lens group G2 is not limited to the arrangement shown in the present embodiment. In addition, the arrangement of the third lens L3 and the fourth lens L4 is changed along the optical axis X, and the fourth lens L4 is disposed on the object side and the third lens L3 is disposed on the image plane side in the second lens group G2. Each may be arranged. In short, the second lens group G2 only needs to have a configuration in which the combined refractive power of two positive and negative lenses is negative.

  The third lens group G3 includes, in order from the object side, a stop ST, a fifth lens L5 having a positive refractive power, and a sixth lens L6 having a negative refractive power. Among these, the 5th lens L5 is formed in the shape used as the biconvex lens in the vicinity of the optical axis X. FIG. The sixth lens L6 is formed in a shape that becomes a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X.

  The third lens group G3 may be configured by arranging, in order from the object side, the aperture stop ST, a lens having a positive refractive power, and a lens group having a negative refractive power as a whole. . For example, the sixth lens L6 may be composed of two lenses, and the combined refractive power of these two lenses may be negative. As a combination of lenses constituting the lens group, a combination of a lens having a positive refractive power and a lens having a negative refractive power or a combination of two lenses having a negative refractive power can be considered. The number of lenses constituting the lens group depends on the miniaturization of the zoom lens.

  The fourth lens group G4 includes a seventh lens L7 having positive refractive power. The seventh lens L7 is formed into a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are negative, that is, a meniscus lens having a concave surface facing the object side in the vicinity of the optical axis X. Is done.

In the present embodiment, the lens surface of each lens is formed in an aspherical shape as necessary. The aspherical shape adopted for these lens surfaces is that the axis in the optical axis direction is Z, the height in the direction orthogonal to the optical axis X is H, the conic coefficient is k, the aspheric coefficient is A ₄ , A ₆ , A ₈ , When A ₁₀ , A ₁₂ , A ₁₄ , and A ₁₆ are used, they are expressed by the following formulas (the same applies to the second embodiment described later).

In the zoom lens according to the present embodiment, the focal length of the first lens group G1 is f1, the focal length of the second lens group G2 is f2, the focal length of the third lens group G3 is f3, and the first lens group G1. The combined focal length at the wide-angle end of the fourth lens group G4 is fw, the focal length of the first lens L1 is f1p, the focal length of the second lens L2 is f1n, the focal length of the fifth lens L5 is f3p, and the sixth lens L6 Where f3n is the focal length, νd1p is the Abbe number of the first lens L1, and νd1n is the Abbe number of the second lens L2, the following conditional expressions (1) to (6) are satisfied.
| F1n / f1p | <0.8 (1)
0.2 <f2 / f1 <1.0 (2)
0.05 <| f3 / f1 | <0.5 (3)
1.0 <f3 / fw <2.0 (4)
0.1 <| f3p / f3n | <1.0 (5)
| Νd1n−νd1p | <30 (6)

The zoom lens according to the present embodiment further satisfies the following conditional expression (6A) in order to correct chromatic aberration better.
| Νd1n−νd1p | <15 (6A)

  In addition, it is not necessary to satisfy all of the conditional expressions (1) to (6A). By satisfying each of the conditional expressions (1) to (6A) independently, an effect corresponding to each conditional expression is obtained. Therefore, it is possible to construct a small zoom lens with high image quality and high performance as compared with a conventional zoom lens.

  Next, numerical examples of the zoom lens according to the present embodiment will be described. In each numerical example, the back focus BF indicates the distance from the image plane side surface of the seventh lens L7 to the paraxial image plane in terms of the air conversion length, and the total lens length L is the length of the first lens L1. The value of the back focus BF is added to the distance from the object side surface to the image plane side surface of the seventh lens L7 (the same applies to the second embodiment described later).

  In addition, i indicates a surface number counted from the object side, R indicates a radius of curvature, d indicates a distance (surface interval) between lens surfaces along the optical axis X, Nd indicates a refractive index with respect to the d line, νd indicates the Abbe number with respect to the d line. An aspheric surface is indicated by adding a symbol of * (asterisk) after the surface number i (the same applies to the second embodiment described later).

Numerical example 1
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 45.478 1.8000 1.74330 49.2 (= νd1p)
2 -55.520 0.8000 1.69680 55.4 (= νd1n)
3 13.137 1.5000
4 ∞ 7.5000 1.71300 53.9
5 ∞ variable
6 * 18.503 1.1500 1.58500 29.0
7 * -27.875 0.4600
8 -5.468 0.5800 1.48749 70.4
9 14.153 Variable
10 (Aperture) ∞ 0.1300
11 * 2.989 1.8400 1.49700 81.6
12 -11.138 0.0600
13 * 6.568 0.6000 1.61420 26.0
14 * 3.250 variable
15 * -15.306 0.8000 1.58500 29.0
16 * -11.984 0.3700
17 ∞ 0.3680 1.51633 64.1
18 ∞ 5.1642
(Image plane IM) ∞

Various data Zoom ratio 2.800
Wide-angle end Medium Telephoto end focal length f 4.749 8.782 13.295
F number 2.884 3.954 5.102
Half angle of view ω (°) 30.07 17.39 11.69
Image height 2.750 2.750 2.750
Total length L 35.137 35.137 35.137
Back focus BF 5.777 5.777 5.777

d5 1.100 2.960 1.096
d9 8.740 3.133 1.395
d14 2.300 6.047 9.649

f1p = 33.891
f1n = -15.173
f3p = 4.956
f3n = -11.248
f1 = −28.944
f2 = -15.124
f3 = 6.835
fw = 4.749

Aspherical data first surface k = 2.052143E + 01, A ₄ = 1.015143E-04, A ₆ = -8.811005E-07, A ₈ = 5.565668E-09,
A ₁₀ = 1.531546E-11
6th surface k = -2.969296E + 01, A ₄ = -1.196055E-03, A ₆ = -1.145242E-04, A ₈ = -4.614369E-07,
A ₁₀ = 9.151571E-07, A ₁₂ = 6.500939E-08, A ₁₄ = -4.931845E-09
7th surface k = 8.591779E + 01, A ₄ = -2.298692E-03, A ₆ = -8.216639E-05, A ₈ = 7.023846E-06,
A ₁₀ = 1.487953E-06
11th surface k = -7.684345E-01, A ₄ = 1.644499E-03, A ₆ = -1.122990E-05
13th surface k = -2.465631, A ₄ = -1.769724E-04, A ₆ = -1.065986E-06, A ₈ = -3.277189E-06,
A ₁₀ = -4.556242E-06
14th surface k = 8.896107E-01, A ₄ = 2.327823E-03, A ₆ = 4.309453E-04, A ₈ = -4.552548E-05,
A ₁₀ = 5.360653E-06, A ₁₂ = 8.138525E-06, A ₁₄ = 9.316258E-07, A ₁₆ = -1.176982E-06
15th surface k = -1.942805E + 02, A ₄ = -1.715586E-03, A ₆ = 4.349233E-04
16th surface k = -9.732677E + 01, A ₄ = -2.453875E-03, A ₆ = 4.255372E-04

The value of each conditional expression is shown below.
| F1n / f1p | = 0.448
f2 / f1 = 0.523
| F3 / f1 | = 0.236
f3 / fw = 1.439
| F3p / f3n | = 0.441
| Νd1n−νd1p | = 6.2
Thus, the zoom lens of Numerical Example 1 satisfies the conditional expressions (1) to (6A).

  2, 4, and 6 show the lateral aberration corresponding to the half angle of view ω in the tangential direction and the sagittal direction for the zoom lens of Numerical Example 1 (FIGS. 9, 11, and 11). 13, 16, 18, 20, 23, 25, 27, 30, 32, 34, 34, 37, 39, and 41). 2 shows lateral aberrations at the wide-angle end (W) (the same applies to FIGS. 9, 16, 23, 30, and 37), and FIG. 4 shows lateral aberrations at the intermediate position (N) (FIGS. 11 and 11). 18, FIG. 25, FIG. 32, and FIG. 39) and FIG. 6 show lateral aberrations at the telephoto end (T) (the same applies to FIGS. 13, 20, 27, 34, and 41). .

  3, 5, and 7 show the spherical aberration SA (mm), astigmatism AS (mm), and distortion aberration DIST (%), respectively, for the zoom lens of Numerical Example 1. FIG. (The same applies to FIGS. 10, 12, 14, 17, 19, 21, 24, 26, 28, 31, 31, 33, 35, 38, 40, and 42). Of these, FIG. 3 shows aberrations at the wide-angle end (W) (same in FIGS. 10, 17, 24, 31, and 38), and FIG. 5 shows aberrations at the intermediate position (N) (FIGS. 19, FIG. 26, FIG. 33, and FIG. 40) and FIG. 7 show each aberration at the telephoto end (T) (the same applies to FIGS. 14, 21, 28, 35, and 42). . In these aberration diagrams, the spherical aberration diagram shows the amount of aberration for each wavelength of 587.56 nm, 435.84 nm, 656.27 nm, 486.13 nm, and 546.07 nm as well as the sine condition violation amount OSC. In the aberration diagram, an aberration amount on the sagittal image surface S and an aberration amount on the tangential image surface T are shown. Thus, according to the zoom lens according to Numerical Example 1, various aberrations are favorably corrected. 2 to 7, 9 to 14, 16 to 21, 23 to 28, 30 to 35, and 37 to 42, the object distance is infinity (∞). ) Shows the aberrations in FIG.

Numerical example 2
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 * 70.280 1.8000 1.61800 63.4 (= νd1p)
2 -54.867 0.8000 1.51823 58.9 (= νd1n)
3 12.045 1.7000
4 ∞ 7.5000 1.71300 53.9
5 ∞ variable
6 * 17.861 1.1500 1.58500 29.0
7 * -27.662 0.4600
8 -5.367 0.5800 1.48749 70.4
9 13.458 Variable
10 (Aperture) ∞ 0.1300
11 * 2.989 1.8400 1.49700 81.6
12 -11.293 0.0600
13 * 6.530 0.6000 1.61420 26.0
14 * 3.251 Variable
15 * -15.302 0.8000 1.58500 29.0
16 * -12.077 0.3700
17 ∞ 0.3680 1.51633 64.1
18 ∞ 5.1818
(Image plane IM) ∞

Various data Zoom ratio 2.798
Wide-angle end Medium Telephoto end focal length f 4.800 8.915 13.429
F number 2.895 3.976 5.120
Half angle of view ω (°) 29.81 17.14 11.57
Image height 2.750 2.750 2.750
Total length L 35.354 35.354 35.354
Back focus BF 5.794 5.794 5.794

d5 1.100 2.960 1.096
d9 8.740 3.133 1.395
d14 2.300 6.047 9.649

f1p = 50.133
f1n = −18.981
f3p = 4.968
f3n = -11.330
f1 = −31.477
f2 = -14.710
f3 = 6.837
fw = 4.800

Aspherical data first surface k = 2.714798E + 01, A ₄ = 1.248390E-04, A ₆ = -7.767869E-07, A ₈ = 4.496668E-09,
A ₁₀ = 4.070339E-11
6th surface k = -2.661163E + 01, A ₄ = -1.129382E-03, A ₆ = -1.096657E-04, A ₈ = -6.526982E-07,
A ₁₀ = 8.896087E-07, A ₁₂ = 6.390252E-08, A ₁₄ = -4.842119E-09
7th surface k = 8.633918E + 01, A ₄ = -2.319369E-03, A ₆ = -8.553969E-05, A ₈ = 7.114406E-06,
A ₁₀ = 1.484657E-06
11th surface k = -7.647182E-01, A ₄ = 1.669716E-03, A ₆ = -1.685006E-05
13th surface k = -2.390824, A ₄ = -1.466771E-04, A ₆ = 7.441145E-06, A ₈ = -3.835669E-06,
A ₁₀ = -4.478852E-06
14th surface k = 8.981109E-01, A ₄ = 2.403249E-03, A ₆ = 4.322386E-04, A ₈ = -3.835845E-05,
A ₁₀ = 8.110285E-06, A ₁₂ = 8.081794E-06, A ₁₄ = 5.119148E-07, A ₁₆ = -1.305499E-06
15th surface k = -1.939775E + 02, A ₄ = -1.544973E-03, A ₆ = 4.456419E-04
16th surface k = -9.744186E + 01, A ₄ = -2.345827E-03, A ₆ = 4.366303E-04

The value of each conditional expression is shown below.
| F1n / f1p | = 0.379
f2 / f1 = 0.467
| F3 / f1 | = 0.217
f3 / fw = 1.424
| F3p / f3n | = 0.438
| Νd1n−νd1p | = 4.5
Thus, the zoom lens according to Numerical Example 2 satisfies the conditional expressions (1) to (6A).

  9, 11, and 13 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 2, and FIGS. 10, 12, and 14 show the spherical aberration SA (mm ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As can be seen from these figures, the zoom lens according to Numerical Example 2 also corrects the image plane well and corrects various aberrations well.

(Second Embodiment)
Next, a second embodiment of the present invention will be described in detail with reference to the drawings.

  15, FIG. 22, FIG. 29, and FIG. 36 show lens cross-sectional views of zoom lenses corresponding to Numerical Examples 3 to 6 of the present embodiment. Each drawing also shows a lens cross-sectional view at the wide-angle end, a lens cross-sectional view at an intermediate position between the wide-angle end and the telephoto end, and a lens cross-sectional view at the telephoto end. Since any of the numerical examples has the same basic lens configuration, the lens configuration of the present embodiment will be described with reference to a lens cross-sectional view of Numerical Example 3.

  The zoom lens according to the present embodiment also has a four-group configuration. As shown in FIG. 15, the first lens group G1 having negative refractive power and the negative refractive power in order from the object side to the image plane side. A second lens group G2 having a positive refractive power, a third lens group G3 having a positive refractive power, and a fourth lens group G4 having a positive refractive power are arranged. A filter 10 is disposed between the fourth lens group G4 and the image plane IM of the image sensor. This filter 10 can be omitted.

  Similarly to the zoom lens according to the first embodiment, the zoom lens according to the present embodiment also has the first lens group G1 and the fourth lens group G4 fixed, and the second lens group G2 and the third lens. The group G3 is configured to be movable along the optical axis X. In this configuration, when zooming from the wide-angle end to the telephoto end, the second lens group G2 moves to the object side after moving to the image plane side, and the third lens group G3 moves to the object side along the optical axis X. Will be moved to. Therefore, the second lens group G2 moves along the optical axis X so that its movement locus is concave toward the object side, and the third lens group G3 has its movement locus in a direction approaching the second lens group G2. It moves along the optical axis X so as to be linear.

  As described above, the zoom lens according to the present embodiment is also zoomed by the movement of the third lens group G3 as well as being focused and moved by the movement of the second lens group G2, as in the first embodiment. The back focus is adjusted, and the image point is kept constant over the entire zoom range.

  In the zoom lens configured as described above, the first lens group G1 includes, in order from the object side, a first lens L1 having a negative refractive power, a second lens L2 having a positive refractive power, and incident light to reflect an optical path. It is comprised from the prism P (optical path changing member) bent at right angles. The first lens L1 and the second lens L2 are meniscus lenses having a shape in which the curvature radius of the object side surface and the curvature radius of the image side surface are both positive, that is, a convex surface facing the object side in the vicinity of the optical axis X. It is formed in the shape to become. With these shapes of the first lens L1 and the second lens L2, the zoom lens can be reduced in size.

  The shapes of the first lens L1 and the second lens L2 are not limited to the shapes shown in the present embodiment. The first lens L1 is formed in a shape in which the radius of curvature of the object side surface is positive and the curvature radius of the image side surface is negative, that is, a shape that becomes a biconvex lens in the vicinity of the optical axis X, The lens L2 may be formed in a shape in which the radius of curvature of the object side surface is negative and the radius of curvature of the image side surface is positive, that is, a shape that becomes a biconcave lens in the vicinity of the optical axis X.

In the present embodiment, the optical path changing member is not limited to the prism P as in the zoom lens according to the first embodiment. Various optical path changing members can be applied as long as they are optical members, and any of prisms, mirrors, and lenses, or a combination thereof can be applied as appropriate. For convenience, in each of the lens cross-sectional views of FIGS. 15, 22, 29, and 36, the prism P is represented as a parallel plane plate equivalent to the optical path length.

  The second lens group G2 includes, in order from the object side, a third lens L3 having a positive refractive power and a fourth lens L4 having a negative refractive power. The third lens L3 is formed in a shape in which the curvature radius of the object side surface is positive and the curvature radius of the image side surface is negative, that is, a shape that becomes a biconvex lens in the vicinity of the optical axis X. The shape of the third lens L3 is not limited to a shape that becomes a biconvex lens in the vicinity of the optical axis X, and may be any shape as long as the radius of curvature of the object side surface is positive. The shape of the third lens L3 may be a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X.

  The fourth lens L4 is formed in a shape in which the radius of curvature of the object side surface is negative and the radius of curvature of the image side surface is positive, that is, a shape that becomes a biconcave lens in the vicinity of the optical axis X. Note that the shape of the fourth lens L4 is not limited to a shape that becomes a biconcave lens in the vicinity of the optical axis X, and may be any shape as long as the radius of curvature of the object side surface is negative. The shape of the fourth lens L4 is a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are negative, that is, a meniscus lens having a concave surface facing the object side in the vicinity of the optical axis X. Shape may be sufficient.

  Further, the arrangement of the third lens L3 and the fourth lens L4 in the second lens group G2 is not limited to the arrangement shown in the present embodiment. In addition, the arrangement of the third lens L3 and the fourth lens L4 is changed along the optical axis X, and the fourth lens L4 is disposed on the object side and the third lens L3 is disposed on the image plane side in the second lens group G2. Each may be arranged. In short, the second lens group G2 only needs to have a configuration in which the combined refractive power of two positive and negative lenses is negative.

  The third lens group G3 includes, in order from the object side, a stop ST, a fifth lens L5 having a positive refractive power, and a sixth lens L6 having a negative refractive power. Among these, the 5th lens L5 is formed in the shape used as the biconvex lens in the vicinity of the optical axis X. FIG. The sixth lens L6 is formed in a shape that becomes a meniscus lens having a convex surface facing the object side in the vicinity of the optical axis X.

  The third lens group G3 may be configured by arranging, in order from the object side, the aperture stop ST, a lens having a positive refractive power, and a lens group having a negative refractive power as a whole. . For example, the sixth lens L6 may be composed of two lenses, and the combined refractive power of these two lenses may be negative. In Numerical Example 6, in order from the object side, the third lens group G3 includes a stop ST, a fifth lens L5 having a positive refractive power, a sixth lens L6 having a positive refractive power, and a negative refractive power. This is an example in which a seventh lens L7 having a lens is disposed and a sixth lens L6 and a seventh lens L7 are cemented to form a cemented lens. By configuring the third lens group G3 in this way, the chromatic aberration is corrected more satisfactorily in the cemented lens configured by the sixth lens L6 and the seventh lens L7.

  The fourth lens group G4 includes a seventh lens L7 having positive refractive power (the eighth lens L8 in Numerical Example 6). The seventh lens L7 is formed into a shape in which both the radius of curvature of the object side surface and the radius of curvature of the image side surface are negative, that is, a meniscus lens having a concave surface facing the object side in the vicinity of the optical axis X. Is done.

In the zoom lens according to the present embodiment, the focal length of the first lens group G1 is f1, the focal length of the second lens group G2 is f2, the focal length of the third lens group G3 is f3, and the first lens group G1. The combined focal length at the wide angle end of the fourth lens group G4 is fw, the focal length of the first lens L1 is f1n, the focal length of the second lens L2 is f1p, the focal length of the fifth lens L5 is f3p, and the sixth lens L6 Where f3n is the focal length, νd1n is the Abbe number of the first lens L1, and νd1p is the Abbe number of the second lens L2, the following conditional expressions (1) to (6) are satisfied. In the zoom lens according to Numerical Example 6, the combined focal length of the sixth lens L6 and the seventh lens L7 is set to f3n.
| F1n / f1p | <0.8 (1)
0.2 <f2 / f1 <1.0 (2)
0.05 <| f3 / f1 | <0.5 (3)
1.0 <f3 / fw <2.0 (4)
0.1 <| f3p / f3n | <1.0 (5)
| Νd1n−νd1p | <30 (6)

  In addition, it is not necessary to satisfy all of the conditional expressions (1) to (6). By satisfying each of the conditional expressions (1) to (6) independently, an effect corresponding to each conditional expression is obtained. Therefore, it is possible to construct a small zoom lens with high image quality and high performance as compared with a conventional zoom lens.

Numerical Example 3
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 41.675 0.7500 1.77250 49.6 (= νd1n)
2 12.107 1.5000
3 * 20.834 1.5000 1.58500 29.0 (= νd1p)
4 * 24.481 1.0000
5 ∞ 7.5000 1.71300 53.9
6 ∞ variable
7 * 16.655 1.1500 1.58500 29.0
8 * -28.017 0.4600
9 -5.502 0.5800 1.48749 70.4
10 13.338 Variable
11 (Aperture) ∞ 0.1300
12 * 2.990 1.8400 1.49700 81.6
13 -10.902 0.0600
14 * 6.639 0.6000 1.61420 26.0
15 * 3.257 Variable
16 * -17.525 0.8000 1.58500 29.0
17 * -14.426 0.3700
18 ∞ 0.3680 1.51633 64.1
19 ∞ 5.2427
(Image plane IM) ∞

Various data Zoom ratio 2.803
Wide-angle end Medium Telephoto end total focal length f 4.399 8.103 12.331
F number 2.942 4.031 5.211
Half angle of view ω (°) 32.01 18.75 12.57
Image height 2.750 2.750 2.750
Total lens length L 35.865 35.865 35.865
Back focus BF 5.855 5.855 5.855

d6 1.100 2.960 1.096
d10 8.740 3.133 1.395
d15 2.300 6.047 9.649

f1p = 207.554
f1n = −22.337
f3p = 4.938
f3n = -11.163
f1 = -24.583
f2 = -15.698
f3 = 6.826
fw = 4.399

Aspheric data 3rd surface k = 3.509335, A ₄ = 2.755611E-04, A ₆ = 1.460797E-06, A ₈ = -1.054260E-08,
A ₁₀ = 1.267022E-09
4th surface k = -9.452414E-02, A ₄ = 1.216176E-04, A ₆ = 1.787719E-06
7th surface k = -3.669898E + 01, A ₄ = -1.128726E-03, A ₆ = -1.129927E-04, A ₈ = -2.250614E-06,
A ₁₀ = 8.683077E-07, A ₁₂ = 7.197789E-08, A ₁₄ = -3.320164E-09
8th surface k = 8.446368E + 01, A ₄ = -2.561455E-03, A ₆ = -6.782921E-05, A ₈ = 7.884073E-06,
A ₁₀ = 1.483586E-06
12th surface k = -7.591143E-01, A ₄ = 1.692338E-03, A ₆ = -9.205934E-06
14th surface k = -2.273233, A ₄ = -1.141013E-04, A ₆ = -2.773267E-05, A ₈ = -1.349021E-05,
A ₁₀ = -1.719046E-06
15th surface k = 9.138825E-01, A ₄ = 2.570563E-03, A ₆ = 3.998257E-04, A ₈ = -8.989558E-06,
A ₁₀ = 1.032031E-05, A ₁₂ = 4.901501E-06, A ₁₄ = -5.200339E-07, A ₁₆ = -6.488491E-07
16th surface k = -1.419108E + 02, A ₄ = -2.588241E-03, A ₆ = 3.250682E-04
17th surface k = -8.401693E + 01, A ₄ = -2.987940E-03, A ₆ = 2.571922E-04

The value of each conditional expression is shown below.
| F1n / f1p | = 0.108
f2 / f1 = 0.539
| F3 / f1 | = 0.278
f3 / fw = 1.552
| F3p / f3n | = 0.442
| Νd1n−νd1p | = 20.6
Thus, the zoom lens according to Numerical Example 3 satisfies the conditional expressions (1) to (6).

  FIGS. 16, 18, and 20 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 3, and FIGS. 17, 19, and 21 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 3 also corrects the image plane well and corrects various aberrations.

Numerical Example 4
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 45.000 0.7500 1.71700 48.0 (= νd1n)
2 12.000 1.0000
3 * 20.567 1.5000 1.68893 31.2 (= νd1p)
4 * 24.588 1.5000
5 ∞ 7.5000 1.71300 53.9
6 ∞ variable
7 * 16.753 1.1500 1.58500 29.0
8 * -28.082 0.4600
9 -5.486 0.5800 1.48749 70.4
10 13.071 Variable
11 (Aperture) ∞ 0.1300
12 * 2.989 1.8400 1.49700 81.6
13 -10.901 0.0600
14 * 6.636 0.6000 1.61420 26.0
15 * 3.256 variable
16 * -17.950 0.8000 1.58500 29.0
17 * -13.900 0.3700
18 ∞ 0.3680 1.51633 64.1
19 ∞ 5.1510
(Image plane IM) ∞

Various data Zoom ratio 2.795
Wide-angle end Medium Telephoto end focal length f 4.441 8.194 12.414
F number 2.901 3.976 5.120
Half angle of view ω (°) 31.77 18.55 12.49
Image height 2.750 2.750 2.750
Total lens length L 35.774 35.774 35.774
Back focus BF 5.764 5.764 5.764

d6 1.100 2.960 1.096
d10 8.740 3.133 1.395
d15 2.300 6.047 9.649

f1p = 158.442
f1n = -23.041
f3p = 4.937
f3n = -11.162
f1 = −26.358
f2 = -15.395
f3 = 6.823
fw = 4.441

Aspherical data third surface k = 2.907486, A ₄ = 2.588203E-04, A ₆ = 1.334757E-06, A ₈ = -1.713144E-08,
A ₁₀ = 1.126350E-09
4th surface k = -9.452414E-02, A ₄ = 1.216176E-04, A ₆ = 1.787719E-06
7th surface k = -3.677568E + 01, A ₄ = -1.149922E-03, A ₆ = -1.136472E-04, A ₈ = -2.384865E-06,
A ₁₀ = 8.571463E-07, A ₁₂ = 7.117301E-08, A ₁₄ = -3.402583E-09
8th surface k = 8.476395E + 01, A ₄ = -2.560318E-03, A ₆ = -6.902640E-05, A ₈ = 7.700514E-06,
A ₁₀ = 1.473763E-06
12th surface k = -7.599271E-01, A ₄ = 1.686772E-03, A ₆ = -7.981991E-06
14th surface k = -2.274364, A ₄ = -1.149941E-04, A ₆ = -2.871803E-05, A ₈ = -1.351655E-05,
A ₁₀ = -1.621984E-06
15th surface k = 9.087991E-01, A ₄ = 2.529295E-03, A ₆ = 3.919201E-04, A ₈ = -9.446522E-06,
A ₁₀ = 1.068374E-05, A ₁₂ = 5.135334E-06, A ₁₄ = -4.249484E-07, A ₁₆ = -6.199797E-07
16th surface k = -1.844843E + 02, A ₄ = -2.616215E-03, A ₆ = 3.139626E-04
17th surface k = -8.951802E + 01, A ₄ = -3.013085E-03, A ₆ = 2.534994E-04

The value of each conditional expression is shown below.
| F1n / f1p | = 0.145
f2 / f1 = 0.484
| F3 / f1 | = 0.259
f3 / fw = 1.536
| F3p / f3n | = 0.442
| Νd1n−νd1p | = 16.8
As described above, the zoom lens according to Numerical Example 4 satisfies the conditional expressions (1) to (6).

  23, 25, and 27 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 4, and FIGS. 24, 26, and 28 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 4 also corrects the image plane well and appropriately corrects various aberrations.

Numerical Example 5
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 47.646 0.7500 1.72000 50.3 (= νd1n)
2 11.881 0.7000
3 * 20.457 1.5000 1.62004 36.3 (= νd1p)
4 * 24.834 1.5000
5 ∞ 7.5000 1.71300 53.9
6 ∞ variable
7 * 16.666 1.1500 1.58500 29.0
8 * -28.015 0.4600
9 -5.498 0.5800 1.48749 70.4
10 13.192 Variable
11 (Aperture) ∞ 0.1300
12 * 2.989 1.8400 1.49700 81.6
13 -10.881 0.0600
14 * 6.620 0.6000 1.61420 26.0
15 * 3.258 Variable
16 * -17.678 0.8000 1.58500 29.0
17 * -13.990 0.3700
18 ∞ 0.3680 1.51633 64.1
19 ∞ 5.1612
(Image plane IM) ∞

Various data Zoom ratio 2.810
Wide-angle end Medium Telephoto end focal length f 4.405 8.128 12.380
F number 2.907 3.976 5.156
Half angle of view ω (°) 31.98 18.69 12.52
Image height 2.750 2.750 2.750
Total length L 35.484 35.484 35.484
Back focus BF 5.774 5.774 5.774

d6 1.100 2.960 1.096
d10 8.740 3.133 1.395
d15 2.300 6.047 9.649

f1p = 165.488
f1n = -22.178
f3p = 4.935
f3n = -11.206
f1 = -25.038
f2 = -15.581
f3 = 6.807
fw = 4.405

Aspheric data 3rd surface k = 3.264352, A ₄ = 2.659854E-04, A ₆ = 1.462847E-06, A ₈ = -1.475123E-08,
A ₁₀ = 1.179264E-09
4th surface k = -9.452414E-02, A ₄ = 1.216176E-04, A ₆ = 1.787719E-06
7th surface k = -3.638029E + 01, A ₄ = -1.143135E-03, A ₆ = -1.134383E-04, A ₈ = -2.388834E-06,
A ₁₀ = 8.582870E-07, A ₁₂ = 7.147831E-08, A ₁₄ = -3.356452E-09
8th surface k = 8.478257E + 01, A ₄ = -2.569631E-03, A ₆ = -6.899825E-05, A ₈ = 7.807461E-06,
A ₁₀ = 1.482291E-06
12th surface k = -7.606723E-01, A ₄ = 1.682452E-03, A ₆ = -8.182965E-06
14th surface k = -2.288671, A ₄ = -1.204413E-04, A ₆ = -2.970860E-05, A ₈ = -1.367017E-05,
A ₁₀ = -1.632636E-06
15th surface k = 9.098794E-01, A ₄ = 2.537245E-03, A ₆ = 3.942353E-04, A ₈ = -8.948781E-06,
A ₁₀ = 1.067477E-05, A ₁₂ = 5.055165E-06, A ₁₄ = -4.818714E-07, A ₁₆ = -6.502081E-07
16th surface k = -1.779248E + 02, A ₄ = -2.606685E-03, A ₆ = 3.138350E-04
17th surface k = -9.487734E + 01, A ₄ = -3.029428E-03, A ₆ = 2.504570E-04

The value of each conditional expression is shown below.
| F1n / f1p | = 0.134
f2 / f1 = 0.622
| F3 / f1 | = 0.272
f3 / fw = 1.545
| F3p / f3n | = 0.440
| Νd1n−νd1p | = 14.0
As described above, the zoom lens according to Numerical Example 5 satisfies the conditional expressions (1) to (6).

  30, FIG. 32 and FIG. 34 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 5, and FIGS. 31, 33 and 35 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 5 also corrects the image plane well and appropriately corrects various aberrations.

Numerical Example 6
Basic lens data is shown below.
Unit mm
Surface data Surface number i R d Nd νd
(Surface) ∞ ∞
1 61.303 0.7500 1.72000 50.3 (= νd1n)
2 12.139 1.0000
3 * 20.912 1.5000 1.62004 36.3 (= νd1p)
4 * 28.372 1.5000
5 ∞ 7.5000 1.71300 53.9
6 ∞ variable
7 * 15.778 1.1500 1.58500 29.0
8 * -28.227 0.4600
9 -5.584 0.5800 1.48749 70.4
10 14.827 Variable
11 (Aperture) ∞ 0.1300
12 * 3.056 1.8400 1.49700 81.6
13 * -10.787 0.0600
14 * 6.798 1.0000 1.61800 63.4
15 -14.204 0.6000 1.83400 37.3
16 * 3.969 variable
17 -27.497 0.8500 1.58500 29.0
18 * -11.087 0.3700
19 ∞ 0.3680 1.51633 64.1
20 ∞ 3.5743
(Image plane IM) ∞

Various data Zoom ratio 2.854
Wide-angle end Medium Telephoto end focal length f 4.300 8.000 12.273
F number 2.721 3.829 4.937
Half angle of view ω (°) 32.60 18.97 12.63
Image height 2.750 2.750 2.750
Total length L 35.247 35.247 35.247
Back focus BF 4.187 4.187 4.187

d6 1.100 2.960 1.096
d10 8.740 3.133 1.395
d16 2.300 6.047 9.649

f1p = 119.105
f1n = -21.158
f3p = 5.013
f3n = −8.583
f1 = −25.335
f2 = -17.586
f3 = 6.698
fw = 4.300

Aspherical data third surface k = 3.264297, A ₄ = 2.988993E-04, A ₆ = 9.851433E-07, A ₈ = -1.952113E-08,
A ₁₀ = 1.297080E-09
4th surface k = -9.452414E-02, A ₄ = 1.216176E-04, A ₆ = 1.787719E-06
7th surface k = -3.401524E + 01, A ₄ = -1.158674E-03, A ₆ = -1.159193E-04, A ₈ = -2.525073E-06,
A ₁₀ = 8.456085E-07, A ₁₂ = 7.028339E-08, A ₁₄ = -3.470701E-09
8th surface k = 8.318965E + 01, A ₄ = -2.596123E-03, A ₆ = -7.588712E-05, A ₈ = 7.099053E-06,
A ₁₀ = 1.419990E-06
12th surface k = -8.779749E-01, A ₄ = 2.043080E-03, A ₆ = 7.878284E-06
13th surface k = -2.724983, A ₄ = -3.644963E-04, A ₆ = -6.892097E-05
14th surface k = -3.041445, A ₄ = -3.942873E-04, A ₆ = -6.020295E-05, A ₈ = -1.537556E-05,
A ₁₀ = -3.842226E-06
16th surface k = 1.194753, A ₄ = 3.344424E-03, A ₆ = 8.763346E-04, A ₈ = 4.251334E-05,
A ₁₀ = -3.705970E-06, A ₁₂ = -4.656010E-06, A ₁₄ = -1.740505E-06, A ₁₆ = 1.953234E-06
18th surface k = -2.499241E-01, A ₄ = -5.758253E-04, A ₆ = -2.173904E-05

The value of each conditional expression is shown below.
| F1n / f1p | = 0.178
f2 / f1 = 0.694
| F3 / f1 | = 0.264
f3 / fw = 1.558
| F3p / f3n | = 0.484
| Νd1n−νd1p | = 14.0
Thus, the zoom lens according to Numerical Example 6 satisfies the conditional expressions (1) to (6).

  37, 39, and 41 show the lateral aberration corresponding to the half angle of view ω for the zoom lens of Numerical Example 6, and FIGS. 38, 40, and 42 show the spherical aberration SA (mm). ), Astigmatism AS (mm), and distortion aberration DIST (%), respectively. As described above, the zoom lens according to Numerical Example 6 also corrects the image plane well and appropriately corrects various aberrations.

  Therefore, when the zoom lens according to the present embodiment is applied to an imaging optical system such as a mobile phone, a digital still camera, a portable information terminal, a security camera, etc., both high performance and downsizing of the camera are to be achieved. Can do.

  The present invention can be applied to a zoom lens mounted on a device that is required to have a small aberration and good aberration correction capability, such as a mobile phone or a digital still camera.

G1 1st lens group G2 2nd lens group G3 3rd lens group G4 4th lens group L1 1st lens L2 2nd lens L3 3rd lens L4 4th lens L5 5th lens L6 6th lens L7 7th lens L8 1st lens 8 lenses P prism ST aperture 10 filter

Claims (11)

In order from the object side to the image plane side, a first lens group having negative refractive power, a second lens group having negative refractive power, a third lens group having positive refractive power, and positive refraction And a fourth lens group having power,
The first lens group includes a lens having a positive refractive power in which the radius of curvature of the object side surface is positive, a lens having a negative refractive power in which the radius of curvature of the image side surface is positive, and these lenses. It is composed of an optical path changing member arranged on the image plane side to change the traveling direction of incident light,
The second lens group includes a lens having a positive refractive power that makes the radius of curvature of the object side surface positive, and a lens having a negative refractive power that makes the radius of curvature of the object side surface negative. And
The third lens group is composed of a lens having a positive refractive power and a lens group having a negative refractive power as a whole,
In zooming from the wide-angle end to the telephoto end, the first lens group and the fourth lens group are fixed, and the second lens group is moved to the image side and then moved to the object side, and the third lens The group is moved to the object side in a straight line,
A zoom lens characterized by that. The optical path changing member is a prism that reflects incident light and bends the optical path.
The zoom lens according to claim 1. The first lens group is configured by arranging one cemented lens closer to the object side than the optical path changing member,
The cemented lens has a positive radius of curvature of the object side surface and a negative radius of curvature of the image side surface, and a negative radius of curvature of the object side surface of the image side surface. Composed of a lens with a positive radius of curvature,
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. The first lens group is configured by disposing, on the object side of the optical path changing member, two lenses in which the curvature radius of the object side surface and the curvature radius of the image side surface are both positive.
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. The first lens group includes a first lens having a negative refractive power, a second lens having a positive refractive power, and the optical path changing member in order from the object side to the image plane side. To be
The zoom lens according to claim 1, wherein the zoom lens is a zoom lens. When the focal length of the lens having positive refractive power in the first lens group is f1p and the focal length of the lens having negative refractive power in the first lens group is f1n, the following conditional expression is satisfied. The zoom lens according to any one of claims 1 to 5, characterized in that:
| F1n / f1p | <0.8 The following conditional expression is satisfied, where f1 is a focal length of the first lens group and f2 is a focal length of the second lens group. Zoom lens.
0.2 <f2 / f1 <1.0 The following conditional expression is satisfied, where f1 is a focal length of the first lens group and f3 is a focal length of the third lens group. Zoom lens.
0.05 <| f3 / f1 | <0.5 When the combined focal length at the wide angle end of the first lens group, the second lens group, the third lens group, and the fourth lens group is fw, and the focal length of the third lens group is f3, The zoom lens according to claim 1, wherein a conditional expression is satisfied.
1.0 <f3 / fw <2.0 When the focal length of the lens having positive refractive power in the third lens group is f3p and the combined focal length of the lens group having negative refractive power in the third lens group is f3n, the following conditional expression is satisfied. The zoom lens according to any one of claims 1 to 9, wherein:
0.1 <| f3p / f3n | <1.0 When the Abbe number of the lens having positive refractive power in the first lens group is νd1p and the Abbe number of the lens having negative refractive power in the first lens group is νd1n, the following conditional expression is satisfied. The zoom lens according to claim 1, wherein the zoom lens is characterized in that:
| Νd1n−νd1p | <30

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