JP2018040948A - Zoom lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zoom lens which features a view angle in excess of 110 degrees at the wide-angle end and a back focus no less than three times a focal length at the wide-angle end, and which offers good optical performance while effectively minimizing imaging performance degradation due to manufacturing error and suppressing an increase in a manufacturing cost.SOLUTION: A zoom lens comprises a first lens group G1 having negative refractive power, a second lens group G2 having positive refractive power, and a third lens group G3 having positive refractive power in order from the object side to the image side. When zooming from the wide-angle end to the telephoto end, all the lens groups move along an optical axis causing a distance between the first lens group and the second lens group to decrease and a distance between the second lens group and the third lens group to increase. The second lens group includes a biconvex lens located on the most object side, and an aperture stop is disposed within the second lens group or adjacent to an image side of the second lens group. The zoom lens satisfies predetermined conditions.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a zoom lens used in a photographing apparatus such as a still camera or a video camera, and more particularly to a zoom lens that ensures a very wide angle of view.

  In recent years, it has been desired that a zoom lens used in a photographing apparatus such as a digital still camera has both a wide angle of view and high performance.

  In order for a wide-angle zoom lens to be compatible with a single-lens reflex camera having a quick return mirror, it is necessary to secure a back focus much longer than the focal length. In order to ensure a long back focus, there is inevitably a tendency to adopt a negative lead type refractive power arrangement in which a negative refractive power is arranged on the object side and a positive refractive power is arranged on the image side.

  Patent Documents 1 and 2 disclose zoom lenses in which the angle of view at the wide-angle end exceeds 110 degrees and a back focus that is at least three times the focal length at the wide-angle end is ensured.

JP 2013-15621 A JP2015-102620A

  In a negative lead type zoom lens that needs to secure a back focus that is at least three times the focal length, the negative refractive power of the object side lens group (front group) and the image side lens group (rear group) It is necessary to increase the positive refractive power.

  Further, in such a zoom lens, it is required to correct distortion aberration, lateral chromatic aberration, and the like in each of the front lens group and the rear lens group.

  Furthermore, in such a zoom lens, it is necessary to convert the axial beam diverged by the strong negative refractive power of the front group into a convergent beam for imaging by the rear group, and compare the axial marginal rays. Therefore, it is required to refract strongly in a short section.

  In order to strongly refract the axial marginal ray in the rear group in a relatively short length section, it is necessary to increase the refractive power of the lens element having a positive refractive power constituting the rear group. In a lens element having a refractive power of, particularly, the amount of aberration tends to increase, for example, spherical aberration tends to occur greatly in the under direction.

  On the other hand, as described above, it is necessary to achieve good aberration correction by the rear group alone, but for this purpose, negative refraction that generates aberrations of the opposite sign to the aberrations generated by the lens elements with strong positive refractive power. Aberration correction is performed by introducing a power lens element or an aspheric lens into the rear group.

  In this way, when a large aberration amount having a different sign is generated in each lens element to correct the aberration of the entire lens group, spherical aberration, axial coma aberration, axis due to decentration of each lens element and manufacturing error in the interval It is a problem to effectively suppress the occurrence of upper astigmatism and single-sided blur.

  If a lens configuration that cannot efficiently suppress the occurrence of these aberrations is used, there is a risk that good imaging performance in the finished product cannot be guaranteed, and in addition, extremely high manufacturing is required to obtain good imaging performance. If the accuracy is required, the manufacturing cost may increase significantly.

  In the super wide-angle lens system described in Patent Document 1, four lens groups move along the optical axis during zooming, and a part of the first lens group moves along the optical axis during focusing. Since there are as many as five lens groups that move, it is difficult to prevent the lens groups from decentering and ensure good imaging performance of the finished product.

  The optical system described in Patent Document 2 has a lens configuration in which three lens groups move along the optical axis during zooming, and the number of moving lens groups is small, but in the rear group particularly at the telephoto end. Since the occurrence of spherical aberration is large, it is difficult to ensure good imaging performance of the finished product due to large aberration fluctuations due to decentration.

  The present invention is a zoom lens in which the angle of view at the wide-angle end exceeds 110 degrees and ensures a back focus that is at least three times the focal length at the wide-angle end. An object of the present invention is to provide a zoom lens that efficiently suppresses deterioration of imaging performance and suppresses an increase in manufacturing cost.

In order to solve the above problems, a zoom lens according to a first aspect of the present invention includes, in order from the object side to the image side, a first lens group having a negative refractive power and a second lens group having a positive refractive power. And a third lens group having a positive refractive power. When zooming from the wide-angle end to the telephoto end, all the lens groups move along the optical axis, so that the first lens group and the second lens A zoom lens in which the distance between the groups decreases and the distance between the second lens group and the third lens group increases, and the second lens group includes a biconvex lens closest to the object side; An aperture stop is disposed inside or adjacent to the image side, and satisfies the following conditions.
(1) LS / ft> 0.25
(2) 3.95 <| (f2 × (β2w−1) / β2w−pp2) / f1 | <4.95
(3) 2.30 <| (f2 × (β2t−1) / β2t−pp2) / f1 | <3.25
(4) 3.00 <BFw / fw <3.30
LS: Length on the optical axis between the lens surface closest to the image side of the first lens unit and the aperture stop in the infinitely focused state at the telephoto end ft: Optical system in the infinitely focused state at the telephoto end Total focal length fw of the entire system: Total focal length f1 of the entire optical system in an infinitely focused state at the wide angle end: Focal length f2 of the first lens group: Focal length β2w of the second lens group: At the wide angle end The imaging magnification β2t of the second lens group in the infinite focus state: the imaging magnification pp2 of the second lens group in the infinite focus state at the telephoto end: the second object lens surface and the second lens surface of the second lens group Length BFw on the optical axis between the object side principal point of the lens group: paraxial back focus in the infinite focus state at the wide angle end

  The zoom lens according to a second aspect of the present invention is the zoom lens according to the first aspect of the present invention, wherein the second lens group moves along the optical axis from the object side to the image side during focusing from an object at infinity to a short distance object. It is characterized by moving to.

  In the zoom lens according to a third aspect of the present invention, in the first or second aspect, the first lens group further includes a negative meniscus lens having a convex surface facing the object side closest to the object side, and the negative lens The lens surface on the object side of the meniscus lens has an aspherical shape in which the local curvature radius decreases from the central portion toward the peripheral portion.

  In the zoom lens according to a fourth aspect of the present invention, in the first to third aspects, the first lens group further includes a cemented lens having a positive refractive power closest to the image side, and the cemented lens is an object. A negative meniscus lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side in order from the image side to the image side.

The zoom lens according to a fifth aspect of the present invention is further characterized in that, in the fourth aspect, the following condition is satisfied.
(5) −0.00067 <(θgFp−θgFn) / (νdp−νdn) <− 0.00057
θgFp: Partial dispersion ratio of g-line and F-line of the positive lens constituting the most image side cemented lens of the first lens group θgFn: G-line of the negative lens constituting the most image-side cemented lens of the first lens group F-line partial dispersion ratio νdp: Abbe number of positive lens constituting the most image-side cemented lens of the first lens group νdn: Abbe number of negative lens constituting the most image-side cemented lens of the first lens group

  In the zoom lens according to a sixth aspect of the present invention, in the first to fifth aspects, the first lens group includes a first negative meniscus having a convex surface directed toward the object side in order from the object side to the image side. It comprises a lens, a second negative meniscus lens having a convex surface facing the object side, a third negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented lens having a positive refractive power.

  The zoom lens according to a seventh aspect of the present invention is the zoom lens according to any one of the first to sixth aspects, wherein the second lens group includes, in order from the object side to the image side, a biconvex lens, a positive lens, a negative lens, and a positive lens. It is characterized by comprising a three-lens cemented lens.

  According to the present invention, a zoom lens in which the angle of view at the wide-angle end exceeds 110 degrees and a back focus that is at least three times the focal length at the wide-angle end is ensured. Thus, it is possible to provide a zoom lens that efficiently suppresses the deterioration in imaging performance caused by the above and suppresses an increase in manufacturing cost.

FIG. 2 is a lens configuration diagram of a zoom lens of Example 1. FIG. 3 is a longitudinal aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 1; FIG. 3 is a longitudinal aberration diagram in a close-up focus state at the wide angle end of the zoom lens according to Example 1; FIG. 3 is a longitudinal aberration diagram in the infinite focus state at the intermediate focal length of the zoom lens according to the first exemplary embodiment. FIG. 6 is a longitudinal aberration diagram in a short-distance focusing state at an intermediate focal length of the zoom lens according to the first exemplary embodiment. FIG. 4 is a longitudinal aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 1; FIG. 6 is a longitudinal aberration diagram in a close-up focus state at the telephoto end of the zoom lens in Example 1; FIG. 4 is a lateral aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 1; FIG. 3 is a lateral aberration diagram in a close-distance in-focus state at the wide angle end of the zoom lens according to Example 1; FIG. 4 is a lateral aberration diagram in the infinitely focused state at the intermediate focal length of the zoom lens in Example 1; FIG. 4 is a lateral aberration diagram in a close-up focusing state at an intermediate focal length of the zoom lens according to the first exemplary embodiment. FIG. 4 is a lateral aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 1; FIG. 4 is a lateral aberration diagram in a close-up focus state at the telephoto end of the zoom lens in Example 1; 6 is a lens configuration diagram of a zoom lens according to Example 2. FIG. FIG. 6 is a longitudinal aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 2; FIG. 6 is a longitudinal aberration diagram in a short-distance focusing state at the wide angle end of the zoom lens according to Example 2; FIG. 6 is a longitudinal aberration diagram in an infinitely focused state at an intermediate focal length of the zoom lens in Example 2; FIG. 6 is a longitudinal aberration diagram in a short-distance in-focus state at an intermediate focal length of the zoom lens according to Example 2; FIG. 6 is a longitudinal aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 2; FIG. 6 is a longitudinal aberration diagram of the zoom lens according to Example 2 in a short distance focusing state at a telephoto end. FIG. 6 is a lateral aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 2; FIG. 6 is a lateral aberration diagram in a short distance focusing state at a wide angle end of a zoom lens according to Example 2; FIG. 6 is a lateral aberration diagram in the infinitely focused state at the intermediate focal length of the zoom lens in Example 2; FIG. 10 is a lateral aberration diagram in a short distance focusing state at an intermediate focal length of the zoom lens according to Example 2; FIG. 6 is a lateral aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 2; FIG. 6 is a lateral aberration diagram in a short distance focusing state at a telephoto end of a zoom lens according to Example 2; 5 is a lens configuration diagram of a zoom lens according to Example 3. FIG. FIG. 6 is a longitudinal aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 3; FIG. 10 is a longitudinal aberration diagram in a close-up focus state at the wide angle end of the zoom lens according to Example 3; FIG. 10 is a longitudinal aberration diagram in the infinite focus state at the intermediate focal length of the zoom lens in Example 3; FIG. 10 is a longitudinal aberration diagram of the zoom lens according to Example 3 in a short distance focusing state at an intermediate focal length. FIG. 6 is a longitudinal aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 3; FIG. 6 is a longitudinal aberration diagram in a close-up in-focus state at the telephoto end of the zoom lens according to Example 3; FIG. 10 is a lateral aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 3; FIG. 10 is a lateral aberration diagram in a short distance focusing state at a wide angle end of a zoom lens according to Example 3; FIG. 10 is a lateral aberration diagram in the infinitely focused state at the intermediate focal length of the zoom lens according to Example 3; FIG. 6 is a lateral aberration diagram in a short distance in-focus state at an intermediate focal length of the zoom lens according to Example 3; FIG. 6 is a lateral aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 3; FIG. 10 is a lateral aberration diagram in a short distance focusing state at the telephoto end of the zoom lens according to Example 3; 6 is a lens configuration diagram of a zoom lens according to Example 4. FIG. FIG. 12 is a longitudinal aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 4; FIG. 10 is a longitudinal aberration diagram in a close-up focus state at the wide angle end of the zoom lens according to Example 4; FIG. 6 is a longitudinal aberration diagram in an infinitely focused state at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is a longitudinal aberration diagram in a short-distance focusing state at an intermediate focal length of the zoom lens according to Example 4; FIG. 10 is a longitudinal aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 4; FIG. 6 is a longitudinal aberration diagram in a close-up in-focus state at the telephoto end of a zoom lens according to Example 4; FIG. 10 is a lateral aberration diagram in the infinitely focused state at the wide angle end of the zoom lens according to Example 4; FIG. 10 is a lateral aberration diagram in a short distance focusing state at a wide angle end of a zoom lens according to Example 4; FIG. 10 is a lateral aberration diagram in the infinitely focused state at the intermediate focal length of the zoom lens according to Example 4; FIG. 10 is a lateral aberration diagram in a close-up focusing state at an intermediate focal length of the zoom lens according to Example 4; FIG. 12 is a lateral aberration diagram in the infinitely focused state at the telephoto end of the zoom lens in Example 4; FIG. 10 is a lateral aberration diagram in a short distance focusing state at a telephoto end of a zoom lens in Example 4;

  Embodiments of the zoom lens according to the present invention will be described below.

  1, FIG. 14, FIG. 27, and FIG. 40 show lens configuration diagrams of Examples 1 to 4 according to the present invention.

  The zoom lens according to the present exemplary embodiment includes, in order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power. Is done.

  Further, during zooming from the wide-angle end to the telephoto end, all the lens groups move along the optical axis, thereby reducing the distance between the first lens group and the second lens group, and the second lens group and the third lens. Group spacing increases.

  The second lens group includes a biconvex lens closest to the object side, and an aperture stop is disposed inside the second lens group or adjacent to the image side.

  In the zoom lens of this embodiment, the first lens unit having a negative refractive power is disposed on the object side as a whole, and the second lens group having a positive refractive power and the third lens group having a positive refractive power are disposed on the image side. A negative lead type lens configuration that is advantageous for securing the back focus is adopted. In this lens configuration, the main zooming function is performed by changing the distance between the first lens group and the second lens group.

  Further, by configuring each lens group so that the axial light beam emitted from the second lens group enters the third lens group in an almost afocal state, the second lens group and the third lens during zooming It is possible to suppress the fluctuation of astigmatism caused by the change in the group interval.

  In the zoom lens of the present embodiment, the second lens group includes a biconvex lens closest to the object side, and has a lens configuration in which an aperture stop is disposed inside the second lens group or adjacent to the image side.

  The aperture stop is disposed in the optical system for the purpose of adjusting the amount of light. However, in order to change the aperture degree of the aperture stop quickly and appropriately, a drive mechanism for that purpose is required. Therefore, when arranging the aperture stop in the optical system, it is necessary to consider not only the space of the aperture stop but also the size of the aperture stop unit including the drive mechanism for driving the aperture stop. A certain space is required for the arrangement.

  The zoom lens of the present embodiment has a lens configuration in which the distance between the first lens group and the second lens group is reduced during zooming from the wide-angle end to the telephoto end. Therefore, the aperture stop is formed between the first lens group and the second lens group. In the case of being arranged between them, the distance between the lens groups must be increased in consideration of the space of the aperture stop unit at the telephoto end.

  On the other hand, since the axial light beam emitted from the first lens group having a negative refractive power is diverged, the second lens group is increased by increasing the distance between the first lens group and the second lens group in order to arrange the aperture stop. There arises a problem that the diameter of the axial light beam incident on the light beam increases. When the diameter of the on-axis light beam incident on the second lens group is increased, the spherical aberration generated on the lens surfaces of the second lens group and the third lens group is increased, which makes it difficult to correct the aberration. There is a possibility that the imaging performance is deteriorated. In addition, the occurrence of spherical aberration, axial coma, and axial astigmatism due to manufacturing errors also increases, which increases the manufacturing cost for ensuring good imaging performance by properly controlling these during manufacturing. There is a risk that.

  In this embodiment, an aperture stop is disposed in the second lens group or adjacent to the image side, so that the distance between the first lens group and the second lens group is not increased, and the second lens group is moved to the second lens group. It is possible to obtain good imaging performance by suppressing an increase in the diameter of the incident on-axis light beam.

  Further, in this embodiment, in order to suppress an increase in the diameter of the axial light beam passing through the second lens group, a biconvex lens is disposed on the most object side of the second lens group, thereby passing through the second lens group. It is possible to obtain good imaging performance by reducing the diameter of the axial light beam.

In addition, the present example satisfies the following conditional expressions (1) to (4).
(1) LS / ft> 0.25
(2) 3.95 <| (f2 × (β2w−1) / β2w−pp2) / f1 | <4.95
(3) 2.30 <| (f2 × (β2t−1) / β2t−pp2) / f1 | <3.25
(4) 3.00 <BFw / fw <3.30
LS: Length on the optical axis between the lens surface closest to the image side of the first lens unit and the aperture stop in the infinitely focused state at the telephoto end ft: Optical system in the infinitely focused state at the telephoto end Total focal length fw of the entire system: Total focal length f1 of the entire optical system in an infinitely focused state at the wide angle end: Focal length f2 of the first lens group: Focal length β2w of the second lens group: At the wide angle end The imaging magnification β2t of the second lens group in the infinite focus state: the imaging magnification pp2 of the second lens group in the infinite focus state at the telephoto end: the second object lens surface and the second lens surface of the second lens group Length BFw on the optical axis between the object side principal point of the lens group: paraxial back focus in the infinite focus state at the wide angle end

  Conditional expression (1) defines the length on the optical axis between the lens surface closest to the image side of the first lens unit and the aperture stop in the infinitely focused state at the telephoto end. An appropriate range for avoiding physical interference between the driving mechanism and the first lens group is defined.

  When the length between the lens surface closest to the image side of the first lens group and the aperture stop becomes shorter than the lower limit of conditional expression (1), physical interference between the aperture stop drive mechanism and the first lens group. It will be difficult to avoid.

  The aperture stop itself is made of a thin plate-like resin or metal, but the drive mechanism including an actuator for driving the aperture stop occupies a large space in the optical axis direction inside the lens barrel. Therefore, even in a lens configuration in which no aperture stop is disposed between the first lens group and the second lens group as in this embodiment, the aperture stop is sufficiently separated from the lens surface closest to the image side of the first lens group. There is a need.

  In addition, the effect by this invention can be made more reliable by making the minimum of conditional expression (1) 0.265.

  Moreover, the effect by this invention can be made more reliable by making the minimum of conditional expression (1) into 0.280 further.

  If the length between the lens surface closest to the image side of the first lens group and the aperture stop becomes too long, a drive mechanism for the aperture stop and a mount mechanism or circuit board provided on the image side of the lens barrel Since it is difficult to avoid physical interference, it is preferable to set the upper limit of conditional expression (1) to 0.95.

  Moreover, it is preferable that the upper limit of conditional expression (1) is further set to 0.80.

  Conditional expressions (2) and (3) are: the focal length of the second lens group at the wide-angle end or the telephoto end, the imaging magnification, the lens surface closest to the object side of the second lens group, and the object side of the second lens group. An appropriate range is defined for the length relationship on the optical axis between the principal point positions.

In the infinite focus state of the zoom lens of the present embodiment, the distance z from the object side focal point of the second lens unit to the image side focal point of the first lens unit is obtained when the imaging magnification of the second lens unit is β2x. It is expressed by the following formula.
z = f2 / β2x

The distance L on the optical axis from the lens surface closest to the object side of the second lens unit to the image side focal point of the first lens unit is expressed by the following equation.
L = z−f2 + pp2 = − (f2 × (β2x−1) / β2x−pp2)

Here, with respect to the axial marginal ray, the incident height on the tangent plane of the lens surface closest to the object side of the first lens group is h1, and the incident height on the tangential plane of the lens surface closest to the object side of the second lens group is When h2, the following equation holds.
h1 / f1 = h2 / L

That is, the incident height h2 on the tangential plane of the lens surface closest to the object side of the second lens group with respect to the axial marginal ray is proportional to L / f1 as represented by the following equation.
h2∝L / f1
L / f1 = (f2 × (β2x−1) / β2x−pp2) / f1

  Therefore, the conditional expressions (2) and (3) relate to the definition of the incident height h2 on the tangential plane of the lens surface closest to the object side of the second lens group with respect to the axial marginal ray.

  When the upper limit of conditional expressions (2) and (3) is exceeded, the diameter of the axial light beam incident on the second lens group becomes large, and it becomes difficult to correct spherical aberration.

  If the lower limit of conditional expressions (2) and (3) is not reached, the diameter of the axial light beam incident on the second lens group can be reduced, but the focal length of the first lens group becomes longer and the second lens becomes longer. The focal length of the first lens group becomes shorter, or the image side principal point position of the first lens group is located closer to the image side, so that the refractive power of the first lens group is arranged on the telephoto side. In these cases, it becomes difficult to ensure the back focus because the retrofocus type refractive power arrangement of the entire optical system is weakened, or the total length of the optical system is increased and the diameter of the first lens unit is suppressed. This makes it difficult to increase the size of the entire product.

  In addition, the effect by this invention can be made more reliable by making the upper limit of conditional expression (2) 4.75.

  Moreover, the effect by this invention can be made more reliable by making the upper limit of conditional expression (2) further 4.65.

  In addition, the effect by this invention can be made more reliable by making the minimum of conditional expression (2) 4.05.

  Moreover, the effect by this invention can be made more reliable by making the minimum of conditional expression (2) further 4.20.

  In addition, the effect by this invention can be made more reliable by making the upper limit of conditional expression (3) 3.15.

  Moreover, the effect by this invention can be made more reliable by making the upper limit of conditional expression (3) further 3.05.

  In addition, the effect by this invention can be made more reliable by making the minimum of conditional expression (3) into 2.40.

  Moreover, the effect by this invention can be made more reliable by making the minimum of conditional expression (3) further into 2.55.

  Conditional expression (4) defines an appropriate range of the relationship between the paraxial back focus in the infinitely focused state at the wide-angle end and the combined focal length of the entire optical system, and the optical system is a single-lens reflex camera. This prescribes an appropriate condition for avoiding physical interference with the reflex mirror included in.

  If the paraxial back focus in the infinitely focused state at the wide-angle end is too short or the combined focal length of the entire optical system is too long, the optical system and reflex are below the lower limit of conditional expression (4). There is a risk of physical interference with the mirror, or it becomes difficult to ensure a sufficient angle of view at the wide-angle end.

  Exceeding the upper limit of conditional expression (4) makes it possible to sufficiently secure paraxial back focus in the infinitely focused state at the wide-angle end, but the combined focal length of the entire optical system becomes too short. Further, the asymmetry of the retrofocus type refractive power arrangement is further increased, and it becomes difficult to correct distortion and lateral chromatic aberration, so that it is difficult to ensure sufficient imaging performance.

  In addition, the effect by this invention can be made more reliable by making the upper limit of conditional expression (4) 3.25.

  Moreover, the effect by this invention can be made more reliable by making the upper limit of conditional expression (4) further 3.20.

  In addition, the effect by this invention can be made more reliable by making the minimum of conditional expression (4) 3.05.

  Moreover, the effect by this invention can be made more reliable by making the minimum of conditional expression (4) further 3.10.

  Further, in the zoom lens of the present embodiment, the second lens group moves from the object side to the image side along the optical axis when focusing from an object at infinity to an object at a short distance.

  As described above, the zoom lens in the present embodiment adopts a negative lead type lens configuration. The negative lead type optical system has a large variation in astigmatism accompanying a change in object distance.

  In the zoom lens of the present embodiment, in focusing, the second lens group is configured to move from the object side to the image side along the optical axis so that the distance between the second lens group and the third lens group is set appropriately. By maintaining this state, it is possible to cancel out the astigmatism variation accompanying the change in the object distance, and to simplify the moving lens group, thereby avoiding the complexity of the lens barrel mechanism.

  Further, in the zoom lens of the present embodiment, the first lens group includes a negative meniscus lens having a convex surface facing the object side closest to the object side, and the lens surface on the object side of the negative meniscus lens moves from the central portion toward the peripheral portion. The aspherical shape has a small local curvature radius.

  In an optical system with a wide angle of view, the height from the optical axis through which the principal ray with the maximum angle of view passes easily increases in the object-side lens, which increases the diameter and weight of the object-side lens. There is a risk of increasing the size.

  In order to prevent the size and weight of the product from becoming excessive, it is preferable that the lens closest to the object side is a negative lens in order to suppress the height of the light beam through which the principal ray having the maximum field angle passes.

  The negative lens preferably has a meniscus shape with a convex surface facing the object side in order to reduce the angle at which the principal ray is incident at the periphery of the lens surface and suppress the occurrence of coma and astigmatism.

  By disposing a negative meniscus lens having a convex surface facing the object side closest to the object side of the first lens group, an increase in the diameter and weight of the first lens group can be suppressed, and a coma generated in the first lens group can be suppressed. Occurrence of aberration and astigmatism is suppressed, and aberration correction in the entire optical system becomes easy.

  In addition, in the lens configuration in which a lens unit having a negative refractive power is disposed on the object side of the stop as in the zoom lens of the present embodiment, strong negative distortion occurs. It is preferable that the lens surface on the object side of the negative meniscus lens disposed closest to the object side in the lens group has an aspherical shape in which the local curvature radius decreases from the central portion toward the peripheral portion.

  Even if this aspherical shape is formed on the image side of a negative meniscus lens, for example, it is possible to correct distortion, but the most object in which the height of the ray through which the light beam varies greatly depends on the angle of view. By forming an aspherical shape on the object-side lens surface of the negative meniscus lens arranged on the side, distortion can be corrected most effectively.

  Further, in the zoom lens of the present embodiment, the first lens group includes a cemented lens having a positive refractive power closest to the image side, and the cemented lens is a negative meniscus lens having a convex surface directed toward the object side in order from the object side to the image side. And a positive lens having a convex surface facing the object side.

  In the negative lead type lens configuration such as the zoom lens of the present embodiment, in order to satisfactorily correct the lateral chromatic aberration in the entire optical system, it is necessary to correct the lateral chromatic aberration by the first lens unit alone. It is necessary to include a lens element having a positive refractive power in the first lens group.

  By disposing the lens element having the positive refractive power on the most image side of the first lens group, the diameter of the lens element itself having the positive refractive power can be suppressed and the diameter of the first lens group can be suppressed.

  Furthermore, this lens element having a positive refractive power can correct chromatic aberration more effectively by using a cemented lens formed by cementing a negative lens and a positive lens.

  Further, the negative lens and the positive lens constituting the cemented lens are a negative meniscus lens having a convex surface facing the object side and a positive lens having a convex surface facing the object side, respectively. It is possible to suppress the occurrence of coma and astigmatism by reducing the angle at which the chief ray is incident.

Furthermore, the zoom lens of the present embodiment satisfies the following conditions.
(5) −0.00067 <(θgFp−θgFn) / (νdp−νdn) <− 0.00057
θgFp: Partial dispersion ratio of g-line and F-line of the positive lens constituting the most image side cemented lens of the first lens group θgFn: G-line of the negative lens constituting the most image-side cemented lens of the first lens group F-line partial dispersion ratio νdp: Abbe number of positive lens constituting the most image-side cemented lens of the first lens group νdn: Abbe number of negative lens constituting the most image-side cemented lens of the first lens group

  Conditional expression (5) shows the relationship between the partial dispersion ratio of the glass material of the negative lens and the positive lens constituting the cemented lens having the positive refractive power arranged on the most image side of the first lens group, and the Abbe number. It defines an appropriate range for satisfactorily achieving the correction of the lateral chromatic aberration of the group.

  If the upper limit of conditional expression (5) is exceeded, the difference in the partial dispersion ratio of the glass material between the negative lens and the positive lens constituting the cemented lens becomes too large, and the correction of the secondary spectrum of the lateral chromatic aberration of the first lens group is increased. It tends to be insufficient.

  If the lower limit of conditional expression (5) is not reached, the Abbe number of the glass material of the negative lens and the positive lens constituting the cemented lens will approach, making it difficult to correct the primary spectrum of the lateral chromatic aberration of the first lens group. End up.

  In addition, the effect by this invention can be made more reliable by making the upper limit of conditional expression (5) into -0.00058.

  Moreover, the effect by this invention can be made more reliable by making the upper limit of conditional expression (5) further -0.000585.

  In addition, the effect by this invention can be made more reliable by making the minimum of conditional expression (5) into -0.00066.

  Moreover, the effect by this invention can be made more reliable by making the minimum of conditional expression (5) further into -0.000655.

  Further, in the zoom lens of the present embodiment, the first lens group includes, in order from the object side to the image side, a first negative meniscus lens having a convex surface directed toward the object side, and a second negative meniscus lens having a convex surface directed toward the object side. And a third negative meniscus lens having a convex surface facing the object side, a biconcave lens, and a cemented lens having a positive refractive power.

  In order to realize a wide angle of view at the wide-angle end and prevent deterioration of coma and astigmatism generated in the negative lens included in the first lens group, the first lens group is negative first in order from the object side to the image side. Three meniscus lenses are placed in succession to loosen the angle between the principal ray at the periphery and the optical axis, then a biconcave lens is placed to increase the negative refractive power and further positive refraction to the most image side. It is preferable to use a lens configuration in which a power cemented lens is arranged to satisfactorily correct lateral chromatic aberration.

  Further, in the zoom lens according to the present exemplary embodiment, the second lens unit includes, in order from the object side to the image side, a biconvex lens, and a cemented three-piece lens including a positive lens, a negative lens, and a positive lens.

  In the second lens group of the zoom lens of the present embodiment, an aperture stop is disposed in the interior or adjacent to the image side, so that the axial luminous flux passes through almost the entire effective diameter of the lens constituting the second lens group. It will be. Therefore, spherical aberration is large in the second lens group.

  In this correction of spherical aberration, the greater the number of lens elements constituting the second lens group, the greater the degree of freedom and the easier it is to achieve good correction. Due to large changes in spherical aberration and axial coma due to errors and decentration, it is difficult to increase the number of lens elements constituting the second lens group to ensure good imaging performance in the finished product. There is a risk of becoming.

  In this embodiment, in order to ensure both good imaging performance in the finished product and to ensure the freedom of aberration correction, the second lens group is arranged with a biconvex lens closest to the object side. The lens configuration is such that three cemented lenses of a positive lens, a negative lens, and a positive lens are arranged on the image side.

  Next, a lens configuration of an example according to the imaging optical system of the present invention will be described. In the following description, the lens configuration is described in order from the object side to the image side.

  FIG. 1 is a lens configuration diagram of a zoom lens according to Example 1 of the present invention.

  The zoom lens according to the first exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Is done.

  The first lens group G1, in order from the object side, includes a negative meniscus lens L1 having a convex surface toward the object side, a negative meniscus lens L2 having a convex surface toward the object side, a negative meniscus lens L3 having a convex surface toward the object side, It is composed of a biconcave lens L4, a cemented lens composed of a negative meniscus lens L5 having a convex surface facing the object side, and a biconvex lens L6, and moves from the object side to the image side during zooming from the wide angle end to the telephoto end. The lens surface on the object side of the negative meniscus lens L1 with the convex surface facing the object side and the lens surfaces on both sides of the negative meniscus lens L3 with the convex surface facing the object side have a predetermined aspheric shape.

  The second lens group G2 is configured by arranging, in order from the object side, a cemented lens composed of a biconvex lens L7, a biconvex lens L8, a biconcave lens L9, and a positive meniscus lens L10 having a convex surface facing the object side. An aperture stop is provided in the second lens group G2, that is, between L7 and L8. When zooming from the wide-angle end to the telephoto end, it moves from the image side to the object side, and when focusing from an infinitely distant object to a near object, it moves from the object side to the image side.

  The third lens group G3 includes, in order from the object side, a cemented lens composed of a biconvex lens L11 and a biconcave lens L12, a biconvex lens L13, a cemented lens composed of a negative meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The lens is composed of a positive meniscus lens L16 having a convex surface facing the image side, and moves from the image side to the object side during zooming from the wide-angle end to the telephoto end. The lens surfaces on both sides of the positive meniscus lens L16 with the convex surface facing the image side have a predetermined aspherical shape.

  FIG. 14 is a lens configuration diagram of a zoom lens according to Example 2 of the present invention.

  The zoom lens according to the second exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Is done.

  The first lens group G1, in order from the object side, includes a negative meniscus lens L1 having a convex surface toward the object side, a negative meniscus lens L2 having a convex surface toward the object side, a negative meniscus lens L3 having a convex surface toward the object side, It is composed of a biconcave lens L4, a cemented lens composed of a negative meniscus lens L5 having a convex surface facing the object side, and a biconvex lens L6, and moves from the object side to the image side during zooming from the wide angle end to the telephoto end. The lens surface on the object side of the negative meniscus lens L1 with the convex surface facing the object side and the lens surfaces on both sides of the negative meniscus lens L3 with the convex surface facing the object side have a predetermined aspheric shape.

  The second lens group G2 is configured by arranging, in order from the object side, a cemented lens composed of a biconvex lens L7, a biconvex lens L8, a biconcave lens L9, and a positive meniscus lens L10 having a convex surface facing the object side. An aperture stop is provided in the second lens group G2, that is, between L7 and L8. When zooming from the wide-angle end to the telephoto end, it moves from the image side to the object side, and when focusing from an infinitely distant object to a near object, it moves from the object side to the image side.

  The third lens group G3 includes, in order from the object side, a cemented lens composed of a biconvex lens L11 and a biconcave lens L12, a biconvex lens L13, a cemented lens composed of a negative meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The lens is composed of a positive meniscus lens L16 having a convex surface facing the image side, and moves from the image side to the object side during zooming from the wide-angle end to the telephoto end. The lens surfaces on both sides of the positive meniscus lens L16 with the convex surface facing the image side have a predetermined aspherical shape.

  FIG. 27 is a lens configuration diagram of a zoom lens according to Example 3 of the present invention.

  The zoom lens according to the third exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Is done.

  The first lens group G1, in order from the object side, includes a negative meniscus lens L1 having a convex surface toward the object side, a negative meniscus lens L2 having a convex surface toward the object side, a negative meniscus lens L3 having a convex surface toward the object side, It is composed of a biconcave lens L4, a cemented lens composed of a negative meniscus lens L5 having a convex surface facing the object side, and a biconvex lens L6, and moves from the object side to the image side during zooming from the wide angle end to the telephoto end. The lens surface on the object side of the negative meniscus lens L1 with the convex surface facing the object side and the lens surfaces on both sides of the negative meniscus lens L3 with the convex surface facing the object side have a predetermined aspheric shape.

  The second lens group G2 is configured by arranging, in order from the object side, a cemented lens composed of a biconvex lens L7, a biconvex lens L8, a biconcave lens L9, and a positive meniscus lens L10 having a convex surface facing the object side. An aperture stop is provided in the second lens group G2, that is, between L7 and L8. When zooming from the wide-angle end to the telephoto end, it moves from the image side to the object side, and when focusing from an infinitely distant object to a near object, it moves from the object side to the image side.

  The third lens group G3 includes, in order from the object side, a cemented lens composed of a biconvex lens L11 and a biconcave lens L12, a biconvex lens L13, a cemented lens composed of a negative meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The lens is composed of a positive meniscus lens L16 having a convex surface facing the image side, and moves from the image side to the object side during zooming from the wide-angle end to the telephoto end. The lens surfaces on both sides of the positive meniscus lens L16 with the convex surface facing the image side have a predetermined aspherical shape.

  FIG. 40 is a lens configuration diagram of a zoom lens according to Example 4 of the present invention.

  The zoom lens according to the fourth exemplary embodiment includes, in order from the object side, a first lens group G1 having a negative refractive power, a second lens group G2 having a positive refractive power, and a third lens group G3 having a positive refractive power. Is done.

  The first lens group G1, in order from the object side, includes a negative meniscus lens L1 having a convex surface toward the object side, a negative meniscus lens L2 having a convex surface toward the object side, a negative meniscus lens L3 having a convex surface toward the object side, It is composed of a biconcave lens L4, a cemented lens composed of a negative meniscus lens L5 having a convex surface facing the object side, and a biconvex lens L6, and moves from the object side to the image side during zooming from the wide angle end to the telephoto end. The lens surface on the object side of the negative meniscus lens L1 with the convex surface facing the object side and the lens surfaces on both sides of the negative meniscus lens L3 with the convex surface facing the object side have a predetermined aspheric shape.

  The second lens group G2 is configured by arranging, in order from the object side, a cemented lens composed of a biconvex lens L7, a biconvex lens L8, a biconcave lens L9, and a positive meniscus lens L10 having a convex surface facing the object side. An aperture stop is provided in the second lens group G2, that is, between L7 and L8. When zooming from the wide-angle end to the telephoto end, it moves from the image side to the object side, and when focusing from an infinitely distant object to a near object, it moves from the object side to the image side.

  The third lens group G3 includes, in order from the object side, a cemented lens composed of a biconvex lens L11 and a biconcave lens L12, a biconvex lens L13, a cemented lens composed of a negative meniscus lens L14 having a convex surface facing the object side, and a biconvex lens L15. The lens is composed of a positive meniscus lens L16 having a convex surface facing the image side, and moves from the image side to the object side during zooming from the wide-angle end to the telephoto end. The lens surfaces on both sides of the positive meniscus lens L16 with the convex surface facing the image side have a predetermined aspherical shape.

  Next, numerical examples and conditional expression corresponding values of the zoom lens according to the present invention will be described.

  In [Surface data], the surface number is the number of the lens surface or aperture stop counted from the object side, r is the radius of curvature of each lens surface, d is the distance between the lens surfaces, and nd is for the d-line (wavelength 587.56 nm). Refractive index, vd is the Abbe number with respect to d-line, and θgF is the partial dispersion ratio of g-line (wavelength 435.84 nm) and F-line (wavelength 486.13 nm).

  The * (asterisk) attached to the surface number indicates that the lens surface shape is an aspherical surface. BF represents back focus.

  The (diaphragm) attached to the surface number indicates that the aperture stop is located at that position. ∞ (infinity) is entered in the radius of curvature for a plane or aperture stop.

  [Aspherical data] indicates the values of the coefficients that give the aspherical shape of the lens surface marked with * in [Surface data]. The shape of the aspherical surface is expressed by the following formula. In the following equation, y is the displacement from the optical axis in the direction perpendicular to the optical axis, z is the displacement (sag amount) in the optical axis direction from the intersection of the aspherical surface and the optical axis, and r is the radius of curvature of the reference spherical surface. The conic coefficient is represented by K. In addition, the third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, eleventh, and twelfth order aspheric coefficients are represented by A3, A4, A5, A6, A7, A8, A9, A10, A11, and A12, respectively. Yes.

  [Various data] shows values such as the focal length when focusing on infinity.

  [Variable interval data] indicates the value of the variable interval of the lens surface when each object distance is focused at each focal length.

  [Lens Group Data] indicates the lens surface number closest to the object side constituting each lens group and the combined focal length of the entire lens group.

  In all the values of the following specifications, the focal length f, the radius of curvature r, the lens surface interval d, and other length units described are in millimeters (mm) unless otherwise specified. In the system, the same optical performance can be obtained even in proportional expansion and proportional reduction, and the present invention is not limited to this.

Numerical example 1
Unit: mm
[Surface data]
Surface number rd nd vd θgF
1 * 117.0460 4.0000 1.69090 52.98 0.5483
2 26.9011 11.0904
3 * 34.7539 1.2255 1.90043 37.37 0.5771
4 * 21.7514 7.0366
5 42.1406 2.0000 1.59051 66.72 0.5367
6 21.1947 13.9807
7 -77.3027 1.0079 1.43700 95.10 0.5335
8 76.7507 1.8574
9 260.4864 1.0013 1.43700 95.10 0.5335
10 33.7547 9.6255 1.88300 40.80 0.5654
11 -5844.2250 d11
12 30.4578 5.3381 1.51823 58.96 0.5441
13 -81.7520 1.9906
14 (Aperture) ∞ 2.0000
15 102.5708 3.1430 1.64769 33.84 0.5923
16 -24.5905 0.8000 1.95375 32.32 0.59
17 41.5882 2.2065 1.92286 20.88 0.6388
18 456.4439 d18
19 180.7582 2.8880 1.43700 95.10 0.5335
20 -30.1392 0.8000 1.88300 40.80 0.5654
21 109.6530 0.1500
22 24.7706 5.3779 1.43700 95.10 0.5335
23 -40.9714 0.1500
24 28.7458 0.8500 1.88300 40.80 0.5654
25 16.2613 6.8094 1.43700 95.10 0.5335
26 -99.6935 1.1543
27 * -34.6883 2.0021 1.55232 71.54 0.5389
28 * -33.1396 BF
Image plane ∞

[Aspherical data]
1 surface 5 surfaces 6 surfaces 27 surfaces 28 surfaces
K 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00
A3 0.00000.E + 00 -4.30477.E-04 -4.03565.E-04 0.00000.E + 00 0.00000.E + 00
A4 8.07443.E-06 2.33594.E-04 2.50468.E-04 2.75767.E-05 4.51807.E-05
A5 0.00000.E + 00 -4.38899.E-05 -5.14202.E-05 0.00000.E + 00 0.00000.E + 00
A6 -7.22856.E-09 3.56778.E-06 5.03397.E-06 2.07778.E-07 2.61156.E-07
A7 0.00000.E + 00 -5.25086.E-08 -2.12341.E-07 0.00000.E + 00 0.00000.E + 00
A8 5.15441.E-12 -7.24485.E-09 3.44914.E-09 -2.24492.E-09 -2.29633.E-09
A9 0.00000.E + 00 2.00040.E-10 -3.43479.E-11 0.00000.E + 00 0.00000.E + 00
A10 -1.99584.E-15 1.52222.E-11 -1.03598.E-11 2.94004.E-12 4.37741.E-12
A11 0.00000.E + 00 -8.51858.E-13 1.08804.E-12 0.00000.E + 00 0.00000.E + 00
A12 3.54307.E-19 1.21988.E-14 -2.72895.E-14 0.00000.E + 00 0.00000.E + 00

[Various data]
Zoom ratio 1.85
Wide angle Medium telephoto Focal length 12.44 16.56 23.04
F number 4.13 4.13 4.12
Full angle of view 2ω 121.05 104.54 85.38
Image height Y 21.63 21.63 21.63
Total lens length 167.0926 157.7021 155.3966

[Variable interval data]
Wide angle Intermediate Shooting distance ∞ 260mm ∞ 260mm
d11 33.8239 38.6846 16.5617 20.1948
d18 5.8952 1.0345 6.1217 2.4886
BF 38.8883 38.8883 46.5335 46.5335

Telephoto shooting distance ∞ 260mm
d11 1.8263 5.2912
d18 6.4422 2.9773
BF 58.6428 58.6428

[Lens group data]
Group Start surface Focal length
G1 1 -21.55
G2 12 61.31
G3 19 59.78

Numerical example 2
Unit: mm
[Surface data]
Surface number rd nd vd θgF
1 * 119.4606 4.0000 1.69090 52.98 0.5483
2 26.7449 11.0768
3 * 34.3172 1.3365 1.90043 37.37 0.5771
4 * 21.6028 6.9121
5 41.3459 2.0000 1.59051 66.72 0.5367
6 21.2029 13.9323
7 -77.5835 1.0295 1.43700 95.10 0.5335
8 75.9615 1.8542
9 252.5536 1.0030 1.43700 95.10 0.5335
10 33.5498 10.4100 1.88300 40.80 0.5654
11 -288751.3819 d11
12 30.4200 3.2595 1.51823 58.96 0.5441
13 -77.0165 1.6983
14 (Aperture) ∞ 2.3012
15 113.0026 3.2605 1.64769 33.84 0.5923
16 -24.5510 0.8000 1.95375 32.32 0.59
17 38.8651 2.5131 1.92286 20.88 0.6388
18 495.7079 d18
19 194.9358 2.9456 1.43700 95.10 0.5335
20 -29.1294 0.8000 1.88300 40.80 0.5654
21 107.5961 0.1500
22 24.6388 5.2927 1.43700 95.10 0.5335
23 -40.3624 0.1500
24 28.2108 0.8500 1.88300 40.80 0.5654
25 16.0244 7.1543 1.43700 95.10 0.5335
26 -89.9068 1.2112
27 * -33.0189 2.1508 1.55232 71.54 0.5389
28 * -31.9796 BF
Image plane ∞

[Aspherical data]
1 surface 5 surfaces 6 surfaces 27 surfaces 28 surfaces
K 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00
A3 0.00000.E + 00 -3.95573.E-04 -3.71355.E-04 0.00000.E + 00 0.00000.E + 00
A4 8.10336.E-06 2.31769.E-04 2.49532.E-04 2.78744.E-05 4.51977.E-05
A5 0.00000.E + 00 -4.38241.E-05 -5.14988.E-05 0.00000.E + 00 0.00000.E + 00
A6 -7.39132.E-09 3.56519.E-06 5.03683.E-06 2.06444.E-07 2.62146.E-07
A7 0.00000.E + 00 -5.24474.E-08 -2.12211.E-07 0.00000.E + 00 0.00000.E + 00
A8 5.33269.E-12 -7.24233.E-09 3.44194.E-09 -2.23703.E-09 -2.29929.E-09
A9 0.00000.E + 00 1.99824.E-10 -3.47559.E-11 0.00000.E + 00 0.00000.E + 00
A10 -2.09340.E-15 1.52294.E-11 -1.03534.E-11 2.81436.E-12 4.38847.E-12
A11 0.00000.E + 00 -8.52063.E-13 1.08822.E-12 0.00000.E + 00 0.00000.E + 00
A12 3.78500.E-19 1.21988.E-14 -2.72868.E-14 0.00000.E + 00 0.00000.E + 00

[Various data]
Zoom ratio 1.86
Wide angle Medium telephoto Focal length 12.42 16.55 23.06
F number 4.12 4.11 4.13
Full angle of view 2ω 121.10 104.60 85.36
Image height Y 21.63 21.63 21.63
Total lens length 166.9795 157.5812 155.2709

[Variable interval data]
Wide angle Intermediate Shooting distance ∞ 260mm ∞ 260mm
d11 33.8240 38.6784 16.5649 20.1962
d18 5.8935 1.0391 6.1244 2.4932
BF 39.1703 39.1703 46.8001 46.8001

Telephoto shooting distance ∞ 260mm
d11 1.8234 5.2859
d18 6.4428 2.9802
BF 58.9131 58.9131

[Lens group data]
Group Start surface Focal length
G1 1 -21.55
G2 12 61.46
G3 19 59.99

Numerical Example 3
Unit: mm
[Surface data]
Surface number rd nd vd θgF
1 * 120.2221 4.0000 1.69090 52.98 0.5483
2 27.0247 11.0374
3 * 35.0300 1.1977 1.90043 37.37 0.5771
4 * 21.5834 6.7614
5 40.7955 2.0000 1.59051 66.72 0.5367
6 21.2492 14.0899
7 -77.6477 1.0000 1.43700 95.10 0.5335
8 81.7407 1.8503
9 358.7370 1.0000 1.43700 95.10 0.5335
10 33.6200 7.1341 1.88300 40.80 0.5654
11 -11005.8210 d11
12 30.2863 5.2526 1.51823 58.96 0.5441
13 -86.6345 2.2838
14 (Aperture) ∞ 2.6810
15 113.0034 3.0709 1.64769 33.84 0.5923
16 -23.8946 0.8000 1.95375 32.32 0.59
17 47.2523 2.2555 1.92286 20.88 0.6388
18 1794.0930 d18
19 418.9759 2.9834 1.43700 95.10 0.5335
20 -27.1261 0.8000 1.88300 40.80 0.5654
21 163.2399 0.1500
22 26.8140 5.3894 1.43700 95.10 0.5335
23 -37.7108 0.1500
24 29.5378 0.8500 1.88300 40.80 0.5654
25 16.7892 6.6147 1.43700 95.10 0.5335
26 -87.8754 0.9251
27 * -37.8372 1.9524 1.55232 71.54 0.5389
28 * -35.0886 BF
Image plane ∞

[Aspherical data]
1 surface 5 surfaces 6 surfaces 27 surfaces 28 surfaces
K 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00
A3 0.00000.E + 00 -3.97797.E-04 -3.74381.E-04 0.00000.E + 00 0.00000.E + 00
A4 8.24391.E-06 2.31953.E-04 2.50648.E-04 2.87105.E-05 4.49938.E-05
A5 0.00000.E + 00 -4.38069.E-05 -5.14831.E-05 0.00000.E + 00 0.00000.E + 00
A6 -7.39213.E-09 3.56595.E-06 5.03895.E-06 2.09742.E-07 2.60250.E-07
A7 0.00000.E + 00 -5.24317.E-08 -2.12105.E-07 0.00000.E + 00 0.00000.E + 00
A8 5.31167.E-12 -7.24195.E-09 3.44378.E-09 -2.22070.E-09 -2.29867.E-09
A9 0.00000.E + 00 1.99780.E-10 -3.47708.E-11 0.00000.E + 00 0.00000.E + 00
A10 -2.09099.E-15 1.52296.E-11 -1.03546.E-11 3.17123.E-12 4.18023.E-12
A11 0.00000.E + 00 -8.52052.E-13 1.08800.E-12 0.00000.E + 00 0.00000.E + 00
A12 3.77867.E-19 1.22084.E-14 -2.73082.E-14 0.00000.E + 00 0.00000.E + 00

[Various data]
Zoom ratio 1.86
Wide angle Medium telephoto Focal length 12.42 16.54 23.05
F number 4.13 4.11 4.13
Full angle of view 2ω 121.16 104.57 85.37
Image height Y 21.63 21.63 21.63
Total lens length 164.7956 155.4823 153.3029

[Variable interval data]
Wide angle Intermediate Shooting distance ∞ 260mm ∞ 260mm
d11 33.8191 38.5729 16.5822 20.122
d18 5.8796 1.1258 6.1095 2.5697
BF 38.8673 38.8672 46.5609 46.561

Telephoto shooting distance ∞ 260mm
d11 1.8325 5.2171
d18 6.4406 3.0561
BF 58.8001 58.8001

[Lens group data]
Group Start surface Focal length
G1 1 -21.44
G2 12 60.07
G3 19 58.42

Numerical Example 4
Unit: mm
[Surface data]
Surface number rd nd vd θgF
1 * 122.4382 4.0000 1.69090 52.98 0.5483
2 26.9211 11.2490
3 * 34.9913 1.0000 1.90043 37.37 0.5771
4 * 21.8761 7.1833
5 41.4990 2.0000 1.59051 66.72 0.5367
6 21.3017 13.8851
7 -77.3081 1.0137 1.43700 95.10 0.5335
8 83.2467 1.8046
9 120.5720 1.0120 1.49700 81.61 0.5387
10 32.4013 10.9615 1.88300 40.80 0.5654
11 798.8730 d11
12 30.2314 3.3947 1.51823 58.96 0.5441
13 -85.3544 2.3962
14 (Aperture) ∞ 2.7472
15 101.6390 3.1293 1.64769 33.84 0.5923
16 -24.4514 0.8000 1.95375 32.32 0.59
17 40.2978 2.2133 1.92286 20.88 0.6388
18 445.2453 d18
19 217.0031 3.1178 1.43700 95.10 0.5335
20 -28.7511 0.8000 1.88300 40.80 0.5654
21 136.5217 0.1500
22 26.1541 5.3597 1.43700 95.10 0.5335
23 -38.6668 0.1500
24 28.8789 0.8500 1.88300 40.80 0.5654
25 16.3046 6.6793 1.43700 95.10 0.5335
26 -102.9941 1.3067
27 * -33.3326 1.8548 1.55232 71.54 0.5389
28 * -31.7274 BF
Image plane ∞

[Aspherical data]
1 surface 5 surfaces 6 surfaces 27 surfaces 28 surfaces
K 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00 0.00000.E + 00
A3 0.00000.E + 00 -4.36956.E-04 -4.14400.E-04 0.00000.E + 00 0.00000.E + 00
A4 8.08533.E-06 2.31987.E-04 2.49581.E-04 2.81818.E-05 4.44433.E-05
A5 0.00000.E + 00 -4.38724.E-05 -5.15354.E-05 0.00000.E + 00 0.00000.E + 00
A6 -7.21212.E-09 3.56663.E-06 5.03384.E-06 2.07052.E-07 2.57654.E-07
A7 0.00000.E + 00 -5.25241.E-08 -2.12257.E-07 0.00000.E + 00 0.00000.E + 00
A8 5.19479.E-12 -7.24487.E-09 3.45077.E-09 -2.22830.E-09 -2.33444.E-09
A9 0.00000.E + 00 1.99977.E-10 -3.42628.E-11 0.00000.E + 00 0.00000.E + 00
A10 -2.01679.E-15 1.52257.E-11 -1.03456.E-11 2.93939.E-12 4.30058.E-12
A11 0.00000.E + 00 -8.51797.E-13 1.08876.E-12 0.00000.E + 00 0.00000.E + 00
A12 3.55434.E-19 1.22084.E-14 -2.72471.E-14 0.00000.E + 00 0.00000.E + 00

[Various data]
Zoom ratio 1.85
Wide angle Medium telephoto Focal length 12.46 16.57 23.01
F number 4.13 4.11 4.12
Full angle of view 2ω 120.87 104.48 85.49
Image height Y 21.63 21.63 21.63
Total lens length 167.5922 158.1689 155.7682

[Variable interval data]
Wide angle Intermediate Shooting distance ∞ 260mm ∞ 260mm
d11 33.8263 38.7198 16.5591 20.2257
d18 5.9081 1.0146 6.1328 2.4662
BF 38.7994 38.7994 46.4187 46.4187

Telephoto shooting distance ∞ 260mm
d11 1.8113 5.311
d18 6.4466 2.9469
BF 58.452 58.452

[Lens group data]
Group Start surface Focal length
G1 1 -21.62
G2 12 61.37
G3 19 59.33

[Conditional expression values]
Example 1 Example 2 Example 3 Example 4
Conditional expression (1) 0.3973 0.2941 0.4064 0.3303
Conditional expression (2) 4.3724 4.3832 4.3141 4.3778
Conditional expression (3) 2.8875 2.8982 2.8222 2.8971
Conditional expression (4) 3.1272 3.1536 3.1298 3.1133
Conditional expression (5) -0.000589319 -0.000589319 -0.000589319 -0.000651801

G1 First lens group G2 Second lens group G3 Third lens group

S Aperture stop I Image plane

Claims (7)

In order from the object side to the image side, a first lens group having a negative refractive power, a second lens group having a positive refractive power, and a third lens group having a positive refractive power,
During zooming from the wide-angle end to the telephoto end, all the lens groups move along the optical axis, thereby reducing the distance between the first lens group and the second lens group, and the second lens group and the second lens group. A zoom lens in which the distance between the three lens groups is increased;
The second lens group includes a biconvex lens closest to the object side,
An aperture stop is disposed in the second lens group or adjacent to the image side;
A zoom lens satisfying the following conditions:
(1) LS / ft> 0.25
(2) 3.95 <| (f2 × (β2w−1) / β2w−pp2) / f1 | <4.95
(3) 2.30 <| (f2 × (β2t−1) / β2t−pp2) / f1 | <3.25
(4) 3.00 <BFw / fw <3.30
LS: Length on the optical axis between the lens surface closest to the image side of the first lens unit and the aperture stop in the infinitely focused state at the telephoto end ft: Optical system in the infinitely focused state at the telephoto end Total focal length fw of the entire system: Total focal length f1 of the entire optical system in an infinitely focused state at the wide angle end: Focal length f2 of the first lens group: Focal length β2w of the second lens group: At the wide angle end The imaging magnification β2t of the second lens group in the infinite focus state: the imaging magnification pp2 of the second lens group in the infinite focus state at the telephoto end: Length BFw on the optical axis between the object side principal point of the lens group: paraxial back focus in the infinite focus state at the wide angle end   2. The zoom lens according to claim 1, wherein the second lens group moves from the object side to the image side along the optical axis during focusing from an object at infinity to an object at a short distance.   The first lens group includes a negative meniscus lens having a convex surface facing the object side closest to the object side, and the lens surface on the object side of the negative meniscus lens has an aspheric surface with a local radius of curvature that decreases from the center toward the periphery. The zoom lens according to claim 1, wherein the zoom lens has a shape.   The first lens group includes a cemented lens having a positive refractive power closest to the image side. The cemented lens has a negative meniscus lens having a convex surface facing the object side in order from the object side to the image side, and a convex surface facing the object side. The zoom lens according to claim 1, comprising a positive lens. The zoom lens according to claim 4, wherein the following condition is satisfied.
(5) −0.00067 <(θgFp−θgFn) / (νdp−νdn) <− 0.00057
θgFp: Partial dispersion ratio of g-line and F-line of the positive lens constituting the most image side cemented lens of the first lens group θgFn: G-line of the negative lens constituting the most image-side cemented lens of the first lens group F-line partial dispersion ratio νdp: Abbe number of positive lens constituting the most image-side cemented lens of the first lens group νdn: Abbe number of negative lens constituting the most image-side cemented lens of the first lens group   The first lens group includes, in order from the object side to the image side, a first negative meniscus lens having a convex surface facing the object side, a second negative meniscus lens having a convex surface facing the object side, and a first negative meniscus lens having a convex surface facing the object side. The zoom lens according to any one of claims 1 to 5, comprising a three-negative meniscus lens, a biconcave lens, and a cemented lens having a positive refractive power.   7. The zoom according to claim 1, wherein the second lens group includes, in order from the object side to the image side, a biconvex lens, and a triplet cemented lens including a positive lens, a negative lens, and a positive lens. lens.

Images